CN100499623C - Method for realizing orthogonal frequency division multiplexing precision time synchronization - Google Patents
Method for realizing orthogonal frequency division multiplexing precision time synchronization Download PDFInfo
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Abstract
The present invention provides a method for realizing orthogonal frequency division multiplexing precision time synchronization. The present invention is characterized in that after an OFDM system synA method for realizing accurate time synchronization of orthogonal frequency division multiplexing includes compensating signal loss to restore signal itself after integer frequency deviation synchronchronously processes a received signal in an integer frequency deviation mode, the OFDM system compensates signal loss and restores the signal; the restored signal is converted by frequency and time tization treatment is carried out on received signal by OFDM system, carrying out frequency-time conversion on restored signal for obtaining time domain reference signal being used to carry out multipao obtain a converted time domain reference signal; the time domain reference signal and the signal after synchronously processes in the integer frequency deviation mode are used for searching multipleth search with signal treated by integer frequency deviation synchronization, confirming arrival time and amplitude phase value of the first path for realizing accurate time synchronization. paths to confirm the reaching time of the head path and an amplitude phase value, and thus, accurate time synchronization is realized. The present invention realizes the accurate time synchronization without a leading signal element, saves system cost, and enhances transmission rate of data. Simultaneously, score frequency deviation resynchronization is carried out by selecting the part which is less affected by the later reaching path, and thus, the present invention enhances accuracy of score frequency deviation estimation, and reduces property loss of the system due to a synchronous error. The present invention also provides a method realizing synchronous tracking on the basis of realizing the accurate time synchronization, so that the OFDM system further gets rid of dependence on the leading signal element.
Description
Technical field
The present invention relates to the technical field of data transmission in the mobile communication technology, be meant a kind of method that realizes OFDM (OFDM) exact time synchronization especially.
Background technology
OFDM (OFDM, Orthogonal Frequency Division Multiplexing) is to utilize parallel transmission to improve a kind of mobile communication technology of communication data transmission rate.The basic thought of this technology is in frequency domain given channel to be divided into many orthogonal sub-channels, uses a subcarrier to modulate on each subchannel, and each subcarrier parallel transmission.Like this, although total channel be non-flat forms, have frequency selectivity, but each subchannel is a relatively flat, what carry out on each subchannel is narrow band transmission, and signal bandwidth is less than the respective bandwidth of channel, so the interference between the erasure signal waveform greatly.OFDM is that its allows subcarrier spectrum to overlap with respect to the difference of general multi-carrier transmission, as long as satisfy between subcarrier mutually orthogonally, just can isolate data-signal from the subcarrier of aliasing.
Because OFDM allows the subcarrier spectrum aliasing, its spectrum efficiency improves greatly, simultaneously, this technology also has the anti-multipath interference and intersymbol interference, channel estimating and equilibrium realize many advantages such as easy, that system's implementation complexity is low, thereby is a kind of modulation system efficiently.And this technology is easy to combine with various multiple access technologies, thereby generally believed it is indispensable core technology in the 4th third-generation mobile communication system.This technology is widely used in digital audio broadcasting (DAB), digital video broadcasting (DVB), ADSL (Asymmetric Digital Subscriber Line) (ADSL), wireless lan (wlan), wireless MAN (WMAN), Wireless Personal Network (WPAN), the unauthorized metropolitan area network of wireless high-speed many data communication systems such as (WHUMAN) at present, determined to use the OFDM technology in 802.16 agreements, 802.20 mobile wide-band wire-less accessing systems that Institute of Electrical and Electric Engineers (IEEE) standardization body is being discussed at present also will adopt this modulation technique.
The OFDM symbol is made of subcarrier in frequency domain, and the number of subcarrier has determined counting of time-frequency conversion (FFT).Subcarrier has three types, and it is respectively data subcarrier, pilot sub-carrier and virtual subnet carrier wave.Wherein, data subcarrier is used for transfer of data; Pilot sub-carrier is used for eliminating residual differing at first, and along with the development of technology, the effect of pilot sub-carrier further enlarges, and can be used to carry out Frequency Synchronization and channel estimating.The virtual subnet carrier wave is meant the carrier wave that does not send any data, and ofdm system is introduced the interference of adjacent band in order to reduce.
