KR20120104824A - Soft bit decision demodulator - Google Patents

Soft bit decision demodulator Download PDF

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KR20120104824A
KR20120104824A KR1020110022460A KR20110022460A KR20120104824A KR 20120104824 A KR20120104824 A KR 20120104824A KR 1020110022460 A KR1020110022460 A KR 1020110022460A KR 20110022460 A KR20110022460 A KR 20110022460A KR 20120104824 A KR20120104824 A KR 20120104824A
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South Korea
Prior art keywords
soft decision
decision bit
value
demodulator
channel
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KR1020110022460A
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Korean (ko)
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정준영
최동준
허남호
김영민
김수영
송상섭
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한국전자통신연구원
전북대학교산학협력단
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Priority to KR1020110022460A priority Critical patent/KR20120104824A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/06—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
    • H04L25/067—Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection providing soft decisions, i.e. decisions together with an estimate of reliability
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0008—Modulated-carrier systems arrangements for allowing a transmitter or receiver to use more than one type of modulation

Abstract

Disclosed is a method of demodulating a soft decision bit detection single demodulator capable of calculating a soft decision value of a plurality of bits constituting a receiving modulation symbol using a single demodulator. The present invention includes the steps of receiving a signal through a wireless channel, calculating an I channel value and a Q channel value, which are constellation coordinate values of the received signal, and first and second bits of the I channel value and the Q channel value. Determining a first initial soft decision bit value for and cyclically calculating a second initial soft decision bit value for a third bit and more bits based on the first initial soft decision bit value And outputting a final soft decision bit value by multiplying first and second initial soft decision bit values by a gain determined based on a magnitude of a fading coefficient of the radio channel and a dispersion of received Gaussian noise.

Description

Soft decision bit detection demodulator

The present invention relates to a soft decision bit detection single demodulator, and more particularly, to a soft decision bit detection single demodulator capable of calculating a soft decision value of a plurality of bits constituting a receiver modulation symbol using a single demodulation method. .

In general, a digital communication system adopts an adaptive modulation and demodulation method that allocates and uses a type of modulation method according to channel conditions and traffic requirements that change over time. Accordingly, the digital communication system must configure a plurality of modulators at the transmitting end for each modulation scheme used, and combine a plurality of demodulators at the receiving end. In order to solve this problem, the modulator uses a phase shift keying (PSK) modulation method or a quadrature amplitude modulation (QAM) modulation method to generate modulated signals of different dimensions in a single modulation structure. Therefore, recently, a technique for recovering different modulation symbols by a demodulator having a single structure has been proposed.

Another feature of digital communication systems is the use of error correcting codes in a number of systems to overcome the degradation conditions occurring in the channel.

The error correcting code uses a turbo code or a low density product code (LDPC). Accordingly, the receiver uses an iterative decoding technique. However, an essential condition for iterative decoding is that the output bit of the decoder must be a soft decision bit value. Therefore, the demodulator of the receiving end must effectively calculate the soft decision bit value for the plurality of bits constituting the receiving scene.

An object of the present invention is a soft decision bit detection unit for calculating soft decision bit values for bits constituting a symbol using a demodulator having a single structure in an adaptive modulation system having multiple modulation schemes of QAM and PSK series. It is to provide a demodulator.

A soft decision bit detection single demodulator according to the present invention comprises the steps of receiving a signal over a wireless channel, calculating an I channel value and a Q channel value, which are constellation coordinate values of the received signal, and the I channel value and the Q channel. Determining a value as a first initial soft decision bit value for the first and second bits and a second initial soft decision bit value for the third and more bits based on the first initial soft decision bit value. Calculating cyclically and outputting a final soft decision bit value by multiplying the first and second initial soft decision bit values by a gain determined based on a magnitude of a fading coefficient of the radio channel and a dispersion of received Gaussian noise. It includes.

The soft decision bit detection single demodulator according to the present invention has the effect of greatly reducing the complexity by calculating the soft decision value for each bit by only one simple distance calculation between the received symbol and the predetermined hard decision boundary value.

Accordingly, the present invention can calculate a soft decision bit value for a modulation method of several M values using a single soft decision demodulator without using a plurality of M-ary QAM and PSK series demodulators. Therefore, the present invention has the effect of reducing the cost in implementing the hardware of the system.

