Multichannel L filters based on marginal data ordering

The extension of single-channel nonlinear filters whose output is a linear combination of the order statistics of the input samples to the multichannel case is presented in the paper. The subordering principle of marginal ordering (M-ordering) is used for multivariate data ordering. Assuming a multichannel signal corrupted by additive white multivariate noise whose components are generally correlated, the coefficients of the multichannel L filter based on marginal ordering are chosen to minimize the output mean-squared-error (MSE) either subject to the constraints of unbiased or location-invariant estimation or without imposing any constraint. Both the case of a constant multichannel signal corrupted by additive white multivariate noise as well as the case of a nonconstant signal is considered. In order to test the performance of the designed multichannel marginal L filters, long-tailed multivariate distributions are required. The derivation and design of such a distribution, namely, the Laplacian (biexponential) distribution that belongs to Morgenstern's family in the 2D case is discussed. It is shown by simulation that the proposed multichannel L filters perform better than other multichannel nonlinear filters such as the vector median, the marginal α-trimmed mean, the marginal-median, the multichannel modified trimmed mean, the multichannel double-window trimmed mean, and the multivariate ranked-order estimator R_E proposed elsewhere as well as their single-channel counterparts     

Multichannel transforms for signal/image processing

This paper presents a novel approach to the Fourier analysis of multichannel time series. Orthogonal matrix functions are introduced and are used in the definition of multichannel Fourier series of continuous-time periodic multichannel functions. Orthogonal transforms are proposed for discrete-time multichannel signals as well. It is proven that the orthogonal matrix functions are related to unitary transforms (e.g., discrete Hartley transform (DHT), Walsh-Hadamard transform), which are used for single-channel signal transformations. The discrete-time one-dimensional multichannel transforms proposed in this paper are related to two-dimensional single-channel transforms, notably to the discrete Fourier transform (DFT) and to the DHT. Therefore, fast algorithms for their computation can be easily constructed. Simulations on the use of discrete multichannel transforms on color image compression have also been performed.     

Multichannel image compression by bijection mappings ontozero-trees

A new approach to multichannel image compression is introduced where the intra- and cross-band correlations are jointly exploited in a surprisingly simple yet very effective manner. The key component of the algorithm is a bijection mapping of the original multichannel image into a virtual two-dimensional (2-D) scalar image. By optimally mapping the multichannel image set into a 2-D array and by subsequently applying a scalar image coding algorithm, the spatial correlation and the spectral correlation of the multichannel data set are jointly exploited. Based on the statistical characteristics of the multichannel data, the bijection mapping can be optimized to minimize the distortion introduced by the compression algorithm. The optimization reduces to the maximization of a function of the second-order statistics of the multichannel data. At high compression rates, the new algorithm outperforms traditional compression algorithms whenever the cross-band correlation is high and it yields comparable performance at low compression rates.     

22.2声道环绕声系统的测试及运用

22.2声道环绕声系统由NHK科学与技术研究实验室开发,用于超高清电视(UHDTV)系统中.介绍了22.2声道环绕声系统方案,并阐述了它的优点,以及实际运用的情况.     

多模式斜视多通道SAR成像方法

方位多通道技术是当前合成孔径雷达（SAR）系统主流的高分宽幅实现方式。而将方位多通道技术与斜视波束扫描（聚束、滑动聚束、TOPS）工作模式相结合可以实现灵活的更高分辨率或者更宽幅宽的遥感观测。然而由于斜视以及波束扫描会使得回波信号的多普勒带宽远大于通道数与脉冲重复频率（PRF）的乘积,使得传统的多通道成像方法失效。为了解决上述问题,本文提出一种基于方位去斜加方位重采样的多模式斜视多通道SAR成像方法,该方法通过对各个通道信号分别进行方位去斜以及对去斜、线性距离走动校正（LRWC）后的信号进行方位重采样来解决方位时变的问题,使得传统的多通道成像方法可以使用。理论分析与实验结果均验证了该方法可以处理多模式的斜视多通道SAR数据,并且得到聚焦良好的图像。     

Error probabilities for Rician fading multichannel reception of binary andn-ary signals

Performance characteristics are derived for two different forms of multireceivers (the coherent and noncoherent) which are used with binary andN-ary signaling through the Rician fading multichannel. The coherent multireceiver is capable of perfectly measuring the channel amplitudes and phases whereas, at the other extreme, the noncoherent multireceiver implies a receiver which requires no channel measurement whatsoever. The multichannel model presumes that each transmission mode supports a specular or fixed component and a random or scatter component which fades according to the Rayleigh distribution. Heretofore, performance analyses of multichannel links have assumed that the fading obeys the Rayleigh law. This multichannel model is sufficiently general to include four practical types: the Rician and the Rayleigh fading multichannels, multichannels whose propagation modes do not fade, and those which simultaneously contain Rician and Rayleigh fading propagation paths or the so called mixed-mode multichannel. Error probabilities are graphically illustrated and compared for various multichannel models. It is found that the effectiveness of multichannel reception is highly dependent on the strength of the specular channel component relative to the mean squared value of the random channel component. In particular, multichannel reception is more effective when applied to the completely random multichannel. For special cases the error-rate expressions reduce to well-known results.     

