Blind Adaptive and Iterative Algorithms for Decision-Feedback DS-CDMA Receivers in Frequency-Selective Channels

• Published in: IEEE transactions on vehicular technology Vol. 56; no. 2; pp. 605 - 618
• Main Authors: de Lamare, Rodrigo C., Sampaio-Neto, Raimundo
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.2007; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptive algorithms; Algorithms; Applied sciences; Blind adaptive algorithms; Blinds; Channels; Concurrent computing; Constraint optimization; d irect-sequence-code-division multiple access (DS-CDMA) systems; decision feedback receivers; Design optimization; Detection, estimation, filtering, equalization, prediction; Detectors; Estimating; Exact sciences and technology; Frequency; Information, signal and communications theory; Iterative algorithms; Iterative methods; Least squares approximation; Multiaccess communication; multiuser detection; Parameter estimation; Receivers; Signal and communications theory; Signal, noise; Stochastic processes; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Fading channels; Multiuser detection; Parameter estimation; Adaptive algorithm; Iterative method; Stochastic method; Recursive algorithm; decision feedback receivers; Constrained optimization; direct-sequence-code-division multiple access (DS- CDMA) systems; Minimal variance; Frequency selection; Simulation; Least squares method; Code division multiple access; Blind adaptive algorithms; Growth of error; Uplink; Direct sequence; Signal detection; Cascade connection
• ISSN: 0018-9545; 1939-9359
• DOI: 10.1109/TVT.2006.889561

In this paper, we examine blind adaptive and iterative decision-feedback (DF) receivers for direct-sequence code-division multiple-access systems in frequency-selective channels. Code-constrained minimum variance and constant modulus design criteria for DF receivers based on constrained optimization techniques are investigated for scenarios subject to multipath. Computationally efficient blind adaptive stochastic gradient and recursive least squares algorithms are developed for estimating the parameters of DF detectors along with successive, parallel, and iterative DF structures. A novel successive parallel arbitrated DF scheme is presented and combined with iterative techniques for use with cascaded DF stages in order to mitigate the deleterious effects of error propagation. Simulation results for an uplink scenario assess the algorithms and the blind adaptive DF detectors against linear receivers and evaluate the effects of error propagation of the new cancellation techniques against previously reported approaches.