CN103905370B - Soft demodulation method and device for quadrature amplitude modulation (QAM) signal and mobile terminal - Google Patents

Abstract

The invention provides a soft demodulation method and device for a quadrature amplitude modulation (QAM) signal and a mobile terminal. The soft demodulation method for the QAM signal comprises carrying out order reduction transformation on a high-order QAM constellation diagram of a high-order QAM signal to obtain a constellation interval boundary of a low-order QAM constellation diagram; and carrying out soft demodulation based on the high-order QAM signal and the constellation interval boundary of the low-order QAM constellation diagram. The soft demodulation method for the QAM signal provided in the invention does not limit the distribution of symbol points of the QAM signal in the constellation diagram; the judgment error for the constellation interval boundary does not increase with the increasing of order of the QAM; and the performance and precision of soft demodulation of the QAM signal can be guaranteed. Meanwhile, the realization process of the soft demodulation of the QAM signal does not involve complex logarithm or exponent operation, thereby improving the speed and efficiency of the soft demodulation.

Description

The soft demodulating method and device of quadrature amplitude modulation signal, mobile terminal

Technical field

The present invention relates to the field of signal processing of communication system, more particularly to a kind of soft demodulation of quadrature amplitude modulation signal Method and apparatus, mobile terminal.

Background technology

In modern communicationses, it is always one of technical staff's focus of attention to improve the availability of frequency spectrum, recently as communication The rapid growth of business demand, finding the digital modulation mode of availability of frequency spectrum raising has turned into digital communication system design, has ground One of main target studied carefully.High-order orthogonal Modulation and Amplitude Modulation（QAM, Quadrature Amplitude Modulation）Into Be improve communication system utilization ratio of transmission resources a kind of effective means, digital microwave communication system, mobile communcations system, It is widely applied in cable TV network and high speed data transfer and Satellite Communication System.

QAM is also called quadrature double sideband modulation, is to carry the baseband waveform of two-way independence to mutually orthogonal same frequency respectively Ripple carries out suppressed-carrier double side band modulation, the process that resulting two-way modulated signal stacks up.In QAM systems, by In two-way modulated signal in identical bandwidth spectrum orthogonal, can in identical frequency band parallel transmission two paths of data information, because This its band efficiency is higher.QAM is a kind of Vector Modulation, is the technology of amplitude and phase combining modulation, while using carrier wave Amplitude and phase carry out transmission information bit.The order of modulation of QAM is generally 2ⁿ, n is that each QAM signal concentrates each signal Soft bit number.Such as 16QAM, n is just 4, then each signal is represented by 4 bits；For 64QAM, n is just 6, Then each signal is represented by 6 bits.As other digital modulation modes, digital qam signal collection can use planisphere Convenient to represent, a point on planisphere just represents a signal of QAM signals concentration.QAM modulation exponent number is higher, then frequency The utilization rate of band is higher.

The demodulation mode of common qam signal has the soft demodulation of hard demodulation, and hard demodulation refers to noisy by what is received The constellation point judgement of sound is corresponding modulation bit, is typically implemented simply, but performance is undesirable, is only suitable for low order QAM signals Demodulation；Soft demodulation refers to that the noisy constellation point judgement that will be received is the Soft Inform ation of corresponding modulation bit, although realized complicated But Performance comparision is good, it is particularly suited for the demodulation of Higher Order QAM Signals.The soft demodulation of current QAM signals is mostly using based on right Number likelihood ratio（LLR, Log-Likelihood Ratio）Algorithm come calculate QAM signals soft bit export, but algorithm is related to To logarithm and exponent arithmetic, complexity is high, and calculating speed is slow.Simultaneously with the raising of order of modulation, each signal in planisphere The distance of point is just smaller, and corresponding signal decision is interval also just smaller, causes the error of the interval judgement of constellation to become big, final to cause The precision of the soft demodulation of QAM also declines therewith.Especially in wireless communication technique field, such as Long Term Evolution（LTE, Long Time Evolution）Technology and TD SDMA（TD-SCDMA, Time Division Synchronous Code Division Multiple Access）It is increasing to use high-order QAM modulation technology in technology, therefore quickly and accurately Demodulation QAM signals turn into technological difficulties in the urgent need to address.Correlation technique refers to the invention of Publication No. US6661282B2 United States Patent (USP).

