Transmitter and receiver

Abstract

This transmitter, which is used for underwater acoustic communication, comprises: a transmission data generation unit that generates a plurality of pieces of divided data of different frequency bands on the basis of transmission data, which is data to be transmitted; and a plurality of transmitters that have different resonance frequencies and that respectively transmit the generated plurality of pieces of divided data.　

Description

Transmitters and receivers

[0001] The present invention relates to a transmitter and a receiver.

[0002] Generally, radio communication on land (electromagnetic wave communication) is carried out using radio waves, while underwater radio communication (acoustic communication) is carried out using sound waves.

[0003] B. Li et al., “MIMO-OFDM for High-Rate Underwater Acoustic Communications”, in IEEE Journal of Oceanic Engineering, vol. 34, no. 4, pp. 634-644, Oct. 2009, doi: 10.1109 / JOE.2009.2032005.

[0004] Transmitters used in acoustic communications have sensitivity characteristics, and when transmitting wideband signals, the gain of band components far from the resonance point decreases, as shown in Figure 6. Conventionally, there are no transmitters with flat power efficiency on the scale of several hundred kHz. Antennas used in land-based wireless communications can be easily designed and manufactured with flat bandwidth characteristics from several MHz to several hundred MHz. On the other hand, it is difficult to design and manufacture transmitters and receivers used in underwater acoustic communications with flat transmission characteristics on the scale of several MHz, resulting in significant degradation of characteristics. As a result, there is a problem of limited transmission capacity.

[0005] In view of the above circumstances, an object of the present invention is to provide a technology that enables communication using wideband signals in underwater acoustic communication.

[0006] One aspect of the present invention is a transmitter for use in underwater acoustic communication, comprising a transmission data generation unit that generates multiple divided data of different frequency bands based on transmission data to be transmitted, and multiple transmitters with different resonant frequencies that respectively transmit the multiple generated divided data.

[0007] One aspect of the present invention is a receiver for use in underwater acoustic communication, comprising a receiver that receives multiple pieces of divided data transmitted from a transmitter by multiple transmitters with different resonant frequencies, and a reception control unit that performs reception processing on the multiple pieces of divided data received by the receiver.

[0008] According to the present invention, it becomes possible to carry out communications using wideband signals in underwater acoustic communications.

[0009] Fig. 1 is a diagram showing a configuration example of an underwater communication system in a first embodiment; Fig. 2 is a diagram for explaining the effect of the underwater communication system in the first embodiment; Fig. 3 is a diagram showing a configuration example of an underwater communication system in a modified example of the first embodiment; Fig. 4 is a diagram showing a configuration example of an underwater communication system in a second embodiment; Fig. 5 is a diagram for explaining a conventional problem;

[0010] An embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) Fig. 1 is a diagram showing an example of the configuration of an underwater communication system 100 in the first embodiment. The underwater communication system 100 includes a transmitter 10 and a receiver 20. The transmitter 10 and the receiver 20 perform acoustic communication via an underwater transmission path. The transmitter 10 transmits an acoustic signal. The receiver 20 receives the acoustic signal transmitted from the transmitter 10.

[0011] The transmitter 10 includes a single carrier modulation unit 11, a band division filter 12, and a plurality of transmitters 13-1 to 13-m, where m is an integer greater than or equal to 2. The single carrier modulation unit 11 and the band division filter 12 are one aspect of a transmission data generation unit.

[0012] The single carrier modulation unit 11 generates modulated data by modulating the input transmission data using a single carrier wave (single carrier modulation). As a result, the single carrier modulation unit 11 generates wideband modulated data as shown in balloon 30 in Fig. 1. The single carrier modulation unit 11 outputs the generated modulated data to the band division filter 12.

[0013] The band-splitting filter 12 receives as input the modulated data generated by the single-carrier modulation unit 11. The band-splitting filter 12 divides the input modulated data into multiple pieces of modulated data. Specifically, the band-splitting filter 12 divides the modulated data into m pieces according to the number of transmitters 13 included in the transmitter 10. As an example, if there are two transmitters 13, the band-splitting filter 12 may divide the modulated data into two pieces based on the center frequency of the modulated data, as shown by the dotted line in the speech bubble 30 in FIG. 1. Note that the division method used by the band-splitting filter 12 is not limited to the above, and any division criteria may be used as long as it can be divided into m pieces.

