JP2006345428A - Receiver associated with digital communication/broadcast, reception method, reception circuit, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a receiver, which generates a received signal at a receiving point moved at a speed of -V (just reverse in a moving direction) with respect to a moving speed V and demodulates the received signal, to surely establish a symbol synchronization. <P>SOLUTION: The receiver uses received signals by way of a plurality of antennas to generate the received signal (hereinafter called a virtual reception signal a) at the receiving point moved at a speed of -v with respect to the moving speed v and inputs a received signal b by one antenna and the virtual reception signal a to a demodulation section. The demodulation section uses the received signal b by the one antenna for a signal to establish the symbol synchronization and a virtual reception signal generating section generates the virtual reception signal "a" returning to a start point by each symbol interval on the basis of symbol positional information after the position of the symbol is established. Then the receiver uses the virtual reception signal "a" to carry out demodulation processing and monitoring of a symbol position. Thus, the receiver can surely provide a timing of the symbol interval required for generating the virtual reception signal to be returned to the start point by each symbol interval so as to stably receive a signal even at reception during moving. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a receiving apparatus for receiving digital communication / broadcasting in a moving body that moves at high speed.

  At present, orthogonal frequency division multiplexing (OFDM) is widely adopted as a transmission method in various digital communications such as terrestrial digital broadcasting and IEEE802.11a. OFDM is a transmission system that is frequency-multiplexed with a plurality of narrowband digitally modulated signals by subcarriers orthogonal to each other, and is excellent in frequency utilization efficiency. Further, in OFDM, one symbol period is composed of an effective symbol period and a guard interval period, and a part of the signal of the effective symbol period is copied to the guard interval period in order to have periodicity within the symbol. Therefore, it is possible to reduce the influence of inter-symbol interference caused by multipath interference, and it has excellent resistance against multipath interference.

  On the other hand, OFDM has a length of one symbol longer than that of a wideband digital modulation signal, and therefore is less resistant to time fluctuations in a channel fading environment that occurs in mobile reception or the like. Further, under a fading environment, not only the time variation of the amplitude of the received signal due to delay dispersion due to multipath interference, but also a frequency variation called Doppler shift occurs. Due to this Doppler shift, the orthogonal relationship between the individual subcarriers is broken, causing mutual interference, and as a result, it becomes difficult to correctly demodulate. Interfering subcarriers with each other is called ICI (Inter-Carrier Interference), and in mobile communication, suppressing deterioration of communication quality due to ICI is a key.

In recent years, several methods have been proposed as means for reducing deterioration due to ICI. As one of them, there is a method of suppressing ICI by controlling an antenna as in Patent Document 1 shown below.
20 shows the arrangement of antennas attached to a mobile unit described in Patent Document 1, FIG. 21 shows the configuration of a transmitting / receiving device of a mobile unit, and FIG. 22 shows the configuration of the transmitting / receiving unit of a base station. Indicates.

  21 includes K antennas 221 to 22K, a modulation unit 201, a modulation parameter control unit 202, an instantaneous fading estimation unit 203, a demodulation unit 204, a modulation parameter estimation unit 211, switching units 205 and 206, 207, a received signal estimation unit 210. Further, the received signal estimation unit 210 includes an interpolation calculation unit 208 and a movement distance estimation unit 209.

As shown in FIG. 20, the K antennas 221 to 22K are arranged on a straight line along the traveling direction in the casing of the moving body. The distance between adjacent antennas is d (m), and the distance from the first antenna to the last antenna is (K-1) · d (m).
The interpolation estimation unit 208 performs a predetermined interpolation operation on the received signals S221 to S22K received via the antennas 211 to 21K, so that the moving direction of the moving object is reversed from the leading antenna 211. A received signal received at a point P separated by x in the direction is estimated. This distance x is calculated by the movement distance estimation unit 209. The movement distance estimation unit 209 receives a signal indicating the speed V at which the moving body moves, calculates a distance x using Equation 1 from this signal and the elapsed time t from the reference time t0, and outputs the distance x to the interpolation calculation unit 208. To do.

  Since the reception point at this distance x moves at a speed V in the direction opposite to the traveling direction of the moving body, the relative speed is zero, that is, fixed with respect to the ground. Therefore, by estimating the reception signal at a fixed reception point, the estimated reception signal can be regarded as a signal received with the moving body stopped, and a reception signal that compensates for fading fluctuation can be obtained. it can.

  The received signal compensated for fading fluctuation obtained by the interpolation calculation unit 208 is input to the modulation parameter estimation unit 211, and the modulation parameter estimation unit 211 estimates the modulation parameter of the signal transmitted from the base station. The demodulator 204 demodulates the signal obtained by the interpolation calculator 208 according to the estimated modulation parameter, and as a result, demodulated data is generated.

22 includes a modulation parameter estimation unit 241, a demodulation unit 242, an instantaneous fading estimation unit 243, a modulation parameter control unit 244, a modulation unit 245, and a switching unit 246.
FIG. 23 shows the timing of communication between the mobile unit and the base station, and the ground positions (relative positions with respect to the ground) of the antennas 221 and 22K.

  At timing 251 shown in FIG. 23, a signal (pilot tone signal) for measuring the propagation characteristics of the transmission path and the measurement (pilot tone signal) is transmitted from the mobile unit to the base station. The base station receives the pilot tone signal transmitted from the mobile unit, and the instantaneous fading estimation unit 243 estimates the propagation characteristics of the propagation path. The modulation parameter control unit 244 selects the parameter having the highest transmission rate among the modulation parameters satisfying the required transmission quality under the estimated transmission characteristics, and the modulation unit 245 modulates the transmission data. The modulated data is transmitted from the base station to the mobile unit in the interval 252 in FIG.

  In the section 252 in FIG. 23, the mobile unit can perform the above-described interpolation processing, whereby the fading fluctuation received by the transmitted signal in the section 252 can be regarded as constant, and good reception is possible. . At this time, in the movement distance estimation unit 209, the reference time t0 is the timing of 251 and is the time when the pilot tone signal is transmitted from the mobile unit to the base station.

Next, a pilot tone signal for measuring the propagation characteristic of the transmission path is transmitted from the base station to the mobile unit in the timing section 253 in FIG. Even in the section 253, fading fluctuation is made constant by interpolation processing.
In such a series of transmissions and receptions, the receiving side in the mobile body performs interpolation processing to make the fading fluctuation received by the signal constant and enable good reception.

