CN101193435B - Method for acquiring pilot detection threshold of random access channel at physical layer - Google Patents

Abstract

The invention relates to a method for obtaining a front detection threshold of physical layer random accessing channel, comprising the following steps: (a) in a stage of setting a system, an actual measurement is carried out in the system to obtain different coherent integral length CA, incoherent integral length N< CA > and noise estimation coefficient C which corresponds to an antenna amount N<ant > and a look-up table is established; (b) when the system is operated, the coherent integral length CA, the incoherent integral length N< CA > and the antenna amount are set according to different cells; a Node B in a base station descrambles, relieves frequency offset, relieves signature and carries out relevant integration processing for inputted signals; the N biggest related amplitude values in related amplitude values of different time delay positions for each signature in the 16 signatures are recorded; (c) the least n amplitude values of the N related amplitude values for each signature are taken, the mean value of the total n is multiplied by 16 amplitude value is figured out. The look-up table is queried to obtain the noise estimation coefficient C, then the noise estimation value I< 0 > is figured out; (d) the front detection threshold is obtained by the noise estimation value I< 0 > and a front detection threshold of signal-to-noise ratio meaning.

Description

A kind of method for acquiring pilot detection threshold of random access channel at physical layer

Technical field

The present invention relates to code division multiple access (CDMA:Code-Division Multiple-Access) communication system, relate in particular to a kind of code division multiple access system random access guiding detection threshold preparation method.

Background technology

In Wideband Code Division Multiple Access (WCDMA) (WCDMA) mobile communication system, physical layer Random Access Channel (PRACH) is very important part of system.UE (User Equipment, subscriber equipment, the terminal equipment in the WCDMA system) needs to initiate random access procedure by PRACH when sub-district registration and the calling of registration back.

In random access procedure, UE the available signatures collection that obtains by broadcasting and available subchannels concentrate at random choose subchannel and signature, send the random access guiding of forming by the signature sequence of choosing in the subchannel time corresponding of choosing.In NodeB (base station) side, set a detection of preamble thresholding, write down the bigger multipath of each signature energy, if the energy of the maximum of certain signature multipath surpasses the detection of preamble thresholding, then thinking has UE to send leadingly signing with this, and this signature is sent confirmation, if UE receives the affirmation information that allows access in the leading back of transmission, to send random accessing message, confiscate confirmation else if, continue to send leading at the available subchannel of the next one raising power.As seen, in random access procedure, the calculating of detection of preamble thresholding and determine to influence a key point of access performance at random, if it is higher that the detection of preamble thresholding is set, can make access difficult, also make simultaneously the UE transmitting power that inserts at random bigger, other users have been introduced interference, lower if the detection of preamble thresholding is set, will detect more by noise produce leading, be that false-alarm is higher, leadingly will take demodulation resource in a large number like this by what noise produced because demodulation resource is limited, just might cause that UE puts forward leading do not have demodulation resource can with and be rejected, cause turn-on time long, even access failure.

In the common random access guiding detection method, at first the signal to input carries out descrambling, separate frequency deviation, separate signature and the correlation product processing that grades, obtain the correlation magnitude value of the different delay positions of each signature, relatively carry out the access lead judgement with wherein maximum range value and detection of preamble thresholding then.The detection of preamble thresholding is defined as the pilot power of reception and the ratio of noise, this is the parameter of system, just sets when system configuration, after configuring the detection of preamble thresholding of signal to noise ratio implication, can calculate the amplitude thresholding of the gross energy behind the corresponding integration, it is as follows to derive:

$P_{N\_\mathrm{CA}}=\left({10}^{\frac{I_0}{10}}\right)*\mathrm{CA}$

$P_{S\_\mathrm{CA}}=\left({10}^{\frac{T+{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">I</figure-callout>}}_0}{10}}\right)*{\mathrm{<figure-callout\; id="2"\; label="CA"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">CA</figure-callout>}}^2$

