JP2018160757A - OFDM transmitter and OFDM receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve transmission efficiency and reduce required C / N. An OFDM transmitter 10 selects a pilot carrier arrangement pattern from predetermined arrangement patterns according to a transmission mode of an OFDM signal, and boosts the power of the pilot carrier according to the selected arrangement pattern. The control circuit 17 for switching and the pilot carrier boosted according to the switched boost value are arranged according to the selected arrangement pattern, and are modulated by the TMCC signal indicating the selected arrangement pattern and the boost value. The control circuit 17 includes a frame component 13 that generates a transmission frame including carriers, and pilot carriers are arranged dispersed in the symbol direction (time direction) and the carrier direction (frequency direction) according to the transmission mode. Select an arrangement pattern or an arrangement pattern in which pilot carriers are arranged continuously in the symbol direction (time direction). [Selection diagram] Fig. 1

Description

  The present invention relates to an OFDM transmitter and an OFDM receiver.

  An OFDM (Orthogonal Frequency Division Multiplexing) transmission system is adopted as a transmission system for terrestrial digital broadcasting and television broadcast program material transmission.

  The OFDM transmission method is a transmission method in which data is modulated using a number of carrier waves (subcarriers) orthogonal to each other in the frequency direction. A transmission symbol of the OFDM transmission scheme is configured by adding a guard interval (GI: Guard Interval) to an effective symbol in order to reduce the influence of multipath. In addition, a pilot carrier is inserted into the subcarrier in order to estimate the channel response in the receiving apparatus and equalize the received signal.

  By the way, there is a fixed relationship between the change in the propagation path response due to the delay wave and the delay time of the delay wave. When the delay time is τ, the period of the change in the propagation path response is 1 / τ. The maximum delay time of the delayed wave to be taken into consideration is the GI length Tg, and the reciprocal of the effective symbol length Te is the subcarrier interval, so the ratio of the effective symbol length to the GI length (GI ratio) Tg / Te reciprocal Te / A pilot carrier may be inserted at intervals of Tg. Although the pilot carrier may be inserted more densely than the Te / Tg interval to improve the estimation accuracy of the propagation path response, it is not preferable from the viewpoint of transmission efficiency.

  Non-Patent Documents 1 and 2 define 1/4, 1/8, 1/16, and 1/32 as GI ratios, but the arrangement of pilot carriers is 12 in the carrier direction (frequency direction). In the symbol direction (time direction), only one rate is defined.

  Further, the pilot carrier is amplified (boosted) to a power larger than the average power of the data carrier and transmitted. In Non-Patent Documents 1 to 3, a value of 16/9 times is used as a boost value for boosting the pilot carrier with respect to the average power of the data carrier.

  On the other hand, it is known that the boost value for reducing the required C / N differs depending on the value of the product Nft of the insertion interval in the carrier direction (frequency direction) of the pilot carrier and the insertion interval in the symbol direction (time direction). (See Non-Patent Document 4).

ETSI 300 744 “Digital video broadcasting (DVB); Frame structure, channel coding and modulation for digital terrestrial television (DVB-T)”, Mar. 1997. "Transmission system for digital terrestrial television", ARIB STD-B31, Japan Radio Industry Association "1.2GHz / 2.3GHz band portable OFDM digital wireless transmission system for transmission of TV broadcast program material", ARIB STD-B57, The Japan Radio Industry Association Transmission characteristics by OFDM symbol length and scattered pilot in terrestrial digital broadcasting, Journal of the Institute of Image Information and Television Engineers, Vol.52, No.11, pp. 1656-1666 (1998) Kimura et al., "Study of high-speed mobile reception by diversity combining using channel-by-symbol estimation", ITE Annual Convention 2005 6-2

  As described above, conventionally, the pilot carrier insertion interval is constant regardless of the GI ratio. In addition, a constant boost value is used regardless of the pilot carrier insertion interval. Therefore, improvement of transmission efficiency and reduction of required C / N have not been sufficiently achieved.

  An object of the present invention is to provide an OFDM transmitter and an OFDM receiver that can solve the above-described problems, improve transmission efficiency, and reduce required C / N.

  In order to solve the above problems, an OFDM transmission apparatus according to the present invention is an OFDM transmission apparatus that transmits an OFDM signal, and an arrangement of pilot carriers that are modulated with a pilot signal according to a transmission mode for transmitting the OFDM signal A pattern is selected from a predetermined arrangement pattern, and the booster value of the pilot carrier power with respect to the average power of the data carrier is switched to a predetermined value according to the selected arrangement pattern, and is switched by the control unit. A pilot carrier boosted to a predetermined power in accordance with the boost value is arranged in a transmission frame in accordance with the selected arrangement pattern, and the TMCC signal indicating the selected arrangement pattern and the boost value. Generating the transmission frame including the TMCC carrier modulated with An arrangement pattern in which pilot carriers are distributed in a symbol direction (time direction) and a carrier direction (frequency direction) according to the transmission mode, or a symbol direction. A pattern in which pilot carriers are continuously arranged in (time direction) is selected.

