JP2008017010A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver that uses any of two or more modes including a CP mode and an SP mode, receives a signal transmitted by the OFDM modulation system and can discriminate what mode is used. <P>SOLUTION: First multiplier means 5, 6 acquire the result of multiplication between a received signal and a signal with a difference of one symbol time from the received signal by each carrier, a first summation means 7 sums up the results of multiplication for a plurality of carriers each for one symbol time, and when the result of totalization exceeds a prescribed threshold value, a first discrimination means 14 discriminates that the mode is the CP mode. Second multiplier means 8, 9, a second total means 10, and second discrimination means 15 execute similar discrimination to above, and the second discrimination means 15 discriminates whether the mode is the synchronous modulation mode or the differential modulation mode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a receiver that performs digital wireless communication using, for example, Orthogonal Frequency Division Multiplexing (OFDM) modulation, and in particular, pilot carriers are distributed in the frequency direction (for example, arranged at equal intervals). In addition, CP (Continuous Pilot) mode that is continuously arranged in the time direction and pilot carriers are distributed in the frequency direction (for example, at equal intervals) and distributed in the time direction (for example, at equal intervals). The present invention relates to a technique for determining which of two or more modes including an SP (Scattered Pilot) mode.

  For example, in a digital television broadcasting system, video and audio as materials for a television broadcast program are acquired by a camera or a microphone, and the acquired video or the like is received from an FPU (Field Pickup Unit) mounted on a car serving as a relay station. It transmits by radio to broadcasting stations. The OFDM modulation scheme is used in such a broadcasting system as an example, and is used in various other systems.

In the OFDM modulation scheme, wireless communication is performed using one of two modes, CP mode and SP mode, and these modes can be switched during communication.
FIG. 2 shows an example of carrier arrangement in the CP mode. The horizontal axis indicates the direction of frequency (carrier), and the vertical axis indicates the direction of time (symbol).
As shown in the figure, the carrier arrangement in the CP mode is mainly configured by arranging a data carrier and a pilot carrier, and the pilot carriers are dispersed in the frequency direction (in this example, at equal intervals of 8 carriers). ) Are arranged continuously in the time direction. Here, the number of all carriers is a large number such as about 800, and the number of pilot carriers is, for example, (1/8) of the number of all carriers.
For example, although about 10 control carriers are arranged as other carriers, illustration is omitted. Other carriers may be arranged, but are omitted in this example for the sake of simplicity.
For example, when the average power of the data carrier is 1 (= 1 ² ), the power of the pilot carrier is (4/3) ² and the power of the control carrier is (4/3) ² is there.

FIG. 3 shows an example of carrier arrangement in the SP mode. The horizontal axis indicates the direction of frequency (carrier), and the vertical axis indicates the direction of time (symbol).
As shown in the figure, the carrier arrangement in the SP mode is mainly configured by arranging data carriers and pilot carriers, and the pilot carriers are distributed in the frequency direction (in this example, at equal intervals of 8 carriers). They are arranged and distributed in the time direction (in this example, at equal intervals of n symbols of 2 or more). Here, the number of all carriers is a large number such as about 800, and the number of pilot carriers is, for example, (1/8) of the number of all carriers.
For example, although about 10 control carriers are arranged as other carriers, illustration is omitted. Other carriers may be arranged, but are omitted in this example for the sake of simplicity.
For example, when the average power of the data carrier is 1 (= 1 ² ), the power of the pilot carrier is (4/3) ² and the power of the control carrier is (4/3) ² is there.

In a receiving apparatus that receives a signal wirelessly transmitted by the OFDM modulation method, it is necessary to accurately grasp the position of the pilot carrier in order to perform processing such as equalization and demodulation on the received signal. For this reason, when the CP mode and the SP mode are switched on the transmission side, it is necessary to manually switch the CP mode and the SP mode on the reception side.
In general, the CP mode is effective for wireless communication while moving, and the SP mode is effective when there is a delayed wave like multipath. Each mode has advantages and disadvantages. It is done.

JP 2004-134883 A "Portable OFDM digital wireless transmission system for transmitting television broadcast program material", ARIB STD-B33, Japan Radio Industry Association

As described above, in the OFDM modulation system having both the CP mode and the SP mode, when the CP mode and the SP mode are switched on the transmission side, it is necessary to manually switch the CP mode and the SP mode also on the reception side. .
However, when assuming a system in which the transmission side adaptively switches between the CP mode and the SP mode such as switching between the CP mode and the SP mode according to the transmission path state, the reception side automatically selects the CP mode. It is desirable to switch the SP mode.
It is also conceivable that modes other than the CP mode and the SP mode are used adaptively.

