JP5103275B2 - Mobile communication system control method - Google Patents

Description

  The present invention relates to a mobile communication system control method. Specifically, the present invention relates to a system control method for a mobile communication system using a small base station (femtocell base station) called a femtocell which covers a radius of about 10 m and provides a call service via the Internet network.

In recent years, an extremely small base station having a cover area (cell radius) of about several tens of meters has been proposed as a base station used in a wireless communication system (Patent Document 1). A cell formed by such a small base station is called a “femto cell”. The cell radius of the femtocell is extremely small compared to a cell having a cell radius of about several kilometers to 10 km, generally called “macrocell”. The femtocell base station is connected to a fixed communication line such as an ADSL (Asymmetric Digital Subscriber Line), an optical fiber, or a coaxial cable, and provides a mobile phone communication service via the fixed communication line.
By installing a femtocell base station in a user's building or the like and connecting to an already laid broadband line, the base station can be easily provided in the building.
Such a femtocell base station is a technology that can be expanded easily and at a lower cost than installing a large macrocell base station. It is.

  Here, a conventional mobile phone communication network using a large-scale cell is a so-called independent network using a dedicated line (for example, an ATM dedicated line), and communication quality is ensured by relaying a call using circuit switching. It is well planned.

However, since the femtocell base station transmits a signal via an existing broadband line, it is not always sufficient to ensure communication quality.
In other words, since communication via a femtocell base station is a data transmission method (packet transmission method) using the Internet network, it is not possible to occupy a transmission path by line switching as in a public mobile phone communication network, and between terminals. Even if a network connection is established, it is not always guaranteed that transmission data can be exchanged in order with good timing.
In particular, there is a concern that data loss will increase during transmission of signals through fixed communication lines such as ADSL, optical fiber, and coaxial cable. If the transmission data loss is large during a call from the femtocell base station via the broadband line or the Internet line, the conversation between the callers is interrupted or difficult to hear, and the mobile phones are connected. Despite this, we are worried that there will be a situation where the conversation is not established just by hearing noise.
Since the telephone calls the other party, if the other party is called frequently even though the telephone call is not made, the telephone partner is extremely inconvenienced. Therefore, ensuring a certain communication quality is very important in communication services.

  For example, in a conventional fixed telephone service, a configuration is known in which when a user makes a call (call) operation to a destination, a communication quality test is performed before the circuit switch makes this call connection. If it is determined that the communication quality cannot be ensured, the call connection is not performed. In this case, for example, a busy tone is emitted from the circuit switch to the calling user to notify that the connection is impossible. This prevented an inconvenient situation where the conversation was not called while calling the other party.

Even in mobile communication services using broadband lines from femtocell base stations, from the viewpoint of ensuring call quality, "If the required communication quality cannot be ensured at the start of a new session, the session will not be performed" etc. By taking these measures, it is said that “it is necessary not to deteriorate the quality or the like as compared with the service provided to the user so far”. (Non-patent document 1: Handling policy (draft) concerning laws and regulations related to the Radio Law and Telecommunications Business Law for utilization of femtocell base stations, February 6, 2008, Ministry of Internal Affairs and Communications)
JP 2007-267424 A Handling policy (draft) regarding laws and regulations related to the Radio Law and Telecommunications Business Law for the use of femtocell base stations, February 6, 2008, Ministry of Internal Affairs and Communications http://www.soumu.go.jp/s-news /2008/pdf/080206_9_bs1.pdf

However, the user is inconvenienced if the call cannot be made despite the important requirement. This is a particularly troublesome problem in case of urgent requirements.
In the future, when a large number of femtocell base stations are installed in the house, since users often make calls from indoors rather than outdoors, communication via the broadband line may not be connected from the femtocell base station. If it occurs frequently, there is a concern that user inconvenience and dissatisfaction will increase.
Furthermore, as the number of users who use mobile phone communication via the network line from the femtocell base station increases, it is expected that the network line will be crowded and data transmission may not be successful. If communication is not connected in such a case, the user's inconvenience is immeasurable.

  An object of the present invention is to provide a mobile communication system control method that improves convenience in a call service while expanding a service area at low cost by using a femtocell base station.

  The mobile communication system control method of the present invention is a base station that is connected to the Internet network via a broadband line and relays calls between mobile communication terminals by performing wireless communication with mobile communication terminals, and is a public mobile phone A femtocell base station that covers an area smaller than a macrocell base station that constitutes a communication network, and is connected to the femtocell base station via the Internet network to perform network control between the femtocell base stations. And a femtocell control station connected to a core network of a public mobile phone communication network via a gateway, wherein the mobile communication terminal controls a mobile communication system for relaying a radio call between mobile communication terminals. Before establishing a call session between each other, the femtocell base station and the femtocell control station A link quality determination step for inspecting the communication quality of the link between networks, and if the communication quality is OK in the link quality determination step, a call between mobile communication terminals from the femtocell base station via the Internet network A call connection step for performing a connection, and a line switching step for switching a line to a call connection via the macro cell base station of the public mobile phone communication network when the communication quality is NG in the link quality determination step. It is characterized by providing.

