11 research outputs found
Support des applications multimédia dans les réseaux de prochaine génération
RĂSUMĂ
Les applications multimĂ©dia sont devenues tellement populaires que certaines dâentre elles sont utilisĂ©es quotidiennement par les usagers. Cette popularitĂ© peut ĂȘtre attribuĂ©e Ă plusieurs facteurs, tels que la diversiïŹcation du contenu et des services oïŹerts, lâaccĂšs en tout temps grĂące Ă la mobilitĂ© et Ă la nomadicitĂ©, ainsi quâaux avancĂ©es au niveau des architectures et des protocoles utilisĂ©s, aïŹn de supporter les requis plus exigeants de ces applications. Par exemple, ce qui Ă©tait jadis un simple appel tĂ©lĂ©phonique, se transforme dĂ©sormais en une vidĂ©oconfĂ©rence, permettant Ă un nombre dynamique dâusagers dây participer. Un autre exemple dâapplication multimĂ©dia, qui connait Ă©galement un essor fulgurant, est IP TeleVision (IPTV), soit la technologie permettant la transmission de la tĂ©lĂ©vision, en direct et sur demande, sur des rĂ©seaux IP. On retrouve Ă©galement sa version mobile, soit Mobile IP TeleVision (MobileTV).
Du cĂŽtĂ© des opĂ©rateurs, le focus est mis sur le dĂ©ploiement des rĂ©seaux de prochaine gĂ©nĂ©ration. Les opĂ©rateurs sans-ïŹl se tournent vers les technologies cellulaires de quatriĂšme gĂ©nĂ©ration, telles que 3GPP Long Term Evolution (LTE), alors que ceux qui oïŹrent les services ïŹlaires regardent plutĂŽt vers les rĂ©seaux basĂ©s sur la ïŹbre optique, tels que Fiber to the Home (FTTH). Ces rĂ©seaux promettent dâaugmenter le dĂ©bit oïŹert, ainsi que de rĂ©duire la latence, soit deux critĂšres importants pour le dĂ©ploiement des applications multimĂ©dia Ă grande Ă©chelle. MalgrĂ© ces avancĂ©es technologiques, il existe encore plusieurs obstacles au bon fonctionnement des applications multimĂ©dia. Dans cette optique, cette thĂšse se penche sur trois problĂ©matiques importantes dans les rĂ©seaux de prochaine gĂ©nĂ©ration, chacune faisant lâobjet dâun article scientiïŹque.
Les deux premiers volets sâattardent sur la convergence des rĂ©seaux ïŹxes et mobiles, ou Fixed-Mobile Convergence (FMC). Cette convergence vient brouiller la distinction entre les rĂ©seaux mobiles et les rĂ©seaux ïŹxes. Entre autre, elle permet Ă un usager dâavoir accĂšs Ă ses services, autant sur le rĂ©seau cellulaire (LTE, par exemple) que sur un rĂ©seau local (Wireless Fidelity (WiFi), par exemple). Pour sây faire, lâusager est gĂ©nĂ©ralement muni dâun terminal pouvant se connecter sur les deux rĂ©seaux. La premiĂšre problĂ©matique soulevĂ©e dans cette thĂšse est au niveau de la prise de dĂ©cision de la relĂšve. En eïŹet, les deux protocoles de mobilitĂ© les plus populaires, soit Mobile IP (MIP) et Proxy Mobile IP (PMIP), adoptent deux approches diamĂ©tralement opposĂ©es. Avec le premier protocole, ce sont lâusager et son terminal qui prennent entiĂšrement en charge la relĂšve. MĂȘme si cette approche permet la FMC, les opĂ©rateurs prĂ©fĂšrent plutĂŽt garder le contrĂŽle sur la prise de dĂ©cision, aïŹn de pouvoir optimiser leur rĂ©seau. En eïŹet, avec MIP, beaucoup de messages de signalisation sont envoyĂ©s, ce qui gaspille des ressources rĂ©seaux, surtout au niveau de lâaccĂšs radio, la partie la plus prĂ©cieuse du rĂ©seau. De plus, en ne sollicitant pas le rĂ©seau, le terminal ne prend pas nĂ©cessairement les meilleures dĂ©cisions. Il peut donc basculer vers un rĂ©seau qui est plus chargĂ© et qui ne garantit