A modified genetic algorithm for resource allocation in OFDM-based cognitive radio systems

In this paper, the problem of jointly allocating bits, subcarriers and power to maximize the total transmit bit rate in an OFDM based cognitive radio (CR) is studied. Moreover, different service requirements of SUs are also considered. Since “underlay“ is adopted as the spectrum shared model, secondary users (SU) in the CR system are allowed to utilize any part of frequency band as long as the interference is under the threshold. We formulate this allocation problem as a multidimensional knapsack problem (MKP) which is NP hard. Considering the real time application, a fast genetic algorithm (FGA) is proposed to obtain a suboptimal solution in short time. For comparison, a reduced complexity (CR) algorithm based on greedy algorithm is also analyzed. Simulation results show that the novel algorithm outperforms RC algorithm and achieves a throughput close to the optimal solution.