多信道无线Mesh网络的多播信道分配算法

无线Mesh网络可用信道和节点接口的缺乏限制了多播树链路的可用带宽,致使网络吞吐量下降。针对该问题,提出支持多播的多信道多接口信道分配算法——LAMCA。该算法能最小化无线Mesh网络的干扰程度,并最大化网络吞吐量。仿真结果表明,与层次信道分配算法LCA相比,该算法在吞吐量性能方面较优。     

多源多播服务功能链优化部署算法

在软件定义网络和网络功能虚拟化环境下,针对多播中的服务功能链（SFC）部署,探究了多源多播中的联合虚拟网络功能（VNF）部署和流量路由问题,目的是最小化节点资源消耗和链路资源消耗总成本。同时考虑到节点、链路及带宽延迟限制,建立了整数线性规划模型,并提出一种名为多源多播树优化的启发式算法。该算法旨在为所有用户找到最近的源节点,获得多个源、目节点组,为每个组构造一棵多播服务功能树,然后优化多播服务功能树。实验仿真结果表明,与其他启发式算法相比,该算法有效地降低了总成本、链路利用率及时延。     

面向多跳无线网络的无冲突MAC协议

多跳无线网络中隐藏节点导致节点之间的冲突频繁、数据重传率高、网络吞吐量下降.而802.11 DCF 中的RTS/CTS(ready-to-send/clear-to-send)机制不能有效地防止隐藏节点,特别是随着网络中节点通信速率的提高,由 于节点的信噪比要求也相应提高,接收节点受到更大范围内隐藏节点的干涉,RTS/CTS 机制防止隐藏节点的效率急剧降低.首先,在考虑网络积累干涉以及环境噪音的情况下分析了多跳无线网络中的隐藏节点问题.然后,提出一种双信道无冲突MAC(media access control)协议DCCFMA(double channel collision free media access).DCCFMA 协议采用双信道结构,接收节点根据数据信道中发送节点的信号强度动态调节控制信道的发射功率,以完全覆盖接收节点周围所有的隐藏节点,保证接收节点在接收过程中不受干涉.DCCFMA 协议能够有效地解决多跳无线网络中的隐藏节点问题.仿真结果表明,与802.11DCF 相比,DCCFMA 机制下的平均网络吞吐量增加了24%.     

一种基于最小生成树的无线多跳网络信道分配算法

在无线多跳网络环境下,提出了一种信道分配算法,该算法可优先考虑最小生成树上的可用信道,为每个节点分配信道资源,然后考虑利用生成树外其他可用链路为节点提供信道资源,以提高吞吐量。该算法通过考虑每个用户的通信需求,可充分利用空闲信道资源。仿真结果显示,相比于不考虑最小生成树外链路时,本算法可有效地提高网络整体的吞吐量。     

一种改进负载均衡的网络编码多播路由算法

已有研究证明,在多播网络中使用网络编码可以显著提高多播通信的性能。总结了网络编码多播理论的研究进展,同时对网络编码多播路由问题进行了研究与分析。考虑到影响链路负载和资源消耗的因素,提出了一种改进链路负载均衡的网络编码多播路由算法,优化了路径间链路的共享。通过使用常见的Waxman网络拓扑模型,产生随机网络拓扑。在这些拓扑中,分别针对传统IP多播路由、低速率网络下的网络编码多播路由以及提出的路由算法进行性能仿真。仿真结果表明,与其他两种路由算法相比,该算法在可达吞吐量、资源消耗和负载均衡等性能上均有很好的表现。     

基于SINR的动态无线网络分布式链路调度

无线信号之间的干扰阻碍了信号的并发传输,降低了无线网络的吞吐量.链路调度是提高无线网络吞吐量、减少信号传输延迟的一种有效方法.因为SINR (signal to interference plus noise ratio)模型准确地描述了无线信号传播的固有特性,能够真实反映无线信号之间的干扰,提出一种在动态无线网络中基于SINR模型的常数近似因子的在线分布式链路调度算法(OLD＿LS).在线的意思是指,在算法执行的过程中任意节点可以随时加入网络,也可以随时离开网络.节点任意加入网络或者从网络中离开体现了无线网络的动态变化的特性. OLD＿LS算法把网络区域划分为多个正六边形,局部化SINR模型的全局干扰.设计动态网络下的领导者选举算法(LE),只要网络节点的动态变化速率小于1/ε, LE就可以在O(log n+log R)ε≤5(1-2^1-α/2)/6,α表示路径损耗指数, n是网络节点的规模, R是最长链路的长度.根据文献调研,所提算法是第1个用于动态无线网络的在线分布式链路调度算法.     

一种适用于移动网络的低代价动态多播路由算法

多播由于能够有效地利用网络资源并减轻服务器的负担因而受到广泛关注,但在移动网络环境中,由于多播组成员的位置可以动态改变,已有的动态多播算法不能获得较好的性能。论文提出了一种适用于移动网络的动态多播路由算法,该算法为目的节点建立最短多播路径时采用了结合链路代价和多播目的节点数的平摊代价函数,以便构建出的多播树在整个通信过程中平均总代价较小。模拟实验结果表明论文提出的算法所构建的多播树的平均总代价要低于其它动态算法。     

无线网络中一类多播网络的网络编码

提出一种无线网络空间构造的新算法,该算法借助基本图模拟网络节点状态,通过节点基本图的加入和离开动态实现无线网络.k冗余多播网络采用网络编码可实现最大多播速率k的信息传输,对于无线网络中的k冗余多播网络,从网络信息流分解的角度给出一种网络编码算法.     

