JP2012529796A - Method and system for canceling adjacent cell interference - Google Patents

Abstract

The present invention provides a method and system for canceling interference of adjacent cells, in which the method divides a base station cover area into an inner loop area and an outer loop area, and frequency bands occupied by adjacent base stations with each other. Negotiate, each occupied frequency band of the outer loop area is different, the base station transmits a detection signal to a terminal in the cover area, the terminal in response to the detection signal A corresponding user type of the terminal is determined based on the generated feedback signal, and the user type is an inner loop user or an outer loop user, and based on the determination result of the user type, The base station applies the frequency band corresponding to the user type to the terminal. No. By using this method, in the same frequency network system of WiMAX, it is possible to accurately determine the type for users in the cell, and in particular, users located at the boundary of the outer loop Avoid the possible ping-pong effect that occurs and improve the overall network performance by self-adaptive threshold adjustment algorithm.
[Selection] Figure 5

Description

  The present invention relates to the field of communications, and more particularly, to a method and system for canceling adjacent cell interference in a WiMAX (Worldwide Interoperability for Microwave Access, abbreviated as WiMAX) network system.

  With the rapid development of network technology, WiMAX wireless networks will gradually become approved by humans and become the new 3rd generation (3G) standard.

  In the WiMAX system, terminals in the overlapping coverage area between the cells can receive the downlink frame signal sent by each cell in the overlapping coverage area. When these cells send signals using the same frequency band, signals sent by cell base stations that are not accessed by the terminals become interference of the terminals.

  FIG. 1 is a schematic diagram in which multiple cells overlap and cover in the prior art. As shown in FIG. 1, the A cell base station, the B cell base station, and the C cell base station simultaneously cover an area where the terminal MS1 exists. Among them, the terminal MS1 is accessed by the A cell base station, and at this time, the signal sent out by the B cell base station and the C cell base station is interference with the terminal MS1.

  Currently, in order to avoid interference occurring in the overlapping coverage area, the always adopted solution is the Fractional Frequency Reuse (FFR) method, which includes shipping frames of different cells. Occupies different frequency bands. FIG. 2 is a schematic diagram for suppressing signal interference in the overlapping cover area by the FFR technique in the prior art. As shown in FIG. 2, the A cell base station, the B cell base station, and the C cell base station use the entire frequency band F1 + F2 + F3 in order to make maximum use of the bandwidth in the non-overlapping area. The frame signal is sent out, and each cell has a different signal strength in the non-overlapping area. Therefore, no interference occurs even at the same frequency. For overlapping areas, the A cell base station sends a partial frequency band F1 to access terminals in the overlapping area, and the B cell base station sends a partial frequency band F2 to access terminals in the overlapping area. Then, the C cell base station sends out a partial frequency band F3 to access terminals in the overlapping area.

  In the method shown in FIG. 2, an area that always uses all frequency bands can be referred to as an inner loop area, and an area that uses partial frequency bands can be referred to as an outer loop area. Thus, since the A, B, C cell base stations occupy different frequency bands in the downlink frames sent out in the outer loop area, the terminal accessing the A cell base station is located in the frequency band F2 or F3. Thus, no interference occurs between the downlink frames sent by each cell to the terminals in the overlapping area, that is, the B cell base station and the C cell base station are not demodulated. The transmitted downlink frame signal does not interfere with the terminal receiving the downlink frame signal from the A cell base station, and similarly, the terminal accessing the C cell base station or the B cell base station is also received from other cell base stations. No down interference.

  In order to realize the above-described method, the base station needs to selectively improve the transmission power in a part of the frequency bands and adopt a lower transmission power for the other frequency bands. For example, for a base station of the A cell, it is necessary to adopt high transmission power in the F1 frequency band and low transmission power in the F2 + F3 frequency band, and thus terminals that are located in non-overlapping areas At the same time, terminals in overlapping areas use different frequency bands in adjacent cells, so that interference does not occur as well, and such a method effectively has interference between cells. The problem can be solved. However, the most important problem of this method is to determine how accurately the user in the cell belongs to the inner loop area or the outer loop area, and in particular, the user can When moving between areas, the user repeatedly switches between inner and outer loop types, thereby causing a ping-pong effect and severely impacting user and network performance. How to accurately determine the user type in a cell is a problem that the present invention seeks to solve.

