Morse code with an easy-to-operate, single switch input system has been shown to be an excellent communication adaptive device. Because maintaining a stable typing rate is not easy for the disabled, the automatic reco...
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Morse code with an easy-to-operate, single switch input system has been shown to be an excellent communication adaptive device. Because maintaining a stable typing rate is not easy for the disabled, the automatic recognition of Morse code is difficult. Therefore, a suitable adaptive automatic recognition method is needed. This paper presents the application of a least-mean-square algorithm to adaptive Morse code recognition for persons with impaired hand coordination and dexterity. Four processes are involved in this adaptive Morse code recognition method: space recognition, tone recognition, adaptive processing, and character recognition. Statistical analyses demonstrated that the proposed method results in a better recognition rate for the participants tested in comparison to other methods from the literature. (C) IPEM. Published by Elsevier Science Ltd. All rights reserved.
Adaptive generalised sidelobe canceller (GSC) implemented with the least-mean-square (LMS) algorithm is a well-proven approach to effectively suppress unwanted interference. However, when the directions-of-arrival (DO...
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Adaptive generalised sidelobe canceller (GSC) implemented with the least-mean-square (LMS) algorithm is a well-proven approach to effectively suppress unwanted interference. However, when the directions-of-arrival (DOAs) of the desired signal and interference sources change over time, its performance may be largely degraded because of the fact that not only the interference-cancelling filter of GSC does not properly cancel the 'moving' interference, but also both the signal-matched filter and blocking matrix of GSC deviate from their best states for the 'moving' desired signal. Recently, a robust adaptive decision-feedback (DF) GSC has been proposed to partly solve the problem, but if the DOAs of all sources vary significantly and continuously, the adaptive DFGSC will eventually lose track of the source motion. In this study, the authors present a new modification for the DFGSC structure, which provides additional robustness in this kind of non-stationary signal environment. Specifically, they extend the use of Householder transformation together with the LMS algorithm for DFGSC, and a new update method is introduced for the whole beamforming processor. In addition, the tracking behaviour of this specially designed adaptive structure is studied and analysed, leading to the derivation of optimal step size for the interference-cancelling filter. Simulation results show that this modified adaptive DFGSC is very effective in mitigating the described non-stationary scenario.
Morse code is now being harnessed for use in rehabilitation applications of augmentative-alternative communication and assistive technology, facilitating mobility, environmental control and adapted worksite access. In...
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Morse code is now being harnessed for use in rehabilitation applications of augmentative-alternative communication and assistive technology, facilitating mobility, environmental control and adapted worksite access. In this paper, Morse code is selected as a communication adaptive device for persons who suffer from muscle atrophy, cerebral palsy or other severe handicaps. A stable typing rate is strictly required for Morse code to be effective as a communication tool. Therefore, an adaptive automatic recognition method with a high recognition rate is needed. The proposed system uses both fuzzy support vector machines and the variable-degree variable-step-size least-mean-square algorithm to achieve these objectives. We apply fuzzy memberships to each point, and provide different contributions to the decision learning function for support vector machines. Statistical analyses demonstrated that the proposed method elicited a higher recognition rate than other algorithms in the literature. (c) 2006 IPEM. Published by Elsevier Ltd. All rights reserved.
Technologically assistive devices are increasingly playing more important roles in the lives of persons with disabilities, with one of the more promising considerations being a combination of the functions of computer...
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Technologically assistive devices are increasingly playing more important roles in the lives of persons with disabilities, with one of the more promising considerations being a combination of the functions of computer software and hardware. However, using a conventional keyboard for Internet access is prohibitive for persons whose hand coordination and dexterity are impaired by ailments such as amyotrophic lateral sclerosis, multiple sclerosis, muscular dystrophy, and other severe handicaps. To assist participants with physical disabilities in sharing the resources of the Internet, we designed and implemented an easy-to-operate wireless input interface using Morse code as an adaptive communication tool. Moreover, an adaptive Morse code recognition process is introduced. After two months' practice on this system, three participants with physical disabilities could conveniently gain access to the Internet. (C) 2009 Elsevier Ltd. All rights reserved.
Distributed estimation using general data selection (DS) has always been applicable for reducing calculation loads in many fields. However, the traditional general DS (GDS) mode can deteriorate algorithm performance a...
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Distributed estimation using general data selection (DS) has always been applicable for reducing calculation loads in many fields. However, the traditional general DS (GDS) mode can deteriorate algorithm performance and usually neglects solving the problem of communication cost. These issues arise because distributed estimation is extremely susceptible to selecting the fused data and requires swapping all data. To solve these problems, a diffusion least-mean-square (DLMS) algorithm with an adaptive DS (ADS) is proposed to improve the GDS mode. The proposed algorithm can choose more reliable information in the data fusion process and diminish the communication cost (by using the saved intermediate data of previous iteration) and the calculation load. In addition, in GDS mode, the DS factor (DSF) selects data based on noise statistics (NS), resulting in some loss of selection ability. To further improve this situation, a novel cross-matching mechanism is proposed to improve the design of the DSF based on an intermediate estimation error. The mean stability and mean-square performance of the proposed DLMS algorithm with the ADS mode are analyzed theoretically, which can derive a convergence condition based on the step-size. Theoretical verification and target localization simulations are implemented to illustrate the effectiveness and robustness of the proposed ADS algorithm under satisfying the convergence condition as compared to other related DS algorithms.
