This document discusses scalability in wireless sensor networks. It addresses hardware and software issues related to scalability, including sensor sensitivity, communication bandwidth, data management, and algorithm complexity. The document compares single-hop and multi-hop communication and their tradeoffs. It describes routing protocols for flat networks and clustered topologies. The document focuses on LEACH, a hierarchical clustering protocol, and discusses its operation, drawbacks, and energy consumption model.

1. 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)

3.  For hardware scalability involves sensitivity
and range of MEMS sensors, communication
bandwidth of the radio, and power usage.
 The software issues include reliability of
command dissemination and data transfer,
management of large volume of data, and
scalable algorithms for analysing the data.
 There are tradeoffs between the Larger
numbers of nodes means increased
management complexity, as well as a more
complex programming model

4.  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.

5. Routing protocols for flat WSNs
1.Flooding and Gossiping
2.SPIN(Sensor Protocol for Information via
Negotiation)
3.SAR(Sequential Assignment Routing)

6.  LEACH(Low Energy Adaptive Clustering Hierarchy)
 PEGAGIS(Power-Efficient Gathering in Sensor
Information Systems)
 TEEN (Threshold-Sensitive Energy Efficient Sensor
Network Protocol)

7.  Clustered Topology : It is more
suitable to ensure scalability. In a
clustered sensor network, all the
nodes are organized into a
hierarchy based on some clustering
algorithm. In each cluster, one
node is selected to act as the
cluster head (CH) and collecting all
the information sensed by the
cluster, aggregating data and
reporting to a base station. All the
other sensor nodes only need to
contact with their cluster head.
 For cluster headers, their power
should be exhausted much faster
so Clustering algorithms in the
former usually adopt rotation of
cluster heads for load balance while
in the latter use fixed cluster
heads.

8.  LEACH (Low Energy Adaptive Clustering Hierarchy):- It is a
hierarchical clustering-based algorithm, which includes
distributed cluster formation. The main idea is to form clusters
of the sensor nodes based on the received signal strength and
use local cluster heads as router to the sink.
 LEACH uses a CDMA-TDMA hybrid communication scheme. Each
cluster has unique spreading code that can minimize
interference between clusters and every cluster head set up a
TDMA schedule for collision-free intra-cluster communication.
 They use power control to set the amount of transmit power
based on the distance to their cluster heads and turn off radios
until their allocated transmission time. At the end of each frame,
the cluster heads perform data aggregation, which can achieve
considerable energy saving, and forward the aggregated data to
the base station.

9. Drawback:-
 Variable number of clusters produced in each round
 Uneven size of clusters
 The cluster head far away from base station will exhaust its
energy quickly
 LEACH does not allocate time slots to cluster heads. Hence,
when cluster head transmit the aggregated data to base
station and at the same time data collected by one of its
members arrive, collision will happen.

10.  In LEACH there is single-hop communication between cluster
head and the base station .
 LEACH uses CSMA for cluster head to transmit the aggregated
data, in which collision is inevitable.
 In EMCA we use Multihop communication from cluster heads
to cluster heads and on to the base station.
 Time-line of EMCA is the same as LEACH, however the
operation in it is different. The set-up phase is divided into
four parts:-
a) Cluster-formation subphase,
b) Routing-establishment subphase,
c) TDMA-schedule subphase and
d) Synchronization subphase.

13.  Total energy consumption for each round of sensing and
transfer is =
Where: -ʎ(=0.01) is poisson intensity for Randomly distributed
sensor 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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 Shamim N. Pakzad1; Gregory L. Fenves2; Sukun Kim3; and David
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16. 
 THANK YOU