lec1-课程概述WSN节点系统组成.ppt

1、Wireless Sensor Networks无线传感器网络,通信与信息工程学院 林水生,1/65,内容提要,课程相关信息 WSN定义与特征 WSN的应用示例 WSN发展前景 WSN节点系统设计 WSN关键技术 概述,2,Twice a week：周二1、2节（B204）、周五3、4节（C107） EMAIL: TEL:61831103（O） Office:科研楼B226(A) Office hours: Thursday 2:30-5:00PM 课件下载途径 电子科大主页互动教学空间课程中心课程中心学号登陆（选课确定后有效）,3/65,课程方法,讲授,实验,同学报告,无线传感器网络,8学时

2、,32学时,课程学时：40学时 课程学分：2学分,课程考核方式：考试/考查 课程考核构成 文献综述or技术报告 30% 实验 30% 开卷考试 40%,4/65,教学参考教材,1.无线传感器网络技术， 李晓维主编， 北京理工大学出版社， 2007年8月,5/65,教学参考教材,3.无线传感器网络， 孙利民等编，清华大学出版社，2005年5月,2.无线传感器网络技术与应用 陈林星编著，电子工业出版社，2009年3月,6/65,教学参考教材,4.无线传感器网络技术及应用 张少军编著， 中国电力出版社，2010年1月,5.无线传感器网络简明教程 崔逊学 等编著， 清华大学出版社，2009年7月,7/

3、65,课堂教学：内容,第一部分:网络支持技术 现状与发展、路由协议、MAC协议、物理层设计、通信标准 第二部分:服务支持技术 时间同步技术、节点定位技术、 容错设计技术、安全设计技术、 服务质量保证 第三部分:应用支持技术 网络管理、操作系统、开发环境,8/65,教学实验,实验环境介绍 处理器基础实验 程序下载实验 串口通信实验 微操作系统实验 基础通信实验 线信道监听实验 无线报警实验 射频休眠实验 自组织网络实验 指定路由多跳网络的实验 基于简单的泛洪协议的多跳路由网络的实验,9/65,基础ZigBee实验 组包发送实验 应答 ACK帧实验 温度传感数据采集的点到点综合通信,内容提要,课程

4、相关信息 WSN定义与特征 WSN的应用示例 WSN发展前景 WSN节点系统设计 WSN关键技术 概述,10,无线传感器网络的意义和前景,现代信息科学的六大组成部分 信息的生成、获取、存储、传输、处理及其应用是现代信息科学的六大组成部分 无线传感器网络定义：无线传感器网络(WSN)是大量的静止或移动的传感器以自组织和多跳的方式构成的无线网络，目的是协作地采集、处理和传输网络覆盖地域内感知对象的监测信息，并报告给用户 无线传感器网络特征：大规模、无线、自组织、多跳、无分区、无基础设施支持；节点同构、体积小、成本低、基本不移动；大量密集撒播；长时间工作,11/65,WSN是一门交叉学科，涉及计算机

5、、微电子、网络、通信、信号处理、传感器等诸多领域,随着现代微电子技术、微机电系统（MEMS)、片上系统soc、纳米材料、无线通信技术、信号处理技术、计算机网络技术等的进步以及互联网的迅猛发展 传统传感器信息获取技术从独立的单一化模式向集成化、微型化，智能化、网络化方向发展，成为信息获取最重要和最基本的技术之一。,12/65,无线传感器网络包含了哪些部分？举例说明。,Sensor Networks: The Vision,Push connectivity out of the PC and into the real world Billions of sensors and actuator

6、s EVERYWHERE! Zero configuration Build everything out of CMOS so that each device costs pennies Enable wild new sensing paradigms,13/65,Why Now?,Combination of: Breakthroughs in MEMS technology Development of low power radio technologies Advances in low-power embedded microcontrollers IC design and

7、foundry technology development,14/65,What are WSN?,Smart sensor = Micro-sensors + on-board processing + low-power wireless interfaces All feasible at very small scale Berkeley Smart Dust,“Challenge of the century” New paradigm for distributed computing!,15/65,内容提要,课程相关信息 WSN定义与特征 WSN的应用示例 WSN发展前景 WS

