WO2014073540A1 - 移動通信システム及び移動通信方法 - Google Patents
移動通信システム及び移動通信方法 Download PDFInfo
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- WO2014073540A1 WO2014073540A1 PCT/JP2013/079928 JP2013079928W WO2014073540A1 WO 2014073540 A1 WO2014073540 A1 WO 2014073540A1 JP 2013079928 W JP2013079928 W JP 2013079928W WO 2014073540 A1 WO2014073540 A1 WO 2014073540A1
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- base station
- radio base
- anchor
- reception quality
- anchor radio
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- 238000000034 method Methods 0.000 title claims description 59
- 238000010295 mobile communication Methods 0.000 title claims description 36
- 230000005540 biological transmission Effects 0.000 claims abstract description 20
- 238000005259 measurement Methods 0.000 claims abstract description 14
- 238000004891 communication Methods 0.000 description 29
- 238000010586 diagram Methods 0.000 description 19
- 238000012545 processing Methods 0.000 description 13
- 238000012986 modification Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 101000741965 Homo sapiens Inactive tyrosine-protein kinase PRAG1 Proteins 0.000 description 4
- 102100038659 Inactive tyrosine-protein kinase PRAG1 Human genes 0.000 description 4
- 230000006870 function Effects 0.000 description 4
- 230000007774 longterm Effects 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000013468 resource allocation Methods 0.000 description 2
- 238000012937 correction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007726 management method Methods 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
- H04W56/0045—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W24/00—Supervisory, monitoring or testing arrangements
- H04W24/10—Scheduling measurement reports ; Arrangements for measurement reports
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/16—Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/0005—Control or signalling for completing the hand-off
- H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
- H04W36/0085—Hand-off measurements
Definitions
- the present invention relates to a mobile communication system including a plurality of radio base stations and a mobile communication method used in the mobile communication system.
- a mobile communication system including a plurality of radio base stations is known.
- LTE Long Term Evolution
- cooperative reception processing, cooperative transmission processing, and the like can be considered as processing performed by a plurality of wireless base stations in cooperation.
- the coordinated reception process and the coordinated transmission process are referred to as CoMP (Coordinated Multi-Point Operation) or the like (see Non-Patent Document 1).
- CoMP Coordinatd Multi-Point Operation
- the cooperative reception process in the uplink selective combining of uplink signals received by a plurality of radio base stations is performed.
- the plurality of radio base stations include one anchor radio base station and the remaining non-anchor radio base stations.
- the non-anchor radio base station transmits an uplink signal to the anchor radio base station via the backhaul network.
- the anchor radio base station selectively combines an uplink signal transmitted from a radio terminal and an uplink signal received from a non-anchor radio base station.
- the timing at which the radio terminal transmits the uplink signal to the plurality of radio base stations is the same, so for each of the plurality of radio base stations, the radio base station and the radio terminal Can not be synchronized between.
- the mobile communication system includes a plurality of radio base stations that communicate with radio terminals.
- the plurality of radio base stations constitute a radio base station group including one anchor radio base station and a non-anchor radio base station other than the anchor radio base station.
- the non-anchor radio base station notifies the anchor radio base station of a reception quality measured by the non-anchor side measurement unit that measures reception quality of an uplink signal received from the radio terminal, and the non-anchor side measurement unit A notification unit.
- the anchor radio base station sends a control signal for adjusting the timing at which the radio terminal transmits the uplink signal so that the timing at which the uplink signal is received from the radio terminal is adjusted to a desired timing.
- a transmission unit that transmits to a wireless terminal, and a determination unit that determines whether or not to exclude the non-anchor radio base station from the group of radio base stations based on reception quality notified from the non-anchor radio base station Prepare.
- the mobile communication method according to the second feature is used in a mobile communication system including a plurality of radio base stations that communicate with radio terminals.
- the plurality of radio base stations constitute a radio base station group including one anchor radio base station and a non-anchor radio base station other than the anchor radio base station.
- the wireless terminal transmits the uplink signal so that the timing of receiving the uplink signal from the wireless terminal is adjusted to a desired timing from the anchor wireless base station to the wireless terminal.
- Step A for transmitting a control signal for adjusting timing
- Step B for measuring the reception quality of the uplink signal received from the wireless terminal in the non-anchor radio base station
- Step C for notifying the anchor radio base station of the reception quality measured in Step B, and the anchor radio base station based on the reception quality notified from the non-anchor radio base station.
- a step D for determining whether or not to exclude the anchor radio base station from the group of radio base stations.
- FIG. 1 is a diagram showing a mobile communication system 100 according to the first embodiment.
- FIG. 2 is a diagram illustrating a radio frame according to the first embodiment.
- FIG. 3 is a diagram illustrating radio resources according to the first embodiment.
- FIG. 4 is a diagram illustrating an application case according to the first embodiment.
- FIG. 5 is a diagram illustrating an application case according to the first embodiment.
- FIG. 6 is a diagram illustrating an application case according to the first embodiment.
- FIG. 7 is a block diagram showing an anchor radio base station 310A according to the first embodiment.
- FIG. 8 is a block diagram showing the non-anchor radio base station 310B according to the first embodiment.
- FIG. 9 is a sequence diagram showing an operation (first method) of the mobile communication system 100 according to the first embodiment.
- FIG. 10 is a sequence diagram showing an operation (second method) of the mobile communication system 100 according to the first embodiment.
- FIG. 11 is a diagram illustrating a first threshold setting method according to the first modification.
- FIG. 12 is a diagram illustrating a first threshold setting method according to the first modification.
- the mobile communication system includes a plurality of radio base stations that communicate with radio terminals.
- the plurality of radio base stations constitute a radio base station group including one anchor radio base station and a non-anchor radio base station other than the anchor radio base station.
- the non-anchor radio base station includes a non-anchor side measurement unit that measures reception quality of the uplink signal received from the radio terminal, and a reception quality measured by the non-anchor side measurement unit to the anchor radio base station.
- the anchor radio base station transmits a control signal for adjusting the timing at which the radio terminal transmits the uplink signal so that the timing at which the radio signal is received from the radio terminal is adjusted to a desired timing.
- the timing for receiving the uplink signal from the radio terminal is adjusted to a timing desired for the anchor radio base station, and then based on the reception quality notified from the non-anchor radio base station, the non-anchor radio base station Is determined to be excluded from the radio base station group. Therefore, radio base stations (non-anchor radio base stations) that do not contribute to the cooperative reception process in the uplink can be appropriately excluded from the radio base station group. Furthermore, since it is not necessary to transmit an uplink signal via a backhaul network from a radio base station (non-anchor radio base station) that does not contribute to cooperative reception processing in the uplink to the anchor radio base station, Wasteful consumption of hall network resources is suppressed.
- FIG. 1 is a diagram showing a mobile communication system 100 according to the first embodiment.
- the mobile communication system 100 includes a radio terminal 10 (hereinafter referred to as UE 10) and a core network 50.
- the mobile communication system 100 includes a first communication system and a second communication system.
- the first communication system is a communication system that supports, for example, LTE (Long Term Evolution).
- the first communication system includes, for example, a base station 110A (hereinafter, MeNB 110A), a home base station 110B (hereinafter, HeNB 110B), a home base station gateway 120B (hereinafter, HeNB-GW 120B), and an MME 130.
- MeNB 110A a base station 110A
- HeNB 110B home base station 110B
- HeNB-GW 120B home base station gateway 120B
- MME 130 Mobility Management Entity
- a radio access network (E-UTRAN; Evolved Universal Terrestrial Radio Access Network) corresponding to the first communication system is configured by MeNB 110A, HeNB 110B, and HeNB-GW 120B.
- the second communication system is a communication system compatible with, for example, UMTS (Universal Mobile Telecommunication System).
- the second communication system includes a base station 210A (hereinafter referred to as MNB 210A), a home base station 210B (hereinafter referred to as HNB 210B), an RNC 220A, a home base station gateway 220B (hereinafter referred to as HNB-GW 220B), and an SGSN 230.
- a radio access network (UTRAN: Universal Terrestrial Radio Access Network) corresponding to the second communication system is configured by MNB 210A, HNB 210B, RNC 220A, and HNB-GW 220B.
- the UE 10 is a device (User Equipment) configured to communicate with the second communication system or the first communication system.
- the UE 10 has a function of performing wireless communication with the MeNB 110A and the HeNB 110B.
- the UE 10 has a function of performing wireless communication with the MNB 210A and the HNB 210B.
- the MeNB 110A is a device (evolved NodeB) that manages the general cell 111A and performs radio communication with the UE 10 existing in the general cell 111A.
- the HeNB 110B is a device (Home evolved NodeB) that manages the specific cell 111B and performs radio communication with the UE 10 existing in the specific cell 111B.
- the HeNB-GW 120B is an apparatus (Home evolved NodeB Gateway) that is connected to the HeNB 110B and manages the HeNB 110B.
- the MME 130 is an apparatus (Mobility Management Entity) that manages the mobility of the UE 10 that is connected to the MeNB 110A and has established a wireless connection with the MeNB 110A. Further, the MME 130 is an apparatus that manages the mobility of the UE 10 that is connected to the HeNB 110B via the HeNB-GW 120B and has established a radio connection with the HeNB 110B.
