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What is 4G?

2011-07-27T04:15:00.000-07:00

As we all know and appreciate, the Internet has changed our lives over the last decade in ways that we never could have imagined. Communication is faster with the additions of Emails and Instant Messaging (IMs) to our lives; Research is simpler and more extensive, as boundless sources of information inhabit thousands and thousands of online Encyclopedias and Articles; and keeping up with Friends and Colleagues is very easy with the invention and seemingly
endless expansion of Social Networking sites like Facebook, Orkut, MySpace, Twitter etc.

A 4G system is expected to provide a comprehensive and secure all-IP (Internet Protocol) based mobile broadband solution to Laptop Computers, Wireless MODEMs, Smartphones, and other Mobile Devices. Facilities such as Ultra-Broadband Internet access, IP telephony, Gaming Services, and Streamed Multimedia may be provided to users.The word MAGIC also refers to 4G technology which stands for Mobile multimedia, Any-where, Global mobility solutions over, Integrated wireless and Customized services!

via techtie

What is the Difference Between GSM and CDMA?

2010-12-08T08:02:00.000-08:00

One of the basic things that differentiates GSM (based on TDMA) and CDMA is the way the carve up bandwidth.
Each bit of radio spectrum used by a handset has to be shared with other people in the area. It is more or less the same as multiplexing for normal data land lines.
The major difference between GSM/TDMA and CDMA is in the way they divide up those signals between multiple users.

GSM/TDMA uses a Time Division method. TDMA, in fact, stands for Time Division Multiple Access. Simply put, this means that each device on the local network is allocated a time slice where it "owns" the bandwidth, and it can send/receive its data.
So lets just pick a number and say there are 30 available time slices in a given cycle. Each phone would then get 1/30th of every cycle that it could send and receive data (aka, voice).
CDMA uses a different method, called Code Division Multiple Access. The specifics of how it breaks the cycle up are beyond me, but how it works out is that the phones only get a slice of the bandwidth cycle when they actually need one. So if you are not talking, and the other person is not talking, nothing is transmitted.
With GSM/TDMA, each phone is transmitting and receiving during its slices of the bandwidth cycle, whether it needs it or not.
Since most coversations are comprised largely of silence, the end result is that CDMA phones have to transmit less data. They don't have to send silence, like GSM/TDMA phones do.
This means a few things. More CDMA calls can be fit into a given amount of frequency spectrum (ie. it is more efficient for the network), less radiation is being created from the phone towards the user (you only get radiation when you are talking, basically), and battery power is conserved since the handset only transmits when it actually has something to send.
There are other differences, too, that I can't get into. For one, it is harder to implement a CDMA network. The tower placement is more difficult. Dealing with hills is more difficult than with GSM/TDMA. Things like that.
But in general, CDMA is vastly superior technology. Not surprising since Qualcomm's version of it (that which is used in CDMA and WCDMA phones) is newer technology, even if the basics were in use by the US military as far back as the 40s.
The important thing for me, though, is the SIM card. Had CDMA implemented the use of a SIM card (something it very easily could have done), then the North American market would be very different today, and there would be more CDMA networks in other countries. The SIM card allows people to easily switch phones, and that helps the market.

What is EDGE?

2010-12-03T04:09:00.000-08:00

Enhanced Data rates for GSM Evolution (EDGE) (also known as Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC), or Enhanced Data rates for Global Evolution) is a digital mobile phone backward-compatible extension of GSM. EDGE is considered a 3G radio technology and is part of ITU's 3G definition. EDGE was deployed on GSM networks beginning in 2003 — initially by Cingular (now AT&T) in the United States. technology that allows improved data transmission rates as a EDGE is standardized by 3GPP as part of the GSM family.

Through the introduction of sophisticated methods of coding and transmitting data, EDGE delivers higher bit-rates per radio channel, resulting in a threefold increase in capacity and performance compared with an ordinary GSM/GPRS connection.

EDGE can be used for any packet switched application, such as an Internet connection.

Evolved EDGE continues in Release 7 of the 3GPP standard providing reduced latency and more than doubled performance e.g. to complement High-Speed Packet Access (HSPA). Peak bit-rates of up to 1Mbit/s and typical bit-rates of 400kbit/s can be expected.

