Method of quadrature-phase amplitude modulation
First Claim
1. A method of quadrature-phase amplitude modulation comprising the step of amplitude modulating two carrier signal components I and Q in phase quadrature in accordance with signal points in a signal point constellation, the signal point constellation comprising 22n+1 signal points, where n is an integer equal to or greater than 4, arranged in a modified rectangular array with substantially 22n-1 points in each of four quadrants defined by I and Q axes intersecting at an origin of a phase-plane diagram, the signal points in each quadrant of the array having I and Q component amplitudes of 1,3,5, . . . units, the rectangular array being modified by relocating a plurality of points in each quadrant from positions adjacent to a corner of the rectangle to positions extrapolated from the rectangular array and having reduced distances from the origin, wherein in each quadrant each of a majority of the points so relocated is located in a position, relative to the position which it would have in the rectangular array, rotated through an angle of 180°
- about a point having I and Q amplitude co-ordinates of substantially (2n,2n).
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Abstract
A rectangular array of signal points forming a QAM signal point constellation is modified by relocating signal points from adjacent corners of the rectangular array to positions extrapolated from the rectangular array and at reduced distances from the origin, corresponding to reduced peak amplitude levels. The location is effected in a manner to maintain, at least for a majority of the relocated points, a Hamming distance of one. To this end for a constellation of 22n+1 points, with n=4 or more and points with I and Q amplitudes 1, 3, 5 . . . units in the rectangular array, a plurality of points in each quandrant are relocated to positions, relative to positions which they would have in the rectangular array, rotated through an angle of 180° about a point having I and Q amplitude co-ordinates of (2n, 2n). In addition, in each quadrant each of a plurality of the signal points which are relocated is located in a position, relative to the position which it would have in the rectangular array, in which one of its I and Q amplitude co-ordinates is increased by 2n and the other is reduced by 2n. Specific examples are described for 512-QAM (n=4).
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Citations
19 Claims
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1. A method of quadrature-phase amplitude modulation comprising the step of amplitude modulating two carrier signal components I and Q in phase quadrature in accordance with signal points in a signal point constellation, the signal point constellation comprising 22n+1 signal points, where n is an integer equal to or greater than 4, arranged in a modified rectangular array with substantially 22n-1 points in each of four quadrants defined by I and Q axes intersecting at an origin of a phase-plane diagram, the signal points in each quadrant of the array having I and Q component amplitudes of 1,3,5, . . . units, the rectangular array being modified by relocating a plurality of points in each quadrant from positions adjacent to a corner of the rectangle to positions extrapolated from the rectangular array and having reduced distances from the origin, wherein in each quadrant each of a majority of the points so relocated is located in a position, relative to the position which it would have in the rectangular array, rotated through an angle of 180°
- about a point having I and Q amplitude co-ordinates of substantially (2n,2n).
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of quadrature-phase amplitude modulation comprising the step of amplitude modulating two carrier signal components I and Q in phase quadrature in accordance with signal points in a signal point constellation, the signal point constellation comprising 512 signal points arranged in a modified rectangular array with 128 points in each of four quadrants defined by I and Q axes intersecting at an origin of a phase-plane diagram, the signal points in each quadrant of the array having I and Q component amplitudes of 1, 3, 5, . . . units, the rectangular array being modified by relocating 32 points in each quadrant from positions adjacent to a corner of the rectangle to positions extrapolated from the rectangular array and having reduced distances from the origin, wherein in each quadrant:
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each of about 22 points so relocated is located in a position, relative to the position which it would have in the rectangular array, rotated through an angle of 180°
about a point having I and Q amplitude co-ordinates of substantially (16,16); andeach of at least about 8 other points so relocated is located in a position, relative to the position which it would have in the rectangular array, in which one of its I and Q amplitude co-ordinates is increased by 16 units and the other is reduced by 16 units. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification