WO2014091527A1

WO2014091527A1 - Wireless communication device, wireless communication system, and wireless communication method

Info

Publication number: WO2014091527A1
Application number: PCT/JP2012/008005
Authority: WO
Inventors: 義博河▲崎▼
Original assignee: 富士通株式会社
Priority date: 2012-12-14
Filing date: 2012-12-14
Publication date: 2014-06-19

Abstract

The purpose of the present invention is to provide: a wireless communication device, which performs a plurality of wireless communications, wherein interference is controlled, allowing communication performance to improve; a wireless communication system, and a wireless communication method. This wireless communication device repeatedly receives a first control signal, which indicates that a transmission power is to be altered or maintained, from another wireless communication device, and determines, on the basis of the first control signal received prior to a first wireless transmission, the transmission power of the first wireless transmission with respect to the other wireless communication device. Furthermore, the wireless communication device is provided with a first wireless communication unit that carries out the first wireless transmission at a second transmission power, which is smaller than the first transmission power based on the aforementioned determination.

Description

Wireless communication apparatus, wireless communication system, and wireless communication method

The present invention relates to a wireless communication device, a wireless communication system, and a wireless communication method.

In recent years, next-generation wireless communication technologies have been discussed in order to further increase the speed and capacity of wireless communication in wireless communication systems such as cellular phone systems (cellular systems). For example, 3GPP (3rd Generation Partnership Project), a standardization organization, proposes a communication standard called LTE (Long Term Evolution) and a communication standard called LTE-A (LTE-Advanced) based on LTE wireless communication technology. Has been.

In such a wireless communication system, for example, a plurality of wireless communications may be simultaneously executed by one wireless terminal. The plurality of wireless communications are, for example, different types of wireless communications, such as LTE communication and wireless LAN (Local Area Network). In this case, for example, a circuit corresponding to each of a plurality of wireless communications is provided in one wireless terminal. Such a situation is called, for example, IDC (In-device coexistence).

A technique for reducing interference with other wireless communications by reducing the transmission power of wireless communications is known.

Japanese Patent Laid-Open No. 2001-308785 Japanese Patent Laid-Open No.8-167872

In the wireless communication system as described above, it is assumed that each wireless communication communicates simultaneously using the same or close frequency band. At this time, in the wireless terminal, if each wireless communication is simultaneously executed by a corresponding circuit, mutual interference may occur in the wireless terminal and communication performance may be deteriorated.

The disclosed technology has been made in view of the above, and is a wireless communication device that performs a plurality of wireless communications, and controls wireless interference in the wireless communication device and improves communication performance. An object is to provide a communication system and a wireless communication method.

In order to solve the above-described problems and achieve the object, the disclosed wireless communication apparatus repeatedly receives a first control signal instructing to change or maintain transmission power from another wireless communication apparatus, and the other wireless communication A wireless communication device that determines a transmission power of a first wireless transmission to a device based on the first control signal received before the first wireless transmission, and a second smaller than the first transmission power based on the determination A first wireless communication unit that performs the first wireless transmission with transmission power is provided.

According to one aspect of the wireless communication device disclosed in the present case, it is possible to control the interference in the wireless terminal and improve the communication performance with a wireless device that performs a plurality of wireless communications.

FIG. 1 is a diagram illustrating an example of frequency band allocation in a wireless communication system. FIGS. 2A and 2B are diagrams illustrating the correspondence between the TPC command value and the change in transmission power in the LTE system. FIG. 3 is a diagram illustrating an example of a processing sequence of transmission power control for PUSCH in a conventional LTE system. FIG. 4 is a diagram illustrating an example of a processing sequence of transmission power control for PUCCH in a conventional LTE system. FIG. 5 is a diagram illustrating an example of a processing sequence of transmission power control for the PUSCH according to the reference technique. FIG. 6 is a diagram illustrating an example of a processing sequence of transmission power control for the PUSCH according to the first embodiment. FIG. 7 is a diagram illustrating an example of a processing sequence of transmission power control for the PUSCH according to the second embodiment. FIG. 8 is a diagram illustrating deterioration in communication characteristics due to deterioration in transmission power. FIG. 9 is a diagram illustrating an example of a processing sequence of transmission power control for the PUSCH according to the third embodiment. FIG. 10 is a diagram for explaining a modification example of the second embodiment. FIG. 11 is a diagram illustrating a configuration of a wireless communication system according to each embodiment. FIG. 12 is a functional block diagram showing the configuration of the radio base station according to each embodiment. FIG. 13 is a functional block diagram showing the configuration of the wireless terminal according to each embodiment. FIG. 14 is a diagram illustrating a hardware configuration of the radio base station according to each embodiment. FIG. 15 is a diagram illustrating a hardware configuration of the wireless terminal according to each embodiment.

Hereinafter, embodiments of a wireless communication device, a wireless communication system, and a wireless communication method disclosed in the present application will be described with reference to the drawings. Note that the wireless communication device, the wireless communication system, and the wireless communication method disclosed in the present application are not limited by the following embodiments.

[Location of problem]
First, before describing each embodiment, the location of problems in the prior art will be described. It should be noted that this problem has been newly found as a result of careful study of the prior art by the inventor and has not been known so far.

As described above, in the present application, it is assumed that a plurality of wireless communications are simultaneously performed in a wireless communication device (for example, a wireless terminal) (for example, a situation like the IDC described above). Hereinafter, as an example, it is assumed that the plurality of wireless communications includes a first wireless communication and a second wireless communication. In the wireless terminal, the first wireless communication is performed using the first antenna, and the second wireless communication is performed using the second antenna. The plurality of wireless communications may be composed of three or more wireless communications.

FIG. 1 shows an example of frequency bands prepared for the first wireless communication and the second wireless communication. In the present application, for convenience, the first wireless communication is wireless communication based on a mobile phone system such as LTE-A (hereinafter referred to as “wireless communication based on LTE-A”). On the other hand, the second wireless communication is a wireless communication method other than a cellular phone system such as LTE-A, for example, wireless communication based on a wireless LAN such as WiFi (registered trademark) or Bluetooth (registered trademark) (hereinafter referred to as “other than LTE-A etc.”). It is referred to as “wireless communication based on the wireless communication method”).

As shown in FIG. 1, the first wireless communication and the second wireless communication are performed using the same or close frequency band. For example, when the frequency band group prepared for the first wireless communication and the frequency band group prepared for the second wireless communication are adjacent to each other, or when the first wireless communication and the second wireless communication are the same frequency band group Is assumed to be shared. For example, ISM (Industry Science Band) (2400-2483.5MHz) is one of the non-licensed bands and is used for Bluetooth and WiFi. At this time, Band 40 (2300-2400MHz) prepared in LTE-A TDD Mode and BandB7 (2500-2570MHz) prepared in LTE A's UL FDD Mode are the frequency bands adjacent to ISM Band. Become. Furthermore, when ISM Band is also used for LTE-A, the same frequency band can be used for LTE-A and Bluetooth or WiFi.

When a frequency band is used as shown in FIG. 1 in a wireless communication apparatus corresponding to IDC, first wireless communication using a first antenna (wireless communication based on LTE-A or the like) and second wireless communication using a second antenna. In a wireless terminal that simultaneously performs (wireless communication based on a wireless communication method other than LTE-A or the like), interference may occur between the first wireless communication and the second wireless communication. Specifically, for example, a transmission signal of the first wireless communication (a transmission signal at the first antenna) interferes with a reception signal of the second wireless communication (a reception signal at the second antenna). Further, the transmission signal of the second wireless communication (transmission signal at the second antenna) interferes with the reception signal of the first wireless communication (the reception signal at the first antenna). That is, in a wireless communication device corresponding to IDC, mutual interference can occur between wireless communication in the device.

It is desirable to perform some kind of interference control in order to remove or reduce such interference with IDC. Various schemes are considered as interference control for IDC related to LTE-A, and these can be used in any combination.

As specific examples of interference control for IDC related to LTE-A, there are mainly four FDM (Frequency Division Multiplexing) method, TDM (Time Division Multiplexing) method, Autonomous Denial (autonomous stop) method, and transmission power reduction method. It is done. Below, these are demonstrated in order.

In the FDM system (sometimes referred to as a network control wireless terminal-assisted FDM system), the frequency band currently used in the first wireless communication (wireless communication based on LTE-A, etc.) is changed to a different frequency band (different frequency band). ). By executing the FDM method, the first wireless communication and the second wireless communication are separated on the frequency axis, so that interference between them can be greatly reduced. However, it can be considered that the FDM system cannot be executed unless there is a handover destination to a different frequency band. In other words, in order to execute the FDM scheme, it is necessary to have a radio base station in a different frequency band that has a relatively large reception power for the radio terminal. Therefore, the FDM method cannot always be executed.

