WO2017022108A1 - 無線送信装置 - Google Patents
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- WO2017022108A1 WO2017022108A1 PCT/JP2015/072269 JP2015072269W WO2017022108A1 WO 2017022108 A1 WO2017022108 A1 WO 2017022108A1 JP 2015072269 W JP2015072269 W JP 2015072269W WO 2017022108 A1 WO2017022108 A1 WO 2017022108A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
- H04B7/0621—Feedback content
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- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
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- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
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- H04B7/046—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account
- H04B7/0465—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account
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- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
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- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2646—Arrangements specific to the transmitter only using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
Definitions
- the present invention relates to a wireless transmission device that performs spatial multiplexing transmission of data using a plurality of antennas.
- MIMO Multiple Input Multiple Output
- Wireless transmitters require a high power amplifier (HPA) to radiate signals from the antenna.
- HPA high power amplifier
- Multi-carrier systems such as OFDM (Orthogonal Frequency Division Multiplexing) are used as radio transmission systems suitable for large-capacity transmission, but this system uses a large PAPR (Peak to Average Power Ratio, peak power vs. average power value). It is known to have.
- PAPR Peak to Average Power Ratio, peak power vs. average power value
- Non-Patent Document 1 PAPR is suppressed by applying a time filter to an instantaneous value of a waveform having a large time fluctuation, thereby mitigating the influence on the amplifier.
- Non-Patent Document 2 assuming a MU (Multi User) -MIMO system, the transmission side is calculated from the back-off of the HPA using the CNR (Carrier and Noise power Ratio) fed back from the reception side.
- CNR Carrier and Noise power Ratio
- a method for adaptively controlling backoff by predictive CINR Carrier and Interference Noise power Ratio
- the present invention has been made in view of the above, and an object of the present invention is to obtain a wireless transmission device capable of controlling input back-off of a high power amplifier.
- a wireless transmission device includes a plurality of antennas having amplifiers, and a transmission signal generation unit that generates a signal to be transmitted to a terminal via the antennas. Prepare.
- the wireless transmission device includes a weighting processing unit that performs weighting processing on a signal transmitted to the terminal generated by the transmission signal generating unit based on transmission path information between the terminal and the output limit value of the amplifier. Prepare.
- FIG. 1 is a diagram illustrating a configuration example of a wireless transmission device according to a first embodiment; A flowchart showing an operation example of the precoder unit according to the first embodiment. Flowchart showing an operation example of the maximum power calculation unit of the first embodiment. A flowchart showing an operation example of the correction value selection unit of the first embodiment.
- FIG. 10 is a diagram illustrating an example of a wireless communication system to which the wireless transmission device according to the second embodiment is applied.
- the figure which shows the structural example of the radio
- FIG. The flowchart which shows an example of the operation
- FIG. 1 is a diagram of a configuration example of a wireless transmission device according to the first embodiment of the present invention. 1 configures a base station of a mobile communication system, for example, and forms one or more beams to each of a plurality of users, that is, mobile terminals (hereinafter referred to as terminals). Provides a function to spatially multiplex signals addressed to users and transmit them simultaneously (including multi-user MIMO and single-user MIMO).
- the wireless transmission device constitutes a base station of a mobile communication system will be described.
- the radio transmitting apparatus 100 includes a modulation unit 1 1 to 1 Ns , a serial-parallel conversion unit (S / P unit) 2 1 to 2 Ns , an FFT (Fast Fourier Transform). ) Section 3 1 to 3 Ns , precoder section 4, IFFT (Inverse Fast Fourier Transform) section 5 1 to 5 Nt , parallel-serial conversion section (P / S section) 6 1 to 6 Nt , multipliers 7 1 to 7 Nt , A maximum power calculator 8, a correction value selector 9, and antennas 10 1 to 10 Nt .
- Ns indicates the number of signal streams to be spatially multiplexed.
- the modulation unit 1 1 ⁇ 1 Ns, the serial - parallel converter 2 1 ⁇ 2 Ns and FFT unit 3 1 ⁇ 3 Ns operates as a transmission signal generating unit.
- the precoder unit 4, the maximum power calculation unit 8, and the multipliers 7 1 to 7 Nt operate as weighting processing units.
- the maximum power calculation unit 8 and the multipliers 7 1 to 7 Nt constitute a power correction unit of a weighting processing unit.
