Relay device, relay method, and program

Abstract

To generate a switching timing signals between an up-link period and a down-link period in an OFDM signal of a time division multiplex system with a small circuit scale.SOLUTION: A relay device according to an embodiment relays between base stations and a terminal. The relay device includes one or more child devices and a parent device. One or more slave units transmit and receive terminal and RF signals by electromagnetic waves via a plurality of antennas. The base unit transmits and receives an RF signal to and from a base station of each of the N operators. The master unit includes N timing signals generation units and a synchronizing signal detection unit. The synchronization signal detection section cyclically selects target businesses, which are synchronization signal detection targets, one at a time from the N businesses for each predetermined search time. The synchronization signal detection unit executes detection processing for detecting a synchronization signal included in an OFDM signal modulated into an RF signal transmitted from a base station of a target business operator for each search time.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a relay device, a relay method, and a program. [Background technology]

[0002] Mobile communication traffic continues to increase. To avoid a shortage of communication lines in the current frequency bands, countries are promoting the allocation of new frequency bands. Furthermore, due to the depletion of radio wave resources, the adoption of the conventional Frequency Division Duplex (FDD) method, in which the uplink and downlink signals have different frequencies, is declining. Instead, the Time Division Duplex (TDD) method, in which the uplink and downlink signals are transmitted on the same frequency in a time-division manner, is gaining popularity, resulting in the allocation of higher frequency bands. When higher frequency bands are used, it is difficult to form an indoor coverage area using electromagnetic waves from outdoor base stations due to the highly directional nature of electromagnetic waves and their low penetration rate through walls and windows.

[0003] Furthermore, in blind areas where a base station and a mobile phone terminal cannot transmit or receive electromagnetic waves, a relay device is known that relays radio frequency signals transmitted and received between the base station and the terminal via an optical line, thereby enabling communication between the terminal devices. Such a relay device is also called an optical repeater device or a distributed antenna system (DAS).

[0004] Previously, relay devices were installed by each operator. Furthermore, relay devices that support the 5G (5th generation) system require the installation of handset units at a higher density. Meanwhile, in commercial facilities and indoor locations, a large number of handset units for relay devices that support the conventional 3G (3rd generation) and 4G (4th generation) communication systems are already installed, making it difficult to install new handset units.

[0005] Additionally, global efforts to mitigate climate change and prevent the loss of biodiversity are underway, with keywords such as SDGs, carbon neutrality, and 30 by 30. This calls for efforts to reduce energy consumption in repeater equipment as well, and for infrastructure sharing to provide a more uniform quality and communications environment.

[0006] Therefore, in recent years, development of a relay device that collectively relays radio frequency signals from a plurality of operators has been progressing.

[0007] However, when relaying a TDD radio frequency signal, the repeater must generate a timing signal that indicates the timing of switching between a downlink period in which a downstream signal is transmitted and an uplink period in which an upstream signal is transmitted, based on the radio frequency signal transmitted from the base station. Therefore, a repeater that relays radio frequency signals from multiple operators must generate an independent timing signal for each of the multiple operators, which results in a larger circuit for generating the timing signals and higher costs. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2024-007110 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide a relay device, a relay method, and a program that can generate timing signals for each of a plurality of operators with a small circuit scale. [Means for solving the problem]

