JP5295666B2 - Communication device, communication method - Google Patents

Description

  The present invention relates to a wireless communication device and a communication method.

In wireless communication, the amplitude and phase of a received signal change over time due to the influence of multipath and the Doppler effect. Therefore, in conventional wireless communication, a reference signal having a predetermined waveform (hereinafter referred to as a known symbol) is inserted between data symbols at a predetermined time interval (symbol interval), and this known symbol is used on the receiving side. The time change of amplitude and phase is corrected. However, the efficiency of signal transmission is reduced by inserting known symbols that do not contribute to actual signal transmission. For this reason, there has been proposed a method for controlling the time interval at which this known symbol is inserted between data symbols in accordance with the time variation state of the amplitude and phase of the received signal, the error rate, etc. (see Patent Documents 1 and 2) ).
Japanese Patent No. 3491549 JP 2003-333008 A

In recent years, in order to increase the communication speed, it has been studied to expand the frequency bandwidth of wireless communication to several GHz. However, the temporal change in the amplitude and phase of the received signal increases in proportion to the frequency. For this reason, in a high frequency band, it is necessary to shorten the time interval which inserts a known symbol between data symbols. However, a conventional communication device inserts known symbols between symbols at a uniform time interval regardless of the frequency band being used. As a result, even in the low frequency band, the time interval for inserting known symbols is short, and the signal transmission efficiency decreases.
In view of the above, an object of the present invention is to provide a communication device and a communication method that can correct temporal changes in amplitude and phase without reducing transmission efficiency even when a wide frequency bandwidth is used.

  A communication apparatus according to an aspect of the present invention is a communication apparatus that transmits a transmission signal forming a data symbol sequence using a plurality of different frequency bands, and the data symbol sequence has a plurality of frequencies in units of a predetermined number of symbols. A plurality of frequency bands for each of an arrangement unit arranged in each band, a first symbol generation unit for generating a first reference symbol having a predetermined waveform, and a data symbol sequence arranged in each of a plurality of frequency bands And a first insertion unit for inserting the first reference symbol into the data symbol sequence at a time interval corresponding to the center frequency of the first symbol.

  A communication method according to an aspect of the present invention is a communication method for transmitting a transmission signal forming a data symbol sequence using a plurality of different frequency bands, and the data symbol sequence is transmitted at a plurality of frequencies in units of a predetermined number of symbols. The step of arranging each in a band, the step of generating a first reference symbol having a predetermined waveform, and the data symbol sequence respectively arranged in a plurality of frequency bands correspond to the center frequencies of the plurality of frequency bands. Inserting a first reference symbol into the data symbol sequence at time intervals.

  According to the present invention, even when a wide frequency bandwidth is used, a communication device and a communication method that can correct temporal changes in amplitude and phase without reducing transmission efficiency can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a base station (communication device) 1 and communication terminals (communication devices) 6A to 6C according to one embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a communication method used between the transmitter 1 and the receivers 6A to 6C according to the first embodiment. A symbol BW1 in FIG. 2 is a frequency bandwidth used in wireless communication between the base station 1 and the communication terminals 6A to 6C according to the first embodiment.

  The base station 1 performs wireless communication with the communication terminals 6A to 6C. In the first embodiment, the OFDM (Orthogonal Wave Frequency Division Multiplexing) scheme shown in FIG. 2 is used for this wireless communication. In the OFDM system, data to be transmitted is arranged from a plurality of carriers having different center frequencies (hereinafter referred to as subcarriers) from 0 to N-1 (N is a natural number) and subjected to inverse fast Fourier transform, and the frequency axis is converted to the time axis. And send the data.

  In this OFDM, the frequency of subcarriers is selected so that the subcarriers are orthogonal to each other. For this reason, there is no interference between the subchannels, and an interference guard band becomes unnecessary. As a result, the transceiver design can be simplified. Specifically, unlike conventional FDM (frequency division multiplexing), there is an advantage that it is not necessary to prepare a separate filter for each subchannel. Also, thanks to this orthogonality, high spectral efficiency can be obtained, and almost all frequency bands arranged as transmission bands can be used.

  Next, the configuration and operation of the base station 1 according to the first embodiment will be described. Although only the base station 1 will be described here, the configuration and operation of the base station 1 and the configuration and operation of the communication terminals 6A to 6C are the same.

  FIG. 3 is a block diagram showing the configuration of the base station 1 according to the first embodiment. FIG. 4 is a flowchart showing the operation at the time of transmission of the base station 1 according to the first embodiment. FIG. 5 is a diagram for explaining operations of the multiplexing unit 14 and the carrier modulation unit 15 according to the first embodiment. FIG. 6 is a flowchart showing the operation at the time of reception of the base station 1 according to the first embodiment.

(Operation at the time of transmission of the base station 1)
First, the encoding unit 11 adds an error detection code to the digital data input from the previous stage. As the error detection code, a parity code, a constant ratio code, a cyclic code, a hash function, or the like is used. Next, the encoding unit 11 performs error correction encoding on the digital data to which the error detection code is added with a predetermined encoding method and encoding rate, and generates encoded data (step S11). For this error correction coding, a Hamming code, a BCH code, a Reed-Solomon code, or the like is used. Next, the encoding unit 11 inputs the generated encoded data to the modulation unit 12.

