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Mobile /Wireless CommunicationWhat 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

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Topics in Wireless Communication

• 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

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Topics in Wireless Communication

• 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

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Topics in Wireless Communication

• 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

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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

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Device mobility, continued• 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

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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

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Mobility means changesHow 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

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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

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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

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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

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Summing upGenerally, 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

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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