This document summarizes various techniques for saving energy in wireless sensor networks. It discusses how sensor nodes consume power through transmission, reception, processing and idle listening. It then describes approaches like sleep-wake scheduling, MAC protocols like S-MAC and T-MAC, in-network processing, network coding and scheduled/contention-based communication protocols to minimize energy usage. The goal is to reduce unnecessary listening and maximize the time sensors spend in sleep mode to improve battery life for sensor network applications.

1. Power Saving in Wireless Sensor Networks Eng. MshariAlabdulkarim

3. Introduction.

4. Power Consumption in WSNs.

5. Sleep-wake Scheduling.

6. MAC Protocol for WSN.

7. In-network Processing.

8. Network Coding.

10. Energy Saving in WSNs Introduction Wireless Sensor Network? A wireless sensor network is a collection of nodes “sensors” organized into a cooperative network. The nodes communicate wirelessly and often self-organize after being deployed in an ad-hoc fashion. Base Station Detection Sensor Field

11. Energy Saving in WSNs Introduction (Cont.) What are the components of the wireless sensor? Processor. Memory. RF transceiver. Power source. Sensor.

12. Energy Saving in WSNs Introduction (Cont.) What is the goal of the sensor node? The goal from the sensor node is to collect the data at regular intervals, then transform the data into an electrical signal and finally send the signal to the sink or the base node.

13. Energy Saving in WSNs Introduction (Cont.)

15. Energy Saving in WSNs Introduction (Cont.) Wireless Sensor Network Example (1):

16. Energy Saving in WSNs Introduction (Cont.) Wireless Sensor Network Example (2):

17. Energy Saving in WSNs Introduction (Cont.) Short Video

18. Energy Saving in WSNs Power Consumption in WSNs The power issue in the wireless sensor network is one of the biggest challenges, because the sensor has a limited source of power which is also hard to replace or recharge “e.g. sensors in the battle field, sensors in a large forest … etc”. Why limited source of power? Inexpensive nature. Limited size and weight. Redundant nature.

20. Processing query requests.

22. Retransmitting because of collisions “e.g. two packets arrived at the same time at the same sensor”.

23. Overhearing “when a sensor received a packet doesn’t belong to it”.

24. Generating and handling control packets.

26. In-network Processing.

27. Network Coding.

29. Energy Saving in WSNs Power consumption model: Time Wake Wake Sleep Sleep Sleep Sleep and Wake Duty Cycle

30. Energy Saving in WSNs

36. Allow each node in the WSN to set its own sleep/wake schedule independently.

38. Energy Saving in WSNs S-MAC Protocol: Stand for: Sensors Medium Access Control. Strategy: All node follow a periodic sleep/wake cycle, where the waking time is about 10% of the sleeping time, and the nodes that are close to each other synchronize their active cycles together. Listen Listen Sleep Sleep Time T

40. Collision Avoidance.

41. Overhearing Avoidance.

43. Energy Saving in WSNs Questions? What S-MAC, T-MAC, B-MAC are doing? Trying to minimize idle listen as mush as possible. Why radio should listen the channel? To minimize collisions. How can we make collision free without listen the channel? TDMA “Time Division Multiple Access”.

44. Energy Saving in WSNs In-network Processing After the sensors detect phenomena or change, they generate an event to the user and by that we will have a huge number of transmissions which will consume the power of the sensors. Strategy: Reduce the number of transmissions by aggregating several eventsinto a single event. Aggregation takes place if the data arriving to the common node have same attributes of the phenomenon being sensed.

48. Energy Saving in WSNs Communication Protocol The goal from adjusting the communication protocol “Medium Access Control” is to avoid the collisions by scheduling nodes onto different sub-channels that are divided either by time “TDMA”, frequency “FDMA” or orthogonal codes “CDMA”.

49. Energy Saving in WSNs Scheduled Protocol: Strategy: Prevent the collisions by reserving and scheduling the resources. Example: The best protocol considered as scheduled protocol is the TDMA “Time Division Multiple Access”, where the time is divided into N slots and each slot can be used by only one sensor. Frame 1 Frame 2 1 2 3 N 1 2 3 N Time TDMA MAC Protocol

51. Saving the power from being wasted by turning off the radio out the allocated time slot.

54. Support peer-to-peer communications.