145 research outputs found
Integrated Support for Handoff Management and Context-Awareness in Heterogeneous Wireless Networks
The overwhelming success of mobile devices and wireless
communications is stressing the need for the development of
mobility-aware services. Device mobility requires services
adapting their behavior to sudden context changes and being
aware of handoffs, which introduce unpredictable delays and
intermittent discontinuities. Heterogeneity of wireless
technologies (Wi-Fi, Bluetooth, 3G) complicates the situation,
since a different treatment of context-awareness and handoffs is
required for each solution. This paper presents a middleware
architecture designed to ease mobility-aware service
development. The architecture hides technology-specific
mechanisms and offers a set of facilities for context awareness
and handoff management. The architecture prototype works with
Bluetooth and Wi-Fi, which today represent two of the most
widespread wireless technologies. In addition, the paper discusses
motivations and design details in the challenging context of
mobile multimedia streaming applications
A packet error recovery scheme for vertical handovers mobility management protocols
Mobile devices are connecting to the Internet through an increasingly heterogeneous network environment. This connectivity via multiple types of wireless networks allows the mobile devices to take advantage of the high speed and the low cost of wireless local area networks and the large coverage of wireless wide area networks. In this context, we propose a new handoff framework for switching seamlessly between the different network technologies by taking advantage of the temporary availability of both the old and the new network technology through the use of an "on the fly" erasure coding method. The goal is to demonstrate that our framework, based on a real implementation of such coding scheme, 1) allows the application to achieve higher goodput rate compared to existing bicasting proposals and other erasure coding schemes;
2) is easy to configure and as a result 3) is a perfect candidate to ensure the reliability of vertical handovers mobility management protocols. In this paper, we present the implementation of such framework and show that our proposal allows to maintain the TCP goodput(with a negligible transmission overhead) while providing in a timely manner a full reliability in challenged conditions
Enhancing TCP with Cross-layer Notifications and Capacity Estimation in Heterogeneous Access Networks
Peer reviewe
A packet error recovery scheme for vertical handovers mobility management protocols
Mobile devices are connecting to the Internet through an increasingly heterogeneous network environment. This connectivity via multiple types of wireless networks allows the mobile devices to take advantage of the high speed and the low cost of wireless local area networks and the large coverage of wireless wide area networks. In this context, we propose a new handoff framework for switching seamlessly between the different network technologies by taking advantage of the temporary availability of both the old and the new network technology through the use of an âon the flyâ erasure coding method. The goal is to demonstrate that our framework, based on a real implementation of such coding scheme, 1) allows the application to achieve higher goodput rate compared to existing bicasting proposals and other erasure coding schemes; 2) is easy to configure and as a result 3) is a perfect candidate to ensure the reliability of vertical handovers mobility management protocols. In this paper, we present the implementation of such framework and show that our proposal allows to maintain the TCP goodput (with a negligible transmission overhead) while providing in a timely manner a full reliability in challenged conditions
Cross-layer Assisted TCP Algorithms for Vertical Handoff
The ever expanding growth of the wireless access to the Internet in recent years has led to the proliferation of wireless and mobile devices to connect to the Internet. This has created the possibility of mobile devices equipped with multiple radio interfaces to connect to the Internet using any of several wireless access network technologies such as GPRS, WLAN and WiMAX in order to get the connectivity best suited for the application. These access networks are highly heterogeneous and they vary widely in their characteristics such as bandwidth, propagation delay and geographical coverage. The mechanism by which a mobile device switches between these access networks during an ongoing connection is referred to as vertical handoff and it often results in an abrupt and significant change in the access link characteristics. The most common Internet applications such as Web browsing and e-mail make use of the Transmission Control Protocol (TCP) as their transport protocol and the behaviour of TCP depends on the end-to-end path characteristics such as bandwidth and round-trip time (RTT). As the wireless access link is most likely the bottleneck of a TCP end-to-end path, the abrupt changes in the link characteristics due to a vertical handoff may affect TCP behaviour adversely degrading the performance of the application.
