CN106817185A - A kind of root sequence optimisation method and device - Google Patents

Abstract

The invention discloses a root sequence optimization method and device, which relate to wireless communication technology. The method includes: when there is a preamble sequence conflict between the current cell and other cells, searching all cells in the adjacent cell search area to obtain the adjacent cell A set of used root sequences in the search area; by searching all cells that have overlapping coverage areas with the current cell in each circular search area that gradually expands outside the adjacent cell search area, obtain The used root sequence set, until the root sequence in the available root sequence set determined by using the currently obtained used root sequence set just meets the quantity requirement for generating 64 leading sequences; the root sequence in the available root sequence set A sequence is allocated to the current cell to replace the previously allocated root sequence. The present invention can effectively avoid the mutual interference caused by the use of the same preamble sequence between cells with ultra-distance coverage or cells not configured with neighbor cell relations.

Description

A root sequence optimization method and device

technical field

The present invention relates to the technical field of wireless communication, in particular to a root sequence optimization method and device.

Background technique

In a standard Long Term Evolution (LTE) system, in order to prevent physical random access channel (Physical Random Access Channel, PRACH) resources of adjacent cells from colliding, it must Any one dimension of the domain distinguishes adjacent cells. Due to the large number of logical root sequences that can be used, adjacent cells are usually distinguished through the code domain resources of PRACH, that is, non-repeated logical root sequences are configured for adjacent cells. A cell consists of 64 fixed preamble sequences to form a PRACH The code domain resource, the 64 leading sequences are generated by the logical root sequence. The root sequence needs to be planned at the initial stage of network construction to ensure that the preamble sequences generated by the logical root sequence are different between adjacent cells. During the network maintenance phase or when a preamble conflict is detected, automatic optimization and adjustment are performed.

The 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP) protocol 32.521 stipulates that random access channel (Random Access Channel, RACH) optimization should minimize manual intervention, but does not specify a specific automatic optimization method.

For root sequence conflict detection, it mainly detects based on the PRACH information of neighboring cells that are exchanged when X2 is established or X2 is updated, and detects whether root sequence conflicts occur between neighboring cells. For cell pairs that are not configured with X2 coupling, root sequence conflicts occur , this detection method cannot detect effectively.

RACH automatic optimization mainly includes the following two methods:

1. Obtain all the root sequence sets available in the cell based on the adjacent cells, and then randomly assign a set of root sequences to the current cell.

This method can solve the problem that the preamble sequence of a cell configured with an adjacent relationship is different, but it cannot solve the mutual interference caused by using the same preamble sequence between cells with ultra-far coverage and no adjacent cell relationship configured.

2. Use the X2 link to adjust the local PRACH base station configuration information according to the PRACH information received by the first base station from the second base station, so as to reduce the interference between the cells under the jurisdiction of the first base station and the second base station.

This method is essentially the same as the first method, that is, it cannot solve the mutual interference caused by using the same preamble sequence between cells with ultra-far coverage and no neighbor cell relationship configured.

Contents of the invention

The purpose of the present invention is to provide a root sequence optimization method and device, which can better solve the problem of mutual interference between cells due to the use of the same preamble sequence by reducing the probability of allocating the same root sequence to the cells.

According to one aspect of the present invention, a kind of root sequence optimization method is provided, comprising:

When there is a preamble conflict between the current cell and other cells, by searching all the cells in the adjacent cell search area, to obtain the used root sequence set in the adjacent cell search area;

By searching all cells that have overlapping coverage areas with the current cell in each circular search area that is gradually expanded outside the adjacent cell search area, obtain the used root sequence set in each circular search area until the current cell is used The root sequence in the available root sequence set determined by the acquired root sequence set just satisfies the quantity requirement for generating 64 leading sequences;

Allocating a root sequence in the set of available root sequences to the current cell to replace a previously allocated root sequence.

Preferably, before obtaining the used root sequence set in the adjacent cell search area, the following steps for detecting whether there is a preamble sequence conflict between the current cell and other cells:

If the current cell receives preamble conflict information of a user equipment that has randomly accessed, determine that there is a preamble conflict between the current cell and other cells;

Wherein, the preamble conflict information is information reported by the user equipment to the current cell when it receives random access responses replied by multiple cells in response to its random access requests.

