JP5924438B2 - Method for measuring signal and base station apparatus - Google Patents

Description

  The present invention relates to a method for measuring a signal, a terminal device, and a base station device.

Conventionally, in a mobile communication system, a wireless communication service has been provided by a base station apparatus (macro base station apparatus) that forms a cell (macro cell) having a radius of several hundred meters to several tens of kilometers.
In recent years, with the introduction of LTE (Long Term Evolution), data communication traffic is expected to increase dramatically. Therefore, it has been studied to arrange a small base station apparatus that forms a cell (such as a pico cell) having a smaller cell radius than a macro cell within the macro cell area (see Non-Patent Document 1).
By moving a terminal device that performs a large amount of data communication from a macro cell to a pico cell and communicating from the pico cell, it is possible to cope with an increasing traffic.

  Also, in order to accommodate more terminal devices in the pico cell, the base station device (pico base station device) that forms the pico cell performs processing for expanding the pico cell (cell range expansion; CRE). Is being considered. When the cell range expansion process is performed, the terminal device can connect to the pico base station device even if the radio wave from the pico base station device is somewhat weak.

  However, even if the terminal device existing at the cell edge of the pico cell is connected to the base station device that forms the pico cell, the power of the signal transmitted from the base station device that forms the macro cell becomes larger, and is susceptible to interference. .

Therefore, in order to avoid interference, it is considered that the macro base station apparatus sets some frequency blocks in the usable frequency range as blank carriers that are not used in the macro cell.
The pico base station apparatus uses the frequency block (component carrier) corresponding to the blank carrier in the macro base station apparatus for communication in the pico cell, so that the terminal apparatus connected to the pico base station apparatus Interference can be avoided.

  Here, as described above, the blank carrier is a component carrier that is not used for communication among the component carriers (frequency blocks) that the base station apparatus can use for communication.

The base station device selects one primary component carrier (Primary Component Carrier) from a plurality of component carriers (frequency blocks) that the base station device can use for communication, and additionally uses it for communication as necessary. The secondary component carrier (Secondary Component Carrier) that is one or a plurality of component carriers to be used is used.
Communication between the base station apparatus and the terminal apparatus is basically performed using a primary component carrier. However, if the terminal device can use the secondary component carrier, communication using the secondary component carrier is additionally performed.

  Among the plurality of component carriers, one or a plurality of component carriers that are not selected as either the primary component carrier or the secondary component carrier are blank carriers.

3GPP, "TS36.104 V10.0.0 Base Station (BS) radio transmission and reception", 2010-09

  The terminal device measures the communication quality of a signal transmitted from a base station device other than the macro base station device while being present in the macro cell. Based on the measurement result, the terminal apparatus may perform a handover, which is a process for changing the base station apparatus (serving base station apparatus) to be connected from the macro base station apparatus to another base station apparatus.

However, it has not yet been proposed to consider a blank carrier as described above when measuring a signal by a terminal device.
Therefore, an object of the present invention is to provide a new technical means considering a blank carrier for signal measurement by a terminal device.

(1) The present invention from one viewpoint is a method in which a terminal apparatus measures a signal, and the terminal apparatus is a first base station apparatus that is a serving base station apparatus to which the terminal apparatus is connected. Information that can identify a blank carrier that is not used for communication is received from the first base station device, and the terminal device uses the frequency of the blank carrier identified based on the received information as a target frequency, This is a method of measuring a signal transmitted from a second base station apparatus.

  According to the present invention, the measurement of the signal transmitted from the second base station apparatus is performed using the frequency of the blank carrier of the first base station apparatus as the target frequency. Since the blank carrier does not cause interference, the signal can be measured while avoiding interference.

(2) After the second base station apparatus becomes a new serving base station apparatus by handover, the terminal apparatus uses the first base station among the carriers that can be used by the second base station apparatus. The signal transmitted from the first base station apparatus can be measured using the frequency of a carrier other than the blank carrier that is not used for communication by the station apparatus as a target frequency. After the handover, the frequency of the carrier other than the blank carrier that is not used for communication by the first base station device is set as the target frequency, so that the measurement at the frequency that the first base station device uses for communication is performed. Yes.

(3) The present invention from another viewpoint is a method in which a terminal apparatus measures a signal, and the first base station apparatus, which is a serving base station apparatus to which the terminal apparatus is connected, has the terminal apparatus A determination process for determining whether or not a target frequency for measuring a signal and a frequency of a blank carrier in the first base station apparatus overlap, a target frequency for measuring the signal by the terminal apparatus, and the first If the frequency of the blank carrier in the base station apparatus of the first base station apparatus does not overlap, the target frequency for measuring the signal by the terminal apparatus and the frequency of the blank carrier in the first base station apparatus are obtained. State change processing for the terminal device, and the terminal device overlaps a target frequency at which the terminal device measures a signal and a frequency of a blank carrier in the first base station device. Under conditions of a method of measuring a signal transmitted from the second base station apparatus.

