CN103905370A - 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 of quadrature amplitude modulation signal and device, mobile terminal

Technical field

The present invention relates to the signal process field of communication system, particularly a kind of soft demodulating method of quadrature amplitude modulation signal and device, mobile terminal.

Background technology

In modern communications, improve the availability of frequency spectrum is one of focus of paying close attention to of technical staff always, along with the rapid growth of communication traffic demand, the digital modulation mode of finding availability of frequency spectrum raising has become one of main target of digital communication system design, research in recent years.High-order orthogonal Modulation and Amplitude Modulation (QAM, Quadrature Amplitude Modulation) become the effective means of one that improve communication system utilization ratio of transmission resources, application widely in digital microwave communication system, mobile communcations system, cable TV network and high speed data transfer and Satellite Communication System.

QAM is called again quadrature double sideband modulation, be by two-way independently baseband waveform respectively mutually orthogonal same frequency carrier wave is carried out to suppressed-carrier double side band modulation, the process that the two-way modulated signal obtaining stacks up.In QAM system, because two-way modulated signal frequency spectrum in identical bandwidth is orthogonal, can be in identical frequency band parallel transmission two paths of data information, therefore its band efficiency is higher.QAM is a kind of Vector Modulation, is the technology of amplitude and phase combining modulation, utilizes the amplitude of carrier wave and phase place to carry out transmission of information bit simultaneously.The order of modulation of QAM is generally 2 ⁿ, n is the soft bit number of each signal in each QAM set of signals.As for 16QAM, n is just 4, and each signal is represented by 4 bits; For 64QAM, n is just 6, and each signal is represented by 6 bits.The same with other digital modulation mode, digital qam signal collection can represent easily with planisphere, and a point on planisphere has just represented a signal in QAM set of signals.QAM order of modulation is higher, and the utilance of frequency band is higher.

The demodulation mode of common qam signal has hard solution to be in harmonious proportion soft demodulation, and hard demodulation refers to that by the constellation point judgement of the Noise receiving be corresponding modulation bit, conventionally realize simple, but performance is undesirable, is only suitable for the demodulation of low order QAM signal; The soft information that it is corresponding modulation bit that soft demodulation refers to the noisy constellation point judgement receiving, although it is better to realize complicated Performance Ratio, is particularly useful for the demodulation of Higher Order QAM Signals.The soft demodulation of QAM signal at present adopts the soft bit output of calculating QAM signal based on log-likelihood ratio (LLR, Log-Likelihood Ratio) algorithm mostly, but algorithm relates to logarithm and exponent arithmetic, and complexity is high, and computational speed is slow.Along with the raising of order of modulation, in planisphere, the distance of each signaling point is just less simultaneously, and corresponding signal decision interval is also just less, causes the error of the interval judgement of constellation to become large, finally makes the precision of the soft demodulation of QAM also decline thereupon.Especially in wireless communication technique field, as Long Term Evolution (LTE, Long Time Evolution) technology and TD SDMA (TD-SCDMA, Time Division Synchronous Code Division Multiple Access) in technology, the increasing high-order QAM modulation technology that uses, therefore demodulation QAM signal becomes technological difficulties in the urgent need to address quickly and accurately.The United States Patent (USP) of the invention that correlation technique can be US6661282B2 with reference to publication number.

Summary of the invention

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

For addressing the above problem, the invention provides a kind of soft demodulating method of orthogonal amplitude QAM signal, comprising:

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 figure;

Constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure is carried out soft demodulation.

Optionally, the order of modulation M=m of described Higher Order QAM Signals ⁱ, wherein i is greater than the exponent number that 1, m is described low order qam constellation figure; The described high-order QAM planisphere to Higher Order QAM Signals carries out depression of order conversion, and the constellation interval border that obtains low order qam constellation figure comprises:

Initialization depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_low=M/m, arrange iteration mark, and wherein Old_Bound is the constellation interval border of described high-order planisphere;

Carry out planisphere switch process based on described Higher Order QAM Signals and New_Bound, obtain QAM signal corresponding to planisphere after conversion;

After described planisphere switch process, if M_low>m arranges M_low=M_low/m, QAM signal update New_Bound corresponding to planisphere based on after described conversion, carries out described constellation switch process again;

After described planisphere switch process, if M_low=m and described iteration mark are set up, after being set, New_Bound=New_Bound*M/m, M_low=M/m cancel iteration mark, again carry out described planisphere switch process;

After described planisphere switch process, if M_low=m and described iteration mark are cancelled, determine that the constellation interval border of described low order qam constellation figure is New_Bound.

