In order to propose a solution for the indoor positioning question, several tests with the repealite-based (similar to Pseudolites and repeaters) system have been carried out. This system uses a single Global Navigation Satellite System signal transmitted by all the indoor antennas. These signals may interfere with the satellite ones outdoors. Hence, the noise level at the outdoor receiver will be higher and the error range larger. To avoid these effects, new codes called Indoor-Modified Binary Offset Carrier codes that are capable of reducing interference with outdoor signals are generated. To analyse the performance of these codes, we carry out a theoretical expression of cross-correlation functions. Then the deployment of the repealite based system in a typical building is simulated. The goal of this step is to compare the interference performance of the new code with the one already used (Gold codes for GPS band and maximal sequence for Glonass one). A specific interest is given to the spectral interference when adding the new signal's spectrum in the considered frequency band