Dissertations / Theses: 'IEEE802.11p'

1

Chakroun, Omar. "Techniques de contrôle de congestion et de dissémination d'informations dans les réseaux véhiculaires." Thèse, Université de Sherbrooke, 2014. http://hdl.handle.net/11143/5893.

Full text

Abstract:

Les réseaux véhiculaires, connus sous le terme VANETs, sont des réseaux impliquant des communications entre deux ou plusieurs véhicules et éventuellement une communication avec des éléments d’infrastructure sur la route. Récemment, le concept de systèmes de transports intelligent a connu beaucoup d’intérêt. Les STI sont des systèmes utilisant les nouvelles technologies de communication sans fil appliquées au domaine du transport pour améliorer la sécurité routière, la logistique et les services d’information. Des défis majeurs ont besoin cependant d'être abordés pour offrir une communication sur la route sécurisée et fiable dans des environnements anonymes et quelquefois hostiles à la communication. Comme dans tout système de communication, les réseaux véhiculaires doivent opérer en respectant des contraintes en termes de qualité de service. Ces contraintes sont d’autant plus strictes quand il s’agit de fournir des services de sécurité sur la route. Ce projet vise à développer des techniques de communication véhiculaires pour le relayage d’informations de manière fiable et à faible délai entre véhicules voyageant à haute vitesse. Ces techniques devront permettre de respecter des contraintes temporelles sévères afin d’envisager leur utilisation dans des applications de sécurité sur la route. Pour ce faire, cette thèse proposera d’abord des techniques efficaces de dissémination d’informations utilisant des approches multi-métriques basées sur différentes mesures en temps-réel. Des méthodes de relayage seront proposées qui permettent de diminuer les délais d’acheminement et augmenter la probabilité de réception. Ces méthodes utiliseront, entre autres, des approches d’adaptation de la portée et/ou de la priorité des messages en fonction de leur type et de l’intérêt éventuels des véhicules récepteurs en la réception de ces messages. Dans un second volet, ce projet proposera des concepts et des méthodes afin de palier au problème de congestion dans les réseaux véhiculaires qui peut résulter conjointement à la dissémination d’informations. Ces concepts et méthodes viseront à respecter la fiabilité exigée par les applications de sécurité, tout en restant conforme aux nouveaux standards de communications véhiculaires.

APA, Harvard, Vancouver, ISO, and other styles

2

Azizian, Meysam. "Partage des ressources dans le nuage de véhicules." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11526.

Full text

Abstract:

Au cours des dernières années, on a observé l'intérêt croissant envers l'accessibilité à l'information et, en particulier, envers des approches innovantes utilisant les services à 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 être 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.

APA, Harvard, Vancouver, ISO, and other styles

3

Karlsson, Carl. "IMPULSIVE NOISE MODELING AND COEXISTENCE STUDY OF IEEE 802.11 AND BLUETOOTH." Thesis, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-308.

Full text

Abstract:

This thesis describes the interference problem between IEEE 802.11 and Bluetooth. These well established communication standards are often used together simultaneously. Since both standards operate in the ISM-band at 2.45 GHz, they interfere with each other. In addition to this, interference from e.g. microwave ovens, heating processes, electric motors and cordless phones also occurs on the ISM-band. Due to this interference problem, a model has been developed in MATLAB to further investigate these interferences and the effects for the user.

The interference is modelled using the well known Class-A model for impulsive noise. The interference model is parameterized in the model and therefore the noise source(s) is described by a set of parameters derived from real measurements. Models for IEEE 802.11 legacy/b and Bluetooth are based on work published on the user community of MATHWORKS. To get a measure of performance, results from the model are presented as BER (Bit Error Rates) and PER (Packet Error Rates). When Bluetooth is used as a voice link, sound quality can also be performance evaluated directly by simply listening to a voice output file. To be able to track down a specific problem cause, measuring tools have also been included in the model to gain insight into what is causing bit/packet error.

A model describing the interference problem has been developed describing the real world usage of the standards by the use of state machines. Due to the complexity of the problem, and also for the model to be user friendly, this thesis is not composed of a thorough mathematical derivation describing BER probability for different modulation forms. The derivations for these has already been done and is therefore summarized and compared to when the model is validated. The model has been developed as a proof of concept for further work to fully support the current and coming IEEE standards for IEEE 802.11 and Bluetooth.

APA, Harvard, Vancouver, ISO, and other styles

4

Benaidja, Amira. "Echange d'informations en temps réel dans les réseaux de véhicules." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCB045/document.

Full text

Abstract:

Les réseaux véhiculaires, connus sous le terme VANETs, sont des réseaux impliquant des communications entre deux ou plusieurs véhicules et éventuellement une communication avec des éléments d’infrastructure sur la route. Récemment, le concept de systèmes de transport intelligents (STI) a connu beaucoup d’intérêt. Les STI sont des systèmes utilisant les nouvelles technologies de communication sans fil appliquées au domaine du transport pour améliorer la sécurité routière, la logistique et les services d’information. Des défis majeurs ont besoin cependant d'être abordés pour offrir une communication sur la route sécurisée et fiable dans des environnements anonymes et quelquefois hostiles à la communication. Comme dans tout système de communication, les réseaux véhiculaires doivent opérer en respectant des contraintes en termes de qualité de service. Ces contraintes sont d’autant plus strictes quand il s’agit de fournir des services de sécurité sur la route. Ce projet vise à développer des techniques de communication véhiculaires pour le transfert des informations de manière fiable entre véhicules roulant à grande vitesse tout en contrôlant la surcharge du réseau. Ces techniques visent la prise en compte des contraintes temporelles sur les délais de transfert afin d’envisager leur utilisation dans des applications critiques telle que la sécurité sur la route. Pour ce faire, cette thèse propose d’abord un protocole optimal de dissémination de messages d’urgence pour les VANETs. Il est basé sur une stratégie de diffusion qui exploite les véhicules sur la direction opposée afin d’accélérer la dissémination du message d’urgence tout en réduisant le nombre de transmissions. Ainsi, et dans le but d’assurer une dissémination fiable et à faible surcoût, une technique de retransmission périodique intelligente permettant l’adaptation du protocol proposé à différentes densités du trafic routier est proposée. Dans un second volet, ce projet propose une approche hybride de dissémination de messages d’urgence qui combine alternativement les avantages des deux principales approches de dissémination existantes (Sender-oriented et Receiver-oriented dont notre première proposition fait partie) afin de garantir une transmission fiable des alertes tout en réduisant les délais. Les approches Receiver-Oriented qui sont les plus adaptées pour les applications de sécurité dans les VANETs peuvent minimiser la latence et les limitations des approches Sender-Oriented. Mais, ilsdoivent aussi mieux exploiter les apports des messages hello (beacons) échangés dans la technologie IEEE802.11P. Ainsi, et dans le but de surmonter les limites des approches de retransmissions périodiques et celles de relais- multiples afin d’assurer des échanges fiables de messages de sécurité tout en réduisant la surcharge de la bande passante, nous introduisons un nouveau mécanisme DR/BDR (Designated Relay/Backup Designated Relay). Le BDR, dans ce mécanisme, doit remplacer le DR et assurer sa tâche quand il détecte, à travers les beacons colorés échangés,l’échec de ce dernier dans la dissémination du message d’urgence
Vehicular Ad hoc NETworks (VANETs) have gained considerable attention in the past few years due to their promising applications such as safety warning, transport efficiency or mobile infotainment. Avoiding accidents and traffic jams are two main immediate benefits of vehicular networks. For instance, most drivers would like to receive real-time alerts about accidents happening at a short distance in front of their vehicles since these accidents could lead to collision chains involving tens of vehicles. Also, the ability to receive an alert about a potential traffic jam would allow drivers to take alternate routes, saving both time and fuel. In both cases, warning messages should be broadcasted to all vehicles traveling over a geographical area, and need to be delivered with high reliability, low delay and low overhead. It is therefore important to develop a reliable and efficient safety information dissemination protocol in vehicular networks. Due to the vehicle mobility and lossy wireless channel, highly reliable, scalable and fast multi-hop broadcast protocol is very challenging to design. A number of solutions have been proposed in the past few years. However, the tradeoff between reliability and efficiency in such solutions needs to be carefully considered. This thesis presents an optimal protocol for the broadcast of safety messages in VANETs. Optimality, in terms of delay and transmission count, is achieved using a broadcast strategy that exploits opposite vehicles. To carry out reliable and efficient broadcast coordination, intelligent periodic rebroadcasts, which effectively adapt our protocol to sparse and dense networks, are proposed. Simulations are conducted and results are presented to show that it has a better performance over existing competing protocols. As a second contribution, we propose an alternative Receiver-Sender approach that combines advantages of the two existing dissemination approaches (Sender-oriented and Receiver-oriented to which our first proposal belongs) to ensure low latency and high reliability. The proposal can use any sender or receiver oriented protocol but the same selected one is used during all the dissemination process. In order to overcome the unreliability and broadcast overhead generated by periodic rebroadcasts and multiple relays schemes, we introduce a DR/BDR (Designated Relay/Backup Designated Relay) mechanism where the BDR has to replace the DR when detecting,from exchanged colored beacons, its failure in informing concerned vehicles

APA, Harvard, Vancouver, ISO, and other styles

5

Zhang, Lei. "Architecture et mecanismes de bout en bout pour les communications mobiles et sans fil dans l'internet." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2009. http://tel.archives-ouvertes.fr/tel-00435868.

Full text

Abstract:

La gestion performante de la mobilité et l'amélioration des performances des couches basses sont deux enjeux fondamentaux dans le contexte des réseaux sans fil. Cette thèse apporte des solutions originales et innovantes qui visent à répondre à ces deux problématiques empêchant à ce jour d'offrir des possibilités de communication performantes et sans couture aux usagers mobiles accédant à l'Internet via des réseaux d'accès locaux sans fil (WLAN). Ces solutions se distinguent en particulier par l'impact minimum qu'elles ont sur les protocoles standards de l'Internet (niveaux transport et réseau) ou de l'IEEE (niveaux physique et liaison de données). S'inscrivant dans les paradigmes de "bout en bout" et "cross-layer", notre architecture permet d'offrir des solutions efficaces pour la gestion de la mobilité : gestion de la localisation et des handover en particulier. En outre, nous montrons que notre approche permet également d'améliorer l'efficacité des transmissions ainsi que de résoudre efficacement plusieurs syndromes identifiés au sein de 802.11 tels que les anomalies de performance, l'iniquité entre les flux et l'absence de contrôle de débit entre la couche MAC et les couches supérieures. Cette thèse résout ces problèmes en combinant des modèles analytiques, des simulations et de réelles expérimentations. Ces mécanismes adaptatifs ont été développés et intégrés dans une architecture de communication qui fournit des services de communication à haute performance pour réseaux sans fils tels que WIFI et WIMAX.

APA, Harvard, Vancouver, ISO, and other styles

6

Hameed, Mohsin. "Performance Investigation of IEEE802 : 11e for Industrial Wireless Network." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-4250.

