A CM based equalizer for space-time spreading over channels with inter-Symbol interference

Space-time block coding (STBC) and a number of derivative techniques have been developed to maximize the diversity gain of a multi-input multi-output (MIMO) channel. This was later generalized for multi-user DS-CDMA systems through space-time spreading (STS), [3] and [4], which assumed flat fading as well as the availability of full channel state information (CSI) at the receiver. This paper focuses on the development of a blind chip-rate method for the equalization of STS over channels with inter-symbol interference (ISI). Simulation results are presented to demonstrate the convergence and noise resilience of the derived algorithm

Blind adaptive equalizer for broadband MIMO time reversal STBC based on PDF fitting

In this paper, we propose a new blind adaptive technique used for the equalisation of space-time block coded (STBC) signals transmitted over a dispersive MIMO channel. The proposed approach is based on minimising the difference between the probability density function (PDF) of the equalizer output — estimated via the Parzen window method — and a desired PDF based on the source symbols. The cost function combines this PDF fitting with an orthogonality criterion derived from the STBC structure of the transmitted data in order to discourage the extraction of identical signals. This cost function motivates an effective and low-cost stochastic gradient descent algorithm for adapting the equaliser. The performance is demonstrated in a number of simulations and benchmarked against other blind schemes for the equalisation of STBC over broadband MIMO channels

MVDR broadband beamforming using polynomial matrix techniques

This paper presents initial progress on formulating minimum variance distortionless response (MVDR) broadband beamforming using a generalised sidelobe canceller (GSC) in the context of polynomial matrix techniques. The quiescent vector is defined as a broadband steering vector, and we propose a blocking matrix design obtained by paraunitary matrix completion. The polynomial approach decouples the spatial and temporal orders of the filters in the blocking matrix, and decouples the adaptive filter order from the construction of the blocking matrix. For off-broadside constraints the polynomial approach is simple, and more accurate and considerably less costly than a standard time domain broadband GSC

A fast converging blind receiver for space-time block codes over frequency selective channels

Space-Time Block Coding (STBC) and a number of derivative techniques have been developed to maximise the diversity gain of a multiple-input multiple-output (MIMO) channel. For frequency selective fading - i.e. dispersive - MIMO channels, solutions in the literature are fewer, and are in their majority block based, such as MIMO OFDM or time-reversal STBC In order to ultimately achieve better tracking behaviour, in this paper we focus on the development of a non-block-based method which utilises the Constant Modulus Algorithm (CMA). Due to the slow convergence of the CMA, we propose the use of Newtons method to find the optimum solution for the equalizer. A comparison of two different techniques of estimating the inverse of the correlation matrix is presented

Blind CM equalisation for STBC over multipath fading

This Letter focuses on the development of a blind adaptive receiver for space-time block coding (STBC) over multipath fading. The constant modulus (CM) criterion is utilised on the received signals, whereby an orthogonality constraint of the transmitted STBC signals prevents the multiple extractions of the same source. Simulation results demonstrate the performance of the proposed algorithm in a fading channel

A non-block based approach to the blind equalization of space-time block codes over frequency selective channels

Space-time block coding (STBC) and a number of derivative techniques have been developed to maximise the diversity gain of a multiple-input multiple-output (MIMO) channel. For frequency selective fading — i.e. dispersive — MIMO channels, solutions in the literature are fewer, and are in their majority block based, such as MIMO OFDM or time-reversal STBC. In order to ultimately achieve better tracking behaviour, in this paper we focus on the development of a non-block-based method. We utilise a constant modulus criterion on the detected signals together with the orthogonality contraint of the transmitted STBC signals, whereby for the later we derive novel criterion and an adaptive optimisation scheme. We demonstrate the proposed system in simulations and compare it to the performance of a TRSTBC system

A blind CM receiver for STBC over channels with inter-symbol interference

Alamouti's Space-Time Block Coding (STBC) scheme has received considerable attention due to its ability to maximize the diversity gain of a Multi-Input-Multi-Output (MIMO) transmission link. For frequency selective fading, only a few receivers can be found in the literature. These are mainly trained and block based, such as Time Reversal STBC (TRSTBC), introduced by [3], [4]. In order to ultimately achieve better tracking behavior, this paper focuses on the development or a non-block-based method. The Constant Modulus (CM) criterion is utilized on the received signals with the orthogonality constraint of the transmitted STBC signals. A novel criterion is derived to enforce the STBC structure on the equalizer outputs and consequently minimize the cross-correlation. Simulation results are presented to demonstrate the performance of the proposed algorithm

Blind adaptive equalizer for broadband MIMO STBC based on PDF matching

In this paper, we propose a new blind adaptive technique used for the equalisation of space-time block coded (STBC) signals transmitted over a dispersive MIMO channel. The proposed approach is based on minimising the difference between the probability density function (PDF) of the equalizer output — estimated via the Parzen window method — and a desired PDF based on the source symbols. The cost function combines this PDF fitting with an orthogonality criterion derived from the STBC structure of the transmitted data in order to discourage the extraction of identical signals. This cost function motivates an effective and low-cost stochastic gradient descent algorithm for adapting the equaliser. The performance is demonstrated in a number of simulations and benchmarked against other blind schemes for the equalisation of STBC over broadband MIMO channels

A concurrent blind receiver for STBC over doubly dispersive channels

Space-time block coding (STBC) achieves the maximum diversity gain of a flat fading multiple input multiple output (MIMO) transmission link. For frequency selective fading, only a few receivers can be found in the literature. These are mainly trained and block based, such as time reversal STBC (TRSTBC). A non-block based blind receiver for STBC over dispersive channels has been derived previously, adding a new term to the cost function of the constant modulus algorithm to orthogonalise the outputs. In this paper a decision directed (DD) equalizer is used concurrently with the CMA receiver to achieve faster convergence. Simulation results demonstrate the benefit of the proposed approach in terms of convergence speed and bit error ratio in a doubly-dispersive scenario

A fast and robust blind detection scheme for the UMTS TDD downlink component

In this paper, we propose a fast and robust blind multiuser equalisation scheme for the time-division duplex (TDD) component of the universal mobile telecommunication system (UMTS). In addition to the training-based equalisation performed using the midamble, blind detection is introduced over data fields to ensure continuous adaptation and better tracking performance. The latter strategy is mainly based on the affine projection scheme and the concurrent adaptation of both the constant modulus and decision directed modes. In computer simulations the performance of the proposed adaptation strategy is assessed for various UMTS TDD time bursts