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。     

无线Mesh网络集中式信道分配算法设计

以集中式无线Mesh网络(WMN)为基础,分析和研究了传统多信道分配算法,并在此基础上提出了以节点优先级和分组为特点的多接口多信道分配算法(Channel Assignment based on Rank of Node and Link group,CAR-NL),该算法结合节点分级和链路负载预期评估机制,通过节点链路分组按级分配信道。通过仿真实验表明,该算法能有效提高无线Mesh网络多业务流并发执行时系统整体吞吐量,并实现较低的丢包率。     

基于贪心算法的无线mesh时空域多信道分配研究

无线mesh网络多接口多信道分配算法中,信道分配与接口数目之间存在相互制约、相互依赖、“涟漪效应”,导致链路无效以及承载网络拓扑的主要业务节点存在时序关系,本文在基于多信道空间和时间联合信道分配算法的基础之上,考虑前一个子时序已分配信道对下一个子时序信道分配的影响,提出了基于贪心算法的无线mesh时空域多信道分配算法.根据贪心算法原理,尽量不改变已分配信道,减少信道切换时间,将剩余的未分配信道分配给要分配的接口,使信道能并行工作以提高整个网络的吞吐量.通过实验仿真,对比了能够抑制“涟漪效应”和链路无效的静态多接口多信道分配算法、空间与时间相结合的多接口多信道分配算法.结果表明,整个mesh网络的吞吐量有明显提高,且随着网络中业务节点变化的减小而增大,随着可利用信道数目的增加而增加.     

WLAN分布式动态信道分配算法研究

本文介绍了一种无线局域网中分布式动态信道分配的算法。该算法是为了适应组网发展,设计出的一种在分布式环境下运行的信道分配算法。由于无线技术的发展,同一网络下会存在大量的无线接入点,传统的信道分配算法在这时候就会突显出时间复杂度高的问题。本文通过引入社区划分的算法,将网络进行分解,在各子网络中进行信道分配,从其他的角度一定程度上解决了时间复杂度的问题。通过NS2模拟仿真,证实了该算法的可行性,可以明显减少信道调整的时间。     

无线网状网中基于信道预留的多信道媒体接入控制方案

目前多信道无线Mesh网络WMN(Wireless Mesh Network)的MAC(Medium Access Contro)l仍然存在信道利用率低的问题,因此提出了具有控制信道和数据信道的多信道WMN的MAC方案。方案采用数据信道预留机制来提高系统的吞吐量,并降低接入时延。该方案通过减小控制信道上的碰撞概率可以有效降低系统接入时延并提高控制信道的利用率。理论分析和性能估计表明此方案具有高的吞吐量和低的接入时延,性能明显优于现有的公共信道控制方案CCC(Common Control Channel)。     

CBLA:多信道无线网状网络负载感知的分簇式信道分配

多信道技术能够显著提升无线网状网络的容量,合理高效的信道分配方案是多信道网状网络的核心问题。本文提出了一种分布式的信道分配方法CBLA（Cluster-Based Load-Aware）,结合了静态信道分配简单和动态信道分配灵活的特点;借助簇结构降低了问题的规模;根据统计开销小的局部信息监测链路负载;自适应的动态分配有效减轻了链路负载;采用了一种新的结合跳步数、信道分布情况和簇信息的选路指标。实验结果表明CBLA有效降低了数据包的平均延迟,并显著提升了网络吞吐量。     

一种基于博弈论的无线Mesh网信道分配算法

为解决无线Mesh网络中的信道分配问题,提出了基于博弈论的信道分配(GBCA)算法。该算法将无线Mesh网中各节点的信道分配过程作为一个博弈过程,信道分配策略作为博弈者的策略选择,信噪比函数为博弈的效用函数。基于NS2的仿真结果表明该算法在吞吐量和丢包率方面都有较好的性能。     

一种基于信道阻力的Ad hoc网络多路径路由算法

该文提出了一种基于信道阻力的Ad hoc网络多路径动态源路由算法。算法中定义了信道阻力的概念,并以信道阻力为依据来进行多条路径的流量分配,由于信道阻力计算中综合考虑了链路质量的各个度量参数,因此能够根据各条路径的传输能力合理分配数据流量。NS2环境下的仿真表明,新算法能够有效地平衡网络负载,提高网络的吞吐量。     

一种消除空闲时间的EPON信道传输方案

动态带宽分配算法是以太网无源光网络系统的关键技术之一,现有采用周期轮询机制的动态带宽分配算法大多存在轮询周期间时隙浪费的问题.文章提出了一种新的消除空闲时间的信道传输方案,理论分析和教值计算证明:新的方案可以有效地消除空闲时间,提高上行链路的利用率.     

