CN101364830A - Method and apparatus for searching position of downlink synchronous code - Google Patents

Abstract

The invention discloses a method for searching the position of SYNC-DL. The method comprises the following steps: correlating each candidate SYNC_DL with signals in a characteristic window in a sliding manner, and acquiring the correlative peak of each candidate SYNC_DL in each time slice; calculating the ratio of the correlative peaks of each candidate SYNC_DL in each time slice and the neighboring time slice to obtain the correlative peak ratio of each candidate SYNC_DL in each time slice; recording the maximal correlative peak ratio of each candidate SYNC_DL in each sub-frame, and the time slice to which the maximal correlative peak ratio belongs; and summing the maximal correlative peak ratio of each candidate SYNC_DL in the same time slice in each sub-frame when the searching period is ended to obtain the maximal correlative peak ratio of each candidate SYNC_DL in the searching period, wherein the candidate SYNC_DL corresponding to the maximal value and the corresponding time slice are respectively the SYNC_DL used at the network side and the position of the SYNC_DL. The invention also discloses a device for searching the position of SYNC-DL.

Description

Method and device for searching downlink synchronous code position

Technical Field

The present invention relates to a signal search technology in a mobile communication system, particularly to a method and a device for searching a downlink synchronization code position in a time division synchronous code division multiple access (TD-SCDMA) system.

Background

Initial Cell Search (ICS) refers to a process in which a User Equipment (UE) must Search for a suitable Cell as soon as possible when the UE is powered on or in a mobile state, and quickly access (generally referred to as login) to use a service provided by a network. The purpose of ICS is to make UE and base station (NB, Node B) have the same frequency and synchronization, determine the starting position of a radio frame, determine the code numbers of downlink synchronization code (SYNC _ DL) and basic training sequence (midamble), further solve Broadcast Channel (BCH) information through detection and demodulation processes, and finally log in a cell.

Subframe data for UE to perform cell initial search is set in the TD-SCDMA system. In the subframe structure, a downlink pilot time slot (DwPTS) for transmitting SYNC _ DL is included. The UE can determine the position of DwPTS by searching and determining the SYNC _ DL code segment in the subframe data, and then logs in by taking the position as an access point. Therefore, the UE determines the accuracy of the DwPTS position directly relates to whether the UE can accurately log in.

As shown in fig. 1, the SYNC _ DL code segment is 64 chips (chips) with 4 symbols, the left and right sides of the SYNC _ DL code segment are provided with guard time slot (GP) code segments, and the left side of the SYNC _ DL code segment is provided with GP code segments with 48 chips with 3 symbols, which are used for trailing protection of the normal time slot 0(TS 0). There are GP code segments with 96 chips of 6 symbols to the right of the SYNC _ DL code segment.

Since the data of the SYNC _ DL code segment is transmitted at full power and the left and right GP code segments are transmitted at zero power, the power value of the SYNC _ DL code segment is a "peak" value compared to the left and right GP code segments without interference. The existing characteristic window searching method just utilizes the characteristic to carry out SYNC _ DL searching. But the signature window search method is susceptible to interference from nearby base stations or UEs.

The existing method for searching for SYNC _ DL further includes a correlation detection method. When searching for SYNC _ DL by using a correlation detection method, it is necessary to perform sliding correlation between a plurality of (at most 32) candidate SYNC _ DLs and a received signal in the whole subframe, find the SYNC _ DL with the largest correlation value and the corresponding position thereof, and complete the search for SYNC _ DL.

Although the flow of ICS can be simplified by using the correlation detection method, because there is a certain correlation between midamble codes and SYNC _ DL codes, and when SYNC _ DL is in sliding correlation with the signal of the whole subframe, the correlation peak not only relates to the correlation between the signal and the SYNC _ DL, but also relates to the strength of the received signal, when there is another UE near the UE, there is a strong uplink interference slot at this time, which will cause the correlation peak to appear in the midamble code portion of the uplink interference slot, thereby causing the failure of searching for SYNC _ DL.

Disclosure of Invention

In view of this, the technical problem to be solved by the present invention is to provide a method and a device for searching a position of a downlink synchronization code, so as to avoid an influence of an uplink interference timeslot on searching for SYNC _ DL and improve a success rate of searching for SYNC _ DL.

Therefore, the technical scheme provided by the invention is as follows:

a method for searching the position of a downlink synchronization code comprises the following steps:

calculating the correlation peak value of each alternative SYNC _ DL in each time slice;

for each alternative SYNC _ DL, calculating the ratio of the correlation peak value of each time slice to the correlation peak value of the adjacent time slice to obtain the correlation peak value ratio of each alternative SYNC _ DL in each time slice;

recording the maximum correlation peak value ratio of each alternative SYNC _ DL in each subframe and the time slice where the maximum correlation peak value ratio is located;

and when the search period is ended, summing the maximum correlation peak ratios of the candidate SYNC _ DL in the same time slice in each subframe according to each candidate SYNC _ DL, and determining the maximum correlation peak ratio of each candidate SYNC _ DL in the search period, wherein the candidate SYNC _ DL corresponding to the maximum value and the corresponding time slice are the positions of the SYNC _ DL used by the network side and the SYNC _ DL.

