CN101834657A - 3GPP (3rd Generation Partnership Project) LET (Long Term Evolution) downlink initial master synchronization detection method - Google Patents
3GPP (3rd Generation Partnership Project) LET (Long Term Evolution) downlink initial master synchronization detection method Download PDFInfo
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Abstract
The invention belongs to the technical field of wireless communication, in particular a 3GPP (3rd Generation Partnership Project) LET (Long Term Evolution) downlink initial master synchronization detection method. The synchronization method comprises the following steps of: using a Zadoff-Chu sequence as a synchronous marker sequence; mapping the synchronous marker sequence into a spectrum according to an LTE standard to form a synchronous frame; correlating a standard Zadoff-Chu sequence locally generated at a receiving end with a receiving sequence to confirm a district in-group marker number and a time synchronization position which are sent by a sending end, wherein a low-pass filter is used at the receiving end to filter out a spectrum occupied by a synchronous signal, avoid the interference of other signals and improve the detection performance; down sampling the filtered signal to be detected; and then mutually correlating with a local standard synchronous sequence; and differentiating and processing signal detection; averaging many times and carrying out relative detection under the condition of a low signal-to-noise ratio. The invention can rapidly and accurately provide master synchronization service for initial LET synchronization and has extremely high anti-interference performance.
Description
Technical field
The invention belongs to wireless communication technology field, be specifically related to the synchronous detection method of a kind of 3GPP LTE down initial master.
Background technology
Third generation partner program (3rd Generat ion Partnership Project, i.e. 3GPP) is a standardizing body that is found in December, 1998.Its member comprises the ETSI in Europe, ARIB and TTC, CCSA, the TTA of Korea S of China and the ATIS of North America of Japan at present.
3GPP Long Term Evolution (LTE) project is the new technology development project of the maximum that starts of 3GPP over the past two years, and this is that the technology of core can be counted as " accurate 4G " technology with OFDM/FDMA.In the 3GPP LTE project there being the main technology of using: adopts OFDM, up employing single carrier-frequency division multiple access (SC-FDMA) technology in descending, utilize the advanced person's who comprises MIMO, SDMA (space division multiple access) multi-antenna technology flexibly, use more the modulation system of high-order (64QAM), based on flexible channels control, quick synchronization, the network technology of flattening and interference mitigation technology.
Cell searching is the significant process of LTE down-going synchronous, and in down-going synchronous, UE (User Equipment, subscriber equipment, for example travelling carriage in the mobile communication) need carry out the synchronous of time, frequency with the sub-district, to obtain the sign of sub-district.The design of Cell searching mainly concentrates in the design of the design of synchronizing channel and sequence of cells.Consider the complexity of Cell searching, LTE tendency employing primary synchronization channel carries out the coarsegrain time synchronized and interior the determining of identifying of cell set of coarse scan, and what auxiliary synchronization channel carried out identifying in fine granularity exact time synchronization and the cell set is further definite.Adopt public pilot frequency sequence at primary synchronization channel, and on auxiliary synchronization channel, adopt different pilot frequency sequences according to each sub-district of main synchronously definite pilot frequency sequence.In the concrete enforcement of LTE, UE is by P-SCH (Primary-Synchronization Channel, primary synchronization channel) signal and S-SCH (Secondary Synchronization Channel, auxiliary synchronization channel) signal is finished down-going synchronous, wherein the P-SCH signal is mainly used in and finishes symbol timing and frequency offset correction, carry number information in the cell ID group, be provided for the channel condition information of coherent detection for S-SCH.S-SCH is used for frame regularly, and S-SCH has also carried cell ID group number information, just can finish down-going synchronous and obtain the primary channel information of some sub-districts by P-SCH and S-SCH co-operation.
Summary of the invention
The objective of the invention is to propose the initial main synchronous detection method of 3GPP LTE Cell searching that a kind of antijamming capability is strong, the amount of calculation of system is little.
