System-Level Performance for MMSE Multiuser Detection in Asynchronous Mixed Service UMTS Networks

The main objective of this paper is to investigate asynchronous linear multiuser detection (MUD) in mixed service UMTS networks in terms of system capacity as well as power reduction at mobile stations. This especially requires to theoretically describe the interaction of linear multiuser detection with radio resource management concepts as power control and load control for asynchronous multirate transmissions. For the system capacity assessments we apply an iterative two-stage power control multiuser detection algorithm where the users are detected by a minimum mean square error (MMSE) block detectiom. By detailed system level simulations we evaluate the UMTS load control parameter noise rise and we show system capacity gains as well as power reductions compared to simple single-user matched filtering. It is important to note that for UMTS the signal-to-noise operating points where the MMSE detector operates are very low (less than 0 dB). For these UMTS constraints, MMSE multiuser detection indicates moderate gains only compared to single-user-matched filtering.