Estimation device, estimation method, and estimation program

Abstract

To provide an estimation device that improves the accuracy of Doppler estimation. [Solution] The estimation device comprises: a preamble sequence correlation unit that outputs a correlation between a received signal and a known preamble sequence; a first extraction unit that extracts a first correlation output and a first timing that becomes the first correlation output from the correlation output between the received signal and the known preamble sequence, which is equal to or greater than a first threshold power; a postamble sequence correlation unit that outputs a correlation between a received signal and a known postamble sequence; a second extraction unit that extracts a second correlation output and a second timing that becomes the second correlation output from the correlation output between the received signal and the known postamble sequence, which is equal to or greater than a second threshold power; a recorrelation unit that outputs a recorrelation between the first correlation output and the second correlation output using any combination of timings between the first timing that becomes the first correlation output and the second timing that becomes the second correlation output; and an estimation unit that estimates the Doppler based on the timing difference of the recorrelation result that maximizes the power among the recorrelation results.

Description

[Technical Field]

[0001] This disclosure relates to an estimation device, an estimation method, and an estimation program. [Background technology]

[0002] Radio waves are absorbed and attenuated very significantly underwater, making wireless communication using radio waves difficult, just as it is on land. For this reason, sound waves below 1 MHz, which have relatively little absorption and attenuation even underwater, are often used for wireless communication. This type of communication is sometimes called underwater acoustic communication. Because sound waves propagate slowly, a large Doppler shift can occur as the communication terminal moves. Furthermore, the underwater environment is a multipath environment, so multipath with Doppler shift can occur. In other words, sound waves may reflect off the sea surface or seabed, and the receiving terminal may receive not only the direct wave but also the multipath wave.

[0003] In response to this, several methods have been proposed for estimating the Doppler frequency. The demodulation unit of a communication device estimates the Doppler frequency offset that occurs in the propagation path. However, the correlation between two known signal intervals has the following problems.

[0004] In the correlation timing difference method (Non-Patent Literature 1), the frequency resolution is limited by the sampling frequency, and when the Doppler difference between two known signal intervals is large, multiple frequency band correlation processes are required. As a result, the computational load and circuit size increase, and estimation errors due to noise and other factors may worsen.

[0005] Furthermore, in the correlated phase difference method, the maximum estimated frequency range is limited by the time difference between the two known signal intervals, and estimation errors due to noise and other factors may worsen. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2022 / 244141 [Non-patent literature]

[0007] [Non-Patent Document 1] BS Sharif, et. al, “A computationally efficient doppler compensation system for underwater acoustic communications,” IEEE J. Oceanic Eng., vol.25, no.1, pp.52-61,Jan. 2000. [Overview of the project] [Problems that the invention aims to solve]

[0008] Accurate Doppler estimation is not possible when the propagation path (fading) fluctuates, that is, when the fading conditions of two known signal intervals change due to propagation path fluctuations. In particular, when the leading wave level is large and the delayed wave level is small in the first half of the propagation path (minimum phase transition (MP) condition), and the leading wave level is small and the delayed wave level is large in the second half of the propagation path (non-minimum phase transition (NMP) condition), the level difference between the two known signal intervals reverses between the first and second halves of the interval, and the estimation error can worsen significantly.

[0009] In contrast, Patent Document 1 proposes a method in which the correlation results of the preamble and the correlation results of the postamble are correlated again (slide correlation), and the Doppler frequency is estimated from the difference in peak timing of the slide correlation.

[0010] However, the estimation accuracy in Patent Document 1 is still insufficient.

