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HomePlug technology works with a "common bus" paradigm, no matter how you connect them or what you want to call the physical architecture. (Incidentally, Ethernet used to work this way back in pre-historic times before the ethernet switch got invented - Wi-Fi still does.) Maybe other brands work differently, but I tend to doubt it.
As such "only one plug at a time" can transmit (onto the mains) and all the rest have to listen. Who's "turn" it is to transmit is mediated by a designated "master" plug - I forget whether that's built into the hardware or whether there's some mechanism where the plugs "elect" a master.
Thusly, the more plugs you have, the more they need to transmit, the more competition there is for access to and control of the transmission medium (the mains circuit) and the "slower" (and possibly more erratic) the usage experience can be from any given endstation. Of course, this is all happening thousands of times a second.
Throw in some interference, poor signalling conditions, and the Half Duplex nature of the technology and so on and it all eats away at the available bandwidth.
At don't forget that the protocol overhead (useful user data throughput versus link rate) is high for HomePlugs - of the order of 45-55% is often cited. AIUI, most HomePlugs come with some kind of "cockpit" software/App the displays the basic link rates between any given pair of HomePlugs (which could all be different, and different in opposite directions.)
As ever, for fast, reliable, high capacity data networking, the best option is to get the drills out, install some UTP cable and build a "proper" ethenet LAN. For all their cleverness, powerline comms is reverse engineering something (the mains) that was never designed for data networking and will always be second best. |
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