The current satellite broadcasting transmits two or three Hi-Vision programs by one transponder (one channel). To broadcast 8K Super Hi-Vision (8K SHV) with 16 times the information volume of Hi-Vision using one satellite transponder, the transmission capacity must be increased. We have been implementing new transmission technologies to realize satellite 8K SHV broadcasting.
 To transmit digital signals, the status of radio wave is divided into groups by phase, amplitude and frequency, whose condition is related to digital data of 0 or 1, and then modulated. The current satellite broadcasting uses eight phase points called 8PSK (8 Phase Shift Keying) to send 3-bit information. 8K SHV employs the 16APSK (16 Amplitude and Phase Shift Keying) modulation scheme that combines conventional phase points with amplitude-directional signal points. It has enabled transmission of 4-bit information.
【 degitaly modulated signal 】

 To increase the transmission capacity of digital signals, it is necessary to increase the speed of switching amplitude and phase data (the symbol rate). The symbol rate is proportional to frequency bandwidth, but the allocated frequency bandwidth of a single channel of the satellite transponder cannot be changed from the current value (34.5MHz) by regulation. So, we have reduced the roll-off factor, a coefficient to show the steepness of signal waveform, from current 0.35 to 0.03 to broaden the effective bandwidth and increase the symbol rate. Thus, we have improved the efficiency of frequency usage by approx. 17%.
【 Signal points before and after passing through a transponder 】
 LDPC (Low Density Parity Check) is used to correct bit errors during transmission. The LDPC coding, which uses distinctive long codes, has a strong error-correcting capability close to the theoretical limit.
 With the above technologies, we have secured the transmission capacity required for the envisioned 8K SHV (approx. 100 Mbps). While a multi-level modulation scheme such as 16APSK can expand the transmission capacity, it incurs different influence from conventional methods when digital signals go through a satellite transponder. The signals become distorted as shown in the figures, affecting reception performance. We therefore conducted a transmission experiment on the new scheme using an actual satellite in January 2014 and proved that a stable broadcasting can be achieved.
 The current satellite broadcasting uses right-handed radio waves, but left-handed radio waves are prospective frequency resources to further increase available channels. For the use of left-handed waves, we are working to conclude an international agreement to prevent wave interference and also develop reception devices.
【 Test broadcasting of Super Hi-Vision 】

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