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A novel design paradigm for wireless data delivery involves use of a scheduler at a base station to schedule users awaiting transmission and send downlink data to these users with all available cell power. This is unlike previous systems that share the available downlink power between users and trade off interference with capacity. The concept is used in 3G wireless standards like 1xEVDO and HSDPA. The scheduler is designed to exploit the peaks in channels seen by different users and transmit data to the user that can support the best rate. In contrast, antenna diversity, where multiple antennas are deployed at the receiver or transmitter; has the effect of improving received signal fidelity by averaging the channel variation. In this thesis, we evaluate the joint effect of user diversity and antenna diversity for various scheduling algorithms. The system is first studied with a single user to calculate theoretical throughput values. A loaded system is then simulated and throughput trends are plotted for each user. Total system capacity is evaluated in terms of served bytes for various combinations of scheduling algorithm, diversity type and channel quality. Multi-user scheduling diversity is studied using the same system simulation model via Tomlinson Harashima precoding. Results are generated for various cell powers. Single-user and multi-user scheduling cases are compared to understand the pros and cons of each approach. / Master of Science

Asymmetric digital subscriber line (ADSL) is a broadband access technology capable of delivering large bandwidth over existing copper telephone line infrastructure. This research aims at characterizing and analyzing TCP/IP performance in presence of a new protocol stack (TCP/IP over PPP and ATM) being promoted for one of the ADSL network architectures. Using extensive simulations, we verify the adverse effects of asymmetric links on the performance of TCP and additional throughput degradation caused by the overhead at the AAL5- ATM layers. This study involves unidirectional as well as bi-directional data transfer using different traffic mixes including bursty and non-bursty types of traffic. Bi-directional data transfer over asymmetric links results in ACK compression wherein TCP acknowledgements (ACKs) get bunched together behind larger data packets, further exacerbating the effect of asymmetry on TCP performance. By implementing the simulation model for PPP encapsulation over AAL5, we characterize its effect in terms of throughput degradation and excessive delay. We quantify the improvement in the throughput obtained by delaying the TCP ACKs and by TCP/IP header compression. These techniques being effective for unidirectional traffic over asymmetric links, however, do not prove as effective when ATM enters the scenario or in presence of bi-directional data transfer. Further, we implemented a simulation model of the Smart ACK Dropper (SAD), a technique to regulate the flow of TCP ACKs. Considerable improvement in performance especially in the presence of unidirectional data transfer is achieved using the SAD technique. Although the improvement is to a lesser extent in the presence of bi-directional data traffic, SAD helps the network in quickly recovering from the impact of ACK compression. We also propose and implement certain customized queuing/scheduling and policing mechanisms to enable differentiated servicing of TCP ACKs and data packets, and mitigate the effect of ACK compression. While providing considerable TCP performance improvement in presence of SAD, custom queuing also allows fair sharing of bandwidth between TCP flows, unlike priority queuing, which starves the low priority flow. The committed access rate (CAR)policing scheme provides considerable performance improvement when used with SAD, and is especially useful when TCP ACKs compete with bursty data traffic over the slower upstream. / Master of Science

This thesis proposes a multi-protocol label switching (MPLS)-based architecture to provide quality of service (QoS) for both internet service provider (ISP) networks and backbone Internet Protocol (IP) networks that are heterogeneous in nature. Heterogeneous networks are present due to the use of different link-layer mechanisms in the current Internet. Copper-based links, fiber-based links, and wireless links are some examples of different physical media that lead to different link-layer mechanisms. The proposed architecture uses generalized MPLS and other MPLS features to combat heterogeneity. The proposed architecture leverages the QoS capabilities of asynchronous transfer mode (ATM) and the scalability advantages of the IP differentiated services (DiffServ) architecture. This architecture is constructed in such a way that MPLS interacts with DiffServ in the backbone networks while performing ATM-like QoS enforcement in the periphery of the networks. The architecture supports traffic engineering through