WO2011052821A1

WO2011052821A1 - Method for calculating log-likelihood ratio and a demodulation device

Info

Publication number: WO2011052821A1
Application number: PCT/KR2009/006293
Authority: WO
Inventors: 박성준
Original assignee: 강릉원주대학교산학협력단
Priority date: 2009-10-28
Filing date: 2009-10-29
Publication date: 2011-05-05
Also published as: KR101072559B1; KR20110046188A

Abstract

A method for calculating a log-likelihood ratio and a demodulation device are provided. The demodulation device for receiving and then demodulating a radio signal comprises: a constellation storage part, which stores constellation points arranged in a triangular form and modulation symbols matching the constellation points; a transformation part, which extracts a received symbol from the radio signal; and a log-likelihood ratio calculation part, which performs exponential operations on a difference between the received symbol and each of the modulation symbols, classifies the exponential operated values into groups, depending on whether a k-th bit of the modulation symbol is 1 or 0, calculates the sum of exponential operated values by group and then calculates a log-likelihood ratio using the sum for each group, wherein the k is at least 1 and a natural number not greater than the number of bits of the modulation symbol. The present invention is advantageous in that it provides the method and device for calculating a log-likelihood ratio in a quadrature amplitude modulation system using a triangular constellation.

Description

Method and demodulation device for calculating log likelihood ratio

The present invention relates to a method and a demodulation device for calculating a large likelihood ratio, and more particularly, to a method and a demodulation device for calculating a log likelihood ratio in triangular orthogonal amplitude modulation.

A typical method of digital modulation is Quadrature Amplitude Modulation (QAM), which classifies digital signals consisting of bit strings by preset bits and modulates them while changing the size and phase of the carrier signal.

The digital modulation scheme uses constellations representing distances between neighboring signals with respect to the digital signal. In particular, the digital modulation method using an orthogonal amplitude modulation method (hereinafter referred to as a triangular modulation method) using a triangular constellation has an advantage of reducing power consumption while maintaining the probability of modulation symbol error.

In addition, in a digital modulation scheme, a log-likelihood ratio may be calculated and used for detection, transmission packet error verification, and the like.

However, there is a problem in that the logarithmic likelihood ratio corresponding to the triangulation modulation method cannot be calculated using the conventional algebraic likelihood ratio calculation method.

The present invention provides a method and a demodulation device for calculating the logarithmic likelihood ratio in an orthogonal amplitude modulation using a triangular constellation.

Technical problems other than the present invention will be easily understood through the following description.

According to an aspect of the present invention, a demodulation device for receiving and demodulating a radio signal, comprising: a constellation storage unit for storing constellation points arranged in a triangular form and modulation symbols matching the constellation points; A converter configured to extract a received symbol from the wireless signal; And perform an exponential operation on the difference between the received symbol and each modulation symbol, classify the exponential calculated value into groups according to the kth bit of the modulation symbol, and classify the group. A logarithm likelihood ratio calculation unit for calculating a sum of the exponentially calculated values and calculating a logarithmic likelihood ratio using the sum for each group, wherein k is a natural number equal to or greater than 1 and less than or equal to the number of bits of the modulation symbol; A demodulation device is provided.

According to another aspect of the present invention, a method for calculating a log likelihood ratio by a demodulation device, the method comprising: receiving a radio signal; Extracting a received symbol from the wireless signal; Performing an exponential operation on the difference between the received symbol and a pre-stored modulation symbol; Classifying the exponentially computed values into groups according to a kth bit of the modulation symbol being 1 or 0; And calculating a sum of the exponential calculated values for each group, and calculating a log likelihood ratio using the sum for each group, wherein k is 1 or more and a natural number less than or equal to the number of bits of the modulation symbol. An algebraic likelihood ratio calculation method is provided.

