Communication device, control method, and program

Abstract

To accurately estimate DL / UL switching timing at a low cost even in the presence of common phase error due to phase noise in TDD system.SOLUTION: In a communication device according to an embodiment, a signal reception unit receives an OFDM signal and converts the signal into a baseband OFDM signal. A temporal waveform calculation unit extracts a portion of a time-axis waveform signal and calculates a degree of similarity to a known signal. An FFT unit performs a Fourier transform on the temporal waveform signal that is an output of the temporal waveform calculation unit. A frequency waveform phase correction unit corrects, on the basis of the degree of similarity to a known signal, the phase of the frequency-axis waveform signal that is an output of the FFT unit. A frequency waveform calculation unit extracts a portion of the frequency-axis waveform signal that is an output of the frequency waveform phase correction unit and calculates a degree of similarity between the extracted signal and a known signal. A switching timing estimation unit estimates, on the basis of results from the frequency waveform calculation unit, the timing for switching between uplink communication and downlink communication in the device.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a communication device, a control method, and a program. [Background technology]

[0002] Distributed Antenna Systems (DAS) are known as one type of wireless communication system. In a distributed antenna system, communication is performed using a time division duplex (TDD) method, which switches between downlink (DL) communication from a base station to a terminal and uplink (UL) communication from a terminal to a base station at predetermined intervals. Such a distributed antenna system needs to detect the DL and UL periods of wireless signals and switch appropriately.

[0003] Conventionally, communication devices first perform AD conversion (Analog-to-Digital Conversion) to convert radio signals from analog to digital. Oversampling, which involves sampling at a rate higher than the input signal's data rate, is often used during AD conversion to improve the S / N ratio and resolution while also mitigating the requirements of anti-aliasing filters. Next, carrier frequency conversion is performed, down-converting the AD-converted signal to a baseband signal. Sampling rate conversion is then performed, down-converting the baseband signal's sampling rate from the clock frequency used during AD conversion to the system clock frequency. TDD synchronization with the base station is achieved by analyzing the synchronization signal contained in the resulting sampling-rate-converted signal.

[0004] Generally, Orthogonal Frequency Division Multiplexing (OFDM) signals are susceptible to the effects of phase noise because they frequency-multiplex a large number of subcarriers. Phase noise has two effects on OFDM signals. The first is subcarrier phase fluctuations caused by the low-frequency components of the phase noise. This is called common phase error because all subcarriers fluctuate at the same angle. The other is inter-carrier interference, in which the signal-to-noise ratio of a carrier deteriorates due to interference from the phase noise of other subcarriers. In particular, in the case of OFDM, common phase error appears as a phase rotation in the constellation after the received time-domain waveform signal is demodulated by the FFT section. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-053769 [Patent Document 2] Japanese Patent Application Publication No. 2020-504568 Summary of the Invention [Problem to be solved by the invention]

[0006] When data modulated with phase shift keying (PSK) or quadrature amplitude modulation (QAM) is judged in the presence of phase rotation due to a common phase error, reception characteristics are significantly degraded. For this reason, data judgment is generally performed after correcting the common phase error. Correcting the common phase error requires a mechanism to control the frequency and phase of the local oscillator clock and baseband system clock, as well as waveform equalization processing to estimate transmission path characteristics and correct the waveform after FFT.

[0007] Therefore, the present invention has been made in consideration of the above circumstances, and aims to provide a communication device, a control method, and a program that can inexpensively and accurately estimate the DL / UL switching timing in a TDD system that switches between DL communication and UL communication at predetermined intervals, even when a common phase error due to phase noise exists. [Means for solving the problem]

[0008] A communication device according to an embodiment is in a distributed antenna system including a master station connected to a base station and one or more slave station devices that relay signals between terminal devices communicating with the base station and the master station. The communication device functions as the master station or the slave station and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted using a time division multiplexing method. The communication device includes a signal receiver, a time waveform calculator, an FFT unit, a frequency waveform phase corrector, a frequency waveform calculator, and a switching timing estimator. The signal receiver receives the OFDM signal and converts it into a baseband OFDM signal. The time waveform calculator extracts a portion of a time domain waveform signal output from the signal receiver and calculates a degree of similarity between the extracted signal and a known signal. The FFT unit performs a Fourier transform (FFT) on the time waveform signal output from the time waveform calculator. The frequency waveform phase correction unit corrects the phase of the frequency axis waveform signal output from the FFT unit based on the degree of similarity with a known signal calculated by the time waveform calculation unit. The frequency waveform calculation unit extracts a portion of the frequency axis waveform signal output from the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal. The switching timing estimation unit estimates the timing of switching between uplink and downlink communications in the device based on the result of the frequency waveform calculation unit. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of a distributed antenna system according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing an example of a data structure of a radio frame. [Figure 3] A diagram showing an example of an SSB placement pattern in a radio frame. [Figure 4] A diagram showing an example of the DL / UL configuration and SSB arrangement of the TDD system [Figure 5] FIG. 1 is a diagram showing an example of the functional configuration of a master station device according to a first embodiment; [Figure 6] FIG. 1 is a diagram showing an example of the functional configuration of a control unit according to a first embodiment; [Figure 7] FIG. 1 is a diagram showing an example of a functional configuration of a switching timing generation unit according to a first embodiment; [Figure 8] FIG. 1 is a diagram illustrating an example of a functional configuration of a PSS detection unit according to a first embodiment. [Figure 9] FIG. 1 is a diagram showing an example of the functional configuration of a phase error detection unit according to a first embodiment; [Figure 10] FIG. 10 is a diagram showing an example of complex data of correlation values calculated by a correlation calculation unit of a phase error detection unit, expressed on a complex plane. [Figure 11] FIG. 1 is a diagram showing an example of the functional configuration of a phase correction unit according to a first embodiment; [Figure 12] FIG. 1 is a diagram showing an example of the functional configuration of an SSS detection unit according to the first embodiment; [Figure 13] FIG. 1 is a diagram illustrating an example of the functional configuration of a DMRS detector according to a first embodiment; [Figure 14] 1 is a flowchart illustrating an example of a TDD detection process according to a first embodiment; [Figure 15] 1 is a flowchart showing an example of time waveform processing according to the first embodiment; [Figure 16] 1 is a flowchart showing an example of FFT processing according to the first embodiment; [Figure 17] 1 is a flowchart illustrating an example of a frequency waveform phase correction process according to the first embodiment; [Figure 18] 1 is a flowchart illustrating an example of a phase error detection process according to the first embodiment. [Figure 19] 1 is a flowchart illustrating an example of a phase correction process according to the first embodiment. [Figure 20] 1 is a flowchart showing an example of frequency waveform processing according to the first embodiment; [Figure 21] 1 is a flowchart illustrating an example of an SSS detection process according to the first embodiment; [Figure 22] 1 is a flowchart illustrating an example of a DMRS detection process according to the first embodiment. [Figure 23] 1 is a flowchart illustrating an example of a switching timing estimation process according to the first embodiment; [Figure 24] FIG. 10 is a diagram showing an example of a functional configuration of a switching timing generation unit according to a first comparative example; [Figure 25] FIG. 10 is a diagram for explaining a constellation when there is a difference in the common phase error, taking quadrature phase shift keying modulated data as an example, when a switching timing generation unit according to Comparative Example 1 is used. [Figure 26] FIG. 10 is a diagram showing an example of the functional configuration of a switching timing generation unit according to a second embodiment; [Figure 27] FIG. 10 is a diagram showing an example of the functional configuration of a phase detection unit according to a second embodiment; [Figure 28] FIG. 10 is a diagram showing an example of the functional configuration of a phase conversion unit according to a second embodiment; [Figure 29] 10 is a flowchart illustrating an example of a TDD detection process according to the second embodiment. [Figure 30] 10 is a flowchart illustrating an example of a sampling phase conversion process according to the second embodiment. [Figure 31] FIG. 10 is a diagram showing an example of a functional configuration of a switching timing generation unit according to a second comparative example. [Figure 32] FIG. 10 is a diagram for explaining a constellation when a difference exists in the common phase error and the sampling phase of the baseband time domain waveform signal deviates from the sampling phase at the time of transmission, using data that has been subjected to quadrature phase shift keying as an example, when a switching timing generation unit according to Comparative Example 2 is used. [Figure 33] FIG. 11 is a diagram showing an example of the functional configuration of a switching timing generation unit according to the third embodiment; [Figure 34] FIG. 11 is a diagram showing an example of the functional configuration of a frequency error detection unit according to the third embodiment; [Figure 35]FIG. 11 is a diagram showing an example of the functional configuration of a frequency error correction unit according to the third embodiment; [Figure 36] 10 is a flowchart illustrating an example of a TDD detection process according to the third embodiment. [Figure 37] 10 is a flowchart illustrating an example of a carrier frequency correction process according to the third embodiment. [Figure 38] FIG. 11 is a diagram showing an example of a functional configuration of a switching timing generation unit according to a third comparative example. [Figure 39] FIG. 10 is a diagram for explaining a constellation when there is a difference in common phase error and a difference in carrier frequency error, taking quadrature phase shift keying modulated data as an example, when a switching timing generation unit according to Comparative Example 3 is used. [Figure 40] FIG. 13 is a diagram showing an example of the functional configuration of a switching timing generation unit according to the fourth embodiment; [Figure 41] 10 is a flowchart illustrating an example of a TDD detection process according to the fourth embodiment. [Figure 42] 10 is a flowchart illustrating an example of a sampling phase conversion process according to the fourth embodiment. [Figure 43] FIG. 13 is a diagram showing an example of a functional configuration of a switching timing generation unit according to a fourth comparative example. [Figure 44] FIG. 10 is a diagram for explaining a constellation when a difference exists in the common phase error, the sampling phase of the baseband time domain waveform signal deviates from the sampling phase at the time of transmission, and there is a difference in the carrier frequency error, using data that has been subjected to quadrature phase shift keying as an example, when a switching timing generation unit according to Comparative Example 4 is used. DETAILED DESCRIPTION OF THE INVENTION

[0010] The communication device, the control method, and the program will be described in detail below with reference to the accompanying drawings. In the following description of each embodiment and modification, parts with the same reference numerals have substantially the same functions, and the description of overlapping parts will be omitted as appropriate.

[0011] (First embodiment) 1 is a diagram showing an example of a schematic of a distributed antenna system 1 according to the first embodiment. The distributed antenna system 1 includes a master station device 10 (MU), a relay device 45 (HU), a slave station device 47 (RU), and a transmission path 80 connecting these devices. More specifically, the distributed antenna system 1 includes the master station device 10 connected to a base station 50, and one or more slave station devices 47 that relay signals between the master station device 10 and a terminal device 60 that communicates with the base station 50.

[0012] The master station device 10 is connected to a plurality of slave station devices 47 within the distributed antenna system 1. As shown in Fig. 1, the master station device 10 may be connected to a plurality of slave station devices 47 via relay devices 45, or may be connected directly to the master station device 10. Furthermore, as shown in Fig. 1, the master station device 10 may be connected to a plurality of relay devices 45 in cascade.

[0013] The master station device 10 is connected to the base station 50 via a coaxial cable, and transmits and receives wireless signals to and from the base station 50. Here, the wireless signals are signals in a wireless communication band that are transmitted to the terminal devices 60. The master station device 10 relays wireless signals received from the base station 50 to the relay device 45 or the slave station device 47. The master station device 10 also relays wireless signals received from the relay device 45 or the slave station device 47 to the base station 50.

[0014] The slave station device 47 is connected by a wired cable to an antenna 70 for wireless communication with the terminal device 60, and transmits and receives wireless signals to and from the terminal device 60 via this antenna 70. The slave station device 47 relays wireless signals received from the terminal device 60 to the master station device 10 or the relay device 45. The slave station device 47 also relays wireless signals received from the master station device 10 or the relay device 45 to the terminal device 60.

