JP2007158424A - Diversity reception method and receiver utilizing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce deterioration in reception quality when a multicarrier signal to be received is changed over. <P>SOLUTION: A selector 12 selects one of a plurality of received multicarrier signals. An equalization processor 18 derives a transmission path estimation value to a pilot signal contained in the selected multicarrier signal. The equalization processor 18 executes interpolation in the direction of a series and that in the direction of a carrier, thus deriving the transmission path estimation value to a data signal contained in the multicarrier signal. The equalization processor 18 reproduces the data signal contained in the multicarrier signal while the derived transmission path estimation value is used. When selection is changed over between adjacent pilot signals in one system, the equalization processor 18 stops the interpolation in the direction of the series when the equalization processor 18 derives the transmission path estimation value to a plurality of data signals arranged between the adjacent pilot signals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to diversity reception technology, and more particularly to a diversity reception method for receiving multicarrier signals by a plurality of antennas and a receiving apparatus using the same.

In mobile communication, terrestrial digital broadcasting, and the like, an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, which is one of multicarrier methods, is used. On the other hand, in mobile communication, received power varies greatly due to the influence of multipath fading. For this reason, when the OFDM modulation scheme is used for mobile communication, diversity reception technology is used as a countermeasure against multipath fading (see, for example, Patent Document 1).
JP 2005-191801 A

  In mobile communications, a channel estimation value for a data signal arranged between pilot signals is derived by interpolating a channel estimation value for a pilot signal. At this time, if the selection of multicarrier signals is switched by selection diversity, discontinuity of transmission path estimation values occurs before and after the switching. This is because the antennas receiving the multicarrier signal before switching and the multicarrier signal after switching are different. If the channel estimation values before and after switching cannot be properly derived due to such discontinuities, the quality of the received signal deteriorates every time switching is performed.

  The present inventor has recognized the above situation and made the present invention, and an object of the present invention is to provide a diversity technique for reducing deterioration in reception quality when a multicarrier signal to be received is switched.

  In order to solve the above-described problem, in a receiving apparatus according to an aspect of the present invention, a sequence in which a pilot signal is periodically inserted between data signals is arranged in at least one of the plurality of carriers, and the plurality of carriers Among the plurality of antennas, and a selection unit for selecting one of the plurality of multicarrier signals received by the reception unit. And a derivation unit for deriving a channel estimation value for the pilot signal included in the multicarrier signal selected by the selection unit, and an interpolation in the direction of the sequence for the channel estimation value derived by the derivation unit; The interpolation unit for deriving the transmission path estimation value for the data signal included in the multicarrier signal by performing the interpolation in the carrier direction and the interpolation unit While using the channel estimation value, and a reproduction unit for reproducing the data signal included in the multicarrier signal. When the selection unit switches between adjacent pilot signals in one series, the interpolation unit estimates transmission paths for a plurality of data signals arranged between the adjacent pilot signals. , The interpolation in the direction of the sequence is stopped.

  According to this aspect, when selection is switched between adjacent pilot signals, the interpolation in the direction of the sequence is stopped, but the interpolation in the direction of the carrier is continued, thereby suppressing the deterioration of the reception quality. it can.

  You may further provide the estimation part which estimates the moving speed of a receiver. The interpolation unit performs interpolation such that transmission path estimation values for each of a plurality of data signals arranged between adjacent pilot signals are different from each other as interpolation in the direction of the sequence. When the selection unit switches between adjacent pilot signals in the sequence and the moving speed estimated in the estimated value is slower than the threshold value, the plurality of data signals As the channel estimation value for each of the above, the channel estimation values for the pilot signals included in the same multicarrier signal may be duplicated.

  The “interpolation in which the transmission path estimation values are different from each other” may be interpolation having different values as a result, and includes, for example, linear interpolation or interpolation using a higher-order function. In this case, if the moving speed is slow, the interpolation in the carrier direction is executed while using the value replicated in the direction of the sequence, so that deterioration of the reception quality can be suppressed. “Duplicate” corresponds to step interpolation.

  As the movement speed estimated in the estimated value becomes faster, the interpolating unit is a data signal that should replicate the channel estimation value for the pilot signal included in the same multicarrier signal as the channel estimation value for the plurality of data signals. May be reduced. In this case, since the number of estimated channel values to be replicated is changed according to the moving speed, correction according to the moving speed can be executed.

  The selection unit also selects another multicarrier signal from among the plurality of multicarrier signals, and the derivation unit and the interpolation unit also select another multicarrier signal selected by the selection unit in the selection unit. The same processing as any one of the multicarrier signals is performed, and the reproduction unit reproduces the data signal, and any one of the multicarrier signals selected by the selection unit and another multicarrier signal selected by the selection unit when reproducing the data signal. Combining diversity with respect to and may be performed. In this case, since the combining diversity is executed, the reception quality can be improved.

