Precise mobile positioning inside a car using outside 2.4 GHz antennas

A mobile phone with the Bluetooth enabled is inside a car. The mobile phone inside the car could be anywhere: in the driver's pocket, on the passenger seat, etc. 2.4GHz antennas used in outdoor conditions and obviously outside the car will be set to create a detection zone of 2 meter diameter. The goal is to be able to send data through Bluetooth 2.4GHz to the mobile phone but only if this one is within the detection zone. This must be very reliable because several cars could be one behind the other or one next to the other. So when the car goes inside the detection zone, the mobile phone must be able to detect the 2.4GHz signal from the outside antennas and start to communicate using Bluetooth. If the car is not inside this detection zone of 2m diameter, the mobile phone cannot detect the signal. If 2 cars is one behind the other, only the mobile inside the car within the detection zone will be detected. The use of 1 or more directional antennas will be certainly a way to do it. The 2.4GHz frequency is well absorbed by the metal parts of the car and by the human body. A special attention will be put on the position of the antennas to avoid too much absorption by the metal parts of the car. The 2.4GHz antennas will be connected to a hardware in order to transmit data to the mobile phone. More details will come when we start the project. Your mission is to find a solution to do what's described above. It includes finding: - What kind of antennas must be used (model, type, gain, etc.) - The antennas positioning - Tests in real conditions