Full text

Abstract:

The advantages of using IEEE 802.11-based Wireless Local Area Networks (WLAN) in industrial automation applications are substantial and include: mobility, ease and speed of installation, flexibility and costs. But wireless applications for industrial automation applications have rigorous requirements on quality of service (QoS) for the transmission of real-time critical process data. IEEE 802.11-based WLANs, which were initially designed only for best effort traffic, did not provide any QoS support for this kind of traffic. Therefore the IEEE 802.11e standard amendment was introduced and ratified in 2005. It defines the concept of a Hybrid Co-ordination Function (HCF) at the MAC layer for medium access control. HCF is a combination of HCF Controlled Channel Access (HCCA) with parameterized quality of service (QoS) and Enhanced Channel Access (EDCA) with prioritized QoS.

The contemporary work deals with the performance evaluation of HCCA for industrial wireless network. A HCCA simulation model has been implemented using OPNET modeler. The simulation results are compared with EDCA in terms of delays for various scenarios.

APA, Harvard, Vancouver, ISO, and other styles

7

Liu, Zuo. "Supporting VoIP in IEEE802.11 distributed WLANs." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/supporting-voip-in-ieee80211-distributed-wlans(1a6225c3-770e-4ce1-8fbb-b1e3f05534d2).html.

Full text

Abstract:

Telecommunications is converging on the use of IP based networks. Due to the low cost of VoIP applications, they are being increasingly used instead of conventional telephony services. IEEE802.11 WLANs are already widely used both commercially and domestically. VoIP applications will also expand from usage over wired networks to voice communications over IEEE802.11 WLANs. This is known as VoWLAN. The use of VoWLAN may reach the maximum capacity of a wireless channel if there are many simultaneous VoIP calls operating close to each other. There is much published research based on a single IEEE802.11 infrastructure WLAN concluding that packet loss, transmission efficiency and latency issues are the major challenges limiting the VoWLAN capacity. The VoIP service quality will drop sharply when the demands exceed the WLAN’s capacity. This thesis demonstrates that these challenges also apply to distributed WLANs. To extend these findings from the existing research, the analysis in this thesis indicates that the capacity of a single IEEE802.11 WLAN channel is 12 VoIP calls. When the number of simultaneous VoIP calls is within the capacity, the WLAN can deliver more than 90% of the voice packets to the receiver within 150 ms (the lowest network performance for supporting acceptable VoIP service). However, as soon as the traffic loads are beyond the wireless channel capacity e.g. the number of simultaneous VoIP calls is greater than 13, the VoIP service quality catastrophically collapses. When the capacity is exceeded there are almost no voice packets that can be delivered to the receiver within 150 ms. Our research results indicate that the delay accumulation for voice packets in the transmitter’s outgoing buffer causes this problem. Our research also found that dropping ‘stale’ voice packets that are already late for delivery to the receiver can give more transmission opportunities to those voice packets that may still be delivered in time. This thesis presents a new strategy called Active Cleaning Queue (ACQ) which actively drops ‘stale’ voice packets from the outgoing buffer and prevents the accumulation of delay in congested conditions. When ACQ is applied in a saturated wireless channel the network performance for supporting VoIP traffic was found to gradually decrease proportional to the numbers of simultaneous VoIP calls rather than catastrophically collapse. There is also published research suggesting that the aggregation of packets can improve the efficiency of WLAN transmissions. An algorithm called Small Packet Aggregation for Wireless Networks (SPAWN) is also presented in this thesis to improve transmission efficiency of small voice packets in WLANs without introducing further delay to VoIP traffic. The evaluation result shows that after applying the SPAWN algorithm, the VoIP capacity of a single wireless channel can be extended up to 24 simultaneous calls.

APA, Harvard, Vancouver, ISO, and other styles

8

Olsson, Mattias. "A Rapid Prototype of an IEEE802.11a Synchronizer." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1457.

Full text

Abstract:

The first part of the thesis consists of a theoretical overview of OFDM, the effects of different imperfections like carrier frequency offset, timing offset and phase noise followed by a short overview of the IEEE802.11a standard for WLAN. The second part consists of an overview of a number of different techniques for synchronization that have been published. A technique based on correlation in the time domain is chosen and implemented as a floaing-point model and later as a fixed-point model using Matlab, Simulink and Xilinx System Generator. The fixed-point model is then synthesized to an FPGA to verify that the design flow works and that a required clock frequency can be achieved.

APA, Harvard, Vancouver, ISO, and other styles

9

Bergamo, Pierpaolo, Daniela Maniezzo, Kung Yao, Matteo Cesana, Giovanni Pau, Mario Gerla, and Don Whiteman. "IEEE802.11 WIRELESS NETWORK UNDER AGGRESSIVE MOBILITY SCENARIOS." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/605385.

Full text

Abstract:

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada
Wireless LAN (WLAN) has been extensively deployed in commercial, scientific and home applications due to the availability of low-cost wireless Network lnterace Cards (NICs) based on the IEEE802.11 standard. The purpose of this work is to study experimentally the behavior of an IEEE802.11 wireless network when the nodes arc characterized by mobility up to the speed of 240 km/h. This study leads to the understanding of the survivability and the performance of a connection under various aggressive mobility conditions. These studies may be adapted for data telemetry from mobile airborne nodes to fixed networks or between airborne nodes.

APA, Harvard, Vancouver, ISO, and other styles

10

Edbom, Emil, and Henrik Henriksson. "Design comparison between HiperLAN/2 and IEEE802.11a services." Thesis, Linköping University, Department of Science and Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1358.

Full text

Abstract:

This paper is a study and comparison between the two Wireless LAN (WLAN) standards HiperLAN/2 and IEEE 802.11a. WLANs are used instead or together with ordinary LANs to increase mobility in for example an office. HiperLAN/2 is an European standard developed by ETSI and the IEEEs standard is American.

A WLAN-card consists roughly of a Medium Access Control (MAC), Physichal layer (PHY) and an antenna. The antenna is the same for the different standards.

Both standards operates at 5.4 GHz with a maximum transmission rate at 54 Mbit/s and they use OFDM to modulate the signal. This means that the physical layer in the two standards is similar.

The differences between the standards are in the Medium Access Control (MAC) layer. HiperLAN/2 has a much more complex MAC since it is developed with the starting point in cellular phones. Therefore this MAC is not very similar to ETHERNET that is the protocol used by regular network. On the other hand it is built to be compatible with cellular phones and other applications.

The 802.11a MAC is very much the same as in the 802.11b standard that is the most used standard at present. The difference is that 802.11a can send at much higher data rates. This MAC is build with starting point in ETHERNET so it has a similar interface to the computer. This makes it less complex.

The different MACs can provide different services. The greatest difference is that 802.11a can use a distributed send mode where any STA can send if the medium is idle. This reminds a lot of ETHERNET but they use different methods to sense if the medium is idle. In HiperLAN/2 are all transmissions scheduled by the AP. 802.11a can operate in a similar way but at the moment this mode is not as fully developed as in HiperLAN/2. There are working groups in IEEE that works toward an improvement of 802.11a so it can use queues with different priorities, this is already implemented in HiperLAN/2.

Another important issue in wireless environment is security. Both standards use encryption to protect their messages. The difference is that HiperLAN/2 changes their encryption key for every connection where 802.11a uses the same key the whole time. This gives HiperLAN/2 a better security with todays standard but thereare working groups dealing with implementing key-exchange functions and Kerberos use in 802.11a. Chapter 8 is a description of a program that we developed in C++. The program is used to monitor the different registers and ports a WLAN-card use. It is written for a 802.11b card and should be used together with Windows 2000. The source code can be found in appendix C.

APA, Harvard, Vancouver, ISO, and other styles

11

Vyčítal, Jaroslav. "Šíření signálů bezdrátových komunikačních systémů IEEE 802.11." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377156.

Full text

Abstract:

This paper deals with the propagation of waves. Here is the wavelength distribution according to the wavelength. It focuses on the UHF and SHF band in which IEEE802.11n operates. Contains model breakdown by cell type. Describes which propagation methods are dominant in the cell type. Several propagation patterns are presented, which are then modeled in Matlab environment.The models are then compared to experimental measurements.

APA, Harvard, Vancouver, ISO, and other styles

12

Yousef, Michael Mousa. "Modellering i SIMULINK av synkronisering i nätverk enligt IEEE802.11a." Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5220.

Full text

Abstract:

Inom detta examensarbete implementeras i SIMULINK en modell av ett trådlöst överföringssystem enligt IEEE802.11a standarden. Modellen klarar av att hantera störningskällor som är vanligt förekommande i den miljö applikationen operar på. Denna modell utvärderas sedan för att avgöra dess belastningsförmåga och vid vilka värden den brister.

Första delen av rapporten beskriver målsättningen och syftet med detta examensarbete, samt metodvalet och rapportens uppläggning som tillämpats.

Rapportens andra del innehåller en allmän beskrivning av digital radiokommunikation och OFDM-baserade system. Därefter beskrivs teorin av både sändaren och mottagaren enligt IEEE802.11a standarden. Slutligen behandlas ett flertal vanligt förekommande synkroniseringsalgoritmer som har blivit publicerade.

I rapportens tredje del diskuteras de verktyg som har använts för att bygga modellen. Denna del fortsätter sedan med att kort beskriva valen av de algoritmer som har tillämpats i modellen.

Fjärde och sista delen av rapporten delas in i två kapitel. I första kapitlet sker de simuleringar som erfordras för att kunna utvärdera modellen. Examensarbetet knyts sedan ihop vid resultatkapitlet, där även förslag på fortsatt arbete diskuteras.

En ny version av examensarbetet har lagts till i listan (nr. 2) på begäran av författaren med anledning av att författaren har bytt namn.

APA, Harvard, Vancouver, ISO, and other styles

13

Meireles, Tiago Hipkin. "Wireless protocols to support vehicular safety applications." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/16287.

