Joint Timing and Channel Estimation for Bandlimited Long-Code-Based MC-DS-CDMA: A Low-Complexity Near-Optimal Algorithm and the CRLB
Joint Timing and Channel Estimation (JTCE) for bandlimited long-code-aided Multi-Carrier Direct-Sequence Code Division Multiple Access (MC-DS-CDMA) systems is investigated. The authors establish the optimal multiuser timing and channel estimates for the uplink MC-DS-CDMA receiver by minimizing a weighted least squares cost function with respect to K independent parameters, where K is the number of active users. A guided random search procedure known as Repeated Weighted Boosting Search (RWBS) is invoked for numerically solving this challenging multivariate optimisation problem, and thereby for producing near-optimal timing and channel estimates. The Cramer-Rao Lower Bound (CRLB) for the JTCE problem of interest is derived to benchmark the performance of the proposed RWBS based estimator.