JP2014093677A - Radio communication device and base station device - Google Patents

Abstract

Provided is a radio communication apparatus capable of improving the transmission rate or the throughput by improving the error rate as compared with a conventional radio communication apparatus by performing different transmission power control depending on the carrier frequency used for transmission. A wireless communication apparatus according to the present invention is a wireless communication apparatus that uses a first carrier frequency when transmitting a signal to a first base station apparatus, and is configured to transmit power control for setting transmission power. The transmission power control unit sends a predetermined signal to the second base station apparatus using a second carrier frequency that is not used when transmitting a signal to the first base station apparatus. When transmitting, the transmission power is set by adding a correction value to the transmission power determined when transmitting the predetermined signal using the first carrier frequency.
[Selection] Figure 3

Description

  The present invention relates to a radio communication apparatus and a base station apparatus.

  The 3GPP (The Third Generation Partnership Project), one of the standardization organizations, has developed 3GPP Long Term Evolution (LTE) Rel-10, one of the fourth generation mobile communication systems (LTE-A (LTE Standardization of LTE Rel-11, which is an extension of Rel-10, is now in progress.

  In the uplink of LTE Rel-11 (communication from a terminal device (UE: User Equipment) to a base station), a macro base station (macro area) that constitutes a macro cell (macro area) that covers an area in the same range as a conventional cellular system ( eNB: enhanced Node B) and LPN (Low Power Node, sometimes referred to as RRH: Radio Remote Head) that constitutes a small cell that covers a narrow range within a macro cell has been studied. ing. In a heterogeneous network, not only cell splitting gain (area splitting gain) obtained by using radio resources as independent cells for each of the macro base station and LPN, but also the transmission point or reception point cooperate. Thus, the influence of interference between the macro base station and the LPN or the interference between the LPN can be reduced. Such a technique is called CoMP (Coordinated Multi-Point transmission and reception), and specifications are currently being developed.

  Furthermore, the study of Rel-12, which is a successor standard of Rel-11, has been started, and it has been studied that a small cell performs transmission using a carrier frequency different from that of a macro cell (for example, Non-Patent Document 1). In this case, the macro base station can offload the data traffic to the small cell without being affected by interference from the macro base station. Therefore, by instructing a terminal device that requires high-speed data transmission to connect the macro base station to the LPN, traffic is offloaded, and the throughput (capacity) in the macro cell composed of the macro base station and the LPN Can be increased.

  Here, a terminal device that supports Rel-12 must support transmission of uplink signals using macro base stations and LPN frequencies. In addition, as in Rel-11, it is necessary for the macro base station and the LPN to support uplink signals using the same frequency. In this case, when the same carrier frequency as that of the macro base station is used for the uplink signal from the terminal device to the LPN, interference occurs with respect to the signal of the same carrier frequency in the macro cell, but when a different carrier frequency is used. Is a carrier frequency that is not used by the macro base station, and does not cause interference. Therefore, when considering the interference plane, when transmitting a signal with a carrier frequency different from that of the macro base station, the transmission quality is improved or transmitted by using higher transmission power than when transmitting a signal with the same carrier frequency. Use of MCS with a high rate becomes possible.

Ericsson, RWS-120003, 3GPP RAN Workshop on Rel-12 and onwards, June, 2012.

  However, since the terminal device generally sets the transmission power in consideration of the target reception power and path loss specified by the macro base station (or LPN), the interference is different depending on the carrier frequency as described above. There is a problem that it is not considered.

  The present invention has been made in view of the above circumstances. By performing different transmission power control depending on the carrier frequency used for transmission, the transmission rate is improved or the error rate is improved as compared with the conventional wireless communication apparatus. It is an object of the present invention to provide a radio communication apparatus and a base station apparatus that can improve the throughput according to the above.

  (1) The present invention has been made to solve the above-described problems, and one aspect of the present invention is a wireless communication that uses the first carrier frequency when transmitting a signal to the first base station apparatus. A transmission power control unit configured to set transmission power, wherein the transmission power control unit sets a second carrier frequency that is not used when transmitting a signal to the first base station device. When transmitting a predetermined signal to the second base station apparatus, a correction value is added to the transmission power determined when transmitting the predetermined signal using the first carrier frequency and transmitted. A wireless communication apparatus is characterized in that power is set.

  (2) According to another aspect of the present invention, there is provided the wireless terminal device, wherein the correction value includes at least one of the first base station device and the second base station device. A value notified from the apparatus is used.

