Code Design for IOT Satellite applications

The signal broadcast by the navigation satellites is usually represented as Signal-In-Space (SIS). these signals must: Allow the user to estimate the pseudo distance user-satellite, carry some useful data, be robust to the transmission through the atmosphere and identify in a unique way the satellites. GPS and Galileo use CDMA (Code Division Multiple Access) to identify the satellites without ambiguity. each satellite transmits a different code (ranging codes), using the same carrier frequencies, without time division. Codes are mutually orthogonal in order to permit to the receiver to separate the signal of the satellite of interest from the others and the data signals are modulated by the ranging codes. To design of a new GNSS signal there is always a trade-off between improving performance and increasing complexity, or even between improving different performance benchmarks such as position accuracy, receiver sensitivity or the Time-To-First-Fix (TTFF). To improve performance of GNSS receivers with respect to these benchmarks adding a new signal component devoted to assist the acquisition process can be helpful. In order to generate this new component, we have to take into account various features such as the spreading modulation, the data navigation content, the channel coding or the Pseudo-Random Noise (PRN) codes. In this Thesis project our goal is to design PRN codes (Random sequences) that can be suitable for this new signal component in order to optimize performance benchmarks. Our optimization process is mainly focused on analyzing auto-correlation and cross-correlation properties of the spreading sequences and their truncated versions in order to select the best codes among them. Our target is to design a sequence that minimizes auto-correlation function side lobe as much as possible, in order to get closer to the ideal spreading sequences which are orthogonal with all of their delayed versions and with all the family codes.