JP2010166619A - Transmitting apparatus, and receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a ratio of average power to a peak of a radio signal in an OFDM radio communication system. <P>SOLUTION: A transmitting apparatus of the OFDM system includes a division inverse Fourier transform means 2204 for dividing a transmitting signal sequence into a plurality of signal sequences, and performing inverse Fourier transform through a plurality of conversion means; peak detection means 2214, 2216 for detecting a peak of an output signal of one conversion means for each conversion means; a peak control means 2218 for outputting a peak control signal based on an output from the peak detection means; and a peak reduction processing means 2206 for adjusting the weight or the sequence order of the output signals of the division inverse Fourier transform means in response to the peak control signal, and synthesizing an adjusted signal and another signal for output. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to the technical field of wireless communication, and more particularly to a transmission apparatus and a reception apparatus that employ an orthogonal frequency division multiplexing (OFDM) scheme.

  The OFDM method that is attracting attention in this type of technical field is a technology that attempts to achieve good signal transmission even in a multipath propagation environment by arranging a plurality of carriers (subcarriers) at frequency intervals that are orthogonal to each other. It is. In the transmitter in this scheme, as shown in FIG. 1, the signal generated by the signal generation unit based on the transmission information is converted into a plurality of parallel signal sequences by the serial / parallel conversion unit (S / P), It is modulated by a fast inverse Fourier transform unit (IFFT unit), converted into a single signal sequence by a parallel-serial conversion unit (P / S), a guard interval is given by a guard interval giving unit (GI), and a power amplification unit After being amplified by (PA), it is wirelessly transmitted as an OFDM signal. As is well known, the guard interval is a duplicate of the tail part of the symbol to be transmitted. On the other hand, in the receiver, as shown in FIG. 2, the guard interval is removed from the received signal by the guard interval remover (GI removal), and the signal is converted into a parallel signal by the serial-parallel converter (S / P). Then, it is demodulated by a fast Fourier transform unit (FFT unit), converted into a serial signal by a parallel / serial conversion unit (P / S), and further demodulated by a signal detection unit to obtain transmission information.

  In the OFDM system, since a plurality of subcarriers having various levels are used, in some cases, a transmission signal having a very large amplitude is formed as shown in FIG. The ratio between the maximum peak power and the average power that can occur is evaluated as a peak-to-average power ratio (PAPR). In general, the maximum peak power may be several times the total power of the average power.

  On the other hand, as shown in FIG. 4, the power amplifier (PA) has a linear region that provides linear input / output characteristics and a nonlinear region that provides nonlinear input / output characteristics. In order to output a transmission signal with less distortion, it is desirable that the power amplifier (PA) operates in a linear region. If it is used in the non-linear region, it may cause problems such as deterioration of transmission quality and unnecessary radiation outside the band. When the peak-to-average power ratio (PAPR) is large, the power amplifier is used not only in the linear region but also in the nonlinear region. On the other hand, it is conceivable to use a power amplifier having a wide linear region, but there arises a problem that the amplification efficiency is sacrificed. Therefore, it is desirable that the peak-to-average power ratio of the transmission signal is small.

In this regard, the invention described in Non-Patent Document 1 employs a so-called predistortion method, examines non-linear distortion introduced into the transmission signal, and gives a weight representing the inverse characteristic to the transmission signal in advance, thereby linearizing the operation. Trying to secure sex. The invention described in Non-Patent Document 2 attempts to suppress the peak-to-average power ratio by clipping a large peak value. Also, a technique called partial transmission sequence (PTS) selects one set from a plurality of sets of phase rotation amounts set in advance for each subcarrier with respect to a signal before modulation. By doing this, the phase is rotated for each subcarrier each time, and the peak-to-average power ratio is suppressed (for example, see Non-Patent Documents 3, 4, and 5). FIG. 5 illustrates an example of a transmitter that employs the PTS scheme, and FIG. 6 illustrates an example of a receiver that employs the PTS scheme. In the illustrated example, the signal sequence generated by the signal generation unit is divided into two by the dividing unit, and serial-parallel conversion and inverse Fourier transform are performed on each of the divided signal sequences. Inverse Fourier transform units IFFT ₁ and ₂ having N input / output points receive N / 2 signals and N / 2 null symbols from the serial-parallel transform unit. The phase rotation amount control unit determines an appropriate phase rotation amount (weight or weight) set {θ ₁ , θ ₂ ,...} Based on the output of the inverse Fourier transform unit, and one of these is determined. Commonly given to each multiplier. The output from the inverse Fourier transform unit is combined with an appropriate weight by the combining unit. The signal group after the inverse Fourier transform after the synthesis is converted into a serial signal by the parallel / serial converter (P / S), a guard interval is added to it by the guard interval (GI), and it is transmitted from the antenna. . On the receiving side, as shown in FIG. 6, the amount of phase rotation is adjusted during demodulation.

M.M. Friese, “On the degradation of OFDM-signal due to peak-clipping in optimally pre- scribed power amplifiers”. proc. of GLOBCOM '98, pp. 939-944, Nov. 1998 X. Li and L.L. J. et al. Cimini, “Effects of clipping and filtering on the performance of OFDM”, IEEE Commun. Lett. , Vol. 2, no. 5, pp. 131-133, May. 1998 L. J and N.J. R. Sollenberger, “Peak-to-Average power ratio reduction of an OFDM signal using partial transmission sequences”, IEEE Commun. Lett. , Vol. 4, no. 3, pp. 86-88, March 2000 S. H. Muller and J.M. B. Huber, “A Novel Peak Power Reduction Scheme for OFDM”, Proc. of PIMRC '97, pp. 1090-1094, 1997 G. R. Hill, Faulkner and J.M. Singh, “Dedicating the peak-to-average power ratio in OFDM by cyclical partial transmission sequences,” “Electronics Letters, vol. 36, no. 6,16th March 2000

  However, in the predistortion system, the input / output characteristics with respect to the power amplifier are only apparently linear, and a signal having a large peak-to-average power ratio is not eliminated. Further, even for a signal having a peak power exceeding the saturation region of the amplifier, it becomes impossible to ensure even input / output linearity.

  In the method of clipping an inconvenient peak power value, only the peak portion is removed, so that orthogonality between subcarriers is lost, intersymbol interference increases, and reception characteristics may be deteriorated.

  In the partial sequence transmission (PTS) method, when weighting each signal sequence, it is necessary to perform complex multiplication for each signal sequence, which increases the amount of calculation. This is particularly inconvenient from the viewpoint of power consumption and circuit scale. It is also conceivable to reduce the computational burden required to generate the transmission signal by reducing the types of weights given to the signal series. However, in such a case, the degree of freedom of weight adjustment is greatly limited.

Furthermore, the weights given only adjust the phase. ^Assuming that S _p is a signal having peak power before being synthesized by the synthesis unit or the addition unit, and S is a partial OFDM signal multiplied by the weight (e ^jθ ), the output from the synthesis unit is S _p + e ^jθ S. The phase rotation amount θ is selected so that the amplitude of this signal after synthesis becomes small. However, if the amplitude of the signal S is very small, it is difficult to reduce the combined amplitude no matter how the phase rotation amount θ is adjusted.

