Patent Application
20160073301
The present invention relates to a wireless communication system such as a cellular system and, more particularly, to communication apparatuses that perform inter-cell handover control and methods for handover control.
In recent years, active studies have been conducted on SON (Self Organizing Network), which autonomously optimizes radio parameters and network configurations in wireless communication systems, in view of operation cost (OPEX) reduction and the like. Standardization of SON functions is under way also in LTE (Long Term Evolution) of 3GPP (3rd Generation Partnership Project).
One of the major SON functions is optimization of handover parameters (Mobility Robustness Optimization: MRO). MRO is a function of adjusting a handover parameter by base stations exchanging information on handover failures that occurred in the past. Causes for a handover failure include “too early handover”, “too late handover”, and “handover to wrong cell”. Of these causes, it is important that a handover source base station (hereinafter, referred to as “source base station” or “source eNB”) should detect a too late handover/handover to wrong cell. It has great impact on the MRO characteristics whether or not a too late handover, in particular, can be detected. Accordingly, several methods have been proposed for notifying such handover failure information to a source base station.
For example, NPLs 1 and 2 describe a method in which a UE (User Equipment) is made to send RLF (Radio Link Failure) Report, information that allows a too late handover/handover to wrong cell to be detected, which is then transferred to a source base station over the X2 interface. Moreover, PTL 1 discloses a method in which RLF information is transferred to a source base station over the X2 interface, whereby the source base station can identify the type of a failure occurring before/during/after a handover. Furthermore, NPL 3 proposes a method in which RLF Report is transferred to a source base station over the S1 interface when there is no X2 interface between base stations that are, for example, geographically far from each other.
However, the methods for notifying handover failure information as described above can only be applied to UEs that support 3GPP Release 10, and information cannot be obtained from UEs that support 3GPP Release 9. A case will be considered as an example in which a radio link failure has occurred when a handover (hereinafter, abbreviated to HO as appropriate) is performed between two base stations as shown in
Referring to
When a connection is thus established with the UE 4, the target base station 2 sends the core network 3 the same handover complete notice that is sent when a handover has succeeded, regardless of the process of a procedure in the handover of the UE 4 with which a connection has been established. That is, if the UE 4 is able to connect to the target cell C2 belonging to the target base station 2 by means of reconnection, the target base station 2, even in a state of waiting to receive a connection reconfiguration complete message from the UE 4 to be handed over, determines that the handover has succeeded and sends a handover complete notice. It is impossible to set in this handover complete notice any information indicating whether the handover has been completed normally by receiving a connection reconfiguration complete message from the UE 4, or whether the handover has succeeded after a radio link failure occurred to the UE 4. The core network 3 therefore can only determine that the handover has been completed normally, and so sends a handover success notice to the source base station 1. Accordingly, the source base station 1 also only recognizes that the handover has been completed normally, and cannot detect a too late handover. In case of a handover to wrong cell as well, if a connection is able to be made to another target cell belonging to the target base station 2, it is determined that the handover has succeeded, and a handover complete notice is sent.
Accordingly, an object of the present invention is to provide a communication apparatus in a wireless communication system and a method for handover control in the same that enable handover information to be notified to the handover source side regardless of the types of UEs.
A communication apparatus according to the present invention is a communication apparatus managed by a upper-level network, characterized by comprising: handover information generation means that, upon establishing a connection with a terminal during operations for a handover of the terminal, generates information about the handover of the terminal; and handover control means that sets the information about the handover in a handover complete message and sends it to the upper-level network.
A communication apparatus according to the present invention is a communication apparatus managed by a upper-level network, characterized by comprising: handover control means that receives a handover success message from the upper-level network during operations for a handover of a terminal and completes the operations for the handover; and handover information analysis means that acquires information about the handover from the handover complete message.
A wireless communication system according to the present invention is a wireless communication system including a plurality of communication apparatuss managed by a upper-level network, characterized in that a target communication apparatus as a target of a handover of a terminal, upon establishing a connection with the terminal during operations for this handover, sets information about the handover of the terminal in a handover complete message and sends it to the upper-level network, and a source communication apparatus as a source of the handover of the terminal acquires the information about the handover from a handover success message received from the upper-level network during operations for the handover of the terminal.
A method for handover control according to the present invention is a method for handover control in a communication apparatus managed by a upper-level network, characterized by comprising: when a connection with a terminal is established during operations for a handover of the terminal, generating information about the handover of the terminal; and setting the information about the handover in a handover complete message and sending it to the upper-level network.