基于稀疏Ad hoc网络环境的链路预补偿算法研究*

着重研究在通信链路易中断的稀疏Ad hoc网络环境中的数据传输问题。提出了链路预补偿算法,首先给出了关键节点的定义与探测算法,然后给出了功率补偿算法,通过增大补偿节点的功率,增强关键节点周围的连接度,进而提高数据的接收率和吞吐量;并且在NS2模拟器中,对该算法搭建仿真平台进行了性能评估。仿真结果表明,链路预补偿算法能够提高网络的吞吐量和数据接收率。     

基于Dijistra算法的多约束多播路由算法的研究

多播业务已被广泛应用于各种流媒体,这些业务对QoS提出了一定的要求,多约束多播路由算法成为解决多播业务QoS 问题的研究热点.该文提出的多约束多播路由算法以带宽和时延作为多约束条件,首先消去不符合带宽要求的所有链路,接着用Dijistra最短路径算法选择从源节点到目的节点之问满足时延最小的路径.通过设计一包含6个网络节点的拓扑结构,用网络仿真工具对该网络中各条链路利用率的统计,证明了该算法找到的路径和理论值完全一致,验证了该算法的有效性和简单性.     

An effective scheduling scheme for multi-hop multicast in wireless mesh networks

With the utilization of concurrent transmission strategy, a throughput-enhanced scheduling scheme is devised for multicast service in wireless multi-hop mesh networks. Since the performance of a multicast mechanism is constrained in a wireless setting due to the interference among local wireless transmissions, the interference relationships are first characterized by introducing a graph transformation method. Based on the graph transformation, the multicast scheduling problem is converted to the graph coloring problem, and then a capacity greedy algorithm is designed to provide concurrent transmission scheduling so that the demanded multicast transmission rate can be achieved. Moreover, the necessary and sufficient conditions of multicast schedulable feasibility are derived. Through corresponding simulations, it is shown that the proposed strategy can enhance the throughput of wireless multi-hop multicast systems significantly.     

An effective scheduling scheme for multi-hop multicast in wireless mesh networks

With the utilization of concurrent transmission strategy, a throughput-enhanced scheduling scheme is devised for multicast service in wireless multi-hop mesh networks. Since the performance of a multicast mechanism is constrained in a wireless setting due to the interference among local wireless transmissions, the interference relationships are first characterized by introducing a graph transformation method. Based on the graph transformation, the multicast scheduling problem is converted to the graph coloring problem, and then a capacity greedy algorithm is designed to provide concurrent transmission scheduling so that the demanded multicast transmission rate can be achieved. Moreover, the necessary and sufficient conditions of multicast schedulable feasibility are derived. Through corresponding simulations, it is shown that the proposed strategy can enhance the throughput of wireless multi-hop multicast systems significantly.     

Suboptimal network coding subgraph algorithms for 5G minimum-cost multicast networks

To reduce the transmission cost in 5G multicast networks that have separate control and data planes, we focus on the minimum-power-cost network-coding subgraph problem for the coexistence of two multicasts in wireless networks. We propose two suboptimal algorithms as extensions of the Steiner tree multicast. The critical 1-cut path eliminating (C1CPE) algorithm attempts to find the minimum-cost solution for the coexistence of two multicast trees with the same throughput by reusing the links in the topology, and keeps the solution decodable by a coloring process. For the special case in which the two multicast trees share the same source and destinations, we propose the extended selective closest terminal first (E-SCTF) algorithm out of the C1CPE algorithm. Theoretically the complexity of the E-SCTF algorithm is lower than that of the C1CPE algorithm. Simulation results show that both algorithms have superior performance in terms of power cost and that the advantage is more evident in networks with ultra-densification.     

认知无线电网络中QoS组播路由调度

在多跳认知无线电网络中,组播的信息通常要经由多个中间节点的转发才能到达最终的目的节点。现有的研究中已经有很多的组播路由协议,然而这些协议都是基于传统无线网络的,并不适合新型的认知无线电网络。本文解决的的问题是:在多跳无线网络中,给定一个具有QoS要求的组播请求,如何建立组播路由以及对路径节点进行传输调度,使得在满足QoS要求下整个传输过程的带宽消耗最小。本文提出了一个分布式的组播路由协议来解决该问题,该协议不仅实现了路由过程的建立,同时还完成了对节点传输过程的合理调度。实验结果证明本文的传输调度策略能有效地减少网络的带宽消耗,同时增加组播请求响应的成功率。     

Fundamental limits on end-to-end throughput of network coding in multi-rate and multicast wireless networks

