JP2018033169A - Radio base station, user terminal, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict an impact of interference even if different DL/UL configurations are applied to adjacent transmission/reception points (radio base stations) in a time division duplex (TDD) system.SOLUTION: A radio base station 20 includes: a baseband signal processing unit including a signal generation unit for generating a change request signal on a change of a DL/UL configuration and/or a change of transmission power on the basis of information on an amount of interference; and a transmission path interface for transmitting the change request signal to another radio base station. The amount of interference is at least one of an amount of interference measured by using a reference signal transmitted by the other base station and an amount of interference measured by a user terminal.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a radio base station, a user terminal, and a radio communication method applicable to a cellular system or the like.

  In a UMTS (Universal Mobile Telecommunications System) network, HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access) are adopted for the purpose of improving frequency utilization efficiency and data rate. A system based on CDMA (Wideband Code Division Multiple Access) is maximally extracted. For this UMTS network, Long Term Evolution (LTE) has been studied for the purpose of further high data rate and low delay (Non-Patent Document 1).

  The third generation system can realize a transmission rate of about 2 Mbps at the maximum on the downlink using a fixed band of 5 MHz in general. On the other hand, in the LTE system, a transmission rate of about 300 Mbps at the maximum in the downlink and about 75 Mbps in the uplink can be realized using a variable band of 1.4 MHz to 20 MHz. In addition, in the UMTS network, a successor system of the LTE system is also studied for the purpose of further widening and speeding up (for example, LTE advanced or LTE enhancement (hereinafter referred to as “LTE-A”). ))).

  In wireless communication, as a duplex format of uplink (UL) and downlink (DL), frequency division duplex (FDD) for dividing uplink and downlink by frequency and time for dividing uplink and downlink by time There is division duplex (TDD). In the case of TDD, the same frequency is applied to uplink and downlink transmission, and the uplink and the downlink are transmitted from one transmission point while being divided by time. Since the same frequency is used for uplink and downlink, the transmission point (radio base station) and the user terminal need to switch between transmission and reception alternately.

  Also, in the TDD of the LTE system, a frame configuration (transmission ratio (DL / UL configuration) between uplink subframes and downlink subframes) corresponding to a plurality of different asymmetric uplink / downlink resource allocations is defined (FIG. 1). In the LTE system, as shown in FIG. 1, seven frame configurations of DL / UL configurations 0 to 6 are defined, subframes # 0 and # 5 are allocated to the downlink, and subframe # 2 is the uplink. Assigned to Further, in order to avoid interference between transmission points (or between cells), the same DL / UL configuration (DL / UL configuration) is applied between adjacent transmission points.

3GPP, TR25.912 (V7.1.0), "Feasibility study for Evolved UTRA and UTRAN", Sept. 2006

  However, in the TDD of the LTE-A system, in order to effectively use radio resources, the transmission ratio between DL and UL is dynamically or semi-statically in the time domain for each transmission / reception point. Fluctuating, that is, changing the DL / UL configuration applied to each transmission / reception point has been studied. When different DL / UL configurations are applied between adjacent transmission / reception points, DL subframes and UL subframes are transmitted simultaneously between adjacent transmission / reception points in the same time domain / frequency domain (uplink signal and downlink signal). Are transmitted at the same time).

  In this case, depending on the position and transmission power of each transmission / reception point (or user terminal), interference may occur between the transmission / reception points and between user terminals, and the communication quality characteristics may deteriorate.

  The present invention has been made in view of this point, and even when different DL / UL configurations are applied at adjacent transmission / reception points (radio base stations), the radio base station can suppress the influence of interference. An object is to provide a user terminal and a wireless communication method.

  A radio base station according to an aspect of the present invention is a radio base station that communicates with a user terminal using a time division duplex (TDD) scheme, and is configured to change a DL / UL configuration based on information on an interference amount and And / or a signal generation unit that generates a change request signal related to a change in transmission power, and a transmission path interface that transmits the change request signal to another radio base station, wherein the interference amount is the other base station It is at least one of the interference amount measured using the reference signal transmitted from and the interference amount measured by the user terminal.

  According to the present invention, even when different DL / UL configurations are applied at adjacent transmission / reception points (radio base stations), the influence of interference can be suppressed.

It is a figure for demonstrating an example of DL / UL structure in TDD. It is a figure which shows an example of the radio | wireless communications system which applies a different DL / UL structure between adjacent radio base stations. It is an example of the sequence diagram which shows the radio | wireless communications system and radio | wireless communication method which concern on this Embodiment. It is an example of the sequence diagram which shows the radio | wireless communications system and radio | wireless communication method which concern on this Embodiment. It is an example of the sequence diagram which shows the radio | wireless communications system and radio | wireless communication method which concern on this Embodiment. It is an example of the sequence diagram which shows the radio | wireless communications system and radio | wireless communication method which concern on this Embodiment. It is a figure which shows an example of the radio | wireless communications system which comprises the centralized control base station in this Embodiment. It is an example of the sequence diagram which shows the radio | wireless communication method in the radio | wireless communications system which comprises the centralized control base station in this Embodiment. It is a figure for demonstrating the whole structure of a wireless base station. It is a functional block diagram corresponding to the baseband process part of a wireless base station. It is a figure for demonstrating the whole structure of a user terminal. It is a functional block diagram corresponding to the baseband process part of a user terminal.

  First, an example of a wireless communication system to which this exemplary embodiment is applied will be described with reference to FIG. 2A. The radio communication system shown in FIG. 2A includes a plurality of transmission / reception points (here, radio base stations # 1 and # 2) and user terminals # 1 and # 2 communicating with the radio base stations # 1 and # 2. It consists of

  In the wireless communication system, wireless communication is performed between the wireless base station # 1 and the user terminal # 1 (between the wireless base station # 2 and the user terminal # 2) by time division duplex (TDD). That is, in the radio base stations # 1 and # 2, the same frequency domain is applied to DL and UL transmission, and DL and UL are transmitted from each radio base station in the time domain.

  In this case, as described above, when a different DL / UL configuration is applied between the adjacent radio base stations # 1 and # 2, interference between the radio base stations # 1 and # 2 and user terminal # in a predetermined subframe. There is a risk that the quality of communication quality may deteriorate due to the interference between No. 1 and # 2.

