Blind multichannel identification for high-speed TDMA

Transmission of multimedia data is the goal of third generation (3G) cellular radio systems necessitating high-speed data links where the multipath delay spread generally encompasses many symbol intervals. The channel impulse response for each antenna in a prototypical high-speed data link is many symbol intervals in duration and generally sparse. In order to reduce the number of parameters that need to be estimated in order to characterize the channel, researchers have recently proposed a number of schemes for direct estimation of the multipath parameters. However, this approach requires a relatively long observation interval in order to accurately estimate the complex gain of each dominant multipath at each antenna. We here propose an alternative approach based on subbanding and the cross-relation method (CRM) of Xu, Liu, Tong, and Kailath (1995). Basically, we apply the CRM in each subband using basis functions derived from the symbol waveform and the bandpass filter to blindly identify the frequency response of each channel in the given subband. A method is presented for proper phasing of each subband channel estimate in order to reconstruct the full channel impulse response associated with each antenna. Simulations are presented demonstrating accurate identification of multiple channels under adverse multipath conditions, moderate SNR, and with a relatively small number of symbols