Next, in the TDM system (also referred to as a network control wireless terminal-assisted TDM system), the first wireless communication (wireless communication based on LTE-A or the like) and the second wireless communication (wireless other than LTE-A or the like) Control is performed so that one is not executed simultaneously with the other. By executing the TDM scheme, the first wireless communication and the second wireless communication are separated on the time axis, and thus the interference between them can be greatly reduced. As an example of the TDM system, the first wireless communication performs intermittent communication, and the second wireless communication performs communication during a period in which the first wireless communication pauses communication. However, when the TDM system is adopted, it is difficult to execute unless a certain degree of regularity exists in the first wireless communication or the second wireless communication, for example, intermittent communication. Therefore, the TDM method cannot always be executed.

Furthermore, in the autonomous Denial method, the wireless terminal autonomously transmits the first wireless communication (wireless communication based on LTE-A or the like) or the second wireless communication (wireless communication based on a wireless communication method other than LTE-A or the like). Stop. In the Autonomous Denial system, the wireless terminal does not stop all the first wireless communication for a predetermined period, for example, and adjusts the frequency and level of autonomous stop in advance. By executing the Autonomous Denial method, interference with the second wireless communication does not occur while the transmission of the first wireless communication is stopped. However, the Autonomous Denial method has a problem that communication efficiency is greatly reduced because transmission is stopped.

Finally, the transmission power reduction method will be described. Specifically, for example, by reducing the transmission power of the first wireless communication (wireless communication based on LTE-A or the like) in the wireless terminal, the second wireless communication (wireless communication method other than LTE-A or the like) in the wireless terminal. Interference with a received signal in the wireless communication based on the above can be reduced. According to the transmission power reduction method, the communication efficiency is slightly reduced by reducing the transmission power, but the range of the decrease in communication efficiency is considered to be small compared to the Autonomous Denial method that stops transmission. In addition, the transmission power reduction method cannot be executed unless a certain condition is satisfied as in the FDM method and the TDM method, and thus it can be said that there are few execution restrictions. For these reasons, it is considered that the transmission power reduction method is often a realistic solution as means for realizing interference control.

Hereinafter, interference control based on a transmission power reduction method for IDCs related to the LTE system will be described in detail. First, as preparation for the explanation, uplink transmission power control in an existing LTE system will be described. The situation of IDC is assumed because it is a wireless terminal, and it is necessary to perform transmission power control for uplink (UL: UpLink) transmission, which is transmission from the wireless terminal to the wireless base station. Incidentally, transmission from a radio base station to a radio terminal is called downlink (DL: DownLink) transmission.

The magnitude of uplink transmission power in the LTE system is specified for each uplink signal (channel) to be transmitted. Hereinafter, transmission power control for a physical uplink shared channel PUSCH (PhysicalPhysUplink Shared CHannel) for transmitting an uplink data signal will be described first.

In the LTE system, the PUSCH transmission power P _{PUSCH, c} (i) of the i-th subframe from the wireless terminal to the serving cell (radio base station managing the wireless terminal) c is determined by the following equation (1). .

Here, P _{CMAX, c} (i) corresponds to the maximum power that the wireless terminal can transmit in the i-th subframe for the serving cell c. In normal times other than this maximum transmission power, the transmission power of PUSCH is determined by the following equation (2). For this reason, Equation (2) will be examined hereinafter.

Each parameter constituting the expression (2) will be briefly described. M _{PUSCH, c} (i) is a bandwidth (number of resource blocks) allocated to the PUSCH of the i-th subframe from the serving cell c. P _{O_PUSCH, c} (j) is a value determined based on a parameter included in higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) notified from the serving cell c. Note that j takes a value of 0, 1, or 2. α _c (j) is a parameter included in higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) notified from the serving cell c, and takes a value of 0 to 1. PL _c is a downlink path loss for the serving cell c. PL _c is obtained from the difference between the received power measured at the wireless terminal and the transmission power notified from the wireless base station by broadcast information (SIB2: System Information Block 2). Δ _{TF, c} (i) is the amount of information (data amount, control information amount, etc.) transmitted from the serving cell c to the serving cell c using the PUSCH of the i-th subframe, and higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) is a value determined based on the parameters included. Finally, f _c (i) is a value determined based on a TPC (Transmission Power Control) command notified from lower serving layer control information (DCI: Downlink Control Information) from serving cell c.

The PUSCH transmission power defined by Equation (2) can be briefly described as follows. Each term constituting Equation (2) can be divided into three groups. _Each term in the first group is P _{O_PUSCH, c} (j) and α _c (j) · PL _c , and each term in the second group is ₁₀ log ₁₀ (M _{PUSCH, c} (i)) and Δ _{TF, c} (i), and each term in the third group is f _c (i). Here, each item of the first group is determined by parameters included in higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) and does not depend on the subframe number (not a function of i). It has become. Here, upper layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) is normally received from a wireless base station when a wireless terminal is connected, and then received as long as the wireless terminal is connected to the wireless base station. It is something that does not. Therefore, each term of the first group is usually set as long as the wireless terminal is connected to the wireless base station once it is connected to the wireless base station (when power is turned on or moved between wireless base stations). The value does not change.

Next, each item of the second group includes parameters included in broadcast information (SIB2) and higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) and parameters related to transmission scale for each subframe (bandwidth and transmission information). Quantity). Here, broadcast information (SIB2) and higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) are normally received from the radio base station when the radio terminal is connected, and then connected to the radio base station. As long as it is, it will not receive. Therefore, when the transmission scale for each subframe is constant, the values of the terms in the second group usually do not change while connected to the radio base station.

From the above, after the wireless terminal is connected to the wireless base station, the transmission power of the PUSCH is increased (or decreased) based on the deterioration (or improvement) of the wireless environment due to movement within the area of the wireless base station. Cannot be realized with terms in the first and second groups. In other words, the terms of the first and second groups in Equation (2) described above are for adjusting the transmission power of the PUSCH when the radio environment changes for the radio terminal connected to the radio base station. It can be said that the component of is not contained. The third group fc (i), that is, the TPC command corresponds to the component for adjusting the PUSCH transmission power. In the LTE system, the TPC command is the only means for the radio base station to adjust the PUSCH transmission power of the radio terminal according to changes in the radio environment. The radio base station can transmit a TPC command to the radio terminal for each subframe as necessary. As a result, the radio base station can adjust the transmission power of the PUSCH of the radio terminal for each subframe.

In the following, in order to simplify the explanation, it is assumed that the uplink transmission scale (bandwidth and amount of transmission information) is constant. Under this premise, the PUSCH transmission power of the radio terminal connected to the radio base station changes based only on the TPC command received from the radio base station.

Next, the TPC command of the LTE system will be described. The TPC command is included in DCI (Downlink Control Information) that is downlink control information. DCI is downlink control information in the physical layer (L1: Layer 1). Several formats are defined for DCI, and they are used properly according to the uplink signal (uplink channel) that is the object of transmission power control.

The TPC and DCI will be described by taking as an example the case where the transmission power control target is PUSCH, which is an uplink data channel. The TPC command for PUSCH is stored in one of

DCI formats

0, 3, 3A, or 4, and transmitted from the radio base station to the radio terminal.

DCI formats 0 and 4 are downlink control information used when the radio base station transmits uplink data to the radio terminal. DCI format 0 is used when uplink data is transmitted with a single antenna, and DCI format 4 is used when uplink data is transmitted with a plurality of antennas. In DCI formats 0 and 4, in addition to the TPC command, a parameter indicating radio resource allocation for transmitting uplink data, and a parameter for specifying an encoding method and a modulation method for transmitting uplink data are MCS (Modulation Coding Scheme). Since DCI formats 0 and 4 are transmitted when the radio base station permits uplink data transmission to the radio terminal, they are sometimes called UL Grant.

Fig. 2A shows the correspondence between TPC command values in DCI format 0 or 4 and changes in transmission power. DCI format 0 and 4 TPC commands are 2-bit information and take four values. The four types of values correspond to transmission power changes of −1, 0, +1, and +3, respectively. The wireless terminal determines transmission power based on Equation (2) according to the values of these TPC commands. For example, when the value of the TPC command is −1, the wireless terminal reduces the transmission power by 1 dB based on Equation (2). On the other hand, when the value of the TPC command is +1 or +3, the wireless terminal increases the transmission power by 1 dB or 3 dB based on Equation (2). When the value of the TPC command is 0, the wireless terminal does not change the transmission power based on Equation (2).

