Designing tributary networks with multiple ring families

Advances in telecommunication technology result in improved service, but can also lead to difficult and challenging network design problems. For example, networks in which nodes are connected by rings of optical fiber can now be used to provide rapid service restoration in the event of a failure. However, as a result, network designers are faced with the new problem of designing networks based on topological ring structures. In this paper, we consider the particular case of tributary network design. In a tributary network, a group of nodes are connected to a hub node, which is used as a point of interconnection with other parts of the network. For a particular network architecture, we describe an algorithm to determine how many topological ring structures are required, and which nodes should be included on each. We highlight connections between this problem and problems in vehicle routing.A common architecture for a telecommunications network consists of several tributary (often called access) networks, which connect locations to hubs, and a backbone network, which interconnects the hubs. This paper describes a heuristic approach for designing tributary networks based on self-healing rings (SHRs). The tributary network consists of multiple ring families, and each of those is comprised of one or more SHRs, called “stacked” rings. The SHRs in a given ring family are routed over the same cycle of optical fiber cables, but each SHR serves only a subset of the locations along the cycle. Each demand location is assigned to a single SHR on one of the ring families, whereas the hub is assigned to all SHRs on all ring families. A link that is used by some ring family incurs a fixed cost plus a variable cost per SHR associated with that family. Each SHR is constrained by the demand volume it can handle and by the number of locations it can serve. This tributary ring network design problem can be viewed as a complex version of a vehicle routing problem with a single-depot andmultiple vehicles. Our algorithm is initiated with numerous ring families. It then attempts to merge these families, while ensuring that savings are realized in terms of the sum of fixed and variable costs.     

Survivable and delay-guaranteed backbone wireless mesh network design

Backbone wireless mesh networks (BWMNs) consisting of wireless mesh routers are emerging alternatives to implementations of metropolitan area networks (MANs). In a BWMN, gateways connect to the Internet via wireline links and provide Internet access services for users. Due to the limited wireless channel bit rate, multiple gateways are usually required in a BWMN, which costs budget and takes time to set up. In this paper, we study the network topology design and the gateway arrangement so that the construction cost of a BWMN is minimal. Two algorithms, namely, the Predefined Gateway Set Algorithm (PGSA) and the Self-Constituted Gateway Algorithm (SCGA), are proposed for the BWMN design. A genetic algorithm and a proposed enhanced Djikstra's algorithm are employed to search for the low-cost network configuration with constraints such as survivability, link capacity, degree limitation and maximum tolerable delay. Computational results show that the PGSA can give an acceptable network configuration rapidly. In case the gateway cost is high, using the SCGA can lower the network construction cost at the expense of more computational time.     

Cross-layer optimization for wireless mesh networks with smart antennas

A cross-layer optimization framework for wireless mesh networks is presented where at each node, various smart antenna techniques such as beam-forming, spatial division multiple access and spatial division multiplexing are employed. These techniques provide interference suppression, capability for simultaneous communication with several nodes and transmission with higher data rates, respectively, through multiple antennas. By integrating different combinations of the multi-antenna techniques in physical layer with various constraints from MAC and network layers, three Mixed Integer Linear Programming (MILP) models are presented to minimize the system activation time. Since these optimization problems are complex combinatorial, the optimal solution is approached by a Column Generation decomposition method. The numerical results for different network scenarios with various node densities, number of antennas, transmission ranges and number of sessions are provided. It is shown that the resulted directive, multiple access and multiplexing gains combined with scheduling, effectively increase both the spectrum spatial reuse and the capacity of the links and therefore, enhance the achievable system throughput. Our cross-layer approach is also extended to consider heterogeneous networks and we present a multi-criteria optimization framework to model the design problem where the objective is to jointly minimize the cost of deployment and the system activation time. Our results reveal the benefits of joint design in terms of reducing the cost of deployment while achieving higher system performance.     

A branch-and-cut algorithm for two-level survivable network design problems

This paper approaches the problem of designing a two-level network protected against single-edge failures. The problem simultaneously decides on the partition of the set of nodes into terminals and hubs, the connection of the hubs through a backbone network (first network level), and the assignment of terminals to hubs and their connection through access networks (second network level). We consider two survivable structures in both network levels. One structure is a two-edge connected network, and the other structure is a ring. There is a limit on the number of nodes in each access network, and there are fixed costs associated with the hubs and the access and backbone links. The aim of the problem is to minimize the total cost. We give integer programming formulations and valid inequalities for the different versions of the problem, solve them using a branch-and-cut algorithm, and discuss computational results. Some of the new inequalities can be used also to solve other problems in the literature, like the plant cycle location problem and the hub location routing problem.     

