  5G millimeter wave (mmWave) technology is envisioned to be an integral part
of next-generation vehicle-to-everything (V2X) networks and autonomous vehicles
due to its broad bandwidth, wide field of view sensing, and precise
localization capabilities. The reliability of mmWave links may be compromised
due to difficulties in beam alignment for mobile channels and due to blocking
effects between a mmWave transmitter and a receiver. To address such
challenges, out-of-band information from sub-6 GHz channels can be utilized for
predicting the temporal and angular channel characteristics in mmWave bands,
which necessitates a good understanding of how propagation characteristics are
coupled across different bands. In this paper, we use ray tracing simulations
to characterize the angular and temporal correlation across a wide range of
propagation frequencies for V2X channels ranging from 900 MHz up to 73 GHz, for
a vehicle maintaining line-of-sight (LOS) and non-LOS (NLOS) beams with a
transmitter in an urban environment. Our results shed light on increasing
sparsity behavior of propagation channels with increasing frequency and
highlight the strong temporal/angular correlation among 5.9 GHz and 28 GHz
bands especially for LOS channels.
