One of the primary tasks of the mobile system designers in order to support high density of devices in a CDMA system is to create a code sequence with a capacity for large number of spreading code sequences having low cross-correlation values between them, in order to ensure accommodation of large number of users and to minimise the effect of multiple access interference. In this research, the design for a novel hybrid orthogonal very large set (HOVLS) code sequence is proposed for high density mobile application scenarios. The design and development of both fixed and variable spreading factor code sequences are presented in this thesis. Both type of code sequences have been implemented via simulation using Matlab/Simulink. The performance of the code sequences has been evaluated and compared with that of existing code sequences. The proposed code sequences are more advantageous for high density mobile networks. The unique feature of the fixed length HOVLS code sequence is that its ACF, CCF, and BER performances are similar to that of orthogonal Gold code sequence and orthogonal m-sequence under Rayleigh flat and frequency selective fading channel conditions while having a significantly higher capacity than those orthogonal code sequences. The proposed HOVLS code sequence could support 134 different cells which is more than twice than that of orthogonal Gold code sequence and orthogonal m-sequence. To the knowledge of the author, this is the largest reported family size in the literature for an orthogonal code sequence for CDMA applications. In order to support variable data rate, fixed length HOVLS code sequence was developed into orthogonal variable spreading factor code sequence. It is shown that the proposed OVSF code sequence has slightly better CCF than those of OVSF Gold code sequence and m-sequence in terms of CM (correlation margin). The ACF of the proposed OVSF code sequence is similar to those of OVSF Gold code sequence and m-sequence. The proposed OVSF code sequence possesses comparable BER performance to those of orthogonal Gold code sequence and orthogonal m-sequence under flat fading channel condition. Whereas, the BER performance of the proposed OVSF code sequence is slightly better than that of Gold code sequence and OVSF m-sequence under frequency selective fading channel. Therefore, the proposed HOVLS code sequence is appropriate code sequence in CDMA systems than those of orthogonal Gold code sequence and orthogonal m-sequence for both fixed and variable rate high density network applications.

O objetivo central desta tese é demonstrar a existência de uma estrutura regenerativa visível para cadeias de alcance variável não limitadas. Também apresentamos um algoritmo de identificação de seqüências de instantes de regeneração que converge quase certamente quando o tamanho da amostra diverge. / Our main aim is prove the existence of a regeneration scheme in unbounded variable length chains. We present an algorithm to identify sequences of regeneration times which converges almost surely as the sample length.

Nessa tese apresentamos uma nova classe de modelos, os processos de saltos com memória de alcance variável, uma generalização a tempo contínuo do processo introduzido em Galves e Löcherbach (2013). Desenvolvemos um novo estimador para a árvore de contexto imersa no processo de salto com memória de alcance variável, considerando mais parâmetros fornecidos pela amostra. Obtivemos também uma cota superior da taxa de convergência da árvore estimada para árvore real, provando a convergência quase certa do estimador. / In this work we deal with a new class of models: the jump processes with variable length memory. This is a continuous-time generalization of the process introduced in Galves and Löcherbach (2013). We present a new estimator for the tree context embedded in this process, considering all information provided by the sample. We also present an exponential upper bound for the rate of convergence, proving then the almost sure convergence of the estimator.

Nessa tese apresentamos uma nova classe de modelos, os processos de saltos com memória de alcance variável, uma generalização a tempo contínuo do processo introduzido em Galves e Löcherbach (2013). Desenvolvemos um novo estimador para a árvore de contexto imersa no processo de salto com memória de alcance variável, considerando mais parâmetros fornecidos pela amostra. Obtivemos também uma cota superior da taxa de convergência da árvore estimada para árvore real, provando a convergência quase certa do estimador. / In this work we deal with a new class of models: the jump processes with variable length memory. This is a continuous-time generalization of the process introduced in Galves and Löcherbach (2013). We present a new estimator for the tree context embedded in this process, considering all information provided by the sample. We also present an exponential upper bound for the rate of convergence, proving then the almost sure convergence of the estimator.

