JP2013121087A - Radio base station device, radio terminal device, communication control method, and communication control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio base station device, a radio terminal device, a communication control method, and a communication control program that are capable of achieving stabilization of communication by discriminating a cause of disconnection of communication connection between the radio terminal device and the radio base station device or suppressing the disconnection of the communication connection.SOLUTION: A radio base station device 101 includes: a measurement information acquisition part 11 for acquiring measurement information indicative of results of measurement by a radio terminal device 202 in a period from disconnection of communication connection between the radio terminal device 202 and the radio base station device 101 to establishment of new communication connection by the radio terminal device 202 with the radio base station device 101; and a discrimination part 12 for discriminating whether a cause of the disconnection of the communication connection is interference between radio signals transmitted by a plurality of radio base station devices 101 in a communication system based on the measurement information acquired by the measurement information acquisition part 11 or not.

Description

  The present invention relates to a radio base station apparatus, a radio terminal apparatus, a communication control method, and a communication control program, and in particular, a radio base station in a communication system capable of communicating with a plurality of radio base station apparatuses by performing a moving operation of the radio terminal apparatus. The present invention relates to a device, a wireless terminal device, a communication control method, and a communication control program.

  Conventionally, in a mobile communication system, a communication service is provided by a radio base station apparatus (hereinafter also referred to as a macro base station) that forms an area in which a cell having a radius of several hundred meters to several tens of kilometers, that is, a radio terminal apparatus can communicate. It was.

  In recent years, due to a dramatic increase in the number of subscribers of mobile communication services and an increase in the amount of communication traffic due to data communication, subscribers and communication traffic are distributed by forming smaller radius cells, and a certain level of communication It is desirable to provide speed to users in a stable manner. In addition, in order to deal with dead zones associated with the increase in the number of buildings, it is desired to install radio base station devices on the corporate floor and in ordinary households.

  Together with these demands, the processing capability of various devices used in the radio base station apparatus has been dramatically improved, and the miniaturization of the radio base station apparatus has progressed. Collecting.

  Since the radius of the femto cell (Femto Cell) formed by this small base station (hereinafter also referred to as a femto base station) is as small as about 10 meters, the femto base station is the macro cell (Macro Cell) formed by the macro base station. It may be used in places such as indoors and underground malls where it is out of service area and it is difficult to install macro base stations.

  In addition, since many femto base stations are installed in a specific area, it is difficult to connect the femto base stations directly to the core network. For this reason, it is conceivable that a large number of femto base stations installed in a specific area are once connected to a gateway device such as a HeNB-GW, and the femto base station and the core network are connected via the HeNB-GW.

  In addition to the femto base station, a pico base station that forms a pico cell having a radius of 100 to 200 meters, for example, has been developed based on a macro base station.

  In a heterogeneous network that is a communication system in which such femto base stations, pico base stations, and macro base stations are mixed, for example, a plurality of femto cells or pico cells are formed in a macro cell. For this reason, handover of a radio terminal device is likely to occur, and the situation of handover is complicated, so that an inappropriate handover operation is performed such as the timing of handover being too early or too late (For example, see 3GPP TR 36.902 V9.3.1 2011.3 (Non-Patent Document 1)).

  In addition to such an inappropriate handover operation, the handover operation fails due to the movement of the wireless terminal device to a coverage hole, which is an area where sufficient radio waves do not reach from any wireless base station device. In some cases (for example, see 3GPP TS 37.320 V10.2.0 2011.7 (Non-Patent Document 2)).

3GPP TR 36.902 V9.3.1 2011.3 3GPP TS 37.320 V10.2.0 2011.7

  When an inappropriate handover operation as described in Non-Patent Document 1 is performed, various problems such as disconnection of communication connection and increase of communication traffic occur in the communication system. In addition, even when the wireless terminal device moves to a coverage hole as described in Non-Patent Document 2, there is a problem of disconnection of communication connection due to failure of handover operation or the like.

  As a method for suppressing the above-described inappropriate handover operation, a method for adjusting the execution judgment criteria of the handover operation and the like can be considered. On the other hand, it is necessary to improve the radio wave environment by adjusting the transmission power etc. of the radio base station device in order to suppress the failure of the handover operation due to the radio wave environment in the radio terminal device such as coverage hole It becomes.

  That is, a technique for determining a cause of disconnection of a communication connection between a wireless terminal device and a wireless base station device, executing an appropriate countermeasure, and constructing a good communication system is desired.

  This invention was made in order to solve the above-mentioned subject, and the object is to determine the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device, or to suppress the disconnection of the communication connection. It is to provide a radio base station apparatus, a radio terminal apparatus, a communication control method, and a communication control program capable of stabilizing communication.

  (1) In order to solve the above problems, a radio base station apparatus according to an aspect of the present invention is a radio terminal in a communication system in which a radio terminal apparatus can communicate with a plurality of radio base station apparatuses by performing a moving operation. A radio base station apparatus for transmitting and receiving radio signals to and from the apparatus, and after the communication connection between the radio terminal apparatus and the radio base station apparatus is disconnected, the radio terminal apparatus newly Based on the measurement information acquired by the measurement information acquisition unit and the measurement information acquired by the measurement information acquisition unit until the communication connection is established. A determination unit for determining whether the cause of the disconnection of the communication connection is interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system.

  As described above, the configuration using the measurement result of the wireless terminal device between the disconnection of the communication connection and the establishment of the new communication connection causes a plurality of causes of the disconnection of the communication connection between the wireless terminal device and the wireless base station device. It is possible to determine that the radio terminal apparatus has moved to a coverage hole in which the radio waves from the radio base station apparatuses have large interference and radio waves from any of the radio base station apparatuses cannot obtain sufficient reception quality. That is, by determining the disconnection of the communication connection due to the radio wave environment in the wireless terminal device, an appropriate countermeasure can be taken and a good communication system can be constructed. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  (2) Preferably, the measurement information acquisition unit acquires the time from the disconnection of the communication connection to the establishment of the communication connection as the measurement information, and the determination unit determines that the time is not less than a predetermined value. It is determined that the cause of the disconnection of the communication connection is interference between the radio signals.

  As described above, the configuration using the time from the disconnection of the communication connection to the establishment of the new communication connection can appropriately determine the disconnection of the communication connection due to the radio wave interference in the wireless terminal device.

  (3) Preferably, the measurement information acquisition unit performs the number of times that the wireless terminal device performs an operation for establishing a communication connection with a wireless base station device between the disconnection of the communication connection and the establishment of the communication connection. And the determination unit determines that the cause of the disconnection of the communication connection is interference between the radio signals when the number of times is equal to or greater than a predetermined value.

  As described above, the configuration using the number of operations for establishing a new communication connection from the disconnection of the communication connection to the establishment of the new communication connection appropriately disconnects the communication connection caused by radio wave interference in the wireless terminal device. Can be determined.

  (4) Preferably, the measurement information acquisition unit transmits received power information indicating a result of the wireless terminal device measuring reception power of a radio signal from each wireless base station device, from the disconnection of the communication connection to the communication connection. A plurality of times until the establishment of the measurement information is acquired as the measurement information, and the determination unit, in the reception power information for the plurality of times, a radio base station that satisfies a predetermined condition for the reception power or reception quality based on the reception power If the devices are different, it is determined that the cause of the disconnection of the communication connection is interference between the radio signals.

  In this way, the configuration for detecting changes in the radio wave environment of the wireless terminal device between the disconnection of the communication connection and the establishment of a new communication connection properly prevents the communication connection from being cut off due to radio wave interference in the wireless terminal device. Can be determined.

  (5) More preferably, the measurement information acquisition unit further indicates a reception power indicating a result of the radio terminal device measuring a radio signal reception power from each radio base station device when the communication connection is disconnected. Information is acquired as the measurement information, and the determination unit further receives a radio signal from a radio base station apparatus that the radio terminal apparatus selects as a communication partner in the received power information when the communication connection is disconnected. If the power is greater than or equal to a predetermined value, or the reception power of a radio signal from a radio base station device other than the radio base station device is greater than or equal to a predetermined value, the cause of the disconnection of the communication connection is between the radio signals It is determined that the interference occurs.

  As described above, with the configuration in which the radio wave environment of the wireless terminal device at the time of disconnection of the communication connection is further used as the determination criterion, it is possible to more accurately determine the disconnection of the communication connection due to the radio wave interference in the wireless terminal device.

  (6) Preferably, the determination unit is configured to transmit, based on the measurement information acquired by the measurement information acquisition unit, a cause of disconnection of the communication connection transmitted by a plurality of radio base station apparatuses in the communication system. It is determined whether it is interference between signals or the timing of the moving operation of the wireless terminal device.

  In this way, in addition to the disconnection of the communication connection due to radio wave interference in the wireless terminal device, the configuration for determining the disconnection of the communication connection due to the timing of the movement operation performs appropriate measures to stabilize the communication. Further efforts can be made.

  (7) More preferably, the determination unit determines that the cause of the disconnection of the communication connection is a radio from each radio base station device in the radio terminal device based on the measurement information acquired by the measurement information acquisition unit. It is determined whether the received power of the signal is low, the timing of the moving operation of the radio terminal apparatus, or the interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system.

  Thus, in addition to disconnection of communication connection due to radio wave interference in the wireless terminal device and disconnection of communication connection due to the timing of the moving operation, disconnection of communication connection due to insufficient strength of the received radio wave in the wireless terminal device With the configuration for discriminating, it is possible to take appropriate measures and further stabilize the communication.

  (8) Preferably, when it is determined that the cause of disconnection of the communication connection is an interference between the radio signals, the radio base station device further includes a plurality of radio base station devices in the communication system. Among these, a transmission control unit for adjusting a transmission operation of a radio signal from at least one of the radio base station apparatuses to the radio terminal apparatus is provided.

  As described above, the configuration of adjusting the radio signal transmission operation of the radio base station apparatus can reduce the radio wave interference in the radio terminal apparatus and suppress the disconnection of the communication connection due to the radio wave environment.

  (9) More preferably, the transmission control unit adjusts transmission power of a radio signal from at least one radio base station device to a radio terminal device among a plurality of radio base station devices in the communication system.

  As described above, the configuration of adjusting the transmission power of the radio signal of the radio base station apparatus can effectively reduce the radio wave interference in the radio terminal apparatus.

  (10) More preferably, the transmission control unit adjusts a resource related to transmission of a radio signal from at least one of the plurality of radio base station apparatuses to the radio terminal apparatus among the plurality of radio base station apparatuses in the communication system. .

  Thus, radio wave interference in the wireless terminal device can be effectively reduced by the configuration that adjusts the resources related to the transmission of the wireless signal of the wireless base station device.

  (11) More preferably, the transmission control unit adjusts a period during which at least one of the information included in the radio signal, the frequency of the radio signal, and the power of the radio signal is limited.

  With such a configuration, it is possible to select an appropriate resource as an adjustment target from among resources related to radio signal transmission of the radio base station apparatus, and reduce radio wave interference in the radio terminal apparatus.

  (12) More preferably, the resource is a frequency used for transmitting the radio signal.

  With such a configuration, it is possible to select an appropriate resource as an adjustment target from among resources related to radio signal transmission of the radio base station apparatus, and reduce radio wave interference in the radio terminal apparatus.

  (13) More preferably, the transmission control unit includes a radio signal from the radio base station apparatus to the radio terminal apparatus provided in at least one radio base station apparatus among the plurality of radio base station apparatuses in the communication system. Adjust the directivity of the antenna for transmitting.

  As described above, the configuration in which the intensity of the beam of the transmission radio wave from the radio base station apparatus is adjusted can reduce radio wave interference in the radio terminal apparatus and suppress the disconnection of the communication connection due to the radio wave environment.

  (14) A radio base station apparatus according to another aspect of the present invention is a radio communication system capable of communicating with a plurality of radio base station apparatuses when the radio terminal apparatus performs a moving operation. A radio base station apparatus for transmitting and receiving signals, and after the communication connection between the radio terminal apparatus and the radio base station apparatus is disconnected, the radio terminal apparatus newly establishes a communication connection with the radio base station apparatus In the communication system based on the measurement information acquired by the measurement information acquisition unit for acquiring measurement information indicating the result of the measurement performed by the wireless terminal device and the measurement information acquisition unit. A transmission control unit for adjusting a transmission operation of a radio signal from at least one of the plurality of radio base station apparatuses to the radio terminal apparatus. .

  As described above, the configuration using the measurement result of the wireless terminal device from the disconnection of the communication connection to the establishment of the new communication connection causes large interference between radio waves from a plurality of wireless base station devices. It is possible to suppress the occurrence of a coverage hole in which sufficient reception quality cannot be obtained for radio waves from the station apparatus. That is, the configuration of adjusting the radio signal transmission operation of the radio base station apparatus can reduce radio wave interference in the radio terminal apparatus and suppress the disconnection of the communication connection due to the radio wave environment. Therefore, communication can be stabilized by suppressing the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  (15) In order to solve the above-described problem, a radio terminal apparatus according to an aspect of the present invention is a radio terminal apparatus capable of communicating with a plurality of radio base station apparatuses by performing a mobile operation. Based on the measurement result of the measurement unit and the measurement unit for performing measurement between the disconnection of the communication connection between the station devices and the establishment of a new communication connection with the radio base station device, the communication A determination unit configured to determine whether the cause of the disconnection is interference between the wireless signals transmitted by the plurality of wireless base station devices.

  As described above, the configuration using the measurement result of itself between the disconnection of the communication connection and the establishment of the new communication connection allows a plurality of wireless base stations to cause the disconnection of the communication connection between itself and the wireless base station device. It can be determined that the radio wave from the apparatus has moved to a coverage hole where interference between radio waves from the apparatus is large and sufficient reception quality is not obtained for any radio base station apparatus. That is, by determining the disconnection of the communication connection due to the radio wave environment in itself, an appropriate countermeasure can be executed and a good communication system can be constructed. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device. In addition, since it is not necessary to transmit the measurement result from the wireless terminal device to the wireless base station device, it is possible to reduce processing and communication traffic in the wireless terminal device and the wireless base station device.

  (16) A radio terminal apparatus according to another aspect of the present invention is a radio terminal apparatus capable of communicating with a plurality of radio base station apparatuses by performing a mobile operation, and is a communication connection between itself and the radio base station apparatus The measurement unit for performing measurement between the time of disconnection and the establishment of a new communication connection with the radio base station device, and the measurement information indicating the measurement result of the measurement unit are transmitted to the radio base station device A transmission unit for measuring the time between the disconnection of the communication connection and the establishment of the communication connection, or a radio base station between the disconnection of the communication connection and the establishment of the communication connection. Measure the number of times of performing an operation for establishing a communication connection with the device, or the received power of the radio signal from each radio base station device between the disconnection of the communication connection and the establishment of the communication connection To measure several times.

  As described above, a plurality of radio base station apparatuses may cause the disconnection of the communication connection between the radio terminal apparatus and the radio base station apparatus by the configuration in which the measurement is performed from the disconnection of the communication connection to the establishment of a new communication connection. To obtain appropriate information to determine that the wireless terminal device has moved to a coverage hole where there is a large amount of interference between the radio waves from the base station and sufficient reception quality is not obtained for any radio base station device. Can do. That is, in the radio base station device, it is possible to acquire appropriate information for determining the disconnection of the communication connection due to the radio wave environment in the radio terminal device, so appropriate measures are taken and a good communication system is constructed. can do. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  (17) In order to solve the above-described problem, a communication control method according to an aspect of the present invention provides a radio terminal apparatus in a communication system in which a radio terminal apparatus can communicate with a plurality of radio base station apparatuses by performing a moving operation. Is a communication control method in a radio base station apparatus for transmitting and receiving radio signals between the radio terminal apparatus and the radio terminal apparatus after the communication connection between the radio terminal apparatus and the radio base station apparatus is disconnected, Until the establishment of the communication connection with the station device, the step of acquiring measurement information indicating the result of the measurement performed by the wireless terminal device, and the cause of the disconnection of the communication connection based on the acquired measurement information Determining whether or not there is interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system.