Wherein the length of the time slice is set according to the length of SYNC _ DL.

The length of a characteristic window is set according to the lengths of two time slices, and each alternative downlink synchronous code SYNC _ DL is subjected to sliding correlation with a signal received in the characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in each time slice.

Taking the first two time slices in the search period as a characteristic window, and receiving a downlink signal sent by a network side in the characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the characteristic window;

sliding the characteristic window backwards by a time slice to form a new characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a new characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the new characteristic window;

and judging whether the searching period is ended or not, if not, continuously sliding the characteristic window backwards for a time slice to form a new characteristic window again.

Wherein, by calculating ${\mathrm{rate}}_{i\_j}^l=\frac{P_{i\_j}^l}{P_{i\_j-1}^l+P_{i\_j+1}^l},$ Obtaining the correlation peak value ratio of each alternative SYNC _ DL in each time slice;

wherein,

indicating the correlation peak ratio of SYNC _ DL with code number l in the jth time slice of the ith sub-frame in the search period,

respectively represents the correlation peak values of the SYNC _ DL with the code number l in the j-1 th, j +1 th time slice of the ith subframe in the search period.

Based on the method, the invention also provides a device for searching the position of the downlink synchronous code, which comprises the following steps:

a correlation peak value calculation unit, configured to calculate a correlation peak value of each candidate SYNC _ DL in each time slice;

a correlation peak ratio calculation unit, configured to calculate, for each candidate SYNC _ DL, a ratio of correlation peaks of each time slice to correlation peaks of adjacent time slices, and obtain a correlation peak ratio of each candidate SYNC _ DL in each time slice;

the recording unit is used for recording the maximum correlation peak value ratio of each alternative SYNC _ DL in each subframe and the time slice where the maximum correlation peak value ratio is located; and the number of the first and second groups,

the summing unit is used for summing the maximum correlation peak value ratio of each alternative SYNC _ DL in the same time slice in each subframe at the end of the search period;

the maximum value unit is used for obtaining the maximum correlation peak value ratio of each alternative SYNC _ DL in the search period according to the summation result of the summation unit;

a decision unit, configured to determine an alternative SYNC _ DL corresponding to a maximum value in the ratios obtained by the maximum value unit and a corresponding time slice;

the alternative SYNC _ DL and the corresponding time slice determined by the decision unit are the SYNC _ DL used by the network side and the location of the SYNC _ DL.

Wherein, the length of the time slice is the length of SYNC _ DL.

The length of the characteristic window is set according to the length of two time slices, and the correlation peak value calculation unit performs sliding correlation on each alternative downlink synchronous code SYNC _ DL and the signal received in the characteristic window to obtain the correlation peak value of each alternative SYNC _ DL in each time slice.

The correlation peak value calculation unit takes the first two time slices in the search period as a characteristic window, and receives a downlink signal sent by a network side in the characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the characteristic window;

sliding the characteristic window backwards by a time slice to form a new characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a new characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the new characteristic window;

and judging whether the searching period is ended or not, if not, continuously sliding the characteristic window backwards for a time slice to form a new characteristic window again.

Wherein the correlation peak ratio calculating unit calculates the correlation peak ratio by calculating ${\mathrm{rate}}_{i\_j}^l=\frac{P_{i\_j}^l}{P_{i\_j-1}^l+P_{i\_j+1}^l},$ Obtaining the correlation peak value ratio of each alternative SYNC _ DL in each time slice;

wherein,

indicating the correlation peak ratio of SYNC _ DL with code number l in the jth time slice of the ith sub-frame in the search period,respectively represents the correlation peak values of the SYNC _ DL with the code number l in the j-1 th, j +1 th time slice of the ith subframe in the search period.

It can be seen that, when the method described in the above embodiment is used to search for SYNC _ DL and its position, if there is strong time slot interference, the correlation peak values of three consecutive time slices in the time slot are all larger, and the correlation peak value ratio of each time slice is smaller, thereby avoiding the influence of the uplink interference time slot on the search for SYNC _ DL and improving the success rate of the search for SYNC _ DL.

Drawings

FIG. 1 is a diagram of a SYNC _ DL code segment;

FIG. 2 is a flow chart of one embodiment of a method provided by the present invention;

FIG. 3 is a flow chart for calculating the correlation peak of each alternative SYNC _ DL at each time slice;

FIG. 4 is a schematic diagram of a sub-frame equally divided into 100 time slices during a search period;

fig. 5 is a schematic diagram of an apparatus for searching for SYNC _ DL location according to the present invention.

Detailed Description

In order that those skilled in the art will better understand the present invention, the methods provided herein are described in detail below with reference to specific examples. Fig. 2 shows the flow of the method.

In step 21, performing sliding correlation on each alternative SYNC _ DL and a signal received in a characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in each time slice;

and in step 22, for each candidate SYNC _ DL, the ratio of the correlation peak value of each time slice to the correlation peak value of the adjacent time slice is calculated, and the correlation peak value ratio of each candidate SYNC _ DL in each time slice is obtained.