  In view of the above problems, the present invention was created, and therefore the main object of the present invention is to provide a method and system for canceling adjacent cell interference.

  According to one aspect of the present invention, there is provided a method for canceling interference of adjacent cells, wherein the method divides a coverage area of a base station into an inner loop area and an outer loop area, and adjacent base stations occupy each other. Negotiate frequency bands, make the occupied frequency bands of each outer loop area different from each other, transmit a detection signal to the terminal in the cover area, the base station Based on the feedback signal generated in response, the corresponding user type of the terminal is determined. Among them, the user type is an inner loop user or an outer loop user, and the base type is determined based on the determination result of the user type. The station includes applying a corresponding frequency band of its user type to the terminal.

  Among them, a guard band is included between the inner loop area and the outer loop area, and the method further includes determining a user type for a terminal in the guard band according to a scheduled rule.

  Among them, in the step of determining the user type according to the schedule rule for the terminal in the guard band, the base station compares the N feedback signals received continuously with the threshold value in a time window manner, and the terminal's response N is a natural number greater than 0.

  The threshold value includes a first threshold value and a second threshold value, and the first threshold value represents a threshold value for switching from the inner loop user to the outer loop user, and the second threshold value. Represents a threshold value for switching from an outer loop user to an inner loop user, and the first threshold value is smaller than the second threshold value.

  Among them, when the user switches from the outer loop area to the inner loop area, or when switching from the inner loop area to the outer loop area, the base station adopts a time window method to statistically calculate the feedback signal. .

  Among them, when the user switches from the outer loop area to the inner loop area, the base station adopts the fixed window statistics method, and for each of the collected N feedback signals, it is larger than the second threshold value. When the number of times is calculated and the number of times is larger than the predetermined value, the user is switched to the inner loop user.

  Among them, when the user switches from the inner loop area to the outer loop area, the base station adopts the sliding window statistics method, and it is smaller than the first threshold for the N feedback signals collected recently. When the number of times is calculated and the number of times is larger than the scheduled value, the user is switched to the outer loop user.

  Among these, the first threshold value and the second threshold value correspond to the outer diameter and inner diameter of the guard band, respectively.

  Among them, the first threshold value and the second threshold value can be dynamically adjusted based on the performance parameters of the cell network.

  Among them, the base station initially presets the corresponding user of the terminal as an outer loop user.

  Among them, the feedback signal includes a ratio of downlink carrier to interference noise, received signal strength information, and / or downlink packet error rate.

  According to another aspect of the present invention, there is provided a system for canceling adjacent cell interference, the system dividing a cover area into an inner loop area and an outer loop area, and frequency bands in which adjacent base stations are occupied by each other. And the base station that transmits the detection signal to the terminals in the coverage area with the occupied frequency band of each of the outer loop areas being different from each other, and feedback in response to the detection signal The base station further includes a determination device that determines a corresponding user type of the terminal based on a feedback signal from the terminal, of which the user type is an inner loop user or an outer loop user Based on the determination result of the user type, the base station Apply the corresponding frequency band.

  Among them, the base station further includes a guard band between the inner loop area and the outer loop area, and the base station further includes a transitional band for determining a user type according to a schedule rule for a terminal in the guard band. Equipment.

  Among them, in the process of determining the user type to the terminal in the guard band according to the schedule rule by the transient device, the transient device uses the N feedback signals continuously received by the base station as a time window method. According to the threshold and determine the corresponding user type of the terminal, of which the threshold includes the first threshold and the second threshold, of which the first threshold is the inner loop Indicates the threshold value for switching from the user to the outer loop user, the second threshold value represents the threshold value for switching from the outer loop user to the inner loop user, and the first threshold value is smaller than the second threshold value. Of these, N is a natural number greater than 0.

