Powerline coming of age

For a number of years we have been promised data services delivered via power line communications (PLC), as opposed to cable TV or copper, or even via wireless. Some of the news of late on PLC has been good and some not so good. In this one-off column, Dr Keith MacLean, one of the top voices in the PLC Forum, which promotes powerline communications, speaks out against recent criticism of the technology by silicon.com columnist Peter Cochrane…

There is little in Peter Cochrane’s article of 28 May 2003 that we can agree with. However, in one respect he is correct – there has been a lot of hype about PLC in the past. Equally, there has been a lot of hype against PLC, in particular from radio amateurs and incumbent telecoms operators – the former with concerns about interference, the latter with concerns about any form of competition.

Both sets of hype have been based on theories and predictions. Fortunately much has happened since the early days of PLC and we no longer have to rely on 'theory' – there is enough real experience and hard data available to replace it.

For example, the PLC Forum has many members who have successfully trialled AND implemented PLC solutions. There are currently approximately 80 companies involved with hundreds of thousands of passed properties and tens of thousands of customers – many of them now paying for a fully commercial service. There have been no cases of interference resulting from these deployments which couldn’t be successfully addressed by the many mitigation methods incorporated into modern PLC systems.

Some facts about PLC in response to points made by Mr Cochrane:

• Services are being provided over PLC with symmetrical bandwidths from about 0.5 – 20 Mbps. • Distances of up to 400m can be reached along the power cables – this represents the maximum normal length of a low voltage cable since the voltage drop over longer ones precludes their use for electricity distribution. • The measured antenna efficiency from real power cables is about 30dB less than for a tuned dipole antenna making them anything but effective radiators/receivers • All the modern PLC systems use digital transmission and are designed to deal with the sporadically noisy environment in which they must operate.

In addition, many of the disadvantages of the electricity network have actually been turned into advantages. For example:

• The losses across the meter and premises distribution board prevent interference from individual premises penetrating into the main distribution cables thus preventing any cumulative effects. The highly efficient modems and the use of TCP/IP mean that the data delivery to individual users can cope with high endemic interference levels before bandwidth is significantly eroded. Transients are, by their nature, short lived and not an issue for data. • The blocking effects of transformers are ideal for preventing cross talk between individual PLC cells.

As for the commercial factors of PLC, equipment costs are rapidly decreasing as mainstream manufacturers like ABB, Mitsubishi, Schneider, Sumitomo and Thomson get involved. It is expected that user modem costs will soon match those of DSL and cable. In addition, the relatively small cell size means the unit of investment is very much smaller than for DSL, cable or wireless solutions and the combination of PLC with other technologies like satellite or radio is increasingly making broadband available to suburban and rural communities not covered by other technologies.

The remaining hurdles in the regulatory arena, that have for a long time discouraged the larger utilities from being involved and creating the real breakthrough, are now being addressed by the European Commission and the FCC, both taking a very supportive position. Perhaps not surprisingly, incumbent telecoms companies are taking a very negative position in this process – perhaps they do take the potential more seriously now.

With the technical and commercial realities now established, it is perhaps the laws of politics rather than physics which will decide the matter.

Dr Keith MacLean is the chairman of the PLC Forum's Commercial and Marketing Working Group.