JP5361986B2 - Wireless terminal and handover control method - Google Patents

Description

  The present invention relates to a radio terminal and a handover control method capable of performing handover between different cells or different communication systems.

  In a general wireless communication system, a wireless terminal performs handover (also referred to as handoff) for switching a connection destination from a first base station to a second base station having better wireless communication quality than the first base station during movement or the like. )I do.

  In recent years, due to the development of radio communication technology, handover between base stations with different cell types (hereinafter referred to as “heterogeneous cell handover”) and handover between base stations with different radio communication schemes (hereinafter referred to as “heterogeneous communication schemes”). A wireless terminal corresponding to “inter-handover” is provided.

  In handover between different cells, a wireless terminal performs handover between, for example, a macro cell base station and a femto cell base station (see Patent Document 1). Here, the femtocell base station is a small base station mainly installed indoors. In handover between different communication schemes, a wireless terminal performs handover between base stations that use different wireless communication schemes among radio communication schemes such as OFDMA, CDMA, and TDMA.

JP 2009-27695 A

  However, depending on the type of application being executed, a wireless terminal that can perform handover between different cells or different communication methods may not always be able to execute an application under the same conditions as before the handover, depending on the type of application being executed. Absent.

  For example, when a wireless terminal executes an application with limited communication delay (voice communication such as VoIP), if the wireless terminal performs a handover to a base station with a large communication delay or a base station with which the communication delay is not guaranteed, However, the performance of the application cannot be fully exhibited, and there is a problem that the convenience of the user is impaired. When the wireless terminal executes an application (file download application) that requires a large communication capacity, if the wireless terminal performs a handover to a base station with a small communication capacity, the same problem as described above occurs.

  Therefore, the present invention provides a wireless terminal capable of avoiding that the performance of the application cannot be sufficiently exhibited due to handover even when handover is performed between different cells or different communication methods while executing the application. An object is to provide a handover control method.

In order to solve the above-described problems, the present invention has the following features. First, a feature of the wireless terminal of the present invention is a wireless terminal that performs communication via a connection-destination base station, and controls a handover that switches the connection destination from the first base station to the second base station. The control unit regulates the handover according to a switching destination communication delay that is a communication delay when the communication is performed by connecting to the second base station, and the control unit is an application to be controlled Is a public communication network that regulates the handover when the second base station is a femtocell base station, and the communication delay is indefinite with the femtocell base station. and gist base station der Rukoto connected to backbone communication network via a.

  In the above feature, the control unit is a case where an application to be controlled is an application whose communication delay is limited, and the switching destination communication delay is connected to the first base station to perform the communication. If it is larger than the switching source communication delay which is the communication delay in the case, the handover is restricted.

  In the above feature, the control unit regulates the handover when the application to be controlled is an application whose communication delay is limited and the switching destination communication delay is indefinite.

  In the above feature, the control unit cancels the handover restriction when the wireless communication quality between the first base station and the wireless terminal falls below a predetermined level in a state where the handover is restricted. To do.

  In the above feature, the control unit detects the switching destination communication delay based on a cell type of the second base station.

  In the above feature, when the application to be controlled is an application that requires a communication capacity that is equal to or greater than a predetermined capacity, the control unit is a communication capacity when the communication is performed by connecting to the first base station. Detecting a switching source communication capacity and a switching destination communication capacity that is a communication capacity when connecting to the second base station and performing the communication, and the detected switching destination communication capacity is greater than the switching source communication capacity If it is smaller, the handover is restricted.

  In the above feature, the control unit detects the switching destination communication capacity based on a wireless communication method used by the second base station.

A feature of the handover control method of the present invention is a handover control method for controlling handover of a wireless terminal that performs communication via a connection destination base station, wherein the connection destination is changed from a first base station to a second base station. A step of controlling a handover to be switched, wherein the step of controlling regulates and controls the handover according to a switching destination communication delay which is a communication delay when the communication is performed by connecting to the second base station. In the step, when the application to be controlled is an application whose communication delay is limited and the second base station is a femtocell base station, the handover is restricted, and the femtocell base station communicates with the femtocell base station. delay is summarized as the base station der Rukoto connected to backbone communication network via the public communication network is indefinite.

  According to the features of the present invention, even when a handover is performed between different cells or different communication methods during execution of an application, it is possible to avoid a situation in which the performance of the application cannot be sufficiently exhibited due to the handover. A terminal and a handover control method can be provided.

