WO2013111784A1 - 無線装置、及びトレーニング信号送信方法 - Google Patents
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
- H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—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
- H04B7/068—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 using space frequency 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
- H04B7/06—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
- H04B7/0684—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 using different training sequences per antenna
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0023—Interference mitigation or co-ordination
- H04J11/0026—Interference mitigation or co-ordination of multi-user interference
- H04J11/003—Interference mitigation or co-ordination of multi-user interference at the transmitter
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
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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
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0226—Channel estimation using sounding signals sounding signals per se
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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
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0014—Three-dimensional division
- H04L5/0023—Time-frequency-space
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/08—Access point devices
Definitions
- the present invention relates to a radio apparatus and a training signal transmission method for estimating channel information between a plurality of transmission ports and a receiving antenna of a communication partner in communication using an orthogonal frequency division multiplexing system.
- OFDM Orthogonal Frequency Division Multiplexing
- Ethernet registered trademark
- FTTH Fiber to the home
- MU-MIMO communication has the potential to increase the throughput in the physical layer to several times the number of transmission antennas.
- channel information for terminals is required in the transmission apparatus.
- FIG. 10 is a sequence diagram for explaining channel information acquisition operation of OFDM communication according to the prior art.
- FIG. 10 shows an example in which the base station AP (Access point) acquires channel information for K terminals STA-1 to STA-K (STA: Station). K is an integer of 1 or more.
- reference numeral 1 is an announcement signal (NDPA: Null Data Packet Announce) indicating that a channel estimation signal is transmitted
- reference numeral 2 is an estimation pilot signal (NDP: Null Data ⁇ Packet)
- reference numeral 3- 1 to 3-K is a channel information feedback signal (CSIFB: Channel State Information Feed Back)
- symbols 4-2 to 4-K are polling signals (Polling) instructing transmission of a response signal from a specific communication partner. Represents.
- the breakdown of the pilot signal 2 is shown in the upper part of FIG.
- the pilot signal 2 includes a first pilot symbol 2-1-1, a last pilot symbol 2-1-2, and N VHT-LTFs that enable channel estimation corresponding to N transmit antennas.
- VHT-LTFs 2-2-1 to 2-2-N In order to acquire channel information for eight transmission antennas, it is necessary to transmit the VHT-LTFs 2-2-1 to 2-2-N for 8 OFDM symbols.
- the signal S k of the k th frequency channel of VHT-LTF2-2-1 ⁇ 2-2-N is described, for example, in Non-Patent Document 2 Equation (19-11), (19-12) , (19-23), (19-24).
- FIG. 11 is a block diagram showing a configuration of a base station (AP) 10 that acquires channel information of a radio section of an OFDM signal according to the prior art.
- Reference numeral 10-2 is a long training frame generation circuit
- reference numeral 10-3 is a radio signal transmission / reception circuit
- reference numerals 10-4-1 to 10-4-N are transmission / reception antennas
- reference numeral 10-5 is a reception signal demodulation circuit.
- Reference numeral 10-6 denotes a feedback information extraction circuit
- reference numeral 10-7 denotes a channel information acquisition circuit.
- the base station (AP) 10 determines a terminal (STA) from which channel information is to be acquired, the announcement signal (NDPA) 1 and pilot signal (NDP) 2 in FIG. 10 are generated in the long training frame generation circuit 10-2,
- the radio signal transmission / reception circuit 10-3 performs conversion to an analog signal, conversion to a carrier frequency, amplification, and the like, and transmits the signals via the transmission / reception antennas 10-4-1 to 10-4-N.
- base station (AP) 10 transmits / receives antenna 10-4-1.
- the signal is received by the radio signal transmitting / receiving circuit 10-3 via at least one of ⁇ 10-4-N, and the digital signal is output to the received signal demodulating circuit 10-5.
- the reception signal demodulation circuit 10-5 synchronizes with the received signal and obtains information acquired from any of the terminals STA-1 to STA-K by using channel information or the like.
- the feedback information extraction circuit 10-6 extracts the feedback portion of the channel information by the feedback signal CSIFB of the channel information from the obtained demodulated bits, and acquires the channel information in each frequency channel by the channel information acquisition circuit 10-7. .
- the channel information fed back here may be propagation channel information with respect to the time axis, may be channel information in each frequency channel of OFDM, or information similar to channel information, for example, the channel information is based on the Gram Schmidt orthogonalization method.
- a basis vector obtained by application, a right singular matrix of a channel information matrix, or the like can be used.