  Further, it is difficult to easily obtain the shift amount in the conventional cyclic shift method and the phase rotation amount in the conventional PTS method, and conventional control for peak reduction has not been easy. In addition, the computational burden related to such control increases as the number of signal sequences after being divided by the division inverse Fourier transform unit increases, which is particularly disadvantageous for small mobile terminals.

  The present invention has been made in order to address at least one of the above-described problems, and a problem thereof is a transmitter and a receiver that use an OFDM system capable of suppressing a peak-to-average power ratio of a radio signal. Is to provide a device.

A transmission device according to one embodiment of the disclosed invention
In a radio communication system using an orthogonal frequency division multiplexing (OFDM) scheme, a transmission apparatus that transmits a transmission signal including first and second pilot signals,
A division inverse Fourier transform unit that divides a signal sequence to be transmitted into a plurality of signals, and performs inverse Fourier transform on each of the divided signal sequences by a plurality of transform units;
Peak control means for outputting a peak control signal based on the peak detected from the output signal of the divided inverse Fourier transform means;
The peak reduction processing means for adjusting the weight of the output signal of the divided inverse Fourier transform means or the order of arrangement according to the peak control signal, and combining and outputting the adjusted signal and another signal;
The transmission apparatus is characterized in that the weight or arrangement order adjustment by the peak reduction processing unit is performed on the second pilot signal but not on the first pilot signal.

  According to the disclosed invention, it is possible to suppress a peak-to-average power ratio of a radio signal in an OFDM wireless communication system.

1 shows a schematic block diagram of a transmitter using an OFDM scheme. 1 shows a schematic block diagram of a receiver using an OFDM scheme. It is a figure which shows an OFDM signal. It is a figure which shows the input / output characteristic of a power amplifier. It is a figure which shows the transmitter which uses the OFDM system using the PTS method. It is a figure which shows the receiver which uses the OFDM system using the PTS method. FIG. 3 shows a partial block diagram of a transmission apparatus according to an embodiment of the present invention. The detailed block diagram of a division | segmentation inverse Fourier-transform part is shown. It is a figure which shows the modification of a peak reduction process part. It is a figure which shows the modification of a peak reduction process part. The block diagram of a transmitter in case the signal before a modulation | alteration is divided into m is shown. FIG. 3 shows a partial block diagram of a receiving apparatus according to an embodiment of the present invention. The frame block diagram showing an example of the insertion place of a pilot signal is shown. FIG. 3 shows a partial block diagram of a receiving apparatus according to an embodiment of the present invention. The frame block diagram showing an example of the insertion place of a pilot signal is shown. The frame block diagram showing an example of the insertion place of a pilot signal is shown. The frame block diagram showing an example of the insertion place of a pilot signal is shown. The frame block diagram showing an example of the insertion place of a pilot signal is shown. FIG. 3 shows a partial block diagram of a transmission apparatus according to an embodiment of the present invention. FIG. 3 shows a partial block diagram of a transmission apparatus according to an embodiment of the present invention. It is a figure which shows the modification of a peak reduction process part. FIG. 3 shows a partial block diagram of a transmission apparatus according to an embodiment of the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described.

  According to one aspect of the present invention, the peaks of the output signals of the plurality of conversion means are detected for each conversion means, the peak control information is output based on the detection results, and the weight of the output signal of the divided inverse Fourier transform means or its The arrangement order is set according to the peak control signal. Thereby, the peak-to-average power ratio can be suppressed with a small calculation burden, and an increase in circuit scale can be suppressed.

  According to one aspect of the present invention, the peak detecting means detects a predetermined number of peaks of the output signal of one converting means, and the peak control signal is formed to suppress the predetermined number of peaks. The Thereby, for example, a plurality of peaks can be suppressed simultaneously.

  According to an aspect of the present invention, the peak reduction processing unit is configured to make a sequence in which a plurality of signals output from at least one of the plurality of conversion units are arranged in an order indicated by the peak control signal. Shift means; and synthesis means for synthesizing an output from the cyclic shift means and an output from a conversion means other than the at least one conversion means. Thereby, the peak-to-average power ratio can be effectively reduced by the improved cyclic shift method.

  According to one aspect of the present invention, the peak reduction processing means adjusts the amplitude and / or phase of each output signal from at least one conversion means according to the peak control signal, and the weight adjustment. Synthesis means for synthesizing the output from the means and the output from the conversion means other than the at least one conversion means. Thereby, the peak-to-average power ratio can be effectively reduced by the improved PTS method.

  According to one aspect of the present invention, the divided inverse Fourier transform means includes at least first, second, and third transform means. The peak reduction processing unit adjusts the weight or order of the plurality of signals output from the first conversion unit according to a peak control signal. The adjusted signal and the signal from the second conversion unit are combined by the combining unit. The peak reduction processing unit further adjusts the weight or arrangement order of the combined signals according to the peak control signal. The adjusted signal and the signal from the third conversion unit are combined by the combining unit. Thereby, instead of using a large-scale peak reduction processing unit that can process a large number of sequences at once, a small-scale peak reduction processing unit can be linked to flexibly cope with a large number of inputs.

  According to an aspect of the present invention, a plurality of the peak reduction processing means are provided. For example, there is provided second peak reduction processing means for synthesizing and outputting a signal output from the first peak reduction processing means and another signal according to the peak control signal. According to another aspect of the present invention, the other signal is an output from the third peak reduction processing means. Thereby, peak reduction processing for a plurality of signal sequences can be performed quickly.

  According to an aspect of the present invention, a plurality of frequency groups including a plurality of subcarriers are prepared, and phase and / or order adjustment in the peak reduction processing unit is performed for each frequency group. The same peak reduction processing is performed within the same group. In this case, according to one aspect of the present invention, the second pilot signal multiplexed with the input signal to the peak reduction processing means and the first pilot signal multiplexed with the output signal from the peak reduction processing means. Pilot signals are transmitted. By comparing the first and second pilot signals on the receiving side, the contents of the peak reduction process can be known. Further, according to one aspect of the present invention, the second pilot signal is inserted into some subcarriers.

  In one aspect of the present invention, the channel estimation value is corrected by averaging a plurality of channel estimation values calculated from a plurality of first pilot signals inserted in the same frequency group. Thereby, the channel estimation value is obtained with high accuracy, and the influence of noise is effectively eliminated.

  According to an aspect of the present invention, the peak of the signal before being synthesized by the peak reduction processing unit is detected, and the amplitude when the other signal is synthesized is reduced at the detected peak position. The weight or the order of arrangement is determined. Thereby, a transmission signal can be generated more easily than in the past. Conventionally, transmission signal candidates are generated for all weight candidates corresponding to a certain information bit sequence, and the candidate having the smallest peak among these candidates is determined as the final transmission signal. It had been. For this reason, in the conventional method, it is not easy to create a transmission signal.

  According to one aspect of the present invention, since the second pilot signal is assigned to a low-frequency subcarrier, it is possible to ensure a large number of distinguishable cyclic shift amounts.

