Wireless World's

Suka-Duka RF Engineer

2009-02-28T22:33:00.002+07:00

Setelah mencoba berbagi macam kerjaan di ranah Telco, akhirnya mantabs juga di RF Planning/Optimization.
Sebelum ini emang udah banyak posisi yang dicoba, mulai dari Drive Test ..... Sebelum lulus dah dapet kerjaan lagi jadi RF LOS Survey,,,keren namanya doank,,,kerjaannya naik tower and propose mo di taruh di mana antenna microwavenya,,,ilmunya nambah seh,, ilmu manjat tower,,,pake GPS,,,pake PathLoss,,,,prediksi terrain,,,pake mobil kantor,,,ups,,,,he...he.. cuman bertahan setahun di sini,,,dah kagak kuat lg naik turun tower, mana tinggi-tinggi banget di kalimantan,,,wuih,,,
So, begitu ada tawaran jadi tukang comissioning BTS Siemens, ya udah cabut ajah :),,,,Ya meski turun dari vendor ke subcont it's ok lah demi ilmu baru,,, :)),,, ealah dapetnya di kalimantan juga..Pontianak tepatnya "0 degree" panas bgt, deket sambas lg,,site Telkomsel lagi,,,mana jauh2 banget ke pedalaman,,, Comissioning hal baru buatku,,mana pegang perangkat langsung. Gak beda ma install komputer baru seh, cuman udah Hi tech gt,,, pake LMT,,,bisa connect ke BSC,,,bisa liat status site lainnya,,,upload and download software buat activin BTS,,,,bangga lah bisa on air in beberapa BTS punya Telkomsel di Pontianak,,, Nambah ilmu and pengalaman baru di Telco.
Cuman 3 bulan bertahan di sini,,,gak ngerti nih,,mungkin emang type quicker kali ya,,, ngrasa ilmunya mandek (gak upgrade lagi) akhirnya mutusin untuk resign,, :)

Cukup lama nganggur seh sambil apply ke mana-mana gitu,,,nah ketemulah dengan istilah baru Internet Marketing yg didalamnya ada Affiliate, Adsense dll,,, banyak deh,,,sekitar sebulanan deh coba2 ngenal dunia ini, bikin blog ditempelin Banner muali Google Adsense sampai yg lokal-lokal gt,,,,:),,, cuman kalo emang gak bakat hasilnya juga gak bagus2 amat kali ya,,,
Sebulanan bermain-main di Internet Marketing datanglah undangan interview di ZTE-Indonesia,,,Karena awalnya pengen naik ke core network milihlah ke posisi core. Setelah beberapa kali interview akhirnya masuk juga ke ZTE,,, guess what "NPO" Network Planning and Optimization untuk GSM Project,,, he...he.. what ever lah yg penting masuk duluan,,,,
Di sini dimulailah kiprah di dunia Optimasi jaringan cellular,,,,,awalnya masuk di project Telkomsel,,,berjalan 1 bulan ada kabar HCPT project di kalimantan BTS nya dah mulai on air,,, karna GSM engineer baru ada 2 jadilah aq di handover ke HCPT,,, dapet kalimantan lagi,,,kayaknya jodoh ma kalimantan :)
Drive test lagi, cuman sekarang sekalian eksekusi optimasinya,,, awalnya emang optimasi antenna doank sih,,,,,ternyata banyak ilmu juga di RF,,,,

Next

VoIP Protocols and Wide-Area Networks

2008-07-06T23:58:00.000+07:00

With the large scale rollout of wireless Ethernet-based VoIP phones in the enterprise, VoIP technology has reached a level of maturity where residential VoIP cordless phones, wireless PBXs and, eventually, future cellular systems based on 802.11 are no longer just a possibility for VoIP over WLAN technology—they are inevitable.

The larger challenge of VoIP over WLANs will be how to handle handoffs of an active call between 802.11 APs or between an 802.11 AP and a cellular network's cell. VoIP residential cordless phones will be the only application that will not require handoff capabilities initially.

The following diagram illustrates the basic mobility challenge for WLAN implementations:

Figure 12

As the diagram illustrates, the hierarchical nature of IP network topology results in two types of mobility:

Micro-Mobility
Macro-Mobility

Micro-mobility and macro-mobility are defined as changes of access point association (attachment) while an ongoing VoIP (or data) session is in progress. They define the requirements for handoffs in the larger system. Micro- and macro-mobility differ from WLAN roaming or nomadic operations where a session is simply terminated and restarted in a new 802.11 AP cell. (This is what happens in WLAN hotspots today.)

Micro-mobility is the simplest form of mobility. The subscriber is moving within a single domain, such as an enterprise, a set of hotspots owned by company A or some other sort of limited WLAN configuration. Micro-mobility essentially involves intra-domain handoffs. There is no need for external coordination. Issues of timing, call control and handoff control can be set (or bounded) by network design. The first wave of VoIP over WLAN services will be based on micro-mobility in the enterprise or in the residence.

Macro-mobility involves moving between two domains that fall under the administration of completely distinct organizations. For example, one hotspot could be run by carrier A and a second is administered by carrier B. The two domains must collaborate to complete the handoff and to conduct authentication, authorization and accounting (AAA) activities between the domains. These arrangements are similar to efforts in the cellular industry that have been developed over the last few years.

Given that micro-mobility solutions will be the first developed and deployed, micro-mobility solutions must consider the larger framework that includes macro-mobility capabilities as well as the eventual evolution to full macro-mobility.

There are two principal approaches for supporting mobility in VoIP services. They are:

SIP (Session Initiated Protocol)
Mobile IP

Mobile IP is a network layer (i.e. layer 3) approach to mobility. While Mobile IP does not directly support VoIP applications, the protocol can be used as a basis for VoIP with additional and potentially proprietary protocols (e.g. Cisco's CCx). The alternate solution is to confront the mobility challenge at the application layer (layer 4/5) by augmenting existing VoIP protocols like SIP or H.323. Currently, the inclusion of SIP in Microsoft Windows® XP has resulted in widespread support and a proliferation of the infrastructure for the simpler SIP protocol over the more rigid H.323 protocol.

The following section gives a brief overview of Mobile IP and SIP for mobility applications and concludes with a discussion of cellular GPRS/WLAN integration for data services. Many in the industry anticipate that cellular data deployments like GPRS/WLAN will be implemented initially and a larger movement to full blown VoIP WLANs will follow later.

Mobile IP Overview

Several elements are needed to implement a WLAN incorporating Mobile IP capabilities for APto- AP handoffs. The following diagram illustrates the elements of a Mobile-IP system:

Figure 13

The elements shown above are defined as follows:

Mobile Node: VoIP caller
RFA: Regional Foreign Agent
AAAF: Authentication, Authorization, Accounting - Foreign Network
GFA: Gateway Foreign Agent
HA: Home Agent
AAAH: Authentication, Authorization, Accounting - Home Network
CN: Corresponding Node (the network that a caller node is attached to)
Caller Node: Another phone caller

Figure 14

When both caller and the mobile node are in the home network (i.e. when the switching occurs within one's own voice network), the PBX function is present. In this case, the VoIP call is routed through a self-contained enterprise network and no Internet domain resources are required.

Mobile IP is based on the concept that a mobile node has a home address associated with a home network. Each time the mobile node connects to a foreign network, it obtains a temporary address which is known as a Care of Address (CoA). The CoA is valid while the mobile node is attached to the foreign network domain. It is deleted or purged from the foreign network once the mobile node leaves the domain.

In Mobile IP WLANs, there are two mobility agents, Home Agents (HA) and Foreign Agents (FA), that coordinate, update and authorize the connections and associated CoAs for clients from foreign networks. When a call is set up between a Caller Node and the Mobile Node, a binding update message is sent by the Home Agent to the Corresponding Node. The binding message allows VoIP traffic and messages to be directly tunneled between the Caller Node and the Mobile Node. Messages need not be routed to the home network. Clearly, tunneling greatly increases the efficiency of Mobile IP.

Difficulty arises when roaming occurs between two foreign networks while a call is in progress between a Caller Node and a Mobile Node. Consider a Mobile Node that is leaving one foreign network and transitioning to a new foreign network. The first foreign network and associated FA must send binding warning messages to the caller's Home Agent (HA), alerting the HA that packets from the CN are arriving, but the Mobile Node is no longer in the first foreign network. The first foreign network redirects any received packets back to the caller's HA. Simultaneously, the Mobile Node will complete the association with the second foreign network. The HA then will establish the new CoA with the second Foreign Agent / foreign network. The HA then provides a new CoA to the second foreign network, and this allows direct tunneling of messages between the Mobile Node on the second foreign network and the caller node in the corresponding network. While this handoff is taking place, the HA acts as a middle man, maintaining the VoIP connection by forwarding packets from the first foreign network to the second foreign network. This stops once the new CoA and binding for direct tunneling are in place.

A complete description of this process is beyond the scope of this paper. However, it is obvious that when the problem is reduced to a single domain (such as an enterprise WLAN where there are no foreign networks), the solution is much more tractable.

In addition to the overall handoff process, controlling several timing issues is imperative for successful macro-mobility and micro-mobility handoffs. The following are some of the timing elements that must concern WLAN or handset designers:

Ts: The period of time needed for a station to associate with an access point (probe and associate)
Tf: The period of time needed by a handset to associate with a foreign network (inter-domain update)
Th: The period of time to bind to a foreign network and create a new CoA
Tmc: The period of time needed to send packets directly between the Mobile Node and a Caller Node
Tno: The period of time needed to bind update messages from an old foreign network to a new foreign network

The time required to register and set up a VoIP call for Mobile IP is:

Tmip_init = 2Ts + 2Th + 2Tmc

For macro-mobility (inter-domain) handoffs between two different foreign networks, Mobile IP has the following timing:

Tmip_inter = Tno + 3Th + Thc + Tmc

During a handoff, as the new tunnel connection is established between a Mobile Node and the Caller Node, a series of packets will be disrupted and may arrive out of order, causing them to be discarded. The period of time for this disruption is given by the same formula for both SIP and Mobil IP. It is:

Tblack_out = 2 Ts + 2 Th + 2 Tno

For micro-mobility handoffs in the same domain, such as a handoff from one AP to another in an enterprise WLAN, Mobile IP has the following timing:

Tmip_intra = 2Ts + 2Tf

At this point, issues relating to intra-domain handoffs will be discussed. In the next section, the SIP approach and its associated timing issues will be described.

Issues for Mobile IP Macro-mobility

There are two major issues relating to the implementation of Mobile IP macro-mobility:

The probe and association time for 802.11 APs is not included in the time delay budgets in the previous discussion. This will exacerbate handoff delays unless improvements are made.

Lost packets may result in short disruption in voice services.
A more important issue is the fact that Mobile IP is not widely supported. The end-to-end deployment of Mobile IP on the Internet will take significant effort to achieve.

SIP Overview

As an alternative to Mobile IP, SIP supports IP mobility for VoIP WLAN applications by providing handoff capabilities at the application layer.

SIP can make direct use of Dynamic Host Control Protocol (DHCP) when connecting to an 802.11 AP for binding an IP address. A number of proposed systems use DIAMETER as the AAA (authentication, authorization, accounting) protocol. SIP makes use of the concept of a visited registrar (VR) in the foreign network. The SIP VR combines some of the functions of a SIP proxy server, location server and user agent. The SIP proxy server concept allows SIP to handle both firewall functions and network address translations (NAT), which are pervasive in home network topologies. SIP was initially designed to support roaming (i.e. moving into a domain while the connection is disabled and then establishing service) so that a user could be found independently of location and network device. For example, with SIP a call on a handheld phone could be transferred to a computer SIP phone. SIP is being modified to support mobility as well as roaming applications.

Like Mobile IP, macro-mobility in an SIP implementation would be based on the concept of foreign networks and home networks. With SIP, the foreign agent of Mobile IP is replaced by an SIP VR in the foreign network. The Mobile IP home agent (HA) is replaced by an SIP home registrar (HR). The SIP HR is a combination of an SIP proxy server, a location server and a user agent server. The following diagram illustrates an SIP network:

Figure 15

The elements in this type of network are defined as follows:

Mobile Node: VoIP caller
DHCP: Dynamic Host Control Protocol
AAAF: Authentication, Authorization, Accounting - Foreign Network
SIP VR: Visited Registrar
SIP HR: Home Registrar
AAAH: Authentication, Authorization, Accounting - Home Network
CN: Corresponding Node (the network that a caller node is attached to)
Caller Node: Another phone caller

When VoIP callers are in their home networks or a self-contained enterprise network that has implemented SIP-based micro-mobility, the VR (visited registrar) is removed and replaced by an HR (home registrar). This is shown in the following diagram:

Figure 16

One of the principal differences between Mobile IP and SIP is the use of DHCP by 802.11 APs. DHCP doubles the number of transactions needed to associate with an access point. It also requires that the client perform an ARP (Address Resolution Protocol) to detect duplicate addresses in the sub-net. The advantage of DHCP is that no modification to the local network is needed.

While there are minor differences between Mobile IP and SIP, the handoff procedures are essentially identical. SIP has the advantage of using the existing IP network without modification. However, this comes at the expense of delays that are typically double those of Mobile IP in a macro-mobility environment.

To its advantage, SIP is fully supported today by the Windows environment (i.e. Windows XP), making possible a rapid deployment in the residential/SOHO marketplace.

Just as with Mobile IP, timing issues must be addressed if SIP handoffs are to be supported. For the most part, SIP's timing elements are identical to those for Mobile IP. The only exception is SIP's use of the Address Resolution Protocol (ARP). In the formulas below, Tarp is defined as the period of time needed for an ARP exchange.

The time required to register and set up a VoIP call with SIP is the following:

Tsip_init = 4Ts + Tarp + 2Th + 2Tmc

(addition of 2Ts + Tarp vs. Mobile IP)

For macro-mobility (inter-domain) handoffs between two different foreign networks, SIP has the following timing:

Tsip_inter = 4Ts + Tarp + 2Th + 2Tmc

(For initially establishing service, SIP's timing is identical to Mobile IP, but much greater than Tmip_inter)

The blackout time for SIP and Mobile IP is given by:

Tblack_out = 2 Ts + 2 Th + 2 Tno

For micro-mobility (intra-domain) handoffs such as an enterprise-based AP-to-AP handoff in the same domain, Mobile IP has the following timing:

Tmip_intra = 4Ts + Tarp + 2Tf

(addition of 2Ts + Tarp vs. Mobile IP)

As these formulas indicate, by using the existing IP network without modification, SIP suffers from delays that can be 2x those of Mobile IP.

SIP for Residential and SOHO Use

SIP can be used on an existing netwok without modification.

SIP is designed into Windows XP and will be in Windows CE

SIP suffers from delays that can be 2x those of Mobile IP. In a larger network, these delays quickly become unacceptable.

For cordless phone VoIP applications in the home, the delay in SIP is negligible and its ease-of-integration will greatly facilitate product introduction.

IPv6 and Protocol Improvement

These discussions of Mobile IP and SIP have assumed WLAN deployments on IPv4 networks. Both SIP and Mobile IP would greatly benefit from the pervasive use of IPv6. In both cases this would allow direct addressing of a mobile node client. If Mobile IP and SIP were revised in light of IPv6, the Foreign Agent could be removed entirely and handoff times would improve.

For Mobile IP to succeed, it must be deployed pervasively. As a result, there is interest in the industry in SIP for consumer applications.

Wide Area Network Integration: WLAN and GPRS Inter-working
While the ultimate goal is to provide seamless IP mobility for all applications including voice, in the near term cellular carriers are planning to integrate data operations through a combination of 802.11 for hotspots and cellular telephony technology for wide area data networking.

