JP6301186B2 - Cell selection method, base station, and radio communication system - Google Patents

Description

  The present invention relates to the communication field, and in particular, to a cell selection method, a base station that implements the method, and a wireless communication system.

  Many types of wireless access points may be deployed in a wireless communication system, and these different types of wireless access points may have different operating frequencies or different levels of coverage. For example, a macro cell base station and a small cell base station belong to two different types of wireless access points. In general, a macrocell base station operates at 2 GHz, while a small cell base station operates at 3.5 GHz. A dense network can include one or more small cells, usually in areas with relatively high traffic, such as stadiums, shopping centers, daytime city centres, rush hour subway platforms, etc. This improves the overall capacity of the wireless communication system. A plurality of small cells arranged in a certain area constitute a small cell group or a small cell layer. As should be explained, the coverage of a small cell is usually smaller than a macro cell, specifically, a micro cell, a pico cell, a femto cell, a remote radio base station (RRH). ) Etc.

  3GPP defines the following scenarios in, for example, Rel-12 SCE SI, and users in the following scenarios may be distributed indoors or outdoors. Scenario 1 is as shown in FIG. 1a, in which the macro cell base station is arranged outside, the base station in the small cell group is also arranged outdoors, and the area covered by the small cell group is the coverage area of the macro cell. Or the coverage of both overlaps. Scenario 2 is as shown in FIG. 1b. Unlike scenario 1, the base stations in the small cell group are placed indoors. Scenario 3 is as shown in FIG. 1c, and only the small cell group arranged in the room provides a communication service to the user terminal. As a matter of explanation, in the case where a macro cell layer and a small cell layer composed of a plurality of small cells exist in the same geographical area, usually, the small cell layer carries most of the traffic in the network.

  In an environment where there is a small cell (for example, FIGS. 1 a to 1 c), when a user terminal (UE) performs cell selection in the small cell layer, a reference signal reception power (RSRP: Reference Signal Receiving Power) that is normally maximum. As a serving cell (hereinafter referred to as an RSRP method), the UE ensures that the UE can receive the strongest signal. FIG. 2 shows an implementation flow of the RSRP method (including steps 202 to 204). In step 201, the macro cell base station obtains an RSRP measurement report from a certain UE. In step 202, the UE performs cell handover. In step 203, the first RSRP base station is selected as a serving base station for the UE, and in step 204, a handover command (handover) is sent to the UE. 2), requesting the UE to access the communication network via the first RSRP base station, and ending the flow of FIG. 2, while ending the flow of FIG. . Here, the first RSRP base station may be a small cell base station having the maximum RSRP.

  However, the RSRP method has one or more of the following problems. For example, a small cell increases the interference of a communication network by starting operation even when the load is low. Further, for example, problems such as whether the small cell load is high or low and whether the communication distribution is uniform are not considered. When the UE distribution and the small cell distribution do not match, the traffic distribution in the small cell group is not uniform, but the RSRP method does not consider such a situation.

  Embodiments of the present invention provide a cell selection method, a base station that implements the method, and a wireless communication system.

  Specifically, in the embodiment of the present invention, a cell selection method in a wireless communication system is provided, and step A for searching for a target cell for each user terminal in a wireless access point to be closed, When there is a corresponding target cell, the method includes a step B of moving the user terminal at the close target wireless access point to the corresponding target cell and closing the close target wireless access point.

  In a specific implementation, the step A includes one or more parameters of a signal strength indication measured at the user terminal, a load indication of a wireless access point in the system, and a coverage of the wireless access point. To search for a target cell for the user terminal.

  In a specific implementation, the step A selects, from the wireless access points of the system, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold as the target cell, or Selecting a wireless access point having an average user throughput smaller than a first predetermined load threshold as the target cell from wireless access points of the system.

  In a specific implementation, the step A is based on the difference between the signal strength indication of the wireless access point to be closed measured at the user terminal and the signal strength indication of other wireless access points in the system. Selecting a target cell, and making another wireless access point having the difference smaller than a predetermined difference threshold as the target cell.

  In a specific implementation, the signal strength indication is at least one of a reference signal received power (RSRP), a reference signal received quality (RSRQ), a signal-to-interference noise ratio (SINR), and a received signal strength indication (RSSI). Contains parameters.

  Prior to step A, the method determines whether the load of the wireless access point to be closed is high or low based on a second predetermined load threshold, and the load of the wireless access point to be closed is the second predetermined load threshold. When the load is lower than the load threshold, Steps A and B are executed, and when the load of the wireless access point to be closed is not lower than the second predetermined load threshold, the signals of the plurality of wireless access points measured at the user terminal Step C for performing cell selection based on the strength instruction is executed, or before step A, the size of the area covered by the wireless access point to be closed is determined based on a predetermined coverage threshold, If the coverage area of the wireless access point is smaller than the predetermined coverage threshold, execute steps A and B, and Performing a cell selection step C based on signal strength indications of a plurality of wireless access points measured by a user terminal when a coverage area of a wireless access point to be used is not smaller than the predetermined coverage threshold; In addition.

