JP4929895B2 - Transmission apparatus and subframe creation method - Google Patents

Description

  The present invention relates to a transmitting apparatus and a method for creating subframes in a digital mobile communication system, and in particular, in a digital communication that uses a plurality of subframes having different GI lengths, and with accurate symbol timing and subframe timing. The present invention relates to a transmission apparatus to be detected and a subframe creation method.

-OFDM transmission system As a radio access system for next-generation mobile communication, an OFDM (Orthogonal Frequency Division Multiplex) transmission system is being studied. The OFDM transmission system has features such as good frequency selectivity and resistance to interference from adjacent paths.
FIG. 19 is a block diagram of a general transmission station that employs the OFDM transmission scheme. The error correction encoder 1 performs error correction encoding processing on the data signal and encodes the data signal, and the data modulation unit 2 performs data modulation (for example, QPSK modulation) on the encoded data signal. The data / pilot signal multiplexing unit 3 time-multiplexes the data signal and a pilot signal known by the receiving station. IFFT section 4 performs IFFT processing in units of a fixed number N ₀ . That is, N ₀ data samples are regarded as subcarrier signal components, IFFT processing is performed on the subcarrier components, converted into discrete time signals, and output. The guard interval insertion unit (GI insertion unit) 5, as shown in FIG. 20, of the N ₀ samples after IFFT, to copy the rear part of the N _G samples inserted at the head of the N ₀ sample as a guard interval GI. Since GI is copied cyclically, it is characterized in that the signal is continuous in the interval of (No + N _G ) samples after GI insertion. This feature allows GI to be a delayed symbol from an adjacent path. It plays a role of removing interference caused by. The DA converter 6 performs D / A conversion, the transmission RF unit 7 performs orthogonal modulation, converts the baseband signal into a radio frequency signal, and transmits the signal from the transmission antenna 8 to the reception station 9.

FIG. 21 is a block diagram of a general receiving station in the OFDM transmission scheme. The reception RF unit 10 receives a radio signal transmitted from the transmission station, converts the radio signal into a baseband signal by frequency down-conversion, and performs orthogonal demodulation. The AD converter 11 converts a signal obtained by quadrature demodulation into a digital signal. The reception timing detection unit 12 detects OFDM subframe timing and symbol timing. The GI deletion unit 13 deletes the guard interval GI from the received signal based on the symbol timing, cuts out an effective signal component of each OFDM symbol, and inputs the effective signal component to the FFT unit 14. FIG. 22 shows an example of how the effective signal component is cut out. For convenience of explanation, the received signal is represented by being decomposed into components of each path (direct wave and indirect wave). From the direct wave of path 1, only the effective signal component (N ₀ sample) of the OFDM symbol n excluding GI is accurately extracted. A signal is cut out from the indirect wave (delayed wave) of path 2 in a form including a part of GI. However, since the effective signal component of the OFDM symbol is cyclically copied in the GI, as a result, the effective signal component of the OFDM symbol n is accurately extracted. That is, multipath components having a delay time equal to or shorter than the GI length are received without causing interference between OFDM symbols.
The FFT unit 14 performs FFT processing on the signal after the GI deletion, and the data / pilot signal separation unit 15 separates the time-multiplexed data signal and pilot signal from the received signal. The channel estimation unit 16 performs correlation calculation between the received pilot signal and the replica of the transmitted pilot signal to estimate channel distortion in the radio channel. On the other hand, the channel compensation unit 17 multiplies the received data signal by the complex conjugate of the channel estimation value to suppress channel distortion, and the data demodulation unit 18 performs demodulation processing of the received data using the channel compensated received signal, resulting in an error. The correction decoder 19 performs error correction decoding processing on the demodulated data.

・ Combination of short GI subframe and long GI subframe
In OFDM transmission, the length of the guard interval GI is determined by the propagation delay of the propagation path (the magnitude of delay dispersion), so a method for switching between multiple guard interval lengths in the same transmission system has been proposed. ing. As such an example, there is LTE (Long Term Evolution) discussed on 3GPP (3rd Generation Partnership Project) (see Non-Patent Document 1). In LTE, there are short GI subframes using a short guard interval and long GI subframes using a long guard interval.
Figure 23 is a sub-frame format of the short GI subframe SF _S and the long GI subframe SF _L, GI length in the short GI subframe SF _S is Ngi_s, GI length in the long GI subframe SF _L is Ngi_l, Ngi_s <Ngi_l. In any subframe, the effective symbol length N ₀ in the OFDM symbol is the same, and the subframe length M is also the same. Short GI number of OFDM symbols included in the subframe SF _S is greater than the number of OFDM symbols included in the long GI subframe SF _L. Note that N ₀ samples obtained by IFFT processing are referred to as effective symbols, and (No + _NG ) samples after GI insertion are referred to as OFDM symbols.

There are mainly two ways to use the short GI subframe and the long GI subframe. The first usage method is a method of using either one based on the magnitude of delay dispersion. In general, a cell with a large radius (hereinafter referred to as a large cell) that is applied to a suburb with little shielding has a large delay spread, and a cell with a small radius that is deployed in an urban area with many shieldings (hereinafter referred to as a small cell) ), The delay spread is small. Therefore, long GI subframes are used in large cells, and short GI subframes are used in small cells. In this case, the subframe transmitted by the base station of each cell is fixed to the short GI subframe or the long GI subframe, and does not change with time.
The second usage method is a method of using a long GI subframe when transmitting MBMS (Multimedia Broadcast Multicast Service) data and using a short GI subframe when transmitting unicast data (unicast data). As multiplexing methods of MBMS data and unicast data, time division multiplexing (Time Division Multiplex) TDM, time frequency division multiplexing (Time Frequency Division Multiplex) TFDM, and the like have been proposed.
In TDM, a short GI subframe and a long GI subframe are time-multiplexed. All bandwidth of short GI subframe is allocated to unicast data, and all bandwidth of long GI subframe is allocated to MBMS data.
In TFDM, a short GI subframe and a long GI subframe are time-multiplexed. Then, the entire bandwidth of the short GI subframe is allocated to unicast data. However, in the long GI subframe, the entire bandwidth is not allocated to MBMS data, and unicast data and MBMS data are frequency-multiplexed.

・ Detection of subframe timing and symbol timing At the start of communication in a cellular system, a mobile terminal performs cell search processing to detect a cell (base station) to which a radio link is connected, and performs symbol timing detection and subframe timing detection. There is a need. Conventional timing detection methods at the time of cell search are roughly divided into two methods: a detection method based on autocorrelation using a repetitive portion of the received signal, and a detection method based on cross-correlation between a replica signal of a known pattern and the received signal. Three timing detection methods are known.
(1) First Timing Detection Method The first timing detection method is a GI correlation calculation method that detects the symbol timing by calculating the correlation of repeated portions of the guard interval GI (see Patent Document 1).
FIG. 24 is a configuration diagram of a timing device that realizes the first timing detection method, and FIG. 25 is an explanatory diagram of the timing detection method. The guard interval GI is because they created by copying the number of samples N _G number of trailing the leading portion of the sample number N _o number of OFDM effective symbol as shown in (a) of FIG. 25, 1 OFDM effective symbol before By calculating the correlation between the received signal (before N ₀ samples) and the current received signal, the correlation value becomes maximum in the guard interval GI portion as shown in FIG. 25 (b). By detecting this maximum correlation value, the symbol timing can be detected.
In FIG. 24, the delay unit 21 delays the received signal by one OFDM effective symbol (number of samples N ₀ ), and the multiplication unit 22 multiplies the complex conjugate P ₂ ^* of the received signal P ₂ before one OFDM effective symbol and the current received signal. Multiply by P ₁ and output the multiplication result. The shift register 23 has a length corresponding to _NG samples of the guard interval, stores the latest _NG multiplication results, and the adder 24 adds the _NG multiplication results to correlate the _NG sample width. Output the value. The correlation value storage unit 25 stores N ₀ correlation values shifted by one sample output from the adder 24, and the adder 26 stores correlation values over a plurality of symbols and a plurality of frames in order to improve the S / N ratio. Accumulate and store in the correlation value storage unit 25. In the guard interval period, the received signal before one OFDM effective symbol and the current received signal are ideally the same, and therefore, as the number of multiplication results of the guard interval period stored in the shift register 23 increases, FIG. 25 (b) correlation value gradually increases as shown in, the correlation value when N _G pieces all of the multiplication results stored in the shift register 23 in the guard interval period is maximized, thereafter, the guard interval period to be stored in the shift register 23 As the number of multiplication results decreases, the correlation value gradually decreases. The peak detection unit 27 detects the peak correlation value with the maximum correlation power among the N ₀ correlation values stored in the correlation value storage unit 25, and sets the timing as the symbol timing. Simultaneously with timing detection, it is possible to estimate the carrier frequency deviation between the mobile terminal and the base station.