  Another aspect of the present invention is a diversity reception method. In this method, a sequence in which a pilot signal is periodically inserted between data signals is arranged in at least one of the plurality of carriers, and a sequence of data signals is arranged in the remaining of the plurality of carriers. A step of receiving a multicarrier signal by each of a plurality of antennas, a step of selecting one of the plurality of received multicarrier signals, and deriving a channel estimation value for a pilot signal included in the selected multicarrier signal And performing interpolation in the direction of the sequence and interpolation in the direction of the carrier on the derived transmission path estimation value, thereby obtaining a transmission path estimation value for the data signal included in the multicarrier signal. The data signal included in the multi-carrier signal is regenerated while using the deriving step and the derived channel estimation value. And a step of. The step of deriving a transmission path estimation value for a data signal includes a plurality of data arranged between adjacent pilot signals when selection switching is performed between adjacent pilot signals in one series. When deriving a channel estimation value for a signal, the interpolation in the direction of the sequence is stopped.

  A step of estimating a moving speed of the receiving device, and the step of deriving a transmission path estimation value for the data signal is performed for each of a plurality of data signals arranged between adjacent pilot signals as interpolation in a sequence direction. Interpolation is performed so that the channel estimation values are different from each other, and the selection is switched between adjacent pilot signals in one series, and the estimated movement When the speed is slower than the threshold value, the transmission path estimation value for the pilot signal included in the same multicarrier signal may be duplicated as the transmission path estimation value for each of the plurality of data signals.

  The step of deriving the transmission path estimation value for the data signal includes the transmission path estimation value for the pilot signal included in the same multicarrier signal as the transmission path estimation value for the plurality of data signals as the estimated moving speed increases. The number of data signals to be copied may be reduced.

  In the selecting step, another multicarrier signal is also selected from among a plurality of multicarrier signals, and the step of deriving the channel estimation value for the pilot signal and the step of deriving the channel estimation value for the data signal are selected. For the other multicarrier signal, the same processing as that for any one of the selected multicarrier signals is performed, and the step of reproducing is performed when any of the selected multicarrier signals is reproduced. And combining diversity with other selected multi-carrier signals.

  It should be noted that any combination of the above-described constituent elements and a representation obtained by converting the expression of the present invention between methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to the present invention, it is possible to reduce deterioration of reception quality when a multicarrier signal to be received is switched.

  Before describing the present invention in detail, an outline will be described. An embodiment of the present invention relates to a receiving apparatus compatible with the ISDB-T system which is one of terrestrial digital television standards. The ISDB-T method uses an OFDM modulation method which is one of multicarrier modulations. Here, “5617” subcarriers are used, and a pilot signal is inserted into one of the three subcarriers. Further, one pilot signal is inserted into four symbols in one subcarrier. In order to perform demodulation, the receiving apparatus estimates transmission path characteristics for the pilot signal. Furthermore, after interpolating the estimated transmission path characteristics in the time direction, the receiving apparatus also estimates the transmission path characteristics for the data signal by interpolating in the frequency direction. That is, the transmission path characteristic for the data signal is estimated by using interpolation.

  Under such circumstances, when any of the multicarrier signals received by the plurality of antennas is selected, the selection may be switched between the two pilot signals in the subcarrier in which the pilot signal is arranged. . At that time, the transmission path characteristics estimated in each of the two pilot signals are values for different transmission paths. If the transmission path characteristic for the data signal arranged between two pilot signals is derived while using such transmission path characteristics, the derived transmission path characteristic becomes inaccurate. As a result, reception characteristics deteriorate. In order to cope with this, the receiving apparatus according to the present embodiment operates as follows.

  When the selection cannot be switched between the two pilot signals in the subcarrier in which the pilot signal is arranged, the receiving apparatus performs interpolation in the time direction and interpolation in the frequency direction. On the other hand, when the selection is switched between the two pilot signals in the subcarrier in which the pilot signal is arranged, the receiving apparatus stops the interpolation in the time direction and executes only the interpolation in the frequency direction.

  In the following description, the received signal is a signal sequence using multicarriers. In this specification, a signal sequence may be referred to as a multicarrier signal, and a signal of an arbitrary symbol may be referred to as a multicarrier signal. Both shall be used without specific indication.

  FIG. 1 shows a configuration of a receiving apparatus 100 according to an embodiment of the present invention. The receiving apparatus 100 includes a first antenna 10a, a second antenna 10b, a fourth antenna 10d, which are collectively referred to as an antenna 10, a selection unit 12, and a tuner 14, a first tuner 14a, a second tuner 14b, and an FFT unit 16. The first FFT unit 16a, the second FFT unit 16b, which are collectively referred to, the first equalization processing unit 18a, the second equalization processing unit 18b, which are collectively referred to as the equalization processing unit 18, the combining unit 20, the specifying unit 22, and the control unit 24 Including.

  The antenna 10 receives a radio frequency signal via a transmission path. Here, the radio frequency signal is a multicarrier signal. As described above, since the ISDB-T system is an object of description, the number of subcarriers included in the multicarrier signal is “5617”, and a pilot signal is arranged in a scattered format in the multicarrier signal. . That is, in a multicarrier signal, a sequence in which a pilot signal is periodically inserted between data signals is arranged in at least one of the plurality of subcarriers, and the data signal is formed in the remaining of the plurality of subcarriers. A series is arranged. Since the number of antennas 10 is “4”, four multicarrier signals are received. Since the four multicarrier signals are transmitted from a single transmission device (not shown), they include the same signal component, but are received through different transmission paths, and therefore have different values.

