Robust Decoding against Unknown Interference for BICM-OFDM Systems

Wireless communications in cognitive radio systems are susceptible to in-band interference caused by other communication systems simultaneously sharing partial frequency band. Thus, if not properly coordinated, the CR systems can critically fall short of the guaranteed system performance. This paper proposes a robust and efficient decoding scheme to combat the nuisance without resorting to laborious estimation of in-band interference statistics, which are generally time-varying and difficult to accurately model. Taking into account the system framework as well as incorporating the clipping operation, the decoding scheme performs an erasure marking of the bit metric regarding a higher order modulation format jointly with the Viterbi algorithm in an iterative manner. Simulation results reveal that, in fairly general scenarios, the proposed method, when appropriately setting the bit metric clipping threshold, can achieve the bit error probability performance of its sophisticated counterpart, which uses the in- band interference statistics. Furthermore, compared with an existing scheme, the complexity of the proposed method is significantly reduced.