Level-Crossing Rate and Average Duration of Fades of the Envelope of Mobile-to-Mobile Fading Channels in Cooperative Networks Under Line-of-Sight Conditions

This paper studies the fading behavior of mobile- to-mobile (M2M) fading channels in relay-based cooperative networks under line-of-sight (LOS) conditions. Here, we assume that LOS components exist in both the direct link between the source mobile station (SMS) and the destination mobile station (DMS) as well as in the link via the mobile relay (MR). In such a propagation environment, the fading channel is referred to as the multiple-LOS second-order scattering (MLSS) channel. The fading behavior of MLSS channels is studied by analyzing the level-crossing rate (LCR) and the average duration of fades (ADF) of the received envelope. We have derived analytical expressions for the LCR, ADF, and cumulative distribution function (CDF) of the envelope of MLSS channels. It is shown that MLSS channels include various other channel models as special cases, e.g., double Rayleigh channels, double Rice channels, single-LOS double-scattering (SLDS) channels, non-line-of-sight (NLOS) second-order scattering (NLSS) channels, and the single- LOS second-order scattering (SLSS) channels. The correctness of all theoretical results is confirmed by simulations. Our studies regarding the fading behavior of MLSS channels are useful for the development and performance evaluation of relay-based cooperative wireless networks in different M2M propagation environments.