pas nĂ©cessairement ses exigences au niveau de la qualitĂ© de service. De ce fait, le protocole PMIP a Ă©tĂ© proposĂ©. Son approche est exactement Ă lâopposĂ© de celle de MIP, soit la mobilitĂ© qui est entiĂšrement gĂ©rĂ©e par le rĂ©seau. De ce fait, la mobilitĂ© est masquĂ©e au niveau du terminal, qui pense toujours se trouver dans son rĂ©seau mĂšre. GrĂące Ă lâajout de nouveaux nĆuds dans le rĂ©seau, qui gĂšrent la mobilitĂ© Ă la place du terminal, on Ă©limine la signalisation sur lâaccĂšs radio. De plus, les informations supplĂ©mentaires que le rĂ©seau dĂ©tient lui permettront de prendre une meilleure dĂ©cision. Par contre, le problĂšme avec ce protocole est que, sans lâintervention du terminal, il lui est impossible de dĂ©tecter toutes les situations de relĂšves. Dans plusieurs cas, le rĂ©seau ïŹxe de lâopĂ©rateur est masquĂ© par un rĂ©seau interne, par exemple un rĂ©seau WiFi, et la dĂ©tection de ce rĂ©seau nâest possible que grĂące Ă lâintervention du terminal. Ainsi, PMIP nâest pas un protocole qui se prĂȘte bien au dĂ©ploiement de FMC.
Le premier article, qui sâintitule « Client-Based Network-Assisted Mobile IPv6 », sâattaque donc Ă ce problĂšme, en proposant un nouveau protocole, basĂ© sur Mobile IP v6 (MIPv6), et qui introduit lâimplication du rĂ©seau. Le rĂ©sultat obtenu est un protocole hybride qui combine les avantages de MIPv6 et de Proxy Mobile IP v6 (PMIPv6). Pour sây faire, deux Ă©tapes ont Ă©tĂ© nĂ©cessaires. La premiĂšre consiste en une refonte du protocole MIPv6 qui, dans son Ă©tat actuel, Ă©tait diïŹcile Ă modiïŹer, Ă cause de ses spĂ©ciïŹcations qui sont lourdes. Le rĂ©sultat de cette Ă©tape est un protocole beaucoup plus lĂ©ger et oïŹrant uniquement les fonctionnalitĂ©s de base. Les autres fonctionnalitĂ©s, telles que les mĂ©canismes de sĂ©curitĂ©, ont Ă©tĂ© sĂ©parĂ©es dans des modules. En deuxiĂšme lieu, un nouveau module a Ă©tĂ© proposĂ©, qui introduit un nouveau nĆud dans le rĂ©seau, capable de gĂ©rer la mobilitĂ© du terminal. Ainsi, la collaboration entre le terminal et ce nĆud permet de rĂ©duire les messages de signalisation et dâoptimiser les dĂ©cisions au niveau des relĂšves, tout en oïŹrant le support pour FMC.
La deuxiĂšme problĂ©matique, sur laquelle la thĂšse porte, se trouve au niveau de la transparence de la relĂšve entre les deux rĂ©seaux. On parle dâune relĂšve qui est transparente si cette derniĂšre nâengendre aucune interruption des services de lâusager. Par exemple, un appel en cours, qui est dĂ©marrĂ© sur le rĂ©seau cellulaire, ne doit pas ĂȘtre interrompu lorsque la connexion bascule sur le rĂ©seau local, et vice-versa. Les applications visĂ©es, par notre travail, sont les applications multimĂ©dia en temps rĂ©Ă©l, notamment IPTV et MobileTV (en mode tĂ©lĂ©vision en direct). Ces applications emploient des protocoles de multidiïŹusion permettant lâenvoi optimisĂ© de donnĂ©es Ă partir dâune ou de plusieurs sources vers plusieurs destinataires, avec un nombre minimal de paquets. Le problĂšme avec ces applications est que, lorsquâune relĂšve verticale survient (dans le cadre de FMC par exemple), la connexion est rompue et doit ĂȘtre rĂ©Ă©tablie. Ceci est dĂ» au fait que le terminal change son adresse IP, ce qui le force Ă rejoindre ses services Ă partir de la nouvelle adresse. Cette dĂ©connexion rĂ©sulte en une perte de paquets, se traduisant par une interruption de lâapplication de lâusager.
