WO2017006642A1 - 送信装置、受信装置、制御局、通信システムおよび送信プレコーディング方法 - Google Patents
送信装置、受信装置、制御局、通信システムおよび送信プレコーディング方法 Download PDFInfo
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- WO2017006642A1 WO2017006642A1 PCT/JP2016/065638 JP2016065638W WO2017006642A1 WO 2017006642 A1 WO2017006642 A1 WO 2017006642A1 JP 2016065638 W JP2016065638 W JP 2016065638W WO 2017006642 A1 WO2017006642 A1 WO 2017006642A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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
- H04B7/0617—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 for beam forming
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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
- H04B7/0413—MIMO systems
- H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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
- H04B7/0413—MIMO systems
- H04B7/0426—Power distribution
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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
- H04B7/10—Polarisation diversity; Directional diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
- H04W16/28—Cell structures using beam steering
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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
- H04B7/0408—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas using two or more beams, i.e. beam diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- 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
- H04B7/0413—MIMO systems
- H04B7/0452—Multi-user MIMO systems
Definitions
- the present invention relates to a transmission device, a reception device, a communication system, and a transmission precoding method for performing multi-user MIMO (Multiple-Input Multiple-Output) transmission.
- MIMO Multiple-Input Multiple-Output
- a MIMO (MU (Multi-User) -MIMO) system has been actively studied.
- the MU-MIMO system there are a plurality of terminals having a plurality of antennas for a base station having a plurality of antennas, and the base station performs simultaneous transmission to a plurality of terminals in the same radio frequency band.
- a received signal at a terminal includes a signal intended for another terminal in addition to a desired signal that is a signal intended for the terminal itself. That is, inter-user interference (IUI), which is interference caused by signals for other terminals, occurs. It is desirable to take IUI countermeasures as much as possible on the base station side where there are few restrictions on the processing amount and the number of antennas compared to the terminal. For this reason, in the downlink in the MU-MIMO system, the base station performs a process called precoding as an IUI countermeasure. Precoding indicates a process of forming a beam by weighting a plurality of signals transmitted from a plurality of antennas.
- a block diagonalization (BD) method has been widely studied as a representative precoding method performed as an IUI countermeasure in the downlink in the MU-MIMO system.
- the BD method is a precoding technique in which a beam space is formed so as to form a directivity that directs nulls to terminals other than the desired terminal, that is, sets reception power at terminals other than the desired terminal to zero.
- the BD technique performs null steering for directing null to other than the desired terminal, the degree of freedom of the beam formed by the plurality of signals transmitted from the plurality of antennas of the base station is lost. For this reason, in precoding using the BD technique, a beam is formed so that the transmission diversity effect is increased, that is, the signal-to-noise power ratio (SNR) of each terminal is improved. It ’s difficult. Particularly in an environment where a large number of terminals exist, the degree of freedom of beam formation is largely lost due to null steering for a plurality of terminals. Thus, the BD technique has a problem that it is difficult to improve the transmission diversity gain.
- the present invention has been made in view of the above, and an object of the present invention is to obtain a transmission apparatus capable of improving transmission diversity gain as compared with the BD method.
- a transmission apparatus includes a plurality of transmission antennas capable of forming a plurality of beams directed to a plurality of reception apparatuses.
- the receiving device excludes a first receiving device that is a transmission destination of a transmission signal among a plurality of receiving devices and a second receiving device that is two or more of the plurality of receiving devices.
- a precoder that performs precoding on signals transmitted from a plurality of transmission antennas so that reception power in a third reception device that is a plurality of reception devices is equal to or less than a threshold value;
- the transmission apparatus according to the present invention has an effect that the transmission diversity gain can be improved as compared with the BD method.
- FIG. 1 is a diagram illustrating a configuration example of a communication system according to a first exemplary embodiment.
- 2 is a diagram illustrating a configuration example of a base station according to Embodiment 1.
- FIG. 3 is a diagram illustrating a configuration example of a terminal according to Embodiment 1.
- FIG. 3 is a diagram illustrating a configuration example of a processing circuit according to the first embodiment.
- FIG. 3 is a diagram illustrating a configuration example of a control circuit according to the first embodiment.
- FIG. 5 is a diagram illustrating a flowchart illustrating an example of a processing procedure in the precoder unit of the first embodiment.
- FIG. 6 is a diagram illustrating a flowchart illustrating an example of a processing procedure of an ordering unit according to the first embodiment. It is a figure which shows the structural example of the base station which is not provided with an ordering part. It is a figure which shows the structure of the control station of Embodiment 2, and the base station controlled by a control station. 6 is a diagram illustrating a configuration example of a base station according to Embodiment 2.
- FIG. FIG. 11 is a diagram illustrating a configuration example of a base station according to the third embodiment.
- FIG. 10 is a diagram illustrating a flowchart illustrating an example of a processing procedure in the precoder unit of the third embodiment.
- FIG. 1 is a diagram of a configuration example of a communication system according to the first embodiment of the present invention.
- the communication system according to the present embodiment includes a base station 1 and terminals 2-1 to 2-m.
- m is an integer of 2 or more.
- the terminals 2-1 to 2-m may be referred to as users. Further, when the terminals 2-1 to 2-m are shown without being distinguished, they are described as the terminal 2.
- the base station 1 is provided with a plurality of antennas, and the terminals 2-1 to 2-m are provided with one or more antennas.
- the base station 1 is a transmitting device and the terminal 2 is a receiving device.
- the MU-MIMO scheme is used in downlink communication, and the base station 1 performs precoding on transmission signals transmitted from a plurality of antennas, and transmits a plurality of terminals 2 to each other.
- a directional beam can be formed.
- the base station 1 and the terminal 2 may perform communication in which the terminal 2 is a transmission device and the base station 1 is a reception device, that is, uplink communication.
- the uplink communication method may be any communication method.
- an array of a plurality of antennas included in one device, that is, an antenna group is referred to as an “array”.
- a plurality of signal arrays corresponding to the array may be simply referred to as an array for convenience.
- An array of a plurality of transmission antennas is called a “transmission array”
- an array of a plurality of reception antennas is called a “reception array”.
- the number of effective antennas observed when multiplying a transmission matrix or a reception array by a weight matrix that is a matrix indicating a weight is called “branch”.
- the number of reception branches that are branches on the reception side is the number of data transmitted in parallel to the terminal 2 that is the reception apparatus, and is the number of rows of the reception weight matrix that is a weight matrix to be multiplied in the terminal 2.
- the number of transmission branches which are branches on the transmission side is a transmission weight matrix which is a weight matrix multiplied by the base station 1 which is a transmission apparatus, that is, the number of transmission precoding columns.
- the number of antennas included in the terminal 2 is not limited, and the present invention can be applied when the number of antennas is different for each terminal 2 or when the number of reception branches is different for each terminal 2.
- the number of antennas included in the terminal 2 is R (R is an integer equal to or greater than 1) regardless of the terminal.
- N w (N w ⁇ R) weight matrices are multiplied by the reception array. Therefore, the number of reception branches per terminal 2 observed from the base station 1 which is a transmission apparatus is N w regardless of the terminal 2.
