Antenna diversity reception appropriate for MMSE combining in frequency domain for forward link OFCDM packet wireless access

This paper presents an optimum antenna diversity combining method associated with despreading that employs minimum mean square error (MMSE) combining over the frequency domain in a frequency-selective fading channel for forward link orthogonal frequency and code division multiplexing (OFCDM) wireless access, in order to achieve the maximum radio link capacity. Simulation results elucidate that the antenna diversity combining method with equal gain combining (EGC) after the despreading employing MMSE combining based on pilot symbol-assisted channel estimation and interference power estimation can decrease the required average received signal energy per bit-to-background noise power spectrum density ratio (E_b/N₀) the most, taking into account the impact of the inter-code interference. Furthermore, we clarify that the required average received E_b/N₀ for the average packet error rate of 10^-2 employing the diversity combining scheme with EGC after despreading with MMSE combining is improved by approximately 0.3 dB compared to the diversity combining scheme with EGC before despreading with MMSE combining at the number of code-multiplexing of 24 for the spreading factor of 32 in a 24-path Rayleigh fading channel.