  A Non-terrestrial Network (NTN) comprising Low Earth Orbit (LEO) satellites
can enable connectivity to underserved areas, thus complementing existing
telecom networks. The high-speed satellite motion poses several challenges at
the physical layer such as large Doppler frequency shifts. In this paper, an
analytical framework is developed for statistical characterization of Doppler
shift in an NTN where LEO satellites provide communication services to
terrestrial users. Using tools from stochastic geometry, the users within a
cell are grouped into disjoint clusters to limit the differential Doppler
across users. Under some simplifying assumptions, the cumulative distribution
function (CDF) and the probability density function are derived for the Doppler
shift magnitude at a random user within a cluster. The CDFs are also provided
for the minimum and the maximum Doppler shift magnitude within a cluster.
Leveraging the analytical results, the interplay between key system parameters
such as the cluster size and satellite altitude is examined. Numerical results
validate the insights obtained from the analysis.