- the weight applied to the reception array is assumed in the calculation of the precoding matrix, and any weight can be applied.
- the number of IUI terminals per desired terminal which will be described later, is L (L ⁇ 2)
- the R ⁇ T true channel matrix from the antenna of the base station 1 to the antenna of the terminal 2-i is H (bold) (hat) i
- the N w ⁇ R reception weight matrix of the terminal 2-i is Let W (bold) i be a true received signal vector before reception weight product of terminal 2-i is y (bold) i (t). Further, the received signal vector after multiplication of the reception weight of terminal 2-i is r (bold) i (t), and the true received thermal noise vector in the transmission path from the antenna of base station 1 to the antenna of terminal 2-i Is n (bold) (hat) i (t).
- a system model obtained by modeling the communication system according to the present embodiment using a mathematical formula can be defined by the following formula (1).
- the N w ⁇ T matrix obtained by multiplying the reception weight matrix W (bold) i and the true transmission path matrix H (bold) (hat) i is the new transmission path matrix H (bold) i , and the true reception heat If the noise vector n (bold) (hat) i (t) is multiplied by the received weight matrix W (bold) i , the N wth order vector is the new received thermal noise vector n (bold) i (t).
- the model can be expressed by the following equation (2).
- H (bold) (bar) is an N w, total ⁇ T system transmission line matrix indicating transmission lines from the antenna of the base station 1 to the branches of all terminals 2 after multiplication of the reception weights.
- B (bold) (bar) is a system precoding matrix of T ⁇ N st for all terminal 2 in the base station 1.
- N st is the total number of signals simultaneously transmitted in parallel to all terminals 2.
- P (bold) (bar) is a system transmission power matrix that is a matrix that defines transmission power distribution to all terminals 2
- s (bold) (bar) (t) is N indicating transmission signals for all terminals 2.
- n (bold) (bar) (t) are N w, total -order system noise vectors that are noise vectors for all the terminals 2 after reception weight multiplication.
- the product of H (bold) (bar) and B (bold) (bar) is an effective system transmission line matrix H (bold) (bar) e by transmission beam formation. Can be considered.
- the BD method is a precoding method using a precoding matrix in which a non-block diagonal term is a zero matrix O (bold).
- a non-block diagonal term is a zero matrix O (bold).
- not all the non-block diagonal terms are made zero matrix O (bold), but one terminal 2 other than the terminal 2 that is the transmission target of the transmission signal as an interference component.
- a precoding matrix is used in which the above components remain. Thereby, the diversity gain in the terminal 2 to be transmitted can be improved as compared with the BD method while ensuring the degree of freedom of beam formation by the transmission array and suppressing the IUI.
- FIG. 2 is a diagram illustrating a configuration example of the base station 1 according to the present embodiment.
- the base station 1 includes primary modulation units 11-1 to 11-m, a precoder unit 12, an ordering unit 13, transmission waveform shaping units 14-1 to 14-T, antennas 15-1 to 15-T, and a receiver 16. .
- the primary modulation performed by the primary modulation unit 11-i includes, for example, channel coding and mapping to primary modulation symbols such as QAM (Quadrature Amplitude Modulation) symbols.
- QAM Quadrature Amplitude Modulation
- the primary modulation performed by the primary modulation unit 11-i includes a discrete Fourier transform process.
- the primary modulation units 11-1 to 11-m are signal generation units that generate a transmission signal to be transmitted to the terminal 2 for each terminal 2 that is a receiving device.
- the precoder unit 12 includes a first receiving device that is a terminal 2 that is a transmission destination of transmission signals output from the primary modulation units 11-1 to 11-m among the terminals 2-1 to 2-m and the terminal 2-
- the received power in the third receiving device that is the terminal 2 excluding the second receiving device that is the two or more terminals 2 other than the first receiving device 1 to 2-m is 0, that is, the threshold value or less.
- the precoder performs precoding on signals transmitted from the antennas 15-1 to 15-T, which are a plurality of transmission antennas.
- the first receiving device is a desired terminal described later
- the second receiving device is an IUI terminal described later.
- the received power at the IUI terminal as the second receiving apparatus is larger than the threshold value.
- the precoder unit 12 multiplies the transmission signal after the primary modulation output from the primary modulation units 11-1 to 11-m by the system precoding matrix of this embodiment described later. Precoding is performed, and the transmission signals after precoding are output to the corresponding transmission waveform shaping sections 14-1 to 14-T.
- the ordering unit 13 instructs the precoder unit 12 to order the terminals 2 in precoding and to distribute power to the terminals 2. That is, the ordering unit 13 determines the order of the terminals 2 in precoding.
- the transmission waveform shaping units 14-1 to 14-T perform secondary modulation, digital analog (D / A) conversion, and conversion from baseband frequency to radio frequency (RF), respectively, on the precoded signals. And the processed signals are transmitted through the antennas 15-1 to 15-T, respectively.
- Secondary modulation is, for example, multicarrier modulation when applying a multicarrier scheme such as OFDM (Orthogonal Frequency Division Multiplex), and single carrier modulation when applying a single carrier scheme such as single carrier block transmission. is there.
- a multicarrier scheme such as OFDM (Orthogonal Frequency Division Multiplex)
- single carrier modulation when applying a single carrier scheme such as single carrier block transmission.
- the modulation method of the secondary modulation there is no limitation on the modulation method of the secondary modulation, and modulation other than the above-described OFDM and single carrier block transmission may be performed.
- the transmission waveform shaping units 14-1 to 14-T for example, perform discrete inverse Fourier transform and CP (Cyclic Prefix) addition processing before D / A conversion.
- block transmission refers to a method of blocking a signal by discrete Fourier transform processing and CP addition, as represented by OFDM and single carrier block transmission.
- the signal processing in the transmission waveform shaping sections 14-1 to 14-T may be digital processing or analog processing.
- the transmission signals input from primary modulation units 11-1 to 11-m to precoder unit 12 correspond to s (bold) (bar) (t) in equation (3), and transmit waveform shaping from precoder unit 12 is performed.
- the output signals output to the units 14-1 to 14-T correspond to B (bold) (bar) P (bold) (bar) s (bold) (bar) (t) in equation (3).
- the antennas 15-1 to 15-T which are a plurality of transmission antennas, can form a plurality of beams directed to the plurality of terminals 2, respectively.
- the receiver 16 performs reception processing on the received signal received from the terminal 2 via the antennas 15-1 to 15-T.
- a reception antenna may be provided separately from the antennas 15-1 to 15-T.
- the receiver 16 estimates the transmission path based on the received signals received from the antennas 15-1 to 15-T. Any method may be used as the transmission path estimation method. For example, an estimation method using a pilot signal which is a known signal may be used.
- pilot signals orthogonal to each other between a plurality of antennas of terminal 2 are transmitted from terminal 2, and receiver 16 of base station 1 identifies each antenna of terminal 2 according to the orthogonal pilot and estimates a transmission path. Can do.
- the receiver 16 outputs the received transmission path information to the precoder unit 12.