  According to an aspect of the present invention, a feedback path is provided between the synthesizing unit and the divided inverse Fourier transform unit, and the feedback path has a predetermined value among outputs from the synthesizing unit that exceed a predetermined threshold. Means for subtracting the threshold value and Fourier transform means for Fourier transforming the output from the means are provided. In addition to the cyclic shift by the cyclic shift unit, the peak-to-average power ratio can be further suppressed by performing recursive voltage suppression by the feedback path.

  FIG. 7 is a partial block diagram of a transmission apparatus according to an embodiment of the present invention. The transmission apparatus includes a signal generation unit 702, a division inverse Fourier transform unit 704, a peak reduction processing unit 706, a parallel / serial conversion unit (P / S) 708, a guard interval provision unit 710, and an antenna 712. Further, the peak reduction processing unit 706 includes a peak reduction control unit 714, a cyclic shift unit 716, and a plurality of combining units 718.

  The signal generation unit 702 receives a bit string representing transmission information, forms signal contents corresponding to each subcarrier, and outputs them as a series of signal sequences.

  As described in detail with reference to FIG. 8, the division inverse Fourier transform unit 704 receives one signal series and outputs the series 1 and the series 2 as two sets of inverse Fourier transformed signals. In this embodiment, for simplicity, the two series 1 and 2 are output, but it is also possible to output a larger number of signal groups.

  The peak reduction processing unit 706 forms a signal group whose peak-to-average power ratio is improved based on the signal contents of the series 1 and the series 2.

The peak reduction control unit 714 outputs cyclic shift information N _shift indicating an appropriate shift amount as described later for the series 1 and the series 2. Further, although not essential, this cyclic shift information N _shift is wirelessly transmitted through the control channel.

Cyclic shift section 716 cyclically shifts and outputs the signals in the sequence 2 signal group so that the order in which the signals are arranged is the order indicated by cyclic shift information N _shift .

  The combining unit 718 combines (adds) the cyclically shifted sequence 2 signal group and the sequence 1 signal group.

  The parallel / serial converter (P / S) 708 converts a plurality of parallel signals into a serial signal sequence.

  A guard interval adding unit (GI) 710 forms an OFDM signal transmitted from the antenna 712 by adding a guard interval to the signal sequence.

  FIG. 8 shows a detailed block diagram of the division inverse Fourier transform unit 704. The division inverse Fourier transform unit 704 includes a division unit 802, a first serial / parallel conversion unit 804, a first inverse Fourier transform unit 806, a second series / parallel conversion unit 808, and a second inverse Fourier transform unit. 810.

  The dividing unit 802 divides the input signal sequence into two. In the present embodiment, a case where the signal is divided into two parts is described, but it is also possible to divide the signal into more signal groups.

  The first serial / parallel converter 804 receives the divided signal sequence and converts it into N / 2 signal groups. N indicates the number of signal points (number of points) of the input and output of the fast inverse Fourier transform. In the illustrated example, N = 8, and the first serial-parallel converter 804 has 8/2 = 4 signals (information in the frequency domain) f (0), f (1), f (2). , F (3) are output.

The first inverse Fourier transform unit (IFFT ₁ ) 806 receives N / 2 signals and N / 2 null symbols, performs inverse Fourier transform on them, and generates a signal group F ₁ (0), F ₁ (1), F ₁ (2), F ₁ (3), F ₁ (4), F ₁ (5), F ₁ (6), and F ₁ (7) are output. What signal is given to the input point of IFFT ₁ (for example, which input point is given a null symbol) is instructed by the subcarrier designation signal.

  Similarly, the second serial / parallel conversion unit 808 receives the divided signal sequences and converts them into N / 2 parallel signal sequence groups. In the illustrated example, the second serial / parallel conversion unit 806 outputs 8/2 = 4 signal sequences f (4), f (5), f (6), and f (7).

The second inverse Fourier transform unit (IFFT ₂ ) 810 receives N / 2 signal groups and N / 2 null symbols, performs inverse Fourier transform on them, and generates a signal group F ₂ (0) of sequence 2. , F ₂ (1), F ₂ (2), F ₂ (3), F ₂ (4), F ₂ (5), F ₂ (6), and F ₂ (7) are output. What kind of signal is given to the input point of IFFT ₂ is also instructed by the subcarrier designation signal.

In this way, since the division inverse Fourier transform unit 704 divides and processes the signals f (0) to f (7), the sequence 1 includes only information regarding the signals f (0) to f (3), Series 2 includes only information related to signals f (4) to f (7). Generally, a signal (information in the frequency domain) included in the k-th sequence among the sequences divided into K pieces is:
[(K−1) × N / K] -th to [k × N / K−1] -th signal. N is the number of IFFT points. In the illustrated example, k = 1 or 2, N = 8, and K = 2.

  In the example shown in FIG. 7, one of the two sequences 1 and 2 is connected to the cyclic shift unit 716, but both are connected to the cyclic shift unit 716, and both the sequence 1 and the sequence 2 are cyclic. It is also possible to rearrange. However, since the arrangement of signals is determined by the relative order between the series 1 and the series 2, all possible combinations can be realized by rearranging the order of either the series 1 or the series 2. From the viewpoint of reducing the circuit scale and the like, it is preferable to cyclically shift only a part of the series as in the illustrated example.

  The operation will be described with reference to FIGS.

  The signal sequence generated by the signal generation unit 702 is input to the division unit 802 of the division inverse Fourier transform unit 704. The signal sequence input to the dividing unit 802 is divided into two signal sequences in accordance with the subcarrier designation signal, and input to the first and second series-parallel conversion units 804 and 808, respectively. The signal series input to the series-parallel converters 804 and 808 are converted into four parallel signals, respectively, and supplied to the first and second fast inverse Fourier transform units 806 and 810, respectively. The signal groups given to the high-speed inverse Fourier transform units 806 and 810 are subjected to inverse Fourier transform together with null symbols, and are output from the division inverse Fourier transform unit 704 as series 1 and series 2 signal groups, respectively.

The output of the division inverse Fourier transform unit 704 (sequence 1 and sequence 2 signal group) is input to the peak reduction control unit 714. The peak reduction control unit 714 obtains a peak power value for each of the signal groups, and examines a combined power value of the signal group of the series 1 and the signal group of the series 2 arranged in a certain order. The certain order is an order obtained by cyclically shifting signals in the signal group of the series 2. In the example shown, the following cyclic shifts are conceivable for shift amounts of 0-7:
Shift amount = 0: {F ₂ (0), F ₂ (1), F ₂ (2), F ₂ (3), F ₂ (4), F ₂ (5), F ₂ (6), F ₂ (7)}
Shift amount = 1: {F ₂ (7), F ₂ (0), F ₂ (1), F ₂ (2), F ₂ (3), F ₂ (4), F ₂ (5), F ₂ (6)}
Shift amount = 2: {F ₂ (6), F ₂ (7), F ₂ (0), F ₂ (1), F ₂ (2), F ₂ (3), F ₂ (4), F ₂ (5)}
Shift amount = 3: {F ₂ (5), F ₂ (6), F ₂ (7), F ₂ (0), F ₂ (1), F ₂ (2), F ₂ (3), F ₂ (4)}
Shift amount = 4: {F ₂ (4), F ₂ (5), F ₂ (6), F ₂ (7), F ₂ (0), F ₂ (1), F ₂ (2), F ₂ (3)}
Shift amount = 5: {F ₂ (3), F ₂ (4), F ₂ (5), F ₂ (6), F ₂ (7), F ₂ (0), F ₂ (1), F ₂ (2)}
Shift amount = 6: {F ₂ (2), F ₂ (3), F ₂ (4), F ₂ (5), F ₂ (6), F ₂ (7), F ₂ (0), F ₂ (1)}
Shift amount = 7: {F ₂ (1), F ₂ (2), F ₂ (3), F ₂ (4), F ₂ (5), F ₂ (6), F ₂ (7), F ₂ (0)}.

