Wireless Sensor Networks
巨型机说：“我认为全球大概只需要五台计算机就够了”；
PC机说：“每个家庭的桌面上都应该有一台电脑”;
Pocket PC说：“太大了，应该每人口袋里放一台”;
WSN说：“每粒沙子都应该是一台计算机”。
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Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• OUR WORK
2
Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• Hot Issues
• OUR WORK
3
Sensor network: A new research hotspot
August 2003 Business Week projects
"Sensors and Sensor Networks". to be one of
4 Key Technology Waves of the Future
《国家中长期科学和技术发展规划纲要》
将传感器网络列为重点研究领域
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Faster, Smaller, Numerous
• Bell’s Law
• Moore’s Law
– New computing class
every 10 years
– “Stuff” (transistors,
etc) doubling every
1-2 years
log (people per computer)
Streaming Data
to/from the
Physical World
Source: The Mote Revolution:
Low Power Wireless Sensor Network Devices
year
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What’s are Wireless Sensor
Networks
• Wireless networks are usually composed of
small, low-cost devices that communicate
wirelessly and have the capabilities of
Processing, Sensing and Storing
• The purpose is to measure different physical
parameters in a given environment, in order
to characterize its properties, or to take
decisions depending on these measurements.
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Network Model
Patch
Network
Sensor Node
Sensor Patch
Gateway
Transit Network
Client Data Browsing
and Processing
Basestation
Base-Remote Link
Internet
Data Service
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Enabling Technologies
Embed numerous distributed
devices to monitor and
interact with physical world
Embedded
Network devices
to coordinate and perform
higher-level tasks
Networked
Exploit
collaborative
Sensing, action
Control system w/
Small form factor
Untethered nodes
Sensing
Tightly coupled to physical world
Exploit spatially and temporally dense, in situ, sensing and
actuation
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Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• Hot Issues
• OUR WORK
9
Wireless Sensor Network Applications
•
•
•
•
•
•
Military Applications
Environmental Applications
Health Applications
Home Applications
Industrial Applications
Other Commercial Applications
Application <——> WSN
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Military Applications
• enemy tracking, battlefield surveillance
• target detection and classification
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An Example:Counter Sniper System
Using the arrival times of the acoustic events
at different sensor locations, the shooter
position can be accurately calculated using
the speed of sound and the location of the
sensors.
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民用领域
森林防火：节点实时
监测周围温度情况，
并在探测到温度过高
时发出警报。
土壤湿度、温度、成
份监测，节点对土壤
进行周期性采样将数
据发送给远端用户
医疗看护：将传感器
配置在身体上，可以
将身体情况传输给远
端监控中心。GE公司
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科技领域
海
洋
环
境
监
测
• sensors and vehicles are
deployed to perform
collaborative monitoring tasks
over a given area under ocean.
• Large number of sensor nodes
collect data from the ocean and
forward to a master node.
研
究
鸟
类
习
性
了
解
火
山
习
性
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Industrial Applications
地面上的
立柱上的
传感节点
传感节点
无线传感网络原型系统拓扑图:
矿井安全检测和防护系统
From talk of Yunhao Luo
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Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• Hot Issues
• OUR WORK
16
Architecture of WSN
• Sensor nodes are scattered in a sensor field(object field)
• Sensor nodes can self organize to form a sensor network
• Data are collected by these scattered nodes and routed
back to the sink in a multi-hop way
• The user communicate with the sink via Internet
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Architecture of WSN(cont'd)
• nodes are still
stationary.
• multiple, mobile
sinks defined as
users.
• sinks may collect
data at any time,
any place.
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Architecture of WSN(cont'd)
无线传感网络
接入网络
核心网络
From Talk of YunHao Luo
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A general work process of WSN
Deploy
Sensing and monitoring
Organize into network
Data collection and
dissemination
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Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• Hot Issues
• OUR WORK
21
Sensor Hardware
• Fundamental Components
– Various Sensing,Processing,Storing, Transceiver,Power
• Application dependent components
– Locating, Mobilizer, Power generator
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Sensor Node Samples
LWIM III
AWAIRS I
UCLA, 1996
UCLA/RSC 1998
Geophone, RFM
Geophone, DS/SS
radio, PIC, star
Radio, strongARM,
network
Multi-hop networks
Sensor Mote
Medusa, MK-2
UCB, 2000
UCLA NESL
RFM radio,
2002
Atmel
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Mote Evolution
Source: The Mote Revolution:
Low Power Wireless Sensor Network Devices
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Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• Hot Issues
• OUR WORK
25
Characteristic of WSN
• Resource Constraints
– battery equipped,recharging the batteries is
impossible or unfeasible
– Radio and embedded CPU
• Self configuring
– Randomly deployed, unattended.
• Dynamic Topology
• Data centric
– Different from traditional network
• Unique traffic model
• Application specific
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Power Consumption
• Power is of most important and directly influencing the
lifetime of WSN
• Consumption in three domains:
– Sensing, communication and data processing
– Energy consumed by Comm. is dominating
• The energy cost of transmitting 1Kb a distance of 100 m is
approximately the same as that for executing 3 million instructions by
a 100 million instructions per second (MIPS)/W processor.
Tx/Rc
electronics
Tx
amplifier
S
k
D
d
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MANET vs WSN: Differences
• Low density vs. high density
• Address centric (IP) vs. content
centric (no IP)
• Resource (constraint vs critical)
• Mobile vs stationary
• First criterion of performance (QoS
vs. Power)
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Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• Hot Issues
• OUR WORK
29
Communication Protocols
A sensor field
• MAC Protocol
– Fairness vs. Energy
• Routing Protocol
– Energy-aware routing
– Geo-routing
• Transport Control Protocol
– Congestion Control
– Reliability
– End-to-end vs. Hop-by-hop
Sensor sources
Event
Directed
Diffusion
Sensor sink
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Coverage Control
• Problem
– Given a set of sensors deployed in a target
area, we want to determine if the area is
sufficiently k-covered, in the sense that every
point in the target area is covered by at least
k sensors, where k is a predefined constant.
• Two Motivations
– One of the measurements of the QoS
– Energy efficient
Communic
ating
radius
Sensing
radius
• Two conflicting objectives:
– minimizing the number of active sensors to
minimize the energy consumption.
– maintaining the coverage.
• Two metrics
– Connectivity and Coverage
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Data and Query Dissemination
• Problem
– The sensor network is a distributed
database.
– How to collect or query the interested data
detected by some nodes in a energyefficient way?
• Application-specific
– Area-based
– Attribute-based
• Pull vs. Push
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Outline
• General Comments
• Wireless Sensor Network
Applications
• Architecture of WSN
• Overview of Sensor Hardware
• Characteristic of WSN
• Hot Issues
• OUR WORK
33
自组织的无源无线Zigbee－WiFi
输电线路在线监测
•
•
•
监测功能
– 图像采集：线下图像、塔架塔基图像、导线及绝缘
子图像
– 弧垂和导线温度的采集
两级数据传输
– 监测数据和报警信息从采集终端上传到塔架上监测
子站采用无线Zigbee技术
– 数据和信息从塔架监测子站接力上传到监控中心
（运行值班、变电站）采用无线WiFi技术
– 监控中心的控制命令可以下传
监控功能
– 监控中心采集监测数据、存储并进行综合分析处理
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监测平台运行示意图
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两层网络架构
802.11b/g
骨干网络
子 网
子 网
Zigbee
采集终端
变电站
图例：
线路监测子站
监控中心
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