CN103079227B - Random access detection method and system used in LTE (Long Term Evolution) system - Google Patents

Abstract

The invention discloses a random access detection method and system used in an LTE (Long Term Evolution) system, which are particularly suitable for detection of random access of a high-speed mobile environment under the large-range coverage of a cell. A frequency offset value is estimated by using relevancy of a ZC (Zadoff-Chu) sequence, and an uplink synchronization lead is estimated according to the estimated frequency offset value and a size and position relation of two peak values obtained by peak value detection. According to the invention, random access of high-speed mobile UE (User Equipment) can be supported in the cell of the large-range coverage, and a Preamble index and the uplink synchronization lead which are sent by the UE are accurately detected. Under general conditions, a high-speed moving environment can support the maximum radius of 33km of the cell. The random access detection method and system are capable of supporting the maximum radius of 103km of the cell.

Description

A kind of random access detecting method for LTE system and system

Technical field

The present invention relates to wireless communication field, more specifically, the present invention be directed to the random access detecting method in third generation mobile communication long-term evolution system (hereinafter referred to as 3G LTE) and system.

Background technology

At LTE(Long Term Evolution, Long Term Evolution) in system, radio access technology is an important technology of subscriber equipment (User Equipment, UE) access control, is that subscriber equipment is used for carrying out up Timing Synchronization.

In LTE system, subscriber equipment passes through at Physical Random Access Channel (Physical Random Access Channel, PRACH) Random Access Channel (Random Access Channel is sent on, RACH), Zadoff-Chu(ZC is adopted in RACH channel) cyclic shift of sequence is as targeting sequencing (Preamble), the information such as the uplink synchronous lead detected are sent to UE after detecting the Preamble in UE transmission RACH channel by base station (eNodeB), UE completes uplink synchronous by the uplink synchronous lead received, uplink synchronous lead is because the round trip transmission delay of UE transmission wireless signal causes.Relate to eNodeB in this process and detect the process that UE sends Preamble, in LTE system, RACH channel adopts the cyclic shift of ZC sequence as Preamble sequence, because ZC sequence to have on the circulation auto-correlation point of sequence except having peak value in starting point, other aspects are all the features of null value, therefore generally adopt in receiving terminal base station the method frequency domain is relevant to realize detecting Preamble on RACH channel.Have in each community in LTE system 64 available leading.The root ZC sequence that first 64 targeting sequencing set in a community are RACH_ROOT_SEQUENCE by logic index produces all cyclically shifted sequences according to the order that cyclic shift increases, if 64 targeting sequencings can not be produced by 1 root ZC sequence, so produced until create 64 targeting sequencings by the root sequence of follow-up logic index.Only need to detect every bar root sequence to receiving terminal, just can obtain the Detection Information of the cyclic shift of all uses under this root sequence.The cyclic shift that ZC sequence is different will detect in different detection window.

Under the scene of high-speed mobile, Doppler frequency shift can corresponding increase, needs ZC sequence to have the ability of enough antagonism frequency deviations.The expression formula x of known ZC sequence _u(n) be:

$x_u\left(n\right)=e^{-j\frac{\mathrm{\πun}(n+1)}{N_{\mathrm{ZC}}}},$ 0≤n≤N _ZC-1 (1)

Wherein u represents physics root sequence, N _zCrepresent the length of ZC sequence, in 3GPP agreement, specify N _zCbe 839, x _un () represents n-th of ZC sequence corresponding value.

D _uthe corresponding ZC sequence cyclic shift that (3GPP agreement specifies that the upper unit subcarrier spacing of PRACH is 1250Hz) produces when Doppler frequency shift is a unit year interval, so at cyclic shift integer d _uafterwards, obtain:

$x(n+d_u)=\exp (-j\·\frac{\mathrm{\π}\·u\·(n+d_u)(n+d_u+1)}{N_{\mathrm{ZC}}})$

$=\exp (-j\·\frac{\mathrm{\π}\·u\·n\·(n+1)}{N_{\mathrm{ZC}}})\·\exp (-j\·\frac{\mathrm{\π}\·u\·d_u\·(d_u+1)}{N_{\mathrm{ZC}}})\·\exp (-j\·\frac{2\·\mathrm{\π}\·\·d_u\·n}{N_{\mathrm{ZC}}})---\left(2\right)$

$=C_{\mathrm{phase}}\·x_u\left(n\right)\·\exp (-j\·\frac{2\·\mathrm{\π}\·u\·d_u\·n}{N_{\mathrm{ZC}}})$

Wherein, x _un () represents ZC sequence, $C_{\mathrm{phase}}=\exp (-j\·\frac{\mathrm{\π}\·u\·d_u\·(d_u+1)}{N_{\mathrm{ZC}}})$ It is a phase rotating constant had nothing to do with n.

