A Hybrid MC-CDMA Precoding Scheme Employing Code Hopping and Partial Beamforming

This paper proposes a hybrid transmission technique based on code optimization and partial linear precoding for interference exploitation on the downlink of phase shift keying (PSK) based mulitcarrier code division multiple access (MC-CDMA) systems. The first stage of the technique is to dynamically allocate codes to the users so that the combination of instantaneous data and user cross correlations yield a favourable constructive to destructive multiple access interference (MAI) ratio. To further optimize the received signal to interference plus noise ratio (SINR), the second stage is to employ a dynamic, partial transmitter based pre-decorrelation scheme specifically designed for the exploitation of constructive MAI. The decorrelation processing is targeted to the destructive interferers, while users that interfere constructively are let correlated. This results in a significant SINR enhancement without the need for additional power-per-user investment. Mathematical analysis and simulations show that significant bit error rate (BER) performance benefits can be achieved with this technique.