Using a dynamic backbone for efficient data delivery in solar-powered WSNs

The periodic nature of solar power requires a different approach to energy consumption in wireless sensor networks (WSNs) from battery-based WSNs. Based on the energy model of a solar-powered node, we develop efficient energy-aware topology-control and routing schemes which utilize a backbone network consisting of energy-rich nodes within the WSN. This backbone handles most of the traffic with low latency, while reconfiguring itself dynamically in response to changes in the availability of energy at each node. Simulation results demonstrate that our schemes can achieve a balance between latency and energy consumption.     

Link weight assignment and loop-free routing table update for link state routing protocols in energy-aware internet

In order to lessen the greenhouse effects and diminish environmental pollution, reducing energy usage is important in designing next generation networks. Shutting down the network devices that carry light load and redirecting their traffic flows to other routes is the most common way to reduce network energy consumption. Since traffic demands among node pairs vary in different time periods, an energy efficient network has to dynamically determine the optimal active links to adapt itself to network traffic changes. However, in current IP networks, shutting down and/or turning on links would trigger link state routing protocols to reconverge to a new topology. Since the convergence time would take tens of seconds, routing table inconsistencies among routers would result in network disconnection and even worse, generating traffic loops during the convergence interval. Removing routing images inconsistent among routers to prevent loops is a critical issue in energy efficient network and this issue is still not considered in the green network design yet. The contribution of the paper is presented in two parts. First, we propose a comprehensive approach to determine a network topology and a link metric for each time period. Traffic engineering is considered in our design such that flows going on the energy-aware network are within a predetermined percentage of the link capacity such that no congestion occurs in a statistical manner. Second, to avoid transient loops during time period changes, we propose a Distributed Loop-free Routing Update (DLRU) scheme to determine the correct sequence for updating the routing table. A scrupulous proof was also presented to ensure the loop-free property of the DLRU. In this paper, we formulate an integer linear programming to determine this multi-topology and link weight assignment problem. Due to its NP-hard property, we propose an efficient algorithm, termed Lagrangian Relaxation and Harmonic Series (LR&HS) heuristic. Numerical results demonstrate that the proposed LRHS approach outperforms the other approaches on several benchmark networks and random networks by providing up to 35%-50% additional energy saving in our experimental cases.     

无线Ad Hoc网络能量感知地理路由协议研究进展

无线Ad Hoc网络（以下简称为Ad Hoc网络）能量感知地理路由协议深度影响网络性能,具有降低网络能量消耗、延长网络寿命等功效,受到越来越多的关注.系统阐述了Ad Hoc网络能量感知地理路由协议的研究进展.首先介绍了Ad Hoc网络地理路由,进而详细概述了能量感知地理路由协议形成的背景、度量指标、节点选择规则、研究意义及分类;然后,详细介绍了典型能量感知地理路由协议,并从多角度对其进行了归纳总结与比较;最后,阐述了能量感知地理路由协议研究存在的问题,指出了未来需要研究的内容,并在此基础上进行总结.     

Dynamic power management in energy-aware computer networks and data intensive computing systems

Energy awareness is an important aspect of modern network and computing system design and management, especially in the case of internet-scale networks and data intensive large scale distributed computing systems. The main challenge is to design and develop novel technologies, architectures and methods that allow us to reduce energy consumption in such infrastructures, which is also the main reason for reducing the total cost of running a network. Energy-aware network components as well as new control and optimization strategies may save the energy utilized by the whole system through adaptation of network capacity and resources to the actual traffic load and demands, while ensuring end-to-end quality of service. In this paper, we have designed and developed a two-level control framework for reducing power consumption in computer networks. The implementation of this framework provides the local control mechanisms that are implemented at the network device level and network-wide control strategies implemented at the central control level. We also developed network-wide optimization algorithms for calculating the power setting of energy consuming network components and energy-aware routing for the recommended network configuration. The utility and efficiency of our framework have been verified by simulation and by laboratory tests. The test cases were carried out on a number of synthetic as well as on real network topologies, giving encouraging results. Thus, we come up with well justified recommendations for energy-aware computer network design, to conclude the paper.     

