JP2011155499A - Radio communication system, radio base station, network controller, and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a radio communication system that suitably reduces interference; a radio base station; a network controller; and a communication control method. <P>SOLUTION: An LTE base station 10-1 accords transmission of an LI message via an X2 connection priority over transmission of the LI message via an S1 connection when the X2 connection with the other LTE base station is established. Specifically, in a state where only the S1 connection is initially established and the X2 connection is not established, the LTE base station 10-1 transmits the LI message to the other LTE base station via the S1 connection and an MME 20, but transmits the LI message to the other LTE base station via the X2 connection when the X2 connection is established thereafter. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention includes a plurality of radio base stations and a network control device in an upper network, and a first connection that is a logical transmission path can be established between the radio base stations. A wireless communication system capable of establishing a second connection, which is a logical transmission path, a wireless base station in the wireless communication system, a network control device in the wireless communication system, and communication control in the wireless communication system Regarding the method.

  In 3GPP (Third Generation Partnership Project), in a wireless communication system such as LTE (Long Term Evolution) currently being developed, the logic between a wireless base station (hereinafter referred to as “LTE base station”) and a core network In addition to the S1 connection that is a typical transmission path, an X2 connection that is a logical transmission path between radio base stations is required in order to realize quick handover, reduction of processing load in the core network, and the like.

  In order to establish an X2 connection, the LTE base station acquires information on other adjacent LTE base stations, and an adjacent base station list (hereinafter referred to as a “neighbor list”) as a list of information on the other LTE base stations. Hold. The adjacent other LTE base station refers to another LTE base station that is close to the LTE base station. When the LTE base station holds the neighbor list, control such as establishment of X2 connection, load distribution between LTE base stations, and regulation during maintenance work can be realized.

  The adoption of ANR (Automatic Neighbor Relation Function) is considered as a method for the LTE base station to acquire a neighbor list. ANR is a method in which an LTE base station receives a measurement report (Measurement Report) transmitted from a wireless terminal periodically or at each event, and obtains a neighbor list based on the measurement report (for example, Non-Patent Document 1).

  In addition, as a method for the LTE base station to select another LTE base station that can establish an X2 connection based on a neighbor list obtained by ANR, a neighbor can be selected based on OAM (Operation and Maintenance) information. A method of updating the White List and Black List as a list has been proposed. Here, the White List is a list made up of information on other LTE base stations that should actively establish X2 connections, and the Black List is a list of other LTE base stations that cannot establish X2 connections. A list of information.

  In addition, as a technique in which an LTE base station performs inter-cell interference coordination (ICIC), a technique based on an LI (Load Information) message exchanged between LTE base stations is defined. The LI message includes OI (Overload Indicator), HII (High Interference Indicator), and RNTP (Relative Narrowband Tx Power) as interference control information for reducing interference.

"3GPP TS 36.300 V8.5.0 (2008-05)", [online], [Search on December 15, 2009], <URL: http://www.arib.or.jp/IMT-2000/V700Sep08/ 5_Appendix / Rel8 / 36 / 36300-850.pdf>

  However, in the ICIC described above, depending on the state of the connection, when the LI message is exchanged between LTE base stations, the transmission delay may increase. If the transmission delay of the LI message becomes large, when the LTE base station receives an LI message from another LTE base station, the interference situation may be significantly different from when the other LTE base station transmits the LI message. . For this reason, even if the LTE base station performs control for reducing interference based on the LI message, the interference may not be appropriately reduced.

  In view of the above problems, an object of the present invention is to provide a radio communication system, a radio base station, a network control apparatus, and a communication control method that can appropriately reduce interference.

  In order to solve the above-described problems, the present invention has the following features. The first feature of the present invention is that the first radio base station and the second radio base station (LTE base stations 10-1, 10-2, 10-3) and the network control device (MME 20, 20) in the higher level network. -2), and a first connection (X2 connection), which is a logical transmission path, can be established between the first radio base station and the second radio base station. A wireless communication system (wireless communication system 1) capable of establishing a second connection (S1 connection), which is a logical transmission path, between a wireless base station and the second wireless base station and the network control device. The first radio base station is information for reducing interference when the first connection is established between the first radio base station and the second radio base station. Some interference control information Is transmitted to the second radio base station via the first connection established between the first radio base station and the second radio base station (LI message transmission). When the first connection is not established between the processing unit 154) and the first radio base station and the second radio base station, the interference control information is transmitted to the first radio base station. And a second transmission unit (LI message transmission processing unit 154) for transmitting to the network control device via the second connection established between the network control device and the network control device, The interference control information from the first radio base station is transmitted to the second radio base station via the second connection established between the network control device and the second radio base station. And gist in that it comprises a relay unit (LI message relay processing unit 252).