8、N节点系统设计 WSN关键技术 概述,16,节点试验平台,第一代（19961999）：代表性的平台有UCLA的WINS61，UC Berkeley的SmartDust62、WeC和Rene63。 第二代（20002001）：典型平台的有UCB的Mica与Dot64，MIT的uAMPS-I和uAMPS-II 65，以及Rockwell公司的HYDRA。 第三代（20022003）：两款代表性的试验平台：Mica2和MicaDot2，以及NASA JPL实验室的Sensor Web66。 第四代（2004）：典型的平台有MicaZ、Telos、EmberNode、Imote、Imote2、BTNo

9、de3和DSYS25。,17,第四代节点平台比较,18,Mica Mote,Two Board Sandwich CPU/Radio board Sensor Board Size Mote: 11 in Pocket PC: 5.23.1 in CPU Mote: 4 MHz, 8 bit Pocket PC: 133 MHz, 32 bit Memory Mote: 4KB SRAM Pocket PC: 32 MB RAM Radio Mote: 50 kbps Bluetooth: 433.8 kbps; Wireless LAN: 10 Mbps,19/65,MICA2 Mote (

10、MPR400CB),20,Applications,Smart sensors massively distributed in environments for sensing and control Enable spatially and temporally dense environmental monitoring Embedded Networked Sensing will reveal previously unobservable phenomena,Seismic Structure response,Contaminant Transport,Marine Microo

11、rganisms,Ecosystems, Biocomplexity,Modified from Deborah Estrin, SIGMETRICS keynote, /estrin/talks/Sigmetrics-June02.ppt,21/65,Acoustic Tracking,Berkeley mote,Modified from Lui Sha et. al.,MURI presentation,22/65,Large Scale,Number of nodes Diameter of networks Density,Radio ra

12、dius R 30 m Surveillance over 9 km2 ,23/65,Severe Resource Constraints,Bandwidth, CPU, memory, and storage Energy Batteries, solar cells Long life time Bird habitat monitoring: 9 months Bridges: years Need power management!,24/65,Unpredictability,Wireless Environmental noises Terrain High fault rate

13、s Unknown and changing topologies,169 motes, 13x13 grid, 2 ft spacing, open area, RFM radio, simple CSMA,Probability of receiving packets vs. distance,Deborah Estrin, SIGMETRICS keynote, /estrin/talks/Sigmetrics-June02.ppt,25/65,Unpredictability,Berkeley mote,When/where/how-man

14、y targets Mobile targets Sensors leave/join/move,26/65,Real-Time Requirements,Berkeley mote,Timing constraints: locate/report targets within 30 sec,27/65,Security,Physically exposed to potential hackers Wireless communication Resource-constrained,28/65,Aggregate performance individual node,Berkeley

15、mote,“Where are the targets in the south?” vs. “What is the sound reading of sensor ?”,29/65,New Computing Paradigms,Aggregate performance individual node Location-based queries Nodes w/o global ID Group coordination Goal: reliable aggregate services on top of thousands of unreliable nodes

16、,30/65,Data-Centric Communication,Maximize information about physical events NOT raw data throughput (as in traditional networks) High redundancy in raw data In-network data aggregation instead of sending everything to base stations,31/65,Acoustic Tracking,Berkeley mote,“Where are the targets in the

17、 south?” vs. “What is the sound reading of sensor ?”,In-network aggregation send positions (not individual sound),32/65,Decentralized Control,Self-adaptation to handle unpredictabilities Routing: avoid hot spots Power management: optimal topology and lifetime data caching/placement Fault-t

18、olerance Scalability: cannot depend on global information Decentralized control Only depend on neighborhood information Need to guarantee aggregate stability!,33/65,Sensor Network Algorithms,Directed Diffusion Data centric routing (Estrin, UCLA) Sensor Network Query Processing (Madden, UCB) Distribu

19、ted Data Aggregation Localization in sensor networks (UCLA, UW, USC, UCB) Multi-object tracking/Pursuer Evader (UCB, NEST) Security,34/65,内容提要,课程相关信息 WSN定义与特征 WSN的应用示例 WSN发展前景 WSN节点系统设计 WSN关键技术 概述,35,WSN具有巨大的应用前景，被认为是将对21世纪产生巨大影响力的技术之一,2001年1月的MIT技术评论将WSN列于十种改变未来世界新兴技术之首。 2003年2 月份美国的技术评论杂志评选出对人类未来生