This section briefly describes the integration of the cellular GPRS (General Packet Radio System) standard with WLAN technology in a seamless data network. This process will take several steps, including:

Common billing and customer care but no inter-working of WLAN and GPRS networks.
A 3GPP-based access control and charging system where all WLAN AAA (authentication, authorization, accounting) will be based on GPRS AAA procedures.
Access to GPRS data services such as WAP are supported on the WLAN system, but there are no handoffs between WLAN and GPRS.
Where jitter and time delay permit, there would be service continuity for the services described in item three above. These services would be provided across the WLAN and GPRS networks. The handoff of IP multimedia may not be supported, but other IP services would be.
Seamless continuity where all services are supported transparently between WLAN and GPRS networks. There is no noticeable difference in the services.
Access to 3GPP switched circuit services is provided and voice services are supported.

There are essentially two schools of thought on how WLANs should interface to the existing GPRS network. These views are:

Tightly coupled WLAN network
Loosely coupled WLAN network

A tightly coupled network is illustrated in the following diagram. The tightly coupled network makes use of all existing GPRS system resources for networking, AAA, security, provisioning and other functionality. These functions are coupled to the WLAN systems. With minor exceptions, the WLAN user will have immediate access to all GPRS services. This type of system would use a strong GPRS inter-working function (GIF) to interface to the WLAN network, and all traffic would be routed through the Serving GPRS Support Node (SGSN).

Figure 17

A loosely coupled network is illustrated in the following diagram. This loosely coupled scheme would be based on Mobile IP. Only minor modifications to installed WLAN networks would be required. However, cellular operators would need to install AAA servers for billing mediation and to support WLANs as well as to support interoperations between the GPRS network and WLANs. In a loosely coupled system, the Internet is used as the traffic backbone. Because service operators would not have complete control over the network, there is some concern that consistent quality might not be provided.

Figure 18

Category	Tight Coupling	Loose Coupling
Authentication	GPRS authentication and cipher key encryption	SIM based authentication/Optional Radius based
Accounting	Reuse GPRS accounting	External Billing for common accounting
WLAN Cellular Mobility	SSGN Call Anchor, mobility by iner-SSGN handovers	Home Agent (HA) is the call anchor, mobile IP between access router and GGSN (gateway)
Context Transfer	Fine grain info on QoS, flows, etc.	limited information between GGSN and WLAN (IETF working on "seamboy")
System / Network Engineering	Impact on WLAN traffic to existing GSN bearer and signaling is an issue	WLAN and GPRS can be designed spearately
New Development	WLAN modification for GPRS for GPRS signaling, possible SGSN modes.	CAG for SIM-based authentication, Billing mediator for accounting
Standards	A new SSN interface	EAP-Sim and EAP-AKA authentication (IETF Ppext working group)
Target Usage	Applies to Cellular owned WLAN or affliated WISP	Broad Application

Table 13

The deployment of WLAN hotspots has taken on a life of its own. It may not be practical to require conformance to certain standards or to modify existing WLAN equipment with cellular security and signaling. The motivation of carriers is clear. Carriers require control over network quality. They also are concerned that Mobile IP has not been widely deployed and, because of this, seamless interfaces may be delayed. Carriers also are concerned that when QoS capabilities are deployed, they may be haphazard at best. Clearly, all indications from the marketplace would suggest that the deployment of seamless networks of WLAN and cellular technology will happen in the near future. Indeed, certain cellular carriers already have acquired and are supporting WLAN hotspot networks, merging the billing and customer care operations for the two technologies.

Access Time Delay

2008-07-06T23:36:00.000+07:00

Regardless of the application, the time delay and jitter of the VoIP system will be a design consideration. As already noted, the two following issues relate to time delay and jitter:

Signaling for call set up, tear down and other call control communications will be delayed. (Worst case delay is the principal concern.)
Jitter in the voice traffic/bearer channel will cause delay.

VoIP signaling and voice traffic are not separate communications channels. VoIP packets exist as virtual communications within a single channel. Only queuing priorities can ensure timely delivery of voice packets when other types of packets are competing for services in an IP network. This situation is complicated when a wireless user is moving and there are AP-to-AP handoffs in the network. Further delays are added into the WLAN as the user must associate with an AP, authorization must take place and the handoff must be completed.

The ITU has set recommendations for the maximum round trip delay in a voice system and the perceived quality of the voice channel. This recommendation is defined in ITU G.113 and is provided in the following table:

G.113 Delay Specification
0 to 150 msec	acceptable to most applications
150 to 400 msec	acceptable for international connections
> 400 msec	acceptable for public network operation

Table 11

Under normal operations, the roundtrip delay should be less than 150 msec. The following diagram illustrates the possible delays in the communication path for an enterprise network with one layer of routing.

Figure 10

Because delay in the PSTN backbone network is beyond the control of mobile device manufacturers, the following table illustrates a residual delay budget for the backbone network (Tbackbone) using short duration G.711 and G.726 VoIP packet structures. The data for this table is taken from measurements that were performed on VoIP software implementations and from worst case delays in an extensive wireless enterprise network.

Round Trip Delay Source	Delay Symbol	G.711 (5msec)	G.726 (10msec)
Encode / Decode	Tenc_dec	5.5	5.5
Assemble / Disassemble	Tasm	10	20
Jitter Buffer (1)	Tbuf	10	20
WLAN Access Delay	Taccess	10	20
Access Point Routing	Tap_route	10	10
Enterprise Routing	Trouting	5	5
Backbone Delay (residual)	Tbackbone	99.5	69.5
Total		150	150

(1) Tbuf can be set as large as Tbackbone
Tabel 12

These figures indicate that the G.726 residual backbone delay will be less than 70 msec, but there is some concern in the industry that in countries with large geographic areas, such as the U.S., Canada and others, the backbone network delay may exceed 70 msec.

For a VoIP cordless phone, the equivalent diagram of the communication path would remove the enterprise router and feature a minimum of 10 msec of additional delay margin (the maximum delay for the POTS PSTN network). The residential delay path is shown in the following diagram:

Figure 11 Any effects communication delay could have on voice quality for a fixed implementation of VoIP over WLAN is readily ameliorated, but larger issues arise when a user is handed off from one AP to another.

In a cellular phone system, a great deal of effort is expended on the handoff operation. The handoff is typically completed in 35 msec with 50 msec being worst case. WLAN systems do not have the interconnect processing capabilities or higher-order switching intelligence that is built into cellular networks. In a WLAN, the following capabilities are relevant to the network's ability to hand off active phone calls:

The WLAN must know when a link has been lost. (This can be a simple rule, such as losing more than N/M packets.)
AP probe and associate.
1. Currently, tests by the University of Maryland show that an AP probe takes place in 250 to 400 msec.
2. Significant effort to improve both AP-to-AP handoffs and authentication are being addressed by the IEEE 802.11 committee's 802.11i (security) and 802.11e (QoS) task groups.
Authentication, security and routing updates.
1. Delays of more than three seconds have been caused by centralized authentication servers.

Clearly, dramatic improvements are needed in AP probe, authentication and routing update operations. WLANs have delays for handoffs nearly 10 times greater than handoffs in cellular systems.

During the handoff between 802.11 APs, there will be short but noticeable loss of voice packets. On the positive side, VPN and call agent servers have timeouts on the order of tens of seconds. While some VoIP packets may be lost in a WLAN, connection should be maintained.

Several proposals for solving the hand-off delay problem have been proposed. These include:

Nearest neighbor or sub-net authorization proxy (authorization across a sub-net).
Highest QoS priority to an AP's probing services.
Shadow registration in enterprise WLANs. That is, a subscriber will be pre-registered and authorized within a sub-net.

FDA reports more cases of salmonella illnesses

2008-07-06T23:17:00.000+07:00

WASHINGTON - The government on Saturday increased the number of people reported being sickened in a record salmonella outbreak in which tomatoes are the leading suspect although investigators are testing other types of fresh produce.

There have been 943 reported cases nationwide, with at least 130 hospitalizations since mid-April after the first salmonella illnesses appeared, the Food and Drug Administration said Saturday. That compares with a total of 922 people about two days ago and 869 reported earlier in the past week.

The FDA also said it had begun looking at jalapeno peppers as a possible cause of the outbreak, as well as ingredients used to make salsa such as cilantro and Serrano peppers. Tomatoes continue to be investigated as well, spokeswoman Stephanie Kwisnek said.

On Tuesday, the government said it would test numerous other kinds of fresh produce commonly served with fresh tomatoes while insisting that tomatoes remained the leading culprit.

Investigators with the Centers for Disease Control and Prevention have interviewed people sickened in June to find out what they ate and to compare their diets with those of healthy relatives and neighbors. Officials so far have not revealed early findings, except to say they supported the investigation's new move.

Among the possibilities FDA has said it was exploring is whether tomatoes and other produce are sharing a common packing or shipping site where both might become contaminated, or whether multiple foods might be tainted while being grown on adjoining farms or with common water sources.

Officials have said some patients have told the Centers for Disease Control and Prevention they ate raw tomatoes in fresh salsa and guacamole.

CDC spokesman Glen Nowak said Saturday that the agency's scientists are working around the clock to try to pinpoint the source of the outbreak but are not ready to single out anything. Salsa ingredients, including peppers, are among the items being tested, Nowak said. "We don't rank the items we're looking at."

Scientists: Watermelon yields Viagra-like effects

2008-07-06T23:14:00.000+07:00

LUBBOCK, Texas - A slice of cool, fresh watermelon is a juicy way to top off a Fourth of July cookout and one that researchers say has effects similar to Viagra — but don't necessarily expect it to keep the fireworks going all night long.

Watermelons contain an ingredient called citrulline that can trigger production of a compound that helps relax the body's blood vessels, similar to what happens when a man takes Viagra, said scientists in Texas, one of the nation's top producers of the seedless variety.

Found in the flesh and rind of watermelons, citrulline reacts with the body's enzymes when consumed in large quantities and is changed into arginine, an amino acid that benefits the heart and the circulatory and immune systems.

"Arginine boosts nitric oxide, which relaxes blood vessels, the same basic effect that Viagra has, to treat erectile dysfunction and maybe even prevent it," said Bhimu Patil, a researcher and director of Texas A&M's Fruit and Vegetable Improvement Center. "Watermelon may not be as organ-specific as Viagra, but it's a great way to relax blood vessels without any drug side effects."

Todd Wehner, who studies watermelon breeding at North Carolina State University, said anyone taking Viagra shouldn't expect the same result from watermelon.

"It sounds like it would be an effect that would be interesting but not a substitute for any medical treatment," Wehner said.

The nitric oxide can also help with angina, high blood pressure and other cardiovascular problems, according to the study, which was paid for by the U.S. Department of Agriculture.

More citrulline — about 60 percent — is found in watermelon rind than in the flesh, Patil said, but that can vary. But scientists may be able to find ways to boost the concentrations in the flesh, he said.

Citrulline is found in all colors of watermelon and is highest in the yellow-fleshed types, said Penelope Perkins-Veazie, a USDA researcher in Lane, Okla.

She said Patil's research is valid, but with a caveat: One would need to eat about six cups of watermelon to get enough citrulline to boost the body's arginine level.

"The problem you have when you eat a lot of watermelon is you tend to run to the bathroom more," Perkins-Veazie said.

Watermelon is a diuretic and was a homeopathic treatment for kidney patients before dialysis became widespread.

Another issue is the amount of sugar that much watermelon would spill into the bloodstream — a jolt that could cause cramping, Perkins-Veazie said.

Patil said he would like to do future studies on how to reduce the sugar content in watermelon.

The relationship between citrulline and arginine might also prove helpful to those who are obese or suffer from type-2 diabetes. The beneficial effects — among them the ability to relax blood vessels, much like Viagra does — are beginning to be revealed in research.

Citrulline is present in other curcubits, like cucumbers and cantaloupe, at very low levels, and in the milk protein casein. The highest concentrations of citrulline are found in walnut seedlings, Perkins-Veazie said.

"But they're bitter and most people don't want to eat them," she said.

Haywire brain chemical linked to sudden baby death

2008-07-06T23:12:00.000+07:00

WASHINGTON - Scientists have new evidence that the brain chemical best known for regulating mood also plays a role in the mystifying killer of seemingly healthy babies — sudden infant death syndrome

Autopsied brain tissue from SIDS babies first raised suspicion that an imbalance in serotonin might be behind what once was called crib death.

But specialists couldn't figure out how that defect could kill. Now researchers in Italy have engineered mice born with serotonin that goes haywire — and found the brain abnormality is enough to spur sudden death, in ways that mesh with other clues from human babies.

Moreover, the work suggests it might one day be possible to test newborns for their risk of SIDS.

For now, even an animal experiment can offer a message for devastated families:

"It should provide them with some sense of comfort that there was nothing they could have done to prevent it," said Dr. Marian Willinger, a SIDS specialist at the National Institute of Child Health and Human Development, who wasn't part of the study. "It is a real disease."

The work was published in Friday's edition of the journal Science.

SIDS is the sudden death of an otherwise healthy infant — anywhere between ages 1 month and 1 year — that can't be attributed to any other cause. It kills more than 2,000 U.S. infants each year, and is the leading killer of babies after the newborn period.

Babies should always be placed to sleep on their backs, as the risk of SIDS increases greatly when babies sleep on their stomachs. And parents are urged not to allow anyone to smoke around their babies, or to let their babies get too warm while sleeping.

But beyond those risk factors, doctors have little advice.

In 2006, Dr. Hannah Kinney of Children's Hospital Boston compared brain tissue from 31 SIDS babies and 10 infants who died of other causes. The SIDS babies had abnormalities in their brain stem that led to imbalances in serotonin, a neurotransmitter or chemical that helps brain cells communicate.

Low serotonin famously plays a role in depression. Less known to laymen is that it also helps regulate some of the body's most basic functions — breathing, heart rate, body temperature, arousal from sleep.

Dr. Cornelius Gross and colleagues at the European Molecular Biology Laboratory in Italy were studying how the serotonin system turns itself on and off when they stumbled onto the SIDS connection.

They genetically engineered mice to have an overactive serotonin-regulating receptor, which in turn reduced the amount of serotonin in the brains of otherwise normal baby mice.

More than half of the mice abruptly died before they were 3 months old. More intriguing, they had erratic episodes where their heart rate would drop and, five to 10 minutes later, so would their body temperature, Gross reported. Sometimes they died in the midst of what Gross calls those crises, other times afterward.

The exact cellular defects in the mice and the human babies studied so far aren't identical, researchers caution.

But heart and temperature problems are consistent with what little human data is available, Willinger noted.

Here's another key: Gross could switch on and off the genetic defect that controlled serotonin levels in the mice. By doing so, he showed that older baby animals were less likely to die from haywire serotonin than younger ones.

"This is a very exciting part of the research," says Willinger — because doctors have long suspected that if at-risk babies just get through a developmental period, they'll be OK. That's impossible to test in humans, however

Study: Orangutan populations declining sharply

2008-07-06T23:08:00.001+07:00

BANGKOK, Thailand - Orangutan numbers have declined sharply on the only two islands where they still live in the wild and they could become the first great ape species to go extinct if urgent action isn't taken, a new study says.

The declines in Indonesia and Malaysia since 2004 are mostly because of illegal logging and the expansion of palm oil plantations, Serge Wich, a scientist at the Great Ape Trust in Iowa, said on Saturday.

The survey found the orangutan population on Indonesia's Sumatra island dropped almost 14 percent since 2004, Wich said. It also concluded that the populations on Borneo island, which is shared by Malaysia, Brunei and Indonesia, have fallen by 10 percent. Researchers only surveyed areas of Borneo that are in Indonesia and Malaysia.

