WO2016175144A1 - 無線基地局 - Google Patents
無線基地局 Download PDFInfo
- Publication number
- WO2016175144A1 WO2016175144A1 PCT/JP2016/062736 JP2016062736W WO2016175144A1 WO 2016175144 A1 WO2016175144 A1 WO 2016175144A1 JP 2016062736 W JP2016062736 W JP 2016062736W WO 2016175144 A1 WO2016175144 A1 WO 2016175144A1
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- WIPO (PCT)
- Prior art keywords
- transmission
- antenna
- reception
- antenna elements
- reception antenna
- Prior art date
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/22—Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
- H01Q21/225—Finite focus antenna arrays
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
- H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
- H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
- H01Q1/246—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for base stations
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
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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
- H04B7/10—Polarisation diversity; Directional 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
-
- 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
-
- 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
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0891—Space-time diversity
- H04B7/0897—Space-time diversity using beamforming per multi-path, e.g. to cope with different directions of arrival [DOA] at different multi-paths
Definitions
- the present invention relates to a radio base station.
- TDD Time Division Duplex
- the on-the-air channel state is basically the same in the uplink and downlink.
- the fact that the uplink and downlink channel states are the same is called channel reciprocity.
- the radio base station can estimate the downlink channel state based on the uplink channel state information (Channel Sate Information), and the parameters for downlink transmission are It is possible to determine. Determining parameters for downlink transmission based on uplink channel state information means parameters for downlink transmission based on downlink channel state information measured by a mobile station (user equipment). This is more advantageous than determining the channel state information because it is not necessary to report downlink channel state information from the mobile station to the radio base station.
- the downlink channel state information measured by the mobile station in the TDD mobile communication system is the uplink channel state measured by the radio base station. This is different from the channel state information of the link.
- These characteristics vary depending on the environment, such as temperature and humidity, and differ depending on the antenna in the same device.
- a characteristic of the transmission circuit is referred to as a transmission gain
- a characteristic of the reception circuit is referred to as a reception gain.
- Non-Patent Document 1 RF (calibration)
- antenna correction antenna correction
- Non-Patent Document 1 The antenna correction described in Non-Patent Document 1 will be described with reference to FIG.
- the radio base station 10 has N transmission / reception antenna elements 11 1 to 11 N
- the user equipment 100 has M transmission / reception antenna elements 101 1 to 101 M. Due to the reversibility of the uplink and downlink channels, the following equation (1) is established.
- Is the uplink channel gain in space from the antenna element 101 m of the user apparatus 100 to the antenna element 11 n of the radio base station 10 Is a downlink channel gain in space from the antenna element 11 n of the radio base station 10 to the antenna element 101 m of the user apparatus 100.
- the subscript m is the antenna number of the user apparatus 100
- the subscript n is the antenna number of the radio base station 10.
- the radio base station 10 each transmit gain for the antenna elements 11 1 ⁇ 11 N In downlink transmission T eNB, 1 ⁇ T eNB, have N, respectively receive the antenna elements 11 1 ⁇ 11 N In the uplink reception Gains R eNB, 1 to R eNB, N are provided.
- User apparatus 100 has reception gains R UE, 1 to R UE, M for antenna elements 101 1 to 101 M in downlink reception, and transmission gain T UE for antenna elements 101 1 to 101 M in uplink transmission, respectively. , 1 to T UE, M.
- the uplink channel coefficient measured by the radio base station 10 Is represented by the following formula (2).
- Downlink channel coefficient measured by user apparatus 100 Is represented by the following formula (3).
- the radio base station 10 determines a parameter for downlink transmission (for example, a downlink transmission precoding matrix) based only on the uplink channel state, the determined parameter is received by the user apparatus 100. It may not be appropriate. Therefore, the user apparatus 100 gives a correction coefficient c UE, m to the uplink signal transmitted from each antenna, and the radio base station 10 applies the correction coefficient c eNB to the downlink signal transmitted from each antenna. , give n .
- a parameter for downlink transmission for example, a downlink transmission precoding matrix
- the corrected channel coefficient should satisfy the following equation.
- Non-Patent Document 1 includes correction coefficients c UE, m and c so as to satisfy the following formulas (7) and (8) derived from formulas (2), (3) and (6): This is done by appropriately determining eNB, n .
- Equation (9) the relationship between the uplink channel coefficient and the downlink channel coefficient is expressed by Equation (9) below.
- Expression (10) is obtained. That is, when antenna correction is not performed, the relationship between the uplink channel matrix and the downlink channel matrix is expressed by Expression (10).
- Expression (10) Is a downlink channel matrix and can be expressed as follows.
- equation (10) can be rewritten as equation (11) below.
- Expressions (7) and (8) are satisfied.
- Expression (8) can be rewritten as Expression (12), and Expression (7) can be rewritten as Expression (13).
- ⁇ n is a parameter of the radio base station 10 corrected by the correction coefficient c eNB, n
- ⁇ m is a parameter of the user apparatus 100 after the correction of the correction coefficient c UE, m .
- ⁇ n and ⁇ m are as follows.
- equation (14) can be rewritten into equation (15).
- the uplink channel matrix To downlink channel matrix Can be understood. Accordingly, parameters for downlink transmission such as a downlink transmission precoding matrix can be appropriately determined based on the uplink channel matrix.
- the correction coefficients c eNB, n and c UE, m can be calculated from the downlink channel information measured by the user apparatus 100 and the uplink channel information measured by the radio base station 10.
- this calculation method cannot be executed when the user apparatus 100 does not exist in the cell area of the radio base station 10.
- it is a waste of time resources and the burden on the user apparatus 100 that the user apparatus 100 receives a dedicated downlink pilot signal for calculating the correction coefficient and reports the result to the radio base station 10. Is big.
- Massive MIMO transmission systems have been studied (for example, Patent Document 1 and Non-Patent Document 3).
- Massive MIMO advanced beamforming using a large number (for example, 100 or more) of transmitting antenna elements (for example, 100 or more) can be performed.
- Beam forming is a method for controlling the direction and shape of a beam of radio waves emitted from a plurality of transmitting antenna elements, by giving weights (weighting coefficients) to the electric signals supplied to the transmitting antenna elements.
- a technique for adjusting the amplitude, including precoding is mainly used in radio base stations.
- Massive MIMO uses a large number of transmitting antenna elements, so it takes time to correct the antenna.
- the correction coefficients c eNB, n and c UE, m are calculated from the downlink channel information measured by the user apparatus 100 and the uplink channel information measured by the radio base station 10 in the user apparatus 100 described above. It is considered that the burden is extremely large and the amount of downlink channel information reported from the user apparatus 100 is enormous.
- the radio base station calculates a correction coefficient from the channel state information. Therefore, there is no burden on the user equipment for calculating the correction coefficient, and there is no need to report downlink channel state information for calculating the correction coefficient. Further, even when the user apparatus 100 does not exist in the cell area of the radio base station 10, the correction coefficient can be calculated.
- the uplink channel matrix To downlink channel matrix Can be understood. Accordingly, parameters for downlink transmission such as a downlink transmission precoding matrix can be appropriately determined based on the uplink channel matrix.
- the radio base station 10 transmits a pilot signal from one reference antenna element (step S1).
- the reference antenna element may be any of the plurality of transmission / reception antenna elements 11 1 to 11 N , for example, may be the transmission / reception antenna element 11 1 .
- the radio base station 10 controls so that other antenna elements do not transmit the pilot signal.
- the radio base station 10 transmits a pilot signal transmitted from a reference antenna element and received by correction target antenna elements (all transmission / reception antenna elements 11 1 to 11 N other than the reference antenna element, for example, transmission / reception antenna elements 11 2 to 11 N ). Based on, channel estimation is executed (step S2). If the reference antenna element is a transmitting and receiving antenna elements 11 1, the radio base station 10 in step S2 is specifically estimate the effective channel coefficients h 1, 2 ⁇ h 1, N. The first subscript indicates the number of the antenna element that has transmitted the pilot signal, and the last subscript indicates the number of the antenna element that has received the pilot signal.
- the radio base station 10 transmits a pilot signal from one correction target antenna element (step S3).
- the correction target antenna element that transmits the pilot signal may be any of a plurality of correction target antenna elements.
- the radio base station 10 controls so that other antenna elements do not transmit the pilot signal.
- the radio base station 10 performs channel estimation based on the pilot signal transmitted from the correction target antenna element and received by the reference antenna element (step S4). If the reference antenna element is a transmitting and receiving antenna elements 11 1, the radio base station 10 in step S4, in particular to estimate the effective channel coefficients h n, 1.
- the first subscript indicates the number of the antenna element that has transmitted the pilot signal, and the last subscript indicates the number of the antenna element that has received the pilot signal.
- the radio base station 10 determines whether there is a correction target antenna element that has not transmitted a pilot signal (step S5). If this determination is affirmative, steps S3 and S4 are executed. When all the correction target antenna elements transmit pilot signals, the radio base station 10 calculates a correction coefficient from the estimated effective channel coefficient (step S6).
- Effective channel coefficients from the antenna element 11 m to the antenna element 11 n h m, n is expressed by the following equation (17).
- h m, n Te eNB, m ⁇ g m, n ⁇ R eNB, n ...
- Effective channel coefficients from the antenna element 11 n to the antenna element 11 m h n, m is represented by the following equation (18).
- h n, m Te eNB, n ⁇ g n, m ⁇ R eNB, m ... (18)
- the channel gain of the downlink space from the antenna element 11 m to the antenna element 11 n g m, n is channel gain g n downlink space from the antenna element 11 n to the antenna element 11 m, equal to m . Therefore, from the equations (17) and (18) , the relationship between the effective channel coefficients h m, n and h n, m is expressed by the following equation (19).
- the correction coefficient c eNB, n is determined so as to satisfy Expression (8).
- the correction coefficient c eNB, n is expressed by the following equation (20) from the equation (8).
- the radio base station 10 determines that the effective channel coefficient estimated in step S2 (eg, h 1, 2 to h 1, N ) and the effective channel coefficient estimated in step S4 ( For example, based on h 2, 1 to h N, 1 ), correction coefficients c eNB, 2 to c eNB, N are calculated for the antenna elements 11 2 to 11 N other than the reference antenna element 11 1 .
- the radio base station 10 controls so that other antenna elements do not transmit the pilot signal.
- a period is required.
- N is the number of transmitting / receiving antenna elements 11 1 to 11 N.
- Massive MIMO radio waves are emitted from a large number of transmitting and receiving antenna elements.
- a technique for easily calculating a plurality of correction coefficients for these many transmitting and receiving antenna elements is desired.
- the present invention provides a radio base station that uses self-correction for antenna correction in a TDD mobile communication system and easily calculates a plurality of correction coefficients for a plurality of transmission / reception antenna elements.
- a radio base station applies a precoding matrix to a downlink signal to perform digital precoding, and a downlink signal subjected to the digital precoding. Then, an analog beamformer that performs analog beamforming that imparts a phase and amplitude change corresponding to a beamforming matrix, and a downlink signal that has been subjected to the analog beamforming are transmitted wirelessly, and the downlink signal is transmitted.
- a plurality of transmission / reception antenna elements that wirelessly receive an uplink signal in the same frequency band as the frequency band used by the user apparatus, and an uplink signal that processes the uplink signals received by the plurality of transmission / reception antenna elements A processing unit.
- the transmission / reception antenna elements are classified into a plurality of antenna groups, each antenna group has a plurality of transmission / reception antenna elements, and the analog beamformer has a plurality of branches respectively corresponding to the plurality of antenna groups.
- Each branch has a plurality of sub-branches, each sub-branch has a variable phase shifter and an amplitude adjuster for performing the analog beam forming, and each sub-branch has one Connected to the transmission / reception antenna element
- the uplink signal processing unit has a plurality of branches respectively corresponding to the plurality of antenna groups, each branch has a plurality of sub-branches, Each sub-branch has a receiving amplifier, and each sub-branch is connected to one of the transmitting and receiving antenna elements. That.
- the radio base station further includes an antenna transmission control unit that controls transmission of pilot signals from the plurality of transmission / reception antenna elements, and a plurality of channel coefficients based on pilot signals received by the plurality of transmission / reception antenna elements.
- an antenna transmission control unit that controls transmission of pilot signals from the plurality of transmission / reception antenna elements, and a plurality of channel coefficients based on pilot signals received by the plurality of transmission / reception antenna elements.
- transmission is performed from the plurality of transmission / reception antenna elements.
- a correction coefficient calculation unit that calculates a correction coefficient to be given to the downlink radio signal.
- the antenna transmission control unit causes only the plurality of transmission / reception antenna elements belonging to a reference antenna group that is one of the plurality of antenna groups to transmit a pilot signal, and the channel estimation unit A plurality of channel coefficients are estimated based on pilot signals received by the plurality of transmission / reception antenna elements belonging to an antenna group other than the reference antenna group.
- the antenna transmission control unit causes only the plurality of transmission / reception antenna elements belonging to an antenna group other than the reference antenna group to transmit a pilot signal, and the channel estimation unit Estimates a plurality of channel coefficients based on pilot signals received by a plurality of the transmitting and receiving antenna elements belonging to the reference antenna group.
- the correction coefficient calculation unit calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- the pilot signal transmitted from the plurality of transmission / reception antenna elements belonging to one antenna group is identified by which transmission / reception antenna element is transmitted after being received by the plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signals received by the plurality of transmission / reception antenna elements belonging to one antenna group can be identified by which transmission / reception antenna element is received.
- a radio base station includes a digital signal processing unit that performs digital precoding by applying a precoding matrix to a downlink signal, and a downlink signal subjected to the digital precoding.
- a digital signal processing unit that performs digital precoding by applying a precoding matrix to a downlink signal, and a downlink signal subjected to the digital precoding.