  Also, in the OFDM transmission apparatus according to the present invention, the control unit may transmit the pilot carrier in a carrier direction (frequency direction) in the first transmission mode in which the number of FFT points is 2048 and the GI ratio is 1/8. It is preferable to insert an arrangement once into eight carriers and select an arrangement pattern continuous in the symbol direction (time direction).

  Also, in the OFDM transmission apparatus according to the present invention, the control unit has an FFT point number of 2048, a GI ratio of 1/8, and the pilot carrier in the second transmission mode in which the pilot carrier is thinned out. Is inserted once every t (t is an integer of 2 or more) times in the symbol direction (time direction), and k (8 ≦ k ≦ 8 × t, and k is an integer) carrier in the carrier direction (frequency direction). It is preferable to select an arrangement pattern to be inserted once.

  In the OFDM transmission apparatus according to the present invention, the control unit may transmit the pilot carrier in a carrier direction (frequency direction) in a third transmission mode in which the number of FFT points is 8192 and the GI ratio is 1/32. It is preferable to select the arrangement pattern that is inserted once in 32 carriers and continuous in the symbol direction (time direction).

  Also, in the OFDM transmission apparatus according to the present invention, the control unit has an FFT point number of 8192, a GI ratio of 1/32, and in the fourth transmission mode in which the pilot carrier is thinned out, the pilot carrier Is inserted once every t (t is an integer of 2 or more) times in the symbol direction (time direction), and j (32 ≦ j ≦ 32 × t, where j is an integer) carrier It is preferable to select an arrangement pattern to be inserted once.

  The OFDM transmission apparatus according to the present invention transmits the OFDM signal by a SISO transmission method in which a signal is transmitted by a single antenna.

  Also, the OFDM transmission apparatus according to the present invention transmits the OFDM signal by a MIMO transmission scheme in which signals are transmitted by a plurality of antennas, and the frame configuration unit is provided corresponding to each of the plurality of antennas.

  In order to solve the above-described problem, an OFDM receiver according to the present invention is an OFDM receiver that receives an OFDM signal transmitted from any of the OFDM transmitters described above, and includes a TMCC carrier included in the transmission frame. A TMCC separation unit that decodes a TMCC signal obtained by demodulating the TMCC signal to obtain the arrangement pattern and the boost value, and a pilot carrier included in the transmission frame based on the arrangement pattern obtained by the TMCC separation unit A pilot carrier separation unit for extracting a channel response, a pilot carrier extracted by the pilot carrier separation unit, and a channel response estimation unit for estimating a channel response based on the boost value acquired by the TMCC separation unit, Prepare.

  According to the OFDM transmitter and the OFDM receiver according to the present invention, it is possible to improve the transmission efficiency and reduce the required C / N.

It is a figure which shows the structural example of the OFDM transmitter which concerns on the 1st Embodiment of this invention. It is a figure which shows the structural example of the frame structure circuit shown in FIG. It is a figure which shows the structural example of the OFDM receiver which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the transmission frame in case the transmission mode is "movement" in the 1st Embodiment of this invention. It is a figure which shows an example of the transmission frame in case the transmission mode is "fixed" in the 1st Embodiment of this invention. It is a figure which shows the simulation result of the BER characteristic with respect to a boost value at the time of using the OFDM transmitter shown in FIG. 1 and the OFDM receiver shown in FIG. 3 under Gaussian noise. It is a figure which shows the structural example of the OFDM transmitter which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structural example of the OFDM receiver which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the transmission frame in case the transmission mode in the 2nd Embodiment of this invention is "movement." It is a figure which shows an example of the transmission frame in case the transmission mode is "fixed" in the 2nd Embodiment of this invention. It is a figure which shows the simulation result of the BER characteristic with respect to a boost value at the time of using the OFDM transmitter shown in FIG. 7, and the OFDM receiver shown in FIG. 8 under Gaussian noise.

  Embodiments of the present invention will be described below.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of an OFDM transmission apparatus 10 according to the first embodiment of the present invention. The OFDM transmission apparatus 10 according to the present embodiment is a transmission apparatus that transmits an OFDM signal by a SISO (Single Input Single Output) transmission method in which a transmission side and a reception side each transmit and receive a signal with a single (single) antenna. is there.