1 is a block diagram of an adaptive modulation system using a soft decision bit detection single demodulator according to a first embodiment.
2 is a detection flowchart of the soft decision bit detection single demodulator according to the first embodiment.
3 is a third step flowchart of a detection flowchart of a soft pre-bit detection single demodulator according to the first embodiment.
4 is a configuration diagram of a plurality of QAM modulation schemes according to a soft decision bit detection single demodulator according to a second embodiment.
5 is a configuration diagram of a plurality of PSK modulation schemes according to a soft decision bit detection single demodulator according to a third embodiment.
6 is a conceptual diagram of a gray coded 8-PSK modulation scheme according to a soft decision bit detection single demodulator according to a fourth embodiment.
7 is a conceptual diagram of a gray coded 16-PSK modulation scheme according to a soft decision bit detection single demodulator according to a fifth embodiment.
8 is a soft decision bit detection constellation diagram for the 8-PSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the sixth embodiment.
9 is a soft decision bit detection constellation diagram for the 16-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the seventh embodiment.
10 is a soft decision bit detection constellation conceptual diagram of D1 for the 32-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the eighth embodiment.
11 is a soft decision bit detection constellation conceptual diagram of D2 for the 32-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the eighth embodiment.
12 is a soft decision bit detection constellation conceptual diagram of D3 for the 32-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the eighth embodiment.
13 is a soft decision bit detection constellation conceptual diagram of D4 for the 32-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the eighth embodiment.
14 is a soft decision bit detection constellation conceptual diagram of D5 for the 32-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the eighth embodiment.

Hereinafter, a soft decision bit detection single demodulator according to a first embodiment will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an adaptive modulation system using a soft decision bit detection single demodulator according to a first embodiment.

As shown in FIG. 1, an adaptive modulation system using a soft decision bit detection single demodulator includes a transmitter 100, a channel 150, and a receiver 200.

The transmitter 100 includes an error correcting encoder 101 and an M-ary adaptive modulator 102.

The error correcting encoder 101 adds parity information for error correction occurring in a binary signal. Accordingly, the error correcting encoder 101 provides the encoded binary bit to the mere adaptive modulator 102.

The echo adaptive modulator 102 maps the binary bits to the channel by mapping M (at least one integer) bits into one symbol in an ary modulation scheme suitable for the current channel state by a control signal of a higher layer.

The channel 150 adds fading to the transmitted signal and adds noise to the receiver 200 to receive the received signal.

Receiving stage 200 includes an adaptive adaptive demodulator 201, error correction decoder 202.

 The echo adaptive demodulator 201 outputs the received received signals as M soft wave bit values. Accordingly, the error correction decoder 202 repeatedly decodes the output M soft decision bit values to extract the original binary signal.

2 is a detection flowchart of the soft decision bit detection single demodulator according to the first embodiment, and FIG. 3 is a third step flowchart of the detection flowchart of the soft decision bit detection single demodulator according to the first embodiment.

2 and 3, in the detection flowchart, the demodulator receives a signal through a wireless channel to perform a first step 300, a second step 400, a third step 500, and a fourth step 600 ).

In a first step (300), the demodulator calculates an I phase channel value, which is a horizontal axis value, and a Qr (Quadrature) channel value, when a symbol s (hereinafter, referred to as a reception symbol) for a received signal is constellation mapped. . The I channel value of the reception symbol is obtained by the value of the real part (Re {s}), and the Q channel value of the reception symbol is obtained by the value of the imaginary part (Im {s}).

In the second step 400, the demodulator determines the I channel value and the Q channel value calculated in the first step 300 as initial soft decision bit values for the first and second bits. In addition, the initial soft decision bit values for the first and second bits are

Figure pat00001
And
Figure pat00002
.

In a third step 500, the demodulator recursively calculates the initial soft decision bit value in the third and more bits based on the initial soft decision bit values for the first and second bits.

In a third step 500, the demodulator determines whether the initial soft decision bit value calculated in the second step 400 is greater than two (501), and performs a fourth step 600 if it is less than two. In addition, when the initial soft decision bit value is greater than 2, the demodulator determines whether the modulation method of the soft decision bit value is a QAM modulation method or a PSK modulation method (502).

This is because the method of calculating the initial soft decision bit value cyclically differs according to the modulation method.

If the initial soft decision bit value modulation method is a QAM modulation method, the demodulator performs a first sub step 503, a second sub step 504, a third sub step 505, and a fourth sub step 506. To perform.

