Mohamed Elhawary Computer Science

Department Cornell University

PERCOM 2008

Zygmunt J. Haas Electrical and

Computer Engineering Department

Cornell University

OutlineIntroductionThe Busy Tone Multi Channel Protocol

(BTMC)SimulationConclusion

IntroductionWireless ad hoc network

To increase the capacity multi-channel 802.11 a → 12 802.11 b → 3

The protocols designed for the multi channel environment To solve the hidden terminal problem How the channel rendezvous is done

IntroductionThis is the first MAC protocol

With a single packet radio per node That does not require synchronization or a

dedicated control channel Does not cause network partitioning

MotivationSolve the hidden terminal problem in multi-

channel. No synchronization. We do not want to have a control channel

that can get saturated. All channels can be used for data or control exchange

GoalTo propose a new distributed multi-channel

MAC protocol The Busy Tone Multi Channel Protocol (BTMC)To increase the capacity

MAC protocolTo use a set of k hash functions; h0, h1,…,

hk-1,A channel number from 0 to m-1

where m is the channel environment was described before in previous works number of channels available

Nodes are aware of MAC addresses of each other and have the same set of the hash functions

MAC protocol

A

B

C

E

D

Ch 1

Ch 2

Ch 3

Ch 4

hash function : A {2, 1, 3, 1, 2}

B {1, 4, 2, 1, 3}

C {4, 3, 2, 1, 2}

D {3, 2, 1, 4, 1}

E {1, 4, 3, 4, 2}

A

E

D

BC

MAC protocol

A

E

DC

A B

C

E

D

Ch 1

Ch 2

Ch 3

Ch 4

hash function : A {2, 1, 3, 1, 2}

B {1, 4, 2, 1, 3}

C {4, 3, 2, 1, 2}

D {3, 2, 1, 4, 1}

E {1, 4, 3, 4, 2}

BRTS

MAC protocol

E

DC

Ch 4

A

BRTS

A

B

RTS

2τ+γ

idle

CTS

DATA

Variable definitions: δ: data packet transmission time γ: RTS/CTS transmission time τ: maximum one way propagation delay td: busy tone detection delay

E

2τ + δ + td

searches for the next free channel

MAC protocol

A

E

DC

A B

C

E

D

Ch 1

Ch 2

Ch 3

Ch 4

hash function : A {2, 1, 3, 1, 2}

B {1, 4, 2, 1, 3}

C {4, 3, 2, 1, 2}

D {3, 2, 1, 4, 1}

E {1, 4, 3, 4, 2}

BRTS

MAC protocol

E

DC

Ch 4

A

BRTS A

B

RTS

2τ+γ

Not idle

Busy tone

E

MAC protocol

E

DC

A B

C

E

D

Ch 1

Ch 2

Ch 3

Ch 4

A

BRTS

wait 2τ + 2δ

hash function : A {2, 1, 3, 1, 2}

B {1, 4, 2, 1, 3}

C {4, 3, 2, 1, 2}

D {3, 2, 1, 4, 1}

E {1, 4, 3, 4, 2}

Variable definitions: δ: data packet transmission time γ: RTS/CTS transmission time τ: maximum one way propagation delay td: busy tone detection delay

Experimental results

Experimental results

Experimental results

ConclusionWe proposed a new multi channel MAC

protocol in ad hoc networkTo use one packet radio per nodeIt has a low overhead

Future workWe want to test the effect of using more

sophisticated hash functionsTo save power like in the IEEE 802.11

specifications