Full text

Abstract:

Doutoramento em Engenharia Electrotécnica
In the last decades the number of vehicles travelling in European road has raised significantly. Unfortunately, this brought a very high number of road accidents and consequently various injuries and fatalities. Even after the introduction of passive safety systems, such as seat belts, airbags, and some active safety systems, such as electronic brake system (ABS) and electronic stabilization (ESP), the number of accidents is still too high. Approximately eight per cent of the fatal accidents occur in motorways, in the Portuguese case, the number of fatalities has remained constant in the first decade of the 21st century. The evolution of wireless communications, along with the north-American and European policies that reserve spectrum near the 5,9GHz band for safety applications in the vehicular environment, has lead to the development of several standards. Many of these applications are based on the possibility of using a wireless communication system to warn drivers and passengers of events occurring on the road that can put at risk their own safety. Some examples of safety applications are the hard-brake warning, the wrong-way warning and the accident warning. This work aims to contribute in defining a communication protocol that guarantees the timely dissemination of safety critical events, occurring in scenarios with a high number of vehicles or in the neighbourhood of so called motorway “blackspots”, to all vehicles in the zone of interest. To ensure information integrity and user trust, the proposed system is based on the motorway infrastructure, which will validate all events reported by the vehicles with the usage of several means, such as video surveillance or other sensors. The usage of motorway infrastructure that has full motorway coverage using fixed stations also known as road side units, allows to have a global vision of the interest zone, avoiding the problems associated to networks that depend solely on vehicle to vehicle communication, generally total ad-hoc networks. By using the infrastructure, it is possible to control medium access, avoiding possible badly intended intrusions and also avoiding the phenomenon known as alarm showers or broadcast storm that occur when all vehicles want to simultaneously access the medium to warn others of a safety event. The thesis presented in this document is that it is possible to guarantee in time information about safety events, using an architecture where the road side units are coordinated among themselves, and communicate with on board units (in vehicles) that dynamically register and deregister from the system. An exhaustive and systematic state of the art of safety applications and related research projects is done, followed by a study on the available wireless communications standards that are able to support them. The set of standards IEEE802.11p and ETSI-G5 was created for this purpose and is found to be the more adequate, but care is taken to define a scenario where WAVE enabled and non-enabled vehicles can coexist. The WAVE medium access control protocol suffers from collision problems that do not guarantee a bounded delay, therefore a new protocol (V-FTT) is proposed, based on the adaptation of the Flexible Time Triggered protocol to the vehicular field. A theoretical analysis of the V-FTT applied to WAVE and ETSI-G5 is done, including quantifying a real scenario based on the A5 motorway from Lisbon to Cascais, one of the busiest Portuguese motorways. We conclude the V-FTT protocol is feasible and guarantees a bounded delay.
Nas últimas décadas tem-se assistido a um aumento do número de veículos a circular nas vias rodoviárias europeias, trazendo consigo um elevado número de acidentes e como consequência muitos feridos e vítimas mortais. Apesar da introdução de sistemas de segurança passivos, tais como cintos de segurança, airbags e de alguns sistemas de segurança activos, tais como o sistema electrónico de travagem (ABS) e o sistema electrónico de estabilidade (ESP), o número de acidentes continua a ser demasiado elevado. Aproximadamente oito por cento dos acidentes fatais na Europa ocorrem em auto-estradas, no caso Português, o número de vítimas mortais tem-se mantido constante ao longo da primeira década do século XXI. A evolução das comunicações sem fios, acompanhada de políticas europeias e norte-americanas no sentido de reservar frequências próximas dos 5,9GHz para aplicações de segurança no ambiente veicular, levou à especificação de várias normas. A maior parte destas aplicações baseiam-se na possibilidade de usar um sistema confiável de comunicação sem fios para alertar os condutores e passageiros de veículos para eventos ocorridos nas estradas que possam colocar em risco a sua segurança. Exemplos de aplicações de segurança crítica são o aviso de travagem brusca, o aviso de veículo em contra mão e o aviso de acidente na estrada. Este trabalho contribui para a definição de protocolos de comunicação capazes de garantir que a informação sobre eventos relacionados com situações de segurança crítica, que ocorram em cenários com um elevado número de veículos em zonas urbanas ou na vizinhança dos chamados “pontos negros” das auto-estradas, é disseminada com pontualidade por todos os veículos localizados na zona de interesse Por uma questão da integridade das comunicações e confiança dos condutores, o sistema proposto baseia-se na infra-estrutura do concessionário da auto-estrada, que validará os eventos reportados pelos veículos usando vários meios à sua disposição, como por exemplo sistemas de videovigilância e outros sensores. O uso de uma infra-estrutura de comunicações, que dispõe de cobertura integral a partir de estações fixas, permite uma visão global da zona coberta, evitando os problemas associados a redes baseadas apenas na comunicação entre veículos, que são em geral totalmente ad-hoc. O uso da infra-estrutura permite, entre outras vantagens, controlar o acesso ao meio, evitando simultaneamente intrusões de estranhos ao sistema e o fenómeno conhecido como “chuva de alarmes” desencadeado quando todos os veículos querem aceder simultaneamente ao meio para avisar os restantes da existência dum evento de segurança crítica. A tese apresentada neste documento defende que é possível garantir informação atempada sobre eventos que põem em risco a segurança dos veículos a partir de uma arquitectura de interligação entre as estações de comunicações fixas, coordenadas entre si, e unidades móveis (veículos) que se registam e se desligam dinamicamente do sistema. Nesta tese faz-se um levantamento exaustivo e sistemático das aplicações de segurança abordando projectos de investigação relacionados, estudam-se as tecnologias de comunicação sem fios disponíveis e a sua possibilidade de suportar aplicações de segurança rodoviária. Desta análise, conclui-se que a norma norte americana WAVE/IEEE802.11p e a europeia ETSI-G5, criadas especificamente para o efeito são as que mais se adequam à finalidade desejada. Considera-se que o cenário de utilização é evolutivo, podendo coexistirem veículos que não dispõem de sistemas de comunicação com outros que suportam a norma WAVE. Dado que o protocolo de acesso ao meio proposto pela norma WAVE não garante um acesso determinístico ao meio partilhado, propõe-se um novo protocolo, o Vehicular Flexible Time-Triggered protocol (VFTT). Faz-se a análise teórica da viabilidade do protocolo proposto para a norma WAVE e respectiva norma europeia (ETSI-G5). Quantifica-se o protocolo VFTT para um cenário real: a auto-estrada A5 Lisboa-Cascais, uma das autoestradas portuguesas mais movimentadas. Conclui-se que o protocolo é viável e garante um atraso restringido temporalmente.

APA, Harvard, Vancouver, ISO, and other styles

14

Shrestha, Sanjeeb. "Addressing the hidden terminal problem in MU-MIMO WLANs with relaxed zero-forcing approach." Thesis, Optimal ZF precoding vector, 2017. http://hdl.handle.net/10453/116766.

Full text

Abstract:

University of Technology Sydney. Faculty of Engineering and Information Technology.
An ever-increasing data rate demand, mainly due to the proliferation of numerous smart devices, enterprises’ mission critical networks, and industry automation, has mounted tremendous pressure on today’s Wireless Local Area Networks (WLANs). Several avenues such as bandwidth, constellation density, the Multiple Input Multiple Output (MIMO) technique, etc., have been explored, e.g., IEEE802.11n/ac standards, to keep up with the demand. Future WLAN standard, e.g., IEEE802.11ax, with potential technologies such as uplink Multi-User (MU)-MIMO, full duplex transmission, etc., is anticipated by 2019. Having said that, there has been a strong emphasis on solving the technical issues with WLANs along with the addition of new frontiers in order to cope with the data rate demanded. One such appending decade-long issue is the inevitable Hidden Terminal (HT) problem in a distributive, decentralised and densely deployed WLANs, which fundamentally arises because of the transmission time overlaps between different transmitters operating at a particular frequency. The consequence is that it causes collisions of signals, which sharply reduces the system throughput. In the context of MU-MIMO based WLANs, several designs for a general network scenario, without the consideration of the HT problem, have been proposed, bringing efficiency by avoiding the collision of signals. However, a dedicated design, which could effectively address the HT problem in MU-MIMO WLANs and also become interoperable (with legacy standards) and feasible with existing hardware, is lacking to the best of our knowledge. In this thesis, we propose a solution for the HT problem which has three fundamental attributes. First, a) at the Physical (PHY) layer, the Zero-forcing (ZF) transmission strategy with fairness and throughput aware precoding is proposed, b) a hybrid scheduling scheme, combining the packet position-based First In First Out (FIFO) and channel quality-based scheme, namely the Best of the Two Choices, is designed, c) at the Medium Access Control (MAC) layer, Degrees-of-Freedom (DoF) based Transmission Opportunity (TXOP) for Access Points (APs) is developed which is backed by an extended Point Coordination Function (PCF), d) an explicit channel acquisition framework is proposed for ZF which has a reduced signaling time overhead of 98.6740 μs compared to IEEE802.11ac. e) performance evaluation methodologies are: i) hardware testbed results of the PHY strategy, which shows a received SNR gain of about 6 dB on average, and about 10 dB in comparison to the HT scenario, ii) simulation results of the MAC design, which shows a constant throughput gain of 4 − 5 times w.r.t. the popular Request to Send/Clear to Send (RTS/CTS) solution. Second, to address the interoperability issue, we purposefully use the standard frame format except for some required logical changes. Notably, the transition mechanism of our design, and for any MAC that uses standard frame formats, is investigated meticulously. The transition condition, transition steps and transition frame formats are detailed. Third, to address a practical constraint of an imperfect Channel State Information (CSI) at APs, a) we incorporate the Finite Rate Feedback (FRF) model in our solution. The effects on system parameters such as quantisation error bounds, throughput loss w.r.t. perfect CSI, etc., are discussed with closed-form analytical expressions, b) instead of an ideal ZF technique, a Relaxed ZF (RZF) framework is considered, in which the interference and power constraints of the optimisation problem are relaxed to the interference upper bound and to the maximum transmit power respectively. Our results lead to a distributive algorithm for calculating the optimal ZF precoding vector which suits the distributive, decentralised and uncoordinated nature of MU-MIMO WLANs.

APA, Harvard, Vancouver, ISO, and other styles

15

Peyre, Thierry. "Evaluation de performances sur le standard IEEE802.16e WiMAX." Phd thesis, Université d'Avignon, 2008. http://tel.archives-ouvertes.fr/tel-00796477.