In such a configuration, the femtocell base station performs radio communication with the mobile communication terminal and performs communication relay as a base station. When the femtocell base station is connected to the Internet network via a broadband line, the femtocell base station relays a call between mobile communication terminals by transmitting and receiving data using a packet transmission method.
At this time, the femtocell base station is connected to the femtocell control station via the Internet from the broadband line, and is connected to the base station that manages the other mobile communication terminal in the cover area through network control by the femtocell control station. .

  One mobile communication terminal communicates via a femtocell base station. The other mobile communication terminal may communicate via a femtocell base station, or via a macrocell base station of a public mobile phone communication network. Also good.

Here, in the communication via the femtocell base station, the femtocell base station and the femtocell control station are connected via the Internet network at least one of the link from the calling side and the link from the receiving side. It will be.
Since such an Internet network uses a packet transmission method rather than a line occupancy method, transmission data loss occurs under the influence of network congestion and noise, and conversations between callers are interrupted and difficult to hear. Furthermore, there is a concern that a situation may occur in which a conversation is not established only by noise being heard although the mobile communication terminals are connected to each other.

Therefore, in the present invention, when there is a call session request via the femtocell base station, a link quality determination step is performed before establishing a call session between mobile communication terminals, and the femtocell base station The communication quality with the femtocell control station is inspected.
Such communication quality inspection is performed by transmitting test data between the femtocell base station and the femtocell control station, calculating the data loss occurrence rate, and determining whether the data loss rate exceeds a predetermined threshold. An example is determining quality.
If it is determined in the link quality determination step that the data transmission between the femtocell base station and the femtocell control station is good, the other party mobile communication so as to start the requested call session. A call is made to the terminal to establish a call connection.
On the other hand, if it is determined in the link quality determination step that the data transmission quality between the femtocell base station and the femtocell control station is poor, the Internet between the femtocell base station and the femtocell control station Line switching is performed so as to make a call connection using another line without performing network connection via the network (line switching step).
That is, instead of a link via a femtocell base station, a requested call session is realized by moving a line to a call line via a macrocell base station of a public mobile phone communication network.
As a result, the call requested by the user is securely connected, and the call quality of the connected call session is guaranteed.
Further, even in an Internet service that is already used by a user, the use of other services is not restricted by narrowing the communication band due to service competition.
In this way, it is possible to provide a mobile communication service that improves convenience by appropriately utilizing an existing band without deterioration in quality.

  In the present invention, the femtocell control station, a pre-connection unit that makes a trial connection with the femtocell base station before making a call connection between mobile communication terminals, a test data storage unit that stores test data, The femtocell base station is transmitted from the femtocell control station and a pre-calling / receiving unit that makes a trial connection request or response to the pre-connection unit in response to a call session request. A communication quality determination unit for determining communication quality of test data, and the link quality inspection step is performed by the femtocell control station and the femtocell base station by the pre-connection unit and the pre-calling / receiving unit. Test data transmitted from the femtocell control station to the femtocell base station while the test data storage unit is connected to the network And a communication quality determining step of receiving the transmitted test data and determining the communication quality by comparing the packet loss rate of the test data with a predetermined threshold at the communication quality determining unit. Is preferred.

In such a configuration, trial connection is made by exchanging communication between the pre-connection unit of the femtocell control station and the pre-calling / receiving unit of the femtocell base station before connecting the mobile communication terminals. In this state, test data is transmitted from the femtocell control station to the femtocell base station (test data transmission step). Then, the packet loss of the test data is determined by the communication quality determination unit of the femtocell base station (communication quality determination step).
According to such a configuration, communication quality can be confirmed in a link (downlink) from the femtocell control station to the femtocell base station.

Here, in determining communication quality by sending test data, both the uplink and the downlink may be checked, but when checking the uplink (direction from the femtocell base station to the femtocell control station) The femtocell base station must have functions such as possessing test data or accessing the test data during pre-connection and transmitting it to the femtocell control station. Become.
Alternatively, it may be possible to exchange test data between mobile communication terminals in a trial connection state, and judge the communication quality for each terminal. However, it is still necessary to avoid the increase in size and cost of mobile communication terminals. I can't.

In this regard, the present invention employs a configuration in which the packet transmission quality is determined only for the downlink from the femtocell control station to the femtocell base station. The femtocell base station side is provided with a pre-connection function and a communication quality determination function. As a result, the communication quality can be determined before call connection while reducing the function of the femtocell base station to reduce the size and cost.
Further, when the femtocell base station which is a relay station, not the mobile communication terminal, performs communication quality determination work on behalf of the terminal, an increase in the function of the mobile communication terminal can be avoided.

  In the communication quality determination step, in addition to the packet loss rate of the test data, the communication quality may be determined by comparing the jitter rate and the delay value with a predetermined threshold.

In the present invention, the test data is preferably data in which video and audio are synchronized.
Since the purpose is to determine the call quality, only audio data may be used. However, in order to ensure sufficient call quality, data of only the audio band is not sufficient, and the video and audio that are the predetermined length of data are synchronized. It is preferable to use data.