The OFDM technology has above-mentioned numerous advantage, but it is to time synchronized, and especially the requirement of time precise synchronization is very high, could guarantee the orthogonality between the subcarrier like this.This be because: if in advance synchronously, can introduce different phase differences for different subcarriers, increase along with the mistake synchronism deviation, the performance of system also is subjected to increasing influence thereupon, can introduce bigger phase difference for the high frequency subcarriers among the OFDM especially, for high order modulation, this deviation will cause performance sharply to reduce and make high order modulation to use.If postpone synchronously, will disturb between created symbol, cause performance sharply to descend.The time mistake can influence the fractional frequency performance of (FFO) synchronously synchronously to a great extent in addition.Therefore, the exact time synchronization in the ofdm system is very important key technology in this system.
Figure 1 shows that OFDM realizes the overview flow chart schematic diagram of Time and Frequency Synchronization.
It is slightly synchronous that step 101, ofdm system are carried out the time to the received signal.Concrete grammar is: adopting leading cell is that targeting sequencing (preamble) carries out time synchronized, promptly by being correlated with the acquisition time slightly synchronous to the two sections identical data in front and back, thereby obtains the sync peaks phase information of received signal.Perhaps, utilize the time window that equates with circulating prefix-length, it is relevant to slide to the received signal, and it is slightly synchronous that the Cyclic Prefix in the dependence orthogonal frequency division multiplex OFDM symbol carries out the time, obtains the sync peaks phase information of received signal.
Step 102, the mark frequency deviation is synchronous.Concrete grammar is: carry out the mark frequency offset estimating according to the described sync peaks phase information of step 101, and revise according to the signal that this mark frequency offset estimating information butt joint is received, make only to have integer frequency bias in the revised received signal.
Step 103, the time-frequency conversion.Concrete grammar is: will be transformed into frequency domain by fast Fourier transform (FFT) or discrete time Fourier transform (DFT) conversion through the signal after step 102 is handled.
Step 104, integer frequency bias is synchronous.Concrete grammar is: at first utilize the known subcarrier information in the Preamble sequence to carry out the filtering of difference relevant matches, estimate to carry out integer frequency bias, and then carry out integer frequency bias compensation, promptly utilize the integer frequency bias information butt joint estimate to collect mail and number revise, make not have integer frequency bias in the revised received signal.
Step 105, the time precise synchronization.Concrete grammar is: the signal after utilizing leading cell and handling through step 104 carries out matched filtering, searches for and obtains multipath information, thereby directly come accurately to locate synchronization point according to head, realizes the time precise synchronization.
Step 106, mark frequency deviation second synchronization.Promptly carry out the mark frequency offset estimating once more, and revise, make only to have integer frequency bias in the revised received signal, thereby realize accurate Time and Frequency Synchronization according to the signal that this mark frequency offset estimating information butt joint is received.
In the method for the accurate Time and Frequency Synchronization of above-mentioned realization, though utilize leading cell can realize exact time synchronization, leading cell is to want additive decrementation system resource.Especially in mobile environment, every certain interval of time just must carry out one time the time precise synchronization, otherwise because the performance loss that time synchronization error brings is that system is intolerable.Like this, the time of at every turn carrying out all must send leading cell during precise synchronization, and this will cause increasing overhead, reduces the speed that data send.Yet,, also do not have effective method to finish exact time synchronization if do not use leading cell.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of method of the OFDM of realization exact time synchronization, making does not need leading cell just can realize that precise time is synchronous, thereby system overhead conserved improves data transmission rate.
For achieving the above object, technical scheme of the present invention is achieved in that
A kind of method that realizes the OFDM exact time synchronization, this method may further comprise the steps:
Ax, orthogonal frequency division multiplex OFDM system carry out thick synchronously, mark frequency offset estimating of time and time-frequency domain conversion process to the received signal;
After a, described ofdm system carried out the integer frequency bias Synchronous Processing to the described signal that carries out after time-frequency domain is changed, the compensating signal loss restored signal itself;
B, the conversion when signal that restores is carried out frequency, obtain the time domain reference signal after the conversion, and the signal of using after this time domain reference signal and the integer frequency bias Synchronous Processing carries out Multipath searching, the time domain reference signal is carried out matched filtering or slided relevant with signal after integer frequency bias is handled, obtain match peak, and choose footpath headed by first footpath that arrives default amplitude threshold, determine that this head directly arrives at constantly and the amplitude-phase value, realizes exact time synchronization.