  In such a radio communication system, the transmission delay when the interference control information is transmitted via the first connection established between the first radio base station and the second radio base station is the first When the interference control information is transmitted via the second connection established between the radio base station and the network control device and the second connection established between the second radio base station and the network control device. Less than the transmission delay. Therefore, it is possible to reduce the transmission delay of the interference control information as much as possible by giving priority to the transmission of the interference control information via the first connection over the transmission of the interference control information via the second connection.

  According to a second aspect of the present invention, when the first connection is established between the first radio base station and the second radio base station, the second transmission unit Stops transmission of the interference control information to the network control device via a connection, and the first transmission unit starts transmission of the interference control information to the second radio base station via the first connection The gist is to do.

  According to a third aspect of the present invention, the first radio base station holds information indicating the second radio base station to establish the first connection with the first radio base station. The gist is to include a holding unit (storage unit 103).

  According to a fourth aspect of the present invention, the first radio base station includes a third transmission unit that transmits position information indicating a position of the first radio base station to the network control device, and the relay unit The gist is to determine the second radio base station as a transmission destination of the interference control information based on the position information.

  According to a fifth aspect of the present invention, the first radio base station includes a fourth transmission unit that transmits transmission power information indicating transmission power of the first radio base station to the network control device. The gist of the relay unit is to determine the second radio base station as a transmission destination of the interference control information based on the transmission power information.

  The sixth feature of the present invention is that, when the first connection is established between the first radio base station and the second radio base station, the second radio base station A first receiver configured to receive the interference control information from the first radio base station via the first connection established between the first radio base station and the second radio base station; (LI message reception processing unit 156) and the interference control from the network control device when the first connection is not established between the first radio base station and the second radio base station. A second receiving unit (LI message reception processing unit 156) that receives information via the second connection established between the second radio base station and the network control device. And

  In a seventh aspect of the present invention, the first transmission unit and the second transmission unit transmit the interference control information including time information indicating a time related to the occurrence of interference, and the first reception unit And the second receiving unit receive the interference control information including the time information, and the second radio base station is at least one of the first receiving unit and the second receiving unit. An interference control unit (interference control unit 158) that controls interference reduction based on the interference control information indicating a time within a period in which the time information is considered to be valid among the interference control information received by It is a summary to provide.

  An eighth feature of the present invention is that in a wireless communication system, a first connection, which is a logical transmission path, can be established with another wireless base station, and a logical connection is established with a network control device in an upper network. If the second connection, which is a typical transmission path, can be established, and the first connection is established between the own radio base station and the other radio base station, interference is caused. First transmission for transmitting interference control information, which is information for reducing, to the other radio base station via the first connection established between the own radio base station and the other radio base station And when the first connection is not established between the own radio base station and the other radio base station, the interference control information is established between the own radio base station and the network control device. Before Further comprising a second transmission unit that transmits to the network controller via the second connection and gist.

  A ninth feature of the present invention is a network control apparatus capable of establishing a connection, which is a logical transmission path, with the radio base station in an upper network of a radio communication system including a plurality of radio base stations. Interference control information, which is information for reducing interference, transmitted from the first radio base station via the connection established between the own apparatus and the first radio base station, The gist is to include a relay unit that transmits to the second radio base station via the connection established between the own apparatus and the second radio base station.

  A tenth feature of the present invention comprises a plurality of radio base stations and a network control device in an upper network, wherein a first connection which is a logical transmission path can be established between the radio base stations, A communication control method in a wireless communication system in which a second connection, which is a logical transmission path, can be established between a wireless base station and the network control device, wherein the wireless base station and other wireless base stations When the first connection is established with the other radio base station, interference control information, which is information for reducing interference, is established between the own radio base station and the other radio base station. Transmitting to the other radio base station via the established first connection, and the radio base station establishes the first connection between the own radio base station and the other radio base station. If not, transmitting the interference control information to the network control device via the second connection established between the radio base station and the network control device; and Transmitting the interference control information from the radio base station to the other radio base station via the second connection established between the own apparatus and the other radio base station. Is the gist.

