CN103796219A - Long distance cofrequency interference source detection and positioning method for TD-LTE system - Google Patents

Abstract

The invention relates to a long distance cofrequency interference source detection and positioning method for a TD-LTE system. According to the detection method, a main synchronization signal of detected interference signals is compared with a main synchronization signal of local district signals in time domains, if time difference surpasses the threshold, the interference signals are a long distance cofrequency interference source; according to the positioning method, physical-level district ID parameters contained in the a secondary synchronization signal and in the main synchronization signal in the interference signals are utilized to acquire the signal district ID, and a position of the interference district is determined according to a signal district ID configuration table. Compared with the prior art, the method has advantages of high accuracy and high operation efficiency.

Description

Remote co-channel interference source detection and positioning method of TD-LTE system

Technical Field

The invention relates to the technical field of wireless communication, in particular to a method for detecting and positioning a remote co-frequency interference source in a TD-LTE system.

Background

In order to provide large capacity communication over limited frequency resources, cellular communication systems employ frequency reuse techniques, i.e., the same communication frequency may be used simultaneously by multiple cells that are geographically sufficiently distant. However, with the rapid increase of the traffic volume of modern cellular communication systems, the frequency reuse is more and more intensive, and the distance of cells using the same frequency (called "co-channel cells") is shortened, so that co-channel interference is inevitable.

Particularly, in a TDD system, on the premise that different base stations maintain strict time synchronization, adjacent co-frequency cells may generate close-range co-frequency interference, which is specifically represented by interference caused by a downlink signal of the adjacent co-frequency cell to a downlink signal of the cell and interference caused by an uplink signal of the adjacent co-frequency cell to an uplink signal of the cell. Under some special climatic effects, the electromagnetic wave transmission loss is very small, and the electromagnetic wave transmission loss can bypass the ground plane to realize over-the-horizon transmission, so in a TDD system, when a far base station reaches a certain base station height, under the condition of some special climatic effects, a downlink signal of a far cell can be remotely transmitted to the cell, and because the remote transmission time exceeds an uplink and downlink protection interval of the TDD system, the downlink signal of the far cell is received by the cell base station in a receiving time slot of the cell base station to interfere with the uplink signal of the cell, thereby generating the remote co-frequency interference of the TDD system.

Most of the existing interference source positioning technologies are more suitable for positioning close-range co-frequency interference sources, for example: the method for positioning the interference source through the wave arrival angle or the power change characteristic of the interference signal or the traditional on-site drive test method which is relatively accurate is adopted, and the two methods have certain defects in the actual use process:

with the first method, after the electromagnetic wave is transmitted over a long distance, the positioning is often inaccurate and cannot adapt to the change of factors such as terrain and weather.

The second method, i.e. the relatively accurate conventional on-site drive test method, requires a sports car to approach the interference source gradually along the direction of the strongest interference signal, and the whole process must be completed by assistance of maintenance personnel, and is more time-consuming and labor-consuming especially in terms of remote positioning, and has great blindness.

Publication No.: chinese patent application No. 201010107250.7 of CN102149096A discloses a method and apparatus for locating a remote co-channel interference source. The method for positioning the remote same-frequency interference source in the disclosed scheme comprises the following steps: after the interference suffered by the interfered base station is determined to be the remote co-channel interference, a distance value between a generating place generating the remote co-channel interference and the interfered base station is determined, scrambling code information used by an interference signal received by the interfered base station is obtained, an interfering base station generating the remote co-channel interference is determined according to the determined distance value and the obtained scrambling code information, and the determined interfering base station is a remote co-channel interference source of the interfered base station.

The positioning method firstly calculates the distance value between the local cell and the interference cell through the transmission delay of the interference signal, screens the cell by using scrambling code information within the range conforming to the distance value, and has the defects that the transmission path of the interference signal is complicated under special climatic conditions and complicated topographic conditions, and the method for calculating the distance of an interference source by only using the delay of the received interference signal is inaccurate.

The application also discloses a method for determining various remote co-channel interference sources:

1. judging whether an undisturbed Orthogonal Frequency Division Multiplexing (OFDM) symbol exists in a disturbed Resource Block (RB) of a disturbed base station, and if so, determining that the interference source is remote co-frequency interference;

2. acquiring the disturbed intensity of each disturbed OFDM symbol in the disturbed RB of the disturbed base station, and if the disturbed intensity of each disturbed OFDM symbol generated in sequence according to time sequence in the disturbed RB is determined to be weakened in sequence, determining that the interference received by the disturbed base station is remote co-channel interference;

3. acquiring allocation information and uplink scheduling information of a base station adjacent to a disturbed base station by using a Physical Random Access Channel (PRACH) of a cross-area base station of the disturbed base station; if the base station adjacent to the interfered base station and the cross-area base station of the interfered base station are determined according to the acquired distribution information and the uplink scheduling information of the PRACH, and the interfered RB of the interfered base station is not distributed to the user, the interference suffered by the interfered base station is determined to be remote co-channel interference;

4. and if the interference in the preset frequency area of the interfered base station is judged to be constant interference, determining the interference on the interfered base station to be remote co-channel interference.

In the above method, the 1 st, the 2 nd and the 4 nd are all based on the power of the received interference signal to judge whether the interference is influenced by the long-distance co-channel interference, and when the interference is influenced by the random noise, the accuracy of the method is reduced. However, in the method 3, the related information of the base station which may apply interference in a large range needs to be obtained, so that the overhead is high and the operation efficiency is low.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for detecting and positioning a remote co-channel interference source of a TD-LTE system, which has good accuracy and high operating efficiency.

The purpose of the invention can be realized by the following technical scheme:

a remote co-channel interference source detection method of a TD-LTE system is characterized in that the detection method compares a main synchronous signal in a detected interference signal with a main synchronous signal of a local cell in a time domain, and if a time difference exceeds a threshold value, the interference signal is a remote co-channel interference source.

The method specifically comprises the following steps:

1) extracting interference signals in a preset time-frequency domain range;

2) detecting a main synchronizing signal in the interference signal, performing type matching with 3 copies of the main synchronizing signal in the cell signal, and determining the type of the main synchronizing signal in the interference signal;

3) and comparing the main synchronous signal of the interference signal with the similar main synchronous signal of the cell in the time domain, wherein if the time difference exceeds a time difference threshold value, the interference signal is a remote co-frequency interference source.

The interference signal extracted in the step 1) is data of the first half frame at the position of 1.08MHz in the center of a frequency domain.

The specific process of type matching in the step 2) is as follows: and (3) transforming copies of the 3 kinds of main synchronous signals of the cell signal from a frequency domain to a time domain, and respectively matching with the time points of the main synchronous signals of the interference signals and then performing sliding correlation operation on the time domain, wherein the main synchronous signal with the maximum correlation is the main synchronous signal type of the interference signals.

The sliding correlation operation specifically comprises: performing IDFT after zero-filling and expanding on the frequency domain signals of the 3 primary synchronization signal copies to obtain time domain signals of the primary synchronization signal copies, and meanwhile, calculating a cross-correlation function value according to the following formula according to the time domain data of the interference signals extracted in the step 1):

<math> <mrow> <mi>R</mi> <mrow> <mo>(</mo> <mi>d</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <msub> <mi>N</mi> <mi>PSS</mi> </msub> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <mi>y</mi> <mrow> <mo>(</mo> <mi>d</mi> <mo>+</mo> <mi>n</mi> <mo>)</mo> </mrow> <msup> <mrow> <mo>(</mo> <msubsup> <mi>p</mi> <mi>time</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>)</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>*</mo> </msup> </mrow> </math>

in the formula,

time domain signal which is a copy of the primary synchronization signal, y (N) is time domain data of the interference signal extracted in step 1), N_PSSIs the number of sampling points of the main synchronous signal, u is the index value of the ZC sequence used by the main synchronous signal sequence, d is the sliding offset, d is more than or equal to 0 and less than or equal to M, and M is the number of sampling points of the first half frame data of the signal.

