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WO2014024502A1 - Appareil de transmission ofdm, procédé de transmission ofdm, appareil de réception ofdm, et procédé de réception ofdm - Google Patents

Appareil de transmission ofdm, procédé de transmission ofdm, appareil de réception ofdm, et procédé de réception ofdm Download PDF

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Publication number
WO2014024502A1
WO2014024502A1 PCT/JP2013/004820 JP2013004820W WO2014024502A1 WO 2014024502 A1 WO2014024502 A1 WO 2014024502A1 JP 2013004820 W JP2013004820 W JP 2013004820W WO 2014024502 A1 WO2014024502 A1 WO 2014024502A1
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Prior art keywords
ofdm
symbol
subcarrier
data
symbols
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English (en)
Japanese (ja)
Inventor
航也 渡邉
喜修 松村
一平 神野
照晃 長谷川
茂 曽我
久輝 小畠
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Panasonic Corp
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Panasonic Corp
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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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H04L27/26134—Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain

Definitions

  • the present disclosure relates to a transmission device that multiplexes and transmits a plurality of subcarriers, and a reception device that receives a signal transmitted in this manner.
  • OFDM Orthogonal Frequency Frequency Division Multiplexing
  • the OFDM scheme is a scheme that transmits a plurality of narrowband digitally modulated signals by frequency multiplexing using a plurality of subcarriers orthogonal to each other, and is therefore a transmission scheme with excellent frequency utilization efficiency.
  • FIG. 1 is an explanatory diagram showing an example of the arrangement of pilot signals defined by IEEE 802.11.
  • IEEE 802.11 In general, in the OFDM scheme, a known signal is added to information data to be transmitted and transmitted in order for the receiving apparatus to effectively receive and demodulate the signal transmitted from the transmitting apparatus.
  • IEEE 802.11 as shown in FIG. 1, STF (Short Training Field), LTF (Long Training Field), and pilot signals arranged on fixed subcarriers over all data symbols are included in data to be transmitted. Added, framed, and transmitted.
  • the STF is mainly used for symbol timing detection, AGC (Auto Gain Control), carrier frequency error correction, and the like.
  • AGC Automatic Gain Control
  • LTF all subcarriers in a symbol are composed of known pilot signals.
  • the LTF is used for measuring transmission path characteristics.
  • the transmission path characteristic represents the amplitude phase distortion received in the transmission path and is important for correcting (equalizing) the distortion.
  • This transmission path characteristic is used over all symbols. However, if there is a carrier frequency error, phase rotation common to the subcarriers occurs as the symbol progresses, so it is necessary to correct the transmission path characteristics obtained using the LTF. This phase rotation is called CPE (Common (Pilot Error).
  • CPE is calculated for each symbol using a pilot signal inserted over all data symbols. Since these pilot signals are arranged on specific subcarriers, the amount of phase rotation generated between symbols can be obtained by comparing the symbols of pilot signals of the same subcarrier. Generally, in IEEE802.11a, 11g, and 11n receiving apparatuses, since the frame length is short, it is considered that the time variation in the symbol direction of the channel characteristics due to fading can be ignored, and only the phase rotation correction in the symbol direction is performed. We are carrying out.
  • FIG. 2 is an explanatory diagram showing an arrangement example of pilot signals for digital television broadcasting defined by DVB-T (Digital Video Broadcasting-Terrestrial) / T2 and ISDB-T (Integrated Services Digital Broadcasting-Terrestrial).
  • DVB-T Digital Video Broadcasting-Terrestrial
  • ISDB-T Integrated Services Digital Broadcasting-Terrestrial
  • known pilot signals spanning SP Scattered Pilot
  • the transmission path characteristics of the symbols between the SPs are calculated.
  • the transmission path characteristic obtained from the pilot signal that is close in time is used while reducing the error due to the noise by the interpolation process, it is possible to follow the time fluctuation of the transmission path characteristic due to fading.
  • the wireless LAN standard in IEEE 802.11 has been focused on indoor communication as the main target, and the physical layer standards are 11b (maximum 11 Mbps), 11a and 11g (maximum 54 Mbps), 11n (maximum 600 Mbps), and 11ac ( Up to 6.9 Gbps) has been formulated. These are mainly aimed at increasing the transmission rate.
  • a full-scale study of smart meters to realize smart grit is in full swing. Accordingly, the need for low data rate transmission outdoors has increased, and discussions such as allocation of frequencies that can be used for specific low power radios for such applications continue.
  • IEEE 802.11 also has a wireless LAN standard using a frequency band of 1 GHz or less as a study content TGah (task group ah) Was launched in 2010.
  • the main required specifications in TGah are “data rate 100 kbps and maximum transmission distance 1 km”.
  • the time per symbol was 3.2 ⁇ s, but in TGah, the clock rate is considered to be 1/10 that of 11a. That is, it is assumed that the symbol length is 10 times 32 ⁇ s.
  • transmission line estimation for data symbols has been performed by ignoring time fluctuations of transmission line characteristics and by phase correction based on transmission line characteristics obtained from LTF and pilot signals.
  • the symbol length becomes 10 times
  • the frame length becomes longer and the influence of time variation becomes 10 times. For this reason, if transmission path estimation is performed while ignoring this time variation, a transmission path estimation error becomes large, and eventually a packet error occurs.
  • the time from when a transmission signal is received to when an ACK (ACKnowledgement) indicating that the transmission has been received is returned is defined as SIFS (Short Inter Frame Space) time.
  • SIFS Short Inter Frame Space
  • An object of the present invention is to suppress errors in estimated transmission path characteristics even when the frame length is relatively long.
  • An OFDM transmission apparatus is an OFDM transmission apparatus that generates and transmits a frame having a plurality of OFDM (Orthogonal Frequency Division Multiplexing) symbols, and transmits the information data to be transmitted and a pilot signal to the OFDM symbol
  • a subcarrier modulation section that generates the OFDM symbol by allocating to a plurality of subcarriers included in the subcarrier, and a conversion section that converts the OFDM symbol generated by the subcarrier modulation section into a signal in the time domain and outputs the signal.
  • the subcarrier modulation unit inserts a pilot signal into M (M is a natural number) subcarriers that are changed according to the position of the data symbol in the frame in the data symbols of the plurality of OFDM symbols. Pilot signals are inserted into N (N is an integer of 2 or more) consecutive data symbols including the data symbols in subcarriers into which pilot signals are inserted in the data symbols.
  • the noise of the transmission path characteristic can be reduced by averaging the transmission path characteristics obtained using each pilot signal. Since pilot signals are inserted into subcarriers that are changed according to the position of data symbols, the number of pilot signals per symbol is small, and pilot signals can be periodically inserted into many subcarriers. Since the number of pilot signals per symbol is small, the amplitude of the pilot signal can be increased without greatly increasing the power of the symbol, and noise in the transmission path characteristics can be reduced. Therefore, the transmission path information can be estimated with high accuracy even in a weak electric field environment with a lot of noise or in a fading environment, and equalization processing can be effectively performed and stable reception is possible.
