Bit Truncated Multiuser OFDM-CDMA Systems in Rayleigh Fading Channel

Abstract

OFDM technique increases the robustness against frequency selective fading or narrowband interference, combined it with code-division multiple accessing implements multiuser communication system. We propose transmission power truncation in OFDM-CDMA systems, when the channel power gain is lower than a certain threshold, corresponding bit is not transmitted. The reason is that bits in deep-fading period are highly likely to be in error, and if transmitted would waste the transmission power and generate interference to other users. So truncating these bits' transmission power and redistributing the power resource will reduce the multi-user interference, increase the SINR and improve communication quality. Subchannel truncation is adopted to combat poor channel situations. We analyze the BER performance of the truncated system under the channel of rayleigh fading and multiuser interference, and compare the BER and throughput performance by simulation.