JP2014090328A - Transmitter, receiver, and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a transmitter capable of suppressing peak power when transmitting a multiplexed symbol.SOLUTION: A transmitter for transmitting a block symbol having a data symbol multiplexed with a pilot symbol includes: a PAPR measurement unit 8 for measuring the PAPR information of a transmission signal; an N-block sequence selector unit 2 for selecting a pilot sequence group-by-group, each group configured by two or more block symbols; by retaining a plurality of frequency allocation candidates in a pilot symbol group constituting the pilot sequence, a frequency domain allocation unit 3 for selecting frequency allocation to be applied from candidate on the basis of the PAPR information group-by-group; a frequency multiplexer unit 4 for multiplexing the data symbol with the pilot symbol on the basis of the frequency allocation selected by the frequency domain allocation unit 3; an IDFT unit 5 for converting the signal multiplexed by the frequency multiplexer unit 4 into a time domain signal; and an antenna 12 for transmitting the time domain signal.

Description

  The present invention relates to a transmitter, a receiver, and a communication system.

  In a digital communication system, transmission path frequency selectivity and time variation occur due to multipath fading caused by reflection of a transmission signal on a building or the like and Doppler fluctuation caused by movement of a terminal. In such a multipath environment, the received signal is a signal in which a transmission symbol interferes with a symbol that arrives after a delay time.

  In order to obtain the best reception characteristics in such a frequency-selective transmission line, the block transmission method has recently attracted attention. Examples include SC (Single Carrier) block transmission (see Non-Patent Document 1), MC (Multiple Carrier) block transmission (refer to Non-Patent Document 2) such as OFDM (Orthogonal Frequency Division Multiplexing), etc. A transmission method is used.

  FDE (Frequency Division Equalizer: frequency domain equalization) can be used during demodulation of the SC block transmission method and the OFDM transmission method, whereby robust characteristics can be obtained in a multipath environment.

N. Benvenuto, R. Dinis, D. Falconer and S. Tomasin, “Single Carrier Modulation With Nonlinear Frequency Domain Equalization: An Idea Whose Time Has Come-Again”, Proceeding of the IEEE, vol. 98, No. 1, Jan 2010, pp. 69-96. D. L. Goeckel and G. Ananthaswamy, “On the Design of Multidimensional Signal Sets for OFDM Systems”, IEEE Trans. Commun., Vol. 50, No. 3, pp. 442-452, Mar. 2002.

  In the SC block transmission method, peak power characteristics equivalent to those of the conventional SC transmission method can be obtained. On the other hand, in the method of transmitting multiplexed symbols like the OFDM method, there is a problem that the peak power is higher than that of the SC transmission method.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a transmitter, a receiver, and a communication system that can suppress peak power when transmitting multiplexed symbols.

  In order to solve the above-described problems and achieve the object, the present invention is a transmitter that transmits block symbols in which data symbols and pilot symbols are multiplexed, and includes peak power information indicating peak power of a signal to be transmitted. A peak power measurement unit to measure, a pilot sequence selection unit that configures one group with two or more block symbols, and selects a pilot sequence for each group, and a candidate for frequency allocation within a group of pilot symbols that form the pilot sequence For each group, a frequency domain arrangement unit that selects a frequency arrangement to be applied from among the candidates based on the peak power information, and data based on the frequency arrangement selected by the frequency domain arrangement unit A frequency multiplexing unit that multiplexes symbols and pilot symbols, and the frequency multiplexing unit And IDFT unit for converting the signal into a time domain signal, characterized in that it comprises an antenna that transmits the time domain signal.

  According to the present invention, it is possible to suppress peak power when transmitting multiplexed symbols.

