An Error Bound for Space-Time MMSE Multiuser Detection in Coded CDMA Systems over Fading Channels

Inhalt:
This paper investigates the use of convolutional coding in space-time minimum mean-square-error (MMSE) multiuser-based receivers over asynchronous multipath Rayleigh fading channels. We focus on the performance gain attained through error control coding when used with Binary-Phase-Shift-Keyed modulation (BPSK) and multiuser access based on direct sequence-code-division multiple access (DS-CDMA). In our analysis, we derive an approximation for the uncoded probability of bit-error in multipath fading channels. This biterror rate (BER) approximation is shown to be very accurate when compared to the exact performance. For a convolutionally coded system, we obtain a closed form expression for the biterror rate upper bound. This error bound is noted to be tight as the number of quantization levels increased beyond eight.