  The modulation unit 12 modulates the amplitude and phase of the encoded data input from the encoding unit 11 using a predetermined modulation method to generate a data symbol sequence (step S12). This modulation method includes modulation methods such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64QAM. Next, the modulation unit 12 inputs the generated data symbol sequence to the multiplexing unit 14.

  Although not shown in FIG. 3, an interleaver or the like may be provided between the encoding unit 11 and the modulation unit 12, and the encoded data may be rearranged in a predetermined order.

  The known signal generation unit 13 inputs a known symbol, which is a signal having a predetermined waveform, to the multiplexing unit 14. This known symbol is also called a pilot symbol, and is a symbol whose waveform, ie, amplitude and phase values are known. This known symbol is used in the communication terminals 6A to 6C for correction of temporal changes in the amplitude and phase of the received signal.

  The multiplexing unit 14 inserts the known symbols input from the known signal generation unit 13 between the data symbols of the data symbol sequence input from the modulation unit 12 to generate multiplexed data (step S13). As illustrated in FIG. 5, the multiplexing unit 14 changes the time interval for inserting a known symbol between data symbols according to the frequency of each subcarrier.

  Next, the multiplexing unit 14 inputs the generated multiplexed data to the carrier modulation unit 15. The configuration and operation of the multiplexing unit 14 will be described in detail later with reference to FIGS.

  The carrier modulation unit 15 multi-modulates the multiplexed data input from the multiplexing unit 14 to generate a modulated signal (step S14). In this multicarrier modulation, the following processing is performed.

  First, multiplex data is serial-parallel converted in units of slots having a predetermined number of symbols, and data symbols are arranged on each subcarrier. As shown in FIG. 5, the carrier modulation unit 15 arranges data symbol sequences in subcarriers 0 to N−1 with a predetermined number of symbols as one unit.

  That is, the carrier modulation unit 15 sequentially arranges Unit 1 from the 0th subcarrier of the first symbol constituting the slot to the N−1th subcarrier, and Unit2 from the 0th subcarrier of the next symbol. N-1 subcarriers are sequentially arranged. When this operation is repeated and the unit 7 is arranged, the symbol arrangement in the slot 1 is completed.

  In FIG. 5, the number of symbols in each slot is 7. However, the number of symbols in each slot is arbitrary. The arrangement of data symbols for each subcarrier may start from an arbitrary symbol.

  Next, the carrier modulation unit 15 performs inverse fast Fourier transform (IFFT) to convert data on the frequency into data on the time. Next, the carrier modulation unit 15 adds a guard interval (GI) and a synchronization preamble signal to the data on the time axis after the inverse fast Fourier transform to generate a modulation signal. Next, the carrier modulation unit 15 inputs the generated modulation signal to the D / A conversion unit 16.

  The D / A conversion unit 16 converts the modulated signal input from the carrier modulation unit 15 from a digital signal to an analog signal to generate a transmission analog signal (step S15). Next, the D / A conversion unit 16 inputs the generated transmission analog signal to the transmission processing unit 17.

  The transmission processing unit 17 performs transmission processing such as quadrature modulation, up-conversion (frequency conversion), band limitation using a filter, power amplification, and the like on the transmission analog signal input from the D / A conversion unit 16 and transmits the transmission signal. Generate (step S16). The antenna 31 transmits the transmission signal generated by the transmission processing unit 17.

(Operation at the time of reception by the base station 1)
First, the antenna 31 receives a transmission signal transmitted from the communication terminals 6A to 6C (hereinafter, a signal received by the antenna 31 is referred to as a reception signal).

  The reception processing unit 21 performs reception processing such as power amplification, band limitation using a filter, down-conversion (frequency conversion), and orthogonal demodulation on the reception signal received by the antenna 31 (step S21), and generates a reception analog signal. To do. Next, the reception processing unit 21 inputs the generated analog signal to the A / D conversion unit 22.

  The A / D conversion unit 22 converts the received reception analog signal from an analog signal to a digital signal to generate a reception digital signal (step S22). Next, the A / D conversion unit 22 inputs the generated received digital signal to the synchronization unit 23 and the carrier demodulation unit.

  The synchronization unit 23 detects the reception timing from the received digital signal input from the A / D conversion unit 22 using a synchronization preamble signal, and notifies the carrier demodulation unit 24 of the detected reception timing.

  The carrier demodulator 24 multicarrier-demodulates the received digital signal input from the A / D converter 22. That is, the guard interval is removed based on the reception timing notified from the synchronization unit 23, fast Fourier transform (FFT) processing is performed, and multiplex data that is a data symbol sequence in which a known symbol is inserted is generated (step S23). . Next, the carrier demodulation unit inputs a known symbol of the generated multiplexed data to the propagation path estimation unit 25 and a data symbol to the demodulation unit 26.

  The propagation path estimation unit 25 estimates temporal changes in the amplitude and phase of the received signal caused by the multipath or Doppler effect based on the known symbol input from the carrier demodulation unit. Next, the propagation path estimation unit 25 inputs this estimation result to the demodulation unit 26.

