On decode-and-forward relaying for the diamond relay channel with multicarrier transmission

In this paper, we propose new decode-and-forward (DF) protocols for the M-relay diamond relay channel with multicarrier transmission. The DF protocols proposed for the case of multicarrier transmission are motivated by recent capacity gap results for the 2-relay single-carrier diamond channel. The protocol for the M-relay case is an extension of the 2-relay case using appropriate relay selection. The various DF protocols studied differ in the choice and number of network states used, the allocation of subcarriers and power in each state, and the resulting operating rate vector for each state. First, we compare the performance of the proposed DF protocol with the cutset upper bound and existing DF relaying protocols for the 2-relay case with multicarrier transmission. We focus on the case of Rayleigh fading models for each of the links and also study the performance for various relay locations. Then, we consider the 3-relay case for performance comparison. From the numerical results, we observe that: (1) the proposed DF protocols perform significantly better than the existing DF protocols, and (2) appropriately chosen DF relaying protocols can perform close to the cutset bound.