[0010] A relay device according to an embodiment relays signals between a base station and a terminal device, thereby transmitting and receiving RF signals (radio frequency signals) between the base station and the terminal device. The relay device includes one or more slave devices and a master device. The one or more slave devices transmit and receive the RF signals to and from the terminal device using electromagnetic waves via multiple antennas. The master device transmits and receives the RF signals to and from the base stations of N operators (N is an integer equal to or greater than 2). The RF signals are modulated by OFDM signals (orthogonal frequency division multiplexing signals) using a time division multiplexing method. The master device includes N timing signal generators and a synchronization signal detector. The N timing signal generators correspond to the N operators, respectively. The synchronization signal detector demodulates the OFDM signals from the RF signals transmitted from the base stations of the N operators, and detects, from the demodulated OFDM signals, synchronization signals allocated to frequency positions and time positions determined by each of the N operators. Each of the N timing signal generators generates, for the RF signal transmitted from the base station of a corresponding one of the N operators, a timing signal indicating a switching timing between a downlink period in which the OFDM signal is transmitted from the base station to the terminal device and an uplink period in which the OFDM signal is transmitted from the terminal device to the base station, based on the synchronization signal. The synchronization signal detector cyclically selects, for each predetermined search time, a target operator from among the N operators as a detection target for the synchronization signal, one by one. The synchronization signal detector executes, for each search time, a detection process to detect the synchronization signal included in the OFDM signal modulated onto the RF signal transmitted from the base station of the target operator. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a configuration of a wireless communication system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a radio frame in the 5G system. [Figure 3] FIG. 3 is a diagram showing the configuration of a synchronization signal block (SSB). [Figure 4] FIG. 4 is a diagram showing an example of the arrangement of SS burst sets. [Figure 5] FIG. 5 is a diagram showing an example of an SS burst set and a timing signal pattern. [Figure 6] FIG. 6 is a diagram showing the configuration of the parent device. [Figure 7] FIG. 7 is a diagram illustrating the configuration of the control unit. [Figure 8] FIG. 8 is a diagram illustrating the configuration of the synchronization signal detection unit. [Figure 9] FIG. 9 is a diagram showing the configuration of each of a plurality of demodulation units. [Figure 10] FIG. 10 is a diagram illustrating an example of a state machine. [Figure 11] FIG. 11 is a flowchart showing the flow of the synchronization signal detection process in the synchronization signal detection unit. [Figure 12] FIG. 12 is a flowchart showing an example of the flow of the process of selecting and setting the pair of the target transmission path and the target synchronous raster channel in S26 by the synchronization signal detection unit. [Figure 13] FIG. 13 is a flowchart showing the flow of the synchronization signal detection process in S27 by the synchronization signal detection unit. [Figure 14] FIG. 14 is a flowchart showing the flow of the synchronization confirmation signal output process in S28 by the synchronization signal detection unit. [Figure 15] FIG. 15 is a timing chart showing the processing timing of the synchronization signal detection unit for each search time. [Figure 16] FIG. 16 is a timing chart showing processing timings for a plurality of transmission paths. [Figure 17] FIG. 17 is a diagram showing a modified example of the configuration of the synchronization signal detection unit. DETAILED DESCRIPTION OF THE INVENTION

[0012] The relay device, relay method, and 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 descriptions of overlapping parts will be omitted as appropriate.

[0013] FIG. 1 is a diagram showing a configuration of a wireless communication system 10 according to an embodiment.

[0014] The wireless communication system 10 includes N base stations 12 (N is an integer equal to or greater than 2), a plurality of terminal devices 14, and a relay device 20.

[0015] Each of the N base stations 12 transmits and receives an RF signal (radio frequency signal) via electromagnetic waves to and from each of the plurality of terminal devices 14. In this embodiment, the wireless communication system 10 includes first to Nth base stations 12-1 to 12-N as the N base stations 12.

[0016] Each of the N base stations 12 forms multiple transmission paths using multiple antennas in a MIMO (Multiple Input Multiple Output) scheme, and transmits and receives RF signals via each of the multiple transmission paths. In this embodiment, each of the N base stations 12 forms four transmission paths in a 4x4 MIMO scheme, and transmits and receives four RF signals in parallel.

[0017] Furthermore, each of the N base stations 12 is used by a different operator. In this embodiment, each of the N base stations 12 is used by one of the N operators. Each of the N operators is assigned a usable frequency band by a public agency or the like that manages radio waves. Each of the N base stations 12 propagates an RF signal in the frequency band assigned to the corresponding operator.

[0018] Each of the plurality of terminal devices 14 transmits and receives RF signals via electromagnetic waves to and from a base station 12 of any of the N number of operators. Each of the plurality of terminal devices 14 may be incorporated in a smartphone or the like and carried and used by a user or the like.

[0019] The relay device 20 relays signals between each of the N base stations 12 and each of the multiple terminal devices 14, thereby transmitting and receiving RF signals between each of the multiple terminal devices 14 and any of the N base stations 12. For example, the relay device 20 is installed in a blind area, such as a commercial facility or indoors, where the base station 12 and the terminal devices 14 cannot directly transmit and receive electromagnetic waves. In this way, the relay device 20 can transmit and receive RF signals between each of the multiple terminal devices 14 and any of the N base stations 12 in the blind area.

[0020] The relay device 20 includes one or more slave devices 22 and a master device 24 .

[0021] Each of the one or more slave devices 22 transmits and receives RF signals to and from each of the multiple terminal devices 14 by electromagnetic waves via multiple antennas. Each of the one or more slave devices 22 forms multiple transmission paths using the MIMO system with multiple antennas, and transmits and receives RF signals on each of the multiple transmission paths. In this embodiment, each of the one or more slave devices 22 forms four transmission paths using the 4x4 MIMO system, and transmits and receives four RF signals in parallel.