Full text

Abstract:

Les dernières décennies ont connu l'apogée des transmissions hertziennes, et celles à venir connaîtront incontestablement le développement et le déploiement intense de systèmes de communications sans-fil. Dès à présent, il est possible de communiquer par onde sur petite et très petite distance (LAN et PAN). Les populations se sont familiariséesavec les interfaces bluetooth (IEEE802.15) présentes dans la majorité des objetscommuniquant (ordinateur portable, téléphone, PDA, etc...). Les foyers s'équipentmaintenant facilement et à bas prix d'interfaceWi-Fi (IEEE802.11), afin de profiter d'uneutilisation nomade de leur accès internet. Ainsi, la forte croissance dumarché des offresinternet combinée avec celle du marché des téléphones mobiles ont habitués un large spectre d'utilisateurs à communiquer sans fil. Ce contexte sociologique et financier encourage donc l'arrivée de solutions nouvelles répondant à des besoins latents. Parmi ceux-là, le marché met en évidence le manque de système de communication sur moyenne distance (MAN). Les réseaux ad-hoc peuvent répondre à ce genre de besoin. Mais àce jour, les performances sont trop faibles pour les besoins des utilisateurs et elles dépendenttrop fortement de la densité desmachines nomades. Aussi, le consortiumIEEEcherche au travers de sa norme IEEE802.16 à fournir un système complet de communicationsans-fil sur moyenne distance (MAN). Appelé aussiWiMAX, ce système se basesur une architecture composée d'une station de base (BS) et de nombreux mobiles utilisateurs(SS). Le standard IEEE802.16 définit les caractéristiques de la couche physiqueet de la couche MAC. Il décrit l'ensemble des interactions et événements pouvant avoirlieu entre la station de base et les stations mobiles. Enfin, le standard fournit différents paramètres et variables servant aux mécanismes de communication. Comme tout nouveau standard émergeant, la norme IEEE802.16 ne profite pas d'un état de l'art aussi développé que celui du IEEE802.11 par exemple. Aussi, de nombreuses études et idées sont à développer.En premier lieu, nous effectuons un large rappel de la norme WiMAX et en particulier le IEEE802.16e. Associé à cela, nous dressons un état de l'art des travaux traitant des aspects et perspectives liés au sujet de notre étude.Par la suite, nous proposons un modèle novateur de performance des communicationsIEEE802.16e. Au travers de ce modèle, nous développons une étude générale et exhaustive des principaux paramètres de communication. L'étude explicite l'impact deces paramètres ainsi que l'influence de leur évolutions possibles. De cela, nous critiquonsla pertinence de chacun d'eux en proposant des alternatives de configurations.5En sus, nous proposons un mécanisme novateur favorisant le respect de qualité de service(QoS) sur couche AC.Nous développons un principe original d'établissement de connexion favorisant l'accès aux communications sensibles aux délais de transmission.Dans une dernière partie, nous déterminons la capacité d'un système IEEE802.16 à gérer les arrivées et départs des utilisateurs. Tout en y associant une étude de performance d'un nouvel algorithme de contrôle d'admission. Cet algorithme d'admission vise à remplir des objectifs multiples : empêcher les famines de ressources sur les trafics les moins prioritaires, favoriser l'admission des utilisateurs en maintenant une gestion optimale de la ressource radio. Notre étude aboutit à une modélisation et une critique des variations de paramètre associés à ce nouvel algorithme. Nous y intégrons par la suite le principe de mobilité où les utilisateurs ont la capacité de se mouvoir au sein d'une cellule. Cette intégration se fait en y associant des mécanismes originaux afin d'assurer la pérennité du service aux utilisateurs mobiles.

APA, Harvard, Vancouver, ISO, and other styles

16

Nguyen, Hai Dang. "Déploiement et ordonnancement dans Wimax avec relais : IEEE802.16j." Phd thesis, Université d'Evry-Val d'Essonne, 2011. http://tel.archives-ouvertes.fr/tel-00878774.

Full text

Abstract:

Les systèmes cellulaires modiles WiMAX ont pour objectif de fournir des services multimédias à haut débit à n'importe quel moment, n'importe quel endroit avec un prix abordable. La combinaison d'orthogonale accès multiples (OFDMA) et le relais en Wimax donnent plusieurs opportunités pour des réseaux moins coûteux et plus performances. La norme Wimax 802.16j élargit non seulement la couverture de la cellule, mais aussi augmente le débit moyen des utilisateurs. Plusieurs recherches de cette norme ont été publiées afin d'optimiser la performance du réseau. Cependant, lorsque nous étudions les architectures existantes du Wimax 802.16j standard et leur rendement, nous nous sommes aperçus que le débit du système pourrait être encore amélioré à l'aide de la réutilisation de fréquence. Dans la première partie de ce travail de recherche, nous avons examiné l'architecture existante de la norme 802.16j. Le débit total du système est légèrement plus élevé dans ces architectures que dans la norme sans relais. Afin d'améliorer le rendement du système de cette norme, nous avons proposé une nouvelle architecture de cette norme avec réutilisation de fréquence et de la technique de sectorisation. Le débit total augmente fortement dans notre approche comparant aux études existantes. Dans la deuxième partie, nous avons étudié l'impact de l'interférence dans notre modèle de relais. Les résultats de simulation montrent que les SINR de station mobile augmentent très légèrement. Cet impact d'interférence est assez faible et pourrait être négligeable. Nous concluons que notre proposition fournit toujours une meilleure performance. Dans la troisième partie, nous avons proposé une nouvelle approche d'allocation de ressources en liaison descendante afin de garantir les mêmes qualités de service pour les utilisateurs en maintenant un haut débit total. Les résultats de simulation montrent qu'il existe un compromis entre l'équité de la qualité de service et le débit total du système.

APA, Harvard, Vancouver, ISO, and other styles

17

Nguyen, Hai Dang. "Deployment & scheduling in Wimax with relays : IEEE802.16j." Thesis, Evry-Val d'Essonne, 2011. http://www.theses.fr/2011EVRY0016.

Full text

Abstract:

WiMAX mobile cellulaire systèmes ont pour objective de fournir des services multimédias à haut débit à n'importe quel moment, n'importe quel endroit avec un prix abordable. La combinaison d'orthogonale accès multiples (OFDMA) et le relais en Wimax donnent plusieurs opportunités pour des réseaux moins coûteux et plus performances. La norme Wimax 802.16j élargit non seulement la couverture de la cellule, mais aussi augmente le débit moyen des utilisateurs. Plusieurs recherches de cette norme ont été publiées afin d'optimiser la performance du réseau. Cependant, lorsque nous étudions les architectures existantes du Wimax 802.16j standard et leur rendement, nous nous sommes aperçus que le débit du système pourrait être encore amélioré à l'aide de la réutilisation de fréquence. Dans la première partie de ce travail de recherche, nous avons examiné l'architecture existante de la norme 802.16j. Le débit total du système est légèrement plus élevé dans ces architectures que dans la norme sans relais. Afin d'améliorer le rendement du système de cette norme, nous avons proposé une nouvelle architecture de cette norme avec réutilisation de fréquence et de la technique de sectorisation. Le débit total augmente fortement dans notre approche comparant aux études existantes. Dans la deuxième partie, nous avons étudié l'impact de l'interférence dans notre modèle de relais. Les résultats de simulation montrent que les SINR de station mobile augmentent très légèrement. Cet impact d’interférence est assez faible et pourrait être négligeable. Nous concluons que notre proposition fournit toujours une meilleure performance. Dans la troisième partie, nous avons proposé une nouvelle approche d’allocation de ressources en liaison descendante afin de garantir les mêmes qualités de service pour les utilisateurs en maintenant un haut débit total. Les résultats de simulation montrent qu'il existe un compromis entre l'équité de la qualité de service et le débit total du système
Wimax mobile cellular systems are envisioned to provide high data rate multimedia services to users at anytime, anywhere at an affordable cost. The combination of orthogonal division multiple accesses (OFDMA) and relaying in Wimax provide rich opportunities for cost-effective and high performance networks. Wimax standard 802.16j extends not only the coverage of the cell but also increases the average throughput of the users. Much research of this standard has been published in order to optimize the performance of this network. However, when we reviewed the existing architectures of Wimax standard 802.16j and assessed their performance, we realized that the throughput of the system could still be enhanced by using a more efficient frequency reuse and scheduling algorithm. In the first part of the thesis, we review the existing standard 802.16j architectures in which the total throughput of system is slightly higher than that in the standard without relay one. To enhance even more the system performance of this standard, we propose a new architecture built on frequency reuse and sectoring technique. The total throughput increased strongly in our approach compared with to the existing studies. In the second part of the thesis, we study the impact of interference in our relay model. The simulation results showed that the SINR of mobile stations in our approach increase very slightly comparing to the one in Wimax with relay without frequency reuse and sectoring. Therefore the impact of interference is small and can be considered as negligible. We concluded that our proposition still provide a better performance. In the third part of the thesis, we proposed a new radio resource management approach in downlink in order to guarantee the user’s fairness but still maintain a high total throughput. The simulation results showed that there was a trade-off between the fairness-aware and the total throughput of the system

APA, Harvard, Vancouver, ISO, and other styles

18

Biazotto, Luiz Henrique. "Consumo de energia e qualidade do servi?o em redes IEEE802.11." Pontif?cia Universidade Cat?lica de Campinas, 2012. http://tede.bibliotecadigital.puc-campinas.edu.br:8080/jspui/handle/tede/523.

Full text

Abstract:

Made available in DSpace on 2016-04-04T18:31:32Z (GMT). No. of bitstreams: 1 Luiz Henrique Biazotto.pdf: 2826699 bytes, checksum: ea3eea233d66bf1af34e5d7f5d20420d (MD5) Previous issue date: 2012-06-28
Nowadays, the growth of energy consumption is a global concern due to the possibility of having lack of primary sources. Specially, the consume of electrical energy associated with communications network also eached significantly levels. In this context, researches related to energy efficiency are extremely important.Therefore, this work aims to evaluate the consumption of electrical energy related to IEEE802.11 networks, searching for the relation between this consumption and different parameters of QoS.
Atualmente, o crescimento do consumo de energia el?trica se constitui em preocupa??o mundial, devido ? possibilidade de escassez das fontes prim?rias. Em especial, o consumo de energia el?trica associado ?s redes de comunica??o tamb?m atingiu n?veis significativos. Nesse contexto, pesquisas associadas ? ?rea de efici?ncia energ?tica s?o de fundamental import?ncia. Assim, este trabalho teve por objetivo avaliar o consumo de energia el?trica associado a redes IEEE802.11, investigando a rela??o dessa grandeza com diferentes par?metros de Qualidade de Servi?o (QoS).

APA, Harvard, Vancouver, ISO, and other styles

19

Narisetti, Mary. "Implementation of Vertical Handoff Algorithm between IEEE802.11 WLAN and CDMA Cellular Network." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/cs_theses/24.

Full text

Abstract:

Today’s wireless users expect great things from tomorrow’s wireless networks. These expectations have been fueled by hype about what the next generations of wireless networks will offer. The rapid increase of wireless subscribers increases the quality of services anytime, anywhere, and by any-media becoming indispensable. Integration of various networks such as CDMA2000 and wireless LAN into IP-based networks is required in these kinds of services, which further requires a seamless vertical handoff to 4th generation wireless networks. The proposed handoff algorithm between WLAN and CDMA2000 cellular network is implemented. The results of the simulation shows the behavior of the handoff and the time spent in WLAN or CDMA. The number of weak signal beacons determines whether a handoff is required or not. In this algorithm, traffic is classified into real-time and non real-time services.

APA, Harvard, Vancouver, ISO, and other styles

20

Kasch, William T., Jack L. Burbank, Julia Andrusenko, and Mark H. Lauss. "Performance of the IEEE 802.11b WLAN Standards for Fast-Moving Platforms." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/605384.

Full text

Abstract:

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada
This paper addresses the physical and MAC layer performance of the IEEE 802.11b wireless local area networking (WLAN) standard in range-extended outdoor applications for high speed network platforms. Physical layer performance is quantified by bit error rate (BER) and packet error rate (PER) vs. range performance as well as acquisition and tracking performance considering Doppler effects caused by such high-speed platforms. This performance assessment is ascertained through the use of modeling and simulation and hardware-in-the-loop testing.

APA, Harvard, Vancouver, ISO, and other styles

21

Argenton, Alexandre Bortolin. "Uma proposta para gerenciamento de QoS em redes IEEE802.16." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/13656.