[0015] The distributed antenna system 1 having such a configuration makes it possible to connect wireless terminals that cannot be directly reached by radio waves to the base station 50, thereby expanding the communication range of the mobile communication network covered by the base station 50. For example, the distributed antenna system 1 is applicable to mobile communication networks such as 5G.

[0016] On the other hand, conventional mobile communications use a TDD (Time Division Duplex) method in which uplink and downlink communications are switched at predetermined intervals. Therefore, when the distributed antenna system 1 is applied to a mobile communications network, the distributed antenna system 1 must detect this switching and appropriately switch between DL processing and UL processing. Therefore, in order to expand the coverage area of the mobile communications network without degrading communication quality, it is necessary to accurately detect the switching between uplink and downlink communications.

[0017] In conventional wireless signals such as 4G, the presence or absence of a DL signal from a base station 50 is determined by power detection, and DL / UL switching is performed according to the determination result. Also, in a communication device that shares one DAS with multiple mobile operators, if the DL / UL switching timing of the multiple operators differs, interference occurs, so the first symbol of the DL wireless frame is detected to detect the difference in the DL / UL switching timing between operators.

[0018] However, in wireless signals such as 5G, there are cases where there is no power (signal) in the first symbol of a wireless frame. Therefore, it is difficult for the master station device 10 to accurately detect the DL / UL switching timing using a conventional power detection method or a method that detects the first symbol.

[0019] In a distributed antenna system 1 including a master station device 10 connected to a base station 50 and one or more slave station devices 47 that relay signals between the master station device 10 and terminal devices 60 that communicate with the base station 50, the master station device 10 functions as the master station device 10 or the slave station device 47 and is a communication device that receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing system. The master station device 10 receives a radio frame including a synchronization signal block (SSB: SS / PBCH Block) in the distributed antenna system 1 that employs a TDD system in which DL communication and UL communication are switched at predetermined intervals. The SSB includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast channel (PBCH). The master station device 10 detects and decodes the SSB from the received radio frame to determine where the received SSB was located within the radio frame.

[0020] The master station device 10 then estimates the DL / UL switching timing based on the position of the SSB within the radio frame and the DL / UL pattern of the TDD system. This allows the master station device 10 to estimate the DL / UL switching timing even when there is no power (signal) in the first symbol of the radio frame, such as a 5G radio signal.

[0021] Figure 2 shows an example of the data structure of a radio frame. Figure 2 shows an example of a 5G radio frame. One frame is transmitted every 10 ms. Each frame consists of 10 subframes, each transmitted every 1 ms. 5G supports multiple subcarrier frequency intervals, which result in different symbol lengths. For this reason, the concept of slots is incorporated into the radio frame, where the number of symbols per subframe is divided into multiple slots. The difference in symbol length due to the difference in subcarrier frequency intervals is absorbed by the number of slots per subframe. One slot contains 14 symbols, regardless of the subcarrier frequency interval. Figure 2 shows a case where the subcarrier frequency interval is 30 kHz, with one subframe consisting of two slots and 28 symbols. As shown in Figure 2, SSBs are placed at specific positions in the radio frame.

[0022] FIG. 3 shows an example of an SSB placement pattern in a radio frame. An SSB consists of four symbols. The SSB also has two synchronization signals, PSS and SSS, and a PBCH signal. The PBCH signal has a DMRS (DeModulation of Reference Signal) for PBCH signal, which is a reference signal for decoding the PBCH signal. An SSB index number is assigned to each SSB position in the radio frame. For example, in Japan, values from 0 to 7 are assigned, as shown in FIG. 3. Since the location of an SSB is up to the operator, after detecting an SSB, it is necessary to identify its location.

[0023] Figure 4 shows an example of a DL / UL configuration and SSB allocation for a TDD system. The SSB shown in Figure 4 has a subcarrier frequency spacing of 30 kHz, an SSB period of 20 ms, and a transmission period of 5 ms. The transmission period includes 10 slots, with the first 6 slots assigned to DL and the last 3 slots assigned to UL, with a buffer slot allocated between the DL and UL slots. In this way, the number of consecutive DL slots and the number of consecutive UL slots within the transmission period are set in advance. The buffer slot is also allocated with consecutive DL symbols, consecutive UL symbols, and blank symbols that function as a guard between them. The SSB shown in Figure 4 has a configuration in which 3 symbols are assigned to DL symbols and 3 symbols are assigned to UP symbols, and 8 symbols are assigned as guard symbols.

[0024] From the above, if the master station device 10 can detect the index number of an SSB placed at a specific position in a radio frame, it can estimate the position within the transmission cycle at which that SSB is placed. Furthermore, if the master station device 10 knows the DL / UL configuration information of the TDD system, it can estimate the DL / UL switching timing within the transmission cycle relative to the SSB placement position.

[0025] In the following, the direction of communication from the base station 50 to the terminal device 60 is referred to as the downstream direction (downlink), and the opposite direction is referred to as the upstream direction (uplink). Correspondingly, a signal transmitted in the downstream direction is referred to as a "DL signal," and a signal transmitted in the upstream direction is referred to as a "UL signal."

[0026] Furthermore, a downstream signal transmitted in the form of a frame is called a "downstream frame," and an upstream signal transmitted in the form of a frame is called an "upstream frame." Furthermore, the upstream side of a device may be referred to as the "upstream" side, and the downstream side as the "downstream." Correspondingly, a device connected to the upstream side of a device may be referred to as the "upstream device," and a device connected to the downstream side may be referred to as the "downstream device."

[0027] For example, the master station device 10 is a higher-level device than the relay device 45 and the slave station device 47, and the relay device 45 is a higher-level device than the slave station device 47. Conversely, the relay device 45 and the slave station device 47 are lower-level devices than the master station device 10, and the slave station device 47 is a lower-level device than the master station device 10 and the relay device 45.

[0028] FIG. 5 is a diagram illustrating an example of the functional configuration of the master station device 10 according to the first embodiment. The master station device 10 includes a central processing unit (CPU), memory, auxiliary storage device, and the like, all connected via a bus, and executes a program. By executing the program, the master station device 10 includes an upper input / output unit 11, a lower input / output unit 12, a downlink processing unit 13, an uplink processing unit 14, and a control unit 15. Note that all or part of the functions of the master station device 10 may be implemented using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA). The program may be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include portable media such as a flexible disk, a magneto-optical disk, a read-only memory (ROM), and a CD-ROM, and storage devices such as a hard disk built into a computer system. The program may be transmitted via a telecommunications line.

[0029] The upper input / output unit 11 is a communication interface for inputting and outputting radio signals to and from an upper device of the parent station device 10. Specifically, the upper input / output unit 11 is a communication interface for inputting and outputting radio signals to and from the base station 50 via a coaxial cable. The upper input / output unit 11 outputs DL signals received from the base station 50 to the downlink processing unit 13, and outputs UL signals input from the uplink processing unit 14 to the base station 50.

[0030] The lower-level input / output unit 12 is a communication interface for inputting and outputting radio signals to and from lower-level devices of the master station device 10. Specifically, the lower-level input / output unit 12 is a communication interface for inputting and outputting radio signals to and from the slave station device 47. The lower-level input / output unit 12 outputs a UL signal received from the slave station device 47 to the uplink processing unit 14, and outputs a DL signal input from the downlink processing unit 13 to the slave station device 47.

[0031] The downlink processing unit 13 executes a process (hereinafter referred to as "DL processing") in which the master station device 10 outputs a DL signal received from a higher-level device to a lower-level device. Specifically, the DL processing of the master station device 10 includes an AD (Analog to Digital) conversion process for the DL signal received from the base station 50, a mapping process for associating the digital signal with a frame, and the like. The downlink processing unit 13 outputs a downstream frame associated with the DL signal in the DL processing to the lower-side input / output unit 12.

[0032] The uplink processing unit 14 executes a process (hereinafter referred to as "UL processing") in which the master station device 10 outputs an UL signal received from a lower-level device to a higher-level device. Specifically, the UL processing of the master station device 10 includes a demapping process for acquiring an UL signal from an upstream frame received from the relay device 45 or the slave station device 47, and a DA (Digital to Analog) conversion process for the UL signal acquired by the demapping process. The uplink processing unit 14 outputs the UL signal converted into an analog signal in the UL processing to the upper-level input / output unit 11.

[0033] The control unit 15 has a function of switching between upstream communication and downstream communication in the master station device 10. Specifically, the control unit 15 has a function of detecting a switch between upstream communication and downstream communication, and switches between DL processing and UL processing (transmission operation) at the timing when the control unit 15 detects a switch between upstream communication and downstream communication.

[0034] 6 is a diagram showing an example of the functional configuration of the control unit 15 in the first embodiment. The control unit 15 includes a switching timing generation unit 153 and a switching unit 154.

[0035] The switching timing generation unit 153 estimates the UL period or the DL period, and notifies the timing of switching between the UL processing and the DL processing. Specifically, the switching timing generation unit 153 notifies the start timing of the estimated UL period or the DL period. The start timing may be notified as the start time of the UL period or the DL period, or may be notified as the elapsed time from the current time. Furthermore, the notification of the start timing may notify the arrival of the start timing.

[0036] The switching unit 154 switches between the UL process and the DL process at the switching timing notified by the switching timing generation unit 153.

[0037] 7 is a diagram showing an example of the functional configuration of the switching timing generation unit 153 according to the first embodiment. The switching timing generation unit 153 includes a signal receiving unit 1001, a time waveform calculation unit 1002, an FFT (Fast Fourier Transform) unit 1004, a frequency waveform phase correction unit 40, a frequency waveform calculation unit 1005, and a switching timing estimation unit 1006.

[0038] The signal receiving unit 1001 includes an ADC unit 1010, a carrier frequency conversion unit 1011, and a sampling rate conversion unit 1012. The signal receiving unit 1001 receives an OFDM signal and converts it into a baseband time domain waveform signal. More specifically, the signal receiving unit 1001 receives a radio frame including an SSB. That is, the signal receiving unit 1001 receives an SSB having a PBCH including a PSS, an SSS, and a DMRS.

[0039] The ADC unit 1010 converts the input analog signal into a digital signal and outputs it to the carrier frequency conversion unit 1011. The carrier frequency conversion unit 1011 down-converts the frequency of the input digital signal into a baseband signal and outputs it to the sampling rate conversion unit 1012. The sampling rate conversion unit 1012 converts the sampling rate of the input baseband signal to generate a baseband time-domain waveform signal, which is a baseband time-domain waveform signal. The sampling rate conversion unit 1012 then outputs the baseband time-domain waveform signal to the PSS detection unit 1013 and the FFT unit 1004.

[0040] The time waveform calculation unit 1002 includes a PSS detection unit 1013. The time waveform calculation unit 1002 extracts a portion of the baseband time domain waveform signal that is the output of the signal receiving unit 1001, and calculates the degree of similarity (for example, a correlation value) between the extracted signal and a known signal.

[0041] The PSS detector 1013 detects a PSS signal included in the time domain waveform signal. More specifically, the PSS detector 1013 detects a PSS signal placed at the beginning of an SSB from the baseband signal after sampling rate conversion, and outputs the detected timing as SSB timing to the FFT unit 1004 and the phase error detector 41 of the frequency waveform phase corrector 40. The PSS detector 1013 also determines which of multiple PSS code sequences the detected PSS signal corresponds to, and outputs this as NID2, a physical layer cell identifier, to the phase error detector 41 of the frequency waveform phase corrector 40 and the SSS detector 1016 of the frequency waveform calculator 1005. The configuration of the PSS detector 1013 will be described in detail later.

