Parallel Interference Cancellation Multiuser Detectors For DS-CDMA Communication Systems

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Title: Parallel Interference Cancellation Multiuser Detectors For DS-CDMA Communication Systems
Author: Liu, Feng
Abstract: A non -linear sub -optimal multiuser detector in the form of parallel interference cancellation (PIC ) has been studied . The main objective of this thesis is to develop an analytical model for PIC performance analysis and propose new near -optimum approach . Since the exact performance analysis of PIC is difficult to derive due to its nonlinear decision function , previous work tends to adopt computer simulation method or evaluate through Gaussian approximation (GA ) method . For PIC detector , the GA method may not apply since there may exist a dominate interference signal . In addition , the central limit theorem is not applicable to model the residual MAI in the case of PIC due to its own structural property . We develop an analytical model to derive the exact BER performance in the case of two users , and extend the method to approximate cases when moderate -to -high SINR can be encountered . We propose a gradient adaptive parallel interference cancellation detector and investigate its performance . The presented PIC detector is equipped with a set of adaptive weights which are adjusted through a new proposed gradient adaptive step size -LMS (GASS -LMS ) algorithm to reduce the cost of wrong interference estimation as existed in the conventional PIC . The initial state is deliberately set based on the function of probability of error to reflect the reliability of the tentative decision from the previous stage . While the most previous work on MUD are restricted to cases where there is no intersymbol interference (ISI ) , we consider the problem of joint detection of MAI and ISI , which is crucial to enhance the performance of the third and future generation systems with high data rate applications . Simulation results are provided to show that our low complexity joint detector can perform very well , yielding the bit error rate (BER ) close to the non -ISI single -user error rate .
URI: http : / /hdl .handle .net /10106 /434
Date: 2007-08-23


Parallel Interference Cancellation Multiuser Detectors For DS-CDMA Communication Systems. Available electronically from http : / /hdl .handle .net /10106 /434 .

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