摘要:

The paper proposes the use of an adaptive window flow control technique to control data access, with the aim of improving voice performance in an integrated voice/data multiplexer. By means of both mathematical analysis and computer simulation, the proposed control technique is shown to yield improvements in the average packet delay of both voice and data at the expense of data throughput. Additionally, the proposed control technique can be made to perform better than the two frame management strategies which have been demonstrated by previous work to be efficient for the integration of voice and data packets.

DOI:10.1049/ip-i-2.1989.0055

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Coding schemes for binary raster document transmission in the mobile radio environment are explored. For many applications, standard facsimile is too costly in terms of capital investment and transmission time. In this paper we present joint source-channel coding as an alternative, cost-effective solution for low resolution graphics transmission. We present SEA-RL coding as a novel and useful example of joint source-channel coding.

DOI:10.1049/ip-i-2.1989.0056

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Quite recently Tuftset al. presented an algorithm for improving conventional leastsquares (LS) estimates of the truncated pulse response of a communication channel. It involves oversampling of the channel output and singular value decomposition (SVD) of the data matrix before LS estimation.In the paper, an approximate expression for the variance of the estimate of each channel sample is derived when the algorithm is applied to the problem of identifying an exponential impulse response channel. SVD is shown to introduce discontinuities in the variance, which repeat periodically at the symbol rate, for those sample estimates outside the interval corresponding to the central tap. Experimental results confirm the validity of the approximations used in the variance computations, and that the disjoint periodic structure exists even for higher order channels.

DOI:10.1049/ip-i-2.1989.0057

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper presents an efficient adaptive predictive coding method using the local characteristics of images. In this method, three coding schemes, namely, mean, subsampling combined with fixed DPCM, and ADPCM/PCM, are used and one of these is chosen adaptively based on the local characteristics of images. The prediction parameters of the 2-d linear predictor in the ADPCM/PCM are extracted on a block by block basis using the 2-d lattice filtering method. The order update 2-d lattice model proposed by Parker and Kayran is extended into order update and time update recursion for more efficient computation. Simulation results show that the proposed method is effective in reducing the slope overload distortion and the granular noise at low bit rates, and thus it can improve the visual quality of reconstructed images. Other advantages of this method are the low computational burden and the suitability for the VLSI implementation.

DOI:10.1049/ip-i-2.1989.0058

出版商:IEE    

年代:1989

数据来源: IET

摘要:

This paper presents a fast search algorithm for vector quantisation (VQ)-based recognition of isolated words. It incorporates the property of high correlation between speech feature vectors of consecutive frames with the method of triangular inequality elimination to relieve the computational burden of vector-quantising the test feature vectors by full codebook search, and uses the extended partial distortion method to compress the incomplete matching computations of wildly mismatched words. Overall computational load can therefore be drastically reduced while the recognition performance of full search can be retained. Experimental results show that about 93% of multiplications and additions can be saved with a little increase of both comparisons and memory space.

DOI:10.1049/ip-i-2.1989.0059

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Motion analysis is an important component of computer vision, dealing with the measurement of motion information from a time varying image sequence. The analysis of dynamic image sequences finds a wide range of applications, including robot navigation, target tracking, traffic monitoring, motion of biological cells, cloud and weather systems tracking, image coding, etc. The paper reviews the various techniques used in motion analysis from image sequences. The approaches are classified according to the methodology in two main groups: methods based on the optical flow constraint equation, and matching. The advantages and disadvantages of both methodologies are also discussed.

DOI:10.1049/ip-i-2.1989.0060

出版商:IEE    

年代:1989

数据来源: IET

摘要:

We present a method of vector quantisation which trades off accuracy for speed of encoding. We achieve this by hierarchically structuring a multistage encoder so that each stage encodes low dimensional input vectors. Such hierarchical encoders may easily be realised as a set of fast table look-up operations. We demonstrate how the Euclidean distortion in such a multistage encoder is approximately minimised by using Kohonen's topographic mapping learning algorithm from neural network theory. We also demonstrate the performance of the technique on various stochastic time series. We find that there is little loss in encoding accuracy, when compared with the exact nearest neighbour encoding using an equivalent single stage encoder.

DOI:10.1049/ip-i-2.1989.0061

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Threshold detection techniques are employed to obtain canonical multiple-bit-observation receivers for detection of weak coherent and incoherent continuous phase-modulated signals buried in non-Gaussian noise. The limiting performance estimates of these receivers are derived, and then used to determine optimum coherent and incoherent threshold signalling schemes that belong to a subclass of CPM signals and find applications over certain bandlimited channels.

DOI:10.1049/ip-i-2.1989.0062

出版商:IEE    

年代:1989

数据来源: IET