Preferably, if there is pilot sub-carrier in the ofdm signal, then the method for the described compensating signal loss of step a is: utilize pilot sub-carrier to carry out channel estimating by linear interpolation or least mean-square error interpolation, and according to channel estimation value, with the conjugation of the signal times after the integer frequency bias Synchronous Processing, realize loss of signal compensation with this signal place channel estimation value.
Preferably, the described method that restores signal itself is: the information behind the signal compensation is carried out rectification.
Preferably, if encoding operation is arranged at transmitting terminal, then the information behind the signal compensation is carried out after the rectification, further comprise: ofdm system judges that current channel transmission quality is whether in the scope that requires, if, direct execution in step b then, otherwise after carrying out corresponding decode operation, execution in step b again.
Preferably, if there is not pilot sub-carrier in the ofdm signal, then the loss of the described compensating signal of step a restores the method for signal itself and is: adopt the method compensating signal loss of Difference Solution modulation, the method that adopts Difference Solution to modulate restores signal itself.
Preferably, this method further comprises: determine arriving at constantly and the amplitude-phase value of multipath, and according to the arriving at constantly and the amplitude-phase value of this multipath, obtain channel estimation value by time-frequency conversion, carry out signal compensation and dynamic sub carrier resource allocation.
Preferably, the described time domain reference signal of step b is: acquired time-domain signal itself, perhaps, the Cyclic Prefix of acquired time-domain signal, perhaps, the common signal that constitutes of acquired time-domain signal itself and Cyclic Prefix thereof, perhaps, arbitrary section signal in the acquired time-domain signal more than or equal to the part formation of its circulating prefix-length, perhaps, the length that is made of jointly the Cyclic Prefix of acquired time-domain signal more than itself and acquired time-domain signal is greater than the signal of a time-domain signal and Cyclic Prefix thereof.
Preferably, this method further comprises: set amplitude threshold according to the requirement to signal quality, select to surpass the moment of this amplitude threshold, these are the moment that multipath arrives constantly, and its pairing amplitude-phase value is the amplitude-phase value of multipath.
Preferably, require synchronization threshold is set according to net synchronization capability, and this synchronization threshold is usually between 0 to 1, after step b was finished, this method further comprised:
01) whether judge ratio by matched filtering or the slide relevant maximum value that obtains and the absolute value of average correlation more than or equal to this synchronization threshold of having set, if, then success synchronously, and continue to keep synchronous tracking mode; Otherwise execution in step 02);
02) system enters intermediateness, judges that system is current whether still can not realize synchronous tracking in predefined number of times, if then declaration loses synchronously, reenters the synchronous searching state, otherwise after re-executing step b, returns step 01 again).
Use the present invention, after ofdm system carried out the integer frequency bias Synchronous Processing to the received signal, the compensating signal loss restored signal itself; The conversion when signal that restores is carried out frequency, and use time-domain signal after this conversion and the signal after the integer frequency bias Synchronous Processing carries out Multipath searching, determine precise synchronization peak phase information, the realization exact time synchronization.Use method of the present invention, do not need leading cell just can realize that precise time is synchronous, saved overhead, improved data transmission rate.
In addition, on the basis of exact time synchronization of the present invention, reach the footpath after being subjected to last OFDM symbol energy big and influence less part and carry out mark frequency deviation second synchronization by choosing, improved the accuracy of mark frequency offset estimating, reduced the performance loss that system brings because of synchronous error.
Have, the present invention is when realizing exact time synchronization again, and ofdm system has been determined the due in and the amplitude-phase value of multipath, thereby can accurately estimate multidiameter delay, and accurately estimates the range value of power delay spectrum.After the method for utilizing Difference Solution modulation realizes precise synchronization, can also utilize moment of multipath and amplitude-phase value to carry out time-frequency conversion and carry out channel estimating, carry out channel compensation and dynamic sub carrier resource allocation again.
At last, realizing on the basis of exact time synchronization that the present invention also provides a kind of method of following the tracks of synchronously of realizing, making ofdm system further break away from dependence leading cell.
Description of drawings
Figure 1 shows that OFDM realizes the overview flow chart schematic diagram of time synchronized;
Figure 2 shows that the schematic flow sheet of using the embodiment of the invention one;
Figure 3 shows that the simulated effect figure that accurately locatees synchronization point under the typical urban channel;
Figure 4 shows that the schematic flow sheet of using the embodiment of the invention two.