  (3) According to another aspect of the present invention, the wireless terminal device is characterized in that the predetermined signal is a signal including at least one of SRS, a data signal, and a control signal. Do

  (4) Further, another aspect of the present invention is the above-described wireless terminal device, wherein the correction value is different depending on whether the predetermined signal is an SRS or a data signal. Characterized by

  (5) Moreover, the other aspect of this invention is a base station apparatus which receives SRS transmitted from a radio | wireless communication apparatus, Comprising: Based on the reception quality of the said SRS, the said radio | wireless communication apparatus is a data signal with respect to an own station. When the carrier frequency used for transmission of the data signal is the first carrier frequency and the second carrier frequency, the scheduling unit for determining the MCS to be applied when transmitting the data signal is provided. The base station apparatus is characterized in that the selection criteria for MCS are different.

  By using the radio terminal apparatus according to the present invention, in a radio communication system composed of a macro base station, an LPN, and a radio terminal apparatus, the throughput in the uplink for transmitting signals from the radio terminal apparatus to the LPN or the macro base station is improved. can do.

1 is a schematic diagram of a cellular system according to a first embodiment of the present invention. It is the schematic which shows the interference which generate | occur | produces in the cellular system based on the 1st Embodiment of this invention. It is a block diagram which shows the simple structure of the terminal device which can be used in the 1st Embodiment of this invention. It is a flowchart which shows the operation | movement in the transmission power control part 26 which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the simple structure of the terminal device which can be used by the 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement in the transmission power control part 41 which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows another operation | movement in the transmission power control part 41 which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the simple structure of LPN which can be used in the 3rd Embodiment of this invention. It is a table which can be used by the scheduling part 85 which concerns on the 3rd Embodiment of this invention. It is another table which can be used by the scheduling part 85 which concerns on the 3rd Embodiment of this invention.

[First Embodiment]
In the first embodiment, the carrier frequency used to transmit a sounding reference signal (SRS) for measuring the transmission quality between the terminal device and the LPN is the transmission quality between the terminal device and the macro base station. The form which correct | amends the transmission power allocated when different from the carrier frequency used for transmission of SRS for measuring SRS is shown.

  FIG. 1 is a schematic diagram of a cellular system according to a first embodiment of the present invention. In FIG. 1, the macro base station 1 configures a macro cell 10 that is an area covering a wide area as in the conventional cellular system. Further, a low power base station 2 (hereinafter referred to as LPN 2) is installed in a macro cell 10 formed by the macro base station 1, and the LPN 2 constitutes a small cell 11 having a small cell radius in the macro cell 10. Here, as an example, the macro base station 1 constituting the macro cell 10 uses 2 GHz as a carrier frequency for transmission, and the LPN 2 constituting the small cell 11 uses the 2 GHz band or the 3.5 GHz band as the carrier frequency. However, this is an example, and other carrier frequencies may be used for the macro base station 1 and the LPN 2. The invention also includes the case where the LPN uses only the 3.5 GHz band, instead of using a plurality of carrier frequencies as described above. The terminal device 3 transmits SRS to the macro base station 1 or the LPN 2 when uplink data is generated. The macro base station 1 or LPN 2 that has received the SRS measures the transmission quality, assigns frequencies when the terminal device 3 performs uplink data transmission to the own station, the modulation multi-level number, and the error correction code coding rate ( The MCS (Modulation and Coding Scheme) is generally determined as the modulation multi-value number and coding rate, and the allocated frequency information and MCS are notified to the terminal device 3 as control information. Then, the terminal device 3 generates a data signal based on the received control information, arranges it at the assigned frequency, and transmits the data signal.

  Here, consider a case where the second terminal apparatus 4 exists in the macro cell 10 not included in the small cell 11 and transmits the SRS 12 to the macro base station using the 2 GHz band as shown in FIG. In this situation, the terminal device 3 is connected to the LPN 2 and transmits the SRS 13 to the LPN 2. Since the SRS 13 is transmitted at the same frequency, the macro base station 1 receives the SRS 13 as the interference signal 14. In this case, the accuracy of channel sounding performed by the macro base station 1 using the SRS 12 is degraded by the interference signal 14. Therefore, when the SRS 13 is transmitted in order to suppress the influence of the interference signal 14, it is necessary to limit the transmission power. However, when the SRS 13 is a signal in the 3.5 GHz band, the interference signal 14 does not interfere with the SRS 12, so that a higher signal power can be set than in the case of the same frequency.

  Next, an SRS transmission method will be described. One or more terminal devices 3 connected to the macro base station 1 or the LPN 2 (hereinafter collectively referred to as a base station) transmit SRS to the base station in a predetermined subframe. As a transmission method of SRS, P-SRS (Periodic SRS) periodically transmitted in the subframe using a predetermined SRS bandwidth, and a base station dynamically instructs (triggers) when necessary, There are two methods of A-SRS (Aperiodic SRS) in which SRS is transmitted only at that timing, but any method is included in the present invention. The transmission method and SRS bandwidth are determined between the base station and each terminal device 3.