Efficient multimedia communication over mobile or wireless channels remains a challenging problem. To deal with that problem so far, the industry has followed mostly a divide and conquer approach, by considering separately the source of data (text, image, video, etc.) and the communication channel (electromagnetic waves across the air, a telephone line, a coaxial cable, etc.). The goal is always the same: to transmit (or store) more data reliably per unit of time, of energy, of physical medium, etc. With today's applications, the divide and conquer approach has, in a sense, started to show its limits. Let us consider, for example, the digital transmission of an image. At the transmitter, the first main step is data compression, at the source level. The number of bits that are necessary to represent the image with a given level of quality is reduced, usually by removing details in the image that are invisible (or less visible) to the human eye. The second main step is data protection, at the channel level. The transmission is made ideally resistant to deteriorations caused by the channel, by implementing techniques such as time/frequency/space expansions. In a sense, the two steps are quite antagonistic --- we first compress then expand the original signal --- and have different goals --- compression enables to transfer more data per unit of time/energy/medium while protection enables to transfer data reliably. At the receiver, the "reversed" operations are implemented. This separation in two steps dates back to Shannon's source and channel coding separation theorem in 1948 and has encouraged the division of the research community in two groups, one focusing on data compression, the other on data protection. This separation has also seduced the industry for the design, thereby supported by theory, of layered communication protocols. But this theorem holds only under asymptotic conditions that are rarely satisfied with today's multimedia content and mobile channels. Therefore, it is usually wise in practice to drop this strict separation and to allow at least some cross-layer cooperation between the source and channel layers. This is what lies behind the words joint source-channel techniques. As the name suggests, these techniques are optimized jointly, without a strict separation. Intuitively, since the optimization is less constrained from a mathematical standpoint, the solution can only be better or equivalent. In this thesis, we investigate a promising subset of these techniques, based on the turbo principle and on variable length codes. The potential of this subset has been illustrated for the first time in 2000, with an example that, since then, has been successfully improved in several directions. Unfortunately, most decoding algorithms have been so far developed on an ad hoc basis, without a unified view and often without specifying the approximations made. Besides, most code-related conclusions are based on simulations or on extrinsic information analysis. A theoretical framework on the error correcting properties of variable length codes in turbo systems is lacking. The purpose of this work, in three parts, is to fill in these gaps up to a certain extent. The first part presents the literature in this field and attempts to give a unified overview. The second part proposes a transmission system that generalizes previous systems from the literature, with the simple addition of a repetition code. While most previous systems are designed for bit streams with a high level of residual redundancy, the proposed system has the interesting flexibility to handle easily different levels of redundancy. Its performance is then analyzed for small levels of redundancy, which is a case not tackled extensively in the literature. This analysis leads notably to the discovery of surprising interleaving gains with reversible variable length codes. The third part develops the mathematical framework that was motivated during the second part but skipped on purpose for the sake of clarity. We first clarify several issues that arise with non-uniform bits and the extrinsic information charts, and propose and discuss two methods to compute these charts. Next, several theoretical results are stated on the robustness of variable length codes concatenated with linear error correcting codes. Notably, an approximate average distance spectrum of the concatenated code is rigorously developed. Together with the union bound, this spectrum provides upper bounds on the symbol and frame/packet error rates. These bounds are then analyzed from an interleaving gain standpoint and it is proved that the variable length code improves the interleaving gain if its spectrum is bounded.

Nesta tese consideramos cadeias de alcance variável não limitado. São cadeias de alcance infinito cuja família de probabilidades de transição é representada por uma árvore de contextos probabilística. Dado uma árvore de contextos probabilística não limitada, as questões que nos interessam são as seguintes: existe ou não uma cadeia estacionária compatível com esta árvore? Se existir, esta cadeia é única? Podemos fazer uma simulação perfeita desta cadeia? Nesta tese, apresentamos novos critérios sucientes que garantem a existência e a unicidade da cadeia estacionária e, sob restrições mais fortes, a possibilidade de fazer uma simulação perfeita. Uma caraterística interessante do nosso trabalho é o fato de não utilizarmos a condição de continuidade. / We present a new perfect simulation algorithm for stationary chains (indexed by Z) having unbounded variable length memory. This is the class of innite memory chains for which the family of transition probabilities is given by probabilistic context tree. Our condition is expressed in terms of the structure of the context tree. In particular, we do not assume the continuity of the family of transition probabilities. We give an explicit construction of the chain using a sequence of i.i.d. random variables uniformly distributed in [0,1[.

