Fairness-constrained rate enhancing superposition coding scheme for a cellular relay system

We consider the Downlink (DL) of a cellular relay system where in each sector, multiple users are served by one Base Station (BS) and one Relay Station (RS). We first design a scheme based on Superposition Coding (SC) that serves two users simultaneously over the same spectral resource. By superposing the messages to the two users into three layers, this scheme allows both users to benefit from the relayed links, thereby improving sum rate. The power allocation parameters of each SC layer are optimized to maximize sum rate while guaranteeing equal rates to each user. Then, this scheme is integrated in the proposed scheduler that exploits simultaneous user allocation. Compared to conventional schedulers based on orthogonal user allocation, the proposed scheduler outperforms the overall sum-rate under the fairness constraint.