  • An OFDM receiver is an OFDM receiver that receives a frame having a plurality of OFDM symbols, a transmission path estimator that determines transmission path characteristics based on a pilot signal included in the OFDM symbol, and the transmission And an equalization unit for equalizing and outputting the OFDM symbol based on the path characteristics.
  • pilot signals are inserted into M (M is a natural number) subcarriers that are changed according to the position of the data symbol in the frame. Pilot signals are inserted in N (N is an integer of 2 or more) consecutive data symbols including the data symbols in subcarriers in which pilot signals are inserted in the data symbols.
  • An OFDM transmission method is an OFDM transmission method in which a frame having a plurality of OFDM symbols is generated and transmitted, and information data to be transmitted and a pilot signal are transmitted from a plurality of sub-frames included in the OFDM symbol.
  • the OFDM symbol is generated by allocating to a carrier, and the OFDM symbol generated by the subcarrier modulation unit is converted into a time domain signal and output.
  • a pilot signal is inserted into M (M is a natural number) subcarriers that are changed according to the position of the data symbol in the frame in the data symbol of the plurality of OFDM symbols. Pilot signals are inserted into N (N is an integer of 2 or more) consecutive data symbols including the data symbols in subcarriers into which pilot signals are inserted in the data symbols.
  • An OFDM reception method is an OFDM reception method for receiving a frame having a plurality of OFDM symbols, and obtains a transmission path characteristic based on a pilot signal included in the OFDM symbol, and based on the transmission path characteristic
  • the OFDM symbol is equalized and output.
  • pilot signals are inserted into M (M is a natural number) subcarriers that are changed according to the position of the data symbol in the frame. Pilot signals are inserted in N (N is an integer of 2 or more) consecutive data symbols including the data symbols in subcarriers in which pilot signals are inserted in the data symbols.
  • the embodiment of the present invention it is possible to suppress an error in the estimated transmission path characteristics even when the frame length is relatively long. Therefore, even when the channel characteristics are easily affected by time fluctuation, it is possible to follow the fluctuation and improve reception performance.
  • FIG. 1 is an explanatory diagram showing an example of arrangement of pilot signals defined by IEEE 802.11.
  • FIG. 2 is an explanatory diagram showing an arrangement example of pilot signals for digital television broadcasting defined by DVB-T / T2 and ISDB-T.
  • FIG. 3 is a block diagram illustrating a configuration example of the OFDM transmission apparatus according to the embodiment of the present invention.
  • FIG. 4 is a schematic diagram illustrating an example of an OFDM frame format.
  • FIG. 5 is a schematic diagram showing the addition of a guard interval.
  • FIG. 6 is a schematic diagram showing addition of a guard interval in the LTF.
  • FIG. 7 is a schematic diagram showing waveform shaping.
  • FIG. 8 is an explanatory diagram showing an example of arrangement of pilot signals in an OFDM frame.
  • FIG. 1 is an explanatory diagram showing an example of arrangement of pilot signals defined by IEEE 802.11.
  • FIG. 2 is an explanatory diagram showing an arrangement example of pilot signals for digital television broadcasting defined by DVB-T / T2 and
  • FIG. 9 is a flowchart illustrating an example of processing related to pilot signal insertion.
  • FIG. 10 is a block diagram illustrating a configuration example of the OFDM receiving apparatus according to the embodiment of the present invention.
  • FIG. 11 is a block diagram illustrating a configuration example of the transmission path estimation unit in FIG.
  • FIG. 12 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 13 is an explanatory diagram illustrating another arrangement example of pilot signals in an OFDM frame.
  • FIG. 14 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 15 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 16 is an explanatory diagram illustrating another arrangement example of pilot signals in an OFDM frame.
  • FIG. 10 is a block diagram illustrating a configuration example of the OFDM receiving apparatus according to the embodiment of the present invention.
  • FIG. 11 is a block diagram illustrating a configuration example of the transmission path estimation unit in
  • FIG. 17 is an explanatory diagram illustrating another arrangement example of pilot signals in an OFDM frame.
  • FIG. 18 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • 19 is a block diagram showing a configuration of a modification of the transmission path estimation unit in FIG.
  • FIG. 20 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 21 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 22 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 23 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 24 is an explanatory diagram showing an arrangement example of pilot signals in an OFDM frame when data is not repeated.
  • FIG. 25 is an explanatory diagram illustrating an example of a symbol with a symbol number p and a symbol with a symbol number p + 1 when data is repeatedly transmitted.
  • FIG. 26 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • FIG. 27 is an explanatory diagram showing another example of the symbol number p and the symbol number p + 1 when data is repeatedly transmitted.
  • IEEE802.11ah format under study by TGah in IEEE802.11 is described as an example, but the application destination is not limited to this, and the description can be made in other formats as well.
  • the format of IEEE 802.11ah as an example may be changed in the future.
  • FIG. 3 is a block diagram showing a configuration example of the OFDM transmitter 300 according to the embodiment of the present invention.
  • An OFDM transmitter 300 in FIG. 3 is a transmitter that generates and transmits a frame having a plurality of OFDM symbols, and includes an OFDM modulator 310, a digital-to-analog (D / A) converter 302, an RF (Radio frequency) output unit 304.
  • the OFDM modulation unit 310 includes an error correction encoding unit 312, an interleaving unit 314, a subcarrier modulation unit 316, a synchronization signal adding unit 318, an inverse Fourier transform unit 322, a guard interval adding unit 324, and a symbol shaping unit. 326.
  • the data SDT to be transmitted is input to the error correction encoding unit 312.
  • the error correction encoding unit 312 adds redundant bits for error correction to the input data, encodes the obtained bit string, and outputs it to the interleaving unit 314.
  • the error correction encoding unit 312 performs convolutional encoding here.
  • Interleaving section 314 changes the order of codes obtained by error correction coding and outputs the result to subcarrier modulation section 316.
  • FIG. 4 is a schematic diagram showing an example of the OFDM frame format.
  • the OFDM frame includes STF (Short Training Field), LTF (Long Training Field), and a plurality of data symbols in this order.
  • Subcarrier modulation section 316 assigns information data to be transmitted and pilot signals to a plurality of subcarriers included in the OFDM symbol, and generates an OFDM symbol.
  • the subcarrier modulation unit 316 particularly forms a data symbol and outputs it to the inverse Fourier transform unit 322.
  • the subcarrier modulation section 316 maps the interleaved code to a digital modulation symbol such as BPSK (Binary Phase Shift Keying) or QAM (Quadrature Amplitude Modulation) in each OFDM subcarrier, and further inserts a pilot signal.
  • BPSK Binary Phase Shift Keying
  • QAM Quadrature Amplitude Modulation
  • the synchronization signal adding unit 318 generates a pilot signal (preamble signal) for synchronization such as STF or LTF, and outputs the pilot signal to the inverse Fourier transform unit 322.
