JP6280439B2 - Radio control apparatus, connection destination switching method, and radio communication control system - Google Patents

Description

  The present invention relates to a wireless control device, a connection destination switching method, and a wireless communication control system.

  In the Third Generation Partnership Projects (3GPP), a mobile communication system called W-CDMA (Wideband-Code Division Multiple Access) based on Code Division Multiple Access (CDMA) technology is specified. (Hereafter referred to as “3G”), it is popular in many countries including Japan and Europe. The W-CDMA system is also called UMTS (Universal Mobile Telecommunications System).

  The Long Term Evolution (LTE) system, which is a further evolution of the 3G communication system, employs Orthogonal Frequency Division Multiplexing (OFDM) technology to achieve higher speed, higher capacity, and lower capacity. The specification is specified to be delayed.

  Such a type of wireless communication system is called RAT (Radio Access Technology). In addition to the above-described W-CDMA and LTE wireless communication systems, RAT also includes wireless communication systems such as the cdma2000 method and the GERAN (GSM / EDGE Radio Access Network) method. These RATs are operated by various operators at various frequencies in various countries and regions, and in some cases, a plurality of RATs can be used in the same region. When a load is distributed between RATs, or when a user desires a service provided only by a specific RAT, a process of moving a user located in one RAT to another RAT is performed.

  For example, when a voice communication service is not provided in an LTE RAT, it is assumed that a user connected to the RAT desires voice communication. In this case, the serviceability is maintained by moving the user to the 3G RAT and providing the voice communication service. This technology is called CS fallback (Circuit-Switched Fallback: CSFB). In addition, even when VoIP (Voice over Internet Protocol) is provided in the LTE system, switching from LTE VoIP to 3G system CS by SRVCC (Single Radio Voice Call Continuity) may be used to continue the voice communication service. Is possible.

  One method for switching connection destinations between different RATs is a method called redirection (Release with Redirection). When it becomes necessary to move a user (mobile station) of a certain RAT to another RAT, the network (NW) notifies the mobile station of a release redirection control signal “RRC Connection Release”. The release redirection control signal includes information indicating the switching destination RAT and the frequency used in the RAT, and notifies that the connection with the switching destination RAT should be established by disconnecting the current RAT. To do. The mobile station that has received the release redirection control signal (RRC Connection Release) disconnects from the current RAT, searches for a cell having a frequency designated as a switching destination, and acquires a synchronization signal. Further, broadcast information is acquired from the switching destination cell, and a connection to the switching destination cell is established. Accordingly, the mobile station is located in the switching destination cell, and can receive a service provided by the switching destination RAT, for example.

  There is handover as another RAT switching method. In the handover, it is possible to switch the RAT while maintaining the connection with the network including the radio. Therefore, there is a feature that packet loss hardly occurs as compared with redirection. In the redirection, there is a high possibility that packet retransmission processing occurs due to wireless disconnection. However, since the handover is performed while maintaining the connection, it is necessary to deal with the entire system, and there is an aspect that the difficulty of adding a function is higher than the redirection. SRVCC is a technique included in handover.

  A method is known in which a PDN bearer connection is temporarily stopped at the time of switching operation from the packet data network PDN to the non-packet data network, redirection is started in response to the termination of CSFB / SRVCC, and the PDN connection is resumed ( For example, see Patent Document 1).

Special table 2014-502831 gazette

3GPP Technical Specifications TS25.331 ver. 8.24.0 3GPP Technical Specification TS36.331 ver. 8.20.0

  When switching from LTE to 3G RAT for voice connection by CSFB, or when switching from VoIP in LTE to 3G CS by SRVCC, or from the state where you are in 3G instead of LTE depending on the communication radio wave situation When the voice connection is performed and the voice connection is terminated, it is conceivable to switch the RAT to LTE again. In this case, redirection is common as the control used. Since handover requires a packet bearer, handover is not possible when only voice is connected.

  However, in the case of a mobile communication terminal having a high communication frequency / communication amount, such as a smartphone, there are many cases in which a packet bearer is set during voice connection. In this case, if RAT switching by redirection is performed at the end of the voice connection, the packet is also disconnected at the same time, which may impair serviceability. Furthermore, in a case where there is a difference between the LTE area and the 3G area, there is a case where after redirection, the LTE area cannot be located and the packet communication is performed again after returning to the 3G area.

  Therefore, it is an object to reduce or suppress adverse effects on services as much as possible when switching the RAT to the second communication system at the end of the voice call in the first communication system.

