JP2012205139A - Radio device and transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which varies a scatter pilot signal value to be transmitted on a segment-by-segment basis, under a circumstance of frequency division multiplexing.SOLUTION: An operation controller 18 selects a first band which is one of bands in which another radio device is transmitting frame signals and a second band in which the other radio device is not transmitting frame signals. A symbol timing generator 32 generates symbol timing, which is synchronous with an OFDM symbol, relative to a received frame signal in the selected first band. A frame timing generator 46 generates frame timing shifted by each OFDM symbol interval unit from the frame timing of the frame signal received in the selected first band. According to the generated frame timing and the generated symbol timing, an OFDM modulator 34 transmits a frame signal in the selected second band.

Description

  The present invention relates to a transmission technique, and more particularly, to a radio apparatus and a transmission method for transmitting an OFDM (Orthogonal Frequency Division Multiplexing) signal.

  In terrestrial digital broadcasting, a plurality of segments are frequency division multiplexed in one channel. In one-segment broadcasting, a signal storing a program is transmitted using only one segment. One transmitter uses a plurality of segments included in one channel when broadcasting a plurality of programs (for example, Patent Document 1).

JP 2010-154416 A

  Area one-segment broadcasting is a service that uses one-segment broadcasting, which is one of terrestrial digital broadcasting, to transmit content data limitedly to a narrow area with transmission power lower than the transmission power used by broadcasters. is there. When the number of programs provided by area one segment broadcasting increases, each wireless device uses another segment in one channel. At that time, when effective use of the frequency is intended, since frequency division multiplexing communication is performed without a guard band, interference between adjacent segments becomes a problem. In order to cope with this, one wireless device operates as a master device, and another wireless device operates as a slave device. When frequency division multiplexing is performed in such a master mode and slave mode, symbol synchronization is executed using the OFDM signal of the adjacent segment as a master. By transmitting an OFDM signal at a symbol-synchronized timing, interference between channels is reduced even if there is no guard band between adjacent segments.

  The scattered pilot signal (SP) is coded and power-spread for each carrier, and is generated with a different initial value for each segment in full-segment terrestrial digital broadcasting. As a result, since the scattered pilot signals of each segment have different values, they are operated so as to spread power. In addition, TMCC (Transmission and Multiplexing Configuration Control) signals are generated and operated based on initial values of different carrier arrangements for each segment in the full segment digital terrestrial broadcasting. On the other hand, in the one-segment broadcasting, the initial value for segment 0 is used. Therefore, when using a plurality of segments included in one channel in area one segment broadcasting, the scattered pilot signal and the TMCC signal have the same value at all of the 13 segment OFDM frame timings. As a result, the amplitude peak in the transmission waveform tends to increase. As the amplitude peak in the transmission waveform increases, distortion is more likely to occur in the transmission amplifier and the reception amplifier. Such distortion deteriorates communication quality.

  The present invention has been made in view of such a situation, and an object thereof is to use a scattered pilot signal to be transmitted while using a scattered pilot having the same pattern in a situation where frequency division multiplexing is performed. Is to provide a technique for preventing each segment from matching when viewed in symbol units.

  In order to solve the above-described problem, a radio apparatus according to an aspect of the present invention transmits a frame signal including a plurality of OFDM symbols from another band among a plurality of bands continuously arranged in the frequency domain. Based on the survey results stored in the survey unit, the survey unit that surveys the surveyed band, and the survey results stored in the storage unit. A selection unit that selects one first band and a second band in which another radio apparatus does not transmit a frame signal, and an OFDM symbol for a frame signal received in the first band selected by the selection unit A frame timing of a frame signal including a plurality of OFDM symbols having a symbol timing generated by a first generation unit that generates a symbol timing synchronized with A second generation unit that generates a frame timing that is shifted in units of an OFDM symbol interval from a frame timing of a frame signal received in the first band selected by the selection unit; a frame timing generated by the second generation unit; and a first generation unit A transmission unit that transmits a frame signal in the second band selected by the selection unit according to the symbol timing generated by.

  According to this aspect, the frame timing is shifted in units of OFDM symbol intervals while synchronizing the symbol timing with respect to the first band, so that frames having different timings in units of processing can be generated between the bands.

  The frame signal transmitted from the transmission unit is relative to at least one of the pilot signal and the TMCC signal included in the frame signal received in the first band selected by the selection unit in the frame signal. May include signals of the same pattern. In this case, since at least one of the pilot signal and the TMCC signal having the same pattern is relatively included in the frame signal, at least one of the pilot signal and the TMCC signal is included for each band. Can be changed.

  The second generation unit may use a shift amount corresponding to the position of the second band in the plurality of bands in order to generate the frame timing. In this case, since the frame timing is shifted using the shift amount corresponding to the position of the second band in the plurality of bands, it can be shifted reliably.

