FT-PDC: an enhanced hybrid congestion-aware fault-tolerant routing technique based on path diversity for 3D NoC

In recent years, using three-dimensional Network-on-Chip (3D-NoC) has increased due to its high performance and integration of processing elements. However, as technology evolves, dimension of processing elements and the number of connections are decreasing and this increases their sensitivity to external factors. Therefore, fault detection is one of the most important challenges of designing 3D-NoC because even a transistor not working well may cause the whole system not to work. Many methods have been provided so far to make three-dimensional NoC tolerant against fault, but most of these methods suffer from some disadvantages. For example, their fault detection models are not strong enough or they do not consider the network traffic. Regarding these problems, in this article, a routing technique called fault-tolerant routing algorithm based on path diversity and congestion (FT-PDC) for three-dimensional mesh connectivity based on NoC is provided that has some features like finding the shortest current path, considering fault in vertical and horizontal links, and considering path diversity and congestion. In addition to these features, FT-PDC could solve the problems of other methods to a great extent considering network traffic conditions and sending the packet from a path in which traffic conditions are two hops better than the other paths. These features have led to the superiority of the proposed method over other methods. The simulation results in the Noxim simulator show that latency and throughput of FT-PDC compared to similar recent methods have significantly improved.

     

一个基于备份路由的AODV路由协议

AODV路由协议每次在源节点只建立一条通向目的节点的路由,未能充分利用从中间节点或者目的节点返回的路由应答信息,针对这一问题,提出了一个改进的方法。在源节点处建立一条主路由的基础上,利用路由应答信息,建立一条备份路由,并且每次将最优的设为主路由,次优的设为备份路由。仿真结果表明,改进的协议和原协议相比,降低了端到端的延时,提高了包投递率     

基于链路中断预测的AODV路由算法研究

在移动自组网中,节点的移动导致拓扑动态变化,已经建立的路由时刻存在中断的可能,而传统的AODV路由协议中的路由修复方法开销大、时延长。针对这一问题,提出了一种基于链路中断预测的改进路由算法。该算法在链路中断之前启用备用节点,尽量避免路由修复;在链路中断后,首先在本地进行链路修复,不成功再逐层由上游节点发起路由搜索。仿真实验结果表明,与传统AODV相比控制开销降低了40%,端到端时延减少了25%,提高了网络性能。     

时延约束的链路选择平衡优化组播路由算法

针对时延约束的最小代价组播树生成方法,提出一种快速有效的时延约束组播路由算法。该算法改进了KPP算法,设计了代价和时延动态优化的链路选择函数。在选择路径时,该算法综合考虑了时延和代价两个参数,保证了组播树的性能,降低了时间复杂度低。仿真结果表明,该算法能正确地构造出时延约束组播树,同时还具有较低的代价和计算复杂度。     

基于节点多样性的域内路由保护算法

已有的路由保护方案都没有考虑网络中节点的重要程度,然而在实际网络中不同节点在网络中的重要程度是不相同的。针对该问题,提出一种基于节点多样性的域内路由保护算法（intra-domain routing protection algorithm based on node diversity,RPBND）。计算节点构造以目的为根的最短路径树（shortest path tree,SPT）,从而保证RPBND算法和目前互联网部署的路由算法的兼容性;在该最短路径树的基础上构造特定结构的有向无环图（directed acyclic graph,DAG）,从而最大化路由可用性。实验结果表明,RPBND极大地提高了路由可用性,降低了故障造成的网络中断时间,为ISP部署域内路由保护方案提供了充分的依据。     

Impact of virtual channels and adaptive routing on applicationperformance

Research on multiprocessor interconnection networks has primarily focused on wormhole switching, virtual channel flow control, and routing algorithms to enhance their performance. The rationale behind this research is that by alleviating the network latency for high network loads, the overall system performance would improve; many studies have used synthetic workloads to support this claim. However, such workloads may not necessarily capture the behavior of real applications. In this paper, we have used parallel applications for a closer examination of the network behavior. In particular, the performance benefit from enhancing a 2D mesh with virtual channels (VCs) and a fully adaptive routing algorithm is examined with a set of shared-memory and message passing applications. Execution time and average message latency of shared memory applications are measured using execution-driven simulation and by varying many architectural attributes that affect the network workload. The communication traces of message passing applications, collected on an IBM-SP2, are used to run a trace-driven simulation of the mesh architecture to obtain message latency. Simulation results show that VCs and adaptive routing can reduce the network latency to varying degrees depending on the application. However, these modest benefits do not translate to significant improvements in the overall execution time because the load on the network is not high enough to exploit the advantages of the network enhancements. Moreover, this benefit may be negated if the architectural enhancements increase the network cycle time. Rather, emphasis should be placed on improving the raw network bandwidth and faster network interfaces     

基于最短路径搜索序列编码的多下一跳路由

多下一跳路由较之单下一跳路由有许多天然的优势,通过分析现有多下一跳路由实现机制下的路由算法,提出了基于最短路径搜索序列编码的多下一跳路由.针对SPT(shortest path tree)路由实现机制无法利用等距离邻居节点之间链路的问题,提出了采用Dijkstra算法对网络节点编码赋值的思想.该方法可以对节点进行严格有序的赋值,规范了链路传输方向,有效地避免了环路,提高了网络资源利用率.仿真分析结果表明了该算法的可行性和有效性.     

