Estimation device, estimation method, and estimation program

Abstract

This invention provides an estimation device that improves the accuracy of Doppler estimation. [Solution] The estimation device according to this disclosure includes: a storage unit that stores a preamble received signal corresponding to the preamble of a received signal; a preamble sequence correlation unit that outputs a preamble sequence correlation between the preamble received signal and a known preamble sequence; a first search unit that searches for a first peak timing or a first frequency which is the peak of the correlation power of the preamble sequence correlation; an autocorrelation unit that outputs an autocorrelation between a postamble received signal corresponding to the postamble of a received signal and the stored preamble received signal; a second search unit that searches for a second peak timing or a second frequency which is the peak of the correlation power of the autocorrelation; and an estimation unit that estimates a Doppler frequency or a Doppler frequency difference from the timing difference between the first peak timing and the second peak timing or the frequency difference between the first frequency and the second frequency.

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 Initiative] [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 storage unit that stores a preamble received signal corresponding to the preamble of a received signal; a preamble sequence correlation unit that outputs a preamble sequence correlation between the preamble received signal and a known preamble sequence; a first search unit that searches for a first peak timing or a first frequency which is the peak of the correlation power of the preamble sequence correlation; an autocorrelation unit that outputs an autocorrelation between a postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal; a second search unit that searches for a second peak timing or a second frequency which is the peak of the correlation power of the autocorrelation; and an estimation unit that estimates a Doppler frequency or a Doppler frequency difference from the timing difference between the first peak timing and the second peak timing or the frequency difference between the first frequency and the second frequency.

[0013] The estimation method according to this disclosure involves saving a preamble received signal corresponding to the preamble of a received signal, outputting a preamble sequence correlation between the preamble received signal and a known preamble sequence, searching for a first peak timing or a first frequency that is the peak of the correlation power of the preamble sequence correlation, outputting an autocorrelation between a postamble received signal corresponding to the postamble of the received signal and the saved preamble received signal, searching for a second peak timing or a second frequency that is the peak of the correlation power of the autocorrelation, and estimating a Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing or the frequency difference between the first frequency and the second frequency.

[0014] The estimation program according to the present disclosure includes a process of storing a preamble reception signal corresponding to a preamble of a reception signal, a process of outputting a preamble sequence correlation between the preamble reception signal and a known preamble sequence, a process of searching for a first peak timing or a first frequency that is a peak of the correlation power of the preamble sequence correlation, a process of outputting an autocorrelation between a postamble reception signal corresponding to a postamble of the reception signal and the stored preamble reception signal, a process of searching for a second peak timing or a second frequency that is a peak of the correlation power of the autocorrelation, and a process of estimating a Doppler frequency or a Doppler frequency difference from a timing difference between the first peak timing and the second peak timing or a frequency difference between the first frequency and the second frequency, and causes a computer to execute operations including these processes.

Advantages of the Invention

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

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 a usage example of a Doppler estimation device according to the present disclosure. [Figure 4] It is a diagram for explaining a case where a reversal 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 (timing difference method) according to the present disclosure. [Figure 7] It is a flowchart for explaining an estimation method (peak frequency method) according to the present disclosure. [Figure 8] It is a diagram for explaining an estimation method according to the present disclosure. [Figure 9] This is a block diagram showing an example of a hardware configuration for an estimation device, etc. [Modes for carrying out the invention]

[0017] Specific embodiments to which the present invention is applied will be described in detail below 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 have been simplified as appropriate.

[0018] <Typical Embodiment> Figure 1 is a block diagram showing an example configuration of the estimation device 100 according to this disclosure. The estimation device 100 includes a preamble received signal storage unit 101, a preamble sequence correlation unit 102, a first search unit 103, an autocorrelation unit 110, a second search unit 112, 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 a known preamble sequence. The receiving terminal may also hold a known postamble sequence. The estimation device 100 is implemented by a computer including one or more processors and one or more memories, etc.

[0019] The storage unit 101 stores the preamble received signal corresponding to the preamble from the received signal. The received signal includes the preamble sequence, the payload, and the postamble sequence. The preamble sequence and the postamble sequence have the same pattern. That is, a modulated signal generated based on the same m-sequence signal can be used for both the postamble and the preamble. The preamble sequence is also called Unique Word 1 (UW1). The postamble sequence is also called Unique Word 2 (UW2).

[0020] The preamble sequence correlation unit 102 outputs the preamble sequence correlation between the received preamble signal corresponding to the preamble of the received signal and a known preamble sequence. In this specification, the correlation between the received signal and a known reference pattern (in this case, a known preamble sequence) held on the receiving terminal side may be referred to as cross-correlation. The first search unit 103 searches for a first peak timing or a first frequency that is the peak of the correlation power of the preamble sequence correlation.

[0021] The autocorrelation unit 110 outputs the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the preamble received signal stored in the storage unit 101. As used herein, autocorrelation refers to obtaining the correlation between the postamble received signal and the stored preamble received signal, rather than obtaining the correlation between the postamble received signal and a known postamble sequence (reference pattern). The second search unit 112 searches for a second peak timing or second frequency that will be the peak of the correlation power of the autocorrelation.

