WSN 無線傳感器網(wǎng)絡(luò)復(fù)習(xí)提綱 整理版3.0

1、1.2 Application examples1.4 Application examples 1.disaster relief applications 2.environment control and biodiversity mapping 3.intelligent buildings 4.facility management 5.machine surveillance and preventive maintenance 6.percision agriculture 7.medicine and health care 8.logistics 9.telematicsun

2、derstand the challenges of WSNs:1.4 WSN的挑戰(zhàn)性1.4 challenges for WSNs 1.4.1 characteristic requirements：要求的特性1. Type of service 2. Quality of Service 3. Fault tolerance 4. Lifetime 5. Scalability 6. Wide range of densities 7. Programmability 8. Maintainability 1.4.2 required mechanisms:要求機(jī)制Some of the

3、mechanisms that will form typical parts of WSNs are:1. Multihop wireless communication 2. Energy-efficient operation 3. Auto-configuration 4. Collaboration and in-network processing 5. Data centric 6. Locality 7. Exploit trade-offs understand the differences between WSNs and other networks:1.5 為什么說傳

4、感器是不同的1.5 Why are sensor networks different?1.5.1 Mobile ad hoc networks and wireless sensor networks （移動Ad hoc網(wǎng)絡(luò)與無線傳感器網(wǎng)絡(luò)）1. Applications, equipment: MANETs more powerful (read: expensive) equipment assumed, often “human in the loop”-type applications, higher data rates, more resources2. Application

5、-specific: WSNs depend much stronger on application specifics; MANETs comparably uniform3. Environment interaction: core of WSN, absent in MANET4. Scale: WSN might be much larger (although contestable)5. Energy: WSN tighter requirements, maintenance issues6. Dependability/QoS: in WSN, individual nod

6、e may be dispensable (network matters), QoS different because of different applications 7. Data centric vs. id-centric networking8. Mobility: different mobility patterns like (in WSN, sinks might be mobile, usual nodes static)1.5.2 Wireless fieldbuses and WSNs（現(xiàn)場總線與無線傳感器網(wǎng)絡(luò)） Differences：1. Scale WSN

7、often intended for larger scale2. Real-time WSN usually not intended to provide (hard) real-time guarantees as attempted by fieldbusesunderstand the enabling technologies for WSNs application1.6無線傳感器網(wǎng)絡(luò)的技術(shù)要求1.miniaturization of hardware2 processing 3.communication 1.2 Application examples:應(yīng)用領(lǐng)域Disaste

8、r relief applications, Environment control and biodiversity mapping, Intelligent buildings, Facility management, Machine surveillance and preventive maintenance, Precision agriculture, Medicine and health care, Logistics, Telematics.1.3 types of application:區(qū)分應(yīng)用類型1. Event detection2. Periodic measur

9、ements3. Function approximation and edge detection4. Tracking第二章：2.1.1，2.1.4,2.1.5，p37,43,2.2.5,2.3.2,2.3.5,Basic requirement:master the hardware components of sensor nodes 2.1節(jié)點(diǎn)的硬件組成2.1 hardware components: 硬件組成部分 Main components of a WSN node Controller Communication device(s) Sensors/actuators Me

10、mory Power supply 2.1.4 communication deviceTransceiver operational states:收發(fā)機(jī)的四個(gè)狀態(tài) Transceivers can be put into different operational states, typically: Transmit - In the transmit state, the transmit part of the transceiver is active and the antenna radiates energy. Receive - In the receive state t

11、he receive part is active. Idle ready to receive, but not doing so Some functions in hardware can be switched off, reducing energy consumption a little Sleep significant parts of the transceiver are switched off Not able to immediately receive something Recovery time and startup energy to leave slee