  According to the present invention, it is possible to appropriately reduce interference.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a block diagram of a LTE base station according to an embodiment of the present invention. It is a figure which shows the establishment state of S1 connection in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the establishment state of X2 connection in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of a measurement start time and a measurement period based on embodiment of this invention. It is a block diagram of MME based on embodiment of this invention. It is a flowchart which shows the operation | movement at the time of new installation of the LTE base station which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement at the normal time of the LTE base station which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement at the time of the LI message reception of the LTE base station which concerns on embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) schematic configuration of radio communication system, (2) configuration of LTE base station, (3) configuration of MME, (4) operation of LTE base station, (5) action / effect, (6) Other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Schematic Configuration of Radio Communication System FIG. 1 is a schematic configuration diagram of a radio communication system according to this embodiment. In the present embodiment, the wireless communication system 1 is configured using LTE technology. A radio communication system 1 illustrated in FIG. 1 includes LTE base stations 10-1, 10-2, and 10-3 that are radio base stations, an MME (Mobile Management Entity) 20 that is a network control device, and a backbone that is a higher level network. A network 30 and a wireless terminal 40 are included.

  The LTE base stations 10-1 to 10-3 and the wireless terminal 40 perform wireless communication via the wireless communication section. In LTE, the communication method between the LTE base stations 10-1 to 10-3 and the radio terminal 40 is referred to as E-UTRAN (Evolved UMTS Terrestrial Radio Access Network).

(2) Configuration of LTE Base Station FIG. 2 is a diagram illustrating a configuration of the LTE base station 10-1. The LTE base station 10-1 illustrated in FIG. 2 includes a control unit 102, a storage unit 103, an I / F unit 104, a wireless communication unit 106, and an antenna 108. The LTE base stations 10-2 and 10-3 also have the same configuration as the LTE base station 10-1.

  The control unit 102 is configured by a CPU, for example, and controls various functions provided in the LTE base station 10-1. The memory | storage part 103 is comprised by memory, for example, and memorize | stores the various information used for the control etc. in the LTE base station 10-1.

  The I / F unit 104 is connected to the backbone network 30. The wireless communication unit 106 includes an RF circuit, a baseband circuit, etc., performs modulation and demodulation, encoding and decoding, etc., and transmits and receives wireless signals to and from the wireless terminal 40 via the antenna 108. .

  The control unit 102 includes a connection establishment processing unit 152, an LI (Load Information) message transmission processing unit 154, an LI message reception processing unit 156, and an interference control unit 158.

(Process when newly installing LTE base station)
Hereinafter, processing when the LTE base station 10-1 is newly installed will be described.

  When the power of the LTE base station 10-1 is turned on, the control unit 102 performs a startup process of the LTE base station 10-1, performs communication with the wireless terminal 40, and communication with the MME 20 Initialize the wired section (backhaul part) for In the initialization of the backhaul portion, the connection establishment processing unit 152 in the control unit 102 establishes an S1 connection that is a logical transmission path of the transport layer with the MME 20 via the backbone network 30.

  FIG. 3 is a diagram illustrating an established state of the S1 connection in the initial state in the wireless communication system 1. In FIG. 3, an S1 connection # 1 is established between the LTE base station 10-1 and the MME 20. Further, an S1 connection # 2 is established between the LTE base station 10-2 and the MME 20, and an S1 connection # 3 is established between the LTE base station 10-3 and the MME 20.

  By the initialization described above, the LTE base station 10-1 transitions to a state (operation state) in which a wireless signal can be transmitted and received with the wireless terminal 40.

  After the LTE base station 10-1 is in an operational state, the connection establishment processing unit 152 periodically or from the wireless terminal 40 connected to the LTE base station 10-1 by an ANR (Automatic Neighbor Relation Function) method, or A measurement report transmitted at each event is received via the antenna 108 and the wireless communication unit 106. Further, the connection establishment processing unit 152 generates a neighbor list based on the received measurement report, and stores the neighbor list in the storage unit 103. The neighbor list may be stored in the storage unit 103 in advance.

  Thereafter, the connection establishment processing unit 152 updates the White List and Black List as the neighbor list based on OAM (Operation and Maintenance) information. Here, the White List includes information on other LTE base stations that should establish an X2 connection with the LTE base station 10-1.

  Further, the LI message transmission processing unit 154 performs communication between another LTE base station (in this case, the LTE base station 10-2 and the LTE base station 10-3) and a wireless terminal connected to the other LTE base station. For each resource block that is a radio resource, the amount of interference received by the LTE base station 10-1 is measured. Here, the amount of interference is, for example, a received signal strength indicator (RSSI).

  Next, the LI message transmission processing unit 154 generates and transmits an LI message for each resource block.

  Specifically, the LI message transmission processing unit 154 adds an OI (Overload Indicator), an HII (OI) to an LI message as interference control information for reducing interference by inter-cell interference coordination (ICIC). At least one of High Interference Indicator) and RNTP (Relative Narrowband Tx Power) is included as each information element (IE) in the message.

