Exploiting Sparse User Activity in Multiuser Detection

—The number of active users in code-division multiple access (CDMA) systems is often much lower than the spreading gain. The present paper exploits fruitfully this a priori information to improve performance of multiuser detectors. A lowactivity factor manifests itself in a sparse symbol vector with entries drawn from a finite alphabet that is augmented by the zero symbol to capture user inactivity. The non-equiprobable symbols of the augmented alphabet motivate a sparsity-exploiting maximum a posteriori probability (S-MAP) criterion, which is shown to yield a cost comprising the ℓ2 least-squares error penalized by the

• Type: Journal
• Year: 2011
• Where: TCOM
• Authors: Hao Zhu, Georgios B. Giannakis
• Keywords: Code-division Multiple Access, Multiuser Detectors, TCOM 2011, Wanted Symbol Vector