JPH0465947A - Quadrature amplitude modulation system - Google Patents

Abstract

PURPOSE:To reduce an error rate at signal transmission by arranging signal points such that the interval of the signal points closer to the origin is taken wider and the interval of the signal points is taken apart as the points are parted from the origin. CONSTITUTION:Signal points are so arranged that the interval of signal points projected to P and Q axes is selected that the relation of DELTA11>DELTA12>DELTA13>DELTA14, and DELTA21>DELTA22>DELTA23 is established from the intervals DELTA11, DELTA21 of the signal points closer to the origin toward the intervals DELTA14, DELTA23 apart from the origin. Thus, the expected value being the total sum of products between criterion frequencies at a criterion level among the signal points and criterion errors of the signal points is minimized by arranging the signal points such that the interval among the signal points around the origin with respect to the P and Q axes is selected wider and the interval among the signal points apart from the origin is selected narrower.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a quadrature amplitude modulation method in digital wireless communication, and in particular, when a honeycomb signal point arrangement is adopted, signal transmission is achieved by changing the signal point arrangement from equal intervals. This paper relates to a quadrature amplitude modulation method that improves the error rate in time.

[Conventional technology]

Quadrature amplitude modulation using a conventional honeycomb signal point arrangement (
As shown in FIG. 2, the signal point arrangement of the 68QAM method (hereinafter referred to as QAM), for example, has two orthogonal P axes.

The interval between signal points 2 in the Q-axis direction is Δ1 on each axis.
．． They are equal, such as Δ2. In addition, Δ2 and Δ
The relationship of 1 is Δ2=EgoΔ1. Now, for example, the number of signal points placed in the rows projected onto the Q axis is 9, 8, and 7 from the row closest to the origin.

There are 6 signal points, and the number of signal points decreases as the distance from the origin increases. Generally, in signal transmission, if the probability of occurrence of all signal point arrangements is equal, then in projection onto the P-axis and Q-axis, the frequency of occurrence of signal points near the origin is large and decreases as the distance from the origin increases.

That is, the determination frequency is large at the determination level near the origin of the P axis and the Q axis, and the determination frequency decreases as the distance from the origin increases. Furthermore, if the signal point judgment error rates at judgment levels between adjacent signal points are all equal, the number of errors at judgment levels near the origin of the P and Q axes is large, and the number of errors at judgment levels far from the origin is large. The number of errors is reduced,
As for the expected value, which is the sum of the products of the judgment frequency at each judgment level and each signal point judgment error rate, the expected value of the minimum state could not be obtained.

[Problem to be solved by the invention]

In the honeycomb signal point arrangement in the conventional orthogonal amplitude modulation method described above, the intervals between each signal point are equal, so the P axis,
The number of signal points arranged is large near the origin where the Q-axis intersects, and the number decreases as you move away from the origin, and the expected value is the sum of the products of the judgment frequency at each judgment level and the judgment error rate of each signal point. That is, the total number of errors does not reach the minimum state, and therefore, the error rate during signal transmission, which is the total number of errors per unit time, does not reach the minimum state either.

[Means for Solving the Problems] The orthogonal amplitude modulation method of the present invention employs a honeycomb signal point arrangement, in which the distance between each signal point projected onto the orthogonal P axis and Q axis is The distance between the signal points closest to the origin of the axes and Q-axes is arranged so that the distance becomes narrower as the distance between the signal points further from the origin becomes smaller, and the distance between the signal points is gradually narrowed. The sum of the products of the judgment frequency and each signal judgment error rate is minimized.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram showing a signal point arrangement of a 68QAM system according to an embodiment of the present invention. In the embodiment shown in FIG.
The interval between each signal point projected onto the axis is defined as the interval between signal points close to the origin Δ11. Interval of signal points distant from Δ21 Δ14. Δ23
Δ11〉Δ12〉Δ13〉Δ14.
The signal points are arranged so as to have a relationship of Δ21>Δ22>Δ23. Therefore, the interval between signal points near the origin of the P-axis and Q-axis should be widened, and should be narrowed as the distance from the origin increases. By arranging them in this way, it is possible to minimize the expected value, which is the sum of the products of the judgment frequency at the judgment level between each signal point and the judgment error rate of each signal point.

〔Effect of the invention〕

As explained above, in a QAM system that employs a honeycomb signal point arrangement, the present invention makes it possible to increase the judgment level between each signal point by widening the interval between signal points near the origin and narrowing the distance from the origin. The expected value, which is the sum of the products of the judgment frequency and each signal point error rate, can be minimized.

Therefore, there is an effect that the error rate during signal transmission can be lowered.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the signal point arrangement of an embodiment of the present invention,
FIG. 2 is an explanatory diagram showing the signal point arrangement of the 68QAM method, which is a conventional quadrature amplitude modulation method. 1.2...Signal point.

Claims (1)

[Claims] In a quadrature amplitude modulation method that employs a honeycomb signal point arrangement, the distance between each signal point projected onto the orthogonal P and Q axes is determined from the distance between the signal points closest to the origin of the P and Q axes to the origin. The signal points are arranged so that the distance becomes narrower as the distance between signal points becomes smaller, and the sum of the product of the judgment frequency at the judgment level between each signal point and each signal judgment error rate is minimized. A quadrature amplitude modulation method characterized by: