JP6194730B2 - Radio station and transmission power control method - Google Patents

Description

  The present invention relates to a radio station and a transmission power control method.

In a mobile communication system, a base station (eNB: evolved NodeB) forms a cell, which is a connectable area of the base station, via a radio interface between the base station and the mobile station (UE: User Equipment). Communicate with each other.

  FIG. 1 is a diagram illustrating an example of a mobile communication system. In the example of FIG. 1, two base stations each form a cell. In addition, each base station can perform mutual communication with a terminal (mobile station) in each cell.

  In carrier aggregation (CA) in LTE-A (Long Term Evolution-Advanced), a plurality of frequency bands (CC: Component Carrier) are bundled, and a plurality of frequency bands are used at the same time, and transmission / reception is performed. As a result, the number of accommodated users can be increased and the maximum throughput can be increased. CC is classified into PCell (Primary Cell) and SCell (Secondary Cell).

  FIG. 2 is a diagram illustrating an example of carrier aggregation in LTE-A. In the example of FIG. 2, frequency band # 0, frequency band # 1, and frequency band # 2 are shown. Here, it is assumed that frequency band # 0 is PCell and frequency band # 1 is SCell.

FIG. 3 is a diagram illustrating a configuration example of a downlink cell. FIG. 3 shows a first RRH (Remote Radio Head) and a first RRH cell, and a second RRH and a second RRH cell. Here, the second RRH cell is included in the first RRH cell. It is assumed that the first RRH and the second RRH are connected to the same C-BBU (Centalized-Base Band Unit). C-BBU is a radio access network device that performs centralized control of baseband processing. In addition, the terminal exists within the range of the second RRH cell. For example, in the downlink cell, the first RRH uses CC # 0, and the second RRH uses CC # 1. The terminal receives a signal from the first RRH and a signal from the second RRH. Here, the distance between the terminal and the first RRH is longer than the distance between the terminal and the second RRH. Further, for example, the first RRH is a macro cell, and the second RRH is a small cell (pico cell).

  FIG. 4 is a diagram illustrating a configuration example of an uplink cell. In FIG. 4, the positions of the first RRH, the second RRH, and the terminal are the same as those in FIG. It is assumed that the first RRH and the second RRH are connected to the same C-BBU. For example, in the uplink cell, the terminal uses CC # 2. The terminal transmits a signal to the first RRH and the second RRH. The C-BBU obtains a signal from the terminal by selecting or combining the signals received by the first RRH and the second RRH.

There is asymmetric CC allocation in DL / UL (Downlink / Uplink), and C-BBU is the first
When selecting and combining both RRH and second RRH received signals, the terminal transmission power can be expected to be reduced by adjusting the terminal transmission power to the value of the small cell target. That is, as shown in FIG. 4, the terminal can adjust the terminal transmission power to the transmission power targeted for the second RRH cell that is the closest RRH, so that the power consumption of the terminal can be expected to be reduced. Also, in Open Loop TPC (Transmit Power Control), the terminal determines UL transmission power based on the DL path loss value calculated from the DL path loss reference (downlink pilot signal).

JP 2011-101313 A JP2013-42310A International Publication No. 2011-018906 JP 2011-182009 A

TS36.300 V10.6.0 7.5 Carrier Aggregation TS36.213 V10.4.0 5.1 Uplink power control, 5.1.1 Physical uplink shared channel, 5.1.2 Physical uplink control channel, 5.1.3 Sounding Reference Symbol

  FIG. 5 is a diagram illustrating an example when the second RRH transitions from the state of FIG. 3 to the DL transmission stop state. At this time, since the DL path loss reference is not transmitted from the second RRH, it is difficult to switch the UL transmission power to the transmission power targeting the second RRH as described above by the Open Loop TPC.

