Method and implementation for adaptive symbol decision mapping
AssigneeCisco Technology, Inc.
InventorsMichael E. Lewis, David M. Theobold
Life of this patent
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Abstract
A method and implementation are disclosed for reducing signal distortion. A symbol detector is provided for establishing at least one decision boundary and assigning symbols extracted from a received signal to constellations of symbols separated by the at least one decision boundary. A quality measure implementation is provided for determining an error rate of the output of the symbol detector with respect to the at least one decision boundary. A boundary generator is provided for receiving the error rate and generating parameters that are fed back to the symbol detector to vary the decision boundary positions and shapes, so as to reduce the error rate of the symbol detector.
Claims18
An apparatus for reducing signal distortion comprising:
- a symbol detector that reduces complex symbols of a demodulated waveform to digital numbers based on at least one decision boundary;
- a quality measure implementation coupled to the output of the symbol detector for determining an error rate of the symbols;
- and
- a boundary generator coupled to the quality measure for receiving the error rate from the quality measure and generating parameters that are fed back to the symbol detector;
- wherein the symbol detector is responsive to the parameters received from the boundary generator to vary the at least one decision boundary to reduce the error rate of the symbol detector;
- wherein the symbol detector varies the decision boundary position and shape in conjunction with a function of a coordinate system in a complex symbol plane;
- and
- wherein the function is determined by a symbol center-of-mass calculation followed by appropriate matrix transformations, so as to transform symbol positions from a distorted constellation map onto an undistorted constellation map.
A method for reducing signal distortion comprising the steps of:
- establishing at least one decision boundary;
- assigning symbols extracted from a received signal to digital numbers based on the at least one decision boundary;
- determining an error rate of the symbols;
- varying the at least one decision boundary to acquire a new at least one decision boundary;
- assigning symbols extracted from the received signal to digital numbers based on the new at least one decision boundary;
- determining an error rate of the symbols extracted based on the new at least one decision boundary;
- and
- selecting one of a group consisting of the at least one decision boundary and the new at least one decision boundary based which decision boundary produces a lower error rate;
- wherein the step of varying the decision boundary position and shape is performed by determining a function of a coordinate system in a complex symbol plane;
- and
- wherein the step of determining the function comprises performing a symbol center-of-mass calculation followed by appropriate matrix transformations, and thereby transforming symbol positions from a distorted constellation map onto an undistorted constellation map.
Dependencies are inferred from the claim text.