Time-Shared Codecs for Multichannel Delta Modulation and Differential PCM

Current practice for multichannel delta modulation (DM) terminals uses one DM codec per channel-end. This paper describes methods by which one high-speed DM codec can be timeshared over a large number of channels. The methods are also applied to multichannel differential PCM (DPCM) terminals. In both cases the time-shared codecs include step-size adaptation determined by the recent past history of the coded digital signal. A method for digital conversions between multichannel linear PCM and adaptive DPCM (ADPCM) formats is also described.     

一种面向自组织麦克风网络的多通道多人语音分离方法

针对自组织麦克风网络,如何充分有效地利用多通道语音数据获得更好的语音分离性能是一个难题。本文介绍了一种新的多通道语音分离方法,通过引入压缩激励脊髓模块,在麦克风位置未知时,也能显式地学习潜在的通道关系,自适应地更新各个通道对应特征的权重,以增加少量的额外计算代价达到增强语音分离的效果。压缩激励脊髓模块通过将多通道的特征信息压缩到通道维度,获得全局通道依赖关系的表征,利用激活函数根据通道关系表征对瓶颈单元筛选出有价值的特征信息。瓶颈单元由脊髓网络组成,通过逐步输入的方式生成全局信息和重新配置权重,更有效地处理数据。本文在基于LibriSpeech仿真的多通道版本数据中进行实验,在评估指标SDR和SI-SDR上相比于单通道基线获得了明显的提升,并取得超越最先进的自组织麦克风多通道方法的效果。      

基于特征分解的方位向多通道SAR相位失配校正方法

作为实现高分辨率宽幅成像的重要技术手段之一,方位多通道合成孔径雷达(Synthetic Aperture Radar, SAR)近年来得到了广泛的研究与发展。在进行多通道数据重建之前,通道之间的传输特性必须校正一致,以避免图像中出现严重的虚假目标。在多通道SAR数据处理中,精确的基带多普勒中心估计对系统的通道失配校正和高分辨率成像具有非常重要的意义。但是单一通道数据的多普勒频谱混叠制约了传统基带多普勒中心估计算法在方位多通道SAR系统中的应用。基于特征分解处理,该文提出一种新的基带多普勒中心估计方法。该方法在推导过程中考虑了波束指向存在斜视的影响,能够实现方位多通道SAR系统基带多普勒中心和通道间相位误差的鲁棒估计。仿真实验和C波段方位向四通道机载SAR实验数据处理分析验证了算法的有效性。      

Gradient Adaptive Paraunitary Filter Banks for Spatio-Temporal Subspace Analysis and Multichannel Blind Deconvolution

Paraunitary filter banks are important for several signal processing tasks, including coding, multichannel deconvolution and equalization, adaptive beamforming, and subspace processing. In this paper, we consider the task of adapting the impulse response of a multichannel paraunitary filter bank via gradient ascent or descent on a chosen cost function. Our methods are spatio-temporal generalizations of gradient techniques on the Grassmann and Stiefel manifolds, and we prove that they inherently maintain the paraunitariness of the multichannel adaptive system over time. We then discuss the necessary practical approximations, modifications, and simplifications of the methods for solving two relevant signal processing tasks: (i) spatio-temporal subspace analysis and (ii) multichannel blind deconvolution. Simulations indicate that our methods can provide simple, useful solutions to these important problems.     

Design of High-Channel-Count Multichannel Fiber Bragg Gratings Based on a Largely Chirped Structure

We propose a novel technique to design a high-channel-count, multichannel fiber Bragg grating (FBG) based on a largely chirped structure. The minimization of refractive-index modulation has been widely discussed in the previously demonstrated multichannel grating designs. The complexity of the grating structure, however, is also important from the point of view of practical fabrication. In this paper, the degree of grating complexity (DGC) is defined. We show that the DGC of a multichannel grating can be significantly reduced by designing a grating with a largely chirped structure. A detailed grating design process based on this technique is discussed, by which four multichannel gratings are designed and numerically studied, for applications such as periodic and nonperiodic spectral filtering, chromatic dispersion compensation and dispersion slope compensation. The proposed theory and examples show that different gratings with high-channel-count and multichannel responses can be designed and fabricated using a single commercially available phase mask, and all the gratings can be realized by a conventional FBG fabrication facility since the gratings have a low DGC with low index modulation.      

