WO2009119645A1 - Mimo受信装置および方法 - Google Patents
Mimo受信装置および方法 Download PDFInfo
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- WO2009119645A1 WO2009119645A1 PCT/JP2009/055916 JP2009055916W WO2009119645A1 WO 2009119645 A1 WO2009119645 A1 WO 2009119645A1 JP 2009055916 W JP2009055916 W JP 2009055916W WO 2009119645 A1 WO2009119645 A1 WO 2009119645A1
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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
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
- H04B7/0842—Weighted combining
- H04B7/0845—Weighted combining per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
- H04B17/318—Received signal strength
- H04B17/327—Received signal code power [RSCP]
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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
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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
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
- H04B7/0842—Weighted combining
- H04B7/0862—Weighted combining receiver computing weights based on information from the transmitter
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0204—Channel estimation of multiple channels
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/022—Channel estimation of frequency response
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0222—Estimation of channel variability, e.g. coherence bandwidth, coherence time, fading frequency
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
- H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
- H04L25/0232—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
- H04L2025/03426—Arrangements for removing intersymbol interference characterised by the type of transmission transmission using multiple-input and multiple-output channels
Definitions
- the present invention relates to a radio communication technique, and more particularly to a MIMO multiplexing system that converts a single carrier signal received by a plurality of receiving antennas into a frequency domain signal and demodulates the signal by frequency domain signal processing.
- MIMO Multiple-Input-Multiple-Output
- FIG. 4 is an explanatory diagram showing a schematic configuration of the MIMO transmitting / receiving apparatus.
- M is an integer of 1 or more
- N is an integer of 1 or more
- the transmitting side is composed of transmitting antennas A 11 to A 1M and a transmitting apparatus 1
- the receiving side is composed of receiving antennas A 21 to A 2N and a receiving apparatus 2.
- Different transmission signals S 1 to S M are transmitted from a plurality of transmission antennas A 11 to A 1M using the same frequency and time, and reception signals R 1 to R N are transmitted using a plurality of reception antennas A 21 to A 2N.
- Receiving enables high-speed data transmission proportional to the number of transmission antennas without increasing the transmission bandwidth.
- the transmission signals S 1 to S M from the plurality of transmission antennas A 11 to A 1M are subjected to signal separation processing from the reception signals R 1 to R N received by the plurality of reception antennas A 21 to A 2N , and demodulated signals It is necessary to output D 1 to D M.
- FIG. 5 is a block diagram showing a configuration of a related MIMO receiving apparatus.
- a configuration example is shown in which the frequency domain equalizer and frequency domain channel estimation described in these documents 1 and 2 are used in a single carrier signal MIMO receiver.
- the MIMO receiving apparatus will be described assuming that the number of transmitting antennas is M (M is an integer of 1 or more) and the number of receiving antennas is N (N is an integer of 1 or more).
- N received signal processing units 10 corresponding to the received signals R 1 to R N a weight calculation unit 31, an equalization filter 32, and a discrete inverse Fourier transform (IDFT) : Inverse Discrete Fourier Transform) sections 33 1 to 33 M are provided.
- IDFT discrete inverse Fourier transform
- Each received signal processing unit 10 n (n is an integer from 1 to N) includes a cyclic prefix (CP) removal unit (hereinafter referred to as CP removal unit) 11 n , a fast Fourier transform, as a main processing unit.
- CP cyclic prefix
- FFT Fast Fourier Transform
- the CP removing unit 11 n receives the received signal R n and removes a portion of the received signal corresponding to the CP.
- the FFT unit 12 n receives the reception signal from which the CP has been removed by the CP removal unit 11 n , performs FFT of NFFT points (NFFT is a power of 2), and outputs the reception signal converted into the frequency domain.
- the subcarrier demapping unit 13 n receives the received signal converted into the frequency domain by the FFT unit 12 n , selects only subcarriers included in the communication band of the target data communication, and thins out unnecessary subcarriers. processing, and outputs as a signal band reception signal of the reception signal R n.
- Each channel estimation value calculation unit 20 mn uses the signal band reception signal of the reception signal R n output from the subcarrier demapping unit 13 n as a reference reception signal, and converts it into the reception signal R n .
- a channel estimation value of the included transmission signal S m is calculated.
- the channel estimation value calculation unit 20 mn includes a reference signal generation unit 21 mn , a correlation processing unit 22 mn , a fast inverse Fourier transform (IFFT) unit (hereinafter referred to as IFFT unit) 23 mn , and noise path removal.
- the unit 24 mn and the FFT unit 25 mn are provided.
- the reference signal generation unit 21 mn generates a reference signal used for correlation processing of the received signal R n with the reference received signal.