On the nominal capacity of multi-radio multi-channel wireless mesh networks

Wireless mesh networking is an emerging technology with a wide range of applications, from community to metropolitan area networking. Mesh networks consist of wireless routers and access points that make up the network backbone which is connected to the wired infrastructure. Client devices are located at the edge. The capacity of a wireless mesh network is an important performance indicator as well as design parameter. It depends on various factors such as network size and topology, expected traffic patterns, number of interfaces per node, number of channels, routing and channel assignment etc. In this paper, we present an analytical framework for estimating the capacity of wireless mesh networks, based on the concept of collision domains. The capacity of grid-oriented mesh networks is investigated for various scenarios to study the impact of different network parameters.     

基于无线自组网络分时发送协议的路由汇聚容量

对于无线自组网而言,由于网络拓扑与路由选择的随机性,容量的分析显得尤为复杂。研究了能量约束对无线自组网容量性能的影响。该网络具有路由汇聚功能,且节点的发送过程基于分时竞争发送协议。在假设能量缓存中的能量值足够大时,节点就能发送数据的前提下,提出了一种基于闭合排队网络的容量分析模型。该模型同时考虑了数据细节、能量缓存以及随机接入协议。然后研究了能量约束对随机接入协议设计参数的影响,以优化网络性能。最后分析了能量约束对最大稳定容量、稳定域以及分组丢弃率的影响。仿真结果验证了所提分析模型的准确性。     

Exploiting transmission opportunities in heterogeneous wireless networks: a transmission power saving perspective

Exploiting transmission opportunities in dimensions of user equipments(UEs),radio access networks(RANs),and radio resource units(RRUs),in heterogeneous wireless networks(HWNs),we focus on a new perspective of saving the uplink transmission power,so as to lengthen the battery life time of UEs.Moreover,to ensure the quality of service for each UE,we guarantee each a minimal transmission rate.To achieve the above HWN control objective,we have to make an efcient matching among UEs,RANs,and RRUs,which is formulated as a binary linear optimization problem.Due to its NP-hard complexity,we develop a rate-power efciency based HWN control algorithm with low computational complexity.We verify the performance of our HWN control scheme through simulation.Extensive simulation results demonstrate the advantage of our HWN control method in saving the uplink transmission power and guaranteeing the UE transmission rate requirement.     

基于功率优化的Ad hoc网络定向媒质接入控制

由于无线Ad hoc网络是一种由移动终端组成、网络拓扑结构动态变化的对等、自组织、多跳网络,使得传输带宽、传输功率成为具有挑战性的任务之一。分析了目前通常采用的信道接入技术(如：全向天线;CSMA／CA和洪泛)及存在的问题;在此基础上,为保证有效利用传输带宽,提高功率利用率,给出了用于定向天线的MAC的解决方案(简称DMAC)。节点通过虚拟载波侦听来重定向,实现定向传输,使功率得到优化。     

面向智慧教室的无线传感网边缘节点智能部署方法

摘 要: 为降低部署后的通信时延,提高智慧教室的数据发送与网络使用效率,提出面向智慧教室的无线传感网边缘节点智能部署方法。以智慧教室场景中良好的通信、最大限度降低部署边缘节点成本为优化目标,构建边缘节点智能部署的目标函数。针对目标函数设定流量约束条件、无线传感网数据流约束条件、节点计算能力约束条件。自适应调整粒子群优化算法的惯性权重、粒子更新速度、Pareto最优解保存策略,设计多目标改进粒子群优化算法求解目标函数,实现面向智慧教室的无线传感网边缘节点智能部署。测试结果表明,该方法的时延较低,网络计算能力较高,保证了智慧教室无线传感网通信和传输质量。     

基于ZigBee的无线传感网络网关的设计

文章介绍了一种基于ZigBee协议的无线传感器网络的网关设计整体方案.以Intel PXA270为核心处理器,处理器通过以太网接入芯片、GPRS模块、符合IEEE802.15.4协议的CC2430射频芯片,分别接入以太网、GPRS网络和无线传感器网络.移植精简的嵌入式TCP/IP协议,分析Z-Stack协议栈,实现两种...     