[0014] The band-splitting filter 12 outputs the split modulated data to the wave transmitters 13-1 to 13-m. When there are two wave transmitters 13, the band-splitting filter 12 generates two split modulated data. Here, the two split modulated data are referred to as first modulated data and second split data. The band-splitting filter 12 outputs the generated first modulated data to the wave transmitter 13-1, and outputs the generated second modulated data to the wave transmitter 13-2.

[0015] The wave transmitters 13-1 to 13-m have different resonant frequencies. The wave transmitters 13-1 to 13-m receive as input different modulated data generated by splitting the data by the band splitting filter 12. The wave transmitters 13-1 to 13-m transmit the input multiple modulated data to the receiver 20.

[0016] When there are two transmitters 13, transmitter 13-1 receives the first modulated data as input, and transmitter 13-2 receives the second modulated data as input. Transmitter 13-1 transmits the received first modulated data to receiver 20 by sound waves. Transmitter 13-2 transmits the received second modulated data to receiver 20 by sound waves. In this way, the wideband modulated data generated by the single carrier modulation unit 11 is band-divided and transmitted from each transmitter 13.

[0017] The receiver 20 includes a wave receiver 21 and a reception processing unit 22. The wave receiver 21 receives a plurality of modulated data transmitted from the transmitter 10. The wave receiver 21 outputs the received plurality of modulated data to the reception processing unit 22. For example, every time the wave receiver 21 receives modulated data transmitted from the transmitter 10, it outputs the received modulated data to the reception processing unit 22.

[0018] The reception processing unit 22 performs reception processing on the modulated data output from the receiver 21. Specifically, the reception processing unit 22 acquires all of the modulated data output from the receiver 21, and then generates one piece of modulated data by combining the acquired multiple pieces of modulated data. This allows the reception processing unit 22 to generate wideband modulated data, as shown in balloon 35 in FIG. 1. The reception processing unit 22 demodulates the generated piece of modulated data. This allows the receiver 20 to restore the received data. The reception processing unit 22 is one aspect of the reception control unit.

[0019] Figure 2 is a diagram for explaining the effects of the underwater communication system 100 in the first embodiment. In Figure 2, line segment l1 represents the power efficiency of the wave transmitter 13-1 at the resonant frequency f1, and line segment l2 represents the power efficiency of the wave transmitter 13-2 at the resonant frequency f2. As shown by line segment l2 in Figure 2, when transmitting with a single wave transmitter 13, the power efficiency decreases near the frequency f1, whereas by dividing the band and transmitting using multiple wave transmitters 13 as in the first embodiment, the efficiency is improved.

[0020] According to the underwater communication system 100 configured as described above, a wideband signal is divided into multiple signals by the band division filter 12 and transmitted by multiple transmitters 13. In this way, band division transmission using multiple transmitters 13 with high wave transmission efficiency can suppress gain reduction. Therefore, it is possible to realize wideband communication of several hundred kHz using multiple transmitters 13 of about several tens of kHz.

[0021] (Variation of the First Embodiment) In the above-described configuration, when multiple modulated data are combined in the receiver 20, composite distortion occurs at positions where the frequencies of the multiple modulated data overlap, as shown in the speech bubble 35 in FIG. 1 . Therefore, the receiver 20 may be configured to include an equalizer as a configuration for compensating for the composite distortion. FIG. 3 is a diagram showing an example configuration of an underwater communication system 100a in a variation of the first embodiment. The underwater communication system 100a includes a transmitter 10 and a receiver 20a. The transmitter 10 and the receiver 20a perform acoustic communication via an underwater transmission path. The transmitter 10 transmits an acoustic signal. The receiver 20a receives the acoustic signal transmitted from the transmitter 10.

[0022] The underwater communication system 100a differs in configuration from the underwater communication system 100 in that it includes a receiver 20a instead of the receiver 20. The underwater communication system 100a is otherwise similar in configuration to the underwater communication system 100. The following description will focus on the differences from the underwater communication system 100. The receiver 20a includes a wave receiver 21 and an equalizer 23.

