JP4440282B2 - OFDM receiver - Google Patents

Description

  The present invention relates to an OFDM receiver having an OFDM demodulation technique for improving reception performance in OFDM (Orthogonal Frequency Division Multiplex) reception.

  When receiving in a transmission line having a delay spread of GI length or more or an SFN (Single Frequency Network) wave environment having a time difference of GI length or more, interference results other than the desired carrier are mixed in the Fourier transform result and the CN ratio is poor. There is a problem of becoming.

  A conventional OFDM demodulation technique performs AD conversion after down-converting a signal from an antenna element. For example, the FFT (Fast Fourier Transform) window position is controlled by BTR (Bit Timing Recovery) which is a clock recovery circuit, and the transmission path is estimated by the scattered pilot (hereinafter referred to as SP) for the FFT result. Thereafter, OFDM demodulation is performed by equalizing the transmission path result and the FFT result, and performing digital demodulation of each carrier such as error correction and multilevel QAM.

  For example, there is a receiving apparatus disclosed in Patent Document 1 as an OFDM receiving apparatus. This receiver effectively uses the GI section of the desired wave using two types of FFT sections.

JP 2003-318857 A

  In a conventional OFDM receiver, when receiving in a transmission line having a delay spread of GI length or more or an SFN wave environment having a time difference of GI length or more, the FFT result is obtained even if the optimum FFT section of the desired wave is extracted and FFT is performed. Is subjected to inter-symbol interference (hereinafter sometimes abbreviated as “ISI”) and inter-carrier interference, and as a result, the CN of each carrier of the received signal deteriorates, resulting in reception deterioration. Further, when the DU ratio of the delayed wave exceeding the GI length is close to 0 dB and fading fluctuation occurs, it is difficult to determine which wave to perform FFT as the desired wave.

  Also, the OFDM receiver disclosed in Patent Document 1 has a problem that reception degradation due to each ISI component is unavoidable when there is a delayed wave exceeding the GI length.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an OFDM receiving apparatus that does not cause reception deterioration even when a delay wave exceeding the GI length is mixed.

An OFDM receiver according to claim 1 of the present invention is an OFDM receiver that receives an OFDM signal having a guard interval, and sets a plurality of Fourier transform sections for the OFDM signal, and the plurality of Fourier transforms A Fourier transform processing unit that performs a plurality of Fourier transform processing in each section and obtains a plurality of Fourier transform processing results, and SP that is equalization processing by transmission path estimation using a pilot carrier for the plurality of Fourier transform processing results A TS data generation unit that performs TS processing and diversity combining processing to obtain TS data, and the Fourier transform processing unit suppresses intersymbol interference (ISI) components in each of a plurality of Fourier transform processing results. gastric line, the Fourier transform processing unit, said plurality of Fourier transform section A window function calculation means for performing window function calculation processing for multiplying the OFDM signals in the plurality of Fourier transform sections with each of the set window functions and obtaining a plurality of window function calculated signals, The window function calculation process includes a suppression process in which the influence is reduced during an ISI component existence period of the OFDM signal in each of the corresponding Fourier transform sections, and the OFDM receiver controls the Fourier transform unit, The system further includes control means for instructing a plurality of Fourier transform sections and controlling the contents of the window function calculation process, and the ISI suppression calculation process includes the window function calculation process.

  According to the first aspect of the present invention, the Fourier transform processing unit of the OFDM receiver performs ISI suppression calculation processing for suppressing the ISI component in each of the plurality of Fourier transform processing results.

  As a result, by obtaining TS data based on a plurality of Fourier transform processing results described above by the TS data generation unit, it is possible to suppress the ISI component even when there is a delayed wave exceeding the GI length. There is an effect that an OFDM receiver that does not occur can be obtained.

<Principle of the invention>
FIG. 8 is a block diagram showing a configuration of a general OFDM receiver. As shown in the figure, a general OFDM receiver includes an antenna unit 10, a time domain processing unit 1, an FFT interval extraction unit 2, an SP conversion unit 3, an FFT unit 4, an SP equalization unit 5, and an FEC ( The forward error correction unit 6 is connected in series.

  The time domain processing unit 1 performs AD conversion and band processing on a received signal obtained via the antenna unit 10 to obtain a time axis (serial) data string.

  The FFT section extraction means 2 extracts a section to be subjected to FFT from the time axis data string based on, for example, the FFT section enable signal EN indicating the FFT section information obtained by the above-described BTR or the like.

The SP conversion means 3 converts the extracted time-series serial data string in the FFT interval into a parallel data string of the number of FFT samples so as to perform FFT, and obtains an SP conversion result. The FFT means 4 performs an FFT on the SP conversion result and obtains an FFT result. The SP equalization means 5 estimates the transmission path from the scattered pilot carrier with respect to the FFT result, and performs carrier equalization. In the present specification, carrier equalization means _obtaining an equalization correction result Y _im described later.

