472 research outputs found
RDSP: Rapidly Deployable Wireless Ad Hoc System for Post-Disaster Management
In post-disaster scenarios, such as after floods, earthquakes, and in war
zones, the cellular communication infrastructure may be destroyed or seriously
disrupted. In such emergency scenarios, it becomes very important for first aid
responders to communicate with other rescue teams in order to provide feedback
to both the central office and the disaster survivors. To address this issue,
rapidly deployable systems are required to re-establish connectivity and assist
users and first responders in the region of incident. In this work, we describe
the design, implementation, and evaluation of a rapidly deployable system for
first response applications in post-disaster situations, named RDSP. The
proposed system helps early rescue responders and victims by sharing their
location information to remotely located servers by utilizing a novel routing
scheme. This novel routing scheme consists of the Dynamic ID Assignment (DIA)
algorithm and the Minimum Maximum Neighbor (MMN) algorithm. The DIA algorithm
is used by relay devices to dynamically select their IDs on the basis of all
the available IDs of networks. Whereas, the MMN algorithm is used by the client
and relay devices to dynamically select their next neighbor relays for the
transmission of messages. The RDSP contains three devices; the client device
sends the victim's location information to the server, the relay device relays
information between client and server device, the server device receives
messages from the client device to alert the rescue team. We deployed and
evaluated our system in the outdoor environment of the university campus. The
experimental results show that the RDSP system reduces the message delivery
delay and improves the message delivery ratio with lower communication
overhead.Comment: 23 pages, 12 figures, accepted for publication in Sensors 202
Contributions to the Performance Analysis of Intervehicular Communications Systems and Schemes
RĂSUMĂ
Le but des systĂšmes de communication intervĂ©hicule (Inter-Vehicle Communication â IVC) est d'amĂ©liorer la sĂ©curitĂ© de conduite en utilisant des capteurs et des techniques de communication sans fil pour ĂȘtre en mesure de communiquer mutuellement sans aucune intervention extĂ©rieure. Avec l'utilisation de ces systĂšmes, les communications vĂ©hicule Ă vĂ©hicule (V2V) peuvent ĂȘtre plus efficaces dans la prĂ©vention des accidents et la dĂ©congestion de la circulation que si chaque vĂ©hicule travaillait individuellement.
Une des solutions proposĂ©es pour les systĂšmes IVC est lâutilisation des systĂšmes de communication coopĂ©rative, qui en principe, augmentent l'efficacitĂ© spectrale et Ă©nergĂ©tique, la couverture du rĂ©seau, et rĂ©duit la probabilitĂ© de dĂ©faillance. La diversitĂ© d'antenne (entrĂ©es multiples sorties multiples « Multiple-Input Multiple-Output » ou MIMO) peut Ă©galement ĂȘtre une alternative pour les systĂšmes IVC pour amĂ©liorer la capacitĂ© du canal et la diversitĂ© (fiabilitĂ©), mais en Ă©change dâune complexitĂ© accrue.
Toutefois, l'application de telles solutions est difficile, car les communications sans fil entre les vĂ©hicules sont soumises Ă dâimportants effets d'Ă©vanouissements des canaux appelĂ©s (canaux sujets aux Ă©vanouissements de n*Rayleigh, « n*Rayleigh fading channels»), ce qui conduit Ă la dĂ©gradation des performances. Par consĂ©quent, dans cette thĂšse, nous proposons une analyse de la performance globale des systĂšmes de transmission coopĂ©ratifs et MIMO sur des canaux sujets aux Ă©vanouissements de n*Rayleigh. Cette analyse permettra dâaider les chercheurs pour la conception et la mise en Ćuvre de systĂšmes de communication V2V avec une complexitĂ© moindre.
En particulier, nous Ă©tudions d'abord la performance de la sĂ©lection du relais de coopĂ©ration avec les systĂšmes IVC, on suppose que la transmission via « Amplify-and-Forward» (AF) ou bien «Decode-and-Forward» (DF) est assurĂ©e par N relais pour transfĂ©rer le message de la source Ă la destination. La performance du systĂšme est analysĂ©e en termes de probabilitĂ© de dĂ©faillance, la probabilitĂ© d'erreur de symbole, et la capacitĂ© moyenne du canal. Les rĂ©sultats numĂ©riques dĂ©montrent que la sĂ©lection de relais rĂ©alise une diversitĂ© de l'ordre de (dâmN/n) pour les deux types de relais, oĂč m est un paramĂštre Ă©vanouissement de Rayleigh en cascade.
Nous Ă©tudions ensuite la performance des systĂšmes IVC Ă sauts multiples avec et sans relais rĂ©gĂ©nĂ©ratifs. Dans cette Ă©tude, nous dĂ©rivons des expressions approximatives pour la probabilitĂ© de dĂ©faillance et le niveau dâĂ©vanouissement lorsque la diversitĂ© en rĂ©ception basĂ©e sur le ratio maximum de combinaison (MRC) est employĂ©e. En outre, nous analysons la rĂ©partition de puissance pour le systĂšme sous-jacent afin de minimiser la probabilitĂ© globale de dĂ©faillance. Nous montrons que la performance des systĂšmes rĂ©gĂ©nĂ©ratifs est meilleure que celle des systĂšmes non rĂ©gĂ©nĂ©ratifs lorsque lâordre de cascade n est faible, tandis quâils ont des performances similaires lorsque n est Ă©levĂ©.