[0023] The equalizer 23 has the function of performing equalization processing in addition to the function of the reception processing unit 22. The equalizer 23 performs equalization processing using, for example, an adaptive filter. The equalizer 23 performs equalization processing using the adaptive filter on each of the modulated data output from the receiver 21, and then generates one modulated data by combining the multiple modulated data. In this way, the equalizer 23 compensates for multipath phase distortion in the underwater transmission path and simultaneously compensates for composite distortion. The equalizer 23 is one aspect of the reception control unit.

[0024] According to the underwater communication system 100a configured in this manner, by using an equalizer for reception processing, it is possible to compensate for multipath phase distortion in the underwater transmission path and simultaneously compensate for composite distortion without increasing the size of the receiving circuit.

[0025] Second Embodiment In the first embodiment, a configuration in which a transmitter performs single-carrier transmission has been described. In the second embodiment, a configuration in which a transmitter performs multi-carrier transmission will be described.

[0026] 4 is a diagram showing an example of the configuration of an underwater communication system 100b according to the second embodiment. The underwater communication system 100b includes a transmitter 10b and a receiver 20b. The transmitter 10b and the receiver 20b perform acoustic communication via an underwater transmission path. The transmitter 10b transmits an acoustic signal. The receiver 20b receives the acoustic signal transmitted from the transmitter 10b.

[0027] The transmitter 10b includes a plurality of wave transmitters 13-1 to 13-m, a serial-to-parallel converter 14, and a plurality of subcarrier modulators 15-1 to 15-n, where n is an integer equal to or greater than 2. The serial-to-parallel converter 14 and the plurality of subcarrier modulators 15-1 to 15-n are an aspect of a transmission data generator.

[0028] The serial-parallel conversion unit 14 performs serial-to-parallel conversion on the input transmission data. The serial-parallel conversion unit 14 divides the serial-parallel converted transmission data into n parts and outputs them to the subcarrier modulation units 15-1 to 15-n. When there are two subcarrier modulation units 15, the serial-parallel conversion unit 14 divides the serial-parallel converted transmission data into two parts and outputs them to each subcarrier modulation unit 15. Hereinafter, the transmission data output from the serial-parallel conversion unit 14 will be referred to as divided data.

[0029] Subcarrier modulation units 15-1 to 15-n generate modulated data by using different subcarriers to modulate the multiple pieces of divided data output from serial-parallel conversion unit 14. For example, subcarrier modulation unit 15-1 generates first modulated data by modulating the divided data output from serial-parallel conversion unit 14 using subcarrier 1, and subcarrier modulation unit 15-n generates nth modulated data by modulating the divided data output from serial-parallel conversion unit 14 using subcarrier n.

[0030] As described above, different divided data are input to each of the subcarrier modulation units 15-1 to 15-n. Therefore, the subcarrier modulation units 15-1 to 15-n generate multiple modulated data by modulating the different divided data using different subcarriers. The subcarrier modulation units 15-1 to 15-n output the generated multiple modulated data to the connected wave transmitters 13-1 to 13-m. In the second embodiment, the number of subcarrier modulation units 15 and the number of wave transmitters 13 are the same (m = n).

[0031] Transmitters 13-1 to 13-m receive modulated data output from subcarrier modulation units 15-1 to 15-n as input. For example, transmitter 13-1 receives the first modulated data output from subcarrier modulation unit 15-1, and transmitter 13-m receives the nth modulated data output from subcarrier modulation unit 15-n as input. Transmitters 13-1 to 13-m transmit the input multiple modulated data to receiver 20b by sound waves. An example of multiple modulated data transmitted from transmitters 13-1 to 13-m is shown in speech bubble 40 in FIG. 4.

[0032] The receiver 20b includes a receiver 21, a plurality of subcarrier demodulation units 24-1 to 24-n, and a parallel-to-serial conversion unit 25. The plurality of subcarrier demodulation units 24-1 to 24-n and the parallel-to-serial conversion unit 25 are an example of a reception control unit.

