速率自适应的无线Mesh 网拥塞控制

在IEEE 802.11s 标准草案基础上,结合TCP 协议中的AIMD算法,提出一种针对无线Mesh 网的速率自适应拥塞控制策略。该策略与IEEE 802.11e EDCA相比,在有效缓解网络拥塞的同时,保证了高优先级业务与低优先级业务之间的公平性。试验结果表明该拥塞控制策略是有效可行的。     

一种802.11e EDCA机制的优化算法

IEEE 802.11e增强型分布式信道访问机制对高优先级业务服务质量的保证,是通过牺牲低优先级业务服务质量来实现的.为避免这种信道资源分配不公平的现象,提出一种优化算法.将信道中部分时隙合并起来构成合并时隙,高优先级和低优先级业务在合并时隙中被先后发送,而单个时隙通常只发送低优先级业务.仿真结果表明,该算法可以提高业务的吞吐量,当站点数目增多时,高优先级业务和低优先级业务的吞吐量均表现稳定,可达到各种业务公平利用信道资源的目的.     

一种支持业务优先级的卫星网络信道动态接入策略

针对远程作战飞机接入卫星信道的业务具有优先级且高优先级业务存在突发性影响信道利用率与吞吐量的问题,提出了一种支持业务优先级的卫星网络信道动态接入策略。该接入策略通过引入认知无线电技术构建频谱池以共享信道,设置高优先级业务透明接入信道的同时通过预留信道保证低优先级业务成功接入信道,未接入信道的业务采用排队模型等待接入。仿真结果表明,该策略能够高效地保证高优先级业务接入信道的成功率,有效降低接入时延;同时较好地减小高优先级业务的突发性对低优先级业务接入的影响,有效地提升了卫星信道的综合利用率,降低了低优先级业务的接入时延,保证了低优先级业务接入卫星网络的吞吐效率。     

WiMAX Mesh网络中一种分布式时隙分配算法

提出了一种基于资源预留的WiMAX Mesh网络支持QoS的微时隙动态分配算法。通过区分数据流优先级的方式将业务分为高优先级业务和低优先级业务两类,对高优先级的业务在每帧中预留一定的微时隙作为分配高优先级业务的时隙,预留时隙大小可以根据网络时隙使用状态动态地进行调整。仿真表明该算法在满足高优先级业务QoS的同时兼顾业务的请求失败率与时隙的利用率,降低了分组的平均时延。     

SDN架构下基于优先级的带宽保障算法研究

针对SDN构建的数据中心,互联网出口带宽无法同时满足所有业务的带宽需求,提出一个基于优先级的带宽保障算法,在满足高优先级业务带宽需求的情况下再满足低优先级业务的带宽需求,保障带宽资源的合理分配。测试结果表明,相比于没有采用带宽保障算法的模拟数据中心,基于优先级的带宽保障算法能确保高优先级业务在总体带宽资源不充足情况下保障业务质量。     

无线区域网中保障QoS的多业务调度算法

针对无线区域网中多业务资源分配和调度问题,基于认知无线电的特点提出一种改进的调度算法.该算法通过计算单用户不同业务的QoS优先级,并兼顾多用户之间的公平性选择业务传输的最优信道,在传输过程中采用节点中断管理方式动态修正业务的QoS优先级.仿真结果表明,该算法能有效利用网络带宽,并且能保障单用户业务的QoS要求和多用户调...     

业务驱动的密集移动终端网络资源预留方法

为提高密集移动终端商圈区域的终端服务质量,提出一种基于业务驱动资源预留的密集移动终端网络接入方法。根据网络属性、终端运动预测轨迹和业务类型,为高优先级业务终端预留资源量,在尽可能少牺牲低优先级业务服务质量的前提下,使高优先级业务终端获得稳定可靠的网络服务,并通过时间触发公平机制保障低优先级业务终端的网络接入资源。仿真结果表明,该方法不仅能够保障高优先级业务移动终端在异构网络中的接入质量,提高网络资源利用率,而且可以降低热点高容量场景下低优先级业务终端的接入失败率,改善用户体验质量。     

机载自组网信道占用统计预测机制

在机载自组网随机竞争类MAC协议中,信道忙闲程度可以作为不同优先级分组接入信道的阈值,通过限制低优先级业务的接入,保证高优先级业务的QoS,从而克服重负载下分组盲目接入信道导致网络性能恶化的问题。提出一种信道占用统计预测机制,在对信道忙闲程度等级划分的基础上,采用滑动窗口机制、加权-马尔科夫链预测模型,通过统计信道负载的历史信息,将负载的多步预测值和真实值的差值作为当前时刻预测值的修正,以当前时刻信道负载的预测值判定信道忙闲,从而为不同优先级分组接入信道的阈值设置提供理论依据。仿真结果表明,该机制对信道负载的正确预测率在90%以上,能够为多优先级业务提供区分服务,并且可以明显改善随机竞争类协议在重负载下的性能。     

