A parallel ICI cancellation technique for OFDM systems

Carrier frequency offset, time variations due to Doppler shift or phase noise lead to a loss in the orthogonality between subcarriers of Orthogonal frequency division multiplexing (OFDM) systems and results in inter-carrier interference (ICI). Further developing the parallel cancellation (PC) scheme to mitigate the ICI of OFDM systems, we investigate the characteristics of this two-branch OFDM symbol-based PC scheme in details. Moreover, with known channel state information, we show that this PC scheme is the same as the optimal maximal ratio combining (MRC) technique for transmitter diversity, but with ICI mitigation capability. Additionally, we integrate this PC scheme into a space-time (ST) coded system to form a simple space-time parallel cancellation (STPC) scheme. This STPC scheme not only inherits advantages of the conventional PC scheme, such as backward compatibility with the existing OFDM systems, low receiver complexity, and two-branch diversity, but also provides better bit error rate (BER) performance with lower error floor, especially in slow and fast frequency selective fading channels at a high signal-noise-ratio (SNR) without increasing computational load.