KR100640352B1 - Method for Minimizing Inter-cell Interference concerning BFN Offset Set-up in a GPS Supporting UTRAN System - Google Patents

Abstract

The present invention provides a method for establishing synchronization by a base station in an asynchronous mobile communication system. In particular, a method for minimizing inter-cell interference and setting a base station synchronization code in an asynchronous mobile communication system receiving external time synchronization is provided.

The present invention is a process for receiving a base station frame offset information of the base station is set to have a channel transmission time point that is different from the other base station from the base station controller and the information indicating the period of the cells controlled by the base station, the base station frame the base station frame Repeatedly transmitting a channel to the user terminal in response to the period of the cells starting from the offset of the number; and receiving the channel to perform communication in synchronization with the signal at the best time. It is done.

Base station frame number, system frame number, T_CELL, first sync code, BFN offset information

Description

Method for Minimizing Inter-cell Interference concerning BFN Offset Set-up in a GPS Supporting UTRAN System in Mobile Communication System             

1 is a diagram illustrating a structure for acquiring slot synchronization for each cell of a base station in a general asynchronous mobile communication system.

2 is a diagram illustrating a structure for acquiring a synchronization code by identifying a first synchronization channel and a second synchronization channel in a general asynchronous mobile communication system.

3 is a diagram showing a structure for changing the acquisition time of a sync code according to an embodiment of the present invention;

4 is a diagram illustrating a case where an offset of a base station frame number is 8 according to an embodiment of the present invention.

5 is a diagram illustrating a mapping relationship between an offset of a base station frame number and a sync code according to an embodiment of the present invention.

6 is a diagram illustrating a process of setting an offset of a base station frame number by a base station according to an embodiment of the present invention.

The present invention provides a method for establishing synchronization by a base station in an asynchronous mobile communication system. In particular, a method for minimizing inter-cell interference and setting a base station synchronization code in an asynchronous mobile communication system receiving external time synchronization is provided.

Typically, the third generation mobile communication method refers to a mobile communication method that supports not only voice services but also packet services. This third generation mobile communication method uses a code division multiple access (CDMA) method. Standardization work for the third generation mobile communication method is carried out separately by the European standard method (3GPPP) and the American standard method (3GPP2). The 3GPP is called UMTS (Universal Mobile Telecommunication System) and performs communication based on asynchronous between base stations. The 3GPP2 is called CDMA 2000 and is based on synchronization between base stations.

Here, the distinction between the synchronous and the asynchronous is divided according to whether to maintain external synchronization by receiving external synchronization time information from the Global Positioning Satellite System (GPS). That is, in the synchronous method, all base stations use the same pseudo-random noise (hereinafter, referred to as a 'PN code'), but use the same PN code by delaying the phase of the PN code. On the other hand, the asynchronous method is characterized in that not all base stations use the same PN code but use different PN codes to distinguish the base stations.

1 is a diagram illustrating a structure for acquiring slot synchronization for each cell in a general W-CDMA system.

Referring to FIG. 1, the start of a frame in a W-CDMA system is a Node B Frame Number Counter (hereinafter referred to as a BFN) generated by a Node-B and the base station itself serves. It is determined by a system frame number counter (hereinafter referred to as SFN) determined by a time offset value (hereinafter referred to as 'T_cell') in consideration of a service area (hereinafter referred to as 'cell'). Here, the BFN is a system clock information for each base station. The BFN of a specific number lasts for a predetermined time, and after a certain period, the counter of the BFN is increased by one and a cycle corresponding to the next BFN is started. In addition, the T_cell is determined as a unit of time for a time duration of 256 chips, that is, a multiple of 66.67 μs. When one base station controls a plurality of cells, the T_cell value has a value of 0-9. Accordingly, all channels transmit information frames as many as T_cells after the BFN starts. Accordingly, the start of the synchronization channel (hereinafter referred to as "SCH") is also determined at a time delayed by T_cell from the BFN. Based on the information frame obtained from the SCH, a user equipment (hereinafter referred to as UE) refers to a primary scrambling code (hereinafter, referred to as 'PSC') for identifying a base station Node-B. Secured. This will be described in more detail with reference to FIG. 2.

2 is a diagram illustrating a structure for acquiring a PSC code by identifying a first synchronization channel and a second synchronization channel in a general W-CDMA system.