  In the present invention, in the line switching step, when the femtocell base station stops wireless connection with the mobile communication terminal wirelessly connected to the femtocell base station, the mobile communication terminal voluntarily It is preferable to communicate with the station and transfer the location management.

  In such a configuration, when it is determined that the communication quality cannot be ensured, the femtocell base station stops the connection with the mobile communication terminal. When the connection with the femtocell base station is disconnected in this way, the mobile communication terminal re-searches the receivable radio wave and establishes communication with the available macrocell base station. Thereby, the mobile communication terminal can execute a call connection not via the femtocell base station but via the macrocell base station.

Here, when the communication quality through the femtocell base station is NG when performing the link quality determination process (including determining that the femto control station fails and the determination process cannot be performed correctly is NG). It is possible that the call session is not connected.
However, if the femtocell base station retains the location management of the mobile communication terminal even though the call session is not connected, the mobile communication terminal cannot make a call to the other party, or the mobile There is a risk that the communication terminal will get stuck in an inconvenient situation where no telephone call is received.
In such a case, when a user cannot bother to make a call without moving to the outside of the coverage area of the femtocell base station, there is a problem that it is inconvenient because there is a femtocell base station. In the case of the incoming side, the user does not notice that the femtocell base station does not connect the call session.

  In this regard, in the present invention, when the communication quality is determined to be NG in the link quality determination step, the femtocell base station stops the wireless connection with the mobile communication terminal and removes the location management. Call connection can be made using a cellular phone communication network.

  In the present invention, the line switching step includes a base station having a sufficiently strong radio wave reception intensity among the surrounding macrocell base stations with respect to the mobile communication terminal in which the femtocell base station is wirelessly connected to the femtocell base station. After instructing, it is preferable to stop the wireless connection with the mobile communication terminal.

  According to such a configuration, since the mobile communication terminal does not need to search for radio waves by itself, the communication line can be switched smoothly.

  In the present invention, it is preferable that the femtocell base station informs a home memory station of a public mobile phone communication network of location information of the mobile communication terminal via the femtocell control station.

According to such a configuration, the location management of the mobile communication terminal can be smoothly transferred even in the home memory station of the public mobile phone communication network.
In addition, the call session connection process may proceed in parallel without waiting for the connection between the mobile communication terminal and the macrocell base station.
When such an operation is executed, subscriber information of a mobile phone that uses the femtocell base station may be registered in advance in the femto base station.

  Note that when a plurality of mobile phones can access the femtocell base station at the same time, each time a call session request is made through the femtocell base station, the above-described operation is performed to determine the link quality, It is a process to connect a session or route it to another line. For example, when the femtocell base station has already relayed a call session of several mobile communication terminals and there is a new call connection request for another mobile communication terminal, the femtocell base station Each unit executes a process such as a link quality determination process and a line switching process.

Embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A first embodiment of the mobile communication system of the present invention will be described.
FIG. 1 is a diagram showing an overall configuration of a mobile communication system 100 according to the first embodiment.
The mobile communication system of this embodiment includes a public mobile phone communication network 200 and a femtocell communication network 300.

The public mobile phone communication network 200 is a known public mobile phone communication network constructed for mobile communication terminals (mobile phones). That is, a base station 210, a radio network controller (RNC) 220, and a core network 230 for mobile phone communication are provided.
The base station 210 here is a base station that constitutes a so-called macro cell, and has a cell radius of about several kilometers to 10 kilometers, and can simultaneously perform multiple simultaneous connections from several tens of mobile phones (mobile communication terminals, mobile stations). is there. In the following description, the macro cell base station 210 will be referred to.
The RNC 220 performs radio channel control, call processing, and the like at the time of mobile phone location registration, outgoing / incoming calls, handover, and the like.
The core network 230 includes an LR (location register: home memory station) 231 and a GW (gateway: mobile communication network gateway control station) 232 and the like, and constitutes a basic dedicated line for mobile phone calls.

The femtocell communication network 300 includes a femtocell base station 400, a broadband line 310, an Internet network 320, and a femtocell control station 330.
The femtocell base station 400 is a small base station that is installed in the building 20 and covers an area (femtocell) having a small output (for example, 20 mW or less) and a radius of several tens of meters (femtocell). The femtocell base station 400 is connected to the broadband line 310 already laid in the building 20 and relays that the mobile phone 10 makes a call via the Internet network 320.

For convenience of explanation of the present invention, the building 20 where the femtocell base station 400 is installed is in an area covered by the macrocell base station 210. An example will be described in which the femtocell base station 400 is provided for the purpose of supplementing a dead area where radio waves from the macrocell base station 210 are weakened in a building or the like.
However, in general, the femtocell base station 400 can be installed even outside the macro cell as long as the broadband line 310 is drawn.
The configuration and operation of the femtocell base station 400 will be described later.

  The type of broadband line 310 is not limited as long as it is a relatively high-speed connection line such as ADSL, coaxial cable, or optical fiber. Of course, when a LAN is constructed in the building 20, the femtocell base station 400 may be connected to such a LAN line, and the femtocell base station may be connected to the broadband via the LAN. .

  The Internet network 320 is not particularly described, and is a network using the TCP / IP protocol and is a so-called known Internet.

