CN103905344A - Signal to noise ratio estimation method and synchronization loss determination method in discontinuous transmission mode - Google Patents

Abstract

The invention relates to a signal to noise ratio estimation method and a synchronization loss determination method in a discontinuous transmission mode. The signal to noise ratio estimation method comprises the following steps: a received signal of special burst is received at a receiving end; and the signal to noise ratio estimation is performed on the received signal. The special burst contains a pair of bit sequences known to the receiving end. The synchronization loss determination method is to further perform synchronization loss determination according to the signal to noise ratio estimation. According to the invention, the problem of inaccurate signal to noise ratio estimation at low signal to noise ratio can be overcome; synchronization loss determination process can be simplified; and accuracy of synchronization loss determination can be improved effectively.

Description

Signal-noise ratio estimation method under non-continuous sending mode and lock-out determination methods

Technical field

The present invention relates to the lock-out determination methods in a kind of mobile communication system, especially relate to the lock-out determination methods under non-continuous sending mode.

Background technology

In the transfer of data of mobile communication system and the process of link maintenance, conventionally subscriber equipment (UE, User Equipment) need to monitor the quality of DPCH (DPCH, Dedicated Physical Channel), for judging whether current time has lost signal in physical layer.Under normal circumstances, the decision gate limit value of definition DPCH quality level: Qout, Qin, Qsbout and Qsbin, be respectively used to judge whether step-out or synchronous of UE.Qout, Qin sends the judgement in conventional burst (NB, Normal Burst) situation for data transfer phase, and Qsbout, Qsbin sends the judgement in special burst (SB, SpecialBurst) situation for the link maintenance stage.

DPCH quality is used signal to noise ratio (SNR, Signal to Noise Ratio) to weigh conventionally.The computing formula of at present conventional SNR method of estimation is as follows:

$\mathrm{SNR}=\frac{{\left[\frac{1}{2N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\left(\right|\mathrm{Re}\left(y_i\right)|+|\mathrm{Im}\left(y_i\right)\left|\right)\right]}^2}{\frac{1}{2N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}[{\left(\right|\mathrm{Re}\left(y_i\right)|-\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}|\mathrm{Re}\left(y_i\right)\left|\right)}^2+{\left(\right|\mathrm{Im}\left(y_i\right)|-\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\mathrm{Im}\left(y_i\right))}^2]}---\left(1\right)$

Wherein, y _iit is the symbol obtaining after i equilibrium; N is symbol numbers; Re () represents to get real part operation, and Im () represents to get imaginary part operation.

The estimation technique of existing SNR is to carry out the in the situation that of current reception data the unknown, in the time that reception data noise is larger, there will be the point on planisphere to occur serious skew, causes SNR estimated value inaccurate.Meanwhile, SNR estimates, in the time of low signal-to-noise ratio, to there will be and survey high phenomenon by mistake, and, along with the reduction of SNR, SNR estimated value there will be an obvious platform (now, SNR estimated value is greater than actual SNR value).The quality of DPCH is estimated inaccurate, directly affects the judgement of lock-out.

At data transfer phase, owing to sending, data volume is larger, and transmission frequency is higher, can, by the SNR means such as on average, improve to a certain extent the accuracy that DPCH quality is estimated, alleviates because SNR estimates that the inaccurate lock-out causing judges inaccurate problem.

But, in the link maintenance stage, in order to save physical channel resources consumption and to reduce inter-user interference, can adopt one to be called the pattern of " discontinuous transmission (DTX, Discontinuous Transmission) ".Under this pattern, because only can periodically sending special burst (under normal circumstances, the cycle is 40ms, distributes a physical channel), transmitting terminal maintains link.Now, send data volume and transmission frequency and greatly reduce, in this case, cannot effectively utilize the SNR means such as on average, even SNR estimated value is revised etc. to means by channel estimating, also or cannot guarantee the accuracy of lock-out judgement.

Summary of the invention

The object of the invention is to propose a kind of improved signal-noise ratio estimation method, to improve the accuracy of the lower signal-to-noise ratio (SNR) estimation of DTX pattern.