[0033] The receiver 21 receives the plurality of modulated data transmitted from the transmitter 10. The receiver 21 outputs the received plurality of modulated data to the subcarrier demodulation units 24-1 to 24-n according to the subcarriers. For example, every time the receiver 21 receives modulated data transmitted from the transmitter 10, it outputs the received modulated data to one of the subcarrier demodulation units 24-1 to 24-n.

[0034] The subcarrier demodulators 24-1 to 24-n perform demodulation processing on the modulated data output from the receiver 21. The subcarrier demodulator 24-1 receives first modulated data corresponding to subcarrier 1, and the subcarrier demodulator 24-n receives nth modulated data corresponding to subcarrier n. The subcarrier demodulators 24-1 to 24-n demodulate the input multiple modulated data. This restores multiple pieces of transmission data. The subcarrier demodulators 24-1 to 24-n output the restored multiple pieces of transmission data to the parallel-to-serial converter 25.

[0035] In addition, because high-frequency components are significantly affected by absorption attenuation in underwater transmission paths, it is possible that high-frequency component signals may not be demodulated. Taking this into consideration, by using error correction codes, it is possible to demodulate modulated data even if some data is missing.

[0036] The parallel-serial converter 25 converts the plurality of transmission data output from the subcarrier demodulators 24-1 to 24-n into parallel serial data to generate one piece of reception data.

[0037] According to the underwater communication system 100b configured as described above, the transmission data is divided into subcarriers and multicarrier transmission is performed from multiple transmitters 13 with high transmission efficiency. This prevents a decrease in gain and provides a frequency diversity effect. Specifically, even if high-frequency components are significantly affected by absorption attenuation and cannot be demodulated, low-frequency components can be demodulated, thereby providing a frequency diversity effect.

[0038] (Third Embodiment) In the first embodiment, a configuration in which a transmitter performs single-carrier transmission has been described. In the second embodiment, a configuration in which a transmitter performs multi-carrier transmission has been described. In the third embodiment, a configuration in which the first embodiment and the second embodiment are combined will be described.

[0039] 5 is a diagram showing an example of the configuration of an underwater communication system 100c according to the third embodiment. The underwater communication system 100c includes a transmitter 10c and a receiver 20c. The transmitter 10c and the receiver 20c perform acoustic communication via an underwater transmission path. The transmitter 10b transmits an acoustic signal. The receiver 20c receives the acoustic signal transmitted from the transmitter 10c.

[0040] The receiver 20c feeds back information about the communication being conducted between the receiver 20c and the transmitter 10c to the transmitter 10c. The information about the communication is, for example, propagation information and communication quality information. The propagation information is information about signal propagation in the underwater transmission path, such as Doppler velocity or absorption attenuation. The communication quality information is, for example, information about communication quality in the underwater transmission path, such as an ACK.

[0041] The transmitter 10c includes a band division filter 12c, a plurality of wave transmitters 13-1 to 13-m, a serial-to-parallel converter 14c, a plurality of subcarrier modulators 15c-1 to 15c-n, and a band division parameter controller 16. The band division filter 12c, the serial-to-parallel converter 14c, and the plurality of subcarrier modulators 15c-1 to 15c-n are an aspect of a transmission data generator.

[0042] The transmitter 10c has a configuration for performing single-carrier transmission and multi-carrier transmission. For example, the subcarrier modulation unit 15c-1 and the band division filter 12c in the transmitter 10c are configured to perform single-carrier transmission, and the subcarrier modulation units 15c-(n-1) to 15-n in the transmitter 10c are configured to perform multi-carrier transmission. Note that the configuration shown in FIG. 5 is just an example, and any of the subcarrier modulation units 15c may be configured to perform single-carrier transmission. In the third embodiment, n is an integer equal to or greater than 3.

[0043] The band division parameter control unit 16 adaptively changes the band division ratio based on propagation information and communication quality information fed back from the receiver 20c. Specifically, when the Doppler velocity is high (above a certain threshold), for example, the band division parameter control unit 16 controls the serial-parallel conversion unit 14 so that the ratio of multi-carrier transmission is smaller than the ratio of single-carrier transmission. This is because when the Doppler velocity is high (above a certain threshold), it is desirable to send a wideband signal that is as less affected by Doppler shift as possible.

