A mobile device can include ranging circuitry to determine distance to another mobile device. A first wireless protocol can establish an initial communication session to perform authentication and/or exchange ranging settings. One mobile device acting as a beacon device can define a ranging round including an initial timeslot and a plurality of non-overlapping response slots for discovering and performing ranging with any mobile device in a vicinity of the beacon. The beacon can broadcast a ranging request including a beacon device identifier at a request time. A first mobile device can transmit a first acknowledgement message during a first response slot. A second mobile device can transmit a second acknowledgement message during a second response slot. The beacon device can calculate a first distance from the first mobile device and a second distance from the second mobile device based at least upon information in the first and second acknowledgement messages.