Joint timing and pilot symbol channel estimation for diversity receivers in Rayleigh fading channels

Abstract

An effective method for joint timing and channel estimation for receive diversity systems in a frequency-flat Rayleigh fading environment is presented. We implement nonsynchronous timing recovery using Gardner's timing error detector, whose insensitivity to phase errors allows for timing recovery prior to pilot symbol based channel estimation. By employing a polyphase filter bank in the timing loop, we are able to simultaneously carry out matched filtering and data interpolation, thus eliminating the need for a separate interpolation filter. In addition, selection diversity combining is used to select the input to the timing loop, thus improving the reliability of the signal used for timing recovery. Pilot assisted channel estimation is performed on the recovered data strobes. For normalized Doppler frequency of 0.01 the system's bit error rate (BER) performance is within 1 dB from the ideal timing and channel estimation error bound, with an additional drop of 1.5 dB for a nonoptimum channel interpolator. In deep fades, the receiver timing is held fixed. We show that the receiver maintains timing lock over such fades up to a normalized timing bandwidth of 1/spl times/10/sup -4/for normalized Doppler frequency up to 0.05.