无线Ad hoc网络中基于Quorum系统的异步节能机制改进

无线Adhoc网络是一种没有外界能量补给的自组织网络，网络中每一个节点都靠最初的能量储备来维持，因此，节能便成为至关重要的问题。基于Quorum分布式系统提出的节能机制，其核心思想是使节点的激活时隙成为一种特定的分布，保证互相之间的时隙有交叠，从而使得通信的两个节点能够监听到对方。本文将介绍在无线Adhoc网络中传统的同步方式面临的挑战，前人对基于Quorum的异步节能机制所做的工作，最后提出一种“Dgrid”自适应的异步节能机制。     

无线Mesh网中的Quorum节能机制

无线Mesh网络节能问题十分重要。文章讨论的基于Quorum的节能机制对网络规模、节点密度、移动性和多跳等因素不敏感,非常适合无线Mesh网络。Quorum节能机制主要基于MANET网络环境设计。Quorum系统根据时钟同步的难易程度,可以应用于同步和异步两种工作模式。目前对Quorum节能系统的研究主要集中在能量效率优化和自适应系统方面。对于异步和同步两种模式的协同,基于Quorum机制的节能与功率控制、MAC路由结合的跨层设计,是值得尝试的课题。     

一种延长网络生存时间的Adhoc路由策略

简要介绍了Adhoc网络中路由协议的特殊性,指出节点能量是Adhoc网络中影响系统路由生存时间的关键性因素,常规无线路由协议的建立大多数是基于源一目的节点跳数多少的的基础上,提出一种基于节点能量高低来优先建立路由的协议DDSR,并利用NS2软件对DSR、DDSR进行仿真,结果显示DDSR相对于DSR提高了系统生存时间。     

无线传感器网络中一种动态节能的MAC协议

媒体访问控制(MAC)协议是无线传感器网络的关键协议之一,它对无线传感网络的运行和性能具有重要的影响.针对基于簇的TDMA机制存在问题,文中提出了一个动态节能的DE-MAC协议,该协议能够根据簇成员节点数目和通信负载动态地分配成员节点的时隙,减少节点的空闲侦听时间.仿真结果表明,DE-MAC协议能够有效地提高信道的利用率和网络能量有效性.     

基于全网休眠的ZigBee网络节能算法

无线传感器网络节点一般由电池供电而且部署后需要长时间工作,这就导致节点的能量成为网络运行的瓶颈。针对无线传感器网络节点能量受限的问题,提出了一种基于全网休眠的节能新算法。该算法使终端节点、路由节点和汇聚节点都能得到休眠,从而为网络中每一种节点节约能量;同时,为路由节点设计了长、短两种休眠策略,在不影响数据收发的前提下减少能耗。基于CC2630芯片的实验结果表明:与现有相关算法相比,该新算法使节点能耗降低10%。     

基于博弈理论的无线传感器网络分布式节能路由算法

为了有效解决无线传感器网络路由节能问题,该文提出适合无线传感器网络的节能路由算法。在引入博弈理论概念建立网络模型的基础上,通过对于以往传感器网络簇首选择方法的研究,设计了一种基于博弈论的,兼顾节点剩余能量及簇首分布的节能路由DEER(DistributedEnergy-EconomicalRouting),大大节省了分布式决策网络协议的能量损耗。仿真证明了该方法在无线传感器网络中,能够有效地平衡网络负载,节省节点能量,延长网络寿命。     

WSN中层次结构化分下的路由协议改进

WSN和Adhoc统称为自组织网络,但WSN有不同于Adhoc的技术要求和特征。WSN的最关键问题在于能量高度受限以及网络中节点的失效频繁等问题,这使得设计一个有效的路由算法协议成为近年研究无线传感器网络相关问题的热点。本文介绍了无线传感器网络的特点及路由设计中的关键因素。总结了层次结构划分下地几种路由算法,并给出了相应的改进。     

基于移动性感知的无线传感器网络GTS自适应分配策略

为解决移动无线传感器网络中节点连通性较弱的问题,提出一种包含不同移动性节点的无线传感器网络提升移动节点连通性的保障时隙(GTS, guaranteed time slot)分配策略.首先,采用Kalman滤波预测模型得到用户下一阶段位置;接下来,引入一种考虑速度、方向和相对移动性的节点移动程度界定方法,并在此基础上进行GTS预约优先级的初步确定;随后,根据移动节点对所预约时隙的使用反馈情况自适应调整预约优先级;最后,根据节点的优先级决定GTS时隙的使用顺序及额外预留时隙的使用权.仿真结果显示,提出的分配策略在具有不同移动性节点的网络中,能够提高移动节点接入的成功率,保证较低的分组平均传输时延及较高的分组投递率.此外,采用基于反馈机制的自适应预约优先级调整策略能够显著增加整个网络中已分配时隙的正确使用率.     