On the other hand, according to the Closed Loop TPC, the transmission power of the terminal can be switched to the transmission power targeting the second RRH in the DL transmission stopped state. By setting the transmission power targeting the second RRH, the power consumption of the terminal can be suppressed. At this time, the terminal transmits with transmission power targeting the first RRH. After that, based on the SINR (Signal to Interference plus Noise Ratio) measured by the second RRH, the terminal UL
The transmission power is adjusted to the transmission power targeting the second RRH by the Closed Loop TPC. However, the magnitude of the transmission power that can be adjusted at once by the Closed Loop TPC is smaller than the desired change width. For this reason, it takes time to adjust the UL transmission power of the terminal. That is, the power consumption of the terminal increases.

  FIG. 6 is a diagram illustrating an example of adjustment of transmission power of a terminal using Closed Loop TPC. The graph of FIG. 6 shows the time change of the transmission power of the terminal. The horizontal axis of the graph of FIG. 6 is time, and the vertical axis is the transmission power of the terminal. When the transmission power of a terminal is changed by Closed Loop TPC, the terminal is instructed to increase or decrease the transmission power by a TPC command. When adjusting from the transmission power targeted for the first RRH to the transmission power targeted for the second RRH, a value larger than the adjustment width by one TPC command is changed, which takes time.

  It is an object of the technology disclosed herein to provide a wireless device that can adjust the transmission power of a terminal in a short time when the situation of a cell around the terminal changes.

  The disclosed technology employs the following means in order to solve the above-described problems.

That is, the disclosed aspect is:
A wireless station including a control unit, a storage unit, a first transmission / reception unit that performs wireless communication with a terminal, and a second transmission / reception unit that performs wireless communication with the terminal,
The control unit estimates a first path loss between the first transmission / reception unit and the terminal, estimates a second path loss between the second transmission / reception unit and the terminal, and determines the first path loss and the first path loss. 2 pass loss is stored in the memory,
The control unit calculates a correction value of uplink transmission power in the terminal based on a difference between the first path loss and the second path loss stored in the storage unit when transmission of the second transmission / reception unit is stopped. And
The first transmission / reception unit is a radio station that transmits the correction value to the terminal.

  An aspect of the disclosure may be realized by executing a program by an information processing device. That is, the disclosed configuration can be specified as a program for causing the information processing apparatus to execute the processing executed by each unit in the above-described aspect, or a computer-readable recording medium on which the program is recorded. Further, the disclosed configuration may be specified by a method in which the information processing apparatus executes the process executed by each of the above-described units. The configuration of the disclosure may be specified as a system including an information processing apparatus that performs the processing executed by each of the above-described units.

  According to the disclosed technology, it is possible to provide a radio apparatus that can adjust the transmission power of a terminal in a short time when the situation of a cell around the terminal changes.

FIG. 1 is a diagram illustrating an example of a mobile communication system. FIG. 2 is a diagram illustrating an example of carrier aggregation in LTE-A. FIG. 3 is a diagram illustrating a configuration example of a downlink cell. FIG. 4 is a diagram illustrating a configuration example of an uplink cell. FIG. 5 is a diagram illustrating an example when the second RRH transitions from the state of FIG. 3 to the DL transmission stop state. FIG. 6 is a diagram illustrating an example of adjustment of transmission power of a terminal using Closed Loop TPC. FIG. 7 is a diagram illustrating a configuration example of the mobile communication system according to the present embodiment. FIG. 8 is a diagram illustrating a configuration example of C-BBU, first RRH, and second RRH. FIG. 9 is a diagram illustrating a hardware configuration example of the terminal. FIG. 10 is a diagram showing an example of an operation sequence in the mobile communication system of the present embodiment. FIG. 11 is a diagram illustrating an example of an operation flow of the C-BBU of the present embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. The configuration of the embodiment is an exemplification, and the disclosed configuration is not limited to the specific configuration of the disclosed embodiment. In implementing the disclosed configuration, a specific configuration according to the embodiment may be appropriately employed.

