JP6443561B2 - Relay node, radio communication system, and communication method in radio communication system - Google Patents

Description

  The technology described in this specification relates to a relay node, a wireless communication system, and a communication method in the wireless communication system.

  In Long Term Evolution (LTE), which is one of the communication methods prescribed by the Third Generation Partnership Project (3GPP), the installation of a gateway (GW) that aggregates multiple inter-base station interfaces called X2 interfaces has been studied. Yes.

  A GW that aggregates a plurality of X2 interfaces may be referred to as an “X2 GW” for convenience. By installing the X2 GW, it is possible to avoid or suppress an increase in load due to concentration of connections by the X2 interface (may be referred to as “X2 connection”) to a specific base station.

JP 2011-41237 A JP 2013-150204 A

3GPP TS 36.300-c50 3GPP TS 36.413-c50 3GPP TS 36.423-c50

  In the radio access network, there are cases where base stations with different versions of 3GPP to be supported are mixed. For example, an older release version of a base station (which may be referred to as a “legacy base station”) may not support an X2 connection with an X2 GW.

  Then, in the radio access network, a part of base stations capable of X2 connection with the X2 GW are limited, and even if the X2 GW is installed, the X2 GW may not be effectively used. Note that the X2 GW may be regarded as an example of a “relay node” that relays communication using an X2 connection.

  In one aspect, one of the objectives of the techniques described herein is a relay node with another base station that supports connection with the relay node, even if the base station does not support connection with the relay node. To establish a connection over the network.

  In one aspect, the relay node relays communication between a core node connected to the first base station and a second base station different from the first base station. The relay node may include a reception unit, a determination unit, and a transmission unit. The receiving unit may receive a base station-core node message from the core node. The determination unit may be configured such that the base station-core node message does not support inter-base station connection with a second relay node in which the second base station connects between base stations via an inter-base station interface. It may be determined whether the message is a message transmitted from the station and includes an information element for requesting the address information of the second base station. The transmission unit includes a message including an information element for requesting the address information of the second base station, wherein the base station-core node message is transmitted from the first base station to the second base station. If it is determined by the determination unit, the base station-core node message may be terminated, and the address information of the first relay node may be transmitted to the first base station.

  In one aspect, the wireless communication system includes a first base station, a second base station, a core node connected to the first base station, and between the second base station and the core node. And a second relay node in which the second base station connects between base stations via an inter-base station interface. The first relay node may include the above-described reception unit, determination unit, and transmission unit.

  Further, in one aspect, a communication method requests address information of the second base station from the first base station that does not support inter-base station connection with the second relay node to the core node. A base station-core node message including the information element may be transmitted. The communication method may transmit the base station-core node message from the core node to the first relay node. Further, in the communication method, in response to the first relay node receiving the base station-core node message including an information element requesting address information of the second base station, the first relay node Relay node address information may be returned to the first base station via the core node.

  As one aspect, even a base station that does not support connection with a relay node can establish a connection via the relay node with another base station that supports connection with the relay node.

It is a block diagram which shows an example of the radio | wireless communications system which has several macro base station (MeNB) connected with MME (Mobility Management Entity) by S1 interface. It is a block diagram which shows an example of the radio | wireless communications system which has several MeNB and small base station (HeNB) connected with MME and S1 interface. It is a schematic diagram which shows an example of the aspect by which the connection between several HeNB and MME in FIG. 2 is collected by a gateway (HeNB GW). It is a block diagram which shows an example of the aspect of X2 connection by the X2 interface between MeNB in FIG. It is a block diagram which shows an example of the aspect of X2 connection between each eNB containing MeNB and HeNB in FIG. FIG. 6 is a schematic diagram illustrating an example of an aspect in which X2 connections between a plurality of HeNBs and MeNBs in FIG. 5 are aggregated in a gateway (X2 GW). It is a schematic diagram which shows an example of the message format which provided the RNL (Radio Network Layer) header to the X2 message, and was encapsulated. It is a schematic diagram which shows an example of the information element (IE) of the RNL header illustrated in FIG. It is a schematic diagram for demonstrating the transfer example of X2 message in the example of FIG. It is a schematic diagram for demonstrating the procedure which establishes X2 connection between eNBs. It is a schematic diagram which shows an example of the procedure which establishes X2 connection via X2 GW between eNBs. It is a figure which shows the example of a format of the S1 message which inquires an IP address. It is a figure which shows the example of a format of the S1 message which responds an IP address. It is a schematic diagram for demonstrating an example of the procedure in which MeNB inquires the IP address of HeNB. It is a schematic diagram for demonstrating an example of the procedure in which a legacy MeNB (LMNB) inquires the IP address of HeNB. It is a flowchart which shows the operation example of HeNB GW illustrated in FIG.14 and FIG.15. It is a figure which shows an example of the X2 mapping table which HeNB GW illustrated in FIG.14 and FIG.15 memorize | stores. FIG. 16 is a sequence diagram for explaining a procedure corresponding to FIG. 15. It is a schematic diagram for demonstrating an example of the establishment procedure of X connection via X2 GW between LMNB and HeNB illustrated in FIG. It is a figure which shows an example of IE of the encapsulated X2 message which HeNB GW transmits to X2 GW in the example of FIG. It is a flowchart which shows the operation example of HeNB GW corresponding to FIG. FIG. 20 is a sequence diagram for explaining a procedure corresponding to FIG. 19. It is a figure which shows an example of the X2 mapping table which HeNB GW which concerns on the operation example of FIG. 19 memorize | stores. It is a schematic diagram for demonstrating an example of the transfer procedure of X2 message which HeNB transmitted to LMeNB. It is a schematic diagram for demonstrating an example of the transfer procedure of X2 message which LM eNB transmitted to HeNB. It is a flowchart which shows the operation example of HeNB GW corresponding to FIG. It is a flowchart which shows the operation example of HeNB GW corresponding to FIG. FIG. 25 is a sequence diagram for explaining a procedure corresponding to FIG. 24. FIG. 26 is a sequence diagram for explaining a procedure corresponding to FIG. 25. It is a schematic diagram for demonstrating the operation example when communication by X2 connection established between LMeNB and HeNB GW cut | disconnects. It is a schematic diagram for demonstrating the operation example when communication by X2 connection between X2 GW and HeNB cut | disconnects. It is a schematic diagram for demonstrating the operation example which HeNB GW cut | disconnects the communication by X2 connection established with LMeNB according to the entry deletion of X2 mapping table. It is a flowchart which shows the operation example of HeNB GW corresponding to FIG. It is a flowchart which shows the operation example of HeNB GW corresponding to FIG.31 and FIG.32. FIG. 31 is a sequence diagram for explaining a procedure corresponding to FIG. 30. FIG. 33 is a sequence diagram for explaining a procedure corresponding to FIGS. 31 and 32. It is a block diagram which shows the structural example of HeNB GW. It is a block diagram which shows the hardware structural example of HeNB GW.

  Hereinafter, embodiments will be described with reference to the drawings. However, the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described below. Various exemplary embodiments described below may be implemented in combination as appropriate. Note that, in the drawings used in the following embodiments, portions denoted by the same reference numerals represent the same or similar portions unless otherwise specified.

  In LTE of 3GPP, a radio base station called “eNB” (simply referred to as “base station”) is defined. “ENB” is an abbreviation for “evolved (Universal Mobile Telecommunications System Terrestrial Radio Access Network) Node B”.

  The radio area formed by the eNB may be a “cell” or a “sector”. A cell formed by an eNB may be referred to as a “macro cell”. A radio base station (eNB) that forms a macro cell may be referred to as a “macro base station”, a “macro eNB”, a “MeNB”, or the like.

  A “cell” is an example of a wireless area formed in accordance with the reachable range (also referred to as “coverage”) of a radio wave transmitted by a radio base station. A wireless device such as a mobile station located in a cell can wirelessly communicate with a wireless base station that forms the cell.

  In LTE, discussions are being made on technology for increasing system capacity by utilizing a small cell (SC) in addition to a macro cell. For example, a “small cell” having a smaller coverage than the macro cell may be arranged in the macro cell (MC).

  “Small cell” may include, for example, cells called “home cell”, “femto cell”, “pico cell”, “micro cell”, “metro cell”, and the like.

  A radio base station forming a small cell may be referred to as a “small base station”. The small base station may include a home base station, a femto base station, a pico base station, a micro base station, a metro base station, and the like according to the designation of the small cell. The home base station may be referred to as HeNB (Home eNodeB).

  Note that each of the macro base station and the small base station is an example of a network element (NE) constituting the radio access network.

  In the following description, for convenience, it is assumed that an example of a small base station is a HeNB, but the small base station is any one of a femto base station, a pico base station, a micro base station, and a metro base station. May be.

  FIG. 1 shows an example of a wireless communication system 1 including a plurality of MeNBs. The radio communication system 1 may be referred to as “network 1” for convenience. The radio communication system 1 illustrated in FIG. 1 may include, for example, three MeNBs # 1 to # 3.

  MeNB # i (i = 1 to n, where n is an integer of 2 or more by way of example) each forms a macro cell MC # i. In addition, when it is not necessary to distinguish MeNB # i and macrocell MC # i, they may be described as “MeNB” and “macrocell MC”, respectively.

  As illustrated in FIG. 1, the MeNB may be communicably connected to the MME. “MME” is an abbreviation for “Mobility Management Entity”, and is an example of an entity or a node in the core network. Therefore, the MME may be referred to as a “core node”. In other words, an example of “core node” is “MME”.

  The MME may function as an access gateway of a control plane (Control Plane) that handles control of the radio access network in the core network. For example, the MME may support management of location registration of a wireless device such as a UE (User Equipment), calling of a wireless device, handover between base stations, and the like in a control plane.

  A connection interface between an eNB that is an example of a base station (any of MeNB and HeNB) and an MME that is an example of a core node may be referred to as an “S1 interface”. Connection by the S1 interface may be referred to as “S1 connection” for convenience. “S1 connection” is an example of “base station-core node connection”.

  For convenience, the signals and messages transmitted and received by the “S1 connection” may be referred to as S1 signals (or S1AP signals) or S1 messages (or S1AP messages). “AP” is an abbreviation for “Application Protocol”. The S1 message is an example of a “base station-core node message”.

  As illustrated in FIG. 2, the macro cell MC # i formed by the MeNB # i includes one or a plurality of HeNB # j (j = 1 to m, where m is a natural number). May be. Each HeNB # j may form a small cell SC # j.