TAP: Traffic-aware topology control in on-demand ad hoc networks

Energy efficiency is crucial to achieve satisfactory network lifetime in ad hoc networks. In order to reduce the energy consumption significantly, a node needs to turn off its transceiver. Many existing energy-saving algorithms are based on constructing a simplified routing backbone for global connectivity. In this paper some problems involved with node sleep in on-demand ad hoc networks are addressed firstly. Then we propose a distributed, cross-layer Traffic-Aware Participation (TAP) algorithm, where nodes make decisions on whether to sleep or not based on both the traffic pattern and local connectivity. Nodes get dynamic traffic characteristics as well as active neighbors within two hops via routing control and data packets periodically. We further present a lightweight algorithm to avoid network partition resulted from node sleeping. Simulation results show that, compared to current sleep-based topology control algorithms, TAP achieves better network service quality and lower delay while allowing comparable energy conservation.     

Energy-aware routing in hybrid optical network-on-chip for future multi-processor system-on-chip

With the development of Multi-Processor System-on-Chip (MPSoC) in recent years, the intra-chip communication is becoming the bottleneck of the whole system. Current electronic network-on-chip (NoC) designs face serious challenges, such as bandwidth, latency and power consumption. Optical interconnection networks are a promising technology to overcome these problems. In this paper, we study the routing problem in optical NoCs with arbitrary network topologies. Traditionally, a minimum hop count routing policy is employed for electronic NoCs, as it minimizes both power consumption and latency. However, due to the special architecture of current optical NoC routers, such a minimum-hop path may not be energy-wise optimal. Using a detailed model of optical routers we reduce the energy-aware routing problem into a shortest-path problem, which can then be solved using one of the many well known techniques. By applying our approach to different popular topologies, we show that the energy consumed in data communication in an optical NoC can be significantly reduced. We also propose the use of optical burst switching (OBS) in optical NoCs to reduce control overhead, as well as an adaptive routing mechanism to reduce energy consumption without introducing extra latency. Our simulation results demonstrate the effectiveness of the proposed algorithms.     

Energy-aware traffic engineering: A routing-based distributed solution for connection-oriented IP networks

The present paper deals with energy saving in IP networks and proposes a distributed energy-aware traffic engineering solution, named DAISIES, for switching off network links according to traffic variations. DAISIES works in a connection-oriented network, e.g. an IP/MPLS network, and follows a routing-based approach, i.e. it acts on the routing algorithm whilst link switch-off/on are consequence of routing decisions. The basic idea is to re-compute the path of each traffic demand when its requested capacity changes. A specific cost function is used to compute link weights into the shortest path routing algorithm with the goal of keeping unused as many links as possible. The main advantages of DAISIES can be summarized as follows: (i) no changes are required to current routing and signaling protocols, (ii) packet loss is completely avoided, (iii) both traffic decreasing and increasing and changing network conditions are automatically managed, and (iv) link switch-off/on take place transparently to the routing protocol and to other nodes. The performance of the proposed solution is evaluated in terms of energy saving relative to a static network optimized to support the peak traffic. Results show that DAISIES is able to save about 30% of energy in several traffic conditions. Moreover, it is shown that it is possible keeping the additional complexity low and still reaching high energy efficiency.     

无线传感器网络中基于网络层的能源有效性研究

如何有效地使用有限的能源是无线传感器网络的一个核心问题。以环境监测为背景，基于网络层建立了无线传感器网络生命期的模型，并时其进行分析，指出能源有效路由算法和数据融合是网络层节省能源的重要因素。最后给出了一种基于网络层的能源有效性解决方案，达到延长网络生命期的目的。     

Bandwidth-aware energy efficient flow scheduling with SDN in data center networks

Nowadays the energy consumption has become one of the most urgent issues for Data center networks. For general network devices, the power is constant and independent from the actual transfer rate. Therefore the network devices are energy efficient when they are in full workload. The flow scheduling methods based on the exclusive routing can reduce the network energy consumption, as the exclusive routing paths can fully utilize all their links. However, these methods will no longer guarantee the energy efficiency of switches, as they handle flows in priority order by greedily choosing the path of available links instantaneously. In a previous work we proposed an extreme case of flow scheduling based on both link and switch utilization. Herein we consider general scenarios in data center networks and propose a novel energy efficient flow scheduling and routing algorithm in SDN. This method minimizes the overall energy for data center traffic in time dimension, and increases the utilization of switches and meet the flow requirements such as deadline. We did a series of simulation studies in the INET framework of OMNet++. The experiment results show that our algorithm can reduce the overall energy with respect to the traffic volume and reduce the flow completion time on average.     

