Elsevier

Ad Hoc Networks

Volume 20, September 2014, Pages 77-95
Ad Hoc Networks

A hybrid MAC protocol for emergency response wireless sensor networks

https://doi.org/10.1016/j.adhoc.2014.03.008Get rights and content

Abstract

We introduce ER-MAC, a novel hybrid MAC protocol for emergency response wireless sensor networks. It tackles the most important emergency response requirements, such as autonomous switching from energy-efficient normal monitoring to emergency monitoring to cope with heavy traffic, robust adaptation to changes in the topology, packet prioritisation and fairness support. ER-MAC is designed as a hybrid of the TDMA and CSMA approaches, giving it the flexibility to adapt to traffic and topology changes. It adopts a TDMA approach to schedule collision-free slots. Nodes wake up for their scheduled slots, but otherwise switch into power-saving sleep mode. When an emergency occurs, nodes that participate in the emergency monitoring change their MAC behaviour by allowing contention in TDMA slots to achieve high delivery ratio and low latency. In its operation, ER-MAC prioritises high priority packets and sacrifices the delivery ratio and latency of the low priority ones. ER-MAC also guarantees fairness over the packets’ sources and offers a synchronised and loose slot structure to allow nodes to join or leave the network. Simulations in ns-2 show the superiority of ER-MAC over Z-MAC, a state-of-the art hybrid MAC protocol, with higher delivery ratio, lower latency, and lower energy consumption. When a cluster of nodes in the network detects fire, nodes with ER-MAC deliver twice as many high priority emergency packets and four times faster than Z-MAC. This is achieved by ER-MAC with only one fifth as much energy as Z-MAC.

Introduction

Wireless Sensor Networks (WSNs) for emergency applications, such as fire, flood and volcano monitoring, must be traffic and topology adaptive. The communication protocol can be delay tolerant during normal monitoring and designed for energy efficiency. However, when an emergency event occurs, energy efficiency is less important than high packet delivery ratio and low latency, and the communication protocol should adapt in response. The protocol must also be able to prioritise high priority packets, as they normally contain important sensed data and require timely delivery. In addition, the protocol must support fairness over the packets’ sources. Fairness is important when a hazard occurs, so the sink can receive complete information from all sensor nodes in the network to monitor the spread of the hazard.

Some traffic and topology adaptive Medium Access Control (MAC) protocols have been designed. S-MAC [1], T-MAC [2], B-MAC [3] and X-MAC [4] are contention-based protocols that adapt to both traffic and topology changes, but suffer from collisions, idle listening and overhearing. Another contention-based protocol that satisfies the objectives for emergency response is MaxMAC [5]. However, this protocol does not support packet prioritisation and and does not guarantee fairness. Hybrid MAC protocols such as Z-MAC [6], Funneling-MAC [7] and BurstMAC [8] can adapt to traffic and topology changes as well as guarantee fairness, but they do not support packet prioritisation.

In this paper, we propose ER-MAC, a hybrid MAC protocol for emergency response WSNs. While our scenario assumption is the fire monitoring in buildings, this protocol is also useful in a range of WSN emergency applications. The contributions of this paper are:

  • ER-MAC allows contention in TDMA slots to cope with large volumes of traffic. This scheme trades energy efficiency for higher delivery ratio and lower latency.

  • ER-MAC maintains two priority queues to separate high priority packets from low priority packets.

  • ER-MAC support fairness so the sink can receive complete information from all sensor nodes in the network.

  • ER-MAC offers a synchronised and loose slot structure, where nodes can modify their schedules locally. This allows nodes to join or leave the network easily.

  • Simulation results validate ER-MAC’s performance, which outperforms Z-MAC [6] with higher delivery ratio and lower latency at low power consumption.

The remainder of this paper is organised as follows. In Section 3, we review the related work on traffic and topology adaptive MAC protocols. We formulate the problem definition in Section 2. We present the proposed ER-MAC protocol in Section 4. We show our simulation results in Section 5. Simulation results validate the performance of ER-MAC, which outperforms Z-MAC [6], a state-of-the-art hybrid MAC protocol, with higher delivery ratio and lower latency at low energy consumption. Section 6 concludes the paper. Parts of this work were presented in [9], [10].

Section snippets

Problem definition

In this section, we describe some assumptions for the network and identify the requirements for our MAC protocol.

Related work

Many MAC protocols have been designed for WSNs. Below, we present a selection of protocols that have relevance to our problem, i.e. traffic and topology adaptive during emergency monitoring. Based on the mechanisms to access the medium for data transmission, we follow the common classification for the MAC protocols: contention-based, schedule-based and hybrid that combines the features of both contention-based and schedule-based protocols. In Table 1, we compare all important issues in MAC

ER-MAC protocol design

The main functions of ER-MAC are to:

  • 1.

    establish a data gathering tree with a sink as the root of the tree and retrieve neighbourhood connectivity (topology discovery),

  • 2.

    establish nodes’ schedules (TDMA slot assignment),

  • 3.

    manage local time synchronisation to minimise clock drifts,

  • 4.

    manage two priority queues for different priority packets,

  • 5.

    respond to emergency events by changing MAC behaviour (MAC prioritisation) to cope with large volume of traffic, and

  • 6.

    manage the network when the topology changes.

ER-MAC

Evaluation of ER-MAC

By these experiments, we want to show that ER-MAC delivers low latency for high priority packets especially during emergency monitoring, it has fair packet delivery and nodes in non-emergency mode behave in an energy-efficient manner. In the simulation, we use the following metrics to measure the performance of ER-MAC:

  • 1.