  The present invention has been made in view of such a conventional situation, and the mode used for the signal received from the transmission side is any of two or more modes including the CP mode and the SP mode. It is an object of the present invention to provide a receiving apparatus that can determine whether or not. In the receiving apparatus according to the present invention, it is possible to switch between the CP mode and the SP mode in accordance with the transmission side based on such a mode discrimination result.

In order to achieve the above object, in the receiving apparatus according to the present invention, the CP mode in which pilot carriers are continuously arranged in the time direction in the frequency direction and the pilot carriers are arranged in the frequency direction and the time direction in a distributed manner. When receiving a signal transmitted by the OFDM modulation method using any one of two or more modes including the SP mode, the mode is determined by the following configuration.
That is, the first multiplication means obtains the multiplication result (for example, the complex multiplication result for the IQ signal) of the received signal and the signal of the one symbol time difference for each carrier. The first summation means sums the multiplication results obtained by the first multiplication means for a plurality of carriers for one symbol time. When the first discriminating means has a summation result obtained by the first summing means exceeding a predetermined threshold (or greater than or equal to a predetermined threshold), the mode used for the received signal is It is determined that the mode is the CP mode.

  Therefore, in the CP mode, it is possible to determine whether or not the mode used for the signal received from the transmission side is the CP mode by utilizing the high correlation at the time of one symbol time at the pilot carrier position. For example, based on the determination result that the mode is the CP mode, the mode can be switched to the CP mode according to the transmission side.

Here, various values may be used as the predetermined threshold value. For example, the threshold value may be generated based on the received signal or the threshold value may be set in advance. Good.
In addition, as an aspect of the magnitude determination with respect to the threshold value in the first determination means, an aspect of determining that “the threshold value is exceeded” may be used, or “is equal to or greater than the threshold value”. A mode of discriminating the above may be used.

The receiving apparatus according to the present invention has the following configuration as one configuration example.
That is, the two or more modes include the CP mode and the SP mode, which are synchronous modulation modes, and the differential modulation mode in which pilot carriers are not used (that is, not used).
In the SP mode, pilot carriers are arranged at intervals of n symbols that are two or more in the time direction.
Then, in the receiving apparatus, the second multiplying unit obtains a multiplication result (for example, a complex multiplication result for the IQ signal) of the reception signal and the signal of the n symbol time difference for each carrier. The second summation means sums the multiplication results obtained by the second multiplication means for a plurality of carriers for one symbol time. When the second discrimination means exceeds the predetermined threshold value (or is equal to or greater than the predetermined threshold value), the mode used for the received signal is determined. Used as a received signal when it is determined that the mode is a synchronous modulation mode and the sum total obtained by the second summing means is less than or equal to a predetermined threshold (or less than a predetermined threshold). It is determined that the selected mode is a differential modulation mode.

Therefore, in the mode of synchronous modulation such as the CP mode or the SP mode, the mode used for the signal received from the transmitting side is synchronously modulated by utilizing the high correlation at the time difference of n symbols at the pilot carrier position. It is possible to determine whether the current mode or the differential modulation mode.
For example, when the CP mode, the SP mode, and the differential modulation mode are switched and used, any mode is selected based on the determination result by the first determination unit and the determination result by the second determination unit. The mode can be switched according to the transmission side based on the determination result.

Here, as the predetermined threshold value used by the first determination unit and the predetermined threshold value used by the second determination unit, for example, a common value is used. A value that is not common to each other may be used.
In addition, as an aspect of the magnitude determination with respect to the threshold value in the second determination means, an aspect of determining “exceeding the threshold value” may be used, or “over the threshold value” May be used. Similarly, an aspect for determining that “below the threshold value” may be used, or an aspect for determining that “below the threshold value” may be used. May be used.