As can be seen here, the impact of frequency deviation on ZC sequence is equivalent to and adds d at transmitting terminal _ucyclic shift amount, and meet

d _u＝(N _zc·m-1)/u (3)

Wherein N _zCrepresent the length of ZC sequence, m makes d _ufor the minimum positive integer of integer.

After descending UE carries out frequency offset correction, the frequency deviation of up PRACH is generally no more than 1 subcarrier spacing, so the relevant peaks of receiving terminal is a sequence without frequency deviation and has the sequence of one times of subcarrier spacing frequency deviation to do the intermediateness after coherent detection, namely C _v(representing the position residing for main peak after the process of overpower time delay spectrum) original relevant peaks peak value in place can be leaked to C _v± d _uplace, forms pseudo-peak, and slowly increases along with frequency deviation, and main window peak energy shifts to both sides gradually.When the energy at pseudo-peak, both sides is greater than the energy in main window, pseudo-peak will be used as main peak and carry out estimating time bias by peak detection algorithm.In order to overcome the impact of serious frequency deviation under high velocity environment, LTE system defines the fast mode of a kind of PRACH, under PRACH fast mode, frequency bias properties for ZC sequence constructs the cyclic shift set being applicable to high speed detection, to limit in high speed detection Doppler frequency shift to the impact of ZC sequence, but PRACH fast mode is to sacrifice cell coverage area for cost.In LTE system, when PRACH is configured to low-speed mode, largest cell radius can support 103km, and when PRACH is configured to fast mode, largest cell radius can only support 33km.But in actual applications, as high ferro covers, requirement is that the area coverage of community is as far as possible large, thus can reduce the switching times of minizone.

Summary of the invention

In order to overcome the impact of cell coverage area area under fast mode, the present invention proposes a kind of Stochastic accessing detection technique scheme under high velocity environment.

Technical scheme of the present invention is a kind of random access detecting method for LTE system, comprises the following steps:

Step one, carries out frequency displacement by the RACH signal received, and is moved in the bandwidth centered by direct current subcarrier by the RACH signal that every root reception antenna receives, and obtains the RACH signal after frequency displacement;

Step 2, to the RACH signal after the frequency displacement of step one gained through down-sampled, is down to the sample frequency comprising RACH bandwidth by the sample rate of RACH signal, obtain down-sampled after data;

Step 3, the data after down-sampled to step 2 gained carry out DFT conversion, and use N point DFT to be transformed into frequency domain the data after down-sampled, obtain the data after DFT conversion, N is parameter preset;

Step 4, coherent detection is carried out to the data of step 3 gained after DFT conversion, comprising tables look-up by the logical root sequence by cell configuration obtains physics root sequence, the frequency domain sequence of local root sequence is generated according to physics root sequence, carry out related operation with the frequency domain sequence of local root sequence generated and the data of step 3 gained after DFT changes, obtain the result of related operation;

Step 5, carry out K point IDFT computing to the result of step 4 gained related operation, obtain the correlation of time domain, K is parameter preset; Step 6, processes through overpower time delay spectrum the correlation of step 5 gained time domain, calculates the power time delay spectrum of RACH signal; The process of described power time delay spectrum asks mould and square operation to the correlation of time domain;

Step 7, carries out peakvalue's checking to the power time delay of step 6 gained RACH signal spectrum, comprises the cyclic shift determining the Preamble sequence that UE uses, and detects 2 maximum peak values;

Step 8, carries out frequency deviation estimation, comprises the correlation according to step 5 gained time domain, the position of the peak-peak that step 7 detects is taken out to the correlation of the time domain on this position, and obtains phase place to the correlation of time domain on this position, estimates frequency deviation value f; Step 9, carries out time offset estimation, comprises and detects 2 maximum peak value acquired results according to the estimated frequency deviation value of step 8 and step 7, estimate RACH signal time inclined, obtain uplink synchronous lead.