分布式TDMA网络的时隙设计技术

时隙分配是分布式TDMA组网的一个基础性工作,直接影响到Adhoc网络的性能。为支持低延迟数据业务,通常选择TDMA组网技术,但常规的固定时隙TDMA网络对时隙的利用率较低。提出了一种基于跳频的固定时隙分配和动态时隙分配相结合的TDMA时隙资源管理技术,有效地解决了TDMA网络的不同类型用户信息传输时隙分配问题。     

无线Ad Hoc网络中基于活跃节点数预测的时隙ALOHA算法

针对采用时隙ALOHA算法的无线Ad Hoc网络,考虑数据包到达的动态性与数据包传输的随机性,以最大化吞吐量为目标,同时满足数据队列稳定性,构建了关于接纳控制与竞争接入的随机优化问题。由于在时隙ALOHA算法中数据包传输的最优概率取决于无线Ad Hoc网络中数据队列非空的活跃节点数,提出了一种基于活跃节点数预测的时隙ALOHA算法。该算法要求无线Ad Hoc网络中的所有发送节点实时地侦听通信信道的忙闲状态,计算基于信道状态的活跃节点数条件期望,从而动态地预测无线Ad Hoc网络在不同时刻的活跃节点数,达到网络节点依据局部网络状态信息自适应地优化数据包传输概率的目的。仿真结果表明,所提算法能够有效估计无线Ad Hoc网络在每个时隙的活跃节点数,从而显著提升网络吞吐量并且降低数据包的平均排队时延。     

A Novel Scheduled Power Saving Mechanism for 802.11 Wireless LANs

Power conservation is a general concern for mobile computing and communication. In this paper, we investigate the performance of the current 802.11 power saving mechanism (unscheduled PSM) and identify that background network traffic can have a significant impact on the power consumption of mobile stations. To improve power efficiency, a novel scheduled PSM protocol based on time slicing is proposed in this paper. The protocol adopts the mechanism of time division, schedules the access point to deliver pending data at designated time slices, and adaptively adjusts the power state of the mobile stations. The proposed scheme is near theoretical optimal for power saving. It greatly reduces the effect of background traffic, minimizes the station idle time, and maximizes its energy utilization. Comprehensive analysis and simulations are conducted to evaluate the new protocol. The results show that the new protocol provides significant energy saving over the unscheduled PSM, particularly in circumstances where multiple traffic streams coexist in a network. Moreover, it achieves the saving at the cost of only a slight degradation of the one-way-delay performance.     

基于冗余抑制技术的低功耗组合电路设计

本文阐明了基于冗余抑制技术的低功耗电路的设计原理,分析了在组合电路中冗余行为的各种抑制结构及工作机理.作为设计实例,本文提出了基于冗余抑制技术的低功耗比较器设计.PSPICE模拟与能耗分析证明该一设计技术能有效地达到节省功耗的目的.     

A novel efficient power‐saving MAC protocol for multi‐hop MANETs

Following recent advances in the performance of ad hoc networks, the limited life of batteries in mobile devices poses a bottleneck in their development. Consequently, how to minimize power consumption in the Medium Access Control (MAC) layer of ad hoc networks is an essential issue. The power‐saving mode (PSM) of IEEE 802.11 involves the Timing Synchronization Function to reduce power consumption for single‐hop mobile ad hoc networks (MANETs). However, the IEEE 802.11 PSM is known to result in unnecessary energy consumption as well as the problems of overheating and back‐off time delay. Hence, this study presents an efficient power‐saving MAC protocol, called p‐MANET, based on a Multi‐hop Time Synchronization Protocol, which involves a hibernation mechanism, a beacon inhibition mechanism, and a low‐latency next‐hop selection mechanism for general‐purpose multi‐hop MANETs. The main purposes of the p‐MANET protocol are to reduce significantly the power consumption and the transmission latency. In the hibernation mechanism, each p‐MANET node needs only to wake up during one out of every N beacon interval, where N is the number of beacon intervals in a cycle. Thus, efficient power consumption is achieved. Furthermore, a beacon inhibition mechanism is proposed to prevent the beacon storm problem that is caused by synchronization and neighbor discovery messages. Finally, the low‐latency next‐hop selection mechanism is designed to yield low transmission latency. Each p‐MANET node is aware of the active beacon intervals of its neighbors by using a hash function, such that it can easily forward packets to a neighbor in active mode or with the least remaining time to wake up. As a consequence, upper‐layer routing protocols can cooperate with p‐MANET to select the next‐hop neighbor with the best forwarding delay. To verify the proposed design and demonstrate the favorable performance of the proposed p‐MANET, we present the theoretical analysis related to p‐MANET and also perform experimental simulations. The numerical results show that p‐MANET reduces power consumption and routing latency and performs well in extending lifetime with a small neighbor discovery time. Copyright © 2011 John Wiley & Sons, Ltd.     