  According to the present invention, even if the target frequency at which the terminal apparatus measures a signal and the frequency of the blank carrier in the first base station apparatus do not overlap, the state change process causes an overlapping state. can get. Since the blank carrier does not cause interference, the signal can be measured while avoiding interference.

(4) The determination process is performed by determining whether or not the frequency of the primary component carrier in the second base station apparatus overlaps with the frequency of the blank carrier in the first base station apparatus. The state change process is preferably executed when the frequency of the primary component carrier in the second base station apparatus and the frequency of the blank carrier in the first base station apparatus do not overlap.
In this case, the determination processing as to whether or not the target frequency for measuring the signal by the terminal device and the frequency of the blank carrier in the first base station device is the primary in the second base station device. This is executed by determining whether or not the frequency of the component carrier and the frequency of the blank carrier in the first base station apparatus overlap. That is, the frequency of the primary component carrier in the second base station apparatus is a target frequency at which the terminal apparatus measures a signal.

(5) In the state change process, a command for causing the terminal device to measure a signal frequency to be a frequency of one or a plurality of secondary component carriers in the second base station device is transmitted to the terminal device. Processing can be included.

(6) Based on the command, the terminal device uses the frequencies of a plurality of secondary component carriers as target frequencies to measure the signal transmitted from the second base station device. It is preferable that the frequency of the blank carrier in the first base station apparatus is measured with priority.

(7) The state change process may include a process of transmitting, to the second base station apparatus, a request for changing the frequency of a primary component carrier to the second base station apparatus.

(8) When the second base station apparatus cannot change the frequency of the primary component carrier in accordance with the change request, it is preferable to transmit a change impossible notification to the first base station apparatus.

(9) The second base station apparatus determines whether or not the frequency of the primary component carrier can be changed according to the change request, based on the frequency of the blank carrier in the third base station apparatus, When it is determined that the frequency of the primary component carrier cannot be changed according to the change request, it is preferable that the change impossible notification is transmitted to the first base station apparatus.

(10) In the state change process, when the first base station apparatus receives the change impossibility notification, the target frequency for measuring the signal by the terminal apparatus is set to 1 or 2 in the second base station apparatus. The process which transmits the instruction | command for making it the frequency of a some secondary component carrier to the said terminal device can be included.

(11) In the state change process, the frequency of the primary component carrier in the second base station apparatus and the frequency of the blank carrier in the first base station apparatus are overlapped with each other in the first base station. A process of changing the frequency of the blank carrier in the apparatus can be included.

(12) In the state change process, when the first base station apparatus receives the change impossibility notification, the frequency of the primary component carrier in the second base station apparatus and the first base station apparatus The process of changing the frequency of the blank carrier in the first base station apparatus so as to overlap with the frequency of the blank carrier in FIG.

(13) The second base station device is preferably a small base station device that forms a smaller cell than a cell formed by the first base station device.

(14) The present invention viewed from another viewpoint is a terminal device that performs communication with a base station device, and a blank carrier that is not used for communication by a first base station device that is a serving base station device. A means for receiving identifiable information from the first base station apparatus, and a signal transmitted from the second base station apparatus with a frequency of a blank carrier identified based on the received information as a target frequency. And a measuring device.

(15) A determination process for determining whether or not a target frequency at which a terminal device measures a signal and a frequency of a blank carrier in the own device overlap with each other in a base station device that performs communication with the terminal device The target frequency at which the terminal device measures the signal and the frequency of the blank carrier at the own device, and the frequency at which the terminal device measures the signal and the frequency of the blank carrier at the own device And a state change processing unit for obtaining a state in which the two overlap each other.

(16) The present invention from another viewpoint is a communication system including the terminal device according to (14) and the base station device according to (15).

  ADVANTAGE OF THE INVENTION According to this invention, a terminal device can measure a signal with the blank carrier of a serving base station apparatus.

It is a block diagram of a communication system. It is a flowchart which shows the process sequence for signal measurement. It is a figure which shows the signal measurement object after a hand-over. It is a block diagram of the communication system which concerns on 2nd Embodiment. It is a flowchart (first half) which shows the process sequence for signal measurement. It is a flowchart (second half) which shows the process sequence for signal measurement. It is a figure which shows a neighbor cell list. It is a modification of the flowchart (latter half) which shows the process sequence for signal measurement.