The femtocell control station 330 supervises a plurality of femtocell base stations 400 via the Internet network 320 and controls connection of the mobile communication terminal (mobile phone 10) via the femtocell base station 400.
The femtocell control station 330 is connected to a core network 230 dedicated to mobile phones via the GW 232.
The configuration and operation of the femtocell control station 330 will be described later.

FIG. 2 is a diagram showing a configuration of the femtocell base station 400. As shown in FIG.
The femtocell base station 400 includes a radio communication unit 410, an RNC unit 412, a protocol control unit 413, an interface (I / F) 414, and a connection control unit 420.
The wireless communication unit 410 performs wireless communication with the mobile phone 10 via the antenna 411. That is, data is encoded and decoded, and communication with the mobile phone 10 is performed via a radio wave having a predetermined output.
In addition to the location registration of the mobile phone 10 connected to the femtocell base station 400, the RNC unit 412 is configured to use a frequency division method when a plurality of (for example, four) mobile phones 10 are simultaneously connected to one femtocell base station 400. Multiple access control is performed by a method such as a time division method or a code division method.
Further, since communication via the femtocell base station 400 passes through the Internet network 320, the protocol control unit 413 performs such protocol conversion according to the TCP / IP protocol.

  The connection control unit 420 includes a pre-call / reception unit 430, a communication quality determination unit 440, a network connection unit 450, and a line switching unit 460.

The pre-calling / receiving unit 430 performs outgoing / incoming calls for simulating the connection between the femtocell base station 400 and the femtocell control station 330 before making a formal call or response to the partner mobile phone.
The pre-calling / receiving unit 430 includes a pre-calling unit 431 and a pre-calling unit 432.
The pre-sending unit 431 sends a pre-sending signal to the femtocell control station 330 when there is a call request from the mobile phone 10 located in the coverage area of the femtocell base station 400. This pre-transmission signal is transmitted in response to a call request from the mobile phone 10, but is not intended for a formal call connection or a call to the other party, and a trial connection is established for the femtocell control station. 330 is requested. Therefore, the pre-transmission signal may not include the destination telephone number included in the call request.
When there is a pre-transmission requesting a trial connection from the femtocell control station 330 to the femtocell base station 400, the pre-incoming unit 432 permits the trial connection to the femtocell control station 330. Send an incoming signal.

The communication quality determination unit 440 determines a reception state of test data transmitted from the femtocell control station 330 in a state where the femtocell base station 400 and the femtocell control station 330 are connected on a trial basis. That is, when predetermined test data is transmitted from the femtocell control station 330 as a packet, the communication quality determination unit 440 determines whether the packet data has arrived correctly in order.
A determination threshold is set in advance in the communication quality determination unit 440. If the packet loss is smaller than the threshold, it is determined that the communication quality is OK, and if the packet loss is equal to or higher than the threshold, the communication quality is NG. Is determined.
The threshold for determining the communication quality varies depending on the desired communication quality, the amount of data to be transmitted, and the like. As an example, the threshold value is whether or not the threshold value is exceeded.
When the communication quality is OK, the communication quality determination unit 440 notifies the result to the network connection unit 450, and when the communication quality is NG, the communication quality determination unit 440 notifies the result to the line switching unit 460.

The network connection unit 450 establishes a formal network connection with the femtocell control station 330 in response to the determination of the communication quality OK in the communication quality determination unit 440.
The network connection unit 450 includes a transmission / reception unit 451 that performs outgoing / incoming calls, and a connection establishment unit 454 that maintains and manages the connected network.
When the outgoing / incoming part 451 of the network connection part 450 performs a formal call connection, the calling / sending part 452 transmits the outgoing call request with the telephone number of the other party mobile phone.
In addition, the incoming call response unit 453 responds to the femtocell control station 330 with a formal network connection, and the connection establishment unit 454 calls the mobile phone 10 that is being called to make a call between mobile phones. Establish a connection.

The line switching unit 460 performs line switching processing in response to the determination of the communication quality NG in the communication quality determination unit 440. That is, when the femtocell base station 400 receives a call request from the mobile phone 10 on the caller side, the mobile phone 10 that is calling is switched to another line instead of via the femtocell base station. Execute the process to communicate.
The other line here is a public mobile phone line 200 via the macrocell base station 210.
The mobile phone 10 on the calling side removes the management of the femtocell base station 400 by the processing of the line switching unit 460 and communicates with the macrocell base station 210 to call and make a call to the counterpart mobile phone 10.

  On the other hand, when the femtocell base station 400 holds the receiving-side mobile phone 10 in the cover area, the femtocell base station 400 cannot maintain communication quality, so that the calling and connection to the called mobile phone 10 is performed. Do not relay. The line switching unit 460 then sends a command to the femtocell control station 330 to call the mobile phone 10 to be called via the public mobile phone communication network 200. As a result, connection relaying is performed on the cellular phone 10 to be called via the macro cell base station 210 of the normal public cellular phone communication network.

Next, the configuration of the femtocell control station 330 will be described.
FIG. 3 is a diagram showing a configuration of the femtocell control station 330. As shown in FIG.
The femtocell control station 330 includes a network control unit 331, a pre-connection unit 332, and a test data storage unit 333.