What is GPRS?

2010-12-01T01:34:00.000-08:00

Short for General Packet Radio Service, a standard for wireless communications which runs at speeds up to 115 kilobits per second, compared with current GSM (Global System for Mobile Communications) systems' 9.6 kilobits.

GPRS, which supports a wide range of bandwidths, is an efficient use of limited bandwidth and is particularly suited for sending and receiving small bursts of data, such as e-mail and Web browsing, as well as large volumes of data.
It is a new nonvoice value added service that allows information to be sent and received across a mobile telephone network. GPRS is NOT related to GPS (Global Positioning System), a similar acronym that is often used in mobile contexts. Allowing information to be transmitted more quickly, immediately and efficiently across the mobile network, GPRS may well be a relatively less costly mobile data service.
GPRS can provide instant connections subject to radio coverage. No dial-up modem connection is necessary.

Battery life could be increased up to 10 times

2010-11-30T01:45:00.000-08:00

United States annually spends about $ 4 billion on so-called “consumer-vampire” electricity that consumer electronics devices and appliances that consume a charge from the outlet even when closed.

These figures are however about to change if ambitious novel research of Professor Adrian Ionescu of the Polytechnic School in Lausanne, France will be realized.

The teacher is involved in a program to develop revolutionary technologies that use energy neglijabilade amount when in sleep mode.

Research uses nanotechnology to a “close” leakage.

“We want to share this research to producers to build the” holy grail “of electronics, a computer that uses negligible energy when the sleep-mode, which we call the zero-watt PC,” said Adrian Ionescu.

Mini Global GPS Tracker

2010-11-29T05:12:00.000-08:00

New Mini Global GPS Tracker for everyone (including yourself, your wife, your kids, your pet, your gold stash and everything else!). With compact design, convenient SMS functions and the latest in GPS tracking technology, it is the one all-purpose tracker for everyone needing to track their valuable asset and loved ones.
Easy to use: All you need is a working SIM card to insert into the unit, charge the battery, and you are ready
to go. With Quad-Band GSM connectivity, it works anywhere in the world. It even comes with a handy weatherproof bag to attach to your belt or backpack.
Tracks Everyone and Everything:

Outdoor sports and recreation: Hiking, biking, skiing, mountaineering, etc, whatever your sport is, take one with you and your loved ones will have peace of mind while knowing exactly where you are.
Surveillance: Secretly put it with a person, or his belonging, and you can monitoring where they are going. It comes with a magnetic back cover to attach itself to any steel object, consciously or “unconsciously”!
Children and Seniors Citizens: drop it in their pocket or backpack and you will never have to worry about them getting lost again. All you need to do is make a call to the Mini Global GPS Tracker and it will text back their exact location to you instantly!

Apart from these simple track-n-trace functions, it also has more advanced functions such as:
- SOS button: It sends “Help ME” and location of the tracker to all authorized numbers.
- Geo-fencing control – When the tracker moves in/out the preset scope, it will send an SMS alarm to the authorized phone number.
- GPRS: With a GPRS enabled SIM card, you can monitor realtime movement of the tracker with the supplied software on your computer.
Great product, versatile usage and our low factory wholesale price make this the first “must have” GPS Gadget of 2010. This cool new gadget is in stock now for single or bulk stock purchases. Whether you are just buying one for yourself or 10 to resell on eBay, with this price you cannot go wrong! Don’t wait, click “add to cart” right now, and we will express ship it out to you tomorrow.
At Glance…

Compact and Easy to use
Global coverage with quad-band GSM frequency
Multiple function through SMS
SOS Function
Silent listener in Monitoring Mode
GPRS and Internet application

via [unlockedcheapmobilephones]

What is 3G Technology?

2010-11-27T05:06:00.000-08:00

If you want augmented bandwidth, multiple mobile applications and clarity of digital signals, then 3G (Thrid Generation Technology) is your gateway. GSM technology was able to transfer circuit switched data over the network. The use of 3G technology is also able to transmit packet switch data efficiently at better and increased bandwidth. 3G mobile technologies proffers more advanced services to mobile users. It can help many multimedia services to function. The spectral efficiency of 3G technology is better than 2G technologies. Spectral efficiency is the measurement of rate of information transfer over any communication system. 3G is also known as IMT-2000.