Embodiment
Below in conjunction with drawings and the specific embodiments, the present invention is done further describing in detail again.
Thinking of the present invention is: after ofdm system carried out the integer frequency bias Synchronous Processing to the received signal, the compensating signal loss restored signal itself; The time domain reference signal after the conversion is obtained in conversion when the signal that restores is carried out frequency, and the signal of using after this time domain reference signal and the integer frequency bias Synchronous Processing carries out Multipath searching, determines that first footpath arrives at constantly and the amplitude-phase value realization exact time synchronization.Use method of the present invention, do not need leading cell just can realize accurate Time and Frequency Synchronization, saved overhead, improved data transmission rate.Simultaneously, by choose be subjected to last OFDM symbol energy bigger after reach the footpath and influence less part and carry out mark frequency deviation second synchronization, improved the accuracy of mark frequency offset estimating, reduced the performance loss that system brings because of synchronous error.Realizing on the basis of exact time synchronization that the present invention also provides a kind of method of following the tracks of synchronously of realizing, making ofdm system further break away from dependence leading cell.
Figure 2 shows that the schematic flow sheet of using the embodiment of the invention one.In the present embodiment, there is pilot sub-carrier in the OFDM symbol.
It is slightly synchronous that step 201, ofdm system are carried out the time to the received signal.Promptly utilize the time window that equates with circulating prefix-length, it is relevant to slide to the received signal, relies on the Cyclic Prefix in the orthogonal frequency division multiplex OFDM symbol to carry out time synchronized, obtains the sync peaks phase information of received signal.
The concrete application number that can adopt the applicant to propose is " 200410042904.7 ", and denomination of invention is carried out integer frequency bias for the method that proposes in the Chinese patent application of " a kind of method of OFDM Time and Frequency Synchronization " and estimated; The denomination of invention that also can adopt the applicant to submit same day is carried out integer frequency bias for the method that proposes in the Chinese patent application of " the synchronous method of a kind of OFDM integer frequency " and is estimated; Certainly, also can adopt maximum-likelihood method to carry out that integer frequency bias is estimated or existing other method is carried out integer frequency bias and estimated.
Above-mentioned time domain reference signal is: acquired time-domain signal itself, i.e. an OFDM symbol; Perhaps, the Cyclic Prefix of acquired time-domain signal; Perhaps, the common signal that constitutes of acquired time-domain signal itself and Cyclic Prefix thereof, promptly an OFDM symbol adds its prefix; Perhaps, arbitrary section part in the acquired time-domain signal more than or equal to its circulating prefix-length, i.e. any a section in OFDM symbol, and the length of this section must be more than or equal to the length of Cyclic Prefix; Perhaps, the length that is made of jointly the Cyclic Prefix of acquired time-domain signal more than itself and acquired time-domain signal is greater than the signal of a time-domain signal itself, for example, two or more OFDM symbols add their Cyclic Prefix, perhaps, the part of an OFDM symbol and Cyclic Prefix thereof, add the part of another OFDM symbol and the time domain reference signal that Cyclic Prefix constituted thereof, or the like, in a word, its length is greater than the length of an OFDM symbol and Cyclic Prefix thereof.
Figure 3 shows that the simulated effect figure that accurately locatees synchronization point under the typical urban channel.The abscissa of this figure is the time, and unit is a chip, and ordinate is the value after the normalization.As can be seen from the figure, be under the static multipath situation of 0db in typical urban channel, the first path position that identifies is identical with the first path position that the mode of the leading cell of application of prior art identifies, and promptly directly discerns error free to head.
Figure 4 shows that the schematic flow sheet of using the embodiment of the invention two.In the present embodiment, the modulation system of OFDM is a differential modulation, does not have pilot sub-carrier in the OFDM symbol.
It is slightly synchronous that step 401, ofdm system are carried out the time to the received signal.Promptly utilize the time window that equates with circulating prefix-length, it is relevant to slide to the received signal, relies on the Cyclic Prefix in the orthogonal frequency division multiplex OFDM symbol to carry out time synchronized, obtains the sync peaks phase information of received signal.
Wherein, owing to do not have pilot sub-carrier in the OFDM symbol of differential modulation, can adopt maximum-likelihood method to carry out integer frequency bias and estimate.