(2) Second timing detection method As shown in FIG. 26, the second timing detection method repeatedly transmits the same signal, for example, an OFDM symbol of a synchronization channel (SCH) twice, and correlates the repeated portion. The peak timing is detected by calculation, and the symbol timing and subframe timing are detected based on the timing (see Non-Patent Document 2). Simultaneously with timing detection, it is possible to estimate the carrier frequency deviation between the mobile terminal and the base station.
(3) Third timing detection method As shown in FIG. 27, the third timing detection method transmits the OFDM symbol of the synchronization channel (SCH) common to all cells from each base station, and the OFDM of the synchronization channel on the receiving side. The correlation between the symbol replica and the received signal is calculated to detect the peak timing, and the symbol timing and subframe timing are detected based on the timing (see Non-Patent Document 2).
3GPP TSG RAN WG1 Ad Hoc on LTE, R1-050590, "Physical Channels and Multiplexing in Evolved UTRA Downlink", NTT DoCoMo Hanada, Higuchi, Sawahashi, "Two-stage high-speed cell search method and its characteristics in broadband Multi-carrier CDMA transmission", IEICE Technical Report (TECHNICAL REPORT OF IEICE. SSE2000-79, RCS2000-68 (2000-07), p. 119-126) International Publication No. 03/032542 Pamphlet

The first timing detection method has the following problems.
(1) Symbol timing can be detected, but subframe timing cannot be detected.
(2) Since the correlation value has a peak characteristic with a width corresponding to the length of the repeated part (GI period) as shown in Fig. 25 (b), an error occurs in the symbol timing position due to the influence of noise and delayed waves. Cheap.
(3) When the short GI subframe and the long GI subframe are used together, the mobile terminal needs to have two correlators corresponding to each subframe.
(4) When the base station transmits the short GI subframe and the long GI subframe in a time multiplexed manner, the correlation value cannot be averaged over a plurality of subframes, so the timing detection accuracy decreases.
-The second timing detection method has the following problems.
(1) Similar to the first timing detection method, the correlation value has a peak characteristic with a width corresponding to the length of the repetitive part (OFDM symbol period), so the symbol timing position and subframe are affected by noise and delayed waves. Error is likely to occur in the timing position
(2) When the short GI subframe and the long GI subframe are used together, the mobile terminal needs to have two correlators corresponding to each subframe.
(3) When the base station transmits a short GI subframe and a long GI subframe in a time-multiplexed manner, the correlation value cannot be averaged over a plurality of subframes, resulting in a decrease in timing detection accuracy.
-The third timing detection method has the following problems.
The third timing detection method has no problem as in the first and second methods. However, in the third timing detection method, it is necessary to use an OFDM symbol common to all cells known on the receiving side as a synchronization channel, and pilot symbols cannot be used for timing detection. For this reason, there is a problem that the number of pilot symbols included in the subframe is reduced and the channel estimation accuracy is deteriorated.

Accordingly, an object of the present invention is to make it possible to use pilot symbols for detection of symbol timing and subframe timing.
Another object of the present invention is to detect each symbol timing / subframe timing even when a plurality of subframes having different GI lengths (for example, a short GI subframe and a long GI subframe) are used in combination. This is to eliminate a correlator corresponding to the subframe.
Another object of the present invention is to enable detection of symbol timing and subframe timing with high accuracy.

The present invention relates to a subframe creation method and a transmission apparatus in a digital communication system using a plurality of types of subframes having different guard interval lengths.
・ How to create subframes
The first subframe creation method of the present invention includes a step of performing phase rotation processing on one of the pilot signals at the end or head of the subframe, the pilot signal subjected to the phase rotation processing, and the phase rotation processing. A step of performing IFFT processing on each of the pilot signals not subjected to the processing and inserting a guard interval into each effective symbol obtained by the IFFT processing to generate an OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe, respectively. The OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are created so that a fixed number of samples are repeated before and after the subframe synchronization timing regardless of the type of subframe to be transmitted.
According to the second subframe creation method of the present invention, IFFT processing is performed on a signal, a guard interval is inserted into an effective symbol obtained by the IFFT processing, and the OFDM symbol at the end of the subframe and the head of the next subframe are inserted. Each OFDM symbol is created, and the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are set so that a predetermined number of samples are repeated before and after the subframe synchronization timing regardless of the type of subframe to be transmitted. The OFDM symbol creating step includes a step of copying the rear part of the effective symbol obtained by performing IFFT processing on the signal, and inserting the copy part as a guard interval in front of the effective symbol. Generating an OFDM symbol at the end of the frame, mapped to the OFDM symbol at the end of the subframe; The first part of the effective symbol obtained by performing IFFT processing on the same signal is copied, and the copy part is inserted as a guard interval at the rear part of the effective symbol to generate the OFDM symbol at the head of the next subframe. Has steps.
According to the second subframe creation method of the present invention, IFFT processing is performed on a signal, a guard interval is inserted into an effective symbol obtained by the IFFT processing, and the OFDM symbol at the end of the subframe and the head of the next subframe are inserted. A step of generating OFDM symbols, respectively, so that an OFDM symbol at the end of a subframe and a next subframe are inverted so that two sample arrays before and after the subframe synchronization timing are inverted regardless of the type of subframe to be transmitted. Create the first OFDM symbol.
・ Transmitter
The first transmission apparatus of the present invention is obtained by a phase rotation unit that performs phase rotation processing on one of the pilot signals that are the end or head of a subframe, an IFFT processing unit that performs IFFT processing on a signal, and the IFFT processing. A guard interval insertion unit that inserts a guard interval into each valid symbol, and a pilot signal that has been subjected to phase rotation processing and a pilot signal that has not been subjected to phase rotation processing are each subjected to IFFT processing, and each effective symbol obtained by the IFFT processing Insert a guard interval into the symbol to create the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe, and a certain number of samples before and after the subframe synchronization timing regardless of the type of subframe transmitted. A control unit that performs control so that the subframe is repeated, and a transmission unit that wirelessly transmits the subframe. .
The second transmission apparatus of the present invention includes an IFFT processing unit that performs IFFT processing on a signal, a guard interval insertion unit that inserts a guard interval into an effective symbol obtained by the IFFT processing, regardless of the type of subframe to be transmitted A control unit that controls to generate an OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe so that the two sample arrays before and after the subframe synchronization timing are inverted from each other; A transmission unit for transmitting is provided.

According to the present invention, since the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are generated so that a predetermined number of samples repeat before and after the subframe synchronization timing, a plurality of different GI lengths are generated. Even when subframes (for example, a short GI subframe and a long GI subframe) are used in combination, a correlator corresponding to each subframe can be eliminated when detecting the subframe timing.
Also, according to the present invention, since the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are generated using the pilot signal, the number of pilots included in the subframe can be increased, Channel estimation accuracy can be improved.
In addition, according to the present invention, since two sample arrays repeated before and after the subframe synchronization timing are inverted from each other, a sharp peak can be generated at the subframe synchronization timing during the correlation calculation, The detection accuracy of subframe synchronization timing can be improved.