A wireless control device that controls wireless communication of a mobile terminal in a first wireless communication system that provides a voice call service,
At the end of the voice call of the mobile terminal, the presence / absence of packet connection and the area coverage status of the second wireless communication system are judged, and there is no packet connection or the amount of packet communication data is below the first threshold. And when the mobile terminal is covered by a service area of the second wireless communication system, a control unit that instructs the mobile terminal to redirect to the second wireless communication system,
Have

  The adverse effect on the service can be reduced or suppressed when switching the RAT to the second communication system at the end of the voice call in the first communication system.

It is a figure which shows the example of the radio | wireless communications system to which the radio | wireless control technique of embodiment is applied. It is a flowchart of the connection destination switching method of the embodiment. It is a schematic block diagram of the radio | wireless control apparatus used with the system of FIG.

  FIG. 1 shows a configuration example of a wireless communication system 1 to which the connection destination switching method of the embodiment is applied. In the wireless communication system 1, LTE services and 3G services are provided in geographically identical or overlapping areas. An eNB (evolved Node B) 22 which is an LTE base station is provided to the LTE core network 21 and has jurisdiction over LTE areas 23a and 23b. The 3G radio controller (RNC) 12 is connected to the 3G core network 11 and controls the 3G areas 13a and 13b. Note that one or more base station apparatuses connected to the RNC 12 and having jurisdiction over the areas 13a and 13b are omitted.

  When a mobile communication terminal (UE: User Equipment) 40 located in the LTE area 23a makes a voice connection, switching to 3G is performed by CSFB. In the embodiment, the voice call service is provided only in the 3G circuit switching domain, and VoIP (Voice over Internet Protocol) is not directly provided on the specific RAT of the LTE system in which the mobile communication terminal 40 is located. And Note that the VoIP service may be provided directly in LTE, but if the mobile communication terminal 40 does not support VoIP, CSFB is implemented, or even if it is compatible with VoIP, SRVCC is switched to 3G CS or wireless quality This includes the case where communication is performed by circuit switching from the 3G area due to the influence of the above. Further, it is assumed that the mobile communication terminal 40 can communicate with both LTE and 3G. When the voice communication service cannot be provided in the state where the mobile communication terminal 40 is still in LTE when the voice connection is made, the connection switching (CSFB) to 3G is performed using the single radio of the mobile communication terminal 40. Is called. In FIG. 1, LTE and 3G are taken as an example, but switching between other RATs such as GSM (Global System for Mobile Communication) and LTE may be used.

  The LTE cell and the 3G cell may cover a substantially equivalent area or may have a difference in the covered area. The case where there is a difference in the covered area includes a case where the frequency band is different, a case where the area is degenerated due to small interference such as a femto cell or a CSG (Closed Subscriber Group) cell.

  When the RAT is switched to 3G by CSFB, there is a problem whether it should be redirected or handed over to LTE after the call is finished. In the embodiment, redirection (forced disconnection) is not performed when a packet bearer is set, instead of simply performing redirection at the end of a call. In addition, even when outside the LTE area, redirection is not performed to LTE. This will be specifically described below.

  FIG. 2 is a flowchart of the connection destination switching method according to the embodiment. The radio network controller 12 determines whether or not there is a packet connection at the timing of voice call disconnection of the mobile communication terminal 40 (S11). When there is no packet connection in the mobile communication terminal 40 (NO in S12), it is determined whether the LTE area is sufficient and the mobile communication terminal 40 can be located (S13). If the LTE area is sufficient for the mobile communication terminal 40 (YES in S13), redirection to LTE is performed (S14). This pattern is a pattern that does not affect the service even if an instruction to disconnect the connection at 3G and return to LTE is issued because there is no packet communication to maintain the connection and it is possible to return to LTE. The radio network controller 12 transmits a release redirection control signal to the mobile communication terminal 40. Based on the LTE cell information and frequency information included in the control signal, the mobile communication terminal releases the connection with 3G and transmits an RRC connection request to the LTE cell.

  The determination whether the LTE area is sufficient for the mobile communication terminal 40 (S13) may be performed based on the measurement result from the mobile communication terminal 40, or a flag indicating whether the LTE area is sufficient at the present time on the system in advance. You may keep it. Alternatively, the wireless control device 12 may hold a past redirection success rate, and may determine that the LTE area coverage is sufficient when the success rate is equal to or greater than a certain value. When the LTE area is restricted due to failure / congestion or the like, the LTE area rate may be determined to be insufficient.