As described above, according to the receiving apparatus according to the present invention, a signal in which one of a mode having a high correlation at the time of one symbol time difference at the pilot carrier position and a mode not using it is used as in the CP mode. , It is possible to determine whether or not the mode is the CP mode by determining whether or not the correlation of the received signal with a one-symbol time difference is high.
Further, according to the receiving apparatus according to the present invention, as in the CP mode and the SP mode, the synchronous modulation mode having a high correlation in the n (n is a predetermined number of 2 or more) symbol time difference in the pilot carrier position and the difference that is not so. When receiving a signal in which one of the modes of dynamic modulation is used, it is determined whether the correlation is high in the n-symbol time difference of the received signal, so that the mode is synchronous modulation or It is possible to determine whether the mode is a differential modulation mode.
Further, the receiving apparatus according to the present invention can perform both of the above-described two types of determination and determine the mode based on both of the determination results.

Embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of an OFDM receiving apparatus according to an embodiment of the present invention.
The OFDM receiving apparatus of this example includes an antenna 1, an RF (Radio Frequency) unit 2, an IF (Intermediate Frequency) unit 3, an FFT (Fast Fourier Transform) processing unit 4, a 1-symbol delay unit 5, a differential unit, Detection unit 6, addition unit 7, n symbol delay unit 8, differential detection unit 9, addition unit 10, squaring unit 11, addition unit 12, multiplication unit 13, and CP / SP provisional discrimination Unit 14, differential / synchronous modulation determination unit 15, and CP / SP determination unit 16.

  In this example, an OFDM transmission apparatus (not shown) and an OFDM reception apparatus are switched between the CP mode of the carrier arrangement shown in FIG. 2 and the SP mode of the carrier arrangement shown in FIG. Wireless communication is performed between the two. In the CP mode or the SP mode, for example, QAM (Quadrature Amplitude Modulation) or QPSK (Quaternary Phase Shift Keying), which is a modulation method using a pilot carrier, is used.

Furthermore, in this example, as another mode, it is also possible to switch to a mode using a DQPSK (Differential Quaternary Phase Shift Keying) method, which is a modulation method that does not use a pilot carrier, and to perform radio communication by an OFDM modulation method. It is.
In such a mode that does not use a pilot carrier, a data carrier is arranged, but a carrier arrangement in which no pilot carrier is arranged is used. For example, in the carrier arrangement shown in FIG. 2 or FIG. A data carrier is used.
For example, about 10 control carriers are arranged as other carriers. Other carriers may be arranged, but are omitted in this example for the sake of simplicity.
For example, when the average power of the data carrier is 1 (= 1 ² ), the power of the control carrier is (4/3) ² .

An example of the operation performed in the OFDM receiver of this example is shown.
A signal transmitted wirelessly using a certain mode from the transmission side is received by the antenna 1, the received signal is processed by the RF unit 2 and IF unit 3, and fast Fourier transformed by the FFT processing unit 4, and each carrier Each signal is acquired.
In this example, the signals from all carriers are output in order from the FFT processing unit 4 in the time of one symbol. As a result, signals of all carriers are processed for each symbol time.

  The 1-symbol delay unit 5 delays the carrier signal output from the FFT processing unit 4 by one symbol, and the differential detection unit 6 delays the carrier signal output from the FFT processing unit 4 and the 1-symbol delay unit 5 Then, the addition unit 7 sums (adds) the complex multiplication results obtained by the differential detection unit 6 for all carriers for each symbol time. This summation is performed, for example, for one row in the frequency (carrier) direction in each time (symbol) direction in the carrier arrangement as shown in FIG. 2 or FIG. 3. The total result is input to the CP / SP temporary determination unit 14.

Here, as shown in FIG. 2, in the CP mode of this example, the pilot carriers are arranged at equal intervals in the frequency direction and are continuously arranged in the time direction. Since the pilot carrier is the same signal, the differential detection unit 6 performs differential detection processing (in this example, complex multiplication processing) between the received signal and the output from the 1-symbol delay unit 5. The output of all pilot carrier positions is the same signal (in this example, a signal of power (4/3) ² ), and the same applies to a small number of control carrier positions. It can be considered that the positions of other carriers (data carriers) are all random values, and in this case, the output from the differential detection unit 6 is a random value and is regarded as zero (0) when averaged. Is possible.
Therefore, when the summation for one symbol of the signal after differential detection is obtained in the adder 7, the same signal is added by the number of pilot carriers and the number of control carriers at the pilot carrier position and the control carrier position, At other carrier positions, random values are added and converge to zero.

