Physical Layer DVB Transmission Optimisation (PLUTO)

DVB, DAB, Diversity, CDD, Plut

Coverage optimization and power reduction in SFN using simulated annealing

An approach that predicts the propagation, models the terrestrial receivers and optimizes the performance of single frequency networks (SFN) for digital video broadcasting in terms of the final coverage achieved over any geographical region, enhancing the most populated areas, is proposed in this paper. The effective coverage improvement and thus, the self-interference reduction in the SFN is accomplished by optimizing the internal static delays, sector antenna gain, and both azimuth and elevation orientation for every transmitter within the network using the heuristic simulated annealing (SA) algorithm. Decimation and elevation filtering techniques have been considered and applied to reduce the computational cost of the SA-based approach, including results that demonstrate the improvements achieved. Further representative results for two SFN in different scenarios considering the effect on the final coverage of optimizing any of the transmitter parameters previously outlined or a combination of some of them are reported and discussed in order to show both, the performance of the method and how increasing gradually the complexity of the model for the transmitters leads to more realistic and accurate results.This work was supported by the Spanish Ministry of Science and Innovation under Projects TEC2008-02730 and TEC2012-33321. The work of M. Lanza and Á. L. Gutiérrez was supported by a Pre-Doctoral Grant from the University of Cantabria

Low complexity channel estimation for OFDM based satellite systems

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Modelling and and measurement analysis of the satellite MIMO radio channel

The increasing demand for terrestrial and satellite delivered digital multimedia services has precipitated the problem of spectrum scarcity in recent years. This has resulted in deployment of spectral efficient technologies such as MIMO for terrestrial systems. However, MIMO cannot be easily deployed for the satellite channel using conventional spatial multiplexing as the channel conditions here are very different from the terrestrial case, and it is often dominated by line of sight fading. Orthogonal circular polarization, which has long been used for increasing both frequency reuse and the power spectral density available to earth-bound satellite terminals, has recently been recommended for directly increasing the throughput available to such devices. Following that theme, this thesis proposes a novel dual circular polarisation multiplexing (DCPM) technique, which is aimed at the burgeoning area of throughput-hungry digital video broadcasting via satellite to handheld devices (DVB-SH) and digital video broadcast to the next generation of hand held (DVB-NGH) systems. In determining the working limits of DCPM, a series of measurement campaigns have been performed, from which extensive dual circular polarised land mobile satellite (LMS) channel data has been derived. Using the newly available channel data and with the aid of statistical channel modelling tools found in literature, a new dual circular polarised LMS MIMO channel model has been developed. This model, in contrast with previously available LMS MIMO channel models, is simpler to implement since it uses a distinct state-based empirical-stochastic approach. The model has been found to be robust and it easily lends itself to rapid implementation for system level MIMO and DCPM analysis. Finally, by way of bit error rate (BER) analysis in different channel fading conditions, it has been determined when best to implement polarisation multiplexing or conventional . MIMO techniques for DVB-type land mobile receivers. It is recommended that DCPM be used when the channel in predominantly Ricean, with eo-polar channel Rice factors and sub-channel cross correlation values greater than 1dB and 0.40 respectively. The recommendations provided by this research are valuable contributions, which may help shape the evolving DVB-NGH standardisation process.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

SRML: Space Radio Machine Learning

Space-based communications systems to be employed by future artificial satellites, or spacecraft during exploration missions, can potentially benefit from software-defined radio adaptation capabilities. Multiple communication requirements could potentially compete for radio resources, whose availability of which may vary during the spacecraft\u27s operational life span. Electronic components are prone to failure, and new instructions will eventually be received through software updates. Consequently, these changes may require a whole new set of near-optimal combination of parameters to be derived on-the-fly without instantaneous human interaction or even without a human in-the-loop. Thus, achieving a sufficiently set of radio parameters can be challenging, especially when the communication channels change dynamically due to orbital dynamics as well as atmospheric and space weather-related impairments. This dissertation presents an analysis and discussion regarding novel algorithms proposed in order to enable a cognition control layer for adaptive communication systems operating in space using an architecture that merges machine learning techniques employing wireless communication principles. The proposed cognitive engine proof-of-concept reasons over time through an efficient accumulated learning process. An implementation of the conceptual design is expected to be delivered to the SDR system located on the International Space Station as part of an experimental program. To support the proposed cognitive engine algorithm development, more realistic satellite-based communications channels are proposed along with rain attenuation synthesizers for LEO orbits, channel state detection algorithms, and multipath coefficients function of the reflector\u27s electrical characteristics. The achieved performance of the proposed solutions are compared with the state-of-the-art, and novel performance benchmarks are provided for future research to reference

Frequency-domain receiver design for doubly-selective channels

This work is devoted to the broadband wireless transmission techniques, which are serious candidates to be implemented in future broadband wireless and cellular systems, aiming at providing high and reliable data transmission and concomitantly high mobility. In order to cope with doubly-selective channels, receiver structures based on OFDM and SC-FDE block transmission techniques, are proposed, which allow cost-effective implementations, using FFT-based signal processing. The first subject to be addressed is the impact of the number of multipath components, and the diversity order, on the asymptotic performance of OFDM and SC-FDE, in uncoded and for different channel coding schemes. The obtained results show that the number of relevant separable multipath components is a key element that influences the performance of OFDM and SC-FDE schemes. Then, the improved estimation and detection performance of OFDM-based broadcasting systems, is introduced employing SFN (Single Frequency Network) operation. An initial coarse channel is obtained with resort to low-power training sequences estimation, and an iterative receiver with joint detection and channel estimation is presented. The achieved results have shown very good performance, close to that with perfect channel estimation. The next topic is related to SFN systems, devoting special attention to time-distortion effects inherent to these networks. Typically, the SFN broadcast wireless systems employ OFDM schemes to cope with severely time-dispersive channels. However, frequency errors, due to CFO, compromises the orthogonality between subcarriers. As an alternative approach, the possibility of using SC-FDE schemes (characterized by reduced envelope fluctuations and higher robustness to carrier frequency errors) is evaluated, and a technique, employing joint CFO estimation and compensation over the severe time-distortion effects, is proposed. Finally, broadband mobile wireless systems, in which the relative motion between the transmitter and receiver induces Doppler shift which is different or each propagation path, is considered, depending on the angle of incidence of that path in relation to the direction of travel. This represents a severe impairment in wireless digital communications systems, since that multipath propagation combined with the Doppler effects, lead to drastic and unpredictable fluctuations of the envelope of the received signal, severely affecting the detection performance. The channel variations due this effect are very difficult to estimate and compensate. In this work we propose a set of SC-FDE iterative receivers implementing efficient estimation and tracking techniques. The performance results show that the proposed receivers have very good performance, even in the presence of significant Doppler spread between the different groups of multipath components