Cooperative Caching in Wireless Multimedia Sensor Nets

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Cooperative Diversity in Wireless Networks 文献翻译

Cooperative Diversity in Wireless Networks 文献翻译————————————————————————————————作者：————————————————————————————————日期：23 无线网络的协作分集：高效协议和中断行为摘要：我们研究和分析了低复杂度的协作分集协议用以抵抗无线网络中多径传播引起的衰落，其底层技术是利用协作终端为其他终端转发信号而获得空间分集。

我们略述几种协同通信策略,包括固定中继方法如放大-转发，译码-转发,基于协同终端间的信道估计的选择中继方式，基于目标终端的有限反馈的增量中继方式。

我们在高SNR 条件下以中断事件、相关中断概率指标讨论了其性能特征，以估计协议对传输衰落的鲁棒性。

除固定的解码—转发协议外，所有的协同分集协议就所达到的全分集（也就是在两个终端下的二阶分集）来说是高效的，而且在某些状态下更加接近于最优（小于1。

5dB ）。

因此，当用分布式天线时，我们可以不用物理阵列而提供很好的空间分集效应，但因为采用半双工工作方式要牺牲频谱效率，也可能要增加额外接收硬件的开销。

协作分集对任何无线方式都适用，包括因空间限制而不能使用物理阵列的蜂窝移动通信和无线ad hoc 网络，这些性能分析显示使用这些协议可减少能耗.索引语——分集技术，衰落信道，中断概率,中继信道，用户协同,无线网络Ⅰ 介绍在无线网络中，多径传播引起的信号衰落是一个特别严重的信道损害问题，可以利用分集技术来减小。

II 系统模型在图1中的无线信道模型中，窄带传输会产生频率非选择性衰落和附加噪声。

我们在第四部分重点分析慢衰落，在时延限制相当于信道相干时间里，用中断概率来评价，与空间分集的优势区分.虽然我们的协同协议能自然的扩展到宽频带和高移动情况,其中面临各自的频域和时域的选择性衰落，当系统采用另一种形式的分集时对我们协议的潜在影响将相对减小。

4A 媒体接入当前的无线网络中,例如蜂窝式和无线局域网，我们将有用的带宽分成正交信道，并且分配这些信道终端，使我们的协议适用于现存的网络.这种选择产生的意外效果是，我们能够同时在I —A 处理多径（单个接收）和干扰（多个接收），相当于在信号接收机传输信号的一对中继信号.对于我们所有的协同协议，传输中的必须同时处理他们接收到的信号；但是，网络实现使终端不能实现全双工，也就是,传输和接收同时在相同的频带中实现。

Cooperative Diversity Techniques for Wireless Networks无线网络中协作分集技术

Laneman, Wornell and Tse (2019) : Impossible to increase sum capacity without knowledge of channel at the transmitter
▪ Cooperation using “dumb” relays ▪ Decode-and-Forward (does not achieve full diversity) ▪ Amplify-and-Forward (full diversity guaranteed)
- Observation
Wireless Information Networking Group
Information Theory (contd.)
Information theory: The Relay Channel
Cover and El Gamal (1979) :
- - Facilitation
Wireless Information Networking Group
Introduction (contd.)
CHALLENGES Array elements are not physically connected Traditional combining techniques (MRC, EGC) require large amount of information to be sent to the combining node
User-Cooperation: The early days
Information theory: The Relay Channel First studied by van der Meulen (1968) Coding theorems proved by Cover and El Gamal (1979)

5G无线通信网络中英文对照外文翻译文献

5G无线通信网络中英文对照外文翻译文献(文档含英文原文和中文翻译)翻译：5G无线通信网络的蜂窝结构和关键技术摘要第四代无线通信系统已经或者即将在许多国家部署。

然而，随着无线移动设备和服务的激增，仍然有一些挑战尤其是4G所不能容纳的，例如像频谱危机和高能量消耗。

无线系统设计师们面临着满足新型无线应用对高数据速率和机动性要求的持续性增长的需求，因此他们已经开始研究被期望于2020年后就能部署的第五代无线系统。

在这篇文章里面，我们提出一个有内门和外门情景之分的潜在的蜂窝结构，并且讨论了多种可行性关于5G无线通信系统的技术，比如大量的MIMO技术，节能通信，认知的广播网络和可见光通信。