- MME 130 Mobility Management Entity
- the MNB 210A is a device (NodeB) that manages the general cell 211A and performs radio communication with the UE 10 existing in the general cell 211A.
- the HNB 210B is a device (Home NodeB) that manages the specific cell 211B and performs radio communication with the UE 10 existing in the specific cell 211B.
- the RNC 220A is an apparatus (Radio Network Controller) that is connected to the MNB 210A and sets up a radio connection (RRC Connection) with the UE 10 existing in the general cell 211A.
- RRC Connection Radio Connection
- the HNB-GW 220B is a device (Home NodeB Gateway) that is connected to the HNB 210B and sets up a radio connection (RRC Connection) with the UE 10 existing in the specific cell 211B.
- RRC Connection Radio Connection
- SGSN 230 is a device (Serving GPRS Support Node) that performs packet switching in the packet switching domain.
- the SGSN 230 is provided in the core network 50.
- an apparatus MSC: Mobile Switching Center
- MSC Mobile Switching Center
- the general cell and the specific cell should be understood as a function of performing radio communication with the UE 10.
- the general cell and the specific cell are also used as terms indicating a cell coverage area.
- cells such as general cells and specific cells are identified by the frequency, spreading code, time slot, or the like used in the cells.
- the coverage area of general cells is wider than the coverage area of specific cells.
- the general cell is, for example, a macro cell provided by a telecommunications carrier.
- the specific cell is, for example, a femto cell or a home cell provided by a third party other than the communication carrier.
- the specific cell may be a CSG (Closed Subscriber Group) cell or a pico cell provided by a communication carrier.
- the first communication system will be mainly described. However, the following description may be applied to the second communication system.
- the OFDMA Orthogonal Frequency Division Multiple Access
- SC-FDMA Single-Carrier Frequency Multiplex
- a method is used.
- an uplink control channel (PUCCH: Physical Uplink Channel) and an uplink shared channel (PUSCH: Physical Uplink Channel) as uplink channels.
- PUSCH Physical Uplink Channel
- a downlink channel there are a downlink control channel (PDCCH; Physical Downlink Control Channel), a downlink shared channel (PDSCH; Physical Downlink Shared Channel), and the like.
- the uplink control channel is a channel that carries a control signal.
- the control signal includes, for example, CQI (Channel Quality Indicator), PMI (Precoding Matrix Indicator), RI (Rank Indicator), SR (Scheduling Request), ACK / NACK, and the like.
- CQI is a signal notifying the recommended modulation method and coding rate to be used for downlink transmission.
- PMI is a signal indicating a precoder matrix that is preferably used for downlink transmission.
- the RI is a signal indicating the number of layers (number of streams) to be used for downlink transmission.
- SR is a signal requesting allocation of uplink radio resources (resource blocks to be described later).
- ACK / NACK is a signal indicating whether or not a signal transmitted via a downlink channel (for example, PDSCH) has been received.
- the uplink shared channel is a channel that carries a control signal (including the control signal described above) and / or a data signal.
- the uplink radio resource may be allocated only to the data signal, or may be allocated so that the data signal and the control signal are multiplexed.
- the downlink control channel is a channel that carries a control signal.
- the control signals are, for example, Uplink SI (Scheduling Information), Downlink SI (Scheduling Information), and TPC bits.
- Uplink SI is a signal indicating uplink radio resource allocation.
- Downlink SI is a signal indicating downlink radio resource allocation.
- the TPC bit is a signal for instructing increase / decrease in power of a signal transmitted via an uplink channel.
- the downlink shared channel is a channel that carries control signals and / or data signals.
- the downlink radio resource may be allocated only to the data signal, or may be allocated so that the data signal and the control signal are multiplexed.
- TA Triming Advance
- TA is transmission timing correction information between UE10 and MeNB110A, and is measured by MeNB110A based on the uplink signal transmitted from UE10.
- the TA is an example of a control signal for adjusting the timing at which the UE 10 transmits an uplink signal so that the timing at which the uplink signal is received from the UE 10 is adjusted to a desired timing.
- ACK / NACK can be cited as a control signal transmitted via a channel other than the downlink control channel (PDCCH) and the downlink shared channel (PDSCH).
- ACK / NACK is a signal indicating whether or not a signal transmitted via an uplink channel (for example, PUSCH) has been received.
- the broadcast information is information such as MIB (Master Information Block) or SIB (System Information Block).
- FIG. 2 is a diagram illustrating a radio frame in the first communication system.