For example, the peak reduction control unit 714 adds a series 2 signal group of a certain shift amount to each of the series 1 signal groups F ₁ (0),..., F ₁ (7), and the peak power value thereof And finds the order of series 2 (shift amount N _shift ) that gives the smallest peak power value.

In order to easily obtain the shift amount N _shift , for example, the following can be performed. It is assumed that a signal of series 1 is S ₁ (t), a signal of series 2 is S ₂ (t), and S ₁ (t) includes an amplitude value (peak) larger than S ₂ (t). The peak reduction control unit 714 determines the magnitude relationship of such peak values, and determines the cyclic shift amount t ′ according to the following equation.

t ′ = Arg min [| S ₁ (t _p ) + S ₂ (t _p + t ″) |]
Here, t "indicates a time parameter for shifting the cyclically signals, Arg min is, .t represents a function that time return a parameter (shift amount) when the argument is a minimum value _p signal series 1 S ₁ shows a time parameter when ₁ (t) takes a maximum value, whereby the optimum shift amount can be found easily and reliably.

  In the present embodiment, the example in which the input signal sequence is divided into two has been described. However, as shown in FIG. 11, it is naturally possible to divide the input signal sequence into more signal sequences.

  FIG. 12 shows a schematic block diagram of a receiving apparatus according to an embodiment of the present invention. The receiving apparatus includes an antenna 1202, a guard interval removal unit 1203, a serial-parallel conversion unit 1204, a fast Fourier transform unit (FFT) 1206, a plurality of multiplication units 1208, a signal detection unit 1210, and a shift amount detection unit 1212. And a phase rotation amount calculation unit 1214.

  The guard interval removing unit 1203 removes the guard interval from the OFDM signal received by the antenna 1202.

  The serial / parallel conversion unit 1204 converts the received signal sequence into a plurality of parallel signals.

  The fast Fourier transform unit 1206 performs demodulation by performing fast Fourier transform on a plurality of parallel signals.

  Multiplier 1208 gives phase rotation to the signal in accordance with the instruction content from phase rotation amount calculator 1214.

  The signal detection unit 1210 restores the content of the transmitted signal based on the received signal.

The shift amount detection unit 1212 acquires cyclic shift information (an amount representing a cyclic shift amount) N _shift from the control channel (or the cyclic shift information is a received signal (pilot signal after Fourier transform, as will be described later). ) Can also be estimated.)

The phase rotation amount calculation unit 1214 obtains the phase rotation amount θ _n to be given to the received signal based on the detected shift amount.

The signal received from the antenna 1202 is converted into a parallel signal after the guard interval is removed, subjected to fast Fourier transform, and provided to one input of the multiplier 1208. In the multiplication unit 1208, the phase rotation calculated by the phase rotation amount calculation unit 1214 is given to the signal after Fourier transform. The phase rotation amount θ _n given is
θ _n = 2πn × (cyclic shift amount) / (number of FFT points N)
Determined by. n indicates a subcarrier number. If the example illustrated in FIGS.
θ _n = 2πn × (0, 1, 2, 3, 4, 5, 6 or 7) / 8
It becomes. In general, the smaller the value of n (the smaller the subcarrier frequency), the more types of shift amounts that can be distinguished, and the larger the value of n, the fewer types of shift amounts that can be distinguished.

According to the present embodiment, the order (shift amount) of the signal groups to be combined is determined so that the peak power after combination is reduced while rearranging the order of the signal groups cyclically. The peak-to-average power ratio can be reduced without performing complex multiplication. For example, it is assumed that the number of subcarriers N is 64, the number of divisions K is 8, and the number of shift patterns (type of shift amount) is 6. In this case, the calculation amount of the inverse Fourier transform is Nlog ₂ N. In the conventional PTS system, the number of complex multiplications is (calculation amount of inverse Fourier transform) + (number of subcarriers) × (number of divisions) × (number of shift patterns) = 64 log ₂ 64 + 64 × 8 × 6. On the other hand, the number of complex multiplications in this embodiment is 64 log ₂ 64 = 64 × 6 because there is only the amount of calculation of inverse Fourier transform. Therefore, the complex multiplication amount is reduced to about (64 × 6) / (64 × 6 + 64 × 8 × 6) = 1/9.

  Hereinafter, some embodiments will be described in the case where data indicating cyclic shift information is not directly transmitted from the transmitter to the receiver. In one embodiment, the pilot signal used for channel estimation is OFDM modulated as described in the first embodiment. That is, the pilot signal is input to the division Fourier transform unit 704 (FIG. 7), and is combined and transmitted by the cyclic shift unit 716 and the combining unit 718 so that the peak-to-average power ratio becomes small. In FIG. 7, the pilot signal is shown as the second pilot signal, but usage examples of the first and second pilot signals will be described later. The pilot signal is transmitted in a signal format as shown in FIG. 13, for example. In the figure, f indicates the frequency direction, and t indicates the time direction. In the illustrated example, pilot signals are inserted into all subcarriers in a certain time slot. One region surrounded by a broken line in the figure represents one group, and how the grouping is performed is determined based on a subcarrier designation signal (FIG. 8) output from a control unit (not shown). The The same cyclic shift amount is used in the same group. In other words, the cyclic shift amount is updated for each group. Note that the grouping may be fixedly set regardless of the control signal. Furthermore, from the viewpoint of obtaining the channel estimation value with high accuracy, it is desirable to average a plurality of channel estimation values obtained from pilot signals inserted in adjacent subcarriers and correct the channel estimation value.

  FIG. 14 shows a partial block diagram of a receiver according to an embodiment of the present invention. The receiving apparatus includes an antenna 1402, a guard interval removing unit 1403, a serial / parallel conversion unit 1404, a fast Fourier transform unit (FFT) 1406, and a signal detection unit 1410. The receiving apparatus includes a channel estimation unit 1412 and a correction unit 1408. The channel estimation unit 1412 estimates amplitude and phase fluctuations introduced in the channel from the pilot signal in the received signal that has been OFDM demodulated (after the Fourier transform), and outputs a control signal for compensating them. Correction section 1408 corrects the data related to each subcarrier according to the control signal, and provides the corrected data to signal detection section 1410.