- an analog beamformer that performs analog beamforming that imparts phase and amplitude changes corresponding to a beamforming matrix, and a downlink signal that has been subjected to the analog beamforming are transmitted wirelessly, and the downlink signal
- a plurality of transmission / reception antenna elements that wirelessly receive uplink signals in the same frequency band as that used for transmission of the user apparatus, and an uplink that processes the uplink signals received by the plurality of transmission / reception antenna elements
- Link signal processor and pilot for antenna correction And at least one antenna correction reference receiving antenna elements to transmit and receive items.
- the transmission / reception antenna elements are classified into a plurality of antenna groups, each antenna group has a plurality of transmission / reception antenna elements, and the analog beamformer has a plurality of branches respectively corresponding to the plurality of antenna groups.
- Each branch has a plurality of sub-branches, each sub-branch has a variable phase shifter and an amplitude adjuster for performing the analog beam forming, and each sub-branch has one Connected to the transmission / reception antenna element
- the uplink signal processing unit has a plurality of branches respectively corresponding to the plurality of antenna groups, each branch has a plurality of sub-branches, Each sub-branch has a receiving amplifier, and each sub-branch is connected to one of the transmitting and receiving antenna elements. That.
- the radio base station further includes an antenna transmission control unit that controls transmission of pilot signals from the antenna correction reference transmission / reception antenna elements and the plurality of transmission / reception antenna elements, and the antenna correction reference transmission / reception antenna elements and the plurality of transmission / reception antennas.
- an antenna transmission control unit controls transmission of pilot signals from the antenna correction reference transmission / reception antenna elements and the plurality of transmission / reception antenna elements, and the antenna correction reference transmission / reception antenna elements and the plurality of transmission / reception antennas.
- a channel estimation unit that estimates a plurality of channel coefficients, and based on a plurality of channel coefficients estimated from uplink radio signals received by the plurality of transmission / reception antenna elements,
- a correction coefficient calculator that calculates a correction coefficient to be given to a downlink radio signal transmitted from the plurality of transmission / reception antenna elements when performing downlink transmission;
- the antenna transmission control unit causes only the antenna correction reference transmission / reception antenna element to transmit a pilot signal
- the channel estimation unit is based on pilot signals received by the plurality of
- the antenna transmission control unit causes only a plurality of transmission / reception antenna elements to transmit pilot signals
- the channel estimation unit is configured to transmit the antenna correction reference transmission / reception antenna elements.
- a plurality of channel coefficients are estimated based on the received pilot signal.
- the correction coefficient calculation unit calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period. Pilot signals transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group can be identified from which transmission / reception antenna elements are transmitted after being received by the antenna correction reference transmission / reception antenna elements. Pilot signals received by the plurality of transmission / reception antenna elements belonging to the antenna group can specify which transmission / reception antenna element has received the pilot signal.
- pilot signals transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group are received by a plurality of transmission / reception antenna elements belonging to another antenna group or the antenna correction reference transmission / reception antenna element.
- the transmission / reception antenna elements can be identified, and the pilot signal received by the plurality of transmission / reception antenna elements belonging to one antenna group can be identified by which transmission / reception antenna element is received. Therefore, it is possible to easily calculate a plurality of correction coefficients for a plurality of transmission / reception antenna elements by using self-correction for antenna correction in a TDD mobile communication system.
- FIG. 1 It is a flowchart which shows the process for the self-correction which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the wireless base station which concerns on the 3rd Embodiment of this invention. It is the figure which simplified FIG. It is a flowchart which shows the process for the self correction which concerns on 3rd Embodiment. It is a block diagram which shows the structure of the wireless base station which concerns on the 4th Embodiment of this invention. It is a block diagram which shows the structure of the wireless base station which concerns on the 5th Embodiment of this invention. It is a block diagram which shows the part relevant to transmission of the radio base station which concerns on the 6th Embodiment of this invention.
- Massive MIMO A radio base station that performs massive MIMO has an antenna set 10A illustrated in FIG.
- the illustrated antenna set 10 ⁇ / b> A has 256 transmission / reception antenna elements 11 of 16 rows and 16 columns.
- the number of antenna elements is not limited.
- Massive MIMO realizes a high wireless communication speed (data rate) by multiplexing a large number of streams.
- data rate data rate
- degree of freedom of antenna control when performing beam forming increases, higher beam forming than before is realized.
- a transmission beam carrying the downlink data signal can be formed toward each user apparatus 100 that is a destination of the downlink data signal. .
- each transmission / reception antenna element 11 for the convenience of control of each transmission / reception antenna element 11, the plurality of transmission / reception antenna elements 11 are classified into a plurality of antenna groups.
- Each antenna group has a plurality of transmitting / receiving antenna elements 11 in the vicinity of each other.
- FIG. 6 shows an example in which 256 transmission / reception antenna elements are classified into 16 antenna groups
- FIG. 7 shows an example in which 256 transmission / reception antenna elements are classified into 4 antenna groups.
- the dotted line in the figure indicates the range of the group.
- each antenna group has 16 transmission / reception antenna elements 11, and in FIG. 7, each antenna group has 64 transmission / reception antenna elements 11.
- antenna grouping is not limited to the illustrated example.
- Hybrid beam forming In various embodiments according to the present invention, a radio base station performs hybrid beam forming.
- Hybrid beamforming is a combination of analog transmission beamforming and digital precoding, and provides rough beam direction control by analog transmission beamforming and high-precision direction control by digital precoding. Can be combined.
- hybrid beamforming can reduce the processing load of digital precoding by analog transmission beamforming. In hybrid beamforming, first, digital precoding is performed, and then analog transmission beamforming is performed.
- FIG. 8 is a block diagram of the radio base station 10 that performs hybrid beamforming, which is the basis of the embodiment of the present invention.
- FIG. 8 shows only the part related to downlink transmission.
- An L-sequence digital baseband signal corresponding to the transmitted L stream is supplied to a baseband processor (digital signal processing unit) 12.
- the baseband processor 12 performs digital precoding by applying a precoding matrix to an L-sequence downlink signal. Therefore, the baseband processor 12 has a digital precoder function.
- the baseband processor 12 is realized by digital signal processing such as DSP (Digital Signal Processor).
- the L-sequence signal output from the baseband processor 12 is converted into an analog signal by a digital-analog converter (DAC) 14 and up-converted by an up converter (frequency converter) 16.
- the L series signals up-converted by the L up-converters 16 are supplied to the analog beam former 18.
- the analog beamformer 18 applies the transmission beamforming matrix to the L-sequence downlink signal to generate an N-sequence signal.
- N is the number of transmitting / receiving antenna elements 11 1 to 11 N.
- the N-series downlink signals subjected to analog beamforming output from the analog beamformer 18 are transmitted wirelessly by the N transmitting / receiving antenna elements 11.
- a filter (not shown) may be provided in the analog beam former 18 or between the analog beam former 18 and the transmission / reception antenna element 11.
- the up-converter 16 may be provided in the analog beam former 18 or between the analog beam former 18 and the transmission / reception antenna element 11.
- the analog beamformer 18 is realized by an analog circuit.
- the analog beamformer 18 has an L branch, and an L-sequence downlink signal corresponding to the L stream is supplied to the L branch.
- Each branch has an N / L sub-branch, and each sub-branch has a variable phase shifter 20 and a power amplifier (amplitude adjuster) 22 for performing analog transmission beam forming.
- each sub-branch is surrounded by one dotted rectangle.
- Each sub-branch is connected to one transmitting / receiving antenna element 11. The signal supplied to each sub-branch and adjusted in phase and amplitude is supplied to the transmission / reception antenna element 11 corresponding to that sub-branch.
- a signal processed in each sub-branch is supplied to one transmission / reception antenna element 11 without being added to a signal processed in another sub-branch.
- the downlink signal supplied to the transmission / reception antenna element 11 is processed independently by only one sub-branch.
- This type of analog beamformer 18 is referred to as a sub-array type analog beamformer.
- the transmission antenna elements # 1 to #N transmit a plurality of streams # 1 to #L.
- L branches each having N / L sub-branches are independent from each other, and one stream is transmitted by N / L transmitting / receiving antenna elements 11.
- stream # 1 is transmitted from transmission / reception antenna elements 11 1 to 11 N / L
- stream #L is transmitted from transmission / reception antenna elements 11 N + 1-N / L to 11 N.
- the transmission / reception antenna elements 11 are classified into a plurality of antenna groups, and each antenna group has a plurality of transmission / reception antenna elements 11.
- One antenna group corresponds to one branch. Therefore, the number of antenna groups is L, and a plurality of (N / L) transmission / reception antenna elements 11 belonging to one antenna group transmit one stream.
- the radio base station 10 further includes a downlink parameter determination unit 24, an antenna transmission control unit 26, a digital phase controller 27, and a digital gain controller 28. Similar to the baseband processor 12, these are functional blocks realized by the DSP executing a computer program stored in a storage unit (not shown) and functioning according to the computer program.
- the downlink parameter determination unit 24 determines parameters for downlink transmission (for example, a downlink precoding matrix and a transmission beamforming matrix) based on uplink channel state information.
- the precoding matrix determined by the downlink parameter determination unit 24 is supplied to the baseband processor 12, and the baseband processor 12 performs digital precoding according to the precoding matrix.
- the digital phase controller 27 controls the phase adjusted by each variable phase shifter 20 of the analog beamformer 18 according to the transmission beamforming matrix determined by the downlink parameter determination unit 24, and the digital phase controller 27 controls the digital phase according to the transmission beamforming matrix.
- the gain controller 28 controls the gain of each power amplifier 22 of the analog beamformer 18.
- the antenna transmission control unit 26 controls transmission of pilot signals from the plurality of transmission / reception antenna elements 11. The function of the antenna transmission control unit 26 will be described in detail later.
- FIG. 9 is a block diagram of the radio base station 10 which is the basis of the embodiment of the present invention.
- FIG. 9 mainly shows parts related to uplink reception.
- the actual radio base station 10 has the components shown in FIG. 8 and the components shown in FIG.
- the transmission / reception antenna elements 11 1 to 11 N receive uplink signals wirelessly from the user apparatus.
- the mobile communication system to which the embodiment is applied is a TDD mobile communication system. Therefore, the transmission / reception antenna elements 11 1 to 11 N receive the uplink signal in the same frequency band as the frequency band used for transmission of the downlink signal from the user apparatus wirelessly.
- the radio base station 10 includes an uplink signal processing unit 30 that processes uplink signals received by a plurality of transmission / reception antenna elements 11.
- the uplink signal processing unit 30 is realized by an analog circuit.
- the uplink signal processing unit 30 has L branches respectively corresponding to L antenna groups, and each branch has N / L sub-branches.
- Each sub-branch has a low noise receiving amplifier 38 and a variable phase shifter 40. In FIG. 9, each sub-branch is surrounded by one dotted rectangle. Each sub-branch is connected to one transmitting / receiving antenna element 11.
- the signal supplied from the transmission / reception antenna element 11 is supplied to the sub-branch corresponding to the transmission / reception antenna element 11, and the amplitude and phase are adjusted by the low noise reception amplifier (LNA)) 38 and the variable phase shifter 40. Is done.
- LNA Low Noise Amplifier
- the signal processed in each sub-branch is added to the signal processed in another sub-branch belonging to the same branch as that sub-branch.
- the uplink signal processing unit 30 outputs an L-sequence signal.
- the L-sequence signal is down-converted by a down converter (frequency converter) 32, converted to an analog signal by an analog-digital converter (ADC) 34, and supplied to the baseband processor 12.
- the down converter 32 may be provided in the uplink signal processing unit 30 or between the uplink signal processing unit 30 and the transmission / reception antenna element 11.
- the radio base station 10 further includes a channel estimation unit 42 and a correction coefficient calculation unit 44. Similar to the baseband processor 12, these are functional blocks realized by the DSP executing a computer program stored in a storage unit (not shown) and functioning according to the computer program.
- the channel estimation unit 42 estimates a plurality of channel coefficients based on radio signals received by the plurality of transmission / reception antenna elements 11. In wireless communication with a user apparatus, the channel estimation unit 42 estimates an uplink channel coefficient based on uplink radio signals transmitted from the user apparatus and received by the plurality of transmission / reception antenna elements 11. In antenna correction, the channel estimation unit 42 calculates channel coefficients for combinations of transmission / reception antenna elements based on radio pilot signals transmitted from the plurality of transmission / reception antenna elements 11 and received by the plurality of transmission / reception antenna elements 11. presume.
- the correction coefficient calculation unit 44 When the radio base station 10 performs downlink transmission based on a plurality of channel coefficients estimated from uplink radio signals received by the plurality of transmission / reception antenna elements 11, the correction coefficient calculation unit 44 performs a plurality of transmission / reception operations. A correction coefficient to be given to the downlink radio signal transmitted from the antenna element 11 is calculated. The correction coefficient calculation unit 44 supplies the correction coefficient to the downlink parameter determination unit 24, and the downlink parameter determination unit 24 controls at least one of digital precoding and analog transmission beamforming based on the correction coefficient. Thus, when the radio base station 10 performs downlink transmission based on a plurality of channel coefficients estimated from uplink radio signals received by the plurality of transmission / reception antenna elements 11, the plurality of transmission / reception antenna elements 11 The transmitted downlink radio signal is corrected. The functions of the channel estimation unit 42 and the correction coefficient calculation unit 44 will be described in detail later.
- FIG. 10 shows components related to radio transmission and radio reception of the radio base station 10 in order to explain antenna correction (self-correction).
- FIG. 10 shows only one branch of the analog beamformer 18 (corresponding to one antenna group) and another branch of the uplink signal processing unit 30 (corresponding to another one antenna group).