The FEC unit 6 performs parallel-serial conversion on the equalization correction result Y _im by an internal _PS conversion function, and then performs deinterleaver, error correction, etc., and transport packet data (hereinafter referred to as “TS”). (May be abbreviated) generated and output.

  Next, the FFT interval indicated by the FFT interval enable signal EN will be described. The FFT interval ideally indicates an interval in which effective symbol length data is extracted from the head data position of the effective symbol. However, it may be a section in which data of effective symbol length is extracted from an arbitrary position in the GI section of the desired wave.

  Next, the SP equalization means 5 will be described. The SP equalization means 5 is means for performing carrier equalization by estimating the transmission path from the scattered pilot carrier or the like for the FFT result obtained from the FFT means 5.

The SP carrier also becomes a known signal on the receiving side because a known PRBS (Pseudo Random Binary Sequence) signal is modulated by DBPSK (Differential Binary Phase Shift Keying). Therefore, for the SP carrier, the transmission path is estimated from the relationship between the SP carrier FFT data and the reference data. Equation (1), which is a transmission path estimation formula for _obtaining the estimated transmission path H _im of the m-th carrier number of the i-th symbol, is shown below.

In the above equation (1), the carrier position C _im represents a known carrier position at the corresponding i-th symbol m-th carrier number, and the FFT result r _im represents the FFT result at the i-th symbol m-th carrier number.

For example, in the case of ISDB-T (Integrated Services Digital Broadcasting-Terrestrial), the SP carrier exists once per twelve carriers for one symbol, and once for every four symbols even for the same carrier. For this reason, for carriers without SP, the result of channel estimation using SP carriers is interpolated in the symbol direction and carrier direction, so that all the carriers are _calculated based on the estimated channel Him obtained by Equation (1). The transmission path estimation HE _im is obtained.

Equalization correction is performed based on the transmission path estimation result and the FFT result described above. When the estimated transmission path HE _im is used, the correction calculation formula is expressed by the following formula (2).

In the above equation (2), the equalization correction result Y _im represents the equivalent result for the i-th symbol m-th carrier number, and the estimated transmission path HE _im represents the transmission-path estimation result for the i-th symbol m-th carrier number.

  From the above equalization result, the FEC unit 6 performs deinterleaver, error correction, etc., and generates and supplies TS data. The description of the receiving means after TS (data) is omitted because it has a low relevance to the features of the present invention.

  In the general OFDM receiver described above, when there is a delayed wave exceeding the GI length, reception degradation due to each ISI component is inevitable. Therefore, the present invention effectively suppresses reception degradation due to the ISI component even when there is a delayed wave exceeding the GI length.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of an OFDM receiving apparatus according to Embodiment 1 of the present invention. As shown in the figure, the time domain processing unit 1 performs AD conversion and band processing on a received signal obtained via the antenna unit 10 to obtain a time axis data string.

  The FFT interval extraction means 2a and 2b are based on the first FFT interval enable signal EN1 and the second FFT interval enable signal EN2, respectively, from the time axis data string to the FFT first interval (first Fourier transform interval) or the second interval (second The time axis data string of the FFT sample section determined by the Fourier transform section) is extracted.

  The SP conversion means 3a and 3b convert the time-series serial data strings in the first and second FFT intervals extracted by the FFT interval extraction means 2a and 2b into parallel data strings having the number of FFT samples to perform FFT.

  The window function generation means 81a and 81b generate arbitrary window functions fil1 and window functions fil2 having coefficients corresponding to the number of FFT samples obtained from the SP conversion means 3a and 3b.

  The window function calculation means 8a multiplies the SP conversion result and the window function generation result fil1 in the FFT first section by each sample to obtain a first multiplication result (first window function calculated data string).

  The window function calculation means 8b multiplies the SP conversion result and the window function generation result fil2 in the FFT second section by each sample to obtain a second multiplication result (second window function calculated data string).

  The FFT means 4a and 4b perform FFT (Fourier transform processing) on the first and second multiplication results to obtain first and second FFT results (Fourier transform processing results).

  The SP equalization means 5a and 5b perform transmission path estimation for the first and second FFT results from a scattered pilot carrier, etc., perform carrier equalization, and obtain first and second SP equalization processing results. .

  The diversity combining unit 9 performs diversity combining from the first and second SP equalization processing results, obtains the diversity combining result, and outputs the result to the FEC unit 6.

  The FEC unit 6 performs PS conversion processing, deinterleaver, error correction, and the like on the diversity combining result, and generates and outputs TS data.

  As described above, the diversity combining unit 9 performs diversity combining on the first and second SP equalization processing results after the Fourier transform processing in which the ISI component is suppressed, so that the accuracy is finally high. There is an effect that TS data can be obtained.

