Efficient Channel Estimation for Wcdma Systems

Abstract

Third generation (3G) cellular communication standards are based on Wideband Code Division Multiple Access (WCDMA). The wideband signals experience frequency-selective fading due to multi-path propagation, hence increasing the Multiple Access Interference (MAI). To combat this effect, an efficient channel estimation algorithm, based on the Maximum Likelihood (ML) approach is derived. The algorithm handles the situation of multiuser, and multi-path by estimating a composite Channel Impulse Response (CIR). This estimation is performed in the reverse link, for each user, without needs of estimating each individual channel parameters. This has the achievement of reducing the computational complexity. The efficiency of the proposed channel estimator is measured in terms of Mean Squared Error (MSE), handling capacity, loss due to estimation, as well as resistance to MAI.

Multiuser Channel Estimation and Deection for Wcdma Systems

“…The performance of the ML estimator, in terms of mean squared error, resistance to MAI and loss due to estimation was shown in [4].…”

“…This accomplished in the acquisition phase by requiring that all users transmit training pilot sequences. The discussion here refers to the maximum likelihood based channel estimation scheme [4]. In this model, it is assumed that the maximum delay spread between the paths is less than half a symbol period.…”

“…The expression for the received signal and hence the detectors consist of the term u z . It may be recalled from [4], that these two terms are the columns of matrix Ψ, the estimation of which is the first step (9) in the maximum likelihood algorithm. Using the developed algorithm to estimate is quite straightforward, and saves computation when compared to estimating k z or the individual parameters.…”