JP2012034057A - Radio base station and communication control method - Google Patents

Abstract

A handover is appropriately executed.
When an eNB 1-1 receives a Handover Request Nack message indicating that a handover from a first handover destination candidate eNB is rejected, the eNB 1-1 is permitted in an EPS bearer 5 that is a logical communication path with the UE 2. In accordance with the allowable delay time in the QCI information indicating the magnitude of the delay, it is determined whether or not a Handover Request message needs to be transmitted to the second handover destination candidate eNB, and if necessary, it is transmitted. If there is no need to send, do not send. At this time, the eNB 1-1 performs control to suppress transmission of the Handover Request message to the second handover destination candidate eNB as the QoS class value is smaller, in other words, as the allowable delay is smaller.
[Selection] Figure 1

Description

  The present invention relates to a communication system in which a logical communication path via a wireless base station is established between a wireless terminal and a network side device, and a communication control method in the communication system.

  LTE (Long Term Evolution) in 3GPP (3rd Generation Partnership Project) is a 3rd generation mobile phone (3G) communication system such as W-CDMA and CDMA2000 that are currently popular, and a 4th generation mobile phone (4G) that will appear in the future. And is also called a communication system for the 3.9th generation mobile phone (3.9G).

  In a radio communication system employing LTE, a logical communication path called a radio bearer is established between a radio terminal (UE) and a radio base station (eNB). Moreover, it is called an EPS (Evoluved Packet System) Bearer (EPS bearer) via an eNB between a UE and an EPC (Evolved Packet Core) which is a network side device including a Mobility Management Entity (MME) and a Serving Gateway (SGW). A logical communication path is established. When the handover of the UE is performed, the handover source eNB (S-eNB) receives radio information referred to as a measurement report message from the UE and should perform the handover of the UE based on the measurement report message Decide whether or not. When execution of the handover is determined, the S-eNB transmits a Handover Request message for requesting acceptance of the UE in advance to the handover destination eNB (T-eNB). When the S-eNB receives a Handover Request Ack message indicating that the UE accepts a request for accepting the UE from the T-eNB, the S-eNB transmits a handover instruction message to the UE (for example, see Non-Patent Document 1). .

3GPP TS 36.300 V9.2.0, December 2009

  In the communication system described above, the EPC may request the radio base station to increase the EPS bearer according to the communication status such as the QoS state. In such a case, the radio base station determines whether or not the enhancement is possible according to the usage status of the EPS bearer via the own radio base station, and returns the determination result to the EPC. When the EPS bearer cannot be augmented, communication using the EPS bearer up to that point is continued, and communication quality deteriorates.

  When the wireless terminal requests call connection to the wireless base station, the wireless base station determines whether call connection is possible according to the usage status of the EPS bearer via the wireless base station. If the call connection is impossible, the call is released.

  In view of the above problems, an object of the present invention is to provide a communication system, a communication control apparatus, a radio base station, and a communication control method that can appropriately establish a logical communication path.

  In order to solve the above-described problems, the present invention has the following features. The first feature of the present invention is a radio base station (eNB1-1) connected to a network side device (EPC3) and wirelessly connected to radio terminals (UE2-1, UE2-2, UE2-3). A control unit (control unit 202) that controls handover of the radio terminal, and the control unit establishes logical communication established between the radio terminal and the network side device in the handover of the radio terminal. Handover request message (Handover Request message) for requesting acceptance of the radio terminal to another radio base station in accordance with permissible delay information (QCI information) indicating the magnitude of the delay allowed in the path (EPS bearer) ) To control transmission.

  Such a radio base station is another candidate for the band-over destination according to the allowable delay information indicating the allowable delay in the logical communication path established between the wireless terminal and the network side device. Controls transmission of handover request information to handover request information to a radio base station. Therefore, in determining whether or not to execute the handover, the allowable delay in the logical communication path established between the wireless terminal and the network side device is taken into consideration, and the handover can be executed appropriately.

  A second feature of the present invention is that, when the control unit is refused to accept the wireless terminal by the first other wireless base station that is a band-over destination candidate, the control unit responds to the allowable delay information. When the handover request information needs to be transmitted to a second other radio base station that is a bandover destination candidate, the handover request information is transmitted to the second other radio base station, When it is not necessary to transmit handover request information to the second other radio base station, control is performed to stop transmission of the handover request information to the second other radio base station. .

