Transmission Technology of High Definition Digital Television

Transmission Technology of High Definition Digital Television

There are four main ways to transmit HDTV signals, including (live) satellite transmission, cable TV, terrestrial/mobile wireless digital TV network and IP network TV system. For high-definition digital TV programs with nationwide coverage, broadcasting via (live) satellite is the most suitable solution. Correspondingly, they are called high-definition satellite digital TV, high-definition cable digital TV, high-definition terrestrial/mobile wireless digital TV and IP high-definition network digital TV. Among them:

1) High-definition digital TV via satellite
For more than a decade, the European satellite digital TV transmission standard DVB-S (ETS 300 421) has been
the standard for digital satellite transmission of MPEG-2 standard definition video. Its data stream is modulated using quadrature phase shift keying (QPSK) modulation, and the operating frequency is C band and Ku band (for live satellite, the operating frequency is only in Ku band). When using MPEG-2 MP@ML (Main Profile @ Main Level) format, the user end can achieve CCIR601 studio quality bit rate of 9Mbps and PAL quality bit rate of 5Mbps. A 54MHz transponder can transmit up to 68Mbps and can be multiplexed for multiple SDTV programs. However, as more video content moves to high-definition formats, DVB-S has proven to be a transmission bottleneck in bandwidth allocation.

2) High-definition digital TV transmitted through cable TV network
China has a good foundation for cable digital TV, with cable TV network as the transmission medium, and its application range is wide and its development is also very fast. Its digital cable
broadcasting system adopts the European standard DVB-C (ETS 300 429), which has several modulation modes such as 16QAM, 32QAM, 64QAM (corresponding to a maximum transmission bandwidth of 38Mbps), 128QAM (corresponding to a maximum transmission bandwidth of 44Mbps) and 256QAM (corresponding to a maximum transmission bandwidth of 50Mbps) quadrature amplitude modulation.

3) High-definition digital TV via terrestrial/mobile wireless transmission
The transmission capacity of terrestrial digital transmission is roughly equivalent to that of cable TV systems in theory, but is limited by the licensing of wireless transmission frequency points; it can
achieve good coverage of wireless digital TV in the region. Due to the use of newer modulation methods, 10~12 sets of standard-definition TV programs, or at least 2 sets of high-definition TV programs, can be transmitted within an 8MHz bandwidth, and the transmission cost is low.

4) HDTV high-definition digital television transmitted through IP network system
IPTV network television, also known as interactive television or broadband television, is a new type of interactive television broadcasting form that transmits television programs through telecommunications broadband Internet (such as ADSL of Telecom and Netcom, community Category 5 lines, etc.), or through FTTH (fiber to the home); it integrates multiple technologies such as the Internet, multimedia, and communications, and provides home users with a variety of interactive digital media services including digital television through Internet protocols. Internet TV users can receive various network television programs at home through personal computers or "network set-top boxes + ordinary or high-definition televisions". It not only provides traditional video services and Internet browsing, but also will develop new interactive services and support digital TV platforms, so that users can enjoy interactive entertainment and services on a comprehensive network service platform, such as online transactions, interactive on-demand, TV voice mailboxes, and online games. And because it has many channels and content, it can meet the needs of a large number of Internet TV users at different levels.

In order to transmit high-definition digital TV programs in the IP network system, in addition to using real-time MPEG-2/MPEG-4/H.264/AVS high-definition streaming media encoding equipment, it is also necessary to ensure the transmission bandwidth of the IP network. A broadband network connection of 3 to 5Mb/s should be guaranteed, and the corresponding IPTV high-definition digital TV receiver set-top box should be used to watch HDTV high-definition digital TV programs in the IP network.

Satellite, cable, terrestrial and mobile wireless digital TV networks can use different modulation methods to transmit digital TV signals. The following table lists the various modulation methods currently or planned to be used based on different commonly used transmission methods for reference.