[0011] This disclosure is made to solve these problems and aims to provide an estimation device, etc., that improves the accuracy of Doppler estimation. [Means for solving the problem]

[0012] The estimation device according to this disclosure includes: a preamble sequence correlation unit that outputs a correlation between a received signal and a known preamble sequence; a first extraction unit that extracts one or more first correlation outputs from the correlation output between the received signal and the known preamble sequence that are equal to or greater than a first threshold power, and one or more first timings that become said one or more first correlation outputs; a postamble sequence correlation unit that outputs a correlation between the received signal and a known postamble sequence; and one or more second correlation outputs from the correlation output between the received signal and the known postamble sequence that are equal to or greater than a second threshold power, and one or more second timings that become said one or more second correlation outputs The system includes: a second extraction unit that extracts one or more second timings; a recorrelation unit that outputs one or more recorrelations between the first correlation output and the second correlation output using any combination of timings between the one or more first timings that become the one or more first correlation outputs and the one or more second timings that become the one or more second correlation outputs; and an estimation unit that estimates the Doppler frequency or the Doppler frequency difference between the preamble and the postamble based on the timing difference of the recorrelation result that maximizes the power or maximizes the total power per certain period of time among the one or more recorrelation results.

[0013] The estimation method according to this disclosure outputs a correlation between a received signal and a known preamble sequence, extracts one or more first correlation outputs and one or more first timings that are equal to or greater than a first threshold power from the correlation output between the received signal and the known preamble sequence, outputs a correlation between the received signal and a known postamble sequence, extracts one or more second correlation outputs and one or more second timings that are equal to or greater than a second threshold power from the correlation output between the received signal and the known postamble sequence, outputs one or more recorrelations between the first correlation output and the second correlation output using any combination of timings between the one or more first timings that are equal to or greater than the one or more second timings that are equal to or greater than the first correlation output, and estimates the Doppler frequency or the Doppler frequency difference between the preamble and the postamble based on the timing difference of the recorrelation result that maximizes the power or maximizes the total power per unit time from among the results of the one or more recorrelations.

[0014] The estimation program according to this disclosure causes a computer to output a correlation between a received signal and a known preamble sequence, extract one or more first correlation outputs and one or more first timings that are equal to or greater than a first threshold power from the correlation output between the received signal and the known preamble sequence, output a correlation between the received signal and a known postamble sequence, extract one or more second correlation outputs and one or more second timings that are equal to or greater than a second threshold power from the correlation output between the received signal and the known postamble sequence, output one or more recorrelations between the first correlation output and the second correlation output using any combination of timings between the one or more first timings that are equal to or greater than the one or more second timings that are equal to or greater than the first correlation output, and estimate the Doppler frequency or the Doppler frequency difference between the preamble and the postamble based on the timing difference of the recorrelation result that maximizes the power or maximizes the total power per unit time from among the results of the one or more recorrelations. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to provide an estimation device or the like with improved Doppler estimation accuracy.

Brief Description of the Drawings

[0016] [Figure 1] It is a block diagram showing a configuration example of an estimation device according to the present disclosure. [Figure 2] It is a flowchart for explaining an estimation method according to the present disclosure. [Figure 3] It is a diagram for explaining an example of use of a Doppler estimation device according to the present disclosure. [Figure 4] It is a diagram for explaining the case where a reverse phenomenon occurs under the influence of multipath. [Figure 5] It is a block diagram showing a configuration example of a communication device according to the present disclosure. [Figure 6] It is a flowchart for explaining an estimation method according to the present disclosure. [Figure 7] Specific examples of UW1 correlation power, UW2 correlation power, and re-correlation power are shown. [Figure 8] Specific examples of UW1 correlation power, UW2 correlation power, and re-correlation power are shown. [Figure 9] Specific examples of UW1 correlation power, UW2 correlation power, and re-correlation power are shown. [Figure 10] It is a block diagram showing a hardware configuration example of an estimation device or the like.

Modes for Carrying Out the Invention

[0017] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings are appropriately simplified.

[0018] <Typical Embodiment> FIG. 1 is a block diagram showing a configuration example of an estimation device 100 according to the present disclosure. The estimation device 100 includes a preamble sequence correlation unit 101, a first extraction unit 102, a postamble sequence correlation unit 110, a second extraction unit 112, a recorrelation unit 130, and an estimation unit 140. The estimation device 100 may be, for example, a receiving terminal that can input a received signal from a transmitting terminal and perform Doppler estimation. The estimation device 100, i.e., the receiving terminal, holds known preamble sequences and known postamble sequences. The estimation device 100 is implemented by a computer including one or more processors and one or more memories, etc.