- the analog beamformer 18 has an L branch corresponding to the L antenna group
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group.
- Antenna correction is executed to appropriately correct the downlink signal based on the uplink channel matrix using the reversibility of the uplink and downlink channels in the TDD mobile communication system.
- self-correction when transmitting radio signals in a plurality of transmitting and receiving antenna elements 11 1 ⁇ 11 N based on the channel coefficients estimated from the received pilot signals in a plurality of transmitting and receiving antenna elements 11 1 ⁇ 11 N, downlink A correction factor for correcting the transmission parameter of the link is calculated. Therefore, when beamforming or precoding is not performed, the correction coefficient for each of all other correction target antenna elements with respect to one reference antenna element is expressed as follows, as described above with reference to FIGS. Calculation may be performed according to (21).
- the radio base station 10 transmits radio pilot signals (self-correction dedicated pilot signals) from a plurality of antenna elements belonging to the reference antenna group including the transmission / reception antenna elements 11 1 to 11 N / L.
- a plurality of antenna elements belonging to the correction target antenna group by estimating a plurality of channel coefficients based on pilot signals received by a plurality of antenna elements belonging to an antenna group (correction target antenna group) other than the reference antenna group
- a wireless pilot signal is transmitted, and a plurality of channel coefficients are estimated based on pilot signals received by a plurality of antenna elements belonging to the reference antenna group.
- the radio base station 10 calculates a correction coefficient for each of all other antenna elements with respect to the reference antenna element.
- the reference antenna group is an antenna group having one reference antenna element which is a reference for antenna correction and is not subjected to antenna correction (a correction coefficient is set to 1)
- the correction target antenna group is an antenna group other than the reference antenna group.
- Antenna correction is performed on the antenna elements belonging to the correction target antenna group (correction coefficient is calculated).
- antenna correction is also performed on antenna elements that belong to the reference antenna group but are not reference antenna elements (a correction coefficient is calculated).
- FIG. 11 shows a configuration of a radio base station 10 according to a first embodiment of the present invention.
- FIG. 11 shows only one branch (corresponding to one antenna group) of the analog beamformer 18 and the other one branch (corresponding to another one antenna group) of the uplink signal processing unit 30.
- the analog beamformer 18 has an L branch corresponding to the L antenna group
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group.
- the antenna transmission control unit 26 transmits a plurality of transmission / reception antenna elements (for example, transmission / reception antenna elements 11 1 to 11 N /) belonging to a reference antenna group that is one of the L antenna groups in the first period. L ) only transmits a wireless pilot signal, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the correction target antenna group. Further, the antenna transmission control unit 26 transmits a radio pilot only to a plurality of transmission / reception antenna elements belonging to the correction target antenna group in a second period (which may be before or after the first period) different from the first period.
- a second period which may be before or after the first period
- the signal is transmitted, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the reference antenna group.
- the correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- a pilot signal transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group. It is preferable that a pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can specify which transmission / reception antenna element is received.
- each sub-branch of the analog beamformer 18 has a transmission-side switch 50 that prevents transmission of a signal, and is provided in one branch of the uplink signal processing unit 30 in the first period and the second period.
- Each sub-branch of the uplink signal processing unit 30 has a receiving-side switch 60 that prevents another sub-branch belonging to the branch from processing the pilot signal when one sub-branch belongs to the pilot signal.
- each sub-branch is surrounded by one dotted rectangle.
- FIG. 12 is a flowchart showing processing for self-correction according to the first embodiment.
- the antenna transmission control unit 26 transmits a pilot signal only from one antenna element (for example, transmission / reception antenna element 11 1 ) of a reference antenna group (for example, transmission / reception antenna elements 11 1 to 11 N / L ) (step S11).
- the transmission-side switch 50 corresponding to the transmission / reception antenna element that transmits the pilot signal of the reference antenna group is closed, and the transmission-side switch 50 corresponding to the other transmission / reception antenna elements of the reference antenna group is opened.
- the antenna transmission control unit 26 controls each transmission side switch 50.
- step S11 the reception-side switch 60 corresponding to one transmission / reception antenna element of each correction target antenna group is closed, and the reception-side switch 60 corresponding to the other transmission / reception antenna elements of each correction target antenna group is opened.
- the antenna transmission control unit 26 controls each reception-side switch 60 so that
- the channel estimation unit 42 estimates the channel coefficient based on the pilot signal transmitted from the antenna element of the reference antenna group and received by the antenna element of each correction target antenna group (step S12).
- the antenna transmission control unit 26 transmits a pilot signal for the current reception antenna element (currently, the transmission / reception antenna element of each correction target antenna group set by the reception-side switch 60 to receive and process the pilot signal). It is determined whether or not there are any antenna elements in the reference antenna group (step S13). If this determination is affirmative, the transmitting side switch 50 associated with the reference antenna group is controlled to control a pilot signal in the reference antenna group. Are switched (step S14). Thereafter, the processing returns to step S11, a pilot signal is transmitted from another antenna element of the reference antenna group, and the channel estimation unit 42 estimates a channel coefficient (step S12).
- step S13 determines whether or not each correction target antenna group includes an antenna element that has not received the pilot signal (step S15). If affirmative, the receiving side switch 60 related to the correction target antenna group is controlled to switch the antenna element that should receive the pilot signal in each correction target antenna group (step S16). Thereafter, the process returns to step S11, and a pilot signal is transmitted again from one antenna element of the reference antenna group, and the channel estimation unit 42 estimates a channel coefficient (step S12).
- step S17 When all the antenna elements belonging to each correction target antenna group receive the pilot signals transmitted from all the antenna elements belonging to the reference antenna group and the channel coefficients regarding these combinations are estimated, the process proceeds to step S17. .
- first period is a period before step S17
- second period is a period before step S25 starting from step S17.
- step S17 the antenna transmission control unit 26 transmits one antenna element (for example, transmission / reception antenna element 11 1 + N ) of one correction target antenna group (for example, transmission / reception antenna element 11 1 + N / L to 11 2N / L ). / L ) to send a pilot signal only.
- the transmission side switch 50 corresponding to the transmission / reception antenna element that transmits the pilot signal of the correction target antenna group is closed, and the transmission side switch 50 corresponding to the other transmission / reception antenna elements of the correction target antenna group is opened.
- the antenna transmission control unit 26 controls each transmission side switch 50.
- step S17 the receiving switch 60 corresponding to one transmitting / receiving antenna element of the reference antenna group is closed, and the receiving switch 60 corresponding to other transmitting / receiving antenna elements of the reference antenna group is opened.
- the antenna transmission control unit 26 controls each reception side switch 60.
- the channel estimation unit 42 estimates a channel coefficient based on a pilot signal transmitted from one antenna element of one correction target antenna group and received by one antenna element of the reference antenna group (step S18). .
- the antenna transmission control unit 26 is an antenna that is not transmitting a pilot signal for the current reception antenna element (currently a transmission / reception antenna element of a reference antenna group that is set by the reception-side switch 60 to receive and process a pilot signal). It is determined whether or not the element is in the correction target antenna group (step S19). If this determination is affirmative, the transmission-side switch 50 associated with the correction target antenna group is controlled, and the correction target antenna group is determined. Among them, the antenna element that should transmit the pilot signal is switched (step S20). Thereafter, the process returns to step S17, where a pilot signal is transmitted from another antenna element of one correction target antenna group, and the channel estimation unit 42 estimates a channel coefficient (step S18).
- step S19 If the determination in step S19 is negative (that is, all antennas belonging to the correction target antenna group for the transmission / reception antenna elements of the reference antenna group currently set by the reception-side switch 60 to receive and process the pilot signal).
- the antenna transmission control unit 26 determines whether or not the antenna element that has not received the pilot signal is in the reference antenna group (step S21), and this determination is positive. If there is, the reception side switch 60 related to the reference antenna group is controlled to switch the antenna element that should receive the pilot signal in the reference antenna group (step S22). Thereafter, the process returns to step S17, and a pilot signal is transmitted again from one antenna element of the correction target antenna group, and the channel estimation unit 42 estimates a channel coefficient (step S18).
- step S23 When all the antenna elements belonging to the reference antenna group receive the pilot signals transmitted from all the antenna elements belonging to the current correction target antenna group, and the channel coefficients regarding these combinations are estimated, the process proceeds to step S23. move on.
- step S23 the antenna transmission control unit 26 determines whether there is a correction target antenna group that does not transmit a pilot signal. If this determination is affirmative, the antenna transmission control unit 26 switches the correction target antenna group (step S24), and thereafter, the process returns to step S17 to start pilot from one antenna element of another correction target antenna group. The signal is transmitted, and the channel estimation unit 42 estimates the channel coefficient (step S18).
- Pilot signals are transmitted from all antenna elements of all correction target antenna groups, and all antenna elements belonging to the reference antenna group receive pilot signals transmitted from all antenna elements belonging to all correction target antenna groups.
- the process proceeds to step S25.
- the correction coefficient calculation unit 44 calculates correction coefficients for all the antenna elements of the correction target antenna group from the plurality of channel coefficients obtained in step S12 and step S18 according to the equation (21).
- the channel coefficient from the antenna element other than the reference antenna element belonging to the reference antenna group to the antenna element belonging to the correction target antenna group and the channel coefficient in the reverse direction are calculated.
- a correction factor for the antenna element to which it belongs is calculated.
- the correction coefficient calculation unit 44 calculates correction coefficients for all antenna elements other than the reference antenna element belonging to the reference antenna group, from these channel coefficients and correction coefficients.
- the correction coefficient calculation unit 44 supplies the calculated correction coefficient to the downlink parameter determination unit 24, and the downlink parameter determination unit 24 performs at least one of digital precoding and analog transmission beamforming based on the correction coefficient. Control.
- the radio base station 10 performs downlink transmission based on a plurality of channel coefficients estimated from uplink radio signals received by the plurality of transmission / reception antenna elements 11, the plurality of transmission / reception antenna elements 11
- the transmitted downlink radio signal is corrected.
- the correction coefficient c eNB, n for a certain transmission / reception antenna element 11 n can be expressed by the following equation.
- a (n) is the amplitude of the downlink signal given to the transmission / reception antenna element 11 n
- ⁇ (n) is the phase of the downlink signal given to the transmission / reception antenna element 11 n
- the downlink parameter determination unit 24 controls the digital gain controller 28 so that the amplitude of the downlink signal given to the transmission / reception antenna element 11 n becomes A in transmission of the downlink signal, and the transmission / reception antenna element 11 n
- the gain of the corresponding power amplifier 22 is adjusted, and the digital phase controller 27 is controlled so that the phase of the downlink signal given to the transmission / reception antenna element 11 n becomes ⁇ (n), so that it corresponds to the transmission / reception antenna element 11 n .
- the phase shift amount of the variable phase shifter 20 is adjusted.
- the downlink parameter determination unit 24 may adjust the precoding matrix provided to the baseband processor 12 based on the correction coefficient.
- pilot signals transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group are transmitted from any of the transmission / reception antenna elements after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can be specified by which transmission / reception antenna element. Therefore, it is possible to easily calculate a plurality of correction coefficients for a plurality of transmission / reception antenna elements by using self-correction for antenna correction in a TDD mobile communication system.
- a transmission side switch 50 is provided to distinguish each transmission / reception antenna element.
- Massive MIMO when downlink transmission is performed while actually performing beamforming, radio waves are simultaneously emitted from a plurality of transmission / reception antenna elements belonging to one antenna group. Therefore, current flows through a plurality of sub-branches of one branch corresponding to one antenna group, and electromagnetic coupling occurs.
- the antenna element that transmits the pilot signal is switched by the transmission side switch 50, the influence of electromagnetic coupling is not reflected in the correction coefficient.
- providing the transmission side switch 50 in each sub-branch complicates the structure and is complicated to control.
- the sub-branch of the analog beamformer 18 is connected to the transmission / reception antenna elements 11 1 and 11 2, and the sub-branch of the uplink signal processing unit 30 is connected to the transmission / reception antenna elements 11 3 and 11 4 .
- Transmission gains T 1 and T 2 are given to pilot signals X 1 and X 2 transmitted by the transmission / reception antenna elements 11 1 and 11 2 , respectively, and pilot signals received by the transmission / reception antenna elements 11 3 and 11 4 , Reception gains R 3 and R 4 are respectively provided.
- the reception result r by the antenna elements 11 3 and 11 4 is expressed by the following equation (22).
- the first embodiment described above is one of the measures for realizing such an independent equation state.
- the first embodiment has the above problem.
- the second to fifth embodiments solve these problems, and simultaneously transmit pilot signals from a plurality of antenna elements belonging to one antenna group (corresponding to one branch) to calculate a correction coefficient.
- FIG. 14 shows a configuration of a radio base station 10 according to a second embodiment of the present invention.
- FIG. 14 shows only one branch of the analog beamformer 18 (corresponding to one antenna group) and the other branch of the uplink signal processing unit 30 (corresponding to another antenna group).
- the analog beamformer 18 has an L branch corresponding to the L antenna group
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group.
- the antenna transmission control unit 26 transmits a plurality of transmission / reception antenna elements (for example, transmission / reception antenna elements 11 1 to 11 N /) belonging to a reference antenna group that is one of the L antenna groups in the first period. L ) only transmits a wireless pilot signal, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the correction target antenna group. Further, the antenna transmission control unit 26 transmits a radio pilot only to a plurality of transmission / reception antenna elements belonging to the correction target antenna group in a second period (which may be before or after the first period) different from the first period.
- a second period which may be before or after the first period
- the signal is transmitted, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the reference antenna group.
- the correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- a pilot signal transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group. It is preferable that a pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can specify which transmission / reception antenna element is received.
- the radio base station 10 when a plurality of transmission / reception antenna elements belonging to one antenna group transmit pilot signals in the first period and the second period, from these transmission / reception antenna elements.
