Estimating the omni-directional pathloss from directional channel sounding

Channel sounding above 6 GHz often uses directional antennas to compensate for the more influential pathloss than below 6 GHz, and rotates the antennas over angles to obtain directional channels. The sounding method sets a nontrivial challenge of estimating omni-directional pathloss, which refers to the pathloss when omni-directional antennas would have been installed at the link ends. The challenge is attributed to the directional channel sounding that receives the same propagation paths over multiple pointing angles of the same directional antenna, making the pathloss underestimated if just summing up the powers measured at different antenna pointing angles. An elaborated method is to detect propagation paths in the environment and sum their powers up, but it is hardly possible to detect all the energy of the channel as paths, ending up with a risk of overestimating the pathloss. This paper therefore proposes to estimate the omni-pathloss from the propagation paths, with compensation of the powers that are not detected as paths and are often called diffuse scattering. The proposed method is tested based on novel channel measurements in a shopping mall performed at 15, 28 and 60 GHz bands. The omni-pathloss estimated by the proposed method always falls between those derived from the conventional methods, demonstrating its expected behavior.