The focus of this thesis is to study the effect of a vertical handoff on TCP behaviour and to propose algorithms that improve the handoff behaviour of TCP using cross-layer information about the changes in the access link characteristics. We begin this study by identifying the various problems of TCP due to a vertical handoff based on extensive simulation experiments. We use this study as a basis to develop cross-layer assisted TCP algorithms in handoff scenarios involving GPRS and WLAN access networks. We then extend the scope of the study by developing cross-layer assisted TCP algorithms in a broader context applicable to a wide range of bandwidth and delay changes during a handoff. And finally, the algorithms developed here are shown to be easily extendable to the multiple-TCP flow scenario. We evaluate the proposed algorithms by comparison with standard TCP (TCP SACK) and show that the proposed algorithms are effective in improving TCP behavior in vertical handoff involving a wide range of bandwidth and delay of the access networks. Our algorithms are easy to implement in real systems and they involve modifications to the TCP sender algorithm only. The proposed algorithms are conservative in nature and they do not adversely affect the performance of TCP in the absence of cross-layer information.KÀytÀmme enenevissÀ mÀÀrin kannettavia pÀÀtelaitteita (esim. matkapuhelin, kannettava tietokone) erilaisiin sovelluksiin kuten sÀhköpostin lukemiseen, verkon selaamiseen, musiikin lataamiseen ja kuuntelemiseen, pelien pelaamiseen ja laskujen maksamiseen riippumatta olinpaikastamme tai liikkuvuudestamme. Pystymme yhdistÀmÀÀn laitteemme Internetiin milloin tahansa missÀ tahansa.
Langattomat verkot, jotka mahdollistavat laitteen kytkemisen Internetiin radion kautta kÀyttÀvÀt moninaisia teknologioita ja eroavat laajalti ominaisuuksiltaan. Esimerkiksi langaton lÀhiverkko (WLAN), jota voidaan kÀyttÀÀ rakennuksen sisÀllÀ, on matkapuhelinverkkoa (esim. GPRS) nopeampi verkko, kun taas GPRS-kenttÀ voi ulottua kokonaisen kaupungin tai maan alueelle ja laajemmallekin. Kannettava pÀÀtelaite, jossa on monia radioliittymiÀ, voi siirtyÀ kÀyttÀmÀÀn mitÀ tahansa monista saatavilla olevistaverkoista riippuen olinpaikasta tai kÀytettÀvÀn sovelluksen tarpeista. Verkonvaihto viittaa tÀhÀn verkosta toiseen siirtymiseen, ja se tunnetaan vertikaalisena verkonvaihtona, kun siirtymisen kohteena olevien verkkojen teknologia eroaa toisistaan.
TCP on tietoliikenneohjelmisto, jota sekÀ tiedon lÀhettÀjÀ ettÀ vastaanottaja kÀyttÀvÀt kuljettamaan sovelluksen tiedon luotettavasti. TCP sÀÀtelee tiedon lÀhetysnopeutta riippuen Internetin resurssien saatavuudesta. TCP:n kÀyttÀytyminen riippuu pÀÀstÀ-pÀÀhÀn polun ominaisuuksista ja erityisesti pullonkaulayhteydestÀ, siitÀ yhteydestÀ, jolla on minimikapasiteetti polulla. Langaton yhteys, joka yhdistÀÀ kannettavan laitteen Internetiin on usein pullonkaulayhteys, ja Àkillinen muutos sen ominaisuuksissa vertikaalisen siirtymÀn aikana vaikuttaa merkittÀvÀsti TCP:n suorituskykyyn ja siten koko sovelluksen laatuun.