In the first sub-step 503, the demodulator initializes the i value of the initial soft decision bit value to one.

In the second sub-step 504, the demodulator calculates the gain of the initial soft decision bit value for the third or more bits by Equation 1 below.

[ Equation  One]

Figure pat00003

A of Equation 1 denotes the lowest power level of the I-channel and the Q-channel of the ary modulation scheme.

In the third sub-step 505, the demodulator determines whether the required initial soft decision bit value has been calculated.

Figure pat00004
Judging by. Accordingly, the demodulator performs a fourth step 600 if the condition is satisfied, and performs a fourth sub step 506 if the condition is not satisfied.

In the fourth substep 506, the demodulator increments the i value of the unsatisfactory initial soft decision bit value by one, thereby repeatedly performing the second substep 504.

If the modulation method of the initial soft decision bit value in the determination step 502 is the PSK method, the demodulator includes the first sub-step 507, the second sub-step 508, the third sub-step 509, and so on. The fourth sub-step 510 is performed.

In the first sub-step 507, the demodulator calculates the magnitude and phase of the received symbol by Equation 2 below, and the phase value of the calculated initial soft decision bit value is

Figure pat00005
The i value of the initial soft decision bit value is initialized to 3.

[ Equation  2]

Figure pat00006
,
Figure pat00007

In the second sub-step 508, the demodulator calculates the phase value of the initial soft decision bit value performed in the first sub-step by using Equation 3 below.

[ Equation  3]

Figure pat00008

Further, in the second sub-step 508, the demodulator takes sin into the calculated phase value of the initial soft decision bit value and multiplies the magnitude of the received symbol. In addition, the demodulator uses the initial soft decision bit value using the magnitude and phase of the received symbol.

Figure pat00009
Calculate

In the third sub-step 509, the demodulator determines whether the required initial soft decision bit value has been calculated.

Figure pat00010
Judging by. Accordingly, the demodulator performs the fourth step 600 when the condition is satisfied, and performs the fourth sub-step 510 when the condition is not satisfied.

In the fourth sub-step 510, the demodulator increments the i value of the initial soft decision bit value by one, thereby repeatedly performing the second sub-step 507. FIG.

In a fourth step 600, the demodulator multiplies and outputs all the initial soft decision bit values calculated by the detection flowchart. Of the gain of the soft decision bit value multiplied in the fourth step.

Figure pat00011
Is the magnitude of the channel's fading coefficient,
Figure pat00012
Is the variance of the received Gaussian noise. Therefore, the final soft decision bit value of the i th bit is
Figure pat00013
.

Hereinafter, a soft decision bit detection single demodulator according to another embodiment will be described in detail with reference to the accompanying drawings.

4 is a configuration diagram of a plurality of QAM modulation schemes according to a soft decision bit detection single demodulator according to a second embodiment, and FIG. 5 is a diagram illustrating a plurality of PSK modulation schemes according to a soft decision bit detection single demodulator according to a third embodiment. It is a block diagram.

As shown in Figs. 4 and 5, using the detection flow chart of the soft decision bit detection single demodulator for the adaptive modulation system described above, since the demodulator only needs to output the soft decision bit values up to the required bits, single demodulation The method can be used to calculate final soft decision bit values for multiple echo QAM modulation schemes and multiple echo PSK modulation schemes.

Hereinafter, a calculation method according to a modulation method of a soft decision bit detection single demodulator according to another embodiment will be described in detail with reference to the accompanying drawings.

The initial soft decision bit value for each component bit of a complex symbol composed of a plurality of bits may be obtained by calculating a distance from a boundary line that determines whether the corresponding soft decision bit value is 0 or 1 to a reception symbol. The present technology is not described by the known technology, which means that the technical scope of the present invention is not limited by the known technology.

6 is a conceptual diagram of a gray coded 8-PSK modulation scheme according to a soft decision bit detection single demodulator according to a fourth embodiment.

As shown in Fig. 6, in the gray coded 8-PSK modulation scheme, the demodulator quotes a known technique so that the boundary (imaginary axis) D1, which determines whether the first bit of the modulation symbol is 0 or 1, The soft decision bit value is obtained based on the boundary line D2 determining whether it is 0 or 1 and the boundary line D3 determining the third bit.

Therefore, the distance between the reception symbol and the boundary line is calculated by Equation 4 below.