  Another aspect of the present invention is a transmission method. This method includes a step of investigating a band in which another wireless device transmits a frame signal including a plurality of OFDM symbols among a plurality of bands continuously arranged in the frequency domain, and the result of the investigation is stored in a memory. Based on the storing step and the investigation result stored in the memory, the first band, which is one of the bands in which the other radio apparatus transmits the frame signal, and the other radio apparatus does not transmit the frame signal. And a step of generating a symbol timing synchronized with an OFDM symbol for a frame signal received in the selected first band, and a plurality of OFDM symbols having the generated symbol timing. The frame timing of the received frame signal and the frame timing of the received frame signal in the selected first band. Comprising the steps of: generating a frame timing deviation interval basis of OFDM symbols from the ring, according to the frame timing and the generated symbol timing generated, and transmitting the frame signal in the second band selected, the.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, in a situation where frequency division multiplexing is performed, while using a scattered pilot of the same pattern, the transmitted scattered pilot signal matches each segment when viewed in symbol units. You can avoid it.

FIGS. 1A to 1B are diagrams showing the arrangement of segments in an area one segment broadcasting system according to an embodiment of the present invention. It is a figure which shows the structure of the radio | wireless apparatus in the area one segment broadcast system of FIG. FIGS. 3A to 3E are diagrams for explaining the outline of the operation in the guard interval correlation processing unit of FIG. It is a figure which shows the structure of the operation | movement control part of FIG. It is a figure which shows the structure of the symbol timing production | generation part of FIG. FIGS. 6A to 6F are diagrams for explaining the outline of the operation in the symbol timing generation unit of FIG. FIGS. 7A to 7D are diagrams illustrating another operation outline in the symbol timing generation unit of FIG. FIGS. 8A and 8B are diagrams for explaining the outline of the operation in the frame timing generation unit of FIG.

  Before describing the present invention specifically, an outline will be given first. An embodiment of the present invention relates to a radio apparatus that transmits an OFDM signal including content data in order to realize a content distribution service in area one segment broadcasting. Each wireless device uses only one segment as in the one-segment broadcasting. In the area one-segment broadcasting, in order to improve the frequency utilization efficiency, a plurality of segments arranged continuously in the frequency band are used, and no guard band is set between the segments. Each wireless device appropriately starts / stops transmission of the OFDM signal as necessary. In such a situation, in order to reduce interference between adjacent segments, the wireless device performs the following processing.

  In the wireless device, a slave mode and a master mode are defined. When a wireless device starts transmission of an OFDM signal, if there is a segment in which another wireless device is first transmitting an OFDM signal, the wireless device selects the operation in the slave mode. Select the action. When operating in slave mode, the wireless device periodically performs OFDM signal detection in multiple segments to detect a segment used by another wireless device and identify one of the already used segments. Select as a master segment, and select one of the unused segments as a segment to be used (hereinafter referred to as “used segment”). The wireless device generates a symbol timing synchronized with the OFDM symbol of the OFDM signal received in the master segment, and generates an OFDM symbol at the generated symbol timing. Further, the wireless device transmits the generated OFDM symbol in the used segment.

  The OFDM signal transmitted in each segment is configured with a predetermined period as a frame, and a scattered pilot signal and a TMCC signal are arranged from the start timing to the end timing of the frame. Here, it is assumed that the pattern of the scattered pilot signal and the TMCC signal in the frame are the same regardless of the segment. As described above, when the frames in a plurality of segments are synchronized, the scattered pilot signal and the TMCC signal having the same value overlap each other, so that the amplitude peak increases. In order to cope with this, the wireless device shifts the frame timing according to the used segment while synchronizing the symbol timing. Therefore, frames in a plurality of segments are not synchronized, and the scattered pilot signals and TMCC having the same value are reduced from overlapping.

  FIGS. 1A to 1B show the arrangement of segments in an area one segment broadcasting system according to an embodiment of the present invention. FIG. 1A corresponds to a segment used in this embodiment. As shown, 13 segments are arranged in the 5.7 MHz bandwidth, which is the same as digital terrestrial broadcasting. Therefore, each segment has a band of about 429 kHz. In digital terrestrial broadcasting, the central segment 0 is used for one-segment broadcasting. In area one segment broadcasting, when the number of channels providing services increases, using only segment 0 results in a shortage of channels. In order to increase the number of channels, 12 segments other than the central segment 0 are also used in this embodiment. In this case, a guard band is not provided between each of the 12 segments used, that is, between each channel that broadcasts each area one segment broadcast.

  FIG. 1B shows the arrangement of segments to be compared with this embodiment. Here, every other segment is used, and the segment in between is used as a guard band. Therefore, only 7 segments can be used in the frequency band having the same width as that in FIG. However, by providing a guard band, interference between segments is reduced. For this reason, transmission of synchronized FFT clocks or the like for different segments is unnecessary, and symbol timing synchronization is also unnecessary. On the other hand, as described above, in the present embodiment, no guard band is provided as shown in FIG.

