Patent ID: 7873111
Filing Date: 2011-01-18
Classification: H04L

Abstract:
1. A method for synchronizing a receiver in an Orthogonal Frequency Division Multiplexing (OFDM) system, the method comprising: transforming, by the receiver, a received signal from the time domain into the frequency domain to produce a transformed signal; rotating, by the receiver, each set of ranging tones of the transformed signal in the frequency domain based on a corresponding tone index to produce a set of phase-rotated frequency domain received ranging tones that is equivalent to time domain shifted ranging signals, each ranging tone in the sets of ranging tones being rotated iteratively over a predefined set of delay-values, wherein each delay-value within the predefined set of delay-values ranges from zero to a predetermined time delay; computing, by the receiver, a detection metric corresponding to each delay-value within the predefined set of delay-values based on the set of phase-rotated frequency domain received ranging tones; and based on the detection metrics determined for the delay values, determining a timing offset of the receiver; wherein computing a detection metric comprises computing a non-coherent detection metric and, when the non-coherent detection metric is greater than a predetermined threshold, the received signal is detected and the timing offset is determined, based on the non-coherent detection metric; and further wherein computing a detection metric comprises computing a coherent detection metric corresponding to each delay-value within the predefined set of delay-values based on the corresponding set of phase-rotated frequency domain received ranging tones if each non-coherent detection metric is less than the predetermined threshold, and when a coherent detection metric is greater than a predetermined threshold, the received signal is detected and the timing offset is determined, based on the coherent detection metric.