Envelope distribution and Doppler spectrum of V2V channels at 5.9 GHz in mountainous roads

Abstract

Land transportation of people and goods often relies on strategic routes that pass through mountains. Despite the importance of these routes, the characteristics of the vehicular radio communication channel in such environments have received little attention. To close the gap, this paper presents the results of a measurement campaign at 5.9 GHz in mountainous roads. Data collected during the measurement campaign were used to quantify the envelope distribution and Doppler spectrum of small-scale vehicle-to-vehicle (V2V) communication channels. The measurements were taken in three different locations, two in San Luis Potosí (SLP), México, and one near Provo, Utah, USA. The locations in SLP are shrubland areas, whereas that in Utah is a coniferous forest. The diverse mountainous environments observed during the experiments were classified into five reference propagation scenarios. For each reference scenario the empirical channel envelope distribution was computed and compared with previously-published theoretical models based on the Rice, Nakagami, Weibull, and Gamma distributions. The Rice model provided the best fitting in 72.3% of the analyzed cases, whereas the Nakagami, Weibull and Gamma distributions were the best option in the remaining 11.3%, 14.9% and 1.3%, respectively. Likewise, the empirical distributions of the instantaneous mean Doppler shift (IMDS) and instantaneous Doppler spread (IDS) were computed. The results show that the IMDS follows the Generalized Extreme Value and Logistic distributions, whereas the Birnbaum-Saunders, Exponential, Burr and Nakagami distributions are proper models for the IDS. Our analysis also shows that the line-of-sight (LOS) path is the dominant factor for V2V communication in mountainous terrain, especially in roads surrounded by rocky structures with sparse vegetation. However, the contribution of non-LOS paths is not negligible, and it appears capable of supporting short intervals of communication. The results presented here can be used as guidelines for the analytical modeling and computer simulation of small-scale V2V channels in mountainous environments.