Analysis of Acquisition Algorithms Using IRNSS Data

Increase in the new Global/Regional Navigation Satellite Systems (GNSS/RNSS) has lead to the design of software receivers for the research and development purpose. GNSS Satellites transmit the navigation signals which contain the information about satellites position and health. The navigation data is modulated using pseudo random noise (PRN) signals and transmitted on air using Radio Frequency(RF) signals. A typical GNSS/RNSS receiver contains important blocks viz. RF fornt end block, signal processing block and navigation data processing block. RF front end receives signal and down converts to Intermediate frequency(IF) and gives it to ADC. Signal processing block receives digitised signal form ADC at IF with a suitable sampling frequency and processes further to remove the moduation and get the navigation data. The last block extracts satellite position information from navigation data. The first stage of the signal procesing block is acquisition where the the frequency value of the actual carrier and code phase value of the pseudorandom noise sequence are extrated which are the prime inputs for further blocks of signal processing. Hence it is very impotrtant to understand the acquisition process while designing a receiver. This paper discusses the three basic methods of acquisition along with its mathematical background using Real IF data for analysis. The data is collected by IRNSS-UR (IRNSS- User Receiver) hardware installed at IRNSS laboratory in Jain University Campus by ISRO (Indian Space Research Organization) and performs the analysis in detail. The results of all three methods are compared and are found very near to the expected values. This work provides a very good reference for an aspirant or a researcher who wishes to work on GNSS receivers.