基于业务区分的IEEE802.15.4 MAC协议分析及改进

针对多种业务并存的动态网络,提出网络负荷概率判断的自适应业务区分动态退避算法——PJNL_ASDB算法。其通过概率机制判断当前网络状况,引入权值参数对优先级不同的业务采用自适应的动态退避方案,以实现不同优先级业务更合理的退避。二维离散时间的马尔科夫链模型数值分析与NS2仿真结果表明,PJNL_ASDB算法在网络状况不断变化的情况下不仅能够保证高优先级业务的传输性能要求,而且提高了低优先级业务的网络性能。     

基于动态分组的M2M上行优先级调度算法

以延迟容忍剩余时长为度量依据,提出一种对业务进行动态分组的上行优先级调度算法。采用资源块(RB)大小可变的分配方式满足RB的邻接约束,引入混合自动轮询机制解决算法对低优先级业务调度不公平的问题。仿真结果表明,相比PF算法、RR算法,该算法的系统吞吐量分别提升约15%、41%,且在业务时延、业务区分度方面具有较好性能。     

A new approach for designing fault-tolerant WDM networks

In recent years, path protection has emerged as a widely accepted technique for designing survivable WDM networks. This approach is attractive, since it is able to provide bandwidth guarantees in the presence of link failures. However, it requires allocating resources for backup lightpaths, which remain idle under normal fault-free conditions. In this paper, we introduce a new approach for designing fault-tolerant WDM networks, based on the concept of survivable routing. Survivable routing of a logical topology ensures that the lightpaths are routed in such a way that a single link failure does not disconnect the network. When a topology is generated using our approach, it is guaranteed to have a survivable routing. We further ensure that the logical topology is able to handle the entire traffic demand after any single link failure. We first present an ILP that optimally designs a survivable logical topology, and then propose a heuristic for larger networks. Experimental results demonstrate that this new approach is able to provide guaranteed bandwidth, and is much more efficient in terms of resource utilization, compared to both dedicated and shared path protection.     

层叠IP/WDM网络中的区分服务

为层叠IP/WDM网络提出基于光通路物理跳距评估的区分服务机制。在使用层叠模型的IP/WDM网络体系中,如IP/MPLS层不了解光通路的物理跳距,现有文献中以此信息为基础的区分服务策略即不再适用。采用光通路区分策略评估光通路的物理跳距,映射为连接消耗的波长资源量,使用QoS接入控制机制拒绝占用大量资源的低优先级连接请求。仿真结果表明,该机制能够为不同等级业务提供良好的区分服务。     

一种综合IP层和WDM层资源的光网络动态路由优化模型及其性能研究

在分层图模型的基础上,本文提出一种以最小化全网光路总代价为优化目标的IP over WDM光网络动态路由优化模型,设计了一种针对该模型的在线综合路由算法——MCTLP（Minimizing the Cost of Total Lightpaths）,MCTLP通过综合考虑IP逻辑层带宽资源分配和WDM光物理层波长链路资源的占用以优化网络资源。与两种有代表性的IP over WDM光网络路由算法的性能仿真时比表明：MCTLP能够在IP逻辑层和WDM光物理层都使用较少的链路以承载IP业务流,接纳更多的IP业务连接请求,有效地降低网络阻塞率．     

A global approach for designing reliable WDM networks and grooming the traffic

In this paper, we address the global problem of designing reliable wavelength division multiplexing (WDM) networks including the traffic grooming. This global problem consists in finding the number of optical fibers between each pair of optical nodes, finding the configuration of each node with respect to transponders, finding the virtual topology (i.e., the set of lightpaths), routing the lightpaths, grooming the traffic (i.e, grouping the connections and routing them over the lightpaths) and, finally, assigning wavelengths to the lightpaths. Instead of partitioning the problem into subproblems and solving them successively, we propose a mathematical programming model that addresses it as a whole. Numerical results are presented and analyzed.     

Two-link failure protection in WDM mesh networks with p-cycles

In WDM networks, it is important to protect connections against link failures due to the high bandwidth provided by a fiber link. Although many p-cycle based schemes have been proposed for single-link failure protection, protection against two-link failures have not received much attention. In this paper, we propose p-cycle based protection schemes for two-link failures. We formulate an ILP model for the p-cycle design problem for static traffic. We also propose two protection schemes for dynamic traffic, namely SPPP (Shortest Path Pair Protection) and SFPP (Short Full Path Protection). Simulation results show that SFPP is more capacity efficient than SPPP under incremental traffic. Under dynamic traffic, SPPP has lower blocking than SFPP when the traffic load is low and has higher blocking than SFPP when the traffic load is high.     