- the reference signal generator 21 mn includes a zero forcing (ZF) method that completely cancels the sign characteristics of the reference received signal, and a minimum mean square error (MMSE) that suppresses noise enhancement in correlation processing. Method, clipping method, etc. are used.
- ZF zero forcing
- MMSE minimum mean square error
- the correlation processing unit 22 mn estimates a channel estimation value in the frequency domain by performing correlation processing between the reference reception signal of the reception signal R n and the reference signal from the reference signal generation unit 21 mn , and subcarrier k (0 ⁇ k ⁇ N DFT1 )
- the channel estimation value H BF, m, n (k) between the transmitting antenna A 1m and the receiving antenna A 2n is calculated by the following equation (1).
- X m * (k) is the reference signal of the transmission antenna A 1m in the subcarrier k generated by the reference signal generation unit 21 mn
- R RS, n (k) is the subcarrier demapping unit 13 n.
- the reference received signal of the receiving antenna A 2n in subcarrier k obtained in step S, and the subscript * indicates a complex conjugate.
- the IFFT unit 23 mn converts the frequency domain channel estimation value estimated by the correlation processing unit 22 mn into a time domain channel response.
- the noise path removing unit 24 mn is replaced with “0” in order to remove the signal (noise path) of only the noise from the channel response in the frequency domain that is the output of the IFFT unit 23 mn .
- the noise path removing unit 24 mn uses a time window filter or noise threshold control.
- the time window filter assumes that the channel response is within the CP width, and replaces signals at points other than the interval corresponding to the CP width with “0” as a noise path.
- the noise threshold control a signal at a point below a predetermined threshold is replaced with “0” as a noise path.
- an average value of noise outside the window of the time window filter can be used as the noise threshold.
- the FFT unit 25 mn performs FFT on the channel response from which the noise path has been removed by the noise path removal unit 24 mn , and outputs a channel estimation value in the frequency domain in which noise is suppressed.
- the weight calculation unit 31 in the channel estimation value calculation units 20 11 to 20 MN of the received signal processing units 10 1 to 10 N has a noise-suppressed frequency domain channel estimation value that is an output of the FFT units 25 11 to 25 MN.
- the weight calculation unit 31 uses an MMSE method or a ZF method.
- the MMSE equalization weight vector W m (k) of the transmission antenna A 1m at the subcarrier k is calculated by the following equation (2).
- H is a complex conjugate transpose
- ⁇ 2 is noise power
- I is a unit matrix.
- H AF, m (k) represents a channel estimation vector between the transmitting antenna A 1m and each of the receiving antennas A 21 to A 2n in the subcarrier k, and is equalized with the channel estimation vector H AF, m (k).
- the vector W m (k) is defined as in equations (3) and (4).
- T represents transposition
- each element of the channel estimation vector H AF, m (k) is a noise-suppressed frequency domain channel that is the output of the FFT units 25 11 to 25 MN. Represents an estimate.
- the equalization filter 32 receives the equalization weights calculated by the weight calculation unit 31 and the reception signals R 1 to R obtained by the subcarrier demapping units 13 1 to 13 N of the reception signal processing units 10 1 to 10 N. N signal band received signals are input, and the received signals are equalized in the frequency domain.
- the transmission signal vector Y (k) in the subcarrier k equalized and signal-separated by the equalization filter 32 is calculated as in Expression (5) and defined as in Expression (6).
- W (k) represents an equalization weight matrix in subcarrier k
- R D (k) represents a received signal vector in subcarrier k. It is defined as (8). Further, each element of the received signal vector R D (k) denotes the subcarrier de obtained by mapping unit 13 1 ⁇ 13 N, the signal band reception signals of the reception signals R 1 ⁇ R N in the frequency domain.
- the IDFT units 33 1 to 33 M receive the frequency domain equalization signal output from the equalization filter 32, perform IDFT of N IDFT points (N IDFT is an integer of 2 or more), and convert it to a time domain signal. And output as demodulated signals D 1 to D M.
- Such a MIMO receiver has a problem in that the amount of calculation from equalization weight generation to signal separation is large, and the processing delay increases as the signal band increases. This is because the equalization weight used for the signal separation equalization process is calculated for each subcarrier in the signal band.
- the present invention is to solve such problems, and in MIMO reception that generates equalization weights and separates transmission signals, the number of subcarriers for calculating equalization weights is increased or decreased according to the propagation environment.
- An object of the present invention is to provide a MIMO receiving apparatus and method that can adaptively control the increase and decrease of the calculation amount and the processing delay.
