CN101043693A - Method and system for inter-cell eliminating interference - Google Patents

Abstract

The invention discloses a method for eliminating interference between cells to solve the problem in the prior art that partial frequency reuse technology is used when eliminating inter-cell interference to affect the frequency use efficiency of the entire system; the method is performed by a base station according to user equipment The related signals of this cell are divided into two types: cell center user and cell edge user; and the time slot specified in the configuration information is used to transmit data between the base station and the cell center user and cell edge user in the cell, and for Adjacent cells, cell edge users in different cells use different time slots to transmit data. The invention also discloses a base station at the same time.

Description

A method and system for eliminating interference between cells

technical field

The present invention relates to the communication field, in particular to a method and system for eliminating interference between cells.

Background technique

Existing commercial wireless communication systems can support uplink and downlink multi-user access. Uplink means that the terminal sends data to the base station, and downlink means that the base station sends data to the terminal. Different users can communicate with the base station at the same time, and the data of different users are multiplexed on one link by means of frequency division, time division or code division to ensure that the channels used by them are orthogonal to each other, that is to say, there will be no communication between users. interfere with each other.

Due to the limited coverage of each base station, in order to allow the system to accommodate more users, the wireless communication coverage area is usually divided into individual cells, usually each cell is in a hexagonal shape, and each cell is adjacent to form a honeycomb shape, so Called the cellular mobile communication system, as shown in Figure 1.

In a cellular mobile communication system, each cell is adjacent to six surrounding cells. If users in adjacent cells use the same frequency band to communicate at the same time, mutual interference will occur. That is to say, channels used by users between cells are non-orthogonal. A common method is to divide the entire frequency band into multiple subbands, and each adjacent cell uses a different subband. Non-adjacent cells use the same subband, as shown in Figure 1, cell 1 uses subband 1, cells 2, 4, and 6 use subband 2, and cells 3, 5, and 7 use subband 3. In this way, users of adjacent cells are orthogonal in frequency, thereby reducing mutual interference. However, for such a system, because each cell only uses a part of the entire frequency band, the frequency utilization efficiency of the system is greatly reduced, thereby degrading the performance of the system.

For inter-cell interference, the greatest interference comes from the interference between edge users of adjacent cells. Because such users are far away from the base station, both the base station and the users need to increase the transmission power, so the interference to adjacent cells is relatively large. Moreover, due to poor channel quality, such users receive weak signals and are most affected by interference from adjacent cells. Therefore, how to improve the communication quality of the cell edge users becomes the key to improving the overall performance of the communication system and expanding the coverage of each cell.

A solution to interference is provided in the prior art, as shown in FIG. 2 . In this scheme, two kinds of regions are defined in one transmission time slot TTI: low inter-cell interference region (LICI region) and normal inter-cell interference region (NICI region). The LICI area occupies several Orthogonal Frequency Division Multiplexing (OFDM) symbols in the time domain. Partial frequency reuse technology is used in this area, that is, each adjacent cell uses a part of the entire frequency band of the system at these moments, and frequency multiplexing Use a factor greater than 1. The NICI area is the OFDM symbols other than LICI in the time domain. In these areas, each cell uses the entire frequency band, that is, the frequency reuse factor is 1. In the LICI area, due to the use of partial frequency reuse technology (see Figure 1), the interference between adjacent cells is small, and this area can be allocated to cell edge users, thereby improving the communication quality of cell edge users. That is to say, the data of the cell edge users is transmitted in the time slots of the LICI area. Correspondingly, the NICI area is assigned to users in the center of the cell. Since users in the cell centers of adjacent cells are far away from each other, the mutual interference is relatively small, so the entire frequency band can be used for communication at these moments, that is, the frequency reuse factor is 1.

Although the technical solution shown in Figure 2 can eliminate inter-cell interference, it is still unavoidable to use partial frequency reuse technology, that is, in the LICI area, the frequency reuse coefficient of the system is greater than 1. In this way, the frequency utilization efficiency of the whole system is greatly reduced.

Contents of the invention

The present invention provides a method and system for eliminating interference between cells to solve the problem in the prior art that partial frequency reuse technology is used when eliminating inter-cell interference, which affects the frequency use efficiency of the entire system.