  Here, OI is interference control information for controlling uplink interference, and indicates the amount of interference of the corresponding resource block in the source LTE base station. HII is interference control information for controlling uplink interference, and a resource to be allocated to a radio terminal existing at an end of a cell formed by the LTE base station of the transmission source LTE base station. Indicates a block. RNTP indicates the transmission power of the corresponding resource block in the LTE base station of the transmission source.

  Further, the LI message transmission processing unit 154 includes the measurement start time and the measurement period (for example, 60 seconds) of the interference amount in the LI message as time information related to the time when the interference occurs. In addition, the LI message transmission processing unit 154 includes the identification information (cell ID) of the other LTE base station included in the White List in the LI message as destination information. Further, the LI message transmission processing unit 154 includes the identification information (cell ID) of the LTE base station 10-1 in the LI message as transmission source information.

  Furthermore, the LI message transmission processing unit 154 periodically transmits an LI message after the LTE base station 10-1 is activated. In this case, if the X2 connection is not established between the LTE base station 10-1 and another LTE base station at the timing when the LI message is transmitted, the LI message transmission processing unit 154 is the I / F unit 104. The LI message is transmitted to the MME 20 via the S1 connection.

  Further, when the X2 connection is not established between the LTE base station 10-1 and another LTE base station, the following is executed.

  The connection establishment processing unit 152 determines another LTE base station corresponding to the information of another LTE base station included in the White List as a candidate (connection candidate) for establishing an X2 connection with the LTE base station 10-1. . Other LTE base stations that are connection candidates are, for example, LTE base stations that exist within a predetermined distance from the LTE base station 10-1, in other words, influences of interference that are greater than or equal to each other with the LTE base station 10-1. The LTE base station receiving.

  Furthermore, the connection establishment processing unit 152 sequentially establishes an X2 connection, which is a logical transmission path of the transport layer, via the backbone network 30 with other LTE base stations that are connection candidates. After establishing the X2 connection, the connection establishment processing unit 152 deletes the information of the other LTE base station that has established the X2 connection with the LTE base station 10-1 from the White List as the neighbor list.

  When the X2 connection is established between the LTE base station 10-1 and another LTE base station at the timing of transmitting the LI message, the LI message transmission processing unit 154 communicates with the LTE base station 10-1. The L1 message is transmitted via the I / F unit 104 and the X2 connection to another LTE base station in which the X2 connection is established. At this time, the LI message transmission processing unit 154 also continues to transmit the LI message to the MME 20 via the S1 connection.

  In this way, when the X2 connection is sequentially established between the LTE base station 10-1 and another LTE base station that is a connection candidate, an LI message is received from the LTE base station 10-1 via the X2 connection. The number of other LTE base stations gradually increases.

  FIG. 4 is a diagram illustrating an established state of the X2 connection in the wireless communication system 1. When the LTE base stations 10-1, 10-2, and 10-3 mutually select other LTE base stations as connection candidates, as shown in FIG. 4, the LTE base station 10-1 and the LTE base station 10-2 In the meantime, X2 connection # 1 is established. Further, an X2 connection # 2 is established between the LTE base station 10-1 and the LTE base station 10-3. Furthermore, an X2 connection # 3 is established between the LTE base station 10-2 and the LTE base station 10-3.

  Thereafter, the LI message transmission processing unit 154 determines whether or not an X2 connection has been established with all the connection candidate other LTE base stations. Specifically, the LI message transmission processing unit 154 establishes an X2 connection with other LTE base stations for all connection candidates when the white list as a neighbor list includes information on other LTE base stations. If no other LTE base station information is included in the White List as a neighbor list, an X2 connection is established with all other connection candidate LTE base stations. judge.

  When the X2 connection is established with all the connection candidates and other LTE base stations, the LI message transmission processing unit 154 stops the transmission of the LI message to the MME 20 via the S1 connection.

(Normal processing of LTE base station)
Hereinafter, normal processing in the LTE base station 10-1 will be described.

  While the LTE base station 10-1 is performing normal processing, the LI message transmission processing unit 154 in the control unit 102 determines whether or not the X2 connection is disconnected or reset. For example, the LI message transmission processing unit 154 transmits a message different from the LI message to another LTE base station via the I / F unit 104 and the X2 connection, and then transmits the other LTE base station within a predetermined time. If the response message is not received from X, it is determined that the X2 connection is disconnected or reset. Note that whether or not the X2 connection has been disconnected or reset can also be determined in communication confirmation at the SCTP (Stream Control Transmission Protocol) level.

  When the X2 connection is disconnected or reset, the LI message transmission processing unit 154 includes the information of the other LTE base station that is the connection partner of the disconnected or reset X2 connection as destination information in the LI message. Further, the LI message transmission processing unit 154 transmits an LI message to the MME 20 via the I / F unit 104 and the S1 connection.

