Maximize sum capacity of multiuser cognitive OFDM systems

Resource allocation is an important issue in multiuser cognitive OFDM systems. In this paper, the highest achievable rate of each OFDM subchannel for a cognitive radio user (also referred to as secondary user, SU) is calculated by jointly considering the channel gain and the interference level. A low complexity algorithm is presented to allocate radio resource to the SUs. Each subchannel is assigned to the SU with the highest achievable rate. Then a simple but efficient algorithm is developed to allocate bits to each subchannel, which is also based on the highest achievable rates of subchannels. Simulation results show the proposed algorithm can produce solutions close to the optimal. Furthermore, the algorithm has lower complexity compared to other existing methods, rendering it promising for practical wireless systems.