A method for handover control according to the present invention is a method for handover control in a communication apparatus managed by a upper-level network, characterized by comprising: receiving a handover success message from the upper-level network during operations for a handover of a terminal; and acquiring information about the handover from the handover complete message.
According to the present invention, information about a handover is set in a handover complete message and sent to a upper-level network, whereby a communication apparatus on the handover source side can acquire handover information regardless of the types of UEs.
According to an exemplary embodiment of the present invention, when a communication apparatus on the handover target side is connected to a UE to be handed over, a predetermined message to which information about this handover is added is notified from the target-side communication apparatus to a source-side communication apparatus via an upper-level network. For example, the target-side communication apparatus generates handover information when detecting a connection with the UE during a handover process and sends the upper-level network a handover complete message to which the handover information is added. The upper-level network having received this handover complete message sends the source-side communication apparatus a handover success message to which the handover information is added. Thus, the source-side communication apparatus can detect a handover status such as too late handover or handover to wrong cell, without depending on the functions of the UE. Hereinafter, an exemplary embodiment of the present invention will be described with reference to
Referring to
In such a wireless communication system, the target-side communication apparatus 20 has completed preparation for a connection with the UE 40 at a handover request from the upper-level network 30 and is in a state of waiting for a connection reconfiguration message from the UE 40. In this state, if the UE 40 has moved into a target cell C20 before the handover is completed and has lost a connection due to weakened radio waves from the source-side communication apparatus 10 (too late handover), the UE 40 searches for a reconnection target and establishes a connection with the target-side communication apparatus 20.
The target-side communication apparatus 20, when establishing a connection with the UE 40, generates handover information indicating that a reconnection has been made after a handover of the UE 40 failed once, sets this handover information in a handover complete notice that is the same as one sent when a handover has succeeded, and sends it to the upper-level network 30. Handover process information and the like can be set as handover information in a handover complete notice. For the handover information, for example, it is possible to set information indicating normal completion if a handover has been completed normally, or to set information indicating a too late handover if a handover has succeeded by means of reconnection after a radio link failure occurred to the UE 40, or to set information indicating a handover to wrong cell if a connection has been made to another cell managed by the target-side communication apparatus 20.
The upper-level network 30, when receiving the handover complete notice from the target-side communication apparatus 20, sets the handover information therein in a notice indicating a handover success and sends it to the source-side communication apparatus 20. Thus, the source-side communication apparatus 20 can learn from the handover information how the handover from its own station's cell C10 to the target cell C20 has succeeded in actuality and can use it for optimization of a handover parameter.
Hereinafter, a description will be given of the respective functions of the source-side communication apparatus 10 and the target-side communication apparatus 20, assuming that they are a source base station 10 and a target base station 20, respectively, and that the upper-level network 30 is a core network 30. However, since a communication apparatus according to the present exemplary embodiment can be any of the source-side and target-side ones depending on the moving direction of a UE, it is conceivable that a single base station is equipped with both source-side and target-side functions. Here, only functional components related to the present exemplary embodiment are depicted, omitting the rest of the functional components of a base station.
Referring to
The target base station 20 includes a wireless communication section 201 for performing wireless communication with UEs, a handover control section 202, a communication section 203 for performing communication with the core network 30, and a container generation section 204 that generates a container for storing handover information, which will be described later. Note that the functions described below of the handover control section 202 and the container generation section 204 can also be implemented by executing programs stored in a memory (not shown) on a computer (CPU: Central Processing Unit).
Moreover, if the communication apparatuses according to the present exemplary embodiment are control stations controlling base stations on the source and target sides, they also have basically the same configurations, only with the difference that the wireless communication sections 101 and 201 are sections for communication with respective radio base stations. Hereinafter, handover control procedures by the source base station 10 and the target base station 20 according to the present exemplary embodiment will be described with reference to
Referring to
The handover control section 202 sets the thus generated container in a handover complete notice and sends it to the core network 30 (Operation 214). Note that if a handover preparation complete notice is received from the UE 40 (Operation 211; YES), the handover control section 202 sends a handover complete notice to the core network 30 (Operation 215). Note that when a handover preparation complete notice is received from the UE 40 (Operation 211; YES), it is also possible that the container generation section 204 stores handover information indicating the normal completion of the handover in a container, sets the thus generated container in a handover complete notice, and sends it to the core network 30.
Referring to
According to the above-described exemplary embodiment of the present invention, when the target base station 20 establishes a connection with the UE 40 during the process of a handover, the target base station 20 sets a container storing information about this handover in a handover complete message and sends it to the core network 30. Accordingly, the source base station 10 can receive the handover information container via the core network 30 and thus can detect a handover status such as too late handover or handover to wrong cell.
