CN103338508A - Method and system for jointly estimating frequency offset - Google Patents

Abstract

The invention provides a method and a system for jointly estimating frequency offset, in order to overcome the detect of an estimation error due to the fact that a range of frequency offset estimation by utilizing two rows of reference signals on a subframe of a PUSCH (Physical Uplink Shared Channel) in a high-speed mode is too small. The method comprises the steps that a frequency offset sign is estimated according to a Preamble detection result in PRACH (Physical Random Access Channel) detection; a relevant estimated frequency offset value within plus-minus 1KHz is calculated according to the two rows of reference signals on the PUSCH; the estimated frequency offset value on the PUSCH is corrected according to the estimated frequency offset sign during Preamble detection; and a final frequency offset value is obtained.

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 frequency deviation estimation approach and system in the 4th third-generation mobile communication system (hereinafter to be referred as 4G).

Background technology

In the 4G system, because the key technology that physical layer adopts is OFDM(Orthogonal Frequency Division Multiplexing, OFDM) technology, the OFDM technology is easy to be subjected to the influence of frequency deviation, therefore need estimate the frequency deviation of system accurately at receiving terminal.

Two row reference signals in the up receiving system of 4G system on subframe of general employing Physical Uplink Shared Channel (PUSCH) ask the relevant frequency deviation of carrying out to estimate, two row reference signals on subframe of Physical Uplink Shared Channel (PUSCH) as shown in Figure 1, one slot represents a time slot unit among the figure, the arrow at reference signal and data place has been indicated reference data and data shared sub-carrier positions in time slot unit respectively, supposes that two row reference signals are respectively r ₁(m) and r ₂(m), 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 on subframe _lFor:

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

R wherein ₂(m) ^*Be expressed as r ₂(m) conjugation, the spacing of two row reference signals on subframe of PUSCH are the N that are that fix _dT _s=0.5ms, N _dBe the sampling number between the two row reference signals, T _sBe sampled point time corresponding interval.Correlation R according to two row reference signals on the subframe of calculating _lCan estimate the frequency deviation Δ f on the PUSCH _c:

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

Because N _dT _s=0.5ms and arg (R _l) ∈ [π, π], can calculate the frequency deviation Δ f that PUSCH estimates according to formula (2) _cScope be [1kHz, 1kHz].Mainly comprise the frequency deviation that the deviation of frequency deviation that Doppler frequency shift produces and base station system and the crystal oscillator of terminal system own causes for the 4G system frequency deviation, for up receiving system, maximum frequency deviation can reach 2 times maximum doppler frequency, calculating maximum doppler frequency with the speed of the carrier frequency of 2.1G and high ferro 300km/h is 583Hz, therefore maximum frequency deviation is 1166Hz in up receiving system, 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, two row reference signals on the subframe of employing PUSCH are carried out frequency deviation estimation meeting and are caused misjudgment owing to the actual frequency deviations value is excessive.

Summary of the invention

Because two row reference signals on the subframe of PUSCH carry out that the frequency deviation estimated ranges is too small to cause misjudgment, the present invention proposes a kind of method and system of estimating frequency deviation of uniting in order to overcome under the fast mode.

Technical scheme of the present invention is a kind of associating frequency deviation estimation approach, unites according to PRACH and PUSCH and estimates that described PRACH is Physical Random Access Channel, and described PUSCH is Physical Uplink Shared Channel, be included in and carry out following steps in the base station,

Step 1, the result who detects according to Preamble among the PRACH estimates the frequency deviation symbol, and described Preamble is targeting sequencing; The estimation mode is as follows,

When the peak energy of positive window Positive window in the Preamble detection window during greater than the peak energy of negative window Negative window, the symbol of judging frequency deviation is for just;

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

Step 2, ask relevant according to two row reference signals on the PUSCH to estimate ± 1KHz is with interior frequency deviation value Δ f _c

Step 3, the frequency deviation value Δ f that the frequency deviation symbol that estimates according to step 1 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 1 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 1 estimates and step 2 estimate _cSymbol inequality, then revise, if the symbol of the frequency deviation value that step 1 estimates for just, revised frequency deviation value Δ f then _c' be Δ f _c'=Δ f _c+ 2000, if the symbol of the frequency deviation value that step 1 estimates for negative, revised frequency deviation value Δ f then _c'=Δ f _c-2000.

