Channel Models for Mobile-to-Mobile Cooperative Communication Systems: A State of the Art Review

This article provides a tutorial survey on channel models for mobile-to-mobile (M2M) cooperative communication systems. The spotlight is on nongeometrical stochastic channel models assuming non-line-of-sight (NLOS) and line-of-sight (LOS) propagation conditions. Furthermore, the studied systems range from very simple configurations, such as a single relay dual-hop arrangement with no direct link between the source mobile station and the destination mobile station, to quite demanding situations characterized by dual-hop multirelay configurations, where the direct link is unobstructed. It has been shown that M2M cooperative channels are strongly dependent on the systems´ topology. They can exhibit more severe fading than classical Rayleigh channels with completely different first- and second-order envelope statistics.