Diagnosis Framework for Locating Failed Segments of Path Delay Faults

Diagnosis tools can be used to speed up the process for finding the root causes of functional or performance problems in a VLSI circuit. In this paper, we propose a method to locate possible segments that cause extra delays on circuit paths. We use the delay bounds of the tested paths to build linear constraints. By guiding the solutions of the linear constraints solved by a linear programming solver, we can identify segments with extra delays. Also, with the ranks of segment delays, we can prioritize the search for possible locations of failed segments. Besides, we also propose to reduce the search space by identifying indistinguishable segments. Essentially, we cannot separate segments in the same category no matter which segments have faults. This approach greatly increases the efficiency of the diagnosis process. Three main features of the proposed method are that: 1) it does not assume any delay fault model; 2) it derives diagnosis results directly from test data; and 3) it is able to diagnose failures caused by multiple delay defects. These features make our proposed method more realistic on solving the real problems occurring in the manufacturing process. In the experimental results, for most cases of injecting 5% of the longest path delay, the probabilities are over 90% for locating faulty segments within the list of top-ten suspects, and the average rankings, that is often referred to as first hit rank (FHR), which is defined as the rank of the first hit of the defect in the ranking list, are among the top five suspect locations for single fault injection. In the experimental results of multiple faults injection, the average FHRs are also lower than 5 for all cases of injecting 1% of the longest path delay.      

On asymptotically fair transmission scheduling over fading channels with measurement delay

We examine the effect of measurement delays on the throughput of certain downlink data packet systems operating over Rayleigh fading channels. In these systems the base station (BS) schedules a single user at a time and transmits at a rate which is based on measurements of the BS's received power performed by the user. The same subject was also discussed in a recent paper, titled "Asymptotically fair transmission scheduling over fading channels" by Berggren and Jantti (2004). They studied the effects of measurement delays on the operation of the scheduler. As a consequence of the delay, it is possible that by the time the BS actually transmits data, the propagation channels might have changed, such that the scheduler's choice no longer conforms to the desired scheduling policy, resulting in loss of system throughput and multi-user gain. Berggren and Jantti assume that perfect link adaptation is nevertheless always assured, i.e., that the BS transmits at a rate that matches precisely the current state of the selected user's channel. However, measurement delays lead also to mismatch between the data rate the BS transmits to the chosen user, and the current state of the propagation channel to that user. We believe that this mismatch must also be taken into account. In this letter we propose to use a backoff factor and analyze its mitigating effect on losses introduced by measurements delay in a Rayleigh fading environment. We then show the resulting gain in system throughput for optimal choices of the backoff factor     

A delay independent decorrelating detector for quasi-synchronousCDMA

The decorrelating detector is a near-far resistant linear joint detector for a code-division multiple-access (CDMA) system. It consists of a bank of matched filters followed by a decorrelating matrix. For proper operation, both the matched filter bank and the decorrelating matrix require knowledge of the delays of all users. The delays are due to the different propagation times from each user to the base station. Delay estimation is a weak link in this system since it is complex and prone to error. The proposed decorrelating detector does not require exact knowledge of the user delays, but instead requires that the delays be bounded to a fraction of a symbol interval. The delays are naturally bounded in this way in many microcell and picocell systems where the round trip propagation time is small compared to the symbol interval. The new delay independent decorrelating detector is shown to be near-far resistant and, through appropriate spreading code selection, to experience a modest 3 dB signal-to-noise ratio (SNR) loss relative to orthogonal access schemes. It is also shown to limit capacity to a maximum of 50% of the spreading gain when the delays are bounded by a single chip interval. The complexity is similar to the conventional correlating receiver which is far less complex than the joint detection schemes proposed to date     

Rake-Based Multiuser Detection for Quasi-Synchronous SDMA Systems

In this letter, a Rake-based multiuser detection technique, consisting of multiuser single-path signal separation, time-delay estimation, and multipath combining, is proposed for quasi-synchronous spatial-division multiple-access (SDMA) systems. Time diversity is achieved for performance improvement. In addition, only the upper bounds of the channel length and the time delays are required. Simulation results verify the effectiveness of the proposed technique, as well as its robustness against overestimation of the maximum channel length and the maximum time delay     

