The Air to Ground Clutter Loss Measurements and Modelling Below 10 GHz

6G-7G Hz (U6G) is one promising frequency band and will be utilized in 5G evolution period, but this frequency band has been occupied by non-terrestrial network (NTN) networks in some countries. The interference assessment between NTN and 5G evolution services in U6G is one of key issues needed to be considered before the large-scale deployment of U6G band in 5G evolution. Therefore, the clutter loss (CL) model is pivotal to the different systems co-existence evaluations. ITU-R has issued a Recommendation (ITU-R P.2108) giving CL model for the estimation of clutter loss at three different terminal environments for varied frequency range. However, the clutter loss model for NTN environment in ITU-R P.2108 only supports the frequency range from 10G Hz to 100 GHz and can be applicable to the terminal heights of below 5 m. In this paper, the clutter loss measurement and simulation below 10 GHz for NTN scenario has been conducted at different terminal heights on the ground in urban and suburban environments. Furthermore, the CL model is extended to the frequency bands below 10G Hz. In the proposed CL model, the terminal height is considered, which has high impact on the CL results. Taking 4-6m base station height as a baseline, we provide different ground station height results analysis based on both real measurement and ray-tracing simulation. An additional adjusting factor α is modelled to reflect different antenna height characteristics. The CL model will be adopted to the NTN and 5G evolution systems co-existence evaluation.

I. Introduction

With the 5G commercial network deployment being matured, the 5G evolution is being discussed in the industry. New frequency bands below 100G Hz are finding, and are planned to be deployed in 5G evolution period. One of potential frequency bands below 100 GHz is 6G-7 GHz (U6G) which has similar path loss and signal coverage. However, U6G band has already been deployed by NTN networks in some areas. Hence, the interference evaluation between NTN and 5G evolution networks must be considered before the deployment of 5G evolution networks at U6G frequency bands, and the clutter loss for NTN channel is one key input for the interference evaluations. According to the definition in ITU-R P.2108 [1], clutter refers to objects, such as buildings or vegetation, which are on the surface of the Earth but not actually terrain. The ITU-R P.2108 clutter loss models consist of three types of environments: i) terminal below representative clutter height, ii) terrestrial terminal within the clutter, iii) one terminal within the clutter and the other being a satellite, aeroplane or other platform above the surface of the Earth.