Elsevier

Ad Hoc Networks

Volume 2, Issue 4, October 2004, Pages 351-367
Ad Hoc Networks

Wireless sensor and actor networks: research challenges☆☆,

https://doi.org/10.1016/j.adhoc.2004.04.003Get rights and content

Abstract

Wireless sensor and actor networks (WSANs) refer to a group of sensors and actors linked by wireless medium to perform distributed sensing and acting tasks. The realization of wireless sensor and actor networks (WSANs) needs to satisfy the requirements introduced by the coexistence of sensors and actors. In WSANs, sensors gather information about the physical world, while actors take decisions and then perform appropriate actions upon the environment, which allows a user to effectively sense and act from a distance. In order to provide effective sensing and acting, coordination mechanisms are required among sensors and actors. Moreover, to perform right and timely actions, sensor data must be valid at the time of acting. This paper explores sensor-actor and actor-actor coordination and describes research challenges for coordination and communication problems.

Introduction

Recent technological advances have lead to the emergence of distributed wireless sensor and actor networks (WSANs) which are capable of observing the physical world, processing the data, making decisions based on the observations and performing appropriate actions. These networks can be an integral part of systems such as battlefield surveillance and microclimate control in buildings, nuclear, biological and chemical attack detection [2], home automation [19] and environmental monitoring.

For example, in the case of a fire, sensors relay the exact origin and intensity of the fire to water sprinkler actors so that the fire can easily be extinguished before it becomes uncontrollable. Similarly, motion and light sensors in a room can detect the presence of people and then command the appropriate actors to execute actions based on the pre-specified user preferences.

In WSANs, the phenomena of sensing and acting are performed by sensor and actor nodes, respectively. Sensors are low-cost, low power devices with limited sensing, computation, and wireless communication capabilities. Actors are resource rich nodes equipped with better processing capabilities, higher transmission powers and longer battery life. Moreover, the number of sensor nodes deployed in a target area may be in the order of hundreds or thousands where such a dense deployment is usually not necessary for actor nodes, since actors have higher capabilities and can act on large areas.

WSANs have the following unique characteristics:

  • Real-time requirement: In WSANs, depending on the application there may be a need to rapidly respond to sensor input. For instance, in a fire application, actions should be initiated on the event area as soon as possible. Moreover, the collected and delivered sensor data must still be valid at the time of acting. For example, if sensors detect a malicious person in an area and transmit this information to the disposer of a tranquilizing gas actors that person must then still be in the same area when actors carry out the task. Therefore, the issue of real-time communication is very important in WSANs.

  • Coordination: Unlike WSNs where the central entity (i.e., sink) performs the functions of data collection and coordination, in WSANs, new networking phenomena called sensor-actor and actor–actor coordination may occur (see Section III). In particular, sensor-actor coordination provides the transmission of event features from sensors to actors. After receiving event information, actors need to coordinate with each other in order to make decisions on the most appropriate way to perform the action.


Many protocols and algorithms have been proposed for WSNs in recent years [2]. However, since the above listed requirements impose stricter constraints, they may not be well-suited for the unique features and application requirements of WSANs. Moreover, although there has been some research effort related to WSANs, to the best of our knowledge, none of the existing studies to date investigate research challenges occurring due to the coexistence of sensors and actors.

For example, both in [6] and [13] control engineering problems and existing technologies about sensor and actor networks are presented, respectively. However, neither of these studies investigates the interaction among sensors and actors. In [10], only actor–actor coordination is handled without any insight into the sensor-actor coordination problem. A TDMA MAC protocol is introduced in [4] where it is assumed that sensor and actor nodes are of same type which obviously does not reflect the actual WSANs. In [15], the routing problems are investigated between sensor and actor nodes. However, no coordination problems in sensor-actor or in actor–actor communications are considered in the study.

As a result, despite some existing research in WSAN, coordination and communication problems that arise in WSANs due to the coexistence of sensors and actors are yet to be investigated.

The remainder of the paper is organized as follows: In Section 2, we present the physical architecture of WSANs. We explain the requirements of sensor-actor and actor–actor coordinations in Sections 3 Effective sensor-actor coordination, 4 Effective coordination among actors, respectively. In Section 5, we investigate the protocol stack of nodes and corresponding challenges both for sensor-actor and actor–actor communications. Finally, the paper is concluded in Section 6.

Section snippets

Physical characteristics of WSANs

In WSANs, the roles of sensor and actor nodes are to collect data from the environment and perform appropriate actions based on this collected data, respectively. Thus, as shown in Fig. 1 these nodes are scattered in the sensor/actor field while the sink monitors the overall network and communicates with the task manager node and sensor/actor nodes.

Sensors detecting a phenomenon either transmit their readings to the actor nodes which process all incoming data and initiate appropriate actions,

Effective sensor-actor coordination

The most important characteristic of sensor-actor communication is to provide low communication delay due to the proximity of sensors and actors. The main problems which should be investigated for the sensor-actor coordination are:

  • 1.

    What are the requirements of this communication?

  • 2.

    Which sensors communicate with which actors?

  • 3.

    How is this communication realized?

In addressing the first problem, one of the main requirements of sensor-actor communication is to consume low energy as in WSNs. Moreover, in

Effective coordination among actors

As stated in Section 2, in WSANs actors communicate with each other in addition to communicating with sensors. Actor–actor communication occur in the following situations:

  • The actor receiving sensor data may not act on the event area due to small action range or insufficient energy.