- the feedback of the channel information may be compressed by expressing the V matrix by angles ⁇ and ⁇ , or may be obtained by acquiring a part of OFDM frequency channel information (for example, non-patent document). 3).
- the channel information acquisition circuit 10-7 estimates and stores the original channel information by decompressing or interpolating the feedback information.
- IEEE "Proposed specification framework for TGac,” doc.:IEEE802.11-09/0992r21, Jan. 2011. IEEE, “IEEE P802.11 REVmb / D8.0,” “pp. 1597, 1606, March 2011. IEEE, "IEEE P802.11n / D11.0,” pp. 55-57, June 2009.
- a base station with a large number of transmission antennas requires a lot of channel information for each terminal that is a communication partner.
- the number of antennas N of the base station (AP) 10 is large, it is necessary to set the number of OFDM symbols (for example, VHT-LTF) for channel estimation to N or more, and the overhead increases.
- the bit amount of the feedback signal by the feedback signal CSIFB of the channel information increases.
- the length of the feedback information packet CSIFB from the terminal becomes long and this also becomes overhead. That is, in the conventional MIMO transmission, training signals corresponding to the number of transmission ports (transmission antennas, transmission beams) are necessary to accurately acquire channel information, so that the number of training signals increases as the number of antennas increases. However, there is a problem that the transmission efficiency deteriorates.
- the present invention has been made in consideration of such circumstances, and its purpose is to reduce the number of OFDM symbols for channel estimation, to reduce overhead due to pilot signals and feedback signals, and to improve throughput. It is an object of the present invention to provide a radio apparatus and a training signal transmission method.
- the present invention provides a wireless device for estimating channel information between a plurality of transmission ports and a receiving antenna of a communication partner in communication using an orthogonal frequency division multiplexing method, and a plurality of transmission ports
- a repetition factor setting unit for setting a repetition factor indicating how many transmission ports share a plurality of frequency channels of a training signal for estimating channel information, and a repetition factor set by the repetition factor setting unit
- a frequency channel is allocated to each transmission port so as to satisfy
- a training signal generation unit that generates L training signals (L is a positive integer) based on the allocated frequency channel and a training signal generation unit
- a radio transmission unit that outputs the training signal thus transmitted to a transmission antenna, and each of the transmissions
- a channel information acquisition unit that acquires channel information estimated from the training signal transmitted from the transmission antenna for the frequency channel allocated to a communication port, and the plurality of frequencies from the acquired channel information.
- a channel information interpolation unit that interpolates channel information of remaining frequency channels other than the frequency
- the repetition coefficient setting unit sets repetition coefficients ⁇ 1 to ⁇ M for each of M transmission ports (M is a positive integer), and the reciprocal of the repetition coefficients ⁇ 1 to ⁇ M.
- the repetition coefficients ⁇ 1 to ⁇ M may be set so that the sum of the two becomes an integer L.
- the training signal generation unit assigns frequency channels so as to satisfy the repetition factor for each transmission port, and L ⁇ L of signals corresponding to the same frequency channel of the L training signals. Multiplying the transformation matrix, assigning the obtained L signals to the L training signals, and causing the wireless transmission unit to output the training signal generated by the training signal generation unit to the transmission antenna. May be.
- the repetition coefficient setting unit sets, for each transmission port, a vector corresponding to a signal space estimated using a set matrix of channel matrices for the receiving antenna of the communication partner estimated in the past as a transmission weight.
- the repetition coefficient set for the transmission port may be set to be smaller than the repetition coefficient corresponding to the null space that is orthogonal to the vector corresponding to the signal space.
- the present invention also relates to a training signal transmission method for a radio apparatus for estimating channel information between a plurality of transmission ports and a receiving antenna of a communication partner in communication using an orthogonal frequency division multiplexing method, A repetition coefficient setting step for setting a repetition coefficient indicating how many transmission ports share a plurality of frequency channels of a training signal for estimating channel information, and a repetition coefficient set by the repetition coefficient setting step
- a frequency channel is allocated to each transmission port, and a training signal generation step for generating L training signals (L is a positive integer) based on the allocated frequency channel and a training signal generation step Output the training signal to the transmitting antenna
- a radio transmission step a channel information acquisition step for acquiring channel information estimated from the training signal transmitted from the transmission antenna for the frequency channel assigned to each transmission port, and the channel information acquisition.
