CN103338508B - A kind of associating frequency deviation estimating method and system - Google Patents

Abstract

In order to overcome under fast mode because two row reference signals in a subframe of PUSCH cause misjudgment so that the scope of carrying out frequency deviation estimation is too small, the present invention proposes a kind of method and system of Combined estimator frequency deviation.The result that during first the present invention detects according to PRACH, Preamble detects estimates frequency deviation symbol, then according to two row reference signals on PUSCH ask correlation estimation go out ± 1KHz within frequency deviation value, the frequency deviation symbol estimated when finally detecting according to Preamble obtains final frequency deviation value to the frequency deviation value correction that PUSCH estimates.

Description

A kind of associating frequency deviation estimating method and system

Technical field

The present invention relates to wireless communication field, more specifically, the present invention be directed to the method and system that the frequency deviation in forth generation mobile communication system (hereinafter referred to as 4G) is estimated.

Background technology

In a 4 g system, the key technology adopted due to physical layer is OFDM(Orthogonal Frequency DivisionMultiplexing, OFDM) technology, OFDM technology is easy to the impact being subject to frequency deviation, therefore needs at receiving terminal the frequency deviation estimating system accurately.

In the uplink receiving system of 4G system, generally adopt two row reference signals in Physical Uplink Shared Channel (PUSCH) subframe to ask relevant carry out frequency deviation estimation, two row reference signals in Physical Uplink Shared Channel (PUSCH) subframe as shown in Figure 1, in figure, one slot represents a time slot units, the arrow at reference signal and data place indicates reference data and the sub-carrier positions of data shared by time slot units respectively, supposes that two row reference signals are respectively r ₁(m) and r ₂m (), wherein m represents the sequence index of reference signal, and the length of two row reference signals is N, then the correlation R of two row reference signals in a subframe _lfor:

$R_1=\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{r}_1\left(m\right)r_2{\left(m\right)}^{*}---\left(1\right)$

Wherein r ₂(m) ^*be expressed as r ₂m the conjugation of (), the spacing of two row reference signals in PUSCH subframe is fixing is N _dt _s=0.5ms, N _dbe the sampling number between two row reference signals, T _sfor the time interval that sampled point is corresponding.According to the correlation R of two row reference signals in the subframe calculated _lthe frequency deviation Δ f on PUSCH can be estimated _c:

$\mathrm{\Δ}{f}_c=\frac{\arg \left(R_l\right)}{2\mathrm{\π}{N}_d{T}_s}---\left(2\right)$

Due to N _dt _s=0.5ms and arg (R _l) ∈ [-π, π], the frequency deviation Δ f of PUSCH estimation can be calculated according to formula (2) _cscope be [-1kHz, 1kHz].Frequency deviation that Doppler frequency shift produces and the frequency deviation that the deviation of base station system and the crystal oscillator of terminal system own causes mainly are comprised for 4G system frequency deviation, for uplink receiving system, maximum frequency deviation can reach the maximum doppler frequency of 2 times, calculating maximum doppler frequency is carried out for 583Hz with the speed of the carrier frequency of 2.1G and high ferro 300km/h, therefore maximum in uplink receiving system frequency deviation is 1166Hz, does not also consider the frequency deviation that the deviation of base station system and the crystal oscillator of terminal system own causes here.Therefore, under high velocity environment, adopt two row reference signals in a subframe of PUSCH to carry out frequency deviation estimation and can cause misjudgment because the frequency deviation value of reality is excessive.

Summary of the invention

In order to overcome under fast mode because two row reference signals in a subframe of PUSCH cause misjudgment so that the scope of carrying out frequency deviation estimation is too small, the present invention proposes a kind of method and system of Combined estimator frequency deviation.

