This paper deals with the effect of inserting random watermarks to the spreading code of GNSS signals. After discussing the effect of watermark insertion on time-to-first-fix, we show that the effect of watermark insertion can be approximated as an interference with normal distribution, whose parameters depend on the time delay and the insert position. From this, we give a condition on the insert positions where the maximum variance of correlations becomes minimized. We also give how to achieve the condition for some cases. To the best of our knowledge, this is the first attempt to minimize the effect on auto-correlation of GNSS signals caused by watermark insertion. All the results can be applied to the design of signal-level authentication scheme and punctured encrypted spreading code.

Keywords: WDSSS, watermarking, insert position

Speaker Min Kyu Song*