12、p state can be significant無線傳感器的微控制器也有三個(gè)狀態(tài)（活躍期，空閑期，睡眠期），兩者有區(qū)別！2.1.5 sensors: 傳感器的分類l Passive, omnidirectional sensors 被動全向傳感器 溫濕度傳感器等 Typical examples for such sensors include thermometer, light sensors, vibration microphones, humidity, mechanical stress or tension in materials, chemical sensors sen

13、sitive for given substances, smoke detectors, air pressure, and so on.l Passive, narrow-beam sensors 被動、窄束 照相機(jī)等 A typical example is a camera, which can “take measurements” in a given direction, but has to be rotated if need be.l Active sensors 主動 雷達(dá) 聲吶等For example, a sonar or radar sensor or some t

14、ypes of seismic sensors, which generate shock waves by small explosions.understand the energy consumption of component module2.2 energy consumption of sensor nodes注意區(qū)分每一個(gè)硬件部分的能量分析，哪一部分是比較針對微控制器的能量分析（whether put into sleep mode should be taken to reduce power consumption）、哪一部分是比較針對收發(fā)機(jī)、哪一部分是比較針對計(jì)算傳輸?shù)裙?jié)

15、約能量時(shí)會用到：調(diào)整控制器的功率消耗時(shí)DVS收發(fā)機(jī)能耗，與調(diào)制結(jié)合，DMS（動態(tài)調(diào)制調(diào)整）（從DVS出發(fā)的）DCS動態(tài)碼調(diào)整DMCS動態(tài)調(diào)制碼調(diào)整計(jì)算和通信之間能量消耗的關(guān)系a controller, typical states are “active”, “idle”, and “sleep”; a radio modem could turn transmitter, receiver, or both on or off; sensors and memory could also be turned on or off. The usual terminology is to spe

16、ak of a “deeper” sleep state if less power is consumed。耗能主體 1.controller 2.radio frontends 3.memory2.2.3 Memory 存儲器On-chip memory of a microcontroller and FLASH memory2.3 節(jié)點(diǎn)的操作系統(tǒng)與運(yùn)行環(huán)境2.3 Operating systems and execution environments無線傳感器網(wǎng)絡(luò)OS基于事件的，而非基于進(jìn)程的Operating system: Event-based programming 基于事件P

17、rotocol stacks : component-based 基于部件Typical OS: Tiny OSEvent-based programmingThe idea is to embrace the reactive nature of a WSN node and integrate it into the design of the operating system. The system essentially waits for any event to happen, where an event typically can be the availability of

18、data from a sensor, the arrival of a packet, or the expiration of a timer. Such an event is then handled by a short sequence of instructions that only stores the fact that this event has occurred and stores the necessary information for example, a byte arriving for a packet or the sensors value some

19、where. The actual processing of this information is not done in these event handler routines, but separately, decoupled from the actual appearance of events. This event-based programming 353 model is sketched in Figure 2.8.understand properties of different nodes.2.4 傳感器節(jié)點(diǎn)的一些例子第三章 選、判、填Basic require

20、ment: understand the Sensor network scenarios3.1 傳感器網(wǎng)絡(luò)工作場景3.1.1 types of sources and sinks(信宿)A source is any entity in the network that can provide information, this is, typically a sensor node; it could also be an actuator node that provides feedback about an operation.A sink is entity where infor

21、mation is required. It belong to the sensor network ; be just another sensor/actuator node; be an entity outside this network.3.1.2 Multihop networksBecause of this limited distances. Store and forward.障礙物 obstacle3.1.4 three types of mobilityNode mobility: the wireless sensor nodes themselves can b

22、e mobile.environmental control will not happen.Sink mobility: the information sinks can be mobile. While this can be a special case of node mobility. The important aspect is the mobility of an information sink that is not part of the sensor network.Event mobility: In applications like event detectio

23、n and in particular in tracking applications, the cause of the events or the objects to be tracked can be mobile. master the design principles of WSNs：3.3 WSN設(shè)計(jì)原則3.3 Design principles for WSNsAppropriate QoS support, energy efficiency, and scalability are important design and optimization goals for

