Adaptive lattice-form IIR blind equaliser

The author describes incorporation of the lattice-form structure in the blind infinite impulse response (IIR) algorithm, based on a cost function which is a modified version of that proposed by Shalvi and Weinstein (1990). The proposed IIR blind equaliser has the advantage of lower complexity; simulation results also indicate that the proposed IIR blind equaliser has a faster convergence rate and a smaller mean square error (MSE)     

Low complexity concurrent constant modulus algorithm and soft decision directed scheme for blind equalisation

The recently introduced concurrent constant modulus algorithm (CMA) and decision-directed (DD) scheme provides a state-of-the-art low-complexity blind equalisation technique for high-order quadrature amplitude modulation (QAM) channels. At a small cost of slightly more than doubling the complexity of the standard CMA blind equaliser, this concurrent CMA and DD blind equaliser achieves a dramatic improvement in equalisation performance over the CMA. In the paper, a new blind equalisation scheme is proposed based on concurrent CMA and a novel soft decision-directed (SDD) adaptation. The proposed concurrent CMA and SDD blind equaliser has simpler computational requirements than the concurrent CMA and DD algorithm. Extensive simulation shows that it has the same steady-state equalisation performance as the concurrent CMA and DD algorithm and a faster convergence speed over the latter scheme     

CAD broadband matching design

In this letter, a CAD technique of designing a broadband matching network using the real frequency approach with the equaliser resistance (conductance) expressed in rational function is discussed.     

Enhanced sequence detector in the presence of intersymbol interference and non-Gaussian noise

A new Viterbi equaliser is proposed for joint mitigation of intersymbol interference and impulsive noise. The new equaliser uses a robust branch metric incorporating the Talwar penalty function. It is shown that the proposed equaliser facilitates considerable performance improvements.     

2-D adaptive CPWL filter for 2-D nonlinear channel equalisation and image restoration

A 2-D adaptive piecewise-linear equaliser is proposed. As an alternative of the 2-D adaptive Volterra equaliser, the proposed equaliser has advantages in its suitability for cases of strong nonlinearity and saving implementation and computation cost. An experiment examples is presented which demonstrates the superior behaviour of this method over either a linear method or the Volterra method in inverse modelling an unknown 2-D channel with blurring and a common point-wise nonlinearity and restoring images degraded by this channel.<>     

Open-loop transversal equaliser of optimal length

As a rule, in equaliser training algorithms complexity increases with efficiency. Unfortunately, complex recursive algorithms do not suit high-bandwidth systems. This letter describes a nonrecursive technique for the derivation of the weight vector in an optimally variable length transversal equaliser.     

Adaptive Kalman filter equaliser

A new adaptive equaliser for digital communication channels is proposed. It is derived from a state-variable representation of the communication channel by means of the extended Kalman filter technique. The equaliser proposed is structured as two Kalman filters, one estimating the transmitted data symbols, the other the unknown channel parameters.     

Voltage-transfer equalisation of general dissipative loads

This letter is concerned with the solution of the problem of synthetising equaliser networks for general dissipative loads when the voltage-transfer function is given as a function of the complex-frequency variable p=?+j?. The necessary and sufficient conditions are given for both lossless and dissipative equaliser networks.     

Turbo equalisation in non-Gaussian impulsive noise

Turbo equalisation is a state-of-the-art receiving scheme for coded data transmission over channels introducing intersymbol interference (ISI). The author investigates turbo equalisation performance in the presence of ISI and impulsive noise. The design imperfections contributing to the non-robustness of the standard turbo equaliser to outliers are identified, and a novel turbo equaliser, at almost no additional increase in complexity, is proposed for joint mitigation of ISI and impulsive noise. The proposed turbo equaliser incorporates a Talwar penalty function into the maximum a posteriori (MAP) component equaliser to serve two purposes. First, it improves the estimation of the transition probabilities for all transitions through the trellis and for subsequent determination of the a posteriori log-likelihood ratio. Secondly, it absorbs the outliers and prevents them from spreading into the MAP constituent decoder. Simulation results based on Proakis's channel models show that the proposed turbo equaliser achieves a dramatic improvement over the standard turbo equaliser in impulsive noise. At a bit error rate (BER) of 10/sup -2/, the performance gain is as large as 3.5 to 5 dB, and as large as 7 to 8 dB at a BER of 10/sup -3/.     

New family of active RC variable equalisers

A new family of active variable equalisers is introduced. The proposed variable equaliser transfer function is generated from Bode's classical transfer function using a new mathematical transformation. The new circuit uses a single operational amplifier and the required full range of variation is obtained by varying a single resistor Rv from zero to Ro (a reference resistance). The variable equaliser circuit requires a single shaping grounded impedance for realisation.     