Embodiment
(Configuration example)
FIG. 7 is a diagram illustrating a configuration example of the mobile communication system according to the present embodiment. The mobile communication system 10 in FIG. 7 includes a C-BBU 100, a first RRH 200, a second RRH 300, and a terminal 400. The C-BBU 100 is connected to the first RRH 200 and the second RRH 300. Terminal 400 is present in the cell of first RRH 200 and in the cell of second RRH 300. The mobile communication system 10 may include other RRHs. The first RRH 200 cell and the second RRH 300 cell at least partially overlap. The mobile communication system 10 may include a plurality of terminals. The C-BBU 100 and the first RRH 200 are connected to each other by, for example, an optical transmission line. The C-BBU 100 and the second RRH 300 are connected to each other by an optical transmission line, for example. Here, for example, the first RRH 200 is a macro cell, and the second RRH 300 is a small cell (pico cell). The C-BBU 100, the first RRH 200, and the second RRH 300 can operate as a radio station (radio base station) as a unit. Moreover, C-BBU100 and 1st RRH200 can operate | move as a radio station (radio base station) integrally.

  FIG. 8 is a diagram illustrating a configuration example of C-BBU, first RRH, and second RRH. The C-BBU 100 includes a bus 102, a host processing processor 110, a baseband processing processor 120, a baseband processing circuit 130, and an NW (Network) side I / F (Interface) 140. The host processing processor 110 includes an uplink target power control unit 112. The baseband processing processor 120 includes a scheduler unit 122. The baseband processing circuit 130 includes a downlink transmission unit 132 and an uplink reception unit 134. The first RRH 200 includes a radio processing circuit 210 and an antenna 220. The second RRH 300 includes a radio processing circuit 310 and an antenna 320.

  The C-BBU 100 is connected to a host device directly or via a network. The C-BBU 100 is connected to the terminal 400 via the first RRH 200 and the second RRH 300.

  The upper processor 110, the baseband processor 120, the baseband processor 130, the NW-side I / F 140, and the storage unit 150 of the C-BBU 100 are connected to each other via a bus.

  The upper processing processor 110 performs upper processing such as layer 2 processing, radio resource management, inter-base station signal transmission / reception processing, and signal transmission / reception with a network side device.

The uplink target power control unit 112 estimates the path loss between the first RRH 200 and the terminal 400 and the path loss between the second RRH 300 and the terminal 400 based on the downlink pilot signal reception power. The uplink target power control unit 112 stores the estimated path loss in the storage unit 150. When the uplink target power control unit 112 instructs the second RRH 300 to stop transmission, the uplink target power control unit 112 calculates the uplink transmission power correction values ( _{PO_UE_PUSCH, c} and _{PO_UE_PUCCH} ).

  The baseband processing processor 120 performs control management of layer 1 and layer 2.

  The scheduler unit 122 allocates frequency and time radio resources to terminals and the like. The scheduler unit 122 controls synchronization between the first RRH 200 and the terminal 400, synchronization between the second RRH 300 and the terminal 400, and the like.

The host processing processor 110 and the baseband processing processor 120 are realized by, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor). The upper processing processor 110 and the baseband processing processor 120 may be realized by an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like. The upper processing processor 110 and the baseband processing processor 120 may be integrated.

The baseband processing circuit 130 performs layer 1 processing. For example, it is realized by LSI (Large Scale Integration) or the like. The downlink transmission unit 132 transmits a signal subjected to baseband processing such as modulation and encoding to the first RRH 200 or the second RRH 300.

  The uplink transmission unit 134 receives a signal from the terminal 400 via the first RRH 200 and the second RRH 300, and performs baseband processing such as decoding and demodulation. Uplink transmission section 134 obtains a signal from terminal 400 by selecting or combining signals received by first RRH 200 and second RRH 300.

  The host processor 110, the baseband processor 120, and the baseband processing circuit 130 may be integrated. The host processing processor 110, the baseband processing processor 120, and the baseband processing circuit 130 are examples of a control unit.

  The NW side I / F 140 relays communication between the host device and the C-BBU 100.

  The storage unit 150 stores data and the like used by the host processor 110, the baseband processor 120, and the like. The storage unit 150 is, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory). The storage unit 150 is, for example, an EPROM (Erasable Programmable ROM) or a hard disk drive (HDD, Hard Disk Drive). The storage unit 150 may be a removable medium, that is, a portable recording medium. The removable media is, for example, a USB (Universal Serial Bus) memory or a disc recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc).

