NETWORK APPARATUS, BASE STATION, COMMUNICATION METHOD, RADIO RESOURCE CONTROL METHOD, AND NON-TRANSITORY COMPUTER READABLE MEDIUM

An object is to provide a network apparatus that can ensure allocable radio resources when the number of communication terminal performing carrier aggregation increases. A network apparatus (10) according to the present disclosure manages a base station (30) that allocates radio resources to a communication terminal (20) and performs communication. The network apparatus (10) includes a communication unit (11) for transmitting, to the base station (30), an instruction message when allocable radio resources are insufficient in the base station (30) or the allocable radio resources are expected to become insufficient in the base station (30). This instruction message instructs the base station (30) to stop using one (or some) of frequency bands for the communication terminal (20) performing communication using a plurality of frequency bands simultaneously.

TECHNICAL FIELD

The present disclosure relates to a network apparatus, a base station, a communication method, a radio resource control method, and a program. In particular, the present disclosure relates to a network apparatus, a base station, a communication method, a radio resource control method, and a program for controlling an operation relating to carrier aggregation.

BACKGROUND ART

Recently, in order to realize high-speed wireless communication, carrier aggregation that offers a wide band by using a plurality of frequency bands is used. For example, a communication terminal capable of performing carrier aggregation may perform wireless communication using a frequency band of a 10 MHz width in an 800 MHz band and a frequency band of a 10 MHz width in a 2 GHz band, which make a frequency band of a 20 MHz width in total.

Non Patent Literature 1 describes a flow of processing when carrier aggregation is applied. To be more specific, Non Patent Literature 1 describes a process in which an evolved NodeB (eNB) establishes an RRC (Radio Resource Control) Connection to a UE (User Equipment) when it communicates with a UE capable of performing carrier aggregation. The eNB is defined by 3GPP (3rd Generation Partnership Project) as a base station that can use LTE (Long Term Evolution) as a wireless communication scheme. The term UE is used by 3GPP as a generic term for communication terminals.

CITATION LIST

Non Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, when the communication terminal performs carrier aggregation, it uses radio resources in a plurality of frequency bands. For example, when the communication terminal performs carrier aggregation using an 800 MHz band and a 2 GHz band, a base station needs to allocate radio resources to the communication terminal in the 800 MHz band and the 2 GHz band. Therefore, when the number of communication terminals performing carrier aggregation increases, there is a problem that the radio resources will become insufficient and the number of communication terminals that can perform wireless communication at the same time decreases as compared to when carrier aggregation is not applied.

An object of the present disclosure is to provide a network apparatus, a base station, a communication method, a radio resource control method, and a program capable of ensuring allocable radio resources when the number of communication terminals performing carrier aggregation increases.

Solution to Problem

A first example aspect of the present disclosure is a network apparatus for managing a base station that allocates radio resources to a communication terminal and performs communication. The network apparatus includes a communication unit for transmitting, to the base station, an instruction message when allocable radio resources are insufficient in the base station or the allocable radio resources are expected to become insufficient in the base station, the instruction message instructing the base station to stop using one (or some) of frequency bands for the communication terminal performing communication using a plurality of frequency bands simultaneously.

A second example aspect of the present disclosure is a base station including: communication unit for receiving, from a network apparatus, an instruction message when allocable radio resources are insufficient or the allocable radio resources are expected to become insufficient, the instruction message indicating a stop of using one (or some) of frequency bands for a communication terminal performing communication using a plurality of frequency bands simultaneously; an evaluation unit configured to evaluate as to whether or not the allocable radio resources are insufficient or whether or not the allocable radio resources are expected to become insufficient; and a control unit for stopping, when the evaluation unit evaluates that the allocable radio resources are insufficient or the allocable radio resources are expected to become insufficient, the one (or some) of the frequency bands for the communication terminal performing the communication using the plurality of frequency bands simultaneously.

A third example aspect of the present disclosure is a communication method performed by a network apparatus for managing a base station that allocates radio resources to a communication terminal and performs communication. The communication method includes transmitting, to the base station, an instruction message when allocable radio resources are insufficient in the base station or the allocable radio resources are expected to become insufficient in the base station, the instruction message instructing the base station to stop using one (or some) of frequency bands for a communication terminal performing communication using a plurality of frequency bands simultaneously.

