CN104935538A - Low complexity Gaussian filtered frequency shift keying (GFSK) intersymbol interference offset processing method and device - Google Patents

Abstract

The invention relates to a low complexity Gaussian filtered frequency shift keying (GFSK) intersymbol interference offset processing method and device. The method comprises a first step that a sign ym+1 is delayed by a second delayer, then a sign ym is obtained, after judgment by a first symbol decision device, the sign (ym+1) is output; a second step that the sign (ym+1) and a sign rm-1 are accumulated through a first summator so as to obtain a first accumulative value; a third step that the first accumulative value is multiplied by an automatic estimation parameter h_Est through a first multiplier so as to obtain a first product; a fourth step that the first product is multiplied by a code element interference adjustable parameter Hm1 through a second multiplier so as to obtain a second product; a fifth step that a second summator performs difference on the second product and the sign ym so as to obtain a second accumulative value; and a sixth step that the second accumulative value output by the second summator is transmitted into a second symbol decision device, so that the second symbol decision device performs symbol judgment so as to obtain a judgment output sign rm. The method has good demodulation ability, realizes a simple judgment feedback structure, and has a wide application range.

Description

The GFSK intersymbol interference cancellation processing method of low complex degree and device

Technical field

The present invention relates to a kind of processing method and device, especially a kind of GFSK intersymbol interference cancellation processing method of low complex degree and device, belong to the technical field of signal transacting.

Background technology

GMSK (Gaussian filtered MSK) signal grows up on the basis of MSK modulation signal, msk signal can regard the continuous phase fsk signal that modulation index is 0.5 as, although it has the advantage of bandwidth sum energy coherent demodulation of constant-envelope, Phase Continuation, relative narrower, it can not meet the strict demand of some communication system to out-of-band radiation.In order to compress the power spectrum of msk signal, before MSK modulation, increasing one-level pre-modulation filter, thus restrained effectively the out-of-band radiation of signal.GMSK signal is exactly the msk signal that pre-modulation filter is gauss low frequency filter.Because it has excellent power spectrum characteristic (the fast attenuation characteristic of power spectrum secondary lobe), be widely used in the various digital communicating fields that signal band is strictly limited, again due to its constant-envelope, advantage more more than BPSK phase-modulation is embodied, so be particularly suitable for satellite communication and mobile communication in the nonlinear channel that the C class A amplifier A with amplitude limiting characteristic is formed.

In bluetooth 4.0 physical layer standard, contain the GFSK modulation system (frequency modulation index (FM index) 0.28 ~ 0.35) of Basic Rate in the GMSK modulation mode (frequency modulation index (FM index), between 0.45 ~ 0.55, wherein 0.5 is GMSK) of BLE and BT.Gaussian filter is while restrained effectively signal out-of-band radiation, introduce intersymbol interference, interference introducing degree depends primarily on the value (product wide when three dB bandwidth and symbol is 0.5 for Bluetooth system) of parameter BT, BT value is less, disturbs larger between created symbol.Certainly, other type compact schemes filter can also be selected in theory, as raised cosine filter etc.

The process complexity of the removal intersymbol interference of existing better performances is high, is not too suitable for consumer electronics.Such as: MLSE method (needing to use Viterbi decoded mode), DFE method (decision feedback equalization).

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, provide a kind of GFSK intersymbol interference cancellation processing method and device of low complex degree, it has good demodulation ability, the simple decision-feedback structure of implementation structure, and wide accommodation is safe and reliable.

According to technical scheme provided by the invention, a kind of GFSK intersymbol interference cancellation processing method of low complex degree, described GFSK intersymbol interference cancellation processing method comprises the steps:

Step 1, determine optimum sampling position judgement after signal y _m+1, described signal y _m+1to obtain signal y after the second delayer time delay _m, and signal y _m+1sign (y is exported after being adjudicated by the first symbol judgement device _m+1);

Step 2, the sign (y that the first symbol judgement device is exported _m+1) transfer in first adder, and first adder also receives the first delayer to judgement output signal r _msignal r after time delay _m-1, first adder is by sign (y _m+1) and signal r _m-1add up, to obtain the first accumulated value;

