WO2014097732A1

WO2014097732A1 - Wireless base station and com munication control method

Info

Publication number: WO2014097732A1
Application number: PCT/JP2013/078557
Authority: WO
Inventors: 優輔佐々木; 聖悟原野; 河辺　泰宏; 匠吾矢葺; 優大▲高▼
Original assignee: 株式会社Ｎｔｔドコモ
Priority date: 2012-12-18
Filing date: 2013-10-22
Publication date: 2014-06-26
Also published as: JP5580393B2; JP2014121010A

Abstract

A wireless base s tation of the present invention has a macro cell, the macro cell forming a macro-cell area and performing wireless communication by using a user device pre sent in the macro-cell area and a first frequency. The wireless base station has a small cell, the small cell having smaller transmission power than the m acro cell and forming a small-cell area smaller in area than the macro-cell area, and performing wireless communication by using a user device present in the small-cell area and a second frequency different from the first frequency. The wireless base station is provided with a handover control unit. When a user device capable of communicating at the first and the second frequencies originates a call, the overhand control unit controls the user device so as to cause handing-over of the user device from the small cell to the macro cell to occur.

Description

Radio base station and communication control method

The present invention relates to a radio base station and a communication control method.

In 3GPP (Third-Generation Partnership Project) LTE (Long Term Evolution) Advanced, a technology called carrier aggregation is defined (see Non-Patent Document 1, Sec. 5.5 and Sec. 7.5). Carrier aggregation is a communication technique in which a plurality of different frequency bands (component carriers) are combined at the same time in order to improve the transmission rate. A UE (user equipment, User Equipment, mobile station) can receive using a plurality of component carriers at the same time according to its capability, and can transmit using a plurality of component carriers at the same time.

FIG. 1 is a schematic diagram showing an outline of carrier aggregation. In FIG. 1, UE1 can use a plurality of frequency bands in conformity with carrier aggregation. UE2 is not compatible with carrier aggregation and can use only one frequency band. In the figure, although 1.5 GHz band and 2 GHz band are shown, this is for illustrative purposes and the frequency band is not limited. Since UE1 can use a plurality of frequency bands, higher-speed communication is possible than UE2 that can use only a single frequency band.

In order to realize carrier aggregation, it is necessary to prepare a radio base station so that a plurality of frequency bands can be used. In an area where a plurality of frequency bands can be used in conformity with carrier aggregation in the service area, UE1 that conforms to carrier aggregation can use a plurality of frequency bands. In the service area, UE1 can use only a single frequency band in an area that does not conform to carrier aggregation and can use only a single frequency band.

In carrier aggregation, component carriers are classified into one main component carrier (PCC) and at least one sub component carrier (SCC). The main component carrier is used for providing NAS (Non-Access Stratum) mobility information, for example, Tracking (Area) identity (TAI), or for providing a security input when the UE originates or performs handover. The sub component carrier is a component carrier that can be used by the UE in addition to the main component carrier. More precisely, there are an uplink main component carrier and a downlink main component carrier, and there are an uplink sub component carrier and a downlink sub component carrier.

The serving cell in which the UE communicates using the uplink and downlink main component carriers is called a primary cell (Primary Cell, PCell), and the serving cell in which the UE communicates using the uplink and downlink subcomponent carriers is defined as the sub cell ( Secondary Cell, SCell). The UE can use a maximum of 5 subcells. In this specification, a cell is not a cell area described later, but a base station device that provides a communication function for the cell area.

FIG. 2 is a schematic diagram showing an example of a mode of use of carrier aggregation. As indicated by an arrow in FIG. 2, UE1 that matches carrier aggregation moves from left to right in the figure. The radio base station 10 uses two frequency bands A and B for both downlink and uplink. The radio base station 10 has

cell areas

10A and 10B, which are ranges where radio waves can reach. The cell area 10A corresponds to the frequency band A, and the cell area 10B corresponds to the frequency band B. The size of the

cell areas

10A and 10B is different because radio waves with a low frequency A reach a longer distance than radio waves with a high frequency B.

UE1 transmits in the cell area 10A on the left side of FIG. 2 (outside the cell area 10B). At this time, in order to perform communication using frequency band A as PCC for both the downlink (DL) and the uplink (UL), the “Radio” Resource “Control” (RRC) “Setup” procedure is executed, and communication starts in frequency band A.

When UE1 reaches cell area 10B, SCC is added, that is, SCell is added. Frequency band B is added as a SCC to a frequency that can be used by UE1. Thereby, UE1 can communicate not only frequency band A (PCC) but frequency band B as SCC with both downlink (DL) and uplink (UL). However, whether UE1 uses SCC depends on the usage status of UE1. Whether the SCell should be added is determined by the radio base station 10 based on a report (Measurement Report) of the reception quality of the component carrier measured by the UE to the radio base station. When the SCell is to be added, the radio base station 10 transmits an RRC Connection Reconfiguration message to the UE. The UE that has received the RRC Connection Reconfiguration message adds the SCell specified in the message (see Non-Patent Document 2, Sec. 5.3.10.3b, etc.). In addition, instead of the reported reception quality, the determination of whether to add a SCell is based on the hardware resources of the radio base station, the usage status of each frequency band, and the operation criteria for adding a cell in a preset carrier aggregation. May be based. Alternatively, whether or not SCells need to be added may be determined based on a combination of these and the reception quality.

When the UE1 moves out of the cell area 10B with the movement, the SCC is deleted, that is, the SCell is deleted. Frequency band B is deleted from the SCC usable by UE1. Thereby, UE1 communicates only with the frequency band A (PCC) with both a downlink (DL) and an uplink (UL). Whether or not the SCell should be deleted is determined by the radio base station 10 based on a report (Measurement Report) of the reception quality of the component carrier measured by the UE to the radio base station. When the SCell is to be deleted, the radio base station 10 transmits an RRC Connection Reconfiguration message to the UE. The UE that has received the RRC Connection Reconfiguration message deletes the SCell specified in the message (see Non-Patent Document 2, Sec. 5.3.10.3a, etc.).

When the UE 1 moves from the cell area 10A to the cell area of another radio base station with the movement, the handover is executed, the PCell is switched, and the PCC is switched.

FIG. 3 is a schematic view showing another example of a mode of use of carrier aggregation. As indicated by an arrow in FIG. 3, UE1 that matches carrier aggregation moves from left to right in the figure. In FIG. 3, for PCC and SCC, illustration of distinction between downlink and uplink is omitted.

The radio base station (eNB) has a macro cell 20 and a plurality of pico cells (small cells) 30, 31, 32, 33. The macro cell 20 uses the frequency band A for communication and has a cell area (macro cell area) 20A. The

pico cells

30, 31, and 32 use the frequency band B for communication, and have cell areas (pico cell areas) 30B, 31B, and 32B, respectively. The pico cell 33 uses the frequency band C for communication and has a cell area (pico cell area) 33C. Since the pico cell uses lower transmission power than the macro cell, the pico cell area is smaller than the macro cell area of the macro cell.

3 UE1 transmits in the macro cell area 20A on the left side of FIG. 3 (outside the pico cell area). At this time, the RRC Setup procedure is executed so that communication is performed using the frequency band A of the macro cell area 20A as PCC, and communication starts in the frequency band A.