A fourth example aspect of the present disclosure is a radio resource control method including: receiving, from a network apparatus, an instruction message when allocable radio resources are insufficient or the allocable radio resources are expected to become insufficient, the instruction message indicating a stop of using one (or some) of frequency bands for a communication terminal performing communication using a plurality of frequency bands simultaneously; evaluating as to whether or not the allocable radio resources are insufficient or whether or not the allocable radio resources are expected to become insufficient; and stopping, when the evaluation unit evaluates that the allocable radio resources are insufficient or the allocable radio resources are expected to become insufficient, the one (or some) of the frequency bands for the communication terminal performing the communication using the plurality of frequency bands simultaneously.

A fifth example aspect of the present disclosure is a program for causing a computer for managing a base station that allocates radio resources to a communication terminal and performs communication to execute a program, the program comprising transmitting, to the base station, an instruction message when allocable radio resources are insufficient in the base station or the allocable radio resources are expected to become insufficient in the base station, the instruction message instructing the base station to stop using one (or some) of frequency bands for a communication terminal performing communication using a plurality of frequency bands simultaneously.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide a network apparatus, a base station, a communication method, a radio resource control method, and a program capable of ensuring allocable radio resources when the number of communication terminals performing carrier aggregation increases.

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Firstly, a configuration example of a communication system according to a first embodiment of the present disclosure will be described with reference toFIG. 1. The communication system ofFIG. 1includes a network apparatus10, a communication terminal20, and a base station30. The network apparatus10, the communication terminal20, and the base station30may each be a computer apparatus that operates by a processor executing a program stored in a memory.

The base station30allocates radio resources to the communication terminal20and performs communication. The communication terminal20may be, for example, a mobile phone terminal, a smartphone, a personal computer having a communication function, or the like. The radio resources may be, for example, radio channels that can be simultaneously used in a certain frequency band, allocable frequency bands, transmission power at the time of signal transmission, and the like.

The base station30performs wireless communication with the communication terminal20. Further, the base station30performs wired communication or wireless communication with the network apparatus10.

Hereinafter, a configuration example of the network apparatus10will be described. The network apparatus10may be, for example, a node apparatus defined by 3GPP. The network apparatus10includes a communication unit11. The communication unit11may be software or a module(s), processing thereof being executed by a processor executing a program stored in a memory. Alternatively, the communication unit11may be composed of a circuit or the like.

When the allocable radio resources are insufficient in the base station30or when the allocable radio resources are expected to become insufficient in the base station30, the communication unit11transmits an instruction message instructing the base station30to stop using one (or some) of the frequency bands for the communication terminal20that is performing communication using a plurality of frequency bands simultaneously.

A case when the allocable radio resources are expected to become insufficient may be, for example, a case when radio resources are not insufficient at the present time but the radio resources are expected to become insufficient after a certain period of time due to a sudden increase in the radio resources to be allocated or the like.

The communication terminal20performing the communication using the plurality of frequency bands simultaneously may be, for example, the communication terminal20performing the carrier aggregation. The communication terminal20may perform communication with the base station30using a plurality of frequency bands simultaneously or may perform communication with a plurality of base stations using a plurality of frequency bands simultaneously. A case when the use of one (or some) of the frequency bands for the communication terminal is stopped may be, for example, the following one. Namely, when the communication terminal20is communicating with the base station30using the 800 MHz band and the 2 GHz band simultaneously, the use of the 2 GHz band is stopped. Alternatively, a case when the use of one (or some) of the frequency bands for the communication terminal is stopped may be the following one. Namely, when the communication terminal20is communicating with the base station30using the 800 MHz band and communicating with another base station different from the base station30using the 2 GHz band, the base station30stops using the 800 MHz band.

The communication unit11transmits the instruction message to the base station30before the allocable radio resources become insufficient in the base station30or before the allocable radio resources are expected to become insufficient in the base station30.

As described above, by using the communication system ofFIG. 1, the network apparatus10can notify the base station30of an instruction related to an operation performed during the communication between the base station30and the communication terminal20using carrier aggregation. In this way, the base station30can dynamically stop the use of one (or some) of the frequency bands used in carrier aggregation according to the radio resources of the base station30even during the communication with the communication terminal20using carrier aggregation.