GSM Call Routing

2010-11-23T14:11:00.000-08:00

Call Originating from MS.

Call Termination to MS.

GSM Operations

2010-11-13T07:09:00.000-08:00

The operation of the GSM system can be understood by studying the sequence of events that takes place when a call is initiated from the Mobile Station.

Call from Mobile Phone to PSTN:

When a mobile subscriber makes a call to a PSTN telephone subscriber, the following sequence of events takes place:

The MSC/VLR receives the message of a call request.
The MSC/VLR checks if the mobile station is authorized to access the network. If so, the mobile station is activated. If the mobile station is not authorized, service will be denied.
MSC/VLR analyzes the number and initiates a call setup with the PSTN.
MSC/VLR asks the corresponding BSC to allocate a traffic channel (a radio channel and a time slot).
The BSC allocates the traffic channel and passes the information to the mobile station.
The called party answers the call and the conversation takes place.
The mobile station keeps on taking measurements of the radio channels in the present cell and neighboring cells and passes the information to the BSC. The BSC decides if handover is required, if so, a new traffic channel is allocated to the mobile station and the handover is performed. If handover is not required, the mobile station continues to transmit in the same frequency.

Call from PSTN to Mobile Phone:

When a PSTN subscriber calls a mobile station, the sequence of events is as follows:

The Gateway MSC receives the call and queries the HLR for the information needed to route the call to the serving MSC/VLR.
The GMSC routes the call to the MSC/VLR.
The MSC checks the VLR for the location area of the MS.
The MSC contacts the MS via the BSC through a broadcast message, that is, through a paging request.
The MS responds to the page request.
The BSC allocates a traffic channel and sends a message to the MS to tune to the channel. The MS generates a ringing signal and, after the subscriber answers, the speech connection is established.
Handover, if required, takes place, as discussed in the earlier case.

GSM Specifications

2010-11-12T02:56:00.001-08:00

GSM 900

Mobile to BTS (uplink): 890-915 Mhz.
BTS to Mobile(downlink): 935-960 Mhz.
Bandwidth : 2* 25 Mhz.
GSM 1800
Mobile to BTS (uplink): 1710-1785 Mhz.
BTS to Mobile(downlink): 1805-1880 Mhz.
Bandwidth : 2* 75 Mhz.

* Carrier Separation : 200 Khz.
* Duplex Distance : 45 Mhz.
* No. of RF carriers : 124.
* Access Method : TDMA/FDD.
* Modulation Method : GMSK.
* Modulation data rate : 270.833 Kbps.

Microwave Engineering Considerations

2010-11-11T14:25:00.000-08:00

Free Space & Atmospheric Attenuation:

Free space & atmospheric attenuation is defined by the loss the signal undergoes traveling through the atmosphere.
Changes in air density and absorption by atmospheric particles.
Reflections:
Reflections can occur as the microwave signal traverses a body of water or fog bank; cause multipath conditions.
Diffraction:
Diffraction is the result of variations in the terrain the signal crosses.
Rain Attenuation:
Raindrop absorption or scattering of the microwave signal can cause signal loss in transmissions.
Skin Affect:
Skin Affect is the concept that high frequency energy travels only on the outside skin of a conductor and does not penetrate into it any great distance.
Skin Affect determines the properties of microwave signals.

Microwave Impairments

2010-11-11T14:21:00.000-08:00

Equipment, antenna, and waveguide failures.
Fading and distortion from multi path reflections.
Absorption from rain, fog, and other atmospheric conditions.
Interference from other frequencies.

What is XPIC?

2010-11-10T14:40:00.000-08:00

Cross Polarization Interference Cancellation (XPIC).

Microwave having XPIC capabilities effectively double the potential capacity of a Microwave Path.
It allows the assignment of the same frequency to both the vertical & horizontal Polarization on a Path.

Where available frequencies are limited then it is possible to assign the same frequency twice on the same path using both Polarizations.
Using standard Microwave equipment from any of the major manufacturers, if a full block of eight frequencies were available for a 6 GHz Lower band path then eight frequencies could be assigned in each direction on the path, four per polarization.
Using equipment with XPIC capability, sixteen frequencies may be assigned each way on the same path (eight per polarization).