When UE1 reaches the picocell area 32B, SCC is added, that is, SCell is added. The frequency band B of the picocell area 32B is added to the frequency that can be used by the UE1 as the SCC. Thereby, UE1 can communicate not only frequency band A (PCC) but frequency band B as SCC. However, whether UE1 uses SCC (frequency band B) depends on the usage status of UE1. Whether or not to add a SCell is determined by the eNB based on the report to the eNB of the reception quality of the component carrier measured by the UE. When SCell is to be added, the eNB uses the macro cell 20 to transmit an RRC Connection Reconfiguration message to the UE. The UE that has received the RRC Connection Reconfiguration message adds the SCell specified in the message.

When UE1 reaches the overlapping portion of the picocell area 32B and the picocell area 33C, SCC addition, that is, SCell addition is performed. The frequency band C of the picocell area 33C is added to the frequency that can be used by the UE1 as the SCC. Thereby, UE1 can further communicate as frequency band C as SCC. However, whether UE1 uses SCC (frequency band C) depends on the usage status of UE1.

If UE1 reaches the overlapping portion of picocell area 32B and picocell area 33C from within macrocell area 20A (outside the picocell area), two SCCs (frequency bands A and B) are added at the same time, that is, SCell (picocell)

Areas

32B and 33C) are added.

∙ Even if the connection with the pico cell that communicates with the addition of the SCell is cut off due to a sudden change in the propagation environment, the connection with the PCell (macro cell) is maintained. And whether UE1 should reconnect with a pico cell (whether SCell should be added) is judged by eNB based on the report to eNB of the reception quality of the component carrier measured by UE.

When UE1 reaches the part outside the picocell area 32B in the picocell area 33C from the overlapping part of the picocell area 32B and the picocell area 33C, the SCC is deleted, that is, the SCell is deleted. Frequency band B is deleted from the SCC usable by UE1. Thereby, UE1 communicates only in the frequency band A (PCC) and the frequency band C (SCC). Whether or not to delete the SCell is determined by the eNB based on the report to the eNB of the reception quality of the component carrier measured by the UE. When the SCell is to be deleted, the eNB uses the macro cell 20 to transmit an RRC Connection Reconfiguration message to the UE. The UE that has received the RRC Connection Reconfiguration message deletes the SCell specified in the message.

When the UE1 leaves the picocell area 33C with the movement, the SCC is deleted, that is, the SCell is deleted. Frequency band C is deleted from the SCC that can be used by UE1. Thereby, UE1 communicates only in the frequency band A (PCC).

As the UE 1 moves from the macro cell area 20A to the macro cell area of another radio base station with the movement, handover is executed, the PCell is switched, and the PCC is switched.

If the handover between macro cells fails, the connection of UE 1 is interrupted for any cell. In this case, UE1 performs reconnection.

If the

pico cells

32 and 33 use the same frequency band, SCell modification is performed for UE 1 that moves back and forth between those pico cell areas. In this case, since the SCC is in the same frequency band, the SCC is not corrected.

FIG. 4 is a sequence diagram illustrating an example of a conventional control procedure from UE transmission to handover in compliance with LTE. When a call is transmitted from the UE, the UE, eNB (radio base station), and MME (mobility management entity) execute a control procedure for transmission for the call. Thereafter, the MME transmits an E-RAB Setup Request message to the eNB. The E-RAB Setup Request message specifies the type of bearer to be set up for the call. The eNB that has received the E-RAB Setup Request message executes internal processing necessary for setting up the designated bearer.

After this, the eNB sends an RRC Connection Reconfiguration message to the UE. This RRC Connection Reconfiguration message specifies the type of bearer to be configured for the call. The UE that has received this RRC Connection Reconfiguration message executes processing necessary for setting the designated bearer. After the completion of the process, the UE transmits an RRC Connection Reconfiguration Complete message indicating completion of bearer setting to the eNB. Then, the eNB transmits an E-RAB Setup Response message indicating completion of bearer setup to the MME.

After this, the eNB sends an RRC Connection Reconfiguration message to the UE. This RRC Connection Reconfiguration message is a reception quality measurement instruction for convenience of different frequency handover for the UE. More specifically, this RRC Connection Reconfiguration message instructs activation of a measurement gap (Measurement Gap) in which the UE measures reception quality in a frequency band (carrier) different from the frequency currently used by the UE for communication. . Further, this RRC Connection Reconfiguration message specifies the frequency band (carrier) that the UE should measure, and instructs the UE to measure the reception quality of that frequency band. The measurement gap is a time interval that appears periodically, and is a time interval for measuring reception quality in a frequency band of a cell to which the UE is not currently communicating. There may be one frequency to be measured, but there may be more than one.

When receiving the RRC Connection Reconfiguration message which is this measurement instruction, the UE activates the measurement gap as instructed by the RRC Connection Reconfiguration message. That is, the UE sets the UE itself so that the UE can measure the reception quality related to the cell with which the UE is not currently communicating at periodic time intervals. Then, the UE sets the UE itself so that the UE can measure the reception quality in the frequency band specified in the RRC Connection Reconfiguration message. After completion of these settings, the UE transmits an RRC Connection Reconfiguration Complete message indicating that these settings of the UE have been completed to the eNB.

After this, the UE measures the reception quality of the frequency of the communicating cell and the reception quality of the frequency band of the non-communication cell, and transmits a report (Measurement Report) indicating the measurement result to the eNB. When receiving the Measurement-Report, the eNB determines whether or not to hand over the UE that has transmitted the Measurement-Report. The criteria for determining handover are well known. For example, handover should be performed when the reception quality of the frequency of the communicating cell is worse than the reception quality of the frequency band of the non-communication cell. In determining the handover, the reception quality may be compared by correcting at least one of the reception quality of the frequency of the communicating cell and the reception quality of the frequency band of the non-communication cell.

When eNB judges that it should not hand over, eNB does not transmit a message to UE. The UE again measures the reception quality of the frequency of the communicating cell and the reception quality of the frequency band of the non-communication cell, and transmits a report indicating the measurement result to the eNB. If handover should not be performed, reception quality measurement and reporting are repeated.

On the other hand, when the eNB determines that the handover should be performed, the eNB transmits an RRC Connection Reconfiguration message to the UE. This RRC Connection Reconfiguration message is an instruction for handover to the UE. When receiving the RRC Connection Reconfiguration message, which is an instruction for handover, the UE executes processing necessary for handover as instructed by the RRC Connection Reconfiguration message. The eNB and MME also execute a control procedure for handover.

As described above, the RRC Connection Reconfiguration message is transmitted from the eNB to the UE at least three times from the UE transmission to the handover. That is, an RRC Connection Reconfiguration message for setting a bearer, an RRC Connection Reconfiguration message that is a different frequency measurement instruction, and an RRC Connection Reconfiguration message that is a handover instruction. In addition, in order for the eNB to instruct a handover, it is necessary to receive a Measurement Report from the UE.

However, if the UE is moving at high speed, even if the UE sends a Measurement Report, the eNB cannot receive it, or even if the eNB sends an RRC Connection Reconfiguration message that is a handover instruction, The UE may not receive it. In particular, for small power cells (small cells), the cell area in which the radio waves reach is small, so when a UE that has transmitted in the small cell cell area while moving at high speed leaves the cell area, it is still in the communication network. Then, the procedure required for handover from cell to cell may not be completed.