- the number of OFDM symbols for channel estimation can be set to be smaller than the number of antennas or transmission beams for which channel information is to be estimated, reducing the overhead for channel estimation and reducing the throughput. The effect that it can be improved is obtained.
- 2nd Embodiment of this invention it is a conceptual diagram which shows the structure of the long training frame for channel estimation (the 2).
- 1st Embodiment of this invention and 2nd Embodiment it is a conceptual diagram which shows the correspondence of the range of correlation value (rho), and the constant value (alpha).
- 5 is a flowchart for explaining an operation of acquiring channel information between a transmission antenna and a communication partner in the first and second embodiments of the present invention.
- 5 is a flowchart for explaining an operation of acquiring channel information between a transmission beam and a communication partner in the first and second embodiments of the present invention.
- FIG. 1 is a block diagram showing a configuration of a base station (AP: radio apparatus) 10 that acquires channel information of a radio section of an OFDM signal according to the first embodiment. Parts corresponding to those in FIG. 11 are denoted by the same reference numerals and description thereof is omitted.
- a repetition factor setting circuit 10-8 determines a repetition factor for each transmission antenna or transmission port that is a transmission beam, and the number L of long training frames (LTFs) that are OFDM symbols used for channel estimation, The transmission port correspondence to each LTF and the frequency channel assignment are determined.
- LTFs long training frames
- the repetition factor is ⁇ described later.
- the frequency channel corresponds to a subcarrier in OFDM transmission.
- NDP In the pilot signal NDP shown in FIG. 10, all frequency channels are assigned to the respective transmission antennas, and N pieces of VHT-LTFs 2-2-1 to 2-2 are used to acquire channel information for all the transmission antennas. N was required. That is, in the prior art, since one transmission port occupied all subcarriers of one LTF, when there are N transmission ports, channel information was estimated using N LTFs. .
- not all frequency channels are allocated to each transmission port, but the channels to be estimated are limited to one in two or one in three.
- the number of frequency channels into which the signal for channel estimation of the transmission port is to be inserted is represented by a repetition factor ⁇ , and is determined as ⁇ 1 to ⁇ M for M transmission ports to be estimated.
- ⁇ M the number of frequency channels into which the signal for channel estimation of the transmission port is to be inserted.
- channel information of subcarriers to be omitted by sharing one training signal with other transmission ports.
- the channel information of subcarriers to be omitted can be interpolated by a method using an average of channel information estimated by subcarriers.
- FIG. 2A and 2B are conceptual diagrams showing the configuration of the pilot signal NDP and the configuration of the channel estimation LTF in the first embodiment.
- the number of frequency channels for transmitting data or control signals is 16 for simplicity.
- the number of frequency channels is 48, 52, 108, 234, 468.
- the configuration of the channel estimation LTF can be determined for other frequency channels.
- FIG. 2A and FIG. 2B when the base station (AP) 10 having the number of transmission antennas “8” transmits a pilot signal NDP for channel estimation at each terminal, the pilot for channel estimation included therein Symbols 20-1-1 and 20-1-2, and a long training frame P-LTF (Proposed LTF) 20-2-1 to 20-2-L are shown.
- the long training frame generation circuit 10-2 assigns a transmission port to the LTF so as to satisfy the determined repetition factor.
- the number L of LTFs can be expressed by the following equation (1).
- the lower missing square brackets indicate the ceiling function
- a between the lower missing square brackets is an integer obtained by rounding up the decimal part of A.
- L is a positive integer.
- Txi represents the i-th transmission port and indicates the i-th transmission antenna or the i-th transmission beam. Since the allocation coefficient of each transmission port is 2, channel information corresponding to 2L transmission ports can be obtained from L P-LTFs. Since the channel information of one frequency channel is estimated, the information of the frequency channel that has not been estimated can be interpolated using the channel information obtained in the frequency channel of the near frequency. Since channel information in each frequency channel has high correlation with channel information of adjacent frequency channels, interpolation, extrapolation, or the like can be used using this correlation. As a larger value is set as ⁇ , the number of P-LTFs to be transmitted can be reduced and the feedback amount of channel information can be reduced.
- FIG. 3 is a conceptual diagram showing the configuration of a channel estimation long training frame (an example in which an independent value is set for each transmission port as ⁇ ) in the first embodiment.
- the number of P-LTFs is 4.
- the sum of the reciprocal of repetitive coefficients is a positive integer, all frequency channels are used as channel estimation signals.
- FIG. 3 shows an example in which the value of ⁇ is different for each transmission port.
