Code-timing acquisition for future DS-CDMA systems

Future CDMA systems will sometimes be required to operate with low processing gain in order to accommodate high rate users. The resulting increase in channel dispersion can have a detrimental impact on code-timing acquisition. In this paper, two maximum likelihood code-timing acquisition algorithms are proposed for multipath channels: a multiuser estimator and a single-user estimator. Multipath diversity is exploited in the estimators via maximum ratio combining to increase the signal-to-interference ratio. In addition, correlations between signals from different paths are explicitly incorporated in the test statistics of both estimators. The computational complexity of each estimator is found and the performance of the estimators are examined via simulations. The results indicate that the estimators and robust to near-far power ratio and channel dispersion. Moreover, the gain achieved by incorporating channel dispersion in estimator design is significant