And, in the 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 on the subframe, N _dBe the sampling number between the two row reference signals, T _sBe sampled point time corresponding interval.

The present invention also provides corresponding a kind of system that frequency deviation is estimated that unites, in the base station, arrange with lower device, PRACH frequency deviation sign estimation device is used for estimating the frequency deviation symbol according to the result that PRACH Preamble detects, and described PRACH is Physical Random Access Channel; The estimation mode is as follows,

When the peak energy of Preamble detection window Positive window during greater than the peak energy of Negative window, the symbol of judging frequency deviation is for just;

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

PUSCH frequency deviation value estimation unit, be used for asking relevant according to two row reference signals on the PUSCH to estimate ± 1KHz is with interior frequency deviation value Δ f _c, described PUSCH is Physical Uplink Shared Channel;

The frequency deviation value correcting device, the frequency deviation value Δ f that the frequency deviation symbol that is used 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 value Δ f that the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and PUSCH frequency deviation value estimation unit estimate _cSymbol identical, then do not revise;

If the frequency deviation value Δ f that the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and step 2 estimate _cSymbol inequality, then revise, if the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates for just, revised frequency deviation value Δ f then _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 the PUSCH frequency deviation value estimation unit _cThe computing formula that adopts 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 on the subframe, N _dBe the sampling number between the two row reference signals, T _sBe sampled point time corresponding interval.

The present invention adopts and detects three detection window Main of Preamble window among the PRACH, the size of peak value is at first judged the sign of frequency deviation value among Negative window and the Positive window, ask relevant according to two row reference signals on traditional PUSCH then to estimate ± 1KHz is with interior frequency deviation value, the symbol that estimates frequency deviation when detecting according to Preamble at last obtains final frequency deviation value to the frequency deviation value correction that estimates on the PUSCH, this method and system can expand frequency offset estimation range to [2KHz, 2KHz], improved the frequency deviation estimated ranges greatly.

Description of drawings

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

Fig. 2 adopts the schematic diagram that detects three detection window Main of Preamble window, Negative window and Positive window under the fast mode for PRACH.

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

Embodiment

The present invention proposes a kind of associating frequency deviation estimation approach and system, and this scheme can expand traditional 4G frequency offset estimation range to [2KHz, 2KHz] from [1KHz, 1KHz], and this method is specially adapted to high velocity environment, covers as high ferro.Specific embodiments of the invention are that it is fast mode that the PRACH channel at first is set, and supposes that the true frequency deviation value in up receiving system is Δ f _c', describe below in conjunction with embodiment and accompanying drawing.

Physical Random Access Channel (Physical Random Access Channel, PRACH) be that the user is used for carrying out uplink synchronous, the user sends Random Access Channel (Random Access Channel at PRACH, RACH), adopting Zadoff-Chu(ZC in the RACH channel) cyclic shift of sequence is as targeting sequencing (Preamble), and base station (eNodeB) detects the uplink synchronous lead according to the Preamble that UE sends in the RACH channel.The RACH channel adopts the cyclic shift of ZC sequence as the Preamble sequence in the LTE system, because the ZC sequence has on the circulation auto-correlation point of sequence except starting point has peak value, all be the characteristics of null value on other aspects, therefore the method that general employing is correlated with at frequency domain in the receiving terminal base station is implemented on the RACH channel Preamble is detected.In the LTE system, have in each residential quarter 64 available leading.64 targeting sequencings set in residential quarter are that the root ZC sequence of RACH_ROOT_SEQUENCE produces all cyclically shifted sequences according to the order that cyclic shift increases by the logic index at first, if 64 targeting sequencings can not be produced by 1 root ZC sequence, the root sequence by follow-up logic index produces up to having produced 64 targeting sequencings so.Only need detect every 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 the ZC sequence is different will detect in different detection window.

Under the scene of high-speed mobile, the corresponding increase of Doppler frequency shift meeting needs the ZC sequence that the ability of enough antagonism frequency deviations is arranged.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 _ZCThe length of expression ZC sequence is stipulated N in the 3GPP agreement _ZCBe the truth of a matter that 839, e represents the natural logrithm function, the unit of j statement imaginary number, x _u(n) the corresponding value of n point of expression ZC sequence.

d _uThe cyclic shift that (the last unit subcarrier spacing of 3GPP agreement regulation PRACH is 1250Hz) produced when corresponding ZC sequence was sub year interval of a unit at Doppler frequency shift is 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 _u(n) expression ZC sequence, x (n+d _u) expression 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 place rotation constant that has nothing to do with n.

