Broadband over Power Lines under pressure
Power Line Telecommunication (PLT) is the official terminology in South Africa for what elsewhere in the world is referred to as PLC and BPL. Its proponents claim it to be the answer to provide cheap broadband to the masses. But will it ever materialise? Can we liken it to a cheap alternative drug which has huge side effects that makes its use undesirable? Is it not a question of too little too late?
I am referring to research done on finding ways to overcome the side effects of huge harmful interference to the high frequency radio spectrum. It is a well established principle that a non-licensed radio service, which is allowed to operate in some parts of the radio spectrum, may not cause interference to licensed radio services. If however interference occurs the unlicensed service must immediately be terminated. In the case of PLT it is not listed in the table of frequencies so strictly speaking it is illegally using the High Frequency spectrum.
Manufacturers of PLT systems have shown how effective PLT is in delivering broadband but they fail to clearly show what testing has been done to establish its side effect. It is all very well for a drug company to launch a new drug to dramatically improve the performance of an athlete but in the process killing his hearing ability. It would not get medicine control council approval as a safe drug. Same should be the case with PLT; it should not be licensed until it gets a clear inference free bill of health.
This does not mean that PLT should be rejected out of hand. If, with more research, a way could be found to eliminate the interference potential PLT could well become a very useful system to deliver last mile broadband. It should however be considered that PLT is only one option. WiFi, WiMAX, HPDA offer similar economies. PLT still requires one of these technologies or fibre optic technology to connect into the Internet.
Manufacturers and suppliers of PLT equipment claim that they have the answer by using notching specific frequencies in the bands used by local emergency services, an HF broadcaster, a maritime safety radio service, a military communication system or a local radio amateur.
But notching is not the real solution; all it does is reducing the power level of that specific frequency or range of frequencies. It is also not practical to notch many frequencies as that would impede the data throughput. Tests carried out by the American Radio Relay League at it laboratories in Newington CT, USA has shown that the current notching limits imposed by the FCC do not provide sufficient reduction in harmful interference.
The radio spectrum is a natural resource for which there is no alternative. It should therefore be used with the utmost respect and consideration. And that surely must also apply to PLT!
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