SmipRef: An efficient method for multi-domain clock skew scheduling

Conventional clock skew scheduling (CSS) for sequential circuits can be solved effectively using methods including the parametric shortest path algorithm and Howard's algorithm. Nevertheless, its application is practically limited due to the difficulties in reliably implementing a large set of arbitrary dedicated clock delays for flip-flops. Thus multi-domain clock skew scheduling (MDCSS) was proposed to tackle this by constraining the total number of clock delays. However, this new problem is hard to solve optimally in general. In this paper, we propose a novel method to efficiently solve it. Under mild restrictions, the problem is transformed into a special mixed integer linear programming problem, which can be solved optimally using similar techniques for the CSS problem. Then the solution quality is further improved by a critical-cycle-oriented refinement. As a result, our method obtains optimal solutions for 88 of the 93 tests on ISCAS89 benchmarks. The experimental results on large circuits in Opencores benchmarks also demonstrate its efficiency of at least one order faster than existing algorithms. To improve the runtime performance, we also devise a graph pruning algorithm that can be applied to methods for the MDCSS problem as a preprocessing step. Its application on our method shows a speedup of 2.66X on average.     

An efficient location and routing scheme for mobile computingenvironments

One of the most important issues affecting host mobility is the location and routing scheme that allows hosts to move seamlessly from one site to another. This paper presents a method that exploits the locality properties of a host's pattern of movement and access history. Two concepts, “local region” and “patron service” are introduced based on the locality features. For each mobile host, the local region is a set of designated subnetworks within which a mobile host often moves, and the patrons are the hosts from which the majority of traffic for the mobile host originated. These are used to confine the effects of a host moving, so location updates are sent only to its local area, and to those source hosts which are most likely to call again. Our scheme has the advantages of limiting location updates, and providing optimal routing, while increasing network and host scalability     

An efficient location forwarding with shortcut scheme for position-based routing in mobile ad-hoc networks

Position-based routing protocols are considered as having better scalability and lower control overhead than topology-based routing protocols in mobile ad-hoc networks (MANETs). Since location services are the most critical part of position-based routing protocols, we present an Efficient Location Forwarding with Shortcuts (ELFS) scheme to improve the performance of location services. The ELFS scheme uses multiple virtual home regions to achieve efficient location discovery. We develop three approaches to reducing the overhead of maintaining multiple virtual home regions. The first approach, shortcut updates, uses the idea of shortcut to decrease the frequency of global updates. The second approach, adaptive broadcasting, alleviates the cost of each global update. In certain conditions, ELFS only broadcasts the messages of location update to the regions with the longest query paths. The third approach, packet forwarding with direction awareness, reduces the path lengths of messages. It can improve the cost of transmitting location information for delay-tolerant applications. With these approaches, the frequency of global broadcasting is decreased, and the overhead of location maintenance is reduced significantly. The simulation results show that the performance of ELFS is comparably fast and stable.     

Zero skew clock routing in X-architecture based on an improved greedy matching algorithm

As technology advances into nanometer territory, clock network layout plays an increasingly important role in determining circuit quality indicated by timing, power consumption, cost, power supply noise and tolerance to process variation. To alleviate the challenges to the existing routing algorithms due to the continuous increase of the problem size and the high-performance requirement, X-architecture has been proposed and applied to routing in that it can reduce wirelength and via counts, and thus improves the performance and routability compared with the conventional Manhattan routing. In this paper, we investigate zero skew clock routing using X-architecture based on an improved greedy matching algorithm (GMZSTX). The fitted Elmore delay model is employed to improve the accuracy over the Elmore delay model. The interactions among distance, delay balance and load balance are analyzed. Based on this analysis, an effective and efficient greedy matching scheme is suggested to reduce wire snaking and to get a more balanced clock tree. The proposed algorithm is simple and fast for practical applications. Experimental results on benchmark circuits show that our algorithm (GMZSTX) achieves a reduction of 8.15% in total wirelength, 30.19% in delay and 55.31% in CPU time on average compared with zero skew clock routing in the Manhattan plane (BB+DME-2, which means using the top-down balanced bipartition (BB) method [T.H. Chao, Y.C. Hsu, J.M. Ho, et al., Zero skew routing with minimum wirelength, IEEE Trans. Circuits Syst. II—Analog & Digital Signal Process 39 (11) (1992) 799–814] to generate the tree topology and using the Deferred-Merge Embedding (DME) algorithm [T.H. Chao, Y.C. Hsu, J.M. Ho, et al., Zero skew routing with minimum wirelength, IEEE Trans. Circuits Syst. II—Analog & Digital Signal Process 39 (11) (1992) 799–814] to embed the internal nodes), and reduces delay and CPU time by 17.44% and 62.21% on average over the BB+DME-4 method (which is similar to BB+DME-2, but routing in X-architecture). Our SPICE simulation further verifies the correctness of the resulting clock tree.     

