Challenges with on-orbit demonstration of satellite sensing platform using low earth orbit satellite MIMO technology
- To achieve ultra-wide area low-power sensing environment that connects everything on Earth -

NTT Corporation (Chiyoda-ku, Tokyo; President: Akira Shimada) is pleased to announce the launch of the Japan Aerospace Exploration Agency's (Headquarters: Chofu, Tokyo; President: Hiroshi Yamakawa, and hereinafter JAXA) Innovative Satellite Technology Demonstration-4^*1, which is scheduled to launch in FY 2024, as part of its on-orbit demonstration of 920-MHz-and satellite Internet-of-Things (IoT) platform using satellite MIMO^*2 technology.
　This demonstration theme will focus on low Earth orbit (LEO) satellite MIMO technology and satellite sensing technology, which are keys to ultra-wide area low-power sensing terminal services to enable everything to be connected around the world, such as IoT devices and sensing services in oceans and mountainous areas with no terrestrial communication network.

1. Background

In August 2019, NTT and JAXA signed a cooperation agreement for the creation of a social infrastructure, including the construction of an innovative optical network infrastructure that will lead to the resolution of social issues. Since then, we have engaged in joint research^*3 to achieve an ultra-high-speed, high-capacity, and secure optical and wireless communications infrastructure that seamlessly connects the ground and space by combining NTT's optical and wireless network technology that contributes to the actualization of IOWN^*4" with JAXA's spacecraft system construction technology.
　We are accelerating our preparations to enter the space business by announcing the Integrated Space Computing Network^*5 and establishing Space Compass Corporation^*6. Space Sensing, one of the concepts of the Integrated Space Computing Network, will enable the creation of an ultra-wide-area satellite sensing platform^*7 that will be responsible for the use of high-definition, large-capacity observation information acquired from satellites and the collection of sensor data acquired from anywhere on the ground. To achieve this, it is essential to develop LEO satellite MIMO technology to improve the spectral efficiency and transmission capacity of radio signals transmitted from LEO satellites to ground base stations, and satellite sensing technology, which enables the accommodation of a variety of LPWA^*8 radio terminals for ground use without requiring a radio station license. For this reason, the demonstration of these technologies^*9,*10, which was planned to be implemented in Innovative Satellite Technology Demonstration-3, will be partially upgraded and demonstrated in Innovative Satellite Technology Demonstration-4.

2. Overview of the demonstration

We will demonstrate the elemental technologies for the development of an ultra-wide-area satellite sensing platform in LEO using a scale model that takes into account the mutability on small demonstration satellites.

Figure 1 On-Orbit Demonstration Image

We will first ensure that the technologies that had been planned to demonstrate in Innovative Satellite Demonstration Unit-3. Specifically, for the LEO satellite MIMO technology, we will demonstrate that 2 x 2 MIMO can achieve twice the peak value and an average of more than 1.5 times the transmission-capacity improvement of SISO^*11 transmission with (1) Time-Frequency Asynchronous Interference Compensation technology and (2) MIMO Propagation Channel Modeling technology. The satellite sensing technology will also demonstrate that the signals of two or more LPWA terminals arriving at the same time and frequency can be separated and demodulated using (3) Blind Beam Control technology and (4) LPWA Multi-Protocol Bulk Demodulation technology.
　We also plan to coordinate with JAXA on the following new technology demonstrations with an eye to future practical applications.

3. Future prospects

By demonstrating and establishing these technologies, it will be possible to use IoT devices and provide sensing services in oceans and mountainous areas where terrestrial communication networks are not available, such as for further improving weather-prediction accuracy through surface marine weather observation using marine buoys and advance detection of flood damage by river monitoring. As part of the NTT Group's vision of the Integrated Space Computing Network, the group will promote its ultra-wide satellite sensing platform and contribute to the development of the infrastructure necessary for a sustainable society.

- Glossary -

^*1JAXA: Innovate Satellite Technology Demonstration-4 (in Japanese)
https://www.jaxa.jp/press/2023/02/20230208-1_j.html

^*2MIMO (multiple-input multiple-output)
The transmitter and receiver communicate with multiple antennas to improve transmission capacity.

^*3"NTT and JAXA Commence Joint Research to Realize Ultra-High-Speed, Secure Optical and Wireless Communications Infrastructure to Link Earth and Space Seamlessly" (in Japanese)
https://group.ntt/jp/newsrelease/2019/11/05/191105c.html

^*4IOWN (Innovative Optical and Wireless Network)
An initiative for future communications infrastructure to create a smarter world by using cutting-edge technologies such as photonics and computing technologies
https://www.rd.ntt/e/iown/

^*5"NTT and SKY Perfect JSAT conclude collaboration agreement on new space enterprise to aid realization of a sustainable society"
https://group.ntt/en/newsrelease/2021/05/20/210520a.html

^*6"NTT and SKY Perfect JSAT Agree to Establish Space Compass Corporation" -Novel Space Integrated Computing Network Enterprise to Aid Realization of a Sustainable Society-
https://group.ntt/en/newsrelease/2022/04/26/220426a.html

^*7NTT Technical Review, Vol. 20, No. 12, pp. 36–40, Dec. 2022.
Satellite sensing Platform
https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr202212fa4_s.html

^*8LPWA (Low Power Wide Area)
Wireless network systems that can cover a wide area with low cost and power saving.

^*9"A technology demonstration plan for realizing "20Gbps+ communications between low earth orbit satellites and the ground and ultra-wide area IoT data collection" was adopted as an Innovative Satellite Technology Demonstration Theme." (in Japanese)
https://group.ntt/jp/newsrelease/2020/05/29/200529a.html

^*10JAXA: Innovate Satellite Technology Demonstration-3 press kit
https://www.kenkai.jaxa.jp/eng/library/pdf/kakushin03.pdf

^*11SISO (single-input single-output)
Technology in which both the transmitter and receiver communicate with a single antenna in wireless communications.