  FIG. 2 shows a configuration of a multicarrier signal received by the antenna 10. The horizontal axis in the figure indicates “subcarrier number”, and the vertical axis in the figure indicates “symbol number”. The “subcarrier number” is a number assigned to identify a subcarrier. For example, a subcarrier number having a small value is assigned to a subcarrier having a low frequency. The “symbol number” is a number assigned to identify the order of input symbols. For example, a symbol number having a smaller value is assigned to a previously input symbol. “P” in the figure indicates the pilot signal described above, and “D” in the figure indicates a data signal. As shown in the figure, in the symbol number “0”, pilot signals are arranged on discrete subcarriers as in subcarrier numbers “0” and “12”.

  In addition, in the symbol number “1”, pilot signals are arranged like the subcarrier numbers “3” and “15”. That is, if the symbol numbers are different, the subcarrier on which the pilot signal is to be arranged is shifted. Further, in the symbol number “4”, pilot signals are arranged like the subcarrier numbers “0” and “12”. This arrangement is the same as in the case of symbol number “0”, and the subcarriers on which pilot signals are to be arranged periodically become the same subcarriers. Returning to FIG.

  The selection unit 12 receives a plurality of multicarrier signals respectively received by the plurality of antennas 10 and selects two multicarrier signals from the plurality of multicarrier signals. Here, at least two multicarrier signals specified by the specifying unit 22 described later are selected. Note that when the selection unit 12 switches the selection of one of the two multicarrier signals, the selection unit 12 does not switch the selection of the other. Further, the selection unit 12 outputs at least two selected multicarrier signals.

  The tuner 14 converts the frequency of the received multicarrier signal from a radio frequency to a baseband. At this time, the tuner 14 selects a program of a channel corresponding to the broadcast station to be viewed from the received multicarrier signal by fixing the reception frequency to a predetermined value. Note that “program” refers to a program that is being broadcast, but here the contents thereof are also included. That is, the program may indicate broadcast audio, broadcast video, and combinations thereof. The first tuner 14a and the second tuner 14b execute similar processing in parallel.

  Here, the tuner 14 determines a gain value for two input multicarrier signals by AGC (not shown), and adjusts the gain of the amplifier included in the tuner 14 according to the determined value. Since AGC may be realized by a known technique, the description thereof is omitted here. The AGC determines a common gain value for the amplifiers included in each of the first tuner 14a and the second tuner 14b. Therefore, the intensity ratio between the two multicarrier signals selected by the selection unit 12 and the ratio between the two multicarrier signals output from the tuner 14 have the same value.

  The FFT unit 16 performs FFT on the multicarrier signal from the tuner 14. As a result, the signal frequency-converted to baseband in the tuner 14 is converted into a frequency domain signal. As described above, the frequency domain signal has “5617” subcarriers.

  The equalization processing unit 18 estimates values of transmission path characteristics (hereinafter referred to as “transmission path coefficients”) for the subcarriers including the pilot signals, from the pilot signals included in each of the two multicarrier signals. . For this purpose, the equalization processing unit 18 extracts subcarriers in which pilot signals are arranged from the multicarrier signal. Here, since the subcarrier in which the pilot signal is arranged is defined in advance, the equalization processing unit 18 performs extraction while using the definition. Further, the channel coefficient estimation is performed using the extracted signal value and the pilot signal value in the subcarrier. The estimation of the channel coefficient may be performed by a known technique. For example, the channel coefficient is estimated by complex multiplication of the inverse value of the pilot signal and the value of the signal on the extracted subcarrier.

  Subsequently, the equalization processing unit 18 estimates the channel coefficient for the subcarrier including the data signal based on the derived channel coefficient. For this purpose, the equalization processing unit 18 performs interpolation on the derived transmission line coefficient. As the interpolation, the selection unit 12 switches the selection between adjacent pilot signals in one subcarrier including the pilot signal (hereinafter referred to as “switching process”), and the case where the selection is not performed (hereinafter referred to as “switching process”). , “Normal processing”), and different processing is executed.

  In the normal processing, the equalization processing unit 18 interpolates transmission path coefficients that should appear periodically in units of one subcarrier. That is, the equalization processing unit 18 interpolates the transmission path coefficient in the time direction. The time direction can also be said to be the direction of the sequence. For example, when the channel coefficient is derived for every four symbols, the equalization processing unit 18 derives the channel coefficient for the symbols between them by interpolation. Here, linear interpolation is used for interpolation, but is not limited thereto, and a predetermined approximate expression may be used. Further, extrapolation may be performed while using channel coefficients at other symbol numbers.

  Through the above processing, continuous channel coefficients are derived in the subcarriers in which pilot signals are arranged. Further, the equalization processing unit 18 interpolates the transmission path coefficient in the frequency direction. The frequency direction can also be said to be the subcarrier direction. More specifically, the equalization processing unit 18 derives the transmission path coefficient for each subcarrier included in the multicarrier signal by interpolating the transmission path coefficient for the subcarrier including the pilot signal. This corresponds to calculating the transmission path coefficient for each of a plurality of multicarrier signals in units of subcarriers. As a result, the channel coefficient for the data signal included in the multicarrier signal is derived.