$T_{\mathrm{Amp}}=\sqrt{P_{S\_\mathrm{CA}}+P_{N\_\mathrm{CA}}}=\sqrt{\left({10}^{\frac{{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">I</figure-callout>}}_0}{10}}\right)*\mathrm{CA}*({10}^{\frac{\mathrm{<figure-callout\; id="10"\; label="T"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">T</figure-callout>}}{10}}*\mathrm{CA}+1)}$

Wherein: P _{S_CA}Be the energy behind the signal integration, P _{N_CA}Energy behind the noise integration, CA are coherent integration length, I ₀Be the energy (dB value) of chip noise, T is detection of preamble thresholding (a dB value), T _AmpIt is the gross energy amplitude thresholding behind the integration.Therefore, the amplitude thresholding of gross energy after after obtaining real-time noise estimation value, just can obtaining corresponding integration, be detection of preamble amplitude thresholding, if but the noise estimation value inaccuracy will cause the detection of preamble thresholding that obtains inaccurate and influence access performance at random.

Summary of the invention

The technical problem to be solved in the present invention is not accurate enough or do not have under the situation of real-time noise estimation module at real-time noise energy estimated value, and a kind of method that obtains the random access guiding detection threshold by the approximate evaluation noise is provided.

The present invention proposes a kind of method for acquiring pilot detection threshold of random access channel at physical layer, comprises following steps:

(a) in system be set the stage, set different coherent integration length CA, non-coherent integration length N according to the different districts needs _CAWith antenna number N _Ant, in system, surveying, the Noise Estimation coefficient C of correspondence set up look-up table when statistics obtained different parameters and is provided with;

When (b) system moves, set coherent integration length CA, non-coherent integration length N according to different districts _CAAnd antenna number, base station node B is carried out descrambling to the signal of input, separates frequency deviation, separates signature and correlation intergal and handles, and it is individual to write down N maximum in the correlation magnitude value of the different delay positions of each signature in 16 signatures;

(c) get n minimum in this N the correlation magnitude value of each signature range value, n * 16 range values are asked on average altogether, according to the CA of (b) middle setting, N _CAWith antenna number inquiry look-up table, obtain Noise Estimation coefficient C, calculate noise estimation value I then ₀

(d) by noise estimation value I ₀Obtain the detection of preamble thresholding with signal to noise ratio implication detection of preamble thresholding.

Described N value is 16 or 24.

Described n value is not more than 4.

Described Noise Estimation coefficient C can be obtained by following formula:

$C=\frac{{{\mathrm{<figure-callout\; id="2"\; label="N\; ant"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_{\mathrm{ant}}}^2*{{\mathrm{<figure-callout\; id="2"\; label="N\; CA"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_{\mathrm{CA}}}^2*\mathrm{CA}*{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">I</figure-callout>}}_0^{\&prime;}}{{\mathrm{<figure-callout\; id="2"\; label="Amp"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">Amp</figure-callout>}}^2}$

Wherein, N _CABe non-coherent integration length, CA is a coherent integration length, I ' ₀Be the energy value of the chip noise of actual measurement, N _AntBe antenna number, Amp is the mean value of minimum 2 range values of each signature of 16 signatures.

The detection of preamble thresholding is detection of preamble amplitude thresholding T in the described step (d) _Amp,

Wherein, T is the detection of preamble thresholding.

The detection of preamble thresholding is detection of preamble energy threshold T in the described step (d) _P, Wherein, T is the detection of preamble thresholding.

The present invention is by setting up coherent integration length CA, non-coherent integration length N _CALook-up table with these three parameters of antenna number and Noise Estimation coefficient C, write down the correlation magnitude value of the different delay positions of each signature in 16 signatures, be reduced to N value of record amplitude maximum, it is average to get a wherein minimum n range value, obtain Noise Estimation coefficient, dynamic estimation noise I thus by look-up table again ₀Thereby, calculate the detection of preamble thresholding.By example as can be known, above-mentioned dynamic noise method of estimation of the present invention can accurately estimating noise, therefore can obtain detection of preamble thresholding accurately.

Description of drawings

Fig. 1 is the probability distribution graph that system surveys noise and dynamic estimation noise in the present invention's one example;

Fig. 2 is a random access guiding detection threshold computational methods flow chart of the present invention.

