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;
generate a correlation result associated with the plurality of multi-path signals based on correlating the received signal of the plurality of multi-path signals with a predefined guard interval;
determine a correlation midpoint associated with the correlation result;
apply a bias correction over a range of data samples of the correlation result that are centered around the correlation midpoint;
generate a biased correlation result responsive to the applied bias correction;
identify a peak of the biased correlation result; and
use the peak of the biased correlation result as a triggering reference for a current data symbol of the received signal.
2. The system of claim 1 , wherein the at least one processor receives at least one of the plurality of multi-path signals via a wireless satellite broadcast.
3. The system of claim 1 , wherein the correlation midpoint is determined based on:
identifying a set of values of the combined correlation result that satisfy a predetermined correlation threshold.
4. The system of claim 3 , wherein the predetermined correlation threshold is based on the combined correlation result.
5. The system of claim 4 , wherein the predetermined threshold is further based on:
determining an approximate minimum value and an approximate maximum value of the combined correlation result over a pre-defined window; and
setting the predetermined threshold to be approximately equal to half of a difference in value between the minimum value and the maximum value.
6. The system of claim 3 , wherein the generating the bias correction is further based on:
determining an expected delay range associated with the plurality of multi-path signals; and
selecting a subset of the combined correlation result that corresponds to the expected delay range.
7. The system of claim 3 , wherein the generating the bias correction is based on using a linear formula.
8. The system of claim 3 , wherein the generating the bias correction is based on using a non-linear formula.
9. The system of claim 1 , wherein the range of data samples are determined based on determining respective signal power levels associated with each of the plurality of multi-path signals.
10. The system of claim 1 , the memory further storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
select the range of data samples based on determining respective signal power levels associated with each of the plurality of path-signals and a predefined value relative to a size of the guard interval.