  A third feature of the present invention is that the control unit suppresses transmission of the handover request information to the other radio base station as the allowable delay indicated by the allowable delay information is smaller. Is the gist.

  According to a fourth aspect of the present invention, the control unit is configured to control the other radio depending on an average value of allowable delays indicated by the allowable delay information for each of a plurality of communication services received by the wireless terminal. The gist is to control transmission of the handover request information to the base station.

  A fifth feature of the present invention is that the transmission control unit suppresses transmission of the handover request information to the other radio base station when voice data is transmitted to the logical communication path. To do.

  A sixth feature of the present invention is a communication control method in a radio base station connected to a network side device and wirelessly connected to a radio terminal, comprising a step of controlling handover of the radio terminal, wherein the control In the handover of the wireless terminal, in response to the allowable delay information indicating the amount of delay allowed in the logical communication path established between the wireless terminal and the network side device, The gist is to control transmission of handover request information for requesting acceptance of the wireless terminal to a station.

  According to the present invention, handover can be appropriately executed.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a block diagram of a radio base station in an embodiment of the present invention. FIG. 6 is a sequence diagram showing a first operation of the radio base station according to the embodiment of the present invention. FIG. 10 is a sequence diagram showing a second operation of the radio base station according to the embodiment of the present invention. FIG. 10 is a sequence diagram showing a third operation of the radio base station according to the embodiment of the present invention. FIG. 10 is a sequence diagram showing a fourth operation of the radio base station 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) the configuration of the radio communication system, (2) the operation of the radio base station, (3) the operation and effect, and (4) 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) Configuration of Radio Communication System First, the configuration of the radio communication system according to the embodiment of the present invention will be described in the order of (1.1) Overall schematic configuration of radio communication system, (1.2) Configuration of radio base station. To do.

(1.1) Overall Schematic Configuration of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system 100 according to an embodiment of the present invention.

  A radio communication system 100 shown in FIG. 1 is an LTE radio communication system. This radio communication system 100 includes LTE base stations (eNB) 1-1, eNB1-2, eNB1-3 as radio base stations, radio terminals (UE) 2-1, UE2-2, UE2-3 (hereinafter, UE2-1 to UE2-3 are collectively referred to as “UE2” as appropriate) and an EPC (Evolved Packet Core) 3 as a network side device. Among these, the EPC 3 includes an MME (Mobility Management Entity) 10 and an SGW (Serving Gateway) 20.

  In FIG. 1, an EPS (Evoluved Packet System) Bearer (EPS bearer) 5-1 which is a logical communication path via the eNB 1-1 is established between the EPC 3 and the UE 2-1. An EPS bearer 5-2, which is a logical communication path via eNB1-1, is established between EPC3 and UE2-2, and a logical communication path via eNB1-1 is established between EPC3 and UE2-3. A certain EPSEPS bearer 5-3 has been established (hereinafter, the EPS bearers 5-1 to 5-3 are collectively referred to as "EPS bearer 5" as appropriate).

  For each communication service received by UE 2, UE 2 allocates SDF (Service Data Flow), which is data corresponding to the communication service, to EPS bearer 5 and performs transmission to EPC 3 in uplink communication. Moreover, EPC3 allocates SDF corresponding to the said communication service to one EPS bearer 5 for every communication service which UE2 receives in downlink communication, and performs transmission with respect to UE2.

  Here, the communication services received by the UE 2 are voice service VoIP (Voice over IP), file transfer service FTP (File Transfer Protocol), web access service HTTP (Hyper Text Transfer Protocol), streaming playback. Services.

  Moreover, eNB1-1, eNB1-2, and eNB1-3 each transmit and receive control data via S1 interface between MME10, and transmit user data via S1 interface between SGW20. And receive. Moreover, eNB1-1, eNB1-2, and eNB1-3 each communicate with another eNB via X2 interface.

(1.2) Configuration of Radio Base Station FIG. 2 is a configuration diagram of the eNB 1-1. In addition, eNB1-2 and eNB1-3 are the same structures. The eNB 1-1 illustrated in FIG. 2 includes a control unit 202, a storage unit 203, a wired communication unit 204, a wireless communication unit 206, and an antenna 208.

  The control unit 202 is configured by, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), and controls various functions included in the eNB 1-1. The memory | storage part 203 is comprised by memory, for example, and memorize | stores the various information used for control etc. in eNB1-1.