  As described above, the configuration using the measurement result of the wireless terminal device between the disconnection of the communication connection and the establishment of the new communication connection causes a plurality of causes of the disconnection of the communication connection between the wireless terminal device and the wireless base station device. It is possible to determine that the radio terminal apparatus has moved to a coverage hole in which the radio waves from the radio base station apparatuses have large interference and radio waves from any of the radio base station apparatuses cannot obtain sufficient reception quality. That is, by determining the disconnection of the communication connection due to the radio wave environment in the wireless terminal device, an appropriate countermeasure can be taken and a good communication system can be constructed. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

(18) According to another aspect of the present invention, there is provided a communication control method in which a radio signal is transmitted to and received from a radio terminal device in a communication system capable of communicating with a plurality of radio base station devices when the radio terminal device performs a moving operation. A communication control method in a radio base station apparatus for transmitting and receiving
The wireless terminal device performs measurement after the communication connection between the wireless terminal device and the wireless base station device is disconnected until the wireless terminal device newly establishes a communication connection with the wireless base station device. A step of obtaining measurement information indicating a result, and a radio signal from at least one radio base station device to a radio terminal device among a plurality of radio base station devices in the communication system based on the obtained measurement information Adjusting the transmission operation.

  As described above, the configuration using the measurement result of the wireless terminal device from the disconnection of the communication connection to the establishment of the new communication connection causes large interference between radio waves from a plurality of wireless base station devices. It is possible to suppress the occurrence of a coverage hole in which sufficient reception quality cannot be obtained for radio waves from the station apparatus. That is, the configuration of adjusting the radio signal transmission operation of the radio base station apparatus can reduce radio wave interference in the radio terminal apparatus and suppress the disconnection of the communication connection due to the radio wave environment. Therefore, communication can be stabilized by suppressing the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  (19) A communication control method according to another aspect of the present invention is a communication control method in a radio terminal apparatus capable of communicating with a plurality of radio base station apparatuses by performing a mobile operation, and includes the self and the radio base station apparatus. Between the disconnection of the communication connection between the communication base station and the establishment of a new communication connection with the radio base station apparatus, and the cause of the disconnection of the communication connection based on the measurement results Determining whether or not there is interference between the radio signals transmitted by the radio base station apparatus.

  As described above, the configuration using the measurement result of itself between the disconnection of the communication connection and the establishment of the new communication connection allows a plurality of wireless base stations to cause the disconnection of the communication connection between itself and the wireless base station device. It can be determined that the radio wave from the apparatus has moved to a coverage hole where interference between radio waves from the apparatus is large and sufficient reception quality is not obtained for any radio base station apparatus. That is, by determining the disconnection of the communication connection due to the radio wave environment in itself, an appropriate countermeasure can be executed and a good communication system can be constructed. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device. In addition, since it is not necessary to transmit the measurement result from the wireless terminal device to the wireless base station device, it is possible to reduce processing and communication traffic in the wireless terminal device and the wireless base station device.

  (20) A communication control method according to another aspect of the present invention is a communication control method in a radio terminal apparatus capable of communicating with a plurality of radio base station apparatuses by performing a mobile operation, and includes the self and the radio base station apparatus. A step of performing measurement during a period from when the communication connection is disconnected until a communication connection is newly established with the radio base station device, and a step of transmitting measurement information indicating the measurement result to the radio base station device. And measuring the time from the disconnection of the communication connection to the establishment of the communication connection, or between the disconnection of the communication connection and the establishment of the communication connection, Each radio base station apparatus measures the number of times of performing an operation for establishing a communication connection or between the disconnection of the communication connection and the establishment of the communication connection The received power of al of the radio signal measured several times.

  As described above, a plurality of radio base station apparatuses may cause the disconnection of the communication connection between the radio terminal apparatus and the radio base station apparatus by the configuration in which the measurement is performed from the disconnection of the communication connection to the establishment of a new communication connection. To obtain appropriate information to determine that the wireless terminal device has moved to a coverage hole where there is a large amount of interference between the radio waves from the base station and sufficient reception quality is not obtained for any radio base station device. Can do. That is, in the radio base station device, it is possible to acquire appropriate information for determining the disconnection of the communication connection due to the radio wave environment in the radio terminal device, so appropriate measures are taken and a good communication system is constructed. can do. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  (21) In order to solve the above-described problem, a communication control program according to an aspect of the present invention provides a wireless terminal device in a communication system in which a wireless terminal device can communicate with a plurality of wireless base station devices by performing a moving operation. A communication control program used in a radio base station apparatus for transmitting and receiving radio signals to and from the computer, after the communication connection between the radio terminal apparatus and the radio base station apparatus is cut by the computer, the radio terminal apparatus Until the communication connection with the radio base station apparatus is newly established, the step of acquiring measurement information indicating the result of measurement performed by the radio terminal apparatus, and the communication based on the acquired measurement information A step of determining whether or not the cause of the disconnection is interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system. Is a program for executing a flop.

  As described above, the configuration using the measurement result of the wireless terminal device between the disconnection of the communication connection and the establishment of the new communication connection causes a plurality of causes of the disconnection of the communication connection between the wireless terminal device and the wireless base station device. It is possible to determine that the radio terminal apparatus has moved to a coverage hole in which the radio waves from the radio base station apparatuses have large interference and radio waves from any of the radio base station apparatuses cannot obtain sufficient reception quality. That is, by determining the disconnection of the communication connection due to the radio wave environment in the wireless terminal device, an appropriate countermeasure can be taken and a good communication system can be constructed. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  (22) A communication control program according to another aspect of the present invention is a communication control program capable of communicating with a plurality of radio base station apparatuses when the radio terminal apparatus performs a moving operation. Is a communication control program used in a radio base station apparatus for transmitting and receiving a wireless base station, after the communication connection between the radio terminal apparatus and the radio base station apparatus is disconnected in the computer, A step of acquiring measurement information indicating a result of measurement performed by the wireless terminal device until a communication connection with the device is established, and a plurality of wireless base stations in the communication system based on the acquired measurement information Adjusting a radio signal transmission operation from at least one of the radio base station apparatuses to the radio terminal apparatus among the station apparatuses Is a program for executing the.

  As described above, the configuration using the measurement result of the wireless terminal device from the disconnection of the communication connection to the establishment of the new communication connection causes large interference between radio waves from a plurality of wireless base station devices. It is possible to suppress the occurrence of a coverage hole in which sufficient reception quality cannot be obtained for radio waves from the station apparatus. That is, the configuration of adjusting the radio signal transmission operation of the radio base station apparatus can reduce radio wave interference in the radio terminal apparatus and suppress the disconnection of the communication connection due to the radio wave environment. Therefore, communication can be stabilized by suppressing the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  (23) A communication control program according to another aspect of the present invention is a communication control program used in a wireless terminal device capable of communicating with a plurality of wireless base station devices by performing a moving operation. And a step of performing measurement after the communication connection between the radio base station apparatuses is disconnected and until a new communication connection is established with the radio base station apparatus, and based on the measurement result, the communication connection is disconnected. For determining whether or not the cause is interference between the radio signals transmitted by a plurality of radio base station apparatuses.

  As described above, the configuration using the measurement result of itself between the disconnection of the communication connection and the establishment of the new communication connection allows a plurality of wireless base stations to cause the disconnection of the communication connection between itself and the wireless base station device. It can be determined that the radio wave from the apparatus has moved to a coverage hole where interference between radio waves from the apparatus is large and sufficient reception quality is not obtained for any radio base station apparatus. That is, by determining the disconnection of the communication connection due to the radio wave environment in itself, an appropriate countermeasure can be executed and a good communication system can be constructed. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device. In addition, since it is not necessary to transmit the measurement result from the wireless terminal device to the wireless base station device, it is possible to reduce processing and communication traffic in the wireless terminal device and the wireless base station device.

  (24) A communication control program according to another aspect of the present invention is a communication control program used in a radio terminal apparatus capable of communicating with a plurality of radio base station apparatuses by performing a mobile operation, And a step of performing measurement from when the communication connection between the radio base station apparatuses is disconnected until a new communication connection is established with the radio base station apparatus, and measurement information indicating the measurement result is transmitted to the radio base station apparatus. In the step of performing the measurement, the time from the disconnection of the communication connection to the establishment of the communication connection is measured, or the communication connection is disconnected to the communication connection. Measure the number of times to perform an operation for establishing a communication connection with the radio base station apparatus until the establishment of During the period from the disconnection of the connection to the establishment of the communication connection is measured a plurality of times the received power of a radio signal from each radio base station apparatus.

  As described above, a plurality of radio base station apparatuses may cause the disconnection of the communication connection between the radio terminal apparatus and the radio base station apparatus by the configuration in which the measurement is performed from the disconnection of the communication connection to the establishment of a new communication connection. To obtain appropriate information to determine that the wireless terminal device has moved to a coverage hole where there is a large amount of interference between the radio waves from the base station and sufficient reception quality is not obtained for any radio base station device. Can do. That is, in the radio base station device, it is possible to acquire appropriate information for determining the disconnection of the communication connection due to the radio wave environment in the radio terminal device, so appropriate measures are taken and a good communication system is constructed. can do. Therefore, communication can be stabilized by determining the cause of the disconnection of the communication connection between the wireless terminal device and the wireless base station device.

  ADVANTAGE OF THE INVENTION According to this invention, stabilization of communication can be aimed at by determining the cause of the disconnection of the communication connection between a radio | wireless terminal apparatus and a radio base station apparatus, or suppressing the disconnection of the said communication connection.

It is a figure which shows the structure of the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the sequence of the hand-over operation | movement in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the condition where the inappropriate hand-over operation (Too Late HO) occurred in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the sequence of an improper handover operation (Too Late HO) and its detection process in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the condition where the inappropriate hand-over operation (Too Early HO) occurred in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the condition where the inappropriate hand-over operation (Too Early HO) occurred in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the sequence of the inappropriate handover operation | movement (Too Early HO) and its detection process in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the condition where the inappropriate hand-over operation (HO to Wron Cell) occurred in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the sequence of an improper handover operation (HO to Wron Cell) and its detection process in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the simulation result of the reception quality of the radio | wireless terminal apparatus in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the structure of the radio base station apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the radio | wireless terminal apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the coverage hole by interference in the radio | wireless communications system which concerns on embodiment of this invention. In the radio | wireless communications system which concerns on embodiment of this invention, it is a figure which shows an example of the fluctuation | variation of the reception power when a radio | wireless terminal apparatus moves to a coverage hole by interference. In the radio | wireless communications system which concerns on embodiment of this invention, it is a figure which shows an example of the condition where the radio | wireless terminal apparatus which approached the coverage hole by interference returns from RLF. It is a figure which shows an example of the optimization process of the hand-over operation | movement in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the timing adjustment of the hand-over operation in the coverage hole by interference in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows the structure of the control part in the radio base station apparatus which concerns on embodiment of this invention. It is a sequence diagram which shows an example of the determination process of the cause of RLF generation in the radio | wireless communications system which concerns on embodiment of this invention. It is a figure which shows an example of the information added to a RLF report in order to discriminate | determine the coverage hole by interference in the radio | wireless communications system which concerns on embodiment of this invention. It is the flowchart which defined the procedure of the discrimination | determination process of the RLF generation | occurrence | production cause by the radio base station apparatus which concerns on embodiment of this invention, and the suppression process of RLF. It is the flowchart which defined the procedure of the discrimination | determination process of the RLF generation | occurrence | production cause by the radio base station apparatus which concerns on embodiment of this invention, and the suppression process of RLF. It is the flowchart which defined the procedure of the discrimination | determination process of the RLF generation | occurrence | production cause by the radio base station apparatus which concerns on embodiment of this invention, and the suppression process of RLF. It is a figure which shows the structure of the control part in the radio | wireless terminal apparatus which concerns on embodiment of this invention. It is a sequence diagram which shows the usage example of ABS in the radio | wireless communications system which concerns on embodiment of this invention. It is a sequence diagram which shows an example of the interference reduction process which uses ABS in the radio | wireless communications system which concerns on embodiment of this invention. It is a sequence diagram which shows the specific example of the interference reduction process which uses ABS in the radio | wireless communications system which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  The radio base station apparatus notifies the radio terminal apparatus of information about the cell and the neighboring cell that it forms, that is, the frequency of the radio signal and the ID (identification) of the neighboring cell. The wireless terminal device detects and measures neighboring cells based on information notified from the wireless base station device. The wireless terminal device starts moving to the neighboring cell based on the measurement result. Here, “movement” of the wireless terminal device means not only handover but also through which cell the wireless terminal device in an idle state starts communication in the future, that is, when a call or data communication is started. This means selecting whether to perform communication.

  For example, when the wireless terminal device is communicating with the wireless base station device, the destination of the wireless terminal device is determined by the wireless base station device or a higher-level device in the core network. For example, when the wireless terminal device is not communicating with the wireless base station device, the wireless terminal device determines the destination of the wireless terminal device.

  In addition, handover means that a radio base station apparatus that is a communication partner of a radio terminal apparatus during a call or data communication is switched.

  The wireless terminal device is located in a cell means that the wireless terminal device selects a wireless base station device forming the cell as a communication destination and can communicate with the wireless base station device. This means that communication is in progress.

  The femtocell and access mode are described in 3GPP (Third Generation Partnership Project) SPEC TS 22.22 as follows. That is, a femto base station is a customer premises apparatus that connects a wireless terminal device connected via a wireless interface to a mobile communication carrier network using an IP backhaul.

  Further, in the femtocell access mode, the femto base station in the closed access mode provides a service only to related CSG (Closed Subscriber Group) members. The hybrid mode femto base station also provides services to the associated CSG members and CSG non-members. The femto base station in the open access mode operates as a normal base station.

  Such a 3GPP definition may also be applied to the wireless communication system according to the embodiment of the present invention.

  Further, the following definitions can be applied together with or separately from the above definitions.

  The macro base station and the pico base station are wireless base station devices that are under the management of the operator and can communicate with the wireless base station device that has contracted with the operator. Further, it is considered that the macro base station and the pico base station are basically not turned off.

  A femto base station is a radio base station apparatus that is installed mainly in an individual or corporate building and may move or be turned off depending on the circumstances of the user.

  Further, the femto base station operates in one of open / hybrid / closed access modes. When the femto base station operates in the closed access mode, only registered members (terminals) can be connected. When operating in the closed access mode, the service is provided only to registered members. When operating in the hybrid mode, the service is provided to both registered members and unregistered members, that is, non-members. When operating in the open access mode, the same operation as that of the macro base station and the pico base station is performed.

[Configuration and basic operation]
FIG. 1 is a diagram showing a configuration of a radio communication system according to an embodiment of the present invention.

  Referring to FIG. 1, the radio communication system is a mobile communication system according to LTE (Long Term Evolution) standardized by, for example, 3GPP (Third Generation Partnership Project), and includes radio base station apparatuses 101A and 101B. In FIG. 1, two radio base station apparatuses are representatively shown, but a larger number of radio base station apparatuses may be provided.

  Radio base station apparatuses 101A and 101B are, for example, femto base stations, pico base stations, or macro base stations.

