摘要:

AbstractAdaptive quantizers/dequantizers are systems that are used to quantize efficiently signals with a large variation in short‐term variance. They are typically found in telecommunication systems where highly non‐stationary signals such as speech need to be represented digitally with the minimum number of bits. Channel errors that are introduced owing to non‐ideal transmission significantly reduce the performance of adaptive dequantizers. In this paper we extend recent Kalman‐filter‐based adaptive quantization techniques to arrive at new dequantization schemes which are more robust to channel errors. This is achieved by utilizing the estimates produced by a Kalman filter based on a linear signal model which embodies the entire encoder/channel combination. Extensions to Kalman smoothing based on the same signal model result in further performance improvement at the expense of a sm

ISSN:0890-6327    

DOI:10.1002/acs.4480080501

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA fast algorithm for enhancement and tracking of periodic signals with fixed or slowly varying central frequency in additive noise is proposed. the algorithm is based on results from discounted least squares identification of a harmonic signal model combined with a recursive update scheme for the estimated fundamental frequency. In particular the gain sequence of the algorithm is determined by the fundamental frequency and an eligible forgetting factor. the performance of the algorithm is compared with theoretical lower bounds and it is shown that the algorithm yields good results.

ISSN:0890-6327    

DOI:10.1002/acs.4480080502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn this paper the techniques of extended Kalman filtering (EKF) and hidden Markov model (HMM) signal processing are combined to adaptively demodulate quadrature amplitude‐modulated (QAM) signals in noisy fading channels. This HMM approach is particularly suited to signals for which the message symbols are not equally probable, as is the case with many types of coded signals. Our approach is to formulate the QAM signal by a finite‐discrete state process and represent the channel model by a continuous state process. themixed state modelis then reformulated in terms of conditional information states using HMM theory. This leads to models which are amenable to standard EKF or related techniques. A sophisticated EKF scheme with an HMM subfilter is discussed, as well as more practical schemes coupling discrete state HMM filters and continuous state Kalman filters. the case of white noise is considered, as well as generalizations to cope with coloured noise. Simulation studies demonstrate the improvement gained over standard sche

ISSN:0890-6327    

DOI:10.1002/acs.4480080503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA new vectorized systolic array for extracting weight coefficients in block RLS is proposed. Our array is based on a generalization of the inverse factorization method of Pan and Plemmons and the array for computing residual vectors in block RLS using the Householder transformation of Liuet al.the new array is obtained by first generalizing the inverse factorizations for the block case and then deriving a formula for updating the tap coefficients without matrix operations.

ISSN:0890-6327    

DOI:10.1002/acs.4480080504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper concerns adaptive stabilization for single‐input/single‐output (SISO) continuous time systems with unknown coefficients and containing stochastic or deterministic disturbances. the conditions used here are possibly the weakest: neither the positive realness condition nor the availability of the upper bound of system disturbances is needed; the only condition imposed on the system structure is stabilizability, which is necessary for stabilizing a system even in the case where the system coefficients are known. the adaptive control given in the paper is switched at stopping times either on external excitations or on certainty equivalence controls defined by the pole assignment method at fixed times. It is shown that after a finite period of time the external excitation is no longer used and the system is stabilized in the long run average se

ISSN:0890-6327    

DOI:10.1002/acs.4480080505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractNew batch‐type methods and their recursive extensions are introduced for blind equalization of digital communication channels. Based on the underlying cost function of the existing Bussgang and cumulantfitting algorithms, simulated annealing (SA) optimization is successfully employed to identify and equalize the communication channels.Many of the existing blind equalization algorithms utilize a stochastic gradient approach to minimize non‐linear cost functions. Owing to the multimodal nature of these functions, the gradient algorithms might converge to the wrong solution. In contrast, the proposed methods are based on a global optimization algorithm. the SA algorithm tends to avoid the local minima encountered.The feasibility and convergence behaviour of the proposed algorithms are examined by means of computer simulations. Computational complexity issues in the implementation of the algorithms are discus

ISSN:0890-6327    

DOI:10.1002/acs.4480080506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0890-6327    

DOI:10.1002/acs.4480080507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY