On the Energy Efficient Design of Wireless Sensor Networks

Tariq M. Jadoon, PhD

Department of Computer ScienceLahore University of Management Sciences

Agenda Overview MAC and Network Layer Simulation Model Results Conclusions & Future Work

Overview What are WSNs? Wireless Sensor Networks (WSNs):

Small sensor nodes (or motes) Monitoring the environment and processing and communicating the gathered

information. Base stations (also called sinks)

centralize the data gathered by sensor nodes. Sensor nodes consist of:

Sensors Embedded processor Radio transceiver Battery

http://www.evaluationengineering.com/archive/articles/0704/Images/dataFIG1-copy.jpg

Energy Conservation Low Traffic Rate / Predefined traffic patterns Low Mobility

Sensor Vs. Adhoc Networks

Main Issues in the Design of WSNs Energy Conservation Low-cost Optimal placement of the sensor nodes

Energy efficient design across all layers

Radio communication is a major source of power consumption MAC layer design => rules of transmitting and receiving over the

wireless medium using the radio.

What is the effect of changing the MAC layer protocol on the average energy consumed for a given network layer protocol?

Is it possible to tune the MAC/ Network layer for optimal energy consumption?

Energy Consumption Transmission Reception

Overhead Collision Idle Listening Overhearing Control Packets

Advantages: • Collision Avoidance,• Idle Listening• Overhearing

Avoidance

Disadvantages: • Frequent

Synchronization• Scalability

Advantages: • No Synchronization• Scalable

Disadvantages: • Collision• Idle Listening, etc.

MAC Layer (who transmits when)

MAC Protocols

Scheduled (TDMA Based)

Random Access (Contention-Based)

Random Access MAC Protocol S-MAC

Periodic Listen and Sleep Collision Avoidance Overhearing Avoidance

Implementation Details Perfect Synchronization Message Passing Overhearing Avoidance Cycle Length – 1 sec 3%, 5% S-MAC Frame Sizes

RTS: 20 Bytes CTS/ACK: 14 Bytes Data Frame: 34 Bytes + Network Layer Packet Size

RTSRTS CTSData ACKData

Sleep Mode Listen Mode

A B C

Power

Time

Wakeup

Time

Cycle Time

Sleep

Time

Duty Cycle = (Wakeup Time) / (Cycle Time)

= n

= n

Scheduled MAC Protocol TDMA-Wakeup (TDMA-W)

S-Slot W-Slot Channel Access

Protocol Incoming Counter Outgoing Counter

Implementation Details No use of Self Organization Perfect Synchronization Cycle Length – 1 sec Slot Time – 13.6 msec 72 Slots per TDMA Cycle Counter – 2, 4, 6 Frame Sizes:

Wakeup Frame: 20 Bytes Data Frame: 34 Bytes + Network Layer Packet Size

S1 S2 W1 W2

S1 S2 W1 W2W1 W2

W1 W2

Sleep State

Wakeup State

Wakeup Frame

Data Frame S1 S2

S1 S2

Node 1

Node 2

Outgoing Counter[2]

Incoming Counter[1]

Network Layer – Energy Aware Routing Protocol

Destination-initiated Reactive Protocol Multiple Paths between Source and Destination Path Probabilistically chosen at each hop Probability function of Cost Metric Cost Metric function of Residual and Transmission Energy

Cij = eijα Ri

-β

Setup Phase Data Communication Phase Route Maintenance Phase

Implementation Details α = 0; β = 1, 10, 100 Packet Sizes

Route Request: 32 Bytes Data: 32 Bytes + Application Layer Message Size

Source

Destination

B

D

CA

E

Simulation Model

120m

120 mDestination Node

Source Node

20 m

Extended LSU SensorSimulator3.1in OMNeT++

Basic Structure Simple Modules

– Protocol Layers– Hardware Components

Compound Modules – Sensor Nodes

System Module – Network

Simulation Design Coordinator Module Protocol Stack

– Application, Network, MAC and Physical Layer

Hardware Components– Battery, Radio and CPU

Wireless Channel Module

Sensor Node Hardware Components

Protocol Stack Application Layer – Light Sensor sending after fixed

interval Network Layer – Energy Aware Routing

β = 1, 10, 100 MAC Layer – S-MAC TDMA-W 3%, 5% Counter = 2, 4, 6 Physical Layer – No attenuation

Battery

Voltage

Radio

Data Rate

SLEEP Current

IDLE Current

TRANSMIT Current

RECEIVE Current

3V 40 kbps 5 μA 4.5 mA 8.25 mA 4.5 mA

Experiments and Results

1.1

1.225

1.35

1.475

1.6

1.725

1.85

10 15 20 25 30

Interarrival Time (sec)

Ene

rgy

Con

sum

ed (

J)

3%_SMACTDMA-w_Counter2TDMA-w_Counter4TDMA-w_Counter6

Experiments and Results

1.5

1.75

2

2.25

2.5

2.75

3

3.25

10 15 20 25 30

Interarrival Time (sec)

En

ergy

Con

sum

ed (

J)

3%_S-MAC

5%_S-MAC

Conclusions