  When it is not necessary to distinguish between the HeNB # j and the small cell SC # j, they may be expressed as “HeNB” and “small cell SC”, respectively. Moreover, when it is not necessary to distinguish MeNB and HeNB, it may only describe with "eNB".

  Similarly to the MeNB # i, the HeNB # j may be communicably connected to the MME through the S1 interface. However, it is assumed that the HeNB is installed in a larger amount in the wireless communication system 1 than the MeNB that forms the macro cell MC. If a large number of HeNBs are directly connected to the MME via S1, the load on the MME may increase.

  In order to suppress or reduce an increase in the load on the MME, the HeNB # j may not be directly connected to the MME by S1, but may be connected to the gateway (GW) by S1 as schematically illustrated in FIG. The GW to which the HeNB # j is connected to the S1 may be referred to as “HeNB GW” for convenience.

  One HeNB GW accommodating a plurality of HeNB # j makes S1 connections to the MME, whereby the number of S1 connections managed by the MME can be reduced. Therefore, the load on the MME can be reduced.

  For example, the HeNB GW may aggregate and notify the SME message received from the HeNB # j and the SCTP message belonging to the lower layer of the S1 connection to the MME. “SCTP” is an abbreviation for “Stream Control Transmission Protocol”.

  For example, in the wireless communication system 1, it is assumed that there are 100 HeNBs # 1 to # 100. When each of the 100 HeNBs directly connects to the MME with S1, 100 sets of SCTP connections and S1 connections are established, so the MME manages 100 sets of SCTP connections and S1 connections.

  On the other hand, as illustrated in FIG. 3, when the HeNB GW is installed, the HeNB GW terminates the SCTP connection and the S1 connection with the HeNB, and sets one SCTP connection and Establish S1 connection.

  In addition, the HeNB GW associates 100 sets of SCTP connections and S1 connections with 100 HeNBs and one set of SCTP connections and S1 connections with the MME. Thereby, MME should just manage 1 set of SCTP connections and S1 connections between HeNB GW, and a load is reduced.

  Of SCTP connections and S1 connections between HeNB and HeNB GW, how many sets of SCTP and S1 connections are associated with one set of SCTP connection and S1 connection between HeNB GW and MME, and which The implementation matter may be used to relate with such logic.

  Further, regardless of whether or not the HeNB GW is installed in the wireless communication system 1, the format of the S1 message may not be changed. This is because, even when the HeNB GW is installed, the SCTP connection and the S1 connection are associated one-to-one as illustrated in FIG.

  By the way, in LTE, in addition to the S1 interface, an X2 interface is defined. The X2 interface is an example of an interface between base stations for performing communication between base stations.

  For example, the MeNB # i illustrated in FIG. 1 can be connected to each other via the X2 interface and communicate via the X2 interface, as illustrated in FIG.

  Connection by the X2 interface may be referred to as “X2 connection” for convenience. X2 connection is an example of “inter-base station connection”. For convenience, signals and messages transmitted and received through the X2 connection may be referred to as X2 signals (or X2AP signals) or X2 messages (or X2AP messages). The X2 message is an example of the “inter-base station message”.

  Moreover, as illustrated in FIG. 2, when HeNB # j is installed in the wireless communication system 1, as illustrated in FIG. 5, between MeNB-MeNB, between MeNB-HeNB, and between HeNB-HeNB. Each may be X2 connected, and communication between base stations by X2 connection may be performed.

  Here, when HeNB # j installed in large quantities in the radio | wireless communications system 1 connects X2 directly with respect to MeNB # i, the load of MeNB may increase.

  In order to suppress or reduce the increase in the load of the MeNB, in 3GPP Release 12 (3GPP Rel. 12) and later, the HeNB is not directly connected to the MeNB by X2, but as shown schematically in FIG. X2 connection is being considered. The GW to which the HeNB is X2 connected may be referred to as “X2 GW” for convenience.

  One X2 GW to which a plurality of HeNBs are X2 connected can connect to the MeNB, so that the number of SCTP connections that belong to the lower layer of the X2 connection managed by the MeNB can be reduced.

  For example, the X2 GW may collect and notify the SCNB messages belonging to the lower layer of the X2 connection received from the HeNB to the MeNB.

  For example, it is assumed that 100 HeNBs # 1 to # 100 exist in the wireless communication system 1. Since 100 HeBNs establish SCTP connection and X2 connection, respectively, when 100 HeNBs directly connect with MeNB by X2, MeNB manages 100 sets of SCTP connection and X2 connection.

  In contrast, as illustrated in FIG. 6, when the HeNB GW is installed in the wireless communication system 1, the X2 GW terminates the SCTP connection with the HeNB and establishes one SCTP connection with the MeNB. May be connected.

  In addition, the X2 GW may associate 100 sets of SCTP and X2 connections with the HeNB and one SCTP connection with the MeNB. As a result, the MeNB has only to manage one SCTP connection and 100 X2 connections, for example, and the load is reduced.

  Note that X2 messages in different formats may be used in the case of direct X2 connection between the MeNB-MeNB, the HeNB-MeNB, and the HeNB-HeNB and the case of the X2 connection via the X2 GW. .

  In the case of X2 connection via X2 GW, as illustrated in FIG. 6, between the MeNB and X2 GW, the X2 connection is not aggregated into one in one SCTP connection, and the SCTP connection and the X2 connection are This is because they are not necessarily associated one-to-one.

  When the X2 connection is via the X2 GW, as illustrated in FIG. 7, an X2 message obtained by encapsulating the X2 message not via the X2 GW together with the RNL header may be used. The X2 message may be referred to as “X2AP: MESSAGE TRANSFER”. “RNL” is an abbreviation for “Radio Network Layer”. The RNL header is an example of an information element (Information Element, IE) of “X2AP: MESSAGE TRANSFER”.

  As illustrated in FIG. 8, the RNL header may include a source eNB identifier (Source eNB ID) and a destination eNB identifier (Target eNB ID) as an example of IE.

  “ENB ID” is an example of eNB identification information. “Source eNB ID” is an example of the source information of the encapsulated X2 message, and “Target eNB ID” is an example of the destination information of the encapsulated X2 message.

  When the X2 GW receives “X2AP: MESSAGE TRANSFER”, the X2 GW may determine the transfer destination of the received “X2AP: MESSAGE TRANSFER” with reference to the destination information “Target eNB ID”.

  FIG. 9 shows a transfer example of “X2AP: MESSAGE TRANSFER”. FIG. 9 illustrates a mode in which three HeNBs # 1 to # 3 are connected to the X2 GW in the same manner as in FIG. Also, it is assumed that the eNB IDs of HeNB # 1 to # 3 are H1, H2, and H3, respectively, and the eNB of MeNB # 1 is M1.

  When transmitting “X2AP: MESSAGE TRANSFER” to the MME, HeNB # 1 sets “H1” to “Source eNB ID” and “M1” to “Target eNB ID”. Is transmitted to the X2 interface.

  When the X2 GW receives the “X2AP: MESSAGE TRANSFER” through the X2 interface, the X2 GW refers to the “Target eNB ID”. Since “M1” that is the eNB ID of MeNB # 1 is set in “Target eNB ID”, the X2 GW transfers the received “X2AP: MESSAGE TRANSFER” to MeNB # 1.

  The same applies when HeNB # 2 and HeNB # 3 transmit "X2AP: MESSAGE TRANSFER" to MeNB # 1.

  Further, when transmitting “X2AP: MESSAGE TRANSFER” to HeNB # 2, HeNB # 3 sets “H3” to “Source eNB ID” and “X2AP” sets “H2” to “Target eNB ID”. : MESSAGE TRANSFER "and send it to the X2 interface.

  When the X2 GW receives the “X2AP: MESSAGE TRANSFER” through the X2 interface, the X2 GW refers to the “Target eNB ID”. Since “H2” that is the eNB ID of HeNB # 2 is set in “Target eNB ID”, the X2 GW transfers the received “X2AP: MESSAGE TRANSFER” to HeNB # 2.

  The same applies when HeNB # 3 sends "X2AP: MESSAGE TRANSFER" to HeNB # 1, HeNB # 1 to HeNB # 2 or # 3, or HeNB # 2 to HeNB # 1 or # 3. It is.

  Note that the X2 GW uses an eNB ID (eNB ID) and an IP (Internet Protocol) address to enable transfer of “X2AP: MESSAGE TRANSFER” to the eNB specified by the “Target eNB ID”. Store it in association. The IP address is an example of address information.

  For example, the eNB connected to the X2 GW may transmit “X2AP: MESSAGE TRANSFER” that does not include the “Target eNB ID” and the X2 message to the X2 GW at the time of startup or the like.

  The X2 GW associates the eNB ID set in the “Source eNB ID” with the IP address that is an example of the source address of the “X2AP: MESSAGE TRANSFER” by receiving the “X2AP: MESSAGE TRANSFER”. It is possible to memorize.

(X2 connection establishment procedure)
Next, an example of the procedure for establishing the X2 connection will be described.
When the first eNB detects that another second eNB exists in the vicinity, the first eNB may attempt to establish an X2 connection to the second eNB. Both the first eNB and the second eNB may be MeNB or HeNB.

  Existence of the second eNB is exemplified by the fact that UE (User Equipment) located in both the first eNB and the second eNB cell includes the second eNB included in the signal received from the second eNB. May be detected by notifying the first eNB of the ID of the eNB. Note that the UE is an example of a wireless terminal or a wireless device.

  For the establishment of the X2 connection, for example, the IP address of each eNB that performs the X2 connection may be used. Therefore, the first eNB acquires the IP address of the second eNB when establishing an X2 connection with the second eNB.

  For example, the MME connected to the second eNB by the S1 interface can acquire the IP address of the second eNB using the S1 message.

  Therefore, when the first eNB establishes an X2 connection not via the X2 GW with the second eNB, as schematically illustrated in FIG. 10, as illustrated in the following procedure, The IP address may be obtained by inquiring of the MME.

  In FIG. 10, it is assumed that the eNB ID of eNB # 1 is “A” and the IP address is “a”. Also, it is assumed that the eNB ID of eNB # 2 is “B” and the IP address is “b”.

  (Procedure 1) The eNB # 1 that has detected the presence of the eNB # 2 sets the eNB ID = B of the partner eNB # 2 whose IP address is to be known in the S1 message “S1AP: eNB CONFIGURATION TRANSFER”, and sends the S1 message It may be sent to the MME.