Furthermore, the following Non-Patent Document 1 is a configuration for generating and demodulating a received signal stationary with respect to the ground, as in Patent Document 1, and an interpolation operation for generating a received signal stationary with respect to the ground. Are also described in detail and are discussed for OFDM demodulation. However, unlike Patent Document 1 having a transmission / reception configuration, it is discussed as a receiving device.
FIG. 24 is a block diagram illustrating a receiving device of Non-Patent Document 1, and FIG. 25 is a diagram illustrating the movement of the reception point x described above with respect to the interpolation processing of Non-Patent Document 1.

In FIG. 24, similarly to Patent Document 1, signals received by the antennas 261 to 26K are interpolated by the interpolator unit 271 to compensate for fading fluctuations. Here, the Interpolator unit 271 corresponds to the interpolation calculation unit 208 of Patent Document 1.
The relative position unit 273 is a block that calculates the distance x necessary for performing the interpolation operation in the interpolator unit 271, and corresponds to the movement distance estimation unit 209 of Patent Document 1. Here, the reference time signal t is output together with the demodulated signal from the OFDM receiver unit 272, and the distance x is calculated using this time signal t. As shown in FIG. 25, the distance x is discontinuous for each symbol section. This is because the distance x is reduced to the start point for each OFDM symbol interval in order to prevent the distance x from increasing monotonously infinitely to be extrapolated. More specifically, the functions for calculating the distance x are expressed by Equations 2 and 3.

It differs from Patent Document 1 in that the distance x is periodically reduced to the start point based on the OFDM symbol interval information that is the reference time signal. Here, as described in the background art, the OFDM symbol period is composed of a guard interval period and an effective symbol period. Hereinafter, the guard interval length is denoted as Tg, the effective symbol period length as Tu, and the 1 symbol period length as Ts. From Equation 2 and FIG. 25, x is reduced to the start point every symbol period, and although it is discontinuous between symbols, there is no problem because it is within the guard interval.

  When the antenna input signal is expressed by Equation 4, the Interpolator unit 271 calculates the received signal r (t; x) at the reception point P by executing the weighting calculation of Equation 5. Here, the weighting is expressed by Equation 6 based on the distance x. p is expressed by Equations 7 and 8, and R is calculated by Equations 9 and 10. Note that T in Equation 4 represents transposition, and H in Equations 6 and 9 represents Hermitian transposition. J0 is a first-order zeroth-order Bessel function, and λ represents the wavelength of the carrier wave.

As a result, by estimating and creating a reception signal at a stationary reception point with respect to the ground, a signal with a constant fading fluctuation can be created, and reception performance is improved in mobile reception.
JP 2002-152105 A (P3 to P6, FIGS. 1 to 3) Effect of improving high-speed mobile reception characteristics of digital terrestrial broadcasting due to time-varying propagation using an array antenna. 2, pp. 237-244 (2002)

  However, in the method disclosed in Patent Document 1, there is only a description that the reference time for calculating the reception point x is “the time when the pilot tone signal is transmitted from the mobile unit to the base station”. Does not describe how the reference time is created. Furthermore, in a service such as terrestrial digital broadcast reception that is not a transmission method such as TDD, there is a problem that the reference time cannot be obtained on the receiving device side.

  In Non-Patent Document 1, as shown in FIG. 25, the reception point x is synchronized with the OFDM symbol and is configured to be reduced for each symbol section, and the symbol timing is used as a reference. Although the time t is described to be output together with the demodulated signal from the OFDM receiver unit 272, it is not specified how to establish symbol synchronization in the first place. That is, if symbol synchronization is not established, a signal at a reception point fixed with respect to the ground cannot be generated. Therefore, in establishing symbol synchronization, equation 2 can be applied when calculating the distance x. There is a problem that it cannot be done.

  In addition, when the moving speed is high, the time until the rear antenna arrives at a certain time position (position relative to the ground) of the antenna ahead in the traveling direction is short, and as a result, there is a correlation ( If the moving speed is very slow while the moving speed is very slow, it takes a long time for the rear antenna to arrive at a certain time position (position relative to the ground). As a result, there is a possibility that the interpolation processing cannot be correctly performed.

  Non-Patent Document 1 also compares the relationship between the distance between antennas and reception performance. For example, when using two antennas, the distance between antennas is 1/10 of the wavelength, and when using four antennas, It has been confirmed that an inter-distance of 1/5 of the wavelength is most suitable. From this, it can be said that the optimum distance between the antennas to be installed depends on the wavelength of the received radio wave. However, for example, in Japanese television broadcasting, the UHF band is 470 MHz to 770 MHz, and there is a difference of 1.5 times or more between the lowest frequency and the highest frequency. For this reason, if the antennas are fixed, optimal interpolation processing cannot be performed for all channels.

The present invention solves the above-described conventional problems, and a first object thereof is to reliably establish symbol synchronization.
It is a second object of the present invention to provide a receiving apparatus capable of stable reception even when the speed is low.
A third object of the present invention is to provide a receiving device whose reception performance does not depend on the wavelength of the received radio wave.

In order to solve the conventional problem, the receiving apparatus of the present invention is:
Using a plurality of received signals, a virtual received signal creating unit that creates a virtual received signal at a point relatively stationary with respect to the ground, and a demodulating unit that performs demodulation, the demodulating unit, Demodulation is performed based on both one received signal of the plurality of received signals and the received signal created by the previous virtual received signal creating unit.

  Further, the demodulation unit includes a symbol synchronization unit that recognizes the effective symbol period and a Fourier transform unit that performs Fourier transform, and the symbol synchronization unit uses one received signal among the plurality of received signals. Then, the one symbol period is recognized, and the Fourier transform unit performs Fourier transform on the reception signal created by the virtual reception signal creation unit.

As a result, the symbol synchronization unit can reliably establish symbol synchronization using one received signal among the plurality of received signals, and the received signal created by the virtual received signal creating unit based on the symbol position. Can be created.
The demodulator includes a symbol synchronization unit that recognizes the effective symbol period and a Fourier transform unit that performs Fourier transform. The symbol synchronization unit is configured to perform the plurality of operations until the one symbol period is identified. Use one of the received signals as an input signal,
After recognizing the one symbol period, the received signal created by the virtual received signal creating unit is used as an input signal until the one symbol period cannot be recognized again.
The Fourier transform unit is configured to perform Fourier transform on the reception signal created by the virtual reception signal creation unit.