Then, in step 23, the maximum correlation peak ratio of each candidate SYNC _ DL in each subframe and the time slice in which the maximum correlation peak ratio exists are recorded.

At the end of the search period, in step 24, for each candidate SYNC _ DL, its maximum correlation peak ratio at the same time slice in each subframe is summed.

In step 25, by comparison, the maximum correlation peak ratio of each candidate SYNC _ DL in the search period is obtained, and the maximum value thereof is determined.

In step 26, the candidate SYNC _ DL corresponding to the maximum value and the corresponding time slice are determined.

The candidate SYNC _ DL corresponding to the maximum value is the SYNC _ DL used by the network side, and the corresponding time slice is the position of the SYNC _ DL.

In the method for searching for the SYNC _ DL position proposed by the present invention, each subframe is divided into several time slices, for example: each subframe is equally divided into 100 time slices. If each subframe is equally divided into 100 time slices, each time slice can receive 4 symbols for 64 chips. In addition, a feature window and search time are set. The length of each characteristic window is 2 time slices, the search time can be set according to specific requirements, the search time is preferably an integer multiple of the length of a subframe, and for example, the search time can be set to 4 subframes. Fig. 4 is a schematic diagram of equally dividing a subframe into 100 time slices during a search period.

In the invention, firstly, each alternative SYNC _ DL is required to be subjected to sliding correlation with a received signal according to a characteristic window, and the correlation peak value of each alternative SYNC _ DL in each time slice is obtained. Fig. 3 shows a flow of calculating the correlation peak of each alternative SYNC _ DL at each time slice.

The UE starts searching for the position of SYNC _ DL, and receives a downlink signal transmitted from the network side in a signature window with the first two time slices as one signature window in step 31.

In conjunction with FIG. 4, t may be used_{i_j}Each time slice in a search period is shown, wherein i represents the sequence number of the subframe in the search period, and i is 1, 2, 3 and 4; j denotes the sequence number of the time slice within the subframe, j 1, 2. For example: time slice t_{1_1}、t_{1_2}That is, time slice 1, time slice 2, and time slice t of the 1 st subframe in the search period_{2_95}Then it is the time slice 95 of the 2 nd subframe within the search period.

t_{1_1}、t_{1_2}I.e. the first two time slices, denoted by t_{1_1}、t_{1_2}As a characteristic window, t_{1_1}Is the previous time slice in the characteristic window, t_{1_2}Is the latter time slice in the signature window. The length of the signal received by the UE in the characteristic window is 8 symbols, which is 128 chips.

In step 32, the signal received by the UE in the characteristic window is respectively subjected to sliding correlation with each alternative SYNC _ DL, so as to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the characteristic window.

According to the current specification requirements, there are 32 SYNC _ DLs that the system may use. Therefore, signals received by the UE in the characteristic window need to be respectively subjected to sliding correlation with 32 SYNC _ DLs, and 32 SYNC _ DLs are obtained in the time slice t₁_₁The correlation peak of (a).

In step 33, the feature window is slid back by one time slice to form a new feature window.

It can be seen that since each feature window consists of two time slices, and each time the feature window slides backwards by only one time slice, the later time slice of the original feature window will become the previous time slice of the new feature window. For example, the feature window in step 31 consists of time slice t_{1_1}、t_{1_2}And in step 33 the new feature window is formed by t_{1_2}、t_{1_3}And (4) forming.

In step 34, the signal received by the UE in the new characteristic window is respectively subjected to sliding correlation with each alternative SYNC _ DL, so as to obtain a correlation peak value of each alternative SYNC _ DL in the previous time slice in the new characteristic window.

It can be seen that the UE only needs to receive the latter time slice of the new feature window, i.e. time slice t_{1_3}The signal of (2). With the UE within the new characteristic window, i.e. time slice t_{1_2}、t_{1_3}In the method, after the received signals are respectively subjected to sliding correlation with 32 SYNC _ DL, 32 SYNC _ DL can be obtained at a time slice t_{1_2}The correlation peak of (a).

In step 35, it is determined whether the search time is over. If so, it is ended, otherwise, it returns to step 33.

During the search, for each candidate SYNC _ DL, the ratio of the correlation peak of each time slice of the SYNC _ DL to the correlation peak of the adjacent time slice is also calculated to obtain the correlation peak ratio of each candidate SYNC _ DL in each time slice. The correlation peak ratio of a certain alternative SYNC _ DL in each time slice can be calculated according to equation (1):

${\mathrm{rate}}_{i\_j}^l=\frac{P_{i\_j}^l}{P_{i\_j-1}^l+P_{i\_j+1}^l}---\left(1\right)$

wherein,

indicating the correlation peak ratio of SYNC _ DL with code number l in the jth time slice of the ith sub-frame in the search period,

SYNC _ DL with code number l in the ith search periodCorrelation peak for the jth time slice of a subframe, for example:

indicating the correlation peak of SYNC _ DL code number 2 in time slice 86 of sub-frame 3 during the search period.

Accordingly, the number of the first and second electrodes,respectively represents the correlation peak values of SYNC _ DL with code number l in j-1 th and j +1 th time slices of the ith subframe in the search period.