A Delay Decomposition Approach to Delay-Dependent Robust Passive Control for Takagi–Sugeno Fuzzy Nonlinear Systems

This paper is concerned with the problem of delay-dependent robust passive control for a fuzzy nonlinear system with time-varying delays. A Takagi–Sugeno fuzzy model approach is exploited to design a passive control for nonlinear systems with time-varying delay. By decomposing the delay interval into multiple equidistant subintervals, new Lyapunov–Krasovskii functionals (LKFs) are constructed on these intervals. Employing these new LKFs, a new robust passive control criterion is proposed in terms of linear matrix inequalities, which is dependent on the size of the time delay. We also design a state feedback controller that guarantees a robustly strictly passive closed-loop system for all admissible uncertainties. Finally, two numerical examples are given to illustrate the effectiveness of the developed techniques.     

Adaptive Delay Optimization of Multicast-Enabled Coded Caching in Device-to-Device Networks

This letter investigates a delay optimization problem in device-to-device(D2D)networks where users have pre-downloaded subfiles following a coded caching rule.Due to acquiring rest subfiles,users may suffer both receiving and transmitting delays.To achieve the delay minimization,we first propose a delay-aware mode-selection strategy to adaptively choose multicast or D2D communications mode to reduce the receiving-caused delay.By matching these transmit modes with distinct subfile sizes,we further formulate a min-max optimization problem to minimize the delivery delay.Finally,numerical results prove that the proposed scheme outperforms existing ones in terms of both receiving and transmitting delays.     

Hybrid access scheme based on one-phase preamble and channel monitoring/assignment for satellite communications

In this letter, we propose a hybrid access scheme for satellite communications, taking into account the long propagation delay. The proposed scheme uses the one-phase preamble of 3GPP2 for fast access and applies the channel monitoring/assignment scheme of 3GPP for more reliable transmission. The results of analysis and simulation show that the proposed scheme achieves high throughput and low delay according to propagation delays in satellite communication environments.     

PERFORMANCE OF CODED OFDM VIA VARIABLE GUARD INTERVAL

This letter presents the principles of Coded Orthogonal Frequency Division Multiplexing (COFDM) system and focuses on the effect of the Guard Interval (GI) on the system performance. The role of the GI parameter period to solve the problem of interferences that occur at the receiver is discussed. A new COFDM concept with a Variable GI (VGI) is proposed in order to improve the Bit Error Rate (BER) performance in the presence of multipaths with variable delays. A series of simulations have been carried out on the BER performance as a function of GI, maximum delay spread, and Signal-to-Noise Ratio (SNR), with QPSK as modulation scheme over multipath fading and Additive White Gaussian Noise (AWGN). The results show that the optimum values of the GI parameter approximately equal to the maximum delay spread, and the proposed system with VGI provides a better performance compared with the fixed length GI.     

一种改进的单向时延测量误差消除算法

针对协同探测系统中收发端之间的相对时钟频差会给单向时延测量带来误差,提出了一种基于最小二乘拟合和凸包的单向时延测量误差消除算法（LSFCH）.该算法首先对单向时延的原始测量数据进行去噪处理,再利用最小二乘法进行线性拟合,并利用凸包保证所有时延的非负性,从而得到精确的单向时延.实验结果表明,该算法能够有效地消除时钟频差对单向时延测量的影响,具有较好的准确性和鲁棒性.     

SAW dispersive delay line utilising apodised IDT with periodic electrodes

In designing SAW dispersive delay lines (DDLs), one usually applies dispersive interdigital transducers with electrode spacing varying according to the frequency-delay time relation of the delay line impulse response. A new method is proposed in the letter, in which a DDL is treated as a bandpass filter with a nonlinear phase response. Such a filter can be synthesised with an IDT having periodic electrodes with apodisation. The experimental result is ?40 dB of sidelobe level obtained in a system of two DDLs, one of which is Hamming-weighted.     