The network control unit 331 controls and manages the network connection. The network control unit 331 does not perform formal network connection processing on the pre-originated signal transmitted from the femtocell base station 400. The process is performed by the pre-connection unit 332.
The pre-connection unit 332 establishes a trial connection between the femtocell base station 400 and the femtocell control station 330 in response to a pre-transmission or pre-incoming call requesting a trial connection from the femtocell base station 400. Further, the pre-connection unit 332 accesses the test data storage unit 333 when the trial connection state is established, reads the test data stored in the test data storage unit 333, and transmits the packet to the femtocell base station 400. To do.

The test data storage unit 333 stores test data for inspecting communication quality.
The test data may consist of only audio data from the viewpoint of confirmation of call quality, but it is data (so-called talkie) that synchronizes video and audio in order to ensure good communication quality. Is preferred.
Since the mobile phone 10 is often equipped with services such as videophones, there is a fear that transmission quality inspection only for the voice band may not be sufficient. To secure the quality of mobile phone communication, use talkies as test data. Is preferable.

An operation of the mobile communication system 100 having such a configuration will be described.
From the spirit of the present invention that provides the mobile communication system 100 including the femtocell base station 400, in the description of the operation, a case where at least one of the calling side and the called side communicates via the femtocell base station 400 will be described.
Such patterns include:
(1) When both the mobile phone on the calling side and the mobile phone on the receiving side communicate via the femtocell base station (first embodiment),
(2) When the originating side communicates via a femtocell base station and the terminating side communicates via a macrocell base station (second embodiment),
(3) There are three cases where the originating side communicates via a macrocell base station and the terminating side communicates via a femtocell base station (third embodiment).

(First embodiment)
First, the first embodiment will be described. That is, (1) A case will be described in which a calling-side mobile phone and a receiving-side mobile phone communicate via a femtocell base station. FIG. 4 is a flowchart showing the overall configuration of the mobile communication system control method in the first embodiment. FIG. 5 is a diagram for explaining the data flow in the first embodiment.

In the present invention, when a manipulation of the call from the user of the portable telephone 10A is (ST100), before reaching the call establishment (ST 200) by calling the mobile phone 10B of the called party, the communication of the originating links _{L A} Check the communication quality of the quality and the terminating link _{L B} (ST110, ST150), when the communication quality can be ensured (ST120, ST160: YES), wherein only the point of executing a call connection via the femtocell base station 400 to Have
Hereinafter, it demonstrates in order.

  The user of the mobile phone 10A performs a calling operation toward the other mobile phone 10B (ST100). Then, the femtocell base station 400A that manages the mobile phone 10A as a mobile station in the area receives the call operation, and starts a connection relay operation process from the caller mobile phone 10A to the partner mobile phone 10B. And a transmission side link quality inspection process (ST110) is performed. The transmission side link quality inspection process (ST110) will be described with reference to FIG.

Figure 6 is a diagram illustrating a sequence of inspecting the communication quality of the originating links L _A between the originating side of the femto cell base station 400A and the femtocell control station 330.
When receiving the call request (ST100) from the mobile phone 10A, the transmitting-side femtocell base station 400A first performs pre-transmission toward the femtocell control station 330 (pre-transmission step ST111). In the pre-transmission step (ST111), the pre-transmission unit 431 transmits a simulated call signal, which signals the femtocell control station 330 to perform a call quality inspection. This pre-transmission signal may include the mobile phone number of the other party, but is not particularly necessary.

When the femtocell control station 330 receives the pre-transmission signal, the femtocell control station 330 passes this signal to the pre-connection unit 332. When the pre-connection unit 332 receives the pre-transmission signal, the pre-connection unit 332 accesses the test data storage unit 333 and reads the test data. This test data is transmitted to the transmitting-side femtocell base station 400A by the packet transmission method (test data transmission step ST112, D _{A in} FIG. 5).

The femtocell base station 400A receives the test data and determines the communication quality based on the received test data. That is, it is determined whether the received test data packet has arrived without missing in sequence order.
The packet data received by the femtocell base station 400A is sent to the communication quality determination unit 440 to determine the communication quality (communication quality determination step ST113).
The communication quality determination unit 440 determines that the communication quality is OK if the packet loss rate is smaller than the predetermined threshold, and conversely determines that the communication quality is poor if the packet loss rate is equal to or higher than the predetermined threshold.

  As described above, the transmission side is determined by the pre-transmission step (ST111) from the femtocell base station 400A, the test data transmission step (ST112) from the femtocell control station 330, and the packet loss rate determination (ST113) by the communication quality determination unit 440. A link quality inspection process (ST110) is configured.

If the communication quality determination unit 440 determines that the communication quality is OK (ST120: YES), the calling-side femtocell base station 400A is in a call connection permission state (ST130).
The quality OK determination by the communication quality determination unit 440 is sent to the network connection unit 450. Then, the network connection unit 450 executes processing for network connection. That is, a call request is sent from the call transmission unit 452 to the femtocell control station 330 together with the telephone number of the other party (ST140).