[1. First Embodiment]
1 to 3 show a communication system according to the first embodiment. This communication system is a cellular system including a plurality of base station devices (BS) 1 (1a, 1b). The radio communication system according to the present embodiment is, for example, a system for a mobile phone to which LTE is applied. Communication between each base station apparatus 1 and a terminal apparatus (UE: User Equipment) 2 is based on LTE. Is done. However, the communication method is not limited to LTE.

The plurality of base station apparatuses 1 constituting the communication system include, for example, a macro base station apparatus (Macro Base Station; MBS) 1a that forms a communication area (macro cell) MC having a size of several kilometers, as well as a macro cell MC. A pico base station (PBS) 1b that forms a small picocell PC is included.
Hereinafter, the macro base station apparatus is referred to as a macro BS, and the pico base station apparatus is referred to as a pico BS.

  As shown in FIG. 1, one or a plurality of pico BSs 1b are installed in a macro cell. By preferentially connecting terminal devices in the macro cell MC to the pico BS 1b instead of the macro BS 1a, the communication load of the macro BS 1a can be reduced, and the throughput of the entire system can be improved. Also, the pico BS 1b can connect more terminal devices to the pico BS 1b by performing cell range extension (CRE). That is, the terminal device regards the power of the signal transmitted from the pico BS 1b as being larger than the actual received power by adding a predetermined value to the actual received power. As a result, the terminal device is preferentially connected to the higher-priority pico BS 1b.

  In addition, base station apparatuses, such as macro BS1a and pico BS1b, are connected by the network between base stations (wired network). The inter-base station network is configured by a line using a communication interface called an X2 interface, and is used for information exchange between base station apparatuses.

As shown in FIG. 1, in the present embodiment, the frequency range that can be used by the base station apparatus 1 is divided into a plurality (five) of component carriers (frequency blocks) # 0 to # 4.
The macro BS 1a uses the four component carriers # 0 and # 2 to # 4 for communication with the terminal device 2 connected to the macro BS 1a. That is, the macro BS 1a uses the # 1 component carrier as a blank carrier and does not use it for signal transmission.

  The pico BS 1b in the macro cell MC uses the component carrier # 1, which is a blank carrier in the macro BS 1a, for communication with a terminal device in the pico cell PC (in particular, a terminal device near the cell edge of the pico cell PC). Accordingly, even if the terminal device (not shown) connected to the pico BS 1b is located at a place where the radio BS 1a is susceptible to radio wave interference, such as near the cell edge of the pico cell PC, the use frequency differs, so the macro BS 1a The radio wave interference from can be avoided.

  The pico BS 1b receives information (hereinafter referred to as “blank carrier information”) that can identify the blank carrier # 1 of the macro BS 1a from the macro BS 1a using the inter-base station network or wireless communication. Based on the received blank carrier information of the macro BS 1a, the pico BS 1b determines the component carrier # 1 as a component carrier (primary component carrier) that the own device 1b uses for communication with the terminal device.

  The pico BS 1b receives the blank carrier information of the macro BS 1a from another device having the blank carrier information (a terminal device connected to the macro BS 1a or a management server on the network between base stations). May be.

  The blank carrier information may directly indicate a component carrier that is a blank carrier among the usable component carriers # 0 to # 4, or the usable component carriers # 0 to # 4. Among these, by indicating the component carrier used for communication, the component carrier that is a blank carrier may be indirectly indicated.

In FIG. 1, it is assumed that the terminal device 2 is connected to the macro BS 1a. That is, the macro BS 1a is a serving base station device (first base station device) for the terminal device 2.
The terminal device (signal measurement device) 2 measures a signal transmitted from one or a plurality of other base station devices (second base station devices) other than the serving base station device for determining whether or not handover is necessary. (Measure communication quality).

  Based on the communication quality with the serving base station device and the communication quality with another base station device, it was determined that it would be better to switch to the other base station device connection destination of the terminal device 2 In this case, a handover process is performed.

  For example, as shown in FIG. 1, the terminal device (signal measurement device) 2 connected to the macro BS 1a is transmitted from the pico BS 1b with the pico BS 1b as a measurement target base station device (second base station device). Measure the measured signal.

Even if the terminal device 2 tries to measure the signal transmitted from the pico BS 1b, it is unknown to the terminal device 2 which component carrier the pico BS 1b is using.
Therefore, when measuring the signal transmitted from the pico BS 1b, the terminal device 2 can be considered to measure the entire frequency range (# 0 to # 4) that can be used by the pico BS 1b, for example. However, in this case, the burden on the terminal device 2 may be increased. For example, when trying to measure each of the component carriers # 0 to # 4 one by one, it is necessary to switch the frequency to be measured for each component carrier, the processing load on the terminal device 2 increases, and the time required for the measurement also increases. Become.