The invention provides the following technical solutions:

A method for eliminating interference between cells, comprising the steps of:

The base station distinguishes the users in the cell into two types: cell center users and cell edge users according to the relevant signals of the user equipment; and

The time slots specified in the configuration information are used to transmit data between the base station and the cell center users and cell edge users in this cell, and for adjacent cells, cell edge users in different cells use different time slots to transmit data.

in:

By comparing the strength value of the pilot signal of the user or the value of other signals related to the pilot signal with the threshold, the user is divided into a cell center user and a cell edge user.

Adjacent base stations regularly report the situation of cell-edge users, and adjust the number of time slots used by cell-edge users according to the range of changes in the number of cell-edge users in adjacent cells.

In each base station, the user time division multiplexing table is used to designate the time slots used by the cell center users and cell edge users of the cell, and the time slots used by the cell edge users specified in the user time division multiplexing tables of adjacent cells are not same.

Include steps when sending downlink data:

The base station divides the user data packets to be sent into two types: cell edge user data packets and cell center user data packets; the base station determines the user type using the current time slot according to the configuration information; and the base station selects the corresponding type from the data packets to be sent User data packets are sent in the current time slot.

The base station adjusts the transmission function when sending different types of user data packets, so that the power for sending user data packets at the edge of the cell is greater than the power for sending user data packets at the center of the cell.

The base station sends the time slots used by the cell edge user and the cell center user specified in the configuration information to the user equipment, and the user sends uplink data in the corresponding time slot.

A communication system, including a plurality of base station devices for performing radio resource management; the base station devices include:

It is used to save the user time division multiplexing table, which defines the time slots used by cell edge users or cell center users, and the time slots used by cell edge users are defined in the user time division multiplexing tables of adjacent cells. device;

A device for dividing the user data packets to be sent into two types of cell edge user data packets and cell center user data packets according to whether the user belongs to a cell edge user or a cell center user;

A device for querying the user time-division multiplexing table according to the current time slot index, determining the type of user data packets that should be sent in the current time slot, and selecting the corresponding type of user data packets from the data packets to be sent;

means for transmitting selected user data packets in the current time slot.

The base station equipment further includes: a device for querying the user time division multiplexing table, respectively obtaining time slots used by cell edge users and cell center users, and assigning them to corresponding user equipments.

A communication system, including a plurality of base station devices for performing radio resource management; the base station devices include:

It is used to save the user time division multiplexing table, which defines the time slots used by cell edge users or cell center users, and the time slots used by cell edge users are defined in the user time division multiplexing tables of adjacent cells. device;

A device for querying the user time-division multiplexing table, respectively acquiring time slots used by cell edge users and cell center users and assigning them to corresponding user equipments.

The beneficial effects of the present invention are as follows:

The present invention uses different time slots for edge users to transmit data between adjacent cells, and on the premise of ensuring that the frequency reuse rate of the entire system is 1, the mutual interference between edge users of adjacent cells is greatly reduced, and the efficiency is improved. The communication quality of cell edge users and the overall performance of the entire communication system.

Description of drawings

FIG. 1 is a schematic diagram of a cell in frequency division multiplexing in the prior art;

FIG. 2 is a schematic diagram of time division multiplexing in the prior art;

FIG. 3 is a flowchart of sending downlink data in an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a base station in an embodiment of the present invention;

FIG. 5 is a schematic diagram of cell boundary distribution in an embodiment of the present invention;

6A, 6B, and 6C are schematic diagrams of time-division multiplexing of edge/central users in each cell in the embodiment of the present invention.

Detailed ways

In a cell covered by a base station Node B, for users who are closer to the serving base station and have better channel quality, both the base station and the user equipment can use lower transmit power. The interference is small; for users who are far away from the serving base station or have poor channel quality, both the base station and the user equipment need to use higher transmission power. At this time, the same-frequency interference to surrounding adjacent cells is relatively large.

In order to reduce the interference between adjacent cells and improve the reuse rate of the system frequency, cell users are divided into cell center users and cell edge users in the present invention. For adjacent cells, cell edge users in different cells Users use different time slots to transmit data, that is, cell edge users of adjacent cells stagger each other in time slots.

