CN103188765A - Frequency scanning method used for TD-LTE system - Google Patents

Abstract

The invention relates to a frequency scanning method used for a TD-LTE system. The method includes the steps of (1) obtaining detection frequency points in a signal frequency band at certain frequency intervals; (2) calculating RSSI of each detection frequency point; (3) sequencing the RSSI and screening out a larger detection frequency point; (4) carrying out master synchronous signal searching on the detection frequency points obtained in the step (3); (5) recording a frequency domain position of a center frequency point of each master synchronous signal and a symbol position in a time domain after the master synchronous signals are searched; (6) calculating the RSSI at the center frequency point of each master synchronous signal; and (7) sequencing the master synchronous signals in the frequency band according to the RSSI obtained in the step (6) and outputting a master synchronous signal sequence after sequencing. Compared with the prior art, the method has fewer detection frequency points needing to be scanned, and is high in precision.

Description

A kind of frequency scanning method for the TD-LTE system

Technical field

The present invention relates to wireless communication technology field, especially relate to a kind of frequency scanning method for the TD-LTE system.

Background technology

At present, 3G (3rd Generation, 3-G (Generation Three mobile communication system)) network is commercial and universal rapidly at home, and at 4G (4th Generation, the 4th third-generation mobile communication system) standard aspect, therefore schedule has also been put in the commercialization that has the TD-LTE standard of China's independent intellectual property right, and seeking a kind of two-forty, high accuracy, self adaptation frequency sweep method for the construction of TD-LTE network is the problem that receives much concern.

In the terminal operating process, PLMN (Public Land Mobile Network, public land mobile network) search is the important function that must support, be that terminal is under the situation that does not have priori and information, network condition around the active searching, by resolving all PLMN signs (PLMN_Id), put out available PLMN tabulation (PLMN_List) and report of user in order in order to realize the process that manual network is selected.

In the processes such as the PLMN background search in starting up of terminal cell initial search, running, need at first carry out frequency sweep, accurately the frequency that may have signal be screened ordering as early as possible, in order to reduce the scope, avoid omitting and erroneous judgement.The key of this process is speed and accuracy.

In addition, because TD-LTE is tdd systems.The same with all TDD systems, its uplink interference is a unavoidable problem.In the frequency sweep process, terminal is in order to search for and recognition network, and the continuous data that must carry out the long period receives.In this process, receive data and inevitably sneaked into the up transmission signal of other-end on every side, polluted thereby cause receiving data.Directly influence correctness and the validity of subsequent result.

Analyze the defective that it exists below by specifically describing present PLMN frequency sweep method.

With reference to shown in Figure 3, PLMN frequency scanning process is finished by following steps at present:

Step S10 is at interval with 100KHz, lists all possible center frequency point.LTE frequency range with 100MHz is example, and may have the center frequency point number is 1000;

Step S11 to each possible frequency, receives the data more than the 5ms continuously in measuring bandwidth range;

Step S12 calculates the measurement bandwidth RSSI (Received Signal Strength Indicator, receive signal strength signal intensity indication) of each frequency;

Step S13 if necessary, changes and measures bandwidth, returns step S11;

Step S14 adds up broadband RSSI, namely selects most possibly to occur the bandwidth of frequency according to the RSSI that measures under the different bandwidth;

Step S15, statistics frequency sweep result namely screens all possible frequency according to broadband RSSI.

Adopt above-mentioned known frequency sweep method, need to receive the above data of more than 1000 frequency 5ms on the one hand, and each frequency RSSI is calculated, the time overhead of ordering is big; In addition, all there is blindness in the data that are used for measure R SSI in time domain and frequency domain, the influence of the up generation that transmits of the user data that network sends and other-end is inevitable, and the accuracy of ordering can't be guaranteed, and then has a strong impact on the correctness of subsequent step.

Summary of the invention

Purpose of the present invention is exactly to provide a kind of frequency scanning method for the TD-LTE system, the detection frequency negligible amounts that this method need scan, and accuracy height for the defective that overcomes above-mentioned prior art existence.

Purpose of the present invention can be achieved through the following technical solutions:

A kind of frequency scanning method for the TD-LTE system may further comprise the steps:

1) with the detection frequency in the certain frequency interval acquiring signal frequency range;

2) calculate the RSSI that each detects the frequency place;

3) RSSI is sorted, filter out bigger detection frequency;

4) the detection frequency that obtains in the step 3) is carried out the master sync signal search;

5) search master sync signal after, record the frequency domain position of this master sync signal center frequency point and the character position in time domain;

6) RSSI at calculating master sync signal center frequency point place;

7) sort according to the master sync signal that obtains in the step 6) in the frequency range of RSSI, and the master sync signal sequence after the output ordering.