FIG. 1 is a schematic configuration diagram of a communication system including a wireless terminal according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the wireless terminal according to the embodiment of the present invention. FIG. 3 is a diagram illustrating base station information stored in the wireless terminal according to the embodiment of the present invention. FIG. 4 is a flowchart showing a basic operation of the wireless terminal according to the embodiment of the present invention. FIG. 5 is a flowchart showing an additional operation of the wireless terminal according to the embodiment of the present invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) schematic configuration of communication system, (2) configuration of wireless terminal, (3) operation of wireless terminal, (4) operational effect, (5) other embodiments will be described.

In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.
(1) Schematic Configuration of Communication System FIG. 1 is a schematic configuration diagram of a communication system 1 including a wireless terminal 100 according to the present embodiment.

  In the present embodiment, the radio terminal 100 is a radio terminal that supports both handover between different types of cells and handover between different types of communication schemes. The radio terminal 100 is wirelessly connected to any one of the macrocell base station 10, the femtocell base station 20, and the macrocell base station 30, and directly or indirectly connected to the backbone communication network 40 via the connection destination base station. Packet communication is performed with the communication destination device 50. For example, a voice call application, a file download application, an interactive game application, or a mail application is used for the packet communication.

  The voice call application is an application whose communication delay is limited and does not require a large capacity (communication capacity greater than a predetermined capacity). The file download application is an application that does not have a restriction on communication delay and that requires a large capacity. The interactive game application is an application with a limited communication delay and requires a large capacity. It is a mail application or an application that does not limit communication delay and does not require a large capacity.

  Each of the macro cell base station 10, the femto cell base station 20, and the macro cell base station 30 forms a cell that is a communicable area. The macro cell base station 10 and the macro cell base station 30 form a large cell (macro cell) of about several hundred meters to several kilometers. On the other hand, the femtocell base station 20 is a small base station that is mainly installed indoors, and forms a small cell (femtocell) of about several meters to several tens of meters. The femtocell base station 20 may be arranged in a macro cell.

  The femtocell base station 20 is connected to the backbone communication network 40 via a public communication network 25 that is a commercial line such as FTTH, DSL, or CATV. Since the backbone communication network 40 is managed by a communication carrier and configured using a dedicated line, the upper limit of communication delay is guaranteed. On the other hand, in the public communication network 25, the upper limit of communication delay is generally not guaranteed.

The macrocell base station 10 and the femtocell base station 20 are configured according to LTE (E-UTRAN) which is one of 3.9 generation mobile phone systems. The macrocell base station 30 is configured according to GSM, which is a second generation mobile phone system. In LTE, the OFDMA method is used as a wireless communication method. In LTE, a large communication capacity of up to about 100 Mbps (downstream theoretical value) is provided. In GSM, the TDMA method is used as a wireless communication method. In GSM, a small communication capacity of about 171 kbps (downstream theoretical value) is provided. Thus, the communication capacity (theoretical value) of LTE is nearly 600 times the communication capacity (theoretical value) of GSM, and the difference in communication capacity is large.
(2) Configuration of Radio Terminal FIG. 2 is a block diagram showing the configuration of the radio terminal 100. As illustrated in FIG. 2, the wireless terminal 100 includes a wireless communication unit 110, a control unit 120, a storage unit 130, a microphone 140, a speaker 150, a display unit 160, and an input unit 170.

  The wireless communication unit 110 includes an LNA, a power amplifier, an up converter, a down converter, and the like, and transmits and receives wireless signals to and from a wireless base station to which the wireless communication unit 110 is wirelessly connected. In the present embodiment, the wireless communication unit 110 has a configuration corresponding to a plurality of wireless communication methods. The wireless communication unit 110 receives a signal (for example, a pilot signal) broadcast from a neighboring base station. The control unit 120 is configured by a CPU, for example, and controls various functions provided in the wireless terminal 100. The storage unit 130 is configured by a memory, for example, and stores various information used for control in the wireless terminal 100.

  The microphone 140 collects sound and inputs sound data based on the collected sound to the control unit 120. The speaker 150 outputs sound based on the sound data acquired from the control unit 120. The display unit 160 displays an image received through the control unit 120 and displays operation details. The input unit 170 is configured by a numeric keypad, function keys, and the like, and is an interface used for inputting user operation details.

