User Pairing Method Using Radio Map for Spectrum Sharing Between Non-Terrestrial Networks and Terrestrial Networks

With the proliferation of the Internet-of-Things (IoT) and cell phones, there is a need to provide high-speed communications to a large number of users. Next-generation mobile communication systems, Beyond 5G/6G, are considering the use of non-terrestrial networks (NTNs) to ensure a wide coverage area and to accommodate the increase in users. Satellite communications, which is one of NTNs, have a wider coverage area than base stations of terrestrial networks (TNs), but utilization of NTNs concerns the impact on terrestrial networks when considering spectrum between NTNs and TNs. For spectrum sharing with the TNs, frequency bands are allocated for each communication link, and an investigation is conducted on the timing schedule method for TNs and NTNs terminals. We consider the impact on each terminal and base station when using reverse pairing, which reverses the up-link and down-link frequency resource links between NTNs and TNs. In addition, a radio map that stores information on radio propagation in space for wireless communication is used for calculating the interference between systems. To avoid interference between terminals, which was found to be necessary when performing reverse pairing, scheduling of terminals is conducted, and a radio map is utilized for this schedule. We simulate and evaluate the permissible number of spectrum shared terminals for terrestrial networks without interference toward terminals of NTNs, which is affected by the error of the information of the radio map. The results show that the spectrum database using a radio map can increase the number of spectrum shared terminals for terrestrial and non-terrestrial networks if the estimation error of received signal power is within 7 [dB].