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。     

用于多信道无线网络的综合链路速率分配算法

This paper presents a link allocation and rate assignment algorithm for multi-channel wireless networks. The objective is to reduce network conflicts and guarantee the fairness among links. We first design a new network model. With this network model, the multi-channel wireless network is divided into several subnets according to the number of channels. Based on this, we present a link allocation algorithm with time complexity O(l2 ) to allocate all links to subnets. This link allocation algorithm adopts conflict matrix to minimize the network contention factor. After all links are allocated to subnets, the rate assignment algorithm to maximize a fairness utility in each subnet is presented. The rate assignment algorithm adopts a near-optimal algorithm based on dual decomposition and realizes in a distributed way. Simulation results demonstrate that, compared with IEEE 802. 11b and slotted seeded channel hopping algorithm, our algorithm decreases network conflicts and improves the network throughput significantly.     

Virtual access network embedding in wireless mesh networks

Network virtualization of a wireless mesh network (WMN) is an economical way for different subscribers to customize their exclusive access networks through a common network infrastructure. The most critical task of network virtualization is virtual network embedding, which can be divided into two sub-problems: node mapping and link mapping. Although there exist approaches to virtual network embedding in wired networks, the characteristics of WMNs make virtual network embedding become a unique and challenging problem. In this paper, virtual access network embedding is studied for WMNs. To support flexible resource allocation in virtual access network embedding, each access node is designed based on orthogonal frequency division multiple access (OFDMA) dual-radio architecture. Through subcarrier allocation on each link, virtual access networks are gracefully separated from each other. To coordinate channel assignment across different links under the constraint of a limited number of orthogonal channels, a novel channel allocation algorithm is proposed to exploit partially-overlapped channels to improve resource utilization. Since the virtual access network embedding problem is NP-hard, a heuristic algorithm is developed based on an enhanced genetic algorithm to obtain an approximate but effective solution. Simulation results illustrate that the virtual access network embedding framework developed in this paper works effectively in WMNs.     

Joint Channel Assignment and Routing for Throughput Optimization in Multiradio Wireless Mesh Networks

Multihop infrastructure wireless mesh networks offer increased reliability, coverage, and reduced equipment costs over their single-hop counterpart, wireless local area networks. Equipping wireless routers with multiple radios further improves the capacity by transmitting over multiple radios simultaneously using orthogonal channels. Efficient channel assignment and routing is essential for throughput optimization of mesh clients. Efficient channel assignment schemes can greatly relieve the interference effect of close-by transmissions; effective routing schemes can alleviate potential congestion on any gateways to the Internet, thereby improving per-client throughput. Unlike previous heuristic approaches, we mathematically formulate the joint channel assignment and routing problem, taking into account the interference constraints, the number of channels in the network, and the number of radios available at each mesh router. We then use this formulation to develop a solution for our problem that optimizes the overall network throughput subject to fairness constraints on allocation of scarce wireless capacity among mobile clients. We show that the performance of our algorithms is within a constant factor of that of any optimal algorithm for the joint channel assignment and routing problem. Our evaluation demonstrates that our algorithm can effectively exploit the increased number of channels and radios, and it performs much better than the theoretical worst case bounds     

Joint Throughput Optimization for Wireless Mesh Networks

In this paper, we address the problem of joint channel assignment, link scheduling, and routing for throughput optimization in wireless networks with multiradios and multichannels. We mathematically formulate this problem by taking into account the interference, the number of available radios the set of usable channels, and other resource constraints at nodes. We also consider the possible combining of several consecutive channels into one so that a network interface card (NIC) can use the channel with larger range of frequencies and thus improve the channel capacity. Furthermore, we consider several interference models and assume a general yet practical network model in which two nodes may still not communicate directly even if one is within the transmission range of the other. We designed efficient algorithm for throughput (or fairness) optimization by finding flow routing, scheduling of transmissions, and dynamic channel assignment and combining. We show that the performance, fairness and throughput, achieved by our method is within a constant factor of the optimum. Our model also can deal with the situation when each node will charge a certain amount for relaying data to a neighboring node and each flow has a budget constraint. Our extensive evaluation shows that our algorithm can effectively exploit the number of channels and radios. In addition, it shows that combining multiple channels and assigning them to a single user at some time slots indeed increases the maximum throughput of the system compared to assigning a single channel.     

Distributed Channel Allocation Using Kernel Density Estimation in Cognitive Radio Networks

Typical channel allocation algorithms for secondary users do not include processes to reduce the frequency of switching from one channel to another caused by random interruptions by primary users, which results in high packet drops and delays. In this letter, with the purpose of decreasing the number of switches made between channels, we propose a nonparametric channel allocation algorithm that uses robust kernel density estimation to effectively schedule idle channel resources. Experiment and simulation results demonstrate that the proposed algorithm outperforms both random and parametric channel allocation algorithms in terms of throughput and packet drops.     