Another effect achieved by the base station30dynamically stopping the use of one (or some) of the frequency bands used in carrier aggregation according to the radio resources will be described below.

When the allocable radio resources are insufficient or when there is no allocable radio resources in the base station30, the base station30needs to reject a connection request from a communication terminal(s) other than the communication terminal currently connected thereto. Commonly, when the base station to which the communication terminal is connected is changed by handing the communication terminal over or when power of the communication terminal is turned on, the communication terminal attempts a connection to a base station with the best radio environment or the best wireless communication environment. However, if the connection is rejected by the base station to which the communication terminal attempts a connection, the communication terminal attempts a connection to a base station with the second best radio environment. In this case, as the radio wave environment of the base station to which the communication terminal attempted a connection for the second time is inferior to the base station to which the communication terminal attempted a connection for the first time, there is a concern over deterioration of communication quality between the base station and the communication terminal.

On the other hand, when the allocable radio resources are insufficient and the like, the base station30can stop the communication terminal that is using more radio resources by performing carrier aggregation than other communication terminals that are not performing carrier aggregation do from using one (or some) of the frequency bands. By doing so, the base station30can ensure or increase the allocable radio resources. Accordingly, the base station30can increase the number of connectable communication terminals.

Second Embodiment

Hereinafter, a configuration example of a communication system according to a second embodiment of the present disclosure will be described with reference toFIG. 2. The communication system ofFIG. 2includes an eNB40, a UE50, an MME (Mobility Management Entity)60, an MME70, an HSS (Home Subscriber Server)71, an S-GW (Serving-Gateway)72, and a P-GW (Packet Data Network Gateway)73.

The UE50corresponds to the communication terminal20ofFIG. 1. The eNB40corresponds to the base station30ofFIG. 1. The MME60and the MME70correspond to the network apparatus10ofFIG. 1.

The eNB40is connected to the UE50via a Uu interface. The UE50performs carrier aggregation, for example, by simultaneously using a plurality of frequency bands that are communicable in the eNB40.

The MME60accommodates the eNB40via an S1-MME interface. The MME70may accommodate another eNB different from the eNB40. The MMEs60and70perform mobility management, authentication, setting processing of user data transfer paths for UEs, and the like. The MME60is connected to the MME70via an inter-external MME interface.

The HSS71manages the subscriber information on the UE50. The subscriber information includes, for example, static information such as contract information between the UE50and a mobile communication carrier and dynamic information such as position information of the UE50. The static information is not frequently changed, while the dynamic information is frequently changed compared with the static information. The HSS71transmits the subscriber information on the UE50to the MME60via an S6a interface, for example, when the MME60executes the authentication process on the UE50.

The S-GW72sends user data. The S-GW72is connected to the MME60via an inter-external MS interface and transmits/receives control data to/from the MME60. Like the S-GW72, the P-GW73sends user data. The P-GW73further performs allocation of an IP address on the UE50and the like. The P-GW73is connected to the S-GW72via an inter-external SP interface and transmits/receives control data to/from the S-GW72. The P-GW73may further be connected to an external network, the Internet, or the like (not shown) via another interface.

Hereinafter, a configuration example of the MME60according to the second embodiment of the present disclosure will be described with reference toFIG. 3. The MME60includes a signal generation unit61and a communication unit (transmission/reception unit)62. The signal generation unit61and the communication unit62may each be software or a module(s), processing thereof being executed by a processor executing a program stored in a memory. The signal generation unit61and the communication unit62may each be composed of a circuit. InFIG. 3, description of a communication interface (or a communication unit) for communicating with a node apparatus other than the eNB40is omitted.

When the allocable radio resources are insufficient in the eNB40or when the allocable radio resources are expected to become insufficient in the eNB40, the signal generation unit61generates an instruction message for instructing the eNB40to stop using one (or some) of the frequency bands for the UE50that is performing carrier aggregation.

In this case, it is assumed that the UE50performs carrier aggregation with the eNB40using a plurality of frequency bands. For example, it is assumed that the UE50performs wireless communication with the eNB40using a frequency band of a 10 MHz width in an 800 MHz band and a frequency band of a 10 MHz width in a 2 GHz band, which make a frequency band of a 20 MHz width in total.

