Extract only the received signal from the transmitted and received superimposed signals
Satellite communication frequency band forward/reverse link sharing technology
Twice the efficiency compared to existing models, enabling more channels.
The Electronics and Telecommunications Research Institute (ETRI) announced that it has successfully developed a satellite communication frequency self-interference cancellation technology that can improve frequency usage efficiency by up to two times.

Late last month, ETRI completed verification of satellite communication frequency overlapping transmission technology that shares transmit and receive frequencies through a central station interference cancellation test using a small terminal modem (VSAT) equipment based on international satellite broadcasting standards and the Ka-band Cheonlian satellite. In the case of existing satellite communication, the frequency band (spectrum) used when sending a signal from a central base station that transmits data is different from the spectrum used by the terminal when responding to the central station. This is because the signal transmitted forward from the central station is stronger than the signal transmitted backward from the terminal, so if the same spectrum is used, the signal from the terminal cannot be received because the frequencies overlap.

ETRI researchers have developed a "self-interference cancellation technology" that can extract terminal signals even when the central station and terminals use the same frequency and their signals overlap. The overlapping signal received by the central station is a mixture of the signal previously transmitted by the central station in the forward direction and the signal transmitted by the terminal in the reverse direction. This technology separates the previously transmitted signal from this overlapping signal, thereby extracting only the signal transmitted by the terminal.

Currently, central station interference cancellation technology is a technology possessed only by world-class satellite technology companies. Domestic satellite equipment manufacturers, lacking proprietary technology, have struggled to enter the market. The technology developed by ETRI has been proven to support world-class self-interference cancellation rates and transmission speeds, enabling stable detection of desired signals from interference caused by frequency overlap. This allows for twice the number of additional channels to be allocated compared to existing satellite communication systems that use different uplink and downlink frequencies, thereby halving the cost of satellite communication repeaters.

Additionally, by securing additional channels, it becomes possible to transmit and receive large amounts of data and high-quality data using limited frequencies. Furthermore, because this technology uses overlapping transmission and reception frequencies, systems without "self-interference cancellation technology" cannot communicate. Therefore, it could be useful for defense communications, where communication security is essential.

ETRI's Oh Deok-gil, PL of the Satellite Technology Research Group, explained, "In the domestic satellite equipment manufacturing market, which is highly dependent on imported equipment, this is very significant in that we have succeeded in securing core technologies that can significantly improve the frequency usage efficiency of satellite communication systems through our own technological prowess and in localizing related equipment."

This technology development was conducted over a three-year period, beginning in 2016, as part of the Ministry of Science and ICT's "Development of Same Satellite Channel Transmission and Frequency Sharing Technology." The research team published 10 academic papers, transferred one technology, and applied for seven domestic and international patents based on this technology. ETRI plans to further transfer this technology to military communications and satellite communications equipment manufacturers, with the goal of commercialization in the second half of this year.

Meanwhile, the development and verification of core technologies such as satellite communication overlapping transmission technology were possible because the government made full use of the Cheonsae communication satellites it owned. However, in the case of Cheonsae-1, the design life of the satellite is almost over, and the launch of a follow-up satellite is urgent for the continued provision of public services, technology development, and commercialization.