In recent years, cellular systems based on orthogonal frequency division multiple access – time division duplex (OFDMA-TDD) have gained considerable popularity. Two of the major reasons for this are, on the one hand, that OFDMA enables the receiver to effectively cope with multipath propagation while keeping the complexity low. On the other hand, TDD offers efficient support for cell-specific uplink (UL)/downlink (DL) asymmetry demands by allowing each cell to independently set its UL/DL switching point (SP). However, cell-independent SP gives rise to crossed slots. In particular, crossed slots arise when neighbouring cells use the same slot in opposing link directions, resulting in base station (BS)-to-BS interference and mobile station (MS)-to-MS interference. BS-to-BS interference, in particular, can be quite detrimental due to the exposed location of BSs, which leads to high probability of line-of-sight (LOS) conditions. The aim of this thesis is to address the BS-to-BS interference problem in OFDMA-TDDcellular networks. A simulation-based approach is used to demonstrate the severity of BS-to-BS interference and a signal-to-interference-plus-noise ratio (SINR) equation for OFDMA is formulated to aid system performance analysis. The detrimental effects of crossed slot interference in OFDMA-TDD cellular networks are highlighted by comparing methods specifically targeting the crossed slots interference problem. In particular, the interference avoidance method fixed slot allocation (FSA) is compared against state of the art interference mitigation approaches, viz: random time slot opposing (RTSO) and zone division (ZD). The comparison is done based on Monte Carlo simulations and the main comparison metric is spectral efficiency calculated using the SINR equation formulated in this thesis. The simulation results demonstrate that when LOS conditions among BSs are present, both RTSO and ZD perform worse than FSA for all considered performance metrics. It is concluded from the results that current interference mitigation techniques do not offer an effective solution to the BS-to-BS interference problem. Hence, new interference avoidance methods, which unlike FSA, do not sacrifice the advantages of TDD are open research issues addressed in this thesis. The major contribution of this thesis is a novel cooperative resource balancing technique that offers a solution to the crossed slot problem. The novel concept, termed asymmetry balancing, is targeted towards next-generation cellular systems, envisaged to have ad hoc and multi-hop capabilities. Asymmetry balancing completely avoids crossed slots by keeping the TDD SPs synchronised among BSs. At the same time, the advantages of TDD are retained, which is enabled by introducing cooperation among the entities in the network. If a cell faces resource shortage in one link direction, while having free resources in the opposite link direction, the free resources can be used to support the overloaded link direction. In particular, traffic can be offloaded to near-by mobile stations at neighbouring cells that have available resources. To model the gains attained with asymmetry balancing, a mathematical framework is developed which is verified by Monte Carlo simulations. In addition, asymmetry balancing is compared against both ZD and FSA based on simulations and the results demonstrate the superior performance of asymmetry balancing. It can be concluded that the novel interference avoidance approach is a very promising candidate to.

Dissertation submitted for obtain the degree of Doctor, at the Faculdade de Engenharia da Universidade do Porto, under supervisory Prof. José António Ruela Simões Fernandes

<p>3GPP LTE (Long Term Evolution) is a project of the Third Generation Partnership Project to improve the UMTS (Universal Mobile Telecommunications System) mobile phone standard to cope with future technology evolutions. Two duplex schemes FDD and TDD are investigated in this thesis. Several computational intensive components of the baseband processing for LTE uplink such as synchronization, channel estimation, equalization, soft demapping, turbo decoding is analyzed. Cost analysis is hardware independent so that only computational complexity is considered in this thesis. Hardware dependent discussion for LTE baseband SDR platform is given according the analysis results.</p>