Thereby, symbol synchronization can establish symbol synchronization using one received signal among the plurality of received signals, and based on the symbol position, a received signal created by the virtual received signal creating unit can be created, After the symbol synchronization is established, the symbol synchronization can be accurately monitored by the received signal with the fading fluctuation suppressed generated by the virtual received signal creation unit.
Further, when the speed of the moving body is greater than a predetermined value, the demodulating unit performs demodulation based on the reception signal created by the virtual reception signal creating unit, and the speed of the moving body is greater than a predetermined value. Is smaller, the demodulation is performed based on one received signal among the plurality of received signals.

As a result, when the moving speed is low, the received signal subjected to the interpolation process is not used, and the received signal from one antenna or a plurality of antennas is switched to the diversity-received signal and demodulated. Deterioration of reception performance due to interpolation processing can be suppressed.
In addition, using a plurality of received signals, a virtual received signal generating unit that generates a received signal at a point relatively stationary with respect to the ground, and demodulation using the received signal generated by the virtual received signal generating unit And a demodulating unit for performing the same operation in the virtual received signal generating unit, where the stationary point relative to the ground is the same speed as the moving body in a direction opposite to the moving direction of the moving body. And at a predetermined periodic time interval, the moving object is returned to the start point, and the predetermined periodic time interval is before and after recognizing the timing of the one symbol period. It is configured to be different.

Thus, before the symbol synchronization is established, the periodic time interval is made longer than one symbol, and even if the symbol position is not known, one symbol is included. Therefore, the symbol synchronization unit 44 has no fading fluctuation. Correlation can be calculated with the virtual received signal a, and symbol synchronization can be achieved with high accuracy.
Furthermore, a virtual reception signal creation unit that creates a virtual reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals, and at least two reception signals among the plurality of reception signals A reception signal combining unit that generates a signal received by combining or selecting diversity using a demodulator, and a demodulating unit that performs demodulation, and the demodulating unit includes the received signal received by the diversity and the previous virtual reception signal generating unit. The configuration is such that demodulation is performed based on both of the generated received signals.

By using the diversity received signal c in order to establish symbol synchronization, the power drop of the received signal can be suppressed and symbol synchronization can be established rather than using a single received signal from a single antenna. It becomes easy.
Furthermore, the configuration is such that the distance between the antennas of the plurality of antennas is controlled or selected according to the tuning information of the tuner.

  As a result, no matter what channel is selected, it is possible to perform an optimum interpolation operation for the wavelength of the channel, and to make the best use of fading resistance due to the interpolation processing.

According to the receiving apparatus of the present invention, symbol synchronization can be reliably established by using a signal received by one antenna or a signal obtained by diversity reception of a plurality of antennas as a signal for establishing OFDM symbol synchronization. it can.
In addition, symbol synchronization is not used as a reference time for reducing x, and the period for reduction is longer than one symbol length until symbol synchronization is established, so that symbol synchronization is established with a signal that is not subject to fading fluctuation. Correlation can be calculated and symbol synchronization can be established reliably.

Also, when the moving speed is low, the received signal that has been subjected to the interpolation process is not used, but the received signal from one antenna or the signals that have been received from a plurality of antennas are switched to a demodulated signal and demodulated. Deterioration of reception performance due to processing can be suppressed.
Furthermore, by controlling the distance between the antennas based on the channel selection information, it is possible to perform an optimal interpolation calculation for any channel wavelength, and to reduce fading resistance due to interpolation processing. You can make the most of it.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
Embodiment 1 of a receiving apparatus according to the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 3, and FIG.
1 is a diagram showing an antenna arrangement of a receiving apparatus according to Embodiment 1 of the present invention. The antenna arrangement in the receiving apparatus shown in FIG. 1 is similar to Patent Document 1, in which a plurality (K) of antennas are installed as the inter-antenna distance d in parallel with the traveling direction in which the moving body moves. Point P2 is an estimated virtual reception point, which will be described later. Here, the inter-antenna distance d and the number of antennas may be arbitrarily set in consideration of restrictions on installation location, cost, and the like.

  FIG. 2 is a block diagram showing a receiving apparatus according to Embodiment 1 of the present invention. The receiving apparatus includes antennas 101 to 10K and tuners 111 to 11K, a virtual reception signal generation unit 5, a moving speed estimation unit 11, a demodulation unit 31 that performs demodulation processing, a signal compressed by MPEG (Moving Picture Experts Group) -2, and the like. Are comprised of a decoding unit 21 for decoding and a display unit 22 for outputting video and audio.

The tuners 111 to 11K select the reception signals of the desired reception channels from the respective antennas 101 to 10K, perform level amplification (level adjustment), A / D conversion, and then pass them to the virtual reception signal generation unit 5. The virtual reception signal generation unit 5 includes a virtual reception signal calculation unit 13 and a movement distance estimation unit 12.
In the movement distance estimation unit 12, when symbol synchronization is established by a symbol synchronization unit 44 described later, the symbol position information signal that is the reference signal t (s) obtained from the demodulation unit 31 and the movement speed estimation unit 11 are estimated. A reception point at time t (s) assuming a virtual reception point P2 that moves at a speed v (m / s) in the direction opposite to the movement direction from the movement speed v (m / s) of the receiver. The distance x (m) from the antenna 101 of P2 is calculated and passed to the virtual received signal calculation unit 13. The distance x may be calculated using Equations 2 and 3 and moved as shown in FIG. 4. However, the distance x is not limited to this. For example, instead of Equation 3, Equation 11 may be used.

The virtual reception signal calculation unit 13 estimates and creates a signal received at the virtual reception point P2 from the reception signals of the antennas 101 to 10K (hereinafter referred to as a virtual reception signal a). The generation of the virtual reception signal a may be performed using Equations 4 to 10, but is not limited thereto, and may be sequentially switched to the antenna closest to the distance x without using the number. .
Here, the moving speed estimator 11 may use a device that is a component outside the receiving device that measures the speed installed in the moving body as an estimation means, or estimates the Doppler shift from the received signal. By doing so, it may be configured to estimate the speed of the moving body, and any process may be used as long as the moving speed can be estimated.

The demodulator 31 receives the virtual received signal a created by the virtual received signal calculator 13 and also receives the received signal b at the antenna 101.
FIG. 3 is a block diagram showing the configuration of the demodulator 31 in FIG. The demodulation unit 31 includes orthogonal demodulation units 41 and 42, an FFT unit 43, a symbol synchronization unit 44, a transmission path estimation unit 45, an equalization unit 46, and an error correction unit 47.