- FIG. 3 is a diagram illustrating a configuration example of the terminal 2 according to the present embodiment.
- the terminal 2 includes antennas 21-1 to 21-R, reception waveform shaping units 22-1 to 22-R, a decoder unit 23, a demodulation unit 24, and a transmitter 25.
- the reception waveform shaping sections 22-1 to 22-R convert the received signals received by the antennas 21-1 to 21-R, respectively, from radio frequency to baseband frequency, analog digital (A / D) Conversion, signal filtering, and the like are performed, and the processed received signal is output to the decoder unit 23.
- the signal filtering process is a process for extracting a signal in a desired frequency band, for example.
- the reception waveform shaping units 22-1 to 22-R also perform CP removal processing and discrete Fourier transform processing.
- the decoder unit 23 performs a later-described MIMO decoding process, which is a process for extracting a desired signal, that is, a signal addressed to the terminal itself, from the reception signals input from the reception waveform shaping units 22-1 to 22-R.
- the processed signal is output to the demodulator 24.
- the decoder unit 23 is a decoder that extracts a desired signal from the signal received from the base station 1.
- the decoder unit 23 performs transmission path estimation processing in the course of MIMO decoding processing.
- the demodulation unit 24 performs demapping processing, channel decoding processing, and the like on the signal output from the decoder unit 23 to restore the signal transmitted from the base station 1. Further, when the single carrier block transmission method is applied, the demodulator 24 performs equalization processing for compensating for frequency distortion and discrete inverse Fourier transform processing.
- the signal processing in the reception waveform shaping units 22-1 to 22-R may be digital processing or analog processing.
- the transmitter 25 generates a transmission signal and transmits it to the base station 1 from the antennas 21-1 to 21-R.
- a transmission antenna may be provided separately from the antennas 21-1 to 21-R.
- the transmitter 25 transmits the transmission path information estimated by the decoder section 23 from the decoder section 23. The transmission path information is acquired, and the transmission path information is transmitted to the base station 1.
- the antennas 21-1 to 21-R are transmission / reception antennas.
- the transmitter 25 transmits transmission signals from the antennas 21-1 to 21-R.
- the primary modulation units 11-1 to 11-m are mappers or modulators. When the primary modulation includes discrete Fourier transform processing, a discrete Fourier transform processing circuit is added.
- the precoder unit 12 is a processing circuit that performs precoding, and the ordering unit 13 is a processing circuit that performs ordering.
- the transmission waveform shaping units 14-1 to 14-T are transmission waveform shaping circuits, and specifically include a D / A converter, a frequency converter, and the like. When the transmission waveform shaping units 14-1 to 14-T perform CP addition and inverse discrete Fourier transform processing, the transmission waveform shaping units 14-1 to 14-T include CP addition circuit and inverse discrete Fourier transform processing. Provide a circuit.
- the processing circuit that implements the precoder unit 12 and the ordering unit 13 is dedicated hardware, a CPU (Central Processing Unit, a central processing unit, a processing unit, an arithmetic unit, A control circuit including a microprocessor, a microcomputer, a processor, and a DSP (Digital Signal Processor) may also be used.
- the memory is, for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory, etc.) Volatile semiconductor memories, magnetic disks, flexible disks, optical disks, compact disks, mini disks, DVDs (Digital Versatile Disks), and the like are applicable.
- the precoder unit 12 and the ordering unit 13 are realized by dedicated hardware, these include, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), or a combination of these.
- this processing circuit is, for example, the processing circuit 500 shown in FIG.
- this control circuit is, for example, a control circuit 400 having the configuration shown in FIG. As shown in FIG. 5, the control circuit 400 includes a processor 401 that is a CPU and a memory 402. When the precoder unit 12 and the ordering unit 13 are realized by the control circuit 400 as shown in FIG. 5, the processor 401 reads the programs corresponding to the processes of the precoder unit 12 and the ordering unit 13 stored in the memory 402. It is realized by executing.
- the memory 402 is also used as a temporary memory in each process executed by the processor 401.
- the primary modulation units 11-1 to 11-m and the transmission waveform shaping units 14-1 to 14-T are made of dedicated hardware, like the precoder unit 12 and the ordering unit 13. It may be realized by a certain processing circuit or control circuit 400.
- the reception waveform shaping units 22-1 to 22-R are reception waveform shaping circuits, and specifically include an A / D converter, a filter, a frequency converter, and the like.
- the received waveform shaping units 22-1 to 22-R perform CP removal and discrete Fourier transform processing
- the received waveform shaping units 22-1 to 22-R include CP removal circuits and discrete Fourier transform processing circuits.
- the decoder unit 23 is a processing circuit
- the demodulation unit 24 is a demodulator or a demapper.
- the demodulation unit 24 includes an equalizer, an inverse discrete Fourier transform circuit, and the like.
- the processing circuit for realizing the decoder unit 23 may be realized by dedicated hardware, or may be realized by the control circuit 400 described above.
- the decoder unit 23 is realized by the control circuit 400 as shown in FIG. 5, it is realized by the processor 401 reading and executing a program stored in the memory 402 and corresponding to the processing of the decoder unit 23.
- the processing circuit or control circuit 400 which is dedicated hardware, like the decoder unit 23 described above. Also good.
- the precoder unit 12 generates a precoding matrix by the following procedure.
- the processing of the transmission waveform shaping units 14-1 to 14-T and the reception waveform shaping units 22-1 to 22-R is omitted in the description in the mathematical expression, but the precoding matrix is calculated. There is no influence by these processes.
- the space between the output terminal of the precoder unit 12 of the base station 1 and the input terminal of the decoder unit 23 of the terminal is expressed by an equivalent low-frequency system.
- the precoding process described below may be performed independently for each discrete frequency in OFDM or single carrier block transmission, or may be performed collectively for the entire band regardless of the frequency.
- precoding matrix calculation process information on the transmission path matrix in the downlink direction, that is, transmission path information is required.
- transmission path information is required.
- this is a frequency division duplex (FDD) in which communication is performed at different frequencies in the downlink and uplink.
- FDD frequency division duplex
- the transmission path information estimated by the terminal 2 received from the terminal 2 is used.
- TDD time division duplex
- the receiver 16 can estimate the transmission path in the uplink direction, and use the estimated transmission path as downlink transmission path information.
- any method may be used for the transmission path estimation method.
- an estimation method using a pilot signal can be used.
- FIG. 6 is a flowchart showing an example of a processing procedure in the precoder unit 12 of the present embodiment.
- a terminal that is the destination terminal 2 of the transmission signal is referred to as a desired terminal.
- the precoder unit 12 determines a desired terminal according to the order determined by the ordering unit 13. Then, in order to obtain a precoding matrix for the desired terminal, L units, ie, L IUI terminals corresponding to the desired terminal, which are terminals 2 that allow IUI, are selected (step S1).
- a beam is formed so as to form a null in order to avoid an IUI for terminals other than the desired terminal.
- IUI is allowed for one terminal 2 other than the desired terminal. That is, a null is not formed for the L terminals 2 other than the desired terminal, and a beam is formed so as to have directivity in the direction of the L terminals 2 other than the desired terminal.