(A) Principle of the Present Invention FIG. 1 is an explanatory diagram of the principle of the present invention.
In a digital communication system using a plurality of types of subframes having different guard interval lengths, it is necessary to detect subframe synchronization timing and symbol synchronization timing.
Therefore, as shown in FIG. 1A, the pilot signal is subjected to IFFT processing, and a guard interval GI is inserted into the effective symbol P obtained by the IFFT processing to generate the OFDM symbol S0 at the end of the subframe. A method may be considered in which IFFT processing is performed on the same pilot signal, and a guard interval GI is inserted into the effective symbol P obtained by the IFFT processing to generate the first OFDM symbol S1 of the next subframe. However, in this method OFDM symbol length N _L long GI subframe SF _L and the short GI subframe SF _S, N _S is different. For this reason, in order for the receiving station (mobile station) to detect the subframe synchronization timing by the correlation calculation, it is necessary to provide a correlator corresponding to each subframe, which is not preferable.
Therefore, in the present invention, as shown in FIG. 1 (B), as a predetermined number of samples N ₀ is repeated before and after T _SYC subframe synchronization timing, leading subframe last OFDM symbol S0 and the next sub-frame An OFDM symbol S1 is created. Specifically, the OFDM valid symbol P having a length of N ₀ is repeated before and after the subframe synchronization timing T _SYC . In this way, the long GI subframe SF _L and the short GI subframe SF _S of the OFDM symbol length N _L, even different N _S, the mobile station need only comprise a correlator length N _0, correlation The subframe synchronization timing T _SYC in each subframe can be detected by calculation. That is, subframe synchronization timing and symbol synchronization timing of subframes having different GI lengths can be detected by using a pilot signal and by one correlator.

As described above, when the correlation calculation is performed so that a predetermined number of samples are repeated before and after T _SYC of the subframe synchronization timing, the correlation value C (t) becomes triangular as shown in FIG. In FIG. 2, the effective symbols are 4 samples a, b, c, and d. If the correlation calculation timing matches the symbol synchronization timing T _SYC , the correlation value C (T) = a ² + b ² + c ² + d ² , indicating the peak value, and deviating back and forth from the symbol synchronization timing T _SYC Correlation value C (T−1) = a ² + b ² + c ² , C (T + 1) = b ² + c ² + d ² , and the smaller the deviation, the smaller the correlation value C (t). Become. As described above, when the correlation value has a peak characteristic having a width corresponding to the length of the repetitive portion (effective symbol period), a symbol synchronization timing detection error is likely to occur due to the influence of noise and a delayed wave.
As shown in FIG. 2 (B), the present invention provides an OFDM symbol at the end of a subframe and a head of the next subframe so that two sample arrays repeated before and after the subframe synchronization timing T _SYC are inverted from each other. Each OFDM symbol is created. In the example of FIG. 2B, the arrangement of the effective symbols at the end of the subframe is a, b, c, d, but the arrangement of the effective symbols at the beginning of the next subframe is d, c, b, a. It is reversed. Thus, by inverting the sample arrangement, the correlation value exhibits a large peak value if the correlation calculation timing matches the symbol synchronization timing _TSYC, and becomes zero if the correlation calculation timing does not match. . That is, if the timing of the correlation calculation coincides with the symbol synchronization timing T _SYC , the correlation value C (T) = a ² + b ² + c ² + d ^{2 is obtained} , indicating a peak value, and before and after the symbol synchronization timing T _SYC When they deviate, the correlation values C (T−1) = 0 and C (T + 1) = 0. As a result, it is possible to accurately detect the symbol synchronization timing.

(B) First Embodiment (a) OFDM Transmitting Device FIG. 3 is a block diagram of the OFDM transmitting device (base station) of the first embodiment. The transmitting device time-divides long GI subframes and short GI subframes as appropriate. It shall be multiplexed and transmitted.
The subframe format storage unit 41 stores the subframe formats of the long GI subframe and the short GI subframe. The transmission subframe format determination unit 42 determines a subframe format based on whether to transmit unicast data or multicast data, and reads the subframe format information from the subframe format storage unit 41 to perform channel multiplexing. This is notified to the control unit 43, the phase rotation processing unit 44, and the guard interval length control unit (hereinafter referred to as GI length control unit) 45.
Based on the control of the channel multiplexing control unit 43, the channel multiplexing unit 46 time-division-multiplexes and outputs a data channel and a pilot channel, which are discrete time signals. In this embodiment, the channel multiplexing unit 46 time-division multiplexes the pilot channel to the data channel so that at least the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are generated using the same pilot signal. . That is, the OFDM symbol at the end of the subframe is created using the pilot of the next subframe.
When the phase rotation processing unit 44 has N ₀ as the effective symbol length of OFDM and _NG as the symbol length of the guard interval, the n-th (n = _{0 to} N _0-1 ) sample of the pilot signal,
w (n) = exp (-jnN G / N 0) (1)
The phase rotation unit 47 is instructed to perform the phase rotation. In response to this instruction, the phase rotation unit 47 performs the phase rotation of w (n) shown in the equation (1) only on the pilot signal that becomes the OFDM symbol at the end of the subframe, and outputs it. The phase rotation unit 47 does not perform phase rotation on the data signal or other pilot signals.
A serial / parallel conversion processing unit (S / P conversion unit) 48 converts a fixed number N ₀ of samples input serially in time series from the phase rotation unit 55 in parallel, and converts it into N ₀ subcarrier signal components. The data is input to the IFFT processing unit 49. FIG. 4 represents the output of the S / P conversion processing unit 48 in a time-frequency two-dimensional region. Note that p (m + 1, n) represents the nth subcarrier component of the pilot signal of the (m + 1) th subframe.
The IFFT processing unit 49 performs IFFT processing on the N ₀ subcarrier signal components and outputs N ₀ time discrete data strings (effective symbols). The GI length control unit 50 instructs the GI insertion unit 50 to insert a _NG of length _NG corresponding to the subframe format. As a result, the GI insertion unit 58 creates a copy of the rear _NG samples of the effective symbol input from the IFFT processing unit 49, inserts the copy portion at the beginning of the effective symbol, and inputs the copy to the wireless processing unit 51. The radio processing unit 51 DA-converts the baseband OFDM symbol input from the GI insertion unit 50, then frequency up-converts the radio signal to a radio signal, amplifies the power, and transmits the radio signal.

(b) Explanation of repetition In the first embodiment, the reason why the sample of the number of effective symbols _NG is repeated before and after T _SYC of the subframe synchronization timing will be described. If the pilot signal composed of N ₀ (= 10) samples is subjected to IFFT processing without phase rotation, the effective symbol 200 is as shown in FIG.
ABCDEFGHIJ
The GI length shall be 2 samples.
When the pilot signal that becomes the OFDM symbol at the end of the subframe is subjected to the phase rotation of w (n) shown in equation (1), the effective symbol 201 created by IFFT processing is counterclockwise as shown in FIG. 5 (B) Rotate by 2 samples
IJABCDEFGH
become. Therefore, when the GI is inserted by the GI insertion unit 50, the OFDM symbol 202 becomes as shown in FIG.
GH IJABCDEFGH
N ₀ sample sequences from the symbol synchronization timing T _SYC are
IJABCDEFGH
become.
On the other hand, since the pilot signal that is the OFDM symbol at the head of the subframe is not subjected to phase rotation, the effective symbol 211 created by IFFT processing is as shown in FIG.
ABCDEFGHIJ
become. Therefore, when GI insertion is performed by the GI insertion unit 50, the OFDM symbol 212 is as shown in FIG.
IJABCDEFGHIJ
N ₀ sample sequences from the symbol synchronization timing T _SYC are
IJABCDEFGH
become. As a result, N ₀ sample sequences are repeated before and after the subframe synchronization timing T _SYC .