Nesta tese consideramos cadeias de alcance variável não limitado. São cadeias de alcance infinito cuja família de probabilidades de transição é representada por uma árvore de contextos probabilística. Dado uma árvore de contextos probabilística não limitada, as questões que nos interessam são as seguintes: existe ou não uma cadeia estacionária compatível com esta árvore? Se existir, esta cadeia é única? Podemos fazer uma simulação perfeita desta cadeia? Nesta tese, apresentamos novos critérios sucientes que garantem a existência e a unicidade da cadeia estacionária e, sob restrições mais fortes, a possibilidade de fazer uma simulação perfeita. Uma caraterística interessante do nosso trabalho é o fato de não utilizarmos a condição de continuidade. / We present a new perfect simulation algorithm for stationary chains (indexed by Z) having unbounded variable length memory. This is the class of innite memory chains for which the family of transition probabilities is given by probabilistic context tree. Our condition is expressed in terms of the structure of the context tree. In particular, we do not assume the continuity of the family of transition probabilities. We give an explicit construction of the chain using a sequence of i.i.d. random variables uniformly distributed in [0,1[.

<p>Modern semiconductor design methods makes it possible to design increasingly complex system-on-a-chips (SOCs). Testing such SOCs becomes highly expensive due to the rapidly increasing test data volumes with longer test times as a result. Several approaches exist to compress the test stimuli and where hardware is added for decompression. This master’s thesis presents a test data compression method based on a modified facsimile code. An embedded processor on the SOC is used to decompress and apply the data to the cores of the SOC. The use of already existing hardware reduces the need of additional hardware. </p><p>Test data may be rearranged in some manners which will affect the compression ratio. Several modifications are discussed and tested. To be realistic a decompressing algorithm has to be able to run on a system with limited resources. With an assembler implementation it is shown that the proposed method can be effectively realized in such environments. Experimental results where the proposed method is applied to benchmark circuits show that the method compares well with similar methods. </p><p>A method of including the response vector is also presented. This approach makes it possible to abort a test as soon as an error is discovered, still compressing the data used. To correctly compare the test response with the expected one the data needs to include don’t care bits. The technique uses a mask vector to mark the don’t care bits. The test vector, response vector and mask vector is merged in four different ways to find the most optimal way.</p>

Modern semiconductor design methods makes it possible to design increasingly complex system-on-a-chips (SOCs). Testing such SOCs becomes highly expensive due to the rapidly increasing test data volumes with longer test times as a result. Several approaches exist to compress the test stimuli and where hardware is added for decompression. This master’s thesis presents a test data compression method based on a modified facsimile code. An embedded processor on the SOC is used to decompress and apply the data to the cores of the SOC. The use of already existing hardware reduces the need of additional hardware. Test data may be rearranged in some manners which will affect the compression ratio. Several modifications are discussed and tested. To be realistic a decompressing algorithm has to be able to run on a system with limited resources. With an assembler implementation it is shown that the proposed method can be effectively realized in such environments. Experimental results where the proposed method is applied to benchmark circuits show that the method compares well with similar methods. A method of including the response vector is also presented. This approach makes it possible to abort a test as soon as an error is discovered, still compressing the data used. To correctly compare the test response with the expected one the data needs to include don’t care bits. The technique uses a mask vector to mark the don’t care bits. The test vector, response vector and mask vector is merged in four different ways to find the most optimal way.

Can we reduce disturbance, swing, and errors by delegating some of the tasks to a subsystem on the tool hanging from a drone to gain precision and dependability? This project covers developing and implementing a user-controlled prototype with an automatic control system and gripper for functionality and controlled movement in 5 DOF. AirForestry is developing a new way of working in the forestry business to provide a greener and healthier solution for the soil and the environment. The forestry industry emits approximately one million tons of CO2 per year from heavy diesel-fueled vehicles. With a renewable energy battery-powered drone of a diameter of 6.2 m and a hanging harvesting tool, they can significantly improve the environmental impact of forestry. The harvesting tool has an automatic control system and is user controlled to perform the thinning and cutting of trees. The main focus is to use IMU sensor data to produce accurate angle estimation to control the stability of a scaled prototype and to implement physical restrictions to make it able to be attached safely and tested on a drone but not limit the controlled mobility of the prototype with a system independent of the control system of the drone itself. The user can control the attitude and elevation and receive real-time sensor data wireless during operation. With the intended spacing of the attachment points on the drone, it can prevent unwanted swing from a push or displaced drop. It uses the accelerometer on the IMUsensor to calculate the angle of roll and pitch, although the accelerometer is sensitive to vibrations and rotations. The control system has a fast response and rise time, but it experiences noise and oscillations. Sensor fusion of the accelerometer and gyroscope in a complementary filter can be implemented to increase the accuracy of the angle estimations and decrease the noise, which will be reflected in the speed of the servos and thereby improve the stability and mobility of the system.