Patent Description:
Technology for providing a wireless communication service by a cell formed by a wireless base station is known (for example, see <CIT>). <CIT> describes a mobile communications system in which an E-UTRAN base station dynamically changes its handover and/or its cell reselection parameters to control the load on the base station and which transmits a message to a non E-UTRAN neighbouring cell, so that it can adapt its handover and/or its cell reselection parameters to avoid repeated handover and/or cell reselection of a mobile communications device between the non E-UTRAN cell and the E-UTRAN cell. <CIT> describes an apparatus and methods of handing over a wireless transmit/receive unit (WTRU) that belongs to a group of WTRUs from an originating base station to a target base station are described. A method includes the WTRU obtaining information regarding a group to which the WTRU has been assigned and the WTRU receiving at least one of handover reconfiguration information that is common to the group and handover reconfiguration information that is specific to the WTRU. On a condition that the WTRU receives the handover reconfiguration information that is specific to the WTRU, the WTRU initiates a synchronization procedure with the target base station based at least on the received handover reconfiguration information. <CIT> describes access nodes in a network which are configured to periodically measure cell loads and exchange cell load measurements with neighbors. At each access node, cell loads are compared with load thresholds, and with neighboring loads, to determine whether or not load balancing operations should be triggered. Load balancing operations include reducing or increasing an effective coverage area of one or both of the congested cell and the neighbor cell by adjusting a handover threshold parameter, such as a threshold signal level. Adjusting thresholds at a congested cell triggers more handovers from the congested cell to the non-congested cell. Similarly, adjusting thresholds at a non-congested cell prevents handovers from the non-congested cell to the congested cell. <CIT> describes a method which comprises receiving a measurement report for a handover at a source evolved Node B (eNodeB) of a Long Term Evolution (LTE) communication network. The measurement report is received from a user equipment (UE) served by the source eNodeB. A determination is made whether the UE is dormant. A determination is made whether a current load level for the handover is over a threshold. The measurement report is discarded if the current load level is over the threshold and the UE is dormant. The handover is triggered based on the measurement report if the current load level is not over the threshold or the UE is not dormant.

It is desirable to provide a technology that can appropriately reduce a load of a wireless base station.

Embodiments of the invention are describedin the dependent claims. According to a first aspect of the present invention, a base station device configured to form a cell to provide a wireless communication service to a user terminal within the cell is provided. The base station device includes a handover threshold storing unit for storing a handover threshold which is set for the user terminal that starts a wireless connection to the base station device. The base station device includes a load determining unit for determining whether a load condition indicating that a load of the base station device is high is satisfied or not. The base station device includes a handover threshold change unit for changing the handover threshold so as to suppress a handover from the base station device of a user terminal which establishes a wireless connection with the base station device when it is determined that the load condition is satisfied.

The load determining unit determines that the load condition is satisfied when the load of the base station device is higher than a predetermined load threshold, and determines that the load condition is not satisfied when the load of the base station device is lower than the load threshold. The load determining unit determines that the load condition is satisfied when a CPU usage rate of the base station device is higher than a predetermined usage rate threshold, and determines that the load condition is not satisfied when the CPU usage rate of the base station device is lower than the usage rate threshold.

The handover threshold change unit increases, when the load determining unit determines that the load condition is satisfied, the handover threshold for determining whether or not received radio wave intensity from a neighbor cell is stronger than received radio wave intensity from a serving cell by the handover threshold or more. The handover threshold change unit may change the handover threshold from a default value to a first handover threshold higher than the default value when the load determining unit determines that the load condition is satisfied. The handover threshold change unit may change the handover threshold to the default value when the load determining unit determines that the load condition is not satisfied after the handover threshold is changed to the first handover threshold. The load determining unit may determine that the load condition is satisfied when the load of the base station device is higher than a predetermined first load threshold, the handover threshold change unit may change the handover threshold to the first handover threshold when the load of the base station device is higher than the first load threshold and lower than a second load threshold which is higher than the first load threshold, and the handover threshold change unit may change the handover threshold to a second handover threshold which is higher than the first handover threshold when the load of the base station device is higher than the second load threshold.

The base station device may include: a measurement report receiving unit for receiving a measurement report to report a measurement result of a received radio wave which is generated by the user terminal and transmitted by the user terminal; a handover determining unit for determining whether or not to handover the user terminal based on the measurement report; and a handover control unit for performing control in order to handover the user terminal which is determined, by the handover determining unit, to be handed over. The handover threshold change unit may use the first handover threshold and the second handover threshold which are determined based on the measurement report when the handover determining unit determines to handover the user terminal.

The base station device may include: a measurement report storing unit for storing a measurement report when the handover determining unit determines to handover the user terminal; and a handover threshold deriving unit for deriving the first handover threshold and the second handover threshold based on a plurality of measurement reports stored in the measurement report storing unit. The base station device may include: a measurement report transmitting unit for transmitting, to a management device, a measurement report in a case of the handover determining unit determining to handover the user terminal; and a handover threshold receiving unit for receiving, from the management device, the first handover threshold and the second handover threshold which are derived, by the management device, based on a plurality of the measurement reports.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to claims. In addition, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

<FIG> and <FIG> are diagrams schematically illustrating an example of a wireless base station <NUM>. A plurality of wireless base stations are positioned around the wireless base station <NUM>, but in <FIG> and <FIG>, only one wireless base station <NUM> adjacent to the wireless base station <NUM> is illustrated. The wireless base station <NUM> may be an example of a base station device. A control device which is mounted on the wireless base station <NUM> to control an operation of the wireless base station <NUM> may be an example of the base station device.

The wireless base station <NUM> forms a cell <NUM> to provide a wireless communication service to a user terminal <NUM> within the cell <NUM>. A user terminal <NUM> may be any terminal as long as it is a communication terminal which can communicate with the wireless base station <NUM>. For example, the user terminal <NUM> is a mobile phone such as a smartphone. The user terminal <NUM> may be a tablet terminal, a PC (Personal Computer) and the like. The user terminal <NUM> may also be a so-called IoT (Internet of Thing) device. The user terminal <NUM> may include all things corresponding to a so-called IoE (Internet of Everything).

The user terminal <NUM> may assume a state in which it is existing within the cell <NUM> but not performing a wireless connection with the wireless base station <NUM>, and a state in which it is existing within the cell <NUM> and performing a wireless connection with the wireless base station <NUM> (the former may be described as an idle state, and the latter may be described as a connected state). In <FIG> and <FIG>, only the user terminal <NUM> existing in the wireless base station <NUM> is illustrated.