  Thereafter, the connection establishment processing unit 152 reestablishes the disconnected or reset X2 connection. When the re-establishment of the X2 connection is completed, the LI message transmission processing unit 154 transmits an LI message to another LTE base station via the I / F unit 104 and the re-established X2 connection.

  Thereafter, the LI message transmission processing unit 154 determines whether or not all X2 connections that have been disconnected or reset have been re-established.

  When all the disconnected or reset X2 connections are re-established, the LI message transmission processing unit 154 stops the transmission of the LI message to the MME 20 via the S1 connection.

(Process when receiving LI message)
Hereinafter, the process at the time of reception of the LI message in the LTE base station 10-1 will be described.

  While the LTE base station 10-1 performs normal processing, the LI message reception processing unit 156 in the control unit 102 receives the LI message from the MME 20 via the S1 connection and the I / F unit 104. . Further, the LI message transmission processing unit 154 receives LI messages from other LTE base stations via the X2 connection and the I / F unit 104. The received LI message is stored in the storage unit 103.

  The interference control unit 158 determines whether or not the aggregation timing of the LI message has arrived. The aggregation timing of the LI message is, for example, 00 minutes per hour, and information on the aggregation timing is stored in the storage unit 103.

  When the LI message count timing arrives, the interference control unit 158 receives the LI message stored so far and stored in the storage unit 103 based on the measurement start time and the measurement period included in the LI message. The measurement time zone is calculated. Here, the start of the measurement time zone is the measurement start time, and the end is the time obtained by adding the measurement period to the measurement start time.

  Next, the interference control unit 158 extracts, from the LI messages stored in the storage unit 103, LI messages whose corresponding measurement time zone overlaps with the valid period. The valid period is a predetermined period (for example, 1 minute) in the past, which is traced back from the LI message count timing, and is stored in the storage unit 103. Here, the interference control unit 158 extracts not only the LI message in which the entire corresponding measurement time period is included in the effective period, but also the LI message in which a part of the corresponding measurement time period is included in the effective period.

  Next, the interference control unit 158 adds up the extracted LI messages. Since the LI message is generated for each resource block, the interference control unit 158 adds up the corresponding LI messages for each resource block.

  Specifically, the interference control unit 158 calculates at least one of an average value of OI included in each LI message, a resource block usage rate based on HII, and an average value of RNTP. Here, the extracted LI message includes those in which the entire corresponding measurement time period is included in the effective period and those in which a part of the corresponding measurement time period is included in the effective period. For this reason, the interference control unit 158 calculates a mean value by performing a weighted average by weighting according to the degree of overlap between the measurement time zone and the effective period.

  FIG. 5 is a diagram illustrating an example of the measurement start time and the measurement period. Here, it is assumed that the valid period is 60 seconds retroactive from 12:00:00, that is, 11:59:01 to 12:00:00.

  In this case, the measurement time zone corresponding to the base station ID 001 is 11:58:01 to 11:59:00, and does not overlap with the valid period. For this reason, the LI message corresponding to the base station ID 001 is not extracted, and the weighting value is 0.

  The measurement time zone corresponding to the base station ID 002 is 11:58:31 to 11:59:30, and 1/2 overlaps with the valid period. For this reason, the weight value of the LI message corresponding to the base station ID 002 is ½.

  The measurement time zone corresponding to the base station ID 003 is 11:59:01 to 11:59:50, and the whole overlaps with the valid period. For this reason, the weight value of the LI message corresponding to the base station ID 002 is 1.

  In this way, after counting at least one of OI, HII, and RNTP in the LI message, the interference control unit 158 controls interference reduction based on the counting result. How the interference control unit 158 performs interference reduction control based on OI, HII, and RNTP is not specifically defined in the LTE standard. For example, the following interference reduction control is performed. It can be carried out.

  The interference control unit 158 sets a scheduling policy in consideration of the OI when the average value of the OI is equal to or greater than the predetermined value, and considers the OI when the average value of the OI is less than the predetermined value. Without setting a scheduling policy.

  Further, when the usage rate of the resource block based on HII is equal to or greater than a predetermined value, the interference control unit 158 transmits the resource block to the radio that exists at the end of the cell formed by the LTE base station 10-1. Do not assign to terminals (cell edge terminals).

  In addition, the interference control unit 158 can assign a corresponding resource block when the average value of RNTP is less than a predetermined value, and the corresponding resource block is assigned when the average value of RNTP is equal to or greater than a predetermined value. Cannot be assigned.

