CN1881867A - Method for eliminating interference between cells - Google Patents

Abstract

The invention discloses a method for eliminating intercell interference. The process of the method includes: the user terminal establishes a connection with at least one adjacent base station, and sends the time-frequency resource information used by itself to the adjacent base station that establishes the connection through the local base station; after the adjacent base station receives the time-frequency resource information , allocate different time-frequency resources to the users under its jurisdiction; if the resources are not enough, the adjacent base station will allocate the same time-frequency resources to the users under its own jurisdiction, and modulate and code the interfering users using the same time-frequency resources The method is sent to the user terminal; the user terminal separates the interference user signal from the received signal according to the modulation and coding mode of the interference user. The method of the present invention eliminates interference from users in adjacent cells to users in the current cell by allocating non-interference time-frequency resources and sending modulation and coding information to interference users.

Description

A method for eliminating inter-cell interference

technical field

The invention relates to mobile communication technology, in particular to a method for eliminating interference between cells.

Background technique

With the development of mobile communication technology, 3GPP and other organizations that formulate wireless communication standards are considering incorporating Orthogonal Frequency Division Multiplexing (OFDM) technology into the next generation wireless communication system. Orthogonal frequency division multiplexing technology can keep the service signals of users belonging to the same cell orthogonal to each other, thereby avoiding mutual interference between users of the same cell and ensuring the accuracy of service signal transmission and reception. However, the OFDM technology cannot eliminate the interference between users in adjacent cells, especially the interference from users in adjacent cells of a certain cell to users at the border of the cell. Wherein, a neighboring cell of a certain cell refers to a cell that is geographically close to the cell. As shown in FIG. 1 , cells A, B, C, D, E, and F are all adjacent cells of cell 1 . For users in cell 1, the base station in this cell is called a local base station, and the base stations in adjacent cells are called adjacent base stations.

In order to solve the problem of inter-cell interference, the 3GPP WG1 R1-050401 proposal proposes a method: assign different modulation and coding methods to different users in adjacent cells that cause mutual interference due to the use of the same time-frequency resources, so that user terminals can utilize multi-user The iterative receiver demodulates and separates the service signals of different users, and eliminates the interference between users using the same time-frequency resources.

The same time-frequency resource refers to: the time period and frequency band occupied by user communication completely overlap.

The different modulation and coding methods refer to: using different scrambling codes to scramble the transmitted signal, or using different channel coding and interleaving methods such as the interleaving multiple access method proposed in 3GPP WG1 R1-050401.

The method proposed by 3GPP WG1 R1-050401 needs to allocate different modulation and coding methods to users using the same time-frequency resources in different cells through joint scheduling between base stations when overcoming inter-cell interference, and notify each other of the allocation results , and then the local base station sends the modulation and coding information of the interfering user in the adjacent cell to the user using the same time-frequency resource in the current cell. After the user receives the modulation and coding information, the user can use the multi-user iterative reception technology to separate the interference signal of the user in the adjacent cell, so as to improve the accuracy of service signal reception.

However, in practical applications, in order to adapt to the ever-changing communication environment, the modulation and coding methods used by users will change frequently, which requires frequent communication between base stations for coordination, but this kind of coordinated communication is difficult to guarantee real-time performance and is difficult to implement.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method for eliminating inter-cell interference, so as to eliminate the interference received by users in a certain cell from users in adjacent cells.

In order to achieve the above object, the technical solution of the present invention is specifically realized in the following way:

A method for eliminating inter-cell interference, characterized in that the method comprises the following steps:

a. The user terminal establishes a connection with at least one adjacent base station, and sends the time-frequency resource information used by itself to the adjacent base station that establishes the connection through the local base station;

b. After receiving the time-frequency resource information, the adjacent base station that establishes a connection with the user terminal in step a allocates time-frequency resources different from the user terminal in step a to the users under its jurisdiction.

Further, the method for establishing a connection with at least one adjacent base station described in step a is:

a1. The user terminal measures signal information of different base stations, and compares the measured value with a preset communication threshold;

a2. The user terminal reports the information of the base station reaching the communication threshold to the local base station, and the local base station establishes a connection between the base station reaching the communication threshold and the user terminal.

Preferably, the signal information in step a1 is signal strength or signal-to-noise ratio.

Further, step b further includes: the adjacent base station judges whether the allocation of time-frequency resources is successful, and if successful, ends the interference cancellation process; otherwise, the following steps are performed:

b1. The adjacent base station allocates the same time-frequency resources used by the user terminal described in step a to the users under its jurisdiction, and through the connection established with the user terminal described in step a, allocates the time-frequency resources of the interfering users using the same time-frequency resources The modulation and encoding method is sent to the user terminal described in step a;

b2. The user terminal in step a separates the interference user signal from the received signal according to the modulation and coding method of the interference user, and obtains the service signal sent by the local base station.

Further, when the time-frequency resource allocation of the neighboring base station is successful, before ending the interference elimination process, the method further includes: the neighboring base station sends a non-interfering user notification to the user terminal described in step a.

