A Novel Method of Feedback Reducing and Cross-layer Scheduling Based on Traffic Rates for Relay System

摘要

This paper studies the scheduling schemes in multiuser downlink relay systems with orthogonal frequency division multiple access (OFDMA) where base station (BS) supports different traffic rates for different users. We formulate the problem as a cross-layer design of joint feedback reducing and OFDMA scheduling to support traffic rates and minimize packet loss rate. In most previous scheduling mechanisms with feedback, the parameters of traffic arrival process were not taken into account, consequently, the requirement of user traffic can not be guaranteed. In this paper, a dynamic threshold feedback mechanism (DTFM) based on traffic rates is proposed, of which the user with channel gain being larger than the dynamic threshold is only allowed to send its channel state information, thereby reducing the number of required feedback users and the computational burden of exhaustive search for best users at the BS. A cross-layer scheduling algorithm of traffic and queue proportional fairness (TQPF) taking into consideration the traffic fairness, the user queue length and the user transmission rate (related to its channel quality) is then proposed. Finally, a method of feedback reducing and cross-layer scheduling, i.e., TQPF based on DTFM (TQPF-DTFM), is proposed. Theoretical and simulation results show that DTFM reduces feedback by more than 90%, and TQPF-DTFM successfully meets user traffic rates that is, the user with high traffic rate can obtain more transmission rate than the user with low traffic rate and deceases packet loss rate of the system by almost 50% than the conventional methods.