Multi-parameter clock skew scheduling

Clock skew scheduling is a powerful technique for circuit optimization. Conventionally it can be formulated as a minimum cost-to-time ratio cycle (MCR) problem, which can be solved efficiently by a set of specialized network optimization algorithms. However, those algorithms can only handle one single parameter at a time, for example, the clock period, the timing slack or the yield. This inflexibility limits the applicability of the scheduling technique because in a real design one may need to consider multiple parameters simultaneously. In this paper, we introduce a multi-parameter extension to the MCR problem. Furthermore, a convex nonlinear extension is also considered. In particular, we generalize Lawler׳s algorithm, which is based on the bisection strategy. When there is more than one parameter, the bisection strategy is naturally replaced by the ellipsoid method. More importantly, the ellipsoid method does not require the knowledge of all constraints explicitly in prior. Instead, for each iteration, only a constraint that is violated by the current solution is required. This constraint turns out to be a negative cycle in our formulation, which can be detected efficiently. As a result, our proposed method could gain up to 12× run-time speedup for linear problems compared with a general linear programming solver and more than 700× run-time speedup for nonlinear problems compared with a general convex programming solver based on our experimental results.     

Energy efficient fault-tolerant multipath routing scheme for wireless sensor networks

In wireless sensor network （MSN）, reliability is the main issue to design any routing technique. To design a comprehensive reliable wireless sensor network, it is essential to consider node failure and energy constrain as inevitable phenomena. In this paper we present energy efficient node fault diagnosis and recovery for wireless sensor networks referred as energy efficient fault tolerant multipath routing scheme for wireless sensor network. The scheme is based on multipath data routing. One shortest path is used for main data routing in our scheme and other two backup paths are used as alternative path for faulty network and to handle the overloaded traffic on main channel. Shortest pat data routing ensures energy efficient data routing. Extensive simulation results have revealed that the performance of the proposed scheme is energy efficient and can tolerates more than 60% of fault.     

An efficient routing protocol for wireless networks

We present the Wireless Routing Protocol (WRP). In WRP, routing nodes communicate the distance and secondto-last hop for each destination. WRP reduces the number of cases in which a temporary routing loop can occur, which accounts for its fast convergence properties. A detailed proof of correctness is presented and its performance is compared by simulation with the performance of the distributed Bellman-Ford Algorithm (DBF), DUAL (a loop-free distance-vector algorithm) and an Ideal Link-state Algorithm (ILS), which represent the state of the art of internet routing. The simulation results indicate that WRP is the most efficient of the alternatives analyzed.This work was supported in part by the Advanced Research Projects Agency (ARPA) under contract F19628-93-C-0175 and by the Office of Naval Research under Contract No. N-00014-92-J-1807.     

Design methodology for synthesizing clock distribution networksexploiting nonzero localized clock skew

An integrated top-down design methodology is presented in this brief for synthesizing high performance clock distribution networks based on application dependent localized clock skew. The methodology is divided into four phases: (1) determining an optimal clock skew schedule composed of a set of nonzero clock skew values and the related minimum clock path delays; (2) designing the topology of the clock distribution network with delays assigned to each branch based on the circuit hierarchy, the aforementioned clock skew schedule, and minimizing process and environmental delay variations; (3) designing circuit structures to emulate the delay values assigned to the individual branches of the clock tree; and (4) designing the physical layout of the clock distribution network. The clock distribution network synthesis methodology is based on CMOS technology. The clock lines are transformed from distributed resistive capacitive interconnect lines into purely capacitive interconnect lines by partitioning the RC interconnect lines with inverting repeaters. Variations in process parameters are considered during the circuit design of the clock distribution network to guarantee a race-free circuit. Nominal errors of less than 2.5% for the delay of the clock paths and 7% for the clock skew between any two registers belonging to the same global data path as compared with SPICE Level-3 are demonstrated     