FIG. 1 is a diagram illustrating a functional configuration example of a transmitter according to the first embodiment. FIG. 2 is a diagram illustrating an example of pilot symbol arrangement according to the first embodiment. FIG. 3 is a diagram illustrating a configuration example of a transmitter when precoding is performed. FIG. 4 is a diagram illustrating a functional configuration example of the transmitter according to the second embodiment. FIG. 5 is a flowchart showing an example of a PAPR reduction processing procedure by arrangement in the frequency domain and pilot sequence selection. FIG. 6 is a diagram illustrating an example of the frequency arrangement. FIG. 7 is a diagram illustrating an example in which the frequency arrangement of pilot sequences is changed. FIG. 8 is a diagram illustrating a configuration example of a transmitter including a pilot sequence candidate / frequency allocation candidate control unit that confirms whether the same sequence is generated due to frequency allocation change. FIG. 9 is a diagram illustrating an internal configuration example of the frequency multiplexing unit. FIG. 10 is a diagram illustrating an arrangement example in which the time domain is rearranged with respect to the arrangement example of FIG. FIG. 11 is a conceptual diagram illustrating a determination error due to deep fade. FIG. 12 is a diagram showing a concept of preventing a determination error when multiple symbols of the same group are separated in time. FIG. 13 is a diagram illustrating a functional configuration example of the receiver according to the third embodiment. FIG. 14 is a flowchart illustrating an example of a reception processing procedure in the receiver according to the third embodiment. FIG. 15 is a diagram illustrating a functional configuration example of the transmitter according to the fourth embodiment.

  Hereinafter, embodiments of a transmitter, a receiver, and a communication system according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a functional configuration example of a first embodiment of a transmitter according to the present invention. The transmitter according to the present embodiment includes an N block data symbol generation unit (data symbol generation unit) 1, an N block pilot sequence selection unit (pilot sequence selection unit) 2, a frequency domain arrangement unit 3, and a frequency multiplexing unit 4. An IDFT (Inverse Discrete Fourier Transform) unit 5, a P / S (Parallel / Serial) unit 6, a transmission processing unit 7, a PAPR (Peak to Average Power Ratio) measuring unit (peak power measuring unit) 8, A transmission path information processing unit 9, a time domain arrangement unit 10, a frame generation unit 11, and an antenna 12 are provided.

FIG. 2 is a diagram illustrating an example of pilot symbol arrangement according to the present embodiment. In this embodiment, the number of block symbols in a frame is F _N , one group is N (N is an integer of 2 or more) block symbols, pilot sequence insertion processing is performed in units of N block symbols, and M in one frame. (M is an integer of 2 or more) A group of multiple symbols is generated. In the present embodiment, a “pilot sequence” indicates a sequence formed by a plurality of complex and / or real pilot symbols. “Multiple symbol” indicates a block symbol in which a data symbol and a pilot symbol are multiplexed on the frequency axis. If the number of block symbols including only data symbols is N _D , the number of block symbols in one frame is F _N = N · M + N _D. One block symbol is a symbol composed of L (L is an integer of 1 or more) symbols on the frequency axis (of different frequencies).

FIG. 2 shows an example in which M = 4, L = 8, N = 2, N _D = 8, and F _N = 16, but the numbers of M, L, N, N _D , and F _N are not limited to these. It is not limited. In the example of FIG. 2, multiple symbols (that is, block symbols including a pilot sequence) are arranged in time zones (symbol times) of even numbers (0, 2, 4,...) In the time domain. In the example of FIG. 2, a pilot sequence of 4 symbols is arranged for each group. The two block symbols of group # 0 are arranged at the 0th and 8th symbol times in the frame, respectively, and pilot sequences s ₀ , s ₁ , s ₂ , and s ₃ are arranged in these 2 block symbols. The two block symbols of group # 1 are arranged at the second and tenth symbol times in the frame, respectively, and pilot sequences q ₀ , q ₁ , q ₂ , q ₃ are arranged in these two block symbols. The two block symbols of group # 2 are arranged at the fourth and twelfth symbol times in the frame, respectively, and pilot sequences p ₀ , p ₁ , p ₂ , and p ₃ are arranged in these two block symbols. The two block symbols of group # 3 are arranged at the sixth and fourteenth symbol times in the frame, respectively, and pilot systems u ₀ , u ₁ , u ₂ , u ₃ are arranged in these two block symbols. The arrangement of pilot sequences in each group on the frequency axis is determined based on information indicating peak power (PAPR information) as described later, and the time domain arrangement of multiple symbols is determined based on transmission path information as described later. It is to be decided. The arrangement of the pilot sequences is not limited to the example of FIG. 2, and any method may be used as long as the pilot sequences in the group are arranged over a plurality of multiple symbols. In the example of FIG. 2, for the sake of simplification, the lengths of the pilot sequences in each group are the same, but the lengths of the pilot sequences in each group need not be the same.

