The current terrestrial broadcasting transmits one Hi-Vision program over one channel (6-MHz bandwidth). To broadcast 8K SHV with 16 times more information of Hi-Vision, the transmission capacity must be largely expanded, in addition to the use of latest video compression technologies. To realize 8K SHV terrestrial broadcasting, we are studying the combination of three new technologies: dual-polarized MIMO (Multiple-Input Multiple-Output), ultra-multilevel OFDM (Orthogonal Frequency Division Multiplexing) and LDPC (Low-Density Parity Check) coding.
 The current terrestrial broadcasting uses either one of the horizontal or vertical polarization to avoid inter-polarization interference. In contrast, the dual-polarized MIMO technology uses horizontal and vertical polarizations simultaneously to transmit twice as much information as single-input single-output.
 The current terrestrial broadcasting transmits only up to 6 bits (26=64 signal points) with a single carrier of OFDM signal. Ultra-multilevel OFDM can transmit up to 12 bits (212=4,096 signal points). With the number of bits per carrier being doubled, double the information amount can be transmitted. Meanwhile, the distance between signal points becomes shorter as the number of signal points increases, which causes more errors due to noise and distortion.
 The LDPC coding is used to minimize the errors. The LDPC coding, which is one of the error correction coding methods, is well known for its high decoding capability close to the theoretical limit. It is widely used in the communications field.
 Besides the three new technologies, we focused on the size of FFT (Fast Fourier Transform) to further maximize the transmission capacity. In digital broadcasting, it is common to convert frequency domain to time domain using IFFT (Inverse FFT) in transmission of OFDM signals. Using a larger FFT can reduce the ratio of guard intervals that eliminate delay waves by reflection. The guard interval ratio of the current terrestrial broadcasting is 1/8, but using a quadruple-sized FFT can reduce it to 1/32, which increases the transmission capacity by 9%.
 We installed an experimental transmission station for 8K SHV with an equal scale of the current terrestrial TV relay station in Hitoyoshi City, Kumamoto Prefecture and conducted a test in January 2014. The 8K SHV signal, encoded at 91 Mbps, was received 27km away from the transmitting station and we confirmed the information was successfully transmitted without errors.
 We plan to measure and analyze propagation in urban areas to achieve early implementation of 8K SHV terrestrial broadcasting. We will also study a new transmission method of 8K SHV terrestrial broadcasting that can coexist with single-polarization broadcast without using MIMO.
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