  Here, when the LPN 2 supports a plurality of carrier frequencies in the 2 GHz band and the 3.5 GHz band, in the terminal device 3, the SRS is arranged only in the carrier frequency band specified by the LPN 2. However, the SRS may be arranged simultaneously or sequentially in all the carrier frequency bands without specifying the carrier frequency at which the LPN 2 transmits the SRS. Alternatively, when there is no instruction from the LPN, the terminal device 3 can arrange the SRS only at 3.5 GHz, and when it receives the instruction, the terminal apparatus 3 can arrange the SRS at 2 GHz.

  Below, the control method of the transmission power allocated to SRS in the terminal device 3 is shown. In LTE Rel-10, the SRS transmission power for the macro base station is determined by equation (1).

However, min (A, B) indicates that A and B take the minimum value. In addition, i in parentheses indicates a subframe number. P _{CMAX, c} is the maximum transmission power that can be used by the terminal apparatus 3 in the cell c, and P _{SRS_OFFSET, c} is the target received power of the SRS with respect to the transmission power assigned to the shared data channel (PUSCH) in the cell c. Power ratio (offset value for target received power of _SRS ), M _{SRS, c} represents the number of resource blocks (RB) used for SRS transmission in cell c. In 3GPP, 1 RB is composed of 12 subcarriers, but in the present invention, the number of subcarriers included in the resource block is not limited. _{PO_PUSCH, c} is the nominal target received power (nominal target received power) of the data signal per RB in cell c, and α _{, c} is multiplied by the path loss value to compensate for the path loss in cell c. A coefficient of 1 or less, PL 1 _{and c} are path loss values measured from a downlink reference signal (RS) using the cell c, and f 1 _{and c} are transmission powers dynamically notified from the base station for the cell c Correction value (also referred to as TPC (Transmission Power Control) command).

  In this embodiment, when transmitting SRS with respect to a macro base station and LPN, Formula (2) is used instead of Formula (1).

However, Δ _{B_SRS} (F _BAND ) is a correction value that varies depending on the carrier frequency F _BAND (GHz) used for transmission of SRS. Δ _{B_SRS} (F _BAND ) may be determined in advance by the system, may be notified from the LPN or the macro base station, and set via an upper layer (specifically, RRC (Radio Resource Control)) May be. When defined by the system, Δ _{B_SRS} (F _BAND ) is set as shown in Expression (3).

In the case of Expression (3), when SRS is transmitted in the 2 GHz band used in the macro base station 1, the correction by Δ _{B_SRS} (F _BAND ) is not performed, and the SRS is transmitted in the 3.5 GHz band different from the macro base station 1. In this case, the transmission power is increased by 3 dB by Δ _{B_SRS} (F _BAND ). On the other hand, when a correction value is not defined by the system, Δ _{B_SRS} (F _BAND ) is set as shown in Expression (4) when a value notified from LPN 2 or macro base station 1 is used.

However, X _{B_SRS} is a value notified from LPN 2 or macro base station 1. This is suitable when the value can be set by deployment because the frequency that can be operated differs depending on the country and the operator. In the case of Expression (4), when SRS is transmitted in the 2 GHz band used in the macro base station 1, correction by Δ _{B_SRS} (F _BAND ) is not performed, and SRS is transmitted in the 3.5 GHz band different from the macro base station 1. When doing so, the transmission power is corrected by the value of _{XB_SRS} notified from the LPN 2 or the macro base station 1.

However, in Expression (3) and Expression (4), Δ _{B_SRS} (2) = 0, but an arbitrary value different from Δ _{B_SRS} (3.5) may be set.

  Further, in the present embodiment, the form in which Expression (2) is applied when signals are transmitted to the macro base station 1 and the LPN 2 is shown. However, when signals are transmitted to the macro base station 1, Expression (1) is used. ) May be applied.

  By controlling as in Expression (3) and Expression (4), when the terminal device 3 transmits SRS to the LPN 2, the macro base station 1 is compared with the case where 2 GHz that causes interference with the macro base station 1 is used. It is possible to set a high transmission power when using the 3.5 GHz band that does not cause interference with the transmission. Further, the LPN 2 determines the MCS when the terminal device 3 transmits a data signal to the own station based on the received power of the SRS. Therefore, based on the received power increased in the 3.5 GHz band, the LPN 2 selects an MCS with a higher transmission rate for the terminal device 3. Thereby, the terminal device 3 can improve the transmission rate in the case of using the 3.5 GHz band when transmitting the data signal as compared with the case of the 2 GHz band.