  The wired communication unit 204 transmits and receives data with the MME 10 and the SGW 20. The wireless communication unit 206 includes an RF circuit, a baseband circuit, and the like, performs modulation and demodulation, encoding, decoding, and the like, and transmits and receives wireless signals to and from the UE 2 via the antenna 208.

  The control unit 202 includes a QCI acquisition unit 251, a threshold adjustment unit 252, and a handover control unit 254.

  The QCI acquisition unit 251 is QCI (QoS Class Indicator) information as allowable delay information indicating the amount of delay allowed in each of the EPS bearers 5 for each UE 2 around the eNB 1-1 that is the local station. Receive. QCI information is transmitted from UE2 or MME10 connected to eNB1-1. When the UE 2 receives a communication service using the EPS bearer 5 established between the UE 2 and the EPC 3, the QCI information includes an identifier (QoS class identifier) indicating a QoS class corresponding to the communication service, a resource Priority level indicating the priority order of allocation and maintenance, delay time allowed in the communication service (packet delay budget), and the like. Here, when the UE 2 receives a plurality of communication services, the QCI acquisition unit 251 receives corresponding CQI information for each communication service.

  The handover control unit 254 receives a measurement report message that is periodically transmitted by each UE 2. In the Measurement Report message, when the source UE 2 receives a reference signal from a surrounding eNB, the received power of the reference signal (RSRP: Reference Signal Received Power) and a cell ID as identification information of the surrounding eNB Are included in association with each other. The handover control unit 254 acquires the RSRP included in the Measurement Report message. The acquired RSRP is information (radio state information) indicating the radio state.

  Next, the handover control unit 254 determines whether or not there is a UE 2 whose radio state with the eNB 1-1 that is its own station has deteriorated, in other words, a UE 2 that is a target of handover.

  Specifically, the handover control unit 254 selects the RSRP associated with the cell ID of the own station from the RSRP included in the Measurement Report message. The handover control unit 254 determines whether or not the selected RSRP is less than or equal to a first reference value that is a predetermined handover threshold. Here, the first reference value is stored in the storage unit 203. When the selected RSRP is less than or equal to the first reference value, the handover control unit 254 determines that the UE 2 corresponding to the selected RSRP is the UE 2 that is the target of the handover.

  When there is a UE 2 (handover target UE 2) to be handed over, the threshold adjustment unit 252 acquires QCI information corresponding to the handover target UE 2, in other words, QCI information for each communication service received by the handover target UE 2. Specifically, the threshold adjustment unit 252 selects the QCI information transmitted from the handover target UE 2 among the QCI information from each UE 2. For example, the threshold adjustment unit 252 acquires the ID of the transmission source of the Measurement Report message that is associated with the cell ID of the local station and includes RSRP equal to or less than the first reference value. The acquired ID is the ID of the handover target UE2. Further, the threshold adjustment unit 252 selects QCI information including the ID of the handover target UE 2 as the ID of the transmission source from the QCI information from each UE 2. The selected QCI information is the QCI information transmitted from the handover target UE2.

  Next, the threshold adjustment unit 252 determines whether the communication service received by the handover target UE 2 includes a VoIP communication service. As described above, when the UE 2 receives a communication service using the EPS bearer 5, the QCI information includes a QoS class identifier corresponding to the communication service on a one-to-one basis. Therefore, the threshold adjustment unit 252 can determine whether or not the VoIP communication service is included in the communication service received by the handover target UE 2 based on the QoS class identifier.

  Next, the threshold adjustment unit 252 performs the following first process or second process.

[First processing]
When the communication service received by the handover target UE2 includes a VoIP communication service, if frequent handovers occur in the handover target UE2, the communication interruption time increases, and therefore there is a high possibility of exceeding the delay allowed in VoIP.

  For this reason, the threshold adjustment unit 252 performs processing for suppressing handover in the handover target UE2. Specifically, the threshold adjustment unit 252 lowers the handover threshold by 20% from the first reference value. The new handover threshold is stored in the storage unit 203.

  On the other hand, when the VoIP communication service is not included in the communication service received by the handover target UE2, the threshold adjustment unit 252 averages the allowable delay time (allowable delay time) included in the QCI information corresponding to the handover target UE2. Calculate the value.