Le second article, qui sâintitule « Seamless handover for multicast Mobile IPv6 traïŹc », propose une solution Ă ce problĂšme. Cette solution consiste en lâajout dâun nouveau nĆud, dans le rĂ©seau, dont le rĂŽle est de mettre en tampon les paquets perdus, lors de la relĂšve du terminal. Ainsi, lorsque ce dernier recouvre sa connectivitĂ©, il est en mesure de rĂ©cupĂ©rer ces paquets auprĂšs de ce nĆud. Lâapplication de lâusager se dĂ©roule alors sans interruption.
La troisiĂšme problĂ©matique abordĂ©e dans cette thĂšse porte sur la planiïŹcation des rĂ©seaux dâaccĂšs, aïŹn de supporter les requis des applications multimĂ©dia au niveau du dĂ©bit. Pour que la FMC soit rĂ©ussie, il faut que le rĂ©seau local puisse supporter les dĂ©bits nĂ©cessaires de lâapplication. Le rĂ©seau WiFi interne nâĂ©tant gĂ©nĂ©ralement pas un problĂšme, la limitation se trouve plutĂŽt au niveau de lâaccĂšs ïŹlaire. AïŹn dâaugmenter les dĂ©bits oïŹerts, les opĂ©rateurs ont introduit la ïŹbre optique dans leurs rĂ©seaux, complĂ©mentant ainsi les mĂ©thodes traditionnelles, tels les paires de cuivre torsadĂ©es et le cĂąble coaxial. Ainsi, de nouvelles technologies optiques hybrides ont Ă©tĂ© proposĂ©es. Dans un contexte o`u une infrastructure est dĂ©jĂ existante, le choix dâune technologie hybride est trĂšs attrayant, car lâopĂ©rateur peut rentabiliser son investissement prĂ©cĂ©dent, minimisant ainsi le coĂ»t de la mise Ă jour. Par contre, dans un environnement vierge, il nâexiste pas dâinfrastructure Ă rĂ©utiliser. Le consensus, dans un tel scĂ©nario, est que la meilleure technologie Ă dĂ©ployer est celle qui nâemploie que des liens en ïŹbre optique, car elle oïŹre les meilleurs dĂ©bits ainsi que la plus grande ïŹexibilitĂ© au niveau de lâĂ©volutivitĂ©. La diïŹĂ©rence, au niveau du coĂ»t, devient moins grande et nâest plus nĂ©cessairement le critĂšre principal au niveau du choix de la technologie Ă dĂ©ployer.
Une des diïŹcultĂ©s, qui compliquent la planiïŹcation, est que ces rĂ©seaux sont souvent dĂ©ployĂ©s par les opĂ©rateurs, en phases. La planiïŹcation doit ĂȘtre alors dynamique et prendre en considĂ©ration la nature Ă©volutive de la demande des clients. Le troisiĂšme article, qui sâintitule « Dynamic GreenïŹeld Fiber to the Home Planning », propose donc une modĂ©lisation dynamique du problĂšme de planiïŹcation des rĂ©seaux dâaccĂšs en ïŹbre optique. Le rĂ©sultat est un modĂšle mathĂ©matique linĂ©aire, en nombres entiers, qui prend en entrĂ©e des paramĂštres, tels que les demandes des clients, et qui produit la planiïŹcation minimisant le coĂ»t total du rĂ©seau et ce, sur plusieurs phases. Les rĂ©sultats numĂ©riques obtenus en simulant notre modĂšle montrent sa supĂ©rioritĂ© par rapport aux mĂ©thodes sĂ©quentielles existantes.--------- ABSTRACT
Multimedia applications have been gaining momentum and are ïŹnding their way into everyday life. Their popularity can be attributed to several factors, such as the diversiïŹcation of content and services, ubiquitous access thanks to the mobility and nomadicity, as well as advances in architectures and protocols used to support their most demanding requirements. For example, what was once a simple phone call has morphed nowadays into a videoconference, allowing a dynamic number of users to participate. Another example of a multimedia application that gained popularity is IP TeleVision (IPTV), which is the technology that allows the transmission of live and on demand television, on IP networks. There also exists a mobile version, called Mobile IP TeleVision (MobileTV). From the operatorsâ point of view, the focus is put on the deployment of next generation networks. Wireless operators are therefore deploying fourth generation cellular technologies, such as 3GPP Long Term Evolution (LTE), while those oïŹering wired connectivity are looking into ïŹber optical based networks, such as Fiber to the Home (FTTH). These new networks increase the rate oïŹered, as well as reduce latency, which are two important criteria for the deployment of large-scale multimedia applications. However, despite these advances, there still exist several obstacles hindering the proper operation of multimedia applications. This thesis therefore focuses on three important issues in next generation networks, each of these subjects leading to a scientiïŹc article.
