A new parallel scheduling system for multiple radio wireless mesh network

To enhance the capacity of wireless mesh networks, a key technique is widely investigated which is the usage of multi-radio and multi-channel diversity. In this paper, a new parallel scheduling system is proposed which exploits MAC diversities by transmitting packets on the radios opportunistically. Compared with conventional packet transmission which follows “one flow one radio”, the new system uses radio diversity to transmit the packets on different radios simultaneously. Two kernel components of this system are selection module and schedule module. A localized selecting algorithm is implemented in the selection model to choose the right radios based on the quality of wireless links; two distributed packet-scheduling algorithms are optional with the schedule component. Finally, a routing metric adapting this system is presented. We have carried out a comprehensive performance evaluation of this system using ns-2. Simulation results show that it can successfully harness diversity of multi-radio and multi-channel to provide considerable improvements over a baseline multi-channel system in several situations.     

Throughput-coverage tradeoff in a scalable wireless mesh network

The wireless mesh network (WMN) is an economical and low-power solution to support ubiquitous broadband services. However, mesh networks face scalability and throughput bottleneck issues as the coverage and the number of users increase. Specifically, if the coverage is extended by multiple hops, the repeatedly relayed traffic will exhaust the radio resource and degrade user throughput. Meanwhile, as the traffic increases because of more users, the throughput bottleneck will occur at the users close to the gateway. The contention collisions among these busy users near the gateway will further reduce user throughput. In this paper, a newly proposed scalable multi-channel ring-based WMN is employed. Under the ring-based cell structure, multi-channel frequency planning is used to reduce the number of contending users at each hop and overcome the throughput bottleneck issue, thereby making the system more scalable to accommodate more users and facilitate coverage extension. This paper mainly focuses on investigating the overall tradeoffs between user throughput and cell coverage in the ring-based WMN. An analytical throughput model is developed for the ring-based WMN using the carrier sense multiple access (CSMA) medium access control (MAC) protocol. In the analysis, we also develop a bulk-arrival semi-Markov queueing model to describe user behavior in a non-saturation condition. On top of the developed analytical model, a mixed-integer nonlinear optimization problem is formulated, aiming to maximize cell coverage and capacity. Applying this optimization approach, we can obtain the optimal number of rings and the associated ring widths of the ring-based WMN.     

A topology control approach for utilizing multiple channels in multi-radio wireless mesh networks

We consider the channel assignment problem in a multi-radio wireless mesh network that involves assigning channels to radio interfaces for achieving efficient channel utilization. We present a graph–theoretic formulation of the channel assignment guided by a novel topology control perspective, and show that the resulting optimization problem is NP-complete. We also present an ILP formulation that is used for obtaining a lower bound for the optimum. We then develop a new greedy heuristic channel assignment algorithm (termed CLICA) for finding connected, low interference topologies by utilizing multiple channels. Our evaluations show that the proposed CLICA algorithm exhibits similar behavior and comparable performance relative to the optimum bound with respect to interference and capacity measures. Moreover, our extensive simulation studies show that it can provide a large reduction in interference even with a small number of radios per node, which in turn leads to significant gains in both link layer and multihop performance in 802.11-based multi-radio mesh networks.     

无线Mesh网络路由攻击及防范

介绍了无线Mesh网络(WMN)的基本概念及组成结构,在此基础之上指出了当前针对WMN的几种主要的路由攻击。最后,以Click架构下的SR2协议为载体,搭建了WMN实验床。在此实验床上实现了黑洞和洪泛两种攻击,进而引出其针对这两种攻击的检测算法并证明其有效性。     

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.     

基于TDMA的无线传感器网络时隙分配算法

传感器技术、微机电系统、网络和无线通信等技术的进步,推动了无线传感器网络的产生和发展.根据无线传感器网络中节点密度大、以数据为中心和能量有限的特点,提出一种基于时分多址(TDMA)的动态分布式时隙分配算法.该算法根据两跳范围内的邻居节点信息动态分配时隙并能有效适应本地拓扑变化.通过仿真对该算法的良好性能进行了分析.     

基于遗传-蚁群算法的无线Mesh网QoS路由算法研究

针对无线Mesh网QoS的路由特点,结合遗传算法扣蚁群算法的特性,设计了一种遗传算法和蚁群算法相融合的算法,提出了遗传-蚁群算法求解无线Mesh网QoS路由问题的解决方案.该算法采用遗传算法生成初始信息素分布,利用蚁群算法求精确解,并在遗传算法运行过程中动态确定遗传算法与蚁群算法的最佳融合时机,实现两个算法的优势互补.实验结果表明,该算法在无线Mesh网QoS路由选择中是高效的,性能明显优于遗传算法和蚁群算法.     