- one radio frame is composed of 10 subframes, and one subframe is composed of two slots.
- the time length of one slot is 0.5 msec
- the time length of one subframe is 1 msec
- the time length of one radio frame is 10 msec.
- One slot is composed of a plurality of OFDM symbols (for example, 6 OFDM symbols or 7 OFDM symbols) in the downlink.
- one slot is configured by a plurality of SC-FDMA symbols (for example, six SC-FDMA symbols or seven SC-FDMA symbols) in the uplink.
- FIG. 3 is a diagram illustrating radio resources in the first communication system.
- radio resources are defined by a frequency axis and a time axis.
- the frequency is composed of a plurality of subcarriers, and a predetermined number of subcarriers (12 subcarriers) are collectively referred to as a resource block (RB).
- RB resource block
- the time has units such as an OFDM symbol (or SC-FDMA symbol), a slot, a subframe, and a radio frame.
- radio resources can be allocated for each resource block. Also, it is possible to divide and allocate radio resources to a plurality of users (for example, user # 1 to user # 5) on the frequency axis and the time axis.
- the radio resource is allocated by the MeNB 110A.
- MeNB110A is allocated to each UE10 based on CQI, PMI, RI, etc.
- FIG. 4 is a diagram for explaining an application scene according to the first embodiment.
- FIG. 4 illustrates a case where one anchor radio base station 310A and a plurality of non-anchor radio base stations 310B are provided as radio base stations.
- the anchor radio base station 310A and the non-anchor radio base station 310B constitute a radio base station group (CoMP set) that cooperatively receives uplink signals transmitted from the UE 10.
- CoMP set radio base station group
- the UE 10 transmits an uplink signal to the anchor radio base station 310A and the non-anchor radio base station 310B.
- the uplink signal transmitted from the UE 10 is encoded.
- the uplink signal transmitted from the UE 10 is transmitted, for example, via the above-described uplink shared channel (PUSCH).
- PUSCH uplink shared channel
- the non-anchor radio base station 310B transmits an uplink signal to the anchor radio base station 310A via the backhaul network.
- the anchor radio base station 310A performs selective combining of the uplink signal transmitted from the UE 10 and the uplink signal received from the non-anchor radio base station 310B.
- the backhaul network may be an X2 interface that directly connects wireless base stations, or may be an S1 interface that connects wireless base stations via an upper node (for example, MME 130).
- the anchor radio base station 310A and the non-anchor radio base station 310B may be radio base stations. That is, in the first embodiment, the anchor radio base station 310A and the non-anchor radio base station 310B are any one of the MeNB 110A, the HeNB 110B, the MNB 210A, and the HNB 210B.
- non-anchor base station 310B As a non-anchor base station 310B, the non-anchor base station 310B 1 and non-anchor base station case 310B 2 is provided, will be described with reference to FIGS.
- the difference between the reception timing of the uplink signal received from the UE 10 and the desired reception timing (ie, TA; Timing Advance) differs for each radio base station as shown in FIG.
- the anchor radio base station 310A controls the control signal (TA for adjusting the timing at which the UE 10 transmits the uplink signal so that the timing at which the uplink signal is received from the UE 10 is adjusted to a desired timing. ) To the UE 10. As a result, as shown in FIG. 6, in the anchor radio base station 310A, the timing of receiving the uplink signal from the UE 10 is aligned with the desired timing.
- non-anchor base station 310B 1 and non-anchor base station 310B 2 as shown in FIG. 6, remains timing of receiving the uplink signal from the UE10 is shifted from a desired timing.
- the non-anchor radio base station 310B 1 and the non-anchor radio base station 310B 2 measure the reception quality of the uplink signal received from the UE 10. Subsequently, non-anchor base station 310B 1 and non-anchor base station 310B 2 notifies the measured reception quality to the anchor radio base station 310A.
- the anchor radio base station 310A is a radio base station configured by radio base stations performing cooperative reception processing in the uplink based on the reception quality notified from the non-anchor radio base station 310B 1 and the non-anchor radio base station 310B 2 It is determined whether or not the non-anchor radio base station 310B is excluded from the group.
- the anchor radio base station 310A excludes from the radio base station group the non-anchor radio base station 310B that measures (notifies) the reception quality whose difference with respect to the best reception quality exceeds the first threshold.
- the best reception quality is the best reception quality among the reception quality measured by the anchor radio base station 310A and the reception quality measured by the non-anchor radio base station 310B.
- the anchor radio base station 310A excludes the non-anchor radio base station 310B that measures (notifies) the reception quality below the second threshold from the radio base station group.
