CN100571084C - A kind of new OFDM frequency synchronization method based on training sequence - Google Patents
A kind of new OFDM frequency synchronization method based on training sequence Download PDFInfo
- Publication number
- CN100571084C CN100571084C CNB031179703A CN03117970A CN100571084C CN 100571084 C CN100571084 C CN 100571084C CN B031179703 A CNB031179703 A CN B031179703A CN 03117970 A CN03117970 A CN 03117970A CN 100571084 C CN100571084 C CN 100571084C
- Authority
- CN
- China
- Prior art keywords
- training sequence
- frequency
- ofdm
- synchronous
- time
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Landscapes
- Synchronisation In Digital Transmission Systems (AREA)
Abstract
The invention discloses a kind of new OFDM frequency synchronization method based on training sequence.Making a start is superimposed upon training sequence on the OFDM useful data, and receiving end utilizes the correlation of received signal and known training sequence to carry out frequency rough simultaneous operation, and it is synchronously smart for the first time to use Cyclic Prefix to do frequency simultaneously; Suppress the operation that the OFDM data are disturbed training, reconstruct training sequence more accurately, do again that frequency is synchronously smart for the second time at receiving terminal.This kind method for synchronous had both overcome the less shortcoming of legacy frequencies method for synchronous frequency acquisition scope based on Cyclic Prefix, also suppressed widely based on the interference of the legacy frequencies method for synchronous training sequence of training sequence, thereby can obtain Frequency Synchronization effect preferably by the good correlation properties of training sequence to the OFDM data.
Description
Technical field
The invention belongs to communication technical field, particularly in the communication technology based on the frequency synchronization method of training sequence.
Background technology
OFDM is owing to have the message transmission rate height, and the anti-multipath interference performance is strong, and the spectrum efficiency advantages of higher more and more comes into one's own.It has been successfully applied to wired, radio communication.As: ADSL (Asymmetric Digital Subscriber Line), Wireless LAN is among DAB (Digital Audio Broadcasting), DVB, IEEE802.11a and the HyperLAN/2.In the IEEE802.16 that is formulating at present, also related to the OFDM technology in large quantities.This new modulation technique of OFDM also can be applicable in the mobile communication system of a new generation.Use the OFDM technology will improve the transmission data rate and the spectrum efficiency of the third generation mobile communication system widely, and have good anti-multipath, cochannel interference and impact noise ability and see document: Bingham, J.A.C., " Multicarrier modulation for data transmission:an idea whose time has come; " IEEECommunications Magazine, Volume:28Issue:5, May 1990, Page (s): 5-14; And document: Yun Hee Kim; IickhoSong; Hong Gil Kim; Taejoo Chang; Hyung Myung Kim, " Performance analysis of a coded OFDM system intime-varying multipath Rayleigh fading channels; " Vehicular Technology, IEEE Transactions on, Volume:48 Issue:5, Sept.1999, Page (s): 1610-1615 is described.
In ofdm system, Frequency Synchronization is the technology of a key, and the purpose of Frequency Synchronization is to obtain and correct the frequency shift (FS) of receiving end, and the module 1 among Fig. 1 is seen in the position of synchronization module.One of weakness of OFDM technology is more much higher than single-carrier system to synchronous requirement.The general system of employing OFDM technology that requires is no more than 2% of its subcarrier spacing in the receiving terminal frequency shift (FS), and content sees document van de Beek, J.J. for details; Sandell, M.; Borjesson, P.O., " ML estimation of time and frequencyoffset in OFDM systems; " Signal Processing, IEEE Transactions on, Volume:45Issue:7, July 1997, Page (s): 1800-1805.
Conventional OFDM frequency synchronization method has three kinds:
1. utilize the intersymbol correlation of Cyclic Prefix and OFDM, can realize Frequency Synchronization.Referring to document van de Beek, J.J.; Sandell, M.; Borjesson, P.O., " ML estimation of time and frequency offset in OFDM systems; " Signal Processing, IEEE Transactions on, Volume:45 Issue:7, July 1997, Page (s): 1800-1805.