  FIG. 2 shows a configuration of the wireless device 100 in the area one segment broadcasting system. The wireless device 100 includes a reception processing unit 10 and a transmission processing unit 12. The reception processing unit 10 also includes a 0th one-segment tuner 14a, a first one-segment tuner 14b, a twelfth one-segment tuner 14m, and a guard interval correlation processing unit 16 that are collectively referred to as a one-segment tuner 14. It includes an interval correlation processing unit 16a, a first guard interval correlation processing unit 16b, a twelfth guard interval correlation processing unit 16m, an operation control unit 18, a switch 20, a transmission carrier setting unit 22, an FFT unit 42, and a TMCC decoder unit 44. The transmission processing unit 12 includes an imaging device 24, a microphone 26, an encoding unit 28, an OFDM frame configuration unit 30, a symbol timing generation unit 32, an OFDM modulation unit 34, a frequency conversion unit 36, a local oscillation unit 38, an RF unit 40, A frame timing generation unit 46 is included.

  The one segment tuner 14 receives a signal transmitted from another wireless device (not shown) via an antenna. Each of the 13 one-segment tuners 14 receives a signal received by an antenna. Each one-segment tuner 14 has a one-to-one correspondence with the segment shown in FIG. That is, each one-segment tuner 14 is set so as to receive signals of different segments. Each one-segment tuner 14 extracts a set segment signal. Each one-segment tuner 14 outputs the extracted signal to the guard interval correlation processing unit 16 and the FFT unit 42.

  13 guard interval correlation processing units 16 are provided in the same manner as the one segment tuner 14, and each of the 13 guard interval correlation processing units 16 corresponds to the one segment tuner 14 on a one-to-one basis. Each guard interval correlation processing unit 16 receives a signal from the one-segment tuner 14. Each guard interval correlation processing unit 16 performs a correlation process at a guard interval on the signal input from the one-segment tuner 14. The received signal is an OFDM signal. This OFDM signal is transmitted after being divided into predetermined unit periods called OFDM symbols. A guard interval is added to the head portion of each OFDM symbol, followed by an effective symbol. The guard interval is created by duplicating the last part of the OFDM symbol. In the following description, an OFDM signal may be referred to as an OFDM symbol or simply a signal.

  The guard interval correlation processing unit 16 delays the input signal by an effective symbol period, and detects a correlation value between the delayed signal and the input signal. The correlation value peaks when the guard interval portion is input. Therefore, the start timing of the OFDM symbol can be detected by detecting the correlation value. This corresponds to detecting that an OFDM signal is received. That is, the guard interval correlation processing unit 16 investigates a band in which another radio apparatus transmits an OFDM signal among a plurality of segments continuously arranged in the frequency domain. Note that the guard interval correlation processing unit 16 repeatedly performs the investigation even when the wireless device 100 transmits an OFDM signal as described later. Hereinafter, a segment that has already been used in advance by another wireless device when the apparatus starts transmission is referred to as an “already occupied segment” for convenience.

  FIGS. 3A to 3E describe an outline of the operation in the guard interval correlation processing unit 16. FIG. 3A shows the structure of the OFDM symbol. As described above, an OFDM symbol is composed of a combination of a guard interval (GI) and a valid symbol. Here, the portion after the effective symbol is cut out and added as a GI before the effective symbol. FIG. 3B shows the configuration of the received OFDM signal. As illustrated, the OFDM symbol shown in FIG. 3A is repeated. FIG. 3C shows a section in which correlation processing is to be executed. As shown in the figure, two windows that are separated by the effective symbol length are set, and each window has a corresponding section of GI length. Here, the high level section indicates a window. The guard interval correlation processing unit 16 performs correlation processing on signals input to the two windows.

  FIG. 3D shows a correlation value generated by the correlation process. The correlation value peaks in the GI. FIG. 3E shows a symbol interval pulse generated based on the correlation value shown in FIG. The symbol interval pulse is a waveform that becomes Low level at the timing near the peak of the correlation value and becomes High level in other periods. Generating the symbol interval pulse corresponds to detecting the start timing of the OFDM symbol. When no OFDM signal is input to the one-segment tuner 14 and the guard interval correlation processing unit 16, the symbol interval pulse maintains a high level. Returning to FIG. The guard interval correlation processing unit 16 outputs a symbol interval pulse to the operation control unit 18.

  The operation control unit 18 inputs the symbol interval pulse from each guard interval correlation processing unit 16. The operation control unit 18 executes predetermined processing based on the symbol interval pulse. The predetermined processing includes (1) recognition processing of already occupied segments, (2) selection processing of used segments, (3) operation mode setting processing, and (4) master segment selection processing in the slave mode. The already-occupied segment recognition process is recognition and storage of the presence or absence of a segment being used. The used segment selection process is a setting of a segment number to be used by the wireless device 100. The operation mode setting process is a setting of the master mode or the slave mode as the operation mode of the wireless device 100. The master segment selection process is the setting of the master segment when operating in the slave mode. By these processes, a predetermined segment, for example, the 0th segment is used as a master segment, another segment, for example, the 2nd segment is used as a used segment, an OFDM signal in the master segment is used as a master, and OFDM symbols are synchronized in the used segment. Send. On the other hand, when the master segment is not set, the master mode is operated.

