JP2017034407A - Base station device, control device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately measure a reference signal transmitted by a base station device in an unlicensed band.SOLUTION: The base station device obtains information concerning a reference signal transmitted from other base station device by the other base station device and notifies a terminal connected to the base station device of the obtained information. The terminal controls measurement of the reference signal transmitted by the other base station device on the basis the notified information.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a reference signal observation procedure in wireless communication.

  In the third generation partnership project (3GPP), it is considered to perform LTE (Long Term Evolution) communication in a non-licensed band used in a wireless LAN or the like (see Non-Patent Document 1). Also, in conventional LTE, carrier aggregation (CA) is used to increase the communication speed. In CA, for example, one primary cell (PCell) that leads radio communication with a terminal and performs radio resource control, and one or more secondary cells (SCell) that perform radio communication with a terminal based on control by the PCell, Communicate with the terminal at the same time. Here, the PCell and the SCell may be provided by one base station apparatus (eNB) or may be provided by different base station apparatuses. In CA, the radio signal from the base station apparatus which becomes a SCell candidate is measured regularly for switching of SCell or addition of SCell (refer nonpatent literature 2). The base station apparatus which is PCell can switch or add SCell according to this measurement result.

3GPP, “Study on Licensed-Assisted Accessing LTE”, RP-141664, September 2014 3GPP, TR36.133

  Conventionally, since an SCell is formed by a base station apparatus of a license band, the base station apparatus always transmits a reference signal. Therefore, the terminal can measure the radio quality of the signal from the base station apparatus having such a license band. However, when the base station apparatus forming the SCell uses a non-licensed band, a period during which the reference signal cannot be transmitted may occur irregularly in order to reduce the influence on the existing system. As a result, the terminal may not be able to measure a signal from the base station apparatus using the unlicensed band. Further, the terminal is conventionally configured to measure a signal from the base station apparatus for 6 milliseconds. However, in Japan, for example, in a non-licensed band of 5 GHz band, it is not permitted to transmit a signal continuously over a period exceeding 4 milliseconds. For this reason, the terminal may determine that the radio quality is not good because the signal is not transmitted for at least 2 milliseconds in the measurement period of 6 milliseconds.

  In view of at least one of the above-described problems, an object of the present invention is to provide a technique for appropriately measuring a reference signal transmitted by a base station apparatus in a non-licensed band.

  In order to achieve the above object, a base station apparatus according to the present invention includes an acquisition unit that acquires information on a reference signal transmitted by another base station apparatus from another base station apparatus, and the acquired information. A notification means for notifying a terminal connected to the base station apparatus, and the terminal controls measurement of a reference signal transmitted by the other base station apparatus based on the notified information It is characterized by.

  According to the present invention, the UE can appropriately measure the reference signal transmitted by the base station apparatus in the unlicensed band.

The figure which shows the structural example of a radio | wireless communications system. The figure which shows the hardware structural example of a base station apparatus. The figure which shows the function structural example of a base station apparatus. The figure which shows the information notification method in the case of notifying information using PDCCH (physical downlink control channel). The figure which shows the information notification method in the case of notifying information using PDSCH (physical downlink shared channel). The figure which shows the information notification method in the case of notifying information using SIB (System Information Block). The flowchart which shows the example of the flow of the process which a base station apparatus performs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Configuration of wireless communication system)
FIG. 1 shows a configuration example of a wireless communication system according to this embodiment. The wireless communication system includes, for example, a master base station apparatus (eNB) that provides one primary cell (PCell) and secondary base stations that provide one or more (two in this example) secondary cells (SCell). Device (eNB). Here, in this embodiment, the license band is used in the primary cell. On the other hand, in the secondary cell, the license band may generally be used, but here, the license band is not used in order to pay attention to the problem regarding the measurement of the reference signal in the non-licensed band. The “cell” here corresponds to, for example, a component carrier having a bandwidth of 20 MHz, and the primary cell and the secondary cell, or a plurality of secondary cells may be provided by one base station apparatus. Further, the primary cell and the secondary cell may correspond to component carriers having different bandwidths. Furthermore, the bandwidth of each component carrier of the plurality of secondary cells may be different from each other.