- the MIMO receiving apparatus receives transmission signals transmitted from a plurality of transmission antennas by a plurality of reception antennas, and equalizes an arbitrary subcarrier generated from these reception signals.
- a MIMO receiving apparatus having a MIMO (Multi-Input-Multi-Output) function for separating a transmission signal from a reception signal based on a weight and outputting the transmission signal, and a time obtained from the reception signal for each path between transmission / reception antennas
- a coherent bandwidth calculation unit that calculates a coherent bandwidth based on the channel response of the region; a weight calculation control unit that determines a target subcarrier for calculating an equalization weight based on the coherent bandwidth; and Target subcarrier equalization based on frequency domain channel estimates obtained for each path between transmit and receive antennas
- a weight calculation unit that calculates Eight respectively, and a weight interpolation unit that calculates the equalization weight of uncalculated subcarriers in the target sub-carrier by interpolating the equalization weights.
- the MIMO reception method receives transmission signals transmitted from a plurality of transmission antennas by a plurality of reception antennas, and based on an equalization weight of an arbitrary subcarrier generated from these reception signals,
- a MIMO reception method using a MIMO (Multi-Input-Multi-Output) function for separating and outputting a transmission signal, based on a time-domain channel response obtained for each path between transmission / reception antennas from the reception signal
- a coherent bandwidth calculation step for calculating a coherent bandwidth
- a weight calculation control step for determining a target subcarrier for calculating an equalization weight based on the coherent bandwidth, and a path between each transmitting and receiving antenna from the received signal.
- the equalization weight of the target subcarrier is A weight calculation step of being calculated, and a weight interpolation calculating the equalization weight of subcarriers uncalculated of target subcarriers by interpolating the equalization weights.
- the calculation is performed by reducing the number of subcarriers for obtaining the equalization weight when the propagation environment is good. By reducing the amount, the processing delay can be reduced. On the other hand, when the propagation environment is poor, the radio quality can be ensured by increasing the number of subcarriers for obtaining equalization weights.
- FIG. 1 is a block diagram showing a configuration of a MIMO receiving apparatus according to the first embodiment of the present invention.
- FIG. 2 is an explanatory diagram showing processing of the weight interpolation unit.
- FIG. 3 is a block diagram showing the configuration of the MIMO receiving apparatus according to the second embodiment of the present invention.
- FIG. 4 is an explanatory diagram showing a schematic configuration of the MIMO transmitting / receiving apparatus.
- FIG. 5 is a block diagram showing a configuration of a related MIMO receiving apparatus.
- FIG. 1 is a block diagram showing the configuration of the MIMO receiving apparatus according to the first embodiment of the present invention, where the same or equivalent parts as those in FIG. 5 are given the same reference numerals.
- the MIMO receiving apparatus has N received signal processing units 10 corresponding to the received signals R 1 to R N , a weight calculation unit 31, and the like as main processing units.
- a coherent bandwidth calculation unit 41 In addition to the filter 32 and discrete inverse Fourier transform (IDFT) units 33 1 to 33 M , a coherent bandwidth calculation unit 41, a weight calculation control unit 42, and a weight interpolation unit 43 are provided.
- IFT discrete inverse Fourier transform
- a coherent bandwidth calculation unit 41 a weight calculation control unit 42, and a weight interpolation unit 43 are provided.
- These may be constituted by a dedicated signal processing circuit, an arithmetic processing unit using a CPU, or a combination thereof.
- Each received signal processing unit 10 n (n is an integer from 1 to N) includes a cyclic prefix (CP) removal unit (hereinafter referred to as CP removal unit) 11 n , a fast Fourier transform, as a main processing unit.
- CP cyclic prefix
- FFT Fast Fourier Transform
- the CP removing unit 11 n has a function of receiving the received signal R n and removing a portion of the received signal corresponding to the CP.
- the FFT unit 12 n has a function of receiving the reception signal from which the CP has been removed by the CP removal unit 11 n as input, performing FFT of NFFT points (NFFT is a power of 2), and outputting the reception signal converted into the frequency domain. is doing.
- the subcarrier demapping unit 13 n receives the received signal converted into the frequency domain by the FFT unit 12 n , selects only subcarriers included in the communication band of the target data communication, and thins out unnecessary subcarriers. processing, and has a function of outputting a signal band reception signal of the reception signal R n.
- Each channel estimation value calculation unit 20 mn uses the signal band reception signal of the reception signal R n output from the subcarrier demapping unit 13 n as a reference reception signal, and converts it into the reception signal R n .
- a channel estimation value of the included transmission signal S m is calculated.
- the channel estimation value calculation unit 20 mn includes a reference signal generation unit 21 mn , a correlation processing unit 22 mn , a fast inverse Fourier transform (IFFT) unit (hereinafter referred to as IFFT unit) 23 mn , and noise path removal.