For example, it is assumed that the UE transmits in the pico cell area 31B of FIG. When the UE is moving at high speed, even if the UE transmits a Measurement-Report, the pico cell 31 cannot receive it, and the eNB that manages the pico-cell 31 cannot recognize the Measurement-Report. An RRC Connection Reconfiguration message as an instruction may not be transmitted to the UE via the picocell 31. Or, even if the eNB can recognize the Measurement Report, even if the UE has already moved outside the picocell area 31B, the eNB may transmit an RRC Connection Reconfiguration message that is a handover instruction via the picocell 31. , UE can not receive it. In such a case, the UE and the communication network are out of synchronization, and the connection between the UE and the communication network is interrupted. The UE needs to reconnect to the communication network in order to resume communication. Although reconnection may be possible automatically, even in that case, the connection between the UE and the communication network is momentarily interrupted.

The problem that occurs when the UE moves at high speed occurs not only when the UE is communicating with the small cell from the beginning, but also after the UE is communicating with the macro cell and is handed over to the small cell.

Therefore, the present invention provides a radio base station and a communication control method that can reduce or prevent disconnection between a user apparatus and a communication network.

The radio base station according to the first aspect of the present invention includes a macro cell that forms a macro cell area and performs radio communication with a user apparatus in the macro cell area using a first frequency, and transmission power is higher than that of the macro cell. A small cell that is small and has a smaller area than the macro cell area, and communicates wirelessly with a user apparatus in the small cell area using a second frequency different from the first frequency; and A handover control unit that causes a handover of the user apparatus from the small cell to the macro cell when a user apparatus capable of communicating at the first frequency and the second frequency transmits within the small cell area.

A communication control method according to a first aspect of the present invention includes a macro cell that forms a macro cell area and performs radio communication with a user apparatus in the macro cell area using a first frequency, and transmission power is higher than that of the macro cell. A radio comprising a small cell area that is small and smaller in area than the macro cell area, and includes a user equipment in the small cell area and a small cell that performs radio communication using a second frequency different from the first frequency In a communication control method in a base station, detecting that a user apparatus capable of communicating at the first frequency and the second frequency transmits within the small cell area; and Causes a handover of the user equipment from the small cell to the macro cell And a Succoth.

The radio base station according to the second aspect of the present invention includes a macro cell that forms a macro cell area and performs radio communication with a user apparatus in the macro cell area using a first frequency, and has transmission power higher than that of the macro cell. A small cell that is small and has a smaller area than the macro cell area, and communicates wirelessly with a user apparatus in the small cell area using a second frequency different from the first frequency; and A handover restricting unit that restricts handover of the user apparatus from the macro cell to the small cell when a user apparatus capable of communicating at the first frequency and the second frequency is communicating with the macro cell;

A communication control method according to a second aspect of the present invention includes a macro cell that forms a macro cell area and performs radio communication with a user apparatus in the macro cell area using a first frequency, and transmission power is higher than that of the macro cell. A radio comprising a small cell area that is small and smaller in area than the macro cell area, and includes a user equipment in the small cell area and a small cell that performs radio communication using a second frequency different from the first frequency In a communication control method in a base station, communicating with a user apparatus capable of communicating at the first frequency and the second frequency using the macro cell, and handover of the user apparatus from the macro cell to the small cell Regulating.

In the first aspect of the present invention, when a user apparatus capable of communicating at the first frequency and the second frequency detects that the transmission is performed within the small cell area of the small cell, the radio base station The user apparatus is controlled so as to cause an early handover of the user apparatus to the macro cell. The radio base station facilitates handover regardless of whether the user equipment is actually at the end of the small cell area. Since the cell area (macro cell area) of the macro cell of the radio base station is larger than the cell area (small cell area) of the small cell, once handed over to the macro cell, even if the user equipment is moving at high speed, By moving from the macro cell area to another cell area, it is highly probable that procedures necessary for subsequent handover from the macro cell to another cell can be completed. Therefore, even when the user device that has transmitted in the small cell area of the small cell is moving at high speed, disconnection between the user device and the communication network can be reduced or prevented.

In the second aspect of the present invention, when a user apparatus that can communicate at the first frequency and the second frequency communicates using the macro cell, the handover of the user apparatus from the macro cell to the small cell is regulated. Since the cell area (macro cell area) of the macro cell of the radio base station is larger than the cell area (small cell area) of the small cell, if the handover from the macro cell to the small cell is restricted, the user apparatus moves at high speed. Even in such a case, it is highly likely that procedures necessary for subsequent handover from the macro cell to another cell can be completed before moving from the macro cell area to another cell area. Therefore, even when the user apparatus is moving at high speed, disconnection between the user apparatus and the communication network can be reduced or prevented.

It is the schematic which shows the outline | summary of a carrier aggregation. It is the schematic which shows an example of the aspect of use of a carrier aggregation. It is the schematic which shows another example of the aspect of use of a carrier aggregation. It is a sequence diagram which shows an example of the conventional control procedure from the transmission of a user apparatus to a handover based on LTE. It is the schematic for demonstrating the term "cell" in this specification. It is the schematic for demonstrating the term "cell" in this specification. It is the schematic for demonstrating the term "cell" in this specification. It is a sequence diagram which shows the control procedure which concerns on the 1st Embodiment of this invention from the transmission of a user apparatus to a hand-over. It is a block diagram which shows the structure of the wireless base station (eNB) which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the radio base station (eNB) which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the radio base station (eNB) which concerns on the 3rd Embodiment of this invention. It is a sequence diagram which shows the control procedure which concerns on the 4th Embodiment of this invention from the transmission of a user apparatus to a hand-over. It is a block diagram which shows the structure of the wireless base station (eNB) which concerns on the 5th Embodiment of this invention.

First, before describing the embodiment, the concept of a cell in this specification will be described. In this specification, a cell refers to a device included in a radio base station (eNB) that provides a communication function for a cell area, not a cell area known as a range where radio waves can communicate. More specifically, for example, as illustrated in FIG. 5, when the eNB 10 includes three sector cell areas 10A1, 10A2, and 10A3, the eNB includes cells corresponding to the three sector cell areas. As shown in FIG. 6, when the eNB uses a plurality of frequency bands, the eNB has a number of cells corresponding to the number of frequency bands. For example, as shown in FIG. 6, the eNB uses two frequency bands A and B, and three sector cell areas (sector cell areas 10A1, 10A2 and 10A3 of the frequency band A, and frequency band B of each frequency band). In the case of having sector cell areas 10B1, 10B2, and 10B3), the eNB has six cells. As shown in FIG. 7, when eNB10 is connected with one or more small cells (for example, picocell 30), eNB has a small cell in addition to a macrocell.

As shown in FIG. 2, when an eNB uses two frequency bands A and B and does not have a sector cell for each frequency band, the eNB has two cells. As illustrated in FIG. 3, the eNB may include a macro cell 20 and small cells (for example,

pico cells

30, 31, 32, and 33).

Hereinafter, various embodiments according to the present invention will be described. In order to simplify the description, one UE and one eNB are shown in the drawing. However, the wireless communication network, of course, has a larger number of eNBs and can communicate with a larger number of UEs.

