Cognitive interference avoidance 4th generation GPS with unjammable radio links
Global Positioning Systems (GPS) have revolutionized the way people in every society are able to locate themselves in a defined region (spatial location) and to guide themselves with the help of the system to a particular place (personal navigation). The need for a positioning system that delivers high spatial location precision under constraining scenarios, such as low SNR and hi-jacking attempts, is essential for developing future technologies. This can be achieved by transmitting a sequence with high autocorrelation properties in combination with other communication algorithms utilized as protocol tools. The Zadoff-Chu sequence encompasses excellent autocorrelation properties which can be used for phase estimation between a phase-shifted sequence and a non-phase-shifted sequence (root sequence). In addition to scenarios where a multipath fading channel affects the transmitted signal, water-filling, can be used as a protocol tool for opportunistic transmission and interference avoidance whenever the signal receives a hi-jacking attempt. The transmission of a Zadoff-Chu sequence in multiple OFDM symbols combined with water-filling, which optimally defines resource elements (subcarriers ) and efficiently allocates signal power to each of them, provides an excellent system for distance estimation between an antenna (eNodeB ) and a defined target (UE). The distance estimation between multiple eNodeBs and a defined target is provided to a Cramer-Rao Bound algorithm, and to the estimation algorithm outlined in the appendices section to convert from range estimate to (X,Y) position in order to provide the estimated spatial location of the target. Simulation results show accurate spatial location of the target in different scenarios, which include the transmission of signals through multipath fading channels and an interferer attempting to jam the transmitted signal. This opens up the doors to implement this system for projects that require precise positioning, reliability and embedded security such as terrestrial non-tripulated vehicles.