The content of the invention

What the technical scheme that the present invention is provided was solved is the poor problem of soft demodulation accuracy of high-order QAM modulation signal.

To solve the above problems, the invention provides a kind of soft demodulating method of orthogonal amplitude QAM signals, including：

High-order QAM planisphere to Higher Order QAM Signals carries out depression of order conversion, and the constellation for obtaining low order QAM constellation is interval Border；

Constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation is soft demodulated.

Optionally, the order of modulation M=m of the Higher Order QAM Signalsⁱ, wherein i is the low order QAM constellation more than 1, m Exponent number；The high-order QAM planisphere to Higher Order QAM Signals carries out depression of order conversion, obtains the constellation area of low order QAM constellation Between border include：

Initialization depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_low=M/m, set iteration Mark, wherein Old_Bound is the constellation interval border of the high-order constellation figure；

Planisphere switch process, the planisphere pair after being changed are performed based on the Higher Order QAM Signals and New_Bound The QAM signals answered；

After the planisphere switch process, if M_low>M, then set M_low=M_low/m, after the conversion The corresponding QAM signal updates New_Bound of planisphere, performs the constellation switch process again；

After the planisphere switch process, if the M_low=m and iteration mark is set, New_Bound=is set Iteration mark is cancelled after New_Bound*M/m, M_low=M/m, the planisphere switch process is performed again；

After the planisphere switch process, if the M_low=m and iteration mark is revoked, it is determined that the low order The constellation interval border of QAM constellation is New_Bound.

Optionally, m=4, the planisphere switch process is based on the corresponding QAM of planisphere after following formula are changed Signal：

Sym_new(n)=|Sym_re(n)|-New_Bound+(|Sym_im(n)|-New_Bound)*j

Wherein, Sym_new (n) is the corresponding QAM signals of planisphere after the conversion, and Sym_re (n) is the high-order The real part of QAM signals Sym (n), Sym_im (n) for Higher Order QAM Signals Sym (n) imaginary part, wherein n be less than or equal to The integer of N-1, N is the symbol total number of the Higher Order QAM Signals.

Optionally, the corresponding QAM signal updates New_Bound of planisphere based on after the conversion is by following public affairs Formula is realized：

Wherein, Sym_new_re (n) is the real part of corresponding QAM signals Sym_new (n) of planisphere after the conversion, Sym_new_im (n) is the imaginary part of corresponding QAM signals Sym_new (n) of planisphere after the conversion, and N is the high-order QAM The symbol total number of signal.

Optionally, the constellation interval border of the high-order constellation figure is obtained according to following formula：

Wherein, Sym_re (n) is the real part of Higher Order QAM Signals Sym (n), and Sym_im (n) believes for the high-order QAM The imaginary part of number Sym (n), wherein N is the symbol total number of the Higher Order QAM Signals.

Optionally, the order of modulation of the Higher Order QAM Signals is 16, described based on the Higher Order QAM Signals and described low The constellation interval border of rank QAM constellation, carries out the soft demodulation of QAM, including obtain the Higher Order QAM Signals by following formula 4 soft bits Bit (k, n) of Sym (n)：

Bit(0,n)=Sym_re(n)

Bit(1,n)=Sym_im(n)

Bit(2,n)=New_Bound-|Sym_re(n)|

Bit(3,n)=New_Bound-|Sym_im(n)|

Wherein, k is the integer less than K, and K is the soft bit number of the Higher Order QAM Signals, and Sym_re (n) is the high-order The real part of QAM signals Sym (n), Sym_im (n) is the imaginary part of Higher Order QAM Signals Sym (n), and n is less than or equal to N-1's Integer, N is the symbol total number of the Higher Order QAM Signals.