In their study, Wich and his 15 colleagues said the declines in Borneo were occurring at an "alarming rate" but that they were most concerned about Sumatra, where the numbers show the population is in "rapid decline."

"Unless extraordinary efforts are made soon, it could become the first great ape species to go extinct," researchers wrote.

The number of orangutans on Sumatra has fallen from 7,500 to 6,600 while the number on Borneo has fallen from 54,000 to around 49,600, according to the survey on the endangered apes, which appears in this month's science journal Oryx.

"It's disappointing that there are still declines even though there have been quite a lot of conservation efforts over the past 30 years," Wich said.

Indonesia and Malaysia, the world's top two palm oil producers, have aggressively pushed to expand plantations amid a rising demand for biofuels which are considered cleaner burning and cheaper than petrol.

Wich and his colleagues said there was room for "cautious optimism" that the orangutan could be saved, noting recent initiatives by Indonesian leaders.

Indonesian President Susilo Bambang Yudhoyono announced a major initiative to save the nation's orangutans at a U.N. climate conference last year, and the Aceh governor declared a moratorium on logging.

Coupled with that are expectations that Indonesia will protect millions of acres of forest as part of any U.N. climate pact that will go into effect in 2012. The deal is expected to include measures that will reward tropical countries like Indonesia that halt deforestation.

"There are promising signs that there is a lot of political will, especially in Aceh, to protect the forest," Wich said, adding however that much more needs to be done.

Michelle Desilets, founding director of Borneo Orangutan Survival Foundation UK, praised the study for offering the first comprehensive look at the species population.

"What matters is that the rate of decline is increasing, and unless something is done, the wild orangutan is on a quick spiral towards extinction, whether in two years, five years or 10 years," Desilets said in an e-mail.

In their paper, the researchers recommended that law enforcement be boosted to help reduce the hunting of orangutans for food and trade. Environmental awareness at the local level must also be increased.

"It is essential that funding for environmental services reaches the local level and that there is strong law enforcement," the study says. "Developing a mechanism to ensure these occur is the challenge for the conservation of the orangutans."

The study is the latest in a long line of research that has predicted the orangutans demise.

In May, the Center for Orangutan Protection said just 20,000 of the endangered primates remain in the tropical jungle of Central Kalimantan on Borneo island, down from 31,300 in 2004. Based on that estimate, it concluded orangutans there could be extinct by 2011

Microsoft, Yahoo mull media partner options: sources

2008-07-06T23:03:00.000+07:00

SAN FRANCISCO/NEW YORK (Reuters) - Microsoft Corp and Yahoo Inc have been holding separate talks with other potential media partners after their negotiations with each other broke down, sources familiar with the companies' thinking said on Wednesday.
Microsoft -- rebuffed this year in efforts to buy all of Yahoo and then just its search business -- is talking about alternative deals with Time Warner Inc, which owns AOL, and News Corp, parent of MySpace, a source close to Microsoft said, but any negotiations remain in preliminary stages.

Meanwhile, talks have continued for months between Yahoo and Time Warner over a potential merger of AOL with Yahoo to create a more formidable advertising and media player, but they are no closer to a deal, a source close to the matter said.

Shares of Yahoo jumped as much as 9 percent on Wednesday after the Wall Street Journal reported that Microsoft, positioning for a new run for Yahoo's search business, had in recent days approached media companies to join together on a deal that would effectively lead to Yahoo's breakup.

However, a Reuters source and a CNBC report, citing unnamed sources, later said there were no new talks or negotiations.

The Journal also said Microsoft met with activist investor Carl Icahn in recent days to encourage him to press his proxy battle for control of Yahoo's board, the first sign Microsoft welcomed his month-old campaign. This development also was attributed to unnamed sources familiar with the talks.

Icahn was not available to comment on the report.

Microsoft, Yahoo, Time Warner and News Corp all declined comment.

REVIVING HOPE

Wall Street analysts said the latest news revived flagging hopes among some investors that Microsoft was still interested in doing a deal with Yahoo. "The hopes that Microsoft would come back were getting crushed over the last 10 trading days," Collins Stewart analyst Sandeep Aggarwal said.

Yahoo stock ended the day up 3.4 percent at $20.88. The stock had traded as low as $19.58 on Tuesday, near its level in late January before Microsoft made its unsolicited takeover bid for Yahoo, sending the stock above $30 by mid-February.

Microsoft shares fell 3.7 percent to $25.88 on Wednesday. In the prior day's trading, Microsoft fell to two-year lows of $23.19, intraday, before recovering.

Analyst Youssef Squali of Jefferies & Co said the sharp Yahoo stock reaction was most likely a defensive move by short-sellers seeking to cover bets a Microsoft deal was off.

"Even the rumor that Microsoft is getting interested again is enough to have people to want to cover their bets against Yahoo stock," Squali said, adding that many investors have shorted Yahoo from the high $20s all the way down below $20.

Adding to the volatility were options investors who placed fresh bets Yahoo would be trading up to $27.50 by October, said analyst Rebecca Engmann Darst of Interactive Brokers Group.

THE WAITING GAME

Several financial analysts said a key detail in the Journal report was that Microsoft and Yahoo executives had sought to revisit the merger on May 17 -- two weeks after Microsoft walked away -- and that two Yahoo board members in the meeting had said they would settle for a merger worth $33-$34 a share.

On May 3, Yahoo rejected a $33-a-share Microsoft offer worth $47.5 billion, and earlier this week questioned whether the software maker was ever serious about a full-scale merger.

The source familiar with Microsoft's thinking confirmed that Yahoo had belatedly sought a deal in mid-May worth $33 to $34, but that Microsoft was no longer interested at that point.

The source said Microsoft executives considered the early May deadline as vital to winning regulatory approval before the end of the year -- when a new presidential administration arrives and months more delays would likely occur.

Microsoft also become convinced that Yahoo executives were passively resisting the deal and unwilling to seriously negotiate. Meanwhile, the economy has taken a toll on the online ad market, and with it, the value of buying Yahoo.

"Microsoft is going to let Icahn do the dirty work and hand Yahoo over to them," Jefferies & Co's Squali said, adding that it was in Microsoft's interest to hang back and let Yahoo shares settle lower as investors quit betting on a takeover premium.

In the long run, however, Microsoft needs Yahoo more than Yahoo needs Microsoft, he argued.

"Microsoft has a gaping hole in its strategy and it's called the Internet and it's only getting worse because Google is encroaching on Microsoft's business," Squali said.

Separately, the U.S. Justice Department is pursuing a formal antitrust investigation into a deal reached last month between Yahoo and Microsoft-archrival Google Inc to team up on Web search advertising.

Google, with more than 60 percent of the Web search market, and Yahoo, with 16.6 percent, agreed to a deal for Google to run search ads on Yahoo's site in a partnership that could mean $250 million to $450 million in new cash flow for Yahoo.

Google said it was confident the deal would enhance overall industry competition, but declined to discuss the probe.

Chipmaker Connects A Wireless World And Makes It Run Faster

2008-07-06T23:00:00.000+07:00

Laptops long ago stopped needing wires to be wired.

Now televisions, digital cameras and game consoles commonly link to the world without those physical ties.

Atheros Communications (NasdaqGS:ATHR - News) is helping cut the tethers.

The Santa Clara, Calif., semiconductor company develops chips for laptops, routers and other electronics that seamlessly link them to the world.

Intel (NasdaqGS:INTC - News) still dominates the market for wireless chips in laptops and routers. Analysts say it has about 70% of the space, with companies such as Atheros and Broadcom (NasdaqGS:BRCM - News) splitting the rest.

But analysts say Atheros is chipping away there and gaining market share. And as wireless Internet connections proliferate in cell phones and game systems, Atheros chips are finding new markets.

An Atheros chip on a digital camera memory card beams the photos to computers or printers without cables.

Its chips are inside Netflix's (NasdaqGS:NFLX - News) new set-top box, which lets viewers stream movies from the Internet to their TVs.

"The game in this segment is all about bringing in innovation and bringing down the cost curve. Atheros has been good at doing that," said Adam Benjamin, a semiconductor analyst with Jefferies & Co.

Faster Connection

The semiconductor industry is transitioning from the 802.11g network standard for wireless local area networks to the next-generation 802.11n.

Those 11n chips promise huge growth for the industry, since they can potentially transmit and receive more data, faster -- critical when beaming high-definition TV and other data-rich files.

And 11g chips are still selling briskly.

Atheros has reported 11 straight quarters of double-digit year-over-year sales growth.

It had record 11g sales in the first quarter.

Most of its chips go to electronics manufacturers in Asia.

Taiwanese hardware manufacturer Hon Hai Precision Industry is its largest customer, accounting for a quarter of last year's sales.

Atheros has deals with major PC makers such as Acer, Hewlett-Packard (NYSE:HPQ - News), Lenovo and Toshiba. This month, Atheros said Advanced Micro Devices (NYSE:AMD - News) would bundle its 11n chip with some of its notebook processors.

Atheros chips were dropped recently by a major PC maker. The company didn't name it, but most analysts think it was Apple (NasdaqGS:AAPL - News).

In part because of that, as well as seasonal fluctuations, Atheros sales were flat between the first and fourth quarters.

But year-over-year sales rose 20% in the first quarter to $114.5 million. Earnings per share climbed 22% to 28 cents.

Atheros' 11g chips gained market share in wireless local area network routers, used to set up Internet hot spots and home networks.

Those 11g sales should taper off in coming years.

But sales should pick up on the higher-priced 11n chips as laptops, wireless routers and cell phones increasingly use the faster next-generation standard.

Those PC and Wi-Fi networks remain a big part of Atheros' business.

The company is also reaching into other communications technology platforms.

It's gaining bigger physical footprints within traditional laptops and wireless routers.

And it's getting into cell phones and portable game players.

"If you think that Atheros is just focused on wireless LAN, frankly we shouldn't be all that interesting to invest in," Atheros Chief Financial Officer Jack Lazar said during an investors conference. "What we're really trying to do is a variety of communications platforms that address the markets that we've already started to open up or the customers that we've already started to open up."

In 2006, Atheros bought Attansic Technology, a Taiwanese developer of ethernet integrated circuits. Last December, it bought u-Nav Microelectronics, a private developer of Global Positioning System chips and software for cell phones and other personal handsets.

Atheros internally developed its own Bluetooth products, which it started selling last year.

The company expects growth in Bluetooth, ethernet and the Global Positioning System. The mobile wireless LAN business is one of its fastest growers.

High-volume consumer items lead the way. Its chips are reaching cell phones, digital music players and other handheld electronics, as cost per chip and power consumption fall. Atheros claims more than 30 design wins for handsets.

One win is likely Nintendo's handheld DS game system, analysts say, though the company won't confirm it.

Atheros says wireless LAN chips in the unnamed game system should drive revenue in the second half of this year.

Analysts at Piper Jaffray think the deal could mean 4 million chips per quarter, at $3 to $4 each.

But Abdul Saleh, an analyst at Zacks Investment Research, thinks those games and other wireless LAN chips might not deliver much until the December quarter.

"It's probably an end-of-the-year story, rather than a second-half story," Saleh said.

So barring some big news when second-quarter results are announced next month, Saleh thinks much of those wins are already priced into the stock.

Competition And Risks

Risks exist. Purchases of wireless routers and PCs could slow. There's the chance of slower-than-expected adoption of wireless technology in handheld electronics.

Competition remains a key challenge. Atheros faces off against larger players, such as Intel , Broadcom , Texas Instruments (NYSE:TXN - News) and Marvell Technology (NasdaqGS:MRVL - News). Smaller firms include Conexant Systems (NasdaqGS:CNXTD - News).

Other competitors might arise as the handset market and the overall 11n market grow. That competition is already pushing prices lower for Atheros' legacy 11g chips, which are still more than half its sales.

Most analysts think sales and revenue should hold up. Those surveyed by Thomson Reuters project 20% top- and bottom-line boosts in the second quarter.

For the year, the consensus is for earnings per share to rise 17% in 2008 to $1.31. For 2009, analysts expect a 19% increase to $1.56.

iPhone 3G queue forms in Manhattan

2008-07-06T22:57:00.001+07:00

The line for the Apple iPhone 3G began to form Friday--an entire week before the device goes on sale.

Frankly, one shouldn't encourage such behavior by actually covering it. But if I were in Manhattan--instead of Austin, Texas--I, too, would have interviewed them in person by now.

The queue outside of Apple's Fifth Avenue store, covered first by GearDiary and then Engadget, apparently hasn't been formed by iPhone co-dependents, though.

It is instead made up of a group of people who may want to 1) set a world's record for standing in line to buy a product and 2) have a social-agricultural-political message they want the world to hear. However, it was difficult from the video interview on Engadget to determine what the group actually stands for.

On Saturday, the Apple 2.0 blog seemed to get further with the group's agenda. The group, which started off with about 10 on Friday and was slimmed down to 5 by Saturday morning after a night of rainfall, apparently supports organic farming and sustainability for the planet. According to Apple 2.0, they may be interested in turning the White House Lawn into an organic garden and they may be planning to buy iPhones for the presidential nominees.

The seemingly ad hoc group is certainly savvy in deciding to use the iPhone 3G to garner some publicity. However, to be perfectly honestly, most mainstream journalists feel more comfortable interviewing gadget nuts rather than alternative souls hoping to use the media to change the world.

New study shows how broccoli helps reduce cancer risk

2008-07-03T10:15:00.000+07:00

WASHINGTON (AFP) - A scientific study published here Wednesday sheds light on why men who eat a lot of broccoli are less likely to develop prostate cancer.

Scientists have already observed that diets rich in cruciferous vegetables -- including broccoli, cauliflower, cabbage, Brussels sprouts, bok choy and kale -- may reduce the risk of prostate cancer and other chronic disease.

But the new research, by scientists at Britain's Institute of Food Research, is the first attempt to show how that works in a clinical study involving people, as opposed to animals or cell models.

For the new study, men at risk of developing prostate cancer ate 400 grams of broccoli or 400 grams of peas a week for 12 months, in addition to their normal diet.

The researchers took samples of prostate gland tissue from the men at the start of the study, at six months and at 12 months, to monitor changes in genes linked to cancer.

"There were more changes in gene expression in men who were on the broccoli-rich diet than on the pea diet, and these changes may be associated with the reduction in the risk of developing cancer," said a statement by the Public Library of Science, which published the work Wednesday in its online journal PLoS ONE.

"The results of the study suggested that relatively low amounts of cruciferous vegetables in the diet -- a few portions per week -- can have large effects on gene expression by changing cell signalling pathways," the statement said.

The signalling pathways are the routes by which information is transmitted to the nucleus of the cell where gene expression occurs.

"Other fruits and vegetables have been shown to also reduce the risk of prostate cancer and are likely to act through other mechanisms," said lead researcher Richard Mithen.

"Once we understand these, we can provide much better dietary advice in which specific combinations of fruit and vegetable are likely to be particularly beneficial.

"Until then, eating two or three portions of cruciferous vegetable per week ... should be encouraged."

Prostate cancer is the most common form of non-skin cancer affecting men in western countries.

Fossil of most primitive 4-legged creature found

2008-07-03T10:07:00.001+07:00

WASHINGTON - Scientists unearthed a skull of the most primitive four-legged creature in Earth's history, which should help them better understand the evolution of fish to advanced animals that walk on land.

