Abstract: A joint resource allocation algorithm is proposed to solve the problem of the proportional fairness and the system efficiency in multi-radio systems based on OFDMA (Orthogonal Frequency Division Multiple Access). The algorithm optimizes the system throughput under the fairness constraint, and considers that the allocated bandwidth should be integer times of the subchannel bandwidth. The bandwidth allocated to each terminal is adjusted according to this consideration. The performance of the proposed algorithm is evaluated by simulations in terms of the system throughput and the fairness.