On the other hand, DCI formats 3 and 3A are mainly TPC commands used for transmission power control of uplink data that is semi-persistent scheduled or transmission power control of uplink ACK / NACK response signal for downlink data that is persistent scheduled. It is used for transmission. Semi-persistent scheduling is mainly applied to transmission of data that is transmitted at a fixed period such as a voice packet and has a certain size, and the data is transmitted using radio resources and radio parameters assigned in advance. A downlink control signal is not used for an instruction to transmit uplink data that is semi-persistent-scheduled except when it is transmitted using a resource different from the radio resource allocated in advance or at the time of retransmission. Therefore, the TPC command cannot be transmitted to the terminal. Therefore, DCI format 3 or 3A dedicated to TPC command transmission is used. Using one DCI format 3 / 3A, it is possible to simultaneously transmit TPC commands to more than a dozen terminals. Note that the uplink signal (uplink channel) whose transmission power is adjusted in DCI formats 3 and 3A includes the uplink control channel PUCCH in addition to the uplink data channel PUSCH.

The TPC command of DCI format 3 is 2-bit information and is the same as FIG. 2A. In contrast, the DCI format 3A TPC command is 1-bit information, as shown in FIG. 2B. When the value of the TPC command is −1, the wireless terminal reduces the transmission power by 1 dB based on Equation (2). When the value of the TPC command is +1, the wireless terminal increases the transmission power by 1 dB based on Equation (2).

In the following description, DCI format 0 may be referred to as DCI0, for example, in the drawings and the descriptions related to the drawings. The same applies to other DCI formats.

FIG. 3 shows an example of a processing sequence of transmission power control for PUSCH. In the case of the frequency division duplex (FDD) method adopted in many countries, the radio terminal 20 transmits uplink data based on the DCI0 in a subframe four frames after the DCI0 received subframe. Send. Now, in S101 of FIG. 3, it is assumed that the radio terminal 20 receives from the radio base station 10 DCI0 whose value of the TPC command is 0 (denoted as TPC = 0 in the following text and in the figure). Next, in S102 (after 4 subframes of S101), the uplink data corresponding to DCI0 of S101 is transmitted from the wireless terminal 20 to the wireless base station 10 using the transmission power P _PUSCH [dBm] defined by Equation 2 as PUSCH. Suppose that it is transmitted via. As described above, for simplification of description, it is assumed that the uplink transmission scale (bandwidth and transmission information amount) is constant.

Next, in S103 of FIG. 3, the radio terminal 20 receives DCI0 with TPC = + 3 from the radio base station 10. At this time, in S104 (after four subframes of S103), the radio terminal 20 transmits the uplink data corresponding to DCI0 of S103 to the radio base station 10 through the PUSCH with the transmission power P _PUSCH +3 [dBm]. become. That is, based on the TPC command, the radio terminal 20 increases the transmission power of the _PUSCH by 3 dB from the previous value P _PUSCH [dBm]. Further, it is assumed that the radio terminal 20 receives DCI3 with TPC = −1 from the radio base station 10 in S105. At this time, the radio terminal 20 reduces the transmission power of the _PUSCH by 1 dB from the previous value P _PUSCH +3 [dBm] to P _PUSCH +2 [dBm]. Note that, unlike DCI0, DCI3 is not control information that prompts the radio terminal 20 to transmit PUSCH, so the radio terminal 20 does not transmit PUSCH according to DCI3. Then, in S106 of FIG. 3, the radio terminal 20 receives DCI0 with TPC = + 1 from the radio base station 10. At this time, in S107 (after 4 subframes in S106), the radio terminal 20 transmits the uplink data corresponding to DCI0 in S106 to the radio base station 10 via the PUSCH with the transmission power P _PUSCH +3 [dBm]. become. That is, based on the TPC command, the radio terminal 20 increases the transmission power of _PUSCH by 1 dB from the previous value P _PUSCH +2 [dBm]. As described above, the radio base station 10 can adjust the transmission power of the PUSCH by the radio terminal 20 by transmitting the TPC command.

Next, transmission power control of the physical uplink control channel PUCCH (Physical Uplink Control Control CHannel), which is an uplink control channel in the LTE system, will be described. The PUCCH transmission power control has a lot in common with the PUSCH transmission power control described in detail above, and will be briefly described below.

In the LTE system, the transmission power P _PUCCH (i) of the PUCCH of the i-th subframe from the radio terminal 20 to the serving cell (the radio base station 10 managing the radio terminal 20) c is determined by the following equation (3). The

Here, in normal times other than the maximum transmission power P _{CMAX, c} (i), the transmission power of PUCCH is determined by the following equation (4). For this reason, Equation (4) will be examined hereinafter.

Each parameter constituting the equation (4) will be briefly described. _{PO_PUCCH} is a value determined based on parameters included in higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) notified from the serving cell. PL _c is a downlink path loss for the serving cell c. h (n _CQI , n _HARQ , n _SR ) is a parameter related to the PUCCH format. Here, n _CQI , n _HARQ , n _SR are CQI (Channel Quality Indicator) which is uplink control information in the subframe, ACK (ACKnowledge) or NACK (Negative ACKnowledge), SRACK in HARQ (Hybrid Automatic Repeat reQuest), respectively. This is the number of bits in (Scheduling Request). Δ _{F_PUCCH} (F) is notified by higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) from the serving cell, and is related to PUCCH format F. Δ _TxD (F ′) is reported from the serving cell through higher layer signaling (RRC Connection Setup or RRC Connection Reconfiguration) when PUCCH is transmitted through two antenna ports, and is related to PUCCH format F ′. Finally, g (i) is a value determined based on the TPC command notified from the serving cell by the lower layer control information DCI.

_Each term constituting the expression (4) will be described in the same manner as the expression (2). _Each term of the first group corresponds to P _{O_PUCCH} and PL _c . _Each second term corresponds to h (n _CQI , n _HARQ , n _SR ), Δ _{F_PUCCH} (F), and Δ _TxD (F ′). Each term in the third group corresponds to g (i). Therefore, the TPC command is the only means for the PUCCH for the radio base station 10 to adjust the transmission power of the radio terminal 20 in accordance with changes in the radio environment, similarly to the PUSCH described above. The radio base station 10 can transmit a TPC command to the radio terminal 20 for each subframe as necessary. As a result, the radio base station 10 can adjust the transmission power of the PUCCH of the radio terminal 20 for each subframe.

Hereafter, in order to simplify the explanation, it is assumed that the uplink transmission scale (transmission information amount, etc.) is constant. Under this assumption, the transmission power of the PUCCH of the radio terminal 20 connected to the radio base station 10 changes based only on the TPC command received from the radio base station 10.

Next, the DCI related to the PUCCH among the DCIs that are control information including the TPC command will be described.
The TPC command for PUCCH is stored in one of

DCI formats

1, 1A, 1B, 1C, 2, 2A, 2B, 2C, 3 or 3A and transmitted from the radio base station 10 to the radio terminal 20. Of these, the DCI formats 3 and 3A have already been described, and a description thereof will be omitted here.

DCI formats 1, 1A, 1B, 1C, 2, 2A, 2B, and 2C are downlink control information used when the radio base station 10 transmits downlink data to the radio terminal 20. DCI formats 1, 1A, 1B and 1C are used when PDSCH codeword transmits one downlink data, and

DCI formats

2, 2A, 2B and 2C transmit two downlink data with PDSCH codeword. Used when. These DCI formats include a TPC command, parameters indicating radio resource allocation for transmitting downlink data, MCS that is a parameter for specifying a coding scheme and a modulation scheme for transmitting downlink data, and the like. It is. One of the differences between the DCI formats 1, 1A, 1B, and 1C is that the radio resource allocation rules are different, but a description thereof is omitted here. The same applies to the difference between

DCI formats

2, 2A, 2B, and 2C. The

DCI format

1, 1A, 1B, 1C, 2, 2A, 2B, and 2C TPC commands are 2-bit information and are the same as in FIG. 2A.

FIG. 4 shows an example of a processing sequence of transmission power control for PUCCH. In the case of the FDD scheme adopted in many countries, the radio terminal 20 transmits an uplink response signal corresponding to the downlink data in a subframe that is four frames after the DCI1 and the subframe that received the downlink data based on the DCI1. (ACK or NACK) is transmitted via PUCCH. Now, it is assumed that the radio terminal 20 receives from the radio base station 10 DCI1 with TPC = 0 and downlink data based on the DCI1 in S201 of FIG. Next, in S202 (after four subframes of S201), the wireless terminal 20 transmits the response signal (ACK / NACK) corresponding to the downlink data of S201 to the transmission power P _PUCCH defined by Equation 4 for the wireless base station 10. Assume that transmission is performed via PUCCH at [dBm]. As described above, for the sake of simplicity, it is assumed that the uplink transmission scale (transmission information amount) is constant.