20、活产生深远影响的十大新兴技术，无线传感网络即被列为其中之一。 美国商业周刊在2003年8 月的技术评论中，已经将无线传感网络定位成21世纪高技术领域的四大支柱型产业之一，其潜在的市场需求十分巨大。 传感器网络、塑料电子学、仿生人体器官是全球未来三大高科技产业 2009年，在无锡成立物联网研究院，标志着产业化方向发展,36/65,物联网（The Internet of things）,其定义是：通过射频识别（RFID）、红外感应器、全球定位系统、激光扫描器等信息传感设备，按约定的协议，把任何物品与互联网连接起来，进行信息交换和通讯，以实现智能化识别、定位、跟踪、监控和管理的一种网络。物联网就是“

21、物物相连的互联网”。 物联网的概念起源于传感网 传感网的概念是在1999年提出的（“传感网是下一个世纪人类面临的又一个发展机遇”）。 第一，传感网的核心和基础仍然是互联网，是在互联网基础上的延伸和扩展的网络，是自组织网络 第二，其用户端延伸和扩展到了任何物品与物品之间，进行信息交换和通讯 传感网被称为继计算机、互联网后，世界信息产业的第三次浪潮,37/65,(2006-2020年)国家中长期科学和技术发展规划纲要,38/65,ITU-T SG15（20092012）首次会议概况,ITU-T SG15（传送网及接入网基础设施）于2008年12月1-12日在瑞士日内瓦召开了（2009-2012年）

22、研究期第一次会议。来自31个国家的25个政府电信主管部门代表团、98个部门成员（16个认可的电信运营公司以及82个科学或工业组织）的代表及专家以及其它国际组织代表、应邀参会人员等共354人参加了本次会议 中国的电信主管部门工业及信息化部代表团和中国的ITU-T部门成员中国电信、中国网通、中国移动、上海贝尔、华为技术、中兴通讯六个代表团等一行共62人参加了会议,39/65,节能Power savings 数字生活Digital life 泛在传感器网络Ubiquitous Sensor Networks (USN) 高性能视频会议Telepresence: High-Performance Vi

23、deo Conferencing 数字安全Sybersecurity 下一代网络及能效Next-Generation Networks and Energy Efficiency 远距离协作工具Remote Collaboration Tools 智能传送网 Intelligent Transport Systems (ITS) Accessibility ,ITU-T 近几年关注的热门话题,40/65,内容提要,课程相关信息 WSN定义与特征 WSN的应用示例 WSN发展前景 WSN节点系统设计 WSN关键技术 概述,41,How to do for WSN,Hypothesize abou

24、t requirements based on potential applications Explore design space based on these requirements Develop hardware platform for experimentation Build test applications on top of hardware platform Evaluate performance characteristics of applications GOTO step 1 (hopefully youll come up with a better se

25、t of requirements),42/65,Sensor Node Requirements,Low Power, Low Power, Low Power Support Multi-hop Wireless Communication Self Configuring Small Physical Size Can Reprogram over Network Meets Research Goals Operating system exploration Enables exploration of algorithm space Instrumentation Network

26、architecture exploration,43/65,First Decision: The central controller,What will control the device? Modern Microcontroller Sidebar Whats inside a microcontroller today? What peripheral equipment do you need to support one? How do you program one?,44/65,Major Axes of Microcontroller Diversity,Flash b

27、ased vs. SRAM based Combination of FLASH and CMOS logic is difficult Internal vs. External Memory Memory Size Digital Only vs. On-chip ADC Operating Voltage Range Operating Current, Power States and wake-up times Physical Size Support Circuitry Required External Clocks, Voltage References, RAM Perip

28、heral Support SPI, USART, I2C, One-wire, Cycle Counters Capture and Analog Compare Tool Chain,45/65,46/65,47/65,Second Decision: Radio Technologies,Major RF Devices Cordless Phones Digital/Analog Single Channel Cellular Phones Multi-channel, Base station controlled 802.11 “wireless Ethernet” Bluetoo