Full text

Abstract:

O padrão IEEE802.16 define uma tecnologia para acesso sem fio em banda larga que deve tornar-se bastante popular nos próximos anos. A tecnologia pode resolver o problema de comunicação em áreas de difícil penetração e prover conectividade com Qualidade de Serviço (QoS), mais agilidade e menor custo em muitas outras situações. Não basta, entretanto, a tecnologia de rede oferecer recursos para Qualidade de Serviço. É necessário que se possa gerenciá-los de maneira simples e eficaz. Sem um estudo que permita desenvolver sistemas de gerenciamento adequados para uma dada tecnologia, o gerenciamento acaba ocorrendo através de ferramentas rudimentares. Este trabalho propõe e avalia uma forma de gerenciar QoS em redes IEEE802.16. Através do estudo destas redes e de modelos de gerenciamento existentes, foram levantados requisitos relevantes ao gerenciamento deste tipo de rede, e foi proposto o gerenciamento baseado em políticas como possível solução. A solução proposta engloba recomendações quanto ao que se deveria poder expressar através das políticas, uma reflexão sobre o mapeamento destas políticas na rede e a escolha da arquitetura de gerenciamento baseado em políticas do IETF (Internet Engineering Task Force) para implementação. Questões práticas, como o uso do processo de ranging para disparar a configuração das políticas, são abordadas e tratadas no momento em que a arquitetura é apresentada, viabilizando a implementação da solução. Tendo em vista a escolha do protocolo SNMP para a configuração dos dispositivos, uma MIB de gerenciamento foi proposta para viabilizar o acesso aos parâmetros de configuração necessários. A MIB foi construída sobre outra MIB já existente, adicionando-lhe os objetos e capacidades faltantes. A forma de operação da MIB é apresentada com maiores detalhes para facilitar o entendimento. Visando validar a solução proposta, o sistema de gerenciamento baseado em políticas QAME foi estendido para permitir o gerenciamento de redes IEEE802.16 dentro da abordagem proposta. A extensão incluiu a implementação de um novo PDP, específico para redes IEEE802.16. Através da emulação de uma rede IEEE802.16 e do uso do sistema de gerenciamento QAME adaptado, a solução proposta foi avaliada. Pôde-se obter conclusões quanto ao uso de gerenciamento baseado em políticas no gerenciamento de QoS de redes IEEE802.16 e também quanto aos limites de aplicabilidade da arquitetura de gerenciamento proposta.
The IEEE802.16 standard defines a broadband wireless access technology that should become very popular in the next years. The technology may solve the communication problem in hard access areas and provide connectivity with Quality of Service (QoS), greater agility and lower costs in many other situations. Offering QoS capabilities is not sufficient to a given network technology. A simple and effective way to manage its capabilities is also required. Without a study that allows the development of adequate management systems, only rudimentary tools will be used for the management task. This work proposes and evaluates a way to manage QoS on IEEE802.16 networks. By studying IEEE802.16 networks and existing management models, the relevant requirements to manage this kind of network have been gathered and the Policy-Based Network Management (PBNM) model has been proposed as a possible solution. The proposed solution includes recommendations on what should be possible to express with policies, a thought on how to map the policies on the network, and the choice of the IETF (Internet Engineering Task Force) PBNM architecture. Some practical matters, such as the use of the ranging process to trigger the policy configuration, are considered when the architecture is presented. Since SNMP has been chosen to configure the devices, a MIB has been proposed to allow access to the required configuration parameters. The MIB has been constructed over a previously existing one by adding the lacking objects and capabilities. The MIB operation is also presented in more details. In order to validate the proposed solution, the QAME PBNM system has been extended to allow IEEE802.16 network management. The extension included a new PDP, developed specifically to manage IEEE802.16 networks. By means of an emulated IEEE802.16 network and the use of the adapted QAME management system, the proposed solution has been evaluated. Conclusions have been taken on the use of PBNM to manage QoS for IEEE802.16 networks and on the applicability limits of the proposed architecture.

APA, Harvard, Vancouver, ISO, and other styles

22

Couto, Paula Cristina da Silva. "Redes de área local sem fios: estudo e desenvolvimento da subcamada MAC IEEE802.11." Master's thesis, Universidade de Aveiro, 1996. http://hdl.handle.net/10773/17779.

Full text

Abstract:

Mestrado em Engenharia Electrónica e Telecomunicações
O trabalho desenvolvido enquadra-se no domínio científico das redes de área local sem fios. Esta dissertação descreve a especificação, implementação e teste da subcamada MAC da rede de área local sem fios definida pela especificação IEEE802.11. Introdutoriamente são apresentados os diferentes tipos de rede de área local sem fios e é feita uma breve comparação entre as duas tecnologias de suporte (radio fiequência e int?avermelhos). São também mencionados os principais organismos que desenvolvem actividades de normalização para este tipo de redes. O protocolo de acesso ao meio é uma das funcionalidades implementadas pela subcamada MAC. Os principais protocolos de acesso ao meio para redes de comunicação de área local são descritos e é feita uma análise qualitativa da aplicabilidade destes em redes de área local sem fios. Concluí-se que um protocolo híbrido, integrando acesso aleatório e não aleatório, está melhor adaptado às características do canal de transmissão e à diversidade de padrões de tráfego. A especificação IEEE802.11 define um protocolo híbrido para a subcamada MAC. Antecedendo a descrição detalhada das fases de desenvolvimento da subcamada MAC é feita uma apresentação da especificação IEEE802.11. São descritas as funções de coordenação do acesso ao meio (distribuída e centralizada), a função de fragmentação e as funções de gestão (sincronismo temporal, conservação do consumo de potência, associação e reassociação). O desenvolvimento da subcamada MAC comporta duas componentes: hardware e software. A componente hardware, baseada no processador RISC ARMóO, não foi desenvolvida no âmbito desta dissertação. Apenas é dada uma visão geral dos principais blocos funcionais que a constituem. A descrição detalhada do desenvolvimento da componente sofbvare inclui as três fases por que este passou: especificação, implementação e teste. A primeira fase incide sobre a função de coordenação do acesso ao meio distribuída (CSWCA) e funções de gestão da especificação IEEE802.11. As duas fases seguintes apenas consideram a função de coordenação do acesso ao meio. A especificação decorreu em duas etapas: na primeira construíram-se os diagramas de transição de estados utilizando a sintaxe da linguagem SDL; na segunda traduziram-se os diagramas para uma linguagem estruturada próxima da linguagem de programação Pascal (pseudo-código). A implementação consistiu na codificação em linguagem C da função de coordenação do acesso ao meio distribuída, especificada na fase anterior. O código foi optimizado no sentido de minimizar o tempo de processamento. Na fase de teste realizaram-se testes funcionais ao nível dos procedimentos e ao nível do protocolo com uma e duas estações, tendo por objectivo a detecção de qualquer erro de lógica na especificação. Todos os testes foram realizados com sucesso permitindo a validação da especificação inicial.

APA, Harvard, Vancouver, ISO, and other styles

23

D’Amico, William P., Patrick A. Stadter, Mark H. Lauss, and Andrew Hooper. "Network Telemetry: Practical Experiences and Unique Features." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/606321.

Full text

Abstract:

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California
The US Army’s Yuma Proving Ground (YPG) uses a wireless local area network (WLAN) to gather test data. It is desired to extend this WLAN to support tests of gun-launched munitions where miniature and rugged data acquisition hardware will be required. The Two Way Robust Acquisition of Data (2-RAD) program has been initiated under the Central Test and Evaluation Investment Program (CTEIP) to develop a process to expand the use of WLAN technology, which is now primarily used at YPG for internal ballistic test data acquisition.

APA, Harvard, Vancouver, ISO, and other styles

24

Hajjar, Charbel el. "Synchronization algorithms for OFDM systems (IEEE802.11a, DVB-T) analysis, simulation, optimization and implementation aspects." Stuttgart Fraunhofer-IRB-Verl, 2007. http://d-nb.info/988796562/04.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Joakim, Carlsson. "CloudMAC Frame Prioritization : QoS and routing of IEEE802.11 frames in a Opendaylight controlled network." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-36313.

Full text

Abstract:

Wireless networks are common in large organisations that can cover multiple floors and buildings. Wireless networks become expensive as they grow and more control and coordination is needed to operate and management them. This thesis describes how CloudMAC, a software defined networking solution (SDN), were implemented in OpenDaylight Hydrogen, a SDN controller. CloudMAC reduces complexity in large wireless local area networks. CloudMAC splits access points (AP) into, a physical (accesses the wireless medium) and a logical (handles the processing of data) part. These two part are then placed in different locations in a wired network. The parts are connected by making tunnels through the network. Some of the communications in wireless networks are time sensitive. Such time sensitive communication is easily disturbed during congestion. To improve CloudMAC, quality of service (QoS) was implemented. QoS was used both in the wired network and in accessing the wireless medium. Evaluations shows how to evaluate queues utilization and performance.

APA, Harvard, Vancouver, ISO, and other styles

26

Rademacher, Michael [Verfasser]. "Evaluation and Optimization of IEEE802.11 multi-hop Backhaul Networks with Directional Antennas / Michael Rademacher." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219476943/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Koujah, Fahad. "A Power-Aware Routing Scheme for Ad Hoc Networks." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28248.

Full text

Abstract:

Wireless network devices, especially in ad hoc networks, are typically battery-powered. The growing need for energy efficiency in wireless networks, in general, and in mobile ad hoc networks (MANETs), in particular, calls for power enhancement features. The goal of this dissertation is to extend network lifetime by improving energy utilization in MANET routing. We utilize the ability of wireless network interface cards to dynamically change their transmission power, as well as the ability of wireless devices to read the remaining battery energy of the device to create a table of what we term "reluctance values," which the device uses to determine how to route packets. Choosing routes with lower reluctance values, on average and with time, leads to better utilization of the energy resources of the devices in the network. Our power-aware scheme can be applied to both reactive and proactive MANET routing protocols. As examples and to evaluate performance, the technique has been applied to the Dynamic Source Routing (DSR) protocol, a reactive routing protocol, and the Optimized Link State Routing (OLSR) protocol, a proactive routing protocol. Simulations have been carried out on large static and mobile networks. Results show improvements in network lifetime in static and certain mobile scenarios. Results also show better distribution of residual node energies at the end of simulations, which means that the scheme is balancing energy load more evenly across network nodes than the unmodified versions of DSR and OLSR. Average change in energy over time in the unmodified protocols show a steady increase with time, while the power-aware protocols show an increase in the beginning, then it levels for sometime before it starts to decrease. The power-aware scheme shows improvements in static and in coordinated mobility scenarios. In random mobility the power-aware protocols show no advantage over the unmodified protocols.
Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

28

D’Amico, W., J. Burbank, W. Kasch, J. Andrusenko, and G. Barrett. "A WLAN Concept for Data Acquisition from Multiple Target Vehicles." International Foundation for Telemetering, 2003. http://hdl.handle.net/10150/605365.

