A Quadratic Modeling-Based Framework for Accurate Statistical Timing Analysis Considering Correlations

The impact of parameter variations on timing due to process variations has become significant in recent years. In this paper, we present a statistical timing analysis (STA) framework with quadratic gate delay models that also captures spatial correlations. Our technique does not make any assumption about the distribution of the parameter variations, gate delays, and arrival times. We propose a Taylor-series expansion-based quadratic representation of gate delays and arrival times which are able to effectively capture the nonlinear dependencies that arise due to increasing parameter variations. In order to reduce the computational complexity introduced due to quadratic modeling during STA, we also propose an efficient linear modeling driven quadratic STA scheme. We ran two sets of experiments assuming the global parameters to have uniform and Gaussian distributions, respectively. On an average, the quadratic STA scheme had 20.5times speedup in runtime as compared to Monte Carlo simulations with an rms error of 0.00135 units between the two timing cummulative density functions (CDFs). The linear modeling driven quadratic STA scheme had 51.5times speedup in runtime as compared to Monte Carlo simulations with an rms error of 0.0015 units between the two CDFs. Our proposed technique is generic and can be applied to arbitrary variations in the underlying parameters under any spatial correlation model     

焊接用大功率YAG激光耦合装置的研制

为增大激光器输出功率,实现中厚度板的激光焊接,研制了一套YAG激光耦合装置.利用非相干合成技术将三束激光合成为一束大功率激光,再通过耦合技术经由一根光纤输出.对耦合装置的焊接性能进行测试表明,与单束激光源相比,该装置可使焊接材料厚度大幅度增加,提高了加工效率.     

Full-Chip Scalable Routing Framework Considering Congestion and Performance

提出一个全新的全芯片可控布线系统框架,同时考虑布线拥挤度和芯片性能.为了在总体布线和详细布线之间架起桥梁,该框架把总体布线和详细布线集成起来,交互进行,每完成一个线网的布线,都及时对布线资源进行更新,由此可以得到精确的资源估计结果,有利于指导后续总体布线决策.该系统框架的主要特征包括快速的基于模式的和基于外框约束下最短路算法的总体布线器、基于迷宫算法的拥挤度驱动的详细布线器以及在两个布线器之间很好的交互性.在该布线系统框架中,为了优化电路性能,在布线中关键线网被赋予更高的优先级.同时,为了优化不同的布线目标,可以采用不同的线网排序策略.该布线系统框架在一套公用的测试电路上完成测试,并与之前提出的多级布线系统框架进行比较,实验结果表明,文中提出的布线系统框架在电路性能、布通率和运行时间方面都取得了很大改进.     

Critical Path Selection for Delay Testing Considering Coupling Noise

The objective of delay testing is to detect any defects or variations that manifest into timing failures. In path based delay testing this is done by testing a subset of paths in the circuit that are more likely to fail and hence are critical. Since path delays are vector dependent, the set of critical paths selected depends on the vectors assumed when estimating the path delays. This implies that to find the real critical paths, it is important to consider the effect of dynamic (vector dependent) delay effects such as coupling noise and supply noise during path selection. In this work a methodology to incorporate the effect of coupling noise during path selection is described. For any given path, both logic and timing constraints are extracted and a constrained optimization problem is formulated to estimate the maximum path delay in the presence of coupling noise.     

Fine‐Grained FSMD Power Gating Considering Power Overhead

As a fine‐grained power gating method for achieving greater power savings, our approach takes advantage of the finite state machine with a datapath (FSMD) characteristic which shows sequential idleness among subcircuits. In an FSMD‐based power gating, while only an active subcircuit is expected to be turned on, more subcircuits should be activated due to the power overhead. To reduce the number of missed opportunities for power savings, we deactivated some of the turned‐on subcircuits by slowing the FSMD down and predicting its behavior. Our microprocessor experiments showed that the power savings are close to the upper bound.     

