Wednesday 31 October, 2007, 05:35 - Spectrum ManagementSpectrum management has traditionally been about the use of technical criteria developed through long-winded compatibility studies to determine what can (and can not) be allowed access without causing harmful interference to other users. Increasingly, however, regulators are using forward looking market-based spectrum management techniques such as administrative incentive pricing, auctions and comparative selection (beauty parades), trading and property rights in order to be able to adapt to the rapidly changing and liberalised markets which use the radio spectrum.
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Mssrs. Cave, Webb and Doyle have documented the current state of play in these forward looking techniques (often lumped together under the banner of 'Spectrum Pricing') in their new publication Essentials of Modern Spectrum Management. They describe developments in both the technical and economic tools used to manage the radio spectrum as well as looking at other related issues such as the need for and benefits of spectrum commons. There's also a good discussion of why Ultra Wide Band (UWB) has made many regulators reflect on whether existing spectrum management techniques are appropriate or have sufficient longevity and flexibility to cope with such new approaches to spectrum use.
The book uses a number of international case studies together with the practical experience of the authors to illustrate many of the concepts involved. Whilst the book would not be suitable for someone wishing to gain an overall understanding of spectrum management, it provides a useful and inciteful reference on these more advanced techniques and would suit anyone who has experience of spectrum regulation and who wanted to understand better how such regulation is being transformed to encourage more efficient spectrum use. Certainly a book that should be on the shelves of any self-respecting modern spectrum manager!
Saturday 22 September, 2007, 07:08 - Spectrum ManagementYears ago I used to know the frequency¹ for the downlink of Capital Radio in London's 'Flying Eye', the aircraft used to scout about for travel blackspots. It was a useful frequency to have as there was no better place to get the latest travel news. I also remembered that there was an uplink from the studio on around 455 MHz too.
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One quiet afternoon I thought I'd have a tune around to see whether or not the old up and downlink frequencies were still active. Listening around 467 MHz, there seemed to be no sign of the downlink (though being around 25 miles outside of central London and with a downlink power of less than a Watt, this wasn't perhaps, that surprising). The uplink, however, is still active on 455.075 MHz.
What was rather odd, however, was to hear dozens of Imam's calling their congregation to prayer on frequencies just below this at around 454.5 MHz. Was this some freak long-distance propagation carrying signals from arabic speaking countries in North Africa or the Middle East? Was it a freak spurious response on my receiver, allowing reception of, perhaps, satellite radio? Were these the link frequencies to the numerous 'Radio Ramadan' stations that appear on the FM band during the festival?
No. It was none of these. Instead it seems that there is a radio service, established in around 2000, called 'On-Site Religious Observation' or OSRO. This a a licensed radio service which allows any religious body to use the old Wide Area Paging (WAP) channels to deliver voice communications to pagers. What a good use for these otherwise quiet channels: to allow Muslim's their right to hear the Imam's call without the need to build noisy minarets, just build unsightly radio towers instead!
A bit more digging revealed that there are all sorts of interesting frequencies in the range 454 to 458 MHz as listed below:
454.0125 to 454.8375 MHz OSRO/WAP
454.84375 to 454.98125 MHz Cab Secure Radio (CSR)²
454.9875 to 455.475 MHz Programme Making and Special Events (PMSE)³
455.475 to 455.850 MHz Airport Security and Operations (455.5125, 455.5375, 455.5875, 455.625, 455.6625, 455.675 and 455.6875 MHz also used for CSR)
455.850 to 456.000 MHz Fire Service
456.000 to 456.9875 MHz Private Mobile Radio (PMR) Simplex and Duplex use
457.000 to 457.250 MHz Fire Service
457.250 to 457.475 MHz PMSE
457.475 to 457.500 MHz Fire Service
457.500 to 458.500 MHz Scanning Telemetry (457.525, 455.5375, 457.550, 455.5625 and 457.575 MHz also used for On-Board Ship Communications)
With Ofcom considering reconsidering its previously aborted plans to re-align the band it will be interesting to see where these services end up. And in the meantime if anyone has the frequency used for the Flying Eye's downlink, do share it with us!
¹467.6625 MHz if I remember correctly.
²Radio system used by Network Rail in areas where rail services have no conductor and thus the driver can not leave the cab to commnunicate with the signaller.
