This letter considers multiuser time delay estimation in a sparse channel environment for radiolocation. The generalized successive interference cancellation (GSIC) algorithm is used to eliminate the multiple access interference (MAI). To adapt GSIC to sparse channels the alternating maximization (AM) algorithm is considered, and the continuous time delay of each path is estimated without requiring a priori known data sequences.

In this letter, we propose a groupwise successive interference cancellation (GSIC) receiver with gradient descent search for multi-rate DS-CDMA system. Proposed receiver incorporates iterative gradient descent search algorithm into conventional GSIC receiver for multi-rate DS-CDMA system. It is shown that the receiver achieves significant performance improvement over the matched filter (MF) receiver, GSIC receiver, multi-stage parallel interference cacnellation (PIC) receiver, multi-stage partial PIC receiver, and GSIC receiver with PIC in a Rayleigh fading channel.

In this letter, we present groupwise successive interference cancellation (GSIC) receiver with adaptive minimum mean squared error (MMSE) detection and extended GSIC (EGSIC) receiver with adaptive MMSE detection for dual-rate DS-CDMA system. The receivers are GSIC receiver and EGSIC receiver combined with adaptive MMSE detection which is introduced to make initial bit detection more reliable. Furthermore, a multi-user detection scheme is introduced to mitigate the effect of multiple access interference (MAI) between users in a group which is usually ignored in conventional GSIC receiver and EGSIC receiver. Specifically, parallel interference cancellation (PIC) is adopted as a multi-user detection scheme within a group. It is shown that performance of the GSIC receiver and EGSIC receiver is significantly improved by employing adaptive MMSE detection. It is also shown that the performance of the receivers can be improved further by using PIC within a group.