- a method of selecting an IUI terminal when a desired terminal is a terminal 2-i, a method of selecting a terminal having a transmission path matrix having a low correlation with H (bold) i which is a transmission path matrix of the terminal 2-i, each terminal And selecting a terminal 2 at a position distant from the desired terminal based on the geographical information of 2.
- the former uses an IUI terminal corresponding to a desired terminal as a correlation between a transmission path matrix between the desired terminal and the base station 1 and a transmission path matrix between the terminal 2 other than the desired terminal and the base station 1. It is a method to select based on.
- the precoder unit 12 uses the cross-correlation matrix H (bold) of H (bold) i and the transmission line matrix H (bold) k of the terminal 2-k when the terminal 2 other than the desired terminal is the terminal 2-k.
- the square sum of the diagonal terms of k H H (in bold) i calculated for all the terminals 2 other than k i, H (bold) k H H L stand in the order sum of the squares of the diagonal terms of (bold) i is smaller
- the terminal 2 is selected. The latter is a method of selecting based on the geographical separation between the desired terminal and the terminals 2 other than the desired terminal.
- the base station 1 calculates the azimuth angle of the terminal 2 viewed from the base station 1 for each terminal 2 based on the position information of each terminal 2 and the position information of the base station 1.
- the L terminals 2 are selected in order of increasing azimuth from the desired terminal.
- the position information of the terminal 2 is acquired by receiving, from the terminal 2, position information obtained by each terminal 2 using GPS (Global Positioning System), for example. Further, as the position information of the base station 1, for example, position information obtained using GPS is used. Note that in a single precoding matrix calculation, the number of times a certain terminal 2 is selected as an IUI terminal is limited to L times. That is, the same terminal cannot be selected as an IUI terminal by overlapping (L + 1) times or more in a certain precoding.
- the ordering unit 13 reduces, for example, the square sum of the diagonal terms of the cross-correlation matrix H (bold) k H H (bold) i between adjacent terminals 2, that is, next to each other.
- an IUI terminal may be selected by a method of grouping a desired terminal and L IUI terminals in the index order of the terminal 2.
- the present invention is not limited thereto, and the present invention is applicable to any number of IUI terminals with L ⁇ 2.
- the precoder unit 12 is a matrix H (bold) (bars) obtained by removing the transmission line components of the desired terminal and the two IUI terminals from the system transmission line matrix. I is calculated (step S2), and H (bold) (bar) i is subjected to singular value decomposition (SVD: Singular Value Decomposition) (step S3).
- H bold
- S3 singular value decomposition
- the system transmission line matrix H (bold) is a matrix indicating transmission paths from the antenna of the base station 1 to the branches of all terminals 2 after multiplication of reception weights. Can be calculated based on A matrix H (bold) (bar) i that is a (N w, total ⁇ (L + 1) ⁇ N w ) ⁇ T matrix obtained by removing the transmission line components of the desired terminal and the IUI terminal from the system transmission line matrix H (bold) It can be represented by the following formula (5). Further, as shown in Equation (5), H (bold) (bar) i is the so singular value decomposition, the precoder 12, H (bold) (bar) i the singular value decomposition (step S3) .
- V (bold) i (s) and V (bold) i (n) corresponding to ⁇ (bold) i (s) and zero matrix 0 (bold), respectively.
- the effective transmission line matrix for the terminal 2-i can be expressed by the following equation (6).
- null steering is performed except for the terminals 2-i, 2-j, and 2-k.
- a null is formed for terminal 2 except for terminal 2-i and terminal 2-j. Null indicates that the received power of the signals transmitted from the antennas 15-1 to 15-T is equal to or lower than the threshold, for example, the received power is zero.
- the precoder unit 12 is a second matrix from the desired component H (bold) i V (bold) i (n) , which is the component corresponding to the terminal 2-i in the equation (6).
- An eigenvector matrix V (bold) i (e) is obtained (step S4). That is, the precoder unit 12 generates a second matrix suitable for the terminal 2-i, that is, for forming a beam space directed to the terminal 2-i.
- precoder 12 i.e., H (bold) i V (in bold) i (n) a singular value decomposition, or non-negative Hermitian matrix H (in bold) i V (in bold) i (n) (H (bold) i V (bold) i (n) ) H H (bold) i V (bold) Apply eigenvalue decomposition to i (n) , and the eigenvector matrix V (bold) i (e )
- a large eigenvalue is an eigenvalue on the front side when a plurality of eigenvalues are arranged in descending order.
- the precoder unit 12 obtains a precoding matrix corresponding to the desired terminal, that is, the terminal 2-i (step S5). Specifically, the precoder unit 12 obtains a precoding matrix corresponding to the terminal 2-i by the following equation (7).
- the terminal 2-i, the terminal 2-j, and the terminal 2-k are multiplied by multiplying the transmission signal by V (bold) i (n). After null-steering the space excluding, the signal space is formed for terminal 2-i, terminal 2-j, and terminal 2-k by multiplying V (bold) i (e) In addition, it is possible to realize beam forming that improves the reception gain at the terminal 2-i.
- the first precoding matrix for reducing the received power at the terminal 2 excluding the desired terminal and the L IUI terminals to a signal transmitted from a plurality of transmission antennas is equal to or less than the threshold value.
- the matrix is multiplied, and the multiplication result is multiplied by a second matrix that is a precoding matrix for forming a beam directed to a desired terminal.
- the precoder unit 12 determines whether or not the process for all the terminals 2, that is, the precoding matrix calculation process has been completed (step S 6), and when the process is completed for all the terminals 2 (step S 6). Yes), the system precoding matrix B (bold) (bar) is calculated (step S7), and the process ends.
- System precoding matrix B (bold) (bar) is a matrix in which precoding matrices for each terminal 2 are arranged in the column direction. If the processing has not been completed for all terminals 2 (No in step S6), the desired terminal is changed and the process returns to step S1.
- the precoder unit 12 first multiplies the transmission signals output from the primary modulation units 11-1 to 11-m by the power distribution matrix P (bold) (bar) generated based on the power distribution notified from the ordering unit 13.
- the system precoding matrix B (bold) (bar) calculated by the above processing is multiplied, and the product result is output to the transmission waveform shaping sections 14-1 to 14-T. That is, the precoder unit 12 has the above-mentioned system precoding matrix B (bold) that is a precoding matrix for performing precoding with a power distribution matrix corresponding to the result of power distribution on signals transmitted from a plurality of transmission antennas. Multiply with (bar).
- the power distribution matrix is a matrix whose diagonal element is the square root of the power P (bold) i distributed to the terminal 2-i.
- Transmission waveform shaping sections 14-1 to 14-T perform the above-described processing and transmit the processed signals from antennas 15-1 to 15-T.
- the precoder unit 12 selects the terminal 2 of the next index of the desired terminal and the terminal 2 of the next index as the IUI terminal of the desired terminal. That is, the beam forming to the terminal 2-1 allows the interference to the terminal 2-2 and the terminal 2-3, and the beam forming to the terminal 2-2 is allowed to the terminal 2-3 and the terminal 2-4.
