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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
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Mobile Computing Architecture
Server
MU(mobile unit)
MSS(mobile support
station)
Fixed network
Wireless radio cell (19.2Kbps) WLAN
无线通信技术
调制解调技术DSSSFHSSOFDM
无线接入技术CSMA/CA ALOHATDMACDMAOFDMA…
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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
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无线个域网 红外技术 蓝牙技术 UWB ZigBee NFC
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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
Radio DesignAll 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
M
A
P
P
P
Scatternet• Multiple pico-nets co-located• Device can be on multiple pico-
nets (Performance tradeoff)
M
A
A
A
P
P
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)
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ZigBee Network Topology
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UWB (超宽带) IEEE 802.15.3 Short distance: 2m-10m, Very low power consumption Impulse based waveforms (simple)
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2.4 GHz
Narr
ow
ban
dN
arr
ow
ban
d
0 1 0 1
3 10 GHzfrequency
Ult
raw
ideb
an
dU
ltra
wid
eb
an
d Time-domain behavior Frequency-domain behavior
time
1 0 1
(FCC Min=500Mhz)
Near Field Communication (NFC)
Very simple wireless communication setup Very small distance (<20cm) Low data rate (~400k) Similar to Infrared (using RF instead)
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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 )
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红外 NFC 蓝牙 ZigBee WiFi UWB
传输速率 115kbps 424kbps 1-3Mkbps 20-250kbps
>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…
IEEE802.15.1
IEEE802.15.4
IEEE802.11
IEEE802.15.3
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
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.
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网络协议与标准
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protocol
Release Freq.(GHz)
Bandwidth (MHz)
Data rate (Mbps) Modulation
Approx. range (m)indoor outdoor
— Jun 1997
2.4 20 1, 2 DSSS, FHSS
20 100
a Sep 1999
5 20 6, 9, 12, 18, 24, 36, 48, 54 OFDM 35 1203.7 — 5,000
b Sep 1999
2.4 20 5.5, 11 DSSS 38 140
g Jun 2003
2.4 20 6, 9, 12, 18, 24, 36, 48, 54 OFDM, DSSS
38 140
n Oct 2009
2.4/5 20 7.2, 14.4, 21.7, 28.9, 43.3, 57.8, 65, 72.2
OFDM 70 250
40 15, 30, 45, 60, 90, 120, 135, 150[B]
70 250
ac (draft)
Nov. 2011
5 80 433, 867160 867, 1.73 Gbit/s, 3.47 Gbit/s,
6.93 Gbit/s
Infrastructure networksAccess 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)
网络拓扑
BSS (Basic Service Set)
AP
wired network
802.11 - Architecture of an infrastructure
Distribution System
802.x LAN
802.11 LAN
BSS2
802.11 LAN
BSS1 STA1
STA2
STA3
ESSExtended Service Set
AP Portal
AP
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 Pointstation integrated into the wireless LAN and the distribution system
Portalbridge to other (wired) networks
Distribution Systeminterconnection network to form one logical network (EES: Extended Service Set) based on several BSS
802.11 - Architecture of an infrastructure
802.11 - Architecture of an ad-hoc network
802.11 LAN
IBSS
STA1
STA2
STA3
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
IEEE standard 802.11
mobile terminal
access point Fixed terminal
infrastructurenetwork
802.11 PHY 802.3 PHY
802.11 MAC 802.3 MAC
LLC
802.3 PHY
802.3 MAC
LLC
IP
TCP
Application
802.3 PHY
802.3 MAC
LLC
IP
TCP
Application
移动自组网( MANET ) Mobile Ad hoc NETworks Multi-hop wireless links Peer-to-peer forwarding 802.11based, usually
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无线传感器网络( WSN ) Wireless Sensor Networks Monitoring Ad hoc configuration ZigBee, 802.11…
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无线 Mesh 网( WMN ) Wireless Mesh Network Hierarchical, ad hoc backbone Extension of WLAN 802.11, 802.11s
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车载网 VANET
Vehicular Ad-Hoc Network Hybrid networks V2V, V2I 802.11p, 3G, etc.
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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 、 CDMAdigital access
2.5G : CPCD 、 EDGE 、 GPRS
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3G Technology
WCDMA 、 CDMA2000 、 TD-SCDMA 2 Mbps, stationary;384 kbps, walking;144 kbps
driving. Multimedia (music / game playing), Internet
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Example of UMTS 3G Network
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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
1G 2G 2.5G 3G 4G
Name AMPS D-AMPS/ GSM/ CDMA
CDPD/ EDGE/ GPRS
WCDMA/ CDMA-2000
MC-CDMA/ OFDMATBD
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 services, great variety of services
Ubiquitous connection uses IPv6
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, ...
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移动终端系统 Mobile phone / tablet
AndroidIOSWinPhoneSymbian BadaOPhone
OthersTinyOS : sensorLinux : router 、 notebookWindows : notebookOS X : notebook
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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
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Characteristics/Challenges
Resource constraintsBandwidth, power, memory, CPU power, etc…
FailuresLink breakage (interference, mobility)
Node failures Mobility Openess …
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Summary
Various wireless networksFlat vs. hierarchical
Ad hoc vs. infrastructure Various mobile devices
Handheld, laptop, vehicle…
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Review Questions
1. 辨析 WLAN 、 IEEE 802.11 与 WiFi 三个概念的关系
2. 什么是 LTE ?
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