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 system comprising:
an orthogonal frequency division multiplexing (OFDM) receiver module comprising an antenna; and
at least one computing device, wherein the at least one computing device comprises:
at least one processor;
memory storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
receive, from the OFDM receiver module, 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;
combine the plurality of multi-path signals into a combined signal;
generate a combined correlation result for the combined signal based on a predefined guard interval;
select a range of data samples associated with the combined correlation result based on a duration of the guard interval;
apply a bias correction over the range of data samples;
generate a biased correlation result responsive to the applied bias correction; and
use, by the at least one data processor, a peak of the biased correlation result as a timing reference for a current OFDM symbol.
2. The system 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 system 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 system 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 system of claim 1 , wherein the bias correction is based on using a linear formula.
6. The system of claim 1 , wherein the bias correction is based on using a non-linear formula.
7. The system 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.