  On the other hand, in the switching process, the equalization processing unit 18 stops the interpolation in the time direction. That is, the equalization processing unit 18 performs only interpolation in the frequency direction. Further, the data signal included in the multicarrier signal is reproduced while using the channel coefficient derived by the equalization processing unit 18 and interpolation. Such playback may be described as follows. The equalization processing unit 18 performs weighting on each of the two multicarrier signals from the FFT unit 16 by the transmission path coefficient. At this time, weighting in units of subcarriers is executed. Note that the complex conjugate value of the transmission path coefficient is used for weighting. The first equalization processing unit 18a and the second equalization processing unit 18b execute the above processing independently. The synthesizer 20 performs carrier unit synthesis on the two multicarrier signals from the equalization processor 18. The synthesis here corresponds to the maximum ratio synthesis.

  The identifying unit 22 determines two to be selected from among a plurality of multicarrier signals received by each of the plurality of antennas 10. In addition, the specifying unit 22 notifies the selection unit 12 of the determined two. Here, the specifying unit 22 measures the reception strengths of the two multicarrier signals output from the tuner 14 and further measures the strength ratio. The strength is, for example, electric power. When the intensity ratio exceeds a predetermined threshold, the specifying unit 22 switches the multicarrier signal having the lower intensity to another signal series. For example, a multicarrier signal from the first antenna 10a (hereinafter referred to as “first multicarrier signal”) and a multicarrier signal from the second antenna 10b (hereinafter referred to as “second multicarrier signal”) are selected. Assume the situation.

  The identifying unit 22 determines switching of the second multicarrier signal. At that time, the specifying unit 22 uses a multicarrier signal from the third antenna 10c (hereinafter referred to as “third multicarrier signal”) and a multicarrier signal from the fourth antenna 10d (hereinafter referred to as “fourth multicarrier signal”). ), A multi-carrier signal having a longer unselected period is selected as a switching destination candidate. As described above, the specifying unit 22 does not switch the other when switching one of the two multicarrier signals. As a result, at least one is constantly input to the specifying unit 22. Further, when executing the switching, the specifying unit 22 outputs the fact to the equalization processing unit 18 as control information.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a reception function loaded in the memory. The functional block realized by those cooperation is drawn. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 3 shows the configuration of the first equalization processing unit 18a. The first equalization processing unit 18a includes a derivation unit 30, a first interpolation unit 32, a second interpolation unit 34, and a reproduction unit 36. The second equalization processing unit 18b has the same configuration.

  The deriving unit 30 derives a transmission path coefficient for the pilot signal included in the multicarrier signal input from the first FFT unit 16a in FIG. The derivation of the transmission path coefficient may be executed as described above.

  As a normal process, the first interpolation unit 32 performs interpolation in the direction of the sequence and interpolation in the direction of the subcarrier with respect to the transmission path coefficient derived by the deriving unit 30. By these interpolations, the first interpolation unit 32 derives a transmission path coefficient for the data signal included in the multicarrier signal. FIG. 4 shows the principle of interpolation processing by the first interpolation unit 32. In FIG. 4, symbol numbers and subcarrier numbers are shown in the same manner as in FIG. Here, for clarity of explanation, the pilot signal “P” is surrounded by a square mark. Further, in order to explain the interpolation processing, attention is paid to subcarrier numbers “12” to “15”. In subcarrier number “12”, a signal sequence including a pilot signal is arranged.

  The first interpolation unit 32 derives a transmission path coefficient for a data signal arranged between them while using transmission path coefficients for a plurality of continuous pilot signals. For example, the channel coefficients for symbol numbers “1” to “3” are derived from the channel coefficients for symbol numbers “0” and “4”. Here, it is assumed that interpolation is performed and linear interpolation is performed. The above processing is executed for the signal sequence including the subcarrier numbers “0”, “3”, “6”, “9”, “15”, etc., that is, the pilot signal. As a result, a channel coefficient is derived for one signal sequence among the three subcarriers. In FIG. 4, the data signal from which the transmission path coefficient is derived by interpolation in the direction of the sequence is surrounded by circles. Returning to FIG.

  Subsequently, the first interpolation unit 32 performs interpolation in the subcarrier direction. In FIG. 4, for symbol number “1”, interpolation is performed on the transmission path coefficient of subcarrier number “12” and the transmission path coefficient of subcarrier number “15”, and subcarrier numbers “13” and “ 14 "channel coefficients are derived respectively. Here, it is assumed that interpolation is performed and linear interpolation is performed. Note that the interpolation may be not a linear interpolation but an interpolation using a higher-order function. The above processing is executed for a signal sequence including only data signals. As a result, channel coefficients are derived for the remaining signal series. In FIG. 4, the data signal from which the channel coefficient is derived by interpolation in the subcarrier direction is surrounded by triangles. Such an interpolation can be said to be an interpolation in which transmission path estimation values for each of a plurality of data signals arranged between adjacent pilot signals are different from each other. Returning to FIG.