- the unit 24 mn and the FFT unit 25 mn are provided.
- the reference signal generation unit 21 mn has a function of generating a reference signal used for correlation processing of the reception signal R n with the reference reception signal.
- the reference signal generator 21 mn includes a zero forcing (ZF) method that completely cancels the sign characteristics of the reference received signal, and a minimum mean square error (MMSE) that suppresses noise enhancement in correlation processing. Method, clipping method, etc. are used.
- ZF zero forcing
- MMSE minimum mean square error
- the correlation processing unit 22 mn estimates a channel estimation value in the frequency domain by performing correlation processing between the reference reception signal of the reception signal R n and the reference signal from the reference signal generation unit 21 mn , and subcarrier k (0 ⁇ k ⁇ N DFT1 ) has a function of obtaining channel estimation values of the transmitting antenna A 1m and the receiving antenna A 2n .
- the IFFT unit 23 mn has a function of converting the frequency domain channel estimation value estimated by the correlation processing unit 22 mn into a time domain channel response.
- the noise path removing unit 24 mn has a function of removing a signal (noise path) of only noise points from the channel response in the frequency domain that is the output of the IFFT unit 23 mn .
- the FFT unit 25 mn has a function of performing FFT on the channel response from which the noise path has been removed by the noise path removing unit 24 mn and outputting a channel estimation value in the frequency domain in which noise is suppressed.
- the coherent bandwidth calculation unit 41 obtains the outputs of the IFFT units 23 11 to 23 MN in the channel estimation value calculation units 20 11 to 20 MN of the reception signal processing units 10 1 to 10 N , that is, the paths between the transmission / reception antennas. It has a function of calculating a coherent bandwidth from a channel response in a given time domain.
- the weight calculation control unit 42 receives the coherent bandwidth obtained by the coherent bandwidth calculation unit 41, determines a target subcarrier whose equalization weight is to be calculated based on the coherent bandwidth, and selects these target subcarriers. It has a function of outputting subcarrier information indicating.
- the weight calculation unit 31 is obtained for each path between the transmission / reception antennas, that is, the outputs of the FFT units 25 11 to 25 MN in the channel estimation value calculation units 20 11 to 20 MN of the reception signal processing units 10 1 to 10 N. It has a function of calculating the equalization weight for each target subcarrier specified by the subcarrier information, with the channel estimation value in the frequency domain and the subcarrier information output from the weight calculation control unit 42 as inputs. .
- the weight interpolation unit 43 receives the equalization weight that is the output of the weight calculation unit 31 and the subcarrier information that is the output of the weight calculation control unit 42 and performs the equalization weight calculation, and the equalization from the weight calculation control unit 42 By interpolating the weight, the weight calculation control unit 42 has a function of calculating an equalized weight of the uncalculated subcarrier among the target subcarriers.
- the equalization filter 32 receives the equalization weights from the weight interpolation unit 43 and the signal band reception signals of the reception signals R 1 to R N obtained by the subcarrier demapping units 13 1 to 13 N and inputs them in the frequency domain. It has a function of obtaining a frequency domain equalized signal in subcarrier k by performing equalization processing of the signal band received signal.
- the IDFT units 33 1 to 33 M receive the frequency domain equalized signals output from the equalization filter 32 and perform IDFT processing on these equalized signals to convert the equalized signals into time domain signals. And a function of outputting demodulated signals D 1 to D M corresponding to the transmission signals S 1 to S M.
- FIG. 2 is an explanatory diagram showing processing of the weight interpolation unit.
- the received signal processing units 10 1 to 10 N are the same as those in FIG. 5 described above, and a description thereof is omitted here.
- the coherent bandwidth calculation unit 41 responds to the channel response in the time domain obtained by the IFFT units 23 11 to 23 MN in the channel estimation value calculation units 20 11 to 20 MN of the received signal processing units 10 1 to 10 N.
- the power profile P m, n (t) in the path from the transmitting antenna A 1m to the receiving antenna A 2n is obtained.
- an average power profile P (t) is obtained from the following equation (9).
- the coherent bandwidth calculation unit 41 obtains the delay dispersion ⁇ from the following equation (10).
- Equation (10) t ⁇ is a time average value weighted with electric power, and is obtained from the following Equation (11).
- the coherent bandwidth calculation unit 41 obtains the coherent bandwidth f coh from the following equation (12) from the delay dispersion ⁇ .
- the weight calculation control unit 42 determines a subcarrier y (target subcarrier) for which an equalization weight is to be calculated, and notifies the weight calculation unit 31 of subcarrier information indicating these target subcarriers.