Optionally, m=4, described planisphere switch process obtains QAM signal corresponding to planisphere after conversion based on following formula:

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

Wherein, Sym_new (n) is the QAM signal that the planisphere after described conversion is corresponding, Sym_re (n) is the real part of described Higher Order QAM Signals Sym (n), Sym_im (n) is the imaginary part of described Higher Order QAM Signals Sym (n), wherein n is the integer that is less than or equal to N-1, the total number of symbol that N is described Higher Order QAM Signals.

Optionally, QAM signal update New_Bound corresponding to the described planisphere based on after described conversion realizes by following formula:

$\mathrm{New}\_\mathrm{Bound}=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\left(\right|\mathrm{Sym}\_\mathrm{new}\_\mathrm{re}\left(n\right)|+|\mathrm{Sym}\_\mathrm{new}\_\mathrm{im}\left(n\right)\left|\right)$

Wherein, Sym_new_re (n) is the real part of the QAM signal Sym_new (n) that the planisphere after described conversion is corresponding, Sym_new_im (n) is the imaginary part of the QAM signal Sym_new (n) that the planisphere after described conversion is corresponding, the total number of symbol that N is described Higher Order QAM Signals.

Optionally, the constellation interval border of described high-order planisphere obtains according to following formula:

$\mathrm{Old}\_\mathrm{Bound}=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\left(\right|\mathrm{Sym}\_\mathrm{re}\left(n\right)|+|\mathrm{Sym}\_\mathrm{im}\left(n\right)\left|\right)$

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

Optionally, the order of modulation of described Higher Order QAM Signals is 16, the described constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure, carry out the soft demodulation of QAM, comprise 4 the soft bit Bit (k, n) that obtain described Higher Order QAM Signals Sym (n) 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 that is less than K, K is the soft bit number of described Higher Order QAM Signals, Sym_re (n) is the real part of described Higher Order QAM Signals Sym (n), Sym_im (n) is the imaginary part of described Higher Order QAM Signals Sym (n), n is the integer that is less than or equal to N-1, the total number of symbol that N is described Higher Order QAM Signals.

Optionally, the order of modulation of described Higher Order QAM Signals is 64, the described constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure, carry out the soft demodulation of QAM, comprise 6 the soft bit Bit (k, n) that obtain described Higher Order QAM Signals Sym (n) 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-|(New_Bound/2-|Sym_re(n)|)|

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

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

For addressing the above problem, technical solution of the present invention also provides a kind of soft demodulating equipment of QAM signal, comprising:

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

Soft demodulating unit, carries out soft demodulation for the constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure.

Optionally, the order of modulation M=m of described Higher Order QAM Signals ⁱ, wherein i is greater than the exponent number that 1, m is described low order qam constellation figure, and described depression of order converting unit comprises:

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

Planisphere converting unit, for carrying out planisphere switch process based on described Higher Order QAM Signals and New_Bound, obtains QAM signal corresponding to planisphere after conversion;

The first cycle criterion unit, for after described planisphere switch process, if M_low>m, M_low=M_low/m is set, QAM signal update New_Bound corresponding to planisphere based on after described conversion, indicates described constellation converting unit again to carry out described constellation switch process;

The second cycle criterion unit, for after described planisphere switch process, if M_low=m and described iteration mark are set up, after being set, New_Bound=New_Bound*M/m, M_low=M/m cancel iteration mark, and indicate described constellation converting unit again to carry out described planisphere switch process;

Determining unit, for after described planisphere switch process, if M_low=m and described iteration mark are cancelled, determines that the constellation interval border of described low order qam constellation figure is New_Bound.

