Interference limiting for surveillance messages
In some examples, a system includes a transceiver configured to transmit a first surveillance message at a first power level at or below a first maximum power level. The system also includes processing circuitry coupled to the transceiver, the processing circuitry configured to determine that a threshold condition exists. The processing circuitry is also configured to determine a second maximum power level in response to determining that the threshold condition exists, where the second maximum power level is lower than the first maximum power level. The transceiver is configured to transmit, in response to the processing circuitry determining that the threshold condition exists, a second surveillance message at a second power level, wherein the second power level is at or below the second maximum power level.
1. A system configured to mount on an ownship vehicle, the system comprising:
processing circuitry configured to:
determine a first maximum power level according for the ownship vehicle according to interference limiting standards;
determine, based on a parameter of the ownship vehicle, that a threshold condition exists; and
determine a second maximum power level in response to determining that the threshold condition exists, the second maximum power level being lower than the first maximum power level; and
a transceiver configured to transmit, in response to the processing circuitry determining that the threshold condition exists, a surveillance message at a power level at or below the second maximum power level.
2. The system of claim 1 ,
wherein the processing circuitry is further configured to:
determine that, based on the parameter of the ownship vehicle, two or more threshold conditions exist; and
determine a third maximum power level in response to determining that the two or more threshold conditions exist, the third maximum power level being lower than the first and second maximum power levels,
wherein the transceiver is configured to transmit, in response to the processing circuitry determining that the two or more threshold conditions exist, a second surveillance message at a second power level at or below the third maximum power level.
3. The system of claim 1 ,
wherein the transceiver includes a TCAS II transmitter, and
wherein the processing circuitry is further configured to:
determine that a power output of the TCAS II transmitter is less than a power output allowed by applicable requirements for a TCAS I system; and
suppress TCAS broadcast interrogations transmitted by the transceiver in response to determining that the power output of the TCAS II transmitter is less than the power output allowed by applicable requirements for the TCAS I system.
4. The system of claim 1 , wherein the parameter of the ownship vehicle comprises a speed of the ownship vehicle, and wherein the processing circuitry is configured to determine that the threshold condition exists by determining that the speed of the ownship vehicle is less than a threshold speed.
5. The system of claim 4 , wherein the parameter of the ownship vehicle further comprises an altitude of the ownship vehicle, and wherein the processing circuitry is configured to determine that the threshold condition exists by further determining that the altitude of the ownship vehicle is less than a threshold altitude.
6. The system of claim 1 , wherein the parameter of the ownship vehicle comprises a geographic location of the ownship vehicle, and wherein the processing circuitry is configured to determine that the threshold condition exists by determining that the ownship vehicle is located in a particular geographic region.
7. The system of claim 1 , wherein the processing circuitry is configured to determine that the threshold condition exists by determining that speeds of vehicles near the ownship vehicle are less than a threshold speed.
8. The system of claim 7 , wherein the processing circuitry is configured to determine that the speeds of the vehicles near the ownship vehicle are less than the threshold speed by determining that a maximum speed of the vehicles near the ownship vehicle is less than the threshold speed.
9. The system of claim 7 , wherein the processing circuitry is configured to determine that the speeds of the vehicles near the ownship vehicle are less than the threshold speed by determining that an average speed of the vehicles near the ownship vehicle is less than the threshold speed.
10. The system of claim 7 , wherein the processing circuitry is configured to classify, based on a speed of the ownship vehicle, vehicles as near the ownship vehicle for purposes of determining whether the speeds of the vehicles near the ownship vehicle are less than the threshold speed.
11. The system of claim 7 ,
wherein the transceiver is configured to receive at least one surveillance message indicating a speed of one of the vehicles near the ownship vehicle,
wherein the processing circuitry is configured to determine the speed of one of the vehicles near the ownship vehicle based on the at least one surveillance message, and
wherein the processing circuitry is configured to use the speed, as determined based on the at least one surveillance message, to determine that the speeds of the vehicles near the ownship vehicle are less than the threshold speed.
12. The system of claim 1 , wherein to determine the second maximum power level in response to determining that the threshold condition exists, the processing circuitry is configured to determine the second maximum power level irrespective of a number of other vehicles within an area around the ownship vehicle.