In the LTE down-going synchronous, the user at first needs to carry out Cell searching, through carrying out the synchronous of time, frequency with the sub-district, obtains the relevant essential information of sub-district, carries out the basis for follow-up communication and prepares.Main be used for obtaining of sign in the cell set synchronously, carry out the synchronously thick of time symbol, frequency, for the auxilliary synchronous meticulous timing of the 5ms that carries out subsequently provides channel parameter.The present invention utilizes the good correlation properties of Zadoff-Chu sequence to carry out initial synchronisation in the LTE down-going synchronous cell searching system.Solved and require synchronous algorithm that stronger anti-interference can be arranged in the initial synchronisation, problems such as simple amount of calculation and low synchronous detecting amount of calculation.
The descending main synchronization detecting method flow process of whole 3GPP LTE as shown in Figure 1.Concrete steps are as follows:
Step 101: transmitting terminal is determined sign N ID2 (value is 0,1 or 2) in the cell set, and to generate length according to sign in the group by the Zadoff-Chu sequence of frequency domain be 62 PSC (synchronously main) signal;
Step 102～103: the PSC signal is mapped in the synchronization frame according to the frequency domain mapping ruler of LTE regulation goes, last transmitting terminal frequency-region signal is converted to time-domain signal and sends;
Step 104: the time-domain signal on the receiving terminal receive channel, carry out synchronous detecting by the method described in the present invention.Promptly judge the signal to noise ratio that receives signal earlier,, then repeat to receive N time (N desirable 3～20) if be judged to be low signal-to-noise ratio, this signal, the each reception all carried out filtering with the signal cut-off frequency that receives for the 0.96MHz low pass filter, and filtered signal is superposeed, and averages; If be judged to be high s/n ratio, then directly the signal that receives is carried out low-pass filtering and enter next step, repeat to receive the step of averaging and skip.Here, so-called low signal-to-noise ratio is meant less than 5dB, greater than the high s/n ratio that is called of 5dB.Again with filtered signal or average after signal carry out down-sampled processing, can be in selection sample rate in 2048: 64～2048: 1024 scopes.Time domain sequences after the down-sampled processing is carried out computing cross-correlation respectively with local three groups of standard sequences that generate obtain three groups of correlations, compare three groups of correlations, identify in the promptly corresponding corresponding cell set of the maximum that obtains.
Step 105: the result according to previous step obtains identifying in the corresponding cell set, obtains time synchronized.
Adopted the following technology among the present invention:
A. carry out time-domain filtering after receiving synchronizing sequence
Because the Zadoff-Chu sequence also has extraordinary correlation in time domain, and consider that receiving system receives to such an extent that be the signal of time domain, therefore the present invention directly detects synchronizing sequence on time domain, so just saved the transform part from the time domain to the frequency domain, reduce synchronism link, shortened the synchronous time.
By the frequency-domain structure of 3GPP LTE initial synchronisation frame as can be seen synchronizing sequence just be distributed on the wide narrow subcarrier frequency range of one section 0.96MHz, other frequency ranges are and irrelevant synchronously data symbol entirely, therefore need synchronously useless signal is removed the master, to reduce the interference that unwanted signal detects sync correlation.
So, the present invention adds the low pass filter of a 0.96MHz bandwidth at receiving terminal, with this filter of synchronizing signal process that receives, other data symbols in the filtering synchronization frame, only stay the symbol that comprises in the synchronizing sequence frequency range, avoid other signals to disturb our synchronous detecting, improve the accuracy of the coherent detection of carrying out later.
B. down-sampled
According to the LTE document specifies, receiving terminal each time receiving terminal to data symbol length be 2048 points, receiving terminal can be received lot of data in synchronous, and the master is a real-time working system synchronously, data volume in order to guarantee to reduce follow-up processing under the prerequisite of checking performance not reducing reduces the complexity of calculating, and shortens detection time, it is down-sampled to carry out one or many to filtered data, reaches the optimal balance between amount of calculation and the performance.
