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.

When new transistor technology is used in a microcontroller design, the transistors become smaller. They cannot withstand the same voltages as older technology, because of their size. The automotive industry still uses 5V as a standard voltage, and the automotive industry is a major costumer for microcontroller companies. The microcontroller must therefore be able to use5V. This must be done without the need of external voltage regulator. To still be a supplier to the automotive industry, the AVR needs to be able to withstand voltages up to 5.5V. The main problem with the new transistor technology is the leakage currents. Traditionally, the CMOS devices have used power only when during switching of logical levels. This is no longer true, since the leakage currents have become so large. When using new transistor technology, the dynamic power usage will be reduced, but the total power usage will be increased, if nothing is done to prevent it. One solution to this is to make a multiple power domain microcontroller. The idea is that one power domain can withstand voltages up to 5.5V. The microcontroller then uses an internal voltage regulator to scale down the voltage to a suitable level. The low voltage area will then have a suitable voltage level, which reduces both the dynamic- and leakage power usage. The different voltage domains uses different clock sources, so communicating between them requires both level shifters to deal with the different voltage levels, and synchronization logic to prevent metastability. This assignment uses two voltage domains, VIO and VCORE. Since voltage regulators are quite inefficient, it is most efficient to use only two domains. The VCORE domain contains most of the digital logic of the microcontroller, such as the CPU, SRAM and timers. This domain uses a high-speed clock source, and a VCORE data bus to communicate between each other. To communicate with the VIO domain, the data bus is connected to the VIO data bus through an asynchronous communication scheme block. This is because the VIO domain uses a low speed clock source. The usage of individual clock sources prevents clock skew problems that may occur when passing level shifters, and there is power saving by using only a low speed clock source on the VIO domain. The VIO domain contains the Power Management Unit (PMU). The PMU shall control the power usage of the microcontroller. During active mode, the PMU can set unused modules in sleep mode, or shut them completely off. Most of the power savings are during sleep mode though. This is because a microcontroller such as the AVR spends most of the time in sleep mode. To reduce the power usage in sleep mode, the leakage currents needs to be reduced. The best way of doing so is to disconnect the power from the circuits. If the voltage regulator is disconnected, and all the inputs are set to high impedance, the VCORE domain is completely disconnected from the power, and uses absolutely no power. An asynchronous wake up circuit is designed to make it possible to wake up the microcontroller from a sleep mode without the usage of synchronized digital logic. Then the low frequency oscillator can be turned off, and even more power is saved. The major disadvantage of the multiple power domain solution is the start up time from a sleep mode. If the power to the low voltage area is disconnected, the start up requires that all the capacitors become charged before the chip can start running again. The oscillator is shut off, and it takes time to stabilize the oscillator. Especially since the oscillator requires some stability in the voltage, and the voltage may not stable until the capacitors are charged. Simulations shows that the multiple power domain solution has great potential of power saving. The proposed asynchronous wake up circuit uses only 1.2275nA. This is significantly smaller than the AVR uses in the deepest sleep mode today. To get a secure microcontroller, a reset circuit has to be on to be able to reset the AVR if necessary. The power usage of the reset circuit used today is confidential Atmel information, and cannot be published in this assignment. By looking at the data sheet of a pico power circuit of the AVR, the ATmega329p, one can see that in the deepest sleep mode, the microcontroller uses 40nA at 1.8V. By assuming that the reset circuit does not use more that half of this current, the total amount of power that saved during a sleep mode by using the multiple power domain solution is about 47%.

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.

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.

In this report a phenomenological characterization technique of received bottom echoes has been developed and studied, to evaluate the potential of locating typical sandeel grounds. Data from a calibrated multi--frequency echosounder collected during a Survey Methods for Abundance Estimation of Sandeel (Ammodytes marinus) Stocks (SMASSC) survey in the sandeel fishing grounds of "Vestbanken" and "Elbow Spit North", were processed with developed scripts in Matlab to extract first received bottom echo parameters. Together with Simrad SEABEC results and sandeel samples, possible distinctive parameters were found for what could be sandeel grounds. However, ambiguities caused by ping to ping fluctuations and complex behavior of the sandeel species make the characterization difficult. Many of the calculated echo parameters showed possible discrimination power for a future multi-variate analysis.

Wireless data networks have seen rapid growth and deployment in the recent years, replacing traditional wired data networks. WesternGeco is currently using a traditional wired data network in the land seismic operations to connect the Head Vibrator with the Recording Truck. The thesis provides a survey of the most important wireless data network technologies available. A comparison between them is done in order to determine the best suited for WesternGeco’s communication mechanism. The study has lead to the conclusion that IEEE 802.11g is the most suited technology. Through the use of high gain antennas, modification of MAC layer parameters and the proper channel allocation, the suggested solution is capable of responding what WesternGeco needs.