Method and apparatus for advanced OFDM triggering techniques
Systems and methods for a non-data-aided (NDA) approach to advanced OFDM timing are provided. This approach allows for accurate OFDM symbol timing and synchronization by avoiding inter-symbol interference (ISI) in multipath environments where an earliest arriving signal may not be the strongest signal. The NDA approach may rely on generating and applying a bias correction to a combined correlation result of the multi-path signals.
1 . A method for advanced orthogonal frequency division multiplexing (OFDM) timing, the method comprising:
receiving, by at least one data processor, a plurality of multi-path signals that correspond to a same signal delayed by different amounts during transmission over a plurality of wireless data paths;
generating, by the at least one data processor, a combined correlation result based on correlating an aggregated signal of the plurality of multi-path signals with a predefined guard interval;
selecting, by the at least one data processor, a range of data samples associated with the combined correlation results based on occurrences of the correlation peaks;
applying, by the at least one data processor, a bias correction over the range of selected data samples;
generating, by the at least one data processor, a biased correlation result responsive to the applied bias correction; and
using, by the at least one data processor, a peak of the biased correlation results as a timing reference for a current OFDM symbol.
2 . The method of claim 1 , wherein the selecting the range of data samples is further based on determining respective signal power levels associated with each of the multi-path signals.
3 . The method of claim 1 , wherein the selecting the range of data samples is further based on a predefined value relative to a size of the guard interval.
4 . The method of claim 1 , wherein the applying the bias correction is further based on:
determining an expected delay range associated with data arriving via the plurality of multi-path signals; and
using a subset of the combined correlation result that corresponds to the expected delay range.
5 . The method of claim 1 , wherein the bias correction is based on using a linear formula.
6 . The method of claim 1 , wherein the bias correction is based on using a non-linear formula.
7 . The method of claim 1 , wherein the bias correction is based on:
determining an expected delay range associated with the multi-path signals; and
using a subset of the combined correlation result that corresponds to the expected delay range.
8 . The method of claim 7 , wherein the determining the expected delay range is based on using channel state information for dynamically controlling an expected range of signal delays.