[0019] The preamble sequence correlation unit 101 outputs a correlation between the received signal and a known preamble sequence. The first extraction unit 102 extracts one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that correspond to the one or more first correlation outputs, from the correlation outputs between the received signal and the known preamble sequence.

[0020] The post-amble sequence correlation unit 110 outputs the correlation between the received signal and a known post-amble sequence. The second extraction unit 112 extracts one or more second correlation outputs that are equal to or greater than the second threshold power, and one or more second timings that correspond to these one or more second correlation outputs, from the correlation outputs between the received signal and the known post-amble sequence.

[0021] The recorrelation unit 130 outputs one or more recorrelations between the first correlation output and the second correlation output in any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs.

[0022] The estimation unit 140 estimates the Doppler frequency or the Doppler frequency difference between the preamble and the postamble based on the timing difference of the recorrelation result that maximizes the power or maximizes the total power per certain period of time from among the one or more recorrelation results. The total power per certain period of time refers, for example, to the total power per predetermined period that includes the timing of the peak power.

[0023] Figure 2 is a flowchart illustrating the estimation method relating to this disclosure. The preamble sequence correlation unit 101 outputs a correlation between the received signal and a known preamble sequence (S11). The first extraction unit 102 extracts one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that correspond to the one or more first correlation outputs, from the correlation outputs between the received signal and the known preamble sequence (S12).

[0024] The post-amble sequence correlation unit 110 outputs a correlation between the received signal and a known post-amble sequence (S13). The second extraction unit 112 extracts one or more second correlation outputs that are equal to or greater than the second threshold power, and one or more second timings that correspond to these one or more second correlation outputs, from the correlation outputs between the received signal and the known post-amble sequence (S14).

[0025] The recorrelation unit 130 outputs one or more recorrelations between the first correlation output and the second correlation output in any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs (S15).

[0026] The estimation unit 140 estimates the Doppler frequency or the Doppler frequency difference between the preamble and the postamble based on the timing difference of the recorrelation result that maximizes the power or maximizes the total power per certain period of time among the one or more recorrelation results (S16).

[0027] According to the embodiments described above, Doppler estimation can be performed with higher accuracy.

[0028] <Other Embodiments> Figure 3 illustrates an example of the use of the Doppler estimation device according to this disclosure. A camera-equipped underwater drone 6 is used for resource exploration and seabed topography surveys. During this time, a support vessel 5 also moves from the surface to assist the underwater drone 6 as it explores the water. In the example shown in Figure 3, underwater acoustic communication is generally used to transmit data such as video images measured by the camera on the underwater drone 6 to the support vessel 5, and to transmit commands such as instructions from the support vessel 5 to the underwater drone 6. Underwater acoustic communication refers to wireless communication that uses sound waves of 1 MHz or less, which have relatively little absorption and attenuation even underwater.

[0029] When the support vessel 5 or the underwater drone 6 moves, a Doppler shift occurs, degrading the communication characteristics. In other words, the possible movement speed and transmission distance for communication are limited in relation to the feasibility of communication and the error rate characteristics. Therefore, in order to conduct surveys efficiently, it is desirable to have a large possible movement speed and transmission distance, as well as good communication quality (low error rate). This disclosure proposes an estimation method for realizing wireless communication with a large possible movement speed and transmission distance, as well as good communication quality (low error rate).

[0030] An estimation device for performing the estimation method described herein may be implemented by a computer having a processor and memory, etc. The estimation device 100 is mounted on a receiving communication terminal that performs underwater acoustic communication. That is, the estimation device 100 may be a communication device mounted on a support vessel 5 or an underwater drone 6.