Step 3, transferred in the first multiplier by the first accumulated value that first adder exports, and the first multiplier also receives automatic estimated parameter h_Est, and the first accumulated value, automatically estimated parameter h_Est are carried out product, to obtain the first product value by the first multiplier;

Step 4, by first multiplier export the first product value transfer in the second multiplier, and the second multiplier also receiving symbol interference adjustable parameters Hm1, first product value, symbol interference adjustable parameters Hm1 are carried out product by the second multiplier, to obtain the second product value;

Step 5, transfer in second adder by the second product value that the second multiplier exports, second adder is Received signal strength y simultaneously _m, second adder is to the second product value, signal y _mit is poor to carry out, to obtain the second accumulated value;

Step 6, by second adder export the second accumulated value transfer in the second symbol judgement device, with undertaken by the second symbol judgement device symbol judgement obtain judgement output signal r _m.

The first accumulated value that first adder exports is 0 ,+1 or-1.

For the GFSK signal of BT=0.5, the duration of the time delay of the first delayer, the second delayer is 1 code element.

A GFSK intersymbol interference signal processing apparatus for low complex degree, comprises for receiving signal y after the criterion of optimum sampling position _m+1the second delayer and the first symbol judgement device, the output of the first symbol judgement device is connected with the input of first adder, the input of first adder is also connected with the output of the first delayer, the output of output first multiplier of first adder connects, the output of the first multiplier is connected with the input of the second multiplier, the input of the second multiplier is connected with the input of second adder, the input of second adder is also connected with the output of the second delayer, the output of second adder is connected with the input of the second symbol judgement device, second symbol judgement device exports judgement output signal r _m, and the output of the second symbol judgement device is also connected with the input of the first delayer,

Signal y _m+1to obtain signal y after the second delayer time delay _m, and signal y _m+1sign (y is exported after being adjudicated by the first symbol judgement device _m+1); First delayer is outputed signal r to judgement by first adder _msignal r after time delay _m-1, first adder is by sign (y _m+1) and signal r _m-1add up, to obtain the first accumulated value;

The first accumulated value received, automatically estimated parameter h_Est are carried out product, to obtain the first product value by the first multiplier; The first product value received, symbol interference adjustable parameters Hm1 are carried out product, to obtain the second product value by the second multiplier;

Second adder is Received signal strength y simultaneously _m, second adder is to the second product value, signal y _mit is poor to carry out, and to obtain the second accumulated value, carries out symbol judgement obtain judgement output signal r by the second symbol judgement device to the second accumulated value _m.

The first accumulated value that first adder exports is 0 ,+1 or-1.

For the GFSK signal of BT=0.5, the duration of the time delay of the first delayer, the second delayer is 1 code element.

Advantage of the present invention: there is good demodulation ability, the simple decision-feedback structure of implementation structure, wide accommodation, safe and reliable.

Accompanying drawing explanation

Gaussian filter integral curve when Fig. 1 is BT=0.5 of the present invention.

The eye pattern of single carrier communication when Fig. 2 is BT=0.5 of the present invention.

Fig. 3 is that one of the present invention specifically implements structured flowchart.

Description of reference numerals: 10-second delayer, 20-first symbol judgement device, 30-first adder, 40-first multiplier, 50-second multiplier, 60-second adder, 70-second symbol judgement device and 80-first delayer.

Embodiment

Below in conjunction with concrete drawings and Examples, the invention will be further described.

For BT system (Bluetooth system), gaussian frequency shift keying (GFSK, Gaussian filteredFrequency Shift Keying) system complex baseband signal can be expressed as:

r _b(t)＝e ^jφ(t)

Wherein, t is the time of reception, r _bt () time dependent base band time domain signal for receiving, φ (t) is time dependent phase signal, and j is imaginary unit.Further,

$\begin{array}{c}\mathrm{\φ}\left(t\right)={\mathrm{\πk}}_{FM}{\∫}_{-\mathrm{\∞}}^{t}s\left(\mathrm{\τ}\right)d\mathrm{\τ}\\ ={\mathrm{\πk}}_{FM}\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_n{\∫}_{-\mathrm{\∞}}^{t}g\left(\mathrm{\τ}-nT\right)d\mathrm{\τ}\\ ={\mathrm{\πk}}_{FM}\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_n{\∫}_{-\mathrm{\∞}}^{t-nT}g\left({\mathrm{\τ}}^{\′}\right){\mathrm{d\τ}}^{\′}\end{array}$

$s\left(\mathrm{\τ}\right)=\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_{n}g(\mathrm{\τ}-nT)$

Particularly, a _nbe+1 or-1 for 2GFSK value, can get other values, g (τ): be Gaussian function for other FSK system, τ ' is only variable when variable is replaced, and wide when T is code element, such as BT system is 1 μ s (microsecond), k _fMfor modulation frequency modulation index.

