1. Wireless Ethernet IEEE 802.11 Standard Overview Dirk Grunwald Assoc. Professor Dept. of Computer Science University of Colorado, Boulder

2. What’s Covered u High level overview of the 802.11 standard l Motivation l Organization l MAC-level protocol

3. Wireless Communication Infrastructure Satellite Macro-Cell Micro-Cell Urban In-Building Pico-Cell Global Suburban dik ©

4. GSM Base Stations in Europe Nokia PrimeSite Ericsson RBS 2000

5. Wireless Network Convergence 2G/3G Mobility-Bandwidth Trade-off Mobility Bandwidth 10K 100K 1M 10M 100M 1G Room GlobalGSM D-AMPS/IS-95 DECT WLAN UMTS National Regional Metropolitan Campus Office 1-7 GHz 0.1-2 GHz 0.1-2.3 GHz 2-4 GHz 2-7 GHz >2 GHz 20-50 GHz

6. UMTS: Universal Mobile Telecomm. Standard u Global seamless operation in multi-cell environment (SAT, macro, micro, pico) u Global roaming: multi-mode, multi-band, low-cost terminal, portable services & QoS u High data rates at different mobile speeds: 144kbps at vehicular speed (80km/h), 384 kbps at pedestrian speed, and 2Mbps indoor (office/home) u Multimedia interface to the internet u Based on core GSM, conforms to IMT-2000. Deployment as early as 2002.

7. Portable Information Appliances Subscriber Identification Module (SIM) CDPD Modem Car Stereo-Phone

8. Beneficiaries of Ubiquitous Computing Commuters Travelers Stock traders Medical Law enforcement Package delivery Education Insurance Emergency Trucking Intelligence Military Clients Adhoc network Servers Intranet Internet

9. 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

10. Heterogeneity of Fragmented Network Infrastructures Randy Katz’ heterogeneous network overlay vision (also: DARPA’s GloMo) Satellite Macro-Cell Micro-Cell Urban In-Building Pico-Cell Global Suburban dik ©

11. Frequent Disconnections u Handoff blank out (>1ms for most cellulars) u Drained battery disconnection u Battery recharge down time u Voluntary disconnection (turned off to preserve battery power, also off overnight) u Theft and damage (hostile environment) u Roam-off disconnections

12. Limited Communication Bandwidth u Orders of magnitude slower than fixed network u Higher transmission bit error rates (BER) u Uncontrolled cell population u Difficult to ensure Quality of Service (QoS) u Asymmetric duplex bandwidth u Limited communication bandwidth exacerbates the limitation of battery lifetime.

13. Limitations Imposed by Mobility u Lack of mobility-awareness by applications l inherently transparent programming model (object-, components-oriented, but not aspect-oriented) l lack of environment test and set API support u Lack of mobility-awareness by the system l network: existing transport protocols are inefficient to use across heterogeneous mix of fixed/wireless networks l session and presentation: inappropriate for the wireless environment and for mobility l operating systems: lack of env. related conditions and signals l client/server: unless changed, inappropriate and inefficient