  Among them, when the user switches from the outer loop area to the inner loop area, or when switching from the inner loop area to the outer loop area, the transient device adopts a time window method to the feedback signal. Stats.

  Among them, when the user switches from the outer loop area to the inner loop area, the transitional device adopts the fixed window statistics method, which is the second threshold value for each collected N feedback signals When the greater number is calculated and the number is greater than the scheduled value, the user is switched to the inner loop user.

  Among them, when the user switches from the inner loop area to the outer loop area, the transitional device adopts the sliding window statistics method, which is the first threshold for the recently collected N feedback signals. When the number of times smaller than the value is calculated and the number of times is larger than the scheduled value, the user is switched to the outer loop user.

  Among these, the first threshold value and the second threshold value correspond to the outer diameter and inner diameter of the guard band, respectively.

  The base station further includes an adjustment device that dynamically adjusts the first threshold value and the second threshold value based on the performance parameters of the cell network.

  Among them, the determination device initially presets a user corresponding to the terminal as an outer loop user.

  Among them, the feedback signal includes a ratio of downlink carrier to interference noise, received signal strength information, and / or downlink packet error rate.

  According to the above technical scheme of the present invention, in the system of the same frequency network of WiMAX, it is possible to accurately determine the type for the users in the cell, and in particular, users located at the boundary of the outer loop may occur. The performance of the whole network is improved by avoiding the ping-pong effect and using the self-adaptive threshold adjustment algorithm.

  The drawings described herein are used to provide a further understanding of the invention, and form a part of this application, and the exemplary embodiments of the invention and the description thereof are used to interpret the invention. This is not a limitation of the present invention. In the drawing

It is the schematic diagram which the multi-cell in a prior art covers and overlaps. It is a schematic diagram which suppresses signal interference in an overlapping cover area by FFR technology in the prior art. It is a schematic diagram of the frequency band resource used for each adjacent cell based on the Example of this invention. It is a principle figure of judgment of an outer loop user type based on the example of the present invention. FIG. 5 is a process diagram of an outer loop user type determination method according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a system for canceling interference of neighboring cells according to another embodiment of the present invention.

FIG. 5 is a process diagram of an outer loop user type determination method according to an embodiment of the present invention, and it is necessary to describe the steps described in the following method as, for example, a set of computer-executable instructions. Although the logical order is illustrated in FIG. 5 in some computer systems, in some cases, the steps shown or described may be performed in a different order. As shown in FIG. 5, the method includes the following processes:
Step S502, the base station cover area is divided into an inner loop area and an outer loop area, the adjacent base stations negotiate with each other about the occupied frequency band, and the occupied frequency band of each outer loop area is determined. Make each different,
Specifically, after each neighboring cell base station is initialized, the inner and outer loop area divisions and outer loop frequency band resource discussions are completed. The frequency bands used for the outer loop area do not interfere with each other, thus effectively eliminating the interference that exists between cells, for example, as shown in FIG. Occupies different frequency bands in the outer loop area, of which the diagonal lattice portion indicates that frequency band 1 is used, the upward-sloping diagonal portion indicates that frequency band 2 is used, and the downward-sloping diagonal portion indicates Indicates that frequency band 3 is used.

