Heuristics for the multi-period orienteering problem with multiple time windows

We present the multi-period orienteering problem with multiple time windows (MuPOPTW), a new routing problem combining objective and constraints of the orienteering problem (OP) and team orienteering problem (TOP), constraints from standard vehicle routing problems, and original constraints from a real-world application. The problem itself comes from a real industrial case. Specific route duration constraints result in a route feasibility subproblem. We propose an exact algorithm for this subproblem, and we embed it in a variable neighborhood search method to solve the whole routing problem. We then provide experimental results for this method. We compare them to a commercial solver. We also adapt our method to standard benchmark OP and TOP instances, and provide comparative tables with state-of-the-art algorithms.     

A survey of models and algorithms for winter road maintenance. Part IV: Vehicle routing and fleet sizing for plowing and snow disposal

This is the last part of a four-part survey of optimization models and solution algorithms for winter road maintenance planning. The two first parts of the survey address system design problems for winter road maintenance. The third part concentrates mainly on vehicle routing problems for spreading operations. The aim of this paper is to provide a comprehensive survey of optimization models and solution methodologies for the routing of vehicles for plowing and snow disposal operations. We also review models for the fleet sizing and fleet replacement problems.     

An approach for efficient ship routing

Ship routing problems are a particular kind of routing problems where the vehicles to be routed are vessels or ships, usually in maritime environments. In contrast to land routing, ship routing has unique features, including overnight trips, disjoint time windows, not necessarily prespecified routes, and a great uncertainty derived from weather conditions. In this work we present a special ship routing problem, which incorporates many features present in general ship routing settings. We discuss aspects related with data gathering and updating, which are particularly difficult in the context of ship routing. Additionally, we present a GRASP algorithm to solve this problem. We apply our solution approach to a salmon feed supplier based in southern Chile, and present computational results on real data.     

A Java™ universal vehicle router for routing unmanned aerial vehicles

We consider vehicle routing problems in the context of the Air Force operational problem of routing unmanned aerial vehicles from base locations to various reconnaissance sites. The unmanned aerial vehicle routing problem requires consideration of heterogeneous vehicles, vehicle endurance limits, time windows, and time walls for some of the sites requiring coverage, site priorities, and asymmetric travel distances. We propose a general architecture for operational research problems, specified for vehicle routing problems, that encourages object‐oriented programming and code reuse. We create an instance of this architecture for the unmanned aerial vehicle routing problem and describe the components of this architecture to include the general user interface created for the operational users of the system. We employ route building heuristics and tabu search in a symbiotic fashion to provide a user‐defined level‐of‐effort solver interface. Empirical tests of solution algorithms parameterized for solution speed reveal reasonable solution quality is attained.     

On the capacity of UWB-based wireless sensor networks

Ultra-wideband (UWB) is a promising wireless communications technology and has great potential for emerging applications such as sensor networks. This paper studies the following fundamental problems for UWB-based sensor networks. For a given network instance, what is the maximum data rate (network capacity) that can be received at the base station (i.e., sink node)? What is the network capacity bound among arbitrary network instances? We show that these problems can be cast into a cross-layer formulation with joint consideration of routing, scheduling, power control, and rate assignment. For a given network instance, we find a closed-form network capacity as well as corresponding optimal routing, scheduling, power control, and rate assignment. We also find a network capacity bound among arbitrary network instances. Our results provide fundamental results for UWB-based sensor networks.     

单播和多播QoS路由问题研究及解决方法

当前的互联网只能提供“尽力而为”的发送服务,使网络层无法控制传输质量,因此,为不同应用提供不同QoS的服务是网络用户的基本要求和互联网面临的重要研究课题。近几年,有关IP QoS的讨论焦点是Intserv、Diffserv、MPLS等服务模型和框架,在资源受限的网络环境下,这些解决方案实现的基础是QoS路由。论文的目的是在明确QoS路由重要性的基础上,通过建立网络模型和度量合成规则,详细分析单播和多播可能遇到的单度量的基本路由问题和多度量的组合路由问题,并给出解决这些路由问题的方法和计算复杂度,这对于设计和实现可行的QoS路由协议或算法有一定参考价值。     

Minimizing hierarchical routing error

In hierarchical routing schemes, nodes are grouped into clusters at multiple levels, and a given node sees only a summarized view of the entire network. Hierarchical routing introduces error, which is the difference between the hierarchical path length and the optimal path length using flat routing. Since in practice the routing table size at each node is limited, we formulate the constrained optimization problems of finding a hierarchy structure that minimizes either the worst case or average case routing error. We prove results characterizing solutions of these problems, and present dynamic programming solution algorithms and computational results.     