Further, when the entire frequency range (# 0 to # 4) that can be used by the pico BS 1b is measured in a lump, the component carriers used for communication by the macro BS 1a are subject to interference from the macro BS 1a. I can't.
That is, when the communication quality of the entire frequency range (# 0 to # 4) that can be used by the pico BS 1b is collectively measured, the macro BS 1a is used for the component carriers # 0 and # 2 to # 4 used by the macro BS 1a. Interference from Therefore, in the component carrier # 1, even if there is little interference, the quality deteriorates when viewed in the entire frequency range (# 0 to # 4).

For this reason, if only the component carrier # 1 without interference is measured, the quality of the signal transmitted from the pico BS 1b is good. As a result, even if the terminal apparatus 2 should be handed over to the pico BS 1b, the terminal apparatus 2 cannot be handed over because the quality is poor when viewed in the entire frequency range (# 0 to # 4).
Then, the terminal device 2 becomes difficult to connect to the pico BS 1b, which is against the policy of preferentially connecting to the pico BS 1b.

Therefore, in the terminal device 2 of this embodiment, the pico BS 1b (second base station device) uses the blank carrier of the macro BS (serving base station device; first base station device) 1a for communication. On the assumption that the frequency of the blank carrier of the macro BS 1a is the frequency to be measured.
As shown in FIG. 1, the terminal device 2 connected to the macro BS 1a can measure the component carrier # 1 corresponding to the blank carrier of the macro BS 1a without causing interference from the macro BS 1a. The signal of pico BS1b can be measured.

FIG. 2 shows a processing procedure performed for signal measurement by the terminal device (signal measurement device) 2 in the communication system shown in FIG.
First, when the macro BS 1a determines a frequency to be a blank carrier in the device 1a, the macro BS 1a transmits blank carrier information for identifying the blank carrier to the pico BS 1b in the vicinity of the macro BS 1a (step S1-1).

  When the pico BS 1b receives the blank carrier information (step S2-1), the pico BS 1b determines the component carrier (primary component carrier) # 1 used in the own apparatus 1b based on the received blank carrier information (step S2-2). . Thereafter, the pico BS 1b performs communication with the terminal device using the primary component carrier # 1.

  The macro BS 1a also transmits blank carrier information to the terminal device 2 connected to the own device 1a (step S1-2). Note that the order in which the steps S1-1 and S1-2 are executed may be reversed. .

  Transmission of blank carrier information from the macro BS 1a to the terminal device 2 can be included in a message transmitted to the terminal device 2, such as RRC Connection Reconfiguration, for example.

The terminal device 2 receives blank carrier information transmitted from the communicating macro BS 1a (step S3-1). Then, the terminal device (signal measurement device) 2 performs signal measurement using the frequency of the blank carrier # 1 identified based on the received blank carrier information as a target frequency (step S3-2).
That is, the terminal device 2 considers that the blank carrier # 1 identified based on the received blank carrier information is used in the other base station device (pico BS 1b), and sets the frequency of the blank carrier # 1. Measure only.

Therefore, the terminal device 2 does not acquire information indicating the component carrier used in the other base station device (pico BS1b), and the component carrier # used in the other base station device (pico BS1b) 1 can be measured.
Further, the terminal device 2 does not need to measure the entire frequency range (# 0 to # 4) that may be used by another base station device (pico BS1b), but only a specific frequency (component carrier # 1). Therefore, the measurement burden is small.

  Moreover, since the terminal device 2 measures frequencies that are not used by the serving base station device (macro BS1a), which is used by other base station devices (pico BS1b), the terminal device 2 is not subject to interference from the macrocell. Can be measured.

  When completing the signal measurement at the frequency of the blank carrier # 1, the terminal device 2 generates a measurement report indicating the measurement result and transmits the measurement report to the macro BS 1a (step S3-3). The macro BS 1a receives the measurement report transmitted from the terminal device 2 (step s1-3).

  When the communication system determines that the terminal apparatus 2 needs to be handed over to the pico BS 1b based on the measurement report received by the macro BS 1a, the communication apparatus moves the terminal apparatus 2 from the serving base station apparatus (macro BS 1a) to the target base station. A process of handing over to the device (pico BS 1b) is performed.

When the pico BS 1b becomes the serving base station device for the terminal device 2 by the handover process, the pico BS 1b transmits information (blank carrier information) that can identify the blank carriers # 0 and # 2 to # 4 of the pico BS 1b to the terminal device. 2 (step S2-3).
Transmission of blank carrier information from the pico BS 1b to the terminal device 2 can also be transmitted in a message transmitted to the terminal device 2, such as RRC Connection Reconfiguration.

