  In this paper, we present the downlink coverage and rate analysis of a
cellular vehicle-to-everything (C-V2X) communication network where the
locations of vehicular nodes and road side units (RSUs) are modeled as Cox
processes driven by a Poisson line process (PLP) and the locations of cellular
macro base stations (MBSs) are modeled as a 2D Poisson point process (PPP).
Assuming a fixed selection bias and maximum average received power based
association, we compute the probability with which a {\em typical receiver}, an
arbitrarily chosen receiving node, connects to a vehicular node or an RSU and a
cellular MBS. For this setup, we derive the signal-to-interference ratio
(SIR)-based coverage probability of the typical receiver. One of the key
challenges in the computation of coverage probability stems from the inclusion
of shadowing effects. As the standard procedure of interpreting the shadowing
effects as random displacement of the location of nodes is not directly
applicable to the Cox process, we propose an approximation of the spatial model
inspired by the asymptotic behavior of the Cox process. Using this asymptotic
characterization, we derive the coverage probability in terms of the Laplace
transform of interference power distribution. Further, we compute the downlink
rate coverage of the typical receiver by characterizing the load on the serving
vehicular nodes or RSUs and serving MBSs. We also provide several key design
insights by studying the trends in the coverage probability and rate coverage
as a function of network parameters. We observe that the improvement in rate
coverage obtained by increasing the density of MBSs can be equivalently
achieved by tuning the selection bias appropriately without the need to deploy
additional MBSs.