For example, when the eNB40performs carrier aggregation with the UE50, the eNB40establishes connections to the UE50in a primary cell and a secondary cell. For example, the primary cell may be a communication area using a frequency of the 800 MHz band, and the secondary cell may be a communication area using a frequency of the 2 GHz band.

The signal generation unit61may include information on the frequency band to be stopped in the instruction message. When the signal generation unit61does not include the information on the frequency band to be stopped in the instruction message, the eNB40may determine the frequency band to be stopped. For example, the eNB40may disconnect the connection in the secondary cell.

Further, the signal generation unit61may include determination reference information on the communication terminal, which is the communication terminal to stop using one (or some) of the frequency bands, in the instruction message. For example, a value of radio field strength or a value of radio signal strength may be set as the determination reference information. When the radio resources are insufficient, and the radio field strength of one (or some) of the frequency bands among the plurality of frequency bands used by the UE50is lower than the value set in the instruction message, the eNB40may stop using the frequency band(s) having the radio field strength lower than the value set in the instruction message.

Alternatively, the signal generation unit61may set a modulation scheme as the determination reference information. For example, if the radio resources are insufficient, and the modulation scheme used by one (or some) of frequency bands among the plurality of frequency bands used by the UE50provides a communication capacity smaller than that of the modulation scheme set in the instruction message, the eNB40may stop using the frequency band(s) that uses the modulation scheme providing a communication capacity smaller than that of the modulation scheme set in the instruction message.

Alternatively, the signal generation unit61may set information on a priority of the UE50as the determination reference information. For example, when the radio resources are insufficient, the eNB40may evaluate the information on the priority set for each UE that uses a plurality of frequency bands and sequentially causes the UEs to stop using one (or some) of the frequency bands in order of the priority set for each UE.

The communication unit62transmits the instruction message generated by the signal generation unit61to the eNB40. For example, the communication unit62transmits the instruction message to the eNB40in Attach processing of the UE50.

The communication unit62may obtain, from the HSS71, information indicating whether or not the UE50corresponds to the UE that can stop using one (some) of frequency bands while the UE50is performing carrier aggregation. The communication unit62outputs the information output from the HSS71to the signal generation unit61.

Hereinafter, a configuration example of the eNB40according to the second embodiment of the present disclosure will be described with reference toFIG. 4. The eNB40includes a communication unit (transmission/reception unit)41, a control unit42, and an evaluation unit43. The communication unit41, the control unit42, and the evaluation unit43may each be software or a module(s), processing thereof being executed by a processor executing a program stored in a memory. The communication unit41, the control unit42, and the evaluation unit43may each be composed of a circuit. InFIG. 4, description of a communication interface (or a communication unit) for communicating with the UE50is omitted.

The communication unit41receives instruction information transmitted from the MME60. The communication unit41outputs the received instruction information to the control unit42.

The evaluation unit43evaluates as to whether or not the allocable radio resources are insufficient or whether or not the allocable radio resources are expected to become insufficient. For example, when the number of the allocable radio channels falls below a predetermined value, the evaluation unit43may evaluate that the allocable radio resources are insufficient. When the number of radio channels allocated within a predetermined period exceeds a predetermined value, the evaluation unit43may evaluate that the allocable radio resources are expected to become insufficient. In other words, when an amount of decrease in the number of the allocable radio channels exceeds a predetermined value, the evaluation unit43may evaluate that the allocable radio resources are expected to become insufficient. The evaluation unit43outputs an evaluation result to the control unit42.

When the control unit42receives, from the evaluation unit43, the evaluation result indicating that the allocable radio resources are insufficient or that the allocable radio resources are expected to become insufficient, the control unit42stops using one (or some) of the frequency bands for the UE50performing carrier aggregation.

Hereinafter, an evaluation process in the control unit42when there are a plurality of UEs performing carrier aggregation will be described. For example, when the determination reference information is not included in the instruction information transmitted from the MME60, the control unit42may sequentially stop using one (or some) of the frequency bands for an arbitrary UE or in an order from a UE having the longest connection to the eNB40. When the determination reference information is included in the instruction information transmitted from the MME60, the control unit42may determine the UE that is to stop using one (or some) of the frequency bands and the frequency band(s) to be stopped from being used in accordance with the determination reference information.