The terminal device 2 receives the blank carrier information transmitted from the communicating pico BS 1b (step S3-4). Then, as shown in FIG. 3, the terminal device (signal measurement device) 2 measures signals using the frequencies of the blank carriers # 0 and # 2 to # 4 identified based on the received blank carrier information as the target frequencies. (Step S3-5).
That is, the terminal device 2 regards the blank carriers # 0 and # 2 to # 4 identified based on the received blank carrier information as being used in other base station devices (macro BS1a), and blanks them. Measurement is performed at the frequencies of carriers # 0 and # 2 to # 4.

  Note that the terminal device 2 has acquired blank carrier information indicating the blank carrier # 1 of the macro BS 1a before the handover. Therefore, the terminal device 2 uses the blank carrier information of the serving base station device (macro BS1a) before the handover even after the handover, and the blank carrier indicated by the blank carrier information of the serving base station device (macro BS1a) before the handover. It is also possible to measure component carriers # 0 and # 2 to # 4 other than # 1. In this case, the terminal device 2 can measure the component carriers # 0 and # 2 to # 4 without acquiring blank carrier information from the pico BS 1b.

  When the terminal device 2 completes the signal measurement at the frequencies of the component carriers # 0 and # 2 to # 4, the terminal device 2 generates a measurement report indicating the measurement result and transmits the measurement report to the pico BS 1b (step S3-6). The pico BS 1b can receive the measurement report transmitted from the terminal device 2 (step s2-4).

[2. Second Embodiment]
4 to 6 show a communication system according to the second embodiment. Regarding the communication system according to the second embodiment, points that are not described are the same as in the first embodiment.

In FIG. 4, a pico BS 1b (second base station apparatus) is arranged near the cell edge of two macro cells formed by two macro BSs 1a and 1b.
The terminal device 2 is connected to one macro BS 1a. The macro BS 1a is a serving base station device (first base station device) for the terminal device 2.

In FIG. 4, the macro BS (MSB1) 1a uses # 0 as the primary component carrier (PCC) among the component carriers # 0 to # 4, and # 2 and # 3 as the secondary component carrier (SCC). To do. Therefore, component carriers # 1 and # 4 are blank carriers.
The macro BS (MSB2) 1c uses # 3 as the primary component carrier (PCC) among the component carriers # 0 to # 4 and uses # 0, # 1 and # 4 as the secondary component carrier (SCC). And Therefore, component carrier # 2 is a blank carrier.

As shown in FIG. 5, a plurality of macro BSs (MSB1... MSBN) transmit blank carrier information in each macro BS1 to the pico BS 1b (steps S11-1 and S12-2).
When the pico BS 1b receives blank carrier information in each macro BS 1 (step S13-1), the pico BS 1b determines a primary component carrier (PCC) in the own apparatus 1b (step S13-2). Moreover, pico BS1b also determines the secondary component carrier (SCC) in the own apparatus 1b (step S13-3).

  In FIG. 4, it is assumed that the pico BS 1b sets # 2 as a primary component carrier (PCC) and # 1 as a secondary component carrier (SCC).

  The terminal device (signal measurement device) 2 measures a signal transmitted from one or a plurality of other base station devices (second base station device) (communication quality measurement) for determining whether or not handover is necessary. I do. The terminal device 2 is set to measure a signal at a frequency used as a primary component among frequencies # 0 to # 4 that can be used by other base station devices (initial setting of the terminal device 2).

Information indicating the primary component carrier of each base station apparatus 1a, 1b, 1c is transmitted from each base station apparatus 1a, 1b, 1c to the inter-base station network, and acquired by the management server in the inter-base station network. The management server notifies each base station device 1a, 1b, 1c of information indicating primary component carriers of a plurality of base station devices (neighboring base station devices).
When the base station devices 1a, 1b, and 1c acquire information indicating the primary component carrier of the base station device from the management server, the base station devices 1a, 1b, and 1c transmit the information to the terminal device 2 as a neighbor cell list.

  The base station devices 1a, 1b, and 1c transmit a neighbor cell list to the terminal device 2 periodically and as necessary. Therefore, the terminal device 2 can always have the latest neighbor cell list.

As shown in FIG. 7A, the neighbor cell list is configured to indicate base station devices (neighboring base station devices) that use the component carriers # 0 to # 4 as primary component carriers.
That is, in the neighbor cell list of FIG. 7A, component carrier # 0 is used as a primary component carrier by macro BS (MBS1) 1a, component carrier # 2 is used as a primary component carrier by pico BS 1b, and component carrier # 3 is used as a primary component carrier by the macro BS (MBS2) 1b (see also FIG. 4).

Component carriers # 1 and # 4 are not used as primary component carriers in any of the base station devices in the vicinity of the macro BS 1a.
The neighbor cell list does not include information about the secondary component carrier. That is, even if the component carriers # 1 and # 4 are used by any of the base station apparatuses 1a, 1b, and 1c as secondary component carriers, information indicating that is not included in the neighbor cell list.