  In a specific implementation, the step C determines whether the communication distribution at the wireless access points to be closed is uniform, and if so, the signal strengths of a plurality of wireless access points measured at the user terminal It further includes performing cell selection based on the instruction, and if not uniform, performing cell selection based on the load balancing method.

  The method selects, as the wireless access point to be closed, one or more wireless access points with the lowest load or the least coverage based on the load indication and / or coverage of the wireless access point in the system Further comprising.

  In addition, a base station is provided in an embodiment of the present invention, and a target cell search module that searches for a target cell for each user terminal in a wireless access point to be closed, and each of the user terminals corresponds to a target cell. A cell close control module for transferring a user terminal at the close target wireless access point to a corresponding target cell and closing the close target wireless access point. including.

  In a specific implementation, the target cell search module includes one or more of a signal strength indication measured at the user terminal, a load indication of a wireless access point in the system, and a coverage of the wireless access point. The target cell is searched for the user terminal based on the parameters.

  In a specific implementation, the target cell search module selects, from the wireless access points of the wireless communication system, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold as the target cell, or A wireless access point having an average user throughput smaller than a first predetermined load threshold is selected as the target cell from the wireless access points of the system.

  In a specific implementation, the target cell search module is based on a difference between a signal strength indication of a wireless access point to be closed measured by the user terminal and a signal strength indication of another wireless access point in the wireless communication system. Then, the target cell is selected, and another wireless access point having the difference smaller than a predetermined difference threshold is set as the target cell.

  The base station, based on signal strength indications of a plurality of wireless access points measured by the user terminal, based on a second cell selection means for performing cell selection and a second predetermined load threshold, When the load of the wireless access point is determined to be lower and the load of the wireless access point to be closed is lower than the second predetermined load threshold, the activation operation of the first cell selection unit is triggered, When the load of the wireless access point is not lower than the second predetermined load threshold, the activation operation of the second cell selection means is triggered, or the cover of the wireless access point to be closed is based on the predetermined coverage threshold Judging the size of the area, if the coverage area of the wireless access point to be closed is smaller than the predetermined coverage threshold, Cell selection control that triggers the activation operation of the first cell selection means and triggers the activation operation of the second cell selection means when the coverage area of the wireless access point to be closed is not smaller than the predetermined coverage threshold Means.

  In a specific realization, the second cell selection means further determines whether or not the communication distribution at the wireless access point to be closed is uniform, and if so, a plurality of measured by the user terminal Cell selection is performed based on the signal strength indication of the wireless access point, and if not uniform, cell selection is performed based on the load distribution method.

  In a specific implementation, the first cell selection means is configured to determine one or more wireless access points with the lowest load or the lowest coverage based on the load indication and / or coverage of the wireless access point in the system. Is further included as a close target cell selection module.

  An embodiment of the present invention also provides a wireless communication system, which includes one or more base stations and a user terminal, wherein the user terminal receives a load indication and / or from the one or more base stations. A cell with a target cell identifier determined by receiving a coverage and searching for a corresponding target cell and / or searching for a target cell based on a signal strength indication measured at the user terminal A selection report is transmitted to the source cell base station of the user terminal, and the source cell base station has the jurisdiction of its own station when all of the user terminals that it has jurisdiction search for the corresponding target cell. After the handover command is transmitted to each user terminal to be completed and the handover is completed, the own station is closed.

  In a specific implementation, the user terminal selects, as the target cell, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold from the wireless access points of the system, or Wireless access points having an average user throughput smaller than a first predetermined load threshold value are selected as the target cells.

  In a specific realization, the user terminal is based on a difference between a signal strength indication of a wireless access point to be closed measured at the user terminal and a signal strength indication of another wireless access point in the system. A target cell is selected, and another wireless access point with the difference smaller than a predetermined difference threshold is set as the target cell.

  As can be seen, the cell selection scheme provided in embodiments of the present invention is less complex and results in improved communication quality, eg, SINR, due to cell closure, thereby improving resource utilization and communication quality (eg, A balance is taken between factors such as SINR). Furthermore, the scheme provided in the embodiment of the present invention reduces the overhead of alternating signaling.