Preferably, the used root sequence set in the adjacent cell search area is obtained through the following steps:

Search all cells within the search range of adjacent cells, and obtain physical random access channel information of all cells;

According to the acquired physical random access channel information of all the cells, the used root sequence set within the search range of the adjacent cells is obtained.

Preferably, the set of used root sequences in each circular search area is obtained through the following steps:

Determine all cells that have overlapping coverage areas with the current cell in each circular search area according to the direction angle of the current cell and the azimuth angle between the current cell and other cells;

According to the determined physical random access channel information of all cells having overlapping coverage areas with the current cell in each circular search area, the used root sequence set in each circular search area is obtained.

Preferably, the set of available root sequences is determined through the following steps:

Merging the used root sequence set in the adjacent cell search area and the used root sequence set in each circular search area to obtain the total used root sequence set;

The total set of used root sequences is removed from the total set of root sequences to obtain the set of available root sequences.

According to another aspect of the present invention, a kind of root sequence optimization device is provided, comprising:

The first search module is used to obtain the used root sequence set in the adjacent cell search area by searching all the cells in the adjacent cell search area when there is a preamble sequence conflict between the current cell and other cells;

The second search module is configured to search for all cells that have overlapping coverage areas with the current cell in each circular search area that gradually expands outside the adjacent cell search area, and obtain the used cell numbers in each circular search area. The root sequence set, until the root sequence in the available root sequence set determined by using the currently obtained used root sequence set just meets the quantity requirement for generating 64 leading sequences;

A root sequence allocation module, configured to allocate a root sequence in the set of available root sequences to the current cell, to replace the previously allocated root sequence.

Preferably, it also includes:

A collision detection module, configured to determine that there is a preamble collision between the current cell and other cells when the current cell receives preamble collision information of a user equipment that has randomly accessed, wherein the preamble collision information is the user equipment Information that the device reports to the current cell when it receives random access responses from multiple cells in response to its random access requests.

Preferably, the first search module searches all cells within the search range of adjacent cells, obtains physical random access channel information of all cells, and obtains the relative The set of used root sequences within the search range of neighboring cells.

Preferably, the second search module determines all cells that have overlapping coverage areas with the current cell in each circular search area according to the direction angle of the current cell and the azimuth angle between the current cell and other cells , and according to the determined physical random access channel information of all cells having overlapping coverage areas with the current cell in each circular search area, the used root sequence set in each circular search area is obtained.

Preferably, the second search module combines the set of used root sequences in the adjacent cell search area and the set of used root sequences in each circular search area to obtain the total set of used root sequences, and The total set of used root sequences is removed from the total set of root sequences to obtain a set of available root sequences.

Compared with the prior art, the beneficial effects of the present invention are:

The present invention can reduce the probability of allocating the same root sequence for the cell, effectively avoid the mutual interference caused by the use of the same preamble sequence between cells with ultra-distance coverage or no adjacent cell relationship configured, and improve the access success rate and the performance of the entire network .

Description of drawings

Fig. 1 is the flow chart of the root sequence optimization method provided by the embodiment of the present invention;

Fig. 2 is a block diagram of a root sequence optimization device provided by an embodiment of the present invention;

Fig. 3 is a flowchart of conflict detection and optimization provided by an embodiment of the present invention;

FIG. 4 is a flowchart of conflict detection provided by an embodiment of the present invention;

FIG. 5 is a schematic diagram of conflict detection provided by an embodiment of the present invention;

FIG. 6 is a flowchart of root sequence optimization provided by an embodiment of the present invention;

Fig. 7 is a schematic diagram of the expansion and contraction of the root sequence optimization search area provided by the embodiment of the present invention;

Fig. 8 is a schematic diagram of calculation of related cells provided by an embodiment of the present invention.

detailed description

The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described below are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

Fig. 1 is a flow chart of the root sequence optimization method provided by the embodiment of the present invention, as shown in Fig. 1, the steps include:

Step S10: When there is preamble conflict between the current cell and other cells, search all the cells in the adjacent cell search area to obtain the used root sequence set in the adjacent cell search area.

Specifically, all cells are searched in the adjacent cell search range, and the physical random access channel information of all cells is obtained. According to the obtained physical random access channel information of all cells, the used root collection of sequences. For example, with the cell as the center, obtain the physical random access channel information of all cells in the _circular area with the search radius R of the adjacent cell, so as to obtain the used root sequence in the circular area, and form the adjacent cell The set of root sequences used within the cell search range.