  The operation of this embodiment will be described with reference to FIGS. First, the N block symbol generation unit 1 generates data symbols for N blocks, that is, data symbols for one group. The N block pilot sequence selection unit 2 selects a pilot sequence from the held pilot sequences based on the PAPR information (peak power information) measured by the PAPR measurement unit 8. For example, the pilot sequence selection method based on PAPR information is not particularly limited. For example, a pilot that holds a plurality of pilot sequence candidates, sequentially applies each candidate to acquire PAPR information, and minimizes the PAPR information. A sequence may be selected, or an initial value of the pilot sequence may be determined, and when the PAPR information when the initial value is applied exceeds a predetermined threshold, another pilot sequence is selected and PAPR is selected. A method may be used in which information is obtained and a candidate whose PAPR falls below a predetermined threshold is selected. The frequency domain arrangement unit 3 arranges the selected pilot sequence in the frequency domain based on the PAPR information measured by the PAPR measurement unit 8. The frequency allocation selection method based on the PAPR information is the same as the pilot sequence selection method and is not particularly limited. For example, the candidate that holds a plurality of candidates and minimizes the PAPR information is the same as the pilot sequence selection. Can be selected. The change of the selected pilot sequence and the change of the frequency arrangement may be performed simultaneously, or one of them may be performed first. Further, the PAPR may be reduced by performing only one of changing the selected pilot sequence and changing the frequency arrangement.

  The frequency multiplexing unit 4 multiplexes the pilot sequence and the data sequence based on the arrangement result by the frequency domain arrangement unit 3. The IDFT unit 5 converts the multiplexed pilot sequence and data sequence into a time domain signal. The P / S unit 6 converts the time domain signal from a parallel signal to a serial signal.

  The PAPR measurement unit 8 measures the PAPR of the serial signal output from the P / S unit 6, that is, the transmission signal for N block symbols (for each group). The measured PAPR value is fed back as PAPR information to the pilot sequence selection unit 2 and the frequency domain arrangement unit 3, and is used for selection of the pilot sequence and the frequency arrangement. The transmission path information processing unit 9 inputs the transmission path information to the time domain arrangement unit 10. The time domain arrangement unit 10 performs optimal arrangement of multiple symbols in the time domain based on the transmission path information. For example, information transmitted from the receiver can be used as the transmission path information. The frame generation unit 11 generates a frame to be transmitted using multiple symbols arranged in the time domain, and outputs the frame to the antenna 12. The antenna 12 transmits a transmission frame as a radio wave. In the above description, generation of multiple symbols has been described. However, data block symbols may be generated in any manner. For example, the frame generation unit 11 may generate a data block symbol, or the N block symbol generation unit may generate a data block symbol and input the data block symbol to the frame generation unit 11.

  Alternatively, multiple symbols may be generated based on the precoded block signal as shown in FIG. FIG. 3 is a diagram illustrating a configuration example of a transmitter when precoding is performed. The transmitter of FIG. 3 is the same as the transmitter of FIG. 1 except that an N block data symbol generator 1a is provided instead of the N block data symbol generator 1 of FIG. The N block data symbol generation unit 1a includes an N block symbol generation unit 1-1 and a DFT (Discrete Fourier Transform) unit 1-2.

  The receiver that receives the signal transmitted from the transmitter according to the present embodiment may have any configuration, but when using the transmission path information received by the time domain arrangement unit 10 of the transmitter from the receiver, The receiver has a function of transmitting the transmission path information estimated using the pilot sequence to the transmitter.

  Thus, in this embodiment, the pilot sequence is inserted over a plurality of multiple symbols. For this reason, a fast fading countermeasure can be implemented and a PAPR suppression effect can be obtained. In the present embodiment, PAPR is used as an index indicating the peak power characteristic, but not limited to this, any measurement quantity may be used as long as it is a measurement quantity related to the power characteristic. In addition, this embodiment can be applied to any modulation method.

Embodiment 2. FIG.
FIG. 4 is a diagram illustrating a functional configuration example of the transmitter according to the second embodiment of the present invention. The transmitter according to the present embodiment is the same as the transmitter according to the first embodiment except that a control unit 13 is added to the transmitter according to the first embodiment. Constituent elements having the same functions as those in the embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description is omitted. Hereinafter, a different part from Embodiment 1 is demonstrated.