On the other hand, as shown in FIG. 3, in the SP mode of this example, the pilot carriers are arranged at equal intervals in the frequency direction and dispersed in the time direction (in this example, the intervals of two symbols or more are provided). Therefore, when differential detection processing (in this example, complex multiplication processing) is performed between the received signal and the output from the 1-symbol delay unit 5 in the differential detection unit 6, a small number of control signals are used. The output at the carrier position is the same signal (in this example, a signal of power (4/3) ² ), and the positions of the other carriers (data carrier, pilot carrier) are all random values.
Therefore, when the summation for one symbol of the signal after differential detection is obtained in the adder 7, the same signal is added by the number of control carriers at the control carrier position, and any carrier at any other carrier position. Even at the position, random values are added and converge to zero.

  In addition, since the pilot carrier is not used in the mode in which the pilot carrier is not used, when the summation for one symbol of the signal after differential detection is obtained in the adder 7, the control carrier position is the same as the number of control carriers. The same signals are added, and random values are added at other carrier (data carrier) positions to converge to zero.

Based on these, in order to determine whether the mode is the CP mode or the CP mode (in this example, the SP mode or the mode not using the pilot carrier), the number of pilot carriers and the number of control carriers are determined. amount corresponding (in this example, the power (4/3) ² of the signal) the same signal as the value obtained by adding, by controlling number of carriers is small number in the same signal (in this example, the power (4/3) ² A method is used in which a threshold value is provided between the signal and the value obtained by adding these signals and the magnitude is determined based on this threshold value. When the output from the adding unit 7 is larger than the threshold value, it is determined that the CP mode is selected, and when the output from the adding unit 7 is smaller than the threshold value, it is determined that the CP mode is not selected.

For such threshold setting, a signal before differential detection is used.
First, the square unit 11 calculates the square of the signal before differential detection (the output signal for each carrier from the FFT processing unit 4), and the adder unit 12 adds the sum of one symbol (addition) for this square value. )
Here, since the adding unit 12 obtains the sum of values obtained by squaring each carrier such as a data carrier and a pilot carrier, the sum result shows the same value as long as the number of each carrier is the same. .
Therefore, in the CP mode and the SP mode in which the number of carriers is the same even if the carrier arrangement is different, the summation result by the adder 12 shows the same value. Specifically, the summation result by the adding unit 12 is obtained by adding the same signal (in this example, a signal of power (4/3) ² ) by the number of pilot carriers and the number of control carriers, and the data carrier It is a sum value with the value obtained by adding the same signal (in this example, a signal with power 1 (= 1 ² )) for several minutes. Thus, in the CP mode and the SP mode, the summation result by the adder 12 becomes the same value regardless of the difference in the arrangement of the pilot carriers, and the threshold value can be set based on this summation result.

In the mode in which no pilot carrier is used, the summation result by the adder 12 is obtained by adding the same signal (in this example, a signal of power (4/3) ² ) by the number of control carriers and the data carrier. It is a sum value with the value obtained by adding the same signal (in this example, a signal with power 1 (= 1 ² )) for several minutes. Although this sum value is considered to be different from the sum value in the CP mode or the SP mode, whether the sum mode is the CP mode or the CP mode (in this example, the SP mode or the pilot carrier It is possible to set a threshold value for determining whether the mode is not used.

The summation result by the adder 12 is input to the multiplier 13 and is multiplied by a predetermined value α to adjust the level, and the value of this multiplication result is used as a threshold value for the CP / SP provisional discriminator 14 and the differential / synchronous modulation. Input to the determination unit 15.
Here, α is a value satisfying (0 <α <1), but is further in the CP mode or not in the CP mode (in this example, the SP mode or the mode not using the pilot carrier). A value suitable for generating a threshold value for discriminating is used.
Specifically, regarding the summation result by the adding unit 7, the pilot carrier is more in the CP mode than in the other mode (in this example, the SP mode or the mode not using the pilot carrier). A threshold value is generated which becomes a large value by adding the same signal (in this example, a signal of power (4/3) ² ) for several minutes, and this difference can be discriminated. It should be noted that the summation result in a mode other than the CP mode is a small value and can be considered to be close to zero.

  As an example, considering that the sum result by the adder 12 in the mode not using the pilot carrier is smaller than the sum result by the adder 12 in the CP mode or the SP mode, the sum by the adder 12 in the mode not using the pilot carrier. A value obtained by multiplying the result by α is larger than the sum result by the adder 7 in the SP mode or the mode not using the pilot carrier, and a value obtained by multiplying the sum result by the adder 12 in the CP mode or the SP mode by α is CP. The value of α can be set so as to be smaller than the summation result by the addition unit 7 in the mode.