[0042] The FFT unit 1004 performs an FFT on the baseband time domain waveform signal that is the output of the sampling rate conversion unit 1012 of the signal receiving unit 1001. More specifically, the FFT unit 1004 extracts the SSB from the baseband time domain waveform signal after sampling rate conversion based on the input SSB timing and performs a Fourier transform on it. The FFT unit 1004 then outputs the SSB frequency domain waveform signal obtained by the Fourier transform to the phase correction unit 42 of the frequency waveform phase correction unit 40.

[0043] Frequency waveform phase correction unit 40 receives the baseband time axis waveform signal from sampling rate conversion unit 1012 of signal receiving unit 1001, the frequency axis waveform signal from FFT unit 1004, and the SSB timing and physical layer cell identifier NID2 from PSS detection unit 1013 of time waveform calculation unit 1002, and performs phase correction processing on the frequency axis waveform signal. Specifically, frequency waveform phase correction unit 40 includes a phase error detection unit 41 and a phase correction unit 42.

[0044] Based on the input SSB timing, the phase error detection unit 41 extracts a signal from the input baseband time domain waveform signal, detects a phase error using a PSS code sequence based on the input physical layer cell identifier NID2, and outputs the phase error to the phase correction unit 42. The configuration of the phase error detection unit 41 will be described in detail later.

[0045] Based on the input phase error, the phase corrector 42 generates a complex signal having a specified argument and absolute value, converts the phase by complex multiplying it by the input frequency axis waveform signal, and outputs the result to the frequency waveform calculator 1005. The configuration of the phase corrector 42 will be described in detail later.

[0046] The SSS detector 1016 detects the SSS signal included in the frequency domain waveform signal. More specifically, the SSS detector 1016 detects the SSS signal from the SSB frequency domain waveform signal. The SSS detector 1016 also determines which of multiple SSS sequences the detected SSS signal corresponds to. The SSS detector 1016 then outputs the determined SSS signal to the DMRS detector 1017 as NID1, which indicates the group of physical layer cell identifiers. The configuration of the SSS detector 1016 will be described in detail later.

[0047] The DMRS detector 1017 detects the DMRS signal included in the frequency domain waveform signal. More specifically, the DMRS detector 1017 detects the DMRS signal from the SSB frequency domain waveform signal. The DMRS detector 1017 determines which of multiple DMRS sequences the detected DMRS signal corresponds to. The DMRS detector 1017 then outputs ibar_SSB corresponding to the DMRS sequence to the switching timing estimation unit 1006. The configuration of the DMRS detector 1017 will be described in detail later.

[0048] The switching timing estimation unit 1006 estimates the timing of switching between uplink and downlink communications in the own device based on the calculation result of the frequency waveform calculation unit 1005. More specifically, the switching timing estimation unit 1006 estimates the position within the transmission cycle at which the SSB is allocated from the input ibar_SSB. The switching timing estimation unit 1006 estimates the DL / UL switching timing within the transmission cycle from the allocation position of the SSB to be estimated and DL / UL configuration information in a known TDD system.

[0049] 8 is a diagram illustrating an example of the functional configuration of the PSS detection unit 1013 according to the first embodiment. The PSS detection unit 1013 includes a time signal extraction unit 1131, a PSS generation unit 1132, a first correlation calculation unit 1133, and an NID2 detection unit 1134.

[0050] The time signal extraction unit 1131 extracts a portion of the time domain waveform signal. More specifically, the time signal extraction unit 1131 extracts data having a length of the OFDM symbol period from the input baseband time domain waveform signal and outputs the data to the first correlation calculation unit 1133. That is, the time signal extraction unit 1131 outputs a portion of the baseband time domain waveform signal to the first correlation calculation unit 1133.

[0051] The PSS generation unit 1132 outputs a plurality of PSS code sequences of the PSS signal and code sequence numbers that identify the PSS code sequences. More specifically, the PSS generation unit 1132 outputs the plurality of PSS code sequences as a PSS sequence to the first correlation calculation unit 1133. The PSS generation unit 1132 also outputs a PSS index, which is a code sequence number that identifies the PSS code sequence, to the NID2 detection unit 1134.

[0052] The first correlation calculation unit 1133 performs a correlation calculation between the time domain waveform signal output from the time signal extraction unit 1131 and the PSS sequence, which is a PSS code sequence from the PSS generation unit 1132, and outputs a correlation value. The first correlation calculation unit 1133 is an example of a first correlation calculation unit. That is, the first correlation calculation unit 1133 performs a correlation calculation between the baseband time domain waveform signal input from the time signal extraction unit 1131 and the PSS sequence, and outputs the correlation value, which is the calculation result, to the NID2 detection unit 1134.

[0053] The NID2 detection unit 1134 outputs the timing within a predetermined time range at which the correlation value calculated by the first correlation calculation unit 1133 is highest as the SSB timing, and outputs the PSS sequence, which is the PSS code sequence number corresponding to the PSS code sequence with the highest correlation value, as NID2, which is the cell identifier of the physical layer. More specifically, the NID2 detection unit 1134 outputs the timing within a predetermined time range at which the input correlation value is highest as the SSB timing. Furthermore, the NID2 detection unit 1134 outputs the PSS index corresponding to the PSS sequence with the highest correlation value as NID2, which is the cell identifier of the physical layer.

[0054] 9 is a diagram showing an example of the functional configuration of the phase error detection unit 41 according to the first embodiment. The phase error detection unit 41 includes a PSS code sequence selection unit 410, a data holding unit 411, a second correlation calculation unit 412, and a phase error detection unit 413.

[0055] The PSS code sequence selection unit 410 selects one of a plurality of PSS code sequences based on the input physical layer cell identifier NID2, and outputs it to the second correlation calculation unit 412.

[0056] The data holding unit 411 extracts and holds a signal from the input baseband time domain signal based on the input SSB timing, and outputs the extracted signal to the second correlation calculation unit 412 .

[0057] The second correlation calculation unit 412 calculates a correlation value between the input baseband time domain signal and the input PSS code sequence, and outputs the result to the phase error detection unit 413 .

[0058] The phase error detector 413 calculates a common phase error of the baseband time domain signal from the input correlation value, and outputs it as the phase error of the baseband time domain signal.

[0059] 10 is a diagram showing an example of complex data of the correlation value calculated by the second correlation calculation unit 412 of the phase error detection unit 41, expressed on a complex plane. When there is no common phase error, there is no phase difference between the corresponding data between the PSS code sequence and the baseband time domain signal, so the complex data of the correlation value is placed on a line with a deflection angle of 0 degrees, i.e., on the I axis. On the other hand, when there is a common phase error, the baseband time domain signal is phase-rotated by the amount of the common phase error relative to the PSS code sequence, so the complex data of the correlation value is placed on a line indicating a deflection angle corresponding to the magnitude of the common phase error. The phase error detection unit 413 of the phase error detection unit 41 calculates the common phase error of the baseband time domain signal from the slope of this line.

[0060] 11 is a diagram showing an example of the functional configuration of the phase correction unit 42 according to the first embodiment. The phase correction unit 42 includes a complex signal generation unit 420 and a phase conversion unit 421.

[0061] The complex signal generator 420 generates a complex signal having a specified argument and absolute value based on the input phase error, and outputs it to the phase converter 421 .

[0062] The phase converter 421 performs complex multiplication of the input complex signal and the baseband frequency axis signal to convert the phase of the baseband frequency axis signal, and outputs the converted signal to the frequency waveform calculator 1005 .

[0063] 12 is a diagram showing an example of the functional configuration of the SSS detection unit 1016 according to the first embodiment. The SSS detection unit 1016 includes an SSS extraction unit 1161, an SSS generation unit 1162, a data determination unit 1163, a comparison operation unit 1164, and an NID1 detection unit 1165.

[0064] The SSS extraction unit 1161 extracts the frequency components to which the SSS signal is assigned from the frequency axis waveform signal. More specifically, the SSS extraction unit 1161 extracts the frequency components to which the SSS signal is assigned from the SSB symbol that is the input frequency axis waveform signal, and outputs the extracted frequency components to the data determination unit 1163. That is, the SSS extraction unit 1161 outputs the frequency components of the SSS signal.

[0065] The SSS generation unit 1162 outputs a plurality of SSS sequences corresponding to NID2, which is the physical layer cell identifier output from the PSS detection unit 1013, and an SSS index that identifies the SSS sequence. More specifically, the SSS generation unit 1162 generates a plurality of SSS code sequences based on the input NID2, and outputs them as SSS sequences to the comparison operation unit 1164. The SSS generation unit 1162 also outputs the SSS index that identifies the SSS sequence to the NID1 detection unit 1165.

[0066] The data determination unit 1163 determines the demodulated data corresponding to the IQ complex coordinate position of the SSS signal output from the SSS extraction unit 1161, and outputs a series of data determined for the entire SSS signal to the comparison operation unit 1164 as an SSS sequence.

[0067] The comparison operation unit 1164 compares the SSS sequence from the data determination unit 1163 with the SSS sequence from the SSS generation unit 1162, and outputs the number of matching values as the comparison result to the NID1 detection unit 1165. Note that the comparison operation unit 1164 may also output a degree of similarity indicating the degree of similarity between the SSS sequence from the data determination unit 1163 and the SSS sequence from the SSS generation unit 1162 to the NID1 detection unit 1165.

[0068] The NID1 detection unit 1165 determines the one with the highest number of matches from the comparison results that are outputs from the comparison operation unit 1164. Then, the NID1 detection unit 1165 outputs the SSS index corresponding to the SSS sequence with the highest number of matches as NID1 that indicates a group of cell identifiers in the physical layer.

[0069] 13 is a diagram showing an example of the functional configuration of the DMRS detector 1017 according to the first embodiment. The DMRS detector 1017 includes a DMRS extractor 1171, a DMRS generator 1172, a data determiner 1173, a comparison calculator 1174, and an ibar_SSB detector 1175.

[0070] DMRS extraction section 1171 extracts frequency components to which DMRS signals are assigned from the frequency domain waveform signal. More specifically, DMRS extraction section 1171 extracts frequency components to which DMRS signals are assigned from SSB symbols, which are the input frequency domain waveform signal, and outputs the extracted frequency components to data determination section 1173. That is, DMRS extraction section 1171 outputs the frequency components of the DMRS signal.

[0071] The DMRS generator 1172 outputs a plurality of DMRS sequences corresponding to NID1 indicating a group of physical layer cell identifiers, which is the output of the SSS detector 1016, and an ibar_SSB index that identifies the DMRS sequences. More specifically, the DMRS generator 1172 generates a plurality of code sequences based on the input NID1, and outputs these as DMRS sequences to the comparison calculation unit 1174. The DMRS generator 1172 also outputs the DMRS index that identifies the DMRS sequence to the ibar_SSB detector 1175.

[0072] The data decision section 1173 decides the demodulated data corresponding to the IQ complex coordinate position of the DMRS signal output from the DMRS extraction section 1171, and outputs the series of decided data for the entire DMRS signal to the comparison operation section 1174 as a DMRS sequence.

[0073] Comparison operation section 1174 compares the DMRS sequence from data determination section 1173 with the DMRS sequence from DMRS generation section 1172, and outputs the number of matches as the comparison result to ibar_SSB detection section 1175.

[0074] ibar_SSB detection section 1175 determines the DMRS sequence with the highest number of matches from the comparison results output by comparison operation section 1174. Then, ibar_SSB detection section 1175 outputs the ibar_SSB index corresponding to the DMRS sequence with the highest number of matches as ibar_SSB.

[0075] Next, the TDD detection process executed by the master station device 10 according to the first embodiment and various processes executed in the TDD detection process, such as frequency waveform phase correction process, will be described.

[0076] FIG. 14 is a flowchart illustrating an example of the TDD detection process according to the first embodiment.

[0077] Here, it is assumed that the distributed antenna system 1 is receiving either a DL signal or an UL analog radio signal, and that the distributed antenna system 1 is capable of referencing identification information indicating whether the TDD detection processing period is enabled or disabled, and TDD DL / UL configuration information.

