Internet-based Fault Recovery for Home Wireless LANsAuthor: UnknownPresenter: Thomas Donahoe

EWLAN vs RWLANHigh speed wired backbone

Centralized controller

Admin coordinates wireless

No private wired connection

Not centralized

No coordination

EWLAN Benefits for RWLAN

Internet as the backbone

Decentralized approach

Automated (no admin)

RxIP: a decentralized network diagnostic and recovery tool, initially targeted at hidden terminal mitigation

RxIP: How will it work?

1. Detect hidden terminal problem

2. Isolate the hidden terminal

3. Recover by coordination (token system)

Is there a hidden terminal?

AP 1 AP 2

A B

Success!

Fail!

Collision!

Success!

Asymmetry delivery ratio or bitrate for upload vs download

Is there a hidden terminal?

AP 1 AP 2

A B

I hear A’s ACK

Where is

AP1’s DATA?

ACK

DATA

Which is the hidden terminal?

RxIP AP’s record timestamp

Challenge-response protocol via the internet

H.T.?

Which is the hidden terminal?

Loss + Concurrent (Collision)

Success + Concurrent (No Collision)

Loss + Not Concurrent

Success + Not Concurrent

Saturation Counter

H.T.?

Recovery By Coordination

Token passed back and forth

AP’s “purchase” transmission timeslot

Abstain notification

Recovery By Coordination

More HT = more complicated

Must purchase from every partner

RxIP: What else?

Ideal token passing (NP hard)

No deadlock

Token loss

Incrementally deployable

Internet latency

Evaluation

Evaluation

Evaluation

Questions?