The communication system according to the present invention includes a macro cell and a small cell as shown in FIG. The eNB has at least one macro cell. The macro cell forms a macro cell area and wirelessly communicates with user equipment in the macro cell area using a first frequency. Moreover, eNB has a small cell (small cell). A small cell (for example, a pico cell) forms a small cell area that has a smaller transmission power than a macro cell and a smaller area than the macro cell area, and uses a second frequency that is different from the first frequency with the UE in the small cell area. Wireless communication.

First Embodiment FIG. 8 is a sequence diagram illustrating a control procedure according to a first embodiment of the present invention from a user apparatus transmission to a handover. User apparatus (UE) can communicate using both the 1st frequency and the 2nd frequency. Therefore, UE can communicate with eNB through a macro cell or a small cell.

As shown in FIG. 8, when a call is transmitted from the UE, the UE, eNB (radio base station), and MME (mobility management entity) execute a control procedure for transmission for the call. The call origination is reported from the eNB to the MME. When the UE transmits within the small cell area, the call transmission is reported to the control unit of the eNB via the small cell and further reported to the MME.

After the control procedure for outgoing call, MME sends E-RAB Setup Request message to eNB. The E-RAB Setup Request message specifies the type of bearer to be set up for the call. The eNB that has received the E-RAB Setup Request message executes internal processing necessary for setting up the designated bearer.

Moreover, eNB judges whether UE transmitted within the small cell area. That is, eNB judges whether UE transmitted via a small cell.

When the UE transmits within the macro cell area, the process proceeds as described above with reference to FIG. That is, after the bearer is set, when the UE detects a deterioration in communication quality, the eNB instructs the UE to perform different frequency measurement, and the different frequency measurement at the UE is performed. When handover is appropriate for the UE, handover from the eNB to another eNB is performed.

On the other hand, when the UE originates within the small cell area, after receiving the E-RAB Setup Request message, as shown in FIG.8, the eNB control unit sends the RRC Connection Reconfiguration message to the UE via the small cell. Send to. This RRC Connection Reconfiguration message is a bearer setting instruction that specifies the type of bearer to be set for the call, and a reception quality measurement instruction for the convenience of different frequency handover for the UE. This RRC Connection Reconfiguration message instructs activation of a measurement gap (Measurement Gap) in which the UE measures reception quality of a frequency band (carrier) different from the frequency that the UE is currently using for communication. Also, this RRC Connection Reconfiguration message specifies the frequency band (carrier) that the UE should measure, more specifically, the frequency band of the macro cell of the eNB, and instructs the UE to measure the reception quality of that frequency band. To do.

The UE that has received this RRC Connection Reconfiguration message executes processing necessary for setting the specified bearer. Further, the UE activates the measurement gap as instructed by the RRC Connection Reconfiguration message. In other words, the UE itself can measure the reception quality (more specifically, the reception quality of the macro cell frequency band) related to the cell with which the UE is not currently communicating at periodic time intervals. Set. Then, the UE sets the UE itself so that the UE can measure the reception quality in the frequency band specified in the RRC Connection Reconfiguration message.

After completion of these settings, the UE transmits an RRC Connection Reconfiguration Complete message indicating that these settings of the UE have been completed to the eNB via the small cell. Then, the eNB transmits an E-RAB Setup Response message indicating completion of bearer setup to the MME.

After this, the UE measures the reception quality of the frequency of the communicating cell and the reception quality of the frequency band of the non-communication cell, and transmits a report (Measurement Report) indicating the measurement result to the eNB. Since the UE has transmitted within the small cell area, the Measurement Report is transmitted to the control unit of the eNB via the small cell. When receiving the measurement report, the eNB control unit determines whether or not to perform handover for the UE that has transmitted the measurement report. The criterion for determining handover immediately after transmission in the small cell area is different from the normal criterion. In order to force the UE to handover from the small cell to the macro cell, if the UE can receive radio waves from the macro cell, the eNB determines that the handover should be performed. For example, if the reception quality in the frequency band of the macro cell indicated in Measurement Report is greater than a threshold, the eNB determines that the handover should be performed. The threshold may be small. For handover determination at this stage, it is not necessary to compare the reception quality of the macro cell frequency band and the reception quality of the small cell frequency band.

When the eNB control unit determines that the handover should be performed, the eNB control unit transmits an RRC Connection Reconfiguration message to the UE via the small cell. This RRC Connection Reconfiguration message is an instruction for handover to the UE, and instructs the UE to perform handover from the small cell to the macro cell. When receiving the RRC Connection Reconfiguration message that is an instruction of this handover, the UE executes processing necessary for the handover to the macro cell as instructed by the RRC Connection Reconfiguration message. The eNB and MME also execute a control procedure for handover from the small cell to the macro cell.

When the eNB control unit determines that handover should not be performed (that is, when the macro cell and the UE cannot communicate), the eNB control unit does not transmit a message to the UE via the small cell. The UE again measures the reception quality of the frequency of the communicating cell and the reception quality of the frequency band of the non-communication cell, and transmits a report indicating the measurement result to the eNB. In this way, when the handover should not be performed, reception quality measurement and reporting are repeated. However, if the entire small cell area is included in any of the macro cell areas managed by the eNB, the eNB does not determine that the handover should not be performed.

FIG. 9 is a block diagram showing a configuration of radio base station (eNB) 110 according to the first embodiment of the present invention. The eNB 110 includes

macro cells

111, 112, and 113, at least one small cell 119, a control unit 120, and an inter-base station communication interface (inter-base station communication unit) 116. Each of the

macro cells

111, 112, and 113 includes a wireless transmission unit 114, a wireless reception unit 115, and a cell communication control unit 117.

The wireless transmission unit 114 is a wireless transmission circuit that transmits a wireless signal to the UE that communicates with the macro cell provided with the wireless transmission unit 114, and the wireless reception unit 115 communicates with the macro cell provided with the wireless reception unit 115. It is a radio reception circuit which receives a radio signal from UE which performs. The cell communication control unit 117 is, for example, a CPU (central processing unit), operates according to a computer program, and controls communication with the UE of the macro cell in which the cell communication control unit 117 is provided. Although not shown in detail, the small cell 119 also includes a wireless transmission unit, a wireless reception unit, and a cell communication control unit. The wireless transmission unit of the small cell 119 is a wireless transmission circuit that transmits a wireless signal to the UE that communicates with the small cell 119, and the wireless reception unit of the small cell 119 receives a wireless signal from the UE that communicates with the small cell 119. It is a radio | wireless receiving circuit and the cell communication control part of the small cell 119 is CPU, for example, operate | moves according to a computer program, and controls communication with UE of the small cell 119.

The control unit 120 controls the entire eNB 110. The control unit 120 is a CPU, for example, and operates according to a computer program. The control unit 120 includes a handover control unit 121. The handover control unit 121 is a functional block realized by the control unit 120 functioning according to a computer program.

The inter-base station communication interface 116 is an interface for communicating with other radio base stations (eNB), and through this, the eNB 110 can communicate with other eNBs and MMEs. Communication between base stations may be wired communication or wireless communication. The control unit 120 of the eNB 110 manages not only the

macro cells

111, 112, and 113 but also the small cell 119.