  As the switching process, the second interpolation unit 34 stops the interpolation in the direction of the sequence with respect to the transmission path coefficient derived by the deriving unit 30, and executes the interpolation in the direction of the subcarrier. By this interpolation, the second interpolation unit 34 derives a transmission path coefficient value for the data signal included in the multicarrier signal. FIG. 5 is a diagram illustrating the principle of the interpolation processing by the second interpolation unit 34. Selection switching is executed at the timing of symbol number “5” in FIG. Therefore, the switching process before the switching timing is executed for symbol numbers “2” to “4” for subcarrier number “3”. That is, the period of three symbols before the switching timing is defined as the period for the switching process. Note that the period for the switching process is different if the symbol into which the pilot signal is inserted is different. For the subcarrier number “0”, the interpolation in the sequence direction is executed using the transmission path coefficient at the symbol number “0” and the transmission path coefficient at “4”. The data signal corresponding to the derived transmission line coefficient is indicated by a circle as described above.

  On the other hand, in subcarrier number “3”, the transmission path coefficient for symbol number “1” and the transmission path coefficient for symbol number “9” are received by antennas 10 of FIG. Therefore, the interpolation in the sequence direction is not executed for the symbol numbers “2” to “4”. For the symbol number “2”, interpolation in the subcarrier direction is performed on the transmission path coefficient at the subcarrier number “0” and the transmission path coefficient at the subcarrier number “6”. ”To“ 5 ”. The data signal for the derived transmission line coefficient is indicated by a triangle as described above. The above processing is similarly executed after the selection is switched, that is, after the symbol number “6”. Returning to FIG.

  The reproducing unit 36 performs equalization processing on the multicarrier signal while using the transmission path coefficient derived by the first interpolation unit 32 or the second interpolation unit 34. Note that the equalization processing is executed in units of subcarriers. In addition, the reproduction unit 36 performs weighting on the multicarrier signal while using the transmission path coefficient derived by the first interpolation unit 32 or the second interpolation unit 34.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a reception function loaded in the memory. The functional block realized by those cooperation is drawn. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The operation of the receiving apparatus 100 having the above configuration will be described. FIG. 6 is a flowchart illustrating a procedure of reception processing by the reception device 100. The antenna 10 receives a plurality of multicarrier signals, respectively (S10). The selection unit 12 selects two multicarrier signals from the received multicarrier signals (S12). The FFT unit 16 performs FFT processing on the two selected multicarrier signals (S14). The equalization processing unit 18 derives transmission path characteristics for each of the two multicarrier signals subjected to the FFT processing (S16). In addition, the equalization processing unit 18 performs equalization processing on each of the two multicarrier signals while using the derived transmission path characteristics (S18). The combining unit 20 performs diversity combining of the two equalized multicarrier signals (S20).

  FIG. 7 is a flowchart showing a procedure for selecting a multicarrier signal. This corresponds to step 12 in FIG. The tuner 14 amplifies the two multicarrier signals with a common gain (S42). The identifying unit 22 derives an intensity ratio for the two multicarrier signals (S44). The identifying unit 22 determines whether it is necessary to switch the multicarrier signal by comparing the derived intensity ratio with a threshold value (S50). As a result of the comparison, if the intensity ratio is smaller than the predetermined threshold value, the specifying unit 22 does not switch the selection of the multicarrier signal (N in S50) and ends the processing. On the other hand, if the intensity ratio is equal to or greater than the threshold value, it is necessary to switch the selection of the multicarrier signal (Y in S50), and the specifying unit 22 outputs the control signal to the equalization processing unit 18 and the combining unit 20. (S52). Furthermore, the selection unit 12 switches the multicarrier signal having the lower strength to another multicarrier signal (S54).

  FIG. 8 is a flowchart showing a procedure for deriving a transmission path estimation value. This corresponds to step 16 in FIG. As a premise, it is assumed that the deriving unit 30 has already estimated the channel coefficient for the pilot signal. If there is no switching between consecutive pilot signals (N in S60), the first interpolation unit 32 performs interpolation in the sequence direction (S64), and performs interpolation in the subcarrier direction (S66). On the other hand, if there is switching between continuous pilot signals (Y in S60), the second interpolation unit 34 performs interpolation in the subcarrier direction (S62).

  FIG. 9 is a flowchart showing the procedure of diversity combining. The synthesizer 20 checks for the presence of a control signal (S142). When there is no control signal (N in S142), the combining unit 20 performs diversity combining of the two multicarrier signals equalized in the equalization processing unit 18 by the maximum ratio combining method (S144). When there is a control signal (Y in S142), the synthesis unit 20 determines whether or not the input multicarrier signal is a signal in the switching period (S146). If the input multicarrier signal is not a signal in the switching period (N in S146), the combining unit 20 performs diversity combining of the two multicarrier signals equalized in the equalization processing unit 18 by the maximum ratio combining method (S144). ). When the input multicarrier signal is a signal in the switching period (Y in S146), the combining unit 20 does not perform combining (S148), selects the multicarrier signal that has not been switched, and outputs it. To do. That is, during the switching period, single branch reception is performed by using only the multicarrier signal that has not been switched.

