CN1647430A - Carrier frequency estimating method and device - Google Patents

Carrier frequency estimating method and device Download PDF

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Publication number
CN1647430A
CN1647430A CN03807993.3A CN03807993A CN1647430A CN 1647430 A CN1647430 A CN 1647430A CN 03807993 A CN03807993 A CN 03807993A CN 1647430 A CN1647430 A CN 1647430A
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frequency
subframe
configuration mode
oscillator
control word
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季晨
刘景波
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Linkair Communications Inc
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Linkair Communications Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/66—Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H04B1/711—Interference-related aspects the interference being multi-path interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0044—Control loops for carrier regulation
    • H04L2027/0063—Elements of loops
    • H04L2027/0065—Frequency error detectors

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)

Abstract

This invention relates to a method and apparatus to estimate carrier frequencies. On an arm of Rake receiver, downward continuous guide channel symbols are dispreaded, then, each dispreaded value is conjugatedly multiplied with fore one, all the products are added to obtain a complex Z = Ae with index of (j x phi).

Description

Carrier frequency estimating method and device
A kind of carrier frequency estimating method and device
Technical field
Concretely it is a kind of carrier frequency estimating method and device the invention belongs to the realization of wireless communication technology field, the more particularly to estimating carrier frequencies in the down-going synchronous subsystem of cdma system.Technical background
In high-performance cdma system, up-downgoing is all using relevant detection, it is desirable to mobile station（) and base station MS（BS accurate carrier wave and Phase synchronization between).When using CP continuous pilot or interpolation frequency pilot sign, Phase synchronization can be completed with channel estimator.Mobile station must accurately control its frequency departure between base station within the specific limits.So, mobile station must accurately estimate the frequency departure between mobile station and base station.
Crystal oscillator in mobile station is usually some ppm, and several KHz to more than ten KHz carrier beat is produced in 2G frequency ranges.Initial synchronization is after mobile platform started：
Initial frame boundary is detected：Detect the frame boundaries that there may be cell；
Initial carrier frequency is captured:Using the result of first step frame boundary detection, the original position of down-going synchronous physical channel is obtained, frequency acquisition is realized, by carrier frequency offset from Ο ζ range shorters to below 500Hz；
Cell searching and selection；
The search and tracking of multipath signal；
Carrier frequency tracking；
Timing frequency is tracked；
After cell searching and selection and original carrier capture is completed, mobile station just can make carrier frequency tracking using descending CP continuous pilot channel, and surplus page difference Minus is small within 100Hz, full ^i tune needs.The content of the invention is it is an object of the present invention to provide a kind of carrier frequency estimating method and device, to detect that the frequency of crystal oscillator changes and random Doppler frequency deviation, are tracked wherein by the correction to VC0 or NC0 Mean deviation, frequency difference is maintained within tolerance interval.
The technical scheme is that：
A kind of carrier frequency estimating method, it is characterised in that comprise the following steps：
On each arm of Rake receivers, descending CP continuous pilot channel symbol is de-spread；The conjugate multiplication of a despread values on each arm of Rake receivers by despread values with before；Conjugate multiplication value on each arm of Rake receivers is added, plural number is obtainedz=^, P is the phase place for the priority symbol estimated here；
Calculate, obtain the phase place between priority symbol；
Figure IMGF000004_0001
The remaining carrier beat Δ of calculating /=/ (2^7), it is here the duration of a symbol；Δ/feeding loop filter is handled, corresponding frequency control word is calculated；Digital controlled oscillator reads in frequency control word, produces corresponding frequency.
Described refers to the progress despreading of descending CP continuous pilot channel symbol：Descending CP continuous pilot channel symbol is de-spread with the chip of length 128 (chips).
Described conjugate multiplication need to meet following condition：
( + jB ){A2 + JB2Y = (A, +jBx\A2 -jB2) = AXA2 +B,B2 + j(A2B, -Α Β2) wherein： j d .
Described loop filter may include two kinds of configuration modes, and two kinds of described configuration modes can be referred to as configuration mode A and configuration mode B;
Wherein：
Configuration mode A is applied to drop to carrier frequency offset from 500Hz 100Hz situation；Configuration mode B is applied to carrier frequency offset being maintained at below 100Hz situation.
Described use oscillator reads in frequency control word and referred to：Digital controlled oscillator can be used（NC0 frequency control word) is read in.