24、wireless sensor networks.在構(gòu)建WSN結(jié)構(gòu)時(shí)的設(shè)計(jì)原則：l 分布式組織Distributed organizationl 網(wǎng)絡(luò)內(nèi)部處理自適應(yīng)的保真度與精度 In-network processing Adaptive fidelity and accuracyl 以數(shù)據(jù)為中心 data centricityl 利用位置信息 Exploit location informationl 利用主動模式 Exploit activity patternsl 利用多樣性 Exploit heterogeneity l 基于部件的協(xié)議棧與層的優(yōu)化 Component-based p

25、rotocol stacks and cross-layer oprimization分布式組織，3.3.1 Distributed organizationBoth the scalability and the robustness optimization goal, and to some degree also the other goals, make it imperative to organize the network in a distributed fashion. That means that there should be no centralized entit

26、y in charge such an entity could, for example, control medium access or make routing decisions, similar to the tasks performed by a base station in cellular mobile networks. The disadvantages of such a centralized approach are obvious as it introduces exposed points of failure and is difficult to im

27、plement in a radio network, where participants only have a limited communication range. Rather, the WSNs nodes should cooperatively organize the network, using distributed algorithms and protocols. Self-organization is a commonly used term for this principle. When organizing a network in a distribut

28、ed fashion, it is necessary to be aware of potential shortcomings of this approach. In many circumstances, a centralized approach can produce solutions that perform better or require less resources (in particular, energy). To combine the advantages, one possibility is to use centralized principles i

29、n a localized fashion by dynamically electing, out of the set of equal nodes, specific nodes that assume the responsibilities of a centralized agent, for example, to organize medium access. Such elections result in a hierarchy, which has to be dynamic: The election process should be repeated continu

30、ously lest the resources of the elected nodes be overtaxed, the elected node runs out of energy, and the robustness disadvantages of such even only localized hierarchies manifest themselves. The particular election rules and triggering conditions for reelection vary considerably, depending on the pu

31、rpose for which these hierarchies are used.網(wǎng)內(nèi)處理：3.3.2 In-network processing 網(wǎng)絡(luò)內(nèi)部處理1. Aggregation2. distributed source coding and distributed compression3. distributed and collaborative signal processing4. mobile code/Agent-based networkingDistributed source coding and distributed compression聚合aggreg

32、ation 搞清原理 網(wǎng)內(nèi)信息處理Aggregation P683.3.4 Data centriciy1. address data, note nodes2. Implementation options for data-centric networking1. Overlay networks and distributed hash tables(peer-to-peer)2. publish/subscribe Any node interested in a given kind of data can subscribe to it, and any node can publ

33、ish data, along with information abut its kind as well.3. Databases(數(shù)據(jù)庫)understand the gateway concepts.3.5 網(wǎng)關(guān)的概念3.5 Gateway conceptsprovides the physical connection to the Internet 提供物理連接regard a gateway as a simple router between Internet and sensor network因特網(wǎng)與傳感器網(wǎng)絡(luò)之間的簡單路由第四章 物理層master the wireles

34、s channel and communication fundamentals,4.2 無線信道的通信基礎(chǔ)4.2.1 Frequency allocationFrequency band ISM433-464MHz Europe902-928MHz Americas2.4-2.5GHz WLAN/WPAN5.725-5.875GHz WLAN4.2.2 區(qū)分symbol rate 和data ratel Symbol rate l The symbol rate is the inverse of the symbol duration; for binary modulation, it

35、is also called bit rate.Data rate The data rate is the rate in bit per second that the modulator can accept for transmission; it is thus the rate by which a user can transmit binary data. For binary modulation, bit rate and data rate are the same and often the term bit rate is (sloppily) used to den

36、ote the data rate.4.2.3 path loss and attenuation 路徑損耗和衰減Wireless waveforms propagating through free space are subject to a distance-dependent loss of power, called path loss. Attenuation because of transmitted in some media, not in the vacuum.P97 WSN信道模型WSN-specific channel models Since in addition