FIG. 4 shows the configuration of the operation control unit 18. The operation control unit 18 includes an already occupied segment storage unit 50, a segment selection unit 52, an operation mode setting unit 54, and a master segment selection unit 56.
(1) Recognition process of already occupied segment The already occupied segment storage unit 50 acquires the presence of the already occupied segment and the corresponding segment information based on the symbol interval pulse from each guard interval correlation processing unit 16. In other words, the already-occupied segment storage unit 50 monitors whether or not each segment is an already-occupied segment by monitoring whether a low-level section is included in the symbol section pulse for each segment. Get information.

  Here, the already-occupied segment storage unit 50 determines that it is an already-occupied segment when a low-level section is included, and determines that it is an empty segment when it does not include a low-level section. . The already-occupied segment storage unit 50 stores the acquired information, that is, the investigation result in the guard interval correlation processing unit 16. As described above, since the guard interval correlation processing unit 16 repeatedly performs an examination even when the wireless device 100 transmits an OFDM symbol as described later, the already-occupied segment storage unit 50 repeatedly performs acquisition. To update and store the survey results. Specifically, when the transmission of the OFDM symbol in the already occupied segment is completed, the update is a process in which the already occupied segment storage unit 50 deletes information on the already occupied segment for which the transmission of the OFDM symbol is completed. Note that a segment that has newly started transmission of an OFDM symbol is not an already occupied segment.

(2) Selection process of used segment When the signal transmission starts, the segment selection unit 52 confirms that the storage in the already occupied segment storage unit 50 is completed, that is, that the already occupied segment initial setting is completed. After the confirmation, the segment selection unit 52 refers to the contents of the already-occupied segment storage unit 50 and selects a segment in which the other radio apparatus 100 does not transmit the OFDM symbol, that is, an arbitrary segment that is not used. The selected segment corresponds to the aforementioned used segment. In addition, the segment selection unit 52 releases the used segment that has been selected until the end of signal transmission. Next, when resuming signal transmission, the segment selection unit 52 newly selects a use segment.

(3) Operation Mode Setting Process The operation mode setting unit 54 confirms that the storage in the already-occupied segment storage unit 50 has ended, that is, that the already-occupied segment initial setting has ended, at the start of signal transmission. After the confirmation, the operation mode setting unit 54 refers to the contents of the already-occupied segment storage unit 50, and if there is an already-occupied segment, that is, if there is a segment in which another wireless device transmits an OFDM signal, Set the mode. On the other hand, the operation mode setting unit 54 sets the master mode when there is no already occupied segment. When the slave mode is set, the operation mode setting unit 54 monitors the selection contents in the master segment selection unit 56 during the signal transmission operation, and shifts to the master mode when there is no master segment. When the master mode is set, the operation mode setting unit 54 maintains the master mode until the end of signal transmission.

(4) Master Segment Selection Processing in Slave Mode When the signal transmission starts, the master segment selection unit 56 confirms that the storage in the already occupied segment storage unit 50 has ended, that is, the already occupied segment initial setting has ended. . After the confirmation, the master segment selection unit 56 refers to the setting content in the operation mode setting unit 54, and executes the initial setting of the master segment when the operation mode is the slave mode. When the operation mode is the slave mode, the already-occupied segment storage unit 50 stores information on at least one already-occupied segment. Therefore, the master segment selection unit 56 arbitrarily selects one of the already occupied segments. The selected already occupied segment corresponds to the master segment.

  The master segment selection unit 56 monitors the signal transmission state of the master segment by referring to the stored contents of the occupied segment storage unit 50 during the signal transmission operation. When the master segment disappears from the already-occupied segment storage unit 50, that is, when signal transmission in the master segment is completed, the master segment selection unit 56 refers to the stored contents of the already-occupied segment storage unit 50. If the already-occupied segment storage unit 50 includes information on the already-occupied segment, the master segment selection unit 56 arbitrarily selects an already-occupied segment different from the already-occupied segment that has been selected as the master segment so far select. Note that completion of signal transmission in the master segment corresponds to non-reception of the OFDM signal. The master segment selection unit 56 sets the newly selected already occupied segment as a new master segment, and continues the slave operation.

