Widely linear receivers for SMT systems with TX/RX frequency-selective I/Q imbalance

Staggered multitone (SMT) modulation scheme has received a considerable attention recently due to its higher spectral efficiency compared to the conventional OFDM systems and robustness to frequency offset and Doppler spread. However, channel equalization in SMT is complicated by the so called intrinsic interference as a result of non-flat channel response in each subchannel. In the presence of I/Q imbalance (IQI), this task becomes even more challenging as the image band and its intrinsic neighborhood contaminates the received signal. This paper deals with widely linear schemes for the effective channel equalization using time-domain and frequency-domain methodologies. Further iterative improvements are proposed for the later, combining enhanced equalization with per-subchannel-pair processing after intrinsic interference cancellation. The proposed techniques are simulated for both the uncoded and coded systems suffering from frequency-selective IQI and their effectiveness with multipath channels is demonstrated.