  The control means 7 generates a first FFT interval enable signal EN1 and a second FFT interval enable signal EN2 that indicate the FFT first interval and the second interval based on the delay profile information DPI, and also generates a window function for generating window functions fil1 and fil2. Control means 81a and 81-2. Therefore, the control means 7 controls the window function calculation processing contents by the window function calculation means 8a and 8b.

  The OFDM receiving apparatus according to the first embodiment includes the above-described FFT section extraction means 2a and 2b, SP conversion means 3a and 3b, FFT means 4a and 4b, window function calculation means 8a and 8b, and window function generation means 81a and 81b. The control means 7 constitutes a Fourier transform processing unit.

  Further, the SP equalization means 5a and 5b, the diversity combining means 9 and the FEC unit 6 constitute a TS data generation unit.

  Hereinafter, the processing content of the OFDM receiver of Embodiment 1 will be described in detail. When the data obtained by the time domain processing unit 1 is r (t), the FFT first section is set to N samples starting at t = t1.

In this case, the data sequence obtained by the SP conversion means 3a in the first FFT section is represented by the following formula (3), where r _S-P1 (k) is the data sequence after the SP conversion.

  In Equation (3), T means a sampling interval.

Similarly, in the case where the FFT second section is set to N samples with t = t2 at the head, if the data sequence after SP conversion of the FFT second section is r _S-P2 (k), the following equation (4) is obtained. It becomes.

Window function calculation result (multiplication result) r _fil1out and FFT function window function fil2 (k) for the first FFT section window function result (multiplication result) ) R _fil2out is as _shown in the following equation (5).

  Next, the window function fil1 and the window function fil2 generated by the window function generation means 81a and 81b will be described. FIG. 2 is an explanatory diagram showing the state of a received signal that receives two signals arriving at a time difference τ.

  In FIG. 2, S1 (t) represents a preceding wave, and S2 (t) represents a delayed wave that arrives with a time difference τ. Actually, since two waves come together, the received signal r (t) is as shown in the following equation (6). Here, for the sake of explanation, the transmission path is expressed separately.

In Equation (6), H ₁ and H ₂ indicate transmission paths until the preceding wave S1 and the delayed wave S2 are received by the receiver, respectively. N is a noise component uncorrelated with the signal.

  FIG. 3 is an explanatory diagram showing the relationship between the received signal and the FFT first section shown in the first embodiment. In the figure, the case where the FFT first section is matched with the effective symbol section of the preceding wave S1 will be described as an example. In the example shown in FIG. 3, when the first FFT interval enable signal EN1, which is a 1-bit signal, is “H”, it means the first interval in which FFT is performed. In FIG. 3, in the time axis data sample, the sampling timing is indicated by a circle, and the FFT first stage shows a data processing image of the FFT processing.

  In this case, since the result of FFT of the preceding wave (signal) S1 (t) is an ideal FFT interval, the constellation of the FFT result with respect to the preceding wave S1 (t) depends on the time difference between the FFT interval and the effective symbol interval. Can be obtained without phase rotation. For example, when the FFT interval includes the GI interval of the preceding wave S1 (t), it is known to cause phase rotation depending on the time difference between the FFT interval and the effective symbol interval from the transmission signal. At this time, since the time axis data of the included GI section is equivalent to the data of the section not included in the effective symbol, ISI does not occur.

  On the other hand, when considering the signal component of the delayed wave S2 (t), the (n-1) th symbol is included for T1 samples in this FFT interval. Therefore, when FFT is performed in this section, the (n−1) -th symbol signal of this T1 sample becomes an interference component at the time of FFT calculation and affects the FFT result. However, the remaining (N-T1) samples only cause phase rotation depending on the time T1 with respect to the FFT operation component not including this interference component. As described above, for the delayed wave S2 (t), the FFT result for suppressing the ISI is obtained by using the window function for suppressing the gain mainly in the 0 to T1 interval with respect to the time axis data of the FFT first interval. It is possible to generate.

  As described above, since the window function calculation processing by the window function calculation means 8a and 8b performs the ISI suppression calculation processing in which the ISI component in the FFT first interval and the FFT second interval is suppressed, the FFT result in which the ISI is suppressed as a result. The effect which can produce | generate is produced.

  FIG. 4 is an explanatory diagram showing an example of the relationship between the FFT first and second intervals and the window functions fill1 and fill2 in the first embodiment. As shown in the figure, each ISI component is applied by applying a window function that suppresses the time axis data of the ISI component in each FFT interval (FFT first interval FFT1n, FFT second interval FFT2n). A suppressed FFT result is generated.

  4, (a) shows temporal changes of the preceding wave S1 (t) and the delayed wave S2 (t), and (b) is the FFT system 1 (FFT section extracting means 2a, SP conversion means 3a, window function). The processing contents of the calculation means 8a, the FFT means 4a and the SP equalization means 5a are shown. (C) is the FFT system 2 (FFT section extraction means 2b, SP conversion means 3b, window function calculation means 8b, The processing contents of the FFT processing unit 4b and the SP equalization unit 5b) are shown.