[0078] The signal receiving unit 1001 performs AD conversion, frequency down-conversion, and sampling rate conversion on the input analog signal, and acquires a baseband time-domain waveform signal as the received signal (step S1).

[0079] Next, the time waveform calculation unit 1002 executes time waveform processing (step S2). That is, the time waveform calculation unit 1002 detects the PSS signal placed at the beginning of the SSB from the baseband signal, and outputs the detected timing as SSB timing to the FFT unit 1004 and the phase error detection unit 41 of the frequency waveform phase correction unit 40. The time waveform calculation unit 1002 also determines which of multiple PSS code sequences the detected PSS signal corresponds to, and notifies the phase error detection unit 41 of the frequency waveform phase correction unit 40, the FFT unit 1004, and the SSS detection unit 1016 of the frequency waveform calculation unit 1005 of this as NID2, which is a cell identifier of the physical layer.

[0080] Next, the FFT unit 1004 extracts the SSB from the baseband signal based on the notified SSB timing, performs a Fourier transform on it, and notifies the frequency waveform phase correction unit 40 of the completion of the FFT process (step S3).

[0081] Next, the frequency waveform phase correction unit 40 receives the baseband time axis waveform signal from the sampling rate conversion unit 1012 of the signal receiving unit 1001, the frequency axis waveform signal from the FFT unit 1004, and the SSB timing and physical layer cell identifier NID2 from the PSS detection unit 1013 of the time waveform calculation unit 1002, and performs phase correction processing on the frequency axis waveform signal (step S4).

[0082] Specifically, in frequency waveform phase correction unit 40, phase error detection unit 41 extracts a signal from the baseband time domain waveform signal input from sampling rate conversion unit 1012 based on the SSB timing notified from PSS detection unit 1013, and detects a phase error using a PSS code sequence based on the physical layer cell identifier NID2 input from PSS detection unit 1013. Phase correction unit 42 converts the phase based on the phase error detected by phase error detection unit 41, and notifies frequency waveform calculation unit 1005 of the completion of frequency waveform phase correction.

[0083] Next, the frequency waveform calculation unit 1005 detects the index number of the SSB, which indicates where the SSB is located within the transmission period (step S5).

[0084] If the TDD detection process is within a valid period (step S6; Yes), the signal receiving unit 1001, the time waveform calculation unit 1002, the FFT unit 1004, the frequency waveform phase correction unit 40, and the frequency waveform calculation unit 1005 repeatedly execute steps S1 to S5.

[0085] When the TDD detection processing period ends (step S6; No), the switching timing estimation unit 1006 estimates where the SSB is located within the transmission period, and estimates the DL / UL switching timing within the transmission period from this SSB location and the known TDD DL / UL configuration information (step S7).

[0086] 15 is a flowchart showing an example of the time waveform processing according to the first embodiment. That is, the flowchart shown in FIG. 15 is the time waveform processing of step S2 shown in FIG.

[0087] The time signal extraction unit 1131 determines whether the TDD detection processing period is valid (step S21). If the TDD detection processing period is invalid (step S21; No), the time signal extraction unit 1131 ends the time waveform processing. On the other hand, if the TDD detection processing period is valid (step S21; Yes), the time waveform calculation unit 1002 executes the subsequent processing.

[0088] Next, the first correlation calculation unit 1133 calculates correlation values by performing correlation calculations between the baseband time domain waveform signal and a plurality of PSS code sequences (step S22).

[0089] Next, the NID2 detection unit 1134 determines whether a significant correlation value exists among the multiple correlation calculations (step S23). A significant correlation value here may be one that exceeds a predetermined threshold value or one that is the largest since the start of time waveform processing. If a significant correlation value does not exist (step S23; No), the NID2 detection unit 1134 returns to step S21. On the other hand, if a significant correlation value exists (step S23; Yes), the NID2 detection unit 1134 executes the subsequent processing.

[0090] The NID2 detection unit 1134 stores the PSS sequence, which is the PSS code sequence number corresponding to the significant correlation value, as NID2 (step S24).

[0091] The NID2 detection unit 1134 stores the system time at which the significant correlation value was calculated as the PSS correlation detection time (step S25).

[0092] The NID2 detection unit 1134 notifies the FFT processing (step S3) shown in step S3 of the system time at which the significant correlation value was calculated as the SSB timing (step S26).

[0093] 16 is a flowchart showing an example of FFT processing according to the first embodiment. That is, the flowchart shown in FIG. 16 is the FFT processing of step S3 shown in FIG.

[0094] The FFT unit 1004 determines whether or not the SSB timing has been notified (step S31). If there has been no notification (step S31; No), the FFT unit 1004 ends the FFT process. On the other hand, if there has been notification (step S31; Yes), the FFT unit 1004 executes the subsequent process.

[0095] Based on the notified SSB timing, the FFT unit 1004 extracts the SSB from the frequency-converted (corrected) baseband signal received from the sampling rate conversion unit 1012 of the signal receiving unit 1001 (step S32).

[0096] The FFT unit 1004 performs a Fourier transform on the extracted SSB time-domain waveform signal to a frequency-domain waveform signal (step S33).

[0097] The FFT unit 1004 notifies the frequency waveform phase correction process shown in step S4 of the completion of the FFT process (step S34).

[0098] 17 is a flowchart showing an example of the frequency waveform phase correction process according to the first embodiment. That is, the flowchart shown in FIG. 17 is the frequency waveform phase correction process of step S4 shown in FIG.

[0099] The frequency waveform phase correction unit 40 determines whether or not the SSB timing has been notified (step S40). If there has been no notification (step S41; No), the phase error detection unit 41 ends the frequency waveform phase correction. On the other hand, if there has been a notification (step S41; Yes), the frequency waveform phase correction unit 40 executes the subsequent processing.

[0100] The frequency waveform phase correction unit 40 reads out the NID2 stored in step S24 (step S42).

[0101] Next, the frequency waveform phase correction unit 40 executes a phase error detection process (step S43).

[0102] Next, the frequency waveform phase correction unit 40 executes a phase correction process (step S44).

[0103] Next, the frequency waveform phase correction unit 40 notifies the frequency waveform processing unit of the end of the frequency waveform phase correction processing (step S45).

[0104] 18 is a flowchart showing an example of the phase error detection process according to the first embodiment. That is, the flowchart shown in FIG. 18 is the phase error detection process of step S43 shown in FIG.

[0105] The data holding unit 411 of the phase error detection unit 41 holds the baseband time domain signal based on the notified SSB timing (step S431).

[0106] Subsequently, the PSS code sequence selection unit 410 of the phase error detection unit 41 reads out the NID2 stored in step S24 (step S432).

[0107] Next, the PSS code sequence selection unit 410 of the phase error detection unit 41 selects a PSS code sequence from among a plurality of PSS code sequences (from PSS code sequence 0, PSS code sequence 1, and PSS code sequence 2 in the example of FIG. 9) based on NID2 (step S433). The PSS code sequence selection unit 410 outputs the selected PSS code sequence to the second correlation calculation unit 412.

[0108] Next, the second correlation calculation unit 412 of the phase error detection unit 41 calculates a correlation value between the time domain signal held by the data holding unit 411 and the PSS code sequence selected by the PSS code sequence selection unit 410 (step S434). The second correlation calculation unit 412 outputs the calculated correlation value to the phase error detection unit 413.

[0109] Next, the phase error detector 413 of the phase error detector 41 calculates the amount of phase rotation of the time domain signal from the correlation value calculated by the second correlation calculator 412, and adopts the calculated amount of phase rotation as the phase error of the time domain signal (step S435). The phase error detector 413 outputs the adopted phase error to the phase corrector 42.

[0110] 19 is a flowchart showing an example of the phase correction process according to the first embodiment. That is, the flowchart shown in FIG. 19 is the phase correction process of step S44 shown in FIG.

[0111] The complex signal generation unit 420 of the phase correction unit 42 generates a complex signal having a specified argument and absolute value based on the phase error calculated by the phase error detection unit 413 of the phase error detection unit 41 (step S441). The complex signal generation unit 420 outputs the generated complex signal to the phase conversion unit 421.

[0112] The phase conversion unit 421 of the phase correction unit 42 converts the phase of the frequency axis signal by complex multiplying the frequency axis signal received from the FFT unit by the complex signal received from the complex signal generation unit 420 (step S442).

[0113] 20 is a flowchart showing an example of frequency waveform processing according to the first embodiment. That is, the flowchart shown in FIG. 20 shows the frequency waveform processing of step S5 shown in FIG.

[0114] The frequency waveform calculation unit 1005 determines whether or not it has received a notification that the FFT process is complete (step S51). If it has not received a notification (step S51; No), the frequency waveform calculation unit 1005 ends the frequency waveform process. On the other hand, if it has received a notification (step S51; Yes), the frequency waveform calculation unit 1005 executes the subsequent process.

[0115] Next, the SSS detection unit 1016 executes the SSS detection process (step S52).

[0116] Next, the frequency waveform calculation unit 1005 determines whether a significant SSS has been detected (step S53). Here, a significant SSS is determined when the similarity to the SSS sequence calculated in the SSS detection process exceeds a predetermined threshold and is at its maximum. If a significant SSS does not exist (step S53; No), the frequency waveform calculation unit 1005 ends the frequency waveform processing. On the other hand, if a significant SSS exists (step S53; Yes), the frequency waveform calculation unit 1005 performs the subsequent processing.

[0117] Next, the DMRS detector 1017 performs DMRS detection processing (step S54).

[0118] Next, the frequency waveform calculation unit 1005 determines whether a significant DMRS has been detected (step S55). A significant DMRS is determined here when the similarity to the DMRS sequence calculated during the DMRS detection process exceeds a predetermined threshold and is at its maximum. If no significant DMRS exists (step S55; No), the frequency waveform calculation unit 1005 ends the frequency waveform process. On the other hand, if a significant DMRS exists (step S55; Yes), the frequency waveform calculation unit 1005 performs the subsequent process.

[0119] Next, the frequency waveform calculation unit 1005 notifies the switching timing estimation process shown in step S7 of the completion of the frequency waveform processing (step S56).

[0120] 21 is a flowchart showing an example of the SSS detection process according to the first embodiment. That is, the flowchart shown in FIG. 21 is the SSS detection process of step S52 shown in FIG.

[0121] The SSS extraction unit 1161 extracts the frequency components in which the SSS signal is allocated from the frequency axis waveform signal (step S521).

[0122] Next, the SSS generation unit 1162 reads out the NID2 stored in step S24 (step S522).

[0123] Next, the SSS generation unit 1162 generates a plurality of SSS sequences and an SSS index for identifying the SSS sequences based on NID2 (step S523).

[0124] Next, the comparison operation unit 1164 detects the SSS sequence that is most similar to the extracted SSS signal (step S524).

[0125] Next, the NID1 detection unit 1165 stores the SSS index corresponding to the most similar SSS sequence as NID1 (step S525).

[0126] 22 is a flowchart showing an example of the DMRS detection process according to the first embodiment. That is, the flowchart shown in FIG. 22 is the DMRS detection process of step S54 shown in FIG.

[0127] The DMRS extraction unit 1171 extracts the frequency components to which the DMRS signals are assigned from the frequency axis waveform signal (step S541).

[0128] Next, the DMRS generator 1172 reads out NID1 stored in step S525 (step S542).

[0129] Next, the DMRS generator 1172 generates a plurality of DMRS sequences and an ibar_SSB index for identifying the DMRS sequences based on NID1 (step S543).

[0130] Next, comparison operation section 1174 detects the DMRS sequence that is most similar to the extracted DMRS signal (step S544).

[0131] Next, ibar_SSB detector 1175 stores the ibar_SSB index corresponding to the DMRS sequence with the highest similarity as ibar_SSB (step S545).