面临潜在技术的未知挑战也被讨论了。

介绍信息通信技术（ICT）创新合理的使用对世界经济的提高变得越来越重要。

无线通信网络在全球ICT战略中也许是最挑剔的元素，并且支撑着很多其他的行业，它是世界上成长最快最有活力的行业之一。

欧洲移动天文台（EMO）报道2010年移动通信业总计税收1740亿欧元,从而超过了航空航天业和制药业。

无线技术的发展大大提高了人们在商业运作和社交功能方面通信和生活的能力无线移动通信的显著成就表现在技术创新的快速步伐。

从1991年二代移动通信系统(2G)的初次登场到2001年三代系统（3G）的首次起飞，无线移动网络已经实现了从一个纯粹的技术系统到一个能承载大量多媒体内容网络的转变。

4G无线系统被设计出来用来满足IMT-A技术使用IP面向所有服务的需求。

在4G系统中，先进的无线接口被用于正交频分复用技术（OFDM），多输入多输出系统（MIMO）和链路自适应技术。

4G无线网络可支持数据速率可达1Gb/s的低流度，比如流动局域无线访问，还有速率高达100M/s的高流速，例如像移动访问。

LTE系统和它的延伸系统LTE-A，作为实用的4G系统已经在全球于最近期或不久的将来部署。

然而，每年仍然有戏剧性增长数量的用户支持移动宽频带系统。

Selective Channel Scanning for Fast Handoff in Wireless LAN using Neighbor

The 2004 International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC2004)Hotel Taikanso, Sendai/Matsushima, Miyagi-Pref., JAPAN July 6-8, 2004 Selective Channel Scanning for Fast Handoff in Wireless LAN using NeighborGraphHye-Soo Kim,Sang-Hee Park,Chun-Su Park,Jae-Won Kim,and Sung-Jea KoDepartment of Electronics Engineering,Korea University,Anam-Dong,Sungbuk-ku,Seoul136-701,KoreaTel.:+82-2-3290-3228,Fax.:+82-2-925-5883E-mail:sjko@dali.korea.ac.krAbstract:Handoff at the link layer2(L2)consists of threephases including scanning,authentication,and reassociation.Among the three phases,scanning is dominant in terms oftime delay.Thus,in this paper,we propose an improved scan-ning mechanism to minimize the disconnected time while awireless station(STA)changes the associated access points(APs).According to IEEE802.11,an STA has to scan allchannels in scanning.In this paper,based on the neigh-bor graph(NG),we introduce a selective channel scanning method with unicast for fast handoff in which an STA scans only channels selected by the NG.Experimental results show that the proposed method reduce the scanning delay drasti-cally.1.IntroductionIn recent years,Wireless Local Area Network(WLAN)with wide bandwidth and low cost has emerged as a competitive technology to adapt the user with strong desire for mobile computing.The main issue on mobile computing is handoff management between APs.Especially,for real-time multime-dia service such as V oIP,the problem of handoff delay has to be resolved.To solve this problem,many techniques[1]-[4] have been proposed by developing new network protocols or designing new algorithms.Their approaches are broken into three distinct categories including network layer(L3),L2,and physical layer(PHY).One of the previous works that have focused on L3uses the reactive context transfer mechanism[1],[2].This mecha-nism is designed solely for access routers(ARs)and is reac-tive rather than pro-active.On the other hand,Nakhjiri[5] proposed a general purpose context transfer mechanism, called SEAMOBY,without detailing transfer triggers.In SEAMOBY,a generic framework for either reactive or pro-active context transfer is provided,though the framework does not deﬁne a method to implement either reactive or pro-active context transfer.To reduce the L2handoff delay in WLAN using IAPP[7], an algorithm on context transfer mechanism utilizing NG[6] was suggested in[7].But originally,IAPP was only reactive in nature and creats an additional delay in an handoff.Thus, this algorithm can not shorten the original L2handoff delay. One approach on PHY is the method using two transceivers.In this method,an STA has two wireless net-work interface cards(WNICs),one for keeping connection to current AP and the other for scanning channels to search alternative APs[8].In this paper,we propose a selective channel scanning(a)(b)Figure1.Type of WLAN(a)ad hoc network(b)infrastructure network.Figure2.IEEE802.11handoff procedure with IAPP.mechanism using NG to solve the L2handoff delay.In the proposed mechanism,an STA scans not all channels but chan-nels selected by NG.And on receiving a ProbeResponse mes-sage,an STA scans the next channels without waiting for the pre-deﬁned time.Therefore,the delay incurred during scan-ning phase can be reduced.This paper is organized as follows.Section2describes the operations in IEEE802.11[9].In Section3,the proposed algorithm is presented.Finally,Section4shows the results experimented on our test platform and presents brief conclu-sion comments.2.IEEE802.11As shown in Fig.1,IEEE802.11MAC speciﬁcation allows for two modes of operation:ad hoc and infrastructure modes. In ad hoc mode,two or more STAs recognize each other through beacons and establish a peer-to-peer relationship.In infrastructure mode,an AP provides network connectivity to its associated STAs to form a Basic Service Set(BSS).Mul-tiple APs form an Extended Service Set(ESS)that constructs the same wireless network.An STA might move to another because of mobility,load conditions,or