For low-power consumption Bluetooth system (BLE:BlueToothwithLowEnergy), k _fM=0.5 (GMSK:GaussianFilteredMinimum ShiftKeying Gaussian-filtered minimum shift keying); And for Bluetooth system (BT:BlueTooth), k _fM=0.32 (GFSK), wherein, for normalization Gaussian filter, also known as frequency shaping function, for normalized parameter, B is three dB bandwidth, and T is symbolic code elementary time width (if BLE/BT system is 1 μ s).Certainly, other type compact schemes filter can also be selected in theory, as raised cosine filter etc.

The present invention is described for BT=0.5.Carry out integration to Gaussian filter, as shown in Figure 1, the time dependent integral result of upper limit of integral can be expressed as:

$G\left(t\right)={\∫}_{-\mathrm{\∞}}^{t}g\left(\mathrm{\τ}\right)d\mathrm{\τ}=\left\{\begin{array}{cc}1& t\∈\left(LT,+\mathrm{\∞}\right)\\ {\∫}_{-LT}^{t}g\left(\mathrm{\τ}\right)d\mathrm{\τ}& t\∈\[-LT,LT\]\\ 0& t\∈\left(-\mathrm{\∞},-LT\right)\end{array}\right.$

Wherein, the integral function that G (t) is Gaussian filter, also known as phase place shaping function, obviously, G (t) has following characteristic:

1), G (t)+G (-t)=1, especially G (0.5)+G (-0.5)=1.

2), to G (t) sample by T interval, and remember G (nT)=G (n), have

$G\left(n\right)=\left\{\begin{array}{cc}0& n\∈Z^{-}\\ 0.5& n=0\\ 1& n\∈Z^{+}\end{array}\right.$

Support Interval width is 2LT (L is interference constraints length factor, and L=1 means current sign only by a previous and rear symbol-interference).

If M is delayed symbol he number, then

Complex baseband signal r _bt () is spaced apart two version r of MT _b(t), r _b(t-MT) conjugate product d _m(t) be:

$\begin{array}{c}{d}_M\left(t\right)=r_b\left(t\right){r_b}^{*}(t-MT)\\ =e^{{\mathrm{j\Δ\φ}}_M\left(t\right)}\end{array}$

Wherein * is complex conjugate operation,

$\begin{array}{c}{\mathrm{\Δ\φ}}_M\left(t\right)=\mathrm{\φ}\left(t\right)-\mathrm{\φ}\left(t-MT\right)\\ ={\mathrm{\πk}}_{FM}\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_n{\∫}_{t-MT}^{t}g\left(\mathrm{\τ}-nT\right)d\mathrm{\τ}\\ \begin{array}{c}=\mathrm{\π}{k}_{FM}\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_n{\∫}_{t-\left(M+n\right)T}^{t-nT}g\left({\mathrm{\τ}}^{\′}\right){\mathrm{d\τ}}^{\′}\\ =\mathrm{\π}{k}_{FM}\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_n\[G\left(t-nT\right)-G\left(t-nT-MT\right)\]\\ =\mathrm{\π}{k}_{FM}\mathrm{\Δ}{{\mathrm{\φ}}_M}^{\′}\left(t\right)\end{array}\end{array}$

${{\mathrm{\Δ\φ}}_M}^{\′}\left(t\right)=\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_n\[G(t-nT)-G(t-nT-MT)\]$

Have BT=0.5 for BT or BLE system, L=1, φ (t-MT) postpone the signal after MT for φ (t).