In recent years, mobile communications have become affordable and popular. High cellular capacity in terms of number of users and data-rates is in need. As the available frequency spectrums for mobile communications are limited, the utilization of the radio resources to achieve high capacity without imposing high equipment cost is of utmost importance. Recently, multi-hop cellular networks (MCNs) were introduced. These networks have the potential of enhancing the cell capacity and extending the cell coverage at low extra cost. However, in a cellular network, the cell or system capacity is inversely related to the cell size. In MCNs, the cell size, the network density and topology affect the coverage of source nodes and the total demands that can be served and, thus, the system throughput. Although the cell size is an important factor, it has not been exploited for maximizing throughput. Another major issue in MCNs is the increase in packet delay because multi-hopping is involved. High packet delay affects quality of service provisioning in these networks. In this thesis, we propose the Optimal Cell Size (OCS) and the Optimal Channel Assignment (OCA) schemes to address the cell size and packet delay issues for a time division duplex (TDD) wideband code division multiple access (W-CDMA) MCN. OCS finds the optimal cell sizes to provide an optimal balance of cell capacity and coverage to maximize the system throughput, whereas OCA assigns channels optimally in order to minimize packet relaying delay. Like many optimized schemes, OCS and OCA are computationally expensive and may not be suitable for large real-time problems. Hence, we also propose heuristics for solving the problems. For the cell size problem, we propose two heuristics: Smallest Cell Size First (SCSF) and Highest Throughput Cell Size First (HTCSF). For the channel assignment problem, we propose the Minimum Slot Waiting First (MSWF) heuristic. Simulation results show that OCS achieves high throughput compared to that of conventional (single-hop) cellular networks and OCA achieves low packet delay in MCNs. Results also show that the heuristics, SCSF, HTCSF and MSWF, provide good results compared to the optimal ones provided by OCS and OCA, respectively. / Thesis (Ph.D, Computing) -- Queen's University, 2009-02-02 22:53:41.825

Le rôle des protéines avec un motif TerD est depuis toujours insaisissable. La séquence en acides aminés qui correspond au motif TerD est répandue dans les génomes de plusieurs espèces bactériennes. Les recherches effectuées dans le cadre de ce doctorat avaient pour objectif d’identifier le rôle du gène tdd8 (SCO2368) qui code pour une protéine avec un motif TerD chez Streptomyces coelicolor. Sur la base d’une étude comparative du transcriptome de souches présentant une expression différentielle de tdd8, il a été possible de déterminer l’implication de tdd8 dans plusieurs systèmes de régulation. Les résultats obtenus ont permis d'établir que le niveau d’expression de tdd8 peut jouer un rôle dans le mécanisme de la différenciation morphologique et de la sporulation, dans le métabolisme de l’azote et dans l’équilibre redox. La protéine Tdd8 semble avoir un rôle dans divers processus cellulaires de par son implication dans l’homéostasie du calcium intracellulaire qui a été démontrée dans cette étude. Parmi les gènes qui semblent affectés par le taux d’expression de tdd8, ces recherches ont identifié un regroupement de gènes impliqués dans la réponse au stress redox. La plupart de ces gènes sont positionnés sur deux loci et leur expression implique un système de régulation analogue au régulon DosR retrouvé chez Mycobactérium tuberculosis. La croissance de la souche M145 de S. coelicolor en conditions de stress (hypoxie et présence d’oxyde nitrique) a permis de confirmer l’induction de ces gènes et des recherches bioinformatiques ont permis d’identifier un motif de liaison DosR dans les séquences qui précèdes la région codante de plusieurs gènes situés dans les deux loci identifiés. Les recherches ont également permis une meilleure caractérisation du métabolisme de l’azote et notamment une implication de tdd8 dans la régulation de ce métabolisme. Ces travaux s’inscrivent dans un processus de recherche fondamentale qui permet de mieux comprendre le rôle des protéines avec un motif TerD.

In this thesis, the Test Driven Development method (TDD) is studied for use in developing embedded software. The required framework is written for the development environment Rhapsody. Integration of TDD into a classical development cycle, without necessitating a transition to agile methodologies of software development and required unit test framework to apply TDD to an object oriented embedded software development project with a specific development environment and specific project conditions are done in this thesis. A software tool for unit testing is developed specifically for this purpose, both to support the proposed approach and to illustrate its application. The results show that RhapUnit supplies the required testing functionality for developing embedded software in Rhapsody with TDD. Also, development of RhapUnit is a successful example of the application of TDD.