[ Equation  4]

Figure pat00014

7 is a conceptual diagram of a gray coded 16-PSK modulation scheme according to a soft decision bit detection single demodulator according to a fifth embodiment.

As shown in Fig. 7, the gray coded 16-PSK modulation scheme is the same as that of the gray coded 8-PSK described above by citing a known technique, and further constitutes D4 for judging the fourth bit. Therefore, the demodulator obtains the soft decision bit value based on D1 to D4.

Therefore, the distance between the reception symbol and the boundary line is calculated by Equation 5 below.

[ Equation  5]

Figure pat00015

8 is a soft decision bit detection constellation diagram for the 8-PSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the sixth embodiment.

As shown in FIG. 8, the 8-PSK modulation scheme adopted in the DVB-S2 standard is the same as the general gray coded 8-PSK modulation scheme described with reference to FIG. 3. In addition, the 8-PSK modulation scheme adopted in the DVB-S2 standard is similar to rotating the general gray coded 8-PSK modulation scheme by π / 4 degrees. Therefore, the demodulator transforms the soft decision bit value for the general gray coded 8-PSK modulation scheme and calculates the distance between the reception symbol and the boundary line by the following equation (6).

[ Equation  6]

Figure pat00016

Hereinafter, the APSK modulation method adopted by the DVB-S2 standard has a point where the boundary line for the first and second bits is discontinuous, rather than the form of a continuous straight line or a circle, unlike the PSK modulation method. Therefore, the APSK modulation method differs from the PSK modulation method in calculating the soft decision bit value calculated according to the position of the received signal.

In addition, the technique of detecting the soft decision bit value using the hard decision boundary has not been described by a known technique, which means that the technical scope of the present invention is not limited by such a known technique.

9 is a soft decision bit detection constellation diagram for the 16-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the seventh embodiment.

As shown in FIG. 9, in the 16-APSK modulation scheme adopted in the DVB-S2 standard, the demodulator obtains a soft decision bit value based on the boundary lines D1 to D4 for each component bit according to the above-described known technique.

In addition, although the method of calculating the soft decision bit value differs depending on the position of the reception signal, the APSK modulation method may be calculated by Equation 7 below.

[ Equation  7]

Figure pat00017
Figure pat00018
Figure pat00019

Accordingly, the soft decision bit value calculated in Equation 6 is calculated as the final soft decision bit value by multiplying the gain as shown in the fourth step (Fig. 2, 600) of the detection flowchart.

10 to 14 are conceptual diagrams of soft decision bit detection properties from D1 to D5 for the 32-APSK modulation method defined in the DVB-S2 standard according to the soft decision bit detection single demodulator according to the eighth embodiment.

 As shown in Fig. 10 to Fig. 14, for the 32-APSK modulation scheme adopted in the DVB-S2 standard, the demodulator uses the soft decision bits based on the boundary lines D1 to D5 for each component bit according to the above-described known technique. Find the value.

The 32-APSK modulation method adopted by the DVB-S2 standard describes the 16-APSK modulation method adopted by the DVB-S2 standard. As described above, the final method is calculated by calculating the distance between the boundary line and the reception symbol in the same manner. The decision bit value can be calculated.

Embodiments of the present invention described above and illustrated in the drawings should not be construed as limiting the technical spirit of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms.

Therefore, such improvements and modifications will fall within the protection scope of the present invention as long as it will be apparent to those skilled in the art.

100: transmitting end
150: channel
200: receiver
300: stage 1
400: step 2
500: 3 levels
600: 4 levels

Claims (1)

Receiving a signal over a wireless channel;
Calculating an I channel value and a Q channel value, which are constellation coordinate values of the received signal;
Determining the I channel value and the Q channel value as first initial soft decision bit values for first and second bits;
Cyclically calculating a second initial soft decision bit value for a third bit and more bits based on the first initial soft decision bit value;
And outputting a final soft decision bit value by multiplying the first and second initial soft decision bit values by a gain determined based on a magnitude of a fading coefficient of the radio channel and a dispersion of received Gaussian noise. Demodulation method.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20190061827A (en) 2017-11-28 2019-06-05 어보브반도체 주식회사 Method for soft decision demodulation of gfsk signal with channel coding applied and receiving apparatus using the method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20190061827A (en) 2017-11-28 2019-06-05 어보브반도체 주식회사 Method for soft decision demodulation of gfsk signal with channel coding applied and receiving apparatus using the method

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