  When the signal transmission in the newly set master segment is completed in this way, the master segment selection unit 56 repeatedly executes the same processing as before. In other words, the master segment selection unit 56 selects an already-occupied segment that is different from the already-occupied segment that has been selected as the master segment so far as the master segment if the information on the already-occupied segment is included in the already-occupied segment storage unit 50. And select a new one arbitrarily. On the other hand, if the already-occupied segment storage unit 50 does not include information on already-occupied segments, the master segment selection unit 56 stops the processing. In such a case, the operation mode setting unit 54 switches from the slave mode to the master mode. When the operation mode initial setting is the master mode, the master segment selection unit 56 does not execute the process. Returning to FIG.

  The switch 20 receives the symbol interval pulse from each guard interval correlation processing unit 16 and the information related to the operation mode from the operation control unit 18. Further, when the operation mode is the slave mode, the switch 20 also inputs information related to the master segment from the operation control unit 18. When the operation mode is the slave mode, the switch 20 selects a symbol interval pulse corresponding to the master segment based on information on the master segment. The switch 20 outputs the selected symbol interval pulse to the symbol timing generation unit 32. On the other hand, the switch 20 stops the output when the operation mode is the master mode. The transmission carrier setting unit 22 inputs information on the used segment from the operation control unit 18. The transmission carrier setting unit 22 sets the frequency for the used segment in the local oscillation unit 38.

  The image sensor 24 captures moving images or still images (hereinafter collectively referred to as “images”). The imaging element 24 outputs digital data of the captured image (hereinafter referred to as “image”) to the encoding unit 28. The microphone 26 acquires sound. The microphone 26 outputs the acquired audio digital data (hereinafter referred to as “voice”) to the encoding unit 28. Note that the image and sound correspond to content data distributed by the wireless device 100. The content data is not limited to this, and may be other data. For example, the content may be an image stored in advance or information acquired via a network (not shown). The encoding unit 28 inputs an image from the image sensor 24 and also inputs sound from the microphone 26. The encoding unit 28 performs encoding on images and sound. In addition, since a well-known technique should just be used for encoding, description is abbreviate | omitted here. The encoding unit 28 outputs the encoding result (hereinafter referred to as “data”) to the OFDM frame configuration unit 30.

  The symbol timing generation unit 32 inputs information regarding the operation mode from the operation control unit 18. When the operation mode is the slave mode, the symbol timing generation unit 32 receives the symbol interval pulse from the switch 20. The symbol timing generation unit 32 generates timing (hereinafter referred to as “symbol timing”) synchronized with the OFDM symbol received by the master segment based on the input symbol interval pulse. When the master segment is switched, the symbol timing generation unit 32 generates symbol timing synchronized with the OFDM symbol received in the newly selected master segment. On the other hand, when the operation mode is the master mode, the symbol timing generation unit 32 generates autonomous timing by operating in a free run without using a reference timing.

  As described above, if the OFDM symbol is not received in the master segment during the operation in the slave mode and the already-occupied segment is not included in the investigation result stored in the already-occupied segment storage unit 50, the symbol timing generation unit 32 switches the operation mode from the slave mode to the master mode. As a result, the symbol timing generation unit 32 operates in a free run. Here, the configuration of the symbol timing generation unit 32 corresponding to the slave mode will be described in more detail.

  FIG. 5 shows the configuration of the symbol timing generator 32. The symbol timing generator 32 includes an OFDM transmission symbol counter 60, a comparator 62, an EN circuit 64, and a gate element 66. The signal includes a symbol interval pulse 200, a symbol interval set pulse 202, a symbol timing 204, an A <C signal 206, and a set pulse disable signal 208. Here, the configuration of the symbol timing generation unit 32 will be described with reference to FIGS. 6A to 6F and FIGS. 7A to 7F. 6A to 6F are diagrams for explaining the outline of the operation in the symbol timing generation unit 32. FIG. FIG. 6A shows the structure of the OFDM signal received in the master segment. FIG. 6B shows a symbol interval pulse 200 input to the symbol timing generation unit 32. FIGS. 6A and 6B are the same as FIGS. 3B and 3E. Returning to FIG. The OFDM transmission symbol counter 60 receives the symbol interval pulse 200.

  The OFDM transmission symbol counter 60 is a 10-bit counter, for example, and executes 1024 counts. The OFDM transmission symbol counter 60 loads “3F7h” into the counter value by the symbol interval pulse 200. The OFDM transmission symbol counter 60 outputs the count data C to the comparator 62. The comparator 62 compares the count data C with the comparison data A “3ECh”. When the comparison result is A <C, the comparator 62 sets the A <C signal 206 to the high level. On the other hand, the comparator 62 sets the A <C signal 206 to the low level in other cases. The comparator 62 outputs the A <C signal 206 to the EN circuit 64.

  The EN circuit 64 receives the A <C signal 206 from the comparator 62 and also receives the symbol timing 204 from the OFDM frame configuration unit 30 (not shown). The symbol timing 204 is a timing used when the OFDM frame construction unit 30 generates an OFDM symbol. The EN circuit 64 sets the set pulse disable signal 208 to the high level when the symbol timing 204 becomes the low level when the A <C signal 206 is at the high level. On the other hand, when the A <C signal 206 is at the low level and the symbol timing 204 becomes the low level, the EN circuit 64 sets the set pulse disable signal 208 to the low level. The set pulse disable signal 208 is a signal for disabling the symbol period set pulse 202. The EN circuit 64 outputs a set pulse disable signal 208 to the gate element 66. FIG. 6C shows the set pulse disable signal 208. Returning to FIG.