Described use oscillator reads in frequency control word and referred to：Can be using voltage controlled oscillators such as VCXOs (VCX0)（), VC0 frequency control word is read in.
Qi Bu Sudden of method of the present invention can further comprise： Described conjugate multiplication need to meet following condition：Wherein： j = d
Described loop filter may include configuration mode A and configuration mode B, wherein：Configuration mode A is applied to drop to carrier frequency offset from 500Hz 100Hz situation；Configuration mode B is applied to carrier frequency offset being maintained at below 100Hz situation.
Described use oscillator reads in frequency control word and referred to：Digital controlled oscillator can be used（NC0 frequency control word) is read in.
According to method of the present invention, the step of its loop is controlled includes：
First by configuration mode A, after M subframe terminates, NC0 frequencies E=is calculated,fl,- Δ/;Then use configuration mode B always, in downlink business subframe generation NC0 frequencies in each time slot [-/；+ -/2+ .. -+], NC0 frequencies are not adjusted in sub-frame of downlink synchronization and in uplink service subframe.
Described configuration mode A Bao include Yi Xia Bu Sudden：
Step 1:16 time slots are had in each subframe, front and rear time slot difference can obtain 15 phase places altogether, be calculated as [, φ2,-. -φ5]；
Step 2:Calculate the average phase rotation ^ of the ' individual subframe=+%+... + )/15；Bu Sudden 3:Average phase rotation the ^ "=Shang 5^., parameter Μ for calculating Μ subframe is average to calculate
M
The number of sub frames that phase place is used；
Step 4:Calculating frequency adjustment Δ /=/ (2^), 7 be the time interval between the 16th time slot of a sub- frame in and the 1st time slot here；
Step 5. after M=individual sub- frame end, calculate NC0 frequencies Δs/, after this until M*C/+1) in subframe time, NC0-directly produce frequency, until M*C/+2) after subframe, NC0 produces frequency；Here original frequency/.Determined by the concrete configuration of down coversion；
Bu Sudden 6:Repeat step 1. Described configuration mode B comprises the following steps：
Bu Sudden 1:16 time slots are had in each subframe, front and rear time slot difference can obtain 15 phase places, be calculated as, φ altogether2,·· -φ15；
Step 2:Phase place [by loop filter, is obtained：
Wherein：
¾,=^-,+¾ ^Vl<i<15; .
Here：Κ is loop bandwidth parameter,.Represent subframe16;
Step 3:Corresponding to 16 time slots of next subframe, the NC0 frequencies in each time slot are produced
[-/, + finilial - + ,uial 5· · - 16+ fMUat I ' cause/；=</ (2 *), V1≤≤ 16, T hereSiFor the duration of the time slot, original frequency/; ,„ϊωDetermined by the concrete configuration of down coversion；
Step 4:Repeat step 1.
Present invention also offers a kind of estimating carrier frequencies device, including：Rake receivers, loop filter, oscillator；Wherein：
On each arm of Rake receivers, descending CP continuous pilot channel symbol is de-spread;
The conjugate multiplication of a despread values on each arm of Rake receivers by despread values with before;Conjugate multiplication value on each arm of Rake receivers is added, plural number is obtained2=^4, here for estimation priority symbol phase place；
Calculate<P=arctan (￡ l), obtains the phase place between priority symbol；
Re[z]
Loop filter is will be fed into, corresponding frequency control word is calculated；
Frequency control word is read in using oscillator, corresponding frequency is produced.
Described oscillator can be：Digital controlled oscillator.
Described oscillator can be：Voltage controlled oscillator.
Described voltage controlled oscillator can be：VCXO. The beneficial effects of the present invention are, by providing a kind of carrier frequency estimating method and device, to detect that the frequency of crystal oscillator changes and random Doppler frequency deviation, mean deviation therein is tracked by the correction to VC0 or NC0, frequency difference is maintained within tolerance interval.Brief description of the drawings
Fig. 1 is the frame assumption diagram of TD- LAS systems（Transfer ratio 1 up and down: 1)；
Fig. 2 is the structure chart of descending CP continuous pilot channel subframes；
Fig. 3 realizes block diagram for carrier frequency tracking.Embodiment
The invention provides a kind of carrier frequency estimating method and device, embodiments of the invention are illustrated by taking TD- I S systems as an example below in conjunction with the accompanying drawings：
In TMAS machine systems, ^^ ^ frames ^^ are as shown in figure 1, downstream transmission ratio is 1: 1.
The subframe structure of descending CP continuous pilot channel is as shown in Fig. 2.The descending CP continuous pilot channel of different districts is closed using different LS+LA code characters, and LS code lengths are 136, the S codes of C codes and 64chips comprising 64chips, and 8cliips intervals.Each subframe totally 16 symbols.2 s are included
6 subframes.
In TD-LAS machines, up-downgoing is all using relevant detection, it is desired to accurate carrier wave and Phase synchronization between MS and BS.Emulation shows, in TD- LAS machines, in order to correctly demodulate 16QAM signals, it is desirable to which carrier beat is less than 100Hz.