[0022] The base station 24 transmits and receives RF signals to and from the base stations 12 of the N operators via coaxial cables including electric wires. The base station 24 transmits and receives multiple RF signals in parallel to and from the base stations 12 of the N operators, corresponding to multiple transmission paths formed by the MIMO system. In this embodiment, the base station 24 transmits and receives four RF signals in parallel to and from the base stations 12 of the N operators via four coaxial cables, each RF signal being transmitted through four transmission paths formed by the 4x4 MIMO system.

[0023] Furthermore, each of the one or more slave units 22 and the master unit 24 are connected by an optical fiber cable.

[0024] Each of the one or more slave units 22 converts the four RF signals received from the terminal device 14 into optical signals. Then, each of the one or more slave units 22 transfers the optical signals to the base unit 24 via an optical fiber cable. Also, each of the one or more slave units 22 receives the optical signals transferred from the base unit 24 via the optical fiber cable, and generates four RF signals from the received optical signals. Then, each of the one or more slave units 22 transmits the generated four RF signals to the terminal device 14 via multiple antennas by electromagnetic waves.

[0025] The master unit 24 converts the four RF signals received from each of the N base stations 12 into optical signals. Then, the master unit 24 transfers the optical signals to each of the one or more slave units 22 via the optical fiber cable. The master unit 24 also receives the optical signals transferred from each of the one or more slave units 22 via the optical fiber cable, and generates four RF signals from the received optical signals. Then, the master unit 24 transmits the generated four RF signals to each of the N base stations 12.

[0026] Here, the RF signal is modulated with a signal defined by the 5G standard. That is, the RF signal is modulated with an OFDM signal (orthogonal frequency division multiplexing signal) of a time division multiplexing method that multiplexes uplink and downlink signals by time division.

[0027] The relay device 20 is connected to the base stations 12 of the N operators and is shared by the N operators. For this reason, the relay device 20 generates, for each of the N operators, a timing signal that indicates the timing of switching between a downlink period in which an OFDM signal is transmitted from the base station 12 to the terminal device 14 and an uplink period in which an OFDM signal is transmitted from the terminal device 14 to the base station 12.

[0028] In particular, in this embodiment, the relay device 20 detects a synchronization signal included in the OFDM signal for each of the N operators, and generates a timing signal for each of the N operators based on the detected synchronization signal.

[0029] In the 5G standard, a synchronization signal is included in a synchronization signal block (SSB). The synchronization signal block (SSB) includes a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) as synchronization signals. In this embodiment, the relay device 20 demodulates an RF signal transmitted from the base station 12, converts it into an OFDM signal, and detects the PSS and SSS from the demodulated OFDM signal. Then, in this embodiment, the relay device 20 estimates a timing signal for each of the N operators based on the time positions of the PSS and SSS, i.e., the time position of the synchronization signal block (SSB).

[0030] FIG. 2 is a diagram showing an example of a radio frame defined by the 5G standard. The 5G standard defines a radio frame as a time unit for communication. In the 5G standard, a radio frame is 10 ms long. The radio frame includes 10 subframes. Each subframe is 1 ms long.

[0031] The 5G standard also defines slots. The 5G standard specifies that a slot must contain 14 symbols. The time length of a symbol varies depending on the subcarrier frequency. Therefore, the number of slots included in one subframe varies depending on the subcarrier frequency. Figure 2 shows an example where a subframe contains two slots.

[0032] Figure 3 shows the configuration of a synchronization signal block (SSB). The 5G standard stipulates that a synchronization signal block (SSB) be inserted into an OFDM signal. The synchronization signal block (SSB) consists of four consecutive symbols. The synchronization signal block (SSB) also consists of a predetermined frequency width. In addition to the PSS and SSS, the synchronization signal block (SSB) also includes a PBCH (Physical Broadcast Channel).

[0033] The 5G standard defines a set of eight synchronization signal blocks (SSBs) in a predetermined arrangement as an SS burst set. Each of the eight synchronization signal blocks (SSBs) included in the SS burst set includes an SSB index for distinguishing it from other synchronization signal blocks (SSBs) included in the SS burst set.

[0034] Figure 4 is a diagram showing an example of the arrangement of SS burst sets. The 5G standard specifies that SS burst sets are arranged to fit within half the range of a radio frame (half frame). SS burst sets are arranged at an SSB period, which is a predetermined time interval. The SSB period can be set arbitrarily by the operator.

