I am conducting a survey to evaluate ComReg’s Wireless Test and Trial License Scheme. This is to assess the extent to which the scheme is serving the people for whom it was intended, as well as the process involved in operation and delivery of the scheme.

The goal of this evaluation is to enhance Ireland’s position as an innovator in radio spectrum usage, by seeking out ideas that will contribute to promoting Ireland as a knowledge economy and push it to the forefront of telecommunications research. To help achieve this, I would like to collect in-depth information about how the scheme is functioning and pinpoint areas where improvements might be made.

The results from the survey will form part of my thesis currently entitled “Radio Spectrum Innovation in Ireland”

If you have availed of ComReg’s Wireless Test or Trial Licence in Ireland, please feel free to fill out the survey here

This questionnaire is COMPLETELY CONFIDENTIAL, anonymous and all information provided will be treated in the strictest confidence. The questionnaire will come directly back to the research team at CTVR and any data presented in the future will only be in a format where the individual or company cannot be identified.

If you have any other feedback on radio spectrum innovation either in Ireland or in other countries (e.g. FCC’s Special Temporary Authority (STA) licensing scheme, Ofcom’s Innovation Licence) and would like to contribute to the study please contact me by email: rashield [at] tcd.ie. I would be most interested to hear your opinions.

Why all the fuss?

For those not familiar with the concept of ‘white spaces’, this is the term used to describe the unoccupied frequencies in a band. The term ‘TV whitespace’ means the occupied frequencies or slots in the 54-698MHz frequency range used for U.S. TV channels 2 to 51.

The upper end of this frequency range is of particular interest though because:

• The antenna sizes needed to operate in this band are shorter than say, at 60MHz.
• There’s enough available bandwidth between occupied channels to roll out useful broadband type services and create new revenue streams.
• Signals in this frequency range can penetrate buildings and operate over non line-of-sight ranges

In November, 2008, the FCC gave the ok for unlicenced use of the U.S. TV bands subject to a set of rules in the second report and order and memoradam opinion and order document.

These rules included the following requirement for a white space database and a request for a third-party interested in creating and maintaining the database:

All devices, except personal/portable devices operating in client mode, must include a
geolocation capability and provisions to access over the Internet a database of protected radio
services and the locations and channels that may be used by the unlicensed devices at each
location. The unlicensed devices must first access the database to obtain a list of the
permitted channels before operating.

A white spaces database is needed is because the TV bands are used differently across the U.S (and indeed, Ireland and many other countries). For example, occupied TV channels in Virginia may not be in use in California. To minimise the possibility of interference to TV receivers and the unlicenced services, companies will need to find out where the available channels are in the area where the new services are to be deployed.

The creation of this database will not be straightforward. Currently, there is no common database standard for representing how spectrum is being used. Unlicenced devices must check the database before operating, which presents a big challenge of how to build in this requirement in rural deployments. A centralised database is a weakness and a distributed database requires a means of replication and updating.

Tom and I carried out the first look at how TV spectrum is used along a route that brought us from Colorado, through Chicago, and onward to Washington DC. We created a monitoring toolset and database for collecting the spectrum-usage information that allows us to query and visualise the measurement database using Google Maps. After visiting a number of groups and companies along the route, including Illinois Institute of Technology, Motorola, and Shared Spectrum, we discovered that each group has their own database structure (including us). The need for a common database standard and means of extracting information from it was raised by us in our IEEE DySPAN 2008 plenary talk and in our 2008 SDR Forum conference presentation in Washington DC.

To make this work, Google, Microsoft, Motorola, Dell, Comsearch, NeuStar and HP are going to need an independent group of people to coordinate with all the interested parties and ensure the needs of each group is represented in a common white space database standard. As we found from our spectrum measurements roadtrip, information from the FCC license database needs to be supplemented with actual spectrum measurements. This task is immense therefore the database should allow for submitted updates from trusted third parties e.g. university research groups conducting measurement programmes.

Talk to us, I may know the right people who can help.

I posted the slides from the first part of Bob’s presentation here and have received the slides from the second half of his talk (well, we all had a hectic few weeks since then). This part of his talk focused on his long and exciting involvement with amateur radio and amateur satellites through his leadership in the Radio Amateur Satellite Corporation AMSAT.