Moreover, since the present exemplary embodiment does not depend on either the types of UEs or radio access systems, it is possible to detect a too late handover/handover to wrong cell even in case of a handover between different access technologies (Inter RAT HO). The present exemplary embodiment can be applied to E-UTRAN (Evolved Universal Terrestrial Access Network), UTRAN, HRPD (High Rate Packet Data), eHRPD (Evolved-HRPD), or GSM (Global System for Mobile Communication), or also to a handover between any of them. Hereinafter, examples of the present invention will be described in detail with reference to drawings.
In a wireless communication system according to a first example of the present invention, both the source base station and the target base station are communication apparatuses of E-UTRAN and here referred to as a source eNB 10a and a target eNB 20a, respectively. Moreover, it is assumed that the core network 30 is a MME (Mobility Management Entity) 30a performing mobility management.
According to the present example, handover control through the S1 interface (hereinafter, referred to as S1 Handover) between the source eNB 10a and the target eNB 20a and the MME 30a enables the source eNB 10a to detect a too late handover/handover to wrong cell. Accordingly, even in the absence of a X2 interface connection, the source eNB 10 can detect a too late handover/HO to wrong cell. Hereinafter, a description will be given of a case where there is no X2 interface connection.
Referring to
The handover control section 202 of the target eNB 20a, when securing resources for the UE 40 to be handed over, sends a S1: Handover Request Acknowledge message to the MME 30a (Operation 304). This S1: Handover Required Acknowledge message includes a RRC Connection Reconfiguration Request message that the source eNB 10a will send to the UE 40 later. After sending this S1: Handover Required Acknowledge message, the target eNB 20a falls in a state of waiting to receive a RRC Connection Reconfiguration Complete message from the UE 40.
The MME 30a having received the S1: Handover Request Acknowledge message sends a S1: Handover Command message for commanding a S1 Handover to the source eNB 10a (Operation 305). At this time, the MME 30a transfers the RRC Connection Reconfiguration Request message from the S1: Handover Request Acknowledge message to the S1: Handover Command. The source eNB 10a having received the S1: Handover Command message sends the RRC Connection Reconfiguration Request message included in the S1: Handover Command message to the UE 40 (Operation 306).
Thereafter, it is assumed that the UE 40 detects a radio link failure due to radio environment deterioration (Operation 307) and makes a reconnection to a target cell C20 belonging to the target eNB 20a (Operation 308). At this time, the target eNB 20a is in a state of waiting to receive a RRC Connection Reconfiguration Complete message as described above. Accordingly, the container generation section 204, when detecting that the UE 40 having made a reconnection is under S1 Handover, sets a container including handover information in a normal S1: Handover Notify message for completing a S1 Handover and sends it to the MME 30a (Operation 309).
The handover information included in the container in this case indicates that a connection has been made to the target cell C20 after a radio link failure occurred, or that a connection has been made to another cell than the target cell C20 after a radio link failure occurred (in such a case, also including information about the connected cell). Note that when the S1 Handover is normally completed without any problem, handover information to that effect is included, or a container itself is not set in the S1: Handover Notify message.
When receiving the S1: Handover Notify message in which the container is set, the MME 30a sets this container in a UE Context Release Command message and sends it to the source eNB 10a (Operation 310).
The container analysis section 104 of the source eNB 10a, when receiving the UE Context Release Command message in which the container is set, analyzes this container and determines whether a too late handover occurred or whether a HO to wrong cell occurred. Then, after releasing a S1 connection related to the UE 40 in accordance with the UE Context Release Command message, the source eNB 10a sends a UE Context Release Complete message to the MME 30a (Operation 311).
In a wireless communication system according to a second example of the present invention, the source base station and the target base station are a communication apparatus of E-UTRAN and a communication apparatus of UTRAN, respectively, and here referred to as a source eNB 10b and a target RAN (Radio Access Network) 20b, respectively. Moreover, it is assumed that the core network issuing a handover command is a core network 30b. According to the present example, handover control through the S1 interface (S1 Handover) between the source eNB 10b and the target RAN 20b and the core network 30b enables the source eNB 10b to detect a too late handover/handover to wrong cell. Hereinafter, in
Referring to
The handover control section 202 of the target RAN 20b, when securing resources for the UE 40 to be handed over, sends a RANAP: Relocation Request Acknowledge message to the core network 30b (Operation 304b). After sending this RANAP: Relocation Request Acknowledge message, the target RAN 20b falls in a state of waiting to receive a handover configuration complete message from the UE 40.
