178 research outputs found
Parallel and Successive Resource Allocation for V2V Communications in Overlapping Clusters
The 3rd Generation Partnership Project (3GPP) has introduced in Rel. 14 a
novel technology referred to as vehicle--to--vehicle (V2V) \textit{mode-3}.
Under this scheme, the eNodeB assists in the resource allocation process
allotting sidelink subchannels to vehicles. Thereupon, vehicles transmit their
signals in a broadcast manner without the intervention of the former one.
eNodeBs will thereby play a determinative role in the assignment of subchannels
as they can effectively manage V2V traffic and prevent allocation conflicts.
The latter is a crucial aspect to be enforced in order for the signals to be
received reliably by other vehicles. To this purpose, we propose two resource
allocation schemes namely bipartite graph matching-based successive allocation
(BGM-SA) and bipartite graph matching-based parallel allocation (BGM-PA) which
are suboptimal approaches with lesser complexity than exhaustive search. Both
schemes incorporate constraints to prevent allocation conflicts from emerging.
In this research, we consider overlapping clusters only, which could be formed
at intersections or merging highways. We show through simulations that BGM-SA
can attain near-optimal performance whereas BGM-PA is subpar but less complex.
Additionally, since BGM-PA is based on inter-cluster vehicle pre-grouping, we
explore different metrics that could effectively portray the overall channel
conditions of pre-grouped vehicles. This is of course not optimal in terms of
maximizing the system capacity---since the allocation process would be based on
simplified surrogate information---but it reduces the computational complexity
Reducing Message Collisions in Sensing-based Semi-Persistent Scheduling (SPS) by Using Reselection Lookaheads in Cellular V2X
In the C-V2X sidelink Mode 4 communication, the sensing-based semi-persistent
scheduling (SPS) implements a message collision avoidance algorithm to cope
with the undesirable effects of wireless channel congestion. Still, the current
standard mechanism produces high number of packet collisions, which may hinder
the high-reliability communications required in future C-V2X applications such
as autonomous driving. In this paper, we show that by drastically reducing the
uncertainties in the choice of the resource to use for SPS, we can
significantly reduce the message collisions in the C-V2X sidelink Mode 4.
Specifically, we propose the use of the "lookahead," which contains the next
starting resource location in the time-frequency plane. By exchanging the
lookahead information piggybacked on the periodic safety message, vehicular
user equipments (UEs) can eliminate most message collisions arising from the
ignorance of other UEs' internal decisions. Although the proposed scheme would
require the inclusion of the lookahead in the control part of the packet, the
benefit may outweigh the bandwidth cost, considering the stringent reliability
requirement in future C-V2X applications.Comment: Submitted to MDPI Sensor
Efficient channel allocation and medium access organization algorithms for vehicular networking
Due to the limited bandwidth available for Vehicular Ad-hoc Networks (VANETs), organizing the wireless channel access to efficiently use the bandwidth is one of the main challenges in VANET. In this dissertation, we focus on channel allocation and media access organization for Vehicle-to-Roadside Units (V2R) and Vehicle-to-Vehicle (V2V) communications. An efficient channel allocation algorithm for Roadside Unit (RSU) access is proposed. The goal of the algorithm is to increase system throughput by admitting more tasks (vehicles) and at the same time reduce the risk of the admitted tasks. The algorithm admits the new requests only when their requirements can be fulfilled and all in-session tasks\u27 requirements are also guaranteed. The algorithm calculates the expected task finish time for the tasks, but allocates a virtual transmission plan for the tasks as they progress toward the edges of the RSU range. For V2V mode, we propose an efficient medium access organization method based on VANETs\u27 clustering schemes. In order to make this method efficient in rapid topology change environment like VANET, it\u27s important to make the network topology less dynamic by forming local strongly connected clustering structure, which leads to a stable network topology on the global scale. We propose an efficient cluster formation algorithm that takes vehicles\u27 mobility into account for cluster formation. The results of the proposed methods show that the wireless channel utilization and the network stability are significantly improved compared to the existing methods
Resource sharing in vehicular cloud
Au cours des dernières annĂ©es, on a observĂ© l'intĂ©rĂŞt croissant envers l'accessibilitĂ© Ă
l'information et, en particulier, envers des approches innovantes utilisant les services Ă distance
accessibles depuis les appareils mobiles à travers le monde. Parallèlement, la communication des
véhicules, utilisant des capteurs embarqués et des dispositifs de communication sans fil, a été
introduite pour améliorer la sécurité routière et l'expérience de conduite à travers ce qui est
communément appelé réseaux véhiculaires (VANET).