[0132] 23 is a flowchart showing an example of the switching timing estimation process according to the first embodiment. That is, the flowchart shown in FIG. 23 is the switching timing estimation process of step S7 shown in FIG.

[0133] The switching timing estimation unit 1006 determines whether or not the completion of frequency waveform processing has been notified (step S71). If there has been no notification (step S71; No), the switching timing estimation unit 1006 ends the switching timing estimation process. On the other hand, if there has been a notification (step S71; Yes), the switching timing estimation unit 1006 executes the subsequent process.

[0134] Next, the switching timing estimation unit 1006 reads out the PSS correlation detection time stored in step S25 (step S72).

[0135] Next, the switching timing estimation unit 1006 reads out the ibar_SSB stored in step S545 (step S73).

[0136] Next, the switching timing estimation unit 1006 estimates the position of the frame in which the currently detected SSB is arranged, based on the known SSB arrangement pattern and the ibar_SSB read out in step S72 (step S74).

[0137] Next, the switching timing estimation unit 1006 estimates the timing at which the next TDD switching will occur based on the known TDD DL / UL configuration information, the PSS correlation detection time read in step S72, and the SSB frame position estimated in step S74 (step S75).

[0138] As described above, the switching timing generation unit 153 according to the first embodiment includes a signal receiving unit 1001, a time waveform calculation unit 1002, an FFT unit 1004, a frequency waveform phase correction unit 40, a frequency waveform calculation unit 1005, and a switching timing estimation unit 1006.

[0139] A signal receiving unit 1001 receives an OFDM signal and converts it into a baseband OFDM signal. A time waveform calculating unit 1002 extracts a portion of the time domain waveform signal that is the output of the signal receiving unit, and calculates the degree of similarity between the extracted signal and a known signal.

[0140] The FFT unit 1004 performs a Fourier transform on the time axis waveform signal of the signal receiving unit 1001. The frequency axis waveform phase correcting unit 40 corrects the phase of the frequency axis waveform signal that is the output of the FFT unit 1004.

[0141] The frequency waveform calculation unit 1005 extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit 40, and calculates the degree of similarity between the extracted signal and a known signal. The switching timing estimation unit 1006 estimates the timing of switching between uplink and downlink communication in the own device based on the result of the frequency waveform calculation unit 1005.

[0142] According to the switching timing generation unit 153 of the first embodiment, a common phase error is calculated from the phase difference between a part of a signal extracted from a time domain waveform signal and a known signal, and the phase of the frequency domain waveform signal is corrected, thereby reducing the phase error. Therefore, the common phase error can be reduced by a simple method that does not require a mechanism for controlling the frequency and phase of a local oscillator clock or a baseband system clock, or waveform equalization processing that estimates transmission path characteristics and corrects the waveform after FFT. As a result, even when a common phase error exists in the TDD system, the DL / UL switching timing can be estimated inexpensively and accurately.

[0143] (Comparative Example 1) The effect of the switching timing generation section 153 according to the first embodiment will be described in more detail with reference to a switching timing generation section 153a according to a first comparative example.

[0144] Fig. 24 is a diagram showing an example of the functional configuration of a switching timing generation unit 153a according to Comparative Example 1. As shown in Fig. 24, the switching timing generation unit 153a includes a signal receiving unit 1001, a time waveform calculation unit 1002, an FFT unit 1004, a frequency waveform calculation unit 1003, and a switching timing estimation unit 1006. That is, when Fig. 24 is compared with Fig. 7, the switching timing generation unit 153a according to Comparative Example 1 shown in Fig. 24 does not include the frequency waveform phase correction unit 40 shown in Fig. 7.

[0145] FIG. 25 is a diagram for explaining a constellation when there is a difference in the common phase error, taking quadrature phase shift keying (QPSK) data as an example, when using the switching timing generation unit 153a according to the first comparative example.

[0146] Figure 25(a) shows an example of a constellation when there is no common phase error. As shown in Figure 25(a), when there is no common phase error, the data in the constellation converges to a single point in each of the four quadrants.

[0147] Figure 25(b) shows a case where the common phase error is 30 degrees. As shown in Figure 25(b), when the common phase error is 30 degrees, the constellation undergoes a 30-degree counterclockwise phase rotation. In the case of quadrature phase-shift keying, a 30-degree phase rotation does not result in data movement beyond the quadrant of the complex plane, and no data discrimination error occurs. However, in the case of phase-shift keying or quadrature amplitude modulation (QAM), which have a higher modulation depth, data movement beyond the quadrant of the complex plane occurs, and this is discriminated as an erroneous value by the frequency waveform calculation unit 1003 located downstream of the FFT unit 1004.

[0148] Figure 25(c) shows a case where the common phase error is 60 degrees. As shown in Figure 25(c), when the common phase error is 60 degrees, the constellation undergoes a phase rotation of 60 degrees in the counterclockwise direction. With a phase rotation of 60 degrees, even in the case of quadrature phase shift keying, the data moves across quadrants of the complex plane, and is determined to be an erroneous value by the frequency waveform calculation unit 1003 located downstream of the FFT unit 1004.

[0149] As described above, when data modulated using phase shift keying (PSK) or quadrature amplitude modulation is judged in the presence of a phase error, the reception characteristics are significantly degraded. For this reason, data judgment is generally performed after correcting the phase error. To correct the phase error, a mechanism for controlling the frequency and phase of the local oscillator clock or baseband system clock, or waveform equalization processing that estimates the transmission path characteristics and corrects the waveform after FFT, can be used.

[0150] However, these processes are complex and expensive to implement. In particular, controlling the clock frequency and phase requires collecting error information from many functional blocks located after the AD converter and carefully changing the clock, which makes implementing the mechanism expensive.

[0151] Furthermore, due to the time restrictions imposed by the time division multiplexing system for switching between transmission and reception, there is a time restriction on the time from signal reception to completion of demodulation of the synchronization signal block, which also applies to the control of the clock frequency and phase and the waveform equalization process.

[0152] As a result, in order to correct the phase error, the processing circuits for demodulating the synchronization signal block, clock control, and waveform equalization must operate at high speed, which increases the cost of implementing the device.

[0153] In contrast to this, the switching timing generation unit 153 according to this embodiment can estimate the DL / UL switching timing inexpensively and accurately, even when a common phase error exists, without requiring the above-mentioned costs.

[0154] (Second embodiment) Next, a description will be given of a switching timing generation unit 153 according to the second embodiment. The switching timing generation unit 153 according to the second embodiment executes a correction process for a common phase error due to phase noise when executing a sampling phase conversion process for correcting a sampling phase that deviates from the original phase.

[0155] Fig. 26 is a diagram showing an example of the functional configuration of the switching timing generation unit 153 according to the second embodiment. When Fig. 26 is compared with Fig. 7, it differs in that the switching timing generation unit 153 according to the second embodiment shown in Fig. 26 further includes a sampling phase conversion unit 30.

[0156] The sampling rate conversion unit 1012 of the signal receiving unit 1001 outputs the baseband time domain waveform signal to the PSS detection unit 1013 and the sampling phase conversion unit 30 .

[0157] The sampling phase conversion unit 30 performs sampling phase conversion processing to convert the sampling phase of the time domain waveform signal that is the output of the signal receiving unit 1001. Specifically, the sampling phase conversion unit 30 includes a phase detection unit 31 and a phase conversion unit 32.

[0158] The phase detector 31 detects the optimum phase that provides the best sampling phase for the time domain waveform signal based on the SSB timing and physical layer cell identifier NID2 that are output from the PSS detector 1013. That is, the phase detector 31 extracts a signal from the input baseband signal after sampling rate conversion based on the input SSB timing, detects the optimum phase from among a plurality of predetermined sampling phases based on the input physical layer cell identifier NID2, and outputs the optimum phase to the phase converter 32.

[0159] 27 is a diagram showing an example of the functional configuration of the phase detection unit 31 in the second embodiment. Specifically, the phase detection unit 31 includes a PSS code sequence selection unit 310, a data holding unit 311, a phase conversion unit 312, a third correlation calculation unit 313, and a phase determination unit 314.

[0160] The PSS code sequence selection unit 310 selects one of a plurality of PSS code sequences based on the input physical layer cell identifier NID2, and outputs the selected PSS code sequence to the third correlation calculation unit 313.

[0161] The data holding unit 311 extracts and holds a signal from the input baseband time domain signal based on the input SSB timing, and outputs the signal to the phase conversion unit 312 .

[0162] The phase converter 312 converts the input baseband time domain signal into a plurality of predetermined sampling phases and outputs the phases to the third correlation calculator 313 .

[0163] The third correlation calculation unit 313 calculates a correlation value between the input PSS code sequence and each of the input phase-converted baseband time domain signals, and outputs the calculated correlation value to the phase determination unit 314 .

[0164] The phase determination unit 314 determines the time axis signal that is most similar to the PSS code sequence from the input correlation value, and outputs the sampling phase corresponding to that signal as the optimum phase.

[0165] The phase conversion unit 32 converts the sampling phase of the baseband time domain waveform signal received from the sampling rate conversion unit 1012 based on the optimal phase that is output from the phase detection unit 31. That is, based on the input optimal phase, the phase conversion unit 32 converts the sampling phase of the input baseband signal after sampling rate conversion into the optimal phase, and outputs the converted phase to the FFT unit 1004.

[0166] 28 is a diagram showing an example of the functional configuration of the phase conversion unit 32 in the second embodiment. The phase conversion unit 32 includes a filter coefficient selection unit 320 and a filter calculation unit 321.

[0167] The filter coefficient selection unit 320 selects one of a plurality of filter coefficients based on the input optimum phase and outputs the selected one to the filter calculation unit 321. For example, the filter coefficient selection unit 320 selects a filter coefficient for making the sampling phase coincident with or approach the optimum phase from among filter coefficient 0, filter coefficient 1, filter coefficient 2, and filter coefficient 3. Note that the four filter coefficients 0, 1, 2, and 3 shown in FIG. 28 are merely an example, and the number of filter coefficients to be selected can be set arbitrarily.

[0168] The filter calculation unit 321 converts the input baseband time domain signal into a predetermined sampling phase based on the input filter coefficient, and outputs the converted signal.

[0169] 26 , the FFT unit 1004 extracts the SSB from the baseband time domain waveform signal after sampling phase conversion received from the phase conversion unit 32 based on the input SSB timing, and performs a Fourier transform on it. The FFT unit 1004 then outputs the SSB frequency domain waveform signal obtained by the Fourier transform to the phase correction unit 42 of the frequency waveform phase correction unit 40.

[0170] The frequency waveform phase correction unit 40 receives a baseband time axis waveform signal from the sampling rate conversion unit 1012 of the signal receiving unit 1001, a frequency axis waveform signal from the FFT unit 1004, and SSB timing and physical layer cell identifier NID2 from the PSS detection unit 1013 of the time waveform calculation unit 1002, and performs phase correction processing on the frequency axis waveform signal.

[0171] Fig. 29 is a flowchart showing an example of TDD detection processing according to the second embodiment. Comparing Fig. 29 with Fig. 14, it differs in that a sampling phase conversion process (step S2a) is inserted before the FFT process in step S3.

[0172] Fig. 30 is a flowchart showing an example of the sampling phase conversion process according to the second embodiment. That is, the flowchart shown in Fig. 30 is the sampling phase conversion process of step S2a shown in Fig. 29.

[0173] The phase detection unit 31 of the sampling phase conversion unit 30 determines whether or not the SSB timing has been notified from the time waveform calculation unit 1002 (step S21a). If no notification has been received, the phase detection unit 31 exits the sampling phase conversion process (No in step S21a), and if a notification has been received, the phase detection unit 31 executes the process of the subsequent step S22a (Yes in step S21a).

