wireless sensor network protocols dr. monir hossen ece, kuet department of electronics and...

Wireless Sensor Network Protocols

Dr. Monir HossenECE, KUET

Department of Electronics and Communication Engineering, KUET

Department of Electronics and Communication Engineering, KUET 2

Clustering Algorithm Clustering of the Large Sensor Network Classification of Clustering Algorithms Popular Clustering Algorithms MAC Protocol Different MAC protocols

Agendas of This Lecture


Clustering Algorithm (1/2)

Clustering is the way where the sensor nodes are grouped in order to => Achieve the network scalability => Solve the network coverage and traffic unbalance problems among the cluster heads (CHs) => Reduce the size of the routing table stored at the individual node => Distribution of nodes among the clusters evenly => Save the energy consumption by reducing data repetition

Improve network lifetime Reduce network traffic and the contention for the channel Data aggregation and updates take place in CHs


• Nodes divided in virtual group according to some rules• Nodes belonging in a group can execute different functions

from other nodes

Cluster member

Clusterhead

Gateway node

Intra-Cluster link

Cross-cluster link

Clustering Algorithm (2/2)


Clustering of the Large Sensor Network (1/2)

An efficient clustering algorithm is important for following reasons:

=> To limit the maximum hop distance => To distribute the nodes among the clusters evenly=> To management of time frame properly => To solve the traffic unbalance problem among CHs => To optimize the no. of CH & hop to ensure the network coverage


Clustering of the Large Sensor Network (2/2)

1 2 3 4 5 6 7 80.0

0.2

0.4

0.6

0.8

1.0

Cov

erag

e ra

tio

Maximum number of hops in a cluster

CH=2 CH=4 CH=6 CH=8

The curves represent the coverage ratio of

total 500 nodes randomly distributed in 500x500 m2 area,

where maximum distance of a hop is

40 m.


Classification of Clustering Algorithms (1/2)

Yes

Grant registration

Report to OLT

Receive registration

request from node

No Hop distance

≤ Hlim

OLT selects ONU to register

Node registration algorithm

Here, Hlim is the maximum no. of hops for a cluster

Major Approaches for clustering of WSN:

1. Independent clustering algorithm2. Cooperative clustering algorithm


Independent Clustering Algorithm (1/2)

Independent clustering Algorithm:

Assignment of large Hmax causes nonsymmetrical node distribution among the clusters

Assignment of small Hmax reduces coverage, all the nodes are not connected

Optimum number of hop selection is required Estimation of the Optimum hop number in

advance is difficult


Independent Clustering Algorithm (2/2)

Nodes under ONU1=175Nodes under ONU2=125Nodes under ONU3=121Nodes under ONU4=79Maximum hop distance=7

Independent clustering for 500 nodes in an area of 500×500 square meter.


Cooperative Clustering Algorithm (1/2)

Cooperative clustering algorithm:

Can obtain even distribution of sensor nodes among the clusters

Provides less number of hops in a cluster

Total aggregated traffic in the network is less than the independent clustering algorithm


Cooperative Clustering Algorithm (2/2)

Nodes under CH1=120, CH2=127, CH3=120, CH4=120 and non-registered nodes=13 up to 4-hops

CH1= 121 CH2= 132 CH3= 123 CH4= 124Up to 5-hops


Popular Clustering Algorithms

Different clustering algorithms have been proposed to achieve energy and delay efficient WSN

Low Energy Adaptive Clustering Hierarchy (LEACH)

Hybrid Energy Efficient Distributed (HEED) Protocol

Weighted Clustering Algorithm (WCA)


Low Energy Adaptive Clustering Hierarchy (LEACH)

Every node elects as CH the node that requires the least energy consumption for communication.Every CH set-up a TDMA schedule and transmitted to the nodes. Every node could transmit data in the corresponding time-slot.

Weakness of LEACH Limited scalability Could be complementary to clustering techniques

based on the construction of a DS


Hybrid Energy Efficient Distributed (HEED) Protocol (1/3)

Assumptions: Sensor quasi-stationary

Links are symmetric

Energy consumption non-uniform for all nodes

Nodes-location unaware

Processing and communication capability-similar



Algorithm:• Cluster head selection

Amount of residual energy (primary) and communication cost (secondary) such as node proximity

• Number of rounds of iterations

• Tentative CHs formed

• Final CH until CHprob=1

• Same or different power levels used for intra cluster communication


Pros:• Balanced clusters• Low message overhead• Uniform & non-uniform node distribution• Inter cluster communication explained• Out performs generic clustering protocols on

various factors

Cons:• Repeated iterations and complex algorithm• Decrease of residual energy smaller

probability number of iterations increased

• Nodes with high residual energy are increased in one region of a network



Weighted Clustering Algorithm (WCA) (1/4)