(3) Configuration of MME FIG. 6 is a diagram illustrating a configuration of the MME 20. The MME 20 illustrated in FIG. 6 includes a control unit 202, a storage unit 203, and an I / F unit 204.

  The control unit 202 is configured by a CPU, for example, and controls various functions provided in the LTE base station 10-1. The storage unit 203 is configured by a memory, for example, and stores various information used for control in the MME 20. The I / F unit 204 is connected to the backbone network 30.

  The control unit 202 includes a LI (Load Information) message relay processing unit 252.

  The LI message relay processing unit 252 receives LI messages from the LTE base stations 10-1 to 10-3 via the S1 connection and the I / F unit 204. Next, the LI message relay processing unit 252 identifies one of the LTE base stations 10-1 to 10-3 that is the destination of the LI message, based on the destination information in the received LI message. Further, the LI message relay processing unit 252 determines the specified LTE base via the I / F unit 204 and the X2 connection established between any of the specified LTE base stations 10-1 to 10-3. The LI message is transmitted to any of the stations 10-1 to 10-3.

(4) Operation of LTE Base Station Next, the operation of the LTE base station 10-1 will be described. Note that the LTE base stations 10-2 and 10-3 also perform the same operation as the LTE base station 10-1.

  FIG. 7 is a flowchart showing an operation when the LTE base station 10-1 is newly installed.

  In step S101, when the power of the LTE base station 10-1 is turned on, the control unit 102 starts up the LTE base station 10-1, and establishes an S1 connection with the MME 20.

  In step S102, the control unit 102 generates an LI message and transmits the LI message to the MME 20 via the S1 connection. The MME 20 transmits the LI message from the LTE base station 10-1 to another LTE base station via the S1 connection.

  In step S103, the control unit 102 determines a candidate (connection candidate) for establishing an X2 connection with the LTE base station 10-1, and establishes an X2 connection with another LTE base station that is the connection candidate. To do.

  In step S104, the control unit 102 generates an LI message, and in step S103, transmits the LI message via the X2 connection to another LTE base station in which the X2 connection is established with the LTE base station 10-1. To do.

  In step S105, the control unit 102 determines whether or not an X2 connection has been established with other connection candidate LTE base stations.

  If an X2 connection has not been established with some other connection candidate LTE base stations, the operations after the establishment of the X2 connection with another connection candidate other LTE base station in step S103 are repeated. .

  On the other hand, when an X2 connection is established with other LTE base stations of all connection candidates, in step S106, the control unit 102 stops transmission of the LI message to the MME 20 via the S1 connection. .

  FIG. 8 is a flowchart showing an operation during normal processing of the LTE base station 10-1.

  In step S201, while the LTE base station 10-1 is performing normal processing, in step S202, the control unit 102 determines whether or not the X2 connection is disconnected or reset.

  When the X2 connection is disconnected or reset, in step S203, the control unit 102 transmits an LI message addressed to the other LTE base station that is the connection partner of the disconnected or reset X2 connection to the MME 20 via the S1 connection. Send.

  In step S204, the control unit 102 reestablishes the disconnected or reset X2 connection.

  In step S205, the control unit 102 generates an LI message, and transmits the LI message via the X2 connection to another LTE base station in which the X2 connection is reestablished with the LTE base station 10-1.

  In step S206, the control unit 102 determines whether or not all the disconnected or reset X2 connections have been established again.

  If some of the disconnected or reset X2 connections have not been reestablished, the operations after reestablishment of the X2 connection in step S203 are repeated.

  On the other hand, if all disconnected or reset X2 connections have been re-established, in step S207, the control unit 102 stops transmitting the LI message to the MME 20 via the S1 connection.

  FIG. 9 is a flowchart showing an operation when the LTE base station 10-1 receives an LI message.

  In step S301, while the LTE base station 10-1 is performing normal processing, in step S302, the control unit 102 receives the LI message from the MME 20 via the S1 connection and via the X2 connection. Then, an LI message from another LTE base station is received.

  In step S303, the control unit 102 determines whether or not the LI message aggregation timing has come.

  If the LI message aggregation timing has not arrived, the operation after the reception of the LI message in step S [302] is repeated.

  On the other hand, when the timing for counting LI messages has arrived, in step S304, the control unit 102 counts LI messages whose corresponding measurement time zones overlap with the valid period.

  Furthermore, in step S305, the control unit 102 controls interference reduction based on the LI message count result.