Optionally, the order of modulation of the Higher Order QAM Signals is 64, described based on the Higher Order QAM Signals and described low The constellation interval border of rank QAM constellation, carries out the soft demodulation of QAM, including obtain the Higher Order QAM Signals by following formula 6 soft bits Bit (k, n) of Sym (n)

Bit(0,n)=Sym_re(n)

Bit(1,n)=Sym_im(n)

Bit(2,n)=New_Bound-|Sym_re(n)|

Bit(3,n)=New_Bound-|Sym_im(n)|

Bit(4,n)=New_Bound-|(New_Bound/2-|Sym_re(n)|)|

Bit(5,n)=New_Bound-|(New_Bound/2-|Sym_im(n)|)|

Wherein, k is the integer less than K, and K=6 is the soft bit number of the Higher Order QAM Signals, and Sym_re (n) is the height The real part of rank QAM signals Sym (n), Sym_im (n) is the imaginary part of Higher Order QAM Signals Sym (n), and n is less than or equal to N-1 Integer, N is the symbol total number of the Higher Order QAM Signals.

To solve the above problems, technical solution of the present invention additionally provides a kind of soft demodulating equipment of QAM signals, including：

Depression of order converting unit, depression of order conversion is carried out for the high-order QAM planisphere to Higher Order QAM Signals, obtains low order QAM The constellation interval border of planisphere；

Soft demodulating unit, enters for the constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation The soft demodulation of row.

Optionally, the order of modulation M=m of the Higher Order QAM Signalsⁱ, wherein i is the low order QAM constellation more than 1, m Exponent number, the depression of order converting unit includes：

Initialization unit, for initializing depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_ Low=M/m, sets iteration mark, and wherein Old_Bound is the constellation interval border of the high-order constellation figure；

Planisphere converting unit, for performing planisphere switch process based on the Higher Order QAM Signals and New_Bound, The corresponding QAM signals of planisphere after being changed；

First circulation judging unit, for after the planisphere switch process, if M_low>M, then set M_low=M_ Low/m, based on the corresponding QAM signal updates New_Bound of planisphere after the conversion, indicates the constellation converting unit again It is secondary to perform the constellation switch process；

Second circulation judging unit, for after the planisphere switch process, if M_low=m and the iteration mark quilt Set, then cancel iteration mark after New_Bound=New_Bound*M/m, M_low=M/m are set, indicate the constellation conversion single Unit performs the planisphere switch process again；

Determining unit, for after the planisphere switch process, if the M_low=m and iteration mark is revoked, The constellation interval border for determining the low order QAM constellation is New_Bound.

To solve the above problems, the soft demodulation present invention also offers a kind of mobile terminal, including described QAM signals is filled Put.

Optionally, the mode of operation of the mobile terminal is LTE standards or TD-SCDMA standards.

The soft demodulating method of the QAM signals that technical solution of the present invention is provided, changes, by high-order QAM star by planisphere Seat figure is converted to low order QAM constellation, and determines the constellation interval border of the low order QAM constellation, then using described low The constellation interval border of rank QAM constellation is soft demodulated to Higher Order QAM Signals.Compared with prior art, the technology of the present invention side The soft demodulating method of the QAM signals that case is provided does not limit distribution of the symbolic point of QAM signals in planisphere, and QAM constellation The decision error of constellation interval border will not increase with the raising of QAM exponent numbers, it is ensured that the property of the soft demodulation of QAM signals Energy and precision.

Meanwhile, the implementation process of the soft demodulating method of the QAM signals that technical solution of the present invention is provided is not related to the right of complexity Number or exponent arithmetic, improve the speed and efficiency of soft demodulation.

Brief description of the drawings

Fig. 1 is the flow chart of the soft demodulating method of the QAM signals of technical solution of the present invention；

Fig. 2 is the schematic flow sheet of the soft demodulating method of the QAM signals of the embodiment of the present invention；

Fig. 3 is the structural representation of the soft demodulating equipment of the QAM signals of the embodiment of the present invention.

Specific embodiment

The exponent number of QAM signals is higher in the prior art, and the error of the interval judgement of its qam constellation is bigger, so as to cause QAM The soft demodulation accuracy of signal is deteriorated, and calculating process is complicated, is difficult to realize.

In order to solve the above problems, technical solution of the present invention provides a kind of QAM signals based on QAM constellation conversion Soft demodulating method, as shown in figure 1, including：

Step S1：High-order QAM planisphere to Higher Order QAM Signals carries out depression of order conversion, obtains the star of low order QAM constellation Seat interval border；

Step S2：Constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation carries out soft solution Adjust.

