Cosine Modulated Filter Banks Systems in the Presende of Multipath Transmission

As broadcasted television is changing from analogue to digital transmission, the television industry has to adapt itself for a new reality. Digitization opens for a wide array of new ways of watching television, where interactivity and mobility are paramount. The difference in the experience lies in the interactive part, inviting the user to take part in what happens on the mobile screen. What the mobile telephone lacks in screen size it can now make up for with its interactive potential. Instead of just watching television, the user now interacts with it. As a result, the television experience can be tailored to suit consumers with different requirements. In this study I look at true-time broadcasted television to handheld devices over the standards achieved in Europe and Korea today, DVB-H and T-DMB, and how interactivity between content provider and end-user can be achieved. I also look into how metadata plays a crucial role in interactive television, and the means to utilize metadata to favor the end-user’s demands according to standards such as XML, MPEG and Tv-Anytime. By supplying metadata to i.e sport or reality shows, and hence creating interactivity between content provider and end-user, a new marked for television is made possible. Electronic program guides (EPGs), teletext and weather forecasts for handhelds are examples of ways that metadata can be utilized to create an interactive experience for the end-user.

Give an introduction to the proposed double CubeSat system and an overview of communication requirements and the propagation characteristics that influence the link budget. Based on the above findings, derive requirements for the ground station antenna. Emphasize simplicity and easy construction and propose an antenna system that may meet the requirements. Investigate it theoretically with available software to optimize its dimensions. A scale model of the antenna should finally be built and its main properties measured in an anechoic chamber.

Power amplifiers are nonlinear devices that traditionally have been tried linearized by means of predistortion. The nonlinear impact can be identified by sidelobes in the frequency domain. By accepting a certain sidelobe level, this implies that we also accept a somewhat nonlinear characteristic on the resulting cascade of our transmitter. The main question raised in this thesis is: How is the optimal nonlinear cascade that maximizes transmitted power defined when some given out-of-band spectral requirements are fulfilled? The problem has been limited such that examinations have been done on a single carrier system seen in context to a chosen set of out-of-band spectral requirements. The different nonlinear characteristics have been represented by means of B-splines. Thus, the results obtained are only the best set of parameters in the model utilized, and hence, only a sub-optimal solution to the problem. Results are presented for different spectral restrictions. Simulations performed suggest that a linear characteristic is the optimal, when restrictions are placed within the sidelobe level close to the mainlobe. When the first sidelobe is allowed to grow unlimited, a parameter set using 2-segments B-spline have proved to give the highest average transmitted

The evolution of services offered using communication technology has yielded a jungle of different services. Many of these services exhibits different QoS requirements; different requirements to delay, probability of packet-loss and throughput. Effectively this means they require different amounts of resources when handled in a network node. This thesis covers descriptions and simulations of four different scheduling algorithms deployed in a high-speed point-to-point radio-link scenario. The different algorithms examined in this thesis are the conventional First-In-First-Out (FIFO) algorithm, the Strict Priority (SP) queuing algorithm, the Deficit Round-Robin (DRR) algorithm and finally the Deficit Weighted Round-Robin (DWRR) algorithm. Theoretical presentations of each of the algorithms are followed by simulations which exhibits the characteristics of the different algorithms. Two of the mentioned algorithms (FIFO, DRR) does not offer capabilities of differentiation between different classified data-flows, while the two remaining algorithms (SP, DWRR) does. The simulations illustrates the advantages of deployment of scheduling algorithms capable of differentiating resource allocation with respect to the different QoS requirements of multiple data-flows. The simulation results reveals that when deployed in a high-speed point-to-point link, where low complexity is emphasized, the DWRR algorithm offers the most promising performances of the examined algorithms.

In this master thesis, full-waveform inversion (FWI) was applied to a synthetic, and very complex, geological structure containing a salt body. The main objective was to evaluate the capabilities of FWI to estimate velocities in this context, and more specially below the salt. Seismic depth imaging is now the preferred seismic imaging tool for today's most challenging exploration projects. Seismic depth imaging problem usually requires the definition of a smooth background velocity model before determining the short wavelength component of the structure by pre-stack depth migration. It is well established that success of pre-stack depth migration in complex geological media strongly depends from the definition of the background velocity model. Standard tools for building velocity models generally fail to reconstruct the correct sub-salt velocities. Sub-salt imaging is a very challenging problem and a lot of resources are spent trying to solve this problem, since salt bodies in the sub-surface are known to be very good hydrocarbon traps. In this master thesis, the work have been performed on a modified version of the 2004 BP velocity benchmark model. This model represents a very interesting salt context, where conventional imaging methods can not provide any good results. After describing the seismic inversion problem, and the FWI theory and code used in this work, the application to the 2004 BP benchmark model is described. FWI was first applied to the synthetic data using a starting model derived by smoothing the true velocity model. This is an easy way to ensure an adequate starting model, as the method is very dependent on a good starting model. In the inversion process 17 frequency components were used, ranging between 1 and 15 Hz. This resulted in a velocity model that accurately recovered both the salt body and the sub-salt velocities. The average deviation between the true and estimated sub-salt velocities was found to be approximately 6 %. A more realistic starting model was then derived using first-arrival traveltime tomography, a well known method for obtaining velocity models. FWI was applied to this starting model, and the result was also positive when using this starting model. The salt body was well delineated, whereas the sub-salt velocities were generally more inaccurate than for the previous application. The sub-salt velocity difference was increased to roughly 10 %. However, if more effort had been spent on reconstructing a more accurate starting model, the results might have improved. When fewer frequency components are used in the inversion, the result declined. A test using only 6 frequency components showed that the final reconstructed model suffered from a lack of recovered wavenumbers, especially at the deeper and more complex parts of the model. In such a complex medium as the 2004 BP benchmark model, it is hence necessary to introduce wavenumbers by including a sufficient number of frequency components in the inversion process. Other tests that were conducted showed that, in this particular case, the non-linearity of the inversion problem increased with higher frequencies, and was reduced by larger offset ranges included in the seismic data. The inversion is hence sensitive to the starting frequency as well as the starting model. The results in this master thesis demonstrate that FWI has a great potential in reconstructing sub-salt velocities in salt media. For the future, both applying the method to real data from a salt basin area, and develop a migration tool and test the effect of FWI on a migrated image, are interesting challenges.

