Analysis of millimetre wave microstrip circulator with a magnetised ferrite sphere by fdtD method with new extrapolation technique

In this article, the least-squares support vector machines (LS-SVM) technique is used in a finite-difference time-domain method to extrapolate the time domain responses. The particle swarm optimization method is used to optimise the hyperparameter of the LS-SVM algorithm, which should be tried again and again randomly. By modelling the novel microstrip circulator, we can eliminate some of the instabilities that arise in late times in the time domain. The frequency-dependent scattering parameters of the microstrip circulator are calculated over a wide band of frequencies with this hybrid method. The numerical results have a good agreement with the measurement.     

SVD-Based Techniques for Zero-Padded Block Transmission Over Fading Channels

In this paper, the performance of filter bank transceivers in the presence of a dispersive time-variant channel is investigated. It is well known that filter bank transceivers can be adapted to the channel transfer function to yield intersymbol interference (ISI) cancellation. When the channel is time variant, several problems arise, since the transceiver should be changed whenever the channel evolves. In this paper, we will allow both the transmitter and the receiver to change and satisfy the interference-free condition, under the assumption of a zero-padded block transmission. In this case, the optimum transmitter-receiver pair can be computed by using a singular value decomposition (SVD) of the channel matrix. A fast receiver adaptation based on SVD tracking is presented. Simulation results show that minimum performance loss with respect to the optimum receiver can be achieved for our reduced complexity receiver     

Synchronous and asynchronous A-D conversion

Analog-digital (A-D) converters with a fixed conversion time are subject to errors due to metastability. It is shown that an asynchronous converter in which the conversion time is not bounded is faster, on average, than the synchronous design. Real-time applications require the data to be produced within a fixed time, and failures may occur with the long conversion times that can arise with fully asynchronous converters. For these applications, we show that an internally asynchronous bounded time converter is both faster and more reliable than a synchronous converter     

Multiview Classification and Dimensionality Reduction of Scalp and Intracranial EEG Data through Tensor Factorisation

Electroencephalography (EEG) signals arise as mixtures of various neural processes which occur in particular spatial, frequency, and temporal brain locations. In classification paradigms, algorithms are developed that can distinguish between these processes. In this work, we apply tensor factorisation to a set of EEG data from a group of epileptic patients and factorise the data into three modes; space, time, and frequency with each mode containing a number of components or signatures. We train separate classifiers on various feature sets corresponding to complementary combinations of those modes and components and test the classification accuracy for each set. The relative influence on the classification accuracy of the respective spatial, temporal, or frequency signatures can then be analysed and useful interpretations can be made. Additionaly, we show that through tensor factorisation we can perform dimensionality reduction by evaluating the classification performance with regards to the number of components in each mode and also by rejecting components with insignificant contribution to the classification accuracy.     

Complementary operators: a method to annihilate artificialreflections arising from the truncation of the computational domain inthe solution of partial differential equations

The ease and simplicity with which the finite difference time domain (FDTD) or the finite elements (FE) techniques can handle complex radiation or scattering problems have lead to a remarkable surge in the use of these methods. While execution time is becoming less of an impediment when solving large problems, the biggest constraint remains the memory needed to run the FDTD or the FE methods. It is precisely this limitation that the article addresses. A boundary operation is developed to minimize the artificial reflections that arise when truncating the computational domain of an open region scattering or radiation problem. The method is based on the use of two boundary operators that are complementary in their action. By solving the problem with each of the two operators and then averaging the two solutions, the first-order reflections that arise from the artificial boundary can be completely eliminated. Numerical results are presented to show that this new technique gives significant reduction in the error when compared to other widely used boundary conditions     

Mobile hosts participating in peer-to-peer data networks: challenges and solutions

Peer-to-peer (P2P) data networks dominate Internet traffic, accounting for over 60% of the overall traffic in a recent study. In this work, we study the problems that arise when mobile hosts participate in P2P networks. We primarily focus on the performance issues as experienced by the mobile host, but also study the impact on other fixed peers. Using BitTorrent as a key example, we identify several unique problems that arise due to the design aspects of P2P networks being incompatible with typical characteristics of wireless and mobile environments. Using the insights gained through our study, we present a wireless P2P client application that is backward compatible with existing fixed-peer client applications, but when used on mobile hosts can provide significant performance improvements.     

Intercarrier interference in MIMO OFDM

In this paper, we examine multicarrier transmission over time-varying channels. We first develop a model for such a transmission scheme and focus particularly on multiple-input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM). Using this method, we analyze the impact of time variation within a transmission block (time variation could arise both from Doppler spread of the channel and from synchronization errors). To mitigate the effects of such time variations, we propose a time-domain approach. We design ICI-mitigating block linear filters, and we examine how they are modified in the context of space-time block-coded transmissions. Our approach reduces to the familiar single-tap frequency-domain equalizer when the channel is block time invariant. Channel estimation in rapidly time-varying scenarios becomes critical, and we propose a scheme for estimating channel parameters varying within a transmission block. Along with the channel estimation scheme, we also examine the issue of pilot tone placement and show that in time-varying channels, it may be better to group pilot tones together into clumps that are equispaced onto the FFT grid; this placement technique is in contrast to the common wisdom for time-invariant channels. Finally, we provide numerical results illustrating the performance of these schemes, both for uncoded and space-time block-coded systems.     