  The eNB ID of the eNB that wants to know the IP address may be set to “Target eNB ID” that is an IE of “S1AP: eNB CONFIGURATION TRANSFER”, as shown in FIG. 12, for example. When the eNB that wants to know the IP address is a HeNB, “X2 TNL Configuration Info.” May be specified in “SON Information Request” of “S1AP: eNB CONFIGURATION TRANSFER”.

  (Procedure 2) Upon receiving “S1AP: eNB CONFIGURATION TRANSFER”, the MME transmits “S1AP: MME CONFIGURATION TRANSFER” requesting an IP address response to the eNB # 2 having the requested eNB ID = “B”. You can do it.

  (Procedure 3) Upon receiving “S1AP: MME CONFIGURATION TRANSFER”, the eNB # 2 requested to respond to the IP address performs “S1AP: eNB CONFIGURATION TRANSFER” in which the IP address of the eNB # 2 = “b” is set. You may reply to the MME.

  Note that the eNB ID of the eNB requested to respond to the IP address (in other words, the inquired) is the “Target eNB-ID” (for example, see FIG. 13) that is an IE of “S1AP: eNB CONFIGURATION TRANSFER”. May be set.

  (Procedure 4) When the MME receives “S1AP: eNB CONFIGURATION TRANSFER” transmitted by the eNB # 2, the MME transmits “S1AP: MME CONFIGURATION TRANSFER” in which the IP address = “b” is set to the eNB # that is the IP address request source. Send to 1

  (Procedure 5) The eNB # 1 can obtain the IP address = b of the partner eNB # 2 by receiving the “S1AP: MME CONFIGURATION TRANSFER” from the MME. Therefore, eNB # 1 can request establishment of X2 connection to the partner eNB # 2 using the IP address = b.

  As described above, when trying to establish an X2 connection not via the X2 GW, the eNB # 1 may inquire the IP address of the partner eNB # 2 to the MME using “S1AP eNB CONFIGURATION TRANSFER”.

  On the other hand, as schematically illustrated in FIG. 11, the eNB # 1 that supports the X2 GW and the X2 connection, the eNB # 2 that also supports the X2 connection with the X2 GW, and the X2 via the X2 GW. Assume that a connection is established.

  In this case, eNB # 1 can acquire the IP address which partner eNB # 2 uses for X2 connection with X2 GW with the following procedures, for example.

  (Procedure 1) When eNB # 1 wants to know the IP address used by partner eNB # 2 for X2 connection with X2 GW, "S1AP: eNB CONFIGURATION TRANSFER" including "IE: eNB Indirect X2 Transport Layer Addresses" It may be sent to the MME. In “IE: eNB Indirect X2 Transport Layer Addresses” (see FIG. 12), the IP address of the X2 GW to which the eNB # 1 can be connected may be set.

  (Procedure 2) The “S1AP: eNB CONFIGURATION TRANSFER” is transferred from the MME to the destination eNB # 2, as in the example of FIG.

  (Procedure 3) The eNB # 2 sets “S1AP: eNB CONFIGURATION TRANSFER” in which the IP address of the X2 GW to which the eNB # 2 can connect X2 is set to “IE: eNB Indirect X2 Transport Layer Addresses” (see FIG. 13). It may be generated and sent back to the MME.

  (Procedure 4) The MME generates “S1AP: MME CONFIGURATION TRANSFER” in which the IP address of the X2 GW notified by the “S1AP: eNB CONFIGURATION TRANSFER” is set to “IE: eNB Indirect X2 Transport Layer Addresses”. Good. The MME may notify and respond to the IP address requesting eNB # 1 of the IP address of the X2 GW by transmitting the “S1AP: MME CONFIGURATION TRANSFER” to the eNB # 1.

  (Procedure 5) By receiving the “S1AP: MME CONFIGURATION TRANSFER” from the MME, the eNB # 1 can acquire the IP address used by the partner eNB # 2 for the X2 connection with the X2 GW.

  Therefore, the eNB # 1 can request the establishment of the X2 connection with the partner eNB # 2 via the X2 GW to the X2 GW to which the partner eNB # 2 can connect X2 using the IP address.

  By the way, as described above, the X2 GW is installed to reduce the load of the MeNB even if a large amount of HeNB is installed in the cell of the MeNB. However, as described above, when X2 messages having different formats are used for the X2 connection via the X2 GW and the X2 connection not via the X2 GW, the compatibility with the existing network may be deteriorated.

  For example, when the MeNB before 3GPP Rel. 11 tries to connect to the HeNB via X2, “S1AP: eNB CONFIGURATION TRANSFER” sent to the MME is “IE: eNB Indirect X2 Transport Layer Addresses” for X2 GW. Not set.

  On the other hand, the HeNB after 3GPP Rel. 12 sets “IE: eNB Indirect X2 Transport Layer Addresses” in “S1AP: MME CONFIGURATION TRANSFER” used for a response addressed to the MME. However, the MeNB before 3GPP Rel. 11 cannot read the IE.

  Therefore, the installation of the X2 GW is based on the premise that the MeNB supports the X2 connection with the X2 GW defined by the 3GPP Rel. 12 or later version.

  Therefore, in the wireless communication system 1, in the wireless communication system 1, an example of a technique that enables an appropriate X2 connection between any eNBs even if a MeNB that supports X2 connection with the X2 GW and a MeNB that does not support it coexist. explain.

  In the following description, a MeNB of a version prior to 3GPP Rel. 11 or a MeNB that is a version of 3GPP Rel. 12 or later but does not support connection with X2 GW is referred to as “LMeNB (Legacy MeNB) ”.

  As a specific example, as illustrated in FIG. 14 and FIG. 15, a radio communication system 1 including an LMeNB, MeNB, HeNB, HeNB GW, X2 GW, and MME will be described as an example.

  The LMeNB is an example of a “first base station”, and the HeNB is an example of a “second base station”. The HeNB GW is an example of a “first relay node” that relays communication between the MME and the HeNB. The X2 GW is an example of a “second relay node” to which the HeNB can connect X2.

  HeNB GW illustrated in FIG.14 and FIG.15 may implement the following processes as an example.

  (1) In addition to the first address information (for example, IP address) used for communication in the S1 connection, the HeNB GW has additional second address information (for example, IP address) used for establishing the X2 connection. Address) may be assigned.

  The second IP address may be referred to as a “pseudo X2 connection IP address” for convenience. The second IP address may be used, for example, when the LMeNB establishes an X2 connection via the X2 GW with a HeNB capable of X2 connection to the HeNB GW.

  (2) When the MeNB or LMNB requests the IP address of the HeNB to the MME in order to establish the X2 connection with the HeNB, as illustrated in FIG. 14 and FIG. 15, “S1AP: MME CONFIGURATION TRANSFER” is transmitted from the MME. Received by the HeNB GW. The operation examples illustrated in FIGS. 14 and 15 will be described later.

  The HeNB GW confirms the IE configuring “S1AP: MME CONFIGURATION TRANSFER” received from the MME, and is “IE: eNB Indirect X2 Transport Layer Addresses” set (may be referred to as “selection”)? It may be determined whether or not.

  If “IE: eNB Indirect X2 Transport Layer Addresses” is selected, the “S1AP: MME CONFIGURATION TRANSFER” can be determined to be an S1 message transmitted to the MME by the MeNB that supports the X2 connection with the X2 GW. .

  On the other hand, if “IE: eNB Indirect X2 Transport Layer Addresses” is not selected, the “S1AP: MME CONFIGURATION TRANSFER” is an S1 message transmitted to the MME by the LMeNB that does not support the X2 connection with the X2 GW. Can be judged.

  The HeNB GW may transfer (may be referred to as “transmission”) to the HeNB for “S1AP: MME CONFIGURATION TRANSFER” in which “IE: eNB Indirect X2 Transport Layer Addresses” is selected.

  For “S1AP: MME CONFIGURATION TRANSFER” in which “IE: eNB Indirect X2 Transport Layer Addresses” is not selected, the HeNB GW may be terminated without being transferred to the HeNB.

  In addition, the HeNB GW may transmit a pseudo X2 connection IP address that is an example of the IP address of the HeNB GW to the MME. The pseudo X2 connection IP address may be set, for example, in “IE: eNB Indirect X2 Transport Layer Addresses” in “S1AP: eNB CONFIGURATION TRANSFER” addressed to the MME.

  In addition, the HeNB GW may store the eNB ID set in each of “IE: Target eNB ID” and “IE: Source eNB ID” in the received “S1AP: MME CONFIGURATION TRANSFER”.

  Illustratively, the HeNB GW registers the X2 mapping table 19 as shown in FIG. 17 in association with the eNB ID set in each of “IE: Target eNB-ID” and “IE: Source eNB ID”. You may remember.

  Here, the eNB ID set in “IE: Target eNB ID” illustratively corresponds to the eNB ID of the HeNB to which the LMeNB has attempted X2 connection. The eNB ID set in “IE: Source eNB ID” illustratively corresponds to the eNB ID of the LMeNB that attempted X2 connection to the HeNB.

  In the X2 mapping table 19, flag information (for example, Yes or No) indicating whether or not the X2 connection has been established may be registered together. The flag information may be referred to as “X2 establishment flag” for convenience. Since the X2 connection is not established at the time when the above association is registered in the X2 mapping table 19, the X2 establishment flag may be set to information indicating “No”.

(Address acquisition process)
Hereinafter, with reference to FIG. 14 to FIG. 18, an operation example focusing on IP address acquisition processing when the MeNB and LMNB try to establish an X2 connection via the HeNB and the X2 GW will be described.

  FIG. 14 shows an example of message transfer when the MeNB tries to make an X2 connection with the HeNB, and FIG. 15 shows an example of message transfer when the LMeNB attempts an X2 connection with the HeNB. Moreover, FIG. 16 is a flowchart which shows the operation example which paid its attention to HeNB GW in the example of FIG.14 and FIG.15. FIG. 18 is a sequence diagram corresponding to the example of FIG.

  As illustrated in FIG. 14, when the MeNB supporting the X2 connection with the X2 GW attempts to establish an X2 connection via the HeNB and the X2 GW, the HeNB uses an IP address used for the X2 connection with the X2 GW as the MME. You may contact (or request)

  For example, the MeNB may transmit an S1 message “S1AP: eNB CONFIGURATION TRANSFER” in which “IE: eNB Indirect X2 Transport Layer Addresses” (see FIG. 12) is set to the MME (procedure 1). The S1 message is an example of a message in which the eNB requests an IP address from the MME, and may be referred to as an “eNB address request message” for convenience.

  When receiving the eNB address request message “S1AP: eNB CONFIGURATION TRANSFER” transmitted from the MeNB, the MME may transmit “S1AP: MME CONFIGURATION TRANSFER” to the HeNB (step 2).

  “S1AP: MME CONFIGURATION TRANSFER” is an example of an S1 message in which the MME requests an IP address from the eNB, and may be referred to as an MME address request message for convenience.

  Here, the MME may set “IE: eNB Indirect X2 Transport Layer Addresses” of the eNB address request message received from the MeNB in the MME address request message.

  With the setting of “IE: eNB Indirect X2 Transport Layer Addresses”, the HeNB can request the IP address of the X2 GW that can connect to the X2 by the MME address request message.

  The MME address request message “S1AP: MME CONFIGURATION TRANSFER” transmitted from the MME to the HeNB is received by the HeNB GW to which the destination HeNB is connected before reaching the destination HeNB.

  When the HeNB GW receives the MME address request message “S1AP: MME CONFIGURATION TRANSFER” (process P10 in FIG. 16), the HeNB GW may confirm the IE configuring the message (process P11 to P13 in FIG. 16).

  For example, the HeNB GW may confirm whether “IE: SON Information Request” is selected in “IE: SON Information” of the received “S1AP: MME CONFIGURATION TRANSFER” (process P11).

  If “IE: SON Information Request” is selected (YES in process P11), the HeNB GW further confirms whether “X2 TNL Configuration Info.” Is selected in “IE: SON Information Request”. (Process P12).

  If “X2 TNL Configuration Info.” Is selected (YES in process P12), the HeNB GW determines whether “IE: eNB Indirect X2 Transport Layer Addresses” is set in “X2 TNL Configuration Info.”. You may confirm (process P13).

  In the example of FIG. 14, “IE: eNB Indirect X2 Transport Layer Addresses” is set in the MME address request message “S1AP: MME CONFIGURATION TRANSFER” received from the MME.

  Therefore, the HeNB GW may transfer the MME address request message “S1AP: MME CONFIGURATION TRANSFER” to the HeNB (may be referred to as “transparency”) (process P15 and procedure 3 in FIG. 14).

  Even when “IE: SON Information Request” is not selected in “IE: SON Information” (NO in process P11 in FIG. 16), the HeNB GW transfers the received “S1AP: MME CONFIGURATION TRANSFER” to the HeNB. You can do it.

  Similarly, when “IE: SON Information Request” is selected but “X2 TNL Configuration Info.” Is not selected (YES in process P11 and NO in process P12), the received “S1AP: MME CONFIGURATION TRANSFER” is also received. May be forwarded to the HeNB.

  When the HeNB receives the MME address request message “S1AP: MME CONFIGURATION TRANSFER” transferred from the HeNB GW, the HeNB may reply to the MME with the IP address of the X2 GW to which the HeNB can connect X2 (FIG. 14). Procedure 4).

  For example, “S1AP: eNB CONFIGURATION TRANSFER” may be used for the IP address response. The S1 message is an example of a message in which an eNB that has received an inquiry about an IP address responds to the MME with an IP address, and may be referred to as an “eNB address response message” for convenience.

  For example, the HeNB generates an eNB address response message “S1AP: eNB CONFIGURATION TRANSFER” in which the IP address of the X2 GW is set to “IE: eNB Indirect X2 Transport Layer Addresses” (see FIG. 13), and returns the response to the MME. You can do it.

  The eNB address response message “S1AP: eNB CONFIGURATION TRANSFER” is received by the HeNB GW before reaching the MME. The HeNB GW may confirm the IE in the same manner as the processes P11 to P13 described above in response to the reception of the eNB address response message “S1AP: eNB CONFIGURATION TRANSFER”.

  Here, “IE: eNB Indirect X2 Transport Layer Addresses” is set in the eNB address response message “S1AP: eNB CONFIGURATION TRANSFER” transmitted by the HeNB. Therefore, it is determined as YES in processes P11 to P13 of FIG.

  Accordingly, the HeNB GW may transfer the eNB address response message “S1AP: eNB CONFIGURATION TRANSFER” received from the HeNB to the MME (process P15 in FIG. 16 and procedure 5 in FIG. 14).

  The MME may generate an S1 message “S1AP: MME CONFIGURATION TRANSFER” in which the IP address of the X2 GW notified in the eNB address response message is set to “IE: eNB Indirect X2 Transport Layer Addresses”.

  The S1 message is an example of a message in which the MME returns or responds to the IP address request source (in other words, the source of the eNB address request message). For convenience, the SME message is referred to as an “MME address response message”. You may call it.

  The MME may transmit the generated MME address response message “S1AP: MME CONFIGURATION TRANSFER” to the MeNB that is the address request source. When the MeNB receives the MME address response message, the IP address of the X2 GW is notified to the MeNB (procedure 6 in FIG. 14).

  As described above, the MeNB can acquire the IP address by inquiring the MME from the S1 message about the IP address used by the HeNB for the X2 connection with the X2 GW.

  As illustrated in FIG. 11, the MeNB can request the X2 GW to which the HeNB can connect X2 to establish the X2 connection with the HeNB via the X2 GW using the acquired IP address. Thereby, MeNB can establish X2 connection via HeNB and X2 GW.

  Next, an operation example when the LMeNB tries to establish an X2 connection with the HeNB via the X2 GW will be described.

  As illustrated in FIG. 15, the LMeNB may transmit an eNB address request message “S1AP: eNB CONFIGURATION TRANSFER” requesting the HeNB IP address to the MME (procedure 1 and process P21 in FIG. 18).

  In the eNB address request message “S1AP: eNB CONFIGURATION TRANSFER”, the eNB ID of the HeNB that the LLMeNB wants to know the IP address is set in “Target eNB ID” of “IE: SON Configuration Transfer” (see FIG. 12). Good. Further, since the eNB that wants to know the IP address is a HeNB, “X2 TNL Configuration Info.” May be specified in “IE: SON Information Request”.

  However, since the LMeNB does not support X2 connection with the X2 GW, “IE: eNB Indirect X2 Transport Layer Addresses” is not set in “X2 TNL Configuration Info.” It may be said).

  When the MME receives the eNB address request message from the LMeNB, the MME may request the reply of the IP address by transmitting the MME address request message “S1AP: MME CONFIGURATION TRANSFER” to the HeNB, as in the example of FIG. . This process corresponds to procedure 2 in FIG. 15 and process P22 in FIG.

  Here, in the eNB address request message “S1AP: eNB CONFIGURATION TRANSFER” received by the MME from the LM eNB, “IE: eNB Indirect X2 Transport Layer Addresses” set when X2 connection with the X2 GW is possible is set. Not.

  Therefore, “IE: eNB Indirect X2 Transport Layer Addresses” is not set in the MME address request message “S1AP: MME CONFIGURATION TRANSFER” transmitted from the MME to the HeNB.

  The MME address request message “S1AP: MME CONFIGURATION TRANSFER” transmitted from the MME to the HeNB is received by the HeNB GW before reaching the destination HeNB.

  Since the HeNB GW receives “S1AP: MME CONFIGURATION TRANSFER”, the HeNB GW may perform the IE confirmation (may be referred to as “determination process”) exemplified in the processes P11 to P13 in FIG. 16 (the process in FIG. 18). P23).

  Here, in the MME address request message “S1AP: MME CONFIGURATION TRANSFER” received by the HeNB GW from the MME, “IE: SON Information Request” is set, and “IE: X2 TNL Configuration Info.” Is specified. Yes. Therefore, YES is determined in the processes P11 and P12 of FIG.

  However, since “IE: eNB Indirect X2 Transport Layer Addresses” that is set when X2 connection with the X2 GW is possible is not set in “IE: X2 TNL Configuration Info.”, The process P13 of FIG. Is determined as NO. In other words, the HeNB GW may determine that the transmission source of the MME address request message received from the MME is the LMNB.

  Accordingly, the HeNB GW may terminate the MME address request message “S1AP: MME CONFIGURATION TRANSFER” received from the MME without forwarding it to the HeNB.

  In addition, the HeNB GW may respond to and notify the MME of the IP address of the HeNB GW. This process corresponds to, for example, the procedure 4 in FIG. 15, the process P14 in FIG. 16, and the process P25 in FIG.

  The IP address of the HeNB GW that responds to and notifies the MME may be the above-described pseudo X2 connection IP address. For example, the HeNB GW generates “S1AP: eNB CONFIGURATION TRANSFER” in which the IP address for pseudo X2 is set in “IE: Target eNB ID” of “IE: SON Configuration Transfer” illustrated in FIG. May be sent.

  In addition, as illustrated in FIG. 17, the HeNB GW associates the eNB ID set in each of the “Source eNB ID” and “Target eNB ID” of the MME address request message received from the MME with the X2 mapping table. 19 may be stored.

  In the example of FIG. 15, the “Source eNB ID” of the MME address request message is set to the eNB ID of the LMeNB, and the “Target eNB ID” is the eNB ID of the HeNB to which the LMeNB has attempted X2 connection. Is set.

  Therefore, the HeNB GW may associate and register the eNB ID of the LMeNB and the eNB ID of the HeNB to which the LMeNB has attempted X2 connection in the X2 mapping table 19.

  The registration to the X2 mapping table 19 may be performed before or after the eNB address response message “S1AP: eNB CONFIGURATION TRANSFER” in which the IP address of the HeNB GW is set is sent back to the MME, and in parallel with the reply processing. May be implemented.

  In FIG. 18, as a non-limiting example, a registration process P24 to the X2 mapping table 19 is performed after the determination process P23 and before the reply process P25 of the eNB address response message “S1AP: eNB CONFIGURATION TRANSFER”. The embodiment to be shown is shown.

  The MME may generate an MME address response message “S1AP: MME CONFIGURATION TRANSFER” including the IP address of the HeNB GW notified from the HeNB GW by the eNB address response message, and transmit the MME address response message to the LMeNB. This process corresponds to, for example, the procedure 5 in FIG. 15 and the process P26 in FIG.

  Also in the MME address response message “S1AP: MME CONFIGURATION TRANSFER”, the IP address of the HeNB GW may be set to “IE: Target eNB ID” of “IE: SON Configuration Transfer” as illustrated in FIG. .

