Adaptive scheme based on status feedback for virtual network mapping

Network virtualization is considered as a powerful way to deploy different network architectures and protocols over a shared physical infrastructure.Virtual network(VN)embedding plays an important role in the network virtualization environment.Virtual network embedding is mainly about mapping virtual nodes and virtual links onto the physical network resources efficiently.However,load balancing of substrate network has not received much consideration.This paper proposes an adaptive virtual network mapping algorithm based on status feedback.The main contribution is to embed the virtual network requests according to the current load distribution of substrate network.This adaptive algorithm differentiates the residual bandwidth of substrate links and takes full advantage of the multi-path to improve the load balancing of the substrate network.Simulation experiments show that the proposed algorithm improves the load distribution of substrate network distinctly while reducing the average substrate link stress significantly.     

Improving the multiple access method of home networks over the electrical wiring

Data communications on domestic low-voltage powerlines benefit from an ubiquitous and already existent infrastructure. Nevertheless, high-speed communications on this environment faces obstacles such as attenuation and noise. The HomePlug standard defines Media Access Control (MAC)- and physical (PHY)-layer protocols for home electrical wiring networks. Its MAC protocol has introduced the deferral counter (DC) mechanism, which adapts the contention of the nodes for the medium according to the network load. This article proposes the Contention window Pro-active Increase (CPI) mechanism to enhance the performance of HomePlug. The CPI mechanism is based on DC and improves the HomePlug efficiency by faster increasing the contention window size. As a consequence, there are fewer collisions and the aggregated throughput increases. Under high network load, our simulation results show a tradeoff concerning throughput and jitter. CPI improves HomePlug throughput by up to 3% with no jitter increase and by up to 15% at the cost of additional jitter.     

LTE网络中多目标优化的动态负载均衡算法

小区间动态负载均衡算法的优劣对网络性能有很大的影响,现有算法大都顾此失彼,难以保证网络关键性能指标(如呼叫阻塞率等)达到最佳。为解决这个问题,该文将负载均衡问题建模为多目标优化问题,分别对不同服务质量要求用户建模其相应目标优化函数,对有服务质量要求用户的目标函数是负载均衡指示函数和网络平均负载函数的联合优化函数,而对没有服务质量要求用户(BE用户)的目标函数是所有BE用户吞吐量的总效用函数,并将小区可用资源数和用户服务质量要求作为约束条件。另外,考虑到在实际系统中运行的计算复杂度问题,提出一种复杂度较低的分布式负载均衡算法。包括资源调度策略,用户切换条件和呼叫接入控制。仿真结果表明,该文算法可达到较好的负载均衡效果,能有效降低有服务质量要求用户的呼叫阻塞率,提高网络资源利用率。     

Cognitive Wireless Mesh Networks with Dynamic Spectrum Access

Wireless Mesh Networks (WMNs) are envisaged to extend Internet access and other networking services in personal, local, campus, and metropolitan areas. Mesh routers (MR) form the connectivity backbone while performing the dual tasks of packet forwarding as well as providing network access to the mesh clients. However, the performance of such networks is limited by traffic congestion, as only limited bandwidth is available for supporting the large number of nodes in close proximity. This problem can be alleviated by the cognitive radio paradigm that aims at devising spectrum sensing and management techniques, thereby allowing radios to intelligently locate and use frequencies other than those in the 2.4 GHz ISM band. These promising technologies are integrated in our proposed Cognitive Mesh NETwork (COMNET) algorithmic framework, thus realizing an intelligent frequency-shifting self-managed mesh network. The contribution of this paper is threefold: (1) A new approach for spectrum sensing is devised without any change to the working of existing de facto mesh protocols. (2) An analytical model is proposed that allows MRs to estimate the power in a given channel and location due to neighboring wireless LAN traffic, thus creating a virtual map in space and frequency domains. (3) These models are used to formulate the task of channel assignment within the mesh network as an optimization problem, which is solved in a decentralized manner. Our analytical models are validated through simulation study, and results reveal the benefits of load sharing by adopting unused frequencies for WMN traffic.     

Performance optimisation through EPT-WBC in mobile ad hoc networks

Mobile ad hoc networks are self-organised, infrastructure-less networks in which each mobile host works as a router to provide connectivity within the network. Nodes out of reach to each other can communicate with the help of intermediate routers (nodes). Routing protocols are the rules which determine the way in which these routing activities are to be performed. In cluster-based architecture, some selected nodes (clusterheads) are identified to bear the extra burden of network activities like routing. Selection of clusterheads is a critical issue which significantly affects the performance of the network. This paper proposes an enhanced performance and trusted weight-based clustering approach in which a number of performance factors such as trust, load balancing, energy consumption, mobility and battery power are considered for the selection of clusterheads. Moreover, the performance of the proposed scheme is compared with other existing approaches to demonstrate the effectiveness of the work.     