HO available area <NUM> schematically illustrates an area in which the user terminal <NUM> can be handed over from the cell <NUM> of the wireless base station <NUM> to a cell <NUM> of the wireless base station <NUM>. A size of the HO available area <NUM> is changed by changing a handover threshold (may be described as an HO threshold) which is set to the user terminal <NUM> by the wireless base station <NUM>.

For example, when an event type trigger A2 is set as a timing for the user terminal <NUM> to transmit a Measurement Report (may be described as an MR) to the wireless base station <NUM>, the lower the HO threshold is, the narrower the HO available area <NUM> is. Also, when an event type trigger A5 is set, the HO available area <NUM> becomes narrower as a threshold to be compared with the received radio wave intensity from the serving cell becomes lower and as a threshold to be compared with the received radio wave intensity from the neighbor cell becomes higher.

Also, when an event type trigger A3 is set, the HO available area <NUM> becomes narrower as an HO threshold indicating an offset becomes higher. In the present embodiment, examples in which the event type trigger A3 is employed as MR transmission timing will be mainly described.

The load of the wireless base station <NUM> increases by various factors, one of which is a control signal received from the user terminal <NUM>. For example, when the wireless base station <NUM> receives MRs from numerous user terminals <NUM>, the load for processing the numerous MRs increases. If the load of the wireless base station <NUM> increases, a situation where the handover of the user terminal <NUM> cannot be processed occurs, and a situation may occur where a user terminal <NUM> which cannot be handed over even though it cannot communicate due to an electric field that is really deteriorated and a user terminal <NUM> which can still communicate but is handed over are interspersed.

The wireless base station <NUM> according to the present embodiment changes the handover threshold which is set for the user terminal <NUM> that starts a wireless connection to the wireless base station <NUM> so that a handover from the wireless base station <NUM> of the user terminal <NUM> which establishes a wireless connection with the wireless base station <NUM> is suppressed when the load of the wireless base station <NUM> is increased. For example, when the load of the wireless base station <NUM> is increased, the wireless base station <NUM> increases the HO threshold for determining whether or not the received radio wave intensity from the neighbor cell is stronger than the received radio wave intensity from the serving cell by the HO threshold or more.

As a specific example, the wireless base station <NUM> changes the HO threshold to a first HO threshold which is higher than a default value when the load of the wireless base station <NUM> is increased. In this way, the first HO threshold which is higher than the default value can be set for the user terminal <NUM> that subsequently starts the wireless connection with the wireless base station <NUM>. The user terminal <NUM> that starts the wireless connection with the wireless base station <NUM> is, for example, a user terminal <NUM> which transits from an idle state to a connected state, a user terminal <NUM> which is handed over to the cell <NUM> of the wireless base station <NUM>, and the like. In this way, as illustrated in <FIG> and <FIG>, the HO available area <NUM> for the user terminal <NUM> that newly established the wireless connection with the wireless base station <NUM> can be narrowed, and the number of transmissions of MR to the wireless base station <NUM> can be reduced. By reducing the number of the MR received by the wireless base station <NUM>, the number of MR processing by the wireless base station <NUM> can be reduced, and the load of the wireless base station <NUM> can be reduced. In particular, a handover of a user terminal <NUM> with a good electric field among the user terminals <NUM> that reached an HO reference by increasing the HO threshold is suppressed, and the load of the wireless base station <NUM> can be reduced while allowing a handover of a user terminal <NUM> with a deteriorated electric field not to be suppressed. By causing targeted user terminals <NUM> with more deteriorated electric fields to perform the handover, a user terminal <NUM> which continues to switch between the same cells can be suppressed, and the number of HO perform signals can be significantly reduced.

The wireless base station <NUM> may reduce the HO threshold when the load of the wireless base station <NUM> is reduced after increasing the HO threshold. As a specific example, the wireless base station <NUM> changes the HO threshold to the default value. In this way, by limiting the handover of the user terminal <NUM> even though the load of the wireless base station <NUM> is not high, the occurrence of a situation where the user terminal <NUM> which normally should be handed over cannot be handed over can be suppressed.

The wireless base station <NUM> may gradually increase the HO threshold in accordance with the increase of the load of the wireless base station <NUM>. For example, the wireless base station <NUM> changes the HO threshold to the first HO threshold when the load of the wireless base station <NUM> becomes higher than the first load threshold, and changes the HO threshold to a second HO threshold which is higher than the first HO threshold when the load of the wireless base station <NUM> becomes higher than a second load threshold which is higher than the first load threshold. In this way, when the load of the wireless base station <NUM> is further increased for some reasons even though the number of MR receptions are reduced by changing the HO threshold to the first HO threshold, further reduction of the MR reception can contribute to the reduction of the load of the wireless base station <NUM>. The steps for increasing the HO threshold are not limited to two steps, but may be <NUM> steps or more.

The wireless base station <NUM> may determine whether the load of the wireless base station <NUM> is high or not, based on whether the load condition indicating that the load of the wireless base station <NUM> is high is satisfied or not. For example, the wireless base station <NUM> determines that the load of the wireless base station <NUM> is high when the load of the wireless base station <NUM> is higher than a predetermined load threshold, and determines that the load of the wireless base station <NUM> is low when the load of the wireless base station <NUM> is lower than the load threshold. As a specific example, the wireless base station <NUM> determines that the load of the wireless base station <NUM> is high when the CPU usage rate of the wireless base station <NUM> is higher than a predetermined usage rate threshold, and determines that the load of the wireless base station <NUM> is low when the CPU usage rate of the wireless base station <NUM> is lower than the usage rate threshold. These thresholds may be set arbitrarily, for example, by an administrator who manages the wireless base station <NUM>.

The wireless base station <NUM> may pre-store a value of the HO threshold set for the user terminal <NUM>. For example, the wireless base station <NUM> pre-stores the default value, the first HO threshold and the second HO threshold. These values may be set arbitrarily, for example, by an administrator who manages the wireless base station <NUM>. Also, these values may be determined by a network management system (may be described as NMS (Network Management System)) for managing the wireless base station <NUM>, and notified to the wireless base station <NUM>. The NMS may be an example of a management device.

<FIG> is a diagram schematically illustrating an example of a system <NUM>. The system <NUM> includes a plurality of wireless base stations <NUM> and an NMS <NUM>.