[0031] Figure 4 illustrates the case where a reversal phenomenon occurs due to the influence of multipath. The frame of the received signal has a unique word (UW1) and a unique word 2 (UW2) before and after the data. The data is sometimes called the payload section. Also, UW1 is sometimes called the preamble section, and UW2 is sometimes called the postamble section. The preamble section and postamble section each contain a preamble sequence signal and a postamble sequence signal known to the receiving device.

[0032] The example shown in Figure 4(a) illustrates the case with only direct waves (i.e., no multipath waves). In this case, the Doppler shift can be correctly estimated.

[0033] In the example shown in Figure 4(b), a multipath wave slightly delayed from the direct wave is received. For the preamble, the peak power of the direct wave is higher than the peak power of the multipath wave, but for the postamble, the peak power of the multipath wave is higher than the peak power of the direct wave. When this reversal occurs, the path for detecting the peak power in the preamble section and the path for detecting the peak power in the postamble section do not coincide. If the same path is not detected, the timing difference cannot be obtained correctly, and the Doppler shift cannot be estimated correctly. As a result, the accuracy of the correction decreases.

[0034] Figure 5 is a block diagram showing an example configuration of a communication device according to this disclosure. The communication device 1 comprises a synchronization unit 10 and an equalization unit 20. The synchronization unit 10 receives the received signal, corrects the received signal, and outputs the corrected received signal to the equalization unit 20. The synchronization unit 10 comprises an estimation device 100, a resampling unit 12, and a phase rotation unit 13. The estimation device 100 estimates the Doppler shift amount (Doppler frequency difference). The resampling unit 12 corrects the sampling timing based on the Doppler shift amount from the estimation device 100. The phase rotation unit 13 applies a phase rotation to the received signal based on the Doppler shift amount from the estimation device 100. The equalization unit 20 includes an FIR (Finite Impulse Response) filter.

[0035] Next, the configuration of the estimation device 100 will be explained. The preamble sequence correlation unit 101 outputs the correlation between the received signal and a known preamble sequence. The first extraction unit 102 extracts one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that correspond to these one or more first correlation outputs, from the correlation outputs between the received signal and the known preamble sequence.

[0036] The post-amble sequence correlation unit 110 outputs a correlation between the received signal and a known post-amble sequence. The second extraction unit 112 extracts one or more second correlation outputs and one or more second timings that are equal to or greater than the second threshold power from the correlation outputs between the received signal and the known post-amble sequence. The first threshold power and the second threshold power may be the same or different. The first and second threshold powers can be set by calculating the expected received level from the assumed communication distance and transmission level, and taking into account a margin.

[0037] The recorrelation unit 130 outputs one or more recorrelations between the first correlation output and the second correlation output at any combination of timings between one or more first timings that result in one or more first correlation outputs and one or more second timings that result in one or more second correlation outputs.

[0038] Any combination of timings for N and M at the time m1N (N=1,2 in the example of Figure 7) above TPL1 in the UW1 correlated power and at the time m2M (M=1,2 in the example of Figure 8) above TPL2 in the UW2 correlated power may include at least a combination of the first timing for a first correlated output and the first timing for a second correlated output, and a combination of the timing for the maximum of the first correlated output and the timing for the maximum of the second correlated output. Any combination of timings can be any combination of one or more timings for one or more first correlated outputs and one or more timings for one or more second correlated outputs (i.e., any combination of N and M in the examples of Figures 7 and 8).

[0039] The estimation unit 140 estimates the Doppler frequency or the Doppler frequency difference between the preamble and the postamble based on the recorrelation result that maximizes the power or the total power per unit time from among one or more recorrelation results. The total power per unit time refers, for example, to the total power over a predetermined period including the timing of the peak power.