- the interference is allowed, the beam forming to the terminal 2-3 is allowed to interfere with the terminal 2-4 and the terminal 2-1, and the beam forming to the terminal 2-4 is allowed to be the terminal 2-1 and the terminal 2 -2 is allowed to interfere.
- the effective system transmission line matrix when the system precoding matrix B (bold) (bar) of the present embodiment is applied can be expressed by the following equation (8).
- the system transmission line matrix is a 16 ⁇ 16 matrix, and each element in the system transmission line matrix is an independent and similar complex Gaussian random number. The number of random number trials was 10,000.
- FIG. 7 shows that the precoding in the embodiment of the present invention can improve the average SNR as compared with the conventional BD method. For example, comparing the case where the SNR is 20 dB when the precoding is not applied, the average SNR can be improved by 10 dB over the conventional BD method by applying the precoding in the embodiment of the present invention. This is because the diversity effect is obtained by forming the beam directed to the desired terminal as described above.
- the ordering unit 13 determines the arrangement order of the terminals 2. Further, the ordering unit 13 determines power distribution to each terminal 2.
- FIG. 8 is a flowchart showing an example of a processing procedure of the ordering unit 13 of the present embodiment.
- the ordering unit 13 determines the order of the terminals 2 (step S11).
- the ordering unit 13 notifies the determined order to the precoder unit 12.
- an ordering method for example, the non-negative eigenvalue or non-negative value of the transmission line matrix between each base station 1 and terminal 2 in the order of the transmission line gain of each terminal 2 (the square of the Frobenius norm of the transmission line matrix) is used.
- Correlation of transmission path matrixes between adjacent terminals, in which the singular values are arranged in order of increasing or decreasing singular values, such as the geographical positions of adjacent terminals, for example, the azimuth angles viewed from the base station 1 are closer or different. That is, the order of the diagonal terms of the cross-correlation matrix of the transmission line matrix between the terminals described above may be increased or decreased, but is not limited thereto.
- the ordering order of the ordering unit 13 may be an order determined so that the terminal 2 next to the desired terminal becomes an IUI terminal corresponding to the desired terminal.
- Examples of such an order include an ordering method in which the neighboring terminals are placed closer to or away from each other, that is, a method of ordering such that the terminals 2 in a sequential order are geographically close or spaced apart, There is a method of ordering so that the correlation of the transmission path matrix between the terminals becomes higher or lower, that is, the ordering so that the correlation between the transmission path matrices of the terminals 2 in the order is higher or lower. is there.
- an arbitrary terminal 2 is selected as the first terminal 2, and the second terminal 2 is the most geographical position with the first terminal 2.
- Select a distant terminal select the terminal 2 that is the most distant geographical position from the second terminal 2 and is not ordered as the third terminal 2, and correspond to each index Terminal 2 is selected.
- the ordering unit 13 determines the power distribution of the terminal 2 (step S12).
- the ordering unit 13 notifies the precoder unit 12 of the power distribution result, that is, the power distributed to each terminal 2.
- the precoder unit 12 Based on the result of power allocation, the precoder unit 12 performs power allocation according to the water injection theorem based on, for example, the transmission channel gain of the terminal 2, or homogenizes the reception quality of all terminals 2, that is, For example, the product of the transmission line gain and the allocated power is distributed so as to have the same value among all the terminals 2, but is not limited thereto.
- the order of said step S11 and step S12 may be reverse.
- terminal 2-i the signal addressed to the terminal 2-p by the base station 1 and the signal addressed to the terminal 2-q are used as interference signals.
- terminal 2-i is selected as the IUI of terminal 2-k in base station 1.
- the received signal received by the terminal 2-i includes a desired transmission path component H (bold) i B (bold) i and an interfered component H (bold) i B (bold) by the signal addressed to the terminal 2-p.
- the received signal r (bold) i (t) received by the terminal 2-i is (9) s (bold) i (t) is a transmission signal transmitted from the base station 1 to the terminal 2-i, and s (bold) k (t) is transmitted from the base station 1 to the terminal 2-k. This is a transmitted signal.
- the decoder unit 23 of the terminal 2 detects a transmission signal s (bold) i (t) transmitted from the received signal r (bold) i (t) to the terminal 2-i. Detection of the transmission signal s from the received signal r (bold) i (t) (bold) i (t) can be realized by a general MIMO decoding processing. For example, “T. Ohgane, T. Nishimura, and Y. Ogawa,“ Applications of Space Division Multiplexing and Those Performance in a MIMO Channel, ”IEICE Trans. Commun., Vol. E88-B, no. 5, pp.
- a linear detection method represented by ZF (Zero-Forcing) and Minimum Mean Square Error (MMSE) standards can be applied.
- MMSE Minimum Mean Square Error
- a nonlinear detection method represented by maximum likelihood estimation or interference canceller (IC: Interference Canceller) is applicable, and any MIMO decoding process may be used.
- the signal processing is performed on r (bold) i (t) after the reception weight multiplication, instead of y (bold) i (t) before the reception weight multiplication. May be implemented.
- the MIMO decoding process in this case is the same as a general MIMO decoding process.
- the present invention can be applied even when the number of antennas is different for each terminal 2 or when the number of reception branches is different for each terminal 2.
- the number of antennas N R, l and the number of branches N w, l of the terminal 2-l satisfy the relationship of N R, l ⁇ N w, l , and the terminal 2-
- the IUI terminals for i are terminal 2-j and terminal 2-k
- T ⁇ ( ⁇ l 1 m (N w, l )) ⁇ N w, j ⁇ N in any desired terminal relationship with base station 1
- the present invention is applicable if w and k are satisfied.
- FIG. 9 is a diagram illustrating a configuration example of the base station 1 a that does not include the ordering unit 13. 9, components having the same functions as those of the base station 1 of FIG. 2 are denoted by the same reference numerals as those of the base station 1 of FIG.
- the ordering unit 13 does not perform rearrangement, but the precoder unit 12 can select two or more IUI terminals by the selection method described above and perform the operation described above.
- the beam which forms null with respect to other than a desired terminal and an IUI terminal can be formed similarly to the beam formation by the base station 1 of FIG.
- base station 1 defines two or more IUI terminals that allow interference for each terminal 2 and forms a beam that forms a null for other than the desired terminal and the IUI terminal. I tried to do it. For this reason, it is possible to improve the diversity gain in the transmission target terminal 2 as compared with the BD method while suppressing the IUI.
- FIG. FIG. 10 is a diagram showing the configuration of the control station 3 according to the second embodiment of the present invention and the base stations 1b-1 to 1b-z controlled by the control station 3.
- z is an integer of 2 or more.
- the present invention is not limited to this, and a system precoding matrix similar to that in Embodiment 1 can be used even when T antennas are distributed and installed in a plurality of base stations.
- the base stations 1b-1 to 1b-z are shown without distinction, they are described as the base station 1b. In the present embodiment, it is assumed that the total number of antennas included in base stations 1b-1 to 1bz is T.