  The OFDM transmitter 10 selects an arrangement pattern of pilot carriers to be modulated by the pilot signal according to either “mobile” or “fixed” transmission mode for transmitting the OFDM signal, and according to the selected arrangement pattern. The boost value of the pilot carrier with respect to the average power of the data carrier is switched. Then, the OFDM transmitter 10 arranges the pilot carrier boosted according to the boost value according to the selected arrangement pattern, and modulates the TMCC carrier modulated with the TMCC signal indicating the selected arrangement pattern and boost value. A transmission frame including is generated.

  1 includes an encoding circuit 11, a mapping circuit 12, a frame configuration circuit (frame configuration unit) 13, an IFFT circuit 14, a GI addition circuit 15, a frequency conversion circuit 16, and a control. A circuit (control unit) 17.

  The encoding circuit 11 receives transmission target data (TS: Transport Stream), performs processing such as energy spreading, error correction encoding, and interleaving on the input data, and outputs the processed data to the mapping circuit 12. As the apologize correction coding, processing by FEC (Forward Error Correction) such as RS (Reed-Solomon) code, convolutional code, turbo code, LDPC (Low Density Parity Check) code is performed.

  The mapping circuit 12 maps the data output from the encoding circuit 11 by a predetermined modulation method, and outputs the mapped data to the frame configuration circuit 13. As a modulation method, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM, 256QAM, 1024AM, and so on are used.

  The frame configuration circuit 13 generates a pilot carrier, a TMCC (Transmission and Multiplexing Configuration Control) carrier, etc., and arranges the transmission frame (frequency) together with the data output from the mapping circuit 12 according to a preset arrangement pattern. Region OFDM signal) and the generated transmission frame is output to the IFFT circuit 14. Details of the configuration of the frame configuration circuit 13 will be described later.

  The IFFT circuit 14 performs an inverse fast Fourier transform (IFFT) on the frequency domain OFDM signal output from the frame configuration circuit 13, generates a time domain OFDM signal, and outputs the time domain OFDM signal to the GI addition circuit 15.

  The GI addition circuit 15 adds a predetermined length of GI to the time-domain OFDM signal output from the IFFT circuit 14 and outputs the OFDM signal with the GI added to the frequency conversion circuit 16.

  The frequency conversion circuit 16 converts the OFDM signal (baseband signal) added with the GI output from the GI addition circuit 15 into an RF (Radio Frequency) signal having a predetermined frequency. This RF signal is transmitted via the antenna.

  The control circuit 17 includes an FEC method and a coding rate in the encoding circuit 11, a modulation method in the mapping circuit 12, a frame pattern used in the frame configuration circuit 13, an FFT sampling number of inverse fast Fourier transform in the IFFT circuit 14, and a GI. A control signal used to select a GI length of the GI added by the addition circuit 15 and a channel used in the frequency conversion circuit 16 is output to each circuit.

  Next, the configuration of the frame configuration circuit 13 will be described.

  FIG. 2 is a diagram illustrating a configuration example of the frame configuration circuit 13.

  The frame configuration circuit 13 shown in FIG. 2 includes a TMCC generation unit 131, a pilot carrier generation unit 132, a boost value multiplication unit 133, a frame configuration pattern memory 134, a switch 135, and a switch control unit 136.

  The TMCC generation unit 131 encodes control information such as the number of FFT samplings, pilot scheme, boost value, frame pattern information, modulation scheme, and FEC type output from the control circuit 17 to generate a TMCC signal. Then, for example, in the case of the BPSK modulation scheme, the TMCC generation unit 131 generates a TMCC carrier so that the generated TMCC signal is modulated to 1 or −1 on the Q axis, and outputs the TMCC carrier to the switch 135.

  The pilot carrier generation unit 132 generates a known pilot signal on the transmission side and the reception side. Then, for example, in the case of the BPSK modulation method, the pilot carrier generation unit 132 converts the pilot carrier (data value is 1 or −1) so that the generated pilot signal is modulated to 1 or −1 on the I axis. Generated and output to the boost value multiplier 133.

  The boost value multiplier 133 is a ratio of power to the average power of the data carrier output from the control circuit 17 and actually transmitting data such as TS to the pilot carrier output from the pilot carrier generator 132 (boost value). ) (Boost (amplify) the pilot carrier) and output to the switch 135.

  The frame configuration pattern memory 134 stores an arrangement pattern in which position information of data carriers, pilot carriers, TMCC and AC (Auxiliary Channel) carriers arranged in a transmission frame is defined for each transmission mode set in advance. Has been. The frame configuration pattern memory 134 outputs a frame pattern signal indicating an arrangement pattern corresponding to the transmission mode output from the control circuit 17 to the switch control unit 136.

