Suppression of Interference due to IQ Modulators in OFDM(A) Based Communication Systems

Multi-carrier modulation techniques, like OFDM, has been gaining significant interest for future wireless communication systems. In spite of all the advantages of OFDM, it has its own challenges. There are several impairments that can degrade the performance of the OFDM systems if the system and transceivers are not designed properly. IQ modulator impairements are among those that can limit the performance significantly. One of the major impacts of the IQ modulator in multiuser OFDM(A) systems (like in WiMAX) is that it introduces interference between the modulated symbols on the image carriers. In this paper, the interference effect caused by IQ modulators will he discussed. Self and multi-access interference caused by the IQ modulators will be explained for multiuser OFDM(A) systems. A joint demodulation based approach to suppress IQ modulator interference will be developed. The performance of the proposed algorithm will he obtained and the performance gains with respect to the conventional receiver will be demonstrated.