Step S20: By searching all cells that have overlapping coverage areas with the current cell in each circular search area that is gradually expanded outside the adjacent cell search area, obtain the used root sequence set in each circular search area until the use of The root sequences in the available root sequence set determined by the currently obtained used root sequence set just meet the quantity requirement for generating 64 leading sequences

Specifically, according to the direction angle of the current cell and the azimuth angle between the current cell and other cells, determine all the cells that have overlapping coverage areas with the current cell in each circular search area outside the adjacent cell search area, and according to The physical random access channel information of all cells in each circular search area outside the determined adjacent cell search area and the current cell's overlapping coverage area is used to obtain the used root sequence set in each circular search area. For example, on the basis of the radius R ₀ , the search radius is increased by R _step . At this time, the physical random access channel information of all cells that may have overlapping coverage areas with the current cell is first obtained in the increased circular search area, and based on the The obtained physical random access channel information is used to obtain the corresponding used root sequence, thereby forming the used root sequence in the circular search area.

Combine the used root sequence set in the adjacent cell search area and the used root sequence set in each circular search area to obtain the total set of used root sequences, and remove the total set of used root sequences from the total set of root sequences , to get the set of available root sequences.

The search area is gradually expanded in order from near to far, until the root sequences in the obtained set of available root sequences just meet the quantity requirement for generating 64 leading sequences.

Step S40: Allocate the root sequence in the set of available root sequences to the current cell to replace the previously allocated root sequence, so as to generate 64 leading sequences by using the newly allocated root sequence.

It should be noted that the present invention can also detect whether there is a preamble sequence conflict between the current cell and other cells before step S10, specifically, if the current cell receives the preamble sequence conflict information of the user equipment that has randomly accessed There is preamble conflict between the cell and other cells, wherein the preamble conflict information is information reported to the current cell by the user equipment when receiving random access responses replied by multiple cells in response to its random access requests. In other words, during the random access period, the user equipment sends a random access request to the cell and waits for the cell to reply with a random access response. If the user equipment receives multiple (for example, 2, 3, etc.) A response message is received, indicating that there is a preamble sequence conflict in more than one cell. At this time, the user equipment sends preamble sequence conflict information to the cell it accesses, so that the cell starts the root sequence optimization process.

FIG. 2 is a block diagram of a root sequence optimization device provided by an embodiment of the present invention. As shown in FIG. 2 , the device includes a first search module 20 , a second search module 30 and a root sequence allocation module 40 .

The first search module 20 is used to obtain the used root sequence set in the adjacent cell search area by searching all cells in the adjacent cell search area when the current cell has a preamble sequence conflict with other cells. When the first search module 20 detects that there is a preamble sequence conflict, it obtains a set of used root sequences within the adjacent cell search range according to the physical random access channel information of all cells searched within the adjacent cell search range.

The second search module 30 is used to obtain the used root sequence in each circular search area by searching all cells that have overlapping coverage areas with the current cell in each circular search area that gradually expands outside the adjacent cell search area Set until the root sequences in the available root sequence set determined by using the currently acquired used root sequence set just meet the quantity requirement for generating 64 leading sequences. Specifically, the second search module 30 obtains the used root in each circular search area according to the physical random access channel information of all cells that may have overlapping coverage areas with the current cell in each expanded circular search area. collection of sequences. The second search module 30 merges the used root sequence set in the adjacent cell search area and the used root sequence set in each circular search area to obtain the used root sequence total set, and removes the used root sequence set from the root sequence total set. Use the total set of root sequences to get the set of available root sequences. The second search module 30 gradually expands the search area in order from near to far, until the obtained root sequences in the set of available root sequences just meet the quantity requirement for generating 64 leading sequences.

The root sequence allocation module 40 is used for allocating the root sequence in the set of available root sequences to the current cell to replace the previously allocated root sequence.

The device may further include a collision detection module 10, which is configured to detect whether the current cell has a preamble sequence conflict with other cells, specifically, the collision detection module 10 receives a preamble sequence of a user equipment that has randomly accessed in the current cell When receiving sequence conflict information, it is determined that the current cell has a preamble sequence conflict with other cells, wherein the preamble sequence conflict information is reported to the current cell by the user equipment when receiving random access responses from multiple cells in response to their random access requests information.