M-CORD下无线接入网络资源分配研究

针对M-CORD架构将传统的无线接入网络解耦并虚拟化的特征,考虑软件定义网络（SDN）的集中控制和全局监测作用,研究无线接入网侧资源的动态分配及优化问题。将数据中心的计算资源纳为资源分配考虑因素之一,综合干扰阈值、前传网络容量限制、用户移动性、服务最低资源保障以及计算资源限制五方面,推导出M-CORD架构下无线接入网资源分配公式,通过改进基于增量的贪心分配算法,求得资源分配的次优解。仿真结果验证了改进算法在M-CORD架构下对无线接入网资源分配的适用性。     

Routing protocols in wireless mesh networks: challenges and design considerations

Wireless Mesh Networks (WMNs) are an emerging technology that could revolutionize the way wireless network access is provided. The interconnection of access points using wireless links exhibits great potential in addressing the “last mile” connectivity issue. To realize this vision, it is imperative to provide efficient resource management. Resource management encompasses a number of different issues, including routing. Although a profusion of routing mechanisms has been proposed for other wireless networks, the unique characteristics of WMNs (e.g., wireless backbone) suggest that WMNs demand a specific solution. To have a clear and precise focus on future research in WMN routing, the characteristics of WMNs that have a strong impact on routing must be identified. Then a set of criteria is defined against which the existing routing protocols from ad hoc, sensor, and WMNs can be evaluated and performance metrics identified. This will serve as the basis for deriving the key design features for routing in wireless mesh networks. Thus, this paper will help to guide and refocus future works in this area.

基于深度强化学习的服务功能链多维资源优化

在网络功能虚拟化(Network Function Virtualization,NFV)环境下,保证用户服务功能链(Service Function Chain,SFC)服务质量的同时节约资源消耗,降低运营成本,对运营商来说至关重要.联合考虑SFC部署和无线接入网资源分配,提出一种基于深度强化学习的SFC多维资源联合...     

Load-aware routing in mesh networks: Models, algorithms and experimentation

In this paper we consider wireless mesh networks (WMNs) used to share the Internet connectivity of sparsely deployed fixed lines with heterogeneous capacity, ranging from ISP-owned high-speed links to subscriber-owned low-speed connections. If traffic is routed in the mesh without considering the load distribution and the bandwidth of Internet connections, some gateways may rapidly get overloaded because they are selected by too many mesh nodes. This may cause a significant reduction of the overall network capacity. To address this issue, in this paper we first develop a queuing network model that predicts the residual capacity of network paths, and identifies network bottlenecks. By taking advantage of this model, we design a novel Load-Aware Route Selection algorithm, named LARS, which improves the network capacity by allocating network paths to upstream Internet flows so as to ensure a more balanced utilization of wireless network resources and gateways’ Internet connections. Using simulations and a prototype implementation, we show that the LARS scheme significantly outperforms the shortest-path first routing protocol using a contention-aware routing metric, providing up to 240% throughput improvement in some network scenarios.     

End-to-end performance aware association mechanism for wireless municipal mesh networks

In a wireless municipal mesh (muni mesh) network, a client station (STA) needs to associate with a mesh access point (MAP) for network access. Previous association mechanisms assume high-speed backhaul and only the access link being the bottleneck. This assumption holds for most WLANs, but in wireless mesh networks traffic could be bottlenecked either by the access link or by the bandwidth-limited wireless backhaul. In this paper, we propose a new joint MAP association mechanism for wireless muni mesh networks to improve STA’s end-to-end communication performance. A STA makes its association decision by jointly considering the quality of the access link between the STA and the associated MAP as well as the cost of the multi-hop path from the associated MAP to the Internet gateway. In addition, we design two new metrics, Contention Aware Expected Transmission Time (CAETT) and Load Aware Expected Transmission Time (LAETT), to measure the access link quality. The main strength of CAETT is incorporating the impact of 802.11 MAC layer contentions on the bandwidth sharing of multi-rate stations. LAETT further captures the real traffic load on the shared medium. In order to reduce the association delay, we use an analytical model to derive a hybrid measurement/estimation method to enable a station to quickly determine the cost of CAETT and LAETT. We conduct extensive simulations to evaluate the performance of the proposed joint MAP association mechanism. Especially within the joint association framework, we investigate the impact of various combinations of access link metrics (RSSI, PB, CAETT, LAETT) and backhaul routing metrics (hopcount, ETT, RALA) on the system performance. We show that the joint association mechanism can significantly improve the network performance in terms of throughput and delay by up to 100%. In particular, the joint association mechanism with LAETT as the access link metric and RALA as the routing metric outperforms other schemes and metrics.     