  By receiving the MME address response message “S1AP: MME CONFIGURATION TRANSFER” from the MME, the LMNB acquires the IP address of the HeNB GW instead of the IP address of the HeNB that has attempted to establish the X2 connection.

  However, the LMeNB recognizes that the acquired IP address of the HeNB GW is the IP address of the HeNB that is attempting to establish the X2 connection. Therefore, the LMeNB is actually making a request to the HeNB GW even though it intends to request the HeNB to establish an X2 connection using the acquired IP address.

  When the establishment of the X2 connection from the LMeNB to the HeNB is requested, the HeNB GW may perform an X2 connection establishment process via the X2 GW between the LMeNB and the HeNB based on, for example, an entry in the X2 mapping table 19.

(X2 connection establishment process via X2 GW)
Hereinafter, the establishment process of the X2 connection between the LMeNB and the HeNB via the X2 GW will be described with reference to FIGS.

  The HeNB GW may confirm whether or not an X2 connection has already been established with the registered LMeNB after the entry registration in the X2 mapping table 19 (process P31 in FIG. 21 and process P41 in FIG. 22).

  If the X2 connection with the LMeNB is not established (NO in the process P31 in FIG. 21 and the process P41 in FIG. 22), the HeNB GW receives the X2 message “X2AP: X2 SETUP REQUEST” requesting establishment of the X2 connection from the LMeNB. The process enters a waiting state (process P32 in FIG. 21). The X2 message may be referred to as an “X2 connection establishment request message” for convenience.

  When receiving “X2AP: X2 SETUP REQUEST” from the LMeNB, the HeNB GW may return the response message “X2AP: X2 SETUP RESPONSE” to the LMeNB and establish the X2 connection with the LMeNB. This process corresponds to, for example, the procedures 1 and 2 in FIG. 19 and the processes P42 and P43 in FIG.

  The HeNB GW transmits the “X2AP: X2 SETUP RESPONSE” to the LMeNB so that the LMeNB can recognize that the X2 connection with the HeNB that wants to establish the X2 connection is normally established.

  In other words, as illustrated in the procedure 5 of FIG. 10, if the LMeNB transmits “X2AP: X2 SETUP REQUEST” to the HeNB desiring to establish the X2 connection as usual, the X2 connection with the HeNB is normal. Can be established.

  Then, HeNB GW may confirm whether X2 connection with LMeNB was established (process P33 of FIG. 21, and process P44 of FIG. 22).

  If the X2 connection with the LMeNB has been established (YES in process P33 and process P44), the HeNB GW may start the process of establishing the X2 connection with the HeNB via the X2 GW (procedure 3 in FIG. 19). . Thereby, HeNB GW can start establishment of X2 connection with HeNB via X2 GW, without burdening an additional process with respect to LMNB.

  For example, the HeNB GW may encapsulate “X2AP: X2 SETUP REQUEST” received from the LMeNB in a transfer message “X2AP: X2AP MESSAGE TRANSFER” and transmit it to the X2 GW. This process corresponds to, for example, the procedure 3 in FIG. 19, the process P34 in FIG. 21, and the process P45 in FIG.

  As illustrated in FIG. 20, “IE: Source eNB ID” of “IE: RNL Header” included in the transfer message “X2AP: X2AP MESSAGE TRANSFER” is the transmission source of “X2AP: X2 SETUP REQUEST”. The eNB ID of the LMeNB may be set. Further, in the “IE: Target eNB ID”, the eNB ID of the HeNB associated with the eNB ID of the LMeNB in the X2 mapping table 19 may be set.

  When the X2 GW receives “X2AP: X2AP MESSAGE TRANSFER” from the HeNB GW, the X2AP sends the received “X2AP: X2AP MESSAGE TRANSFER” to the HeNB identified by the eNB ID set in “IE: Target eNB ID”. May be forwarded.

  When the HeNB receives “X2AP: X2 MESSAGE TRANSFER” from the X2 GW, the response message “X2AP: X2 SETUP RESPONSE” to “XAP: X2 SETUP REQUEST” is encapsulated in “X2AP: X2 MESSAGE TRANSFER” and addressed to the X2 GW Send back.

  The above-described transmission / reception process of “X2AP: X2 MESSAGE TRANSFER” between the X2 GW and the HeNB is illustratively equivalent to the processes P46 and P47 of FIG. 22, whereby the X2 connection between the X2 GW and the HeNB Established.

  When the “X2AP: X2 MESSAGE TRANSFER” including “X2AP: X2 SETUP RESPONSE” is received from the HeNB, the X2 GW may transfer the “X2AP: X2 MESSAGE TRANSFER” to the HeNB GW (processing in FIG. 22). P48).

  When the HeNB GW receives “X2AP: X2 MESSAGE TRANSFER” including “X2AP: X2 SETUP RESPONSE” from the X2 GW, the X2 connection between the HeNB GW and the X2 GW is established. Thereby, X2 connection via X2 GW is established between HeNB GW and HeNB (process P34 of FIG. 21). Therefore, X2 connection via HeNB GW and X2 GW is established between LMeNB and HeNB.

  When the X2 connection between the LMeNB and the HeNB is established, the HeNB GW updates the X2 establishment flag of the entry corresponding to the LMeNB and the HeNB with which the X2 connection has been established in the X2 mapping table 19 to information indicating established (Yes). It's okay. This process corresponds to, for example, the process P35 in FIG. 21 and the process P49 in FIG.

  Note that there may be a case where the LMeNB registered in the X2 mapping table 19 has already established an X2 connection with one or more other HeNBs.

  In other words, the LMeNB registered in the X2 mapping table 19 and the HeNB GW may have already established an X2 connection. In this case, in the X2 mapping table 19, for example, as illustrated in FIG. 23, another entry whose X2 establishment flag is “Yes” has already been registered for the LMeNB having the same eNB ID.

  If another entry whose X2 establishment flag is “Yes” has already been registered, the HeNB GW does not wait for the reception of “X2AP: X2 SETUP REQUEST” from the LMeNB, and the X2 via the X2 GW with the HeNB described above. A connection establishment process may be started.

  The process corresponds to, for example, a process in a case where YES is determined in the procedure 3 in FIG. 19 and the process P31 in FIG. 21 and the process P41 in FIG.

  Accordingly, the HeNB GW can quickly establish an X2 connection via the X2 GW with the HeNB to which the LMeNB desires an X2 connection without burdening the LMeNB with additional processing.

  In addition, although the establishment process of the X2 connection is started, for example, when the X2 connection cannot be established even after a certain set time has elapsed (NO in the process P33 of FIG. 21 and the process P44 of FIG. 22), the HeNB GW The process may be terminated without updating the X2 establishment flag.

(Message transfer process in X2 connection between LMeNB and HeNB)
Next, an example of the message transfer process in the X2 connection established between the LMeNB and the HeNB as described above will be described with reference to FIGS.

  The HeNB GW may relay the X2 message transmitted / received through the X2 connection established between the LMeNB and the HeNB based on the entry of the X2 mapping table 19.

  For example, the relay process may include a process of encapsulating an X2 message and a process of releasing the encapsulated X2 message (may be referred to as “decapsulation”).

  The encapsulation of the X2 message and the decapsulation of the encapsulated X2 message may be regarded as an example of the format conversion of the X2 message. The format conversion may be regarded as conversion between the old and new X2 interfaces.

  For example, it may be considered that the X2 interface used for the X2 connection by the LMeNB corresponds to the “old X2 interface”, and the X2 interface used by the 3GPP Rel. 12 or later version eNB for the X2 connection corresponds to the “new X2 interface”.

  By the mutual conversion of the old and new X2 interfaces in the HeNB GW, it becomes possible to normally connect the old X2 interface of the LMeNB and the new X2 interface of the X2 GW to which the HeNB connects with the new X2 interface.

  24 and 28 show an example of the X2 message transfer process from the HeNB to the LMeNB, and FIGS. 25 and 29 show an example of the X2 message transfer process from the LMeNB to the HeNB. FIG. 26 shows an operation example in the HeNB GW corresponding to FIGS. 24 and 28, and FIG. 27 shows an operation example in the HeNB GW corresponding to FIGS.

  (Transfer process of X2 message from HeNB to LMeNB)

  As illustrated in FIG. 24 and FIG. 28, it is assumed that the HeNB transmits “X2AP: X2AP MESSAGE TRANSFER” in which the X2 message is encapsulated to the LMeNB (procedure 1 in FIG. 24 and process P71 in FIG. 28). ).

  The “X2AP: X2AP MESSAGE TRANSFER” is received by the X2 GW, and the X2 GW transfers the received “X2AP: X2AP MESSAGE TRANSFER” to the HeNB GW (step 2 in FIG. 24 and process P72 in FIG. 28).

  Since “X2AP: X2AP MESSAGE TRANSFER” transferred to the HeNB GW is encapsulated as illustrated in FIG. 24, “IE: Target eNB ID” and “IE: Source eNB ID” are included. RNL Header "is set. For example, eNB ID of LMeNB is set in “IE: Target eNB ID”, and eNB ID of HeNB is set in “IE: Source eNB ID”.

  The encapsulated X2 message is received by the HeNB GW (process P51 in FIG. 26). The HeNB GW checks whether the combination of eNB IDs set in “IE: Target eNB ID” and “IE: Source eNB ID” of the encapsulated X2 message is registered in the X2 mapping table 19. (Process P52 in FIG. 26 and Process P73 in FIG. 28).

  In the example of FIGS. 24 and 28, since the combination of the eNB IDs of the LMeNB and the HeNB has already been registered in the X2 mapping table 19, YES is determined in process P52 of FIG.

  Therefore, the HeNB GW may decapsulate the X2 message encapsulated in “X2AP: X2AP MESSAGE TRANSFER” and forward the X2 message to the LMeNB specified by “IE: Target eNB ID”. The process corresponds to, for example, the procedures 3 and 4 in FIG. 24, the process P53 in FIG. 26, and the processes P74 and P75 in FIG.

  If the combination of eNB IDs set in “IE: Target eNB ID” and “IE: Source eNB ID” of the message received from the X2 GW is not registered in the X2 mapping table 19, the HeNB GW receives You can discard the message. This process corresponds to, for example, a determination of NO in process P52 of FIG. 26 and execution of process P54.