  Next, the threshold adjustment unit 252 determines whether or not the calculated average value of the allowable delay time is less than a predetermined second reference value. Here, the second reference value is stored in the storage unit 203. When the average value of the allowable delay time is less than the second reference value, the threshold adjustment unit 252 performs the handover threshold to suppress handover in the handover target UE 2 as compared with the case where the handover threshold is the first reference value. Is reduced by 10% from the first reference value. The new handover threshold is stored in the storage unit 203. On the other hand, when the average value of the allowable delay times is equal to or greater than the second reference value, the threshold adjustment unit 252 keeps the handover threshold as the first reference value.

[Second processing]
When the communication service received by the handover target UE 2 includes a VoIP communication service, the threshold adjustment unit 252 multiplies the allowable delay time included in the QCI information corresponding to the VoIP communication service by a coefficient α smaller than 1. On the other hand, when the communication service received by the handover target UE2 does not include a VoIP communication service, the threshold adjustment unit 252 does not multiply the allowable delay time by the coefficient α.

  Regardless of whether the allowable delay time is multiplied by the coefficient α or not, the threshold adjustment unit 252 next calculates the average value of the allowable delay time included in the QCI information corresponding to the handover target UE 2. Is calculated. Here, the allowable delay time included in the QCI information corresponding to the VoIP communication service is a value after being multiplied by the coefficient α.

  Next, the threshold adjustment unit 252 determines whether or not the calculated average value of the allowable delay time is less than a predetermined second reference value. When the average value of the allowable delay time is less than the second reference value, the threshold adjustment unit 252 performs the handover threshold to suppress handover in the handover target UE 2 as compared with the case where the handover threshold is the first reference value. Is reduced by 10% from the first reference value. The new handover threshold is stored in the storage unit 203. On the other hand, when the average value of the allowable delay time is equal to or greater than the second reference value, the threshold adjustment unit 252 keeps the handover threshold as the first reference value.

  After the handover threshold is adjusted by the threshold adjuster 252, the handover controller 254 determines whether or not the radio state between the handover target UE 2 and the own station is equal to or less than the handover threshold. Specifically, the handover control unit 254 selects an RSRP associated with the cell ID of the own station from the RSRP included in the Measurement Report message from the handover target UE2. Further, the handover control unit 254 determines whether or not the selected RSRP is equal to or less than a predetermined handover threshold.

  When the selected RSRP is equal to or less than a predetermined handover threshold, the handover control unit 254 switches the connection destination of the handover target UE 2 from its own eNB 1-1 to another eNB (handover destination eNB). I do.

  Specifically, the handover control unit 254 selects an RSRP associated with a cell ID other than the cell ID of the own station from the RSRP included in the Measurement Report message from the handover target UE2. Furthermore, the handover control unit 254 selects a cell ID associated with an RSRP greater than a handover threshold by a predetermined value or more from the selected RSRP. The selected cell ID is the cell ID of an eNB (handover destination candidate eNB) that is a handover destination candidate. Next, the handover control unit 254 transmits a Handover Request message to the eNB having the largest corresponding RSRP (first handover destination candidate eNB) among the handover destination candidate eNBs.

  Thereafter, when receiving a Handover Request Ack message indicating that a handover from the first handover destination candidate eNB is accepted, the handover control unit 254 determines the first handover destination candidate eNB as a handover destination, and sends a Handover command to the handover target UE 2. Send.

  On the other hand, when the handover control unit 254 receives the Handover Request Nack message indicating that the handover from the first handover destination candidate eNB is rejected, whether or not the communication service received by the handover target UE2 includes the VoIP communication service. Determine. Specifically, the handover control unit 254 can determine whether or not the communication service received by the handover target UE2 includes a VoIP communication service, based on the QoS class identifier included in the QCI information corresponding to the handover target UE2. .

  Next, the handover control unit 254 performs the following third process or fourth process.

[Third processing]
When the communication service received by the handover target UE2 includes a VoIP communication service, the handover control unit 254 determines not to transmit a Handover Request message to the second handover destination candidate eNB. Here, the second handover destination candidate eNB includes the cell ID in the Measurement Report message from the handover target UE 2 and the second RSRP corresponding to the second eNB (handover destination candidate eNB) other than the own station. Large eNB, or all eNBs other than the first handover destination candidate eNB.

  On the other hand, when the VoIP communication service is not included in the communication service received by the handover target UE2, the handover control unit 254 calculates the average value of the allowable delay time included in the QCI information corresponding to the handover target UE2.