- transmission port # 1, # 2 shares one P-LTF 20-2-1
- transmission port # 3, # 4 shares one P-LTF 20-2-2
- transmission port # 5, # 2 6 and # 7 share one P-LTF 20-2-3
- transmission ports # 8, # 9, # 10 and # 11 share one P-LTF 20-2-4.
- the effect of reducing the number of LTFs conventionally required to 11 to 4 can be obtained.
- ⁇ j is reduced, more accurate channel information can be acquired.
- set small beta j conversely, can be or is set smaller beta j as transmit port signal power level is small.
- the configuration of the base station (AP: wireless device) 10 is the same as that in FIG.
- a mode in which a transformation matrix D is used to transmit from a plurality of transmission antennas or transmission beams to a P-LTF at a certain frequency channel and a certain timing will be described.
- the repetition coefficient setting circuit 10-8 sets a repetition coefficient for each transmission port, and after assigning the transmission port to the frequency channel in the long training frame generation circuit 10-2, for the obtained L P-LTFs
- the transmission signal of the transmission port assigned in this way can be converted by the conversion matrix D, and a transmission port can be newly assigned to L P-LTFs.
- a long training frame to be allocated first as in the first embodiment is defined as VP-LTF (provisional P-LTF: Virtual P-LTF), and is transmitted after conversion using the conversion matrix D.
- provisional P-LTF Virtual P-LTF
- D conversion matrix
- the transmission port numbers assigned to the kth frequency channel are t k, 1 , t k, 2 ,..., t k, L, and the signals in the kth frequency channel transmitted from the transmission ports tk , g. Is S k (t k, g ), the transmission signal X k, j of the j -th P-LTF is expressed by the following equation (4).
- Non-Patent Document 2 the signal of the frequency channel corresponding to Equations (19-11), (19-12), (19-23), and (19-24) of Non-Patent Document 2 is used as S k (t k, g ). be able to.
- the 1st to Lth transmission signals X k, 1 to X k, L are expressed by the following equation (5).
- I is a diagonal matrix of off-diagonal terms 0 and diagonal terms 1.
- FIG. 4 is a conceptual diagram showing the configuration of a long training frame for channel estimation (part 1) in the second embodiment.
- FIG. 4 shows an example in which the number M of transmission antennas for channel estimation is 8, ⁇ 1 to ⁇ 8 are 2, and the number L of P-LTFs is 4. That is, ⁇ 1 to ⁇ 8 are determined for transmission ports # 1 to # 8, transmission ports are assigned to VP-LTFs 21-2-1 to 21-2-4, and then P-LTF20- An example of generating 2-1 to 20-2-4 is shown.
- one frequency channel is assigned to ⁇ i for the i-th transmission port. This assignment can be regarded as an assignment to L VP-LTFs 21-2-1 to 21-2-L.
- D the following equation (6) can be used.
- the transmission signals in the 1st to Lth P-LTFs 20-2-1 to 20-2-L in the first frequency channel ch1 are respectively S 1 (1) + S 1 (3) + S 1 (5) + S 1 (7), S 1 (1) -S 1 (3) + S 1 (5) -S 1 (7), S 1 (1) + S 1 (3) -S 1 (5) -S 1 (7 ), S 1 (1) ⁇ S 1 (3) ⁇ S 1 (5) + S 1 (7).
- an OFDM symbol is generated by Fourier transform and a guard interval is given, whereby a P-LTF signal can be generated. Even if the signals are mixed and generated in this way, the channel information of the original transmission port can be obtained by performing conversion using the same Hadamard matrix in the communication partner.
- FIG. 5 is a conceptual diagram showing the configuration of the long training frame for channel estimation (part 2) in the second embodiment.
- ⁇ 1 to ⁇ 11 are determined for transmission ports # 1 to # 11 in the same manner as in FIG. 3, and transmission ports are assigned to VP-LTFs 21-2-1 to 21-2-4.
- P-LTFs 20-2-1 to 20-2-4 are generated using
- a P-LTF can be generated for an arbitrary ⁇ .
- transmission signals in the 1st to Lth P-LTFs in the fifth frequency channel ch5 are S 1 (1) + S 1 (3) + S 1 (5), respectively. + S 1 (8), S 1 (1) -S 1 (3) + S 1 (5) -S 1 (8), S 1 (1) + S 1 (3) -S 1 (5) -S 1 (8 ), S 1 (1) ⁇ S 1 (3) ⁇ S 1 (5) + S 1 (8).