(Transfer process of X2 message from LMeNB to HeNB)
On the other hand, it is assumed that the LMeNB transmits an X2 message that is not encapsulated in “X2AP: X2AP MESSAGE TRANSFER” to the HeNB (procedure 1 in FIG. 25 and process P81 in FIG. 29).

  The X2 message is received by the HeNB GW (process P61 in FIG. 27). The HeNB GW may confirm whether or not the eNB ID of the LMeNB that is the transmission source of the received X2 message is registered in the X2 mapping table 19 (process P62 in FIG. 27).

  If registered (YES in process P62), the HeNB GW may further confirm whether or not the received X2 message is a message specifying (or specifying) a destination (process P63 in FIG. 27 and FIG. 29). Process P82).

  Here, the LMeNB does not recognize that the communication partner HeNB is connected to the X2 GW by X2, so the SCTP connection and the X2 connection do not correspond one-to-one (for example, see FIG. 6). We do not recognize that there is sex.

  In other words, the LMeNB does not recognize that the X2 GW intervenes in the X2 connection established with the HeNB, and thus recognizes that the X2 connection and the SCTP connection have a one-to-one correspondence. ing.

  Therefore, even if the LMeNB transmits an X2 message that does not specify a destination, the LMeNB recognizes that the X2 message reaches the HeNB correctly. Therefore, an X2 message designating a destination may be transmitted from the LMeNB, or an X2 message not designating a destination may be transmitted.

  The X2 message designating the destination is, for example, a message in which the eNB ID of a specific eNB, a specific cell formed by the eNB, an ID for identifying a sector into which the cell is divided, or the like is set in the destination information of the X2 message. It's okay. The X2 message may include control information related to handover and control information for transmission power control in a cell or sector.

  If the X2 message received from the LMeNB is a message specifying the destination (YES in process P63 in FIG. 27 and process P82 in FIG. 29), the HeNB GW may specify the destination from the IE of the received X2 message (FIG. 27, process P64).

  Then, the HeNB GW may confirm whether or not the eNB ID corresponding to the identified destination is registered in the X2 mapping table 19 in association with the eNB ID of the transmission source LMeNB of the received X2 message (FIG. 27). Process P65).

  If registered (YES in process P65), the HeNB GW may encapsulate the X2 message received from the LM eNB in “X2AP: X2AP MESSAGE TRANSFER” and transmit it to the X2 GW (process P66 in FIG. 27).

  The destination specified from the IE of the received X2 message is set in “IE: Target eNB ID” of “IE: RNL Header”, and the eNB ID of the source LMeNB of the X2 message is set in “IE: Source eNB ID” May be set.

  In other words, the processes P64 to P66 of FIG. 27 described above determine and determine the transfer destination of the received X2 message based on the IE included in the received X2 message, and the received one transfer destination has received it. This process encapsulates the X2 message and transmits it to the X2 GW. The process corresponds to, for example, the procedure 2 (2a) and the procedure 3 in FIG. 25 and the processes P84 and P85 in FIG.

  When the X2 GW receives the X2 message encapsulated in “X2AP: X2AP MESSAGE TRANSFER” from the HeNB GW, the X2 GW sends “X2AP: X2AP to the HeNB indicated in“ IE: Target eNB ID ”of“ IE: RNL Header ”. "MESSAGE TRANSFER" may be transferred. This process corresponds to, for example, the procedure 4 in FIG. 25 and the process P86 in FIG.

  In addition, in the case of NO in the process P62 or the process P65 in FIG. 27, the HeNB GW may discard the X2 message received from the LMeNB (process P68 in FIG. 27).

  On the other hand, in the process P63 of FIG. 27 and the process P82 of FIG. 29, when the X2 message received from the LMeNB is a message that does not specify a destination (in the case of NO), the HeNB GW The transfer destination may be determined and determined.

  For example, the HeNB GW determines and determines eNBs corresponding to all the eNB IDs associated with the eNB ID of the source LMeNB of the received X2 message in the X2 mapping table 19 as the transfer destination of the received X2 message. It's okay.

  In this case, the HeNB GW may generate “X2AP: X2AP MESSAGE TRANSFER” encapsulating the received X2 message by the number of determined transfer destination eNBs and transmit the generated X2AP to the X2 GW.

  In “IE: RNL Header” of “X2AP: X2AP MESSAGE TRANSFER” for each transfer destination, the ID of the corresponding transfer destination eNB may be set in “IE: Target eNB ID”. The “IE: Source eNB ID” of the “IE: RNL Header” may be set to the eNB ID of the source LMeNB of the X2 message.

  The above-described processing that is performed when the received X2 message is a message that does not specify a destination is exemplified by the steps 2 (2b) and 3 in FIG. 25, the processing P67 in FIG. 27, and the processing in FIG. This corresponds to processes P87 to P89.

  When the X2 GW receives “X2AP: X2AP MESSAGE TRANSFER” generated for each transfer destination from the HeNB GW, the X2 GW transmits the “X2AP: X2AP:” to the destination eNB indicated by the eNB ID set in each “IE: Target eNB ID”. "MESSAGE TRANSFER". This process corresponds to, for example, the procedure 4 in FIG. 25 and the process P90 in FIG.

  As described above, according to the above-described embodiment, even if old and new eNBs of an eNB that supports X2 connection with an X2 GW and an unsupported eNB are mixed in the network 1, all eNBs are connected via the HeNB GW. X2 connection can be established and X2 communication can be performed.

  In other words, by installing the HeNB GW in the network 1, the X2 connection via the X2 GW can be established between the old eNB and the new eNB, so that the X2 GW can be effectively used.

(Operation example when SCTP abnormality occurs)
Next, as described above, after the X2 connection via the X2 GW is established between the LMeNB and the HeNB, for example, at least one X2 connection between the LMeNB and the HeNB and between the X2 GW and the HeNB. An example of operation when an abnormality occurs will be described.

  FIG. 30 and FIG. 35 show an operation example when an abnormality occurs in the SCTP connection between the LMeNB and the HeNB and the SCTP connection is disconnected. When the SCTP connection is disconnected, the X2 connection corresponding to the upper layer of SCTP is also disconnected.

  FIG. 31, FIG. 32 and FIG. 36 show an operation example when the SCTP connection is disconnected due to an abnormality in the SCTP connection between the HeNB and the X2 GW. Further, FIG. 33 shows an operation example in the HeNB GW corresponding to FIGS. 30 and 35, and FIG. 34 shows an operation example in the HeNB GW corresponding to FIGS. 31, 32, and 36.

(When SCTP connection between LMeNB and HeNB is disconnected)
As illustrated in FIGS. 30 and 35, when an abnormality occurs in the SCTP connection between the LMeNB and the HeNB and the SCTP connection is disconnected, the disconnection is detected in the HeNB GW. The disconnection detection corresponds to, for example, the procedure 1 in FIG. 30, the process P101 in FIG. 33, and the process P121 in FIG.

  In response to detecting the disconnection of the SCTP connection of the X2 connection with the LMeNB, the HeNB GW checks whether or not the HeNB eNB ID registered in association with the eNB ID of the LMeNB exists in the X2 mapping table 19 You can do it. This process corresponds to, for example, the process P102 in FIG. 33 and the process P122 in FIG.

  If the eNB ID of the corresponding HeNB exists in the X2 mapping table 19 (YES in process P102 of FIG. 33), the HeNB GW generates “X2AP: X2 RELEASE” requesting the release of the X2 connection by the number of the corresponding HeNB. Then, it may be transmitted to the X2 GW.

  The eNB ID of the LMeNB registered in the X2 mapping table 19 may be set in “IE: Global eNB ID” of each “X2AP: X2 RELEASE”. Each of “X2AP: X2 RELEASE” may be encapsulated in “X2AP: X2 MESSAGE TRANSFER” and transmitted to the X2 GW.

  The processes related to the generation, encapsulation, and transmission to the X2 GW of “X2AP: X2 RELEASE” described above correspond to the procedures 2 and 3 in FIG. 30, the process P103 in FIG. 33, and the process P123 in FIG. .

  Each “X2AP: X2 MESSAGE TRANSFER” transmitted from the HeNB GW to the X2 GW is received by the X2 GW and transferred from the X2 GW to the corresponding HeNB (in FIG. 30, procedure 5 and FIG. 35). Process P124). Thereby, in HeNB GW, the X2 connection which became unnecessary to maintain and manage can be reliably released, and the effective use of the resource for X2 communication can be aimed at.

  In response to (or in combination with) transmission of “X2AP: X2 MESSAGE TRANSFER”, the HeNB GW may delete all of the entries associated with the same LMeNB from the X2 mapping table 19.

  Thereby, the storage capacity prepared for the X2 mapping table 19 can be reduced. The deletion process corresponds to, for example, the procedure 4 in FIG. 30, the process P104 in FIG. 33, and the process P125 in FIG.

(When SCTP connection between X2 GW and HeNB is disconnected)
As illustrated in FIGS. 31 and 32, it is assumed that the SCTP connection between the X2 GW and the HeNB is disconnected.

  In the disconnection of the SCTP connection between the X2 GW and the HeNB, in addition to the abnormal disconnection, the HeNB transmits an X2 message “X2AP: X2 RELEASE” requesting the release of the X2 connection with the X2 GW to the X2 GW. It also occurs in some cases. These correspond to the procedure 1 in FIGS. 31 and 32 and the process P131 in FIG. 36, for example.

  The X2 GW detects the disconnection of the SCTP connection or receives “X2AP: X2 RELEASE” from the HeNB, and sets the eNB ID of the corresponding HeNB to “Source eNB ID”. You may send it to. The “X2AP: X2 RELEASE” may be encapsulated in “X2AP: X2 MESSAGE TRANSFER”. This process corresponds to, for example, the procedure 3 in FIGS. 31 and 32 and the process P132 in FIG.

  The HeNB GW receives “X2AP: X2 MESSAGE TRANSFER” in which “X2AP: X2 RELEASE” is encapsulated from the X2 GW (process P111 in FIG. 34).

  The HeNB GW checks whether or not the eNB ID of the LM eNB registered in the X2 mapping table 19 is set in “IE: Target eNB ID” in “IE: RNL Header” of “X2AP: X2 MESSAGE TRANSFER”. It's okay.

  Also, the HeNB GW has the eNB ID of the HeNB registered in the X2 mapping table 19 in “IE: Target eNB ID” of “X2AP: X2 RELEASE” encapsulated in the received “X2AP: X2 MESSAGE TRANSFER”. You may check whether it is set.