- the precoder unit 4 is composed of a plurality of precoders 41, and the antennas 10 1 to 10 Nt that are array antennas are composed of a plurality of array elements 11.
- Each array element 11 includes a phase shifter 11A and an HPA (High Power Amplifier) 11B, and can adjust the phase and amplitude of a signal to be transmitted.
- the HPA 11A is an amplifier included in the antennas 10 1 to 10 Nt .
- this invention is not limited to the case where a multicarrier signal is transmitted, It can apply also when transmitting a single carrier signal. It is.
- Modulators 1 1 to 1 Ns modulate input signal streams # 1 to #Ns according to a predetermined modulation scheme such as QPSK (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation).
- a predetermined modulation scheme such as QPSK (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation).
- the serial-parallel conversion units 2 1 to 2 Ns perform serial-parallel conversion on the input signals from the modulation units 1 1 to 1 Ns and output the signals to the FFT units 3 1 to 3 Ns .
- FFT unit 3 1 ⁇ 3 Ns is serial - converts the signal input from the parallel converting section 2 1 ⁇ 2 Ns from a signal on a time axis into a signal on a frequency axis, and outputs it to the precoder unit 4.
- the frequency-axis signals output from the FFT units 3 1 to 3 Ns are input to the corresponding precoder 41 of the precoder unit 4 for each frequency component.
- the precoder unit 4 performs spatial multiplexing on each precoder 41 based on transmission path information (CSI: Channel State Information) with each terminal for each frequency bin (bin) f1 to fm, that is, for each frequency component.
- CSI Channel State Information
- This embodiment assumes a TDD type system that does not require feedback of CSI from a terminal that is a signal receiving side. That is, based on the known signal transmitted from the terminal, the CSI in the uplink direction is obtained on the wireless transmission device 100 side, and this is used as the CSI in the downlink direction to perform the weighting process between the antennas.
- the CSI is calculated by, for example, a wireless reception device not shown in FIG. 1, that is, a wireless reception device that constitutes a base station together with the wireless transmission device 100, and the calculated CSI is input to the precoder unit 4. To. Since the calculation method of CSI is widely known, description of the calculation method is omitted.
- FIG. 2 is a flowchart showing an operation example of the precoder unit 4.
- the precoder 4 first acquires CSI (step S11), and then calculates the transmission weight of each antenna based on the acquired CSI (step S12).
- step S12 the precoder 4 calculates the transmission weight of each antenna for each signal stream.
- the precoder 4 calculates the transmission weight by, for example, a known BD (Block Diagonalization) method.
- BD Block Diagonalization
- the transmission weight of each antenna is calculated so that a beam that does not interfere with transmission of a signal stream addressed to a certain terminal is formed.
- the transmission weight calculation method is not limited to the BD method.
- the transmission weight may be calculated by other known methods.
- the precoder 4 uses the calculated transmission weight to weight the transmission signal (step S13). Specifically, each precoder 41 multiplies the transmission weight calculated in step S12 by the transmission signal that is a signal input from the FFT units 3 1 to 3 Ns to perform weighting.
- the transmission signal after the weighting is performed in the precoder unit 4 is output to IFFT units 5 1 to 5 Nt according to the destination terminal.
- IFFT section 5 1 ⁇ 5 Nt converts the transmission signal inputted from the precoder unit 4 into a signal in the time axis parallel - output to serial converter 6 1 ⁇ 6 Nt.
- the parallel-serial conversion units 6 1 to 6 Nt perform parallel-serial conversion on the input signals from the IFFT units 5 1 to 5 Nt .
- guard interval addition processing and up-conversion processing are performed thereafter, but this is not an essential processing for realizing the present invention. Therefore, in FIG. 1, components for performing these processing are omitted. ing.
- the transmission weight generated by the precoder unit 4 varies variously according to the CSI between the wireless transmission device 100 that performs spatial multiplexing and the terminal that receives the spatially multiplexed signal. Further, depending on conditions, power may be concentrated on a specific antenna, and the average power value of a signal transmitted from the specific antenna may be high. As already described, HPA for amplifying a signal is mounted on radio transmitting apparatus 100, but the output of HPA has a limit, that is, a saturated power value. For high-power signals, the linearity of the signal at the time of amplification is high. Cannot be maintained.
