Channel estimation for the W-CDMA system, performance and robustness analysis from a terminal perspective

Two different approaches for channel estimation for the wideband code division multiple access (W-CDMA) system are compared by means of simulations. As W-CDMA uses time-multiplexed pilots, there is a need for interpolating primary channel estimates obtained from using these pilot symbols. Both channel estimators are similar in that they linearly combine primary channel estimates to perform this interpolation. The first channel estimator uses simple linear interpolation and the second channel estimator uses a Wiener filter approach. The Wiener filter approach requires a knowledge of the Doppler spread and the signal-to-interference ratio (SIR). The channel estimators are compared in terms of the resulting bit-error rate (BER). This is done with respect to deviations in the SIR and Doppler spread as used for the design of the Wiener filter, from their nominal values. For the evaluation a Rayleigh fading channel, with three independent and equally strong paths, are assumed. No power control is used. On the one hand, for low velocities, the simulations indicate that the Wiener filter approach is quite robust against model errors in terms of SIR and Doppler spread. For high vehicular velocities, on the other hand, and in the presence of model errors, the interpolator performs well compared to the Wiener filter approach.