  The demodulator 26 corrects the phase and amplitude shift of the data symbol from the estimation result input from the propagation path estimator 25. Next, the demodulator 26 demodulates the corrected data symbol to generate encoded data (step S24). Next, the demodulation unit 26 inputs the generated encoded data to the decoding unit 27.

  The decoding unit 27 outputs the digital data obtained by decoding the encoded data input from the demodulation unit 26 to the subsequent stage (step S25).

(Details of configuration and operation of multiplexing unit 14)
Next, the configuration and operation of the multiplexing unit 14 of the base station 1 according to this embodiment will be described. FIG. 7 is a block diagram showing the configuration of the multiplexing unit 14. FIG. 8 is a diagram illustrating an example of the format data according to the first embodiment. In FIG. 8, the frequency is shown on the vertical axis and the time is shown on the horizontal axis. FIG. 9 is a diagram for explaining an example of a method for determining a time interval for inserting a known symbol into data arranged in each subcarrier.

  The format recording unit 141 records format data in which a known symbol input from the known signal generation unit 13 is to be inserted in a data symbol string input from the modulation unit 12. This format data holds insertion positions for the number of symbols included in one slot (13 * N in the example of FIG. 8). The insertion unit 142 refers to this format data and is known in slot units. Insert a symbol into the data symbol sequence.

  Then, the insertion unit 142 repeats the operation of inserting a known symbol in the data symbol sequence for each slot. A method for calculating a time interval for inserting a known symbol in each subcarrier will be described later with reference to FIG.

  The insertion unit 142 inserts the known symbol input from the known signal generation unit 13 into the data symbol sequence input from the modulation unit 12 based on the format data recorded in the format recording unit 141. At this time, the insertion unit 142 inserts known symbols between data symbols so that known symbols are arranged at predetermined subcarrier intervals and predetermined time intervals (symbol intervals) in one slot (Slot). .

  In the example of FIG. 8, the multiplexing unit 14 inserts known symbols every three symbols into data symbols arranged on subcarriers having a relatively high frequency. Also, known symbols are inserted every six symbols in data symbols arranged on subcarriers having a relatively low frequency.

  That is, the multiplexing unit 14 according to this embodiment shortens the time interval for inserting a known symbol in a subcarrier having a relatively high frequency within the frequency band BW1 used in this embodiment. In addition, in a subcarrier having a relatively low frequency, the time interval for inserting a known symbol is lengthened.

  Next, a method for calculating the format data recorded in the format recording unit 141 of the multiplexing unit 14 will be described. A symbol BW1 in FIG. 9 is a frequency bandwidth used in wireless communication between the base station 1 and the communication terminals 6A to 6C according to the first embodiment. The symbol FC is the center frequency of this frequency bandwidth. A symbol ΔF is a frequency difference between subcarriers. The code ΔT is the symbol length.

In this case, the time interval INTi (i is a unique number assigned to each subcarrier and takes a value in the range of 0 to N-1 (N is a natural number)) for inserting a known symbol in each subcarrier is as follows: (1). Moreover, (2) Formula represents the code | symbol Fdi in (1) Formula.
INTi = 1 / (Fdi × ΔT) (1)
Fdi = {V × (FC−BW1 / 2 + ΔF × i)} / C (2)

  Here, the symbol Fdi in the equation (1) is a parameter representing the magnitude of temporal change in amplitude and phase generated in a signal arranged in each subcarrier due to multipath or Doppler effect. It is expressed by a formula. Symbol C is the speed of light. A symbol V represents a moving speed of the base station 1 or the communication terminals 6A to 6C.

  In Expression (1), a time interval INTi for inserting a minimum known symbol necessary for correcting temporal changes in amplitude and phase due to multipath and Doppler effect is calculated. Therefore, Formula (1) may be calculated by multiplying Fdi by one or more arbitrary constants. As a result, the time interval INTi for inserting the known symbol is shortened, and there is a margin for correction of temporal changes in amplitude and phase due to multipath and Doppler effects.

(Details of operation of propagation path estimation unit 25)
Next, the operation of the propagation path estimation unit 25 will be described with reference to FIG.
First, when a carrier demodulated signal is input from the carrier demodulator 24, the propagation path estimator 25 uses a known symbol included in the carrier demodulated signal to detect the amplitude of the received signal generated by the multipath or Doppler effect and The temporal change in phase is estimated for all subcarriers.

  In other words, the propagation path estimation unit 25 compares the phase and amplitude values of the known symbols input from the carrier demodulation unit with the phase and amplitude values of the known symbols recorded in advance in the transmission path. It is calculated how much the phase and amplitude values are shifted.

  At this time, for the subcarriers that do not include the known symbols, the propagation path estimation unit 25 estimates temporal changes in the amplitude and phase of the received signal using the estimation results of the subcarriers that include the known symbols. To do.

  Note that the time interval at which the known symbol is inserted differs for each subcarrier. For this reason, the propagation path estimation unit 25 estimates the temporal change in the amplitude and phase of the received signal every three symbols for subcarriers having a relatively high frequency using the inserted known symbols, For subcarriers having a low frequency, temporal changes in the amplitude and phase of the received signal are estimated every six symbols.