The CP / SP temporary determination unit 14 determines the magnitude of the summation result after differential detection input from the addition unit 7 and the threshold value input from the multiplication unit 13, and the summation result is greater than the threshold value. Is determined to be the CP mode, and if the total result is smaller than the threshold value, it is determined to be another mode (in this example, the SP mode or the mode not using the pilot carrier). This determination result is input to the CP / SP determination unit 16.
Here, for example, when only two modes of the CP mode and the SP mode are switched and used, it is possible to identify which mode is the mode based on the determination result by the CP / SP temporary determination unit 14. .

FIG. 4 shows an example of the temporary discrimination processing result between the CP mode and the SP mode. The horizontal axis indicates the sum total result after differential detection output from the adder 7 or the value calculated for each symbol as the threshold value output from the multiplier 13, and the vertical axis indicates the frequency (%). The total result is shown as a histogram.
As shown in the figure, the sum result for one symbol after differential detection in the CP mode is a relatively large value, and the sum result for one symbol after differential detection in the SP mode is a relatively small value. The threshold value is set so that these two types of values can be distinguished.

Next, as a case where communication is performed using a modulation method that does not use a pilot carrier, a case where communication is performed using a differential modulation method such as DQPSK will be described.
In this case, if the differential detection process with one symbol difference similar to the above is performed, the outputs are all random values except the position of the control carrier, which is a small number, and the sum of the values for one symbol is It will converge to zero. As a result, the CP / SP temporary determination unit 14 determines that the mode is not the CP mode.

FIG. 5 shows an example of a result of provisional discrimination processing between the CP mode and the SP mode during differential modulation. The horizontal axis indicates the sum total result after differential detection output from the adder 7 or the value calculated for each symbol as the threshold value output from the multiplier 13, and the vertical axis indicates the frequency (%). The total result is shown as a histogram.
As shown in the figure, the summation result for one symbol after differential detection in the DQPSK mode that does not use the pilot carrier is a relatively small value, as in the SP mode, and the same determination as in the SP mode. Results are obtained.

However, as defined in “ARIB STD-B33” (Non-Patent Document 1), for example, when the arrangement of some carriers (for example, control carriers) conforms to the CP mode during differential modulation. Needs to be determined as the CP mode in the final determination result of the CP / SP mode. For this reason, in this example, when the CP / SP temporary determination unit 14 determines that the mode is not the CP mode, the differential / synchronous modulation determination unit 15 further determines whether the differential modulation method or the synchronous modulation is used. It is determined whether the mode is the SP mode.
Note that the CP mode and the SP mode are synchronous modulation schemes.

In this example, the differential detection unit 9 performs differential detection processing (in this example, complex multiplication processing) between the received signal and the output from the n-symbol delay unit 8, and the result is 1 symbol in the addition unit 10. Is obtained and input to the differential / synchronous modulation determination unit 15.
Specifically, the n symbol delay unit 8 delays the carrier signal output from the FFT processing unit 4 by n symbols, and the differential detection unit 9 outputs the carrier signal output from the FFT processing unit 4 and the n symbol delay. The signal delayed by the unit 8 is subjected to complex multiplication (complex multiplication for the IQ signal), and the addition unit 10 sums the complex multiplication results obtained by the differential detection unit 9 for all carriers for each symbol time ( to add. This summation is performed, for example, for one row in the frequency (carrier) direction in each time (symbol) direction in the carrier arrangement as shown in FIG. 2 or FIG. 3. The total result is input to the differential / synchronous modulation determination unit 15.

Here, as n, the value of the interval n in which pilot carriers are distributed and arranged in the time (symbol) direction in the carrier arrangement in the SP mode shown in FIG. 3 is used. In the example of FIG. 3, n = 4.
In this case, when a pilot carrier is included in the signal as in the CP mode shown in FIG. 2 or the SP mode shown in FIG. 3, the differential detection output at the pilot carrier position or the position of the control carrier is used. The differential detection output at the same signal (in this example, a signal of power (4/3) ² ) is added and the differential detection output at other carrier (data carrier) positions is random. It becomes a value and converges to zero when added.
Further, in a mode that does not use a pilot carrier as in DQPSK, since the pilot carrier is not included in the signal, the differential detection output at the position of a small number of control carriers is the same signal (in this example, power ( 4/3) ² of the signal) and a one, the differential detection output at the position of the other carrier (data carrier) converges to zero when added become random values.