The time difference threshold in the step 3) is determined according to the configuration situation of the special subframe in the frame structure of the synchronization signal and the type of the cyclic prefix.

The positioning method comprises the steps of firstly adopting a remote co-frequency interference source detection method of the TD-LTE system to detect and determine interference signals sent by the remote co-frequency interference source, then utilizing physical layer cell ID parameters contained in auxiliary synchronous signals and main synchronous signals in the interference signals to calculate and obtain a physical layer cell ID, and determining the position of a cell where the remote co-frequency interference source is interfered according to a configuration table of the physical layer cell ID.

The positioning method comprises the following steps:

A) detecting and determining an interference signal serving as a remote co-frequency interference source by adopting a remote co-frequency interference source detection method of a TD-LTE system;

B) obtaining parameters of the physical layer cell ID group sending the interference signal according to the auxiliary synchronization signal of the interference signal

C) Obtaining parameters of the physical layer cell ID in the physical layer cell ID group sending the interference signal according to the type of the primary synchronization signal detected in the step A)

D) Obtaining the ID of the physical layer cell where the remote co-frequency interference source is located by the following formula to realize the positioning of the interference source:

$N_{\mathrm{ID}}^{\mathrm{cell}}=N_{\mathrm{ID}}^{\left(2\right)}+3N{N}_{\mathrm{ID}}^{\left(1\right)}$

wherein,

for the parameters of the cell physical layer cell ID group,

a parameter for a physical layer cell ID within a physical layer cell ID group,is a physical layer cell ID;

E) and searching a configuration table of the cell ID to determine the position of the interference cell according to the physical layer cell ID where the remote co-channel interference source is located.

The step B) comprises the following steps:

B1) determining the time domain position of an auxiliary synchronous signal in the interference signal according to the time domain position of a main synchronous signal in the interference signal;

B2) converting the obtained time domain auxiliary synchronous signal into a frequency domain auxiliary synchronous signal;

B3) detecting the frequency domain secondary synchronization signal to obtain the parameters of the ID group of the physical layer cell

And the auxiliary synchronization signal is detected by adopting a sequence detection method.

Compared with the prior art, the method utilizes the main synchronous signal to determine that the received interference is the remote co-frequency interference, and combines the detection result of the auxiliary synchronous signal to determine the position of the remote co-frequency interference source. The whole process does not need the participation of maintenance personnel, saves a large amount of manpower and material resources, improves the positioning efficiency, and simultaneously, because the synchronous signals have good correlation characteristics, the invention can adapt to the changes of factors such as different terrains, weather and the like, and has better stability and accuracy.

Drawings

FIG. 1 is a schematic diagram of co-channel interference of a TD-LTE system, wherein (A) is a schematic diagram of short-range co-channel interference and (B) is a schematic diagram of long-range co-channel interference;

FIG. 2 is a schematic flow chart of a method for detecting a remote co-channel interference source;

FIG. 3 is a schematic flow chart of a method for locating a remote co-channel interference source;

fig. 4 is a schematic diagram of positions of a primary synchronization signal and a secondary synchronization signal of the TD-LTE system.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Examples

Referring to fig. 1(a) and fig. 1(B), schematic diagrams of short-distance co-channel interference and long-distance co-channel interference of the TD-LTE system are shown, respectively. As can be seen from the figure, when the interfering cell is relatively close, the time delay is relatively small when the signal of the interfering cell is transmitted to the cell, and the time delay does not exceed the uplink and downlink guard interval GP of the TD-LTE system, and therefore, the short-distance co-channel interference appears as interference of the downlink signal of the interfering cell to the downlink signal of the cell, and interference of the uplink signal of the interfering cell to the uplink signal of the cell. However, if under the factors of special terrain and climate conditions, the signal of the remote cell can reach the local cell through long-distance transmission, the transmission delay is large and exceeds the guard interval GP, and the interference appears as the interference of the downlink signal of the interference cell to the uplink signal of the local cell.