Because BT system symbol chip rate is 1MHz, so carry out intersymbol interference to offset process in 1MHz speed, i.e. M=1, then have

${{\mathrm{\Δ\φ}}_1}^{\′}\left(t\right)={\underset{n=-}{\overset{+\mathrm{\∞}}{\Σ}}}_{\mathrm{\∞}}{a}_n\[G(t-nT)-G(t-nT-T)\]$

Above formula Δ φ ₁' (t) be the expression of Received signal strength in angle domain, if fold by the cycle, can obtain the eye pattern in carrier wave communication system, as shown in Figure 2.

Maximum place (being dotted line position in figure) the Δ φ for 1MHz demodulates is opened in eye pattern ₁(m+0.5).

According to single-carrier system demodulation principle, select eye pattern to open maximum place (being dotted line position in figure) as optimum sampling judgement position, after optimum sampling judgement position operation, the signal that 1MHz demodulates is

Δφ ₁(m+0.5)＝πk _FMΔφ ₁'(m+0.5)

Wherein, by G (0.5)+G (-0.5)=1, then Δ φ ₁' (m+0.5) be

$\begin{array}{c}\mathrm{\Δ}{{\mathrm{\φ}}_1}^{\′}\left(m+0.5\right)=\underset{n=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}{a}_n\[G\left(m-n+0.5\right)-G\left(m-n-0.5\right)\]\\ =\underset{k=-1}{\overset{+\mathrm{\∞}}{\Σ}}{a}_{m-k}\[G\left(k+0.5\right)-G\left(k-0.5\right)\]\\ =a_{m+1}G\left(-0.5\right)+a_m\[G\left(0.5\right)-G\left(-0.5\right)\]+a_{m-1}\[G\left(1.5\right)-G\left(0.5\right)\]\\ =a_{m+1}G\left(-0.5\right)+a_m\[G\left(0.5\right)-G\left(-0.5\right)\]+a_{m-1}\[1-G\left(0.5\right)\]\\ =\left(a_{m+1}+a_{m-1}\right)G\left(-0.5\right)+a_m\[1-2G\left(-0.5\right)\]\\ a_m=\frac{{{\mathrm{\Δ\φ}}_1}^{\′}\left(m+0.5\right)-\left(a_{m+1}+a_{m-1}\right)G\left(-0.5\right)}{1-2G\left(-0.5\right)}\\ =\frac{\frac{{\mathrm{\Δ\φ}}_1\left(m+0.5\right)}{{\mathrm{\πk}}_{FM}}-\left(a_{m+1}+a_{m-1}\right)G\left(-0.5\right)}{1-2G\left(-0.5\right)}\end{array}$

From above formula, in order to demodulation a _m, must a be obtained _m-1and a _m+1.Due to a _m+1for future signal, can replace with the direct judgement of next symbol, be Δ φ ₁' the symbol of (m+1.5).

In practical implementations, only a is paid close attention to _msymbol, namely

r _m＝sign(a _m)

＝sign[Δφ ₁'(m+0.5)-(a _m+1+a _m-1)G(-0.5)]

＝sign{Δφ ₁'(m+0.5)-[sign(Δφ ₁'(m+1.5))+r _m-1]G(-0.5)}

Assuming that y _m=Δ φ ₁' (m+0.5), ζ=G (-0.5)=0.1057, then r _m=sign{y _m-[sign (y _m+1)+r _m-1] ζ.

As shown in Figure 3, according to the above description, to the Bluetooth system of BT=0.5, in order to the GFSK intersymbol interference carrying out low complex degree is eliminated, the present invention includes for receiving signal y after the criterion of optimum sampling position _m+1the second delayer 10 and the first symbol judgement device 20, the output of the first symbol judgement device 20 is connected with the input of first adder 30, the input of first adder 30 is also connected with the output of the first delayer 80, the output of output first multiplier 40 of first adder 30 connects, the output of the first multiplier 40 is connected with the input of the second multiplier 50, the input of the second multiplier 50 is connected with the input of second adder 60, the input of second adder 60 is also connected with the output of the second delayer 10, the output of second adder 60 is connected with the input of the second symbol judgement device 70, second symbol judgement device 70 exports judgement output signal r _m, and the output of the second symbol judgement device 70 is also connected with the input of the first delayer 80,