degraded signal strength.The mechanism or sequence of messages between an STA and the APs is hand-off.During the handoff,physical layer connectivity is re-leased and state information is transferred from one AP to another with respect to the STA.2.1Handoff ProcedureThe complete handoff procedure can be divided into three dis-tinct logical phases:scanning,authentication,and reassocia-tion.In theﬁrst phase,an STA scans for APs by either send-ing ProbeRequest messages(Active Scanning)or by listening for Beacon messages(Passive Scanning).After scanning all channels,an AP is selected by the STA using the Received Signal Strength Indication(RSSI),link quality,and etc.,and the selected AP exchanges IEEE802.11authentication mes-sages with the STA.Finally,if the AP authenticates the STA, the STA sends ReassociationRequest message to the new AP. In this phase,the old AP and new AP exchanges messages de-ﬁned in IAPP.The delay incurred during these exchanges is referred as the L2handoff delay,that consists of probe delay, authentication delay,and reassociation delay.Fig.2shows the three phases,delays,and messages exchanged in each phase.2.2Passive and Active Scanning ModesAn STA operates in either a passive scanning mode or an active scanning mode depending on the current value of the ScanMode parameter of the MLME-SCAN.request primitive. To become a member of a particular ESS using the passive scanning,an STA scans for Beacon message containing the ESS’s Service Set Identiﬁer(SSID)whether the Beacon mes-sage comes from an Infrastructure BSS or Independent Ba-sic Service Set(IBSS).Fig.3(a)shows exchanged messages during the active scanning.To actively scan,after contend-ing to access the medium,the STA sends a ProbeRequest message with the desired SSID and broadcast BSSID,then starts a ProbeTimer.If the STA has not received a ProbeRe-sponse message before the ProbeTimer reaches MinChannel-Time,then the STA scans the next channel.Otherwise,the STA has to wait until the ProbeTimer reaches MaxChannel-Time,then scans the next channel.Upon completion of scan-ning,an MLME-SCAN.conﬁrm is issued by the MLME indi-cating all of the BSS information received.During active scanning,the bound of scanning delay can be calculated asN×T b≤t≤N×T t,(1)STA(a)STA(b)Figure3.Active Scanning(a)full channel scanning(b)selec-tive channelscanning.ABCED(b)Figure4.Concept of neighbor graph(a)placement of APs(b) corresponding neighbor graph with channel information.where N is the total number of channels which can used in a country,T b is MinChannelTime,T t is MaxChannelTime,and t is the total measured scanning delay.Our paper focuses on the reduction of the active scanning delay time.3.Proposed Scanning MethodBefore introducing our proposed method,we brieﬂy review the NG.The NG is an undirected graph with each edge rep-resenting a mobility path between APs.Therefore,given an edge,the neighbors of an edge represent the set of potential next APs.Fig.4shows the physical topology of a wireless network and the corresponding NG.The undirected graph representing the NG is deﬁned as G=(V,E),V={ap1,ap2,...,ap i},e=(ap i,ap j),N(ap i)={ap ik:ap ik∈V,(ap i,ap ik)∈E},(2)where G is the data structure of NG,V is the set containing all APs,E is the set which consists of edge(e),and N is the neighbor APs of a AP.There are two methods that the NG can be automatically generated.Theﬁrst one uses ReassociationRequest message from an STA that contains the BSSID of the old AP.In theﬁrst method,the NG is created by following algorithm by usingmanagement message of IEEE802.11.(1)If an STA sends Reassociate Request to AP i with old−ap =AP j,then create new neighbors(i,j)(i.e.an entry in AP i, for j and vice versa);(2)Learns costs only one‘high latency handoff’per edge in the graph;(3)Enables mobility of APs which can be extended to wire-less networks with an ad hoc backbone infrastructure. Secondly,a receipt of a Move-Notify message from another AP via IAPP[7]also establishes the relationship.Mishra[10]showed that scanning delay is dominant among three delay.Therefore,to solve the problem of L2 handoff delay,scanning delay has to be reduced.To reduce the scanning time,we must reduce the values of T b(MinChannelTime),T t(MaxChannelTime),or N in(1). Among three values,T b and T t can not be reduced because of physical restriction.And because the frequency ranges are subject to the geographic-speciﬁc regulatory authorities,N is ﬁxed in each country.However,the channels which are occu-pied by APs are not same in all Basic Service Areas(BSAs)or Extended Service Areas(ESAs).Thus,if we know the used channels in each site,STAs do not need to scan