Browsing by Subject "Wireless ad hoc networks"

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    ItemOpen Access
    A link-state based on-demand routing protocol supporting real-time traffic for wireless mobile ad hoc networks
    (2007) Görbil, Gökçe
    Wireless ad hoc networks have gained a lot of popularity since their introduction and as many wireless network interface cards provide support for ad hoc networking, such networks have also seen real-life deployment for non-specialized purposes. Wireless mobile ad hoc networks (MANETs) are currently the most common type of ad hoc networks, and such networks are especially esteemed for their mobility support and ease of deployment due to their ad hoc nature. As most common network applications, such as the Web, FTP, email, and instant messaging, are data-centric and do not operate under strict time constraints, MANETs have been deployed to enable such non-real-time applications in the past. However, with the increasing use of real-time applications over ad hoc networks, such as teleconferencing, VoIP, and security and tracking applications where timeliness is of importance, real-time traffic support in multi-hop wireless mobile ad hoc networks has become an issue. We propose an event-driven, link-state based, on-demand routing protocol to enable real-time traffic support in such multi-hop wireless mobile ad hoc networks. Our protocol, which is named Elessar, is based on link-state topology dissemination, but instead of the more common periodic link-state messaging scheme, we employ event-driven link-state messages in Elessar, where topology changes are the events of interest. Through such an approach, we aim to lower the overhead of our protocol, especially for low-mobility cases, which is currently the most commonly encountered case with ad hoc networks deployed with machines directly interacting with humans, such as PDAs and laptops. Due to its link-state nature, our protocol is able to support non-real-time traffic without any further action. In order to support real-time traffic, however, we employ a direct cost dissemination mechanism, which only operates on-demand when there are one or more real-time flows in the network. We aim to provide soft quality-of-service (QoS) guarantees to real-time flows through intelligent path selection, without any resource reservation. We also aim to provide such QoS guarantees throughout the lifetime of a real-time flow, even in the face of node failures and mobility, by dynamic path adaptation during the lifetime of the flow. Elessar is able to support real-time and non-real-time traffic concurrently, as well as various different types of concurrent real-time traffic, such as delay- and loss-sensitive traffic. Our protocol, therefore, does not aim to support a single type of real-time traffic, but rather a plethora of different types of real-time traffic. Elessar is completely distributed, dynamic and adaptive, and does not require the underlying MAC protocol to be QoS-aware. We analyse our design choices and the performance of our protocol through realistic simulation experiments conducted on the OMNeT++ discrete event simulation platform, using the INET framework. We have used the IEEE 802.11b MAC protocol during our simulations and have employed the random waypoint mobility model to simulate mobility. Our experimental results show that Elessar is able to efficiently provide real-time traffic support for different types of traf- fic flows, even in the face of mobility. Our protocol operates best for smallto-medium-sized networks where mobility rates are low-to-medium. Once the mobility rate exceeds a certain threshold, intelligent path selection cannot cope satisfactorily with the high dynamism of the environment and the overhead of Elessar exceeds acceptable levels due to its event-driven link-state nature.
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    A novel method for scheduling of wireless ad hoc networks in polynomial time
    (IEEE, 2020-09-28) Köse, A.; Gökcesu, Hakan; Evirgen, N.; Gökcesu, K.; Médard, M.
    In this article, we address the scheduling problem in wireless ad hoc networks by exploiting the computational advantage that comes when scheduling problems can be represented by claw-free conflict graphs where we consider a wireless broadcast medium. It is possible to formulate a scheduling problem of broadcast transmissions as finding the maximum weighted independent set (MWIS) in the conflict graph of the network. Finding the MWIS of a general graph is NP-hard leading to an NP-hard complexity of scheduling. In a claw-free conflict graph, MWIS may be found in polynomial time leading to a throughput-optimal scheduling. We show that the conflict graphs of certain wireless ad hoc networks are claw-free. In order to obtain claw-free conflict graphs in general networks, we suggest introducing additional conflicts (edges) with the aim of keeping the decrease in MWIS size minimal. To this end, we introduce an iterative optimization problem to decide where to introduce edges and investigate its efficient implementation. We conclude that the claw breaking method by adding extra edges can perform very close to optimal scenario and better than the polynomial time maximal independent set scheduling benchmark under the necessary assumptions.
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    ItemOpen Access
    PETAL: a fully distributed location service for wireless ad hoc networks
    (Academic Press, 2017) Ilkhechi, A. R.; Korpeoglu, I.; Güdükbay, Uğur; Ulusoy, Özgür
    Location service is an essential prerequisite for mobile wireless ad hoc networks (MANETs) in which the underlying routing protocol leverages physical location information of sender and receiver nodes. Fulfillment of this requirement is challenging partly due to the mobility and unpredictability of nodes in MANETs. Moreover, scalability and location information availability under various circumstances are also substantial factors in designing an effective location service paradigm. By and large, utilizing centralized or distributed location servers responsible for storing the location information of all, or a subset of participant mobile devices, is a method employed in a significant portion of location service schemes. However, from the fairness point of view, it is more suitable to employ a location service scheme that treats participant nodes fairly, without mandating an unlucky subset to undertake the responsibility of serving as location server(s). In this work, we propose a scalable and fully decentralized location service scheme (PETAL) in which the burden of location update and inquiry tasks is almost evenly distributed among the nodes, resulting in an improvement in resilience against individual node failures. PETAL does not require hashing which results in more complexity, it is resilient against swarm mobility pattern, it requires minimal periodic location update messages when nodes do not move, and finally it does not require too many parameter configurations on all nodes. Our simulation results reveal that PETAL performs efficiently, particularly in environments densely populated by wireless devices. © 2017 Elsevier Ltd