CN101335729B - Fixed-point soft decision demodulation method of quadrature amplitude modulation technique - Google Patents

Abstract

Aiming at solving the defects of large error and high calculation and hardware implementation complexity of QAM (quadrature amplitude modulation) demodulation method in prior art, the invention proposes a fixed-point soft-decision demodulation method using QAM technology. The fixed-point soft-decision demodulation method for using QAM technology of the invention carries out soft decision on part defined bits of a received symbol with the mean of the absolute values of real part and imaginary part of the received symbol and then carries fixed-point soft decision on other bits with the hard-decision information of the part defined bits, thus simplifying the calculation and guaranteeing the modulation performance. In addition, the method is easy to be implemented with chip fixed-point algorithm.

Description

Fixed-point soft decision demodulation method of quadrature amplitude modulation technique

Technical field

The present invention relates to quadrature amplitude modulation demodulation techniques in the communications field, particularly 64 fixed-point soft decision demodulation method of quadrature amplitude modulation technique in the wireless communication system.

Background technology

For improving the availability of frequency spectrum, speeding up data transmission speed, the normal quadrature amplitude modulation demodulation techniques (being designated hereinafter simply as QAM) that adopt are carried out transfer of data in the modern communication field.For example: all adopted 64 quadrature amplitude modulation demodulation techniques (being designated hereinafter simply as 64QAM) in WCDMA (being designated hereinafter simply as WCDMA) and time division multiplexing S-CDMA (the being designated hereinafter simply as TD-SCDMA) wireless communication system.Be about 2.6bit/s/Hz with the modulation limit spectrum efficiency of 16 quadrature amplitude modulation demodulation techniques (being designated hereinafter simply as 16QAM) and compare, 64QAM can provide the availability of frequency spectrum that is about 3.9bit/s/Hz, the message transmission rate of raising system that can be by a relatively large margin.

Usually, the QAM demodulation method can be divided into two kinds, and a kind of is so-called simple metric programmed algorithm, and a kind of in addition is dual minimum metric programmed algorithm.These two kinds of methods all need be calculated logarithm (the being Log) maximum likelihood ratio (being designated hereinafter simply as LLR) of each output bit; Wherein: the simple metric programmed algorithm is deformed into complicated LLR computing formula the approximate formula of simple shape; Though this algorithm calculates simple; But owing to adopt approximate formula, make that the LLR error that calculates is bigger, thereby cause the reduction of systematic function; And dual minimum metric programmed algorithm adopts the computing formula that more approaches original LLR, compare with the simple metric programmed algorithm and improved systematic function greatly, but the computation complexity of this method and hardware implementation complexity is all high than simple metric programmed algorithm.

According to the court verdict of 64QAM demodulation, can the 64QAM demodulation be divided into two kinds of soft decision demodulation and hard decision demodulation.So-called hard decision demodulation is exactly search and the immediate symbol of receiving symbol in the 64QAM planisphere, and rules out 6 binary bits according to its mapping relations.So-called soft decision demodulation also is search and the immediate symbol of receiving symbol in the 64QAM planisphere; But the court verdict of soft decision demodulation is not 6 binary bits; But 6 soft decision informations, and each soft decision information can be represented by a plurality of binary bits.6 soft decision informations of soft decision demodulation have reflected the degree of reliability of corresponding symbol in the symbol that receives and the planisphere, have also reflected the reliability of pairing each bit of this symbol.This soft decision information can provide more information for the channel decoding of back, all need import the performance that soft decision information improves decoding like Turbo decoding and Viterbi decoding etc.Hard decision information can obtain through the judgement to soft decision information; As representing soft decision information with 4 binary systems, promptly the scope of soft decision information is [8,7]; Here the peculiar very high probability of ratio that 7 expressions are sent is 1, and the peculiar very high probability of ratio that-8 expressions are sent is 0.Therefore, can judge the hard decision result through soft decision information whether more than or equal to 0, if promptly soft decision information is more than or equal to 0, then the hard decision result is 1, otherwise the hard decision result is 0.

Summary of the invention

The error that prior art QAM demodulation method exists is big in order to solve, computation complexity and the more high defective of hardware implementation complexity, and the present invention proposes a kind of fixed-point soft decision demodulation method of quadrature amplitude modulation technique.Fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention utilizes the real part of receiving symbol and the absolute value mean value of imaginary part that the part designated bit in the receiving symbol is carried out soft-decision; Utilize the hard decision information of part designated bit that other bits are carried out fixed-point soft decision again; Simplified computing; Guarantee demodulation performance, and utilized the chip fixed-point algorithm to be easy to realize.

Fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention utilizes the real part of receiving symbol and the absolute value mean value of imaginary part that the part designated bit in the receiving symbol is carried out soft-decision; Hard decision result according to the part designated bit in the receiving symbol carries out soft-decision to other bits in the receiving symbol respectively, obtains the hard decision result of bit separately according to the soft decision information of each bit in the receiving symbol.

Fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention utilizes the real part of receiving symbol and the absolute value mean value of imaginary part that the part designated bit in the receiving symbol is carried out soft-decision, comprising:

According to the real part of computes receiving symbol and the absolute value average value P of imaginary part:

$P=\frac{1}{2N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\left(\right|a_i|+|b_i\left|\right)$

In the formula: P is the real part of receiving symbol and the absolute value mean value of imaginary part, and N is a sample length, and span is 352-704, and receiving symbol is expressed as y _i=a _i+ j * b _i, a _iBe the real part of receiving symbol, b _iFor receiving the imaginary part of symbol;

According to the absolute value average value P of the real part of receiving symbol and imaginary part to the C in the receiving symbol ₅And C ₆Carry out soft-decision:

${\hat{C}}_5=\left|\right|a_i|-P|-\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="S2008100696915E00041.png,S2008100696915E00051.png"\; state="\{\{state\}\}">P</figure-callout>}}{2}$

${\hat{C}}_6=\left|\right|b_i|-P|-\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="S2008100696915E00041.png,S2008100696915E00051.png"\; state="\{\{state\}\}">P</figure-callout>}}{2}$

In the formula: serial C _kThe corresponding binary bits C of expression receiving symbol ₁, C ₂, C ₃, C ₄, C ₅And C ₆,

Expression C _k(k=1,2 ... 6) soft decision information, P are the real part of receiving symbol and the absolute value mean value of imaginary part, and receiving symbol is expressed as y _i=a _i+ j * b _i, a _iBe the real part of receiving symbol, b _iFor receiving the imaginary part of symbol.

Fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention carries out soft-decision to other bits in the receiving symbol respectively according to the hard decision result of part designated bit, comprising: according to the hard decision information D ₅To C ₃Carry out soft-decision, according to the hard decision information D ₆To C ₄Carry out soft-decision, according to the hard decision information D ₃And D ₅To C ₁Carry out soft-decision, according to the hard decision information D ₄And D ₆To C ₂Carry out softly declaring, wherein:

According to the hard decision information D ₅To C ₃Carry out soft-decision, comprising:

${\hat{C}}_3=\mathrm{\&alpha;}\left|a_i\right|-\mathrm{\&beta;P}$

In the formula: if C ₃| a _i|≤P/2, α=2 then, β=1.5, otherwise judge C ₅Hard decision D as a result ₅Whether equaling 1, is α=2 then, β=2.5, otherwise α=1, β=1;

According to the hard decision information D ₆To C ₄Carry out soft-decision, comprising:

${\hat{C}}_4=\mathrm{\&alpha;}\left|b_i\right|-\mathrm{\&beta;P}$

In the formula: if C ₄| b _i|≤P/2, α=2 then, β=1.5, otherwise judge C ₆The hard decision information D ₆Whether equaling 1, is α=2 then, β=2.5, otherwise α=1, β=1;

According to the hard decision information D ₃And D ₅To C ₁Carry out soft-decision, comprising:

${\hat{C}}_1=\mathrm{\&gamma;}\left(\mathrm{\&alpha;}\right|a_i|-\mathrm{\&beta;P})$

In the formula: if D ₅D ₃=00, α=2 then, β=1/2; If D ₅D ₃=01, α=3 then, β=3/2; If D ₅D ₃=10, α=1 then, β=0; If D ₅D ₃=11, α=4 then, β=3; If α _i>=0, γ=-1 then; If a _i＜0, γ=1 then;

According to the hard decision information D ₄And D ₆To C ₂Carry out softly declaring, comprising:

${\hat{C}}_2=\mathrm{\&gamma;}\left(\mathrm{\&alpha;}\right|b_i|-\mathrm{\&beta;P})$

In the formula: if D ₆D ₄=00, α=2 then, β=1/2; If D ₆D ₄=01, α=3 then, β=3/2; If D ₆D ₄=10, α=1 then, β=0; If D ₆D ₄=11, α=4 then, β=3; If b _i>=0, γ=-1 then; If b _i＜0, γ=1 then.

Fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention is obtained the hard decision information of bit separately according to the soft decision information of each bit in the receiving symbol, comprising: if soft decision information

More than or equal to 0 o'clock, the hard decision information D that it is corresponding _k Be 1, otherwise, D _kBe 0, wherein: C _k(k=1,2 ... 6) the binary bits series that the expression receiving symbol is corresponding,

Expression C _k(k=1,2 ... 6) pairing soft decision information series.

Description of drawings

Fig. 1 is the planisphere of 64QAM.

Fig. 2 is a fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment flow chart of the present invention;

The flow chart of Fig. 3 fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment of the present invention step 4;

Fig. 4 is the flow chart of fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment step 5 of the present invention;

Fig. 5 is the flow chart of fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment step 6 of the present invention;

Fig. 6 is the flow chart of fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment step 7 of the present invention.

Below in conjunction with accompanying drawing and specific embodiment fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention is further described.

Accompanying drawing 1 is the planisphere of 64QAM, can be known by figure, and the 64QAM planisphere is to be mapped on 64 symbols by 6 binary bits combinations, and each symbol is made up of an I portion and a Q portion, and mapping relations are as shown in table 1.Modulate and transfer out according to the mapping relations of table 1 during the transmitting terminal modulation; Receiving terminal carries out fixed-point soft decision demodulation to signal after receiving the signal of 64QAM; The soft decision information that obtains can be used for the channel decoding of back, and it is 1 probability that soft decision information uses and the logarithm that is 0 probability is recently represented.The hard decision result can obtain through the judgement to soft decision information.

Obviously, the symbol that receives of receiving terminal can be expressed as y _i=a _i+ j * b _i, a wherein _iThe real part of expression receiving symbol, b _iThe imaginary part of expression receiving symbol, corresponding binary bits is C ₁, C ₂, C ₃, C ₄, C ₅And C ₆

Embodiment

Fig. 2 is a fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment flow chart of the present invention, can know that by figure fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention may further comprise the steps:

Step 1, be the average absolute P that the symbol that receives of N is asked its real part and imaginary part to one section sample length according to following formula:

$P=\frac{1}{2N}\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\right|a_i|+|b_i\left|\right)$

In the formula: P is the real part of receiving symbol and the absolute value mean value of imaginary part, and N is a sample length, and span is 352-704, and the value of N is 704 in the present embodiment, and receiving symbol is expressed as y _i=a _i+ j * b _i, a _iBe the real part of receiving symbol, b _iFor receiving the imaginary part of symbol;

Step 2, according to the absolute value average value P of the real part of receiving symbol and imaginary part to the C in the receiving symbol ₅And C ₆Carry out soft-decision:

${\hat{C}}_5=\left|\right|a_i|-P|-\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="S2008100696915E00041.png,S2008100696915E00051.png"\; state="\{\{state\}\}">P</figure-callout>}}{2}$

${\hat{C}}_6=\left|\right|b_i|-P|-\frac{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="S2008100696915E00041.png,S2008100696915E00051.png"\; state="\{\{state\}\}">P</figure-callout>}}{2}$

In the formula: serial C _kThe corresponding binary bits C of expression receiving symbol ₁, C ₂, C ₃, C ₄, C ₅And C ₆,

Expression C _k(k=1,2 ... 6) soft decision information.If soft decision information here

More than or equal to 0 o'clock, the hard decision information D that it is corresponding _k Be 1, otherwise, D _kBe 0; P is the real part of receiving symbol and the absolute value mean value of imaginary part; Receiving symbol is expressed as y _i=a _i+ j * b _i, a _iBe the real part of receiving symbol, b _iFor receiving the imaginary part of symbol;

Table 1:64QAM mapping relations table

Step 3, according to C ₅And C ₆Soft decision information obtain hard decision information D separately ₅And D ₆, comprising: if ${\hat{C}}_5\&GreaterEqual;0$ Set up, then D ₅=1, otherwise D ₅=0, if ${\hat{C}}_6\&GreaterEqual;0$ Set up, then D ₆=1, otherwise D ₆=0.

Step 4, according to the hard decision information D ₅To C ₃Carry out soft-decision, and obtain C ₃The hard decision information D ₃, comprising:

${\hat{C}}_3=\mathrm{\&alpha;}\left|a_i\right|-\mathrm{\&beta;P}$

If ${\hat{C}}_3\&GreaterEqual;0$ Set up, then D ₃=1, otherwise D ₃=0.

