  In this paper, the feasibility of implementing a lightweight key distribution
scheme using physical layer security for secret key generation (SKG) is
explored. Specifically, we focus on examining SKG with the received signal
strength (RSS) serving as the primary source of shared randomness. Our
investigation centers on a frequency-selective line-of-sight (LoS) multipath
channel, with a particular emphasis on assessing SKG rates derived from the
distributions of RSS. We derive the received signal distributions based on how
the multipath components resolve at the receiver. The mutual information (MI)
is evaluated based on LoS 3GPP channel models using a numerical estimator. We
study how the bandwidth, delay spread, and Rician K-factor impact the estimated
MI. This MI then serves as a benchmark setting bounds for the SKG rates in our
exploration.