- a transmission-side phase control unit that varies the phase of the transmitted pilot signal.
- the transmission side phase control unit may be a digital phase controller 27.
- the digital phase controller 27 adjusts the phase of the variable phase shifter 20 for analog transmission beam forming, and in the antenna correction, the digital phase controller 27 changes the phase of the pilot signal. Adjust the phase given by.
- digital phase controller transmission side phase controller 27 for example, a sub-branch of the pilot signal X 1 of the phase corresponding to the transmission and reception antenna elements 11 1 [1,1], it corresponds to the transmission and reception antenna elements 11 2 the sub-branch of the pilot signal X 2 the phase of [1, -1] so that, by adjusting the variable phase shifter 20, orthogonal the pilot signals of these sub-branches (i.e. diffusion).
- each sub-branch of the uplink signal processing unit 30 has a reception-side switch 60 that prevents the branch from processing the pilot signal.
- the baseband processor 12 has a despreader 62.
- the despreading unit 62 performs the reverse operation (that is, despreading) that the variable phase shifter 20 spreads the pilot signal as a result of the operation of the digital phase controller (transmission side phase control unit) 27.
- the pilot signal transmission side digital phase controller (transmission side phase control unit) 27 spreads and the pilot signal reception side despreading unit 62 despreads a plurality of transmission / reception antenna elements belonging to one antenna group.
- the pilot signal transmitted simultaneously can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by the plurality of transmission / reception antenna elements belonging to one antenna group can be identified by which transmission / reception antenna element is received by the action of the reception-side switch 60 on the pilot signal reception side.
- each sub-branch is surrounded by one dotted rectangle.
- FIG. 15 is a flowchart showing processing for self-correction according to the second embodiment.
- the antenna transmission control unit 26 transmits pilot signals from all antenna elements of only the reference antenna group (for example, the transmission / reception antenna elements 11 1 to 11 N / L ) (step S111).
- the digital phase controller 27 gives different phases to a plurality of sub-branches of the reference antenna group.
- the reception-side switch 60 corresponding to one transmission / reception antenna element of each correction target antenna group is closed, and the reception-side switch 60 corresponding to the other transmission / reception antenna elements of each correction target antenna group is opened.
- the antenna transmission control unit 26 controls each reception-side switch 60 so that
- the channel estimation unit 42 estimates a channel coefficient based on a pilot signal transmitted from each antenna element of the reference antenna group and received by one antenna element of each correction target antenna group (step S112).
- the despreading unit 62 performs despreading and identifies the antenna element that is the transmission source of the pilot signal.
- the antenna transmission control unit 26 determines whether each correction target antenna group includes an antenna element that has not received the pilot signal (step S115). If this determination is affirmative, the antenna transmission control unit 26 relates to the correction target antenna group.
- the reception side switch 60 is controlled to switch the antenna element that should receive the pilot signal in each correction target antenna group (step S116). Thereafter, the process returns to step S111, and pilot signals are transmitted again from all antenna elements of the reference antenna group, and the channel estimation unit 42 estimates channel coefficients (step S112).
- step S117 When all the antenna elements belonging to each correction target antenna group receive the pilot signals transmitted from all the antenna elements belonging to the reference antenna group and the channel coefficients regarding these combinations are estimated, the process proceeds to step S117. .
- the “first period” described above is a period before step S117
- the “second period” is a period before step S125 starting from step S117.
- step S117 the antenna transmission control unit 26 transmits pilot signals from all antenna elements of only one correction target antenna group (for example, transmission / reception antenna elements 11 1 + N / L to 11 2N / L ).
- the digital phase controller 27 gives different phases to the plurality of sub-branches of the correction target antenna group.
- the reception-side switch 60 corresponding to one transmission / reception antenna element of the reference antenna group is closed, and the reception-side switch 60 corresponding to the other transmission / reception antenna elements of the reference antenna group is opened.
- the antenna transmission control unit 26 controls each reception side switch 60.
- the channel estimation unit 42 estimates a channel coefficient (step S118).
- the despreading unit 62 performs despreading and identifies the antenna element that is the transmission source of the pilot signal.
- the antenna transmission control unit 26 determines whether or not the antenna element that has not received the pilot signal is in the reference antenna group (step S121). If this determination is affirmative, the reception side related to the reference antenna group is determined. The switch 60 is controlled to switch the antenna element that should receive the pilot signal in the reference antenna group (step S122). Thereafter, the process returns to step S117, and pilot signals are transmitted again from all the antenna elements of the correction target antenna group, and the channel estimation unit 42 estimates the channel coefficient (step S118).
- step S123 When all the antenna elements belonging to the reference antenna group receive the pilot signals transmitted from all the antenna elements belonging to the current correction target antenna group and the channel coefficients regarding these combinations are estimated, the process proceeds to step S123. move on.
- step S123 the antenna transmission control unit 26 determines whether there is a correction target antenna group that does not transmit the pilot signal. If this determination is affirmative, the antenna transmission control unit 26 switches the correction target antenna group (step S124), and then the process returns to step S117, and pilots are transmitted from all antenna elements of the other correction target antenna groups. The signal is transmitted, and the channel estimation unit 42 estimates the channel coefficient (step S118).
- Pilot signals are transmitted from all antenna elements of all correction target antenna groups, and all antenna elements belonging to the reference antenna group receive pilot signals transmitted from all antenna elements belonging to all correction target antenna groups.
- the process proceeds to step S125.
- the correction coefficient calculation unit 44 calculates correction coefficients for all antenna elements of the correction target antenna group from the plurality of channel coefficients obtained in steps S112 and S118.
- the channel coefficient from the antenna element other than the reference antenna element belonging to the reference antenna group to the antenna element belonging to the correction target antenna group and the channel coefficient in the reverse direction are calculated.
- a correction factor for the antenna element to which it belongs is calculated.
- the correction coefficient calculation unit 44 calculates correction coefficients for all antenna elements other than the reference antenna element belonging to the reference antenna group, from these channel coefficients and correction coefficients.
- the correction coefficient calculation unit 44 supplies the calculated correction coefficient to the downlink parameter determination unit 24, and the downlink parameter determination unit 24 performs digital precoding based on the correction coefficient as in the first embodiment. And / or analog transmit beamforming.
- pilot signals transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group are transmitted from any of the transmission / reception antenna elements after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can be specified by which transmission / reception antenna element. Therefore, it is possible to easily calculate a plurality of correction coefficients for a plurality of transmission / reception antenna elements by using self-correction for antenna correction in a TDD mobile communication system.
- Massive MIMO when downlink transmission is performed while actually performing beamforming, radio waves are simultaneously emitted from a plurality of transmission / reception antenna elements belonging to one antenna group. Therefore, current flows through a plurality of sub-branches of one branch corresponding to one antenna group, and electromagnetic coupling occurs.
- the pilot signal is simultaneously transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group in the antenna correction, a correction coefficient reflecting the influence of electromagnetic coupling can be calculated.
- the transmission-side switch 50 is not provided in each sub-branch on the transmission side, the structure is simplified and the control of the components is also simplified. Further, as apparent from comparison between FIG. 12 and FIG. 15, the step of switching the antenna element that transmits the pilot signal is unnecessary, and the processing is simplified.
- FIG. 16 shows a configuration of a radio base station 10 according to a third embodiment of the present invention.
- FIG. 16 shows only one branch of the analog beamformer 18 (corresponding to one antenna group) and another branch of the uplink signal processing unit 30 (corresponding to another antenna group).
- the analog beamformer 18 has an L branch corresponding to the L antenna group
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group.
- the antenna transmission control unit 26 transmits a plurality of transmission / reception antenna elements (for example, transmission / reception antenna elements 11 1 to 11 N /) belonging to a reference antenna group that is one of the L antenna groups in the first period. L ) only transmits a wireless pilot signal, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the correction target antenna group. Further, the antenna transmission control unit 26 transmits a radio pilot only to a plurality of transmission / reception antenna elements belonging to the correction target antenna group in a second period (which may be before or after the first period) different from the first period.
- a second period which may be before or after the first period
- the signal is transmitted, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the reference antenna group.
- the correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- a pilot signal transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group. It is preferable that a pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can specify which transmission / reception antenna element is received.
- the radio base station 10 when a plurality of transmission / reception antenna elements belonging to one antenna group transmit pilot signals in the first period and the second period, from these transmission / reception antenna elements.
- a transmission-side phase control unit that spreads a transmitted pilot signal with different first orthogonal spreading sequences, and a plurality of sub-branches belonging to one branch of the uplink signal processing unit 30 in the first period and the second period has a digital phase controller (reception-side phase control unit) 64 that spreads the pilot signal processed in these sub-branches with different second orthogonal spreading sequences when processing the pilot signal.
- the transmission side phase control unit may be a digital phase controller 27.
- the digital phase controller 27 adjusts the phase of the variable phase shifter 20 for analog transmission beam forming, and in the antenna correction, the digital phase controller 27 changes the phase of the pilot signal. Adjust the phase given by.
- digital phase controller (transmission side phase controller) 27 for example, pilot signal X 1 sub-branch of the transmitting side corresponding to the transmitting and receiving antenna elements 11 1 [1,1, ...], the transmitting and receiving antennas pilot signal X 2 is a sub-branch of the transmitting side corresponding to the element 11 2 [1, -1, ... so that, by adjusting the phase of the variable phase shifter 20, a pilot of these sub-branches Orthogonalize the signal. That is, in the antenna correction, the digital phase controller 27 spreads the pilot signal transmitted from the transmission / reception antenna element with different first orthogonal spreading sequences.
- the digital phase controller 64 is a functional block realized by the DSP executing a computer program stored in a storage unit (not shown) and functioning according to the computer program. In the normal uplink reception, the digital phase controller 64 adjusts the phase of the variable phase shifter 40 for reception beam forming, and in the antenna correction, the digital phase controller 64 adjusts the phase of the received pilot signal. The phase given by 40 is adjusted. In antenna correction, the digital phase controller (reception side phase control unit) 64 multiplies the pilot signal of the reception side sub-branch corresponding to a certain antenna element by [1, 1, 1, 1,. The phase of the variable phase shifter 40 is adjusted so that the pilot signal of the receiving side sub-branch corresponding to the other antenna element is multiplied by [1, -1, 1, -1,.
- the pilot signals of these sub-branches are orthogonalized. That is, in the antenna correction, the digital phase controller 64 spreads the pilot signal received by the transmission / reception antenna element with a different second orthogonal spreading sequence.
- the second orthogonal spreading sequence is longer than the period of the first orthogonal spreading sequence. That is, the second orthogonal spreading sequence is a long code, and the first orthogonal spreading sequence is a short code.
- the baseband processor 12 has a double despreader 66.
- the double despreading unit 66 is the reverse of the effect that the variable phase shifter 40 spreads the pilot signal as a result of the operation of the digital phase control unit (reception side phase control unit) 64 on the reception side (that is, the reverse to the long code (Spreading) and the reverse action of the variable phase shifter 20 spreading the pilot signal as a result of the action of the digital phase control part (transmission side phase control part) 27 on the transmission side (that is, despreading for the short code) ).
- the double despreading unit 66 performs double despreading.
- a plurality of signals belonging to one antenna group are spread by the pilot phase transmission side digital phase control unit (transmission side phase control unit) 27 and the pilot signal reception side despreading unit 66 despreads the short code.
- the pilot signals transmitted simultaneously from the transmission / reception antenna elements can be identified from which transmission / reception antenna elements are transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- a plurality of signals belonging to one antenna group are spread by the pilot phase receiving side digital phase control unit (receiving side phase control unit) 64 and the pilot signal receiving side despreading unit 66 despreads the long code.
- the pilot signal received by the transmitting / receiving antenna element can identify which transmitting / receiving antenna element is received.
- the operations of the digital phase controller 27 and the constituent elements other than the digital phase controller 64 and the double despreading unit 66 are the configurations of the radio base station 10 which is the basis of the embodiment described above with reference to FIGS.
- the same reference numerals are used in FIG. 16 to indicate the same components.
- each sub-branch is surrounded by one dotted rectangle.
- FIG. 17 is a simplified diagram of FIG. 16.
- N / L 2.
- the sub-branch of the analog beamformer 18 is connected to the transmission / reception antenna elements 11 1 and 11 2
- the sub-branch of the uplink signal processing unit 30 is connected to the transmission / reception antenna elements 11 3 and 11 4 .
- Transmission gains T 1 and T 2 are given to pilot signals X 1 and X 2 transmitted by the transmission / reception antenna elements 11 1 and 11 2 , respectively, and pilot signals received by the transmission / reception antenna elements 11 3 and 11 4 , Reception gains R 3 and R 4 are respectively provided.
- the reception result r by the antenna elements 11 3 and 11 4 is expressed by the above equation (22).
- a common pilot signal X is given to each sub-branch on the transmission side.
- X is a sequence [1,1,1,1,1,1,1,1,1,1,1,1, ...].
- Digital phase controller 27 controls the phase of each variable phase shifter 20 of the analog beamformer 18, a sub-branch of the transmitting side corresponding to the antenna element 11 first pilot signal X 1 is [1,1,1, 1,1,1,1,1,1,1,1,1,1, ...], the sub-branch of the transmitting side corresponding to the antenna element 11 second pilot signal X 2 is [ 1, -1,1, -1,1, -1,1, -1,1, -1,1, -1,1, -1,1, ...].
- variable phase shifter 20 corresponding to the antenna element 11 1 has a first orthogonal spreading sequence [1,1,1,1,1,1,1,1,1,1,1,1 , 1,1, multiplied by ... to the pilot signal X
- the variable phase shifter 20 corresponding to the antenna element 11 2 the first orthogonal spreading sequence [1, -1,1, -1,1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1 ...] is multiplied by the pilot signal X.
