A novel amplify-and-forward relay channel model for mobile-to-mobile fading channels under line-of-sight conditions

Mobile-to-mobile (M2M) fading channels in cooperative networks can efficiently be modeled using the multiple scattering concept. In this paper, we propose a new second-order scattering channel model for M2M fading channels in amplify-and-forward relay links under line-of-sight (LOS) conditions, where the received signal comprises only of the single and double scattered components. In the proposed model, LOS components exist in the direct link between the source mobile station (SMS) and the destination mobile station (DMS) as well as the link via the mobile relay (MR). Analytical expressions are derived for the probability density function (PDF) of the envelope and phase of M2M fading channels. It is shown mathematically that the proposed model includes as special cases double Rayleigh, double Rice, single-LOS double-scattering (SLDS), non-line-of-site (NLOS) second-order scattering (NLSS), and single-LOS second-order scattering (SLSS) processes. The validity of all theoretical results is confirmed by simulations. Our novel M2M channel model is important for the investigation of the overall system performance in different M2M fading environments under LOS conditions.