1 Energy Efficient Communication in Wireless Sensor Networks Yingyue Xu 8/14/2015

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 Sensor Node Architecture Power Unit Power Generator Location Finding System Mobilizer Sensor ADC Processor Storage Transceiver

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 –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) Design Factors ( Akyildiz et al, IEEE Comm. Mag. Aug. 2002)

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

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

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

10 1.linear model 2.discharge rate dependent model 3.relaxation model Battery model

11 Radio model

12 Computation model

13 Sensing model

14 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 Power saving mode

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

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

17 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 Mobile agent paradigm