  • the inverse Fourier transform unit 322 performs inverse Fourier transform on the preamble signal generated by the synchronization signal adding unit 318 and the data symbol into which the pilot signal is inserted by the subcarrier modulation unit 316. That is, inverse Fourier transform section 322 converts the OFDM symbol (frequency domain signal) generated by subcarrier modulation section 316 or the like into a time domain signal and outputs the signal to guard interval adding section 324.
  • the inverse Fourier transform unit 322 may perform wavelet inverse transform or the like instead of the inverse Fourier transform.
  • FIG. 5 is a schematic diagram showing the addition of a guard interval.
  • FIG. 6 is a schematic diagram showing addition of a guard interval in the LTF.
  • the guard interval adding unit 324 copies the latter half of the OFDM effective symbol and adds it to the head.
  • the guard interval adding unit 324 adds one guard interval to two OFDM effective symbols as shown in FIG.
  • the guard interval adding unit 324 outputs the signal with the guard interval added to the symbol shaping unit 326.
  • FIG. 7 is a schematic diagram showing waveform shaping.
  • Symbol shaping section 326 performs waveform shaping on the OFDM symbol and outputs the result to D / A converter 302. Specifically, the symbol shaping unit 326 performs a process of halving the amplitude on the first sample and the last sample of the OFDM symbol as shown in FIG. As a result, spectrum out-of-band power can be suppressed.
  • the D / A converter 302 D / A converts the output signal of the symbol shaping unit 326 into an analog signal and outputs the analog signal to the RF output unit 304.
  • the RF output unit 304 converts the output signal of the D / A conversion unit 308 into a signal having a predetermined carrier frequency, and transmits the signal from the antenna 306.
  • the OFDM transmitter 300 in FIG. 3 generates and transmits an OFDM signal in this way.
  • the pilot signal insertion in subcarrier modulation section 316 will be described in more detail.
  • Subcarrier modulation section 316 transmits a pilot signal to M (M is a natural number) subcarriers that are changed according to the position of the data symbol in the OFDM frame, among data symbols of a plurality of OFDM symbols included in the OFDM frame. insert. Pilot signals are inserted into N (N is an integer of 2 or more) consecutive data symbols including data symbols in subcarriers into which pilot signals are inserted in data symbols.
  • FIG. 8 is an explanatory diagram showing an arrangement example of pilot signals in the OFDM frame.
  • each row extending in the horizontal direction represents one OFDM symbol
  • each column extending in the vertical direction represents one subcarrier. That is, the vertical axis represents time and the horizontal axis represents frequency.
  • a plurality of data symbols are shown after 10 symbols of STF and 2 symbols of LTF.
  • the hatched cells indicate that pilot signals are arranged.
  • an OFDM symbol is also simply referred to as a symbol.
  • the data symbol number p is assumed to be 0, 1, 2,... In order from immediately after the LTF.
  • the subcarrier number q is assumed to be 0, 1, 2,..., 51 in order from the left end. However, the center null subcarrier (DC) is skipped.
  • p and q are integers of 0 or more.
  • 31 data symbols are shown, but data symbols may continue after this.
  • the number of effective subcarriers S per symbol is 52
  • the number of data carriers is 48
  • the number of pilot signals M is 4
  • the number of pilots N consecutive in the same subcarrier is 2. It is not limited to (S is a natural number).
  • FIG. 9 is a flowchart showing an example of processing related to pilot signal insertion.
  • the synchronization signal adding unit 318 generates a pilot signal in the STF and outputs the pilot signal to the inverse Fourier transform unit 322.
  • the synchronization signal adding unit 318 generates a pilot signal in the LTF and outputs the pilot signal to the inverse Fourier transform unit 322.
  • the subcarrier modulation unit 316 sets the data symbol number p held therein to 0.
  • the subcarrier modulation unit 316 determines whether the number of generated data symbols exceeds the number of data symbols SMAX of the OFDM frame to be transmitted. If it has exceeded, the process of FIG. 9 is terminated, and if not, the process proceeds to block 920. In block 920, the subcarrier modulation unit 316 sets the subcarrier number q held therein to 0.
  • the subcarrier modulation unit 316 determines whether or not the subcarrier number q exceeds the number of valid subcarriers S. If so, proceed to block 924; otherwise, proceed to block 926. In block 924, the subcarrier modulation unit 316 adds 1 to the data symbol number p and returns to block 918.
  • the subcarrier modulation unit 316 determines whether or not the position indicated by the data symbol number p and the subcarrier number q in FIG. 8 is a position where the pilot signal is to be inserted, in other words, the subcarrier number q, It is determined whether or not the subcarrier number C p_i of the subcarrier into which the pilot signal is to be inserted matches.
  • subcarrier modulation section 316 determines the subcarrier into which the pilot signal is inserted by modulo calculation for number p corresponding to the position of the data symbol in the frame. If the position indicated by the data symbol number p and the subcarrier number q is a position where a pilot signal is to be inserted, the process proceeds to block 928; otherwise, the process proceeds to block 930.
  • the subcarrier modulation unit 316 inserts a pilot signal into the subcarrier having the subcarrier number C p_i .
  • the subcarrier modulation unit 316 inserts a data signal indicating data to be transmitted into the subcarrier of the subcarrier number q.
  • the subcarrier modulation unit 316 adds 1 to the subcarrier number q and returns to block 922.
  • subcarrier modulation unit 316 inserts pilot signals into subcarriers with subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 for the data symbol with symbol number p.
  • the subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 are obtained according to the above-described formula 1, and when p is 0, specifically, they are 0, 13, 26, and 39, respectively.
  • the value of the pilot signal to be inserted may be known, but here it is assumed to be a value by BPSK modulation.
  • the value of the pilot signal only needs to be uniquely determined on the transmission side and the reception side, and may be generated by, for example, PRBS (pseudorandom binary sequence) according to the subcarrier number, or may be defined by a table.
  • PRBS pseudorandom binary sequence
  • the values of pilot signals of subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 are respectively expressed as A p_1 (4 / 3,0), A p_2 (4 / 3,0), A p_3 (4 / 3,0), A p_4 (-4 / 3,0).
  • the values of these pilot signals are represented by complex numbers.
  • the pilot signal amplitude is larger than the average amplitude of the subcarriers that transmit the information data to be transmitted. This average amplitude corresponds to 1. For this reason, it is possible to suppress the influence of noise when obtaining the transmission path characteristics.
  • Subcarrier modulation section 316 also inserts a pilot signal into the same subcarrier as the data symbol of symbol number p for the data symbol of symbol number p + 1. That is, the position of the pilot signal of the data symbol with symbol number p + 1 is the subcarrier with subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 . At this time, it is desirable that the pilot signals of the same subcarrier as in the immediately preceding data symbol have the same value.
