DME/TACAN Multipath Impact on GNSS L5/E5a Airborne Receivers Part II: Air–Ground Channel Model and Application

This article is the second part of a two-part article addressing the distance measuring equipment/tactical air navigation (DME/TACAN) multipath impact on the future airborne global navigation satellite system L5/E5a receivers. Part I developed the analytical carrier-to-noise-ratio degradation model due to DME/TACAN considering multipath in the presence of a temporal blanker. Part II introduces an air–ground channel model, which is wideband, geometry-based, and combines deterministic and statistical parts. The model includes an Okumura-Hata path loss for computing the scatterer illumination, an analytical formula for the additional delay, and the mathematical expression of the scattered power. Given the very large number of illuminated scatterers to be considered for an air–ground scenario, a statistical simplification of the physical optics approach is introduced to simplify the derivation of the scattered powers. The propagation channel model and the mathematical model of the carrier-to-noise-ratio degradation are applied to two low-altitude operational hot spots, JALTO (Pennsylvania, United States) and TIXAK (Frankfurt, Germany). It is shown that only a few illuminated scatterers generate a scattered power above the blanking threshold and that the additional carrier-to-noise-ratio degradation generated by the DME/TACAN multipath is only smaller than 0.52 dB.