[0022] The estimation unit 140 can estimate the Doppler frequency from the timing difference between the first peak timing and the second peak timing using the timing difference method. Alternatively, the estimation unit 140 can estimate the Doppler frequency difference from the frequency difference between the first frequency and the second frequency using the peak frequency method. In other words, the estimation unit 140 can estimate Doppler using either the timing difference method or the peak frequency method.

[0023] Figure 2 is a flowchart illustrating the estimation method relating to this disclosure. The storage unit 101 of the estimation device 100 stores the preamble received signal corresponding to the preamble from the received signal (S11). The preamble sequence correlation unit 102 outputs the preamble sequence correlation between the preamble received signal corresponding to the preamble of the received signal and a known preamble sequence (S12). The first search unit 103 searches for a first peak timing or a first frequency that is the peak of the correlation power of the preamble sequence correlation (S13).

[0024] The autocorrelation unit 110 outputs the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the preamble received signal stored in the storage unit 101 (S14). The second search unit 112 searches for a second peak timing or a second frequency that is the peak of the correlation power of the autocorrelation (S15).

[0025] The estimation unit 140 estimates the Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing, or from the frequency difference between the first frequency and the second frequency.

[0026] According to the estimation apparatus and method described above, by using autocorrelation, characteristics such as frequency distortion and nonlinear distortion can be improved, and more accurate Doppler estimation can be achieved.

[0027] <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.

[0028] 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).

[0029] 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.

[0030] 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. Also, UW1 is sometimes called the preamble, and UW2 is sometimes called the postamble. The preamble and postamble have signals of a known preamble sequence and a known postamble sequence, respectively, in the receiving device.

[0031] The example shown in Figure 4(a) illustrates the case with only direct waves (i.e., no multipath waves). In this case, the timing difference can be correctly obtained, and the Doppler shift can be correctly estimated.

[0032] 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 and the path for detecting the peak power in the postamble 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.

[0033] Figure 5 is a block diagram showing an example configuration of a communication device according to this disclosure. Figure 8 is a diagram illustrating the estimation method according to this disclosure. This estimation method uses cross-correlation and autocorrelation (details will be described later). As shown in Figure 5, the communication device 1 includes 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 includes 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.

[0034] Next, the configuration of the estimation device 100 will be explained. The preamble received signal storage unit 101 stores the preamble received signal corresponding to the preamble of the received signal, as shown in Figure 8. The stored preamble received signal can be used for autocorrelation, which will be described later. The preamble sequence correlation unit 102 outputs the preamble sequence correlation between the preamble received signal and a known preamble sequence. The first search unit 103 searches for a first peak timing (mct1 in Figure 8) or a first frequency that is the peak of the correlation power of the preamble sequence correlation.

[0035] The autocorrelation unit 110 outputs the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal. That is, as shown in Figure 8, the postamble received signal is not cross-correlated with known postamble sequences, but instead is autocorrelated with the stored preamble received signal. Since the stored preamble received signal may have noise and frequency distortion equivalent to that of the postamble received signal compared to known postambles, it is expected that the characteristics against nonlinear distortion and frequency distortion will be improved.

[0036] The second search unit 112 searches for a second peak timing (mct2 in Figure 8) or a second frequency that corresponds to the peak of the correlation power of the autocorrelation.

[0037] The estimation unit 140 estimates the Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing (mct1) and the second peak timing (mct2), or from the frequency difference between the first frequency and the second frequency.

[0038] Figure 6 is a flowchart illustrating the estimation method (timing difference method) related to this disclosure. First, the preamble received signal corresponding to the preamble of the received signal is saved (S101). The preamble received signal corresponding to the preamble of the received signal is the received signal near the UW1 peak timing, and more precisely, it is the received signal that is estimated to correspond to the preamble of the received signal during a predetermined period including the UW1 peak timing. Cross-correlation processing of UW1 is performed (S102). That is, the result of the correlation between the preamble received signal and a known preamble sequence, c1 (a complex signal called a correlation waveform), is output. Specifically, the result of the cross-correlation of UW1, c1, is given by the following formula.

number

[0039] Next, the UW1 correlated power peak time m ct1Search (S103). If the correlation peak time deviates from the Doppler initial estimation 1, the correlation peak time may be re-searched within a range of about ± several [symbol] in the time direction from the correlation peak time m of the initial estimation 1. ct1 The UW1 correlation peak time [sample] is given by the following formula.

Equation

[0040] Next, perform the autocorrelation processing of UW2 (S104). That is, perform the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal. Note that the postamble received signal corresponding to the postamble of the received signal is the received signal near the UW2 peak timing, and more precisely, it refers to the received signal estimated to correspond to the postamble of the received signal. In the case of a single frequency band, the results of the autocorrelation of UW1 and UW2 are given by the following formula.

Equation

[0041] In the case of multiple frequency bands, the results of the autocorrelation of UW1 and UW2 are given by the following formula.

Equation

[0042] Next, search for the UW1 and UW2 autocorrelation power peak time m ct2 The UW1 and UW2 autocorrelation peak time [sample] is given by the following formula.

