Optimal Power Control and Relay Capacity for PLC-Embedded Cooperative Systems

In cooperative communication single antenna mobiles can share their antennas to improve communication links and increase channel capacity. Node cooperation generates a virtual multiple-antenna system which attains close to optimal multiple input multiple output (MIMO) gains. At the same time, power line communication (PLC) offers stable high data rate for indoor communications, and also benefits from cooperative communication scheme since power lines can be used between relays. Thus it is of interest to investigate a hybrid PLC/wireless relying network. Towards that goal, in this paper, we derive analytic forms of single-user and multiuser MIMO channel capacities. We then evaluate relay channel capacities for two relevant cases. One when the channel is perfectly known to the transmitter, i.e. full channel state information (CSI) is known, and the other when the channel state is unknown (no CSI). We propose adaptive communication scheme which involves the decode-and-forward (DF) relaying and orthogonal frequency division multiplexing (OFDM). We investigate optimal allocation of transmit powers for the scheme at both source and relay nodes under total power constraints. For a realistic scenario our numerical tests indicate that PLC/wireless link performs better then a typical wireless link.