Tracking of time-varying mobile radio channels with WLMS algorithms: a case study on D-AMPS 1900 channels

Low-complexity WLMS adaptation algorithms, of use for channel estimation, have been presented in a companion paper. Their use and design is here evaluated on the fast fading radio channels encountered in TDMA systems based on IS-136. An exact analytical expression for the tracking MSE on two-tap FIR channels is presented and utilized. With this tool, the MSE performance and robustness of WLMS algorithms based on different statistical models can be investigated. A simulation study compares the uncoded bit error rate of detectors, where channel trackers are used in decision directed mode in conjunction with Viterbi algorithms. A Viterbi detector combined with WLMS, based on second order autoregressive fading models possibly combined with integration, provides good performance and robustness at a reasonable complexity.