The frequency interval that detects frequency in the step 1) is 100KHZ.

Step 2) and step 6) may further comprise the steps:

A) receive detection frequency or the center frequency point data of the interior 10ms of certain bandwidth range on every side;

B) these data are carried out the frequency domain conversion, obtain the frequency domain data of each subcarrier in the described bandwidth range;

C) frequency domain data according to each subcarrier calculates the RSSI that detects frequency or center frequency point place.

The method of described frequency domain conversion is fast Fourier transform, and receiving the scope that detects frequency or the reception of center frequency point ambient data is 1.08MHz, and the bandwidth of described subcarrier is 15KHz, and quantity is 72.

RSSI is according to formula in the step 3): Calculate, wherein S _{I, k}Represent that i is detected the frequency signal strength signal intensity of k subcarrier on every side, n is the quantity of subcarrier.

Described master sync signal is made of the Zadoff-Chu sequence.

Compared with prior art, the present invention has the following advantages:

1, only the power of master sync signal is checked, on time domain and frequency domain, effectively avoided the influence of upward signal;

2, a secondary data finish receiving many may frequencies ionization meter can tens times raise the efficiency;

3, by coarse scan for the first time, exclude the center frequency point that does not have signal or weak output signal, further improved efficient;

4, because the good correlation of Zadoff-Chu sequence makes check result very accurate.

5, parameter of the present invention can be done suitable adjustment and has certain flexibility, to adapt to different network environments.

Description of drawings

Fig. 1 is the frequency-domain structure figure of the master sync signal of TD-LTE system;

Fig. 2 is the time domain structure chart of the master sync signal of TD-LTE system;

Fig. 3 is the flow chart of existing frequency scanning method;

Fig. 4 is flow chart of the present invention.

Embodiment

The present invention is described in detail below in conjunction with the drawings and specific embodiments.

Embodiment

The master sync signal of TD-LTE system (PSS, Primary Synchronization Signal) is produced by frequency domain Zadoff-Chu sequence, and one to have 3 length be 62 main synchronizing sequence, as follows formula:

$d_u\left(n\right)=\left\{\begin{array}{cc}{e}^{-j\frac{\mathrm{\πun}(n+1)}{63}}& n=\mathrm{0,1},...,30\\ e^{-j\frac{\mathrm{\πu}(n+1)(n+2)}{63}}& n=\mathrm{31,32},...,61\end{array}\right.$

Index u and 3 physical-layer cells of the ZC sequence of 3 main synchronizing sequence uses

Mapping relations are one by one arranged, as shown in the table:

The root sequence sequence number table of master sync signal

By as depicted in figs. 1 and 2 master sync signal in the TD-LTE system is analyzed, can obtain following conclusion:

1) position to occur be the cycle with 5ms to time-frequency, and the length of master sync signal is 1 symbol.

2) frequency domain position relative fixed: in 72 sub-reference carrier waves of center frequency point two sides, 62 at center subcarriers of effective information, two sides respectively have the protection interval of 5 subcarriers, do not have signal to send in the protection subcarrier.

3) the Zadoff-Chu sequence has good correlation.

4) formation of synchronizing signal and distribution situation and system bandwidth are irrelevant.

5) both sides of PSS are respectively descending (DL) control channel and protection interval, this segment data are measured the interference that can prevent effectively that upward signal from receiving data.

Fig. 4 is a kind of flow chart of the frequency scanning method for the TD-LTE system, may further comprise the steps:

Step S20: all that obtain in the signal frequency range with the frequency interval of 100KHz detect frequencies, are example with the signal frequency range of 100MHz, and then the detection frequency number in its frequency range has 1000.

Step S21: receive each and detect the frequency interior data of 1.08MHz bandwidth range on every side, received data are to calculate the foundation of RSSI, just detect the basis of frequency ordering, and its accuracy and pure property are the assurances that obtains the correct measurement result.

Step S22: the data that receive are carried out 2048 fast Fourier transform, obtain the frequency domain data of 72 subcarriers in the 1.08MHz bandwidth range, the bandwidth of this subcarrier is 15KHz.