  The radio base station apparatus 101A can communicate with the radio terminal apparatus 202 by forming a cell CA and transmitting and receiving radio signals to and from the radio terminal apparatus 202 existing in the cell CA. The radio base station apparatus 101B can communicate with the radio terminal apparatus 202 by forming a cell CB and transmitting and receiving radio signals to and from the radio terminal apparatus 202 existing in the cell CB.

  Here, the direction from the wireless terminal device to the core network is referred to as an uplink direction, and the direction from the core network to the wireless terminal device is referred to as a downlink direction.

  The radio base station apparatus and the radio terminal apparatus in the radio communication system according to the embodiment of the present invention read and execute a program including the following sequences and steps of each flowchart from a memory (not shown). This program can be installed externally. The installed program is distributed in a state stored in a recording medium, for example.

  FIG. 2 is a diagram showing an exemplary sequence of a handover operation in the radio communication system according to the embodiment of the present invention.

  Here, as shown in FIG. 1, it is assumed that the wireless terminal device 202 is located in the cell CA and is in communication with the wireless base station device 101A, and moves to an overlapping area of the cell CA and the cell CB. To do.

  Referring to FIG. 2, first, radio base station apparatus 101A sets a frequency to be measured by radio terminal apparatus 202 in communication with itself and another radio base station apparatus that transmits a radio signal of the frequency. (Step S1).

  Next, the wireless base station device 101A sends a measurement start request (Measurement Configuration) to the wireless terminal device 202 to cause the wireless terminal device 202 to measure the reception level of the wireless signal transmitted from the other wireless base station device that has been set. Send. This measurement start request includes neighboring cell information, that is, the cell ID of the radio base station apparatus to be measured. Further, the measurement start request includes the transmission frequency of each radio base station device (step S2).

  Next, the wireless terminal device 202 receives the measurement start request from the wireless base station device 101A and starts the power measurement process (Measurement), that is, the wireless indicated by the measurement start request at the frequency indicated by the received measurement start request. The received power of the radio signal transmitted from the base station apparatus is measured (step S3).

  Next, the wireless terminal device 202 transmits a measurement result notification (Measurement Report) indicating the measurement result of the received power to the wireless base station device 101A. For example, the wireless terminal device 202 periodically measures the received power, when the communication state with the wireless base station device 101A deteriorates, and with other wireless base station devices other than the wireless base station device 101A When the state becomes better, a measurement result notification is transmitted to the radio base station apparatus 101A (step S4).

  Next, 101 A of radio base station apparatuses acquire the measurement information which shows the measurement result for every cell ID based on the measurement result notification received from the radio | wireless terminal apparatus 202, and preserve | save it in the memory | storage part which is not shown in figure (step S5).

  Next, based on the measurement result notification received from the wireless terminal device 202, the wireless base station device 101A determines whether or not the wireless terminal device 202 should be handed over. For example, the radio base station apparatus 101B is determined as a handover destination with reference to the information (step S6).

  Next, the radio base station device 101A transmits a handover request indicating the radio base station device 101B to the higher-level device (step S7).

  Next, the host device receives the handover request from the radio base station device 101A and transmits the handover request to the radio base station device 101B (step S8).

  Next, the radio base station device 101B receives the handover request from the higher-level device and transmits a handover response to the handover request to the higher-level device (step S9).

  Next, the higher-level apparatus receives a handover response from the radio base station apparatus 101B, and transmits a handover instruction to the radio base station apparatus 101A (step S10).

  Next, the radio base station apparatus 101A receives a handover instruction from the host apparatus and transmits an RRC (Radio Resource Control) connection reconfiguration instruction (RRC Connection Reconfiguration) to the radio terminal apparatus 202 (step S11).

  Next, the radio base station apparatus 101A transmits a status notification indicating its own communication status and the like to the higher level apparatus (step S12).

  Next, the higher-level device receives the state notification from the wireless base station device 101A, and transmits a state notification indicating the communication contents and the like with the wireless terminal device 202 to the wireless base station device 101B (step S13).

  Further, when the RRC connection is established between the wireless terminal device 202 and the wireless base station device 101B, the wireless terminal device 202 transmits an RRC connection reconfiguration completion notification (RRC Connection Reconfiguration Complete) to the wireless base station device 101B ( Step S14).

  Next, the radio base station apparatus 101B receives the RRC connection reconfiguration completion notification from the radio terminal apparatus 202 and transmits a handover completion notification to the higher-level apparatus (step S15).

  Next, the higher-level apparatus receives a handover completion notification from the radio base station apparatus 101B, and transmits a terminal information release instruction to the radio base station apparatus 101A (step S16).

  Next, the wireless base station device 101A receives a terminal information release instruction from the higher-level device, releases information related to the wireless terminal device 202, and transmits a terminal information release completion notification to the higher-level device (step S17).

[Example of inappropriate handover operation]
Hereinafter, a radio base station apparatus communicating with the radio terminal apparatus 202 or a handover source radio base station apparatus is also referred to as a serving base station, and a handover destination radio base station apparatus is also referred to as a target base station.

  FIG. 3 is a diagram illustrating an example of a situation where an inappropriate handover operation (Too Late HO) occurs in the wireless communication system according to the embodiment of the present invention.

  FIG. 4 is a diagram showing an example of an inappropriate handover operation (Too Late HO) and its detection processing sequence in the wireless communication system according to the embodiment of the present invention.

  “Too Late HO” refers to the following cases, for example. That is, before the handover starts or during the handover process, a radio link failure (RLF) occurs in the handover source radio base station apparatus, and a radio base station other than the handover source radio base station apparatus. This is a case where connection re-establishment of the wireless terminal device 202 to the device has occurred.

  The detection method of “Too Late HO” is as follows, for example. That is, when the radio terminal device 202 reestablishes the radio link to the radio base station device 101B after causing the RLF for the radio base station device 101A, the radio base station device 101B notifies the radio base station device 101A of the RLF. Send. Thereby, the wireless base station device 101A detects “Too Late HO”.

  Here, as shown in FIG. 3, it is assumed that radio terminal apparatus 202 is located in cell CA and is communicating with radio base station apparatus 101A.

  Referring to FIG. 3 and FIG. 4, first, radio terminal apparatus 202 measures the received power of a radio signal transmitted from each radio base station apparatus, and wirelessly sends a measurement result notification indicating the measured result of the received power. It transmits to base station apparatus 101A (step S51).

  Next, based on the measurement result notification received from the wireless terminal device 202, the wireless base station device 101A determines whether or not the wireless terminal device 202 should be handed over. When it is determined that the radio terminal apparatus 202 should be handed over, the radio base station apparatus 101A refers to the neighboring cell information and determines, for example, the radio base station apparatus 101B as a handover destination (step S52).

  Next, the radio base station apparatus 101A transmits a handover request indicating the radio base station apparatus 101B to the radio base station apparatus 101B via the X2 interface that is an inter-base station interface (step S53).

  Next, the radio base station apparatus 101B receives the handover request from the radio base station apparatus 101A, and transmits a handover response to the handover request to the radio base station apparatus 101A via the X2 interface (step S54).

  Here, while preparing for handover on the network side, that is, while the radio base station apparatuses 101A and 101B are transmitting and receiving a message for handover as described above, the radio terminal apparatus 202 is out of service area of the cell CA, and Move to within the cell CB (step S55).

  Due to the movement of the wireless terminal device 202, the RRC connection reconfiguration instruction (step S56) for instructing the handover transmitted from the wireless base station device 101A does not reach the wireless terminal device 202, and RLF is generated (step S56). S57).

  Next, when the radio terminal apparatus 202 detects the occurrence of RLF, the radio terminal apparatus 202 searches for a neighboring radio base station apparatus by measuring the reception power of the radio signal and reconnects to the searched radio base station apparatus 101B. A connection re-establishment request (RRC Connection Reestablishment Request) is transmitted (step S58).

  Next, the radio base station apparatus 101B receives the RRC connection re-establishment request from the radio terminal apparatus 202, and transmits an RRC connection re-establishment response to the radio terminal apparatus 202 (step S59). Thereby, an RRC connection is established between the wireless terminal device 202 and the wireless base station device 101B.

  Next, the wireless terminal device 202 transmits an RRC connection reestablishment completion notification (RRC Connection Reestablishment Complete) to the wireless base station device 101B (step S60).

  This RRC connection re-establishment completion notification includes, for example, a parameter “rlf-InfoAvailable”. The wireless terminal device 202 sets this parameter and transmits an RRC connection re-establishment completion notification. Thereby, the radio base station apparatus 101B recognizes that an RLF has occurred in the radio terminal apparatus 202. The radio base station apparatus 101B transmits a terminal information request (UE Information Request) to the radio terminal apparatus 202 in order to acquire detailed information of the RLF (step S61).

  Next, the wireless terminal device 202 receives a terminal information request from the wireless base station device 101B, and transmits a terminal information response (UE Information Response) including an RLF report to the wireless base station device 101B (step S62). The RLF report includes the PCI (Physical Cell ID) of the radio base station apparatus in which the RLF has occurred, the PCI and ECGI (E-UTRAN Cell Global Identifier) of the radio base station apparatus in which the RRC connection has been reestablished, and the own radio terminal apparatus 202. C-RNTI (Cell Radio Network Temporary Identifier) and the like. Here, the PCI of the RLF occurrence is the ID of the radio base station apparatus 101A, the PCI and ECGI of the RRC connection re-establishment occurrence are the ID of the radio base station apparatus 101B, and the C-RNTI is assigned by the radio base station apparatus 101A ID.

  Next, the radio base station apparatus 101B recognizes that RLF has occurred in the radio base station apparatus 101A by referring to the PCI of the RLF report received from the radio terminal apparatus 202. Then, the radio base station apparatus 101B transmits an RLF notification (RLF INDICATION) including the contents of the RLF report to the radio base station apparatus 101A via the X2 interface in order to notify that it is “Too Late HO” ( Step S63).

  Next, the radio base station apparatus 101A recognizes that “Too Late HO” has occurred to the cell CB by referring to the PCI, ECGI, and C-RNTI of the RLF notification received from the radio base station apparatus 101B. (Step S64).

  Next, the radio base station apparatus 101A performs a handover operation optimization process so as to suppress the occurrence of “Too Late HO” in the cell CB (step S65).

  5 and 6 are diagrams illustrating an example of a situation in which an inappropriate handover operation (Too Early HO) occurs in the wireless communication system according to the embodiment of the present invention.

  5 and 6, cell CB formed by radio base station apparatus 101B includes cell CB1 including the installation area of radio base station apparatus 101B, and radio base station apparatus 101B formed in cell CA. The cell CB2 does not include an installation area.

  FIG. 7 is a diagram showing an example of an inappropriate handover operation (Too Early HO) and its detection processing sequence in the wireless communication system according to the embodiment of the present invention.

  “Too Early HO” refers to the following case, for example. That is, after the wireless terminal device 202 has successfully connected to the handover destination wireless base station device, RLF occurs in a short time, and the wireless terminal device 202 is reconnected to the handover source wireless base station device. This is the case when establishment occurs.

  The detection method of “Too Early HO” is as follows, for example. That is, when the handover destination radio base station apparatus 101B receives the RLF report from the handover source radio base station apparatus 101A, the handover to the radio terminal apparatus 202 itself is performed within a predetermined time from the reception timing. When the terminal information release instruction due to the completion of is transmitted to the radio base station apparatus 101A, the radio base station apparatus 101A is notified that “Too Early HO”.

  Here, the radio base station apparatus 101B uses a timer to measure the predetermined time. Thereby, when the radio base station apparatus 101B receives the RLF report, whether the RLF has occurred due to its own “Too Late HO” or whether the RLF has occurred due to “Too Early HO” of the radio base station apparatus 101A. Can be determined.

  Here, as shown in FIG. 5, a case is assumed in which radio terminal apparatus 202 moves into cell CB2 from a state where it is located in cell CA and is communicating with radio base station apparatus 101A (step S70). .

  5 to 7, first, radio terminal apparatus 202 measures the reception power of a radio signal transmitted from a radio base station apparatus, and sends a measurement result notification indicating the measurement result of the measured reception power to radio base station. It transmits to station apparatus 101A (Source eNB, Serving eNB) (step S71).

  Next, based on the measurement result notification received from the wireless terminal device 202, the wireless base station device 101A determines whether or not the wireless terminal device 202 should be handed over. When determining that the radio terminal apparatus 202 should be handed over, the radio base station apparatus 101A refers to the neighboring cell information and determines, for example, the radio base station apparatus 101B as a handover destination (step S72).

  Next, the radio base station apparatus 101A transmits a handover request indicating the radio base station apparatus 101B to the radio base station apparatus 101B via the X2 interface that is an inter-base station interface (step S73).

  Next, the radio base station apparatus 101B receives the handover request from the radio base station apparatus 101A, and transmits a handover response to the handover request to the radio base station apparatus 101A via the X2 interface (step S74).

  Next, the radio base station apparatus 101A receives a handover response from the radio base station apparatus 101B, and transmits an RRC connection reconfiguration instruction (RRC Connection Reconfiguration) to the radio terminal apparatus 202 (step S75).

  Next, when the RRC connection is established between the wireless terminal device 202 and the wireless base station device 101B, the wireless terminal device 202 transmits an RRC connection reconfiguration complete notification to the wireless base station device 101B. (Step S76).

  Next, the radio base station apparatus 101B receives the RRC connection reconfiguration completion notification from the radio terminal apparatus 202, and transmits a terminal information release instruction to the radio base station apparatus 101A (step S77).

  Further, the radio base station apparatus 101B starts a timer in order to measure the stay time in the cell CB of the radio terminal apparatus 202 (step S78).

  Next, the radio base station apparatus 101A receives a terminal information release instruction from the radio base station apparatus 101B, and releases information (UE Context) on the radio terminal apparatus 202 (step S79).

  Thus, the handover of the wireless terminal device 202 from the wireless base station device 101A to the wireless base station device 101B is completed (step S80).

  Here, before transmitting the measurement result notification (Measurement Report) to the radio base station apparatus 101B, the radio terminal apparatus 202 moves out of the cell CB and into the cell CA (step S81).

  Then, since the wireless terminal device 202 cannot communicate with the wireless base station device 101B, RLF occurs (step S83).

  Next, when the radio terminal apparatus 202 detects the occurrence of RLF, the radio terminal apparatus 202 searches for a neighboring radio base station apparatus by measuring the reception power of the radio signal and reconnects to the searched radio base station apparatus 101A. A connection reestablishment request (RRC Connection Reestablishment Request) is transmitted (step S84).

  Next, since the wireless base station device 101A has released and does not hold the information (UE Context) regarding the wireless terminal device 202, the wireless base station device 101A can accept the RRC connection re-establishment request from the wireless terminal device 202. If it is not possible (step S85), an RRC connection re-establishment rejection is transmitted to the wireless terminal device 202 (step S86).

  Next, when receiving the RRC connection re-establishment rejection from the radio base station apparatus 101A, the radio terminal apparatus 202 starts a normal connection procedure with the radio base station apparatus 101A (step S87).

  That is, first, the wireless terminal device 202 transmits an RRC connection request to the wireless base station device 101A (step S88).

  Next, the wireless base station device 101A receives the RRC connection request from the wireless terminal device 202, and transmits RRC connection information (RRC Connection Setup) to the wireless terminal device 202 (step S89).

  Next, the wireless terminal device 202 receives RRC connection information from the wireless base station device 101A, and transmits an RRC connection completion notification (RRC Connection Setup Complete) (step S90).

  Next, the wireless base station device 101A receives the RRC connection completion notification from the wireless terminal device 202, and transmits security information (Security Mode Command) to the wireless terminal device 202 (step S91).