  FIG. 3 shows an example of the configuration of the terminal device 3 according to the first embodiment of the present invention. The terminal device 3 includes an SRS generation unit 21, a signal selection unit 22, an IDFT unit 23, a CP insertion unit 24, a radio transmission unit 25, a transmission power control unit 26, a transmission antenna 27, a reception antenna 28, a radio reception unit 29, and a reception signal. It comprises a separation unit 30 and a data signal generation unit 31. In the figure, one transmitting antenna 27 and one receiving antenna 28 are provided, but a plurality of antennas may be provided. One antenna may have the functions of the transmission antenna 27 and the reception antenna 28.

Although not shown, the terminal device 3 connected to the macro base station 1 or the LPN 2 is notified of information about the RS sequence and sequence length information necessary for generating an SRS through an upper layer, and is input to the SRS generating unit 21. Is done.
The SRS generating unit 21 generates an SRS based on information on the RS data length that is set in advance or input. Further, the generated SRS is arranged at a preset frequency and input to the signal selection unit 22.

  The signal selection unit 22 receives a frequency domain data signal from the data signal generation unit 31 and a frequency domain SRS from the SRS generation unit 21. The transmission timing (also referred to as subframe) of the data signal and the SRS is determined with the macro base station 1 or LPN2 that is the receiving station, and the signal selection unit 22 uses the determined signal in the subframe. Is input to the IDFT unit 23. However, although not shown, the signal selection unit 22 receives an uplink control signal and the like in addition to the data signal and SRS, and may similarly input the IDFT unit 23 in a predetermined subframe.

The IDFT unit 23 performs IDFT (Inverse Discrete Fourier Transform) on the input frequency domain signal, converts the frequency domain signal into a time domain signal, and inputs the signal to the CP insertion unit 24.
The CP insertion unit adds a cyclic prefix (CP) to the input time domain signal and then inputs the signal to the wireless transmission unit 25. The wireless transmission unit 25 performs D / A (Digital to Analog) conversion and up-conversion to a carrier frequency on the signal input from the wireless transmission unit, and inputs the signal to the transmission power control unit 26.

The transmission power control unit 26 sets the transmission power of the input signal and amplifies it using an amplifier. A transmission power control method will be described with reference to the flowchart of FIG. The transmission power control unit 26 identifies whether the input signal is an SRS (S1). If the input signal is an SRS (S1-YES), the transmission power control unit 26 formulas according to the carrier frequency F _BAND to which the SRS is assigned. (3) (or Expression (4)) is used to set Δ _{B_SRS} (F _BAND ) (S2). Furthermore, the transmission power control unit 26 substitutes the set Δ _{B_SRS} (F) into the equation (2) to set the transmission power of the SRS. If the input signal is a data signal (S1-NO), arbitrary transmission power control may be performed, but here, the transmission power of the data signal is set by equation (5) (S4).

Where M _{PUSCH, c} is the data signal allocation bandwidth in units of RB in cell c, and Δ _{TF, c} is a correction value for compensating the required received power of MCS set for each cell c. Therefore, in this embodiment, when transmitting a data signal, even when transmission power is not corrected according to the carrier frequency, the transmission power of the data signal is reduced by selecting a higher MCS according to the received power of SRS. It changes according to MCS. The amplified signal is transmitted from the transmitting antenna 27 to the receiving station.

Further, in the terminal device 3 of FIG. 3, a signal transmitted from the macro base station 1 or LPN 2 that is the transmission destination of the SRS is input to the radio reception unit 29 via the reception antenna 28. The radio reception unit 29 performs processing such as down-conversion from the carrier frequency to the baseband, A / D (Analog to Digital) conversion, and the like, and inputs the received signal to the reception signal separation unit 30.
The reception signal separation unit 30 extracts control information indicating the MCS and the allocated band used when the terminal device 3 transmits a signal from the reception signal, and inputs the control information to the data signal generation unit 31.

  The data signal generator 31 performs error correction coding, modulation processing, and the like on the transmission data based on the control information input from the received signal separator 30, and generates a frequency domain data signal to generate a signal selector. 22 is input.

However, in the present embodiment, the terminal device 3 performs transmission power correction by Δ _{B_SRS} (F _BAND ) using Equation (2) when transmitting the SRS to the LPN 2, but performs the same processing. Different methods may be used if present. For example, as one method, even when SRS is transmitted to LPN2, Equation (1) is used similarly to the transmission power control in LTE Rel-10, and the target reception power is obtained when the 3.5 GHz band is used. It is conceivable to read _{PO_PUSCH} as a different value. The _{PO_PUSCH} is notified to the terminal device 3 from the LPN2 that is the receiving station through the upper layer, but the terminal device 3 transmits the SRS by interpreting the notified value as a different value between the 2 GHz band and the 3.5 GHz band. Different transmission powers can be set according to the carrier frequency. As a replacement method, the terminal device 3 may add a predetermined value to _{PO_PUSCH} , or the terminal device 3 holds a correction value corresponding to _{PO_PUSCH} as a table and _replaces it according to the table. Also good.