When receiving the neighbor cell list, the terminal device 2 can identify which component carrier each base station device 1a, 1b, 1c uses as the primary component carrier.
Based on the neighbor cell list, the terminal device 2 measures the signal of the component carrier that is set as the primary component carrier by the other base station devices 1b and 1c. For example, component carrier # 2 is measured using the signal transmitted from pico BS 1b as a measurement target signal.

In the second embodiment, primary component carriers mainly used by the other base station apparatuses 1b and 1c are measured. The primary component carriers of the other base station apparatuses 1b and 1c communicate with each other in the serving base station apparatus (macro BS 1a). May have been used.
For example, in FIG. 4, the primary component carrier # 2 of the pico BS 1b is used as a secondary component carrier in the macro BS 1a that is a serving base station device. For this reason, if the terminal device 2 tries to measure a signal having a frequency corresponding to the primary component carrier # 2 of the pico BS 1b, the terminal device 2 receives radio wave interference from the macro cell.

However, as shown in FIG. 4, the pico BS 1b is in a state where the component carrier # 1 is also used for communication as a secondary component carrier, and this component carrier # 1 is a blank carrier in the macro BS 1a.
Therefore, even if the primary component carrier # 2 of the pico BS 1b receives radio wave interference from the macro cell, the terminal device 2 does not receive radio wave interference if the component carrier # 1.
Therefore, under the above circumstances, the terminal device 2 does not measure the signal of the primary component carrier # 2 of the pico BS 1b as in the initial setting, but measures the signal of the component carrier # 1 that is the blank carrier of the macro BS 1a. It is desirable.

The processes after S13-4 in FIG. 5 are processes for dealing with the above situation.
First, the pico BS 1b that has determined the primary component carrier and the secondary component carrier transmits information (PCC position information and SCC position information) indicating the determined primary component carrier and secondary component carrier to the other base station apparatuses 1a and 1c. Notification is made (step S13-4).

The macro BS 1a acquires information (PCC position information and SCC position information) indicating the primary component carrier and secondary component carrier of the pico BS 1b (step S11-2).
The macro BS 1a determines whether the frequency of the primary component carrier # 2 (the target frequency according to the initial setting) indicated by the received PCC position information matches the frequencies of the blank carriers # 1 and # 4 of the own device 1a (overlapping). It is determined whether or not (step S11-3).

  If the frequency of the primary component carrier indicated by the received PCC position information (the frequency at which the terminal device 2 measures the signal according to the initial setting) matches the frequency of the blank carrier of the own device 1a, The terminal device 2 measures the signal of the pico BS 1b without receiving interference from the macro cell. Therefore, the macro BS 1a does not need to perform any special processing thereafter. That is, if the terminal device 2 measures the signal of the primary component carrier of the pico BS 1b as the initial setting, the terminal device 2 measures the signal in the blank carrier of the macro BS 1a.

  On the other hand, the frequency of the primary component carrier # 2 indicated by the received PCC position information (the target frequency according to the initial setting) and the frequencies of the blank carriers # 1 and # 4 of the own apparatus 1a do not match (overlapping). If not, the macro BS 1a performs a process (state change process) of transmitting a primary component carrier change request to the pico BS 1b (step S11-4). The change request preferably includes the change destinations desired by the macro BS 1a (for example, component carriers # 1 and # 4), but they may not be included.

  When receiving the change request (step S13-5), the pico BS 1b determines whether or not the primary component carrier can be changed (step S13-6). The pico BS 1b determines whether or not the change is possible in consideration of the change destination desired by the macro BS 1a and / or the setting status of the primary component carrier in the other base station apparatus 1c.

  If it is determined that the primary component carrier can be changed, the pico BS 1b determines a change destination desired by the macro BS 1a or another appropriate change destination (step S13-7). The pico BS 1b transmits a change response including the determined change destination to the macro BS 1a (step S13-8).

  For example, as shown in FIG. 4, after the change, the primary component carrier (PCC) is set to # 1. The secondary component carrier (SCC) is also changed and set to # 2.

  The change response transmitted by the pico BS 1b may include information indicating the change destination (# 1) determined by the pico BS 1b. In this case, the macro BS 1a can immediately notify the terminal device 2 of the change destination (# 1). Even if the change destination (# 1) determined by the pico BS 1b is not included in the change response transmitted by the pico BS 1b, the location of the primary component carrier # 1 of the pico BS 1b is notified to the macro BS 1a via the management server. The FIG. 7B shows the neighbor cell list after the change. The neighbor cell list in FIG. 7B indicates that the pico BS 1b uses the component carrier # 1 as the primary component carrier.

