Wireless Ethernet IEEE 802.11 Standard Overview - PowerPoint PPT Presentation

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Wireless Ethernet IEEE 802.11 Standard Overview. Dirk Grunwald Assoc. Professor Dept. of Computer Science University of Colorado, Boulder. What’s Covered. High level overview of the 802.11 standard Motivation Organization MAC-level protocol. Global. Satellite. Suburban. Urban.

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Wireless Ethernet IEEE 802.11 Standard Overview

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Wireless ethernet ieee 802 11 standard overview l.jpg

Wireless EthernetIEEE 802.11 StandardOverview

Dirk GrunwaldAssoc. ProfessorDept. of Computer ScienceUniversity of Colorado, Boulder


What s covered l.jpg

What’s Covered

  • High level overview of the 802.11 standard

    • Motivation

    • Organization

    • MAC-level protocol


Wireless communication infrastructure l.jpg

Global

Satellite

Suburban

Urban

In-Building

Pico-Cell

Micro-Cell

Macro-Cell

dik

©

Wireless Communication Infrastructure


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GSM Base Stations in Europe

Ericsson RBS 2000

Nokia PrimeSite


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Wireless Network Convergence2G/3G Mobility-Bandwidth Trade-off

1-7 GHz

0.1-2 GHz

0.1-2.3 GHz

2-4 GHz

2-7 GHz

>2 GHz

20-50 GHz

Global

GSM

UMTS

D-AMPS/IS-95

Mobility

National

Regional

Metropolitan

Campus

DECT

DECT

Office

WLAN

Room

DECT

10K 100K 1M 10M 100M 1G

Bandwidth


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UMTS: Universal Mobile Telecomm. Standard

  • Global seamless operation in multi-cell environment (SAT, macro, micro, pico)

  • Global roaming: multi-mode, multi-band, low-cost terminal, portable services & QoS

  • High data rates at different mobile speeds: 144kbps at vehicular speed (80km/h), 384 kbps at pedestrian speed, and 2Mbps indoor (office/home)

  • Multimedia interface to the internet

  • Based on core GSM, conforms to IMT-2000. Deployment as early as 2002.


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Portable Information Appliances

Car Stereo-Phone

Subscriber Identification

Module (SIM)

CDPD

Modem


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Internet

  • Commuters

  • Travelers

  • Stock traders

  • Medical

  • Law enforcement

  • Package delivery

  • Education

  • Insurance

  • Emergency

  • Trucking

  • Intelligence

  • Military

Intranet

Adhoc network

Clients

Servers

Beneficiaries of Ubiquitous Computing


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Limitations of the Mobile Environment

  • Limitations of the Wireless Network

    • heterogeneity of fragmented networks

    • frequent disconnections

    • limited communication bandwidth

  • Limitations Imposed by Mobility

  • Limitations of the Mobile Computer


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Global

Satellite

Suburban

Urban

In-Building

Pico-Cell

Micro-Cell

Macro-Cell

dik

©

Heterogeneity of Fragmented Network Infrastructures

Randy Katz’ heterogeneous

network overlay vision

(also: DARPA’s GloMo)


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Frequent Disconnections

  • Handoff blank out (>1ms for most cellulars)

  • Drained battery disconnection

  • Battery recharge down time

  • Voluntary disconnection (turned off to preserve battery power, also off overnight)

  • Theft and damage (hostile environment)

  • Roam-off disconnections


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Limited Communication Bandwidth

  • Orders of magnitude slower than fixed network

  • Higher transmission bit error rates (BER)

  • Uncontrolled cell population

  • Difficult to ensure Quality of Service (QoS)

  • Asymmetric duplex bandwidth

  • Limited communication bandwidth exacerbates the limitation of battery lifetime.


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Limitations Imposed by Mobility

  • Lack of mobility-awareness by applications

    • inherently transparent programming model (object-, components-oriented, but not aspect-oriented)

    • lack of environment test and set API support

  • Lack of mobility-awareness by the system

    • network: existing transport protocols are inefficient to use across heterogeneous mix of fixed/wireless networks

    • session and presentation: inappropriate for the wireless environment and for mobility

    • operating systems: lack of env. related conditions and signals

    • client/server: unless changed, inappropriate and inefficient


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