Over the last few years the ship traffic in polar areas have been steadily increasing, especially north of Norway. This is largely due to the growing activity in that area and in northern Russia, mainly from oil and gas exploration and production. All indications suggest that this will continue into the foreseeable future. In this report a satellite based system for broadband communications to the area north of 65 northern latitude is discussed. Possible carrier frequency configurations and their propagation properties is analysed, and it is found that Ka-band, 20/30GHz, will give best performance. Various satellite orbits are then discussed, and a constellation that give continueous coverage and allow for easy handover is designed. It consists of four satellites in Molniya orbits with an eccentricity of approximately 0.72. Each satellite is then operational and quasi-stationary for six hours of every orbit, with two satellites above the coverage area at any time. Solutions for the satellite antennas are considered, and link budgets are presented. Active phased arrays are found to provide the best performance. A total uplink capacity of 1.6 Gbps is teoretically possible with a user terminal output power of 100W, but it is not deemed realizable. Instead a configuration with a total capacity on both uplink and downlink of about 1 Gbps is suggested. At the end of the report a range of issues, related to the realization of the satellite system, requiring future attention is summarized and briefly discussed.

PlaneRay, an acoustic underwater propagation model based on ray tracing and plane- wave reection coecients, has been used to model wave propagation in shallow water environments. The program has emulated a seismic vessel towing a source-receiver setup and represented the shape of the sea oor as time responses plotted for a xed source- receiver distance over an increasing source range. The eects of the water's sound speed prole and the sea oor's topography have been studied in detail, and the program's robustness and capability to handle these problems have been discussed and found sat- isfying.

Wireless communication systems suffer a great deal from the inherent nonlinear nature of power amplifiers. Effects such as signal distortion and spectral broadening can seriously degrade the performance of both the system at hand and neighboring ones. These problems need to be dealt with, both in the sense of mitigating them and observing the implications caused. For the case of problem mitigation, some sort of linearization of the power amplifier is needed, while simulation tools provide a way of observing the implications. Data from three different power amplifiers are used in the experiments carried out in this study. All three sets use 16-QAM modulation and have a relatively narrow bandwidth of about 190 kHz. Digital predistortion is a well known technique for linearization of power amplifiers. An important part of this technique is the modeling of the power amplifier. In this study, two different models are investigated. Both models employ cubic splines to approximate the nonlinearity. The first model is memoryless, consisting only of the spline approximation, while the second one also accounts for memory effects by inserting a linear transversal filter subsequent to the spline approximation. The models have been tested and evaluated, proving the model with memory effects to be the superior one. However, this superiority is by no means general. Radio communication simulation tools need accurate models of power amplifiers to achieve high performance. This area of modeling power amplifiers is called system-level modeling. Two empirical models have been investigated in this study, both applicable as system-level models. Both models exploit physically-based memory effects related to the RF frequency response, self-heating and the biasing network to obtain highly accurate results. The models differ only in the basis functions employed when approximating nonlinearities; the first model employs polynomials while the second one employs cubic splines. The two models have been tested and evaluated, both performing at a very high level. The empirical models presented have many degrees of freedom, and it was discovered that the optimal structure of the model depended on the power amplifier it was set to characterize. Hence, the optimal structures of the models were found not to be general. The results obtained are evaluated both in time- and frequency-domain. Problems and limitations concerning both the models themselves and the model coefficient estimation procedures are analyzed and discussed along with proposals for further work.

In this master thesis a software, MapMonit, that use real measurement data as a basis to calculate noise maps was studied. The project focus on noise from roads. Simulations in MapMonit based on measurements were compared with control measurements and simulations of existing noise computation software. The software used for comparison was CadnaA. The project started with measurements of road traffic noise with four microphone heights at four distances that would be used as input to the software called MapMonit. Since this was the first time the software ever got tested with real measurements, the first test site was chosen to be as simple as possible with a long, straight road and surrounding flat fields. The microphone distances from the road edge were 5 m, 10 m, 20 m and 100 m with microphone heights 0.4 m, 1.5 m, 2 m and 4 m at each of the distances. A grid of control microphones were positioned in the vicinity from 10 m to 180 m from the road edge. At distances 5 m to 20 m for microphone heights 1.5 m to 4 m, the results turned out to be very good. The difference between the A-weighted levels of MapMonit simulations and the control measurements was generally less than 1 dB for all control positions. Compared to CadnaA, the two simulated levels were very similar for propagation paths up to 100 m with differences below 1.4 dB. At control distances over 170 m, the difference was very high, up to 5.3 dB, with MapMonit simulating the highest values. A complicated test site in the vicinity of a noise screen were also studied. The reference microphones for input to MapMonit were placed in front, above and behind the screen, and one behind a garage also on the quiet side. The control measurements were placed around the neighborhood at the quiet side of the noise screen. Due to a flaw with the MapMonit software implementation, the results were presented with flat topography. The reference microphone in front of and above the noise screen gave satisfying results, with differences less than 2 dB at all control positions except for a position just behind a garage. Obstacles along the propagation path included both a noise screen and buildings. Choosing the microphone mounted just above the noise screen, the difference between the A-weighted levels of CadnaA and MapMonit was less than 1 dB for all positions except the one behind the garage.