Next, in S203 of FIG. 4, the radio terminal 20 receives DCI1 with TPC = + 3 and downlink data based on the DCI1 from the radio base station 10. At this time, in S204 (after 4 subframes of S203), the wireless terminal 20 transmits the response signal (ACK / NACK) corresponding to the downlink data of S203 to the wireless base station 10 with the transmission power P _PUCCH +3 [dBm]. Will be sent through. That is, based on the TPC command, the radio terminal 20 increases the transmission power of _PUCCH by 3 dB from the previous value P _PUCCH [dBm]. Further, it is assumed that the radio terminal 20 receives DCI3 with TPC = −1 from the radio base station 10 in S205. At this time, the radio terminal 20 reduces the PUCCH transmission power by 1 dB from the previous value P _PUCCH +3 [dBm] to P _PUCCH +2 [dBm]. Unlike DCI1, DCI3 is not control information that prompts radio terminal 20 to transmit a PUCCH (response signal), so radio terminal 20 does not transmit PUCCH according to DCI3.

Next, in S206, the radio terminal 20 transmits the CQI to the radio base station 10 via the PUCCH with the transmission power P _PUCCH +2 [dBm]. The transmission timing of periodic CQI (periodic CQI) is notified to the radio terminal 20 in advance by signaling from the radio base station 10, and S206 corresponds to the transmission timing. In S207 of FIG. 4, the radio terminal 20 receives from the radio base station 10 DCI1 with TPC = + 1 and downlink data based on the DCI1. At this time, in S208 (after 4 subframes of S207), the wireless terminal 20 transmits the response signal (ACK / NACK) corresponding to the downlink data of S207 to the wireless base station 10 with the transmission power P _PUCCH +3 [dBm]. Will be sent through. That is, based on the TPC command, the radio terminal 20 increases the transmission power of _PUCCH by 1 dB from the previous value P _PUCCH +2 [dBm]. As described above, the radio base station 10 can adjust the transmission power of the PUCCH by the radio terminal 20 by transmitting the TPC command.

Based on the above, consider performing interference control for IDC in accordance with the uplink transmission power control framework in the LTE system.

In order to realize interference control for IDC in accordance with the uplink transmission power control framework in the LTE system, the following procedure (hereinafter referred to as reference technology for convenience) can be considered as an example. Now, the wireless terminal 20 reduces the transmission power of the first wireless communication (wireless communication based on LTE-A or the like), thereby reducing the second wireless communication (wireless communication based on a wireless communication method other than LTE-A or the like). Suppose you want to reduce interference. At this time, the radio terminal 20 requests the radio base station 10 to reduce the transmission power of the first radio communication by some means. For example, this request may be made by diverting an existing MAC control parameter such as PHR (Power HeadRoom). Upon receiving this request, the radio base station 10 transmits a TPC command (including DCI) to reduce the transmission power of the radio terminal 20. The radio terminal 20 reduces the transmission power of the first radio communication based on Equations 2 and 4 according to the received TPC command.

According to this reference technique, since the interference generated by the first wireless communication with the second wireless communication in the wireless terminal 20 is reduced, it seems that the desired purpose has been achieved. However, this reference technique has several problems as follows.

As a first problem in the reference technology, even when the radio base station 10 is requested to reduce transmission power by the PHR or the like from the radio terminal 20, the first radio communication (radio communication based on LTE-A or the like) in the radio terminal 20 is performed. It is difficult to estimate how much the transmission power should be reduced. As described above, for example, the wireless terminal 20 can make this request with a PHR indicating the difference between the current transmission power of the wireless terminal 20 and the maximum transmission power of the wireless terminal 20. However, simple control such as controlling the direction in which the transmission power of the first wireless communication is not reduced if the value of PHR is large, and controlling in the direction of decreasing the transmission power of the first wireless communication if the value of PHR is small is insufficient. It is clear that there is. This is because the amount of decrease in the first wireless communication depends on the magnitude of interference received by the second wireless communication. The PHR is mainly used for the base station to know how much the transmission power of the terminal can be increased.

Also, a second problem in the reference technology is that interference control is delayed because it takes time to greatly reduce the transmission power with the TPC command. As described above, when the transmission power is increased by TPC, the increase width can be increased by 3 dB. On the other hand, when the transmission power is reduced based on TPC, the reduction amount must be 1 dB.

FIG. 5 is a processing sequence showing a second problem in the reference technology. As shown in FIG. 5, when the radio terminal 20 wants to reduce the transmission power after detecting interference, the transmission power can be reduced by only 1 dB with one TPC transmission (for example, included in DCI0) by the radio base station 10. For this reason, if it is desired to lower the transmission power by 10 dB, the radio base station 10 needs to transmit a TPC command for instructing a reduction of 1 dB 10 times. Therefore, in the above procedure, since it takes time to reduce the transmission power to a desired level after the occurrence of interference, it is considered that this leads to a delay in interference suppression. The TPC command can also be interpreted as not good at greatly reducing the transmission power.

Furthermore, as a third problem in the reference technology, the TPC command is originally unsuitable for use in adjusting the transmission power of an arbitrary wireless terminal 20 at an arbitrary timing. As described above, the TPC command is included in each DCI format. Here, DCI0, DCI1, DCI2, and DCI4 cannot be transmitted at any timing because they cannot be transmitted inherently unless uplink data or downlink data is generated. Further, since DCI3 and DCI3A are for all the radio terminals 20 under the radio base station 10, they cannot be transmitted to any radio terminal 20. Therefore, there is no DCI (including a TPC command) that can be transmitted to an arbitrary wireless terminal 20 at an arbitrary timing.

Even if no downlink data is generated, the radio base station 10 transmits, for example, DCI1 (including a TPC command) to a specific radio terminal 20 for the purpose of adjusting the transmission power of an arbitrary radio terminal 20. However, it is considered possible. In that case, the radio base station 10 transmits empty data as downlink data. However, even in such a case, the radio terminal 20 needs to perform demodulation and decoding of downlink data (empty data) and transmission of a response signal (ACK / NACK). Therefore, such DCI transmission is considered undesirable from the viewpoint of wasting computer resources and radio resources.

In summary, IDC interference control based on transmission power control using a TPC command (the above-mentioned reference technique) has a plurality of problems, and thus interference control cannot be performed effectively. As described above, this problem was newly found as a result of careful study of the prior art by the inventor, and has not been known so far. Hereinafter, each embodiment of the present application for solving this problem will be described in order.

[First Embodiment]
In the first embodiment, the radio terminal 20 autonomously lowers transmission power from a value determined based on a TPC command. In other words, the wireless communication device (wireless terminal 20) in the first embodiment repeatedly receives the first control signal instructing to change or maintain the transmission power from the other wireless communication device, and receives the first control signal for the other wireless communication device. A wireless communication apparatus that determines transmission power of one wireless transmission based on the first control signal received before the first wireless transmission, with a second transmission power smaller than the first transmission power based on the determination A transmission unit that performs the first wireless transmission is provided.

The premise of this embodiment will be described. First, it is assumed that the wireless terminal 20 supports IDC. More specifically, the wireless terminal 20 simultaneously performs the first wireless communication (wireless communication based on LTE-A or the like) and the second wireless communication (wireless communication based on a wireless communication method other than LTE-A or the like). Suppose you can. Also in this embodiment, it is assumed that the uplink transmission scale (bandwidth and amount of transmission information) is constant for the sake of simplicity.

FIG. 6 shows an example of a processing sequence of the wireless communication system according to the first embodiment. In FIG. 6, the transmission power control target is PUSCH as an example, but the present invention can be similarly applied to PUCCH and other transmission power control.

First, in S401 of FIG. 6, the radio terminal 20 receives DCI0 with TPC = 0 as an example from the radio base station 10. Next, in S402 (after four subframes of S401), the uplink data corresponding to DCI0 received in S401 is transmitted to the radio base station 10 by the radio terminal 20 using the transmission power P _PUSCH [dBm] defined by Equation 2. Send. 6 are processes corresponding to S101 to S102 in FIG.

Next, in S403 of FIG. 6, the wireless terminal 20 performs wireless communication based on a wireless communication method other than LTE-A or the like using a transmission signal of IDC first wireless communication (wireless communication based on LTE-A or the like). The occurrence of interference with the received signal is detected. Here, the detection method of interference generation shall not be ask | required. For example, the wireless terminal 20 can detect the occurrence of interference by determining whether the reception error rate of the second wireless communication is equal to or greater than a predetermined value when transmitting the first wireless communication. Here, the transmission of the first wireless communication may be transmission of an SRS (Sounding Reference Signal) that is an uplink reference signal for scheduling, or transmission of a data signal (PUSCH) or a control signal (PUCCH). . In S403, the magnitude of the generated interference may be measured (detected) as well as the presence or absence of the occurrence of interference. For example, the radio terminal 20 can set the difference value between the reception error rate of the second radio communication at the time of transmission of the first radio communication and a predetermined value as the magnitude of the generated interference.

In S404 of FIG. 6, the wireless terminal 20 determines the transmission power reduction amount ΔP [dB] of the first wireless communication. Here, the transmission power reduction amount determination method is not limited. For example, the radio terminal 20 can determine the transmission power reduction amount based on the magnitude of interference detected in S403.