Technical scheme of the present invention is a kind of method of combining frequency deviation and estimating, combine according to PRACH and PUSCH and estimate, described PRACH is Physical Random Access Channel, and described PUSCH is Physical Uplink Shared Channel, comprises and performs following steps in a base station,

Step one, estimate frequency deviation symbol according to the result that Preamble in PRACH detects, described Preamble is targeting sequencing; Estimation mode is as follows,

When the peak energy of window Positive window positive in Preamble detection window is greater than the peak energy of negative window Negative window, judge that the symbol of frequency deviation is as just;

When the peak energy of window Positive window positive in Preamble detection window is less than the peak energy of negative window Negative window, judge that the symbol of frequency deviation is as negative;

Step 2, according to two row reference signals on PUSCH ask correlation estimation go out ± 1KHz within frequency deviation value Δ f _c;

Step 3, the frequency deviation value Δ f that the frequency deviation symbol estimated according to step one estimates step 2 _crevise, obtain final frequency deviation value, correcting mode is as follows,

If the frequency deviation value Δ f that the frequency deviation symbol that step one estimates and step 2 estimate _csymbol identical, then do not revise;

If the frequency deviation value Δ f that the frequency deviation symbol that step one estimates and step 2 estimate _csymbol not identical, then revise, if the symbol of frequency deviation value that estimates of step one is for just, then revised frequency deviation value Δ f _c' be Δ f _c'=Δ f _c+ 2000, if the symbol of frequency deviation value that step one estimates is negative, then revised frequency deviation value Δ f _c'=Δ f _c-2000.

And, in step 2, described frequency deviation value Δ f _ccomputing formula as follows,

$\mathrm{\Δ}{f}_c=\frac{\arg \left(R_l\right)}{2\mathrm{\π}{N}_d{T}_s}$

Wherein, R _lbe the correlation of two row reference signals in a subframe, N _dbe the sampling number between two row reference signals, T _sfor the time interval that sampled point is corresponding.

Present invention also offers corresponding a kind of system of combining frequency deviation and estimating, arrange in a base station with lower device, PRACH frequency deviation sign estimation device, estimate frequency deviation symbol for the result detected according to Preamble in PRACH, described PRACH is Physical Random Access Channel; Estimation mode is as follows,

When the peak energy of Preamble detection window Positive window is greater than the peak energy of Negative window, judge that the symbol of frequency deviation is as just;

When the peak energy of Preamble detection window Positive window is less than the peak energy of Negative window, judge that the symbol of frequency deviation is as negative;

PUSCH frequency deviation value estimation unit, for ask according to two row reference signals on PUSCH correlation estimation go out ± 1KHz within frequency deviation value Δ f _c, described PUSCH is Physical Uplink Shared Channel;

Frequency deviation value correcting device, the frequency deviation value Δ f that the frequency deviation symbol for estimating according to PRACH frequency deviation sign estimation device estimates PUSCH frequency deviation value estimation unit _crevise, obtain final frequency deviation value, correcting mode is as follows,

If the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and the frequency deviation value Δ f that PUSCH frequency deviation value estimation unit estimates _csymbol identical, then do not revise;

If the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and the frequency deviation value Δ f that step 2 estimates _csymbol not identical, then revise, if the symbol of frequency deviation value that estimates of PRACH frequency deviation sign estimation device is for just, then revised frequency deviation value Δ f _c' be Δ f _c'=Δ f _c+ 2000,

If the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates is negative, then revised frequency deviation value Δ f _c'=Δ f _c-2000.

And, calculate frequency deviation value Δ f in PUSCH frequency deviation value estimation unit _cthe computing formula adopted is as follows,

$\mathrm{\Δ}{f}_c=\frac{\arg \left(R_l\right)}{2\mathrm{\π}{N}_d{T}_s}$

Wherein, R _lbe the correlation of two row reference signals in a subframe, N _dbe the sampling number between two row reference signals, T _sfor the time interval that sampled point is corresponding.

The present invention adopts in PRACH and detects Preamble tri-detection window Main window, in Negative window and Positive window, first the size of peak value judges the sign of frequency deviation value, then according to two row reference signals on traditional PUSCH ask correlation estimation go out ± 1KHz within frequency deviation value, the symbol estimating frequency deviation when finally detecting according to Preamble obtains final frequency deviation value to the frequency deviation value correction that PUSCH estimates, the method and system can expand frequency offset estimation range to [-2KHz, 2KHz], improve the scope that frequency deviation is estimated greatly.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of two row reference signal positions on PUSCH channel;

Fig. 2 is the schematic diagram detecting Preamble tri-detection window Main window, Negative window and Positive window under PRACH adopts fast mode.