[0035] However, the 5G standard specifies a maximum SSB period of 160 ms. Therefore, operators must include at least one SS burst set in an OFDM signal at least every 160 ms. Figure 4 shows an example of SS burst sets arranged with the default SSB period of 20 ms.

[0036] Furthermore, the synchronization signal block (SSB) is inserted into an OFDM signal modulated into an RF signal to be transmitted through a transmission path designated by a carrier among a plurality of transmission paths. The synchronization signal block (SSB) is also arranged at an arbitrary frequency position. The frequency position at which the synchronization signal block (SSB) is arranged is arranged at the frequency position designated by the carrier.

[0037] However, the 5G standard specifies multiple synchronization raster channels that represent frequency ranges in which synchronization signal blocks (SSBs) can be inserted in OFDM signals. Therefore, the synchronization signal blocks (SSBs) are inserted into any of the multiple synchronization raster channels in the OFDM signal modulated onto any of the multiple RF signals transmitted over multiple transmission paths.

[0038] That is, each of the N base stations 12 inserts a synchronization signal block (SSB) into an OFDM signal modulated into an RF signal to be transmitted through a transmission path determined by an operator from among a plurality of transmission paths. Furthermore, each of the N base stations 12 inserts a synchronization signal block (SSB) into a synchronization raster channel determined by the corresponding operator from among a plurality of synchronization raster channels in the target OFDM signal.

[0039] In the 5G standard, each of the multiple synchronization raster channels on which synchronization signal blocks (SSBs) can be allocated is identified by a number called a Global Synchronization Raster Channel Number (GSCN).

[0040] FIG. 5 is a diagram showing an example of an SS burst set and a timing signal pattern.

[0041] The relay device 20 can estimate the pattern of the timing signal by detecting the time position of the SS burst set. Note that in the example of Figure 5, D in the timing signal indicates a downlink period, U indicates an uplink period, and B indicates a buffer period. The buffer period indicates the symbol at the boundary between the downlink period and the uplink period.

[0042] 6 is a diagram showing the configuration of the base unit 24. The base unit 24 includes a control unit 30 and N transfer processing units 32.

[0043] The control unit 30 acquires a plurality of RF signals from the base stations 12 of the N operators. The plurality of RF signals corresponds to a plurality of transmission paths formed by MIMO.

[0044] In this embodiment, the control unit 30 acquires four RF signals corresponding to four transmission paths from the base stations 12 of the N operators. For example, a first RF signal of the four RF signals is an RF signal for a first transmission path output from a corresponding base station 12 of the N base stations 12. For example, a second RF signal of the four RF signals is an RF signal for a second transmission path output from a corresponding base station 12 of the N base stations 12. For example, a third RF signal of the four RF signals is an RF signal for a third transmission path output from a corresponding base station 12 of the N base stations 12. For example, a fourth RF signal of the four RF signals is an RF signal for a fourth transmission path output from a corresponding base station 12 of the N base stations 12.

[0045] Then, the control unit 30 generates N timing signals for each of the N operators based on the four RF signals for each of the N operators.

[0046] For example, the control unit 30 generates first to N-th timing signals. The first timing signal indicates the timing of switching between a downlink period in which OFDM signals are transmitted from the first base station 12-1 to the terminal device 14 and an uplink period in which OFDM signals are transmitted from the terminal device 14 to the first base station 12-1. The second timing signal indicates the timing of switching between a downlink period in which OFDM signals are transmitted from the second base station 12-2 to the terminal device 14 and an uplink period in which OFDM signals are transmitted from the terminal device 14 to the second base station 12-2. The N-th timing signal indicates the timing of switching between a downlink period in which OFDM signals are transmitted from the N-th base station 12-N to the terminal device 14 and an uplink period in which OFDM signals are transmitted from the terminal device 14 to the N-th base station 12-N.

[0047] The N forwarding processing units 32 correspond one-to-one to the N base stations 12. For example, the base station 24 includes first to N-th forwarding processing units 32-1 to 32-N as the N forwarding processing units 32. The first forwarding processing unit 32-1 corresponds to the first base station 12-1. The second forwarding processing unit 32-2 corresponds to the second base station 12-2. The N-th forwarding processing unit 32-N corresponds to the second base station 12-N.

[0048] Each of the N forwarding processors 32 is connected to a corresponding one of the N base stations 12 via four coaxial cables. Each of the N forwarding processors 32 is also connected to one or more slave units 22 via an optical fiber cable.