Embodiment

The present invention has mainly proposed pilot detection threshold of random access channel at physical layer computational methods in a kind of WCDMA system, under the situation that can not get accurate real-time noise estimated value, utilize the dynamic noise method of estimation among the present invention, can obtain comparatively accurate detection of preamble amplitude or energy threshold.

In random access guiding detects, at first the signal to input carries out descrambling, separate frequency deviation, separate signature and the correlation product processing that grades, obtain the correlation magnitude value of the different delay positions of each signature in 16 signatures, wherein therefore n minimum correlation magnitude value of each signature can utilize each minimum n range value of signing to be averaged dynamic estimation noise I near the average level of noise ₀Simultaneously according to inserting the Multipath searching needs at random and realizing simplifying and only to write down maximum in each signature multipath correlation magnitude value N (N=16 or 24 etc., the resource of the big more consumption of value is many more, certain N gets other values and also is fine, just realize complicated, consumption of natural resource can be many), get wherein each minimum n (n=2 or 4 that sign, all can between the 1-4, certainly n is greater than 4, also be fine such as getting 5, just realize complicatedly, consumption of natural resource can be many) mean value of range value carries out the dynamic noise estimation.

Before the estimating noise, need set up a Noise Estimation coefficient table, this coefficient can survey in system or obtain by Theoretical Calculation in advance, and carries out and search use when look-up table moves the dynamic estimation noise for system.During actual measurement, in system, set corresponding coherent integration length CA and non-coherent integration length N _CA, can obtain corresponding Noise Estimation coefficient C by following formula:

$C=\frac{{{\mathrm{<figure-callout\; id="2"\; label="N\; ant"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_{\mathrm{ant}}}^2*{{\mathrm{<figure-callout\; id="2"\; label="N\; CA"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_{\mathrm{CA}}}^2*\mathrm{CA}*{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">I</figure-callout>}}_0^{\&prime;}}{\mathrm{Am}{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">p</figure-callout>}}^2}$

Wherein, N _CABe non-coherent integration length, CA is a coherent integration length, I ' ₀Be the energy value of the chip noise of actual measurement, N _AntBe antenna number, Amp is the mean value of minimum two range values of each signature.Parameter in the formula: C, N _CA, N _Ant, CA, I ' ₀, Amp, wherein N _CA, N _Ant, these three parameters of CA are got different value when system operation different situations, but all are that we know in advance and configure, and we just can obtain I ' by actual measurement before system's operation ₀And Amp, thereby obtain N by statistics _CA, N _Ant, the relation of these three parameters of CA and C when moving in system like this, has known that 2 minimum range values of each signature are Amp, can be according to the runtime parameter N of system _CA, N _Ant, CA and corresponding C obtain I ₀, obtain real-time I ₀After, just can utilize

This formula obtains detection of preamble amplitude thresholding or detection of preamble energy threshold, is used for the access lead judgement.

Fig. 1 is in the specific embodiment of this method, the probability distribution graph of the noise of the noise of system's actual measurement and employing the inventive method dynamic estimation.As seen from the figure, above-mentioned dynamic noise method of estimation can accurately estimating noise.

Fig. 2 is a random access guiding detection threshold computational methods flow chart of the present invention, here suppose N=16, n=2, promptly only write down in 16 signatures 16 maximum in each signature multipath correlation magnitude value, utilize 2 wherein minimum range values to carry out Noise Estimation, as follows in conjunction with Fig. 2 concrete implementation step of the present invention:

Step 210: in system be set the stage, set different coherent integration length CA, non-coherent integration length N according to different sub-district needs _CAAnd antenna number, in system, surveying, the Noise Estimation coefficient C of correspondence set up look-up table when statistics obtained different parameters and is provided with;

What determine in the look-up table is exactly coherent integration length CA, non-coherent integration length N _CAWith the relation of these three parameters of antenna number and coefficient C, can pass through coherent integration length CA, non-coherent integration length N easily with look-up table _CA, these three parameter references of antenna number are to coefficient C, also can with other other expression methods without look-up table.