Referring to fig. 4, in the TD-LTE system, downlink synchronization signals are divided into primary synchronization signals PSS and secondary synchronization signals SSS, which are fixed in time domain position in the whole frame structure and always located at the central 1.08MHz position of the whole system bandwidth in frequency domain. Therefore, the primary synchronization signal of the interference cell can be detected firstly, compared with the primary synchronization signal of the cell, if the time difference exceeds a certain range, the received interference is considered as long-distance co-frequency interference, otherwise, the received interference is considered as short-distance co-frequency interference.

Since there are three primary synchronization signals in the TD-LTE system, the three primary synchronization signals are known to the base station of each cell (the base station of each cell will backup the 3 primary synchronization signal sequences of the system), and the primary synchronization signal of each cell is transmitted using only one of the sequences, and the used sequence is related to the signal cell ID. Therefore, when detecting the primary synchronization signal of the interfering cell, the copies of the three primary synchronization signals of the cell are respectively used to compare in the received signal (i.e. performing sliding correlation operation for matching), thereby determining the primary synchronization signal sequence used by the interfering cell.

The method is used for judging the time difference threshold value and is determined according to the configuration condition of the special subframe and the type of the cyclic prefix.

As can be seen from fig. 4, the subframes 1 and 6 are different from other subframes, and are composed of DwPTS, GP, and UpPTS, which are called special subframes, and in the TD-LTE system, the special subframes have the following configuration situations, as shown in table 1:

the time difference threshold for judging the remote co-channel interference source can be determined according to the configuration condition of the special subframe and the type of the cyclic prefix. If the same special subframe configuration and the same cyclic prefix type are adopted by the cell and the interference signal transmitting cell, the time threshold is the time length occupied by the uplink and downlink guard interval GP of the cell. For example, the special subframe of the cell adopts configuration 0 and a conventional cyclic prefix, and then 10 OFDM symbols may be selected as the time difference threshold, which is 0.714ms according to the TD-LTE standard.

TABLE 1

And the positioning of the remote co-channel interference cell can be realized by detecting the cell ID of the interference cell. The cell ID of the TD-LTE system is closely related to the sequence used by the synchronization signal. LTE supports 504 physical layer cell IDs that are divided into 168 groups, called physical layer cell ID groups, each group containing 3 physical layer cell IDs. Thus, a physical layer cell ID can be defined by a parameter representing a physical layer cell ID group

(ranging from 0 to 167, carried by SSS) and parameters representing physical layer cell ID in the set of physical layer cell IDs

(range 0-2, carried by PSS) by unique definition, i.e., by

And obtaining the ID of the co-channel interference cell.

The primary synchronization signal PSS is generated from the frequency domain ZC sequence, with a total of 3 primary synchronization sequences of length 62, as follows:

<math> <mrow> <msub> <mi>d</mi> <mi>u</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mi>&pi;um</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> <mn>63</mn> </mfrac> </mrow> </msup> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mn>30</mn> </mtd> </mtr> <mtr> <mtd> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mi>j</mi> <mfrac> <mrow> <mi>&pi;u</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> <mn>63</mn> </mfrac> </mrow> </msup> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>31,32</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mn>61</mn> </mtd> </mtr> </mtable> </mfenced> </mrow> </math>

wherein, 3 primary synchronization sequences use ZC sequence index u and 3 numbers representing physical layer cell ID in the physical layer cell ID group

There is a one-to-one mapping relationship, as shown in table 2:

TABLE 2

Therefore, the parameter is obtained by detecting the index u corresponding to the sequence used by the PSS

The SSS sequence is composed of two binary sequences s with the length of 31₀(n) and s₁(n) sequences formed by interleaving and concatenating the sequences, denoted as d (n), the two sequences of length 31 being merged in an even numberSubframe 0 and odd subframe 5 are different, and the specific way is shown in the following formula:

wherein n is more than or equal to 0 and less than or equal to 30, m₀And m₁Is a parameter set by physical layer cell ID

The relationship is determined as follows:

m₀＝m′mod31

to round down, m 'qq', etc. are intermediate variables needed for the calculation.