  The received signal received by the antenna 1402 is converted into a plurality of parallel signal sequences after the guard interval is removed, and is subjected to fast Fourier transform. Thereby, OFDM demodulation is performed.

By the way, if the channel impulse response value for the n-th subcarrier is H _n and the transmission signal of each subcarrier for the pilot signal is s _n (t), the received signal s _n ′ (t) is
s _n ′ (t) = H _n exp (jθ _n ) s _n (t)
It is expressed. However, θ _n represents the influence of the phase change introduced in the cyclic shift unit. The channel estimation unit 1412 estimates H _n exp (jθ _n ) based on the received signal after Fourier transform and a known pilot signal pattern. The effect of H _n exp (jθ _n ) is compensated by the correction unit 1408.

  In the example of FIG. 13, pilot signals are inserted into all subcarriers, but it is also possible to insert pilot signals into only some subcarriers as shown in FIG. In this case, channel estimation values for other subcarriers are obtained by interpolation. It should be noted that this interpolation is performed in the same group surrounded by a broken line in the figure. The overhead due to the pilot signal is reduced, and the transmission rate can be increased accordingly.

  FIG. 16 shows another example of inserting a pilot signal. In this example, the first pilot signal 1602 is inserted in all subcarriers in a certain time slot, and the second pilot signal 1604 is inserted in a subcarrier in another time slot. Both the first and second pilot signals represent the same known signal. Although not shown, specifically, the first pilot signal 1602 is inserted between the output of the cyclic shift unit 716 and the input of the parallel-serial conversion unit 708 in FIG. Unlike the first pilot signal, the second pilot signal 1604 is input to the division inverse Fourier transform unit 704 of FIG. 7 in the same manner as the data signal, and thus transmitted after being arranged in an appropriate order by the cyclic shift unit. Is done. Therefore, the second pilot signal is transmitted in a state including information on rearrangement in the cyclic shift unit, but the first pilot signal is transmitted without including such information.

In the receiver, the channel estimation unit 1412 compares the received first and second pilot signals so as to grasp only the influence (exp (jθ _n )) introduced by the cyclic shift unit. Is possible. In the examples of FIGS. 13 and 15, the entire H _n exp (jθ _n ) can be known, but the breakdown is unknown. By using the first and second pilot signals, it is possible to increase the accuracy of correction in the correction unit 1408. The reason why only one second pilot 1604 is inserted into the group is that cyclic shift is performed in the embodiment of the present invention. When the phase rotation amount θ _n1 of the n _1st subcarrier is known, the phase rotation amount θ _n2 of the n _2nd subcarrier can be obtained by the following equation:
θ _n2 = (n ₂ / n ₁ ) θ _n1 .

  From the viewpoint of detecting the cyclic shift amount with high accuracy, it is desirable to insert a plurality of second pilot signals in the same group. By the way, the cyclic shift amount that can be discriminated by the second pilot signal inserted in the subcarrier number n satisfies the following relational expression.

(Amount of cyclic shift that can be discriminated) <(number of FFT points N) / n
In the examples of FIGS. 7 and 8, the FFT point number N is 8, and the subcarrier number n can take a value of 1 to 8. From the above equation, it can be seen that if the subcarrier number n is large, that is, if the second pilot signal is inserted into a high-frequency subcarrier, the discriminable cyclic shift amount decreases. Therefore, from the viewpoint of increasing the identifiable cyclic shift amount, it is desirable to insert the second pilot signal into a low-frequency subcarrier. Note that the second pilot signal is preferably arranged on a low subcarrier other than a DC component in OFDM modulation (IFFT).

  FIG. 17 shows another example in which the first and second pilot signals are inserted. In this example, the first pilot is inserted in all subcarriers, and the data signal is divided into three groups indicated by broken lines. The second pilot signal used for each group is inserted in each subcarrier having a low frequency. That is, one second pilot signal is commonly used in one group. Since the second pilot signal is inserted in the subcarrier of the lowest frequency for all three groups, the identifiable cyclic shift amount can be set to be about the same for all groups.

  FIG. 18 shows another example in which the first and second pilot signals are inserted. The pilot signals shown in FIGS. 13, 15, and 16 are inserted so as to have the same arrangement pattern in each group. In the example shown in FIG. 18, pilot signals are inserted at regular intervals in the frequency direction, but the locations where pilot signals are arranged are different between group 1 and group 2. Channel estimation values for all subcarriers can be obtained by interpolation in the frequency direction, and the cyclic shift amount can be obtained by comparing the first and second pilot signals. The frequency interval of the first pilot signal can be determined by the impulse response length in the channel between the transceivers. The frequency interval of the second pilot signal is preferably determined by subcarrier grouping.

  There may be various pilot signal insertion methods other than the above. For example, although pilot signals are arranged in the frequency direction in the above example, channel fluctuation in the time direction can be tracked with high accuracy by increasing the number of pilot signals arranged in the time axis direction. In a use environment such as a mobile terminal moving at high speed, it is desirable to consider channel fluctuations in the time axis direction.

In this embodiment, an example in which the cyclic shift method is employed has been described, but the PTS method can also be used. When the PTS method is used, the phase rotation amount θ _n1 for the n _1st subcarrier and the phase rotation amount θ _n2 for the n _2nd subcarrier are equal in the same group. It is not necessary to calculate the amount of phase rotation.

  FIG. 19 is a partial block diagram of a transmission apparatus according to an embodiment of the present invention. The transmission apparatus includes a signal generation unit 1902, a division inverse Fourier transform unit 1904, a peak reduction control unit 1906, a cyclic shift unit 1916, a plurality of multiplication units 1922, a plurality of synthesis units 1918, and a parallel-serial conversion unit ( P / S) 1908, a guard interval providing unit 1910, and an antenna 1912.

  Transmission information is input to the signal generator 1902, signal contents corresponding to each subcarrier are formed, and these are output as a series of signal sequences.

  The divided inverse Fourier transform unit 1904 is generally the same as that described with reference to FIG. 8, receives one signal sequence, and outputs sequence 1 and sequence 2 as two sets of inverse Fourier transformed signals. To do.

The peak reduction control unit 1906 outputs cyclic shift information N _shift indicating an appropriate shift amount for the series 1 and the series 2. Cyclic shift information N _shift indicating the shift amount can be known on the receiving side through a control channel or a pilot signal. The weight given by the peak reduction control unit 1906 to the multiplying unit 1922 is the peak when the amplitude and / or phase (weight or weight) of the sequence 2 signal group rearranged is combined. The weight is such that the amplitude is suppressed. Information about the weight can also be known on the receiving side through a control channel, a pilot signal, or the like.

Cyclic shift section 1916 cyclically shifts and outputs the sequence 2 signal group in the order indicated by cyclic shift information N _shift .

  Multiplier 1922 gives a weight to each signal based on a control signal from weight controller 1920.

  The combining unit 1918 combines (adds) the cyclically shifted and weighted series 2 signal group and the weighted series 1 signal group.