The object of the invention is to propose a kind of improved lock-out determination methods, to solve the lock-out decision problem under DTX pattern.

The present invention proposes the signal-noise ratio estimation method under a kind of non-continuous sending mode, comprises the following steps: receive the reception signal of a special burst at receiving terminal, this special burst comprises one for the known bit sequence of this receiving terminal; And this reception signal is carried out to signal-to-noise ratio (SNR) estimation.

In one embodiment of this invention, should be for the predefined fixed bit sequence of the known bit sequence of this receiving terminal.

In one embodiment of this invention, this signal-to-noise ratio (SNR) estimation comprises maximal possibility estimation.

In one embodiment of this invention, this maximal possibility estimation comprises: the log-likelihood function that calculates this reception signal; Obtain the maximal possibility estimation of this special burst according to this log-likelihood function; And calculate signal-to-noise ratio (SNR) estimation value according to this maximal possibility estimation.

The present invention also proposes a kind of lock-out method under non-continuous sending mode, comprises the following steps: receive the reception signal of a special burst at receiving terminal, this special burst comprises one for the known bit sequence of this receiving terminal; This reception signal is carried out to signal-to-noise ratio (SNR) estimation; And carry out lock-out judgement according to this signal-to-noise ratio (SNR) estimation.

In one embodiment of this invention, should be for the predefined fixed bit sequence of the known bit sequence of this receiving terminal.

In one embodiment of this invention, this signal-to-noise ratio (SNR) estimation comprises maximal possibility estimation.

In one embodiment of this invention, this maximal possibility estimation comprises: the log-likelihood function that calculates this reception signal; Obtain the maximal possibility estimation of this special burst according to this log-likelihood function; And calculate signal-to-noise ratio (SNR) estimation value according to this maximal possibility estimation.

In one embodiment of this invention, the judgment criterion of this lock-out judgement comprises: in continuous Preset Time, the signal-to-noise ratio (SNR) estimation value of neither one special burst during higher than the first decision gate limit value Qsbout, is judged to desynchronizing state; In this continuous Preset Time, the signal-to-noise ratio (SNR) estimation value of all special bursts during all higher than the second decision gate limit value Qsbin, is judged to synchronous regime.

The present invention utilizes known transmission data under non-continuous sending mode, can overcome the inaccurate problem of signal-to-noise ratio (SNR) estimation under low signal-to-noise ratio.Further, the present invention can simplify the process of lock-out judgement, effectively improves the accuracy of lock-out judgement.

Accompanying drawing explanation

For above-mentioned purpose of the present invention, feature and advantage can be become apparent, below in conjunction with accompanying drawing, the specific embodiment of the present invention is elaborated, wherein:

Fig. 1 illustrates that the special burst in TD-SCDMA system sends form.

Fig. 2 illustrates the signal-noise ratio estimation method flow chart of one embodiment of the invention.

Fig. 3 illustrates the lock-out determination methods flow chart of one embodiment of the invention.

Embodiment

Summarily say, embodiments of the invention provide the lock-out determination methods under known transmission data cases in a kind of mobile communication system, utilize " known transmission data " this prior information, improve the accuracy that SNR estimates, thereby improve the accuracy of lock-out judgement under discontinuous transmission (DTX) pattern.

The following examples will be with TD-SCDMA(TD SDMA, TimeDivision-Synchronous Code Division Multiple Access) under DTX pattern, SNR estimates and the determination methods of lock-out is example in system, sets forth SNR method of estimation based on given data and lock-out determination methods accordingly.

Under DTX pattern, the transmission form of special burst (Special Burst) as shown in Figure 1.Mainly comprise data division, Midamble part, TFCI part and TPC/SS part.Wherein, transmitting terminal can comprise the sequence known to receiving terminal at data division.For example, transmitting terminal can comprise predefined fixed bit sequence at data division.Fixed bit sequence can be the bit sequence replacing as " 0 ", " 1 ".In addition, this predefined fixed bit sequence can also be to send, receive other known any fixed bit sequences of both sides.

