Research on Spectrum Needs Prediction Method for HAPS as IMT Base Station

The High-Altitude Platform Station (HAPS) is an integral component in Non-Terrestrial Network (NTN) which is potential 6G technology. The HAPS as IMT Base Stations (HIBS) in the mobile service is an emerging and promising approach to achieve vertical heterogeneous network. Therefore, some efforts have been made in order to harmonize the worldwide usage of HIBS, including investigations of the spectrum needs, usage, and technical and operational characteristics of HIBS, among which the spectrum needs has drawn particular attention because it should be determined in advance prior to the commercial deployment of HIBS. However, there are very few investigations devoted to the prediction of the spectrum needs for future HIBS deployments currently due to some tough difficulties. Firstly, there has no actual deployment precedent of HIBS so that the future capacity demands are not clear. Secondly, both the networking and its performance of HIBS deployment are questions to be answered. Therefore, taking into account the study under WRC-23 Agenda Item 1.4 HIBS-CHARACTERISTICS, this paper proposes an evaluation method of the spectrum needs prediction for HIBS deployed as a supplementary for grounded base station, and presents the results of spectrum needs for HIBS in certain frequency bands identified for IMT. The capacity demand of HIBS in 2025 is predicted and the spectral efficiency of HIBS system is obtained by simulation, and the spectrum needs is defined as Capacity Demand/Spectral Efficiency. The main contributions of this paper are as follows: Firstly, to obtain the spectral efficiency of HIBS systems, we set up a simulation model with 7-cell networking in accordance with configuration parameters of WRC-23 AI 1.4, which equipped with beamforming antenna to improve spectral efficiency. And calculating the CDF curve of spectral efficiency by using Monte Carlo method allows the simulation result to more closely match the actual deployment. Secondly, in order to solve the problem of no actual HIBS traffic data, we propose a method based on the methodology provided in Recommendation ITU-R M.1768-1 to simulate the capacity demand, and then to predict the capacity demand of HIBS in 2025 by polynomial fitting. Finally, we have predicted the spectrum needs by calculating Capacity Demand/Spectral Efficiency. The spectrum demand range of HIBS for China rural area in 2025 predicted by the proposed method is from 80.30 MHz to 122.97 MHz. This method can effectively predict the spectrum needs of HIBS for various deployment scenarios, which plays an important role in driving the commercial deployment of HIBS.