Fig. 3 is the flow chart of the embodiment of the present invention.

Embodiment

The present invention proposes a kind of method and system of combining frequency deviation and estimating, traditional 4G frequency offset estimation range can expand to [-2KHz, 2KHz] from [-1KHz, 1KHz] by the program, and the method is specially adapted to high velocity environment, as high ferro covers.Specific embodiments of the invention are, first arranging PRACH channel is fast mode, suppose that the true frequency deviation value in uplink receiving system is Δ f _c', be described below in conjunction with embodiment and accompanying drawing.

Physical Random Access Channel (Physical Random Access Channel, PRACH) be that user is used for carrying out uplink synchronous, user sends Random Access Channel (Random Access Channel on prach, RACH), Zadoff-Chu(ZC is adopted in RACH channel) cyclic shift of sequence is as targeting sequencing (Preamble), and the Preamble that base station (eNodeB) sends in RACH channel according to UE detects uplink synchronous lead.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:

$x_u\left(n\right)=e^{-j\frac{\mathrm{\πun}(n+1)}{N_{\mathrm{ZC}}}},0\≤n\≤N_{\mathrm{ZC}}-1---\left(3\right)$

Wherein u represents physics root sequence, N _zCrepresent the length of ZC sequence, in 3GPP agreement, specify N _zCbe the truth of a matter that 839, e represents natural logrithm function, j states the unit of imaginary number, 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:

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

$=\exp (-j\·\frac{\mathrm{\π}\·u\·n\·(n+1)}{N_{\mathrm{ZC}}})\·\exp (-j\·\frac{\mathrm{\π}\·u\·d_u\·(d_u+1)}{N_{\mathrm{ZC}}})\·\exp (-j\·\frac{2\·\mathrm{\π}\·u\·d_u\·n}{N_{\mathrm{ZC}}})---\left(4\right)$

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

Wherein, x _un () represents ZC sequence, x (n+d _u) represent ZC sequence x _u(n) cyclic shift integer d _usequence afterwards, $C_{\mathrm{phase}}=\exp (-j\·\frac{\mathrm{\π}\·u\·d_u\·(d_u+1)}{N_{\mathrm{ZC}}})$ 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 (5)

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.As shown in Figure 2, N _cSrepresent the length of PRACH detection window, under PRACH adopts fast mode, have three detection windows, Main window, Negative window and Positive window represent main window, negative window and positive window respectively.When frequency deviation is larger, the energy of Main window can shift to Negative window or Positive window gradually, when frequency deviation value is positive number, the energy of Main window can greatly progressively transfer to Positive window along with the change of frequency deviation value, when frequency deviation value is negative, the energy of Main window can greatly progressively transfer to Negative window along with the change of frequency deviation value.According to this characteristic of PRACH, we can estimate the sign of frequency deviation value.It is the characteristic all met in [-2.5kHz, 2.5kHz] scope above in frequency deviation.

According to above analysis, technical scheme of the present invention proposes, and the result first detected according to Preamble in PRACH estimates the sign of frequency deviation; Due to when frequency deviation value is positive number, the energy of Main window can greatly progressively transfer to Positive window along with the change of frequency deviation value, when frequency deviation value is negative, the energy of Main window can greatly progressively transfer to Negative window along with the change of frequency deviation value, can estimate the sign of frequency deviation according to this feature as follows:

Then judge that when the peak energy of Preamble detection window Positive window is greater than the peak energy of Negative window the symbol of frequency deviation is as just;

Then judge that when the peak energy of Preamble detection window Positive window is less than the peak energy of Negative window the symbol of frequency deviation is as negative;

Then according to two row reference signals on PUSCH ask correlation estimation go out ± 1KHz within frequency deviation value Δ f _c, Δ f _ccomputational methods be traditional account form, specific formula for calculation is as shown in formula (2).