  A parallel / serial converter (P / S) 1908 converts a plurality of parallel signals into a serial signal sequence.

  A guard interval adding unit (GI) 1910 forms an OFDM signal transmitted from the antenna 1912 by adding a guard interval to the signal sequence.

  In the illustrated embodiment, in addition to the rearrangement of signal groups by the cyclic shift unit 1916, the amplitude and / or phase of each transmitted signal can be controlled. Appropriate weights and cyclic shift amounts are given to the respective signals so that the combined peak power value falls within an appropriate magnitude. Therefore, the peak-to-average power ratio of the signals output from the combining unit 1918 is appropriately suppressed, these signals are converted into serial signals, a guard interval is given to them, and it is transmitted from the antenna. According to the present embodiment, more transmission signal candidates can be created than in the case of the first embodiment, so that the peak-to-average power ratio can be suppressed. According to the present embodiment, it is possible to appropriately suppress the peak regardless of the amplitude of the signal before synthesis.

  According to the present embodiment, PAPR can be suppressed by the cyclic shift method, the weight control method, or both. When both methods are used, a third pilot signal weighted with respect to weight control may be used in addition to the second pilot signal multiplexed into the signal input to the cyclic shift unit. . The first pilot signal is naturally transmitted without any cyclic shift or weighting. In this case, a frame configuration similar to the pattern shown in FIGS.

  FIG. 20 is a partial block diagram of a transmission apparatus according to an embodiment of the present invention. The transmission apparatus includes a signal generation unit 2002, a division inverse Fourier transform unit 2004, a peak reduction control unit 2014, a cyclic shift unit 2016, a plurality of synthesis units 2018, a parallel-serial conversion unit (P / S) 2008, A guard interval providing unit 2010 and an antenna 2012 are included. The division inverse Fourier transform unit 2004 includes a division unit 2802, a first serial / parallel conversion unit 2804, a second inverse Fourier transform unit 2806, a second series / parallel conversion unit 2808, and a first inverse Fourier transform unit. 2810 and a plurality of combining units 2812. Further, the transmission apparatus has a feedback path between the output of the synthesis unit 2018 and the input of the synthesis unit 2812, and a peak component detection unit 2020 and a Fourier transform unit 2022 are provided in this feedback path. . Elements similar to those described in the first embodiment have the same configuration and perform similar operations, and thus detailed description thereof is omitted. In this embodiment, in addition to the configuration of the first embodiment, a feedback path is provided.

The peak component detection unit 2020 subtracts the threshold from the output of the synthesis unit 2018 exceeding the predetermined threshold C _th and outputs the result. If the output of the combining unit 2018 does not exceed a predetermined threshold, zero is output.

  The Fourier transform unit 2022 performs fast Fourier transform on the output of the peak component detection unit 2020.

  The combining unit 2812 in the divided inverse Fourier transform unit 2004 subtracts the signal (feedback signal) after the Fourier transform from the signal to be transmitted, and gives the subtraction result to the inverse Fourier transform units 2806 and 2810, respectively.

The signal after the Fourier transform represents a signal component that exceeds a predetermined threshold C _th among the signal components output from the synthesis unit 2018. If this signal component is subtracted from the signal sequence to be transmitted and the signal after the subtraction is subjected to inverse Fourier transform, a signal with a suppressed peak-to-average power ratio can be obtained. In addition to the cyclic shift by the cyclic shift unit 2016, the peak-to-average power ratio can be further suppressed by performing recursive voltage suppression by the feedback path.

  FIG. 22 shows a partial block diagram of a transmitting apparatus according to an embodiment of the present invention. The transmission apparatus includes a signal generation unit 2202, a division inverse Fourier transform unit 2204, a peak reduction control unit 2205, a peak reduction processing unit 2206, a parallel / serial conversion unit (P / S) 2208, and a guard interval provision unit 2210. And an antenna 2212. The peak reduction control unit 2205 includes a peak detection unit 2214 for the series 1, a peak detection unit 2216 for the series 2, and a peak reduction control amount determination unit 2218.

  The signal generation unit 2202 receives transmission information, forms signal contents corresponding to each subcarrier, and outputs them as a series of signal sequences.

  The divided inverse Fourier transform unit 2204 is generally the same as that described with reference to FIG. 8, receives one signal sequence, and outputs sequence 1 and sequence 2 as two sets of inverse Fourier transformed signals. To do.

  Peak reduction control section 2205 detects the peak positions for series 1 and series 2 and outputs a peak control signal so that an OFDM signal in which PAPR is suppressed is formed.

Peak detector 2214 monitors the amplitude of the series 1 of the signal from the dividing inverse Fourier transform part 2204, and detects the amplitude values exceeding a predetermined value, and outputs the amplitude value and the timing t _p as a peak position. The peak detector 2216 monitors the amplitude of the series 2 signal, detects an amplitude value exceeding a predetermined value, and outputs the amplitude value and timing t _p ′ as a peak position.

  The peak reduction control amount determination unit 2218 outputs a peak control signal based on the outputs from the peak detection units 2214 and 2216 so that an OFDM signal with PAPR suppressed is formed. The peak control signal may be a signal indicating the cyclic shift amount as described above, or may be an amount indicating a phase rotation amount (that is, a weighting coefficient or a weight) as described later. That is, in the present embodiment, the PAPR of the OFDM signal is suppressed by the peak reduction method by cyclic shift, the peak reduction method by weight control (an improvement of the conventional PTS method), or both.

  The peak reduction processing unit 2206 adjusts the output signal from the division inverse Fourier transform unit 2204 based on the peak control signal from the peak reduction control unit 2205. When the cyclic shift method is employed, the order of combining between the series 1 and the series 2 is appropriately adjusted according to the peak control signal. When the weight control method is employed, the weights including the phase rotation amounts of the series 1 and the series 2 are appropriately adjusted according to the peak control signal.

  A parallel / serial converter (P / S) 2208 converts a plurality of parallel signals into a serial signal sequence.

In the present embodiment, peak positions are detected by the peak detectors 2214 and 2216 for each series (for each of a plurality of inverse Fourier transform units included in the divided inverse Fourier transform unit 2204). The peak position is specified by the amplitude value and the timing at that time. The detected peak positions are not limited to one, and the top n peak positions may be detected. For the sake of simplicity, the operation when n = 1 and the cyclic shift method is employed will be described. Similar processing can be performed for n> 1. It is assumed that a signal of series 1 is S ₁ (t), a signal of series 2 is S ₂ (t), and S ₁ (t) includes an amplitude value (peak) larger than S ₂ (t). The peak reduction control amount determination unit 2218 determines the magnitude relationship of such peak values, and determines the cyclic shift amount t ′ according to the following equation.

t ′ = Arg min [| S ₁ (t _p ) + S ₂ (t _p + t ″) |]
Here, t "indicates a time parameter for shifting the cyclically signals, Arg min is, .t represents a function that time return a parameter (shift amount) when the argument is a minimum value _p signal series 1 S ₁ shows a time parameter when (t) takes the maximum value.