C. to the synchronizing sequence coherent detection
Through filtering and down-sampled after utilize Zadoff-Chu sequence still good correlation properties on time domain, directly on time domain, synchronizing sequence is correlated with.By screening the sync bit that relevant maximum just can be judged the time, in screening process, also can obtain simultaneously in the main synchronizing symbol, cell set in synchronously and indicate relevant informations such as numbering, channel estimating information.
The relevant back with three standard sequences that generate in this locality of synchronizing sequence compares the maximum of three correlated results, the standard sequence at maximum related value place promptly is judged as the standard sequence of transmission, produce to indicate in the cell set of this standard sequence to be in the cell set that transmitting terminal sends and indicate, and can judge the synchronous time by inspection to the maximum position of correlated results.
D. the synchronous detecting under the low signal-to-noise ratio
Because under the situation of low signal-to-noise ratio, noise power is too big, can disturb the coherent detection to synchronizing signal, reduce net synchronization capability, for this reason, the present invention need be to receiving the processing that signal is correlated with, to improve the detection effect to synchronizing signal.
In invention, adopt and get repeatedly the power that the method for synchronizing sequence mean value reduces noise, to improve the synchronous detecting effect.Concrete way is: received only a synchronization frame originally at receiving terminal, (N desirable 3～20 for the reception N frame synchronization sequence that repeats now, the suggestion signal to noise ratio is low more, number of repetition is many more), at each frame synchronization sequence process low-pass filtering, then the filtered synchronizing sequence stack of this N frame is sued for peace, and then average, the mean value synchronizing sequence is equally carried out the down-sampled and coherent detection of back according to high s/n ratio.By top method, can under the situation of low-down signal to noise ratio, effectively carry out time synchronized, according to emulation experiment repeatedly, the number of times that preferably repeats to receive is taken as 3～5 times.
The invention advantage:
A) system's antijamming capability of the inventive method is strong, through the emulation testing checking, can identify in the detected cells group accurately under the situation of low signal-to-noise ratio, carries out time synchronized regularly.
B) owing to carry out directly carrying out in synchronous processing on the time domain at receiving terminal, simultaneously the signal after filtering is carried out down-sampledly, and then carry out follow-up coherent detection, above-mentioned method can reduce the system-computed amount greatly.
Therefore C) because the method for invention only has been to use low pass filter, down-sampled, sum-average arithmetic, do not carry out special complex process, less demanding to hardware can be used under kinds of platform.
Description of drawings
Fig. 1. be the algorithm flow chart of 3GPP LTE master synchronous detecting.
Fig. 2. be the synchronizing sequence testing process of receiving terminal.
Embodiment
Transmitting terminal uses the Zadoff-Chu sequence to generate the PSC synchronizing sequence, according to LTE frequency spectrum rule the frequency domain synchronizing sequence is mapped to send in the sequence subsequently and goes, and the simulation transmitting terminal sends the transmission sequence that comprises synchronizing sequence.Whole sequence adds the influence to signal of channel, noise when the channel.Receiving terminal carries out cross-correlation relatively with the synchronizing sequence that the signal that receives carries out down-sampled back and the local standard that generates, by finding out the identifier number that maximum correlation value determines that transmit leg adopts.
1. received signal produces
Generate the PSC signal in the Zadoff-Chu of frequency domain sequence, the frequency domain mapping ruler that the PSC sequence is stipulated according to LTE is mapped in the synchronization frame and goes then, and last transmitting terminal frequency-region signal is converted to time domain and sends
2. Design of Filter, type, parameter
By the frequency-domain structure of 3GPP LTE initial synchronisation frame and top synchronous frame generating method as can be seen synchronizing sequence just be distributed on the wide narrow subcarrier frequency range of one section 0.96MHz, other frequency ranges are and irrelevant synchronously data symbol entirely, just differ 5 very narrow gap carrier waves between the two, therefore when useless signal is removed, need the reasonable filter of rolloff-factor to leach synchronizing signal, to reduce the interference that unwanted signal detects sync correlation.
