Japan Broadcasting Corporation (NHK) on Monday announced that it has succeeded in long-distance terrestrial transmission experiment of 8K Super Hi-Vision content. NHK had previously reported the world's first 8K transmission experiment at a distance of 4.2km (May 2012.) But the latest succesfull transmission reached a distance of 27km.

NHK has been researching and developing Super Hi-vision for a next-generation ultra-high-definition broadcasting system.

The Super Hi-Vision system consists of ultra-high-definition video, with four thousand scan lines and 16 times the number of pixels as conventional HDTV.

The broadcster used ultra-multilevel OFDM and dual polarized MIMO technologies designed for high capacity transmission, along with the essential modulators/demodulators.

The 8K signal was sent from an experimental test station installed at NHK's hitoyoshi TV relay station in Kumamoto Prefecture Hitoyoshi. The signal was compressed using the MPEG-4 AVC/H.264 algorithm. For the transmission NHK used the ultra-multilevel Orthogonal frequency-division multiplexing (OFDM) method, which increases transmission capacity by extending the carrier modulation scheme to 4096QAM. The transmission capacity was 91.8 Mbps for a single channel (4,096 QAM, r = 3/4).



The dual-polarized MIMO technology utilizes pilot signals for polarization de-multiplexing, making it possible to transmit both horizontally and vertically polarized signals simultaneously.

NHK has proved that the two differently-polarized signals can be accurately separated on the receiver side by using these pilot signals to estimate the MIMO channel response, and that transmitted information can be correctly demodulated as a result.