CN106850483A - A kind of phase error estimation method and device for wireless communication system - Google Patents
A kind of phase error estimation method and device for wireless communication system Download PDFInfo
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- CN106850483A CN106850483A CN201610795854.2A CN201610795854A CN106850483A CN 106850483 A CN106850483 A CN 106850483A CN 201610795854 A CN201610795854 A CN 201610795854A CN 106850483 A CN106850483 A CN 106850483A
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- phase error
- error estimation
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- estimation method
- pilot
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2691—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation involving interference determination or cancellation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2692—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
- H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
- H04L27/3872—Compensation for phase rotation in the demodulated signal
Abstract
The invention discloses a kind of phase error estimation method and device for wireless communication system.In the phase error estimation method, the pilot tone on pilot sub-carrier is extracted from transmission signal, pilot tone is descrambled；Deflect to calculate common phase error using the phase across multiple frequency pilot signs, carry out averagely removing the influence of noise, obtain the phase error estimation and phase error value in predetermined OFDM symbol.Compared with prior art, phase error estimation method provided by the present invention and device across multiple frequency pilot signs using by the way of calculating phase deflection and long-term smoothing processing, can effectively lifting the precision of phase error estimation and phase error.
Description
Technical field
The present invention relates to a kind of phase error estimation method, more particularly to a kind of radio communication used in using OFDM technology
In system (referred to as ofdm system), estimated based on the phase deflection to frequency pilot sign, realize the side of phase error estimation and phase error
Method, also relates to corresponding phase error estimation and phase error device, belongs to wireless communication technology field.
Background technology
In wireless communication technology, the difference between phase and desired phase after transmission signal is demodulated is referred to as phase
Position error.In the receiving terminal of wireless communication system, in order to lift the radiofrequency characteristicses of receptivity and analysis transmitting terminal, it is necessary to take
Effective technical measures carry out high-precision estimation and compensation to phase error.
On the other hand, in current 4G wireless communication systems, OFDM (Orthogonal Frequency Division
Multiplexing, OFDM) technology is a kind of physical-layer techniques of main flow.Its technical characterstic is by sub- load
The orthogonal overlap of ripple, has saved protection sub-carrier resources, improves spectrum efficiency.Compared with conventional radio transmission technology,
Ofdm system also has the following advantages that：(1) good mitigating frequency-selective fading characteristic, (2) channel equalization is fairly simple.
Although ofdm system has above-mentioned advantage, for the overall performance of ofdm system, topmost influence
One of factor is the nonideal characteristic of the oscillator of transmitting terminal and receiving terminal.In transmitting terminal, become through on the signal demand of ovennodulation
Frequency is radiofrequency signal.In receiving terminal.It is intermediate frequency or baseband signal that radiofrequency signal will be downconverted.Transmitting terminal and receiving terminal shake
Swing often variant between the frequency of device output, by after the correcting frequency deviation of receiving terminal, it is also possible to can there is remaining frequency deviation,
There is a common phase error in this OFDM symbol that will be received at each, so as to have a strong impact on receptivity.
For the phase error estimation and phase error in ofdm system, conventional method is to be embedded in known leading in the transmitted signals at present
Frequently, the feature that receiving terminal is showed according to the pilot tone for receiving, calculates common phase error.Samsung Electronics Co., Ltd is special
Profit number for ZL 200410084932.5 Chinese patent in just employ this conventional method.That is, using receiving front and rear two
Individual frequency pilot sign carries out related operation, obtains the phase error between former and later two OFDM symbols, then carries out multiple phase mistakes
It is poor average to lift estimated accuracy.In the method, the reason for choosing former and later two frequency pilot signs as basic operation group be
In view of the time-varying characteristics of channel, the degree of correlation highest between adjacent-symbol in time.
In addition, in the Chinese patent application of Publication No. CN 101594338A, disclosing a kind of for reducing public phase
The method and device of position error.The method comes together to participate in difference estimation using the data symbol and frequency pilot sign after hard decision,
To tackle multipath effect.Wherein when data symbol is selected, the judgement of annoyance level is also carried out, selected disturbed degree less
Symbol is lifting the degree of accuracy of phase error estimation and phase error.But, need to carry out the hard judgement of data symbol in the method so that for
The estimation of common phase error must increased the complexity of receiving terminal sequential after data demodulation.