- the control station 3 includes a precoder calculation unit 31, an ordering unit 32, and a transceiver 33.
- the precoder calculation unit 31 performs the same processing as the precoder unit 12 of the first embodiment.
- the precoder calculation unit 31 in the terminal 2 excluding the desired terminal that is the terminal 2 that is the transmission destination of the transmission signal transmitted by the base stations 1b-1 to 1b-z and the IUI terminal that is the terminal 2 other than the desired terminal.
- a precoding matrix for performing precoding is calculated so that the received power is equal to or less than a threshold value.
- the transmission path information used for calculating the system precoding matrix is received from the base stations 1b-1 to 1b-z via the transceiver 33.
- the method for the base stations 1b-1 to 1b-z to acquire the transmission path information is the same as in the first embodiment.
- the ordering unit 32 performs the same process as the ordering unit 13 of the first embodiment.
- the transceiver 33 performs reception processing for signals received from the base stations 1b-1 to 1b-z and transmission processing for signals transmitted to the base stations 1b-1 to 1b-z.
- the transceiver 33 transmits the system precoding matrix, which is the precoding matrix calculated by the precoder calculation unit 31, and the power distribution calculated by the ordering unit 32 to the base stations 1b-1 to 1b-z, respectively.
- Each of the base stations 1b-1 to 1b-z includes one or more transmission antennas.
- FIG. 11 is a diagram illustrating a configuration example of the base station 1b according to the present embodiment.
- base station 1 b adds base transceiver 1 to base station 1 of Embodiment 1 and includes precoder unit 12 a instead of precoder unit 12.
- Base station 1 of Embodiment 1 It is the same. However, the number of transmission waveform shaping sections and the number of antennas is c. c is an integer of 1 or more. Components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description is omitted.
- the transceiver 17 performs reception processing for signals received from the control station 3 and transmission processing for signals transmitted to the control station 3.
- the transceiver 17 acquires the transmission path information from the receiver 16 and transmits it to the control station 3. Further, the transceiver 17 outputs the system precoding matrix and power distribution received from the control station 3 to the precoder unit 12a.
- the precoder unit 12a multiplies the power distribution matrix P (bold) i generated based on the power distribution received from the transceiver 17, and further obtains the system precoding matrix B (bold) (bar) received from the transceiver 17.
- the transmission signals output from the primary modulation units 11-1 to 11-m are multiplied, and the multiplication results are output to the transmission waveform shaping units 14-1 to 14-c.
- the precoder calculation unit 31 and the ordering unit 32 of the control station 3 are processing circuits.
- the precoder calculation unit 31 and the ordering unit 32 like the processing circuit that implements the precoder unit 12 and the ordering unit 13 of the first embodiment, can store the memory and the program stored in the memory.
- a control circuit including a CPU to be executed may be used.
- the control circuit for realizing the precoder calculation unit 31 and the ordering unit 32 is, for example, the control circuit 400 shown in FIG.
- the precoder unit 12a is also a processing circuit, and this processing circuit may be dedicated hardware or a control circuit including a memory and a CPU that executes a program stored in the memory.
- a control circuit for realizing the precoder unit 12a is, for example, the control circuit 400 shown in FIG.
- the transceiver 33 of the control station 3 includes a transmitter and a receiver.
- the transceiver 17 of the base station 1b is also composed of a transmitter and a receiver.
- the control station 3 calculates the same system precoding matrix B (bold) (bar) as in the first embodiment, and sends the system precoding matrix B (bold) ( Bar). For this reason, even when a plurality of base stations 1b are provided, the same effect as in the first embodiment can be obtained.
- FIG. 12 is a diagram illustrating a configuration example of the base station 1c according to the third embodiment of the present invention.
- the base station 1c of the present embodiment is the same as the base station 1 of the first embodiment except that the precoder 12 of the base station 1 of the first embodiment is replaced with a precoder unit 12b and a nonlinear processing unit 18 is added.
- Terminals 2-1 to 2-m in the present embodiment are the same as terminals 2-1 to 2-m in the first embodiment.
- Components having the same functions as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description is omitted.
- terminal 2-1 to terminal 2- (m ⁇ L) from terminal 2-1 to terminal 2- (m ⁇ L), one IUI terminal is selected for each desired terminal as in the first embodiment, and a precoding matrix is obtained.
- L is the number of IUI terminals described in the first embodiment.
- the branch numbers of the codes from terminal 2-1 to terminal 2- (m-1) are the order after ordering by the ordering unit 13, and the ordering unit 13 starts from the next index of the desired terminal. It is assumed that rearrangement is performed so that the terminal 2 can be selected as an IUI terminal in order.
- terminals having consecutive indexes are ordered so that their geographical positions are separated or the correlation of the transmission path matrix is low.
- terminal 2- (m ⁇ L + 1) to terminal 2-m which are L terminals 2 from the end
- the number of IUI terminals is set to less than L, that is, the number of IUI terminals is set to terminal 2-
- the number is reduced from the number of IUI terminals of each terminal from 1 to terminal 2- (m ⁇ L).
- FIG. 13 is a flowchart showing an example of a processing procedure in the precoder unit 12b of the present embodiment.
- the precoder unit 12b selects the desired terminal as in the first embodiment, and determines whether the desired terminal is a terminal from the terminal 2- (m ⁇ L + 1) to the terminal 2-m (step S20). If the desired terminal is not the m-th terminal 2 (No in step S20), the process proceeds to step S1. Steps S1 to S7 are the same as in the first embodiment.
- the precoder unit 12b uses L units corresponding to terminal 2-i (i ⁇ m ⁇ L + 1). A small number of IUI terminals, that is, a number less than L, is selected (step S21). For the terminal 2-i (i ⁇ m ⁇ L + 1), a matrix H (bold) i ′ (bar) obtained by removing the desired transmission line component from the system transmission line matrix shown in Expression (9) is calculated (step S22).
- the matrix H (bold) i ′ (bar) can be decomposed by the following singular value as shown in the equation (10), and the precoder unit 12b uses the matrix H (bold) i ′ (bar) as the singular value. Decompose (step S23).
- V (bold) i ′ (s) and V (bold) i ′ (n) corresponding to ⁇ (bold) m (s) and zero matrix 0 (bold), respectively.
- V (bold) i ′ (n) is the precoding matrix of terminal 2-i
- the effective transmission line matrix for terminal 2-i can be expressed by the following equation (11).
- null steering is performed from the terminal 2-i to the terminals other than the terminal 2-m.
- the precoder unit 12b calculates V (bold) i ′ (n) , and then a component corresponding to the terminal 2-i (i ⁇ m ⁇ L + 1), which is the desired terminal in the equation (11), that is, the desired component H ( A beam space suitable for the terminal 2-i is formed from (bold) i V (bold) i ′ (n) .
- SVD is applied to H (bold) i V (bold) i ′ (n) or non-negative Hermitian matrix (H (bold) i V (bold) i ′ (n) ) H H (bold) i V (Bold) Eigenvalue decomposition is applied to i ′ (n ) to obtain an eigenvector matrix V (bold) i ′ (e) corresponding to a large eigenvalue (step S24).
