Optimal Combination of Galileo Inter-Frequencies

There are four different frequencies in Galileo system, which can form more combinations than that of GPS. Therefore, it is worth, not only theoretically but also practically, to find the best or at least good combination for fast positioning. In this paper we first introduce the criteria for optimally combining the four frequencies based on 5 kinds of cost functions or constraints, then solve the correspondent coefficients for combinations. At last, we propose an algorithm for ambiguity resolution using optimally combined observables.