1

Chih-Min Chao and Yao-Zong Wang

Department of Computer Science and EngineeringNational Taiwan Ocean University, Taiwan

IEEE WCNC 2010A Multiple Rendezvous Multichannel MAC Protocolfor Underwater Sensor NetworksOutlineIntroductionRelate WorkGoalMM-MACSimulationConclusion

IntroductionThe world's oceans cover over 70 % of its surfaceUnderwater Wireless Sensor Networks (UWSNs)

IntroductionUnderwater Environment Long propagation delayThe propagation speed for an acoustic link is 1500 meters/sec 2 105 times lower than the speed of a radio linkExpensive transmitting power consumptionThe transmit power is 10 WLower available bandwidth

IntroductionUnderwater Environment + MultichannelEnhance network throughputAchieves low average delay

GoalThis paper proposes a multichannel MAC protocolfor UWSNsReceiver-based protocolOnly one transceiver is needed To solve the missing receiver problem in multichannel protocolsData packets will not be collided by control packetsEnhances the network performance in a multi-hop UWSNFairnessAssumptionsTotally m equal-bandwidth channels are available.Each node is equipped with one half-duplex modem which is able to switch to any channel dynamically.Nodes are time synchronized. Each node knows the identifications (IDs) of its one hop neighbors.

System Model Superframe Superframe Superframe Channel 1Superframe Superframe Superframe Channel 2Superframe Superframe Superframe Channel 30ACK12DataSuperframeControl periodData periodDeviceslot8System Model 0ACK12DataControl periodData period3450ACK12Data3450ACK12Data3450ACK12Data345ABCDHome-channel=1Home-channel=2Home-channel=3Home-channel=4ADCBChallengeshow to decide the slots which the node should stay in its home-channel.how does the sender know the slots which the receiver stay in its home-channel.How to overcome the long propagation delay in the UWSNs.MM-MACDefault slots A node will stay on its default channel, waiting for transmission requests.Switching slotsA node may switch to its intended receivers default channel to initiate a transmission0ACK12DataSuperframeControl periodData periodMM-MACCyclic Quorum SystemsZn : n = 4 ~ 111

Z6

G0 = {0,1,3}G1 = {1,2,4}G2 = {2,3,5}G3 = {3,4,0}G4 = {4,5,1}G5 = {5,0,2}Z8

G0 = {0,1,2,4}G1 = {1,2,3,5}G2 = {2,3,4,6}G3 = {3,4,5,7}G4 = {4,5,6,0}G5 = {5,6,7,1}G6 = {6,7,0,2}G7 = {7,0,1,3}The number of slotsany difference set under ZnPlus oneeach time12Superframe # 1MM-MACZ6G0 = {0,1,3}G1 = {1,2,4}G2 = {2,3,5}G3 = {3,4,0}G4 = {4,5,1}G5 = {5,0,2}ABSlot 023451DCA=1DCB=2DSA={2,3,5}DSB={3,4,0}

2+1=3G3={3,4,0}111222default slotswitching slot0ACK12DataSuperframeControl periodData periodMM-MAC0ACK12DataSuperframeControl periodData periodMaximumPropagation Delay+CTSMM-MACExampleSuperframe # 522220000DATARTSCTSDATADATADATADATADATADATADATANTF222222222220020RTSCTSRTSNTFNTFNTFNTFNTFNTFNTF012345control perioddata perioddefault slotswitching slotACKACKipacket X sent through channel ixABCDDCA = 3DSA = {2,3,5}DCB = 2DSB = {1,2,4}DCC = 1DSC = {0,1,3}DCD = 0DSD = {0,2,5}Z6G0 = {0,1,3}G1 = {1,2,4}G2 = {2,3,5}G3 = {3,4,0}G4 = {4,5,1}G5 = {5,0,2}SimulationLanguageC++EnvironmentMulti-hopTransmission range1kmControl/Data packets size20/200bytesNumber of nodes 49Side length4kmCyclic quorum systemZ6Number of channels 3Times 60 runs SimulationSlotted FAMARTSRTSRTSCTSCTSDATADATARTSCTSDEFERS TRANSMISSIONSABCMaximumPropagation Delay+CTSIn a multihop environment, the RTS/CTS packets may collide with data packets.SimulationMultiple Sinks Model

SimulationSingle Sink Model

ConclusionThe proposed MM-MAC protocol Is a multiple rendezvous Only one modem is required for each nodeSolves the missing receiver problem.Reduce the collision probability of data packetsAchieves higher throughput and keeps the retransmission overhead lowThank You