- an OFDM symbol is generated by Fourier transform and a guard interval is given, whereby a P-LTF signal can be generated.
- the channel information correlation value ⁇ and the channel power value P in the channel information acquired in the past can be used.
- the correlation value ⁇ can be represented by the following equation (7), for example. it can. E ( ⁇ ) is a function representing an expected value, and
- FIG. 6 is a conceptual diagram showing a correspondence relationship between the range of the correlation value ⁇ and the constant value ⁇ in the first embodiment and the second embodiment described above. As shown in FIG. 6, a constant value ⁇ can be selected according to the range of ⁇ . Similarly, ⁇ can be determined using the channel power value and past communication quality as an index.
- control using ⁇ j can be performed as information collection for transmission antenna selection or transmission beam selection.
- communication is performed using a number smaller than the number N of transmission antennas, J transmission antennas, or transmission beams, the number of transmission antennas to be newly used, or remaining transmission antennas when increasing the number of transmission antennas, Alternatively, Q transmission ports can be selected as transmission ports for newly performing channel estimation from the transmission beams.
- N 16
- channel information for the remaining 8 transmit ports can be obtained collectively channel information for the remaining 8 transmit ports. Also, channel information for the remaining many antennas can be acquired simply by adding a small number ( ⁇ ) of long training frames.
- a transmission weight can be calculated and stored for each frequency channel from channel information estimated in the past.
- K communication partner respectively N r, 1 ⁇ N r
- the maximum number of multiplexed users is assumed to be B 1 ⁇ B K used for these communication partners.
- Min (A, B) is a function indicating the smaller number of A and B.
- the channel information between the i-th communication partner in the k-th frequency channel can be expressed as N r, i ⁇ N channel matrix H k, i as shown in the following equation (8).
- H k, i, xy represents channel coefficients between the y th transmission port and the x th reception antenna.
- channel information between the reception antenna and the transmission port is used, but channel information for a reception beam formed by the communication partner using the kth frequency channel may be used.
- channel information for the i-th communication partner of the k-th frequency channel acquired by the wireless device in the past channel estimation sequence is expressed by the following equation (9).
- H k, i G k, i .
- N r, 1 + N r, 2 +... + N r, K the transmission weight can be calculated from the estimated channel matrix G k, i , for example.
- An aggregate channel matrix for a terminal that is a communication partner is defined as the following equation (10).
- G k need not be perfect.
- Transmission weight to the transmission port may be used basis vectors obtained by using orthogonalization Gram Schmidt against column vector of the complex conjugate transposed matrix of G k.
- N r, 1 + N r, 2 + ... + N r, K the column vector of the unitary matrix E k obtained as the following equation (11) is obtained. The same applies to the transmission weight.
- R k is an upper triangular matrix
- E k is an N ⁇ (N r, 1 + N r, 2 +... + N r, K ) matrix.
- V k (1) corresponding to the singular value obtained by singular value decomposition can be used as the transmission weight for the transmission port.
- V k is a left singular vector
- ⁇ k is a singular value matrix that is a diagonal matrix with singular values as diagonal elements
- V k (0) is a right singular vector corresponding to the zero matrix.
- V k (1) is an N ⁇ (N r, 1 + N r, 2 +... + N r, K ) matrix.
- the (N r, 1 + N r, 2 +... + N r, K ) N ⁇ 1 vectors obtained in this way are used as transmission weights W k, 0 to multiply the output signal to each transmission port. By doing so, a transmission beam is formed, and channel information can be estimated.
- the set matrix H k can be estimated perfectly. That is, if each column vector of W k, 0 is a vector of absolute value 1, the following equation (13) is obtained, and there is no loss of signal power due to the use of W k, 0 .
- ⁇ k represents the signal power when the transmission weights W k, N are used.
- transmission weights W k, 0 for channel estimation that are optimal for the wireless device are used, a deviation from the actual propagation environment occurs, and in order to estimate channel information for all transmission ports, the same number N as the number of transmission antennas.
- One transmission beam must be prepared.
- the transmission weight W k conditions orthogonal to the transmission weight W k, 0, because the power value of the channel information obtained by N is significantly less than the power value obtained by the transmission weight W k, 0, the transmission weight W
- the repetition coefficient ⁇ can be set large for the transmission beams corresponding to k and N.