  Hereinafter, modifications of the embodiment will be described. In the normal processing in the embodiment, in order to derive a transmission line coefficient for a data signal, interpolation in the time direction and interpolation in the frequency direction are executed. In the switching process, interpolation in the frequency direction is executed. In the modification, the moving speed of the receiving apparatus 100 is measured, and the interpolation method in the switching process is switched according to the measured moving speed. If the moving speed is high, the correlation between the transmission path coefficients between symbols is small. Therefore, the switching process in the embodiment is executed. On the other hand, if the moving speed is slow, the correlation between the transmission path coefficients between symbols increases. Therefore, the channel coefficient for the data signal is derived by duplicating the channel coefficient for the pilot signal as interpolation in the time direction. Following this, interpolation in the frequency direction is performed.

  FIG. 10 shows another configuration of the first equalization processing unit 18a. In the first equalization processing unit 18a of FIG. 10, a third interpolation unit 40 is added to the first equalization processing unit 18a of FIG. The other configuration is the same as that of the first equalization processing unit 18a in FIG.

  The specifying unit 22 (not shown) estimates the moving speed of the receiving device 100. The movement speed may be estimated by an arbitrary technique. For example, when the receiving device 100 is provided in an automobile, the moving speed may be estimated by receiving the result measured by the automobile speedometer. Further, the movement speed may be estimated from the signal received by the antenna 10. At that time, the Doppler frequency is measured. Further, the specifying unit 22 compares the estimated moving speed with a threshold value. When the moving speed is equal to or higher than the threshold value, the specifying unit 22 selects the second interpolation unit 34 during the switching process. On the other hand, when the moving speed is smaller than the threshold value, the specifying unit 22 selects the third interpolation unit 40 during the switching process.

  The third interpolation unit 40 performs sequence direction interpolation on the signal sequence in which the pilot signal is inserted between the plurality of data signals during the switching process. Interpolation is performed so as to duplicate the channel coefficient for the pilot signal included in the same multicarrier signal, that is, the pilot signal received by the same antenna 10, as the channel estimation value for each of the plurality of data signals. Is done. In addition, the third interpolation unit 40 performs interpolation in the subcarrier direction after performing interpolation in the sequence direction.

  FIG. 11 shows the principle of interpolation processing by the third interpolation unit 40. Also in FIG. 11, the selection is switched at the symbol number “5”. Therefore, the switching process is executed for symbol numbers “2” to “4” for subcarrier number “3” before the switching timing. For the subcarrier number “0”, the interpolation in the sequence direction is executed using the transmission path coefficient at the symbol number “0” and the transmission path coefficient at “4”.

  On the other hand, in the subcarrier number “3”, the channel coefficient at the symbol number “3” and the channel coefficient at the symbol number “9” are received by the antennas 10 of FIG. Therefore, the channel estimation at symbol number “1” is copied as it is as interpolation in the sequence direction from symbol numbers “2” to “4”. The data signal corresponding to the derived transmission line coefficient is indicated by a circle as described above. Further, as interpolation in the subcarrier direction, for the symbol number “2”, the transmission path coefficient in the subcarrier number “3” and the transmission path coefficient in the subcarrier number “6” are in the subcarrier direction. Interpolation is performed, and channel coefficients at subcarrier numbers “4” and “5” are derived. The data signal for the derived transmission line coefficient is indicated by a triangle as described above. The above processing is similarly executed after the selection is switched, that is, after the symbol number “6”. At this time, the channel estimation at symbol number “9” is copied as it is as interpolation in the sequence direction from symbol numbers “6” to “8” at subcarrier number “3”. That is, duplication is executed so as to go against the passage of time.

  12A and 12B show signals to be combined in the combining unit 20. FIG. 12 (a) shows a method of interpolating transmission line coefficients when focusing on one subcarrier in FIG. FIG. 12B shows a method of interpolating transmission path coefficients for another multicarrier signal in the case of FIG.

  In FIGS. 12A to 12B, the vertical axis represents the transmission path estimated value, and the horizontal axis represents time. A black circle indicates a transmission path estimation value for the pilot signal. The transmission path estimation value generally includes an I component and a Q component, but here, in order to simplify the description, this will be described as a power value.

  In FIG. 12A, a transmission line coefficient for a pilot signal (hereinafter referred to as “first pilot signal”) is indicated by a black square before the switching timing, and by a black square after the switching timing, The channel coefficient for the pilot signal (hereinafter referred to as “second pilot signal”) is shown. The white circles indicate the transmission path coefficients linearly interpolated by the first interpolation unit 32. A white square indicated before the switching timing is a transmission path coefficient obtained by duplicating the transmission path coefficient for the first pilot signal in the third interpolation unit 40. That is, this is the transmission line coefficient for the first data signal.

  What is indicated by a white square after the switching timing is a transmission path coefficient obtained by duplicating the transmission path coefficient for the second pilot signal in the third interpolation unit 40. That is, this is the transmission line coefficient for the second data signal. Further, the fact that the transmission line coefficient for the signal at the switching timing is not drawn indicates that the signal at the switching timing is not used for diversity combining in the combining unit 20 as will be described later. In FIG. 12B, the white circles indicate the transmission path coefficients linearly interpolated by the first interpolation unit 32.

