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第 2 讲 无线网络与移动终端

第 2 讲 无线网络与移动终端. §2.1 无线通信与网络 §2.2 移动终端及接入. Mobile Computing Architecture. Server. MU (mobile unit). Fixed network. MSS (mobile support station). Wireless radio cell (19.2Kbps). WLAN. 无线通信技术. 调制解调技术 DSSS FHSS OFDM 无线接入技术 CSMA/CA ALOHA TDMA CDMA OFDMA …. 无线网络. P31 图

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第 2 讲 无线网络与移动终端

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  1. 第2讲 无线网络与移动终端 §2.1 无线通信与网络 §2.2 移动终端及接入

  2. Mobile Computing Architecture Server MU (mobile unit) Fixed network MSS (mobile support station) Wireless radio cell (19.2Kbps) WLAN

  3. 无线通信技术 • 调制解调技术 • DSSS • FHSS • OFDM • 无线接入技术 • CSMA/CA • ALOHA • TDMA • CDMA • OFDMA • …

  4. 无线网络 P31图 无线个域网 无线局域网络 无线城域网 无线广域网 卫星通信网络

  5. 无线个域网 红外技术 蓝牙技术 UWB ZigBee NFC

  6. 红外通信技术 • Low cost and not interfered by radio signal. • Can connect up to 2 miles with line-of-sight. • There are two standards: IrDA and 802.11 IR. • IrDA (Infrared Data Association) compatible: • Use regular Infrared. • Data rate from 9.6 kbps to 4 Mbps. • Must follow the IrDA specification. • Wireless Ethernet 802.11 IR: • Use diffused Infrared, without line-of-sight. • Can connect to LAN. • Standard not updated for a while. • Signal can be swamped by sunlight. • Bandwidth is still limited.

  7. Bluetooth • Also defined as 802.15b. • Variation 802.15c at higher data rate and 802.15d consuming little power. • Connect devices up to a distance of 10m. • Use master/slave design, known as a piconet. • Built upon scattered net with many piconets. • Support up to 7 active slaves, and 255 in total. • Support 13 specific applications, including service discovery, LAN access and FTP. • Bandwidth 1 to 10 Mbps. • Low power consumption. • Higher cost than infrared, but low cost compared with wireless LAN.

  8. A P M M P P A P A P A • Scatternet • Multiple pico-nets co-located • Device can be on multiple pico-nets (Performance tradeoff) Bluetooth Network Topology • Radio Design • All radios are symmetric (can be master or slave) • Pico-net • 1 master: • 7 active slaves • 200+ parked slaves • Each network has a unique hopping pattern / ID

  9. ZigBee • IEEE 802.15.4, brother of Bluetooth • Low cost, low power consumption • High node density, long range • Low data rate • Mainly used for • Human Input Devices • Remote controller • Mouse, keyboard… • Sensors (WSN)

  10. ZigBee Network Topology

  11. Time-domain behavior Frequency-domain behavior 1 1 0 Ultrawideband frequency time 3 10 GHz (FCC Min=500Mhz) 1 0 1 0 Narrowband 2.4 GHz UWB（超宽带） IEEE 802.15.3 Short distance: 2m-10m, Very low power consumption Impulse based waveforms (simple)

  12. Near Field Communication (NFC) Very simple wireless communication setup Very small distance (<20cm) Low data rate (~400k) Similar to Infrared (using RF instead)

  13. 比较 NFC:消费支付；红外：设备控制；蓝牙：设备通信互联； ZigBee：大量节点（WSN）

  14. 无线局域网（WLAN） Most common variant is 802.11n, with data rate up to 150Mbps. Alternative version 802.11a/b/g. Compatible with Ethernet using access point. Can also support ad hoc networking. High bandwidth. Initially high cost, but now becomes very affordable.