  Next, the handover control unit 254 determines whether or not the calculated average value of the allowable delay time is less than a predetermined fourth reference value. Here, the fourth reference value is stored in the storage unit 203. When the average value of the allowable delay time is less than the fourth reference value, the handover control unit 254 determines not to transmit the Handover Request message to the second handover destination candidate eNB.

  On the other hand, when the average value of the allowable delay time is equal to or greater than a predetermined fourth reference value, the handover control unit 254 determines to transmit a Handover Request message to the second handover destination candidate eNB. Furthermore, the handover control unit 254 transmits a Handover Request message to the second handover destination candidate eNB.

[Fourth processing]
When the communication service received by the handover target UE 2 includes a VoIP communication service, the handover control unit 254 multiplies the allowable delay time included in the QCI information corresponding to the VoIP communication service by a coefficient β smaller than 1. On the other hand, when the VoIP communication service is not included in the communication service received by the handover target UE 2, the handover control unit 254 does not multiply the allowable delay time by the coefficient β.

  Whether or not the allowable delay time is multiplied by the coefficient β, the handover control unit 254 next calculates the average value of the allowable delay times included in the QCI information corresponding to the handover target UE2. Is calculated. Here, the allowable delay time included in the QCI information corresponding to the VoIP communication service is a value after being multiplied by the coefficient β.

  Next, the handover control unit 254 determines whether or not the calculated average value of the allowable delay time is less than a predetermined fourth reference value. When the average value of the allowable delay time is less than the fourth reference value, the handover control unit 254 determines not to transmit the Handover Request message to the second handover destination candidate eNB.

  On the other hand, when the average value of the allowable delay time is equal to or greater than a predetermined fourth reference value, the handover control unit 254 determines to transmit a Handover Request message to the second handover destination candidate eNB. Furthermore, the handover control unit 254 transmits a Handover Request message to the second handover destination candidate eNB.

(2) Operation of Radio Base Station Next, the operation of the eNB 1-1 will be described. FIG. 3 is a sequence diagram illustrating a first operation of the eNB 1-1.

  In step S101, the eNB 1-1 receives the QCI information of the EPS bearer 5 for each UE 2 from the surrounding UE 2.

  In step S102, the eNB 1-1 receives the Measurement Report message from the UE2. Furthermore, the eNB 1-1 acquires RSRP (radio state information) included in the Measurement Report message.

  In step S103, the eNB 1-1 determines whether or not there is a UE 2 (handover target UE 2) whose radio state with the own station is deteriorated based on the acquired radio state information. When the handover target UE2 does not exist, the series of operations ends.

  On the other hand, when the handover target UE2 exists, in step S104, the eNB 1-1 acquires the QCI information corresponding to the handover target UE2.

  In step S105, the eNB 1-1 determines whether the communication service received by the handover target UE 2 includes a VoIP communication service.

  If the communication service received by the handover target UE2 includes a VoIP communication service, in step S106, the eNB 1-1 lowers the handover threshold by 20% from the first reference value.

  On the other hand, if the VoIP communication service is not included in the communication service received by the handover target UE2, in step S107, the eNB 1-1 calculates an average value of the allowable delay time included in the QCI information corresponding to the handover target UE2. .

  In step S108, the eNB 1-1 determines whether or not the calculated average value of allowable delay times is less than a predetermined second reference value.

  When the average value of the allowable delay time is less than the second reference value, in step S109, the eNB 1-1 lowers the handover threshold by 10% from the first reference value.

  After step S106, after step S109, or after a negative determination is made in step S108, in step S110, the eNB 1-1 determines whether the radio state between the handover target UE 2 and the own station is equal to or less than the handover threshold. Determine whether. When the radio state between the handover target UE2 and the own station exceeds the handover threshold, a series of operations ends. On the other hand, when the radio state between the handover target UE2 and the own station is equal to or less than the handover threshold, the eNB 1-1 performs handover control in step S111.

  FIG. 4 is a sequence diagram illustrating a second operation of the eNB 1-1.

  In step S151, the eNB 1-1 receives the QCI information of the EPS bearer 5 for each peripheral UE 2 from the MME 10.

  The operations in steps S152 through S155 are the same as the operations in steps S102 through S105 in FIG.

