ImprovedMultistageDetectorby Mean-FieldAnnealing in Multi-UserCDMA
We proposea multistage multi-user detector for Code Division Multiple Accessthat implements Mean-Field Annealing. Annealing is a well known technique to avoid local minima in detection and optimisation problems. Local minima certainly occurs in CDMA multi-user detection leading to anomalousBit Err or Rate curves. Annealing is implementedasa standard multi-user detector implementing interfer encecancellation,but with a control parameter determining the slopeof the squashing/mappingfunction. We deri ve a bound on the control parameter for the first stageof the detector. We alsoproposean annealingscheme.Weshow empirically the performanceof the proposeddetector, which follows closelythe optimum detector implementedby exhaustive search, i.e. has gains of several dB’s compared to standard multiuser detectors lik e linear-MMSE, linear-MMSE first stagefollowed by interferencecancellation,and multi-stage interfer encecancellationwith clipped soft decision,the lastbeingthe closestto our proposeddetector. Theproposeddetector gainsup to dB compared to the Clipped Soft DecisionMultistage detector at no addedcomplexity. Keywords—CDMA, Multistage Multi-User Detection, Interfer enceCancellation, Anomalous -curves.