| CPC H04W 56/0075 (2013.01) [H04W 56/0035 (2013.01)] | 19 Claims |
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1. A method of calculating a time of flight between two network devices in a wireless network, comprising:
transmitting a packet from a first network device, referred to as an initiator, to a second network device, referred to as a reflector;
starting an initiator timer at the initiator when the packet begins transmission;
receiving a return packet from the reflector in response to the packet;
stopping the initiator timer when the return packet is present at the initiator;
using a parabolic estimate to correct for resolution error in the initiator timer, wherein the parabolic estimate uses a value of a prompt sample (P), an early sample (E) and a late sample (L), each generated based on an oversample clock to provide an estimated fractional delay, which is a fraction of a period of the initiator timer;
using the estimated fractional delay to calculate an estimation error, which is an error associated with the estimated fractional delay calculated using the parabolic estimate;
receiving a reflector time from the reflector; and
determining the time of flight based on the initiator timer, the reflector time, the estimated fractional delay and the estimation error.
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