  As the redirection success rate, communication connection information on the LTE side may be used. The communication connection information on the LTE side may be acquired from the LTE core network 21 via the 3G core network 11. When communication connection information on the LTE side cannot be acquired, a case where packet communication connection is performed in the 3G area within a certain time after redirection may be regarded as failure. This is a case where the user cannot stay in the LTE area after the voice ends but stays in 3G. When a time exceeding a certain time has elapsed after the redirection, it may be considered that the redirection is successful.

  If there is a packet connection at the end of the voice (YES in S12), it is determined whether the amount of packet communication data is equal to or less than a threshold (S15). This threshold is a value held on the system, and may be manually changeable from an external system. Further, for example, when the degree of regulation is strong due to congestion on the LTE side, the threshold value may be automatically lowered to control the redirection to LTE. If the threshold is lowered to zero, it is possible to always suppress redirection. Conversely, when the 3G side is congested, it is possible to raise the threshold value so that there is substantially no packet communication data amount and always perform redirection. As described above, the threshold value can be used like a redirection execution switch.

  If the packet communication data amount is equal to or smaller than the threshold value (YES in S15), it means that the influence on the packet communication service is slight even if switching to the LTE side with a single radio. In this case, it progresses to S13, it is judged whether it is covered by the LTE area, and if it is covered by the LTE area, the redirection to LTE is performed (S14). When the redirection to LTE is determined, a release redirection control signal is transmitted from the network to the mobile communication terminal 40. The mobile communication terminal 40 is located in the LTE side by releasing the 3G connection.

  When the amount of packet communication data exceeds the threshold (NO in S15), it means that the influence on the service due to packet disconnection is large. In this case, it is determined whether or not to perform handover to LTE, not redirection with disconnection (S16).

  When performing handover to LTE (YES in S16), handover to LTE is performed (S18). With a handover, packet loss can be minimized or avoided. When handover to LTE is not performed (NO in S16), 3G connection is maintained (S17). That is, instead of transmitting an RRC connection Reconfiguration or Release with Redirection control signal to the mobile communication terminal 40, a control signal for continuing the 3G service is transmitted. As a result, it is possible to avoid disconnection of packet communication performed in parallel at the end of the voice call.

  For determination of handover execution (S16), a second threshold (a threshold for handover) based on the amount of packet communication data may be set. The second threshold value is generally set to a value larger than the first threshold value for determining whether or not there is an effect of service disconnection due to redirection. As an example, when there is an amount of packet communication data exceeding the second threshold, handover is performed to LTE with a high communication speed. When the 3G communication speed is sufficient, 3G communication is continued without performing handover to LTE.

  Even when the LTE area is not covered in S13 (NO in S13), the process proceeds to the determination of whether or not handover to LTE is possible (S16). When it is not covered by the LTE area, handover to LTE is not normally performed, but the mobile communication terminal 40 is proceeding toward the LTE service providing area, and a relatively large amount of packet communication is performed. If so, a handover to LTE may be performed. In addition, when the LTE service provision area coverage is a certain value or more, a handover to LTE may be performed.

  FIG. 3 is a schematic configuration diagram of the wireless control device 12 according to the embodiment. The wireless control device 12 includes a core network communication processing unit 121 that performs communication with a core network, a mobile communication terminal communication processing unit 122 that performs communication with a mobile communication terminal in a wireless access section, a control unit 128, and a storage unit 129. Have. The storage unit 129 includes a communication data amount threshold holding unit 123 and an LTE area cover information holding unit 124. The control unit 128 includes a packet communication state determination unit 125, an LTE area determination unit 126, and a RAT switching determination unit 127.

  When the core network communication processing unit 121 receives a voice disconnection signal for the mobile communication terminal 40 from the core network 11, the packet communication state determination unit 125 determines whether or not the mobile communication terminal 40 has packet communication. When the mobile communication terminal 40 is currently performing packet communication, the communication data amount threshold value holding unit 123 is referred to, and the current packet communication amount of the mobile communication terminal 40 is compared with the first threshold value. A threshold (including a first threshold and a second threshold described later) regarding the communication data amount can be changed from the external threshold setting system 50. Alternatively, the wireless control device 12 may automatically update based on LTE restriction information or the like.

