OFDM Transceiver Techniques for Interference Tolerant Cognitive Radio

Interference, either unintentional (from heterogeneous users in spectrum sharing systems) or intentional (jamming), degrades the performance of existing licensed and unlicensed spectrum services. In particular, interference will be of increased importance in future cognitive radio spectrum sharing systems, which are likely to be based on orthogonal frequency division multiplexing (OFDM). This paper examines the effects of wideband interference on two aspects of OFDM system performance: pilot symbol assisted detection and coded bit error rate. Digital signal processing strategies for interference mitigation are proposed to reduce the number of retransmissions due to interference. It is shown that the combination of robust spectrum sensing and wideband excision filtering provides impressive interference tolerance, while erasure marking alone provides some improvement compared to methods without spectrum sensing. The interference mitigation performance of various combinations of different types of forward error correction and frequency diversity also is compared.