This paper considers subcarrier allocation for the multihop orthogonal frequency division multiple-access (OFDMA) broadcast networks consisting of one source, multiple destinations, and one amplify-and-forward (AF) relay. In this paper, proportional fair (PF) based subcarrier allocation is discussed to get a tradeoff between the system transmission rate and fairness. First, the problem is formulated as an optimization problem with prohibitive complexity. Second, by analyzing the optimal solution for the subcarrier allocation problem without PF constraint, two suboptimal schemes are proposed. The simulation results indicate that with the same fairness performance, the proposed schemes achieve considerable capacity gain compared with the conventional PF scheduling method which is extended simply from the single-hop system.
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