Fig. 3 is a conflict detection and optimization flowchart provided by an embodiment of the present invention, as shown in Fig. 3, the steps include:

Step S100: UE reports collision detection.

UE initial access or contention-based cut-in (that is, cell handover), using primary and secondary signals to achieve frequency and time synchronization, and broadcasting according to the master system information block (Master Information Block, MIB)/system information block (System Information Block, SIB) information, after the downlink synchronization is completed, the random access process is entered, the UE sends the first message (Message1, MSG1) to the base station, that is, the random access request message, and the base station sends the second message (Message2, MSG2) to the UE, namely Random access response message, if there is no conflict in the preamble sequence, the UE will only receive MSG2 from a normal cell; if the UE receives MSG2 from two base stations at the same time, and parses out one of them, it means that the normal parsing of the cell and other There is a preamble conflict in the cell. Since the normal cell does not know the existence of the preamble conflict, the UE needs to notify the normal cell that it detects the preamble conflict information, and requires the normal cell to start collision optimization.

Step S200: Automatic optimization based on the combination of azimuth and telescoping search radius.

Taking this cell as the center, obtain the PRACHs of all cells in a circular area with a radius R ₀ , and obtain the used root sequence set S ₀ . It should be noted that, with the own cell as the center, the cells in a circular area with a radius of R ₀ are the own cell and its adjacent cells.

Take _RN as the radius, increase the search area by expanding _RN , in the search area, according to the azimuth and direction angle information, screen the relevant cells that may have overlapping coverage areas with this cell, and obtain the cells screened in the area PRACH information, and obtain the used root sequence S _N . It should be noted that the selected cells are related cells in areas other than adjacent cells that may have overlapping coverage areas with the current cell.

The larger the search radius, the more root sequences have been used. Use the total number of root sequences S _all to remove (S ₀ ∪S _N ) to obtain the set of available root sequences S _R,avail , if and only if the optimal search radius is R _max , the set of available root sequences just satisfies the number requirement for generating 64 leading sequences, and at this time, the probability of root sequence conflicts will also be reduced to the minimum.

FIG. 4 is a flowchart of conflict detection provided by an embodiment of the present invention. As shown in FIG. 4 , the steps of conflict detection based on the preamble sequence reported by the UE include:

Step S101: UE initial access or contention-based hand-in, after completing the cell search process according to MIB/SIB information, the UE initiates a random access process.

Step S102: The UE randomly selects a preamble sequence from the defined preamble sequences, and sends MSG1 to the cell of the base station.

Step S103: The UE judges whether two MSG2s are received at the same time, if yes, execute step S105, otherwise execute step S104.

When the base station cell receives MSG1 from the UE, it will send MSG2 to the UE. Under normal circumstances, only one cell will reply MSG2 to the UE; if within a certain period of time (for example, within 10ms), the UE receives two MSG2, indicating that the The MSG1 at the location is parsed and responded by two base station cells. At this time, there is a preamble sequence conflict between the two base station cells, and the root sequence needs to be adjusted.

Step S104: the detection ends, and the UE continues to perform the remaining random access procedures.

Step S105: The UE detects the preamble conflict and reports the preamble conflict information to the base station cell after completing the random access procedure.

Step S106: the base station performs a root sequence optimization process according to the preamble sequence conflict information reported by the UE.

Fig. 5 is a schematic diagram of conflict detection provided by the embodiment of the present invention. As shown in Fig. 5, UE sends MSG1 to the cell of the base station at the current location. At this time, cell 1 and cell 2 both receive MSG1 and reply MSG2 to UE. The UE receives more than one MSG2 within a short period of time, and judges that there is preamble sequence collision between two cells. After accessing cell 1, the UE sends preamble conflict information to the cell.

Fig. 6 is a flow chart of root sequence optimization provided by an embodiment of the present invention. As shown in Fig. 6, the root sequence optimization steps based on azimuth and telescopic search radius include:

Step S201: Obtain the latitude and longitude, direction angle and azimuth angle information between the two cells in the whole network from the planning data.

Step S202: Take the current cell as the center and obtain PRACH information of all cells in a circular area with a radius of R ₀ , and obtain root sequence sets S ₀ of all cells that have been used according to the obtained PRACH information.

