A High-Throughput MAC A High-Throughput MAC Protocol for Wireless Protocol for Wireless Ad Hoc NetworksAd Hoc Networks

Wanrong Yu, Jiannong Cao, Xingming Zhou, Wanrong Yu, Jiannong Cao, Xingming Zhou, Xiaodong Wang, Keith C. C. Chan, Alvin T. S. Chan,Xiaodong Wang, Keith C. C. Chan, Alvin T. S. Chan,and H.V. Leongand H.V. Leong

School of Computer, National University of Defense School of Computer, National University of Defense Technology, Changsha, ChinaTechnology, Changsha, ChinaDepartment of Computing, Department of Computing, HongKong Polytechnic UniversityHongKong Polytechnic University

IEEE Transaction on Wireless IEEE Transaction on Wireless Communications,Communications,Vol. 7, No.1, January 2008Vol. 7, No.1, January 2008

OutlineOutline

IntroductionIntroduction CTMACCTMAC Performance evaluationPerformance evaluation ConclusionsConclusions

Inefficiency of IEEE Inefficiency of IEEE 802.11802.11

Background and Background and related workrelated work Effort has been made on Effort has been made on

increasing the throughput of increasing the throughput of MANETsMANETs– Adding additional control gapAdding additional control gap– Transmission power control (TPC)Transmission power control (TPC)

Additional control gapAdditional control gap

To add control gap between To add control gap between between RTS/CTS and DATA between RTS/CTS and DATA packets for scheduled transmissionpackets for scheduled transmission– [6]:MACA-P, IEEE PerCom 2003[6]:MACA-P, IEEE PerCom 2003– [7]:enhancement of MACA-P, [7]:enhancement of MACA-P,

BoradNets 2004BoradNets 2004 Do not consider tolerable Do not consider tolerable

interferenceinterference

Transmission power Transmission power controlcontrol TPC is used per-packet to increase TPC is used per-packet to increase

the spatial channel reusethe spatial channel reuse– [5]: A power control MAC protocol for [5]: A power control MAC protocol for

ad hoc networks, ACM/Kluwer Wireless ad hoc networks, ACM/Kluwer Wireless Networks, 2005Networks, 2005

– [12]: POWMAC, IEEE J. Select Areas [12]: POWMAC, IEEE J. Select Areas Commun., 2005Commun., 2005

Latency in change of transmission Latency in change of transmission power is huge [11], which make power is huge [11], which make TPC-based solutions difficult to use TPC-based solutions difficult to use in practicein practice

Goal of the paperGoal of the paper

To propose a MAC protocol works To propose a MAC protocol works onon– Single channelSingle channel– Single transceiverSingle transceiver– Single transmission powerSingle transmission power

Basic operation of Basic operation of CTMACCTMAC

Masterpair

Slavepair

CTMACCTMAC

In CTMAC, every node maintains In CTMAC, every node maintains an Active Neighbor List (ANL)an Active Neighbor List (ANL)

For node i, ANLFor node i, ANLii contains contains

Address of u

Channel gain

bewteen i and u

Starting time of DATA and

ACK

To distinguish the

transmitter and receiver

Maximum tolerable

interference of u

Handshakes in CTMAC: Handshakes in CTMAC: case 1case 1 RTS-CTSRTS-CTS

– Successful in information exchangeSuccessful in information exchange– The receiver agrees with the sender The receiver agrees with the sender

and reply a normal CTSand reply a normal CTS

Handshakes in CTMAC: Handshakes in CTMAC: case 2case 2 RTS-CTS-ATS (adjust-to-send)RTS-CTS-ATS (adjust-to-send)

– The slave receiver modify the value The slave receiver modify the value of Tof Tdatadata and T and Tackack declared by the declared by the sender in RTSsender in RTS

– The slave receiver includes the new The slave receiver includes the new value in CTSvalue in CTS

– The slave sender has to inform its The slave sender has to inform its neighbors the new value by ATSneighbors the new value by ATS

Handshakes in CTMAC: Handshakes in CTMAC: case 3case 3 RTS-NCST-ATS (abort-to-send)RTS-NCST-ATS (abort-to-send)

– The slave receiver finds it is The slave receiver finds it is implssible to continue the slave implssible to continue the slave transmissiontransmission

– The slave sender informs its The slave sender informs its neighbor by ATSneighbor by ATS

Minimum reaching powerMinimum reaching power

Accumulated interference powerAccumulated interference power

Total future interference that Total future interference that node v can tolerate, Pnode v can tolerate, Prxrx is the is the raching powerraching power

Tolerable interference Tolerable interference estimation estimation

Tolerable interference Tolerable interference estimationestimation Maximum tolerable interference that Maximum tolerable interference that

each future neighboring node can addeach future neighboring node can add

α is the ratio between the interference α is the ratio between the interference caused by nodes outside and inside caused by nodes outside and inside the transmission range the transmission range – α = 0.5 for two ray models and uniform α = 0.5 for two ray models and uniform

distributed nodesdistributed nodes

Concurrent Concurrent transmisson controltransmisson control RC0: requirement of timeRC0: requirement of time

– For the slave sender to check if the For the slave sender to check if the master transmission’s ACG is long master transmission’s ACG is long enough for exchanging of control enough for exchanging of control packetspackets

RC1: for slave transmitterRC1: for slave transmitter– Check if transmission will collide with Check if transmission will collide with

any scheduled transmissionany scheduled transmission– For all u in ANL, check if For all u in ANL, check if

Concurrent Concurrent transmission controltransmission control RC2: for slave receiverRC2: for slave receiver

– To determine if the accumulated To determine if the accumulated should not violate the slave should not violate the slave receiver’s SINRreceiver’s SINR

– RC3: ACK transmissionRC3: ACK transmission

– To postpone the transmission of ACKTo postpone the transmission of ACK

Parameters in the Parameters in the simulationsimulation

Line topologyLine topology

Throughput of line Throughput of line topologytopology

Random grid topologyRandom grid topology

800 meter square area800 meter square area The square is split into n*n small The square is split into n*n small

squaressquares one node placed in a small square one node placed in a small square

randomlyrandomly mm transmission pairs transmission pairs

Throughput (m=2)Throughput (m=2)

Throughput (m=3)Throughput (m=3)

Throughput (m=4)Throughput (m=4)

Cluster topologyCluster topology

An area of 400*400 mAn area of 400*400 m 16 nodes, split into 4 equal groups16 nodes, split into 4 equal groups Each group occupying a 100*100 Each group occupying a 100*100

squaresquare The receiver is selected from The receiver is selected from

another cluster with a probability of another cluster with a probability of pp

Throughput (p=0.25)Throughput (p=0.25)

Throughput (p=0)Throughput (p=0)

Random topologyRandom topology

1000*1000 meter area1000*1000 meter area 100 nodes placed randomly100 nodes placed randomly M end-to-end flowsM end-to-end flows Size of control gap is 640B Size of control gap is 640B

Throughput at random Throughput at random topologytopology

ConclusionConclusion

CTMACCTMAC– Is based on a single transceiver Is based on a single transceiver

circuitrycircuitry– Operates over a single channelOperates over a single channel– Works on single transmission powerWorks on single transmission power

Thank you!!Thank you!!