2. make a start and fill the OFDM symbol, following two kinds of filling modes can be arranged: a) training sequence is placed in the Cyclic Prefix of OFDM with training sequence; B) training sequence is placed on the Cyclic Prefix of OFDM before.Receiving terminal carries out Frequency Synchronization according to the correlation of received signal and known training sequence then.
3. making a start is superimposed upon training sequence on the OFDM useful data, and receiving end is carried out Frequency Synchronization according to the correlation of received signal and known training sequence.Referring to document Tufvesson, F.; Edfors, O.; Faulkner, M., Time andfrequency synchronization for OFDM using PN-sequence preambles; " Vehicular TechnologyConference, 1999.VTC 1999-Fall.IEEE VTS 50th, Volume:4,1999, Page (s): 2203-2207.
Yet the synchronous method for designing of above-mentioned OFDM all has shortcoming, and method shortcoming 1. is that the correlation peak of receiving end is not obvious, and the scope of its frequency offset estimating has only 1/2 of ofdm system subcarrier spacing.Method shortcoming 2. is to be time-division (perhaps frequency division) multiplexed form between training sequence and the OFDM initial data that this has caused the decline of data transmission efficiency.Method shortcoming 3. is that training sequence is excessive to the data interference, and the energy efficiency of emission data is lower.
Summary of the invention
Task of the present invention provides a kind of high performance frequency synchronization method based on training sequence, promptly adopts method of the present invention, can overcome many shortcomings of conventional method, thereby can obtain synchronous effect preferably by the good correlation properties of training sequence.
Innovation part of the present invention is: 1. at first training sequence is superimposed upon on the OFDM useful data making a start, receiving end utilizes the correlation of received signal and known training sequence to carry out frequency rough simultaneous operation, and it is synchronously smart for the first time to use Cyclic Prefix to do frequency simultaneously; 2. pass through frequency rough synchronously and for the first time frequency smart synchronously after, suppress the OFDM data to the operation that training sequence disturbs, reconstruct training sequence more accurately at receiving terminal then, do again that frequency is synchronously smart for the second time.Its Frequency Synchronization performance is better than conventional method.
According to a kind of new OFDM frequency synchronization method based on training sequence of the present invention, transmitting terminal comprises:
Step 1 as shown in Figure 2, c represents that useful length is the training sequence signal of N, d represents that useful length is the OFDM data-signal of N, and training sequence and OFDM data-signal are carried out the power normalization processing respectively, makes the power of training sequence and OFDM data be respectively ρ and 1-ρ.
It is characterized in that receiving terminal comprises following step:
Step 4 for the first time frequency is synchronously smart: shown in Fig. 3 module 8, the smart synchronous function of frequency is for the first time, the fractional part after utilizing Cyclic Prefix emending frequency deviation with respect to sub-carrier separation Δ f normalization.
Step 5 suppresses the influence of OFDM data to training sequence: as shown in Figure 3, synchronous and the smart synchronous result of the frequency first time according to frequency rough, to carrying out frequency correction 9 through the signal behind the module 2 removal protection time slots, finish the demodulation function of multi-carrier modulation then through FFT conversion module 3, obtain signal R; Carry out OFDM data and training sequence lock out operation then, promptly reconstruct earlier and receive the OFDM data-signal
From total received signal r ', deduct the OFDM data-signal that reconstructs then
Just obtained the training sequence in the received signal, through after the aforesaid operations, the OFDM data-signal of receiving terminal and training sequence is separated comes, the OFDM data-signal has been reduced widely to the interference of training sequence.
Need to prove that before receiving terminal carried out frequency rough synchronizing step 3, received signal had obtained time synchronized.
From above-mentioned steps as can be seen, adopt frequency synchronization method of the present invention, promptly can overcome the shortcoming that adopts Cyclic Prefix to carry out simultaneous operation in the conventional method, also can overcome the shortcoming that adopts training sequence to carry out simultaneous operation in the conventional method, make system obtain higher Frequency Synchronization performance.