L'accès sans fil à l’Internet à partir des véhicules a déclenché l'émergence de nouveaux services
pouvant être disponibles à partir ceux-ci. Par ailleurs, une extension du paradigme des réseaux
véhiculaires a été récemment promue à un autre niveau. Le nuage véhiculaire (Vehicular Cloud)
(VC) est la convergence ultime entre le concept de l’infonuagique (cloud computing) et les
réseaux véhiculaires dans le but de l’approvisionnement et la gestion des services. Avec cette
approche, les véhicules peuvent être connectés au nuage, où une multitude de services sont
disponibles, ou ils peuvent aussi ĂŞtre des fournisseurs de services. Cela est possible en raison de
la variété des ressources disponibles dans les véhicules: informatique, bande passante, stockage
et capteurs.
Dans cette thèse, on propose des méthodes innovantes et efficaces pour permettre la délivrance
de services par des véhicules dans le VC. Plusieurs schémas, notamment la formation de
grappes ou nuages de véhicules, la planification de transmission, l'annulation des interférences et
l'affectation des fréquences à l'aide de réseaux définis par logiciel (SDN), ont été développés et
leurs performances ont été analysées.
Les schémas de formation de grappes proposés sont DHCV (un algorithme de clustering D-hop
distribué pour VANET) et DCEV (une formation de grappes distribuée pour VANET basée sur
la mobilité relative de bout en bout). Ces schémas de regroupement sont utilisés pour former
dynamiquement des nuages de véhicules. Les systèmes regroupent les véhicules dans des nuages
qui ne se chevauchent pas et qui ont des tailles adaptées à leurs mobilités. Les VC sont créés de
telle sorte que chaque véhicule soit au plus D sauts plus loin d'un coordonnateur de nuage. La
planification de transmission proposée implémente un contrôle d'accès moyen basé sur la contention où les conditions physiques du canal sont entièrement analysées. Le système
d'annulation d'interférence permet d'éliminer les interférences les plus importantes; cela améliore
les performances de planification d’utilisation de la bande passante et le partage des ressources
dans les nuages construits. Enfin, on a proposé une solution à l'aide de réseaux définis par
logiciel, SDN, où différentes bandes de fréquences sont affectées aux différentes liens de
transmission de chaque VC afin d’améliorer les performances du réseau.Abstract : In recent years, we have observed a growing interest in information accessibility and especially innovative approaches for making distant services accessible from mobile devices across the world. In tandem with this growth of interest, there was the introduction of vehicular communication, also known as vehicular ad hoc networks (VANET), leveraging onboard sensors and wireless communication devices to enhance road safety and driving experience.
Vehicles wireless accessibility to the internet has triggered the emergence of service packages that can be available to or from vehicles. Recently, an extension of the vehicular networks paradigm has been promoted to a new level. Vehicular cloud (VC) is the ultimate convergence between the cloud computing concept and vehicular networks for the purpose of service provisioning and management. Vehicles can get connected to the cloud, where a multitude of services are available to them. Also vehicles can offer services and act as service providers rather than service consumers. This is possible because of the variety of resources available in vehicles: computing, bandwidth, storage and sensors.
In this thesis, we propose novel and efficient methods to enable vehicle service delivery in VC. Several schemes including cluster/cloud formation, transmission scheduling, interference cancellation, and frequency assignment using software defined networking (SDN) have been developed and their performances have been analysed.
