Ranging between mobile devices

A first mobile device, comprising:

• one or more memories configured to store processor-executable instructions;
• and
• one or more processors in communication with the one or more memories and configured to execute the instructions stored in the one or more memories to perform operations including:
• receiving, at a user interface of the first mobile device, user input configuring a notification to be provided by the first mobile device based on a proximity of the first mobile device to a second mobile device of a second user;
• transmitting, by the first mobile device, an advertisement signal that includes a first authentication tag of the first mobile device;
• receiving, from the second mobile device, a second authentication tag of the second mobile device;
• authenticating the second mobile device using the second authentication tag, wherein the second mobile device uses the first authentication tag to authenticate the first mobile device;
• communicating, by the first mobile device, one or more ranging settings with the second mobile device for a ranging operation to be performed;
• transmitting, by the first mobile device, a first set of one or more pulses in a ranging request message to the second mobile device in accordance with the one or more ranging settings;
• receiving, by the first mobile device, a second set of one or more pulses in one or more ranging response messages from the second mobile device;
• determining distance information corresponding to one or more transmission times of the first set of one or more pulses and one or more reception times of the second set of one or more pulses;
• comparing a distance of the distance information to a threshold;
• and
• providing the notification based on the distance exceeding the threshold.