10,113 research outputs found

    RECOMAC: a cross-layer cooperative network protocol for wireless ad hoc networks

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    A novel decentralized cross-layer multi-hop cooperative protocol, namely, Routing Enabled Cooperative Medium Access Control (RECOMAC) is proposed for wireless ad hoc networks. The protocol architecture makes use of cooperative forwarding methods, in which coded packets are forwarded via opportunistically formed cooperative sets within a region, as RECOMAC spans the physical, medium access control (MAC) and routing layers. Randomized coding is exploited at the physical layer to realize cooperative transmissions, and cooperative forwarding is implemented for routing functionality, which is submerged into the MAC layer, while the overhead for MAC and route set up is minimized. RECOMAC is shown to provide dramatic performance improvements of eight times higher throughput and one tenth of end-to-end delay than that of the conventional architecture in practical wireless mesh networks

    Cooperative Medium Access Mechanisms and Service-oriented Routing in Multi-hop Wireless Networks

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    Doktorgradsavhandling i informasjons- og kommunikasjonsteknologi, Universitetet i Agder, Grimstad, 2011Multi-hop wireless networks have been regarded as a promising path towards future wireless communication landscape. In the past decade, most related work has been performed in the context of mobile ad hoc networks. In very recent years, however, much effort has been shifted to more static networks such as wireless mesh networks and wireless sensor networks. While significant progress has been achieved through these years, both theoretically and experimentally, challenges still exist in various aspects of these networks. For instance, how to use multi-hop networks as a means for providing broadband Internet services with reliability and balanced load remains as a challenging task. As the number of end-users is increasing rapidly and more and more users are enjoying multimedia services, how to provide Quality of Service (QoS) with user satisfaction in such networks remains also as a hot topic. Meanwhile, another direction which has recently attracted lots of efforts in the international research community is the introduction of cooperative communications. Cooperative communications based on relaying nodes are capable of improving network performance in terms of increased spectral and power efficiency, extended network coverage, balanced QoS, infrastructure-less deployment, etc. Cooperation may happen at different communication layers, at the physical layer where the received signal is retransmitted and at the MAC and routing layers where a packet is forwarded to the next hop in a coordinated manner towards the destination, respectively. However, without joint consideration and design of physical layer, MAC layer and network layer, the benefit of cooperative communication cannot be exploited to the maximum extent. In addition, how to extend one-hop cooperative communication into multi-hop wireless network scenarios remains as an almost un-chartered research frontier. In this dissertation, we enhance the state of the art technologies in the field of multi-hop wireless networks from a layered perspective. While efficient scheduling mechanisms are proposed at the MAC layer, elaborate routing protocols are devised at the network layer. More specifically, by taking into account of cross layer design we cope with network congestion problems in wireless mesh networks mainly at the network layer. In order to further improve the performance of cooperative wireless networks, we propose a contention-based cooperative MAC protocol in the presence of multiple relay nodes. Since a large majority of existing cooperative MAC protocols are designed based on widely-used IEEE 802.11 MAC protocol which exhibits inherent design constraint when applied in multi-hop wireless networks, it is imperative to develop a novel cooperative MAC protocol which is appropriate for multi-hop network scenarios. Next, we propose a TDMA-based MAC protocol supporting cooperative communications in static multi-hop wireless networks. Furthermore, a cooperative lifetime maximization MAC protocol is proposed to cope with the energy hole problem in wireless sensor networks

    Data analytics methods for attack detection and localization in wireless networks

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    Wireless ad hoc network operates without any fixed infrastructure and centralized administration. It is a group of wirelessly connected nodes having the capability to work as host and router. Due to its features of open communication medium, dynamic changing topology, and cooperative algorithm, security is the primary concern when designing wireless networks. Compared to the traditional wired network, a clean division of layers may be sacrificed for performance in wireless ad hoc networks. As a result, they are vulnerable to various types of attacks at different layers of the protocol stack. In this paper, I present real-time series data analysis solutions to detect various attacks including in- band wormholes attack in the network layer, various MAC layer misbehaviors, and jamming attack in the physical layer. And, I also investigate the problem of node localization in wireless and sensor networks, where a total of n anchor nodes are used to determine the locations of other nodes based on the received signal strengths. A range-based machine learning algorithm is developed to tackle the challenges --Abstract, page iii

    Improve Energy Efficiency In Cooperative Medium Access Control Protocol For Wireless Networks