TÀmÀ työssÀ on keskitytty tutkimaan TCP:n toimintaa vertikaalisessa verkonvaihdon yhteydessÀ ja suunnittelemaan algoritmeja, jotka parantavat sen suorituskykyÀ vertikaalisen verkonvaihdon yhteydessÀ. Suunnitellut algoritmit kÀyttÀvÀt hyvÀksi tietoa vertikaaliseen verkonvaihtoon liittyvien langattomien yhteyksien ominaisuuksista. EnsimmÀinen tapaustutkimuskohde liittyy WLAN-GPRS -ympÀristöön, jossa TCP saa minimimÀÀrÀn tietoa verkonvaihtoon liittyen. Tulokset nÀyttÀvÀt, ettÀ TCP:n suorituskykyÀ voidaan parantaa huomattavasti. Tutkimusta on laajennettu kattamaan verkonvaihto yleisemmÀssÀ tapauksessa kÀyttÀen karkeita arvioita ko. verkkojen ominaisuuksista. Kehitettyjen algoritmien toiminnallisuus on evaluoitu simulaatiokokeilla kattaen laajan joukon ominaisuuksiltaan erilaisia verkkoja. Tulokset osoittavat, ettÀ TCP-suorituskykyÀ voidaan parantaa vertikaalisen verkonvaihdon yhteydessÀ huomattavasti tÀtÀ lÀhestymistapaa kÀyttÀen. Kehitetyt algoritmit voivat olla hyödyksi etsiessÀmme ratkaisuja kannettavien laitteiden todellisen kÀytön tarpeisiin
Handoff management for infotainment services over vehicular networks
Intelligent Transportation Systems (ITS) has impulsed the vehicular communications at the present time. The vehicular communications field is a hot research topic and is attracting a great interest in the automotive industry and telecommunications. There are essentially two main lines of work: (1) communication services related to road safety and traffic information; and (2) information and entertainment services, also named infotainment services. These latter services include both transmitting multimedia (voice over IP, streaming, on-line gaming, etc.) and classic data services (e-mail, access to private networks, web browsing, file sharing, etc.). In this thesis we will focus on these infotainment services because further research in this immature research field is necessary and, until nowadays, the main effort of the research community regarding vehicular communication has been focused on road safety and traffic information.
Vehicular nodes need to be reached from the Internet and vice versa to be able to access to infotainment services. While vehicles move along the road infrastructure, they change their wireless point of attachment to the network. During this process, connectivity breaks down until the vehicle is connected again to a new road side unit in its area. This disconnection causes a disruption in the communications. Fast handoffs are a crucial requirement for vehicular networks to avoid long disruption times, since the high speed of vehicular nodes involves suffering a lot of handoffs during an Internet connection.
This thesis is focused on Vehicular-to-Infrastructure (V2I) real-time infotainment services. The main contributions of this thesis are: i) a new testing framework for V2I communications to be able to test infotainment services in an easy way; ii) the analysis of the deployability of infotainment video services in vehicular networks using mobility protocols; and iii) the development of a new TCP architecture that will provide a better performance for all TCP-based infotainment services in a vehicular scenario with handoffs.
In this thesis, firstly, we propose a new testing framework for vehicular infotainment applications. This framework is a vehicular emulation platform that allows testing real applications installed on Linux virtual machines. Using emulation, we are able to evaluate the performance of real applications with real-time requirements, so we can test multimedia applications used to offer infotainment services in vehicular scenarios in a straightforward way.
Secondly, using the testing framework implemented in the first part of the thesis, we have done a performance evaluation of an infotainment service. Among these services, we think that video on demand services on highways will be interesting for users, and generate revenue to network operators. So we evaluated how network-layer handoffs can limit the deployment of a video streaming service. According to the results obtained, driving at high speeds will be an issue for a correct playback of video content, even using fast handoffs techniques.