  As described above, the FFT means 4a and 4b each effectively suppress the ISI component to obtain the first and second FFT results. As shown in FIG. 4 (b), when performing the FFT process in the FFT first section of the symbol n in the FFT system 1, the section TS1 in which the ISI component due to the delayed wave S2 (t) exists has a value greater than that of the other sections. Is set to a small window function fil1. Similarly, as shown in FIG. 4 (c), when performing the FFT processing of the FFT second section of the symbol n in the FFT system 2, the other in the section TS2 where the ISI component due to the preceding wave S1 (t) exists. A window function fil2 having a value smaller than the interval is set.

  The SP equalization means 5a and 5b perform SP equalization on the first and second FFT results to obtain first and second SP equalization.

  The diversity combining means 9 performs diversity combining based on the first and second SP equalization processing results as described above, and outputs the combining result to the FEC unit 6. The FEC unit 6 diversity result is deinterleaved, error corrected, etc., and TS data is generated and output.

  The delay profile information generating means 15 receives the FFT related information S30, generates delay profile information DPI indicating the ISI component existence period in the FFT first section and the FFT second section based on the FFT related information S30, and sends it to the control means 7 Output.

  As the FFT related information S30, for example, first and second FFT results by the FFT means 4a and 4b, first and second SP equalization processing results by the SP equalization means 5a and the SP equalization means 5b, etc. Various processing results in the Fourier transform processing unit can be considered. It is possible to calculate at least one of these processing results as FFT related information S30 and perform inverse FFT to generate delay profile information DPI based on the calculation result. One of the first and second FFT results (first and second SP equalization processing results) may be used. The SP symbol interpolation result in the SP equalization means 5a and 5b may be used as the FFT related information S30.

  By supplying the delay profile information DPI generated by the delay profile information generating unit 15 described above to the control unit 7, the control unit 7 can recognize the arrival time arrival information with high accuracy, and can respond to the response performance. It is possible to improve. Note that the arrival wave arrival time means, for example, the time difference τ between the preceding wave S1 (t) and the delayed wave S2 (t) in the case of FIG.

  As described above, the OFDM receiving apparatus according to Embodiment 1 can perform diversity combining using an FFT result obtained by suppressing an ISI component that is a cause of deterioration for one received signal from which the time domain processing unit 1 can be obtained. Therefore, the reception performance can be improved. Also, when there is a difference in DU ratio, the CN ratio of one of the first and second FFT results is high, and even when the DU ratio is reversed, the CN ratio is determined from the other FFT result without changing the FFT interval. A stable reception performance can be expected by obtaining a high SP equalization processing result.

  Further, as described above, the delay profile information DPI is calculated by performing inverse FFT using the (first and second) SP equalization processing results of the (first and second) FFT results, for example. By supplying the result to the control means 7, more accurate arrival wave arrival time information can be obtained, and response performance can be improved. At this time, one of the first and second FFT results may be used. Also, the SP symbol interpolation result in the SP equalization means may be used.

  In this way, the control means 7 is based on the delay profile information DPI obtained by the delay profile information generation means 15, so that the first and second FET interval enable signals that indicate the accurate first and second FFT intervals. The outputs of EN1 and EN2 and the window function fil1 and the window function fil2 can be accurately controlled by the window function generation means 81a and 81b.

  As a result, since the FFT means 4a and the FFT means 4b can obtain the first and second FFT results in which the ISI component is suppressed, respectively, OFDM in which reception degradation does not occur even when delay waves exceeding the GI length are mixed. The effect which can obtain a receiver is produced.

  Note that the method for determining the FFT first interval and the FFT second interval is arbitrary. For example, it may be estimated by using GI correlation on the time axis, and may be given. The optimum value may be estimated.

  Even when there is no delayed wave exceeding the GI length, for example, the first FFT section may be near the GI head of the most preceding wave, and the second section may be near the head of the effective symbol of the most delayed wave.

  The window function generation means 91a and 81b may be configured in a memory and supplied with data corresponding to the FFT sample. In this case, the window function memory may be shared by assuming that the read address order of the memory is reversed as the file fi2.

  It is desirable to provide a coefficient that suppresses the ISI component that is included in the FFT first interval for the window function fil1, and the ISI component that is included in the FFT second interval for the window function fil2. Specific characteristics are arbitrary.

  With respect to the diversity combining method by the diversity combining means 9, the reception performance is improved as compared with the conventional combining, but it is also possible to perform processing such as equal gain combining, maximum ratio combining, SIR (Signal to Interference power Ratio) combining.