Step S504, the base station sends a detection signal to a terminal within the coverage area, and the terminal generates a feedback signal in response to the detection signal,
Among them, the detection signal is a preamble signal, the feedback signal includes a downlink CINR (Carrier to Interference Noise Ratio) value, and the feedback signal further includes a received signal strength (Receive Signal). Strength Indicator, abbreviated as RSSI)
Specifically, the terminal calculates the downlink CINR value based on the preamble signal from the base station and reports the value in real time, and for each cell base station, the transmission is performed in both the inner loop area and the outer loop area. The power of the preamble signal is fixed, and according to the Wimax discussion rules, the preamble signal is higher than the transmission power of a normal packet and the power value is fixed, and the terminal is within the range covered by the cell base station. The closer to the base station, the stronger the received preamble signal, and the farther the terminal is from the base station, the weaker the received preamble signal.For this reason, the downlink CINR value and RSSI calculated by the strength of the preamble signal are The terminal can reflect the distance from the cell base station, and also processes the preamble from the base station In addition to calculating the downlink CINR value, the downlink CINR value can be calculated based on the pilot from the base station, and the distance from the terminal to the base station is not properly reflected only by the downlink CINR value and RSSI. In some cases, other parameters corresponding to the feedback signal can be increased, for example, subparameters such as the downlink packet error rate, and these subparameters can further improve the judgment of the user signal strength of the base station. Thus, the user type can be determined more accurately.

Steps S506 and S508, the base station determines a corresponding user type of the terminal based on a feedback signal generated by the terminal in response to the detection signal, and the user type is an inner loop user or an outer loop user. Yes,
Specifically, the cell base station performs outer loop user determination based on the downlink CINR value and RSSI information fed back by the terminal, and the base station determines the terminal parameter from the local database based on the downlink CINR value reported from the terminal. The terminal user is classified into an inner loop user and an outer loop user, and when the terminal user is currently an outer loop user, the terminal user reports that the downlink CINR value reported by the terminal is greater than CINR_THS_HIGH. Fig. 4 shows a schematic diagram for judging the threshold value, and the judgment threshold value includes the first threshold value CINR_THS_LOW and the second threshold value CINR_THS_HIGH, and CINR_THS_LOW Down CINR threshold when switching from loop user to outer loop user CINR_THS_HIGH represents a downlink CINR threshold when switching from an outer loop user to an inner loop user, and CINR_THS_LOW <CINR_THS_HIGH. Including a guard band between the inner loop area and the outer loop area, the base station determines the user type according to the schedule rule for the terminals in the guard band, and the thresholds CINR_THS_LOW and CINR_THS_HIGH are outside and inside the guard band, respectively. Configure. At the same time, in order to prevent the `` ping-pong effect '' due to the terminal frequently switching between the inner loop and the outer loop, when the base station installs the guard band according to the downlink CINR value and the terminal accesses initially, In order to guarantee the stability at the time of initial access when the attributes of the inner outer loop of the terminal cannot be determined, the base station sets the initial state of the user type to the outer loop user regardless of the position of the terminal. Install.

Further, the method includes the step of applying the frequency band corresponding to the user type to the terminal based on the determination result of the user type,
In the above step, when the user switches from the outer loop area to the inner loop area, or when switching from the inner loop area to the outer loop area, the base station adopts a time window method to the feedback signal. The N consecutively received feedback signals (where N is a natural number greater than 0) are compared with a threshold according to a time window scheme to determine the corresponding user type of the terminal.

Specifically,
When it is determined in step S508 that the user is an outer loop user, steps S510 to S516 are executed, and when the user switches from the outer loop area to the inner loop area, a “fixed window” statistical method is adopted, That is, when the downlink CINR values reported by N terminals are collected, the number of times greater than CINR_THS_HIGH is determined, and if the number is higher than a set value, the terminal is switched to the inner loop. After completing the statistics for each order, clear all the statistics, and start statistics for the next N downlink CINR values, again after N statistics, then perform the next inner / outer loop determination,
When it is determined in step S508 that the user is an inner loop user, steps S518 to S524 are executed, and when the user switches from the inner loop area to the outer loop area, the terminal is positioned at the edge of the inner loop. Can generate a lot of packet errors, so it needs to be done at a fast rate, so we have adopted the “sliding window” statistical method, ie completed the first Nth order statistics After that, when the downlink CINR value reported by the next terminal arrives without clearing the statistical value, only the first acquisition amount in the downlink CINR value that was just statistics is switched to the new value, and the inner and outer loops are judged. Do. If this N-th statistic has a number of times smaller than CINR_THS_LOW and is higher than a set value, the terminal is switched to the outer loop.