Traffic recovery time constrained shared sub-path protection algorithm in survivable WDM networks

With the development of real-time applications, the traffic recovery time, which is defined as the duration between the failure occurrence on the working path and the interruptive traffic has been successfully switched to the backup path, has become the basic Quality-of-Service (QoS) requirement in survivable WDM networks. In this paper, we address the problem of shared sub-path protection with considering the constraint of traffic recovery time and propose a new heuristic algorithm called Traffic recovery time Constrained Shared Sub-Path Protection (TC_SSPP) to compute the working path and the Shared-Risk-Link-Group (SRLG)-disjoint backup sub-paths. The main target of our work is to improve the resource utilization ratio and reduce the blocking probability for dynamic network environment. By properly setting the delay parameter for each link and running the Delay Constrained Shortest Path Algorithm (DCSPA) to compute the backup sub-paths, TC_SSPP can effectively guarantee the traffic recovery time. Simulation results show that the proposed TC_SSPP can outperform the traditional algorithms.     

Spare capacity provisioning for quasi-static traffic

Resource provisioning has for long been an important area of research in network design. The traffic grooming problem in optical networks is a design problem of aggregating sub-wavelength traffic demands onto lightpaths and lightpaths onto fiber links such that the required electronic switching capability, hence network cost, can be minimized. Because of the reconfiguration cost in optical grooming networks, a reactive resource provisioning approach may become inefficient, and result in revenue loss. In this paper, we propose an over-provisioning scheme, which pre-allocates the spare capacity of lightpaths to dynamic sub-wavelength traffic demands such that the network can be more agile in responding to traffic increment requests. For the single-link case, we formulate the problem as a non-linear programming problem, and for under reasonable assumptions, we prove the objective function is convex. We provide an exact algorithm to find the optimal solution. The problem with general topologies is then studied. We prove the NP-hardness in this case, and propose heuristics. Numerical results show our heuristics perform well.     

Multicast protection scheme in survivable WDM optical networks

The protection design is a key issue in survivable wavelength division multiplexing (WDM) optical networks. Most researches focused on protecting unicast traffic against the failure of a single network component such as a link or a node. In this paper, we investigate the protection scheme for multicast traffic in meshed WDM optical networks under dual-link failure consideration, and propose a novel protection algorithm called shared segment protection with reprovisioning (SSPR). Through dynamically adjusting link-cost according to the current network state, SSPR establishes a primary light-tree and corresponding link-disjoint backup segments for each multicast connection request. A backup segment can efficiently share wavelength capacity of its working tree or the common resource of other backup segments. Capacity reprovisioning establishes new segments for the vulnerable connections after a link failure and tolerates following link failures. The simulation results show that SSPR not only can make good use of wavelength resources and protect multicast sessions against any single-link failure, but also can greatly improve the traffic restorability in the event of dual-link breakdown.     

Rerouting schemes for dynamic traffic grooming in optical WDM networks

Traffic grooming in optical WDM mesh networks is a two-layer routing problem to effectively pack low-rate connections onto high-rate lightpaths, which, in turn, are established on wavelength links. The objective of traffic grooming is to improve resource efficiency. However, resource contention between lightpaths and connections may result in inefficient resource usage or even the blocking of some connections. In this work, we employ a rerouting approach to alleviate resource inefficiency and improve the network throughput under a dynamic traffic model. We propose two rerouting schemes, rerouting at lightpath level (RRLP) and rerouting at connection level (RRCON) and a qualitative comparison is made between the two. We also propose two heuristic rerouting algorithms, namely the critical-wavelength-avoiding one-lightpath-limited (CWA-1L) rerouting algorithm and the critical-lightpath-avoiding one-connection-limited (CLA-1C) rerouting algorithm, which are based on the two rerouting schemes. Simulation results show that rerouting reduces the blocking probability of connections significantly.     

A new shared-risk link groups (SRLG)-disjoint path provisioning with shared protection in WDM optical networks

This paper addresses the protection problem in WDM optical networks and presents a New Shared-risk link groups (SRLG)-Disjoint Path Provisioning (NSDPP) approach with shared protection to tolerate the single-risk failure. Comparing to previous Shared-risk link groups (SRLG)-Disjoint Path Provisioning (SDPP) approach, NSDPP is able to obtain better performance, because in NSDPP some primary path and backup paths of other primary paths can share the common resources if the corresponding rules can be satisfied. Simulation results are shown to be promising.