  When the weight control method is employed, the peak reduction control amount determination unit 2218 determines the weight to be given to each signal by obtaining the phase rotation amount θ that satisfies the following equation.

arg [S ₁ (t _p )] + π = arg [S ₂ (t _p )] + θ
Here, arg represents the phase angle of the argument. As understood from this equation, the phase rotation amount θ is determined so that the peak position of the series 1 and the peak position of the series 2 are combined in opposite phases (weakening each other). The peak reduction control amount determination unit 2218 examines such a phase relationship, determines the phase rotation amount θ so that they are synthesized in the opposite phase, and creates a peak control signal.

  When the phase rotation amount that can be set by the peak reduction processing unit 2206 is limited to a predetermined value, among those predetermined values, the phase rotation amount obtained as described above is used. The closest one is selected.

Further, when both the cyclic shift method and the weight control method are used, first, cyclic shift is performed on the sequence 2 by (t _p −t _p ′). t _p represents a peak position with respect to the signal S ₁ (t) of the series 1. t _p ′ indicates a peak position with respect to the signal S ₂ (t) of the series 2. Next, for the signal S ₂ (t) of series 2,
arg [S ₁ (t _p )] + π-arg [S ₂ (t _p ′)]
The phase is rotated by the amount indicated by. That is, the peak positions of the signals of the series 1 and the series 2 are aligned by the cyclic shift method, and the phase is rotated so that they are synthesized in the opposite phase by the weight control method.

  Thereafter, according to the peak control signal, the signal after the cyclic shift or phase rotation is performed on the output of the division inverse Fourier transform unit is converted into a serial signal, a guard interval is added to it, and the PAPR is finally suppressed. An OFDM signal is created.

  According to the present embodiment, peak detection is performed on a signal before synthesis, and synthesis is performed when all possible cyclic shift amounts and weight candidates are applied only to a synthesis output corresponding to the peak signal before synthesis. Output is generated. The cyclic shift amount and the weight that minimize the peak in the combined output are determined as the final control amount (peak control signal). For this reason, a transmission signal is created for all possible weights and the like corresponding to a certain information bit sequence, and the optimal transmission signal is determined more easily than the conventional method in which the optimal one is selected. be able to.

  In the above embodiment, the divided inverse Fourier transform means has two transform means, and two series of signals are output. In the following example, a technique for handling more than two sequences is described.

  In a method according to the present invention, when there are three sequences 1, 2, 3 (when the dividing unit 802 in FIG. 8 divides the signal sequence into three), for example, as in any of the above embodiments Thus, the optimum shift amount or weight between the two sequences is first determined. Then, a sequence obtained by synthesizing the sequence 1 and the sequence 2 adjusted according to the shift amount or weight thereof is obtained, and the same procedure is repeated between the synthesized sequence and the sequence 3, and the optimum shift amount for the sequence 3 is obtained. Alternatively, the weight is determined. Similarly, when there are more sequences, the shift amount can be obtained. According to this method, as shown in FIG. 21, the optimum shift amount can be obtained by sequentially determining N−1 shift amounts for N sequences. Since the shift amount or weight is obtained for each sequence, if at least one peak reduction processing unit is prepared for at least two sequences, the shift amount or weight for a large number of sequences can be appropriately determined.

  In another method according to the present invention, a plurality of peak reduction control units provided in a tree shape are used, and shift amounts or weights for many sequences are obtained (FIG. 9). Thereby, a transmission signal can be determined promptly. The arrangement of the plurality of peak reduction processing units is not limited to that shown in FIG. 9, and various forms may be adopted depending on the capability of the peak reduction processing unit used (number of sequences that can be processed at one time, etc.). it can. For example, as shown in FIG. 10, it is also possible to use a peak reduction processing unit that obtains shift amounts or weights for a large number of sequences at once. In the example shown in the figure, the peak reduction processing units 1 and 2 obtain the optimum shift amounts for four sequences at the same time. Thereby, compared with the case shown by FIG. 9, the number of peak reduction process parts can be decreased. Thereby, the freedom degree of the design regarding arrangement | positioning, a structure, etc. of a peak reduction process part can be increased.

  The means taught by the disclosed invention will be listed below as an example.

(Section 1)
A transmitter used in an orthogonal frequency division multiplexing (OFDM) wireless communication system,
A division inverse Fourier transform unit that divides a signal sequence to be transmitted into a plurality of signals, and performs inverse Fourier transform on each of the divided signal sequences by a plurality of transform units;
Peak detecting means for detecting the peak of the output signal of the converting means for each converting means;
Peak control means for outputting a peak control signal based on the output from the peak detection means;
A peak reduction processing unit that adjusts the weight or order of the output signals of the divided inverse Fourier transform unit according to a peak control signal, and combines and outputs the adjusted signal and another signal. A transmitting device.

(Section 2)
The peak detection means detects a predetermined number of peaks of the output signal of one conversion means,
The transmitting apparatus according to claim 1, wherein the peak control signal is formed so as to suppress the predetermined number of peaks.

(Section 3)
The peak reduction processing means
A cyclic shift means for changing the order of the plurality of signals output from at least one of the plurality of conversion means to the order indicated by the peak control signal;
The transmission apparatus according to claim 2, further comprising: a combining unit that combines an output from the cyclic shift unit and an output from a conversion unit other than the at least one conversion unit.

(Section 4)
The peak reduction processing means
Weight adjusting means for adjusting the amplitude and / or phase of each output signal from at least one converting means according to the peak control signal;
The transmission apparatus according to claim 2, further comprising: a combining unit that combines an output from the weight adjusting unit and an output from a conversion unit other than the at least one conversion unit.

(Section 5)
A transmitter used in an orthogonal frequency division multiplexing (OFDM) wireless communication system,
A divided inverse Fourier transform unit that divides a signal sequence to be transmitted into a plurality of signals, and performs inverse Fourier transform on the divided signal sequences by at least first, second, and third transform units;
Peak control means for outputting a peak control signal based on the peak detected from the output signal of the divided inverse Fourier transform means;
A peak reduction processing means for adjusting the weight of the output signal of the divided inverse Fourier transform means or the order of arrangement according to a peak control signal, and combining and outputting the adjusted signal and another signal; and The reduction processing unit adjusts the weight or order of the plurality of signals output from the first conversion unit according to a peak control signal, and the adjusted signal and the signal from the second conversion unit are combined. Synthesized by means,
The peak reduction processing unit further adjusts the weight or arrangement order of the combined signals according to the peak control signal, and the adjusted signal and the signal from the third conversion unit are combined by the combining unit. A transmission apparatus characterized by the above.

(Section 6)
A transmitter used in an orthogonal frequency division multiplexing (OFDM) wireless communication system,
A division inverse Fourier transform unit that divides a signal sequence to be transmitted into a plurality of signals, and performs inverse Fourier transform on each of the divided signal sequences by a plurality of transform units;
Peak control means for outputting a peak control signal based on the peak detected from the output signal of the divided inverse Fourier transform means;
The peak reduction processing means for adjusting the weight of the output signal of the divided inverse Fourier transform means or the order of arrangement according to the peak control signal, and combining and outputting the adjusted signal and another signal;
A transmission apparatus comprising: another peak reduction processing unit configured to synthesize and output a signal output from the peak reduction processing unit and another signal according to a peak control signal.

