Layered space-time receiver for downlink multiple-input multiple-output multi-carrier code division multiple access systems

Multi-carrier code division multiple access (MC-CDMA) allows multiuser communication with frequency diversity. To increase the system data rates, spatial multiplexing for multiple-input multiple-output (MIMO) MC-CDMA has been investigated. This study proposes a chip level layered space-time (LST) receiver architecture for coded downlink MIMO MC-CDMA systems. As the conventional chip level ordered successive interference cancellation (OSIC) receiver is unable to overcome multiple access interference and performs poorly in multiuser scenarios, the proposed receiver cancels both spatial and multiuser interference in an ordered LST detection process by requiring only the knowledge of the desired user's spreading sequence. Simulation results show that the proposed receiver not only performs better than the existing linear detectors but also outperforms both the chip and symbol level OSIC receivers. In this study the authors also compare the error rate performance between the proposed system and MIMO orthogonal frequency division multiple access (MIMO OFDMA) system and they justify the comparisons by deriving and analysing the pairwise error probability (PEP) for both systems. MIMO MC-CDMA demonstrates a better performance over MIMO OFDMA under low system load. If all users' spreading sequences are known, multiuser interference can be reduced and MIMO MC-CDMA performs better than MIMO OFDMA at all system loads.