The cut-off frequency that has defined low pass filter above is 0.96MHz, needs good rolloff-factor, simultaneously, because synchro system is carried out synchronous detecting on time domain really, so we need add a digital filter that rolloff-factor is good at this.By experiment with comparison after, determine to use cut-off frequency to carry out filtering to the received signal as 32～50 exponent number word low pass filters that 0.96MHz adds Hamming window.
3. down-sampled
According to the LTE document specifies, receiving terminal each time receiving terminal to data symbol length be 2048 points, receiving terminal can be received lot of data in synchronous, and the master is a real-time working system synchronously, in order to reduce the data volume of follow-up processing, reduce the complexity of calculating, shorten detection time, need carry out once down-sampled filtered data.
Carry out down-sampled in, can in 2048: 64～2048: 1024 scopes, select sample rate, can select sample rate is 2048: 64,2048: 128,2048: 256,2048: 512 or 2048: 1024.Through simulation calculation repeatedly, preferred down-sampled rate is 2048: 128, promptly to the data of 128 of the down-sampled one-tenth of 2048 point data of each synchronization slot, gets 1 data point every 16.
4. correlation ratio
In order to determine to select best acceptance area to identify little group number simultaneously lock in time, we utilize Zadoff-Chu sequence good cross correlation on time domain and frequency domain to judge calculating, therefore, number in the cell ID group that need when the transmission signals of the Zadoff-Chu sequence of the generation standard of this locality and acceptance determines that by cross-correlation lock in time and transmitting terminal send, adopt.
Sequence process when the standard sequence of receiving terminal generation sends with transmitting terminal is the same, the unique 38-2012 position of 62 PSC sequences in the middle of being mapped to behind 2048 points that be not both do not add any LTE data-signal, so just do not had any interference, same is that frequency-region signal is converted to time-domain signal.For the judgement of the best that can carry out, N_ID2 need be got 0,1,2 respectively, and calculate standard sequence respectively.
The relevant back with three standard sequences that generate in this locality of synchronizing sequence compares the maximum of three correlated results, the standard sequence at maximum related value place promptly is judged as the standard sequence of transmission, to in receiving sequence, find the position of sync mark simultaneously, be converted to the time then, therefore the maximum value position after needing basis relevant is calculated the original position at synchronization frame, so just can determine synchronous time point.So far, found the position of synchronizing sequence in receiving sequence, finished synchronously.
5. low signal-to-noise ratio is handled
Because under the situation of low signal-to-noise ratio, noise power is too big, serious disturbance to the coherent detection of synchronizing signal, the non-constant of net synchronization capability, we need be to receiving the processing that signal is correlated with, to improve the detection effect to synchronizing signal.
In invention, we adopt and get repeatedly the power that the method for synchronizing sequence mean value reduces noise, with the synchronous detecting effect.Concrete way is: received only a frame synchronization sequence originally at receiving terminal, the present reception N frame synchronization sequence (N desirable 3～20) that repeats, at each section synchronizing sequence process low-pass filtering, then with the filtered synchronizing sequence stack of this N frame summation, and then average, the mean value synchronizing sequence is equally carried out the down-sampled and coherent detection of back according to high s/n ratio.By top method, can under the situation of low-down signal to noise ratio, effectively carry out time synchronized, according to emulation experiment, the times N that repeats to receive is taken as 3 times and gets final product.