The search area is gradually expanded in order from near to far, until the root sequences in the obtained set of available root sequences just meet the quantity requirement for generating 64 leading sequences. Specifically, execute according to the following steps S203 to S209:

_{Step S203} : FIG. ₇ is a schematic diagram of the scaling of the root sequence optimization search area provided by the embodiment of the present invention. As shown in _FIG . If the value is 1, the search area is expanded. In the newly added circular search area, according to the direction angle covered by the cell antenna and the azimuth angle information between the cell pairs, the newly added circular search area may have overlapping coverage with this cell. related districts.

Fig. 8 is a schematic diagram of calculation of related cells provided by the embodiment of the present invention. As shown in Fig. 8, the steps for judging whether a certain cell has a coverage overlap area with this cell are as follows:

According to the direction angle of the plot, it is defined as ∠A, and a ray is drawn in the direction of ∠A±120 degrees, and a total of four rays in the direction of ∠A±60 degrees divide the plane into four areas, which are respectively defined as S1, S2, S3, S4, the boundaries of the four regions are: (∠A-60, ∠A+60]; (∠A+60, ∠A+120]; (∠A+120, ∠A+240]; (∠A +240,∠A-60].

Take the angle between the connection line between the two cells and the direction of 0 degrees as the azimuth angle, and judge the area to which the searched cell belongs according to the azimuth angle, as shown in Figure 8, with the cell B∈S1, the direction angle ∠B; the cell C∈ S2, direction angle ∠C; cell D∈S3, direction angle ∠D; cell E∈S4, direction angle ∠E are taken as examples, and the specific judgment methods are described respectively.

When cell B∈S1, cell B and cell A have overlapping coverage areas regardless of the size of the direction angle ∠B.

When cell C∈S2, when the two boundaries of the direction angle ∠C±60∈∠α range, there is an overlapping coverage area between cell C and cell A, otherwise there is no overlapping coverage area between cell C and cell A. Among them, the range of ∠α is a fan-shaped area formed by the vertex being cell C, one side being the line connecting cell A and cell C, and one side being the parallel line of ∠A+60.

When the cell D∈S3, when the two boundaries of the direction angle ∠D±60∈∠β range, there is an overlapping coverage area between the cell D and the cell A, otherwise there is no overlapping coverage area between the cell D and the cell A. Among them, the range of ∠β is a fan-shaped area formed by the vertex being the cell D, one side being the parallel line of ∠A+120, and the other side being the parallel line of ∠A+240.

When the cell E∈S4, when the two boundaries of the direction angle ∠E±60∈∠γ range, there is an overlapping coverage area between the cell E and the cell A, otherwise there is no overlapping coverage area between the cell E and the cell A. Among them, the range of ∠γ is the fan-shaped area formed by the vertex being cell E, one side being the connection line between cell A and cell E, and one side being the parallel line of ∠A-60.

Step S204: Calculate the used root sequence set S _N from the obtained PRACH information of all cells with overlapping coverage in the circular search area, and calculate the root sequence set S ₀ and the root sequence set S _N by merging the calculation, Obtain the used root sequence set S _used .

Step S205: Calculate the available root sequence set S _R,avail =S _all -(S ₀ ∪S _N ), and judge whether the available root sequence set S _R,avail is empty, if not, execute step S206 , if the available root sequence set _SR,avail is empty, then step S207 is executed.

Step S206: N=N+1, continue to expand the search area, and reduce the probability of using the same preamble sequence between cells.

Step S207: return, determine the set of available root sequences S _R,avail =S _all -(S ₀ ∪S _N ) when N=N-1.

Step S208: Determine whether the available root sequence set _SR,avail has the number of root sequences required to generate 64 leading sequences by cyclic shifting N _Cs , if yes, execute step S209; if not, continue to execute step S207.

Step S209: Return the first root sequence index of the root sequence that can be used, and automatically configure it for the current cell.

It should be noted that the aforementioned overlapping coverage areas refer to overlapping coverage areas between cells, including same coverage and partial same coverage.

In summary, the present invention has the following technical effects:

1. In the process of RACH automatic optimization, the present invention effectively detects whether a root sequence conflict occurs between cells through the UE reporting preamble sequence conflict information, for example, a cell pair that is not configured with X2 coupling;

2. The present invention optimizes the cells with root sequence conflicts through the azimuth and stretching search radius. During the RACH optimization process, the used root sequence index is changed by stretching the search radius. When the optimal search radius is reached , the set of available root sequences just meets the requirement of generating the number of preambles, minimizing the probability of assigning the same logical root sequence to the cell;

3. The maximization of the search distance in the present invention is beneficial to solve the mutual interference caused by the use of the same preamble sequence between cells with ultra-distance coverage or no neighbor cell relationship configured, and improve the access success rate and the performance of the entire network.