Types of Microwave Links

2010-11-08T10:30:00.000-08:00

Hot Standby:

A method of redundancy in which the primary and secondary (i.e., backup) systems run simultaneously. The data is mirrored to the secondary server in real time so that both systems contain identical information.

Frequency Diversity:

Frequency Diversity uses separate frequencies (dual transmit and receive systems).

It monitors primary for fail over and switches to standby.

Interference usually affects only one range of frequencies.

Not allowed in non-carrier applications because of spectrum scarcity.

Space Diversity:

Space Diversity protects against multi-path fading by automatic switch over to another antenna place below the primary antenna.This is done at the BER failure point or signal strength attenuation point to the secondary antenna that is receiving the transmitted signal at a stronger power rating.

Line of Sight (LOS)

2010-11-07T02:27:00.000-08:00

Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted, refracted, reflected, or absorbed by atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles. Especially radio signals, like all electromagnetic radiation including light emissions, travel in straight lines. At low frequencies (below approximately 2 MHz or so) these signals travel as ground waves,
which follow the Earth's curvature due to diffraction with the layers of atmosphere. This enables AM radio signals in low-noise environments to be received well after the transmitting antenna has dropped below the horizon. Additionally, frequencies between approximately 1 and 30 MHz, can be reflected by the F1/F2 Layer, thus giving radio transmissions in this range a potentially global reach (see shortwave radio), again along multiply deflected straight lines. The effects of multiple diffraction or reflection lead to macroscopically "quasi-curved paths".
However, at higher frequencies and in lower levels of the atmosphere, neither of these effects apply. Thus any obstruction between the transmitting antenna and the receiving antenna will block the signal, just like the light that the eye may sense. Therefore, since the ability to visually see a transmitting antenna (disregarding the limitations of the eye's resolution) roughly corresponds to the ability to receive a radio signal from it, the propagation characteristic of high-frequency radio is called "line-of-sight". The farthest possible point of propagation is referred to as the "radio horizon".
In practice, the propagation characteristics of these radio waves vary substantially depending on the exact frequency and the strength of the transmitted signal (a function of both the transmitter and the antenna characteristics). Broadcast FM radio, at comparatively low frequencies of around 100 MHz, easily propagates through buildings and forests.

[via wikipedia]

Repeaters

2010-11-06T16:54:00.000-07:00

A microwave repeater with antenna isolation comprises a first receiving antenna for receiving an input signal from a distant source.
An amplifier section for amplifying and modulating the input signal to produce an output signal.
A transmitting antenna coupled to the amplifier section and an isolation control means including a second receiving antenna for isolating the first receiving antenna from the transmitting antenna.
In one preferred embodiment, the second receiving antenna is aligned so as to match the gain and phase from the transmitting antenna to the first receiving antenna.
The isolation control means comprises a phase shifter coupled to the second receiving antenna; and a power combiner having inputs coupled to the first receiving antenna and the phase shifter and an output coupled to the amplifier section.
The power combiner receives the input signal from the first receiving antenna and a 1 SO phased shifted signal from the phase shifter.

Synchronous Digital Hierarchy (SDH)

2010-11-05T11:19:00.000-07:00

Management is very inflexible in PDH, So SDH was developed.
Synchronous Digital Hierarchy (SDH) originates from Synchronous Optical Network (SONET) in the US.
It includes capabilities for bandwidth on demand and is also made up of multiples of E1.
STM-1 (155Mb/s) is 63 x E1, STM-4 (622Mb/s) is 4 x STM-1 and STM-16 (2.5Gb/s) is 4 x STM-4.
The benefits of SDH are:
1) Different interfaces or different bandwidths can connect (G708, G781).
2) Network topologies are more flexible.
3) There is flexibility for growth.
4) The optical interface is standard (G957).
5) Network Management is easier to perform (G774 and G784).

Plesiochronous Digital Hierarchy (PDH)

2010-11-04T23:33:00.000-07:00

The Plesiochronous Digital Hierarchy (PDH) is a technology used in telecommunication networks to transport large quantities of data over digital transport equipment such as fiber optic and microwave radio systems.
The term plesiochronous is derived from Greek plesio, meaning near, and chronos, time, and refers to the fact that PDH networks run in a state where different parts of the network are nearly, but not quite perfectly, synchronized.