- the pilot signal X n in the analog beamformer 18 can be expressed by the following equation.
- B (n) is the amplitude of the pilot signal given to the transmitting / receiving antenna element 11 n
- ⁇ (n) is the phase of the pilot signal given to the antenna element 11 n .
- the digital gain controller 28 gives the same amplitude B to the pilot signals X 1 and X 2
- the digital phase controller 27 always sets the phase ⁇ (n) of the pilot signal X 1 to 0 and the phase ⁇ of the pilot signal X 2 .
- (n) is periodically switched between 0 and ⁇ .
- the pilot signal X 1 of the transmission side sub-branch corresponding to the antenna element 11 1 is [ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1,1, ...]
- the antenna element 11 2 in the pilot signal X 2 sub-branch of the transmitting side corresponding [1, -1,1, -1,1, -1,1, -1,1 , -1, -1, -1,1, -1,1, -1, ...].
- digital phase controller 64 on the reception side controls the phase of each variable phase shifter 40 of the uplink signal processing unit 30, a pilot signal on the receiving side of the sub-branch corresponding to the antenna element 11 3 second orthogonal spreading sequence S 3 that is, [1,1,1,1, ...]) is multiplied by the second orthogonal spreading sequence S pilot signal of the receiving side sub branch corresponding to the antenna element 11 4 4 Let [1, -1,1, -1, ...] be multiplied.
- variable phase shifter 40 corresponding to the antenna element 11 3 is variable by the second orthogonal spreading sequence [1,1,1,1, ...] and multiplies the pilot signal, corresponding to the antenna element 11 4
- the phase shifter 40 multiplies the pilot signal X by the second orthogonal spread sequence [1, -1,1, -1, ...].
- the second orthogonal spreading sequences S 3 and S 4 are orthogonal to each other.
- the period of the second orthogonal spreading sequence is four times that of the first orthogonal spreading sequence.
- S 3 * X 1 [1,1,1,1,1,1,1,1,1,1,1,1,1,1, ...]
- S 4 * X 2 [1, -1,1, -1, -1, -1, -1, -1,1,1, -1,1, -1, -1, -1, -1,1, ... ].
- S 3 * X 1 and S 4 * X 2 are orthogonal to each other.
- the reception result r 3 at the antenna element 11 3 and the reception result r 4 at the antenna element 11 4 are expressed by the following equations.
- the combined reception result r r 3 + r 4 .
- the double despreading unit 66 multiplies the reception result r by the first orthogonal spread sequence and the second orthogonal spread sequence (double despread), thereby obtaining the following result.
- the effective channel coefficients g 1, 3, g 2, 3, g 1, 4, g 2, 4 can be calculated. From the above description, when the antenna elements 11 1 and 11 2 transmit pilot signals and the antenna elements 11 3 and 11 4 receive pilot signals, channel coefficients g 1, 3 , g 2, 3 , g 1, It will be understood that 4 , g 2, 4 can be calculated. Conversely, when the antenna elements 11 3 and 11 4 transmit pilot signals and the antenna elements 11 1 and 11 2 receive pilot signals, the effective channel coefficient g 3, 1 in the reverse direction is determined according to the same theory. , G 3, 2 , g 4, 1 , g 4, 2 can be calculated as follows.
- the correction coefficients c eNB, 3 and c eNB, 4 for the antenna elements 11 3 and 11 4 can be calculated according to the following formula. here, It is.
- the antenna element 11 first correction factor for the antenna element 11 2 belonging to the same reference antenna group and c eNB, 2 is unknown, the process up to here, the effective channel coefficients g 3, 2, g 2, 3 is It is known, the correction coefficient c eNB, 3 are calculated regarding the antenna element 11 3. Accordingly, the correction coefficient c eNB, 2 an antenna element 11 2 may be the effective channel coefficients g 3, 2, g 2, 3 and the correction coefficient c eNB, 3 is calculated as follows. Alternatively, the antenna element 11 second correction coefficient c eNB, 2 relates to the effective channel coefficients g 4, 2, g 2, 4 and the correction coefficient c eNB, 4 may be calculated as follows.
- the correction coefficients related to the antenna elements of all antenna groups when the correction coefficient c eNB, 1 related to the reference antenna elements of the reference antenna group is set to 1 are found.
- FIG. 18 is a flowchart showing a process for self-correction according to the third embodiment.
- the antenna transmission control unit 26 transmits pilot signals from all antenna elements of only the reference antenna group (for example, the transmission / reception antenna elements 11 1 to 11 N / L ) (step S211).
- the digital phase controller 27 gives different phases to a plurality of sub-branches of the reference antenna group.
- the digital phase controller 64 gives different phases to a plurality of sub-branches of each correction target antenna group.
- the channel estimation unit 42 estimates an effective channel coefficient based on the pilot signal transmitted from each antenna element of the reference antenna group and received by each antenna element of each correction target antenna group (step S212).
- the double despreading unit 66 performs double despreading, and identifies the antenna element that has transmitted the pilot signal and the received antenna element.
- the processing is performed.
- the process proceeds to S217.
- the “first period” described above is a period before step S217
- the “second period” is a period before step S225 starting from step S217.
- step S217 the antenna transmission control unit 26 transmits pilot signals from all antenna elements of only one correction target antenna group (for example, transmission / reception antenna elements 11 1 + N / L 1 to 11 2N / L ).
- step S217 the digital phase controller 27 gives different phases to the plurality of sub-branches of the correction target antenna group.
- the digital phase controller 64 gives different phases to the plurality of sub-branches of the reference antenna group.
- the channel estimation unit 42 estimates an effective channel coefficient based on a pilot signal transmitted from each antenna element of one correction target antenna group and received by each antenna element of the reference antenna group (step S218). ).
- the double despreading unit 66 performs double despreading and identifies the antenna element that has transmitted the pilot signal and the received antenna element.
- step S223 the antenna transmission control unit 26 determines whether there is a correction target antenna group that does not transmit a pilot signal. If this determination is affirmative, the antenna transmission control unit 26 switches the correction target antenna group (step S224), and then the process returns to step S217, and pilots are transmitted from all antenna elements of the other correction target antenna groups. The signal is transmitted, and the channel estimation unit 42 estimates an effective channel coefficient (step S218).
- step S225 the correction coefficient calculation unit 44 calculates correction coefficients for all antenna elements of the correction target antenna group from the plurality of effective channel coefficients obtained in steps S212 and S218.
- the correction coefficient calculation unit 44 calculates correction coefficients for all antenna elements other than the reference antenna elements belonging to the reference antenna group, from these effective channel coefficients and correction coefficients.
- the correction coefficient calculation unit 44 supplies the calculated correction coefficient to the downlink parameter determination unit 24, and the downlink parameter determination unit 24 performs digital precoding based on the correction coefficient as in the first embodiment. And / or analog transmit beamforming.
- pilot signals transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group are transmitted from any of the transmission / reception antenna elements after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can be specified by which transmission / reception antenna element. Therefore, it is possible to easily calculate a plurality of correction coefficients for a plurality of transmission / reception antenna elements by using self-correction for antenna correction in a TDD mobile communication system.
- FIG. 19 shows the configuration of a radio base station 10 according to a fourth embodiment of the present invention.
- FIG. 19 shows only one branch of the analog beamformer 18 (corresponding to one antenna group) and the other one branch of the uplink signal processing unit 30 (corresponding to another one antenna group).
- the analog beamformer 18 has an L branch corresponding to the L antenna group
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group.
- the antenna transmission control unit 26 transmits a plurality of transmission / reception antenna elements (for example, transmission / reception antenna elements 11 1 to 11 N /) belonging to a reference antenna group that is one of the L antenna groups in the first period. L ) only transmits a wireless pilot signal, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the correction target antenna group. Further, the antenna transmission control unit 26 transmits a radio pilot only to a plurality of transmission / reception antenna elements belonging to the correction target antenna group in a second period (which may be before or after the first period) different from the first period.
- a second period which may be before or after the first period
- the signal is transmitted, and the channel estimation unit 42 estimates a plurality of channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the reference antenna group.
- the correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- a pilot signal transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group. It is preferable that a pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can specify which transmission / reception antenna element is received.
- the radio base station 10 when a plurality of transmission / reception antenna elements belonging to one antenna group transmit pilot signals in the first period and the second period, When a plurality of transmission / reception antenna elements belonging to one antenna group transmit a pilot signal in a first period and a second period, a sequence supply unit that gives the same sequence to signals supplied to a plurality of corresponding sub-branches And a delay adding unit for changing the transmission timing of these pilot signals.
- the affiliated supply unit may be the baseband processor 12.
- the baseband processor (sequence supply unit) 12 supplies a sequence with high autocorrelation and low cross-correlation to the DAC 14 as a source of the pilot signal.
- a sequence may be, for example, a PN (pseudo-noise) sequence or a Zadoff-Chu sequence.
- the delay applying unit may be one or more delay units 52, or cables having different lengths in a plurality of sub branches on the transmission side.
- each sub-branch of the uplink signal processing unit 30 has a reception-side switch 60 that prevents the branch from processing the pilot signal.
- the baseband processor 12 has an inverse correlator 68.
- the inverse correlation unit 68 inversely correlates the received pilot signal with the sequence supplied by the baseband processor (sequence supply unit) 12 when the pilot signal is transmitted.
- pilot signals transmitted simultaneously from a plurality of transmission / reception antenna elements belonging to one antenna group by different delays on the transmission side of the pilot signal and inverse correlation by the inverse correlation unit 68 on the reception side of the pilot signal are transmitted to other antenna groups. It is possible to specify which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to the.
- the pilot signal received by the plurality of transmission / reception antenna elements belonging to one antenna group can be identified by which transmission / reception antenna element is received by the action of the reception-side switch 60 on the pilot signal reception side.
- the components other than the operation of the baseband processor 12 and the delay adding unit, the receiving-side switch 60, and the inverse correlation unit 68 are the configurations of the radio base station 10 that is the basis of the embodiment described above with reference to FIGS.
- the same reference numerals are used in FIG. 19 to indicate the same components.
- each sub-branch is surrounded by one dotted rectangle.
- FIG. 15 is a flowchart showing the process for self-correction according to the second embodiment.
- the digital phase controller 27 does not give different phases to a plurality of sub-branches of each antenna group.
- the correction coefficient calculation unit 44 supplies the calculated correction coefficient to the downlink parameter determination unit 24, and the downlink parameter determination unit 24 performs digital precoding based on the correction coefficient as in the first embodiment. And / or analog transmit beamforming.
- pilot signals transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group are transmitted from any of the transmission / reception antenna elements after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can be specified by which transmission / reception antenna element. Therefore, it is possible to easily calculate a plurality of correction coefficients for a plurality of transmission / reception antenna elements by using self-correction for antenna correction in a TDD mobile communication system.
- Massive MIMO when downlink transmission is performed while actually performing beamforming, radio waves are simultaneously emitted from a plurality of transmission / reception antenna elements belonging to one antenna group. Therefore, current flows through a plurality of sub-branches of one branch corresponding to one antenna group, and electromagnetic coupling occurs.
- the pilot signal is simultaneously transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group in the antenna correction, a correction coefficient reflecting the influence of electromagnetic coupling can be calculated.
- the transmission-side switch 50 is not provided in each sub-branch on the transmission side, the structure is simplified and the control of the components is also simplified. Further, as apparent from comparison between FIG. 12 and FIG. 15, the step of switching the antenna element that transmits the pilot signal is unnecessary, and the processing is simplified.
- FIG. 20 shows a configuration of a radio base station 10 according to a fifth embodiment of the present invention.
- FIG. 20 shows only one branch of the analog beamformer 18 (corresponding to one antenna group) and another branch of the uplink signal processing unit 30 (corresponding to another one antenna group).
- the analog beamformer 18 has an L branch corresponding to the L antenna group
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group.
- the antenna transmission control unit 26 transmits a plurality of transmission / reception antenna elements (for example, transmission / reception antenna elements 11 1 to 11 N /) belonging to a reference antenna group that is one of the L antenna groups in the first period. L ) only transmit a wireless pilot signal, and the channel estimation unit 42 estimates a plurality of effective channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the correction target antenna group. . Further, the antenna transmission control unit 26 transmits a radio pilot only to a plurality of transmission / reception antenna elements belonging to the correction target antenna group in a second period (which may be before or after the first period) different from the first period.
- a second period which may be before or after the first period
- the signal is transmitted, and the channel estimation unit 42 estimates a plurality of effective channel coefficients based on pilot signals received by a plurality of transmission / reception antenna elements belonging to the reference antenna group.
- the correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of effective channel coefficients estimated in the first period and the plurality of effective channel coefficients estimated in the second period.
- a pilot signal transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group. It is preferable that a pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can specify which transmission / reception antenna element is received.
- the radio base station 10 when a plurality of transmission / reception antenna elements belonging to one antenna group transmit pilot signals in the first period and the second period, When a plurality of transmission / reception antenna elements belonging to one antenna group transmit a pilot signal in a first period and a second period, a sequence supply unit that gives the same sequence to signals supplied to a plurality of corresponding sub-branches And a delay adding unit for changing the transmission timing of these pilot signals.
- the affiliated supply unit may be the baseband processor 12.
- the baseband processor (sequence supply unit) 12 supplies a sequence with high autocorrelation and low cross-correlation to the DAC 14 as a source of the pilot signal.
- a sequence may be, for example, a PN (pseudo-noise) sequence or a Zadoff-Chu sequence.
- the delay applying unit may be one or more delay units 52, or cables having different lengths in a plurality of sub branches on the transmission side.