It is a figure which shows the dense network defined by 3GPP. It is a figure which shows the dense network defined by 3GPP. It is a figure which shows the dense network defined by 3GPP. It is a figure which shows the implementation | achievement flow of a RSRP method. 3 is an implementation flowchart of an IA method according to an embodiment of the present invention. 6 is an implementation flowchart of an IA method according to another embodiment of the present invention. It is a figure which shows the specific scenario of isolation | separation of a user plane and a control plane in one Example of this invention. It is an implementation scenario of the flow shown in FIG. It is a figure which shows the specific flow which employ | adopts IA method and selects a cell in one Example of this invention. It is a figure which shows the specific flow which employs IA method and RSRP method in another Example of this invention, and performs cell selection. It is a figure which shows the specific flow which employs | adopts IA method, RSRP method, and RA method in another Example of this invention, and performs cell selection. 4 is a flowchart of a method for controlling cell selection by a UE in an embodiment of the present invention. 6 is a flowchart of a method for controlling cell selection by a UE in another embodiment of the present invention. 6 is a flowchart of a method for controlling cell selection by a UE in yet another embodiment of the present invention. It is a figure which shows the structure of the base station for implement | achieving the cell selection in one Example of this invention. It is a figure which shows the structure of the base station for implement | achieving the cell selection in another Example of this invention. It is a figure which shows the structure of the radio | wireless communications system for implement | achieving cell selection in one Embodiment of this invention.

  In order to further clarify the object, solution, and merit of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings.

  In an embodiment of the present invention, a cell selection method is provided, and a target cell is searched for each user terminal in a wireless access point to be closed (step 301), and each of the user terminals has a corresponding target cell. If it exists, the user terminal at the wireless access point to be closed is moved to the corresponding target cell, and the wireless access point to be closed is closed (step 302). As should be explained, closing a wireless access point may close its data channel so that the wireless access point does not transmit data. In another specific implementation, the wireless access point may be closed so that the wireless access point does not transmit data and does not transmit a reference signal. In addition, the method may include the lowest load or highest interference or coverage based on one or more parameters of a load indication, interference indication, and coverage of a wireless access point in a wireless communication system. One or more smallest wireless access points are selected as the wireless access points to be closed (step 300). Instead, the method may determine whether it can be closed one by one for all wireless access points in the system.

  In a specific implementation of step 301, the user terminal is searched for a target cell based on one or more parameters of a load instruction, an interference instruction, and a coverage of a wireless access point in the wireless communication system. You may do it. Here, the load instruction may be the number of connected users, resource usage rate or average user throughput, etc., and the interference instruction evaluates the degree of interference to other cells by the wireless access point, and the coverage is determined by antenna arrangement (For example, antenna configuration, size, left position, etc.) or transmission power. Alternatively, the target cell may be searched based on the signal strength instruction measured at the user terminal in another specific implementation of step 301. Alternatively, the target cell is searched for the user terminal based on one or more parameters such as a load instruction of the wireless access point, an interference instruction, a coverage, and a signal strength instruction measured at the user terminal. For example, for the user terminal based on one or more parameters of a signal strength indication measured at the user terminal, a load indication of a wireless access point in the system, and a coverage of the wireless access point You may make it search a target cell.

  Specifically, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold value may be selected from all wireless access points in the wireless communication system as the target cell. A wireless access point having an average user throughput smaller than a first predetermined load threshold may be selected as the target cell from wireless access points in the wireless communication system. Specifically, a wireless access point with transmission power larger than a predetermined coverage threshold value may be selected as a target cell.

  In another specific realization of the present invention, based on the difference between the signal strength indication of the wireless access point to be closed measured at the user terminal and the signal strength indication of another wireless access point in the system, A target cell may be selected, and another wireless access point having the difference smaller than a predetermined difference threshold may be set as the target cell. Here, the signal strength indication includes at least one parameter of reference signal received power (RSRP), reference signal received quality (RSRQ), signal-to-interference noise ratio (SINR), received signal strength indication (RSSI), and the like. You may make it.

  As a matter of explanation, the method of selecting a wireless access point to be closed based on parameters such as a load instruction, an interference instruction, and a cover range searches for a target cell based on parameters such as a load instruction, an interference instruction, and a cover range. It is different from the method to do. When selecting a wireless access point to be closed, a wireless access point with low load, large interference, and low coverage may be preferentially selected. Conversely, when searching for a target cell, a wireless access point with high load, low interference, and large coverage is determined as the base station of the target cell.

  In a specific implementation of the present invention, the wireless access point to be closed may be one or more small cells in a small cell group. That is, an embodiment of the present invention may mute, for example, a relatively low traffic load cell in the small cell group, thereby reducing interference of the wireless communication system. Hereinafter, the cell selection method according to the embodiment of the present invention may be referred to as an interference awareness (IA) method.