PDH is typically being replaced by Synchronous Digital Hierarchy (SDH) or Synchronous optical networking (SONET) equipment in most telecommunications networks.
PDH allows transmission of data streams that are nominally running at the same rate, but allowing some variation on the speed around a nominal rate.
By analogy, any two watches are nominally running at the same rate, clocking up 60 seconds every minute.
However, there is no link between watches to guarantee they run at exactly the same rate, and it is highly likely that one is running slightly faster than the other.

What is E1

2010-11-04T04:24:00.000-07:00

An E1 link operates over two separate sets of wires, usually twisted pair cable. A nominal 3 Volt peak signal is encoded with pulses using a method that avoids long periods without polarity changes. The line data rate is 2.048 Mbit/s (full duplex, i.e. 2.048 Mbit/s downstream and 2.048 Mbit/s upstream) which is split into 32 time slots, each being allocated 8 bits in turn. Thus each time slot sends and receives an 8-bit sample 8000 times per second (8 x 8000 x 32 = 2,048,000). This is ideal for voice telephone calls where the voice is sampled into an 8 bit number at that data rate and reconstructed at the other end. The time slots are numbered from 0 to 31.

One time slot (TS0) is reserved for framing purposes, and alternately transmits a fixed pattern. This allows the receiver to lock onto the start of each frame and match up each channel in turn. The standards allow for a full Cyclic Redundancy Check to be performed across all bits transmitted in each frame, to detect if the circuit is losing bits (information), but this is not always used.
One time slot (TS16) is often reserved for signaling purposes, to control call setup and tear down according to one of several standard telecommunications protocols. This includes Channel Associated Signaling (CAS) where a set of bits is used to replicate opening and closing the circuit (as if picking up the telephone receiver and pulsing digits on a rotary phone), or using tone signaling which is passed through on the voice circuits themselves. More recent systems used Common Channel Signaling (CCS) such as ISDN or Signaling System 7 (SS7) which send short encoded messages with more information about the call including caller ID, type of transmission required etc. ISDN is often used between the local telephone exchange and business premises, whilst SS7 is almost exclusively used between exchanges and operators. SS7 can handle up to 4096 circuits per signaling channel[citation needed], thus allowing slightly more efficient use of the overall transmission bandwidth (for example: uses 31 voice channels on an E1).
Unlike the earlier T-carrier systems developed in North America, all 8 bits of each sample are available for each call. This allows the E1 systems to be used equally well for circuit switch data calls, without risking the loss of any information.
While the original CEPT standard G.703 specifies several options for the physical transmission, almost exclusively HDB3 format is used.

E-carrier

2010-11-03T23:20:00.000-07:00

In digital telecommunications, where a single physical wire pair can be used to carry many simultaneous voice conversations, worldwide standards have been created and deployed.

The European Conference of Postal and Telecommunications Administrations (CEPT) originally standardized the E-carrier system, which revised and improved the earlier American T-carrier technology, and this has now been adopted by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T).

This is now widely used in almost all countries outside the USA, Canada and Japan.
The E-carrier standards form part of the Plesiochronous Digital Hierarchy (PDH) where groups of E1 circuits may be bundled onto higher capacity E3 links between telephone exchanges or countries.
This allows a network operator to provide a private end-to-end E1 circuit between customers in different countries that share single high capacity links in between.
In practice, only E1 (30 circuit) and E3 (480 circuit) versions are used. Physically E1 is transmitted as 32 timeslots and E3 512 timeslots, but one is used for framing and typically one allocated for signalling call setup and tear down.
Unlike Internet data services, E-carrier systems permanently allocate capacity for a voice call for its entire duration.
This ensures high call quality because the transmission arrives with the same short delay (Latency) and capacity at all times.
E1 circuits are very common in most telephone exchanges and are used to connect to medium and large companies, to remote exchanges and in many cases between exchanges.
E3 lines are used between exchanges, operators and/or countries, and have a transmission speed of 34.368 Mbit/s.

Microwave antenna alignment (Cont..)