  For example, as shown in FIG. 2B, when radio base station # 1 applies DL / UL configuration 1 and radio base station # 2 applies DL / UL configuration 2 in a certain period (here, one frame), subframe # 3 , # 8, UL transmission is applied to the radio base station # 1, and DL transmission is applied to the radio base station # 2. That is, in the same time domain and the same frequency domain, the downlink signal is transmitted from the radio base station # 2 to the user terminal # 2, and the uplink signal is transmitted from the user terminal # 1 to the radio base station # 1.

  In this case, the downlink signal transmitted from the radio base station # 2 to the user terminal # 2 is interfered with the uplink signal transmitted from the user terminal # 1 to the radio base station # 1 (radio base station # 1). , # 2 interference). Further, the uplink signal transmitted from the user terminal # 1 to the radio base station # 1 is interfered with the downlink signal transmitted from the radio base station # 2 to the user terminal # 2 (user terminals # 1, #). 2). As a result, in subframes # 3 and # 8, the reception quality of radio base station # 1 and the reception quality of user terminal # 2 may be degraded.

  Therefore, the present inventors consider the amount of interference between transmission / reception points (radio base stations) and between user terminals, and each radio base station has a DL / UL configuration, radio base station transmission power, user terminal It has been found that by appropriately controlling transmission power and the like, the influence of interference can be suppressed even when different DL / UL configurations are applied between adjacent transmission / reception points.

  Hereinafter, details of the present embodiment will be described in detail with reference to the accompanying drawings. In the present specification, two or three transmission / reception points (wireless base stations) are described as examples, but the number of transmission / reception points to which the present invention can be applied is not limited thereto. In addition, in this specification, as a DL / UL configuration (DL / UL configuration) applied to each transmission / reception point, a configuration defined in the LTE system (see FIG. 1) is given as an example. The applicable DL / UL configuration is not limited to this. In the radio communication system according to the present embodiment, each transmission / reception point can appropriately set the DL / UL configuration according to the communication environment.

(First aspect)
FIG. 3A shows an example of a wireless communication system in the first mode. The wireless communication system in FIG. 3A includes a plurality of transmission / reception points (here, wireless base stations # 1 to # 3) and user terminals # 1 to # 3 respectively connected to the wireless base stations # 1 to # 3. It consists of Note that the radio base station # 1 to # 3 each other, wired connection such as X ₂ signaling or fibers, or can be carried out the transmission of information by a wireless connection.

  Radio communication between the radio base station # 1 and the user terminal # 1, between the radio base station # 2 and the user terminal # 2, and between the radio base station # 3 and the user terminal # 3 is time-division complex. Communication (TDD) is applied. In the wireless communication system shown in FIG. 3A, the wireless base stations # 1 to # 3 individually (independently) control the DL and UL transmission ratio (DL / UL configuration) by varying them in the time domain. Yes. In this case, each of the radio base stations # 1 to # 3 may select an arbitrary DL / UL configuration from a predefined DL / UL configuration (see FIG. 1), or depending on the communication environment or the like It is also possible to arbitrarily define the DL / UL configuration.

  When different DL / UL configurations are applied between adjacent radio base stations # 1 to # 3, the downlink signal and the uplink signal have the same frequency domain and the same time domain between adjacent radio base stations (or between cells). Sent by For example, as shown in FIG. 3A, the downlink signals transmitted from the other radio base stations # 2 and # 3 to the user terminals # 2 and # 3, respectively, are radio signals that receive the uplink signal from the user terminal # 1. Interference signal for base station # 1.

  Therefore, in the first aspect, each radio base station changes DL / UL configuration and / or changes transmission power with respect to other radio base stations based on the amount of interference received from other different radio base stations. By reducing the influence of interference.

  Hereinafter, referring to FIG. 3B, the radio base station # 1 performs DL / DL to the other radio base stations # 2 and # 3 based on the amount of interference from the other radio base stations # 2 and # 3. A case will be described in which a UL configuration change and / or a transmission power change request (hereinafter also simply referred to as “change request”) is notified. In the following description, when radio base station # 1 (interfered station in FIG. 3A) transmits a change request signal to other radio base stations # 2 and # 3 (interfering station in FIG. 3A). However, the other radio base stations # 2 and # 3 can perform the same processing as the radio base station # 1.

  First, the radio base station # 1 measures the amount of interference from the other radio base stations # 2 and # 3 (step S101). Note that the amount of interference in this embodiment refers to path loss, penetration loss, antenna gain, and the like. For example, the path loss of the uplink channel (between radio base station # 1 and user terminal # 1) can be measured. In this case, the amount of interference obtained is the total amount of interference from the other radio base stations # 2 and # 3.

  In addition, in step S101, the radio base station # 1 has a measured interference amount (for example, a total value of interference amounts from the radio base stations # 2 and # 3) larger than a predetermined reference value (threshold # 1) regarding the interference amount. Determine whether or not. The threshold value # 1 is a reference value for determining the influence of interference from the other radio base stations # 2 and # 3 to the radio base station # 1, and the radio base station # 1 makes a change request based on the threshold value # 1. Determine the presence or absence.

Note that the predetermined reference value (threshold # 1) may be common to each radio base station or may be different. Further, the predetermined reference value (threshold # 1) can be notified to the radio base station # 1 by a broadcast signal, higher layer signaling (for example, RRC signaling) or the like. Moreover, it can also be set as the structure notified to radio base station # 1 with the downlink control signal (DCI) transmitted via a downlink control channel (PDCCH, ePDCCH) etc. Further, it may be notified to the radio base station # 1 through X ₂ signaling and fiber. In addition, it is also possible to store the threshold value # 1 in the storage unit of the radio base station # 1 in advance and apply the threshold value # 1 in which the radio base station # 1 is stored.

  Note that the PDCCH (downlink control channel) is a downlink control channel arranged in a predetermined OFDM symbol (1 to 3 OFDM symbols) from the top of the subframe, and is a control channel that is time-division multiplexed with the PDSCH (downlink shared data channel). . Also, ePDCCH (also called enhanced downlink control channel, E-PDCCH, Enhanced PDCCH, FDM type PDCCH, UE-PDCCH, etc.) is a control channel arranged to be frequency division multiplexed with PDSCH.