  When there is no packet communication or when the packet communication amount is equal to or less than the first threshold, the LTE area determination unit 126 refers to the LTE area cover information holding unit 124 and the position of the mobile communication terminal 40 is more sufficient in the LTE area. To determine if it is covered. The LTE area cover information holding unit 124 may indicate whether or not the LTE area is covered by the flag information, or may hold a redirection success rate to the past LTE system. Instead of the redirection success rate to LTE, the LTE service providing area coverage rate may be maintained. Further, the radio network controller 12 may change the area cover information based on LTE regulation information.

  Based on the determination results of the packet communication state determination unit 125 and the LTE area determination unit 126, the RAT switching determination unit 127 determines whether to perform redirection to LTE, perform handover, or continue 3G communication. judge. The RAT switching determination unit 127 may determine whether or not to perform the handover by referring to the second threshold value for handover determination held in the communication data amount threshold holding unit 123, or the LTE area cover information holding unit 124. Whether or not handover can be performed may be determined with reference to the LTE cover information held in FIG.

  With this configuration, it is possible to perform RAT switching control for the mobile communication terminal 40 while minimizing the influence on the service.

1 Radio Communication System 11 3G Core Network 12 Radio Control Unit (RNC)
13a, 13b 3G area 21 LTE core network 22 Base station (eNB)
23a, 23b LTE area 40 Mobile communication terminal 121 Core network communication processing unit 122 Mobile communication terminal communication processing unit 123 Communication data amount threshold holding unit 124 LTE area cover information holding unit 125 Packet communication state determination unit 126 LTE area determination unit 127 RAT switching Determination unit 128 Control unit 129 Storage unit

Claims (6)

A wireless control device that controls wireless communication of a mobile terminal in a first wireless communication system that provides a voice call service,
At the end of the voice call of the mobile terminal, the presence / absence of packet connection and the area coverage status of the second wireless communication system are judged, and there is no packet connection or the amount of packet communication data is below the first threshold. And when the mobile terminal is covered by a service area of the second wireless communication system, a control unit that instructs the mobile terminal to redirect to the second wireless communication system,
A wireless control device comprising: The control unit is configured to cover at the end of a voice call of the mobile terminal, when there is a packet connection with an amount of packet communication data exceeding the first threshold, or to cover the position of the mobile terminal in the area of the second wireless communication system. even if not, and if the mobile terminal is in progress in the direction of the service providing area of the second wireless communications system, the actual performing handover to the second radio communication system , to the front Symbol mobile terminal, radio network controller according to claim 1, wherein instructing a handover to the second radio communication system, characterized in that. The control unit is configured to cover at the end of a voice call of the mobile terminal, when there is a packet connection with an amount of packet communication data exceeding the first threshold, or to cover the position of the mobile terminal in the area of the second wireless communication system. even if it not, and, if the packet connection is a packet communication data amount exceeding the first threshold value is greater than a second threshold, performing a handover to the second radio communication system When the amount of packet communication data is less than or equal to the second threshold, the mobile terminal is instructed to continue packet communication in the first wireless communication system without performing the handover. The wireless control device according to claim 1 . Storage unit for storing the information of the first threshold value, the area cover information of said second radio communication system,
Further comprising, said control unit, based on the control information of the first and second wireless communication system, and changing at least one of the information and the area coverage information of the first threshold value The radio control apparatus according to claim 1. In the first wireless communication system that provides the voice call service, when the mobile terminal disconnects the voice call, in the wireless control device of the first wireless communication system, the presence / absence of packet connection in the mobile terminal, To determine the area coverage of the wireless communication system
When the mobile terminal has no packet connection or the amount of packet communication data is less than or equal to a first threshold and the mobile terminal is covered by the service area of the second wireless communication system, Transmitting a control signal instructing redirection to the second radio communication system from the radio controller to the mobile terminal;
A connection destination switching method characterized by that. A first wireless communication system providing a voice call service;
A second wireless communication system different from the first wireless communication system;
A mobile terminal capable of communicating with both the first wireless communication system and the second wireless communication system;
A radio network controller that controls radio communication of the mobile terminal in the first radio communication system;
Including
The radio control device determines whether or not there is a packet connection in the mobile terminal and the area coverage status of the second radio communication system at the end of the voice call of the mobile terminal,
When the mobile terminal has no packet connection or the amount of packet communication data is less than or equal to a first threshold and the mobile terminal is covered by the service area of the second wireless communication system, Transmitting a control signal instructing redirection to the second radio communication system from the radio controller to the mobile terminal;
A wireless communication control system.

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