- Massive-MIMO with a large number of antenna elements requires a large amount of CSI feedback in an FDD (Frequency Division Duplex) type system. Therefore, in this embodiment, CSI feedback is not required by performing transmission path estimation using propagation path reversibility of the TDD scheme.
- FDD Frequency Division Duplex
- the wireless transmission device 100 sets a correction value according to the average power value of the input signal to the HPA.
- the correction value selection unit 9 performs a process of selecting a correction value corresponding to the average power value of the input signal from the correction table, and the antennas 10 1 to 10 Nt are selected by the correction value selection unit 9. The correction value is used to correct the phase and amplitude of the transmission signal.
- the correction table is a table in which a plurality of average power values of an input signal to the HPA and a plurality of phase and amplitude correction values corresponding to each of the plurality of average power values are registered. It is created at the time of design and is held in advance by the correction value selection unit 9.
- radio transmitting apparatus 100 includes maximum power calculation unit 8 and multipliers 7 1 to 7 Nt , and adjusts the power of the input signal to antennas 10 1 to 10 Nt .
- the maximum power calculation unit 8 which is a correction value calculation unit determines a power correction value ⁇ for adjusting the power of the transmission signal, and the multipliers 7 1 to 7 Nt multiply the transmission signal by the power correction value ⁇ . Adjust power.
- FIG. 3 is a flowchart showing an operation example of the maximum power calculation unit 8.
- the maximum power calculation unit 8 first acquires the transmission weight of each antenna calculated by the precoder unit 4 from the precoder unit 4 (step S21).
- the maximum power calculator 8 calculates the power correction value ⁇ based on the acquired transmission weight (step S22).
- step S22 the maximum power calculation unit 8 first calculates an average power value for each antenna when the signal streams to be transmitted to all users are combined.
- the precoder unit 4 the stream number k, the transmission weight w k of the frequency bin number is f, f is represented by the following formula (1).
- Nt represents the number of transmission antennas.
- Equation (1) the vector element is the transmission weight of each antenna.
- Ns indicates the number of signal streams to be transmitted
- Nf indicates the number of frequency bins.
- the maximum power calculation unit 8 obtains a power correction value ⁇ based on the average power value P m obtained according to the above equation (2).
- the maximum power calculation unit 8 includes a limit value that can maintain the nonlinear characteristics of the HPA provided in the antennas 10 1 to 10 Nt and the calibration of the antenna element 11 and the high-frequency circuit not shown in FIG. It is assumed that the maximum power threshold Th taking into consideration is set in advance.
- the maximum power threshold Th is determined by simulation or the like when designing the wireless transmission device 100, for example.
- ⁇ is calculated.
- Pmax was calculated according to the equation (2) shows a maximum value of the average power value P m of the signal input to each antenna.
- the maximum power calculation section 8 calculating the power correction value ⁇ in step S22, and outputs the calculated power correction value ⁇ to the multiplier 7 1 ⁇ 7 Nt (step S23).
- the multipliers 7 1 to 7 Nt multiply the input signals to the antennas 10 1 to 10 Nt by the power correction value ⁇ calculated by the maximum power calculation unit 8 in the above step S22, thereby breaking the orthogonality between users. Therefore, it is possible to avoid the problem of calibration.
- FIG. 4 is a flowchart showing an operation example of the correction value selection unit 9.
- the correction value selection unit 9 first acquires the transmission weight of each antenna calculated by the precoder unit 4 from the precoder unit 4 (step S31).
- Average power value P m for each antenna is the same as the average power value P m the maximum power calculation unit 8 calculates the time for obtaining the power correction value beta, like the maximum power calculation unit 8, the above equation (2 ).
- the correction value selection unit 9 may obtain the average power value P m for each antenna from the maximum power calculation unit 8 instead of calculating the average power value P m for each antenna based on the transmission weight of each antenna. That is, the correction value selecting unit 9, instead of the steps S31 and S32, the average power value P m for each antenna may be executed the steps of obtaining the maximum power calculation unit 8.
- the correction value selection unit 9 After calculating the average power value P m for each antenna, the correction value selection unit 9 next uses the correction value used in the correction process in each of the antennas 10 1 to 10 Nt based on the average power value P m for each antenna. Is selected from the correction table (step S33). That is, the correction value selecting unit 9 selects the correction values corresponding to the average power value P 1 ⁇ P Nt in each of the antenna 10 1 ⁇ 10 Nt for each antenna 10 1 ⁇ 10 Nt.