  If it is determined in step S155 that the communication service received by the handover target UE2 includes the VoIP communication service, in step S156, the eNB 1-1 determines the allowable delay time included in the QCI information corresponding to the VoIP communication service. Is multiplied by a coefficient α smaller than 1.

  After step S156 or after a negative determination is made in step S155, in step S157, the eNB 1-1 calculates an average value of allowable delay times included in the QCI information corresponding to the handover target UE2.

  In step S158, the eNB 1-1 determines whether or not the calculated average value of the allowable delay time is less than a predetermined second reference value. When the average value of the allowable delay time is less than the second reference value, in step S159, the eNB 1-1 lowers the handover threshold by 10% from the first reference value.

  After step S159 or after a negative determination is made in step S158, in step S160, the eNB 1-1 determines whether or not the radio state between the handover target UE2 and the own station is equal to or less than the handover threshold. When the radio state between the handover target UE2 and the own station exceeds the handover threshold, a series of operations ends. On the other hand, when the radio state between the handover target UE2 and the own station is equal to or less than the handover threshold, the eNB 1-1 performs handover control in step S161.

  FIG. 5 is a sequence diagram illustrating a third operation of the eNB 1-1. The operation shown in FIG. 5 is performed as part of the operation in step S111 in FIG. 3 and step S161 in FIG.

  In step S201, the eNB 1-1 transmits a Handover Request message to the first handover destination candidate eNB.

  In step S202, the eNB 1-1 determines whether or not a Handover Request Ack message has been received from the first handover destination candidate eNB. When the Handover Request Ack message is received, the series of operations ends. Then, the eNB 1-1 determines the first handover destination candidate eNB as the handover destination, and transmits a Handover command to the handover target UE2.

  On the other hand, when the Handover Request Ack message has not been received, the eNB 1-1 determines whether or not a Handover Request Nack message has been received from the first handover destination candidate eNB. If the Handover Request Nack message has not been received, the operations after step S202 are repeated.

  On the other hand, when the Handover Request Nack message is received, in step S204, the eNB 1-1 determines whether or not the communication service received by the handover target UE2 includes a VoIP communication service.

  If the communication service received by the handover target UE2 includes a VoIP communication service, in step S205, the eNB 1-1 determines not to transmit a Handover Request message to the second handover destination candidate eNB.

  On the other hand, when the VoIP communication service is not included in the communication service received by the handover target UE2, in step S206, the eNB 1-1 determines the average value of the allowable delay time included in the QCI information corresponding to the handover target UE2. calculate.

  In step S207, the eNB 1-1 determines whether or not the calculated average value of the allowable delay time is less than a predetermined fourth reference value.

  When the average value of the allowable delay time is less than the fourth reference value, in step S205, the eNB 1-1 determines not to transmit the Handover Request message to the second handover destination candidate eNB.

  On the other hand, when the average value of the allowable delay time is greater than or equal to the fourth reference value, in step S208, the eNB 1-1 determines to transmit a Handover Request message to the second handover destination candidate eNB. In step S209, the eNB 1-1 transmits a Handover Request message to the second handover destination candidate eNB.

  FIG. 6 is a sequence diagram illustrating a fourth operation of the eNB 1-1. The operation shown in FIG. 6 is performed as part of the operation in step S111 in FIG. 3 and step S161 in FIG.

  The operations in steps S251 through S254 are the same as the operations in steps S201 through S204 in FIG.

  If it is determined in step S254 that the communication service received by the handover target UE2 includes the VoIP communication service, in step S255, the eNB 1-1 determines the allowable delay time included in the QCI information corresponding to the VoIP communication service. Is multiplied by a coefficient β smaller than 1.

  After step S255 or after a negative determination is made in step S254, the eNB 1-1 calculates an average value of the allowable delay time included in the QCI information corresponding to the handover target UE2.

  In step S257, the eNB 1-1 determines whether or not the calculated average value of the allowable delay time is less than a predetermined fourth reference value. When the average value of the allowable delay time is less than the fourth reference value, in step S258, the eNB 1-1 determines not to transmit the Handover Request message to the second handover destination candidate eNB.

  On the other hand, if the average value of the allowable delay time is greater than or equal to the predetermined fourth reference value, in step S259, the eNB 1-1 transmits a Handover Request message to the second handover destination candidate eNB. To decide. Further, in step S260, the eNB 1-1 transmits a Handover Request message to the second handover destination candidate eNB.

