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On the Energy Efficient Design of Wireless Sensor Networks
Tariq M. Jadoon, PhD
Department of Computer ScienceLahore University of Management Sciences
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
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