Digital Terrestrial Television Broadcasting Over Cable TV Networks
-A simple passthrough transmission method-

A transmission scheme to re-transmit digital terrestrial television broadcasting (DTTB) services over cable TV networks (the official name is 'Technical Requirements for Digital Terrestrial Television Broadcasting Transmission over Cable Television Network Facilities') was reported on by the Telecommunications Technology Council at the end of January this year.

When digital terrestrial television broadcasting begins, the services have to be re-transmitted over cable TV networks.
Different than digital BS broadcasting or digital CS broadcasting, digital terrestrial television broadcasting utilizes a 6MHz frequency band, the same as present terrestrial television broadcasting, thus allowing the re-transmission of signals without any modulation conversion.
The OFDM modulation scheme has been adopted for digital terrestrial television broadcasting. Reported on at this time is the passthrough scheme that enables a cable TV operator to receive digital terrestrial broadcast programming and re-transmit the data over cable TV networks. The scheme consists of two formats, and they are as follows:

1. Same frequency passthrough
   The re-transmission is performed on the same frequency as the broadcasting channel.
2. Frequency conversion passthrough
   This converts the frequency for re-transmission when the same channel is not available.

Both formats can employ a regular digital terrestrial television receiver. The above format 2 requires a frequency converter for reception.

Cable TV operators have already been re-transmitting existing broadcasting services including terrestrial television broadcasting and digital CS broadcasting through their networks. A re-transmission standard has been established, thus, protecting the existing services.