  • the values of the pilot signals of subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 are respectively A p + 1,1 (4 / 3,0), A p + 1,2 (4 / 3,0), A p + 1,3 (4 / 3,0), A p + 1,4 (-4 / 3,0) It is desirable that The value of the pilot signal may be a value obtained by inverting the sign of all values of the pilot signal of the immediately preceding symbol number p.
  • the values of the pilot signals in the subcarriers with subcarrier numbers C p_1 , C p_2 , C p_3 , C p_4 are A p + 1,1 ( ⁇ 4 / 3,0), A p + 1, 2 ( ⁇ 4 / 3,0), A p + 1,3 ( ⁇ 4 / 3,0), and A p + 1,4 (4 / 3,0).
  • subcarrier modulation section 316 inserts a pilot signal in a subcarrier different from symbol numbers p and p + 1.
  • subcarrier modulation section 316 inserts a pilot signal in the right subcarrier with respect to the case of symbol number p + 1.
  • subcarrier modulation section 316 inserts a pilot signal having the same value on the same subcarrier as that of symbol number p + 2.
  • the subcarrier modulation unit 316 inserts a pilot signal in any of data symbols for transmitting information data to be transmitted to a plurality of subcarriers included in the OFDM symbol.
  • the pilot signal is inserted so as to make a round of all subcarriers with 26 data symbols.
  • Subcarrier modulation section 316 changes the subcarrier into which the pilot signal is inserted into the adjacent subcarrier for every N symbols in a certain direction. Specifically, each pilot signal is arranged over two symbols on the same subcarrier. The subcarrier into which the pilot signal is inserted is changed in a certain direction as the symbol number increases. When attention is paid to a certain subcarrier, pilot signals over two symbols are arranged for each predetermined number of symbols.
  • FIG. 10 is a block diagram showing a configuration example of the OFDM receiving apparatus 1000 according to the embodiment of the present invention.
  • 10 includes a tuner 1054, an A / D (analog-to-digital) converter 1056, and an OFDM demodulator 1060.
  • OFDM demodulation section 1060 includes orthogonal transformer 1062, synchronization section 1064, Fourier transform section 1066, channel characteristic estimation section 1080, equalization section 1068, demapper section 1072, deinterleave section 1074, and error correction. Part 1076.
  • Tuner 1054 selects a received signal of a desired reception channel from signals received by antenna 1052 and outputs the selected signal to A / D converter 1056.
  • the A / D converter 1056 converts the output of the tuner 1054 into a digital signal and outputs the digital signal to the orthogonal transformer 1062.
  • the orthogonal transformer 1062 orthogonally demodulates the IF signal output from the A / D converter 1056 using a fixed frequency signal and converts the IF signal into a complex baseband signal.
  • the synchronization unit 1064 performs synchronization processing such as carrier frequency synchronization and timing synchronization on the complex baseband signal using the STF signal and the LTF signal included therein, and the result is sent to the Fourier transform unit 1066. Output.
  • Fourier transform section 1066 performs Fourier transform on the effective OFDM symbol period portion of the output signal of synchronization section 1064, and outputs received data FR after Fourier transform to transmission path estimation section 1080 and equalization section 1068.
  • the Fourier transform is performed by, for example, FFT, but is not limited thereto.
  • the Fourier transform unit 1066 may perform wavelet transform or the like instead of the Fourier transform.
  • the transmission path estimation unit 1080 estimates the transmission path characteristics, that is, the distortion characteristics of the amplitude phase received by the received signal in the transmission path for each subcarrier based on the received data FR, and obtains the obtained transmission path characteristics CR.
  • the data is output to the equalization unit 1068.
  • the transmission path estimation unit 1080 estimates transmission path characteristics using, for example, an LTF signal or a pilot signal included in a data symbol.
  • the equalization unit 1068 equalizes the received data FR (OFDM symbol) input from the Fourier transform unit 1066 with the transmission path characteristic CR estimated by the transmission path estimation unit 1080, and outputs the equalized data to the demapper unit 1072.
  • the demapper unit 1072 performs hard decision or soft decision on the digital modulation signal equalized by the equalization unit 1068 based on mapping according to the modulation method, and outputs the decision result to the deinterleave unit 1074. .
  • the deinterleaving unit 1074 performs deinterleaving on the determination result, and outputs the result to the error correction unit 1076.
  • the error correction unit 1076 corrects a transmission error with respect to the deinterleaved signal, restores transmission information data, and outputs the obtained data RDT.
  • FIG. 11 is a block diagram illustrating a configuration example of the transmission path estimation unit 1080 in FIG.
  • the transmission path estimation unit 1080 includes a pilot division unit 1182, a transmission path information update unit 1184, and a transmission path information holding unit 1186.
  • Pilot division section 1182 divides each pilot signal included in the LTF or data symbol by its known value (value at the time of transmission as described above), and transmission path characteristics (transmission path information) corresponding to each pilot signal. Is output to the transmission path information update unit 1184. This division of the pilot signal by its known value is hereinafter referred to as pilot division.
  • Transmission path information update section 1184 reads out the transmission path characteristics of the same subcarrier as the pilot signal subcarrier used in pilot division section 1182 from transmission path information holding section 1186, and reads the read transmission path characteristics and pilot division.
  • a new transmission line characteristic is obtained from the transmission line characteristic output from unit 1182 and is output to transmission line information holding unit 1186 as the transmission line characteristic of the subcarrier.
  • the transmission path information holding unit 1186 stores the transmission path characteristics obtained by the transmission path information updating unit 1184 and continues to hold the transmission path characteristics of each subcarrier until updated with new transmission path characteristics.
  • the transmission path information holding unit 1186 outputs the held transmission path characteristic CR to the equalization unit 1068.
  • Pilot division section 1182 obtains transmission path characteristics H L1 — 0 to H L1 — 51 by performing pilot division on all subcarriers when the first symbol of LTF is input.
  • the transmission information update unit 1184 causes the transmission line information holding unit 1186 to update and hold transmission line characteristics in all subcarriers.
  • pilot division section 1182 obtains transmission path characteristics H L2 — 0 to H L2 — 51 by performing pilot division on all subcarriers.
  • Transmission information update section 1184 has transmission path characteristics H L2 — 0 to H L2 — 51 newly obtained from pilot signal of the second symbol of LTF by pilot division section 1182 and transmission path characteristics held in transmission path information holding section 1186. A process of averaging H L1 — 0 to H L1 — 51 between the same subcarriers is performed. This reduces errors due to noise.
  • the transmission information update unit 1184 causes the transmission line information holding unit 1186 to update and hold transmission line characteristics in all subcarriers.
  • Transmission path estimation section 1080 averages the transmission path characteristics obtained for each of N consecutive data symbols into which pilot signals are inserted. Specifically, when a data symbol of symbol number p is input, pilot division section 1182 uses the subcarriers of predetermined subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 determined by the symbol number as pilot signals. And perform pilot division.