  In other words, the HeNB GW determines whether the pair of the received destination of “X2AP: X2 MESSAGE TRANSFER” and the source of the encapsulated “X2AP: X2 RELEASE” is registered in the X2 mapping table 19. You can check that. The confirmation process corresponds to, for example, the process P112 in FIG. 34 and the process P133 in FIG.

  As a result of the confirmation, if the transmission source of “X2AP: X2 RELEASE” encapsulated in “X2AP: X2 MESSAGE TRANSFER” addressed to the LMeNB is a HeNB registered in the X2 mapping table 19, the HeNB GW May be deleted. Therefore, the storage capacity prepared for the X2 mapping table 19 can be reduced.

  The entry deletion corresponds to, for example, procedure 4 in FIGS. 31 and 32, process P113 in the case where YES is determined in process P112 in FIG. 34, and process P134 in FIG.

  In response to the entry deletion, the HeNB GW checks in the X2 entry table 19 whether or not there is an entry of the LMeNB in which the number of HeNB eNB IDs associated with the eNB ID of the LMeNB is “0”. Good. The confirmation process corresponds to, for example, the process P114 in FIG. 34 and the process P135 in FIG.

  In the X2 entry table 19, if there is an entry of the LMeNB in which the number of eNB IDs of the HeNB associated with the eNB ID of the LMeNB is “0”, the HeNB GW disconnects the SCTP connection with the corresponding LMeNB. You can do it.

  The cutting process corresponds to, for example, the procedure 5 in FIG. 32, the process P115 in FIG. 34, and the process P136 in FIG. Thereby, in HeNB GW, X2 connection with LMNB which has not been maintained and managed can be cut off reliably. Therefore, it is possible to effectively use resources for X2 communication between the HeNB GW and the LMeNB.

(Summary of operation example)
For convenience, the operation examples of the wireless communication system 1 in the above-described embodiment are listed as follows.

  -HeNB GW can transmit / receive a message between a base station and X2 GW.

  When the HeNB GW reads an S1 message for establishing an X2 connection that is transmitted and received between the base stations and satisfies a specific condition, the S1 message is terminated at the HeNB GW without being transferred to the destination base station. It's okay. An example of the “specific condition” is that the source of the S1 message is a base station that does not support the X2 connection with the X2 GW.

-HeNB GW may notify the address information of HeNB GW addressed to the 1st base station which is the transmission origin of S1 message. The address information of the HeNB GW may be used for the first base station to establish an X2 connection via the X2 GW with a second base station that can connect to the X2 GW.
-HeNB GW may memorize | store the combination of the base station in which establishment of X2 connection is desired from the S1 message which confirmed the content.

  When the HeNB GW receives an X2 connection establishment request from the first base station that has notified the address information of the HeNB GW, the HeNB GW accepts the request and establishes an X2 connection with the first base station. It's okay.

  -The HeNB GW refers to the combination of the base stations that wants to establish the stored X2 connection in response to the establishment of the X2 connection with the first base station. A message for establishing the X2 connection may be transmitted to the X2 GW to establish the X2 connection.

  -If the HeNB GW has already established an X2 connection with the first base station, the HeNB GW does not wait for reception of an X2 connection establishment request from the first base station, The process of establishing an X2 connection with the second base station may be started.

  -HeNB GW memorize | stores the combination of the 1st base station with which Hex GW and X2 connection were established without going through X2 GW, and the 2nd base station with which HeNB GW and X2 connection were established through X2 GW You can do it.

  When the HeNB GW receives a message from the second base station via the X2 GW, the HeNB GW may release the encapsulation of the received message and transmit the message to the first base station.

  -HeNB GW may specify a destination from the information element of the received message, when the message which designated the destination was received from the 1st base station by X2 connection not via X2 GW. Then, the HeNB GW may encapsulate the received message with the base station ID corresponding to the identified destination and the ID of the first base station, and transmit the encapsulated message to the X2 GW.

  When the HeNB GW receives a message not specifying a destination from the first base station via the X2 connection not via the X2 GW, the HeNB GW selects the destination from the combination of the stored base stations that have established the X2 connection. It's okay. Then, for each selected destination, the HeNB GW encapsulates the received message by assigning the base station ID corresponding to the destination and the ID of the first base station, and sends the encapsulated message to the X2 GW. May be sent.

  When the HeNB GW detects that the X2 connection with the first base station with which the X2 connection is established is disconnected, the HeNB GW may delete the stored combination of the corresponding base stations.

  When the HeNB GW receives a message indicating that the X2 connection between the X2 GW and the second base station is disconnected from the X2 GW, the HeNB GW may delete the stored combination of the corresponding base stations.

  -When the combination of the base station memorize | stored in HeNB GW disappears according to deletion of the combination of an applicable base station, HeNB GW may cut | disconnect X2 connection between 1st eNB.

  In the above-described embodiment, the S1 connection by the S1 interface is given as an example of the “base station-core node connection” which is a connection between the base station and the core node. However, the connection between the base station and the core node is described. The connection corresponding to is not limited to the S1 connection.

  In other words, the connection between the base station and the core node corresponds to the “connection between the base station and the core node” even if the connection is different from the S1 connection. Therefore, the message transmitted in the “base station-core node connection” is not limited to the S1 message. If the message is transmitted in the connection between the base station and the core node, the message “between the base station and the core node” is used. Corresponds to "Message".

  Similarly, “inter-base station connection” is not limited to X2 connection by the X2 interface, and corresponds to “inter-base station connection” if the connection is between base stations. Therefore, the message transmitted in the “inter-base station connection” is not limited to the X2 message, and if the message is transmitted in the connection between the base stations, it corresponds to the “inter-base station message”.

(Functional configuration example of HeNB GW)
In FIG. 37, the functional structural example of HeNB GW which can implement | achieve the operation example of embodiment mentioned above is illustrated. As illustrated in FIG. 37, the HeNB GW may include, for example, an S1 transmission / reception unit 11 for HeNB, an S1 transmission / reception unit 12 for MME, an X2 transmission / reception unit 13 for X2 GW, and an X2 transmission / reception unit 14 for LMENB.

  Moreover, HeNB GW may be provided with S1 message determination part 15, X2 establishment part 16, X2 process part 17, X2 monitoring part 18, and X2 mapping table 19, for example.

  The S1 transmission / reception unit 11 for HeNB illustratively performs transmission / reception of the S1 message with the HeNB.

  The S1 transmission / reception unit 12 for MME illustratively performs transmission / reception of S1 messages with the MME. The S1 transmission / reception unit 12 for MME is an example of a first reception unit that receives an S1 message from the MME. Moreover, the S1 transmission / reception part 12 for MME is also an example of the 1st transmission part which transmits the S1 message addressed to LMeNB including the IP address of HeNB GW to MME.

  The X2 GW X2 transmission / reception unit 13 illustratively performs transmission / reception of an X2 GW with an X2 message.

  The X2 transmission / reception unit 14 for LMeNB illustratively performs transmission / reception of an X2 message with the LMeNB. The X2 transmission / reception unit 14 for LMeNB is an example of a second reception unit that receives a request for establishing an X2 connection with the HeNB from the LMeNB that has received the IP address of the HeNB GW. Moreover, the X2 transmission / reception unit 14 for LMeNB is also an example of a second transmission unit that transmits a response to the establishment request to the LMeNB.

  For example, the S1 message determination unit 15 determines whether to establish an X2 connection with the transmission source eNB in response to reception of “MME CONFIGURATION TRANSFER” which is an example of the S1 message.

  The S1 message determination unit 15 may update the X2 mapping table 19 according to the determination result. For example, the operation example described in the flowchart of FIG. 16 may be performed by the S1 message determination unit 15.

  For example, the S1 message determination unit 15 may determine whether or not the received S1 message is an address request message whose source is an LMeNB.

  In response to determining that the message is an address request message with the LMeNB as a transmission source, the S1 message determination unit 15 may terminate the received address request message without transferring it to the HeNB.

  Then, the S1 message determination unit 15 may transmit an address response message including the IP address of the HeNB GW to the LMeNB that is the IP address request source through the S1 transmission / reception unit 12 for MME.

  The X2 establishment unit 16 is an example of the “inter-base station connection establishment unit”, and may exemplarily perform a process of establishing an X2 connection between the X2 GW and the LMeNB. Therefore, X2 establishment part 16 may be provided with X2 establishment part 161 for X2 GW, and X2 establishment part 162 for LMeNB, for example.

  The X2 GW-oriented X2 establishment unit 161 illustratively performs a process of establishing an X2 connection with the X2 GW.

  The L2 eNB-oriented X2 establishment unit 162 illustratively performs a process of establishing an X2 connection with the LMeNB.

  In response to the establishment of the X2 connection, the X2 establishment unit 16 may update the X2 mapping table 19. For example, the operation example described in the flowchart of FIG. 21 may be performed by the X2 establishment unit 16.

  The X2 processing unit 17 is an example of an “inter-base station message processing unit”, and may exemplarily process X2 messages transmitted / received through the X2 transmitting / receiving units 13 and 14. Therefore, the X2 processing unit 17 may include, for example, a message processing unit 171 for LMeNB and a message processing unit 172 for X2 GW.

  For example, the message processing unit 171 for the LMeNB decapsulates the X2 message received by the X2 transmission / reception unit 13 for X2 GW. The decapsulated X2 message is exemplarily transmitted to the LMeNB through the X2 transmission / reception unit 14 for LMeNB.

  The message processing unit 172 for X2 GW illustratively encapsulates the X2 message received by the X2 transmission / reception unit 14 for LMeNB, and sets an appropriate “IE: Target eNB ID”. The encapsulated X2 message is, for example, transmitted to the X2 GW through the X2 GW-oriented X2 transmission / reception unit 13.

  In the X2 processing unit 17, for example, the operation example described with reference to the flowcharts of FIGS. 26 and 27 may be performed.

  Therefore, the X2 processing unit 17 is an example of a processing unit that performs transfer processing of an X2 message transmitted and received through an X2 connection established between the LMeNB and the HeNB via the X2 GW based on the entry of the X2 mapping table 19. is there.

  For example, the X2 monitoring unit 18 may monitor the establishment state of the X2 connection and delete an unnecessary entry in the X2 mapping table 19. In addition, the X2 monitoring unit 18 may perform a process of disconnecting communication over an X2 connection that does not need to be established according to deletion of an unnecessary entry.