- the subcarrier y for calculating the equalization weight is obtained as follows. First, the subcarrier spacing f SC and the coherent bandwidth f coh are compared. When the subcarrier interval f SC is large, y is set to all subcarriers (0 ⁇ y ⁇ N DFT ⁇ 1).
- the subcarrier y for calculating the equalization weight is set as a subcarrier having a subcarrier interval not exceeding the coherent bandwidth f coh , for example, as shown in the following equation (13).
- the reason why the subcarrier interval does not exceed the coherent bandwidth f coh is that the frequency characteristic can be regarded as being constant within the coherent bandwidth.
- the weight calculation unit 31 calculates an equalization weight for the subcarrier y that calculates the equalization weight notified from the weight calculation control unit 42.
- the weight interpolation unit 43 performs an interpolation process on the subcarriers other than the subcarrier y for calculating the equalization weight notified from the weight calculation control unit 42 using the equalization weight of the subcarrier y. For example, as shown in FIG. 2, the equalization weight of the subcarrier y is copied to the subcarriers in the range of f coh centering on the subcarrier y, and is used as an uncalculated subcarrier equalization weight.
- the subcarriers for calculating the equalization weight can be increased / decreased according to the coherent bandwidth in which the frequency characteristics can be regarded as constant, so that the processing delay is reduced when the propagation environment is good.
- the coherent bandwidth is obtained from the average power profile.
- the coherent bandwidth is obtained from the power profile P m, n (t) in the path from the transmitting antenna A 1m to the receiving antenna A 2n , and These processes may be performed by individual routes.
- FIG. 3 is a block diagram showing a configuration of a MIMO receiving apparatus according to the second embodiment of the present invention, and the same or equivalent parts as in FIG.
- the MIMO receiving apparatus includes channel estimation value calculation units 20 11 to 20 MN of the reception signal processing units 10 1 to 10 N and a power fluctuation detection unit 26 11.
- ⁇ 26 MN has been added.
- the power fluctuation detection unit 26 mn has a function of detecting a subcarrier whose power is fluctuated by receiving the received signal converted into the frequency domain by the FFT unit 25 mn and the coherent bandwidth from the coherent bandwidth calculation unit 41. Have.
- the weight calculation control unit 42 receives the coherent bandwidth obtained by the coherent bandwidth calculation units 41 11 to 41 MN and the detection results of the power fluctuation detection units 26 11 to 26 MN , and inputs the coherent bandwidths. It has a function of determining a target subcarrier for calculating equalization weight from the detection result and obtaining subcarrier information for calculating equalization weight.
- Other configurations of the MIMO receiving apparatus according to the present embodiment are the same as those in the first embodiment, and a detailed description thereof is omitted here.
- the power fluctuation detection units 26 11 to 26 MN in the channel estimation value calculation units 20 11 to 20 MN of the received signal processing units 10 1 to 10 N obtain the average received power in the frequency domain at the coherent bandwidth interval, and receive the average reception thereof. From the power, XdB is set as a detection threshold value and compared with the received power of each subcarrier within the coherent bandwidth. The subcarriers whose subcarrier received power is equal to or lower than the detection threshold are notified to the weight calculation control unit 42. Here, you may make it notify the weight calculation control part 42 of the subcarrier which became more than a detection threshold value.
- the weight calculation control unit 42 obtains a detected subcarrier z, which is a logical sum of the subcarrier information detected by the power fluctuation detection units 26 11 to 26 MN , and equalizes the same operation as in the first embodiment described above.
- subcarrier information indicating the target subcarrier is output.
- the weight calculation unit 31 calculates equalization weights for the subcarrier y and the detected subcarrier z based on the subcarrier information notified from the weight calculation control unit 42.
- the weight interpolation unit 43 obtains equalization weights of subcarriers other than the subcarrier y by the same operation as in the first embodiment described above, and then detects the detection subcarrier z detected by the weight calculation unit 31. Replace with equalization weight of carrier z.
- the present invention is suitable for a MIMO receiving apparatus that converts a single carrier signal received by a plurality of receiving antennas into a frequency domain signal and demodulates the signal by frequency domain signal processing, and particularly generates and transmits an equalization weight. This is useful for a MIMO receiving apparatus that performs signal separation.
