Fundamentals of modulation schemes for low-budget LEO satellites

Abstract

Educational and academic spaceflight using low earth orbit low-budget satellites (LEO) has been becoming more and more popular during the last years.<br />To permit continuous data transmission during the satellite's way around the globe, ground networks have been established to interconnect ground stations all over the world. Actually the most popular network is the Global Educational Network for Satellite Operations (GENSO). To optimize allocation of ground stations to satellites, an estimate of transmission qualitity is necessary. To investigate the quality of the data link and the influency of various parameters, the launch of a special measurement satellite is planned. In this thesis a study of different modulation schemes proposed for this measurement satellite is made.<br />An aim was to clearly work out the measures used for transmission quality comparisons, especially the bit error probability, starting from the fundamentals. The focus was on mathematically clearing up the terminology used in communications engineering without bringing it to an abstract level, which would make further investigations cumbersome. So all relevant terms and definitions usually used in communications are explained in a rather general way. These definitions and principles are then applied to investigate the proposed modulation schemes. Finally the bit error probabilities for binary and quadrature phase shift keying as well as for minimum shift keying for a specical channel model are derived. The thesis concludes with an overview about different aspects of digital communication, which can serve as a basis for further investigations.