Qian Zhang and Christopher LIM

Department of Computer Science and Engineering, Hong Kong University of Science and Technology

IEEE ICC 2009

OutlineIntroductionPerformance of existing channel

assignment metricsEffective Channel Air Time (ECAT)Performance EvaluationConclusion

IntroductionTo improve the system performance in

wireless mesh network (WMN)Multiple channelMultiple radios

The channel assignment for the APs with the access radio will affect the overall systemCity-wide WMN

The mesh APs are densely deployed It will interfere with each other

IntroductionTo proposed a new channel assignment

metricThe Effective Channel Air Time (ECAT)The traffic in the adjacent channels has

been explicitly taken into account The channel condition estimation can be

provided

Testbed configurationsEach of mesh APs associated with 2

clientsClients continuously download tftp data

Experiments on the accuracy of CATTraffic from different adjacent channel

and how it affect the current channel bandwidthAccess radio are set to channel 13

Experiments on the accuracy of CATThe effect of distance between the

transmitting node and interfering node

Experiments on the accuracy of CATThe accuracy of CAT metric

The RSSI of the interfering nodes is of 77-79

Experiments on the accuracy of CATThe accuracy of CAT metric

The RSSI of the interfering nodes is of 59-62

Effective Channel Air Time (ECAT)The experiments demonstrated

CAT channel metric tends to underestimate the channel’s utilization

Effective Channel Air Time (ECAT)It can have a effectiveness channel air

time of channel NThe CAT of that channelThe busy period in its overlapping

channel

21

NNNN BPgBPfCATECAT

The neighboring channels and the neighbor’s neighboring channel

Busy period

factorIMRIRSSICAT

factorIMRIRSSICATCATECAT

iiNNi

i

iiiNNi

iNN

)(

)(

2,2

1,1

Effective Channel Air Time (ECAT)

The maximum RSSI signal measured at the mesh AP

The maximum transmitter’s power measured at transmitter’s channel

Effective Channel Air Time (ECAT)

2,2

1,1

/

/

NNiii

NNiiiiNN

MRIMTPCCAT

MRIMTPCCATCATECAT

The maximum transmitter’s power measured at the channel i

Effective Channel Air Time (ECAT)

Effective Channel Air Time (ECAT)

Performance EvaluationLab environment testing

Performance EvaluationReal-world environment testing

ConclusionTo discuss the performance of a

hierarchical multi-radio mesh networkTo introduce a new metric to estimate

the channel utilizationReal experiments demonstrated that

ECAT gives a more accurate measurement about the channel utilization