Adaptive power allocation for Decode-and-Forward OFDM transmission with multi-hop relaying

We investigated the adaptive power allocation in an point-to-point orthogonal frequency Division multiplexing (OFDM) cooperative system subject to the individual power constraint with an objective of maximize the sum transmission rate, and derived the optimal power allocation by assuming independent and identically distributed (i.i.d.) sub-channels in each Decode-and-Forward (DF) relay. To improve the wireless coverage, we extended the conventional two-hop system model to a three-hop structure without considering the effect of inter-relay interference. The structure can effectively overcome the transmission bottleneck in the conventional two-hop system. This paper also considered relay selection for the proposed cooperative transmission. In other words, depending on the quality of the sub-channels, each relay decides whether to forward data itself. The simulation results shows that the sum rate of the proposed algorithm monotonically increases with the increasing of both the power of each node and sub-channel numbers. Numerical results prove the goodness of the three-hop model in terms of sum rate and validate the proposed theoretical analysis.