Description of drawings
Fig. 1 is traditional operation of receiver schematic diagram based on training sequence
Wherein, the 1st, lock unit, the 2nd, remove protection time slot unit, the 3rd, FFT unit, the 4th, channel estimating unit, the 5th, channel fading compensating unit, the 6th, data demodulates and decision unit.
Fig. 2 is the stacked system figure of training sequence and OFDM data in the transmitter of this patent.
Wherein, c represents the training sequence signal, and d represents the OFDM data-signal,
Be the amplitude factor of training sequence,
Amplitude factor for the OFDM data-signal.
Fig. 3 is the receiver structure block diagram in this patent.
Wherein, the 7th, the frequency rough lock unit, the 8th, the smart lock unit of frequency for the first time, the 9th, frequency correction unit, the 10th, rebuild and receive the OFDM data cell, the 11st, the smart lock unit of frequency for the second time.R represents received signal, and the received signal after the protection prefix is got rid of in r ' expression, and R represents the received signal after the demodulation of process multicarrier,
The reception OFDM data-signal that expression reconstructs.
Fig. 4 is the synchronous and smart synchronization structure block diagram of the frequency first time of frequency rough that adopts in the embodiment.
Wherein, the 12nd, received signal and local training sequence correlation unit, the 13rd, frequency rough synchronous difference relevant treatment unit, the 14th, ask the unit, phase angle, the 15th, normalization unit, the 16th, the smart synchronous difference relevant treatment of frequency unit (correlation length is different with module 13 with the difference distance) for the first time.K represents the relevant treatment length of received signal and local training sequence, Ω and N represent the synchronous and smart synchronous difference distance of the frequency first time of frequency rough respectively, Γ and G represent the synchronous and smart synchronous difference processing length of the frequency first time of frequency rough respectively, τ represents time delay, ξ (n, τ) and ζ (n τ) represents the frequency rough smart synchronous final relevant treatment result of frequency synchronously and for the first time respectively, Δ f represents subcarrier spacing, and f represents the Frequency offset estimation result.
Fig. 5 is the block diagram that the reconstruction adopted in the embodiment receives the OFDM data-signal.
Wherein, the 17th, time delay unit, the 18th, CAZAC sequence generator, the 19th, IFFT unit, the 20th, the frequency shift (FS) unit that frequency rough is synchronous and the first time, time synchronized obtained.λ is the part interference cancellation factor by the decision of channel estimating confidence level
Fig. 6 is the implementation step block diagram of this patent.
Embodiment:
Below to provide a concrete OFDM configuration down, the performing step of this patent.Need to prove down that the parameter in the example does not influence the generality of this patent.
If the useful symbol lengths of OFDM is N=4096, the protection gap length is G=1024.Training sequence selects to have the CAZAC sequence of good period correlation properties and normal amplitude characteristic.
At transmitting terminal: to useful length is that the training sequence signal of N and OFDM data-signal that useful length is N carry out power normalization respectively and handle, and makes the power of training sequence and OFDM data be respectively ρ and 1-ρ; Then with this training sequence signal therewith ofdm signal superpose at transmitting terminal, be transmitted into channel after adding the protection prefix, carry out Frequency Synchronization handle before our hypothesis obtained time synchronized, i.e. τ=0.
