managing chaotic wireless networks
Download
Skip this Video
Download Presentation
Managing Chaotic Wireless Networks

Loading in 2 Seconds...

play fullscreen
1 / 17

Managing Chaotic Wireless Networks - PowerPoint PPT Presentation


  • 76 Views
  • Uploaded on

Managing Chaotic Wireless Networks. David Wetherall University of Washington. Credits. UW/CSE wireless group John Zahorjan, Maya Rodrig, Charlie Reis, Ratul Mahajan, Ed Lazowska Intel Research Seattle Yatin Chawathe, Mike Chen, Brian Noble, Anthony Nicholson CMU

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Managing Chaotic Wireless Networks' - wan


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
managing chaotic wireless networks

Managing Chaotic Wireless Networks

David Wetherall

University of Washington

credits
Credits
  • UW/CSE wireless group
    • John Zahorjan, Maya Rodrig, Charlie Reis, Ratul Mahajan, Ed Lazowska
  • Intel Research Seattle
    • Yatin Chawathe, Mike Chen, Brian Noble, Anthony Nicholson
  • CMU
    • Srini Seshan et. al. for “Chaotic” wireless
context wifi boom
Context: WiFi boom

deployments

  • Advantages: minimal infrastructure, mobility
  • Technologies: 802.11 a/b/g/n, and more
  • Deployments: hotspots, home networks

measure

cost-performance

time

chaotic wireless networks
Chaotic Wireless Networks

Two consequences of growth:

  • Overlapping (dense) deployments
    • Compete for spectrum
    • Seen in urban areas today
  • That are independently managed
    • Limited visibility into the operation of others
    • Focus on their own goals; no central planning

Chaotic = overlapping + independent

Claim for chaotic environments:

  • Today’s 802.11 designs won’t fare well
  • There’s an opportunity to do much better
a single 802 11 network architecture
CSE Allen Center, 3rd floor

10 802.11b/g APs per floor, managed as a whole:

Channels 1, 6, 11

20/30 mW power

Omni-directional antennas

Site surveys, sparse deployments, and decoupling are the basis for good coverage and performance.

A single 802.11 network architecture
adverse interactions across networks
Adverse interactions across networks
  • 802.11 won’t degrade gracefully in chaotic environments
    • Ideally CSMA/CA would provide reasonable sharing …
  • Default channel assignments
    • Crowding, non-orthogonal effects
  • Static power management
    • Wastefully high, leads to interference
  • Rate diversity
    • High rate transmissions beat out by low rates
  • Hidden terminals and capture
    • Poor access from some locations
  • Other unlicensed band transmissions
    • Don’t argue with a phone/microwave …
  • Problems increase with density, load and heterogeneity
a band aid dynamic tuning
A Band-aid: Dynamic tuning
  • One possible fix: dynamic parameter tuning
    • Each network measures environment and chooses the channel/power/routes that works best for it
  • Claim: dynamic tuning isn’t enough
    • Adaptation is necessary but not sufficient
    • There are opportunities to do much better
pitfalls 1 you can get stuck
Top: AP conflict on channel 1 (middle two blue nodes) can’t be resolved by individual tuning

Bottom: but a solution needs only a simple switch between two adjacent nodes

Pitfalls (1) – you can get stuck

1

5

4

3

2

6

1

5

4

3

2

6

pitfalls 2 lack of stability
Pitfalls (2) – lack of stability
  • To avoid getting stuck, need to perturb the system, changing channels even without immediate gain
  • Q: What happens to in the configuration below?
  • A: Four APs dance around three channels
  • Tradeoff between stability and convergence

4

1

3

2

pitfalls 3 power escalation
Pitfalls (3) – power escalation
  • Suppose APs adjust their transmit power (between min and max) based on delivery to their clients
  • What will the APs on channel 1 do?
    • Higher power increases delivery/rate and interference
    • Potential tragedy of the commons (lose/lose)

4

1

3

2

opportunities for coordination
Opportunities for Coordination
  • Suppose we go beyond dynamic tuning …
    • Coordination = actively exchange information and make joint decisions (for selfish gain), rather than merely try to avoid each other
  • Claim: coordination beats tuning
    • Improves outcome for pitfalls
    • Enables new beneficial scenarios
relaying for coverage performance
Relaying for coverage/performance
  • Relaying can leave both networks better off
    • Use of better links allows higher rates,
    • i.e., one transmission per packet at 1 Mbps vs. two transmissions per packet, each at 55Mbps

1

AP1

C1

55

55

55

55

1

AP2

C2

backup for reliability performance
Backup for reliability/performance
  • Use neighbor AP for backup Internet access
    • Or always use neighbor’s surplus for performance
    • Need to consider AUP issues

Internet

Internet

X

AP1

AP2

C1

C2

goal wireless internetworking
Goal: Wireless internetworking
  • Wireless Internet = architecture that coordinates multiple individual wireless networks for better coverage, performance and reliability
    • Predictably allocate wireless and access bandwidths
    • Leave individual networks better off than before
  • Architectural roles:
    • Effectively allocate underlying resource
    • Allow new applications to flourish
    • IP does both; 802.11 does neither …
research agenda
Research agenda
  • How does wireless work in practice?
    • Predict what will happen for a given choice of channel/power/routes and protocols
  • What information is exchanged where?
    • Need to find small regions with tight coupling
  • How do we make this win-win?
    • Choices that benefit all players
  • How do we foster a grassroots effort?
    • Deployment incentives
aside wifi vs cellular data
Aside: WiFi vs Cellular data
  • WiFi
    • Local = high bandwidth, inexpensive
    • Many islands of coverage
  • Cellular data
    • Wide-area = low bandwidth, expensive
    • Build-out for good coverage “away from home”
  • So concentrate on WiFi here
    • Potential for combining the best of both worlds
ad