414Lecture21

414Lecture21 - Lecture 21 Link Layer 802.11, CDMA, Analog...

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Lecture 21 Link Layer 802.11, CDMA, Analog vs. Digital Transmission, Line Coding ECSE 414 – Fall 2010
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ECSE 414, Lecture 21 2 Announcements Homework Assignment #5 Due Thursday, November 23 Project Presentations During usual class time Starting Thursday, November 25 2010 Michael Rabbat
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ECSE 414, Lecture 21 3 Characteristics of selected wireless link standards Indoor 10-30m Outdoor 50-200m Mid-range outdoor 200m – 4 Km Long-range outdoor 5Km – 20 Km .056 .384 1 4 5-11 54 IS-95, CDMA, GSM 2G UMTS/WCDMA, CDMA2000 3G 802.15 802.11b 802.11a,g UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO 3G cellular enhanced 802.16 (WiMAX) 802.11a,g point-to-point 200 802.11n Data rate (Mbps) data 2010 Michael Rabbat
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ECSE 414, Lecture 21 4 Wireless network characteristics Multiple wireless senders and receivers create additional problems (beyond multiple access): A B C Hidden terminal problem B, A hear each other B, C hear each other A, C can not hear each other means A, C unaware of their interference at B A B C A’s signal strength space C’s signal strength Signal attenuation: B, A hear each other B, C hear each other A, C can not hear each other interfering at B 2010 Michael Rabbat
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ECSE 414, Lecture 21 5 IEEE 802.11 Wireless LAN 802.11b 2.4 GHz unlicensed spectrum up to 11 Mbps direct sequence spread spectrum (DSSS) in physical layer all hosts use same chipping code 802.11a 5-6 GHz range up to 54 Mbps 802.11g 2.4 GHz range up to 54 Mbps 802.11n: multiple antennae 5 & 2.4 GHz ranges up to 300 Mbps all use CSMA/CA for multiple access all have base-station and ad-hoc network versions 2010 Michael Rabbat
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ECSE 414, Lecture 21 6 802.11 LAN architecture wireless host communicates with base station base station = access point (AP) Basic Service Set (BSS) (aka “cell”) in infrastructure mode contains: wireless hosts access point (AP): base station ad hoc mode: hosts only BSS 1 BSS 2 Internet hub, switch or router AP AP 2010 Michael Rabbat
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ECSE 414, Lecture 21 7 802.11: Channels, association 802.11b: 2.4GHz-2.485GHz spectrum divided into 11 channels at different frequencies AP admin chooses frequency for AP interference possible: channel can be same as that chosen by neighboring AP! host: must associate with an AP scans channels, listening for beacon frames containing AP’s name (SSID) and MAC address selects AP to associate with may perform authentication [Chapter 8] will typically run DHCP to get IP address in AP’s subnet 2010 Michael Rabbat
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ECSE 414, Lecture 21 8 802.11: passive/active scanning AP 2 AP 1 H1
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This note was uploaded on 05/09/2011 for the course ECSE 414 taught by Professor Rabbat during the Fall '10 term at McGill.

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414Lecture21 - Lecture 21 Link Layer 802.11, CDMA, Analog...

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