Fig. 2 illustrates the signal-noise ratio estimation method flow chart of one embodiment of the invention.Shown in Fig. 2, the signal-noise ratio estimation method under the non-continuous sending mode of embodiment, comprises the following steps:

In step 201, receive the reception signal of a special burst at receiving terminal, this special burst comprises one for the known bit sequence of this receiving terminal.For example, this bit sequence can be above-mentioned predefined fixed bit sequence.Therefore receiving terminal will be known the content of data division of special burst in advance.

In step 202, carry out to received signal signal-to-noise ratio (SNR) estimation.

Here by exemplifying a kind of method of signal-to-noise ratio (SNR) estimation, be called maximal possibility estimation.It will be appreciated by persons skilled in the art that embodiments of the invention also can use other method of estimation, for example: the computational methods that formula (in 1) is conventional.

Suppose, through after receiver equalization, only to exist Gauss's white noise to disturb, the reception signal of output is:

y _i=a·x _i+n _i,i＝1,…,N （2）

In above formula (1), a is signal strength signal intensity, is a scalar; n _ibe the Equivalent Base-Band noise of i symbol, its average is 0, and variance is σ ²; x _ifor the QPSK symbol of transmitting terminal, it is known symbol.

First maximal possibility estimation calculates the log-likelihood function that receives signal, as follows:

It is two-dimentional receiving the probability density distribution of signal, and I, two branch roads of Q are separate.So the log-likelihood function of receiving sequence can be write:

$p(y_1,y_2,...y_N;a)$

$=\frac{1}{{\left(2\mathrm{\π}{\mathrm{\σ}}^2\right)}^{\frac{N}{2}}}\exp [-\frac{1}{2{\mathrm{\σ}}^2}\underset{i=1}{\overset{N-1}{\mathrm{\Σ}}}{(\mathrm{Re}\left(y_i\right)-a\·\mathrm{Re}\left(x_i\right))}^2]---\left(3\right)$

$\·\frac{1}{{\left(2\mathrm{\π}{\mathrm{\σ}}^2\right)}^{\frac{N}{2}}}\exp [-\frac{1}{2{\mathrm{\σ}}^2}\underset{i=1}{\overset{N-1}{\mathrm{\Σ}}}{(\mathrm{Im}\left(y_i\right)-a\·\mathrm{Im}\left(x_i\right))}^2]$

Then, obtain the maximal possibility estimation of this special burst according to this log-likelihood function.

Specifically, log-likelihood function is asked partial derivative to a, makes it equal zero.The maximal possibility estimation that obtains a is:

$a=\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(\mathrm{Re}\left(y_i\right)\·\mathrm{Re}\left(x_i\right)+\mathrm{Im}\left(y_i\right)\·\mathrm{Im}\left(x_i\right))---\left(4\right)$

Then, calculate signal-to-noise ratio (SNR) estimation value according to this maximal possibility estimation.

SNR estimated value is calculated as follows:

$\mathrm{SNR}=\frac{a^2}{\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{\left|y_i\right|}^2-a^2}$

$=\frac{{\left[\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(\mathrm{Re}\left(y_i\right)\·\mathrm{Re}\left(x_i\right)+\mathrm{Im}\left(y_i\right)\·\mathrm{Im}\left(x_i\right))\right]}^2}{\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{\left|y_i\right|}^2-{\left[\frac{1}{N}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}(\mathrm{Re}\left(y_i\right)\·\mathrm{Re}\left(x_i\right)+\mathrm{Im}\left(y_i\right)\·\mathrm{Im}\left(x_i\right))\right]}^2}---\left(5\right)$

This formula is exactly under known transmission data cases, the maximal possibility estimation of SNR.This estimation can effectively overcome the problem that platform appears in low signal-to-noise ratio SNR estimated value in prior art.

By above-mentioned improved SNR method of estimation, can obtain SNR measured value accurately, therefore do not need to adopt other means, as methods such as average or channel estimating corrections, improve the accuracy that SNR estimates.Can directly carry out lock-out judgement according to SNR estimated value.