The core network 30b having received the RANAP: Relocation Request Acknowledge message sends a S1: Handover Command message for commanding a S1 Handover to the source eNB 10b (Operation 305). The source eNB 10b having received the S1: Handover Command message sends a MobilityFromEUTRACommand message to the UE 40 (Operation 306b).
Thereafter, it is assumed that the UE 40 detects a radio link failure due to radio environment deterioration (Operation 307) and makes a reconnection to a target cell C20b belonging to the target RAN 20b (Operation 308). At this time, the target RAN 20b is in a state of waiting to receive a handover configuration complete message from the UE 40 as described above. Accordingly, the container generation section 204, when detecting that the UE 40 having made a reconnection is under RANAP Relocation, sets a container including handover information in a normal RANAP: Relocation Complete message for completing a RANAP Relocation and sends it to the core network 30b (Operation 309b). The handover information included in the container is similar to that of the first example.
When receiving the RANAP: Relocation Complete message in which the container is set, the core network 30b sets this container in a UE Context Release Command message and sends it to the source eNB 10b (Operation 310). The container analysis section 104 of the source eNB 10b, when receiving the UE Context Release Command message in which the container is set, analyzes this container and determines whether a too late handover occurred or whether a HO to wrong cell occurred. Then, after releasing a S1 connection related to the UE 40 in accordance with the UE Context Release Command message, the source eNB 10b sends a UE Context Release Complete message to the core network 30b (Operation 311).
Note that the present example can also be applied to a handover from EUTRAN to GSM because such a handover follows approximately the same sequence as in
In a wireless communication system according to a third example of the present invention, the source base station and the target base station are a communication apparatus of UTRAN and a communication apparatus of E-UTRAN, respectively, and here referred to as a source RAN 10c and a target eNB 20c, respectively. Moreover, it is assumed that the core network issuing a handover command is a core network 30c. According to the present example, handover control through the S1 interface (S1 Handover) between the source RAN 10c and the target eNB 20c and the core network 30c enables the source RAN 10c to detect a too late handover/handover to wrong cell. Hereinafter, in
Referring to
The handover control section 202 of the target eNB 20c, when securing resources for the UE 40 to be handed over, sends a S1: Handover Request Acknowledge message to the core network 30c (Operation 304). After sending this S1: Handover Required Acknowledge message, the target eNB 20c falls in a state of waiting to receive a RRC Connection Reconfiguration Complete message from the UE 40.
The core network 30c having received the S1: Handover Request Acknowledge message sends a RANAP: Relocation Command message to the source RAN 10c (Operation 305c). The source RAN 10c having received the RANAP: Relocation Command message sends a HandoverfromUTRAN message to the UE 40 (Operation 306c).
Thereafter, it is assumed that the UE 40 detects a radio link failure due to radio environment deterioration (Operation 307) and makes a reconnection to a target cell C20c belonging to the target eNB 20c (Operation 308). At this time, the target eNB 20c is in a state of waiting to receive a RRC Connection Reconfiguration Complete message as described above. Accordingly, the container generation section 204, when detecting that the UE 40 having made a reconnection is under handover, sets a container including handover information in a normal S1: Handover Notify message for completing a S1: Handover and sends it to the core network 30c (Operation 309). The handover information included in the container is similar to that of the first example.
When receiving the S1: Handover Notify message in which the container is set, the core network 30c sets this container in a RANAP: Iu Release Command message and sends it to the source RAN 10c (Operation 310c). The container analysis section 104 of the source RAN 10c, when receiving the RANAP: Iu Release Command message in which the container is set, analyzes this container and determines whether a too late handover occurred or whether a HO to wrong cell occurred. Then, after releasing all resources related to the Iu interface of the UE 40 in accordance with the RANAP: Iu Release Command message, the source RAN 10c sends a RANAP: Iu Release Complete message to the core network 30c (Operation 311c).
Note that the present example can also be applied to a handover from GSM to EUTRAN because such a handover follows approximately the same sequence as in
In a wireless communication system according to a fourth example of the present invention, a case of Intra-UMTS (Universal Mobile Telecommunications System) SRNS (Serving Radio Network Subsystem) Relocation will be shown. Both the source base station and the target base station are communication apparatuses of UTRAN and here referred to as a source RAN 10d and a target RAN 20d, respectively. Moreover, it is assumed that the core network issuing a handover command is a core network 30d. According to the present example, handover control through the Iu interface (RANAP: Relocation) between the source RAN 10d and the target RAN 20d and the core network 30d enables the source RAN 10d to detect a too late handover/handover to wrong cell. Hereinafter, in
Referring to
The handover control section 202 of the target RAN 20d, when securing resources for the UE 40 to be handed over, sends a RANAP: Relocation Request Acknowledge message to the core network 30d (Operation 304d). After sending this RANAP: Relocation Request Acknowledge message, the target RAN 20d falls in a state of waiting to receive a handover configuration complete message from the UE 40.
