The Register stumbled upon an eye-opening report commissioned by the UK telecom regulator, Ofcom, on sources of Wi-Fi interference in the UK:
What Mass discovered (pdf) is that while Wi-Fi users blame nearby networks for slowing down their connectivity, in reality the problem is people watching retransmitted TV in the bedroom while listening to their offspring sleeping, and there’s not a lot the regulator can do about it.
Outside central London that is: in the middle of The Smoke there really are too many networks, with resends, beacons and housekeeping filling 90 per cent of the data frames sent over Wi-Fi. This leaves only 10 per cent for users’ data. In fact, the study found that operating overheads for wireless Ethernet were much higher than anticipated, except in Bournemouth for some reason: down on the south coast 44 per cent of frames contain user data.
When 90% of the frames are overhead, the technology itself has a problem, and in this case it’s largely the fact that there’s such a high backward-compatibility burden in Wi-Fi. Older versions of the protocol weren’t designed for obsolescence, so the newer systems have to take steps to ensure the older systems can see them, expensive ones, or collisions happen, and that’s not good for anybody. Licensed spectrum can deal with the obsolescence problem by replacing older equipment; open spectrum has to bear the costs of compatibility forever. So this is one more example of the fact that “open” is not always better.