The plurality of wireless base stations <NUM> and the NMS <NUM> are communicating via a network <NUM>. The network <NUM> includes a mobile communication network. The mobile communication network may comply with any of <NUM> (<NUM>rd Generation) communication scheme, LTE (Long Term Evolution) communication scheme, <NUM> (<NUM>th Generation) communication scheme and a communication scheme after <NUM> (<NUM>th Generation) communication scheme. The network <NUM> may include the Internet.

Each of the plurality of wireless base stations <NUM> reports the MR which is a handover trigger (may be described as an HO trigger) of the existing user terminal <NUM> to the NMS <NUM>. The NMS <NUM> produces a distribution of the offset value based on the MR which is reported from the wireless base station <NUM> for each cell. The NMS <NUM> may compute the offset value based on a cumulative distribution for each cell. The NMS <NUM> may set HO thresholds at a high load gradually for each cell based on the computed offset value for the wireless base station <NUM>.

When the load of the wireless base station <NUM> is increased, the wireless base station <NUM> may set an HO threshold set from the NMS <NUM> as a handover threshold set for the user terminal <NUM> that starts the wireless connection to the wireless base station <NUM>. The wireless base station <NUM> may gradually change the HO threshold according to a load situation of the wireless base station <NUM>, and may continue the change of the HO threshold until the load falls below a reference load. The wireless base station <NUM> may return the HO threshold to the default value when the load of the wireless base station <NUM> falls below the reference load.

The NMS <NUM> may periodically perform an update of the HO threshold. The NMS <NUM> performs the update of the HO threshold for each predetermined period of time such as on a weekly basis, daily basis, or per hour basis, for example. For example, for each of the plurality of wireless base stations <NUM>, the NMS <NUM> derives the HO threshold based on the MR received during each period and sets the derived HO threshold.

The NMS <NUM> may reduce a frequency of the update of the HO threshold if the same tendency is found in continuous periods of time based on past statistics. In this way, the load of the NMS <NUM> and the wireless base station <NUM> required for the update can be reduced.

<FIG> is a diagram schematically illustrating an example of a flow of a processing performed by the system <NUM>. Herein, a flow of a processing which starts from establishing a wireless connection with a wireless base station <NUM> by one user terminal <NUM> and ends by a handover to a wireless base station <NUM> which is a neighbor cell of the wireless base station <NUM> is schematically illustrated.

In step (the step may be described as S for short) <NUM>, the user terminal <NUM> and the wireless base station <NUM> establish a connection.

In S104, the wireless base station <NUM> performs various settings for the user terminal <NUM>. For example, the wireless base station <NUM> transmits an RRC connection reconfiguration to the user terminal <NUM>, and the user terminal <NUM> transmits an RRC connection reconfiguration complete to the wireless base station <NUM>.

The wireless base station <NUM> may cause the user terminal <NUM> to set the transmission trigger and the HO threshold of the MR by the RRC connection reconfiguration. The wireless base station <NUM> causes the user terminal <NUM> to set the transmission trigger of the MR as an event type trigger A3 and set the HO threshold as a default value, for example.

In S106, the user terminal <NUM> transmits the MR to the wireless base station <NUM> in accordance with the fact that a difference between received radio wave intensity from the wireless base station <NUM> and received radio wave intensity from the wireless base station <NUM> exceeds the HO threshold. The MR may include the received radio wave intensity of the wireless base station <NUM> and the received radio wave intensity of the wireless base station <NUM>. The wireless base station <NUM> determines whether to handover the user terminal <NUM> or not based on the received MR. Herein, the description continues assuming that no handover is determined to be performed.

In S108, the user terminal <NUM> transmits the MR to the wireless base station <NUM> in accordance with the fact that a difference between the received radio wave intensity from the wireless base station <NUM> and the received radio wave intensity from the wireless base station <NUM> exceeds the HO threshold. In S110, the wireless base station <NUM> determines to handover the user terminal <NUM> to the wireless base station <NUM> based on the MR received in S <NUM>.

In S112, the wireless base station <NUM> transmits, to the wireless base station <NUM>, an HO request for handing over the user terminal <NUM> to the wireless base station <NUM>. In S114, the wireless base station <NUM> transmits an HO instruction to the user terminal <NUM> instructing that it will be handed over to the wireless base station <NUM>. It should be noted that, the case where an X2 handover is performed is illustrated herein, but the wireless base station <NUM> may perform another handover such as an S1 handover.

In S116, the wireless base station <NUM> transmits, to the NMS <NUM>, the MR received from the user terminal <NUM> in S108, wherein the MR is the HO trigger of the user terminal <NUM>. In S118, an HO processing is performed between the user terminal <NUM> and the wireless base station <NUM>, and the user terminal <NUM> is handed over to the wireless base station <NUM>.

By transmitting the MR which is the HO trigger to the NMS <NUM> each time the wireless base station <NUM> causes the user terminal <NUM> to be handed over, the NMS <NUM> can collect a plurality of MRs. The NMS <NUM> may derive the HO threshold based on the plurality of MRs that are collected.

<FIG> is a diagram schematically illustrating an example of a functional configuration of an NMS <NUM>. The NMS <NUM> includes a measurement report receiving unit <NUM>, a measurement report storing unit <NUM>, an HO threshold deriving unit <NUM>, and an HO threshold transmitting unit <NUM>.

The measurement report receiving unit <NUM> receives, from the wireless base station <NUM>, an MR in the case where it is determined that the wireless base station <NUM> causes the user terminal <NUM> to be handed over based on the MR from the user terminal <NUM> existing in the wireless base station <NUM> (the MR which is the HO trigger).

The measurement report storing unit <NUM> stores, in association with base station identification information of the wireless base station <NUM>, the MR that the measurement report receiving unit <NUM> received from the wireless base station <NUM>. The measurement report storing unit <NUM> stores, in association with base station identification information of each of the plurality of wireless base station <NUM>, the MR that the measurement report receiving unit <NUM> received from each of the plurality of wireless base station <NUM>.

The HO threshold deriving unit <NUM> derives, for each of the plurality of wireless base stations <NUM>, an HO threshold based on the plurality of MRs corresponding to the wireless base stations <NUM> which are stored in the measurement report storing unit <NUM>.

The HO threshold deriving unit <NUM> may derive the HO threshold for each transmission trigger of the MRs. For example, when an event type trigger A3 is employed, the HO threshold deriving unit <NUM> derives the HO threshold based on the received radio wave intensity from the serving cell and the received radio wave intensity from the neighbor cell included in the MRs. The HO threshold deriving unit <NUM> may derive the HO threshold based on a differential between the received radio wave intensity from the serving cell and the received radio wave intensity from the neighbor cell. The HO threshold deriving unit <NUM> derives the HO threshold based on a cumulative distribution of a plurality of differentials acquired from the plurality of MRs, for example.