Design and Performance of PRAN: A System for Physical Implementation of Ad Hoc Network Routing Protocols

Simulation and physical implementation are both valuable tools in evaluating ad hoc network routing protocols, but neither alone is sufficient. In this paper, we present the design and performance of PRAN, a new system for the physical implementation of ad hoc network routing protocols that unifies these two types of evaluation methodologies. PRAN (physical realization of ad hoc networks) allows existing simulation models of ad hoc network routing protocols to be used - without modification - to create a physical implementation of the same protocol. We have evaluated the simplicity and portability of our approach across multiple protocols and multiple operating systems through example implementations in PRAN of the DSR and AODV routing protocols in FreeBSD and Linux using the standard existing, unmodified ns-2 simulation model of each. We illustrate the ability of the resulting protocol implementations to handle real, demanding applications by describing a demonstration with this DSR implementation transmitting real-time video streams over a multihop mobile ad hoc network; the demonstration features mobile robots being remotely operated based on the real-time video stream transmitted from the robot over the network. We also present a detailed performance evaluation of PRAN to show the feasibility of our architecture     

Congestion‐Aware Handover in LTE Systems for Load Balancing in Transport Network

Long‐Term Evolution employs a hard handover procedure. To reduce the interruption of data flow, downlink data is forwarded from the serving eNodeB (eNB) to the target eNB during handover. In cellular networks, unbalanced loads may lead to congestion in both the radio network and the backhaul network, resulting in bad end‐to‐end performance as well as causing unfairness among the users sharing the bottleneck link. This work focuses on congestion in the transport network. Handovers toward less loaded cells can help redistribute the load of the bottleneck link; such a mechanism is known as load balancing. The results show that the introduction of such a handover mechanism into the simulation environment positively influences the system performance. This is because terminals spend more time in the cell; hence, a better reception is offered. The utilization of load balancing can be used to further improve the performance of cellular systems that are experiencing congestion on a bottleneck link due to an uneven load.     

基于AODV的多度量无线路由算法研究

随着移动自组网络的快速发展,对距离矢量按需路由协议(AODV)的服务质量提出了越来越高的要求.为了提升AODV在无线传感器网络通信中的表现,文章提出了一种新型的基于AODV的多度量无线路由协议(MWR-AODV).MWR-AODV综合考虑了对路由协议性能影响重大的最小跳数、剩余能量、能量流失率和网络节点密度这四个因素,并且引入了一种低成本且高效的本地修复策略.通过Network Simulator-2仿真平台对MWR-AODV与标准AODV、DSDV协议的表现进行了仿真分析.结果表明,所提出的MWR-AODV能为无线传感器网络提供更好的通信服务,并且在均衡能量消耗延长网络寿命和平衡网络通信负载方面也有上佳表现.     

Providing fault tolerance in wireless access networks

Research and development on network survivability has largely focused on public switched telecommunications networks and high-speed data networks with little attention on the survivability of wireless access networks supporting cellular and PCS communications. This article discusses the effects of failures and survivability issues in PCS networks with emphasis on the unique difficulties presented by user mobility and the wireless channel environment. A simulation model to study a variety of failure scenarios on a PCS network is described, and the results show that user mobility significantly worsens network performance after failures, as disconnected users move among adjacent cells and attempt to reconnect to the network. Thus, survivability strategies must be designed to contend with spatial as well as temporal network behavior. A multilayer framework for the study of PCS network survivability is presented. Metrics for quantifying network survivability are identified at each layer. Possible survivability strategies and restoration techniques for each layer in the framework are also discussed     

