Generation and Analyzation of Spectral Density for IRNSS SPS PRN Code

Abstract

The Indian Regional Navigational Satellite System (IRNSS) satellites provide two services namely standard Positioning Service (SPS) and Restricted Service (RS). L5 and S are the frequency bands from which both the services are utilized. To transmit the navigational information in SPS downlink gold codes are used. Most of the GNSS will work on the principle of CDMA where PRN sequences are the heart of the system. In this paper Pseudo Random Noise (PRN) codes are generated for an SPS signal which is called as SPS PRN code. A CDMA signal is generated using these sequences by using BPSK modulation. The analysis is done based on a time domain signal basis and is used to derive the Power Spectral Density of a CDMA signal. The spectrum analyser optimal operating conditions are observed by using the analytical results. To generate these codes, the polynomials Gl & G2 are selected, which are similar to ones used by GPS C/ A signal and are as per the preconditions provided in IRNSS_SPS_ICD_June 2014. This paper also covers the process of selection of codes to be computed and the properties of PN-sequence are also analysed. The Xilinx ISE test system and Mat lab apparatus were used for the simulation of SPS PRN codes and additionally the implementation of PRN code is done on FPGA hardware wherein positive results have been obtained. These obtained simulated test results are within the theoretical limits.