The HO threshold deriving unit <NUM> may derive a value of a differential among the plurality of differentials, in which the cumulative distribution exceeds a predetermined first percentage, as a first HO threshold, and derive a value of a differential among the plurality of differentials, in which the cumulative distribution exceeds a second percentage, as a second HO threshold, for example. The second percentage is greater than the first percentage. The first percentage and the second percentage may be set arbitrarily, for example, by an administrator and the like of the NMS <NUM>.

Also, for example, when an event type trigger A2 is employed, the HO threshold deriving unit <NUM> derives the HO threshold based on the received radio wave intensity from the serving cell included in the MRs. The HO threshold deriving unit <NUM> derives the HO threshold based on a cumulative distribution of the received radio wave intensity from the serving cell included in the plurality of MRs, for example. The HO threshold deriving unit <NUM> may derive a value of received radio wave intensity among the plurality of received radio wave intensities, in which the cumulative distribution exceeds a predetermined first percentage, as a first HO threshold, and derive a value of received radio wave intensity among the plurality of received radio wave intensities, in which the cumulative distribution exceeds a second percentage which is greater than the first percentage, as a second HO threshold, for example.

Also, for example, when an event type trigger A5 is employed, the HO threshold deriving unit <NUM> derives an HO threshold for the serving cell and an HO threshold for the neighbor cell based on the received radio wave intensity from the serving cell and the received radio wave intensity from the neighbor cell included in the MR. The HO threshold deriving unit <NUM> derives an HO threshold for the serving cell and an HO threshold for the neighbor cell based on the cumulative distribution of the received radio wave intensity from the serving cell included in the plurality of MRs and a cumulative distribution of received radio wave intensity from the neighbor cell included in the plurality of MRs, for example.

The HO threshold deriving unit <NUM> may intermittently derive the HO threshold according to a predetermined timing. The HO threshold deriving unit <NUM> periodically derives the HO threshold according to a predetermined period, for example. The HO threshold deriving unit <NUM> performs the derivation of the HO threshold for each predetermined period of time such as on a weekly basis, daily basis, or per hour basis, for example. The HO threshold deriving unit <NUM> derives the HO threshold based on the MR received during each period, for example.

The HO threshold deriving unit <NUM> may reduce a frequency of the derivation of the HO threshold if the same tendency is found in continuous periods of time based on past statistics. For example, the HO threshold deriving unit <NUM> changes a derivation timing of the HO threshold from a daily basis to a weekday basis and Saturday, Sunday and National holiday basis, in the case in which the HO threshold is derived on a daily basis and in which a difference between the HO thresholds derived on weekdays are within a predetermined range, a difference between the HO thresholds derived on Saturday, Sunday and National holiday are within a predetermined range, and a difference between the HO thresholds derived on weekdays and the HO thresholds derived on Saturday, Sunday and National holiday exceeds a predetermined range. In this way, the load of the NMS <NUM> and the wireless base station <NUM> required for the update can be appropriately reduced.

The HO threshold transmitting unit <NUM> transmits the HO threshold derived by the HO threshold deriving unit <NUM> to the wireless base station <NUM>. The HO threshold transmitting unit <NUM> transmits, to each of the plurality of wireless base stations <NUM>, the HO threshold derived by the HO threshold deriving unit <NUM> for each of the plurality of wireless base stations <NUM>.

<FIG> is a diagram schematically illustrating an example of a cumulative distribution graph <NUM>. Herein, examples in which the event type trigger A3 is employed as a transmission trigger of the MR will be described. The horizontal axis represents an offset value indicating a differential between the received radio wave intensity from the serving cell and the received radio wave intensity from the neighbor cell included in the MR. The vertical axis represents a percentage of each of the plurality of offset values relative to the total.

In the example indicated in <FIG>, the NMS <NUM> may assume 5dB that is an offset value for which the cumulative distribution exceeds X% as a first HO threshold, and assume 9dB that is an offset value whose cumulative distribution exceeds Y% as a second HO threshold. The values of X and Y may be set arbitrarily, for example, by an administrator and the like of the NMS <NUM>.

<FIG> is a diagram schematically illustrating an example of a cumulative distribution graph <NUM>. The cumulative distribution graph <NUM> corresponds to a cell different from the cumulative distribution graph <NUM>.

In the example indicated in <FIG>, the NMS <NUM> assumes 6dB that is an offset value whose cumulative distribution exceeds X% as a first HO threshold, and assume 8dB that is an offset value whose cumulative distribution exceeds Y% as a second HO threshold. As illustrated in <FIG> and <FIG>, since the distribution of the MR is different for each cell, different HO thresholds may be derived for each cell.

<FIG> is a diagram schematically illustrating an example of a functional configuration of a base station device <NUM>. The base station device <NUM> is mounted on the wireless base station <NUM>. The base station device <NUM> includes an HO threshold storing unit <NUM>, a terminal control unit <NUM>, a measurement report receiving unit <NUM>, an HO determining unit <NUM>, a measurement report storing unit <NUM>, a measurement report transmitting unit <NUM>, an HO threshold receiving unit <NUM>, an HO threshold deriving unit <NUM>, a load determining unit <NUM>, and an HO threshold change unit <NUM>. It should be noted that it is not always necessary for the base station device <NUM> to include all these components.

The HO threshold storing unit <NUM> stores the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM>. The HO threshold storing unit <NUM> may store the plurality of HO thresholds which corresponds to the height of the load of the base station device <NUM>.

The HO threshold storing unit <NUM> may store the HO threshold for each transmission trigger of the MRs. The HO threshold storing unit <NUM> stores, for example, an HO threshold for an event type trigger A3, an HO threshold for an event type trigger A2, an HO threshold for an event type trigger A5.

The terminal control unit <NUM> performs various controls with the user terminal <NUM>. The terminal control unit <NUM> establishes a communication connection with the user terminal <NUM>, for example. Also, the terminal control unit <NUM> performs various settings for the user terminal <NUM>, for example. The terminal control unit <NUM> may set a transmission trigger of the MR for the user terminal <NUM>. Also, the terminal control unit <NUM> may set the HO threshold for the user terminal <NUM>. The terminal control unit <NUM> transmits, for example to the user terminal <NUM> that starts a wireless connection to the base station device <NUM>, a transmission trigger of a preset MR, and an HO threshold to be set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM>, the HO threshold being stored in the HO threshold storing unit <NUM>, and then sets the HO threshold for the user terminal <NUM>.