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Abstract
Description
また周波数イコライザは等化ウエイトを計算するため、周波数領域のチャネル推定が必要となり、リファレンス受信信号を直接周波数領域に変換し、周波数領域でリファレンス信号との相関をとることによりチャネル推定を推定する方法が提案されている(例えば、文献2:木全,吉田,"上りシングルキャリアIFDMAにおける周波数領域復調方式の検討," 2006年信学総大,B-5-36.など参照)。
FFT部12nは、CP除去部11nでCPを除去した受信信号を入力とし、NFFTポイント(NFFTは2のべき数)のFFTを行い、周波数領域に変換した受信信号を出力する。
サブキャリアデマッピング部13nは、FFT部12nで周波数領域に変換した受信信号を入力とし、対象となるデータ通信の通信帯域に含まれるサブキャリアだけを選択して、不要なサブキャリアを間引き処理し、受信信号Rnの信号帯域受信信号として出力する。
相関処理部22mnは、受信信号Rnのリファレンス受信信号とリファレンス信号生成部21mnからのリファレンス信号との相関処理により、周波数領域のチャネル推定値を推定し、サブキャリアk(0≦k≦NDFT1)における送信アンテナA1mと受信アンテナA2nとのチャネル推定値HBF,m,n(k)を、次式(1)で計算する。
雑音パス除去部24mnは、IFFT部23mnの出力である周波数領域のチャネル応答から雑音だけのポイントの信号(雑音パス)を除去するため「0」に置換する。
FFT部25mnは、雑音パス除去部24mnで雑音パス除去したチャネル応答をFFTし、雑音抑圧した周波数領域のチャネル推定値を出力する。
本発明はこのような課題を解決するためのものであり、等化ウエイトを生成し送信信号の分離を行うMIMO受信において、伝搬環境に応じて等化ウエイトを計算するサブキャリアを増減させることで、演算量、処理遅延の増減を適応的に制御できるMIMO受信装置および方法を提供することを目的としている。
[第1の実施形態]
まず、図1を参照して、本発明の第1の実施形態にかかるMIMO受信装置について説明する。図1は、本発明の第1の実施形態にかかるMIMO受信装置の構成を示すブロック図であり、前述した図5と同じまたは同等部分には同一符号を付してある。
FFT部12nは、CP除去部11nでCPを除去した受信信号を入力とし、NFFTポイント(NFFTは2のべき数)のFFTを行い、周波数領域に変換した受信信号を出力する機能を有している。
サブキャリアデマッピング部13nは、FFT部12nで周波数領域に変換した受信信号を入力とし、対象となるデータ通信の通信帯域に含まれるサブキャリアだけを選択して、不要なサブキャリアを間引き処理し、受信信号Rnの信号帯域受信信号として出力する機能を有している。
IFFT部23mnは、相関処理部22mnで推定した周波数領域のチャネル推定値を時間領域のチャネル応答に変換する機能を有している。
FFT部25mnは、雑音パス除去部24mnで雑音パス除去したチャネル応答をFFTし、雑音抑圧した周波数領域のチャネル推定値を出力する機能を有している。
ウエイト計算制御部42は、コヒーレント帯域幅計算部41で得られたコヒーレント帯域幅を入力とし、このコヒーレント帯域幅に基づいて、等化ウエイトを計算すべき対象サブキャリアを決定し、これら対象サブキャリアを示すサブキャリア情報を出力する機能を有している。
ウエイト補間部43は、ウエイト計算部31の出力である等化ウエイトと、ウエイト計算制御部42の出力である等化ウエイト計算するサブキャリア情報とを入力とし、ウエイト計算制御部42からの等化ウエイトを補間処理することにより、対象サブキャリアのうちウエイト計算制御部42で未計算のサブキャリアの等化ウエイトを計算する機能を有している。
IDFT部331~33Mは、等化フィルタ32の出力である周波数領域の等化信号を入力とし、これら等化信号についてIDFT処理を行うことにより、等化信号を時間領域の信号に変換し、各送信信号S1~SMに対応する復調信号D1~DMを出力する機能を有している。
次に、図1および図2を参照して、本発明の第1の実施形態にかかるMIMO受信装置の動作について説明する。図2は、ウエイト補間部の処理を示す説明図である。なお、本実施形態にかかるMIMO受信装置のうち、受信信号処理部101~10Nについては、前述した図5と同等であり、ここでの説明は省略する。
まず、サブキャリア間隔fSCとコヒーレント帯域幅fcohを比較する。サブキャリア間隔fSCが大きい場合には、yを全サブキャリア(0≦y≦NDFT-1)とする。