- the anchor radio base station 310A may exclude the non-anchor radio base station 310B that satisfies both the first technique condition and the second technique condition from the radio base station group.
- the anchor radio base station 310A may exclude the non-anchor radio base station 310B that satisfies either the condition of the first technique or the condition of the second technique from the radio base station group.
- the reception quality is, for example, SINR (Signal to Interference Ratio), C / I (Carrier to Interference), reception level, and the like of the uplink signal transmitted from the UE 10.
- the uplink signal whose reception quality is to be measured is, for example, DM RS (Demodulation Reference Signal) or SRS (Sounding Reference Signal).
- DM RS is a reference signal used for demodulation of PUSCH.
- SRS is a reference signal distributed over the entire uplink band.
- FIG. 7 is a block diagram showing an anchor radio base station 310A according to the first embodiment.
- the anchor radio base station 310A includes a reception unit 313A, a transmission unit 314A, an interface 315A, and a control unit 316A.
- the receiving unit 313A receives an uplink signal from the UE 10 connected to the cell managed by the anchor radio base station 310A.
- the reception unit 313A receives an uplink signal via an uplink shared channel (PUSCH).
- PUSCH uplink shared channel
- the transmission unit 314A transmits a downlink signal to the UE 10 connected to the cell managed by the anchor radio base station 310A.
- the transmission unit 314A transmits to the UE 10 a control signal (TA) for adjusting the timing at which the UE 10 transmits the uplink signal so that the timing at which the uplink signal is received from the UE 10 is adjusted to a desired timing.
- TA control signal
- the transmission unit 314A transmits radio resources (scheduling information) allocated by the anchor radio base station 310A to the UE 10 that uses the anchor radio base station 310A as a serving base station (serving cell).
- the interface 315A is an interface that communicates with other radio base stations via a backhaul network.
- the interface 315A is an X2 interface that directly connects wireless base stations.
- the interface 315A is an S1 interface that connects wireless base stations to each other via an upper node (for example, the MME 130).
- the interface 315A indicates the reception quality measured by the non-anchor radio base station 310B (reception quality of the uplink signal received by the non-anchor radio base station 310B from the UE 10) via the backhaul network. Obtained from the non-anchor radio base station 310B.
- the interface 315A receives an uplink signal (PUSCH) received by the non-anchor radio base station 310B from the non-anchor radio base station 310B via the backhaul network.
- PUSCH uplink signal
- the control unit 316A controls the operation of the anchor radio base station 310A. For example, the control unit 316A performs selective combining of an uplink signal (PUSCH) received from the UE 10 and an uplink signal (PUSCH) received from the non-anchor radio base station 310B.
- PUSCH uplink signal
- PUSCH uplink signal
- control unit 316A performs non-anchor radio transmission from a radio base station group configured by radio base stations that perform cooperative reception processing in the uplink based on the reception quality notified from the non-anchor radio base station 310B. It is determined whether or not to exclude the base station 310B.
- the control unit 316A excludes the non-anchor radio base station 310B that measures (notifies) the reception quality whose difference with respect to the best reception quality exceeds the first threshold from the radio base station group.
- the control unit 316A configures an anchor side measurement unit that measures reception quality of the uplink signal received from the UE 10.
- the best reception quality is the best reception quality among the reception quality measured by the anchor radio base station 310A and the reception quality measured by the non-anchor radio base station 310B.
- control unit 316A excludes the non-anchor radio base station 310B that measures (notifies) the reception quality below the second threshold from the radio base station group.
- the reception quality is, for example, SINR (Signal to Interference Ratio), C / I (Carrier to Interference), reception level, and the like of the uplink signal transmitted from the UE 10.
- the uplink signal whose reception quality is to be measured is, for example, DM RS (Demodulation Reference Signal) or SRS (Sounding Reference Signal).
- DM RS is a reference signal used for demodulation of PUSCH.
- SRS is a reference signal distributed over the entire uplink band.
- FIG. 8 is a block diagram showing the non-anchor radio base station 310B according to the first embodiment.
- the non-anchor radio base station 310B includes a reception unit 313B, a transmission unit 314B, an interface 315B, and a control unit 316B.
- the receiving unit 313B receives an uplink signal from the UE 10 connected to a cell managed by the non-anchor radio base station 310B.
- the reception unit 313B receives an uplink signal via an uplink shared channel (PUSCH).
- PUSCH uplink shared channel
- the transmission unit 314B transmits a downlink signal to the UE 10 connected to the cell managed by the non-anchor radio base station 310B.
- the transmission unit 314B transmits radio resources (scheduling information) allocated by the non-anchor radio base station 310B to the UE 10 that uses the non-anchor radio base station 310B as a serving base station (serving cell).
