Transcript 第2讲无线通信与网络
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 1 Mobile Computing Architecture Server MU (mobile unit) MSS Fixed network (mobile support station) Wireless radio cell (19.2Kbps) WLAN 2 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 … 3 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 4 无线个域网 红外技术 蓝牙技术 UWB ZigBee NFC 5 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. 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. Bluetooth Network Topology Pico-net • 1 master: • 7 active slaves • 200+ parked slaves • Each network has a unique hopping pattern / ID A P M P P A P P M A A Radio Design All radios are symmetric (can be master or slave) Scatternet • Multiple pico-nets co-located • Device can be on multiple piconets (Performance tradeoff) 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) 9 ZigBee Network Topology 10 UWB（超宽带） IEEE 802.15.3 Short distance: 2m-10m, Very low power consumption Narrowband Ultrawideband Impulse based waveforms (simple) Time-domain behavior 1 Frequency-domain behavior 1 0 time 3 frequency 10 GHz (FCC Min=500Mhz) 0 1 0 1 2.4 GHz 11 Near Field Communication (NFC) Very simple wireless communication setup Very small distance (<20cm) Low data rate (~400k) Similar to Infrared (using RF instead) 12 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） 红外 NFC 蓝牙 ZigBee WiFi UWB 传输速率 115kbps 424kbps 1-3Mkbps 20250kbps >150Mbps 1Mbps 传输距离 5m 10cm 10-100m 100-300m >100m 100m 频段 / 13.5G 2.45G 2.45G 2.45G、5G 2.45G 通信协议 IrDA ISO18092 … IEEE802.1 5.1 IEEE802.1 5.4 IEEE802.1 1 IEEE802.1 5.3 功耗 低 很低 低 低 低 低 安全性 高 高 中 中 中 高 成本 低 低 高 中 高 中 方便性 高 高 中 中 中 中 13 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. 14 网络协议与标准 protoc Release Freq. Bandwidth Data rate (Mbps) ol (GHz) (MHz) Modul Approx. range (m) ation indoor outdoor — DSSS, 20 FHSS OFDM 35 — 100 DSSS 38 140 OFDM, 38 DSSS 7.2, 14.4, 21.7, 28.9, 43.3, OFDM 70 57.8, 65, 72.2 140 15, 30, 45, 60, 90, 120, 135, 150[B] 433, 867 867, 1.73 Gbit/s, 3.47 Gbit/s, 6.93 Gbit/s 250 a b g n Jun 1997 Sep 1999 2.4 20 1, 2 5 3.7 20 6, 9, 12, 18, 24, 36, 48, 54 Sep 1999 Jun 2003 Oct 2009 2.4 20 5.5, 11 2.4 20 6, 9, 12, 18, 24, 36, 48, 54 2.4/5 20 40 ac Nov. (draft) 2011 5 80 160 70 120 5,000 250 15 网络拓扑 Infrastructure networks Access point + mobile station Medium access: wired network AP 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) BSS (Basic Service Set) 802.11 - Architecture of an infrastructure 802.11 LAN BSS1 802.x LAN STA1 Portal AP Distribution System AP ESS Extended Service Set STA2 BSS2 802.11 LAN STA3 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 802.11 - Architecture of an ad-hoc network Direct communication within a limited range 802.11 LAN STA1 STA3 IBSS STA2 Station (STA): terminal with access mechanisms to the wireless medium Independent Basic Service Set (IBSS): group of stations using the same radio frequency 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 移动自组网（MANET） Mobile Ad hoc NETworks Multi-hop wireless links Peer-to-peer forwarding 802.11based, usually 21 无线传感器网络（WSN） Wireless Sensor Networks Monitoring Ad hoc configuration ZigBee, 802.11… 22 无线Mesh网（WMN） Wireless Mesh Network Hierarchical, ad hoc backbone Extension of WLAN 802.11, 802.11s 23 车载网VANET Vehicular Ad-Hoc Network Hybrid networks V2V, V2I 802.11p, 3G, etc. 24 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. 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 26 3G Technology WCDMA、CDMA2000、TD-SCDMA 2 Mbps, stationary;384 kbps, walking;144 kbps driving. Multimedia (music / game playing), Internet 27 Example of UMTS 3G Network 28 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. Wireless Communications Technology Name 1G AMPS 2G D-AMPS/ GSM/ CDMA 2.5G 3G CDPD/ WCDMA/ EDGE/ GPRS CDMA-2000 4G MC-CDMA/ OFDMA TBD Format Analog Digital Digital Digital Digital Bandwidth 30 kHz (for voice) 8 – 23 kbps 19.2 – 384 kbps 144 kbps – 2 Mbps 50 – 100 Mbps Feature Large cells, small number of calls per cell Most commonly used Based on 2G to deliver also data packets High quality Ubiquitous services, connection great variety uses IPv6 of services 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. 移动终端 Mobile terminal/mobile client/mobile station/mobile node… Laptop, SmartPhone, Tablet, PDA, Netbook, sensor node, vehicle, ... 32 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 33 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 34 Characteristics/Challenges Resource constraints Bandwidth, power, memory, CPU power, etc… Failures Link breakage (interference, mobility) Node failures Mobility Openess … 35 Summary Various wireless networks Flat vs. hierarchical Ad hoc vs. infrastructure Various mobile devices Handheld, laptop, vehicle… 36 Review Questions 1. 辨析WLAN、IEEE 802.11与WiFi三个概念的关系 2. 什么是LTE？ 37