Wherein, the order of modulation M=m of the Higher Order QAM Signalsⁱ, wherein i is the low order QAM constellation more than 1, m Exponent number.It should be noted that comparatively the high-order, low order described in technical solution of the present invention be, for example, conventional QAM is adjusted System such as 256QAM, 64QAM, 16QAM, 4QAM, wherein, 4QAM signals are relative to 16QAM signals, 64QAM signals, 256QAM signals Referred to as low order QAM signals, 16QAM signals are referred to as low order QAM signals relative to 64QAM signals, 256QAM signals.Or, high-order QAM signals are referred to as a QAM signals, low order QAM signals and are referred to as the 2nd QAM signals, wherein first QAM The order of modulation of signal is higher than the 2nd QAM signals.Step S1 is exactly that the of a relatively high QAM signals of order of modulation are passed through into star Seat figure is converted to the relatively low QAM signals of order of modulation, such as by 16QAM signals, 64QAM signals, the conversion of 256QAM signals It is 4QAM signals, 256QAM signals is converted into 16QAM signals etc..

The soft demodulating method of the QAM signals that technical solution of the present invention is provided, is turned by the depression of order to the Higher Order QAM Signals Change, the Higher Order QAM Signals are converted into low order QAM signals, and determine the low order QAM signals and corresponding low order The constellation interval border of QAM constellation, then using the constellation interval border of the low order planisphere to the Higher Order QAM Signals It is soft demodulated, exports the corresponding soft bit of each symbol of QAM signals.With realize QAM's based on LLR algorithms in the prior art Soft demodulating method is compared, the soft demodulating method of the QAM signals based on QAM constellation conversion that technical solution of the present invention is provided, meter Calculate easier, precision is higher.

To make above-mentioned purpose of the present invention, feature and becoming apparent a little understandable, carried out in detail with reference to embodiment and accompanying drawing Describe in detail bright.

As shown in Fig. 2 a kind of soft demodulating method of the QAM signals for the embodiment of the present invention, in the present embodiment, m values are 4, that is, the exponent number for representing the low order QAM constellation after depression of order is changed is 4, the Higher Order QAM Signals be 16QAM, 64QAM or 256QAM, the soft demodulating method includes：

Step S21：Initialization depression of order constellation interval border New_Bound, depression of order exponent number M_low, set iteration mark I.

Specifically, New_Bound=Old_Bound, M_low=M/4, I=0.Wherein Old_Bound is high-order QAM planisphere Constellation interval border, computing formula is as follows：

Sym(n)=Sym_re(n)+Sym_im(n)*j

Wherein Sym_re (n) is the real part of Higher Order QAM Signals Sym (n), and Sym_im (n) is the void of 16QAM signals Sym (n) Portion, n is the integer less than or equal to N-1, and N is the symbol total number of the Higher Order QAM Signals.For example in LTE system or TD- In SCDMA systems, N is the symbol total number of the QAM signals included in a wireless sub-frame.

The setting of iteration mark is primarily used to indicate interative computation, as long as therefore indicating effect can be reached, In the present embodiment, 0 expression is entered as to I there is provided iteration is indicated.It is of course also possible to use other modes, such as refer to iteration Show that being entered as 0xff represents that it is set.

Step S22：Constellation switch process is performed, QAM signals Sym_new (n) corresponding with M_low is obtained.

It is actual that a depression of order treatment has been carried out to high-order QAM planisphere in the initialization procedure of step S21, because This first has to obtain QAM signals corresponding with the planisphere after depression of order treatment, is that follow-up depression of order is prepared.Specifically, and M_ The computing formula of corresponding QAM signals Sym_new (n) of low is as follows：

Sym_new(n)=|Sym_re(n)|-New_Bound+(|Sym_im(n)|-New_Bound)*j

Step S23：Judge whether M_low is equal to 4.

If step S23 judged results are no, actually M_low is more than 4, then perform step S24：Update New_ Bound, M_Low, then perform step S22 again.Specifically, it is M_low=M_low/4 to update M_low formula, New_ is updated The formula of Bound is：

Wherein, the real part of Sym_news (n) of the Sym_new_re (n) obtained by being calculated in step S22, Sym_new_im (n) The imaginary part of the Sym_new (n) obtained by being calculated in step S22.