  A terminal can simultaneously establish a connection with one master eNB and one or more secondary eNBs, and can perform high-speed communication with these eNBs using carrier aggregation. The terminal measures the reference signal from the secondary eNB and notifies the master eNB of the measurement result. Note that the secondary eNB receives communication from the master eNB and establishes connection with the terminal to perform communication.

  Here, as described above, when the secondary eNB uses the non-licensed band, a case where the reference signal is not transmitted periodically, a case where the reference signal transmission period is short, or the like may occur. For this reason, in this embodiment, the eNB that has established a connection with the terminal notifies the terminal of information related to the reference signal transmitted by the secondary eNB that is a connection candidate. For example, the eNB that is connected to the terminal notifies the terminal of information related to the transmission end time of the reference signal transmitted by the connection candidate secondary eNB. In addition, when the connection candidate secondary eNB notifies this information before starting the transmission of the reference signal, the information on the transmission start time may be notified to the terminal. At this time, the eNB that is connected to the terminal can notify the terminal of information related to the transmission end time after the connection candidate secondary eNB starts transmission of the reference signal. At this time, the eNB that is connected to the terminal may notify the terminal of the information related to the transmission end time after observing that the secondary eNB that is a connection candidate actually transmits the reference signal.

  In this case, the terminal can control the measurement so that the measurement is not continued beyond the notified transmission end time. As a result, the terminal performs measurement only during the period in which the reference signal is transmitted. For this reason, it is possible to prevent degradation of the radio quality of the measurement result by continuing the measurement in a period in which the reference signal is not transmitted.

  In addition, the eNB that is connected to the terminal indicates that the transmission is invalid when the reference eNB is not transmitted even though the connection candidate secondary eNB schedules the transmission of the reference signal. Information may be notified to the terminal. In this case, the terminal performs measurement of the reference signal in a period in which the reference signal is not actually transmitted, but discards or ignores the measurement result regarding the reference signal indicated to be invalid. The measurement can be controlled. In addition, instead of discarding or ignoring the measurement result, the terminal may use the measurement result by, for example, multiplying by a very small weighting factor. As a result, it is possible to prevent the secondary eNB that is originally suitable for connection from being selected as a connection destination from the measurement result of the reference signal that is not actually transmitted.

  In this case, the eNB currently connected to the terminal may notify the terminal of the reference signal transmission schedule by the secondary eNB before the connection candidate secondary eNB starts transmitting the reference signal. Further, in this case, the eNB that is connected to the terminal transmits information that specifies which of the reference signals that were scheduled to be transmitted by the secondary eNB as a connection candidate was not actually transmitted to the terminal. You can be notified. At this time, the eNB connected to the terminal can collectively notify the terminal of the transmission schedules of the plurality of reference signals.

  Here, the eNB that is connected to the terminal can acquire information on the reference signal transmitted by the connection candidate secondary eNB from the connection candidate secondary eNB by inter-base station communication. The communication between base stations can be performed, for example, via a core network (not shown) connecting these base station devices, or via a line directly connecting the base station devices. In addition, the communication between base stations here is a concept including communication between baseband units (BBUs), and may be performed via a line directly connecting between BBUs. For example, internal communication within one BBU is performed. The exchange of signals related to processing can also be included. Note that the master eNB and the secondary eNB provide cells that cover adjacent or overlapping areas, and the master eNB obtains information related to the reference signal through communication between conventional adjacent eNBs. Can do.

  At this time, the eNB connected to the terminal notifies the terminal of a control channel such as a physical downlink control channel (PDCCH), a data channel such as a physical downlink shared channel (PDSCH), or a broadcast channel, for example. Can be used. In the broadcast channel, information can be notified, for example, by SIB (System Information Block). Here, the eNB that notifies the information may be either the master eNB or the secondary eNB. Further, in some cases, the first eNB notifies the reference signal transmission schedule, and the second eNB notifies that the reference signal is not actually transmitted. May share and transmit. Further, the same information may be transmitted by a plurality of eNBs.

  The configuration of eNB and the flow of processing as described above will be described below with reference to the drawings.