  • the respective signal values are A p_1 (4 / 3,0), A p_2 (4 / 3,0), A p_3 (4 / 3,0), A p_4 (-4/3 , 0), the pilot division unit 1182 obtains the channel characteristics H p_1 , H p_2 , H p_3 , and H p_4 of each subcarrier by complex division of the pilot signal by the respective values.
  • the transmission information updating unit 1184 uses the transmission path characteristics H p_1 , H p_2 , H p_3 , and H p_4 obtained from these pilot signals to subcarrier numbers C p_1 , C p_2 , The transmission path characteristics of the subcarriers of C p — 3 and C p — 4 are updated.
  • pilot division section 1182 recognizes subcarriers with subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 that are the same as symbol number p as pilot signals, Pilot division is performed to obtain transmission path characteristics H p + 1_1 , H p + 1_2 , H p + 1_3 , and H p + 1_4 .
  • the transmission information update unit 1184 transmits the transmission path characteristics H p + 1_1 , H p + 1_2 , H p + 1_3 , H p + 1_4 obtained from these pilot signals, and the transmission path information holding section 1186.
  • the transmission information update unit 1184 updates the transmission path characteristics while reducing errors due to noise, and causes the transmission path information holding unit 1186 to hold the transmission path characteristics.
  • Transmission path information holding section 1186 outputs the determined transmission path characteristics to equalization section 1068 as transmission path characteristics CR of each subcarrier. In the case of FIG. 8, the transmission path characteristics of each subcarrier are updated at a rate of once every 26 symbols at maximum.
  • the equalization unit 1068 performs equalization using the average of the obtained transmission path characteristics.
  • the transmission path characteristics can be estimated with high accuracy even in a weak electric field environment with a lot of noise or in a fading environment, and equalization processing can be effectively performed, and stable reception is possible.
  • each of all the subcarriers can have the pilot signal in any symbol in the frame. In such a case, it is not necessary to interpolate the transmission path characteristics in the subcarrier direction, and the reception process is simplified. Note that pilots may exist only in specific subcarriers among all subcarriers through symbols of the entire frame. In this case, transmission path characteristics may be interpolated in the subcarrier direction.
  • the number of subcarriers, the number of pilot signals per symbol, the number of consecutive symbols of pilot signals in the same subcarrier, the regularity of pilot signal insertion positions, etc. are not limited to the example of FIG. Variations can exist. Below, some modified examples are demonstrated.
  • FIG. 12 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 2, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2. Further, the subcarrier of the pilot signal after 2 symbols is shifted to the right subcarrier by one.
  • the symbol interval at which no pilot signal exists is longer for a certain subcarrier as compared with the arrangement of FIG. 8, but the number of pilot signals per symbol is reduced, so an improvement in transmission rate is expected. And the amplitude of the pilot signal can be increased.
  • FIG. 13 is an explanatory diagram showing another arrangement example of pilot signals in the OFDM frame.
  • the number of pilots in one symbol is 4, and the number of symbols in which pilot signals are continuous on the same subcarrier is 4. Further, the subcarrier of the pilot signal after 4 symbols is shifted to the right subcarrier by one.
  • the symbol interval at which no pilot signal exists is longer for a certain subcarrier as compared with the arrangement of FIG. 8, but the number of consecutive pilot signals in the symbol direction is increased, and therefore noise with respect to transmission path characteristics is increased. The suppression effect is increased, and improvement in noise resistance can be expected.
  • FIG. 14 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 2, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2.
  • the left pilot signal is shifted to the right subcarrier by one, and the right pilot signal is shifted by one to the left subcarrier.
  • the symbol interval at which no pilot signal exists is longer for a certain subcarrier as compared with the arrangement of FIG. 8, but the number of pilot signals per symbol is reduced, and an improvement in transmission rate can be expected. .
  • FIG. 15 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 2, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2.
  • the left pilot signal is shifted to the left subcarrier by one, and the right pilot signal is shifted to the right subcarrier by one.
  • the symbol interval at which no pilot signal exists is longer for a certain subcarrier, but the number of pilot signals per symbol is reduced, and an improvement in transmission rate can be expected. .
  • FIG. 16 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 2, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2.
  • the pilot subcarriers after 2 symbols are shifted to the right subcarrier by three.
  • the subcarrier into which the pilot signal is inserted may be determined by modulo calculation for the symbol number.
  • the symbol interval at which no pilot signal exists is longer for a certain subcarrier as compared with the arrangement of FIG. 8, but the number of pilot signals per symbol is reduced, and an improvement in transmission rate can be expected.
  • the symbol number of the subcarrier in which the pilot signal exists and the symbol number in which the pilot signal exists in the subcarrier adjacent to the subcarrier are not continuous, and several symbols are separated from each other. For this reason, it is possible to avoid the loss of the pilot signal over several symbols due to fading.
  • FIG. 17 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 8, the number of symbols in which pilot signals are continuous on the same subcarrier is 2, and there are also conventional pilot signals as shown in FIG.
  • the pilot subcarriers after two symbols shift to the right subcarrier by one.
  • the amplitude of the pilot signal inserted into the same subcarrier over all symbols may be different from the amplitude of the pilot signal that changes the subcarrier every two symbols.
  • the former amplitude is 1 and the latter amplitude is 1 or more.
  • the latter amplitude may be changed according to the number of the latter pilot signals inserted per symbol.
  • pilot signals existing in the same specific subcarrier may be included over all data symbols, as in FIG.
  • the subcarrier modulation unit 316 may change the amplitude of the pilot signal according to at least one value of the number of pilot signals M and the number of pilots N consecutive to the same subcarrier. For example, the subcarrier modulation unit 316 may make the amplitude of the pilot signal inversely proportional to the value of the number of pilot signals M. Then, it is possible to prevent the power of the OFDM symbol from becoming too large.
  • FIG. 18 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of effective subcarriers S per symbol is 52
  • the number of data carriers is 48
  • the number of pilot signals M is 4
  • the number of pilot signals N consecutive in the same subcarrier is 2.
  • the present invention is not limited to this.
  • An OFDM transmission apparatus corresponding to the OFDM frame in FIG. 18 will be described.
  • This apparatus is configured in substantially the same manner as the OFDM transmission apparatus in FIG. 3 except for the processing in subcarrier modulation section 316. Processing of the subcarrier modulation unit 316 will be described.
  • the subcarrier modulation unit 316 generates an OFDM frame according to the flowchart of FIG.
  • the processing by the subcarrier modulation unit 316 is summarized as follows.
  • subcarrier modulation section 316 inserts pilot signals into subcarriers with subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 for the data symbol with symbol number p.
  • subcarrier modulation section 316 places only two of the pilot signals on the same subcarrier as the data symbol of symbol number p, and the remaining 2 Place them on different subcarriers.
  • subcarrier modulation section 316 inserts a pilot signal into the subcarrier on the right side in the case of symbol number p. That is, the position of the pilot signal of the data symbol of symbol number p + 1 is the subcarrier of subcarrier numbers C p_1 , C p_2 +1, C p_3 , C p_4 +1.
