Efficient time-domain residual ISI cancellation for OFDM-based WLAN systems

In orthogonal frequency-division multiplexing (OFDM) systems, the multipath components whose delays exceed cyclic prefix (CP) cause intersymbol interference (ISI) and intercarrier interference (ICI), which may degrade system performance severely. In this paper, we propose two novel iterative cyclicity restoration (CR) schemes to efficiently cancel these interferences for OFDM-based wireless local area network (WLAN) systems. The time-domain parallel CR (PCR) scheme is introduced first. Using time-domain iterative solution, PCR provides much lower computational complexity than conventional CR. Furthermore, in order to improve the performance of PCR, we present successive CR (SCR) method based on Gauss-Seidel iteration. SCR offers faster convergence speed than PCR without increasing the computational cost. It is shown that both PCR and SCR need only a few iterations to approach the system performance with sufficient CP. SCR has approximately the same performance as conventional CR with much lower computational complexity for WLAN applications.