(Hardware configuration of base station device)
FIG. 2 is a diagram illustrating a hardware configuration example of the base station apparatus (eNB). In one example, the base station apparatus has a hardware configuration as shown in FIG. 2, and includes, for example, a CPU 201, a ROM 202, a RAM 203, an external storage device 204, and a communication device 205. In the base station device, for example, a program for realizing each function of the base station device, which is recorded in any of the ROM 202, the RAM 203, and the external storage device 204, is executed by the CPU 201. And a base station apparatus controls the communication apparatus 205, for example by CPU201, and performs communication between other base station apparatuses or between terminals. In FIG. 2, the base station device has one communication device 205. However, for example, the base station device has a communication device for communication between base station devices and a communication device between terminals. May be.

  Note that the base station apparatus may include dedicated hardware that executes all functions, or some functions may be realized by hardware, and other parts may be realized by a computer that operates a program. Further, all functions of the base station device may be realized by a computer and a program.

(Functional configuration of base station equipment)
FIG. 3 is a diagram illustrating a functional configuration example of the base station apparatus (eNB). The base station apparatus includes, for example, a wired communication unit 301, a wireless communication unit 302, an information acquisition unit 303, and an information notification unit 304 as functional configurations.

  The wired communication unit 301 is a communication interface for performing communication between base stations via a core network, for example. The base station apparatus can acquire information from other base station apparatuses or provide information to other base station apparatuses through the wired communication unit 301. Note that a wireless interface may be used in the communication between base stations. In this case, the wired communication unit 301 may be omitted. Further, the connection path used in the communication between base stations may be configured only by a wired section or a wireless section, or may be configured by a combination of a wired section and a wireless section. In any case, the base station apparatus has a communication interface for performing communication for the first section among the connection paths used in the communication between base stations.

  The wireless communication unit 302 is a communication interface for connecting and communicating with a terminal, for example. The base station apparatus establishes a communication link with the terminal through the wireless communication unit 302, transmits a radio signal to the terminal in the downlink, and receives a radio signal transmitted from the terminal in the uplink. When the base station apparatus performs communication between base stations by radio, the radio communication unit 302 can also function as a communication interface for communication between base stations.

  The information acquisition unit 303 acquires information related to a reference signal transmitted by another eNB from another eNB. For example, when another base station function that performs communication in the unlicensed band exists in the base station device itself, the information acquisition unit 303 can acquire information from the other base station function. In this case, for example, the wired communication unit 301 can be an interface for accessing an internal bus in the base station apparatus. Below, the case where the information acquisition part 303 acquires information from another eNB is demonstrated.

  In one example, the information acquisition unit 303 acquires information related to the transmission end time of a reference signal transmitted in another non-licensed band by another eNB. Note that the “transmission end time” information here may be absolute time information, or information on the length of time from the start of transmission to the end of transmission (for example, 4 milliseconds). May be. When absolute time information is used, it is assumed that time synchronization is established between eNBs.

  In another example, the information acquisition unit 303 acquires information specifying a reference signal that was not actually transmitted among reference signals that were scheduled to be transmitted in a non-licensed band by another eNB. The information specifying the reference signal that was not actually transmitted can be, for example, information specifying the serial number when serial numbers are assigned to the reference signals to be transmitted. The designation of a reference signal that is not actually transmitted by this serial number can be particularly useful when information related to a plurality of reference signals is acquired together. That is, for example, the information acquisition unit 303 acquires one piece of information for a plurality of reference signal transmission schedules, so that the reference signal is actually transmitted in any of the plurality of reference signal transmission schedules. It is possible to specify whether or not it was done.

  Note that the information acquisition unit 303 may acquire information (for example, 1 bit) indicating whether or not the reference signal is actually transmitted for each reference signal transmission schedule. That is, the information acquisition unit 303 may acquire information regarding the reference signal regardless of whether the reference signal is actually transmitted.

  Further, the information acquisition unit 303 can acquire information indicating whether the reference signal is actually transmitted immediately after the scheduled time at which the reference signal is transmitted from another eNB. In this case, when the base station apparatus acquires the information, even if it is not specified which reference signal transmission schedule is related to the information, the base station apparatus transmits the reference signal regarding the transmission schedule immediately before the time when the information is acquired. It is possible to specify that the transmission is actually information.

