Scalability in Wireless Sensor Network

In the guidance of

Dr Alok Nath De/alokde_telecom@yahoo.co.in

By:-

ANJANI SHANKAR TIWARI(2010JTM2385)

SHASHI MANGAL (2010JTM2391)

For hardware scalability involves sensitivityand range of MEMS sensors, communicationbandwidth of the radio, and power usage.

The software issues include reliability ofcommand dissemination and data transfer,management of large volume of data, andscalable algorithms for analysing the data.

There are tradeoffs between the Largernumbers of nodes means increasedmanagement complexity, as well as a morecomplex programming model

Single Hop-single-hop networks are spatially limited by the radio range and cannot span long distances without a large power supply.

Multi Hop-Multihop communication is the transfer of data and commands between two nodes that are not in the direct radio range, using intermediary nodes . Thus required less energy by a node to send data.

Multihop communication is essential for scalability of low-power wireless sensor networks but at the cost of more complex routing protocols.

Routing protocols for flat WSNs

1.Flooding and Gossiping

2.SPIN(Sensor Protocol for Information via

Negotiation)

3.SAR(Sequential Assignment Routing)

LEACH(Low Energy Adaptive Clustering Hierarchy)

PEGAGIS(Power-Efficient Gathering in Sensor

Information Systems)

TEEN (Threshold-Sensitive Energy Efficient Sensor

Network Protocol)

Clustered Topology : It is moresuitable to ensure scalability. In aclustered sensor network, all thenodes are organized into ahierarchy based on some clusteringalgorithm. In each cluster, onenode is selected to act as thecluster head (CH) and collecting allthe information sensed by thecluster, aggregating data andreporting to a base station. All theother sensor nodes only need tocontact with their cluster head.

For cluster headers, their powershould be exhausted much fasterso Clustering algorithms in theformer usually adopt rotation ofcluster heads for load balance whilein the latter use fixed clusterheads.

LEACH (Low Energy Adaptive Clustering Hierarchy):- It is ahierarchical clustering-based algorithm, which includesdistributed cluster formation. The main idea is to form clustersof the sensor nodes based on the received signal strength anduse local cluster heads as router to the sink.

LEACH uses a CDMA-TDMA hybrid communication scheme. Eachcluster has unique spreading code that can minimizeinterference between clusters and every cluster head set up aTDMA schedule for collision-free intra-cluster communication.

They use power control to set the amount of transmit powerbased on the distance to their cluster heads and turn off radiosuntil their allocated transmission time. At the end of each frame,the cluster heads perform data aggregation, which can achieveconsiderable energy saving, and forward the aggregated data tothe base station.

Drawback:-

Variable number of clusters produced in each round

Uneven size of clusters

The cluster head far away from base station will exhaust itsenergy quickly

LEACH does not allocate time slots to cluster heads. Hence,when cluster head transmit the aggregated data to basestation and at the same time data collected by one of itsmembers arrive, collision will happen.

In LEACH there is single-hop communication between clusterhead and the base station .

LEACH uses CSMA for cluster head to transmit the aggregateddata, in which collision is inevitable.

In EMCA we use Multihop communication from cluster headsto cluster heads and on to the base station.

Time-line of EMCA is the same as LEACH, however theoperation in it is different. The set-up phase is divided intofour parts:-

a) Cluster-formation subphase,

b) Routing-establishment subphase,

c) TDMA-schedule subphase and

d) Synchronization subphase.

Total energy consumption for each round of sensing andtransfer is =

Where: -ʎ(=0.01) is poisson intensity for Randomly distributedsensor node with square area of side M;

-An l bit(=500bit) packet is transmitted distance at r;

-Eelec, (= 50nJ/bit)is the electronics energy;

-εfs (= 10pJ/bit/m2.)is amplifier coefficient;

-Probability of becoming a cluster head is p;

-EDA(=5nJ/bit) be the energy consumption for aggregating one bit of data;

The total energy LEACH spend in a frame is given by:

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Lubna K. Alazzawi, Ali M. Elkateeb, and AiyappaRamesh“Scalability Analysis for wireless sensor networks RoutingProtocols” 2008 IEEE

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THANK YOU