According to another aspect of the present invention, a demodulation device for receiving and demodulating a radio signal, comprising: a constellation storage unit for storing constellation points arranged in a triangular form and modulation symbols matching the constellation points; A converter configured to extract a received symbol from the wireless signal; The squared difference between the received symbol and each modulation symbol is classified into a group according to a value of 1 or 0 of the kth bit of the modulation symbol, and a log likelihood ratio is calculated using the difference between the minimum values of the respective groups. A demodulation device including a logarithmic likelihood ratio calculation unit, wherein k is 1 or more and is a natural number less than or equal to the number of bits of the modulation symbol.

According to another aspect of the present invention, a method for calculating a large likelihood ratio by a demodulation device, the method comprising: receiving a radio signal; Extracting a received symbol from the wireless signal; Classifying the received symbol and the group according to a value where a k-th bit of the modulation symbol is 1 or 0 among squared values of the difference between the modulation symbols; And calculating a large likelihood ratio using a difference between the minimum values of the groups, wherein k is a natural number equal to or greater than 1 and less than or equal to the number of bits of the modulation symbol. .

According to another aspect of the present invention, a demodulation device for receiving and demodulating a radio signal, comprising: a constellation storage unit for storing constellation points arranged in a triangular form and modulation symbols matching the constellation points; A converter configured to extract a received symbol from the wireless signal; A logarithm likelihood ratio calculation unit for calculating an index according to the received symbol, rearranging the index according to a size, and calculating a logarithmic likelihood ratio according to a predetermined number of upper indexes among the rearranged indexes, wherein the index Is an exponent of a value obtained by performing an exponential operation on the square of the difference between the received symbol and each modulation symbol.

According to another aspect of the present invention, a method for calculating a large likelihood ratio by a demodulation device, the method comprising: receiving a radio signal; Extracting a received symbol from the wireless signal; Calculating an index according to the received symbol; Rearranging the indexes according to size; Calculating an algebraic likelihood ratio according to a predetermined number of upper exponents among the rearranged indices, wherein the exponent is an exponent of a value obtained by performing an exponential operation on the square of the difference between the received symbol and each modulation symbol. An algebraic likelihood ratio calculation method is provided.

1 is a diagram illustrating a demodulation device according to an embodiment of the present invention.

Figure 2 illustrates a triangular constellation diagram used in the demodulation device according to an embodiment of the present invention.

3 is a flowchart illustrating a process of calculating a log likelihood ratio of a demodulation device according to a first embodiment of the present invention.

4 is a flowchart illustrating a process of calculating a log likelihood ratio of a device of a demodulation device according to a second embodiment of the present invention.

5 is a flowchart illustrating a process of calculating a log likelihood ratio of a demodulation device according to a third embodiment of the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

In addition, in the description with reference to the accompanying drawings, the same components regardless of reference numerals will be given the same reference numerals and duplicate description thereof will be omitted. In the following description of the present invention, if it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Referring to FIG. 1, the demodulation device includes a converter 110, a constellation storage unit 120, and an algebraic likelihood ratio calculator 130.

The converter 110 extracts a modulation symbol from a wireless signal received through the antenna. At this time, the modulation symbol is a modulation symbol generated according to the constellation of the triangular form. The constellation according to the present embodiment will be described later with reference to FIG. 2.

The constellation storage unit 120 stores the constellation for reference in the process of demodulating the modulation symbol. In this case, the constellation may include a plurality of constellation points, and may include a bit string of modulation symbols corresponding to each constellation point.

The algebraic likelihood ratio calculation unit 130 is a modulation symbol extracted from a radio signal received from the conversion unit 110 (hereinafter referred to as a reception symbol), and a modulation symbol stored in the constellation storage unit 120 (hereinafter referred to as a storage symbol). The algebraic likelihood ratio is calculated according to a predetermined equation using.

Hereinafter, the triangular constellations used in an embodiment of the present invention will be described before describing an equation for calculating the algebraic likelihood ratio performed by the algebraic likelihood ratio calculation unit 130.