网络对抗下的情报推送自适应寻径模型

计算机网络对抗中,情报资源在推送时,由于网络中部分节点失效等因素,导致无法正确寻径。针对以上问题,运用自适应对等网络理论,提出将寻径建立在自适应对等网络平台上的思想,构建自适应寻径模型。论述模型的体系结构、功能和协议,给出自适应寻径策略和算法。仿真结果表明,该模型所采取的寻径方法能提供较为广泛、高效的情报推送能力。     

Robust routing and optimal partitioning of a traffic demand polytope

In this paper we consider the problem of optimal partitioning of a traffic demand polytope using a hyperplane. In our model all possible demand matrices belong to a polytope. The polytope can be divided into parts, and different routing schemes can be applied while dealing with traffic matrices from different parts of the polytope. We consider three basic models: Robust‐Routing, No‐Sharing and Dynamic‐Routing. We apply two different partitioning strategies depending on whether the reservation vectors on opposite sides of the hyperplane are required to be identical, or allowed to differ. We provide efficient algorithms that solve these problems. Moreover, we prove polynomiality of some of the considered cases. Finally, we present numerical results proving the applicability of the introduced algorithms and showing differences between the routing strategies.     

TRECON: A Trust-Based Economic Framework for Efficient Internet Routing

The fragility and the poor resilience of the Internet are manifested by the severe impact of network activities and the slow recovery after an earthquake damaged undersea cables and disrupted telephone and Internet access in East Asia in December 2006. Except the inefficiency of routing protocols, lack of efficient network monitoring mechanisms and lack of economic incentives to encourage service providers (SPs) to act cooperatively and promptly are other important reasons. In this paper, we build a trust-based economic framework called TRECON to address these open problems in Internet routing. The novelty of TRECON is combining an adaptive personalized trust model with an economic approach to provide independent trust-based routing among SPs. TRECON provides flexible policy support based on the trust-based economic mechanism so that autonomous organizations with varied interests and optimization criteria can be smoothly integrated together to achieve better adaptiveness and self-management. Through introducing the economic model, TRECON explores a new way to solve the economic problems and incentives issues in the collaboration among SPs. To show the flexibility of routing policies support, we propose four typical routing policies under the TRECON framework. We evaluate our approach by comparing these four trust-derived routing policies with the classical global shortest path routing approach. We find that the policy based on trustworthiness performs much better than all other policies under different network topologies in terms of delay, success delivery rate, and economic effects.     

Genetic local search for multicast routing with pre-processing by logarithmic simulated annealing

Over the past few years, several local search algorithms have been proposed for various problems related to multicast routing in the off-line mode. We describe a population-based search algorithm for cost minimisation of multicast routing. The algorithm utilises the partially mixed crossover operation (PMX) under the elitist model: for each element of the current population, the local search is based upon the results of a landscape analysis that is executed only once in a pre-processing step; the best solution found so far is always part of the population. The aim of the landscape analysis is to estimate the depth of the deepest local minima in the landscape generated by the routing tasks and the objective function. The analysis employs simulated annealing with a logarithmic cooling schedule (logarithmic simulated annealing—LSA). The local search then performs alternating sequences of descending and ascending steps for each individual of the population, where the length of a sequence with uniform direction is controlled by the estimated value of the maximum depth of local minima. We present results from computational experiments on three different routing tasks, and we provide experimental evidence that our genetic local search procedure that combines LSA and PMX performs better than algorithms using either LSA or PMX only.     

