University of Electronic Science and Technology of China
Wireless Sensor Networks
第五章
通信标准
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University of Electronic Science and Technology of China
Wireless Sensor Networks
概述
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传感器网络中的应用一般不需要很高的信道带宽，却要求 具有较低的传输延时和极低的功率消耗，使用户能在有限 的电池寿命内完成任务 IEEE 802.15.4/ZigBee标准把低功耗、低成本作为主要目 标，为传感器网络提供了一种互连互通的平台，各大射频 芯片厂商也陆续推出支持该标准的无线收发芯片 另外，现有成熟的IPv6协议也可以很好地满足传感器网络 中节点地址数量庞大以及网络安全性等要求，IEEE于2004 年11月成立了一个6Lowpan（IPv6 over IEEE 802·15·4或 IPv6 over LR PAN）工作组，专门致力于如何实现IPv6数 据包在IEEE 802.15.4上的传输，研究基于1Pv6 over IEEE 与无线传感器网络协议相关的通信标准
Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
内容提要
一． IEEE 二． IEEE
802.11 标准 802.15.4 标准 标准
三． ZigBee
四． 6LowPan草案
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
The 802.15.4 / Zigbee sandbox
Faster Wireless Video Applications
UWB
802.11g
Peak Data Rate
IrDA
802.11a 802.11b
Wireless Data Applications
WiFi
2.5G/3G
Bluetooth HomeRF
ISM Link
ZigBee 802.15.4
Slower
Closer
Range
Prof. Shuisheng Lin, 2010
Farther
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University of Electronic Science and Technology of China
Wireless Sensor Networks
Wireless Technologies Compared
Common Name IEEE standard Max Data Rate TX power Standby Idd Stack Size Network Type Network Join/Formation Max Packet Size(bytes) Range Devices
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"Zigbee" 802.15.4 250Kbps 30+ ma 3ua 8-60KB
Star, Cluster, Mesh
Bluetooth 802.15.1 750Kbps 40+ ma 200ua 100+ KB Star(8 nodes max) seconds 359 100 meters 8
WiFi 802.11 54Mbps 400+ ma 20ma 100+ KB Star seconds 4095
UWB 802.15.3
1000+ Mbps
ms 132 Over 1200 meters 2^16
100 meters* 10 meters
Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
无线网络标准
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
无线局域网(wireless
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local area networks，WLAN)
局部区域是距离受限的区域，是相对于广域（wide area） 而言的。两者的区别主要在于数据传输的范围不同（但覆 盖范围界限的区别并不十分明显），由此而引起网络设计 和实现方面的一些区别
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介于广域网WAN和局域网LAN之间还有一种局部网络，称 为城域网（metropolitan area networks, MAN）,比局域 网覆盖范围更小的局部网络称为个域网(personal area networks，PAN） 广义的无线局域网还包含无线城域网（WMAN）和无线个 域网（WPAN） 无线网络则可以粗略地分为无线广域网和无线局域网
Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
无线局域网(WLAN)
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WLAN就是在局部区域内以无线（no wire or wireless)媒体或介质进行通信的无线网络 WLAN是一种能在几十米到几千米范围内支持较高 数据速率（如2Mb/s以上）的无线网络,可以采用微 蜂窝（microcell)、微微蜂窝(Picocell）结构，也 可以采用非蜂窝（如Ad Hoc）结构 目前无线局域网领域的两个典型标准是IEEE 802 系列标准和HiperLAN系列标准
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
WLAN的需求
吞吐量 ? 节点数量 ? 与主干LAN连接
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服务区域 ? 电池能量消耗 ? 鲁棒性和安全性 ? 配置网络操作 ? 非许可操作 ? 切换/漫游
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动态配置
Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.11系列标准
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IEEE 802. 11系列标准指由IEEE 802.11标准任务组提出的协议族，它 们是IEEE 802.11 、EEE 802.11a、IEEE 802.11b和IEEE 802.11g等 IEEE 802. 11和IEEE802. 11b用于无线以太网(wireless ethernet)，其 工作频率大多在2. 4GHz上，传输速度为：IEEE 802.11是1~2Mb/s； IEEE 802.11b的速率为5.5~11Mb/s，并兼容IEEE 802.11速率
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IEEE 802.11a的工作频率为5~6GHz，使用正交频分复用(orthogonal frequency division multiplex, OFDM)技术，使传输速率可以达到 54Mb/s
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IEEE 802.11g工作在2.4GHz频率上,采用CCK、OFDM、PBCC(分组 二进制卷积码，packet binary convolutional code)调制，可提供 54Mb/s的速率并兼容IEEE 802.11b标准
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HiperLAN是欧洲ETSI开发的标准
Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.11协议系列
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802 网络标准
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE802.11a
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE802.11b
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE802.11g
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
传输距离与速度的关系
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
内容提要
一． 二． 三． 四．
IEEE 802.11标准 IEEE 802.15.4标准 ZigBee标准 6LowPan草案
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4