MPLS explicit paths. MPLS network management, bandwidth broker capabilities, and customizability is handled through domain specific MPLS management entities that use the Common Open Policy Service (COPS) protocol to interact with other MPLS entities like MPLS label switch routers and label edge routers. The thesis provides a description of MPLS and QoS, followed by a discussion of the motivation for a new architecture. The MPLS-based architecture is then discussed and compared against similar architectures. To integrate the ATM and DiffServ QoS attributes into this architecture, MPLS signaling protocols are used. There are two common MPLS signaling protocols. They are Resource Reservation Protocol with traffic engineering extensions (RSVP-TE) and Constraint-Routed Label Distribution Protocol (CR-LDP). Both these protocols offer comparative MPLS features for constraint routed label switch path construction, maintenance, and termination. RSVP-TE uses UDP and IP, while CR-LDP uses TCP. This architecture proposes a multi-level domain of operation where CR-LDP operates in internet service provider (ISP) networks and RSVP- TE operates in backbone networks along with DiffServ. Qualitative analysis for this choice of domain of operation of the signaling protocols is then presented. Quantitative analysis through simulation demonstrates the advantages of combining DiffServ and MPLS in the backbone. The simulation setup compares the network performance in handling mixed ill-behaved and well-behaved traffic in the same link, with different levels of DiffServ and MPLS integration in the network. The simulation results demonstrate the advantages of integrating the QoS features of DiffServ, ATM functionality, and MPLS into a single architecture. / Master of Science

L'étude de la ramification chez le pois, à partir des mutants hyper-ramifiés ramosus (rms) a permis de mettre en évidence l'existence d'une nouvelle famille d'hormones végétales : les strigolactones, inhibant la ramification des plantes à graines. La découverte de cette hormone végétale ouvre de nouvelles pistes de recherche sur la biosynthèse et la perception de cette nouvelle hormone. Nous avons montré le rôle du gène PsBRC1, codant un facteur de transcription de type TCP et homologue du gène TEOSINTE BRANCHED1 du maïs, dans la voie de signalisation des strigolactones. L’étude de ce gène nous a permis d'avoir une meilleure compréhension de l’interaction entre strigolactones et cytokinines dans le contrôle de la ramification, de la dynamique de la levée de dormance des bourgeons axillaires, et d'effectuer les premières études de relations structure-activité des strigolactones sur l’inhibition de la ramification chez le pois.Nous avons étudié et caractérisé d'autres éléments dans la voie de signalisation. Chez le pois, deux mutants, autres que Psbrc1, ne répondent pas à l’application de strigolactones, rms3 et rms4. Le gène RMS4 code pour une protéine à boîte F. Nous nous sommes focalisés ici sur le mutant hyper-ramifié rms3. Nous avons montré que RMS3 est l'homologue du gène D14 du riz, codant pour une protéine de la superfamille des α-β/hydrolases. Ces protéines peuvent avoir une activité enzymatique et ainsi pourraient modifier les strigolactones en un composé actif. Le récepteur des gibbérellines GID1 appartient aussi à cette famille, RMS3 est donc un bon candidat pour être le récepteur des strigolactones. Nous avons utilisé une strigolactone radiomarquée afin d’étudier le métabolisme de l'hormone. Nous avons découvert que la strigolactone synthétique, 3H-GR24 est clivée en un composé inconnu au contact des racines, indépendamment de l'activité de la protéine RMS3. Ce composé de structure inconnue se retrouve aussi dans la sève du xylème alors que 3H-GR24 y est absent.Outre un phénotype hyperbranché les mutants rms présentent une diminution de la taille de leurs entre-nœuds, qui n'est pas due à l’augmentation de la ramification. Nous avons étudié l'origine du nanisme des mutants déficients en strigolactones et affectés dans la réponse à l’hormone. Des approches génétiques et moléculaires ont été utilisées pour tester une interaction possible entre les strigolactones et les gibbérellines. Nous avons montré que les strigolactones régulaient l’élongation des entre-nœuds indépendamment des gibbérellines.Le pois est un excellent modèle en génétique et en physiologie. Avec le développement de nouvelles techniques à l'INRA (TILLING; UNIGENE : ensemble de plus de 40000 séquences exprimées de pois), nous avons pu identifier de nouveaux gènes de biosynthèse des strigolactones chez le pois et obtenir plusieurs nouveaux mutants de pois. Ces mutants seront essentiels pour les futures études du laboratoire et pourront permettre d'identifier de nouveaux intermédiaires dans la biosynthèse et le métabolisme des strigolactones. / The study of shoot branching in pea, using the high branching ramosus (rms) mutants has highlighted the existence of a new family of plant hormones: the strigolactones, inhibiting shoot branching in seed plants. The discovery of this novel plant hormone opens novel research areas in the deciphering of strigolactone biosynthesis and strigolactone perception. We have shown the role of the pea TCP transcription factor, PsBRC1, the homolog of the maize TEOSINTE BRANCHED (TB1) in strigolactone signaling. The PsBRC1 gene was shown to have a role in integrating strigolactone and cytokinin pathways, and allowed to have a better understanding of the dynamics of bud outgrowth, and to perform the first strigolactone Structure-Activity Relationship studies for branching inhibition in pea. We investigated and characterized other elements in the signaling pathway, including the strigolactone receptor. In pea, two mutants, other than Psbrc1, do not respond to the application of strigolactones, rms3 and rms4. The RMS4 gene encodes an F-BOX protein and here we focused on the high branching rms3 pea mutant. We have shown that RMS3 is the homolog of the rice D14 gene encoding a protein of the α-β/hydrolase superfamily. Consequently RMS3 may have an enzymatic activity to modify strigolactone into an active compound. The gibberellin receptor GID1 also belongs to this family, therefore RMS3 is also a good candidate for the strigolactone receptor. We used a radiolabeled synthetic strigolactone, 3H-GR24, to investigate the metabolism of the hormone. We discovered that the synthetic strigolactone, 3H-GR24 is cleaved in an unknown compound in the root media independently of RMS3 activity, compound which is also found in the xylem sap in contrast to 3H-GR24. The rms mutants exhibit not only a high branching phenotype but also a reduced height which is not due to this high branching. We investigated the origin of the dwarfism of strigolactone-deficient and response mutants in pea. Genetic and molecular approaches have been used to test a possible interaction between strigolactones and gibberellins. We have shown that strigolactones regulate stem elongation independently of gibberellin. Pea is a powerful model plant for genetics and physiology. With the development of new facilities at INRA (TILLING; UNIGENE set of more than 40000 expressed sequences), we were able to identify new biosynthesis genes in pea and to obtain several novel pea mutants. These mutants will be essential for future studies of the laboratory in particular to identify new intermediates in strigolactone biosynthesis and metabolism.

Com o recente desenvolvimento de tecnologias de redes de altas taxas de transmissão, tais como Asynchronous Transfer Mode (ATM), o problema da carência por largura de banda foi solucionado. A questão atual é a implementação de sistemas que suportem os protocolos ATM de forma nativa e integral. Atualmente tem-se utilizado aplicativos tradicionais baseados nos protocolos TCP(UDP)/IP no topo da pilha de protocolos ATM. Tal modelo traz redundâncias que implicam diretamente em aumento de overhead na comunicação. Muitos modelos têm sido desenvolvidos para levar de forma direta a aplicação os serviços ATM. O propósito deste trabalho foi comparar o desempenho de transmissões de dados utilizando os protocolos TCP(UDP)/IP sobre ATM com transmissões de dados no modo ATM nativo. Para tal, utilizamos a plataforma de pesquisa HARP do sistema operacional FreeBSD. Tal plataforma implementa o modelo Classical IP sobre ATM utilizando os serviços AAL5 e ainda fornece uma API para sockets ATM permitindo que uma aplicação tenha acesso direto a camada AALS. Testes de taxa de transmissão, perda de células, e atraso na rede, foram realizados com base na modificação de parâmetros relacionados à aplicação e sistema operacional, tais como tamanho da mensagem sendo transmitida e tamanho dos buffers de socket. / The solution for the lack of bandwidth was solved by the recent development of high speed networks technologies, such as Asynchronous Transfer Mode - ATM. The question now is the implementation of systems, which provide support for ATM protocols in an integral way. Nowadays, legacy network applications, based in TCP/IP protocols have been used on top of ATM protocol stack. Such approach generates redundances that have as consequence an increase in the communication overhead. Many models have been developed to provide ATM services directly to applications. The goal of this study was to evaluate the performance of data transfers comparing the TCP/IP protocols over ATM with the performance of data transfers in native ATM mode. The Host ATM Research Plataform (HARP) was utilized on the FreeBSD operating system. This plataform implements Classical IP over ATM, utilizing AAL5 services. Furthermore, it provides an API for ATM sockets, allowing that an application directly access the AAL5 services. Measurements of throughput and investigations about cell loss and delay were carried out altering parameters related to the application and operating system. The parameters adopted were message size and socket buffer sizes.