  The control unit 120 includes a wireless communication quality measurement unit 121, an application execution unit 122, a detection unit 123, and a handover control unit 124.

  The wireless communication quality measuring unit 121 measures wireless communication quality (for example, received SNR and RSSI) from the signal received by the wireless communication unit 110. The wireless communication quality measured by the wireless communication quality measuring unit 121 is notified to the handover control unit 124.

  Based on the radio communication quality corresponding to each base station, the handover control unit 124 controls a handover for switching the connection destination from the neighboring base stations to a base station with better radio communication quality.

  The application execution unit 122 corresponds to the highest layer in the communication protocol stack, and executes the application as described above. Information regarding the application being executed in the application execution unit 122 is notified to the handover control unit 124.

  The storage unit 130 stores base station information as shown in FIG. 3 in advance. The base station information is information that associates the attributes (wireless communication method and cell type) of the base station, communication delay, and communication capacity.

  In the example of FIG. 3, communication delay “small” and communication capacity “large” are associated with an OFDMA (LTE) macrocell base station. A communication delay “large (or indefinite)” and a communication capacity “large” are associated with an OFDMA (LTE) femtocell base station. A communication delay “small” and a communication capacity “small” are associated with a macro cell base station of TDMA (GSM).

  The detection unit 123 includes a switching source communication delay that is a communication delay when performing communication via a base station (hereinafter referred to as a switching source base station) to which the wireless communication unit 110 is wirelessly connected, and A switching destination communication delay that is a communication delay when communication is performed by connecting to any one (hereinafter referred to as a switching destination base station) is detected.

  Since the signal broadcast from each base station includes attribute information indicating the attribute of the base station, the detection unit 123 stores the attribute information included in the signal from a certain base station and the storage unit 130. Based on the received base station information, the communication delay corresponding to the attribute information can be detected as the communication delay of the base station.

  However, the detection unit 123 may detect the communication delay of the switching source base station from the communication delay (actual value) in actual communication. Further, the detection unit 123 may detect the communication delay using only the cell type information in the attribute information.

  The communication delay detected by the detection unit 123 is notified to the handover control unit 124. In the handover control unit 124, the application executed in the application execution unit 122 is an application whose communication delay is limited, and the switching destination communication delay is larger than the switching source communication delay or the switching destination communication delay is indefinite. In this case, the handover to the switching destination base station is restricted.

  In the present embodiment, the detection unit 123 has a switching source communication capacity that is a communication capacity when communication is performed by connecting to the switching source base station, and a communication capacity when communication is performed by connecting to the switching destination base station. The switching destination communication capacity is further detected.

  Specifically, the detection unit 123 determines the communication capacity corresponding to the attribute information based on the attribute information included in the signal from a certain base station and the base station information stored in the storage unit 130. It can be detected as the communication capacity.

  However, the detection unit 123 may detect the communication capacity of the switching source base station from the communication capacity (actually measured value) in actual communication. The detection unit 123 may detect the communication capacity using only the wireless communication method information in the attribute information.

  The communication capacity detected by the detection unit 123 is notified to the handover control unit 124. When the application executed in the application execution unit 122 is an application that requires a large capacity, and the switching destination communication capacity is smaller than the switching source communication capacity, the handover control unit 124 Regulate handover.

  The handover control unit 124 may cancel the handover restriction when the wireless communication quality between the switching source base station and the wireless terminal 100 falls below a predetermined level in a state where the handover is restricted.

In addition, the handover control unit 124, when the application executed in the application execution unit 122 is an application whose communication delay is limited and the switching destination base station is a femtocell base station, The handover may be restricted.
(3) Operation of Wireless Terminal Next, the operation of the wireless terminal 100 will be described in the order of (3.1) basic operation and (3.2) additional operation.
(3.1) Basic Operation FIG. 4 is a flowchart showing the basic operation of the radio terminal 100.

  The handover control unit 124 starts this operation flow when the handover to the switching destination base station becomes possible based on the wireless communication quality measured with the wireless communication quality measuring unit 121 and the switching destination base station. To do. The state where handover is possible is a state where, for example, the wireless communication quality with the switching destination base station is better than the wireless communication quality with the switching source base station.

