  In order to develop and analyze reliable communications links for unmanned
aerial vehicles (UAVs), accurate models for the propagation channel are
required. The radio channel properties in the urban scenario are different from
those in the suburb scenario and open area due to so many scattering paths from
office buildings, especially when the UAV flies in the low altitude. We took
some measurement campaigns on the campus of Tsinghua University with crowded
apartments and office buildings. Based on the measurement result we extract the
main parameters of pathloss model, and propose a simplified Saleh-Valenzuela
(SV) model with specific parameters. The typical scene of central lawn is
compared with the office buildings in the analysis of K-factor and
root-mean-square (RMS) delay spread.