基于源区域路径选择的层次化片上网络路由算法

针对较大规模片上网络(NoC)远端节点和邻近节点之间的通信问题,提出一种基于区域划分的层次化簇状分层网（CHM）结构。在此基础上,针对中间节点拥塞严重导致网络性能降低的问题,提出一种基于源区域路径选择的自适应算法。该算法利用CHM结构区域特性将路由决策由源节点移至源区域,同时在原有底层和上层节点对的基础上增加自适应节点对,并增加该部分节点对路由选择性,从而缓解网络拥塞状况。仿真实验表明,与最短路径算法相比,在合成流量和局部化流量模式下,该算法下的CHM结构饱和注入率最多可分别提升约51%和31%,因此该算法可有效提升网络整体吞吐性能。     

一种基于非线性长度的多约束路由算法

满足多个约束的QoS路由问题已经被证明是NP完全问题。在分析了多种路由算法的基础上,设计了一种高效的多约束路由算法。该算法采用非线性路径长度计算方法。为提高算法的成功率,在节点的松弛过程中设计了节点动态路径长度计算,允许节点作多次松弛。为提高算法的执行效率,在节点正向松弛和反向估计过程中引入了受控路径的思想,使算法得到了优化。大量仿真表明,该算法在最短路径获取和路由发现成功率方面都有高效的表现。     

基于路径探索的车载自组网贪婪路由算法

为了提高城市中车辆间信息的传输效率，实现车辆间的信息共享，针对目前车载自组网（VANET）中基于地理位置转发的多跳单播路由算法没有考虑城市场景的特殊性，不能很好地适应城市中车辆的高度动态性，使车辆之间的数据包可能在错误的路径上传播，造成丢包率较高、时延较长的问题，提出了一种新的基于路径探索的贪婪路由算法。首先，以数据包传输时延为标准，运用人工蜂群算法对数字地图规划出的多条路由路径进行探索。其次，优化数据包在车辆之间的多跳转发方式。仿真结果表明，与贪婪周边无状态路由（GPSR）协议和最大持续时间最小角的GPSR（MM-GPSR）改进算法比较，在最好情况下，所提算法的数据包到达率分别提高了13.81%和9.64%，而该算法的数据包平均端到端时延分别降低了61.91%和27.28%。     

Complexity results on labeled shortest path problems from wireless routing metrics

Metrics to assess the cost of paths through networks are critical to ensuring the efficiency of network routing. This is particularly true in multi-radio multi-hop wireless networks. Effective metrics for these networks must measure the cost of a wireless path based not only on traditional measures such as throughput, but also on the distribution of wireless channels used. In this paper, we argue that routing metrics over such networks may be viewed as a class of existing shortest path problems, the formal language constrained path problems.On this basis, we describe labeled path problems corresponding to two multi-radio wireless routing metrics: Weighted Cumulative Expected Transmission Time (WCETT), developed by Draves et al., and Metric for Interference and Channel-switch (MIC), developed by Yang et al. For the first, we give a concise proof that calculating shortest WCETT paths is strongly NP-Complete for a variety of graph classes. We also show that the existing heuristic given by Draves et al. is an approximator. For the second, we show that calculating loop-free (simple) shortest MIC paths is NP-Complete, and additionally show that the optimization version of the problem is NPO PB-Complete. This result implies that shortest simple MIC paths are only poorly approximable in the worst case.Furthermore, we demonstrate how the polynomial-time algorithm for shortest MIC paths is derivable from an existing language constrained shortest path algorithm. We use this as a basis to exhibit the general utility of viewing multi-channel wireless routing metrics as labeled graph problems, and discuss how a class of related polynomial-time computable metrics are derivable from this algorithm.     

时延受限组播路由的最短路径加速算法求解

分析了时延受限的Steiner树问题,总结了在构建组播树过程中的代价和计算复杂度变化规律,并根据实际网络环境,从优化最短路径出发,提出了一种基于优化最短路径的时延受限组播路由算法AOSPMPH。该算法以MPH算法为基础,利用Floyd最短路径优化算法求出节点对之间的最短路径,选择满足时延要求的最小代价路径加入组播树,进而产生一棵满足时延约束的最小代价组播树。仿真结果表明,AOSPMPH不但能正确地构造时延约束组播树,而且其代价和计算复杂度与其他同类算法相比得到了优化。     

Time complexity of a path formulated optimal routing algorithm

A detailed analysis of convergence rate is presented for an iterative path formulated optimal routing algorithm. In particular, it is quantified, analytically, how the convergence rate changes as the number of nodes in the underlying graph increases. The analysis is motivated by a particular path formulated gradient projection algorithm that has demonstrated excellent convergence rate properties through extensive numerical studies. The analytical result proven in this note is that the number of iterations for convergence depends on the number of nodes only through the network diameter     

路径优化的无线传感器网络CTP路由算法

针对无线传感器网络普遍存在因负载不均衡导致的转发率过高,网络寿命短的问题,提出了一种基于汇聚树协议(CTP)的路径转发优化协议深度和孩子汇聚树协议(DC-CTP).通过研究节点路径深度和孩子节点个数对当前节点以及对全网络转发数据量的影响,对CTP网络节点的路由算法进行优化.TOSSIM仿真的结果表明:DC-CTP协议选择优化后的路径,将整个网络的节点的数据转发量减少了平均10.25％左右,能够延长无线传感器网络的存活时间.     