- Equation (10) a 30 ⁇ 6 matrix E k is obtained in each frequency channel, and six transmission beams are obtained. If transmission beams whose transmission weights are all orthogonal to each other are prepared, transmission beams for the remaining 24 null spaces can be generated.
- the repetition coefficient for the transmission beam corresponding to the signal space obtained by Expression (11) or Expression (12) is set small, and the repetition coefficient for other transmission beams is set larger than these.
- the repetition factor for the transmission beam corresponding to the signal space may be determined based on the correlation between the frequency channels, the power of the channel with the communication partner, and the past communication quality. By setting ⁇ to 1, the highest estimation accuracy can be obtained.
- the minimum number of transmission ports present on the same training frame is defined as F 0 (F 0 ⁇ 2)
- the repetition factor ⁇ is set to the transmit beam for the null space can be set to F / F 0 or less .
- FIG. 7 is a conceptual diagram showing the configuration of the long training frame for channel estimation (part 3) in the second embodiment.
- P-LTF 20-2 is converted from VP-LTF 21-2-1 to 21-2-4 by conversion matrix D.
- -1 to 20-2-4 are generated.
- channel estimation result by the transmission beam for this null signal is not used for the calculation of the transmission weight calculated for data transmission, but may be considered only for W k, 0 calculated in the next channel estimation. it can.
- channel estimation for a null signal there is a case where the terminal that receives the signal does not receive a value sufficiently larger than noise. In this case, since the reliability of the channel estimation result is low, feedback information is not fed back from the reception side, or channel information with a low reception level may not be used as transmission weight calculation information.
- the transmission weight for the transmission port has been described. How the transmission weight for the transmission port is expressed as the transmission weight for the transmission antenna will be described. It is considered that the channel matrix represented by Expression (8) and Expression (9) corresponds to channel information between the transmission antenna and the reception antenna. From the obtained channel matrix, the transmission weight W k used for channel estimation selected from the transmission weight W k, 0 for the signal space and the transmission weight W k, N for the null space can be calculated. Next, channel estimation is performed using ⁇ transmission beams formed by the transmission weight W k as transmission ports.
- the transmission weight W k is an N ⁇ ⁇ matrix.
- channel information in a frequency channel that is not actually estimated by transmission using the transmission weight is extrapolated or interpolated. Interpolated.
- the channel information of the k-th frequency estimated by the i-th communication partner can be expressed by the following equation (17).
- N k, i represents a noise matrix having a noise component in each diagonal term.
- G ′ k, i is a channel matrix between each transmission beam and the i-th receiving antenna, and is an N r, i ⁇ ⁇ matrix.
- G ′ k, i is converted into bit information and then fed back to the wireless device.
- the aggregate channel matrix G ′ k is obtained as the following equation (18).
- the transmission weight for the transmission beam is converted to the transmission weight for the transmission antenna. It is necessary to multiply the transmission weight of the original transmission beam by the newly calculated transmission weight. In this way, channel information corresponding to many antennas can be acquired using LTFs smaller than the number of antennas while updating transmission weights for channel estimation.
- FIG. 8 is a flowchart for explaining an operation of acquiring channel information between the transmission antenna and the communication partner in the first and second embodiments of the present invention.
- the repetition coefficient determination circuit 10-8 determines an antenna from which channel information is acquired (step S1), and determines repetition coefficients ⁇ 1 to ⁇ M for each antenna (step S2). .
- the number of P-LTFs is determined so as to satisfy the repetition factors ⁇ 1 to ⁇ M of each antenna, frequency channels are allocated (step S3), and each transmission antenna is assigned.
- a signal corresponding to the frequency channel generated in each P-LTF is generated, inverse Fourier transform is performed, a guard interval is given, and L P-LTF signals are generated (step S4).
- a signal of a certain frequency channel can be reassigned to L P-LTFs 20-2-1 to 20-2-L by the transformation matrix D.
- the PAPR Peak to average power ratio
- FIG. 9 is a flowchart for explaining an operation of acquiring channel information between a transmission beam and a communication partner in the first and second embodiments of the present invention.
- the transmission weight of the transmission beam is determined and stored using channel information obtained from past communication (step S10).
- step S10 when there is no channel acquisition information by past communication, channel information for randomly determining a transmission weight, storing a fixed transmission weight in advance, or acquiring a signal from a communication partner It is also possible to use the transmission weight calculated from the above.
- the repetition coefficient determination circuit 10-8 determines a transmission beam for estimating channel information (step S11), and sets repetition coefficients ⁇ 1 to ⁇ M for each transmission beam (step S11). S12).
