Move cautiously on BPL assessment and approval, CBC urges Industry Canada

Late last year, Canada’s broadcasters had a chance to comment on an Industry Canada consultation paper examining the emerging technology of broadband over powerline (BPL), which allows high-speed networking over electrical wiring. In its comment, an excerpt from which appears below, the Canadian Broad-casting Corp. urged Industry Canada to examine BPL’s impact on it and other broadcasters before allowing deployment to proceed. The Corporation strongly believes…that in considering proposals to allow BPL Communication systems to operate in Canada, the principle of "no interference" to existing radiocommunication services, licensed or not, must be of paramount and primary importance. The documentation available on this subject indicates that it is highly probable that BPL systems will significantly interfere with existing broadcasting services to the public, as well as other essential and critical radiocommunication services. The Corporation stresses the need for the Department to clearly identify the frequency spectrum that BPL might use and the level of interference that BPL systems might produce in order to protect the existing services and spectrum users. The Corporation suggests that the limits applicable to BPL systems should be at least as stringent as the existing limits applicable Radio Standards Specifications (RSSs). CBC/Radio-Canada’s Concerns About BPL SystemsBecause of the nature of the types of cables, which transport power, BPL systems operation presents a special situation in regards to the creation of interference. Since the power cables are designed to transport efficiently power at a frequency of 60 Hz, they are consequently not suited for transmitting electromagnetic signals in higher frequencies such as the Radio-Frequency (RF) range. Advances in technology may overcome some of the challenges presented by the use of power cables to transport RF signals, but they will never compensate for their physical characteristics. Power cables are not shielded and will act as unintentional radiators. In addition to this fact, the nature of the power grid increases the complexity of the problems caused by this type of unintentional radiation. A power grid has the following characteristics: In the vast majority, distribution cables are in the air at around 10 metres high; These cables reaches every dwelling and are installed inside walls of dwellings; The impedance at cable junctions is not matched for RF frequencies; Power cables are unbalanced; The characteristics of the power grid network changes in time with the load. The other critical aspects of the BPL systems are the frequencies that are used to carry the information. If the BPL operators are granted the right to use the complete spectrum between 1.7 and 80 MHZ, the type of propagations the BPL signals will be using are as follows:1.7 MHz – 3MHz: Ground Waves and Ionosphere Reflection (1 hop at night); 3 MHz – 30 MHz: Ionosphere Reflections and Ground Wave over sea; 30 MHZ – 80 MHz: Direct path and Ground Reflections. Ionosphere propagation poses a real difficult problem, as distances are long enough to create interferences in another country.The regulation process of BPL systems will require international coordination to assure that every country is included in the process and is aware of the BPL systems effects on the electromagnetic (EM) spectrum. The frequencies used by exiting BPL systems pose a threat to the following services provided by CBC/Radio-Canada:HF Broadcasting (Radio-Canada International and its commercial clients) DRM Broadcasting (present and future) AM Broadcasting Low VHF NTSC TV Broadcasting Low VHF DTV Broadcasting (near future in rural areas) FM Broadcasting Some TV stations might be returning to their original channel in the low VHF spectrum after the DTV transition, especially in rural areas. As BPL systems are aimed to operate particularly in rural areas to provide broadband Internet access, the risk of collision/interference between DTV broadcast services and BPL systems will be high in rural areas. DTV service contours have lower field strength, exposing the DTV services to BPL interference even more than to existing NTSC TV services. Interference effects on DTV services are greater than on NTSC services. Interference on NTSC signals degrades gradually the picture quality as the interference level increases. On DTV, the effects are more dramatic and total lost of picture can happen very quickly. Canadian Strategy Regarding BPL Systems RegulationTo assess if the previous concerns about the suitability of power lines to carry RF frequencies, field tests were put in place in countries all around the world. Field tests have shown harmful interferences creation to existing spectrum usages. Many of these trials have been ceased, some even before their completion. CBC/Radio-Canada stresses the fact that numerous standard development forums, field trials and regulatory processes related to BPL systems are still ongoing in several countries. CBC/Radio-Canada recommends that the Department should wait until these activities are completed and the results are known before any entity to go into operation in Canada using the current BPL technologies. The opposition that BPL systems are facing all around the world, the results of several field trials as well as field measurements that are available, justifies this conservative approach. In addition, CBC/Radio-Canada suggests that the Canadian Government be proactive in the regulations of BPL systems and initiates activities and studies within international committees. This way the work could be started soon and help interested countries to reach agreements in this domain. In addition this would help countries in their own regulatory process. A sound approach to assure harmonious relation between BPL systems operators and other spectrum users would be to consider the BPL systems also as spectrum users. Since the frequencies used and the propagation of the unwanted emissions is similar to other spectrum usages, BPL operation should be treated the same way. This way, current spectrum users and BPL operators would be treated as equals. In addition, the regulatory framework is already in place and well defined, this enabling a smooth addition of BPL transmissions in the EM spectrum. Finally, historically, the ability to receive radiocommunication signals has been dependent on the noise floor, which varies depending on the type of location (i.e. urban versus rural), and also varies by frequency band. Generally, there has been no authorized spectrum usage, which increases the noise floor in frequency bands other than those specifically identified for unlicensed devices. BPL systems operation would set a precedent.

Move cautiously on BPL assessment and approval, CBC urges Industry Canada

Broadcast | January 27, 2006

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