  In the IA method provided in the embodiment of the present invention, when one or more small cells are closed, it may be controlled by the base station side (eNB), and is cooperatively controlled by the UE and the base station. The target cell may be selected by the UE side. The flow controlled by the base station side may be controlled mainly by the macro cell base station, or may be controlled by a small cell base station in a small cell group.

  FIG. 4 is a flowchart illustrating the implementation of the IA method according to an embodiment of the present invention. In the method of FIG. 4, the user plane (U-plane) and the control plane (C-plane) are separated, and the control plane is While implemented in the macrocell layer, the user plane is implemented in the small cell layer, see FIG. 5a for the scenario. Specifically, FIG. 4 includes the following steps.

  A user (hereinafter referred to as UE1) in the small cell A performs normal RSRP measurement in Step 401, and then transmits an RSRP measurement report to the macro cell base station in Step 402. The small cell A base station also transmits a load indicator to the macro cell base station at step 403. In a specific implementation, the load instruction may include the number of connected users, a resource usage rate, an average user throughput, and the like. In another specific implementation, the small cell A base station may transmit an interference instruction to the macro cell base station in step 403, or may notify the macro cell base station of its coverage. As should be described, in this embodiment, the order of execution of step 403 and steps 401 to 402 is not limited.

  In step 404, the macro cell base station selects the small cell A as a small cell to be closed, and selects a target cell for each user (including UE1) in the small cell A. Specifically, the condition for the macro cell base station to select the small cell to be closed is that interference to the adjacent cell by the small cell is larger than a predetermined threshold, or the number of connected users of the small cell is the first predetermined load threshold It may be smaller. Further, the target cell may be selected based on one or more of the following promise conditions. For example, a target cell with the number of connected users greater than 0 is selected. Further, for example, when the difference between the RSRP of the cell A (that is, the small cell A) and the RSRP of the cell B is within a predetermined difference threshold, the cell B may be selected as the target cell.

  In step 405, the macro cell base station determines whether the target cell has been selected for all users in the small cell A, and if one or more target cells have been selected for all users, A handover command is transmitted to all users of the small cell A. In step 407, after receiving the handover command, UE1 transmits a physical random access channel (PRACH) random access request to the base station of the corresponding target cell (for example, small cell B), and performs communication. Data is transferred from small cell A to small cell B. Other users in the small cell A may be processed with reference to the processing flow of the UE 1 to transfer the communication data from the small cell A to the corresponding target cell selected for the user.

  For example, in the scenario shown in FIG. 5b, before cell selection, small cell 1 has two users (UE1 and UE2), and small cells 2 and 3 each have three users, while small cell 1 In cell 4, the data channel is closed. After selecting the small cell 1 as the small cell to be closed, it is necessary to select a target cell for the UE1 and the UE2. As can be seen from this, the target cell of UE1 is the small cell 3, while the target cell of UE2 is the small cell 2. Accordingly, UE1 is transferred to small cell 3, UE2 is transferred to small cell 2, and small cell 1 is closed.

  FIG. 6 shows a specific flow for performing cell selection using the IA method in an embodiment of the present invention, where the macro cell base station plays a main control role and is closed by the macro cell base station. A target cell is selected for the UE in the target small cell.

  In step 601, the macro cell base station receives RSRP measurement reports of one or more UEs within its coverage. In step 602, the macro cell base station obtains a load instruction for each small cell in the small cell group corresponding to the macro cell. In step 603, the macro cell base station sorts all the small cells according to the load to obtain a load reordering list. In step 604, it is determined whether a corresponding target cell can be found for all UEs in the small cell with the lowest load in the list. If the corresponding target cell is found for all UEs in the small cell with the lowest load in the list, the process proceeds to step 605, and the corresponding target cell is selected as the new serving cell of the UE. In step 606, the macro cell base station transmits a handover command to all UEs in the small cell with the lowest load, and proceeds to step 607. If no corresponding target cell is found for all UEs in the small cell with the lowest load in the list, the process proceeds to step 607 as it is. In step 607, the small cell with the lowest load is deleted from the load reordering list. In step 608, it is determined whether the number of cells in the load reordering list is larger than a predetermined operation cell threshold. If the number of cells in the load reordering list is larger than the predetermined operation cell threshold, the process returns to step 604 to load reordering. If the number of cells in the list is not greater than the predetermined operating cell threshold, the flow ends. In a specific implementation, the condition for the end of the flow in step 608 may be set according to the actual situation. For example, it is determined whether to end based on the cell close ratio, and the cell close ratio is 50. If it exceeds%, the flow ends.

  What is fed back from the small cell base station in steps 403 and 602 above may be an interference instruction, and the macro cell base station appropriately selects the small cell to be closed based on the interference instruction. The subsequent flow is executed.