  When the total amount of interference from other radio base stations # 2 and # 3 is larger than a predetermined reference value (threshold # 1), downlink signals transmitted from other radio base stations # 2 and / or # 3 are This will affect the radio base station # 1 that receives the uplink signal transmitted from the user terminal # 1. In this case, the radio base station # 1 requests the other radio base stations # 2 and # 3 to change the DL / UL configuration and / or change the transmission power (steps S102a and S102b).

  For example, when the amount of interference from the other radio base stations # 2 and # 3 is large, the radio base station # 1 transmits the number of DL subframes and / or transmission to the other radio base stations # 2 and # 3. A change request signal for requesting to reduce power is transmitted. Or, the radio base station # 1 requests the other radio base stations # 2 and # 3 to change the DL / UL configuration so that the same DL / UL configuration as the radio base station # 1 is applied. Send a request signal.

  The other radio base stations # 2 and # 3 that have received the change request signal from the radio base station # 1 determine whether to comply with the change request (steps S103a and S103b). In the first mode, the radio base stations # 2 and # 3 that have received the change request signal change the DL / UL configuration and / or the transmission power according to the change request. For example, when the radio base station # 1 requests that the number of DL subframes be reduced, the radio base stations # 2 and # 3 may transmit a predetermined DL subframe (the UL subframe of the radio base station # 1) in the subframe. (DL subframe transmitted in the same time domain) is reduced (downlink signal transmission is not performed).

  Thereafter, each of the radio base stations # 1 to # 3 applies the DL / UL configuration reflecting the change request notified from the other radio base stations and / or the transmission power, thereby controlling the user terminals # 1 to # 1 under the control. 3 to perform wireless communication (steps S104a to S104c). Thus, even when different DL / UL configurations are applied between adjacent transmission / reception points (radio base stations), a change request is notified based on the amount of interference from other radio base stations, and transmission parameters are transmitted. By controlling this, interference between adjacent transmission / reception points can be suppressed.

  In FIG. 3 described above, the method of controlling interference between radio base stations has been described by notifying a change request between different transmission / reception points. However, the present embodiment is also effective in suppressing interference between user terminals. Can be applied. In the following, referring to FIG. 4, each user terminal makes a request to change the transmission power of another user terminal to a radio base station to which the other user terminal is connected based on the amount of interference from the other user terminal. A case of notification will be described.

  In the description of FIG. 4, the user terminal # 2 (interfered station in FIG. 4A) is connected to the other user terminal 1 (interfering station in FIG. 4A) via the radio base station # 2. Although a case where a request for changing the transmission power of the user terminal 1 is notified to # 1 is shown, the user terminal # 1 can perform the same processing as the user terminal # 2.

  First, user terminal # 2 measures the amount of interference from other user terminal # 1 connected to a different radio base station # 1 (step S111). As described above, the interference amount indicates a path loss, a penetration loss, an antenna gain, and the like. For example, the path loss of the downlink channel (between radio base station # 2 and user terminal # 2) can be measured.

  The user terminal # 2 generates information related to the interference amount and transmits it to the radio base station # 2 (step S112). The radio base station # 2 determines whether or not the interference amount is greater than a predetermined reference value (threshold # 1 ') based on the information regarding the interference amount transmitted from the user terminal # 2 (step S113). The threshold value # 1 ′ is a reference value for determining the influence of interference from the other user terminal # 1 to the user terminal # 2, and it is possible to determine whether there is a change request based on the threshold value # 1 ′. .

  Note that the information related to the interference amount transmitted by the user terminal # 2 to the radio base station # 2 to which the user terminal # 2 is connected (in the serving cell) may be the interference amount itself measured by the user terminal # 2, or the user terminal It may be the result of determining whether or not the amount of interference is larger than the threshold value # 1 ′ in # 2. In the latter case, when the amount of interference from the user terminal # 1 is larger than the threshold value # 1 ′, the user terminal # 2 sends a change request signal for requesting a change in transmission power of the other user terminal # 1 to the radio base station #. 2 to send.

  The predetermined reference value (threshold # 1 ') can be notified to the user terminal # 2 by a broadcast signal, higher layer signaling (for example, RRC signaling) or the like. Moreover, it can also be set as the structure notified to user terminal # 2 by the downlink control signal (DCI) transmitted via a downlink control channel (PDCCH, ePDCCH) etc. In addition, the threshold value # 1 'can be stored in advance in the storage units of the radio base station # 2 and the user terminal # 2, and the stored threshold value # 1' can be applied.

  When the measured interference amount is larger than the threshold # 1 ′, the uplink signal transmitted from the user terminal # 1 to the radio base station # 1 is changed to the downlink signal transmitted from the radio base station # 2 to the user terminal # 2. It will have an effect on it. In this case, the radio base station # 2 requests the radio base station # 1 to reduce the transmission power of the uplink signal of the user terminal # 1 (step S114).

  The radio base station # 1 that has received the change request signal from the radio base station # 2 determines whether to comply with the change request (step S115). In the first mode, the radio base station # 1 that has received the notification of the change request reduces the transmission power of the user terminal # 1 according to the change request. Thereafter, each of the radio base stations # 1 and # 2 sets the transmission power of the subordinate user terminal based on the change request notified from the other radio base station, and wirelessly communicates with the subordinate user terminals # 1 and # 2 respectively. Communication is performed (steps S116a and S116b). In FIG. 4B, since the transmission power of user terminal # 1 is set low, the influence of interference on user terminal # 2 can be reduced.

  In the first mode, the control method for changing the DL / UL configuration and transmission power for the radio base station shown in FIG. 3 and the control method for changing the transmission power for the user terminal shown in FIG. 4 are appropriately combined. Can be done. In this way, even when different DL / UL configurations are applied in adjacent radio base stations, the DL / UL configuration and / or the transmission power is determined based on the amount of interference between radio base stations and between user terminals. By controlling the change, it is possible to effectively suppress a decrease in communication quality due to interference.