The content of the invention
In view of the shortcomings of the prior art, primary technical problem to be solved by this invention is to provide a kind of for channel radio
The phase error estimation method of letter system.
Another technical problem to be solved by this invention is to provide a kind of phase error for wireless communication system to estimate
Counter device.
For achieving the above object, the present invention uses following technical schemes：
First aspect according to embodiments of the present invention, there is provided a kind of phase error estimation method, used in using OFDM technology
Wireless communication system in, comprise the following steps：
The pilot tone on pilot sub-carrier is extracted from transmission signal, the pilot tone is descrambled；
Deflected using the phase across multiple frequency pilot signs and calculate common phase error, carry out averagely removing the shadow of noise
Ring, obtain the phase error estimation and phase error value in predetermined OFDM symbol.
Wherein more preferably, for the measurement result of multiple packets, length of the common phase error in time domain is carried out
Phase smoothing processing.
Wherein more preferably, the phase error estimation method is used in the application scenarios of non-real-time service.
Wherein more preferably, for short packages, the number of institute's mutual conductance frequency symbol is relatively small to have enough numbers with guarantee
According to right；For packet long, the relatively large precision improvement to obtain under large span of number of institute's mutual conductance frequency symbol.
Second aspect according to embodiments of the present invention, there is provided a kind of phase error estimation and phase error device, used in using OFDM technology
Wireless communication system in, including signal receiving unit, computing unit and output unit；Wherein,
The signal receiving unit extracts the pilot tone on pilot sub-carrier from transmission signal；
The computing unit descrambles to the pilot tone, is deflected using the phase across multiple frequency pilot signs public to calculate
Phase error, carries out averagely removing the influence of noise, obtains the phase error estimation and phase error value in predetermined OFDM symbol；
The computing unit externally exports the phase error estimation and phase error value by the output unit.
Wherein more preferably, the computing unit carries out the common phase error for the measurement result of multiple packets
Long-term smoothing processing in time domain.
Compared with prior art, phase error estimation method provided by the present invention and device are used across multiple pilot tones symbol
Number calculate the mode of phase deflection and long-term smoothing processing, can effectively lift the precision of phase error estimation and phase error.
Specific embodiment
Detailed specific description is launched to technology contents of the invention with reference to specific embodiment.
In the 4G wireless communication systems using OFDM technology, largely there are the application scenarios of non-real-time service.For example,
Wi-Fi testers carry out the application scenarios of reception processing to Wi-Fi signal to be measured；Magnanimity number is downloaded by ofdm signal
According to application scenarios etc..In these application scenarios not high to signal transacting requirement of real-time, the present invention is used and led across multiple
Frequency symbol calculates the mode of phase deflection and long-term smoothing processing, can effectively lift the precision of phase error estimation and phase error.
Below to this by taking the application scenarios that Wi-Fi testers carry out reception processing to Wi-Fi signal to be measured as an example
The there is provided phase error estimation method of invention is illustrated.
Assuming that there are multiple pilot sub-carriers known to receiving terminal in transmission signal, Wi-Fi testers are to IEEE
In the measurement of 802.11a signals, for i-th OFDM symbol (i is positive integer, similarly hereinafter) for receiving, 4 pilot tones are extracted respectively
Pilot tone on subcarrier.For example extract pilot tone on pilot sub-carrier { -21, -7,7,21 } respectively.In other embodiments
In, the pilot tone of diverse location can also be extracted on the pilot sub-carrier of varying number (such as 6 or 8), just differ herein
One illustrates.
After the pilot tone to above-mentioned extraction descrambles, it is possible to use LS (least square) methods or other are similar
Method such as MMSE (least mean-square error) estimates common phase deviation Ii.Specifically,
It is as follows firstly, for the actual signal modeling for receiving：Wherein r (t) for receive signal, x (t), h (t) andRespectively
It is transmission signal, channel impulse response and common phase deviation, and n (t) is white noise.