Multichannel restoration of single channel images using awavelet-based subband decomposition

We present a new matrix vector formulation of a wavelet-based subband decomposition. This formulation allows for the decomposition of both the convolution operator and the signal in the subband domain. With this approach, any single channel linear space-invariant filtering problem can be cast into a multichannel framework. We apply this decomposition to the linear space-invariant image restoration problem and propose a family of multichannel linear minimum mean square error (LMMSE) restoration filters. These filters explicitly incorporate both within and between subband (channel) relations of the decomposed image. Since only within channel stationarity is assumed in the image model, this approach presents a new method for modeling the nonstationarity of images. Experimental results are presented which test the proposed multichannel LMMSE filters. These experiments show that if accurate estimates of the subband statistics are available, the proposed multichannel filters provide major improvements over the traditional single channel filters.     

Architecture of multichannel DQDB network

The authors explain the basic architecture of the multichannel DQDB (distributed queue dual bus) network which is a generalisation of the single channel DQDB to the multichannel case by wavelength division multiplexing technology     

多通道实时光电混合联合变换相关器

提出一种多通道实时光电混合联合变换相关器,其中用一个液晶光阀(LCLV)作为非相干--相干图象转换元件,用一个多通道全息透镜阵列作为付氏变换元件实现多通道联合变换相关.这种相关器有效地利用了液晶光阀的有效使用面积和读出光能量,提高了相关识别性能.文中给出了实验结果.     

Multichannel medium access control for ad hoc wireless networks

In this paper, we study the multichannel exposed terminal problem in multihop wireless networks. We propose a multichannel medium access control (MAC) protocol, called multichannel MAC protocol with hopping reservation (MMAC‐HR), to resolve the multichannel exposed terminal problem. MMAC‐HR uses two radio interfaces; one interface is fixed over the control channel, and the other interface switches dynamically between data channels. The fixed interface supports broadcast information and reserves a data channel for any data transmission. The switchable interface, on other hand, is for data exchanges and follows independent slow hopping without requiring clock synchronization. In addition, the proposed protocol is a distributed one. By using the ns‐2 simulator, extensive simulations are performed to demonstrate that MMAC‐HR can enhance the network throughput and delay compared with existing multichannel MAC protocol. Copyright © 2011 John Wiley & Sons, Ltd.     

Multichannel linear and quadratic adaptive filtering based on theChandrasekhar fast algorithm

A new fast algorithm for multichannel linear and quadratic adaptive filtering using the Chandrasekhar equations is presented. Based on the shift-invariance property, the multichannel linear model could be described by a time-invariant state-space model to which we apply the Chandrasekhar factorization technique, which provides interesting numerical properties. Furthermore, a new method for nonlinear filtering is given where the multichannel Chandrasekhar algorithm is applied on the second-order Volterra (SOV) filter after suitable transformations     

Performance evaluation of a multichannel transceiver system forADSL and VHDSL services

The authors study the performance of a multichannel modulation method for asymmetric digital subscriber lines (ADSLs) and very high-speed digital subscriber lines (VHDSLs). In the ADSL case, over all unloaded North American subscriber lines in the test set, a unidirectional 1.536 Mb/s data rate service from the end office to the customer premises is possible on a single twisted pair at an error rate of 10^-7 with at least a 6 dB margin used coded multichannel modulation with sufficient transmit power. In the VHDSL case, data rates in excess of 100 Mb/s can be transmitted reliably, at an error rate of 10^-7, using uncoded multichannel modulation on a single twisted pair over a distance ⩽150 ft with a sufficiently high sampling rate (≈24 MHz) and transmit power. It is shown that a cost-effective multichannel transceiver design suggested for high-speed digital subscriber line (HDSL) service will also work well for ADSL and VHDSL services with only minimal modifications     

An approximate model of a switching network carrying mixture ofdifferent multichannel traffic streams

An approximate model of a multistage switching network carrying a mixture of different multichannel traffic streams is proposed. In the model the multistage switching network is reduced to a single-channel system, that is, to an Erlang ideal grading to which a mixture of different multichannel traffic is offered. An approximate method for recurrence determination of the distribution of being busy in such grading is presented. The determined distribution enables calculation of blocking probabilities for traffic streams of various classes. The derived formula is a generalization of Kaufman (1981) and Robert's (1981) recurrence formula covering a full-availability trunk group with various multichannel traffic streams, and it can be useful for the analysis of ISDN systems     

Space-time processing for multichannel synthetic aperture radar

Synthetic aperture radar (SAR) provides high-resolution images of a non-moving ground scene, but fails to indicate the presence and position of moving objects. As in airborne MTI (moving-target indication) systems the solution to this problem is to use an array of antennas or subapertures and several receiving channels (`MSAR', or multichannel SAR), and to apply multichannel clutter suppression. One of the most efficient methods is adaptive space-time processing (STAP), which can be simplified to frequency-dependent spatial processing in the Doppler domain. Some of these techniques applied to SAR are reviewed and illustrated with data gathered by the German experimental multichannel SAR system `AER-II'