(Second aspect)
FIG. 5A shows an example of a wireless communication system in the second mode. The wireless communication system in FIG. 5A is located in a plurality of transmission / reception points (here, wireless base stations # 1 to # 3) and wireless base stations # 1 to # 3, respectively, as in the first aspect. It includes user terminals # 1 to # 3.

  In the second aspect, a radio base station that is notified of a DL / UL configuration and / or transmission power change request from another radio base station requests a change according to the reception level with the request-target radio base station. Judge whether to follow

  For example, when the measured interference amount (for example, the total interference amount from the radio base stations # 2 and # 3) is larger than a predetermined reference value (threshold # 1), the radio base station # 1 A change request is notified to the stations # 2 and # 3. The other radio base stations # 2 and # 3 measure the reception level with the radio base station # 1 that is the request instruction target, and a reference value (a reference value for determining whether to apply the reception level and the change request) Threshold value # 2) is compared, and it is determined whether or not the change request from radio base station # 1 is followed.

  The DL / UL configuration of a radio base station that has a large influence of interference on the request instruction target when the radio base station notified of the change request determines application of the change request according to the reception level with the request instruction target. And transmission power can be selectively changed.

  In the following, referring to FIG. 5B, the application / non-application of the change request notified from the radio base station # 1 based on the reception level of the radio base stations # 2 and # 3 with the radio base station # 1. A case of determination will be described. Note that description of the same parts as those in the first aspect is omitted.

  First, the radio base station # 1 measures the amount of interference from the other radio base stations # 2 and # 3 (step S201). Also, in step S201, the radio base station # 1 determines whether or not the measured interference amount is greater than a predetermined reference value (threshold # 1).

  When the amount of interference is larger than the predetermined reference value (threshold # 1), the radio base station # 1 transmits a change request signal to the other radio base stations # 2 and # 3 (steps S202a and S202b). For example, when the total amount of interference from the other radio base stations # 2 and # 3 is larger than the threshold value # 1, the radio base station # 1 transmits a DL subframe to the other radio base stations # 2 and # 3. And / or a change request signal that requests to reduce transmission power. Alternatively, the radio base station # 1 requests the other radio base stations # 2 and # 3 to change the DL / UL configuration so that the same DL / UL configuration as the radio base station # 1 is applied.

  Furthermore, in the second mode, in steps 202a and 202b, a change request signal is transmitted from the radio base station # 1 to the other radio base stations # 2 and # 3, and whether or not the change request is applied. The information regarding the reference value (threshold value # 2) serving as the determination criterion can be notified.

  Receiving the change request from the wireless base station # 1, the wireless base stations # 2 and # 3 compare the reception level from the wireless base station # 1 that is the request instruction target with the reference value (threshold # 2). Then, it is determined whether or not the change request is followed (steps S203a and S203b). Specifically, each of the radio base stations # 2 and # 3 follows the change request from the radio base station # 1 when the reception level with the radio base station # 1 is larger than the threshold value # 2. On the other hand, when the reception level with the radio base station # 1 is equal to or lower than the threshold value # 2, the change request is not followed because the influence of interference on the radio base station # 1 is small.

5B shows the case where the reference value (threshold # 2) is notified together with the change request signal from the radio base station # 1 that is the request instruction target, but the notification method of the threshold # 2 is not limited to this. For example, the base station apparatus # 1 can be configured to notify the threshold # 2 to the other base station apparatuses # 2 and # 3 by a broadcast signal and higher layer signaling (for example, RRC signaling). In addition, other base station apparatuses # 2 and # 3 may be notified by a downlink control signal (DCI) transmitted via a downlink control channel (PDCCH, ePDCCH) or the like. Further, it may be notified to the radio base station # 1 through X ₂ signaling and fiber. It is also possible to store the threshold value # 2 in the storage unit of the other radio base stations # 2 and # 3 in advance and apply it as a criterion for determining whether or not to comply with the change request notified from the radio base station # 1. It is.

  Thereafter, each of the radio base stations # 1 to # 3 applies the DL / UL configuration and the transmission power set by the change request signal notified from the other radio base stations, and the subordinate user terminals # 1 to # 3 And perform wireless communication (steps S204a to S204c).

  In this way, by determining whether or not the change request can be applied based on the reception level with the radio base station that is the request instruction target, the DL / UL configuration change or transmission power of the radio base station having a large influence of interference is determined. Can be selectively changed.

(Third aspect)
FIG. 6A shows an example of a wireless communication system in the third mode. The radio communication system of FIG. 6A is similar to the first and second aspects described above, and includes a plurality of transmission / reception points (here, radio base stations # 1 to # 3) and radio base stations # 1 to # 3. Are configured to include user terminals # 1 to # 3, respectively.

  In the third aspect, each radio base station measures an interference amount (interference power) for each different radio base station using a reference signal for interference measurement, and the interference amount is larger than a predetermined reference value (threshold # 1). A change request is individually notified to the radio base station.

  For example, the radio base station # 1 uses cell-specific (or transmission / reception point-specific and radio base station-specific) reference signal sequences transmitted from the radio base stations # 2 and # 3, respectively. The amount of interference (interference power) for each # 3 is measured. Then, out of the interference amounts from the radio base stations # 2 and # 3, DL / individually with respect to a radio base station (for example, the radio base station # 2) whose interference amount is larger than a predetermined reference value (threshold # 1) Request a change in UL configuration and / or a change in transmission power. Thereby, each radio base station can selectively notify a change request only to a radio base station having a large influence of interference among a plurality of adjacent radio base stations.

  In the following, referring to FIG. 6B, radio base station # 1 measures the amount of interference from radio base stations # 2 and # 3 based on a reference signal for interference measurement, and makes a change request individually. The case will be described. In addition, description is abbreviate | omitted about the part similar to the said 1st, 2nd aspect.

  First, the radio base station # 1 receives interference measurement reference signals transmitted from the other radio base stations # 2 and # 3 (steps S301a and S301b). Subsequently, the radio base station # 1 measures the amount of interference (interference power) for each of the radio base stations # 2 and # 3 based on the reference signal (step S302). In addition, in step S302, the radio base station # 1 determines whether or not the amount of interference from each of the radio base stations # 2 and # 3 is greater than a predetermined reference value (threshold # 1).