Step S526, the base station statistics the network performance parameters of the entire cell system over a long period of time, adjusts the inner and outer loop thresholds in a self-adaptive manner according to the actual environmental changes, and the overall network performance Improve
As described above, the first threshold value and the second threshold value can be dynamically adjusted based on the performance parameters of the cell network. Among them, the network performance index in a cell can be structured by a plurality of parameters, for example, the proportion of inner and outer loop users, the change in the throughput of the entire cell, and the like. When the proportionality between the number of inner loop users and the number of outer loop users in a cell is too large, or the throughput ratio of inner loop users and outer loop users is too large, the threshold value of outer loop users can be improved appropriately. Increase the number of outer loop users, decrease the number of inner loop users, improve the utilization of network bandwidth, the proportion of the number of inner loop users and outer loop users in the cell is too small, or the throughput and outer loop of inner loop users When the loop user's throughput ratio is too small, the threshold of the inner loop user can be lowered appropriately, the outer loop user is decreased, the inner loop user is increased, and the network band Improve the utilization of the width, thereby, improve the performance of the entire network.

FIG. 6 shows a system for canceling adjacent cell interference according to another embodiment of the present invention. As shown in FIG.
The cover area is divided into an inner loop area and an outer loop area, and the adjacent base stations negotiate the frequency bands occupied, the frequency bands occupied by the respective outer loop areas differ, and the base station Sends a detection signal to terminals in its coverage area, of which the base station 602 is a preamble signal,
A terminal 604 that generates a downlink CINR value in response to the detection signal is included.

  The base station 602 further determines a user type corresponding to the terminal based on the downlink CINR value from the terminal, and the user type is an inner loop user or an outer loop user, and the base type is determined based on the determination result of the user type. The station includes a determination device 606 that applies a frequency band corresponding to the user type to the terminal.

  Among them, the base station 602 further includes a guard band between the inner loop area and the outer loop area, and the base station 602 further transitions to determine a user type according to a schedule rule for terminals in the guard band. In the process of determining the user type according to the scheduling rule for the terminal in the guard band by the transient device, the transient device receives the N devices continuously received by the base station. Compare the downstream CINR value with the threshold value in the time window method for the downstream CINR value (N is a natural number greater than 0) to determine the corresponding user type of the terminal, of which the threshold value is the first threshold Including a value CINR_THS_LOW and a second threshold CINR_THS_HIGH, wherein CINR_THS_LOW represents a threshold for switching from the inner loop user to the outer loop user, and CIN R_THS_HIGH represents a threshold value for switching from the outer loop user to the inner loop user, and CINR_THS_LOW <CINR_THS_HIGH. When determining that a user is a loop user, when the user switches from the outer loop area to the inner loop area, the transitional device adopts the “fixed window” statistics method, that is, the downlink reported by N terminals. Each time the CINR value is collected, the number of times larger than CINR_THS_HIGH is judged, and if this number is higher than a set value, the terminal is switched to the inner loop. After completing statistics every time, clear all statistics and start statistics for the next N downlink CINR values. After statistics are again counted for N, the next inner / outer loop judgment is performed and the judgment is made. The device can generate many packet errors when determining that the user is an inner loop user, when the user switches from the inner loop area to the outer loop area, and when the terminal is located at the edge of the inner loop Therefore, it is necessary to perform at a high speed, and for this reason, the “sliding window” statistical method is adopted, that is, after completing the first N-th statistics, the statistical values are not cleared, When the downlink CINR value reported by the terminal of the terminal arrives, only the first acquisition amount in the downlink CINR value that was just statistics is switched to a new value, and the inner loop is judged. . If this N-th statistic has a number of times smaller than CINR_THS_LOW and is higher than a set value, the terminal is switched to the outer loop.