  • One actor may not be enough to perform the required action, thus, other nearby actors should be triggered.

  • If multiple actors receive the same event information and there is an action threshold, these actors should

Protocol stack for WSANs

To date there exists no standardized protocol stack for WSNs and WSANs. We suggest that the protocol stack for sensor and actor nodes may basically consist of three planes, (i.e., communication plane, coordination plane, and management plane) shown in Fig. 8. Communication plane3 enables the information exchange among the nodes of the network. Data received by a node

Conclusion

The effectiveness of the sensor networking can experience a profound leap if the actors are also an integral part of the deployed network. When the sensor field is complemented with actors, there will be one more option called acting as well as sensing and deciding for human controller. On the other hand, realization of wireless sensor and actor networks (WSANs) needs to satisfy the requirements introduced by the coexistence of sensors and actors. Throughout this paper, we explain the research

Acknowledgment

We thank Ozgur Akan and Eylem Ekici for their feedback and suggestions.

Ian F. Akyildiz received his BS, MS, and PhD degrees in Computer Engineering from the University of Erlangen-Nuernberg, Germany, in 1978, 1981 and 1984, respectively.

Currently, he is the Ken Byers Distinguished Chair Professor with the School of Electrical and Computer Engineering, Georgia Institute of Technology and Director of Broadband and Wireless Networking Laboratory.

He is an Editor-in-Chief of Computer Networks (Elsevier) and for the newly launched Ad-Hoc Networks (Elsevier) Journal.

He

References (24)

  • I.F. Akyildiz et al.

    Wireless sensor networks: A survey

    Computer Networks

    (2002)
  • I. Chlamtac et al.

    Mobile ad-hoc networking: imperatives and challenges

    Ad Hoc Networks

    (2003)
  • K. Akkaya, M. Younis, A survey on routing protocols for wireless sensor networks, Ad Hoc Networks, in press,...
  • M. Caccamo, L.Y. Zhang, L. Sha, G. Buttazzo, An implicit prioritized access protocol for wireless sensor networks, in:...
  • T.W. Carley, M.A. Ba, R. Barua, D.B. Stewart, Contention-free periodic message scheduler medium access control in...
  • M. Chow, Y. Tipsuwan, Network-based control systems, in: Proc. of IEEE IECon 2001 Tutorial, Denver, CO, November...
  • M. Conti et al.

    Cross-layering in mobile ad-hoc network design

    IEEE Computer, Special Issue on Ad Hoc Networks

    (2004)
  • DARPA Tactical Mobile Robotics, http://www.darpa.mil/ato/programs/tmr.htm, visited in March...
  • H.R. Everett, D.W. Gage, A Third Generation Security Robot, SPIE Mobile Robot and Automated Vehicle Control Systems,...
  • B.P. Gerkey, M.J. Mataric’, A market-based formulation of sensor-actuator network coordination, in: Proc. of the AAAI...
  • B.P. Gerkey et al.

    Sold!: Auction methods for multi-robot coordination

    IEEE Transactions on Robotics and Automation, Special Issue on Multi-robot Systems

    (2002)
  • A.J. Goldsmith et al.

    Design challenges for energy-contrained ad-hoc wireless networks

    IEEE Wireless Communications

    (2002)
  • Cited by (1351)

    View all citing articles on Scopus

    Ian F. Akyildiz received his BS, MS, and PhD degrees in Computer Engineering from the University of Erlangen-Nuernberg, Germany, in 1978, 1981 and 1984, respectively.

    Currently, he is the Ken Byers Distinguished Chair Professor with the School of Electrical and Computer Engineering, Georgia Institute of Technology and Director of Broadband and Wireless Networking Laboratory.

    He is an Editor-in-Chief of Computer Networks (Elsevier) and for the newly launched Ad-Hoc Networks (Elsevier) Journal.

    He is an IEEE FELLOW (1995), an ACM FELLOW (1996). He served as a National Lecturer for ACM from 1989 until 1998 and received the ACM Outstanding Distinguished Lecturer Award for 1994.

    He received the 1997 IEEE Leonard G. Abraham Prize award (IEEE Communications Society) for his paper entitled “Multimedia Group Synchronization Protocols for Integrated Services Architectures” published in the IEEE Journal of Selected Areas in Communications (JSAC) in January 1996.

    He received the 2002 IEEE Harry M. Goode Memorial award (IEEE Computer Society) with the citation “for significant and pioneering contributions to advanced architectures and protocols for wireless and satellite networking”.

    He received the 2003 IEEE Best Tutorial Award (IEEE Communication Society) for his paper entitled “A Survey on Sensor Networks”, published in IEEE Communication Magazine, in August 2002.

    He received the 2003 ACM SIGMOBILE award for his significant contributions to mobile computing and wireless networking.

    His current research interests are in Sensor Networks, InterPlaNetary Internet, Wireless Networks and Satellite Networks.

    Ismail H. Kasimoglu received his B.Sc. degree in Electrical and Electronics Engineering from Bilkent University, Ankara, Turkey, in 2003. He is currently a Research Assistant in the Broadband and Wireless Networking Laboratory and pursuing his Ph.D. degree at the School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA. His current research interests include wireless sensor and actor networks.

    ☆☆

    This work is supported by the National Science Foundation under contract ECS-0428329.

    We refer to entities that can act on the network as actors They are sometimes referred to as actuators in related literature.

    View full text