A robust blind multiuser receiver based on a linearly constrained constant modulus algorithm (LCCMA) with multiple constraints and Quadratic Inequality (QI) constraint on the weight vector norm is developed in this pa...
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ISBN:
(纸本)0780389662
A robust blind multiuser receiver based on a linearly constrained constant modulus algorithm (LCCMA) with multiple constraints and Quadratic Inequality (QI) constraint on the weight vector norm is developed in this paper. Quadratic constraints have been a prevalent approach to improve the robustness against mismatch and modeling errors, uncertainties in estimating the data autocovariance matrix, and random perturbations in detector parameters. In this paper, the LCCMA is realized using a fast steepest descent adaptive algorithm based on the partition linear interference canceller (PLIC) structure with multiple constraints and a QI constraint on the weight vector norm. The Lagrange multiplier methodology is exploited to solve the QI constraint problem. Simulations are carried out in a loaded multipath environment with near-far effect to validate the robustness of the proposed detector.
The constant modulus algorithm (CMA) enjoys widespread popularity as methods for blind beamforming and equalization of communication signals. CMA is straightforward to implement, robust, and computationally of modest ...
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The constant modulus algorithm (CMA) enjoys widespread popularity as methods for blind beamforming and equalization of communication signals. CMA is straightforward to implement, robust, and computationally of modest complexity. Despite its effectiveness and apparent simplicity, adaptive implementation of the CMA comes along with several complicating factors that have never really been solved. In particular, convergence can be unpredictable and slow depending on the stepsize. In this paper, Convergence behaviors of the constant modulus algorithm based on "1-2" cost function (CMA1-2) and "2-1" cost function (CMA2-1) are investigated. We found that certain signal could be quickly removed from the output data choosing special stepsize if at least two signals were with different power. Simulation examples confirm the results.
This paper investigates a wordlength effect on an adaptive phased array antenna using the constant modulus algorithm (CMA). The antenna is a flat four-beam compact phased array whose main beam can be switched into fou...
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ISBN:
(纸本)078039433X
This paper investigates a wordlength effect on an adaptive phased array antenna using the constant modulus algorithm (CMA). The antenna is a flat four-beam compact phased array whose main beam can be switched into four directions by using four one-bit phase shifters. A beam with maximum received power is exploited as an initial beam for CMA. The wordlength investigation will be shown in term of the signal constellations, SINR trajectories and antenna patterns.
In this paper we present an approach to equalize multipath transmitted video signals without any reference signal. This approach takes advantage of the constant envelope feature of the color burst signal, which is tra...
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In this paper we present an approach to equalize multipath transmitted video signals without any reference signal. This approach takes advantage of the constant envelope feature of the color burst signal, which is transmitted in the blanking interval of each TV line and can be considered as an angle-modulated signal. The constant modulus algorithm (CMA) after Treichler is modified for our purpose. Special attention is given to the equalization of video signals in PAL systems. By making full use of the genuine phase feature of the color burst signal in PAL systems, the Hilbert transform needed by CMA can be saved for equalizing PAL system video signals. In addition to equalize analog TV signal, this paper can also lead to a joint echo cancellation of analog and digital TV signals transmitted in cable network. (C) 2001 Elsevier Science B.V. All rights reserved.
The convergence behavior of the constant modulus algorithm (CMA) is examined in the proper initialization condition of locking onto the desired signal. An improved CMA converging approach is proposed that has the adva...
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The convergence behavior of the constant modulus algorithm (CMA) is examined in the proper initialization condition of locking onto the desired signal. An improved CMA converging approach is proposed that has the advantage of suppressing multiple access interference without explicit knowledge of interference parameters for synchronous DS-CDMA systems. Simulation results demonstrate that the method overcomes the slower convergence of the CMA in the sudden birth of the number of users and outperforms the CMA detector and matched filter.
A Pre-processing Decision-FeedBack Least Squares constantmodulus blind multiuser detection algorithm (P-DFB-LSCMA) using antenna arrays is proposed in this paper. It pre-processes the received signals from the antenn...