For addressing the above problem, the present invention also provides a kind of mobile terminal, comprises the soft demodulating equipment of described QAM signal.

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

The soft demodulating method of the QAM signal that technical solution of the present invention provides, by planisphere is changed, high-order QAM planisphere is converted to low order qam constellation figure, and the constellation interval border of definite described low order qam constellation figure, then utilize the constellation interval border of described low order qam constellation figure to carry out soft demodulation to Higher Order QAM Signals.Compared with prior art, the distribution of the symbolic point that the soft demodulating method of the QAM signal that technical solution of the present invention provides does not limit QAM signal in planisphere, and the decision error of the constellation interval border of qam constellation figure can not increase along with the raising of QAM exponent number, can ensure performance and the precision of the soft demodulation of QAM signal.

Meanwhile, the implementation procedure of the soft demodulating method of the QAM signal that technical solution of the present invention provides does not relate to complicated logarithm or exponent arithmetic, has improved speed and the efficiency of soft demodulation.

Brief description of the drawings

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

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

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

Embodiment

In prior art, the exponent number of QAM signal is higher, and the error of the interval judgement of its qam constellation is just larger, thereby causes the soft demodulation accuracy variation of QAM signal, and computational process complexity, is difficult for realizing.

In order to address the above problem, technical solution of the present invention provides a kind of soft demodulating method of the QAM signal based on qam constellation figure conversion, as shown in Figure 1, comprising:

Step S1: the 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 figure;

Step S2: the constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure is carried out soft demodulation.

Wherein, the order of modulation M=m of described Higher Order QAM Signals ⁱ, wherein i is greater than the exponent number that 1, m is described low order qam constellation figure.It should be noted that, high-order described in technical solution of the present invention, low order are comparatively speaking, for example, conventional QAM modulates as 256QAM, 64QAM, 16QAM, 4QAM, wherein, 4QAM signal is called low order QAM signal with respect to 16QAM signal, 64QAM signal, 256QAM signal, and 16QAM signal is called low order QAM signal with respect to 64QAM signal, 256QAM signal.Or Higher Order QAM Signals also can be called a QAM signal, low order QAM signal also can be called the 2nd QAM signal, the order of modulation of a wherein said QAM signal is higher than described the 2nd QAM signal.Step S1 is converted to the relatively low QAM signal of order of modulation by QAM signal relatively high order of modulation by planisphere, as 16QAM signal, 64QAM signal, 256QAM signal are converted to 4QAM signal, 256QAM signal is converted to 16QAM signal etc.

The soft demodulating method of the QAM signal that technical solution of the present invention provides, by the depression of order conversion to described Higher Order QAM Signals, described Higher Order QAM Signals is converted to low order QAM signal, and determine the constellation interval border of described low order QAM signal and the low order qam constellation figure corresponding with it, then utilize the constellation interval border of described low order planisphere to carry out soft demodulation to described Higher Order QAM Signals, the soft bit corresponding to each symbol of output QAM signal.With in prior art, realize compared with the soft demodulating method of QAM based on LLR algorithm, the soft demodulating method of the QAM signal based on qam constellation figure conversion that technical solution of the present invention provides, calculates easylier, precision is higher.

For making above-mentioned purpose of the present invention, feature and a little more becoming apparent, be elaborated below in conjunction with embodiment and accompanying drawing.

As shown in Figure 2, be the soft demodulating method of a kind of QAM signal of the embodiment of the present invention, in the present embodiment, m value is 4, the exponent number that represents the low order qam constellation figure after depression of order is changed is 4, and described Higher Order QAM Signals is 16QAM, 64QAM or 256QAM, and described soft demodulating method comprises:

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

Concrete, New_Bound=Old_Bound, M_low=M/4, I=0.Wherein Old_Bound is the constellation interval border of high-order QAM planisphere, and computing formula is as follows:

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

$\mathrm{Old}\_\mathrm{Bound}=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\left(\right|\mathrm{Sym}\_\mathrm{re}\left(n\right)|+|\mathrm{Sym}\_\mathrm{im}\left(n\right)\left|\right)$

Wherein Sym_re (n) is the real part of Higher Order QAM Signals Sym (n), Sym_im (n) is the imaginary part of 16QAM signal Sym (n), n is the integer that is less than or equal to N-1, the total number of symbol that N is described Higher Order QAM Signals.For example, in LTE system or TD-SCDMA system, N is the total number of symbol of the QAM signal that comprises in a wireless sub-frame.