  Furthermore, in this case, the information acquisition unit 303 can acquire information on a reference signal transmission schedule by another eNB from another eNB. Here, the transmission schedule information may be, for example, information on the transmission start time. Also, the information to be transmitted may be information on the transmission end time when the transmission duration of the reference signal is known, for example. For example, when the transmission duration is 4 milliseconds, it is understood that the transmission of the reference signal is started 4 milliseconds before the transmission end time. Further, the transmission schedule information may include both the transmission start time and the transmission end time. The information acquisition unit 303 does not necessarily have to acquire the information scheduled for transmission. For example, when another eNB plans to periodically transmit a reference signal, the information acquisition unit 303 does not acquire the transmission schedule because the reference signal transmission schedule does not become irregular. However, it is possible to know when the reference signal is scheduled to be transmitted. In this case, another eNB determines whether the reference signal cannot be transmitted, such as whether the non-licensed band is used by another system, and transmits the reference signal for each reference signal transmission cycle. Send reference signals only when possible. And when another eNB cannot transmit a reference signal at least, the information which shows that is notified to a neighboring eNB.

  The information notification unit 304 notifies the terminal of the information acquired by the information acquisition unit 303 via the wireless communication unit 302. The notification at this time can be performed using a control channel such as PDCCH, a data channel such as PDSCH, or a broadcast channel. In the broadcast channel, information can be notified by, for example, SIB (System Information Block). Here, the information notification method at this time will be described.

  FIGS. 4A and 4B show an example of an information notification method in the case of notifying information using PDCCH (physical downlink control channel). When the information is notified by the PDCCH, the terminal can acquire the information of the reference signal by confirming only the PDCCH.

  FIG. 4A schematically shows a method of notifying information on the transmission end time of a reference signal transmitted in a connection candidate cell in the PDCCH. In this example, after transmission of the reference signal is started in the connection candidate cell (for example, immediately after), in the connected cell (cell provided by at least one of the master eNB and the secondary eNB), the reference signal A PDCCH including information related to the transmission end time is transmitted. In one example, the terminal, after acquiring information related to the transmission end time of the reference signal in the connection candidate cell, performs measurement of the reference signal transmitted in the connection candidate cell until the notified transmission end time. .

  FIG. 4 (B) notifies that the reference signal is not transmitted when the reference signal transmission schedule in the connection candidate cell is notified in the PDCCH, and then the reference signal is not actually transmitted. An example is shown. In this example, first, the reference signal transmission schedule in the connection candidate cell is notified. For example, when the reference signal is scheduled to be transmitted periodically, the reference signal transmission schedule is transmitted. May not be notified. In this example, when the scheduled reference signal is not actually transmitted, the fact that the reference signal could not be transmitted from the eNB of the connection candidate cell indicates that the connected cell (adjacent to the connection candidate cell Cell) eNB. Then, the connected cell (at least one of the master eNB and the secondary eNB) notifies the terminal through the PDCCH that the scheduled reference signal was not actually transmitted. According to the transmission schedule of the reference signal, the terminal starts measuring the reference signal even though it is not actually transmitted, but receives a notification that the transmission of the scheduled reference signal has not actually been performed. Discard or ignore the measurement results. In FIG. 4B, the terminal continues the measurement after receiving the notification that the scheduled reference signal was not actually transmitted, but immediately after receiving the notification, the terminal performs the measurement. You may make it cancel. Even in this case, the terminal discards or ignores the measurement result obtained until the terminal stops. In the example of FIG. 4B, the PDCCH immediately after the scheduled transmission time of the reference signal that has not been transmitted is notified that the reference signal has not been transmitted, but the PDCCH at a later time is used. This notification may be performed.