Although the present invention has been described in detail above, the present invention is not limited thereto, and various modifications can be made by those skilled in the art based on the principle of the present invention. Therefore, any modifications made according to the principles of the present invention should be understood as falling within the protection scope of the present invention.

Claims (10)

1. a root sequence optimization method, is characterized in that, described method comprises: When there is a preamble conflict between the current cell and other cells, by searching all the cells in the adjacent cell search area, to obtain the used root sequence set in the adjacent cell search area; By searching all cells that have overlapping coverage areas with the current cell in each circular search area that is gradually expanded outside the adjacent cell search area, obtain the used root sequence set in each circular search area until the current cell is used The root sequence in the available root sequence set determined by the acquired root sequence set just satisfies the quantity requirement for generating 64 leading sequences; Allocating a root sequence in the set of available root sequences to the current cell to replace a previously allocated root sequence. 2. The method according to claim 1, characterized in that, before obtaining the used root sequence set in the adjacent cell search area, it also includes the following steps for detecting whether there is a preamble conflict between the current cell and other cells: If the current cell receives preamble conflict information of a user equipment that has randomly accessed, determine that there is a preamble conflict between the current cell and other cells; Wherein, the preamble conflict information is information reported by the user equipment to the current cell when it receives random access responses replied by multiple cells in response to its random access requests. 3. The method according to claim 1, characterized in that, obtain the used root sequence set in the adjacent cell search area by the following steps: Search all cells within the search range of adjacent cells, and obtain physical random access channel information of all cells; According to the acquired physical random access channel information of all the cells, the used root sequence set within the search range of the adjacent cells is obtained. 4. The method according to claim 1, characterized in that, obtain the used root sequence collection in each circular search area by the following steps: Determine all cells that have overlapping coverage areas with the current cell in each circular search area according to the direction angle of the current cell and the azimuth angle between the current cell and other cells; According to the determined physical random access channel information of all cells having overlapping coverage areas with the current cell in each circular search area, the used root sequence set in each circular search area is obtained. 5. The method according to claim 1, wherein the available root sequence set is determined through the following steps: Merging the used root sequence set in the adjacent cell search area and the used root sequence set in each circular search area to obtain the total used root sequence set; The total set of used root sequences is removed from the total set of root sequences to obtain the set of available root sequences. 6. A root sequence optimization device, characterized in that said device comprises: The first search module is used to obtain the used root sequence set in the adjacent cell search area by searching all the cells in the adjacent cell search area when there is a preamble sequence conflict between the current cell and other cells; The second search module is configured to search for all cells that have overlapping coverage areas with the current cell in each circular search area that gradually expands outside the adjacent cell search area, and obtain the used cell numbers in each circular search area. The root sequence set, until the root sequence in the available root sequence set determined by using the currently obtained used root sequence set just meets the quantity requirement for generating 64 leading sequences; A root sequence allocation module, configured to allocate a root sequence in the set of available root sequences to the current cell, to replace the previously allocated root sequence. 7. The device according to claim 6, further comprising: A collision detection module, configured to determine that there is a preamble collision between the current cell and other cells when the current cell receives preamble collision information of a user equipment that has randomly accessed, wherein the preamble collision information is the user equipment Information that the device reports to the current cell when it receives random access responses from multiple cells in response to its random access requests. 8. The device according to claim 6, wherein the first search module searches all cells within the adjacent cell search range, obtains physical random access channel information of all cells, and performs The physical random access channel information is obtained to obtain the used root sequence set within the search range of the adjacent cell. 9. The device according to claim 6, characterized in that, the second search module determines the location of each circular search area according to the direction angle of the current cell and the azimuth angle between the current cell and other cells. All cells that have overlapping coverage areas with the current cell, and according to the determined physical random access channel information of all cells that have overlapping coverage areas with the current cell in each circular search area, obtain each ring search The collection of used root sequences in the region. 10. The device according to claim 6, wherein the second search module combines the used root sequence set in the adjacent cell search area with the used root sequence in each circular search area The sets are combined to obtain the total set of used root sequences, and the total set of used root sequences is removed from the total set of root sequences to obtain the set of available root sequences.