  FIG. 5 is a block diagram showing another configuration of the OFDM receiving apparatus according to the first embodiment of the present invention. The other configuration shown in FIG. 5 is a configuration in which the diversity combining unit 9 is arranged before the SP equalizing units 5a and 5b, and the diversity result is SP equalized by the SP equalizing unit at the subsequent stage.

  Hereinafter, a description will be given focusing on differences from the configuration shown in FIG. The diversity combining means 9 diversity-combines the first and second FFT results to obtain a diversity combining result. Diversity combining means 9 is composed of phase adjusting means 91 a and 91 b and combining means 92.

  The phase adjusting units 91a and 92b perform phase adjustment based on the first and second FFT interval enable signals EN1 and EN2 on the first and second FFT results to obtain first and second post-phase-adjusted FFT results. As a result, the phases of the first and second phase-adjusted FFT results are the same.

  Since the phase rotation amount depends on the shift amount between the first and second FFT sections and the corresponding desired wave effective symbol sections with respect to the first and second FFT results, the first and second FFT results. Based on the FFT interval enable signals EN1 and EN2, phase adjustment by the phase adjustment means 91a and 91b can be performed.

  The combining unit 92 combines the first and second phase-adjusted FFT results and outputs the diversity combining result to the SP equalizing unit 5.

  The SP equalization means 5 estimates a transmission path from a scattered pilot carrier with respect to the diversity combining result, performs carrier equalization, and obtains an SP equalization processing result.

  The FEC unit 6 performs PS conversion processing, deinterleaver, error correction, and the like on the SP equalization processing result, and generates and outputs TS data. Other configurations and operations are the same as those shown in FIG.

  Compared to the configuration shown in FIG. 1, the other configuration shown in FIG. 5 can be configured with a single SP equalization means 5, and the circuit is not required to have a plurality of SP equalization means 5a and 5b. Scale reduction can be expected.

  Further, since the phase adjustment is performed by the phase adjustment units 91a and 91b in the diversity combining unit 9 prior to the SP equalization process, the content of the SP equalization process is improved along with the improvement of the phase path estimation accuracy for the SP equalization process. Can be expected.

  As described above, another configuration of the OFDM receiver of the first embodiment shown in FIG. 5 is that diversity combining is performed on the first and second FFT results in which the ISI component is suppressed by the diversity combining unit 9. As a result, it is possible to finally obtain highly accurate TS data. Further, the circuit configuration can be simplified by the amount that can be realized by the SP equalization means 5 having a single configuration. Since the circuit scales of the phase adjusting units 91a and 91b are sufficiently smaller than that of the SP equalizing unit 5, the circuit configuration is hardly complicated by providing the phase adjusting units 91a and 91b.

  Further, by obtaining the first and second post-phase-adjusted FFT results in which the phases are matched by the phase adjusting means 91a and 91b, it is possible to obtain an accurate diversity combining result.

  In the OFDM receiver shown in FIG. 1, SP equalization means 5 a and 5 b are provided before the diversity combining means 9. Therefore, since the first and second SP equalization processing results whose phases have been adjusted by the SP equalization means 5a and 5b are obtained, the diversity combining means 9 subsequent to the SP equalization means 5a and 5b is used as the phase adjustment means 91a. , 91b is generally not provided inside.

  Next, a method for correcting the phase rotation amount depending on the time difference between the FFT interval and the effective symbol interval will be described. When the time difference of the FFT window position is assumed, the equation representing the relationship of each Fourier transform of the same baseband signal is as the following equation (7), and the relationship between the Fourier transform result and the time difference τ is equal to that obtained by phase rotation. It is generally known that

  Here, r means a baseband time domain signal, and t means an arbitrary time.

Further, the phase rotation component when the time difference of the FFT window position is T _OFST can be expressed as the following equation (8).

  In equation (8), f0 is the OFDM carrier interval, m is the carrier number, T is the OFDM effective symbol length, N is the number of DFT samples, and n is the amount of sample deviation between the FFT window interval and the effective symbol interval of the desired wave. Means.

  From the equation (8), it is clear that the phase rotation amount due to the FFT window position of the same baseband signal is uniquely determined by the window position sample shift amount n, the FFT sample number N, and the carrier number m.

<Embodiment 2>
In the first embodiment, the FFT section is extracted based on the first and second sections of the FFT, but in this embodiment, the OFDM reception is performed in such a manner that the time axis data of the time difference between the first and second sections of the FFT is delayed. Device.

  FIG. 6 is a block diagram showing a configuration of an OFDM receiving apparatus according to the second embodiment of the present invention. As shown in the figure, the OFDM receiving apparatus according to the second embodiment includes a time domain processing unit 1, FFT section extracting means 2, SP conversion means 3a and 3b, FFT means 4a and 4b, SP equalizing means 5a and 5b, diversity combining means 9, FEC section 6, control means 7, data string multiplexing means 11a and 11b, multiplication means 13, data string dividing means 12, delay profile information generating means 15, window function generating means 82a and 82b, and delay adjustment Consists of means 83.