And the peak value implementation that in step 7, detection 2 is maximum is as follows,

Peakvalue's checking thresholding according to composing the power time delay of step 6 gained RACH signal and preset detects, and finds out the maximum in power time delay spectrum and is designated as A;

If this maximum A does not exceed peakvalue's checking thresholding, then do not detect peak value;

If this maximum A exceedes peakvalue's checking thresholding, then detect the 1st peak value, be designated as peak value 1; In power time delay being composed after detecting the 1st peak value, the 1st peak value and each m, these peak value both sides value assignment are 0, and then find out the maximum in the spectrum of the power time delay after process and be designated as B, m is parameter preset;

If this maximum B ultrasonic crosses peakvalue's checking thresholding, be the 2nd peak value detected, be designated as peak value 2;

If this maximum B does not exceed peakvalue's checking thresholding, in the power time delay spectrum of step 6 gained RACH signal, 1 peak value can only be detected.

And, detect 2 maximum peak value acquired results according to the estimated frequency deviation value of step 8 and step 7 described in step 9, estimate RACH signal time inclined, obtain uplink synchronous lead, implementation is as follows,

First determine main peak, determine that mode is as follows,

When detecting 1 peak value, this peak value is main peak;

When detecting 2 peak values,

(1) when frequency deviation estimated value is positive frequency deviation, if being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak; If being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak;

(2) when frequency deviation estimated value is negative frequency deviation, if being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak; If being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak;

Then uplink synchronous lead is calculated according to the value n of main peak in x-axis

Wherein, d _urepresent the cyclic shift that ZC sequence produces when Doppler frequency shift is a unit year interval, N _zCrepresent the length of ZC sequence, N _prepresent the length of PRACH after IDFT process in time domain, T _srepresent basic time quantum.

The present invention is also corresponding provides a kind of Stochastic accessing detection system for LTE system, comprises with lower module,

Frequency displacement module, carries out frequency displacement for the RACH signal that will receive, and is moved in the bandwidth centered by direct current subcarrier by the RACH signal that every root reception antenna receives, and obtains the RACH signal after frequency displacement;

Down-sampled module, for by the RACH signal after the frequency displacement of frequency displacement module gained through down-sampled, the sample rate of RACH signal is down to the sample frequency comprising RACH bandwidth, obtain down-sampled after data;

DFT module, carries out DFT conversion for the data after down-sampled to down-sampled module gained, and use N point DFT to be transformed into frequency domain the data after down-sampled, obtain the data after DFT conversion, N is parameter preset;

Coherent detection module, for carrying out coherent detection to the data of DFT module gained after DFT conversion, comprising tables look-up by the logical root sequence by cell configuration obtains physics root sequence, the frequency domain sequence of local root sequence is generated according to physics root sequence, carry out related operation with the frequency domain sequence of local root sequence generated and the data of DFT module gained after DFT changes, obtain the result of related operation;

IDFT module, for carrying out K point IDFT computing to the result of coherent detection module gained related operation, obtain the correlation of time domain, K is parameter preset;

Power time delay spectrum computing module, for processing through overpower time delay spectrum the correlation of IDFT module gained time domain, calculates the power time delay spectrum of RACH signal; The process of described power time delay spectrum asks mould and square operation to the correlation of time domain;

Peak detection block, for carrying out peakvalue's checking to the power time delay spectrum of power time delay spectrum computing module gained RACH signal, comprises the cyclic shift determining the Preamble sequence that UE uses, and detects 2 maximum peak values;

Frequency deviation estimating modules, for carrying out frequency deviation estimation, comprising the correlation according to IDFT module gained time domain, the position of the peak-peak that peak detection block detects being taken out to the correlation of the time domain on this position, and phase place is obtained to the correlation of time domain on this position, estimate frequency deviation value f;

Time offset estimation module, for carrying out time offset estimation, comprising and estimating that estimated frequency deviation value and peak detection block detect 2 maximum peak value acquired results according to frequency deviation, estimate RACH signal time inclined, obtain uplink synchronous lead.