  A radio base station having an interference amount with respect to the radio base station # 1 larger than the threshold value # 1 may affect the radio base station # 1 that receives an uplink signal transmitted from the user terminal # 1. Therefore, the radio base station # 1 operates so as to individually reduce the interference with respect to the radio base station whose interference amount is larger than the threshold value # 1.

  For example, when the interference amount from the radio base station # 2 is higher than the threshold value # 1 and the interference amount from the radio base station # 3 is smaller than the threshold value # 1, the radio base station # 1 sends a change request signal to the radio base station # 1. 2 is selectively transmitted (step S303). On the other hand, the radio base station # 1 does not transmit a change request signal to the radio base station # 3.

  Receiving the change request signal transmitted from the wireless base station # 1, the wireless base station # 2 changes the DL / UL configuration and / or reduces the transmission power in accordance with the change request (step S304). Thereafter, each of the radio base stations # 1 to # 3 applies the DL / UL configuration and transmission power set in accordance with the change request signal transmitted from the other radio base station, and subordinates the user terminals # 1 to # 3. And perform wireless communication (steps S305a to S305c).

  In this way, each radio base station measures the amount of interference for each radio base station based on the reference signal, and selectively transmits a change request signal to the radio base station with a large amount of interference, thereby preventing interference. Transmission of the change request signal to the radio base station having a small influence can be omitted.

  In addition, although the control method of the interference between radio base stations was demonstrated in the said FIG. 6, it is applicable also to the interference between user terminals.

  For example, in step S113 of FIG. 4B described above, when the information (for example, the interference amount) related to the interference amount notified from the user terminal # 2 to the radio base station # 2 is equal to or less than the threshold value # 1 ′, the radio base station # 2 The change request signal is not transmitted to the radio base station # 1. Alternatively, when the interference amount measured at the user terminal # 2 is equal to or less than the predetermined reference value, the user terminal # 2 does not notify the radio base station # 2 of information regarding the interference amount. Thus, only when the amount of interference from other user terminals is large, by transmitting information about the amount of interference, radio resources can be used efficiently.

(Fourth aspect)
In the first aspect to the third aspect, each radio base station has shown a case in which a DL / UL configuration and / or transmission power change request is directly notified to other radio base stations. The embodiment is not limited to this. For example, a configuration provided with a centralized control base station that aggregates the interference amount (or change request) measured by each radio base station and controls the DL / UL configuration and transmission power of each radio base station based on the aggregated information It is good. A radio communication system having a centralized control base station will be described below.

FIG. 7 shows an example of a wireless communication system in the fourth mode. The radio communication system in FIG. 7 includes a plurality of transmission / reception points (here, radio base stations # 1 to # 3), user terminals # 1 to # 3 located in the radio base stations # 1 to # 3, Each of the radio base stations # 1 to # 3 includes a DL / UL configuration and / or a centralized control base station that controls transmission power. And each radio base station # 1 to # 3 and the centralized-control base station, a wired connection such as X ₂ signaling or fibers, or can be carried out the transmission of information by a wireless connection.

  In the fourth aspect, each of the radio base stations # 1 to # 3 measures the amount of interference from other radio base stations, and notifies the central control base station of information related to the amount of interference (see FIG. 7A). The centralized control base station appropriately transmits a change request signal to each of the radio base stations # 1 to # 3 based on the information on the interference amount notified from each of the radio base stations # 1 to # 3 (see FIG. 7B). ).

  For example, when there is a radio base station # 1 whose total amount of interference from the other radio base stations # 2 and # 3 is larger than a predetermined reference value (threshold 1), the other radio base stations # 2 and # 3 A change request signal is transmitted. Specifically, it is possible to request the other radio base stations # 2 and # 3 to apply the same DL / UL configuration as the radio base station # 1 or reduce the transmission power. .

  The information regarding the interference amount notified from each of the radio base stations # 1 to # 3 to the central control base station may be the interference amount itself measured by each of the radio base stations # 1 to # 3. It may be a result of determining whether or not the amount of interference is greater than a predetermined reference value (threshold # 1) in each of the radio base stations # 1 to # 3.

  For example, the radio base station # 1 in which the total amount of interference from the other radio base stations # 2 and # 3 is larger than the threshold value # 1 changes the DL / UL configuration and transmission power for the radio base stations # 2 and # 3 Is sent to the central control base station. On the other hand, the radio base stations # 2 and # 3 whose total interference amount is smaller than the threshold value # 1 do not transmit the change request signal.

  The radio base stations # 2 and # 3 that have received the change request signal from the central control base station change the DL / UL configuration, transmission power, and the like according to the change request. In this case, as shown in the second mode, it may be determined whether or not the radio base stations # 2 and # 3 comply with the request according to the reception level with the radio base station # 1 that is the request instruction target. Alternatively, each radio base station notifies the central control base station of the reception level with other radio base stations, and the central control base station transmits a change request signal in consideration of the reception level between the radio base stations. It is also possible to select a radio base station.

  Hereinafter, referring to FIG. 8, the centralized control base station controls transmission of the change request signal to each radio base station based on the information on the interference amount notified from each radio base station # 1 to # 3. The case will be described.

  First, each of the radio base stations # 1 to # 3 measures the total amount of interference from other radio base stations (steps S401a to S401c). Subsequently, each of the radio base stations # 1 to # 3 notifies the central control base station of information on the interference amount (for example, the measured interference amount) (steps S402a to S402c). The centralized control base station determines whether or not the amount of interference notified from each of the radio base stations # 1 to # 3 is larger than the threshold value # 1, and selects the radio base station that transmits the change request signal (step S403).

  Note that each radio base station may determine whether the interference amount is larger than the threshold value # 1 after measuring the interference amount, and notify the centralized control base station of a change request for another radio base station.