[0044] The band division parameter control unit 16 controls the serial-parallel conversion unit 14 and the subcarrier modulation units 15c-1 to 15c-n so that multi-carrier transmission is performed in high frequency bands with large absorption attenuation, and controls the serial-parallel conversion unit 14 and the subcarrier modulation units 15c-1 to 15c-n so that single-carrier transmission is performed in low frequency bands with small absorption attenuation. This is because high frequency bands with large absorption attenuation have poor communication quality, so transmitting and receiving narrowband signals improves the S / N ratio and improves communication quality, and conversely, low frequency bands with small absorption attenuation have good communication quality, so transmitting and receiving wideband signals improves frequency utilization efficiency and increases transmission speed.

[0045] The band division parameter control unit 16 controls the sub-channels for which it is found, for example, by ACK, that the communication quality is good (communication quality is equal to or higher than a threshold) to perform single-carrier transmission, and controls the sub-carrier modulation units 15c-1 to 15c-n to perform multi-carrier transmission for sub-channels for which it is found that the communication quality is poor (communication quality is less than a threshold).This is because, when the communication quality is good (communication quality is equal to or higher than a threshold), single-carrier transmission has better frequency utilization efficiency and therefore improves the transmission speed, and conversely, when the communication quality is poor (communication quality is less than a threshold), multi-carrier transmission uses narrowband signals for the sub-carriers, improving the S / N ratio and improving the communication quality.

[0046] The serial-parallel converter 14c performs serial-to-parallel conversion on the input transmission data. The serial-to-parallel converter 14c divides the serial-to-parallel converted transmission data in accordance with instructions from the band division parameter controller 16. The serial-to-parallel converter 14c outputs the plurality of divided data obtained by the division to the subcarrier modulators 15c-1 to 15c-n.

[0047] Here, the division performed by the serial-parallel conversion unit 14c will be described. As described above, when the Doppler velocity is high (above a certain threshold), the band division parameter control unit 16 reduces the proportion of multi-carrier transmission compared to the proportion of single-carrier transmission. Therefore, the band division parameter control unit 16 controls the division proportion of the transmission data after serial-parallel conversion in the serial-parallel conversion unit 14c so that the transmission data output to the subcarrier modulation unit 15c-1 is higher than that output to the subcarrier modulation units 15c-(n-1) to 15c-n. As a result, more transmission data is allocated to the subcarrier modulation unit 15c-1, and as a result, the proportion of single-carrier transmission is higher than that of multi-carrier transmission.

[0048] Furthermore, the band division parameter control unit 16 determines the ratio between single-carrier transmission and multi-carrier transmission so as to ensure the required S / N ratio in accordance with absorption attenuation. As described above, single-carrier transmission, which produces a wideband signal, has higher frequency efficiency than multi-carrier transmission, and in low frequency bands where absorption attenuation is low and the required S / N ratio can be ensured, single-carrier transmission, which has high frequency utilization efficiency, can improve the transmission speed of the entire system. Furthermore, the band division parameter control unit 16 adaptively determines the ratio between single-carrier transmission and multi-carrier transmission based on ACK information. As described above, when communication quality is good (communication quality is above a threshold), single-carrier transmission has better frequency utilization efficiency. Therefore, when communication quality improves due to a change in the communication environment, the transmission speed of the entire system can be improved by increasing the ratio of single-carrier transmission.

[0049] The subcarrier modulation units 15c-1 to 15c-n generate modulated data by modulating the multiple divided data output from the serial-parallel conversion unit 14c using different subcarriers. The subcarrier modulation units 15c-1 to 15c-n output the multiple modulated data thus generated to the connected wave transmitters 13-1 to 13-m. In the third embodiment, the number of subcarrier modulation units 15c is different from the number of wave transmitters 13.