The above is the case where the GI length is 2 samples, but in the case of 3 samples, the effective symbol at the end of the subframe is rotated by 3 samples.
HIJABCDEFG
The OFDM symbol at the end of the subframe is
EFGHIJABCDEFG
N ₀ sample sequences from the symbol synchronization timing T _SYC are
HIJABCDEFG
It becomes.
The OFDM symbol at the beginning of the subframe is
HIJABCDEFGHIJ
N ₀ sample sequences from the symbol synchronization timing T _SYC are
HIJABCDEFG
It becomes. As a result, N ₀ sample sequences are repeated before and after the subframe synchronization timing T _SYC .
That is, 10 samples (symbols) are repeated before and after the subframe synchronization timing T _SYC for both the short GI subframe and the long GI subframe.
6 is an explanatory view of a long GI subframe SF _L and the short GI subframe SF _S subframes end of OFDM symbol 202, 202 'and the sub-frame head of the OFDM symbol 212, 212' in. Since the effective number of symbols N ₀ symbol is constant regardless of the type of sub-frame, the long GI subframe SF _L and a short GI subframe SF _S together, N ₀ samples are before and after T _SYC subframe synchronization timing Can be repeated.

(c) Timing Synchronization Detection in Receiving Device FIG. 7 is a configuration diagram of a timing synchronization detection processing unit in the receiving device (mobile station) of the first embodiment. The radio processing unit 61 frequency-converts the radio signal transmitted from the transmission device into a baseband signal, AD converts the baseband signal, and inputs the converted signal to the timing synchronization detection processing unit 62. The timing synchronization detection processing unit 62 includes a correlation calculation unit 63, an average calculation unit 64, and a synchronization timing detection unit 65.
In the correlation calculation unit 63, the shift register 63a stores the latest 2 × N ₀ samples r (0) to r (2N ₀ −1) while sequentially shifting, assuming that the effective symbol length is N ₀ . N ₀ multipliers 63b, the latest N ₀ samples r (j) (j = 0,1 , ..., N 0 -1) and the corresponding sample r in from the previous N ₀ samples it ( j + N ₀ ) are multiplied together, and the adder 63c calculates the correlation value by adding the multiplication results and inputs the correlation value to the average calculation unit 64. The adder 63c calculates and outputs a correlation value every time one sample is input, and outputs M correlation values per subframe, where M is the number of symbols in the subframe. In the average calculation unit 64, the correlation value storage unit 64a stores the M adder outputs, and the adder 64b is stored in the M correlation values sequentially output from the correlation calculation unit 63 and the correlation value storage unit 64a. The corresponding correlation values are added, and the addition result is stored in the correlation value storage unit. The average calculation unit 64 inputs the M correlation values added over the L subframes to the synchronization timing detection unit 65. The number M of subframe samples is constant regardless of the type of subframe (see FIG. 23),
M = Nofdm_s × Nf_s = Nofdm_1 × Nf_l
It is. However,
Nf_s: Number of OFDM symbols in one short GI subframe,
Nf_l: Number of OFDM symbols per long GI subframe,
Nofdm_s: Number of samples per OFDM symbol in the short GI subframe,
Nofdm_l: The number of samples per OFDM symbol of the long GI subframe.
The synchronization timing detection unit 65 detects the maximum timing among the M correlation values, and outputs the timing as a subframe synchronization timing and a symbol synchronization timing.
As described above, according to the first embodiment, it is possible to detect the subframe synchronization timing and the symbol synchronization timing of subframes having different GI lengths using a pilot signal and using one correlator.

(d) Modified Example-First Modified Example In the first example, the phase rotation unit 55 outputs the pilot signal that is the OFDM symbol at the end of the subframe, with the phase rotation of w (n) shown in Equation (1) being output. Is the following formula only for the pilot signal that is the OFDM symbol at the beginning of the subframe.
W (n) = exp (+ jnN G / N 0) (2)
It is possible to configure so that IFFT processing is performed with the phase rotation. In this way, a predetermined number of samples are repeated before and after T _SYC of the subframe synchronization timing. The reason will be described below. When IFFT processing is performed on a pilot signal composed of N ₀ (= 10) samples without performing phase rotation, an effective symbol 200 is obtained as shown in FIG.
ABCDEFGHIJ
The GI length shall be 2 samples.
Since the pilot signal that is the OFDM symbol at the end of the subframe is not subjected to phase rotation, the effective symbol 201 created by IFFT processing is as shown in FIG.
ABCDEFGHIJ
become. Therefore, when GI insertion is performed by the GI insertion unit 50, the OFDM symbol 202 is as shown in FIG.
IJABCDEFGHIJ
N ₀ sample sequences from the symbol synchronization timing T _SYC are
ABCDEFGHIJ
become.
On the other hand, when the pilot signal that is the OFDM symbol at the head of the subframe is subjected to the phase rotation of w (n) shown in Equation (2), the effective symbol 211 created by IFFT processing is clocked as shown in FIG. Rotate 2 samples in the direction
CDEFGHIJAB
become. Therefore, when the GI is inserted by the GI insertion unit 50, the OFDM symbol 212 is as shown in FIG.
AB CDEFGHIJAB
N ₀ sample sequences from the symbol synchronization timing T _SYC are
ABCDEFGHIJ
become. As a result, N ₀ samples are repeated before and after the subframe synchronization timing T _SYC . The above is a case where the GI length is 2 samples, but in the case of 3 samples, N ₀ samples are repeated before and after the subframe synchronization timing T _SYC . That is, 10 samples are repeated before and after the subframe synchronization timing T _SYC for both the short GI subframe and the long GI subframe.

Other Modifications In the first embodiment, pilot samples are arranged on all N ₀ subcarriers, but the present invention is not limited to this. Pilot samples may be arranged only on some subcarriers, and other channels such as data channels and BCH (Broadcast Channel) may be arranged on other subcarriers. In that case, only the pilot may be repeatedly arranged or may be repeatedly arranged including other channels.
In the first embodiment, N ₀ symbol sequences are repeated before and after the subframe timing T _SYC , but the present invention is not limited to this. For example, N ₀ symbol sequences may be repeated before and after the symbol synchronization timing of the fourth OFDM symbol. In this way, the symbol synchronization timing can be detected.
In the first embodiment, there are two types of GI lengths, but the number is not limited to two.

(C) Second Embodiment The first embodiment realizes a repetitive structure that does not depend on the GI length by rotating the phase on the frequency axis, but the second embodiment adds a GI on the time axis. Repetitive structure independent of GI length is realized.
FIG. 9 is a block diagram of the OFDM transmission apparatus (base station) of the second embodiment. Components identical with those of the transmission apparatus of the first embodiment in FIG. The difference is that (1) the phase rotation processing unit and the phase rotation unit are deleted, and (2) a GI forward insertion unit 71 and a GI backward report insertion unit 72 are provided as GI insertion units.
The subframe format storage unit 41 stores the subframe formats of the long GI subframe and the short GI subframe. The transmission subframe format determination unit 42 determines a subframe format based on whether to transmit unicast data or multicast data, and reads the subframe format information from the subframe format storage unit 41 to perform channel multiplexing. The control unit 43 and the GI length control unit 45 are notified.
Based on the control of the channel multiplexing control unit 43, the channel multiplexing unit 46 time-division-multiplexes and outputs a data channel and a pilot channel, which are discrete time series signals. In this embodiment, the channel multiplexing unit 46 time-division multiplexes the pilot channel to the data channel so that at least the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are generated using the same pilot signal. . That is, the OFDM symbol at the end of the subframe is created using the pilot of the next subframe.
Serial-parallel conversion unit (S / P conversion unit) 48 converts the samples of the predetermined number N ₀ to be input to the series in the serial time from the channel multiplexer 46 in parallel, as N ₀ sub-carrier signal component The data is input to the IFFT processing unit 49.
The IFFT processing unit 49 performs IFFT processing on the N ₀ subcarrier signal components and outputs N ₀ time-series data (effective symbols). The changeover switch 73 inputs the effective symbol at the end of the subframe to the GI front insertion unit 71, and inputs the effective symbol at the beginning of the subframe to the GI rear insertion unit 72. Note that the changeover switch 73 inputs only the effective symbol at the head of the subframe to the GI backward insertion unit 72, and inputs other effective symbols to the GI front insertion unit 71.