- a large eigenvalue is an eigenvalue that is equal to or greater than a threshold value.
- the precoding matrix for terminal 2-i in the present embodiment can be expressed by the following equation (12).
- the precoding matrix calculated in step S5 is used as the precoding matrix of terminals 2-1 to 2- (m ⁇ L), and terminal 2- (m ⁇ L + 1) to terminal
- the precoding matrix as the desired terminal is a matrix for performing precoding so that the received power with respect to the fourth receiving apparatus which is the terminal 2 excluding the desired terminal and the L IUI terminals is equal to or less than a threshold value.
- the received power in the third receiving apparatus that is the terminal 2 excluding the desired terminals and the number of IUI terminals less than L is less than the threshold. It is a matrix for performing pre-coding as follows.
- the number less than L includes 0.
- the effective system transmission line matrix in the present embodiment is tridiagonalized under the block. That is, a hierarchy is realized in which the component corresponding to the desired terminal exists in the diagonal component, and the component of the IUI terminal exists below the diagonal component, that is, in the second and third layers. This makes it possible to apply nonlinear MU-MIMO processing that performs successive interference cancellation on the transmission side as described below.
- the precoder unit 12b outputs the system precoding matrix B (bold) (bar) calculated by the above processing, the transmission signals output from the primary modulation units 11-1 to 11-m, and the power distribution to the nonlinear processing unit 18.
- the non-linear processing unit 18 uses the above-described lower tridiagonalization to perform a process of previously removing a component that becomes an interference signal on the reception side on the transmission side, as described below.
- the nonlinear processing unit 18 performs nonlinear MU-MIMO processing on the signal output from the precoder unit 12b. From equation (13), the received signal when the signal output from the precoder unit 12b is received by the terminal 2-i can be expressed by the following equation (14).
- Equation (14) the transmission signal s (bold) 1 (t) is known. Using this, s (bold) 2 (t) is obtained sequentially. If the transmission signal s (bold) iL (t),..., S (bold) i-1 (t) from the terminal 2- ( iL ) to the terminal 2- (i-1) is known, s ( By correcting (bold) i (t) to the signal given by equation (15), it is possible to eliminate interference on the receiving side.
- the nonlinear processing unit 18 corrects s (bold) i (t) according to the above equation (15). Since the terminal 2-1 is not set as an IUI terminal, that is, no IUI is generated in the received signal of the terminal 2-1, the above correction is applied to the transmission signal s (bold) 1 (t) to the terminal 2-1. There is no need to apply. Therefore, as a known and s (bold) 1 (t), s (in bold) 2 corrected (t), using the post-correction s (bold) 2 (t) s (bold) 3 (t) By correcting and sequentially determining the transmission signal, the IUI generated on the reception side can be removed in advance on the transmission side, that is, the base station 1c.
- the non-linear processing unit 18 is an interference removing unit that performs successive interference removal that sequentially determines transmission signals from transmission signals of terminals 2 that are not set as IUI terminals and removes interference.
- the process of sequentially determining transmission signals from the transmission signals of terminals 2 that are not set as IUI terminals as described above and removing interference is referred to as sequential interference cancellation.
- the number of interference cancellations is limited to only L terminals. can do. For this reason, compared with general non-linear MU-MIMO processing, it is possible to suppress the calculation amount reduction and deterioration due to signal subtraction.
- the nonlinear processing unit 18 performs successive interference cancellation on the transmission signal, then multiplies the power distribution matrix P (bold) i generated based on the power distribution, and further calculates the system precoding matrix B (bold) calculated by the above processing. ) (Bar) is output to transmission waveform shaping sections 14-1 to 14-T.
- the nonlinear processing unit 18 is disclosed in “H. Harashima and H. Miyakawa,“ Matched-Transmission Technology for Channels With Intersymbol Interference, ”IEEE Trans. Commun., Vol.20, Aug. 1972.” Modulo arithmetic, or “BM Hochwald, CB Peel, AL Swindlehurst,“ A Vector-Perturbation Technology for Near-Capacity Multiantenna Multiuser Communication-Part II: Perturbation, ”IEEE Trans. Commun., Vol.53, no.3, pp .537-544, March 2005. ”may be applied to stabilize the transmission signal waveform by the perturbation process.
- the precoder unit 12b and the nonlinear processing unit 18 of the present embodiment are processing circuits.
- the precoder unit 12b and the nonlinear processing unit 18 may be dedicated hardware or a control circuit including a memory and a CPU that executes a program stored in the memory.
- the control circuit for realizing the precoder unit 12b and the nonlinear processing unit 18 is, for example, the control circuit 400 shown in FIG.
- L IUI terminals are set for terminals 2-1 to 2- (m ⁇ L) as in the first embodiment, and terminal 2- (m ⁇ L + 1) is configured.
- the system precoding matrix is generated with the number of IUI terminals being less than L, and the transmission signal is corrected by the non-linear processing unit 18 so as to eliminate interference generated on the receiving side in advance on the transmitting side. For this reason, the same effects as those of the first embodiment can be obtained, the multi-user space can be hierarchized, and a non-linear MU-MIMO scheme in which deterioration due to a reduction in calculation amount and signal subtraction is suppressed can be realized.
- 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.