  As described above, the base station (communication device) 1 according to the first embodiment has a time interval for inserting a known symbol in a subcarrier having a relatively high frequency within the frequency band used in this embodiment. Is shortened. In addition, in a subcarrier having a relatively low frequency, the time interval for inserting a known symbol is lengthened.

  For this reason, even if the time variation of the amplitude and phase of the received signal differs depending on the frequency (subcarrier) by using a wide frequency bandwidth, the time variation of the amplitude and phase can be reduced without reducing the transmission efficiency. Can be corrected.

  In the first embodiment, format data describing in which position a known symbol input from the known signal generator 13 is inserted in the data symbol string input from the modulator 12 is previously recorded in the format recording unit 141. To record. However, instead of the format recording unit 141, a calculation unit for calculating the expressions (1) and (2) is provided, and a known symbol may be inserted between data symbols based on the calculation result of the calculation unit. good. Further, the format recording unit 141 may be provided in the known signal generation unit 13, and the known signal generation unit 13 may input a known symbol to the multiplexing unit 14 based on the format recording unit 141.

  In the first embodiment, the base station 1 and the communication terminals 6A to 6C are provided with a transmission function and a reception function. However, only the transmission function or the reception function may be provided. In the case of only the transmission function, the encoder 11, the modulator 12, the known signal generator 13, the multiplexer 14, the carrier modulator 15, the D / A converter 16, the transmission processor 17, and the antenna 31 may be provided. In the case of only the reception function, the antenna 31, the reception processing unit 21, the A / D conversion unit 22, the synchronization unit 23, the carrier demodulation unit 24, the propagation path estimation unit 25, the demodulation unit 26, and the decoding unit 27 may be provided. .

(Modification of the first embodiment)
In this modification, a plurality of subcarriers are grouped into one group, and known symbols are inserted in units of groups. FIG. 10 is a diagram illustrating an example of format data according to a modification of the first embodiment. In FIG. 10, a known symbol is inserted with three subcarriers as one group unit. In FIG. 10, the frequency is shown on the vertical axis and the time is shown on the horizontal axis.

  In the example illustrated in FIG. 10, the multiplexing unit 14 inserts known symbols every three symbols for a group of subcarriers having a relatively high frequency. Also, known symbols are inserted every six symbols for groups of subcarriers having a relatively low frequency.

  Thus, as in the first embodiment, in this modified example, the time interval for inserting known symbols is shortened for data symbols arranged in a group of subcarriers having a relatively high frequency, In particular, the time interval for inserting known symbols is increased for data symbols arranged in frequency subcarrier groups.

  As described above, in the modification of the first embodiment, a plurality of subcarriers are set as one group, and a time interval for inserting a known symbol is set for each group.

(Second Embodiment)
FIG. 11 is a block diagram showing the configuration of the base station (communication device) 2 according to the second embodiment. In this embodiment, two types of known symbols are used to change the amplitude and phase of the received signal, as well as the time of the amplitude and phase of the signal due to time-dependent changes and deviations of the noise in the communication device and the oscillator for frequency conversion. To compensate for changes. Although only the base station 2 will be described here, the configuration and operation of the communication terminal corresponding to the base station 2 of the second embodiment are the same.

  The known signal generation unit 13A and the known signal generation unit 13B input known symbols A and B, which are signals having predetermined waveforms, to the multiplexing unit 14A, respectively. Here, the known symbol of the known signal generation unit 13A is used to correct temporal changes in the amplitude and phase of the received signal due to multipath and the Doppler effect.

  Further, the known signal generation unit 13B corrects temporal changes in the amplitude and phase of the signal due to noise in the communication devices such as the base station 1 and the communication terminals 6A to 6C and the change and deviation of the oscillator for frequency conversion over time. Used. The known symbols A and B may be known symbols having different waveforms or may be known symbols having the same waveform.

  The multiplexing unit 14A inserts the known symbols A and B input from the known signal generation units 13A and 13B into the data symbol sequence input from the modulation unit 12 to generate multiplexed data. Next, the multiplexing unit 14 </ b> A inputs the generated multiplexed data to the carrier modulation unit 15. Since the other components have been described with reference to FIG. 3, common components are denoted by the same reference numerals, and redundant description is omitted.

Next, the configuration and operation details of the multiplexing unit 14A will be described.
FIG. 12 is a block diagram showing the configuration of the multiplexing unit 14A. FIG. 13 is a diagram illustrating an example of format data according to the second embodiment. In FIG. 13, the frequency is shown on the vertical axis and the time is shown on the horizontal axis.

  The format recording unit 141A records format data that describes in which position in the data symbol string input from the modulation unit 12 the known symbol input from the known signal generation units 13A and 13B is to be inserted.

  The insertion unit 142 inserts the known symbols A and B input from the known signal generation units 13A and 13B into the data symbol sequence input from the modulation unit 12 based on the format data recorded in the format recording unit 141A. To do. At this time, the insertion unit 142 inserts the known symbol A between the data symbols so that the known symbol A is arranged at a predetermined time interval in one slot (Slot). The insertion unit 142 inserts the known symbols B between the data symbols so that the known symbols B are arranged at a predetermined subcarrier interval in one slot (Slot).