It has been shown that, in intensely noisy environments, adaptive algorithms based on higher-order statistics can enjoy better performance, as compared with the well known second-order least-mean-square (LMS) algorith...
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It has been shown that, in intensely noisy environments, adaptive algorithms based on higher-order statistics can enjoy better performance, as compared with the well known second-order least-mean-square (LMS) algorithm. By contrast, this advantage diminishes for low signal-to-noise ratio (SNR) levels, where the LMS algorithm outperforms. One remedy is to employ the LMS algorithm in conjunction with a higher-order adaptation algorithm, in a mixed mode. least-mean kurtosis (LMK) is a higher-order algorithm that has been shown to be advantageous to use if the noise distribution is Gaussian or super-Gaussian. In this study, the authors propose the LMS/kurtosis algorithm, a stochastic gradient-based adaptive algorithm that is a combination of the LMS and the LMK algorithms. Simulation results demonstrate the privilege of the proposed algorithm, in comparison with its counterparts, for a wide range of noise distributions and SNR levels. This improvement is achieved in spite of a negligible increase in computational complexity. An analytical model is also derived for the mean weight as well as the weight-error covariance matrix, from which the mean-square-error behaviour of the algorithm can be predicted. Simulation results show the high accuracy of the derived model in different conditions.
We developed a new algorithm for supervised adaptive classifications with rapid incremental learning characteristics in dynamic environments. The new algorithm outperforms the Widrow-Hoff algorithm in applications whe...
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We developed a new algorithm for supervised adaptive classifications with rapid incremental learning characteristics in dynamic environments. The new algorithm outperforms the Widrow-Hoff algorithm in applications where: (a) real-time response is required, (b) the classifer is subjected to repeated train-then-apply cycles, and (c) the class distributions may change dynamically. The algorithm introduces (a) a dynamic cluster center representation, (b) a “balancing training” strategy, and (c) look-ahead learning by guard bands. Computational overhead for the improved performance is not excessive and strategies are further devised to reduce the overall computational complexity. The new algorithm is benchmarked against the Widrow-Hoff algorithm working as a clutter rejection unit in a target tracking system. Performance is shown for three sets of FLIR image sequence. The new algorithm outperformed the Widrow-Hoff algorithm (in terms of reduced misclassifications, and missed and false target rates). The improvement in missed target rate is very dramatic. The results also show that the new algorithm is not sensitive to parameter-setting.
Single-switch communication is an effective auxiliary method for persons with disabilities. However, it is not easy to recognize the Morse codes typed by them. In our earlier proposed Morse code auto-recognition metho...
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Single-switch communication is an effective auxiliary method for persons with disabilities. However, it is not easy to recognize the Morse codes typed by them. In our earlier proposed Morse code auto-recognition method, using the least-mean-square (LMS) adaptive algorithm, it was demonstrated that the system could successfully recognize the Morse-coded messages at unstable typing speeds. However, the speed variation had to be limited to a range between 0.67 and two times the present speed. In the case of beginners or those with heavy disabilities, this rule can not always be complied with, producing a low recognition rate of 20%. To address this limitation, this paper offers an advanced recognition method which combines the least-mean-square algorithm with a character-by-character matching technique. The recognition rate for this method from simulated and real data from various sources is as high as 75% or more on average. This practical application of the single-switch method means a step forward toward alternative communication for disabled persons. (C) 1997 Elsevier Science Ireland Ltd.
Morse code, with its single switch operation, has been shown to be an excellent adaptive communication device for the disabled, especially those with impaired hand coordination and dexterity. Because a stable typing r...
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Morse code, with its single switch operation, has been shown to be an excellent adaptive communication device for the disabled, especially those with impaired hand coordination and dexterity. Because a stable typing rate is required for an accurate recognition of Morse code, it presents a major hindrance to disabled persons in applying Morse code as a useful communication tool. Therefore, a suitable adaptive recognition method is needed. This paper applies the least-mean-square algorithm to an adaptive Chinese phonetic Morse code recognition system which includes four processes: space recognition, tone recognition, adaptive processing, and character recognition. Statistical analyses demonstrated that the proposed method results in a better recognition rate compared to alternative methods in the literature.
In this paper, a novel algorithm based on fuzzy logic and neural networks is proposed to find an approximation of the optimal step size mu for least-mean-squares (LMS) adaptive beamforming systems. A new error ensembl...
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In this paper, a novel algorithm based on fuzzy logic and neural networks is proposed to find an approximation of the optimal step size mu for least-mean-squares (LMS) adaptive beamforming systems. A new error ensemble learning (EEL) curve is generated based on the final prediction value of the ensemble-average learning curve of the LMS adaptive algorithm. This information is classified and fed into a back propagation neural network, which automatically generates membership functions for a fuzzy inference system. An estimate of the optimal step size is obtained using a group of linguistic rules and the corresponding defuzzification method. Computer simulations show that a useful approximation of the optimal step size is obtained under different signal-to-noise plus interference ratios. The results are also compared with data obtained from a statistical analysis performed on the EEL curve. As a result of this application, a better meansquare -error is observed during the training process of the adaptive array beamforming system, and a higher directivity is achieved in the radiation beam patterns.
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