一种新的基于最大流的无线Mesh网络信道分配算法

在无线Mesh网络中,为节点配置多接口多信道MAC协议成为提高网络性能、扩大网络容量的有效手段之一。有效的信道分配策略在多信道无线Mesh网络中显得尤为重要。本文提出一种基于最大流的信道分配算法。该算法通过最大流计算网络中可达到的最大吞吐量,以此作为网络负载标准进行信道分配,将降低整个网络的总体干扰作为目标函数进行优化。仿真结果表明,即使在网络负载较重的情况下,算法仍能保持较好的性能。     

基于拓扑分割的无线Mesh网络信道分配策略

该文根据无线Mesh网络流量呈现树状拓扑汇聚的特点提出基于拓扑分割的信道分配策略。依据无线干扰对不同链路的影响程度,把无线干扰分类为有确定方向的纵向干扰和横向干扰;提出沿着纵向干扰方向逐跳分割网络拓扑算法;提出最少信道隔离纵向干扰和为吞吐量最小的子拓扑增加信道的子拓扑间信道分配策略;提出横向干扰分块的子拓扑内信道使用方法;理论分析子拓扑内的冲突域及网络性能瓶颈,仿真研究子拓扑的吞吐性能及信道分配顺序。仿真结果表明,隔离纵向干扰和增加信道的分配策略能够有效保证和提升网络吞吐量,横向干扰分块的方法优于802.11s中定义的公共信道框架多信道机制。     

多信道无线Mesh网络的性能研究

在无线Mesh网络中使用多信道可以减少碰撞和干扰,提高系统吞吐量.本文先介绍无线Mesh网络,然后介绍多信道在无线Mesh网络中的应用,分析了几种常用的多信道MAC协议.接着着重阐述了多信道无线Mesh网络所面临的问题与挑战,对信道分配、路由选择和隐蔽终端这3个主要问题进行分析,并对其研究设计方向进行了展望.     

基于网络分割的无线传感器网络多信道MAC协议

无线传感器网络中,可用正交信道数目较少和噪声干扰问题制约着多信道MAC协议性能的提升,结合数据采集应用的特点,提出一种基于网络分割的多信道MAC协议。在最小化网络总干扰值的基础上,网络分割引入碰撞因子进一步优化子树结构、降低树内干扰。并利用基于图着色理论的分配策略为每棵子树分配一条高质量信道。仿真实验结果表明,该协议显著提高了网络吞吐量,并且大幅降低了传输延迟和分组丢失率。     

不确定流量条件下多跳无线网络的信道分配与链路调度研究

本文以网络吞吐量最大化为目标,提出了传输流约束、信道资源约束以及干扰约束条件下的资源分配联合优化模型,以及基于不确定流量条件下资源分配最优解的链路调度策略.仿真实验结果证明：本文提出的信道分配及链路调度方案能够更好地适应网络流量需求的变化.     

无线mesh网络中的信道分配问题研究

在多接口无线mesh网络中使用多信道可以减少碰撞和干扰,提高系统吞吐量。因此,合理的信道分配是无线mesh网络中多信道技术的关键。用图论理论建立信道分配数学模型以及用图着色理论研究信道分配问题是无线网络中解决信道分配问题的有效方法。因此针对无线mesh网络中多接口多信道(multi-radio and multi-channel)的特点,重点介绍了无线mesh网络中信道分配的基本理论、主要约束和图论模型等,最后提出应用图着色理论解决信道分配问题的一般途径。     

多射频无线Mesh网中的接口分域信道分配

在多射频多信道无线Mesh网中,是无线宽带接入的重要候选技术之一.为了满足无线宽带接入的容量要求,Mesh路由器节点常需要配置多个无线接口并使用多个正交信道.已有的信道分配方法虽能减少干扰和碰撞,但不能完全避免.本文提出一种域内中心式调度的接口分域信道分配(ICCA)方案,旨在完全避免干扰与碰撞以提高网络吞吐量,尤其能...     

有限用户数多认知网络部分信道共享性能分析

认知网络中动态信道共享是提高频谱资源利用率的关键.针对有限用户数下多认知网络共存场景,该文建立3维马尔科夫链部分信道共享模型,仿真分析用户有/无信道切换功能下认知网络间部分信道共享的性能.分别就阻塞概率、强迫终止概率、切换概率和系统吞吐量等,与静态频谱分配策略和分级共享策略进行比较仿真测试,结果表明,采用部分信道共享策略的系统在容忍较小的切换概率和强迫终止概率下可以获得较大的系统吞吐量.     

