Wireless sensor and actor networks: research challenges Ian F. Akyildiz, Ismail H. Kasimoglu Elsevier Ad Hoc Networks 2004 JY Hong 2008. 9. 11

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

WSAN : Research Challenges Questions or Comments WSAN : Research Challenges