- the interface 315B is an interface that communicates with other radio base stations via the backhaul network.
- the interface 315B is an X2 interface that directly connects wireless base stations.
- the interface 315B is an S1 interface that connects wireless base stations via an upper node (for example, the MME 130).
- the interface 315B anchors the reception quality measured by the non-anchor radio base station 310B via the backhaul network (the reception quality of the uplink signal received by the non-anchor radio base station 310B from the UE 10). Notify the radio base station 310A.
- the interface 315B transmits an uplink signal (PUSCH) received by the non-anchor radio base station 310B to the anchor radio base station 310A via the backhaul network.
- PUSCH uplink signal
- the control unit 316B controls the operation of the non-anchor radio base station 310B.
- the control part 316B comprises the non-anchor side measurement part which measures the reception quality of the said uplink signal received from UE10.
- the reception quality is, for example, SINR (Signal to Interference Ratio), C / I (Carrier to Interference), reception level, and the like of the uplink signal transmitted from the UE 10.
- the uplink signal whose reception quality is to be measured is, for example, DM RS (Demodulation Reference Signal) or SRS (Sounding Reference Signal).
- DM RS is a reference signal used for demodulation of PUSCH.
- SRS is a reference signal distributed over the entire uplink band.
- FIGS. 9 and 10 are sequence diagrams showing operations of the mobile communication system 100 according to the first embodiment.
- the anchor radio base station 310A adjusts the timing at which the UE 10 transmits the uplink signal so that the timing at which the uplink signal is received from the UE 10 is adjusted to a desired timing.
- the control signal (TA) is transmitted to the UE 10.
- step 12 the UE 10 adjusts the transmission timing of the uplink signal based on the control signal (TA) received from the anchor radio base station 310A.
- TA control signal
- Step 13 the UE 10 transmits an uplink signal (PUSCH) at the timing adjusted in Step 12.
- the anchor radio base station 310A and the non-anchor radio base station 310B perform cooperative reception processing in the uplink.
- step 14A the anchor radio base station 310A measures reception quality of an uplink signal (for example, “DM RS” or “SRS”) received from the UE 10.
- step 14B the non-anchor radio base station 310B measures reception quality of an uplink signal (for example, “DM RS” or “SRS”) received from the UE 10.
- the non-anchor radio base station 310B receives the reception quality measured by the non-anchor radio base station 310B via the backhaul network (the reception quality of the uplink signal that the non-anchor radio base station 310B receives from the UE 10). To the anchor radio base station 310A.
- the anchor radio base station 310A determines whether or not the difference between the best reception quality and the reception quality notified from the non-anchor radio base station 310B is larger than the first threshold value.
- the best reception quality is the best reception quality among the reception quality measured by the anchor radio base station 310A and the reception quality measured by the non-anchor radio base station 310B.
- the anchor radio base station 310A proceeds to the process of step 17. If the determination result is “NO”, the anchor radio base station 310A ends a series of processing.
- step 17 the anchor radio base station 310 ⁇ / b> A notifies the non-anchor radio base station 310 ⁇ / b> B that measures (notifies) the reception quality whose difference with respect to the best reception quality exceeds the first threshold to be excluded from the radio base station group. To do.
- step 14A is omitted in the flow shown in FIG.
- step 16X is performed.
- Step 16X the anchor radio base station 310A determines whether or not the reception quality notified from the non-anchor radio base station 310B is lower than the second threshold value.
- step 17 the anchor radio base station 310A notifies the non-anchor radio base station 310B that measures (notifies) the reception quality below the second threshold to be excluded from the radio base station group. If the determination result is “NO”, the anchor radio base station 310A ends a series of processing.
- the anchor radio base station 310A determines whether or not the reception quality notified from the non-anchor radio base station 310B is lower than the second threshold.
- the second method is not limited to this.
- the non-anchor radio base station 310B may determine whether or not the reception quality of the uplink signal received by the non-anchor radio base station 310B from the UE 10 is below a second threshold value. If the reception quality is below the second threshold, the non-anchor radio base station 310B notifies the anchor radio base station 310A that the reception quality is below the second threshold.
- the anchor radio base station 310A may exclude the non-anchor radio base station 310B that satisfies both the condition of the first technique and the condition of the second technique from the radio base station group.
- the anchor radio base station 310A may exclude the non-anchor radio base station 310B that satisfies either the condition of the first technique or the condition of the second technique from the radio base station group.