The GI length control unit 45 instructs the GI front insertion unit 71 and the GI rear insertion unit 72 to insert a GI of length _NG corresponding to the subframe format. As a result, the GI front insertion unit 71 creates a copy of the rear _NG symbols of the effective symbol input via the changeover switch 73, and inserts the copy portion at the head of the effective symbol as a GI. Enter in 74. Further, the GI backward insertion unit 72 creates a copy of the front _NG symbols of the effective symbol input via the changeover switch 73, and inserts the copy portion as a GI at the rear of the effective symbol, Enter in 74.
The combining unit 74 combines the OFDM symbols input from the GI front insertion unit 71 and the GI rear insertion unit 72 and inputs them to the wireless processing unit 51. The radio processing unit 51 DA-converts the baseband OFDM symbol, and then up-converts the frequency into a radio signal, amplifies the power, and transmits the radio signal.

As described above, a predetermined number of samples are repeated before and after T _SYC of the subframe synchronization timing. The reason will be described below. When IFFT processing is performed on a pilot signal composed of N ₀ (= 10) samples, the effective symbol 200 is obtained as shown in FIG.
ABCDEFGHIJ
The GI length shall be 2 samples.
When the GI is inserted into the effective symbol at the end of the subframe in the GI forward insertion unit 71, the OFDM symbol 251 is as shown in FIG. 10 (B).
IJ ABCDEFGHIJ
It becomes. Further, when the GI is inserted into the effective symbol at the head of the subframe in the GI backward insertion unit 72, the OFDM symbol 261 is as shown in FIG. 10 (C).
ABCDEFGHIJAB
It becomes. As a result, N ₀ samples are repeated before and after the subframe synchronization timing T _SYC . Although the GI length is 2 samples as described above, N ₀ sample sequences are repeated before and after the subframe synchronization timing T _{SYC in} the case of 3 samples. That is, 10 samples are repeated before and after T _SYC of the subframe synchronization timing, _whether it is a short GI subframe or a long GI subframe.

(D) Third Example
(a) OFDM transmitter In the third embodiment, the OFDM symbol at the end of the subframe and the next subframe are arranged so that the arrangement of N ₀ samples repeated before and after the subframe synchronization timing T _SYC is inverted. Create the first OFDM symbol of.
FIG. 11 is a block diagram of an OFDM transmission apparatus (base station) according to the third embodiment. Components identical with those of the transmission apparatus according to the first embodiment in FIG. The difference lies in the changeover switch 81, the rearrangement unit 82, and the composition for making the arrangement of the pilot signal that becomes the OFDM symbol at the end of the subframe and the arrangement of the pilot signal that becomes the OFDM symbol at the beginning of the next subframe invert each other. This is the point where the part 83 is provided.
The subframe format storage unit 41 stores the subframe formats of the long GI subframe and the short GI subframe. The transmission subframe format determination unit 42 determines a subframe format based on whether to transmit unicast data or multicast data, and reads the subframe format information from the subframe format storage unit 41 to perform channel multiplexing. Notify the control unit 43, the phase rotation processing unit 44, and the GI length control unit 45.
The changeover switch 81 performs switching control so that only the pilot signal that becomes the OFDM symbol at the end of the subframe is input to the rearrangement processing unit 82 and the other pilot signals are directly input to the synthesis unit 83. N ₀ sample sequences of pilot signals that are OFDM symbols at the end of the m-th subframe
p (m + 1,0), p (m + 1,1), p (m + 1,2), ..., p (m + 1, N0-2), p (m + 1, N0-1 )
If this is the case, the reordering unit 82 defines the sample sequence of the pilot signal as follows:
p (m + 1, N0-1), p (m + 1, N0-2), ..., p (m + 1,2), p (m + 1,1), p (m + 1 , 0)
Are rearranged as shown in FIG. The combining unit 83 combines the pilot signal rearranged with the pilot signal directly input from the changeover switch 81 and inputs the combined pilot signal to the channel multiplexing unit 46.

Based on the control of the channel multiplexing control unit 43, the channel multiplexing unit 46 time-division-multiplexes and outputs the data channel and the pilot channel. In this embodiment, the channel multiplexing unit 46 time-division multiplexes the pilot channel to the data channel so that at least the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are generated using the same pilot signal. . However, the arrangement of pilot signals is reversed.
The phase rotation processing unit 44 instructs the phase rotation unit 47 to perform the phase rotation w (n) of equation (1). In response to this instruction, the phase rotation unit 47 performs the phase rotation of w (n) shown in the equation (1) only on the pilot signal that becomes the OFDM symbol at the end of the subframe, and outputs it. The phase rotation unit 47 does not perform phase rotation on the data signal or other pilot signals.
A serial / parallel conversion processing unit (S / P conversion unit) 48 converts a fixed number N ₀ of samples input serially in time series from the phase rotation unit 47 in parallel, and converts it into N ₀ subcarrier signal components. The data is input to the IFFT processing unit 49. FIG. 12 represents the output of the S / P conversion processor 48 in a time-frequency two-dimensional region. What should be noted is that the arrangement of the pilot signals at the end of the subframe is inverted.
The IFFT processing unit 49 performs IFFT processing on the N ₀ subcarrier signal components and outputs N ₀ discrete time-series data (effective symbols). The GI length control unit 45 instructs the GI insertion unit 50 to insert a _NG of length _NG corresponding to the subframe format. As a result, the GI insertion unit 50 creates a copy of the rear _NG symbols of the effective symbol input from the IFFT processing unit 49, inserts the copy portion at the beginning of the effective symbol, and inputs the copy to the wireless processing unit 59. The radio processing unit 59 DA-converts the baseband OFDM symbol, and then up-converts the frequency to a radio signal, amplifies the power, and transmits the radio signal.
Since the arrangement of the pilot signal serving as the OFDM symbol at the end of the subframe and the pilot signal serving as the OFDM symbol at the beginning of the next subframe are inverted, the OFDM symbol output from the GI insertion unit 50 is represented in FIG. As shown. (A) is a case of a long GI subframe, and (B) is a case of a short GI subframe.
From the above, regardless of the type of subframe, N ₀ symbols are temporally inverted at the subframe synchronization timing T _SYC as a boundary. That is, N ₀ symbols are symmetric about the subframe synchronization timing T _SYC .

(B) Receiving device FIG. 14 is a block diagram of the timing synchronization detection processing unit in the receiving device (mobile station) of the third embodiment, and the same parts as those of the receiving device of the first embodiment in FIG. is doing. A different point is a combination of two samples multiplied by N ₀ multipliers 63b.
The wireless processing unit 61 converts the frequency of the wireless signal transmitted from the transmission device into a baseband signal, AD converts the baseband signal, and inputs the converted signal to the timing synchronization detection processing unit 62. If the effective symbol length is N ₀ , the shift register 63a of the correlation calculation unit 63 stores the latest 2 × N ₀ samples r (0) to r (2N ₀ −1) while sequentially shifting. N ₀ multipliers 63b, the latest N ₀ samples r (j) (j = 0,1 , ..., N 0 -1) and the corresponding sample r in from the previous N ₀ samples it ( 2N ₀ -1-j) is multiplied, and the adder 63c adds the multiplication results and inputs them to the average calculation unit 64. As in the first embodiment, the average calculation unit 64 inputs M adder outputs to the synchronization timing detection unit 65 when the number of subframe samples is M. The synchronization timing detection unit 65 detects the maximum timing among the M correlation values, and outputs the timing as a subframe synchronization timing and a symbol synchronization timing.
As a result, as described with reference to FIG. 2B, a correlation value is generated only when the timing of the correlation calculation coincides with the symbol synchronization timing T _SYC and shows a large peak value. Thus, the detection accuracy of the symbol synchronization timing T _SYC can be improved.

(c) Modification In the third embodiment, the arrangement of the pilot signal that becomes the OFDM symbol at the end of the subframe is inverted. However, the arrangement of the pilot signal that becomes the OFDM symbol at the beginning of the next subframe can also be inverted. In such a case, the output of the S / P converter 48 can be expressed in a two-dimensional time-frequency region as shown in FIG.
In the third embodiment, the pilot signal that becomes the OFDM symbol at the end of the subframe is output after being subjected to the phase rotation of w (n) shown in Equation (1), but only the pilot signal that becomes the OFDM symbol at the beginning of the subframe (2 It is possible to configure so that IFFT processing is performed by applying the phase rotation of equation (1).
Further, other variations of the first embodiment are possible in the third embodiment.