Signal y _m+1to obtain signal y after the second delayer 10 time delay _m, and signal y _m+1sign (y is exported after being adjudicated by the first symbol judgement device 20 _m+1); First delayer 80 is outputed signal r to judgement by first adder 30 _msignal r after time delay _m-1, first adder 30 is by sign (y _m+1) and signal r _m-1add up, to obtain the first accumulated value;

The first accumulated value received, automatically estimated parameter h_Est are carried out product, to obtain the first product value by the first multiplier 40; The first product value received, symbol interference adjustable parameters Hm1 are carried out product, to obtain the second product value by the second multiplier 50;

Second adder 60 is Received signal strength y simultaneously _m, second adder 60 is to the second product value, signal y _mit is poor to carry out, and to obtain the second accumulated value, carries out symbol judgement obtain judgement output signal r by the second symbol judgement device 70 to the second accumulated value _m.

Particularly, Dat_1x (1 in figure, 1,6) eye pattern for receiving opens the signal value of maximum position, BT system realizes example employing 8bit and represents that (first 1 is bit symbol position, second 1 is 1 bit integer position, and 6 is 6 bit decimal places), the numerical value in figure can adopt (x, y, z) quantization means form, wherein, x is sign bit figure place, y is integer number of bits, z is decimal number of bits, is expressed as signed number when x value is 1, and value is 0 be expressed as unsigned number.

Automatic estimated parameter h_Esth_Est value is π k _fM, be constant for fixed modulation index.Symbol interference adjustable parameters Hm1 is that the size of ζ, ζ=G (-0.5), ζ is corresponding with the interference size that front and back code element is brought.When realizing, symbol interference adjustable parameters Hm1 is by register configuration.In order to consider the impact of other filters, unique parameters ζ can be adjusted.When being 0 by ζ optimum configurations, namely deteriorating in traditional sense and the most directly adjudicating structure.The present invention can improve 1 ~ 2dB than the performance of direct judgement mode demodulation.

SgnAC (end): Access Code map to +/-1 sequence after last bit. (Interference Cancellation after Access Code synchronization decisions, 1MHz speed is carried out), in figure: the first delayer 80 (D1) be initialized as SgnAC (end), the second delayer 10 (D2) be initialized as 0.

Further, the first accumulated value that first adder 30 exports is 0 ,+1 or-1.For the GFSK signal of BT=0.5, the duration of the time delay of the first delayer 80, second delayer 10 is 1 code element.

From the above, GFSK intersymbol interference cancellation processing method of the present invention comprises the steps:

Step 1, determine optimum sampling position judgement after signal y _m+1, described signal y _m+1to obtain signal y after the second delayer 10 time delay _m, and signal y _m+1sign (y is exported after being adjudicated by the first symbol judgement device 20 _m+1);

Step 2, the sign (y that the first symbol judgement device 20 is exported _m+1) transfer in first adder 30, and first adder 30 also receives the first delayer 80 to judgement output signal r _msignal r after time delay _m-1, first adder 30 is by sign (y _m+1) and signal r _m-1add up, to obtain the first accumulated value;

Step 3, the first accumulated value exported by first adder 30 transfer in the first multiplier 40, and the first multiplier 40 also receives automatic estimated parameter h_Est, first accumulated value, automatically estimated parameter h_Est are carried out product, to obtain the first product value by the first multiplier 40;

Step 4, the first product value that the first multiplier 40 exports is transferred in the second multiplier 50, and receiving symbol interference adjustable parameters Hm1 gone back by the second multiplier 50, first product value, symbol interference adjustable parameters Hm1 are carried out product by the second multiplier 50, to obtain the second product value;

Step 5, transfer in second adder 60 by the second product value that the second multiplier 50 exports, second adder 60 is Received signal strength y simultaneously _m, second adder 60 is to the second product value, signal y _mit is poor to carry out, to obtain the second accumulated value;

Step 6, the second accumulated value exported by second adder 60 transfer in the second symbol judgement device 70, obtain judgement output signal r to be carried out symbol judgement by the second symbol judgement device 70 _m.

The present invention can improve the receptivity of GFSK system 1 ~ 2dB, is also applicable to continuous phase (CPM) modulating system, and the code element number that there is intersymbol interference is just more, and Interference Cancellation operation exponent number is higher, specifically no longer describes in detail.

