Abstract

In this paper, a proper model of downlink OFDMA systems for the allocation of subcarrier, power and bit is established. Based on the requirements of rate-adaptive algorithms, it aims for maximizing the total system capacity under the constraint of fixed total transmitting power and the proportional fairness of various subscribers. Then, a suboptimal fairness algorithm based on demand function is proposed to enhance the system capacity. In this algorithm, subcarrier allocation and power allocation are divided into two separate steps. In both steps, the proportional fairness is implemented. With the employment of multiuser diversity scheduling and the Greedy bit allocation algorithm, this algorithm could realize high system throughput with low computing complexity. Through the simulation of non-real-time services, we have proved that while guaranteeing the fairness of subscribers, the OFDMA system using the suboptimal fairness algorithm proposed in this paper could reach a higher performance than that using the optimal fairness algorithm.

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