  In this embodiment, an example will be described in which the frame configuration such as the number of multiplexed symbols and the number of pilot symbols included in one group is adaptively changed according to the state of the transmission path. The control unit 13 shown in FIG. 4 changes the frame configuration such as the number of pilot symbols, the number of data symbols, and the number of multiplexed symbols based on the transmission path information. Transmission path parameters that affect the frame configuration are the number of multipaths, the Doppler frequency, and the like. For example, when the number of paths between the transmitter and the receiver is large, in order to estimate the transmission path of each path, it is necessary to prepare pilot symbols for the number of paths in one block symbol. Therefore, the control unit 13 changes the number of pilot symbols according to the number of paths. Further, when the value of the Doppler frequency of the transmission path is high, the transmission path fluctuates at a high speed, so it is necessary to increase the number of multiplexed symbols including pilot symbols. Therefore, the control unit 13 changes the number of multiplexed symbols including pilot symbols according to the Doppler frequency.

FIG. 5 is a flowchart showing an example of a PAPR reduction processing procedure by arrangement in the frequency domain and pilot sequence selection. First, the control unit 13 instructs the N block data symbol generation unit 1 to generate N block data symbols for one frame, initializes (sets to 0) a group counter for multiple symbols (step S1), and executes a pilot. The sequence candidate counter is initialized (set to 0) (step S2). The control unit 13 instructs the N block pilot sequence selection unit 2 to select one of the pilot sequence candidates (candidate sequences) held for the group corresponding to the value of the group counter, and in the frequency domain The placement unit 3 is instructed to initialize (set to 0) the frequency placement counter (step S3). Based on the instruction, the N block pilot sequence selection unit 2 selects one of the held pilot sequences. As long as the candidate sequence is a pilot sequence that can reduce the PAPR, any sequence may be used. For example, in the example shown in FIG. 2, when the length of one pilot sequence is 4 symbols, the number of sequence candidates C is C = 4, and the j-th pilot symbol in the i-th candidate is s _j ⁽ⁱ⁾ , A BPSK (Binary Phase Shift Keying) sequence as shown in the following equation (1) can be used as a pilot sequence candidate.

Next, the control unit 13 instructs the frequency domain arrangement unit 3 to select the frequency arrangement for the group corresponding to the value of the group counter, and the frequency domain arrangement unit 3 selects the frequency arrangement for the group. (Step S4). The frequency domain arrangement unit 3 holds a plurality of types of frequency arrangement candidates in advance, and the frequency domain arrangement unit 3 selects a frequency arrangement to which one of the frequency arrangement candidates is applied as a frequency arrangement. Determine placement. FIG. 6 is a diagram illustrating an example of the frequency arrangement, and FIG. 7 is a diagram illustrating an example in which the frequency arrangement of the pilot sequence is changed. In FIG. 6, for convenience, the position (frequency position and time position) of the pilot symbol in the group # 0 is identified by a number indicated by numbers (0, 1, 2, 3) indicated in the symbol. Here, the position of each block symbol in the time domain is the same as in FIG. In FIG. 6, s ₀ is arranged at the position of number 0, s ₁ is arranged at the position of number 1, s ₂ of number ₂ is arranged, and s ₃ of number ₃ is arranged. Here, if the number indicating the position where s _j is arranged is k _j , k ₀ = 0, k ₁ = 1, k ₂ = 2 and k ₃ = 3 in FIG. On the other hand, in FIG. 7, the position of the pilot symbol in group # 0 is changed from the arrangement of FIG. 6, and k ₀ = 0, k ₁ = 3, k ₂ = 2 and k ₃ = 1. Thus, in this Embodiment, the frequency arrangement | positioning of the pilot symbol in a group is changed for every group using the same pilot series.

As described above, the frequency domain arrangement unit 3 holds a plurality of frequency arrangement candidates and selects one of these candidates. When the number of frequency arrangement candidates is C ′ = 4 and the arrangement position of pilot symbols s _j in the h-th candidate is denoted by k _j ^(h) , for example, the frequency arrangement shown in the following equation (2) is used as a candidate. Is possible.