Further, in step b1, the adjacent base station sends the modulation and coding scheme of the interfering user to the user terminal once in each transmission time interval.

Further, the method for separating the interfering user signal from the received signal in step b2 is:

b21. Demodulate and decode the received signal according to the modulation and coding method of the interfering user, and obtain the decoded signal of the interfering user;

b22. Encoding and modulating the decoded signal to obtain the transmitted signal of the interfering user;

b23. Subtracting the transmitted signal of the interfering user obtained in step b22 from the received signal to separate the interfering user signal.

Preferably, the method for separating interference user signals in step b2 is implemented by a multi-user iterative receiver.

Preferably, the modulation and coding schemes include at least one of three schemes: scrambling, channel coding and interleaving.

It can be seen from the above technical solution that in the method for eliminating inter-cell interference of the present invention, the user terminal establishes a connection with at least one base station through fast cell selection, and reports its own time-frequency resource information to the adjacent base station through the local base station. When the base station allocates time-frequency resources to users in the jurisdiction area, it does not allocate the same time-frequency resources as the user terminal to the users in the jurisdiction area, so as to avoid interference users of the user terminal in the jurisdiction area.

When the number of users of the adjacent base station is large, the adjacent base station allocates the same time-frequency resources as the user terminal, and directly sends the modulation and coding information of the interfering user to the user through the control channel between the user terminal and the user terminal. The terminal enables such users to use the received modulation and coding information of the interfering users to perform interference cancellation, thereby effectively eliminating the interference received by such users.

Description of drawings

FIG. 1 is a schematic diagram of the positional relationship between a certain cell and its adjacent cells in the prior art;

Fig. 2 is a schematic diagram of the connection relationship between a user in a fast cell selection state and two base stations in a preferred embodiment of the present invention;

Fig. 3 is an implementation flow chart of a preferred embodiment of the method of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples.

In a wireless communication system, the base station is responsible for allocating the time-frequency resources and modulation and coding methods of users in the cell. The user terminal can not only maintain connection with the local base station, but also maintain connection with multiple adjacent base stations through the local base station. This process can be adopted Realization of fast cell selection technology (Fast cell selection). The procedure for the user terminal to perform fast cell selection is as follows:

First, the user terminal measures the intensity or signal-to-noise ratio of signals sent by different base stations among the received signals, and compares the measured value with the communication threshold.

The communication threshold is preset by the user terminal and may be signal strength or signal-to-noise ratio.

Next, the user terminal reports the neighboring base stations that have reached the communication threshold to the local base station of the user terminal, and the local base station reports to the network to establish connections with all neighboring base stations that have reached the communication threshold. The above-mentioned set of adjacent base station cells that establish a connection with the user is called an active set.

Then, the user terminal selects a base station with the best signal strength or signal-to-noise ratio in the active set, and sends a selection signal to the base station through an uplink. After receiving the selection signal, the selected base station becomes the new local base station of the user terminal.

Wherein, the downlink established between the user terminal and the local base station includes a traffic channel and a control channel, and the service signal of the user is delivered through the traffic channel, while the downlink established between the user terminal and the adjacent base station is only a control channel.

In the present invention, during the above process, users who are simultaneously connected with the local base station and multiple adjacent base stations are called users in the fast cell selection state.

Fig. 2 is a schematic diagram of an embodiment in which a user in the fast cell selection state maintains connections with two base stations at the same time.

In Figure 2, base station 1 is the local base station of user 1, that is, user 1 is in the cell covered by base station 1. At this time, the downlink established between user 1 and base station 1 includes traffic channels and control channels, and the service data of user 1 passes through Base station 1 transmits, so the connection between user 1 and base station 1 is represented by a solid line; base station 2 is the adjacent base station of user 1, and the downlink established between user 1 and base station 2 is only a control channel, so the connection between user 1 and base station 2 Indicated by dashed lines. In addition, base station 2 is the local base station of users 2, 3 and 4, the time-frequency resources used by user 2 are the same as those of user 1, and the time-frequency resources used by users 3 and 4 are different from those of user 1. Therefore, user 2 is referred to as an interfering user of user 1 in this embodiment.

Based on the connection shown in Figure 2, the flow of the method for eliminating inter-cell interference according to the present invention is shown in Figure 3, including the following steps:

Step 301: User 1 selects base station 1 as a local base station by using a fast cell selection method, establishes a downlink control channel with base station 2, and reports the time-frequency resources used by itself to base station 2 through base station 1.

Step 302, base station 2 allocates different time-frequency resources to the users under its jurisdiction according to the time-frequency resource information of user 1, and judges whether the interference-free allocation is successful. If successful, base station 2 will control the cell without user 1 interfering users through the control channel Notify user 1 of the information of , and end the interference elimination process; otherwise, go to step 303 .

The successful non-interference allocation means that the adjacent base station can meet the time-frequency resource usage requirements of the users in the area under its jurisdiction without using the same time-frequency resource as user 1 . Since the adjacent base station avoids using the same time-frequency resource as user 1, it will not cause interference to user 1.