Full text

Abstract:

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada
Tests for missile defense systems are very complex, and present challenging issues for the extraction of target lethality data. Future tests will involve the use of multiple interceptors and targets with some of these assets following over-the-horizon (OTH) trajectories. The use of wireless local area network (WLAN) technologies for the acquisition of test data offers a novel approach to manage data bandwidths and link margins over-the-air (OTA) as functions of time and asset. Notional test scenarios are examined for the suitability of WLAN technologies to missile defense intercept testing.

APA, Harvard, Vancouver, ISO, and other styles

29

CORDEIRO, CARLOS DE MORAIS. "MEDIUM ACCESS CONTROL PROTOCOLS AND ROUTING STRATEGIES FOR WIRELESS LOCAL AND PERSONAL AREA NETWORKS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1070579302.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Benaidja, Amira. "Echange d'informations en temps réel dans les réseaux de véhicules." Electronic Thesis or Diss., Sorbonne Paris Cité, 2016. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=1763&f=9560.

Full text

Abstract:

Les réseaux véhiculaires, connus sous le terme VANETs, sont des réseaux impliquant des communications entre deux ou plusieurs véhicules et éventuellement une communication avec des éléments d’infrastructure sur la route. Récemment, le concept de systèmes de transport intelligents (STI) a connu beaucoup d’intérêt. Les STI sont des systèmes utilisant les nouvelles technologies de communication sans fil appliquées au domaine du transport pour améliorer la sécurité routière, la logistique et les services d’information. Des défis majeurs ont besoin cependant d'être abordés pour offrir une communication sur la route sécurisée et fiable dans des environnements anonymes et quelquefois hostiles à la communication. Comme dans tout système de communication, les réseaux véhiculaires doivent opérer en respectant des contraintes en termes de qualité de service. Ces contraintes sont d’autant plus strictes quand il s’agit de fournir des services de sécurité sur la route. Ce projet vise à développer des techniques de communication véhiculaires pour le transfert des informations de manière fiable entre véhicules roulant à grande vitesse tout en contrôlant la surcharge du réseau. Ces techniques visent la prise en compte des contraintes temporelles sur les délais de transfert afin d’envisager leur utilisation dans des applications critiques telle que la sécurité sur la route. Pour ce faire, cette thèse propose d’abord un protocole optimal de dissémination de messages d’urgence pour les VANETs. Il est basé sur une stratégie de diffusion qui exploite les véhicules sur la direction opposée afin d’accélérer la dissémination du message d’urgence tout en réduisant le nombre de transmissions. Ainsi, et dans le but d’assurer une dissémination fiable et à faible surcoût, une technique de retransmission périodique intelligente permettant l’adaptation du protocol proposé à différentes densités du trafic routier est proposée. Dans un second volet, ce projet propose une approche hybride de dissémination de messages d’urgence qui combine alternativement les avantages des deux principales approches de dissémination existantes (Sender-oriented et Receiver-oriented dont notre première proposition fait partie) afin de garantir une transmission fiable des alertes tout en réduisant les délais. Les approches Receiver-Oriented qui sont les plus adaptées pour les applications de sécurité dans les VANETs peuvent minimiser la latence et les limitations des approches Sender-Oriented. Mais, ilsdoivent aussi mieux exploiter les apports des messages hello (beacons) échangés dans la technologie IEEE802.11P. Ainsi, et dans le but de surmonter les limites des approches de retransmissions périodiques et celles de relais- multiples afin d’assurer des échanges fiables de messages de sécurité tout en réduisant la surcharge de la bande passante, nous introduisons un nouveau mécanisme DR/BDR (Designated Relay/Backup Designated Relay). Le BDR, dans ce mécanisme, doit remplacer le DR et assurer sa tâche quand il détecte, à travers les beacons colorés échangés,l’échec de ce dernier dans la dissémination du message d’urgence
Vehicular Ad hoc NETworks (VANETs) have gained considerable attention in the past few years due to their promising applications such as safety warning, transport efficiency or mobile infotainment. Avoiding accidents and traffic jams are two main immediate benefits of vehicular networks. For instance, most drivers would like to receive real-time alerts about accidents happening at a short distance in front of their vehicles since these accidents could lead to collision chains involving tens of vehicles. Also, the ability to receive an alert about a potential traffic jam would allow drivers to take alternate routes, saving both time and fuel. In both cases, warning messages should be broadcasted to all vehicles traveling over a geographical area, and need to be delivered with high reliability, low delay and low overhead. It is therefore important to develop a reliable and efficient safety information dissemination protocol in vehicular networks. Due to the vehicle mobility and lossy wireless channel, highly reliable, scalable and fast multi-hop broadcast protocol is very challenging to design. A number of solutions have been proposed in the past few years. However, the tradeoff between reliability and efficiency in such solutions needs to be carefully considered. This thesis presents an optimal protocol for the broadcast of safety messages in VANETs. Optimality, in terms of delay and transmission count, is achieved using a broadcast strategy that exploits opposite vehicles. To carry out reliable and efficient broadcast coordination, intelligent periodic rebroadcasts, which effectively adapt our protocol to sparse and dense networks, are proposed. Simulations are conducted and results are presented to show that it has a better performance over existing competing protocols. As a second contribution, we propose an alternative Receiver-Sender approach that combines advantages of the two existing dissemination approaches (Sender-oriented and Receiver-oriented to which our first proposal belongs) to ensure low latency and high reliability. The proposal can use any sender or receiver oriented protocol but the same selected one is used during all the dissemination process. In order to overcome the unreliability and broadcast overhead generated by periodic rebroadcasts and multiple relays schemes, we introduce a DR/BDR (Designated Relay/Backup Designated Relay) mechanism where the BDR has to replace the DR when detecting,from exchanged colored beacons, its failure in informing concerned vehicles

APA, Harvard, Vancouver, ISO, and other styles

31

Myers, Robert L. "SMART SENSORS VS DISTRIBUTED DATA ACQUISITION." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/606371.

Full text

Abstract:

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada
Distributed processing is coming to data acquisition. The desire for smart sensors that can preprocess data, is growing. Making sensors themselves intelligent will reverse the historic trend toward smaller and cheaper sensors. Incorporating current sensor technology into data acquisition nodes in a network will create a distributed data acquisition, DAQ, environment that can acquire data from around the world over the Internet. The future is now.

APA, Harvard, Vancouver, ISO, and other styles

32

Parks, Jeremy. "A Texas Instruments C33 DSP PCI platform for high-speed real-time implementation of IEEE802.11a Wireless LAN algorithms." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0002880.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Goes, Adriano Almeida. "M?todo de Handover considerando balanceamento de tr?fego para sistemas com modula??o adaptativa." Pontif?cia Universidade Cat?lica de Campinas, 2009. http://tede.bibliotecadigital.puc-campinas.edu.br:8080/jspui/handle/tede/512.

Full text

Abstract:

Made available in DSpace on 2016-04-04T18:31:28Z (GMT). No. of bitstreams: 1 Adriano Almeida Goes.pdf: 1890295 bytes, checksum: 24b4098cee62cc9c7d9d7e7d523ea3c2 (MD5) Previous issue date: 2009-10-30
This work proposes a methodology for intelligent distribution of traffic between users and cells in a mobile network with adaptive modulation. In this dissertation a new method of handover to enable the proposal for load balancing traffic, serving as support for the planning and design of these networks. An example of this case is the IEEE802.16e adopted as a platform in this work. As developed a simulation platform that contains the requirements necessary to analyze and compare the current method of handover with the proposed method under different topologies. The results show a gain in the effective data rate of the cell 25% of the proposed method of handover for the current method of handover. Index: IEEE802.16e, Load Balance, Handover, mobile WiMAX
Este trabalho prop?e uma metodologia para distribui??o inteligente de usu?rios e tr?fego entre c?lulas de uma rede m?vel com modula??o adaptativa. Para isso foi proposto nesta disserta??o um m?todo de Handover que viabiliza a proposta de balanceamento de tr?fego servindo de apoio para o planejamento e dimensionamento destas redes, Como ? o caso da IEEE802.16e, plataforma utilizada neste trabalho. Foi desenvolvida uma plataforma de simula??o que cont?m os requisitos necess?rios para analisar e comparar o m?todo atual de Handover com o m?todo proposto sob topologias diferentes. Os resultados mostram um ganho efetivo na taxa de dados geral da c?lula de 25% do m?todo de Handover proposto em rela??o a m?todo de Handover atual.

APA, Harvard, Vancouver, ISO, and other styles

34

CORRADO, RICCARDO. "Audio/Video Transmission over IEEE 802.11e Networks: Retry Limit Adaptation and Distortion Estimation." Doctoral thesis, Università degli Studi di Trieste, 2016. http://hdl.handle.net/11368/2908059.

Full text

Abstract:

The objective of this thesis focuses on the audio and video transmission over wireless networks adopting the family of the IEEE 802.11x standards. In particular, this thesis discusses about the resolution of four issues: the adaptive retransmission, the comparison of video quality indexes for retry limit adaptation purposes, the estimation of the distortion and the joint adaptation of the maximum number of retransmissions of voice and video flows.

APA, Harvard, Vancouver, ISO, and other styles

35

Wu, Feng-Ming, and 吳峯銘. "A Study of Channel Estimation for IEEE802.11p Wireless Vehicle Communications." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/36663007590196916483.

Full text

Abstract:

碩士
國立臺灣海洋大學
通訊與導航工程學系
101
Intelligent transportation system uses the wireless communication technology to increase the traffic safety and transportation efficiency. However, the Doppler and Multipath problems severely attenuate the received signal in the vehicle communications environment. Therefore, system synchronization and channel estimation become the serious issues be solved precisely to improve the bit error rate performance at the reciver. Besides, ITS adopts the IEEE802.11p standard as its protocol. The channel estimation can be classified into three types based on usage of the preamble, the pilot and its combination. In the first type, the Frequency Domain Least Square, Time Domain Least Square and the proposed Modified Time Domain Least Square are discussed in this thesis. The Linear interpolation, and Discrete Fourier Transform channel estimation belong to the second type and their performance are also evaluated on various channel scenarios. The third one combines the preamble and Data OFDM symbols including Cyclic-Prefix method, the proposed Modified Cyclic-Prefix based method and the Correlation Invariant method. The paper will compare these three different types of estimation methods via computer simulations and outdoor measurements. Results show that the proposed methods have the satisfactory channel estimation and bit error rate performance compared with the literary methods. Keyword: IEEE802.11p, Channel Estimation, Modified Time Domain Least Square Method, Modified Cyclic-Prefix based Method, Correlation Invariant Method.

APA, Harvard, Vancouver, ISO, and other styles

36

Lin, Yu-De, and 林育德. "IEEE802.11b WLAN Circuits Design and Test." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/35360347316243800065.