Returning to the description with reference to FIG. After selection of the frequency arrangement in step S4, PAPR measurement is performed by the PAPR measurement unit 8 (step S5). The PAPR measurement unit 8 selects the largest PAPR among the PAPRs of a plurality of blocks and sets it as PAPR information. For example, if N _F multiplex symbols are included in one group and the PAPR of the i-th multiplex symbol is denoted as PAPR _i , PAPR _max represented by the following equation (3) is PAPR information.

  The measurement result (PAPR information) is input to the frequency domain arrangement unit 3 and the N block pilot sequence selection unit 2. The frequency domain arrangement unit 3 determines whether or not the minimum PAPR value is obtained (step S6). Judgment whether or not the minimum PAPR value has been obtained is, for example, setting the value of the minimum value to the PAPR measurement value of the first measurement, and changing the candidate of the second time (either one of the frequency candidates and the pilot sequence) ) In the subsequent PAPR measurement, the PAPR value obtained by the measurement is compared with the minimum value, and it can be determined whether or not the minimum PAPR value is obtained based on whether or not the PAPR value is smaller than the minimum value. .

  When it is determined that the minimum PAPR value has been obtained (Yes in step S6), the frequency domain arrangement unit 3 notifies the control unit 13 of the fact, and the control unit 13 determines the selected pilot sequence candidate and the frequency arrangement. The candidate is stored as a set value candidate (step S7), and the frequency arrangement candidate counter is incremented (step S8). Thereafter, the frequency domain arrangement unit 3 determines whether or not the number of frequency arrangement candidates held by the frequency arrangement candidate counter is greater than or equal to the number (No in step S9). Return to. If it is determined in step S6 that the PAPR value is not the minimum (No in step S6), the process proceeds to step S8.

  If the number of candidates is greater than or equal to the number of candidates in step S9 (step S9 Yes), the N block pilot sequence selection unit 2 increments the pilot sequence candidate counter (step S10), and whether or not the pilot sequence candidate counter is greater than or equal to the number of pilot sequence candidates. Is determined (step S11). If the number is not greater than the number of pilot sequence candidates (No in step S11), the process returns to step S3.

  When the number is equal to or greater than the number of pilot sequence candidates in step S11 (step S11 Yes), the control unit 13 increments the group counter (step S12) and determines whether the group counter is equal to or greater than the number of groups in one frame. (Step S13). If it is not more than the number of groups (No at step S13), the process returns to step S2. In step S13, when the group counter is equal to or greater than the number of groups in one frame (Yes in step S13), the control unit 13 selects the N block pilot sequence selection unit 2 so as to select each candidate held as a setting value candidate. Instructing the frequency domain arrangement unit 3, the N block pilot sequence selection unit 2 and the frequency domain arrangement unit 3 select a candidate based on the instruction, and end the generation of multiple symbols for the frame (step S 14). In the above description, the frequency allocation unit 3 determines whether or not the PAPR is the minimum PAPR. However, the control unit 13 may acquire the PAPR information and perform this determination. .

  In the above processing, since the pilot sequence is changed and the frequency arrangement is also changed, the pilot sequence candidates may be different from each other even if the frequency arrangement is changed, as exemplified in (1) above. Select a different series. Moreover, even if a transmitter changes frequency arrangement, a function may be provided to check whether or not the same series is used. FIG. 8 is a diagram illustrating a configuration example of a transmitter including a pilot sequence candidate / frequency allocation candidate control unit (candidate control unit) 14 for confirming whether the same sequence is generated due to the frequency allocation change. The pilot sequence candidate / frequency allocation candidate control unit 14 shown in FIG. 8 performs a correlation process for each pilot sequence candidate and frequency allocation candidate, checks to prevent the occurrence of the same series, and does not generate the same series. And the N block pilot sequence selection unit 2 and the frequency domain allocation unit 3 are notified.