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为满足低功耗、低成本的无线网络要求，城服标准委员会 在2000年12月正式批准并成立802.15.4工作组，工作组的 任务是开发一个低速率数据传输的WPN(LR-WPAN)标准 IEEE 802.15.4标准就是802.15.4工作小组开发出的标准， 它具有复杂度低，成本极少，功耗很小的特点，能在低成 本设备之间低速率传输数据
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标准满足国际标准组织开放系统互联（OSI）参考模式,包 括物理层、介质访问、网络层和高层 802.I5.4标准定义了无线个域网中的设备互联进行无线通信 的协议，它采用了CSMA/CA介质访问机制和支持星型和对 等拓扑结构网络
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4标准的主要特征
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四种传输速率：20kbps、40kbps、100kbps、250kbps 支持星型和点到点两种拓扑结构 在网络中采取两种地址方式：16位地址和64位地址 采用可选的时槽保障(Guaranteed Time Slots,GTS)机制 采用CSMA/CA信道访问机制 支持ACK机制以保证可靠传输； 低功耗机制； 信道能量检测（Energy Detection，ED）； 链路质量指示（Link quality indication，LQI）； 工作在ISM频段上，其中在2450 MHz波段上有16个信道,在 915MHz波段上有10个信道，在868MHz上有1个信道 数据安全策略
Prof. Shuisheng Lin, 2010
z z z z z z z z
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z
University of Electronic Science and Technology of China
Wireless Sensor Networks 802.15.4 has 16 channels in the 2.4Ghz band
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4标准 IEEE 802.15.4标准概述 ? 网络组成及拓扑结构 ? 协议栈架构 ? 物理层规范 ? 信道分配及调制方式 ? 物理层帧格式 ? 物理层功能实现 ? MAC子层规范 ? MAC子层的信道访问方式 ? MAC子层的帧格式 ? MAC子层的功能实现
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4 Topologies
PAN Coordinator
Full Function Device (FFD) Star ?Any topology ?Network coordinator capable ?Talks to any other device ?3 modes: PAN Coordinator, Coordinator, Device ?49 primitives (14 PHY+ 35 MAC) (1/3 of Bluetooth) Reduced Function Device (RFD) ?Limited to being leaf devices ?Cannot become a network coordinator ?Talks only to a network coordinator ?Very simple implementation ?simple devices; e.g. Light switch, infrared sensor ?38 primitives
Prof. Shuisheng Lin, 2010
Mesh
Cluster Tree
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University of Electronic Science and Technology of China
Wireless Sensor Networks
802.15.4 Topology：Peer-Peer
Topology
Combined Topology
Point to point
Full function device
Clustered stars - for example, cluster nodes exist between rooms of a hotel and each room has a star network for control.
Full function device Reduced function device
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
Network Pieces –PAN Coordinator
? PAN
Coordinator ?“owns” the network
Starts it Allows other devices to join it ? Provides binding and addresstable services ? Saves messages until they can be delivered ? And more… could also have i/o capability
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“full-function device” – FFD ?Mains powered
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
Network Pieces - Router
?Routers
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messages ? Does not own or start network
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Scans to find a network to join z Given a block of addresses to assign
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“full-function device” – FFD ? Mains powered depending on topology ? Could also have i/o capability
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
Network Pieces – End Device
?End
Device
? Communicates
with a single device ? Does not own or start network ? Scans to find a network to join ? Can be an FFD or RFD (reduced function device) ? Usually battery powered
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4协议架构
Upper Layers
IEEE 802.15.4 SSCS
IEEE 802.2 LLC, Type I
IEEE 802.15.4 MAC
IEEE 802.15.4 868/915 MHz PHY
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IEEE 802.15.4 2400 MHz PHY
Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4超帧结构
信标帧 竞争访问时段(CAP)
无竞争访问 时段(CFP) GTS GTS 不活跃时段(Inactive)
信标帧
超帧持续时间长度(SD) 信标帧周期(BI)
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
超帧结构
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超帧是指一种用来组织网络通信时间分配的逻辑结 构 超帧的时间分配由网络协调器定义，包括：活跃时 段和非活跃时段 网络中的所有通信都必须在活跃时段进行，而在非 活跃时段，设备可以进入休眠模式以达到省电的目 的 每个超帧都以网络协调器发出信标帧为开始，并划 分为16个等宽的时槽
Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4标准 IEEE 802.15.4标准概述 ? 网络组成及拓扑结构 ? 协议栈架构 ? 物理层规范 ? 信道分配及调制方式 ? 物理层帧格式 ? 物理层功能实现 ? MAC子层规范 ? MAC子层的信道访问方式 ? MAC子层的帧格式 ? MAC子层的功能实现
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Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
信道分配和调制方式
