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Presented by:

 Ambica Sud(07520)

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� Haifang Feng, Lixiang Ma, Supeng Leng, A

Low Overhead Wireless Sensor Networks

MAC protocol, IEEE transactions onNetworking, 2010.

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� Energy efficiency is the kernel issue in the designing of wirelesssensor network (WSN) MAC protocols. S-MAC is a WSN MACprotocol based on the listen and sleep mechanism to reduceenergy consumption. Synchronous frame in S-MAC protocol

belongs to control information, so its better to reduce it as muchas possible. In addition, S-MAC protocol adopts virtual clustersynchronization mechanism which leads to the generation of border nodes, and the border nodes will exhaust energy moreeasily and earlier. The Paper analyzes S-MAC, and simulates LO-MAC protocol. The LO-MAC protocol improves S-MAC by

decreasing the control energy consumption and thus prolongsnetwork lifetime compared with S-MAC protocol, furthermore, itresolves the problem of border nodes

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Wireless sensor networks(WSNs) are composed of manydensely distributed sensor nodes. These sensor nodes can

monitor environment and collect data. It can also detect andidentify specific events. At the end of layouts of the sensor

nodes in the networks, they exchange mutual informationand form a communication networks. Each node has verylimited energy, low processing capability and small

storage capacity. The power supply on the nodes usuallycouldnt be replaced, so on the basis of the energy efficiency

to solve the problem of rational share of the network

communication channel, that is Media AccessControl(MAC), becomes the key technology of the wirelesssensor networks.

When we design WSN MAC protocols, in order toguarantee the networks long-term effective running, the most

important aim becomes maximizing the network lifetime.

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� Reduce idle listening.

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� Avoid message collision.

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� Overhearing

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� Transmitting control message

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Invalid sending

When nodes is not ready to receivemessages, sending node transmits its message,

and at this time sending node will wasteenergy, so we should avert sending failure as

much as possible.

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� Creating or Designing a MAC Protocol which

reduces the above mentioned problems and

also the control Overhead encountered inSMAC.

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� SMAC

In S-MAC protocol, the sum of listen time and sleep time is aschedule period. When the node is initialized, it needs

to choose a schedule to listen and sleep periodically. Firstly,it listens for a while ,during this time, if it doesnt receiveany SYNC packet, it will choose a schedule randomly andbroadcast the schedule as SYNC packet through CSMA/CAmechanism. If it receives SYNC packet in that time, it will

follow the schedule of the SYNC packets source node andbroadcast the received schedule as well. If it receives twodifferent schedule modes, it will merge the two schedules,and becomes a border node with longer listen time thannormal nodes.

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� Unlike S-MAC protocol, LO-MAC protocol

uses unified schedule, and spends less time to

synchronize. It needs some assumptions asfollows:

The sink node has enough energyEvery node in the networkcan receive

synchronization packet from sink node.Nodes have uniform duty cycle.

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� Periodic listen and sleep

sleep sleeplisten listen

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� Two types of Schedule periods:

Schedule 1- repeated k-1 times

Schedule 2- occurs once after k-1 times Schedule 1occurs

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� B. Scheduling process

Every node in the network has the same schedule

mode as they all receive synchronization packetsfrom sink node and extracts the scheduling typeof the sink node, and then adopts the scheduletype.

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� Simulation of LOMAC basic MAC protocol for

WSN..

� A comparitive study of SMAC and LOMAC..Based on Omnet++ Simulation

� Analytical study on the energy consumptionand latency

� Analyze the effect of topology changes

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� THANK YOU!!