[0174] Next, the phase detection unit 31 reads out the NID2 stored in step S24 (step S22a).

[0175] Next, the phase detection unit 31 executes a phase detection process (step S23a).

[0176] Next, the phase conversion unit 32 executes a phase conversion process (step S24a).

[0177] Next, the phase conversion unit 32 notifies the FFT unit 1004 of the SSB timing (step S25a).

[0178] The effect of the switching timing generation section 153 according to the second embodiment will be described in more detail with reference to a switching timing generation section 153b according to a second comparative example.

[0179] Fig. 31 is a diagram showing an example of the functional configuration of a switching timing generation unit 153b according to comparative example 2. When Fig. 31 is compared with Fig. 26, the switching timing generation unit 153b according to comparative example 2 in Fig. 31 does not include the frequency waveform phase correction unit 40 shown in Fig. 26.

[0180] FIG. 32 is a diagram illustrating a constellation when there is a difference in the common phase error and a difference in the sampling phase of the baseband time domain waveform signal, using data that has been quadrature phase-shift keyed as an example, when using the switching timing generation unit 153b according to Comparative Example 2.

[0181] The top of Figure 32 shows an example of a constellation when there is only a common phase error and no deviation from the sampling phase at the time of transmission (corresponding to Figure 25). As shown in the top of Figure 32, although phase rotation due to the common phase error can be seen, there is no effect related to deviation from the sampling phase.

[0182] The middle part of FIG. 32 shows an example of a constellation when the sampling phase deviates by 25% from the upper part.

[0183] The lower part of FIG. 32 shows an example of a constellation when the sampling phase deviates by 50% from that shown in the upper part.

[0184] As can be seen by comparing (a), (d), and (g) in the left column of Figure 32, when the sampling phase deviates, the constellation rotates in the phase direction, and the greater the degree of deviation, the greater the amount of phase rotation. Focusing on the rotation in the phase direction in the center and right columns also shows the same tendency as in the left column.

[0185] When the signals in the middle and bottom rows of Figure 32 are provided to the switching timing generation unit 153b according to Comparative Example 2, the sampling phase conversion unit 30 suppresses phase rotation due to deviation in the sampling phase, correcting (d) and (g) in Figure 32 to a state close to (a), (e) and (h) to (b), and (f) and (j) to a state close to (c). However, the switching timing generation unit 153b according to Comparative Example 2 does not include the frequency waveform phase correction unit 40. Therefore, the phase rotation due to the phase error cannot be suppressed, and the phase rotation remains as it is, as shown in (b) and (c).

[0186] In contrast, the switching timing generation unit 153 according to the second embodiment, when performing sampling phase conversion processing to correct a sampling phase that deviates from the original phase, calculates a common phase error from the phase difference between a portion of a signal extracted from a time-domain waveform signal and a known signal, and corrects the phase of the frequency-domain waveform signal, thereby reducing the phase error. Therefore, it is possible to reduce the common phase error using a simple method that does not require a mechanism for controlling the frequency and phase of a local oscillator clock or a baseband system clock, or waveform equalization processing that estimates transmission path characteristics and corrects the waveform after FFT. As a result, even when a common phase error exists in the TDD system, it is possible to accurately estimate the DL / UL switching timing at low cost.

[0187] (Third embodiment) Next, a description will be given of a switching timing generation unit 153 according to the third embodiment. The switching timing generation unit 153 according to the third embodiment executes a correction process for a common phase error due to phase noise when executing a correction process for a carrier frequency to remove inter-carrier interference due to a carrier frequency error.

[0188] Fig. 33 is a diagram showing an example of the functional configuration of the switching timing generation unit 153 according to the third embodiment. When Fig. 33 is compared with Fig. 7, the difference is that the switching timing generation unit 153 according to the third embodiment shown in Fig. 33 further includes a carrier frequency correction unit 20.

[0189] The sampling rate conversion unit 1012 of the signal receiving unit 1001 outputs the baseband time axis waveform signal to the PSS detection unit 1013 and the carrier frequency correction unit 20 .

[0190] The carrier frequency correction unit 20 receives the baseband time domain signal from the sampling rate conversion unit 1012 of the signal receiving unit 1001, and the SSB timing and the physical layer cell identifier NID2 from the PSS detection unit 1013, and performs carrier frequency correction processing. Specifically, the carrier frequency correction unit 20 includes a frequency error detection unit 21 and a frequency error correction unit 22.

[0191] The frequency error detection unit 21 extracts a signal from the input sampling rate converted baseband signal based on the input SSB timing, detects a carrier frequency error using a PSS code sequence based on the input physical layer cell identifier NID2, and outputs the detected carrier frequency error to the frequency error correction unit 22. The configuration of the frequency error detection unit 21 will be described in detail later.

[0192] The frequency error correction unit 22 generates a complex sine wave of a specified frequency based on the input carrier frequency error, corrects the carrier frequency by complex multiplying it by the input baseband signal after sampling rate conversion, and outputs the corrected carrier frequency to the FFT unit 1004. The configuration of the frequency error correction unit 22 will be described in detail later.

[0193] 34 is a diagram showing an example of the functional configuration of the frequency error detection unit 21 according to the third embodiment. The frequency error detection unit 21 includes a PSS code sequence selection unit 210, a data holding unit 211, a fourth correlation calculation unit 212, and an error detection unit 213.

[0194] The PSS code sequence selection unit 210 selects one of a plurality of PSS code sequences based on the input physical layer cell identifier NID2, and outputs the selected PSS code sequence to the fourth correlation calculation unit 212.

[0195] The data holding unit 211 extracts and holds a signal from the input baseband time domain signal based on the input SSB timing, and outputs the extracted signal to the fourth correlation calculation unit 212 .

[0196] The fourth correlation calculation unit 212 calculates a correlation value between the input baseband time domain signal and the input PSS code sequence, and outputs the result to the error detection unit 213 .

[0197] The error detection unit 213 calculates the amount of phase rotation of the baseband time domain signal from the input correlation value, and outputs it as a carrier frequency error of the baseband time domain signal.

[0198] 35 is a diagram showing an example of the functional configuration of the frequency error corrector 22 according to the third embodiment. The frequency error corrector 22 includes a sine wave generator 220 and a frequency converter 221.

[0199] The sine wave generating unit 220 generates a complex sine wave of a specified frequency based on the input frequency error, and outputs it to the frequency converting unit 221 .

[0200] The frequency conversion unit 221 performs complex multiplication of the input complex sine wave and the baseband time domain signal to convert the carrier frequency of the baseband time domain signal and outputs the converted signal to the FFT unit 1004 .

[0201] 33, based on the input SSB timing, the FFT unit 1004 extracts the SSB from the carrier frequency corrected baseband time domain waveform signal received from the carrier frequency correction unit 20 and performs a Fourier transform on it. The FFT unit 1004 then outputs the SSB frequency domain waveform signal obtained by the Fourier transform to the phase correction unit 42 of the frequency waveform phase correction unit 40.

[0202] The frequency waveform phase correction unit 40 receives a baseband time axis waveform signal from the sampling rate conversion unit 1012 of the signal receiving unit 1001, a frequency axis waveform signal from the FFT unit 1004, and SSB timing and physical layer cell identifier NID2 from the PSS detection unit 1013 of the time waveform calculation unit 1002, and performs phase correction processing on the frequency axis waveform signal.

[0203] Fig. 36 is a flowchart showing an example of TDD detection processing according to the third embodiment. Comparing Fig. 36 with Fig. 14, a difference is that a carrier frequency correction processing (step S2b) is inserted before the FFT processing in step S3.

[0204] 37 is a flowchart showing an example of the carrier frequency correction process according to the third embodiment. That is, the flowchart shown in FIG. 37 is the carrier frequency correction process of step S2b shown in FIG.

[0205] 37, the frequency error detection unit 21 of the carrier frequency correction unit 20 determines whether or not the SSB timing has been notified from the time waveform calculation unit 1002 (step S21b). If no notification has been received, the carrier frequency correction unit 20 exits the carrier frequency correction process (No in step S21b), and if notification has been received, the carrier frequency correction unit 20 executes the process of the subsequent step S22b (Yes in step S21b).

[0206] Next, the frequency error detection unit 21 reads out the NID2 stored in step S24 (step S22b).

[0207] Subsequently, the frequency error detection unit 21 executes a frequency error detection process (step S23b).

[0208] Subsequently, the frequency error correction unit 22 executes the frequency error correction process (step S24b).

[0209] Next, the frequency error correction unit 22 notifies the FFT processing of the SSB timing (step S25b).

[0210] The effect of the switching timing generation section 153 according to the third embodiment will be described in more detail with reference to a switching timing generation section 153c according to a third comparative example.

[0211] Fig. 38 is a diagram showing an example of the functional configuration of a switching timing generation unit 153c according to comparative example 3. When Fig. 38 is compared with Fig. 33, the switching timing generation unit 153c according to comparative example 3 in Fig. 38 does not include the frequency waveform phase correction unit 40 shown in Fig. 33.

[0212] FIG. 39 is a diagram illustrating a constellation when there is a difference in the common phase error and a difference in the carrier frequency error of the baseband time domain waveform signal, using data that has been quadrature phase-shift keyed as an example, when using the switching timing generation unit 153c according to Comparative Example 3.

[0213] The top part of Figure 39 shows an example of a constellation when there is only a common phase error and no carrier frequency error (corresponding to Figure 25).

[0214] As shown in the upper part of Figure 39, although phase rotation due to a common phase error is observed, when there is no carrier frequency error, the constellation data converges to a single point.

[0215] The middle part of FIG. 39 shows an example of a constellation when the carrier frequency error is 10% of the subcarrier spacing compared to the upper part.

[0216] The lower part of FIG. 39 shows an example of a constellation when the carrier frequency error is 20% of the subcarrier spacing compared to the upper part.

[0217] As can be seen by comparing (a), (d), and (g) in the left column of Figure 39, the presence of a carrier frequency error causes a phase rotation in the constellation, and data that had converged to a single point spreads. This data spread is caused by demodulation with the OFDM center frequency shifted by the amount of the carrier frequency error. Demodulation with a shifted center frequency destroys the orthogonality between OFDM subcarriers, causing inter-carrier interference and resulting in data spread. Furthermore, as the degree of carrier frequency error increases, the data spread becomes even greater. Focusing on the degree of data spread in the center and right columns also shows the same trend as the left column.

[0218] When the signals in the middle and bottom rows of Figure 39 are provided to the switching timing generation unit 153c according to Comparative Example 3, the carrier frequency correction unit 20 removes inter-carrier interference, correcting (d) and (g) in Figure 39 to a state close to (a), (e) and (h) to (b), and (f) and (j) to a state close to (c). However, the switching timing generation unit 153c according to Comparative Example 3 does not include the frequency waveform phase correction unit 40. Therefore, the phase rotation caused by the phase error cannot be suppressed, and the phase rotation remains as it is, as shown in (b) and (c).

[0219] In contrast, when the switching timing generation unit 153 according to the third embodiment performs a carrier frequency correction process to remove inter-carrier interference due to a carrier frequency error, the switching timing generation unit 153 calculates a common phase error from the phase difference between a part of a signal extracted from the time domain waveform signal and a known signal, and corrects the phase of the frequency domain waveform signal, thereby reducing the phase error.

[0220] Therefore, it is possible to reduce the common phase error using a simple method that does not require a mechanism for controlling the frequency and phase of the local oscillator clock or the baseband system clock, or waveform equalization processing that estimates the transmission path characteristics and corrects the waveform after FFT.As a result, in the TDD system, even if a common phase error exists, it is possible to estimate the DL / UL switching timing inexpensively and accurately.

[0221] (Fourth embodiment) Next, a description will be given of a switching timing generation unit 153 according to a fourth embodiment. The switching timing generation unit 153 according to the fourth embodiment executes a sampling phase conversion process for correcting a phase deviated from the original sampling phase, and also executes a correction process for a common phase error due to phase noise when executing a correction process for a carrier frequency for removing inter-carrier interference due to a carrier frequency error.

