First, with the technology currently available, aircraft will not have the ability to be properly equipped and certified with Automatic Dependent Surveillance-Broadcast (ADS-B) In only. Next, even in a properly equipped and certified aircraft with both ADS-B In and Out, why would you want to exclude the reception of ground transmissions? The ground transmissions are necessary for the proper operation of the system. The codes transmitted by all parts of the ADS-B communication network are identified within the digital code of their particular transmission.
Your question brings up another subject I’d like to address: Portable ADS-B In Equipment.
There are several models of portable ADS-B In equipment now available on the market. This portable equipment is a lower cost alternative for operators. However, it has limitations compared to properly equipped and certified aircraft with both ADS-B In and Out. Portable ADS-B In equipment is able to receive ADS-B Out from other aircraft but not from the ground stations. This limitation is motivation for operators to upgrade to ADS-B Out earlier than January 1, 2020.
ADS-B equipage standards will be via Supplemental Type Certificate (STC), and ADS-B In only, will not be an option for properly equipped and certified aircraft.
Future versions of TCAS processors will use ADS-B data from the transponders to verify "targets" in order to reduce the need to directly interrogate them, shifting priority to other "targets" through a process called "Hybrid Surveillance." Exactly how the software algorithms and processes work are different for each equipment manufacturer and remains unknown as it is proprietary data information.
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