  FIG. 9 is a diagram illustrating an internal configuration example of the frequency multiplexing unit 4. As shown in FIG. 9, the frequency multiplexing unit 4 includes a pilot symbol arrangement circuit (pilot symbol arrangement unit) 41 and a pilot / data symbol arrangement circuit (pilot and data symbol arrangement unit) 42. The pilot symbol allocation circuit 41 receives a pilot symbol of the selected pilot sequence from the N block pilot sequence selection unit 2 and receives a pilot allocation position (frequency allocation of pilot symbols) from the frequency domain allocation unit 3. The pilot symbol arrangement circuit 41 rearranges the input pilot symbols based on the pilot arrangement positions, and inputs the rearranged pilot symbols to the pilot / data symbol arrangement circuit 42. The pilot / data symbol arrangement circuit 42 arranges the data symbols and pilot symbols in the time and frequency domains and outputs them to the IDFT unit 5. The IDFT unit 5 converts the input signal into a time domain signal and outputs it to the P / S unit 6. The time domain signal is input to the time domain arrangement unit 10 via the P / S unit 6, the transmission processing unit 7 and the PAPR measurement unit 8.

  The time domain arrangement unit 10 rearranges the arrangement of the time domain based on the transmission path information. The arrangement of the time domain affects the accuracy of pilot sequence determination. FIG. 10 is a diagram illustrating an arrangement example in which the time domain is rearranged with respect to the arrangement example of FIG. For example, in the case of the arrangement shown in FIG. 10, when multiple symbols of the same group are transmitted in close time and the power of the transmission line drops in the time domain such as deep fade, there is a possibility that an error may occur in the pilot sequence determination result. There is. FIG. 11 is a conceptual diagram illustrating a determination error due to deep fade. In such a transmission path in which deep fading occurs, by arranging multiple symbols of the same group separated in time as shown in FIG. 7, diversity in the time domain is obtained as shown in FIG. It is possible to prevent. FIG. 12 is a diagram showing a concept of preventing a determination error when multiple symbols of the same group are separated in time. The distance separating multiple symbols of the same group within a frame varies depending on transmission path fluctuation (transmission path moving speed). The time domain arrangement unit 10 determines the distance separating multiple symbols of the same group based on transmission path information indicating transmission path fluctuations, and performs time domain rearrangement. For example, a Doppler frequency or the like is used as a parameter indicating transmission path fluctuation.

  As described above, in the present embodiment, a plurality of pilot sequence candidates and frequency allocation candidates are held, PAPR is obtained for each candidate combination, and a candidate combination that minimizes the PAPR is selected. . For this reason, peak power can be effectively suppressed. In addition, the determination error in the receiver can be reduced by arranging multiple symbols of the same group separated in the time domain according to the transmission path information. Furthermore, it is possible to appropriately select a pilot sequence by performing a check so that the same sequence does not occur even if the frequency arrangement is changed.

Embodiment 3 FIG.
FIG. 13: is a figure which shows the function structural example of Embodiment 3 of the receiver concerning this invention. The receiver of the present embodiment is a receiver that receives a signal transmitted from the transmitter of the first or second embodiment, and includes an antenna 21, a reception processing unit 22, a multiple symbol separation unit 23, and a pilot sequence determination unit 24. , A demodulation / decoding processing unit (demodulation decoding unit) 25 is provided.

  The reception processing unit 22 performs synchronization processing and sampling on the reception signal received by the antenna 21 and inputs the processed reception signal to the multiple symbol separation unit 23. Multiplex symbol separation section 23 extracts multiple symbols including pilot symbols from the input received signal. The pilot sequence determination unit 24 determines the transmitted pilot sequence and frequency arrangement position based on the multiplexed symbols. The demodulation / decoding processing unit 25 performs transmission path estimation based on the determination result of the pilot sequence and frequency arrangement position and the received signal, and performs symbol demodulation and decoding.

  FIG. 14 is a flowchart illustrating an example of a reception processing procedure in the receiver of this embodiment. First, the reception processing unit 22 performs synchronization processing and the like on the received signal, and inputs the processed signal to the multiple symbol separation unit 23 (step S21). The pilot sequence determination unit 24 initializes the group counter (step S22). Multiplex symbol separator 23 separates multiple symbols including pilot symbols (step S23), and inputs them to pilot sequence determination unit 24.

  The pilot sequence determination unit 24 extracts a received signal including a pilot signal (pilot symbol separation) in accordance with the frequency allocation candidate held on the frequency axis for the group corresponding to the group counter (step S24). It is assumed that the receiver holds the same candidate as the frequency arrangement candidate held by the transmitter. Next, the pilot sequence determination unit 24 performs transmission path estimation and pilot symbol determination using the held pilot sequence candidates (step S25). The pilot sequence determination unit 24 determines whether a pilot sequence has been found by determining the pilot symbol (whether the determination result based on the received signal matches the value of the pilot sequence held) (step S26). If not found, the process returns to step S24. After returning to step S24, the frequency arrangement candidates are changed, and the processes up to step S26 are performed again. If the pilot series cannot be found even if the processing up to step S26 is performed for all the frequency arrangement candidates, the pilot series The pilot sequence selected from the candidates is changed, and the processing from step S24 is repeated.