Hereinafter, a flow of the Attach processing according to the second embodiment of the present disclosure will be described with reference toFIG. 5. First, the UE50transmits a NAS:Attach Request message to the eNB40(S1). The NAS:Attach Request message is transmitted, for example, when the UE50transitions from a power-off state to a power-on state. The NAS:Attach Request message is used in the NAS (Non-Access Stratum) protocol defined between UEs and a core network apparatus. The core network apparatus may be, for example, an MME.

Next, the eNB40transfers the NAS:Attach Request message transmitted from the UE50to the MME60(S2). Next, when the MME60receives the NAS:Attach Request message transmitted from the eNB40, it transmits an Update Location Request message to the HSS71(S3). The MME60transmits the Update Location Request message to the HSS71in order to obtain the subscriber information from the HSS71. For example, the MME60sets an identifier for identifying the UE50in the Update Location Request message and transmits it to the HSS71.

Next, the HSS71transmits an Update Location Ack message to the MME60as a response message to the Update Location Request message (S4). The HSS71transmits the Update Location Ack message in which the subscriber information on the UE50is set to the MME60.

When, while the UE50is performing carrier aggregation, it is evaluated that the allocable radio resources are insufficient in the eNB40or when it is evaluated that the allocable radio resources are expected to become insufficient in the eNB40, the HSS71sets information indicating a stop of using one (or some) of the frequency bands for the UE50in the Update Location Ack message.

When, while the UE50is performing carrier aggregation, it is evaluated that the allocable radio resources are insufficient in the eNB40or when it is evaluated that the allocable radio resources are expected to become insufficient in the eNB40, the information indicating a stop of using one (or some) of the frequency bands for the UE50may be included in the subscriber information.

Next, the MME60transmits an Initial Context Setup Request message to the eNB40(S5). When, while the UE50is performing carrier aggregation, it is evaluated that the allocable radio resources are insufficient in the eNB40or when it is evaluated that the allocable radio resources are expected to become insufficient in the eNB40, the MME60sets the information indicating a stop of using one (or some) of the frequency bands for the UE50in the Initial Context Setup Request message.

Further, when, while the UE50is performing carrier aggregation, it is evaluated that the allocable radio resources are insufficient in the eNB40or when it is evaluated that the allocable radio resources are expected to become insufficient in the eNB40, the MME60may set information indicating a disconnection of a connection in the secondary cell in the Initial Context Setup Request. Moreover, when, while the UE50is performing carrier aggregation, it is evaluated that the allocable radio resources are insufficient in the eNB40or when it is evaluated that the allocable radio resources are expected to become insufficient in the eNB40, the information indicating a disconnection of a connection in the secondary cell may be set in the Update Location Ack message transmitted by the HSS71.

Next, the eNB40transmits an RRC Connection Reconfiguration/NAS:Attach Accept message to the UE50in order to establish an RRC Connection to the UE50(S6).

Next, the UE50transmits an RRC Connection Reconfiguration Complete message to the eNB40as a response message to the RRC Connection Reconfiguration/NAS:Attach Accept message (S7).

Next, the eNB40transmits an Initial Context Setup Response message to the MME60as a response message to the Initial Context Setup Request message (S8). Next, the UE50transmits a Direct Transfer/NAS:Attach Complete message to the eNB40in order to notify the eNB40that the process relating to the Attach Request has been completed (S9). Next, the eNB40transmits a NAS:Attach Complete message to the MME60(S10).

Hereinafter, a flow of processing for stopping the use of one (or some) of the frequency bands for the UE50performing carrier aggregation according to the second embodiment of the present disclosure will be described with reference toFIG. 6. InFIG. 6, it is assumed that the UE50has already executed the Attach processing ofFIG. 5and is in communication using carrier aggregation.

Firstly, the eNB40evaluates that the allocable radio resources are insufficient (S21). For example, the eNB40may evaluate that the number of allocable radio channels is insufficient.