Next, in S405 of FIG. 6, the radio terminal 20 receives DCI0 with TPC = 0 from the radio base station 10 as an example. At this time, in S406 (after 4 subframes of S405), the radio terminal 20 transmits the uplink data corresponding to DCI0 received in S405 to the radio base station 10 with the transmission power P _PUSCH -ΔP [dBm]. .

Here, regarding the transmission power of the wireless terminal 20 after the occurrence of interference due to IDC, the above-described reference technique and this embodiment are compared. In S306 corresponding to uplink data transmission of the radio terminal 20 after interference detection (S303) in FIG. 5 showing the reference technique, the radio terminal 20 uses the TPC command (S305) to transmit the transmission power P _PUSCH [dBm] for the _PUSCH so far. The PUSCH transmission power P _PUSCH -1 [dBm] is determined by adjusting based on the value of -1 [dBm]. On the other hand, in S406 corresponding to the uplink data transmission of the radio terminal 20 after interference detection in FIG. 6, the radio terminal 20 detects the detected interference with respect to the transmission power P _PUSCH [dBm] so far with respect to the _PUSCH (S403). After reducing the transmission power reduction amount ΔP (S404) determined based on the above, and further adjusting based on the value 0 [dB] of the TPC command (S405), the PUSCH transmission power P _PUSCH −ΔP [dBm] To decide. That is, the transmission power in S406 of FIG. 6 according to the first embodiment is lower by the transmission power reduction amount ΔP determined based on the interference than in S104 of FIG.

As an example, the transmission power reduction amount ΔP determined in S404 is 10 [dB]. At this time, in FIG. 6 according to the first embodiment, the transmission power of the PUSCH after the interference is generated without receiving 10 TPC commands (TPC = −1) as in FIG. 5 according to the reference technique. It is possible to reduce the transmission power of PUSCH before the occurrence by 10 [dB]. As a result, the transmission power of the first wireless communication can be rapidly and greatly reduced after the interference of the transmission signal of the first wireless communication with the reception signal of the second wireless communication occurs. Therefore, according to the first embodiment, it is possible to quickly and significantly reduce interference between the transmission signal of the first wireless communication and the reception signal of the second wireless communication.

Note that after S406, the radio base station 10 may transmit a DCI including a TPC command (for example, TPC = + 3) instructing the radio terminal 20 to increase transmission power (not shown). This is because the radio base station 10 cannot recognize that the radio terminal 20 has autonomously reduced transmission power. At this time, the radio terminal 20 may increase the transmission power based on the TPC command, or may ignore the TPC command and maintain the transmission power. When the TPC command is ignored, the period may be a predetermined period or may be a period that satisfies a predetermined condition. Here, the predetermined condition can be, for example, whether reception of the second wireless communication is ongoing.

Further, after S406, the radio terminal 20 may autonomously increase the transmission power after a predetermined period has elapsed or when a predetermined condition is satisfied. The predetermined condition may be, for example, whether reception of the second wireless communication is ongoing.

According to the first embodiment described above, when interference based on IDC occurs, it is possible to quickly and significantly reduce the transmission power of wireless communication that is an interference source. Therefore, according to the first embodiment, interference based on IDC can be quickly and significantly reduced.

[Second Embodiment]
In the second embodiment, the radio terminal 20 notifies the radio base station 10 that the transmission power is autonomously reduced. In other words, the wireless communication device (wireless terminal 20) in the second embodiment is the wireless communication device in the first embodiment, and the transmission unit further performs the first wireless transmission with the second transmission power. Is transmitted to the other wireless communication device.

The second embodiment has many points in common with the first embodiment. In the following, the second embodiment will be described with a focus on differences from the first embodiment.

The premise in the second embodiment is the same as that in the first embodiment. The wireless terminal 20 is compatible with IDC, and more specifically, the wireless terminal 20 includes a first wireless communication (wireless communication based on LTE-A or the like) and a second wireless communication (wireless communication other than LTE-A or the like). Wireless communication based on the system) can be performed simultaneously. For simplicity of explanation, it is assumed that the uplink transmission scale (bandwidth and transmission information amount) is constant.

FIG. 7 shows an example of a processing sequence of the wireless communication system according to the second embodiment. In FIG. 7, the transmission power control target is PUSCH as an example, but the present invention can be similarly applied to PUCCH and other transmission power control. First, since S501 to S504 in FIG. 7 are the same as S401 to S404 in FIG. 6, the description thereof is omitted here.

In S505 of FIG. 7, the wireless terminal 20 notifies the wireless base station 10 of a transmission power reduction notification that is a notification to reduce the transmission power. The transmission power reduction notification may include the transmission power reduction amount determined in S504. The transmission power reduction notification can be performed by, for example, uplink RRC signaling. In addition, it is desirable to maintain the transmission power when transmitting the transmission power reduction notification without reflecting the transmission power reduction amount determined in S504 (in order to place importance on the certainty of communication). It doesn't matter.

In S506 of FIG. 7, the wireless terminal 20 receives DCI0 from the wireless base station 10 as an example. Here, the radio base station 10 recognizes that the radio terminal 20 autonomously lowers the transmission power based on the transmission power reduction notification received in S505. Therefore, in step S506, the radio base station 10 can reflect the received transmission power reduction notification on each parameter of DCI0 transmitted to the radio terminal 20.

For example, in step S506, the radio base station 10 can set the value of the TPC command included in DCI0 transmitted to the radio terminal 20 to 0 or less for a predetermined time in response to reception of the transmission power reduction notification. This is because if the transmission power autonomously reduced by the radio terminal 20 is immediately increased due to the convenience of the radio base station 10, the effect of autonomous transmission power reduction is weakened.

Also, in S506, the radio base station 10 can adjust the value of MCS, which is a parameter indicating the modulation and coding scheme, in response to reception of the transmission power reduction notification. As a result, it is possible to suppress deterioration of communication characteristics due to a reduction in transmission power. In general, the radio base station 10 determines the MCS value so that the uplink reception error rate becomes a constant level. On the other hand, the uplink reception error rate depends on the uplink signal-to-interference noise ratio (SINR: Signal to Interference plus Noise Ratio), and SINR depends on the transmission power of the signal (desired signal).

FIG. 8 is a diagram showing deterioration of communication characteristics due to deterioration of transmission power. As shown in FIG. 8, the radio base station 10 has a constant reception error rate on the premise that the transmission power on the radio terminal 20 side is at a constant level and that SINR is at a constant level SINR1. The MCS is determined to be level ER1. However, when the radio terminal 20 autonomously reduces the transmission power, SINR is reduced to SINR2 accordingly, and the reception error rate is further increased to ER2. In order to suppress the deterioration of the communication characteristics due to the deterioration of the transmission power, the radio base station 10 in S506 is based on the transmission power reduction amount indicated by the transmission power reduction notification as compared with the case where there is no transmission power reduction. An MCS that is resistant to errors can be selected, and a DCI that includes the MCS can be transmitted to the radio terminal 20.

It should be noted that an MCS table created in advance may be used in determining the MCS in S506. Here, the MCS table is a table in which the SINR threshold (range) is associated with the MCS. The radio base station 10 can create an MCS table by, for example, a closed-loop method, but a detailed description is omitted here. In S506, the radio base station 10 can obtain an assumed value of SINR after transmission power reduction based on the transmission power reduction amount, and can select an MCS based on the assumed value and the MCS table.

Further, after receiving the transmission power reduction notification in S505, the radio base station 10 adjusts various parameters that affect the correctness of reception of the uplink signal from the radio terminal 20, or sets the parameters as necessary. Can be notified. As an example, the radio base station 10 can notify the radio terminal 20 by increasing the maximum number of HARQ uplink retransmissions in response to the reception of the transmission power reduction notification. As another example, the radio base station 10 can lengthen the HARQ uplink timeout period in response to the reception of the transmission power reduction notification.

Finally, in S507 (after 4 subframes in S506), the radio terminal 20 transmits uplink data corresponding to DCI0 received in S506 to the radio base station 10 with transmission power P _PUSCH −ΔP [dBm].

In S507, the radio terminal 20 may autonomously transmit the PUSCH with a transmission power higher than P _PUSCH −ΔP [dBm] when the predetermined condition is satisfied. This is because even if the wireless terminal 20 transmits the PUSCH with higher transmission power than the wireless base station 10 assumes, the disadvantage is small. One demerit is that the MCS defined by the radio base station 10 becomes excessive quality, and the use efficiency of radio resources is reduced. However, the effect is considered to be limited. Note that the predetermined condition for autonomously increasing the transmission power can be, for example, that reception of the second wireless communication is not ongoing.

Also, if the TPC is a value other than 0 in S506 or subsequent PUSCH transmission, the wireless terminal 20 may change the transmission power based on the TPC command, or ignore the TPC command. The transmission power may be maintained.