  When the primary component carrier of the pico BS 1b is changed to # 1, the terminal apparatus 2 measures the signal in the blank carrier # 1 of the macro BS 1a if the signal of the primary component carrier # 1 of the pico BS 1b is measured as initially set. Will be.

  Thus, even if the primary component carrier # 2 of the pico BS 1b does not match the blank carriers # 1 and # 4 of the macro BS 1a, the pico BS 1b executes the process of changing the primary component carrier to # 1. The primary component carrier # 1 (frequency to be measured) of the pico BS 1b overlaps with the blank carriers # 1 and # 4 of the macro BS 1a.

  In step S13-6, the pico B1b may determine that the primary component carrier cannot be changed. For example, when the change destination desired by the macro BS 1a is already used (as a primary component carrier) by another base station apparatus (third base station apparatus) such as the macro BS 1c, and there is no appropriate change destination Is determined to be unchangeable.

When the change is impossible, as shown in FIG. 6, the pico BS 1b transmits a change impossible notification to the macro BS 1a (step S13-9).
When the macro BS 1a receives the change impossibility notification (step S11-5), the macro BS 1a executes a process (state change process) of transmitting a command to change the signal measurement target frequency to the terminal device 2 (step S11-6). . The command is for causing the terminal device 2 to measure one or a plurality of secondary component carriers of the base station device (pico BS 1b) that is the target of signal measurement.
The command also includes information indicating one or more secondary component carriers # 1 of the pico BS 1b.

  Upon receiving the instruction (step S14-1), the terminal device 2 measures the signal of the secondary component carrier # 1 of the pico BS 1b regardless of the initial setting in the terminal device 2 that measures the signal of the primary component carrier # 2. (Step S14-2).

  Even if the primary component carrier # 2 receives interference from the macro cell, the secondary component carrier may not receive interference from the macro cell. Therefore, while measuring the signal of the secondary component carrier, avoiding interference. The possibility to perform measurement is born.

  In FIG. 4, the secondary component carrier of the pico BS 1b is # 1, which matches the blank carrier # 1 of the macro BS 1a. Therefore, the terminal device 2 measures the signal in the blank carrier # 1 of the macro BS 1a by measuring the secondary component carrier # 1.

  Thus, even if the primary component carrier # 2 of the pico BS 1b does not match the blank carrier # 1 of the macro BS 1a, the terminal device 2 uses the frequency to be measured and the pico BS 1b uses the frequency of the secondary component carrier # 1. By changing to, a state in which the measurement target frequency # 1 overlaps with the blank carrier # 1 of the macro BS 1a is obtained.

  When there are a plurality of secondary component carriers of the pico BS 1b, the terminal device 2 measures each secondary component carrier one by one. In that case, the terminal device 2 gives priority to the component carrier that is the blank carrier in the macro BS 1a among the plurality of secondary component carriers, and performs the measurement first. For example, if there are two secondary component carriers of pico BS 1b, # 0 and # 1, # 1 that is a blank carrier of macro BS 1a is measured first, and then # 0 is measured.

  By measuring with priority to the blank carrier in the macro BS 1a, the measurement report of the component carrier # 1 that has been measured first can be transmitted to the macro BS 1a before the measurement of the component carrier # 0 is completed ( Step S14-3). Therefore, the macro BS 1a can obtain a measurement report of the component carrier # 1 in which interference is avoided at an early point. By obtaining a measurement report of component carrier # 1 in which interference is avoided at an early time, the terminal device 2 can be handed over to the pico B1b at an early time.

FIG. 8 shows a modification of the process (FIG. 6) subsequent to the process shown in FIG. 5 (the process shown in FIG. 8 also follows the process shown in FIG. 5).
In step S13-6 in FIG. 5, if the pico B1b determines that the primary component carrier cannot be changed, the pico BS 1b also transmits a change impossible notification to the macro BS 1a in the process shown in FIG. 8 (step S13- 9).

  When the macro BS 1a receives the change impossible notification (step S11-5), the macro BS 1a executes a process (state change process) of changing the frequency position of the blank carrier of the own apparatus 1a to the primary component carrier # 2 of the pico BS 1b (step S11-5). S11-8).

  When the blank carrier of the macro BS 1a is changed to the frequency position of the primary component carrier # 2 of the pico BS 1b, the terminal device 2 measures the signal of the primary component carrier # 2 of the pico BS 1b as initially set (step S14). -4) The signal is measured in the blank carrier # 2 of the macro BS 1a.

  The terminal device 2 transmits a measurement report that is a measurement result of the primary component carrier # 2 of the pico BS 1b to the macro BS 1a (step S14-5), and the macro BS 1a receives the measurement report (step S11-9).