  As described above, by using this embodiment, it is possible to increase the reception power when transmitting the SRS from the terminal apparatus to the LPN at a carrier frequency different from that of the macro cell, and it is possible to improve the reception quality of the SRS and to improve the data transmission. The MCS can be set high and the transmission rate can be improved.

[Second Embodiment]
In 1st Embodiment, when the terminal device transmitted SRS to LPN, the form which correct | amends transmission power according to the carrier frequency to be used was shown. In the second embodiment, when the terminal device transmits a data signal to the LPN, the transmission power is corrected according to the carrier frequency to be used.

  The cellular system according to the second embodiment of the present invention is the same as that of FIG. 1 in the first embodiment. The terminal device 3 transmits the SRS using the macro base station 1 or the LPN 2 as a receiving station separately from the data transmission. The receiving station that has received the SRS measures the transmission quality, assigns a frequency to the terminal device 3 and determines the MCS, and notifies the terminal device 3 as control information. The terminal device 3 generates a data signal according to the notified control information, and transmits the data signal to the receiving station.

  A method for controlling the transmission power allocated to the data signal in the terminal device 3 will be described below. In LTE Rel-10, the transmission power of the data signal to the macro base station is determined by Equation (5). In this embodiment, Equation (6) is used when transmitting a data signal to the macro base station and the LPN.

However, Δ _{B_PUSCH} (F _BAND ) is a correction value that varies depending on the carrier frequency F _BAND used for transmitting the data signal. Δ _{B_PUSCH} (F _BAND ) may be determined in advance by the system, or may be notified from the LPN 2 or the macro base station 1. When it is determined by the system, Δ _{B_PUSCH} (F _BAND ) is set as shown in Expression (7).

In the case of Expression (7), when a data signal is transmitted in the 2 GHz band used in the macro base station 1, correction by Δ _{B_PUSCH} (F _BAND ) is not performed, and when a data signal is transmitted in the 3.5 GHz band, Δ _This means that the transmission power is increased by 3 dB by _{B_PUSCH} (F _BAND ). On the other hand, when the value notified from the LPN 2 is used, Δ _{B_PUSCH} (F _BAND ) is set as shown in Expression (8).

However, _{XB_PUSCH} is a value notified from LPN2. In the case of Expression (8), when data signals are transmitted in the 2 GHz band used in the macro base station 1, correction by Δ _{B_PUSCH} (F _BAND ) is not performed, and when data signals are transmitted in the 3.5 GHz band, LPN2 This means that the transmission power is corrected by the value of _{XB_PUSCH} notified from the above.

However, although Δ _{B_PUSCH} (2) = 0 in Equation (7) and Equation (8), an arbitrary value different from Δ _{B_PUSCH} (3.5) may be set.
Further, in the present embodiment, the form in which Expression (6) is applied when signals are transmitted to the macro base station 1 and the LPN 2 is shown. However, when signals are transmitted to the macro base station 1, Expression (5) is used. ) May be applied.

  By controlling as in Expression (7) and Expression (8), when the terminal device 3 transmits a data signal to the LPN 2, the terminal apparatus 3 transmits higher when using the 3.5 GHz band than when using 2 GHz. Set the power. Thereby, the terminal device 3 can transmit a data signal so that the reception power in LPN2 becomes high when the carrier frequency which does not become interference to a macro cell is used, and can improve reception quality.

  FIG. 5 shows the configuration of the terminal device 3 according to the second embodiment of the present invention. The terminal device 3 of FIG. 5 has the same configuration as the terminal device 3 of FIG. 3 shown in the first embodiment, except that the transmission power control unit 26 is a transmission power control unit 41. Since the other blocks having the same reference numerals have the same functions, the description thereof is omitted here.

The transmission power control unit 41 sets the transmission power of the input signal and amplifies it using an amplifier. A transmission power control method will be described with reference to the flowchart of FIG. The transmission power control unit 41 identifies whether the input signal is a data signal (S11). However, although it is defined as SRS when it is not a data signal in S11, different processing may be performed in the case of other signals such as a control signal. If it is a data signal (S11-YES), Δ _{B_PUSCH} (F _BAND ) is set using Expression (7) (or Expression (8)) according to the carrier frequency F _BAND to which the data signal is assigned. (S12). Further, the transmission power control unit 41 substitutes the set Δ _{B_PUSCH} (F _BAND ) into the equation (6) to set the transmission power of the data signal. When the input signal is SRS (S11-NO), the transmission power control unit 41 may perform arbitrary transmission power control, but here, the transmission power of SRS is set according to Equation (1) (S14). ). The amplified signal is transmitted from the transmitting antenna 27 to the receiving station.