Finally, we developed a new TCP architecture to enhance performance during handoffs. Most of the non-safety services on ITS rely on the Transport Control Protocol (TCP), one of the core protocols of the Internet Protocol Suite. However there exists several issues related to TCP and mobility that can affect to TCP performance, and these issues are particularly important in vehicular networks due to its high mobility. Using new IEEE 802.21 MIH services, we propose a new TCP architecture that is able to anticipate handoffs, permitting to resume the communication after a handoff, avoiding long delays caused by TCP issues and adapting the TCP parameters to the new characteristics of the network. Using the architecture proposed, the performance of TCP is enhanced, getting a higher overall throughput and avoiding TCP fairness issues between users.Els Sistemes de Transport Intel·ligents (ITS) han impulsat les comunicacions vehiculars en l'actualitat. Les comunicacions vehiculars Ă©s un camp d'investigaciĂł de moda, i estĂ atraient un gran interĂšs en la indĂșstria automobilĂstica i de les telecomunicacions. En el camp de les comunicacions vehiculars, hi ha principalment dues lĂnies de treball: (1) serveis de comunicacions relacionats amb la seguretat viĂ ria i la informaciĂł del trĂ nsit; i (2) serveis d'informaciĂł i entreteniment, tambĂ© anomenats serveis d'infotainment. Aquests Ășltims inclouen tant serveis multimĂšdia (veu sobre IP, streaming, jocs on-line, etc.), com serveis clĂ ssics de dades (correu electrĂČnic, accĂ©s a xarxes privades, navegaciĂł web, compartir arxius, etc.). En aquesta tesi ens centrarem en aquests serveis d'infotainment ja que Ă©s necessari aprofundir en la investigaciĂł per aquests tipus de serveis, ja que, fins avui, els esforços de la comunitat cientĂfica en el camp de les comunicacions vehiculars s'ha centrat en els serveis relacionats amb la seguretat viĂ ria i la informaciĂł del trĂ nsit. Els nodes vehiculars necessiten tenir connexiĂł a Internet per a poder tenir accĂ©s als serveis d'infotainment. Mentre els vehicles estan en moviment a travĂ©s de la xarxa viĂ ria, els vehicles han d'anar canviant el punt de connexiĂł sense fils amb la xarxa. Durant aquest procĂ©s de canvi de punt de connexiĂł, anomenat handoff, es perd la connectivitat fins que el vehicle es reconnecta a un altre punt de connexiĂł viĂ ria prop de la seva Ă rea. Aquesta desconnexiĂł causa interrupcions en les comunicacions. Uns handoffs rĂ pids sĂłn bĂ sics a les xarxes vehiculars per a evitar llargs perĂodes d'interrupciĂł durant les comunicacions, ja que la gran velocitat a la que es mouen els nodes vehiculars significa un gran nombre de handoffs durant una connexiĂł a Internet. Aquesta tesi es centra en serveis d'infotaiment en temps real per a comunicacions Vehicle-a-Infraestructura (V2I). Les principals contribucions d'aquesta tesi son: i) un nou marc de proves per a les comunicacions (V2I) per a poder provar serveis d'infotainment d'una manera fĂ cil; ii) l'anĂ lisi de la viabilitat del desplegament de serveis d'infotainment de vĂdeo en xarxes vehiculars utilitzant protocols de mobilitat IP; i iii) el desenvolupament d'una nova arquitectura TCP que proporciona un millor funcionament per a tots aquells serveis d'infotainment basats en el protocol TCP en un escenari vehicular amb handoffs. En aquesta tesi, primer proposem un nou marc de proves per a aplicacions vehiculars d'infotainment. Aquest marc Ă©s una plataforma d'emulaciĂł vehicular que permet provar aplicacions reals instal·lades en mĂ quines virtuals Linux. Utilitzant l'emulaciĂł, som capaços d'avaluar el rendiment d'aplicacions reals amb caracterĂstiques de temps real. D'aquesta manera es poden avaluar aplicacions multimĂšdia utilitzades per oferir serveis d'infotainment d'una forma senzilla en escenaris vehiculars. Segon, utilitzant el marc de prova implementat en la primera part de la tesi, hem avaluat el rendiment d'un servei d'infotainment. Entre aquest tipus de servei, creem que els serveis de vĂdeo sota demanda en autopistes/autovies serĂ interessant pels usuaris i generarĂ beneficis per als operadors de la xarxa. Per tant, hem avaluat com els handoffs a nivell de la capa de xarxa poden limitar el desplegament d'un servei de streaming de vĂdeo sota demanda. D'acord amb els resultats obtinguts, conduir a grans velocitats podria ser un problema per a poder reproduir un vĂdeo correctament, tot i utilitzar tĂšcniques de handoffs rĂ pids. Finalment, hem desenvolupat una nova arquitectura TCP per a millorar el rendiment del protocol durant els handoffs. La majoria dels serveis d'infotainment utilitzen el Protocol de Control de Transport (TCP), un dels principals protocols de la pila de protocols d'Internet. PerĂČ existeixen forces problemes relacionats amb l'Ășs de TCP i la mobilitat que n'afecta el rendiment, i aquests problemes sĂłn particular
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Game theory for dynamic spectrum sharing cognitive radio