The mapping relationship is shown in Table 3.

The two sequences are m-sequences

The two cyclic shift sequences of (a) are as follows:

$s_0^{\left(m_0\right)}\left(n\right)=\tilde{s}\left((n+m_0)\mathrm{mod}31\right)$

$s_1^{\left(m_1\right)}\left(n\right)=\tilde{s}\left((n+m_1)\mathrm{mod}31\right)$

wherein,

i is 0. ltoreq. i.ltoreq.30, defined as

The initial conditions are x (0) 0, x (1) 0, x (2) 0, x (3) 0, and x (4) 1.

c₀(n)、c₁(n) andare scrambling sequences that produce SSS. Two scrambling sequences c₀(n) and c₁(n) is determined by the primary synchronization signal and is an m-sequence

See the following formula.

$c_0\left(n\right)=\tilde{c}\left((n+N_{\mathrm{ID}}^{\left(2\right)})\mathrm{mod}31\right)$

$c_1\left(n\right)=\tilde{c}\left((n+N_{\mathrm{ID}}^{\left(2\right)}+3)\mathrm{mod}31\right)$

Wherein,

i is 0. ltoreq. i.ltoreq.30, defined as

The initial conditions are x (0) 0, x (1) 0, x (2) 0, x (3) 0, and x (4) 1.

Scrambling sequence

Is an m sequence

Cyclic shift of (d), see the following equation:

$z_1^{\left(m_0\right)}\left(n\right)=\tilde{z}(n+\left(m_0\mathrm{mod}8\right)\mathrm{mod}31)$

i is 0. ltoreq. i.ltoreq.30, defined as <math> <mrow> <mi>x</mi> <mrow> <mo>(</mo> <mover> <mi>i</mi> <mo>&OverBar;</mo> </mover> <mo>+</mo> <mn>5</mn> <mo>)</mo> </mrow> <mo>=</mo> <mrow> <mo>(</mo> <mi>x</mi> <mrow> <mo>(</mo> <mover> <mi>i</mi> <mo>&OverBar;</mo> </mover> <mo>+</mo> <mn>4</mn> <mo>)</mo> </mrow> <mo>+</mo> <mi>x</mi> <mrow> <mo>(</mo> <mover> <mi>i</mi> <mo>&OverBar;</mo> </mover> <mo>+</mo> <mn>2</mn> <mo>)</mo> </mrow> <mo>+</mo> <mi>x</mi> <mrow> <mo>(</mo> <mover> <mi>i</mi> <mo>&OverBar;</mo> </mover> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>+</mo> <mi>x</mi> <mrow> <mo>(</mo> <mover> <mi>i</mi> <mo>&OverBar;</mo> </mover> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mi>mod</mi> <mn>2</mn> <mo>,</mo> </mrow> </math>

The initial conditions are x (0) 0, x (1) 0, x (2) 0, x (3) 0, and x (4) 1.

Thus, the parameter m may be derived by detecting SSS₀And m₁According to m₀、m₁Andto determine the objectParameters of physical layer cell ID groupsThereby combining the parameters of the physical layer cell ID in the physical layer cell ID group detected by the PSS

And determining the cell ID of the interference cell so as to locate the remote co-channel interference source.

TABLE 3

Based on the above principle, the steps of the method for detecting a remote co-channel interference source in the TD-LTE system according to the present embodiment are shown in fig. 2, and include the following steps:

step 1: extracting interference signals in a preset time-frequency domain range;

fig. 4 shows a schematic diagram of the locations of the primary synchronization signal PSS and the secondary synchronization signal SSS, and it can be seen that the PSS and SSS signals are always located at the central 1.08MHz position in the entire system bandwidth in the frequency domain. The main synchronization signal is transmitted once every 5ms, sequences used by a front half frame and a rear half frame in a wireless frame are the same, in addition, the SSS detection of the invention adopts a sequence detection method, namely, the detection is carried out by using data of even number subframes, therefore, the invention only needs to extract the data of the front half frame at the position of 1.08MHz in the center on a frequency domain.