  The radio processing circuit 210 of the first RRH 200 performs mutual conversion between a baseband frequency and a radio frequency on a signal transmitted from the antenna 220 or a signal received by the antenna 220. The wireless processing circuit 210 is realized by an LSI or the like, for example. The antenna 220 is connected to the wireless processing circuit 210 and transmits / receives a wireless signal to / from the terminal 400 or the like. The first RRH 200 is an example of a first transmission / reception unit.

  The radio processing circuit 310 of the second RRH 300 performs mutual conversion between a baseband frequency and a radio frequency on a signal transmitted from the antenna 320 or a signal received by the antenna 320. The radio processing circuit 310 can stop downlink transmission according to an instruction from the C-BBU 100. The wireless processing circuit 310 can receive a signal from the terminal 400 or the like even when the downlink transmission is stopped. The wireless processing circuit 310 is realized by an LSI or the like, for example. The antenna 320 is connected to the wireless processing circuit 310 and transmits / receives a wireless signal to / from the terminal 400 or the like. The second RRH 300 is an example of a second transmission / reception unit.

  When the terminal 400 receives the downlink pilot signal from the first RRH 200 or the second RRH 300, the terminal 400 measures the reception power of the downlink pilot signal. Terminal 400 transmits the received power of the received downlink pilot signal to first RRH 200. Received power is an example of received quality.

  Terminal 400 calculates uplink transmission power based on information from C-BBU 100 and the like. The uplink transmission power is calculated as follows.

Here, P _{PUSCH, C} (i) is a transmission power setting value of PUSCH (Physical Uplink Shared Channel). PUSCH is a shared data channel for transmitting uplink data. In PUSCH, PUCCH is used to transmit ACK / NACK for PDSCH, downlink reception quality, and scheduling allocation request signal.

C represents a serving cell number, i represents a subframe number, and j represents a PUSCH type. P _{CMAX, c} (i) is the maximum transmission power, and M _{PUSCH, c} (i) is the number of RBs (Resource Blocks). The number of RBs corresponds to the allocated frequency bandwidth. P _{O_NORMINAL_PUSCH, c} (j) is a target power setting value for each cell, and P _{O_UE_PUSCH, c} (j) is a target power setting value for each UE (terminal). alpha _c (j) is DL path loss compensation factor, PL _C is DL path loss estimate value estimated by the terminal. Δ _{TF, c} (i) is an MCS-dependent offset value, and f _c (i) is an offset value by Closed Loop TPC. M _{PUSCH, c} (i), P _{O_NORMINAL_PUSCH, c} (j), P _{O_UE_PUSCH, c} (j), α _c (j), Δ _{TF, c} (i) are notified from the C-BBU 100 in advance. f _c (i) is adjusted by a TPC command from the C-BBU 100.

P _PUCCH (i) is a transmission power setting value of PUCCH (Physical Uplink Control Channel).

Further, g (i) is an offset value by Closed Loop TPC, and h (n _CQI , n _HARQ , n _SR ) is an offset value by the number of information bits of PUCCH. Δ _{F_PUCCH} (F
) Is an offset value by PUCCH format, and Δ _TxD (F ′) is an offset value by terminal transmission antenna setting. F and F ′ are index values to the PUCCH format.

The terminal 400 receives the _{P O_UE_PUSCH, c} and _{P O_UE_PUCCH} from the 1RRH200. P _{O_UE_PUSCH, c} and P _{O_UE_PUCCH} correspond to correction values for uplink transmission power. Terminal 400 calculates uplink transmission power based on P _{O_UE_PUSCH, c} and P _{O_UE_PUCCH} , and changes the uplink transmission power to the calculated value.

FIG. 9 is a diagram illustrating a hardware configuration example of the terminal. 9 includes a processor 410, a storage unit 420, a baseband processing circuit 430, a wireless processing circuit 440, and an antenna 4.
50 and bus 460. The processor 410 calculates transmission power. The storage unit 450 stores data and the like used for transmission power calculation. The storage unit 450 is, for example, a RAM, a ROM, an HDD, or the like. The antenna 450 is connected to the wireless processing circuit 440. The processor 410, the storage unit 420, and the baseband processing circuit 430 are connected to each other via a bus 460.