基于流量的域间路由优化技术研究

域间路由优化技术是域间路由研究的一个热点问题。本文分析了当前BGP路由存在的问题,总结了域间路由优化技术的主要研究方向,指出了其中需要进一步研究与解决的关键技术与问题。     

三维AD-HOC 网络地理信息路由算法

在二维AD-HOC 网络中,可以充分利用节点的地理信息进行路由,即AD-HOC 中节点根据邻居节点的距离目标节点的距离,选择下一跳节点进行路由转发.由于AD-HOC 中节点部署通常不满足均匀分布,造成网络中出现路由空洞,贪婪转发算法在遭遇空洞的情况下将无法正确执行.在二维AD-HOC 网络环境中,往往采用贪婪(Greedy)算法结合表面路由(Face Routing)的方法跳出路由空洞.但是在三维条件下,目前没有很好跳出路由空洞的算法能够实现有效的路由.提出了一种在三维AD-HOC 网络中的地理信息路由算法GSG,该算法使用3D RDT 图和3D RRNG 图的方法实现三维网络空间的划分.采用3D 表面路由的方法进行信息传递,在遭遇局部最小点时,可有效跳出路由空洞.仿真实验结果表明,GSG 算法可提升三维AD-HOC 网络条件下地理信息路由的效率,具有良好的可扩展性.     

区分服务模型下多目标最优化安全路由算法

将安全度量作为一种QoS参数进行路由选择是目前网络安全路由研究的一个新思路,针对现有方法采用一个安全度量参数描述链路安全性,进行路由选择存在的问题,提出一种多安全度量的链路安全性描述策略,能够更加全面准确地描述网络链路的安全特征;该描述策略应用于区分服务模型下的安全路由选择,并提出了基于改进的非支配遗传算法的多目标最优化安全路由算法求解这一多目标多约束的NP完全问题。随机网络的仿真结果表明,算法能为用户提供安全性能较高的路由,并能满足不同等级要求的服务质量。     

Airline network design and hub location problems

Due to the popularity of hub-and-spoke networks in the airline and telecommunication industries, there has been a growing interest in hub location problems and related routing policies. In this paper, we introduce flow-based models for designing capacitated networks and routing policies. No a priori hub-and-spoke structure is assumed. The resulting networks may suggest the presence of “hubs”, if cost efficient. The network design problem is concerned with the operation of a single airline with a fixed share of the market. We present three basic integer linear programming models, each corresponding to a different service policy. Due to the difficulty of solving (even small) instances of these problems to optimality, we propose heuristic schemes based on mathematical programming. The procedure is applied and analyzed on several test problems consisting of up to 39 U.S. cities. We provide comments and partial recommendations on the use of hubs in the resulting network structures.     

Vehicle routing problems with split deliveries

This paper is a survey on the vehicle routing problems with split deliveries, a class of routing problems where each customer may be served by more than one vehicle. Starting from the most classical routing problems, we introduce the split delivery vehicle routing problem (SDVRP). We review a formulation, the main properties and exact and heuristic solution approaches for the SDVRP. Then, we present a general overview of several variants of the SDVRP and of the literature available.     

Ad Hoc网络中基于DSR的QoS路由协议研究

AdHoc网络的特性决定为各种多媒体业务的服务质量提供保证是很难解决的问题。AdHoc网络路由协议的QoS研究正是试图解决这样的问题。本文介绍了DSR路由协议和AdHoc网络QoS路由技术的相关概念。然后,对基于DSR的QoS实现的路由协议进行了详细的分析。最后探讨了其今后的发展动态和研究方向。     

带有引线端预处理的区域布线算法

提出一种带有引线端优化处理的多层区域布线算法,能处理端点障碍在区域内任意分布的大量布线问题,首先将多端线网划分为二端子线网,并在此基础上根据二端子线网之间的相对位置关系进行分类;然后对每个类型的二端子线网,采用双向迷宫和朝向目标的深度优先搜索策略依次布线;最后通过拆线-重布策略来解决布线冲突．在进行布线搜索之前,对引线端映射到网格点上这一过程引入了一种有效的优化预处理机制,采用二分图中多目标约束寻找最佳匹配的思想和策略来解决引线端优化映射问题．测试并比较了有／无这种优化处理的2种情况,实验结果表明,该算法有效地改善了网格映射的精度和准确性,可缩短线长和提高布通率．