ウエイト補間部43は、ウエイト計算制御部42から通知される等化ウエイトを計算するサブキャリアy以外のサブキャリアについて、サブキャリアyの等化ウエイトを用いて補間処理を行う。例えば、図2のように、サブキャリアyを中心にfcohの範囲のサブキャリアに対し、サブキャリアyの等化ウエイトをコピーし、未計算のサブキャリアの等化ウエイトとして用いる。
このように、本実施形態によれば、周波数特性が一定とみなせるコヒーレント帯域幅に従って等化ウエイトを計算するサブキャリアを増減させることができるため、伝搬環境が良好な場合には処理遅延を減少させ、伝搬環境が劣悪な場合には受信品質を確保することができる。
また、本実施形態では、平均電力プロファイルからコヒーレント帯域幅を求めているが、送信アンテナA1mから受信アンテナA2nの経路における電力プロファイルPm、n(t)からコヒーレント帯域幅を求めて、上記の処理を個別の経路で行ってもよい。
次に、図3を参照して、本発明の第2の実施形態にかかるMIMO受信装置について説明する。図3は、本発明の第2の実施形態にかかるMIMO受信装置の構成を示すブロック図であり、図1と同じまたは同等部分には同一符号を付してある。
電力変動検出部26mnは、FFT部25mnで周波数領域に変換した受信信号と、コヒーレント帯域幅計算部41からのコヒーレント帯域幅を入力とし、電力が変動しているサブキャリアを検出する機能を有している。
本実施形態にかかるMIMO受信装置の他の構成については、第1の実施形態と同様であり、ここでの詳細な説明は省略する。
次に、本発明の第2の実施形態にかかるMIMO受信装置の動作について説明する。
各受信信号処理部101~10Nのチャネル推定値計算部2011~20MNにおける電力変動検出部2611~26MNは、コヒーレント帯域幅間隔で周波数領域の平均受信電力を求め、その平均受信電力からXdBを検出閾値とし、コヒーレント帯域幅内の各サブキャリアの受信電力と比較する。サブキャリアの受信電力が検出閾値以下となったサブキャリアをウエイト計算制御部42に通知する。ここで、検出閾値以上となったサブキャリアをウエイト計算制御部42に通知するようにしてもよい。
ウエイト計算部31は、ウエイト計算制御部42から通知されたサブキャリア情報に基づいて、サブキャリアyと検出サブキャリアzに対して等化ウエイトを計算する。
ウエイト補間部43は、前述した第1の実施形態と同様の動作でサブキャリアy以外のサブキャリアの等化ウエイトを求めた後、検出サブキャリアzについては、ウエイト計算部31で求めた検出サブキャリアzの等化ウエイトに置き換える。
このように、本実施形態によれば、等化ウエイトの位相変動が激しい場合でも、特性劣化を防ぐことができる。
Claims (16)
- 複数の送信アンテナから送信した送信信号を複数の受信アンテナで受信し、これら受信信号から生成した任意のサブキャリアの等化ウエイトに基づいて、前記受信信号から前記送信信号を分離して出力する、MIMO(Multi Input Multi Output)の機能を有するMIMO受信装置であって、
前記受信信号から前記各送受信アンテナ間の経路ごとに得られた時間領域のチャネル応答に基づいて、コヒーレント帯域幅を計算するコヒーレント帯域幅計算部と、
前記コヒーレント帯域幅に基づいて、等化ウエイトを計算する対象サブキャリアを決定するウエイト計算制御部と、
前記受信信号から前記各送受信アンテナ間の経路ごとに得られた周波数領域のチャネル推定値に基づいて、前記対象サブキャリアの等化ウエイトをそれぞれ計算するウエイト計算部と、
前記等化ウエイトを補間処理することにより前記対象サブキャリアのうち未計算のサブキャリアの等化ウエイトを計算するウエイト補間部と
を備えることを特徴とするMIMO受信装置。 - 請求項1に記載のMIMO受信装置において、
前記ウエイト計算制御部は、前記コヒーレント帯域幅計算部で求めたコヒーレント帯域幅を用いて、コヒーレント帯域幅を超えないサブキャリア間隔で前記対象サブキャリアを決定することを特徴とするMIMO受信装置。 - 請求項2に記載のMIMO受信装置において、
前記コヒーレント帯域幅計算部は、平均電力プロファイルからコヒーレント帯域幅を計算することを特徴とするMIMO受信装置。 - 請求項2に記載のMIMO受信装置において、
前記コヒーレント帯域幅計算部は、前記各送受信アンテナ間の経路における電力プロファイルからコヒーレント帯域幅を計算することを特徴とするMIMO受信装置。 - 請求項2に記載のMIMO受信装置において、
前記等化ウエイト補間部は、等化ウエイトを計算したサブキャリアを中心として、両側のコヒーレント帯域幅内のサブキャリアに前記ウエイト計算部で計算した等化ウエイトを、未計算のサブキャリアの等化ウエイトとして用いることを特徴とするMIMO受信装置。 - 請求項1記載のMIMO受信装置において、
各サブキャリアの電力変動を検出する電力変動検出部をさらに備えることを特徴とするMIMO受信装置。 - 請求項6に記載のMIMO受信装置において、