A Statistical Framework for Estimation of Full-Chip Leakage-Power Distribution Under Parameter Variations

This paper presents a novel framework for accurate estimation of key statistical parameters of the subthreshold-and gate-leakage distributions of a chip under parameter variations while considering both within-die and die-to-die variabilities in process (P), temperature (T), and supply voltage (V). For the first time, temperature variations and, more importantly, electrothermal couplings between junction (substrate or die) temperature and leakage power have been accounted for in a full-chip leakage estimation methodology. In the proposed framework, instead of exact leakage distribution profile, its statistically important parameters, such as nominal value and spread, are computed. Initially, at the transistor level, a quantitative analysis of the relative sensitivities of device leakage components to P-T-V variations is performed to extract a transistor-level variation model. It is shown that the proposed statistical model, as compared to others in the literature, shows better agreement with BSIM¹ model-based simulations. It is also demonstrated that failing to account for temperature variations and electrothermal couplings can result in significant inaccuracy in chip-level leakage estimation. Furthermore, the full-chip leakage-power distribution is used to estimate the leakage-constrained yield under the impact of variations. The calculations show that yield is significantly lowered due to the within-die and die-to-die process and temperature variations. Subsequently, the proposed framework is applied in the leakage estimation of complex logic circuits with a consideration of spatial correlations of process parameters and transistor stacking effects.     

A Mobility-Prediction-Based Relay Deployment Framework for Conserving Power in MANETs

There has been a growing interest in designing mobile systems consisting of special relay nodes whose mobility can be controlled by the underlying network. In this paper, we consider the design of a heterogeneous mobile ad hoc network (MANET) consisting of two kinds of mobile nodes-traditional nodes with limited energy and a few controllable mobile relay nodes with relatively abundant energy resources. We propose a novel relay deployment framework that utilizes mobility prediction and works in tandem with the underlying MANET routing protocol to optimally define the movement of the relay nodes. We present two instances of the relay deployment problem, together with the solutions, to achieve different goals. Instance 1, termed Min-Total, aims to minimize the total energy consumed across all the traditional nodes during data transmission, while instance 2, termed Min-Max, aims to minimize the maximum energy consumed by a traditional node during data transmission. Our solutions also enable the prioritization of individual nodes in the network based on residual energy profiles and contextual significance. We perform an extensive simulation study to understand the trade-offs involved in deploying an increasing fraction of such relay nodes in the network. We also investigate the performance of the proposed framework under different mobility prediction schemes. Results indicate that even when the relay nodes constitute a small fraction of the total nodes in the network, the proposed framework results in significant energy savings. Further, we observed that while both the schemes have their potential advantages, the differences between the two optimization schemes are clearly highlighted in a sparse network.     

一种基于电压岛的片上网络低功耗设计

功耗问题一直是片上网络设计中最为关心的问题之一.基于全局异步局部同步(GALS)的电压岛(VFI)机制的引入不但提供了极大地降低片上功耗的可能,也解决了片上单时钟传输的瓶颈问题.本文改善了现有的两种电压岛划分、核映射及路由分配方法,提出了一种更优的综合解决方案,并进行了验证.仿真结果显示,本文的方案可以显著降低系统功耗,同时提高了片上网络性能.     

A Multi-Model Engine for High-Level Power Estimation Accuracy Optimization

Register transfer level (RTL) power macromodeling is a mature research topic with a variety of equation and table-based approaches. Despite its maturity, macromodeling is not yet widely accepted as a de facto industrial standard for power estimation at the RT level. Each approach has many variants depending upon the parameters chosen to capture power variation. Every macromodeling technique has some intrinsic limitation affecting either its performance or its accuracy. Therefore, alternative macromodeling methods can be envisaged as part of a power modeling toolkit from which multiple models for a given component could be exploited so as to reduce the estimation errors resulting from conventional single-model approaches. This paper describes two different approaches for a new multi-model power estimation engine. The first one selects the macromodeling technique that leads to the least estimation error, for a given system component, depending on the properties of its input-vector stream. A proper selection function is built after component characterization and used during estimation. Though simple, this approach has revealed a substantial improvement in estimation accuracy. The second one builds a power estimate function that captures the correlation between individual macromodel estimates and input-stream properties. Experimental results show that our multi-model engine improves the robustness of power analysis with negligible usage overhead. Accuracy becomes seven times better on average, as compared to conventional single-model estimators, while the overall maximum estimation error is divided by 9.     

