Energy Efficient Communication in Wireless Sensor Networks

1. Energy Efficient Communication in Wireless Sensor Networks Yingyue Xu 7/16/2014

2. Characteristics of Sensor Devices • Ability to monitor a wide variety of ambient conditions: • temperature, • pressure, • mechanical stress level on attached objects… • Will be equipped with significant processing, memory, and wireless communication capabilities.

3. Location Finding System Mobilizer Sensor ADC Processor Transceiver Storage PowerUnit Power Generator Sensor Node Architecture

4. Sensor Networks • Large number of heterogeneous sensor devices • Scalable • Energy constrained • Dynamic, adaptive to changeing • Data centric: data is requested based on certain attributes, SPIN and Direct diffusion • Application specific • Unattended operation, configuration done automatically and repeatedly

5. Sensor Networks Architecture

6. Design Factors(Akyildiz et al, IEEE Comm. Mag. Aug. 2002) • Fault Tolerance (sustain functionalities) • Scalability (hundreds or thousands) • Production Cost (now $10, near future $1) • Hardware Constraints(small, environment, unattended) • Network Topology (pre-, post-, and re-deployment) • Transmission Media (RF (WINS), Infrared (Bluetooth), and Optical (Smart Dust)) • Power Consumption (with < 0.5 Ah, 1.2 V)

7. Energy Save Ideas Task Level Acceptable Functionality with Reduced Computations Application and QoS Driven Energy, Delay, and Bandwidth Management Algorithm Level Collaborative Signal Processing and Coordinated Communications Protocols Level Power Aware Routing and Selective Multicasting Physical Level Radio Power Control and Dynamic Bandwidth Management

8. Put a node into sleep state Assign per-node transmit powers Energy Save Methods Shutdown [Srinivasan01] MAC layer Scaling Power Save Protocols Synchronous IEEE 802.11 Network layer Topology based Span, LEACH Asynchronous BECA/AFECA Mobile-agent-based Application layer Energy aware application, localization, tracking Power Control Techniques Topology control [Tang01] Maximum PA route Maximum lifetime routing Minimum energy route Minimum hop route Maximum minimum PA node route

9. Micro Sensor Node Power Model (Energy Consumers and Providers) Radio Model CPU Model Sensor #1 Model Sensor #2 Model Battery Model Sensor node energy model

10. Battery model • linear model • discharge rate dependent model • relaxation model

11. Radio model

12. Computation model

13. Sensing model

14. Power saving mode • Turning the transceiver off may not always be efficient. Operation in a power-saving mode is energy-efficient only if the time spent in that mode is greater than a certain threshold

15. Multiple hops • Using several short hops may be more energy efficient than using one large hop.

16. Some notes • Sending>Receiving>Idle>Sleep • Small packets (such as “hello” message) are a relatively expensive mechanism • Broadcast is expensive in a dense network

17. Mobile agent paradigm • Good for distributed environment, such as sensor networks • Low delay • Energy efficient • Migrate the nodes near the phenomenon, other nodes can keep in sleep state • Reduce network traffic • Itinerary design can further improve the lifetime of sensor network • Fault tolerant