When the eNB 110 receives an E-RAB Setup Request message from the MME after the above-described control procedure for transmission, the control unit 120 of the eNB 110 includes the eNB 110 internal necessary for setting the bearer specified by the E-RAB Setup Request message. Execute the process. In addition, the handover control unit 121 of the control unit 120 determines in which cell area the UE has transmitted.

When the UE transmits within the macro cell area (any of the cell areas corresponding to the

macro cells

111, 112, and 113), the process proceeds as described above with reference to FIG. In this case, the handover control unit 121 of the control unit 120 uses the radio transmission unit 114 and the radio reception unit 115 of the macro cell (any one of the

macro cells

111, 112, and 113) corresponding to the macro cell area transmitted by the UE, Processes related to setting, UE different frequency measurement, and UE handover as necessary are executed.

On the other hand, when the handover control unit 121 detects that the UE has transmitted within the small cell area, the handover control unit 121 receives the RRC Connection Reconfiguration message (bearer) after receiving the E-RAB Setup Request message from the MME. , Setting instructions, and different frequency measurement instructions) are transmitted to the UE via the small cell. As described above, this RRC Connection Reconfiguration message specifies the frequency band of the macro cell that the UE should measure, and instructs the UE to measure the reception quality of that frequency band. The RRC Connection Reconfiguration message may specify the frequency bands of all the

macro cells

111, 112, and 113 of the eNB 110. Alternatively, the RRC Connection Reconfiguration message may specify the frequency band of the macro cell closest to the small cell area transmitted by the UE (in this case, the eNB needs to manage the geographical relationship between the small cell and the macro cell) Is).

When the UE transmits an RRC Connection Reconfiguration Complete message in response to the RRC Connection Reconfiguration message, the handover control unit 121 receives the RRC Connection Reconfiguration Complete message via the small cell. Then, the control unit 120 transmits an E-RAB Setup Response message indicating completion of bearer setup to the MME.

After this, the UE sends a Measurement Report to the eNB. Since the UE has transmitted within the small cell area, the Measurement Report is transmitted to the eNB via the small cell. When the Measurement-Report is received via the small cell, the handover control unit 121 determines whether or not the UE should be handed over based on the Measurement-Report. In this embodiment, the handover control unit 121 confirms whether or not the UE can receive a radio wave from the

macro cell

111, 112 or 113.

When the handover control unit 121 determines that the handover should be performed (when the UE can receive radio waves from the macro cell), the handover control unit 121 sends an RRC Connection Reconfiguration message (handover instruction to the macro cell). Send to UE via small cell. Further, the handover control unit 121 controls the

macro cell

111, 112, or 113 for handover.

When the handover control unit 121 determines that the handover should not be performed (when the UE cannot receive radio waves from the macro cell), the handover control unit 121 does not transmit a message to the UE via the small cell. The UE again transmits Measurement Report to the eNB, and based on the Measurement Report, the handover control unit 121 determines whether or not the UE should be handed over.

As described above, when detecting that the UE has transmitted within the small cell area of the small cell, the eNB controls the UE so as to cause a UE handover from the small cell to the macro cell at an early stage. That is, the eNB facilitates handover regardless of whether or not the UE is actually at the end of the small cell area. Since the cell area (macro cell area) of the macro cell of the eNB is larger than the cell area (small cell area) of the small cell, even if the UE is moving at a high speed once it is handed over to the macro cell, By moving to another cell area, it is highly probable that procedures necessary for subsequent handover from the macro cell to another cell can be completed. Therefore, even when the UE transmitted in the small cell area of the small cell is moving at high speed, disconnection between the UE and the communication network can be reduced or prevented.

In this embodiment, in order to cause the UE handover from the small cell to the macro cell, the eNB causes the UE to measure the reception quality of the macro cell frequency band, and can the UE receive radio waves from the macro cell? If the UE can receive radio waves from the macro cell, a handover instruction is transmitted to the UE. Therefore, an RRC Connection Reconfiguration message is transmitted from the eNB to the UE at least twice from the UE transmission to the handover. That is, an RRC Connection Reconfiguration message that is a bearer setting instruction and a different frequency measurement instruction, and an RRC Connection Reconfiguration message that is a handover instruction. As is clear from comparison between FIG. 4 and FIG. 8, in this embodiment, since the first RRC Connection Reconfiguration message is used as both a bearer setting instruction and a different frequency measurement instruction, handover from the UE's origination is performed. The number of RRC Connection Reconfiguration message transmissions up to can be reduced.

In this embodiment, when the UE can receive radio waves from the macro cell, the handover control unit 121 causes handover of the UE from the small cell to the macro cell. For this reason, it is possible to prevent the UE from receiving radio waves from the macro cell due to handover from the small cell to the macro cell. Such an inconvenience may occur when the small cell area is not included in the macro cell area.

Second Embodiment FIG. 10 is a block diagram showing a configuration of a radio base station (eNB) according to a second embodiment of the present invention. The configuration of the eNB 110 according to the second embodiment is almost the same as that of the first embodiment, but the control unit 120 further includes a communication type determination unit 122 and a handover determination unit 123. The communication type determination unit 122 and the handover determination unit 123 are functional blocks realized by the control unit 120 functioning according to the computer program.

The communication type determination unit 122 determines the type of communication to be provided to the UE when the UE transmits within the small cell area. The handover determining unit 123 determines whether or not to cause the UE handover from the small cell to the macro cell at an early stage according to the communication type determined by the communication type determining unit 122. When the handover determination unit 123 determines that the handover should be caused early, the handover control unit 121 controls the UE so as to cause the handover of the UE from the small cell to the macro cell.

In the first embodiment, the process shown in FIG. 4 or FIG. 8 is executed according to the cell area transmitted by the UE. In 2nd Embodiment, when UE transmits in a small cell area, the process shown by FIG. 4 or FIG. 8 is performed according to the classification of the communication which should be provided to UE.

As shown in FIG. 8, when a call is transmitted from the UE, the UE, the eNB (radio base station), and the MME execute a control procedure for transmission for the call. The call origination is reported from the eNB to the MME. When the UE transmits in the small cell area, the call transmission is reported from the small cell to the eNB and further reported to the MME.

When the eNB 110 receives an E-RAB Setup Request message from the MME after the control procedure for transmission, the control unit 120 of the eNB 110 performs processing inside the eNB 110 necessary for setting the bearer specified by the E-RAB Setup Request message. Execute. In addition, the handover control unit 121 of the control unit 120 determines in which cell area the UE has transmitted.

macro cells

On the other hand, when the handover control unit 121 detects that the UE has transmitted within the small cell area, the communication type determination unit 122 determines the type of communication to be provided to the UE. There are at least two types of communication among voice communication (VoLTE, Voice Over LTE), videophone (videophone), video streaming, and other data communication. For example, the communication type determination unit 122 may be able to distinguish between voice call and data communication only, or may be able to distinguish between voice call, videophone (videophone), and data communication. The index for the communication type determination unit 122 to determine the type of communication is not particularly limited. For example, the communication type determination unit 122 may determine the communication type from the E-RAB Setup Request message transmitted from the MME.