Non-Patent Document 1 is a configuration in which demodulation processing is performed in the OFDM receiver unit 272 using a received signal at a reception point P resulting in a symbol interval, and it is assumed that symbol synchronization has already been established. There was a discrepancy in establishing the symbol position synchronization using the received signal at.
In order to solve the contradiction, the reception signal b of the antenna 101 is orthogonally demodulated by the orthogonal demodulation unit 42 and output to the symbol synchronization unit 44, and the symbol synchronization unit 44 converts the orthogonally demodulated reception signal b of the antenna 101. Based on this, the OFDM symbol interval is synchronized. By using the received signal b of the antenna 101 instead of using the virtual received signal a in order to establish symbol synchronization, the symbol synchronization unit 44 can reliably establish synchronization and resolve inconsistencies.

  When symbol synchronization is established, the symbol synchronization unit 44 outputs a timing signal synchronized with the symbol (hereinafter referred to as symbol position information signal) to the FFT unit 43 and the movement distance estimation unit 12. In addition, a symbol synchronization establishment signal indicating whether or not symbol synchronization has been established is output to the movement distance estimation unit 12. The moving speed estimation unit 12 receives the symbol synchronization establishment signal and the symbol position information signal that is the reference signal, and calculates the distance x (m) as described above.

  On the other hand, the virtual received signal a is quadrature demodulated by the quadrature demodulator 41 and output to the FFT unit 43. Based on the symbol position information signal, the FFT unit 43 performs a Fourier transform on the orthogonally demodulated signal to obtain a frequency domain signal. Thereafter, the transmission path estimation unit 45 performs transmission path estimation, and the equalization unit 46 equalizes the frequency domain signal based on the transmission path estimation. The equalized signal is input to the error correction unit 47 and error correction is performed.

With the above configuration, the symbol synchronization unit 44 can reliably establish symbol synchronization using the reception signal of the antenna 101, and is a virtual reception signal with reduced fading fluctuation created based on the symbol position. The received data can be demodulated using a, and stable reception is possible.
Note that the received signal b from the antenna 101 is used as an input signal to the symbol synchronization unit 44. However, any of the antennas 102 to 10K may be used regardless of the antenna 101, and not limited to the antennas 102 to 10K. A separate antenna may be provided.

In addition, each component of the receiving apparatus according to Embodiment 1 may be realized by 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.
Furthermore, a program that performs at least a part of the reception processing in the receiving apparatus according to the first embodiment may be used, and is realized by using a reception method that performs at least a part of the reception processing in the receiving apparatus according to the first embodiment. May be.

Further, Embodiment 1 may be realized by combining any receiving device, receiving method, receiving circuit, or program that performs a part of the receiving processing that realizes Embodiment 1.
(Embodiment 2)
Embodiment 2 of the receiving apparatus according to the present invention will be described with reference to FIGS. The same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 5 is a block diagram showing a receiving apparatus according to the second embodiment of the present invention. Compared to Embodiment 1, the present invention uses a signal obtained by combining diversity reception of signals received from antennas 101 to 10K instead of a signal received from antenna 101 as a reception signal input to demodulation unit 91. Is different.
The receiving apparatus in FIG. 5 newly includes a received signal combining unit 14 as compared with FIG. The reception signal combining unit 14 receives the reception signals selected by the tuners 111 to 11K, creates a combined diversity reception signal c, and outputs the combined diversity reception signal c to the demodulation unit 91. The demodulator 91 is shown in FIG. 27, and only the input signal is different from that of the demodulator 31 shown in FIG.

  FIG. 6 shows a configuration diagram of the reception signal synthesis unit 14. The reception signal combining unit 14 includes a reception signal weight determination unit 51 and a combination calculation unit 52. The reception signal weight determination unit 51 measures each reception signal strength (signal level) of the reception signals of the antennas 101 to 10K, The ratio of the received signal strength between the received signals is calculated. The combining calculation unit 52 combines the received signals of the antennas 101 to 10K using the power ratio calculated by the received signal weight determination unit 51 as a weighting coefficient, and outputs the combined signal to the demodulation unit 91. The combined diversity reception signal c is improved in S / N (Signal Power / Noise Power) compared to the reception signals of the individual antennas. When calculating the weighting coefficient, normalization may be performed based on the total power of all received signals.

Then, in order to solve the contradiction of the non-patent document and reliably establish the symbol synchronization by the processing in the first embodiment, the symbol synchronization unit 44 of the demodulation unit 91 is based on the diversity reception signal c demodulated orthogonally. The OFDM symbol period is synchronized.
With this configuration, the symbol synchronization unit 44 uses the diversity received signal c, so that a drop in the power of the received signal can be suppressed and symbol synchronization can be easily established rather than using a single received signal from a single antenna. . Then, stable reception is possible using the virtual reception signal a created based on the symbol position.

  In addition, although the example which performs diversity using all the antennas 101 to 10K is shown, the number of antennas to be used is not limited to this. For example, two antennas 101 and 10K may be used. Furthermore, the method of combining in diversity used the power value of the received signal for weighting coefficient calculation, but is not limited to this, for example, a means of combining a plurality of received signals after having the same phase, Means such as determining the synthesis ratio according to the signal quality and S / N may be used, or selection diversity may be used.

In addition, each component of the receiving apparatus according to the second embodiment may be realized by 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.
Furthermore, a program that performs at least a part of the reception processing in the receiving apparatus according to the second embodiment may be used, and may be realized by using a reception method that performs at least a part of the reception processing in the receiving apparatus according to the second embodiment. May be.

Further, the second embodiment may be realized by combining any receiving device, receiving method, receiving circuit, or program that performs a part of the receiving process for realizing the second embodiment.
(Embodiment 3)
Embodiment 3 of the receiving apparatus of the present invention will be described with reference to FIGS. 7, 8, and 9. FIG. The same components as those in FIGS. 2 and 3 are denoted by the same symbols, and description thereof is omitted.

FIG. 7 is a block diagram showing a receiving apparatus according to the third embodiment of the present invention. FIG. 8 is a block diagram illustrating a configuration of the demodulator 32. The present invention is different from the first embodiment in that the demodulator 32 switches the input signal of the symbol synchronizer 44 before and after the establishment of symbol synchronization.
Compared with FIG. 3, the demodulator 32 has a new selector 61 and inputs and selects the signals demodulated by the quadrature demodulators 41 and 42. The symbol synchronization unit 44 outputs a symbol synchronization establishment signal indicating whether or not symbol synchronization has been established to the selector 61 and the movement distance estimation unit 12, and a symbol position information signal synchronized with the symbol to the FFT unit 43 and the movement distance estimation. To the unit 12. The selector 61 selects a signal obtained by orthogonally demodulating the reception signal b received by the antenna 101 when the symbol synchronization is not established by the symbol synchronization establishment signal output from the symbol synchronization unit 44, and when the symbol synchronization is established. Then, a signal obtained by orthogonally demodulating the virtual reception signal a created by the virtual reception signal calculation unit 13 is selected and output to the symbol synchronization unit 44.