The measurement report receiving unit <NUM> receives the MR from the user terminal <NUM> existing in the wireless base station <NUM>. The measurement report receiving unit <NUM> receives the MR transmitted by the user terminal <NUM>, in accordance with the transmission trigger which is set by the terminal control unit <NUM>.

The HO determining unit <NUM> determines, when the measurement report receiving unit <NUM> receives the MR, whether or not to handover the user terminal <NUM> which has transmitted the MR, based on the MR. The HO determining unit <NUM> may determine whether or not to handover the user terminal <NUM> based on the MR as with the existing wireless base station.

When the HO determining unit <NUM> determines to handover the user terminal <NUM>, the terminal control unit <NUM> performs control to handover the user terminal <NUM>. The terminal control unit <NUM> may be an example of a handover control unit.

A handover manner may be similar to the existing manner. For example, when performing an X2 handover, the terminal control unit <NUM> transmits an HO request to the wireless base station <NUM> which is a handover destination, and transmits an HO instruction to the user terminal <NUM>. The terminal control unit <NUM> transmits the HO request to an MME (Mobility Management Entity) when performing an S1 handover, for example.

The measurement report storing unit <NUM> stores the MR in the case where the HO determining unit <NUM> is determined to handover the user terminal <NUM>. The measurement report transmitting unit <NUM> transmits the MR which is stored in the measurement report storing unit <NUM> to the NMS <NUM>.

The measurement report transmitting unit <NUM> may transmit the MR to the NMS <NUM> according to a preset timing. The measurement report transmitting unit <NUM> transmits the MR to the NMS <NUM> every time the measurement report storing unit <NUM> stores the MR, for example. Also, for example, for each predetermined period of time, the measurement report transmitting unit <NUM> transmits, to the NMS <NUM>, the MR which is stored by the measurement report storing unit <NUM> during each period.

It should be noted that the measurement report storing unit <NUM> may store all the MRs received by the measurement report receiving unit <NUM> and the measurement report transmitting unit <NUM> may transmit only MRs that are the HO triggers to the NMS <NUM>, among the MRs stored in the measurement report storing unit <NUM>.

The HO threshold receiving unit <NUM> receives, from the NMS <NUM>, the HO threshold derived by the NMS <NUM> based on the MR which is transmitted by the measurement report transmitting unit <NUM>. The NMS <NUM> may derive the HO threshold for each transmission trigger of the MR and transmit it to the base station device <NUM>.

The HO threshold deriving unit <NUM> derives the HO threshold based on the MR stored in the measurement report storing unit <NUM>. The HO threshold deriving unit <NUM> may derive the HO threshold using a similar method as the NMS <NUM>.

The load determining unit <NUM> determines whether a load condition indicating that a load of the base station device <NUM> is high is satisfied or not. The load determining unit <NUM> determines that the load condition is satisfied when the load of the base station device <NUM> is higher than a predetermined load threshold, and determines that the load condition is not satisfied when the load of the base station device <NUM> is lower than the load threshold, for example. The load determining unit <NUM> may determine that the load condition is satisfied when a CPU usage rate of the base station device <NUM> is higher than a predetermined usage rate threshold, and determine that the load condition is not satisfied when the CPU usage rate of the base station device <NUM> is lower than the usage rate threshold.

When the load determining unit <NUM> determines that the load condition is satisfied, the HO threshold change unit <NUM> changes the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM>, which is stored in the HO threshold storing unit <NUM>, such that a handover from the base station device <NUM> of the user terminal <NUM> which establishes the wireless connection between the base station device <NUM> is suppressed.

The HO threshold change unit <NUM> may gradually change the HO threshold until the load of the base station device <NUM> becomes lower than a predetermined load threshold when the load of the base station device <NUM> is higher than the predetermined load threshold. In this way, the load of the base station device <NUM> can be appropriately reduced to the predetermined load without excessively suppressing the handover of the user terminal <NUM>.

The HO threshold change unit <NUM> may change the HO threshold to the HO threshold which corresponds to the height of the load of the base station device <NUM>. In this way, the appropriate HO threshold can be set for the user terminal <NUM>, the appropriate HO threshold corresponding to a situation of the load of the base station device <NUM>.

When an event type trigger A3 is employed as the transmission trigger of the MR, the HO threshold change unit <NUM> increases the HO threshold for determining whether or not received radio wave intensity from a neighbor cell is stronger than received radio wave intensity from a serving cell by the HO threshold or more. The HO threshold change unit <NUM> may change the HO threshold from a default value to a first HO threshold which is higher than the default value. The HO threshold change unit <NUM> uses a first HO threshold which is preset by an administrator and the like of the wireless base station <NUM>, for example. Also, the HO threshold change unit <NUM> may use a first HO threshold that the HO threshold receiving unit <NUM> received from the NMS <NUM>. Also, the HO threshold change unit <NUM> may use a first HO threshold derived from the HO threshold deriving unit <NUM>. The HO threshold change unit <NUM> may change the HO threshold to the default value when the load determining unit <NUM> determines that the load condition is not satisfied after the HO threshold is changed to the first HO threshold. The HO threshold change unit <NUM> may change the HO threshold into the first HO threshold when the load of the base station device <NUM> is higher than a first load threshold and lower than a second load threshold, and the HO threshold change unit <NUM> may change the HO threshold to a second HO threshold which is higher than the first HO threshold when the load of the base station device <NUM> is higher than the second load threshold. The HO threshold change unit <NUM> uses a second HO threshold which is preset by an administrator and the like of the wireless base station <NUM>, for example. Also, the HO threshold change unit <NUM> may use a second HO threshold that the HO threshold receiving unit <NUM> received from the NMS <NUM>. Also, the HO threshold change unit <NUM> may use a second HO threshold derived from the HO threshold deriving unit <NUM>.

When an event type trigger A2 is employed as the transmission trigger of the MR, the HO threshold change unit <NUM> reduces the HO threshold for determining whether or not received radio wave intensity from the serving cell is lower than the HO threshold. The HO threshold change unit <NUM> may change the HO threshold from a default value to a first HO threshold which is lower than the default value. The HO threshold change unit <NUM> uses a first HO threshold which is preset by an administrator and the like of the wireless base station <NUM>, for example. Also, the HO threshold change unit <NUM> may use a first HO threshold that the HO threshold receiving unit <NUM> received from the NMS <NUM>. Also, the HO threshold change unit <NUM> may use a first HO threshold derived from the HO threshold deriving unit <NUM>. The HO threshold change unit <NUM> may change the HO threshold to the default value when the load determining unit <NUM> determines that the load condition is not satisfied after the HO threshold is changed to the first HO threshold. The HO threshold change unit <NUM> may change the HO threshold into the first HO threshold when the load of the base station device <NUM> is higher than a first load threshold and lower than a second load threshold, and the HO threshold change unit <NUM> may change the HO threshold to a second HO threshold which is higher than the first HO threshold when the load of the base station device <NUM> is lower than the second load threshold. The HO threshold change unit <NUM> uses a second HO threshold which is preset by an administrator and the like of the wireless base station <NUM>, for example. Also, the HO threshold change unit <NUM> may use a second HO threshold that the HO threshold receiving unit <NUM> received from the NMS <NUM>. Also, the HO threshold change unit <NUM> may use a second HO threshold derived from the HO threshold deriving unit <NUM>.

When an event type trigger A5 is employed as the transmission trigger of the MR, the terminal control unit <NUM> reduces a serving cell HO threshold for determining whether the received radio wave intensity from a serving cell is lower than the serving cell HO threshold or not, and increases a neighbor cell HO threshold for determining whether received radio wave intensity from a neighbor cell is higher than the neighbor cell HO threshold or not. The terminal control unit <NUM> may change the serving cell HO threshold from the default value to a first serving cell HO threshold which is lower than the default value, and change the neighbor cell HO threshold from the default value to a first neighbor cell HO threshold which is higher than the default value. The HO threshold change unit <NUM> uses the first serving cell HO threshold and the first neighbor cell HO threshold which are preset by an administrator and the like of the wireless base station <NUM>, for example. Also, the HO threshold change unit <NUM> may use the first serving cell HO threshold and the first neighbor cell HO threshold that the HO threshold receiving unit <NUM> received from the NMS <NUM>. Also, the HO threshold change unit <NUM> may use the first serving cell HO threshold and the first neighbor cell HO threshold derived by the HO threshold deriving unit <NUM>. The HO threshold change unit <NUM> may change the serving cell HO threshold to the default value and change the neighbor cell HO threshold to the default value when the load determining unit <NUM> determines that the load condition is not satisfied after transmitting a changing instruction. The HO threshold change unit <NUM> may change the serving cell HO threshold to the first serving cell HO threshold when the load of the base station device <NUM> is higher than the first load threshold and lower than the second load threshold, change the neighbor cell HO threshold to the first neighbor cell HO threshold, change the serving cell HO threshold to a second serving cell HO threshold which is lower than the first serving cell HO threshold when the load of the base station device <NUM> is higher than the second load threshold, and change the neighbor cell HO threshold to a second neighbor cell HO threshold which is higher than the first neighbor cell HO threshold. The HO threshold change unit <NUM> uses the second serving cell HO threshold and the second neighbor cell HO threshold which are preset by an administrator and the like of the wireless base station <NUM>, for example. Also, the HO threshold change unit <NUM> may use the second serving cell HO threshold and the second neighbor cell HO threshold that the HO threshold receiving unit <NUM> received from the NMS <NUM>. Also, the HO threshold change unit <NUM> may use the second serving cell HO threshold and the second neighbor cell HO threshold derived by the HO threshold deriving unit <NUM>.

<FIG> is a diagram schematically illustrating an example of a flow of processing performed by the base station device <NUM>. Herein, a state in which a plurality of user terminals <NUM> are existing in the base station device <NUM>, an event type trigger A3 is employed as the transmission trigger of the MR, and an HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM> is set as a default value is described as an initialized state.

In S202, the load determining unit <NUM> determines whether a CPU usage rate of the base station device <NUM> is higher than a threshold or not. If the CPU usage rate of the base station device <NUM> is higher than a threshold is determined to be higher, the process proceeds to S204.

In S204, the HO threshold change unit <NUM> changes the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM> to a value higher than the default value. After the change, the HO threshold is set for the user terminal <NUM> to be a value higher than the default value that starts a wireless connection to the base station device <NUM>, and the transmission of the MR from the user terminal <NUM> which newly established a wireless connection with the base station device <NUM> is suppressed.

In S206, the load determining unit <NUM> determines whether a CPU usage rate of the base station device <NUM> is lower than a threshold or not. If the CPU usage rate of the base station device <NUM> is lower than a threshold is determined to be higher, the process proceeds to S208.

In S208, the HO threshold change unit <NUM> changes the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM> to the default value. The process returns to S202. The base station device <NUM> may terminate the process indicated in <FIG> according to an instruction by an administrator of the base station device <NUM>, for example.

In S302, the load determining unit <NUM> determines whether a CPU usage rate of the base station device <NUM> is higher than a first threshold or not. If the CPU usage rate of the base station device <NUM> is higher than a threshold is determined to be higher, the process proceeds to S304.

In S304, the HO threshold change unit <NUM> changes the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM> to a first HO threshold higher than the default value.

In S306, the load determining unit <NUM> determines whether a CPU usage rate of the base station device <NUM> is higher than a second threshold which is higher than the first threshold or not. If the CPU usage rate of the base station device <NUM> is determined to be higher than the second threshold, the process proceeds to S308. If the CPU usage rate of the base station device <NUM> is not determined to be higher than the second threshold, the process proceeds to S312. In S308, the HO threshold change unit <NUM> changes the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM> to a second HO threshold higher than the first HO threshold.

In S310, the load determining unit <NUM> determines whether a CPU usage rate of the base station device <NUM> is lower than the second threshold or not. If the CPU usage rate of the base station device <NUM> is lower than a threshold is determined to be higher, the process proceeds to S312. In S312, the HO threshold change unit <NUM> changes the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM> to the first HO threshold.

In S314, the load determining unit <NUM> determines whether a CPU usage rate of the base station device <NUM> is lower than the first threshold or not. If the CPU usage rate of the base station device <NUM> is determined to be lower than the first threshold, the process proceeds to S316. If the CPU usage rate of the base station device <NUM> is not determined to be lower than the first threshold, the process returns to S306. In S316, the HO threshold change unit <NUM> changes the HO threshold set for the user terminal <NUM> that starts a wireless connection to the base station device <NUM> to the default value. The process returns to S302. The base station device <NUM> may terminate the process indicated in <FIG> according to an instruction by an administrator of the base station device <NUM>, for example.