- the number of P-LTFs is determined so as to satisfy the repetition factors ⁇ 1 to ⁇ M of each transmission beam, and transmission ports are assigned to frequency channels (step S13).
- a signal corresponding to the frequency channel generated in each P-LTF is generated, inverse Fourier transform is performed, a guard interval is given, and L P-LTF signals are generated (step S14).
- a signal of a certain frequency channel can be reassigned to L P-LTFs 20-2-1 to 20-2-L by the transformation matrix D.
- channel estimation is performed by including channel estimation signals for a plurality of antennas or transmission beams in one OFDM symbol. Can reduce the number of OFDM symbols, reduce overhead due to pilot signals and feedback signals, and improve throughput.
- a program for realizing the functions of the processing units shown in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is stored in the computer.
- the wireless communication processing may be performed by reading the system and executing it.
- the “computer system” includes hardware such as an OS (Operating System) and peripheral devices.
- “Computer-readable recording medium” means a portable medium such as a flexible disk, a magneto-optical disk, a ROM (Read Only Memory), a CD (Compact Disk) -ROM, or a hard disk built in a computer system. Refers to the device.
- the “computer-readable recording medium” means a volatile memory (RAM (Random Access) inside a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. Memory)) as well as those that hold programs for a certain period of time.
- RAM Random Access
- the program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium.
- the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
- the program may be for realizing a part of the functions described above. Further, the program may be a so-called difference file (difference program) that can realize the above-described functions in combination with a program already recorded in the computer system.
- the present invention can be used, for example, for communication by orthogonal frequency division multiplexing.
- the number of OFDM symbols for channel estimation can be set smaller than the number of antennas or transmission beams for which channel information is to be estimated. Further, according to the present invention, it is possible to reduce overhead for channel estimation and improve throughput.
Abstract
Description
本願は、2012年1月27日に日本へ出願された特願2012-015917号に基づき優先権を主張し、その内容をここに援用する。
まず、本発明の第1実施形態について説明する。
図1は、本第1実施形態による、OFDM信号の無線区間のチャネル情報を取得する基地局(AP:無線装置)10の構成を示すブロック図である。図11に対応する部分については同一の符号を付けて説明を省略する。図1において、繰り返し係数設定回路10-8は、各送信アンテナ、または送信ビームである送信ポートに対し、繰り返し係数を決定し、チャネル推定に用いるOFDMシンボルであるロングトレーニングフレーム(LTF)数L、各LTFへの送信ポートの対応と周波数チャネルの割り当てを決定する。
次に、本発明の第2実施形態について説明する。