For the discrimination between the cell center user and the cell edge user in the cell, the pilot signal strength of the user can be measured in the reverse link, or the pilot signal strength of the cell can be measured by the user in the forward link, and the The information is fed back to the base station for implementation. The cell base station can sort the users directly according to the strength of the user's pilot signal, and by comparing the value of the pilot signal strength with the threshold, the users whose pilot signal strength is lower than the threshold are classified as cell edge users, and divide the remaining users into cell center users. In addition, the base station can also use other signals related to the pilot signal to distinguish between the cell center user and the cell edge user, such as using the signal-to-noise ratio or channel quality information CQI obtained according to the strength of the pilot signal.

The configuration information of the base station in each cell specifies the time slots used by users at the center of the cell and users at the edge of the cell. A better way is to establish a user time division multiplexing table in the base station, and specify time slots used by cell center users and cell edge users in the table. The establishment of the time division multiplexing table needs to be coordinated and determined by each cell according to the conditions of adjacent cells. For adjacent cells, the time slots used by the edge users of the cell specified in the user time division multiplexing table of different cells are different, that is, adjacent cells The time slots used by cell edge users are staggered from each other. The establishment of the time division multiplexing table of each base station can be formed when the system is established.

Table 1 and Table 2 show the user time division multiplexing tables of adjacent cell A and cell B respectively. In cell A, time slot 1 is used between cell edge users and the base station to send data, while in cell B , the cell edge user and the base station use time slot 3 to send data (of course, as far as the two cells are concerned, the cell edge user in cell B can also use time slot 2). That is to say, when the base station of cell A uses time slot 1 to intensively send information to the cell edge users in this cell, its neighboring cell B can only send data to the cell center users of this cell in this time slot.

Table 1 (community A) slot index 1 2 3 user type cell edge users community center users community center users

Table 2 (community B) slot index 1 2 3 user type community center users community center users cell edge users

Since the movement of the user equipment will change the user at the center of the cell and the user at the edge of the cell, the base station can periodically re-distinguish the user type according to the strength of the pilot signal of the user. Further, in order to adjust the load of the cell, adjacent base stations regularly report the situation of cell-edge users, and the base station can automatically adjust the number of time slots used by cell-edge users according to the variation range of the number of cell-edge users in adjacent cells. For example, after adjacent cells announce the number of cell-edge users, the number of cell-edge users in one of the cells increases more (can be judged by a given threshold), and the number of time slots used by the cell-edge users is increased accordingly, as The original one time slot is increased to two time slots, but after the time slot adjustment, the time slots used by the cell edge users in adjacent cells must be staggered from each other.

When sending downlink data, the base station can divide the data packets to be sent into two types: cell edge user data packets and cell center user data packets according to different user types, and then determine the current time slot by querying the user time division multiplexing table. Which user type to use, and select the corresponding type of data package. For the division of data packets, the data packets can be sorted according to the strength of the pilot signal of the user to which they belong, and a part of the data packets with weak pilot signals of the users to which they belong are divided into cell edge user data packets, and the remaining data packets are divided It is the cell center user data packet.

Referring to Figure 3, the process of the base station sending downlink data is as follows:

In step 300, the base station classifies the user data packets to be sent, and divides them into cell edge user data packets and cell center user data packets; in step 310, query the user time division multiplexing table to determine the user type using the current time slot; Step 320, select a corresponding type of user data packet according to the type of user using the current time slot; and in step 330, transmit the user data packet.

A structure of a base station in this embodiment is shown in Figure 4. In addition to the existing coding/modulation unit 10, mapping unit 15, inverse fast Fourier transform unit 16 and antenna 20, the base station also includes a classification unit 11, a second A storage unit 12 , a second storage unit 13 , a third storage unit 17 and a data packet selection unit 14 .