And it is as follows that peak detection block detects 2 maximum peak value implementations,

Peakvalue's checking thresholding according to composing the power time delay of power time delay spectrum computing module gained RACH signal and preset detects, and finds out the maximum in power time delay spectrum and is designated as A;

If this maximum A does not exceed peakvalue's checking thresholding, then do not detect peak value;

If this maximum A exceedes peakvalue's checking thresholding, then detect the 1st peak value, be designated as peak value 1; In power time delay being composed after detecting the 1st peak value, the 1st peak value and this peak value the right and left each m value assignment are 0, and then find out the maximum in the spectrum of the power time delay after process and be designated as B, m is parameter preset;

If this maximum B ultrasonic crosses peakvalue's checking thresholding, be the 2nd peak value detected, be designated as peak value 2;

If this maximum B does not exceed peakvalue's checking thresholding, in the power time delay spectrum of step 6 gained RACH signal, 1 peak value can only be detected.

And according to frequency deviation, time offset estimation module estimates that estimated frequency deviation value and peak detection block detect 2 maximum peak value acquired results, estimate RACH signal time inclined, the implementation obtaining uplink synchronous lead is as follows,

First determine main peak, determine that mode is as follows,

When detecting 1 peak value, this peak value is main peak;

When detecting 2 peak values,

(1) when frequency deviation estimated value is positive frequency deviation, if being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak; If being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak;

(2) when frequency deviation estimated value is negative frequency deviation, if being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak; If being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak;

Then uplink synchronous lead is calculated according to the value n of main peak in x-axis

Wherein, d _urepresent the cyclic shift that ZC sequence produces when Doppler frequency shift is a unit year interval, N _zCrepresent the length of ZC sequence, N _prepresent the length of PRACH after IDFT process in time domain, T _srepresent basic time quantum.

The present invention estimates the position of main peak according to the position relationship of the frequency deviation estimated and two peak-peaks, then according to the position of main peak obtain PRACH time inclined, i.e. uplink synchronous lead TA(Timing Adjustments).Because the present invention does not need the PRACH form using restriction set under high-speed mobile environment, the PRACH form under low-speed mode is used to improve area coverage, therefore the method scene of being applicable to high velocity environment and covering on a large scale, as the high ferro covering etc. covered on a large scale.The Stochastic accessing of high-speed mobile UE can be supported in the community that the present invention covers on a large scale, accurately detect the Preamble index that UE sends and uplink synchronous lead.Because Random Access Channel still adopts low-speed mode, therefore coverage radius of cell is maximum can support 103km.

Accompanying drawing explanation

The Stochastic accessing testing process schematic diagram that Fig. 1 provides for the embodiment of the present invention;

The time offset estimation schematic diagram that Fig. 2 provides for the embodiment of the present invention.

Embodiment

The Stochastic accessing that the Stochastic accessing detection technique scheme that the present invention proposes is mainly used in when community covers lower UE high-speed mobile on a large scale detects, in order to support that radius of society covers on a large scale (as supported 103km) and high velocity environment, needing to arrange PRACH channel is fast mode, suppose to adopt PRACH physical transport format 0, adopt physics root sequence u=384.Be described below in conjunction with embodiment and accompanying drawing.

As shown in Figure 1, embodiment is as follows in base station execution flow process:

Step one, carries out frequency displacement by the RACH signal received, and is moved in the bandwidth centered by direct current subcarrier by the RACH signal that every root reception antenna receives, and obtains the RACH signal after frequency displacement.

Now the sample frequency of RACH signal is still the sample frequency (sample frequency 30.72MHz as corresponding in 20MHz bandwidth) of system.

Step 2, to the RACH signal after the frequency displacement of step one gained through down-sampled, is down to the sample frequency (as 1.92MHz) comprising RACH bandwidth by the sample rate of RACH signal, obtain down-sampled after data.

Step 3, the data after down-sampled to step 2 gained carry out DFT conversion, use N point DFT to be transformed into frequency domain the data after down-sampled, obtain the data after DFT conversion.N is parameter preset, and suggestion N value is 2048.

Step 4, coherent detection is carried out to the data of step 3 gained after DFT conversion, comprising tables look-up by the logical root sequence by cell configuration obtains physics root sequence, the frequency domain sequence of local root sequence is generated according to physics root sequence, with the frequency domain sequence of local root sequence generated and step 3 the data after DFT changes carry out related operation, obtain the result of related operation.

With the frequency domain sequence of local root sequence generated and step 3 the data after DFT changes carry out related operation, namely carry out complex conjugate multiplication.

Step 5, carries out K point IDFT computing to the result of step 4 gained related operation, obtains the correlation of time domain.Suggestion value principle N _zc≤ K≤N, N _zCfor the length of ZC sequence, embodiment gets K=1536.

