In ray-tracing-based propagation modelling, the electromagnetic field at the receiver is obtained by coherent summation of the fields of multipath components. It is therefore crucial to accurately calculate the phase of the electromagnetic field of each ray. In practice, when preparing the plan of the environment for ray tracing simulation, the lateral positions of the walls may not be included accurately in the database. This alters the phases of the fields as well as the delays of arrival of multipath components which may consequently lead to less accurate results. In this study, the sensitivity of ray tracing results to this type of geometrical inaccuracy is investigated through the propagation of uncertainty approach. The lateral wall positions are assumed random variables and the statistical moments of the received power and rms delay spread are analytically derived and confirmed. A reliability measure is then defined to explore the impact of the geometrical inaccuracy on the ray tracing results. Numerical results are presented for a typical indoor environment at 2.44 GHz. It is observed that the rms delay spread has negligible sensitivity to lateral wall position uncertainty whereas the received power shows more sensitivity with errors of the order of a few dB.

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