Mobile /Wireless Communication What can change for Mobility?

Spring 2008 Instructor: Yuhao Wang

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What is Mobility?

• • A device that moves

– Between different geographical locations – Between different networks

A person who moves

– Between different geographical locations – Between different networks – Between different communication devices – Between different applications 2

Topics in Wireless Communication

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Wireless Communications

– Space-time, OFDM, MIMO – UWB and Impulse Radio – Channel Modeling and Characterization – Modulation/Coding/Signal Processing – B3G Systems, WiMAX and WLAN – Advances in Wireless Video – RFID Technologies – Mobility and Handoff Management 3

Topics in Wireless Communication

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Services and Application

– Wireless/mobile networked Applications – Multimedia in Wireless Ad-hoc Networks – Authentication, Authorization and Billing – Advances in Wireless Video – Location Based Services (LBS) – Applications and Services for B3G/4G era – Radio Resource Management 4

Topics in Wireless Communication

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Networking and Systems

– Wireless sensors networking – Security in wireless networks – Network measurement and Management – Ad hoc and sensor networks – Multimedia QoS and traffic Management – Network protocols for Mobile Networks – Internetworking of WLAN & Cellular Networks 5

Device mobility

• Plug in laptop at home/work on Ethernet – Occasional long breaks in network access – Wired network access only (connected => well-connected) – Network address changes – Only one type of network interface – May want access to information when no network is available: hoard information locally • Cell phone with access to cellular network – Continuous connectivity – Phone # remains the same (high-level network address) – Network performance may vary from place to place 6

Device mobility, continued

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Can we achieve best of both worlds?

– Continuous connectivity of wireless access – Performance of better networks when available

Laptop moves between Ethernet and Wireless LAN

– Wired and wireless network access – Potentially continuous connectivity, but may be breaks in service – Network address changes – Radically different network performance on different networks 7

People mobility

• • •

Phone available at home or at work

– Multiple phone numbers to reach me – Breaks in my reachability when I’m not in

Cell phone

– Only one number to reach me – Continuously reachable – Sometimes poor quality and expensive connectivity

Cell phone, networked PDA, etc.

– Multiple numbers/addresses for best quality connection – Continuous reachability – Best choice of address may depend on sender’s device or message content 8

Mobility means changes

How does it affect the following?

• Hardware – Lighter – More robust – Lower power • Wireless communication – Can’t tune for stationary access • Network protocols – Name changes – Delay changes – Error rate changes 9

Changes, continued

• Fidelity – High fidelity may not be possible • Data consistency – Strong consistency no longer possible • Location/transparency awareness – Transparency not always desirable • Names/addresses – Names of endpoints may change • Security – Lighter-weight algorithms – Endpoint authentication harder – Devices more vulnerable 10

Changes, continued, again

• Performance – Network, CPU all constrained – Delay and delay variability • Operating systems – New resources to track and manage: energy • Applications – Name changes – Changes in connectivity – Changes in quality of resources • People – Introduces new complexities, failures, devices 11

Example changes

• Addresses – Phone numbers, IP addresses • Network performance – Bandwidth, delay, bit error rates, cost, connectivity • Network interfaces – PPP, eth0, strip • Between applications – Different interfaces over phone & laptop • Within applications – Loss of bandwidth triggers change from B&W to color • Available resources – Files, printers, displays, power, even routing 12

Summing up

Generally, mobility stresses all resources further: • CPU • Power • Bandwidth • Delay tolerance • Radio spectrum • Human attention • Physical size • Constraints on peripherals and GUIs (modality of interaction) • Locations (body parts!) for device placement 13

References

• T. S. Rappaport, "Wireless Communications: Principles & Practice," 2nd Ed., Prentice-Hall:Upper Saddle River, NJ, 2002, ISBN 0-13-042232-0. • Jon Mark, Weihua Zhuang, "Wireless Communications and Networking," Prentice Hall. ISBN: 0130409057; 2003. • David Tse, Pramod Viswanath, "Fundamentals of Wireless Communications," Cambridge University Press, 2005. • Harri Holma and Antti Toskala (ed.), ``WCDMA for UMTS : radio access for third generation mobile communications,'' Chichester ; New York : Wiley, c2000.

• John G. Proakis, ``Digital communications,'' 4th ed., Boston : McGraw-Hill, c2001. • . D. Parsons, "The Mobile Radio Propagation Channel," 2nd Edition, Wiley, 2000. • G. L. Stueber, ``Principles of mobile communication,'' 2nd Ed., Norwell, MA: Kluwer, 2001. • http://www.wu.ece.ufl.edu/books/EE/wireless/wireless.html

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