An iterative resource allocation algorithm for multi-user OFDM-CR system with low complexity

A low complexity resource allocation scheme is proposed for an underlay scheme over OFDM-based multi-user cognitive radio system. The resource allocation problem in an OFDM-based CR system includes subcarrier, power and bit allocation that is a combinational optimization problem. In the proposed scheme, subcarrier and power allocation is accomplished in two separate stages. The power allocation problem under the interference channel model is a constraint optimization problem. It is notable that one of problem complexity source is coupling between the power budget and interference temperature constraints sets. In this algorithm the power budget constraint is used to determine initial point within iterative algorithm. Additionally, a margin parameter that depends on similarity of the interference channel branches is introduced. The simulation results for two statistical models, namely Rayleigh and Nakagami, show that the proposed algorithm performance is close to an optimal solution with lower complexity.