If the number of users in the adjacent base station is large, the above-mentioned non-interference allocation fails, and the adjacent base station must allocate the same time-frequency resources as user 1 to users within the jurisdiction.

In this embodiment, user 2 uses the same time-frequency resource as user 1, that is, the interference-free allocation fails, so step 303 is executed.

Step 303 , the base station 2 allocates a modulation and coding scheme different from that of the user 1 to the interfering user, and transmits the modulation and coding schemes of all interfering users to the user 1 through the control channel between the base station 2 and the user 1 .

In this embodiment, the time-frequency resource used by user 2 is the same as that of user 1, so base station 2 will deliver the modulation and coding scheme of user 2 to user 1.

Each base station has its own specific scrambling code or interleaving mode, so the modulation and coding mode assigned by base station 2 to interfering user 2 must be different from that of user 1.

Since the modulation and coding method will be adjusted and changed according to the change of the communication environment, base station 2 will send the modulation and coding method of the interfering user once in each transmission time interval (TTI), so as to ensure that user 1 can receive effective information in real time. Interfering information.

Step 304, user terminal 1 activates its own multi-user iterative receiver, removes the interference signal from the signal received by user 1 according to the modulation and coding scheme of the interfering user, and obtains the service signal delivered by local base station 1 to user 1.

The multi-user iterative reception refers to: when the received signal is superimposed by multiple user signals, the received signal is detected according to the information of multiple users, other user signals are removed from the received signal, and the required signal is improved. receiving performance. This method of separating signals using a multi-user iterative receiver is known in the prior art.

In this embodiment, the specific processing of step 304 is as follows: User 1 first demodulates and decodes the received signal according to the modulation and coding method of the interfering user to obtain the decoded signal of the interfering user; then performs decoding on the decoded signal Coding and modulation to restore the transmitted signal of the interfering user; finally, subtract the transmitted signal of the interfering user from the signal received by the user end to obtain the service signal sent by the local base station 1 to user 1.

It can be seen from the above-mentioned embodiments that the method for eliminating inter-cell interference of the present invention allocates non-interference time-frequency resources to adjacent base station users, and after the non-interference allocation fails, the adjacent base station directly sends the modulation of the interfering user. The coded information is given to the user in the fast cell selection state in a certain cell, so that the user can use the received interfering user modulation coded information to perform interference cancellation, thereby effectively eliminating the interference received by the user in the cell.

Claims (9)

1, a kind of method of eliminating presence of intercell interference is characterized in that, this method may further comprise the steps:

A, user terminal and at least one adjacent base station connect, and by home base stations the running time-frequency resource information of self using are sent to the adjacent base station that connects;

After b, the adjacent base station that connects with the described user terminal of step a are received described running time-frequency resource information, give self user that administers of institute distribution and the different running time-frequency resource of the described user terminal of step a.

2, method according to claim 1 is characterized in that, the method that connects with at least one adjacent base station described in the step a is:

The signal message of a1, user terminal measurement different base station, and measured value compared with the thresholding of communicating by letter that sets in advance;

The base station information that a2, user terminal will arrive the communication thresholding reports home base stations, being connected between the base station of being set up described arrival communication thresholding by home base stations and the user terminal.

3, method according to claim 2 is characterized in that, the described signal message of step a1 is signal strength signal intensity or signal to noise ratio.

4, method according to claim 1 is characterized in that, step b further comprises: adjacent base station is judged the whether success of distribution of running time-frequency resource, if success then finish this interference cancellation process; Otherwise execution following steps:

B1, described adjacent base station are given the user who self administers with the identical time-frequency resource allocating that the described user terminal of step a uses, and by using the modulation coding mode of the interference user of identical running time-frequency resource to send to the described user terminal of step a with the connection that the described user terminal of step a is set up;

The described user terminal of b2, step a is isolated the interference user signal according to the modulation coding mode of interference user from the signal that receives, obtain the service signal that home base stations sends.

5, method according to claim 4, it is characterized in that, when the success of the time-frequency resource allocating of adjacent base station, before finishing this interference cancellation process, this method further comprises: adjacent base station sends noiseless user notification to the described user terminal of step a.

6, method according to claim 4 is characterized in that, among the step b1, adjacent base station sends the modulation coding mode of an interference user to user terminal at each Transmission Time Interval.

7, method according to claim 4 is characterized in that, the method for isolating the interference user signal among the step b2 from the signal that receives is:

B21, according to the modulation coding mode of interference user, separate to the received signal and be in harmonious proportion decoding, obtain the decoded signal of interference user;

B22, decoded signal is encoded and modulated, obtain transmitting of interference user;

B23, from the signal that receives, deduct transmitting of step interference user that b22 obtains, realize the separation of interference user signal.

According to claim 4 or 7 described methods, it is characterized in that 8, the method for the described separation interference user of step b2 signal is realized by multi-user's iterative receiver.

9, method according to claim 4 is characterized in that, described modulation coding mode comprise scrambler, chnnel coding and the three kinds of modes that interweave at least a mode.

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