Full text

Abstract:

碩士
國立臺灣大學
電信工程學研究所
93
In this thesis, the design and test of IEEE 802.11b WLAN circuits are described. The circuit blocks consist of baseband processor RF3002, IF and RF transceiver RF2958, power amplifier RF5189, RF filter, RF switches, IF SAW filter and regulators. The circuits are fabricated with four-layer PCB process. The implemented wireless LAN card can provide four kinds of data rates which are 1Mbps(DSSS), 2Mbps(DSSS), 5.5Mbps(CCK), and 11Mbps(CCK) based on IEEE802.11b specification. For the software implementation, the C language code compiled by Keil is downloaded to the microprocessor by the USB interface to control and coordinate the functions between the circuit blocks of WLAN card. The introduction of IEEE 802.11 WLAN standard is presented in Chapter 1. Chapter 2 describes the specification of the 802.11b WLAN physical layer and circuit system design. The circuit design consisted of baseband processor, IF and RF transceiver, power amplifier, front-end circuit, dc power circuits, PHY interface circuits, MAC control circuits, and link budget are described in Chapter 3. Chapter 4 gives the circuit layout to realize the designed circuit on a four layer PCB. Chapter 5 describes the test results of each circuit and demonstrates the data transmitting and receiving of the developed WLAN cards. Finally, the conclusion is given in the Chapter 6.

APA, Harvard, Vancouver, ISO, and other styles

37

Huang, Shi-Jie, and 黃世傑. "Power Analysis for IEEE802.11 Wireless LAN." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/79424005906752337808.

Full text

Abstract:

碩士
國立成功大學
電腦與通信工程研究所
93
Power consumption is one of the bottlenecks for mobile devices。 In thesis， a new Markov model is developed to analyze the power efficiency of IEEE 802.11 Wireless LANs Distributed Coordination Function (DCF) protocol by taking into account the idle channel and the error channel， collisions， packet retry limits and no retry limit and freezing mechanism in backoff。 Based on the proposed mathematical model and power dissipation due to transmission and receiving， the power consumptions in different states of a tagged station performing the DCF protocol are computed。 The total power consumption and power efficiency of the DCF protocol is calculated accordingly。 We then investigate the influence of the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol upon the power efficiency of IEEE 802.11a and IEEE 802.11b Wireless LANs through combining the joint effect of MAC and PHY layers。 Finally， system performance and design criterions for IEEE 802.11 Wireless LANs are concluded。

APA, Harvard, Vancouver, ISO, and other styles

38

Tzeng, Sheng-Tai, and 曾聖太. "IEEE802.11 Wireless LAN and Multimedia Transmission." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/79208171972149136938.

Full text

Abstract:

碩士
國立成功大學
電腦與通信工程研究所
93
In recent years,mobile ad hoc network has become a widely used technology which is based on IEEE 802.11 standards.First,we study FCR(FAST COLLISION RESULOTION and compare with DCF(Distributed Coordination Function). 　　Recently,more and more attention has been attracted to providing quality of service (QoS) for real-time traffic in wireless ad hoc networks as the increase of real-time applications. However, the Distributed Coordination Function (DCF), the popular communication protocol in IEEE 802.11 standard, fails to provide QoS guarantee for real-time applications. 　　In this thesis, we proposed a dynamic adaptive area based on Utilization Ratio control to improve the throughput and delay and then to transmit multimedia in wireless local area network.

APA, Harvard, Vancouver, ISO, and other styles

39

Hsiung, Po-Hsiang, and 熊柏翔. "IEEE802.11 Hardware Implementation of Collision Protocol." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/45615314937834277350.

Full text

Abstract:

碩士
國立臺灣科技大學
電子工程系
104
IEEE 802.11 defined MAC and PHY layers which built network between base station (BS) and access point (AP). IEEE 802.11 use collision protocol which define inter-frame space (IFS), utilize RTS/CTS and ACK in every transmission to avoid collisions. WARP v3 FPGA board design by Mango Company has been well-known reference design for IEEE 802.11. This reference design implements collision protocol with software. To further improve this reference, this thesis uses hardware implementation.

APA, Harvard, Vancouver, ISO, and other styles

40

Hsu, Ming-Shean, and 許銘顯. "IEEE802.11b WLAN RF Front Research and Implement." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/08409835968512413480.

Full text

Abstract:

碩士
中華技術學院
電子工程研究所碩士班
92
There are two types of transceiver framework. One is the super heterodyne framework and the other is the framework with zero intermediate frequency (ZIF). In the report, we present the procedure for how to realize the RF front circuit (including transceiver and power amplifier) of a super heterodyne transceiver. How to make the simulation and how to realize the RF circuit will be presented. The SystemView software is used to simulate a 2.4GHz IEEE802.11b RF front circuit. In the circuit realization part, the PowerLogic software was used for routing the implementation circuit, and then, the PowerPCB software was used to accomplish the printed circuit board layout. This paper is also talked about how to build up the routing rules for the realization of a 2.4GHz RF circuit and how to reduce the size of the realized printed circuit board for mass production cost down. Finally, if the designer is lack of passive components such as accurate chip capacitors, accurate chip inductances, or filters, the designer can replace these passive components by transmission line circuits and use HP ADS software for simulation.

APA, Harvard, Vancouver, ISO, and other styles

41

Lin, Po-Niang, and 林柏年. "5GHz CMOS Transmitter Front-End for IEEE802.11a." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/29179402015658858114.

Full text

Abstract:

碩士
國立交通大學
電子工程系
91
In this thesis, a direct-conversion transmitter front-end for IEEE 802.11a is designed and fabricated using UMC 0.18μm 1P6M CMOS technology. The transmitter front-end contains quadrature mixer in I, Q branches and a preamp. Both chip and package assembly had been implemented. The measurement result of the on-wafer version shows that the conversion gain is 0.94 dB, 1-dB compression voltage is 315 mV and maximum output power of 0 dBm which can meet the specification of our IEEE 802.11a system. The packaged version has the spurious suppression of at least 30 dBc and carrier suppression of 29 dBc. However, due to the PCB and imprecise package model the conversion gain is lower than expected. The conversion gain is -14.5 dB, 1-dB compression voltage is 880 mV and maximum output power is -6.6 dBm.

APA, Harvard, Vancouver, ISO, and other styles

42

Kuan, Ching-Chien, and 管清健. "A QoS Provision Multipolling Mechanism for IEEE802.11e Standard." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/27422230230684166495.

Full text

Abstract:

碩士
東海大學
資訊工程與科學系
93
With flexibility and mobility, Wireless Local Area Network (WLAN) has rapidly become one of the most emergent computer research fields. It attracts significant interests both in academic and industry communities. IEEE 802.11, the standard of WLAN, encompasses Distributed Coordination Function (DCF) and Point Coordination Function (PCF) operational modes to process asynchronous and time-bounded traffic respectively. However, the protocol suffers from lacking priority and access control policy so that it is hard to cope with various types of multimedia traffic as well as user mobility (handoff). For applying a higher Quality of Service (Qos) to network applications, the 802.11e Task Group has deployed hybrid coordination function (HCF) to improve the original IEEE 802.11 Medium Access Control (MAC) protocol. The HCF defines two medium access mechanisms, one of them is channel access control. Nevertheless, how to choose the right MAC parameters and QoS mechanism so as to achieve a predictable performance still remain unsolved. In this paper, we propose a Qos Provision Multi-polling Mechanism(QPMM) which is in the PCF mode deploys non-preemptive priority in order to transfer voice packets more efficiently. The voice traffic characterized by packet rate of voice source and the maximum tolerable jitter (packet delay variation) is forecasted. We record the scheduling results in a queue, with which AP (Access Point) can poll and then enable mobile users to communicate with their opposite sites. This occurrence also solves the problem that some voice packets do not suit QoS in IEEE 802.11e standard with multi-polling. During the time-gap while transmitting no voice packets, the scheme changes to DCF mode to transfer data packets. Furthermore we simulate and analyze the performance of the scheme in a WLAN environment. The experimental results show that our approach can dramatically improve the quality of network service.

APA, Harvard, Vancouver, ISO, and other styles

43

Liu, Hsuan-Yu, and 劉軒宇. "An OFDM Baseband Transceiver for IEEE802.11a WLAN Application." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/19789458897091376209.

Full text

Abstract:

碩士
國立交通大學
電子工程系
89
Orthogonal frequency division multiplexing (OFDM) system has been applied for high-speed baseband transceiver for IEEE802.11a standard such the wireless LAN (WLAN) in 5GHz band. Due to that OFDM system is an effective modulation technique for high-rate and high-speed transmission over frequency selective fading channels, OFDM baseband transceiver has been applied for advanced high-speed WLAN. This thesis presents a complete architecture of OFDM baseband transceiver. Both high-level simulation and hardware optimization improve the hardware architecture to get high data rate, high transmission performance, and low hardware cost. The simulation environment with OFDM system and AWGN channel has been established in order to estimate performance of overall WLAN transmission system. Due to quantization error induced by OFDM baseband transceiver such a fixed-point approach, the wordlength of FFT, resolution of both digital-to-analog converter (DAC) and analog-to-digital converter (ADC) will influence the error rate performance of OFDM system. So high-level simulation proceeds with AWGN channel. Radix-64 64-point pipeline FFT processor is proposed for low memory requirement. Hardware optimization improves it to a high efficiency of hardware sharing design. For lower synchronization error, dynamic ADC sampling methodology with a digital frequency synthesizer (DFS) is proposed for timing recovery. The all cell-base DFS can reduce turnaround time and improve synchronization performance of OFDM baseband transceiver. The complete hardware architecture of OFDM baseband transceiver, algorithm of radix-64 64-point pipeline FFT processor, and the simulation of OFDM system with AWGN channel will be introduced and discussed particularly in this thesis.

APA, Harvard, Vancouver, ISO, and other styles

44

Peng, Chih-An, and 彭志安. "Cooperative Communications with IEEE802.11a/g Wireless LAN Systems." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/64241450747484162189.

Full text

Abstract:

碩士
國立交通大學
電機學院碩士在職專班電信組
96
Diversity is a well-known technology combating fading effects in wireless communications. Diversity, in time, frequency or space, can be obtained with signals transmited through independent fading channels, and received by some combining technique. Spatial or antenna diversity has the advantage that it does not have to increase the transmition time and bandwidth. However, in many case, the transmitter have limits on its phisical size or cost. As a result, multiple antennas are either not allowed, or the diversity gain is not significant. Cooperative diversity is a recently developed diversity technique. With the technique, a transmitter with only one antenna can have spatial diversity provided by the virtual antenna array, joined formed with other transmitters. In the literature, most works in cooperative communications focus on theoretic inverstigation. Few results are reported in the performance evaluation of real-world systems. In this thesis, we fill this gap by investigating the cooperative communications with IEEE 802.11a/g wireless LAN systems. Using well-knonw cooperative protocols, we conduct performance evaluation with extensive simulations. The results show that the performance of the wilress LAN system can be significantly enhanced through user cooperation.

APA, Harvard, Vancouver, ISO, and other styles

45

Zhang, Jie, and 張傑. "IEEE802.11 ac WLAN 5.25GHz CMOS RF Transmitter Design." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/83583404376247869109.