  In this way, even if the primary component carrier # 2 of the pico BS 1b does not match the blank carriers # 1 and # 4 of the macro BS 1a, the macro BS 1a executes the process of changing the blank carrier to # 2, A state is obtained in which the primary component carrier # 2 (measurement target frequency) of the pico BS 1b overlaps with the blank carrier # 2 of the macro BS 1a.

As described above, in the first embodiment, the terminal device measures a signal on a blank carrier in the serving base station device, thereby avoiding interference from the serving base station device, and signals from other base station devices. Can be measured.
Further, in the second embodiment, even if the terminal device is configured to measure the primary component carrier of the base station device, the frequency to be measured is the frequency of the blank carrier in the serving base station device by the state change process. Therefore, it is possible to measure signals from other base station apparatuses while avoiding interference from the serving base station apparatus.
Thus, in both the first and second embodiments, signal measurement is performed in consideration of the blank carrier.

With respect to the present invention, the embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not meant to be described above, but is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.
For example, the macro BS and the pico BS in the embodiment may be a femto BS that forms a smaller cell than the pico BS and the pico BS.

DESCRIPTION OF SYMBOLS 1 Base station apparatus 1a Macro base station apparatus 1b Pico base station apparatus 1c Macro base station apparatus 2 Terminal apparatus

Claims (12)

A method in which a terminal device measures a signal,
The first base station device which is a serving base station device to which the terminal device is connected is
A determination process for determining whether a target frequency for measuring a signal by the terminal device and a frequency of a blank carrier in the first base station device overlap;
When the target frequency at which the terminal apparatus measures a signal and the frequency of the blank carrier at the first base station apparatus do not overlap, the target frequency at which the terminal apparatus measures the signal and the first base station A state change process for obtaining a state where the frequency of the blank carrier in the station device overlaps,
Run
The terminal device transmits a signal transmitted from the second base station device under a state in which a target frequency at which the terminal device measures a signal and a frequency of a blank carrier in the first base station device overlap. How to measure. The determination process is executed by determining whether or not the frequency of the primary component carrier in the second base station apparatus and the frequency of the blank carrier in the first base station apparatus overlap,
The method according to claim 1, wherein the state change process is executed when a frequency of a primary component carrier in the second base station apparatus and a frequency of a blank carrier in the first base station apparatus do not overlap. The state change process includes a process of transmitting, to the terminal device, a command for causing the terminal device to measure a signal frequency to be a frequency of one or a plurality of secondary component carriers in the second base station device. The method of claim 2. When the terminal device measures the signal transmitted from the second base station device using the frequency of a plurality of secondary component carriers as a target frequency based on the command, the terminal device includes the first of the target frequencies. The method according to claim 3, wherein the frequency of the blank carrier in one base station apparatus is preferentially measured. The method according to claim 2, wherein the state change process includes a process of transmitting, to the second base station apparatus, a request for changing a frequency of a primary component carrier to the second base station apparatus. The method according to claim 5, wherein the second base station apparatus transmits a change impossible notification to the first base station apparatus when the frequency of the primary component carrier cannot be changed according to the change request. The second base station apparatus determines whether or not the frequency of the primary component carrier can be changed according to the change request based on the frequency of the blank carrier in the third base station apparatus, and the change request 7. The method according to claim 6, wherein when it is determined that the frequency of the primary component carrier cannot be changed according to, the change impossible notification is transmitted to the first base station apparatus. In the state change process, when the first base station apparatus receives the change impossibility notification, the target frequency for the terminal apparatus to measure a signal is set to one or a plurality of secondary in the second base station apparatus. The method of Claim 6 or 7 including the process which transmits the instruction | command for making it the frequency of a component carrier to the said terminal device. The state change process is performed so that the frequency of the primary component carrier in the second base station apparatus and the frequency of the blank carrier in the first base station apparatus overlap with each other in the blank in the first base station apparatus. The method according to claim 2, further comprising changing the frequency of the carrier. In the state change process, when the first base station apparatus receives the change impossibility notification, the frequency of the primary component carrier in the second base station apparatus and the blank carrier in the first base station apparatus The method of Claim 6 or 7 including the process which changes the frequency of the blank carrier in a said 1st base station apparatus so that it may overlap with frequency of 1st. The method according to any one of claims 1 to 10, wherein the second base station device is a small base station device that forms a cell smaller than a cell formed by the first base station device. A base station device that communicates with a terminal device,
A determination processing unit that determines whether or not the target frequency at which the terminal device measures a signal and the frequency of the blank carrier in the own device overlap;
When the target frequency at which the terminal device measures the signal and the frequency of the blank carrier in the own device do not overlap, the target frequency at which the terminal device measures the signal and the frequency of the blank carrier in the own device are A state change processing unit for obtaining overlapping states;
A base station apparatus.