[0040] Figure 6 is a flowchart illustrating the estimation method according to this disclosure. The estimation method according to this disclosure is Doppler correction with two known signal interval correlations, and utilizes the correlation timing difference method (Non-Patent Literature 1). Figures 7 to 9 show specific examples of UW1 correlation power, UW2 correlation power, and recorrelation power. Figures 7 to 9 show the UW1 correlation power and UW2 correlation power for the same received signal, but with different combinations (i.e., pairs) of different peak powers for UW1 correlation power and UW2 correlation power. Therefore, the recorrelation power may also differ in Figures 7 to 9.

[0041] First, correlation processing is performed on UW1 (S101). That is, the result c1 of the correlation between the received signal and a known preamble sequence (the correlation waveform of the complex signal UW1) is output. Specifically, the result c1 of the UW1 correlation is given by the following formula.

number

[0042] Next, the UW1 correlated power peak time m ct1 We explore (S102). If the correlation peak time deviates from the initial Doppler estimate 1, the correlation peak time m of the initial estimate 1 is determined in the time direction. ct1The correlation peak time may be re-searched within a range of about ± several [symbols]. The UW1 correlation peak time [sample] is given by the following formula.

Number

[0043] Next, the correlation power and its time when the correlation power of UW1 is greater than or equal to the threshold value are extracted (S103). As shown in the upper diagram of FIG. 7, those (UW1_P1, UW1_P2) in which the correlation power of UW1 exceeds the first threshold power TPL1 are extracted, and their timing times (m11, m12) are also extracted. In FIGS. 7 to 9, m11 corresponds to m ct11 and m12 corresponds to m ct12 corresponds to.

[0044] Similarly, the correlation process of UW2 is performed (S104). That is, the result c2 of the correlation between the received signal and the known postamble sequence (the correlation waveform of UW2 which is a complex signal) is output. The correlation process of UW2 is performed in the vicinity of the UW2 reception time (a time range considering the expansion and contraction of the assumed Doppler around the ideal time) from the Doppler initial estimation 1 or the correlation peak time m ct1 of the above c1. Specifically, the result of the correlation of UW2 is given by the following formula.

Number

[0045] Next, the UW2 correlation power peak time m ct2 is searched (S105). The UW2 correlation peak time [sample] is given by the following formula.

Number

[0046] Next, the correlation powers of UW2 that are above the threshold and their corresponding times are extracted (S106). As shown in the middle diagram of Figure 7, the correlation powers of UW2 that exceed the second threshold power TPL2 (UW2_P1, UW2_P2) are extracted, and their timing times (m21, m22) are also extracted. Note that in Figures 7 to 9, m21 is m ct21 In response to this, m22 is m ct22 It corresponds to.

[0047] Recorrelation is performed on any combination of the extracted UW1 correlated power and the extracted UW2 correlated power (S107). In the example shown in Figures 7 to 9, the extracted UW1 correlated power consists of two peak powers, UW1_P1 and UW1_P2, and the extracted UW2 correlated power consists of two peak powers, UW2_P1 and UW2_P2. In this case, the combinations shown in Figures 7, 8, and 9 are possible.

[0048] In the case of Figure 7, the timing times of UW1_P1, the first correlation peak of UW1, and UW2_P1, the first correlation peak of UW2, are aligned and recorrelation is performed. That is, in the graph of Figure 7, the timing time m11 of UW1_P1 and the timing time m21 of UW2_P1 are aligned (m11 is delayed to m21), and the correlation power of UW1 and the correlation power of UW2 are recorded. In this case, the recorded power is shown as RC1 in the lower part of Figure 7. In the same figure, RC1 and RC2 indicate the peaks of the recorded power. Furthermore, the second correlation power of UW1, UW1_P2, and the first correlation power of UW2, UW2_P1, are recorded. That is, in the graph of Figure 9, the timing time m12 of UW1_P1 and the timing time m22 of UW2_P1 are aligned, and the correlation power of UW1 and the correlation power of UW2 are recorded. In this case, the recorrelated power is shown as RC2 in the lower part of Figure 9. In the same figure, RC5 and RC6 indicate the peaks of the recorrelated power.