Referring to FIG. 2, the PN codes used to distinguish the base stations in the W-CDMA system are configured as 512, which are further classified into 64 groups. One group is assigned eight PN codes. The reason for classifying the PN codes into a plurality of groups in the asynchronous manner as described above is to provide the UE with initial synchronization for finding the type and starting point of the PN codes. Here, the SCH is composed of a first synchronization channel (Primary Synchronization Channel) and a second synchronization channel (Secondary Synchronization Channel), the mobile terminal acquires the slot synchronization through the first synchronization channel, and then through the second synchronization channel The synchronization is achieved by acquiring the synchronization and the base station PN codes. The first synchronization channel consists of a frame of 10 ms, and the frame consists of 15 slots. In addition, a first synchronization code having a length of 256 bits is repeatedly transmitted for each time slot. Accordingly, the UE, which has confirmed the best signal among the first synchronization channels, checks the second synchronization channel after synchronizing with the corresponding slot. That is, the UE identifies the slot start point through the first synchronization channel. The second synchronization channel transmits using a different code for every slot. That is, 64 orthogonal codes of 256 chips are allocated. Therefore, the PN code group of the base station to which it belongs is identified as a combination of orthogonal codes assigned to each slot. Accordingly, the UE, which has known the PN code group to which it belongs through the second synchronization channel, searches for eight PN codes within the group and checks the PN code of its own base station.

In this regard, the W-CDMA system proposes a method of synchronizing using external time information (GPS) in order to obtain the advantage of handover between base stations. This is because synchronizing at the time of handover between base stations is an important technique.

However, in the W-CDMA system using GPS, the start time of the BFN is the same by all cells based on the reference time received through the GPS, so the start time of the SFN and the start time of the slot are T. There is a problem defined by -cell. Also, in general, the number of cells affected by a particular UE exceeds 10 to the second layer. Accordingly, the specific UE may receive two or more sync codes at the same time from neighboring cells.

Therefore, a UE that has received two or more sync codes at the same time has a problem in that it cannot properly check the sync codes due to an increase in inter-signal interference. As a result, the UE cannot acquire the PSC.

Accordingly, an object of the present invention, which was devised to solve the problems of the prior art operating as described above, is to provide a method for minimizing inter-cell interference and setting a base station synchronization code in an asynchronous mobile communication system receiving external time synchronization. .

Another object of the present invention is to provide a method for setting an offset in a frame number of a base station for providing a synchronization code in an asynchronous mobile communication system receiving external time synchronization.

In order to achieve the above object, an embodiment of the present invention provides a user terminal, a cell in which a user terminal is located, a base station managing a plurality of cells adjacent to the cell, and a transmission time point of a synchronization channel to the base station. In the asynchronous mobile communication system having a base station controller for providing a method for performing communication by the base station to minimize the interference between the cells, the base station controller is time information allocated to distinguish the base station based on the external time information Transmitting a combination of offset information and time information of cells managed by the base station to the base station; and transmitting, by the base station, a synchronization code by repeating the time information of the cells at a delayed time of the set offset information. It is characterized by including.

In order to achieve the above object, an embodiment of the present invention provides a method for performing communication by minimizing cell interference of a user terminal in an asynchronous mobile communication system indicating a transmission point of a channel using external time information. The method of claim 1, further comprising: receiving, by the base station controller, information indicating an offset of a base station frame number set to have a channel transmission time point distinguished from other base stations and a period of cells controlled by the base station; Repeatedly transmitting a channel to the user terminal in response to the period of the cells starting from the offset of the base station frame number, and the user terminal receives the channel and performs communication in synchronization with the signal at the best time. It is characterized by.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Definitions of terms to be described below should be made based on the contents throughout the specification.

The present invention provides a method of minimizing cell interference of a UE affected by a plurality of cells by varying a transmission start time of a synchronization code for each base station. The present invention sets a BFN offset to allocate different BFN transmission time points. That is, the purpose is to minimize the interference between a plurality of sync codes by setting different transmission time points of the sync codes, and to accurately receive the PSC of each base station.

3 is a diagram illustrating a structure for changing a point of time of acquiring a sync code according to an embodiment of the present invention.

Referring to FIG. 3, one frame is divided into 15 time slots in a W-CDMA system. One time slot has a 2560 chip size and is divided into 10 blocks of 256 chips by T cell value. The SFN indicating the start time of the frame may be determined through the combination of the ten different T_cells and the BFN.

In this regard, the T_cells are already set to 256 chip sizes according to the standard, so that 10 T_cells exist in one slot. In the present invention, a plurality of SFN transmission time points are set by allocating an offset to a BFN start time point indicating clock information of the base station. That is, BFN offsets are assigned to different BSN starting points for each base station so that synchronization codes are transmitted at different time references. By minimizing the interference between the sync codes, the UE can more efficiently acquire the sync codes so that the PSC of each base station can be more effectively received. Here, the range of the offset value of the BFN is limited to 0 to 256 chips. Accordingly, the number S of starting points of the BFNs divided by the BFN offsets is expressed by Equation 1 below.

case 1: S = 2

offset: 0, 128

case 2: S = 4

offset: 0, 64, 128, 192

case 3: S = 8

offset: 0, 32, 64, 96, 128, 160, 192, 224

case 4: S = 16

offset: 0, 16, 32, 48, ....., 240

In this regard, FIG. 4 illustrates a case in which the number of starting time points of the BFN offset is 8 according to the embodiment of the present invention according to Equation (1).

