Diversity GMSK-receiver with interference cancellation and methods therein
View Patent ↗Method in a diversity antenna GMSK receiver of determining interference canceling equalizers and corresponding equalizers are described. The method includes providing a plurality of GMSK received signals; de-rotating and splitting each of the plurality of received signals into in phase and quadrature parts to provide a multiplicity of real valued branches; calculating linear equalizers for each of a multiplicity of subsets of the multiplicity of real valued branches; and providing an interference canceling equalizer for each of the multiplicity of real valued branches, each interference canceling equalizer corresponding to a weighted combination of the linear equalizers. A corresponding equalizer includes eight linear equalizers processing four branch signals corresponding to real (I) and quadrature (Q) parts of a GMSK diversity signal from two antennas.
1. A method in a diversity antenna Gaussian Minimum Shift Keyed (GMSK) receiver of determining interference canceling equalizers, the method comprising:
providing a plurality of GMSK received signals;
de-rotating and splitting each of the plurality of GMSK received signals into in-phase (I) and quadrature (Q) parts to provide a multiplicity of real valued branches;
calculating linear equalizers including calculating corresponding filter taps for each of a multiplicity of subsets of the multiplicity of real valued branches; and
providing an interference canceling equalizer for each of the multiplicity of real valued branches, each interference canceling equalizer corresponding to a weighted combination of the linear equalizers.
2. The method of claim 1 further comprising:
determining corresponding weighting factors associated with each of the interference canceling equalizers; and
wherein the providing an interference canceling equalizer for each of the multiplicity of real valued branches, each interference canceling equalizer corresponding to a weighted combination of the linear equalizers further comprises weighting the linear equalizers in accordance with the corresponding weighting factors.
3. The method of claim 1 further comprising:
finding an error sequence corresponding to the linear equalizers for each of the multiplicity of subsets to provide a multiplicity of error sequences, the error sequence depending on a training sequence; and
wherein the providing each of the interference canceling equalizers further comprises weighting the linear equalizers dependent on relationships among the multiplicity of the error sequences.
4. The method of claim 3 further comprising:
determining correlations between the multiplicity of error sequences corresponding to the linear equalizers for each of the multiplicity of subsets; and
determining, using the correlations, corresponding weighting parameters for weighting the linear equalizers to provide the interference canceling equalizer for each of the multiplicity of real valued branches.
5. The method of claim 1 wherein the calculating linear equalizers comprises determining a multiplicity of filter taps for each equalizer and a timing parameter for each subset.
6. The method of claim 1 :
wherein the providing a plurality of GMSK received signals further comprises providing a first and a second GMSK received signal, each including a training symbol sequence;
wherein the de-rotating and splitting comprises de-rotating and splitting each of the first and the second GMSK received signals into corresponding in-phase and quadrature parts to provide four real valued branches; and
wherein the calculating linear equalizers including calculating corresponding filter taps comprises calculating two equalizers including calculating corresponding filter taps for each pair of four pairs of the four real valued branches.
7. The method of claim 1 wherein the calculating linear equalizers further comprises calculating the linear equalizers at each of a plurality of time trials to determine a timing parameter associated with each of the multiplicity of subsets.
8. The method of claim 7 wherein the timing parameter is selected as the timing trial that minimizes a timing error value.
9. A method of interference cancellation in a diversity Gaussian Minimum Shift Keyed (GMSK) receiver, the method comprising:
providing a first and a second GMSK received signal from a, respective, first and second antenna, each of the first and the second GMSK received signal including a training symbol sequence;
de-rotating and splitting the first and the second GMSK received signal into, respective and corresponding in-phase (I) and quadrature (Q) parts to provide four real valued branches;
calculating first and second linear equalizers including calculating corresponding filter taps for each of four unique pairs of branches selected from the four real valued branches to provide eight linear equalizers; and
providing an interference canceling equalizer for each of the four real valued branches, each interference canceling equalizer corresponding to a weighted combination of two of the eight linear equalizers; and
processing one of the four real valued branches to cancel interference.
10. The method of claim 9 further comprising:
determining corresponding weighting factors associated with each of the interference canceling equalizers; and
wherein the providing an interference canceling equalizer for each of the four real valued branches, each interference canceling equalizer corresponding to a weighted combination of two of the eight linear equalizers further comprises weighting the two of the eight linear equalizers in accordance with the corresponding weighting factors.
11. The method of claim 9 further comprising:
finding an error sequence corresponding to the first and second linear equalizers for each of the four unique pairs of branches to provide four error sequences; and
wherein the providing each of the interference canceling equalizers further comprises weighting the linear equalizers dependent on relationships among the four error sequences.
12. The method of claim 11 further comprising:
determining correlations between the four error sequences; and
determining, using the correlations, corresponding weighting parameters for weighting the two of the eight linear equalizers to provide the interference canceling equalizer for each of the four real valued branches.
13. The method of claim 9 wherein the calculating first and second linear equalizers including calculating corresponding filter taps further comprises determining a plurality of filter taps for each linear equalizer and a timing parameter for the first and the second linear equalizer for each unique pair of branches.
14. The method of claim 9 wherein the calculating first and second linear equalizers including calculating corresponding filter taps further comprises calculating the first and second linear equalizers for each of the four unique pairs at each of a plurality of time trials to determine a timing parameter associated with the first and second linear equalizer for each of the four unique pairs.
15. The method of claim 14 wherein the timing parameter is selected as the timing trial that minimizes a timing error value determined over a known training sequence.
16. The method of claim 9 wherein the calculating and the providing are performed using the training sequence observations corresponding to the first and the second GMSK received signal as compared to a known training sequence.
17. The method of claim 9 wherein the calculating first and second linear equalizers including calculating corresponding filter taps is performed over a plurality of time trials and further comprises iteratively calculating the first and second linear equalizer including calculating corresponding filter taps at a next time trial relying on relationships between the eight equalizers over the plurality of time trials.
18. An interference canceling equalizer in a diversity Gaussian Minimum Shift Keyed (GMSK) receiver, the interference canceling equalizer comprising,
eight linear equalizers processing four branch signals corresponding to real (I) and quadrature (Q) parts of a diversity signal comprising two GMSK received signals from two antennas, wherein the eight linear equalizers including corresponding filter taps are calculated from four pairs of the four branch signals, with each pair having an associated timing parameter determined during calculation of two linear equalizers corresponding to the pair; and
a weighting function for weighting the outputs from linear equalizers as adjusted by the associated timing parameter for each pair of the four branch signals to provide four weighted soft symbols corresponding, respectively, to the four pairs; and
a combiner for combining the four weighted soft symbols to provide soft symbols for the diversity signal.
19. An interference canceling equalizer in a diversity Gaussian Minimum Shift Keyed (GMSK) receiver, the interference canceling equalizer comprising,
four canceling equalizers processing four branch signals corresponding to real (I) and quadrature (Q) parts of a diversity signal, the diversity signal comprising two GMSK received signals from two antennas, to provide soft symbols corresponding to each of the four branch signals, the four canceling equalizers determined as a weighted combination of linear equalizers, where the linear equalizers including corresponding filter taps are calculated for four different respective pairs of the branch signals and a timing parameter is calculated for each pair; and
a combiner for combining the soft symbols corresponding to each of the four branch signals, to provide soft symbols corresponding to the diversity signal.