  Next, an example in which PDSCH (physical downlink shared channel) is used for information notification will be described. By using PDSCH, the information to be notified can be surely notified to the terminal even if the amount of information increases. FIGS. 5A and 5B are diagrams illustrating an information notification method in the case of notifying information using PDSCH. The PDCCH includes information for assigning a resource block in the PDSCH to each terminal, and the terminal acquires information on a reference signal in a connection candidate cell from the resource block assigned to the terminal. In the case of FIG. 5A, after the reference signal transmission is started in the connection candidate cell, the PDSCH including information related to the transmission end time of the reference signal is transmitted in the connected cell. In the case of FIG. 5B, when the scheduled reference signal is not actually transmitted, the connected cell indicates that the scheduled reference signal is not actually transmitted by the PDSCH. To the terminal through In FIG. 5B, the terminal continues the measurement after receiving the notification that the scheduled reference signal was not actually transmitted, but immediately after receiving the notification, the terminal performs the measurement. You may make it cancel. Further, although it is notified that the reference signal has not been transmitted by the PDSCH immediately after the scheduled transmission time of the reference signal that has not been transmitted, this notification may be performed by the PDSCH at a later time. Note that the information acquired by the terminal and the subsequent processing of the terminal are the same as those in the example of FIGS. 4A and 4B, and thus description thereof is omitted.

  Next, an example in which SIB (System Information Block) is used for information notification will be described. FIGS. 6A and 6B are diagrams illustrating an information notification method in the case of notifying information using SIB among broadcast channels. The SIB is transmitted every 80 milliseconds, 160 milliseconds, 240 milliseconds, or 320 milliseconds. In the case of FIG. 6A, after the transmission of the reference signal is started in the connection candidate cell, the SIB including information on the transmission end time of the reference signal is transmitted in the connected cell. In the case of FIG. 6B, when the scheduled reference signal is not actually transmitted, the connected cell indicates that the scheduled reference signal is not actually transmitted by the SIB. To the terminal through In FIG. 6B, the terminal continues the measurement after receiving the notification that the scheduled reference signal was not actually transmitted, but immediately after receiving the notification, the terminal performs the measurement. You may make it cancel. Here, when the scheduled reference signal transmission is not actually performed, the SIB transmission interval may be shortened. That is, for example, when the SIB is transmitted every 160 milliseconds and the scheduled reference signal is not actually transmitted, the SIB transmission interval may be shortened to 80 milliseconds. Since the SIB transmission interval has a large value, information on whether or not an actual reference signal has been transmitted may be notified at a time for a plurality of reference signal transmission schedules. Note that the information acquired by the terminal and the subsequent processing of the terminal are the same as those in the example of FIGS. 4A and 4B, and thus description thereof is omitted.

  Each notification described above may be performed a plurality of times, and in that case, notification may be performed from different eNBs. For example, the eNB that performs the first notification may be different from the eNB that performs the second notification. In particular, for example, when the first notification is performed by a secondary eNB that uses a non-licensed band, the secondary eNB may not be able to transmit a signal for notification. In this case, the second notification may be performed by the master eNB.

  Based on this notification, the terminal obtains information such as the transmission end time of the reference signal transmitted by another unconnected eNB and the fact that the reference signal was not actually transmitted, and controls the reference signal measurement process. To do.

(Operation of base station equipment)
FIG. 7 shows an example of the processing flow of the base station apparatus according to this embodiment. In addition, since this process example is an example of the flow of the process in the base station apparatus which transmits the information regarding the reference signal transmitted by the connection candidate secondary eNB, if it is connected to the information notification target terminal, the master eNB And the secondary eNB may execute. When the secondary eNB using the non-licensed band notifies the terminal of information, a process (Listen Before Talk) for confirming that the non-licensed band is not used by another system is performed before the notification. Is called. That is, the secondary eNB that uses the non-licensed band can notify the terminal of information when the non-licensed band is not used by another system.

  First, a base station apparatus (a master eNB or a secondary eNB that is connected to a terminal) acquires information on a reference signal transmitted by the secondary eNB from a connection candidate secondary eNB (S701). Here, this information can be, for example, information related to the transmission end time of the reference signal, or information indicating that the reference signal was not actually transmitted although it was scheduled.

