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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

Wireless EthernetIEEE 802.11 StandardOverview

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

what s covered
What’s Covered
  • High level overview of the 802.11 standard
    • Motivation
    • Organization
    • MAC-level protocol
wireless communication infrastructure
Global

Satellite

Suburban

Urban

In-Building

Pico-Cell

Micro-Cell

Macro-Cell

dik

©

Wireless Communication Infrastructure
gsm base stations in europe
GSM Base Stations in Europe

Ericsson RBS 2000

Nokia PrimeSite

wireless network convergence 2g 3g mobility bandwidth trade off
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

umts universal mobile telecomm standard
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.
portable information appliances
Portable Information Appliances

Car Stereo-Phone

Subscriber Identification

Module (SIM)

CDPD

Modem

beneficiaries of ubiquitous computing
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
limitations of the mobile environment
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
heterogeneity of fragmented network infrastructures
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)

frequent disconnections
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
limited communication bandwidth
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.
limitations imposed by mobility
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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