2 is a diagram illustrating a triangular constellation diagram used in a demodulation device according to an embodiment of the present invention.

Referring to FIG. 2, in the constellation diagram, a plurality of constellation points m1 to m16 are disposed at vertices of a triangle, and modulation symbols are matched to each constellation point. For example, the storage symbol 1101 is matched with the constellation point m1.

The conversion unit 110 calculates coordinates corresponding to the magnitude and phase of the radio signal received in the coordinate system on the constellation. The converter 110 extracts a storage symbol matched to a constellation point corresponding to a region in which the calculated coordinates are located among the plurality of regions set on the constellation diagram as a received symbol corresponding to the corresponding radio signal.

Hereinafter, the process of calculating the logarithmic likelihood ratio by the demodulation device according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The algebraic likelihood ratio calculation unit 130 substitutes the received symbols corresponding to the storage symbols stored in the constellation storage unit 120 and the received radio signals into the following Equation 1

To calculate.

[Equation 1]

Where m is a natural number of two or more, x is an m-modulated symbol transmitted, y is a received symbol,

Is the k th bit constituting the modulation symbol, and the function P (a) is the probability of satisfying condition a. If Equation 1 is converted to an equation including sigma, it can be expressed as Equation 2.

[Equation 2]

At this time,

Is the variance of the additive white Gaussian noise generated during the transmission process. The additive white Gaussian noise is a noise representing a normal distribution of a general channel, and the variance of the additive white Gaussian noise in the demodulation device according to the present embodiment may be a predetermined value.

Substituting 1 to 4 into k in Equation 2 may be derived as in Equation 3 to Equation 6 below.

[Equation 3]

[Equation 4]

[Equation 5]

[Equation 6]

The process of calculating the algebraic likelihood ratio described above with reference to Equations 1 to 6 includes a large number of log and exponential operations, and thus has a high computational complexity. Hereinafter, a demodulation device having a lower computational complexity than the logarithmic likelihood ratio calculation process of the demodulation device according to the first embodiment will be described.

The demodulation device according to the second embodiment of the present invention can reduce the computational complexity by replacing the log and exponential operations used in Equations 1 to 6 with operations for calculating the maximum and minimum values.

Operations that replace the log and exponential operations may be represented by Equations 7 and 8 below.

[Equation 7]

[Equation 8]

At this time,

Is

Is the exponent of, Max [A, B] is the maximum value of A and B, and Min [A, B] is the minimum value of A and B.

In Equations 7 and 8, the values of terms except Max [A, B] or Min [-A, -B] are so small that they can be ignored. Therefore, in the present embodiment, only Max [A, B] or Min [-A, -B] is substituted into the equations (3) to (6).

In Equations 3 and 6, since an exponential operation is performed on negative numbers, Equation 8 is substituted into Equation 2 to simplify the expression. That is, the demodulation device according to the present embodiment may calculate a value approximating the calculation result according to Equations 1 to 6 by replacing the operations of Equations 3 to 6 with the maximum or minimum operations.

The algebraic likelihood ratio according to k to which the calculation process according to the second embodiment of the present invention is applied is derived as in Equations 9 to 12 below.

[Equation 9]

[Equation 10]

[Equation 11]

[Equation 12]

Hereinafter, a method for calculating a large likelihood ratio of a demodulation device according to a third embodiment of the present invention will be described.

The last term in Equation 8 includes a large number of logarithmic and exponential operations. In the second embodiment of the present invention, an approximation value of the corresponding term is deleted. In this embodiment, an algebraic likelihood ratio is calculated by using an approximated equation without deleting the last term of Equation 8.

Rearrange the values in ascending order

In this case, Equation 8 is modified as in Equation 14 below.

[Equation 14]

At this time, the last term of Equation 14 satisfies the condition of Equation 15 below.

[Equation 15]

Applying equation (15) to equation (14), the following equation (16) is derived.

[Equation 16]

At this time,

Is defined as in Equation 17 below.