多信道无线Mesh网络的性能研究

在无线Mesh网络中使用多信道可以减少碰撞和干扰,提高系统吞吐量。本文先介绍无线Mesh网络,然后介绍多信道在无线Mesh网络中的应用,分析了几种常用的多信道MAC协议。接着着重阐述了多信道无线Mesh网络所面临的问题与挑战,对信道分配、路由选择和隐蔽终端这3个主要问题进行分析,并对其研究设计方向进行了展望。     

Multi-Radio传感器网络信道分配算法的研究

为了减少通信冲突与信道干扰,本文研究了Multi-Radio Multi-Channel 传感器网络无冲突通信的信道数上界与Radio数上界,在理论上证明了当网络的通信半径NCR>3×Dis(PK)且Sensor 节点规模大于2K+1时,网络无冲突信道分配的信道数上界为△(CG),其中K为网络可采用的功率级数,Dis(PK)为网络最大功率的通信半径,△(CG)为网络信道冲突图的最大度.在此上界基础上,提出了一种信道分配算法,该算法消除了数据通信时的冲突与干扰.理论分析与实验结果表明:本文提出的无冲突信道分配算法能够显著地改善传感器网络的通信效率,提高网络的吞吐量.     

A topology preserving cluster‐based channel assignment for wireless mesh networks

Wireless Mesh Networks (WMN) with multiple radios and multiple channels are expected to resolve the capacity limitation problem of simpler wireless networks. However, optimal WMN channel assignment (CA) is NP complete, and it requires an optimal mapping of available channels to interfaces mounted over mesh routers. Acceptable solutions to CA must minimize network interference and maximize available network throughput. In this paper, we propose a CA solution called as cluster‐based channel assignment (CBCA). CBCA aims at minimizing co‐channel interference yet retaining topology through non‐default CA. Topology preservation is important because it avoids network partitions and is compatible with single‐interface routers in the network. A ‘non‐default’ CA solution is desired because it uses interfaces over different channels and reduces medium contention among neighbors. To the best of our knowledge, CBCA is a unique cluster‐based CA algorithm that addresses topology preservation using a non‐default channel approach. The main advantage of CBCA is it runs in a distributed manner by allowing cluster heads to perform CA independently. CBCA runs in three stages, where first the WMN nodes are partitioned into clusters. The second stage performs binding of interfaces to neighbors and third stage performs CA. The proposed algorithm improves over previous work because it retains network topology and minimizes network interference, which in turn improves available network throughput. Further, when compared with two other CBCA algorithms, CBCA provides better performance in terms of improved network interference, throughput, delay, and packet delivery ratios when tested upon network topologies with various network densities and traffic loads. Copyright © 2014 John Wiley & Sons, Ltd.     

无线Mesh网络关键技术

无线Mesh网络(WMN)是一种特殊的Adhoc网络,具有分层的网络结构,其传输骨干网具有多跳、拓扑稳定、无供电约束、业务流量相对汇聚等特性。提高WMN频谱空间复用度是增加网络容量有效的方法,而其设计的关键是有效控制无线链路间的干扰范围。基于多信道的组网技术是WMN关键技术之一,其核心是信道的分配,通过合理的信道分配以获得最大信道利用率。WMN中路由度量的选取需要考虑多跳无线链路间的相互干扰,而通过采用负载均衡路由技术可以均衡网络资源的使用,从而提高网络容量和节点的吞吐率。     

DMesh: Incorporating Practical Directional Antennas in Multichannel Wireless Mesh Networks

Wireless mesh networks (WMNs) have been proposed as an effective solution for ubiquitous last-mile broadband access. Three key factors that affect the usability of WMNs are high throughput, cost-effectiveness, and ease of deployability. In this paper, we propose DMesh, a WMN architecture that combines spatial separation from directional antennas with frequency separation from orthogonal channels to improve the throughput of WMNs. DMesh achieves this improvement without inhibiting cost-effectiveness and ease of deployability by utilizing practical directional antennas that are widely and cheaply available (e.g., patch and yagi) in contrast to costly and bulky smart beamforming directional antennas. Thus, the key challenge in DMesh is to exploit spatial separation from such practical directional antennas despite their lack of electronic steerability and interference nulling, as well as the presence of significant sidelobes and backlobes. In this paper, we study how such practical directional antennas can improve the throughput of a WMN. Central to our architecture is a distributed, directional channel assignment algorithm for mesh routers that effectively exploits the spatial and frequency separation opportunities in a DMesh network. Simulation results show that DMesh improves the throughput of WMNs by up to 231% and reduces packet delay drastically compared to a multiradio multichannel omni antenna network. A DMesh implementation in our 16-node 802.11b WMN testbed using commercially available practical directional antennas provides transmission control protocol throughput gains ranging from 31% to 57%     

Interference and traffic aware channel assignment in WiFi-based wireless mesh networks

Wireless mesh networks (WMN) typically employ mesh routers that are equipped with multiple radio interfaces to improve network capacity. The key aspect is to cleverly assign different channels (i.e., frequency bands) to each radio interface to form a WMN with minimum interference. The channel assignment must obey the constraints that the number of different channels assigned to a mesh router is at most the number of interfaces on the router, and the resultant mesh network is connected. This problem is known to be NP-hard. In this paper we propose a hybrid, interference and traffic aware channel assignment (ITACA) scheme that achieves good multi-hop path performance between every node and the designated gateway nodes in a multi-radio WMN network. ITACA addresses the scalability issue by routing traffic over low-interference, high-capacity links and by assigning operating channels in such a way to reduce both intra-flow and inter-flow interference. The proposed solution has been evaluated by means of both simulations and by implementing it over a real-world WMN testbed. Results demonstrate the validity of the proposed approach with performance increase as high as 111%.     