  As to be described, before adopting the IA method in the flow shown in FIG. 3, based on a second predetermined load threshold, the load level of the wireless access point to be closed is determined and If the load of the wireless access point is lower than the second predetermined load threshold, the IA method is executed, and if the load of the wireless access point to be closed is not lower than the second predetermined load threshold, it is measured at the user terminal. Alternatively, cell selection may be performed based on signal strength instructions from a plurality of wireless access points. Alternatively, prior to step 301, based on a predetermined interference threshold, it is determined whether or not the close target wireless access point interferes with another wireless access point, and the close target wireless access point interferes with the predetermined interference. If it is higher than the threshold, execute the IA method of steps 301 and 302, and if the interference of the wireless access point to be closed is not higher than the predetermined interference threshold, signal strength indications of a plurality of wireless access points measured at the user terminal Based on the above, cell selection is performed. Alternatively, before step 301, based on a predetermined coverage threshold, the size of the area covered by the wireless access point to be closed is determined, and the coverage area of the wireless access point to be closed is smaller than the predetermined coverage threshold Steps 301 and 302 are performed, and if the coverage area of the wireless access point to be closed is not smaller than the predetermined coverage threshold, the cell is determined based on the signal strength indications of the plurality of wireless access points measured at the user terminal. Make a selection.

  In a specific implementation, for a situation where the load of the wireless access point to be closed is higher than a second predetermined load threshold, or a situation in which the interference of the wireless access point to be closed is lower than a predetermined interference threshold, the wireless to be closed Determine whether the communication distribution at the access points is uniform. If so, perform cell selection based on the signal strength indication of multiple wireless access points measured at the user terminal. If not, load distribution Cell selection may be performed based on the method. As should be explained, the load distribution method here can also be referred to as a resource awareness (RA) method. Specifically, in the RA method, a plurality of cells in a wireless communication system can achieve load sharing by transferring a UE from a high load cell to a low load cell.

  FIG. 7 shows a specific flow for performing cell selection using the IA method and the RSRP method in another embodiment of the present invention. In the embodiment shown in FIG. 7, as shown in Table 1, the macro cell base station employs different cell selection methods for different small cells based on, for example, the level of load.

  Specifically, step 701 corresponds to step 601, and step 702 corresponds to step 602, and description thereof is omitted here. In step 703, the macro cell base station determines whether the load of each small cell is high or low. Step 704 is executed for a small cell with a low load, step 705 is executed for a small cell with a high load, and the flow is terminated. As a matter of explanation, the macro cell base station may determine whether the load is high or low based on the second predetermined load threshold value. If the load is higher than the threshold value, the load is high. If the load is lower than the threshold value, the load is low. is there. For the IA method in Step 704, the flow of Steps 603 to 608 can be referred to, and for the RSRP method in Step 705, the flow of Steps 202 to 204 can be referred to, and description thereof is omitted here. Further, in step 703, the macro cell base station determines whether the closed small cell interferes with other wireless access points and / or based on the size of the area covered by the closed small cell. Whether to select the RSRP method may be determined. In general, the IA method can be selected in situations of low load, high interference and / or low coverage.

  FIG. 8 shows a specific flow for performing cell selection using the IA method, the RSRP method, and the RA method in still another embodiment of the present invention. Here, the RA method is a load distribution method, and for example, a UE managed by a small cell with a high load is transferred to a small cell with a low load so as to balance the load among a plurality of small cells. Specifically, steps 801 to 804 correspond to steps 701 to 704 in FIG. In step 805, it is determined whether the distribution of the small cells is uniform. If the distribution is uniform, step 806 is performed to perform cell selection using the RSRP method. If the distribution is not uniform, step 805 is performed. Step 807 is executed to adopt the RA method and perform cell selection. Thereafter, the flow ends. In step 805, the macro cell base station may consider whether the communication load in the small cell group is uniform, whether the UE distribution is uniform, or the like.

  That is, in the embodiment shown in FIG. 8, as shown in Table 2, the macro cell base station takes different cell selection methods for small cells in different situations in consideration of situations such as high and low loads and uniform distribution. adopt. Specifically, Table 3 compares the RSRP method, RA method, and IA method in detail.

  For a scenario without a macro cell base station (for example, FIG. 1c), the function of the macro cell base station in FIGS. 3 to 8 can be completed by a certain small cell A in the small cell group. Here, the description is omitted. As a matter of explanation, the small cell A not only obtains an RSRP measurement report from a UE under its jurisdiction, but also an RSRP provided from a UE of the other small cell from another small cell in the small cell group. A measurement report is also received. In one implementation, the other small cells first obtain an RSRP measurement report from their own UE, and then perform a target cell selection for the small cell A so that all the UE's RSRP measurement reports are obtained. To small cell A.