  Next, the wireless terminal device 202 receives the security information from the wireless base station device 101A, and transmits a security completion notification (Security Mode Complete) to the wireless base station device 101A (step S92).

  Next, the radio base station apparatus 101A transmits an RRC connection reconfiguration instruction (RRC Connection Reconfiguration) to the radio terminal apparatus 202 (step S93).

  Next, when the RRC connection is established between the wireless terminal device 202 and the wireless base station device 101A, the wireless terminal device 202 transmits an RRC connection reconfiguration complete notification (RRC Connection Reconfiguration Complete) to the wireless base station device 101A. (Step S94).

  Here, the RRC connection completion notification and the RRC connection reconfiguration completion notification include, for example, a parameter “rlf-InfoAvailable”. The wireless terminal device 202 sets this parameter and transmits an RRC connection completion notification and an RRC connection reconfiguration completion notification. As a result, the radio base station apparatus 101A recognizes that an RLF has occurred in the radio terminal apparatus 202. The wireless base station device 101A transmits a terminal information request (UE Information Request) to the wireless terminal device 202 in order to acquire detailed information of the RLF (step S95).

  Next, the wireless terminal device 202 receives a terminal information request from the wireless base station device 101A, and transmits a terminal information response (UE Information Response) including an RLF report to the wireless base station device 101A (step S96). The RLF report includes the PCI of the radio base station apparatus in which the RLF has occurred, the PCI and ECGI of the radio base station apparatus in which the RRC connection re-establishment has occurred, and the C-RNTI of the own radio terminal apparatus 202. Here, the PCI of the RLF generation is the ID of the radio base station apparatus 101B, the PCI and ECGI of the RRC connection re-establishment are the ID of the radio base station apparatus 101A, and the C-RNTI is assigned by the radio base station apparatus 101B ID.

  Next, the radio base station apparatus 101A recognizes that RLF has occurred in the radio base station apparatus 101B by referring to the PCI of the RLF report received from the radio terminal apparatus 202, and performs “Too Late HO” to the cell CA. "Is generated (step S97).

  Next, the radio base station apparatus 101A transmits an RLF notification (RLF INDICATION) including the contents of the RLF report to the radio base station apparatus 101B via the X2 interface in order to notify that it is “Too Late HO”. (Step S98).

  Next, when the radio base station apparatus 101B receives the RLF notification from the radio base station apparatus 101A, the radio base station apparatus 101B checks the timer that has been started. If the timer is operating, that is, a predetermined time has elapsed since the timer was started. If not, it is determined that it is not “Too Late HO” for the cell CA but “Too Early HO” for the cell CB. When the radio base station apparatus 101B receives the RLF notification from the radio base station apparatus 101A and the timer is not operating, that is, when the predetermined time has elapsed since the timer was started, the cell CA And “Too Late HO”.

  If the radio base station apparatus 101B determines that it is “Too Early HO” to the cell CB (step S99), it transmits a handover report to the radio base station apparatus 101A (step S100). The handover report includes, for example, a parameter “Handover Report Type”. The radio base station apparatus 101B notifies the radio base station apparatus 101A of “Too Early HO” by setting this parameter to a predetermined value.

  Next, the radio base station apparatus 101A receives the handover report from the radio base station apparatus 101B, recognizes that “Too Early HO” has occurred to the cell CB (step S101), and performs “Too Early HO”. A handover operation optimization process is executed so as to suppress the occurrence of (step S102).

  FIG. 8 is a diagram illustrating an example of a situation where an inappropriate handover operation (HO to Wron Cell) occurs in the wireless communication system according to the embodiment of the present invention.

  Referring to FIG. 8, the radio communication system further includes radio base station apparatus 101C as compared with the radio communication system shown in FIG. Radio base station apparatus 101C is, for example, a femto base station, a pico base station, or a macro base station.

  The radio base station apparatus 101C can communicate with the radio terminal apparatus 202 by forming a cell CC and transmitting and receiving radio signals to and from the radio terminal apparatus 202 existing in the cell CC.

  FIG. 9 is a diagram illustrating an example of an improper handover operation (HO to Wong Cell) and its detection processing sequence in the wireless communication system according to the embodiment of the present invention.

  “HO to Wong Cell” refers to the following case, for example. That is, after the wireless terminal device 202 has successfully connected to the handover destination wireless base station device, RLF occurs in a short time, and wireless communication is performed with respect to wireless base station devices other than the handover source and handover destination wireless base station devices. This is a case where the connection re-establishment of the terminal device 202 occurs.

  The detection method of “HO to Wong Cell” is, for example, as follows. That is, when the radio base station apparatus 101B that is the handover destination receives the RLF report from the radio base station apparatus 101C other than the radio base station apparatus 101A that is the handover source, the radio terminal is traced back from the reception timing within a predetermined time. When the terminal information release instruction due to the completion of the handover of the apparatus 202 to itself is transmitted to the radio base station apparatus 101A, the radio base station apparatus 101A is notified that “HO to Wong Cell”.

  Here, the radio base station apparatus 101B uses a timer to measure the predetermined time. Thereby, when the radio base station apparatus 101B receives the RLF report, whether the RLF has occurred due to its own “Too Late HO” or whether the RLF has occurred due to the “HO to Wong Cell” of the radio base station apparatus 101A Can be determined.

  Here, as shown in FIG. 8, when the wireless terminal device 202 is located in the cell CA and is communicating with the wireless base station device 101A, the wireless terminal device 202 moves to the overlapping area of the virtual cell CBV and the cell CA ( Assume step S110). The virtual cell CBV is a virtual cell expanded from the cell CB in accordance with the offset OST that is a parameter in order to promote handover from the radio base station apparatus 101A to the radio base station apparatus 101B. In this case, the offset OST is a parameter held by the radio base station apparatus 101A.

  With reference to FIG. 8 and FIG. 9, first, the radio terminal apparatus 202 measures the received power of the radio signal transmitted from the radio base station apparatus, and sends a measurement result notification indicating the measurement result of the measured received power to the radio base station. Transmit to the station apparatus 101A (step S111).

  Next, based on the measurement result notification received from the wireless terminal device 202, the wireless base station device 101A determines whether or not the wireless terminal device 202 should be handed over. When it is determined that the radio terminal apparatus 202 should be handed over, the radio base station apparatus 101A refers to the neighboring cell information and determines, for example, the radio base station apparatus 101B as a handover destination (step S112).

  Next, the radio base station apparatus 101A transmits a handover request indicating the radio base station apparatus 101B to the radio base station apparatus 101B via the X2 interface that is an inter-base station interface (step S113).

  Next, the radio base station apparatus 101B receives the handover request from the radio base station apparatus 101A, and transmits a handover response to the handover request to the radio base station apparatus 101A via the X2 interface (step S114).

  Next, the radio base station apparatus 101A receives a handover response from the radio base station apparatus 101B, and transmits an RRC connection reconfiguration instruction (RRC Connection Reconfiguration) to the radio terminal apparatus 202 (step S115).

  Next, when the RRC connection is established between the wireless terminal device 202 and the wireless base station device 101B, the wireless terminal device 202 transmits an RRC connection reconfiguration complete notification to the wireless base station device 101B. (Step S116).

  Next, the radio base station apparatus 101B receives the RRC connection reconfiguration completion notification from the radio terminal apparatus 202, and transmits a terminal information release instruction to the radio base station apparatus 101A (step S117).

  Also, the radio base station apparatus 101B starts a timer in order to measure the stay time in the cell CB of the radio terminal apparatus 202 (step S118).

  Next, the wireless base station device 101A receives the terminal information release instruction from the wireless base station device 101B, and releases information (UE Context) on the wireless terminal device 202 (step S119).

  Thus, the handover of the wireless terminal device 202 from the wireless base station device 101A to the wireless terminal device 101B is completed (step S120).

  Here, before transmitting the measurement result notification (Measurement Report) to the radio base station apparatus 101B, the radio terminal apparatus 202 moves outside the cell CB and within the virtual cell CBV and cell CC (step S121).

  Then, the radio terminal apparatus 202 has a large interference of radio signals transmitted from the radio base station apparatus 101C (Other eNB), and cannot communicate with the radio base station apparatus 101B, so that RLF occurs (step S123). .

  Next, when detecting the occurrence of RLF, the wireless terminal device 202 searches for nearby wireless base station devices by measuring the reception power of the wireless signal or the like. In this case, since the reception power of the radio signal from the radio base station apparatus 101C is maximized, the radio terminal apparatus 202 is requested to reestablish an RRC connection reestablishment request (RRC Connection) in order to reconnect to the searched radio base station apparatus 101C. Reestablishment Request) is transmitted to the radio base station apparatus 101C (step S124).

  Next, since the wireless base station device 101C does not hold information (UE Context) regarding the wireless terminal device 202, the wireless base station device 101C cannot accept the RRC connection re-establishment request from the wireless terminal device 202 (step S125). ), RRC connection re-establishment rejection is transmitted to the wireless terminal device 202 (step S126).

  Next, the radio terminal apparatus 202 receives the RRC connection re-establishment rejection from the radio base station apparatus 101C, and starts a normal connection procedure with the radio base station apparatus 101C (step S127).

  That is, first, the wireless terminal device 202 transmits an RRC connection request to the wireless base station device 101C (step S128).

  Next, the wireless base station device 101C receives the RRC connection request from the wireless terminal device 202, and transmits RRC connection information (RRC Connection Setup) to the wireless terminal device 202 (step S129).

  Next, the wireless terminal device 202 receives the RRC connection information from the wireless base station device 101C, and transmits an RRC connection completion notification (RRC Connection Setup Complete) (step S130).

  Next, the wireless base station device 101C receives the RRC connection completion notification from the wireless terminal device 202, and transmits security information (Security Mode Command) to the wireless terminal device 202 (step S131).

  Next, the wireless terminal device 202 receives security information from the wireless base station device 101C, and transmits a security completion notification (Security Mode Complete) to the wireless base station device 101C (step S132).

  Next, the wireless base station device 101C transmits an RRC connection reconfiguration instruction (RRC Connection Reconfiguration) to the wireless terminal device 202 (step S133).

  Next, when the RRC connection is established between the wireless terminal device 202 and the wireless base station device 101C, the wireless terminal device 202 transmits an RRC connection reconfiguration completion notification (RRC Connection Reconfiguration Complete) to the wireless base station device 101C. (Step S134).

  Here, the RRC connection completion notification and the RRC connection reconfiguration completion notification include, for example, a parameter “rlf-InfoAvailable”. The wireless terminal device 202 sets this parameter and transmits an RRC connection completion notification and an RRC connection reconfiguration completion notification. Thereby, the radio base station apparatus 101C recognizes that an RLF has occurred in the radio terminal apparatus 202. The wireless base station device 101C transmits a terminal information request (UE Information Request) to the wireless terminal device 202 in order to acquire detailed information of the RLF (step S135).

  Next, the wireless terminal device 202 receives a terminal information request from the wireless base station device 101C, and transmits a terminal information response (UE Information Response) including an RLF report to the wireless base station device 101C (step S136). The RLF report includes the PCI of the radio base station apparatus in which the RLF has occurred, the PCI and ECGI of the radio base station apparatus in which the RRC connection re-establishment has occurred, and the C-RNTI of the own radio terminal apparatus 202. Here, the PCI of the RLF occurrence is the ID of the radio base station apparatus 101B, the PCI and ECGI of the RRC connection re-establishment are the ID of the radio base station apparatus 101C, and the C-RNTI is assigned by the radio base station apparatus 101B ID.

  Next, the wireless base station device 101C recognizes that RLF has occurred in the wireless base station device 101B by referring to the PCI of the RLF report received from the wireless terminal device 202, and performs “Too Late HO” to the cell CC. "Is generated (step S137).

  Next, the radio base station apparatus 101C transmits an RLF notification (RLF INDICATION) including the contents of the RLF report to the radio base station apparatus 101B via the X2 interface in order to notify that it is “Too Late HO”. (Step S138).

  Next, when the radio base station apparatus 101B receives the RLF notification from the radio base station apparatus 101C, the radio base station apparatus 101B checks the timer that has been started. If the timer is operating, that is, a predetermined time has elapsed since the timer was started. If not, it is determined that it is not “Too Late HO” to the cell CC, and further, since the RLF notification is received from the radio base station apparatus 101C other than the radio base station apparatus 101A, It is determined that it is not “Too Early HO” but “HO to Wron Cell” to the cell CB. When the radio base station apparatus 101B receives the RLF notification from the radio base station apparatus 101C and the timer is not operating, that is, when the predetermined time has elapsed since the timer was started, the cell CC And “Too Late HO”.

  If the radio base station apparatus 101B determines that it is “HO to Wron Cell” to the cell CB (step S139), it transmits a handover report to the radio base station apparatus 101A (step S140). The handover report includes, for example, a parameter “Handover Report Type”. The radio base station apparatus 101B notifies the radio base station apparatus 101A of “HO to Wron Cell” by setting this parameter to a predetermined value.

  Next, the radio base station apparatus 101A receives the handover report from the radio base station apparatus 101B, recognizes that “HO to Wong Cell” has occurred in the cell CB (step S141), and performs “HO to Wong”. The optimization process of the handover operation is executed so that the occurrence of “Cell” is suppressed (step S142).

  In addition to the above “Too Late HO”, “Too Early HO”, and “HO to Wong Cell”, there is “Ping Pong HO” as an inappropriate handover operation.

  This is a case where two radio base station apparatuses determine a handover to another radio base station apparatus for a certain radio terminal apparatus. When this “Ping Pong HO” occurs, the connection between the wireless terminal device and the wireless base station device is not disconnected, but the processing for the handover operation is repeated for the wireless terminal device, and the call and data communication Cannot be performed, and the load on the upper network side increases.

[Control parameters for handover operation]
FIG. 10 is a diagram showing a simulation result of reception quality of the wireless terminal device in the wireless communication system according to the embodiment of the present invention.

  FIG. 10 shows RSSI (Received Signal Strength Indication) of the wireless terminal device 202 for 100 seconds until the wireless terminal device 202 passes near the pico base station at a speed of 30 km per hour and passes near the macro base station.

  In FIG. 10, graphs G1 and G3 indicate RSSIs of radio signals transmitted from the macro base station, and graphs G2 and G4 indicate RSSIs of radio signals transmitted from the pico base station. The graphs G1 and G2 take into account the temporal change in the received power of the radio signal in the radio terminal device 202 caused by shadowing, that is, the relative position change between the radio terminal device 202 and other objects. Simulation results, and graphs G3 and G4 are simulation results that do not consider shadowing.

  Referring to FIG. 10, the ideal position for handover from the pico base station to the macro base station of wireless terminal apparatus 202 is the vicinity of the intersection of the graph, that is, the position where the movement time is about 17 seconds. However, in practice, it is difficult to grasp the future communication environment of the wireless terminal device 202 in the wireless communication system. Therefore, it is possible to optimize the handover operation by adjusting the timing of the handover operation based on various measurement results. It is important to make it easier.

  In addition, since the radio signal from each radio base station apparatus is intricate during the movement time of 15 to 20 seconds, for example, “Too Early HO” or “Ping Pong HO” is likely to occur. Also, near the timing at which the moving time is 20 seconds, the received power of the radio signal from the pico base station suddenly decreases, the received power of the radio signal from the macro base station suddenly increases, and SINR (Signal to Interference) Since “-plus-Noise Ratio” deteriorates rapidly, “Too Late HO” is likely to occur.

  Here, if an evaluation function of MRO (Mobility Robustness Optimization) that optimizes handover specified in 3GPP is Y = MRO (X), Y is, for example, the occurrence frequency of “Too Late HO”, “Too Early HO” "Occurrence frequency", "HO to Wrong Cell" occurrence frequency, unnecessary ping occurrence frequency such as "Ping Pong HO", or immediately after transmitting the RRC connection information, that is, the radio terminal apparatus 202 connects to the radio base station apparatus This is the frequency of occurrence of handover immediately after being performed.