  • subcarrier modulation section 316 inserts a pilot signal into the same subcarrier as the two subcarriers newly inserted with a pilot signal at symbol number p + 1 in the data symbol with symbol number p + 2, and the remaining two pilot signals Is inserted in the right subcarrier. That position of the pilot signal of the symbol number p + 2 data symbol, the subcarriers of subcarrier numbers C p_1 + 1, C p_2 + 1, C p_3 + 1, C p_4 +1.
  • subcarrier modulation section 316 inserts a pilot signal into the data symbol. Focusing on the pilot signal of the data symbol of symbol number p, the pilot signals of subcarrier numbers C p_2 and C p_4 are inserted in the same subcarrier as the pilot signal of symbol number p ⁇ 1, and subcarrier numbers C p_1 , pilot signal C p_3 is inserted in the same sub-carrier pilot signal symbol number p + 1.
  • the position of the pilot signal makes a round of all subcarriers with 26 symbols.
  • the arrangement of pilot signals has the following characteristics. For any data symbol, each pilot signal is arranged over two symbols on the same subcarrier as the data symbol before or after that. The subcarrier into which the pilot signal is inserted is changed in a certain direction as the symbol number increases. When attention is paid to a certain subcarrier, pilot signals over two symbols are arranged for each predetermined number of symbols.
  • a part of the subcarrier into which the pilot signal is inserted in the data symbol is the same as the immediately preceding data symbol, and the rest is different from the immediately preceding data symbol. Since there are always subcarriers in which pilot signals are continuously inserted in two adjacent symbols, the phase rotation caused by the transmission path can be obtained in each symbol using the pilot signals of such subcarriers.
  • FIG. 19 is a block diagram showing a configuration of a modification of transmission path estimation section 1080 in FIG.
  • This receiving apparatus is configured in substantially the same manner as the OFDM receiving apparatus in FIG. 10 except for the processing in the transmission path estimation unit 1980. Processing of the transmission path estimation unit 1980 will be described.
  • phase noise estimation unit 1988 obtains the fluctuation of the transmission path characteristics between symbols from the transmission path characteristics of the subcarriers into which the pilot signals are continuously inserted in the symbol direction. At this time, the phase noise estimation unit 1988 reads and uses the transmission path characteristics stored in the transmission path information holding unit 1986. The obtained variation is averaged within the symbol, and the result is output as the estimated phase noise from the previous data symbol.
  • the transmission path information update unit 1984 reads out the transmission path characteristic of the same subcarrier as the pilot signal subcarrier used in the pilot division section 1182 from the transmission path information holding section 1186, and is obtained by the phase noise estimation section 1988. The correction is made with the phase noise, and the corrected transmission line characteristic is output to the transmission line information holding unit 1986 as the transmission line characteristic of the subcarrier.
  • the transmission path information holding unit 1986 stores the transmission path characteristics obtained by the transmission path information update unit 1184 and continues to hold the transmission path characteristics of each subcarrier until updated with new transmission path characteristics.
  • the transmission path information holding unit 1986 outputs the held transmission path characteristic CR to the equalization unit 1068.
  • Transmission path estimation section 1980 calculates the phase rotation between data symbols from the transmission path characteristics obtained for each of N consecutive data symbols into which pilot signals are inserted.
  • the processing in the LTF is the same as that of the transmission path estimation unit 1080 in FIG.
  • pilot division section 1182 When a data symbol of symbol number p is input, pilot division section 1182 recognizes subcarriers of predetermined subcarrier numbers C p_1 , C p_2 , C p_3 , C p_4 determined by the symbol number as pilot signals, and pilots Division is performed to determine transmission path characteristics H p_1 , H p_2 , H p_3 , and H p_4 of each subcarrier.
  • the phase noise estimation unit 1988 transmits the channel characteristics H p-1_2 , H from the transmission channel information holding unit 1986.
  • the phase noise estimation unit 1988 averages the fluctuation amounts D p_2 and D p_4 to obtain the fluctuation amount from the data symbol with the symbol number p-1 in the data symbol with the symbol number p, and further sets the phase as the phase rotation ⁇ p. calculate.
  • the pilot signal is inserted in the same subcarrier as any of the data symbols before and after each data symbol. For this reason, the phase rotation ⁇ p is obtained for all data symbols.
  • the transmission path characteristics obtained from the LTF can be used as the transmission path characteristics of the previous symbol.
  • the transmission path information update unit 1984 relates to the transmission path characteristics H p_1 , H p_2 , H p_3 , H p_4 obtained by the pilot division unit 1182, and subcarrier numbers C p_1 , C held in the transmission path information holding unit 1986.
  • p_3 the channel characteristic of the subcarriers, the transmission path characteristic H p_1 and as updated in H p_3, transmission path characteristics H p_2 and the transmission path characteristic H p read from the transmission path information holding unit 1986 for H P_4 -1_2 performs averaging after the phase correction with respect to H p-1_4.
  • the transmission path information updating unit 1984 updates the transmission path characteristics by performing only phase correction on H p-1_X read by the transmission path information holding unit 1986.
  • the transmission path information holding unit 1986 outputs the obtained transmission path characteristics to the equalization unit 1068 as the transmission path characteristics CR of each subcarrier.
  • the equalization unit 1068 performs equalization using the obtained phase rotation.
  • the phase noise estimation unit 1988 obtains a phase rotation ⁇ p + 1 from the subcarrier pilot signals of the subcarrier numbers C p + 1_1 and C p + 1_3 .
  • the transmission path information updating unit 1984 holds the transmission path characteristics H p + 1_1 , H p + 1_2 , H p + 1_3 , and H p + 1_4 obtained by the pilot division unit 1182 in the transmission path information holding unit 1986.
  • the channel characteristics H p + 1_2 and H p + 1_4 of the subcarriers with the subcarrier numbers C p + 1_2 and C p + 1_4 are updated as they are with the obtained channel characteristics H p + 1_2 and H p + 1_4.
  • the transmission path information holding unit 1986 outputs the held transmission path characteristics to the equalization unit 1068 as the transmission path characteristics of each subcarrier.
  • the transmission path characteristics of each subcarrier are updated at a rate of once every 26 symbols, and the phase is corrected for each symbol.
  • the transmission path characteristics can be reduced.
  • the transmission path characteristics can be estimated with high accuracy even in a weak electric field environment with a lot of noise or in a fading environment, and equalization processing can be effectively performed, and stable reception is possible.
  • the number of subcarriers, the number of pilot signals per symbol, the number of consecutive symbols of pilot signals in the same subcarrier, the regularity of pilot signal insertion positions, etc. are not limited to the example of FIG. Variations can exist. Below, some modified examples are demonstrated.
  • FIG. 20 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 8, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2.
  • the subcarrier of the pilot signal after one symbol is shifted to the right subcarrier by one.