基于ARIMA-ANN预测模型的能量感知路由算法

针对传统能量感知OLSR协议在减少传输功率消耗和均衡节点剩余能量之间不能兼顾的特点,提出了一种新型的基于剩余能量比例和传输功率消耗的OLSR路由协议OLSR_RC,它利用上述两方面的指标构造复合能量开销,并将其作为路由选择的度量值。在减小网络开销的同时,也防止了部分低电量节点的能量被快速耗尽,延长了网络的生存周期。此外,新路由还采用ARIMA-ANN组合能量预测模型对节点的剩余电量进行预测,降低了由于拓扑控制(TC)消息丢失对选择路由所造成的影响。这种新型路由协议在无线传感器网络领域有比较广阔的应用前景。     

无线传感器网络能量多路径路由研究

研究了无线传感器分层网络模型及能量多路径路由机制．为解决现有协议的缺陷，提出了改进型能量多路径路由协议(IMP-EA)，建立了路由算法．以网络寿命和丢包率作为评价指标，对改进型能量多路径路由协议和其它3种路由协议进行了仿真实验．仿真结果表明，改进后的协议有效地延长了网络的生存时间，提高了数据转发效率．     

云基础设施中TPL2-SW网络模型的优化

为解决传统树型网络拓扑对大规模云集群造成的性能瓶颈,针对一种新的网络模型TPL 2-SW进行优化,提出了多路径负载均衡路由策略(MCLBR)和转发路由的硬件加速方案。通过在节点间建立网状链路,将负载指数纳入路由判定因素,并允许节点间负载分流;同时基于FPGA实现硬件转发路由器,并验证了在二层语义对多跳传输加速的可行性。仿真实验证明,优化方案可以在TPL 2-SW基础上显著提高网络的吞吐量和传输效率。     

Optimally designing caches to reduce P2P traffic

Traffic caused by P2P services dominates a large part of traffic on the Internet and imposes significant loads on the Internet, so reducing P2P traffic within networks is an important issue for ISPs. In particular, a huge amount of traffic is transferred within backbone networks; therefore reducing P2P traffic is important for transit ISPs to improve the efficiency of network resource usage and reduce network capital cost. To reduce P2P traffic, it is effective for ISPs to implement cache devices at some router ports and reduce the hop length of P2P flows by delivering the required content from caches. However, the design problem of cache locations and capacities has not been well investigated, although the effect of caches strongly depends on the cache locations and capacities. We propose an optimum design method of cache capacity and location for minimizing the total amount of P2P traffic based on dynamic programming, assuming that transit ISPs provide caches at transit links to access ISP networks. We apply the proposed design method to 31 actual ISP backbone networks and investigate the main factors determining cache efficiency. We also analyze the property of network structure in which deploying caches are effective in reducing P2P traffic for transit ISPs. We show that transit ISPs can reduce the P2P traffic within their networks by about 50-85% by optimally designing caches at the transit links to the lower networks.     

基于网络编码的Ad Hoc网络能量感知路由策略

针对Ad Hoc网络终端节点能量受限对全网路由的影响,提出了一种基于网络编码的能量感知路由协议(Energy-aware Routing Protocol for Ad Hoc Network based on Network Coding,ERPNC)。ERPNC采用数据流速率匹配的方法,利用节点编码机会降低能量消耗,同时通过节点剩余能量值和节点能耗速度预测节点剩余生存时间,并结合路径总能耗和节点剩余生存时间提出新的路由评价函数和路由发现策略。此外,ERPNC通过引入本地路由维护策略来减少路由断裂和数据包重传情况的发生。仿真结果表明:与其他相关路由协议相比,ERPNC能够有效降低传输能耗,均衡网络能量消耗,延长网络寿命,提高网络吞吐量。     

Energy-aware IP traffic engineering with shortest path routing

Internet energy consumption is rapidly becoming a critical issue due to the exponential traffic growth and the rapid expansion of communication infrastructures worldwide. We address the problem of energy-aware intra-domain traffic engineering in networks operated with a shortest path routing protocol. We consider the problem of switching off (putting in sleep mode) network elements (links and routers) and of adjusting the link weights so as to minimize the energy consumption as well as a network congestion measure. To tackle this multi-objective optimization problem with priority (first minimize the energy consumption and then the network congestion), we propose a Mixed Integer Linear Programming based algorithm for Energy-aware Weights Optimization (MILP-EWO). Our heuristic exploits the Interior Gateway Protocol Weight Optimization (IGP-WO) algorithm for optimizing the OSPF link weights so as to minimize the total cost of link utilization. The computational results obtained for eight real network topologies and different types of traffic matrices show that it is possible to switch off a substantial number of nodes and links during low and moderate traffic periods, while guaranteeing that network congestion is low enough to ensure service quality. The proposed approach is also validated on two networks of emulated Linux routers.     

