Design and Implementation of Receivers and Measurement Equipment for Next-Generation Satellite Networks

Abstract

The ever-increasing demand for high data rate satellite services is necessitated by the vast number of new or planned services involving multimedia transmission or other data rate-intensive applications in the upcoming 5G era; the spectrum scarcity problem (congestion of the lower frequency bands such as the C and the Ku bands) naturally leads to the use of higher frequencies such as those at Ka- and Q-band. Signal propagation at Ka-band frequencies and above is, nevertheless, highly impaired by the various atmospheric phenomena, upping the ante on system design. The end-user Quality of Service (QoS) is to great extent dictated by the system’s resilience to the various propagation effects; such effects could - unless carefully addressed, jeopardize the throughput and/or the link availability potentially resulting into severe degradation of the overall system performance. In the past, merely allocating a fade margin for earth-space systems operating in lower frequency bands such as e.g. C and Ku was the common practice in order to compensate for the signal fading due to the various atmospheric phenomena; nonetheless, when considering the signal propagation at higher frequency bands, the sole use of a conventional fade margin is generally an insufficient counter-measure since signal fading could be in excess of 20-30 dB for a non-negligible fraction of time. In order to compensate for the atmospheric attenuation, Propagation Impairment Mitigation Techniques (PIMTs) are employed, also commonly referred to as Fading Mitigation Techniques (FMTs); they are vital in order to meet the required Quality of Service - QoS) imposed by the services, keeping at same time the resource usage at an optimal level. To enable the design of High Throughput Satellite (HTS) systems with FMTs, accurate propagation modelling is of utmost importance; compiling new propagation models is nevertheless a very challenging task, as it has to be supported by long-term experimental campaigns. Furthermore, the various parameters can vary across different geographic/climatic regions and hence the results cannot be easily generalized. Considering the imminent migration of satellite services to the Ka- and Q- bands, a payload dedicated to propagation measurements in these bands has become available from the Alphasat satellite under the coordination of the European Space Agency (ESA). This has strongly motivated the formation of many measurement campaigns across Europe in an effort to enhance the scientific databases with new, more reliable propagation data. In the framework of the present thesis, an experimental propagation campaign has been initiated at the National Technical University of Athens (NTUA) in Greece. Six beacon receivers have been designed and installed, four of them targeting the Alphasat’s Ka-band and Q-band beacons while one of them targets Arabsat’s BADR5 Ku-band beacon and Eutelsat’s KaSAT’s beacon. The receivers make use of the relatively new Software Defined Radio (SDR) paradigm and besides the beacon measurements themselves, additional noise measurements are performed in order to supplement the campaign. Apart from an elaborate description on the receiver’s architecture, design choices and principles of operation, the whole obtained measurement dataset has been processed to allow for a comprehensive statistical evaluation. The thesis begins with a brief outline of the fundamental propagation effects along with possible FMTs and measurement techniques; it continues with a detailed presentation on the design and deployment of new beacon receivers in Attica, Greece. An evaluation of the first order and second order (fade dynamics) statistics based on the obtained measurement dataset from all available receivers is conducted; after examining the performance of the various FMTs using the actual attenuation timeseries statistical evidence is provided for the efficiency of site, time and orbital diversity techniques; an investigation on the potential frequency scaling across Ku/Ka/Q bands is also considered. Finally, scintillation analysis is performed followed by an evaluation of a large-scale site diversity scenario across Greece and the UK using the actual, concurrent measurements at each location. To the best of the author’s knowledge, this work constitutes the most comprehensive work regarding actual satellite propagation measurements in Greece and the Southern Mediterranean area available to date, especially at so high frequency bands such as Ka- and Q-band. Up until now, any estimation regarding the propagation phenomena in this region relied almost exclusively on statistical/physical-mathematical models or time series synthesizers based on inference and extrapolation from measurements performed in other regions. It is now possible to test systems, techniques and models using actual measurement data.