On the reliability of ad hoc routing protocols for loss-and-delay sensitive applications
Introduction
Many deployment scenarios of multihop wireless networks require high transmission reliability. Transmission reliability is particularly important for mission-critical applications such as remote patient monitoring, battlefield monitoring, monitoring of disaster-struck regions, home automation, and tracking of chemical and explosive agents. These applications are loss-and-delay sensitive and therefore reliable and timely delivery of information is critical. In addition to loss-and-delay sensitivity – implying high reliability, these applications are also concerned with energy efficiency because ad hoc nodes have limited battery capacity.
In this paper, we analyze the packet delivery reliability of ad hoc routing protocols for loss-and-delay sensitive applications. In view of the above motivation, our reliability analysis is based on the following two constraints:
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The data packets must be routed reliably to the destination node with a lower delay.
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Energy required for reliable delivery of packets must be kept to a low value.
Retransmission of packets at the medium access control layer (MAC) is a common method used to achieve higher reliability. However, we ignore these retransmissions because they adversely affect Constraint 1.
As an alternative to retransmissions, we investigate the use of multiple simultaneous paths for delivering a data packet to its final destination by routing a copy through more than one paths. In this context, we show that flooding-based ad hoc routing algorithms discover node-disjoint paths only [16]; some protocols discover a single path while others maintain multiple paths between a given 〈source, destination〉 pair. We then model the reliability of multiple node-disjoint paths and show that the reliability function is a concave function of the total number of paths. Consequently, while an initial set of paths results in an exponential increase in the reliability, addition of more paths beyond a certain threshold yields negligible improvements in the reliability. Therefore, we advocate the use of a small subset of available paths as they incur less discovery and maintenance overhead.
Routing a packet through a small set of node-disjoint paths can achieve higher packet delivery reliability and lower delay. However, it may not be an energy-efficient option. Therefore, we analyze an alternate routing mechanism in which we model and compare the reliability of partially-disjoint paths [12] with that of node-disjoint paths. We show that a partially-disjoint path is more reliable and energy-efficient than a node-disjoint path. Hence, we argue that ad hoc routing protocols should discover and maintain a small set of partially-disjoint paths rather than the conventional node-disjoint paths. Based on this outcome, we suggest modifications to a typical RREQ-based route discovery mechanism to discover partially-disjoint paths. Furthermore, to complement the reliability analysis, we compare the performance of the two variants of Dynamic Source Routing (DSR) protocol namely DSR-PD (where PD refers to partially-disjoint) and DSR-FD (where FD refers to fully-disjoint) through extensive simulations. The empirical results demonstrate that DSR-PD performs extremely well than DSR-FD in all assumed scenarios which is completely in agreement with the theoretical findings of this paper.
Finally, we analyze an alternate solution to enhance the packet delivery reliability by introducing high-end beacon nodes in the network [11], [25]. For such beacon-based routing protocols, we derive an upper bound on the flooding distance up to which a packet may be flooded under given reliability constraints. If the number of paths between a source and a beacon node is higher, i.e. the network is dense, the packet can be flooded to a larger distance.
The rest of this paper is organized as follows. Section 2 briefly summarizes the previous research efforts in the area. Section 3 introduces the definitions of the terms used in the reliability analysis. A typical flooding-based route discovery and the reliability of ad hoc routing protocols with node-disjoint paths are discussed in Section 4. Comparison of partially-disjoint paths and the node-disjoint paths is explained in Section 5. Modifications to a typical flooding-based route discovery mechanism to discover partially-disjoint paths are described in Section 6. Section 7 contains the empirical evaluation of the two variants of DSR protocol namely DSR-PD and DSR-FD. Reliability analysis of beacon-based ad hoc routing protocols is presented in Section 8. Section 9 summarizes the key conclusions of the paper.
