《计算机网络 Computer Networking》课程教学资源（PPT课件讲稿，英文版）Chapter 6 Wireless and Mobile Networks

Lecture 2 Fundamentals of Wireless and mobile computer Networks networking James F Kur Keith W. Ross A note on the use of these ppt slides Were making these slides freely available to all (faculty, students, readers) They re in PowerPoint form so you can add, modify and delete slides Computer Networking (including this one)and slide content to suit your needs. They obviously represent a lot of work on our part. In retum for use, we only ask the A Top Down Approach following Featuring the Internet O if you use these slides(e.g, in a class) in substantially unaltered form, 3rd edition that you mention their source(after all, we'd like people to use our book! O if you post any slides in substantially unaltered form on a w site, that Jim Kurose, Keith Ross you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this materi Addison-Wesley, July 2004. Thanks and enjoy! JFK/KWR All material copyright 1996-2006 J F Kurose and K.W. ross, All Rights reserved 6: Wireless and Mobile Networks 6-1

6: Wireless and Mobile Networks 6-1 Lecture 2 Fundamentals of Wireless and Mobile Networks Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2004. A note on the use of these ppt slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: ❑ If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!) ❑ If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Thanks and enjoy! JFK/KWR All material copyright 1996-2006 J.F Kurose and K.W. Ross, All Rights Reserved

Wireless and Mobile Networks Background: D# wireless(mobile) phone subscribers now exceeds #f wired phone subscribers D computer nets: laptops, palmtops, PDAs Internet-enabled phone promise anytime untethered Internet access o two important(but different)challenges o communication over wireless link o handling mobile user who changes point of attachment to network 6: Wireless and Mobile Networks 6-2

6: Wireless and Mobile Networks 6-2 Wireless and Mobile Networks Background:  # wireless (mobile) phone subscribers now exceeds # wired phone subscribers!  computer nets: laptops, palmtops, PDAs, Internet-enabled phone promise anytime untethered Internet access  two important (but different) challenges  communication over wireless link  handling mobile user who changes point of attachment to network

Chapter 6 outline 6.1 Introduction Mobility 口65 Principles: Wireless addressing and routing 06.2 Wireless links to mobile users characteristics 066 Mobile ip O CDMA 06.7 Handling mobility in 6.3IEEE802.11 cellular networks wireless LANscwi-fi")D6.8 Mobility and higher 06.4 Cellular Internet yer proToco ls Access o architecture 6.9 Summary o standards(e.g, GSM) 6: Wireless and Mobile Networks 6-3

6: Wireless and Mobile Networks 6-3 Chapter 6 outline 6.1 Introduction Wireless  6.2 Wireless links, characteristics  CDMA  6.3 IEEE 802.11 wireless LANs (“wi-fi”)  6.4 Cellular Internet Access  architecture  standards (e.g., GSM) Mobility  6.5 Principles: addressing and routing to mobile users  6.6 Mobile IP  6.7 Handling mobility in cellular networks  6.8 Mobility and higher￾layer protocols 6.9 Summary

Elements of a wireless network wireless hosts o laptop, PDA, IP phone 口 run applications o may be stationary (non-mobile or mobile network o wireless does not infrastructure always mean mobility 6: Wireless and Mobile Networks 6-4

6: Wireless and Mobile Networks 6-4 Elements of a wireless network network infrastructure wireless hosts  laptop, PDA, IP phone  run applications  may be stationary (non-mobile) or mobile  wireless does not always mean mobility

Elements of a wireless network base station typically connected t wired network elay-responsible for sending packets between wired network network and wireless infrastructure host(s in its"area o e.g., cell towers 802.11 access oints 6: Wireless and mobile ks6-5

6: Wireless and Mobile Networks 6-5 Elements of a wireless network network infrastructure base station  typically connected to wired network  relay - responsible for sending packets between wired network and wireless host(s) in its “area”  e.g., cell towers 802.11 access points

Elements of a wireless network wireless link 口 typically used to connect mobile(s)to base station d also used as backbone link network o multiple access infrastructure protocol coordinates ink access various data rates transmission distance 6: Wireless and Mobile Networks 6-6

6: Wireless and Mobile Networks 6-6 Elements of a wireless network network infrastructure wireless link  typically used to connect mobile(s) to base station  also used as backbone link  multiple access protocol coordinates link access  various data rates, transmission distance

Characteristics of selected wireless link standards 54 Mbps 802.11(a,g 5-11 Mbps 802.11b 11 p-to-p link 1 Mbps 802.15 3G 384 Kbps UMTS/CDMA CDMA2000 56 Kbps IS-95 CDMA GSM 2G Indoor Outdoor Mid range Long range outdoor outdoor 10-30m 50-200m 200m-4Km 5Km-20Km 6: Wireless and Mobile Networks 6-7

6: Wireless and Mobile Networks 6-7 Characteristics of selected wireless link standards 384 Kbps 56 Kbps 54 Mbps 5-11 Mbps 1 Mbps 802.15 802.11b 802.11{a,g} IS-95 CDMA, GSM UMTS/WCDMA, CDMA2000 .11 p-to-p link 2G 3G Indoor 10 – 30m Outdoor 50 – 200m Mid range outdoor 200m – 4Km Long range outdoor 5Km – 20Km

Elements of a wireless network infrastructure mode o base station connects mobiles into wired network g handoff: mobile changes base station network providing connection infrastructure into wired network 6: Wireless and Mobile Networks 6-8

6: Wireless and Mobile Networks 6-8 Elements of a wireless network network infrastructure infrastructure mode  base station connects mobiles into wired network  handoff: mobile changes base station providing connection into wired network

Elements of a wireless network Ad hoc mode g no base stations 口 nodes can only transmit to other nodes within ink coverage g nodes organize themselves into a network: route among themselves 6: Wireless and mobile ks6-9

6: Wireless and Mobile Networks 6-9 Elements of a wireless network Ad hoc mode  no base stations  nodes can only transmit to other nodes within link coverage  nodes organize themselves into a network: route among themselves

Wireless Link Characteristics Differences from wired link o decreased signal strength: radio signal attenuates as it propagates through matter (path loss o interference from other sources: standardized wireless network frequencies(e. g, 2.4 GHz) shared by other devices (e.g, phone ) devices motors)interfere as well o multipath propagation: radio signal reflects off objects ground, arriving ad destination at slightly different times make communication across ( even a point to point) wireless link much more"difficult 6: Wireless and Mobile Networks 6-10

6: Wireless and Mobile Networks 6-10 Wireless Link Characteristics Differences from wired link ….  decreased signal strength: radio signal attenuates as it propagates through matter (path loss)  interference from other sources: standardized wireless network frequencies (e.g., 2.4 GHz) shared by other devices (e.g., phone); devices (motors) interfere as well  multipath propagation: radio signal reflects off objects ground, arriving ad destination at slightly different times …. make communication across (even a point to point) wireless link much more “difficult