Channel‐switching and power control mechanisms for improving network connectivity in wireless mesh networks

A Wireless Mesh Network (WMN) consists of fixed wireless routers, each of which provides service for mobile clients within its coverage area and inter‐connects mesh routers to form a connected mesh backbone. Wireless mesh routers are assigned with a channel or a code to prevent collisions in transmission. With a power control mechanism, each router could be assigned with a power level to control connectivity, interference, spectrum spatial reuse, and topology. Assigning high transmitting power level to a router can enhance the network connectivity but may increase the number of neighbors and worsen the collision problem. How to assign an appropriate power level to each router to improve the network connectivity with a constraint of limited channels is one of the most important issues in WMNs. Given a network topology and a set of channels that has been assigned to mesh routers, the proposed channel‐switching mechanism further reassigns each router with a power level and switches channels of routers to optimize both power efficiency and connectivity. A matrix‐based presentation and operations are proposed to respectively identify and resolve the channel switching problems. Simulation study reveals that the proposed mechanisms increase network throughput and provides a variety of route selection, and thus improves the performance of a given WMN. Copyright © 2009 John Wiley & Sons, Ltd.     

Distributed channel assignment combined with routing over multi-radio multi-channel wireless mesh networks

In order to realize the reduction of equipment cost and the demand of higher capacity,wireless mesh network(WMN) router devices usually have several interfaces and work on multi-channels.Jointing channel allocation,interface assignment and routing can efficiently improve the network capacity.This paper presents an efficient channel assignment scheme combined with the multi-radio link quality source routing(MR-LQSR) protocol,which is called channel assignment with MR-LQSR(CA-LQSR).In this scheme,a physical interference model is established:calculated transmission time(CTT) is proposed as the metric of channel assignment,which can reflect the real network environment and channel interference best,and enhanced weighted cumulative expected transmission time(EWCETT) is proposed as the routing metric,which preserves load balancing and bandwidth of links.Meantime,the expression of EWCETT contains the value of CTT,thus the total cost time of channel assignment and routing can be reduced.Simulation results show that our method has advantage of higher throughput,lower end-to-end time delay,and less network cost over some other existing methods.     

Characterization of the impact of network topology on the performance of single-radio wireless mesh networks

Stub Wireless Mesh Networks (WMNs) are used to extend Internet access. The use of multiple channels improves the capacity of WMN but significant challenges arise when nodes are limited to a single-radio interface to form the WMN. In particular, the assignment of mesh nodes to channels results on the creation of multiple sub-networks, one per channel, where individual capacity may depend on the sub-network topologies This paper identifies the relevant topological characteristics of the sub-networks resultant from the channel assignment process and studies, through simulation, the impact and relative importance of those characteristics on the maximal throughput enabled by the stub WMN. The number of nodes in the gateways neighborhood and the hidden node problem in the gateways neighborhood were identified as the characteristics having the highest impact on the WMN throughput.     

An efficient channel assignment algorithm for multicast wireless mesh networks

Multicast can enhance the performance of wireless mesh networks (WMNs) effectively, which has attracted great attentions in recent years. However, multicast communication in WMNs requires efficient channel assignment strategy to reduce the total network interference and maximize the network throughput. In this paper, the concept of local multicast is proposed to measure interference and solve hidden channel problem in multicast communication. Basing on the concept, we propose a channel assignment algorithm considering the interference of local multicast and forwarding weight of each node (LMFW). The algorithm fully considers partially overlapped channels and orthogonal channels to improve the network performance. Simulations show that the proposed algorithm can reduce interference and improve network capacity of WMNs.     

A weighted interference estimation scheme for interface‐switching wireless mesh networks

The co‐channel interference problem in wireless mesh networks (WMN) is extremely serious due to the heavy aggregated traffic loads and limited available channels. It is preferable for mesh routers to dynamically switch channels according to the accurate estimation of co‐channel interference level in the neighborhood. Most developed interference estimation schemes, however, do not consider the impact of interface switching. Furthermore, the interference in wireless networks has been extensively considered as an all‐or‐nothing event. In this paper, we develop a weighted interference estimation scheme (WIES) for interface‐switching WMN. WIES takes a new version of multi‐interface conflict graph that considers the impacts of frequent interface switching as the interference relationship estimation scheme. Besides, WIES uses a weight to estimate the interference level between links. The weight utilizes two empirical functions to denote the impacts of the relative distance and characteristics of traffic loads in WMN. Extensive NS2 simulations show that WIES achieves significant performance improvements, especially when the interference level of the network is high. We also validate that the interference level of networks is affected by several system parameters such as the number of available channels and the ratio between interference range and transmission range. Copyright © 2008 John Wiley & Sons, Ltd.