Constant modulus algorithm aided soft decision directed scheme for blind space–time equalisation of SIMO channels

Abstract

This paper investigates a blind space-time equaliser (STE) designed for single-input multiple-output (SIMO) systems that employ high-throughput quadrature amplitude modulation schemes. A constant modulus algorithm (CMA) aided soft decision-directed (SDD) scheme, originally derived for low-complexity blind equalisation of single-input single-output channels, is extended to the SIMO scenario. Simulations are conducted to compare the performance of this blind adaptive scheme with another low-complexity blind STE referred to as the CMA aided decision directed (DD) scheme. The results obtained demonstrate that for SIMO systems the CMA aided SDD scheme exhibits advantages over the CMA aided DD arrangement, in terms of its faster convergence speed and lower computational complexity. r

Fuzzy-logic tuned constant modulus algorithm and soft decision-directed scheme for blind equalisation

“…The initial w c and w d are simply set to w c (0) = w d (0) = 0.5w(0). In particular, the weight vector w c is updated using the CMA of (12) by substituting w c in the place of w. The weight vector w d by contrast is updated using the SDD scheme [10][11][12], which has its root in the blind equalisation scheme of [13]. Specifically, the complex phasor plane is divided into the M/4 square or rectangular regions, as illustrated in Fig.…”

“…, a local approximation of the marginal probability density function (PDF) of y(k) is given by [10][11][12] p w,…”

“…More recently, a novel combined CMA and soft DD (SDD) blind equaliser has been proposed [10][11][12], which achieves a faster convergence and has simpler implementation than the combined CMA and DD scheme of [8]. This combined CMA and SDD scheme operates a CMA-based equaliser and the last-stage SDD equaliser of [13] in a truly parallel manner.…”

A class of constant modulus algorithms for uniform linear arrays with a conjugate symmetric constraint

“…Constant modulus (CM) based algorithms have been studied extensively in the past for both blind beamforming and equalization [1][2][3][4][5]. Many of the algorithms are deEmail addresses: lei.zhang@sheffield.ac.uk (Lei Zhang), w.liu@sheffield.ac.uk (Wei Liu (member, EURASIP)), r.j.langley@sheffield.ac.uk (Richard J Langley).…”

Semi-Blind Spatial Equalisation for MIMO Channels with Quadrature Amplitude Modulation

“…We propose to use a constant modulus algorithm (CMA) assisted soft DD (SDD) blind adaptive algorithm to adapt the spatial equalisers. The concurrent CMA and SDD algorithm was originally derived for blind equalisation of single-input single-output (SISO) QAM systems [14], and it was extended to singleinput multiple-output (SIMO) systems in [15]. This blind adaptive scheme has a very low computational complexity.…”