基于时分复用的无线传感器网络MAC协议研究

对近年来无线传感器网络(W SNs)的基于时分复用(TDMA)的媒质访问控制(MAC)协议的最新研究进展进行了讨论和综述,描述了设计W SNs的MAC协议应该考虑的问题,详细论述了传感器网络的MAC协议的能量有效性问题,着重对一些具有代表性的基于TDMA的MAC协议进行对比、分析,并在此基础上提出了将来设计这类MAC协议的方向和建议。     

无线网格网的路由与拓扑优化

在无线网格网(Wireless Mesh Network,WMN)节点通过一跳或者多跳连接到网关,网关为节点用户提供接入Internet的入口,如何构建合理并且高效的拓扑结构是提高整个无线mesh性能的关键因素。结合布尔变量来描述WMN节点数据传输无回路,节点到网关的总跳数最少,数据流量符合节点与网关的承载能力这些问题使网络拓扑达到需求,验证利用邻接矩阵来确定网关节点,通过Network Simulator Version2(NS2)验证了满足上述问题的拓扑结构相对最优。     

基于树形拓扑的无线Mesh网络路由协议研究

研究和分析了无线Mesh网络路由协议及其特点,提出了无线Mesh网络路由协议设计原则.遵循这些原则,充分利用Mesh网络全相连的优点构建出树形逻辑拓扑结构,该拓扑结构能满足无线Mesh网络业务特点的要求.在该拓扑树基础上设计了一种基于树形拓扑的无线Mesh网络路由协议(TTRP),该协议采用无开销的源地址学习方式构建路由相关表项,快速链路切换和路由重定向机制大大提高了TTRP路由协议的健壮性和网络的抗毁性.网络仿真结果表明了该路由协议的可行性.     

Deployment of wireless mesh network using RSSI-based swarm robots

This paper proposes a novel method for deploying a wireless mesh network (WMN) using a group of swarm robots equipped with wireless transceivers. The proposed method uses the rough relative positions of the robots estimated by their Radio Signal Strength Indicators (RSSIs) to deploy the WMN. The employed algorithm consists of three parts, namely, (1) a fully distributed and dynamic role decision method among the robots, (2) an adaptive direction control using the time difference of the RSSIs, and (3) a narrow corridor for the robots to pass by movement function along walls. In our study, we evaluated the performances of the proposed deployment method and a conventional method in a real environment using 12 real robots for simple deployment, and 10 real robots for passing the narrow corridor. The results of the performed experiments showed that (1) the proposed method outperformed the conventional method with regard to the deployment time, power consumption, and the distances traveled by the robots, and (2) the movement function along the walls is effective while passing a narrow corridor unlike any other function.     

基于无线网络的远程测试系统研究

传统的测试设备因为受到电缆的约束,严重影响了其机动能力,基于蓝牙的测试设备虽然能够满足短距离无线测试的需求,但却无法实现远程测试.本文设计的ATS采用无线网络和远程测试技术满足了测试仪器的机动性能.通过综合运用蓝牙技术和计算机远程控制技术,有效地提高了ATE的机动性和实时测试需求而且易于转移和维护.     

一种基于mesh网络的多径路由协议

针对无线mesh网络的特点提出了一种基于源节点建立、目的节点维护的多径路由协议。该协议采用目的节点更新mesh结构的机制,能实时维护最优路径和其余多条路径,当节点移动或其他原因造成链路断开时,不需要路由修复或重建,从而降低了丢包率和端到端时延,且通过基于源节点建立路由的方式有效地减少了控制开销。仿真结果表明,该算法具有良好的性能。     

Throughput analysis in wireless networks with multiple users and multiple channels

We consider the problem of maximizing throughput in a multi-carrier wireless network that employs predictive link adaptation. We explicitly consider the time-penalty incurred due to link adaptation. The contributions of this paper are twofold. Firstly, several high performance algorithms (offline and online) are developed for efficient performance in multiple user and multiple channel environment under the practicable lookahead prediction of one time slot. Secondly, the presented algorithms and heuristics are shown to be competitive by deterministic and probabilistic analyses. Our results show that a modest consumption of resources for channel prediction and link adaptation may result in a significant throughput improvement.     