前記電力変動検出部は、コヒーレント帯域幅間隔で周波数領域の平均受信電力から検出閾値を決定し、コヒーレント帯域幅内の各サブキャリアの受信電力と比較し、検出閾値以下、または検出閾値以上となったサブキャリアを検出サブキャリアとして検出することを特徴とするMIMO受信装置。 - 請求項6に記載のMIMO受信装置において、
前記ウエイト計算制御部は、前記電力変動検出部で検出した検出サブキャリアを、等化ウエイトを計算すべきサブキャリアとして、前記対象サブキャリアに含めることを特徴とするMIMO受信装置。 - 複数の送信アンテナから送信した送信信号を複数の受信アンテナで受信し、これら受信信号から生成した任意のサブキャリアの等化ウエイトに基づいて、前記受信信号から前記送信信号を分離して出力する、MIMO(Multi Input Multi Output)の機能を用いたMIMO受信方法であって、
前記受信信号から前記各送受信アンテナ間の経路ごとに得られた時間領域のチャネル応答に基づいて、コヒーレント帯域幅を計算するコヒーレント帯域幅計算ステップと、
前記コヒーレント帯域幅に基づいて、等化ウエイトを計算する対象サブキャリアを決定するウエイト計算制御ステップと、
前記受信信号から前記各送受信アンテナ間の経路ごとに得られた周波数領域のチャネル推定値に基づいて、前記対象サブキャリアの等化ウエイトをそれぞれ計算するウエイト計算ステップと、
前記等化ウエイトを補間処理することにより前記対象サブキャリアのうち未計算のサブキャリアの等化ウエイトを計算するウエイト補間ステップと
を備えることを特徴とするMIMO受信方法。 - 請求項9に記載のMIMO受信方法において、
前記ウエイト計算制御ステップは、前記コヒーレント帯域幅計算ステップで求めたコヒーレント帯域幅を用いて、コヒーレント帯域幅を超えないサブキャリア間隔で前記対象サブキャリアを決定するステップを含むことを特徴とするMIMO受信方法。 - 請求項10に記載のMIMO受信方法において、
前記コヒーレント帯域幅計算ステップは、平均電力プロファイルからコヒーレント帯域幅を計算するステップを含むことを特徴とするMIMO受信方法。 - 請求項10に記載のMIMO受信方法において、
前記コヒーレント帯域幅計算ステップは、前記各送受信アンテナ間の経路における電力プロファイルからコヒーレント帯域幅を計算するステップを含むことを特徴とするMIMO受信方法。 - 請求項10に記載のMIMO受信方法において、
前記等化ウエイト補間ステップは、等化ウエイトを計算したサブキャリアを中心として、両側のコヒーレント帯域幅内のサブキャリアに前記ウエイト計算ステップで計算した等化ウエイトを、未計算のサブキャリアの等化ウエイトとして用いるステップを含むことを特徴とするMIMO受信方法。 - 請求項9記載のMIMO受信方法において、
各サブキャリアの電力変動を検出する電力変動検出ステップをさらに備えることを特徴とするMIMO受信方法。 - 請求項14に記載のMIMO受信方法において、
前記電力変動検出ステップは、コヒーレント帯域幅間隔で周波数領域の平均受信電力から検出閾値を決定し、コヒーレント帯域幅内の各サブキャリアの受信電力と比較し、検出閾値以下、または検出閾値以上となったサブキャリアを検出サブキャリアとして検出するステップを含むことを特徴とするMIMO受信方法。 - 請求項14に記載のMIMO受信方法において、
前記ウエイト計算制御ステップは、前記電力変動検出ステップで検出した検出サブキャリアを、等化ウエイトを計算すべきサブキャリアとして、前記対象サブキャリアに含めるステップを含むことを特徴とするMIMO受信方法。
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WO2014002384A1 (ja) * | 2012-06-26 | 2014-01-03 | 日本電気株式会社 | ターボ等化装置、ターボ等化方法およびターボ等化プログラム |
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JPWO2009119645A1 (ja) | 2011-07-28 |
US8477865B2 (en) | 2013-07-02 |
US20110044383A1 (en) | 2011-02-24 |
CN101981845A (zh) | 2011-02-23 |
CN101981845B (zh) | 2013-11-06 |
KR20100127231A (ko) | 2010-12-03 |
EP2259465A1 (en) | 2010-12-08 |
JP5093343B2 (ja) | 2012-12-12 |
EP2259465A4 (en) | 2016-04-20 |
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