This shows that frequency deviation is equivalent at transmitting terminal the influence of ZC sequence has increased d _uThe cyclic shift amount, and satisfy

d _u＝(N _zc·m-1)/u (5)

N wherein _ZCThe length of expression ZC sequence, m makes d _uMinimum positive integer for integer.

After descending UE carried out the frequency deviation calibration, the frequency deviation of up PRACH generally was no more than 1 subcarrier spacing, so the relevant peaks of receiving terminal is the intermediateness after the sequence of a no frequency deviation and the sequence that one times of subcarrier spacing frequency deviation is arranged are done coherent detection, just C _v(expression is the residing position of main peak after overpower time-delay spectrum is handled) located original relevant peaks peak value and can be leaked to C _v± d _uThe place form pseudo-peak, and along with frequency deviation slowly increases, main window peak energy shifts to both sides gradually.When the energy at pseudo-peak, both sides during greater than the energy in the main window, peak detection algorithm will be used as main peak with pseudo-peak and come estimating time bias.In order to overcome the influence of serious frequency deviation under the high velocity environment, LTE system definition the fast mode of a kind of PRACH, under the PRACH fast mode, constructed the cyclic shift set that is applicable to high speed detection at the frequency bias properties of ZC sequence, with Doppler frequency shift in the restriction high speed detection to the influence of ZC sequence.As shown in Figure 2, N _CSThe length of expression PRACH detection window has three detection windows under PRACH employing fast mode, Main window, Negative window and Positive window represent main window, negative window and positive window respectively.When frequency deviation is big, 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 be transferred to Positive window along with the change of frequency deviation value, when frequency deviation value was negative, the energy of Main window can greatly progressively be transferred to Negative window along with the change of frequency deviation value.According to this specific character of PRACH, we can estimate the sign of frequency deviation value.It is the characteristic above all satisfying in [2.5kHz, 2.5kHz] scope in frequency deviation.

According to above analysis, technical scheme of the present invention proposes, and at first the result who detects according to Preamble among the PRACH estimates the sign of frequency deviation; Because when frequency deviation value is positive number, the energy of Main window can greatly progressively be transferred 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 be transferred to Negative window along with the change of frequency deviation value, can estimate the sign of frequency deviation as follows according to this feature:

The symbol of then judging frequency deviation during greater than the peak energy of Negative window when the peak energy of Preamble detection window Positive window is for just;

When the peak energy of Preamble detection window Positive window judges that then the symbol of frequency deviation is for negative during less than the peak energy of Negative window;

Ask relevant according to two row reference signals on the PUSCH then to estimate ± 1KHz is with interior frequency deviation value Δ f _c, Δ f _cComputational methods be traditional account form, concrete computing formula is as shown in Equation (2).

The frequency deviation symbol that estimates in detecting according to Preamble is at last gone up PUSCH and is estimated that the frequency deviation value that obtains revises, and obtains final frequency deviation value, and the concrete method of revising is as follows:

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

If the Δ f that estimates on the symbol of the frequency deviation value that Preamble estimates in detecting and the PUSCH _cSymbol inequality, then revise,

If the symbol of the frequency deviation value that estimates during Preamble detects is being for just, revised frequency deviation value Δ f then _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)

When specifically implementing, technical solution of the present invention can adopt software engineering to realize automatic operational process.As shown in Figure 3, embodiment is as follows in base station execution flow process:

Step 1, the result who detects according to Preamble among the PRACH estimates the sign of frequency deviation; Method of estimation for the frequency deviation symbol is:

The symbol of then judging frequency deviation during greater than the peak energy of Negative window when the peak energy of Preamble detection window Positive window is for just;

When the peak energy of Preamble detection window Positive window judges that then the symbol of frequency deviation is for negative during less than the peak energy of Negative window;

Step 2, ask relevant according to two row reference signals on the PUSCH to estimate ± 1KHz is with interior 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 is revised the frequency deviation value that step 2 estimates according to the frequency deviation symbol that step 1 estimates, and obtains final frequency deviation value, and the method for correction is as follows:

If the Δ f that the symbol of the frequency deviation value that step 1 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 1 estimates and step 2 estimate _cSymbol inequality, then revise,

If the symbol of the frequency deviation value that step 1 estimates is being for just, revised frequency deviation value Δ f then _c' be:

Δf _c′＝Δf _c+2000 (6)

If the symbol of the frequency deviation value that step 1 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, corresponding a kind of system that frequency deviation is estimated that unites is provided, and is included in to arrange in the base station with lower device:

PRACH frequency deviation sign estimation device is used for estimating the frequency deviation symbol according to the result that PRACH Preamble detects, and described PRACH is Physical Random Access Channel; The estimation mode is as follows,

When the peak energy of Preamble detection window Positive window during greater than the peak energy of Negative window, the symbol of judging frequency deviation is for just;

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

PUSCH frequency deviation value estimation unit, be used for asking relevant according to two row reference signals on the PUSCH to estimate ± 1KHz is with interior 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 on the subframe, N _dBe the sampling number between the two row reference signals, T _sBe sampled point time corresponding interval;

The frequency deviation value correcting device, the frequency deviation value Δ f that the frequency deviation symbol that is used 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 inequality, then revise,

If the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates is being for just, revised frequency deviation value Δ f then _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 only is that the present invention's spirit is illustrated.Those skilled in the art can make various modifications or replenish or adopt similar mode to substitute described specific embodiment, but can't depart from spirit of the present invention or surmount the defined scope of appended claims.

Claims (4)

1. associating frequency deviation estimation approach is characterized in that: unite according to PRACH and PUSCH and estimate that described PRACH is Physical Random Access Channel, described PUSCH is Physical Uplink Shared Channel, be included in and carry out following steps in the base station,

Step 1, the result who detects according to Preamble among the PRACH estimates the frequency deviation symbol, and described Preamble is targeting sequencing; The estimation mode is as follows,

When the peak energy of positive window Positive window in the Preamble detection window during greater than the peak energy of negative window Negative window, the symbol of judging frequency deviation is for just;

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

Step 2, ask relevant according to two row reference signals on the PUSCH to estimate ± 1KHz is with interior frequency deviation value Δ f _c

Step 3, the frequency deviation value Δ f that the frequency deviation symbol that estimates according to step 1 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 1 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 1 estimates and step 2 estimate _cSymbol inequality, then revise, if the symbol of the frequency deviation value that step 1 estimates for just, revised frequency deviation value Δ f then _c' be Δ f _c'=Δ f _c+ 2000, if the symbol of the frequency deviation value that step 1 estimates for negative, revised frequency deviation value Δ f then _c'=Δ f _c-2000.

2. according to the described associating frequency deviation of claim 1 estimation approach, it is characterized in that: in the 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 on the subframe, N _dBe the sampling number between the two row reference signals, T _sBe sampled point time corresponding interval.

3. unite the system that frequency deviation is estimated for one kind, it is characterized in that: in the base station, arrange with lower device,

PRACH frequency deviation sign estimation device is used for estimating the frequency deviation symbol according to the result that PRACH Preamble detects, and described PRACH is Physical Random Access Channel; The estimation mode is as follows,

When the peak energy of Preamble detection window Positive window during greater than the peak energy of Negative window, the symbol of judging frequency deviation is for just;

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

PUSCH frequency deviation value estimation unit, be used for asking relevant according to two row reference signals on the PUSCH to estimate ± 1KHz is with interior frequency deviation value Δ f _c, described PUSCH is Physical Uplink Shared Channel;

The frequency deviation value correcting device, the frequency deviation value Δ f that the frequency deviation symbol that is used 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 value Δ f that the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and PUSCH frequency deviation value estimation unit estimate _cSymbol identical, then do not revise;

If the frequency deviation value Δ f that the frequency deviation symbol that PRACH frequency deviation sign estimation device estimates and step 2 estimate _cSymbol inequality, then revise, if the symbol of the frequency deviation value that PRACH frequency deviation sign estimation device estimates for just, revised frequency deviation value Δ f then _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.

4. the system that estimates according to the described associating frequency deviation of claim 3 is characterized in that: calculate frequency deviation value Δ f in the PUSCH frequency deviation value estimation unit _cThe computing formula that adopts 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 on the subframe, N _dBe the sampling number between the two row reference signals, T _sBe sampled point time corresponding interval.

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