If the judged result of step S23 is yes, step S25 is performed：Judge whether iteration mark I is set.In this reality Apply in example, I=0 is represented and is set, I ≠ 0 represents and is revoked.

If the judged result of step S25 is yes, step S26 is performed；

Step S26：New_Bound and M_low is reset, and cancels iteration mark, then perform step S22.Specifically, The formula for setting New_Bound and M_low is as follows：

New_Bound=New_Bound*M/4

M_low=M/4

The revocation of iteration mark I, can be the integer that any non-zero is entered as to I, in embodiments of the present invention, Ke Yishe Put I=I+1.

If the judged result of step S25 is no, step S27 is performed：Based on Higher Order QAM Signals Sym (n) and New_ Bound is soft demodulated.

For example, by taking 16QAM signals as an example, i.e. M=16 specifically holds according to the soft demodulation of step S21 to step S27 Row process is：

Perform step S21：New_Bound=Old_Bound, M_low=M/4=4, I=0；

Perform step S22：Calculate Sym_new (n)；

Perform step S23：Judged result is yes（M_low=4）；

Perform step S25：Judged result is yes（I=0）；

Perform step S26：New_Bound=New_Bound*M/4=New_Bound*4, M_low=M/4=4, I=1 are returned Step S22；

Perform step S22：Calculate Sym_new (n)；

Perform step S23：Judged result is yes（M_low=4）；

Perform step S25：Judged result is no（I=1）；

Perform step S27：Based on New_Bound and Sym (n), 16QAM signals are soft demodulated, according to equation below Corresponding 4 soft bits of output Sym (n)：

Bit(0,n)=Sym_re(n)

Bit(1,n)=Sym_im(n)

Bit(2,n)=New_Bound-|Sym_re(n)|

Bit(3,n)=New_Bound-|Sym_im(n)|

By taking 64QAM signals as an example, i.e. M=64 is according to the specific implementation procedure of the soft demodulation of step S21 to step S27：

Perform step S21：New_Bound=Old_Bound, M_low=M/4=16, I=0；

Perform step S22：Calculate Sym_new (n)；

Perform step S23：Judged result is no（M_low=16）；

Perform step S24：M_low=M_low/4=4, updates New_Bound, return to step S22；

Perform step S22：Calculate Sym_new (n)；

Perform step S23：Judged result is yes（M_low=4）；

Perform step S25：Judged result is yes（I=0）；

Perform step S26：New_Bound=New_Bound*M/4=New_Bound*16, M_low=M/4=16, I=1 are returned Return step S22；

Perform step S22：Calculate Sym_new (n)；

Perform step S23：Judged result is no（M_low=16）；

Perform step S24：M_low=M_low/4=4, updates New_Bound, return to step S22；

Perform step S22：Calculate Sym_new (n)；

Perform step S23：Judged result is yes（M_low=4）；

Perform step S25：Judged result is no（I=1）；

Perform step S27：Based on New_Bound and Sym (n), 64QAM signals are soft demodulated, according to equation below Corresponding 6 soft bits of output Sym (n)：

Bit(0,n)=Sym_re(n)

Bit(1,n)=Sym_im(n)

Bit(2,n)=New_Bound-|Sym_re(n)|

Bit(3,n)=New_Bound-|Sym_im(n)|

Bit(4,n)=New_Bound-|(New_Bound/2-|Sym_re(n)|)|

Bit(5,n)=New_Bound-|(New_Bound/2-|Sym_im(n)|)|

It should be noted that the formula of above-mentioned steps S27 is only a kind of citing, it is soft demodulated using constellation interval border Other various existing modes can be used, it is low that those skilled in the art can accordingly derive that other are based on according to prior art The formula that the constellation interval border of rank QAM signals is soft demodulated to Higher Order QAM Signals, will not enumerate herein.

As can be seen that with the raising of QAM exponent numbers, the number of times of calculating is more, but it is simple due to being pertained only to when calculating Summation, the computing such as be averaging, be not related to the complicated computing such as logarithm, index, the speed of calculating can't be significantly affected.