Modeling and Analysis in Frequency of the UWB Channel with Lognormal Statistics for MB-OFDM Systems

In this paper, the ultra-wideband channel with multiband orthogonal frequency division multiplexing (MB-OFDM-UWB) is analyzed in the frequency domain. For UWB channels with Lognormal small-scale fading in time domain, we obtain closed analytical expressions for the parameters that model the sub-carrier fading statistics of MB-OFDM-UWB system, and we show that magnitudes of the channel frequency responses of each subcarrier can be approximated by a Nakagami-m random variable, where the fading parameter (m), mean power Omega and the correlation rho_{ij} are expressed in terms of the following parameters: arrival time of the clusters, inter-arrival time of the rays inside the clusters, and power decay constants of the rays and clusters.     

Proportionate NSAF algorithms with sparseness-measured for acoustic echo cancellation

In acoustic echo cancellation (AEC), the sparseness of impulse responses can vary over time or/and context. For such scenario, the proportionate normalized subband adaptive filter (PNSAF) and μ-law (MPNSAF) algorithms suffer from performance deterioration. To this end, we propose their sparseness-measured versions by incorporating the estimated sparseness into the PNSAF and MPNSAF algorithms, respectively, which can adapt to the sparseness variation of impulse responses. In addition, based on the energy conservation argument, we provide a unified formula to predict the steady-state mean-square performance of any PNSAF algorithm, which is also supported by simulations. Simulation results in AEC have shown that the proposed algorithms not only exhibit faster convergence rate than their competitors in sparse, quasi-sparse and dispersive environments, but also are robust to the variation in the sparseness of impulse responses.     

A Robust Power Gating Structure and Power Mode Transition Strategy for MTCMOS Design

The large magnitude of supply/ground bounces, which arise from power mode transitions in power gating structures, may cause spurious transitions in a circuit. This can result in wrong values being latched in the circuit registers. We propose a design methodology for limiting the maximum value of the supply/ground currents to a user-specified threshold level while minimizing the wake up (sleep to active mode transition) time. In addition to controlling the sudden discharge of the accumulated charge in the intermediate nodes of the circuit through the sleep transistors during the wake up transition, we can eliminate short circuit current and spurious switching activity during this time. This is, in turn, achieved by reducing the amount of charge that must be removed from the intermediate nodes of the circuit and by turning on different parts of the circuit in a way that causes a uniform distribution of current over the wake up time. Simulation results show that, compared to existing wakeup scheduling methods, the proposed techniques result in a 1-2 orders of magnitude improvement in the product of the maximum ground current and the wake up time     

无源光网络主干保护系统中提前测距原理与应用

文章在分析无源光网络及其主干保护系统的基础上,为了提高保护倒换的效率,提出了一种无源光网络主干保护系统中的提前测距方法。该方法主要通过主用OLT在主用通道上测距,备用OLT在备用通道上被动侦听测距响应及其到达时间。通过测距信息、测距响应及到达时间便可计算出备用通道的测距结果。文章还提出了提前测距方法在无源光网络主干保护系统的实际应用中所涉及的主备OLT之间的信息交换和时间同步、测距过程发起、测距结果更新等具体措施。     

A GUIDE TO INSTRUMENT DESIGN

In this paper we provide a theoretical explanation of some of the phenomena which can arise in experiments using the retarding potential difference (R.P.D.) technique. In particular we can account for the occurrence of negative and of non-linear signals, and possibly also for the appearance of spurious peaks.     

Transfer matrix model of multilayer graphene nanoribbon interconnects

A general, algorithmic and exact transfer matrix model is presented for multilayer graphene nanoribbon (MLGNR) interconnects that is based on multi transmission line method (MTLM). In the proposed transfer matrix formulation the effect of Fermi level shift in GNR layers is considered. Also the capacitive and inductive coupling between the GNR layers is regarded in this matrix model. Moreover, in order to get the precise results, the block number parameter for distributed property of the interconnects is proposed for the first time. The straightforward, general and algorithmic format of the proposed matrix model causes it to be used for different technology nodes and length of the interconnects. Moreover any variation in the physical parameters can be involved simply in this formulation. Using this matrix model, one can examine different analytical prospects such as Nyquist, Bode, and Nichols stability criteria, zero and poles and step time responses for on-chip MLGNR interconnects, implemented for integrated circuit applications. Also this matrix model can be used in circuit simulators such as HSPICE in order to simulate the VLSI-ULSI circuits. As the couple of examples, we have extracted Nyquist diagrams and step time responses for 10 nm, 14 nm, and 22 nm technology nodes. The results show that relative stability of MLGNR interconnects increases with increasing technology node and interconnect length. The results demonstrate a considerable difference between the responses obtained using traditional MLGNR interconnect formulation and the exact proposed matrix model.     

