Mobile and Wireless Networks and Applications: Introduction/Overview

1
Mobile and Wireless Networks and
ApplicationsIntroduction/Overview

• CS 444N, Spring 2002
• Instructor Mary Baker

2
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

3
Device mobility

• Plug in laptop at home/work on Ethernet
• Occasional long breaks in network access
• Wired network access only (connected gt
  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

4
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, WaveLAN and
  Metricom networks
• Wired and wireless network access
• Potentially continuous connectivity, but may be
  breaks in service
• Network address changes
• Radically different network performance on
  different networks

5
People mobility

• Phone available at home or at work
• Multiple phone numbers to reach me
• Breaks in my reachability when Im 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 senders
  device or message content

6
Mobility means changes

• How does it affect the following?
• Hardware
• Lighter
• More robust
• Lower power
• Wireless communication
• Cant tune for stationary access
• Network protocols
• Name changes
• Delay changes
• Error rate changes

7
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

8
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

9
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 color to
  BW
• Available resources
• Files, printers, displays, power, even routing

10
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