Step 6, calculates through overpower time delay spectrum the correlation of step 5 gained time domain, calculates power time delay spectrum (Power Delay Profile, PDP) of RACH signal.Described power time delay spectrum asks mould and square operation to the correlation of time domain at last.

Step 7, carries out peakvalue's checking to the power time delay of step 6 gained RACH signal spectrum, comprises the cyclic shift determining the Preamble sequence that UE uses, and detects 2 maximum peak values.

For the sake of ease of implementation, provide the peak value implementation that in the step 7 of embodiment, detection 2 is maximum as follows further:

Peakvalue's checking thresholding according to composing the power time delay of step 6 gained RACH signal and preset detects, and finds out the maximum in power time delay spectrum and is designated as A;

If this maximum A does not exceed peakvalue's checking thresholding, then do not detect peak value;

If this maximum A exceedes peakvalue's checking thresholding, then detect the 1st peak value, be designated as peak value 1; In power time delay being composed after detecting the 1st peak value, the 1st peak value and each m(m of this peak value the right and left are parameter preset, m advises m value 20 in value 10 ~ 30 embodiment) individual value assignment is 0, then finds out the maximum in the spectrum of the power time delay after process and is designated as B;

If this maximum B ultrasonic crosses peakvalue's checking thresholding, be the 2nd peak value detected, be designated as peak value 2;

If this maximum B does not exceed peakvalue's checking thresholding, in the power time delay spectrum of step 6 gained RACH signal, 1 peak value can only be detected.

Described peak value threshold is that general general PRACH detection algorithm calculates gained thresholding, is not described in detail thresholding computational methods herein.

As shown in Figure 2, the present embodiment obtains 2 peak values as shown in Figure 2 by this and is designated as peak value 1 and peak value 2, and the position of peak value 1 place x-axis is 523, and the position of peak value 2 place x-axis is 10, distance between the two in x-axis is 513, u=384 is substituted into formula (3) and calculates d _u=280, so in figure, x-axis represents counting after PDP calculates, and y-axis represents the power spectrum after PDP calculates.

Step 8, carry out frequency deviation estimation, comprise the correlation according to step 5 gained time domain, the position of the peak-peak that step 7 detects is taken out to the correlation of the time domain on this position, and phase place is obtained to the correlation of time domain on this position, estimate frequency deviation value f, the frequency deviation value f that the present embodiment estimates is 720Hz.

Step 9, carries out time offset estimation, comprises and detects 2 maximum peak value acquired results according to the estimated frequency deviation value of step 8 and step 7, estimate RACH signal time inclined, obtain uplink synchronous lead.

For the sake of ease of implementation, provide the uplink synchronous lead extracting mode of embodiment as follows further:

First determine main peak, determine that mode is as follows,

When detecting 1 peak value, this peak value is main peak;

When detecting 2 peak values,

(1) when frequency deviation estimated value is positive frequency deviation, if being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak; If being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak, adopts K=1536, N in the present embodiment _zc=839, adopt physics root sequence u=384, can be calculated d according to formula (2) _u=280;

(2) when frequency deviation estimated value is negative frequency deviation, if being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak; If being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak;

According to method shown in above-mentioned, the frequency deviation estimated due to the present embodiment is 720Hz is positive frequency deviation, and being spaced apart between 2 peak values therefore the peak value 2 shown in Fig. 2 is main peak.

Then uplink synchronous lead is calculated according to the value n of main peak in x-axis the position n=10 of peak value 2 in x-axis in the present embodiment, can be calculated uplink synchronous lead is T _a=5.2 × 10 ^-6(s).

Wherein, d _urepresent the cyclic shift that ZC sequence produces when Doppler frequency shift is a unit year interval, N _zCrepresent the length of ZC sequence, N _prepresent the length of PRACH after IDFT process in time domain, in 3GPP agreement, be defined as 24576, T _srepresent basic time quantum, be defined as 1/30720000 (s) in 3GPP agreement.

The Stochastic accessing detection system for LTE system that the present invention proposes comprises frequency displacement module, down-sampled module, DFT module, coherent detection module, IDFT module, power time delay spectrum computing module, peak detection block, frequency deviation estimating modules and time offset estimation module.Frequency displacement module in the Stochastic accessing detection algorithm that the present invention proposes, down-sampled module, DFT module, correlation module, IDFT module and power time delay spectrum computing module are consistent with traditional Stochastic accessing detection algorithm, are not described in detail here.