The frequency deviation symbol estimated in finally detecting according to Preamble, to PUSCH estimating the frequency deviation value obtained is revised, obtains final frequency deviation value, and the concrete method revised is as follows:

If the Δ f that the symbol of frequency deviation value that Preamble estimates in detecting and PUSCH estimate _csymbol identical, then do not revise;

If the Δ f that the symbol of frequency deviation value that Preamble estimates in detecting and PUSCH estimate _csymbol not identical, then revise,

If the symbol of the frequency deviation value that Preamble estimates in detecting just is, then revised frequency deviation value Δ f _c' be:

Δf _c′＝Δf _c+2000 (6)

If the symbol of the frequency deviation value that Preamble estimates in detecting is negative, then revised frequency deviation value Δ f _c' be:

Δf _c′＝Δf _c-2000 (7)

Software engineering can be adopted when technical solution of the present invention is specifically implemented to realize automatic operational process.As shown in Figure 3, embodiment is as follows in base station execution flow process:

Step one, estimates the sign of frequency deviation according to the result of Preamble detection in PRACH; Method of estimation for frequency deviation symbol is:

Then judge that when the peak energy of Preamble detection window Positive window is greater than the peak energy of Negative window the symbol of frequency deviation is as just;

Then judge that when the peak energy of Preamble detection window Positive window is less than the peak energy of Negative window the symbol of frequency deviation is as negative;

Step 2, according to two row reference signals on PUSCH ask correlation estimation go out ± 1KHz within frequency deviation value Δ f _c, Δ f _ccomputational methods be:

$\mathrm{\Δ}{f}_c=\frac{\arg \left(R_l\right)}{2\mathrm{\π}{N}_d{T}_s}---\left(2\right)$

Step 3, revise the frequency deviation value that step 2 estimates according to the frequency deviation symbol that step one estimates, obtain final frequency deviation value, the method for correction is as follows:

If the Δ f that the symbol of the frequency deviation value that step one estimates and step 2 estimate _csymbol identical, then do not revise;

If the Δ f that the symbol of the frequency deviation value that step one estimates and step 2 estimate _csymbol not identical, then revise,

If the symbol of the frequency deviation value that step one estimates just is, then revised frequency deviation value Δ f _c' be:

Δf _c′＝Δf _c+2000 (6)

If the symbol of the frequency deviation value that step one estimates is negative, then revised frequency deviation value Δ f _c' be:

Δf _c′＝Δf _c-2000 (7)

Software provided by the present invention can adopt modular mode to realize, and provides corresponding a kind of system of combining frequency deviation and estimating, comprises and arrange with lower device in a base station:

PRACH frequency deviation sign estimation device, estimate frequency deviation symbol for the result detected according to Preamble in PRACH, described PRACH is Physical Random Access Channel; Estimation mode is as follows,

When the peak energy of Preamble detection window Positive window is greater than the peak energy of Negative window, judge that the symbol of frequency deviation is as just;

When the peak energy of Preamble detection window Positive window is less than the peak energy of Negative window, judge that the symbol of frequency deviation is as negative;

PUSCH frequency deviation value estimation unit, for ask according to two row reference signals on PUSCH correlation estimation go out ± 1KHz within frequency deviation value Δ f _c, described PUSCH is Physical Uplink Shared Channel; Δ f _ccomputing formula as follows,

$\mathrm{\Δ}{f}_c=\frac{\arg \left(R_l\right)}{2\mathrm{\π}{N}_d{T}_s}---\left(2\right)$

Wherein, R _lbe the correlation of two row reference signals in a subframe, N _dbe the sampling number between two row reference signals, T _sfor the time interval that sampled point is corresponding;

Frequency deviation value correcting device, the frequency deviation value Δ f that the frequency deviation symbol for estimating according to PRACH frequency deviation sign estimation device estimates PUSCH frequency deviation value estimation unit _crevise, obtain final frequency deviation value, correcting mode is as follows,

If the Δ f that the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates and PUSCH frequency deviation value estimation unit estimate _csymbol identical, then do not revise;

If the Δ f that the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates and PUSCH frequency deviation value estimation unit estimate _csymbol not identical, then revise,

If the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates just is, then revised frequency deviation value Δ f _c' be:

Δf _c′＝Δf _c+2000 (6)

If the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates is negative, then revised frequency deviation value Δ f _c' be:

Δf _c′＝Δf _c-2000 (7)