The handover determining unit 123 determines whether or not to cause a UE handover from the small cell to the macro cell at an early stage according to the type of communication determined by the communication type determining unit 122. If the communication type is a voice call or videophone, the disconnection of communication will be confusing to the user of the UE, so the UE handover from the small cell to the macrocell to avoid disconnection of the user equipment and the communication network Should be caused. In this case, the handover determining unit 123 determines that a handover should be caused early.

If the type of communication is data communication, even if communication is interrupted, if the user is reconnected, the user of the UE will not be annoying so much, so the UE handover from the small cell to the macro cell is not necessary. Conceivable. In this case, the handover determining unit 123 determines that a handover should not be caused. As a result, the load on the macro cell can be reduced.

If the communication type is video streaming, the disconnection of communication will be confusing to the user of the UE, so the handover determination unit 123 may determine that the handover should be caused early. However, some operators may consider that a handover should not be caused for video streaming, taking into account the burden of the communication network or other circumstances. For video streaming, the handover determining unit 123 may determine that a handover should not be caused.

If the handover determining unit 123 determines that the handover should not be caused, the process proceeds as described above with reference to FIG. In this case, the handover control unit 121 of the control unit 120 uses the radio transmission unit and the radio reception unit of the small cell 119 corresponding to the small cell area transmitted by the UE to set the bearer, and to make a difference at the UE as necessary. Processes related to frequency measurement and UE handover are executed.

When the handover determining unit 123 determines that the handover should be caused early, as shown in FIG. 8, the handover control unit 121 sends an RRCRRConnection Reconfiguration message (bearer setting instruction, different frequency measurement instruction) Send to UE via small cell. As described above, this RRC Connection Reconfiguration message specifies the frequency band of the macro cell that the UE should measure, and instructs the UE to measure the reception quality of that frequency band. The RRC Connection Reconfiguration message may specify the frequency bands of all the

macro cells

After this, the UE sends a Measurement Report to the eNB. Since the UE has transmitted within the small cell area, the Measurement Report is transmitted to the eNB via the small cell. When the Measurement Report is received via the small cell 119, the handover control unit 121 determines whether or not the UE should be handed over based on the Measurement Report. In this embodiment, the handover control unit 121 confirms whether or not the UE can receive a radio wave from the

macro cell

111, 112 or 113.

macro cell

111, 112, or 113 for handover.

In this embodiment, according to the type of communication to be provided to the UE, the handover determination unit 123 determines whether or not to cause the UE handover from the small cell to the macro cell at an early stage. In communication types where the disruption of communication confuses the user of the UE, it is possible to cause a UE handover from the small cell to the macro cell at an early stage, and in other communication types, from the small cell to the macro cell. It is possible not to cause the UE handover at an early stage.

Third Embodiment FIG. 11 is a block diagram showing a configuration of a radio base station (eNB) according to a third embodiment of the present invention. The configuration of the eNB 110 according to the third embodiment is almost the same as that of the first embodiment, but the control unit 120 further includes a communication type determination unit 122 and a sub cell determination unit 124. The communication type determination unit 122 and the sub cell determination unit 124 are functional blocks realized by the control unit 120 functioning according to the computer program.

The communication type determination unit 122 determines the type of communication to be provided to the UE when the UE transmits within the small cell area. The communication type determination unit 122 may be the same as that of the second embodiment. However, in this embodiment, as in the first embodiment, the eNB detects that the UE transmits within the small cell area of the small cell regardless of the type of communication to be provided to the UE. The UE is controlled so as to cause a handover of the UE from the small cell to the macro cell at an early stage. As a result of the handover, the main cell (PCell) of the UE becomes a macro cell (

macro cell

111, 112 or 113).

Should the secondary cell determination unit 124 designate a small cell corresponding to the small cell area transmitted by the UE as a secondary cell (SCell) for carrier aggregation for the UE according to the type of communication determined by the communication type determination unit 122 Judge whether or not. When the communication type is a voice call, generally, a high communication speed is not necessary, so that there is little need for carrier aggregation and little need for adding a subcell. On the other hand, if the audio type is videophone, video streaming, and other data communication, it may be necessary to increase the communication speed by carrier aggregation (whether the subcell is actually used or not). Depending on usage).

In this embodiment, when the communication type is a voice call, the sub cell determination unit 124 determines that a small cell corresponding to the small cell area transmitted by the UE should not be designated as a sub cell for carrier aggregation for the UE. . In other cases, the sub cell determination unit 124 determines that the small cell corresponding to the small cell area transmitted by the UE should be designated as a sub cell for carrier aggregation for the UE.

When the sub cell determination unit 124 determines that the small cell corresponding to the small cell area transmitted by the UE should be designated as a sub cell for the UE, the control unit 120 (sub cell addition instruction unit) of the eNB 110 A sub cell addition instruction for instructing the UE to add the small cell as a sub cell is transmitted to the UE. For example, the control unit 120 may transmit a sub cell addition instruction to the UE via a small cell corresponding to the small cell area transmitted by the UE. The sub cell addition instruction may be included in, for example, an RRCconfigurationConnection Reconfiguration message that is an instruction for handover to the macro cell. Or the control part 120 may transmit the subcell addition instruction | indication to UE using the macrocell 111,112 or 113 which became the main cell after completion of a handover.

In this embodiment, according to the type of communication to be provided to the UE, the sub cell determination unit 124 should designate the small cell corresponding to the small cell area transmitted by the UE as the sub cell for carrier aggregation for the UE. Judge whether or not. In communication types that may require high communication speeds, it is possible to add subcells for the UE, and in other communication types it is possible not to add subcells.

Fourth Embodiment FIG. 12 is a sequence diagram illustrating a control procedure according to a fourth embodiment of the present invention from a user apparatus transmission to a handover. The configuration of the radio base station (eNB) of the fourth embodiment may be the same as that of the first embodiment.

As shown in FIG. 12, when a call is transmitted from the UE, the UE, the eNB, and the MME execute a control procedure for transmission for the call. The call origination is reported from the eNB to the MME. When the UE transmits in the small cell area, the call transmission is reported from the small cell to the eNB and further reported to the MME.

macro cells

On the other hand, when the handover control unit 121 detects that the UE has transmitted within the small cell area, the handover control unit 121 transmits an RRC Connection Reconfiguration message to the UE via the small cell. This RRC Connection Reconfiguration message is a bearer setting instruction that specifies the type of bearer to be set for the call, as well as a handover instruction to the UE, instructing the UE to perform handover from the small cell to the macro cell. To do. The eNB 110 manages the geographical relationship between the small cell and the macro cell, and the handover control unit 121 specifies the macro cell closest to the small cell area transmitted by the UE in the RRC Connection Reconfiguration message.

The UE that has received this RRC Connection Reconfiguration message executes processing necessary for setting the specified bearer, and also executes processing necessary for handover to the macro cell as instructed by the RRC Connection Reconfiguration message. The handover control unit 121 controls the

macro cell

111, 112, or 113 for handover.

As described above, in this embodiment, when detecting that the UE has transmitted within the small cell area of the small cell, the handover control unit 121 does not check whether the UE can receive radio waves from the macro cell. Immediately triggers the UE handover from the small cell to the macro cell. Therefore, the UE can be handed over from the small cell to the macro cell forcibly and early. As is apparent from a comparison between FIG. 8 and FIG. 12, in this embodiment, the RRC Connection Reconfiguration message is used as both a bearer setting instruction and a handover instruction. The number of transmissions of Connection Reconfiguration message can be reduced.