  If a pilot sequence is found in step S26 (step S26 Yes), the pilot sequence determination unit 24 increments the group counter (step S27), and determines whether the group counter is equal to or greater than the number of groups (step S28). ). If the group counter is not equal to or greater than the number of groups (No at step S28), the process returns to step S23. If the group counter is equal to or greater than the number of groups (when all groups have been searched) (step S28 Yes), transmission path estimation, demodulation and decoding are performed using the found pilot sequence (step S29).

  Here, the receiver holds pilot sequence candidates and frequency allocation candidates, and performs pilot symbol determination for each candidate so as to obtain the pilot sequence and frequency allocation selected on the transmitter side. However, the pilot sequence and frequency arrangement selected by the transmitter may be notified.

  As described above, in the present embodiment, the operation of the receiver that receives the transmission signal transmitted from the transmitter according to Embodiments 1 and 2 has been described. By such an operation, it is possible to perform communication with PAPR suppressed in the communication system configured by the transmitters of the first and second embodiments and the receiver of the present embodiment.

Embodiment 4 FIG.
FIG. 15 is a diagram illustrating a functional configuration example of the transmitter according to the fourth embodiment of the present invention. The transmitter according to the present embodiment is the same as the transmitter according to the first embodiment except that an N-block PAPR reduction processing unit (peak power reduction processing unit) 15 is added to the transmitter according to the first embodiment. Constituent elements having the same functions as those in the embodiment are denoted by the same reference numerals as those in the first embodiment, and redundant description is omitted. Hereinafter, a different part from Embodiment 1 is demonstrated.

  In the present embodiment, PAPR reduction processing is performed on the data symbols in order to further reduce the PAPR as compared with the transmitter of the first embodiment. In the present embodiment, the N block PAPR reduction processing unit 15 performs a predetermined PAPR reduction process on the data symbols input from the N block data symbol generation unit 1 and uses the processed data symbols to the frequency multiplexing unit 4. Enter. There is no restriction on the PAPR reduction process, and a commonly performed PAPR reduction process can be applied. Further, a plurality of PAPR reduction processing candidates may be implemented, and the PAPR reduction processing may be performed by selecting from a plurality of candidates. In this case, the content of the PAPR reduction process applied to the data may be transmitted to the receiving side. At this time, for example, the number of pilot sequence candidates is prepared as many as the number of PAPR reduction processing candidates to be given to the data, and the PAPR reduction processing candidate and the pilot sequence candidate are determined in a one-to-one relationship and set in the receiver and the transmitter. Keep it. Thereby, the receiving side can grasp | ascertain the kind of PAPR reduction process which the transmission side gave by determining the transmitted pilot series.

  Note that an N-block PAPR reduction processing unit 15 may be added to the transmitter of Embodiment 2 to similarly perform PAPR reduction processing of data symbols.

  Thus, in this embodiment, the PAPR reduction process is performed on the data symbols. For this reason, the PAPR reduction effect can be further enhanced as compared with the first embodiment.

  As described above, the transmitter, the receiver, and the communication system according to the present invention are useful for a communication system that multiplexes and transmits symbols.

  1 N block data symbol generation unit, 2 N block pilot sequence selection unit, 3 frequency domain arrangement unit, 4 frequency multiplexing unit, 5 IDFT unit, 6 P / S unit, 7 transmission processing unit, 8 PAPR measurement unit, 9 transmission path Information processing unit, 10 time domain allocation unit, 11 frame generation unit, 12, 21 antenna, 13 control unit, 14 pilot sequence candidate / frequency allocation candidate control unit, 15 N block PAPR reduction processing unit, 22 reception processing unit, 23 multiplexing Symbol separation unit, 24 pilot sequence determination unit, 25 demodulation / decoding processing unit, 41 pilot symbol arrangement circuit, 42 pilot / data symbol arrangement circuit.

