Methods and apparatus for correcting timing and frequency offsets between communications receivers and transmitters
A processor-implemented method includes receiving a signal representing a first encoded data and calculating an estimated timing offset and/or an estimated frequency offset associated with the signal. A correction of at least one of a timing offset or a frequency offset of the signal is performed based on the estimated timing offset and/or the estimated frequency offset, to produce a modified signal. An effective channel is subsequently detected based on the signal or the modified signal. A second encoded data is generated based on the modified signal, a known vector, at least one left singular vector of the effective channel, and at least one right singular vector of the effective channel. A signal representing the second encoded data is transmitted to a communication device for identification of contents of a message at a different processor.
1. A method, comprising:
receiving, at a first processor, a signal representing a first encoded data;
calculating, via the first processor, at least one of an estimated timing offset associated with the signal or an estimated frequency offset associated with the signal;
performing, via the first processor, a correction of at least one of a timing offset of the signal based on the estimated timing offset or a frequency offset of the signal based on the estimated frequency offset associated with the signal, to produce a modified signal;
detecting, via the first processor and after the calculating and the performing, an effective channel based on one of the signal or the modified signal;
generating, after the calculating and the performing, a second encoded data based on the modified signal, a known vector, at least one left singular vector of the effective channel, and at least one right singular vector of the effective channel; and
transmitting a signal representing the second encoded data to a communication device for identification of contents of a message at a second processor different from the first processor and co-located with the communication device.
2. The method of claim 1 , wherein at least one of (1) the calculating the at least one of an estimated timing offset or an estimated frequency offset, or (2) the performing the correction, includes performing rational resampling of the signal in the time domain.
3. The method of claim 2 , wherein the rational resampling is performed using a matched filter.
4. The method of claim 1 , wherein at least one of (1) the calculating the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes oversampling of the signal.
5. The method of claim 1 , wherein at least one of (1) the calculating the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes upsampling of the signal and decimating on a subset of the signal.
6. The method of claim 1 , wherein each of (1) the calculating the at least one of the estimated timing offset or the estimated frequency offset and (2) the performing the correction, is performed based on a training sequence.
7. The method of claim 1 , further comprising performing singular value decompositions of the effective channel to identify the at least one left singular vector of the effective channel and the at least one right singular vector of the effective channel.
8. A method, comprising:
receiving, at a first processor, a signal representing an encoded data and a channel transformation;
identifying, via the first processor, at least one of an estimated timing offset associated with the signal or an estimated frequency offset associated with the signal;
performing, via the first processor, a correction of at least one of a timing offset of the signal based on the estimated timing offset or a frequency offset of the signal based on the estimated frequency offset associated with the signal, to produce a modified signal;
detecting, via the first processor and after the identifying and the performing, a representation of an effective channel based on one of the signal or the modified signal;
performing, after the identifying and the performing, a singular value decomposition of the representation of the effective channel to identify right singular vectors thereof; and
querying a codebook of unitary matrices to identify contents of a message associated with the modified signal based on the right singular vectors and a unitary matrix.
9. The method of claim 8 , wherein at least one of (1) the identifying the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes performing rational resampling of the signal in a time domain.
10. The method of claim 9 , wherein the rational resampling is performed using a matched filter.
11. The method of claim 8 , wherein at least one of (1) the identifying the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes oversampling of the signal.
12. The method of claim 8 , wherein at least one of (1) the identifying the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes upsampling of the signal and decimating on a subset of the signal.
13. The method of claim 8 , wherein each of (1) the identifying the at least one of the estimated timing offset or the estimated frequency offset and (2) the performing the correction, is performed based on a training sequence.
14. A non-transitory, processor-readable medium storing instructions that, when executed by a first processor, cause the first processor to:
receive a signal representing (1) a first symbol of a first encoded data, and (2) a channel transformation;
calculate at least one of an estimated timing offset associated with the signal or an estimated frequency offset associated with the signal;
perform a correction of at least one of a timing offset of the signal based on the estimated timing offset or a frequency offset of the signal based on the estimated frequency offset associated with the signal, to produce a modified signal;
detect, after the calculating and the performing, a representation of an effective channel based on the signal;
perform, after the calculating and the performing, a singular value decomposition of the representation of the effective channel to identify a left singular vector of the representation of the effective channel and a right singular vector of the representation of the effective channel;
select a precoding matrix from a codebook of unitary matrices, the precoding matrix associated with an index for a message for transmission;
generate a second encoded data based on a known vector, the modified signal, the precoding matrix, a complex conjugate of the left singular vector, and the right singular vector of the representation of the effective channel; and
cause transmission of (1) a signal representing a first symbol of the second encoded data and (2) a signal representing a second symbol of the second encoded data, through a communication channel, to a communication device for identification of contents of the message at a second processor that is associated with the communication device.
15. The non-transitory, processor-readable medium of claim 14 , wherein at least one of (1) the calculating the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes performing rational resampling of the signal in the time domain.
16. The non-transitory, processor-readable medium of claim 15 , wherein the rational resampling is performed using by instructions implementing a matched filter.
17. The non-transitory, processor-readable medium of claim 14 , wherein at least one of (1) the calculating the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes oversampling of the signal.
18. The non-transitory, processor-readable medium of claim 14 , wherein at least one of (1) the calculating the at least one of the estimated timing offset or the estimated frequency offset, or (2) the performing the correction, includes upsampling of the signal and decimating on a subset of the signal.
19. The non-transitory, processor-readable medium of claim 14 , wherein each of (1) the calculating the at least one of the estimated timing offset or the estimated frequency offset and (2) the performing the correction, is performed based on a training sequence.