Low-cost Real-time Software Receiver for IRNSS/NavIC short broadcast messaging services

IRNSS/NavIC is one of the rapidly evolving regional satellite navigation system, developed independently by the Indian Space Research Organization (ISRO), India. At present there are six NavIC satellites (1B, 1C, 1D, 1E, 1F, 1I) transmitting signals, which are useful for finding the navigation solution i.e., position, velocity and time. Remaining two satellites (1A, 1G) are transmitting short messaging services useful for disaster management and information about potential fishing zones to the fishermen. Despite this it also facilitates to use short messaging services for the commercial applications. Of course users can define different messaging formats for different services and can transmit through these two satellites. Generally, these services can reach to the common man easily using a Low-cost NavIC receiver, capable of receiving and decoding the data from 1A satellite. The main aim of this work is to develop a software module to decode NavIC 1A messages for a NavIC Software Receiver (NavICSR), developed in MATLAB at NERTU of Osmania University. The same module is also incorporated into the Global Navigation Satellite System-Software Defined Receiver (GNSS-SDR) developed by CTTC, which works in both post-processing and real-time modes. A low-cost RTL-SDR front-end is used to receive the digitized NavIC L5 IF signal of 1A satellite. The developed messaging receiver is validated by verifying the decoded Potential Fishing Zones (PFZ) information, with the messages disseminated by Indian National Centre for Ocean Information Services (INCOIS). This receiver is useful to test and monitor the messaging services in real-time and further useful for enhancing the usage of messaging services for other commercial and civilian applications.