  In step S11, the handover control unit 124 determines whether or not the application being executed in the application execution unit 122 is an application with a limited communication delay. For example, the handover control unit 124 performs the determination by acquiring application identification information from the application execution unit 122 or acquiring information indicating the presence or absence of delay limitation from the application execution unit 122.

  In step S12, the detection unit 123 detects the switching source communication delay and the switching destination communication delay by the above method.

  In step S13, the handover control unit 124 determines whether or not the switching destination communication delay is indefinite. That is, it is determined whether the upper limit of the switching destination communication delay is guaranteed. If it is determined that the switching destination communication delay is indefinite, the process proceeds to step S16. Otherwise, the process proceeds to step S14.

  In step S14, the handover control unit 124 determines whether or not the switching destination communication delay is larger than the switching source communication delay. If it is determined that the switching destination communication delay is greater than the switching source communication delay, the process proceeds to step S16. Otherwise, the process proceeds to step S15.

  In step S15, the handover control unit 124 executes handover to the switching destination base station. Specifically, the handover control unit 124 transmits a handover request to the switching destination base station, and then connects to the switching destination base station and disconnects from the switching source base station.

  In step S16, the handover control unit 124 regulates handover to the switching destination base station. That is, the handover control unit 124 stops the handover to the switching destination base station and waits until another switching destination base station is found. When another switching destination base station is found, this operation flow is applied again.

With such an operation flow, for example, when the wireless terminal 100 that is executing an application with a limited communication delay is connected to the macrocell base station 10, handover to the femtocell base station 20 can be regulated. .
(3.2) Additional Operation FIG. 5 is a flowchart showing the additional operation of the wireless terminal 100. The wireless terminal 100 can execute the operation flow of FIG. 5 in addition to the operation flow of FIG.

  The operation flow in FIG. 5 may be executed in parallel with the operation flow in FIG. 4 or may be executed only while an application that requires a large capacity is being executed.

  In step S21, the handover control unit 124 determines whether or not the application being executed in the application execution unit 122 is an application that requires a large capacity. For example, the handover control unit 124 performs the determination by acquiring the application identification information from the application execution unit 122 or by acquiring information indicating the presence or absence of the capacity restriction from the application execution unit 122.

  In step S22, the detection unit 123 detects the switching source communication capacity and the switching destination communication capacity by the above method.

  In step S23, the handover control unit 124 determines whether or not the switching destination communication capacity is smaller than the switching source communication capacity. If it is determined that the switching destination communication capacity is smaller than the switching source communication capacity, the process proceeds to step S25; otherwise, the process proceeds to step S24.

  In step S24, the handover control unit 124 executes handover to the switching destination base station. Specifically, the handover control unit 124 transmits a handover request to the switching destination base station, and then connects to the switching destination base station and disconnects from the switching source base station.

  In step S25, the handover control unit 124 regulates handover to the switching destination base station. That is, the handover control unit 124 stops the handover to the switching destination base station and waits until another switching destination base station is found. When another switching destination base station is found, this operation flow is applied again.

With such an operation flow, for example, when the wireless terminal 100 that is executing an application that requires a large capacity is connected to the macro cell base station 10, handover to the macro cell base station 30 can be regulated.
(4) Operational Effect As described above, according to the wireless terminal 100, when the application execution unit 122 is executing an application whose communication delay is limited, the switching destination communication delay is larger than the switching source communication delay. Alternatively, when the switching destination communication delay is indefinite, the handover control unit 124 regulates the handover to the switching destination base station, so that it is possible to prevent the performance of the application from being sufficiently exhibited due to the handover.

  While the handover to the switching destination base station is regulated, if a new switching destination base station is discovered and the communication delay of the switching destination base station is equal to or less than the switching source communication delay, the handover control unit 124 A handover to the switching destination base station can also be executed.

  In the present embodiment, the handover control unit 124 cancels the handover restriction when the wireless communication quality between the switching source base station and the wireless terminal 100 falls below a predetermined level in a state where the handover is restricted. For this reason, the application can be continued by the handover before the application cannot be executed in the switching source base station.

  In the present embodiment, the detection unit 123 detects a switching destination communication delay based on the cell type of the switching destination base station. Therefore, the switching destination communication delay can be easily detected without actually connecting to the switching destination base station and measuring the communication capacity.

  In this embodiment, when the application execution unit 122 is executing an application that requires a large capacity, the handover control unit 124 determines that the switching destination communication capacity is smaller than the switching source communication capacity. Restricts handovers. As a result, it is possible to avoid that the performance of the application cannot be sufficiently exhibited due to handover.

