Abstract: In relay-aided systems, the available data rate of a relay link user is determined by the minimum rate of the first hop link and the second hop link. Separate resource allocation in two-hop links may deteriorate system performance. Therefore, based on the throughput balance, a forward allocation (FA) algorithm and a backward allocation (BA) algorithm are proposed. In FA algorithm, resource allocation in the first hop greatly affects that of the second hop. In BA algorithm, resource allocation in the first hop is based on the throughput of the second hop. Simulation results show that the proposed algorithms are beneficial to solve the bottleneck problem of two-hop relay networks. In particular, the BA algorithm considers the optimal rates of users, and thus it can further improve system throughput and reduce power assumption.