CN104581787A - LTE system multi-cell search method based on interference cancellation - Google Patents

Abstract

The invention relates to an LTE system multi-cell search method based on interference cancellation. The method comprises the steps that received signals are detected by a common LTE system and a cell with the strongest signal at present is detected out to serve as the main cell; master synchronization signals and auxiliary synchronization signals of a frequency domain of the main cell are extracted and compared with master synchronization signals and auxiliary synchronization signals of a locally generated main cell to obtain respective frequency domain channel responses; interference is converted to a time domain for filtering, and then filtering results are converted back to the frequency domain; the master synchronization signals and auxiliary synchronization signals of the frequency domain of the main cell are reestablished by using the channel responses obtained in the last step; the reestablished master synchronization signals and auxiliary synchronization signals of the frequency domain are converted to the time domain and then eliminated at the corresponding positions in the received signals; finally, the cells searched every time are judged according to the relative peak-to-average ratio of the master synchronization signals and the auxiliary synchronization signals, and the eligible and effective cells are retained. According to the LTE system multi-cell search method based on interference cancellation, the detection success rate of the weak cells under the multi-cell condition is improved, and the multi-cell search result can reflect the real condition around to the uttermost.

Description

A kind of LTE system multi-cell search method based on Interference Cancellation

Technical field

The invention belongs to wireless communication technology field, be specifically related to the LTE system multi-cell search method based on Interference Cancellation, can be widely used in LTE tester.

Background technology

Current LTE system has started extensive commercialization, and thing followed existing network is disposed and extensively carried out, and also the demand of the network optimization served by band thus.Because LTE system occupied bandwidth is wider, in order to solve the problem of frequency spectrum resource anxiety, improve spectrum efficiency, LTE adopts identical networking, namely all communities all adopt identical frequency, such design makes the availability of frequency spectrum improve, and saves frequency resource, and it is convenient also to bring to frequency planning when network design, construction, dilatation; But also it should be noted that thing followed problem, that be exactly between neighbor cell co-channel interference serious.In order to reach the object of the network optimization, needing to identify community as much as possible at testing location, then each cell power being measured, and by the Signal analysis from different co-frequency cell be out how the difficult point place of this work.

Mention in patent " a kind of co-frequency cell detection method of FDD-LTE system " and adopt the mode of Interference Cancellation to detect, the odd numbered sequences of auxiliary synchronous signals is utilized to carry out channel estimating, then carry out interpolation and obtain complete channel response, carry out leading reconstruction that is synchronous and auxiliary synchronous signals with this, but the error in channel estimating under larger interference is larger, particularly for TD-LTE system, in frame structure, master sync signal and auxiliary synchronous signals are apart from farther, replace the channel response of master sync signal can cause more big error with the channel response of auxiliary synchronous signals, synchronizing signal is rebuild inaccurate, some community is caused not to be detected thus, also can detect some these non-existent communities simultaneously.

Summary of the invention

The searching method of the LTE system multiple cell that the object of the present invention is to provide a kind of accuracy high is low and the problem of false community detected to solve prior art small area discrimination.

For solving the problems of the technologies described above, the invention provides a kind of LTE system multi-cell search method based on Interference Cancellation, comprising:

1) community using general LTE system small region search method to detect that current demand signal is the strongest is to received signal as main plot;

2) extract the synchronous and auxiliary synchronous signals of the frequency domain master of main plot, with auxiliary synchronous signals compare synchronous with the master of the main plot that this locality generates obtains respective domain channel response;

3) channel response now contains a lot of interference, it is transformed to respectively time domain and carries out filtering, then filter result is switched back to frequency domain again;

4) obtain channel response by previous step and rebuild the synchronous and auxiliary synchronous signals of the frequency domain master of this community;

5) the frequency domain master of reconstruction is synchronous and auxiliary synchronous signals transforms to time domain, and then in Received signal strength, correspondence position is eliminated it;

6) search of next community is carried out; Repeat above step pre-determined number;

7) finally the community at every turn searched is judged according to main correlation peak-to-mean ratio that is synchronous and auxiliary synchronous signals, retain qualified efficient cell.

The present invention compared with prior art has following beneficial effect: the present invention is by the method for Interference Cancellation, the weak cell signal making to be submerged under main plot can reveal, by to channel response filtering, cell synchronous signal reconstruction is obtained more accurate, eliminate also cleaner, under substantially increasing multiple cell situation small and weak district be detected as power, add and repeatedly search for the true and false judgement in Hou Dui community, make multi-cell search result must reflect real situation around to greatest extent.

Utilize MATLAB to emulate the situation of Liang Ge community superposition, simulation parameter is as shown in table 1, utilizes conventional method and method of the present invention to carry out multi-cell search respectively, and contrast two communities at different capacity than being detected as power in situation, result as shown in Figure 2.

Table 1

Accompanying drawing explanation

Fig. 1 is the flow chart of multiple cell detection method in the present invention;

Fig. 2 is the Performance comparision figure of method of the present invention and conventional method;

Fig. 3 is the performance map of method of the present invention multiple cell situation under different channels condition.