Full text

Abstract:

碩士
國立臺灣海洋大學
電機工程學系
102
In this thesis, we design a 5.25GHz RF transmitter front-end, mainly used in IEEE 802.11ac system and composed of a voltage-controlled oscillator, a mixer, and a power amplifier. The circuit components are simulated using TSMC 0.18 um 1P6M CMOS Mixed-Signal model and the Agilent Advanced Design System (ADS) software provided by National Chip Implementation Center. The voltage controlled oscillator uses current reused architecture and gm boosting technique to reduce power consumption and uses the mutual inductance to increase the circuit Q value and reduce the chip area. Measurement results show that the tuning range is up to 11.7%. When the oscillation frequency is 5.03GHz, the output power is -4.5dBm, the phase noise is -110dBc/Hz at 1MHz offset, the performance indicators FOMT is -173.7dBc. When the supply voltage is 1.8V, the power consumption is 15.3mW and the chip area is 0.725 #westeur024# 0.540mm2. The mixer is designed with double balanced mixer architecture and common mode feedback architecture for the load level to improve conversion gain. In the transconductance stage, we use a modified two common source architecture to amplify the IF signal. Measurement results show that the output signal frequency is 5.25GHz, the conversion gain is 9.11dB, input 1dB compression point is -16dBm, input third-order intercept point is -5dBm, LO-RF isolation is 29.3dB, LO-IF isolation is 45.6dB, IF-RF isolation is 113.3dB. When the supply voltage is 1.8V, the power consumption is 9.54mW and the chip area is 1.209 #westeur024# 1.421 mm2. The overall architecture of power amplifier is divided into two stages. The first stage adopts current reused architecture to reduce power consumption, and uses the folded cascode architecture to increase the gain. The second stage uses a common source architecture to increase the output power and the linear bias circuit to improve the linearity. Measurement results show that the output signal frequency is 5.25GHz, the conversion gain is 10.248dB, output 1dB compression point is 6.5dBm, output third-order intercept point is 19dBm, power added efficiency is 12.8%. When the supply voltage is 1.8V, the power consumption is 79.7mW and the chip area is 1.291 #westeur024# 0.857mm2. The RF transmitter front-end is designed with direct up-conversion architecture to reduce passive components and power consumption. Simulation results show that when the input IF signal frequency is 10MHz and local oscillator signal frequency is 5.24GHz, the output RF signal is 5.25GHz, power gain is 38.543dB, output 1dB compression point is 14.568dBm, input 1dB compression point is -22dBm, output third-order intercept point is 40dBm, input third-order intercept point is 1.5dBm. When the supply voltage is 1.8V, the power consumption is 110.52mW.

APA, Harvard, Vancouver, ISO, and other styles

46

Martins, Marco Filipe Luz. "Plataforma de Visualização de Dados para uma Rede Wi-Fi." Master's thesis, 2021. http://hdl.handle.net/10348/10558.

Full text

Abstract:

Dissertação submetida à UNIVERSIDADE DE TRÁS-OS-MONTES E ALTO DOURO para obtenção do grau de MESTRE em Engenharia Eletrotécnica e de Computadores
Numa sociedade cada vez mais evoluída e com o aumento de dispositivos eletrónicos ligados à Internet que cada utilizador possui, verificamos que alguns métodos de análise de tráfego na rede Wi-Fi não acompanham as novas tendências. Desde que existe Internet, existe necessidade de a monitorizar para manter um acesso estável e de qualidade de serviço, essa necessidade é maior nos dias atuais devido à quantidade de serviços dos quais a Internet é o elemento chave para a sua realização. Atualmente procuramos sempre a rede com o melhor serviço e é com isto em mente que foi desenvolvido um sistema para monitorizar o tráfego na rede através de testes de largura de banda, análise da potência e disponibilidade de rede. Para o desenvolvimento deste projecto serão utilizadas sondas para analisar tráfego da rede Wi-Fi gerado pelos APs (Access Points) colocados na UTAD (Universidade de Trás os Montes e Alto Douro), a rede será analisada a partir da sonda que fará a recolha de dados e os envia para um servidor do qual será realizada uma avaliação de performance. Esses dados podem ser utilizados no futuro para tomada de decisão dos órgãos gestores como a UTAD - SIC (Universidade Montes e Alto Douro - Serviços de Informática e Comunicações). A aplicação desenvolvida foi testada usando a eduroam na UTAD. O objetivo desta dissertação é desenvolver uma aplicação Web que leve em consideração o uso da rede, permitindo ao administrador tomar uma decisão de forma facilitada e fundamentada no caso de ocorrer um problema.
In a developed society and with an increase in the numbers of electronic devices connected to the Internet that each user possesses, we find that some methods for analyzing traffic on the Wi-Fi network do not keep up with the new trends. Since there is an Internet, there is a need to monitor it to maintain stable access and quality of service, this need is greater nowadays due to the quantity of services of which the Internet is the key element for its realization. Currently we always look for the network with the best service and it is with this in mind that a system has been developed to monitor traffic on the network, perform coverage tests and test the authentication of users who want to access the network. For the development of this project, probes will be used to analyze Wi-Fi network traffic generated by the Access Points placed at UTAD (Universidade de Trás os Montes e Alto Douro), the network will be analyzed from the probe that will collect data data and sends it to a server from which a performance evaluation will be carried out. These data can be used in the future for decision-making by management bodies such as UTAD - SIC (Universidade Montes and Alto Douro - Serviços de Informática e Comunicações). The developed application was tested using textit eduroam at UTAD. The objective of this dissertation is to develop a Web application that takes into account the use of the network, allowing the administrator to make an easy and fundamentally decision in the event of a problem.

APA, Harvard, Vancouver, ISO, and other styles

47

Lee, Yi-Ron, and 李宜融. "Design of Synchronization Techniques for IEEE802.16e." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/xqkbg8.

Full text

Abstract:

碩士
國立交通大學
電子工程系所
96
We propose an overall synchronization scheme suitable for IEEE 802.16e in this thesis. Based on existing methods, we proposed some improved methods including carrier frequency offset estimation, symbol time estimation, integer carrier frequency offset (ICFO) estimation and preamble identification. The proposed method of carrier frequency offset estimation can overcome an error due to imperfectly periodic property of the preamble. The proposed method of symbol time estimation can be designed on time domain without known preamble index. The proposed methods of ICFO estimation and preamble identification have low computation complexity.

APA, Harvard, Vancouver, ISO, and other styles

48

Ghose, Debasish, and Debasish Ghose. "Soft Detection for STBCs in IEEE802.11ac." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/98616337050685200719.

Full text

Abstract:

碩士
國立臺北大學
通訊工程研究所
102
The Multiple-Input Multiple-Output (MIMO) system applications are very important for many next generation communication standards, i.e. LTE, LTE-Advance and IEEE 802.11ac etc. Multiple-Input Multiple-Output (MIMO) techniques are used to improve the throughput and link quality of wireless systems. One of the MIMO techniques is space-time block coding (STBC), which improves the system performance by providing a higher diversity order. Gradually STBCs became popular because of its fast signal detection profile at the receiver end. The Maximum Likelihood (ML) detector is optimum, but its complexity is too high. The purpose of this thesis is to propose a well organized and fixed complexity soft-output STBC detection criterion for an important standard IEEE 802.11ac which will be easier for hardware implementation. In the first part of this thesis, we investigate the performance of various sub-optimum detection methods. Then we focus on the near optimal detection scheme that combines efficient candidate selection technique and derive its general solutions. Finally, a fixed complexity soft-output STBC detector is proposed based on the modified ML detection metric and parallel smart candidate adding algorithm which has a wide range of trade-off between performance and complexity.

APA, Harvard, Vancouver, ISO, and other styles

49

Zhu, Yingbo. "Design of a direct downconversion receiver for IEEE802.11a WLAN." 2008. http://hdl.handle.net/2440/48040.

Full text

Abstract:

Wireless communication technologies are no longer limited for voice band applications, but have entered the era for multimedia data link. The IEEE802.11 family, which occupies a bandwidth in the multi-mega hertz region with the highest data rate of 54 Mbps, now has become the most widely deployed wireless LAN standards. The rapid adoption of IEEE802.11 for computer wireless networks and their growing popularity in mobile applications highlight the need for a low cost, low power consumption, and monolithic solution. To meet this challenge, traditional RF techniques, which revolved around the superheterodyne architecture can no longer be used. On the contrary, new receiver frontend architectures need to be developed to satisfy the demand of system level integration. Direct downconversion receivers directly translate the RF spectrum to the baseband by setting the LO frequency equal to the RF. Due to the single frequency translation, expensive and bulky off-chip filters and 50 ohm I/O matching networks at IF are no longer required. Also, the single-stage quadrature mixers further simplify the receiver design and reduce the power dissipation. Subsequent baseband components and ADCs are also possible to be integrated with the RF frontend to achieve a monolithic receiver chip. Despite the previously mentioned advantages, the implementation of a direct downconversion receiver has its own set of performance challenges. In particular, the performance is plagued by DC offset, flicker noise, linearity and mismatches etc. The main objective of this project is to investigate the feasibility of using direct downconversion architecture for the IEEE802.11a standard, and implement the design in a 0.18 µm CMOS technology. By approaching the design issue at a theoretic point of view, extensive modeling and simulations based on a SIMULINK IEEE802.11a physical layer theme have been carried out to evaluate the receiver performance. SER results of the receiver demonstrate that the impairments associated with zero IF can be minimised to an acceptable level. Under the guidance of the system level analysis, the circuit level design of a monolithic direct downconversion receiver has been implemented in a 0.18 µm RF CMOS process, including the building blocks of an LNA, mixer, baseband amplifier and a channel-selection filter. Particularly, a novel LNA design methodology with an improved noise figure and less power consumption has been developed. The mixer conversion gain and phase noise have been analysed by a novel approach. The combination topology of the highpass DC offset removal filter and the baseband amplifier provids the best linearity with a negligible noise figure degradation. Circuit simulations are performed using the foundry provided RF design kit with enhanced noise models to capture the extra noise of passive and deep submicron devices. Circuit level simulations show a qualified receiver frontend for the IEEE802.11a standard. As data converters are important building blocks in wireless receivers, research on high performance Sigma-Delta modulators is also included. MATLAB based programs have been developed for both the discrete and continuous time transfer function synthesis. A BPSDM chip with variable centre frequencies has been developed to verify the SDM transfer function algorithm and the design methodology. The design of an ultra fast continuous time SDM is particularly focused on for a broadband data conversion. To alleviate the challenge of the comparator speed limit, a novel noise transfer function with a unit clock delay has been synthesised. With such a delayed transfer function, a three-stage comparator can be acheieved that solves the comparator gain and speed tradeoff. The full chip simulation shows an acceptable performance for the IEEE802.11a standard.
Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

APA, Harvard, Vancouver, ISO, and other styles

50

Zhu, Yingbo. "Design of a direct downconversion receiver for IEEE802.11a WLAN." 2007. http://digital.library.adelaide.edu.au/dspace/handle/2440/48040.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'IEEE802.11p'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles