CN100518157C - Method and device for frequency deviation compensation of mobile communication system - Google Patents

Abstract

This invention relates to frequency-offset compensation method and a device immobile communication system. The device includes a pre-frequency set compensator, a frequency-offset and phase shift discriminator, a phase shift compensator and a ring circuit filter. The said pre-offset compensator utilize the evaluation to the offset from the filer to carry out pre-compensation to the current two modulation symbols and output it to the discriminator and phase shift compensator, the discriminator utilizes two-dimension non-linear estimation for offset estimation and correction, the compensator compensates the current modulation symbols.

Description

A kind of method and apparatus of mobile communication system compensate of frequency deviation

Technical field

The present invention relates to the method and apparatus that a kind of frequency deviation that mobile communication is produced compensates, relate in particular to the novel frequency bias compensation method and the device of a kind of TD-SCDMA system or other uses M-PSK communication system for modulation.

Background technology

In mobile communication system, transmit leg is modulated to carrier wave f to information _cThe recipient will accurately receive information this carrier wave of must regenerating, nominally though this carrier wave transmit leg and recipient are known in advance, exist frequency shift (FS) between transmit leg and the recipient because following two main causes in the transmission make: 1. travelling carriage local clock precision is not high; 2. location of mobile station moves the Doppler frequency shift that brings.

The existing frequency compensation method of TD-SCDMA system is: the data after the demodulation are modulated again, calculate the phase difference between the corresponding received signal, estimate thus and compensating for frequency offset.This method is wanted demodulation twice at receiving terminal, modulates once, and phase deviation estimates that once therefore compensation once realizes that complexity and amount of calculation are very big.

Therefore, there is defective in prior art, and awaits improving and development.

Summary of the invention

The method and apparatus that the purpose of this invention is to provide a kind of mobile communication system compensate of frequency deviation, estimate more efficiently and compensate frequency deviation between mobile communication system transmit leg and the recipient, improve receptivity, the inventive method and device both can be applied in system side and also can be applied in mobile station side.

Implementation of the present invention is:

A kind of device of mobile communication system compensate of frequency deviation, wherein, this device comprises compensate of frequency deviation device in early stage, frequency deviation and phase shift discriminator, phase shift compensation device and loop filter;

Described early stage, the compensate of frequency deviation device was used to from the frequency offset estimating of described loop filter current two-way modulation symbol be carried out the frequency pre compensation, outputed to simultaneously in described frequency deviation and phase shift discriminator and the described phase shift compensation device;

Described frequency deviation and phase shift discriminator utilize the two-dimension non linearity estimation technique to carry out frequency offset estimating and correction;

Described phase shift compensation device utilizes phase shift to estimate current modulation symbol is compensated, and its input modulation symbol is from compensate of frequency deviation device in described early stage, and its phase shift is estimated from described frequency deviation and phase shift discriminator.

Described device, wherein, described frequency deviation and phase shift discriminator comprise two-dimension non linearity transducer, phase shift estimator, delayer, divider and adder;

Described two-dimension non linearity transducer will be imported and do two-dimension non linearity conversion;

Described phase shift estimator will be handled from the result of described two-dimension non linearity transducer, obtains phase shift and estimates that this phase shift estimates to be sent to the positive sign input and the described phase shift compensation device of described adder;

Described delayer obtains symbol period of described phase shift estimated delay adjacent phase shift and estimates, then this result is sent to the negative sign input of described adder;

The phase difference of modulation symbol was delivered to described divider before and after described adder obtained;

Described divider is delivered to described loop filter by the frequency offset estimating that phase difference calculating obtains.

Described device, wherein, being treated to of described compensate of frequency deviation device in early stage: establishing current modulation symbol sequence is I _n+ iQ _n, N ₁≤ n≤N ₂Be distributed as N in time ₁T...N ₂T, T are mark space, and then the phase deviation of n symbol bringing of frequency deviation is 2 π n (Δ f ') T, and each modulation symbol be multiply by factor e ^{-j2 π n (Δ f) T}To play frequency compensation effect in early stage, obtain x after the compensation _n+ iy _n=(I _n+ iQ _n) * e ^{-j2 π n (Δ f) T}, N ₁≤ n≤N ₂

Described device, wherein, the input of described frequency deviation and phase shift discriminator is from compensate of frequency deviation device x in described early stage _n+ iy _n, its output phase shift is estimated described phase shift compensation device, the output frequency offset estimating is to described loop filter.

Described device, wherein, being treated to of described phase shift compensation device: establishing current modulation symbol sequence is x _n+ iy _n, N ₁≤ n≤N ₂Be distributed as N in time ₁T...N ₂T, T are mark space, then each modulation symbol are carried out phasing: $x_n^{\′}+i{y}_n^{\′}=(x_n+i{y}_n)*e^{-j{\widehat{\mathrm{\θ}}}_n},$ N ₁≤n≤N ₂。

Described device, wherein, described loop filter is an integrator.

Described device, wherein, described loop filter is an accumulator.

A kind of method of mobile communication system compensate of frequency deviation wherein, said method comprising the steps of:

One early stage the compensate of frequency deviation device be used to current two-way modulation symbol be carried out the frequency pre compensation from the frequency offset estimating of described loop filter, output to simultaneously in a frequency deviation and phase shift discriminator and the phase shift compensation device;

Described frequency deviation and phase shift discriminator utilize the two-dimension non linearity estimation technique to carry out frequency offset estimating and correction;

Described phase shift compensation device utilizes phase shift to estimate current modulation symbol is compensated, and its input modulation symbol is from compensate of frequency deviation device in described early stage, and its phase shift is estimated from described frequency deviation and phase shift discriminator.

Described method, wherein, described frequency deviation and phase shift discriminator are carried out following operation:

One two-dimension non linearity transducer will be imported and do two-dimension non linearity conversion;

One phase shift estimator will be handled from the result of described two-dimension non linearity transducer, obtains phase shift and estimates that this phase shift estimates to be sent to the positive sign input and the described phase shift compensation device of an adder;

One delayer obtains symbol period of described phase shift estimated delay adjacent phase shift and estimates, then this result is sent to the negative sign input of described adder;

The phase difference of modulation symbol was delivered to a divider before and after described adder obtained;

Described divider is delivered to a loop filter by the frequency offset estimating that phase difference calculating obtains.

The method and apparatus of a kind of mobile communication system compensate of frequency deviation provided by the present invention, by a kind of two-dimension non linearity estimation technique, the characteristic that makes full use of TD-SCDMA application M-PSK modulation is carried out frequency offset estimating and compensation, realizes simple, amount of calculation is little, and the precision height.

Description of drawings

Fig. 1 is the overall realization flow block diagram of frequency offset estimating of the present invention and compensation method;

Fig. 2 is the frequency deviation of the inventive method and the realization block diagram of phase shift discriminator.

Embodiment

Describe the present invention below in conjunction with accompanying drawing.

The method and apparatus of a kind of mobile communication system compensate of frequency deviation of the present invention, as shown in Figure 1, be the overall realization block diagram of frequency offset estimating and compensation, it comprises compensate of frequency deviation device 110, frequency deviation and phase shift discriminator 120, phase shift compensation device 130, loop filter 140 4 parts in earlier stage.

The frequency offset estimating Δ f ' that described early stage, compensate of frequency deviation device 110 was used to self loop filter 140 is to current I, and Q two-way modulation symbol carries out the frequency pre compensation, obtains x _n+ iy _n, output to simultaneously in frequency deviation and phase shift discriminator 120 and the phase shift compensation device 130.

Described early stage, compensate of frequency deviation device 110 specific implementations were: establishing current modulation symbol sequence is I _n+ iQ _n, N ₁≤ n≤N ₂Be distributed as N in time ₁T...N ₂T, T are mark space.Then the phase deviation of n symbol bringing of frequency deviation is 2 π n (Δ f ') T, and each symbol be multiply by factor e ^{-j2 π n (Δ f ') T}Just play frequency compensation effect in early stage, obtained x after the compensation _n+ iy _n=(I _n+ iQ _n) * e ^{-j2 π n (Δ f ') T}, N ₁≤ n≤N ₂

Described frequency deviation and phase shift discriminator 120 utilize a kind of two-dimension non linearity estimation technique to carry out frequency offset estimating and correction.Be illustrated in figure 2 as a specific implementation of described frequency deviation and phase shift discriminator 120.Being input as of it from compensate of frequency deviation device 110 x in described early stage _n+ iy _n, its output phase shift is estimated

To described phase shift compensation device 130, output frequency offset estimating Δ f is to described loop filter 140.

Described phase shift compensation device 130 utilizes the phase shift information estimated value that current modulation symbol is compensated, its input modulation symbol x _n+ iy _nFrom compensate of frequency deviation device 110 in described early stage, its phase shift is estimated

From described frequency deviation and phase shift discriminator 120.

The specific implementation of described phase shift compensation device 130 is: establishing current modulation symbol sequence is x _n+ iy _n, N ₁≤ n≤N ₂Be distributed as N in time ₁T...N ₂T, T are mark space, then each symbol are carried out phasing: $x_n^{\′}+i{y}_n^{\′}=(x_n+i{y}_n)*e^{-j{\widehat{\mathrm{\θ}}}_n},$ N ₁≤n≤N ₂。

Described loop filter 140 can realize also having possessed the removal High-frequency Interference simultaneously by an integrator or accumulator, the ability of level and smooth frequency offset estimating.