Above-mentioned time domain reference signal is: acquired time-domain signal itself, i.e. an OFDM symbol; Perhaps, the Cyclic Prefix of acquired time-domain signal; Perhaps, the common signal that constitutes of acquired time-domain signal itself and Cyclic Prefix thereof, promptly an OFDM symbol adds its prefix; Perhaps, arbitrary section part in the acquired time-domain signal more than or equal to its circulating prefix-length, i.e. any a section in OFDM symbol, and the length of this section must be more than or equal to the length of Cyclic Prefix; Perhaps, the length that is made of jointly the Cyclic Prefix of acquired time-domain signal more than itself and acquired time-domain signal is greater than the signal of a time-domain signal itself, for example, two or more OFDM symbols add their Cyclic Prefix, perhaps, the part of an OFDM symbol and Cyclic Prefix thereof, add the part of another OFDM symbol and the time domain reference signal that Cyclic Prefix constituted thereof, or the like, in a word, its length is greater than the length of an OFDM symbol and Cyclic Prefix thereof.
In the present embodiment, the frequency domain channel estimated value that is transmission channel that obtains will be carried out after FFT or DFT be transformed into frequency domain according to the multipath due in that obtains in the step 407 and amplitude-phase value.Utilization obtains frequency domain channel to be estimated, can carry out channel compensation and subcarrier Dynamic Resource Allocation for Multimedia.
Adopt the foregoing description one or two methods that propose, the use Cyclic Prefix adds the OFDM symbol of a recovery, at static multipath, the subcarrier error rate is 10% o'clock when remapping, in typical urban channel, under the 0dB condition, emulation 200,000 frames, error free to the identification of most powerful path.In typical urban channel, the subcarrier error rate is 10% o'clock when remapping, under the mobile multipath 0dB condition, about 1 chip of the standard deviation of relatively accurate timing, carry out smart synchronization performance of time much at one with the application targeting sequencing of prior art, when using 2 OFDM and Cyclic Prefix as the reference signal, performance surmounts the top performance that can reach with leading cell, and this is that prior art is beyond one's reach.
In addition, because the every certain interval of time of system just must carry out a subsynchronous tracking, based on time precise synchronization of the present invention, can implement synchronous tracking effectively, the method that specific implementation is followed the tracks of synchronously is as follows:
Require to be provided with synchronization threshold according to net synchronization capability, and this threshold value is usually between 0 and 1, after each realization time precise synchronization, whether the ratio of judgement by matched filtering or the slide relevant maximum value that obtains and the absolute value of average correlation is more than or equal to this preset threshold, if then expression is followed the tracks of successfully synchronously; Otherwise not success is followed the tracks of in expression synchronously.
If success synchronously, then continue to keep following the tracks of synchronously, if fail success synchronously, then enter a kind of intermediateness, and carry out time precise synchronization operation again, repeat above-mentioned judgement afterwards to determine whether to realize synchronous tracking, if in certain number of times, still can not realize synchronous tracking, then declaration loses synchronously, reenters the synchronous searching state.
The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (9)
1, a kind of method that realizes the OFDM exact time synchronization is characterized in that, this method may further comprise the steps:
Ax, orthogonal frequency division multiplex OFDM system carry out thick synchronously, mark frequency offset estimating of time and time-frequency domain conversion process to the received signal;
After a, described ofdm system carried out the integer frequency bias Synchronous Processing to the described signal that carries out after time-frequency domain is changed, the compensating signal loss restored signal itself;
B, the conversion when signal that restores is carried out frequency, obtain the time domain reference signal after the conversion, and the signal of using after this time domain reference signal and the integer frequency bias Synchronous Processing carries out Multipath searching, the time domain reference signal is carried out matched filtering or slided relevant with signal after integer frequency bias is handled, obtain match peak, and choose footpath headed by first footpath that arrives default amplitude threshold, determine that this head directly arrives at constantly and the amplitude-phase value, realizes exact time synchronization.
2, method according to claim 1, it is characterized in that, if there is pilot sub-carrier in the ofdm signal, then the method for the described compensating signal loss of step a is: utilize pilot sub-carrier to carry out channel estimating by linear interpolation or least mean-square error interpolation, and according to channel estimation value, with the conjugation of the signal times after the integer frequency bias Synchronous Processing, realize loss of signal compensation with this signal place channel estimation value.
3, method according to claim 2 is characterized in that, the described method that restores signal itself is: the information behind the signal compensation is carried out rectification.