The term "1", 2 ", as well as 32" i ", 1, 2, 3, 4, and" j "1, 2", and "1.

It should be noted that, when calculating the correlation peak ratio of the first time slice of the current subframe, the correlation peak of the last time slice of the previous subframe needs to be used, and this time, the calculation is performed according to equation (2):

${\mathrm{rate}}_{i\_1}^l=\frac{P_{i\_1}^l}{P_{i-1\_100}^l+P_{i\_2}^l}---\left(2\right)$

it can be seen that for integerThe first time slice (t) within a search period_{1_1}) And the last time slice (t)_{4_100}) In other words, it cannot be calculated according to equation (1)

And

in practical applications, one more time slice may be received before and after each time slice for calculation.

Alternatively, the correlation peak of the last time slice may be used to calculate the correlation peak ratio of the first time slice, and the correlation peak of the first time slice may be used to calculate the correlation peak ratio of the last time slice, i.e., by calculation ${\mathrm{rate}}_{1\_1}^l=\frac{P_{1\_1}^l}{P_{4\_100}^l+P_{1\_2}^l}$ And ${\mathrm{rate}}_{4\_100}^l=\frac{P_{4\_100}^l}{P_{4\_99}^l+P_{1\_1}^l},$ to obtain

And ${\mathrm{rate}}_{4\_100}^l.$

and after the correlation peak value ratio of each alternative SYNC _ DL in each time slice is obtained, only the maximum correlation peak value ratio of each alternative SYNC _ DL in each subframe and the time slice where the maximum correlation peak value ratio is located are recorded.

That is, for SYNC _ DL with code number l, only recording $\max \{{\mathrm{rate}}_{1\_1}^l,...,{\mathrm{rate}}_{1\_100}^l\},$ $\max \{{\mathrm{rate}}_{2\_1}^l,...,{\mathrm{rate}}_{2\_100}^l\},$ $\max \{{\mathrm{rate}}_{3\_1}^l,...,{\mathrm{rate}}_{3\_100}^l\}$ And $\max \{{\mathrm{rate}}_{4\_1}^l,...,{\mathrm{rate}}_{4\_100}^l\}.$

max { } is a function taking the maximum value, for example, max { a, b, c } denotes taking the maximum value among a, b, c.

Then, for each alternative SYNC _ DL, the maximum correlation peak ratios of the alternative SYNC _ DL in the same time slice in each subframe are summed to obtain the maximum correlation peak ratio of each alternative SYNC _ DL in the search time. Taking SYNC _ DL as an example, the process of obtaining the maximum correlation peak ratio of SYNC _ DL in the search time will be described.

Determining whether the maximum correlation peak value ratio of the SYNC _ DL in each subframe is in the same time slice;

superposing and summing the maximum correlation peak ratios in the same time slice to obtain the sum of the correlation peak ratios of the SYNC _ DL in the time slice;

and taking the sum of the maximum correlation peak ratios as the maximum correlation peak ratio of the SYNC _ DL in the search time, and recording the corresponding time slice.

If there is no maximum correlation peak ratio at the same time slice, the comparison is directly made.

It can be seen that for the same time slice, the probability of the occurrence of a plurality of correlation peak ratios corresponding to the presence of the SYNC _ DL code in the time slice is increased, and the correlation peak values are accumulated, which is equivalent to accumulating the confidence, so that the judgment is more accurate.

More specifically, assume that for SYNC _ DL with code number 19,

${\mathrm{rate}}_{1\_47}^{19}=\max \{{\mathrm{rate}}_{1\_1}^{19},...,{\mathrm{rate}}_{1\_100}^{19}\},$

${\mathrm{rate}}_{2\_45}^{19}=\max \{{\mathrm{rate}}_{2\_1}^{19},...,{\mathrm{rate}}_{2\_100}^{19}\},$

${\mathrm{rate}}_{3\_47}^{19}=\max \{{\mathrm{rate}}_{3\_1}^{19},...,{\mathrm{rate}}_{3\_100}^{19}\},$

${\mathrm{rate}}_{4\_45}^{19}=\max \{{\mathrm{rate}}_{4\_1}^{19},...,{\mathrm{rate}}_{4\_100}^{19}\},$

the maximum correlation peak ratio of SYNC _ DL with code number 19 in the search time is $\max \{{\mathrm{rate}}_{1\_47}^{19}+{\mathrm{rate}}_{3\_47}^{19},{\mathrm{rate}}_{2\_45}^{19}+{\mathrm{rate}}_{4\_45}^{19}\}.$

It is assumed that,

${\mathrm{rate}}_{1\_47}^{19}=\max \{{\mathrm{rate}}_{1\_1}^{19},...,{\mathrm{rate}}_{1\_100}^{19}\},$

${\mathrm{rate}}_{2\_46}^{19}=\max \{{\mathrm{rate}}_{2\_1}^{19},...,{\mathrm{rate}}_{2\_100}^{19}\},$

${\mathrm{rate}}_{3\_47}^{19}=\max \{{\mathrm{rate}}_{3\_1}^{19},...,{\mathrm{rate}}_{3\_100}^{19}\},$