all channels allowed in the country.Therefore,we propose using an NG to select the channels to be scanned.The NG proposed in [6]uses the topological information on APs.But our algo-rithm needs to use not only topological information but also channels of APs.Thus,we modify the data structure of NG deﬁned in(2)as follows:G =(V ,E),V ={v i:v i=(ap i,channel),v i∈V},e=(ap i,ap j),N(ap i)={ap ik:ap ik∈V ,(ap i,ap ik)∈E},(3)where G is the modiﬁed NG,and V is the set which consists of APs and their channels.Assumed an STA is associated to B in Fig.4,the STA scans only4channels of its neighbors(A,C,D,E)instead of all channels.Fig.3(b)shows that an STA scans the poten-tial APs selected by NG.As shown in Fig.3(a),in order to scan channels,after transmitting ProbeRequest message whose destination is all APs,STAs must wait for MinChannelTime or MaxChannel-Time because an STA does not know how many APs wouldFigure5.Experimental platform.response to ProbeRequest message.However,if using uni-cast instead of broadcast,ProbeRequest message is sent to the potential APs selected by NG.And on receiving ProbeRe-sponse message,STAs can transmit other ProbeRequest mes-sages without waiting for MaxChannelTime or MinChannel-Time.Thus,if using the proposed scanning algorithm,scan-ning delay can be expected ast=N ×rtt+α,(4)where N is the number of the potential APs,rtt is the round trip time,andαis the message processing pared with(1),we can know that the scanning delay is reduced through the proposed algorithm.4.Experimental Results and Conclusion Figure5shows our experimental platform consisting of an STA,APs,router,and Correspondent Node(CN).To ex-change the NG information,socket interface is used,and Mo-bile IPv6is applied to maintain L3connectivity while exper-imenting.The device driver of a common WNIC was modi-ﬁed such that the STA operates as an AP.And emulated APs perform the foreign agents on our experimental platform.To simulate the operation of proposed mechanism,we developed three programs.Fig.6shows theﬂow charts of the developed three programs.NG Client and Monitor are deployed at an STA,and NG Server is deployed at CN in Fig.5.We deﬁned the scanning delay as the duration taken from theﬁrst ProbeRequest message to the last ProbeResponse message.To capture two kinds of messages,a sniffer pro-gram,AiroPeek,was used.To evaluate the proposed algorithm,we experimented three mechanisms:basic active scanning mechanism;selec-tive scanning;and selective scanning with unicast as increas-ing the number of neighbors.As shown in Table1,the scan-ning delay by the selective scanning is shorter than the full channel active scanning.Note that the selective scanning with unicast produces a smallest delay time among the three mech-anisms.Therefore,we expect that the proposed algorithm can be an useful alternative to the existing full channel active scanning due to its reduced delay time.(a)(b)(c) Figure6.Flow charts of simulation programs(a)NG Server(b)NG Client(c)Monitor.Table1.Average probe delay of each method. Neighbors Method delay[ms]Basic active scanning322 1Selective Scanning55Selective Scanning with Unicast12Basic active scanning322 2Selective Scanning332Selective Scanning with Unicast21Basic active scanning322 3Selective Scanning145Selective Scanning with Unicast30References[1]R.Koodli,and C.Perkins,“Fast Handovers and Context Relocation in Mobile Networks,”ACM SIGCOMM Com-puter Communication Review vol.31Oct.2001.[2]R.Koodli,“Fast Handovers for Mobile IPv6,”IETF Draft,Oct.2003.[3]T.Cornall,B.Pentland,and K.Pang“Improved Han-dover Performance in wireless Mobile IPv6,”ICCS2002 vol.2pp.857-861Nov.2003.[4]S.H.Park,and Y.H.Choi,“Fast Inter-AP Handoff Us-ing Predictive Authentication Scheme in a Public Wireless LAN,”IEEE Networks ICN,Aug.2002.[5]M.Nakhjiri,C.Perkins,and R.Koodli,“Context Transfer Protocol,”Internet Draft:draft-ietf-seamoby0ctp-01.txt Mar.2003.[6]A.Mishra,M.H.Shin,and W Albaugh,“Context Caching using Neighbor Graphs for Fast Handoff in aWireless,”Computer Science Technical Report CS-TR-4477,2003.[7]IEEE“Recommended Practice for Multi-Vendor Access Point Interoperability via an Inter-Access Point Protocol Across Distribution Systems Supporting IEEE802.1Op-eration,”IEEE Standard802.11,2003.[8]M.Ohta,“Smooth Handover over IEEE802.11Wireless LAN,”Internet Draft:draft-ohta-smooth-handover-wlan-00.txt Jun.2002.[9]IEEE“Part11:Wireless LAN Medium Access Control (MAC)and Physical Layer(PHY)Speciﬁcations,”IEEE Standard802.11,1999.[10]A.Mishra,M.H.Shin,and W.Albaugh,“An Empiri-cal Analysis of the IEEE802.11MAC Layer Handoff Pro-cess,”ACM SIGCOMM Computer Communication Review vol.3pp.93-102Apr.2003.。