(E) Fourth Embodiment In the fourth embodiment, as in the third embodiment, the end of the subframe is such that the arrangement of N ₀ symbols repeated before and after the subframe synchronization timing T _SYC is inverted with respect to each other. OFDM symbols and the first OFDM symbol of the next subframe are created.
FIG. 16 is a block diagram of an OFDM transmission apparatus (base station) according to the fourth embodiment. Components identical with those of the transmission apparatus according to the second embodiment in FIG. The difference lies in the changeover switch 81, the rearrangement unit 82, and the composition for making the arrangement of the pilot signal that becomes the OFDM symbol at the end of the subframe and the arrangement of the pilot signal that becomes the OFDM symbol at the beginning of the next subframe invert each other. This is the point where the part 83 is provided.
The subframe format storage unit 41 stores the subframe formats of the long GI subframe and the short GI subframe. The transmission subframe format determination unit 42 determines a subframe format based on whether to transmit unicast data or multicast data, and reads the subframe format information from the subframe format storage unit 41 to perform channel multiplexing. The control unit 43 and the GI length control unit 45 are notified.
The changeover switch 81 performs switching control so that only the pilot signal that becomes the OFDM symbol at the end of the subframe is input to the rearrangement processing unit 82 and the other pilot signals are directly input to the synthesis unit 83. N ₀ sample sequences of pilot signals that are OFDM symbols at the end of the m-th subframe
p (m + 1,0), p (m + 1,1), p (m + 1,2), ..., p (m + 1, N0-2), p (m + 1, N0-1 )
If this is the case, the reordering unit 82 uses the pilot signal sample sequence as follows:
p (m + 1, N0-1), p (m + 1, N0-2), ..., p (m + 1,2), p (m + 1,1), p (m + 1 , 0)
As shown in FIG. The combining unit 83 combines the pilot signal rearranged with the pilot signal directly input from the changeover switch 81 and inputs the combined pilot signal to the channel multiplexing unit 46.

Based on the control of the channel multiplexing control unit 43, the channel multiplexing unit 46 time-division-multiplexes and outputs the data channel and the pilot channel. In this embodiment, the channel multiplexing unit 46 time-division multiplexes the pilot channel to the data channel so that at least the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are generated using the same pilot signal. . However, the arrangement of pilot signals is reversed.
Serial-parallel conversion unit (S / P conversion unit) 48 converts the samples of the predetermined number N ₀ to be input to the series in the serial time from the channel multiplexer 46 in parallel, as N ₀ sub-carrier signal component The data is input to the IFFT processing unit 49. FIG. 17 represents the output of the S / P conversion processing unit 48 in a two-dimensional area of time-frequency. What should be noted is that the arrangement of the pilot signals at the end of the subframe is inverted.
The IFFT processing unit 49 performs IFFT processing on the N ₀ subcarrier signal components and outputs N ₀ time-series data (effective symbols). The changeover switch 73 inputs the effective symbol at the end of the subframe to the GI front insertion unit 71, and inputs the effective symbol at the beginning of the subframe to the GI rear insertion unit 72. Note that the changeover switch 73 inputs only the effective symbol at the head of the subframe to the GI backward insertion unit 72, and inputs other effective symbols to the GI front insertion unit 71.
The GI length control unit 45 instructs the GI front insertion unit 71 and the GI rear insertion unit 72 to insert a GI of length _NG corresponding to the subframe format. As a result, the GI forward insertion unit 71 creates a copy of the rear _NG samples of the effective symbol input via the changeover switch 73, and inserts the copy portion as a GI at the beginning of the effective symbol. Enter in 74. Further, the GI backward insertion unit 72 creates a copy of _NG samples of the front part of the effective symbol input via the changeover switch 73, and inserts the copy part as a GI into the rear part of the effective symbol, Enter in 74.
The combining unit 74 combines the OFDM symbols input from the GI front insertion unit 71 and the GI rear insertion unit 72 and inputs them to the wireless processing unit 51. The radio processing unit 51 DA-converts the baseband OFDM symbol, and then up-converts the frequency into a radio signal, amplifies the power, and transmits the radio signal.

As described above, the arrangement of N ₀ samples repeated before and after the subframe synchronization timing T _SYC is inverted. The reason will be described below.
When IFFT processing is performed on a pilot signal composed of N ₀ (= 10) samples, an effective symbol 301 is obtained as shown in FIG.
ABCDEFGHIJ
It becomes. Further, when IFFT processing is performed by inverting the arrangement of pilot signals composed of N ₀ samples, as shown in FIG.
JIHGFEDCBA
It becomes.
When the GI is inserted into the effective symbol 302 at the end of the subframe in the GI forward insertion unit 71, the OFDM symbol 303 is as shown in FIG.
BA JIHGFEDCBA
It becomes. Further, when the GI is inserted into the effective symbol at the head of the subframe in the GI backward insertion unit 72, the OFDM symbol 304 is as shown in FIG.
ABCDEFGHIJAB
It becomes. As a result, the arrangement of N ₀ samples repeated before and after the subframe synchronization timing T _SYC is inverted. The above is a case where the GI length is 2 samples. However, even in the case of 3 samples, the arrangement of N ₀ samples repeated before and after the subframe synchronization timing T _SYC is inverted.