  The base station 602 may further include an adjusting device (not shown) that dynamically adjusts the first threshold and the second threshold according to cell network performance parameters. The coordinator statistics the network performance of the entire cell system over a long period of time, adjusts the inner loop threshold in a self-adaptive manner according to actual environmental changes, and improves the overall network performance. Among them, the network performance index in the cell can be structured by a plurality of parameters, for example, the proportion of the inner and outer loop users, the change of the throughput of the whole cell, and the like. When the proportion of the number of inner loop users and the number of outer loop users in the cell is too large, or the proportion of the throughput of the inner loop user and the throughput of the outer loop user is too large, the threshold value of the outer loop user can be improved appropriately. Increase the number of outer loop users, decrease the number of inner loop users, improve the utilization of network bandwidth, the proportion of the number of inner loop users and the number of outer loop users in the cell is too small, or the throughput of inner loop users and When the proportion of the throughput of the outer loop user is too small, the threshold value of the inner loop user can be lowered appropriately, the outer loop user is decreased, the inner loop user is increased, and the network is increased. Improve bandwidth utilization, thereby, improve the performance of the entire network.

  Among them, the determination device 606 in the system cannot determine the attributes of the inner and outer loops of the terminal when the user accesses the initial stage. Even if it is located, the initial state of the user type is set for the outer loop user.

  According to the above, according to the technical solution of the present invention, the adjacent loop is effectively adjacent by negotiating the occupied frequency band of the outer loop and accurately classifying the cell user type and installing the protection band. Eliminates cell-to-cell interference, avoids possible ping-pong effects caused by users at the inner and outer loop boundaries, and improves overall network performance through self-adaptive adaptive threshold adjustment algorithm Let

  Obviously, for this area employee, each of the modules or steps of the present invention described above can be realized by a general purpose computing device, which can be concentrated on a single computing device, or multiple computations Distributed in a network of devices, optionally they can be realized by program code executable by a computing device, so that they can be stored in a storage device and executed by a computing device, or they can be It should be appreciated that each integrated circuit module can be manufactured, or multiple modules or steps thereof can be manufactured and implemented in a single integrated circuit module. Thus, the present invention is not limited to any specific combination of hardware and software.

  The above description is not intended to limit the invention to the preferred embodiments of the invention, but for employees, the invention has various modifications and changes. Any modifications, changes, improvements, etc. made to the spirit and principle of the present invention should all fall within the protection scope of the present invention.

Claims (21)

