Surveillance and Broadcast Services, Western Service Area (WSA)

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GBT's (Ground-Based Tranceivers) Role in Supporting Broadcast Data Link Services

The fundamental role of the GBT is to support broadcast data link services. These services are known as Automatic Dependent Surveillance-Broadcast (ADS-B), Traffic Information Services-Broadcast (TIS-B) and Flight Information Services-Broadcast (FIS-B). Aircraft equipped with Capstone Avionics Suites, such as Global Positioning Systems (GPS) and Multi-Function Displays (MFD) use GBT's to interface ADS-B reports for transmission over the GBT's Ground Interface to an end system.

Basic Data Link Functions of the GBT

The GBT’s primary function is that of translating data link traffic between the GBT’s Air Interface (the RF medium) and the GBT’s Ground Interface (interface to other ground systems). The GBT is an event driven system that performs the following three fundamental tasks:

• Reception of ADS-B messages received over the GBT’s Air Interface is mapped into ADS-B reports for transmission over the GBT’s Ground Interface to an end system
• Reception of TIS-B reports over the GBT’s Ground Interface are mapped into TIS-B messages for transmission over the GBT’s Air Interface to aircraft
• Reception of Uplink Data Blocks containing FIS information over the GBT’s Ground Interface are mapped into Ground Uplink messages for transmission over the GBT’s Air Interface to aircraft

Figure 1-1 is a simplified diagram of the GBT relative to other elements

Figure 1-1: The GBT in Context of Other Elements

GBT Pictures

Figure 1-3: Sunnahae Mountain GBT

Figure 1-4: Sunnahae Mountain GBT

Figure 1-5: Sunnahae Mountain GBT

Figure 1-6: Sunnahae Mountain GBT

Figure 1-7: Gunnuk Mountain GBT

Figure 1-8: Gunnuk Mountain GBT

Figure 1-9: Sisters Island GBT

Figure 1-10: Sisters Island GBT

Figure 1-11: Cape Spencer GBT