  The switch 135 is output from the data carrier modulated by the transmission target data, the TMCC carrier output from the TMCC generation unit 131, the AC carrier modulated by the AC signal, and the boost value multiplication unit 133 according to the control of the switch control unit 136. A transmission frame in which the pilot carrier thus inserted is inserted at a predetermined carrier arrangement position is formed and output to the IFFT circuit 14.

  The switch control unit 136 controls the switch 135 according to the frame pattern signal output from the frame configuration pattern memory 134, and switches the carrier to be inserted at a predetermined carrier arrangement position of the transmission frame.

  Next, the configuration of the OFDM receiver 20 according to the present embodiment will be described with reference to FIG. The OFDM receiver 20 according to the present embodiment is a receiver that receives an OFDM signal transmitted from the OFDM transmitter 10 shown in FIG. 1 using a single antenna by the SISO transmission method.

  The OFDM receiver 20 shown in FIG. 3 includes a frequency conversion circuit 21, a GI removal circuit 22, an FFT circuit 23, a TMCC separation circuit 24 (TMCC separation unit), and a pilot carrier separation circuit 25 (pilot carrier separation unit). , A propagation path response estimation circuit 26 (a propagation path response estimation unit), a decoding circuit 27, a demapping circuit 28, and an error correction decoding circuit 29 are provided.

  When the antenna of the OFDM receiver 20 receives the OFDM signal (RF signal) transmitted by the OFDM transmitter 10 shown in FIG. 1, the frequency converter 21 converts the OFDM signal into a baseband signal, and a GI removal circuit. 22 to output.

  The GI removal circuit 22 removes the GI in the OFDM signal output from the frequency conversion circuit 21 and outputs it to the FFT circuit 23.

  The FFT circuit 23 performs a fast Fourier transform (FFT) on the OFDM signal output from the GI removal circuit 22 to generate a frequency domain OFDM signal, and a TMCC separation circuit 24, a pilot carrier separation circuit 25, and a decoding circuit. 27.

  The TMCC separation circuit 24 separates and demodulates a TMCC carrier from the frequency domain OFDM signal output from the FFT circuit 23 to obtain a TMCC signal, decodes control information from the obtained TMCC signal, and a pilot carrier separation circuit 25. To the propagation path response estimation circuit 26, the decoding circuit 27, the demapping circuit 28 and the error correction decoding circuit 29.

  The pilot carrier separation circuit 25 uses the control information (frame pattern information) output from the TMCC separation circuit 24 to separate (extract) the pilot carrier from the frequency-domain OFDM signal output from the FFT circuit 23, and to receive pilot signals. It outputs to the propagation path response estimation circuit 26 as a carrier.

  The propagation path response estimation circuit 26 estimates the propagation path response using the received pilot carrier output from the pilot carrier separation circuit 25 and the control information (boost value) output from the TMCC separation circuit 24, and the decoding circuit 27. Output to.

  The boost value may be shared by the OFDM transmitter 10 and the OFDM receiver 20 and associated with frame pattern information or the like. In this case, it is not necessary to include a boost value in the TMCC signal, and information superimposed on the TMCC signal can be reduced. Further, the boost value to be used may be limited, and the boost value may be specified by comparing the average power of the data carrier and the average power of the pilot carrier.

  The decoding circuit 27 decodes the carrier in the OFDM signal output from the FFT circuit 23 using the control information output from the TMCC separation circuit 24 and the propagation path response output from the propagation path response estimation circuit 26. The decoded data is output to the demapping circuit 28.

  The demapping circuit 28 demaps the data output from the decoding circuit 27 based on the control information (modulation method) output from the TMCC separation circuit 24 and outputs the data to the error correction decoding circuit 29.

  The error correction decoding circuit 29 uses the control information output from the TMCC separation circuit 24 to perform deinterleaving, error correction code decoding, energy corresponding to the transmission side for the data output from the demapping circuit 28. Processing such as despreading is performed, and the original data (TS) is output.

  An example of the transmission mode in this embodiment is shown in Table 1. Table 1 shows a case where the operation status is “move” and a case where the operation status is “fixed”. The case where the operation status is “fixed” is a case where it is assumed that radio stations (OFDM transmitter 10 and OFDM receiver 20) are fixedly operated. In this case, hereinafter, the transmission mode is “fixed”. ". The case where the operation status is “move” is a case where it is assumed that at least one of the OFDM transmitter 10 and the OFDM receiver 20 moves and operates. In this case, hereinafter, the transmission mode is “ Called “move”.

