Proportional Fair Scheduling in Hierarchical Modulation Aided Wireless Networks

Abstract

Theoretically, superposition coding (SPC) can achieve the capacity of a degraded Gaussian broadcast channel. A practical implementation of SPC, hierarchical modulation (HM), has recently been adopted in industry. Using HM, how to explore the multi-user diversity gain in a time-varying wireless environment to maximize throughput and maintain fairness is an open issue. Using greedy opportunistic scheduling algorithms will lead to a severe starvation problem. In this paper, we study the proportional fair scheduling (PFS) problem in an HM aided wireless network, jointly considering the user selection and utility maximization problems. Shannon capacity based and practical HM based optimal scheduling problems are formulated. An optimal algorithm and a low complexity suboptimal algorithm are proposed to solve the practical scheduling problem combining the opportunistic PFS and HM. Simulation results demonstrate that the proposed algorithms can achieve 50% to 100% throughput gain compared to the single-user opportunistic PFS solution depending on the number of users and have better fairness performance than the existing single-user and HM-based solutions.