UWB ranging methods and apparatus are disclosed. The method comprises a ranging communication with a plurality of responder devices, the ranging communication comprising: transmitting, by an initiator device, a polling signal in a time slot; receiving a respective response from each of the plurality of responder devices, overlapping and in a next time slot, each response comprising: synchronization bits, and a frame comprising Start of Frame Delimiter, and a Scrambled Timestamp Sequence; wherein the STS comprises a sequence of segments each preceded by a respective guard interval, wherein a specific one of the segments comprises data derived from a ranging key and a responder-identifier each unique to the respective responder among the plurality of responders, wherein a sequence-number of the specific segment is unique to the respective response, and wherein a remainder of the segments each comprise the same data derived from a predetermined common key and predetermined common data.