基于nRF905的无线网络的设计与实现

无线网络是一个多跳的自组织网络,是未来通信技术的一个重要组成部分,现已应用于工业、农业、交通、监控等领域,具有广阔的发展前景。以ATmega16单片机和n RF905射频收发器为核心设计了一种无线网络节点和基于这种节点的网络通信。给出了节点的整体结构,详细阐述了软件设计流程。实验表明该节点实现了多跳数据传输,通信稳定可靠,基本达到网络的要求。     

Multi-portal association based dispatching and a virtual-queue method in wireless mesh networks

Single-portal association has long been adopted as the basic assumption in wireless mesh network (WMN) research. Whereas this assumption can simplify the overall design, it cannot meet the increasing growth of traffic volume. We propose the use of multi-portal association in this paper, which allows traffic to go through multiple mesh portals so as to ease the performance bottleneck problem caused by single-portal association. We propose the multi-portal association scheme, and a method using the virtual-queue concept to support traffic dispatching within such multi-portal association scheme. The operation of the virtual-queue method is based on the centralized link state estimation and virtual queue emulation. The simulation results show that the proposed multi-portal association outperforms the conventional single-portal association. For the UDP traffic, in the simple-structured and short-distanced networks, the use of multi-portal association (with the virtual-queue dispatching method) is able to reduce 99% of packet loss and increase 500% of throughput, when comparing to the case of using single-portal association. In the more-complex structured networks, it can provide 60% reduction in packet loss and achieve 1500% increase of throughput. On the other hand, for the TCP traffic, in the simple-structured networks, the proposed solution can achieve 92% reduction in latency and 91% increase of throughput.     

基于Wireless USB的无线传感器网络节点设计

在研究2．4G技术的基础上,分析了Wireless USB技术应用于无线传感器网络领域的技术优势,并以此为平台,以通用MCU为处理器,基于软件无线电理念分别设计制作了传感节点和Sink节点。软件设计依托认知无线电技术组建分簇型结构网络,并在安全机制、抗干扰机制和低功耗方面作了深入研究．经调试系统达到了设计指标。     

Interference-aware channel assignment in a metropolitan multi-radio wireless mesh network with directional antennas

We investigate the problem of channel assignment in a metropolitan multi-radio wireless mesh network with directional antennas. Our contributions include a new conflict graph model for capturing the interference between links in a mesh network with a known wireless interface communication graph, and a new channel assignment procedure which accounts for interference both between links inside the mesh network, and from external sources. Additionally, we have implemented and evaluated the proposed channel assignment procedure in an actual metropolitan mesh network with 1.6-5 km links. Key components of the channel assignment procedure are the interference model, the link ordering, and the channel selection metric. The experimental results demonstrate how link ordering and the channel selection metric affect performance, in terms of the average packet delay and http latency. The results show that the proposed channel assignment procedure achieves performance very close to a lower bound of the average packet delay, and significantly higher than the performance achieved with a simpler interference-unaware procedure, and a measurement-based scheme that has appeared in the literature, and accounts for interference only from external 802.11 sources. Moreover, we investigate the performance when a different number of channels are available, and the timescales for channel re-assignment.     

Fault tolerant multiple event detection in a wireless sensor network

With an increasing acceptance of Wireless Sensor Networks (WSNs), the health of individual sensor is becoming critical in identifying important events in the region of interest. One of the key challenges in detecting event in a WSN is how to detect it accurately transmitting minimum information providing sufficient details about the event. At the same time, it is also important to devise a strategy to handle multiple events occurring simultaneously. In this paper, we propose a Polynomial-based scheme that addresses these problems of Event Region Detection (PERD) by having a aggregation tree of sensor nodes. We employ a data aggregation scheme, TREG (proposed in our earlier work) to perform function approximation of the event using a multivariate polynomial regression. Only coefficients of the polynomial (P$P$) are passed instead of aggregated data. PERD includes two components: event recognition and event report with boundary detection. This can be performed for multiple simultaneously occurring events. We also identify faulty sensor(s) using the aggregation tree. Performing further mathematical operations on the calculated P$P$ can identify the maximum (max) and minimum (min) values of the sensed attribute and their locations. Therefore, if any sensor reports a data value outside the [min, max] range, it can be identified as a faulty sensor. Since PERD is implemented over a polynomial tree on a WSN in a distributed manner, it is easily scalable and computation overhead is marginal. Results reveal that event(s) can be detected by PERD with error in detection remaining almost constant achieving a percentage error within a threshold of 10%$10\%$ with increase in communication range. Results also show that a faulty sensor can be detected with an average accuracy of 94%$94\%$ and it increases with increase in node density.