A kind of Stochastic accessing detection system for LTE system of embodiment, comprises with lower module:

Frequency displacement module, carries out frequency displacement for the RACH signal that will receive, and is moved in the bandwidth centered by direct current subcarrier by the RACH signal that every root reception antenna receives, and obtains the RACH signal after frequency displacement;

Down-sampled module, for by the RACH signal after the frequency displacement of frequency displacement module gained through down-sampled, the sample rate of RACH signal is down to the sample frequency comprising RACH bandwidth, obtain down-sampled after data;

DFT module, carries out DFT conversion for the data after down-sampled to down-sampled module gained, and use N point DFT to be transformed into frequency domain the data after down-sampled, obtain the data after DFT conversion, N is parameter preset, and suggestion N value is 2048;

Coherent detection module, for carrying out coherent detection to the data of DFT module gained after DFT conversion, comprising tables look-up by the logical root sequence by cell configuration obtains physics root sequence, the frequency domain sequence of local root sequence is generated according to physics root sequence, carry out related operation with the frequency domain sequence of local root sequence generated and the data of DFT module gained after DFT changes, obtain the result of related operation;

IDFT module, for carrying out K point IDFT computing to the result of coherent detection module gained related operation, obtain the correlation of time domain, K is parameter preset, suggestion value principle N _zc≤ K≤N, N _zCfor the length of ZC sequence, embodiment gets K=1536;

Power time delay spectrum computing module, for processing through overpower time delay spectrum the correlation of IDFT module gained time domain, calculates the power time delay spectrum of RACH signal; The process of described power time delay spectrum asks mould and square operation to the correlation of time domain;

Peak detection block, for carrying out peakvalue's checking to the power time delay spectrum of power time delay spectrum computing module gained RACH signal, comprises the cyclic shift determining the Preamble sequence that UE uses, and detects 2 maximum peak values;

Frequency deviation estimating modules, for carrying out frequency deviation estimation, comprising the correlation according to IDFT module gained time domain, the position of the peak-peak that peak detection block detects being taken out to the correlation of the time domain on this position, and phase place is obtained to the correlation of time domain on this position, estimate frequency deviation value f;

Time offset estimation module, for carrying out time offset estimation, comprising and estimating that estimated frequency deviation value and peak detection block detect 2 maximum peak value acquired results according to frequency deviation, estimate RACH signal time inclined, obtain uplink synchronous lead.

Correspondingly, peak detection block detects 2 maximum peak values and implementation can be adopted as follows,

Peakvalue's checking thresholding according to composing the power time delay of power time delay spectrum computing module gained RACH signal and preset detects, and finds out the maximum in power time delay spectrum and is designated as A;

If this maximum A does not exceed peakvalue's checking thresholding, then do not detect peak value;

If this maximum A exceedes peakvalue's checking thresholding, then detect the 1st peak value, be designated as peak value 1; In power time delay being composed after detecting the 1st peak value, the 1st peak value and each m(m of this peak value the right and left are parameter preset, m advises m value 20 in value 10 ~ 30 embodiment) individual value assignment is 0, then finds out the maximum in the spectrum of the power time delay after process and is designated as B;

If this maximum B ultrasonic crosses peakvalue's checking thresholding, be the 2nd peak value detected, be designated as peak value 2;

If this maximum B does not exceed peakvalue's checking thresholding, in the power time delay spectrum of step 6 gained RACH signal, 1 peak value can only be detected.

Correspondingly, according to frequency deviation, time offset estimation module estimates that estimated frequency deviation value and peak detection block detect 2 maximum peak value acquired results, estimate RACH signal time inclined, the adopted implementation obtaining uplink synchronous lead is as follows,

First determine main peak, determine that mode is as follows,

When detecting 1 peak value, this peak value is main peak;

When detecting 2 peak values,

(1) when frequency deviation estimated value is positive frequency deviation, if being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak; If being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak;

(2) when frequency deviation estimated value is negative frequency deviation, if being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak; If being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak;

Then uplink synchronous lead is calculated according to the value n of main peak in x-axis

Wherein, d _urepresent the cyclic shift that ZC sequence produces when Doppler frequency shift is a unit year interval, N _zCrepresent the length of ZC sequence, N _prepresent the length of PRACH after IDFT process in time domain, in 3GPP agreement, be defined as 24576, T _srepresent basic time quantum, be defined as 1/30720000 (s) in 3GPP agreement.

