Subspace-based blind adaptive joint interference suppression and channel estimation in multipath CDMA channels

A blind adaptive technique for demodulating a user's signal in the multipath CDMA channel is proposed. This technique is based on signal subspace estimation. The receiver employs a linear filter-bank at the front end to mitigate the multiple-access interference and the multipath interference. A channel estimator is used to estimate the channel state for diversity combing. It is shown that, based on the signal subspace estimation, both the decorrelating filter-bank and the linear MMSE filter-bank can be obtained blindly, i.e., they can be estimated from the received data with the prior knowledge of only the signature waveform of the user of interest. A blind adaptive implementation based on a signal subspace tracking algorithm is developed. A blind adaptive technique for estimating the channel state is also developed, which produces the post-combining decision statistic as a by-product.