Step 2: detecting a main synchronizing signal in the interference signal, performing type matching with 3 copies of the main synchronizing signal in the cell signal, and determining the type of the main synchronizing signal in the interference signal;

the main synchronizing signal uses a ZC sequence which is converted into a time domain signal and still has good orthogonality, so that 3 local main synchronizing signal copies can be converted into a time domain from a frequency domain, sliding correlation operation on the time domain is carried out on the time domain and the signal extracted in the step 1 from the time point of the main synchronizing signal of the cell, and the main synchronizing signal with the maximum correlation is the main synchronizing signal type of the interference signal.

The specific process of the sliding correlation operation is as follows: performing IDFT after zero-filling and expanding on the frequency domain signals of the 3 primary synchronization signal copies to obtain time domain signals of the primary synchronization signal copies, and meanwhile, calculating a cross-correlation function value according to the following formula according to the time domain data of the interference signals extracted in the step 1):

<math> <mrow> <mi>R</mi> <mrow> <mo>(</mo> <mi>d</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <msub> <mi>N</mi> <mi>PSS</mi> </msub> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <mi>y</mi> <mrow> <mo>(</mo> <mi>d</mi> <mo>+</mo> <mi>n</mi> <mo>)</mo> </mrow> <msup> <mrow> <mo>(</mo> <msubsup> <mi>p</mi> <mi>time</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>)</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>*</mo> </msup> </mrow> </math>

in the formula,

time domain signal which is a copy of the primary synchronization signal, y (N) is time domain data of the interference signal extracted in step 1), N_PSSIs the number of sampling points of the main synchronous signal, u is the index value of the ZC sequence used by the main synchronous signal sequence, d is the sliding offset, d is more than or equal to 0 and less than or equal to M, and M is the number of sampling points of the first half frame data of the signal.

In this step, the time domain position of the primary synchronization signal and the corresponding parameter representing the physical layer ID in the physical layer ID group can be recorded at the same time

The method is used for positioning the remote co-channel interference source.

Step 3; and comparing a main synchronous signal of the interference signal with a similar main synchronous signal of a signal of the cell in a time domain, if the time difference exceeds a time difference threshold value, the interference signal is a remote co-channel interference source, wherein the time difference threshold value is determined according to the configuration condition of a special subframe in a synchronous signal frame structure and the type of a cyclic prefix.

The invention also provides a method for positioning a remote co-channel interference source of a TD-LTE system, which needs to be applied to the detection method, and the specific steps are shown in figure 3,

step A: detecting and determining an interference signal serving as a remote co-frequency interference source by adopting a remote co-frequency interference source detection method of a TD-LTE system;

and B: detecting an auxiliary synchronization signal in an interference signal, and obtaining a parameter of a physical layer cell ID group sending the interference signal according to the auxiliary synchronization signal of the interference signal

It can be seen from fig. 3 that PSS occupies the 3 rd OFDM symbol of subframes 1, 6, and SSS occupies the last 1 symbol of subframes 0, 5. The time domain positions of the PSS and SSS signals are relatively fixed, and differ by 3 OFDM symbols, so the time domain position of the SSS of the interfering cell can be determined according to the time domain position of the PSS of the interfering cell recorded in step 21.

The m-sequence adopted by the SSS only has good orthogonality on the frequency domain, so that the m-sequence needs to be converted into the frequency domain and then subjected to correlation detection. The SSS has two detection modes, sequence detection and joint detection. Sequence detection utilizes only one SSS symbol, while joint detection requires the use of SSS symbols for the first and second fields. Considering that the sequence detection can reduce 30% of the calculation amount compared with the joint detection, the invention adopts a sequence detection method, and the specific method is as follows:

the received frequency domain auxiliary synchronization signal is recorded as w (n), n is more than or equal to 0 and less than or equal to 61, w (2n) and w (2n +1) respectively represent an even sequence and an odd sequence, m sequence s (n) for constructing SSS, n is more than or equal to 0 and less than or equal to 30 times are repeated to obtain a reference sequence s_ref(n)，0≤n≤61。

m₀，m₁Detected value of (2)