Be illustrated in figure 2 as the frequency deviation of the inventive method and device and the realization block diagram of phase shift discriminator, comprise two-dimension non linearity transducer 210, phase shift estimator 220, delayer 230, divider 240, adder 250 5 parts.

For the M-PSK modulation symbol, can be with polar coordinate representation:

$x_n+i{y}_n={\mathrm{\ρ}}_n{e}^{j{\mathrm{\φ}}_n}---\left(1\right)$

Here ${\mathrm{\ρ}}_n=\sqrt{x_n^2+y_n^2},$ φ _n=tan ^-1(y _n/ x _n), φ _nSpan is a predefined M value: 0,2 π/M ... (M-1) 2 π/M}.Come the symbol of processing formula (1) expression again with a Nonlinear Two-Dimensional function:

$x_n^{\′}+i{y}_n^{\′}=F\left({\mathrm{\ρ}}_n\right)e^{\mathrm{jM}{\mathrm{\φ}}_n}---\left(2\right)$

Two-dimension non linearity transducer 210 just will be imported x according to the principle of formula (2) among Fig. 2 _n+ iy _nMake a two-dimension non linearity and be converted to x ' _n+ iy ' _n, desirable in realization F (ρ _n)=ρ or F (ρ _n)=ρ ²

Phase shift estimator 220 among Fig. 2 will be handled from the result of two-dimension non linearity transducer 210 exactly, obtains ${\widehat{\mathrm{\θ}}}_n={\tan }^{-1}(x_n^{\′}/y_n^{\′})/M,$ This result has comprised and has disturbed on n the symbol and phase-shift information that frequency deviation is brought.Obviously because M-PSK modulates, if do not have interference and frequency deviation to have tan ^-1(x ' _n/ y ' _n)/M=0.Phase shift is estimated

To be sent to the positive sign input of adder 250 among Fig. 2, also will be sent to the phase shift compensation device 130 of Fig. 1 in addition.

The effect of described delayer 230 be with

Postpone a symbol period, obtain

Then the result is sent to the negative sign input of described adder 250.

The phase difference of modulation symbol before and after described adder 250 obtains: $\mathrm{\Δ}{\widehat{\mathrm{\θ}}}_n={\widehat{\mathrm{\θ}}}_n-{\widehat{\mathrm{\θ}}}_{n-1},$ Deliver to described divider 240.

If symbol period is T, whole estimation duration is a N symbol, and frequency deviation is Δ f, is reference point with first symbol, and so to n symbol, the relation of phase difference and frequency deviation just is:

$\mathrm{\Δ}{\widehat{\mathrm{\θ}}}_n=2\mathrm{\πn}\left(\mathrm{\Δf}\right)T,n=0,...N-1.---\left(3\right)$

The effect of described divider 240 is to calculate frequency deviation according to following formula by differing, and the frequency offset estimating Δ f that obtains will be sent to the described loop filter 140 among Fig. 1.

In theory with the method and equipment to the variance estimated of phase shift be:

$\mathrm{var}\left(\widehat{\mathrm{\θ}}\right)=1/(N*4*\mathrm{Eb}/N0)$ When Eb/N0＞0dB;

$\mathrm{var}\left(\widehat{\mathrm{\θ}}\right)\≤{(\mathrm{\π}/4)}^2/3$ When Eb/N0＜0dB.

N is an observation data length, if N=44, Eb/N0=0dB, the method and equipment estimate variance only are 1/156, therefore precision height on phase shift, frequency offset estimating.

Above-described method and apparatus is applicable to φ _nSpan is a predefined M value: 0,2 π/M ... (M-1) if 2 π/M} is φ _nThe form of value and above-mentioned different can be suitable for method and apparatus described in the invention equally, and just at two-dimension non linearity transducer 210,240 li of dividers change constant M into certain other value P, as long as make P* φ _n=k π, k are natural number.

More than for carry out frequency offset estimating and compensation method and device in the TD-SCDMA system, the method and device can not only be used in the TD-SCDMA system, can also be widely used in the mobile communication system of M-PSK modulation.The frequency deviation between transmit leg and the recipient can be estimated and compensate to the inventive method and device, improve receptivity, the precision height, and realize easily, only need make non-linear estimations one time at receiving terminal, a demodulation, twice compensation, do not need to modulate again, frequency compensated utilization in early stage makes the present invention higher than existing method precision.