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Abstract
Description
図1は、本発明の実施の形態1にかかる通信システムの構成例を示す図である。図1に示すように、本実施の形態の通信システムは、基地局1と、端末2-1~端末2-mとを備える。mは、2以上の整数である。以下、端末2-1~2-mをユーザと呼ぶこともある。また、端末2-1~2-mを区別せずに示す場合は、端末2と記載する。基地局1は、複数のアンテナを備え、端末2-1~2-mは、1本以上のアンテナを備えることとする。
図10は、本発明にかかる実施の形態2の制御局3の構成と制御局3により制御される基地局1b-1~1b-zを示す図である。zは2以上の整数である。実施の形態1では、基地局1が搭載するアンテナ15-1~15-Tによりビームを形成する例を説明した。これに限らず、T本のアンテナが複数の基地局に分散して搭載されている場合にも、実施の形態1と同様のシステムプレコーディング行列を用いることができる。基地局1b-1~1b-zを区別せずに示す場合は、基地局1bと記載する。本実施の形態では、基地局1b-1~1b-zが有するアンテナの数の総数がTであるとする。
図12は、本発明にかかる実施の形態3の基地局1cの構成例を示す図である。本実施の形態の基地局1cは、実施の形態1の基地局1のプレコーダ12をプレコーダ部12bに替え、非線形処理部18を追加する以外は、実施の形態1の基地局1と同様である。本実施の形態の端末2-1~2-mは、実施の形態1の端末2-1~2-mと同様である。実施の形態1と同様の機能を有する構成要素は、実施の形態1と同一の符号を付して重複する説明を省略する。
Claims (25)
- 複数の受信装置のそれぞれに向けた複数のビームを形成可能な複数の送信アンテナと、
前記複数の受信装置のうちの送信信号の送信先となる第1の受信装置と前記複数の受信装置のうちの2つ以上である第2の受信装置とを除く前記複数の受信装置である第3の受信装置における受信電力が閾値以下となるように前記複数の送信アンテナから送信される信号にプレコーディングを行うプレコーダ、
を備えることを特徴とする送信装置。 - 前記第2の受信装置における受信電力は前記閾値より大きいことを特徴とする請求項1に記載の送信装置。
- 前記複数の送信アンテナから送信される信号に、前記第3の受信装置における受信電力を閾値以下とするためのプレコーディング行列である第1の行列を乗算し、乗算結果に前記第1の受信装置を指向するビームを形成するためのプレコーディング行列である第2の行列を乗算することを特徴とする請求項1または2に記載の送信装置。
- 前記第1の受信装置に対応する前記第2の受信装置を、前記第1の受信装置と前記送信装置との間の伝送路行列と、前記第1の受信装置以外の前記受信装置と前記送信装置との間の伝送路行列との間の相関に基づいて選定することを特徴とする請求項1、2または3に記載の送信装置。
- 前記第1の受信装置に対応する前記第2の受信装置を、前記第1の受信装置と前記第1の受信装置以外の前記受信装置との間の地理的な離隔度に基づいて選定することを特徴とする請求項1、2または3に記載の送信装置。
- 前記プレコーディングにおける前記受信装置の順序を決定するオーダリング部、
を備えることを特徴とする請求項1から5のいずれか1つに記載の送信装置。 - 前記オーダリング部は、前記受信装置に対する電力配分を実施し、
前記プレコーダは、前記複数の送信アンテナから送信される信号に前記電力配分の結果に対応する電力配分行列と前記プレコーディングを実施するためのプレコーディング行列とを乗算することを特徴とする請求項6に記載の送信装置。 - 前記電力配分は、注水定理に従って実施されることを特徴とする請求項7に記載の送信装置。
- 前記電力配分は、前記受信装置における受信品質を均等化する電力配分であることを特徴とする請求項7に記載の送信装置。
- 前記順序は、前記第1の受信装置の次の順番の前記受信装置が、該第1の受信装置に対応する前記第2の受信装置となるよう定められた順序であることを特徴とする請求項6に記載の送信装置。
- 前記オーダリング部は、順番が連続する前記受信装置が地理的に近接するようにまたは離隔するように順序付けする、ことを特徴とする請求項10に記載の送信装置。
- 前記オーダリング部は、順番が連続する前記受信装置の伝送路行列間の相関が高くなるようにまたは低くなるように順序付けすることを特徴とする請求項10に記載の送信装置。
- 逐次干渉除去を行う干渉除去部、を備え、
Kを2以上の整数とし、Lを2以上の整数とするとき、前記オーダリング部により順序付けされた前記複数の受信装置のうちの第1番目から第K番目までの前記受信装置を前記第1の受信装置とするプレコーディング行列は、前記第3の受信装置における受信電力が閾値以下となるようにプレコーディングを行うための行列であり、前記複数の受信装置のうちK+1番目以降の前記受信装置を前記第1の受信装置とするプレコーディング行列は、前記第1の受信装置とL台より少ない台数の前記第2の受信装置とを除く前記複数の受信装置である第4の受信装置における受信電力が閾値以下となるようにプレコーディングを行うための行列であり、
前記干渉除去部は、前記逐次干渉除去として、逐次、次の順番の前記受信装置において生じる干渉を除去する処理を実施することを特徴とする請求項10、11または12に記載の送信装置。 - 前記オーダリング部は、前記順序を前記送信装置と前記受信装置との間の伝送路利得の順とすることを特徴とする請求項6から9のいずれか1つに記載の送信装置。
- 前記オーダリング部は、前記順序を前記送信装置と前記受信装置との間の伝送路行列が持つ非負固有値または非負特異値の大きい順とすることを特徴とする請求項6から9のいずれか1つに記載の送信装置。
- 前記オーダリング部は、前記順序を前記送信装置と前記受信装置との間の伝送路行列が持つ非負固有値または非負特異値の小さい順とすることを特徴とする請求項6から9のいずれか1つに記載の送信装置。
- 請求項1から16のいずれか1つに記載の送信装置から送信された信号を受信する受信装置であって、
前記送信装置から受信した信号から所望信号を抽出するデコーダを備えることを特徴とする受信装置。 - 前記デコーダは、Zero-Forcing法による線形検出により前記所望信号を抽出することを特徴とする請求項17に記載の受信装置。
- 前記デコーダは、最小平均二乗誤差基準に基づく線形検出により前記所望信号を抽出することを特徴とする請求項17に記載の受信装置。
- 前記デコーダは、最尤推定による非線形検出により前記所望信号を抽出することを特徴とする請求項17に記載の受信装置。
- 前記デコーダは、干渉キャンセラによる非線形検出により前記所望信号を抽出することを特徴とする請求項17に記載の受信装置。
- 複数の送信装置に搭載された複数の送信アンテナにより複数の受信装置のそれぞれに向けた複数のビームを形成可能な通信システムにおける制御局であって、
前記複数の受信装置のうちの送信信号の送信先となる第1の受信装置と前記複数の受信装置のうちの2つ以上である第2の受信装置とを除く前記複数の受信装置である第3の受信装置における受信電力が閾値以下となるようにプレコーディングを行うためのプレコーディング行列を算出するプレコーダ算出部と、
前記プレコーディング行列を前記複数の送信装置へ送信する送受信機と、
を備えることを特徴とする制御局。 - 請求項1から16のいずれか1つに記載の送信装置と、
請求項17から21のいずれか1つに記載の受信装置と、
を備えることを特徴とする通信システム。 - 制御局と、複数の送信装置とを備え、複数の送信装置に搭載された複数の送信アンテナにより複数の受信装置のそれぞれに向けた複数のビームを形成可能な通信システムであって、
前記制御局は、
前記複数の受信装置のうちの送信信号の送信先となる第1の受信装置と前記複数の受信装置のうちの2つ以上である第2の受信装置とを除く前記複数の受信装置である第3の受信装置における受信電力が閾値以下となるようにプレコーディングを行うためのプレコーディング行列を算出するプレコーダ算出部と、
前記プレコーディング行列を前記複数の送信装置へ送信する送受信機と、
を備え、
前記送信装置は、
前記プレコーディング行列を受信する送受信機と、
前記送受信機により受信された前記プレコーディング行列を用いてプレコーディングを行うプレコーダと、
を備えることを特徴とする通信システム。 - 複数の受信装置のそれぞれに向けた複数のビームを形成可能な複数の送信アンテナを備える送信装置における送信プレコーディング方法であって、
送信信号の送信先となる前記受信装置である第1の受信装置と前記第1の受信装置以外の前記受信装置である2台以上の第2の受信装置とを決定する第1のステップと、
前記第1の受信装置と前記第2の受信装置とを除く前記複数の受信装置における受信電力が閾値以下となるように前記複数の送信アンテナから送信される信号にプレコーディングを行う第2のステップと、
を含むことを特徴とする送信プレコーディング方法。
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