波达方向估计的一种互耦修正方法

阵列天线中互耦的存在,严重影响了天线的性能。基于分析天线阵列模型中阵元间的相互关联的特征的方法,构造互耦矩阵C,用C矩阵来修正波达方向估算中的互耦,并在MUSIC算法中实现。理论分析与计算仿真均表明该算法切实可行,有效并易于实现。     

半导体激光器光束耦合效率研究

在远距离无线光通信中,接收点光功率与光束发散角平方成反比。为了获得小的光束发散角和大的功率耦合效率,必须研究光束准直系统与耦合效率的关系。根据非傍轴远场光分布理论,用光线追迹法对半导体激光器光束准直系统中的功率耦合效率进行研究,给出半导体激光器光束耦合效率的计算方法,并进行计算机模拟。这里的研究结果对半导体激光器光束准直系统设计具有一定的指导作用。     

A Unified Framework for Transmitter Power Control in Cellular Radio Systems

In earlier works on transmitter power control in cellular radio systems, the problem of whether a signal‐to‐interference ratio (SIR) threshold is achievable is determined by apparently different rules for homogeneous and heterogeneous SIR systems. In this paper, we present a unified and more universal framework for both cases. We also highlight the conditions under which a given SIR threshold vector for the heterogeneous SIR system is achievable, although so far there is no general solution to this problem.     

Power Estimation Using Probability Polynomials

We describe a method of polynomial simulation to calculate switching activities in a general-delay logic circuit. This method is a generalization of the exact signal probability evaluation method due to Parker and McCluskey, which has been extended to handle temporal correlation and arbitrary transport delays. The method can target both combinational and sequential circuits.Our method is parameterized by a single parameter l, which determines the speed-accuracy tradeoff. l indicates the depth in terms of logic levels over which spatial signal correlation is taken into account. This is done by only taking into account reconvergent paths whose length is at most l. The rationale is that ignoring spatial correlation for signals that reconverge after many levels of logic introduces negligible error. When l = L, where L is the total number of levels of logic in the circuit, the method will produce the exact switching activity under a zero delay model, taking into account all internal correlation.We present results that show that the error in the switching activity and power estimates is very small even for small values of l. In fact, for most of the examples, power estimates with l = 0 are within 5% of the exact. However, this error can be higher than 20% for some examples. More robust estimates are obtained with l = 2, providing a good compromise between speed and accuracy.     

一种基于LS自适应AR建模的高分辨率时间延迟估计方法

本文提出了一种基于最小二乘（ＬＳ）自适应ＡＲ建模的时延估计方法。这种方法以接收信号的功率谱密度函数为时间序列，利用最小二乘格型自适应滤波器经由ＡＲ建模而得到高分辨率的时间延迟估计。文中给出了这种方法的原理、具体实现及性能分析，并以相关时延估计方法为参照进行了计算机模拟。     

一种鲁棒的变导频功率多径信道估计方法

文章提出了一种基于一阶统计量变导频功率多径信道估计方法,导出了信道估计和方差运算表达式,进行了估计器性能及峰均功率比分析.没有信息速率损失,且具有很强的估计鲁棒性.理论分析和仿真结果均证明了该方法的有效性.     

Sparse Power Angle Spectrum Estimation

A novel method for estimating the power angle spectrum (PAS) is presented that decomposes the true PAS into a small set of basis functions. The basis coefficients for this sparse representation are found by enforcing equality to the covariance or Bartlett PAS subject to a minimum $ell_{1}$-norm constraint. The method, referred to as sparse PAS estimation (SPASE), can be implemented conveniently using existing linear-programming (LP) solvers. Further, because only a few clusters are required in the representation, the method enables reduced-complexity stochastic models for the channel and possibly allows reduced overhead in channel feedback schemes. Application of the method to simulated channels and multiple-input multiple-output (MIMO) propagation data demonstrates the utility of the method.      

ELF Earth Return Coupling Into Power Systems

With the advent of the U.S. Navy's proposed ELF Communications System (Sanguine System), which would use an earth-return circuit to excite the earth-ionosphere cavity, earth-return current coupling into power systems has become important. The theoretical basis for coupling into power distribution systems is developed. A comparison is made between measured and predicted values of the induced voltage. Techniques which are useful in eliminating the effects of the induced voltage are described. The effectiveness of these interference mitigation techniques is demonstrated by comparing measurements on actual systems. Finally, data on power system interference are developed for use in communication system design tradeoff studies.