Space Time Regularized Zero Forcing in Downlink Code Division Multiple Access Systems with Complementary Codes

Abstract

Complementary coded code-division multiple access (CC-CDMA) has been originated as one of the extremely robust multiuser access technique in designing high data rate systems with frequency diversity for futuristic wireless communication. The integration of multiple-input multiple-output (MIMO) systems with CC-CDMA offers space diversity gain in addition to the achievable frequency diversity in CC-CDMA systems. However, the performance of conventional chip level space–time receiver in MIMO CC-CDMA is deteriorated due to multiple access interference (MAI) and spatial interference under frequency selective fading channels. A zero-forcing receiver used for minimizing MAI provides unsatisfactory performance in interference limited environments due to amplification of noise and hence the use of regularized zero-forcing (RZF) receiver is proposed and investigated in this study to achieve a space–time interference cancellation (STIC) system. Simulation results are performed to reveal the significance of RZF-STIC in achieving performance gain than conventional equalization schemes, and at the same time enhancing frequency diversity and spatial diversity gain with less complexity at all system loads.