  • the number of pilot signals per symbol increases and the transmission rate decreases compared to the arrangement of FIG. 18, but the period of symbols in which no pilot signal exists is shortened for a certain subcarrier, resulting in transmission path characteristics. It can be expected to improve resistance to time fluctuations.
  • FIG. 21 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 4, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2.
  • the subcarrier of the pilot signal after one symbol is shifted to the right subcarrier by one.
  • FIG. 22 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 2, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2.
  • the subcarrier of the pilot signal after one symbol is shifted to the right subcarrier by one on the left side.
  • the symbol interval at which no pilot signal exists is longer for a certain subcarrier, but the number of pilot signals per symbol is reduced, and an improvement in transmission rate can be expected.
  • FIG. 23 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame.
  • the number of pilots in one symbol is 4, and the number of symbols in which pilot signals are continuous on the same subcarrier is 2.
  • the subcarrier of the pilot signal after one symbol is shifted by 3 to the right subcarrier.
  • the present invention is not limited to this, and various rules may be combined.
  • a symbol group in which a pilot signal is inserted in accordance with a predetermined rule as described above may be combined with a symbol group in which such a pilot signal is not inserted.
  • pilot signals existing in the same specific subcarrier over all data symbols are not regarded as pilot signals to be inserted.
  • FIG. 24 is an explanatory diagram showing an arrangement example of pilot signals in an OFDM frame when data is not repeated.
  • the number of subcarriers S per symbol is 52
  • the number of data carriers is 48
  • the number of pilot signals M is 4, and the pilot signals are not continuous to the same subcarrier, but this is not restrictive. .
  • Subcarrier modulation section 316 inserts a pilot signal into subcarriers with subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 for the data symbol with symbol number p.
  • subcarrier modulation section 316 inserts the pilot signal into a subcarrier different from the pilot signal of the data symbol with symbol number p.
  • subcarrier modulation section 316 inserts the pilot signal in the subcarrier on the right side of each subcarrier into which the pilot signal is inserted in the case of symbol number p.
  • That position of the pilot signal of the data symbol of the symbol number p + 1 becomes subcarrier number C p_1 + 1, C p_2 + 1, C p_3 + 1, C p_4 +1.
  • subcarrier modulation section 316 inserts a pilot signal into the data symbol.
  • FIG. 25 is an explanatory diagram illustrating an example of a symbol with a symbol number p and a symbol with a symbol number p + 1 when data is repeatedly transmitted.
  • Subcarrier modulation section 316 repeatedly generates the same data symbol N times, in which a pilot signal is inserted in the subcarrier and transmits information data. Transmission of data twice is described in Non-Patent Document 2 and the like. Here, as an example, a case where the same data is transmitted twice will be described.
  • the subcarrier modulation unit 316 generates data symbols of symbol numbers p and p + 1 as shown in FIG.
  • the information data to be transmitted included in the data symbol of symbol number p + 1 is the same as the information data to be transmitted included in the data symbol of symbol number p, and should be transmitted included in the data symbol of symbol number p.
  • Information data is repeatedly transmitted with symbol number p + 1.
  • subcarrier modulation section 316 also inserts pilot signals into the same subcarrier for the symbol number p and the symbol number p + 1.
  • a data unit to be transmitted is displayed as a BPSK or QAM modulated signal X_n (n is an integer of 0 or more).
  • FIG. 26 is an explanatory diagram showing another arrangement example of pilot signals in an OFDM frame. Since the same symbol is repeated as shown in FIG. 25, an OFDM frame as shown in FIG. 26 is transmitted. As for the arrangement of the pilot signals, FIG. 26 and FIG. 8 are the same.
  • FIG. 27 is an explanatory diagram showing another example of the symbol with the symbol number p and the symbol with the symbol number p + 1 when data is repeatedly transmitted.
  • subcarrier modulation section 316 may invert the order of data unit X_n to be transmitted included in the data symbol with symbol number p in the data symbol with symbol number p + 1.
  • the subcarrier into which the pilot signal is inserted is the same for the data symbol of symbol number p and the data symbol of symbol number p + 1.
  • the OFDM transmitter 300 thus generates an OFDM signal and transmits it.
  • the pilot position makes a round of all subcarriers with 13 symbols
  • the pilot position makes a round of all subcarriers with 26 symbols.
  • the pilot signal is arranged over two symbols on the same subcarrier only during repeated transmission. Further, the pilot signal is arranged so as to circulate through the subcarrier. When attention is paid to a certain subcarrier, the pilot signal over two symbols is arranged at a predetermined symbol interval. Thus, the arrangement of pilot signals is determined depending on whether or not information data to be transmitted is repeatedly transmitted.
  • the subcarrier modulation unit 316 may not repeatedly generate the same data symbol.
  • the case where the same data symbol is repeatedly generated and the case where it is not repeatedly generated may be in the same frame.
  • the transmission path estimation unit 1080 of FIG. 11 updates the transmission path characteristics of the transmission path information holding unit 1186 as it is with the transmission path characteristics input from the pilot division unit 1182.
  • the transmission path information update unit 1184 reads the transmission path characteristics of the same subcarrier as the subcarrier of the pilot signal used in the pilot division section 1182 from the transmission path information holding section 1186 and reads the read transmission path.
  • a new transmission line characteristic is obtained from the characteristic and the transmission line characteristic output from the pilot division unit 1182, and is output to the transmission line information holding unit 1186 as the transmission line characteristic of the subcarrier.
  • the transmission path information holding unit 1186 stores the transmission path characteristics obtained by the transmission path information update unit 1184 and continues to hold the transmission path characteristics of each subcarrier until updated with new transmission path characteristics.
  • the transmission path information holding unit 1186 outputs the held transmission path characteristic CR to the equalization unit 1068.
  • Other components of the OFDM receiving apparatus 1000 are the same as those described with reference to FIG.
  • the transmission path estimation process in the transmission path estimation unit having this configuration will be described.
  • the processing in the LTF is the same as that described with reference to FIG.
  • pilot division section 1182 When a data symbol of symbol number p is input, pilot division section 1182 recognizes subcarriers of predetermined subcarrier numbers C p_1 , C p_2 , C p_3 , C p_4 determined by the symbol number as pilot signals, and pilots Division is performed to determine transmission path characteristics H p_1 , H p_2 , H p_3 , and H p_4 of each subcarrier.
  • the transmission information updating unit 1184 uses the transmission path characteristics H p_1 , H p_2 , H p_3 , and H p_4 obtained from these pilot signals, so that the subcarrier numbers C p_1 , C p_2 , C held by the transmission path information holding unit 3103 are obtained.
  • the transmission path characteristics of the subcarriers p_3 and Cp_4 are updated.
  • transmission information updating section 1184 transmits transmission line characteristics H p + 1_1 , Subcarriers of subcarrier numbers C p + 1_1 , C p + 1_2 , C p + 1_3 , C p + 1_4 held by the transmission path information holding unit 1186 by H p + 1_2 , H p + 1_3 , H p + 1_4 Update carrier channel characteristics.