(5) Operation and Effect As described above, in the wireless communication system 1 according to the embodiment of the present invention, the transmission delay when the LI message is transmitted via the X2 connection established between the LTE base stations is the LTE base. In other words, it is smaller than the transmission delay when the LI message is transmitted via the MME 20 via the S1 connection established between the station and the MME 20. In view of this, when the X2 connection is established with another LTE base station, the LTE base station 10-1 transmits the LI message via the X2 connection to the LI message via the S1 connection. Prioritizes transmission.

  Specifically, when only the S1 connection is initially established and the X2 connection is not established, the LTE base station 10-1 passes through the S1 connection and the MME 20 to other LTE base stations. To send an LI message. However, when the X2 connection is subsequently established, the LTE base station 10-1 transmits an LI message to the other LTE base station via the X2 connection.

  When the X2 connection is disconnected or reset, the LTE base station 10-1 starts to transmit an LI message via the S1 connection and reestablishes the X2 connection. When the X2 connection is established again, the LTE base station 10-1 transmits an LI message to the other LTE base station via the X2 connection.

  Therefore, the transmission delay of the LI message between LTE base stations can be reduced as much as possible.

  In addition, the storage unit 103 holds a White List as a neighbor list including information on other LTE base stations that should establish an X2 connection with the LTE base station 10-1, and the White List. Is updated as needed, so that the LTE base station 10-1 can appropriately recognize other LTE base stations that should establish the X2 connection in accordance with the connection establishment status that changes from time to time.

  Moreover, the LTE base station 10-1 performs interference reduction control based on the LI message from the other LTE base station via the X2 connection. More specifically, the LTE base station 10-1 targets only the LI messages whose corresponding measurement time zone overlaps the valid period among the received LI messages, and controls interference reduction based on the aggregation result. I do. Therefore, appropriate interference reduction control can be performed based on the LI message with a small transmission delay.

  Furthermore, the LTE base station 10-1 counts not only the LI message in which the entire corresponding measurement time period is included in the effective period but also the LI message in which a part of the corresponding measurement time period is included in the effective period. set to target. Furthermore, the LTE base station 10-1 performs weighting according to the degree of duplication of the LI messages in which a part of the corresponding measurement time zone overlaps the valid period, and tabulates them. Therefore, it is possible to appropriately control interference reduction that reflects the interference state within the effective period as much as possible.

(6) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the above-described embodiment, when the LI message transmission processing unit 154 in the control unit 102 of the LTE base station 10-1 transmits an LI message to the MME 20 via the S1 connection, information on other LTE base stations that are destinations Is included in the LI message so that the MME 20 can identify the transfer destination of the LI message.

  However, the LI message transmission processing unit 154 detects the position of the LTE base station 10-1 by the GPS function or the like, and replaces the information of the other LTE base station as the destination with the information on the detected position (for example, longitude and (Latitude information) may be included in the LI message and transmitted to the MME 20. In this case, the MME 20 performs LTE based on the location information of the LTE base station 10-1 included in the LI message from the LTE base station 10-1 and the location information of the other LTE base stations held in advance. Another LTE base station existing within a predetermined distance from the base station 10-1 is determined as a transfer destination of the LI message from the LTE base station 10-1.

  When the LTE base station 10-1 is newly set up, it is possible that the MME 20 does not hold the location information of the LTE base station 10-1, and thus the LTE base station 10-1 itself By transmitting the location information of the station in the LI message, the MME 20 can recognize the location of the LTE base station 10-1, and further appropriately determine the transfer destination of the LI message from the LTE base station 10-1. can do.

  Further, the LI message transmission processing unit 154 acquires the transmission power value of the LTE base station 10-1, and includes the acquired transmission power value in the LI message instead of the information of the other LTE base station as the destination. You may transmit to MME20. In this case, the range in which the LTE base station 10-1 gives interference increases as the transmission power of the LTE base station 10-1 increases. For this reason, MME20 expands the area | region centering on LTE base station 10-1, so that the transmission power value contained in the LI message from LTE base station 10-1 is large, and the other LTE base station in the said area | region Is determined as the transfer destination of the LI message from the LTE base station 10-1. Accordingly, it is possible to appropriately determine the transfer destination of the LI message in consideration of the range in which the LTE base station 10-1 gives interference.

  In the above-described embodiment, the LTE radio communication system 1 has been described. However, the present invention can be similarly applied to any radio communication system in which a logical transmission path is established between radio base stations. .

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  According to the wireless communication system, the wireless base station, the network control apparatus, and the communication control method of the present invention, it is possible to appropriately reduce interference, which is useful as a wireless communication system or the like.

