Abstract
This thesis deals with the adaptation of the forward link of DVB-S2/RCS systems to mobile satellite systems providing services to nomadic vehicular satellite receiving terminals such as fast trains and maritime vessels. The work undertaken focuses on the adaptation of ACM and SNR estimation to mobile satellite environments. Error-based SNR estimation is revisited and extended to enable accurate SNR estimation in mobile satellite channels. The proposed algorithm employs un-coded DVB-S2 pilot symbols and provides improved estimation accuracy and stability in the presence of Rice fading, rain attenuation and short term shadowing events from the estimation process. The use of accurate Rice factor estimates as input to the SNR estimator is noted as a key requirement and, although Rice factor estimation in itself is outside the context of this thesis, references of candidate solutions are provided in the penultimate chapter. Adaptive Threshold Adjustment is employed to mitigate the need for fixed predefined switching thresholds in ACM. The proposed ATA algorithm builds on existing approaches and provides improved threshold stability, convergence time and overall performance through the use of conditional adjustment. Performance comparisons for both of the above algorithms are provided against algorithms found in the literature. The SNR estimator is shown to outperform a moment based estimator by up to one order of magnitude in terms of estimation MSE, depending on the Rice factor and average signal SNR. The proposed ATA algorithm is shown to improve throughput as compared to continuous threshold adjustment by up to 1.8% in static fading conditions depending on the average received Es/N0. In the presence of rain attenuation this throughput improvement rises to a maximum of 2.5% for a specific MCS, and 1.24% on average throughput. Finally, system level analyses indicate that the system throughput improvements achieved through the use of ACM in mobile satellite environments can be comparable to those already demonstrated in fixed satellite environments.