Performance Improvement of Relaying in Downlink Networks Using Superposition Coding

Abstract

In this paper, we investigate a joint relaying and superposition coding (SupC-R) transmission strategy for downlink networks. By relaxing the orthogonality constraint between different users, the SupC-R strategy facilitates coordination and channel sharing among different data flows, by which the disparity in the channel qualities of different users, as an inherent feature of downlink network topology, is utilized as benefits for potential performance gains. The inter-user interference due to non-orthogonality can be steered by smart design of superposition coding (SupC), including both the selection of the superposition factor and the decoding order. At the same time, channel sharing saves time and leads to more efficient utilization of network resources. The analytical and numerical results show significant gains of SupC-R over its conventional relaying counterpart. The effect of the channel disparity on the design of SupC and the performance of the resultant SupC-R strategy is highlighted.