The 365 million-year-old fossil skull, shoulders and part of the pelvis of the water-dweller, Ventastega curonica, were found in Latvia, researchers report in a study published in Thursday's issue of the journal Nature. Even though Ventastega is likely an evolutionary dead-end, the finding sheds new details on the evolutionary transition from fish to tetrapods. Tetrapods are animals with four limbs and include such descendants as amphibians, birds and mammals.

While an earlier discovery found a slightly older animal that was more fish than tetrapod, Ventastega is more tetrapod than fish. The fierce-looking creature probably swam through shallow brackish waters, measured about three or four feet long and ate other fish. It likely had stubby limbs with an unknown number of digits, scientists said.

"If you saw it from a distance, it would look like a small alligator, but if you look closer you would find a fin in the back," said lead author Per Ahlberg, a professor of evolutionary biology at Uppsala University in Sweden. "I imagine this is an animal that could haul itself over sand banks without any difficulty. Maybe it's poking around in semi-tidal creeks picking up fish that got stranded."

This all happened more than 100 million years before the first dinosaurs roamed Earth.

Scientists don't think four-legged creatures are directly evolved from Ventastega. It's more likely that in the family tree of tetrapods, Ventastega is an offshoot branch that eventually died off, not leading to the animals we now know, Ahlberg said.

"At the time there were a lot of creatures around of varying degrees of advancement," Ahlberg said. They all seem to have similar characteristics, so Ventastega's find is helpful for evolutionary biologists.

Ventastega is the most primitive of these transition animals, but there are older ones that are oddly more advanced, said Neil Shubin, professor of biology and anatomy at the University of Chicago, who was not part of the discovery team but helped find Tiktaalik, the fish that was one step earlier in evolution.

"It's sort of out of sequence in timing," Shubin said of Ventastega.

Ahlberg didn't find the legs or toes of Ventastega, but was able to deduce that it was four-limbed because key parts of its pelvis and its shoulders were found. From the shape of those structures, scientists were able to conclude that limbs, not fins were attached to Ventastega.

One question that scientists are trying to figure out is why fish started to develop what would later become legs.

Edward Daeschler, associate curator of vertebrate zoology at the Academy of Natural Sciences in Philadelphia, theorizes that the water was so shallow that critters like Ventastega had an evolutionary advantage by walking instead of swimming

Nature: http://www.nature.com/nature

Salmonella probe adds foods served with tomatoes

2008-07-03T09:53:00.000+07:00

WASHINGTON - Adding to tomato confusion, the government is about to start testing numerous other types of fresh produce in the hunt for the source of the nation's record salmonella outbreak — even as it insists tomatoes remain the leading suspect.

Investigators are mum on exactly what other vegetables are getting tracked.

Items commonly served with fresh tomatoes is the only hint Food and Drug Administration food safety chief Dr. David Acheson would give, calling it "irresponsible" to point a finger until he has more evidence that some other food really deserves the extra scrutiny.

"Tomatoes aren't off the hook," he stressed. "It's just that there is clearly a need to think beyond tomatoes."

Still, Acheson widened FDA's probe on Tuesday, activating an emergency network of food laboratories around the country in anticipation of lots of additional samples to test.

The reason is that the outbreak continues, with 869 people now confirmed having taken ill. Most troublesome, at least 179 of them fell ill in June, the latest on June 20. That is more than two months after the first salmonella illnesses appeared, meaning the outbreak is continuing weeks longer than food-poisoning specialists had expected — and suggesting the culprit is still on the market.

Over the weekend, disease detectives with the Centers for Disease Control and Prevention began interviewing people sickened in June to find out what they ate and to compare their diets with those of healthy relatives and neighbors. Officials wouldn't reveal early findings, except to say they supported the investigation's new move.

Among the possibilities FDA is exploring is whether tomatoes and other produce are sharing a common packing or shipping site where both might become contaminated, or whether multiple foods might be tainted while being grown on adjoining farms or with common water sources.

Pressure is increasing on the FDA to solve the case, with the tomato industry suffering millions of dollars in losses and pushing for Congress to investigate how the agency handled the outbreak.

But Acheson said Tuesday that there's a growing misconception in the public that if tomatoes really were to blame, the outbreak would only have lasted six weeks.

That's just not true, he said, pointing to farms that rotate harvests so as to keep producing tomatoes for months.

Tomatoes first became a suspect because of what are called "case-control" studies rapidly conducted in New Mexico and Texas, the outbreak's center, CDC food-poisoning specialist Dr. Robert Tauxe said.

Those kinds of studies compare the sick to people who are otherwise similar — in income, lifestyle, where they live — but healthy. In those initial studies, about 80 percent of the ill reported eating certain types of fresh tomatoes, far more than the healthy group did, Tauxe said. Statistically, the association was too strong to think it a coincidence.

Some food-poisoning experts say the CDC missed a key step in not taking those studies a step further and trying to trace why some of the healthy ate tomatoes without harm.

For now, the FDA continues to urge consumers nationwide to avoid raw red plum, red Roma or red round tomatoes unless they were grown in specific states or countries that the agency has cleared of suspicion. Check the FDA's Web site — http://www.fda.gov — for an updated list. Also safe are grape tomatoes, cherry tomatoes and tomatoes sold with the vine still attached.

That advice is coming under fire too because tomatoes are sent through multiple repacking and distribution sites around the country, even to Mexico and back, regardless of where they're grown. But Acheson said the advice would be fine-tuned only if new science emerges.

Even Health and Human Services Secretary Michael Leavitt expressed frustration Tuesday that the case isn't solved.

"Nothing happens fast enough when you have a problem like this," Leavitt said as he asked Congress for more funds and stronger legal powers for food and consumer safety agencies. Still, "I feel confident we will find the solution to this problem."

Including VoIP over WLAN in a Seamless Next-Generation Wireless Environment Part 2

2008-07-02T15:22:00.000+07:00

2. Network Interfaces, Architectures, and Timing Issues

This section reviews the requirements of the PSTN with regards to a VoIP application as well as the timing issues that are critical for toll quality voice deployment.

How VoIP over WLAN applications will be deployed will have an effect on the design and integration of the equipment. The following issues have a bearing on equipment design:

VoIP voice compression algorithm(s)
Voice packet size, packet rate and delay
Timing requirements for signaling and call set up
Call control protocol
Capacity and range of QoS capabilities that will be supported beyond voice

The market can be roughly divided between residential/SOHO and enterprise deployments.

The following figure illustrates enterprise deployments:

Figure 8

VoIP integration in the enterprise will be evolutionary, not revolutionary. Greater than 90 percent of enterprises use analog and ISDN (P-Phone)-based PBX equipment. In some cases the PBX equipment is modular and supports VoIP interface LRUs (line replaceable units). For older legacy PBX equipment, a VoIP gateway can introduce VoIP into the enterprise.

Given the expense of analog PBXs and phones, enterprises typically decide to gradually transition the deployment of VoIP. The enterprise deployment diagram above illustrates a phased deployment such as the following:

The analog PBX/voice mail system connects to the PSTN. A small number of users have VoIP phones connected via a VoIP gateway. (See Hybrid Network-1.)
A VoIP PBX/gateway connects the enterprise to the PSTN. A majority of users have VoIP phones. Legacy phones are supported by an IP/PBX converter. This network will be typical in larger enterprises with a large number of PSTN connections. (See Hybrid Network-2.)
The enterprise has an IP connection to a remote gateway/PBX that may serve one or more business customers. Legacy analog phones, if any, are supported by an IP/PBX converter. This network will be typical in small and medium size enterprises and in the remote facilities of large enterprises. (See IP Network.)

The enterprise solution is highly dependent on the data network topology. A large number of routers and the type of hierarchy among the routers could delay the network's throughput. The transition through each router will add to the delay budget for IP packets. Additional delay in the network could be caused by centralized security and authentication servers. Depending on the network topology, 802.11 clients who are roaming between APs may experience extended delays in accessing centralized authentication servers as well as longer latencies in completing= handoffs between APs.

A residential network topology, as shown in the following diagram, will have its own set of challenges.

Figure 9

Residential/SOHO customers typically have one or more analog voice circuits which are connected directly to the PSTN through a CLASS 5 switch or through a DLC remote terminal. In many cases, subscribers are served by advanced DLC/DSLAM (DSL access multiplexer) remote terminals that provide a combination of DSL and POTS service on a single line as well as standard POTS voice circuits.

As the PSTN network has been upgraded to support DSL, integrated voice/data service (VoDSL) using ATM AAL1/2 packet voice has become available. In general, most residential and SOHO users will continue to have POTS as the primary voice interface. The following are several of the interface configurations that will emerge for home users:

POTS voice interfaces to the PSTN in a way that is identical to a cordless phone. VoIP conversion to/from the analog wire pair would be integrated into the VoIP-enabled access point.
VoDSL interfaces to the PSTN and VoATM is converted to VoIP for use with a WLAN AP.

Integrated DSL/WLAN gateways will become a trend because these gateways will be able to serve both of these residential/SOHO configurations.

If the residential/SOHO user is interfacing to a broadband cable modem, the topology is nearly identical to that of DSL. Where voice over cable is available, it is typically an independent system from the DOCSIS® cable modem interface. An example of this independent interface is the ARRIS system, which results in termination of two-wire analog POTS interfaces at the customer premise. As DOCSIS 1.1 and 2.0 become readily available, integrated VoIP over cable modem will become prevalent.

The time delay of the communications path for 802.11 VoIP in a cordless residential application will typically be much shorter and have a limited number of sources of delay. The voice interface to the home will typically be a POTS interface. Specific signaling requirements must be supported with analog line pairs to DLC and/or CLASS 5 switching equipment. (See note below.)

WLAN Lower Sleep Modes and POTS Call Processing

The design of DLC and Class 5 switch equipment is based on the premise that the wire connection to the phone is in place and operational. Typically, establishing a call with Q.391 protocol is completed in less than 200 msec. The caller ID modulation receiver (FSK Modem) must be ready after the first ring, which is less than or equal to two seconds. Worst case signaling delay should be less than 100 msec.

This creates a problem.

Any WLAN implementation will include VoIP handsets that are often in power-saving sleep modes where much of the device is not operating. In this mode, the WLAN will "wake up" and establish communication in intervals of 200 msec to one sec, well beyond the telephony system delay specification.

Clearly, the 802.11 AP will have to maintain an attached state for a given handset and provide a call proxy during call set up until the call can be handed off to the handset after it has awakened from sleep mode.

Including VoIP over WLAN in a Seamless Next-Generation Wireless Environment

2008-07-02T14:01:00.000+07:00

1. WLAN Network Capacity Analysis

For network planners who are deploying a VoIP over WLAN application, one of the first issues to be addressed should be network capacity. To ensure the network is able to deliver the required QoS capabilities for a voice application, designers must anticipate and analyze how the WLAN will be used. Several questions, such as the following, must be answered:

What types of QoS capabilities will be deployed?
How much network capacity must be set aside for these QoS capabilities?
What is the projected growth rate for QoS capabilities on the WLAN?

The questions above are network design considerations for a variety of contemporary applications, including VoIP, video and other services requiring QoS capabilities.

The purpose of this discussion is to explore the various facets of network capacity planning for the future deployment of WLANs. While the intent here is to analyze VoIP-enabled systems, network designers should also expect a significant amount of multimedia traffic over home/SOHO WLANs as well as video conferencing traffic over enterprise WLANs.

The remainder of this section describes the following:

Over-subscription of voice networks (voice concentration)
Throughput requirements for typical voice, video and media applications using IP packet technology
WLAN network capacity for enterprise applications
- RF frequency planning and reuse for large network deployments
WLAN network capacity for home applications
- Consideration of wireless repeaters (mesh) to extend home coverage

Over-subscription of Voice Services (Concentration)
It is important for designers of VoIP over WLAN applications to understand some of the basic concepts that have been applied for years in the PSTN. A basic understanding of oversubscription, for example, can assist network planners who are evaluating network capacity for enterprise VoIP over WLAN applications.

Telephone systems have been very closely monitored for over 100 years. The public telephone system has always incorporated "statistical over-subscription" of phone lines. In the United States, there are typically between four and eight phones per active (served) phone line in the network. POTS (plain old telephone system) networks are designed to have a specific probability that a call can be blocked from time to time. In the United States, call blocking is typically limited to 1% or 0.5% of total calls.

Phone lines typically are terminated at a Class 5 switch or a Digital Loop Carrier (DLC) connected to a Class 5 switch. The Class 5 switch manages call connections and rejects calls when the system capacity has been reached. (A caller is aware of this when receiving a fast busy tone or the "all circuits busy" message.) In cellular networks, some consideration is given to reserve a fraction of the active phone line capacity for handoff purposes between one cell and the next.

A measure of phone usage capacity is the ERLANG function, which equates to one active call hour (or 3,600 call seconds) of voice line use. The amount of phone concentration (oversubscription) can be determined with the ERLANG-B function, (the ERLANG blocked call function). Because the telephone network must be designed for the worst-case load, phone usage is defined as that level that is achieved during the busiest hour of the day. Accurate average measurements for peak busy hour phone usage in the United States are as follows:

0.15 ERLANG (15 me) for a business phone
0.1 ERLANG (10 me) for a residential phone

Based on the ERLANG B function and an acceptable percentage of blocked calls, the following diagram illustrates the number of active phone lines needed to support a set of phone users attached to a given switch or bandwidth resource.

Figure 2

As the pool of attached phone lines increases, efficiency, in terms of fewer blocked calls, and over-subscription also will increase. This should not be surprising because the efficiency of all systems that use statistical multiplexing improves as the number of channel resources increases at the multiplexer. The concentration level moves from around 2:1 at 10 subscriber phone lines to more than 3:1 at 60 user phone lines.

Voice, Video and Media Throughput over IP
The following sections discuss several WLAN network capacity issues as they relate to the transmission of voice, video and multimedia data using IP.

Voice Compression and VoIP
Voice compression algorithms help network designers derive as much capacity from an infrastructure as possible, but compression algorithms involve tradeoffs between efficiency and overhead that planners should consider.

In wireless networks, voice is digitized with the G.711 coding standard and transported at 64 Kbps. While G.711 is the mainstream digital codec for toll-quality voice services, a number of more efficient codes are used for both cellular and voice "pair gain applications." In an IP network, voice codecs are placed into packets with durations of 5, 10 or 20 msec of sampled voice, and these samples are encapsulated in a VoIP packet.

The following figure illustrates the encapsulation for various protocols, including IPv4, UDP and RTP (Real Time Protocol). For IPv4, the packet overhead is 40 Bytes. As the industry transitions to IPv6, this overhead will grow to 60 bytes.

Figure 3

Clearly VoIP has an overhead issue that is compounded when high levels of voice compression are deployed in conjunction with voice packets of short duration. The tradeoff between overhead and packet duration is shown in the following table. Other issues affecting VoIP network capacity planning, such as delay, jitter and packet duration, are discussed later in this tutorial.

	Voice Packet Frame duration (msec) efficiency
CODEC	5	10	20	40
IPv4 G.711	47.6%	64.5%	78.4%	87.9%
IPv6 G.711	38.5%	55.6%	71.4%	83.3%
IPv4 G.726	31.3%	47.6%	64.5%	78.4%
IPv6 G.726	23.8%	38.5%	55.6%	71.4%
IPv4 G.729	10.2%	18.5%	31.3%	47.6%
IPv6 G.729	7.2%	13.5%	23.8%	38.5%

Table 1

The following table lists the one-way throughput requirements for typical voice codecs using VoIP. For the purposes of capacity analysis, a typical throughput of 64 Kbps per direction was used, assuming a combination of G.726 and G.711 codecs.

