ADS-B ground stations can transmit information to aircraft, which is specifically divided into two categories: Traffic Information Service Broadcast (TIS-B) and Flight Information Services-Broadcast (FIS-B).

TIS-B: The ADS-B ground station receives ADS-B position reports transmitted by aircraft and transfers this data to the Surveillance Data Processing System (SDPS). Simultaneously, the SDPS also receives data from radar and other surveillance equipment. The SDPS fuses this data into unified target position information and sends it to the TIS-B server. The TIS-B server integrates and filters the information to generate a comprehensive air traffic surveillance picture, which is then sent to the aircraft via the ADS-B ground station. This allows the flight crew to obtain complete and clear air traffic information. The application of TIS-B enables users of different ADS-B data link types to obtain surrounding airspace operational information, thereby achieving indirect mutual visibility.

FIS-B: The ADS-B ground station transmits information such as weather and aeronautical intelligence to the aircraft. This information can be in text or image format. Text-based weather information includes METARs, SPECIs, and Terminal Aerodrome Forecasts (TAF). Image-based information includes composite radar images, temporary flight restriction areas, and other operational information. FIS-B enables the flight crew to obtain more operational information, timely understand weather conditions along the route and airspace restrictions, providing support for more flexible and safe flight operations.

In a data communication network, telecommunication facilities that connect two or more data stations according to the technical requirements of a link protocol are called data links, or data links for short. Besides physical lines, a data link must also have communication protocols to control the transmission of this data. The OUT and IN functions of ADS-B are both based on data link communication technology. There are three types of data links available for ADS-B use: the 1090ES data link based on Mode S transponders; the Universal Access Transceiver (UAT); and Mode 4 VHF Data Link (VDL-4).

FAA regulations:

• The 1090 ES data link is used for international transport flights and domestic flights at 18,000 feet and above;
• The UAT data link is used exclusively for aircraft flying below 18,000 feet;
• Aircraft equipped with different data link devices do not communicate with each other (unless the aircraft is equipped with both types of data link devices).

It is clear that 1090 ES data link communication is primarily used for high-altitude airway operations, aimed at improving Air Traffic Control surveillance capabilities; while UAT data link communication is used exclusively for General Aviation flight activities at low altitudes, aimed at improving the mid-air collision avoidance capability and flight information capture capability of GA aircraft.

Reference Materials:

Application of Automatic Dependent Surveillance-Broadcast (ADS-B) in Flight Operations Overview of ADS-B Main Technologies and Related Equipment ADS-B in the USA ADS-B in Australia

Updated on August 25

Found a good article on Weibo, let me introduce it: Interpretation of the ADS-B Automatic Dependent Surveillance System