  With this configuration, the symbol synchronization unit 44 receives a signal received by the antenna 101 until synchronization is established. When symbol synchronization is established, the symbol synchronization unit 44 uses the virtual reception signal a based on the synchronization timing to correlate the OFDM signal. The calculation is continued, and on the other hand, the demodulation process is performed in the FFT unit 43 and later using the virtual received signal a to reproduce the demodulated data. After the synchronization is established, the symbol synchronization unit 44 can calculate the correlation with respect to the virtual reception signal a in which fading fluctuation is suppressed, so that the accuracy of the correlation calculation is improved.

The demodulator 32 may be configured as the demodulator 33 shown in FIG. With this configuration, only one quadrature demodulator is required, which reduces the circuit scale. The input signal of the FFT unit 43 becomes a received signal of the antenna 101 before the symbol synchronization is established. However, the FFT unit 44 does not operate until the symbol synchronization is established, so there is no influence.
The received signal b from the antenna 101 is used as an input signal to the symbol synchronization unit. However, regardless of the antenna 101, any of the antennas 102 to 10K may be used, and a symbol synchronization antenna may be provided separately. In addition, the received signal c obtained by diversifying the received signals of the antennas 101 to 10K or the separately provided antenna for symbol synchronization by the received signal combining unit 14 as shown in FIG. 5 may be used. The diversity configuration is not limited to that shown in FIG. 6. For example, a combination ratio is determined according to signal quality and S / N, such as means for combining a plurality of received signals after having the same phase. May be used, or may be selected diversity.

In addition, each component of the receiving apparatus according to Embodiment 3 may be realized by 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.
Furthermore, a program that performs at least a part of the reception processing in the receiving apparatus according to the third embodiment may be used, and is realized by using a reception method that performs at least a part of the reception processing in the receiving apparatus according to the third embodiment. May be.

Further, Embodiment 3 may be realized by combining any receiving device, receiving method, receiving circuit, or program that performs a part of the receiving processing that realizes Embodiment 3.
(Embodiment 4)
Embodiment 4 of the receiving apparatus of the present invention will be described with reference to FIG. 10, FIG. 11, and FIG. The same components as those in FIG. 2 and FIG.

FIG. 10 is a block diagram showing a receiving apparatus according to the fourth embodiment of the present invention, and FIG. 11 is a block diagram showing a configuration of demodulator 34.
The third embodiment is significantly different from the first and second embodiments in that the demodulator 34 uses the output signal of the moving speed estimator 11.
As shown in FIG. 10, the moving speed estimation unit 11 estimates the speed of the moving object, and outputs it to the moving distance estimation unit 12 and also outputs it to the demodulation unit 34.

Compared with FIG. 3, the demodulator 34 of FIG. 11 has a selector 71 and a comparison / determination unit 72. The selector 71 receives signals orthogonally demodulated by the quadrature demodulators 41 and 42. A signal indicating the speed from the moving speed estimation unit 11 and a predetermined value are input to the comparison / determination unit 72.
The comparison / determination unit 72 compares the speed of the moving body with a predetermined value and outputs a comparison / determination result to the selector 71.

  In the selector 71, based on the output result of the comparison / determination unit 72, the received signal b from the antenna 101 is used when the speed of the moving body is lower than a predetermined value, and the speed of the moving body is higher than the predetermined value. For this, the virtual reception signal a generated by the virtual reception signal calculation unit 13 is selected and passed to the FFT unit 43 and the symbol synchronization unit 44. Here, the switching timing in the selector 71 is performed only when the symbol position information signal synchronized with the symbol period is input from the symbol synchronization unit 44 and the OFDM symbol is switched to the next OFDM symbol, as shown in FIG. The signal becomes discontinuous by switching, but there is no influence on reception characteristics because it is a guard interval section.

When the speed is low, switching to a reception signal from one antenna and performing demodulation processing can suppress degradation of reception performance due to erroneous interpolation processing.
The demodulator 34 may be configured as the demodulator 35 shown in FIG. As a result, a single quadrature demodulator can be configured, which reduces the circuit scale.
In this configuration, the received signal b from the antenna 101 and the virtual received signal a are selected using the magnitude of the moving speed as an index. However, a configuration using another index may be used. .

  An example will be described with reference to FIG. The demodulating unit 39 in FIG. 26 newly includes an error rate measuring unit 85 and a comparison / determination unit 86 that are not particularly specified in FIG. This error rate measuring unit 85 measures the bit error rate of demodulated and error-corrected data. The selector 87 for inputting the error rate and the second predetermined value to the comparison / determination unit 86, performing the comparison determination, and selecting the reception signal b or the virtual reception signal a of the antenna 101 has a predetermined error rate. When the value is exceeded, switch from the currently selected one to the other. As shown in FIG. 12, the switching timing is every symbol section. As a result, when the error rate is high, the reception performance can be improved by using the other received signal.

The calculation of the error rate is not limited to using data after error correction.
In the third embodiment, the input signals of the symbol synchronization unit 44 may be combined as shown in the first and second embodiments. The configurations of the demodulation units 36 and 37 at this time are shown in FIGS. The demodulator 36 of FIG. 14 differs from the demodulator 34 in that the symbol-synchronized input signal is not the output of the selector 71 but always the received signal b of the antenna 101. The demodulator 37 shown in FIG. 15 switches the received signal by the selector 73, and inputs a symbol synchronization establishment signal in addition to the output signal of the comparison / determination unit 72 and the symbol position information signal synchronized with the symbol. The selector 73 is different from the selector 71 in FIG. 11 in that when the symbol synchronization is not established, the selector 73 forcibly selects the reception signal b of the antenna 101. After the symbol synchronization is established, the virtual reception signal a or the reception signal b of the antenna 101 is selected based on the output result of the comparison / determination unit 72 and the symbol position information signal, similarly to the selector 71. As a result, symbol synchronization can be reliably established by using the received signal of the antenna 101, and when the speed is low, switching to the received signal from one antenna and performing demodulation processing can cause erroneous internal Deterioration of reception performance due to insertion processing can be suppressed.

  Further, although the received signal b from the antenna 101 is used as an input signal to the symbol synchronization unit, any of the antennas 102 to 10K may be used regardless of the antenna 101, and a symbol synchronization antenna may be separately provided. Alternatively, a received signal c obtained by diversity receiving signals from the antennas 101 to 10K or an antenna provided separately for symbol synchronization by the received signal combining unit 14 shown in FIG. 5 may be used. The diversity configuration is not limited to that shown in FIG. 6. For example, a combination ratio is determined according to signal quality and S / N, such as means for combining a plurality of received signals after having the same phase. May be used, or may be selected diversity.

In addition, each component of the receiving apparatus according to Embodiment 4 may be realized by 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.
Furthermore, a program that performs at least a part of the reception processing in the receiving apparatus according to the fourth embodiment may be used, and is realized by using a reception method that performs at least a part of the reception processing in the receiving apparatus according to the fourth embodiment. May be.

Further, Embodiment 4 may be realized by combining any receiving device, receiving method, receiving circuit, or program that performs a part of the receiving processing that realizes Embodiment 4.
(Embodiment 5)
A receiving apparatus according to a fifth embodiment of the present invention will be described with reference to FIGS. The same reference numerals are used for the same components as those in FIGS. FIG. 16 is a block diagram of the receiving apparatus according to the fourth embodiment, and FIG. 17 is a block diagram of the demodulator 38.

In the fifth embodiment, as compared with the first, second, third, and fourth embodiments, the moving distance estimation unit 81 reduces the distance x from the antenna 101 at the reception point P2 as shown in FIG. However, there is a significant difference in the difference before and after the establishment of symbol synchronization. FIG. 18 shows the movement of the distance x in the movement distance estimation unit 81 in the present embodiment.
The movement distance estimation unit 81 receives, from the demodulation unit 38, a symbol synchronization establishment signal indicating whether or not symbol synchronization has been established and a symbol position information signal that is symbol timing information. Before the symbol synchronization is established, the symbol position information signal is not used as the reference time information when the distance x is calculated, and the distance x is set with a cycle of 2 symbols as shown in Equations 12 and 11. Try to bring it back. Thus, by setting the period of the return to be 2 symbols long, one symbol is always included even if the symbol position is unknown, so the symbol synchronization unit 44 calculates the correlation with the virtual received signal a having no fading fluctuation. And symbol synchronization can be achieved with high accuracy. Here, since the symbol position information signal is not used as the reference time signal, it may be set arbitrarily.

When the symbol synchronization is established, the moving distance estimation unit 81 calculates the distance x using the symbol position information signal synchronized with the symbol as a reference time signal using Equations 2 and 3, and the demodulation unit 38 determines the virtual received signal a. To perform demodulation processing.
In the present embodiment, the period for reducing the distance x in the movement distance estimation unit 81 is set to twice the symbol length before the establishment of symbol synchronization. However, the present invention is not limited to this and may be set arbitrarily. For example, the period for reducing the distance x may remain the symbol length before and after the establishment of symbol synchronization, and the symbol position information may not be used as a reference time signal before the establishment of symbol synchronization. Since the period is the same, the circuit configuration is simplified. Also, the time of (K-1) d / V, which is the distance from the antenna 101 to the antenna 10K divided by the speed, is a time during which interpolation processing can be performed. 1) The period may be d / V.

  Note that this embodiment may be combined with a configuration in which the received signal of one antenna and the received signal generated by the virtual received signal calculation unit 13 are switched according to the speed V as shown in the third embodiment. FIG. 19 shows a block diagram of a receiving apparatus having such a configuration. The demodulator 34 is the same as that shown in FIG. As described above, the moving distance estimation unit 12 changes the period for reducing the distance x before and after the establishment of symbol synchronization, and the demodulation unit 34 uses the speed information as described in the third embodiment. The received signal is switched by the selector 71.

As a result, symbol synchronization can be accurately performed, and when the speed is low, switching to a reception signal from one antenna and performing demodulation processing suppress deterioration of reception performance due to erroneous interpolation processing. be able to.
The received signal b from the antenna 101 is used as an input signal to the symbol synchronization unit. However, regardless of the antenna 101, any of the antennas 102 to 10K may be used, and a symbol synchronization antenna may be provided separately. Alternatively, a received signal c obtained by diversity receiving signals from the antennas 101 to 10K or an antenna provided separately for symbol synchronization by the received signal combining unit 14 shown in FIG. 6 may be used. The diversity configuration is not limited to that shown in FIG. 6. For example, a combination ratio is determined according to signal quality and S / N, such as means for combining a plurality of received signals after having the same phase. May be used, or may be selected diversity.

Further, each component of the receiving apparatus according to the fifth embodiment may be realized by 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.
Furthermore, a program that performs at least a part of the reception processing in the reception apparatus according to the fifth embodiment may be used, and is realized by using a reception method that performs at least a part of the reception processing in the reception apparatus according to the fifth embodiment. May be.

Further, Embodiment 5 may be realized by combining any receiving device, receiving method, receiving circuit, or program that performs a part of the receiving processing that realizes Embodiment 5.
Further, in the first to fifth embodiments, the distance between antennas shown in FIG. 1 is controlled to a distance d suitable for the wavelength of a desired frequency channel based on information selected by the tuners 111 to 11K. Also good. As a control method, the antenna distance may be varied by physically moving the antennas 101 to 10K, but is not limited to this, and for example, the antenna distance may be as shown in FIG. FIG. 28 is a diagram showing the distance between antennas by the arrangement of antennas 101 to 105 and the combination of two antennas. At this time, the distance between the antennas becomes 1.0d to 1.5d (m) by combining two of the antennas 101 to 105, and two of them have the optimum distance between the antennas for the wavelength of the channel to be selected. And the virtual received signal a may be created. The antenna arrangement, distance, and number are merely examples, and are not limited thereto. With these configurations, no matter what channel is selected, it is possible to perform an interpolation operation optimal for the wavelength of that channel.

  In the first to fifth embodiments, the guard interval period has been described on the assumption that a part of the signal of the effective symbol period is copied to the guard period. It is not a thing. Moreover, although Embodiment 1-5 demonstrated as an OFDM signal, not only this but single carrier transmission may be sufficient, and in order to return the distance x to a starting point, a preamble signal etc. It is only necessary to include a signal corresponding to the guard interval period.

  The receiving apparatus according to the present invention has a function to reduce inter-carrier interference caused by frequency fluctuations caused by Doppler shift, and has a wide range of communication such as wireless LAN and ADSL, terrestrial / satellite digital broadcasting, and measurement Useful in field receivers.