  The hardware configurations of the C-BBU 100, the first RRH 200, the second RRH 300, and the terminal 400 are not limited to the examples illustrated in FIGS. 8 and 9, and components may be appropriately omitted, replaced, or added.

  The units of the C-BBU 100, the first RRH 200, the second RRH 300, and the terminal 400 may be realized as hardware components, software components, or a combination thereof.

The hardware component is a hardware circuit, for example, an FPGA (Field Programmable Gate Array), an application specific integrated circuit (ASIC), a gate array, a combination of logic gates, an analog circuit, or the like.

  The software component is a component that realizes predetermined processing as software. The components of software are not a concept that limits the language, development environment, etc. for realizing software.

  A series of processes can be executed by hardware, but can also be executed by software.

(Operation example)
An operation in the mobile communication system of this embodiment will be described.

  FIG. 10 is a diagram showing an example of an operation sequence in the mobile communication system of the present embodiment. Here, it is assumed that terminal 400 exists in the cell of first RRH 200 and the cell of second RRH 300. Here, it is assumed that terminal 400 has a lower transmission power for communicating with second RRH 300 than a transmission power for communicating with first RRH 200 due to the presence of second RRH 300 in the vicinity.

  C-BBU 100 sets the transmission power of the downlink pilot signal of first RRH 200. The C-BBU 100 generates a downlink pilot signal transmitted by the first RRH 200 and transmits the downlink pilot signal to the first RRH 200 (SQ1001). Further, the C-BBU 100 notifies the first RRH 200 of the transmission power of the set downlink pilot signal.

  When the first RRH 200 receives the downlink pilot signal and the transmission power from the C-BBU 100, the first RRH 200 transmits the downlink pilot signal to the terminal 400 with the notified transmission power (SQ1002).

  Moreover, C-BBU100 sets the transmission power of the downlink pilot signal of 2nd RRH300. The C-BBU 100 generates a downlink pilot signal transmitted by the second RRH 300 and transmits the downlink pilot signal to the second RRH 300 (SQ1003). Further, the C-BBU 100 notifies the second RRH 200 of the transmission power of the set downlink pilot signal.

When the second RRH 300 receives the downlink pilot signal and the transmission power from the C-BBU 100, the second RRH 300 transmits the downlink pilot signal to the terminal 400 with the notified transmission power (
SQ1004).

  Terminal 400 measures the received power of each received downlink pilot signal (SQ1005).

  Terminal 400 notifies first RRH 200 of the measured received power of the downlink pilot signal (SQ1006).

  When receiving the reception power of the downlink pilot signal from terminal 400, first RRH 200 transmits the reception power of the received downlink pilot signal to C-BBU 100 (SQ1007). The C-BBU 100 receives the reception power of the downlink pilot signal from the first RRH 200.

  The C-BBU 100 estimates the path loss based on the received power of the downlink pilot signal and the transmission power of the downlink pilot signal. The C-BBU 100 estimates and holds path loss between the first RRH 200 and the terminal 400, and between the second RRH 300 and the terminal 400.

  The C-BBU 100 determines to stop the downlink transmission of the second RRH 300 based on a predetermined condition or the like, and instructs the second RRH 300 to stop the downlink transmission (SQ1009).

  When the second RRH 300 is instructed to stop downlink transmission from the C-BBU 100, the second RRH 300 stops downlink transmission (SQ1010). That is, the second RRH 300 stops transmission of radio waves (signals) from the antenna 320. Even if the transmission of the second RRH 300 is stopped, the second RRH 300 continues to receive signals at the antenna 320.

In addition, when the C-BBU 100 instructs the second RRH 300 to stop downlink transmission, the C-BBU 100 calculates uplink transmission power correction values ( _{PO_UE_PUSCH, c} and _{PO_UE_PUCCH} ) to be notified to the terminal 400 (SQ1011). Here, the C-BBU 100 calculates a correction value for uplink transmission power so that the terminal 400 has transmission power targeted for the second RRH 300. The uplink transmission power correction value is calculated as follows using the estimated path loss.

