CN1449204A - Signal-to-noise ratio measuring method based on array antennas mobile communication system - Google Patents

Abstract

46. A measurement method of signal/noise ratio based on an array antenna mobile communication system: customer initial transmitted power, and get the customer initial transmitted power; control and valuate results by the fed-back power, and adjust the customer transmitted power, get the customer transmitted power of the frame; the transmitted power of the frame passing a radio transmission channel, antennas in a base station receive the customer signals, and convert them into baseband digital signals; estimate the customer channel, get the estimated values after the customer experiences the channel impulse response; based on the estimated values of the customer channel impulse response in each array element, estimate the covariance matrix; decompose eigenvalues, get the eigenvalues and eigenvectors of the customer, determine the average noise power and the signal power of the customer, measure the signal/noise ratio; compare the measured signal/noise ratio with the goal signal/noise ratio, get results about the controlled transmitted power, and feedback.

Description

A kind of signal-to-noise ratio measuring method based on array antennas mobile communication system

One, technical field

The present invention relates to a kind of signal-to-noise ratio measuring method based on array antennas mobile communication system.

Two, background technology

In mobile communication CDMA (code division multiple access) system,, therefore in system, must carry out snr measurement because power control needs the signal to noise ratio parameter with switching.

In mobile communication system, in order to reduce to disturb and the influence of noise better, increase additional gain to user performance, adopt array antenna system usually.As shown in Figure 1, general array antenna system comprises: array antenna battle array 1O1, radiofrequency signal processing module 102, and baseband signal processing module 103.Wherein, array antenna battle array 101 is made up of many 001 antenna element, and the array antenna shape of employing has two kinds, promptly is applicable to the circle and the linear battle array that is suitable for sector cell of omni cell; Radiofrequency signal processing module 102 is from array antenna battle array 101 received RF signals, carries out on power amplifier, ADC/DAC (modulus/digital-to-analogue) conversion, the numeral down-conversion etc., obtains baseband digital signal; Baseband signal processing module 103 is mainly realized digital signal processing algorithm, as processes such as physical layer encoding and decoding, parameter measurements, finishes the measurement of signal to noise ratio.

In the mobile communication cdma system, because the nonorthogonality of pseudo noise code makes that the performance of cdma system is closely related with interference.Based on this consideration, obtain more performance (power system capacity, communication quality etc.) in order to make system, cdma system needs accurate power controls, so that overcome problems such as near-far interference, shadow effect and multipath fading effectively.For realizing accurate power control, generally adopt exterior ring power control and inner loop power control way of combining, wherein inner loop power control shows as closed-loop structure.Base stations in mobile communication system is the signal to noise ratio of period measurement up link with frame (or subframe, time slot), if measured value greater than threshold value (being provided by exterior ring power control), then produces corresponding power control command and reduces transmitting power by down link notice travelling carriage; Otherwise the notice travelling carriage increases transmitting power.Equally, travelling carriage is the signal to noise ratio of period measurement down link with frame (or subframe, time slot), if measured value then produces corresponding power control command and reduces transmitting power by the up link informing base station greater than threshold value (being provided by exterior ring power control); Otherwise informing base station increases transmitting power.

And the effect of inner loop power control depends on the certainty of measurement of SNR (signal to noise ratio).

As shown in Figure 2, existing signal-to-noise ratio measuring method is: at first the signal that receives is carried out despreading, then the signal after the despreading is carried out snr measurement, carry out power control again and judge, and the output judged result, thus finish a snr measurement process.Because the signal to noise ratio snr measurement is to obtain afterwards in despreading (joint-detection/RAKE (Rake) reception), and both contained useful signal data in a certain subscriber signal that recovers after the despreading, there is decline to rise and fall again, this community user disturbs and Gaussian noise (adjacent area interference), and decline rises and falls and can bring bigger influence with disturbing the measurement to signal to noise ratio, cause the result who tests to produce very macrorelief, therefore, this method of measurement is a kind of inclined to one side estimation that has, the signal to noise ratio of measuring after the despreading is not linear with true signal to noise ratio, and along with the progressively abominable measurement result deviation of channel is bigger, power control is judged gone wrong, finally cause systematic function to descend.

Three, summary of the invention

The object of the present invention is to provide a kind of signal-to-noise ratio measuring method that is used for array antennas mobile communication system, this method has solved the inclined to one side estimation problem of having of traditional snr measurement, accurately measure the ratio of certain user's signal power with noise power, thereby carry out power control effectively, improve the performance of system.