[0049] In the case of Figure 8, the timing times of UW1_P1, the first correlated power peak of UW1, and UW2_P2, the second correlated power peak of UW2, are aligned, and recorrelation is performed. That is, in the graph of Figure 8, the timing time m11 of UW1_P1 and the timing time m22 of UW2_P2 are aligned, and the correlated power of UW1 and the correlated power of UW2 are recorded. In this case, the recorded power is shown as RC4 in the lower part of Figure 8.

[0050] In this case, the correlation power UW1_P0 at time m10, which corresponds to the timing time m21 of UW2_P1, the first correlation power of UW2, is also recorrelated. The correlation power UW1_P0 at time m10 is less than or equal to the threshold TPL1. The correlation power UW2_P1, the first correlation power of UW2, and the correlation power UW1_P0 at time m10 of UW1, which has the same timing, are recorrelated. In this case, the recorrelated power is shown as RC3 in the lower part of Figure 8.

[0051] In other words, Figure 8 is an example of recorrelation processing by matching the timing time m11 of UW1_P1, which is the maximum peak power among the correlated powers of UW1, with the timing time m22 of UW2_P2, which is the maximum peak power among the correlated powers of UW2.

[0052] In the case of Figure 9, the timing time of UW1_P2, the second correlated power peak of UW1, and UW2_P1, the first correlated power peak of UW2, are aligned, and recorrelation is performed. That is, in the graph of Figure 9, the timing time m12 of UW1_P2 and the timing time m21 of UW2_P1 are aligned, and recorrelation is performed on the correlated power of UW1_P2 and the correlated power of UW2_P1. The recorrelation power in this case is illustrated in the lower part of Figure 9.

[0053] In this case, the correlation power UW1_P3 at time m13 of UW1, which corresponds to the timing time m22 of UW2_P2, the second correlation power of UW2, is also recorrelated. The correlation power UW1_P3 at time m13 of UW1 is less than or equal to the threshold TPL1. The recorrelation process is performed on UW2_P2, the second correlation power of UW2, and UW1_P3 at time m13 of UW1, which has the same timing. The recorrelation power in this case is illustrated in the lower part of Figure 9.

[0054] Figures 7 to 9 show examples of recorrelation processing performed on various combinations of two extracted UW1 correlated powers and two extracted UW2 correlated powers. In other embodiments, recorrelation processing may be performed on various combinations of various numbers of UW1 correlated powers and various numbers of UW2 correlated powers.

[0055] From the recorrelation results (RC1, RC2, RC3, RC4, RC5, RC6), the one with the maximum peak power is selected (S108). In the examples in Figures 7 to 9, the recorrelation power is maximum when it is RC1 in Figure 7, so m11 and m21 (i.e., m ct11、 m ct21 The timing difference of ) is used. In some embodiments, the recorrelation results may also be used to select the one with the maximum total power per unit time. For example, the one with the maximum total power for the 2 seconds before and after the peak power time (e.g., m11 and m21) can be selected.

[0056] From the selected timing difference, the Doppler frequency and the Doppler frequency difference between UW1 and UW2 are estimated (S109). The estimated Doppler compression ratio is given by the following formula.

number

[0057] Furthermore, the symbol frequency difference [Hz] between UW1 and UW2 is given by the following formula.

number

[0058] According to the estimation device and method described above, it is possible to improve the accuracy of estimating the Doppler compression ratio and the Doppler frequency difference between UW1 and UW2, even when receiving various multipath waves.

[0059] Figure 10 is a block diagram showing an example of the hardware configuration of the estimation device 100 and the communication device 1 (hereinafter referred to as the estimation device 100, etc.). Referring to Figure 10, the estimation device 100, etc. includes a network interface 1201, a processor 1202, and memory 1203. The network interface 1201 is used to communicate with other network node devices that constitute the communication system. The network interface 1201 may also be used for wireless communication. For example, the network interface 1201 may be used for wireless LAN communication as defined in the IEEE 802.11 series, or for mobile communication as defined in 3GPP (3rd Generation Partnership Project) (registered trademark). Alternatively, the network interface 1201 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0060] The processor 1202 reads and executes software (computer programs) from the memory 1203 to perform processing such as that of the estimation device 100 described using a flowchart or sequence in the above embodiment. The processor 1202 can be, for example, a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), a DSP (Digital Signal Processor), an MPU (Micro Processing Unit), an FPU (Floating point number Processing Unit), a PPU (Physics Processing Unit), a TPU (Tensor Processing Unit), a quantum processor, a microcontroller, or a combination thereof.