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    Cooperative communication has drawn a substantial attention in recent years due to the efficient and optimal utilization of constraint resources in dynamic wireless networks at a reduced infrastructural deployment and cost. In the medium access control (MAC) layer perspective, two major problems are associated with cooperative networks. The ability of cooperative MAC (CMAC) protocols to achieve multi-objective target orientation limit their adaptation to the future generation of wireless networks, since most of the existing protocols focus only on a single target objective. Besides, the sustainability of energy-constrained wireless networks due to limited energy supply capacity hinders their performance to ensure stable and reliable communication. These aforementioned problems limit the adaptation of the existing protocols to fit into the future generation of wireless networks. To adequately address these problems, two distinct CMAC protocols are proposed in this thesis to cater for the unpredictable and dynamic nature of the wireless network. Firstly, a new network lifetime-aware CMAC protocol named LEA-CMAC is proposed for energy-constrained wireless ad-hoc networks. An optimization problem is formulated with an objective of extending the lifetime of the network. The solution to this non-linear problem is provided in terms of optimal transmit power at the source and relay terminals in symmetric and asymmetric transmit power policies. The solution provided by this protocol is limited in terms of energy efficiency and network lifetime since the network totally rely on the helper nodes limited-powered batteries for their transmissions. Secondly, a novel CMAC protocol with radio frequency (RF) energy harvesting (EH) capability named EH-CMAC is proposed in a reactive relaying energy-constrained wireless ad-hoc networks to address the limitation in the earlier proposed LEA-CMAC protocol. The protocol possesses the ability to ensure a sustainable and reliable wireless connectivity in a dynamic wireless environment through the selection of an appropriate transmission mode that best suits the instantaneous network requirement. The protocol comprises of two distinct energy-efficient techniques namely, the outage probability quality-of-service (QoS) requirement and the transmit power optimization techniques which are applied in both traditional and EH relaying schemes. These techniques are selected and adapted based on the instantaneous network information and target objectives. In addition, a distributed and adaptive relay selection backoff process is proposed in each case to satisfy the available network information and achieve a multi-objective target oriented protocol. Through extensive simulation and comparison with existing CMAC protocols, the results show that LEA-CMAC extend the network lifetime by 85.67% over an existing CMAC protocol, while EH-CMAC extends the network lifetime by 90.99% over a traditional CMAC protocol. Thus, both protocols achieve a multi-objective target orientation under general circumstances

    A Cross-Layer Design Based on Geographic Information for Cooperative Wireless Networks

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    Most of geographic routing approaches in wireless ad hoc and sensor networks do not take into consideration the medium access control (MAC) and physical layers when designing a routing protocol. In this paper, we focus on a cross-layer framework design that exploits the synergies between network, MAC, and physical layers. In the proposed CoopGeo, we use a beaconless forwarding scheme where the next hop is selected through a contention process based on the geographic position of nodes. We optimize this Network-MAC layer interaction using a cooperative relaying technique with a relay selection scheme also based on geographic information in order to improve the system performance in terms of reliability.Comment: in 2010 IEEE 71st Vehicular Technology Conference, 201

    A cross layer multi hop network architecture for wireless Ad Hoc networks

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    In this paper, a novel decentralized cross-layer multi-hop cooperative network architecture is presented. Our architecture involves the design of a simple yet efficient cooperative flooding scheme,two decentralized opportunistic cooperative forwarding mechanisms as well as the design of Routing Enabled Cooperative Medium Access Control (RECOMAC) protocol that spans and incorporates the physical, medium access control (MAC) and routing layers for improving the performance of multihop communication. The proposed architecture exploits randomized coding at the physical layer to realize cooperative diversity. Randomized coding alleviates relay selection and actuation mechanisms,and therefore reduces the coordination among the relays. The coded packets are forwarded via opportunistically formed cooperative sets within a region, without communication among the relays and without establishing a prior route. In our architecture, routing layer functionality is submerged into the MAC layer to provide seamless cooperative communication while the messaging overhead to set up routes, select and actuate relays is minimized. RECOMAC is shown to provide dramatic performance improvements, such as eight times higher throughput and ten times lower end-to-end delay as well as reduced overhead, as compared to networks based on well-known IEEE 802.11 and Ad hoc On Demand Distance Vector (AODV) protocols

    Spectrum sharing security and attacks in CRNs: a review

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    Cognitive Radio plays a major part in communication technology by resolving the shortage of the spectrum through usage of dynamic spectrum access and artificial intelligence characteristics. The element of spectrum sharing in cognitive radio is a fundament al approach in utilising free channels. Cooperatively communicating cognitive radio devices use the common control channel of the cognitive radio medium access control to achieve spectrum sharing. Thus, the common control channel and consequently spectrum sharing security are vital to ensuring security in the subsequent data communication among cognitive radio nodes. In addition to well known security problems in wireless networks, cognitive radio networks introduce new classes of security threats and challenges, such as licensed user emulation attacks in spectrum sensing and misbehaviours in the common control channel transactions, which degrade the overall network operation and performance. This review paper briefly presents the known threats and attacks in wireless networks before it looks into the concept of cognitive radio and its main functionality. The paper then mainly focuses on spectrum sharing security and its related challenges. Since spectrum sharing is enabled through usage of the common control channel, more attention is paid to the security of the common control channel by looking into its security threats as well as protection and detection mechanisms. Finally, the pros and cons as well as the comparisons of different CR - specific security mechanisms are presented with some open research issues and challenges
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