Section snippets
Related work
While hop-by-hop and end-to-end reliabilities of unicast transmissions in an ad hoc network have been investigated, reliability analysis of RREQ-based ad hoc routing protocols is largely unexplored. Gnawali et al. investigated the tradeoffs of three techniques; link layer retransmissions, blacklisting the poor quality links and the use of reliability metrics to improve the data delivery reliability in sensor networks [13]. They concluded that blacklisting of bad links or the use of reliability
System description
We consider an ad hoc network in which nodes are distributed randomly on a two-dimensional plane. The resultant network is connected and all the links – or edges – are symmetric. We assume a CSMA/CA-based MAC layer protocol for contention resolution. Even in the case of no contention, we account for the possibility that a packet may get lost due to channel errors, e.g. attenuation, fading, interference, thermal noise, etc. We also assume that there is no transport layer protocol to provide
Packet delivery reliability of ad hoc routing protocols
Flooding is the most common technique used by on-demand ad hoc routing protocols for route discovery [3], [29]. Such a route discovery mechanism can discover node-disjoint paths only. We elaborate this argument with reference to the route discovery process used in two prominent ad hoc routing protocols e.g., Ad hoc On-demand Distance Vector (AODV) routing protocol [20] and DSR [16], BeeSensor [30]. Fig. 2 gives an illustration of this process. A source node S initiates the route discovery by
Improving packet delivery reliability using partially-disjoint paths
We propose to improve the reliability of a path by adding node or edge level redundancy. The resulting path is partially-disjoint – the concept of partially-disjoint paths already exists in ad hoc routing literature [12][19]. A partially-disjoint path provides parallel links through which a packet can be forwarded to a next hop node. For instance, node 2 in Fig. 1b can receive a copy of packet either from node 1 or node 3. Consequently, it is more reliable than a node-disjoint path shown in
Discovering partially-disjoint paths in ad hoc routing protocols
We have already discussed the basic route discovery mechanism in Section 4. Therefore, in this section, we only describe modifications to the process to realize partially-disjoint paths.
Empirical validation of the reliability models
Theoretical models are generally based on some simplifying assumptions. Therefore, it is compulsory to support the outcome of this analysis through simulation studies. We used ns-2 simulator for this purpose. The major objective of this empirical study is to show that a protocol using partially-disjoint paths is more reliable and energy-efficient. Therefore, it is suitable for loss-and-delay sensitive applications. Ideally, one would like to analyze the impact of node-disjoint
Beacon-based flooding in large-scale ad hoc networks
Flooding is considered as one of the most reliable and robust packet delivery mechanism. However, the reliability of a flooding-based packet delivery system iswhere Nopt, N1, N2, … , Nn are the number of optimal paths (shortest path), 1-suboptimal paths, 2-suboptimal and n-suboptimal paths and h is the minimum flooding distance between a 〈source, destination〉 pair. As can be intuitively argued, as h → ∞, Rf(pf) → 0, irrespective of the network density.
A viable solution
Conclusions
In this paper, we analyzed the impact of multiple node-disjoint paths on the reliability of a typical ad hoc routing system in the context of delay-and-loss sensitive applications. We proved that the reliability of multiple paths increases exponentially with the addition of first few paths and then saturates at a steady-state value. Therefore, we propose that it is sufficient to maintain and use a small set of redundant paths. We also conclude that partially-disjoint paths play a key role in
Muhammad Saleem received the B.E. degree in electronics from NED University of Engineering and Technology, Karachi, Pakistan, and the M.S. in computer engineering from Center for Advanced Studies in Engineering affiliated with University of Engineering and Technology, Taxila, Pakistan. He is currently pursuing his Ph.D. studies at Center for Advanced Studies in Engineering, Islamabad, Pakistan, in the area of natural computing with application to routing in wireless ad hoc and sensor networks.
References (30)
- Wireless LAN medium access control (MAC) and physical layer (PHY) specification,...
- et al.
Event-to-sink reliable transport in wireless sensor networks
IEEE/ACM Transactions on Networking
(2005) - et al.
A survey on routing protocols for wireless sensor networks
Ad Hoc Networks
(2003) - et al.
Connectivity of wireless multihop networks in a shadow fading
ACM/Kluwer Wireless Networks Journal
(2005) - V. Bhandari, N.H. Vaidya, Reliable broadcast in wireless networks with probabilistic failures, in: Proceedings of IEEE...
- J. Broch, D.A. Maltz, D.B. Johnson, Y.-C. Hu, J. Jetcheva, A performance comparison of multi-hop wireless ad hoc...
- et al.
AntHocNet: an adaptive nature-inspired algorithm for routing in mobile ad hoc networks
European Transactions on Telecommunications (ETT), Special Issue on Self Organization in Mobile Networking
(2005) - et al.
Critical connectivity phenomena in multihop radio models
IEEE Transactions on Communications
(1989) - B. Deb, S. Bhatnagar, B. Nath, ReInForM: reliable information forwarding using multiple paths in sensor networks, in:...
- M. Farooq, Bee-Inspired Protocol Engineering: From Nature to Networks, Natural Computing Series, Springer-Verlag, 2009,...
Highly-resilient, energy-efficient multipath routing in wireless sensor networks
Mobile Computing and Communications Review
Aging analysis in large-scale wireless sensor networks
Ad Hoc Networks
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2019, HeliyonCitation Excerpt :In 2007 [25], focused their survey on clustered algorithms only and discussed their objectives, features, and complexity. An extensive study on Nature-inspired routing protocols is presented by [26] and [14]. It discusses the principles and applications of the protocols and their simulation environments.