  9-11 illustrate the main control flow in a method for performing cell selection by the UE side in one or more embodiments of the present invention.

  In FIG. 9, UE1 performs RSRP measurement in step 901. In step 902, the source cell base station transmits a load instruction (or an interference instruction, a cover range, etc.) to all UEs that are in charge of the station. In step 903, UE1 selects a target cell based on the IA method. In step 904, UE1 transmits a cell selection report to the source cell base station. In a specific implementation, the cell selection report may be given a target cell ID and further a cell selection method indicator. Here, the cell selection method indicator indicates whether the UE has adopted the RSRP method, the RA method, or the IA method. Specifically, the cell selection report can be realized by newly adding signaling or adopting existing signaling (for example, RSRP measurement report). In step 905, the source cell base station determines whether all the users who are in charge of the local station have selected the target cell, and all the users who are in charge of the local station select the target cell. If so, the process proceeds to step 906. In step 906, the source cell base station transmits a handover command to each user who has jurisdiction over the source cell base station. In step 907, the UE 1 that has received the handover command transmits a PRACH random access request to the target cell base station.

  In FIG. 10, step 1001 corresponds to step 901, and step 1002 corresponds to step 902. In step 1003, the UE locates one or more target cells based on the IA method. In step 1004, the UE transmits a cell selection report to the base station. The above steps 1001 to 1004 are processes executed on the UE side. In step 1005, the base station determines a target cell for the UE. In step 1006, the base station determines whether or not a target cell has been determined for each UE that is under its control. When the target cell is determined for each UE managed by the local station, the process proceeds to step 1007, and the determined target cell is selected as a new serving cell of the corresponding UE. If the target cell has not been determined for each UE managed by the local station, the process proceeds to step 1008, and the first RSRP cell (ie, the small cell having the largest RSRP) is selected as a new serving cell based on the RSRP method. To do. Thereafter, the process proceeds to step 1009, where a handover command is transmitted to the corresponding UE, requesting the UE to handover to a new serving cell.

  Although the flows shown in FIG. 11 and FIG. 9 are similar, the differences that need to be explained are as follows. In step 1102, UE1 may receive a load indication broadcast (or coverage coverage broadcast) of its neighboring base stations (including the source cell base station and the target cell base station). In step 1103, the source cell base station transmits a base station close wait command to UE1, and causes UE1 to execute step 1104 to cause the local cell to select a target cell. In step 1105, UE1 provides the selected target cell ID to the source cell base station through a virtual RSRP measurement report. It should be noted that the virtual RSRP measurement report may be structured by adding a corresponding field to the normal RSRP measurement report, and the added field is optional, not the target cell is essential. To the source cell base station. In step 1106, the source cell base station determines whether or not to close the source cell base station. For example, the source cell base station closes when all user terminals managed by the source cell base station find the target cell. When the close is determined, the source cell base station transmits a handover command to all the user terminals (including UE1) serving the source cell base station.

  Correspondingly, the base station shown in FIG. 12 can execute the cell selection flow according to the above method embodiment (for example, FIGS. 3 to 8). Specifically, the base station uses a target cell search module 1201 for searching for a target cell for each user terminal in a wireless access point to be closed, and each of the user terminals has a corresponding target cell. A cell close control module 1202 for transferring a user terminal at the close target wireless access point to a corresponding target cell and closing the close target wireless access point. The base station may have the lowest load or highest interference or most coverage based on one or more parameters of a wireless access point load indication, interference indication, and coverage in a wireless communication system. It further includes a close target cell selection module 1203 that selects one or more small wireless access points as the close target wireless access points.

  In a specific realization, the target cell search module 1201 may provide the user terminal with the user terminal based on one or more parameters of a load instruction, an interference instruction, and a coverage of a wireless access point in a wireless communication system. Search for a target cell and / or search for a target cell based on a signal strength indication measured at the user terminal.

  In a specific implementation, the target cell search module 1201 selects, as the target cell, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold from wireless access points of a wireless communication system. Alternatively, a wireless access point having an average user throughput smaller than a first predetermined load threshold is selected as the target cell from the wireless access points of the system.

  In a specific realization, the target cell search module 1201 determines the difference between the signal strength indication of the wireless access point to be closed measured by the user terminal and the signal strength indication of another wireless access point in the wireless communication system. Based on this, the target cell is selected, and another wireless access point having the difference smaller than a predetermined difference threshold is set as the target cell.

  In another embodiment of the present invention, the base station shown in FIG. 13 can execute the cell selection flow according to the above method embodiment (for example, FIGS. 3 to 8). Specifically, the base station includes first cell selection means 131 provided with a target cell search module 1201 and a cell close control module 1202. Here, the functions of the target cell search module 1201 and the cell close control module 1202 are referred to the related description in FIG. 11, and the description thereof is omitted here. Further, the first cell selection unit 131 includes a close target cell selection module 1203.