4, method according to claim 3, it is characterized in that, if encoding operation is arranged at transmitting terminal, then the information behind the signal compensation is carried out after the rectification, further comprise: ofdm system is judged current channel transmission quality whether in the scope that requires, if, direct execution in step b then, otherwise after carrying out corresponding decode operation, execution in step b again.
5, method according to claim 1, it is characterized in that, if there is not pilot sub-carrier in the ofdm signal, then the loss of the described compensating signal of step a restores the method for signal itself and is: adopt the method compensating signal loss of Difference Solution modulation, the method that adopts Difference Solution to modulate restores signal itself.
6, method according to claim 5, it is characterized in that, this method further comprises: determine arriving at constantly and the amplitude-phase value of multipath, and arriving at constantly and the amplitude-phase value according to this multipath, obtain channel estimation value by time-frequency conversion, carry out signal compensation and dynamic sub carrier resource allocation.
7, method according to claim 1, it is characterized in that, the described time domain reference signal of step b is: acquired time-domain signal itself, perhaps, the Cyclic Prefix of acquired time-domain signal, perhaps, the common signal that constitutes of acquired time-domain signal itself and Cyclic Prefix thereof, perhaps, arbitrary section signal in the acquired time-domain signal more than or equal to the part formation of its circulating prefix-length, perhaps, the length that is made of jointly the Cyclic Prefix of acquired time-domain signal more than itself and acquired time-domain signal is greater than the signal of a time-domain signal and Cyclic Prefix thereof.
8, method according to claim 1, it is characterized in that, this method further comprises: set amplitude threshold according to the requirement to signal quality, select to surpass the moment of this amplitude threshold, these are the moment that multipath arrives constantly, and its pairing amplitude-phase value is the amplitude-phase value of multipath.
9, method according to claim 1 is characterized in that, require synchronization threshold is set according to net synchronization capability, and this synchronization threshold is usually between 0 to 1, and after step b was finished, this method further comprised:
01) whether judge ratio by matched filtering or the slide relevant maximum value that obtains and the absolute value of average correlation more than or equal to this synchronization threshold of having set, if, then success synchronously, and continue to keep synchronous tracking mode; Otherwise execution in step 02);
02) system enters intermediateness, judges that system is current whether still can not realize synchronous tracking in predefined number of times, if then declaration loses synchronously, reenters the synchronous searching state, otherwise after re-executing step b, returns step 01 again).
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| EP2122962B1 (en) * | 2007-01-18 | 2013-05-29 | Thomson Licensing | Method for symbol synchronization of received digital signal and digital signal receiver using the same method |
| JP5493803B2 (en) * | 2009-12-15 | 2014-05-14 | ソニー株式会社 | Receiving apparatus and method, program, and receiving system |
| CN102377711A (en) * | 2010-08-11 | 2012-03-14 | 中国科学院微电子研究所 | Method for synchronizing OFDM (Orthogonal Frequency Division Multiplexing) wireless terminals |
| CN102611665B (en) * | 2011-01-24 | 2016-04-27 | 上海华虹集成电路有限责任公司 | Integer frequency bias in CMMB system and thin regularly combined estimation method and device |
| CN103546414A (en) * | 2012-07-16 | 2014-01-29 | 京信通信系统（广州）有限公司 | Frequency deviation estimation method and device for LTE systems |
| CN103716261B (en) * | 2012-09-29 | 2017-04-19 | 电信科学技术研究院 | Frequency-offset estimation method and device |
| CN103560872B (en) * | 2013-11-13 | 2016-05-25 | 中国人民解放军国防科学技术大学 | A kind of precise time measuring method based on OFCDM |
| CN104735012B (en) * | 2013-12-24 | 2019-01-11 | 江苏卓胜微电子股份有限公司 | Digit wireless communication system receiving end head path position detection device |
| CN103986543B (en) * | 2014-05-28 | 2017-01-25 | 上海航天电子通讯设备研究所 | Time slot synchronization method for satellite-borne AIS signal receiving system |
| WO2017151027A1 (en) * | 2016-03-02 | 2017-09-08 | Telefonaktiebolaget Lm Ericsson (Publ) | Methods and devices operating with fine timing reference signals transmitted occasionally |
| CN109302366B (en) * | 2017-12-26 | 2023-02-07 | 上海创远仪器技术股份有限公司 | WCDMA signal demodulation method suitable for signal analyzer platform |
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