At receiving terminal: 1. as shown in Figure 3, at first carry out frequency rough synchronous 7 and frequency smart synchronous 8 for the first time, concrete steps are referring to Fig. 4, received signal r (n) is carried out relevant treatment operations through unit 12 and local training sequence, the relevant treatment length K is less than N, and then carry out the difference relevant treatment that spacing is Ω through unit 13, relevant treatment length is Γ, after above two step operations, obtain decision signal ξ (n, τ), through asking unit, phase angle 14, obtain corresponding frequency departure, frequency departure is carried out normalized 15 to sub-carrier separation Δ f, get final product the integer part of emending frequency deviation; Simultaneously received signal is done the difference relevant treatment of ordering at a distance of N through unit 16, relevant treatment length is G, and (n τ), through asking unit, phase angle 14, obtains corresponding frequency departure, gets final product the fractional part of emending frequency deviation to obtain decision signal ζ.2. then as Fig. 3, according to the frequency rough smart synchronous result of frequency synchronously and for the first time, the signal of removing through unit 2 behind the protection time slots is carried out frequency correction 9, finish the demodulation function of multi-carrier modulation then through FFT converter unit 3, obtain signal R.3. once more, rebuild the operation of receiving terminal OFDM data-signal, i.e. the function finished of module 10, concrete steps are referring to Fig. 5: extract guidance information and 4 carry out the first-order linear channel estimating in the unit from sequence R; Carry out the reconstruction of training sequence received signal simultaneously, promptly produce the CAZAC sequence of making a start used by training sequence generator unit 18 earlier, the sequence that produces be multiply by amplitude factor
Training sequence after will rebuilding then and channel estimation results and part interference cancellation factor lambda multiply each other, from sequence R, deduct this result of product again, promptly finish part and disturb right function, reduce the interference of training sequence, just obtained than direct demodulation data message more accurately to data-signal; The output result of this data message and channel estimation module is got reciprocal multiplication, just remove the channel fading of data message, the signal after the compensation is by data demodulates and decision unit 6 outputs; The result that will export then multiply by amplitude factor again through IFFT converter unit 19
Channel estimation results multiplies each other with frequency shift (FS) unit 20 then, carries out frequency offset compensation, obtains signal
Finish the reconstruction of receiving terminal OFDM data-signal.4. from total received signal, deduct the OFDM data-signal that reconstructs then, the training sequence signal that has just obtained receiving terminal has been eliminated training sequence that the OFDM data-signal disturbs in that to carry out second time frequency smart synchronous with this at last, it is the function that unit 11 is finished among Fig. 3, synchronizing process is identical with unit 7, just obtains more accurate Frequency Synchronization effect.
Claims (1)
1, a kind of new OFDM frequency synchronization method based on training sequence, transmitting terminal comprises:
Step 1 a couple training sequence symbols c and an OFDM data symbol d carry out power normalization respectively to be handled, make the power of training sequence and OFDM data be respectively ρ and 1-ρ, c represents that a length is the training sequence symbols of N, and d represents the OFDM data symbol that a length is N;
Step 2 superposes training sequence symbols c and OFDM symbol d then at transmitting terminal, be transmitted into channel after the interpolation protection prefix;
It is characterized in that the step below receiving terminal comprises:
Step 3 frequency rough is synchronous: frequency rough is the correlation that module (7) is utilized receiving terminal received signal and local training sequence synchronously, the integer part of correcting frequency shift deviation after with respect to sub-carrier separation Δ f normalization;
Step 4 frequency for the first time is synchronously smart: the frequency essence is the fractional part after module (8) utilizes Cyclic Prefix emending frequency deviation with respect to sub-carrier separation Δ f normalization synchronously for the first time;
Step 5 suppresses the influence of OFDM data to training sequence: the synchronous and smart synchronous result of the frequency first time according to frequency rough, to carrying out frequency correction (9) through the signal behind module (2) the removal protection time slot, pass through FFT conversion module (3) then and finish the demodulation function of multi-carrier modulation, obtain signal R; Carry out OFDM data and training sequence lock out operation then, promptly reconstruct earlier and receive the OFDM data-signal
From total received signal r ', deduct the OFDM data-signal that reconstructs then
