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1IntroductionIn the coming ultra-high-speed satellite communica-tion era, high-speed data transmission via geostationary orbit satellites is one of the most promising technologies. In 1992, the National Institute of Information and Communication Technology (NICT) collaborated with the Japan Aerospace Exploration Agency (JAXA) to develop a gigabit satellite, called Wideband InterNetworking engi-neering test and Demonstration Satellite (WINDS). One of the goals of high-speed satellite communication technology in the Ka band of WINDS aer its launch in February 2008 is to realize high-speed data transmission over Internet protocol (IP) at high throughput (up to the Gbps level).ere are two kinds of transponders onboard WINDS, which are dierent communication modes in service. In the bent-pipe mode used for the past satellites, frequency of uplinked codes transmitted from earth stations are converted and amplied to be downlinked to earth stations. In the regenerative mode, uplinked codes transmitted from earth stations are demodulated. e codes are regenerative baseband switched, and then the modulated codes are downlinked to earth stations. NICT has conducted satellite communication experiments with point-to-point connec-tion based on the bent-pipe mode using direct modulation and demodulation apparatus (modem) developed on its own. In 2014, throughput of 3.2 Gbps (eectively 2.75 Gbps) was realized in the datagram type video streaming experi-ment using User Datagram Protocol (UDP) in the WINDS network [1]. In addition, in 2016, the throughput of 2.6 Gbps was achieved in the experiment of data stream type data transmission using High-performance and Flexible Protocol (HpFP) developed by NICT [2].In the near future, networks with both robustness and reliability will be very useful in emergencies such as disas-ters. For example, ultra-high-speed satellite communication using geostationary orbit satellites will be used to comple-ment terrestrial high-speed communication networks. For this purpose, the quality of satellite communication links is important. e code error rate or bit error rate (BER) is the percentage of bits that have errors relative to the total number of bits received in a transmission, and is used as 3-12 A Network Quality Check Tool via HpFP Protocol on WINDS Satellite LinkKen T. MURATA, Kazunori YAMAMOTO, Praphan PAVARANGKOON, Kenji SUZUKI, Toshio ASAI, Tomoshige KAN, Kazuya MURANAGA, Takamichi MIZUHARA, Yuya KAGEBAYASHI, Yasunori KAKIZAWA, and Masatomo YAHATANowadays, the concept of high throughput satellites (HTS) is developed to provide high data rates to users. The modern HTS is widely used in high-speed network communications, especially on geostationary orbits and deep space networks. It is well known that a network throughput of transmission control protocol (TCP), which is one of the most popular protocols, is limited due to latency and inevitable packet loss on the network link between the Earth and the satellite. Ku-band and Ka-band operations for the HTS tend to suffer from more packet losses than the lower frequency band operations, such as X-band and S-band operations. In this paper, we develop a new protocol on the HTS network, named the High-performance and Flexible Protocol (HpFP). A network quality measurement tool, called hperf, is introduced to prove that the HpFP is able to achieve 1.6 Gbps with single connection, theoretically maximum throughput, on the WINDS satellite link with bent-pipe mode. The Cyclic Redundancy Check (CRC) function is additionally implemented on the hperf. The experiment results show that the HpFP enables data transfer up to 100 Mbps associated with simultaneous CRC of all packets over the WINDS network. In addition, the correlation between packet loss on the HpFP and bit error detected by the CRC is provided to show a weak dependence on each other.1673 Ultra-High-Speed Satellite Communication Technology