Temporal fairness guarantee in multi-rate wireless LANs for per-flow protection

Wireless LAN technologies such as IEEE 802.11a and 802.11b support high bandwidth and multi-rate data transmission to match the channel condition (i.e., signal to noise ratio). While some wireless packet fair queuing algorithms to achieve the per-flow throughput fairness have been proposed, they are not appropriate for guaranteeing QoS in multi-rate wireless LAN environments. We propose a wireless packet scheduling algorithm that uses the multi-state (multi-rate) wireless channel model and performs packet scheduling by taking into account the channel usage time of each flow. The proposed algorithm aims at per-flow protection by providing equal channel usage time for each flow. To achieve the per-flow protection, we propose a temporally fair scheduling algorithm called Contention-Aware Temporally fair Scheduling (CATS) which provides equal channel usage time for each flow. Channel usage time is defined as the sum of the packet transmission time and the contention overhead time due to the CSMA/CA mechanism. The CATS algorithm provides per-flow protection in wireless LAN environments where the channel qualities of mobile stations are dynamic over time, and where the packet sizes are application-dependent. We also extend CATS to Decentralized-CATS (D-CATS) to provide per-flow protection in the uplink transmission. Using an NS-2 simulation, we evaluate the fairness property of both CATS and D-CATS in various scenarios. Simulation results show that the throughput of mobile stations with stable link conditions is not degraded by the mobility (or link instability) of other stations or by packet size variations. D-CATS also shows less delay and less delay jitter than FIFO. In addition, since D-CATS can coordinate the number of contending mobile stations, the overall throughput is not degraded as the number of mobile stations increases. This work was supported in part by the Brain Korea 21 project of Ministry of Education and in part by the National Research Laboratory project of Ministry of Science and Technology, 2004, Korea.     

认知无线多跳网中结合QoS查找的跨层多信道MAC协议

针对认知无线多跳网中频谱资源具有较大时变性及差异性的问题,设计了一种结合QoS查找的跨层多信道MAC协议。该协议将按需QoS查找与动态频谱分配跨层相结合,仅让参与传输的节点执行频谱分配并按QoS要求获取频谱资源。此外,协议使用频分双工收发机实现了对公共控制信道的不间断监听,并设计了一套支持不同数量收发机节点间混合通信的接入算法。大量仿真结果表明,该协议能有效保证对端到端传输的QoS要求的满足,并显著提高端到端吞吐量及时延。     

Multipath selection and channel assignment in wireless mesh networks

In wireless networks, it is very important to optimize the number of channels, due to the limit on the number of usable channels in a given network. In addition, multimedia services with high QoS requirements with respect to throughput and delay have recently become popular. To satisfy these requirements, it has become important to find a way of providing multipath transmission. A channel assignment algorithm is presented that minimizes the number of required channels while satisfying the throughput requirements of source–destination pairs in multichannel, multiradio, multirate wireless mesh networks. A mathematical model is proposed that considers interference effect, link capacity, and throughput requirements. A novel channel assignment algorithm is developed that takes into account multipath selection, channel reusability, link capacity sharing, and global optimization. The performance of the algorithm is compared with that of CPLEX, using 24 network scenarios. The maximum gap between the CPLEX solutions and those of the proposed algorithm is, on average, only 4.8%.     

ORCA-MRT: an optimization-based approach for fair scheduling in multirate TDMA wireless networks

This paper presents an optimization-based approach to solve the wireless fair scheduling problem under a multirate time division multiple access (TDMA)-based medium access control (MAC) framework. By formulating the fair scheduling problem as an assignment problem, the authors propose the optimal radio channel allocation for multirate transmission (ORCA-MRT) algorithm for fair bandwidth allocation in wireless data networks that support MRT at the radio link level. The key feature of ORCA-MRT is that while allocating transmission rate to each flow fairly, it keeps the interaccess delay bounded under a certain limit. The authors investigate the performance of the proposed ORCA-MRT scheduler in comparison to another recently proposed multirate fair scheduling algorithm. They also propose two channel prediction models and perform extensive simulations to investigate the performance of ORCA-MRT for different system parameters such as channel state correlation, number of flows, etc.     

Multi-layer optimization with backpressure and genetic algorithms for multi-hop wireless networks

This paper presents an efficient scheme to optimize multiple layers in multi-hop wireless networks with throughput objectives. Considering channel sensing and power control at the physical layer, a non-convex throughput optimization problem is formulated for resource allocation and a genetic algorithm is designed to allow distributed implementation. To address link and network layers, a localized back-pressure algorithm is designed to make routing, scheduling, and frequency band assignments along with physical-layer considerations. Our multi-layer scheme is extended to cognitive radio networks with different user classes and evaluate our analytical solution via simulations. Hardware-in-the-loop emulation test results obtained with real radio transmissions over emulated channels are presented to verify the performance of our distributed multi-layer optimization solution for multi-hop wireless networks. Finally, a security system is considered, where links have their security levels and data flows require certain security levels on each of its links. This problem is addressed by formulating additional constraints to the optimization problem.