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 10-1, 10-2, 10-3 ... LTE base station, 20 ... MME, 30 ... Backbone network, 40 ... Wireless terminal, 102 ... Control part, 103 ... Memory | storage part, 104 ... I / F unit, 106 ... wireless communication unit, 108 ... antenna, 152 ... connection establishment processing unit, 154 ... LI message transmission processing unit, 156 ... LI message reception processing unit, 158 ... interference control unit, 202 ... control unit, 203 ... storage , 204... I / F unit, 252... LI message relay processing unit

Claims (10)

A first wireless base station, a second wireless base station, and a network control device in an upper network; a logical transmission path between the first wireless base station and the second wireless base station; A radio in which a first connection can be established, and a second connection, which is a logical transmission path, can be established between the first radio base station and the second radio base station and the network control device. A communication system,
The first radio base station is
When the first connection is established between the first radio base station and the second radio base station, interference control information, which is information for reducing interference, is transmitted to the first radio base station. A first transmitter for transmitting to the second radio base station via the first connection established between the base station and the second radio base station;
When the first connection is not established between the first radio base station and the second radio base station, the interference control information is transmitted to the first radio base station and the network control device. A second transmission unit for transmitting to the network control device via the second connection established during
The network controller is
The interference control information from the first radio base station is transmitted to the second radio base station via the second connection established between the network control device and the second radio base station. A wireless communication system including a relay unit. When the first connection is established between the first radio base station and the second radio base station,
The second transmission unit stops transmission of the interference control information to the network control device via the second connection;
2. The radio communication system according to claim 1, wherein the first transmission unit starts transmitting the interference control information to the second radio base station via the first connection.   The first radio base station includes a holding unit that holds information indicating the second radio base station with which the first connection should be established with the first radio base station. The wireless communication system according to 1. The first radio base station includes a third transmission unit that transmits position information indicating a position of the first radio base station to the network control device,
4. The radio communication system according to claim 1, wherein the relay unit determines the second radio base station that is a transmission destination of the interference control information based on the position information. 5. The first radio base station includes a fourth transmission unit that transmits transmission power information indicating transmission power of the first radio base station to the network control device,
4. The radio communication system according to claim 1, wherein the relay unit determines the second radio base station that is a transmission destination of the interference control information based on the transmission power information. 5. The second radio base station is
When the first connection is established between the first radio base station and the second radio base station, the interference control information from the first radio base station is changed to the first radio base station. A first receiving unit for receiving via the first connection established between a radio base station and the second radio base station;
When the first connection is not established between the first radio base station and the second radio base station, the interference control information from the network control device is used as the second radio base station. The wireless communication system according to claim 1, further comprising: a second receiving unit that receives the second connection established between the network control device and the network control device. The first transmission unit and the second transmission unit transmit the interference control information including time information indicating a time related to the occurrence of interference,
The first receiving unit and the second receiving unit receive the interference control information including the time information,
The second radio base station is
Of the interference control information received by at least one of the first receiver and the second receiver, based on the interference control information indicating a time within a period in which the time information is considered valid The radio communication system according to claim 6, further comprising an interference control unit that controls interference reduction. In a wireless communication system, a first connection, which is a logical transmission path, can be established with another wireless base station, and a second connection, which is a logical transmission path, with a network control device in a higher level network. Is a radio base station that can be established,
When the first connection is established between the own radio base station and the other radio base station, interference control information, which is information for reducing interference, is sent to the own radio base station and the other radio base station. A first transmitter for transmitting to the other radio base station via the first connection established with a base station;
When the first connection is not established between the own radio base station and the other radio base station, the interference control information is established between the own radio base station and the network control device. A radio base station comprising: a second transmission unit configured to transmit to the network control device via a second connection. In a host network of a wireless communication system including a plurality of wireless base stations, a network control device capable of establishing a connection as a logical transmission path between the wireless base stations,
Interference control information, which is information for reducing interference, transmitted from the first radio base station via the connection established between the own device and the first radio base station, And a second wireless base station, a network control device comprising a relay unit for transmitting to the second wireless base station via the connection established between the first wireless base station and the second wireless base station. A plurality of radio base stations and a network control device in an upper network, wherein a first connection that is a logical transmission path can be established between the radio base stations, and the radio base station, the network control device, A communication control method in a wireless communication system capable of establishing a second connection which is a logical transmission path between
When the first connection is established between the radio base station and another radio base station, the radio base station transmits interference control information that is information for reducing interference to the radio base station. Transmitting to the other radio base station via the first connection established between the first radio base station and the other radio base station;
When the first connection is not established between the radio base station and the other radio base station, the radio base station transmits the interference control information between the radio base station and the network control device. Transmitting to the network control device via the second connection established between;
The network control device transmits the interference control information from the radio base station to the other radio base station via the second connection established between the own device and the other radio base station. A communication control method comprising the steps.

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