${\mathrm{rate}}_{4\_48}^{19}=\max \{{\mathrm{rate}}_{4\_1}^{19},...,{\mathrm{rate}}_{4\_100}^{19}\},$

the maximum correlation peak ratio of SYNC _ DL with code number 19 in the search time is $\max \{{\mathrm{rate}}_{2\_46}^{19},{\mathrm{rate}}_{1\_47}^{19}+{\mathrm{rate}}_{3\_47}^{19},{\mathrm{rate}}_{4\_48}^{19}\}.$

It is assumed that,

${\mathrm{rate}}_{1\_47}^{19}=\max \{{\mathrm{rate}}_{1\_1}^{19},...,{\mathrm{rate}}_{1\_100}^{19}\},$

${\mathrm{rate}}_{2\_46}^{19}=\max \{{\mathrm{rate}}_{2\_1}^{19},...,{\mathrm{rate}}_{2\_100}^{19}\},$

${\mathrm{rate}}_{3\_45}^{19}=\max \{{\mathrm{rate}}_{3\_1}^{19},...,{\mathrm{rate}}_{3\_100}^{19}\},$

${\mathrm{rate}}_{4\_48}^{19}=\max \{{\mathrm{rate}}_{4\_1}^{19},...,{\mathrm{rate}}_{4\_100}^{19}\},$

the maximum correlation peak ratio of SYNC _ DL with code number 19 in the search time is $\max \{{\mathrm{rate}}_{1\_47}^{19},{\mathrm{rate}}_{2\_46}^{19},{\mathrm{rate}}_{3\_45}^{19},{\mathrm{rate}}_{4\_48}^{19}\}.$

And after the maximum correlation peak ratio of each candidate SYNC _ DL in the search time is obtained, taking the SYNC _ DL corresponding to the maximum value and the corresponding time slice as the SYNC _ DL used by the network side and the position of the SYNC _ DL.

More specifically, assuming that of the 32 maximum correlation peak ratios,

if the maximum value is found, SYNC _ DL with number 19 is used as SYNC _ DL used by the network side, and the position of SYNC _ DL is located in the sub-frameThe 48 th time slice.

It can be seen that, when the method described in the above embodiment is used to search for SYNC _ DL and its position, if there is strong time slot interference, the correlation peak values of three consecutive time slices in the time slot are all larger, and the correlation peak value ratio of each time slice is smaller, thereby avoiding the influence of the uplink interference time slot on the search for SYNC _ DL and improving the success rate of the search for SYNC _ DL.

In addition, in the above embodiment, each subframe is equally divided into 100 time slices, because it is ensured that the number of chips in each time slice is equal to the number of chips of the SYNC _ DL code segment. Thus, after the SYNC _ DL is determined, the time slice of the SYNC _ DL can be determined, so that the position of the SYNC _ DL can be directly determined, and the position searching time of the SYNC _ DL is greatly prolonged.

It can also be seen that in the method described in the above embodiment, the maximum value of the correlation peak ratio is recorded in the process of searching for the position of SYNC _ DL, and it is not necessary to record all the correlation peak ratios. This also contributes to reducing the requirements on the UE memory space.

Based on the above method, the present invention further provides an apparatus for searching for a SYNC _ DL position, and fig. 5 is a schematic diagram of the apparatus, which includes a correlation peak value calculation unit S51, a correlation peak value ratio calculation unit S52, a recording unit S53, a summation unit S54, a maximum value unit S55, and a decision unit S56.

The correlation peak value of each candidate SYNC _ DL at each time slice can be calculated by the correlation peak value calculation unit S51. The correlation peak ratio calculation unit S52 is configured to calculate, for each candidate SYNC _ DL, a ratio of correlation peaks of each time slice to correlation peaks of adjacent time slices, and obtain a correlation peak ratio of each candidate SYNC _ DL in each time slice. The maximum correlation peak ratio of each candidate SYNC _ DL at each sub-frame and the time slice in which the maximum correlation peak ratio exists are recorded by the recording unit S53.

At the end of the search period, the summing unit S54 will sum, for each candidate SYNC _ DL, its maximum correlation peak ratio at the same time slice in each sub-frame. By comparing the summation results of the summation unit S54, the maximum unit S55 will obtain the maximum correlation peak ratio of each candidate SYNC _ DL within the search period.

By comparison, the decision unit S56 can determine the maximum value of the ratios obtained by the maximum value unit S55, and determine the candidate SYNC _ DL corresponding to the maximum value and the corresponding time slice.

The candidate SYNC _ DL and the corresponding time slice determined by the decision unit S56 are the SYNC _ DL used by the network side and the location of the SYNC _ DL.

In the device for searching for the SYNC _ DL position proposed by the present invention, each subframe is divided into several time slices, for example: each subframe is equally divided into 100 time slices. Each subframe is equally divided into 100 time slices, so that the number of chips in each time slice is equal to that of chips of the SYNC _ DL code segment. After SYNC _ DL is determined, the time slice of the SYNC _ DL can be determined, so that the position of the SYNC _ DL can be directly determined, and the position searching time of the SYNC _ DL is greatly prolonged.

