Introduction: Satellite navigation systems are widely used for today's high accuracy applications demanding the most accurate ranging information obtainable, which is the carrier phase observable. Before the carrier phase observable can be utilized as a range information its inherent integer cycle ambiguity must be resolved. Unfortunately, high dynamics, shadowing and multipath may cause cycle-slips, i.e. jumps of the carrier phase observable by an integer multiple of wavelengths. Any cycle-slip if remained undetected would deteriorate the high ranging and positioning accuracy. Proposal: The objective of this Master Thesis is to design novel algorithms for cycle-slip detector, which must be implemented in a real-time algorithm to detect the cycle-slips for multi-frequency GNSS signals. Moreover, the detector must work either with GPS and Galileo satellite constellations. An efficient validation must be done, also including simulations to ensure the reliability of the entire algorithm.