_{Here, P O_UE_PUSCH_before, c} and _{P O_UE_PUCCH_before,} respectively, uncorrected _{P O_UE_PUSCH,} a _c and _{P O_UE_PUCCH.} PL _m2ue is a DL path loss estimated value between the first RRH 200 and the terminal 400. PL _p2ue is an estimated DL path loss between the second RRH 300 and the terminal 400. Here, c (serving cell) is the first RRH 200.

P _{O_UE_PUSCH_after, c} and P _{O_UE_PUCCH_after} calculated here are respectively the uplink power correction values (P _{O_UE_PUSCH, c} and P _{O_
UE_PUCCH} ) is transmitted to the first RRH 200 (SQ1012). The uplink power correction value is transmitted by, for example, an RRC (Radio Resource Control) message.

The first RRH 200 transmits the _{PO_UE_PUSCH, c} and _{PO_UE_PUCCH} received from the C-BBU ₁₀₀ to the terminal 400 (SQ1013). Terminal 400 receives the _{P O_UE_PUSCH, c} and _{P O_UE_PUCCH} from the 1RRH200.

Terminal 400, _{P O_UE_PUSCH} received from the _1RRH200, based on _c and _{P O_UE_PUCCH,} calculates the uplink transmission power (SQ1014). The uplink transmission power (P _{PUSCH, C} (i), P _PUCCH (i)) in terminal 400 is calculated as described above. The terminal 400 transmits data or the like with each calculated uplink transmission power. The transmission power of the terminal 400 is transmission power targeting the second RRH 300.

  FIG. 11 is a diagram illustrating an example of an operation flow of the C-BBU of the present embodiment. FIG. 11 shows an example of the operation flow of the C-BBU 100 in the operation sequence of FIG.

  In step S101, the uplink target power control unit 112 of the C-BBU 100 notifies the scheduler unit 122 of the downlink pilot signal transmission power setting value of the first RRH 200. The downlink pilot signal transmission power setting value is stored in the storage unit 150, for example. The scheduler unit 122 notifies the downlink pilot signal transmission instruction of the first RRH 200 to the downlink transmission unit 132 of the baseband processing circuit 130. The downlink pilot signal transmission instruction includes a pilot signal and pilot signal transmission power. The downlink transmission unit 132 of the baseband processing circuit 130 transmits a downlink pilot signal to the first RRH 200. Also, the uplink target power control unit 112 notifies the scheduler unit 122 of the downlink pilot signal transmission power setting value of the second RRH 300. The scheduler unit 122 notifies the downlink pilot signal transmission instruction of the second RRH 300 to the downlink transmission unit 132 of the baseband processing circuit 130. The downlink transmission unit 132 of the baseband processing circuit 130 transmits a downlink pilot signal to the second RRH 300.

  In step S102, the uplink reception unit 134 of the baseband processing circuit 130 receives the downlink pilot signal reception power from the terminal 400 via the first RRH 200. The downlink pilot signal reception power includes the reception power of the pilot signal from the first RRH 200 to the terminal 400 and the reception power of the pilot signal from the second RRH 300 to the terminal 400. The downlink pilot signal reception power is notified to the uplink target power control unit 112.

In step S103, the uplink target power control unit 112 estimates the path loss based on the received power of the downlink pilot signal and the transmission power of the downlink pilot signal. Uplink target power controller 112, path loss between the first 1RRH200 and the terminal _{400 (PL} m2ue), and estimates the path loss _{(PL p2ue)} between the first 2RRH300 and terminal 400. The uplink target power control unit 112 stores the estimated path loss in the storage unit 150.

  In step S104, the uplink target power control unit 112 instructs the second RRH 300 to stop downlink transmission. The downlink transmission stop instruction is performed based on a predetermined condition. The downlink transmission stop instruction is performed, for example, when the number of terminals existing in the second RRH 300 cell decreases.

In step S105, when the uplink target power control unit 112 instructs the second RRH 300 to stop downlink transmission, the uplink target power control unit 112 calculates an uplink transmission power correction value to be notified to the terminal 400. The path loss estimated in step S103 is used for calculating the uplink transmission power correction value. The uplink transmission power correction values are P _{O_UE_PUSCH, c} and P _{O_UE_PUCCH} .

