[SADXA] HOMEPLUG

[A.J. PAWLOWSKI]

One of the concerns with all powerline systems, when compared to dedicated data wiring, is that the route of the wiring is not known in advance, and is generally already optimized for power transmission. This means that there will be situations where the system will radiate a significant fraction of the energy, in the form of radio frequency interference, or be vulnerable to the ingress of external signals. Given that the shortwave band is used both by low-power long-range telemetry and high-power broadcast signals, this is a potentially serious drawback. To attempt to minimize the effects of incoming interference and frequency-dependent path losses, the HomePlug standard requires each node to maintain 'tone maps' updates during operation, so the equipment 'learns' to avoid certain troublesome frequencies and to put more data onto those frequencies that exhibit a low loss. However, while this mitigates against ingress, if there is sensitive receiving equipment nearby then there is no easy way to tell the HomePlug apparatus to 'turn down' the radiated interference. In comparison to the received signals in a radio communication equipment, the signal levels in a powerline system are quite high. Typically the power density is −50dBm per Hz, as each carrier occupies a channel of 24 kHz, each carrier is injected at a level of −6.6dBm (220 microwatts), making the total full channel power 24dBm, (250 milliwatts). Typical short wave radio receiver sensitivities are at −100dBm (tenths of a nanowatt) level.

In the UK there have been suggestions that users of powerline equipment should be prosecuted under the Wireless Telegraphy Act<https://en.m.wikipedia.org/wiki/Wireless_Telegraphy_Act>, if they cause interference to official radio systems.[20]<https://en.m.wikipedia.org/wiki/HomePlug?fbclid=IwAR0uvEoZ-vEFrN11ldiRPLQ8OjmsrApDZOGErqY8WuV1PSTP4zQp5BXN2JQ#cite_note-20> Also GCHQ<https://en.m.wikipedia.org/wiki/Government_Communications_Headquarters> has published concerns that such interference affects its ability to monitor radio activity in the UK.[21]<https://en.m.wikipedia.org/wiki/HomePlug?fbclid=IwAR0uvEoZ-vEFrN11ldiRPLQ8OjmsrApDZOGErqY8WuV1PSTP4zQp5BXN2JQ#cite_note-21>