A kind of signal-to-noise ratio measuring method provided by the present invention based on array antennas mobile communication system, it comprises the following steps: the first step, in a certain period, one user's Initial Trans of a certain sub-district obtains user's Initial Trans by the open Loop Power control in the array antennas mobile communication system; Second step, adjust above-mentioned user emission power according to the power control judged result that the 8th step feeds back to, obtain the user emission power of this frame; In the 3rd step, this frame transmitting power is received subscriber signal through radio propagation channel by the antenna for base station termination, and radiofrequency signal is converted into baseband digital signal; The 4th step, carry out subscriber channel according to baseband digital signal and estimate, obtain the estimated value that this user experiences channel impulse response; The 5th step, carry out its covariance matrix according to the estimated value of the subscriber channel impulse response on each array element, obtain this user's covariance matrix; The 6th step, carry out characteristic value decomposition by user's covariance matrix, obtain this user's eigen vector; The 7th step, determine multipath source number according to this user's characteristic value, and determine average noise power according to the characteristic value of all users in this sub-district and multipath source number separately, and this user's signal power, measure signal to noise ratio; In the 8th step,, obtain transmitting power control judged result, and feed back to second step according to the signal to noise ratio of measuring and the comparison of target signal to noise ratio.

In the above-mentioned signal-to-noise ratio measuring method based on array antennas mobile communication system, the radio propagation channel in the third step is the space-time radio propagation channel.

Adopt above-mentioned technical scheme, because only comprising decline, the signal after the subscriber channel impulse response is estimated rises and falls and Gaussian noise, and the decline fluctuating embodies the characteristic of the channel of user's process, it can take it is useful signal as, therefore the present invention's (before despreading) after channel estimating carries out the measurement of signal to noise ratio, can overcome the decline fluctuating influence in the existing signal-to-noise ratio measuring method, and the training sequence that receives by up link or the frequency pilot sign signal power and the average noise power that estimate certain user, thereby acquisition snr value, the signal-to-noise ratio (SNR) estimation error of avoiding declining and rising and falling and bring, carry out power control effectively, improve the performance of system.

Four, description of drawings

Fig. 1 is the structured flowchart of array antenna system,

Fig. 2 is the flow chart of traditional signal-to-noise ratio measuring method.

Fig. 3 is a signal to noise ratio snr method of measurement flow chart of the present invention.

Five, embodiment

Referring to Fig. 3, the present invention, promptly a kind of signal-to-noise ratio measuring method based on array antennas mobile communication system comprises the following steps:

Step 301: in a certain period, user's Initial Trans of a certain sub-district obtains user's Initial Trans by the open Loop Power control in the array antennas mobile communication system.The user should compensate path loss with open Loop Power control at set intervals, with closed power control meticulous compensation is carried out in decline again.

Step 302: the power control command word TPC that feeds back to according to step 309 generates TPC_cmd, thereby this user's transmitting power is adjusted into P _i=P _I-1+ Δ _Adjusted, Δ wherein _Adjusted=Δ _TPC* TPC_cmd, P _i, P _I-1Be respectively the transmitting power of i frame (or subframe, time slot) and i-1 frame, Δ _TPCAdjust step-length for power, determine by system.

The TPC_cmd create-rule is as follows:

if?TPC＝0?TPC_cmd＝-1；

else?TPC_cmd＝1.

Step 303: this frame transmitting power P _iThrough the space-time radio propagation channel, receive subscriber signal in the antenna for base station termination, and radiofrequency signal is converted into baseband digital signal.This propagation channel can be used h (t, τ _i, θ _i) expression.T express time wherein, τ _iRepresent the time delay of i footpath, θ with respect to the 0th footpath _iRepresent the angle of arrival of i footpath with respect to the antenna normal direction.

Step 304: according to the baseband digital signal that base station transceiver receives, carry out subscriber channel and estimate, finish and estimate that this user experiences the channel impulse response function.

This step is the cycle impulse response that all users in this time period experience channel to be estimated that the reference signal of use is training sequence or frequency pilot sign with frame (or subframe, time slot).Estimate all users' channel impulse response (h on each bay _i=[h _{I, l}..., h _{I, k}..., h _{I, K}], wherein, i=1 ..., KA represents array element, k=1 ..., K represents the user, h _{I, k}=[h _{I, k, l}..., h _{I, k, W}] umber of beats of W sample of expression-soon), and arrange in proper order with the front and back of code channel.