According to the second embodiment described above, similarly to the first embodiment, when interference based on the IDC occurs, the transmission power of the wireless communication that is the interference source can be quickly and significantly reduced. Therefore, according to the second embodiment, it is possible to quickly and significantly reduce IDC-based interference.

Furthermore, according to the second embodiment, an effect that cannot be obtained in the first embodiment can be obtained. Specifically, since the radio base station 10 can adjust various parameters related to the uplink signal according to the transmission power reduction notification, there is an effect of suppressing an increase in reception errors due to the transmission power reduction of the radio terminal 20. can get.

[Third Embodiment]
The first embodiment and the second embodiment are based on the premise that the wireless terminal 20a supports IDC. However, in the present invention, it is not essential that the wireless terminal 20a supports IDC. The third embodiment is an embodiment corresponding to a case where the present invention is applied to a wireless terminal 20a that does not support IDC.

The entire third embodiment will be described. In the third embodiment, it is not necessary for the wireless terminal 20a to support IDC. In the third embodiment, it is assumed that the radio terminal 20a and the radio base station 10a are compatible with downlink multi-point coordinated (CoMP: Coordinated Multiple Point) transmission. Specifically, it is assumed that the radio terminal 20a can receive downlink signals transmitted in cooperation from the radio base station 10a and the adjacent radio base station 10b. There are several types of coordinated transmission. Here, a mode is assumed in which the radio base station 10a and the adjacent radio base station 10b are switched at high speed and signals are received from one side.

FIG. 9 shows an example of the processing sequence of the third embodiment. In FIG. 9, the transmission power control target is PUSCH as an example, but the present invention can be similarly applied to PUCCH and other transmission power control. Since S601 to S602 in FIG. 9 are the same processing as S401 to S402 in FIG. 6, the description thereof is omitted.

In S603 of FIG. 9, the adjacent radio base station 10b detects the interference generated based on the uplink signal transmitted from the radio terminal 20a in S602. Here, the detection method of interference generation shall not be ask | required. For example, the adjacent radio base station 10b can detect the occurrence of interference by determining whether the reception error rate from the other radio terminal 20b (not shown) is equal to or higher than a predetermined value at the time of transmission of the radio terminal 20a. In S603, not only the presence / absence of interference, but also the magnitude of the generated interference may be measured (detected). For example, the adjacent radio base station 10b can set the difference value between the reception error rate from the other radio terminal 20b and the predetermined value at the time of transmission of the radio terminal 20a as the magnitude of the generated interference.

In S604 of FIG. 9, the adjacent radio base station 10b transmits a transmission power reduction request that is a signal requesting the radio terminal 20a to reduce transmission power. The transmission power reduction request may include the interference magnitude measured in S603. The transmission power reduction notification can be performed by downlink RRC signaling, for example.

In S605 of FIG. 9, the radio terminal 20a determines the transmission power reduction amount ΔP [dBm] in response to the transmission power reduction request received in S604. Here, the transmission power reduction amount determination method is not limited. For example, the radio terminal 20a can determine the transmission power reduction amount based on the magnitude of interference included in the transmission power reduction request received in S604.

Next, in S606 of FIG. 9, the radio terminal 20a receives DCI0 with TPC = 0 as an example from the radio base station 10a. At this time, in S607 (after 4 subframes of S606), the radio terminal 20a transmits the uplink data corresponding to DCI0 received in S606 to the radio base station 10a with the transmission power P _PUSCH −ΔP [dBm]. .

The significance of the processing sequence of FIG. 9 will be described. In S604, the adjacent radio base station 10b transmits a transmission power reduction request to the radio terminal 20a. For example, when the adjacent radio base station 10b transmits a transmission power reduction request to the radio base station 10a, the transmission of the radio terminal 20a is performed. There seems to be a way to reduce power. However, according to such a method, since the instruction to reduce the transmission power from the radio base station 10a to the radio terminal 20a is performed using the conventional TPC command, problems such as the delay in implementing interference countermeasures as described above remain. It will be. Furthermore, since communication between the radio base stations 10a has a large transmission delay (average of about 20 msec), implementation of interference countermeasures is further delayed, which is not desirable. As shown in FIG. 9, by transmitting a transmission power reduction request directly from the adjacent radio base station 10b to the radio terminal 20a (without going through the radio base station 10a), it is possible to minimize the delay until the countermeasure against interference is implemented. It can be done.

In the processing sequence of FIG. 9, the radio terminal 20a does not transmit a transmission power reduction notification to the radio base station 10a after determining the power reduction amount (S605). However, also in FIG. 9, similarly to S505 in FIG. 7, the radio terminal 20a may transmit a transmission power reduction notification to the radio base station 10a. In S606, the radio base station 10a may adjust various parameters for the transmission of the radio terminal 20a based on the transmission power reduction notification received from the radio terminal 20a. The details of the processing have been described for S505 to 506 in FIG. 7, and will not be described here.

According to the third embodiment described above, when interference occurs in the adjacent radio base station 10b based on the transmission of the radio terminal 20a, the transmission power of the radio terminal 20a, which is an interference source, can be rapidly and greatly reduced. it can. Therefore, according to the third embodiment, it is possible to quickly and significantly reduce interference in the adjacent radio base station 10b based on the transmission of the radio terminal 20a.

[Variation regarding determination of transmission power reduction amount]
Here, modified examples of the first and second embodiments will be described. This modification relates to determination of the transmission power reduction amount.

In the first embodiment, the magnitude of interference is first measured in S403, and the transmission power reduction amount is determined in S404 based on the magnitude of the interference. Here, as an example, the magnitude of the interference is a difference value between the reception error rate of the second wireless communication at the time of transmission of the first wireless communication and a predetermined value. On the other hand, in the present modification to the first embodiment, when the wireless terminal 20 detects interference and decides to reduce the transmission power, the measurement in which the transmission power is reduced to determine the transmission power reduction amount. Send for use. Specifically, when interference is detected in a transmission signal with transmission power P ₀ [dBm], for example, the radio terminal 20 transmits the transmission power P ₀ -5 [dBm], P ₀ -10 [dBm], P ₀ − Transmission for measurement is performed at each of 15 [dBm] P ₀ -20 [dBm], and the magnitude of each interference is measured. Then, the radio terminal 20 determines a transmission power reduction amount based on the measured magnitude of each interference. For example, the radio terminal 20 can determine the transmission power reduction amount from the transmission power at the time of transmission corresponding to the case where the magnitude of interference is the maximum within a predetermined value. Here, the measurement signal may be transmission of an SRS (Sounding Reference Signal) that is an uplink reference signal for scheduling, or may be transmission of a data signal (PUSCH) or a control signal (PUCCH).

FIG. 10 is a diagram for explaining this modification example with respect to the second embodiment. The processing sequence of FIG. 10 corresponds to the processing of S503 to S504 of the processing sequence of FIG. In S701 of FIG. 10, and it transmits the SRS by the transmission power P _0. Next, in S702, it is assumed that interference with the second radio communication is detected in the radio terminal 20, and the radio terminal 20 determines transmission power reduction. At this time, in S703, the radio terminal 20 transmits a transmission power temporary reduction notification indicating that the transmission power is temporarily reduced to the radio base station 10. Thereafter, in steps S704 to S707, the wireless terminal 20 transmits transmissions for measurement at transmission powers P ₀ -5 [dBm], P ₀ -10 [dBm], and P ₀ -15 [dBm] P ₀ -20 [dBm]. And measure the magnitude of each interference. In step S708, the radio terminal 20 determines the transmission power reduction amount ΔP based on the measured magnitudes of interference. For example, the radio terminal 20 can determine the transmission power reduction amount from the transmission power at the time of transmission corresponding to the case where the magnitude of interference is the maximum within a predetermined value. In addition, by notifying the radio base station 10 beforehand that the transmission power is temporarily reduced by the transmission power temporary reduction notification in FIG. 10, scheduling by the radio base station 10 based on the SRS transmitted thereafter is appropriately performed. The effect of being performed is obtained. Further, in FIG. 10, the measurement signal may be a data signal (PUSCH) or a control signal (PUCCH) transmission in addition to the SRS.

[Other variations]
Below, the other modification in each embodiment is demonstrated. These can be implemented in combination with each embodiment as appropriate.

In the second embodiment, the transmission power reduction notification is notified in advance (before transmission power reduction). Specifically, in FIG. 7, the radio terminal 20 transmits a transmission power reduction notification to the radio base station 10 in S505 before the PUSCH transmission in S507. On the other hand, the transmission power reduction notification may not be transmitted in advance, but may be notified in communication for reducing transmission power. Specifically, in FIG. 7, the wireless terminal 20 can transmit the transmission power reduction notification in the same subframe as the PUSCH transmission in S507 without transmitting the transmission power reduction notification to the wireless base station 10 in S505. Since the value of BSR (Buffer Status Report) is quantized, there is usually some room for radio resources for PUSCH transmission allocated to the radio terminal 20 by the radio base station 10. The radio terminal 20 can transmit a transmission power reduction notification in the same subframe as the PUSCH transmission in this room.