- the timing of receiving an uplink signal from the UE 10 is adjusted to a timing desired by the anchor radio base station 310A, and then based on the reception quality notified from the non-anchor radio base station 310B, It is determined whether or not to exclude the radio base station 310B from the radio base station group. Therefore, radio base stations (non-anchor radio base stations 310B) that do not contribute to cooperative reception processing in the uplink can be appropriately excluded from the radio base station group. Furthermore, there is no need to transmit an uplink signal via a backhaul network from a radio base station (non-anchor radio base station 310B) that does not contribute to uplink cooperative reception processing to the anchor radio base station 310A. , Wasteful consumption of backhaul network resources is suppressed.
- the first threshold is variable. Specifically, the first method and the second method will be described as a method for setting the first threshold.
- the first threshold is determined according to the best reception quality. Specifically, a smaller value is adopted as the first threshold value as the best reception quality is better. That is, when the reception quality of the uplink signal (PUSCH) is good, a small value is adopted as the first threshold value.
- PUSCH uplink signal
- the first threshold value when the best reception quality (SINR) is 10 dB or more, 0 dB is adopted as the first threshold value. That is, the fact that the first threshold is 0 dB means that cooperative reception processing in the uplink is not performed.
- the best reception quality (SINR) when the best reception quality (SINR) is less than 0 dB, 10 dB is adopted as the first threshold value. That is, the first threshold value is determined so that many non-anchor radio base stations 310B are included in the radio base station group.
- the first threshold is determined according to the modulation scheme of the uplink signal (PUSCH). Specifically, a lower value is adopted as the first threshold value as the modulation scheme is lower order. That is, when it is assumed that the reception quality of the uplink signal (PUSCH) is good, a small value is adopted as the first threshold value.
- the modulation method is BPSK
- 5 dB is adopted as the first threshold value.
- 10 dB is adopted as the first threshold value.
- the first threshold value may be determined by a combination of the first method and the second method. In such a case, a smaller value is adopted as the first threshold value as the best reception quality is better and the modulation scheme is lower.
- the anchor radio base station 310A is generally a serving base station (serving cell) for the UE 10 that is a target of the cooperative reception process in the uplink.
- the best reception quality is generally the reception quality measured at the anchor radio base station 310A.
- a program for causing a computer to execute each process performed by the UE 10, the anchor radio base station 310A, and the non-anchor radio base station 310B may be provided.
- the program may be recorded on a computer readable medium. If a computer-readable medium is used, a program can be installed in the computer.
- the computer-readable medium on which the program is recorded may be a non-transitory recording medium.
- the non-transitory recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or a DVD-ROM.