无线传感器网络权衡生存时间与数据分组跳数的分流路由算法*

无线传感器网络的节点大多采用电池供电.因而节能对无线传感器网络就显得至关重要.该文提出一种能耗感知的优化网络生存时间的路由算法,称之为分流路由算法(DTRA,Diffluent Traffic Routing Algorithm).DTRA算法采用一个优化模型以优化每个节点发出的数据比例,从而达到权衡网络生存时间和数据分组跳数.此外,采用一个简单的遗传算法求解该优化问题.仿真结果表明:DTRA算法能显著地提高网络的生存时间,同时将数据分组平均跳数保持在一个较低的水平;在网络生存时间上,DTRA算法比一些已有的知名算法更优.     

QoS vs. energy: A traffic-aware topology management scheme for green heterogeneous networks

Increasing environmental awareness combined with the high energy prices has driven the network operators to reduce their carbon dioxide footprint by adopting energy efficient green methods. In this paper, we aim to save energy by both switching base stations on/off and adaptively adjusting their transmission power according to the present traffic conditions for heterogenous wireless cellular networks. We formulate a novel linear programming model for the Traffic-Aware Topology Management (TAM) problem to find the best possible topology which minimizes the overall power consumption of the network while satisfying a certain Quality of Service level in Wideband Code Division Multiple Access packet-switched cellular networks. Although the optimization tools provide the optimum solutions, it is not possible to handle large instances due to the space and computational complexity. Hence, we propose a Green TAM Algorithm to solve the large-scale realistic instances of the formulated problem and compare our results with the results of two previously proposed methods, a greedy heuristic and a commercial optimization tool. We show that the proposed TAM scheme helps to maintain an energy-aware network and saves significant amount of energy by adjusting the network topology to the current traffic conditions adaptively.     

无线传感器/执行器网络中能量有效的实时分簇路由协议

无线传感器/执行器网络(WSANs)主要应用于自动控制领域,实时性问题是其面临的首要挑战.根据实际环境中的节点部署情况,建立了系统模型;研究了分簇策略与功率控制技术对于自组织网络实时性的影响,提出了一种可适用于WSANs的能量有效的实时分簇路由协议--RECRP协议.该协议采用二级成簇策略使网络中的各类节点稳定分簇.分簇后的各类节点具有不同发射功率,利用执行器节点的强大通信能力有效降低网络延时.采用能量有效性算法使网络中的传感器节点轮换担任簇首,从而使网络能量均匀消耗,延长网络的生存时间.实验结果证明,在WSANs中RECRP协议可使网络稳定分簇,并且在网络的实时性与能量有效性方面与现有典型路由协议相比具有更优越的性能.     

一种基于能量感知的无线传感器网络混合路由协议

针对无线传感器网络的资源局限性、自组织性和网络拓扑结构的不确定性,提出了一种基于能量感知的平面路由和层次路由的混合路由协议。该协议可根据节点剩余能量的表现来判断节点的当前状态和路由选择,网络中各节点以"尽力而为"传输数据和"不得已"动态建立自适应簇头的方式进行网络通信。仿真结果比较表明:该协议具有较高簇头生成率和可靠的数据交付率,能更有效降低网络能量消耗。     

按需能量多路径的路由协议研究

微机电系统、处理器、无线通信及存储技术的进步促进了无线传感器网络的飞速发展,使得无线传感器网络成为一种全新的信息获取和处理技术,也因此与传统网络有着许多不同之处.介绍了无线传感器网络的特点及其通信协议体系结构,着重讨论了传感器网络路由协议的设计问题.在分层模型基础上,动态地选择汇聚节点和分层模型的能量多径路由协议可使能量均衡,延长网络寿命,提高数据转发率,这也是传感器网络路由设计的主要目标.