37、 the data rates are moderate, it is reasonable to expect frequency nonselective fading channels with noise and a low-to-negligible degree of ISI. Accordingly, no special provisions against ISI like equalizers are needed. 典型的信道模型：頻率非選擇性衰弱信道，并且可以忽略符號間干擾4.2.3 Wave propagation effects and noise4.2.4 cha

38、nnel modelsunderstand physical layer and transceiver design considerations in WSNs.4.3WSN物理層和收發(fā)機(jī)設(shè)計(jì)考慮4.3.1 能量使用的特點(diǎn)（作業(yè)）：輻射的能量的影響；發(fā)射能量和接收能量的比較；啟動能量、啟動時(shí)間l the radiated energy is small；the overall transceiver (RF front end and baseband part) consumes much more energy than is actually radiated輻射能量較小。l for

39、 small transmit powers the transmit and receive modes consume more or less the same power；it is even possible that reception requires more power than transmission; depending on the transceiver architecture, the idle modes power consumption can be less or in the same range as the receive power?；鞠嗤琹

40、startup energy/startup time，a transceiver has to spend upon waking up from sleep mode。Startup energy/time penalty can be high4.3.3 Dynamic modulation scaling 108頁動態(tài)調(diào)制調(diào)整：原理如果增加B和m的值，比特延遲會減小，每個(gè)比特的能量消耗主要取決于m，與B也有關(guān)，事實(shí)上，對于特別的參數(shù)選取，已經(jīng)表明，當(dāng)符號率最大時(shí)，每個(gè)比特消耗的能量和每個(gè)比特的延遲是最小的。分組數(shù)增加，m增加Antenna第五章Basic requirement: ma

41、ster the fundamentals of MAC protocols 5.1 無線MAC協(xié)議的基礎(chǔ)知識113 隱藏終端、暴露終端The hidden-terminal problem occurs specifically for the class of Carrier Sense Multiple Access (CSMA) protocols, where a node senses the medium before starting to transmit a packet.Using simple CSMA in an exposed terminal scenario t

42、hus leads to needless waiting.5.1.2 114頁 MAC協(xié)議的分類l 固定配置協(xié)議 Fixed assignment protocolsl 按要求配置協(xié)議 demand assignment protocolsl 隨機(jī)接入?yún)f(xié)議 random access protocols116 解決隱藏終端的手段2個(gè)l the busy-tone solution 忙音技術(shù)l the RTS/CTS handshake 握手技術(shù)5.1.2 important classes of MAC protocols1.Fixed Assignment protocols 固定配置協(xié)議

43、 TDMA FDMA CDMA SDMA(不能)2.Demand assignment protocols 按需分配的協(xié)議 LEACH3.Random access protocols 隨機(jī)接入?yún)f(xié)議 ALOHA slotted ALOHA(higher through put) CSMA Nonpersistent CSMA backoff algorithm busy-tone solution 解決了隱藏終端和暴露終端的問題，與數(shù)據(jù)傳輸距離相同之處能偵聽到忙音信號。RTS/CTS握手方法 基于WACAW協(xié)議 一個(gè)信道兩個(gè)控制分組 RTS請求發(fā)送 CTS清除發(fā)送 Data數(shù)據(jù) Ack確認(rèn) 將

44、一個(gè)較大的分組拆分為幾個(gè)較小的分組 保證cts比rts長119 5.1.3 MAC層的能量問題 Collisions 碰撞 wasted effort when two packets collide fixed assignment/TDMA or demand assignment protocols，CSMA protocols Overhearing 偷聽 waste effort in receiving a packet destined for another node Idle listening 空閑監(jiān)聽 sitting idly and trying to receive

