- In this paper, we analyze the first-order (FO) statistics of two new geometry-based statistical models for small-scale nonstationary time-frequency (TF) dispersive mobile-to-mobile (M2M) fading channels. We derive exact analytic expressions for the joint and marginal probability density functions (PDFs) of the envelope and phase of both models. In addition, we analyze the asymptotic behavior of these PDFs as the number of multipath components of the received signal approaches infinity. The obtained results are of practical relevance, as they can be used as a benchmark to investigate the influence of the small-scale fading statistics of nonstationary channels on the M2M communication systems' performance. © 2016 IEEE.