Efficient UWB ranging

A method of operating a first device to determine a distance, d, between the first device and a further device, the method comprising:

• transmitting a first broadcast frame comprising an identifier of the first device, A, and a transmission timestamp;
• receiving a further broadcast frame from the further device, the further broadcast frame comprising
• an identifier of the further device, B, and a transmission timestamp of the further device,
• and at least one data pair, each data pair comprising a transmitting device identifier, Q, and a reception timestamp, wherein the reception timestamp is indicative of the arrival time at the further device of a prior broadcast frame broadcast from the transmitting device;
• determining a reception timestamp of the further broadcast frame;
• comparing each transmitting device identifier, Q, with the identifier of the first device, A;
• in response to matching a one of the at least one transmitting device identifiers with the identifier of the first device, determining the distance between the first device and the further device;
• at the end of a time interval after transmitting the first broadcast frame, transmitting a subsequent broadcast frame,
• wherein the subsequent broadcast frame comprises
• the identifier of the first device, A, and a transmission timestamp, T2TxA,
• and at least one data pair,
• each data pair comprising a transmitting device identifier, P, and a reception timestamp, wherein the reception timestamp records the arrival time, TRxPA at the first device of a broadcast frame previously broadcast from the transmitting device, and wherein the time interval has a duration between 0.5 and 1.5 times a broadcast interval.

A first device having a device identifier, A, and comprising:

• a clock-circuit configured to generate one or more time-stamps;
• an ultra-wideband (UWB) transceiver, configured to:
• transmit a first broadcast frame, TxA, comprising the device identifier, A and a first transmission timestamp, TTxA generated by the clock, wherein the first transmission timestamp indicates a first time of departure that corresponds to a first moment when the first device transmitted the first broadcast frame, and
• receive, at a second moment, a further broadcast frame, TxB, from a further device, B;
• and
• a processor configured to determine, from the further broadcast frame:
• an identifier of the further device, B,
• a second transmission timestamp, TTxB, which indicates a second time of departure that corresponds to a third moment when the further device transmitted the further broadcast frame,
• a first data pair, which includes the identifier of the first device, A, and a first reception timestamp, TRxAB, which indicates a first time of arrival that corresponds to a fourth moment when the further device received the first broadcast frame,
• and a second data pair, which includes an identifier of a third device, C, and a second reception timestamp, TRxCB, which indicates a second time of arrival that corresponds to a fifth moment when the further device received another further broadcast frame;
• wherein the processor is further configured to:
• determine a third reception timestamp, TRxBA, of the further broadcast frame, wherein the third reception timestamp corresponds to the second moment when the further broadcast frame, TxB, was received;
• and, in response to determining, by the first device, that the first data pair includes the identifier of the first device,
• determine the distance between the first device and the further device.