  Further, for example, X is a parameter for power measurement processing (Measurement), and hysteresis HS: 0 dB to +15 dB, TTT (Time to Trigger): 0 ms to 5120 ms, or offset OST (Cell Individual Offset): −24 dB to +24 dB It is. Alternatively, X is a parameter for cell reselection processing.

  For example, the offset OST can be set for each serving cell formed by the serving base station and each neighboring cell.

  The radio base station apparatus 101 controls the timing of the handover operation by adjusting the parameters as described above, for example, and performs the optimization process of the handover operation.

[Radio base station equipment]
FIG. 11 is a diagram showing a configuration of a radio base station apparatus according to the embodiment of the present invention.

  Referring to FIG. 11, radio base station apparatus 101 includes antenna 91, circulator 92, radio reception unit 93, radio transmission unit 94, signal processing unit 95, and control unit 98. The signal processing unit 95 includes a reception signal processing unit 96 and a transmission signal processing unit 97. The signal processing unit 95 and the control unit 98 are realized by a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).

  The circulator 92 outputs the radio signal from the radio terminal device 202 received by the antenna 91 to the radio reception unit 93 and outputs the radio signal received from the radio transmission unit 94 to the antenna 91.

  Radio receiving section 93 converts the radio signal received from circulator 92 into a baseband signal or IF (Intermediate Frequency) signal, converts the frequency-converted signal into a digital signal, and outputs the digital signal to received signal processing section 96.

  The received signal processing unit 96 performs signal processing such as despreading in the CDMA (Code Division Multiple Access) method on the digital signal received from the wireless receiving unit 93, and part or all of the digital signal after this signal processing is performed. It is converted into a predetermined frame format and transmitted to the core network side.

  The transmission signal processing unit 97 performs IFFT (Inverse Fast Fourier Transform) in an OFDM (Orthogonal Frequency Division Multiplex) method on communication data obtained by converting communication data received from the core network side into a predetermined frame format or communication data generated by itself. The digital signal after the signal processing is output to the wireless transmission unit 94.

  The radio transmission unit 94 converts the digital signal received from the transmission signal processing unit 97 into an analog signal, converts the frequency of the converted analog signal into a radio signal, and outputs the radio signal to the circulator 92.

  The control unit 98 exchanges various types of information with each unit and the core network in the radio base station apparatus 101.

[Wireless terminal device]
FIG. 12 is a diagram showing a configuration of the wireless terminal apparatus according to the embodiment of the present invention.

  Referring to FIG. 12, radio terminal apparatus 202 includes antenna 81, circulator 82, radio reception unit 83, radio transmission unit 84, signal processing unit 85, control unit 88, and input / output unit 89. Prepare. The signal processing unit 85 includes a reception signal processing unit 86 and a transmission signal processing unit 87. The signal processing unit 85 and the control unit 88 are realized by a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or the like.

  Circulator 82 outputs the radio signal received from antenna 81 from radio base station apparatus 101 to radio reception unit 83, and outputs the radio signal received from radio transmission unit 84 to antenna 81.

  Radio receiving section 83 converts the radio signal received from circulator 82 into a baseband signal or IF (Intermediate Frequency) signal, converts the frequency-converted signal into a digital signal, and outputs the digital signal to received signal processing section 86.

  The received signal processing unit 86 performs signal processing such as FFT (Fast Fourier Transform) in the OFDM (Orthogonal Frequency Division Multiplex) method on the digital signal received from the wireless receiving unit 83, and outputs one of the digital signals after the signal processing. Part or all of the data is output to the control unit 88.

  The control unit 88 converts the digital signal received from the reception signal processing unit 86 into, for example, audio data and video data, and converts it into an analog signal as necessary. And the control part 88 outputs to the input-output part 89 containing a speaker, a microphone, a display, a key input device, etc.

  Further, the control unit 88 receives, for example, voice data and a control signal for controlling the wireless terminal device 202 received by the key input device from the input / output unit 89. Control unit 88 performs predetermined signal processing on the audio data and control signal received from input / output unit 89 to generate communication data, and outputs the communication data to transmission signal processing unit 87.

  The transmission signal processing unit 87 performs signal processing such as spreading processing in the CDMA (Code Division Multiple Access) system on the communication data received from the control unit 88 or communication data generated by itself, and the digital signal after this signal processing Is output to the wireless transmission unit 84.

  The wireless transmission unit 84 converts the digital signal received from the transmission signal processing unit 87 into an analog signal, converts the frequency of the converted analog signal into a wireless signal, and outputs the radio signal to the circulator 82.

  3 to 9, the inappropriate handover operation and its detection process have been described. As described above, the cause of the occurrence of RLF accompanying the movement of the wireless terminal device 202 includes, as described above, an area where a sufficiently strong radio wave does not reach from any wireless base station device 101 in addition to an inappropriate handover operation (hereinafter, A failure of the handover operation or the like due to the movement of the wireless terminal device 202 to the coverage hole due to low power may be considered.

  Further, the inventor of the present application, as a cause of occurrence of RLF accompanying the movement of the wireless terminal device 202, macrocells, femtocells, etc. are densely populated, and interference between radio waves from each wireless base station device 101 is large. It has been discovered that a failure of a handover operation or the like due to the movement of the wireless terminal device 202 to an area where sufficient reception quality cannot be obtained even for radio waves from the device 101 (hereinafter also referred to as a coverage hole due to interference) is considered. .

  In addition to this, the coverage hole due to interference includes a case in which sufficient reception quality can be obtained instantaneously for any radio base station apparatus 101. That is, in order for the handover operation to succeed, sufficient reception quality is required for radio waves from any one of the radio base station apparatuses 101 for a certain period of time, and this certain period of time cannot be secured in a coverage hole due to interference.

  FIG. 13 is a diagram illustrating an example of a coverage hole due to interference in the wireless communication system according to the embodiment of the present invention.

  Referring to FIG. 13, the wireless communication system is a mobile communication system according to LTE standardized by 3GPP, for example, and includes a macro base station 151 and femto base stations 161 to 163.

  Here, in a state where the wireless terminal device 202 is located in the macro cell MC formed by the macro base station 151 and is communicating with the macro base station 151, the femto cell FC1 formed by each of the femto base stations 161, 162, and 163, respectively. , FC2 and FC3 are assumed to move to the overlapping area.

  FIG. 14 is a diagram illustrating an example of fluctuations in received power when a wireless terminal device moves to a coverage hole due to interference in the wireless communication system according to the embodiment of the present invention. In FIG. 14, the vertical axis represents the received power of the wireless terminal device 202, and the horizontal axis represents the travel time of the wireless terminal device 202.

  Referring to FIG. 14, first, when the wireless terminal device 202 enters the femtocell FC3, the reception power of the femtocell FC3, that is, the reception power of the radio signal from the femto base station 163 becomes larger than the others. When the wireless terminal device 202 stays at this position, the handover operation from the macro base station 151 to the femto base station 163 is normally performed.

  However, if the wireless terminal device 202 further moves toward the overlapping area of the femtocells FC1, FC2, and FC3, the wireless terminal apparatus 202 enters an area where interference is large. In this region, the difference between the received powers of the cells becomes small, and the magnitude relationship between the received powers of the cells changes with a short movement time. In this case, regardless of which radio base station apparatus is handed over, RLF occurs due to interference from other radio base station apparatuses.

  FIG. 15 is a diagram illustrating an example of a situation in which a wireless terminal device that has entered a coverage hole due to interference returns from the RLF in the wireless communication system according to the embodiment of the present invention.

  Referring to FIG. 15, first, radio terminal apparatus 202 enters a coverage hole due to interference, and RLF occurs due to failure of the handover operation (step S201).

  Next, the wireless terminal device 202 moves out of the femtocell FC1, FC2, FC3 and into the macrocell MC. The wireless terminal device 202 searches for a reconnection destination wireless base station device by performing power measurement processing. The wireless terminal device 202 executes a normal connection procedure with the searched macro base station 151, establishes a communication connection with the macro base station 151, and returns from the RLF (step S202).

  Next, the wireless terminal device 202 transmits an RLF report including information for assisting determination of the cause of occurrence of RLF to the macro base station 151 (step S203).

  In addition to the above-mentioned contents, the RLF report includes, for example, received power such as RSSI of a radio signal from the connection-destination radio base station apparatus 101 when RLF occurs, as described in 3GPP TR 36.331 V10.2.0, for example. And reception quality such as SINR. Further, the RLF report includes the ID of the neighboring base station when the RLF occurs, the received power such as RSSI of the radio signal from the neighboring base station, and the received quality such as SINR. The information of each neighboring base station is arranged in an order suitable as a connection destination, for example. Further, the RLF report includes the ID of the radio base station apparatus at the time of RLF occurrence. This ID may be either EGCI or PCI, and becomes the ID of the target base station when RLF occurs during the handover operation, and becomes the ID of the serving base station when it occurs in other situations. In addition, the RLF report includes the ECGI of the serving base station in the final handover operation of the wireless terminal device 202, that is, the connection destination when the wireless terminal device 202 last received the RRC connection reconfiguration instruction including the handover instruction. The ID of the radio base station apparatus 101 is included. The RLF report includes the ECGI of the radio base station apparatus 101 that the radio terminal apparatus 202 first attempted to establish a communication connection after the RLF has occurred. Further, the RLF report includes the time from when the wireless terminal apparatus 202 last initialized the handover operation, that is, from the last reception of the RRC connection reconfiguration instruction including the handover instruction to when the RLF occurs. This time is counted in units of 100 ms.

  Next, the macro base station 151 determines the cause of occurrence of RLF based on the RLF report received from the wireless terminal device 202, and performs various processes for suppressing the occurrence of RLF.

  FIG. 16 is a diagram illustrating an example of a handover operation optimization process in the wireless communication system according to the embodiment of the present invention. The way of viewing the figure is the same as in FIG.

  Referring to FIG. 16, at timing t11, the wireless terminal device 202 selects the macro base station 151 as a communication partner because the reception power of the macro cell MC is larger than the reception power of the femtocell FC3 that is a neighboring cell. Communication connection is established.

  Next, with the movement of the wireless terminal device 202, the received power of the femtocell FC3 becomes larger than the received power of the macro cell MC. Even in such a situation, if the handover operation from the macro base station 151 to the femto base station 163 is not performed, RLF occurs due to interference from the femto base station 163 (timing t13).

  After the occurrence of the RLF, the wireless terminal device 202 newly establishes a communication connection with the femto base station 163 and transmits an RLF report to the femto base station 163. The femto base station 163 refers to the RLF report and transmits an RLF notification including the content of the RLF report to the macro base station 151 via, for example, the X2 interface.

  Based on the received power of the macro cell MC and the received power of the femto cell FC3 included in the RLF notification received from the femto base station 163, the macro base station 151 receives “Too Late” from the macro cell MC formed by itself to the femto cell FC3. Recognize that "HO" has occurred. Then, the macro base station 151 executes a handover operation optimization process so that the occurrence of “Too Late HO” in the femtocell FC3 is suppressed. That is, the macro base station 151 performs control to advance the timing of the handover operation from itself to the femto base station 163. Thus, for example, the handover operation is executed at timing t12.

  FIG. 17 is a diagram showing timing adjustment of a handover operation in a coverage hole due to interference in the radio communication system according to the embodiment of the present invention. The way of viewing the figure is the same as in FIG.

  Referring to FIG. 17, here, it is assumed that radio terminal apparatus 202 communicating with femto base station 163 enters the overlapping area of femtocells FC1, FC2, and FC3, and RLF occurs at timing t21, for example.

  In this overlapping region, unlike the situation shown in FIG. 16, the difference in received power of each cell is small, and the magnitude relationship of the received power of each cell changes in a short movement time. For this reason, even if the timing of the handover operation is changed before and after the timing t21 based on the instantaneous received power of each cell when the RLF occurs, the RLF cannot be avoided.

  That is, if the coverage hole due to interference cannot be distinguished from the poor adjustment of the timing of the handover operation as the cause of the occurrence of RLF, meaningless changes in the timing of the handover operation are made, and RLF occurs frequently due to inappropriate changes. There is a possibility that.

  Therefore, in the radio base station apparatus according to the embodiment of the present invention, a coverage hole due to interference can be identified as a cause of occurrence of RLF by the following configuration and operation.

  FIG. 18 is a diagram illustrating a configuration of a control unit in the radio base station apparatus according to the embodiment of the present invention.

  Referring to FIG. 18, control unit 98 includes a measurement information acquisition unit 11, a determination unit 12, a transmission control unit 13, and a movement operation control unit 14.

  After the communication connection between the wireless terminal device 202 and the wireless base station device 101 is disconnected, the measurement information acquisition unit 11 newly establishes a communication connection with the wireless base station device 101 described above or other than the above. In the meantime, measurement information indicating the result of measurement performed by the wireless terminal device 202 is acquired.

  Based on the measurement information acquired by the measurement information acquisition unit 11, the determination unit 12 transmits whether the cause of the disconnection of the communication connection is a coverage hole due to interference, that is, a plurality of radio base station apparatuses 101 in the communication system transmit It is determined whether or not the interference is between radio signals.

  When the determination unit 12 determines that the cause of the disconnection of the communication connection is interference between radio signals, the transmission control unit 13 at least one of the plurality of radio base station devices 101 in the communication system The radio signal transmission operation from the radio base station apparatus 101 to the radio terminal apparatus 202 is adjusted.

  Further, the determination unit 12 determines whether the cause of the disconnection of the communication connection is the timing of the handover operation of the wireless terminal device 202 based on the measurement information acquired by the measurement information acquisition unit 11 It is discriminated whether the radio base station apparatus 101 is an interference between radio signals transmitted.

  When the determination unit 12 determines that the cause of the disconnection of the communication connection is the timing of the handover operation, the mobile operation control unit 14 performs the handover operation in its own radio base station apparatus 101 or another radio base station apparatus 101. The process for adjusting the timing is performed.

  FIG. 19 is a sequence diagram showing an example of determination processing of the cause of RLF occurrence in the wireless communication system according to the embodiment of the present invention.

  Referring to FIG. 19, first, a communication connection is established between the wireless terminal device 202 and the serving base station (step S251).

  Next, RLF occurs between the wireless terminal device 202 and the serving base station (step S252), and the wireless terminal device 202 starts a cell reselection procedure (step S253). In this cell reselection procedure, various types of information are exchanged between the wireless terminal device 202 and the target base station (step S254). Here, the cell reselection procedure includes transmission / reception of an RRC connection re-establishment request, an RRC connection re-establishment response, and an RRC connection re-establishment completion notification shown in FIG.

  Next, a communication connection is established between the wireless terminal device 202 and the target base station (step S255), and the wireless terminal device 202 transmits an RLF report to the target base station (step S256).

  Next, the target base station performs RLF generation cause determination processing and RLF suppression processing based on the RLF report received from the wireless terminal device 202 (step S257).

  Hereinafter, the process of determining the cause of RLF and the process of suppressing RLF by the radio base station apparatus 101 will be described in detail.

  In the radio base station apparatus 101, the determination unit 12 determines that the cause of the disconnection of the communication connection from each radio base station apparatus 101 in the radio terminal apparatus 202 is based on the measurement information acquired by the measurement information acquisition unit 11, for example. Whether the reception power of the radio signal is low, the timing of the handover operation of the radio terminal apparatus 202, or the coverage hole with low power, that is, radio transmitted by a plurality of radio base station apparatuses 101 in the communication system It is determined whether the interference is between signals.