45、when nobody is sending TDMA-based protocols Protocol overhead協(xié)議開銷 Protocol overhead is induced by MAC-related control frames like, for example, RTS and CTS packets or request packets in demand assignment protocols,understand the low duty cycle protocols and wakeup concepts, 5.2低占空比協(xié)議與喚醒的概念每個(gè)協(xié)議針對能量問題

46、的算法的區(qū)分，最突出，最不同的點(diǎn)S-MACSMACS占空比=偵聽階段/喚醒周期Avoid spending much time in the idle state and to reduce the communication activities of a sensor node to a minimum.大部分時(shí)間處于休眠狀態(tài) 并周期性的被喚醒來接收來自其他節(jié)點(diǎn)的分組 periodic wakeup 周期性喚醒 掌握發(fā)送目標(biāo)的監(jiān)聽時(shí)段5.2.4 wakeup radio concepts無線喚醒的概念節(jié)點(diǎn)發(fā)送或者接受或者休眠 不存在空閑狀態(tài) FDMA低功耗喚醒收發(fā)機(jī)處于經(jīng)常工作的狀態(tài) 信道

47、空閑 收到喚醒信號 喚醒數(shù)據(jù)收發(fā)機(jī) 有通信量自適應(yīng)功能 負(fù)載增加 MAC越來越活躍understand contention and schedule based protocols, 5.3 基于競爭的協(xié)議5.3哪些是基于競爭的協(xié)議 contention-based ALOHA、CSMA哪些基于調(diào)度表協(xié)議 schedule-based LEACH SMACS TRAMA哪些基于分配的協(xié)議 5.4 基于時(shí)間的協(xié)議5.4.1LEACH 自適應(yīng)的低功耗的分簇算法 LEACH協(xié)議將一個(gè)基于TDMA的MAC協(xié)議與聚類協(xié)議和一個(gè)簡單的“路由”協(xié)議集成在一起 分簇 簇頭節(jié)點(diǎn) 負(fù)責(zé)確定和維護(hù)TDMA時(shí)間表

48、對成員節(jié)點(diǎn)分配TDMA時(shí)隙 能量消耗大 每個(gè)成員節(jié)點(diǎn)輪流擔(dān)任簇頭節(jié)點(diǎn) 簇頭節(jié)點(diǎn)在網(wǎng)絡(luò)節(jié)點(diǎn)中所占的百分比是一個(gè)有用的網(wǎng)絡(luò)參數(shù)重點(diǎn)CSMARPSCTSmaster the IEEE 802.15.4 MAC protocol.5.5.1Network architecture and types/roles of nodes一個(gè)標(biāo)準(zhǔn)的MAC層分為兩種不同的節(jié)點(diǎn)1. 全功能設(shè)備FFD PAN網(wǎng)絡(luò)協(xié)調(diào)器 簡單協(xié)調(diào)器 設(shè)備 三種功能2. 精簡功能設(shè)備RFD 只用作設(shè)備一個(gè)設(shè)備必須與一個(gè)協(xié)調(diào)器一起工作并僅與其進(jìn)行通信構(gòu)成一個(gè)星狀網(wǎng)絡(luò) 協(xié)調(diào)器可以工作于對等模式協(xié)調(diào)器完成四個(gè)任務(wù)超幀的結(jié)構(gòu) IEEE 802.

49、15.4活躍時(shí)段 不活躍時(shí)段信標(biāo) 競爭介入時(shí)段 保障時(shí)隙節(jié)點(diǎn)在CAP時(shí)段必須發(fā)送數(shù)據(jù)分組或管理控制分組時(shí)采用Slotted CSMA-CA protocol CSMA protocol區(qū)別 不包含關(guān)于隱藏終端的規(guī)定 使用隨機(jī)延遲 使用帶有碰撞避免的CSMA協(xié)議 回退時(shí)段Basic requirement: understand the role and significance of the time synchronization problem, 8.1 理解時(shí)間同步問題的概念和意義202 各個(gè)時(shí)間的概念物理時(shí)間 大多數(shù)應(yīng)用和協(xié)議都要求物理時(shí)間 邏輯時(shí)間 分布式系統(tǒng)中事件發(fā)生的順序關(guān)系l

