Iterative Interference Cancellation for SFBC-OFDM System in Time Varying Multipath Fading Channel

Abstract

Alamouti coded Space Frequency Block Code (SFBC) based Orthogonal Frequency Division Multiplexing (OFDM) is very attractive due to its robustness against fast fading channel as the Channel Frequency Response (CFR) remain constant over Alamouti code period (two adjacent OFDM subcarrier). However, the channel is frequency selective as well as time selective. In frequency selective channel, the CFR are not constant for two adjacent OFDM subcarriers and hence leads to inter-symbol-interference (ISI) in SFBC-OFDM system. The inter-carrier-interference (ICI) also arises in OFDM system for time varying fast fading channel due to the loss of orthogonality among the subcarriers. Hence, both the ISI and ICI degrade the system performance for SFBC-OFDM system over time varying multipath fading channel. In this paper, we have proposed an iterative interference cancellation scheme which cancels the effect of ISI and ICI jointly. The proposed scheme cancels the interferences in two steps. In the first step, the Diagonalized Zero Forcing Detection (DZFD) method is used to suppress the effect of ISI. Then, in the second step, a simplified parallel interference cancellation (PIC) scheme coupled with decision statistics combining (DSC) is used to cancel the ICI effect and hence improves the system performance. The theory and simulation results verify that the proposed scheme achieves good performance in high time selective and high frequency selective channel environment for SFBC OFDM system.