Reconfiguration and Dynamic Load Balancing in Broadcast WDM Networks*

In optical WDM networks, an assignment of transceivers to channels implies an allocation of the bandwidth to the various network nodes. Intuition suggests, and our recent study has confirmed, that if the traffic load is not well balanced across the available channels, the result is poor network performance. Hence, the time-varying conditions expected in this type of environment call for mechanisms that periodically adjust the bandwidth allocation to ensure that each channel carries an almost equal share of the corresponding offered load. In this paper we study the problem of dynamic load balancing in broadcast WDM networks by retuning a subset of transceivers in response to changes in the overall traffic pattern. Assuming an existing wavelength assignment and some information regarding the new traffic demands, we present two approaches to obtaining a new wavelength assignment such that (a) the new traffic load is balanced across the channels, and (b) the number of transceivers that need to be retuned is minimized. The latter objective is motivated by the fact that tunable transceivers take a non-negligible amount of time to switch between wavelengths during which parts of the network are unavailable for normal operation. Furthermore, this variation in traffic is expected to take place over larger time scales (i.e., retuning will be a relatively infrequent event), making slowly tunable devices a cost effective solution. Our main contribution is a new approximation algorithm for the load balancing problem that provides for tradeoff selection, using a single parameter, between two conflicting goals, namely, the degree of load balancing and the number of transceivers that need to be retuned. This algorithm leads to a scalable approach to reconfiguring the network since, in addition to providing guarantees in terms of load balancing, the expected number of retunings scales with the number of channels, not the number of nodes in the network.     

基于深度动态贝叶斯网络的服务功能链故障诊断算法

针对5G端到端网络切片场景下底层物理节点出现故障会导致运行在其上的多条服务功能链出现性能异常的问题,该文提出一种基于深度动态贝叶斯网络(DDBN)的服务功能链故障诊断算法。首先根据网络虚拟化环境下故障的多层传播关系,构建故障与症状的依赖图模型,并采用在物理节点监测其上多个虚拟网络功能相关性能数据的方式收集症状。其次,考虑到基于软件定义网络(SDN)和网络功能虚拟化(NFV)的架构下网络症状观测数据的多样性以及物理节点和虚拟网络功能的空间相关性,引入深度信念网络对观测数据特征进行提取,使用加入动量项的自适应学习率算法对模型进行微调以加快收敛速度。最后,利用故障传播的时间相关性,引入动态贝叶斯网络对故障根源进行实时诊断。仿真结果表明,该算法能够有效地诊断故障根源且具有良好的诊断准确度。     

无线mesh网络中编码感知且负载均衡的组播路由

提出一种新的基于网络编码的负载均衡路由量度CRM-LB(coding-aware routing metric with load balancing),CRM-LB在CRM(coding-aware routing metric)的基础上增加了对路径p上所有节点通信密集程度与网络拥塞程度的考虑。进一步提出了基于CRM-LB的无线mesh网络多播路由CLR(coding and load-balancing routing)。该协议可以增加网络编码机会,同时考虑到网络中的负载均衡。通过性能分析和仿真实验表明,该协议在提高多播吞吐量的前提下,不仅能更好地支持网络编码,而且网络负载基本均衡。     

面向多节点故障的生存性虚拟网络映射方法

针对网络虚拟化环境中虚拟网络的生存性问题,提出一种面向多节点故障的生存性虚拟网络映射方法。该方法预先在物理网络中按比例留出备份资源并根据拓扑属性构造节点的候选集合,在发生节点故障后从故障节点的候选集合中选取重映射目标并动态分配预留的备用资源来恢复受到影响的虚拟网络,提高长期运营利润。仿真实验在多节点故障模型下从适用性、稳定性及性能方面验证了该方法的有效性。     

Simulation models for performance evaluation of satellite multipleaccess protocols

Simulation models are described for the performance evaluation of satellite multiple-access protocols used in VSAT (very small aperture terminal) data networks. Since the design of VSAT-based wide-area networks for interactive applications is critically dependent on the delay-throughput characteristics of the channel access protocol used, detailed simulation models have been developed to augment analytical performance-evaluation methods. Simulation models for several candidate VSAT access protocols, including random-access techniques such as Aloha, selective reject Aloha and slotted Aloha and demand-assignment multiple-access based techniques, are discussed in terms of traffic-source models, access algorithms, and performance-evaluation criteria. Numerical results for a realistic interactive data VSAT network environment are presented     

基于mean-variance的服务集群负载均衡方法

大量并发请求任务进行分配时,负载调度机制是通过最小化响应时间及最大化节点利用率实现网络中节点的负载均衡,在基于遗传算法的负载均衡算法中,适应度函数设计对服务集群负载均衡效率产生重要的影响.对此提出了一种基于mean-variance的服务集群负载均衡方法对适应度函数进行优化,采用投资组合选择模型mean-variance进行最小化响应时间,以得到每个服务器资源利用率的权重,从而获得最优的分配组合,进而提高适应度函数的准确性和有效性.在不同服务环境下与其他模型进行比较,仿真结果表明,本文的负载均衡算法在节点利用率和响应时间方面使服务集群得到了更好的均衡.     

