Throughput Improvement by Joint Relay Selection and Link Scheduling in Relay-Assisted Cellular Networks

We consider joint relay selection and link scheduling to maximize the network throughput in relay-assisted cellular networks. The spatial reuse is leveraged by scheduling multiple links to simultaneously transmit. The coupling among relay selection, link scheduling, and the interference that is introduced by simultaneous transmissions makes this problem hard to solve. We summarize spatial reuse into two forms. The first form of spatial reuse exists among second-hop links, where relay stations transmit to mobile users. The second form of spatial reuse exists between second- and first-hop links, where the base station transmits to relay stations or mobile users. A framework is proposed to de-couple the joint problem into the following two subproblems: 1) a frame segmentation problem and 2) a relay selection problem. Under this framework, we propose two algorithms for either only the first form of spatial reuse exists or both forms of spatial reuse exist. Numerical results show that, with the first form of spatial reuse, the performance of the proposed heuristic relay selection algorithm is very close to the optimum. In the given scenario, when both forms of spatial reuse exist and the proposed heuristic frame segmentation algorithm is applied, the throughput is improved by up to more than 50% compared with the case without spatial reuse.