Context: Developer’s within software companies work chosen choice of software development process. Choice of a particular Software Development Process impacts the work environment, end-product and might also have financial risks due to delay in delivering in the final software product. Objectives: we are investigating if the TDD could impact/applicable in large-scale industries. To achieve that we first identify the strengths and challenges while using TDD in large-scale industries. Identify what modifications can enhance the impact of TDD in large-Scale industries. Methods: Systematic Literature Review (SLR) has been used to investigate the application of TDD in large-scale industries. Using the info from SLR we conducted an online survey for validating the results obtained from SLR. As a last step we have conducted semi structured interviews to gather information from developers across industries practicing and practiced TDD. The data from the qualitative and quantitative methods is triangulated by identifying the strengths, challenges and modifications in applying TDD to large-scale industries. Results: The findings from our SLR, results validated from Survey and responses from interview participants show that TDD have both strengths, Challenges and modifications. Conclusions: Some challenges encountered when using TDD in large-scale industries are Negative test cases, linking test case modules of several developers, Communication, Overall idea about project, lack of TDD knowledge for developers practicing TDD, also lack of automation tools supporting the development of unit test-cases.

3GPP LTE (Long Term Evolution) is a project of the Third Generation Partnership Project to improve the UMTS (Universal Mobile Telecommunications System) mobile phone standard to cope with future technology evolutions. Two duplex schemes FDD and TDD are investigated in this thesis. Several computational intensive components of the baseband processing for LTE uplink such as synchronization, channel estimation, equalization, soft demapping, turbo decoding is analyzed. Cost analysis is hardware independent so that only computational complexity is considered in this thesis. Hardware dependent discussion for LTE baseband SDR platform is given according the analysis results.

Ingeniero Civil en Computación / En el mundo del desarrollo de software, existe una necesidad constante de construir sistemas capaces de enfrentar los desafíos de un ambiente siempre cambiante. Uno de los movimientos que acepta el riesgo como parte de su proceso son las metodologías ágiles de desarrollo de software, y dentro de ellas, las metodologías de desarrollo guiado por pruebas (TDD). El objetivo del Trabajo de Titulo es analizar estas metodologías, en particular el desarrollo guiado por pruebas clásico y el desarrollo guiado por comportamiento, con el fin de entender las fortalezas y debilidades de cada una de ellas. De ésta forma, a partir de este análisis, se espera dar una guía a aquellas personas que se interesan por la calidad, pero se ven abrumadas por la cantidad de estilos o variantes de TDD. Con el fin de entender a fondo las metodologías, se realizaron experimentos técnicos, los cuales fueron analizados considerando diferentes criterios, entre ellos la necesidad de un diseño a priori, valor entregado al cliente y la curva de aprendizaje. Sin embargo, al momento de la comparación, estos criterios mostraron ser insuficientes pues resultaron ser cualitativos y muy subjetivos. Posteriormente, se intentó un análisis más abstracto, enfocado en el proceso mismo de desarrollo. A partir de los resultados obtenidos, fue posible comprender que las técnicas presentadas no eran excluyentes, y que cada una de ellas puede entregar recursos interesantes tanto al equipo de desarrollo como al cliente de la aplicación o sistema, fortaleciendo la comunicación entre los actores del desarrollo de software o bien dándole la capacidad de responder de forma confiable al cambio.

Today, smart-phones have revolutionized wireless communication industry towards an era of mobile data. To cater for the ever increasing data traffic demand, it is of utmost importance to have more spectrum resources whereby sharing under-utilized spectrum bands is an effective solution. In particular, the 4G broadband Long Term Evolution (LTE) technology and its foreseen 5G successor will benefit immensely if their operation can be extended to the under-utilized unlicensed spectrum. In this thesis, first we analyze WiFi 802.11n and LTE coexistence performance in the unlicensed spectrum considering multi-layer cell layouts through system level simulations. We consider a time division duplexing (TDD)-LTE system with an FTP traffic model for performance evaluation. Simulation results show that WiFi performance is more vulnerable to LTE interference, while LTE performance is degraded only slightly. Based on the initial findings, we propose a Q-Learning based dynamic duty cycle selection technique for configuring LTE transmission gaps, so that a satisfactory throughput is maintained both for LTE and WiFi systems. Simulation results show that the proposed approach can enhance the overall capacity performance by 19% and WiFi capacity performance by 77%, hence enabling effective coexistence of LTE and WiFi systems in the unlicensed band.