基于切换原理的非均匀采样系统输出反馈控制

在非均匀采样系统中,存在着刷新时间间隔不确定和时变的情况,这给系统控制器的设计造成了很大困难.针对此问题,本文将刷新时间间隔看作时延变量,将不同时延的系统动态变化过程转化为不同子系统的动态变化过程,从而将时延的变化转化为不同子模型之间的切换,最终将非均匀采样系统描述为一类具有有限个子系统的离散时间切换系统.利用输出反馈控制方法,基于平均驻留时间条件,使输出反馈闭环非均匀采样系统指数稳定.最后,通过一个非均匀采样系统仿真实例证明了提出方法的有效性.     

Experimental Demonstration and Characterization of a Tunable CRLH Delay Line System for Impulse/Continuous Wave

A new tunable delay system is presented and demonstrated experimentally in this letter. This system, which incorporates a composite right/left-handed (CRLH) transmission line, two mixers, and a low-pass filter, achieves a tunable group delay for impulse and continuous-wave signals, controlled by a local oscillator. This group delay tunability follows from the dispersion property of the CRLH transmission line and is achieved without suffering from the drawbacks of conventional delay lines in terms of matching, frequency of operation, and planar circuit implementation. The realized prototype exhibits measured group delays tunable between 5.1 and 8.54 ns over a frequency range of 2-4.5 GHz.     

用于信号逼近的自适应时延小波神经网络

小波神经网络是一种强有力的函数逼近工具。本文结合时延神经网络和小波分析概念提出一种新的小波神经网络摸型自适应时延小波神经网络(ATDWNN:adaptive timedelay wavelet neural network).ATDWNN可以对同一类存在不同时延的多个信号用同一个超小波(superwavelet)进行逼近。为了训练ATDWNN,本文提出一种基于时间机理的竞争学习算法。实验表明,ATDWNN不仅可以成功地对同一类存在不同时延的多个信号采用同一个超小波进行逼近,而且可以用来估计各样本信号的时延。     

Near-Optimal Power Allocation and Multiuser Scheduling with Outage Capacity Constraints Exploiting Only Channel Statistics

In this letter, we consider a delay-constrained wireless communication system where a delay constraint is characterized by the information outage probability in a transmission of K-block Rayleigh flat-fading channels. With multiple users, each given an individual delay requirement, this letter aims to minimize the total transmitted power by optimizing jointly the power distribution and the time sharing of a time-division (TD) multiuser system where the transmitter knows only the channel statistics (CST) but the mobile receivers (or users) have perfect knowledge of the channels. A suboptimal solution which utilizes Gaussian approximation with the mean and variance derived on the instantaneous mutual information and convex optimization, is proposed. Numerical results show that the proposed scheme performs nearly the same as the global optimum.     

Robust Delay-Dependent Stability Criteria for Dynamic Systems with Nonlinear Perturbations and Leakage Delay

This paper studies the global asymptotic stability for uncertain systems with mixed delays. The mixed delays include constant delay in the leakage term (i.e., leakage delay) and time-varying delays. The uncertainties under consideration are nonlinear time-varying parameter perturbations and norm-bounded uncertainties. Based on a appropriate Lyapunov–Krasovskii functional with triple integral terms, some integral inequalities and convex combination technique, a novel delay-dependent stability criterion is derived in terms of linear matrix inequalities (LMIs). Finally, three numerical examples are included to show the superiority of the proposed method.     

An LMI approach to the H/sub /spl infin// filter design for uncertain systems with distributed delays

This paper investigates the problem of robust H/sub /spl infin// filter design for linear distributed delay systems with norm-bounded time-varying parameter uncertainties. The distributed delays are assumed to appear in both the state and measurement equations. The problem we address is the design of a filter, such that for all admissible uncertainties, the resulting error system is asymptotically stable and satisfies a prescribed H/sub /spl infin// performance level. A sufficient condition is obtained to guarantee the existence of desired H/sub /spl infin// filters, which can be constructed by solving certain linear matrix inequalities. The effectiveness of the proposed design method is demonstrated by a numerical example.     

