The Spreading and Overlay Codes for the L1C Signal

Joseph J. Rushanan

Peer Reviewed

Abstract: We describe the rationale and construction of the family of L1C spreading codes and the associated family of overlay codes. The length-10230 spreading codes comprise 210 pilot/data sequence pairs. The codes are perfectly balanced and exhibit good even and odd auto- and crosscorrelation. They are constructed using prime-length Weil codes: selected length-10223 Weil-codes were padded with a fixed 7-bit pad. A search over all Weil codes and insertion points yielded a set of 739 codes from which the final set of 420 codes was chosen. Two separate families of codes were optimized based on modulation scheme (BOC(1,1) and MBOC). The length-1800 overlay codes are truncated linear feedback shift register sequences of length 2047, including both m-sequences and Gold sequences. Besides full period even auto- and cross-correlation, the overlay code search considered the correlation when a small subsequence (100 or 200 symbols) is correlated against the full code.
Published in: NAVIGATION: Journal of the Institute of Navigation, Volume 54, Number 1
Pages: 43 - 51
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