面向LEO卫星网络的高效路由算法

由于卫星星上处理以及存储能力有限,随着卫星网络的规模越来越庞大,迫切需要一种简单高效的路由算法.为此,提出了一种基于网络拥塞程度感知的路由策略(Network Congestion-Aware Routing Algorithm,NCARA).NCARA路由策略在网络处于非拥塞状态时采用Dijkstra算法寻路,网络拥...     

基于临时节点的无线体域网高效节能路由算法

以优化网络路由、延长网络生存期为目的,提出了一种基于临时节点的无线体域网(Wireless Body Area Network,WBAN)高效节能路由算法-A WBAN Efficient Energy-saving Routing Scheme Utilizing Temporary Nodes(RSUTN).该算法针对WBAN应用中出现的新的情况,通过充分利用临时节点富余能量,优化网络路由,平衡网络节点间能量消耗,延长网络生存期.理论分析和仿真结果表明,该算法能明显地平衡网络能量消耗,显著地延长网络生存期.     

An energy‐efficient utility‐based distributed data routing scheme for heterogenous sensor networks

A utility‐based distributed data routing algorithm is proposed and evaluated for heterogeneous wireless sensor networks. It is energy efficient and is based on a game‐theoretic heuristic load‐balancing approach. It runs on a hierarchical graph arranged as a tree with parents and children. Sensor nodes are considered heterogeneous in terms of their generated traffic, residual energy and data transmission rate and the bandwidth they provide to their children for communication. The proposed method generates a data routing tree in which child nodes are joined to parent nodes in an energy‐efficient way. The principles of the Stackelberg game, in which parents as leaders and children as followers, are used to support the distributive nature of sensor networks. In this context, parents behave cooperatively and help other parents to adjust their loads, while children act selfishly. Simulation results indicate the proposed method can produce on average more load‐balanced trees, resulting in over 30% longer network lifetime compared with the cumulative algorithm proposed in the literature. Copyright © 2014 John Wiley & Sons, Ltd.     

An efficient data routing scheme for multi-patient monitoring in a biomedical sensor network through energy equalization strategy

Wireless Networks - Biomedical sensor networks find wide applications in human health monitoring. In such applications, routing strategies in the sensor nodes play a key role towards energy...     

解决EPON兼容性的有效方案

文章介绍了一种在以太网无源光网络(EPON)中共享局域网(LAN)仿真的方法,即在光线路终端(OLT)的媒体接入控制(MAC)层中定义一个上层共享LAN仿真模块(ULSLE),既可以最大限度地利用PON的下行SCB能力,又可以为用户提供点到点的通信能力．而且,具有ULSLE的OLT可以与任何一个现有的以太网设备互通．     

An efficient receiver scheme for downlink ZP-CDMA

A signal transmitted through a wireless channel may be severely distorted by intersymbol interference (ISI) and multiple access interference (MAI). In this paper, we propose an efficient CDMA receiver based on frequency domain equalization (FDE) with a regularized zero forcing (RZF) equalizer and parallel interference cancellation with a unit clipper decision function (CPIC) to combat both the ISI and the MAI. We call this receiver the FDE-RZF-CPIC receiver. This receiver is suitable for downlink zero padding CDMA cellular systems. The effects of the decision function, the channel estimation, the number of cancelled users, and the user loading on the performance of the proposed receiver are discussed in the paper. The bit error rate (BER) of the data received by the proposed receiver is evaluated by computer simulations. The experimental results show that the proposed receiver provides a good performance, even with a large number of interfering users. At a BER of 10^?3, the performance gain of the proposed receiver is about 2 dB over the RAKE receiver with a clipper decision function and PIC in the half-loaded case (eight users) and is much larger in the full-loaded case (16 users).     