  As described above, according to the method shown in the present embodiment, it is possible to improve the reception quality of the data signal by setting the transmission power when transmitting the data signal from the terminal device to the LPN at a carrier frequency different from that of the macro cell. it can.

However, in the second embodiment, the case where the terminal apparatus corrects the transmission power of only the data signal according to the carrier frequency for transmitting the signal to the LPN has been described. However, transmission power control for correcting the transmission power of SRS and data signals is also conceivable. FIG. 7 shows a flowchart when the transmission power control is applied to the transmission power control unit 41 of FIG. The flowchart in FIG. 7 is different from the flowchart in FIG. 6 in the process in the case of S11-NO, and will be described below. When the input signal is an SRS, the transmission power control unit 41 uses Δ _{B_SRS} (F _BAND ) using Expression (3) (or Expression (4)) according to the carrier frequency F _BAND to which the SRS is assigned. Is set (S2). Further, the transmission power control unit 41 substitutes the set Δ _{B_SRS} (F _BAND ) into the equation (2) to set the transmission power of the SRS. Here, when the transmission power control unit 41 increases the transmission power of the SRS when the terminal device 3 uses a carrier frequency different from that of the macro cell, the MCS set in the data signal becomes higher, and Δ _{B_PUSCH} (F _BAND ) The transmission power of the data signal increases even when not using. Therefore, it is preferable that Δ _{B_PUSCH} (F _BAND ) and Δ _{B_SRS} (F _BAND ) are set individually. However, since the notice information reductions from base station, _{X B_PUSCH} in Formula _{X B_SRS} and formula in (4) (8) may be the same information.

  However, in the first embodiment and the second embodiment, the form in which the correction value is used in the control of the transmission power of the data signal and the SRS has been described, but it can be similarly applied to other signals. For example, in LTE Rel-10, the transmission power of an uplink control signal (referred to as PUCCH (Physical Uplink Control Channel)) for a macro base station is set by Expression (9) in the transmission power control unit of the terminal device.

However, P _{0_PUCCH} is a target received power serving as a reference at the receiving station, Δ _{F_PUCCH} (F) is a correction value determined by the PUCCH format, and h (n _CQI , n _HARQ , n _SR ) is in a specified format. A correction value based on the number of transmission bits, Δ _TxD (F ′) is a correction value determined by whether or not transmission antenna diversity is performed, and g (i) is a transmission power control value based on a TPC command.

  On the other hand, in the present invention, when an uplink control signal is transmitted to the macro base station 1 and the LPN 2, the transmission power of the control signal is set by the transmission power control unit by Expression (10).

However, Δ _{B_PUCCH} (F _BAND ) is a correction value that varies depending on the carrier frequency F _BAND used for transmission of the uplink control signal. Δ _{B_PUCCH} (F _BAND ) may be determined in advance by the system, or may be notified from the LPN 2 or the macro base station 1. When determined by the system, Δ _{B_PUCCH} (F _BAND ) is set as shown in Expression (11) in the transmission power control unit.

In the case of Expression (11), when an uplink control signal is transmitted in the 2 GHz band used in the macro base station 1, correction by Δ _{B_PUCCH} (F _BAND ) is not performed, but in a 3.5 GHz band different from the macro base station 1. When transmitting an uplink control signal, the transmission power is increased by 3 dB by Δ _{B_PUCCH} (F _BAND ). On the other hand, when using the value notified from _LPN2 , Δ _{B_PUCCH} (F _BAND ) is set as shown in Expression (12) in the transmission power control unit.

However, _{XB_PUCCH} is a value notified from LPN2. In the case of Expression (12), when an uplink control signal is transmitted in the 2 GHz band used in the macro base station 1, correction by Δ _{B_PUCCH} (F _BAND ) is not performed, but in a 3.5 GHz band different from the macro base station 1. When transmitting an uplink control signal, the transmission power is corrected by the value of _{XB_PUCCH} notified from _LPN2 .

However, in Expression (11) and Expression (12), Δ _{B_PUCCH} (2) = 0, but an arbitrary value different from Δ _{B_PUCCH} (3.5) may be set.
Further, in the present embodiment, the form in which Expression (10) is applied when signals are transmitted to the macro base station 1 and the LPN 2 is shown, but when the signal is transmitted to the macro base station 1, Expression (9) is used. May be applied.