[0061] Memory 1203 is composed of a combination of volatile and non-volatile memory. Memory 1203 may also include storage located away from the processor 1202. In this case, the processor 1202 may access memory 1203 via an I / O interface not shown.

[0062] In the example shown in Figure 10, memory 1203 is used to store a group of software modules. The processor 1202 can read these software modules from memory 1203 and execute them, thereby enabling the processing of the estimation device 100 and other systems described in the above embodiment.

[0063] As explained using the flowchart in Figure 6, each processor in the estimation device 100, etc., executes one or more programs that include a set of instructions for causing the computer to perform the algorithm described in the diagram.

[0064] In the examples described above, the program includes a set of instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more of the functions described in the embodiments. The program may be stored on a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray® disc or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited to, include temporary computer-readable medium or a communication medium that includes electrically, optically, acoustically or otherwise propagating signals.

[0065] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0066] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments rather than with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps shown in any of the drawings may be changed as appropriate.

[0067] Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) A preamble sequence correlation unit that outputs the correlation between the received signal and a known preamble sequence, A first extraction unit extracts one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that constitute the one or more first correlation outputs, from the correlation outputs between the received signal and a known preamble sequence. A post-amble sequence correlation unit outputs the correlation between the received signal and a known post-amble sequence, A second extraction unit extracts one or more second correlation outputs that are equal to or greater than a second threshold power, and one or more second timings that are said to be the one or more second correlation outputs, from the correlation outputs between the received signal and a known post-amble sequence. A recorrelation unit that outputs one or more recorrelations between the first correlation output and the second correlation output in any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs, An estimation device comprising: an estimation unit that estimates the Doppler frequency or the Doppler frequency difference between a preamble and a postamble based on the recorrelation result among the one or more recorrelation results that maximizes the power or maximizes the total power per certain period of time. (Note 2) The estimation apparatus according to Appendix 1, wherein the arbitrary timing combination includes at least a combination of the first timing that results in the first correlation output and the first timing that results in the second correlation output, and a combination of the timing that results in the maximum of the first correlation output and the timing that results in the maximum of the second correlation output. (Note 3) A synchronization unit that performs synchronization processing on the received signal according to the Doppler frequency difference, The estimation device according to Appendix 1, comprising an equalization unit that performs equalization processing on the received signal that has undergone the synchronization processing. (Note 4) Outputs the correlation between the received signal and a known preamble sequence. From the correlation output between the received signal and a known preamble sequence, one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that correspond to said one or more first correlation outputs are extracted. The correlation between the received signal and a known post-amble sequence is output. From the correlation output between the received signal and a known post-amble sequence, one or more second correlation outputs that are equal to or greater than the second threshold power, and one or more second timings that correspond to said one or more second correlation outputs are extracted. One or more recorrelations between the first correlation output and the second correlation output are output in any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs. An estimation method for estimating the Doppler frequency or the Doppler frequency difference between a preamble and a postamble based on the recorrelation result that maximizes the power or the total power per unit time among the results of one or more recorrelations. (Note 5) Outputs the correlation between the received signal and a known preamble sequence. From the correlation outputs between the received signal and a known preamble sequence, one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that correspond to said one or more first correlation outputs are extracted. The correlation between the received signal and a known post-amble sequence is output. From the correlation output between the received signal and a known post-amble sequence, one or more second correlation outputs that are equal to or greater than the second threshold power, and one or more second timings that correspond to said one or more second correlation outputs are extracted. One or more recorrelations between the first correlation output and the second correlation output are output at any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs. An estimation program that causes a computer to estimate the Doppler frequency or the Doppler frequency difference between the preamble and the postamble based on the recorrelation result that maximizes the power or the total power per unit time among the results of one or more recorrelations.

