CN108881097B

CN108881097B - Gray code-based square QAM constellation diagram coding method and system

Info

Publication number: CN108881097B
Application number: CN201810617163.2A
Authority: CN
Inventors: 刘磊; 张光山; 刘世超
Original assignee: CETC 41 Institute
Current assignee: CETC 41 Institute
Priority date: 2018-06-15
Filing date: 2018-06-15
Publication date: 2021-01-22
Anticipated expiration: 2038-06-15
Also published as: CN108881097A

Abstract

The invention discloses a method and a system for encoding a square QAM constellation diagram based on Gray codes, wherein the method comprises the following steps: performing inter-quadrant coding and intra-quadrant coding on constellation points of the square QAM modulation signal based on Gray codes, and determining the coding of the constellation points in a first quadrant; and determining the code of the whole constellation diagram based on the characteristic that all constellation points in the constellation diagram are symmetrical about the I axis, the Q axis and the origin. The invention not only improves the coding and decoding efficiency and the testing efficiency, but also greatly reduces the bit error rate.

Description

Gray code-based square QAM constellation diagram coding method and system

Technical Field

The invention belongs to the technical field of testing, and particularly relates to a method and a system for encoding a square QAM constellation diagram based on Gray codes.

Background

The constellation diagram is usually adopted to represent the quality of a modulation signal in vector signal analysis, the coding method of constellation points in the constellation diagram directly influences the BER (bit error rate) after signal demodulation, the existing constellation diagram coding usually has a Gray code coding mode, a sequential code coding mode and the like, the sequential code coding mode directly codes according to the sequence of symbols, the bit error rate is higher, the Gray code coding mode codes the symbols according to the Gray code mode, only one bit is different between adjacent symbols, and the bit error rate is reduced.

The Gray code coding belongs to reliable coding and is a coding mode with minimized error, and because only one bit is different between two adjacent constellation points of the coding, the instantaneous fuzzy state of the constellation points from one state to the next state is greatly reduced, and the anti-interference capability is improved. Taking a 16QAM constellation as an example, a typical gray code constellation encoding method is shown in fig. 1, and encoding is performed in a gray code manner according to the diagram sequence with the upper left corner in the constellation as a starting point, and all constellation points are traversed during state switching, so that each constellation point is ensured to be different from the surrounding constellation points by only one bit.

The error rate of a constellation point coding mode based on Gray codes is low, but because there is no rule in coding, all points in a constellation diagram need to be coded in sequence, the running time of one coding is O (n), n is the number of constellation points in a square QAM constellation diagram, and for 256QAM, n is 256. When the received symbols are coded and decoded, each symbol needs to be compared with all constellation points in sequence, so that the symbols are judged and coded, the time cost is high, and the efficiency is low.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method and a system for encoding a square QAM constellation diagram based on Gray codes. According to the method, the constellation points of the square QAM modulation signals are coded, firstly, the sign bits of I, Q data corresponding to the constellation points are used as high-order two-bit bits to distinguish quadrants where the constellation points are located, the low-order bit bits of the constellation points are arranged in a first quadrant in a Gray code mode, specific constellation point positions are determined according to the data bits of I, Q data, the constellation points can be determined by coding in the first quadrant according to I, Q values, coding and decoding efficiency and testing efficiency are improved, and bit error rate is greatly reduced.

In order to achieve the purpose, the invention adopts the following technical scheme:

a gray code-based square QAM constellation map coding method comprises the following steps:

carrying out inter-quadrant coding on constellation points of square QAM (quadrature amplitude modulation) modulation signals based on Gray codes;

performing intra-quadrant coding on the first quadrant, and determining the codes of the constellation points in the first quadrant;

determining intra-quadrant codes of other quadrants of the constellation diagram based on the characteristic that all constellation points in the constellation diagram are symmetrical about an I axis, a Q axis and an origin;

and combining the inter-quadrant coding and the intra-quadrant coding to determine the coding of the whole constellation diagram.

Further, the square QAM modulation signal comprises: 16QAM, 64QAM, and 256 QAM.