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. combine the method that frequency deviation is estimated, it is characterized in that: combine according to PRACH and PUSCH and estimate, described PRACH is Physical Random Access Channel, and described PUSCH is Physical Uplink Shared Channel, comprises and performs following steps in a base station,

Step one, estimate frequency deviation symbol according to the result that Preamble in PRACH detects, described Preamble is targeting sequencing; Estimation mode is as follows,

When the peak energy of window Positive window positive in Preamble detection window is greater than the peak energy of negative window Negative window, judge that the symbol of frequency deviation is as just;

When the peak energy of window Positive window positive in Preamble detection window is less than the peak energy of negative window Negative window, judge that the symbol of frequency deviation is as negative;

Step 2, according to two row reference signals on PUSCH ask correlation estimation go out ± 1KHz within frequency deviation value Δ f _c;

Step 3, the frequency deviation value Δ f that the frequency deviation symbol estimated according to step one estimates step 2 _crevise, obtain final frequency deviation value, correcting mode is as follows,

If the frequency deviation value Δ f that the frequency deviation symbol that step one estimates and step 2 estimate _csymbol identical, then do not revise;

If the frequency deviation value Δ f that the frequency deviation symbol that step one estimates and step 2 estimate _csymbol not identical, then revise,

If the symbol of the frequency deviation value that step one estimates just is, then revised frequency deviation value Δ f ' _cfor Δ f ' _c=Δ f _c+ 2000,

If the symbol of the frequency deviation value that step one estimates is negative, then revised frequency deviation value Δ f ' _c=Δ f _c-2000.

2. combine the method that frequency deviation is estimated according to claim 1, it is characterized in that: in step 2, described frequency deviation value Δ f _ccomputing formula as follows,

${\mathrm{\Δf}}_c=\frac{\arg \left(R_l\right)}{2{\mathrm{\πN}}_d{T}_s}$

Wherein, R _lbe the correlation of two row reference signals in a subframe, N _dbe the sampling number between two row reference signals, T _sfor the time interval that sampled point is corresponding.

3. combine the system that frequency deviation is estimated, it is characterized in that: arrange with lower device in a base station,

PRACH frequency deviation sign estimation device, estimate frequency deviation symbol for the result detected according to Preamble in PRACH, described PRACH is Physical Random Access Channel; Estimation mode is as follows,

When the peak energy of Preamble detection window Positive window is greater than the peak energy of Negative window, judge that the symbol of frequency deviation is as just;

When the peak energy of Preamble detection window Positive window is less than the peak energy of Negative window, judge that the symbol of frequency deviation is as negative;

PUSCH frequency deviation value estimation unit, for ask according to two row reference signals on PUSCH correlation estimation go out ± 1KHz within frequency deviation value Δ f _c, described PUSCH is Physical Uplink Shared Channel;

Frequency deviation value correcting device, the frequency deviation value Δ f that the frequency deviation symbol for estimating according to PRACH frequency deviation sign estimation device estimates PUSCH frequency deviation value estimation unit _crevise, obtain final frequency deviation value, correcting mode is as follows,

If the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and the frequency deviation value Δ f that PUSCH frequency deviation value estimation unit estimates _csymbol identical, then do not revise;

If the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and the frequency deviation value Δ f that PUSCH frequency deviation value estimation unit estimates _csymbol not identical, then revise, if the symbol of frequency deviation value that estimates of PRACH frequency deviation sign estimation device is for just, then revised frequency deviation value Δ f ' _cfor Δ f ' _c=Δ f _c+ 2000,

If the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates is negative, then revised frequency deviation value Δ f ' _c=Δ f _c-2000.

4. combine the system that frequency deviation is estimated according to claim 3, it is characterized in that: in PUSCH frequency deviation value estimation unit, calculate frequency deviation value Δ f _cthe computing formula adopted is as follows,

${\mathrm{\Δf}}_c=\frac{\arg \left(R_l\right)}{2{\mathrm{\πN}}_d{T}_s}$

Wherein, R _lbe the correlation of two row reference signals in a subframe, N _dbe the sampling number between two row reference signals, T _sfor the time interval that sampled point is corresponding.