Secondly, the time-domain signal of i-th OFDM symbol in signal is received, by FFT to frequency domain presentation, it can be obtained
K-th value of pilot sub-carrier (k is positive integer)：
Ri(k)=Xi(k)·Hi(k)·Ii,k∈[-N/2,N/2] (2)
Finally, using LS methods, the common phase deviation I in i-th OFDM symbol can be obtainedi, wherein SPIt is pilot tone
The set of carrier wave.
Because the pilot sub-carrier number in an OFDM symbol is typically very limited, therefore above-mentioned computational methods may
Can be not high enough due to precision, it is impossible to fully meet the requirement of receiving terminal.In order to lift the certainty of measurement for common phase error,
Phase error estimation method provided by the present invention further employs following two Optimized Measures on the basis of above-mentioned steps：
(1) deflect to calculate common phase error using the phase across multiple frequency pilot signs, carry out averagely removing noise
Influence.
The deflection of the phase of frequency pilot sign is estimated, phase error estimation and phase error is realized
In view of the influence very little of time varying channel in the application scenarios of non-real-time service, and requirement of real-time is low, therefore
Can further deflect by calculating across multiple frequency pilot signs phase and carry out averagely to remove the influence of noise.Led across m
The algorithm principle of frequency symbol such as formula (4) and (5), wherein Δ I is the phase deflection difference between adjacent pilot symbols, NsIt is whole data
Symbol numbers in bag, with the addition of lower target IiThe value in i-th OFDM symbol is then represented, m represents positive integer.
Ii=i Δs I (5)
, it is necessary to select the suitable m values to carry out the calculating of Δ I in above-mentioned Optimized Measures.Selected principle is：For short
Packet, m values are answered relatively small to ensure having enough data pair；For packet long, larger m values can be selected to obtain
Take the precision improvement under large span.
It should be noted that above-mentioned formula (3) is each OFDM symbol calculates a phase error, i.e. Ii.But only
The I calculated by formula (3)iAccuracy may be not high enough.Therefore, in the present invention further with formula (4) and
(5), by by all of I on the basis of formula (3) result of calculationiAfter carrying out averagely, then export a new Ii.Formula (5)
The I being calculatediCan be than the I in formula (3)iIt is more accurate.
(2) for the measurement result of multiple packets, long-term smoothing processing of the common phase error in time domain is carried out.
In the Optimized Measures, measured piece often needs to send multiple packets to obtain some measurement amounts in make use of measurement
The characteristics of, the certainty of measurement for common phase error is further increased, its algorithm can have many kinds, such as formula (6) institute
Single Exponential Smoothing for showing etc..Subscript st and lt, p is with the addition of in formula (6) to characterize currency and on p-th packet
Long-term smooth value, wherein p is positive integer, and α is smoothing constant, and its span is [0,1].
ΔIlt,p=α Δs Ist+(1-α)·ΔIlt,p-1 (6)
Further, I is usedi=i Δs Ilt,pObtain the phase error estimation and phase error value in i-th OFDM symbol.The phase is missed
Difference estimate is the optimum results obtained using phase error estimation method provided by the present invention.As can be seen here, pass through
Above-mentioned Optimized Measures can realize high-precision phase error estimation and phase error.
It should be noted that the Single Exponential Smoothing used in above-mentioned long-term smoothing processing is by way of example only, it is real
Other smoothing processing algorithms, such as Secondary Exponential Smoothing Method, third index flatness or kernel can also be used to put down in trampling
Sliding method etc., does not just repeat one by one herein.
On the basis of above-mentioned phase error estimation method, invention further provides a kind of phase error estimation and phase error dress
Put.The phase error estimation and phase error device includes signal receiving unit, computing unit and output unit.Wherein, signal receiving unit from
The pilot tone on pilot sub-carrier is extracted in transmission signal；Computing unit is obtained after these pilot tones, and they are descrambled；Use
Common phase error is calculated across the phase deflection of multiple frequency pilot signs, is carried out averagely to remove the influence of noise, wherein for
The measurement result of multiple packets, carries out long-term smoothing processing of the common phase error in time domain；By above-mentioned steps, obtain
Phase error estimation and phase error value in i-th OFDM symbol.Computing unit is obtained after above-mentioned phase error estimation and phase error value, by above-mentioned
Output unit is externally exported.