50、physical time = wall clock time, real-time, coordinated universal time (UTC)l logical time：allows to determine the ordering of events in a distributed system but does not necessarily show any correspondence to real time8.1.2 Node clocks and the problem of accuracy 203 External synchronization: synch

51、ronization with external real time scale like UTC Nodes i=1, ., n are accurate at time t within bound d when |Li(t) t|d for all i Hence, at least one node must have access to the external time scale Internal synchronization No external timescale, nodes must agree on common time Nodes i=1, ., n agree

52、 on time within bound d when |Li(t) Lj(t)|d for all i,j Metrics: Precision: maximum synchronization error for deterministic algorithms, error mean / stddev / quantiles for stochastic ones Energy costs, e.g. # of exchanged packets, computational costs Memory requirements Fault tolerance: what happens

53、 when nodes die?8.2基于發(fā)送/接收的時(shí)間同步協(xié)議8.2 Protocols based on sender/receiver synchronization 207 基于公共步驟1.成對同步 2.全網(wǎng)同步Lightweight time synchronization protocol LTS比對同步協(xié)議完成兩個(gè)相鄰節(jié)點(diǎn)的同步建立一個(gè)從參考節(jié)點(diǎn)到所有節(jié)點(diǎn)的層次最少的生成樹發(fā)送接收的同步計(jì)算方法 計(jì)算題 作業(yè)分布式多跳LTS 不需要構(gòu)造生成樹 每個(gè)節(jié)點(diǎn)需要知道許多參考節(jié)點(diǎn) 并沿著適當(dāng)?shù)穆窂降竭_(dá)他們 這些參考節(jié)點(diǎn)的責(zé)任就是周期性的啟動再同步8.2.3 Time-Sync for

54、sensor networks TPSN非對稱 i可以與j但是反過來不行8.3基于接收/接收的時(shí)間同步協(xié)議8.3.1 Reference broadcast synchronization(RBS)參考廣播同步多跳范圍內(nèi)的網(wǎng)絡(luò)同步Network synchronization over multiple hops多廣播域RBS 不斷變換時(shí)間 確保最后到達(dá)信宿的時(shí)間是準(zhǔn)確的 以UTC時(shí)間表示Basic requirement: understand the properties of localization and positioning procedures, 9.1 9.2 WSN定位網(wǎng)絡(luò)

55、的特點(diǎn)和方法9.1 Properties of localization and positioning proceduresl Physical position versus symbolic locationl Absolute versus relative coordinatesl Localized versus centralized computationl Accuracy and precisionAccuracy：估計(jì)值與實(shí)際值的最大距離Precision：達(dá)到準(zhǔn)確性的百分比l Scalel Limitationsl Costs9.2 定位的三種方法 Possible a

56、pproaches1. Proximity 利用相鄰節(jié)點(diǎn)的信息進(jìn)行定位2.Trilateration and triangulation 三邊定位和三角定位Determining distances三種測距方法 RSSI TOA TDOA3.Scene analysis 情景分析9.3 Mathematical basics for the lateration problem 測邊定位understand the differences between the single-hop and multihop localizations, 9.4 9.5 單跳定位與多跳定位的區(qū)別9.4.6 A

57、pproximate point in triangle 近似三角形內(nèi)點(diǎn)測試法對于所有的鄰居節(jié)點(diǎn)，如果三個(gè)頂點(diǎn)到鄰居節(jié)點(diǎn)的距離沒有同時(shí)更近或更遠(yuǎn)，那么未知節(jié)點(diǎn)在三角形內(nèi)，否則在三角形外。understand the impact of anchor placement.9.5 DV HOP：9.5.2 P245 Count number of hops, assume length of one hop is known (DV-Hop) Start by counting hops between anchors, divide known distance If range estimates between neigh