In addition, a feature window and search time are set. The length of each characteristic window is 2 time slices, the search time can be set according to specific requirements, the search time is preferably an integer multiple of the length of a subframe, and for example, the search time can be set to 4 subframes. Fig. 4 is a schematic diagram of equally dividing a subframe into 100 time slices during a search period.

With the above arrangement, the correlation peak calculation unit S51 may perform sliding correlation on each candidate downlink synchronization code SYNC _ DL and the signal received in the characteristic window, so as to obtain a correlation peak of each candidate SYNC _ DL in each time slice.

More specifically, at the start of the search, correlation peak calculation section S51 receives the downlink signal transmitted from the network side in the signature window, with the first two time slices of the search period as one signature window; and performing sliding correlation on each alternative SYNC _ DL and the signal received in the characteristic window to obtain the correlation peak value of each alternative SYNC _ DL in the previous time slice in the characteristic window.

In conjunction with FIG. 4, t may be used_{i_j}Each time slice in a search period is shown, wherein i represents the sequence number of the subframe in the search period, and i is 1, 2, 3 and 4; j denotes the sequence number of the time slice within the subframe, j 1, 2. For example: time slice t_{1_1}、t_{1_2}That is, time slice 1, time slice 2, and time slice t of the 1 st subframe in the search period_{2_95}Then it is the time slice 95 of the 2 nd subframe within the search period.

t_{1_1}、t_{1_2}I.e. the first two time slices, denoted by t_{1_1}、t_{1_2}As a characteristic window, t_{1_1}Is the previous time slice in the characteristic window, t_{1_2}Is the latter time slice in the signature window. The length of the signal received by the UE in the characteristic window is 8 symbols, which is 128 chips.

According to the current specification requirements, there are 32 SYNC _ DLs that the system may use. Therefore, signals received by the UE in the characteristic window need to be respectively subjected to sliding correlation with 32 SYNC _ DLs, and 32 SYNC _ DLs are obtained in the time slice t_{1_1}The correlation peak of (a).

After calculating the correlation peak value of the previous time slice in the feature window, the correlation peak value calculating unit S51 will slide the feature window backward by one time slice to form a new feature window; and performing sliding correlation on each alternative SYNC _ DL and the signal received in the new characteristic window to obtain the correlation peak value of each alternative SYNC _ DL in the previous time slice in the new characteristic window.

It can be seen that since each feature window consists of two time slices, and each time the feature window slides backwards by only one time slice, the later time slice of the original feature window will become the previous time slice of the new feature window. For example, the original characteristic window consists of time slices t_{1_1}、t_{1_2}Is composed of t, and the new characteristic window is composed of_{1_2}、t_{1_3}And (4) forming. It can be seen that the UE only needs to receive the new oneThe last time slice of the characteristic window, i.e. time slice t_{1_3}The signal of (2). With the UE within the new characteristic window, i.e. time slice t_{1_2}、t_{1_3}In the method, after the received signals are respectively subjected to sliding correlation with 32 SYNC _ DL, 32 SYNC _ DL can be obtained at a time slice t_{1_2}The correlation peak of (a).

After calculating the correlation peak value of the previous time slice in the new feature window, the correlation peak value calculating unit S51 will determine whether the search period is over, and if not, continue to slide the feature window backward by one time slice to form a new feature window again.

During the search, for each candidate SYNC _ DL, the ratio of the correlation peak of each time slice of the SYNC _ DL to the correlation peak of the adjacent time slice is also calculated to obtain the correlation peak ratio of each candidate SYNC _ DL in each time slice.

The correlation peak ratio calculation unit S52 can calculate the correlation peak ratio of any alternative SYNC _ DL in each time slice according to equation (1).

It should be noted that, when calculating the correlation peak ratio of the first time slice of the current subframe, the correlation peak of the last time slice of the previous subframe needs to be used, and then the correlation peak ratio calculating unit S52 calculates according to equation (2).

It can be seen that for the first and last time slices within the entire search period, the corresponding correlation peak ratios cannot be calculated according to equation (1).

In practical applications, one more time slice may be received before and after each time slice for calculation.

Alternatively, the correlation peak of the last time slice may be used to calculate the correlation peak ratio of the first time slice, and the correlation peak of the first time slice may be used to calculate the correlation peak ratio of the last time slice.

After obtaining the correlation peak ratio of each candidate SYNC _ DL in each time slice, the recording unit S53 records only the maximum correlation peak ratio of each candidate SYNC _ DL in each subframe and the time slice in which the maximum correlation peak ratio is located.

That is, for SYNC _ DL of code number l, the recording unit S53 records only $\max \{{\mathrm{rate}}_{1\_1}^l,...,{\mathrm{rate}}_{1\_100}^l\},$ $\max \{{\mathrm{rate}}_{2\_1}^l,...,{\mathrm{rate}}_{2\_100}^l\},$ $\max \{{\mathrm{rate}}_{3\_1}^l,...,{\mathrm{rate}}_{3\_100}^l\}$ And $\max \{{\mathrm{rate}}_{4\_1}^l,...,{\mathrm{rate}}_{4\_100}^l\}.$

then, the summing unit S54 sums the maximum correlation peak ratios of the candidate SYNC _ DLs located in the same time slice in each subframe for each candidate SYNC _ DL, and obtains the maximum correlation peak ratio of each candidate SYNC _ DL in the search time. The following describes a process of calculating the maximum correlation peak ratio of SYNC _ DL in the search time by the summation unit S54, taking SYNC _ DL as an example.