・ Additional notes
(Appendix 1)
In a method for creating a subframe in a digital communication system using a plurality of types of subframes having different guard interval lengths,
The signal is subjected to IFFT processing, and a guard interval is inserted into an effective symbol obtained by the IFFT processing to create an OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe,
In the OFDM symbol creation step, the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe are created so that a predetermined number of samples are repeated before and after the subframe synchronization timing regardless of the type of subframe to be transmitted. To
A method of creating a subframe characterized by the above.
(Appendix 2)
The OFDM symbol creation step includes:
Copying the rear part of the effective symbol obtained by performing IFFT processing on the signal, and inserting the copy part into the front part of the effective symbol as a guard interval to generate an OFDM symbol at the end of the subframe;
Copy the front part of the effective symbol obtained by performing IFFT processing on the same signal as the signal mapped to the OFDM symbol at the end of the subframe, and insert the copy part as a guard interval at the rear part of the effective symbol. Generating an OFDM symbol at the beginning of the next subframe;
The method for creating a subframe as set forth in appendix 1, wherein:
(Appendix 3)
The OFDM symbol creation step includes a step of creating an OFDM symbol at the end of the subframe and a step of creating an OFDM symbol at the beginning of the subframe,
Creating an OFDM symbol at the end of the subframe,
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the nth (n = _{0 to} N _0-1 ) samples constituting the pilot signal
exp (−jnN _G / N ₀ )
The first step of applying IFFT processing with the phase rotation of
A second _NG symbol is copied after the effective symbol obtained by the IFFT process, and the copied portion is inserted as a guard interval at the front of the effective symbol to generate an OFDM symbol at the end of the subframe. Step,
And creating the OFDM symbol at the head of the subframe,
A first step for performing IFFT processing on the same signal as the pilot signal without phase rotation;
Copying _NG samples at the rear of the effective symbol obtained by the IFFT processing, inserting the copy unit at the front of the effective symbol as a guard interval to generate the OFDM symbol at the head of the subframe,
The method for creating a subframe as set forth in appendix 1, wherein:
(Appendix 4)
The OFDM symbol creation step includes a step of creating an OFDM symbol at the end of the subframe and a step of creating an OFDM symbol at the beginning of the subframe,
Creating an OFDM symbol at the end of the subframe,
A first step of performing IFFT processing on the signal;
Copying _NG samples at the rear of the effective symbol obtained by the IFFT processing, inserting the copy part at the front of the effective symbol as a guard interval to generate an OFDM symbol at the end of the subframe,
And creating the OFDM symbol at the head of the subframe,
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the nth (n = _{0 to} N _0-1 ) samples constituting the signal
exp (+ jnN _G / N ₀ )
The first step of applying IFFT processing with the phase rotation of
Copying the _NG sample at the rear of the effective symbol obtained by the IFFT process, and inserting the copy unit as a guard interval at the front of the effective symbol to generate the OFDM symbol at the head of the subframe;
The method for creating a subframe as set forth in appendix 1, wherein:
(Appendix 5)
The supplementary note 1, wherein an OFDM symbol at the end of a subframe and an OFDM symbol at the beginning of a next subframe are respectively generated so that two sample arrays repeated before and after the subframe synchronization timing are inverted from each other. How to create subframes.
(Appendix 6)
The OFDM symbol creation step includes:
Inverting the arrangement of the signals;
The IFFT process is performed on one of the signals in which the array is inverted and the signal that is not inverted, the rear part of the effective symbol obtained by the IFFT process is copied, and the copy part is used as a guard interval at the front part of the effective symbol. Inserting and generating an OFDM symbol at the end of the subframe;
Copy the front part of the effective symbol obtained by performing IFFT processing on the other signal of the inverted signal and the non-inverted signal, and insert the copy part at the rear part of the effective symbol as a guard interval. Generating an OFDM symbol at the beginning of the next subframe;
The method of creating a subframe according to appendix 5, wherein:
(Appendix 7)
The OFDM symbol creation step includes:
Inverting the arrangement of the signals;
Creating an OFDM symbol at the end of the subframe using one of the signals with the inverted array and the non-inverted signal;
Creating the OFDM symbol at the head of the subframe using the other signal of the signal that is inverted and the signal that is not inverted,
Creating an OFDM symbol at the end of the subframe,
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the n-th (n = _{0 to} N ₀₋₎ constituting one of the inverted signal and the non-inverted signal. ₁ ) Sample on
exp (−jnN _G / N ₀ )
The first step of IFFT processing with phase rotation of
A second _NG symbol is copied after the effective symbol obtained by the IFFT process, and the copied portion is inserted as a guard interval at the front of the effective symbol to generate an OFDM symbol at the end of the subframe. Step,
And creating the OFDM symbol at the head of the subframe,
A first step of performing IFFT processing without performing phase rotation on the other signal of the inverted signal and the non-inverted signal;
Copying _NG samples at the rear of the effective symbol obtained by the IFFT processing, inserting the copy unit at the front of the effective symbol as a guard interval to generate the OFDM symbol at the head of the subframe,
The method of creating a subframe according to appendix 5, wherein:
(Appendix 8)
The OFDM symbol creation step includes:
Inverting the arrangement of the signals;
Creating an OFDM symbol at the end of the subframe using one of the signals with the inverted array and the non-inverted signal;
Creating the OFDM symbol at the head of the subframe using the other signal of the signal that is inverted and the signal that is not inverted,
Creating an OFDM symbol at the end of the subframe,
A first step of performing IFFT processing on the one signal without phase rotation;
Copying _NG samples at the rear of the effective symbol obtained by the IFFT processing, inserting the copy part at the front of the effective symbol as a guard interval to generate an OFDM symbol at the end of the subframe,
And creating the OFDM symbol at the head of the subframe,
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the nth (n = _{0 to} N _0-1 ) samples constituting the other signal are used.
exp (+ jnN _G / N ₀ )
The first step of IFFT processing with phase rotation of
Copying _NG samples at the rear of the effective symbol obtained by the IFFT processing, inserting the copy unit at the front of the effective symbol as a guard interval to generate the OFDM symbol at the head of the subframe,
The method of creating a subframe according to appendix 5, wherein:
(Appendix 9)
In a transmission apparatus in a digital communication system using a plurality of types of subframes having different guard interval lengths,
IFFT processing unit that performs IFFT processing on the signal,
A guard interval insertion unit that inserts a guard interval into effective symbols obtained by the IFFT processing;
A control unit that controls to create an OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe so that a predetermined number of samples repeat before and after the subframe synchronization timing;
A transmitter that wirelessly transmits the subframe;
A transmission device comprising:
(Appendix 10)
The guard interval insertion portion includes a guard interval front insertion portion and a guard interval rear insertion portion,
The guard interval forward insertion unit copies the rear part of the effective symbol obtained by performing IFFT processing on the signal under the control of the control unit, and inserts the copy unit at the front part of the effective symbol as a guard interval. To generate an OFDM symbol at the end of the subframe,
The front part of the effective symbol obtained by performing IFFT processing on the same signal as the signal under the control of the guard interval backward insertion wave and the control part is copied, and the copy part is guarded at the rear part of the effective symbol. The transmitter according to appendix 9, wherein the OFDM symbol at the head of the next subframe is generated by being inserted as an interval.
(Appendix 11)
The transmitting device according to appendix 9, wherein the transmitting device further includes:
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the nth (n = _{0 to} N _0-1 ) samples constituting the signal
exp (−jnN _G / N ₀ )
Phase rotation unit for performing phase rotation of
With
The phase rotation unit outputs a signal obtained by performing phase rotation on the signal and a signal not subjected to phase rotation,
The IFFT processing unit performs IFFT processing on the phase-rotated signal, the guard interval insertion unit copies _NG symbols after the effective symbol obtained by the IFFT processing, and the copy unit Is inserted as a guard interval in front of the effective symbol to generate an OFDM symbol at the end of the subframe, and
The IFFT processing unit performs IFFT processing on the signal that is not subjected to phase rotation, the guard interval insertion unit copies _NG samples at the rear of the effective symbol obtained by the IFFT processing, and the copy unit is Inserting as a guard interval at the front of the symbol to generate an OFDM symbol at the beginning of the subframe,
A transmission apparatus characterized by the above.
(Appendix 12)
The transmitting device according to appendix 9, wherein the transmitting device further includes:
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the nth (n = _{0 to} N _0-1 ) samples constituting the signal
exp (+ jnN _G / N ₀ )
Phase rotation unit for performing phase rotation of
With
The phase rotation unit outputs a signal obtained by performing phase rotation on the signal and a signal not subjected to phase rotation,
The IFFT processing unit performs IFFT processing on a signal that is not subjected to phase rotation, the guard interval insertion unit copies _NG symbols after the effective symbol obtained by the IFFT processing, and the copy unit is Insert an OFDM symbol at the end of the subframe by inserting it as a guard interval in front of the effective symbol, and
The IFFT processing unit performs IFFT processing on the phase-rotated signal, the guard interval insertion unit copies the _NG sample at the rear of the effective symbol obtained by the IFFT processing, and the copy unit is Inserting as a guard interval at the front of the symbol to generate an OFDM symbol at the beginning of the subframe,
A transmission apparatus characterized by the above.
(Appendix 13)
The control unit controls to create an OFDM symbol at the end of a subframe and an OFDM symbol at the beginning of the next subframe so that two sample arrays repeated before and after the subframe synchronization timing are inverted from each other Item 9. The transmission device according to appendix 9, wherein
(Appendix 14)
The transmitting apparatus according to appendix 13, further comprising an array inversion unit that inverts the array of the signals,
The guard interval insertion portion includes a guard interval front insertion portion and a guard interval rear insertion portion,
The guard interval forward insertion part copies the rear part of the effective symbol obtained by performing IFFT processing on one of the signals with the inverted array and the non-inverted signal, and copies the copy part to the front part of the effective symbol. Inserted as a guard interval to generate an OFDM symbol at the end of the subframe,
The guard interval backward insertion unit copies the front part of the effective symbol obtained by performing IFFT processing on the other signal of the signal whose arrangement is inverted and the signal which is not inverted, and uses the copy part as the effective symbol. A transmitter characterized by being inserted as a guard interval at the rear to generate an OFDM symbol at the head of the next subframe.
(Appendix 15)
The transmitting device according to attachment 13, wherein the transmitting device further includes:
An arrangement inverting unit for inverting the arrangement of the signals;
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the nth (n = _{0 to} N _0-1 ) samples constituting the signal
exp (−jnN _G / N ₀ )
Phase rotation unit for performing phase rotation of
With
The phase rotation unit performs phase rotation on one of the signals in which the arrangement is inverted and the signal that is not inverted, the IFFT processing unit performs IFFT processing on the phase-rotated signal, and the guard interval insertion unit _NG of the rear part of the effective symbol obtained by the IFFT process is copied, the copy part is inserted as a guard interval in front of the effective symbol to generate an OFDM symbol at the end of the subframe, and ,
The phase rotation unit does not perform phase rotation on the other of the signals with the array inverted and the signal not inverted, and the IFFT processing unit performs IFFT processing on the signal without phase rotation, and inserts the guard interval. The unit copies _NG samples at the rear of the effective symbol obtained by the IFFT process, and inserts the copy unit at the front of the effective symbol as a guard interval to generate the OFDM symbol at the head of the subframe.
A transmission apparatus characterized by the above.
(Appendix 16)
The transmitting device according to attachment 13, wherein the transmitting device further includes:
An arrangement inverting unit for inverting the arrangement of the signals;
When N ₀ is the symbol length of the effective symbol and _NG is the symbol length of the guard interval, the nth (n = _{0 to} N _0-1 ) samples constituting the signal
exp (+ jnN _G / N ₀ )
Phase rotation unit for performing phase rotation of
With
The phase rotation unit does not perform phase rotation on one of the signals in which the array is inverted and the signal that is not inverted, and the IFFT processing unit performs IFFT processing on the signal that is not subjected to phase rotation, and the guard interval insertion unit Copies the _NG symbols at the rear of the effective symbol obtained by the IFFT process, inserts the copy part at the front of the effective symbol as a guard interval, and generates an OFDM symbol at the end of the subframe, And,
The phase rotation unit performs phase rotation on the other signal of the signal whose arrangement is inverted and the signal which is not inverted, the IFFT processing unit performs IFFT processing on the signal subjected to phase rotation, and the guard interval insertion unit Is a copy of the _NG sample at the rear of the effective symbol obtained by the IFFT process, and inserts the copy unit as a guard interval at the front of the effective symbol to generate the OFDM symbol at the head of the subframe.
A transmission apparatus characterized by the above.