[Equation 17]

In order to reduce the computational complexity, the demodulation device according to the present embodiment

You can save the table whose value is matched in the look-up value in advance. That is, the demodulation device according to the present embodiment

Depending on the

Tables with matching values can be stored in advance.

3 is a flowchart illustrating a process of calculating a log likelihood ratio of a demodulation device according to a first embodiment of the present invention. Since the operation performed in each step in the process of calculating the algebraic likelihood ratio has been described above with reference to Equations 1 to 6, a detailed description thereof will be omitted.

Referring to FIG. 3, the demodulation device receives a radio signal (310).

The demodulation device extracts the received symbol from the wireless signal (320). For example, the demodulation device extracts a storage symbol corresponding to the magnitude and phase of the received radio signal as a modulation symbol by referring to the constellation diagram.

The demodulation device calculates a squared difference between the received symbol and the stored symbol (330).

The demodulator performs an exponential operation on the value obtained by dividing the variance of the additive white Gaussian noise by the squared value (340).

The demodulation device classifies the value calculated in step 340 into a group in which a specific bit of the corresponding storage symbol is 1 and a group in which a specific bit of the corresponding storage symbol is 0 (350).

The demodulation device calculates the sum of the values of the groups classified in operation 350 (360).

The demodulation device calculates a logarithmic likelihood ratio by taking the logarithm of the sum of the group of the specific bit is 0 and the sum of the group of the specific bit is 0 (370).

4 is a flowchart illustrating a process of calculating a log likelihood ratio of an apparatus of a demodulation device according to a second embodiment of the present invention. Since the operation performed in each step in the process of calculating the algebraic likelihood ratio has been described above with reference to Equations 1 to 12, a detailed description thereof will be omitted.

Referring to FIG. 4, the demodulation device receives a radio signal (410).

The demodulation device extracts the received symbol from the wireless signal (420). For example, the demodulation device extracts a storage symbol corresponding to the magnitude and phase of the received radio signal as a modulation symbol by referring to the constellation diagram.

The demodulation device calculates a squared difference between the received symbol and the stored symbol (430).

The demodulation device divides the value calculated in operation 430 into groups of a value of a specific symbol of 1 and a value of 0 of a specific symbol, and selects a minimum value of each group (440).

The demodulation device calculates the difference between the minimum values selected in step 440, and calculates the logarithmic likelihood ratio by dividing the variance of the additive white Gaussian noise by the calculated value (450).

5 is a flowchart illustrating a process of calculating a log likelihood ratio of a demodulation device according to a third embodiment of the present invention. Since the operation performed in each step in the process of calculating the algebraic likelihood ratio has been described above with reference to Equations 1 to 16, a detailed description thereof will be omitted.

Referring to FIG. 5, the demodulation device receives a radio signal (510).

The demodulation device extracts the received symbol from the wireless signal (520). For example, the demodulation device extracts a storage symbol corresponding to the magnitude and phase of the received radio signal as a modulation symbol by referring to the constellation diagram.

The demodulation device calculates a squared difference between the received symbol and the stored symbol (530).

The demodulation device performs an exponential operation on the value calculated in operation 530 (540).

The demodulation device arranges, in ascending order, a value obtained by multiplying -1 by the exponent of the value calculated in step 540 (550).

The demodulation device calculates an algebraic likelihood ratio that is the difference between the upper two of the values arranged in step 550 and the extracted value with reference to the table and the highest value (minimum value) of the values arranged in step 550 (560).

The above-described logarithmic likelihood ratio calculation process of the demodulation device has been described taking the constellation of 16 modulation symbols as an example. However, the present invention is not limited thereto, and it is apparent that constellations having a different number of modulation symbols may be used.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

The present invention has the effect of providing a method and apparatus for calculating the logarithmic likelihood ratio in an orthogonal amplitude modulation using a triangular constellation.