  FIG. 20 is a diagram illustrating an example of information added to the RLF report in order to determine a coverage hole due to interference in the wireless communication system according to the embodiment of the present invention. The way of viewing the figure is the same as in FIG.

  Referring to FIG. 20, radio terminal apparatus 202 includes in the RLF report information at the time of reconnection operation, for example, time TR from timing t1 when RLF occurs to timing t2 when the cell reselection procedure is completed. . That is, the time TR is a time from the disconnection of the communication connection between the wireless terminal device 202 and the wireless base station device 101 to the establishment of the communication connection.

  More specifically, in the radio base station apparatus 101, the measurement information acquisition unit 11 acquires the time TR as measurement information. Further, the measurement information acquisition unit 11 further receives received power information, that is, a measurement result notification indicating the result of the wireless terminal device 202 measuring the received power of the wireless signal from each wireless base station device 101 when the communication connection is disconnected. Is acquired as measurement information.

  Then, the determination unit 12 determines that the reception power of the radio signal from the radio base station apparatus 101 selected as the communication partner by the radio terminal apparatus 202 is equal to or higher than a predetermined value in the reception power information when the communication connection is disconnected, or When the reception power of the radio signal from the radio base station apparatus 101 other than the radio base station apparatus 101 is equal to or greater than a predetermined value and the time TR is equal to or greater than the predetermined value, the cause of the disconnection of the communication connection is between the radio signals Judged as interference.

  Specifically, when the time TR is long, the determination unit 12 takes a long time for the wireless terminal device 202 to search for the reconnection destination wireless base station device 101 or the radio wave environment is bad. For this reason, it is considered that communication errors with the radio base station apparatus 101 occur frequently, so it is determined that the cause of RLF is a coverage hole due to interference. This is because, in the coverage hole due to interference, as described above, the difference in the received power of each cell becomes small, and the magnitude relationship of the received power of each cell changes in a short movement time.

  On the other hand, when the time TR is short, the determination unit 12 determines that the cause of RLF is not a coverage hole due to interference, and determines, for example, that the timing setting for the handover operation is inappropriate.

  FIG. 21 is a flowchart defining the procedure of RLF occurrence cause determination processing and RLF suppression processing by the radio base station apparatus according to the embodiment of the present invention.

  Referring to FIG. 21, control unit 98 receives the RLF report from radio terminal apparatus 202 (step S301), and receives the desired signal power at the time of RLF generation, that is, the received power of the radio signal from the serving base station, and interference. The power of the wave, that is, the reception power of the radio signal from the neighboring base station is confirmed from the RLF report (step S302).

  When the power of the desired wave is smaller than the predetermined threshold and the power of the interference wave is smaller than the predetermined threshold (YES in step S302), the control unit 98 determines that the cause of the RLF is the wireless terminal device It is determined that 202 has entered a coverage hole with low power (step S303). In this case, for example, the mobile communication carrier takes measures to increase the transmission power of the radio signal of the serving base station (step S304).

  On the other hand, when the power of the desired wave is larger than the predetermined threshold or the power of the interference wave is larger than the predetermined threshold (NO in step S302), the control unit 98 sets the time TR included in the RLF report. Confirmation (step S305). Note that these threshold values may be the same value or different values.

  When the time TR is larger than a predetermined threshold, that is, when the time required from the occurrence of RLF until the wireless terminal device 202 establishes a communication connection is long (YES in step S305), the control unit 98 generates the RLF. It is determined that the cause is that the wireless terminal device 202 has entered a coverage hole due to interference (step S306).

  Then, when determining that the coverage hole due to the interference is the cause, the control unit 98 performs an interference reduction process to be described later for reducing the interference in the area where the coverage hole is generated (step S307).

  On the other hand, when the time TR is smaller than the predetermined threshold, that is, when the time required from the occurrence of RLF until the wireless terminal device 202 establishes the communication connection is short (NO in step S305), the control unit 98 determines the RLF. It is determined that the cause of occurrence is improper timing setting of the handover operation from the serving base station to the target base station (step S308).

  Then, the control unit 98 performs processing for adjusting the parameter of the handover operation in the own radio base station apparatus or another radio base station apparatus (step S309).

  FIG. 22 is a flowchart defining the procedure of RLF occurrence cause determination processing and RLF suppression processing by the radio base station apparatus according to the embodiment of the present invention.

  The radio terminal apparatus 202 may be configured to include, in place of the time TR, the number of times that cell reselection processing has been performed from the occurrence of RLF until a new communication connection is established in the RLF report.

  That is, in the radio base station apparatus 101, the measurement information acquisition unit 11 performs an operation for the radio terminal apparatus 202 to establish a communication connection with the radio base station apparatus 101 from the disconnection of the communication connection to the establishment of the communication connection. Is obtained as measurement information.

  Then, the determination unit 12 determines that the reception power of the radio signal from the radio base station apparatus 101 selected as the communication partner by the radio terminal apparatus 202 is equal to or higher than a predetermined value in the reception power information when the communication connection is disconnected, or When the reception power of the radio signal from the radio base station apparatus 101 other than the radio base station apparatus 101 is equal to or greater than a predetermined value, and the number of times is equal to or greater than the predetermined value, the cause of the disconnection of the communication connection is between the radio signals Judged as interference.

  Specifically, referring to FIG. 22, control unit 98 receives an RLF report from wireless terminal apparatus 202 (step S311), and receives the power of a desired wave at the time of RLF occurrence, that is, the wireless signal from the serving base station. The received power and the power of the interference wave, that is, the received power of the radio signal from the neighboring base station are confirmed from the RLF report (step S312).

  When the power of the desired wave is smaller than the predetermined threshold and the power of the interference wave is smaller than the predetermined threshold (YES in step S312), the control unit 98 determines that the cause of the RLF is the wireless terminal device It is determined that 202 has entered a coverage hole with low power (step S313). In this case, for example, the mobile communication carrier takes measures to increase the transmission power of the radio signal of the serving base station (step S314).

  On the other hand, when the power of the desired wave is larger than the predetermined threshold or the power of the interference wave is larger than the predetermined threshold (NO in step S312), the control unit 98 reselects the cell included in the RLF report. The number of processes is confirmed (step S315). Note that these threshold values may be the same value or different values.

  When the number of cell reselection processes is greater than a predetermined threshold, that is, when the number of cell reselection process failures from the occurrence of RLF to the time when the wireless terminal device 202 establishes a communication connection is large, the control unit 98 ( It is determined that the cause of the RLF is that the wireless terminal device 202 has entered the coverage hole due to interference (YES in step S315) (step S316).

  Then, when determining that the coverage hole due to the interference is the cause, the control unit 98 performs an interference reduction process, which will be described later, for reducing the interference in the region where the coverage hole is generated (step S317).

  On the other hand, when the number of cell reselection processes is smaller than a predetermined threshold, that is, when the number of cell reselection process failures from the occurrence of RLF until the wireless terminal device 202 establishes a communication connection is small, the control unit 98 (NO in step S315), it is determined that the cause of the RLF is improper timing setting of the handover operation from the serving base station to the target base station (step S318).

  Then, control unit 98 performs processing for adjusting parameters for handover operation in its own radio base station apparatus or another radio base station apparatus (step S319).

  FIG. 23 is a flowchart defining the procedure of the RLF generation cause determination process and the RLF suppression process by the radio base station apparatus according to the embodiment of the present invention.

  Instead of including the time TR in the RLF report, the wireless terminal device 202 is configured to perform power measurement processing a plurality of times from the occurrence of the RLF until a new communication connection is established, and include the result in the RLF report. Also good. In this case, the radio base station apparatus 101 determines a coverage hole due to interference based on the transition of the magnitude relationship of the received power of each cell from the occurrence of RLF to the establishment of a new communication connection.

  That is, in the radio base station apparatus 101, the measurement information acquisition unit 11 obtains the received power information indicating the result of the radio terminal apparatus 202 measuring the received power of the radio signal from each radio base station apparatus 101 from the disconnection of the communication connection. Acquired as measurement information for multiple times until the establishment of communication connection.

  Then, the determination unit 12 determines that the reception power of the radio signal from the radio base station apparatus 101 selected as the communication partner by the radio terminal apparatus 202 is equal to or higher than a predetermined value in the reception power information when the communication connection is disconnected, or When the received power of the radio signal from the radio base station apparatus 101 other than the radio base station apparatus 101 is equal to or greater than a predetermined value, the received power or the received quality based on the received power is predetermined in the received power information for a plurality of times. When the radio base station apparatuses 101 satisfying the conditions are different, it is determined that the cause of the disconnection of the communication connection is interference between radio signals.

  Specifically, referring to FIG. 23, control unit 98 receives the RLF report from wireless terminal apparatus 202 (step S321), and receives the power of the desired wave at the time of occurrence of RLF, that is, the wireless signal from the serving base station. The received power and the power of the interference wave, that is, the received power of the radio signal from the neighboring base station are confirmed from the RLF report (step S322).

  If the power of the desired wave is smaller than the predetermined threshold and the power of the interference wave is smaller than the predetermined threshold (YES in step S322), the control unit 98 determines that the cause of the RLF is the wireless terminal device It is determined that 202 has entered a coverage hole with low power (step S323). In this case, for example, the mobile communication carrier takes measures to increase the transmission power of the radio signal of the serving base station (step S324).

  On the other hand, when the power of the desired wave is larger than the predetermined threshold or the power of the interference wave is larger than the predetermined threshold (NO in step S322), the control unit 98 changes the superiority or inferiority of each base station, That is, the transition of the magnitude relationship of the received power of each cell is confirmed (step S325). Note that these threshold values may be the same value or different values.

  When the superiority or inferiority of each base station is not constant, that is, when the magnitude relationship of the received power of each cell is not constant between the occurrence of RLF and the establishment of a new communication connection (YES in step S325). ), It is determined that the cause of the RLF is that the wireless terminal device 202 has entered the coverage hole due to interference (step S326).

  Then, when determining that the coverage hole due to the interference is the cause, the control unit 98 performs an interference reduction process to be described later for reducing the interference in the area where the coverage hole is generated (step S327).

  On the other hand, when the superiority or inferiority of each base station is constant, that is, when the magnitude relationship of the received power of each cell is constant between the occurrence of RLF and the establishment of a new communication connection, the control unit 98 ( In step S325, NO, it is determined that the cause of RLF is an inappropriate timing setting for the handover operation from the serving base station to the target base station (step S328).

  Then, control unit 98 performs processing for adjusting parameters for handover operation in its own radio base station apparatus or other radio base station apparatus (step S329).

  In the flowcharts shown in FIGS. 21 to 23, the control unit 98 may be configured to determine the coverage hole due to interference without performing the determination based on the received power information (steps S302, S312 and S322).

  FIG. 24 is a diagram showing a configuration of a control unit in the wireless terminal device according to the embodiment of the present invention.

  Referring to FIG. 24, control unit 88 includes a measurement unit 21 and a determination unit 22.

  The measurement unit 21 performs measurement after the communication connection between itself and the radio base station apparatus 101 is disconnected and until a new communication connection with the radio base station apparatus 101 is established.

  More specifically, the measurement unit 21 measures a time TR from the disconnection of the communication connection to the establishment of the communication connection, or establishes a communication connection with the radio base station apparatus 101 between the disconnection of the communication connection and the establishment of the communication connection. The number of times of performing the operation for establishment is measured, or the reception power of the radio signal from each radio base station apparatus 101 is measured a plurality of times from the disconnection of the communication connection to the establishment of the communication connection.

  Then, the transmission signal processing unit 87 transmits measurement information indicating the measurement result of the measurement unit 21 to the radio base station apparatus 101.

  In the radio communication system according to the embodiment of the present invention, the radio base station apparatus 101 is configured to determine the cause of occurrence of RLF. However, the present invention is not limited to this. The configuration may be such that the wireless terminal device 202 determines the cause of occurrence of the RLF, not limited to the wireless base station device 101.

  That is, the measurement unit 21 performs measurement after the communication connection between itself and the radio base station apparatus 101 is disconnected until a new communication connection with the radio base station apparatus 101 is established.

  Based on the measurement result of the measurement unit 21, the determination unit 22 determines whether the cause of the disconnection of the communication connection is interference between radio signals transmitted by the plurality of radio base station devices 101 in the communication system. To do.

  As described above, with the configuration in which the wireless terminal device 202 determines the cause of occurrence of RLF, information transmitted and received between the wireless terminal device 202 and the wireless base station device 101 can be reduced.

  Also, the radio base station apparatus 101 and the radio terminal apparatus 202 may combine the coverage hole determination conditions (steps S305, S315, and S325) due to interference described with reference to FIGS. That is, if any one of the determination conditions is satisfied, it may be determined that the hole is a coverage hole due to interference, and if any two or all of the determination conditions are satisfied, it may be determined that the hole is a coverage hole due to interference. Good.

  Next, interference reduction processing in the radio communication system according to the embodiment of the present invention will be described in detail.

  In the radio base station apparatus 101, the transmission control unit 13, when the determination unit 12 determines that the cause of the communication connection disconnection is interference between radio signals, Among them, the resource relating to the transmission of the radio signal from at least one of the radio base station apparatuses 101 to the radio terminal apparatus 202 is adjusted.

  The transmission control unit 13 adjusts resources in the time axis direction, for example. More specifically, the transmission control unit 13 is a period in which at least one of information included in the radio signal, the frequency of the radio signal, and the power of the radio signal is limited as a resource, for example, ABS (Almost Blank Sub-frame). Adjust. First, the ABS will be described in detail.

  Since the transmission power of the pico base station is smaller than that of the macro base station, it is necessary to take measures against interference in the vicinity of the cell edge, that is, in the vicinity of the cell boundary.

  In order to disperse communication traffic, a method of expanding the pico cell area and increasing the number of wireless terminal devices communicating with the pico base station (Range Expansion) has been studied. As this method, a solution in the time domain using ABS is described in 3GPP TS 36.423 v. 10.2.0. This is called eICIC (enhanced Inter-Cell Interference Cordination).

  That is, the radio base station apparatus 101 transmits almost no information in the ABS set by itself among one frame for transmission. Here, the subframe is, for example, a resource allocation unit for the wireless terminal device 202 and has a length of 1 ms.

  Specifically, the macro base station periodically provides an ABS, and the wireless terminal device 202 connected to the pico base station receiving interference from the macro base station communicates with the pico base station at the ABS. By causing the wireless terminal device 202 located near the cell edge of the macro cell to use the ABS of the macro base station, interference from the macro base station is reduced in the wireless terminal device 202, and the communication environment with the pico base station is good. Become.

  FIG. 25 is a sequence diagram showing an example of using the ABS in the radio communication system according to the embodiment of the present invention.

  Referring to FIG. 25, first, a radio base station apparatus that gives interference (hereinafter also referred to as an interfering base station) receives ABS information indicating an ABS pattern set by itself as a radio base station apparatus that receives interference. (Hereinafter also referred to as an interfered base station). Here, the interfering base station is mainly a macro base station, and the interfered base station is mainly a pico base station. The ABS pattern is expressed by a bitmap, for example.

  Next, the interfered base station transmits an ABS setting request indicating an ABS pattern usable by itself to the interfering base station. This is because, when there are a plurality of interfering base stations, even if one interfering base station sets an ABS, it is not always possible to use the ABS in the interfered base station. The ABS setting request includes, for example, an ABS usage rate.

  Next, the interfering base station readjusts its own ABS pattern based on the received ABS setting request.

  In the radio communication system according to the embodiment of the present invention, ABS is used to suppress the occurrence of coverage holes due to interference.

