They "hybrid BPL" technology bypasses the medium high voltage lines and instead uses a wireless backhaul. The hybrid BPL technology by Motorola also bypass the transformer in order to avoid the eddy currents in the inner windinigs of the transformer via the Motorola Canopy wireless backhaul. There is an alliance called Home Plug Alliance which now establishes standards. The present HomePlug protocol, Motorola OFDM implementation includes 83 carriers with 8 carriers turned off to reduce interference to the 3.5-4, 7-7.3, 10.1-10.15, 14-14.35, and 18.068-18.168 MHz licensed Amateur Radio operation. Motorola's Powerline LV uses only the low voltage power lines, since these lines are relatively short there is less opportunity for creating RF interference.
In addition, the hybrid BPL approach by Motorola further mitigates potential RF interference by using relatively low -13dBm transmit power, the data signal is coupled to both sides of the low voltage line providing differential data transmission which suppresses common mode interference and internal filtering to provide additional attenuation at Amateur Radio frequencies.
However, some large users need the traditional BPL which indeed "touches" the medium high voltage lines. This is because some see the traditional BPL as a method of better monitoring of utilitiy lines, sensing of what's going on in the utility grid' sorta like a nervous system. But yes, there are many repeaters placed along the lines and thus the issue of perceived interference.
It is all very interesting. I worked with a WiSP and they are looking forward to hybrid BPL because it will enable them to hook up many more customers at one time.
From a network management point of view, the network manager needss to consider how to manage the elements the field, network analytics, bandwidth shaping, bandwidth limiting, security, and throughput.
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