However, it is desirable that the entire small cell area is included in the macro cell area in order to prevent the UE from receiving radio waves from the macro cell due to handover from the low power base station to the macro cell. From this point of view, the fourth embodiment can be realized in a communication network in which many small cell areas are entirely included in any one of the macro cell areas. Alternatively, the handover control unit 121 confirms whether the small cell area transmitted from the UE is entirely covered by the macro cell area, and the small cell area transmitted from the UE is entirely covered by the macro cell area. Alternatively, an RRC Connection Reconfiguration message, which is a bearer setting instruction and an instruction for handover to the UE, may be transmitted. For convenience of confirmation, it is preferable that the eNB 110 records a small cell area that is entirely covered by a macro cell area.

Although the fourth embodiment is a modification of the first embodiment, the second embodiment or the third embodiment may be similarly modified. That is, according to the type of communication to be provided to the UE, the eNB may determine whether or not to cause the UE handover from the small cell to the macro cell at an early stage. Or according to the classification of the communication which should be provided to UE, you may judge whether the small cell corresponding to the small cell area which UE transmitted should be designated as a subcell for UE.

Fifth Embodiment FIG. 13 is a block diagram showing a configuration of a radio base station (eNB) according to a fifth embodiment of the present invention. The configuration of the eNB 110 according to the fifth embodiment is almost the same as that of the third embodiment, but the control unit 120 further includes a second handover determination unit 125. The second handover determining unit 125 is a functional block realized by the control unit 120 functioning according to the computer program.

The second handover determination unit 125 allows the UE to be handed over when an appropriate communication service is provided from the macro cell to the UE, assuming that the UE has been handed over to the macro cell. More specifically, the reception quality of the radio wave transmitted from the macro cell at the UE, the resource usage at the macro cell, the number of UEs currently connected to the macro cell, the traffic at the macro cell, and the Based on at least one of the restriction information indicating that the UE connection in the macro cell is restricted, the second handover determining unit 125 determines whether or not to cause the UE handover from the small cell to the macro cell. . When the second handover determining unit 125 determines that the handover should not be caused, the handover control unit 121 does not cause the UE handover from the small cell to the macro cell. When the second handover determining unit 125 determines that a handover should be caused, the handover control unit 121 causes a UE handover from the small cell to the macro cell.

When using the reception quality at the UE of the radio wave transmitted from the macro cell as a reference, the second handover determining unit 125 refers to the reception quality related to the macro cell reported from the UE, and this reception quality is a threshold value. If it is lower, no handover is allowed. This is to avoid degradation of reception quality and communication interruption at the UE.

When using the resource usage in the macro cell as a reference, the second handover determining unit 125 refers to the resource usage of the macro cell reported from the macro cell, and allows the handover if the resource usage is higher than the threshold. do not do. This is to avoid an overload in the macro cell due to the handover of the UE, and thus a deterioration in the quality of service to this UE and many other UEs. The resource here is any of various IDs used in the macro cell, a memory area in the macro cell, and a CPU usage in the macro cell.

When using the number of UEs currently connected to the macro cell as a reference, the second handover determination unit 125 refers to the number of UEs currently connected to the macro cell reported from the macro cell, and determines the number of UEs. If is higher than the threshold, handover is not allowed. This is to avoid an overload in the macro cell due to the handover of the UE, and thus a deterioration in the quality of service to this UE and many other UEs.

When using the traffic volume in the macro cell as a reference, the second handover determining unit 125 refers to the traffic volume in the macro cell reported from the macro cell, and does not allow handover if the traffic volume is higher than the threshold. This is to avoid an overload in the macro cell due to the handover of the UE, and thus a deterioration in the quality of service to this UE and many other UEs.

When the restriction information indicating that the UE connection in the macro cell is restricted is used as a reference, the second handover determination unit 125 performs the handover when the UE connection in the macro cell is restricted. Not allowed. Here, “connection restriction” means that when a large number of UEs connect to a cell and congestion occurs, the communication network prohibits or restricts connection of a new UE. When the connection is restricted in the macro cell, the UE cannot connect to the macro cell in principle, and a call loss occurs due to the handover to the macro cell. In order to prevent call loss, the second handover determination unit 125 does not allow handover when the connection of the UE in the macro cell is restricted.

In this embodiment, assuming that the UE has been handed over to the macro cell, the UE is allowed to hand over when an appropriate communication service is provided from the macro cell to the UE. it can.

The fifth embodiment is a modification of the third embodiment, but other embodiments may be similarly modified.

Other Modifications The illustrated eNB 110 includes three

macro cells

111, 112, and 113 and one small cell 119, but the number of macro cells provided in the eNB 110 is not limited to three. The number of small cells provided in the eNB 110 is not limited to one.

In the eNB 110, each function executed by the CPU may be executed by hardware instead of the CPU, or may be executed by a programmable logic device such as FPGA (Field Programmable Gate Array) or DSP (Digital Signal Processor). Also good.

The present invention relates to a transmission of a user device, and this transmission is not limited to a transmission when the user device is in an idle state, but may be a transmission of another type of communication when the user device is already communicating. . That is, when the user apparatus is already communicating with the small cell and the user apparatus makes a call to the small cell within the small cell area, a handover of the user apparatus from the small cell to the macro cell may be caused. As a result of the handover, the user equipment may communicate with both the small cell and the macro cell. For example, when a user device in data communication with a small cell as a PCell transmits for a voice call within the small cell area and hands over to the macro cell, the user device sets the macro cell as a PCell and the handover source small cell as a SCell. Communication may be performed, and control may be performed such that the user apparatus performs a voice call with the PCell (macro cell) and performs data communication with the PCell and the SCell (small cell).

The problem of disconnection between the UE and the communication network that occurs when the UE is moving at high speed can occur because the UE communicates with the small cell. Therefore, this problem can be reduced or prevented by not handing over the UE communicating with the macro cell to the small cell. From this viewpoint, when a UE that can communicate with both the macro cell and the small cell at the first frequency and the second frequency is communicating with the macro cell (any one of the

macro cells

111, 112, and 113), the control unit 120 of the eNB The handover control unit 121 (handover regulation unit) may regulate the UE handover from the macro cell to the small cell. Since the cell area (macro cell area) of the macro cell of the eNB 110 is larger than the cell area (small cell area) of the small cell, if the handover from the macro cell to the small cell is restricted, even if the UE moves at high speed, the macro cell By moving from the area to another cell area, it is highly probable that procedures necessary for subsequent handover from the macro cell to another cell can be completed. Therefore, even when the UE is moving at high speed, disconnection between the UE and the communication network can be reduced or prevented.