  Below, each item of Table 1 is demonstrated.

  The number of FFT points and the FFT sampling frequency are parameters used for IFFT in the IFFT circuit 14 shown in FIG. 1 and FFT in the FFT circuit 23 shown in FIG. If the number of FFT points is increased while the FFT sampling frequency is constant, the effective symbol length of the OFDM signal is increased. If the GI length is fixed, the ratio of the GI to the entire transmission symbol is decreased, and the transmission capacity is increased. On the other hand, in a mobile reception environment where the time variation of the channel response is large, it is advantageous that the symbol length is short due to the influence of channel fluctuation within one symbol, and a small number of FFT points is desirable.

  Regarding the pilot scheme, the CP (Continuous Pilot) scheme is a scheme in which pilot carriers are continuously arranged in a symbol direction (time direction) for a specific carrier. Since the propagation path response can be estimated with the pilot carrier in one symbol to be equalized, it is advantageous for mobile reception in which the time variation of the propagation path response is large. The SP (Scattered Pilot) scheme is a scheme in which pilot carriers are distributed over a specific carrier and symbol (pilot carriers are distributed in the time direction and the frequency direction). Since the propagation path response is estimated by accumulating a plurality of symbols including symbols before and after the symbol to be equalized, pilot carriers can be thinned out and transmission efficiency can be increased as compared with the CP method. However, since the symbols are processed by accumulating symbols, the SP method is degraded in characteristics as compared with the CP method in a reception environment where the time variation of the channel response is large (see Non-Patent Document 5).

  Examples of transmission frames for each transmission mode in Table 1 are shown in FIGS. FIG. 4 shows a transmission frame when the transmission mode is “move”, and FIG. 5 shows a transmission frame when the transmission mode is “fixed”.

  In the transmission frame shown in FIG. 4, the product Nft of the pilot carrier insertion interval in the carrier direction (frequency direction) and the pilot carrier insertion interval in the symbol direction (time direction) is 8. In the transmission frame shown in FIG. 5, the product Nft of the pilot carrier insertion interval in the carrier direction (frequency direction) and the pilot carrier insertion interval in the symbol direction (time direction) is 128. FIG. 6 shows a simulation result of BER (Bit Error Rate) characteristics with respect to a boost value when the OFDM transmitter 10 and the OFDM receiver 20 are used under Gaussian noise in each transmission mode.

  As shown in FIG. 6, when the transmission mode is “movement”, the boost value is around 1.5, the BER is minimum, and when the transmission mode is “fixed”, the boost value is 2.6. The BER is minimum in the vicinity. Therefore, the control circuit 17 selects a pilot carrier arrangement pattern (for example, SP method or CP method) according to the transmission mode of the OFDM signal, and switches the boost value according to the selected pilot carrier arrangement pattern to perform boosting. What is necessary is just to output to the value multiplication part 133.

  As described above, the pilot carrier insertion interval can be set according to the transmission mode, and the pilot carrier can be multiplied by the boost value corresponding to the insertion interval. As a result, since the minimum number of pilot carriers can be set and the number of data carriers can be increased, the transmission efficiency can be improved, and an optimum boost value corresponding to the pilot carrier insertion interval can be set. By using it, the required C / N can be reduced.

  Note that the transmission mode is not limited to the example described above. As a transmission mode, for example, there is a transmission mode (first transmission mode) in which the FFT sampling frequency is 20.45 MHz, the number of FFT points is 2048, and the GI ratio is 1/8. In the case of the first transmission mode, the control circuit 17 selects, for example, an arrangement pattern (arrangement pattern shown in FIG. 4) in which pilot carriers are inserted once in 8 carriers in the carrier direction (frequency direction). Switch to the boost value according to the pattern.

  As the transmission mode, for example, the FFT sampling frequency is 20.45 MHz, the number of FFT points is 2048, the GI ratio is 1/8, and the pilot carrier is thinned out (second transmission mode). ) In the case of the second transmission mode, for example, the control circuit 17 inserts a pilot carrier once in t (t is an integer of 2 or more) times in the symbol direction (time direction) and k in the carrier direction (frequency direction). (8 ≦ k ≦ 8 × t, and k is an integer) An arrangement pattern to be inserted once in the carrier is selected.

  As a transmission mode, for example, there is a transmission mode (third transmission mode) in which the FFT sampling frequency is 20.45 MHz, the number of FFT points is 8192, and the GI ratio is 1/32. In the case of the third transmission mode, the control circuit 17 selects, for example, an arrangement pattern in which pilot carriers are inserted once in 32 carriers in the carrier direction (frequency direction).