扩频参数
频段 (MHz) 片速率
(kchip/s) 868–868.6 902–928 868–868.6* 902–928* 868–868.6* 902–928* 2400–2483.5 300 600 400 1600 400 1000 2000
数据参数
比特速率
(kb/s) 20 40 250 250 100 250 250
调制方式
BPSK BPSK ASK ASK O-QPSK O-QPSK O-QPSK
符号速率
(ksymbol/s) 20 40 12.5 50 25 62.5 62.5
符号
二进制 二进制 20-bitSPSS 5-bitSPSS 16-ary正交 16-ary正交 16-ary正交
注：* 项为可选项目，系802.15.4-2006新增内容
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4 PHY - Operating Frequency Bands
Channel 0
Channels 1-10
868MHz / 915MHz PHY
868.3 MHz 902 MHz
2 MHz
928 MHz
2.4 GHz PHY
Channels 11-26
5 MHz
2.4 GHz
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Prof. Shuisheng Lin, 2010
2.4835 GHz
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University of Electronic Science and Technology of China
Wireless Sensor Networks
The 2.4Ghz ISM band
2.412 2.437 2.462
2.4835
(end of ISM Band)
2.40
2.41
2.42
2.43
2.44
2.45
2.46
2.47
2.48
802.11 DSSS
Possible 802.11 Channel(North America) 802.11 Spectrum Occupancy (Typical)
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
Channel Access
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channel access mechanism
network
? Non-beacon
Standard ALOHA CSMA-CA communication ? Positive acknowledgement for successfully received packets
? Beacon-enables
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z z
network
Superframe structure
For dedicated bandwidth and low latency Set up by network coordinator to transmit beacons at predetermined intervals z 15ms to 252s z 16 equal-width slots between beacons z Contention and contention free
Prof. Shuisheng Lin, 2010
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University of Electronic Science and Technology of China
Wireless Sensor Networks
Example of superframe structure
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Every beacon specifies ? the duration of the superframe, ? the duration of active frame, ? for whom the GTSs are, ? who has data pending on the coordinator, ? is the coordinator accepting new devices ?, ? etc. .... Frame Beacons Contention Access Period (CAP)
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Superframe structure without GTSs
Prof. Shuisheng Lin, 2010
time
University of Electronic Science and Technology of China
Wireless Sensor Networks
SuperFrame Structure (No GTS)
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LR-WPAN标准可选的超帧结构，超帧结构由协调器定义 由信标(Beacons)作界限的超帧由协调器发送，并划分为16个相等的时 槽，信标帧在每个超帧的第1个时槽发送 如果协调器不准备使用超帧结构，将关闭超帧发送 信标用于同步其他设备、描述超帧结构、确认PAN 任何设备如果要在2个信标间的争用访问周期(CAP)期间进行通信，都 要通过CSMA/CA机制与其他设备争用时槽 所有传送需要在下个信标处结束
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Frame Beacons Superframe structure without GTSs Contention Access Period (CAP)
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Prof. Shuisheng Lin, 2010
time
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University of Electronic Science and Technology of China
Wireless Sensor Networks
SuperFrame Structure ( GTS )
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
IEEE 802.15.4 PHY -Packet Structure
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PHY Packet Fields
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Preamble (32 bits) – synchronization Start of Packet Delimiter (8 bits) PHY Header (8 bits) – PSDU length PSDU (0 to 1016 bits) – Data field
Preamble
Start of Packet Delimiter
PHY Header
PHY Service Data Unit (PSDU)
6 Octets
0-127 Octets
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Prof. Shuisheng Lin, 2010
19
University of Electronic Science and Technology of China
Wireless Sensor Networks
物理帧格式
Ocets：4 字节 1 字节 1 字节 可变
前导码（preamble）
SFD
Frame length (7 比特)
Reserved (1 比特)
PSDU
同步头(SHR)
物理帧头(PHR)
PHY 负载
(PPDU，PHY Protocol Data Unit)，(SFD，Start-Of-Frame Delimiter), (PSDU，PHY service Data Unit)
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Prof. Shuisheng Lin, 2010
University of Electronic Science and Technology of China
Wireless Sensor Networks
物理层参考模型
zPD-SAP：物理层数据访问接口，Physical layer Data SAP zPLME-SAP：物理层管理实体访问接口，Physical Layer Management Entity SAP
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Prof. Shuisheng Lin, 2010
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