- Advancing integrated satellite and terrestrial network operations with “Next-Gen Satellite Communications AI”

Tokyo - Rakuten Mobile today announced that its joint proposal with the University of Tokyo for dynamic frequency sharing technology has been selected by the Japan Aerospace Exploration Agency (JAXA) for its Space Strategy Fund program. Research and development for this Satellite and Terrestrial Network Integration for Seamless Frequency Sharing-themed project is eligible for up to 11 billion yen in funding^*1. The University of Tokyo’s Graduate School of Engineering is participating as a key collaborating institution.

The R&D aims to develop frequency-sharing technology that enables seamless handover between satellite communications and terrestrial wireless networks through Next-Gen Satellite Communications AI. In direct satellite-to-mobile communication, the same frequency bands are frequently shared with terrestrial networks, requiring interference management based on real-time conditions. Advanced correction is particularly crucial for voice and video calls due to Doppler effect^*2 and propagation delays.

Through AI-powered integration of satellite and terrestrial network operations, Next-Gen Satellite Communications AI will enable seamless connectivity, even as users transition between coverage areas. Additionally, it demonstrates strong potential to support next-generation services that demand uninterrupted connectivity, including autonomous vehicles, flying cars and drones.

Rakuten Mobile and the University of Tokyo have a history of collaboration in AI-driven satellite communication research. This includes providing a virtualized Open RAN testing environment on the university campus^*3 and conducting joint R&D into ultra-wide IoT coverage utilizing low Earth orbit (LEO) satellites^*4. Through this new initiative, the two organizations will conduct verification tests for integrated satellite-terrestrial network operations using Next-Gen Satellite Communications AI.

JAXA’s Space Strategy Fund supports multi-year technology development projects by private companies, startups and academic institutions in three key areas: transportation, satellites and related technologies, and exploration. The program aims to expand markets, address societal challenges and pioneer new frontiers.

Conceptual diagram of the integrated satellite-terrestrial network operations.

R&D Details
This R&D focuses on developing Next-Gen Satellite Communications AI to monitor and control direct satellite-to-mobile communications and terrestrial networks sharing the same frequency bands. The goal is to avoid interference and improve operations and service quality for satellite direct communication. The research will include:

1. AI-driven power control: Development of an AI application to automatically power on and off satellite communication based on coverage data collected from both satellite and terrestrial base stations.
2. Interference management and traffic optimization: Implementation of an AI application to manage interference mitigation, frequency adjustments and traffic load balancing. This will ensure optimal connectivity during disasters, user transition and handover scenarios.

Project period: March 2026 – March 2031 (planned) ^*5
Total funding amount: 11 billion yen (maximum) ^*1

Through this R&D, Rakuten Mobile aims to advance satellite communication networks and deliver superior connectivity to customers, contributing to the evolution of Japan’s telecommunications technology.

Notes
*1 Maximum support amount. Subject to change based on future stage-gate reviews and related evaluations.
*2 Doppler effect: A phenomenon where the frequency of a wave changes due to the relative motion between the source and the observer.
*3 Press release: Rakuten Mobile Open Innovation Lab Established for Open vRAN Technology Verification (August 23, 2022)
*4 Press release: Rakuten Mobile and the University of Tokyo Begin Joint R&D into IoT Ultra Coverage Utilizing LEO Satellites (November 29, 2021)
*5 The initial funding project period runs from the date of the funding grant decision through the end of the fiscal year in which the first stage-gate evaluation is completed. Extensions to the project period will be decided based on stage-gate reviews.