  Hereinafter, the OFDM receiving apparatus according to the second embodiment will be described focusing on the configuration and operation different from those of the OFDM receiving apparatus according to the first embodiment.

  In the first embodiment, mutual FFT intervals are generated, and extraction and window function calculation are performed respectively. However, in this embodiment, the time axis data string itself and the time axis data are converted into the FFT first interval and the FFT number. The delayed time axis data delayed by the FFT time difference ΔFFT, which is the time difference from the two sections, is multiplexed at the data sampling interval by the data sequence multiplexing means 11a to obtain a multiplexed time axis serial data sequence. Hereinafter, this point will be described in detail.

  The delay adjustment unit 83 receives the FFT time difference information FFT from the control unit 7, and the data sequence obtained by delaying the time axis data sequence obtained from the time domain processing unit 1 by the FFT time difference ΔFFT indicated by the FFT time difference information FFT. The delayed time axis data string is output to the data string multiplexing means 11a.

  As a result, when the FFT second section is set for the time axis data string and the FFT first section is set for the delay time axis data string, both sections coincide in time. That is, in the example of FIG. 4, the FFT first section FFT1n shown in (b) of FIG. 4 and the FFT second section FFT2n shown in (c) of FIG.

  The data sequence multiplexing unit 11a multiplexes the time axis data sequence received directly from the time domain processing unit 1 and the delay time axis data sequence received from the delay adjustment unit 83 at a multiple of the data sampling interval to multiplex time axis serial data. Get a column.

  Similarly, the data sequences of the window functions fil1 (k) and fil2 (k) output from the window function generating means 82a and 82 are multiplexed by the data string multiplexing means 11b at twice the data sampling interval to obtain a multiplexed window function. Here, “k” is a value from 0 to (N−1), and “N” is the number of FFT samples. In addition, the timing is controlled so that the time axis data can be output at the same time as the position of (N = 0) from k = 0.

  Then, the multiplication means 13 performs a multiplication process of the multiplexed time axis serial data string and the multiplexed window function to obtain a multiple multiplication result. The multiple multiplication results include the respective window function calculation results in the first FFT section and the second FFT section.

  The FFT section extraction means 2 follows the multiple FFT section enable signal EN3 obtained from the control means 7 and outputs the multiple multiplication results (window function calculation results) in the multiple FFT sections (FFT first and second sections) to the subsequent data string dividing means 12. Output to.

  The data string dividing unit 12 divides the multiple multiplication result in the multiple FFT interval into a first multiplication result for the FFT first interval and a second multiplication result for the FFT second interval based on the data sampling interval. Then, the data string dividing unit 12 outputs the first multiplication result to the SP conversion unit 3a, and outputs the second multiplication result to the SP conversion unit 3b.

  The SP conversion means 3a and 3b convert the time-series serial data strings obtained by the first and second multiplication results divided by the data string dividing means 12 into parallel data strings having the number of FFT samples so as to perform FFT. .

  Note that the processing of the FFT means 4a and 4b and the SP equalization means 5a and 5b are the same as those in the first embodiment, and thus the description thereof is omitted.

  The diversity combining unit 9 performs diversity combining from the first and second SP equalization processing results, obtains the diversity combining result, and outputs the result to the FEC unit 6.

  The FEC unit 6 performs PS conversion processing, deinterleaver, error correction, and the like on the diversity combining result, and generates and outputs TS data.

  As described above, in the OFDM receiving apparatus according to the second embodiment, the multiplication process (window function calculation process) is performed on the data sequence in which the FFT first section and the second section are multiplexed, thereby reducing the number of arithmetic circuits. I can expect.

  Further, when there is a means for performing clock reproduction or carrier frequency reproduction using the GI correlation from the time axis data string, the delay adjusting means 13 stores the memory or delay contents of the 1-symbol delay means result used for that purpose. By sharing, it becomes unnecessary to have a delay means such as a memory or a DFF as the delay adjustment means, so that a reduction in circuit scale can be expected.

  The delay profile information generation means 15 outputs the delay profile information DPI to the control means 7 based on the FFT related information S30. As the FFT-related information S30, for example, the first and second SP equalization processing results can be considered, and the control means 7 is obtained by obtaining by performing inverse FFT using the first and second SP equalization processing results. Is supplied with delay profile information DPI. As a result, it is possible to improve response performance associated with real-time control by the control means 7. At this time, the delay profile information generation means 15 may use the first and second FFT results as the FFT related information S30. The SP symbol interpolation results in the SP equalization means 5a and 5b may be used as the FFT related information S30.