Embodiment

Be described in detail below in conjunction with accompanying drawing 1 pair of technical solution of the present invention, but protection scope of the present invention is not limited to described embodiment.

MATLAB is utilized to simulate the transmitting terminal signal of five community superpositions, parameter is as shown in table 2, five minizone relative power 0dB respectively,-3dB,-6dB ,-9dB ,-15dB, send into receiving terminal after the multipath channel models EPA that signal specifies respectively through LTE, EVA, ETU, the LTE system multi-cell search method based on Interference Cancellation then using the present invention to propose carries out multi-cell search.

Table 2

The LTE system multi-cell search method based on Interference Cancellation that the present invention proposes, can point following steps carry out:

(1) community using general LTE system small region search method to detect that current demand signal is the strongest to received signal as main plot, and generates the synchronous and auxiliary synchronous signals of this landlord corresponding to this community, is designated as X _pSSand X _sSS;

(2) in Received signal strength, find the synchronous and OFDM symbol position, auxiliary synchronous signals place of the master of main plot, respectively discrete Fourier transform is carried out to it, extract frequency domain master synchronously and auxiliary synchronous signals, be designated as Y _pSSand Y _sSS;

(3) data of and auxiliary synchronous signals synchronous according to the master on frequency domain and this landlord synchronously and the data of auxiliary synchronous signals carry out LS channel estimation and obtain (consistent with the method that auxiliary synchronous signals carries out channel estimating for master sync signal);

${\hat{H}}_{\mathrm{LS}}=Y/X---\left(1\right)$

(4) to channel frequency response obtained in the previous step carry out filtering, be specially and channel response is done inverse discrete Fourier transform obtain to time domain

${\hat{h}}_{\mathrm{LS}}=\mathrm{IDFT}\left({\hat{H}}_{\mathrm{LS}}\right)---\left(2\right)$

Then carry out filtering in time domain, only retain the maximum sampled point of amplitude, other points are set to 0 and obtain

${\hat{h}}_{\mathrm{DFT}}\left(n\right)=\left\{\begin{array}{cc}{\hat{h}}_{\mathrm{LS}}\left(n\right)& n=1\\ 0& n\≠1\end{array}\right.---\left(3\right)$

Again time domain sequences is carried out discrete Fourier transform to change back to frequency domain and obtain

${\hat{H}}_{\mathrm{DFT}}=\mathrm{DFT}\left({\hat{h}}_{\mathrm{DFT}}\right)---\left(4\right)$

(5) filtered channel frequency response is used be multiplied by the synchronous and auxiliary synchronous signals of this local landlord, reconstruct the data on the synchronous and each subcarrier of auxiliary synchronous signals of the master of the main plot received;

(6) inverse discrete Fourier transform is carried out to data obtained in the previous step, and add Cyclic Prefix, obtain the synchronous and auxiliary synchronous signals of master in the time domain of main plot;

(7) in the data received, deduct the synchronous and auxiliary synchronous signals of master in the time domain of main plot obtained in the previous step;

(8) repeat step 1-7 to time-domain signal obtained in the previous step, hunting zone is set to before and after the sync bit of main plot within the scope of 1+CP sampled point, and searching times is 9;

(9) judge according to each autonomous correlation peak-to-mean ratio that is synchronous and auxiliary synchronous signals 9 communities that above step obtains, the community being simultaneously greater than default threshold value is efficient cell.

Method of the present invention detects first three community (first three community all detects and do not occur wrong cell), detects Qian Sige community (Qian Sige community all detects and do not occur wrong cell), detects the probability of the first five community (the first five community all detects and do not occur wrong cell) as shown in Figure 3 under three kinds of channel situation.

As mentioned above, although represented with reference to specific preferred embodiment and described the present invention, it shall not be construed as the restriction to the present invention self.Under the spirit and scope of the present invention prerequisite not departing from claims definition, various change can be made in the form and details to it.

Claims (1)

1., based on a LTE system multi-cell search method for Interference Cancellation, it is characterized in that step is as follows:

1) community using general LTE system small region search method to detect that current demand signal is the strongest is to received signal as main plot;

2) extract the synchronous and auxiliary synchronous signals of the frequency domain master of main plot, with auxiliary synchronous signals compare synchronous with the master of the main plot that this locality generates obtains respective domain channel response;

3) channel response now contains a lot of interference, it is transformed to respectively time domain and carries out filtering, then filter result is switched back to frequency domain again;

4) obtain channel response by previous step and rebuild the synchronous and auxiliary synchronous signals of the frequency domain master of this community;

5) the frequency domain master of reconstruction is synchronous and auxiliary synchronous signals transforms to time domain, and then in Received signal strength, correspondence position is eliminated it;

6) search of next community is carried out; Repeat above step pre-determined number;

7) finally the community at every turn searched is judged according to main correlation peak-to-mean ratio that is synchronous and auxiliary synchronous signals, retain qualified efficient cell.