Specific embodiment described herein is only to the explanation for example of the present invention's spirit.Those skilled in the art can make various amendment or supplement or adopt similar mode to substitute to described specific embodiment, but can't depart from spirit of the present invention or surmount the scope that appended claims defines.

Claims (4)

1. for a random access detecting method for LTE system, it is characterized in that: comprise the following steps,

Step one, carries out frequency displacement by the RACH signal received, and is moved in the bandwidth centered by direct current subcarrier by the RACH signal that every root reception antenna receives, and obtains the RACH signal after frequency displacement;

Step 2, to the RACH signal after the frequency displacement of step one gained through down-sampled, is down to the sample frequency comprising RACH bandwidth by the sample rate of RACH signal, obtain down-sampled after data;

Step 3, the data after down-sampled to step 2 gained carry out DFT conversion, and use N point DFT to be transformed into frequency domain the data after down-sampled, obtain the data after DFT conversion, N is parameter preset;

Step 4, coherent detection is carried out to the data of step 3 gained after DFT conversion, comprising tables look-up by the logical root sequence by cell configuration obtains physics root sequence, the frequency domain sequence of local root sequence is generated according to physics root sequence, carry out related operation with the frequency domain sequence of local root sequence generated and the data of step 3 gained after DFT changes, obtain the result of related operation;

Step 5, carry out K point IDFT computing to the result of step 4 gained related operation, obtain the correlation of time domain, K is parameter preset;

Step 6, processes through overpower time delay spectrum the correlation of step 5 gained time domain, calculates the power time delay spectrum of RACH signal; The process of described power time delay spectrum asks mould and square operation to the correlation of time domain;

Step 7, carries out peakvalue's checking to the power time delay of step 6 gained RACH signal spectrum, comprises the cyclic shift determining the Preamble sequence that UE uses, and detects 2 maximum peak values;

Step 8, carries out frequency deviation estimation, comprises the correlation according to step 5 gained time domain, the position of the peak-peak that step 7 detects is taken out to the correlation of the time domain on this position, and obtains phase place to the correlation of time domain on this position, estimates frequency deviation value f;

Step 9, carries out time offset estimation, comprises and detects 2 maximum peak value acquired results according to the estimated frequency deviation value of step 8 and step 7, estimate RACH signal time inclined, obtain uplink synchronous lead; Detect 2 maximum peak value acquired results according to the estimated frequency deviation value of step 8 and step 7 described in step 9, estimate RACH signal time inclined, obtain uplink synchronous lead, implementation is as follows,

First determine main peak, determine that mode is as follows,

When detecting 1 peak value, this peak value is main peak;

When detecting 2 peak values,

(1) when frequency deviation estimated value is positive frequency deviation, if being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak; If being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak;

(2) when frequency deviation estimated value is negative frequency deviation, if being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak; If being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak;

Then uplink synchronous lead is calculated according to the value n of main peak in x-axis

Wherein, d _urepresent the cyclic shift that ZC sequence produces when Doppler frequency shift is a unit year interval, N _zCrepresent the length of ZC sequence, N _prepresent the length of PRACH after IDFT process in time domain, T _srepresent basic time quantum.

2. according to claim 1 for the random access detecting method of LTE system, it is characterized in that: the peak value implementation that in step 7, detection 2 is maximum is as follows,

Peakvalue's checking thresholding according to composing the power time delay of step 6 gained RACH signal and preset detects, and finds out the maximum in power time delay spectrum and is designated as A;

If this maximum A does not exceed peakvalue's checking thresholding, then do not detect peak value;

If this maximum A exceedes peakvalue's checking thresholding, then detect the 1st peak value, be designated as peak value 1; In power time delay being composed after detecting the 1st peak value, the 1st peak value and each m, these peak value both sides value assignment are 0, and then find out the maximum in the spectrum of the power time delay after process and be designated as B, m is parameter preset;

If this maximum B ultrasonic crosses peakvalue's checking thresholding, be the 2nd peak value detected, be designated as peak value 2;

If this maximum B does not exceed peakvalue's checking thresholding, in the power time delay spectrum of step 6 gained RACH signal, 1 peak value can only be detected.

3. for a Stochastic accessing detection system for LTE system, it is characterized in that: comprise with lower module,

Frequency displacement module, carries out frequency displacement for the RACH signal that will receive, and is moved in the bandwidth centered by direct current subcarrier by the RACH signal that every root reception antenna receives, and obtains the RACH signal after frequency displacement;

Down-sampled module, for by the RACH signal after the frequency displacement of frequency displacement module gained through down-sampled, the sample rate of RACH signal is down to the sample frequency comprising RACH bandwidth, obtain down-sampled after data;

DFT module, carries out DFT conversion for the data after down-sampled to down-sampled module gained, and use N point DFT to be transformed into frequency domain the data after down-sampled, obtain the data after DFT conversion, N is parameter preset;

Coherent detection module, for carrying out coherent detection to the data of DFT module gained after DFT conversion, comprising tables look-up by the logical root sequence by cell configuration obtains physics root sequence, the frequency domain sequence of local root sequence is generated according to physics root sequence, carry out related operation with the frequency domain sequence of local root sequence generated and the data of DFT module gained after DFT changes, obtain the result of related operation;

IDFT module, for carrying out K point IDFT computing to the result of coherent detection module gained related operation, obtain the correlation of time domain, K is parameter preset;

Power time delay spectrum computing module, for processing through overpower time delay spectrum the correlation of IDFT module gained time domain, calculates the power time delay spectrum of RACH signal; The process of described power time delay spectrum asks mould and square operation to the correlation of time domain;

Peak detection block, for carrying out peakvalue's checking to the power time delay spectrum of power time delay spectrum computing module gained RACH signal, comprises the cyclic shift determining the Preamble sequence that UE uses, and detects 2 maximum peak values;

Frequency deviation estimating modules, for carrying out frequency deviation estimation, comprising the correlation according to IDFT module gained time domain, the position of the peak-peak that peak detection block detects being taken out to the correlation of the time domain on this position, and phase place is obtained to the correlation of time domain on this position, estimate frequency deviation value f;

Time offset estimation module, for carrying out time offset estimation, comprising and estimating that estimated frequency deviation value and peak detection block detect 2 maximum peak value acquired results according to frequency deviation, estimate RACH signal time inclined, obtain uplink synchronous lead; According to frequency deviation, time offset estimation module estimates that estimated frequency deviation value and peak detection block detect 2 maximum peak value acquired results, estimate RACH signal time inclined, the implementation obtaining uplink synchronous lead is as follows,

First determine main peak, determine that mode is as follows,

When detecting 1 peak value, this peak value is main peak;

When detecting 2 peak values,

(1) when frequency deviation estimated value is positive frequency deviation, if being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak; If being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak;

(2) when frequency deviation estimated value is negative frequency deviation, if being spaced apart between 2 peak values so distance y-axis peak value is farthest main peak; If being spaced apart between 2 peak values the peak value that so distance y-axis is nearest is main peak;

Then uplink synchronous lead is calculated according to the value n of main peak in x-axis

Wherein, d _urepresent the cyclic shift that ZC sequence produces when Doppler frequency shift is a unit year interval, N _zCrepresent the length of ZC sequence, N _prepresent the length of PRACH after IDFT process in time domain, T _srepresent basic time quantum.

4. according to claim 3 for the Stochastic accessing detection system of LTE system, it is characterized in that: it is as follows that peak detection block detects 2 maximum peak value implementations,

Peakvalue's checking thresholding according to composing the power time delay of power time delay spectrum computing module gained RACH signal and preset detects, and finds out the maximum in power time delay spectrum and is designated as A;

If this maximum A does not exceed peakvalue's checking thresholding, then do not detect peak value;

If this maximum A exceedes peakvalue's checking thresholding, then detect the 1st peak value, be designated as peak value 1; In power time delay being composed after detecting the 1st peak value, the 1st peak value and this peak value the right and left each m value assignment are 0, and then find out the maximum in the spectrum of the power time delay after process and be designated as B, m is parameter preset;

If this maximum B ultrasonic crosses peakvalue's checking thresholding, be the 2nd peak value detected, be designated as peak value 2;

If this maximum B does not exceed peakvalue's checking thresholding, in the power time delay spectrum of step 6 gained RACH signal, 1 peak value can only be detected.