Further, the quadrant coding determines the quadrant where the constellation point is located according to I, Q data sign bits.

Further, determining the quadrant in which the constellation point is located according to the I, Q data symbol bits includes: if I >0 and Q >0, the code is 00 and is in the first quadrant; if I <0, Q >0, the code is 01, and the code is in the second quadrant; if I <0 and Q <0, the code is 11 and the code is in the third quadrant; if I >0 and Q <0, the code is 10, in the fourth quadrant.

Further, the quadrant inner coding determines the position of a specific constellation point according to the data bit of I, Q data.

Further, determining the specific constellation point position according to the data bit of the I, Q data includes: and coding in a Gray code mode in sequence by taking the upper left corner as a first starting point, traversing all constellation points in the first quadrant during state switching, and ensuring that each constellation point is different from peripheral constellation points by only one bit.

According to the second object of the present invention, the present invention further provides a decoding method for the constellation encoding, comprising:

determining I, Q the sign bit of the data according to the quadrant of the constellation point in the constellation diagram;

decoding with a gray code to determine I, Q the data bits of the data;

the sign bit and the data bit are combined to obtain I, Q data of the constellation point.

According to a third object of the present invention, the present invention further provides a gray code-based square QAM constellation encoding system, including a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the encoding method when executing the program.

According to a fourth object of the present invention, there is also provided a computer-readable storage medium, on which a computer program is stored, which when executed by a processor, implements the gray code-based square QAM constellation encoding method.

The invention has the advantages of

Based on the Gray code constellation diagram coding method, constellation points are symmetrical about an I axis, a Q axis and an origin of a coordinate axis, a quadrant where the constellation points are located is judged according to I, Q data sign bits during coding and decoding, then coding is carried out in a first quadrant according to I, Q data bits to determine the position of a first quadrant constellation point, all constellation points in a constellation diagram can be determined by integrating the quadrant where the constellation points are located and the position of the first quadrant where the constellation points are located, the running time is O (n/4+2), the running time is O (n), n is the order of square QAM, and the running time is greatly reduced and the efficiency, especially high-order QAM, is improved based on the existing typical Gray code arrangement mode. In addition, due to the optimization of the constellation point arrangement mode, when the signal-to-noise ratio is 19dB, the bit error rate is reduced by two orders of magnitude, as shown in fig. 2. The method of the invention not only improves the coding and decoding efficiency and the testing efficiency, but also greatly reduces the bit error rate.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 is a typical 16QAM Gray code constellation;

FIG. 2 is a bit error rate comparison curve;

fig. 3 is a constellation diagram obtained by the method for encoding a square QAM constellation diagram based on gray codes according to the present invention.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The embodiments and features of the embodiments in the present application may be combined with each other without conflict.

Example one

The embodiment discloses a gray code-based square QAM constellation diagram coding method, which comprises the following steps:

step 1: carrying out inter-quadrant coding on constellation points of square QAM (quadrature amplitude modulation) modulation signals based on Gray codes;

the square QAM modulated signal comprises: 16QAM, 64QAM, 256QAM, etc.

And determining the quadrant where the constellation point is located according to the I, Q data sign bit, wherein the quadrant is coded into the upper two bits of the final constellation point code. The specific encoding rule is as follows: if I >0 and Q >0, the code is 00 and is in the first quadrant; if I <0, Q >0, the code is 01, and the code is in the second quadrant; if I <0 and Q <0, the code is 11 and the code is in the third quadrant; if I >0 and Q <0, the code is 10, in the fourth quadrant.

Step 2: performing intra-quadrant coding on the first quadrant, and determining the codes of the constellation points in the first quadrant;

first, I, Q data is subjected to absolute value operation to remove the influence of the sign bit on the encoding.

Then, determining the position of a specific constellation point according to the data bit of I, Q data; in particular, the amount of the solvent to be used,

the intra-quadrant codes are the low order bits of the final constellation point code. The encoding method is carried out according to a conventional Gray code encoding mode, the upper left corner is used as a first starting point, encoding is carried out in a Gray code mode according to the sequence, all constellation points in a first quadrant are traversed during state switching, and each constellation point is ensured to be different from peripheral constellation points by only one bit;

and step 3: and determining the code of the whole constellation diagram based on the characteristic that all constellation points in the constellation diagram are symmetrical about the I axis, the Q axis and the origin.

