1. Wireless sensor and actor networks: research challenges
Ian F. Akyildiz, Ismail H. Kasimoglu
Elsevier Ad Hoc Networks 2004
JY Hong

2. WSAN : Research Challenges
Contents
Introduction
Physical characteristics of WSAN
Effective sensor-actor coordination
Effective actor-actor coordination
Protocol stack for WSAN
Conclusion
WSAN : Research Challenges

3. WSAN : Research Challenges
Introduction (1/3)
WSAN (Wireless Sensor and Actor Network)
Definition
Observing the physical world
Processing the data and Making decisions
Performing appropriate actions
Applications
Battlefield surveillance, microclimate control in building, nuclear, biological and chemical attack detection, home automation, environmental monitoring
WSAN : Research Challenges

4. WSAN : Research Challenges
Introduction (2/3)
Elements of WSAN
Sensor
Low-cost
Limited sensing, computation wireless communication capabilities
Hundreds or thousands sensors are deployed in target area
Actor
Resource rich nodes
Higher transmission power
Dense deployment not necessary
WSAN : Research Challenges

5. WSAN : Research Challenges
Introduction (3/3)
WSAN unique characteristics
Real-time requirement
Rapid respond to sensor input
Coordination
In order to make decisions on the most appropriate action
Sensor-actor and actor-actor coordination may occur
Example
Fire extinguisher system, Malicious person detecting system
Difference from WSN
Actor exists
Complex coordination
WSN is not be well-suited for WSAN
WSAN : Research Challenges

6. Battle field Surveillance system - 1
Satellite
Communication
Main Task Manager
Target Detection
Target Tracking
Target Identification
Battle field Monitoring
Sensor Node
Sink Node
Gateway
Military Tactical
Networks
Sensing Field
WSAN : Research Challenges

7. Battle field Surveillance system - 2
Types of actors
WSAN : Research Challenges

8. WSAN : Research Challenges
DARPA Urban Challenge 2007
November 3, at California Victorvile
Driverless car racing
Traffic Signal detection sensor
Collision prevention sensor
Central computer and GPS
WSAN : Research Challenges

9. Physical characteristics of WSAN (1/4)
The physical architecture
WSAN : Research Challenges

10. Physical characteristics of WSAN (2/4)
Automated vs. Semi-Automated Architecture
Focus on the Automated Architecture
Low latency
Long network lifetime
Automated Architecture
Semi-Automated Architecture
WSAN : Research Challenges

11. Physical characteristics of WSAN (3/4)
The component of Sensors
The component of Actors
Sensor와 Actor 가 하나의 node로 구성되기도 하는데, 대표적인 것이 로봇이다.
로봇 하나가 센싱한 데이터는 reliable 하지 않기 때문에, 주변에 설치된 센서로부터 정보를 읽어 들여서, 행동을 결정하게 된다.
실제 어플리케이션에서는 로봇은 actor 역할 담당.
WSAN : Research Challenges

12. Physical characteristics of WSAN (4/4)
Example of Several Actors
WSAN : Research Challenges

13. Effective sensor-actor coordination (1/5)
Most important characteristic
To provide low communication delay
Main investigating problems
What are the requirements of this communication?
Consume low energy
Real-time traffic
Ordered delivery of information
Synchronization
Which sensors communicate with which actors?
Redundancy Elimination
Actor selection
How is this communication realized?
Single hop vs. Multi hop
Depends on the deployment and location of actor node
Real-time traffic에 대해 WSN에는 솔루션이 없다. 왜냐하면 Actor가 없기 때문에
WSAN : Research Challenges

14. Effective sensor-actor coordination (2/5)
Redundancy elimination
Minimal set of actors and sensors
Some applications
Level of Redundancy
Mutually Exclusive
Some level of redundancy
Mutually exclusive : do not overlap, for example; 식물에 물주는 액터의 경우
WSAN : Research Challenges

15. Effective sensor-actor coordination (3/5)
Multi-Actor vs. Single-Actor
(a) Multi-Actor : Drawback of lack of coordination
- Too many unnecessary actors can be activated
(b) Single-Actor : To avoid above situation
- Sensors should coordinate with sensors
- One actor to collect the data
WSAN : Research Challenges

16. Effective sensor-actor coordination (4/5)
Single Actor
Main challenges is to determine the single actor node
Select SA based on below criteria
Distance
Minimum energy path
The action range of the actor
No guarantee
One actor is not well-suited due to the coverage and energy constraints
Actor-Actor Coordination
Actor publishes the announcement message
Select one or more other actors to perform the appropriate actions
WSAN : Research Challenges

17. Effective sensor-actor coordination (5/5)
Research Challenges
For both Single-Actor and Multiple-Actor
Ordered delivery of information
Synchronization
Selection of an actor or a set of actors
In Multiple-Actor
The redundancy in the set of actors
Trade-offs between Single-Actor and Multiple-Actor
WSAN : Research Challenges

18. Effective actor-actor coordination (1/3)
In case of actor-actor communication occur
Small action range or insufficient energy by one actor
Multiple actors receive the same event information
Multiple actors are required to cover the entire event region
Synchronization requirement
The event is spreading to other actors’ acting areas
Task assignment problem
Single-Actor Task (SAT) vs. Multi-Actor Task (MAT)
Centralized Decision (CD) vs. Distributed Decision (DD)
WSAN : Research Challenges

19. Effective actor-actor coordination (2/3)
Task assignment
In MAT, if multiple actors receive event information
Distributed Decision case
Negotiate with each actors
Choose “Best” Actors
Centralized Decision case
Actors directly transmit to the pre-determined actor node
In MAT, if only one actor (SA) receives event information
Centralized Decision
“Announcement message” to other actors
Select “Best” Actors
WSAN : Research Challenges

20. Effective actor-actor coordination (3/3)
Research challenges
Algorithms
Communication model between actors
Ordered execution of tasks for a series of events
Synchronization
Executed by a set of actors
Redundancy in the set of actors
The partial execution of tasks
Efficient data transmission algorithm for announcement message and negotiation
Minimize the task completion time
Communication protocol, Real time properties of WSAN
WSAN : Research Challenges

21. Protocol stack for WSAN
No standard protocol stack for WSN and WSAN
WSAN protocol stack
Communication plane, Coordination plane, Management plane
Cross Layering
WSAN : Research Challenges

22. WSAN : Research Challenges
Conclusion
The effectiveness of WSN will be increased
The actors are deployed in the network ,WSAN
Many applications
Realization of WSAN
Satisfy the requirements of the coexistence of sensors and actors
We investigated research challenge
Real-time communication protocol
Sensor-Actor coordination
Actor-Actor coordination
WSAN : Research Challenges

23. WSAN : Research Challenges
Questions or Comments
WSAN : Research Challenges