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On the Energy Efficient Design of Wireless Sensor Networks. Tariq M. Jadoon, PhD Department of Computer Science Lahore University of Management Sciences. Agenda . Overview MAC and Network Layer Simulation Model Results Conclusions & Future Work. Overview. What are WSNs?
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On the Energy Efficient Design of Wireless Sensor Networks Tariq M. Jadoon, PhD Department of Computer Science Lahore 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
Sensor Vs. Adhoc Networks • Energy Conservation • Low Traffic Rate / Predefined traffic patterns • Low Mobility
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 MAC Layer (who transmits when) • Advantages: • Collision Avoidance, • Idle Listening • Overhearing Avoidance • Disadvantages: • Frequent Synchronization • Scalability MAC Protocols • Advantages: • No Synchronization • Scalable • Disadvantages: • Collision • Idle Listening, etc. Scheduled(TDMA Based) Random Access(Contention-Based)
Random Access MAC Protocol Power Cycle Time • 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 Sleep Time Wakeup Time Time Duty Cycle = (Wakeup Time) / (Cycle Time) Data Data ACK CTS RTS RTS A B C Sleep Mode Listen Mode
Node 1 S1 S2 W1 W2 S1 S2 W1 W2 Node 2 S1 S2 W1 W2 S1 S2 W1 W2 Sleep State Wakeup Frame Wakeup State Data Frame 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 Outgoing Counter[2] = n Incoming Counter[1] = n
Source Destination 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 B C A D E
20 m 120m Source Node Destination Node 120 m Simulation Model
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