  As the transmission mode, for example, the FFT sampling frequency is 20.45 MHz, the number of FFT points is 8192, the GI ratio is 1/32, and the pilot carrier is thinned out (fourth transmission mode). ) In the case of the fourth transmission mode, for example, the control circuit 17 inserts a pilot carrier once in t (t is an integer of 2 or more) times in the symbol direction (time direction) and j in the carrier direction (frequency direction). (32 ≦ j ≦ 32 × t, and j is an integer) An arrangement pattern (arrangement pattern shown in FIG. 5) to be inserted once in the carrier is selected.

  In Table 1, in the transmission mode in which the number of FFT points is 8192 and the GI ratio is 1/32, the operation status is “fixed” (the OFDM transmitter 10 and the OFDM receiver 20 are fixed). In the case of the transmission mode), but is not limited thereto. As a transmission mode when the propagation state is “movement”, a transmission mode in which the number of FFT points is 8192 and the GI ratio is 1/32 may be selected.

(Second Embodiment)
FIG. 7 is a diagram illustrating a configuration example of the OFDM transmitter 30 according to the second embodiment of the present invention. The OFDM transmitter 30 according to the present embodiment is a transmitter that transmits an OFDM signal by a MIMO (Multi Input Multi Output) transmission scheme that transmits and receives signals with a plurality of antennas (two antennas in FIG. 7). In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  7 includes an encoding circuit 11, a mapping circuit 12, a dividing circuit 31, frame configuration circuits 13a and 13b, IFFT circuits 14a and 14b, GI addition circuits 15a and 15b, and a frequency. Conversion circuits 16a and 16b and a control circuit 32 are provided. A frame configuration circuit 13a, an IFFT circuit 14a, a GI addition circuit 15a, and a frequency conversion circuit 16a are provided corresponding to one antenna, and a frame configuration circuit 13b, an IFFT circuit 14b, a GI addition circuit 15b, and a frequency conversion circuit 16b are provided on the other side. It is provided corresponding to the antenna. The frame configuration circuits 13a and 13b, the IFFT circuits 14a and 14b, the GI addition circuits 15a and 15b, and the frequency conversion circuits 16a and 16b are the frame configuration circuit 13, the IFFT circuit 14, and the GI addition circuit in the first embodiment, respectively. 15. Since this corresponds to the frequency conversion circuit 16, description thereof is omitted.

  The dividing circuit 31 divides the data output from the mapping circuit 12 into two parts (divided into the number of antennas included in the OFDM transmission apparatus 30), and frame configuration circuits 13a and 13b provided corresponding to the respective antennas. Output to.

  As with the control circuit 17, the control circuit 32 outputs control signals to each circuit (encoding circuit 11, mapping circuit 12, frame configuration circuits 13a and 13b, IFFT circuits 14a and 14b, GI addition circuits 15a and 15b, and a frequency conversion circuit. 16a, 16b).

  FIG. 8 is a diagram illustrating a configuration example of the OFDM receiver 40 according to the second embodiment of the present invention. The OFDM receiver 40 according to the present embodiment is a receiver that receives OFDM signals transmitted from the OFDM transmitter 30 shown in FIG. 7 by a plurality of antennas (two antennas in FIG. 8) by the MIMO transmission method. . In FIG. 8, the same components as those in FIG. 3 are denoted by the same reference numerals and description thereof is omitted.

  The OFDM receiver 40 shown in FIG. 8 includes frequency conversion circuits 21a and 21b, GI removal circuits 22a and 22b, FFT circuits 23a and 23b, TMCC separation circuits 24a and 24b, pilot carrier separation circuits 25a and 25b, A propagation path response estimation circuit 41, a MIMO detection circuit 42, a demapping circuit 28, and an error correction decoding circuit 29 are provided. A frequency conversion circuit 21a, a GI removal circuit 22a, an FFT circuit 23a, a TMCC separation circuit 24a, and a pilot carrier separation circuit 25a are provided corresponding to one antenna, and the frequency conversion circuit 21b, the GI removal circuit 22b, the FFT circuit 23b, and the TMCC are provided. Separation circuit 24b and pilot carrier separation circuit 25b are provided corresponding to the other antenna. The frequency conversion circuits 21a and 21b, the GI removal circuits 22a and 22b, the FFT circuits 23a and 23b, the TMCC separation circuits 24a and 24b, and the pilot carrier separation circuits 25a and 25b are respectively the frequency conversion circuit 21 in the first embodiment. Since it corresponds to the GI removal circuit 22, the FFT circuit 23, the TMCC separation circuit 24, and the pilot carrier separation circuit 25, description thereof will be omitted.