  Furthermore, the base station shown in FIG. 13 includes second cell selection means 132 and cell selection control means 133.

  In a specific implementation of the present invention, the second cell selection means 132 can perform cell selection based on signal strength indications of a plurality of wireless access points measured at the user terminal. The cell selection control unit 133 determines the load level of the wireless access point to be closed based on a second predetermined load threshold, and the load of the wireless access point to be closed is higher than the second predetermined load threshold. When the load is low, the activation operation of the first cell selection unit 131 is triggered. When the load of the wireless access point to be closed is not lower than the second predetermined load threshold value, the activation of the second cell selection unit 132 is performed. Trigger an action. That is, the base station may perform cell selection using the IA method, or may perform cell selection using the RSRP method.

  Alternatively, the cell selection control unit 133 determines the size of the area covered by the wireless access point to be closed based on a predetermined coverage threshold, and the coverage area of the wireless access point to be closed is lower than the predetermined coverage threshold The first cell selection unit 131 is triggered, and if the coverage area of the wireless access point to be closed is not lower than the predetermined coverage threshold, the second cell selection unit 132 is triggered. To do.

  In another specific realization of the present invention, the second cell selection means 132 further determines whether or not the communication distribution at the wireless access point to be closed is uniform. Cell selection is performed based on the measured signal strength indications of a plurality of wireless access points, and if not uniform, cell selection is performed based on the load distribution method.

  Correspondingly, the wireless communication system shown in FIG. 14 can perform the cell selection flow according to the above-described method embodiments (eg, FIGS. 9 to 11), which includes one or more base stations. (For example, base station 1412 and base station 1422) and user terminal 1401 are included.

  Here, the user terminal 1401 receives one or more parameters of a load instruction, an interference instruction, and a coverage from the one or more base stations, and searches for a corresponding target cell. And / or, based on the signal strength indication measured at the user terminal, search for a target cell and send a cell selection report with the determined target cell identifier to the source cell base station of the user terminal ( Base station 1412).

  The source cell base station 1412 transmits a handover command to each user terminal managed by the local station when all the user terminals 1401 managed by the source cell search for the corresponding target cell. After over is completed, close your station.

  Specifically, the user terminal 1401 selects, as the target cell, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold from the wireless access points of the system, or A wireless access point having an average user throughput smaller than a first predetermined load threshold is selected from the wireless access points as the target cell.

  Specifically, the user terminal 1401 determines the target based on a difference between a signal strength instruction of a wireless access point to be closed measured by the user terminal and a signal strength instruction of another wireless access point in the system. A cell is selected, and another wireless access point having the difference smaller than a predetermined difference threshold is set as the target cell.

  As can be seen, the cell selection methods, base stations, and wireless communication systems provided in the embodiments of the present invention have low implementation complexity and cell closure results in improved communication quality such as SINR. This balances between factors such as resource utilization and SINR.

  The above are only preferred embodiments of the present invention and do not limit the protection scope of the present invention. Various modifications, equivalent replacements, improvements and the like made within the spirit and principle of the present invention should all be included in the protection scope of the present invention.

Claims (18)

