Benchmarking GPS L1C Decoding in Harsh Environmental Conditions

Radu-Andrei Cioaca, Andrea Emmanuele, Luca Siniscalco

Peer Reviewed

Abstract:	This paper investigates the decoding performance of the GPS L1C data component, focusing on its forward error correction (FEC) schemes and interleaving strategies across the three subframes. Using simulations under Additive White Gaussian Noise (AWGN), controlled fading, and in realistic Land Mobile Satellite (LMS) channel conditions, we evaluate both BCH and LDPC decoding approaches, including their standard implementations and several practical variants. For BCH coded subframe 1, hard- and soft-decision decoding are analyzed using a maximum likelihood decoder based on a precomputed frame dictionary. For LDPC coded subframes 2 and 3, decoding using the full Sum-Product Algorithm and the Min-Sum approximation are investigated, through a comparative analysis of their performance and complexity. Results in terms of Bit Error Rate (BER) or Frame Error Rate (FER) show that L1C signal design and in particular their FEC schemes provide a strong resilience in challenging environments, with soft-decision decoding offering superior performance than the hard one, and full implementation performing better than the approximated ones. Besides, other relevant metrics like the number of iterations performed by the decoders complete the full trade-off, when selecting a decoder variant. To address LDPC’s computational demands, optimization strategies are presented such as message pre-aggregation and exploitation of the LDPC matrix sparsity. These methods, on one side, significantly reduce decoding complexity while presenting a minimal impact on the error-correcting capability level. Overall, the findings confirm L1C data component robustness and efficiency in AWGN and harsh environmental conditions, positioning it as a benchmark signal for future GNSS application. The proposed optimizations finally pave the way for practical real-time receiver implementations.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	1829 - 1840
Cite this article:	Cioaca, Radu-Andrei, Emmanuele, Andrea, Siniscalco, Luca, "Benchmarking GPS L1C Decoding in Harsh Environmental Conditions," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 1829-1840. https://doi.org/10.33012/2025.20417
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