[0049] Each of the N forwarding processors 32 converts the four RF signals received from the corresponding base station 12 into an optical signal. Then, each of the N forwarding processors 32 forwards the optical signal to one or more slave units 22 via an optical fiber cable.

[0050] Each of the N forwarding processors 32 receives an optical signal from one or more slave units 22 via an optical fiber cable, converts the received optical signal into four RF signals, and transmits the four RF signals to the corresponding base station 12 via four coaxial cables.

[0051] Here, each of the N transfer processing units 32 acquires a timing signal from the control unit 30. The timing signal acquired by each of the N transfer processing units 32 corresponds to the operator of the base station 12 connected via the coaxial cable. For example, the first transfer processing unit 32-1 acquires a first timing signal. The second transfer processing unit 32-2 acquires a second timing signal. Then, the Nth transfer processing unit 32-N acquires the second timing signal.

[0052] Then, each of the N transfer processing units 32 switches between processing for the uplink signal transmitted from the terminal device 14 to the base station 12 and processing for the downlink signal transmitted from the base station 12 to the terminal device 14 according to the timing indicated in the acquired timing signal.

[0053] 7 is a diagram showing the configuration of the control unit 30. The control unit 30 includes N timing signal generating units 34 and a synchronization signal detecting unit 36.

[0054] The N timing signal generation units 34 correspond one-to-one to the N operators. For example, the control unit 30 includes first to Nth timing signal generation units 34-1 to 34-N as the N timing signal generation units 34. For example, the first timing signal generation unit 34-1 corresponds to a first operator of the N operators. The second timing signal generation unit 34-2 corresponds to a second operator of the N operators. And the Nth timing signal generation unit 34-N corresponds to the Nth operator of the N operators.

[0055] The synchronization signal detector 36 acquires multiple RF signals from the base stations 12 of the N operators. In this embodiment, the synchronization signal detector 36 acquires four RF signals from the base stations 12 of the N operators.

[0056] The synchronization signal detector 36 demodulates the four RF signals into an OFDM signal for each of the N operators and detects the synchronization signal included in the demodulated OFDM signal. Specifically, the synchronization signal detector 36 detects the PSS and SSS included in the synchronization signal block (SSB).

[0057] The synchronization signal detector 36 supplies the detected synchronization signal and synchronization timing information indicating the detection timing for each of the N operators to the corresponding one of the N timing signal generators 34.

[0058] Each of the N timing signal generation units 34 generates a timing signal indicating the timing of switching between the downlink period and the uplink period based on the detected synchronization signal for the RF signal transmitted from the base station 12 of the corresponding one of the N operators. Then, each of the N timing signal generation units 34 provides the generated timing signal to a corresponding one of the N transfer processing units 32. For example, the first timing signal generation unit 34-1 provides the first timing signal to the first transfer processing unit 32-1. The second timing signal generation unit 34-2 provides the second timing signal to the second transfer processing unit 32-2. Then, the Nth timing signal generation unit 34-N provides the Nth timing signal to the Nth transfer processing unit 32-N.

[0059] Here, the synchronization signal detection unit 36 ​​cyclically selects a target operator for detecting a synchronization signal from among the N operators at each predetermined search time. Then, at each search time, the synchronization signal detection unit 36 ​​executes a detection process to detect a synchronization signal included in an OFDM signal modulated onto an RF signal transmitted from the base station 12 of the target operator. This allows the synchronization signal detection unit 36 ​​to execute the synchronization signal detection process in parallel for each of the N operators.

[0060] 8 is a diagram showing the configuration of the synchronization signal detector 36. The synchronization signal detector 36 includes a plurality of pre-stage selectors 40, a plurality of demodulators 42, a selector 44, a frequency shifter 46, a PSS detector 48, an FFT unit 50, an SSS detector 52, a DMRS detector 54, an output unit 56, and a sequence controller 60.

[0061] The multiple pre-selectors 40 correspond one-to-one to the multiple transmission paths formed by MIMO. Each of the multiple pre-selectors 40 acquires an RF signal of the corresponding transmission path among the multiple transmission paths, which is transmitted from each of the N base stations 12.