  FIG. 26 is a sequence diagram showing an example of interference reduction processing using ABS in the wireless communication system according to the embodiment of the present invention.

  Referring to FIG. 26, the target base station first detects a coverage hole due to interference (step S351). Here, the target base station acquires the ID of the serving base station and the IDs of the neighboring base stations when the RLF occurs from the RLF report received from the wireless terminal device 202.

  Then, the target base station transmits an ABS setting request to the neighboring base stations based on the acquired ID (step S352).

  Next, the neighboring base station sets its own ABS pattern based on the ABS setting request received from the target base station (step S353).

  Next, the neighboring base station transmits ABS information indicating the set ABS pattern to the serving base station and the target base station (steps S354 and S355).

  Next, the serving base station and the target base station instruct the wireless terminal device 202 in the handover operation to use the ABS indicated by the ABS information received from the neighboring base stations. Specifically, the serving base station and the target base station transmit the ABS pattern indicated by the ABS information to the radio terminal apparatus 202, for example, in an RRC connection reconfiguration instruction.

  Based on the ABS pattern notified from the serving base station and the target base station, the wireless terminal device 202 performs processing for a handover operation such as power measurement processing in an ABS with less interference from neighboring base stations. Thereby, for example, in the radio terminal apparatus 202, the reception quality of the radio signal from the target base station is improved, and the high priority state of the target base station as the handover destination is maintained, so that RLF does not occur and serving The handover operation from the base station to the target base station can be completed early.

  Considering a specific example, for example, in the example shown in FIG. 17, the serving base station in the sequence corresponds to the femto base station 163, the target base station corresponds to the macro base station 151, and the neighboring base stations are the femto base station 161 and 162.

  That is, in this example, interference from the femto base stations 161 and 162 with respect to communication with the femto base station 163 and the macro base station 151 in the wireless terminal device 202 can be reduced. As a result, even if the wireless terminal device 202 in communication with the femto base station 163 enters the overlapping area of the femtocells FC1, FC2, and FC3, the RLF does not occur, and the femto base station 163 transfers to the macro base station 151. The handover operation can be completed early.

  The radio base station apparatus 101 is not limited to the configuration instructing the radio terminal apparatus 202 during handover operation to use the ABS, but the radio base station apparatus 101 is searching for a reconnection-destination radio base station apparatus due to the occurrence of RLF. The terminal device 202, that is, the wireless terminal device 202 during cell reselection may be instructed to use the ABS.

  Further, when the serving base station or the neighboring base station receives the RLF report, for example, the ID of the target base station is acquired from the RLF report, and the handover operation from the serving base station to the target base station is performed favorably. In addition, processing for reducing interference of neighboring base stations is performed.

  FIG. 27 is a sequence diagram showing a specific example of interference reduction processing using ABS in the wireless communication system according to the embodiment of the present invention. FIG. 27 shows a case where one frame is composed of 10 subframes.

  Referring to FIG. 27, femto base stations 161 and 162 that are neighboring base stations set subframes SF2, SF5, and SF9 as ABSs.

  The femto base station 163 serving as the serving base station and the macro base station 151 serving as the target base station instruct the wireless terminal apparatus 202 to use the subframes SF2, SF5, and SF9.

  Note that the radio base station apparatus 101 may be configured to reduce interference in the radio terminal apparatus 202 and suppress the occurrence of coverage holes due to interference by controlling resources related to frequency.

  That is, the transmission control unit 13 adjusts resources in the frequency axis direction. More specifically, the transmission control unit 13 adjusts a frequency used for transmitting a radio signal as a resource.

  Specifically, the radio base station apparatus 101 divides resources related to radio signal transmission in the time axis direction and the frequency axis direction in radio signal transmission to the radio terminal apparatus 202 according to the OFDMA scheme. Then, resources divided for each wireless terminal apparatus 202 are allocated.

  The radio base station apparatus 101 adjusts the amount of a blank resource block (Blank Resource Block) containing almost no information in a resource block unit with a bandwidth of 180 kHz assigned to each radio terminal apparatus 202, for example. -Cell Interference Coordination).

  Similarly to the ABS, the neighboring base station notifies the serving base station and the target base station of the blank resource block set by itself, and the serving base station and the target base station use the blank resource block to transmit the wireless terminal device 202. By communicating with the wireless terminal device 202, it is possible to reduce interference of neighboring base stations in the wireless terminal device 202.

  Also, the radio base station apparatus 101 may perform CA based ICIC (Carrier Aggregation based ICIC) that adjusts the number of blank carriers that hardly contain information in a unit of a bandwidth of several tens of MHz in which resource blocks are bundled. Good.

  Further, the radio base station apparatus 101 may be configured to reduce interference in the radio terminal apparatus 202 and control coverage holes due to interference by controlling resources related to a beam of transmission radio waves.

  That is, when the determination unit 12 determines that the cause of the disconnection of the communication connection is interference between radio signals, the transmission control unit 13 is at least one of the plurality of radio base station devices 101 in the communication system. The directivity of the antenna 91 for transmitting a radio signal from the radio base station apparatus 101 to the radio terminal apparatus 202 provided in one radio base station apparatus 101 is adjusted.

  Specifically, the peripheral base station controls the directivity of its own antenna 91 according to an instruction from the radio base station apparatus 101 that has detected a coverage hole due to interference, thereby transmitting to the serving base station and the target base station. Reduce the intensity of the radio beam. Thereby, the interference of the surrounding base station in the radio | wireless terminal apparatus 202 which communicates with a serving base station and a target base station can be reduced.

  Also, the radio base station apparatus 101 is configured to reduce the interference in the radio terminal apparatus 202 by adjusting the transmission power of radio signals to the radio terminal apparatus 202 and suppress the occurrence of coverage holes due to the interference. Good.

  That is, in the radio base station apparatus 101, the transmission control unit 13 determines that the cause of the disconnection of the communication connection is interference between radio signals when the determination unit 12 determines that a plurality of radio base station apparatuses in the communication system 101, the transmission power of a radio signal from at least one of the radio base station apparatuses 101 to the radio terminal apparatus 202 is adjusted.

  Note that the radio base station apparatus 101 may combine a part or all of the above methods as a method of adjusting the transmission operation of the radio signal to the radio terminal apparatus 202.

  Further, the radio base station apparatus 101 is not limited to the process of reducing interference from neighboring base stations, and the radio base station apparatus 202 increases the serving base station and the target base station by increasing the transmission power of the serving base station and the target base station. The structure which performs the process which improves the reception quality of the radio signal from may be sufficient.

  By the way, as a method for suppressing an inappropriate handover operation, a method for adjusting the execution judgment criterion of the handover operation and the like can be considered. On the other hand, it is necessary to improve the radio wave environment by adjusting the transmission power etc. of the radio base station device in order to suppress the failure of the handover operation due to the radio wave environment in the radio terminal device such as coverage hole It becomes.

  On the other hand, in the radio base station apparatus according to the embodiment of the present invention, the measurement information acquisition unit 11 disconnects the communication connection between the radio terminal apparatus 202 and the radio base station apparatus 101 before the radio terminal apparatus 202. Until the communication connection with the wireless base station apparatus 101 is newly established, the wireless terminal apparatus 202 acquires measurement information indicating the result of the measurement. Based on the measurement information acquired by the measurement information acquisition unit 11, the determination unit 12 causes the disconnection of the communication connection to be interference between radio signals transmitted by the plurality of radio base station apparatuses 101 in the communication system. It is determined whether or not.

  As described above, the configuration using the measurement result of the wireless terminal device 202 from the disconnection of the communication connection to the establishment of the new communication connection causes the disconnection of the communication connection between the wireless terminal device 202 and the wireless base station device 101. As described above, the radio terminal apparatus 202 has moved to a coverage hole in which radio waves from a plurality of radio base station apparatuses 101 have large interference and sufficient reception quality is not obtained for any radio base station apparatus 101. Can be determined. That is, by determining the disconnection of the communication connection due to the radio wave environment in the wireless terminal device 202, an appropriate countermeasure can be taken and a good communication system can be constructed.

  Therefore, in the radio base station apparatus according to the embodiment of the present invention, it is possible to stabilize the communication by determining the cause of the disconnection of the communication connection between the radio terminal apparatus and the radio base station apparatus.

  Further, in the radio base station apparatus according to the embodiment of the present invention, measurement information acquisition unit 11 acquires time TR from disconnection of communication connection to establishment of communication connection as measurement information. Then, when the time TR is equal to or greater than a predetermined value, the determination unit 12 determines that the cause of the disconnection of the communication connection is interference between radio signals.

  As described above, the configuration using the time from the disconnection of the communication connection to the establishment of the new communication connection can appropriately determine the disconnection of the communication connection caused by the radio wave interference in the wireless terminal device 202.

  In the radio base station apparatus according to the embodiment of the present invention, the measurement information acquisition unit 11 establishes communication connection between the radio terminal apparatus 202 and the radio base station apparatus 101 between the disconnection of the communication connection and the establishment of the communication connection. The number of times the operation for establishing is performed is acquired as measurement information. Then, when the number of times is equal to or greater than a predetermined value, the determination unit 12 determines that the cause of the disconnection of the communication connection is interference between radio signals.

  As described above, the communication terminal disconnection caused by the radio wave interference in the wireless terminal device 202 is achieved by the configuration using the number of operations for establishing a new communication connection between the disconnection of the communication connection and the establishment of a new communication connection. It can be determined appropriately.

  In the radio base station apparatus according to the embodiment of the present invention, the measurement information acquisition unit 11 receives received power information indicating the result of the radio terminal apparatus 202 measuring the received power of the radio signal from each radio base station apparatus 101. Are obtained as measurement information for a plurality of times from the disconnection of the communication connection to the establishment of the communication connection. Then, in the reception power information for a plurality of times, the determination unit 12 determines that the cause of the disconnection of the communication connection is a radio signal when the radio base station apparatus 101 that satisfies the predetermined condition for the reception power or the reception quality based on the reception power is different. It is determined that the interference is between.

  As described above, the communication connection disconnection caused by the radio wave interference in the wireless terminal device 202 is detected by the configuration for detecting the change in the radio wave environment of the wireless terminal device 202 between the disconnection of the communication connection and the establishment of a new communication connection. Can be properly determined.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the measurement information acquisition unit 11 further receives the radio signal reception power from each radio base station apparatus 101 by the radio terminal apparatus 202 when the communication connection is disconnected. As a result, the received power information indicating is obtained as measurement information. Then, the determination unit 12 further determines whether the reception power of the radio signal from the radio base station apparatus 101 selected by the radio terminal apparatus 202 as the communication partner is equal to or greater than a predetermined value in the received power information when the communication connection is disconnected. Alternatively, when the reception power of the radio signal from the radio base station apparatus 101 other than the radio base station apparatus 101 is equal to or greater than a predetermined value, it is determined that the cause of the disconnection of the communication connection is interference between the radio signals.

  As described above, the configuration in which the radio wave environment of the wireless terminal device 202 at the time of disconnection of the communication connection is further used as the determination criterion can more accurately determine the disconnection of the communication connection caused by the radio wave interference in the wireless terminal device 202. .

  In the radio base station apparatus according to the embodiment of the present invention, the determination unit 12 determines that the cause of the disconnection of the communication connection is based on the measurement information acquired by the measurement information acquisition unit 11. It is determined whether the interference is between radio signals transmitted by the base station apparatus 101 or the timing of the handover operation of the radio terminal apparatus 202.

  In this way, in addition to the disconnection of the communication connection due to radio wave interference in the wireless terminal device 202, the configuration for determining the disconnection of the communication connection due to the timing of the handover operation performs appropriate countermeasures and stabilizes the communication. Can be further planned.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the determination unit 12 determines that the cause of the disconnection of the communication connection is based on the measurement information acquired by the measurement information acquisition unit 11. The reception power of the radio signal from the radio base station apparatus 101 is low, the timing of the handover operation of the radio terminal apparatus 202, or between radio signals transmitted by a plurality of radio base station apparatuses 101 in the communication system Determine if it is interference.

  Thus, in addition to disconnection of communication connection due to radio wave interference in the wireless terminal device 202 and disconnection of communication connection due to the timing of the handover operation, communication connection due to insufficient strength of received radio waves in the wireless terminal device 202 With the configuration for discriminating disconnection, appropriate measures can be taken to further stabilize the communication.

  Further, in the radio base station apparatus according to the embodiment of the present invention, when it is determined that the cause of the disconnection of the communication connection is interference between radio signals, the transmission control unit 13 performs a plurality of radios in the communication system. A radio signal transmission operation from at least one of the base station apparatuses 101 to the radio terminal apparatus 202 is adjusted.

  As described above, the configuration of adjusting the radio signal transmission operation of the radio base station apparatus 101 can reduce the radio wave interference in the radio terminal apparatus 202 and suppress the disconnection of the communication connection due to the radio wave environment.

  Moreover, in the radio base station apparatus according to the embodiment of the present invention, the transmission control unit 13 transmits from at least one radio base station apparatus 101 to the radio terminal apparatus 202 among the plurality of radio base station apparatuses 101 in the communication system. The transmission power of the radio signal to is adjusted.

  As described above, the configuration of adjusting the transmission power of the radio signal of the radio base station apparatus 101 can effectively reduce radio wave interference in the radio terminal apparatus 202.

  Moreover, in the radio base station apparatus according to the embodiment of the present invention, the transmission control unit 13 transmits from at least one radio base station apparatus 101 to the radio terminal apparatus 202 among the plurality of radio base station apparatuses 101 in the communication system. Coordinate resources for transmitting radio signals to

  In this way, radio wave interference in the wireless terminal device 202 can be effectively reduced by the configuration in which the resources related to the transmission of the wireless signal of the wireless base station device 101 are adjusted.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the transmission control unit 13 is limited as a resource at least one of information included in the radio signal, the frequency of the radio signal, and the power of the radio signal. Adjust the period.

  With such a configuration, it is possible to select an appropriate resource as an adjustment target from among the resources related to radio signal transmission of the radio base station apparatus 101, and reduce radio wave interference in the radio terminal apparatus 202.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the resource to be adjusted by the transmission control unit 13 is a frequency used for radio signal transmission.

  With such a configuration, it is possible to select an appropriate resource as an adjustment target from among the resources related to radio signal transmission of the radio base station apparatus 101, and reduce radio wave interference in the radio terminal apparatus 202.

  Further, in the radio base station apparatus according to the embodiment of the present invention, the transmission control unit 13 includes a radio base station provided in at least one of the radio base station apparatuses 101 in the communication system. The directivity of antenna 91 for transmitting a radio signal from station apparatus 101 to radio terminal apparatus 202 is adjusted.

  As described above, the configuration in which the intensity of the beam of the transmission radio wave from the radio base station apparatus 101 is adjusted can reduce radio wave interference in the radio terminal apparatus 202 and suppress the disconnection of the communication connection due to the radio wave environment. .

  Further, in the radio terminal apparatus according to the embodiment of the present invention, measurement unit 21 establishes a new communication connection with radio base station apparatus 101 after the communication connection between itself and radio base station apparatus 101 is disconnected. Measurement is performed until Based on the measurement result of the measurement unit 21, the determination unit 22 determines whether the cause of the disconnection of the communication connection is interference between radio signals transmitted by the plurality of radio base station devices 101 in the communication system. To do.

  As described above, the configuration using the own measurement result between the disconnection of the communication connection and the establishment of the new communication connection allows a plurality of wireless base stations to cause the disconnection of the communication connection between itself and the wireless base station apparatus 101. It can be determined that the radio wave from the station apparatus 101 has moved to a coverage hole where interference between radio waves from the radio base station apparatus 101 is large and sufficient reception quality cannot be obtained for any radio base station apparatus 101. That is, by determining the disconnection of the communication connection due to the radio wave environment in itself, an appropriate countermeasure can be executed and a good communication system can be constructed.