This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University on 21 June 2010.âGame Theoryâ is the formal study of conflict and cooperation. The theory is based on a set of tools that have been developed in order to assist with the modelling and analysis of individual, independent decision makers. These actions potentially affect any decisions, which are made by other competitors. Therefore, it is well suited and capable of addressing the various issues linked to wireless communications. This work presents a Green Game-Based Hybrid Vertical Handover Model. The model is used for heterogeneous wireless networks, which combines both dynamic (Received Signal Strength and Node Mobility) and static (Cost, Power Consumption and Bandwidth) factors. These factors control the handover decision process; whereby the mechanism successfully eliminates any unnecessary handovers, reduces delay and overall number of handovers to 50% less and 70% less dropped packets and saves 50% more energy in comparison to other mechanisms. A novel Game-Based Multi-Interface Fast-Handover MIPv6 protocol is introduced in this thesis as an extension to the Multi-Interface Fast-handover MIPv6 protocol. The protocol works when the mobile node has more than one wireless interface. The protocol controls the handover decision process by deciding whether a handover is necessary and helps the node to choose the right access point at the right time. In addition, the protocol switches the mobile nodes interfaces âONâ and âOFFâ when needed to control the mobile nodeâs energy consumption and eliminate power lost of adding another interface. The protocol successfully reduces the number of handovers to 70%, 90% less dropped packets, 40% more received packets and acknowledgments and 85% less end-to-end delay in comparison to other Protocols. Furthermore, the thesis adapts a novel combination of both game and auction theory in dynamic resource allocation and price-power-based routing in wireless Ad-Hoc networks. Under auction schemes, destinations nodes bid the information data to access to the data stored in the server node. The server will allocate the data to the winner who values it most. Once the data has been allocated to the winner, another mechanism for dynamic routing is adopted. The routing mechanism is based on the source-destination cooperation, power consumption and source-compensation to the intermediate nodes. The mechanism dramatically increases the sellerâs revenue to 50% more when compared to random allocation scheme and briefly evaluates the reliability of predefined route with respect to data prices, source and destination cooperation for different network settings. Last but not least, this thesis adjusts an adaptive competitive second-price pay-to-bid sealed auction game and a reputation-based game. This solves the fairness problems associated with spectrum sharing amongst one primary user and a large number of secondary users in a cognitive radio environment. The proposed games create a competition between the bidders and offers better revenue to the players in terms of fairness to more than 60% in certain scenarios. The proposed game could reach the maximum total profit for both primary and secondary users with better fairness; this is illustrated through numerical results
Support infrastructures for multimedia services with guaranteed continuity and QoS
Advances in wireless networking and content delivery systems are enabling new challenging provisioning scenarios where a growing number of users access multimedia services, e.g., audio/video streaming, while moving among different points of attachment to the Internet, possibly with different connectivity technologies, e.g., Wi-Fi, Bluetooth, and cellular 3G. That calls for novel middlewares capable of dynamically personalizing service provisioning to the characteristics of client environments, in particular to
discontinuities in wireless resource availability due to handoffs. This dissertation proposes a novel middleware solution, called MUM, that performs effective and context-aware handoff management to transparently avoid service interruptions during both horizontal and vertical handoffs. To achieve the goal, MUM exploits the full visibility of wireless connections available in client localities and their handoff implementations (handoff awareness), of service quality requirements and handoff-related quality degradations (QoS awareness), and of network topology and resources available in current/future localities (location awareness). The design and implementation of the all main MUM components along with extensive on the field trials of the realized middleware architecture confirmed the validity of the proposed full
context-aware handoff management approach. In particular, the reported experimental results demonstrate that MUM can effectively maintain service continuity for a wide range of different multimedia services by exploiting handoff prediction mechanisms, adaptive buffering and pre-fetching techniques, and proactive re-addressing/re-binding
Adaptive Streaming On Heterogeneous Networksâ,
ABSTRACT Specific network protocols, like MobileIP, offer seamless connectivity to mobile systems. However, the QoS requirements of streaming applications and video conferencing systems require an approach that spans across different layers of the network stack. In this paper we study how to integrate an efficient method for vertical handoff and adaptation support for multimedia streaming through heterogeneous networks. We also present experimental results obtained with our prototype on IEEE 802.11 and UMTS networks
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