Determining whether the maximum correlation peak value ratio of the SYNC _ DL in each subframe is in the same time slice;

and superposing and summing the maximum correlation peak ratios in the same time slice to obtain the sum of the correlation peak ratios of the SYNC _ DL in the time slice.

By comparing the summation results of the summation unit S54, the maximum unit S55 will obtain the maximum correlation peak ratio of each candidate SYNC _ DL in the search period, and record the corresponding time slice with the sum of the maximum correlation peak ratios as the maximum correlation peak ratio of the SYNC _ DL in the search time.

If there is no maximum correlation peak ratio at the same time slice, the maximum unit S55 will directly proceed to compare the maximum correlation peak ratios.

It can be seen that for the same time slice, the probability of the occurrence of a plurality of correlation peak ratios corresponding to the presence of the SYNC _ DL code in the time slice is increased, and the correlation peak values are accumulated, which is equivalent to accumulating the confidence, so that the judgment is more accurate.

More specifically, assume that for SYNC _ DL with code number 19,

${\mathrm{rate}}_{1\_47}^{19}=\max \{{\mathrm{rate}}_{1\_1}^{19},...,{\mathrm{rate}}_{1\_100}^{19}\},$

${\mathrm{rate}}_{2\_45}^{19}=\max \{{\mathrm{rate}}_{2\_1}^{19},...,{\mathrm{rate}}_{2\_100}^{19}\},$

${\mathrm{rate}}_{3\_47}^{19}=\max \{{\mathrm{rate}}_{3\_1}^{19},...,{\mathrm{rate}}_{3\_100}^{19}\},$

${\mathrm{rate}}_{4\_45}^{19}=\max \{{\mathrm{rate}}_{4\_1}^{19},...,{\mathrm{rate}}_{4\_100}^{19}\},$

the maximum correlation peak ratio of SYNC _ DL with code number 19 in the search time is $\max \{{\mathrm{rate}}_{1\_47}^{19}+{\mathrm{rate}}_{3\_47}^{19},{\mathrm{rate}}_{2\_45}^{19}+{\mathrm{rate}}_{4\_45}^{19}\}.$

It is assumed that,

${\mathrm{rate}}_{1\_47}^{19}=\max \{{\mathrm{rate}}_{1\_1}^{19},...,{\mathrm{rate}}_{1\_100}^{19}\},$

${\mathrm{rate}}_{2\_46}^{19}=\max \{{\mathrm{rate}}_{2\_1}^{19},...,{\mathrm{rate}}_{2\_100}^{19}\},$

${\mathrm{rate}}_{3\_47}^{19}=\max \{{\mathrm{rate}}_{3\_1}^{19},...,{\mathrm{rate}}_{3\_100}^{19}\},$

${\mathrm{rate}}_{4\_48}^{19}=\max \{{\mathrm{rate}}_{4\_1}^{19},...,{\mathrm{rate}}_{4\_100}^{19}\},$

the maximum correlation peak ratio of SYNC _ DL with code number 19 in the search time is $\max \{{\mathrm{rate}}_{2\_46}^{19},{\mathrm{rate}}_{1\_47}^{19}+{\mathrm{rate}}_{3\_47}^{19},{\mathrm{rate}}_{4\_48}^{19}\}.$

It is assumed that,

${\mathrm{rate}}_{1\_47}^{19}=\max \{{\mathrm{rate}}_{1\_1}^{19},...,{\mathrm{rate}}_{1\_100}^{19}\},$

${\mathrm{rate}}_{2\_46}^{19}=\max \{{\mathrm{rate}}_{2\_1}^{19},...,{\mathrm{rate}}_{2\_100}^{19}\},$

${\mathrm{rate}}_{3\_45}^{19}=\max \{{\mathrm{rate}}_{3\_1}^{19},...,{\mathrm{rate}}_{3\_100}^{19}\},$

${\mathrm{rate}}_{4\_48}^{19}=\max \{{\mathrm{rate}}_{4\_1}^{19},...,{\mathrm{rate}}_{4\_100}^{19}\},$

the maximum correlation peak ratio of SYNC _ DL with code number 19 in the search time is $\max \{{\mathrm{rate}}_{1\_47}^{19},{\mathrm{rate}}_{2\_46}^{19},{\mathrm{rate}}_{3\_45}^{19},{\mathrm{rate}}_{4\_48}^{19}\}.$

After obtaining the maximum correlation peak ratio of each candidate SYNC _ DL within the search time, the decision unit S56 uses the SYNC _ DL corresponding to the maximum value and the corresponding time slice as the SYNC _ DL used by the network side and the position of the SYNC _ DL.

More specifically, assuming that of the 32 maximum correlation peak ratios,

at the maximum, the SYNC _ DL with number 19 is used as the SYNC _ DL used by the network side, and the position of the SYNC _ DL is located at the 48 th time slice of the subframe.