- the correction value selection unit 9 selects a correction value to be used in the correction process in each of the antennas 10 1 to 10 Nt , next, the correction value selection unit 9 outputs the selected correction value to the corresponding antennas 10 1 to 10 Nt and a multiplier. 7 1 instructs to correct the amplitude and phase of the input signal from ⁇ 7 Nt (step S34).
- the antennas 10 1 to 10 Nt correct the amplitude and phase using the correction value received from the correction value selection unit 9 and radiate it to the space.
- the phase shifter 11A corrects the phase of the signal
- the HPA 11B corrects the signal amplitude, that is, amplifies it.
- multipliers 7 1 to 7 Nt are provided between the parallel-serial converters 6 1 to 6 Nt and the antennas 10 1 to 10 Nt, and input signals to the antennas 10 1 to 10 Nt are provided.
- the power adjustment is performed by multiplying the power correction value ⁇
- the position where the multipliers 7 1 to 7 Nt are provided may be anywhere between the precoder unit 4 and the antennas 10 1 to 10 Nt .
- radio transmitting apparatus 100 corrects the power of the input signal to each antenna to be equal to or less than a predetermined threshold based on the transmission weight of each antenna, and transmits from each antenna.
- the amplitude and phase of the signal are corrected for each antenna using a correction value corresponding to the average power value of the input signal to the antenna.
- the input back-off of the high power amplifier can be controlled.
- the input back-off of the high power amplifier can be controlled, it is possible to solve the calibration between the transmission side and the reception side and the calibration between the antennas, which are problems in the TDD type system. Therefore, it is possible to obtain a radio transmission apparatus capable of realizing highly accurate user multiplexing without requiring CSI feedback from the receiving side of the spatial multiplexing signal.
- the TDD type system includes the maximum power calculation unit 8 and the correction value selection unit 9
- the FDD type system that is, the base station to the terminal direction fed back from the terminal.
- a system that calculates a transmission weight based on (downlink) CSI may include a maximum power calculation unit 8 and a correction value selection unit 9. The operations of maximum power calculation unit 8 and correction value selection unit 9 in this case are the same as in the present embodiment.
- the modulation units 1 1 to 1 Ns can be realized by a modulator, a modem, or the like.
- the serial-parallel conversion units 2 1 to 2 Ns , the FFT units 3 1 to 3 Ns , the IFFT units 5 1 to 5 Nt , the parallel-serial conversion units 6 1 to 6 Nt and the multipliers 7 1 to 7 Nt are various logic circuits. It is realized by an electronic circuit configured to include Antennas 10 1 ⁇ 10 Nt is phase shifter is realized by an electronic circuit which is configured to include a like HPA.
- the precoder 4, the maximum power calculator 8, and the correction value selector 9 are realized, for example, when the processor 101 illustrated in FIG. 5 executes a program stored in the memory 102. That is, the precoder unit 4, the maximum power calculation unit 8, and the correction value selection unit 9 read out from the memory 102 a program for the processor 101 to operate the precoder unit 4, the maximum power calculation unit 8, and the correction value selection unit 9. It is realized by executing.
- the processor 101 is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP (Digital Signal Processor)), system LSI (Large Scale Integration), or the like.
- the memory 102 is a nonvolatile or volatile semiconductor such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), etc. Memory, magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD (Digital Versatile Disc) or the like.
- the memory 102 selects the storage area of the maximum power threshold Th used when the maximum power calculation unit 8 obtains the power correction value ⁇ , and the correction value used by the correction value selection unit 9 in the correction processing in the antennas 10 1 to 10 Nt . It is also used as a storage area for a correction table to be referred to when doing so.
- the precoder unit 4, the maximum power calculation unit 8, and the correction value selection unit 9 may be realized by dedicated hardware, some of which are realized by dedicated hardware, and the rest are software, firmware, or software. And a combination of firmware and firmware.
- a hardware configuration in the case where these units are realized by dedicated hardware is, for example, as shown in FIG. That is, the precoder unit 4, the maximum power calculation unit 8, and the correction value selection unit 9 are realized by the processing circuit 110.