[Network configuration of wireless communication system of each embodiment]
Next, the network configuration of the wireless communication system 1 of each embodiment and each modification will be described with reference to FIG. As illustrated in FIG. 11, the wireless communication system 1 includes a wireless base station 10 and a wireless terminal 20. The radio base station 10 forms a cell C10. The radio terminal 20 exists in the cell C10. Note that in the present application, the radio base station 10 and the radio terminal 20 may be collectively referred to as “radio station”.

The wireless base station 10 is connected to the network device 3 via a wired connection, and the network device 3 is connected to the network 2 via a wired connection. The radio base station 10 is provided so as to be able to transmit and receive data and control information to and from other radio base stations via the network device 3 and the network 2.

The radio base station 10 may separate the radio communication function with the radio terminal 20 and the digital signal processing and control function to be a separate device. In this case, a device having a wireless communication function is called RRH (Remote Radio Head), and a device having a digital signal processing and control function is called BBU (Base Band Unit). The RRH may be installed overhanging from the BBU, and may be wired by an optical fiber between them. The radio base station 10 is a radio base station of various scales besides a small radio base station (including a micro radio base station, a femto radio base station, etc.) such as a macro radio base station and a pico radio base station. Good. When a relay station that relays wireless communication between the wireless base station 10 and the wireless terminal 20 is used, the relay station (transmission / reception with the wireless terminal 20 and its control) is also included in the wireless base station 10 of the present application. It is good.

On the other hand, the wireless terminal 20 communicates with the wireless base station 10 by the first wireless communication. The radio terminal 20 communicates with an access point other than the radio base station 10 and a communication device by the second radio communication. Examples of the first wireless communication include LTE and LTE-A. In addition, as the second wireless communication, for example, wireless LAN such as WiFi (registered trademark) and WiMAX (registered trademark), Bluetooth (registered trademark), GPS, Zigbee (registered trademark), GSM (registered trademark, Global System for Mobile Communications) ), UMTS (Universal Mobile Telecommunications System) or the like can also be used.

The first wireless communication and the second wireless communication are performed using the same or close frequency band. For example, when the frequency band group prepared for the first wireless communication and the frequency band group prepared for the second wireless communication are adjacent to each other, or when the first wireless communication and the second wireless communication are the same frequency band group Is assumed to be shared.

The wireless terminal 20 may be a wireless terminal such as a mobile phone, a smartphone, a PDA (Personal Digital Assistant), a personal computer (Personal Computer), various devices or devices (such as sensor devices) having a wireless communication function. When a relay station that relays radio communication between the radio base station 10 and another radio terminal 20 is used, the relay station (transmission / reception with the radio base station 10 and its control) is also included in the radio terminal 20 of this paper. It is also possible that

The network device 3 includes, for example, a communication unit and a control unit, and these components are connected so that signals and data can be input and output in one direction or in both directions. The network device 3 is realized by a gateway, for example. As a hardware configuration of the network device 3, for example, the communication unit is realized by an interface circuit, and the control unit is realized by a processor and a memory.

In addition, the specific mode of distribution / integration of each component of the radio base station 10 and the radio terminal 20 is not limited to the mode of the first embodiment, and all or a part thereof can be used for various loads, usage conditions, and the like. Accordingly, it may be configured to be functionally or physically distributed / integrated in an arbitrary unit. For example, the memory may be connected as an external device of the radio base station 10 and the radio terminal 20 via a network or a cable.

[Functional Configuration of Each Device in Radio Communication System of Each Embodiment]
Next, the functional configuration of each device in the wireless communication system of each embodiment and each modification will be described with reference to FIGS.

FIG. 12 is a functional block diagram showing the configuration of the radio base station 10. As illustrated in FIG. 12, the radio base station 10 includes a transmission unit 11, a reception unit 12, and a control unit 13. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.

The transmission unit 11 transmits a data signal and a control signal by first wireless communication via an antenna. The antenna may be common for transmission and reception. The transmitter 11 transmits a downlink signal via, for example, a downlink data channel or a control channel. The downlink physical data channel includes, for example, a dedicated data channel PDSCH (Physical Downlink Shared Channel). The downlink physical control channel includes, for example, a dedicated control channel PDCCH (PhysicalPhysDownlink Control Channel). The signal to be transmitted is, for example, an L1 / L2 control signal transmitted to the connected wireless terminal 20 on the dedicated control channel, a user data signal transmitted to the connected wireless terminal 20 on the dedicated data channel, or RRC (Radio). Resource (Control) signaling included. The signal to be transmitted includes, for example, a reference signal used for channel estimation and demodulation.

Specific examples of signals transmitted by the transmission unit 11 include signals transmitted by each radio base station in FIGS. 6 to 7 or FIGS. 9 to 10. Specifically, the transmission unit 11 can transmit various DCI formats including the TPC command in FIGS. 6 to 7 or 9 to 10 via the PDCCH. Moreover, the transmission part 11 can transmit the transmission power reduction request | requirement in FIG. 9 by RRC signaling via PDSCH, for example.

The receiving unit 12 receives the data signal and the control signal transmitted from the wireless terminal 20 through the first wireless communication via the antenna. The receiving unit 12 receives an uplink signal via, for example, an uplink data channel or a control channel. The uplink physical data channel includes, for example, a dedicated data channel PUSCH (Physical Uplink Shared Channel). Further, the uplink physical control channel includes, for example, a dedicated control channel PUCCH (Physical Uplink Control Channel). The received signal is, for example, an L1 / L2 control signal transmitted from the connected wireless terminal 20 on the dedicated control channel, a user data signal transmitted from the connected wireless terminal 20 on the dedicated data channel, or RRC (Radio). Resource (Control) signaling included. The received signal includes, for example, a reference signal used for channel estimation and demodulation.

Specific examples of signals received by the receiving unit 12 include signals received by the respective radio base stations in FIGS. 6 to 7 or FIGS. 9 to 10. Specifically, the receiving unit 12 can receive the uplink data in FIGS. 6 to 7 or 9 via the PUSCH. Moreover, the receiving part 12 can receive the transmission power reduction notification in FIG. 7 by RRC signaling via PUSCH, for example. In addition, the receiving unit 12 can receive the transmission power temporary reduction notification in FIG. 10 by RRC signaling via PUSCH, for example, and can receive SRS.

The control unit 13 outputs data to be transmitted and control information to the transmission unit 11. The control unit 13 inputs received data and control information from the reception unit 12. The control unit 13 acquires data and control information from the network device 3 and other wireless base stations via a wired connection or a wireless connection. In addition to these, the control unit 13 performs various controls related to various transmission signals transmitted by the transmission unit 11 and various reception signals received by the reception unit 12.

Specific examples of the process controlled by the control unit 13 include various processes executed in each radio base station in FIGS. 6 to 7 or 9 to 10. In FIGS. 6 to 7 and 9, the control unit 13 can control each process of transmission of various formats of DCI including a TPC command and reception of uplink data. In FIG. 7, the control unit 13 can control the process of receiving the transmission power reduction notification. In FIG. 9, the control unit 13 can control each process of interference detection and transmission of a transmission power reduction request. In FIG. 10, the control unit 13 can control the SRS reception process.

FIG. 13 is a functional block diagram showing the configuration of the wireless terminal 20. As illustrated in FIG. 13, the wireless terminal 20 includes transmission units 21A and 21B,

reception units

22A and 22B, and

control units

23A and 23B. Each of these components is connected so that signals and data can be input and output in one direction or in both directions.

21 A of transmission parts transmit a data signal and a control signal by 1st wireless communication via an antenna. The antenna may be common for transmission and reception. The transmission unit 21A transmits an uplink signal via, for example, an uplink data channel or a control channel. The uplink physical data channel includes, for example, a dedicated data channel PUSCH. Further, the uplink physical control channel includes, for example, a dedicated control channel PUCCH. The signal to be transmitted is, for example, an L1 / L2 control signal transmitted on the dedicated control channel to the connected radio base station 10, or a user data signal or RRC transmitted on the dedicated data channel to the connected radio base station 10. (Radio-Resource-Control) signaling included. The signal to be transmitted includes, for example, a reference signal used for channel estimation and demodulation.

Also, the transmission unit 21A can perform each transmission performed by each wireless communication in FIGS. 6 to 7 and FIGS. 9 to 10 based on the transmission power controlled by the control unit 23A.

Specific examples of signals transmitted by the transmission unit 21A include signals transmitted by the wireless terminals in FIGS. 6 to 7 or FIGS. 9 to 10. Specifically, the transmission unit 21A can transmit the uplink data in FIGS. 6 to 7 or 9 via the PUSCH. Further, the transmission unit 21A can transmit the transmission power reduction notification in FIG. 7 by RRC signaling via the PUSCH, for example. Further, the transmission unit 21A can transmit the transmission power temporary reduction notification in FIG. 10 by RRC signaling via PUSCH, for example, and can also transmit SRS.