³Links and talkback for radio stations, TV studios, film sets, theatres and so on. Could be used by production team at a Kylie Minogue concert for example...
Thursday 5 October, 2006, 11:39 - Spectrum ManagementSomething that's always been a nuisance is that the International Telecommunications Union (ITU) has made it's frequency allocation tables (i.e. the table which shows which frequencies are allocated to which services in which countries) something that has to be paid for if you want a full copy. The 'ITU Radio Regulations' is a large set of documents that describe radio usage and the heart of it is a set of 3 regional tables that allocate frequencies to specific uses and currently costs 252 Swiss Francs (about GBP107 at today's exchange rate). If you just want to know whether fixed links have an allocation at 8 GHz in France, that's rather a lot to pay.
I was delighted, therefore, to discover that the Region 1 (Europe, Africa, the Middle East and Asiatic Russia) and Region 3 (Asia and Australasia) information can now be access for free on the web-site of telecommunications consultants 'InterConnect Communications'. Their Electronic Frequency Allocation Table (E-FAT) service allows you to query the ITU tables viewing either the whole table or just the allocations to specific services.
A similar service, but only for specific European countries (well certain CEPT members) is provided by the European Communications Office (ECO) in the form of their European Frequency Information Services (EFIS).
Thursday 4 May, 2006, 09:08 - Spectrum ManagementOne question which many unlicensed radio users of any kind (e.g. pirate radio operators) often ask themselves is, "What are the chances of me getting caught?" Clearly there is a lot of illegal radio usage which goes on, some of it over very prolonged periods of time, or at regular intervals, so not all transmitters get closed down.
Let's start by examining the tools available to the 'powers that be' which they can use to track down naughty radio transmitters. Most of the devices used would come under the umberella term of direction finding (DF) equipment, which often forms part of an overall spectrum monitoring system which logs details of all radio usage. The DF equipment informs the operator the direction from which a transmission is emanating. If such equipment is located in (or moved to) several locations within the coverage of a transmitter, the resulting direction measurements can be combined using triangulation and the location of the errant transmitter identified. The accuracy of such equipment varies: Fixed units can provide measurements to within +/- 1 degree whereas portable units may only have a resolution of +/- 10 degrees. With a resolution of 1 degree, it is not uncommon that the location of a transmitter can be identified to within about 500 metres, even with fixed receivers on the outskirts of the area of interest. Portable units are of more use close-in where the utmost accuracy is less important as the distances involved are much smaller and thus even +/- 10 degrees allows a transmitter to be located within 100 metres or so.
The last 100 metres become the most difficult. At this point the signal from the transmitter becomes so strong that direction finding equipment fails and the person doing the tracking has to resort to more traditional methods. By far the most useful method to find a transmitter when you are within 100 metres of it is to look! At this distance, the antenna may be easily visible - for pirate FM broadcasters, the 'double stack' aerials roughly strewn on top of tower blocks are a dead giveaway.
So tracking down illegal radio users is relatively straightforward and, for a continuous transmission, can be done in a couple of hours. Most (modern) radio regulators or administrations have the necessary equipment. Some even know how to use it. For sporadic or occasional transmissions, the authorities have to be ready to pounce, which is one of the reasons that so many pirate radio stations are only on-air at weekends when most radio enforcement officers are watching the football, playing golf or enjoying time with their families.
But there is a further question which needs asking... "What would cause the authorities to look for a transmission in the first place?" The simple answer is usually: Interference.
If an unauthorised radio transmitter is not causing anyone a problem, it will largely go unnoticed. If, however, it is causing interference to another radio user, that user will notice and will usually go straight to the authorities. For pirate stations, this situation is ameliorated by the fact that legitimate broadcasters might see a pirate as a problem, not because of interference, but because the station is taking its listeners away and thus has the potential to damage its advertising revenue (or so they would claim). The main exception to this is in certain bands where the authorities tend to use their monitoring equipment regularly, knowing in advance that illegal operation takes place. This might include, for example, the 6.6 MHz 'Echo Charlie' illegal CB band, well known pirate short-wave frequencies, or indeed the FM band itself.
So what are the chances of being caught? Once you get noticed, the chances are relatively high. Keep your head down and don't tread on anyone's toes and you might just get away with it.