- a chip configured by a memory that stores a program for executing each process performed by the UE 10 and a processor that executes the program stored in the memory may be provided.
- the present invention is not limited to the LTE system, and the present invention may be applied to a system other than the LTE system.
- the mobile communication system and the mobile communication method according to the present invention can appropriately exclude radio base stations that do not contribute to uplink cooperative reception processing from the radio base station group, they are useful in the mobile communication field. It is.
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Abstract
Description
実施形態に係る移動通信システムは、無線端末と通信を行う複数の無線基地局を備える。前記複数の無線基地局は、1つのアンカー無線基地局と前記アンカー無線基地局以外の非アンカー無線基地局とを含む無線基地局群を構成する。前記非アンカー無線基地局は、前記無線端末から受信する前記上りリンク信号の受信品質を測定する非アンカー側測定部と、前記非アンカー側測定部によって測定された受信品質を前記アンカー無線基地局に通知する通知部とを備える。前記アンカー無線基地局は、前記無線端末から上りリンク信号を受信するタイミングを所望のタイミングに調整するように、前記無線端末が前記上りリンク信号を送信するタイミングを調整するための制御信号を前記無線端末に送信する送信部と、前記非アンカー無線基地局から通知された受信品質に基づいて、前記非アンカー無線基地局を前記無線基地局群から除外するか否かを判定する判定部とを備える。
(移動通信システム)
以下において、第1実施形態に係る移動通信システムについて説明する。図1は、第1実施形態に係る移動通信システム100を示す図である。
以下において、第1通信システムにおける無線フレームについて説明する。図2は、第1通信システムにおける無線フレームを示す図である。
以下において、第1通信システムにおける無線リソースについて説明する。図3は、第1通信システムにおける無線リソースを示す図である。
以下において、第1実施形態に係る適用シーンについて説明する。図4は、第1実施形態に係る適用シーンを説明するための図である。図4では、1つのアンカー無線基地局310A及び複数の非アンカー無線基地局310Bが無線基地局として設けられるケースについて例示する。アンカー無線基地局310A及び非アンカー無線基地局310Bは、UE10から送信される上りリンク信号を協調して受信する無線基地局群(CoMPセット)を構成する。
以下において、第1実施形態に係るアンカー無線基地局について説明する。図7は、第1実施形態に係るアンカー無線基地局310Aを示すブロック図である。
以下において、第1実施形態に係る非アンカー無線基地局について説明する。図8は、第1実施形態に係る非アンカー無線基地局310Bを示すブロック図である。
以下において、第1実施形態に係る移動通信システムの動作について説明する。図9及び図10は、第1実施形態に係る移動通信システム100の動作を示すシーケンス図である。
第1実施形態では、UE10から上りリンク信号を受信するタイミングがアンカー無線基地局310Aにとって所望のタイミングに調整された上で、非アンカー無線基地局310Bから通知された受信品質に基づいて、非アンカー無線基地局310Bを無線基地局群から除外するか否かが判定される。従って、上りリンクにおける協調受信処理に寄与しない無線基地局(非アンカー無線基地局310B)を無線基地局群から適切に除外することができる。さらには、上りリンクにおける協調受信処理に寄与しない無線基地局(非アンカー無線基地局310B)からアンカー無線基地局310Aに対して、バックホール・ネットワークを介して上りリンク信号を送信する必要がないため、バックホール・ネットワークのリソースの無駄な消費が抑制される。
以下において、第1実施形態の変更例1について説明する。以下においては、第1実施形態に対する相違点について主として説明する。
本発明は上述した実施形態によって説明したが、この開示の一部をなす論述及び図面は、この発明を限定するものであると理解すべきではない。この開示から当業者には様々な代替実施形態、実施例及び運用技術が明らかとなろう。
Claims (6)
- 無線端末と通信を行う複数の無線基地局を備える移動通信システムであって、
前記複数の無線基地局は、1つのアンカー無線基地局と前記アンカー無線基地局以外の非アンカー無線基地局とを含む無線基地局群を構成しており、
前記非アンカー無線基地局は、
前記無線端末から受信する上りリンク信号の受信品質を測定する非アンカー側測定部と、
前記非アンカー側測定部によって測定された受信品質を前記アンカー無線基地局に通知する通知部とを備え、
前記アンカー無線基地局は、
前記無線端末から前記上りリンク信号を受信するタイミングを所望のタイミングに調整するように、前記無線端末が前記上りリンク信号を送信するタイミングを調整するための制御信号を前記無線端末に送信する送信部と、
前記非アンカー無線基地局から通知された受信品質に基づいて、前記非アンカー無線基地局を前記無線基地局群から除外するか否かを判定する判定部とを備えることを特徴とする移動通信システム。 - 前記アンカー無線基地局は、前記無線端末から受信する前記上りリンク信号の受信品質を測定するアンカー側測定部を備え、
前記判定部は、前記アンカー側測定部によって測定された受信品質及び前記非アンカー側測定部によって測定された受信品質に含まれる最良の受信品質に対する差異が第1閾値を超える受信品質を測定する非アンカー無線基地局を前記無線基地局群から除外すると判定することを特徴とする請求項1に記載の移動通信システム。 - 前記判定部は、前記非アンカー側測定部によって測定された受信品質が第2閾値を下回る受信品質を測定する非アンカー無線基地局を前記無線基地局群から除外すると判定することを特徴とする請求項1に記載の移動通信システム。
- 前記第1閾値は、前記最良の受信品質に応じて定められることを特徴とする請求項2に記載の移動通信システム。
- 前記第1閾値は、前記上りリンク信号の変調方式に応じて定められることを特徴とする請求項2に記載の移動通信システム。
- 無線端末と通信を行う複数の無線基地局を備える移動通信システムで用いる移動通信方法であって、
前記複数の無線基地局は、1つのアンカー無線基地局と前記アンカー無線基地局以外の非アンカー無線基地局とを含む無線基地局群を構成しており、
前記アンカー無線基地局から前記無線端末に対して、前記無線端末から上りリンク信号を受信するタイミングを所望のタイミングに調整するように、前記無線端末が前記上りリンク信号を送信するタイミングを調整するための制御信号を送信するステップAと、
前記非アンカー無線基地局において、前記無線端末から受信する前記上りリンク信号の受信品質を測定するステップBと、
前記非アンカー無線基地局から前記アンカー無線基地局に対して、前記ステップBで測定された受信品質を通知するステップCと、
前記アンカー無線基地局において、前記非アンカー無線基地局から通知された受信品質に基づいて、前記非アンカー無線基地局を前記無線基地局群から除外するか否かを判定するステップDとを備えることを特徴とする移動通信方法。
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