  In the X2 monitoring unit 18, the operation described with reference to the flowcharts of FIGS. 33 and 34 may be performed. The X2 monitoring unit 18 that performs the operation described in the flowchart of FIG. 33 is an example of a first monitoring unit. The X2 monitoring unit 18 that performs the operation described in the flowchart of FIG. 34 is an example of a second monitoring unit.

  As described above, the X2 mapping table 19 may be associated with the eNB ID of the LMNB and the eNB of the HeNB and stored together with the X2 establishment flag.

(Example of hardware configuration of HeNB GW)
FIG. 38 illustrates a hardware configuration example of the HeNB GW. The HeNB GW illustrated in FIG. 38 exemplarily includes a processor 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, an HDD (Hard Disc Drive) 304, and a network interface (NW-IF) 305. You may be prepared.

  Further, the HeNB GW may include, for example, all or part of the input interface (IF) 306, the output IF 307, the input / output IF 308, and the drive device 309 as options.

  The processor 301, the RAM 302, the ROM 303, the HDD 304, the IFs 305 to 308, and the drive device 309 may be connected to the communication bus 310 and can communicate with each other via the processor 301.

  The processor 301 is an example of a processor circuit or a processor device having a computing capability. The processor 301 is an integrated circuit (IC) such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), or DSP (Digital Signal Processor). Etc. may be used. A processor circuit or processor device with computing power may be referred to as a “computer”.

  The RAM 302 and the ROM 303 are both examples of memories that store various data and programs. The “program” may be referred to as “software” or “application”.

  The RAM 302 may be used as a work memory for the CPU 301. For example, data and programs stored in the ROM 303 and the HDD 304 may be expanded in the RAM 302 and used for computation by the processor 301.

  The HDD 304 is an example of a storage device, and stores various data and programs. Other examples of the storage device include a semiconductor drive device such as a solid state drive (SSD), a nonvolatile memory such as a flash memory, and the like. Therefore, the HDD 304 may be replaced with an SSD or a flash memory.

  The program stored in the HDD 304 may include a program capable of realizing all or part of various functions as the HeNB GW illustrated in FIG. 37 (may be referred to as a “HeNB GW program” for convenience). . Note that all or part of the program code constituting the HeNB GW program may be stored in the ROM 303 or may be described as part of the operating system (OS).

  The data stored in the HDD 304 may include the above-described X2 mapping table 19.

  Various functions as the HeNB GW are realized by the processor 301 expanding and executing the OFC program stored in the HDD 304 in, for example, the RAM 302. Note that the RAM 302, the ROM 303, and the HDD 304 may be collectively referred to as the “storage unit 311” of the HeNB GW for convenience.

  The program and data may be provided in a form recorded on a computer-readable recording medium 80. Examples of the recording medium include a flexible disk, CD-ROM, CD-R, CD-RW, MO, DVD, Blu-ray disk, portable hard disk, and the like. A semiconductor memory 70 such as a USB (Universal Serial Bus) memory is also an example of the recording medium 80.

  The program and data stored in the semiconductor memory 70 may be read by the CPU 301 through the input / output IF 308, for example. Further, the program and data stored in the recording medium 80 may be read by the CPU 301 through the drive device 309, for example.

  The program and data may be provided (in other words, “downloaded”) from the server computer or the like to the HeNB GW via a communication line. For example, a program and data may be provided to the HeNB GW through the NW-IF 305. Further, the program and data may be provided from the input device 50 to the HeNB GW through the input IF 306.

  NW-IF305 is an interface which enables S1 communication or X2 communication with HeNB, MME, X2 GW, and LMNB, and one or more may be provided in HeNB GW.

  With one or a plurality of NW-IFs 305, part or all of the S1 transmission / reception unit 11 for HeNB, the S1 transmission / reception unit 12 for MME, the X2 transmission / reception unit 13 for X2 GW, and the X2 transmission / reception unit 14 for LMENB illustrated in FIG. May be realized.

  For example, the input device 50 may be connected to the input IF 306. An example of the input device 50 is a keyboard, a mouse, operation buttons, a microphone, or the like.

  For example, a display device 60 as an example of an output device may be connected to the output IF 307. A liquid crystal display or the like may be applied to the display device 60. The touch panel liquid crystal display may be regarded as corresponding to the input device 50. Note that a printer, a speaker, and the like may be connected to the output IF 307 as another example of the output device.

  The input device 50 may be used for operations such as registration and change of settings for the HeNB GW, various operations of the HeNB GW, and data input by an administrator of the HeNB GW. The display device 60, which is an example of an output device, may be used for confirmation of settings by the HeNB GW administrator or the like, or for outputting various notifications to the administrator or the like.

  In addition, the hardware structural example of HeNB GW illustrated in FIG. 38 is an illustration to the last, and hardware increase / decrease may be performed suitably in HeNB GW. For example, addition or deletion of an arbitrary hardware block, division, integration in an arbitrary combination, addition or deletion of a communication bus, and the like may be appropriately performed in the HeNB GW.

DESCRIPTION OF SYMBOLS 1 Radio communication system 11 S1 transmission / reception part for HeNB 12 S1 transmission / reception part for MME 13 X2 X2 transmission / reception part for GW 14 X2 transmission / reception part for LMeNB 15 S1 message determination part 16 X2 establishment part 161 X2 X2 establishment part for GW 162 X2 establishment for LMeNB Unit 17 X2 processing unit 171 message processing unit for LMeNB 172 message processing unit for X2 GW 18 X2 monitoring unit 19 X2 mapping table 50 input device 60 display device 70 semiconductor memory 80 recording medium 301 processor 302 RAM
303 ROM
304 HDD
305 Network interface (NW-IF)
306 Input interface (IF)
307 Output IF
308 I / O IF
309 Drive device 311 Storage unit MC Macro cell SC Small cell

Claims (14)

A first relay node that relays communication between a core node connected to the first base station and a second base station different from the first base station,
A first receiver for receiving a base station-core node message from the core node;
The base station-core node message is transmitted from the first base station that does not support inter-base station connection with a second relay node where the second base station connects between base stations via an inter-base station interface. A determination unit that determines whether the message includes an information element that requests address information of the second base station,
The base station-core node message is a message including an information element for requesting the address information of the second base station, transmitted from the first base station to the second base station. A first transmitter that terminates the message between the base station and the core node and transmits address information of the first relay node to the first base station, when determined by the determination unit;
A relay node with A second receiving unit that receives a request for establishing an inter-base station connection with the second base station from the first base station that has received the address information of the first relay node;
An inter-base station connection establishment unit that establishes an inter-base station connection with the first base station in response to reception of the establishment request;
The relay node according to claim 1, further comprising: a second transmission unit that transmits a response to the establishment request to the first base station.   The inter-base station connection establishment unit starts processing for establishing an inter-base station connection with the second base station via the second relay node in response to receiving the establishment request. The described relay node.   The inter-base station connection establishment unit waits for the reception of the request when the inter-base station connection with the first base station has already been established before receiving the request from the first base station. 3. The relay node according to claim 2, wherein the base station connection establishment process with the second base station via the second relay node is started. The identification information of the first base station that is the transmission source of the base station-core node message and the identification information of the second base station that is the destination of the base station-core node message are stored in association with each other. A storage unit;
Based on the identification information in the storage unit, between base stations transmitted / received through the inter-base station connection established between the first base station and the second base station via the second relay node The relay node according to claim 3, further comprising: a message processing unit between base stations that performs message transfer processing. The inter-base station message processing unit
When the inter-base station message is received from the first base station with which the inter-base station connection is established, the inter-base station message is set in the source information with the identification information of the first base station, and the second The relay node according to claim 5, wherein the base station identification information is encapsulated in a message set in destination information and transmitted to the second relay node. The inter-base station message processing unit
An inter-base station message encapsulated with source information set in the identification information of the second base station and destination information set in the identification information of the first base station is received from the second relay node. Then, the relay node according to claim 5, wherein the inter-base station message that has been decapsulated is transmitted to the first base station. The inter-base station message processing unit
When an inter-base station message not specifying a destination is received from the first base station, a destination is determined based on the identification information in the storage unit, and the inter-base station message is encapsulated for each determined destination. The relay node according to claim 6, wherein the relay node transmits to two relay nodes.   The communication in the inter-base station connection established with the first base station is monitored, and when the disconnection of the communication is detected, the communication is associated with the identification information of the first base station in which the disconnection is detected. The relay node according to claim 5, further comprising a first monitoring unit that deletes a stored entry from the storage unit. The inter-base station message processing unit
The inter-base station message for requesting the release of the inter-base station connection in which the identification information of the second base station deleted from the storage unit is set as destination information is transmitted to the second relay node. Relay node described in.   The encapsulated base station transmitted from the second relay node in response to disconnection or release of an inter-base station connection between the second relay node and the second base station 8. A second monitoring unit that deletes an entry corresponding to the identification information of the second base station set in the transmission source information of the inter-base station message when the inter-base message is received, from the storage unit. Relay node described in. The inter-base station message processing unit
In response to deletion of the entry by the second monitoring unit, in the storage unit, the first base station that is no longer associated with the identification information of the second base station is connected to the first base station. The relay node according to claim 11, wherein a communication disconnection process is performed by inter-base station connection established therebetween. A first base station;
A second base station;
A core node connected to the first base station;
A first relay node that relays communication between the second base station and the core node;
A second relay node in which the second base station connects between base stations via an interface between base stations, and
The first relay node is
A receiving unit for receiving a base station-core node message from the core node;
The base station-core node message is a message transmitted from the first base station that does not support inter-base station connection with the second relay node, and requests address information of the second base station. A determination unit that determines whether the message includes an information element to be performed;
The base station-core node message is a message including an information element for requesting the address information of the second base station, transmitted from the first base station to the second base station. A wireless communication unit comprising: a transmission unit that terminates the message between the base station and the core node and transmits address information of the first relay node to the first base station when determined by the determination unit system. A first base station, a second base station, a core node connected to the first base station, a first relay node that relays communication between the second base station and the core node; A communication method in a wireless communication system comprising: a second relay node in which the second base station connects between base stations via an interface between base stations,
A base station-core node message including an information element requesting address information of the second base station from the first base station that does not support inter-base station connection with the second relay node to the core node. Send
Transmitting the base station-core node message from the core node to the first relay node;
In response to the first relay node receiving the base station-core node message including an information element requesting the second base station address information, the first relay node address information is A communication method in a wireless communication system, which responds to the first base station via a core node.

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