The classification unit 11 is used to distinguish the encoded/modulated data packet into a cell edge user data packet and a cell center user data packet, save the cell edge user data packet to the first storage unit 12, and save the cell center user data packet to the second storage unit 12. Two storage unit 13; The 3rd storage unit 17 is used to preserve the user time division multiplexing table of this sub-district; Packet selection unit 14 inquires user time division multiplexing table from the 3rd storage unit 17 and determines that current time slot is used by which user type , and select a corresponding type of data packet from the first storage unit 13 or the second storage unit 13 and output it; the mapping unit 14 performs orthogonal frequency multiplexing OFDM carrier mapping on the data; the IFFT conversion unit 16 modulates the carrier, and passes The antenna 20 transmits the modulated carrier.

The user equipment demodulates and decodes the data at a corresponding moment, and the processing method is the same as that of the prior art.

For the uplink, the base station queries the user time-division multiplexing table according to the type of the user (that is, the cell edge user or the cell center user), allocates the corresponding time slot for the uplink channel of the user equipment, and sends it to the user equipment through control signaling , and then, the user equipment sends data to the base station in a specified time slot. Correspondingly, the base station includes a functional unit for querying the user time division multiplexing table, obtaining the time slots used by the cell edge users and the cell center users respectively, and sending them to the user equipment.

The above method can be used solely on the downlink or on the uplink, but the best way is to use the above method on both the downlink and the uplink.

The technical solution of the present invention is further illustrated by an example below, which is not intended to limit the present invention.

FIG. 5 is a schematic diagram of a typical hexagonal cell boundary, where each cell is adjacent to six cells. Users at the edge of a cell are interfered by at most two adjacent cells. For example, the user at the black dot at the junction of cells 1, 3, and 4 in the figure assumes that its serving cell is cell 1. When the user communicates with the base station of cell 1, it will be interfered by signals transmitted by the base stations or users of cells 3 and 4.

Table 3, Table 4 and Table 5 respectively give the user time division multiplexing table of each cell. It can be seen from the three user time division utilization tables that the cell edge users of adjacent cells use different time slots. For example, cell-edge users in cell 1 use time slot 1, cell-edge users in cell 3 use time slot 3, and cell-edge users in cell 4 use time slot 2. The three time slots are interleaved and do not cover each other.

Table 3 (Time Division Multiplexing Table of Cell 1) slot index 1 2 3 Corresponding intra-subframe OFDM symbol index 1st and 2nd code elements The 3rd and 4th code elements The 5th and 6th code elements user type cell edge users community center users community center users

Table 4 (time-division multiplexing tables of cells 3, 5, and 7) slot index 1 2 3 Corresponding intra-subframe OFDM symbol index 1st and 2nd code elements The 3rd and 4th code elements The 5th and 6th code elements user type community center users cell edge users community center users

Table 5 (time-division multiplexing tables of cells 2, 4, and 67) slot index 1 2 3 Corresponding intra-subframe OFDM symbol index 1st and 2nd code elements The 3rd and 4th code elements The 5th and 6th code elements user type community center users community center users cell edge users

Referring to Figures 6A, 6B, and 6C, it is assumed that a subframe is composed of 6 OFDM symbols, and time slot 1 is defined as the 1st and 2nd OFDM symbols, that is, the base station of cell 1 is sending the 1st OFDM symbol of each subframe. , 2, two OFDM symbols communicate with the cell edge users, and communicate with the cell center users at other times. Frame synchronization between cells. Time slot 2 is defined as the 3rd and 4th OFDM symbols of each subframe, that is, the base stations of cells 3, 5, and 7 communicate with cell edge users when sending the 3rd and 4th OFDM symbols of each frame, and at other times The base station communicates with the cell center users of the respective cells. Time slot 3 is defined similarly. It can be seen from the above that when the cell-edge users and cell-center users of the serving cell and adjacent cells adopt the multiplexing patterns in Figures 6A, 6B, and 6C, the time slots for the cell-edge users of each adjacent cell when communicating with the base station Stagger each other. That is to say, when a cell edge user of a certain cell communicates with its base station, a base station of an adjacent cell only communicates with a cell center user of this cell. Since the adjacent cell only communicates with the cell center user of this cell, the quality of the channel is relatively good, so the base station can reduce the transmit power while ensuring the QoS of the user. In this way, the interference caused to the cell edge users of the current cell is small, thereby improving the communication quality of the cell edge users. As shown in Figures 6A, 6B, and 6C, the base station in cell 1 communicates with its cell edge users in time slot 1, while the base stations in cells 2, 3, 4, 5, 6, and 7 only communicate with local users in time slot 1. The cell center user of the cell communicates. Therefore, the cell-edge users of cell 1 are less interfered by the base stations of cells 2, 3, 4, 5, 6, and 7, thereby improving the communication quality of the cell-edge users of cell 1. When this technology is adopted, no matter it is a cell edge user or a cell center user, its frequency reuse is 1, which improves the utilization rate of spectrum. Moreover, by adopting this technology, the communication quality of users at the edge of the cell is improved, while users at the center of the cell are not affected. Therefore, the overall performance of the system can be greatly improved.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (10)