A cell selection method in a wireless communication system, comprising:
Searching for a target cell for each user terminal at a wireless access point to be closed; and
When each of the user terminals has a corresponding target cell, the user terminal in the close target wireless access point is transferred to the corresponding target cell, and the close target wireless access point is closed. B and
A method comprising the steps of: Step A includes
A target cell for the user terminal based on one or more parameters of a signal strength indication measured at the user terminal, a load indication of a wireless access point in the system, and a coverage of the wireless access point Search for, including,
The method according to claim 1. Step A includes
From the wireless access points of the system, select a wireless access point whose number of connected users or resource usage is greater than a first predetermined load threshold as the target cell,
Or
Selecting from the wireless access points of the system as a target cell a wireless access point with an average user throughput less than a first predetermined load threshold;
The method according to claim 1. Step A includes
The target cell is selected based on a difference between a signal strength indication of a wireless access point to be closed measured by the user terminal and a signal strength indication of another wireless access point in the system, and the difference is a predetermined difference Including, as the target cell, another wireless access point smaller than a threshold value,
The method according to claim 1. The signal strength indication includes at least one parameter of a reference signal received power (RSRP), a reference signal received quality (RSRQ), a signal to interference noise ratio (SINR), and a received signal strength indication (RSSI).
The method according to claim 4. Prior to step A, based on a second predetermined load threshold value, the load level of the wireless access point to be closed is determined, and the load of the wireless access point to be closed is lower than the second predetermined load threshold value. If the load of the wireless access point to be closed is not lower than the second predetermined load threshold, the steps A and B are executed, based on the signal strength indications of the plurality of wireless access points measured at the user terminal Step C for cell selection is performed,
Or
Before step A, based on a predetermined coverage threshold, the size of the area covered by the wireless access point to be closed is determined, and if the coverage area of the wireless access point to be closed is smaller than the predetermined coverage threshold, A and B are executed, and when the coverage area of the wireless access point to be closed is not smaller than the predetermined coverage threshold, cell selection is performed based on the signal strength indications of a plurality of wireless access points measured by the user terminal Further comprising performing step C,
The method according to claim 1. Step C includes
It is determined whether the communication distribution in the wireless access point to be closed is uniform, and if it is uniform, cell selection is performed based on the signal strength indications of a plurality of wireless access points measured at the user terminal. If not, further comprising performing cell selection based on a load balancing method,
The method according to claim 6. Selecting one or more wireless access points with the lowest load or the lowest coverage as the wireless access points to be closed based on the load indication and / or coverage of the wireless access points in the system. In addition,
8. A method according to any one of claims 1 to 7, characterized in that A base station,
A target cell search module for searching for a target cell for each user terminal in a wireless access point to be closed, and a user in the wireless access point to be closed when each of the user terminals has a corresponding target cell. Including a first cell selection means provided with a cell close control module for transferring a terminal to a corresponding target cell and closing the wireless access point to be closed.
A base station characterized by that. The target cell search module is based on one or more parameters of a signal strength indication measured at the user terminal, a load indication of a wireless access point in a wireless communication system, and a coverage of the wireless access point. Searching for a target cell for the user terminal;
The base station according to claim 9. The target cell search module selects, from the wireless access points of the wireless communication system, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold as the target cell, or wireless access of the system A wireless access point with an average user throughput less than a first predetermined load threshold is selected as the target cell from the points;
The base station according to claim 9. The target cell search module determines the target cell based on a difference between a signal strength instruction of a wireless access point to be closed measured by the user terminal and a signal strength instruction of another wireless access point in a wireless communication system. And select another wireless access point whose difference is smaller than a predetermined difference threshold as the target cell,
The base station according to claim 9. Second cell selection means for performing cell selection based on signal strength indications of a plurality of wireless access points measured at the user terminal;
Based on a second predetermined load threshold, the level of the load on the wireless access point to be closed is determined, and when the load on the wireless access point to be closed is lower than the second predetermined load threshold, the first Triggers the activation operation of the cell selection means, and triggers the activation operation of the second cell selection means when the load of the wireless access point to be closed is not lower than the second predetermined load threshold; Based on a threshold, the size of the area covered by the wireless access point to be closed is determined, and when the coverage area of the wireless access point to be closed is smaller than the predetermined coverage threshold, the first cell selection unit is activated. Triggering the operation, and the coverage area of the wireless access point to be closed is the predetermined coverage threshold If not smaller, further including a cell selection control means for triggering the start-up operation of the second cell selection means,
The base station according to claim 9. The second cell selection means further determines whether or not the communication distribution at the wireless access points to be closed is uniform, and if so, the signal strength of the plurality of wireless access points measured at the user terminal Cell selection based on instructions, if not uniform, cell selection based on load balancing method,
The base station according to claim 13. The first cell selection means includes:
Closed target cell that selects one or more wireless access points with the lowest load or the lowest coverage as the wireless access point to be closed based on the load indication and / or coverage of the wireless access point in the system Further including a selection module;
The base station according to any one of claims 9 to 14, characterized in that: A wireless communication system,
Including one or more base stations and a user terminal;
The user terminal receives a load indication and / or coverage from the one or more base stations to search for a corresponding target cell and / or to a signal strength indication measured at the user terminal. Search for a target cell based on, and transmit a cell selection report with the determined target cell identifier to the source cell base station of the user terminal,
The source cell base station sends a handover command to each user terminal managed by the local station when all the user terminals managed by the source cell search for the corresponding target cell. After completion, close your station,
A wireless communication system. The user terminal selects, as the target cell, a wireless access point whose number of connected users or resource usage rate is greater than a first predetermined load threshold from the wireless access point of the system, or from the wireless access point of the system, Selecting a wireless access point with an average user throughput less than a first predetermined load threshold as the target cell;
The wireless communication system according to claim 16. The user terminal selects the target cell based on the difference between the signal strength indication of the wireless access point to be closed measured by the user terminal and the signal strength indication of another wireless access point in the system, Another wireless access point whose difference is smaller than a predetermined difference threshold is the target cell.
The wireless communication system according to claim 16.

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