Crystal oscillator in mobile station is usually some ppm, and several KHz to more than ten KHz carrier beat is produced in 2G frequency ranges.Initial synchronization is after mobile platform started,
Initial frame boundary is detected：Detect the frame boundaries that there may be cell；
Initial carrier frequency is captured：Using the result of first step frame boundary detection, obtain the original position of down-going synchronous physical channel, realize frequency acquisition, by carrier frequency offset from KHz range shorter to 500Hz below；
Cell searching and selection；
The search and tracking of multipath signal； The blunt track of carrier frequency；
Timing frequency is tracked；
Initial frequency difference is reduced within 500Hz-Ι Κ Η ζ by capturing carrier unit, cell identification unit obtains the LA+LS combinations used in this cell.So mobile station just can make carrier frequency tracking using descending CP continuous pilot channel, and residual frequency is reduced within 100Hz, meet demodulation needs.The effect of carrier frequency tracking is the frequency change for detecting crystal oscillator and random Doppler frequency deviation, and mean deviation therein is tracked by the correction to VC0 or NC0, frequency difference is maintained within tolerance interval.
Carrier beat is estimated using difference detector in the algorithm, VC0 is adjusted by feedback control loop.The block diagram of carrier frequency tracking is as shown in figure 3, step is as follows：
Descending CP continuous pilot channel symbol is de-spread with length 128chips on each arm of Rake receivers；- despread values conjugate multiplication on each arm of Rake receivers by despread values with before；Conjugate multiplication value on each arm of Rake receivers is added, plural number is obtainedZ=here P be exactly estimation priority symbol phase place；Calculating=arctan (^), obtains the phase place between priority symbol；
Re[z]
P is sent into loop filter, corresponding frequency control word is calculated；
NC0 or VCX0 reads in frequency control word, produces corresponding frequency
Td represents the time of a time slot in figure.
Conjugate multiplication computing herein is：
(4 +ΛΧΑ + JB2 y = (Al + jB, )(A2 -jB2) = AlA2 +j{A2B{ - A,B2) wherein J'=^T;
Loop filter is described in detail below（LOOP FILTER)：
Loop filter in AFC has two kinds of configuration modes：Configuration mode A is applied to drop to carrier frequency offset from 500Hz 100Hz situation, and configuration mode B is applied to carrier frequency offset being maintained at below 100Hz.
Configuration mode A: Step 1:16 time slots are had in each subframe, front and rear time slot difference can obtain 15 phase places, be calculated as θ altogetherί¾,· . Ψι5]；
Step 2:Calculate the average phase rotation ^+of the subframe)/15；Step 3:The average phase rotation parameter Μ of Μ subframe is calculated to calculate the number of sub frames that average phase rotation is used；
Step 4:Calculate frequency adjustment Δ /=/ (2^7>), 7 be the time interval between the 16th time slot of a sub- frame in and the 1st time slot here；
Step 5:After Μ * _/sub- frame end, calculate NC0 frequencies Δs/, after this until M*+1) in subframe time, NC0-directly produce frequency, until after M* (+2) subframe, NC0 produces frequency:^.Here original frequency/QDetermined by the concrete configuration of down coversion；
Step 6:Repeat step 1.
Configuration mode B:
Bu Sudden 1:16 time slots are had in each subframe, front and rear time slot difference can obtain 15 phase places, be calculated as [φ altogether{ n ];
Step 2:By phase place15] by loop filter, obtain [^, ^, ζ ^, ^, wherein：<PIA ',
K is loop bandwidth parameter, here ζ.Represent the ζ of a subframeδ;
Step 3:Corresponding to 16 time slots of next subframe, the NC0 frequency i-+Λ in each time slot are producedι!αΙ "Λ + ,--fi6+ f rn] ' cause=/(2 *), V1≤≤ 16, T hereSiFor the duration of the time slot, original frequency Λ, ^ are determined by the concrete configuration of down coversion；
Step 4:Repeat step 1.
Automatic frequency is controlled（AFC a kind of loop control during) is as follows： First by loop configuration A, after M subframe terminates, calculating NC0 frequencies τ=Λ,¾.α/— Δ/;Then loop configuration Β is used always, produces NC0 frequencies [- f+F-f in each time slot in lower property service subframe2 +F,-~fl6+ F], NC0 frequencies are not adjusted in sub-frame of downlink synchronization and in uplink service subframe. '
I/O and parameter：
Input：RAKE receiver to D-PIPCH on each time slot, to the despread values of each arm；Output：The tall and erect control word of frequency for adjusting NC0 or VCX0.
Parameter configuration and loop bandwidth in configuration mode A（It is shown in Table 1).
Parameter configuration and loop bandwidth in configuration mode B（It is shown in Table 2).Table 1
Figure IMGF000010_0001
Table 2
Figure IMGF000010_0002
The beneficial effects of the present invention are, by providing a kind of method and device of carrier track, to detect that the frequency of crystal oscillator changes and random Doppler frequency deviation, mean deviation therein is tracked by the correction to VC0 or NC0, frequency difference is maintained within tolerance interval.
It is bright that above embodiment is merely to illustrate this spring, not for limiting the present invention.I.e. narration of the invention is with LAS-CDMA TDD systems（TD-LAS systems）Exemplified by, but its principle is applied to one：Cdma system.