(3) Operation / Effect In the radio communication system 100 according to the embodiment of the present invention, the eNB 1-1 is established between the UE 2 and the PC 3, and is communicated in the EPS bearer 5 that is a logical communication path via the eNB 1-1. It is determined whether or not the UE 2 should be handed over according to the allowable delay time in the QCI information indicating the allowable delay for each service. The eNB 1-1 adjusts the handover threshold to be compared with the radio state with the UE 2 in this determination. Specifically, the eNB 1-1 adjusts the handover threshold so as to suppress the handover of the UE 2 as the allowable delay time is smaller, in other words, as the allowable delay is smaller. Therefore, in determining whether or not to execute the handover, the smaller the delay allowed in the EPS bearer 5 with the UE 2, the more the handover is suppressed.

  Further, when the eNB 1-1 receives a Handover Request Nack message indicating that the handover from the first handover destination candidate eNB is rejected, the eNB 1-1 transmits a Handover Request message to the second handover destination candidate eNB according to the allowable delay time. If it is necessary to transmit, it is transmitted. If it is not necessary to transmit, it is not transmitted. Specifically, the eNB 1-1 performs control such that the smaller the allowable delay time, in other words, the smaller the allowable delay is, the more difficult it is to transmit the Handover Request message to the second handover destination candidate eNB. I do. Therefore, in determining whether or not to execute the handover, the smaller the delay allowed in the EPS bearer 5 with the UE 2, the more the handover is suppressed.

(4) 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.

  In the above-described embodiment, the MeNB 1-1 performs the adjustment of the handover threshold and the determination of the necessity of transmission of the Handover Request message for the second handover destination candidate eNB based on the allowable delay time included in the QCI information. If the information indicates the amount of delay allowed in the EPS bearer 5, based on this information, it is possible to adjust the handover threshold and determine whether or not to transmit a Handover Request message to the second handover destination candidate eNB. it can.

  Although the LTE system has been described in the above-described embodiment, the present invention may be applied to other wireless communication systems such as a wireless communication system based on WiMAX (IEEE 802.16).

  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.

  1-1, 1-2, 1-3 ... eNB, 2-1, 2-2, 2-3 ... UE, 3 ... EPC, 5-1, 5-2, 5-3 ... EPS bearer, 10 ... MME 20 ... SGW, 100 ... wireless communication system, 202 ... control unit, 203 ... storage unit, 204 ... wired communication unit, 206 ... wireless communication unit, 208 ... antenna, 251 ... QCI acquisition unit, 252 ... threshold adjustment unit, 254 ... Handover controller

Claims (6)

A wireless base station connected to a network side device and wirelessly connected to a wireless terminal,
A control unit for controlling handover of the wireless terminal;
The controller is
In handover of the wireless terminal, according to the allowable delay information indicating the amount of delay allowed in the logical communication path established between the wireless terminal and the network side device, the wireless terminal to the other wireless base station A radio base station that controls transmission of handover request information for requesting acceptance of a radio terminal.   When the first other radio base station, which is a bandover destination candidate, refuses to accept the radio terminal, the control unit is a bandover destination candidate according to the allowable delay information. When it is necessary to transmit the handover request information to two other radio base stations, the handover request information is transmitted to the second other radio base station and to the second other radio base station. The radio base station according to claim 1, wherein when there is no need to transmit handover request information, control is performed to stop transmission of the handover request information to the second other radio base station.   The radio base station according to claim 1, wherein the control unit suppresses transmission of the handover request information to the other radio base station as the allowable delay indicated by the allowable delay information is smaller.   The control unit transmits the handover request information to the other radio base station according to an average value of allowable delays indicated by the allowable delay information for each of a plurality of communication services received by the wireless terminal. The radio base station according to claim 1, wherein the radio base station is controlled.   The radio base according to any one of claims 1 to 4, wherein the transmission control unit suppresses transmission of the handover request information to the other radio base station when voice data is transmitted to the logical communication path. Bureau. A communication control method in a wireless base station connected to a network side device and wirelessly connected to a wireless terminal,
Controlling the handover of the wireless terminal,
The controlling step includes
In handover of the wireless terminal, according to the allowable delay information indicating the amount of delay allowed in the logical communication path established between the wireless terminal and the network side device, the wireless terminal to the other wireless base station A communication control method for controlling transmission of handover request information for requesting acceptance of a radio terminal.

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