It is a principle explanatory view of the present invention. It is correlation calculation explanatory drawing. 1 is a configuration diagram of an OFDM transmission apparatus according to a first embodiment. FIG. In this example, the output of the S / P conversion processing unit is expressed in a two-dimensional time-frequency region. FIG. 6 is a diagram for explaining the reason why a predetermined number of samples repeat before and after subframe synchronization timing in the first embodiment. It is explanatory drawing of the OFDM symbol of the sub-frame end in a long GI sub-frame and a short GI sub-frame, and the OFDM symbol of a sub-frame head. FIG. 3 is a configuration diagram of a timing synchronization detection processing unit in the receiving apparatus of the first embodiment. It is a figure explaining the reason why a predetermined number of samples repeat before and after sub-frame synchronization timing in a modification. FIG. 6 is a configuration diagram of an OFDM transmitter according to a second embodiment. FIG. 10 is a diagram for explaining the reason why a predetermined number of samples repeat before and after subframe synchronization timing in the second embodiment. FIG. 10 is a configuration diagram of an OFDM transmitter according to a third embodiment. This is an example in which the output of the S / P conversion processing unit of the third embodiment is expressed in a two-dimensional time-frequency region. It is an example which represented the OFDM symbol output from the GI insertion part of 3rd Example in the time domain. FIG. 10 is a configuration diagram of a timing synchronization detection processing unit in the receiving apparatus of the third embodiment. It is an example in which the output of the S / P conversion processing unit in a modification of the third embodiment is expressed in a two-dimensional time-frequency region. FIG. 10 is a configuration diagram of an OFDM transmitter according to a fourth embodiment. It is an example in which the output of the S / P conversion processing unit in a modification of the fourth embodiment is expressed in a two-dimensional time-frequency region. FIG. 10 is an explanatory diagram illustrating the reason why the arrangement of N ₀ symbols repeated before and after subframe synchronization timing in the fourth example is inverted from each other. 1 is a block diagram of a general transmission station that employs an OFDM transmission scheme. FIG. It is guard interval insertion explanatory drawing. It is a block diagram of a general receiving station of the OFDM transmission system. It is an example showing the mode of cutting out an effective signal component. It is a subframe format of a short GI subframe and a long GI subframe. FIG. 2 is a configuration diagram of a timing device that implements a first timing detection method. FIG. 6 is an explanatory diagram of a first timing detection method. FIG. 10 is an explanatory diagram of a second timing detection method. FIG. 10 is an explanatory diagram of a third timing detection method.

Explanation of symbols

P valid symbol
GI guard interval
SF _L Long GI subframe
SF _S Short GI Subframe
S0 OFDM symbol at the end of the subframe
OFDM symbol at the beginning of the S1st subframe

Claims (5)

In a method for creating a subframe in a digital communication system using a plurality of types of subframes having different guard interval lengths,
Applying a phase rotation process to one of the pilot signals at the end or head of the subframe;
The OFDM signal at the end of the subframe is obtained by performing IFFT processing on each of the pilot signal subjected to the phase rotation processing and the pilot signal not subjected to the phase rotation processing , and inserting a guard interval into each effective symbol obtained by the IFFT processing. Creating a symbol and the first OFDM symbol of the next subframe, respectively,
Create an OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe so that a certain number of samples repeat before and after the subframe synchronization timing regardless of the type of subframe to be transmitted.
A method of creating a subframe characterized by the above. In a method for creating a subframe in a digital communication system using a plurality of types of subframes having different guard interval lengths,
The signal is subjected to IFFT processing, and a guard interval is inserted into the effective symbol obtained by the IFFT processing to create an OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe, respectively, and the transmitted subframe Creating a OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe so that a predetermined number of samples repeat before and after the subframe synchronization timing regardless of the type of
The OFDM symbol creation step includes:
Copying the rear part of the effective symbol obtained by performing IFFT processing on the signal, and inserting the copy part into the front part of the effective symbol as a guard interval to generate an OFDM symbol at the end of the subframe;
The front part of the effective symbol obtained by performing IFFT processing on the same signal mapped to the OFDM symbol at the end of the subframe is copied, and the copy part is inserted as a guard interval at the rear part of the effective symbol to Generating an OFDM symbol at the beginning of the subframe;
A method for creating a subframe, comprising: In a method for creating a subframe in a digital communication system using a plurality of types of subframes having different guard interval lengths,
The signal is subjected to IFFT processing, and a guard interval is inserted into an effective symbol obtained by the IFFT processing to create an OFDM symbol at the end of the subframe and an OFDM symbol at the beginning of the next subframe,
Regardless of the type of transmitted subframe, the last OFDM symbol at the end of the subframe and the first OFDM symbol at the next subframe are created so that the two sample arrays before and after the subframe synchronization timing are inverted. How to create a featured subframe. In a transmission apparatus in a digital communication system using a plurality of types of subframes having different guard interval lengths,
A phase rotation unit that performs phase rotation processing on one of the pilot signals at the end or head of the subframe,
IFFT processing unit that performs IFFT processing on the signal,
A guard interval insertion unit that inserts a guard interval into effective symbols obtained by the IFFT processing;
Each of the pilot signal subjected to the phase rotation processing and the pilot signal not subjected to the phase rotation processing is subjected to IFFT processing, and a guard interval is inserted into each effective symbol obtained by the IFFT processing, so that OFDM at the end of the subframe is obtained. A control unit that creates an OFDM symbol at the beginning of each symbol and the next subframe, and controls so that a fixed number of samples repeat before and after the subframe synchronization timing, regardless of the type of subframe transmitted;
A transmitter that wirelessly transmits the subframe;
A transmission device comprising: In a transmission apparatus in a digital communication system using a plurality of types of subframes having different guard interval lengths,
IFFT processing unit that performs IFFT processing on the signal,
A guard interval insertion unit that inserts a guard interval into effective symbols obtained by the IFFT processing;
Control to create the OFDM symbol at the end of the subframe and the OFDM symbol at the beginning of the next subframe so that the two sample arrays before and after the subframe synchronization timing are inverted regardless of the type of subframe transmitted. Control unit,
A transmitter that wirelessly transmits the subframe;
Transmitting apparatus characterized by comprising a.

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