Should be understood that above-mentioned explanation is only at concrete preferred embodiment of the present invention, therefore description is too detailed and concrete, but can not therefore become the restriction that the present invention asks for protection scope, and scope of patent protection of the present invention should be as the criterion with claims.

Claims (9)

1, a kind of device of mobile communication system compensate of frequency deviation is characterized in that, this device comprises compensate of frequency deviation device in early stage, frequency deviation and phase shift discriminator, phase shift compensation device and loop filter;

Described early stage, the compensate of frequency deviation device was used to from the frequency offset estimating of described loop filter current two-way modulation symbol be carried out the frequency pre compensation, outputed to simultaneously in described frequency deviation and phase shift discriminator and the described phase shift compensation device;

Described frequency deviation and phase shift discriminator utilize the two-dimension non linearity estimation technique to carry out frequency offset estimating and correction;

Described phase shift compensation device utilizes phase shift to estimate current modulation symbol is compensated, and its input modulation symbol is from compensate of frequency deviation device in described early stage, and its phase shift is estimated from described frequency deviation and phase shift discriminator.

2, device according to claim 1 is characterized in that, described frequency deviation and phase shift discriminator comprise two-dimension non linearity transducer, phase shift estimator, delayer, divider and adder;

Described two-dimension non linearity transducer will be imported and do two-dimension non linearity conversion;

Described phase shift estimator will be handled from the result of described two-dimension non linearity transducer, obtains phase shift and estimates that this phase shift estimates to be sent to the positive sign input and the described phase shift compensation device of described adder;

Described delayer obtains symbol period of described phase shift estimated delay adjacent phase shift and estimates, then this result is sent to the negative sign input of described adder;

The phase difference of modulation symbol was delivered to described divider before and after described adder obtained;

Described divider is delivered to institute and is reached loop filter by the frequency offset estimating that phase difference calculating obtains.

3, device according to claim 2 is characterized in that, being treated to of described compensate of frequency deviation device in early stage: establishing current modulation symbol sequence is I _n+ iQ _n, N ₁≤ n≤N ₂Be distributed as N in time ₁T...N ₂T, T are mark space, and then the phase deviation of n symbol bringing of frequency deviation is 2 π n (Δ f ') T, and each modulation symbol be multiply by factor e ^{-j2 π n (Δ f) T}To play frequency compensation effect in early stage, obtain x after the compensation _n+ iy _n=(I _n+ iQ _n) * e ^{-j2 π n (Δ f) T}, N ₁≤ n≤N ₂

4, device according to claim 3 is characterized in that, the input of described frequency deviation and phase shift discriminator is from compensate of frequency deviation device x in described early stage _n+ iy _n, its output phase shift is estimated described phase shift compensation device, the output frequency offset estimating is to described loop filter.

5, device according to claim 4 is characterized in that, being treated to of described phase shift compensation device: establishing current modulation symbol sequence is x _n+ iy _n, N ₁≤ n≤N ₂Be distributed as N in time ₁T...N ₂T, T are mark space, then each modulation symbol are carried out phasing: $x_n^{\′}+i{y}_n^{\′}=(x_n+i{y}_n)*e^{-j{\widehat{\mathrm{\θ}}}_n},$ N ₁≤n≤N ₂。

6, device according to claim 1 is characterized in that, described loop filter is an integrator.

7, device according to claim 1 is characterized in that, described loop filter is an accumulator.

8, a kind of method of mobile communication system compensate of frequency deviation is characterized in that, said method comprising the steps of:

One early stage the compensate of frequency deviation device be used to current two-way modulation symbol be carried out the frequency pre compensation from the frequency offset estimating of described loop filter, output to simultaneously in a frequency deviation and phase shift discriminator and the phase shift compensation device;

Described frequency deviation and phase shift discriminator utilize the two-dimension non linearity estimation technique to carry out frequency offset estimating and correction;

Described phase shift compensation device utilizes phase shift to estimate current modulation symbol is compensated, and its input modulation symbol is from compensate of frequency deviation device in described early stage, and its phase shift is estimated from described frequency deviation and phase shift discriminator.

9, method according to claim 8 is characterized in that, described frequency deviation and phase shift discriminator are carried out following operation:

One two-dimension non linearity transducer will be imported and do two-dimension non linearity conversion;

One phase shift estimator will be handled from the result of described two-dimension non linearity transducer, obtains phase shift and estimates that this phase shift estimates to be sent to the positive sign input and the described phase shift compensation device of an adder;

One delayer obtains symbol period of described phase shift estimated delay adjacent phase shift and estimates, then this result is sent to the negative sign input of described adder;

The phase difference of modulation symbol was delivered to a divider before and after described adder obtained;

Described divider is delivered to a loop filter by the frequency offset estimating that phase difference calculating obtains.