Arranging of iteration mark is mainly used to refer to interative computation, as long as therefore can reach indicating effect, in the present embodiment, is that 0 expression is provided with iteration instruction to I assignment.Certainly, also can adopt other modes, for example, be that 0xff represents that it is set up etc. to iteration instruction assignment.

Step S22: carry out constellation switch process, obtain the QAM signal Sym_new (n) corresponding with M_low.

In the initialization procedure of step S21, reality has been carried out a depression of order processing to high-order QAM planisphere, therefore first will obtain the QAM signal corresponding with depression of order planisphere after treatment, for follow-up depression of order is prepared.Concrete, the computing formula of the QAM signal Sym_new (n) corresponding with M_low is as follows:

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

Step S23: judge whether M_low equals 4.

If step S23 judged result is no, be exactly in fact that M_low is greater than 4, perform step S24: upgrade New_Bound, M_Low, and then execution step S22.Concrete, upgrading M_low formula is M_low=M_low/4, the formula that upgrades New_Bound is:

$\mathrm{New}\_\mathrm{Bound}=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\left(\right|\mathrm{Sym}\_\mathrm{new}\_\mathrm{re}\left(n\right)|+|\mathrm{Sym}\_\mathrm{new}\_\mathrm{im}\left(n\right)\left|\right)$

Wherein, Sym_new_re (n) is for calculating the real part of the Sym_new (n) of gained in step S22, and Sym_new_im (n) is for calculating the imaginary part of the Sym_new (n) of gained in step S22.

If the judged result of step S23 is yes, perform step S25: judge whether iteration mark I is set up.In the present embodiment, I=0 represents to be set up, and I ≠ 0 represents to be cancelled.

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

Step S26: reset New_Bound and M_low, and cancel iteration mark, then perform step S22.Concrete, the formula that New_Bound and M_low are set is as follows:

New_Bound=New_Bound*M/4

M_low=M/4

Iteration mark I cancels, and can be the integer that is any non-zero to I assignment, in embodiments of the present invention, I=I+1 can be set.

If the judged result of step S25 is no, perform step S27: carry out soft demodulation based on Higher Order QAM Signals Sym (n) and New_Bound.

For instance, taking 16QAM signal as example, i.e. M=16, according to step S21 to the concrete implementation of the soft demodulation of step S27 is:

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

Execution step S22: calculate Sym_new (n);

Execution step S23: judged result is for being (M_low=4);

Execution step S25: judged result is for being (I=0);

Execution step S26:New_Bound=New_Bound*M/4=New_Bound*4, M_low=M/4=4, I=1, returns to step S22;

Execution step S22: calculate Sym_new (n);

Execution step S23: judged result is for being (M_low=4);

Execution step S25: judged result is no (I=1);

Execution step S27: based on New_Bound and Sym (n), 16QAM signal is carried out to soft demodulation, 4 soft bits according to following formula output Sym (n) correspondence:

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)|

Taking 64QAM signal as example, i.e. M=64, according to step S21 to the concrete implementation of the soft demodulation of step S27 is:

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

Execution step S22: calculate Sym_new (n);

Execution step S23: judged result is no (M_low=16);

Execution step S24:M_low=M_low/4=4, upgrades New_Bound, returns to step S22;

Execution step S22: calculate Sym_new (n);

Execution step S23: judged result is for being (M_low=4);

Execution step S25: judged result is for being (I=0);

Execution step S26:New_Bound=New_Bound*M/4=New_Bound*16, M_low=M/4=16, I=1, returns to step S22;

Execution step S22: calculate Sym_new (n);

Execution step S23: judged result is no (M_low=16);

Execution step S24:M_low=M_low/4=4, upgrades New_Bound, returns to step S22;

Execution step S22: calculate Sym_new (n);

Execution step S23: judged result is for being (M_low=4);

Execution step S25: judged result is no (I=1);

Execution step S27: based on New_Bound and Sym (n), 64QAM signal is carried out to soft demodulation, 6 soft bits according to following formula output Sym (n) correspondence:

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 for example a kind of, utilize constellation interval border to carry out soft demodulation and can adopt other multiple existing modes, those skilled in the art can derive other constellation interval border based on low order QAM signal are carried out soft demodulation formula to Higher Order QAM Signals according to prior art is corresponding, will not enumerate at this.

