Adaptive Code Allocation for Interference Exploitation on the Downlink of MC-CDMA Systems

This paper presents a new technique based on adaptive code-to-user allocation for interference management on the downlink of BPSK based MC-CDMA systems. The principle of the proposed technique is to exploit the dependency of multiple access interference on the instantaneous symbol values of the active users. The objective is to adaptively allocate the available spreading sequences to users on a symbol-by-symbol basis to optimize the decision variables at the downlink receivers. The resulting SINR improvement happens by making use of the energy that is already in the system so the performance benefit is attained with no additional power-per-user investment. The presented simulations show a significant BER performance improvement with the proposed technique while the adaptation overhead is kept less than 10% of the available bandwidth.