Microsoft PowerPoint - Review12

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1 WLAN (Wireless Local Area Network) Everywhere

2 Inssider: : Copyright MetaGeek

3 Infrastructure WLAN AP 1 AP 2

4 BSS (Basic Service Set) DS (Distribution System) ESS (Extended Service Set) AP (Access Point) SSID (Service Set ID) Channel Portal

5 Useful Equipment 3G Router Wireless Router Repeater (Same SSID and PSW) Bridge with AP (Different SSID and PSW)

6 Home Network

7 Passive Scanning beacon frame including SSID and supported accessing ratio Active Scanning probe request frame probe response frame

8 AP --- Hot point Hot Zone WISP (Wireless Internet Service Provider)

9 AD Hoc Network Multi-Hop Wireless Network Self-Organized Network Infrastructureless Network no AP no control center, equal nodes, leave and join network anytime, high survivability self-organized no pre-organized devices, fast and auto organizing network multi-hop multi-hop finished by nodes dynamic topology

10 WSN (Wireless Sensor Network)

11 WSN (Wireless Sensor Network) 电池 CPU 无线收发器存储器传感器硬件

12 fixed access mobility access portable access nomadic access

13 = WiFi = Wireless Fidelity 标准频段数据速率物理层优缺点 b 2.4 GHz 最高为 11 Mb/s HR-DSSS 最高数据率较低, 价格最低, 信号传播距离最远, 且不易受阻碍 a 5 GHz 最高为 54 Mb/s OFDM 最高数据率较高, 支持更多用户同时上网, 价格最高, 信号传播距离较短, 且易受阻碍 g 2.4 GHz 最高为 54 Mb/s OFDM 最高数据率较高, 支持更多用户同时上网, 信号传播距离最远, 且不易受阻碍, 价格比 b 贵 n 2.4 GHz 5 GHz 最高为 600 Mb/s MIMO MIMO- OFDM 技术先进标准滞后, 产品早产 2009 年 IEEE 通过

14 Channel Range: 2.4GHz~2.4835GHz 22MHz per Channel b: US/Canada: 11 Channel Euro/China: 13 Channel JPN: 14 Channel

802.11 Channel Co-Channel Channel Interference ADVICE: Use 1,6,11; 2,7,12; 3,8,13

15 Channel Co-Channel Channel Interference ADVICE: Use 1,6,11; 2,7,12; 3,8,13 Channel Group Pre-Check the channels used in nearby WLAN and reasonable planning your channels

16 CSMA/CD Why not CSMA/CD CSMA/CA High cost Hidden/Exposed Station Problem Hidden Station Problem Exposed Station Problem A B C D A? B C D

17 CSMA/CD CA = Collision Avoidance Stop and Wait Protocol CSMA/CA Mac of PCF (Point Coordination Function) Non contention service DCF (Distributed Coordination Function) Contention service

18 CSMA/CD IFS = Inter Frame Space CSMA/CA Short IFS = SIFS SIFS+slot = PIFS = Point IFS PIFS+slot = DIFS = Distributed IFS EIFS = Extended IFS 媒体空闲 DIFS 发送第 1 帧时间源站目的站有帧要发送 SIFS ACK NAV( 媒体忙 ) DIFS 争用窗口发送下一帧时间时间其他站有帧要发送推迟接入等待重试时间

19 CSMA/CD Virtual Carrier Sense CSMA/CA NAV (Network Allocation Vector) Contention Window

20 的退避机制 DIFS DIFS DIFS DIFS A 帧争用窗口 t B 冻结冻结冻结帧 t C 退避帧争用窗口 t D 退避冻结帧争用窗口 t E 退避冻结帧争用窗口 t 退避图例冻结剩余的退避时间

21 CSMA/CD CSMA/CA Binary exponential backoff algorithm Backoff Timer t(i)= {0,1,,2 2+i -1 } For example: 1 st : 0,1,,7,7 slot(s) 2 nd :0,1,,15,15 slot(s) 6 th :0,1,,255,255 slot(s) >6 th :0,1,,255,255 slot(s)

22 CSMA/CD Channel Reservation CSMA/CA DIFS RTS 数据时间源站 SIFS SIFS SIFS 目的站 CTS ACK DIFS 争用窗口时间其他站 NAV(RTS) NAV(CTS) NAV( 数据 ) 时间推迟接入

