Patent ID: 8463290

Claim:
A method of determining ranges between a plurality of communication devices, the plurality of communication devices including at least one mobile communication device, the method comprising: receiving, at a first communication device, receive messages transmitted from a plurality of other communication devices, each receive message including a transmit count stamp corresponding to a remote counter value at the transmission of the receive message from the corresponding other communication device, wherein the first communication device generates a receive count stamp for each receive message corresponding to a local counter value at receipt of the receive message from the other communication devices and for messages received from the mobile communication device; as the mobile communication device travels along a path relative to the plurality of other communication devices, dynamically associating and disassociating the mobile communication device with a plurality of sub-groups of the plurality of other communication devices, wherein the associating and disassociating are based at least in part on receiving receive messages from a predetermined number of other communication devices for each sub-group; and for each sub-group currently associated with the mobile communication device, generating range estimates between the mobile communication device and the other communication devices in the sub-group currently associated with the mobile communication device, the range estimates based on a combination of the transmit count stamps and the receive count stamps; and wherein at least one of the range estimates is a mobile device range estimate between the mobile device and a second communication device that the mobile communication device is newly associated with in one of the sub-groups, and the mobile device range estimate is computed as a function of a local clock time of the second communication device, and a delta time relating the local clock time to a time for a group of communication devices computed based on count stamps previously communicated between the second communication device and other communication devices in the plurality of sub-groups.