Claims (14)

  1. Claim
    1. a kind of method of carrier track, it is characterised in that comprise the following steps：
    On each arm of Rake receivers, descending CP continuous pilot channel symbol is de-spread；The conjugate multiplication of a despread values on each arm of Rake receivers by despread values with before；By on each arm of Rake receivers conjugate multiplication value be added, obtain plural z- ^, here for estimation priority symbol phase place；P=arctan (￡ l) is calculated, the phase place between priority symbol is obtained；
    Re[z]
    Remaining carrier beat Δ /=ρ/(2 τ 2) is calculated, is here the duration of a symbol；Δ/feeding loop filter is handled, corresponding frequency control word is calculated；Frequency control word is read in using oscillator, corresponding frequency is produced.
    2. according to the method described in claim 1, it is characterised in that described to refer to the progress despreading of descending CP continuous pilot channel symbol：Descending CP continuous pilot channel symbol is de-spread with the chip of length 128.
    3. according to the method described in claim 1, it is characterised in that described conjugate multiplication need to meet following condition：
    ( + 2y = ( +j )( -jB2) = AA2 +B,B2 +j{A2B -AXB2) wherein： j = fl.
    4. according to the method described in claim 1, it is characterised in that described loop filter may include two kinds of configuration modes, two kinds of described configuration modes can be referred to as configuration mode A and configuration mode B;Wherein：
    Configuration mode A is applied to drop to carrier frequency offset from 500Hz 100Hz situation；Configuration mode B is applied to carrier frequency offset being maintained at below 100Hz situation.
    5. according to the method described in claim 1, it is characterised in that described use oscillator reads in frequency control word and referred to：Digital controlled oscillator can be used（NC0 frequency control word) is read in.
    6. according to the method described in claim 1, it is characterised in that described use oscillator reads in frequency control word and referred to：VCXO can be used（The voltage controlled oscillator such as VCX0)（VC0), Read in frequency control word.
    7. according to the method described in claim 1, it is characterised in that its step can further comprise：Described conjugate multiplication need to meet following condition：
    { +BXB2 +j-(A2B -A,B2)
    Figure IMGF000012_0001
    Wherein： j = 1.
    Described loop filter may include configuration mode A and configuration mode B, wherein：Configuration mode A is applied to drop to carrier frequency offset from 500Hz 100Hz situation；Configuration mode B is applied to carrier frequency offset being maintained at below lOQHz situation.
    Described use oscillator reads in frequency control word and referred to：Digital controlled oscillator can be used（NC0 frequency control word) is read in.
    8. method according to claim 7, its ' be characterised by, its loop control Bu Sudden include：First by configuration mode A, after M subframe terminates, calculating NC0 frequencies=Λ, ^- Δs/;Then configuration mode Β is used always, produces NC0 frequencies in each time slot in downlink business subframe
    ^[- +F-f2+F,----fi6+ F], NC0 frequencies are not adjusted in sub-frame of downlink synchronization and in uplink service subframe.
    9. the method according to claim 4 or 6 or 8, it is characterised in that described configuration mode A comprises the following steps：
    Step 1:16 time slots are had in each subframe, front and rear time slot difference can obtain 15 phase places, be calculated as altogether,<¾,·· ·φΧ5]；
    Step 2:The average phase rotation ^-^ of a calculating the/subframe++ ...+^);Step 3:Average phase rotation ^=Shang parameters Μ of Μ subframe is calculated to calculate the number of sub frames that average phase rotation is used；
    Step 4:Calculate frequency adjustment 4^^/(2;^), it is here the time interval between the 16th time slot of a sub- frame in and the 1st time slot；
    Step5：After a M*_/sub- frame end, NC0 frequencies are calculated after this Until M*/'+l) in subframe time, NC0-directly produce frequency/, until M*C+2) after subframe, NC0 produces frequency fj+、；Here original frequency f.Determined by the concrete configuration of down coversion；
    Bu Sudden 6:Repeat step 1.
    10. the method according to claim 4 or 6 or 8, it is characterised in that described configuration mode B comprises the following steps：
    Step 1:16 time slots are had in each subframe, front and rear time slot difference can obtain I altogether5Individual phase place, is calculated as
    Step 2:By phase place by loop filter, obtain：Wherein： Pu = Ψυ-ι +^-/^, l<i<15;Here：κ is loop bandwidth parameter, ^.Represent subframe<¾16；
    Step 3:Corresponding to 16 time slots of next subframe, produce in each time slot C0 frequencies [-+Λ, -/2+Λ, ,… -/16+ ¾..So that/：.=</ (2), ν≤ζ≤16, here TSiFor the duration of a/time slot, original frequency(Determined by the concrete configuration of down coversion；
    Step 4:Repeat step 1.
    11. a kind of device of carrier track, including：Rake receivers, loop filter, oscillator；Wherein：
    On each arm of Rake receivers, descending CP continuous pilot channel symbol is de-spread；The conjugate multiplication of a despread values on each arm of Rake receivers by despread values with before；Conjugate multiplication value on each arm of Rake receivers is added, plural number is obtained2=^4, here for estimation priority symbol phase place；P is calculated, the phase place between priority symbol is obtained；
    Figure IMGF000013_0001
    By ^) feeding loop filter, calculate corresponding frequency control word； Frequency control word is read in using oscillator, corresponding frequency is produced.
    12. device according to claim 11, it is characterised in that described oscillator can be：Digital controlled oscillator.
    13. device according to claim 11, it is characterised in that described oscillator can be：Voltage controlled oscillator.
    14. device according to claim 13, it is characterised in that described voltage controlled oscillator can be：VCXO. '
CN03807993.3A 2003-02-25 2003-02-25 Carrier frequency estimating method and device Pending CN1647430A (en)