In the formula: if | a _i|≤P/2, α=2 then, β=1.5, otherwise judge C ₅The hard decision information D ₅Whether equaling 1, is α=2 then, β=2.5, otherwise α=1, and β=1, P is the real part of receiving symbol and the absolute value mean value of imaginary part;

Accompanying drawing 3 is the flow chart of fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment step 4 of the present invention.

Step 5, according to the hard decision information D ₆To C ₄Carry out soft-decision, and obtain C ₄The hard decision information D ₄, comprising:

${\hat{C}}_4=\mathrm{\&alpha;}\left|b_i\right|-\mathrm{\&beta;P}$

If ${\hat{C}}_4\&GreaterEqual;0$ Set up, then D ₄=1, otherwise D ₄=0.

In the formula: if | b _i|≤P/2, α=2 then, β=1.5, otherwise judge C ₆The hard decision information D ₆Whether equaling 1, is α=2 then, β=2.5, otherwise α=1, and β=1, P is the real part of receiving symbol and the absolute value mean value of imaginary part;

Accompanying drawing 4 is the flow chart of fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment step 5 of the present invention.

Step 6, according to the hard decision information D ₃And D ₅To C ₁Carry out soft-decision, comprising:

${\hat{C}}_1=\mathrm{\&gamma;}\left(\mathrm{\&alpha;}\right|a_i|-\mathrm{\&beta;P})$

According to D ₅, D ₃And a _iSign bit confirm each values of parameters in the following formula:

1) if D ₅D ₃=00, α=2 then, β=1/2;

2) if D ₅D ₃=01, α=3 then, β=3/2;

3) if D ₅D ₃=10, α=1 then, β=0;

4) if D ₅D ₃=11, α=4 then, β=3;

5) if a _i>=0, γ=-1 then;

6) if a _i＜0, γ=1 then;

In the formula, P is the real part of receiving symbol and the absolute value mean value of imaginary part;

Accompanying drawing 5 is the flow chart of fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment step 6 of the present invention.

Step 7, according to the hard decision information D ₄And D ₆To C ₂Carry out soft-decision, comprising:

${\hat{C}}_2=\mathrm{\&gamma;}\left(\mathrm{\&alpha;}\right|b_i|-\mathrm{\&beta;P})$

According to D ₄, D ₆And b _iSign bit confirm each values of parameters in the following formula:

1) if D ₆D ₄=00, α=2 then, β=1/2;

2) if D ₆D ₄=01, α=3 then, β=3/2;

3) if D ₆D ₄=10, α=1 then, β=0;

4) if D ₆D ₄=11, α=4 then, β=3;

5) if b _i>=0, γ=-1 then;

6) if b _i＜0, γ=1 then;

In the formula: P is the real part of receiving symbol and the absolute value mean value of imaginary part;

Accompanying drawing 6 is flow charts of fixed-point soft decision demodulation method of quadrature amplitude modulation technique embodiment step 7 of the present invention.

Just obtained C so far ₁, C ₂, C ₃, C ₄, C ₅And C ₆Soft decision information.

The obviously clear and understanding of those of ordinary skill in the art; The above embodiment that fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention is lifted only is used to fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention is described, and is not limited to fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention.Though effectively described fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention through embodiment; Those of ordinary skills know that there are many variations in fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention and do not break away from other embodiment of spirit of the present invention.Under the situation of spirit that does not deviate from fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention and essence thereof; Those skilled in the art work as can make various corresponding changes or distortion by fixed-point soft decision demodulation method of quadrature amplitude modulation technique according to the present invention, but these corresponding changes or distortion all belong to the claim protection range of fixed-point soft decision demodulation method of quadrature amplitude modulation technique of the present invention.