The proposed cluster formation schemes are DHCV (a distributed D-hop clustering algorithm for VANET) and DCEV (a distributed cluster formation for VANET based on end-to-end relative mobility). These clustering schemes are used to dynamically form vehicle clouds. The schemes group vehicles into non-overlapping clouds, which have adaptive sizes according to their mobility. VCs are created in such a way that each vehicle is at most D-hops away from a cloud coordinator. The proposed transmission scheduling implements a contention-free-based medium access control where physical conditions of the channel are fully analyzed. The interference cancellation scheme makes it possible to remove the strongest interferences; this improves the scheduling performance and resource sharing inside the constructed clouds. Finally, we proposed an SDN based vehicular cloud solution where different frequency bands are assigned to different transmission links to improve the network performance
Performance analysis of vehicular networks for motorway scenario.
Abstract Not Provided
Achieving reliable and enhanced communication in vehicular ad hoc networks (VANETs)
A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirement for the degree of Doctor of PhilosophyWith the envisioned age of Internet of Things (IoTs), different aspects of Intelligent Transportation System (ITS) will be linked so as to advance road transportation safety, ease congestion of road traffic, lessen air pollution, improve passenger transportation comfort and significantly reduce road accidents. In vehicular networks, regular exchange of current position, direction, speed, etc., enable mobile vehicle to foresee an imminent vehicle accident and notify the driver early enough in order to take appropriate action(s) or the vehicle on its own may take adequate preventive measures to avert the looming accident. Actualizing this concept requires use of shared media access protocol that is capable of guaranteeing reliable and timely broadcast of safety messages. This dissertation investigates the use of Network Coding (NC) techniques to enrich the content of each transmission and ensure improved high reliability of the broadcasted safety messages with less number of retransmissions. A Code Aided Retransmission-based Error Recovery (CARER) protocol is proposed. In order to avoid broadcast storm problem, a rebroadcasting vehicle selection metric η, is developed, which is used to select a vehicle that will rebroadcast the received encoded message. Although the proposed CARER protocol demonstrates an impressive performance, the level of incurred overhead is fairly high due to the use of complex rebroadcasting vehicle selection metric. To resolve this issue, a Random Network Coding (RNC) and vehicle clustering based vehicular communication scheme with low algorithmic complexity, named Reliable and Enhanced Cooperative Cross-layer MAC (RECMAC) scheme, is proposed. The use of this clustering technique enables RECMAC to subdivide the vehicular network into small manageable, coordinated clusters which further improve transmission reliability and minimise negative impact of network overhead. Similarly, a Cluster Head (CH) selection metric ℱ(\u1d457) is designed, which is used to determine and select the most suitably qualified candidate to become the CH of a particular cluster. Finally, in order to investigate the impact of available radio spectral resource, an in-depth study of the required amount of spectrum sufficient to support high transmission reliability and minimum latency requirements of critical road safety messages in vehicular networks was carried out. The performance of the proposed schemes was clearly shown with detailed theoretical analysis and was further validated with simulation experiments
Fine-grained performance analysis of massive MTC networks with scheduling and data aggregation
Abstract. The Internet of Things (IoT) represents a substantial shift within wireless communication and constitutes a relevant topic of social, economic, and overall technical impact. It refers to resource-constrained devices communicating without or with low human intervention. However, communication among machines imposes several challenges compared to traditional human type communication (HTC). Moreover, as the number of devices increases exponentially, different network management techniques and technologies are needed. Data aggregation is an efficient approach to handle the congestion introduced by a massive number of machine type devices (MTDs). The aggregators not only collect data but also implement scheduling mechanisms to cope with scarce network resources.
This thesis provides an overview of the most common IoT applications and the network technologies to support them. We describe the most important challenges in machine type communication (MTC). We use a stochastic geometry (SG) tool known as the meta distribution (MD) of the signal-to-interference ratio (SIR), which is the distribution of the conditional SIR distribution given the wireless nodes’ locations, to provide a fine-grained description of the per-link reliability. Specifically, we analyze the performance of two scheduling methods for data aggregation of MTC: random resource scheduling (RRS) and channel-aware resource scheduling (CRS). The results show the fraction of users in the network that achieves a target reliability, which is an important aspect to consider when designing wireless systems with stringent service requirements. Finally, the impact on the fraction of MTDs that communicate with a target reliability when increasing the aggregators density is investigated
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