29、th Emerging, low-power frequency hopping ,48/65,What is in your cell phone?,Texas Instruments TCS2500 Chipset,ARM9, 120Mhz + DSP, 270.833 kbps,49/65,RFM TR1000 Radio,916.5 Mhz fixed carrier frequency No bit timing provided by radio 5 mA RX, 10 mA TX Receive signal digitized based on analog threshold

30、s Able to operate in OOK (10 kb/s) or ASK (115 kb/s) mode 10 Kbps design using programmed I/O Design SPI-based circuit to drive radio at full speed full speed on TI MSP, 50 kb/s on ATMEGA Improved Digitally controlled TX strength DS1804 1 ft to 300 ft transmission range, 100 steps Receive signal str

31、ength detector,50/65,TR 1000 internals,51/65,Why not use federation of CPUs?,Divide App, RF, Storage and Sensing Reproduce PC I/O hierarchy Dedicated communications processor could greatly reduce protocol stack overhead and complexity Providing physical parallelism would create a partition between a

32、pplications and communication protocols Isolating applications from protocols can prove costly Flexibility is Key to success,Apps CPU,Sensing CPU,Storage CPU,RF CPU,Storage,Sensors,Radio,52/65,Example 1: The RENE architecture,Atmel AT90LS8535 4 Mhz 8-bit CPU 8KB Instruction Memory 512B RAM 5mA activ

33、e, 3mA idle, 5uA powered down 32 KB EEPROM 1-4 uj/bit r/w RFM TR1000 radio Programmed I/O 10 kb/s OOK Network programmable 51-pin expansion connector GCC based tool/programming chain,1.5”x1” form factor,AT90LS8535 Microcontroller,TR 1000 Radio Transceiver,32 KB External EEPROM,51-Pin I/O Expansion C

34、onnector,8 Analog I/O,8 Programming Lines,SPI Bus,Coprocessor,Transmission Power Control,Digital I/O,53/65,What is the software environment?,Do I run JINI? Java? What about a real time OS? IP? Sockets? Threads? Why not?,54/65,Key Software Requirements,Capable of fine grained concurrency Small physic

35、al size Efficient Resource Utilization Highly Modular Self Configuring,55/65,State Machine Programming Model,System composed of state machines Command and event handlers transition modules from one state to another Quick, low overhead, non-blocking state transitions Many independent modules allowed

36、to efficiently share a single execution context,56/65,TinyOS,OS/Runtime model designed to manage the high levels of concurrency required Gives up IP, sockets, threads Uses state-machine based programming concepts to allow for fine grained concurrency Provides the primitive of low-level message deliv

37、ery and dispatching as building block for all distributed algorithms,57/65,What is TinyOS?,58,研究进展：操作系统TinyOS,TinyOS是UC Berkeley的David Culler领导的研究小组为WSN量身定制的嵌入式操作系统。 WSN对操作系统的特殊要求主要表现在： （1）节点的计算资源有限，需要尽可能的减小系统 开销； （2）节点由电池供电，且要求较长的工作周期，因 此需要系统的能耗管理策略与方案，包括操作 系统的支持； （3）节点的各模块之间需要一定的调度协调机制， 同时支持并发控制；

38、（4）观测任务需要操作系统支持实时性。,59,Tiny OS Concepts,Scheduler + Graph of Components constrained two-level scheduling model: threads + events Component: Commands, Event Handlers Frame (storage) Tasks (concurrency) Constrained Storage Model frame per component, shared stack, no heap Very lean multithreading Effic

39、ient Layering,Messaging Component,init,Power(mode),TX_packet(buf),TX_packet_done (success),RX_packet_done (buffer),Internal State,init,power(mode),send_msg(addr, type, data),internal thread,Commands,Events,60/65,Application = Graph of Components,RFM,Radio byte,Radio Packet,UART,Serial Packet,ADC,Tem

40、p,photo,Active Messages,clocks,bit,byte,packet,Route map,router,sensor appln,application,HW,SW,Example: ad hoc, multi-hop routing of photo sensor readings,3450 B code 226 B data,Graph of cooperating state machines on shared stack,61/65,System Analysis,After building apps, system is highly memory con