[0222] Fig. 40 is a diagram showing an example of the functional configuration of the switching timing generation unit 153 of the fourth embodiment. When Fig. 40 is compared with Fig. 7, it differs in that the switching timing generation unit 153 of the fourth embodiment shown in Fig. 40 further includes a sampling phase conversion unit 30 and a carrier frequency correction unit 20.

[0223] The sampling rate conversion unit 1012 of the signal receiving unit 1001 outputs the baseband time domain waveform signal to the PSS detection unit 1013 and the sampling phase conversion unit 30 .

[0224] The sampling phase conversion unit 30 performs sampling phase conversion processing to convert the sampling phase of the time domain waveform signal that is the output of the signal receiving unit 1001. Specifically, the sampling phase conversion unit 30 includes a phase detection unit 31 and a phase conversion unit 32.

[0225] The phase detector 31 detects the optimum phase that provides the best sampling phase for the time domain waveform signal based on the SSB timing and physical layer cell identifier NID2 output from the PSS detector 1013. That is, the phase detector 31 extracts a signal from the input sampling rate converted baseband signal based on the input SSB timing, detects the optimum phase from a plurality of predetermined sampling phases based on the input physical layer cell identifier NID2, and outputs the optimum phase to the phase converter 32. The functional configuration of the phase detector 31 is as already described using FIG. 27.

[0226] The phase converter 32 converts the sampling phase of the baseband time domain waveform signal received from the sampling rate converter 1012 based on the optimal phase output from the phase detector 31. That is, based on the input optimal phase, the phase converter 32 converts the sampling phase of the input baseband signal after sampling rate conversion to an optimal phase, and outputs the phase to the frequency error corrector 22 of the carrier frequency corrector 20. The functional configuration of the phase converter 32 is as already described using FIG. 28.

[0227] The carrier frequency correction unit 20 receives the baseband time domain signal from the sampling phase conversion unit 30 and the SSB timing and physical layer cell identifier NID2 from the PSS detection unit 1013, and performs carrier frequency correction processing. Specifically, the carrier frequency correction unit 20 includes a frequency error detection unit 21 and a frequency error correction unit 22.

[0228] The frequency error detection unit 21 extracts a signal from the input sampling rate converted baseband signal based on the input SSB timing, detects a carrier frequency error using a PSS code sequence based on the input physical layer cell identifier NID2, and outputs the detected carrier frequency error to the frequency error correction unit 22. The functional configuration of the frequency error detection unit 21 is as already described with reference to Fig. 34.

[0229] The frequency error correction unit 22 generates a complex sine wave of a specified frequency based on the input carrier frequency error, corrects the carrier frequency by complex multiplying the result by a signal obtained by converting the sampling phase of the input sampling rate converted baseband signal to an optimal phase, and outputs the result to the FFT unit 1004. The functional configuration of the frequency error correction unit 22 has already been described using FIG.

[0230] 40, based on the input SSB timing, the FFT unit 1004 extracts the SSB from the carrier frequency corrected baseband time domain waveform signal received from the carrier frequency correction unit 20 and performs a Fourier transform. The FFT unit 1004 then outputs the SSB frequency domain waveform signal obtained by the Fourier transform to the phase correction unit 42 of the frequency waveform phase correction unit 40.

[0231] The frequency waveform phase correction unit 40 receives a baseband time axis waveform signal from the sampling rate conversion unit 1012 of the signal receiving unit 1001, a frequency axis waveform signal from the FFT unit 1004, and SSB timing and physical layer cell identifier NID2 from the PSS detection unit 1013 of the time waveform calculation unit 1002, and performs phase correction processing on the frequency axis waveform signal.

[0232] Fig. 41 is a flowchart showing an example of TDD detection processing according to the fourth embodiment. Comparing Fig. 41 with Fig. 14, there is a difference in that a sampling phase conversion processing (step S2c) and a carrier frequency correction processing (step S2b) are inserted before the FFT processing in step S3.

[0233] Fig. 42 is a flowchart showing an example of the sampling phase conversion process according to the fourth embodiment. That is, the flowchart shown in Fig. 42 is the sampling phase conversion process of step S2c shown in Fig. 41.

[0234] 42, the phase detection unit 31 of the sampling phase conversion unit 30 determines whether or not the SSB timing has been notified from the time waveform calculation unit 1002 (step S21c). If there has been no notification, the phase detection unit 31 exits the sampling phase conversion process (No in step S21c), and if there has been a notification, the phase detection unit 31 proceeds to the process of the subsequent step S22c (Yes in step S21c).

[0235] Subsequently, the phase detection unit 31 reads out the NID2 stored in step S24 (step S22c).

[0236] Subsequently, the phase detection unit 31 executes a phase detection process (step S23c).

[0237] Next, the phase conversion unit 32 executes a phase conversion process (step S24c).

[0238] Next, the phase conversion unit 32 notifies the carrier frequency correction unit 20 of the SSB timing (step S25c). The carrier frequency correction unit 20 executes carrier frequency correction processing based on the SSB timing notified from the phase conversion unit 32. This carrier frequency correction processing is similar to the content described in FIG.

[0239] The effect of the switching timing generation section 153 according to the fourth embodiment will be described in more detail with reference to a switching timing generation section 153d according to a fourth comparative example.

[0240] Fig. 43 is a diagram showing an example of the functional configuration of a switching timing generation unit 153d according to comparative example 4. When Fig. 43 is compared with Fig. 40, the switching timing generation unit 153d according to comparative example 4 in Fig. 43 does not include the frequency waveform phase correction unit 40 shown in Fig. 40.

[0241] FIG. 44 is a diagram illustrating a constellation when using the switching timing generation unit 153d according to Comparative Example 4, taking as an example data subjected to quadrature phase shift keying, there is a difference in the common phase error, there is a difference in the sampling phase of the baseband time domain waveform signal, and there is a difference in the carrier frequency error of the baseband time domain waveform signal.

[0242] The top part of Figure 44 shows an example of a constellation when there is only a common phase error, no deviation from the sampling phase at the time of transmission, and no carrier frequency error (corresponding to Figure 25). As shown in the top part of Figure 44, although phase rotation due to the common phase error can be seen, there is no effect from deviation in the sampling phase, and there is also no effect from carrier frequency error, and the constellation data converges to a single point.

[0243] The middle part of FIG. 44 shows an example of a constellation when the sampling phase deviation is 25% compared to the upper part and the carrier frequency error is 10% of the subcarrier spacing.

[0244] The bottom part of FIG. 44 shows an example of a constellation when the sampling phase deviation is 50% compared to the top part and the carrier frequency error is 20% of the subcarrier spacing.

[0245] As can be seen by comparing the left column (a), (d), and (g) in Figure 44, the deviation in sampling phase causes the constellation to rotate in the phase direction, and the carrier frequency error causes further phase rotation in the constellation, causing the data that had converged at one point to spread out.

[0246] As the deviation of the sampling phase and the degree of carrier frequency error increase, the amount of phase rotation and data spread become even larger. Looking at the amount of phase rotation and data spread in the center and right columns, we see the same trends as in the left column.

[0247] When the signals in the middle and bottom rows of Figure 44 are provided to the switching timing generation unit 153d according to Comparative Example 4, the sampling phase conversion unit 30 suppresses phase rotation due to deviation in sampling phase, and the carrier frequency correction unit 20 removes inter-carrier interference, correcting (d) and (g) in Figure 44 to a state close to (a), (e) and (h) to (b), and (f) and (j) to (c). However, the switching timing generation unit 153d according to Comparative Example 4 does not include the frequency waveform phase correction unit 40. Therefore, the phase rotation due to phase error cannot be suppressed, and the phase rotation remains as it is, as shown in (b) and (c).

[0248] In contrast, the switching timing generation unit 153 according to the fourth embodiment performs sampling phase conversion processing to correct a phase that deviates from the original sampling phase, and also performs carrier frequency correction processing to remove inter-carrier interference due to carrier frequency error. In this case, the switching timing generation unit 153 calculates a common phase error from the phase difference between a part of a signal extracted from the time domain waveform signal and a known signal, and corrects the phase of the frequency domain waveform signal, thereby reducing the phase error.

[0249] Therefore, it is possible to reduce the common phase error using a simple method that does not require a mechanism for controlling the frequency and phase of the local oscillator clock or the baseband system clock, or waveform equalization processing that estimates the transmission path characteristics and corrects the waveform after FFT.As a result, in the TDD system, even if a common phase error exists, it is possible to estimate the DL / UL switching timing inexpensively and accurately.

[0250] The program executed by the parent station device 10 of this embodiment is provided as a file in an installable or executable format, recorded on a computer-readable recording medium such as a semiconductor storage device such as a DVD (Digital Versatile Disk), a USB (Universal Serial Bus) memory, or an SSD (Solid State Drive).

[0251] The program may also be configured to be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network, or to be provided or distributed via a network such as the Internet, or to be provided by being pre-installed in a ROM or the like. [Explanation of symbols]

[0252] 1...Distributed antenna system, 10...Master station unit (MU), 11...High-order input / output unit, 12...Lower-order input / output unit, 13...Downlink processing unit, 14...Uplink processing unit, 15...Control unit, 20...Carrier frequency correction unit, 21...Frequency error detection unit, 22...Frequency error correction unit, 30...Sampling phase conversion unit, 31...Phase detection unit, 32...Phase conversion unit, 40...Frequency waveform phase correction unit, 41...Phase error detection unit, 42...Phase correction unit, 45...Relay unit (HU), 47...Slave station unit (RU), 50...Base station, 60...Terminal unit, 70...Antenna, 153...Switching timing generation unit, 80...Transmission path, 154...Switching unit, 210...P SS code sequence selection unit, 211...data holding unit, 212...fourth correlation calculation unit, 213...error detection unit, 220...sine wave generation unit, 221...frequency conversion unit, 310...PSS code sequence selection unit, 311...data holding unit, 312...phase conversion unit, 313...third correlation calculation unit, 314...phase determination unit, 320...filter coefficient selection unit, 321...filter calculation unit, 410...PSS code sequence selection unit, 411...data holding unit, 412...second correlation calculation unit, 413...phase error detection unit, 420...complex signal generation unit, 421...phase conversion unit, 1001...signal receiving unit, 1002...time waveform calculation unit, 1004...FFT (Fourier transform: Fast Fourier Transform unit, 1005... frequency waveform calculation unit, 1006... switching timing estimation unit, 1010... ADC unit, 1011... carrier frequency conversion unit, 1012... sampling rate conversion unit, 1013... PSS detection unit, 1016... SSS detection unit, 1131... time signal extraction unit, 1132... PSS generation unit, 1133... first correlation calculation unit, 1134... NID2 detection unit, 1161... SSS extraction unit, 1162... SSS generation unit, 1163... data determination unit, 1164... comparison calculation unit, 1165... NID1 detection unit, 1171... DMRS extraction unit, 1172... DMRS generation unit, 1173... data determination unit, 1174... comparison calculation unit, 1175... ibar_SSB detection unit

Claims

1. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: functioning as the master station device or the slave station device, A communication device that receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the time waveform calculation unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A communication device comprising:

2. The signal receiving unit receives a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a synchronization signal block (SS / PBCH block) having a physical broadcast channel (PBCH) including a demodulation reference signal (DMRS); The communication device according to claim 1 .

3. the time waveform calculation unit includes a PSS detection unit that detects a PSS signal included in the time-domain waveform signal; The communication device according to claim 2 .