Energy cooperation in energy harvesting wireless communications

Energy Cooperation in Energy Harvesting Wireless Communications
Berk Gurakan1 , Omur Ozel1 , Jing Yang2 , and Sennur Uluectrical and Computer Engineering, University of Maryland, College Park, MD 20742 Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706
energy queue
energy queue
data queue S
data queue R
D
Fig. 1. Two-hop communication network with energy harvesting source and relay nodes and energy transfer from the source to the relay.
This work was supported by NSF Grants CCF 07-29127, CNS 09-64632, CCF 09-64645, CCF 10-18185 and CNS 11-47811.
management policies of the source and the relay in this multi-hop communication scenario with energy harvesting and wireless energy transfer. Ofﬂine throughput maximization for an energy harvesting transmitter has been recently analyzed by many researchers [2]–[12]. In [2]–[4], the problem of throughput maximization by a deadline is solved for an energy harvesting transmitter in a static channel. In [5]–[10], the throughput maximization problem and its solution are extended to fading, broadcast and multiple access channels. In [11], [12], end-to-end throughput maximization problem is solved in a two-hop cooperative network where jointly optimal policy for the source and the relay turns out to be separable: The source performs singleuser throughput maximization subject to its own energy arrival proﬁle without regard to the relay energy proﬁle and the relay adapts its transmission policy according to the data ﬂow coming from the source as well as its own energy arrival proﬁle. Moreover, this separable solution is not unique and thus there may be other optimal solutions that spend less energy at the source [11]. Unlike the problem in [11], [12], in our problem where energy cooperation is possible, the source is forced to be energy efﬁcient so that it can further increase the throughput by sending some of its energy to the relay. Another related line of research in wireless communications with energy harvesting nodes has been presented in [13]–[15]. In [13], capacity-energy function in simultaneous information and energy transfer is introduced and in [14] the tradeoff between the information rate and power transfer in a practical frequency selective wireless system is investigated. In [15], the tradeoff between energy and information transfer is characterized in a MIMO broadcast system. While the energy