Step 220: the detection of preamble thresholding that sets the signal to noise ratio implication according to the sub-district difference, correlation intergal length, irrelevant integration lengths and antenna number, NodeB carries out descrambling to the signal of input, separate frequency deviation, separate signature and correlation product processings that grade, to 16 signatures, the N=16 that writes down maximum in each signature multipath correlation magnitude value is individual;

Step 230: get in each above-mentioned N=16 correlation magnitude value of signing n=2 minimum range value totally 32 range values ask average, obtain an amplitude equalizing value of representing noise, then according to the correlation intergal length that is provided with in the step 220, irrelevant integration lengths and antenna number are tabled look-up and are obtained Noise Estimation coefficient C, just can be calculated the noise I of estimation by following formula ₀

${\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">I</figure-callout>}}_0=\frac{C\&times;{\mathrm{Amp}}^2}{{{\mathrm{<figure-callout\; id="2"\; label="N\; ant"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_{\mathrm{ant}}}^2*{{\mathrm{<figure-callout\; id="2"\; label="N\; CA"\; filenames="H061G0732220061205E000011.png"\; state="\{\{state\}\}">N</figure-callout>}}_{\mathrm{CA}}}^2*\mathrm{CA}}$

The value that obtains Amp and C does not have strict front and back order, and also can just table look-up in step 220 obtains Noise Estimation coefficient C value, but generally is to calculate Amp earlier to table look-up and obtain C during system's realization, carries out subsequent calculations again.

Step 240: by the noise I of signal to noise ratio implication detection of preamble thresholding and dynamic estimation ₀Just can obtain detection of preamble amplitude thresholding, carry out follow-up detection of preamble and handled.

Describe specific implementation process of the present invention above in conjunction with the embodiments in detail, the technical staff in same field can be easy to realize the present invention according to describing, simultaneously without departing from the spirit and substance in the present invention, by change relevant parameters maybe the amplitude thresholding that calculates is changed into energy threshold (amplitude square be energy, promptly

) etc., can make the present invention that many distortion are arranged, protection scope of the present invention is limited to the appended claims.

Claims (5)

1. method for acquiring pilot detection threshold of random access channel at physical layer comprises following steps:

(a) in system be set the stage, set different coherent integration length CA, non-coherent integration length N according to the different districts needs _CAWith antenna number N _Ant, in system, surveying, the Noise Estimation coefficient C of correspondence set up look-up table when statistics obtained different parameters and is provided with;

When (b) system moves, set coherent integration length CA, non-coherent integration length N according to different districts _CAAnd antenna number, base station node B is carried out descrambling to the signal of input, separates frequency deviation, separates signature and correlation intergal and handles, and it is individual to write down N maximum in the correlation magnitude value of the different delay positions of each signature in 16 signatures;

(c) get n minimum in this N the correlation magnitude value of each signature range value, n * 16 range values are asked on average altogether, according to the CA of (b) middle setting, N _CAWith antenna number inquiry look-up table, obtain Noise Estimation coefficient C, calculate noise estimation value I then ₀, described Noise Estimation coefficient C can be obtained by following formula:

$C=\frac{{N_{\mathrm{ant}}}^2*{N_{\mathrm{CA}}}^2*\mathrm{CA}*I_0^{\text{'}}}{{\mathrm{Amp}}^2}$

Wherein, N _CABe non-coherent integration length, CA is a coherent integration length, I ' ₀Be the energy value of the chip noise of actual measurement, N _AntBe antenna number, Amp is the mean value of minimum 2 range values of each signature of 16 signatures;

(d) by noise estimation value I ₀Obtain the detection of preamble thresholding with signal to noise ratio implication detection of preamble thresholding.

2. the method for claim 1, it is characterized in that: described N value is 16 or 24.

3. the method for claim 1, it is characterized in that: described n value is not more than 4.

4. the method for claim 1 is characterized in that: the detection of preamble thresholding is detection of preamble amplitude thresholding TAmp in the described step (d), Wherein, T is the detection of preamble thresholding.

5. the method for claim 1 is characterized in that: the detection of preamble thresholding is detection of preamble energy threshold TP in the described step (d),

Wherein, T is the detection of preamble thresholding.

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