Design Principles for Design Principles for Distributed Channel Distributed Channel Assignment in Wireless Ad Assignment in Wireless Ad Hoc NetworksHoc Networks

Michele X. Gong, Scott F. Midkiff and Shiwen Mao

The Bradley Department of Electrical and Computer Engineering, Virginia Polytechnic Institute and State

University

IEEE ICC 2005

OutlineOutline

IntroductionIntroduction Performance metricsPerformance metrics Design principlesDesign principles CA-AODV (Channel Assignment AODV)CA-AODV (Channel Assignment AODV) ECA-AODV (Enhanced CA-AODV)ECA-AODV (Enhanced CA-AODV) Analysis of the algorithmAnalysis of the algorithm Simulations resultsSimulations results ConclusionsConclusions

IntroductionIntroduction

Channel assignment remains a Channel assignment remains a challenging problemchallenging problem

Existing protocols tend to be Existing protocols tend to be complex and usually not suitable complex and usually not suitable for practical implementationfor practical implementation

Problem formulationProblem formulation

Parameter Parameter kk– A user-defined neighborhood sizeA user-defined neighborhood size– Interference rangeInterference range

kk will have an optimal range will have an optimal range Neighbor setNeighbor set

– – l l ((vv,,ww) is the distance from ) is the distance from vv to to ww

Performance metrics Performance metrics (1)(1) Minimize the average number of nodMinimize the average number of nod

es sharing the same channel within a es sharing the same channel within a node’s node’s kk-hop-hop

– nnkk((vv) is the number of nodes in ) is the number of nodes in NNkk((vv) tha) that share the same channelt share the same channel

Performance metrics Performance metrics (2)(2) Minimize the summation of interferencMinimize the summation of interferenc

e sourcee source

– VVtt: set of active transmitters: set of active transmitters– VVrr: set of active receivers: set of active receivers– : the received power at node : the received power at node vvr,ir,i – : 0/1, indicate if nodes are using th: 0/1, indicate if nodes are using th

e same channel e same channel

Design principles (1)Design principles (1)

The use of cross layer design The use of cross layer design approachapproach– Channel assignment is combined with Channel assignment is combined with

ad hoc routingad hoc routing– Piggybacking channel information in Piggybacking channel information in

routing control messages can greatly routing control messages can greatly reduce the complexity of channel reduce the complexity of channel assignmentassignment

Design principles (2)Design principles (2)

Channels should be assigned only to Channels should be assigned only to active nodesactive nodes– Most existing schemes assign channel tMost existing schemes assign channel t

o all nodeso all nodes– Existing schemes require more wireless Existing schemes require more wireless

channels than necessarychannels than necessary

Design principles (3)Design principles (3)

Distinct channel should assigned in a Distinct channel should assigned in a way the avoids collisions and interfeway the avoids collisions and interferencerence– To resolve one-hop and two-hop interfeTo resolve one-hop and two-hop interfe

rencerence

CA-AODVCA-AODV

Channel assignment in Route Channel assignment in Route discovery phasediscovery phase– Channel info. about a node’s k-hop Channel info. about a node’s k-hop

neighbors on the same route is neighbors on the same route is carried by the broadcast RREQcarried by the broadcast RREQ

– Nodes receive RREQ update its next-Nodes receive RREQ update its next-hop table and indices of used hop table and indices of used channelschannels

– Selects a channel from the available Selects a channel from the available channel listchannel list

ECA-AODVECA-AODV

Based on CA-ADOVBased on CA-ADOV Add a ChannelTaken messageAdd a ChannelTaken message

– broadcast in the route discovery phasebroadcast in the route discovery phase– Used by a node Used by a node on an established routeon an established route

detects a new route in the detects a new route in the kk-hop neighb-hop neighborhoodorhood

– Use Use k k as the as the TTL fieldTTL field of the ChannelTak of the ChannelTaken messageen message

ECA-AODVECA-AODV

To allow sufficient time for ChannelTakTo allow sufficient time for ChannelTaken messages to propagate to all nodes en messages to propagate to all nodes within k-hops rangewithin k-hops range– Destination or node that has a valid route tDestination or node that has a valid route t

o the destination should wait for a period oo the destination should wait for a period of timef time

Channel assignment is done in the routChannel assignment is done in the route reply phasee reply phase

Example of ECA-AODVExample of ECA-AODV

Analysis of the Analysis of the algorithmalgorithm Proposition 1: the channels Proposition 1: the channels

required has an upper bound of required has an upper bound of nn*(*(kk+1)+1)– n: the number of active routesn: the number of active routes– k: routes lie within k-hop range of k: routes lie within k-hop range of

any node in the network any node in the network Can be proven by inductionCan be proven by induction

Analysis of the Analysis of the algorithmalgorithm Proposition 2: each along the Proposition 2: each along the

route is assigned a distinct route is assigned a distinct channel among its channel among its kk-hop -hop neighborsneighbors

Algorithm Algorithm ComparisonsComparisons

Simulation setupSimulation setup

25 random scenarios25 random scenarios 64 wireless nodes distributed over 8064 wireless nodes distributed over 80

0*800 m area0*800 m area 2-ray ground path lost model2-ray ground path lost model Radio range is 180 mRadio range is 180 m Static topologyStatic topology

Average number of Average number of conflicting nodes conflicting nodes (C=12)(C=12)

Accumulated interference Accumulated interference levels at each receiver levels at each receiver (C=12)(C=12)

Impact of neighborhood Impact of neighborhood size on performance size on performance (C=18)(C=18)

ConclusionsConclusions

This paper presented 3 design This paper presented 3 design principles for efficient distributed principles for efficient distributed channel assignmentchannel assignment

ECA-AODV exhibits lower ECA-AODV exhibits lower communication, computation, and communication, computation, and storage complexity than existing storage complexity than existing channel assignment schemeschannel assignment schemes

Thank you!!Thank you!!