1, a kind of method of disturbing of eliminating in the minizone is characterized in that, comprises the steps:

The base station is according to the coherent signal of subscriber equipment, and this community user is divided into two types of Cell Center User and Cell Edge User; And

Use the slot transmission data of appointment in the configuration information between Cell Center User in base station and this sub-district and the Cell Edge User, and for neighbor cell, the Cell Edge User in the different districts uses different slot transmission data.

2, the method for claim 1 is characterized in that, the value of strong and weak value of the pilot signal by the user or other signals relevant with pilot signal and threshold ratio are divided into Cell Center User and Cell Edge User with the user.

3, the method for claim 1 is characterized in that, regularly announces the Cell Edge User situation between the adjacent base station, and adjusts the number of timeslots that Cell Edge User uses according to cell edge number of users amplitude of variation in the neighbor cell.

4, the method for claim 1, in each base station, adopt user's time division multiplexing table to specify the Cell Center User and the employed time slot of Cell Edge User of this sub-district, and the time slot that specified Cell Edge User uses in each user's time division multiplexing table of neighbor cell is inequality.

5, as each described method of claim 1 to 4, it is characterized in that the base station comprises step when the user sends downlink data:

The base station is divided into two types of Cell Edge User packet and Cell Center User packets with user data package to be sent;

The user type of current time slots is determined to use in the base station according to configuration information; And

The base station is selected the user data of respective type to wrap in the current time slots from packet to be sent to send.

6, method as claimed in claim 5 is characterized in that, emission function is adjusted in the base station when sending dissimilar user data package, makes the transmission Cell Edge User count the power of bag greater than the power that sends the Cell Center User packet.

As each described method of claim 1 to 4, it is characterized in that 7, subscriber equipment is handed down to the time slot of specifying Cell Edge User and Cell Center User to use in the configuration information in the base station, the user sends upstream data at corresponding time slot.

8, a kind of communication system comprises a plurality of base station equipments that are used to carry out RRM; It is characterized in that described base station equipment comprises:

Be used to preserve user's time division multiplexing table, definition has Cell Edge User or the employed time slot of Cell Center User in this table, and the time slot device inequality that the definition Cell Edge User uses in each user's time division multiplexing table of neighbor cell;

Be used for belonging to Cell Edge User or Cell Center User, user data package to be sent is divided into Cell Edge User packet and Cell Center User packet two kind of means according to the user;

Be used for determining the type of the user data package that current time slots should send, and from packet to be sent, select the device of the user data package of respective type according to current time slots search index user time division multiplexing table;

Be used for device in the user data package of current time slots emission selection.

9, communication system as claimed in claim 8 is characterized in that, described base station equipment also comprises:

Be used to inquire about described user's time division multiplexing table, obtain the employed time slot of Cell Edge User and Cell Center User respectively and be handed down to the device of corresponding user equipment.

10, a kind of communication system comprises a plurality of base station equipments that are used to carry out RRM; It is characterized in that described base station equipment comprises:

Be used to preserve user's time division multiplexing table, definition has Cell Edge User or the employed time slot of Cell Center User in this table, and the time slot device inequality that the definition Cell Edge User uses in each user's time division multiplexing table of neighbor cell;

Be used to inquire about described user's time division multiplexing table, obtain the employed time slot of Cell Edge User and Cell Center User respectively and be handed down to the device of corresponding user equipment.

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