Ensuite, nous considĂ©rons le problĂšme de la dĂ©tection de puissance des signaux inconnus aux n* canaux de Rayleigh. Dans ce travail, de nouvelles expressions approximatives sont dĂ©rivĂ©es de la probabilitĂ© de dĂ©tection moyenne avec et sans diversitĂ© en rĂ©ception MRC. En outre, la performance du systĂšme est analysĂ©e lorsque la dĂ©tection de spectre coopĂ©rative (CSS) est considĂ©rĂ©e sous diverses contraintes de canaux (par exemple, les canaux de communication parfaits et imparfaits). Les rĂ©sultats numĂ©riques ont montrĂ© que la fiabilitĂ© de dĂ©tection diminue Ă mesure que l'ordre n augmente et sâamĂ©liore sensiblement lorsque CSS emploie le schĂ©ma MRC.
Il est dĂ©montrĂ© que CSS avec le schĂ©ma MRC maintient la probabilitĂ© de fausse alarme minimale dans les canaux dâinformation imparfaite plutĂŽt que d'augmenter le nombre d'utilisateurs en coopĂ©ration. Enfin, nous prĂ©sentons une nouvelle approche pour l'analyse des performances des systĂšmes IVC sur n*canaux de Rayleigh, en utilisant n_T antennes d'Ă©mission et n_R antennes de rĂ©ception pour lutter contre l'effet dâĂ©vanouissement. Dans ce contexte, nous Ă©valuons la performance des systĂšmes MIMO-V2V basĂ©s sur la sĂ©lection des antennes d'Ă©mission avec un ratio maximum de combinaison (TAS/MRC) et la sĂ©lection combinant (TAS/SC).
Dans cette Ă©tude, nous dĂ©rivons des expressions analytiques plus prĂ©cises pour la probabilitĂ© de dĂ©faillance, la probabilitĂ© d'erreur de symbole, et lâĂ©vanouissement sur n*canaux Rayleigh. Il est montrĂ© que les deux rĂ©gimes ont le mĂȘme ordre de diversitĂ© maximale Ă©quivalent Ă (dâmn_T n_R /n) . En outre, TAS / MRC offre un gain de performance mieux que TAS/ SC lorsque le nombre d'antennes de rĂ©ception est plus que celle des antennes dâĂ©mission, mais lâamĂ©lioration de la performance est limitĂ©e lorsque n augmente.----------Abstract
The purpose of intervehicular communication (IVC) systems is to enhance driving safety, in which vehicles use sensors and wireless communication techniques to talk to each other without any roadside intervention. Using these systems, vehicle-to-vehicle (V2V) communications can be more effective in avoiding accidents and traffic congestion than if each vehicle works individually.
A potential solution can be implemented in this research area using cooperative communications systems which, in principle, increase spectral and power efficiency, network coverage, and reduce the outage probability. Antenna diversity (i.e., multiple-input multiple output (MIMO) systems) can also be an alternative solution for IVC systems to enhance channel capacity and diversity (reliability) but in exchange of an increased complexity. However, applying such solutions is challenging since wireless communications among vehicles is subject to harsh fading channels called ân*Rayleigh fading channelsâ, which leads to performance degradation. Therefore, in this thesis we provide a comprehensive performance analysis of cooperative transmission and MIMO systems over n*Rayleigh fading channels that help researchers for the design and implementation of V2V communication systems with lower complexity.
Specifically, we first investigate the performance of cooperative IVC systems with relay selection over n*Rayleigh fading channels, assuming that both the decode-and-forward and the amplify-and-forward relaying protocols are achieved by N relays to transfer the source message to the destination. System performance is analyzed in terms of outage probability, symbol error probability, and average channel capacity. The numerical results have shown that the best relay selection approach achieves the diversity order of (dâmN/n) where m is a cascaded Rayleigh fading parameter.
Second, we investigate the performance of multihop-IVC systems with regenerative and non-regenerative relays. In this study, we derive approximate closed-form expressions for the outage probability and amount of fading when the maximum ratio combining (MRC) diversity reception is employed. Further, we analyze the power allocation for the underlying scheme in order to minimize the overall outage probability. We show that the performance of regenerative systems is better than that of non-regenerative systems when the cascading order n is low and they have similar performance when n is high.
Third, we consider the problem of energy detection of unknown signals over n*Rayleigh fading channels. In this work, novel approximate expressions are derived for the average probability of detection with and without MRC diversity reception. Moreover, the system performance is analyzed when cooperative spectrum sensing (CSS) is considered under various channel constraints (e.g, perfect and imperfect reporting channels). The numerical results show that the detection reliability decreases as the cascading order n increases and substantially improves when CSS employs MRC schemes. It is demonstrated that CSS with MRC scheme keeps the probability of false alarm minimal under imperfect reporting channels rather than increasing the number of cooperative users.