  Then, the summation result from the addition unit 10 in the CP mode or the SP mode, which is a synchronous modulation mode, is the summation result from the addition unit 7 in the CP mode (for example, similar to the CP mode shown in FIG. 4). Value). Further, the summation result from the adder 10 in the mode not using the pilot carrier which is a differential modulation mode is the summation result from the adder 7 in the SP mode or the mode not using the pilot carrier (for example, FIG. 4 is the same value as the SP mode shown in FIG.

  Therefore, the differential / synchronous modulation discriminating unit 15 uses the threshold value input from the multiplying unit 13 (same as the threshold value used in the CP / SP provisional discriminating unit 14) to determine the magnitude, Whether it is synchronous modulation or differential modulation can be determined. Specifically, the differential / synchronous modulation discriminating unit 15 determines the magnitude based on the summation result after differential detection input from the adding unit 10 and the threshold value input from the multiplying unit 13, and the summation result is obtained. If it is larger than the threshold value, it is determined that it is synchronous modulation (CP mode or SP mode in this example), and if the total result is smaller than the threshold value, differential modulation (in this example, a pilot carrier is used) Discriminating mode). This determination result is input to the CP / SP determination unit 16.

The CP / SP discriminator 16 discriminates whether or not the CP mode is input from the CP / SP temporary discriminator 14 and the synchronous modulation (in this example, input from the differential / synchronous modulation discriminator 15). The mode is finally determined based on the determination result of whether it is the CP mode or the SP mode) or the differential modulation (in this example, the mode not using the pilot carrier). Specifically, when the CP / SP temporary determination unit 14 determines that the CP mode is selected, the CP / SP temporary determination unit 14 determines that the CP mode is used regardless of the determination result of the differential / synchronous modulation determination unit 15. When the / SP provisional determination unit 14 determines that the mode is not the CP mode (for example, the SP mode), the differential / synchronous modulation determination unit 15 determines that the modulation is differential. Is determined to be the CP mode (in this example, a CP mode-compliant mode that does not use a pilot carrier), and when it is determined to be synchronous modulation, it is determined to be the SP mode.
For example, the mode used for the reception process can be switched to match the mode determined for the received signal (that is, the mode used on the transmission side).

  As described above, in the discriminator of the OFDM receiver of this example, the CP mode in which pilot carriers are distributed in the frequency direction and continuously in the time direction, and the pilot carriers are distributed in the frequency direction and the time direction. On the receiving side of the system having both SP modes to be arranged, the received signal is subjected to FFT processing, the 1-symbol delay unit 5 delays the signal after FFT processing in symbol units, and the differential detection unit 6 performs FFT processing. Differential detection processing is performed between the signal and the delayed signal, the sum of one symbol is calculated for the signal differentially detected by the adder 7, and the square of the signal after FFT processing is calculated by the squaring unit 11 Then, the sum of one symbol is calculated for the signal squared by the adder 12, and the level is adjusted by the multiplier 13 for the sum of the signals after the square. The pilot used in the received signal is automatically discriminated by comparing the total result of the differential detection signal with the level-adjusted result (threshold value) by the SP temporary discriminating unit 14. The arrangement can be determined.

  Further, in the discriminator of the OFDM receiving apparatus of this example, the n symbol delay unit 8 and the differential detection are provided when the SP mode in which pilot carriers are dispersedly arranged in the time direction with an n symbol period and the mode in which the pilot carrier is not used are provided. The differential detection processing is performed between the received signal and the signal before n symbols by the unit 9 and the addition unit 10 to obtain a summation result for one symbol, and the differential detection signal is obtained by the differential / synchronous modulation discrimination unit 15 Is compared with the result after adjusting the level (threshold value), it is possible to determine whether the mode is the SP mode or the mode in which the pilot carrier is not used.

  Therefore, in the OFDM receiving apparatus of this example, the differential detection process is performed between the received signal and the signal obtained by delaying the received signal in symbol units, and the result of adding one symbol for the signals before and after the differential detection process is compared. By performing the above, it is possible to determine whether the mode is the CP mode or the SP mode, and it is further possible to determine whether the mode is the SP mode or the mode that does not use the pilot carrier. Thereby, for example, even when the mode such as the CP mode or the SP mode is switched on the transmission side, the mode used on the transmission side can be automatically determined on the reception side, and the determined mode is automatically set. Can be switched.

