Assessing spoofing impact on GNSS receivers: Carrier-to-noise density ratio ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si533.svg" display="inline" id="d1e243"> <mml:mrow> <mml:mi>C</mml:mi> <mml:mo>/</mml:mo> <mml:msub> <mml:m

In the context of GNSS signal processing, the carrier-to-noise density ratio ( C / N 0 ) is a powerful metric for evaluating GNSS performance, analyzing interference effects, and monitoring reception quality. Although the modeling of C / N 0 in the presence of interference has been extensively discussed in the literature, the specific impact of spoofing remains unexplored. In fact, due to the similar structure between authentic and spoofed signals, the latter directly interferes with the true signal and cannot be considered as an equivalent additional and independent noise source. This paper investigates the impact of spoofing on both true and estimated C / N 0 and proposes analytical expressions for their biases in the presence of spoofing. It reveals situations where the correlator output becomes non-ergodic, inducing divergence between the true and estimated values, as well as significant C / N 0 degradation. Additionally, there is a high dependence on the receiver architecture (estimation method) and spoofing geometry. Finally, beyond GNSS spoofing applications, this study highlights the effect of non-ergodicity on estimation and underscores the importance of studying estimation under non-ergodic conditions. • Derives complete expressions for correlator output under spoofing. • Formalizes the definition of estimated C / N 0 in GNSS receivers. • Provides analytical expressions for C / N 0 estimation bias under spoofing. • Reveals the threat posed by induced-multipath spoofing situations. • Highlights the impact of non-ergodicity on signal estimation.