Extension of SAFNAQ algorithm for MC-CDMA using channel allocation

Abstract

For future systems of wireless communication, multi-carrier code division multiple access (MC-CDMA) is becoming much attractive due to its high data rate and multiple access capability. Continuing our research on main issues of MC-CDMA, which mainly include power and channel allocation, here we have considered power allocation following the channel allocation to improve overall performance of the system. In the current work, adaptive sub-channel allocation scheme has been incorporated into SAFNAQ algorithm to improve bit error rate (BER) performance of MC-CDMA system. SAFNAQ is an algorithm for transmission power allocation in MC-CDMA system. A projection matrix receiver based MC-CDMA system has been considered. The Rayleigh fading channel was used for simulations. The SAFNAQ algorithm, cohesion of frequency domain power allocation (FDPA) and eigen vector based power allocation (EBPA) algorithms, allocates available transmission power to adaptively chosen strongest sub-carriers with respect to corresponding coefficients of power balance vector computed using EBPA algorithm. In adaptive sub-channel allocation, different sub-channels are allocation to different users on the base of channel state information (CSI). In sub-channel allocation module, sub-channels were divided into small groups. Number of sub-channels in each group was equal to the length of pseudo random codes used to gain multiple access capability. At most one user can be allocated to each group simultaneously and corresponding user's desired power is allocated to sub-channels of that group in accordance with SAFNAQ algorithm. The system was simulated for different number of users and channel paths. Simulation results showed that usage of adaptive sub-channel allocation along with SAFNAQ algorithm improves the overall system bit error rate (BER) performance.