A method for canceling neighboring cell interference, the method comprising:
Dividing the base station cover area into an inner loop area and an outer loop area;
The adjacent base stations are allowed to negotiate with each other about the occupied frequency band, thereby making the occupied frequency band of the respective outer loop area different from each other,
The base station transmitting a detection signal to a terminal within its coverage area;
The base station determines a user type corresponding to the terminal based on a feedback signal generated by the terminal in response to the detection signal, and the user type is an inner loop user or an outer loop user. ,as well as,
Based on the determination result of the user type, the base station includes applying the frequency band corresponding to the terminal user type to the terminal. Further comprising a guard band between the inner loop area and the outer loop area, the method further comprises:
2. The method according to claim 1, comprising determining a user type according to a schedule rule for the terminal in the guard band. In the step of determining the user type according to a schedule rule for the terminal in the guard band, the base station compares the N received feedback signals successively with a threshold value in a time window manner; Determine the corresponding user type of the device,
3. The method according to claim 2, wherein N is a natural number greater than 0.   The threshold value includes a first threshold value and a second threshold value, wherein the first threshold value represents a threshold value for switching from the inner loop user to the outer loop user, and the second threshold value. The threshold value represents a threshold value for switching from the outer loop user to the inner loop user, and the first threshold value is smaller than the second threshold value. the method of.   When the user switches from the outer loop area to the inner loop area, or when switching from the inner loop area to the outer loop area, the base station adopts a time window method to statistically calculate the feedback signal. 4. A method according to claim 3, characterized in that   When the user switches from the outer loop area to the inner loop area, the base station adopts a fixed window statistic scheme, which is second for each collected N feedback signals. 6. The method according to claim 5, wherein a number of times greater than a threshold value is calculated, and the user is switched to the inner loop user when the number of times is greater than a predetermined value.   When the user switches from the inner loop area to the outer loop area, the base station adopts a sliding window statistics method, and for the N collected feedback signals recently collected, this is the first threshold. 6. The method of claim 5, wherein a number of times less than a value is calculated and the user is switched to the outer loop user when the number is greater than a predetermined value.   5. The method according to claim 4, wherein the first threshold value and the second threshold value respectively correspond to an outer diameter and an inner diameter of the guard band.   5. The method of claim 4, wherein the first threshold and the second threshold are dynamically adjustable based on cell network performance parameters.   The method of claim 1, wherein the base station initially presets a corresponding user of the terminal to an outer loop user.   The method according to any one of claims 1 to 10, wherein the feedback signal includes a ratio of a downlink carrier and interference noise, received signal strength information, and / or a downlink packet error rate. A system for canceling adjacent cell interference, the system comprising:
The cover area is divided into an inner loop area and an outer loop area, and the adjacent base stations negotiate with each other about the occupied frequency band, and thus the occupied frequency bands of the respective outer loop areas are mutually shared. And a base station that transmits a detection signal to terminals within its coverage area,
Generating a feedback signal in response to the detection signal,
The base station further includes a determination device that determines a corresponding user type of the terminal based on a feedback signal from the terminal, of which the user type is an inner loop user or an outer loop user,
The base station applies the frequency band corresponding to the terminal user type to the terminal based on the user type determination result. The base station further includes a guard band between the inner loop area and the outer loop area,
13. The system of claim 12, wherein the base station further includes a transient device for determining a user type according to a schedule rule for the terminal in the guard band. In the process of determining the user type according to a schedule rule for the terminal in the guard band by the transient device, the transient device receives the N feedback signals continuously received by the base station. Determining a corresponding user type of the terminal according to a time window scheme, wherein the threshold includes a first threshold and a second threshold, of which the The first threshold represents a threshold for switching from the inner loop user to the outer loop user, the second threshold represents a threshold for switching from the outer loop user to the inner loop user, and The first threshold is less than the second threshold;
14. The system according to claim 13, wherein N is a natural number greater than 0.   When the user switches from the outer loop area to the inner loop area, or when switching from the inner loop area to the outer loop area, the transient device employs a time window method to statistically measure the feedback signal. 15. The system according to claim 14, wherein:   When the user switches from the outer loop area to the inner loop area, the transient device employs a fixed window statistics scheme for each collected N feedback signals that is 16. The system according to claim 15, wherein a number of times greater than two thresholds is calculated and the user is switched to the inner loop user when the number is greater than a predetermined value.   When the user switches from the inner loop area to the outer loop area, the transitional device employs a sliding window statistics method for the N collected feedback signals recently collected. 16. The system according to claim 15, wherein the number of times less than one threshold is calculated, and the user is switched to the outer loop user when the number is greater than a predetermined value.   15. The system according to claim 14, wherein the first threshold value and the second threshold value respectively correspond to an outer diameter and an inner diameter of the guard band.   15. The system of claim 14, wherein the base station further includes an adjustment device that dynamically adjusts the first threshold and the second threshold based on a performance parameter of a cell network. .   13. The system according to claim 12, wherein the determination device initially presets a user corresponding to the terminal to an outer loop user.   21. The system according to claim 12, wherein the feedback signal includes a ratio between a downlink carrier and interference noise, received signal strength information, and / or a downlink packet error rate.

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