2010-11-03T03:22:00.000-07:00

Simplifying the Process:

We have laid the groundwork for establishing the Path Align-R™ test set as a viable and effective solution for the path alignment process. We will now describe how this process of aligning the microwave link is greatly simplified.

1. Review the Engineering Profile to determine the expected RSL (received signal level, or path loss)for the link under test (this should include the free space path loss and the gain of the antennas). Note that the loss exhibited by the installed cable or waveguide transmission lines are not included in this value because the Path Align-R™ test sets are connected directly to the antennas with a short coax cable with minimal insertion loss to impact the test.

2. Both tower climbers (technicians) should go over their check lists, prior to climbing the tower, to assure that, included with the Path Align-R™, they have:

• A charged battery installed (possibly a spare if you are planning to be up for over 4–5 hours);
• The proper waveguide-to-coax adapter for the antenna;
• A coax cable (SMA to coax connector on the coax-to-waveguide adapter);
• The supplied headset; and,
• A cabinetry and a nylon runner, strap, or lanyard of appropriate length to attach the back-pack's'D' ring to the tower.

3. Set one Path Align-R™ unit to ‘Master’ and the other Path Align-R™ unit to ‘Slave’ (it doesn’t matter which is which, as long as they’re different).

4. Using the front panel thumb-wheel switches, select the proper link frequency (Note: both units must be set to the same frequency, e.g. 6.2 GHz).

5. After reaching the antenna, check that the antenna polarization is properly setup.

6. Locate each Align-R™ unit near the back of the antenna, with its weather-resistant instrument backpack’s‘D’ ring attached to the tower structure using a carabiner and a nylon runner, strap, or lanyard.

7. Attach the coax-to-waveguide adapter at the back of the antenna’s waveguide flange.

8. Connect the coax cable from the appropriate output connector on the Path Align-R™ to the adapter.

9. Connect the headset to the Path Align-R™.

10. Turn the Power Switch ON. An LED will indicate which output connector is active (make sure the cable is connected to that connector) and begin talking. Typically, the antennas can be off alignment by as much as several beam widths and the voice channel will still operate.

11. While one technician simply observes the reading of the path loss meter at his/her site, the other site commences Azimuth (horizontal) adjustment. As the voice channel is full duplex (FM), each technician can communicate with the other during the alignment process. Check for both side lobes as well as the main lobe response to ensure that the antenna is being aligned to the main lobe and no tone of the side lobes. The Path Align-R™ test sets have enough sensitivity (-100 dB) and update speed(300 ms) to quickly check for side lobe and main lobe response.

12. Once Azimuth has been optimized, the Elevation adjustment is performed.

13. When steps 11 & 12 have been completed at the first site, the technicians switch roles and steps 11 &12 are repeated by the other technician at the second site.

14. Once step 13 is completed, for both Azimuth and Elevation, the link is aligned. As a record, note the final path loss value displayed on the meter.

Summary:

The difficulties of scheduling an antenna alignment test with the radios can cause significant delays, as described earlier. Furthermore, traditional test methods can produce significant costs in mobilization,deployment and testing of the antenna system. If the transmission lines (waveguides, etc.) connecting the antenna to the radio were to have a problem, the test is in jeopardy until they are corrected. If the path under test is questionable (due to site choice, obstructions, etc.), the Path Align-R™ can step right in with minimal effort to verify if there are any problems. Using the Path Align-R™ test set, the overhead associated with offering path alignment services (cost of equipment, level of expertise required, and training time) has been greatly reduced. Offering path alignment services with the Path Align-R™ translates to providing more revenue opportunities for your company.

Microwave antenna alignment (Cont)

2010-11-03T03:18:00.000-07:00

Alternative Methods:

Traditionally, the radios that will be placed at each site are used to complete the task of optimizing the path.However, there are several reasons for not utilizing the radios to complete the process. The radios may not be available at the time the test has been scheduled or their reliability may be questionable, thus alternate methods are needed. Another possible reason the radios might not be able to be used is that the FCC permit shave not been granted, but the contractor needs to complete the path test on time to meet the customer’s requirements, or ahead of expected turbulent weather. In addition, if the anticipated path is questionable, a quick, cost effective, reliable method is needed to test the link, prior to the significant investment of constructing towers, purchasing radios and other expensive equipment and hardware, etc.

