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Limited Contribution of Self-Management in Chaotic Wireless Deployments. Presented by Karl Deng. Limited Contribution. No. Measurement Devise self-managing algorithms: Channel assignment algorithm Rate adaptation algorithm Power control algorithm. No. No. Yes (but problematic).

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slide1

Limited Contribution of

Self-Management in Chaotic Wireless Deployments

Presented by Karl Deng

slide2

Limited Contribution

No

  • Measurement
  • Devise self-managing algorithms:
    • Channel assignment algorithm
    • Rate adaptation algorithm
    • Power control algorithm

No

No

Yes (but problematic)

slide3

Channel assignment algorithm

  • Effect of Optimal Static Channel Allocation (Section 4.3.1)
    • Improves performance significantly

In combination with careful channel assignment, our power control algorithms attempt to minimize the interference between neighboring APs by ...

Where is the channel assignment algorithm?

slide4

Rate adaptation algorithm

  • Bear little relationship with minimizing interference.
  • Fixed power Rate Selection Algorithms (Section 7.2)
    • ARF (Auto Rate Fallback)
    • ERF (Estimated Rate Fallback)
  • Two algorithms that combine power and rate control to try to minimize interference (Section 7.3)
    • PARF (Power-controlled Auto Rate Fallback)
    • PERF (Power-controlled Estimated Rate Fallback)
slide5

Rate adaptation algorithm

  • How do you combine power and rate control?
  • ARF - Rate selection via in-band probing
  • PARF - Power selection via in-band probing

ERF - Rate selection via SNR measurement

PERF - Power selection via SNR measurement

The only “combine”:

    • “If failures continue, the transmit power is raised until the maximum transmit power is reached after which rate fallback begins.”  Rate control only happens when using maximum transmit power.  Such rate control does not help to reduce interference.

Such relation is not “combine”, but only some “similarity”

slide6

Rate adaptation algorithm

In Section 9 (“Discussion”):

LPERF (Load-sensitive, Power-controlled Estimated Rate Fallback)

Reduce the power as long as the resulting transmission

rate is sufficient to support the actual traffic demands.

Conclusion: Using the LPERF technique is very difficult.

slide7

Power control algorithm

  • Problematic:
  • Socially responsible power control algorithms
    • Individual access points and clients behave in an altruistic manner
  • Not simply relying on the altruism of end users
    • Equipment vendors implement the algorithms (From their point-of-view, reducing interference is beneficial.)
    • Regulatory mandates
    • New technology is quickly adopted in chaotic networks.
    • Many users in chaotic networks do not change factory default settings
slide8

Power control algorithm

  • (Continue)
  • Backward compatibility
    • Heterogeneous transmit power levels cause problems

Example: “asymmetric carrier sense” (Section 8.1, Figure 13)

“When using power control, care must be taken …, an AP-client link should not reduce power so much that it becomes overwhelmed by neighboring uncooperative high power nodes.”  But how?

  • Barrier for future technology (forward compatibility)

E.g., signal measurement could be even harder. (Recall why we use CSMA/CA not CSMA/CD.)

slide9

Power control algorithm

  • (Continue)
  • Backward compatibility
    • Heterogeneous transmit power levels cause problems

 Compatibility with old APs

    • Compatibility with clients

PERF requires receiver side cooperation:

      • SNR is measured at receiver (client)
      • Receiver feeds back power decrease decision
  • Client side power control is ignored
    • Assumption: Amount of upload traffic is small.
    • What about p2p traffic?
    • What about multiple clients, variant range?
slide10

Limited Contribution

?

  • Measurement
  • Devise self-managing algorithms:
    • Channel assignment algorithm
    • Rate adaptation algorithm
    • Power control algorithm

No

No

Yes (but problematic)

slide11

Measurement Contribution

  • Qualitative results are straightforward:
    • Lower transmission power  lower interference
    • Lower client or AP density  lower interference
    • Optimize channel allocation  lower interference
  • Quantitative results are not representative:
    • Only one sample – a 20-node

topology derived from the Metropolis

Wardrive data set.