A robust PN code tracking algorithm for frequency selective Rayleigh-fading channels

In this letter, we propose a new tracking scheme that is robust against multipath fading for pseudonoise (PN) code tracking in direct-sequence-spread spectrum systems. The proposed scheme employs an adaptive filter whose taps are adapted using a block least-mean square algorithm and it results in minimizing the effect of multipath interference on the tracking performance. We show that the mean-squared tracking error performance of the proposed scheme is not affected by the presence of closely spaced paths (e.g., one to three chips), unlike that of conventional delay locked loops. We also show that the tap-weight distribution of the filter provides accurate estimates of the multipath delays. For example, at E/sub b//N/sub 0/=5 dB, 98% of the time the path estimates lie within one sample (1/5 of a chip) from the actual delays. Furthermore, simulation results suggest that multipath delays over a wide range of terminal speeds can be tracked successfully. The proposed scheme is well suited for wideband code-division multiple-access systems where a large number of closely-spaced multipath components need to be tracked and used in RAKE combining.     

A predictor for operator input for time-delayed teleoperation

In this paper we describe a method for bridging internet time delays in a free motion type teleoperation scenario in an unmodeled remote environment with video feedback. The method proposed uses minimum jerk motion models to predict the input from the user a time into the future that is equivalent to the round-trip communication delay. The predictions are then used to control a remote robot. Thus, the operator can in effect observe the resulting motion of the remote robot with virtually no time-delay, even in the presence of a delay on the physical communications channel. We present results from a visually guided teleoperated line tracing experiment with 100 ms round-trip delays, where we show that the proposed method makes a significant performance improvement for teleoperation with delays corresponding to intercontinental distances.     

Frequency estimation of a single complex sinusoid using a generalized Kay estimator

This letter introduces a generalized version of Kay's estimator for the frequency of a single complex sinusoid in complex additive white Gaussian noise. The Kay estimator is a maximum-likelihood (ML) estimator at high signal-to-noise ratio (SNR) based on differential phase measurements with a delay of one symbol interval. In this letter, the corresponding ML estimator with an arbitrary delay in the differential phase measurements is derived. The proposed estimator reduces the variance at low SNR, compared with Kay's original estimator. For certain delay values, explicit expressions for the window function and the corresponding high SNR variance of the proposed generalized Kay (GK) estimator are presented. Furthermore, for some delay values, the window function is nearly uniform and the implementation complexity is reduced, compared with the original Kay estimator. For a delay value of two, we show that the variance at asymptotically high SNR approaches the Cramer-Rao bound as the sequence length tends to infinity. We also explore the effect of exchanging the order of summation and phase extraction for reduced-complexity reasons. The resulting generalized weighted linear predictor estimator and the GK estimator are compared with both autocorrelation-based and periodogram-based estimators in terms of computational complexity, estimation range, and performance at both low and high SNRs.     

Global Stability of Fuzzy Cellular Neural Networks with Mixed Delays and Leakage Delay Under Impulsive Perturbations

This paper investigates the global asymptotic stability of a kind of fuzzy cellular neural networks with mixed delays under impulsive perturbations. The mixed delays include constant delay in the leakage term (i.e., “leakage delay”), time-varying delays, and continuously distributed delays. By using the quadratic convex combination method, reciprocal convex approach, Jensen integral inequality, and linear convex combination technique, several novel sufficient conditions are derived to ensure the global asymptotic stability of the equilibrium point of the considered networks. The proposed results, which do not require the differentiability and monotonicity of the activation functions, can be easily checked via Matlab software. Finally, two numerical examples are given to demonstrate the effectiveness and less conservativeness of our theoretical results over existing literature.