  As described above, the OFDM receiver of the second embodiment multiplies the multiplexed data sequence obtained by multiplexing the time axis data sequence and the delay time axis data sequence by the multiplexing window function sequence by the multiplying means 13. Thus, a multiple multiplication result which is a window function calculation result data string is obtained. This window function calculation result data string is a data string obtained by multiplying the OFDM signal in the first and second FFT intervals by the window function fil1 and the window function fil2, respectively.

  As a result, the OFDM receiving apparatus of the second embodiment can complete the window function calculation processing in the first and second FFT sections by one multiplication process, and can expect improvement in reception performance while suppressing the circuit scale. There is an effect.

  FIG. 7 is a block diagram showing another configuration of the OFDM receiving apparatus according to the second embodiment of the present invention. The other configuration shown in FIG. 7 is a configuration in which the diversity combining unit 9 is arranged in front of the SP equalizing units 5a and 5b, and the diversity result is SP equalized by the subsequent SP equalizing unit.

  Hereinafter, a description will be given focusing on differences from the configuration shown in FIG. The diversity combining means 9 diversity-combines the first and second FFT results to obtain a diversity combining result. Diversity combining means 9 is composed of phase adjusting means 91 a and 91 b and combining means 92.

  The phase adjusting units 91a and 91b perform phase adjustment on the first and second FFT results based on the first and second FFT interval enable signals EN1 and EN2, and obtain first and second post-phase-adjusted FFT results. As a result, the phases of the first and second phase-adjusted FFT results are the same.

  Since the phase rotation amount depends on the shift amount between the first and second FFT sections and the corresponding desired wave effective symbol sections with respect to the first and second FFT results, the first and second FFT results. Based on the FFT interval enable signals EN1 and EN2, phase adjustment by the phase adjustment means 91a and 91b can be performed.

  The combining unit 92 combines the first and second phase-adjusted FFT results and outputs the diversity combining result to the SP equalizing unit 5.

  The SP equalization means 5 estimates the transmission path from the scattered pilot carrier for the diversity combining result, performs carrier equalization, and obtains the SP equalization processing result.

  The FEC unit 6 performs PS conversion processing, deinterleaver, error correction, and the like on the SP equalization processing result, and generates and outputs TS data. The other configuration and operation are the same as the configuration shown in FIG.

  Compared to the configuration shown in FIG. 6, the other configuration shown in FIG. 7 can be configured with a single SP equalization means 5 and the circuit is not required to have a plurality of SP equalization means 5a and 5b. Scale reduction can be expected.

  Further, since the phase adjustment is performed by the phase adjustment units 91a and 91b in the diversity combining unit 9 prior to the SP equalization process, the content of the SP equalization process is improved along with the improvement of the phase path estimation accuracy for the SP equalization process. Can be expected.

<Others>
In the first embodiment and the second embodiment, the configuration in which the first and second FFT results are obtained by the first and second FFT intervals has been described. However, this concept is extended to provide a plurality of FFTs by a plurality of FFT intervals. A configuration that obtains results is also feasible.

It is a block diagram which shows the structure of the OFDM receiver which is Embodiment 1 of this invention. It is explanatory drawing which shows the state of the received signal which receives the signal of two waves which arrives by predetermined time difference. 6 is an explanatory diagram showing a relationship between a received signal and an FFT first section shown in Embodiment 1. FIG. 6 is an explanatory diagram showing an example of the relationship between FFT first and second intervals and window functions fill1 and fill2 in Embodiment 1. FIG. It is a block diagram which shows the other structure of the OFDM receiver which is Embodiment 1 of this invention. It is a block diagram which shows the structure of the OFDM receiver which is Embodiment 2 of this invention. It is a block diagram which shows the other structure of the OFDM receiver which is Embodiment 2 of this invention. It is a block diagram which shows the structure of a general OFDM receiver.

Explanation of symbols

  1 time domain processing unit, 2a, 2b FFT interval extraction unit, 3a, 3b SP conversion unit, 4a, 4b FFT unit, 5a, 5b SP equalization unit, 6 FEC unit, 7 control unit, 8a, 8b window function Arithmetic means, 9 diversity combining means, 11a, 11b data string multiplexing means, 12 data string dividing means, 13 multiplying means, 81a, 81b, 82a, 82b window function generating means, 83 delay adjusting means, 91a, 91b phase adjusting means, 92 Synthesis means.