The ïŹrst two works deal with the issues of the Fixed-Mobile Convergence (FMC). This convergence is blurring the distinction between mobile and ïŹxed networks. Among other things, it allows a user to have access to its services, both on the cellular network (LTE, for example) as well as on a local network (Wireless Fidelity (WiFi), for example). This is usually accomplished by equipping the user with a device with that can connect to both networks. The ïŹrst issue raised in this thesis is about the decision of when to execute a handover. The two most popular mobility protocols, Mobile IP (MIP) and Proxy Mobile IP (PMIP), approach this problem with diametrically opposed views. With the ïŹrst protocol, the decision is made by the user and his device. Although this approach allows for FMC, operators would much rather have complete control over the decision-making, in order to optimize their network. Indeed, with MIP, many signaling messages are sent, wasting valuable network resources, especially at the radio access, which is the most precious part of the network. Furthermore, by not involving the network, the decision taken by the device will not be necessarily optimal. It might request to switch to a more overloaded network, that cannot meet its demands of Quality of Service (QoS). For these reasons, the PMIP protocol was proposed. Its approach is the opposite of that of MIP, the mobility being managed entirely by the network. By doing so, the device is actually shielded from any aspect of the mobility, and is fooled into thinking that its always in its home network. This is possible by introducing new nodes in the networks that act on its behalf, which eliminates all signaling on the radio link. In addition, since the network is usually better suited to make the right decision, because of the additional information it holds, the mobility is optimized. However, the big issue that arises is that, without the intervention of the terminal, it is impossible to detect all the handover possibilities. In many cases, the operatorâs ïŹxed network is hidden by an internal network, usually a WiFi network, and the detection of the network is only possible with the help of the terminal. Thus, PMIP is not a protocol that is well suited to deploy FMC.
The ïŹrst article, entitled âClient-Based Network-Assisted Mobile IPv6â, therefore addresses this problem by proposing a new protocol based on Mobile IP v6 (MIPv6), in which we introduce the involvement of the network. The result is a hybrid protocol that draws upon the strength of MIPv6 and Proxy Mobile IP v6 (PMIPv6). To accomplish this, two steps were required. The ïŹrst consisted of a complete overhaul of the MIPv6 protocol, as in its current state, it was near impossible to make any modiïŹcations, because of the complexity and heaviness of its speciïŹcations. The result is a much more lightweight protocol which provides only basic functionality. Other features, such as security mechanisms, were separated into modules. In the second step, we proposed a new module, which introduces a new node in the network that can handle the terminal mobility. Thus, the collaboration of the terminal and the new node reduces the signaling messages and optimizes the decisions for handing over, while still oïŹering support for FMC.
The second issue that this thesis tackles is the seamlessness of a handover between two networks. A handover is deemed seamless if it does not cause any disruption to the userâs services. For example, a call that is in progress on the cellular network should not be interrupted when the connection switches to a local network, and the same goes for the other way around. The applications targeted by our work are multimedia applications operating in real-time , such as IPTV and MobileTV (in live television mode). These applications employ multicast protocols that are optimized for the transmission of data from one or more sources to multiple receivers, while using the minimum number of packets required. The problem, however, with these applications is that when a vertical handover occurs (in the case of FMC, for example), the connection is lost and must be re-established. This is because the terminal changes its IP address, which forces it to rejoin the services from the new address. This disconnection results in a packet loss, which entails an interruption of the user application.