The structural representation of the soft demodulating equipment of the QAM signals of the embodiment of the present invention as shown in figure 3, including：Depression of order is changed Unit 31, depression of order conversion is carried out for the high-order QAM planisphere to Higher Order QAM Signals, obtains the constellation area of low order QAM constellation Between border；Soft demodulating unit 32, for the constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation It is soft demodulated.

Wherein, the depression of order converting unit 31 includes：Initialization unit 311, for initializing depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_low=M/m, set iteration mark, and wherein Old_Bound is the high-order star The constellation interval border of seat figure；Planisphere converting unit 312, for performing star based on the Higher Order QAM Signals and New_Bound Seat figure switch process, the corresponding QAM signals of planisphere after being changed；First circulation judging unit 313, in the star After seat figure switch process, if M_low>M, then set M_low=M_low/m, based on the corresponding QAM of planisphere after the conversion Signal update New_Bound, indicates the constellation converting unit to perform the constellation switch process again；Second circulation judges single Unit 314, for after the planisphere switch process, if the M_low=m and iteration mark is set, sets New_ Iteration mark is cancelled after Bound=New_Bound*M/m, M_low=M/m, indicates the constellation converting unit to perform again described Planisphere switch process；Determining unit 315, for after the planisphere switch process, if M_low=m and the iteration mark It is revoked, it is determined that the constellation interval border of the low order QAM constellation is New_Bound.

Although the present invention is disclosed as above with preferred embodiment, it is not for limiting the present invention, any this area Technical staff without departing from the spirit and scope of the present invention, may be by the methods and techniques content of the disclosure above to this hair Bright technical scheme makes possible variation and modification, therefore, every content without departing from technical solution of the present invention, according to the present invention Any simple modification, equivalent variation and modification for being made to above example of technical spirit, belong to technical solution of the present invention Protection domain.

Claims (8)

1. a kind of soft demodulating method of quadrature amplitude modulation QAM signals, it is characterised in that including：

High-order QAM planisphere to Higher Order QAM Signals carries out depression of order conversion, obtains the constellation interval border of low order QAM constellation；

Constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation is soft demodulated；The high-order The order of modulation M=m of QAM signalsⁱ, wherein i is more than the exponent number that 1, m is the low order QAM constellation；It is described that high-order QAM is believed Number high-order QAM planisphere carry out depression of order conversion, the constellation interval border for obtaining low order QAM constellation includes：

Initialization depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_low=M/m, set iteration mark Will, wherein Old_Bound are the constellation interval border of the high-order constellation figure；

Planisphere switch process is performed based on the Higher Order QAM Signals and New_Bound, the planisphere after being changed is corresponding QAM signals；

After the planisphere switch process, if M_low>M, then set M_low=M_low/m, based on the star after the conversion The corresponding QAM signal updates New_Bound of seat figure, performs the constellation switch process again；

After the planisphere switch process, if the M_low=m and iteration mark is set, New_Bound=is set Iteration mark is cancelled after New_Bound*M/m, M_low=M/m, the planisphere switch process is performed again；

After the planisphere switch process, if the M_low=m and iteration mark is revoked, it is determined that the low order QAM stars The constellation interval border of seat figure is New_Bound.

2. the soft demodulating method of QAM signals according to claim 1, it is characterised in that it is described based on the conversion after The corresponding QAM signal updates New_Bound of planisphere is realized by following formula：

$New\_Bound=\frac{1}{N}\underset{n=0}{\overset{N-1}{\Σ}}\left(\right|Sym\_new\_re\left(n\right)|+|Sym\_new\_im\left(n\right)\left|\right)$

Wherein, Sym_new_re (n) is the real part of corresponding QAM signals Sym_new (n) of planisphere after the conversion, Sym_ New_im (n) is the imaginary part of corresponding QAM signals Sym_new (n) of planisphere after the conversion, and N is the Higher Order QAM Signals Symbol total number.