  Therefore, in the radio terminal apparatus according to the embodiment of the present invention, it is possible to stabilize the communication by determining the cause of the disconnection of the communication connection between the radio terminal apparatus and the radio base station apparatus.

  In addition, since it is not necessary to transmit the measurement result from the wireless terminal device 202 to the wireless base station device 101, processing in the wireless terminal device 202 and the wireless base station device 101 and communication traffic can be reduced.

  Further, in the radio terminal apparatus according to the embodiment of the present invention, measurement unit 21 establishes a new communication connection with radio base station apparatus 101 after the communication connection between itself and radio base station apparatus 101 is disconnected. Measurement is performed until Measurement unit 21 measures time TR from disconnection of communication connection to establishment of communication connection, or operation for establishing communication connection with radio base station apparatus 101 between the disconnection of communication connection and the establishment of communication connection Or the reception power of the radio signal from each radio base station apparatus 101 is measured a plurality of times between the disconnection of the communication connection and the establishment of the communication connection. Then, the transmission signal processing unit 87 transmits measurement information indicating the measurement result of the measurement unit 21 to the radio base station apparatus 101.

  As described above, with the configuration in which measurement is performed between the disconnection of the communication connection and the establishment of a new communication connection, a plurality of wireless base stations are caused as the cause of the disconnection of the communication connection between the wireless terminal device 202 and the wireless base station device 101 Appropriate for determining that the radio terminal device 202 has moved to a coverage hole where the interference between radio waves from the station device 101 is large and sufficient reception quality is not obtained for any radio base station device 101. Information can be acquired. That is, in the radio base station apparatus 101, it is possible to acquire appropriate information for determining disconnection of communication connection due to the radio wave environment in the radio terminal apparatus 202. Can be built.

  Therefore, in the radio terminal apparatus according to the embodiment of the present invention, it is possible to stabilize the communication by determining the cause of the disconnection of the communication connection between the radio terminal apparatus and the radio base station apparatus.

  In the radio base station apparatus according to the embodiment of the present invention, based on the measurement information acquired by the measurement information acquisition unit 11, the determination unit 12 causes the disconnection of the communication connection to be caused by a plurality of radios in the communication system. The base station apparatus 101 is configured to determine whether or not the interference is between radio signals transmitted from the base station apparatus 101. However, the present invention is not limited to this.

  Based on the measurement information acquired by the measurement information acquisition unit 11 without the transmission control unit 13 performing the determination by the determination unit 12, at least one of the plurality of radio base station devices 101 in the communication system. The configuration may be such that the radio signal transmission operation from the base station apparatus 101 to the radio terminal apparatus 202 is adjusted.

  As described above, the configuration using the measurement result of the wireless terminal device 202 from the disconnection of the communication connection to the establishment of a new communication connection causes large interference between radio waves from the plurality of wireless base station devices 101. It is possible to suppress the occurrence of a coverage hole in which sufficient reception quality is not obtained for radio waves from the radio base station apparatus 101. That is, with the configuration that adjusts the radio signal transmission operation of the radio base station apparatus 101, radio interference in the radio terminal apparatus 202 can be reduced, and disconnection of communication connection due to radio wave environment can be suppressed.

  Therefore, in the radio base station apparatus according to the embodiment of the present invention, communication can be stabilized by suppressing the disconnection of the communication connection between the radio terminal apparatus and the radio base station apparatus.

  In the embodiment of the present invention, the handover operation of the radio terminal apparatus has been specifically described. However, the inter-base station movement (inter-cell movement) operation performed by the radio terminal apparatus in communication with the radio base station apparatus. The present invention is applied not only to a certain handover but also to an inter-base station movement (inter-cell movement) operation performed by an idle wireless terminal device. That is, in the embodiment of the present invention, the present invention is also applied to a configuration and operation in which “handover” is replaced with “movement”.

  In addition, the radio base station apparatus according to the embodiment of the present invention is configured to acquire various information at the time of occurrence of RLF from radio terminal apparatus 202 using an RLF report. This “at the time of RLF occurrence” is not limited to a specific timing, and may be a timing at which the wireless terminal apparatus 202 recognizes the occurrence of RLF and any timing immediately before and after the timing.

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 11 Measurement information acquisition part 12 Discriminating part 13 Transmission control part 14 Mobile operation control part 21 Measuring part 22 Discriminating part 81 Antenna 82 Circulator 83 Wireless receiving part 84 Wireless transmitting part 85 Signal processing part 86 Received signal processing part 87 Transmission signal processing part 88 Control unit 89 Input / output unit 91 Antenna 92 Circulator 93 Wireless reception unit 94 Wireless transmission unit 95 Signal processing unit 96 Reception signal processing unit 97 Transmission signal processing unit 98 Control unit 101A, 101B, 101C Wireless base station device 202 Wireless terminal device

Claims (24)

In a communication system capable of communicating with a plurality of radio base station devices by performing a mobile operation of the radio terminal device, a radio base station device for transmitting and receiving radio signals to and from the radio terminal device,
The wireless terminal device performs the measurement after the communication connection between the wireless terminal device and the wireless base station device is disconnected until the wireless terminal device newly establishes a communication connection with the wireless base station device. A measurement information acquisition unit for acquiring measurement information indicating the result;
Based on the measurement information acquired by the measurement information acquisition unit, it is determined whether the cause of the disconnection of the communication connection is interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system. A radio base station apparatus comprising: a determination unit for The measurement information acquisition unit acquires the time from the disconnection of the communication connection to the establishment of the communication connection as the measurement information,
The radio base station apparatus according to claim 1, wherein the determination unit determines that the cause of disconnection of the communication connection is interference between the radio signals when the time is equal to or greater than a predetermined value. The measurement information acquisition unit uses, as the measurement information, the number of times that the wireless terminal device performs an operation for establishing a communication connection with a wireless base station device between the disconnection of the communication connection and the establishment of the communication connection. Acquired,
The radio base station apparatus according to claim 1 or 2, wherein the determination unit determines that the cause of disconnection of the communication connection is interference between the radio signals when the number of times is equal to or greater than a predetermined value. . The measurement information acquisition unit obtains received power information indicating a result of the wireless terminal device measuring a received power of a radio signal from each wireless base station device between the disconnection of the communication connection and the establishment of the communication connection. Obtain multiple times as the measurement information,
In the reception power information for the plurality of times, when the radio base station apparatus satisfying a predetermined condition with respect to the reception power or reception quality based on the reception power is different, the determination unit causes the disconnection of the communication connection to The radio base station apparatus according to claim 1, wherein the radio base station apparatus determines that the interference is between radio signals. The measurement information acquisition unit further acquires, as the measurement information, reception power information indicating a result of the radio terminal device measuring reception power of a radio signal from each radio base station device when the communication connection is disconnected. And
The determination unit further includes, in the received power information at the time of disconnection of the communication connection, whether the received power of the radio signal from the radio base station device selected as the communication partner by the radio terminal device is a predetermined value or more, Alternatively, when the reception power of a radio signal from a radio base station apparatus other than the radio base station apparatus is a predetermined value or more, it is determined that the cause of the disconnection of the communication connection is interference between the radio signals. The radio base station apparatus according to any one of claims 2 to 4.   Based on the measurement information acquired by the measurement information acquisition unit, the determination unit is caused by interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system, due to the disconnection of the communication connection. 6. The radio base station apparatus according to claim 1, wherein the radio base station apparatus determines whether the timing is a moving operation timing of the radio terminal apparatus.   Based on the measurement information acquired by the measurement information acquisition unit, the determination unit is caused by low reception power of a radio signal from each radio base station device in the radio terminal device due to the disconnection of the communication connection. The wireless terminal according to claim 6, wherein the wireless terminal device determines whether the wireless terminal device is a moving operation timing of the wireless terminal device or interference between wireless signals transmitted by a plurality of wireless base station devices in the communication system. Base station device. The radio base station device further includes:
When it is determined that the cause of the disconnection of the communication connection is interference between the radio signals, at least any one of the radio base station apparatuses in the communication system to the radio terminal apparatus The radio base station apparatus according to any one of claims 1 to 7, further comprising a transmission control unit for adjusting a transmission operation of a radio signal to the radio.   The radio according to claim 8, wherein the transmission control unit adjusts transmission power of a radio signal from at least one radio base station apparatus to a radio terminal apparatus among a plurality of radio base station apparatuses in the communication system. Base station device.   The said transmission control part adjusts the resource regarding the transmission of the radio signal from at least any one radio base station apparatus to the radio | wireless terminal apparatus among the several radio base station apparatuses in the said communication system. 9. The radio base station apparatus according to 9.   The radio base station apparatus according to claim 10, wherein the transmission control unit adjusts a period during which at least one of information included in the radio signal, a frequency of the radio signal, and power of the radio signal is limited. .   The radio base station apparatus according to claim 10 or 11, wherein the resource is a frequency used for transmitting the radio signal.   The transmission control unit includes an antenna for transmitting a radio signal from the radio base station apparatus to a radio terminal apparatus, which is included in at least one radio base station apparatus among a plurality of radio base station apparatuses in the communication system. The radio base station apparatus according to any one of claims 8 to 12, which adjusts directivity. In a communication system capable of communicating with a plurality of radio base station devices by performing a mobile operation of the radio terminal device, a radio base station device for transmitting and receiving radio signals to and from the radio terminal device,
The wireless terminal device performs the measurement after the communication connection between the wireless terminal device and the wireless base station device is disconnected until the wireless terminal device newly establishes a communication connection with the wireless base station device. A measurement information acquisition unit for acquiring measurement information indicating the result;
Based on the measurement information acquired by the measurement information acquisition unit, an operation of transmitting a radio signal from at least one radio base station apparatus to a radio terminal apparatus among a plurality of radio base station apparatuses in the communication system is performed. A radio base station apparatus comprising: a transmission control unit for adjusting. A wireless terminal device capable of communicating with a plurality of wireless base station devices by performing a moving operation,
A measurement unit for performing measurement in a period from when the communication connection between itself and the radio base station apparatus is disconnected until establishing a new communication connection with the radio base station apparatus;
A determination unit for determining whether the cause of disconnection of the communication connection is interference between the radio signals transmitted by a plurality of radio base station devices, based on the measurement result of the measurement unit; Wireless terminal device. A wireless terminal device capable of communicating with a plurality of wireless base station devices by performing a moving operation,
A measurement unit for performing measurement in a period from when the communication connection between itself and the radio base station apparatus is disconnected until establishing a new communication connection with the radio base station apparatus;
A transmission unit for transmitting measurement information indicating a measurement result of the measurement unit to a radio base station device;
The measurement unit measures the time from the disconnection of the communication connection to the establishment of the communication connection, or establishes the communication connection with the radio base station apparatus between the disconnection of the communication connection and the establishment of the communication connection. A wireless terminal device that measures the number of times the operation is performed or measures the received power of a wireless signal from each wireless base station device a plurality of times during the period from the disconnection of the communication connection to the establishment of the communication connection. A communication control method in a radio base station apparatus for transmitting and receiving radio signals to and from a radio terminal apparatus in a communication system capable of communicating with a plurality of radio base station apparatuses by performing a mobile operation of the radio terminal apparatus,
The wireless terminal device performs the measurement after the communication connection between the wireless terminal device and the wireless base station device is disconnected until the wireless terminal device newly establishes a communication connection with the wireless base station device. Obtaining measurement information indicating the results;
Determining whether the cause of disconnection of the communication connection is interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system based on the acquired measurement information. Control method. A communication control method in a radio base station apparatus for transmitting and receiving radio signals to and from a radio terminal apparatus in a communication system capable of communicating with a plurality of radio base station apparatuses by performing a mobile operation of the radio terminal apparatus,
The wireless terminal device performs the measurement after the communication connection between the wireless terminal device and the wireless base station device is disconnected until the wireless terminal device newly establishes a communication connection with the wireless base station device. Obtaining measurement information indicating the results;
Adjusting a transmission operation of a radio signal from at least one radio base station apparatus to a radio terminal apparatus among a plurality of radio base station apparatuses in the communication system based on the acquired measurement information. Communication control method. A communication control method in a wireless terminal device capable of communicating with a plurality of wireless base station devices by performing a moving operation,
Measuring between the time when the communication connection between itself and the radio base station apparatus is disconnected until a new communication connection with the radio base station apparatus is established;
Determining whether or not the cause of the disconnection of the communication connection is interference between the radio signals transmitted by a plurality of radio base station apparatuses based on the measured result. A communication control method in a wireless terminal device capable of communicating with a plurality of wireless base station devices by performing a moving operation,
Measuring between the time when the communication connection between itself and the radio base station apparatus is disconnected until a new communication connection with the radio base station apparatus is established;
Transmitting measurement information indicating a measurement result to the radio base station apparatus,
In the step of performing the measurement, the time from the disconnection of the communication connection to the establishment of the communication connection is measured, or the communication connection with the radio base station apparatus is established between the disconnection of the communication connection and the establishment of the communication connection. Communication control for measuring the number of times of performing the operation for establishing or measuring the reception power of the radio signal from each radio base station apparatus a plurality of times during the period from disconnection of the communication connection to establishment of the communication connection Method. A communication control program used in a radio base station apparatus for transmitting and receiving radio signals to and from a radio terminal apparatus in a communication system capable of communicating with a plurality of radio base station apparatuses by performing a moving operation of the radio terminal apparatus. To the computer
The wireless terminal device performs the measurement after the communication connection between the wireless terminal device and the wireless base station device is disconnected until the wireless terminal device newly establishes a communication connection with the wireless base station device. Obtaining measurement information indicating the results;
Determining whether the cause of the disconnection of the communication connection is interference between radio signals transmitted by a plurality of radio base station apparatuses in the communication system based on the acquired measurement information Communication control program. A communication control program used in a radio base station apparatus for transmitting and receiving radio signals to and from a radio terminal apparatus in a communication system capable of communicating with a plurality of radio base station apparatuses by performing a moving operation of the radio terminal apparatus. To the computer
The wireless terminal device performs the measurement after the communication connection between the wireless terminal device and the wireless base station device is disconnected until the wireless terminal device newly establishes a communication connection with the wireless base station device. Obtaining measurement information indicating the results;
Adjusting a transmission operation of a radio signal from at least one radio base station apparatus to a radio terminal apparatus among a plurality of radio base station apparatuses in the communication system based on the acquired measurement information Communication control program for A communication control program used in a wireless terminal device capable of communicating with a plurality of wireless base station devices by performing a moving operation,
Measuring between the time when the communication connection between itself and the radio base station apparatus is disconnected until a new communication connection with the radio base station apparatus is established;
A communication control program for determining whether or not the cause of the disconnection of the communication connection is interference between the radio signals transmitted by a plurality of radio base station apparatuses based on the measured result . A communication control program used in a wireless terminal device capable of communicating with a plurality of wireless base station devices by performing a moving operation,
Measuring between the time when the communication connection between itself and the radio base station apparatus is disconnected until a new communication connection with the radio base station apparatus is established;
A program for executing the step of transmitting measurement information indicating a measurement result to the radio base station device,
In the step of performing the measurement, the time from the disconnection of the communication connection to the establishment of the communication connection is measured, or the communication connection with the radio base station apparatus is established between the disconnection of the communication connection and the establishment of the communication connection. Communication control for measuring the number of times of performing the operation for establishing or measuring the reception power of the radio signal from each radio base station apparatus a plurality of times during the period from disconnection of the communication connection to establishment of the communication connection program.

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