[0062] In this embodiment, the synchronization signal detector 36 includes four pre-stage selectors 40. A first pre-stage selector 40-1 of the four pre-stage selectors 40 acquires N RF signals for a first transmission path transmitted from N base stations 12. A second pre-stage selector 40-2 of the four pre-stage selectors 40 acquires N RF signals for a second transmission path transmitted from N base stations 12. A third pre-stage selector 40-3 of the four pre-stage selectors 40 acquires N RF signals for a third transmission path transmitted from N base stations 12. A fourth pre-stage selector 40-4 of the four pre-stage selectors 40 acquires N RF signals for a fourth transmission path transmitted from N base stations 12.

[0063] Each of the multiple pre-stage selectors 40 acquires an operator designation signal indicating one of the N operators from the sequence control unit 60. Each of the multiple pre-stage selectors 40 selects, from the acquired N RF signals, an RF signal transmitted from the base station 12 of the operator indicated in the operator designation signal, and outputs the selected RF signal.

[0064] The multiple demodulators 42 correspond one-to-one to the multiple pre-stage selectors 40. That is, the multiple demodulators 42 correspond one-to-one to the multiple transmission paths formed by MIMO. The multiple demodulators 42 acquire RF signals output from the corresponding pre-stage selectors 40. In this embodiment, the synchronization signal detector 36 includes four demodulators 42. A first demodulator 42-1 of the four demodulators 42 acquires an RF signal of the first transmission path of the operator indicated in the operator designation signal from the first pre-stage selector 40-1. A second demodulator 42-2 of the four demodulators 42 acquires an RF signal of the second transmission path of the operator indicated in the operator designation signal from the second pre-stage selector 40-2. A third demodulator 42-3 of the four demodulators 42 acquires an RF signal of the third transmission path of the operator indicated in the operator designation signal from the third pre-stage selector 40-3. A fourth demodulator 42-4 of the four demodulators 42 acquires the RF signal of the fourth transmission path of the operator indicated in the operator designation signal from the fourth pre-stage selector 40-4.

[0065] Each of the demodulation units 42 acquires from the sequence control unit 60 an operator designation signal indicating one of the N operators.

[0066] Each of the multiple demodulators 42 detects the acquired RF signal using a carrier frequency signal at the center frequency of the frequency band used by the operator indicated in the operator designation signal to generate an intermediate frequency signal. Next, each of the multiple demodulators 42 performs analog-to-digital conversion on the intermediate frequency signal. Then, each of the multiple demodulators 42 performs filtering on the digitized intermediate frequency signal to pass frequency components corresponding to the operator indicated in the operator designation signal.

[0067] The selector 44 acquires the digital intermediate frequency signals output from each of the multiple demodulators 42. The selector 44 acquires a route designation signal that designates one of the multiple transmission routes from the sequence control unit 60. The selector 44 selects, from the digital intermediate frequency signals output from each of the multiple demodulators 42, the digital intermediate frequency signal output from the demodulator 42 that corresponds to the transmission route indicated in the route designation signal, and outputs the selected digital intermediate frequency signal to the frequency shifter 46.

[0068] The frequency shifter 46 acquires the digital intermediate frequency signal output from the selector 44. The frequency shifter 46 also acquires from the sequence control unit 60 a frequency designation signal indicating the center frequency of one of multiple synchronous raster channels in the frequency band used by the operator indicated in the operator designation signal. The frequency shifter 46 frequency-shifts the digital intermediate frequency signal output from the selector 44 to generate a baseband OFDM signal whose center frequency is the frequency indicated in the frequency designation signal.

[0069] Furthermore, the frequency shifter 46 acquires a CFO signal indicating the offset amount of the carrier frequency from the PSS detector 48. For example, the frequency shifter 46 corrects the amount of frequency shift by the offset amount indicated in the CFO signal.

[0070] The PSS detector 48 detects a PSS, which is a synchronization signal included in a synchronization signal block (SSB), from the OFDM signal output from the frequency shifter 46. The PSS detector 48 provides information indicating the timing at which the PSS was detected to the FFT unit 50. The PSS detector 48 also generates a CFO signal based on the detected PSS. For example, the PSS calculates an offset amount by comparing the phase of the detected PSS with a predetermined phase.

[0071] Based on the detected PSS and the timing at which the PSS was detected, the FFT unit 50 performs an FFT (Fast Fourier Transform) on symbols in the baseband OFDM signal that are estimated to contain at least a synchronization signal block (SSB), and demodulates the phase and amplitude of each of the multiple signals modulated into the synchronization signal block (SSB).

[0072] The SSS detector 52 detects the SSS based on a plurality of signals modulated into symbols that are presumed to be synchronization signal blocks (SSBs).