基于分簇加权的认知无线电协作检测算法

基于分簇加权的认知无线电协作检测算法李涛【摘要】Cooperative detection is an important part in cognitiveradio.Through the cooperation of some cognitive users,the per⁃formance of weak detection can improve in the case of channel fading and shadow effect.Traditional cooperative detection sometimes is weak because of too many detection users and individual user’s bad channel.Moreover,each user has the same proportion in the deci⁃sion of the center,and the detection performance of the single user is often ignored.A multi⁃cluster cooperative detection algorithm based on weighing is proposed.Through giving cognitive users different weights according to their SNR,the detection probability can reach the maximum.And through dividing the uses into clusters and choosing the user with the best channel characteristic to report to the decision centre,the precision of final decision can be improved effectively. Simulations show that our algorithm has a better detection perform⁃ance,increases the detection probability,and decreases the alarm probability comparing with the traditional algorithm.%协作检测是认知无线电技术（ Cognitive Radio）的重要组成部分，通过多认知用户协作可以提高信道衰落或者阴影效应而带来的低检测性能。

5G无线接入和有线传输之间的协同优化

Telecom Power Technology144通信网络技术无线接入和有线传输之间的协同优化李鹏江（中通服咨询设计研究院有限公司，江苏无线接入和有线传输的协同优化是当前网络领域的研究热点之一。

文章详尽分析了线传输的协同优化问题，目标在于充分发挥两者的优势，以提升整体网络性能。

分析术的特性，以及协同运作中所遭遇的挑战，将网络架构优化与传输资源调度作为核心议题。

文章重点探讨协同调度、资源分配、总体延迟优化、数据缓存与预取优化以及服务质量管理等重要策略，旨在为增强5G；协同优化；网络架构；资源调度；时延优化Cooperative Optimization Between 5G Wireless Access and Wired TransmissionLI Pengjiang(China Information Cosulating and Designing Institute Co., Ltd., NanjingAbstract: The cooperative optimization of 5G wireless access and wired transmission is a current focal point in the field of network research. This study thoroughly analyzes the challenges and opportunities of cooperative optimization大规模MIMO天线大规模MIMO天线Sub-6 Ghz 5G无缝移动NOLS5 G毫米波5 G毫米波图1 大规模MIMO技术然而，5G无线接入技术尽管拥有众多优势，但仍面临一些困境，如信号传输范围有限。

毫米波的传收稿日期：2024-01-15作者简介：李鹏江（1988—），男，陕西宝鸡人，本科，工程师，主要研究方向为传输、有线接入网。

协同中继4翻译

Co-UWSN: Cooperative Energy-Efficient Protocol forUnderwater WSNsCo-UWSN：水下无线传感器网络协同高效节能协议摘要传感器网络特点主要体现在具有无线网络能力、有限的传输功率、受限制的资源和有限的电池能量的低消耗传感器器件。

协同路由利用无线介质的广播特性，并利用附近的传输节点作为继电器的协同传输。

这是一种很有前途的技术，利用协同通信来提高单天线传感器节点的通信质量。

在本文中，我们提出了一个水下传感器网络协同传输方案（UWSNs）以提高网络性能。

协同分级技术已被引入到抗衰落。

提出的协同水下传感器网络Co-UWSN对水下传感器网络来说是一个可靠地、高效节能的和高吞吐量的路由协议。

利用距离和信噪比计算信道条件作为成本函数来选择目的地和潜在的中继。

这有助于充分的减少在链路和数据传输中产生的路径损耗。

仿真结果表明Co-UWSN协议在端到端的延迟、能量损耗和网络寿命等方面表现得更好。

被选作比较的路由协议有：基于深度高效节能路由EEDBR、基于深度阈值优化的改进快递节点自适应迁移路由iAMCTD、水下传感器网络协同路由协议UWSN、协同路由笼的合作伙伴节点选择标准（Re和dth）。