Coding algorithm		Bandwidth	Sample	Typical IP bandwidth (one way)
G.711	PCM	64kbps	0.125ms	80kbps
G.723.1	ACELP	5.6kbps	30ms	16.27kbps
G.723.1	ACELP	6.4kbps	30ms	17.07kbps
G.726	ADPCM	32kbps	0.125ms	48kbps
G.728	LD-CELP	16kbps	0.625ms	32kbps
G.729(A)	CS-ACELP	8kbps	10ms	24kbps

Table 2

VoIP Complexity Options

To deploy VoIP WLANs, two tiers of voice-capable access points (APs) probably will be needed:

Low-end consumer VoIP APs will use G.711 and/or G736
APs for the enterprise and wide-area applications will support a full suite of possible cellular and standard codecs for a wide variety of user devices such as PDAs and others.

To achieve completely seamless ubiquity of IP services even low-APs must support handoffs from cell phone traffic as well as a full set of codecs.

Video Media over IP
Although voice will be the first application requiring QoS capabilities over WLANs, several other multimedia applications will soon follow, including the distribution of audio (net radio, MP3 music, etc.) and video (streaming video, DVD, HDTV, etc.) over WLANs. Fortunately for network planners, media compression codecs will ease the bandwidth requirements for these multimedia applications. Specifically, improvements in the quality of video codecs like MPEG4 will allow DVD-quality compression at throughput rates of approximately one Mbps. For HDTV, the standard MPEG2 video stream can be reduced from 19.2 Mbps to around eight Mbps.

The following table illustrates the one-way throughput for various consumer video codec devices using maximum IP packet lengths.

Video Media	Bandwidth (MBPS)	Packet Size	Packets/sec	Delivered Bandwidth (MBPS)	Overhead (%)
MPEG-1 Basic Media	2.5	1,500	2083	2.5663	2.58%
MPEG-2 SDTV format (DVD)	8	1,500	6666	8.2125	2.59%
HDTV MPEG 2 committee 18	19.2	1,500	16000	19.7120	2.60%

Table 3

It should be noted that the FCC has mandated that by 2006 all televisions sold in the U.S. must include digital receivers. At that point, the integration of wireless interfaces into television electronics could be widespread.

Video Conferencing and IP Streaming Media
WLAN planners and designers should realize that video conferencing is an application that will have an impact on WLAN network capacity even though video conferencing has not yet become as pervasive in the enterprise or home markets as had been expected. This will change over the next few years as broadband connections become pervasive in households, the number of telecommuting workers increases, and enterprises improve their IT resources to allow greater use of video. As a result, WLAN designers should consider the requirements of video conferencing as they deploy infrastructure.

The following table provides a summary of the throughput requirements for several typical video conferencing and streaming media applications. Similarly to DVD and HDTV, the same types of improvements in lower resolution video and conferencing compression are expected in the years ahead. Network capacity models, especially in home networks, should anticipate increasing use of these applications.

Video Product	Bandwidth (MBPS)	Packet Size	Packets/sec	Delivered Bandwidth (MBPS)	Overhead (%)
Business-Quality Conference	915	781,693	107	735,466	6.3%
NetMeeting Video LAN	779	478,312	77	445,156	7.4%
NetMeeting Video DSL	363	187,726	64	159,800	17.4%
NetMeeting Video 28K	288	10,497	5	8,529	23.1%
Read Audio Radio	681	165,118	30	152,025	8.6%
Media Player 80K Stream	687	81,171	15	74,882	8.4%
Media Player 20K Stream	476	27,600	7	24,469	12.8%
Real video 28K Stream	384	25,173	8	21,633	16.4%

Table 4

Throughput of WLAN Access Points (AP)
To optimize the network capacity of a WLAN with a voice or multimedia application, network planners must give special attention to the throughput of the APs which govern how quickly data of any sort can be placed on the network.

The following two basic functions affect the throughput of an AP:

Area and modulation density supported by the cell
1. Small cells can support high data rate modulations (peak rates)
2. Larger cells will use lower rate 802.11 modulations and are an aggregate sum of areas covered and the modulation rate
The WLAN MAC protocols have the following effects:
1. The Ethernet (CSMA/CA) protocols, DCF and EDCF, limit capacity at approximately 37% of the peak data rate
2. Scheduled TDMA protocols such as HCF can theoretically reach around 90% capacity of the network, but under full load they will typically carry only approximately 75% of capacity
3. DCF/EDCF MAC protocols do not effectively manage network latencies as the capacity limit is approached
4. HCF protocols control latencies by providing fair weighted queuing so that all users will receive service even under full load conditions

The following table shows the throughput rates for HCF and DCF/EDCF for various modulations. These values can be de-rated when applied to larger cells that operate with lower capacity modulations.

	Throughput (MBPS)
Modulation	HCF (75%)	DCF/EDCF (37%)
54 MBPS OFDM	40.5	19.98
22 MBPS PBCC	16.5	8.14
11 MBPS CCK	8.25	4.07
5.5 MBPS CCK	4.125	2.035

Table 5

By and large, network designers do not use theoretical peak performance rates when planning a WLAN. As a rule of thumb, most network planners de-rate the theoretical performance figures to approximately 70% to 80% of the peak capacity.

Note: With packet aggregation and proper use of 802.11 protection mechanisms, DCF/EDCF can achieve higher levels of throughput (approximately 50% to 55% higher) with a limited number of users and limited number of connections requiring QoS capabilities. This does not address the concern many enterprise WLAN designers have for the stability of DCF/EDCF under a high user load.

Enterprise Capacity Analysis
Because an enterprise 802.11 WLAN deployment will involve covering a workplace with a series of APs, the network planner must analyze the bandwidth capacity of each cell and the bandwidth demands that users will make on each cell in the network. In an enterprise deployment, the APs will be connected to a router either directly or through an Ethernet switch. In larger enterprises, multiple sub-nets may be connected hierarchically so that a wireless subscriber actually passes through several routers before reaching the IP network.

This type of WLAN essentially represents a micro-cellular architecture using 802.11 Aps interconnected via broadband IP links over Ethernet. APs have a certain coverage range which provides network access to users in a circular area around the location of the AP.

The analysis of enterprise network capacity that follows was based on the following assumptions:

The average density of enterprise users is one per 200 square feet of floor space.
The work day is eight hours long.
150 Mbytes of data as file downloads, e-mails and web accesses are transferred per user over the WLAN. No streaming media is supported.
A sustained peak-to-average data throughput rate of three was used, essentially making the average data load three x 150 Mbytes or 450 Mbytes.
Users require 0.15 ERLANG (15 me) of voice load. (This is based on current Bellcore and SBC business user peak busy hour loads.)
A VoIP connection places a load on the WLAN of 64 Kbps in each direction (a combination G.726 and G.711).

Based on this profile, the following table illustrates the peak busy hour load on a WLAN cell as a function of the radius of the cell.

Cell Radius (feet)	50	75	100	125
Users	39	88	157	245
Active Phone Lines	12	22	34	49
Concentration X:1	3.25	4.00	4.62	5.00
Bandwidth (MBPS)
Voice Uplink	0.77	1.41	2.18	2.18
Voice Downlink	0.77	1.41	2.18	2.18
Data Downlink	3.25	7.33	13.08	20.42
Data Uplink	1.63	3.67	6.54	10.21
Total Throughput	6.41	13.82	23.98	34.98

Table 6

This network capacity analysis shows that even for a small cell with a radius of just 50 feet, a typical 802.11b network would not have the capacity for applications like VoIP or the "completely unwired workplace." However, if an 802.11a/802.11g WLAN with 54 Mbps modulation were combined with an HCF MAC in a cell with a 100-ft. radius, the cell would have nearly 40 percent reserve (excess) bandwidth. Alternately, if the inefficient EDCF MAC were used, a dual-mode 802.11a/g solution would be required to cover the same cell. Two RF channels would be required if the EDCF MAC were used.

"Wired When Docked" Workplace
The analysis presented above is abased on the unrealistic assumption that users of a WLAN would always be completely wireless. In reality, a typical workplace will consist of wired and wirelss users, and most wireless users will be "docked," or connected to a wired network, when they are at their desks.

Windows XP supports intelligent docking. Users are automatically switched from the WLAN network to a wired IP backbone when a device is docked. WLAN planners should take into consideration the effects that "wired when docked" will have on wireless networks' capacity requirements. For example, what if fewer than 20 percent of a workforce are un-tethered wireless workers. This has a profound impact on WLAN capacity needs, as shown in the following table.

Cell Radius (feet)	50	75	100	125
20% wireless	1.28	2.76	4.80	7.00
30% wireless	1.92	4.14	7.19	10.49
40% wireless	2.56	5.53	9.59	13.99

Based on this analysis, planners can conclude that an enterprise WLAN with a "wired when docked" strategy can be supported by 802.11a/b/g dual-frequency access points using either HCF or EDCF. In other words, a deployment of a "sea of simple Ethernet-powered access points" would be sufficient.

Table 7

In order to fully utilize the bandwidth of an access point, co-channel and adjacent channel interference must be addressed. The following section will briefly address RF planning.

RF Frequency Planning for Enterprise Deployment

To analyze properly the overall capacity of a WLAN deployment, planners must consider the effects co-channel and adjacent channel interference will have on the throughput and bandwidth of the APs in the infrastructure. As WLAN APs are deployed for wide area coverage, WLAN RF interference issues take on characteristics similar to those that are faced in the planning of micro-cellular RF networks.

RF network planning begins with a consideration of the frequencies that are available. 802.11 a/b/g radios have the following independent frequencies:

5.1 to 5.3 GHz with eight frequencies
2.4 GHz with three frequencies (There is some discussion in the industry that four frequencies actually could be used.)

For access points that are based on simple omni-directional antenna configurations, the following diagram illustrates both the seven-frequency and the three-frequency repeat patterns with frequency reuse of one. The seven-frequency plan can be used for 5.x GHz 802.11a, and the three-frequency plan can be used for 802.11b/g systems.

Figure 4

For these types of deployments, the cell reuse distance, Ru, can be defined as follows:

C = 7 (7 frequency): Ru = Rcell*sqrt (3C) = 4.48* Rcell
C = 3 (3 frequency): Ru = Rcell *sqrt (3C) = 3.00* Rcell

Where:

C is the cluster size, which is the number of frequencies used in the reuse pattern
Ru is the reuse radius of the cell cluster
Rcell is the radius of coverage of a single cell

For distances greater than the AP's cell radius, it is assumed that RF propagation loss will not be free space (R²) but will be R³ to R⁴. This would result in interference reductions between cells of at least the following:

C = 7: 19.5 dB to 26.1 dB (allows 36 to 54 Mbps OFDM)
C = 3: 14.3 dB to 19.1 dB (allows 22 Mbps PBCC to 36 Mbps OFDM)

Based on larger deployments, it would be possible to implement 802.11 a/b/g WLANs with omni-directional antenna coverage and allow automatic frequency selection at the access point so that the AP is able to establish the most effective frequency plan.

It is possible to use sectored access points and improve frequency reuse. However, in an enterprise environment this would require very careful placement of the APs and alignment of cell sectors. Where frequencies are at a premium, deployments based on four-frequency sectors per AP can provide optimal reuse. The interference reduction is equivalent to the omnidirectional seven-frequency plan previously discussed. The following diagram illustrates the optimal four-frequency reuse plan.

Figure 5

Home Capacity Analysis

Unlike the enterprise market where some assumptions can be made about typical usage patterns, network capacity analysis for WLANs in the residential market will be greatly influenced by the rate of market penetration and the implementation of multimedia applications.

The following are some probable multimedia applications for the home:

802.11 VoIP cordless phones and home PBX/voice mail integrated into an 802.11 access point
Streaming audio distribution to 802.11 speaker systems
- Home PC as an MP3 audio service
Streaming video from a cable television network, DVD system, etc.
Telemetry applications, such as:
- 802.11-enabled cameras/video for security
- Meter reading for utilities
- Smart appliances
Wireless print server connections

If none of these applications are in demand by residential consumers in the near term, 802.11b with security features and QoS enhancements (802.11e/i) will meet the needs of most consumers. (Note: For consumers, speed will always sell. The concept that "faster is better" is compelling. For this reason, dual-mode 802.11b/g devices will have strong market acceptance as long as devices are backwards compatible with the nearly 20 million 802.11b subscriber base.)

Considering that the FCC has mandated that all TVs sold in the US must have a digital tuner, there is a very strong possibility of some level of wireless video distribution in the home. Video applications certainly will have the largest effect on the throughput and capacity requirements of home WLANs. The following table lists the bandwidth requirements for a number of current video codecs:

Video Media	Bandwidth (MBPS)	Packet Size	Packets/sec	Delivered Bandwidth (MBPS)	Overhead (%)
MPEG-1 Basic Media	2.5	1,500	2083	2.5663	2.58%
MPEG-2 SDTV format (DVD)	8	1,500	6666	8.2125	2.59%
HDTV MPEG 2 committee 18	19.2	1,500	16000	19.7120	2.60%

Table 8

This data indicates that a single MPEG2 SDTV/DVD quality channel requiring eight Mbps of bandwidth cannot be supported by current 802.11b MAC/PHY components. Fortunately, advances in video compression (MPEG-4) should reduce the bandwidth requirements for video applications to approximately one Mbps for DVD-quality video and about eight Mbps for HDTVquality applications.

Over the next two to three years, many in the industry expect that a typical broadband-enabled household could have WLAN peak capacity needs as indicated in the table below:

Service	Rate Upstream MBPS	Rate Downstream	Number of Channels	Total Rate Upstream	Total Rate Downstream
MPEG DVD-TV	0.5	8	2	1	16
Toll Quality Voice	0.064	0.064	2	0.128	0.128
Streaming Media	0.01875	0.3	2	0.0375	0.6
ABR Web Service	0.0965	0.386	1	0.0965	0.386
TOTAL				1.262	17.114

Table 9

As shown in the following table, the market acceptance of HDTV and the absence of MPEG-4 compression could increase a home's WLAN throughput needs by a factor of four over the next four to five years.

Service	Rate Upstream MBPS	Rate Downstream	Number of Channels	Total Rate Upstream	Total Rate Downstream
HD-TV	1.5625	25	2	3.125	50
Toll Quality Voice	0.064	0.064	4	0.256	0.256
Streaming Media	0.01875	0.3	1	0.01875	0.3
ABR Web Service	0.0965	0.386	2	0.193	0.772
TOTAL				3.59275	51.328

Table 10

These numbers indicate that high-throughput 802.11g/a PHY technology will be needed as a minimum in order to support these applications. Further, an efficient MAC (HCF) will be needed to optimize throughput.

VoIP applications do not require a significant amount of bandwidth in any of these capacity scenarios. Given the small number of phones in a typical home, the system must be designed for 1:1 concentration (that is, there would be no over-subscription of phone lines in the home). The more important benefits of WLAN-enabled cordless phones are twofold:

Removing cordless phones as a source of RF interference in the 2.4 GHz and 5.2-5.8 GHz frequencies could accelerate the acceptance of video applications over WLANs.
A new market for 802.11 cordless phones would be created with a sales potential of approximately 100 million units a year.

Residential 802.11 Link Asymmetry

Usage models of residential applications show that the typical data transfer load is very asymmetric. That is, the downlink from the AP to the subscriber usually requires 10 times more throughput than the up-link from the subscriber to the AP.

Radio archetectures for 802.11 APs can be differentiated to improve coverage and throughput by simply "bolting on" a booster LNA and PA capability (much like an "afterburner"). This capability is most appropriate in North America where spectrum rules allow 10 dB greater EIRP (power) than in Europe.

The range of an AP can be nearly doubled at the highest modulation rate with simple link budget improvemetns in the AP.