An energy-aware grid-based routing scheme for wireless sensor networks

As an important field of emerging technology, wireless sensor networks (WSN) offer many new possibilities for applications such as target tracking and environmental surveillance by allowing the observer to move around freely. However, disseminating sensing data to the mobile observer raises significant design challenges for the routing scheme. In addition, WSN often operate under certain energy constraints, and therefore reducing energy dissipation in order to prolong the lifetime of the WSN is another challenge that must be faced. Most proposed routing protocols focus on achieving effective data dissemination and energy efficiency at the same time as working to satisfy the requirements of the mobile observer. However, almost all of these methods use frequent rerouting as a way of handling the mobility issue. Such rerouting increases both overheads and energy consumption, resulting in a trade-off between the need for rerouting to optimize network operations and that of maximizing network lifetime. This paper presents the Energy-aware Grid-based Routing Scheme (EAGER) for WSN with mobile observers, which is an approach that seeks to save more energy in the context of dynamic topology. In this paper, EAGER is compared to other proposed grid-based schemes by using extensive simulations. These simulations clearly show that EAGER outperforms other grid-based schemes in terms of both energy efficiency and routing performance.     

一种适用于异步无线传感器网络的机会路由机制

无线传感器网络通常使用低占空比的异步睡眠调度来降低节点能耗。由于发送节点在接收节点醒来后才能向其发送数据,这将引入额外的等待时延。在最近的一些任播路由机制中,发送节点动态地选择最先醒来的候选节点转发数据,以最小化等待时延。但是,由于从最先醒来的候选节点到基站的时延可能并不低,任播路由机制并不一定能最小化端到端总时延。为此,提出了一种适用于异步无线传感器网络的机会路由机制,将路由决策建模为强马尔科夫过程,并根据最优停止理论推导出该过程一种简化的停止规则。仿真结果表明,节点到基站的最大端到端时延仅为基于地理位置的机会路由的68.5%。     

一种基于能耗均衡的ZigBee网络高效混合路由算法

针对目前ZigBee网络混合路由算法寻找开销偏大、能耗不均的问题,提出一种高效混合路由算法( EHCA)。通过采用跨层泛听与优先使用深度大、剩余能量多的节点进行路由的方式,减少部分泛洪寻路分组的转发,均衡节点能耗。仿真结果表明,EHCA的节点能耗均衡、路由开销和网络寿命等性能均优于混合路由算法和树路由算法。     

用于多级交换网络的一种高效自寻路技术

自寻路交换是多级交换网络中的一种常用技术,但它容易因冲突而形成网络内部阻塞.为减少连续冲突,进一步提升网络性能,基于三级交换网络前端采取“信元间插”策略,将分组的连续信元在时间轴上打散,保证业务被均匀地发送至网络中,从而大大减轻了网络内部阻塞;同时,通过在第一级交换单元中设置“逻辑指示器”,为不同的业务流合理地选取第二级交换单元,一定程度上保证了第二级的负载均衡.理论分析和仿真实验表明,与CRRD(Current Round-Robin Dispatching)等其他交换调度方式相比,新自寻路机制下的信元平均网络时延明显减小Clos网络,提出了一种新的高效自寻路机制.通过在     

An efficient scheme for single-cell point-to-multipoint e-MBMS transmission

多媒体广播多播业务（MBMS）是3GPP-R6版本中定义的一种典型的广播、多播业务。随着技 术的演进,在LTE系统中 提出了增强的MBMS,即e-MBMS业务。针对e-MBMS业务,提出了一种有效的技术解决 方案。该方案可看作下行发射分集、基于DoA的波束赋形与HARQ技术的结合。同时,仿真结 果也表明,该方案相对于单独的发射分集来说能带来显著的性能增益。     

追踪洋葱包的高级标记方案与实现

洋葱路由技术是实现信息隐藏而提出的一种新的匿名连接技术，使攻击者既不能进行窃听，也不能实施流量分析。然而攻击者一旦利用此技术进行拒绝服务式攻击，受害者无法追踏出攻击者。为此本文提出一种可追踪洋葱数据包的高级标记方案，使洋葱路由技术在保持原有隐匿性的同时受害者还可以近似地追踪出攻击者，本方案有很低的网络和路由器开销，也容易扩充到IPV6和未来的主干网。