  • Transmission path information holding section 1186 outputs the held transmission path characteristics of each subcarrier to equalization section 1068.
  • the transmission information updating unit 1184 holds the transmission path characteristics H p + 1_1 , H p + 1_2 , H p + 1_3 , H p + 1_4 obtained from the pilot signal with the symbol number p + 1, and the transmission path information holding unit 1186.
  • a process of averaging the channel characteristics H p_1 , H p_2 , H p_3 , and H p_4 of the subcarriers of the subcarrier numbers C p_1 , C p_2 , C p_3 , and C p_4 between the same subcarriers is performed.
  • the transmission information update unit 1184 updates the transmission path characteristics while reducing errors due to noise, and causes the transmission path information holding unit 1186 to hold the transmission path characteristics.
  • Transmission path information holding section 1186 outputs the determined transmission path characteristics to equalization section 1068 as transmission path characteristics CR of each subcarrier.
  • each subcarrier is updated at a rate of once every 13 symbols at the time of normal transmission and once every 26 symbols at the time of repeated transmission.
  • the noise of the transmission path characteristic can be reduced based on the pilot signal arranged on the same subcarrier over two symbols at the time of repeated transmission.
  • the pilot signal is arranged with a maximum of 13 symbols for normal transmission and a maximum of 26 symbols for repetitive transmission, so that the transmission line characteristics can be updated in that period, and the time fluctuation of the transmission line characteristics can be tracked. It is also possible to improve the resistance to time fluctuations during normal transmission compared to repeated transmission.
  • the number of pilot signals per symbol is reduced by moving subcarriers in which pilots exist according to symbol numbers. For this reason, the amplitude of the pilot signal can be increased without significantly increasing the power of the symbol, and the noise of the transmission path characteristic can be reduced.
  • the transmission path characteristics can be estimated with high accuracy even in a weak electric field environment with a lot of noise or in a fading environment, and equalization processing can be effectively performed, and stable reception is possible.
  • the pilot arrangement when repeatedly transmitting may be the arrangement shown in FIG. 20, and the pilot arrangement when not repeatedly transmitting may be the arrangement shown in FIG.
  • the pilot arrangement becomes a period of 13 symbols, and the resistance to time fluctuations of the transmission path characteristics can be made equal.
  • various examples FIG. 8, FIG. 12 to FIG. 18, etc. in which the pilot signal is continuous over a plurality of symbols on the same subcarrier as described above can be adopted.
  • pilots may exist only for specific subcarriers among all subcarriers through symbols of the entire frame, and in this case, transmission path characteristics may be interpolated in the subcarrier direction.
  • the transmission path characteristics are obtained and held.
  • the present invention is not limited to this, and both pilots are held when the input pilot signal is held and the next pilot signal is inputted.
  • An average process may be performed by obtaining a transmission line characteristic corresponding to the signal.
  • the amplitude of the pilot signal is boosted by 4/3 times, the present invention is not limited to this, and the boost magnification may be 3/2 times.
  • the noise suppression effect of the transmission path characteristics changes according to the amplitude of the pilot signal.
  • the amplitude of the pilot signal may be changed according to the number of pilot signals included in one symbol. It is not always necessary to boost the amplitude of the pilot signal.
  • the amplitude of the pilot signal may be changed in accordance with the number of symbols in which the pilot signal continues in the same subcarrier.
  • the OFDM symbol according to the above embodiment may or may not have a conventional pilot signal in a predetermined subcarrier in all data symbols as shown in FIG.
  • center subcarrier is null, and neither data nor pilot signals are arranged.
  • present invention is not limited to this, and data and pilot signals may be inserted into the center subcarrier.
  • the present invention is not limited to this, and a device having both functions of the described OFDM transmitter and OFDM receiver may be configured. In this case, at least a part of each component related to the transmission process and each component related to the reception process may be shared.
  • the OFDM transmitter and the OFDM receiver may perform at least a part of the described processing.
  • each component of the above OFDM transmitter and OFDM receiver may be realized by an LSI (large-scale integration) that is an integrated circuit. At this time, each component may be individually made into one chip, or may be made into one chip so as to include a part or all of them.
  • LSI large-scale integration
  • IC integrated circuit
  • system LSI super LSI
  • ultra LSI ultra LSI depending on the degree of integration.
  • the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible.
  • An FPGA Field Programmable Gate Array
  • a reconfigurable processor capable of reconfiguring connection and setting of circuit cells inside the LSI may be used.
  • integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Possible applications include biotechnology.
  • Some or all of the functional blocks of the above-described OFDM transmitter and OFDM receiver can be realized by software.
  • a functional block can be realized by a processor such as a CPU (Central Processing Unit) and a program executed on the processor.
  • each functional block described in the present specification may be realized by hardware, may be realized by software, or may be realized by any combination of hardware and software.
  • the program may be recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, an optical recording medium, or a magneto-optical recording medium.
  • the recording medium can be a non-transient medium.

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Abstract

La présente invention a pour objectif de supprimer l'erreur d'une caractéristique de voie de transmission estimée, même si la longueur de la trame est relativement longue. Afin d'atteindre l'objectif visé, la présente invention se rapporte à un appareil de transmission OFDM. L'appareil de transmission OFDM selon l'invention comprend : un module de modulation de sous-porteuses, qui alloue à la fois des données d'information devant être transmises et des ondes pilotes, à une pluralité de sous-porteuses qui est incluse dans un symbole OFDM, de sorte à générer ainsi le symbole OFDM ; et un module de conversion, qui convertit le symbole OFDM généré en un signal dans le domaine temporel et qui délivre en sortie le signal dans le domaine temporel. Le module de modulation de sous-porteuses insère, dans le symbole de données, l'onde pilote dans l'une respective de M sous-porteuses, qui peut changer en fonction de la position du symbole de données dans la trame. Comme décrit dans ce qui précède, les ondes pilotes sont insérées dans les sous-porteuses respectives pour chacun de N symboles de données consécutifs comprenant ledit symbole de données.
PCT/JP2013/004820 2012-08-10 2013-08-09 Appareil de transmission ofdm, procédé de transmission ofdm, appareil de réception ofdm, et procédé de réception ofdm Ceased WO2014024502A1 (fr)

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Publication number Priority date Publication date Assignee Title
JP2019504565A (ja) * 2016-02-09 2019-02-14 テレフオンアクチーボラゲット エルエム エリクソン（パブル） 復調基準信号を用いた位相ノイズトラッキング基準信号シーケンス生成のためのシステム及び方法
JP2019537855A (ja) * 2016-09-30 2019-12-26 チャイナ アカデミー オブ テレコミュニケーションズ テクノロジー 位相雑音補償基準信号の伝送方法、送信機器および受信機器
CN116155657A (zh) * 2022-11-14 2023-05-23 上海金卓科技有限公司 一种ofdm的信道估计方法与装置、信号接收方法与装置

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