Can find out, along with the raising of QAM exponent number, the number of times of calculating is just more, but only relates to simple summation when calculating, the computing such as be averaging, and does not relate to the complex calculations such as logarithm, index, can't obviously affect the speed of calculating.

The structural representation of the soft demodulating equipment of the QAM signal of the embodiment of the present invention as shown in Figure 3, comprising: depression of order converting unit 31, carry out depression of order conversion for the high-order QAM planisphere to Higher Order QAM Signals, and obtain the constellation interval border of low order qam constellation figure; Soft demodulating unit 32, carries out soft demodulation for the constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure.

Wherein, described depression of order converting unit 31 comprises: initialization unit 311, for initialization depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_low=M/m, iteration mark is set, wherein Old_Bound is the constellation interval border of described high-order planisphere; Planisphere converting unit 312, for carrying out planisphere switch process based on described Higher Order QAM Signals and New_Bound, obtains QAM signal corresponding to planisphere after conversion; The first cycle criterion unit 313, for after described planisphere switch process, if M_low>m, M_low=M_low/m is set, QAM signal update New_Bound corresponding to planisphere based on after described conversion, indicates described constellation converting unit again to carry out described constellation switch process; The second cycle criterion unit 314, for after described planisphere switch process, if M_low=m and described iteration mark are set up, after New_Bound=New_Bound*M/m, M_low=M/m are set, cancel iteration mark, indicate described constellation converting unit again to carry out described planisphere switch process; Determining unit 315, for after described planisphere switch process, if M_low=m and described iteration mark are cancelled, determines that the constellation interval border of described low order qam constellation figure is New_Bound.

Although the present invention with preferred embodiment openly as above; but it is not for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; can utilize method and the technology contents of above-mentioned announcement to make possible variation and amendment to technical solution of the present invention; therefore; every content that does not depart from technical solution of the present invention; any simple modification, equivalent variations and the modification above embodiment done according to technical spirit of the present invention, all belong to the protection range of technical solution of the present invention.

Claims (11)

1. a soft demodulating method for quadrature amplitude modulation QAM signal, is characterized in that, comprising:

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 figure;

Constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure is carried out soft demodulation.

2. the soft demodulating method of QAM signal according to claim 1, is characterized in that, the order of modulation M=m of described Higher Order QAM Signals ⁱ, wherein i is greater than the exponent number that 1, m is described low order qam constellation figure; The described high-order QAM planisphere to Higher Order QAM Signals carries out depression of order conversion, and the constellation interval border that obtains low order qam constellation figure comprises:

Initialization depression of order constellation interval border New_Bound=Old_Bound, depression of order exponent number M_low=M/m, arrange iteration mark, and wherein Old_Bound is the constellation interval border of described high-order planisphere;

Carry out planisphere switch process based on described Higher Order QAM Signals and New_Bound, obtain QAM signal corresponding to planisphere after conversion;

After described planisphere switch process, if M_low>m arranges M_low=M low/m, QAM signal update New_Bound corresponding to planisphere based on after described conversion, carries out described constellation switch process again;

After described planisphere switch process, if M_low=m and described iteration mark are set up, after being set, New_Bound=New_Bound*M/m, M_low=M/m cancel iteration mark, again carry out described planisphere switch process;

After described planisphere switch process, if M_low=m and described iteration mark are cancelled, determine that the constellation interval border of described low order qam constellation figure is New_Bound.