  By controlling as in Expression (11) and Expression (12), the terminal device 3 transmits a uplink control signal to the LPN 2, compared with a case where 2 GHz that causes interference with the macro base station 1 is used. When a 3.5 GHz band that does not cause interference with the base station 1 is used, a high transmission power is set. As a result, the terminal device 3 can transmit an uplink control signal so that the reception power at the LPN 2 becomes high when a carrier frequency that does not cause interference with the macro cell is used, and the reception quality can be improved.

[Third Embodiment]
In the first embodiment, when a signal is transmitted from the terminal device to the LPN at a carrier frequency different from that of the macro cell, the terminal device improves the SRS reception quality by setting the SRS transmission power high, and from the terminal device. In this example, the MCS for uplink data transmission, that is, the transmission rate is set high.

  In the third embodiment of the present invention, the SRS transmission method according to the first embodiment is not applied, and the LPN 2 that receives the SRS sets a different MCS depending on the carrier frequency. However, in this embodiment, the apparatus for setting the MCS is preferably an LPN, but the same processing can be applied to the macro base station 1 as well.

  FIG. 8 shows an example of the configuration of the LPN 2 according to the third embodiment of the present invention. LPN 2 includes a reception antenna 81, a radio reception unit 82, a reception signal separation unit 83, a propagation path estimation unit 84, a scheduling unit 85, a control signal generation unit 86, a radio transmission unit 87, and a transmission antenna 88. In the figure, one reception antenna 81 and one transmission antenna 88 are provided, but a plurality of reception antennas 81 and transmission antennas 88 may be provided. In addition, one antenna may have the functions of the reception antenna 81 and the transmission antenna 88.

The radio reception unit 82 performs processing such as down-conversion from carrier frequency to baseband, A / D conversion, and the like on the signal from one or more terminal devices received by the reception antenna 81, and the received signal separation unit 83 input.
The reception signal separation unit 83 extracts an SRS used when measuring reception quality from the input reception signals and inputs the SRS to the propagation path estimation unit 84.
The propagation path estimation unit 84 measures the reception quality of the signal transmitted from the transmission antenna of the terminal device serving as the transmission station using the input SRS at the reception antenna 81 of the local station, and determines the propagation path characteristics (referred to as frequency response). Estimated). The estimated value is calculated for each terminal device and input to the scheduling unit 85.

  The scheduling unit 85 receives a channel estimation value corresponding to one or more terminal devices connected to the own station from the channel estimation unit 84, and uses the channel estimation value to use a frequency used by the terminal device in uplink data transmission. Assignment and MCS determination. For the frequency allocation, existing scheduling such as Round Robin (RR) or Proportional Fairness (PF) is applied. The determination of MCS will be described later. The scheduling unit 85 inputs an allocation frequency and an index indicating MCS determined for each corresponding terminal device to the control signal generation unit 86.

The control signal generation unit 86 generates a control signal for notifying the terminal device of the input allocation frequency information and MCS information, allocates a predetermined frequency resource of a predetermined subframe, and inputs the control signal to the radio transmission unit 87. To do.
The radio transmission unit 87 performs D / A conversion and up-conversion to a carrier frequency, and transmits a control signal from the transmission antenna 88 to each terminal device.

  Hereinafter, an MCS determination method in the scheduling unit 85 will be described. The scheduling unit 85 determines the MCS using the channel estimation value input from the channel estimation unit 84. When the carrier frequency used here is the same as the carrier frequency used in the macro cell, the SINR (Signal to Interference and Noise power Ratio) expressed by Equation (13) is used as the propagation path estimation value. Use.

Here, SINR _measured is a SINR calculated from a propagation path estimation value input from the propagation path estimation unit 84. On the other hand, when the carrier frequency to be used is a carrier frequency different from that of the macro cell, higher transmission power can be set. Therefore, SINR represented by Expression (14) is used as the propagation path estimation value.

However, OFFSET _BAND is a correction value assuming that data transmission is performed using higher transmission power in the terminal device.

The scheduling unit 85 selects the MCS by comparing the SINR calculated by the equation (13) or the equation (14) with the table shown in FIG. 9 according to the assigned carrier frequency. FIG. 9 is a table showing the correspondence between SINR, MCS (modulation scheme and coding rate), and MCS index indicating the MCS when six types of MCS can be selected. For example, “SINR <R ₁ ”. In some cases, MCS index I _MCS = 0 indicating QPSK and coding rate 1/2 is selected. R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are MCS selection threshold values, respectively, and are predetermined by the system. However, when the carrier frequency to be used is a carrier frequency different from that of the macro cell, the threshold values R ₁ , R ₂ , R ₃ , R ₄ are used after using the SINR of Equation (13) instead of the SINR of Equation (14). can also be used to determine the MCS on obtained by subtracting the value of the _{OFFSET BAND} from _{R 5} performs the same processing.