(Section 7)
The transmission apparatus according to claim 6, wherein the another signal is an output from still another peak reduction processing means.

(Section 8)
A transmitter used in an orthogonal frequency division multiplexing (OFDM) wireless communication system,
A division inverse Fourier transform unit that divides a signal sequence to be transmitted into a plurality of signals, and performs inverse Fourier transform on each of the divided signal sequences by a plurality of transform units;
Peak control means for outputting a peak control signal based on the peak detected from the output signal of the divided inverse Fourier transform means;
The peak reduction processing means for adjusting the weight of the output signal of the divided inverse Fourier transform means or the order of arrangement according to the peak control signal, and combining and outputting the adjusted signal and another signal;
When a plurality of frequency groups including a plurality of subcarriers are prepared, and the phase and / or order adjustment in the peak reduction processing means is performed for each frequency group,
Transmitting a second pilot signal multiplexed on an input signal to the peak reduction processing means and a first pilot signal multiplexed on an output signal from the peak reduction processing means apparatus.

(Section 9)
When a plurality of frequency groups including a plurality of subcarriers are prepared, and the phase and / or order adjustment in the peak reduction processing unit is performed for each frequency group,
The transmitting apparatus according to claim 8, wherein the second pilot signal is inserted into some subcarriers.

(Section 10)
The peak of the signal before being synthesized by the peak reduction processing means is detected, and the weight or the order of arrangement is determined so that the amplitude when the other signal is synthesized is reduced at the detected peak position. The transmitting apparatus according to claim 1, wherein:

(Section 11)
A transmitter used in an orthogonal frequency division multiplexing (OFDM) wireless communication system,
The signal sequence to be transmitted is divided into a plurality of signals, and the divided signal sequences are each subjected to inverse Fourier transform by a plurality of conversion means,
The peak of the output signal of the conversion means is detected for each conversion means,
A peak control signal is output based on the detection result,
The weight of the output signal of the division inverse Fourier transform means or the order of arrangement is adjusted according to the peak control signal, and the adjusted signal and another signal are combined and output,
A plurality of frequency groups including a plurality of subcarriers are prepared, and phase and / or order adjustment in the peak reduction processing means is performed for each frequency group and multiplexed on an input signal to the peak reduction processing means. When the second pilot signal and the first pilot signal multiplexed with the output signal from the peak reduction processing means are transmitted,
Adjusting means for adjusting the received signal according to the content of the peak control signal, and averaging a plurality of channel estimation values calculated from a plurality of first pilot signals inserted in the same frequency group, A receiving apparatus, wherein an estimated value is corrected.

702 Signal generation unit; 704 division inverse Fourier transform unit; 706 parallel-serial conversion unit; 708 peak reduction control unit; 710 guard interval giving unit; 712 antenna; 714 peak reduction control unit; 716 cyclic shift unit;
802 division unit; 804, 808 serial-parallel conversion unit; 806, 810 inverse Fourier transform unit;
1202 Antenna; 1203 Guard interval removal unit; 1204 Series-parallel conversion unit; 1206 Fast Fourier transform unit; 1208 Multiply unit: 1210 Signal detection unit: 1212 Shift amount detection unit; 1214 Phase rotation amount calculation unit;
1402 antenna; 1403 guard interval removal unit; 1404 series-parallel conversion unit; 1406 fast Fourier transform unit; 1408 correction unit; 1410 signal detection unit; 1412 channel estimation unit;
1602 Pilot signal not cyclically shifted; 1604 Pilot signal already cyclically shifted;
1902 signal generation unit; 1904 division inverse Fourier transform unit; 1906 peak reduction control unit; 1908 parallel-serial conversion unit; 1910 guard interval grant unit; 1912 antenna; 1916 cyclic shift unit; 1918 synthesis unit; 1922 multiplication unit 2002 signal generation unit; 2004 division inverse Fourier transform unit; 2006 peak reduction control unit; 2008 parallel-serial conversion unit; 2010 guard interval providing unit; 2012 antenna; 2016 cyclic shift unit; 2018 synthesis unit; 2020 peak component detection unit; 2022 Fourier transform unit;
2802 division unit; 2804, 2808 series-parallel conversion unit; 2806, 2810 inverse Fourier transform unit; 2812 subtraction unit;
2202 signal generation unit; 2204 division inverse Fourier transform unit; 2205 peak reduction control unit; 2206 peak reduction processing unit; 2208 parallel-serial conversion unit; 2210 guard interval provision unit; 2212 antenna; 2214, 2216 peak detection unit; Quantity determination part

Claims (4)

In a radio communication system using an orthogonal frequency division multiplexing (OFDM) scheme, a transmission apparatus that transmits a transmission signal including first and second pilot signals,
A division inverse Fourier transform unit that divides a signal sequence to be transmitted into a plurality of signals, and performs inverse Fourier transform on each of the divided signal sequences by a plurality of transform units;
Peak control means for outputting a peak control signal based on the peak detected from the output signal of the divided inverse Fourier transform means;
The peak reduction processing means for adjusting the weight of the output signal of the divided inverse Fourier transform means or the order of arrangement according to the peak control signal, and combining and outputting the adjusted signal and another signal;
The transmission apparatus is characterized in that the adjustment of the weight or arrangement order by the peak reduction processing unit is performed on the second pilot signal but not on the first pilot signal. A plurality of frequency groups including a plurality of subcarriers and a plurality of time slots are defined, and adjustment of weights or arrangement order by the peak reduction processing unit is performed for each frequency group,
The transmission apparatus according to claim 1, wherein each of the frequency groups includes the second pilot signal but does not include the first pilot signal. The peak of the signal before being synthesized by the peak reduction processing means is detected, and the weight or the order of arrangement is determined so that the amplitude when the other signal is synthesized is reduced at the detected peak position. The transmission device according to claim 1, wherein: A transmitter used in an orthogonal frequency division multiplexing (OFDM) wireless communication system,
The divided inverse Fourier transform means divides the signal sequence to be transmitted into a plurality of parts, and each of the divided signal series is inverse Fourier transformed by the plurality of transform means,
The peak of the output signal of the conversion means is detected for each conversion means,
A peak control signal is output based on the detection result,
By the peak reduction processing means, the weight or order of the output signals of the divided inverse Fourier transform means is adjusted according to the peak control signal, and the adjusted signal and another signal are combined and output,
A transmission signal including the signal sequence to be transmitted and the first and second pilot signals is transmitted, and the adjustment of the weight or arrangement order by the peak reduction processing unit is performed on the second pilot signal. When not applied to one pilot signal,
Receiving means for receiving the transmission signal and performing Fourier transform on the received signal;
Channel estimation means for estimating the influence of the radio channel from the received first pilot signal, and estimating the weight or arrangement order adjustment performed by the peak reducing means by the received second pilot channel;
And a correction unit that corrects the received signal after the Fourier transform using an estimation result obtained by the channel estimation unit.

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