  The propagation path response estimation circuit 41 receives a reception pilot carrier from each of the pilot carrier separation circuits 25a and 25b, and uses the input reception pilot carrier to receive an antenna included in the OFDM transmission apparatus 30 and an antenna included in the OFDM reception apparatus 40. All the propagation path responses between and are estimated and output to the MIMO detection circuit.

  The MIMO detection circuit 42 performs waveform equalization and MIMO separation of the OFDM signal in the frequency domain output from the FFT circuits 23a and 23b using the channel response output from the channel response estimation circuit 41, and a demapping circuit To 28.

  An example of the transmission mode in this embodiment is shown in Table 2. Table 2 shows a case where the operation status is “fixed” (when the transmission mode is “fixed”) and the operation status is “moving” (when the transmission mode is “moving”).

  As shown in Table 2, each item (number of FFT points, pilot scheme, guard interval ratio) is the same as in the first embodiment regardless of whether the transmission mode is “fixed” or “moving”. is there. Examples of transmission frames for each transmission mode in Table 2 are shown in FIGS. FIG. 9 shows a transmission frame when the transmission mode is “move”, and FIG. 10 shows a transmission frame when the transmission mode is “fixed”.

  In the MIMO transmission method, a pilot carrier transmitted from one antenna (transmission system 1) of the two antennas included in the OFDM transmitter 30 is distinguished from a pilot carrier transmitted from the other antenna (transmission system 2). There is a need. Therefore, in the CP scheme, the OFDM transmitter 30 inverts the phase of the pilot carrier of the transmission system 2 as shown in FIG. Further, the OFDM receiver 40 estimates the channel response for the transmission system 1 and the transmission system 2 from the sum and difference of the two symbols. In the SP scheme, as shown in FIG. 10, the OFDM transmitter 30 assigns pilot carriers only to the transmission system 1 with even symbols and assigns pilot carriers only to the transmission system 2 with odd symbols. The OFDM receiver 40 estimates the channel response for the transmission system 1 and the transmission system 2 for each symbol.

  In the transmission frame shown in FIG. 9, the product Nft of the pilot carrier insertion interval in the carrier direction (frequency direction) and the pilot carrier insertion interval in the symbol direction (time direction) is 8. In the transmission frame shown in FIG. 10, the product Nft of the pilot carrier insertion interval in the carrier direction (frequency direction) and the pilot carrier insertion interval in the symbol direction (time direction) is 128. FIG. 11 shows a simulation result of the BER characteristic with respect to the boost value when the OFDM transmitter 30 and the OFDM receiver 40 are used under Gaussian noise in each transmission mode.

  As shown in FIG. 11, when the transmission mode is “movement”, the BER is minimum when the boost value is near 1.5, and when the transmission mode is “fixed”, the boost value is 2.9. The BER is minimum in the vicinity. Therefore, the control circuit 32 selects a pilot carrier arrangement pattern (for example, SP scheme or CP scheme) according to the transmission mode of the OFDM signal, switches the boost value according to the selected pilot carrier arrangement pattern, What is necessary is just to output to the boost value multiplication part 133 with which the frame structure circuits 13a and 13b are provided.

  In this way, even in the MIMO transmission scheme, the maximum pilot carrier insertion interval can be set according to the transmission mode, and the pilot carrier can be multiplied by a boost value corresponding to the insertion interval. As a result, since the minimum number of pilot carriers can be set and the number of data carriers can be increased, the transmission efficiency can be improved, and an optimum boost value corresponding to the pilot carrier insertion interval can be set. By using it, the required C / N can be reduced.

  Note that the transmission mode is not limited to the above-described example, and the first to fourth transmission modes described above can also be used in this embodiment.

  In the present embodiment, the configurations and operations of the OFDM transmitters 10 and 30 and the OFDM receivers 20 and 40 have been described. However, the present invention is not limited to this, and transmits OFDM signals in the OFDM transmitters 10 and 30. This method may be configured as a method for receiving an OFDM signal in the OFDM receivers 20 and 40.

  Although not particularly mentioned in the embodiment, a program for causing a computer to execute each process performed by the OFDM transmitters 10 and 30 and the OFDM receivers 20 and 40 may be provided. The program may be recorded on a computer readable medium. If a computer-readable medium is used, it can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or a DVD-ROM.

  Alternatively, the program for executing each process performed by the OFDM transmitters 10 and 30 and the OFDM receivers 20 and 40 includes a memory to be stored and a processor to execute the program stored in the memory. In addition, a chip mounted on the OFDM receivers 20 and 40 may be provided.

  Although the present invention has been described based on the drawings and embodiments, it should be noted that those skilled in the art can easily make various variations or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, functions included in each block or the like can be rearranged so that there is no logical contradiction, and a plurality of blocks can be combined into one or divided.