  Thereafter, the base station apparatus notifies the terminal of the acquired information by, for example, a radio signal (S702). Based on this notification, the terminal obtains information such as the transmission end time of the reference signal transmitted by another unconnected eNB and the fact that the reference signal was not actually transmitted, and controls the reference signal measurement process. To do.

  With the above processing, for example, when the transmission period of the reference signal is less than 6 milliseconds (for example, 4 milliseconds), the measurement is not continued even during the period when the reference signal is not transmitted, and the terminal can improve the wireless quality. An excessively low evaluation can be prevented. Similarly, it is possible to prevent the terminal from evaluating the radio quality excessively as a result of measuring the reference signal in a period in which the reference signal was not actually transmitted even though the reference signal was scheduled to be transmitted. Is possible.

  In addition, although it does not specifically limit in the above-mentioned description, a terminal can be connected simultaneously with one master eNB and two or more secondary eNBs, for example. That is, a terminal may measure a reference signal by the above-described method, and the master eNB may further add a secondary eNB according to the measurement result. At this time, it is sufficient that at least one of one master eNB and two or more secondary eNBs notifies the terminal of the information related to the reference signal of the secondary eNB to be added. That is, for example, when one secondary eNB notifies the terminal of information regarding the reference signal of the secondary eNB to be added, the master eNB and the other secondary eNBs do not have to notify the terminal of the information.

Claims (15)

A base station device,
An acquisition means for acquiring information on a reference signal transmitted by the other base station apparatus from another base station apparatus;
Notifying means for notifying the acquired information to a terminal connected to the base station device;
Have
The terminal controls measurement of a reference signal transmitted by the other base station apparatus based on the notified information.
A base station apparatus. The information includes information on a time at which the other base station apparatus ends transmission of the reference signal.
The base station apparatus according to claim 1. The notifying means notifies the terminal of the information after the other base station apparatus starts transmitting the reference signal.
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. The information is that the reference signal is not actually transmitted when the reference signal is not transmitted even though the other base station apparatus plans to transmit the reference signal. Including information indicating that
The terminal can discard or ignore the result of the measurement performed on the reference signal indicated not actually transmitted.
The base station apparatus according to claim 1. The notification means further notifies the terminal of the schedule of transmission of the reference signal by the other base station apparatus before the other base station apparatus starts transmission of the reference signal.
The base station apparatus according to claim 4. The notifying means notifies the terminal of a plurality of schedules for transmitting the reference signal by the other base station device,
The information includes information for designating the plurality of schedules in which the reference signal was not actually transmitted.
The base station apparatus according to claim 5. The notifying means notifies the terminal of the information using a control channel;
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. The notifying means notifies the terminal of the information using a data channel;
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. The notifying means notifies the terminal of the information using a broadcast channel;
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. The notifying means notifies the terminal of the information using a broadcast channel;
The notification means, when notifying the information indicating that the reference signal was not actually transmitted, shortens the transmission interval of the broadcast channel;
The base station apparatus according to claim 4, wherein the base station apparatus is a base station apparatus. The acquisition means acquires the information by inter-base station communication between the base station apparatus and the other base station apparatus.
The base station apparatus according to any one of claims 1 to 10, wherein: The terminal is connected to the first base station apparatus and the second base station apparatus,
The second base station apparatus is connected to the terminal with the assistance of the first base station apparatus,
The base station device is the first base station device;
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. The terminal is connected to the first base station apparatus and the second base station apparatus,
The second base station apparatus is connected to the terminal with the assistance of the first base station apparatus,
The base station device is the second base station device;
The base station apparatus according to claim 1, wherein the base station apparatus is a base station apparatus. A control method for a base station apparatus,
An acquisition unit that acquires information on a reference signal transmitted by the other base station device from another base station device; and
A notification step of notifying the acquired information to the terminal connected to the base station apparatus;
Have
The terminal measures the reference signal transmitted by the other base station apparatus based on the notified information.
A control method characterized by that. In the computer provided in the base station device,
An acquisition step of acquiring information on a reference signal transmitted by the other base station device from another base station device;
A notification step of notifying the acquired information to a terminal connected to the base station device;
A program for executing
The terminal measures the reference signal transmitted by the other base station apparatus based on the notified information.
A program characterized by that.

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