  Here, in the OFDM receiving apparatus of this example, the configuration for calculating the threshold value used in the CP / SP temporary determination unit 14 and the differential / synchronous modulation determination unit 15 based on the received signal is shown. A configuration in which such a threshold value is set in advance may be used, or when the threshold value is adjusted according to the condition of the transmission path through which the signal is transmitted, the condition of the transmission path is detected and It is also possible to use a configuration in which a threshold value is generated by adjusting a preset value based on the detection result.

In the receiving apparatus (OFDM receiving apparatus) of this example, a differential detection result (in this example, a complex multiplication result) with a time difference of 1 symbol is obtained for each carrier by the 1-symbol delay unit 5 and the differential detection unit 6. The first multiplying unit is configured by the function to perform, and the differential detection result is added to the plurality of carriers for one symbol time by the adder 7 (for example, in the horizontal direction in the carrier arrangement as shown in FIG. 2 or FIG. 3). The first summing means is constituted by the function of summing (for one row), and the first discriminating means is provided by the CP / SP provisional discriminating unit 14 for judging the magnitude of the summation result and a predetermined threshold value. Is configured.
In the receiving apparatus (OFDM receiving apparatus) of this example, the n symbol delay unit 8 and the differential detection unit 9 obtain differential detection results (in this example, complex multiplication results) at an n symbol time difference for each carrier. The second multiplying means is configured by the function to perform, and the differential detection result is added to the plurality of carriers for one symbol time by the adder 10 (for example, in the horizontal direction in the carrier arrangement as shown in FIG. 2 or FIG. 3). The second summing means is configured by the function of summing (for one row), and the second discrimination is performed by the function of determining the magnitude of the summation result and a predetermined threshold by the differential / synchronous modulation discrimination unit 15. Means are configured.

Here, the configuration of the system and apparatus according to the present invention is not necessarily limited to the configuration described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various systems and devices.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the system and apparatus according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in hardware resources including a processor and a memory. A controlled configuration may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

It is a figure which shows the structural example of the OFDM receiver which concerns on one Example of this invention. It is a figure which shows an example of the carrier arrangement | positioning at the time of CP mode. It is a figure which shows an example of the carrier arrangement | positioning at the time of SP mode. It is a figure which shows an example of the temporary discrimination | determination processing result of CP / SP mode. It is a figure which shows an example of the temporary determination process result of CP / SP mode at the time of differential modulation.

Explanation of symbols

  1 .. Antenna, 2 .. RF unit, 3 .... IF unit, 4 .... FFT processing unit, 5 .... 1 symbol delay unit, 6, 9 .... Differential detection unit, 7, 10, 12, ... Addition , 8 ·· n symbol delay unit, 11 ·· square unit, 13 ·· multiply unit, 14 ·· CP / SP provisional discrimination unit, 15 ·· Differential / synchronous modulation discrimination unit, 16 ·· CP / SP Discriminator,

Claims (2)

Any one of two or more modes including a CP mode in which pilot carriers are continuously arranged in the time direction in the frequency direction and an SP mode in which pilot carriers are distributed in the frequency direction and the time direction. In a receiving apparatus for receiving a signal transmitted by an OFDM modulation scheme using a mode,
First multiplication means for obtaining a multiplication result of the received signal and the signal of the one symbol time difference for each carrier;
First summing means for summing the multiplication results obtained by the first multiplying means for a plurality of carriers for one symbol time;
First discrimination for discriminating that the mode used for the received signal is the CP mode when the summation result obtained by the first summing means exceeds a predetermined threshold value or exceeds a predetermined threshold value Means, and
A receiving apparatus. The receiving device according to claim 1,
The two or more modes include the CP mode and the SP mode, which are synchronous modulation modes, and the differential modulation mode, in which a pilot carrier is not used,
In the SP mode, pilot carriers are arranged at intervals of n symbols that are two or more in the time direction,
The receiving apparatus includes a second multiplying unit that obtains a multiplication result of the received signal and the signal of the n symbol time difference for each carrier;
Second summing means for summing the multiplication results obtained by the second multiplying means for a plurality of carriers for one symbol time;
Determining that the mode used for the received signal is a mode of synchronous modulation when the summation result obtained by the second summing means exceeds a predetermined threshold value or exceeds a predetermined threshold value; A first discriminating that the mode used for the received signal is the mode of differential modulation when the summation result obtained by the second summing means is less than or equal to a predetermined threshold value or less than the predetermined threshold value. 2 determination means,
A receiving apparatus.

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