  In this way, when using a carrier frequency different from that of the macro cell, a higher MCS is selected by correcting the SINR value, which is a reference for MCS selection, higher than when using the same carrier frequency, and the terminal device changes to the LPN. The transmission rate of data transmission can be improved.

However, although it is necessary for the terminal device 3 to set the required transmission power high by selecting a higher MCS, the formula (5) that is the conventional transmission power control formula shown in the first embodiment is used. optionally even delta _TF can be set higher transmission power in accordance with the MCS.

However, in the above, the scheduling unit 85 always uses the MCS selection table of FIG. 9 and corrects the SINR value used as a parameter. However, depending on whether the same carrier frequency as that of the macro cell is used, Different tables may be used in the scheduling unit 85. For example, the scheduling unit 85 determines the MCS using the table of FIG. 9 when using the same carrier frequency as the macro cell, and determines the MCS using the table of FIG. 10 when using a different carrier frequency. . The table of FIG. 10 has threshold values R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , and R _{15 as} compared to the table of FIG. 9, and QPSK coding rate 1/2 is deleted from the selectable MCS. , 64QAM coding rate ½ is added. By using different tables in this way, it is possible to select an MCS that is assumed to use higher transmission power without increasing control information. In addition, when the 64QAM coding rate 1/2 is not added in the table of FIG. 10, the types of MCS indexes can be reduced, so that the amount of control information can be suppressed.

  The program that operates in the terminal device, the macro base station, and the LPN related to the present invention is a program (a program that causes a computer to function) that controls the CPU and the like so as to realize the functions of the above-described embodiments related to the present invention. Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU, and corrected and written as necessary. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient.

  In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized. In the case of distribution in the market, the program can be stored and distributed in a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention.

  Moreover, you may implement | achieve part or all of the terminal device, macro base station, and LPN in embodiment mentioned above as LSI which is typically an integrated circuit. Each functional block of the terminal device, the macro base station, and the LPN may be individually chipped, or a part or all of them may be integrated into a chip. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and the like within the scope not departing from the gist of the present invention are also claimed. Included in the range. For example, in the present invention, the embodiment is divided into three, but may be configured by combining two or more embodiments.

  The present invention is suitable for use in a wireless terminal device, a wireless communication system, and a wireless communication method.

DESCRIPTION OF SYMBOLS 1 ... Macro base station, 2 ... LPN, 3 ... Terminal device, 4 ... 2nd terminal device,
10 ... macro cell, 11 ... small cell, 12 ... SRS, 13 ... SRS, 14 ... interference signal,
DESCRIPTION OF SYMBOLS 21 ... SRS production | generation part, 22 ... Signal selection part, 23 ... IDFT part, 24 ... CP insertion part, 25 ... Wireless transmission part, 26 ... Transmission power control part, 27 ... Transmission antenna, 28 ... Reception antenna, 29 ... Radio reception , 30... Reception signal separation unit, 31... Data signal generation unit,
41 ... transmission power control unit,
DESCRIPTION OF SYMBOLS 81 ... Reception antenna, 82 ... Radio reception part, 83 ... Reception signal separation part, 84 ... Propagation path estimation part, 85 ... Scheduling part, 86 ... Control signal generation part, 87 ... Radio transmission part, 88 ... Transmission antenna

Claims (5)

A wireless communication device that uses a first carrier frequency when transmitting a signal to a first base station device,
A transmission power control unit for setting transmission power;
When the transmission power control unit transmits a predetermined signal to the second base station apparatus using a second carrier frequency that is not used when transmitting a signal to the first base station apparatus, A wireless communication apparatus, wherein a transmission power is set by adding a correction value to transmission power determined when transmitting the predetermined signal using the first carrier frequency.   The radio communication apparatus according to claim 1, wherein a value notified from at least one of the first base station apparatus and the second base station apparatus is used as the correction value.   The wireless communication apparatus according to claim 1, wherein the predetermined signal is a signal including at least one of an SRS, a data signal, and a control signal.   The wireless communication apparatus according to claim 3, wherein the correction value uses a different value depending on whether the predetermined signal is an SRS or a data signal. A base station device that receives an SRS transmitted from a wireless communication device,
A scheduling unit that determines an MCS to be applied when the wireless communication apparatus transmits a data signal to the local station based on the reception quality of the SRS;
The base station characterized in that the scheduling unit uses different MCS selection criteria depending on whether the carrier frequency used for transmission of the data signal is the first carrier frequency or the second carrier frequency. Station equipment.