Finally, we present a new approach for the performance analysis of IVC systems over n*Rayleigh fading channels, using n_T transmit and n_R receive antennas to combat fading influence. In this context, we evaluate the performance of MIMO-V2V systems based on the transmit antenna selection with maximum ratio combining (TAS/MRC) and selection combining (TAS/SC) schemes. In this study, we derive tight analytical expressions for the outage probability, the symbol error probability, and the amount of fading over n*Rayleigh fading channels. It is shown that both schemes have the same maximum diversity order equivalent to (dâmn_T n_R /n). In addition, TAS/MRC offers a better performance gain than TAS/SC scheme when the number of receive antennas is more than that of transmit antennas, but the performance improvement is limited as n increases
Hybrid-Vehfog: A Robust Approach for Reliable Dissemination of Critical Messages in Connected Vehicles
Vehicular Ad-hoc Networks (VANET) enable efficient communication between
vehicles with the aim of improving road safety. However, the growing number of
vehicles in dense regions and obstacle shadowing regions like Manhattan and
other downtown areas leads to frequent disconnection problems resulting in
disrupted radio wave propagation between vehicles. To address this issue and to
transmit critical messages between vehicles and drones deployed from service
vehicles to overcome road incidents and obstacles, we proposed a hybrid
technique based on fog computing called Hybrid-Vehfog to disseminate messages
in obstacle shadowing regions, and multi-hop technique to disseminate messages
in non-obstacle shadowing regions. Our proposed algorithm dynamically adapts to
changes in an environment and benefits in efficiency with robust drone
deployment capability as needed. Performance of Hybrid-Vehfog is carried out in
Network Simulator (NS-2) and Simulation of Urban Mobility (SUMO) simulators.
The results showed that Hybrid-Vehfog outperformed Cloud-assisted Message
Downlink Dissemination Scheme (CMDS), Cross-Layer Broadcast Protocol (CLBP),
PEer-to-Peer protocol for Allocated REsource (PrEPARE), Fog-Named Data
Networking (NDN) with mobility, and flooding schemes at all vehicle densities
and simulation times
Recommended from our members
Information collection algorithm for vehicular ad-hoc networks (application domain: Urban Traffic Wireless Vehicular Ad-Hoc Networks (VANETs))
Vehicle to vehicle communication (V2VC) is one of the modern approaches for exchanging and generating traffic information with (yet to be realized) potential to improve road safety, driving comfort and traffic control. In this research, we present a novel algorithm which is based on V2V communication, uses in-vehicle sensor information and in collaboration with the other vehicles' sensor information can detect road conditions and determine the geographical area where this road condition exists â e.g. geographical area where there is traffic density, unusual traffic behaviour, a range of weather conditions (raining), etc. The algorithms' built-in automatic geographical restriction of the data collection, aggregation and dissemination mechanisms allows warning messages to be received by any car, not necessarily sharing the identified road condition, which may then be used to identify the optimum route taken by the vehicle e.g. avoid bottlenecks or dangerous areas including accidents or congestions on their current routes. This research covers the middle ground between MANET [1] and collaborative data generation based on knowledge granularity (aggregation). It investigates the possibility of designing, implementing and modelling of the functionality of an algorithm (as part of the design of an intelligent node in an Intelligent Transportation System - ITS) that ensures active participation in the formation, routing and general network support of MANETs and also helps in-car traffic information and real-time control generation and distribution. The work is natural extension of the efforts of several large EU projects like DRIVE [2], GST [3] and SAFESPOT [4]
V2X Content Distribution Based on Batched Network Coding with Distributed Scheduling
Content distribution is an application in intelligent transportation system
to assist vehicles in acquiring information such as digital maps and
entertainment materials. In this paper, we consider content distribution from a
single roadside infrastructure unit to a group of vehicles passing by it. To
combat the short connection time and the lossy channel quality, the downloaded
contents need to be further shared among vehicles after the initial
broadcasting phase. To this end, we propose a joint infrastructure-to-vehicle
(I2V) and vehicle-to-vehicle (V2V) communication scheme based on batched sparse
(BATS) coding to minimize the traffic overhead and reduce the total
transmission delay. In the I2V phase, the roadside unit (RSU) encodes the
original large-size file into a number of batches in a rateless manner, each
containing a fixed number of coded packets, and sequentially broadcasts them
during the I2V connection time. In the V2V phase, vehicles perform the network
coded cooperative sharing by re-encoding the received packets. We propose a
utility-based distributed algorithm to efficiently schedule the V2V cooperative
transmissions, hence reducing the transmission delay. A closed-form expression
for the expected rank distribution of the proposed content distribution scheme
is derived, which is used to design the optimal BATS code. The performance of
the proposed content distribution scheme is evaluated by extensive simulations
that consider multi-lane road and realistic vehicular traffic settings, and
shown to significantly outperform the existing content distribution protocols.Comment: 12 pages and 9 figure
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