Claims (9)

A transmitter for transmitting a block symbol obtained by multiplexing data symbols and pilot symbols,
A peak power measurement unit that measures peak power information indicating the peak power of a signal to be transmitted;
A pilot sequence selection unit that forms one group with two or more block symbols and selects a pilot sequence for each group;
A frequency domain arrangement unit that holds a plurality of frequency arrangement candidates in a group of pilot symbols constituting a pilot sequence and selects a frequency arrangement to be applied from among the candidates based on the peak power information for each group;
A frequency multiplexing unit that multiplexes data symbols and pilot symbols based on the frequency allocation selected by the frequency domain allocation unit;
An IDFT unit for converting a signal multiplexed by the frequency multiplexing unit into a time domain signal;
An antenna for transmitting the time domain signal;
A transmitter comprising: The pilot sequence selection unit holds a plurality of pilot sequence candidates, selects a pilot sequence from the pilot sequence candidates based on the peak power information,
The transmitter according to claim 1, wherein the frequency multiplexing unit multiplexes the pilot symbol of the pilot sequence selected by the pilot sequence selection unit and the data symbol. Find a minimum setting candidate that is a combination of a pilot sequence and frequency arrangement that minimizes the peak power information,
The frequency domain arrangement unit selects a frequency arrangement corresponding to the minimum setting candidate,
The transmitter according to claim 2, wherein the pilot sequence selection unit selects a pilot sequence corresponding to the minimum setting candidate. A time domain arrangement unit that arranges the time domain signal in the time domain so that the time domain distance between block symbols in the same group is a certain value or more with respect to the time domain signal converted by the IDFT unit,
Further comprising
The transmitter according to claim 1, 2, or 3, wherein the antenna transmits a signal after being arranged by the time domain arrangement unit.   The transmitter according to claim 4, wherein the time domain arrangement unit determines a time domain distance between block symbols in the same group based on transmission path information.   6. The transmitter according to claim 1, wherein the number of pilot symbols is determined based on transmission path information and the number of block symbols in one frame. A peak power reduction processing unit for performing peak power reduction processing on the data symbol;
Further comprising
The transmitter according to claim 1, wherein the frequency multiplexing unit multiplexes the data symbols processed by the peak power reduction processing unit. A receiver that receives a signal transmitted from a transmitter that transmits a block symbol obtained by multiplexing data symbols and pilot symbols,
In the signal, one group is composed of two or more block symbols, and a pilot sequence selected for each group is inserted. In the transmitter, the pilot symbols constituting the pilot sequence for each group have peak power. Based on the peak power information indicating a signal that is arranged and transmitted by a frequency arrangement selected from a plurality of frequency arrangement candidates,
A pilot sequence determination unit that holds the plurality of frequency allocation candidates and determines a frequency allocation selected in the transmitter based on a determination result of a pilot symbol determined using the signal and the candidates;
A demodulation and decoding unit that performs demodulation and decoding processing based on the determination result by the pilot sequence determination unit and the signal;
A receiver comprising: A communication system comprising a transmitter that transmits block symbols obtained by multiplexing data symbols and pilot symbols, and a receiver that receives a signal transmitted from the transmitter,
The transmitter is
A peak power measurement unit that measures peak power information indicating the peak power of a signal to be transmitted;
A pilot sequence selection unit that forms one group with two or more block symbols and selects a pilot sequence for each group;
A frequency domain arrangement unit that holds a plurality of frequency arrangement candidates in a group of pilot symbols constituting a pilot sequence and selects a frequency arrangement to be applied from among the candidates based on the peak power information for each group;
A frequency multiplexing unit that multiplexes data symbols and pilot symbols based on the frequency allocation selected by the frequency domain allocation unit;
An IDFT unit for converting a signal multiplexed by the frequency multiplexing unit into a time domain signal;
An antenna for transmitting the time domain signal;
With
The receiver
The frequency arrangement selected by the transmitter based on the determination result of the pilot symbol determined by using the time domain signal transmitted from the antenna and the candidate, holding the plurality of frequency arrangement candidates. A pilot sequence determination unit for determining;
A demodulation decoding unit that performs demodulation and decoding processing based on the determination result by the pilot sequence determination unit and the time domain signal;
A communication system comprising:

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