Fig. 3 illustrates the lock-out determination methods flow chart of one embodiment of the invention.In Fig. 3, step 301-302 is identical with the step 201-202 in last flow process, does not repeat them here.On the basis that the lock-out determination methods of the present embodiment is estimated at SNR, perform step 303, estimate to carry out lock-out judgement according to SNR.

Exemplary judgment criterion is as follows:

Step-out judgement: in continuous Preset Time, the SNR estimated value of neither one special burst during higher than the first judgement thresholding Qsbout, is judged to desynchronizing state;

Synchronous judgement: in this continuous Preset Time, the SNR estimated value of all special bursts during all higher than the second judgement thresholding Qsbin, is judged to synchronous regime.

Above-mentioned Preset Time can be adjusted according to actual conditions, and an exemplary time is 160ms.

In the present embodiment, owing to carrying out lock-out judgement based on signal-to-noise ratio (SNR) estimation value comparatively accurately, thereby compare mode in the past, can improve the accuracy of lock-out judgement.

It should be noted that, although above-described embodiment estimate and lock-out judge as example using the SNR under the DTX pattern in TD-SCDMA system, the present invention is equally applicable to comprise the estimation of the SNR based on given data and lock-out under DTX pattern and judges.For example, the present invention is applicable under the DTX pattern of WCDMA system that the SNR based on given data estimates and lock-out judges.

Although the present invention describes with reference to current specific embodiment, but those of ordinary skill in the art will be appreciated that, above embodiment is only for the present invention is described, in the situation that not departing from spirit of the present invention, also can make variation or the replacement of various equivalences, therefore, as long as the variation to above-described embodiment, modification all will drop in the application's the scope of claims within the scope of connotation of the present invention.

Claims (9)

1. the signal-noise ratio estimation method under non-continuous sending mode, comprises the following steps:

Receive the reception signal of a special burst at receiving terminal, this special burst comprises one for the known bit sequence of this receiving terminal; And

This reception signal is carried out to signal-to-noise ratio (SNR) estimation.

2. the method for claim 1, is characterized in that, should be for the predefined fixed bit sequence of the known bit sequence of this receiving terminal.

3. the method for claim 1, is characterized in that, this signal-to-noise ratio (SNR) estimation comprises maximal possibility estimation.

4. method as claimed in claim 3, is characterized in that, this maximal possibility estimation comprises:

Calculate the log-likelihood function of this reception signal;

Obtain the maximal possibility estimation of this special burst according to this log-likelihood function; And

Calculate signal-to-noise ratio (SNR) estimation value according to this maximal possibility estimation.

5. the lock-out method under non-continuous sending mode, comprises the following steps:

Receive the reception signal of a special burst at receiving terminal, this special burst comprises one for the known bit sequence of this receiving terminal;

This reception signal is carried out to signal-to-noise ratio (SNR) estimation; And

Carry out lock-out judgement according to this signal-to-noise ratio (SNR) estimation.

6. method as claimed in claim 5, is characterized in that, should be for the predefined fixed bit sequence of the known bit sequence of this receiving terminal.

7. method as claimed in claim 5, is characterized in that, this signal-to-noise ratio (SNR) estimation comprises maximal possibility estimation.

8. method as claimed in claim 7, is characterized in that, this maximal possibility estimation comprises:

Calculate the log-likelihood function of this reception signal;

Obtain the maximal possibility estimation of this special burst according to this log-likelihood function; And

Calculate signal-to-noise ratio (SNR) estimation value according to this maximal possibility estimation.

9. method as claimed in claim 5, is characterized in that, the judgment criterion of this lock-out judgement comprises:

In continuous Preset Time, the signal-to-noise ratio (SNR) estimation value of neither one special burst during higher than the first decision gate limit value Qsbout, is judged to desynchronizing state;

In this continuous Preset Time, the signal-to-noise ratio (SNR) estimation value of all special bursts during all higher than the second decision gate limit value Qsbin, is judged to synchronous regime.

Images