<FIG> is a diagram schematically illustrating HAPS (High Altitude Platform Station) <NUM>. The HAPS <NUM> may be an example of a flying object. The HAPS <NUM> includes a vehicle <NUM>, a central part <NUM>, a propeller <NUM>, a pod <NUM>, and a solar panel <NUM>. The central part <NUM> has a flight control device and a base station device <NUM> which are not shown.

An electrical power generated by the solar panel <NUM> is stored in one or more batteries positioned in at least any of the vehicle <NUM>, the central part <NUM>, and the pod <NUM>. The electrical power stored in the battery is utilized by each component included in the HAPS <NUM>.

The flight control device controls the flight of the HAPS <NUM>. The flight control device controls the flight of the HAPS <NUM> by controlling the rotation of the propeller <NUM>, for example. Also, the flight control device may control the flight of the HAPS <NUM> by changing the angle of the flap or the elevator which are not shown. The flight control device may include various sensors such as a positioning sensor for example a GPS sensor and the like, a gyrosensor, and an acceleration sensor and the like, to manage the position, the moving direction, and the moving speed of the HAPS <NUM>.

The base station device <NUM> provides a wireless communication service to the user terminal <NUM> on the ground by using an FL (Feeder Link) antenna <NUM>, and an SL (Service Link) antenna <NUM>. The FL antenna <NUM> is an antenna for a feeder link. The base station device <NUM> forms a feeder link between itself and a terrestrial gateway <NUM> by the FL antenna <NUM>.

The SL antenna <NUM> is an antenna for a service link. The SL antenna <NUM> may be an antenna with lower directivity than the FL antenna <NUM>. The base station device <NUM> forms a cell <NUM> on the ground by the SL antenna <NUM>.

The base station device <NUM> establishes a feeder link between itself and each gateway <NUM> positioned at each location on the ground and then communicates with a network <NUM> on the ground via the gateway <NUM>, for example. The base station device <NUM> may communicate with an NMS <NUM> via the gateway <NUM> and the network <NUM>. The HAPS <NUM> covers a terrestrial area by the cell <NUM> while performing circular flight along a circular flight path over the terrestrial area to be covered and adjusting a beam direction determined by the FL antenna <NUM> and the SL antenna <NUM>, for example. Besides of precise circles and ovals and the like, the flight path may be shaped like a number <NUM> and the like. The adjustment of the beam direction may be performed by at least any of a physical orientation change of the antenna and beamforming.

In the case of the HAPS <NUM>, since a range of the terrestrial area covered by the cell <NUM> is broader compared to a terrestrial wireless base station, and an electric field variation in the terrestrial area becomes intense by a vehicle oscillation due to the flight, more control signals is generated compared to the terrestrial wireless base station. Therefore, the effect of changing, by the base station device <NUM>, the HO threshold in accordance with the load of the base station device <NUM> is more significant.

Also, in the case of the HAPS <NUM>, the appropriate HO threshold is likely to vary for each HAPS <NUM>, depending on positioning conditions of the cell in the covering target area, wind conditions in the flight area, performance errors of the vehicle, communication traffic tendency in the covering target area, seasonal variations, or the like. In contrast, in the present embodiment, since the HO threshold is derived for each HAPS <NUM>, the HO threshold suitable for each HAPS <NUM> can be applied and the load reduction can be appropriately realized.

Also, in the case of the HAPS <NUM>, it is predicted that the value distribution of offset values in the MR which is the HO trigger will become wider. Accordingly, a configuration with good time efficiency can be realized compared to the case in which the HO threshold is gradually adjusted, by aggregating the distribution of the offset values in the MR which is the HO trigger, derive the HO threshold based on the cumulative distribution in advance, and applying, according to the load of the base station device <NUM>, the HO threshold which is derived in advance.

Also, in the case of the HAPS <NUM>, computing resources are limited and the available electrical power is limited compared to the terrestrial wireless base station, but the message exchange between the base station device <NUM> and the NMS <NUM> can be reduced and a countermeasure at a high load is immediately performed while reducing the load of the base station device <NUM>, by performing the HO threshold derivation with the NMS <NUM> and performing the high load determination by the base station device <NUM>.

<FIG> is a diagram schematically illustrating an example of a hardware configuration of a computer <NUM> serving as the base station device <NUM> or the NMS <NUM>. a program installed in the computer <NUM> can cause the computer <NUM> to function as one or more "units" of the device according to the above embodiment, or can cause the computer <NUM> to perform operations or one or more "units" associated with the device according to the above embodiment, and/or can cause the computer <NUM> to perform a process or steps of the process according to the above embodiment. Such a program may be executed by a CPU <NUM> so as to cause the computer <NUM> to perform specific operations associated with some or all of the blocks in the flowcharts and block diagrams described in the present specification.

The computer <NUM> according to the present embodiment includes the CPU <NUM>, a RAM <NUM>, and a graphics controller <NUM> which are mutually connected by a host controller <NUM>. Also, the computer <NUM> includes input/output units such as a communication interface <NUM>, a storage device <NUM>, a DVD drive and an IC card drive, which are connected to the host controller <NUM> via an input/output controller <NUM>. The storage device <NUM> may be a hard disk drive, a solid state drive and the like. The computer <NUM> also includes a legacy input/output unit such as a ROM <NUM> and a keyboard, which are connected to the input/output controller <NUM> via an input/output chip <NUM>.

The CPU <NUM> operates according to the program stored in the ROM <NUM> and the RAM <NUM>, thereby controlling each unit. The graphics controller <NUM> is configured to acquire image data generated by the CPU <NUM> in a frame buffer or the like provided in the RAM <NUM> or in itself, and cause the image data to be displayed on a display device <NUM>.

The communication interface <NUM> communicates with other devices via a network. The storage device <NUM> stores programs and data used by the CPU <NUM> in the computer <NUM>. The IC card drive reads programs and data from an IC card, and/or writes programs and data into the IC card.

The ROM <NUM> stores therein boot programs or the like executed by the computer <NUM> at the time of activation, and/or stores programs depending on the hardware of the computer <NUM>. The input/output chip <NUM> may also connect various input/output units to the input/output controller <NUM> via a USB port, a parallel port, a serial port, a keyboard port, a mouse port or the like.

