Initiating UWB communication between vehicle system and portable identifier

A method for using a vehicle system that has stored a portable identifier, the portable identifier comprising an electrical energy source, the vehicle system and the portable identifier being configured to communicate using an Ultra-WideBand (UWB) communication protocol within a first perimeter around a vehicle and to communicate using a Bluetooth Low Energy (BLE) communication protocol within a second perimeter around the vehicle, the second perimeter including the first perimeter, the method comprising, while a user carrying the portable identifier is approaching the vehicle:

• detecting that the portable identifier is located within the second perimeter;
• performing, after the detection and before the user reaches the first perimeter, a first and a second distance measurement between the user and the vehicle using the BLE communication protocol, the second measurement being performed after the first measurement;
• determining a speed of the user on a basis of the first and second distance measurements;
• predicting a time remaining for the user to reach a predetermined near distance from the vehicle on the basis of the determined speed;
• and
• initiating a communication using the UWB communication protocol after the predicted remaining time has elapsed.