GPS satellite transmitted spread spectrum codes SNR modeling over the Indian subcontinent for precise positioning applications

GPS satellites transmission consists of two pseudorandom noise codes, modulated on two carriers. For position determination of a GPS receiver on the earth two parameters, satellite position and pseudo ranges of each Satellite Vehicle are to be estimated by decoding the Navigation message from each satellite which depends on the Carrier to Noise Ratio (C/N₀) at the receiver. GPS employs spread spectrum CDMA therefore the power levels of received signals play important role in design of GPS receiver. If the received power level from one SV is higher than the other then the received signal of the other satellites get masked and experiences `Near and Far´ effect hampering detection. In this paper, the received C/N₀s of all SVs are modeled over the low latitude region for accurate decoding of composite GPS signal. The modeled parameters are validated with the dual frequency GPS receiver measurements located at Andhra University College of Engineering (Latitude/Longitude 17.73⁰ N/83.32⁰ E).