A program is provided by a computer-readable storage medium such as the DVD-ROM or the IC card. The program is read from the computer-readable storage medium, installed in the storage device <NUM>, the RAM <NUM>, or the ROM <NUM>, which are also examples of the computer-readable storage medium, and is executed by the CPU <NUM>. Information processing written in these programs is read by the computer <NUM>, and provides cooperation between a program and the above-mentioned various types of hardware resources. An apparatus or a method may be configured by realizing the operation or processing of the information according to the usage of the computer <NUM>.

For example, when communication is performed between the computer <NUM> and an external device, the CPU <NUM> may execute a communication program loaded in the RAM <NUM>, and instruct the communication interface <NUM> to execute communication processing based on processing written in the communication program. The communication interface <NUM>, under control of the CPU <NUM>, reads transmission data stored on a transmission buffer region provided in a recording medium such as the RAM <NUM>, the storage device <NUM>, the DVD-ROM, or the IC card, and transmits the read transmission data to a network or writes reception data received from a network to a reception buffer region or the like provided on the recording medium.

In addition, the CPU <NUM> may cause all or a necessary portion of a file or a database to be read into the RAM <NUM>, the file or the database having been stored in an external recording medium such as the storage device <NUM>, the DVD drive (DVD-ROM), the IC card, etc., and perform various types of processing on the data on the RAM <NUM>. Next, the CPU <NUM> may write back the processed data into the external recording medium.

Various types of information, such as various types of programs, data, tables, and databases, may be stored in the recording medium, and subjected to information processing. The CPU <NUM> may execute various types of processing on the data read from the RAM <NUM> to write back a result to the RAM <NUM>, the processing being described throughout the present disclosure, specified by instruction sequences of the programs, and including various types of operations, information processing, conditional determinations, conditional branching, unconditional branching, information retrievals/replacements, or the like. In addition, the CPU <NUM> may search for information in the file, the database, or the like in the recording medium. For example, when a plurality of entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored in the recording medium, the CPU <NUM> may search, from the plurality of entries, for an entry that matches a condition in which the attribute value of the first attribute is specified, and read the attribute value of the second attribute stored in the entry, and thereby acquiring the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition.

The above-described program or software module may be stored on the computer <NUM> or in a computer-readable storage medium near the computer <NUM>. Also, a recording medium such as a hard disk or a RAM provided in a server system connected to a dedicated communication network or the Internet can be used as a computer-readable storage medium, thereby providing the program to the computer <NUM> via the network.

In the flowcharts and the block diagrams in the present embodiment, the blocks may represent "units" of an apparatus having a role to perform steps of the process for performing operations or to perform the operations. A specific step or "unit" may be implemented by a dedicated circuit, a programmable circuit provided along with computer-readable instructions stored on a computer-readable storage medium, and/or a processor provided along with the computer-readable instructions stored on the computer-readable storage medium. The dedicated circuit may include a digital and/or analog hardware circuit, or may include an integrated circuit (IC) and/or a discrete circuit. The programmable circuit may include a reconfigurable hardware circuit, such as a field-programmable gate array (FPGA) and a programmable logic array (PLA), for example, including logical AND, logical OR, logical XOR, logical NAND, logical NOR, and other logical operations, flip-flops, registers, and memory elements.

The computer-readable storage medium may include any tangible device that can store instructions to be executed by a suitable device, so that the computer-readable storage medium having instructions stored thereon comprises a product including instructions that can be executed to configure means for performing operations specified in the flowcharts or block diagrams. Examples of the computer-readable storage medium may include an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storage medium, a semiconductor storage medium, etc. More specific examples of computer-readable storage media may include a floppy (registered trademark) disk, a diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an electrically erasable programmable read-only memory (EEPROM), a static random access memory (SRAM), a compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a BLU-RAY(registered trademark) disc, a memory stick, an integrated circuit card, etc..

The computer-readable instructions may include assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcodes, firmware instructions, state-setting data, or any of source codes or object codes described in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk (registered trademark), JAVA (registered trademark), or C++, and conventional procedural programming languages, such as "c" programming languages or similar programming languages.

The computer-readable instructions may be provided to a processor of a general-purpose computer, a special purpose computer or other programmable data processing apparatuses, or a programmable circuit, locally or via the local area network (LAN) or the wide area network (WAN) such as the Internet, so that the processor of the general-purpose computer, the special purpose computer or other programmable data processing apparatuses, or the programmable circuit executes the computer-readable instructions to generate means for performing the operations specified in the flowcharts or block diagrams. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, etc..

The above-described embodiment includes the NMS <NUM> as an example of the management device, but not limited thereto. The system <NUM> may include the management device aside from the NMS <NUM>. The management device may be connected to the network <NUM>, and include a measurement report receiving unit <NUM>, a measurement report storing unit <NUM>, an HO threshold deriving unit <NUM>, and an HO threshold transmitting unit <NUM>.

While the embodiments of the present invention have been described, the technical scope of the invention is not limited to the above-described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. However, the scope of protection is defined by the claims.

Claim 1:
A base station device (<NUM>) configured to form a cell (<NUM>) to provide a wireless communication service to a user terminal (<NUM>) within the cell (<NUM>), the base station device (<NUM>) comprising:
a handover threshold storing unit (<NUM>) for storing a handover threshold for a transmission trigger of a measurement report, whereby the handover threshold is set for the user terminal (<NUM>) that starts a wireless connection to the base station device (<NUM>),
a load determining unit (<NUM>) for determining whether a load condition indicating that a load of the base station device (<NUM>) is high is satisfied or not, and
a handover threshold change unit (<NUM>) for changing the handover threshold so as to suppress a handover from the base station device (<NUM>) of a user terminal (<NUM>) which establishes a wireless connection with the base station device (<NUM>) when it is determined that the load condition is satisfied, a terminal control unit (<NUM>) for transmitting the handover threshold being stored in the handover threshold storing unit for setting the handover threshold for the user terminal,
wherein the load determining unit (<NUM>) is configured to determine that the load condition is satisfied when a CPU (<NUM>) usage rate of the base station device (<NUM>) is higher than a predetermined usage rate threshold and to determine that the load condition is not satisfied when the CPU (<NUM>) usage rate of the base station device (<NUM>) is lower than the usage rate threshold, and
wherein the handover threshold change unit (<NUM>) is configured to increase, when the load determining unit (<NUM>) determines that the load condition is satisfied, the handover threshold for determining whether or not received radio wave intensity from a neighbor cell (<NUM>) is stronger than received radio wave intensity from a serving cell (<NUM>) by the handover threshold or more,
such that the number of measurement reports received by the wireless base station (<NUM>) is reduced and consequently the load of the base station for processing the measurement reports is decreased.