Linearly Constrained RLS Algorithm with Variable Forgetting Factor for DS-CDMA Systems

[[abstract]]In this paper we present a novel linearly constrained (LC) RLS algorithm with variable forgetting factor (VFF), and apply to the DS-CDMA system for suddenly joined narrowband interference suppression. Under Rayleigh fading channel environment, the VFF could be employed to improve the tracking capability compared with the conventional LC-RLS algorithm with fixed value of forgetting factor (FF). From computer simulation results, we verify that the proposed scheme outperforms the conventional optimal FF LC-RLS algorithm in terms of rapid tracking capability and strong narrow-band suppression.[[incitationindex]]EI[[conferencetype]]國際[[conferencedate]]2014 12 01~2014 12 04[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Kuching , Sarawak, Malaysia (古晉, 馬來西亞

Blind adaptive constrained reduced-rank parameter estimation based on constant modulus design for CDMA interference suppression

This paper proposes a multistage decomposition for blind adaptive parameter estimation in the Krylov subspace with the code-constrained constant modulus (CCM) design criterion. Based on constrained optimization of the constant modulus cost function and utilizing the Lanczos algorithm and Arnoldi-like iterations, a multistage decomposition is developed for blind parameter estimation. A family of computationally efficient blind adaptive reduced-rank stochastic gradient (SG) and recursive least squares (RLS) type algorithms along with an automatic rank selection procedure are also devised and evaluated against existing methods. An analysis of the convergence properties of the method is carried out and convergence conditions for the reduced-rank adaptive algorithms are established. Simulation results consider the application of the proposed techniques to the suppression of multiaccess and intersymbol interference in DS-CDMA systems

New approximate qr-ls algorithms for minimum output energy (MOE) receivers in ds-cdma communication systems

This paper proposes a new family of approximate QR-based least-squares (LS) adaptive algorithms called p-AQR- LS for blind minimum output energy (MOE) detection in CDMA communications systems. It extends the A-QR-LS algorithm by retaining different numbers of diagonal plus p -1 off-diagonals of the triangular factor of the augmented data matrix. For p =1 and N ( N is the length of the weighting vector), it reduces to the A-QR-LS and the QR-RLS algorithms, respectively. It not only provides a link between the QR-LMS-type and the QR-RLS algorithms through a well-structured family of algorithms, but also offers more freedom in the complexity-performance tradeoffs for practical receiver design in communication systems. The performance of the proposed algorithm is verified by computer simulations. © 2005 IEEE.published_or_final_versio

Adaptive interference suppression for DS-CDMA systems based on interpolated FIR filters with adaptive interpolators in multipath channels

In this work we propose an adaptive linear receiver structure based on interpolated finite impulse response (FIR) filters with adaptive interpolators for direct sequence code division multiple access (DS-CDMA) systems in multipath channels. The interpolated minimum mean-squared error (MMSE) and the interpolated constrained minimum variance (CMV) solutions are described for a novel scheme where the interpolator is rendered time-varying in order to mitigate multiple access interference (MAI) and multiple-path propagation effects. Based upon the interpolated MMSE and CMV solutions we present computationally efficient stochastic gradient (SG) and exponentially weighted recursive least squares type (RLS) algorithms for both receiver and interpolator filters in the supervised and blind modes of operation. A convergence analysis of the algorithms and a discussion of the convergence properties of the method are carried out for both modes of operation. Simulation experiments for a downlink scenario show that the proposed structures achieve a superior BER convergence and steady-state performance to previously reported reduced-rank receivers at lower complexity