Alternative test instrumentation must be utilized, in lieu of the radios, whenever the previously mentioned circumstances arise. Scheduling of the path alignment test and installation of the associated hardware (cables,waveguide, antenna, etc.) can be facilitated to reduce excess mobilization costs. Some of the most widely used equipment for this application are signal generators (used as the transmitter) and spectrum analyzers(used as the receiver). The signal generator should be a broadband, synthesized device (phase locked to a reference clock) with accurate output power, equal to or greater than 0 dBm. The spectrum analyzer should betunable, and have at least –100 dBm of sensitivity at the frequency band of interest. Signal acquisition speedof the receiver is essential to quickly spot subtle changes in antenna response or to support investigation of problem paths. Most importantly, ease of use is vital in order to reduce the training costs of test technicians.Much of the test equipment used in this alternate method of path alignment tends to be expensive and complicated.

Application Specific Solution:

Recent test instrumentation has brought on feature rich, expensive systems that shoot for the stars in offeringthe latest and greatest in technology. However, these systems are mostly not fit, nor are they practical, forspecific applications such as antenna path alignment. The most successful new instrumentation in the industryhas been equipment that is application specific, portable, battery powered, and easy to use, withoutcompromising performance. The Path Align-R™, is a new addition to this practical, application specific category.It is specifically designed for use as a microwave path alignment test set. Among its many features andfunctions, eight specific traits fit those identified as important to microwave antenna path alignment.

1. Portable - Each of the two units in the Path Align-R™ Test Set weighs only 7 pounds, fully loaded, andis 3.5” x 8.375” x 13.1” (HxWxD) in size. This significantly reduces the shipping costs and logisticsof transporting test equipment to and from the site.

2. Battery Powered – A rechargeable lead acid battery is fitted to provide four to five hours of operation.Not only is this ideal for field use but each unit can easily be taken up the tower, in its weatherresistantinstrument back-pack, and attached directly behind the antenna using a carabiner and a nylonrunner, strap, or lanyard.

3. Ease of Use – A pair of units (sold as a ‘set’), one at each site, reads out the path loss, identically, atboth ends of the link. Simply turn them on, connect the output to the antenna using the supplied cable,tune the frequency, connect the headset, and you are ready to test. Rarely has an instrument been soeasy to use without compromising on performance.

4. Performance – A Path Align-R™ test set provides 100 dB of effective dynamic range. This is the resultof the 100 dBm sensitivity of the receiver and 0 dBm output power of the transmitter. Four bands(1.8–2.5 GHz, 5.8–6.6 GHz, 11–12 GHz and 18.1–19.4 GHz) are provided in the standard Test Set.The specific operating frequency can be tuned by the operator within these band limits, using thethumbwheel switches, to a resolution of 1 MHz. An antenna system whose link frequency is designed outside the frequency band edge of the Path Align-R™ (e.g. 6.8 GHz) can still have its path alignmentcorrectly adjusted, as long as the antenna system (antenna, waveguide, etc.) can operate at both thelink frequency (6.8 GHz) and a nearby frequency covered by the Path Align-R™ (e.g. 6.6 GHz).

5. Speed - An LCD readout of direct path loss, with a 0.1 dB resolution, automatically updates itsreading every 300 milliseconds, and can quickly find subtle changes to the antenna response, thusallowing for small adjustments to antenna azimuth or elevation for optimum signal transfer.

6. Voice Channel – Communication between sites, and from radio room to tower top, is significantlyimproved, with a full duplex voice channel. Each tower technician can speak to the other through theincluded headset, without having to key a radio. Voice communication is enabled immediately aftersetup and activation. The antennas do not even have to be fully aligned for the voice channel to work.

7. Accurate – The Path Align-R™’s output is a synthesized source that provides a very accurate and stablesignal. When compared to a synthesized source (HP 8360) and a fully featured spectrum analyzer (HP8594E), the Path Align-R™ test set measures path loss within 1.0 dB of each other.