Next, the eNB40identifies a UE that stops using one (or some) of the frequency bands from among the plurality of UEs performing carrier aggregation, that is, identifies a UE that stops carrier aggregation (S22). For example, the eNB40may cause a UE that is performing communication using a signal having a radio field strength lower than a predetermined threshold to stop carrier aggregation. Alternatively, the eNB40may check the priority information set for each UE and cause the UEs to stop carrier aggregation in an order from the UE having the lowest priority. Further, in the Attach processing, the eNB40identifies the UE that stops carrier aggregation from among the UEs that have been notified about the information indicating a stop of using one (or some) of the frequency bands.

Next, the eNB40transmits an RRC Connection Reconfiguration message to the UE identified in Step S22and causes the identified UE to stop carrier aggregation (S23). For example, the eNB40may set a disconnection of a connection in the secondary cell in the RRC Connection Reconfiguration message.

Next, the UE50transmits the RRC Connection Reconfiguration Complete message to the eNB40(S24). When the UE50transmits the RRC Connection Reconfiguration Complete message to the eNB40, the communication using carrier aggregation between the UE50and the eNB40is stopped.

As described above, by executing the communication system according to the second embodiment of the present disclosure, when the radio resources are insufficient in the eNB40or when the radio resources are expected to become insufficient in the eNB40, the MME60can transmit a message indicating a stop of carrier aggregation. Moreover, when it is evaluated that the radio resources are insufficient or when it is evaluated that the radio resources are expected to become insufficient, the eNB40can stop applying carrier aggregation to the communication with the identified UE. In this way, it is possible to solve the problem of the shortage of the radio resources in the eNB40. Accordingly, the eNB40can allocate the radio resources to a UE requesting a new connection to the eNB40.

Moreover, by obtaining the determination reference information from the MME60, the eNB40can determine a UE to stop carrier aggregation in accordance with the determination reference information from among the plurality of UEs performing carrier aggregation. For example, if a communication carrier determines the determination reference information, the eNB40can determine a UE to stop carrier aggregation in accordance with the policy of the communication carrier.

Third Embodiment

Hereinafter, a configuration example of a communication system according to a third embodiment will be described with reference toFIG. 7. The communication system ofFIG. 7further includes an eNB80in the configuration of the communication system ofFIG. 2. The eNB80is accommodated in the MME60. The eNB80is connected to the eNB40via an X2 interface.

In this case, it is assumed that the UE50is performing carrier aggregation by simultaneously communicating with the eNB40and the eNB80. For example, the UE50may perform communication with the eNB40using an 800 MHz band and perform communication with the eNB80using a 2 GHz band. Further, when the UE50performs carrier aggregation, a communication area formed by the eNB40may be used as a primary cell and a communication area formed by the eNB80may be used as a secondary cell.

When the UE50performs carrier aggregation, the eNB40and the eNB80may determine which one of the communication areas formed by the eNBs40and80is used as the primary cell or the secondary cell by transmitting and receiving control signals via the X2 interface.

In such a case, for example, the MME60may transmit, to the eNBs40and80, the instruction message instructing the eNBs40and80to disconnect a connection in the secondary cell when the allocable radio resources become insufficient.

In this case, as the eNB80forms the secondary cell, the eNB80may disconnect the communication with the UE50when it is evaluated that the allocable radio resources are insufficient in the eNB80.

As described above, by using the communication system according to the third embodiment, even when the UE50is performing carrier aggregation using a plurality of eNBs, one (or some) of eNBs among the plurality of eNBs can stop communication with the UE50. Accordingly, it is possible to stop communication in one (or some) of the frequency bands among the plurality of frequency bands used by the UE50.

In the above embodiments, the present disclosure has been described as a hardware configuration, but the present disclosure is not limited to this. The present disclosure can be implemented by causing a CPU (Central Processing Unit) to execute a computer program that performs processing of the UE, the MME, and the eNB.

Note that the present disclosure is not limited to the above embodiments, and modifications can be made as appropriate without departing from the scope thereof.

Although the present disclosure has been described with reference to the embodiments, the present disclosure is not limited by the above. Various modifications and changes, understood by those skilled in the art within the scope of the present disclosure, can be made to the configurations and details of the present disclosure.

The present application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-058151, filed on Mar. 20, 2015, the entire contents of which are hereby incorporated by reference.

REFERENCE SIGNS LIST