- the processing circuit 110 corrects the correction value for correcting the input signal to the antenna, processing for weighting the signal transmitted to the terminal, calculating the power correction value for adjusting the power of the transmission signal It is the electronic circuit which performs the process selected from a table.
- the processing circuit 110 is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. .
- Embodiment 2 The radio transmission apparatus according to Embodiment 1 obtains a power correction value ⁇ for adjusting the power of an input signal to each antenna to be equal to or lower than the maximum power threshold Th based on the transmission weight of each antenna, and corrects the power.
- the value ⁇ was used to adjust the input signal to each antenna.
- the power of the input signal to each antenna is suppressed below the maximum power threshold Th by adjusting the transmission weight of each antenna.
- FIG. 7 is a diagram illustrating an example of a wireless communication system to which the wireless transmission device of the second embodiment is applied.
- FIG. 7 shows a configuration example of MU-MIMO in which four users, that is, terminals # 1 to # 4 and a base station equipped with the radio transmission apparatus of the present embodiment communicate simultaneously.
- the base station only the antenna is shown.
- the base station has 16 antennas, and the terminals # 1 to # 4 each have 4 antennas.
- a total of 16 streams are spatially multiplexed from the base station and transmitted to the terminals # 1 to # 4.
- the base station allocates four streams to one terminal and transmits signals. In this case, in the base station, it is not necessary to perform nulling (Nulling) for four streams addressed to a specific terminal, and it is only necessary to achieve nulling for 12 antennas possessed by other terminals.
- Nulling nulling
- a base station calculates a transmission weight so as to perform eigenmode transmission with four antennas of each user (terminal), and weights and transmits a signal to each user.
- the weighting of the signal by the transmission weight is performed for each frequency bin, but the description of the frequency bin number is omitted here.
- the degree of spatial freedom that is, the number of basis vectors increases accordingly.
- the spatial multiplexing number here corresponds to the number of signal streams addressed to each user, that is, the number of signal streams to be spatially multiplexed.
- the power of the input signal to each antenna is limited to the maximum power threshold Th or less.
- FIG. 8 is a diagram of a configuration example of the wireless transmission device according to the second embodiment.
- Radio transmitting apparatus 100a according to the present embodiment deletes multipliers 7 1 to 7 Nt from radio transmitting apparatus 100 according to the first embodiment, and precoder unit 4 and maximum power calculating unit 8 are replaced by precoder unit 4a and maximum power calculating unit. This is replaced with 8a. Since the components other than the precoder unit 4a and the maximum power calculation unit 8a are the same as those of the wireless transmission device 100 of the first embodiment, the description thereof is omitted.
- the maximum power calculation unit 8a of the wireless transmission device 100a calculates the above-described power correction value ⁇ according to the same procedure as the maximum power calculation unit 8 described in the first embodiment. Further, when the maximum power calculation unit 8a calculates the power correction value ⁇ , it outputs this to the precoder unit 4a.
- the precoder unit 4a calculates the transmission weight of each antenna for each signal stream, similarly to the precoder unit 4 of the wireless transmission device 100 of the first embodiment. At this time, the wireless transmission device 100a cooperates with the maximum power calculation unit 8a to obtain a transmission weight such that the power of the input signal to each antenna is equal to or less than the maximum power threshold Th.
- the maximum power threshold Th is the same as the maximum power threshold Th described in the first embodiment.
- FIG. 9 is a flowchart illustrating an example of an operation in which the precoder unit 4a and the maximum power calculation unit 8a cooperate to calculate a transmission weight.
- the precoder unit 4a uses the BD method or the like, like the precoder unit 4 of the wireless transmission device 100 of the first embodiment.
- the transmission weight of each antenna is calculated (step S41). This is called a temporary transmission weight which is the first transmission weight. Note that, even when the transmission weight is calculated by a method other than the BD method, the transmission weight is calculated so that eigenmode transmission is performed.
- the maximum power calculation unit 8a calculates a power correction value ⁇ based on the temporary transmission weight and the maximum power threshold Th and outputs it to the precoder unit 4a (step S42).
- the signal average power value for each antenna is calculated based on the temporary transmission weights input from the FFT unit 3 1 ⁇ 3 Ns the precoder portion 4a when the maximum power calculation unit 8a calculates the power correction value ⁇
- the precoder 4a uses this to calculate the final transmission weight that is the second transmission weight, that is, the transmission weight used in the transmission signal weighting process ( Step S43).