  When there is a radio base station whose amount of interference is larger than a predetermined interference amount value (threshold # 1), the central control base station changes the DL / UL configuration and / or transmission power of other radio base stations. A change is requested (steps S404a to S404c). For example, when only the amount of interference from the other radio base station with respect to the radio base station # 1 is larger than the threshold value # 1, a change request signal is transmitted to the other radio base stations # 2 and # 3. Further, when the interference amount of a plurality of (for example, radio base stations # 1 and # 2) is larger than the threshold value # 1, it is determined that interference occurs between the plurality of radio base stations, and these radio base stations Can be notified of a change request to apply the same DL / UL configuration.

  The radio base station that has received the change request notification from the centralized control base station changes the DL / UL configuration and / or transmission power according to the change request (steps S405a to S405c). Thereafter, each of the radio base stations # 1 to # 3 applies a DL / UL configuration and transmission power reflecting the change request and performs radio communication with subordinate user terminals # 1 to # 3 (steps S406a to S406c). ).

  In this way, even when different DL / UL configurations are applied at adjacent transmission / reception points (radio base stations), information on the amount of interference from other radio base stations is aggregated in the centralized control base station. By controlling the DL / UL configuration and / or transmission power of the radio base station, it is possible to effectively suppress a decrease in communication quality due to interference.

  In addition, although the control method of the interference between radio base stations was demonstrated in the said FIG. 8, it is applicable also to the interference between user terminals.

  For example, information on the amount of interference from other user terminals connected to different radio base stations from each user terminal is notified to the centralized control base station directly or via the connected radio base station. Then, the central control base station can control the transmission power of each user terminal based on the information regarding the amount of interference with each user terminal and the predetermined reference value (threshold # 1 '). In this case, the centralized control base station transmits a change request signal for changing the transmission power of the user terminal to the radio base station to which the user terminal that changes the transmission power is connected.

(5th aspect)
In the fifth aspect, each radio base station measures an interference amount (interference power) for each different radio base station using a reference signal for interference measurement, and the interference amount is greater than a predetermined reference value (threshold # 1). A case will be described in which information on radio base stations is selectively notified to the centralized control base station.

  For example, in the wireless communication system shown in FIG. 7, each of the wireless base stations # 1 to # 3 uses a cell-specific (or transmission / reception point-specific or wireless base station-specific) reference signal sequence to The amount of interference (interference power) for each station is measured. That is, the radio base station # 1 individually measures the interference amount of the radio base stations # 2 and # 3, the radio base station # 2 individually measures the interference amount of the radio base stations # 1 and # 3, Radio base station # 3 individually measures the amount of interference of radio base stations # 1 and # 2.

  Then, of the interference amounts from other radio base stations, the central control base station is selectively notified only of information relating to the interference amount where the interference amount is greater than a predetermined value (threshold # 1). For example, in the case shown in FIG. 7, the radio base station # 1 selectively notifies only the amount of interference from the radio base station # 2 to the centralized control base station. On the other hand, the radio base stations # 2 and # 3 do not notify the amount of interference (only step S402a among steps S402a to S402c in FIG. 8 is performed). As a result, each radio base station only needs to transmit to the centralized control base station information related to the amount of interference with a radio base station having a large influence of interference among a plurality of adjacent radio base stations.

  The centralized control base station transmits a change request signal to each radio base station based on the information regarding the interference amount transmitted from the radio base station. For example, in the case shown in FIG. 7, the centralized control base station transmits a change request signal only to the radio base station # 2 (only step S404b among steps S404a to S404c in FIG. 8 is performed). For example, the centralized control base station applies the same DL / UL configuration as that of the radio base station # 1 to the radio base station # 2, and the DL sub in the same time domain as the UL subframe of the radio base station # 1. Notification of reducing frames and / or reducing transmission power.

  Receiving the change request signal transmitted from the centralized control base station, the radio base station # 2 changes the DL / UL configuration and transmission power in accordance with the change request (step S405b in FIG. 8). Thereby, the change request signal transmitted by the centralized control base station can be reduced.

  Thereafter, each of the radio base stations # 1 to # 3 performs a radio communication with the subordinate user terminals # 1 to # 3 by applying the DL / UL configuration and transmission power reflecting the change request (steps in FIG. 8). S406a to S406c). In this way, even when different DL / UL configurations are applied in adjacent radio base stations, information on the interference amount is individually notified to the centralized control base station based on the interference amount from other radio base stations. By doing so, it becomes possible to suppress transmission of unnecessary signals.

  In the above description, the method for controlling interference between radio base stations has been described, but it can also be applied to interference between user terminals.

  For example, when notifying the central control base station of information on the amount of interference from other user terminals connected to different radio base stations from each user terminal to the centralized control base station directly or via the connected radio base station, The central control base station is notified only when the amount of interference is equal to or greater than a predetermined reference value. Thereby, effective utilization of radio resources can be achieved.

  The overall configuration of the radio base station according to the present embodiment will be described below with reference to FIG. In the following description, the radio base station and the centralized control base station can be configured in the same manner, and will be described as the radio base station 20.

Incidentally, the centralized-control base station and the radio base station can transmit the information via a wired link such as X ₂ signaling and fiber. Further, the radio base station may be connected to the centralized control base station via a radio link. In addition, each of the radio base station and the centralized control base station is connected to an upper station apparatus (not shown) on the core network. The upper station device includes, for example, an access gateway device, a mobility management entity (MME), and the like, but is not limited thereto.

  The radio base station may be a base station called eNodeB, a transmission / reception point, or a pico base station, a femto base station, a Home eNodeB, an RRH (Remote Radio Head), a micro base station, a transmission / reception point, or the like. It may be a base station having a local coverage area. Further, the centralized control base station is a control station that controls the radio base station, and may be a base station called an eNodeB, a transmission / reception point, or the like as long as it has a control function of the radio base station. For example, a device provided on a core network, an RNC (Radio Network Controller), or the like may be used.

  The radio base station 20 includes a transmission / reception antenna 201, an amplifier unit 202, a transmission / reception unit (transmission unit / reception unit) 203, a baseband signal processing unit 204, a call processing unit 205, and a transmission path interface 206. Yes. Transmission data transmitted from the radio base station 20 to the user terminal via the downlink is input from the higher station apparatus 30 to the baseband signal processing unit 204 via the transmission path interface 206.

