Patent ID: 8548033

Claim:
A method for determining a carrier frequency offset and a corresponding sample-to-sample phase shift present in a sampled digital signal from a radio of a wireless transceiver, said method comprising the steps of: dividing a carrier frequency offset (CFO) range to be covered into a plurality of intervals; creating from a received signal as many parallel derived streams as there are intervals and pre-compensating (“back rotating”) signals received by the sample-to-sample phase shift corresponding to a midpoint of a particular one of the plurality of intervals; computing magnitude and phase resulting from a correlation of an expected preamble pattern period waveform with a preamble segment of each derived stream in parallel; selecting a largest resulting magnitude value(s) to zoom in on an actual CFO present in an input stream of the signals received; repeating a search for a shorter interval centered on a CFO value located in a first run, if needed, in order to improve accuracy in the presence of noise and provided there is still input preamble left to work on; and determining an actual CFO from the CFO values belonging to the selected interval and the result of the corresponding computed correlation phase.