SNR Estimation for Pilot-assisted Frequency-domain MMSE Channel Estimation

Abstract— The bit error rate (BER) performance of DS-CDMA in a frequency-selective fading channel can be significantly improved by the use of frequency-domain equalization (FDE) based on minimum mean square error (MMSE) criterion. Accurate estimation of the channel transfer function and the signal-to-noise power ratio (SNR) are necessary for MMSE-FDE. Direct application of pilot-assisted channel estimation (CE) degrades the BER performance, since the frequency spectrum of the pilot chip sequence is not constant over the spreading bandwidth. To overcome this problem, we proposed a pilotassisted frequency-domain MMSE-CE. In this paper, we propose an SNR estimation scheme for pilot-assisted MMSE-CE. Its BER performance in a frequency-selective Rayleigh fading channel is evaluated by computer simulation. It was found that the Eb/N0 degradation with MMSE-CE from the ideal CE case is as small as 0.5 dB at BER=10 (an Eb/N0 loss of 0.28 dB due to the pilot insertion is included).