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Cited By (3)

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CN101179316B (en) * 2007-11-30 2012-02-29 华为技术有限公司 Clock regulating method, device and access point
CN1917499B (en) * 2006-09-08 2012-05-16 清华大学 Method for solving deviation existed between transmitting and receiving oscillations of crystal in OFDM system
CN111585924A (en) * 2020-03-25 2020-08-25 北京理工大学 Frequency offset correction method and receiver

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US8184675B2 (en) 2006-07-12 2012-05-22 Telefonaktiebolaget L M Ericsson (Publ) Residual frequency offset exploitation
US7809344B2 (en) * 2006-07-20 2010-10-05 Industrial Technology Research Institute Fractional carrier frequency offset estimator and method of estimating fractional carrier frequency offset between transmitter and receiver
CN113311225B (en) * 2021-05-06 2022-03-04 武汉大学 Method for estimating LTE residual carrier frequency deviation

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US6363102B1 (en) * 1999-04-23 2002-03-26 Qualcomm Incorporated Method and apparatus for frequency offset correction
JP2001016135A (en) * 1999-06-29 2001-01-19 Nec Corp Method and system for automatically controlling frequency and cdma receiver
CN1114291C (en) * 2000-09-05 2003-07-09 华为技术有限公司 Frequency deviation estimation method applicable to code division multiple address access system

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CN1917499B (en) * 2006-09-08 2012-05-16 清华大学 Method for solving deviation existed between transmitting and receiving oscillations of crystal in OFDM system
CN101179316B (en) * 2007-11-30 2012-02-29 华为技术有限公司 Clock regulating method, device and access point
CN111585924A (en) * 2020-03-25 2020-08-25 北京理工大学 Frequency offset correction method and receiver

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