Scheduling using Superposition Coding: Design and Software Radio implementation

Abstract

Cellular base stations typically orthogonalize downlink transmissions, although this approach is not always throughput-optimal. Indeed, it can be shown that removing the orthogonality constraint (as in Superposition Coding) can provide significant benefits in some scenarios. Based on this principle, we propose a scheduling algorithm for a two-user downlink that leverages the disparity in their respective channel qualities. By a judicious reallocation of the transmit power and bandwidth, this algorithm improves the throughput to both users vis-à-vis an orthogonal scheme. We design a software-defined radio platform to implement the scheduler and experimentally verify the gains promised by theory.