Load Awareness Multi-Channel MAC Protocol Design for Ad Hoc

Networks

Chih-Min Chao and Kuo-Hsiang Lu

Department of Computer Science and EngineeringNational Taiwan Ocean University

IEEE Sensor Networks, Ubiquitous and Trustworthy Computing (SUTC) 2008

OutlineIntroductionRelated WorkProposed Load-awareness Multichannel MAC

(LAMM) ProtocolPerformance EvaluationConclusions

Introduction The MAC protocol of IEEE 802.11 standard is

designed for accessing a single channel.It is well known that utilizing multiple

channels can increase spatial reuse and hence enhance network throughput.

Channel allocation problem

With dedicated

control channel

Without dedicated

control channel

Multiple-transceiver

[4, 5, 10, 11] [3, 9]

Single-transceiver

[6, 12] [2, 7, 8, LAMM]

Related work [2]P. Bahl, R. Chandra, and J. Dunagan. SSCH: Slotted Seeded Channel Hopping for

Capacity Improvement in IEEE 802.11 Ad-Hoc Wireless Networks.

In Proceedings of ACM MobiCom, 2004.

SSCHA

A

A

A

A

A

A

A

A

A

B

B

B

B

B

B

B

B

B

B

Related work [7]J. So and N. Vaidya. Multi-Channel MAC for Ad Hoc Networks:

Handling Multi-Channel Hidden Terminals Using A Single Transceiver.

In Proceedings of ACM MobiHoc, 2004.

Related work [7] -- MMAC

Beacon

ATIM window

DATA window

ATIM

ATIM-ACK

ATIM-RES

Preferable Channel List (PCL)

A

B

Related work [8]C. Son, N.-H. Lee, B. Kim, and S. Bahk. MAC Protocol using Asynchronous Multi-

Channels in Ad Hoc Networks. In Proceedings of IEEE WCNC, 2007.

Related work [8] -- SLKBEach beacon interval is divided into three

subintervalsThree asynchronous channels

Related workAll the above mentioned multi-channel

protocols operate in an environment where the number of channels is fixed.

They may suffer from either longer delay or higher collision probability when network load changes.

Proposed LAMM protocolThe main idea of LAMM is to

Use less number of channels When lightly loaded

Use more channels When heavily loaded.

Proposed LAMM protocolSingle transceiverNo control channelThe structure is similar to IEEE 802.11 PSM.In LAMM, the ATIM/ATIM-ACK include

The number of pending packets

Proposed LAMM protocolDefine a node A to be inactive if one of the

following conditions holdsAttempt to send ATIM But fails to deliverSend ATIM Not receive ATIM-ACKNo ATIM to send & Not receive any ATIM

Proposed LAMM protocolEach node maintains a variable CUi to

estimate the usage of channel iAt the beginning of each beacon interval, CUi

is set to zero.CUmax： indicates the maximum number of

packets that can be sent during a data window.Data rate： 2MbpsBeacon interval： 100msData interval： 80msPacket size： 512Bytes

408*512

0.08*Mbps2max CU

Proposed LAMM protocolIf CUi >= CUthrd

The inactive node switch to next channel (i+1) mod n

If CUi < CUthrd for successively k timesNodes reside on this channel should switch

back to the default channel at the next beacon interval.

Proposed LAMM protocol

Performance Evaluation

Parameter Value

SIFS 10μs

DIFS 50μs

CWmin 31

CWmax 1023

ATIM Retry Limit 3

Short Retry Limit 7

Long Retry Limit 4

Preamble Length 144bits

PLCP Length 48bits

Performance Evaluation

Performance Evaluation

Performance Evaluation

Performance Evaluation

ConclusionsThe authors propose a multi-channel MAC

protocol LAMM that dynamically adjust the number of channels being utilized according to traffic load.

Reduces the packet delay when the network is lightly loaded.

Increases spatial reuse when heavily loaded.

The simulation results verify that LAMM performs well.

Thank you