Cooperative resource allocation in OFDM-based multicell cognitive radio systems

In this paper, we investigate the resource allocation problem for an orthogonal frequency division multiplexing (OFDM) based multicell cognitive radio (CR) system. Secondary users (SUs) served by the CR system distribute randomly in multiple cells and share radio spectrum with primary users (PUs) in a licensed system, where the interference introduced to the PUs must be kept below their tolerable thresholds. In our system model, SUs in different CR cells can transmit signals with the same OFDM subchannel, so cochannel interference among the SUs should also be considered. We propose an efficient algorithm, named as multi-level waterfilling (MLWF), to allocate power among OFDM subchannels for all CR cells by jointly considering transmission power and interference constraints. The MLWF always allocates much power to a subchannel which generates less interference to the PUs. Simulation results show that our proposed algorithm provides better performance than other existing ones. Moreover, the complexity of the MLWF is much lower than other representative algorithms.