Performance comparison of SWCE and Kalman-based HSDPA receivers

Equalisers can provide significant improvement in the performance of CDMA-based systems such as UMTS. Naturally, the level of improvement introduced depends on the employed equalisation technique. Reported are the results of an investigation into the performance of a Kalman-based channel-estimator/equaliser for use in high speed downlink packet access (HSDPA) receivers. Also, the performances of the Kalman and the sliding window chip rate equaliser (SWCE) algorithms are compared.     

Filtre correcteur de phase pour égaliseurs sous-optimaux

We propose a receiver structure intended for high bit rate transmissions. In order to ensure a good compromise between performance and complexity, the receiver is composed of a transversal phase- corrective filter followed by an equaliser, which takes only partially the channel impulse response into account. We propose a non-iterative technique to adjust the filter tap coefficients, based on the cepstral properties of a minimum phase response. The performance of the filter is evaluated and shown by simulating a transmission system including a multipath mobile radio channel, the filter and a dfse equaliser (decision feedback sequence estimator).     

Complexity reduction for a multisensor Viterbi equaliser

A multisensor equaliser based on the Viterbi algorithm is presented. The equaliser consists of a multisensor Viterbi estimator and adaptive channel estimators. Its complexity is described and its performance over mobile channels is analysed. It is concluded that the multisensor Viterbi equaliser is capable of considering truncated channels, thereby allowing a considerable reduction in complexity     

Decision feedback demodulation-based adaptive linear equalisers fordifferentially coherent DPSK systems

The authors propose to combine linear feedback equalisation and decision feedback demodulation for the equalisation of differentially coherent PSK signalling. By modifying the equaliser output based on the decision feedback demodulation before feeding back, the proposed equaliser can be made to behave like one with a decision feedback structure. Indeed, computer simulation results demonstrate that this equaliser performs much better than existing equalisers, such as linear equalisers for differentially coherent detection. Furthermore its performance is even comparable to that of a decision feedback equaliser with coherent detection     

Adaptive retraining equalisation based on channel change detections

By adaptively detecting abrupt changes in the channel tap coefficients and requesting the training sequence to be transmitted whenever changes are detected, an adaptive retraining equaliser has been designed. The performance of the equaliser is evaluated by numerical simulations, and the results show that the equaliser outperforms the traditional periodical retraining equaliser and requires fewer training sequences.     

Planar lightwave circuit dispersion equaliser with a wideoperational frequency range

The authors report an integrated-optic dispersion equaliser with an amplitude flattening circuit on a planar lightwave circuit. The equaliser consists of six asymmetrical Mach-Zehnder interferometers cascaded in series. The operational frequency range of the equaliser is successfully extended from 12.6 to 21.2 GHz by amplitude flattening without deteriorating the delay characteristics     

Planar lightwave circuit dispersion equaliser module withpolarisation insensitive properties

The authors report the fabrication of an integrated-optic dispersion equaliser module based on a planar lightwave circuit (PLC). The equaliser consists of five asymmetrical Mach-Zehnder interferometers cascaded in series. Polyimide half waveplates inserted in the interferometers eliminate the polarisation dependent path length differences of the equaliser     

Variable-gradient method for adaptive equaliser

A simple technique for the implementation of an adaptive equaliser is a gradient-seeking method. Two critical parameters associated with adaptive equalisation are the rate of convergence and the steady-state mean-square error attainable. When a fixed gradient is used in the gradient-search procedure for an adaptive equaliser, rapid convergence and a small steady-state mean-square error are two conflicting requirements. Use of a variable gradient parameter at each iteration provides a good compromise. A method for iteratively computing the gradient parameter is introduced, so that the random walk in the gradient-search procedure is executed, on the average, with decreasing step size as the iterative algorithm converges.     

Performance of adaptive multisensor decision feedback equaliser fortime-varying frequency selective radio channels

A multisensor decision feedback equaliser based on the minimum mean squared error (MMSE) criterion is studied. The superiority of the performance of the multisensor equaliser is shown by simulation of a whole communication system in which the adaptive equaliser is incorporated. The recursive least squares (RLS) algorithm is used to update the coefficients. From the results obtained for a time-varying urban terrain channel model, the extremely interesting tracking capability of the multisensor equaliser is shown     

Recursive single-most-likely-replacement channel equaliser

The paper proposes a recursive single-most-likely-replacement (SMLR) equaliser, that is a fixed-lag block signal processing algorithm indexed by the block size L and the number of decisions N⩽L at each recursion, for channels in the presence of intersymbol interference of finite or infinite length and additive white Gaussian noise. Both computational load and storage required by the proposed recursive SMLR equaliser are linearly proportional to the block size. Two simulation examples illustrate the performance of the proposed recursive SMLR equaliser