When the femtocell control station 330 receives a formal call request transmitted from the call transmission unit 452 of the calling-side femtocell base station 400A, the femtocell control station 330 manages the mobile phone 10B that is the call destination as a mobile station in the area. A call is made to the cell base station 400B to enter the connection process, and before that, a terminating link quality inspection step (ST150) is executed.
The incoming link quality inspection process (ST150) will be described with reference to FIG.

Figure 7 is a diagram for explaining a sequence for performing the communication quality inspection of the terminating link L _B between the femtocell base station 400B and the femto cell control station 330 of the called party.
The femtocell control station 330 receives a call request from the calling-side femtocell base station 400A, and the network control unit 331 reads out the destination telephone number and specifies the serving base station. In this case, the counterpart mobile phone 10B is within the coverage area of the femtocell base station 400B.
In this way, when the other party's mobile phone 10B is within the coverage area of the femtocell base station 400B, this is communicated to the pre-connection unit 332 and the communication quality inspection with the receiving side femtocell base station 400B is performed. Let it be done.

That is, a pre-transmission requesting a pre-connection from the pre-connection unit 332 is performed to the identified incoming-side femtocell base station 400B (pre-transmission step ST153). This pre-transmission may include information on the mobile phone number of the other party, but is not particularly necessary.
Receiving-side femtocell base station 400B receives this pre-transmission and returns a pre-incoming signal from pre-incoming unit 432 to femtocell control station 330 (pre-incoming response step ST154).
When the pre-connection unit 332 of the femtocell control station 330 receives this pre-incoming call, it confirms that the pre-connection has been established, and transmits the test data in the test data storage unit 333 to the receiving-side femtocell base station 400B. (Test data transmission step ST155, D _{B in} FIG. 5).

  Receiving-side femtocell base station 400B receives the test data, and determines communication quality at communication quality determination section 440 based on the received test data (communication quality determination step ST156). This is the same as the communication quality inspection step (ST113) in the originating femtocell base station 400A. The communication quality determination unit 440 determines whether the received test data packet has arrived without missing in sequence order, and packet loss If the rate is smaller than the predetermined threshold, it is determined that the communication quality is OK.

  Thus, the pre-transmission process from the femtocell control station 330 (ST153), the pre-incoming response process from the femtocell base station 400B (ST154), the test data transmission process from the femtocell control station 330 (ST155), communication quality The incoming link quality inspection step (ST150) is configured by the packet loss rate determination (ST156) by the determination unit 440.

If the communication quality determination unit 440 determines that the communication quality is OK (ST160: YES), the incoming femtocell base station 400B is in a call connection permission state (ST170).
The communication quality determination unit 440 sends a quality OK determination to the network connection unit 450. Then, the network connection unit 450 executes processing for network connection. That is, the incoming call response unit 453 transmits an incoming call response to the femtocell control station 330 (ST180).

When the femtocell control station 330 receives the incoming call response, the femtocell control station 330 executes a call connection process (call connection step ST190). That is, the network control unit 331 sends a call request including the other party telephone number to the receiving side femtocell base station 400B.
Receiving-side femtocell base station 400B specifies a telephone number at connection establishment unit 454 and calls mobile phone 10B.
When the user of the incoming mobile phone 10B performs incoming operation, the connection between the outgoing mobile phone 10A and the incoming mobile phone 10B is established via the outgoing femtocell base station, the femtocell control station, and the incoming femtocell base station. It is established and a call is made (ST200).

Here, in the transmission side link quality inspection step (ST110), when the packet loss is not less than a predetermined threshold value and communication quality cannot be ensured (ST120: NO), the communication quality determination unit 440 sends a message to the line switching unit 460. Tell the result. Then, the line switching step (ST210) is executed by the line switching unit 460. That is, when the calling-side mobile phone 10A and the femtocell base station 400A are currently connected wirelessly, the line switching unit 460 cuts off the connection between the femtocell base station 400A and the mobile phone 10A, and at the same time, 10A is caused to execute communication on another line.
Another line is the public mobile phone communication network 200 via the macrocell base station 210 including the mobile phone 10A in the cover area.
As the connection blocking process by the line switching unit 460, the line switching unit 460 instructs the RNC unit 412 not to accept a signal from the mobile phone 10A so that the connection with the mobile phone 10A cannot be established. As an example.
When the femtocell base station 400A thus cuts off the connection with the mobile phone 10A, the location registration of the mobile phone 10A is removed from the femtocell base station 400A.
When the connection with the femtocell base station 400A is disconnected, the mobile phone 10A establishes a connection with the macrocell base station 210 including the mobile phone 10A in the cover area (S _{A in} FIG. 5). Then, the cellular phone 10A calls the partner cellular phone 10B using the public cellular phone communication network 200 via the macrocell base station 210 (ST220).

Note that when the mobile phone 10A switches the line to another line, the femtocell base station 400A searches the surrounding macrocell base station 210 and instructs the mobile phone 10A of the macrocell base station 210 having the highest radio field strength. It may be.
Thus, by transmitting the macro cell base station 210 of the line switching destination to the mobile phone 10A, the mobile phone 10A does not need to search for the base station, and the call connection can be smoothly executed.