  The gate element 66 receives the symbol interval pulse 200 and the set pulse disable signal 208. If the set pulse disable signal 208 is at a high level, the gate element 66 maintains the symbol period set pulse 202 at a high level. On the other hand, if the set pulse disable signal 208 is at the low level, the gate element 66 sets the symbol interval set pulse 202 to the low level while the symbol interval pulse 200 is at the next low level. FIG. 6D shows the symbol interval set pulse 202. FIG. 6E shows symbol timing 204 generated in the OFDM frame configuration unit 30 (not shown) based on the symbol interval set pulse 202. FIG. 6F shows an OFDM signal generated in the OFDM frame configuration unit 30 (not shown) based on the symbol timing 204. Returning to FIG. The OFDM frame configuration unit 30 uses the timing at which the symbol interval set pulse 202 is at the low level as the start timing of the OFDM symbol, and generates the symbol timing 204 that is at the low level at the OFDM symbol interval.

  Such a process can be said to be a monitoring process in the symbol timing generator 32. More specifically, the symbol timing generation unit 32 monitors whether the error between the symbol timing 204 and the symbol interval pulse 200 is within a certain interval (hereinafter referred to as “symbol synchronization interval”). In order to explain this, FIGS. 7A to 7D are used. FIGS. 7A to 7D are diagrams illustrating another operation outline in the symbol timing generation unit 32. FIG. FIG. 7A shows a part of the symbol interval pulse 200.

  FIG. 7B shows the A <C signal 206. A section in which the A <C signal 206 is at a high level is a section in which symbol synchronization is determined, that is, an inner section that does not exceed GI. If the low level of the symbol timing 204 arrives within this interval, it can be said that synchronization is maintained. At this time, since the set pulse disable signal 208 is at a high level, the symbol interval set pulse 202 is not at a low level. On the other hand, if the low level of the symbol timing 204 arrives in the section where the A <C signal 206 is at the low level, synchronization is not maintained. At this time, since the set pulse disable signal 208 is at the low level, the symbol interval set pulse 202 becomes the low level according to the low level of the next incoming symbol interval pulse 200.

  FIG. 7C shows the symbol timing 204 when the A <C signal 206 is at the low level, and FIG. 7D shows the set pulse disable signal 208 when the A <C signal 206 is at the low level. Indicates. As a result of such comparison, when the timing deviation exceeds the symbol synchronization interval before GI, the symbol interval set pulse 202 is output to reset the symbol timing 204 with the symbol interval pulse 200. At that time, the OFDM symbol before being reset by the symbol interval set pulse 202 shown in FIG. 6F is shortened by about half or less of GI, but there is no problem because the effective symbol length is secured.

  Also, the OFDM symbol is set at a rough timing within the GI by the symbol interval set pulse 202. This is because area one-segment broadcasting is an environment in which transmission power is low and reflected waves arriving from a distance need not be assumed unlike terrestrial digital broadcasting. For example, the period of an OFDM symbol in mode 3, GI = 1/8 is about 1.125 ms. Assuming that this reference is the timing of the master segment, and assuming that the frequency of the OFDM symbol in radio apparatus 100 is shifted by 1 ppm with respect to the reference, the timing is set at a period of about 62.5 seconds. Returning to FIG.

  The FFT unit 42 inputs a signal from the one segment tuner 14. That is, the FFT unit 42 inputs a signal of each segment. The FFT unit 42 converts the time domain signal into a frequency domain signal by performing FFT on the signal of each segment. The FFT unit 42 outputs the frequency domain signal of each segment to the TMCC decoder unit 44. Note that the FFT unit 42 may omit the FFT for a segment for which no signal is transmitted.

  The TMCC decoder unit 44 receives the signal from the FFT unit 42. The TMCC decoder unit 44 captures and decodes TMCC for each segment. The TMCC decoder unit 44 obtains frame timing for each segment by recognizing TMCC for each segment. The frame is composed of a plurality of OFDM symbols and is repeated continuously. The frame timing is specified by the start timing and end timing of the frame. When the frame period has a fixed length, the frame timing may be specified only by the start timing of the frame. Here, the latter is assumed for the sake of clarity. When signals are transmitted from a plurality of segments, their frame timings are different for each OFDM symbol. The TMCC decoder unit 44 outputs the frame timing for each segment to the frame timing generation unit 46. The frame timing for any one of the segments may be output.

