Channel-, Queue-, and Delay-Aware Resource Allocation in Buffer-Aided Relay-Enhanced OFDMA Networks

Resource allocation is an important factor in providing different varieties of services in next-generation broadband wireless systems. In this paper, we consider dynamic routing and subchannel allocation for providing quality of service (QoS) in the downlink of orthogonal frequency-division multiple-access (OFDMA) networks enhanced with buffering relays. Specifically, we consider satisfying the QoS requirements of both delay-sensitive users with the goal of meeting packet deadline constraints and delay-tolerant users who need guarantees on their average throughputs. We provide a framework for "time-domain scheduling" and "frequency-domain resource allocation," and based on this, we propose novel channel-, queue-, and delay-aware policies for formulating and solving the joint routing and resource allocation problem. In particular, these policies take different approaches to decide on the set of users considered in the utility function, the delay budget division between the base station and relays, the routing path of delay-sensitive users' packets, and the computation of minimum rate requirements for serving their queues. We present an iterative algorithm to solve the resulting problems. Numerical results show significant improvements in throughput and delay performance of the proposed resource allocation mechanisms compared with existing algorithms.