- the radio base station 10 is configured such that when a plurality of sub-branches belonging to one branch of the uplink signal processing unit 30 process pilot signals in the first period and the second period, A digital phase controller (reception-side phase control unit) 64 that varies the phase of the pilot signal processed in each sub-branch.
- the digital phase controller 64 is a functional block realized by the DSP executing a computer program stored in a storage unit (not shown) and functioning according to the computer program. In the normal uplink reception, the digital phase controller 64 adjusts the phase of the variable phase shifter 40 for reception beam forming, and in the antenna correction, the digital phase controller 64 adjusts the phase of the received pilot signal. The phase given by 40 is adjusted. In the antenna correction, the digital phase controller (reception side phase control unit) 64 corresponds to other antenna elements, for example, the pilot signal of the reception side sub-branch corresponding to a certain antenna element is [1, 1, 1, 1]. The phase of the variable phase shifter 40 is adjusted so that the pilot signals of the receiving side sub-branches are [1, 1, ⁇ 1, ⁇ 1], and the pilot signals of these sub-branches are orthogonalized (that is, Spread.
- the baseband processor 12 has a despreading / inverse correlation unit 70.
- the despreading / decorrelation unit 70 has an operation opposite to that in which the variable phase shifter 40 spreads the pilot signal as a result of the operation of the digital phase control unit (reception side phase control unit) 64 on the reception side (ie, despreading).
- the received pilot signal is inversely correlated with the sequence supplied by the baseband processor (sequence supply unit) 12 when transmitting the pilot signal.
- pilot signals transmitted simultaneously from a plurality of transmission / reception antenna elements belonging to one antenna group due to different delays on the transmission side of the pilot signal and inverse correlation by the despreading / inverse correlation unit 70 on the reception side of the pilot signal It is possible to identify which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to the antenna group.
- a plurality of transmission / reception belonging to one antenna group is performed by spreading by the digital phase control unit (reception side phase control unit) 64 on the reception side of the pilot signal and despreading by the despreading / inverse correlation unit 70 on the reception side of the pilot signal.
- the pilot signal received by the antenna element can specify which transmission / reception antenna element is received.
- the components other than the operation of the baseband processor 12 and the delay adding unit, the digital phase controller 64, and the despreading / decorrelating unit 70 are the radio bases that form the basis of the embodiment described above with reference to FIGS.
- the same reference numerals are used in FIG. 20 to denote the same components as station 10 and to indicate the same components.
- each sub-branch is surrounded by one dotted rectangle.
- the flowchart showing the process for self-correction according to the fifth embodiment may be the same as FIG. 18 which is a flowchart showing the process for self-correction according to the third embodiment.
- the digital phase controller 27 does not give different phases to the plurality of sub-branches of each antenna group, and the digital phase controller 64 also applies to the plurality of sub-branches of each antenna group. Do not give a different phase.
- the correction coefficient calculation unit 44 supplies the calculated correction coefficient to the downlink parameter determination unit 24, and the downlink parameter determination unit 24 performs digital precoding based on the correction coefficient as in the first embodiment. And / or analog transmit beamforming.
- pilot signals transmitted from a plurality of transmission / reception antenna elements belonging to one antenna group are transmitted from any of the transmission / reception antenna elements after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by a plurality of transmission / reception antenna elements belonging to one antenna group can be specified by which transmission / reception antenna element. Therefore, it is possible to easily calculate a plurality of correction coefficients for a plurality of transmission / reception antenna elements by using self-correction for antenna correction in a TDD mobile communication system.
- FIGS. 21 and 22 show the configuration of a radio base station 10 according to a sixth embodiment of the present invention.
- FIG. 21 shows only a part related to transmission
- FIG. 22 mainly shows a part related to reception.
- the sixth embodiment is a modification to the first embodiment, and the radio base station 10 transmits a pilot signal for antenna correction in addition to the transmission / reception antenna elements 11 1 to 11 N for communication.
- the antenna correction reference transmitting / receiving antenna elements 111 1 to 111 N / L for receiving are included.
- the radio base station 10 has N / L antenna correction reference transmission / reception antenna elements, but the number of antenna correction reference transmission / reception antenna elements is not limited and may be one.
- pilot signal In transmitting a pilot signal from a correction reference transmission / reception antenna element for antenna correction, the pilot signal is converted into an analog signal by the DAC 14 for the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L , and the up converter 16, the phase and amplitude are adjusted by the variable phase shifter 20 and the power amplifier 22 of the analog beamformer 18, and transmitted by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L (see FIG. 21). ). Pilot signals transmitted from the corrected reference transmitting / receiving antenna elements are received by the transmitting / receiving antenna elements 11 1 to 11 N for communication.
- Pilot signals transmitted from the transmitting and receiving antenna elements 11 1 to 11 N for antenna correction are received by the antenna correction reference transmitting and receiving antenna elements 111 1 to 111 N / L.
- the pilot signals received by the antenna correction reference transmitting / receiving antenna elements 111 1 to 111 N / L are adjusted in amplitude and phase by the low noise receiving amplifier 38 and the variable phase shifter 40, down-converted by the down converter 32, and analog by the ADC 34.
- the signal is converted into a signal and supplied to the baseband processor 12.
- Other components are the same as those of the radio base station 10 of the first embodiment, and the same reference numerals are used in FIGS. 21 and 22 to indicate the same components.
- FIG. 23 shows the configuration of radio base station 10 according to the sixth embodiment of the present invention.
- FIG. 23 shows one branch of the analog beamformer 18 (corresponding to the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ) and another branch of the uplink signal processing unit 30 (transmission / reception antenna for communication).
- the analog beamformer 18 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna elements.
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna element.
- the antenna transmission control unit 26 causes only the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L to transmit radio pilot signals in the first period, and the channel estimation unit 42 A plurality of channel coefficients are estimated based on the pilot signal received by the transmitting / receiving antenna element 11 for communication. Further, the antenna transmission control unit 26 transmits a radio pilot signal only to the plurality of transmission / reception antenna elements 11 in a second period (which may be before or after the first period) different from the first period. Then, the channel estimation unit 42 estimates a plurality of channel coefficients based on the pilot signals received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L. The correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- the pilot signal transmitted from the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L is identified by which antenna correction reference transmission / reception antenna element 111 is transmitted after being received by the communication transmission / reception antenna element 11. It is preferable that the pilot signal received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L can identify which antenna correction reference transmission / reception antenna element 111 has received. Also, pilot signals transmitted from a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group are received by the antenna correction reference transmitting / receiving antenna elements 111 1 to 111 N / L , and then any of the transmitting / receiving antenna elements 11 is received. It is preferable that the pilot signal received by a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group can be specified by which transmitting / receiving antenna element 11 is received. .
- the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L transmits a pilot signal in the first period
- another antenna correction reference transmission / reception antenna element transmits the pilot signal.
- the analog beamformer 18 has a transmission-side switch 50 that prevents the transmission
- the sub-branch belonging to one branch of the uplink signal processing unit 30 processes the pilot signal in the first period.
- the uplink signal processing unit 30 includes a reception side switch 60 that prevents other sub-branches belonging to the branch from processing the pilot signal.
- another transmission / reception antenna element belonging to the antenna group transmits the pilot signal.
- the analog beamformer 18 has a transmission-side switch 50 that prevents transmission, and one sub-branch corresponding to one antenna correction reference transmission / reception antenna element 111 of the uplink signal processing unit 30 is a pilot in the second period.
- the uplink signal processing unit 30 includes a reception-side switch 60 that prevents another sub-branch corresponding to another antenna correction reference transmission / reception antenna element from processing the pilot signal.
- FIG. 12 is a flowchart showing a process for self-correction according to the first embodiment.
- the “reference antenna group” in FIG. 12 is read as “antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ”, and the “correction target antenna group” in FIG. It is read as “antenna group”.
- all communication transmitting / receiving antenna elements 11 are antenna correction targets.
- the transmission side switch 50 and the reception side switch 60 for the antenna correction reference transmission / reception antenna element 111 are not necessary.
- FIG. 24 shows the structure of the wireless base station 10 which concerns on the 7th Embodiment of this invention.
- FIG. 24 shows one branch of the analog beamformer 18 (corresponding to the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ) and another branch of the uplink signal processing unit 30 (transmission / reception antenna for communication).
- the analog beamformer 18 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna elements.
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna element.
- the antenna transmission control unit 26 causes only the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L to transmit radio pilot signals in the first period, and the channel estimation unit 42 A plurality of channel coefficients are estimated based on the pilot signal received by the transmitting / receiving antenna element 11 for communication. Further, the antenna transmission control unit 26 transmits a radio pilot signal only to the plurality of transmission / reception antenna elements 11 in a second period (which may be before or after the first period) different from the first period. Then, the channel estimation unit 42 estimates a plurality of channel coefficients based on the pilot signals received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L. The correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- the pilot signal transmitted from the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L is identified by which antenna correction reference transmission / reception antenna element 111 is transmitted after being received by the communication transmission / reception antenna element 11. It is preferable that the pilot signal received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L can identify which antenna correction reference transmission / reception antenna element 111 has received. Also, pilot signals transmitted from a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group are received by the antenna correction reference transmitting / receiving antenna elements 111 1 to 111 N / L , and then any of the transmitting / receiving antenna elements 11 is received. It is preferable that the pilot signal received by a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group can be specified by which transmitting / receiving antenna element 11 is received. .
- the radio base station 10 when the plurality of antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L transmit pilot signals in the first period, A transmission-side phase control unit that varies the phase of the pilot signal transmitted from the element. Also, the radio base station 10 according to this embodiment transmits a transmission signal from these transmission / reception antenna elements when a plurality of communication transmission / reception antenna elements 11 belonging to one antenna group transmit pilot signals in the second period. A transmission-side phase control unit that varies the phase of the pilot signal to be transmitted.
- the transmission side phase control unit may be a digital phase controller 27.
- the digital phase controller 27 adjusts the phase of the variable phase shifter 20 for analog transmission beam forming, and in the antenna correction, the digital phase controller 27 changes the phase of the pilot signal. Adjust the phase given by.
- the digital phase controller (transmission-side phase control unit) 27 sets the phase of the pilot signal X 1 of the sub-branch corresponding to the antenna element 111 1 to [1, 1] and the sub-corresponding to the antenna element 111 2 , for example. the branch of the pilot signal X 2 phase [1, -1] so that, by adjusting the variable phase shifter 20, orthogonal the pilot signals of these sub-branches (i.e. diffusion).
- each sub-branch of the uplink signal processing unit 30 has a reception-side switch 60 that prevents the branch from processing the pilot signal.
- the baseband processor 12 has a despreader 62.
- the despreading unit 62 performs the reverse operation (that is, despreading) that the variable phase shifter 20 spreads the pilot signal as a result of the operation of the digital phase controller (transmission side phase control unit) 27.
- a plurality of transmission / reception antenna elements belonging to one antenna group are performed.
- a pilot signal transmitted simultaneously from the transmission / reception antenna element 11 or the antenna correction reference transmission / reception antenna element 111) is transmitted from any of the transmission / reception antenna elements after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by the plurality of transmission / reception antenna elements belonging to one antenna group can be identified by which transmission / reception antenna element is received by the action of the reception-side switch 60 on the pilot signal reception side.
- FIG. 15 is a flowchart showing a process for self-correction according to the second embodiment.
- the “reference antenna group” in FIG. 15 is read as “antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ”, and the “correction target antenna group” in FIG. It is read as “antenna group”.
- all communication transmitting / receiving antenna elements 11 are subject to antenna correction.
- the transmission-side phase control unit and the reception-side switch 60 for the antenna correction reference transmission / reception antenna element 111 are unnecessary, and the antenna correction reference transmission / reception antenna element In the reception processing of the pilot signal transmitted from 111, the despreading unit 62 is also unnecessary.
- FIG. 25 shows the configuration of a radio base station 10 according to an eighth embodiment of the present invention.
- FIG. 25 shows one branch of the analog beamformer 18 (corresponding to the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ) and another branch of the uplink signal processing unit 30 (transmission / reception antenna for communication).
- the analog beamformer 18 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna elements.
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna element.
- the antenna transmission control unit 26 causes only the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L to transmit radio pilot signals in the first period, and the channel estimation unit 42 A plurality of effective channel coefficients are estimated based on the pilot signal received by the transmitting / receiving antenna element 11 for communication. Further, the antenna transmission control unit 26 transmits a radio pilot signal only to the plurality of transmission / reception antenna elements 11 in a second period (which may be before or after the first period) different from the first period. Then, the channel estimation unit 42 estimates a plurality of effective channel coefficients based on the pilot signals received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L. The correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of effective channel coefficients estimated in the first period and the plurality of effective channel coefficients estimated in the second period.
- the pilot signal transmitted from the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L is identified by which antenna correction reference transmission / reception antenna element 111 is transmitted after being received by the communication transmission / reception antenna element 11. It is preferable that the pilot signal received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L can identify which antenna correction reference transmission / reception antenna element 111 has received. Also, pilot signals transmitted from a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group are received by the antenna correction reference transmitting / receiving antenna elements 111 1 to 111 N / L , and then any of the transmitting / receiving antenna elements 11 is received. It is preferable that the pilot signal received by a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group can be specified by which transmitting / receiving antenna element 11 is received. .
- the radio base station 10 when the plurality of antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L transmit pilot signals in the first period,
- the pilot signals transmitted from the elements are spread with different first orthogonal spreading sequences (short codes), and a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group transmit the pilot signals in the second period.
- a transmission-side phase control unit that spreads pilot signals transmitted from these transmission / reception antenna elements with different first orthogonal spreading sequences is provided.
- the radio base station 10 is configured such that when a plurality of sub-branches belonging to one branch of the uplink signal processing unit 30 process pilot signals in the first period and the second period, A digital phase controller (reception-side phase control unit) 64 that spreads pilot signals processed in the sub-branches with different second orthogonal spreading sequences (long codes). Similar to the third embodiment, the transmission-side phase control unit may be a digital phase controller 27.