41、strained Communication bandwidth is limited by CPU overhead at key times. Communication has bursty phases. Where did the Energy/Time go? 50% of CPU used when searching for packets With 1 packet per second, 90% of energy goes to RX!,62/65,Architectural Challenges,Imbalance between memory, I/O and CPU

42、 Increase memory (Program and Data) by selecting different CPU Time/energy spent waiting for reception Solution: Low-power listening software protocols Peak CPU usage during transmission Solution: Hardware based communication accelerator,63/65,Example 2: The MICA architecture,Atmel ATMEGA103 4 Mhz 8

43、-bit CPU 128KB Instruction Memory 4KB RAM 5.5mA active, 1.6mA idle, 1uA powered down 4 Mbit flash (AT45DB041B) SPI interface 1-4 uj/bit r/w RFM TR1000 radio 50 kb/s ASK Communication focused hardware acceleration Network programmable 51-pin expansion connector Analog compare + interrupts GCC based t

44、ool/programming chain,Cost-effective power source,2xAA form factor,Atmega103 Microcontroller,TR 1000 Radio Transceiver,4Mbit External Flash,51-Pin I/O Expansion Connector,8 Analog I/O,8 Programming Lines,SPI Bus,Coprocessor,Transmission Power Control,Digital I/O,64/65,Start Symbol Search,Receiving i

45、ndividual bits,Start Symbol Detection,Synchronization,Radio Samples,MAC Delay,Transmitting encoded bits,Start Symbol Transmission,Bit Modulations,Transmission,Reception,Encoded data received,Data Received,Encoded data to be Transmitted,Data to be Transmitted,Encode processing,Decode processing,Trans

46、mit command provides data and starts MAC protocol.,Wireless Communication Phases,65/65,Radio Interface,Highly CPU intensive CPU limited, not RF limited in low power systems Example implementations RENE node: 19,200 bps RF capability 10,000 bps implementation, 4Mhz Atmel AVR Chipcon application note

47、example: 9,600 bps RF capability Example implementation 1,200bps with 8x over sampling on 16 Mhz Microchip PICmicro (chipcon application note AN008),66/65,Node Communication Architecture Options,67/65,Accelerator Approach,Standard Interrupt based I/O perform start symbol detection Timing accelerator

48、 employed to capture precise transmission timing Edge capture performed to +/- 1/4 us Timing information fed into data serializer Exact bit timing performed without using data path CPU handles data byte-by-byte,68/65,Results from accelerator approach,Bit Clocking Accelerator 50 Kbps transmission rat

49、e 5x over Rene implementation 8x reduction in peak CPU overhead Timing Accelerator Edge captured to +/- us Rene implementation = +/- 50 us CPU data path not involved,69/65,Power Optimization Challenge,Scenario: 1000 node multi-hop network Deployed network should be “dormant” until RF wake-up signal

50、is heard After sleeping for hours, network must wake-up with-in 20 seconds Goal: Minimize Power consumption,70/65,What are the important characteristics?,Transmit Power? Receive Power consumption of the radio? Clock Skew? Radio turn-on time?,71/65,Solutions,Minimize the time to check for “wake-up” m

51、essage “check” time must be greater than length of wake-up message If data packets are used for wake up signal, then “check” time must exceed packet transmission time Instead use long wake-up tone,72/65,Tone-based wake-up protocol,Each node turns on radio for 200us and checks for RF noise If present

52、, then node continues to listen to confirm the tone If not, node goes back to sleep for 4 seconds Resulting duty cycle? .0002/4 = .005 %. 200us due to wake-up time of the radio,73/65,内容提要,课程相关信息 WSN定义与特征 WSN的应用示例 WSN发展前景 WSN节点系统设计 WSN关键技术 概述,74,通信能力有限 节点通信覆盖范围只有几十到几百米,关键之一 如何在有限的通信能力条件下, 完成探测数据的传输？ 无线通信技术是第一项关键技术！,无线传感器网络的关键技术,电源能量有限 通常电池供电，工作环境恶劣，一次部署终生使用，更换电池困难,关键之二 如何节省电源、最大化网络的使用寿命？ 低功耗设计问题是第二项关键技