  FIG. 13 is a flowchart showing a procedure for deriving a transmission path estimation value by the first equalization processing unit 18a. As a premise, it is assumed that the deriving unit 30 has already estimated the channel coefficient for the pilot signal. If there is no switching between continuous pilot signals (N in S200), the first interpolation unit 32 performs interpolation in the sequence direction (S210), and performs interpolation in the subcarrier direction (S212). On the other hand, if there is switching between consecutive pilot signals (Y in S200) and the moving speed is not slower than the threshold value (N in S202), the second interpolation unit 34 performs interpolation in the subcarrier direction. (S204). If the moving speed is slower than the threshold (Y in S202), the third interpolation unit 40 performs duplication in the sequence direction (S206), and performs interpolation in the subcarrier direction (S208).

  According to the embodiment of the present invention, when selection is switched between adjacent pilot signals, the interpolation in the direction of the sequence is stopped, so that transmission line coefficients corresponding to different transmission lines can be separately obtained. It can be processed. In addition, deterioration of reception quality can be suppressed by performing separate processing. Further, although correction in the direction of the sequence is stopped, since the interpolation in the direction of the subcarrier is continued, the influence of noise can be reduced. Moreover, since the influence of noise can be reduced, it is possible to suppress the deterioration of reception quality. In addition, when selection is not switched between adjacent pilot signals, interpolation with respect to the direction of the sequence and the direction of the subcarrier is performed, so that it is possible to suppress a reduction in reception quality. Also, stopping the processing in the direction of the sequence may use part of the processing for the direction of the sequence and the direction of the subcarrier, so that an increase in circuit scale can be suppressed. Also, if the moving speed is slow, interpolation in the carrier direction is performed while using a value duplicated in the direction of the sequence, so that deterioration in reception quality can be suppressed. Further, since the combining diversity is executed, the reception quality can be improved. Moreover, since the synthetic diversity is executed for each subcarrier, the confidence quality can be improved.

  Further, since the number of tuners is reduced as compared with the number of antennas, the cost can be reduced. In addition, since step interpolation is performed to derive transmission line coefficients for data signals before and after switching of multicarrier signals, transmission path coefficients before and after switching in a switched multicarrier signal can be appropriately interpolated. Further, even when the multicarrier signal is switched, it is possible to derive a transmission line coefficient with little deterioration of the received signal, and it is possible to improve the diversity gain despite the low cost configuration. In addition, since linear interpolation and step interpolation require a small amount of calculation, processing can be executed at high speed. In addition, since the multicarrier signal that has been switched is not used for combining diversity, it is possible to reduce the deterioration of quality that occurs at the time of switching. In addition, since the two multicarrier signals are amplified with a common gain, the intensity ratio between the two received multicarrier signals becomes a value close to that at the time of reception, so that the selection can be appropriately switched. Moreover, since the one with a bad reception condition is identified among the selected multicarrier signals, and the identified multicarrier signal is switched to another multicarrier signal, reception characteristics can be improved.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the receiving apparatus 100 receives a digital television broadcast program. However, the present invention is not limited to this. For example, the receiving apparatus 100 may receive a radio broadcast program, and may further receive a signal in a wireless LAN using an OFDM modulation scheme. An example of the latter is a wireless LAN in the IEEE 802.11a standard. At this time, since the arrangement of pilot signals is different from that in the embodiment, the processing content may be changed according to the arrangement. According to this modification, the receiving device 100 can be applied to various communication systems and broadcast systems. In addition, the effect by this invention becomes large, so that there are many subcarriers. That is, it is sufficient that the OFDM modulation method is used.

  In the embodiment of the present invention, the case where only the interpolation in the direction of the subcarrier is executed and the case where the replication in the direction of the sequence is executed are switched according to the moving speed. However, the present invention is not limited to this. For example, the identifying unit 22 may reduce the number of data signals whose replication path coefficients should be duplicated with respect to the third interpolation unit 40 as the estimated moving speed increases. That is, since the correlation between symbols changes according to the moving speed, the number of data signals to be duplicated is reduced so as to correspond to the change in correlation. In this case, since the number of transmission path coefficients to be duplicated is changed according to the moving speed, correction according to the moving speed can be executed. That is, the transmission path coefficient for the data signal may be derived from the transmission path coefficient for one pilot signal.

  In the embodiment of the present invention, the selection unit 12 selects two of the multicarrier signals received by the four antennas 10. However, the present invention is not limited to this. For example, one or three or more multicarrier signals may be selected. According to this modification, the number of antennas 10 and the number of multicarrier signals to be selected can be selected. Therefore, the number of antennas 10 is increased when high quality is required, and is selected when low cost is required. By reducing the number of multi-carrier signals, it is possible to respond flexibly to quality and cost requirements. That is, the number of multicarrier signals smaller than the number of antennas 10 may be selected.

  In the embodiment of the present invention, the identifying unit 22 identifies a multicarrier signal with poor reception status among the selected multicarrier signals and switches it to another multicarrier signal. However, the present invention is not limited to this. For example, the specifying unit 22 may monitor multicarrier signals received by the four antennas 10 and select multicarrier signals corresponding to the two antennas 10 having good reception states. According to this modification, since the multicarrier signals received by the four antennas 10 are monitored, the selection accuracy can be improved. That is, as a result, two multicarrier signals may be selected.