The figure which shows arrangement | positioning of the antenna of the receiver in Embodiment 1 of this invention Block diagram of receiving apparatus in embodiment 1 of the present invention Block diagram of demodulator 31 in Embodiment 1 of the present invention The figure showing the relationship between the distance x of the movement distance estimation part 12 in FIG. 2, and time. The block diagram of the receiver in Embodiment 2 of this invention Block diagram of the received signal synthesizer 14 in FIG. The block diagram of the receiver in Embodiment 3 of this invention Block diagram of demodulator 32 in Embodiment 3 of the present invention Block diagram of demodulator 33 in Embodiment 3 of the present invention The block diagram of the receiver in Embodiment 4 of this invention Block diagram of demodulator 34 in Embodiment 4 of the present invention The figure showing the timing which switches the virtual received signal a in the selector 71, and the received signal b of the antenna 101 Block diagram of demodulator 35 with one orthogonal demodulator Block diagram of demodulator 36 combining Embodiments 1 and 4 Block diagram of demodulator 37 combining Embodiments 3 and 4 Block diagram of receiving apparatus in embodiment 5 of the present invention Block diagram of demodulator 38 in Embodiment 5 of the present invention The figure showing the periodicity of the distance x in the movement distance estimation part 81 Block diagram of a receiving apparatus combining Embodiments 4 and 5 The block diagram which shows antenna arrangement | positioning in the conventional transmission / reception apparatus (patent document 1) Block diagram showing a conventional transmission / reception apparatus (Patent Document 1) The block diagram which shows the structure of the conventional (patent document 1) base station The figure showing the relative position with respect to the ground of the transmission / reception timing of Patent Document 1 and the antennas 221 and 22K Block diagram showing a conventional (non-patent document 1) receiving device The figure showing the periodicity of the distance x in the relative position part 237 of the past (nonpatent literature 1). FIG. 9 is a block diagram showing a demodulator 39 that switches between a virtual received signal a and a received signal b of the antenna 101 using an error rate in the fourth embodiment of the present invention. The block diagram showing the demodulation part 91 in Embodiment 2 of this invention The figure which shows the antenna arrangement | positioning in an example of control of the distance between antennas

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mobile body 2 Virtual reception point 5 Virtual reception signal production part 6 Virtual reception signal production part 11 Movement speed estimation part 12 Movement distance estimation part 13 Virtual reception signal calculating part 14 Reception signal synthetic | combination part 21 Decoding part 22 Display part 31- 39 Demodulator 41 Orthogonal Demodulator 42 Orthogonal Demodulator 43 FFT Unit 44 Symbol Synchronizer 45 Transmission Path Estimator 46 Equalizer 47 Error Corrector 51 Received Signal Weight Determining Unit 52 Combining Operation Unit 61 Selector 71 Selector 72 Comparison Determinator 73 Selector 81 Moving distance estimation unit 85 Error rate measurement unit 86 Comparison / determination unit 87 Selector 91 Demodulation unit 101 to 10K Antenna 111 to 11K Tuner 201 Modulation unit 202 Modulation parameter control unit 203 Instantaneous fading estimation unit 204 Demodulation unit 205 to 207 Switching unit 208 Interpolation calculation unit 209 Movement distance estimation unit 210 Received Signal Estimator 221-22K Antenna 230 Mobile 241 Modulation Parameter Estimator 242 Demodulator 243 Instantaneous Fading Estimator 244 Modulation Parameter Controller 245 Modulator 246 Switching Unit 261-26K Antenna 271 Interpolator 272 OFDM Receiver 273 P Part

Claims (22)

