WSN 无线传感器网络复习提纲 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的挑战性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:要求机制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 为什么说传

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 （移动Ad hoc网络与无线传感器网络）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（现场总线与无线传感器网络） 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无线传感器网络的技术要求1.miniaturization of hardware2 processing 3.communication 1.2 Application examples:应用领域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:区分应用类型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节点的硬件组成2.1 hardware components: 硬件组成部分 Main components of a WSN node Controller Communication device(s) Sensors/actuators Me

10、mory Power supply 2.1.4 communication deviceTransceiver operational states:收发机的四个状态 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无线传感器的微控制器也有三个状态（活跃期，空闲期，睡眠期），两者有区别！2.1.5 sensors: 传感器的分类l Passive, omnidirectional sensors 被动全向传感器 温湿度传感器等 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 被动、窄束 照相机等 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 主动 雷达 声呐等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注意区分每一个硬件部分的能量分析，哪一部分是比较针对微控制器的能量分析（whether put into sleep mode should be taken to reduce power consumption）、哪一部分是比较针对收发机、哪一部分是比较针对计算传输等节

15、约能量时会用到：调整控制器的功率消耗时DVS收发机能耗，与调制结合，DMS（动态调制调整）（从DVS出发的）DCS动态码调整DMCS动态调制码调整计算和通信之间能量消耗的关系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。耗能主体 1.controller 2.radio frontends 3.memory2.2.3 Memory 存储器On-chip memory of a microcontroller and FLASH memory2.3 节点的操作系统与运行环境2.3 Operating systems and execution environments无线传感器网络OS基于事件的，而非基于进程的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 传感器节点的一些例子第三章 选、判、填Basic require

20、ment: understand the Sensor network scenarios3.1 传感器网络工作场景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.障碍物 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设计原则3.3 Design principles for WSNsAppropriate QoS support, energy efficiency, and scalability are important design and optimization goals for

24、wireless sensor networks.在构建WSN结构时的设计原则：l 分布式组织Distributed organizationl 网络内部处理自适应的保真度与精度 In-network processing Adaptive fidelity and accuracyl 以数据为中心 data centricityl 利用位置信息 Exploit location informationl 利用主动模式 Exploit activity patternsl 利用多样性 Exploit heterogeneity l 基于部件的协议栈与层的优化 Component-based p

25、rotocol stacks and cross-layer oprimization分布式组织，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.网内处理：3.3.2 In-network processing 网络内部处理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 网内信息处理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(数据库)understand the gateway concepts.3.5 网关的概念3.5 Gateway conceptsprovides the physical connection to the Internet 提供物理连接regard a gateway as a simple router between Internet and sensor network因特网与传感器网络之间的简单路由第四章 物理层master the wireles

34、s channel and communication fundamentals,4.2 无线信道的通信基础4.2.1 Frequency allocationFrequency band ISM433-464MHz Europe902-928MHz Americas2.4-2.5GHz WLAN/WPAN5.725-5.875GHz WLAN4.2.2 区分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 路径损耗和衰减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：频率非选择性衰弱信道，并且可以忽略符号间干扰4.2.3 Wave propagation effects and noise4.2.4 cha

38、nnel modelsunderstand physical layer and transceiver design considerations in WSNs.4.3WSN物理层和收发机设计考虑4.3.1 能量使用的特点（作业）：辐射的能量的影响；发射能量和接收能量的比较；启动能量、启动时间l the radiated energy is small；the overall transceiver (RF front end and baseband part) consumes much more energy than is actually radiated辐射能量较小。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。基本相同l

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页动态调制调整：原理如果增加B和m的值，比特延迟会减小，每个比特的能量消耗主要取决于m，与B也有关，事实上，对于特别的参数选取，已经表明，当符号率最大时，每个比特消耗的能量和每个比特的延迟是最小的。分组数增加，m增加Antenna第五章Basic requirement: ma

41、ster the fundamentals of MAC protocols 5.1 无线MAC协议的基础知识113 隐藏终端、暴露终端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页 MAC协议的分类l 固定配置协议 Fixed assignment protocolsl 按要求配置协议 demand assignment protocolsl 随机接入协议 random access protocols116 解决隐藏终端的手段2个l the busy-tone solution 忙音技术l the RTS/CTS handshake 握手技术5.1.2 important classes of MAC protocols1.Fixed Assignment protocols 固定配置协议

43、 TDMA FDMA CDMA SDMA(不能)2.Demand assignment protocols 按需分配的协议 LEACH3.Random access protocols 随机接入协议 ALOHA slotted ALOHA(higher through put) CSMA Nonpersistent CSMA backoff algorithm busy-tone solution 解决了隐藏终端和暴露终端的问题，与数据传输距离相同之处能侦听到忙音信号。RTS/CTS握手方法 基于WACAW协议 一个信道两个控制分组 RTS请求发送 CTS清除发送 Data数据 Ack确认 将