- step S43 the precoder unit 4a calculates the final transmission weight of each antenna so as to satisfy the condition expressed by the following equation (4).
- Equation (4) bold wk, f with “ ⁇ ” added is the final transmission weight.
- f represents a frequency bin number
- m represents an antenna number
- k represents a user number.
- Q f, m is the average power value before correction of the signal of the frequency bin f input to the antenna m
- M max is the number of the antenna having the largest average power value of the input signal.
- Q f to which “ ⁇ ” is added is an average power value after the signal of the frequency bin f is corrected by the power correction value ⁇ .
- the average power value before correction is an average power value of a signal after weighting when weighting is performed using a temporary transmission weight.
- u j is the weighting coefficient of the j-th basis vector of the temporary transmission weight calculated in step S41, Nr is the number of multiple streams per user.
- Nr is the number of multiple streams per user.
- the precoder 41 when the final transmission weight of each antenna is calculated, the precoder 41 multiplies this by the signal of each frequency bin, and weights the transmission signal.
- the maximum power calculation unit 8a calculates the power correction value ⁇ .
- the precoder unit 4a may calculate the power correction value ⁇ .
- correction value selection unit 9 that calculates the average power value P m for each antenna based on the transmission weight calculated by the precoder unit 4a uses the above-described final transmission weight calculated by the precoder unit 4a to perform an average. calculating a power value P m.
- the radio transmission apparatus 100a determines the transmission weight of each antenna in consideration that the power of the input signal to each antenna is equal to or less than a specified threshold. Specifically, first, a transmission weight for eigenmode transmission is calculated as a temporary transmission weight, and an average power value of an input signal to each antenna that can be calculated from the temporary transmission weight and a predetermined threshold value are obtained. Based on this, the power correction value is calculated, and the final transmission weight is calculated in consideration of the power correction value. As a result, the maximum power value can be limited without destroying the orthogonality between users, and the influence on the transmission signal, that is, the influence of the HPA that is a nonlinear amplifier and the calibration error can be suppressed.
- the hardware configuration for realizing the wireless transmission device 100a is the same as that of the wireless transmission device 100 of the first embodiment.
- the configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.
