We are studying the FTTH (Fiber to the Home) digital baseband transmission system for transmitting 4K/8K programs to homes over cable TV networks. This system divides multichannel streams of 2K/4K/8K broadcasting into IP packets, multiplexes them using time-division multiplexing and transmits them by optical signals. With its capability of large-capacity transmission of 10 Gbps, it can transmit about 100 channels of 4K/8K programs.
  In FY 2018, we studied an intra-building transmission system for condominium buildings installed only with coaxial cables, without optical fibers⁽¹⁾. Coaxial cables in condominium buildings cannot transmit baseband signals directly because there is a limit to the transmission bandwidth. We therefore devised a method that selects IP packets in response to a viewer request for a program and converts them to radio frequency (RF) signals. By transmitting signals only for the programs being viewed in the building, this method can transmit multiple channels of 4K/8K programs to individual households over existing coaxial cables. The Data Over Cable Service Interface Specifications (DOCSIS) standard used for internet communications on cable TV can be used as a way of transmitting IP packets in the form of RF signals. With existing DOCSIS, however, it is difficult to control in detail which RF signal transmits which program, preventing the effective use of transmission bandwidth. To address this problem and enable efficient delivery, we added an additional IP address for DOCSIS to an IP packet for a program so that transmission by a DOCSIS transmitter can be controlled by changing the IP address according to the viewer request for a program. We call this technology "IP encapsulation". We also studied measures against packet loss because the bit-error rate specified by the DOCSIS standard is too high to maintain video quality in intra-building transmission of programs. We prototyped intra-building transmission equipment having these functions and demonstrated the effectiveness of our new method.

 

[References]
(1)	T. Kusunoki, T. Kurakake, K. Otsuki and K. Saito: "Improvement of transmission efficiency of 4K/8K multi-channel IP multicast using DOCSIS over in-building coaxial cable network," IEEE International Conference on Consumer Electronics 2019 (ICCE 2019), (2019)