4. The PSS detection unit a time signal extracting unit that extracts a portion of the time-domain waveform signal; a PSS generating unit that outputs a plurality of PSS code sequences of the PSS signal and code sequence numbers that identify the PSS code sequences; a first correlation calculation unit that performs a correlation calculation between a time-axis waveform signal output from the time signal extraction unit and a PSS code sequence from the PSS generation unit, and outputs a correlation value; an NID2 detection unit that outputs, within a predetermined time range, the timing at which the correlation value is highest as an SSB timing, and outputs, as a physical layer cell identifier NID2, a PSS code sequence number corresponding to the PSS code sequence at which the correlation value is highest; The communication device according to claim 3 , comprising:

5. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: functioning as the master station device or the slave station device, A communication device that receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; a sampling phase conversion unit that converts a sampling phase of a time waveform signal that is an output of the signal receiving unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the sampling phase conversion unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A communication device comprising:

6. The signal receiving unit receives a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a synchronization signal block (SS / PBCH block) having a physical broadcast channel (PBCH) including a demodulation reference signal (DMRS); The communication device according to claim 5 .

7. the time waveform calculation unit includes a PSS detection unit that detects a PSS signal included in the time-domain waveform signal; The communication device according to claim 6.

8. The PSS detection unit a time signal extracting unit that extracts a portion of the time axis waveform signal; a PSS generator that outputs a plurality of PSS code sequences of the PSS signal and code sequence numbers that identify the PSS code sequences; a time-axis waveform signal that is an output of the time signal extraction unit; a first correlation calculation unit that performs a correlation calculation with the PSS code sequence from the PSS generation unit and outputs a correlation value; an NID2 detection unit that outputs, within a predetermined time range, the timing at which the correlation value is highest as an SSB timing, and outputs, as a physical layer cell identifier NID2, a PSS code sequence number corresponding to the PSS code sequence at which the correlation value is highest; The communication device of claim 7 , comprising:

9. The sampling phase conversion unit a phase detection unit that detects an optimum phase at which the sampling phase of the time domain waveform signal is most favorable based on the SSB timing and physical layer cell identifier NID2 that are outputs of the PSS detection unit; a phase conversion unit that converts the sampling phase of the time domain waveform signal based on the optimum phase output from the phase detection unit; The communication device of claim 8 .

10. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: functioning as the master station device or the slave station device, A communication device that receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; a carrier frequency correction unit that corrects a carrier frequency of the time waveform signal that is an output of the signal receiving unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the carrier frequency correction unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A communication device comprising:

11. The signal receiving unit receives a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a synchronization signal block (SS / PBCH block) having a physical broadcast channel (PBCH) including a demodulation reference signal (DMRS); The communication device according to claim 10.

12. the time waveform calculation unit includes a PSS detection unit that detects a PSS signal included in the time-domain waveform signal; The communication device according to claim 11.

13. The PSS detection unit a time signal extracting unit that extracts a portion of the time axis waveform signal; a PSS generator that outputs a plurality of PSS code sequences of the PSS signal and code sequence numbers that identify the PSS code sequences; a first correlation calculation unit that performs a correlation calculation between a time-axis waveform signal output from the time signal extraction unit and a PSS code sequence from the PSS generation unit, and outputs a correlation value; an NID2 detection unit that outputs, within a predetermined time range, the timing at which the correlation value is highest as an SSB timing, and outputs, as a physical layer cell identifier NID2, a PSS code sequence number corresponding to the PSS code sequence at which the correlation value is highest; The communication device of claim 12 , comprising:

14. The carrier frequency correction unit includes a frequency error detection unit that detects a carrier frequency error of the time domain waveform signal based on the SSB timing and a physical layer cell identifier NID2 output from the PSS detection unit; a frequency error correction unit that corrects a carrier frequency of the time domain waveform signal based on a frequency error that is an output of the frequency error detection unit; The communication device of claim 13, comprising:

15. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: functioning as the master station device or the slave station device, A communication device that receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; a sampling phase conversion unit that converts a sampling phase of a time waveform signal that is an output of the signal receiving unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a carrier frequency correction unit that corrects a carrier frequency of the time waveform signal that is an output of the sampling phase conversion unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the carrier frequency correction unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A communication device comprising:

16. The signal receiving unit receives a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a synchronization signal block (SS / PBCH block) having a physical broadcast channel (PBCH) including a demodulation reference signal (DMRS); 16. The communication device of claim 15.

17. the time waveform calculation unit includes a PSS detection unit that detects a PSS signal included in the time-domain waveform signal; 17. The communication device of claim 16.

18. The PSS detection unit a time signal extracting unit that extracts a portion of the time axis waveform signal; a PSS generator that outputs a plurality of PSS code sequences of the PSS signal and code sequence numbers that identify the PSS code sequences; a first correlation calculation unit that performs a correlation calculation between a time-axis waveform signal output from the time signal extraction unit and a PSS code sequence from the PSS generation unit, and outputs a correlation value; an NID2 detection unit that outputs, within a predetermined time range, the timing at which the correlation value is highest as an SSB timing, and outputs, as a physical layer cell identifier NID2, a PSS code sequence number corresponding to the PSS code sequence at which the correlation value is highest; 20. The communication device of claim 17, comprising:

19. The sampling phase conversion unit a phase detection unit that detects an optimum phase at which the sampling phase of the time domain waveform signal is most favorable based on the SSB timing and physical layer cell identifier NID2 that are outputs of the PSS detection unit; a phase conversion unit that converts the sampling phase of the time domain waveform signal based on the optimum phase output from the phase detection unit; 20. The communication device of claim 18, comprising:

20. The carrier frequency correction unit a frequency error detection unit that detects a carrier frequency error of the time domain waveform signal based on the SSB timing and physical layer cell identifier NID2 output from the PSS detection unit; a frequency error correction unit that corrects a carrier frequency of the time domain waveform signal based on a frequency error that is an output of the frequency error detection unit; 20. The communication device of claim 19, comprising:

21. The frequency waveform phase correction unit a phase error detection unit that detects a phase error of the time domain waveform signal based on the SSB timing and a physical layer cell identifier NID2 that are outputs of the PSS detection unit; a phase correction unit that corrects the phase of the frequency axis waveform signal that is the output of the FFT unit based on the phase error that is the output of the phase error detection unit; 21. The communication device according to claim 4, 9, 14 or 20, comprising:

22. the phase error detection unit includes a data holding unit that holds a part of the time domain waveform signal based on the SSB timing output from the PSS detection unit; a PSS code sequence selection unit that selects one of a plurality of PSS code sequences based on a physical layer cell identifier NID2 output from the PSS detection unit; a second correlation calculation unit that calculates a correlation value between the time-axis waveform signal stored in the data storage unit and the PSS code sequence selected by the PSS code sequence selection unit; a phase error detection unit that calculates a phase rotation amount of the time axis from the correlation value calculated by the second correlation calculation unit and detects a phase error of the time axis waveform signal; 22. The communication device of claim 21, comprising:

23. The phase correction unit a complex number generator that generates a complex number of an arbitrary argument based on the phase error output from the phase error detector; a phase correction unit that performs complex multiplication of a complex number output from the complex number generation unit and a frequency axis waveform signal output from the FFT unit to correct the phase of the frequency axis waveform signal; 23. The communication device of claim 22, comprising:

24. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: A control method for a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, comprising: receiving and converting the OFDM signal to a baseband OFDM signal; A portion of the time-axis waveform signal is extracted, and a degree of similarity between the extracted signal and a known signal is calculated. performing a Fast Fourier Transform (FFT) on the time-domain waveform signal; correcting the phase of the frequency axis waveform signal obtained by the Fourier transform based on the degree of similarity with a known signal; extracting a portion of the corrected frequency axis waveform signal, and calculating a degree of similarity between the extracted signal and a known signal; estimating a timing for switching between upstream communication and downstream communication in the own device based on the degree of similarity; A control method for a communication device comprising:

25. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: A computer incorporated in a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the time waveform calculation unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A program to make it function as such.

26. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: A control method for a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, comprising: receiving and converting the OFDM signal to a baseband OFDM signal; A portion of the time-axis waveform signal is extracted, and a degree of similarity between the extracted signal and a known signal is calculated. converting a sampling phase of the time domain waveform signal based on the degree of similarity with a known signal; performing a Fast Fourier Transform (FFT) on the time-domain waveform signal after the sampling phase conversion; correcting the phase of the frequency axis waveform signal obtained by the Fourier transform based on the degree of similarity with a known signal; extracting a portion of the corrected frequency axis waveform signal, and calculating a degree of similarity between the extracted signal and a known signal; estimating a timing for switching between upstream communication and downstream communication in the own device based on the degree of similarity; A control method for a communication device comprising:

27. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: A computer incorporated in a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; a sampling phase conversion unit that converts a sampling phase of a time waveform signal that is an output of the signal receiving unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the sampling phase conversion unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A program to make it function as such.

28. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: A control method for a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, comprising: receiving and converting the OFDM signal to a baseband OFDM signal; A portion of the time-axis waveform signal is extracted, and a degree of similarity between the extracted signal and a known signal is calculated. correcting a carrier frequency of the time domain waveform signal based on the degree of similarity with a known signal; performing a Fast Fourier Transform (FFT) on the corrected time-domain waveform signal; correcting the phase of the frequency axis waveform signal obtained by the Fourier transform based on the degree of similarity with a known signal; extracting a portion of the frequency axis waveform signal, and calculating a degree of similarity between the extracted signal and a known signal; estimating a timing for switching between upstream communication and downstream communication in the own device based on the degree of similarity; A control method for a communication device comprising:

29. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: A computer incorporated in a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; a carrier frequency correction unit that corrects a carrier frequency of the time waveform signal that is an output of the signal receiving unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the carrier frequency correction unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A program to make it function as such.

30. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: A control method for a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, comprising: receiving and converting the OFDM signal to a baseband OFDM signal; A portion of the time-axis waveform signal is extracted, and a degree of similarity between the extracted signal and a known signal is calculated. converting a sampling phase of the time waveform signal based on the degree of similarity with a known signal; correcting a carrier frequency of the time-domain waveform signal after the sampling phase conversion based on the degree of similarity with a known signal; performing a Fast Fourier Transform (FFT) on the corrected time waveform signal; correcting the phase of the frequency axis waveform signal obtained by the Fourier transform based on the degree of similarity with a known signal; extracting a portion of the frequency axis waveform signal, and calculating a degree of similarity between the extracted signal and a known signal; estimating a timing for switching between upstream communication and downstream communication in the own device based on the degree of similarity; A control method for a communication device comprising:

31. a master station connected to the base station; one or more slave station devices that relay signals between terminal devices that communicate with the base station and the master station device; A distributed antenna system comprising: a computer incorporated in a communication device that functions as the master station device or the slave station device and receives an Orthogonal Frequency Division Multiplexing (OFDM) signal transmitted by a time division multiplexing method, a signal receiving unit that receives the OFDM signal and converts it into a baseband OFDM signal; a time waveform calculation unit that extracts a portion of a time-axis waveform signal that is an output of the signal receiving unit and calculates a degree of similarity between the extracted signal and a known signal; a sampling phase conversion unit that converts a sampling phase of a time waveform signal that is an output of the signal receiving unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a carrier frequency correction unit that corrects a carrier frequency of the time waveform signal that is an output of the sampling phase conversion unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; an FFT unit that performs a Fast Fourier Transform (FFT) on the time waveform signal that is the output of the carrier frequency correction unit; a frequency waveform phase correction unit that corrects the phase of a frequency axis waveform signal that is an output of the FFT unit based on the degree of similarity to a known signal calculated by the time waveform calculation unit; a frequency waveform calculation unit that extracts a portion of the frequency axis waveform signal that is the output of the frequency waveform phase correction unit and calculates the degree of similarity between the extracted signal and a known signal; a switching timing estimation unit that estimates a switching timing between uplink communication and downlink communication in the own device based on a result of the frequency waveform calculation unit; A program to function as a

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