Claims (6)

1. a GFSK intersymbol interference cancellation processing method for low complex degree, is characterized in that, described GFSK intersymbol interference cancellation processing method comprises the steps:

Step 1, determine optimum sampling position judgement after signal y _m+1, described signal y _m+1to obtain signal y after the second delayer (10) time delay _m, and signal y _m+1sign (y is exported after being adjudicated by the first symbol judgement device (20) _m+1);

Step 2, the sign (y that the first symbol judgement device (20) is exported _m+1) transfer in first adder (30), and first adder (30) also receives the first delayer (80) to judgement output signal r _msignal r after time delay _m-1, first adder (30) is by sign (y _m+1) and signal r _m-1add up, to obtain the first accumulated value;

Step 3, the first accumulated value that first adder (30) exports is transferred in the first multiplier (40), and the first multiplier (40) also receives automatic estimated parameter h_Est, first accumulated value, automatically estimated parameter h_Est are carried out product, to obtain the first product value by the first multiplier (40);

Step 4, the first product value that the first multiplier (40) exports is transferred in the second multiplier (50), and receiving symbol interference adjustable parameters Hm1 gone back by the second multiplier (50), first product value, symbol interference adjustable parameters Hm1 are carried out product by the second multiplier (50), to obtain the second product value;

Step 5, transfer in second adder (60) by the second product value that the second multiplier (50) exports, second adder (60) is Received signal strength y simultaneously _m, second adder (60) is to the second product value, signal y _mit is poor to carry out, to obtain the second accumulated value;

Step 6, the second accumulated value that second adder (60) exports is transferred in the second symbol judgement device (70), obtain judgement output signal r to be carried out symbol judgement by the second symbol judgement device (70) _m.

2. the GFSK intersymbol interference cancellation processing method of low complex degree according to claim 1, is characterized in that: the first accumulated value that first adder (30) exports is 0 ,+1 or-1.

3. the GFSK intersymbol interference cancellation processing method of low complex degree according to claim 1, it is characterized in that: for the GFSK signal of BT=0.5, the duration of the time delay of the first delayer (80), the second delayer (10) is 1 code element.

4. a GFSK intersymbol interference signal processing apparatus for low complex degree, is characterized in that: comprise for receiving signal y after the criterion of optimum sampling position _m+1the second delayer (10) and the first symbol judgement device (20), the output of the first symbol judgement device (20) is connected with the input of first adder (30), the input of first adder (30) is also connected with the output of the first delayer (80), the output of output first multiplier (40) of first adder (30) connects, the output of the first multiplier (40) is connected with the input of the second multiplier (50), the input of the second multiplier (50) is connected with the input of second adder (60), the input of second adder (60) is also connected with the output of the second delayer (10), the output of second adder (60) is connected with the input of the second symbol judgement device (70), second symbol judgement device (70) exports judgement output signal r _m, and the output of the second symbol judgement device (70) is also connected with the input of the first delayer (80),

Signal y _m+1to obtain signal y after the second delayer (10) time delay _m, and signal y _m+1sign (y is exported after being adjudicated by the first symbol judgement device (20) _m+1); First delayer (80) is outputed signal r to judgement by first adder (30) _msignal r after time delay _m-1, first adder (30) is by sign (y _m+1) and signal r _m-1add up, to obtain the first accumulated value;

The first accumulated value received, automatically estimated parameter h_Est are carried out product, to obtain the first product value by the first multiplier (40); The first product value received, symbol interference adjustable parameters Hm1 are carried out product, to obtain the second product value by the second multiplier (50);

Second adder (60) is Received signal strength y simultaneously _m, second adder (60) is to the second product value, signal y _mit is poor to carry out, and to obtain the second accumulated value, carries out symbol judgement obtain judgement output signal r by the second symbol judgement device (70) to the second accumulated value _m.

5. the GFSK intersymbol interference signal processing apparatus of low complex degree according to claim 4, is characterized in that: the first accumulated value that first adder (30) exports is 0 ,+1 or-1.

6. the GFSK intersymbol interference signal processing apparatus of low complex degree according to claim 4, it is characterized in that: for the GFSK signal of BT=0.5, the duration of the time delay of the first delayer (80), the second delayer (10) is 1 code element.