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A Pre-processing Decision-FeedBack Least Squares constantmodulus blind multiuser detection algorithm (P-DFB-LSCMA) using antenna arrays is proposed in this paper. It pre-processes the received signals from the antenna arrays and utilizes the least squares constant modulus algorithm based on decision feedback to detection the DS-CDMA signals. Simulation results show that the proposed P-DFB-LSCMA algorithm is superior to DFB-LSCMA and LSCMA, especially with low SNR.
Periodically time varying (PTV) filters can offer significant performance gains over conventional filtering methods in DS-CDMA communications systems that are either multirate or corrupted by narrow band interference....
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ISBN:
(纸本)0780386051
Periodically time varying (PTV) filters can offer significant performance gains over conventional filtering methods in DS-CDMA communications systems that are either multirate or corrupted by narrow band interference. This paper develops a new blind adaptive PTV linear multiuser detector based on the frequency shift (FRESH) architecture. The blind adaptive algorithm is based on the linearly constrained constant modulus algorithm (LCCMA), but is modified for the FRESH architecture. The resulting stochastic gradient algorithm has significantly less computational complexity than the recently proposed recursive and cyclic subspace tracking algorithms, and can offer comparable performance. The robustness of the FRESH-LCCMA algorithm is ensured through a proof of convergence which is carried out in the paper.
In this paper, we present channel estimation methods for space-time block coding (STBC) transmissions using constant modulus algorithm (CMA). The channel estimates are directly calculated from the convergence value of...
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In this paper, we present channel estimation methods for space-time block coding (STBC) transmissions using constant modulus algorithm (CMA). The channel estimates are directly calculated from the convergence value of the CMA. Two algorithms using the channel-vector-based and channel-gain-based constantmodulus ( CM) criteria are proposed. An approximation of the CM cost function is introduced to allow the use of the recursive least-square (RLS) technique in designing fast RLS-CMA's. Performance of the proposed schemes is evaluated and compared with others using simulation. Illustrative results show that the proposed scheme outperforms the cross-correlated method and can approach the performance of the training-based method.
Symbol spaced blind channel estimation methods are presented which can essentially use the results of any existing blind equalization method to provide a blind channel estimate of the channel. Blind equalizer's ta...
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Symbol spaced blind channel estimation methods are presented which can essentially use the results of any existing blind equalization method to provide a blind channel estimate of the channel. Blind equalizer's task is reduced to only phase equalization (or identification) as the channel autocorrelation is used to obtain the amplitude response of the channel. Hence, when coupled with simple algorithms such as the constant modulus algorithm (CMA) these methods at baud rate processing provide alternatives to blind channel estimation algorithms that use explicit higher order statistics (HOS) or second-order statistics (subspace) based fractionally-spaced/multichannel algorithms. The proposed methods use finite impulse response (FIR) filter linear receiver equalizer or matched filter receiver based infinite impulse response+FIR linear cascade equalizer configurations to obtain blind channel estimates. It is shown that the utilization of channel autocorrelation information together with blind phase identification of the CMA is very effective to obtain blind channel estimation. The idea of combining estimated channel autocorrelation with blind phase estimation can further be extended to improve the HOS based blind channel estimators in a way that the quality of estimates are improved.
The paper investigates blind tinite-impulse-response (FIR) equalization schemes for quadrature amplitude modulation signalling. We compare a bootstrap maximum a posteriori probability (MAP) equalizer witha recently in...
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The paper investigates blind tinite-impulse-response (FIR) equalization schemes for quadrature amplitude modulation signalling. We compare a bootstrap maximum a posteriori probability (MAP) equalizer witha recently introduced concurrent constant modulus algorithm (CMA) and decision directed (DD) equalizer (CMA+DD). Both equalizers are known to outperform the CMA considerably in the situations where carrier recovery is performed and the signal constellation is known. The concurrent CMA+DD equalizer has a complexity that is slightly more than twice of the CMA, and the bootstrap MAP equalizer has computational requirements that are only slightly more complex than the CMA. Simulation results indicate that the bootstrap MAP blind FIR equalizer has a faster convergence rate and better steady-state performance than the concurrent CMA+DD blind FIR equalizer, but tuning of the former is more complicated than the latter. (C) 2003 Elsevier Inc. All rights reserved.
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