Claims (3)

1. fixed-point soft decision demodulation method of quadrature amplitude modulation technique; It is characterized in that: utilize the real part of receiving symbol and the absolute value mean value of imaginary part that the part designated bit in the receiving symbol is carried out soft-decision; Hard decision result according to the part designated bit in the receiving symbol carries out soft-decision to other bits in the receiving symbol respectively; Obtain the hard decision result of bit separately according to the soft decision information of each bit in the receiving symbol; Wherein: utilize the real part of receiving symbol and the absolute value mean value of imaginary part that the part designated bit in the receiving symbol is carried out soft-decision, comprising:

According to the real part of computes receiving symbol and the absolute value average value P of imaginary part:

$P=\frac{1}{2N}\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\left(\right|a_i|+|b_i\left|\right)$

In the formula: P is the real part of receiving symbol and the absolute value mean value of imaginary part, and N is a sample length, and span is 352-704, and receiving symbol is expressed as y _i=a _i+ j * b _i, a _iBe the real part of receiving symbol, b _iFor receiving the imaginary part of symbol;

According to the absolute value average value P of the real part of receiving symbol and imaginary part to the C in the receiving symbol ₅And C ₆Carry out soft-decision:

${\hat{C}}_5=\left|\right|a_i|-P|-\frac{P}{2}$

${\hat{C}}_6=\left|\right|b_i|-P|-\frac{P}{2}$

In the formula: C _k(k=1,2 ... 6) the binary bits series that the expression receiving symbol is corresponding, (k=1,2 ... 6) expression C _k(k=1,2 ... 6) soft decision information series, P is the absolute value mean value of receiving symbol real part and imaginary part, receiving symbol is expressed as y _i=a _i+ j * b _i, a _iBe the real part of receiving symbol, b _iFor receiving the imaginary part of symbol.

2. according to the said fixed-point soft decision demodulation method of quadrature amplitude modulation technique of claim 1; It is characterized in that: the hard decision result according to the part designated bit in the receiving symbol carries out soft-decision to other bits in the receiving symbol respectively, comprising: according to the hard decision information D ₅To C ₃Carry out soft-decision, according to the hard decision information D ₆To C ₄Carry out soft-decision, according to the hard decision information D ₃And D ₅To C ₁Carry out soft-decision, according to the hard decision information D ₄And D ₆To C ₂Carry out softly declaring, wherein:

According to the hard decision information D ₅To C ₃Carry out soft-decision, comprising:

${\hat{C}}_3=\mathrm{\&alpha;}\left|a_i\right|-\mathrm{\&beta;P}$

In the formula: if C ₃| a _i|≤P/2, α=2 then, β=1.5, otherwise judge C ₅Hard decision D as a result ₅Whether equaling 1, is α=2 then, β=2.5, otherwise α=1, β=1;

According to the hard decision information D ₆To C ₄Carry out soft-decision, comprising:

${\hat{C}}_4=\mathrm{\&alpha;}\left|b_i\right|-\mathrm{\&beta;P}$

In the formula: if C ₄| b _i|≤P/2, α=2 then, β=1.5, otherwise judge C ₆The hard decision information D ₆Whether equaling 1, is α=2 then, β=2.5, otherwise α=1, β=1;

According to the hard decision information D ₃And D ₅To C ₁Carry out soft-decision, comprising:

${\hat{C}}_1=\mathrm{\&gamma;}\left(\mathrm{\&alpha;}\right|a_i|-\mathrm{\&beta;P})$

In the formula: if D ₅D ₃=00, α=2 then, β=1/2; If D ₅D ₃=01, α=3 then, β=3/2; If D ₅D ₃=10, α=1 then, β=0; If D ₅D ₃=11, α=4 then, β=3; If a _i>=0, γ=-1 then; If a _i＜0, γ=1 then;

According to the hard decision information D ₄And D ₆To C ₂Carry out softly declaring, comprising:

${\hat{C}}_2=\mathrm{\&gamma;}\left(\mathrm{\&alpha;}\right|b_i|-\mathrm{\&beta;P})$

In the formula: if D ₆D ₄=00, α=2 then, β=1/2; If D ₆D ₄=01, α=3 then, β=3/2; If D ₆D ₄=10, α=1 then, β=0; If D ₆D ₄=11, α=4 then, β=3; If b _i>=0, γ=-1 then; If b _i＜0, γ=1 then.

3. according to the said fixed-point soft decision demodulation method of quadrature amplitude modulation technique of claim 1, it is characterized in that: obtain the hard decision information of bit separately according to the soft decision information of each bit in the receiving symbol, comprising: if soft decision information

More than or equal to 0 o'clock, the hard decision information D that it is corresponding _kBe 1, otherwise, D _kBe 0, wherein: C _k(k=1,2 ... 6) the binary bits series that the expression receiving symbol is corresponding,

(k=1,2 ... 6) expression C _k(k=1,2 ... 6) pairing soft decision information series.

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