And 4, step 4: and combining the inter-quadrant Gray code coding and the intra-quadrant Gray code coding to complete the Gray code coding of the final constellation point.

The embodiment also provides a corresponding constellation diagram coding method, which comprises the following steps:

decoding with a gray code to determine I, Q the data bits of the data;

Example two

It is an object of the present embodiments to provide a computing system.

A gray code based square QAM constellation encoding system, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the following steps when executing the program, comprising:

EXAMPLE III

An object of the present embodiment is to provide a computer-readable storage medium.

A computer-readable storage medium, on which a computer program is stored which, when executed by a processor, performs the steps of:

The steps involved in the apparatuses of the above second and third embodiments correspond to the first embodiment of the method, and the detailed description thereof can be found in the relevant description of the first embodiment. The term "computer-readable storage medium" should be taken to include a single medium or multiple media containing one or more sets of instructions; it should also be understood to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor and that cause the processor to perform any of the methods of the present invention.

The invention has the advantages of

Based on the Gray code constellation diagram coding method, constellation points are symmetrical about an I axis, a Q axis and an origin of a coordinate axis, a quadrant where the constellation points are located is judged according to I, Q data sign bits during coding and decoding, then coding is carried out in a first quadrant according to I, Q data bits to determine the position of a first quadrant constellation point, all constellation points in a constellation diagram can be determined by integrating the quadrant where the constellation points are located and the position of the first quadrant where the constellation points are located, the running time is O (n/4+2), the running time is O (n), n is the order of square QAM, and the running time is greatly reduced and the efficiency, especially high-order QAM, is improved based on the existing typical Gray code arrangement mode. In addition, due to the optimization of the constellation point arrangement mode, when the signal-to-noise ratio is 19dB, the bit error rate is reduced by two orders of magnitude. The method of the invention not only improves the coding and decoding efficiency and the testing efficiency, but also greatly reduces the bit error rate.

Those skilled in the art will appreciate that the modules or steps of the present invention described above can be implemented using general purpose computer means, or alternatively, they can be implemented using program code that is executable by computing means, such that they are stored in memory means for execution by the computing means, or they are separately fabricated into individual integrated circuit modules, or multiple modules or steps of them are fabricated into a single integrated circuit module. The present invention is not limited to any specific combination of hardware and software.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.

Claims

1. A gray code-based square QAM constellation map coding method is characterized by comprising the following steps:

combining the inter-quadrant coding and the intra-quadrant coding to determine the coding of the whole constellation diagram; the quadrant coding determines the quadrant of the constellation point according to I, Q data sign bit; the quadrant inner coding determines the position of a specific constellation point according to the data bit of I, Q data; determining the specific constellation point location from the data bits of the I, Q data includes: and coding in a Gray code mode in sequence by taking the upper left corner as a first starting point, traversing all constellation points in the first quadrant during state switching, and ensuring that each constellation point is different from peripheral constellation points by only one bit.

2. The gray code based square QAM constellation encoding method of claim 1, wherein the square QAM modulated signal comprises: 16QAM, 64QAM, and 256 QAM.

3. The gray code based square QAM constellation encoding method of claim 1, wherein determining a quadrant in which a constellation point is located according to I, Q data symbol bits comprises: if I >0 and Q >0, the code is 00 and is in the first quadrant; if I <0, Q >0, the code is 01, and the code is in the second quadrant; if I <0 and Q <0, the code is 11 and the code is in the third quadrant; if I >0 and Q <0, the code is 10, in the fourth quadrant.

4. A decoding method for constellation encoding as claimed in any of claims 1-3, comprising:

decoding with a gray code to determine I, Q the data bits of the data;

5. A gray code based square QAM constellation encoding system comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor when executing said program implements the encoding method according to any of claims 1 to 3.

6. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out a method for square QAM constellation encoding based on gray codes according to any one of claims 1 to 3.