Step S23: one that selects all to detect in the frequency is detected frequency.

Step S24: each center frequency point around the calculating monitoring frequency in the 1.08MHz band is the signal strength signal intensity sum of 72 subcarriers on every side, that is:

$\mathrm{RSSI}\left(i\right)=\underset{k=1}{\overset{72}{\mathrm{\Σ}}}{S}_{i,k}$

Because master sync signal, be present in the 1.08MHz scope around the center frequency point, take 72 subcarriers altogether, so to the statistics of these subcarrier intensity, can reflect the possibility that has master sync signal around the frequency.

Step S25: because the terminal of TD-LTE system must support to be limited to the bandwidth varying setting of 20MHz, so capable data that once receive the 20MHz bandwidth of terminal, the bandwidth of whole TD-LTE system is 100MHz, whether the frequency range that therefore needs to judge the detection frequency that has scanned is covered and has been covered whole frequency, if not, then change in execution in step S26 and receive frequency ranges of data, get back to S21 then and repeat; Otherwise, then continue downward execution in step S27.

Step S27: all RSSI that detect frequency are sorted, by comparing with preset threshold, choose frequency that wherein RSSI is bigger as the detection frequency that may have master sync signal, can effectively exclude the detection frequency that does not exist signal or signal very faint by this step, improved testing efficiency, wherein the difference that threshold value can actual frequency range is set.

Step S28: all that filter out in step S27 detect and select a detection frequency in the frequency.

Step S29: the detection frequency of selecting is carried out the scanning of each symbol on the time domain, because effective information is therein on 62 subcarriers of the heart, therefore carry out the master sync signal detection on frequency 62 subcarriers on every side to detecting, detected after the frequency, judge whether to finish after testing whole frequencies, if do not detected, then execution in step 32, re-execute step 28 behind the replacing frequency; If finish after testing, execution in step 30 downwards then;

Step S30: note the center frequency point frequency domain position and the time-domain symbol position that detect master sync signal in the whole frequency band.Because the good correlation of master sync signal, the location can be very accurate.

Step S31: to detecting the center frequency point of master sync signal, 72 subcarriers are at the RSSI of master sync signal character position, as the foundation of master sync signal ordering around computer center's frequency.

Step S32: the result to frequency scanning adds up, and draws complete results.

Claims (6)

1. a frequency scanning method that is used for the TD-LTE system is characterized in that, may further comprise the steps:

1) with the detection frequency in the certain frequency interval acquiring signal frequency range;

2) calculate the RSSI that each detects the frequency place;

3) RSSI is sorted, filter out the detection frequency greater than setting threshold;

4) the detection frequency that obtains in the step 3) is carried out the master sync signal search;

5) search master sync signal after, record the frequency domain position of this master sync signal center frequency point and the character position in time domain;

6) RSSI at calculating master sync signal center frequency point place;

7) sort according to the master sync signal that obtains in the step 6) in the frequency range of RSSI, and the master sync signal sequence after the output ordering.

2. a kind of frequency scanning method for the TD-LTE system as claimed in claim 1 is characterized in that, the frequency interval that detects frequency in the step 1) is 100KHZ.

3. a kind of frequency scanning method for the TD-LTE system as claimed in claim 1 is characterized in that step 2) and step 6) may further comprise the steps:

A) receive detection frequency or the center frequency point data of the interior 10ms of certain bandwidth range on every side;

B) these data are carried out the frequency domain conversion, obtain the frequency domain data of each subcarrier in the described bandwidth range;

C) frequency domain data according to each subcarrier calculates the RSSI that detects frequency or center frequency point place.

4. a kind of frequency scanning method for the TD-LTE system as claimed in claim 3, it is characterized in that, the method of described frequency domain conversion is fast Fourier transform, receiving the scope that detects frequency or the reception of center frequency point ambient data is 1.08MHz, the bandwidth of described subcarrier is 15KHz, and quantity is 72.

5. a kind of frequency scanning method for the TD-LTE system as claimed in claim 3 is characterized in that, described RSSI is according to formula:

Calculate, wherein S _{I, k}Represent that i is detected the frequency signal strength signal intensity of k subcarrier on every side, n is the quantity of subcarrier.

6. a kind of frequency scanning method for the TD-LTE system as claimed in claim 1 is characterized in that described master sync signal is made of the Zadoff-Chu sequence.

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