なお、基地局(AP:無線装置)10の構成は、図1と同様であるので説明を省略する。本第2実施形態では、変換行列Dを用いることで、ある周波数チャネル、あるタイミングのP-LTFに複数の送信アンテナ、または送信ビームから送信する形態について説明する。繰り返し係数設定回路10-8は、各送信ポートに繰り返し係数を設定し、ロングトレーニングフレーム生成回路10-2において、周波数チャネルに送信ポートを割り当てた後、得られたL個のP-LTFに対して割り当てられた送信ポートの送信信号を、変換行列Dにより変換し、新たにL個のP-LTFに送信ポートを割り当てることもできる。
まず、(Nr,1+Nr,2+...+Nr,K)<Nの場合を考える。この場合には、送信ウエイトは、例えば、これら推定されたチャネル行列Gk,iから計算できる。通信相手となる端末に対する集合チャネル行列を、次式(10)と定義する。
以上説明したように、本発明の実施形態によれば、チャネル情報用の各OFDMシンボルに対し、複数の送信アンテナ、または送信ビームを割り当てることで、チャネル推定用のOFDMシンボルの数を減らし、MAC効率を改善することでスループットを増大する通信システムを実現する。
10-2 ロングトレーニングフレーム生成回路
10-3 無線信号送受信回路
10-4-1~10-4-N 送受信アンテナ
10-5 受信信号復調回路
10-6 フィードバック情報抽出回路
10-7 チャネル情報取得回路
10-8 繰り返し係数設定回路
Claims (6)
- 直交周波数分割多重方式による通信における複数の送信ポートと通信相手の受信アンテナとの間のチャネル情報を推定する無線装置であって、
前記複数の送信ポートに対し、前記チャネル情報を推定するためのトレーニング信号の複数の周波数チャネルを、何個の送信ポートで共有するか示す繰り返し係数を設定する繰り返し係数設定部と、
前記繰り返し係数設定部によって設定された前記繰り返し係数を満たすように、前記各送信ポートに対して周波数チャネルを割り当て、割り当てた周波数チャネルに基づいてL個(Lは正の整数)のトレーニング信号を生成するトレーニング信号生成部と、
前記トレーニング信号生成部によって生成された前記トレーニング信号を送信アンテナへ出力する無線送信部と、
前記各送信ポートに割り当てた前記周波数チャネルについて、前記送信アンテナにより送信される前記トレーニング信号から推定されるチャネル情報を前記通信相手から取得するチャネル情報取得部と、
取得した前記チャネル情報から、前記複数の周波数チャネルのうち、前記各送信ポートに割り当てた前記周波数チャネル以外の残りの周波数チャネルのチャネル情報を補間するチャネル情報補間部と
を備える無線装置。 - 前記繰り返し係数設定部は、
M個(Mは正の整数)の各送信ポートに対し、繰り返し係数をβ1~βMと設定し、前記繰り返し係数β1~βMの逆数の和が整数Lとなるように、前記繰り返し係数β1~βMをそれぞれ設定する請求項1に記載の無線装置。 - 前記トレーニング信号生成部は、
前記各送信ポートに対し、前記繰り返し係数を満たすように周波数チャネルを割り当て、前記L個のトレーニング信号の同じ周波数チャネルに対応する信号に対し、L×Lの変換行列を乗算し、得られたL個の信号を前記L個のトレーニング信号に割り当て、
前記無線送信部は、前記トレーニング信号生成部によって生成された前記トレーニング信号を前記送信アンテナへ出力する請求項1または2に記載の無線装置。 - 前記繰り返し係数設定部は、
前記各送信ポートに対し、過去に推定した前記通信相手の前記受信アンテナに対するチャネル行列の集合行列を用いて推定した信号空間に対応するベクトルを送信ウエイトとした送信ポートに対して設定した繰り返し係数を、前記信号空間に対応する前記ベクトルと直交条件になるヌル空間に対応する繰り返し係数より小さくなるように設定する請求項1または2に記載の無線装置。 - 前記繰り返し係数設定部は、
前記各送信ポートに対し、過去に推定した前記通信相手の前記受信アンテナに対するチャネル行列の集合行列を用いて推定した信号空間に対応するベクトルを送信ウエイトとした送信ポートに対して設定した繰り返し係数を、前記信号空間に対応する前記ベクトルと直交条件になるヌル空間に対応する繰り返し係数より小さくなるように設定する請求項3に記載の無線装置。 - 直交周波数分割多重方式による通信における複数の送信ポートと通信相手の受信アンテナとの間のチャネル情報を推定する無線装置のトレーニング信号送信方法であって、
前記複数の送信ポートに対し、前記チャネル情報を推定するためのトレーニング信号の複数の周波数チャネルを、何個の送信ポートで共有するか示す繰り返し係数を設定する繰り返し係数設定ステップと、
前記繰り返し係数設定ステップによって設定された前記繰り返し係数を満たすように、前記各送信ポートに対して周波数チャネルを割り当て、割り当てた周波数チャネルに基づいてL個(Lは正の整数)のトレーニング信号を生成するトレーニング信号生成ステップと、
前記トレーニング信号生成ステップによって生成された前記トレーニング信号を送信アンテナへ出力する無線送信ステップと、
前記各送信ポートに割り当てた前記周波数チャネルについて、前記送信アンテナにより送信される前記トレーニング信号から推定されるチャネル情報を前記通信相手から取得するチャネル情報取得ステップと、
前記チャネル情報取得ステップによって取得した前記チャネル情報から、前記複数の周波数チャネルのうち、前記各送信ポートに割り当てた前記周波数チャネル以外の残りの周波数チャネルのチャネル情報を補間するチャネル情報補間ステップと
を備えるトレーニング信号送信方法。
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CN104040922A (zh) | 2014-09-10 |
EP2790338B1 (en) | 2019-09-18 |
US9313007B2 (en) | 2016-04-12 |
EP2790338A4 (en) | 2015-09-02 |
JP5775610B2 (ja) | 2015-09-09 |
EP2790338A1 (en) | 2014-10-15 |
JPWO2013111784A1 (ja) | 2015-05-11 |
US20140376355A1 (en) | 2014-12-25 |
CN104040922B (zh) | 2016-12-14 |
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