  In the baseband signal processing unit 204, the downlink data channel signal is transmitted from the RLC layer such as PDCP layer processing, transmission data division / combination, RLC (Radio Link Control) retransmission control transmission processing, MAC (Medium Access), and so on. Control) Retransmission control, for example, HARQ transmission processing, scheduling, transmission format selection, channel coding, inverse fast Fourier transform (IFFT) processing, and precoding processing are performed. Also, transmission processing such as channel coding and inverse fast Fourier transform is performed on the signal of the physical downlink control channel that is the downlink control channel.

  Moreover, the baseband signal processing unit 204 notifies the control information for each user terminal to perform radio communication with the radio base station 20 to the user terminal connected to the same cell through the broadcast channel. Information for communication in the cell includes, for example, system bandwidth in uplink or downlink, and root sequence identification information (Root Sequence) for generating a random access preamble signal in PRACH (Physical Random Access Channel). Index) etc. are included.

  The transmission / reception unit 203 converts the baseband signal output from the baseband signal processing unit 204 into a radio frequency band. The amplifier unit 202 amplifies the radio frequency signal subjected to frequency conversion and outputs the amplified signal to the transmission / reception antenna 201.

  On the other hand, for the signal transmitted from the user terminal to the radio base station 20 via the uplink, the radio frequency signal received by the transmission / reception antenna 201 is amplified by the amplifier unit 202 and is frequency-converted by the transmission / reception unit 203 to become a baseband signal. The signal is converted and input to the baseband signal processing unit 204.

  The baseband signal processing unit 204 performs FFT processing, IDFT processing, error correction decoding, MAC retransmission control reception processing, RLC layer, PDCP layer reception processing on transmission data included in the baseband signal received in the uplink I do. The decoded signal is transferred to the upper station apparatus via the transmission path interface 206.

  The call processing unit 205 performs call processing such as communication channel setting and release, state management of the radio base station 20, and radio resource management.

  FIG. 10 is a block diagram showing a configuration of a baseband signal processing unit in the radio base station shown in FIG. The baseband signal processing unit 204 includes a layer 1 processing unit 2041, a MAC processing unit 2042, an RLC processing unit 2043, an interference amount measuring unit 2044, a change request signal generating unit 2045, and a change request setting unit 2046. It is mainly composed.

  The layer 1 processing unit 2041 mainly performs processing related to the physical layer. For example, the layer 1 processing unit 2041 performs channel decoding, discrete Fourier transform (DFT), frequency demapping, and inverse fast Fourier transform (IFFT) on a signal received on the uplink. Processing such as data demodulation. Further, the layer 1 processing unit 2041 performs processing such as channel coding, data modulation, frequency mapping, and inverse fast Fourier transform (IFFT) on a signal transmitted in the downlink.

  The MAC processing unit 2042 performs processing such as retransmission control at the MAC layer for signals received in the uplink, scheduling for the uplink / downlink, selection of the PUSCH / PDSCH transmission format, selection of the PUSCH / PDSCH resource block, and the like. .

  The RLC processing unit 2043 performs packet division, packet combination, retransmission control at the RLC layer, etc. on packets received on the uplink / packets transmitted on the downlink.

  The interference amount measuring unit 2044 measures the amount of interference from other radio base stations. For example, in the case of the first mode (see FIG. 3), the interference amount measurement unit 2044 in the radio base station # 1 measures the total value of the interference amounts from the other radio base stations # 2 and # 3. For the measurement of the amount of interference, path loss, penetration loss, antenna gain, and the like can be used. For example, the path loss of the uplink channel (between the radio base station # 1 and the user terminal # 1) can be measured.

  Further, in the case of the third mode (see FIG. 6), the interference amount measuring unit 2044 in the radio base station # 1 is cell-specific (or transmission / reception point-specific, transmitted from each of the radio base stations # 2 and # 3, The amount of interference (interference power) for each of the radio base stations # 2 and # 3 is measured using a reference signal sequence (specific to the radio base station).

  Based on the interference amount measured by the interference amount measurement unit 2044, the change request signal generation unit 2045 generates a change request signal for requesting another base station to change the DL / UL configuration and / or change the transmission power. Generate. For example, in the case of the first aspect (see FIG. 3), the change request signal generation unit 2045 in the radio base station # 1 has a total interference amount from the other radio base stations # 2 and # 3 as a predetermined reference value. It is determined whether or not it is larger than (threshold # 1), and if it is larger, a change request signal is generated.

  In this case, the change request signal generation unit 2045 in the radio base station # 1 requests the other radio base stations # 2 and # 3 to reduce the number of DL subframes and / or transmission power. Is generated. Alternatively, the change request signal generation unit 2045 requests the other radio base stations # 2 and # 3 to change the DL / UL configuration so that the same DL / UL configuration as that of the radio base station # 1 is applied. A change request signal is generated. The change request signal generated by the change request signal generation unit 2045 is transmitted to the other radio base stations # 2 and # 3 by wire or wireless.

  Further, in the case of the third mode (see FIG. 6), the change request signal generation unit 2045 in the radio base station # 1 has an interference amount for each of the radio base stations # 2 and # 3 as a predetermined reference value (threshold # 1). Each is judged whether it is larger. Then, a change request signal for the radio base station # 2 having an interference amount larger than the threshold value # 1 is generated, and a change request signal for the radio base station # 3 is not generated.

  The change request setting unit 2046 determines whether to comply with the change request based on a change request signal transmitted from another radio base station. When following the change request, the change request setting unit 2046 changes the DL / UL configuration and / or transmission power. For example, in the case of the second mode (see FIG. 5), the change request setting unit 2046 in the radio base stations # 2 and # 3 applies the reception level and change request with the radio base station # 1 that is the request instruction target. A reference value (threshold value # 2) that is a criterion for determining whether or not to perform the comparison is compared. If the reception level is greater than the threshold value # 2, the change request is followed.

  Next, the overall configuration of the user terminal according to the present embodiment will be described with reference to FIG. The user terminal 10 includes a transmission / reception antenna 101, an amplifier unit 102, a transmission / reception unit (transmission unit / reception unit) 103, a baseband signal processing unit 104, and an application unit 105.