Also, in the incoming link quality inspection step (ST150), when the packet loss is equal to or greater than a predetermined threshold value and communication quality cannot be ensured (ST160: NO), the communication quality determination unit 440 sends a result to the line switching unit 460. Tell. Then, the incoming line switching step (ST230) is executed by the line switching unit 460. That is, the line switching unit 460 sends a command to the femtocell control station 330 to call the mobile phone 10B to be called via the public mobile phone communication network 200.
Thus, the connection relay is performed via a macrocell base station 210 of the normal public mobile telephone network 200 to the cellular phone 10B being invoked (S _B in FIG. _5).

(Second embodiment)
Next, as a second embodiment, a case will be described in which the originating side communicates via a femtocell base station and the terminating side communicates via a macrocell base station.
In the second embodiment, and thus to utilize the femtocell network 300 only to the originating link L _A. Accordingly, examination of the communication quality may be performed only on the originating link L _A.
In this case, referring to the flowchart of FIG. 4, ST100 to ST140, ST210, and ST220 are necessary steps in the second embodiment.
In the transmission side link quality inspection step ST110, the sequence described in FIG. 6 is executed to determine the communication quality. When the communication quality is ensured, a call is transmitted using the femtocell communication network (ST140).
On the other hand, when the communication quality cannot be maintained (ST120: NO), a call is made by calling the other party's mobile phone via the public mobile phone communication network 200 by switching the outgoing line (outgoing line switching step ST210). .

(Third embodiment)
As a third embodiment, a case will be described in which the originating side communicates via a macrocell base station and the terminating side communicates via a femtocell base station.
In the third embodiment, and thus to utilize the femtocell network 300 only to the called side link L _B. Accordingly, examination of the communication quality may be performed only on the terminating link L _B.
In this case, referring to the flowchart of FIG. 4, ST150 to ST180, ST230, and ST230 are necessary steps in the third embodiment.
In the incoming link quality inspection step ST150, the sequence described in FIG. 7 is executed to determine the communication quality.
When the communication quality is ensured, an incoming call response (ST180) is performed using the femtocell communication network.
On the other hand, when the communication quality cannot be maintained (ST160: NO), a mobile phone from the other party is received via the public mobile phone communication network 200 by switching the incoming line (incoming line switching step ST230).

According to such 1st Embodiment, there exists the following effect.
(1) When a call session is requested via the femtocell base station 400, a link quality determination step (ST110, ST150) is executed before establishing a call connection between mobile phones, and the femtocell base station 400 and the femto Since the communication quality with the cell control station 330 is inspected, the call quality of the call session via the femtocell base station 400 can be guaranteed.

(2) In the link quality determination step (outgoing side link quality determination step ST110, incoming side link quality determination step ST150), it is determined that the data transmission quality between the femtocell base station 400 and the femtocell control station 330 is poor. In this case, since the femtocell base station 400 and the femtocell control station 330 do not perform network connection via the Internet network, but perform line switching so as to make a call connection using another line. The call requested by the user can be reliably connected.

(3) In determining the communication quality, a configuration is adopted in which the packet transmission quality is determined only for the downlink from the femtocell control station 330 to the femtocell base station 400. The femtocell base station 400 side is provided with a pre-connection function and a communication quality determination function, so that the femtocell base station 400 has as few functions as possible to reduce the size and cost. Communication quality can be determined before call connection.

(4) Since test data uses data (talkie) in which video and audio are synchronized, it can be reasonably inferred whether or not sufficient call quality can be secured.

(Modification 1)
Modification 1 of the present invention will be described.
The femtocell base station 400 is a small base station installed in a building. When the user who uses the femtocell base station 400 is almost fixed, the subscriber information of the mobile phone that uses the femtocell base station 400 is used. May be registered in advance in the femtocell base station 400.
For example, when the femtocell base station 400 is installed in a house, it is considered that the resident of the house is fixed as a user, so the resident of the home is registered as a user of the femtocell base station 400.
As described in the first embodiment, the femtocell base station 400 checks the communication quality of the calling side link or the called side link at the time of outgoing / incoming calls, and switches the line when determining that the communication quality cannot be secured. In this case, the subscriber information may be sent directly to the LR 231 to inform the subscriber that the management of the femtocell base station 400 is transferred to the management of the macrocell base station 210.
In this way, if the femtocell base station 400 switches the location registration to the LR 231 of the mobile phone operator instead of the mobile phone 10, the line switching process becomes very smooth.

(Modification 2)
In the above-described embodiment, the case where the femtocell base station 400 removes the management of the mobile phone 10 and the mobile phone 10 is wirelessly connected to the macrocell base station 210 in the line switching process has been described as an example. Even if the femtocell base station 400 receives and amplifies and relays the radio wave of the mobile phone 10 and the radio wave from the macrocell base station 210, the so-called repeater becomes a so-called repeater and switches the line on which the mobile phone 10 talks. Good.
Since the femtocell base station 400 uses a broadband line, the simultaneous connection is limited to several units (for example, four units) at the maximum due to the problem of the bandwidth of the broadband line, and the communication quality of the broadband line is stable due to the influence of noise and the like. Although there may be cases where it cannot be ensured automatically, the wireless connection between the femtocell base station 400 and the mobile phone 10 can be made more simultaneously and better.
Therefore, when it is determined that the communication quality cannot be maintained over the broadband line, the femtocell base station 400 may perform a relay operation with the macrocell base station 210 for the session as a repeater.