The receiving unit 22A receives the data signal and the control signal transmitted from the radio base station 10 through the first radio communication via the antenna. The receiving unit 22A receives a downlink signal via, for example, a downlink data channel or a control channel. The downlink physical data channel includes, for example, a dedicated data channel PDSCH. Further, the downlink physical control channel includes, for example, a dedicated control channel PDCCH. The received signal is, for example, an L1 / L2 control signal transmitted on the dedicated control channel from the connected radio base station 10, or a user data signal or RRC transmitted on the dedicated data channel from the connected radio base station 10. (Radio-Resource-Control) signaling included. The received signal includes, for example, a reference signal used for channel estimation and demodulation.

Specific examples of signals received by the receiving unit 22A include the signals received by the wireless terminals in FIGS. 6 to 7 or FIGS. 9 to 10. Specifically, the receiving unit 22A can receive various DCI formats including the TPC command in FIGS. 6 to 7 or 9 to 10 via the PDCCH. Further, the reception unit 22A can receive the transmission power reduction request in FIG. 9 by RRC signaling via, for example, PDSCH.

The control unit 23A outputs data to be transmitted and control information to the transmission unit 21A. The control unit 23A inputs received data and control information from the reception unit 22A. In addition to these, the control unit 23A performs various controls related to various transmission signals transmitted by the transmission unit 21A and various reception signals received by the reception unit 22A.

Further, the control unit 23A can control the transmission power of each transmission performed by each wireless communication in FIGS. 6 to 7 and FIGS. 9 to 10.

Specific examples of the process controlled by the control unit 23A include various processes executed in each wireless terminal in FIGS. The control unit 23A can control the power reduction amount determination process in FIGS. 6 to 7 and FIGS. 9 to 10. In FIGS. 6 to 7 and FIG. 9, the control unit 23A can control each process of reception of various formats of DCI including a TPC command and transmission of uplink data. The control unit 23A can control the interference detection process in FIGS. 6 to 7 and FIG. In FIG. 7, the control unit 23 </ b> A can control the transmission process of the transmission power reduction notification. In FIG. 9, the control unit 23 </ b> A can control processing for receiving a transmission power reduction request. In FIG. 10, the control unit 23A can control the transmission power temporary reduction notification transmission and the SRS transmission processing.

The transmitting unit 21B transmits a data signal and a control signal by second wireless communication via the antenna. The antenna may be common for transmission and reception.

The receiving unit 22B receives the data signal and the control signal transmitted from the radio base station by the second radio communication via the antenna.

The control unit 23B outputs data to be transmitted and control information to the transmission unit 21. In addition, the control unit 23 inputs data and control information received from the receiving unit 22.

For example, the control unit 23B detects the occurrence of interference in the second wireless communication based on the error characteristics of the received signal on the second wireless communication side when the first wireless communication and the second wireless communication are operating ( Alternatively, the deterioration of the communication performance in the second wireless communication is determined).

The control unit 23B notifies the measured reception signal level to the control unit 23A. The control unit 23B may determine deterioration of communication performance in the second wireless communication based on the measured received signal level and notify the determination result to the control unit 23A.

[Hardware Configuration of Each Device in Radio Communication System of Each Embodiment]
Based on FIGS. 14 to 15, the hardware configuration of each device in the wireless communication system of each embodiment and each modification will be described.

FIG. 14 is a diagram illustrating a hardware configuration of the radio base station 10. As shown in FIG. 14, the radio base station 10 includes, as hardware components, an RF (Radio Frequency) circuit 32 including an antenna 31, a CPU (Central Processing Unit) 33, and a DSP (Digital Signal Processor) 34, for example. And a memory 35 and a network IF (Interface) 36. The CPU is connected via a network IF 36 such as a switch so that various signals and data can be input and output. The memory 35 includes, for example, at least one of a RAM (Random Access Memory) such as SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), and a flash memory, and stores programs, control information, and data. The transmission unit 11 and the reception unit 12 are realized by the RF circuit 32 or the antenna 31 and the RF circuit 32, for example. The control unit 13 is realized by, for example, a CPU 33, a DSP 34, a memory 35, a digital electronic circuit (not shown), and the like. Examples of the digital electronic circuit include ASIC (Application Specific Integrated Circuit), FPGA (Field-Programming Gate Array), LSI (Large Scale Integration), and the like.

FIG. 15 is a diagram illustrating a hardware configuration of the wireless terminal 20. As illustrated in FIG. 15, the wireless terminal 20 includes, as hardware components,

RF circuits

42A and 42B each including antennas 41A and 41B,

CPUs

43A and 43B, and

memories

44A and 44B, for example. Further, the wireless terminal 20 may include a display device such as an LCD (Liquid Crystal Display) connected to the

CPUs

43A and 43B. The

memories

44A and 44B include at least one of RAM such as SDRAM, ROM, and flash memory, for example, and store programs, control information, and data. The transmitting unit 21A and the receiving unit 22A are realized by, for example, the RF circuit 42A, or the antenna 41A and the RF circuit 42A. The control unit 23A is realized by, for example, the CPU 43A, the memory 44A, a digital electronic circuit (not shown), and the like. Examples of digital electronic circuits include ASIC, FPGA, LSI, and the like. Similarly, the transmission unit 21B and the reception unit 22B are realized by, for example, the RF circuit 42B, or the antenna 41B and the RF circuit 42B. The control unit 23B is realized by a CPU 43B, a memory 44B, a digital electronic circuit (not shown), and the like.

1 wireless communication system 2 network 3 network device 10 wireless base station C10 cell 20 wireless terminal

Claims

The first control signal instructing to change or maintain the transmission power is repeatedly received from the other radio communication apparatus, and the transmission power of the first radio transmission to the other radio communication apparatus is received before the first radio transmission. A wireless communication device that determines based on the first control signal,
A wireless communication apparatus comprising a first wireless communication unit that performs the first wireless transmission with a second transmission power smaller than the first transmission power based on the determination.
The wireless communication device according to claim 1, wherein the first wireless communication unit further transmits a second control signal indicating that the first wireless transmission is performed with the second transmission power to the other wireless communication device.
A second wireless communication unit capable of receiving during transmission of the first wireless transmission;
The radio according to claim 1, wherein, when interference is detected in the second radio communication unit during transmission of the first radio transmission, the first radio communication unit performs the first radio transmission with the second transmission power. Communication device.
The first control signal indicates a change amount of transmission power within a predetermined value,
The radio communication apparatus according to claim 1, wherein the second transmission power is used to reduce an amount of transmission power that exceeds the predetermined value from the first transmission power.
A wireless communication device;
With other wireless communication devices,
The wireless communication device
A first control signal instructing to change or maintain the transmission power is repeatedly received from the other radio communication device, and the transmission power of the first radio transmission to the other radio communication device is received before the first radio transmission. A control unit for determining based on the first control signal,
A wireless communication system comprising: a first wireless communication unit that performs the first wireless transmission with a second transmission power smaller than the first transmission power based on the determination.
The wireless communication system according to claim 5, wherein the first wireless communication unit further transmits a second control signal indicating that the first wireless transmission is performed with the second transmission power to the other wireless communication device.
The wireless communication device further includes a second wireless communication unit capable of receiving during transmission of the first wireless transmission,
The radio according to claim 5, wherein when the second radio communication unit detects interference during transmission of the first radio transmission, the first radio communication unit performs the first radio transmission with the second transmission power. Communications system.
The first control signal indicates a change amount of transmission power within a predetermined value,
The wireless communication system according to claim 5, wherein the second transmission power is a value that reduces an amount of transmission power that exceeds the predetermined value from the first transmission power.
The first control signal instructing to change or maintain the transmission power is repeatedly received from the other radio communication apparatus, and the transmission power of the first radio transmission to the other radio communication apparatus is received before the first radio transmission. A wireless communication method in a wireless communication device that is determined based on the first control signal,
The radio | wireless communication method with which the 1st radio | wireless communication part with which the said radio | wireless communication apparatus is provided performs said 1st radio | wireless transmission with 2nd transmission power smaller than the 1st transmission power based on the said determination.
The wireless communication method according to claim 9, wherein the first wireless communication unit transmits a second control signal indicating that the first wireless transmission is performed with the second transmission power to the other wireless communication device.
In the second radio communication unit that can be received during transmission of the first radio transmission, when interference is detected during transmission of the first radio transmission, the first radio communication unit uses the second transmission power to The wireless communication method according to claim 9, wherein the first wireless transmission is performed.
The first control signal indicates a change amount of transmission power within a predetermined value,
The wireless communication method according to claim 9, wherein the second transmission power is to reduce an amount of transmission power that exceeds the predetermined value from the first transmission power.