Reliability and energy-efficiency analysis of safety message broadcast in VANETs
2018, Computer CommunicationsCitation Excerpt :M-RHB tries to maximize the reliability of local links to achieve its objectives. The problem of packet delivery reliability in wireless networks in general has also been studied separately [19–21], which we skip here for the sake of brevity. This concludes our discussion on the background and the related work.
BeeSensor: An energy-efficient and scalable routing protocol for wireless sensor networks
2012, Information SciencesA1: An energy efficient topology control algorithm for connected area coverage in wireless sensor networks
2012, Journal of Network and Computer ApplicationsSwarm intelligence based routing protocol for wireless sensor networks: Survey and future directions
2011, Information SciencesCitation Excerpt :Saleem et al. [73] have also proposed a mathematical modeling framework for the study of the behavior and the performance of the algorithm. They have extended their evaluation framework in [72,74] which can not only be adapted to a variety of ad hoc routing protocols but is particularly useful when dealing with large scale networks. Selvakennedy et al. [78] have proposed T-ANT which is a distributed, cluster-based data gathering protocol for WSNs.
MMSR-AOMDV: An enhanced multi-service support routing protocol for mobile ad hoc networks
2020, International Journal of Sensors, Wireless Communications and Control
Muhammad Saleem received the B.E. degree in electronics from NED University of Engineering and Technology, Karachi, Pakistan, and the M.S. in computer engineering from Center for Advanced Studies in Engineering affiliated with University of Engineering and Technology, Taxila, Pakistan. He is currently pursuing his Ph.D. studies at Center for Advanced Studies in Engineering, Islamabad, Pakistan, in the area of natural computing with application to routing in wireless ad hoc and sensor networks. His other research interests include performance modeling of ad hoc routing algorithms.
Israr Ullah received his MCS degree from Institute of Computing and Information Technology (ICIT), Gomal University, Pakistan, in 2004. He completed his M.S. in computer science from National University of Computer and Emerging Sciences (NUCES), Islamabad, Pakistan, in 2009. Currently, he is pursuing his Ph.D. studies at NUCES Islamabad, Pakistan, in the field of grid networks dimensioning and modeling. His research interests also include design and analysis of optimization algorithms.
Syed Ali Khayam received his B.E. degree in Computer Systems Engineering from National University of Sciences and Technology (NUST), Pakistan, in 1999 and his M.S. and Ph.D. degrees in Electrical Engineering from Michigan State University in 2003 and 2006, respectively. In February 2007, he joined the School of Electrical Engineering & Computer Science (SEECS), National University of Sciences & Technology (NUST), Pakistan, as an assistant professor. AT NUST-SEECS, he directs the Wireless and Secure Networks (WiSNet) Research Lab. Khayam has received research awards from Nokia Research, Korean Research Foundation and Pakistan National ICT R&D Fund. He offers consultancy for some Silicon Valley based technology companies. He also worked at Communications Enabling Technologies as a Design Engineer from October 2000 to August 2001. His research interests include analysis and modeling of statistical phenomena in computer networks, network security, cross-layer design for wireless networks, and real-time multimedia communications. He has more than 50 publications and 4 pending patents in this area.
Muddassar Farooq received his B.E. degree in Avionics Engineering from National University of Sciences and Technology (NUST), Pakistan, in 1996. He completed his M.S. in Computer Science and Engineering from University of New South Wales (UNSW), Australia, in 1999. He completed his D.Sc. in Informatics from Technical University of Dortmund, Germany, in 2006. In 2007, he joined the National University of Computer & Emerging Sciences (NUCES), Islamabad, Pakistan, as an associate professor. He is also the Director of Next Generation Intelligent Networks Research Center (nexGIN RC) at NUCES. He is the author of the book “Bee-inspired Protocol 1107 Engineering: from Nature to Networks” published by Springer in 2009. He has also has coauthored two book chapters in different books on swarm intelligence. He is on the editorial board of Springer’s Journal of Swarm Intelligence. He is also the workshop chair of European Workshop on Nature-inspired Techniques for Telecommunication and Networked Systems (EvoCOMNET) held with EuroGP. He also serves on the PC of well-known EC conferences like GECCO, CEC, ANTS. He is the guest editor of a special issue of Journal of System Architecture (JSA) on Nature-inspired algorithms and applications. His research interests include agent based routing protocols for fixed and mobile ad hoc networks (MANETs), nature inspired applied systems, natural computing and engineering and nature inspired computer and network security systems, i.e. artificial immune systems.
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