Above by taking the application scenarios in Wi-Fi testers as an example, principle of the invention and implementation method are described.This hair
Bright to be primarily adapted for use in the application scenarios not high to signal transacting requirement of real-time, such as Wi-Fi testers are carried out to common phase
The scene of accurate estimation, common phase error measurement scene of ofdm modulation signal etc., as long as receiving terminal can be utilized fully
Whole packet information carries out the estimation of common phase error.It should be noted that above-mentioned specific embodiment should be regarded
For illustrative and not restrictive, the present invention should not be considered limited to above-mentioned specific embodiment.Received in other ofdm systems
In scene and measurement scene, specific embodiment of the invention can be changed accordingly.
The phase error estimation method and device for wireless communication system provided by the present invention has been carried out in detail above
Thin explanation.For one of ordinary skill in the art, it is done on the premise of without departing substantially from true spirit
Any obvious change, will all belong to the protection domain of patent right of the present invention.
Claims (7)
1. a kind of phase error estimation method, in the wireless communication system using OFDM technology, it is characterised in that including such as
Lower step：
The pilot tone on pilot sub-carrier is extracted from transmission signal, the pilot tone is descrambled；
Deflect to calculate common phase error using the phase across multiple frequency pilot signs, carry out averagely to remove the influence of noise,
Obtain the phase error estimation and phase error value in predetermined OFDM symbol.
2. phase error estimation method as claimed in claim 1, it is characterised in that：
For the measurement result of multiple packets, long-term smoothing processing of the common phase error in time domain is carried out.
3. phase error estimation method as claimed in claim 1 or 2, it is characterised in that：
The phase error estimation method is used in the application scenarios of non-real-time service.
4. phase error estimation method as claimed in claim 1 or 2, it is characterised in that：
For short packages, the number of institute's mutual conductance frequency symbol is relatively small to have enough data pair with guarantee；For data long
Bag, the relatively large precision improvement to obtain under large span of number of institute's mutual conductance frequency symbol.
5. a kind of phase error estimation and phase error device, in the wireless communication system using OFDM technology, it is characterised in that including letter
Number receiving unit, computing unit and output unit；Wherein,
The signal receiving unit extracts the pilot tone on pilot sub-carrier from transmission signal；
The computing unit descrambles to the pilot tone, deflects to calculate common phase using the phase across multiple frequency pilot signs
Error, carries out averagely removing the influence of noise, obtains the phase error estimation and phase error value in predetermined OFDM symbol；
The computing unit externally exports the phase error estimation and phase error value by the output unit.
6. phase error estimation and phase error device as claimed in claim 5, it is characterised in that：
The computing unit carries out the common phase error long-term flat in time domain for the measurement result of multiple packets
Sliding treatment.
7. phase error estimation method as claimed in claim 1 or phase error estimation and phase error device as claimed in claim 5, its
It is characterised by：
In the transmitted signals, there are multiple pilot sub-carriers known to receiving terminal.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111224765A (en) * | 2020-01-08 | 2020-06-02 | 中国科学院计算技术研究所 | Pilot frequency sequence generation method and corresponding signal transmitting and receiving method and device |
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| CN105490980A (en) * | 2015-12-11 | 2016-04-13 | 航天恒星科技有限公司 | Carrier wave frequency deviation estimation method and system |
| US20160197710A1 (en) * | 2009-12-07 | 2016-07-07 | Qualcomm Incorporated | Enabling phase tracking for a communication device |
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| CN101499991A (en) * | 2009-03-17 | 2009-08-05 | 广东工业大学 | MIMO-OFDM system carrier frequency bias and sampling offset combined estimation method under IQ unbalance |
| US20160197710A1 (en) * | 2009-12-07 | 2016-07-07 | Qualcomm Incorporated | Enabling phase tracking for a communication device |
| CN102739579A (en) * | 2011-04-06 | 2012-10-17 | 普天信息技术研究院有限公司 | Frequency offset correction method |
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| CN111224765A (en) * | 2020-01-08 | 2020-06-02 | 中国科学院计算技术研究所 | Pilot frequency sequence generation method and corresponding signal transmitting and receiving method and device |
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