[0073] The DMRS detector 54 detects a DM-RS (DeModulation of Reference Signal) based on a plurality of signals modulated into symbols that are estimated to be synchronization signal blocks (SSBs).

[0074] The output unit 56 acquires the PSS, SSB, and DM-RS. The output unit 56 also receives an operator designation signal from the sequence control unit 60. Furthermore, the output unit 56 acquires from the sequence control unit 60 a synchronization confirmation signal indicating that the synchronization signal block (SSB) has been stably detected.

[0075] The output unit 56 generates synchronization timing information indicating the timing at which the synchronization signal block (SSB) was detected based on the PSS, SSB, and DM-RS. Then, on condition that a synchronization confirmation signal is supplied, the output unit 56 supplies the synchronization timing information to one of the N timing signal generators 34 corresponding to the operator indicated in the operator designation signal. If a synchronization confirmation signal is not supplied, the output unit 56 does not output the synchronization timing information.

[0076] In addition, the output unit 56 may select, for example, the most accurate synchronization signal block (SSB) from the eight synchronization signal blocks (SSB) for each SS burst set, and output an SSB index indicating the timing of the selected synchronization signal block (SSB) and the position of the synchronization signal block (SSB) in the SS burst set as synchronization timing information.

[0077] The sequence control unit 60 manages a state machine for each operator and controls the processing of each unit of the synchronization signal detection unit 36 ​​based on the state of the state machine. The sequence control unit 60 acquires the detection results of the PSS and SSS. Furthermore, the sequence control unit 60 generates an operator designation signal, a route designation signal, a frequency designation signal, and a synchronization confirmation signal. The configuration and processing flow of the sequence control unit 60 will be described in detail later.

[0078] The sequence control unit 60 includes, for example, a central processing unit (CPU), memory, and auxiliary storage device connected via a bus, and executes a program. All or part of the functions of the sequence control unit 60 may be realized using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), and a field programmable gate array (FPGA). The program executed by the sequence control unit 60 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 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.

[0079] 9 is a diagram showing the configuration of each of the plurality of demodulation units 42. Each of the plurality of demodulation units 42 includes an oscillator 62, a PLL (Phase Locked Loop) circuit 64, a multiplier 66, an AD converter 68, a filter circuit 70, and a setting circuit 72.

[0080] The oscillator 62 outputs a periodic signal of a preset frequency. The PLL circuit 64 outputs a carrier signal of a frequency that is multiplied by a factor specified by a setting circuit 72 with respect to the periodic signal output from the oscillator 62.

[0081] The multiplier 66 outputs a product signal obtained by multiplying the RF signal by the carrier signal output from the PLL circuit 64. The AD converter 68 outputs a digital signal obtained by analog-to-digital conversion of the product signal. The filter circuit 70 performs band-pass filtering to pass frequency components in a frequency band specified by the setting circuit 72 and remove other components, thereby outputting a digital intermediate frequency signal.

[0082] The setting circuit 72 acquires the operator designation signal from the sequence control unit 60. The setting circuit 72 sets the magnification of the PLL circuit 64 so that the frequency of the carrier signal from the PLL circuit 64 becomes the center frequency of the frequency band used by the operator indicated in the operator designation signal. The setting circuit 72 also sets the pass frequency band of the filter circuit 70 so that components of the frequency band corresponding to the operator indicated in the operator designation signal are passed.

[0083] Each of the plurality of demodulation units 42 can output a digital intermediate frequency signal obtained by modulating the RF signal with an OFDM signal output from the base station 12 of the operator indicated in the operator designation signal.

[0084] 10 is a diagram showing an example of a state machine. The sequence control unit 60 manages a state machine for each of N operators.

[0085] The state machine represents the operating states of the synchronization signal detection unit 36. The state machine includes an acquisition state ST11, a synchronization protection state ST12, and a synchronization established state ST13 as operating states. While executing synchronization processing, the sequence control unit 60 sets the operating state for each of the N operators to the acquisition state ST11, the synchronization protection state ST12, or the synchronization established state ST13.

[0086] The acquisition state ST11 is a state in which a synchronization signal block (SSB) is detected while cyclically selecting a pair of a transmission path and a synchronization raster channel. The synchronization protection state ST12 is a state in which a synchronization signal block (SSB) is detected while a pair of a transmission path and a synchronization raster channel is fixed. The synchronization establishment state ST13 is a state in which a synchronization signal block (SSB) is detected while a pair of a transmission path and a synchronization raster channel is fixed, and synchronization timing information indicating the detected synchronization signal block (SSB) and the detection timing of the detected synchronization signal block (SSB) is output.