  In the example of FIG. 13, the multiplexing unit 14A inserts the known symbols A input from the known signal generation unit 13A every 10 symbols into the data symbols arranged on subcarriers having a relatively high frequency. Further, the known symbol A input from the known signal generation unit 13A is inserted every 20 symbols into the data symbol sequence arranged on the subcarriers having a low frequency.

  Further, the multiplexing unit 14A arranges the known symbols B input from the known signal generation unit 13B with respect to a predetermined subcarrier.

  Here, the temporal change in the amplitude and phase of the signal caused by the noise in the communication device and the change or shift of the oscillator for frequency conversion with time has almost no frequency dependence. For this reason, the interval between the predetermined subcarriers into which the known symbol B is inserted can be increased. Further, since the known symbol B can be used for correction of temporal changes in the amplitude and phase of the received signal due to the multipath or Doppler effect, the time interval for inserting the known symbol A can be increased.

  As described above, since the base station 2 according to the second embodiment has inserted two types of known symbols, the temporal change in the amplitude and phase of the received signal due to multipath and the Doppler effect, and in the communication device It is possible to correct temporal changes in the amplitude and phase of the signal due to noise and changes in frequency of the oscillator for frequency conversion. Other effects are the same as those of the first embodiment.

  Similar to the first embodiment, the format recording unit 141A is provided in the known signal generation units 13A and 13B, and the known signal generation units 13A and 13B multiplex the known symbol into the multiplexing unit 14 based on the format recording unit 141A. You may make it input into.

(Modification 1 of 2nd Embodiment)
FIG. 14 is a diagram illustrating an example of format data according to the first modification of the second embodiment. In FIG. 14, the frequency is represented on the vertical axis and the time is represented on the horizontal axis.
This modification is suitable when the number of symbols constituting each slot is variable, and the time interval for inserting the known symbol A input from the known signal generator 13A is variable.

  Specifically, as shown in FIG. 14, the known symbol A is inserted into the data symbol sequence arranged on the subcarriers having a relatively high frequency in the format data recorded in the format recording unit 141A of the multiplexing unit 14A. The time interval at which the known symbol A is inserted into the data symbol sequence arranged on the subcarrier having a relatively low frequency is INT_L.

Then, the time interval at which the known symbol A is inserted is controlled so that the relationship between the time interval INT_H and the time interval INT_L satisfies the following expression (3).
INT_L <= INT_H (3)
In this way, if the time interval for inserting the known symbol A is controlled, the known symbol A can be appropriately inserted according to the number of symbols constituting each slot. Note that INT_H and INT_L can be determined, for example, by the method described using equations (1) and (2).

(Modification 2 of the second embodiment)
FIG. 15 is a diagram illustrating an example of format data according to the second modification of the second embodiment. In FIG. 15, the frequency is represented on the vertical axis and the time is represented on the horizontal axis.
In this modification, the time interval at which the known symbol A input from the known signal generator 13A is inserted is constant regardless of the subcarrier frequency, and the known symbol B input from the known signal generator 13B is arranged. The carrier interval is changed according to the subcarrier frequency.

  Specifically, the interval between subcarriers into which the known symbol B is inserted is widened at a relatively low frequency, and the interval between subcarriers into which the known symbol is inserted is narrowed at a relatively high frequency. In the example of FIG. 15, known symbols B are inserted every four subcarriers at a relatively low frequency, and known symbols are inserted every three or every other subcarrier at a relatively high frequency. Even when the known symbol B is inserted in this way, the same effect as in the second embodiment can be expected.

  Although not shown in FIG. 15, as in the second embodiment, the time interval for inserting the known symbol A is shortened for data symbols arranged on subcarriers having a relatively high frequency, The time interval at which the known symbol A is inserted may be increased for data symbols arranged on subcarriers having a relatively low frequency.

(Third embodiment)
FIG. 16 is a diagram for explaining a communication method used in the base station 3 according to the third embodiment. A symbol BW2 in FIG. 16 is a frequency bandwidth used in the third embodiment. FIG. 17 is a block diagram illustrating a configuration of the base station (communication device) 3 according to the third embodiment. In the third embodiment, a given frequency bandwidth is divided into a plurality of frequency bands 1 to N (N is a natural number excluding 0), and each divided frequency band is divided into those in the first embodiment. Apply the described OFDM scheme. Although only the base station 3 will be described here, the configuration and operation of the communication terminal corresponding to the base station 3 of the third embodiment are the same.

  The distributor 41 distributes the signal from the previous stage to the encoding unit 11_N provided for each frequency band. The combiner 42 combines the transmission signals input from the transmission processing unit 17 </ b> _N provided for each frequency band and inputs the combined signals to the antenna 31. The distributor 43 distributes the reception signal received by the antenna 31 to the reception processing unit 21_N provided for each frequency band. The synthesizer 44 synthesizes the decoded encoded signal input from the decoding unit 27_N provided for each frequency band and inputs it to the subsequent stage.