Claims (6)

An OFDM receiver that receives an OFDM signal having a guard interval,
A Fourier transform processing unit that sets a plurality of Fourier transform sections for the OFDM signal, performs a plurality of Fourier transform processes in each of the plurality of Fourier transform sections, and obtains a plurality of Fourier transform processing results;
A TS data generation unit that obtains TS data by performing SP equalization processing and diversity combining processing, which is equalization processing by channel estimation using a pilot carrier, for the plurality of Fourier transform processing results,
The Fourier transform processor may have rows ISI suppression processing for suppressing inter-symbol interference (ISI) component in each of the plurality of Fourier transform processing result,
The Fourier transform processing unit
A window function that performs a window function calculation process to obtain a plurality of window function-calculated signals by multiplying the OFDM signals in the plurality of Fourier transform sections by a plurality of window functions set in the plurality of Fourier transform sections, respectively. The window function calculation process includes a suppression process that has less influence during the ISI component existence period of the OFDM signal in each of the corresponding Fourier transform sections,
The OFDM receiver
Controlling the Fourier transform unit, instructing the plurality of Fourier transform sections, further comprising a control means for controlling the window function calculation processing content,
The ISI suppression calculation process includes the window function calculation process,
OFDM receiver. The OFDM receiver according to claim 1, wherein
Delay profile information generating means for receiving processing contents of the Fourier transform processing section as Fourier transform related information, and outputting delay profile information defining ISI component suppression sections in a plurality of Fourier transform sections based on the Fourier transform related information Prepared,
The control means, based on the delay profile information, outputs a Fourier transform section control signal for instructing the plurality of Fourier transform sections to the Fourier transform unit, and controls the window function calculation processing content.
OFDM receiver. An OFDM receiver that receives an OFDM signal having a guard interval,
A Fourier transform processing unit that sets a plurality of Fourier transform sections for the OFDM signal, performs a plurality of Fourier transform processes in each of the plurality of Fourier transform sections, and obtains a plurality of Fourier transform processing results;
A TS data generation unit that obtains TS data by performing SP equalization processing and diversity combining processing, which is equalization processing by channel estimation using a pilot carrier, for the plurality of Fourier transform processing results,
The Fourier transform processing unit performs ISI suppression calculation processing for suppressing intersymbol interference (ISI) components in each of a plurality of Fourier transform processing results,
The Fourier transform processing unit
Delay adjusting means for receiving the time axis data sequence by the OFDM signal and delaying the time axis data sequence by a time difference in the plurality of Fourier transform sections to generate at least one delay time axis data sequence;
Data sequence multiplexing means for multiplexing the time axis data sequence and the at least one delay time axis data sequence to obtain a multiplexed data sequence, and the time axis data sequence and the at least one of the multiplexed data sequences The delay time axis data string can set a common Fourier transform section of the same time zone as a plurality of Fourier transform sections,
Window function generating means for supplying a plurality of window functions set in the plurality of Fourier transform sections;
Window function multiplexing means for obtaining a multiplexed window function sequence obtained by multiplexing the plurality of window functions,
Multiplication means for performing window function calculation processing for multiplying the multiplexed data string and the multiplexed window function string to obtain a window function calculation result data string;
Fourier transform section extracting means for extracting the common Fourier transform section from the window function multiplication result data string,
Data string dividing means for dividing the window function multiplication result data string extracted by the Fourier transform section into a plurality of Fourier transform data strings;
A plurality of Fourier transform means for obtaining a plurality of Fourier transform processing results for performing Fourier transform processing on the plurality of Fourier transform data strings,
The OFDM receiver
Control the delay adjusting means, the window function generating means and the Fourier transform section extracting means, including time difference information in the plurality of Fourier transform sections, a control means for indicating the common Fourier transform section,
The window function calculation result data sequence obtained by the window function calculation processing by the multiplication means performed under the control of the control means is data obtained by multiplying the OFDM signal in the plurality of Fourier transform sections by the plurality of window functions. The window function calculation process includes a suppression process that reduces the influence during the ISI component existence period of the OFDM signal in each of the corresponding Fourier transform sections,
The ISI suppression calculation process includes the window function calculation process,
OFDM receiver. The OFDM receiver according to any one of claims 1 to 3, wherein
TS data generator
A plurality of SP equalization means for performing the SP equalization processing on a plurality of Fourier transform processing results to obtain a plurality of SP equalization processing results;
Diversity combining means for performing diversity combining processing on the plurality of SP equalization processing results and obtaining diversity combining results;
An error correction unit that performs error correction on the diversity combining result and obtains the TS data,
OFDM receiver. The OFDM receiver according to any one of claims 1 to 3, wherein
TS data generator
Diversity combining means for performing diversity combining processing on the plurality of Fourier transform processing results and obtaining diversity combining results;
SP equalization means for performing the SP equalization processing on the diversity combining result to obtain an SP equalization processing result;
An error correction unit that performs error correction on the SP equalization processing result and obtains the TS data,
OFDM receiver. The OFDM receiver according to claim 5, wherein
The diversity combining means includes:
Phase adjustment means for performing phase adjustment in the plurality of Fourier transform sections for the plurality of Fourier transform processing results to obtain a plurality of phase-adjusted Fourier transform processing results;
Combining a plurality of phase-adjusted Fourier transform processing results to obtain the diversity combining result,
OFDM receiver.

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