Application of Repeaters/Small-mesh Access Points for Residential/SOHO Coverage
For developers of WLAN access points for the residential/SOHO marketplace, cell coverage and throughput are the most crucial issues facing WLAN implementations in this market. Wireless repeaters, which can be used to implement small mesh residential networks, are a low-cost method of improving coverage and throughput.

One possible technique for extending coverage and improving residential service is the use of multiple APs in a mesh/repeater architecture. A simple example featuring two access points is illustrated in the diagram below:

Figure 6

Access point B is a repeater (mesh element) to access point A, which connects to the Internet. Access point A functions as a router to access point B. Access point A must maintain a routing list for all clients in the home network while access point B only must maintain a routing list of attached clients. For example, B may be a simple bridge or a more intelligent router. Clearly, the mobility/roaming between the cells in this sort of arrangement will generate overhead messaging to update and maintain the routing information.

A real-world example of mesh WLAN architecture was the Aironet system, which was one of the first large-scale deployment platforms for WLANs. In this system, a client would probe for APs that could provide coverage, and the APs would reply with information on signal quality and on how much of their resources were currently in use. The subscriber would then associate and authenticate with the AP with the best signal quality and lowest usage. Once this was completed, re-routing updates would be completed.

Mesh networks can be nested deeper than a single connection. This is known as multi-hop. However, this creates even greater delays because of the cumulative time needed to route and retransmit from one AP to another. For voice, video phone and video conferencing, the round trip delay would be excessive for any architecture with more than one hop.

There are two possibilities for operating a residential mesh network. They are the following:

Single-Frequency Mode: Access points are not dual-mode and can only support a single frequency of operation from an AP to another AP and from an AP to a client/subscriber.
Dual-Frequency Mode: Access points are dual frequency, supporting two separate links on two separate frequencies simultaneously.

The single frequency mode of operation is backwards compatible to older single-frequency APs, but it is highly inefficient because the coverage provided by all APs in a WLAN is overlapping. Any communication initiated by an AP or a subscriber can interfere with any other communication. Under worst case conditions, the throughput is reduced by 1/(N+1) where N is the number of repeater/mesh APs attached to an AP.

The dual-frequency mode requires that all access points support two frequencies simultaneously. Typically, 802.11a (5.x GHz) would be used for AP-to-AP backbone communications while AP-to-subscriber communication would be provided by 802.11b/g (2.4 GHz). Using the 2.4 GHz frequency for subscriber coverage ensures support for low-cost and legacy 802.11b clients/subscribers. Because three independent 802.11b/g frequencies are available in the 2.4 GHz band, WLANs designed with a primary AP and one or two repeater Aps actually improve the coverage of the home. Stated another way, as long as three APs are implemented, the coverage area is greater and throughput will be consistently high without RF interference between the APs.

The dual frequency configuration is shown in the following diagram:

Figure 7 Mesh/Micro-Cell and the Interface Environment

The IEEE community is debating whether to use MIMO and/or beam steering techniques for 802.11 standards as a way to improve throughput and coverage.

A simople mesh extension for the 802.11g standard combined with improved video compression could be available to consumers immediately, and this would provide a "virtual" performance improvement. Final approval of IEEE 802.11 HTSG is at least three years away.

The mesh repeater architechture has another benefit in that it improves signal-to-interference (S/I) performanace because the architecture ensures subscribers are consistently closer to access points. This, in turn, ensures better link margins.

Network Evolution toward IP Multimedia Subsystem

2008-07-02T13:56:00.001+07:00

Abstract
As opposed to mobile next generation network (NGN) approach aiming at just carrying circuit services on top of the Internet protocol (IP), the IP multimedia subsystem (IMS) offers operators the opportunity to build an open IP based service infrastructure that will enable an easy deployment of new rich multimedia communication services mixing telecom and data services. Before trying to emulate circuit switched domain, IMS will first provide new services (such as instant messaging, presence, push-to-talk over cellular [PoC]) that are not too demanding for the underlying radio access network. These services will attract customers and create new telecommunication needs without inducing the technical risks and costs of speech with stringent quality over packet radio.

Introduction
IMS is a new framework, basically specified for mobile networks, for providing IP telecommunication services. It has been introduced by the third generation partnership project (3GPP) in two phases (Release 5 and Release 6) for universal mobile telecommunications system (UMTS) networks. An IP multimedia framework was later introduced by 3GPP2 as the multimedia domain (MMD) for third generation code division multiple access 2000 (CDMA2000) networks, and finally harmonized with IMS. Real-time services can only be properly supported using the Release 6 IMS specifications. Currently, a Release 7 is being worked out by 3GPP taking into account the requirements from Telecoms and Internet-Converged Services and Protocols for Advanced Networking (TISPAN) and European Telecommunications Standard Institute (ETSI) on fixed IMS and NGN requirements.

The IMS concept was introduced to address the following network and user requirements:

Deliver person-to-person real-time IP-based multimedia communications (e.g. voice or videotelephony) as well as person-to-machine communications (e.g. gaming service).
Fully integrate real-time with non-real-time multimedia communications (e.g. live streaming and chat).
Enable different services and applications to interact (e.g. combined use of presence and instant messaging).
Easy user setup of multiple services in a single session or multiple simultaneous synchronized sessions.

3GPP(2) defines a reference architecture, functional splits, protocol specifications, use cases, and so on, for the IMS phases in the context of packet-based UMTS (CDMA2000) access. Many of the features, such as quality of service (QoS) control, full security and full roaming, need specific features to be available in the radio access and/or core network. Other features, such as the session initiation protocol (SIP) session control, integrated access and charging for combined applications, open up the integration of third-party applications. They can be provided today on pre-IMS packet access networks, such as the general packet radio service (GPRS), enhanced data rates for Global System of Mobile Communications (GSM) evolution (EDGE), and CDMA 1x as well as fixed NGN based packet access.

IMS Market Trends and Business Challenge
Global carriers are facing decreasing average revenues per user (ARPU). Due to strong competition, the prices of voice calls and Internet access are declining and the carriers' margins are being reduced. Carriers can no longer afford to offer only voice and ever faster Internet access because these items are becoming mere commodities. They need to identify attractive services that can be bundled with their basic access offer in order to reduce churn.

Most carriers have started looking for such services. Mobile networks operators have introduced portals (CDMA, i-modeTM, and GPRS) with the aim of offering content on mobile phones. Initial attempts were met with varying degrees of success: i-mode was successful in Japan, while the wireless application protocol (WAP) proved to be unsuccessful in Western Europe.

Besides e-mail, most of these portal services are person-to-server services in which a user interacts with a content server. One of the drawbacks of such services is that carriers have to obtain content, which means entering a new business field and negotiating with content providers. This process is costly and undermines the anticipated revenue opportunities from portal services.

Today, however, mobile network operators derive the bulk of their revenues from person-to-person services, mainly voice and short message service (SMS). The core of their business is to enable two users to communicate. Content is created by the users, so wouldn't it make sense to look for new person-to-person services?

E-mail and instant messaging are proving to be successful mobile services, as they already are on the wireline Internet. The multimedia messaging service (MMS), which enables mobile users to exchange pictures, is an example of carriers launching a new person-to-person service.

One area that mobile carriers have not yet been able to address is in real-time rich multimedia person-to-person communication. Video telephony over a UMTS network is a first step in this direction; the communication is enriched with a real-time video component. A UMTS videophone enables you to see the person to whom you are talking, and vice versa. However, because it is based on circuit switching, UMTS video telephony suffers some limitations; for example, a chat component cannot be added to a video telephone call.

Mobile carriers cannot offer their customers the freedom to mix multimedia components (text, pictures, audio, voice, video) within one call. Nowadays, a two party voice call cannot be extended to a multi-party audio and video conference. IMS overcomes such limitations and makes the previous scenario possible.

Moreover, in the future, it will make sense for operators to bridge the gap between traditional telecom services (voice call, SMS) and data services (e-mail, browsing, and instant messaging). Why would not it be possible to start a video call from an Internet directory, extend a text chat to a voice call, show a web and WAP page while making a video call, or show a photograph (provided by the caller) instead of a numerical caller identifier? Mobile carriers will make their offer more attractive if they can provide their customers with the right blend of telecommunication and data services seamlessly interwoven. Because of its IP foundations and the extensibility of SIP, along with the IMS signaling protocol, IMS enables telecommunication and data services to be mixed.

Real-time rich multimedia communication mixing telecom and data services has started to happen in wireline broadband networks. The major instant messaging providers are offering a mix of e-mail, text chat, multimedia file exchange, voice and video calls, and video chat. They have been successful in attracting millions of young people to this service mix, who are in turn tomorrow's adult consumers. Mobile carriers will have to offer them the same multimedia rich environment if they want to prevail over the pure information technology (IT) players, like Microsoft MSN, Yahoo, and America Online (AOL).

However, mobile carriers will have to choose whether they want to become IP pipe providers or IP telco providers. On the one hand, if they become "IP pipe providers", they will focus on transporting IP packets while the value-added services will be offered by others. This is similar to the situation in fixed networks in which broadband access is offered by the carriers, while the most successful IP services (e-mail, instant messaging, peer-to-peer file exchange) are offered by application service providers (ASP). The risk is that network access might become a commodity, thus leaving only small margins for the carrier. On the other hand, if the mobile carriers can become "IP telco providers" they will retain a greater part from the value chain, not only network access but also applications and services, payment, service brokering and even content. The portals and associated payment facilities (money charged for the application service providers and sharing the revenue with them) are a first step in this direction. IMS is a further step because it is carrier-centric, thus enabling them to retain control over rich multimedia sessions.

Evolution toward Work-Style Services
The integration of different media opens up new possibilities for far richer services than those available today and for which users will probably be willing to pay.

IMS is concerned with the creation and deployment of multimedia telecommunication services over any IP network. Most importantly, this includes person-to-person real-time services (such as voice) over packet switched (PS) networks, removing the need for a circuit switched (CS) domain. However, emulation of mobile CS services is not the primary goal of IMS, although their replacement by IMS services is unavoidable in the long run. Furthermore, it will be necessary for IMS to interwork with external CS networks, such as the public switched telephone network (PSTN) or public land mobile network (PLMN), even if there is no longer a circuit switched core network (CN) domain.

The main argument for introducing IMS is to support creative services, for example, from IT-oriented third parties.

IMS brings the power and wealth of Internet services to the mobile environment to a far greater extent than is possible today. In effect, IMS takes the best from the switched and packet worlds. In this context, a more controlled value chain is possible which is of greater benefit to the operators than are current Internet business models. For mobile operators, such models should continue to persist since users will certainly be willing to pay for the combination of rich Internet services and mobility.

IMS enables sessions to be established between multiple users and devices, and allows multiple services to be carried on a single bearer channel. Examples are the ability to set up:

Separate services within a single session; these may be synchronized (e.g. voice and video for video telephony) or not (e.g. video and chat).
Multiple simultaneous single sessions of unrelated services (e.g. voice call in parallel with a presence session).
Easy switching between point-to-point and point-to-multipoint person to person sessions, without the burden of pre-programmed conference services on the PSTN. Combined with the flexibility of packet networks, this will allow walkie-talkie like services, such as PoC, in which a user simply has to push a button to send voice messages to a group of peers.
Ease of simultaneously ringing a called users different terminals.

The service combination also guarantees session completion, which does not depend on the called party having a compatible terminal. For instance, a session can be accepted without the video component or the video component can be routed to another destination. Together all these features enable IMS to provide a significantly enhanced user experience and promises to be the basis for radically new services.

IMS is designed to be agnostic to the underlying access network, although initially it has been designed to run over mobile packet networks (e.g. GPRS, EDGE, UMTS, CDMA-based). In a second phase, it will also run on fixed (wireless) broadband networks (e.g. x digital subscriber line (xDSL), wireless local area network [WLAN], and cable). Consequently, IMS holds out the promise of seamlessly supporting converged services on fixed and mobile networks.

Safe Deployment of IMS
Although IMS is access agnostic, initially it will be deployed in mobile networks. Consequently, taking an end-to-end service perspective, mobility and particularly radio constraints must be taken into account. However, some other network-related constraints are also relevant, although not necessarily linked to mobile networks.

The use of IPv6 for IMS — as required by 3GPP — makes it necessary for an operator to deploy almost entirely new network layers at the same time as rolling out IMS:

New service layer elements to provide new IMS services
Totally new session layer, that is, a new networking layer based on SIP
New transport layer based on IPv6
Associated back-office features, such as security, routing and charging. Since some IMS services are totally new they might require new charging concepts and new charging information to be stored in the relevant network nodes.

Providing initial support for IPv4 over IMS overcomes the challenge of deploying IMS services over a new transport layer. Furthermore, deploying IMS solely on IPv6 may be an issue for communication services provided by the mobile operator to enterprise networks, which might be deploying IPv6 at their own pace.

IMS is indeed a good tool to deliver the same set of services to both wire-line and wireless users. For this reason, it might prove beneficial to deploy IMS over IPv4, at least during the roll-out phase. Nevertheless, the operator should not wait too long to carry out the necessary migration to IPv6 in order to avoid high migration costs when IMS has become established. The efficient transport of voice over a radio interface is another challenge that must be met when delivering real-time conversational services (such as VoIP over IMS). As the radio is the most expensive part of a PLMN, it must be optimized, otherwise the reduction capital expenditures (CAPEX) and operational expenditures (OPEX) potentially brought by IMS in the CN would be ruined.

A first step in providing efficient transmission of conversational voice over radio has been provided by robust header compression (RoHC), but further improvements are still needed. Answers to various questions, including the following, have to be provided before deploying IMS services that supersede the CS domain services:

How is it possible to cope with variations in the length of voice frames over radio as a result of RoHC compression?
How can one deal with real-time control protocol (RTCP) considering that its traffic is very sporadic but may correspond to frames with very different lengths which might delay real-time protocol (RTP) traffic?
How to optimize the transfer of adaptive multi-rate (AMR) speech over the packet domain using techniques such as AMR codec mode control and unequal error protection (UEP)?

It is important to point out that the level of end-to-end QoS supported by the infrastructure determines the nature of the services that can be supported (e.g. real-time or non-real-time). In the case of real-time mobile services over IMS, the GPRS and UMTS infrastructure has to meet hard QoS constraints, for instance, full support for conversational quality. Such constraints cannot be met by today's network, for example, because of the lack of handover support for 2.5G packet radio.

Conclusion
IMS can provide new person-to-person multimedia communication services going beyond those available on today's 3G networks. Because IMS is IP based, it will blend telecommunication and data services, keeping the best of both the circuit-switched and packet worlds. As IMS was designed for network operators, it keeps multimedia call control with the mobile carriers, who can thus win a bigger part of the value chain (access, application and services, brokering, payment, etc.) and can become IP telco providers instead of "IP pipe providers".

Educational Content Provided by:

Sajid Soormally, IMS Solution Manager, Alcatel-Lucent
Michael Tadault, Technical Director, Alcatel-Lucent
Laurent Thiebaut, Senior End-to-End Solution Architect, Alcatel-Lucent

"Good" cholesterol may protect memory, study finds

2008-07-02T13:33:00.000+07:00

WASHINGTON (Reuters) - Middle-aged people with low levels of so-called good cholesterol may be at higher risk for memory decline that could foreshadow Alzheimer's disease or other forms of dementia, European researchers said on Monday.

The study, involving about 3,700 British men and women, found that falling levels of high-density lipoprotein, or HDL, cholesterol were linked to declining memory by age 60. Such memory declines often precede the development of dementia such as Alzheimer's in the elderly.