A cluster head can ideally supports nodes to

Ensures efficient MAC functioning

Minimizes delay and maximizes throughput

A cluster head uses more battery power

because it:

Does extra work due to packet forwarding

Communicates with more number of nodes



A cluster head should be less mobile Helps to maintain same configuration Avoids frequent WCA invocation

A better power usage with physically closer

nodes More power for distant nodes due to signal

attenuation


It is desirable to balance the loads among the clusters

Load balancing factor (LBF) has defined as

i i

cLBF

xn

2

where,

nc is the number of cluster heads xi is the number of nodes of cluster i and

nc

ncN is the average number of neighbors of a

cluster head

Load Balancing Factor (LBF)




For clusters to communicate with each other, it is

assumed that cluster heads are capable of operating

in dual power mode

A cluster head uses low power mode to communicate

with its immediate neighbors within its transmission

range and high power mode is used for

communication with neighboring clusters

Connectivity is defined as (for multiple component

graph)

Connectivity

N

componentlargestofsizetyconnectivi


MAC Protocol MAC protocols play a vital role for efficient data

transmission and collision avoidance in a wireless communication system

Different MAC protocols have been proposed to reduce latency as well as energy consumption in WSN

S-MAC, Adaptive S-MAC, LE-MAC, T-MAC, E2-MAC, Sync-LS (Synchronised Latency Secured) MAC


Zigbee

PANC N1 N2 N3 N4Time

frame 1


frame 2


frame 3


frame 4

Data Beacon

Data transmission is followed by beacon from PANC In each time frame 1-hop transmission is occurred Requirement of time frames are proportional to the

number of hops in the networks


Adaptive S-MAC

ListenSleep

SYNC

1

3

4

Data

ACKCTS

RTS

2

SYNC

Source

Sink

Time Frame 1 Time Frame 2

Sleep Delay

Sleep Delay

SleepListen

SYNC

Data

ACKCTS

RTS

RTS

Listen

Data

ACKCTS

RTS

Data

ACKCTS

Data

ACKCTS

5RTS

Sync signal is transmitted at the starting of time frame

In each time frame 2-hops transmission is occurred

End to end Latency =½*Latency in Zigbee


LE-MAC

ListenSleep

SYNC

1

3

4

Data

ACKCTS

RTS

2

Source

Sink

Time Frame 1

RTSData

ACKCTS

ACK

5

RTS

Data

ACKCTS Data

CTS

Listen

Data

ACKCTS

RTS

RTS

T-wakeup

Carriersensing

Carriersensing

Carriersensing

Sleep Delay

Sync signal is transmitted at the starting of time frame

In each time frame 4-hops transmission is occurred

End to end latency= ¼*Zigbee


Sync-LS Protocol

N1

N2

N3

N4

Beacon +F. Data

Sleep Time

Sleep Time Sleep Time

Forward Time Frameof Sync-LS

Reverse Time Frame ofSync-LS

Single Time Frame of Sync-LS

Coordinator

Beacon

Data

Time frame is divided into two parts- Forward time frame- Reverse time frame


Sync-LS Protocol In forward time frame, beacon and forward data are

transmitted up to end node To save energy, every node goes to sleep mode after forward

data transmission In reverse time frame, parent nodes transmit beacon to its

children nodes and receives the reverse data Transmission of beacon is controlled by the wakeup timer Wakeup timer is maintained by the following equation

Where, N= Maximum hop number, K= hop distance from edge node, tmargin= additional sleep time before reverse time frame, ∆tr = time interval between two reverse beacon, ∆tf = time interval between two forward beacon

frinmbfbr tktktkNtkNt )1()()( arg


Comparison of Average Latency

1 2 3 4 5 6 7 8 9 100

1

2

3

4

5

6

7

8

9

10

Lat

ency

[Sec

]

Hop distance

Sync-LS LE-MAC Adaptive S-MAC Zigbee

Sync-LS protocol provides lowest latency it requires a single time frame


Comparison of Energy Consumption

1 2 3 4 5 6 7 8 9 100.0

0.5

1.0

1.5

2.0

2.5

3.0

Ene

rgy

cons

umpt

ion

[mj]

Hop distance

Zigbee Sync-LS

Energy consumption depends on the modes of a sensor node

- Active mode (Transmission and Reception state)

- Sleep mode Energy consumption expressed by the

following equation

Where, n=number of nodes in the network, P t = power consumption per sec for data transmission, Tt = data transmission time, Pr = power consumption per sec for data reception or idle, Ta = active time

- Sleep mode energy consumption is neglected

Simulation result shows that energy consumption in Sync-LS is little higher than Zigbee because Sync-LS requires two beacons.

Thanks for Your Kind Attention


wireless sensor network protocols dr. monir hossen ece, kuet department of electronics and...

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