8. Cost Effective – The Path Align-R™ test set is priced far below that of a synthesized source and spectrumanalyzer combination. However, price is not the only savings achieved with the use of the test set.The cost of communicating between sites can become quite expensive when using cellular technology(about $300 per event when considering long distance, roaming, and calling time charges that aretypically the case in a remote microwave test). The use of two technicians operating the radios, andtwo tower climbers working behind the antennas, can potentially be reduced to three; with thesupervisor level on the ground floor and two tower climbers. The transportation costs of shipping thetest sets to job sites from the central office can significantly reduce company expenses.

It is apparent that the Path Align-R™ test set is well featured to offer impressive results in accomplishing the goalof an optimum solution for the microwave path alignment test process.

Microwave antenna alignment

2010-11-02T14:20:00.000-07:00

Simplifying the Path Alignment of Microwave Communication Systems:
Wherever microwave links exist, the path between antennas has always required accurate antenna alignment. This process requires highly trained tower crews to physically align the antennas as well as ground technicians and sophisticated, expensive, and complex test equipment to monitor the results. The process of optimizing the transmission path of microwave communication systems is about to undergo a significant development in process, simplification and cost benefit without compromising performance or accuracy. The process can now be accomplished with the use of the Path Align-R™ , Models 2200–2241, µ wave Antenna Path Alignment Test Sets from Pendulum Instruments, formally XL Microwave. Tower installation crews can now perform the entire alignment process themselves, up the tower, at the antenna,
without the need of additional ground technicians, equipment, or indeed, even the waveguides or radios installed.

The Traditional Process:

The traditional process, more typically described as “microwave path alignment,” requires the use of a transmitter and a receiver located at each end of the microwave link. The transmitter generates the signal that passes through the transmission line to the antenna, which radiates the signal over the free space link. The signal propagates towards the other end of the path and is received by the antenna, forwarding the signal through the transmission line to the receiver, connecting the two sites. The receiver processes the signal,producing information on its value relative to the amount that was originally generated at the transmitting end. If the antennas are optimally pointed to each other (aligned), the largest concentration of signal (main beam) is emitted and received, reducing the free space attenuation of the signal. Provided the transmission lines do not lose too much of the signal between the antennas and the radios, maximum signal transfer is achieved. If the antennas are not optimally aligned, then signal transfer is degraded and received dynamic range is lost.

There are several steps involved in the traditional preparation and process of aligning the antennas of a microwave communication system. These steps may include making sure the cable or waveguide transmission line was properly installed, with minimal RF reflection of the microwave signal; that each antenna polarization is properly setup; and that the transmitter output power is calibrated. A voice communication link between the personnel inside the radio room of each site and the tower technicians,located at each antenna, needs to be established using two way mobile radios or cellular phones. Some spread spectrum radios have an order wire over which to communicate, however, communication to each of the tower technicians will still need to be completed. The engineering profile is reviewed to determine the expected RSL (receive signal level) for the path under test and any adjustments for output power are applied.Once this setup is complete, the tower technicians are instructed to commence the adjustment of the azimuth alignment (bearing) of the antennas, one at a time. The antennas are panned over their azimuth profile and readings of the receiver signal output power are taken. Careful observation of the output power reading is necessary to distinguish the antenna side-lobe to main-lobe response. Once the maximum signal is achieved,the antennas are aligned for elevation optimization. It is evident that the communication between site to site and tower technician to receiver technician needs to be continuous and clear to ensure that the antennas optimum alignment setting is achieved.

Microwave Transmission System

2010-11-02T01:38:00.001-07:00

Microwave Spectrum:
Range is approximately 1 GHz to 40 GHz
Total of all usable frequencies under 1 GHz gives a reference on the capacity of in the microwave range.
Components of a Microwave System:
1) Digital Modem.
2) Radio Frequency (RF) Unit.
3) Antenna.
Digital Modem:
The digital modem modulates the information signal.
(intermediate frequency or IF)
RF Unit:
IF is fed to the RF unit which is mounted as close physically to the antenna as possible.
(direct connect is optimal)
Waveguides:
Waveguides are hollow channels of low-loss material used to direct the signal from the RF unit to the antenna.

Satellite Network & Capacity Allocation

2010-11-01T01:33:00.000-07:00

Frequency division multiple access (FDMA)

Time division multiple access (TDMA)

Code division multiple access (CDMA)