Experts predict increasing numbers of people worldwide will develop Alzheimer's in the coming decades as populations in many countries grow older. Scientists are trying to identify risk factors that may appear years before the onset of dementia to help find ways to prevent or postpone it.

"Considering the way the population is aging -- the 65-plus age group being the fastest-growing age group -- we are facing a dementia time bomb," said Archana Singh-Manoux of the French National Institute for Health and Medical Research and the University College London, who led the study.

Singh-Manoux said she hoped the findings will focus attention on the possible role of higher levels of HDL cholesterol in protecting against memory loss.

The researchers looked at blood cholesterol readings and the results of a simple memory test collected when the people in the study were on average 55 years old and then again when they were on average 60.

WORD QUIZ

In the memory test, the participants had 20 words read to them, and then were asked to write down in 2 minutes all the words they could remember.

At age 55, those with low HDL cholesterol had a 27-percent higher risk of memory loss when compared to those with high HDL. At age 60, those with low HDL had a 53-percent higher risk of memory loss compared to those with high HDL levels.

The study did not track whether or not the people went on to develop dementia.

Low HDL was defined as less than 40 milligrams per deciliter (mg/dL) and high HDL was defined as at least 60 mg/dL in the study, published in the American Heart Association's journal Arteriosclerosis, Thrombosis and Vascular Biology.

Cholesterol is a fatty substance made naturally by the body and also found in many foods. High HDL levels can cut heart attack risk.

As opposed to low-density lipoprotein (LDL) cholesterol that can build up in artery walls, making them hard and narrow, HDL cholesterol takes excess cholesterol back to the liver.

LDL cholesterol is dubbed the "bad" cholesterol.

In the study, total levels of cholesterol and triglycerides

-- another type of fat found in the blood -- had no association with memory decline.

Singh-Manoux said the study did not look at the reasons that HDL cholesterol may protect memory. She said one possible explanation is that it wards off formation of beta-amyloid plaques in the brain that are a hallmark of Alzheimer's.

Previous studies have identified other early risk factors for Alzheimer's disease. In March, U.S. researchers found that having a big belly in middle age appears to greatly increase one's risk of developing Alzheimer's or another form of dementia decades later.

Mental Test Spots Alzheimer's Risk

2008-07-02T13:30:00.000+07:00

TUESDAY, July 1 (HealthDay News)

A new questionnaire may help in both diagnosing older adults facing dementia and also in identifying individuals who need help with daily living.

The Everyday Cognition instrument consists of 39 questions to be answered by people who know the patient well.

"There have been a number of studies that show that people with mild cognitive impairment who have functional problems in addition to performing poorly on neuropsychological testing are more likely to progress in the near future," said study author Sarah Tomaszewski Farias, an assistant professor of neurology at the University of California, Davis, Medical Center in Sacramento. "One of our hopes is that this instrument will be able to help identify very early on those people at increased risk for developing Alzheimer's disease."
That would help both patients and family members prepare for what lies ahead and identify patients who need to be more closely monitored.

In addition, Farias said, the test would also help identify "people who are having [functional] problems so that we know who needs help and who doesn't."

"What's nice about this is that it is designed to pick up very early memory problems, and it's an entirely caregiver-based survey," said Dr. Scott Turner, incoming director of the Memory Disorders Program at Georgetown University Medical Center, in Washington, D.C. "This is something the caregiver can fill out, while the practitioner is looking at the patient. It could be used for screening, for diagnosis and for drug development, if you want to look for some proof that your drug is having some effect, so it has a lot of potential uses."

"They want something that they could use to ask a family member about the potential patient's everyday functioning to see if that's sensitive to picking up the likelihood of dementia early on," added Dr. Gary J. Kennedy, director of geriatric psychiatry at Montefiore Medical Center in New York City.

The findings were published in the July issue of Neuropsychology.

Existing neuropsychological tests tend to be very abstract. For the last 40 years, these tests have looked at two categories: so-called "basic" activities (such as grooming, feeding, dressing), which are affected in later stages of dementia, and "instrumental" activities of daily living (such as managing medication, finances, cooking, driving).

"I was interested in understanding how our neuropsychology tests translated into everyday problems, how our cognitive tests . . . translate into everyday problems that a person is experiencing and that a caregiver is concerned about," Farias explained.

Farias and her colleagues divided everyday functioning into seven cognitive "domains:" memory, language, semantic or factual knowledge, visual and spatial abilities, planning, organization and divided attention.

An original list of 138 items was eventually culled to 39, which was then tested in 576 older adults: 174 of whom were cognitively normal, 126 who had mild cognitive impairment (MCI), and 276 who had been diagnosed with dementia.

"Informants" (people who had known the patient for an average of almost 45 years) provided details on whether the patient could remember shopping items without a list, reading a map, balancing the checkbook, and cooking or working and talking at the same time.

Not only did the instrument confirm established diagnoses, it was also able to distinguish people with MCI from those with full-blown dementia, meaning it was able to pick up on subtle differences in function.

The results also weren't highly influenced by occupation and education levels, as are existing tests.

"This is really the first step in development the instrument," Farias said. "What we're really interested in doing is to track people over time to get a better understanding of the early signs of functional impairment."

More information

Visit the Alzheimer's Association for more on this condition.

Ericsson Equips Toshiba Laptops With Mobile Broadband

2008-07-01T23:50:00.000+07:00

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Ericsson will equip Toshiba's business laptops with integrated support for mobile broadband access using HSPA (High Speed Packet Access), it announced on Tuesday.

The plan is to release the first laptops in the second half of 2008 in Europe, the Middle East and Africa.

Ericsson's module offers data rates of up to 7.2 M bps (bits per second) in the downlink and up to 2M bps in the uplink, using HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). The module also features support for GPS (Global Positioning System).

Using an integrated module, as opposed to an external modem, has several advantages.

"The single most important thing is that it becomes easier to use, and you also get better battery time," said Eva Sparr, marketing director at Ericsson's mobile broadband modules unit.

Another advantage is that you can't misplace or leave an integrated module at home. It's one less thing to remember, according to Sparr.

One disadvantage is that you can't upgrade the modem and take advantage of the fast-paced development of HSPA. But that doesn't matter much, according to Ericsson.

"We are convinced that the current bandwidth will be good enough during the three-year lifecycle of a laptop, said Sparr.

Built-in support for wireless broadband has really taken off-- there are currently 84 models that support HSPA in some way, according to the GSM Association's device database.

For Ericsson it's the third deal it has signed with a major laptop manufacturer this year. Besides Toshiba it signed deals with Dell in May and Lenovo in February.

"Since Ericsson entered this market in 2007 the interest has been enormous, helped by the current forward momentum of mobile broadband" said Sparr.

Put to the Test: Best Smartphone Platforms For Business

2008-07-01T23:14:00.000+07:00

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Examine Platform Options

Once you know what level of access you need to support and how the hardware will be used day in and day out, comes the time to pick the best platform. Current Analysis' Avi Greengart said, "There is no best platform, but there are several good ones to choose from. The best for one will not be the best for another, and vice versa."

Greengart cuts to the chase and recommends that you "do whatever your senior executive says to do." He's not kidding. "From a practical standpoint, a newbie IT manager will learn the hard way if he/she doesn't follow an executive's wishes. Just because you [in IT] know that Google's Android is a completely untested platform doesn't mean you should tell your executive 'No' if they get one at Best Buy [when it's released] and ask you to support it."

Supporting one device to make an executive happy, however, is a bit different from supporting many. Let's look more at what each platform has to offer, and what they don't.

Windows Mobile:

"Right now in terms of in terms of just e-mail, voice, and simple browsing, Microsoft's Windows Mobile should probably be number one," said Gartner analyst Ken Dulaney. The main reason is that Microsoft has the widest base of third-party applications that will run on it. "When it comes to on-device apps, Microsoft is dominant."

Windows Mobile also has the advantage if you are a Windows development shop. You can use the same tools you are already familiar with for Windows Mobile. Windows Mobile has been around a long time and has a tremendous library of business applications ready to go.

Training is another factor to consider. In terms of ease of use and training, a lot of people have been focused on "WinMo" and how desktop-like it is relative to the iPhone. Many consider Windows Mobile's desktop appearance to be a negative, but when it comes to training users, it has a shallower learning curve than the BlackBerry operating system. "The desktop metaphor is extremely familiar," said Greengart.

Another advantage that Windows Mobile has is the wide variety and breadth of device selection available. "There are a lot of Windows Mobile licensees out there," noted Greengart. "You can get Windows Mobile in touch or non-touch, QWERTY or non-QWERTY, slider or slab, rugged or non-rugged." There's no doubt that Windows Mobile devices cover a lot of ground.

BlackBerry OS:

If you don't need the higher degree of customization, BlackBerry OS and RIM's devices are more than enough to fit the bill for e-mail retrieval, simple applications, and basic browsing. RIM has worked hard to expand its device portfolio lately to compete with the device selection offered by its competitors. As Greengart puts it, BlackBerrys now come in "thin, wide, and wider," referencing the Pearl, Curve, and 8800 series.

If your IT shop is already invested in the BlackBerry Enterprise Server and devices, there is no need to change systems unless your needs aren't being met. "RIM would be fine if you're running light-duty Web-based apps," said Gartner's Dulaney.

Only recently has BlackBerry been able to garner the same third-party vendor support from its partners that Windows Mobile enjoys. Microsoft still has a big lead here, though.

Not all smartphones are created equal. They draw their productivity-enhancing powers from the platform they use, rather than the hardware running it. What, then, makes for the best enterprise smartphone platform?

There is no single answer to that question. According to the experts we spoke to, different platforms are suited to different purposes. Each has its strengths and weaknesses, but in the long run, Microsoft's Windows Mobile and Research In Motion's BlackBerry OS are the two clear winners for most enterprise purposes. Here's a step-by-step primer on how to pick the platform most appropriate for you.

Determine What It Will Be Used For

Gartner classifies smartphones into three categories. Devices that can access e-mail without security measures, as well as run other, simple applications are granted "concierge" status. In short, what this really means is if your CEO comes down to the IT shop and says, "Support this device," it can (and probably should, if he's the one signing your paycheck) be done. But it isn't recommended. The first-generation iPhone falls into this category.

Next up are what Gartner terms "appliance-level" devices. These devices can sync with Exchange, have basic security measures, such as device wipe and passwords, and can run a wide range of third-party applications. This is where BlackBerrys, Nokia's S60 smartphones, and many Windows Mobile devices fall.

Last, there's "platform-grade" devices. These are devices that Gartner recommends for companies that wish to develop their own in-house applications, but can also run third-party apps and have the necessary vendor support. Windows Mobile also falls here.

If all your organization needs to do is mobilize e-mail, the appliance-level devices will be just fine. If you have a deep base of internally developed line-of-business applications that are core to what your mobile workforce needs each day, you'll need to choose devices that fall into the platform grade.

Figure Out Where It Will Be Used

Figuring out how a device will be used is the next question IT needs to answer in choosing an OS. If you're equipping a field workforce that will roam near and far and expose their hardware to the elements, a standard smartphone isn't going to be appropriate. A field force requires hardware that's more robust, rugged, and able withstand the rough-and-tumble life in a truck. That means something along the lines of a Motorola MC-35 Enterprise Data Assistant or an Intermec 700. Right now, Windows Mobile pretty much has a stranglehold on this market.

Typical road warriors, however, can get away with an off-the-shelf smartphone from RIM, Nokia, or any Windows Mobile licensee and pretty much be safe. Once this question in answered, you can move on to step number three.

Nokia S60:

Despite the strong capabilities of this platform, S60 simply doesn't have a notable presence in the U.S. This is confounded by a few factors.

First and foremost, you can't buy an enterprise Nokia device directly from the carriers, and you can't get one that works on CDMA networks (which half of U.S. smartphone customers use). These two alone are big roadblocks.

Not having a carrier partner for distribution is the real killer. "Because of Nokia's weakness in the U.S.," said Greengart, "not even its middleware -- which is good -- has good traction here. But its business devices have gotten a lot better."

You can get Nokia S60 devices from resellers and Nokia has done a good job of mandating that its E Series devices have quad-band radios and Wi-Fi, so you know they will work all over the world. But some have 3G, and others don't.

Gartner's Dulaney argues that most of what Nokia calls smartphones are really not business-class devices, however. Nokia calls anything that runs the S60 platform a smartphone. It has only several phones in its current E Series business devices, with many more S60 phones focused on multimedia functions instead. "If you're committed to Symbian, and you're in Europe and build Java apps, then Nokia's S60 will work fine."

iPhone OS:

iPhone 2.0 will no doubt support Exchange, remote wipe, and passwords, making it qualify for Gartner's "appliance" rating, but it does have a big Achilles' heel: third-party applications.

You might argue that the iPhone SDK and upcoming AppStore negate this argument, but they don't. Support for all those nifty third-party apps is a key aspect of using them. If vendor support isn't there, they aren't worth installing. Another concern is that Apple has yet to make it clear exactly how -- and if -- it will support internally developed corporate applications. Details needs to be made clearer -- and vetted -- before the iPhone gets even a yellow, cautionary light from Dulaney and Greengart.

"Putting local code on that device would be risky because there are no back-up vendors," said Dulaney.

Despite this drawback, both believe the iPhone will get some traction in the enterprise. If you want/need secure e-mail, the iPhone will deliver it... at a price premium. The ease-of-use factor alone is quite compelling. It is doubtful that many enterprises will supply it directly. Rather, it will be a device that individual employees pick up on their own and expense back to IT.

Android:

Sorry to dash any hopes you might have had, but Android is not going to be an enterprise-grade platform. At least not in the short term. It will remain a consumer play well into 2009, and likely won't begin to see traction in the enterprise until the first half of 2010. The reason? It isn't proven, and the security issues haven't been clearly hashed out.

It does have some intriguing factors. Based on recent demonstrations, there are some cool things that can be done with Android. The core is based on open-source Linux, and the upper layers are based on Java. These are known factors. The in-house development possibilities appear to be endless. There will certainly be early adopters who test it and consider it. Until the operating system is released in late 2008, it isn't even worth putting on your IT roadmap. "I would expect any IT manager to be wary of [Android] until it has been proven," said Greengart.

Make The Decision

In the end, from the device side, your organization needs to look at what it really needs, beyond the narrow views offered by thought-leaders. If your business has a wide variety of needs and you want to consolidate, then perhaps choose Microsoft's Windows Mobile. Don't fool yourself, however, into thinking that you'll ever be able to trim down to just one platform.

"In many cases, you can't consolidate 100% because people have certain preferences," said Gartner's Dulaney. "And some of them are the ones running your company. Two platforms would be reasonable. If you start from scratch, you might be able to live with one. If you're global, however, that possibility is remote. There are different geographic preferences and more choices for end users to select from."

The best smartphone platform is the one that allows your IT organization to properly equip all your different employees with the right device for their jobs.

See original article on InformationWeek.com

Wireless Standart

2008-07-01T13:53:00.000+07:00

Sudahkah kamu mengunakan wireless hari ini? Saat ini, mungkin hampir semua laptop keluaran terbaru, telah dilengkapi dengan kemampuan untuk melakukan koneksi menggunakan wireless, atau biasa disebut dengan wireless networking.

Nah, jika kamu punya laptop, atau baru membeli laptop, atau ingin punya laptop, atau mimpi ingin punya laptop, atau malah kepingin ngetop, dan beberapa atau lainnya... namun kamu tidak tahu apa dan bagaimana cara memanfaatkan teknologi wireless ini, bukankah itu adalah suatu kerugian?