And

is obtained by the following formula:

<math> <mrow> <msub> <mover> <mi>m</mi> <mo>^</mo> </mover> <mn>0</mn> </msub> <mo>=</mo> <munder> <mrow> <mi>arg</mi> <mi> </mi> <mi>max</mi> </mrow> <msub> <mi>m</mi> <mn>0</mn> </msub> </munder> <mo>=</mo> <mrow> <mo>(</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>30</mn> </munderover> <mi>w</mi> <mrow> <mo>(</mo> <mn>2</mn> <mi>n</mi> <mo>)</mo> </mrow> <mo>&CenterDot;</mo> <msub> <mi>c</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>&CenterDot;</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>s</mi> <mi>ref</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>m</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>*</mo> </msup> <mo>)</mo> </mrow> </mrow> </math>

<math> <mrow> <msub> <mover> <mi>m</mi> <mo>^</mo> </mover> <mn>1</mn> </msub> <mo>=</mo> <munder> <mrow> <mi>arg</mi> <mi>max</mi> </mrow> <msub> <mi>m</mi> <mn>1</mn> </msub> </munder> <mo>=</mo> <mrow> <mo>(</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>30</mn> </munderover> <mi>w</mi> <mrow> <mo>(</mo> <mn>2</mn> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>&CenterDot;</mo> <msub> <mi>c</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>&CenterDot;</mo> <msubsup> <mi>z</mi> <mn>1</mn> <mrow> <mo>(</mo> <msub> <mi>m</mi> <mn>0</mn> </msub> <mo>=</mo> <msub> <mover> <mi>m</mi> <mo>^</mo> </mover> <mn>0</mn> </msub> <mo>)</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>&CenterDot;</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>s</mi> <mi>ref</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <msub> <mi>m</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>*</mo> </msup> <mo>)</mo> </mrow> </mrow> </math>

0≤m₀≤29，1≤m₁≤30

wherein, c₀(n)、c₁(n) and z₁(n) is a scrambling sequence as previously described. Obtained by the above formula

And

finding in TD-LTE standard

And m₀And m₁Table of mapping relationships between

And C: obtaining the parameters of the physical layer cell ID in the physical layer cell ID group sending the interference signal according to the type of the primary synchronization signal detected in the step A

Step D: obtaining the ID of the physical layer cell where the remote co-frequency interference source is located by the following formula to realize the positioning of the interference source:

$N_{\mathrm{ID}}^{\mathrm{cell}}=N_{\mathrm{ID}}^{\left(2\right)}+3N_{\mathrm{ID}}^{\left(1\right)}$

wherein,

for the parameters of the cell physical layer cell ID group,

a parameter for a physical layer cell ID within a physical layer cell ID group,

is a physical layer cell ID;

e, step E; and searching a configuration table of the cell ID to determine the position of the interference cell according to the physical layer cell ID where the remote co-channel interference source is located.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. A remote co-channel interference source detection method of a TD-LTE system is characterized in that the detection method compares a main synchronous signal in a detected interference signal with a main synchronous signal of a local cell in a time domain, and if a time difference exceeds a threshold value, the interference signal is determined to be a remote co-channel interference source.

2. The method according to claim 1, wherein the method specifically comprises the following steps:

1) extracting interference signals in a preset time-frequency domain range;

2) detecting a main synchronizing signal in the interference signal, performing type matching with 3 copies of the main synchronizing signal in the cell signal, and determining the type of the main synchronizing signal in the interference signal;

3) and comparing the main synchronous signal of the interference signal with the similar main synchronous signal of the cell in the time domain, and if the time difference exceeds a time difference threshold value, determining that the interference signal is a remote co-frequency interference source.

3. The method as claimed in claim 2, wherein the interference signal extracted in step 1) is data of a first half frame located at a position of 1.08MHz at the center of a frequency domain.