  As for downlink data, a radio frequency signal received by the transmission / reception antenna 101 is amplified by the amplifier unit 102, frequency-converted by the transmission / reception unit 103, and converted into a baseband signal. The baseband signal is subjected to FFT processing, error correction decoding, retransmission control reception processing, and the like by the baseband signal processing unit 104. Among the downlink data, downlink transmission data is transferred to the application unit 105. The application unit 105 performs processing related to layers higher than the physical layer and the MAC layer. Also, the broadcast information in the downlink data is also transferred to the application unit 105.

  On the other hand, uplink transmission data is input from the application unit 105 to the baseband signal processing unit 104. The baseband signal processing unit 104 performs mapping processing, retransmission control (HARQ) transmission processing, channel coding, DFT processing, and IFFT processing. The transmission / reception unit 103 converts the baseband signal output from the baseband signal processing unit 104 into a radio frequency band. Thereafter, the amplifier unit 102 amplifies the frequency-converted radio frequency signal and transmits it from the transmission / reception antenna 101.

  FIG. 12 is a block diagram showing a configuration of a baseband signal processing unit in the user terminal shown in FIG. The baseband signal processing unit 104 includes a layer 1 processing unit 1041, a MAC processing unit 1042, an RLC processing unit 1043, an interference amount measuring unit 1044, an interference amount information generating unit 1045, and a transmission power setting unit 1046. It is mainly composed.

  The layer 1 processing unit 1041 mainly performs processing related to the physical layer. For example, the layer 1 processing unit 1041 performs processing such as channel decoding, discrete Fourier transform (DFT), frequency demapping, inverse fast Fourier transform (IFFT), and data demodulation on a signal received on the downlink. Also, the layer 1 processing unit 1041 performs processing such as channel coding, data modulation, frequency mapping, and inverse fast Fourier transform (IFFT) on a signal transmitted on the uplink.

  The MAC processing unit 1042 performs retransmission control (HARQ) at the MAC layer for a signal received on the downlink, analysis of downlink scheduling information (specification of PDSCH transmission format, identification of PDSCH resource block), and the like. Further, the MAC processing unit 1042 performs processing such as MAC retransmission control for signals transmitted on the uplink, analysis of uplink scheduling information (specification of PUSCH transmission format, specification of PUSCH resource block), and the like.

  The RLC processing unit 1043 performs packet division, packet combination, retransmission control in the RLC layer, etc. on packets received on the downlink / packets transmitted on the uplink.

  The interference amount measurement unit 1044 measures the amount of interference from other user terminals connected to different radio base stations. For example, in the case of the first mode (see FIG. 4), the interference amount measurement unit 1044 in the user terminal # 2 measures the interference amount from the other user terminal # 1. For the measurement of the interference amount, path loss, penetration loss, antenna gain, and the like can be used, and the path loss of the downlink channel (between the radio base station # 2 and the user terminal # 2) can be measured.

  The interference amount information generation unit 1045 generates information related to the interference amount based on the interference amount measured by the interference amount measurement unit 1044. The information related to the interference amount may be the interference amount itself measured by the user terminal, or may be a result of determining whether the interference amount is greater than a predetermined reference value (threshold # 1 ′) (change request signal) in the user terminal. Good. Information regarding the interference amount generated by the interference amount information generation unit 1045 is transmitted to the radio base station via the transmission / reception unit 103.

  The transmission power setting unit 1046 controls uplink signal transmission power in accordance with an instruction from the radio base station. For example, in the case of the first mode (see FIG. 4), since a change request for reducing the transmission power of the user terminal # 1 is notified to the radio base station # 1, the transmission power setting unit in the user terminal # 1 1046 sets the transmission power of the uplink signal low based on the instruction from the radio base station # 1.

  As described above, even when a different DL / UL configuration is applied between adjacent radio base stations, the DL / UL configuration and / or the transmission power is determined based on the amount of interference from other radio base stations. By notifying a change request and controlling transmission parameters, interference between adjacent radio base stations can be suppressed.

  Although the present invention has been described in detail using the above-described embodiments, it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modified and changed modes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention.

DESCRIPTION OF SYMBOLS 10 User terminal 20 Wireless base station 101 Transmission / reception antenna 102 Amplifier part 103 Transmission / reception part 104 Baseband signal processing part 105 Application part 201 Transmission / reception antenna 202 Amplifier part 203 Transmission / reception part 204 Baseband signal processing part 205 Call processing part 206 Transmission path interface 1041, 2041 Layer 1 processing unit 1042, 2042 MAC processing unit 1043, 2043 RLC processing unit 1044 Interference amount measuring unit 1045 Interference amount information generating unit 1046 Transmission power setting unit 2044 Interference amount measuring unit 2045 Change request signal generating unit 2046 Change request setting unit

Claims (6)

A radio base station that communicates with a user terminal using a time division duplex (TDD) scheme,
A signal generation unit that generates a change request signal related to a change in DL / UL configuration and / or a change in transmission power based on information on the amount of interference;
A transmission path interface for transmitting the change request signal to another radio base station,
The radio base station, wherein the interference amount is at least one of an interference amount measured using a reference signal transmitted from the other base station and an interference amount measured by the user terminal.   The radio base station according to claim 1, wherein the reference signal is a cell-specific, transmission / reception point-specific or radio base station-specific reference signal.   The radio base station according to claim 1 or 2, wherein the interference amount measured by the user terminal includes an interference amount from another user terminal communicating with the other radio base station.   The change request signal generated based on the amount of interference measured at the user terminal is used for changing the transmission power of the other user terminal in the other radio base station. The radio base station according to claim 3. A user terminal that communicates with a radio base station using a time division duplex (TDD) scheme,
A measurement unit for measuring the amount of interference from other user terminals communicating with other radio base stations;
A transmitter that transmits information on the amount of interference to the radio base station,
The information on the amount of interference is used for generating a change request signal for changing the transmission power of the other user terminal in the other radio base station. A wireless communication method in a user terminal that communicates with a wireless base station using a time division duplex (TDD) scheme,
Measuring the amount of interference from other user terminals communicating with other radio base stations;
Transmitting information on the amount of interference to the radio base station,
The information on the amount of interference is used to generate a change request signal for changing the transmission power of the other user terminal in the other radio base station.

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