  Further, the base station 3 performs, for each frequency band, the encoding unit 11_N, the modulation unit 12_N, the known signal generation unit 13_N, the multiplexing unit 14_N, the carrier modulation unit 15_N, the D / A conversion unit 16_N, and the transmission processing described in FIG. Unit 17_N, reception processing unit 21_N, A / D conversion unit 22_N, synchronization unit 23_N, carrier demodulation unit 24_N, channel estimation unit 25_N, demodulation unit 26_N, and decoding unit 27_N. Note that the encoding unit 11_N to the decoding unit 27_N have been described with reference to FIG.

Next, the operation of the multiplexing unit 14_N will be described.
FIG. 18 is a diagram illustrating an example of format data according to the third embodiment. In FIG. 18, the frequency is shown on the vertical axis and the time is shown on the horizontal axis. For convenience of explanation, it is assumed that the number of divided frequency bands is three.

  In the example of FIG. 18, the multiplexing unit 14_3 according to the third embodiment inserts known symbols every five symbols. In addition, the multiplexing unit 14_2 inserts known symbols every 10 symbols. The multiplexing unit 14_1 inserts known symbols every 20 symbols.

  That is, in the third embodiment, the time for inserting a known symbol is narrowed in a subband having a relatively high center frequency in the frequency band BW2 used in this embodiment. Further, in the subband having a relatively low center frequency, the time interval for inserting the known symbol is increased.

  Next, a method for calculating the format data recorded in the multiplexing unit 14_N will be described. FIG. 19 is a diagram illustrating an example of a method for determining a time interval for inserting a known symbol. A symbol Fci (i = 1... N) in FIG. 19 is a center frequency of each frequency band in which wireless communication is performed by the multiband wireless communication method. Reference sign BW2 is a frequency bandwidth used in the third embodiment.

In this case, a time interval INTi for inserting a known symbol in each frequency band (i is a unique number assigned to each subband and takes a value in the range of 1 to N (N is a natural number)) is as follows ( 4) It can be determined by the equation. Moreover, (5) Formula represents code | symbol Fdi in (4) Formula.
INTi = 1 / (Fdi × ΔT) (4)
Fdi = (V × FCi) / C (5)

  Here, the symbol Fdi in the equation (4) is a parameter representing the magnitude of temporal change in amplitude and phase generated in a signal arranged in each subcarrier due to multipath or Doppler effect. (5) It is expressed by a formula. Symbol C is the speed of light. A symbol V is a moving speed of the communication terminal corresponding to the base station 3.

  In equation (4), the time interval INTi for inserting the minimum known symbols necessary for correcting temporal changes in amplitude and phase due to multipath and Doppler effect is calculated. Therefore, Formula (4) may be calculated by multiplying Fdi by one or more arbitrary constants. As a result, the time interval INTi for inserting the known symbol is shortened, and there is a margin for correction of temporal changes in amplitude and phase due to multipath and Doppler effects.

  As described above, the base station (communication device) 3 according to the third embodiment inserts a known symbol in a subband having a relatively high center frequency within the frequency band BW2 used in this embodiment. The time interval is shortened. Further, in the subband having a relatively low center frequency, the time interval for inserting the known symbol is increased.

  For this reason, even when a wide frequency bandwidth is used, it is possible to correct temporal changes in amplitude and phase without reducing transmission efficiency. Other effects are the same as those of the first embodiment.

  Also in the third embodiment, similarly to the first embodiment, the multiplexing unit 14_N includes a calculation unit that calculates the equations (4) and (5), and the calculation result in this calculation unit is included in the calculation result. Based on this, a known symbol may be inserted into the data symbol string. Further, as shown in FIG. 10 of the modification of the first embodiment, a plurality of subcarriers may be set as one group, and a time interval for inserting a known symbol may be set for each group.

(Fourth embodiment)
FIG. 20 is a block diagram showing the configuration of the base station (communication device) 4 according to the fourth embodiment. In this embodiment, using two types of known symbols, a signal due to a temporal change in amplitude and phase of a received signal due to multipath or Doppler effect, a noise in a communication device, and a change or deviation with time of an oscillator for frequency conversion. Corrects temporal changes in the amplitude and phase of.

  Note that the components shown in FIG. 20 are the same as the components described in FIG. 11 and FIG. For this reason, about the common component, the same code | symbol is attached | subjected and duplication description is abbreviate | omitted. Although only the base station 4 will be described here, the configuration and operation of the communication terminal corresponding to the base station 4 of the fourth embodiment are the same.

Next, the operation of the multiplexing unit 14A_N will be described.
FIG. 21 is a diagram illustrating an example of format data according to the fourth embodiment. In FIG. 21, the frequency is shown on the vertical axis and the time is shown on the horizontal axis. In addition, data arranged in each subcarrier and known symbols inserted in this data are shown in symbol units. For convenience of explanation, it is assumed that the number of divided frequency bands is three.

  As illustrated in FIG. 21, the multiplexing unit 14A_3 according to the fourth embodiment inserts the known symbol A input from the known signal generation unit 13A every five symbols. In addition, the multiplexing unit 14A_2 inserts the known symbol A input from the known signal generation unit 13A every 10 symbols. The multiplexing unit 14A_1 inserts the known symbol A input from the known signal generation unit 13A every 20 symbols.