Claims

A demodulation device for receiving and demodulating a radio signal,

A constellation storage unit configured to store constellation points arranged in a triangular form and modulation symbols matching the constellation points;

A converter configured to extract a received symbol from the wireless signal; And

Perform an exponential operation on the difference between the received symbol and each modulation symbol, classify the exponential calculated value into groups according to a k-th bit of the modulation symbol being 1 or 0; Comprising an arithmetic likelihood ratio calculation unit for calculating the sum of the exponentially calculated value, the arithmetic likelihood ratio using the sum of each group,

K is 1 or more and is a natural number that is less than or equal to the number of bits of the modulation symbol.
According to claim 1,

The algebraic likelihood ratio calculation unit calculates the algebraic likelihood ratio according to the following equation,
Is the logarithmic likelihood ratio, m is a natural number of 2 or more, Is the variance of the additive white Gaussian noise generated during the transmission of the radio signal, x is the modulation symbol,
Is a kth bit constituting the modulation symbol, and y is the received symbol.
The method of claim 2,

And the log likelihood ratio is a log likelihood ratio for the kth bit of the received symbol.
According to claim 1,

The conversion unit converts the magnitude and phase of the radio signal into a coordinate system on the constellation,

And a modulation symbol matched to an area where a point corresponding to the radio signal is located on the constellation diagram as a reception symbol.
According to claim 1,

And the conversion unit restores data transmitted from a terminal that has transmitted the radio signal by combining a predetermined number of the received symbols.
In the method for the demodulation device to calculate the log likelihood ratio,

Receiving a wireless signal;

Extracting a received symbol from the wireless signal;

Performing an exponential operation on the difference between the received symbol and a pre-stored modulation symbol;

Classifying the exponentially computed values into groups according to a kth bit of the modulation symbol being 1 or 0; And

Calculating a sum of the exponential calculated values for each group, and calculating a log likelihood ratio using the sum for each group,

K is a natural number equal to or more than 1 and equal to or less than the number of bits of the modulation symbol.
The method of claim 6,

And the modulation symbol is a modulation symbol that matches a constellation point arranged in a triangular form.
The method of claim 6,

Computing the algebraic likelihood ratio may include calculating the algebraic likelihood ratio according to the following equation,
Is the logarithmic likelihood ratio, m is a natural number of 2 or more,
Is the variance of the additive white Gaussian noise generated during the transmission of the radio signal, x is the modulation symbol,
Is a k-th bit constituting the modulation symbol, y is the received symbol, and m is a natural likelihood ratio calculation method.
The method of claim 8,

And the log likelihood ratio is a log likelihood ratio for the k-th bit of the received symbol.
The method of claim 7, wherein

The extracting of the received symbol may include converting the magnitude and phase of the radio signal into a coordinate system on the constellation,

And a modulation symbol matched to a region where the point corresponding to the radio signal is located on the constellation diagram as a reception symbol.
A demodulation device for receiving and demodulating a radio signal,

A constellation storage unit configured to store constellation points arranged in a triangular form and modulation symbols matching the constellation points;

A converter configured to extract a received symbol from the wireless signal;

The squared difference between the received symbol and each modulation symbol is classified into a group according to a value whose k th bit of the modulation symbol is 1 or 0, and an algebraic likelihood ratio is calculated using the difference between the minimum values of the respective groups. Including a large likelihood ratio calculation unit,

K is 1 or more and a natural number that is less than or equal to the number of bits of the modulation symbol.
The method of claim 11, wherein

And the algebraic likelihood ratio calculation unit calculates an algebraic likelihood ratio by dividing the variance of the additive white Gaussian noise generated during the transmission of the radio signal from the difference between the minimum values of the respective groups.
The method of claim 11, wherein

And the log likelihood ratio is a log likelihood ratio for the kth bit of the received symbol.
The method of claim 11, wherein

The conversion unit converts the magnitude and phase of the radio signal into a coordinate system on the constellation,

And a modulation symbol matched to an area where a point corresponding to the radio signal is located on the constellation diagram as a reception symbol.
The method of claim 11, wherein

