An Iterative CDMA Multiuser

This paper proposes an iterative multiuser detector for a direct-sequence code division multiple access (DS-CDMA) system based on the iterative technique of Gauss-Seidel for solving linear algebraic equations. The detector starts with soft iterations, that is, no hard decisions are made until (near) signal decorrelation is achieved. The signals at this point are passed to an amplitude/phase estimator, and the iterative detector continues using hard decisions of the estimated symbols to achieve improved reliability. Only small blocks of data are required for estimation and no phase tracking loop and power control loops are needed. It is shown that this detection method achieves substantial gains over the decorrelator in systems with high load at a computational complexity of O(NK) per bit rather than O(NK 2) per bit for decorrelation (K is the number of users and N is the processing gain).