  That is, in the fourth embodiment, the time interval for inserting a known symbol is shortened in a subband having a relatively high center frequency within the frequency band used in this embodiment. Further, in the subband having a relatively low center frequency, the time interval for inserting the known symbol is increased.

  Further, the multiplexing unit 14A arranges the known symbols B input from the known signal generation unit 13B with respect to a predetermined subcarrier.

  As described above, since the base station 4 according to the fourth embodiment inserts two types of known symbols, the temporal change in the amplitude and phase of the received signal due to multipath and the Doppler effect, It is possible to correct temporal changes in the amplitude and phase of the signal due to noise and changes in frequency of the oscillator for frequency conversion. Other effects are the same as those of the third embodiment.

(Modification 1 of 4th Embodiment)
FIG. 22 is a diagram illustrating an example of format data according to the first modification of the fourth embodiment. In FIG. 22, the frequency is shown on the vertical axis and the time is shown on the horizontal axis. For convenience of explanation, it is assumed that the number of divided frequency bands is three.

  In this modification, the time interval for inserting the known symbol A input from the known signal generator 13A is constant regardless of the center frequency of the frequency band, and the known symbol B input from the known signal generator 13B is inserted. The number of subcarriers is changed according to the center frequency band.

  Specifically, the subcarrier interval for inserting the known symbol B is lengthened in the subband of a relatively low frequency, and the subcarrier interval for inserting the known symbol is shortened in the subband of a relatively high frequency. In the example of FIG. 22, in frequency bands 1 and 2, a known symbol B is inserted every third subcarrier, and in frequency band 3, a known symbol is inserted every two subcarriers. Even if comprised in this way, the effect similar to 4th Embodiment can be anticipated.

(Application examples of the third and fourth embodiments)
In the third and fourth embodiments, the time interval for inserting a known symbol is changed according to the center frequency of each frequency band. For this reason, a difference arises in the transmission rate of each frequency band. In this application example, a method for correcting the difference in transmission rate will be described.

  FIG. 23 is a diagram illustrating a relationship between each frequency band and the number of subcarriers included in the frequency band. Note that the code N in FIG. 23 is a natural number excluding 0, and the code NSCN is the number of subcarriers included in the frequency band N. The code BWN is a frequency bandwidth in the frequency band N.

  As described in the third and fourth embodiments, in a subband having a relatively high center frequency in the frequency band to be used, a subband having a relatively low center frequency with a short time interval for inserting a known symbol. In this case, the time interval for inserting known symbols is increased. For this reason, if the number of subcarriers in a relatively high frequency band is set to be equal to or greater than the number of subcarriers in a relatively low frequency band, the difference in transmission rate between the frequency bands can be corrected.

Specifically, the number of subcarriers in each frequency band is adjusted so as to satisfy the following formula (6).
NSC1 ≦ NSC2 ≦ ... ≦ NSCN (6)

  As described above, in this application example, the number of subcarriers in each frequency band is set so that the number of subcarriers in the frequency band of relatively high frequency is equal to or greater than the number of subcarriers in the frequency band of relatively low frequency. Since the adjustment is made, the difference in the transmission rate of each frequency band can be corrected.

(Fifth embodiment)
FIG. 24 is a schematic diagram for explaining a communication method used in the base station 5 according to the fifth embodiment. Symbol BW3 in FIG. 24 is a frequency bandwidth used in this embodiment. FIG. 25 is a block diagram showing a configuration of a base station (communication device) 5 according to the fifth embodiment. In this embodiment, a given frequency bandwidth is further divided into a plurality of frequency bands (subbands 1 to N (N is a natural number excluding 0)) for wireless communication. Although only the base station 5 will be described here, the configuration and operation of the communication terminal corresponding to the base station 5 of the fifth embodiment are the same.

  In this embodiment, wireless communication is performed using one frequency carrier within each divided frequency band. For this reason, the point which does not comprise 15_N and 24_N differs from 3rd Embodiment. Since the other components have been described with reference to FIG. 17, common components are denoted by the same reference numerals, and redundant description is omitted.

Next, the operation of the multiplexing unit 14_N will be described.
FIG. 26 is a diagram illustrating an example of format data according to the fifth embodiment. In FIG. 26, the frequency is shown on the vertical axis, and the time is shown on the horizontal axis. In addition, data arranged in each subband and known symbols inserted into this data are shown in symbol units. For convenience of explanation, it is assumed that the number of divided frequency bands is three.

  In the example of FIG. 26, the multiplexing unit 14_3 according to the fifth embodiment inserts known symbols every three symbols. In addition, the multiplexing unit 14_2 inserts known symbols every five symbols. In addition, the multiplexing unit 14_1 inserts known symbols every 10 symbols.

  That is, in the fifth embodiment, the time interval for inserting the known symbol is shortened in the subband having a relatively high center frequency in the frequency band BW3 used in this embodiment. Further, in the subband having a relatively low center frequency, the time interval for inserting the known symbol is increased.

  As described above, the base station (communication device) 5 according to the fifth embodiment inserts a known symbol in a subband having a relatively high center frequency within the frequency band BW3 used in this embodiment. The time interval is shortened. Further, in the subband having a relatively low center frequency, the time interval for inserting the known symbol is increased.

