Transmission of 8K Video from Wireless Cameras Moves Closer to Reality

Wireless cameras have become indispensable in broadcast production, adding flexibility, movement and energy to both sporting events and live entertainment. And the soaring demand for Ultrahigh-Definition content, spurred in Japan by several years of 4K and 8K public broadcasting, has created a need to broadcast UHD content from wireless cameras. Yet existing technology does not provide the network capacity and speeds necessary to transmit 8K signals wirelessly. Now researchers from Japan Broadcasting Corporation (NHK) have successfully demonstrated the transmission of low latency, high quality 8K signals using a whole new area of the spectrum: high-frequency, short wavelength millimeter bands. Their paper, “Development of an 8K UHDTV Wireless Camera Using Millimeter-Wave Bands” (in this month’s SMPTE Motion Imaging Journal) explains how they developed and tested their prototype.

The NHK team created an 8K wireless camera system by combining a prototype compact transmitter (using the high-frequency 42 GHz band) with a portable 8K video encoder, testing it both in the laboratory and in the field with wireless transmission experiments. Key was increasing transmission capacity, power efficiency and robustness, while reducing the system’s size to ensure portability.

On the Transmitter side, the video signal is carried from the 8K camera to four serial digital interfaces to the 8K encoder, then converted to a transport stream, and finally carried to the prototype compact transmitter which subjects it to single-carrier modulation, converts it to radio frequency, amplifies and transmits it via an antenna as a 42 GHz-band radio wave. On the Receiver side, the 42 GHz signal is received by multiple receivers, demodulated, carried to the 8K decoder, and then through four serial digital interfaces.

There are currently no existing portable low-latency 8K video encoders or decoders. So, for their transmission experiments, the NHK researchers constructed an 8K encoder by combining four serial digital interfaces, four portable ultralow-latency 4K encoders, and a transmission stream multiplexer. For video decoding, the digital distribution amplifier distributed the transport stream into four signals which were input to each 4K decoder using the preset program number that matches each 4K encoder. The streams were converted into four serial digital interface signals, producing synchronized 8K video.

In the lab, the team showed that their method produced wireless transmission of 8K video with low latency of about 50ms. Approximately 10ms are lost in modulation and demodulation, 20ms in video encoding and decoding, and 20ms for transport stream multiplexing. They also evaluated one-antenna single reception and two-antenna diversity reception, finding that diversity reception is most effective, improving carrier-to-noise ratio by 9.5 dB in a simulated concert hall and 5.7 dB on a simulated golf course. Finally, they tested the prototype 8K wireless camera system on the move, with one camera operator and one antenna operator carrying the transmitter, encoder and an omnidirectional antenna over a distance of 100 meters.

NHK says this prototype is the first ever realization of a portable 8K wireless camera system with low latency. In the future, their plans will focus on improving transmission performance and increasing transmission capacity. For more details on NHK’s wireless transmission of 8K over high-frequency millimeter waves, read the complete article in the UHD-focused June issue of the SMPTE Motion Imaging Journal.  https://www.smpte.org/motion-imaging-journal