For this purpose, when the handover control unit 121 (handover restriction unit) of the eNB control unit 120 detects that the UE has transmitted in the macro cell area, the handover control unit 121 executes at least one of the following.
(1) In the RRC Connection Reconfiguration message, which is a different frequency measurement instruction, the handover control unit 121 uses a frequency of a small cell near the macro cell corresponding to the macro cell area transmitted by the UE as a frequency band (carrier) to be measured by the UE. No band is shown. Therefore, the UE does not measure the reception quality in the small cell frequency band, and does not transmit a measurement report that leads to handover to the small cell.
(2) The handover control unit 121 instructs the UE not to measure the frequency band of the small cell near the macro cell corresponding to the macro cell area transmitted by the UE. Therefore, the UE does not measure the reception quality in the small cell frequency band, and does not transmit a measurement report that leads to handover to the small cell.
(3) Upon receiving a Measurement Report that leads to a handover from the UE to the small cell, the handover control unit 121 discards the Measurement Report or does not hand over the UE to the small cell. In any case, the UE request by the Measurement Report is ignored.
(4) Upon receiving a Measurement Report that leads a handover from the UE to a small cell or another macro cell, the handover control unit 121 instructs the UE to perform a handover to another macro cell.

In addition, the control unit 120 includes a communication type determination unit 122 similar to that of the second embodiment, and the communication type determination unit 122 is a type of communication provided to the UE before or during communication of the UE with the macro cell. Depending on the type of communication determined by the communication type determination unit 122, the handover control unit 121 (handover restriction unit) may regulate the handover of the UE from the macro cell to the small cell. If the type of communication is a voice call or a videophone, the disconnection of communication will be confusing to the user of the UE, so a small cell is used for the UE to avoid disconnection of the UE and the communication network. It should not be. In this case, the handover determining unit 123 determines that a handover from the macro cell to the small cell should not be caused. On the other hand, if the communication type is data communication, even if communication is interrupted, if the user is reconnected, the user of the UE will not be disturbed so much, so the UE may be handed over from the macro cell to the small cell. it is conceivable that. In this case, the handover determining unit 123 determines that a handover from the macro cell to the small cell should be caused. As a result, the load on the macro cell can be reduced.

In the above embodiment, when the UE transmits within the small cell area, the eNB causes the UE to handover from the small cell to the macro cell. However, without this feature, the eNB may regulate the handover of the UE from the macro cell to the small cell.

1, 2 UE (user equipment), 10, 20 macro cell, 10A, 10B, 20A cell area (macro cell area), 30, 31, 32, 33 pico cell (small cell), 30B, 31B, 32B, 33C cell area (pico cell) Area), 110 eNB (radio base station, macro base station), 111, 112, 113 macro cell, 116 inter-base station communication interface, 114 radio transmitter, 115 radio receiver, 117 cell communication controller, 119 small cell, 120 Control unit (sub cell addition instruction unit), 121 handover control unit (handover restriction unit), 122 communication type determination unit, 123 handover determination unit, 124 sub cell determination unit, 125 second handover determination unit.

Claims

A macro cell that forms a macro cell area and communicates wirelessly with user equipment in the macro cell area using a first frequency;
A small cell area having a transmission power smaller than that of the macro cell and a smaller area than the macro cell area is formed, and wireless communication is performed using a second frequency different from the first frequency with a user apparatus in the small cell area. A small cell to do,
A handover control unit that causes a handover of the user apparatus from the small cell to the macro cell when a user apparatus capable of communicating at the first frequency and the second frequency transmits within the small cell area. A wireless base station characterized by that.
The handover control unit confirms whether or not the user apparatus can receive radio waves from the macro cell, and when the user apparatus can receive radio waves from the macro cell, the handover control unit The radio base station according to claim 1, wherein a handover of the user apparatus from a small cell to the macro cell is caused.
When the user apparatus transmits within the small cell area, if the entire small cell area is included in the macro cell area, whether or not the user apparatus can receive radio waves from the macro cell. The radio base station according to claim 1, wherein the handover control unit causes a handover of the user apparatus from the small cell to the macro cell without confirmation.
A communication type determination unit that determines a type of communication to be provided to the user device when the user device makes a call within the small cell area;
In accordance with the type of communication determined by the communication type determination unit, further comprising a handover determination unit for determining whether to cause a handover of the user apparatus from the small cell to the macro cell,
The radio according to claim 1, wherein when the handover determination unit determines that a handover should be caused, the handover control unit causes a handover of the user apparatus from the small cell to the macro cell. base station.
A communication type determination unit that determines a type of communication to be provided to the user device when the user device makes a call within the small cell area;
A sub-cell determining unit that determines whether or not the small cell should be designated as a sub-cell of carrier aggregation for the user apparatus according to the type of communication determined by the communication type determining unit;
A sub cell for instructing the user apparatus to add the small cell as a sub cell when the sub cell determining unit determines that the small cell should be designated as a sub cell for the user apparatus. The radio base station according to claim 1, further comprising a sub cell addition instruction unit that transmits an addition instruction to the user apparatus.
Reception quality of radio waves transmitted from the macro cell at the user equipment, resource usage at the macro cell, number of user equipments connected to the macro cell, communication volume at the macro cell, and UE connection at the macro cell. A second handover determining unit for determining whether to cause a handover of the user apparatus from the small cell to the macro cell based on at least one of restriction information indicating that the restriction is present;
2. The handover control unit does not cause a handover of the user apparatus from the small cell to the macro cell when the second handover determining unit determines that a handover should not be caused. The radio base station described in 1.
A handover restricting unit for restricting handover of the user apparatus from the macro cell to the small cell when a user apparatus capable of communicating at the first frequency and the second frequency is communicating with the macro cell; The radio base station according to claim 1.
The radio base station according to claim 7, wherein the handover restricting unit restricts handover of the user apparatus from the macro cell to the small cell according to a type of communication provided to the user apparatus. .
A macro cell area is formed, a macro cell wirelessly communicating with a user apparatus in the macro cell area using a first frequency, and a small cell area having a transmission power smaller than that of the macro cell and smaller than the macro cell area. Then, in a communication control method in a radio base station comprising a user apparatus in the small cell area and a small cell that performs radio communication using a second frequency different from the first frequency,
Detecting that a user apparatus capable of communicating at the first frequency and the second frequency transmits within the small cell area;
Initiating a handover of the user apparatus from the small cell to the macro cell when the user apparatus makes a call within the small cell area.
A macro cell that forms a macro cell area and communicates wirelessly with user equipment in the macro cell area using a first frequency;
A small cell area having a transmission power smaller than that of the macro cell and a smaller area than the macro cell area is formed, and wireless communication is performed using a second frequency different from the first frequency with a user apparatus in the small cell area. A small cell to do,
A handover restricting unit that restricts a handover of the user apparatus from the macro cell to the small cell when a user apparatus capable of communicating at the first frequency and the second frequency is communicating with the macro cell; A wireless base station characterized by that.
Before or during communication of the user device with the macro cell, further comprising a communication type determination unit for determining the type of communication provided to the user device,
The radio according to claim 10, wherein the handover restricting unit restricts handover of the user apparatus from the macro cell to the small cell according to the type of communication determined by the communication type determining unit. base station.
A macro cell area is formed, a macro cell wirelessly communicating with a user apparatus in the macro cell area using a first frequency, and a small cell area having a transmission power smaller than that of the macro cell and smaller than the macro cell area. Then, in a communication control method in a radio base station comprising a user apparatus in the small cell area and a small cell that performs radio communication using a second frequency different from the first frequency,
Communicating with the user equipment capable of communicating at the first frequency and the second frequency using the macro cell;
Regulating a handover of the user equipment from the macro cell to the small cell.