Nah, untuk mengetahui bagaimana cara menggunakan wireless, ada baiknya jika kita mengenal dulu bagaimana teknologi wireless ini diatur. Siapa yang berhak mengeluarkan aturan-aturan tersebut.

Berikut ini beberapa organisasi yang berhak mengeluarkan aturan-aturan standard yang harus diikuti dan di patuhi oleh setiap orang ataupun organisasi yang ingin memanfaatkan teknologi wireless ini.
Federal Communications Commission (FCC)

Organisasi ini adalah organisasi yang bergerak di bidang pertelekomunkasian. Organisasi ini yang mengatur segala jenis komunikasi baik yang keluar ataupun ke dalam negara Amerika Serikat.

Wireless, sebagai sarana telekomunikasi, tentu saja ikut menjadi wewenang dari FCC ini. Tujuan FCC mengatur komunikasi wireless, adalah agar tidak terjadi kesimpang siuran, maupun penyalahgunaan dalam hal penggunaan sinyal atau frekuensi radio yang digunakan dalam teknologi wireless.

FCC adalah organisasi independent yang didirikan oleh pemerintah US. FCC bertanggung jawab untuk mengatur segala jenis penggunaan perangkat telekomunikasi, baik yang menggunakan radio, televisi, wire, satellite, dan kabel. Wilayah kekuasaan FCC ini meliputi 50 negara bagian yang ada di US, dan beberapa distrik yang menjadi teritori dari Negara US.

Ok... itu kalo di US, bagaimana dengan negara lain? Hampir disetiap negara mempunyai badan atau organisasi yang serupa dengan FCC ini. Bagaimana dengan Indonesia? Siapa yang berhak mengatur dan mengawasi segala bentuk penggunaan teknologi untuk telekomunikasi?

FCC dan berbagai organisasi sejenis, secara umum mengatur dua jenis penggunaan teknologi wireless untuk melakukan komunikasi, yaitu yang berlisensi dan yang tidak berlisensi. Apa bedanya yang berlisensi dengan yang tidak berlisensi?

Perbeaanya, jika yang tidak belisensi, maka berarti user tersebut bisa menginstall dan menggunakan wireless tanpa harus mengikuti berbagai prosedure yang dibutuhkan untuk mendapatkan lisensi. Sedangkan yang berlisensi harus mengikuti berbagai prosedure untuk mendapatkan lisensi.

Sekalipun begitu, baik yang berlisensi ataupun tidak, mereka tetap harus mengikuti aturan-aturan yang telah ditetapkan. Aturan ini meliputi dalam hal penggunaan:

* Frequency.
* Bandwidth.
* Maximum power of the intentional radiator.
* Maximum equivalent isotropically radiated power (EIRP)
* Use (indoor dan/atau outdoor).

FCC dan organisasi sejenis, adalah organisasi yang bertugas, sekaligus yang berhak untuk membuat berbagai aturan yang menyangkut mengenai apa saja yang boleh, dan tidak boleh dilakukan oleh seorang user dalam hal penggunaan wireless, khususnya yang menyangkut penggunaan Frekuensi Radio (RF) untuk melakukan transmisi.

Dari aturan-aturan inilah, FCC dan organisasi sejenis membuat prosedure dan standar kerja. Organisasi-organisasi ini dibentuk dan bekerja sama, dengan tujuan untuk membantu memenuhi kebutuhan akan meningkatnya permintaan yang menyangkut teknologi wireless, yang sedang berkembang dengan pesat saat ini.
International Telecommunication Union Radiocommunication Sector (ITU-R)

Sebuah organisasi global yang ada dan didirikan untuk mengatur penggunaan frekuensi radio (RF) diseluruh penjuru dunia. The United Nations (PBB), menugaskan kepada International Telecommunication Union Radiocommunication Sector (ITU-R) ini, untuk mengatur dalam hal skala penggunaan frekuensi, secara global.

Nah, karena dunia ini luas, maka kemudian ITU-R membaginya menjadi beberapa wilayah. Hingga masing-masing wilayah, diatur oleh organisasi yang berbeda. Pembagian wilayah ini yaitu meluputi:

* Region A: North and South America
Inter-American Telecommunication Commission (CITEL) www.citel.oas.org

* Region B: Western Europe
European Conference of Postal and Telecommunications Administrations (CEPT) www.cept.org

* Region C: Eastern Europe and Northern Asia
Regional Commonwealth in the field of Communications (RCC) www.rcc.org

* Region D: Africa
African Telecommunications Union (ATU) www.atu-uat.org

* Region E: Asia and Australasia
Asia-Pacific Telecommunity (APT) www.aptsec.org

Dari masing-masing wilayah atau region ini, kemudian bekerja sama dan dibagi-bagi lagi dengan organisasi-organisasi dari masing-masing negara setempat. Contohnya:

* Australia, Australian Communications Authority (ACA)
* Japan, Association of Radio Industries and Businesses (ARIB)
* New Zealand, Ministry of Economic Development
* United States, Federal Communications Commission (FCC)

Institute of Electrical and Electronics Engineers (IEEE)

Institute of Electrical and Electronics Engineers atau biasa dikenal juga sebagai IEEE, adalah sebuah perkumpulan profesional yang bersifat global. Perkumpulan ini mempunyai anggota lebih dari 35.000 orang profesional yang berasal dari berbagai negara.

IEEE ini mempunyai misi untuk "promote the engineering process of creating, developing, integrating, sharing, and applying knowledge about electro and information technologies and sciences for the benefit of humanity and the profession." Nah.. terjemahin sendiri aje deh!

Para profesional yang bergerak dalam bidang networking, dan tergabung dalam IEEE ini, bekerjasama dalam suatu porject yang bertujuan untuk membuat berbagai prosedure standard yang berkaitan dengan komunikasi. Mereka sangat dikenal karena salah satu project standarisasi LAN yang mereka kerjakan, yaitu IEEE 802 project telah digunakan sebagai standard saat ini.

IEEE 802 project hanyalah salah satu dari sekian banyak project yang telah ataupun sedang mereka kerjakan. Agar mudah mengaturnya, maka dibuatlah kelompok-kelompok kerja atau working group. Masing-masing kelompok mengerjakan project yang berbeda. Kelompok-kelompook ini diberi nama sesuai dengan project yang sedang mereka kerjakan. Misalnya project IEEE 802 tadi.

Namun seiring semakin kompleknya permasalahan, dan semakin meningkatknya permintaan akan kebutuhan pada masalah-masalah yang lebih spesifik, maka kelompok-kelompok project tadi di bagi-bagi lagi menjadi kelompok-kelompok yang lebih spesifik.

Sebagai contoh, IEEE 802.3 adalah working group atau kelompok yang bertanggung jawab dalam hal standarisasi untuk Ethernet, dan the IEEE 802.11 adalah working group yang bertanggung jawab dalam hal standarisasi wireless.

Angka yang terdapat di belakang tanda titik (.), adalah angka yang menunjukkan working group. Dari situ kita bisa mengetahui bahwa kedua contoh tadi berada dalam satu project yang sama, yaitu IEEE 802, tapi berada dalam working group yang berbeda (11 dan 3).

Untuk beberapa waktu model penomoran ini cukup memadai. Namun lagi-lagi, karena permasalahan dan permintaan kembali meningkat, maka dibuat lagi kelompok-kelompok yang lebih spesifik. Dan untuk masalah penomoran atau penamaan working group, mereka memutuskan untuk menambahkan abjad di belakang nama working group.

Contohnya, 802.11a, 802.11g, and 802.3af. Namun ternyata tidak semua abjad bisa digunakan. Beberapa abjad tidak bisa digunakan, misalnya o dan l. Ini untuk menghindari kesalahan yang mengira bahwa hurup o itu adalah 0, dan hurup l itu adalah angka 1.

Lalu timbul satu pertanyaan, mengapa IEEE mau bersusah-payah membuat standarisasi dalam hal penggunaan teknologi wireless ini. Yup, tentu saja dengan tujuan untuk menyamakan teknik dan prosedure yang akan digunakan dalam penggunaan teknologi wireless networking ini.

Tanpa standarisasi ini, maka akan sulit untuk mengkomunikasikan berbagai produk wireless yang sejenis, namun di produksi oleh vendor yang berbeda. Misalnya wireless card merk A tidak bisa berkomunikasi dengan wireless card merk B karena diproduksi oleh vendor yang berbeda.
Wi-Fi Alliance

Wi-Fi Alliance, adalah sebuah assosiasi merk dagang dari sebuah industri global yang bersifat non-profit, yang beranggotakan lebih dari 200 perusahaan. Wi-Fi Alliance di dedikasikan untuk mempromosikan perkembangan dari Wireless LANs (WLANs).

Untuk memastikan bahwa suatu produk WLAN benar-benar bisa berfungsi, adalah salah satu tujuan utama dari Wi-FI Alliance ini. Jadi, Wi-Fi Alliance ini bertugas untuk menguji setiap produk WLAN yang akan direlease ke pasaran. Jika ternyata produk tersebut benar-benar berfungsi sesuai dengan standard, maka Wi-Fi Alliance akan memberikan sertifikat sebagai tanda produk tersebut telah lulus uji kelayakan.

Pada Agustus 1999, Wi-Fi Alliance didirikan. Kala itu, Wi-Fi Alliance masih dikenal dengan nama Wireless Ethernet Compatibility Alliance (WECA). Namun, pada Oktober 2002, WECA akhirnya resmi berganti nama menjadi Wi-Fi Alliance. Semenjak April 2000, Wi-Fi Alliance telah memberikan sertifikat kepada lebih dari 1.500 produk Wi-Fi.

Sertifikat yang diberikan oleh Wi-Fi Alliance ini meliputi tiga kategori, yaitu:

* Wi-Fi products based on IEEE radio standards - 802.11a, 802.11b, 802.11g in single-mode, dual-mode (802.11b and 802.11g), and multiband (2.4 GHz and 5 GHz) products.

* Wi-Fi wireless network security - Wi-Fi Protected Access (WPA), Personal and Enterprise; Wi-Fi Protected Access 2 (WPA2), Personal and Enterprise.

* Support for multimedia content over Wi-Fi networks - Wi-Fi Multimedia (WMM).

International Organization for Standardization

Atau seringkita kenal sebagai ISO. ISO itu adalah sebuah organsasi non pemerintah dan bersifat global. ISO bertujuan untuk mengidentifikasi bisnis, pemerintahan, atau perkumpulan yang membutuhkan dan mengembangkan standarisasi dalam hal kerjasama dengan sektor yang akan mereka gunakan.

ISO bertanggung jawab untuk membuat Open Systems Interconnection (OSI) model, yang telah menjadi referensi standard dalam hal komunikasi data antar komputer semenjak akhir tahun 1970-an.

Nah... itu tadi beberapa organisasi yang telah berjasa dan bekerja sama hingga kita akhirnya bisa menikmati teknologi wireless. Sekarang kita jadi tahu, bahwa ada aturan standard yang harus diikuti dan dipatuhi dalam pengguaan teknologi wireless ini.

http://belajar-yok.blogspot.com

Clickbooth Affiliate Network

2008-06-28T12:38:00.000+07:00

There are so many affiliate on the internet in many kind of types such as: pay per sales, pay per click, pay per action etc, now I will try join a program called Clickbooth affiliate network, this affiliate using CPA (cost per acquisition or cost per action) from clickbooth.com, from the main page this site is designed exclusively, there are three selection main menus, it is for publisher, advertisers, and network.

Well like I said before, I will review by join as an publisher on this site, when I sign up I fill the forms and the forms are standard like sign up at other affiliate program, first step I can easily sign up, at the seconds steps I must fill my phone number and they will call me, only one minutes after I fill my phone number the call machine from them immediately call me and give my PIN, wow this is new for me, but I think its too complicated for newbie, and the load page when sign up is take too long time, I don’t know is this because the server or my internet connection, at the last steps I need to fill my website information, at this page I can select website type and traffic type. But after I finishing my application and click “send my application” I always return into the that page anymore, I have already repeat several time but always back into the third form page, I don’t know why though I have already fill the data correctly. Maybe at the third form information need to be repairs.

Best IP Phone Product

2008-06-28T12:18:00.000+07:00

Get the best products of IP Phones for various usages such as for international use, office use, small business, computer, and all uses. Go to the website at wize.com and browse for IP Phones, and you can find the top products available in different designs and various prices. You can see and compare the 115 products based on their functions or match them with your preferences. You can filter the products result based on the usage, price, brands, protocol, codec, networking connectivity, and more.

It will be easier for you to shop online, because this site gives you brief information about the rating of each product, which is based on the reviews. Some examples of the products available are the Linksys CIT400 Dual-Mode Internet Telephony Kit, Panasonic KX-WP1050, Logitech Cordless Internet Handset 9805900403, Radian Technologies SkyTone RST102, Cisco 7962G IP, D-link VoiceCenter™ DPH-125MS, DLink Systems DVX-2000MS-5, Compucessory CCS 30585, and Nortel 6812. The products images are displayed on the web which you can see and choose.

For more details about each product you can click on the products thumbnails and you will see more descriptions about the product specifications. There are reviews from people which should help you on considering which product to buy, so start your online shopping now.

Number Portability

2008-06-25T13:28:00.000+07:00

Number portability is the ability of a customer to retain their existing phone number(s) when changing their carriage service provider (CSP). This allows consumers to choose between competing CSPs based on price, quality, type of service and (for mobile phone users) coverage without the inconvenience and expense of having to take a new number when moving between providers.

Number portability also eliminates the need for callers to contact directory services to find someone's new number or for people to miss calls as callers continue to dial the old number.

Industry provision of number portability is managed under the Telecommunications Act 1997 and the Telecommunications Numbering Plan 1997 (the Numbering Plan).

Number portability applies to the following services:

local services-predominantly supplied using numbers in the (02), (03), (07) and (08) number ranges (but excludes telex or paging services)
freephone services-numbers which start with the digits 18 and local rate services-numbers which start with the digits 13
mobile services-numbers which start with the digits 04 (excluding analogue mobile phone service numbers)

Geographic Number Portability

Local number portability (LNP) was introduced for geographic numbers in 1997. While in general, LNP allows customers to change their telephone provider and keep their telephone number, it does not guarantee consumers can keep their telephone number if they move to a different geographic location. Local numbers in Australia contain specific geographic information. Further information on LNP is available from the Australian Communications and Media Authority (ACMA).

Freephone and Local Rate Number Portability

Freephone and Local Rate number (FLRN) portability allows porting for customers with telephone numbers beginning with the digits 13x or 180x. FLRNs are managed differently from other numbers for the purposes of allocation and porting. The Numbering Plan delegates responsibility for allocating FLRNs to an industry body called Industry Number Management Services (INMS), an independent not-for-profit organisation that administers a centralised reference database of FLRNs released by the ACMA for allocation to CSPs, and for porting between CSPs. Please visit ACMA Number Portability for further information.

Mobile Number Portability

Mobile number portability (MNP) covers all digital mobile service numbers irrespective of the technology used (GSM or CDMA networks) except for satellite-only mobile services.

Australian Goverment

SONY VAIO N30

2008-06-25T13:11:00.001+07:00

Sony France announced the new VAIO N30 series, offering a wide range of configurations in the portable computer range. With an Intel Core 2 Duo processor and up to 2GB RAM on certail models, the N30 guarantees optimal Windows Vista performance.

The hard drive has been upgraded, with 120GB being the standard minimum and up to 200GB (on the VGN-SZ5VWN/X model, available on Sony Style). Among standard security features, you find a fingerprint reader and TPM module.

The N30 includes protection for the hard drive in case it is dropped. Select models also include an HSDPA card for high-speed internet access on the go.

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