- the baseband processor 12 has a double despreader 66.
- the double despreading unit 66 is the reverse of the effect that the variable phase shifter 40 spreads the pilot signal as a result of the operation of the digital phase control unit (reception side phase control unit) 64 on the reception side (that is, the reverse to the long code (Spreading) and the reverse action of the variable phase shifter 20 spreading the pilot signal as a result of the action of the digital phase control part (transmission side phase control part) 27 on the transmission side (that is, despreading for the short code) ).
- the double despreading unit 66 performs double despreading.
- a plurality of signals belonging to one antenna group are spread by the pilot phase transmission side digital phase control unit (transmission side phase control unit) 27 and the pilot signal reception side despreading unit 66 despreads the short code.
- Pilot signals simultaneously transmitted from the transmission / reception antenna elements are received by a plurality of transmission / reception antenna elements belonging to another antenna group, It can be specified whether the signal is transmitted from the antenna element.
- a plurality of signals belonging to one antenna group are spread by the pilot phase receiving side digital phase control unit (receiving side phase control unit) 64 and the pilot signal receiving side despreading unit 66 despreads the long code.
- the pilot signal received by the transmitting / receiving antenna element can identify which transmitting / receiving antenna element is received.
- FIG. 18 is a flowchart showing a process for self-correction according to the third embodiment.
- the “reference antenna group” in FIG. 18 is replaced with “antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ”, and the “correction target antenna group” in FIG. It is read as “antenna group”.
- all communication transmitting / receiving antenna elements 11 are antenna correction targets.
- the transmission-side phase control unit and the reception-side phase control unit for the antenna correction reference transmission / reception antenna element 111 are unnecessary, and the antenna correction reference transmission / reception antenna 111
- despreading for the short code by the double despreading unit 66 is unnecessary, and in the reception processing of the pilot signal received by the antenna correction reference transmission / reception antenna element 111, double despreading is performed.
- Despreading of the long code by the unit 66 is not necessary.
- FIG. 26 shows the configuration of a radio base station 10 according to a ninth embodiment of the present invention.
- FIG. 26 shows one branch of the analog beamformer 18 (corresponding to the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ) and another branch of the uplink signal processing unit 30 (transmission / reception antenna for communication).
- the analog beamformer 18 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna elements.
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna element.
- the antenna transmission control unit 26 causes only the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L to transmit radio pilot signals in the first period, and the channel estimation unit 42 A plurality of channel coefficients are estimated based on the pilot signal received by the transmitting / receiving antenna element 11 for communication. Further, the antenna transmission control unit 26 transmits a radio pilot signal only to the plurality of transmission / reception antenna elements 11 in a second period (which may be before or after the first period) different from the first period. Then, the channel estimation unit 42 estimates a plurality of channel coefficients based on the pilot signals received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L. The correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of channel coefficients estimated in the first period and the plurality of channel coefficients estimated in the second period.
- the pilot signal transmitted from the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L is identified by which antenna correction reference transmission / reception antenna element 111 is transmitted after being received by the communication transmission / reception antenna element 11. It is preferable that the pilot signal received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L can identify which antenna correction reference transmission / reception antenna element 111 has received. Also, pilot signals transmitted from a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group are received by the antenna correction reference transmitting / receiving antenna elements 111 1 to 111 N / L , and then any of the transmitting / receiving antenna elements 11 is received. It is preferable that the pilot signal received by a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group can be specified by which transmitting / receiving antenna element 11 is received. .
- the radio base station 10 when the plurality of antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L transmit pilot signals in the first period, when a plurality of antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L transmit pilot signals, a sequence supply unit that gives the same sequence to signals supplied to a plurality of sub-branches corresponding to the elements, these pilot signals Has a delay adding unit that changes the transmission timing of the. Also, the radio base station 10 according to this embodiment corresponds to these transmission / reception antenna elements when a plurality of communication transmission / reception antenna elements 11 belonging to one antenna group transmit pilot signals in the second period.
- the sequence supply unit may be a baseband processor 12.
- the baseband processor (sequence supply unit) 12 supplies a sequence with high autocorrelation and low cross-correlation to the DAC 14 as a source of the pilot signal.
- Such a sequence may be, for example, a PN (pseudo-noise) sequence or a Zadoff-Chu sequence.
- the delay adding unit may be one or more delay units 52, or cables having different lengths in a plurality of sub branches on the transmission side.
- each sub-branch of the uplink signal processing unit 30 has a reception-side switch 60 that prevents the branch from processing the pilot signal.
- the baseband processor 12 has an inverse correlator 68.
- the inverse correlation unit 68 inversely correlates the received pilot signal with the sequence supplied by the baseband processor (sequence supply unit) 12 when the pilot signal is transmitted.
- a plurality of transmission / reception antenna elements (transmission / reception antenna element 11 for communication or antenna correction reference transmission / reception) belonging to one antenna group are caused by different delays on the transmission side of the pilot signal and inverse correlation by the inverse correlation unit 68 on the reception side of the pilot signal.
- the pilot signal transmitted simultaneously from the antenna element 111) can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- the pilot signal received by the plurality of transmission / reception antenna elements belonging to one antenna group can be identified by which transmission / reception antenna element is received by the action of the reception-side switch 60 on the pilot signal reception side.
- FIG. 15 is a flowchart showing a process for self-correction according to the second embodiment.
- the “reference antenna group” in FIG. 15 is read as “antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ”, and the “correction target antenna group” in FIG. It is read as “antenna group”.
- all communication transmitting / receiving antenna elements 11 are antenna correction targets.
- the digital phase controller 27 does not give different phases to a plurality of sub-branches of each antenna group.
- the delay applying unit and the reception-side switch 60 for the antenna correction reference transmission / reception antenna element 111 are not necessary.
- the inverse correlation unit 68 is also unnecessary.
- FIG. 27 shows the configuration of a radio base station 10 according to a tenth embodiment of the present invention.
- FIG. 27 shows one branch of the analog beamformer 18 (corresponding to the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ) and another branch of the uplink signal processing unit 30 (transmission / reception antenna for communication).
- the analog beamformer 18 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna elements.
- the uplink signal processing unit 30 has an L branch corresponding to the L antenna group of the transmission / reception antenna elements for communication and one branch corresponding to the antenna correction reference transmission / reception antenna element.
- the antenna transmission control unit 26 causes only the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L to transmit radio pilot signals in the first period, and the channel estimation unit 42 A plurality of effective channel coefficients are estimated based on the pilot signal received by the transmitting / receiving antenna element 11 for communication. Further, the antenna transmission control unit 26 transmits a radio pilot signal only to the plurality of transmission / reception antenna elements 11 in a second period (which may be before or after the first period) different from the first period. Then, the channel estimation unit 42 estimates a plurality of effective channel coefficients based on the pilot signals received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L. The correction coefficient calculation unit 44 calculates a plurality of correction coefficients from the plurality of effective channel coefficients estimated in the first period and the plurality of effective channel coefficients estimated in the second period.
- the pilot signal transmitted from the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L is identified by which antenna correction reference transmission / reception antenna element 111 is transmitted after being received by the communication transmission / reception antenna element 11. It is preferable that the pilot signal received by the antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L can identify which antenna correction reference transmission / reception antenna element 111 has received. Also, pilot signals transmitted from a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group are received by the antenna correction reference transmitting / receiving antenna elements 111 1 to 111 N / L , and then any of the transmitting / receiving antenna elements 11 is received. It is preferable that the pilot signal received by a plurality of communication transmitting / receiving antenna elements 11 belonging to one antenna group can be specified by which transmitting / receiving antenna element 11 is received. .
- the radio base station 10 when the plurality of antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L transmit pilot signals in the first period, when a plurality of antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L transmit pilot signals, a sequence supply unit that gives the same sequence to signals supplied to a plurality of sub-branches corresponding to the elements, these pilot signals Has a delay adding unit that changes the transmission timing of the. Also, the radio base station 10 according to this embodiment corresponds to these transmission / reception antenna elements when a plurality of communication transmission / reception antenna elements 11 belonging to one antenna group transmit pilot signals in the second period.
- the sequence supply unit may be a baseband processor 12.
- the baseband processor (sequence supply unit) 12 supplies a sequence with high autocorrelation and low cross-correlation to the DAC 14 as a source of the pilot signal.
- Such a sequence may be, for example, a PN (pseudo-noise) sequence or a Zadoff-Chu sequence.
- the delay adding unit may be one or more delay units 52, or cables having different lengths in a plurality of sub branches on the transmission side.
- the radio base station 10 has a plurality of sub-stations belonging to one branch of the uplink signal processing unit 30 in the first period and the second period.
- the branch processes the pilot signal
- it has a digital phase controller (reception-side phase control unit) 64 that changes the phase of the pilot signal processed in these sub-branches.
- the baseband processor 12 has a despreading / inverse correlation unit 70.
- the despreading / decorrelation unit 70 has an operation opposite to that in which the variable phase shifter 40 spreads the pilot signal as a result of the operation of the digital phase control unit (reception side phase control unit) 64 on the reception side (ie, despreading).
- the received pilot signal is inversely correlated with the sequence supplied by the baseband processor (sequence supply unit) 12 when transmitting the pilot signal.
- a plurality of transmission / reception antenna elements (communication transmission / reception antenna elements 11 or antennas) belonging to one antenna group are caused by different delays on the transmission side of the pilot signal and inverse correlation by the despreading / inverse correlation unit 70 on the reception side of the pilot signal.
- the pilot signal transmitted simultaneously from the corrected reference transmission / reception antenna element 111) can be identified from which transmission / reception antenna element is transmitted after being received by a plurality of transmission / reception antenna elements belonging to another antenna group.
- a plurality of transmission / reception belonging to one antenna group is performed by spreading by the digital phase control unit (reception side phase control unit) 64 on the reception side of the pilot signal and despreading by the despreading / inverse correlation unit 70 on the reception side of the pilot signal.
- the pilot signal received by the antenna element can specify which transmission / reception antenna element is received.
- FIG. 18 is a flowchart showing a process for self-correction according to the third embodiment.
- the “reference antenna group” in FIG. 18 is replaced with “antenna correction reference transmission / reception antenna elements 111 1 to 111 N / L ”, and the “correction target antenna group” in FIG. It is read as “antenna group”.
- all communication antenna elements 11 for communication are antenna correction targets.
- the digital phase controller 27 does not give different phases to a plurality of sub-branches of each antenna group.
- the delay applying unit and the reception-side phase control unit for the antenna correction reference transmission / reception antenna elements 111 are not necessary.
- the inverse spread by the despreading / decorrelation unit 70 is unnecessary, and in the reception process of the pilot signal received by the antenna correction reference transmission / reception antenna element 111, the despreading / inverse correlation unit 70 No despreading is necessary.
- the antenna element transmits and receives a wireless pilot signal
- the correction coefficient is calculated based on the wireless pilot signal propagating in space.
- transmission / reception of a wireless pilot signal is based on a procedure, in which a pilot signal is transmitted and received in a wired manner between antenna elements via a coupling circuit that couples the antenna elements, and is transmitted through a coupling circuit.
- a correction factor may be calculated based on the effective channel coefficient of the pilot signal.
- each function executed by the DSP may be executed by hardware instead of the DSP, and programmable such as, for example, FPGA (Field Programmable Gate Array) and CPU (Central Processing Unit) It may be executed by a logic device.
- programmable such as, for example, FPGA (Field Programmable Gate Array) and CPU (Central Processing Unit) It may be executed by a logic device.