3. the soft demodulating method of QAM signal according to claim 2, is characterized in that, m=4, and described planisphere switch process obtains QAM signal corresponding to planisphere after conversion based on following formula:

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

Wherein, Sym_new (n) is the QAM signal that the planisphere after described conversion is corresponding, Sym_re (n) is the real part of described Higher Order QAM Signals Sym (n), Sym_im (n) is the imaginary part of described Higher Order QAM Signals Sym (n), wherein n is the integer that is less than or equal to N-1, the total number of symbol that N is described Higher Order QAM Signals.

4. the soft demodulating method of QAM signal according to claim 2, is characterized in that, the QAM signal update New_Bound that the described planisphere based on after described conversion is corresponding realizes by following formula:

$\mathrm{New}\_\mathrm{Bound}=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\left(\right|\mathrm{Sym}\_\mathrm{new}\_\mathrm{re}\left(n\right)|+|\mathrm{Sym}\_\mathrm{new}\_\mathrm{im}\left(n\right)\left|\right)$

Wherein, Sym_new_re (n) is the real part of the QAM signal Sym_new (n) that the planisphere after described conversion is corresponding, Sym_new_im (n) is the imaginary part of the QAM signal Sym_new (n) that the planisphere after described conversion is corresponding, the total number of symbol that N is described Higher Order QAM Signals.

5. the soft demodulating method of QAM signal according to claim 2, is characterized in that, the constellation interval border of described high-order planisphere obtains according to following formula:

$\mathrm{Old}\_\mathrm{Bound}=\frac{1}{N}\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\left(\right|\mathrm{Sym}\_\mathrm{re}\left(n\right)|+|\mathrm{Sym}\_\mathrm{im}\left(n\right)\left|\right)$

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

6. the soft demodulating method of QAM signal according to claim 1, it is characterized in that, the order of modulation of described Higher Order QAM Signals is 16, the described constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure, carry out the soft demodulation of QAM, comprise 4 the soft bit Bit (k, n) that obtain described Higher Order QAM Signals Sym (n) 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 that is less than K, K=6, for the soft bit number of described Higher Order QAM Signals, Sym_re (n) is the real part of described Higher Order QAM Signals Sym (n), Sym_im (n) is the imaginary part of described Higher Order QAM Signals Sym (n), and n is the integer that is less than or equal to N-1, the total number of symbol that N is described Higher Order QAM Signals.

7. the soft demodulating method of QAM signal according to claim 1, it is characterized in that, the order of modulation of described Higher Order QAM Signals is 64, the described constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure, carry out the soft demodulation of QAM, comprise 6 the soft bit Bit (k, n) that obtain described Higher Order QAM Signals Sym (n) 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-|(New_Bound/2-|Sym_re(n)|)|

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

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

8.. a soft demodulating equipment for QAM signal, comprising:

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

Soft demodulating unit, carries out soft demodulation for the constellation interval border based on described Higher Order QAM Signals and described low order qam constellation figure.

9. the soft demodulating equipment of QAM signal according to claim 8, is characterized in that, the order of modulation M=m of described Higher Order QAM Signals ⁱ, wherein i is greater than the exponent number that 1, m is described low order qam constellation figure, and described depression of order converting unit comprises:

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

Planisphere converting unit, for carrying out planisphere switch process based on described Higher Order QAM Signals and New_Bound, obtains QAM signal corresponding to planisphere after conversion;

The first cycle criterion unit, for after described planisphere switch process, if M_low>m, M_low=M_low/m is set, QAM signal update New_Bound corresponding to planisphere based on after described conversion, indicates described constellation converting unit again to carry out described constellation switch process;

The second cycle criterion unit, for after described planisphere switch process, if M_low=m and described iteration mark are set up, after being set, New_Bound=New_Bound*M/m, M_low=M/m cancel iteration mark, and indicate described constellation converting unit again to carry out described planisphere switch process;

Determining unit, for after described planisphere switch process, if M_low=m and described iteration mark are cancelled, determines that the constellation interval border of described low order qam constellation figure is New_Bound.

10. a mobile terminal, is characterized in that, comprises the soft demodulating equipment of QAM signal described in claim 8 or 9.

11. mobile terminals according to claim 10, is characterized in that, the mode of operation of described mobile terminal is LTE standard or TD-SCDMA standard.

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