Active subchannel detection for non-contiguous OFDM-based cognitive radio systems

For non-contiguous OFDM (NC-OFDM) based cognitive radio (CR) systems, one of huge challenges is to establish spectrum synchronization before data transmissions. In this paper, we propose a novel active subchannel detection scheme for the NC-OFDM receiver without out-of-band spectrum synchronization information. The key idea of the proposed scheme is to employ the received training symbol to calculate the a posterior probability (APP) of each subchannel being active, and then APPs are used to make a decision on which subchannels are active and to be processed in data detection. Furthermore, performance analysis of active subchannel detection is given. Both theoretical analysis and simulation results show that the proposed scheme can provide satisfactory performance of the symbol error rate (SER) when the interference from primary users is considered.