A receiving device for performing digital communication,
A virtual reception signal creation unit that creates a virtual reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A demodulation unit for performing demodulation,
The demodulator performs demodulation based on both one received signal of the plurality of received signals and the received signal created by the previous virtual received signal creating unit. A receiving apparatus that receives a transmission signal in which one symbol period is formed by a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
The demodulator
A symbol synchronization unit for recognizing the effective symbol period;
A Fourier transform unit for performing Fourier transform;
The symbol synchronization unit recognizes the one symbol period using one received signal among the plurality of received signals,
The receiving device according to claim 1, wherein the Fourier transform unit performs Fourier transform on the reception signal created by the virtual reception signal creation unit. A receiving apparatus that receives a transmission signal in which one symbol period is formed by a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
The demodulator
A symbol synchronization unit for recognizing the effective symbol period;
A Fourier transform unit for performing Fourier transform;
The symbol synchronization unit uses one of the plurality of reception signals as an input signal until the one symbol period is identified,
After recognizing the one symbol period, the received signal created by the virtual received signal creating unit is used as an input signal until the one symbol period cannot be recognized again.
The receiving device according to claim 1, wherein the Fourier transform unit performs Fourier transform on the reception signal created by the virtual reception signal creation unit. The demodulator
When the speed of the moving body is greater than a predetermined value, demodulation is performed based on the received signal created by the virtual received signal creating unit, and when the speed of the moving body is less than a certain value, the plurality of The receiving apparatus according to claim 1, wherein demodulation is performed based on one of the received signals. A receiving apparatus that receives a transmission signal in which one symbol period is formed by a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
A virtual reception signal creation unit that creates a reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A demodulation unit that performs demodulation using the reception signal created by the virtual reception signal creation unit,
In the virtual reception signal creation unit, the point stationary relative to the ground moves in the direction opposite to the moving direction of the moving body at the same speed as the moving body,
Return to the starting point for the moving body at a certain periodic time interval,
The receiving apparatus, wherein the predetermined periodic time interval is made different before and after recognizing the timing of the one symbol period. A receiving device for performing digital communication,
A virtual reception signal creation unit that creates a virtual reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A received signal combining unit that generates a signal that is combined or selected and received using at least two received signals of the plurality of received signals; and
A demodulation unit that performs demodulation,
The demodulator performs demodulation based on both the diversity received reception signal and the reception signal created by the previous virtual reception signal creation unit. A receiving apparatus that receives a transmission signal in which one symbol period is formed by a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
The demodulator
A symbol synchronization unit for recognizing the effective symbol period;
A Fourier transform unit for performing Fourier transform;
The symbol synchronization unit recognizes the one symbol period using the diversity received signal,
The receiving apparatus according to claim 6, wherein the Fourier transform unit performs Fourier transform on the reception signal created by the virtual reception signal creation unit. A receiving apparatus that receives a transmission signal in which one symbol period is formed by a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
The demodulator
A symbol synchronization unit for recognizing the effective symbol period;
A Fourier transform unit for performing Fourier transform;
The symbol synchronization unit uses the diversity received signal as an input signal until the one symbol period is identified,
After recognizing the one symbol period, the received signal created by the virtual received signal creating unit is used as an input signal until the one symbol period cannot be recognized again.
The receiving apparatus according to claim 6, wherein the Fourier transform unit performs Fourier transform on the reception signal created by the virtual reception signal creation unit. The demodulator
When the speed of the moving body is greater than a predetermined value, demodulation is performed based on the received signal created by the virtual received signal creating unit, and when the speed of the moving body is less than the predetermined value, the diversity reception is performed. The receiving apparatus according to claim 6, wherein demodulation is performed based on the received signal. A receiving device for performing digital communication,
A plurality of tuners for selecting signals in a desired frequency band from reception signals received via a plurality of antennas;
A virtual reception signal creation unit that creates a virtual reception signal at a point relatively stationary with respect to the ground using the reception signals selected by the plurality of tuners;
A demodulator for demodulating;
A decoding unit that decodes the demodulated signal demodulated by the previous demodulation unit;
A display unit for outputting audio or video of the signal decoded by the decoding unit,
The demodulator performs demodulation based on both a received signal received via one of the plurality of tuners and a received signal created by the previous virtual received signal creating unit. A receiving apparatus that receives a transmission signal in which one symbol period is formed by a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
A plurality of tuners for selecting signals in a desired frequency band from reception signals received via a plurality of antennas;
Using the received signals selected by the plurality of tuners, a virtual received signal creating unit that creates a received signal at a point stationary relative to the ground;
A demodulation unit that performs demodulation using the reception signal created by the virtual reception signal creation unit;
A decoding unit for decoding the demodulated signal demodulated by the demodulation unit;
A display unit for outputting audio or video of the signal decoded by the decoding unit,
In the virtual reception signal creation unit, the point stationary relative to the ground moves in the direction opposite to the moving direction of the moving body at the same speed as the moving body with respect to the moving body.
Return to the starting point for the moving body at a certain periodic time interval,
The receiving apparatus, wherein the predetermined periodic time interval is made different before and after recognizing the timing of the one symbol period. A receiving device for performing digital communication,
A plurality of tuners for selecting signals in a desired frequency band from reception signals received via a plurality of antennas;
A virtual reception signal creation unit that creates a virtual reception signal at a point relatively stationary with respect to the ground using the reception signals selected by the plurality of tuners;
A received signal combining unit that generates a signal that is combined or selected and received using at least two received signals of the plurality of received signals; and
A demodulator for demodulating;
A decoding unit that decodes the demodulated signal demodulated by the previous demodulation unit;
A display unit for outputting audio or video of the signal decoded by the decoding unit,
The demodulator performs demodulation based on both of the diversity received reception signal and the reception signal created by the previous virtual reception signal creation unit.   The receiving device according to claim 10, further comprising controlling or selecting a distance between the plurality of antennas according to tuning information of the tuner. A receiving method for performing digital communication,
A virtual reception signal creation step of creating a virtual reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A demodulation step for performing demodulation,
The demodulation method, wherein the demodulation step performs demodulation based on both one reception signal of the plurality of reception signals and the reception signal created in the previous virtual reception signal creation step. A receiving method for receiving a transmission signal in which one symbol period is formed by a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
A virtual reception signal creation step of creating a reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A demodulation step for performing demodulation using the reception signal created in the virtual reception signal creation step,
In the virtual reception signal creation step, the point that is stationary relative to the ground moves at the same speed as the moving body in the direction opposite to the moving direction of the moving body with respect to the moving body.
Return to the starting point for the moving body at a certain periodic time interval,
The reception method, wherein the predetermined periodic time interval is made different before and after recognizing the timing of the one symbol period. A receiving method for performing digital communication,
A virtual reception signal creation step of creating a virtual reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A received signal combining step of creating a signal that is received by combining or selecting diversity using at least two received signals of the plurality of received signals; and
A demodulation step for performing demodulation,
The demodulating step performs demodulation based on both the diversity received reception signal and the reception signal created in the previous virtual reception signal creation step. A receiving circuit for performing digital communication,
A virtual received signal creation circuit that creates a virtual received signal at a point relatively stationary with respect to the ground using a plurality of received signals;
A demodulation circuit for performing demodulation,
The demodulator circuit performs demodulation based on both one received signal of the plurality of received signals and a received signal created by the previous virtual received signal creating circuit. A receiving circuit that receives a transmission signal in which one symbol period is formed of a guard period and an effective symbol period, and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. There,
A virtual received signal creation circuit that creates a received signal at a point relatively stationary with respect to the ground using a plurality of received signals;
A demodulation circuit that performs demodulation using the reception signal created by the virtual reception signal creation circuit, and
In the virtual reception signal generation circuit, the point that is relatively stationary with respect to the ground moves at the same speed as the moving body in a direction opposite to the moving direction of the moving body,
Return to the starting point for the moving body at a certain periodic time interval,
The receiving circuit, wherein the predetermined periodic time interval is made different before and after recognizing the timing of the one symbol period. A receiving circuit for performing digital communication,
A virtual received signal creation circuit that creates a virtual received signal at a point relatively stationary with respect to the ground using a plurality of received signals;
A received signal combining circuit that generates a signal that is combined or selected and received using at least two received signals among the plurality of received signals; and
A demodulation circuit for performing demodulation,
The demodulator circuit performs demodulation based on both the diversity received reception signal and the reception signal created by the previous virtual reception signal creation circuit. A program for receiving processing in digital communication,
A virtual reception signal creation step of creating a virtual reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A demodulation step for performing demodulation,
The demodulating step performs demodulation based on both one received signal of the plurality of received signals and the received signal created in the previous virtual received signal creating step. A reception process for receiving a transmission signal in which one symbol period is formed by a guard period and an effective symbol period and a part of the signal of the effective symbol period is copied to the guard period in order to have periodicity within the symbol. A program to perform,
A virtual reception signal creation step of creating a reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A demodulation step for performing demodulation using the reception signal created in the virtual reception signal creation step,
In the virtual reception signal creation step, the point that is stationary relative to the ground moves at the same speed as the moving body in the direction opposite to the moving direction of the moving body with respect to the moving body.
Return to the starting point for the moving body at a certain periodic time interval,
The program in which the predetermined periodic time interval is made different before and after recognizing the timing of the one symbol period. A program for receiving processing in digital communication,
A virtual reception signal creation step of creating a virtual reception signal at a point relatively stationary with respect to the ground using a plurality of reception signals;
A received signal combining step of creating a signal that is combined or selected diversity received using at least two or more received signals of the plurality of received signals; and
A demodulation step for performing demodulation,
The demodulating step performs demodulation based on both the diversity received reception signal and the reception signal created in the previous virtual reception signal creation step.

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