Integrating operation scheduling and binding for functional unit power-gating in high-level synthesis

Power-gating-aware design has been an active area of research in the last decade, aiming at reducing power dissipation while meeting a desired system throughput. In this study, an algorithm integrating both scheduling and binding processes is developed with the functional unit (FU) power-gating technique, to achieve maximum leakage energy reduction under both performance and resource constraints. Firstly, the possible leakage energy reductions of all idle intervals are analyzed by evaluating the operation mobilities. Secondly, a split network indicating the leakage energy reduction in each idle interval is constructed, and a min-cost flow-based algorithm is conducted to this network to evaluate the total leakage energy saving from power-gating FUs; operations are scheduled to the clock cycles and bound to FUs with a maximization of leakage energy saving. Finally, proper FUs are clustered under power domain constraints to maximize the leakage energy saving while reducing the area and wirelength penalties for fine grain power-gating. Experimental results show the effectiveness of our proposed algorithms in saving leakage energy.     

一种基于功率控制的无线传感器网络MAC协议

提出了一种基于功率控制机制的无线传感器网络MAC协议 Distance Prediction Power Control MAC (DPPC-MAC).DPPC-MAC协议基于目前十分成熟的SMAC协议[1-2],引入了功率控制机制以降低数据包发送时的能耗,并且提出了一种新的通过功率预测距离来解决暴露终端和隐藏终端的方法.仿真结果表明,DPPC-MAC能有效降低网络能耗,同时吞吐量性能也得到了一定的改善.     

Design of Predictive and Dynamic Energy-Efficient Mechanisms for IEEE 802.16e

Three predictive and dynamic sleep time planning (PDSTP) energy-efficient mechanisms are proposed in this paper to simultaneously improve energy efficiency and packet delay for IEEE 802.16e. To estimate the time instant when a mobile station (MS) should wake up for receiving downlink packets, a prediction method is designed. With the predicted time instant, an MS is then allowed to sleep as much as possible using multiple maximum sleep intervals followed by a smaller sleep interval before the predicted time instant. After the predicted time instant, a few smaller sleep intervals with a trend of constant level (CL), exponential decrease (ED), or linear decrease (LD) can be further arranged. To react to the outlier of prediction, exponential increase for sleep intervals can be extended. The combination of the aforementioned designs then forms our three proposed mechanisms, namely, PDSTP-CL, PDSTP-ED, and PDSTP-LD. Via simulations, we show that PDSTP-CL not only performs better than PDSTP-ED and PDSTP-LD under general situations but also outperforms the standard sleep mode operation of the type-I power saving class (PSC-I) in IEEE 802.16e and the exponential sleep time backoff mechanism (ESTBM) in the literature in terms of energy efficiency and packet delay.     

An adaptive quorum-based energy conserving protocol for IEEE 802.11 ad hoc networks

The lifetime of a mobile ad hoc network (MANET) depends on the durability of the mobile hosts' battery resources. In the IEEE 802.11 Power Saving Mode, a host must wake up at every beacon interval, to check if it should remain awake. Such a scheme fails to adjust a host's sleep duration according to its traffic, thereby reducing its power efficiency. This paper presents new MAC protocols for power saving in a single hop MANET. The essence of these protocols is a quorum-based sleep/wake-up mechanism, which conserves energy by allowing the host to sleep for more than one beacon interval, if few transmissions are involved. The proposed protocols are simple and energy-efficiency. Simulation results showed that our protocols conserved more energy and extended the lifetime of a MANET.     

RA-PSM: a rate-aware power saving mechanism in multi-rate wireless LANs

Improving energy efficiency is one of the most important issues in wireless local area networks (WLANs) and a power saving mechanism (PSM) has been proposed in IEEE 802.11 WLANs. However, the conventional PSMs do not consider multi-rate transmissions and thus the waiting time for retrieving buffered frames from the access point can be unnecessarily long and more energy can be consumed. In this paper, we propose a rate-aware power saving mechanism (RA-PSM) in multi-rate WLANs. In RA-PSM, a station sets its contention window size inversely proportional to the transmission rate and thus a station with higher transmission rate can request the buffered frames at the access point with higher priority. As a result, the overall channel waiting time can be reduced and the energy consumption can be saved accordingly. Analytical and simulation results demonstrate that RA-PSM can reduce the average channel waiting time and the energy consumption by up to 77 and 40.3 %, respectively, compared with the conventional IEEE 802.11 PSM.     

工厂供电系统节能方法研究

假如有人说在当前是属于什么样的时代,那么在我们的大脑中浮现出来的一定是一串串数字和不断变化的科技技术,那么,我们该称其为电子时代还是称其为技术时代好呢?我个人觉得在当前的世界中,21世纪可以说属于是一个绿色的节能时代,一方面,在科技和经济以及技术不断发展的时代中,人们已经非常的关注经济和能源的发展,同时也就更加的注重节能与环保方面的问题.当前,电能的应用在厂商的成本里占到了非常大的比例,所以,供电系统的节能方式的研究也变成了每一个厂商所关注的焦点问题.