[0050] The band splitting filter 12c receives modulated data generated by the subcarrier modulation unit 15c-1 as input. The band splitting filter 12c splits the input modulated data into multiple pieces of modulated data. Specifically, the band splitting filter 12c splits the modulated data according to the number of transmitters 13 connected to the band splitting filter 12c. As an example, if two transmitters 13 are connected to the band splitting filter 12c, the band splitting filter 12c may split the modulated data into two pieces based on the center frequency of the modulated data. The splitting method used by the band splitting filter 12c is not limited to the above, and any criterion may be used as long as it allows for multiple divisions. The splitting criterion and the number of divisions used by the band splitting filter 12c may be specified by the band splitting parameter control unit 16.

[0051] The band-splitting filter 12c outputs the split modulated data to each of the wave transmitters 13 connected to the band-splitting filter 12c. When two wave transmitters 13 are connected to the band-splitting filter 12c, the band-splitting filter 12c generates two split modulated data (e.g., first modulated data and second modulated data). The band-splitting filter 12c outputs the generated first modulated data to the wave transmitter 13-1 and outputs the generated second modulated data to the wave transmitter 13-2.

[0052] Transmitters 13-1 to 13-m receive the modulated data output from band-splitting filter 12c and the modulated data output from subcarrier modulation units 15c-1 to 15c-n as input. For example, transmitter 13-1 receives the first modulated data output from band-splitting filter 12c, transmitter 13-2 receives the second modulated data output from band-splitting filter 12c, transmitter 13-(m-1) receives the modulated data output from subcarrier modulation unit 15c-(n-1), and transmitter 13-m receives the modulated data output from subcarrier modulation unit 15c-n. Transmitters 13-1 to 13-m transmit the modulated data received to receiver 20c via sound waves. An example of the modulated data transmitted from transmitters 13-1 to 13-m is shown in speech bubble 45 in FIG. 5.

[0053] The receiver 20c includes a wave receiver 21, a plurality of subcarrier demodulation units 24-1 to 24-n, and a parallel-serial conversion unit 25. The wave receiver 21 receives a plurality of modulated data transmitted from the transmitter 10. The wave receiver 21 outputs the received plurality of modulated data to the subcarrier demodulation units 24-1 to 24-n according to the subcarriers. For example, every time the wave receiver 21 receives modulated data transmitted from the transmitter 10, it outputs the received modulated data to one of the subcarrier demodulation units 24-1 to 24-n.

[0054] The parallel-serial converter 25 converts the plurality of transmission data output from the subcarrier demodulators 24-1 to 24-n into parallel serial data to generate one piece of reception data.

[0055] As shown in speech bubble 50 in Figure 5, the signals received by receiver 20c are transmitted by transmitters 13-(m-1) to 13-m corresponding to the high frequency band, and are subject to large absorption attenuation, whereas the signals transmitted by transmitters 13-1 to 13-2 corresponding to the low frequency band are subject to small absorption attenuation.

[0056] According to the underwater communication system 100b configured as described above, high-frequency components are transmitted by multicarrier transmission, and low-frequency components are transmitted by band division. That is, by using a hybrid format in which high-efficiency communication is performed by band division for low-frequency components that are less susceptible to absorption attenuation, and multicarrier transmission is performed for high-frequency components that are more susceptible to absorption attenuation, it is possible to suppress a decrease in the gain of the transmitter during wideband transmission while also mitigating the effects of Doppler fluctuations. As a result, high-speed, stable communication can be achieved.

[0057] (Modifications common to the first to third embodiments) The transmitter and receiver shown in each of the first to third embodiments may be provided in a single housing to form a transceiver. Specifically, in the first embodiment, the transmitter 10 and the receiver 20 may be provided in a single housing to form a transceiver, or the transmitter 10 and the receiver 20a may be provided in a single housing to form a transceiver. In the second embodiment, the transmitter 10b and the receiver 20b may be provided in a single housing to form a transceiver. In the third embodiment, the transmitter 10c and the receiver 20c may be provided in a single housing to form a transceiver.

[0058] Some or all of the functional units of the transmitters 10, 10b, and 10c in the first to third embodiments, and some or all of the functional units of the receivers 20, 20a, 20b, and 20c in the first to third embodiments, are realized as software by a processor such as a CPU (Central Processing Unit) executing a program stored in a storage device having a non-volatile storage medium (non-transitory storage medium) and a storage unit. The program may be recorded on a computer-readable non-transitory storage medium. Examples of computer-readable non-transitory storage media include portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), and CD-ROMs (Compact Disc Read Only Memory), and storage devices such as hard disks built into computer systems.