In step S106, the uplink target power control unit 112 instructs the downlink transmission unit 132 of the baseband processing circuit 130 to transmit the calculated uplink transmission power correction value to the terminal 400. The downlink transmission unit 132 transmits the uplink transmission power correction values ( _{PO_UE_PUSCH, c} and _{PO_UE_PUCCH} ) to the first RRH 200 that has not stopped the downlink transmission. First RRH 200 transmits the uplink transmission power correction value toward terminal 400.

  Terminal 400 calculates uplink transmission power based on the uplink transmission power correction value, and changes the uplink transmission power.

The transmission power of SRS (Sounding Reference Signal) can also be corrected in the same manner as the transmission power of PUSCH. SRS is used for reception quality measurement and timing adjustment necessary for applying frequency scheduling.

(Operation and effect of the embodiment)
The C-BBU 100 receives downlink pilot signal reception power from the terminal 400 when the first RRH 200 and the second RRH are performing downlink transmission. Also, the C-BBU 100 estimates path loss between the first RRH 200 and the terminal 400 and between the second RRH and the terminal 400 based on downlink pilot signal reception power and the like. The C-BBU 100 holds the estimated path loss in the storage unit 150. When the second RRH 300 transitions from the downlink transmission state to the downlink transmission stop state, the C-BBU 100 sets the transmission power correction value so that the terminal 400 sets the transmission power targeting the second RRH 300 using the held path loss. calculate. The C-BBU 100 transmits the transmission power correction value to the terminal 400 via the first RRH 300 in the downlink transmission state. Terminal 400 calculates uplink transmission power based on the transmission power correction value from C-BBU 100, and changes the uplink transmission power. The C-BBU 100 can calculate the transmission power correction value after the transmission of the second RRH 300 is stopped by using the path loss calculated before the transmission of the second RRH 300 is stopped. The terminal 400 can control the uplink transmission power to a value targeting the second RRH 300 in a shorter time after the transmission of the second RRH 300 is stopped, compared to the case where it is controlled by the TPC command. Thereby, the transmission power (power consumption) of the terminal is reduced. Moreover, interference with other radio | wireless apparatuses etc. is suppressed by reducing the transmission power of a terminal.

10 Mobile communication system
100 C-BBU
102 bus
110 Host processor
112 Uplink target power control unit
120 Baseband processor
122 Scheduler part
130 Baseband processing circuit
132 Downlink transmission unit
134 Uplink receiver
140 NW side I / F
150 storage unit
200 1st RRH
210 Wireless processing circuit
220 Antenna
300 2nd RRH
310 Wireless processing circuit
320 antenna
400 terminals
410 processor
420 Storage unit
430 Baseband processing circuit
440 Wireless processing circuit
450 antenna

Claims (2)

A wireless station including a control unit, a storage unit, a first transmission / reception unit that performs wireless communication with a terminal, and a second transmission / reception unit that performs wireless communication with the terminal,
The control unit estimates a first path loss between the first transmission / reception unit and the terminal, estimates a second path loss between the second transmission / reception unit and the terminal, and determines the first path loss and the first path loss. 2 pass loss is stored in the memory,
The control unit instructs the second transmission / reception unit to stop transmission when the number of the terminals existing in the cell of the second transmission / reception unit decreases, and the first path loss and the second stored in the storage unit Based on the difference between the path loss and the uplink transmission power correction value in the terminal,
The first transmission / reception unit is a radio station that transmits the correction value to the terminal. In a radio station comprising a first transmission / reception unit that performs radio communication with a terminal and a second transmission / reception unit that performs radio communication with the terminal,
Estimating a first path loss between the first transceiver and the terminal, estimating a second path loss between the second transceiver and the terminal,
When the number of the terminals existing in the cell of the second transceiver unit decreases, the second transceiver unit is instructed to stop transmission , and based on the difference between the first path loss and the second path loss, Calculate the uplink transmission power correction value,
Transmitting the correction value to the terminal;
Transmission power control method.

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