Neural networks for shortest path computation and routing incomputer networks

The application of neural networks to the optimum routing problem in packet-switched computer networks, where the goal is to minimize the network-wide average time delay, is addressed. Under appropriate assumptions, the optimum routing algorithm relies heavily on shortest path computations that have to be carried out in real time. For this purpose an efficient neural network shortest path algorithm that is an improved version of previously suggested Hopfield models is proposed. The general principles involved in the design of the proposed neural network are discussed in detail. Its computational power is demonstrated through computer simulations. One of the main features of the proposed model is that it will enable the routing algorithm to be implemented in real time and also to be adaptive to changes in link costs and network topology.     

Impact of sensing coverage on greedy geographic routing algorithms

Greedy geographic routing is an attractive localized routing scheme for wireless sensor networks due to its efficiency and scalability. However, greedy geographic routing may fail due to routing voids on random network topologies. We study greedy geographic routing in an important class of wireless sensor networks (e.g., surveillance or object tracking systems) that provide sensing coverage over a geographic area. Our analysis and simulation results demonstrate that an existing geographic routing algorithm, greedy forwarding (GF), can successfully find short routing paths based on local states in sensing-covered networks. In particular, we derive theoretical upper bounds on the network dilation of sensing-covered networks under GF. We also propose a new greedy geographic routing algorithm called Bounded Voronoi Greedy Forwarding (BVGF) that achieves path dilation lower than 4.62 in sensing-covered networks as long as the communication range is at least twice the sensing range. Furthermore, we extend GF and BVGF to achieve provable performance bounds in terms of total number of transmissions and reliability in lossy networks.     

最小时间路径算法的改进及在路径优化中的应用

由于城市交通网络中路径行程时间是随着时间的变化而变化的,求解最小时间路径比较困难,为此提出把交通网络抽象为时间依赖的网络模型的解决方法。对时间依赖网络模型和理论基础进行分析,指出文献［1］描述的最小时间路径算法存在的不足,即不能正确记录路径;通过引入一个记录路径的数组来对此算法进行改进,改进后的算法不仅解决了原算法存在的问题,而且可以满足n∶1的最短路径搜索,扩展了原算法的应用范围。最后用实验验证了改进算法的正确性和有效性。     

具有路由过期预测的按需路由算法的设计

在Ad hoc 网络路由协议中,动态源路由DSR(dynamic source routing)协议是按需路由的典型代表.它的一个缺陷是对路由缓存中的路由缺乏相应的更新机制.通过对DSR路由协议缓存机制的研究,提出了一个基于历史的路由过期信息即主动过期和被动过期所占的权重,及当前网络信息对每条新加入的路由进行了存活期的预测,这个缓存过期值对于每一条新加入的路由都是动态设定的,它在一定程度符合当前网络的状况,能最终降低了因使用过期路由而带来的影响,从而达到了提高AD HOC网络性能的目的.     

基于软件定义网络的多约束QoS双路径路由优化方法

针对当前SDN架构存在路由算法复杂度高、QoS流满意度低和单链路故障等问题,提出了一种基于软件定义网络的多约束QoS双路径路由优化算法(SDN＿MCQDP)。利用控制器获得全局网络状态信息,生成基于目的节点的有向无环图。在多约束QoS路由选择阶段,通过拉格朗日松弛对偶算法将多约束问题转化为线性规划问题。使用反向链路删减得到满足多约束QoS的节点不相交的双路径冗余链路,使链路故障后的数据传输得到保障。从路由计算时间、链路利用率、QoS流满意度等方面对算法进行仿真实验。结果表明,与MODLARAC、QT、RMCDP＿RD、H＿MCOP算法比较,SDN＿MCQDP能够有效降低传输时延,减少路由计算时间,提高链路利用率,且在链路发生故障后仍能满足QoS需求。     

基于非均匀分簇与路径优化的WSN路由协议

在无线传感网络中,传感节点的能量有限性,使得能量有效利用成为其"热点"问题。针对LEACH协议簇头的随机选择,导致成簇不合理或簇头节点加速死亡,簇首与基站直接通信能量消耗大的问题。提出了一种高能效路由协议UCPO。该协议根据最佳簇头个数划分区域,综合考虑簇内能量消耗和节点剩余能量选择簇头,以多跳方式完成数据的发送。仿真表明,改进协议显著减少整个网络能量消耗,延长了网络的生存周期。