[0059] Some or all of the functional units of the transmitters 10, 10b, and 10c in the first to third embodiments and some or all of the functional units of the receivers 20, 20a, 20b, and 20c in the first to third embodiments may be realized using hardware including an electronic circuit (electronic circuit or circuitry) using, for example, an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0060] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0061] The present invention is applicable to underwater acoustic communications.

[0062] 10, 10b, 10c... Transmitter, 20, 20a, 20b, 20c... Receiver, 11... Single carrier modulation unit, 12, 12c... Band division filter, 13, 13-1 to 13-m... Transmitter, 14, 14c... Serial-to-parallel conversion unit, 15, 15-1 to 15-n, 15c-1 to 15c-n... Subcarrier modulation unit, 16... Band division parameter control unit, 21... Receiver, 22... Reception processing unit, 23... Equalizer, 24, 24-1 to 24-n... Subcarrier demodulation unit, 25... Parallel-to-serial conversion unit, 100, 100a, 100b, 100c... Underwater communication system

Claims

1. A transmitter for use in underwater acoustic communication, comprising: a transmission data generation unit that generates multiple divided data of different frequency bands based on transmission data to be transmitted; and multiple transmitters having different resonant frequencies that respectively transmit the multiple generated divided data.

2. The transmitter according to claim 1, wherein the transmission data generation unit includes a band splitting filter unit that splits a transmission signal band into a plurality of bands based on the transmission data, and the plurality of transmitters transmit a plurality of split data pieces split by the band splitting filter unit.

3. The transmitter of claim 1, wherein the transmission data generation unit includes: a serial-parallel conversion unit that performs serial-to-parallel conversion on the transmission data; and a plurality of subcarrier modulation units that modulate the transmission data serial-to-parallel converted by the serial-parallel conversion unit with different subcarriers; and the plurality of transmitters transmit the plurality of modulated data modulated by the plurality of subcarrier modulation units as the plurality of divided data.

4. The transmitter of claim 1, wherein the transmission data generation unit includes: a serial-parallel conversion unit that performs serial-to-parallel conversion on the transmission data; a plurality of subcarrier modulation units that modulate the transmission data serial-to-parallel converted by the serial-to-parallel conversion unit with different subcarriers; and a band splitting filter unit that is connected to some of the plurality of subcarrier modulation units and splits the modulated data output from the connected subcarrier modulation units into a plurality of bands; and the plurality of transmitters transmit the plurality of split data split by the band splitting filter unit, and transmit as the plurality of split data the plurality of modulated data modulated by each of a plurality of subcarrier modulation units among the plurality of subcarrier modulation units to which the band splitting filter unit is not connected.

5. A transmitter as described in claim 4, further comprising a band splitting parameter control unit that controls the split ratio of the transmission data generated by the transmission data generation unit, the band splitting parameter control unit being determined based on propagation information, which is information regarding the propagation of a signal in an underwater transmission path, or communication quality information, which is information regarding the quality of communication in the underwater transmission path.

6. The transmitter according to claim 5, wherein the propagation information is Doppler velocity or absorption attenuation.

7. The transmitter according to claim 5, wherein the communication quality information is ACK information transmitted from the receiver.

8. A receiver for use in underwater acoustic communication, comprising: a receiver that receives multiple pieces of divided data transmitted from a transmitter by multiple transmitters having different resonant frequencies; and a reception control unit that performs reception processing on the multiple pieces of divided data received by the receiver.

9. The receiver according to claim 8, wherein the reception control section performs waveform equalization processing as the reception processing.

10. The receiver according to claim 8, wherein the plurality of divided data received by the receiver are modulated data modulated with different subcarriers, and the reception control unit includes: a plurality of subcarrier demodulation units that demodulate the modulated data corresponding to each subcarrier; and a parallel-to-serial conversion unit that performs parallel-to-serial conversion using the plurality of transmission data obtained by demodulation by the plurality of subcarrier demodulation units.

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