Abstract
Description
wn = TeNB, n/ReNB, n
である。vnは、ユーザ装置100のパラメータであり、
vm = RUE, m/TUE, m
である。
hm, n = TeNB, m・gm, n・ReNB, n ...(17)
アンテナ素子11nからアンテナ素子11mへの実効的なチャネル係数hn, mは、下記の式(18)で表される。
hn, m = TeNB, n・gn, m・ReNB, m ...(18)
Massive MIMO
Massive MIMOを実行する無線基地局は、図4に例示するアンテナセット10Aを有する。図示のアンテナセット10Aは、16行16列の256個の送受信アンテナ素子11を有する。但し、アンテナ素子の数は、限定されない。
本発明に係る各種の実施の形態では、無線基地局がハイブリッドビームフォーミング(hybrid beamforming)を実行する。ハイブリッドビームフォーミングは、アナログ送信ビームフォーミング(analog transmission beamforming)とディジタルプリコーディング(digital precoding)の組み合わせ技術であり、アナログ送信ビームフォーミングによるおおまかなビームの方向制御とディジタルプリコーディングによる高精度な方向制御を組み合わせることができる。また、ハイブリッドビームフォーミングは、ディジタルプリコーディングの処理負担をアナログ送信ビームフォーミングにより軽減することができる。ハイブリッドビームフォーミングでは、まずディジタルプリコーディングを行い、次にアナログ送信ビームフォーミングを行う。
図11は、本発明の第1の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図11は、アナログビームフォーマ18の1ブランチ(1アンテナグループに対応)および上りリンク信号処理部30の他の1ブランチ(他の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、Lアンテナグループに対応するLブランチを有し、上りリンク信号処理部30はLアンテナグループに対応するLブランチを有する。
図14は、本発明の第2の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図14は、アナログビームフォーマ18の1ブランチ(1アンテナグループに対応)および上りリンク信号処理部30の他の1ブランチ(他の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、Lアンテナグループに対応するLブランチを有し、上りリンク信号処理部30はLアンテナグループに対応するLブランチを有する。
図16は、本発明の第3の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図16は、アナログビームフォーマ18の1ブランチ(1アンテナグループに対応)および上りリンク信号処理部30の他の1ブランチ(他の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、Lアンテナグループに対応するLブランチを有し、上りリンク信号処理部30はLアンテナグループに対応するLブランチを有する。
図19は、本発明の第4の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図19は、アナログビームフォーマ18の1ブランチ(1アンテナグループに対応)および上りリンク信号処理部30の他の1ブランチ(他の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、Lアンテナグループに対応するLブランチを有し、上りリンク信号処理部30はLアンテナグループに対応するLブランチを有する。
図20は、本発明の第5の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図20は、アナログビームフォーマ18の1ブランチ(1アンテナグループに対応)および上りリンク信号処理部30の他の1ブランチ(他の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、Lアンテナグループに対応するLブランチを有し、上りリンク信号処理部30はLアンテナグループに対応するLブランチを有する。
図21および図22は、本発明の第6の実施の形態に係る無線基地局10の構成を示す。図21は、送信に関連する部分のみを示し、図22は、主に受信に関連する部分を示す。第6の実施の形態は、第1の実施の形態に修正であり、無線基地局10は、通信用の送受信アンテナ素子111~11Nに加えて、アンテナ補正のためのパイロット信号を送信および受信するアンテナ補正基準送受信アンテナ素子1111~111N/Lを有する。図示の実施の形態では、無線基地局10はN/L本のアンテナ補正基準送受信アンテナ素子を有するが、アンテナ補正基準送受信アンテナ素子の数は限定されず、1つでもよい。
図24は、本発明の第7の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図24は、アナログビームフォーマ18の1ブランチ(アンテナ補正基準送受信アンテナ素子1111~111N/Lに対応)および上りリンク信号処理部30の他の1ブランチ(通信用の送受信アンテナ素子の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有し、上りリンク信号処理部30は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有する。
図25は、本発明の第8の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図25は、アナログビームフォーマ18の1ブランチ(アンテナ補正基準送受信アンテナ素子1111~111N/Lに対応)および上りリンク信号処理部30の他の1ブランチ(通信用の送受信アンテナ素子の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有し、上りリンク信号処理部30は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有する。
図26は、本発明の第9の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図26は、アナログビームフォーマ18の1ブランチ(アンテナ補正基準送受信アンテナ素子1111~111N/Lに対応)および上りリンク信号処理部30の他の1ブランチ(通信用の送受信アンテナ素子の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有し、上りリンク信号処理部30は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有する。
図27は、本発明の第10の実施の形態に係る無線基地局10の構成を示す。説明の便宜上、図27は、アナログビームフォーマ18の1ブランチ(アンテナ補正基準送受信アンテナ素子1111~111N/Lに対応)および上りリンク信号処理部30の他の1ブランチ(通信用の送受信アンテナ素子の1アンテナグループに対応)のみを示すが、実際には、アナログビームフォーマ18は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有し、上りリンク信号処理部30は、通信用の送受信アンテナ素子のLアンテナグループに対応するLブランチとアンテナ補正基準送受信アンテナ素子に対応する1ブランチを有する。
上記の実施の形態では、アンテナ素子が無線のパイロット信号を送信および受信し、空間を伝搬する無線のパイロット信号に基づいて、補正係数が計算される。しかし、無線のパイロット信号の送受信とは手順に基づいて,各アンテナ素子を結合する結合回路(coupling circuit)を介してアンテナ素子間で有線でパイロット信号を送信および受信し、結合回路を伝搬する有線のパイロット信号の実効的なチャネル係数に基づいて、補正係数が計算されてもよい。
Claims (7)
- 下りリンク信号にプリコーディング行列を適用して、ディジタルプリコーディングを実行するディジタル信号処理部と、
前記ディジタルプリコーディングが施された下りリンク信号に対して、ビームフォーミング行列に相当する位相および振幅の変化を付与するアナログビームフォーミングを実行するアナログビームフォーマと、
前記アナログビームフォーミングが施された下りリンク信号を無線で送信し、前記下りリンク信号の送信に利用される周波数帯と同じ周波数帯での上りリンク信号をユーザ装置から無線で受信する複数の送受信アンテナ素子と、
前記複数の送受信アンテナ素子で受信された前記上りリンク信号を処理する上りリンク信号処理部と
を備え、
前記送受信アンテナ素子は、複数のアンテナグループに分類され、各アンテナグループは複数の送受信アンテナ素子を有しており、
前記アナログビームフォーマは、前記複数のアンテナグループにそれぞれ対応する複数のブランチを有しており、各ブランチは複数のサブブランチを有しており、各サブブランチは、前記アナログビームフォーミングを実行するための可変移相器と振幅調整器を有しており、各サブブランチは1つの前記送受信アンテナ素子に接続されており、
前記上りリンク信号処理部は、前記複数のアンテナグループにそれぞれ対応する複数のブランチを有しており、各ブランチは複数のサブブランチを有しており、各サブブランチは受信増幅器を有しており、各サブブランチは1つの前記送受信アンテナ素子に接続されており、
さらに、前記複数の送受信アンテナ素子からのパイロット信号の送信を制御するアンテナ送信制御部と、
前記複数の送受信アンテナ素子で受信されたパイロット信号に基づいて、複数のチャネル係数を推定するチャネル推定部と、
前記複数の送受信アンテナ素子で受信された上りリンクの無線信号から推定される複数のチャネル係数に基づいて、下りリンク送信を行う場合に、前記複数の送受信アンテナ素子から送信される下りリンクの無線信号に与えられるべき補正係数を計算する補正係数計算部とを備え、
第1の期間に、前記アンテナ送信制御部は、前記複数のアンテナグループの1つである基準アンテナグループに属する複数の前記送受信アンテナ素子だけにパイロット信号を送信させて、前記チャネル推定部は、前記基準アンテナグループ以外のアンテナグループに属する複数の前記送受信アンテナ素子で受信されたパイロット信号に基づいて、複数のチャネル係数を推定し、
前記第1の期間とは異なる第2の期間に、前記アンテナ送信制御部は、前記基準アンテナグループ以外のアンテナグループに属する複数の前記送受信アンテナ素子だけにパイロット信号を送信させて、前記チャネル推定部は、前記基準アンテナグループに属する複数の前記送受信アンテナ素子で受信されたパイロット信号に基づいて、複数のチャネル係数を推定し、
前記補正係数計算部は、前記第1の期間で推定された複数の前記チャネル係数と、前記第2の期間で推定された複数の前記チャネル係数から、複数の前記補正係数を計算し、
1つのアンテナグループに属する複数の前記送受信アンテナ素子から送信されるパイロット信号は、他のアンテナグループに属する複数の前記送受信アンテナ素子に受信された後に、いずれの送受信アンテナ素子から送信されたか特定することができ、
1つのアンテナグループに属する複数の前記送受信アンテナ素子で受信されるパイロット信号は、いずれの送受信アンテナ素子で受信されたか特定することができる
無線基地局。 - 前記第1の期間および前記第2の期間で、1つのアンテナグループに属する1つの送受信アンテナ素子がパイロット信号を送信する時に、そのアンテナグループに属する他の送受信アンテナ素子がパイロット信号を送信することを防止する送信側スイッチと、
前記第1の期間および前記第2の期間で、前記上りリンク信号処理部の1つのブランチに属する1つのサブブランチがパイロット信号を処理する時に、そのブランチに属する他のサブブランチがパイロット信号を処理することを防止する受信側スイッチとを
さらに備える請求項1に記載の無線基地局。 - 前記第1の期間および前記第2の期間で、1つのアンテナグループに属する複数の送受信アンテナ素子がパイロット信号を送信する時に、これらの送受信アンテナ素子から送信されるパイロット信号の位相を異ならせる送信側位相制御部と、
前記第1の期間および前記第2の期間で、前記上りリンク信号処理部の1つのブランチに属する1つのサブブランチがパイロット信号を処理する時に、そのブランチに属する他のサブブランチがパイロット信号を処理することを防止する受信側スイッチとを
さらに備える請求項1に記載の無線基地局。 - 前記第1の期間および前記第2の期間で、1つのアンテナグループに属する複数の送受信アンテナ素子がパイロット信号を送信する時に、これらの送受信アンテナ素子から送信されるパイロット信号を異なる第1の直交拡散系列で拡散する送信側位相制御部と、
前記第1の期間および前記第2の期間で、前記上りリンク信号処理部の1つのブランチに属する複数のサブブランチがパイロット信号を処理する時に、これらのサブブランチで処理されるパイロット信号を異なる第2の直交拡散系列で拡散する受信側位相制御部とを
さらに備える請求項1に記載の無線基地局。 - 前記第1の期間および前記第2の期間で、1つのアンテナグループに属する複数の送受信アンテナ素子がパイロット信号を送信する時に、これらの送受信アンテナ素子に対応する複数のサブブランチに供給される信号に同じ系列を与える系列供給部と、
前記第1の期間および前記第2の期間で、1つのアンテナグループに属する複数の送受信アンテナ素子がパイロット信号を送信する時に、これらのパイロット信号の送信時期を異ならせる遅延付与部と、
前記第1の期間および前記第2の期間で、前記上りリンク信号処理部の1つのブランチに属する1つのサブブランチがパイロット信号を処理する時に、そのブランチに属する他のサブブランチがパイロット信号を処理することを防止する受信側スイッチとを
さらに備える請求項1に記載の無線基地局。 - 前記第1の期間および前記第2の期間で、1つのアンテナグループに属する複数の送受信アンテナ素子がパイロット信号を送信する時に、これらの送受信アンテナ素子に対応する複数のサブブランチに供給される信号に同じ系列を与える系列供給部と、
前記第1の期間および前記第2の期間で、1つのアンテナグループに属する複数の送受信アンテナ素子がパイロット信号を送信する時に、これらのパイロット信号の送信時期を異ならせる遅延付与部と、
前記第1の期間および前記第2の期間で、前記上りリンク信号処理部の1つのブランチに属する1つのサブブランチがパイロット信号を処理する時に、これらのサブブランチで処理されるパイロット信号の位相を異ならせる受信側位相制御部とを
さらに備える請求項1に記載の無線基地局。 - 下りリンク信号にプリコーディング行列を適用して、ディジタルプリコーディングを実行するディジタル信号処理部と、
前記ディジタルプリコーディングが施された下りリンク信号に対して、ビームフォーミング行列に相当する位相および振幅の変化を付与するアナログビームフォーミングを実行するアナログビームフォーマと、
前記アナログビームフォーミングが施された下りリンク信号を無線で送信し、前記下りリンク信号の送信に利用される周波数帯と同じ周波数帯での上りリンク信号をユーザ装置から無線で受信する複数の送受信アンテナ素子と、
前記複数の送受信アンテナ素子で受信された前記上りリンク信号を処理する上りリンク信号処理部と、
アンテナ補正のためのパイロット信号を送信および受信する少なくとも1つのアンテナ補正基準送受信アンテナ素子と
を備え、
前記送受信アンテナ素子は、複数のアンテナグループに分類され、各アンテナグループは複数の送受信アンテナ素子を有しており、
前記アナログビームフォーマは、前記複数のアンテナグループにそれぞれ対応する複数のブランチを有しており、各ブランチは複数のサブブランチを有しており、各サブブランチは、前記アナログビームフォーミングを実行するための可変移相器と振幅調整器を有しており、各サブブランチは1つの前記送受信アンテナ素子に接続されており、
前記上りリンク信号処理部は、前記複数のアンテナグループにそれぞれ対応する複数のブランチを有しており、各ブランチは複数のサブブランチを有しており、各サブブランチは受信増幅器を有しており、各サブブランチは1つの前記送受信アンテナ素子に接続されており、
さらに、前記アンテナ補正基準送受信アンテナ素子および前記複数の送受信アンテナ素子からのパイロット信号の送信を制御するアンテナ送信制御部と、
前記アンテナ補正基準送受信アンテナ素子および前記複数の送受信アンテナ素子で受信されたパイロット信号に基づいて、複数のチャネル係数を推定するチャネル推定部と、
前記複数の送受信アンテナ素子で受信された上りリンクの無線信号から推定される複数のチャネル係数に基づいて、下りリンク送信を行う場合に、前記複数の送受信アンテナ素子から送信される下りリンクの無線信号に与えられるべき補正係数を計算する補正係数計算部とを備え、
第1の期間に、前記アンテナ送信制御部は、前記アンテナ補正基準送受信アンテナ素子だけにパイロット信号を送信させて、前記チャネル推定部は、複数の前記送受信アンテナ素子で受信されたパイロット信号に基づいて、複数のチャネル係数を推定し、
前記第1の期間とは異なる第2の期間に、前記アンテナ送信制御部は、複数の前記送受信アンテナ素子だけにパイロット信号を送信させて、前記チャネル推定部は、前記アンテナ補正基準送受信アンテナ素子で受信されたパイロット信号に基づいて、複数のチャネル係数を推定し、
前記補正係数計算部は、前記第1の期間で推定された複数の前記チャネル係数と、前記第2の期間で推定された複数の前記チャネル係数から、複数の前記補正係数を計算し、
1つのアンテナグループに属する複数の前記送受信アンテナ素子から送信されるパイロット信号は、前記アンテナ補正基準送受信アンテナ素子に受信された後に、いずれの送受信アンテナ素子から送信されたか特定することができ、
1つのアンテナグループに属する複数の前記送受信アンテナ素子で受信されるパイロット信号は、いずれの送受信アンテナ素子で受信されたか特定することができる
無線基地局。
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CN106489242A (zh) | 2017-03-08 |
JP6650408B2 (ja) | 2020-02-19 |
JPWO2016175144A1 (ja) | 2018-02-22 |
US20180040964A1 (en) | 2018-02-08 |
US10020596B2 (en) | 2018-07-10 |
CN106489242B (zh) | 2020-09-15 |
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