The disclosed embodiments are provided to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope or spirit of the invention. The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A method for searching the position of a downlink synchronous code is characterized by comprising the following steps:

calculating the correlation peak value of each alternative SYNC _ DL in each time slice;

for each alternative SYNC _ DL, calculating the ratio of the correlation peak value of each time slice to the correlation peak value of the adjacent time slice to obtain the correlation peak value ratio of each alternative SYNC _ DL in each time slice;

recording the maximum correlation peak value ratio of each alternative SYNC _ DL in each subframe and the time slice where the maximum correlation peak value ratio is located;

and when the search period is ended, summing the maximum correlation peak ratios of the candidate SYNC _ DL in the same time slice in each subframe according to each candidate SYNC _ DL, and determining the maximum correlation peak ratio of each candidate SYNC _ DL in the search period, wherein the candidate SYNC _ DL corresponding to the maximum value and the corresponding time slice are the positions of the SYNC _ DL used by the network side and the SYNC _ DL.

2. The method of claim 1, wherein a length of a time slice is set by a length of SYNC _ DL.

3. The method of claim 1, wherein the length of the characteristic window is set according to the length of two time slices, and each alternative downlink synchronization code SYNC _ DL is subjected to sliding correlation with the signal received in the characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in each time slice.

4. The method of claim 3,

taking the first two time slices in the search period as a characteristic window, and receiving a downlink signal sent by a network side in the characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the characteristic window;

sliding the characteristic window backwards by a time slice to form a new characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a new characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the new characteristic window;

and judging whether the searching period is ended or not, if not, continuously sliding the characteristic window backwards for a time slice to form a new characteristic window again.

5. The method of claim 1,

by calculation of ${\mathrm{rate}}_{i\_j}^l=\frac{P_{i\_j}^l}{P_{i\_j-1}^l+P_{i\_j+1}^l},$ Obtaining the correlation peak value ratio of each alternative SYNC _ DL in each time slice;

wherein,

indicating the correlation peak ratio of SYNC _ DL with code number l in the jth time slice of the ith sub-frame in the search period,

respectively represents the correlation peak values of the SYNC _ DL with the code number l in the j-1 th, j +1 th time slice of the ith subframe in the search period.

6. An apparatus for searching a position of a downlink synchronization code, comprising:

a correlation peak value calculation unit, configured to calculate a correlation peak value of each candidate SYNC _ DL in each time slice;

a correlation peak ratio calculation unit, configured to calculate, for each candidate SYNC _ DL, a ratio of correlation peaks of each time slice to correlation peaks of adjacent time slices, and obtain a correlation peak ratio of each candidate SYNC _ DL in each time slice;

the recording unit is used for recording the maximum correlation peak value ratio of each alternative SYNC _ DL in each subframe and the time slice where the maximum correlation peak value ratio is located; and the number of the first and second groups,

the summing unit is used for summing the maximum correlation peak value ratio of each alternative SYNC _ DL in the same time slice in each subframe at the end of the search period;

the maximum value unit is used for obtaining the maximum correlation peak value ratio of each alternative SYNC _ DL in the search period according to the summation result of the summation unit;

a decision unit, configured to determine an alternative SYNC _ DL corresponding to a maximum value in the ratios obtained by the maximum value unit and a corresponding time slice;

the alternative SYNC _ DL and the corresponding time slice determined by the decision unit are the SYNC _ DL used by the network side and the location of the SYNC _ DL.

7. The apparatus of claim 6, wherein a length of a time slice is a length of SYNC _ DL.

8. The apparatus of claim 6, wherein the length of the characteristic window is set according to the length of two time slices, and the correlation peak calculation unit performs sliding correlation on each candidate downlink synchronization code SYNC _ DL and the signal received in the characteristic window to obtain the correlation peak of each candidate SYNC _ DL in each time slice.

9. The apparatus of claim 8, wherein the correlation peak calculation unit

Taking the first two time slices in the search period as a characteristic window, and receiving a downlink signal sent by a network side in the characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the characteristic window;

sliding the characteristic window backwards by a time slice to form a new characteristic window;

performing sliding correlation on each alternative SYNC _ DL and a signal received in a new characteristic window to obtain a correlation peak value of each alternative SYNC _ DL in a previous time slice in the new characteristic window;

and judging whether the searching period is ended or not, if not, continuously sliding the characteristic window backwards for a time slice to form a new characteristic window again.

10. The apparatus of claim 6, wherein the correlation peak ratio calculating unit calculates by calculation ${\mathrm{rate}}_{i\_j}^l=\frac{P_{i\_j}^l}{P_{i\_j-1}^l+P_{i\_j+1}^l},$ Obtaining the correlation peak value ratio of each alternative SYNC _ DL in each time slice;

wherein,

indicating the correlation peak ratio of SYNC _ DL with code number l in the jth time slice of the ith sub-frame in the search period,

respectively represents the correlation peak values of the SYNC _ DL with the code number l in the j-1 th, j +1 th time slice of the ith subframe in the search period.

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