23 Mac Frame of Format 字节 ~ 帧控制协议版本持续期地址 1 地址 2 地址 3 类型子类型到 DS 从 DS 序号控制地址 4 更多分片重试功率管理更多数据帧主体位 WEP 顺序 FCS

24 Mac Frame of Address 字节 ~ 帧控制协议版本持续期地址 1 地址 2 地址 3 类型子类型到 DS 从 DS 序号控制地址 4 更多分片重试功率管理更多数据帧主体位 WEP 顺序 FCS 到 DS 从 DS 地址 1 地址 2 地址 3 地址目的地址 AP 地址源地址 1 0 AP 地址源地址目的地址

25 Mac Frame of 字节 ~ 帧控制协议版本持续期地址 1 地址 2 地址 3 类型子类型到 DS 从 DS 序号控制地址 4 更多分片重试功率管理更多数据帧主体位 WEP 顺序 FCS Serial control 12+4 bits Serial number 0-15 Fragment number

26 Mac Frame of 字节 ~ 帧控制协议版本持续期地址 1 地址 2 地址 3 类型子类型 Duration Frame control 到 DS 从 DS 序号控制地址 4 更多分片 Protocol Version = 0 Fragment = 0 or 1 WEP = 1 : Encrypted with WEP 重试功率管理更多数据帧主体位 WEP 顺序 FCS

27 Mac Frame of Fragment Why Stop and Wait SIFS 长的帧划分为许多分片源站 RTS 分片 1 分片 2 分片 3 t 目的站 CTS ACK ACK ACK t 其他站 NAV (RTS) NAV (CTS) t

28 WPAN = Wireless Personal Area Network 2.4GHz ISM = Industrial Scientific Medical Bluetooth Low Bit Rate WPAN = Zigbee High Bit Rate WPAN WMAN = Wireless Metropolitan Area Network WiMAX = Worldwide Interoperability for Macrowave Access

29 Bluetooth 1994 IEEE M S Bit rate 720 kb/s P S Range 10m S 皮可网 1S S S P S TDM + FHSS Piconet = Max 1 Master Device + 7 Slave Device More Piconet = Scatternet 扩散网皮可网 M2

30 Bluetooth M S P S S 皮可网 1 扩散网 S 皮可网 M2 Bluetooth 2.0 4Mb/s, 8Mb/s, 12Mb/s Range still 10m S S P S Distributed Protocol = No Master = Everyone could be Master Bluetooth

31 Low Bit Rate WPAN Industrial Area, Office Automation kb/s IEEE Typical: Zigbee

32 ZigBee Characteristics Low Power : Even more than 10 years High Capacity: 255 nodes/zigbee Zigbee,, Max to nodes Low Cost: less than 1/10 of Bluetooth Protocol, free of patents Low Bit Rate: kb/s Low Distance: m 100m Low Delay: 15ms from sleep to work, 30ms access network High Security Free Frequency: ISM

33 ZigBee Protocol IEEE ZigBee 协议栈应用层网络层 MAC 层物理层 ZigBee 联盟定义 IEEE 定义

34 ZigBee Topology Full Function Device: Router Reduced Function Device 端设备 RFD FFD 路由器 FFD FFD 协调器 FFD FFD FFD FFD

35 High Bit Rate WPAN IEEE Mb/s Ultra Wide Band: GHz 10.6GHz Microwave Support Mb/s Transfer Image and DVD multimedia

36 WMAN: Wireless Metropolitan Area Network IEEE The Last Mile Alternative for Cable Broadband

37 WiMAX: : Worldwide Interoperability for Microwave Access WiMAX = WMAN Two Standard: d: 2-66GHz e: 2-6GHz2

38 1 Gb/s 用户数据率 100 Mb/s 10 Mb/s 超宽带 Wi-Fi g, a b WiMAX G 移动通信 1 Mb/s 100 kb/s 10 kb/s 蓝牙 ZigBee 3G 移动通信 2G 移动通信覆盖范围 PAN LAN MAN WAN

WLAN 2

WLAN 2 1 WLAN 2 IEEE 802.11 HomeRF GSM/ GPRS CDMA 3 ( ) (Infrared) (Laser) (Microwave) (DSSS) (FHSS) (HomeRF) (Bluetooth) 4 ( ) IrDA (Direct-Beam IR, DB/ IR) (Diffuse IR, DF/ IR) (Ominidirectional IR, Omini/