Furthermore, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention described above.
Although the example in which the test data storage unit is provided as one component of the femtocell control station has been shown, a server storing the test data is separately provided, and when the pre-connection state is entered, the server from the femtocell control station The test data may be read out and transmitted.
In the above embodiment, the case where the femtocell base station has the RNC unit is taken as an example. However, each femtocell base station does not incorporate the RNC, and there is an RNC that separately manages a plurality of femtocell base stations. Also good.
The macro cell base station is not particularly limited as long as it is a base station of a public mobile phone communication network and covers a wider area than the cover area of the femto cell base station. For example, the macro cell base station may be a base station that covers a range called a micro cell having a radius of about several hundred meters.

The figure which shows the whole structure of the mobile communication system which concerns on 1st Embodiment. The figure which shows the structure of a femtocell base station. The figure which shows the structure of a femtocell control station. The flowchart which shows the whole structure of the mobile communication system control method in 1st Example. The figure for demonstrating the flow of the data in 1st Example. Diagram illustrating a sequence of inspecting the communication quality of the originating links L _A between the originating side of the femtocell base station and a femtocell control station. Diagram for explaining a sequence for performing the communication quality inspection of the terminating link L _B between the incoming side of the femtocell base station and a femtocell control station.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10A, 10B ... Mobile phone, 20 ... Building, 100 ... Mobile communication system, 200 ... Public mobile phone communication network, 210 ... Macrocell base station, 220 ... RNC, 230 ... Core network, 300 ... Femtocell communication network, 310 ... Broadband line, 320 ... Internet network, 330 ... Femtocell control station, 331 ... Network control unit, 332 ... Pre-connection unit, 333 ... Test data storage unit, 400, 400A, 400B ... Femtocell base station, 410 ... Wireless communication 411 ... antenna, 412 ... RNC unit, 413 ... protocol control unit, 420 ... connection control unit, 430 ... pre-transmission / reception unit, 431 ... pre-transmission unit, 432 ... pre-incoming unit, 440 ... communication quality judgment unit, 450 ... Network connection part, 451 ... Calling and receiving part, 452 ... Calling and calling part, 453 ... Arrival Response unit, 454 ... connection establishment unit, 460 ... line switching unit,

Claims (5)

More than a macro cell base station that is connected to the Internet network via a broadband line and relays a call between mobile communication terminals by performing wireless communication with a mobile communication terminal and constituting a public mobile phone communication network A femtocell base station covering a small area,
A femtocell control station that is connected to the femtocell base station via the Internet network and performs network control between the femtocell base stations and is connected to a core network of a public mobile phone communication network via a gateway; A mobile communication system control method for relaying a wireless call between mobile communication terminals,
A link quality determination step of checking communication quality of an inter-network link between the femtocell base station and the femtocell control station before establishing a call session between mobile communication terminals;
If the communication quality is OK in the link quality determination step, a call connection step of performing a call connection between mobile communication terminals from the femtocell base station via the Internet,
A line switching step of switching the line to a call connection via the macro cell base station of the public mobile phone communication network when the communication quality is NG in the link quality determination step. Mobile communication system control method. The mobile communication system control method according to claim 1,
The femtocell control station includes a pre-connection unit that performs trial connection with the femtocell base station before making a call connection between mobile communication terminals, and a test data storage unit that stores test data.
The femtocell base station includes a pre-calling / receiving unit that requests or responds to a trial connection with the pre-connection unit in response to a call session request, and test data transmitted from the femtocell control station. A communication quality determination unit for determining communication quality,
The link quality inspection process includes:
The test data stored in the test data storage unit is transmitted from the femtocell control station in a state where the femtocell control station and the femtocell base station are trially connected to the network by the pre-connecting unit and the pre-calling / receiving unit. A test data transmission process for transmitting to the femtocell base station;
A communication quality determination step of receiving the transmitted test data and determining the communication quality by comparing the packet loss rate of the test data with a predetermined threshold in the communication quality determination unit. A mobile communication system control method. In the mobile communication system control method according to claim 1 or 2,
In the line switching step, the mobile communication terminal spontaneously communicates with the macro cell base station by stopping the wireless connection with the mobile communication terminal wirelessly connected with the femto cell base station. A method for controlling a mobile communication system, characterized in that the management of a location is shifted. In the mobile communication system control method according to claim 1 or 2,
The line switching step includes
The femtocell base station instructs a mobile communication terminal that is wirelessly connected to the femtocell base station to a base station having sufficiently high radio wave reception intensity among surrounding macrocell base stations, and then communicates with the mobile communication terminal. A mobile communication system control method, comprising: stopping a wireless connection. In the mobile communication system control method according to claim 4,
The method of controlling a mobile communication system, characterized in that the femtocell base station informs a home memory station of a public mobile phone communication network of the location information of the mobile communication terminal via the femtocell control station.

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