10, 30 Transmitting device 11 Encoding circuit 12 Mapping circuit 13, 13a, 13b Frame configuration circuit (frame configuration unit)
14, 14a, 14b IFFT circuit 15, 15a, 15b GI addition circuit 16, 16a, 16b Frequency conversion circuit 17, 32 Control circuit (control unit)
20, 40 Receiver 21, 21a, 21b Frequency conversion circuit 22, 22a, 22b GI elimination circuit 23, 23a, 23b FFT circuit 24, 24a, 24b TMCC separation circuit 25, 25a, 25b Pilot carrier separation circuit 26 Propagation path response estimation Circuit 27 decoding circuit 28 demapping circuit 29 error correction decoding circuit 31 division circuit 41 propagation path response estimation circuit 42 MIMO detection circuit 131 TMCC generation unit 132 pilot carrier generation unit 133 boost value multiplication unit 134 frame configuration pattern memory 135 switch 136 switch control Part

Claims (8)

An OFDM transmitter for transmitting an OFDM signal,
According to the transmission mode for transmitting the OFDM signal, an arrangement pattern of pilot carriers modulated by a pilot signal is selected from predetermined arrangement patterns, and a pilot for the average power of the data carrier is selected according to the selected arrangement pattern. A controller that switches the boost value of the carrier power to a predetermined value;
In accordance with the boost value switched by the control unit, a pilot carrier boosted to a predetermined power is arranged in a transmission frame according to the selected arrangement pattern, and the selected arrangement pattern and the A frame composing unit that generates the transmission frame including a TMCC carrier modulated with a TMCC signal indicating a boost value;
According to the transmission mode, the control unit continuously distributes pilot carriers in the symbol direction (time direction) and the carrier direction (frequency direction), or continuously in the symbol direction (time direction). An OFDM transmitter characterized by selecting an arrangement pattern in which pilot carriers are arranged. The OFDM transmitter according to claim 1, wherein
In the first transmission mode in which the number of FFT points is 2048 and the GI ratio is 1/8, the control unit inserts the pilot carrier once in 8 carriers in the carrier direction (frequency direction), and the symbol direction An OFDM transmitter characterized by selecting an arrangement pattern continuous in the (time direction). The OFDM transmitter according to claim 1, wherein
In the second transmission mode in which the number of FFT points is 2048, the GI ratio is 1/8, and the pilot carrier is thinned out, the control unit sets the pilot carrier to t ( t is an integer greater than or equal to 2) times, and an arrangement pattern to be inserted once in the carrier direction (frequency direction) k (8 ≦ k ≦ 8 × t and k is an integer) carrier is selected. A featured OFDM transmitter. The OFDM transmitter according to claim 1, wherein
In the third transmission mode in which the number of FFT points is 8192 and the GI ratio is 1/32, the control unit inserts the pilot carrier once in 32 carriers in the carrier direction (frequency direction), and the symbol direction An OFDM transmitter characterized by selecting an arrangement pattern continuous in the (time direction). The OFDM transmitter according to claim 1, wherein
In the fourth transmission mode in which the number of FFT points is 8192, the GI ratio is 1/32, and the pilot carrier is thinned out, the control unit transmits the pilot carrier in the symbol direction (time direction) by t ( t is an integer greater than or equal to 2) times, and an arrangement pattern to be inserted once in the carrier direction (frequency direction) j (32 ≦ j ≦ 32 × t, where j is an integer) carrier is selected. A featured OFDM transmitter. In the OFDM transmitter according to any one of claims 1 to 5,
The OFDM transmission apparatus transmits the OFDM signal by a SISO transmission method in which a signal is transmitted by a single antenna. In the OFDM transmitter according to any one of claims 1 to 5,
The OFDM transmitter transmits the OFDM signal by a MIMO transmission scheme that transmits a signal using a plurality of antennas,
The OFDM transmission apparatus, wherein the frame configuration unit is provided corresponding to each of the plurality of antennas. An OFDM receiver that receives an OFDM signal transmitted from the OFDM transmitter according to any one of claims 1 to 7,
A TMCC separation unit that decodes a TMCC signal obtained by demodulating a TMCC carrier included in the transmission frame to obtain the arrangement pattern and the boost value;
A pilot carrier separation unit that extracts a pilot carrier included in the transmission frame based on the arrangement pattern acquired by the TMCC separation unit;
An OFDM receiving device comprising: a pilot carrier extracted by the pilot carrier separation unit; and a channel response estimation unit that estimates a channel response based on the boost value acquired by the TMCC separation unit. .

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