- 1 1 to 1 Ns modulation unit 2 1 to 2 Ns serial-parallel conversion unit (S / P unit), 3 1 to 3 Ns FFT unit, 4, 4a precoder unit, 5 1 to 5 Nt IFFT unit, 6 1 to 6 Nt parallel-serial conversion unit (P / S unit), 7 1 to 7 Nt multiplier, 8, 8a maximum power calculation unit, 9 correction value selection unit, 10 1 to 10 Nt antenna, 11 array element, 11A phase shift 11B HPA (High Power Amplifier), 41 Precoder, 100, 100a Wireless transmission device, 101 processor, 102 memory, 110 processing circuit.
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Abstract
Description
図1は、本発明の実施の形態1にかかる無線送信装置の構成例を示す図である。図1に示した無線送信装置100は、例えば、移動体通信システムの基地局を構成し、1つ以上のビームを形成して複数のユーザ、すなわち移動端末(以下、端末)に対して、各ユーザ宛信号を空間多重して同時に伝送する機能を提供する(マルチユーザMIMO、シングルユーザMIMOを含む)。以下、無線送信装置が移動体通信システムの基地局を構成している場合の例について説明する。
実施の形態1の無線送信装置は、各アンテナの送信ウェイトに基づいて、各アンテナへの入力信号の電力が最大電力閾値Th以下となるように調整するための電力補正値βを求め、電力補正値βを使用して各アンテナへの入力信号を調整することとしていた。これに対して、本実施の形態の無線送信装置では、各アンテナの送信ウェイトを調整することにより、各アンテナへの入力信号の電力を最大電力閾値Th以下に抑える。
Claims (9)
- 増幅器を有する複数のアンテナと、
前記アンテナを介して端末へ送信する信号を生成する送信信号生成部と、
前記端末との間の伝送路情報および前記増幅器の出力限界値に基づいて、前記送信信号生成部で生成された前記端末へ送信する信号に対して重み付け処理を実行する重み付け処理部と、
を備えることを特徴とする無線送信装置。 - 前記重み付け処理部は、
前記端末へ送信する信号を重み付けするための送信ウェイトを前記伝送路情報に基づいて生成するとともに、生成した送信ウェイトを前記端末へ送信する信号に乗算して重み付けを行うプリコーダ部と、
前記プリコーダ部で生成された送信ウェイトと、前記増幅器の出力限界値に基づいて予め決められている閾値とに基づいて、前記プリコーダ部で重み付けされた信号の電力を補正する電力補正部と、
を備えることを特徴とする請求項1に記載の無線送信装置。 - 前記電力補正部は、
前記プリコーダ部から出力された信号の平均電力値を前記送信ウェイトに基づいて算出し、算出した平均電力値および前記閾値に基づいて、前記プリコーダ部で重み付けされた信号の電力を補正するための電力補正値を算出する補正値算出部と、
前記電力補正値を前記プリコーダ部で重み付けされた信号に乗算する乗算器と
を備えることを特徴とする請求項2に記載の無線送信装置。 - 前記送信ウェイトに基づいて、前記複数のアンテナに入力された信号の振幅および位相を補正するための補正値を予め決められた複数の補正値の中から前記複数のアンテナごとに選択する補正値選択部、
を備え、
前記複数のアンテナは、入力された信号の振幅および位相を前記補正値選択部で選択された前記補正値を使用して補正する、
ことを特徴とする請求項2または3に記載の無線送信装置。 - 前記補正値選択部は、前記送信ウェイトに基づいて、前記プリコーダ部から出力された信号の平均電力値を当該信号が入力される前記アンテナごとに算出し、算出した平均電力値に基づいて前記補正値を前記複数のアンテナごとに選択する、
ことを特徴とする請求項4に記載の無線送信装置。 - 前記重み付け処理部は、
前記端末へ送信する信号を重み付けするための送信ウェイトを前記伝送路情報に基づいて生成するとともに、生成した送信ウェイトを前記端末へ送信する信号に乗算するプリコーダ部と、
前記プリコーダ部が前記送信ウェイトを生成する際に使用する電力補正値を算出する補正値算出部と、
を備え、
前記複数のアンテナの数は空間多重伝送する信号ストリームの数以上であり、
前記プリコーダ部は、固有モード伝送を実現する第1の送信ウェイトを算出し、当該第1の送信ウェイトおよび前記補正値算出部で算出された電力補正値に基づいて、前記端末へ送信する信号に乗算する第2の送信ウェイトを算出し、
前記補正値算出部は、前記第1の送信ウェイトに基づいて、前記第1の送信ウェイトで前記端末へ送信する信号を重み付けした場合の重みづけ後の信号の平均電力値を算出し、算出した平均電力値と、前記増幅器の出力限界値に基づいて予め決められている閾値とに基づいて、前記電力補正値を算出する、
ことを特徴とする請求項1に記載の無線送信装置。 - 前記プリコーダ部は、前記端末へ送信する信号を前記第1の送信ウェイトで重み付けした場合の重み付け後の信号の平均電力値を、前記端末へ送信する信号が入力されるアンテナ毎に算出し、算出した平均電力値の最大値を前記電力補正値で補正して電力上限値を生成し、前記端末へ送信する信号を前記第2の送信ウェイトで重み付けした場合の重みづけ後の信号の平均電力値が前記電力上限値以下となるよう、前記第1の送信ウェイトの各基底ベクトルを線形結合して前記第2の送信ウェイトを生成する、
ことを特徴とする請求項6に記載の無線送信装置。 - 前記第2の送信ウェイトに基づいて、前記複数のアンテナに入力された信号の振幅および位相を補正するための補正値を予め決められた補正値の中から前記複数のアンテナごとに選択する補正値選択部、
を備え、
前記複数のアンテナは、入力された信号の振幅および位相を前記補正値選択部で選択された前記補正値を使用して補正する、
ことを特徴とする請求項6または7に記載の無線送信装置。 - 前記補正値選択部は、前記第2の送信ウェイトに基づいて、前記プリコーダ部から出力された信号の平均電力値を当該信号が入力される前記アンテナごとに算出し、算出した平均電力値に基づいて前記補正値を前記複数のアンテナごとに選択する、
ことを特徴とする請求項7に記載の無線送信装置。
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