Requirements Analysis of LDPC Code for C-band High Precision Wide Area Differential GNSS Applications

Jing Ke, Xiaochun Lu, Xue Wang, Xiaofei Chen

Peer Reviewed

Abstract:	This paper considers a data transmission system that uses a geostationary earth orbit (GEO) satellite data link to broadcast signal of wide area differential corrections which can provide increased accuracy to users of Global Navigation Satellite Systems (GNSS). C-band are first selected to transmit the differential data from uplink station to the GEO satellite at frequency of 6051 MHz and from the satellite to the end users at frequency of 3826 MHz, so as to avoid the overlapping situation and the interference with other signals in the conventionally used L-band. A link budget analysis is also provided to calculate the quality of the C-band transmission link in terms of carrier-power-to-noise density ratio (C/N0). The relation between C/N0 and data rate is given to suggest the measure to increase differential correction data rate and impose demand on the Forward Error Correction (FEC) techniques. As a result, the FEC scheme based on Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) code is introduced to encode the differential information, in order to overcome the C-band link budget deficiencies and derive position accuracy benefits by increasing correction data rate. Finally, the feasibility of C-band frequencies is investigated by taking account of the phase lock loop (PLL) and delay lock loop (DLL) thermal noise jitter performance with respect to tracking loop of user terminals. The results show that stable PLL and DLL can be achieved at C-band, which is therefore acceptable for user terminals. In addition, the possibility of QC-LDPC code to increase differential data rate in C-band is also assessed by performance comparison with the well-known convolutional code used in Wide Area Augmentation System (WAAS), and it is shown that QC-LDPC code outperforms the convolutional code in aspect of lower decoding threshold and the differential data can be transmitted up to 1000 bits per second (bps).
Published in:	Proceedings of the 2015 International Technical Meeting of The Institute of Navigation January 26 - 28, 2015 Laguna Cliffs Marriott Dana Point, California
Pages:	179 - 184
Cite this article:	Ke, Jing, Lu, Xiaochun, Wang, Xue, Chen, Xiaofei, "Requirements Analysis of LDPC Code for C-band High Precision Wide Area Differential GNSS Applications," Proceedings of the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, California, January 2015, pp. 179-184.
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