  The frame timing generation unit 46 acquires symbol timing from the symbol timing generation unit 32 and also acquires frame timing from the TMCC decoder unit 44. The frame timing generation unit 46 generates frame timing of a frame signal including a plurality of OFDM symbols having the symbol timing generated by the symbol timing generation unit 32. At this time, the frame timing is generated so as to deviate from the frame timing of the signal received in the master segment selected by the master segment selection unit 56 in units of OFDM symbol intervals. Here, the relationship between each of the plurality of segments and the shift amount is predetermined, and the frame timing generation unit 46 specifies the shift amount according to the position of the used segment in the plurality of segments from the relationship. use.

  The above process will be described more specifically. The frame timing generation unit 46 specifies a shift amount with respect to the frame timing, that is, a delay amount for each OFDM symbol from the obtained segment number of the frame timing. Here, it is assumed that the segment number is a delay amount. For example, if the segment number is “0”, the delay amount is “0” OFDM symbol, and if the segment number is “1”, the delay amount is “1” OFDM symbol and the segment number is “2”. If so, the delay amount is defined to be “2” OFDM symbols. The frame timing generation unit 46 uses the acquired symbol timing to generate a frame timing that is not delayed. Furthermore, the frame timing generation unit 46 also specifies the delay amount for the used segment from the segment number of the used segment in units of OFDM symbols. The frame timing generation unit 46 generates the frame timing by delaying the undelayed symbol timing by the specified delay amount. The frame timing generation unit 46 outputs the generated frame timing to the OFDM frame configuration unit 30.

  FIGS. 8A and 8B are diagrams for explaining the outline of the operation in the frame timing generation unit 46. FIG. FIG. 8A shows the frame timing and symbol timing in the master segment. Here, it is assumed that the master segment is the segment number “0”. As shown in the figure, one frame is composed of a plurality of OFDM symbols. FIG. 8B shows the frame timing and symbol timing in the used segment. The frame period is the same as the frame period in the master segment. On the other hand, the frame start timing is delayed by 6 OFDM symbols from the frame start timing in the master segment.

  The OFDM frame configuration unit 30 inputs the symbol interval set pulse 202 from the symbol timing generation unit 32. As described above, the OFDM frame configuration unit 30 generates the symbol timing 204 based on the symbol interval set pulse 202. Also, the OFDM frame configuration unit 30 feeds back the symbol timing 204 to the symbol timing generation unit 32. The OFDM frame configuration unit 30 inputs the frame timing from the frame timing generation unit 46. The OFDM frame configuration unit 30 generates a frame including a plurality of OFDM symbols based on the frame timing and the symbol timing 204.

  The OFDM frame configuration unit 30 inputs data from the encoding unit 28. The OFDM frame configuration unit 30 arranges data according to the frame and symbol timing 204. This corresponds to collecting data in symbol units indicated by the symbol timing 204. A plurality of OFDM symbols included in a frame are collectively referred to as a frame signal. Further, the OFDM frame configuration unit 30 may perform error correction coding on the data. A signal generated in the OFDM frame configuration unit 30 corresponds to a frame signal in the frequency domain. The frame signal includes a scattered pilot signal.

  Here, compared to the scattered pilot signal when transmitting the one-segment broadcast from the segment number “0”, a scattered pilot signal having a relatively same pattern is included in the frame signal. That is, regardless of the segment, a scattered pilot signal having a relatively same pattern is included in the frame signal. Since the pattern of the scattered pilot signal when transmitting the one-segment broadcast from the segment number “0” is a known technique, the description thereof is omitted here. The OFDM frame configuration unit 30 outputs the frequency domain frame signal to the OFDM modulation unit 34.

  The OFDM modulation unit 34 generates an effective symbol by executing an IFFT (Inverse Fast Fourier Transform) on the frequency domain signal from the OFDM frame configuration unit 30. In addition, the OFDM modulation unit 34 generates a baseband OFDM symbol by adding the GI to the effective symbol. The OFDM modulation unit 34 outputs the baseband OFDM symbol to the frequency conversion unit 36. The local oscillation unit 38 outputs a local signal having a frequency set by the transmission carrier setting unit 22. The frequency corresponds to the used segment.

  The frequency converter 36 receives baseband OFDM symbols from the OFDM modulator 34 and also receives local signals from the local oscillator 38. The frequency conversion unit 36 generates a radio frequency OFDM symbol by performing frequency conversion on the baseband OFDM symbol using the local signal. The frequency converter 36 outputs the radio frequency OFDM symbol to the RF unit 40. The RF unit 40 amplifies the radio frequency OFDM symbol from the frequency conversion unit 36 and then transmits it from the antenna. With these processes, when operating in the slave mode, OFDM symbols are transmitted from the used segment according to the frame timing that is different from the frame timing in other segments and the symbol timing synchronized with the symbol timing in the master segment. The

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

  According to the embodiment of the present invention, since the frame timing is changed for each segment, even if the scatter duplication signal and the TMCC signal are relatively the same in the frame, the same scatter duplication signal and the TMCC signal The possibility that the values are arranged in the same OFDM symbol can be reduced. In addition, since the possibility that the values of the same scatter Dubailot signal and TMCC signal are arranged in the same OFDM symbol is reduced, the possibility that the signal size continues to increase can be reduced. In addition, since the shift amount is determined according to the segment number, the frame timing of a plurality of segments can be changed. Also, since the OFDM symbols are synchronized, the difference in frame timing can be maintained.