The second article, entitled âSeamless handover for multicast Mobile IPv6 traïŹcâ, proposes a solution to this problem. This is accomplished by introducing a new node in the network, whose role is to buïŹer the lost packets while the handover is occurring. Thus, when the device reconnects, it is able to recover these packets. The user application is therefore able to proceed without interruption.
The third issue addressed in this thesis focuses on the planning of access networks, to support the high bandwidth required by multimedia applications. For the FMC to be successful, it is necessary that the local network supports the bandwidth requirements. The internal WiFi network is generally not an issue, the limitation rather lies in the wired network. To increase the oïŹered rates, operators have started introducing ïŹber optic links in their networks, complementing the traditional links, such as twisted pair copper and coaxial cable. Thus, new hybrid optical technologies have been proposed.
In a context where an infrastructure already exists, the choice of a hybrid technology is very attractive, because the operator can leverage its previous investment and minimize the cost of the upgrade. However, in a new environment, there is no infrastructure to reuse. Therefore, the consensus in such a scenario is that the best technology to deploy is the one that only uses ïŹber optic links, as it oïŹers the best rates and the greatest scalability. The cost diïŹerence is smaller and therefore no longer the main criterion for selecting the technology to deploy.
One of the diïŹculties of network planning is that these networks are often deployed by operators in phases. Therefore, the planning must be dynamic and take into account the changing nature of customer demands. The third article, entitled âDynamic GreenïŹeld Fiber to the Home Planningâ, proposes a dynamic model for the network planning problem of ïŹber optic networks. The result is a linear integer mathematical model, which takes input parameters, such as customer demands, and produces a planning that minimizes the total cost of the network, over all of the phases. The numerical results obtained when simulating our solution show its superiority compared to existing sequential methods
Nouveau protocole de partage de fichiers pair à pair pour réseau ad hoc
Caractérisation des réseaux mobiles ad hoc et des réseaux pair a pair -- Stratégie de partage de fichiers proposée -- Analyse de performance
Primary Carcinoid Tumor of the Testis: A Case Report and Review of the Literature
Carcinoid tumors usually arise in the gastrointestinal tract. Immunocytohistochemical and radiologic studies are important in detecting the primary tumor site. Primary carcinoid tumors of the testis are particularly rare with a high malignant potential warranting long-term follow-up. We present the case of a primary carcinoid tumor of the testis with long-term surveillance
Intra-cavernosal injection of botulinum toxin in the treatment of erectile dysfunction : a systematic review and meta-analysis
OBJECTIVE To evaluate the role of botulinum toxin in treating erectile dysfunction as a novel treatment strategy avoiding morbid and irreversible surgeries.
METHODS A systematic review of literature was conducted from January 1990 through July 31, 2021. Search engines used included PubMed, Embase and Medline databases, to identify studies investigating botulinum toxin in erectile dysfunction, published in English. Seven studies in total were included in our review including two pre-clinical studies. A meta-analysis was performed on three outcomes included commonly in at least two studies. Among the different parameters assessed were, Erection Hardness Score (EHS), Peak Systolic Velocity in cavernosal artery (PSV) and the Sexual Health Inventory for Men (SHIM) score.
RESULTS A clear benefit was noted for intracavernosal injection (ICI) of botulinum toxin (BoNT-A) on PSV with a mean difference (MD) of 10.82 [4.99, 16.65] and a heterogeneity of I2=61%. EHS results favored BoNT-A as well over placebo with a MD of 0.7 [0.47, 0.93] and heterogeneity of I2=94%. As for SHIM score, with a heterogeneity of I2=85%, no statistically significant difference was found (MD 0.58 [-0.03, 1.20]).
CONCLUSION Our review and meta-analysis have shown statistical significance for the benefit of BoNT-A in terms of EHS and PSV. However, this statistical significance should be interpreted in light of the given limitations: small sample size, heterogeneity in data collection, patient selection bias, and clinical significance of the measured differences. ICI of BoNT-A should currently be limited to clinical studies to further elucidate its clinical benefit. (c) 2022 Elsevier Inc
SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study
Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling.
Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty.
Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year.
Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population