Domain load balancing routing for multi-gateway wireless mesh networks

As Wireless Mesh Networks (WMNs) are typically used for Internet access, most traffic is routed through the gateways which connect WMN to the wired network. As a result, the gateways tend to get congested and balancing of the traffic load of gateways is critical. In this paper, we consider applications that require continuous provision of a certain bandwidth to a server located at the wired network. If a path that satisfies the bandwidth request cannot be found, the request will be rejected, so that load imbalance will result underutilization of the network capacity. We present a novel load balancing routing algorithm for maximizing the network utilization (i.e., accommodating service requests as many as possible) for multi-gateway WMNs. In the proposed scheme, a WMN is divided into domains. Each domain is served by one gateway, so that all traffic of a domain is served by the corresponding gateway. Our scheme determines routing to balance the traffic load among domains, and then performs load balancing routing within each domain. Simulation results show that in square grid topologies, our intra-domain routing achieves near optimal performance with about 70% less overhead than the existing schemes. Our inter-domain load balancing scheme outperforms the existing heuristics by up to 25% while achieving about 80% performance of the optimal solution.     

中继蜂窝网中基于负载均衡的中继节点选择算法

提出了一种中继蜂窝网络的基于负载均衡的中继节点选择策略(Load Balancing Relay Selection,LB-Rs).根据每个用户的具体信道状况以及中继节点服务的用户数目,LB-RS以分布式的方式为每个用户选择最优的中继节点.仿真结果表明,与基于单一物理层参数的中继节点选择算法相比,所提出的中继选择算法综...     

Load-balancing routing in multichannel hybrid wireless networks with single network interface

A hybrid wireless network is an extension of an infrastructure network, where a mobile host may connect to an access point (AP) using multihop wireless routes, via other mobile hosts. The APs are configured to operate on one of multiple available channels. Mobile hosts and wireless routers can select its operating channel dynamically through channel switching. In this environment, a routing protocol that finds routes to balance load among channels while maintaining connectivity was proposed. The protocol works with nodes equipped with a single network interface, which distinguishes the work with other multichannel routing protocols that require multiple interfaces per node. The protocol discovers multiple routes to multiple APs, possibly operating on different channels. Based on a traffic load information, each node selects the "best" route to an AP and synchronizes its channel with the AP. With this behavior, the channel load is balanced, removing hot spots and improving channel utilization. The protocol assures every node has at least one route to an AP, where all intermediate nodes are operating on the same channel. The simulation results show that the proposed protocol successfully adapts to changing traffic conditions and improves performance over a single-channel protocol and a multichannel protocol with no load balancing.     

Evaluation of the implementation cost of cache coherence protocols using omniscient actions

This paper presents a novel simulation-based approach which targets the performance estimation of cache coherence protocol implementations. Our approach allows to model a cache coherence protocol where coherence transactions take zero cycle and do not generate communication accesses, in the hope that it will provide a close lower bound on latency and traffic. The protocol modeling approach relies on cycle-accurate simulation models in which components can access instantaneously and transparently internal states of other components. Using this strategy, the access time and the traffic due to cache misses are taken into account as it would be on a multiprocessor system without cache coherence. However, the proposed approach still ensures that processors receive coherent data. We detail the implementation of this approach in a cycle accurate multiprocessor simulation environment. To show its effectiveness, we implement cache and memory models for two coherence protocols both with and without our omniscient cache coherence (OCC) proposal. We show with a formal method that this approach makes it possible to preserve the consistency models implied by the cache coherence protocols, and experimentally that the OCC strategy protocol gives a close lower bound on latency and traffic.     

Optimized BS assignment and resource allocation in cooperative OFDM networks

Cooperative transmission (CT) and orthogonal frequency division multiple (OFDM) are promising technologies for extending coverage and increasing throughput in broadband wireless access (BWA) networks. Therefore, we propose a novel BWA network architecture, that can set up inter-cell collaboration using physical layer cooperative transmissions among distributed wired access networks with a powerful coordination capability at the central office. However, conventional base station (BS) assignment and resource allocation schemes cannot be used directly because a user can be serviced by more than one BS with cooperative transmission technology. This study proposes a novel framework of BS assignment and resource allocation in a cooperative OFDM network. We provide three approaches of resource allocation for minimizing bandwidth usage, minimizing transmission power consumption, and balancing resource costs respectively. An optimized resource allocation scheme can be implemented by flexibly choosing one of these approaches based on network load. The simulation results show the efficiency of the proposed mathematical formulations and linearization approach of our scheme. The performance benefit of CT technology on the bandwidth saving is demonstrated by comparing the new BS assignment and resource allocation scheme with conventional non-cooperative transmission.