  In addition, when the OFDM symbol in the master segment is not received, another already occupied segment is newly selected as the master segment based on the information on the already occupied segment, so that the OFDM symbol in the master segment is not received. Even after receiving, the new master segment can be used immediately. In addition, since a new master segment is used immediately, synchronized timing can be generated even when the use of the previous master segment ends. In addition, since synchronized timing is generated, interference between segments can be reduced.

  Moreover, since interference between segments is reduced, a guard band can be eliminated. Further, since the guard band is not required, it is possible to improve the frequency utilization efficiency when transmitting the OFDM signal in a situation where frequency division multiplexing is performed. In addition, since the frequency utilization efficiency when transmitting an OFDM signal is improved, it is possible to provide many area one segment distribution services within the same area. Further, if the already occupied segment information is included in the already occupied segment information, one of them is newly selected as the master segment, so that interference can be reduced. Also, if the already-occupied segment information does not include the already-occupied segment, even if there is a device that generates autonomous timing and performs transmission, those devices are slaves with this device as a master. Since it operates in the mode, autonomous timing can be generated without causing interference.

  In addition, when there are a plurality of devices and any one of those devices becomes a master and communicates with each other using a common communication path (such as IEEE 1394), there are the following differences. In the communication bus, when a certain master device terminates communication, the next master device is determined by “first come first served” after the master disappears. On the other hand, in the embodiment of the present invention, the next master device is already determined, and after the communication of the master device is completed, the next master is determined from the remaining slave devices first. Never happen.

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

  DESCRIPTION OF SYMBOLS 10 Reception processing part, 12 Transmission processing part, 14 One segment tuner, 16 Guard interval correlation processing part, 18 Operation control part, 20 Switch, 22 Transmission carrier setting part, 24 Image sensor, 26 Microphone, 28 Encoding part, 30 OFDM frame Configuration unit, 32 symbol timing generation unit, 34 OFDM modulation unit, 36 frequency conversion unit, 38 local oscillation unit, 40 RF unit, 42 FFT unit, 44 TMCC decoder unit, 46 frame timing generation unit, 50 already occupied segment storage unit, 52 segment selection unit, 54 operation mode setting unit, 56 master segment selection unit, 60 OFDM transmission symbol counter, 62 comparator, 64 EN circuit, 66 gate element, 100 wireless device.

Claims (4)

An investigation unit that investigates a band in which another wireless device transmits a frame signal including a plurality of OFDM symbols among a plurality of bands continuously arranged in the frequency domain;
A storage unit for storing the results of the investigation by the investigation unit;
Based on the investigation result stored in the storage unit, the first band, which is one of the bands in which other wireless devices are transmitting frame signals, and the first band in which the other wireless devices are not transmitting frame signals. A selection unit for selecting two bands;
A first generator for generating a symbol timing synchronized with an OFDM symbol for a frame signal received in the first band selected by the selector;
An OFDM symbol interval from the frame timing of a frame signal received in the first band selected by the selection unit, which is a frame timing of a frame signal including a plurality of OFDM symbols of the symbol timing generated by the first generation unit. A second generation unit that generates frame timings shifted in units;
A transmission unit that transmits a frame signal in the second band selected by the selection unit according to the frame timing generated by the second generation unit and the symbol timing generated by the first generation unit;
A wireless device comprising:   The frame signal transmitted from the transmission unit includes, in the frame signal, at least one of a pilot signal and a TMCC signal included in the frame signal received in the first band selected by the selection unit. The radio apparatus according to claim 1, wherein signals having relatively the same pattern are included.   The radio apparatus according to claim 1, wherein the second generation unit uses a shift amount corresponding to a position of a second band in a plurality of bands in order to generate a frame timing. Investigating a band in which another wireless device transmits a frame signal including a plurality of OFDM symbols among a plurality of bands continuously arranged in the frequency domain;
Storing the results of the investigation in a memory;
Based on the investigation result stored in the memory, the first band, which is one of the bands in which other wireless devices transmit frame signals, and the second band, in which the other wireless devices do not transmit frame signals A step of selecting and
Generating a symbol timing synchronized with an OFDM symbol for a frame signal received in the selected first band;
A step of generating a frame timing of a frame signal including a plurality of OFDM symbols of the generated symbol timing and deviating from the frame timing of the frame signal received in the selected first band by an OFDM symbol interval unit. When,
Transmitting a frame signal in the selected second band according to the generated frame timing and the generated symbol timing;
A transmission method comprising:

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