4. The method according to claim 2, wherein the specific process of type matching in step 2) is as follows: and (3) transforming copies of the 3 kinds of main synchronization signals of the cell signal from a frequency domain to a time domain, and respectively carrying out sliding correlation operation on the copies and the time point of the main synchronization signal of the interference signal in the time domain to match the main synchronization signals, wherein the main synchronization signal with the maximum correlation is the main synchronization signal type of the interference signal.

5. The TD-LTE system remote co-channel interferer positioning method of claim 4, wherein the sliding correlation operation specifically is: performing IDFT after zero-filling and expanding on the frequency domain signals of the 3 primary synchronization signal copies to obtain time domain signals of the primary synchronization signal copies, and meanwhile, calculating a cross-correlation function value according to the following formula according to the time domain data of the interference signals extracted in the step 1);

<math> <mrow> <mi>R</mi> <mrow> <mo>(</mo> <mi>d</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <msub> <mi>N</mi> <mi>PSS</mi> </msub> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <mi>y</mi> <mrow> <mo>(</mo> <mi>d</mi> <mo>+</mo> <mi>n</mi> <mo>)</mo> </mrow> <msup> <mrow> <mo>(</mo> <msubsup> <mi>p</mi> <mi>time</mi> <mrow> <mo>(</mo> <mi>u</mi> <mo>)</mo> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>)</mo> </mrow> <mo>*</mo> </msup> </mrow> </math>

in the formula,time domain signal which is a copy of the primary synchronization signal, y (N) is time domain data of the interference signal extracted in step 1), N_PSSIs the number of sampling points of the main synchronous signal, u is the index value of the ZC sequence used by the main synchronous signal sequence, d is the sliding offset, d is more than or equal to 0 and less than or equal to M, and M is the number of sampling points of the first half frame data of the signal.

6. The method as claimed in claim 2, wherein the time difference threshold in step 3) is determined according to the configuration of the special subframe in the synchronization signal frame structure and the type of the cyclic prefix.

7. A long-distance co-channel interference source positioning method of a TD-LTE system applying the detection method of claim 1 is characterized in that the positioning method firstly adopts the long-distance co-channel interference source detection method of the TD-LTE system to detect and determine interference signals emitted by a long-distance co-channel interference source, then calculates and obtains a physical layer cell ID by using physical layer cell ID parameters contained in an auxiliary synchronizing signal and a main synchronizing signal in the interference signals, and determines the position of a cell where the interference long-distance co-channel interference source is located according to a configuration table of the physical layer cell ID.

8. The method of claim 7, wherein the method comprises the following steps:

A) detecting and determining an interference signal serving as a remote co-frequency interference source by adopting a remote co-frequency interference source detection method of a TD-LTE system;

B) obtaining parameters of the physical layer cell ID group sending the interference signal according to the auxiliary synchronization signal of the interference signal

C) Obtaining parameters of the physical layer cell ID in the physical layer cell ID group sending the interference signal according to the type of the primary synchronization signal detected in the step A)

D) Obtaining the ID of the physical layer cell where the remote co-frequency interference source is located by the following formula to realize the positioning of the interference source:

$N_{\mathrm{ID}}^{\mathrm{cell}}=N_{\mathrm{ID}}^{\left(2\right)}+3N{N}_{\mathrm{ID}}^{\left(1\right)}$

wherein,

is a cellThe parameters of the physical layer cell ID group,

a parameter for a physical layer cell ID within a physical layer cell ID group,is a physical layer cell ID;

E) according to the ID of the physical layer cell where the remote co-frequency interference source is located, searching a configuration table of the cell ID to determine the location of the cell where the remote co-frequency interference source is located.

9. The method of claim 7, wherein the step B) comprises the following steps:

B1) determining the time domain position of an auxiliary synchronous signal in the interference signal according to the time domain position of a main synchronous signal in the interference signal;

B2) converting the obtained time domain auxiliary synchronous signal into a frequency domain auxiliary synchronous signal;

B3) detecting the frequency domain secondary synchronization signal to obtain the parameters of the ID group of the physical layer cell

10. The method of claim 7, wherein the secondary synchronization signal is detected by a sequence detection method.

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