    Average energy consumption per node is presented to compare the energy efficiency of communication protocols. The average energy consumption per node is calculated as the total

Conclusion

In this paper, we present ER-MAC, a hybrid MAC protocol for emergency response WSNs with flexibility to adapt well to traffic and topology changes. ER-MAC schedules collision-free slots, so during the normal monitoring, nodes only wake up for their scheduled slots, but otherwise sleep to save energy. During an emergency, nodes that participate in the emergency monitoring change their MAC behaviour by allowing contention in each slot to achieve high delivery ratio and low latency, but have to

Acknowledgment

This research is funded by the Irish Higher Education Authority PRTLI-IV research programme through the NEMBES Project and by the Science Foundation Ireland through the CTVR Project (SFI CSET 10/CE/I1853).

Lanny Sitanayah is a postdoctoral researcher in the Department of Computer Science at University College Cork, Ireland. She has a PhD degree in Computer Science from University College Cork in 2013 and an MSc degree in Computer Science from the University of Western Australia in 2009. Her research interests are in design, optimisation and test of real-time, adaptive and distributed systems; including wireless, mobile, ad hoc and sensor networks.

References (38)

  • D.T. Gottuk et al.

    Advanced fire detection using multi-signature alarm algorithms

    Fire Safety J.

    (2002)
  • A. Boukerche et al.

    Fault-tolerant wireless sensor network routing protocols for the supervision of contex-aware physical environments

    J. Parallel Distrib. Comput.

    (2006)
  • W. Ye, J. Heidemann, D. Estrin, An energy-efficient MAC protocol for wireless sensor networks, in: Proc. 21st Ann....
  • T. van Dam, K. Langendoen, An adaptive energy-efficient MAC protocol for wireless sensor networks, in: Proc. 1st Int’l...
  • J. Polastre, J. Hill, D. Culler, Versatile low power media access for wireless sensor networks, in: Proc. 2nd Int’l...
  • M. Buettner, G.V. Yee, E. Anderson, R. Han, X-MAC: a short preamble MAC protocol for duty-cycled wireless sensor...
  • P. Hurni, T. Braun, MaxMAC: a maximally traffic-adaptive MAC protocol for wireless sensor networks, in: J.S. Silva, B....
  • I. Rhee, A. Warrier, M. Aia, J. Min, Z-MAC: a hybrid MAC for wireless sensor networks, in: Proc. 3rd Int’l Conf....
  • G. Ahn, E. Miluzzo, A.T. Campbell, S.G. Hong, F. Cuomo, Funneling-MAC: a localized, sink-oriented MAC for boosting...
  • Z. Merhi, M. Elgamel, M. Bayoumi, EB-MAC: an event based medium access control for wireless sensor networks, in: Proc....
  • L. Sitanayah, C.J. Sreenan, K.N. Brown, Poster abstract: emergency response MAC protocol (ER-MAC) for wireless sensor...
  • L. Sitanayah, C.J. Sreenan, K.N. Brown, ER-MAC: a hybrid MAC protocol for emergency response wireless sensor networks,...
  • S. Chen, H. Bao, X. Zeng, Y. Yang, A fire detecting method based on multi-sensor data fusion, in: Proc. IEEE Int’l...
  • T. Tabirca, K.N. Brown, C.J. Sreenan, A dynamic model for fire emergency evacuation based on wireless sensor networks,...
  • A. El-Hoiydi, J.D. Decotignie, WiseMAC: an ultra low power MAC protocol for multi-hop wireless sensor networks, in:...
  • H. Gong, M. Liu, Y. Mao, L. Chen, L. Xie, Traffic adaptive MAC protocol for wireless sensor network, in: X. Lu, W. Zhao...
  • V. Rajendran, K. Obraczka, J.J. Garcia-Luna-Aceves, Energy-efficient collision-free medium access control for wireless...
  • V. Rajendran, J.J. Garcia-Luna-Aceves, K. Obraczka, Energy-efficient, application-aware medium access for sensor...
  • E. Egea-Lopez, J. Vales-Alonso, A.S. Martinez-Sala, J. Garcia-Haro, P. Pavon-Marino, M.V. Bueno-Delgado, A real-time...
  • Cited by (0)

    Lanny Sitanayah is a postdoctoral researcher in the Department of Computer Science at University College Cork, Ireland. She has a PhD degree in Computer Science from University College Cork in 2013 and an MSc degree in Computer Science from the University of Western Australia in 2009. Her research interests are in design, optimisation and test of real-time, adaptive and distributed systems; including wireless, mobile, ad hoc and sensor networks.

    Cormac J. Sreenan received the PhD degree in Computer Science from Cambridge University. He is a professor of Computer Science at University College Cork (UCC) in Ireland. Prior to joining UCC in 1999, he was on the Research Staff at AT&T Labs–Research, Florham Park, New Jersey, and at Bell Labs, Murray Hill, New Jersey. He is currently on the editorial boards of the IEEE Transactions on Mobile Computing, the ACM Transactions on Sensor Networks, and the ACM/Springer Multimedia Systems Journal. He is a fellow of the British Computer Society and a member of the IEEE and the ACM.

    Kenneth N. Brown joined UCC Computer Science Department as a senior lecturer in 2003, where he is the Deputy Director of 4C: Cork Constraint Computation Centre. Prior to that he was a lecturer at the University of Aberdeen, a Research Fellow at Carnegie Mellon University, and a Research Associate at the University of Bristol. His research interests are in the application of AI, optimisation and distributed reasoning, with a particular focus on wireless networks.

    View full text