Claims (1)
1. synchronous detection method of 3GPP LTE down initial master is characterized in that concrete steps are as follows:
Step 1: transmitting terminal is determined sign N_ID2 in the cell set, and to generate length according to sign in the group by the Zadoff-Chu sequence of frequency domain be 62 master sync signal;
Step 2: with master sync signal N.ID2 value 0,1 or 3; Be mapped in the synchronization frame according to the frequency domain mapping ruler of LTE regulation and go, at last the transmitting terminal frequency-region signal is converted to time-domain signal and sends;
Step 3: the time-domain signal on the receiving terminal receive channel, carry out synchronous detecting, the steps include: to judge earlier the signal to noise ratio that receives signal, if be judged to be low signal-to-noise ratio, then repeat to receive this signal N time, the each reception all carried out filtering with the signal cut-off frequency that receives for the 0.96MHz wave digital lowpass filter, and filtered signal is superposeed, average, N gets 3～20; If be judged to be high s/n ratio, then directly the signal that receives is carried out low-pass filtering and enter next step, repeat to receive the step of averaging and skip; Again with filtered signal or average after signal carry out down-sampled processing, the sample rate of sampling is 2048: 64～2048: 1024; Time domain sequences after the down-sampled processing is carried out computing cross-correlation respectively with local three groups of standard sequences that generate obtain three groups of correlations, compare three groups of correlations, identify in the promptly corresponding corresponding cell set of the maximum that obtains;
Step 4: the result according to previous step obtains identifying in the corresponding cell set, obtains time synchronized.
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| CN102075237A (en) * | 2010-12-23 | 2011-05-25 | 大唐移动通信设备有限公司 | Method and device for searching master sync signal |
| CN102122997A (en) * | 2011-03-21 | 2011-07-13 | 中兴通讯股份有限公司 | Method, device and terminal for detecting long term evolution (LTE) master synchronizing signal |
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| CN102832981A (en) * | 2011-06-15 | 2012-12-19 | 中兴通讯股份有限公司 | Method and apparatus for determining time synchronization position |
| CN104735750A (en) * | 2013-12-20 | 2015-06-24 | 联芯科技有限公司 | Cell searching method and terminal |
| CN106534031A (en) * | 2016-11-29 | 2017-03-22 | 重庆邮电大学 | Low-complexity LTE downlink frame synchronization method |
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| CN109783770A (en) * | 2018-11-27 | 2019-05-21 | 中国农业大学 | Frequency analysis method and device |
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| CN102075237A (en) * | 2010-12-23 | 2011-05-25 | 大唐移动通信设备有限公司 | Method and device for searching master sync signal |
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| CN102695263A (en) * | 2011-03-23 | 2012-09-26 | 上海无线通信研究中心 | Method for robust downlink timing synchronization of LTE system |
| US20140036779A1 (en) * | 2011-03-23 | 2014-02-06 | Shanghai Research Centre For Wireless Communicatio | Robust downlink timing synchronization method in lte system |
| CN102695193A (en) * | 2011-03-25 | 2012-09-26 | ***通信集团公司 | Cross subframe interference detection method, positioning method and base station thereof |
| CN102695193B (en) * | 2011-03-25 | 2015-12-02 | ***通信集团公司 | A kind of subframe interference detection method, localization method and base station of intersecting |
| WO2012171407A1 (en) * | 2011-06-15 | 2012-12-20 | 中兴通讯股份有限公司 | Method and device for determining time synchronization location |
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| CN104735750A (en) * | 2013-12-20 | 2015-06-24 | 联芯科技有限公司 | Cell searching method and terminal |
| CN104735750B (en) * | 2013-12-20 | 2018-11-20 | 联芯科技有限公司 | A kind of small region search method and terminal |
| CN106534031A (en) * | 2016-11-29 | 2017-03-22 | 重庆邮电大学 | Low-complexity LTE downlink frame synchronization method |
| CN106534031B (en) * | 2016-11-29 | 2019-11-12 | 重庆邮电大学 | A kind of LTE downlink frame synchronization method of low complex degree |
| CN108965189A (en) * | 2018-07-02 | 2018-12-07 | 天津市德力电子仪器有限公司 | It is a kind of applied to the symbol timing synchronization method for resisting big frequency deviation in NB-IOT system |
| CN109783770A (en) * | 2018-11-27 | 2019-05-21 | 中国农业大学 | Frequency analysis method and device |
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Application publication date: 20100915 |