This paper investigates the interaction between network coding and link-layer transmission rate diversity in multi-hop wireless networks. By appropriately mixing data packets at intermediate nodes, network coding allows a single multicast flow to achieve higher throughput to a set of receivers. Broadcast applications can also exploit link-layer rate diversity, whereby individual nodes can transmit at faster rates at the expense of corresponding smaller coverage area. We first demonstrate how combining rate-diversity with network coding can provide a larger capacity for data dissemination of a single multicast flow, and how consideration of rate diversity is critical for maximizing system throughput. Next we address the following question: given a specific topology of wireless nodes, what is the maximum rate that can be supported by the resultant network exploiting both network coding and multi-rate? We present a linear programming model to compute the maximal throughput that a multicast application can achieve with network coding in a rate-diverse wireless network. We also present analytical results where we observe noticeably better throughput than traditional routing. This suggests there is opportunity for achieving higher throughput by combining network coding and multi-rate diversity.     

Joint routing, scheduling, and power control for multichannel wireless sensor networks with physical interference

Reliability and real-time requirements bring new challenges to the energy-constrained wireless sensor networks, especially to the industrial wireless sensor networks. Meanwhile, the capacity of wireless sensor networks can be substantially increased by operating on multiple nonoverlapping channels. In this context, new routing, scheduling, and power control algorithms are required to achieve reliable and real-time communications and to fully utilize the increased bandwidth in multichannel wireless sensor networks. In this paper, we develop a distributed and online algorithm that jointly solves multipath routing, link scheduling, and power control problem, which can adapt automatically to the changes in the network topology and offered load. We particularly focus on finding the resource allocation that realizes trade-off among energy consumption, end-to-end delay, and network throughput for multichannel networks with physical interference model. Our algorithm jointly considers 1) delay and energy-aware power control for optimal transmission radius and rate with physical interference model, 2) throughput efficient multipath routing based on the given optimal transmission rate between the given source-destination pairs, and 3) reliable-aware and throughput efficient multichannel maximal link scheduling for time slots and channels based on the designated paths, and the new physical interference model that is updated by the optimal transmission radius. By proving and simulation, we show that our algorithm is provably efficient compared with the optimal centralized and offline algorithm and other comparable algorithms.     

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.     

AD hoc网络中的机会分组调度算法

无线多跳Ad hoc网络中节点在业务发送过程中需要竞争共享信道,容易发生局部拥塞导致网络性能下降,而且节点内部采用的先入先出(FIFO)队列容易使队头阻塞,影响队列中后续分组的发送。本文提出了一种机会分组调度算法CBOS,发送节点采用多播RTS的方式同时指向多个接收节点,可以支持可变长分组,提高了Ad hoc网络的空间重用率,接收节点根据拥塞程度按照一定概率返回CTS,有利于节点网络的拥塞控制。仿真结果表明,该算法提高了网络端到端的饱和吞吐量和信道利用率,并提高了业务流之间的公平性。     

A novel minimum delay maximum flow multicast algorithm to construct a multicast tree in wireless mesh networks

The construction of multicast tree within given constraints, such as delay and capacity, is becoming a major problem in many wireless networks, especially wireless mesh networks (WMN). Due to the limited capacity of the wireless node, a multicast call may be dropped if there is no multicast tree formed within the given constraints. In this paper, we propose a new multicast tree construction algorithm which has maximum traffic flow and minimum delay under capacity constraints. The problem of multicast is formulated as a Linear Programming (LP) problem with associated constraints. A cost function (CF) is defined to choose the less loaded route among the available ones. A Minimum Delay Maximum Flow Multicast (MDMF) algorithm is proposed to solve this problem using CF and associated constraints. The performance of the proposed algorithm and CF is evaluated and compared with well-known algorithms with respect to packet delivery fraction, latency, and network throughput. The results obtained show that the proposed algorithm has a lesser number of transmissions for a given CF. Moreover, the proposed algorithm has high throughput, packet delivery fraction and less latency compared to other well-known algorithms in this category.     

Efficient Multicast Algorithms for Multichannel Wireless Mesh Networks

The wireless mesh network is an emerging technology that provides high quality service to end users as the "last mile” of the Internet. Furthermore, multicast communication is a key technology for wireless mesh networks. Multicast provides efficient data distribution among a group of nodes. However, unlike other wireless networks, such as sensor networks and MANETs, where multicast algorithms are designed to be energy efficient and to achieve optimal route discovery among mobile nodes, wireless mesh networks need to maximize throughput. This paper proposes two multicast algorithms: the Level Channel Assignment (LCA) algorithm and the Multichannel Multicast (MCM) to improve the throughput for multichannel and multi-interface mesh networks. The algorithms build efficient multicast trees by minimizing the number of relay nodes and total hop count distances of the trees. The algorithms use dedicated channel assignment strategies to reduce the interference to improve the network capacity. We also demonstrate that using partially overlapping channels can further diminish the interference. Furthermore, additional interfaces help to increase the bandwidth, and multiple gateways can further shorten the total hop count distance. Simulations show that those algorithms greatly outperform the single-channel multicast algorithm. We also observe that MCM achieves better throughput and shorter delay while LCA can be realized in distributed manner.