Other countries have sightly later schedules. This didn't quite work out as you will find out, but is getting closer. By 2020 all planes in US airspace were to have had ADSB transmitters to broadcast their full information and status. Light planes can transmit shorter packets that simply identify them. Commercial aircraft use these packets to periodically broadcast their tail number, flight, altitude, direction, and speed. This is based on transmitters that are currently carried by all planes in the US. This system of radars is being replaced with a new system called Automatic Dependent Surveillance-Broadcast, or ADS-B. It is also very expensive to keep all of this hardware up and running constantly, for decades. It does less well for localizing the plane in angle space, due to the beam width, and has no idea which plane it is interrogating. This does a great job of detecting planes, and measuring their range and velocity towards the radar.
In the past planes were tracked with radar. The key element in making air travel safe is keeping track of where all of the planes are and where they are going. Lots of devices talk to each other with this sort of approach. This is a nice example of on-off keying (OOK) that you talked about during the last class, and shows how digital data can be transmitted on an analog RF waveforms. This week we'll look at another way of tracking planes using digital packets. Last week we listened to airband signals, and pilots talking to air traffic control using AM modulation. Assignment 4: Automatic Dependent Surveillance-Broadcast (ADS-B) Overview
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