Step 305: the channel impulse response (H that utilizes the user k on the different array elements _k={ h _{I, k, j}, i=1 ..., KA, j=1 ..., W), carry out its covariance matrix, form covariance matrix $(R_{\mathrm{hh},k}=\frac{1}{W}{H}_k\·H_k^H)$ 。

Step 306: according to this user's covariance matrix $R_{\mathrm{hh},k}=\frac{1}{W}{H}_k\·H_k^H$ Carry out characteristic value decomposition, because R _{Hh, k}Be the special matrix (R of multiple ell rice _{Hh, k}=A+jB, A and B are respectively the real part and the imaginary parts of this complex matrix), real symmetric matrix then Characteristic value be R _{Hh, k}Characteristic value each all repeat once.The characteristic value of real symmetric matrix and characteristic vector are found the solution with Jacobi (Jacobi) decomposition method, reject duplicate keys, can obtain matrix R _{Hh, k}KA characteristic value With characteristic of correspondence vector respectively ( s ₁..., s _KA).

Step 307: calculate other user's characteristic value decomposition process, its principle is equal to step 306, obtains the characteristic value of all users in this sub-district.

Step 308: characteristic value is arranged in order by descending order $({\widehat{\mathrm{\σ}}}_1^{\′}\≥{\widehat{\mathrm{\σ}}}_2^{\′}\≥...\≥{\widehat{\mathrm{\σ}}}_{\mathrm{KA}}^{\′})$ , determine the multipath source of user k experience channel with method of information theory (AIC or MDL criterion) and count P $({\widehat{\mathrm{\σ}}}_1^{\′},...,{\widehat{\mathrm{\σ}}}_P^{\′},{\widehat{\mathrm{\σ}}}_{P+1}^{\′},...,{\widehat{\mathrm{\σ}}}_{\mathrm{KA}}^{\′})$ 。Can obtain this user's signal power and average noise power thus, (this average noise power is adjacent area interference can to obtain the overall average noise power by each user's characteristic value and the multipath source number that experiences channel separately, each user's noise can be on average), unite the snr value of determining each user with this subscriber signal power.

The average noise power of user k is expressed as: ${\mathrm{var}}_k=\mathrm{mean}({\widehat{\mathrm{\σ}}}_{P+1}^{\′},...,{\widehat{\mathrm{\σ}}}_{\mathrm{KA}}^{\′})$

Overall average noise power: var=mean (var ₁..., var _K)

The signal power of user k can be expressed as: $P_{s,k}=\mathrm{sum}({\widehat{\mathrm{\σ}}}_1^{\′},...,{\widehat{\mathrm{\σ}}}_P^{\′})-P\·\mathrm{var}$

The SNR measured value of user k: SNR _k=P _{S, k}/ var

The user k signal to noise ratio snr of Que Dinging above _kBe the signal to noise ratio after handling through some, this value deducts the signal to noise ratio that a processing gain value can obtain the antenna for base station connector end.This processing gain can obtain by statistical method.

Step 309: measurement signal to noise ratio and target signal to noise ratio according to the antenna for base station connector end compare, and obtain the emissive power control command word, and feed back to step 302.

Emissive power control command word generative process is as follows:

if?SNR _measured＞SNR _target?TPC＝0；

else?TPC＝1.

Claims (2)

1 one kinds of signal-to-noise ratio measuring methods based on array antennas mobile communication system, it comprises the following steps:

The first step, in a certain period, user's Initial Trans of a certain sub-district obtains user's Initial Trans by the open Loop Power control in the array antennas mobile communication system;

Second step, adjust above-mentioned user emission power according to the power control judged result that the 8th step feeds back to, obtain the user emission power of this frame;

In the 3rd step, this frame transmitting power is received subscriber signal through radio propagation channel by the antenna for base station termination, and radiofrequency signal is converted into baseband digital signal;

The 4th step, carry out subscriber channel according to baseband digital signal and estimate, obtain the estimated value that this user experiences channel impulse response;

The 5th step, carry out its covariance matrix according to the estimated value of the subscriber channel impulse response on each array element, obtain this user's covariance matrix;

The 6th step, carry out characteristic value decomposition by user's covariance matrix, obtain this user's eigen vector;

The 7th step, determine multipath source number according to this user's characteristic value, and determine average noise power with multipath source number separately according to the feature of all users in this sub-district is straight, and this user's signal power, measure signal to noise ratio;

In the 8th step,, obtain transmitting power control judged result, and feed back to second step according to the signal to noise ratio of measuring and the comparison of target signal to noise ratio.

2 a kind of signal-to-noise ratio measuring methods based on array antennas mobile communication system according to claim 1 is characterized in that the radio propagation channel in the described third step is the space-time radio propagation channel.

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