The core network 30d having received the RANAP: Relocation Request Acknowledge message sends a RANAP: Relocation Command message to the source RAN 10d (Operation 305d). The source RAN 10d having received the RANAP: Relocation Command message sends a RRC message to the UE 40 (Operation 306d).
Thereafter, it is assumed that the UE 40 detects a radio link failure due to radio environment deterioration (Operation 307) and makes a reconnection to a target cell C20d belonging to the target RAN 20d (Operation 308). At this time, the target RAN 20d is in a state of waiting to receive a handover configuration complete message from the UE 40 as described above. Accordingly, the container generation section 204, when detecting that the UE 40 having made a reconnection is under RANAP Relocation, sets a container including handover information in a normal RANAP: Relocation Complete message for completing a RANAP Relocation and sends it to the core network 30d (Operation 309d). The handover information included in the container is similar to that of the first example.
When receiving the RANAP: Relocation Complete message in which the container is set, the core network 30d sets this container in a RANAP: Iu Release Command message and sends it to the source RAN 10d (Operation 310d). The container analysis section 104 of the source RAN 10d, when receiving the RANAP: Iu Release Command message in which the container is set, analyzes this container and determines whether a too late handover occurred or whether a HO to wrong cell occurred. Then, after releasing all resources related to the Iu interface of the UE 40 in accordance with the RANAP: Iu Release Command message, the source RAN 10d sends a RANAP: Iu Release Complete message to the core network 30d (Operation 311d).
In a wireless communication system according to a fifth example of the present invention, a case of Intra-UMTS Enhanced Relocation will be shown. Both the source base station and the target base station are communication apparatuses of UTRAN and here referred to as a source RAN 10e and a target RAN 20e, respectively. Moreover, it is assumed that the core network issuing a handover command is a core network 30e. According to the present example, handover control (RANAP: Relocation) is performed between the source RAN 10e and the target RAN 20e, and handover information is transferred from the target RAN 20e to the source RAN 10e via the core network 30e, whereby the source RAN 10e can detect a handover status such as too late handover/handover to wrong cell.
Referring to
Subsequently, the handover control section 102 of the source RAN 10e sends a RRC message to the UE 40 to be handed over (Operation 404) and sends a RANAP: Relocation Commit message to the target RAN 20e (Operation 405). After this RANAP: Relocation Commit message has been sent, the target RAN 20e falls in a state of waiting to receive a handover configuration complete message from the UE 40.
Thereafter, it is assumed that the UE 40 detects a radio link failure due to radio environment deterioration (Operation 406) and makes a reconnection to a target cell C20e belonging to the target RAN 20e (Operation 407). At this time, the target RAN 20e is in a state of waiting to receive a handover configuration complete message from the UE 40 as described above. Accordingly, the container generation section 204, when detecting that the UE 40 having made a reconnection is under RANAP Relocation, sends a normal RANAP: Enhanced Relocation Complete Request message for completing a handover to the core network 30e (Operation 408). It is possible to set a container including handover information in this RANAP: Enhanced Relocation Complete Request message. The handover information included in the container is similar to that of the first example.
The core network 30e, in response to the RANAP: Enhanced Relocation Complete Request message, returns a RANAP: Enhanced Relocation Complete Response message (Operation 409), and the target RAN 20e, in response to this, returns a RANAP: Enhanced Relocation Complete Confirm message to the core network 30e (Operation 410). A container is set in this RANAP: Enhanced Relocation Complete Confirm message when no container is set in the RANAP: Enhanced Relocation Complete Request message in Operation 408.
When receiving the RANAP: Enhanced Relocation Complete Confirm message, the core network 30e sets a container in a RANAP: Iu Release Command message and sends it to the source RAN 10e (Operation 411). The container analysis section 104 of the source RAN 10e, when receiving the RANAP: Iu Release Command message in which the container is set, analyzes this container and determines whether a too late handover occurred or whether a HO to wrong cell occurred. Then, after releasing all resources related to the Iu interface of the UE 40 in accordance with the RANAP: Iu Release Command message, the source RAN 10e sends a RANAP: Iu Release Complete message to the core network 30e (Operation 412).
The present invention is applicable to handover control in mobile communication systems.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-074908 | Mar 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/001699 | 3/25/2014 | WO | 00 |