Equation

[0043] Estimate the Doppler frequency from the selected timing difference (S106). The estimation result of the Doppler compression rate is given by the following formula.

number

[0044] Furthermore, the symbol frequency difference [Hz] between UW1 and UW2 is given by the following formula.

number

[0045] Figure 7 is a flowchart illustrating the estimation method (peak frequency method) described herein. Steps S101 to S104 in Figure 7 are the same as in Figure 6, so their explanation is omitted.

[0046] We search for the frequency and time of the UW1,2 autocorrelation power peaks (S205). These are given by the following equations.

number

number

[0047] The Doppler frequency difference between UW1 and UW2 is estimated from the difference in peak frequencies. The estimated Doppler compression ratio is given by the following formula.

number

[0048] Furthermore, the symbol frequency difference [Hz] between UW1 and UW2 is given by the following formula.

number

[0049] The correction is applied to the beginning of UW1, α. lmax2 ,UW2 to α l’max2 And the other samples are α lmax2 ,UW2 to α l’max2 This is done using the result of linear correction.

[0050] 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.

[0051] Figure 9 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 9, 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.

[0052] 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.

[0053] 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.

[0054] In the example shown in Figure 9, 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 devices as described in the above embodiment.

[0055] As explained using the flowcharts in Figures 2, 6, and 7, 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 diagrams.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) A storage unit that stores the preamble received signal corresponding to the preamble of the received signal, A preamble sequence correlation unit outputs a preamble sequence correlation between the received preamble signal and a known preamble sequence, A first search unit searches for a first peak timing or a first frequency that is the peak of the correlation power of the preamble sequence correlation, An autocorrelation unit that outputs the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal, A second search unit searches for a second peak timing or a second frequency that corresponds to the peak of the correlation power of the autocorrelation, An estimation device comprising: an estimation unit that estimates a Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing or the frequency difference between the first frequency and the second frequency. (Note 2) The preamble and postamble of the received signal are the same pattern, as described in Appendix 1 of the estimation device. (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) The preamble received signal corresponding to the preamble of the received signal is saved. The preamble sequence correlation between the received preamble signal and a known preamble sequence is output. A first peak timing or first frequency is searched for, which is the peak of the correlation power of the preamble sequence correlation. The autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal is output. A second peak timing or second frequency is searched for, which corresponds to the peak of the correlation power of the autocorrelation. An estimation method for estimating a Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing, or the frequency difference between the first frequency and the second frequency. (Note 5) The process of saving the preamble received signal corresponding to the preamble of the received signal, A process to output the preamble sequence correlation between the received preamble signal and a known preamble sequence, A process for searching for a first peak timing or a first frequency that is the peak of the correlation power of the preamble sequence correlation, A process to output the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal, A process for searching for a second peak timing or second frequency that corresponds to the peak of the correlation power of the autocorrelation, An estimation program that causes a computer to perform an operation including a process of estimating a Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing or the frequency difference between the first frequency and the second frequency.

[0060] 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]

[0061] 1. Communication device 5. Support ships 6. Underwater Drone 10 Classmates 12 Resample section 13 Phase rotation section 20 Equalization section 100 Estimator 101 Preservation Department 102 Preamble series correlation 103 1st Exploration Department 110 Autocorrelation section 112 2nd Exploration Department 140 Estimation part

Claims

1. A storage unit that stores the preamble received signal corresponding to the preamble of the received signal, A preamble sequence correlation unit outputs a preamble sequence correlation between the received preamble signal and a known preamble sequence, A first search unit searches for a first peak timing or a first frequency that is the peak of the correlation power of the preamble sequence correlation, An autocorrelation unit that outputs the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal, A second search unit searches for a second peak timing or a second frequency that corresponds to the peak of the correlation power of the autocorrelation, An estimation device comprising: an estimation unit that estimates a Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing or the frequency difference between the first frequency and the second frequency.

2. The estimation device according to claim 1, wherein the preamble and postamble of the received signal have the same pattern.

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. The preamble received signal corresponding to the preamble of the received signal is saved. The preamble sequence correlation between the received preamble signal and a known preamble sequence is output. A first peak timing or first frequency is searched for, which is the peak of the correlation power of the preamble sequence correlation. The autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal is output. A second peak timing or second frequency is searched for, which is the peak of the correlation power of the autocorrelation. An estimation method for estimating a Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing, or the frequency difference between the first frequency and the second frequency.

5. The process of saving the preamble received signal corresponding to the preamble of the received signal, A process to output the preamble sequence correlation between the received preamble signal and a known preamble sequence, A process for searching for a first peak timing or a first frequency that is the peak of the correlation power of the preamble sequence correlation, A process to output the autocorrelation between the postamble received signal corresponding to the postamble of the received signal and the stored preamble received signal. A process for searching for a second peak timing or second frequency that corresponds to the peak of the correlation power of the autocorrelation, An estimation program that causes a computer to perform an operation including a process of estimating a Doppler frequency or Doppler frequency difference from the timing difference between the first peak timing and the second peak timing or the frequency difference between the first frequency and the second frequency.

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