ISRO introduced L1 navigation band from NVS-01 satellite for enhanced interoperability and compatibility with other GNSS operators. To evade the potential denial of code and structures indigenous development of signal structure was initiated. A completely new L1 signal structure developed is mentioned below. This novel signal structure includes indigenously developed LDPC code and BCH codes. The performance of channel codes are better or comparable with that from the existing GNSS signals. Patents have been granted for Z4 sequence code, LDPC code and BCH Code.

L1-band Frame structure

No Parameters Scheme Finalized
1 Ranging code
  • Primary
  • Overlay
Z4 Sequence *
2 Frame Format 18 sec Master Frame
SF-1:52sym, SF-2:1200sym,
3 Channel Code
  • SF-1
  • SF-2/SF-3
1/2 Rate LDPC*
4 Navigation Parameters Primary Bits:576
5 Modulation Scheme:SBOC*
* Patented