1、介绍UWSN形成了一个新兴的技术，有望实现或增强海洋研究中的几个关键应用。

这些措施包括数据采集，污染监测，战术侦察和灾害防治。

不像传统的地面传感器节点，大量水下移动传感器节点的被降到兴趣集中处以形成配水生（SEA）的传感器群。

每个传感器配有一个低带宽的声学调制解调器和一个单天线。

它可以通过一个鱼形膀胱装置和一个压力计控制其深度。

该群是由水槽汇护送的，汇既是在海面上配备了声音和无线电通信装备的声呐浮标。

在一个配水生传感器群架构下SEA，每个传感器监视本地水下活动以及利用声音多次反射将关键时刻数据报告到在海水表面的任意水槽汇。

本文的主要焦点设计一个高效的路由协议，能够通过一个移动的传感器向海面上任意的一个水槽汇可靠地传输数据。

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• Variable nnel capacity
• multi-hop nature of WMSNs implies that wireless link capacity depends on the interference level among nodes
• Multimedia in-network processing
• multiple sensor nodes share and coordinate cache data to cut communication cost and exploit the aggregate cache space of cooperating sensors • Each sensor node has a moderate local storage capacity associated with it, i.e., a flash memory
Articulation nodes (in bridges), e.g., 3, 4, 7, 16, 18 With large fanout, e.g., 14, 8, U Therefore: geodesic nodes
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The cache discovery protocol (1/2)
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What’s so special about WMSNs ?
• [Ian Akyildiz: Dec’06] We have to rethink the computation-communication paradigm of traditional WSNs
• which focused only on reducing energy consumption
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The cache discovery protocol (2/2)
When a mediator receives a request, searches its cache
• If it deduces that the request can be satisfied by a neighboring node (remote cache hit), forwards the request to the neighboring node with the largest residual energy • If the request can not be satisfied by this mediator node, then it does not forward it recursively to its own mediators, since this will be done by the routing protocol, e.g., AODV • If none of the nodes can help, then requested datum is served by the Data Center (global hit )
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Relevant work (2/2)
Protocols that deviated from such approaches: • CacheData: intermediate nodes cache the data to serve future requests instead of fetching data from their source • CachePath: mobile nodes cache the data path and use it to redirect future requests to the nearby node which has the data instead of the faraway origin node • Amalgamation of them: the champion HybridCache cooperative caching for MANETs • One caching work on WSNs
• concerns the placement of caches
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Our contributions …
• Definition of a metric for estimating the importance of a sensor node, which will imply short latency in retrieval • Description of a cooperative caching protocol which takes into account the residual energy • Datum discovery and cache replacement component subprotocols • Performance evaluation of the protocol and comparison with the state-of-the-art cooperative caching for MANETs, with J-Sim
• More powerful nodes, and one-hop communication with resource-rich base stations
• Most relevant research works:
• cooperative caching protocols for MANETs
3rd MobiMedia Conference, Nafpaktos, Greece, 27-29/August/20071
Wireless Sensor Networks (WSNs)
Wireless Sensor Networks features • Homogeneous devices • Stationary nodes • Dispersed network • Large network size • Self-organized • All nodes acts as routers • No wired infrastructure • Potential multihop routes
• Large values for the NI index of a node v indicate that this node can reach others on relatively short paths, or that v lies on considerable fractions of shortest paths connecting others
• WMSNs applications have a second goal, as important as the energy consumption
• delivery of application-level quality of service (QoS) • mapping of this requirement to network layer metrics, like latency
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A measure of sensor importance
• Let σuw=σwu denote the number of shortest paths from u V to w V (by definition, σuu=0) • Let σuw(v) denote the number of shortest paths from u to w that some vertex v V lies on • We define the node importance index NI(v) of a vertex v as:
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WSNs - Applications
• Applications • Habitat monitoring • Disaster relief • Target tracking • Agriculture
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Wireless Multimedia Sensor Nets (WMSNs)
Cheap CMOS cameras: Cyclops imaging module is a light-weight imaging module which can be adapted to MICA2 or MICAz sensor nodes
• GroCoca: organize nodes into groups based on their data request pattern and their mobility pattern • ECOR, Zone Co-operative, Cluster Cooperative: form clusters of nodes based either in geographical proximity or utilizing widely known node clustering algorithms for MANETs
A sensor node issues a request for a multimedia item
• Searches its local cache and if it is found (local cache hit) then the K most recent access timestamps are updated • Otherwise (local cache miss), the request is broadcasted and received by the mediators • These check the 2-hop neighbors of the requesting node whether they cache the datum (proximity hit) • If none of them responds (proximity cache miss), then the request is directed to the Data Center