3. the soft demodulating method of QAM signals according to claim 1, it is characterised in that the constellation of the high-order constellation figure Interval border is obtained according to following formula：

$Old\_Bound=\frac{1}{N}\underset{n=0}{\overset{N-1}{\Σ}}\left(\right|Sym\_re\left(n\right)|+|Sym\_im\left(n\right)\left|\right)$

Wherein, Sym_re (n) is the real part of Higher Order QAM Signals Sym (n), and Sym_im (n) is the Higher Order QAM Signals Sym N the imaginary part of (), wherein N are the symbol total number of the Higher Order QAM Signals.

4. the soft demodulating method of QAM signals according to claim 1, it is characterised in that the modulation of the Higher Order QAM Signals Exponent number is 16, the constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation, carries out the soft solutions of QAM Adjust, including 4 soft bits Bit (k, n) that Higher Order QAM Signals Sym (n) are obtained by following formula：

Bit (0, n)=Sym_re (n)

Bit (1, n)=Sym_im (n)

Bit (2, n)=New_Bound- | Sym_re (n) |

Bit (3, n)=New_Bound- | Sym_im (n) |

Wherein, k is the integer less than K, and K=6 is the soft bit number of the Higher Order QAM Signals, and Sym_re (n) is the high-order The real part of QAM signals Sym (n), Sym_im (n) is the imaginary part of Higher Order QAM Signals Sym (n), and n is less than or equal to N-1's Integer, N is the symbol total number of the Higher Order QAM Signals.

5. the soft demodulating method of QAM signals according to claim 1, it is characterised in that the modulation of the Higher Order QAM Signals Exponent number is 64, the constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation, carries out the soft solutions of QAM Adjust, including 6 soft bits Bit (k, n) that Higher Order QAM Signals Sym (n) are obtained by following formula

Bit (0, n)=Sym_re (n)

Bit (1, n)=Sym_im (n)

Bit (2, n)=New_Bound- | Sym_re (n) |

Bit (3, n)=New_Bound- | Sym_im (n) |

Bit (4, n)=New_Bound- | (and New_Bound/2- | Sym_re (n)) |

Bit (5, n)=New_Bound- | (and New_Bound/2- | Sym_im (n)) |

Wherein, k is the integer less than K, and K is the soft bit number of the Higher Order QAM Signals, and Sym_re (n) believes for the high-order QAM The real part of number Sym (n), Sym_im (n) is the imaginary part of Higher Order QAM Signals Sym (n), and n is the integer less than or equal to N-1, N is the symbol total number of the Higher Order QAM Signals.

6. a kind of soft demodulating equipment of QAM signals, including：

Depression of order converting unit, depression of order conversion is carried out for the high-order QAM planisphere to Higher Order QAM Signals, obtains low order qam constellation The constellation interval border of figure；

Soft demodulating unit, is carried out soft for the constellation interval border based on the Higher Order QAM Signals and the low order QAM constellation Demodulation；The order of modulation M=m of the Higher Order QAM Signalsⁱ, wherein i is more than the exponent number that 1, m is the low order QAM constellation, institute Stating depression of order converting unit includes：

Initialization unit, for initializing depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_low= M/m, sets iteration mark, and wherein Old_Bound is the constellation interval border of the high-order constellation figure；

Planisphere converting unit, for performing planisphere switch process based on the Higher Order QAM Signals and New_Bound, obtains The corresponding QAM signals of planisphere after conversion；

First circulation judging unit, for after the planisphere switch process, if M_low>M, then set M_low=M_low/ M, based on the corresponding QAM signal updates New_Bound of planisphere after the conversion, indicates the constellation converting unit to hold again The row constellation switch process；

Second circulation judging unit, for after the planisphere switch process, if the M_low=m and iteration mark is set Put, then cancel iteration mark after New_Bound=New_Bound*M/m, M_low=M/m are set, indicate the constellation conversion single Unit performs the planisphere switch process again；

Determining unit, for after the planisphere switch process, if the M_low=m and iteration mark is revoked, it is determined that The constellation interval border of the low order QAM constellation is New_Bound.

7. a kind of mobile terminal, it is characterised in that including the soft demodulating equipment of QAM signals described in claim 6.

8. mobile terminal according to claim 7, it is characterised in that the mode of operation of the mobile terminal is LTE standards Or TD-SCDMA standards.