Well, now you can download these slides and learn some more about his involvement as co-founder of the open source DttSP project, which is used with Flex Radio, and on co-designing AMSAT’s new satellite.

Download the slides as a zip archive [3.9MB]

A further presentation from Tom Clark K3IO regarding this satellite, the Geostationary Eagle, is also included in the zip archive. Tom prepared these slides for the 2008 AMSAT Space Symposium in Atlanta, GA, which was held during the last week of October. This is a goldmine of information for anyone interested in satellites.

Spectrogram showing Shared Spectrum Company's transmissions and a frequency-agile narrowband FM interference source.

A spectrogram displays frequency usage over time. In this case, the colours range from blue to red; blue indicates little or no activity towards red, which would indicate a very strong received signal.

This spectrogram, captured using an Anritsu MS2721B analyser, shows Shared Spectrum Company’s nodes operating in a ‘detect and avoid’ mode and sucessfully avoiding channels occupied by the narrowband source. When the frequency-agile narrowband interferer, controlled by me, moved onto the channel used by SSC, SSC’s OFDM transmitting node switched to an unoccupied channel.

Karl and Filip from Shared Spectrum Company were initially unaware of this demonstration so there was no preparation beforehand on their part other than running their demonstration as normal. SSC’s application in this case involved video streaming. This continued to operate just fine even though the nodes were changing channels to avoid the intentional interference.

To make things more interesting, the TX power of the narrowband interferer was reduced until it just about reached the detection threshold used by SSC’s nodes. As people moved between the interferer and SSC’s location, the interferer alternated between the detection and non-detection region over at SSC’s area. In this case, the TX power of the interferer was -18dBm using a suboptimal antenna, ~15 feet between the two locations, and obstructed by a pillar and members of the public in the room.

This was a 25kHz bandwidth example. Wireless microphones typically use approximately 200kHz of bandwidth. It is important to note also that wireless microphones certainly would not be roaming around in the spectrum segment in this manner either. The combination of wider bandwidths and static frequency usage for long periods of time makes them even easier to detect and avoid.

This was a dynamic spectrum access system operating under the shadow of several high power TV transmitters located a couple of blocks away, and no, the sky didn’t fall in.

This is actually two demonstrations in one:

1. Our reconfigurable radio plaform called Implementing Radio in Software (IRIS) is being used for the cylcostationary signatures-based OFDM transceiver chain.
2. The IBM Cell broadband engine in the form of a Playstation 3 is being used for the cyclostationary feature analysis signal processing and Matlab is being used purely for the visualisation.

Following our demonstrations at DySPAN in Chicago, Keith, Hicham and I spent a week doing some fine tuning in preparation for the SDR Forum Tech Conference in Washington. Here I am in the “lab”, hard at work…

The spectrum measurements have been converted into a Google map representation showing our route and the intensity of the spectral activity in the 698MHz-806MHz frequency range; the “700MHz band”. Click on the image below to go to this Google Maps page.

This webpage may be somewhat slow to render. The chosen zoom level dictates the number of points displayed on the map. At the highest zoom level, all points will be displayed.

The 24,000 measurements covering this route, and used for the Google map page have also been made freely available in the form of a MySQL database table. This table can be imported into a database and easily queried using code of your own chosing e.g. Matlab, PHP, Java, etc.

You can download the MySQL database as a zip file here [15.3MB]

The format is as follows:

Notes:

1. ID corresponds to the measurement identity
2. Latitude and Longitude were taken from the on-board GPS in the Anritsu Spectrum Master handheld. Note: we experienced occasional GPS drop-outs.
3. Maximum Power corresponds to the maximum power that was mseasured across the entire 700MHz band.
4. Highest Power Frequency corresponds to the frequency of the highest power signal measured in the 700MHz band.
5. Traces: 551 values specified in dBm representing the power spectral density measured across the entire 698MHz-806MHz range. Each bin corresponds to a frequency resolution of 196kHz. Each measurement comprises an averaged measurement over four traces. The sweep time for each trace was approximately 220ms-300ms therefore each measurement corresponds to approximately one second of spectral activity.

If you find this resource useful, feedback would be most welcome!