Referring to FIG. 4, the BFN start time is separated from the plurality of base stations Node-B. When S = 8, the number of start points of the BFN, one base station sets a combination of 10 T_cells that can exist in one base station to generate a total of 80 different SFN generation points. 4 illustrates a case where two base stations exist, and there are NODE B # 1 and NODE B # 2. Here, it is assumed that each NODE B has three SFN transmission time points, which means that one base station is composed of three sectors. Therefore, if a GPS reference time is determined according to external time information and the BFN offset of NODE B # 1 is assigned to O, the SFN start time of NODE B # 1 has 10 cycles in T_cell. (SFN11, SFN12, SFN13 ... SFN19) Accordingly, the BFN offset of NODE B # 2 is allocated to 32 and has a BFN start time delayed by the size of 32 chips around the reference time point, and according to the period of the T-cell. Start times exist for the two SFNs. (SFN 21, SFN 22, SFN 23 ... SFN 29)

5 is a diagram illustrating a mapping relationship between an offset of a base station frame number and a sync code according to an embodiment of the present invention.

Referring to FIG. 5, determining the SFN start time, that is, the sync. Code transmission start time generated using the BFN offset and T_cell, is appropriately assigning {BFN Offset, T_cell} to each cell. Is done. That is, different {BFN Offset, T_cell} combinations for each cell map to 64 second sync codes transmitted through a second SCH for easy network design and minimization of inter-cell interference. This is because the PSC, which is a unique value for each cell, corresponds to one of the sync codes of the 64 second sync channels.

That is, since there are 64 second synchronous channels, BFN offset is set to 32 chip size units, that is, 32, 64, 96, 128, 160, 192, and 224, and T_cell is all 10 to correspond to each of them. A total of 80 {BFN Offset, T_cell} combinations are generated. Each cell is configured by mapping the generated {BFN Offset, T_cell} combination to a second synchronization code of the second synchronization channel.

6 is a diagram illustrating a process of setting an offset of a base station frame number by a base station according to an embodiment of the present invention.

Referring to FIG. 6, when power is applied to the base station system in step 610, the base station receives system operation information from the base station controller in step 620. The system operation information includes information for setting the base station for communicating with a user equipment, and the base station receives from the base station controller a combination information of a BFN offset and a T_cell for setting a system frame number. do. In step 630, the base station generates BFN time information in 32 chip periods according to the received BFN offset. In step 640, the base station delays the BFN start time according to the BFN offset based on the reference time. In step 650, the SFN start time is generated in the T_cell period with respect to the delayed BFN time. In step 660, the base station transmits a sync code according to the generated SFN start time.

Here, the base station can artificially adjust the BFN offset by the system operator. That is, the base station receiving the BFN offset changed by the system operator using an external terminal may generate the SFN start time in T-cell units according to the set offset.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention has the effect of minimizing the confusion of the inter-cell sync codes by dividing the cells by the SFN start time, that is, the transmission time of the sync code indicated by the combination of {BFN Offset, T_cell}, in the WCDMA system using GPS. That is, by allocating an offset at the start of the BFN and assigning one T_cell value to each cell according to the changed start of the BFN, the transmission time of the sync code is changed from cell to cell so that the handover advantage of using the GPS is continuously maintained. Has

As a result, the UE can obtain the PSC of each base station in a short time and effectively perform a cell search process, thereby improving the call quality and efficiently using the system capacity.

Claims (7)

Inter-cell interference in an asynchronous mobile communication system having a user terminal, a cell in which the user terminal is located, a base station managing a plurality of cells adjacent to the cell, and a base station controller providing a transmission point of a synchronization channel to the base station In a method of performing communication while minimizing Transmitting, by the base station controller, a combination of offset information, which is time information allocated to distinguish base stations based on external time information, and time information of cells managed by the base station, to the base station; And transmitting, by the base station, a synchronization code by repeating the time information of the cells at a delayed time point of the set offset information. The method of claim 1, The offset information, which is time information allocated to distinguish the base station, indicates a time point at which clock information is generated at a different time point for each base station based on the external time information. The method of claim 1, The synchronization code repeatedly transmitted as the time information of the cells based on the offset information and the offset information, which are allocated time information for identifying the base station, is a synchronization code for acquiring a scrambling code of the base station where the user terminal is located. Said method. In a method for performing communication by the base station to minimize the cell interference of the user terminal in the asynchronous mobile communication system indicating the transmission time of the channel using the external time information, Receiving information indicating an offset of a base station frame number and a period of cells controlled by the base station, the base station configured to have a channel transmission time point that is different from another base station from a base station controller; Transmitting, by the base station, a channel repeatedly to a user terminal in response to a period of the cells starting from the offset of the base station frame number; The user terminal receives the channel and performs a communication in synchronization with the signal at the best time. The method of claim 4, wherein The base station sets the frame transmission time according to the period of the cells controlled by the base station based on the offset of the base station frame number. The method of claim 4, wherein The offset of the base station frame number can be set within the range of 256 chips. The method of claim 4, wherein The base station controller generates 64 sync codes by combining the offset of the base station frame number and the period of cells controlled by the base station.

Images