Poisson shock models leading to new classes of non-monotonic aging life distributions

Suppose a device is subjected to a sequence of shocks occurring randomly in time according to a homogeneous Poisson process. In this paper we introduce a class of non-monotonic aging distributions, the so-called New Worse then Better than Used in Failure Rate (NWBUFR) and New Worse then Better than Average Failure Rate (NWBAFR). It is shown under appropriate conditions on the probability of surviving a given number of shocks that the non-monotonic aging classes NWBUFR and NWBAFR arise from suitable Poisson shock models.     

Feedback-testing by using multiple input signature registers

In this article, the use of Multiple Input Signature Registers (MISRs) as random pattern generators is investigated. This additional function helps to reduce hardware overhead and testing time, when BIST (Built-In Self-Test) structures are integrated on the chip, because the MISR can at the same time generate test patterns and collect test responses. A formula is presented, which determines the number of clock cycles needed to generate a given number of random patterns. Finally we suggest a method for how the number of test patterns can be reduced when the MISR acts as test pattern generator and compressor in a feedback loop.     

Modeling and efficient optimization for object-based scalabilityand some related problems

MPEG-4 is the first visual coding standard that allows coding of scenes as a collection of individual audio-visual objects. We present mathematical formulations for modeling object-based scalability and some functionalities that it brings with it. Our goal is to study algorithms that aid in semi-automating the authoring and subsequent selective addition/dropping of objects from a scene to provide content scalability. We start with a simplistic model for object-based scalability using the "knapsack problem"-a problem for which the optimal object set can be found using known schemes such as dynamic programming, the branch and bound method and approximation algorithms. The above formulation is then generalized to model authoring or multiplexing of scalable objects (e.g., objects encoded at various target bit-rates) using the "multiple choice knapsack problem." We relate this model to several problems that arise in video coding, the most prominent of these being the bit allocation problem. Unlike previous approaches to solve the operational bit allocation problem using Lagrangean relaxation, we discuss an algorithm that solves linear programming (LP) relaxation of this problem. We show that for this problem the duality gap for Lagrange and LP relaxations is exactly the same. The LP relaxation is solved using strong duality with dual descent-a procedure that can be completed in "linear" time. We show that there can be at most two fractional variables in the optimal primal solution and therefore this relaxation can be justified for many practical applications. This work reduces problem complexity, guarantees similar performance, is slightly more generic, and provides an alternate LP-duality based proof for earlier work by Shoham and Gersho (1988). In addition, we show how additional constraints may be added to impose inter-dependencies among objects in a presentation and discuss how object aggregation can be exploited in reducing problem complexity. The marginal analysis approach of Fox (1966) is suggested as a method of re-allocation with incremental inputs. It helps in efficiently re-optimizing the allocation when a system has user interactivity, appearing or disappearing objects, time driven events, etc. Finally, we suggest that approximation algorithms for the multiple choice knapsack problem, which can be used to quantify complexity vs. quality tradeoff at the encoder in a tunable and universal way.     

System aspects of cellular radio

The greatest single factor in enhancing spectral efficiency of a network is the mass deployment of microcells. By this simple technique we can repeatedly and efficiently reuse the precious spectrum. The number of users a network can support is fundamentally dependent on the common air interface (CAI) over which users communicate. User capacity is dependent on many factors, but the cardinal ones are the amount of spectrum the regulators allocate, the size of the radio coverage area from a base station (BS), and the amount of interference a particular radio link can tolerate. In this article we are primarily concerned with the system aspects associated with the CAI. We focus on the critical importance of BS siting. Starting with existing large cells, we deliberate on the problems that might arise in siting BSs in three dimensional microcells, in order to consider suitable multiple access methods for future cellular environments     

Conditions and Performance of Ideal RAKE Reception for Ultra-Wideband Signals in Lognormal Fading Channels

In this paper, the conditions and performance of ideal RAKE reception for time hopping Ultra-Wideband (UWB) investigated. Owing to the complex propagation phenomena and specific structure of UWB signals, new problems relevant to the operation of RAKE receivers arise. This motivates us to reconsider the conditions under which a RAKE receiver can work effectively with negligible interference between fingers. Key findings are that the conditions not only relate to the property of time hopping codes, but also modulation methods. An analytical technique is introduced to derive explicit expressions of RAKE performance for various combining methods for a lognormal fading channel. Numerical results show that RAKE reception can largely improve the performance, and equal gain combining has comparable performance to maximum ratio combining.     

A statistical technique for measuring synchronism between cortical regions in the EEG during rhythmic stimulation

The coherence function has been widely applied in quantifying the degree of synchronism between electroencephalogram (EEG) signals obtained from different brain regions. However, when applied to investigating synchronization resulting from rhythmic stimulation, misleading results can arise from the high correlation of background EEG activity. We, thus propose a modified measure, which emphasizes the synchronized stimulus responses and reduces the influence of the spontaneous EEG activity. Critical values for this estimator are derived and tested in Monte Carlo simulations. The effectiveness of the method is illustrated on data recorded from 12 young normal subjects during rhythmic photic stimulation.