44、一个较大的分组拆分为几个较小的分组 保证cts比rts长119 5.1.3 MAC层的能量问题 Collisions 碰撞 wasted effort when two packets collide fixed assignment/TDMA or demand assignment protocols，CSMA protocols Overhearing 偷听 waste effort in receiving a packet destined for another node Idle listening 空闲监听 sitting idly and trying to receive

45、when nobody is sending TDMA-based protocols Protocol overhead协议开销 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低占空比协议与唤醒的概念每个协议针对能量问题

46、的算法的区分，最突出，最不同的点S-MACSMACS占空比=侦听阶段/唤醒周期Avoid spending much time in the idle state and to reduce the communication activities of a sensor node to a minimum.大部分时间处于休眠状态 并周期性的被唤醒来接收来自其他节点的分组 periodic wakeup 周期性唤醒 掌握发送目标的监听时段5.2.4 wakeup radio concepts无线唤醒的概念节点发送或者接受或者休眠 不存在空闲状态 FDMA低功耗唤醒收发机处于经常工作的状态 信道

47、空闲 收到唤醒信号 唤醒数据收发机 有通信量自适应功能 负载增加 MAC越来越活跃understand contention and schedule based protocols, 5.3 基于竞争的协议5.3哪些是基于竞争的协议 contention-based ALOHA、CSMA哪些基于调度表协议 schedule-based LEACH SMACS TRAMA哪些基于分配的协议 5.4 基于时间的协议5.4.1LEACH 自适应的低功耗的分簇算法 LEACH协议将一个基于TDMA的MAC协议与聚类协议和一个简单的“路由”协议集成在一起 分簇 簇头节点 负责确定和维护TDMA时间表

48、对成员节点分配TDMA时隙 能量消耗大 每个成员节点轮流担任簇头节点 簇头节点在网络节点中所占的百分比是一个有用的网络参数重点CSMARPSCTSmaster the IEEE 802.15.4 MAC protocol.5.5.1Network architecture and types/roles of nodes一个标准的MAC层分为两种不同的节点1. 全功能设备FFD PAN网络协调器 简单协调器 设备 三种功能2. 精简功能设备RFD 只用作设备一个设备必须与一个协调器一起工作并仅与其进行通信构成一个星状网络 协调器可以工作于对等模式协调器完成四个任务超帧的结构 IEEE 802.

49、15.4活跃时段 不活跃时段信标 竞争介入时段 保障时隙节点在CAP时段必须发送数据分组或管理控制分组时采用Slotted CSMA-CA protocol CSMA protocol区别 不包含关于隐藏终端的规定 使用随机延迟 使用带有碰撞避免的CSMA协议 回退时段Basic requirement: understand the role and significance of the time synchronization problem, 8.1 理解时间同步问题的概念和意义202 各个时间的概念物理时间 大多数应用和协议都要求物理时间 逻辑时间 分布式系统中事件发生的顺序关系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基于发送/接收的时间同步协议8.2 Protocols based on sender/receiver synchronization 207 基于公共步骤1.成对同步 2.全网同步Lightweight time synchronization protocol LTS比对同步协议完成两个相邻节点的同步建立一个从参考节点到所有节点的层次最少的生成树发送接收的同步计算方法 计算题 作业分布式多跳LTS 不需要构造生成树 每个节点需要知道许多参考节点 并沿着适当的路径到达他们 这些参考节点的责任就是周期性的启动再同步8.2.3 Time-Sync for

54、sensor networks TPSN非对称 i可以与j但是反过来不行8.3基于接收/接收的时间同步协议8.3.1 Reference broadcast synchronization(RBS)参考广播同步多跳范围内的网络同步Network synchronization over multiple hops多广播域RBS 不断变换时间 确保最后到达信宿的时间是准确的 以UTC时间表示Basic requirement: understand the properties of localization and positioning procedures, 9.1 9.2 WSN定位网络

55、的特点和方法9.1 Properties of localization and positioning proceduresl Physical position versus symbolic locationl Absolute versus relative coordinatesl Localized versus centralized computationl Accuracy and precisionAccuracy：估计值与实际值的最大距离Precision：达到准确性的百分比l Scalel Limitationsl Costs9.2 定位的三种方法 Possible a

56、pproaches1. Proximity 利用相邻节点的信息进行定位2.Trilateration and triangulation 三边定位和三角定位Determining distances三种测距方法 RSSI TOA TDOA3.Scene analysis 情景分析9.3 Mathematical basics for the lateration problem 测边定位understand the differences between the single-hop and multihop localizations, 9.4 9.5 单跳定位与多跳定位的区别9.4.6 A

57、pproximate point in triangle 近似三角形内点测试法对于所有的邻居节点，如果三个顶点到邻居节点的距离没有同时更近或更远，那么未知节点在三角形内，否则在三角形外。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