  15. 网络协议与标准

  16. 网络拓扑 • Infrastructure networks • Access point + mobile station • Medium access: • collision: wireless nodes and AP are not coordinated • collision free: AP controls medium access • Ad-hoc (peer-to-peer) networks • medium access: collision • wireless node may transfer data (router) wired network AP BSS (Basic Service Set)

  17. Distribution System 802.11 - Architecture of an infrastructure 802.11 LAN 802.x LAN BSS1 STA1 Portal AP ESS AP Extended Service Set STA3 BSS2 STA2 802.11 LAN

  18. 802.11 - Architecture of an infrastructure • Station (STA) • terminal with access mechanisms to the wireless medium and radio contact to the access point • Basic Service Set (BSS) • group of stations using the same radio frequency • Access Point • station integrated into the wireless LAN and the distribution system • Portal • bridge to other (wired) networks • Distribution System • interconnection network to form one logical network (EES: Extended Service Set) based on several BSS

  19. 802.11 - Architecture of an ad-hoc network • Direct communication within a limited range • Station (STA):terminal with access mechanisms to the wireless medium • Independent Basic Service Set (IBSS):group of stations using the same radio frequency 802.11 LAN STA1 STA3 IBSS STA2

  20. IEEE standard 802.11 mobile terminal infrastructure network access point Fixed terminal Application Application TCP TCP IP IP LLC LLC LLC 802.3 MAC 802.11 MAC 802.3 MAC 802.3 MAC 802.3 PHY 802.11 PHY 802.3 PHY 802.3 PHY

  21. 移动自组网（MANET） Mobile Ad hoc NETworks Multi-hop wireless links Peer-to-peer forwarding 802.11based, usually

  22. 无线传感器网络（WSN） Wireless Sensor Networks Monitoring Ad hoc configuration ZigBee, 802.11…

  23. 无线Mesh网（WMN） Wireless Mesh Network Hierarchical, ad hoc backbone Extension of WLAN 802.11, 802.11s

  24. 车载网VANET Vehicular Ad-Hoc Network Hybrid networks V2V, V2I 802.11p, 3G, etc.

  25. 无线城域网（Wireless MAN) • WiMAX (Worldwide Interoperability for Microwave Access) • Also called broadband wireless network. • Standard 802.16. • Assume service delivery to buildings which will not move. • Due to signal attenuation, different modulation schemes give different baud rates and hence bandwidths to clients at different distance. • All services are connection-oriented. • Constant bit rate service. • Real-time variable bit rate service. • Non-real-time variable bit rate service. • Best-efforts service. • Very high aggregate bandwidth. • High bandwidth to each subscriber.

  26. 无线广域网 • 蜂窝通信网络 • Base station + mobile terminal • 1G: AMPS • analog access • 2G: GSM、CDMA • digital access • 2.5G：CPCD、EDGE、GPRS

  27. 3G Technology WCDMA、CDMA2000、TD-SCDMA 2 Mbps, stationary;384 kbps, walking;144 kbps driving. Multimedia (music / game playing), Internet

  28. Example of UMTS 3G Network

  29. 4G technology • LTE Advanced and/or IEEE 802.16m ? • Wireless broadband infrastructure to support multimedia information society. • Entirely packet switched networks. • All digital network elements. • Expectation include • High bandwidth of 50 - 100 Mbps. • Low system cost. • Ubiquitous connection. • Seamless integration with wired network and the support of IPv6. • Adaptive resource and spectrum management with proper QoS. • Software radio. • High quality multimedia.

  30. Wireless Communications

  31. 卫星通信网络 • Act as transponder for signal and data transfer. • Geostationary Earth Orbit (GEO) • Satellite at stationary position. • Long delay. • High energy consumption. • Low Earth Orbit (LEO) • Satellite at lower orbit. • Lower energy consumption, but frequent change of satellite.

  32. 移动终端 Mobile terminal/mobile client/mobile station/mobile node… Laptop, SmartPhone, Tablet, PDA, Netbook, sensor node, vehicle, ...

  33. 移动终端系统 • Mobile phone / tablet • Android • IOS • WinPhone • Symbian • Bada • OPhone • Others • TinyOS：sensor • Linux： router、notebook • Windows： notebook • OS X： notebook

  34. 移动Internet接入 • 基于Cellular网络 vs. 基于Ethernet • 网络协议的改进 • 网络层、传输层 • 应用层 • WAP：Open Mobile Alliance • iMode：日本DoCoMo公司

  35. Characteristics/Challenges • Resource constraints • Bandwidth, power, memory, CPU power, etc… • Failures • Link breakage (interference, mobility) • Node failures • Mobility • Openess • …

  36. Summary • Various wireless networks • Flat vs. hierarchical • Ad hoc vs. infrastructure • Various mobile devices • Handheld, laptop, vehicle…

  37. Review Questions 辨析WLAN、IEEE 802.11与WiFi三个概念的关系 什么是LTE？

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