Tracking performance of coherent decision-directed delay-locked loop in quasi-synchronous CDMA

In direct sequence code-division multiple access (DS-CDMA), the multiuser interference can be substantially reduced when the users are quasi-synchronized and special symbol-length sequences are used. If a conventional noncoherent delay-locked loop (DLL) is used in quasi-synchronous CDMA (QS-CDMA), its code tracking may be impossible. We propose the coherent decision-directed DLL (CDD-DLL) as a code tracking scheme for QS-CDMA using symbol-length spreading sequences and analyze its performance. It is shown that the CDD-DLL is an appropriate code tracking scheme for QS-CDMA