  For this reason, even when a wide frequency bandwidth is used, it is possible to correct temporal changes in amplitude and phase without reducing transmission efficiency. Other effects are the same as those of the third embodiment.

  In the second to fourth embodiments, similarly to the first embodiment, a calculation unit is provided instead of the format recording unit, and a known symbol is converted into a data symbol string based on the calculation result in the calculation unit. It may be inserted into. Further, the base stations 2 to 5 may have only a transmission function, and the communication terminals 6A to 6C may have only a reception function.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is the figure which showed the base station which concerns on 1st Embodiment. It is the figure which showed the communication system used in 1st Embodiment. It is the block diagram which showed the structure of the base station which concerns on 1st Embodiment. It is the flowchart which showed operation | movement of the base station which concerns on 1st Embodiment. It is a figure explaining operation | movement of the multiplexing part and carrier modulation part which concern on 1st Embodiment. It is the flowchart which showed operation | movement of the base station which concerns on 1st Embodiment. It is the block diagram which showed the structure of the multiplexing part which concerns on 1st Embodiment. It is the figure which showed an example of format data. It is a figure explaining an example of the determination method of the time interval which inserts a known symbol. It is the figure which showed an example of format data. It is the block diagram which showed the structure of the base station which concerns on 2nd Embodiment. It is the block diagram which showed the structure of the multiplexing part which concerns on 2nd Embodiment. It is the figure which showed an example of format data. It is the figure which showed an example of format data. It is the figure which showed an example of format data. It is the figure which showed the communication system used in 3rd Embodiment. It is the block diagram which showed the structure of the base station which concerns on 3rd Embodiment. It is the figure which showed an example of format data. It is a figure explaining an example of the determination method of the time interval which inserts a known symbol. It is the block diagram which showed the structure of the base station which concerns on 4th Embodiment. It is the figure which showed an example of format data. It is the figure which showed an example of format data. It is a figure which shows the relationship between a frequency band and the frequency subcarrier number. It is the figure which showed the communication system used in 5th Embodiment. It is the block diagram which showed the structure of the base station which concerns on 5th Embodiment. It is the figure which showed an example of format data.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 thru | or 5 ... Base station (communication apparatus), 6 ... Communication terminal (communication apparatus), 11 ... Encoding part, 12 ... Modulation part, 13 ... Known signal generation part (reference symbol generation part), 14 ... Multiplexing part, 15 ... carrier modulation section (array section), 16 ... D / A conversion section, 17 ... transmission processing section, 18 ... antenna, 21 ... reception processing section, 22 ... A / D conversion section, 23 ... synchronization section, 24 ... carrier demodulation Reference numeral 25: Propagation path estimation unit 26: Demodulation unit 27: Decoding unit 31, 33 ... Distributor 32, 34: Synthesizer 141: Format recording unit 1, 142: Insertion unit

Claims (7)

A communication device that transmits a transmission signal forming a data symbol sequence using a plurality of different frequency bands,
An arrangement unit for arranging the data symbol sequences in the plurality of frequency bands in units of a predetermined number of symbols;
A first symbol generator for generating a first reference symbol having a predetermined waveform;
A first reference symbol is inserted into the data symbol sequence at a time interval calculated from a frequency and a data symbol length of the plurality of frequency bands with respect to the data symbol sequences respectively arranged in the plurality of frequency bands. And a communication device. The first insertion part is
2. The communication device according to claim 1, wherein the first reference symbol is inserted into the data symbol sequence at a time interval calculated based on a frequency of the plurality of frequency bands, a data symbol length, and a moving speed of the self or a communication partner. The first insertion part is
To the data symbol sequence arranged on the frequency band with high frequency among the plurality of frequency bands, shortening the time interval for inserting the first reference symbol, the data symbol sequence arranged on the frequency band lower frequency contrast, the communication apparatus according to 請 Motomeko 1 or claim 2 extends the time interval of inserting the first reference symbol. Second symbol generating means for generating a second reference symbol having a predetermined waveform; and a second insertion unit for inserting the second reference symbol into the data symbol sequence;
The second insertion part is
To the data symbol sequence arranged each of the plurality of frequency bands, wherein the second reference symbol from 請 Motomeko 1 to inserting into the data symbol sequence in the frequency interval which is calculated by the frequency of the plurality of frequency bands Item 4. The communication device according to any one of item 3. Wherein the plurality of frequency bands, the communication apparatus as set forth 請 Motomeko 1 is a plurality of sub-carriers to any one of claims 4. A communication method for transmitting a transmission signal forming a data symbol sequence using a plurality of mutually different frequency bands,
Arranging each of the data symbol sequences in the plurality of frequency bands in units of a predetermined number of symbols;
Generating a first reference symbol having a predetermined waveform;
Inserting the first reference symbol into the data symbol sequence at a time interval calculated from the frequency and data symbol length of the plurality of frequency bands for the data symbol sequences respectively arranged in the plurality of frequency bands; A communication method comprising: The communication method according to claim 6, wherein the plurality of frequency bands are a plurality of subcarriers.

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