  In the present embodiment, the detection unit 123 detects the switching destination communication capacity based on the wireless communication scheme used by the switching destination base station. Therefore, the switching destination communication capacity can be easily detected without actually connecting to the switching destination base station and measuring the communication capacity.

In the present embodiment, the handover control unit 124 regulates handover when the application executed in the application execution unit 122 is an application whose communication delay is limited and the switching destination base station is a femtocell base station. To do. Thereby, the hand-over to a femtocell base station can be prevented more reliably.
(5) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the macro cell base station is exemplified as the base station whose communication delay is limited. However, the base station is not limited to the macro cell base station and is connected to the backbone communication network without going through the public communication network. For example, a microcell base station may be used.

  In the embodiment described above, handover between LTE and GSM is taken as an example of handover between different types of communication methods. However, the handover is not limited to between LTE and GSM, and any combination is possible as long as handover is performed between different wireless communication methods. For example, UTRAN (W-CDMA) defined by 3GPP, cdma2000 defined by 3GPP2, or a wireless communication system such as WiMAX or wireless LAN may be used.

  In the embodiment described above, terminal-driven handover has been described, but the present invention may be applied to base station-driven handover. In the handover initiated by the base station, the switching destination base station is designated by the switching source base station. The radio terminal 100 applies the above-described handover control to the designated switching destination base station, and when the designated switching destination base station does not satisfy the application restrictions, the handover to the switching destination base station is performed. Can be refused. That is, the radio terminal 100 executes a handover to the switching destination base station only when the switching destination base station designated by the switching source base station satisfies the application restrictions.

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

  Note that the entire content of Japanese Patent Application No. 2009-051378 (filed on Mar. 4, 2009) is incorporated herein by reference.

  As described above, the wireless terminal and the handover control method according to the present invention have sufficient performance of the application along with the handover even when the handover is performed between different cells or different communication systems while the application is being executed. Therefore, it is useful in wireless communication such as mobile communication.

Claims (8)

A wireless terminal that performs communication via a connected base station,
A control unit for controlling a handover for switching the connection destination from the first base station to the second base station;
The control unit regulates the handover according to a switching destination communication delay that is a communication delay when the communication is performed by connecting to the second base station ,
The control unit regulates the handover when the application to be controlled is an application whose communication delay is limited and the second base station is a femtocell base station,
Wireless terminal wherein the femtocell base station, Ru base station der connected to the backbone network communication delay through the public communication network is indefinite.   The control unit is a communication delay when the application to be controlled is an application whose communication delay is limited, and the switching destination communication delay is a communication delay when the communication is performed by connecting to the first base station. The wireless terminal according to claim 1, wherein the handover is restricted when a switching source communication delay is greater than a certain switching source communication delay.   The wireless terminal according to claim 1, wherein the control unit regulates the handover when the application to be controlled is an application whose communication delay is limited and the switching destination communication delay is indefinite.   2. The control unit according to claim 1, wherein the control unit cancels the handover restriction when a wireless communication quality between the first base station and the wireless terminal falls below a predetermined level in a state where the handover is restricted. The wireless terminal described.   The radio terminal according to claim 1, wherein the control unit detects the switching destination communication delay based on a cell type of the second base station. When the application to be controlled is an application that requires a communication capacity greater than or equal to a predetermined capacity,
A switching source communication capacity that is a communication capacity when the communication is performed by connecting to the first base station, and a switching destination communication capacity that is a communication capacity when the communication is performed by connecting to the second base station. Detect
The radio terminal according to claim 1, wherein the handover is restricted when the detected switching destination communication capacity is smaller than the switching source communication capacity.   The wireless terminal according to claim 6, wherein the control unit detects the switching destination communication capacity based on a wireless communication method used by the second base station. A wireless terminal handover control method for performing communication via a connected base station,
Comprising a step of controlling a handover for switching the connection destination from the first base station to the second base station,
The controlling step regulates the handover according to a switching destination communication delay which is a communication delay when the communication is performed by connecting to the second base station ,
The controlling step regulates the handover when the application to be controlled is an application whose communication delay is limited and the second base station is a femtocell base station,
Wherein the femtocell base station, the base station der Ru handover control method, which is connected to the backbone network communication delay through the public communication network is indefinite.

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