[0068] Some or all of the elements (e.g., configuration and function) described in Appendices 2 and 3 that are subordinate to Appendice 1 may also be subordinate to Appendices 4 and 5 in the same manner as those described in Appendices 2 and 3. Some or all of the elements described in any appendice may be applied to various hardware, software, recording means, systems, and methods for recording software. [Explanation of Symbols]

[0069] 1. Communication device 5. Support ships 6. Underwater Drone 10 Classmates 12 Resample section 13 Phase rotation section 20 Equalization section 100 Estimator 101 Preamble series correlation 102 Extraction part 110 Post-Amble Series Correlation 112 Extraction part 130 Recorrelation Section 140 Estimation part

Claims

1. A preamble sequence correlation unit that outputs the correlation between the received signal and a known preamble sequence, A first extraction unit extracts one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that constitute the one or more first correlation outputs, from the correlation outputs between the received signal and a known preamble sequence. A post-amble sequence correlation unit outputs the correlation between the received signal and a known post-amble sequence, A second extraction unit extracts one or more second correlation outputs that are equal to or greater than a second threshold power, and one or more second timings that are said to be the one or more second correlation outputs, from the correlation outputs between the received signal and a known post-amble sequence. A recorrelation unit that outputs one or more recorrelations between the first correlation output and the second correlation output in any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs, An estimation device comprising: an estimation unit that estimates a Doppler frequency or a Doppler frequency difference between a preamble and a postamble based on the timing difference of the recorrelation result that maximizes power or maximizes total power per certain period of time among the results of one or more recorrelations.

2. The estimation apparatus according to claim 1, wherein the arbitrary timing combination includes at least a combination of the first timing that results in the first correlation output and the first timing that results in the second correlation output, and a combination of the timing that results in the maximum of the first correlation output and the timing that results in the maximum of the second correlation output.

3. A synchronization unit that performs synchronization processing on the received signal according to the Doppler frequency difference, The estimation device according to claim 1, further comprising an equalization unit that performs equalization processing on the received signal that has undergone the synchronization processing.

4. Outputs the correlation between the received signal and a known preamble sequence. From the correlation output between the received signal and a known preamble sequence, one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that correspond to said one or more first correlation outputs are extracted. The correlation between the received signal and a known post-amble sequence is output. From the correlation output between the received signal and a known post-amble sequence, one or more second correlation outputs that are equal to or greater than the second threshold power, and one or more second timings that correspond to said one or more second correlation outputs are extracted. One or more recorrelations between the first correlation output and the second correlation output are output in any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs. An estimation method for estimating the Doppler frequency or the Doppler frequency difference between a preamble and a postamble based on the timing difference of the recorrelation result that maximizes the power or maximizes the total power per unit time among the one or more recorrelation results.

5. Outputs the correlation between the received signal and a known preamble sequence. From the correlation output between the received signal and a known preamble sequence, one or more first correlation outputs that are equal to or greater than a first threshold power, and one or more first timings that correspond to said one or more first correlation outputs are extracted. The correlation between the received signal and a known post-amble sequence is output. From the correlation output between the received signal and a known post-amble sequence, one or more second correlation outputs that are equal to or greater than the second threshold power, and one or more second timings that correspond to said one or more second correlation outputs are extracted. One or more recorrelations between the first correlation output and the second correlation output are output in any combination of timings between the one or more first timings that result in one or more first correlation outputs and the one or more second timings that result in one or more second correlation outputs. An estimation program that causes a computer to estimate the Doppler frequency or the Doppler frequency difference between a preamble and a postamble based on the timing difference of the recorrelation result that maximizes the power or the total power per unit time among the one or more recorrelation results.

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