  In the embodiment of the present invention, the first pilot signal is the last received pilot signal before switching, and the second pilot signal is the first received pilot signal after switching. However, the present invention is not limited to this. For example, the first pilot signal may be a pilot signal received before switching, and the second pilot signal may be a pilot signal received after switching. Further, the first pilot signal and the second pilot signal do not need to be one signal. According to this modification, it is possible to increase the options for the method for deriving the transmission path estimation value for the first data signal and the second data signal.

  In the embodiment of the present invention, the combining unit 20 combines the two multicarrier signals with diversity. However, the present invention is not limited to this, and for example, there may be a case where synthesis is not executed and one multicarrier signal is used. According to this modification, the configuration of the synthesis unit 20 and the like can be deleted.

It is a figure which shows the structure of the receiver which concerns on the Example of this invention. It is a figure which shows the structure of the multicarrier signal received with the antenna of FIG. It is a figure which shows the structure of the 1st equalization process part of FIG. It is a figure which shows the principle of the interpolation process by the 1st interpolation part of FIG. It is a figure which shows the principle of the interpolation process by the 2nd interpolation part of FIG. It is a flowchart which shows the procedure of the reception process by the receiver of FIG. It is a flowchart which shows the procedure of selection of the multicarrier signal of FIG. It is a flowchart which shows the derivation | leading-out procedure of the transmission line estimated value of FIG. It is a flowchart which shows the procedure of the diversity synthetic | combination of FIG. It is a figure which shows another structure of the 1st equalization process part of FIG. It is a figure which shows the principle of the interpolation process by the 3rd interpolation part of FIG. 12A and 12B are diagrams illustrating signals to be combined in the combining unit in FIG. It is a flowchart which shows the derivation | leading-out procedure of the transmission line estimated value by the 1st equalization process part of FIG.

Explanation of symbols

  10 antenna, 12 selection unit, 14 tuner, 16 FFT unit, 18 equalization processing unit, 20 combining unit, 22 specifying unit, 24 control unit, 100 receiving apparatus.

Claims (5)

A multicarrier signal in which a sequence in which a pilot signal is periodically inserted between data signals is arranged in at least one of the plurality of carriers and a sequence of data signals is arranged in the remaining of the plurality of carriers. A receiver for receiving by each of a plurality of antennas;
A selection unit for selecting any of a plurality of multicarrier signals received by the reception unit;
A derivation unit for deriving a transmission path estimation value for a pilot signal included in the multicarrier signal selected by the selection unit;
By performing interpolation in the direction of the sequence and interpolation in the direction of the carrier on the transmission path estimation value derived by the deriving unit, the transmission path estimation value for the data signal included in the multicarrier signal An interpolation unit for deriving
A reproduction unit that reproduces the data signal included in the multicarrier signal while using the channel estimation value derived by the interpolation unit;
The interpolator is configured to transmit transmission paths for a plurality of data signals arranged between adjacent pilot signals when selection is switched between adjacent pilot signals in one series by the selector. A receiving apparatus characterized by stopping interpolation in the direction of a sequence when an estimated value is derived. An estimation unit for estimating a moving speed of the receiving device;
The interpolation unit performs interpolation so that transmission path estimation values for each of a plurality of data signals arranged between adjacent pilot signals are different from each other as interpolation in the direction of the sequence. When the selection unit switches between adjacent pilot signals in the sequence and the moving speed estimated in the estimated value is slower than a threshold value. 2. The receiving apparatus according to claim 1, wherein a transmission path estimation value for a pilot signal included in the same multicarrier signal is duplicated as a transmission path estimation value for each of the data signals.   The interpolation unit should replicate the transmission path estimation value for the pilot signal included in the same multicarrier signal as the transmission path estimation value for the plurality of data signals as the moving speed estimated in the estimation value increases. The receiving apparatus according to claim 2, wherein the number of data signals is reduced. The selection unit also selects another multicarrier signal from among a plurality of multicarrier signals,
The derivation unit and the interpolation unit also perform processing similar to the processing for any of the multicarrier signals selected by the selection unit for another multicarrier signal selected by the selection unit,
The reproduction unit, when reproducing a data signal, performs synthesis diversity on any multicarrier signal selected by the selection unit and another multicarrier signal selected by the selection unit. Item 4. The receiving device according to any one of Items 1 to 3. A multicarrier signal in which a sequence in which a pilot signal is periodically inserted between data signals is arranged in at least one of the plurality of carriers and a sequence of data signals is arranged in the remaining of the plurality of carriers. Receiving at each of a plurality of antennas;
Selecting one of the received multi-carrier signals;
Deriving a channel estimation value for a pilot signal included in the selected multicarrier signal;
Deriving a channel estimation value for the data signal included in the multicarrier signal by performing interpolation in the direction of the sequence and interpolation in the direction of the carrier on the derived channel estimation value; ,
Regenerating the data signal included in the multicarrier signal while using the derived transmission path estimation value,
The step of deriving a transmission path estimation value for the data signal includes a plurality of pilot signals arranged between adjacent pilot signals when selection switching is performed between adjacent pilot signals in one sequence. A diversity receiving method, wherein interpolation in the direction of a sequence is stopped when a channel estimation value for a data signal is derived.

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