Just obtained the training sequence in the received signal;
Step 6 frequency for the second time is synchronously smart: module (11) utilizes the training sequence that obtains in the step 5 to carry out the smart simultaneous operation of the frequency second time, and method for synchronous is identical with step 3.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031179703A CN100571084C (en) | 2003-05-30 | 2003-05-30 | A kind of new OFDM frequency synchronization method based on training sequence |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031179703A CN100571084C (en) | 2003-05-30 | 2003-05-30 | A kind of new OFDM frequency synchronization method based on training sequence |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1553604A CN1553604A (en) | 2004-12-08 |
| CN100571084C true CN100571084C (en) | 2009-12-16 |
Family
ID=34320710
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB031179703A Expired - Fee Related CN100571084C (en) | 2003-05-30 | 2003-05-30 | A kind of new OFDM frequency synchronization method based on training sequence |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100571084C (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100361424C (en) * | 2005-05-13 | 2008-01-09 | 北京航空航天大学 | Data transmitting method in short-distance radio network |
| CN1980210B (en) * | 2005-12-08 | 2010-11-10 | 北京邮电大学 | Method for realizing sign blind synchronization in zero-prefix orthogonal frequency-division multiplexing system |
| CN101277290B (en) * | 2007-03-26 | 2011-01-26 | 富士通株式会社 | Method and apparatus for synchronization of orthogonal frequency division multiplexing system frequency |
| CN101022443B (en) * | 2007-03-26 | 2010-05-26 | 重庆邮电大学 | OFDM frequency-offset estimating method based on allocycly adjacent structure |
| CN101340416B (en) * | 2008-08-28 | 2011-02-16 | 北京交通大学 | Synchronization and channel response estimation method suitable for OFDM system |
| CN101667990B (en) * | 2009-07-23 | 2012-07-04 | 中国科学院微电子研究所 | OFDM frequency offset joint estimation method |
| CN103067094A (en) * | 2013-01-04 | 2013-04-24 | 南京信息工程大学 | Self-adaption interference cancellation method and device for improving cancellation bandwidth |
-
2003
- 2003-05-30 CN CNB031179703A patent/CN100571084C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CN1553604A (en) | 2004-12-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN100561999C (en) | A kind of MIMO-OFDM system method for synchronous | |
| CN102148785B (en) | Methods and devices for detecting main synchronous signal and generating sequence in LTE (Long Term Evolution) system | |
| CN101083645B (en) | Low complexity OFDM quick synchronising method | |
| CN1988525B (en) | Synchronizing method for orthogonal frequency division multiplex system | |
| CN102223696B (en) | Cell searching method in LTE (long term evolution) system | |
| CN100481826C (en) | Transmitting and receiving method for signal of orthogonal frequency division multiplexing system | |
| CN101431497B (en) | Multi-antenna signal transmission method adopting time domain and frequency domain combined orthogonal frequency division multiplexing | |
| CN101005307B (en) | Synchronizing method for broad band time division duplex honey comb system and cell primary searching | |
| CN101277290B (en) | Method and apparatus for synchronization of orthogonal frequency division multiplexing system frequency | |
| CN101827052B (en) | Method and device for time synchronization and frequency synchronization of LTE system | |
| CN107086974A (en) | A kind of OFDM synchronous method under high dynamic environment | |
| CN104168224B (en) | Offset estimation and compensation method | |
| CN102761957A (en) | Method for realizing initial synchronization of TD-LTE (Time Division-Long Term Evolution) digital relay technology | |
| CN105245481A (en) | Apparatus and method for obtaining symbol timing synchronization robust to frequency offset in cell search of wireless communication system | |
| CN101841507B (en) | Method and device for generating primary synchronous channel sequence and multi-antenna transmitting method of primary synchronous channel sequence | |
| CN101119350A (en) | OFDM system, fast synchronous method and sending terminal equipment | |
| CN100499622C (en) | OFDM time and frequency synchronization method | |
| CN100571084C (en) | A kind of new OFDM frequency synchronization method based on training sequence | |
| CN102158453A (en) | OFDM (Orthogonal Frequency Division Multiplexing) physical layer system under Mesh mode implemented on basis of IEEE802.16d/e | |
| CN100483978C (en) | OFDM frequency synchronizing method at multi-path channel | |
| CN101883067A (en) | Training sequence construction and synchronization algorithm suitable for OFDM time synchronization | |
| CN102832981B (en) | A kind of method and apparatus for determining time synchronized position | |
| CN101001236A (en) | Parallel training sequence design method | |
| CN101282128A (en) | Method for reinforcing predecessor of broadband radio communication system | |
| CN101883069A (en) | Training sequence construction and OFDM time synchronization method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20091216 Termination date: 20110530 |