And the converting unit combines a predetermined number of the received symbols with each other to restore data transmitted from a terminal that has transmitted the radio signal.
In the method in which the demodulation device calculates the log likelihood ratio,

Receiving a wireless signal;

Extracting a received symbol from the wireless signal;

Classifying the received symbol and the group according to a value where a k-th bit of the modulation symbol is 1 or 0 among squared values of the difference between the modulation symbols; And

Computing the logarithmic likelihood ratio using the difference between the minimum value of each group,

K is a natural number equal to or more than 1 and equal to or less than the number of bits of the modulation symbol.
The method of claim 16,

And the modulation symbol is a modulation symbol that matches a constellation point arranged in a triangular form.
The method of claim 16,

The method for calculating the algebraic likelihood ratio is a step of calculating the algebraic likelihood ratio by dividing the variance of the additive white Gaussian noise generated during the transmission of the radio signal from the difference between the minimum values of the groups. .
The method of claim 16,

And the log likelihood ratio is a log likelihood ratio for the k-th bit of the received symbol.
The method of claim 16,

The extracting of the received symbol may include converting the magnitude and phase of the radio signal into a coordinate system on the constellation,

And a modulation symbol matched to a region where the point corresponding to the radio signal is located on the constellation diagram as a reception symbol.
A demodulation device for receiving and demodulating a radio signal,

A constellation storage unit configured to store constellation points arranged in a triangular form and modulation symbols matching the constellation points;

A converter configured to extract a received symbol from the wireless signal;

A logarithm likelihood ratio calculation unit for calculating an index according to the received symbol, rearranging the index according to a size, and calculating an algebraic likelihood ratio according to a predetermined number of upper indexes among the rearranged indexes,

And the exponent is an exponent of a value obtained by performing an exponential operation on the square of the difference between the received symbol and each modulation symbol.
The method of claim 21,

And the modulation symbol is a modulation symbol that matches a constellation point arranged in a triangular form.
The method of claim 21,

The conversion unit converts the magnitude and phase of the radio signal into a coordinate system on the constellation,

And a modulation symbol matched to an area where a point corresponding to the radio signal is located on the constellation diagram as a reception symbol.
The method of claim 21,

And the converting unit combines a predetermined number of the received symbols with each other to restore data transmitted from a terminal that has transmitted the radio signal.
The method of claim 21,

The constellation storage unit stores a table including a value corresponding to a predetermined number of exponents,

The algebraic likelihood ratio calculation unit extracts a value corresponding to a predetermined number of higher indices among the rearranged indices with reference to the table, and calculates an algebraic likelihood ratio that is a difference between the extracted value and the minimum value of the rearranged indices Demodulation device, characterized in that.
In the method in which the demodulation device calculates the log likelihood ratio,

Receiving a wireless signal;

Extracting a received symbol from the wireless signal;

Calculating an index according to the received symbol;

Rearranging the indexes according to size;

Calculating a logarithmic likelihood ratio according to a predetermined number of upper indices among the rearranged indices,

And said exponent is an exponent of the value obtained by taking an exponential operation on the square of the difference between said received symbol and each modulation symbol.
The method of claim 26,

And the modulation symbol is a modulation symbol that matches a constellation point arranged in a triangular form.
The method of claim 26,

The extracting of the received symbol may include converting the magnitude and phase of the radio signal into a coordinate system on the constellation,

And a modulation symbol matched to a region where the point corresponding to the radio signal is located on the constellation diagram as a reception symbol.
The method of claim 26,

The demodulation device stores a table including a value corresponding to a predetermined number of exponents,

The calculating of the algebraic likelihood ratio may include extracting a value corresponding to a predetermined number of upper indices among the rearranged indices with reference to the table, and algebraic likelihood which is a difference between the minimum value of the extracted value and the rearranged indices. The method for calculating the algebraic likelihood ratio, which is a step of calculating the ratio.