Energy-efficient multipath routing in wireless sensor network considering wireless interference

Due to the energy and resource constraints of a wireless sensor node in a wireless sensor network (WSN), design of energy-efficient multipath routing protocols is a crucial concern for WSN applications. To provide high-quality monitoring information, many WSN applications require high-rate data transmission. Multipath routing protocols are often used to increase the network transmission rate and throughput. Although large-scale WSN can be supported by high bandwidth backbone network, the WSN remains the bottleneck due to resource constraints of wireless sensors and the effects of wireless interference. In this paper, we propose a multipath energy-efficient routing protocol for WSN that considers wireless interference. In the proposed routing protocol, nodes in the interference zone of the discovered path are marked and not allowed to take part in the subsequent routing process. In this way, the quality of wireless communication is improved because the effects of wireless interference can be reduced as much as possible. The network load is distributed on multiple paths instead of concentrating on only one path, and node energy cost is more balanced for the entire wireless network. The routing protocol is simulated in NS2 software. Simulation result shows that the proposed routing protocol achieves lower energy cost and longer network lifetime than that in the literature.     

一种最大化网络吞吐量的认知无线Ad Hoc网络跨层优化算法

认知无线Ad hoc网络(cognitive wireless ad hoc networks)是由一组具有认知决策能力的节点以多跳无线方式组成的智能网络.网络容量的求解与网络吞吐量的优化是该类网络研究的难点.作者首先推导了混叠模式下认知无线Ad hoc网络容量上界的闭合表达式,并指出该上界只与用户空间分布特性相关;然后提出了一种新的基于遗传算法的跨层优化算法,通过联合优化邻居选择与功率分配实现网络吞吐量的最大化;最后仿真验证了该算法的有效性,结果表明网络吞吐量能较好地逼近网络容量上界.     

基于S5PV210的矿井综合接入网关的设计

针对现有矿井接入网关的专用网关存在可重用性差的问题,提出了一种基于S5PV210的矿井综合接入网关设计方案,介绍了网关的硬件结构和软件的设计,详细分析了多种协议之间的转换原理。该网关采用S5PV210微处理器、嵌入式操作系统和Socket软件技术实现了无线网络、现场总线网络、控制设备与工业以太网的互联,完成了多种协议之间的互转。     

一种低功耗无线传感器网络时间同步算法

间同步对无线传感器网络的应用至关重要,为提高同步精度,多数算法都以较多的消息交换或复杂的计算为代价来达到这一目的,因而能耗较大.为减少时间同步的消息交换开销,节约节点能量,提出了一种简单低功耗时间同步算法,该算法结合了单向广播同步机制和双向成对同步机制,有效利用网络中节点的广播信息,使网络中节点单跳广播域内只有一个下层节点与之进行双向成对同步,从而达到了减少消息开销和节约能量的目的.最后通过仿真验证了该算法的性能.     

Understanding optimal data gathering in the energy and latency domains of a wireless sensor network

The problem of optimal data gathering in wireless sensor networks (WSNs) is addressed by means of optimization techniques. The goal of this work is to lay the foundations to develop algorithms and techniques that minimize the data gathering latency and at the same time balance the energy consumption among the nodes, so as to maximize the network lifetime. Following an incremental-complexity approach, several mathematical programming problems are proposed with focus on different network performance metrics. First, the static routing problem is formulated for large and dense WSNs. Optimal data-gathering trees are analyzed and the effects of several sensor capabilities and constraints are discussed, e.g., radio power constraints, energy consumption model, and data aggregation functionalities. Then, dynamic re-routing and scheduling are considered. An accurate network model is proposed that captures the tradeoff between the data gathering latency and the energy consumption, by modeling the interactions among the routing, medium access control and physical layers.For each problem, extensive simulation results are provided. The proposed models provide a deeper insight into the problem of timely and energy efficient data gathering. Useful guidelines for the design of efficient WSNs are derived and discussed.