Performance of forward link broadband OFCDM packet wireless access using MMSE combining scheme based on SIR estimation

This paper proposes a pilot channel assisted minimum mean square error (MMSE) combining scheme in orthogonal frequency and code division multiplexing (OFCDM) based on actual signal-to-interference power ratio (SIR) estimation and investigates the throughput performance in a broadband channel with a near 100-MHz bandwidth. In the proposed MMSE combining scheme, the combining weight of each sub-carrier component is accurately estimated from the channel gain, noise power, and transmission power ratio of all the code-multiplexed channels to the desired one, by exploiting the time-multiplexed common pilot channel in addition. to the coded data channel. Simulation results elucidate that the required average received signal energy per bit-to-noise spectrum density ratio (E_b/N₀) for the average packet error rate (PER)=10^-2 is improved by 0.6 and 1.2 dB by using the proposed MMSE combining Instead-of the conventional equal gain combining (EGC) in a 24-path Rayleigh fading channel (exponential decay path model, maximum delay time is approximately 1 μsec) in an isolated cell environment, when the number of multiplexed codes = 8 and 32, respectively, with the spreading factor of 32. Furthermore, when the average received E_b/N₀=10 dB, the achievable throughput, i.e., the number of simultaneously multiplexed codes for the average PER=10^-2 in the proposed MMSE combining, is increased by approximately 1.3 fold that of the conventional EGC.