[0087] The synchronization protection state ST12 also includes a backward synchronization protection state ST14 and a forward synchronization protection state ST15.

[0088] The synchronization signal detection unit 36 ​​cyclically selects a target operator from among the N operators for each search time as a target for detecting a synchronization signal, and executes a detection process to detect a synchronization signal block (SSB) included in an OFDM signal modulated onto an RF signal transmitted from the target operator's base station 12. For each search time, the synchronization signal detection unit 36 ​​changes the operating state of the state machine of the target operator depending on whether or not a synchronization signal block (SSB) has been detected in the detection process.

[0089] Specifically, the state machine transitions as follows:

[0090] First, when processing starts, the state machine transitions to an acquisition state ST11. If a synchronization signal block (SSB) is not detected in the acquisition state ST11 (NG), the state machine maintains the acquisition state ST11. If a synchronization signal block (SSB) is detected in the acquisition state ST11 (OK), the state machine transitions to a backward synchronization protection state ST14.

[0091] The state machine transitions to the synchronization established state ST13 when a synchronization signal block (SSB) is detected j times (j is an integer equal to or greater than 1) consecutively in the backward synchronization protection state ST14 (when j times consecutively OK). The state machine maintains the backward synchronization protection state ST14 when a synchronization signal block (SSB) is detected less than j times consecutively in the backward synchronization protection state ST14. The state machine transitions to the acquisition state ST11 when a synchronization signal block (SSB) is not detected (NG) in the backward synchronization protection state ST14.

[0092] If a synchronization signal block (SSB) is detected in the synchronization established state ST13 (OK), the state machine maintains the synchronization established state ST13. If a synchronization signal block (SSB) is not detected in the synchronization established state ST13 (NG), the state machine transitions to the forward synchronization protection state ST15.

[0093] The state machine transitions to the acquisition state ST11 when a synchronization signal block (SSB) is not detected k times (k is an integer equal to or greater than 1) consecutively in the forward synchronization protection state ST15 (when k times are NG). The state machine maintains the forward synchronization protection state ST15 when a synchronization signal block (SSB) is not detected less than k times consecutively in the forward synchronization protection state ST15. The state machine transitions to the synchronization established state ST13 when a synchronization signal block (SSB) is detected (OK) in the forward synchronization protection state ST15.

[0094] FIG. 11 is a flowchart showing the flow of the synchronization signal detection process in the synchronization signal detector 36.

[0095] In executing the synchronization signal detection process, the synchronization signal detection unit 36 ​​cyclically selects and sets one target operator from among the N operators as a target operator for detecting the synchronization signal. Note that the order in which the N operators are selected as target operators is predetermined.

[0096] Furthermore, in executing the synchronization signal detection process, the synchronization signal detection unit 36 ​​cyclically selects and sets one by one from the plurality of transmission paths as a target transmission path for detecting the synchronization signal. Note that the order in which the plurality of transmission paths are selected as target transmission paths is determined in advance.

[0097] In addition, the synchronization signal detector 36 cyclically selects and sets one target synchronization raster channel from the plurality of synchronization raster channels as a synchronization signal detection target in the synchronization signal detection process. The order in which the plurality of synchronization raster channels are selected as target synchronization raster channels is predetermined. The number of synchronization raster channels included in the OFDM signal may differ for each operator.

[0098] First, in S21, the synchronization signal detection unit 36 ​​transitions the state machine for each of the N operators to the acquisition state ST11.

[0099] Next, in S22, the synchronization signal detection unit 36 ​​sets the target transmission route for each of the N operators to the first transmission route among the multiple transmission routes.

[0100] Next, in S23, the synchronization signal detection unit 36 ​​sets the target synchronous raster channel for each of the N operators to the first synchronous raster channel among the plurality of synchronous raster channels.

[0101] Next, the synchronization signal detection unit 36 ​​repeatedly executes the processes of S25 to S29 every predetermined search time (loop process between S24 and S30).

[0102] The 5G standard defines a synchronization signal block (SSB), which is a block of frequency and time ranges that includes a synchronization signal. In this embodiment, the synchronization signal is a PSS and an SSS. Furthermore, the 5G standard defines a maximum value of the SSB period, which is the period of the synchronization signal block (SSB). In other words, the 5G standard defines that at least one synchronization signal block is included in the OFDM signal for each maximum value of the SSB period.

[0103] The search time is longer than the maximum period of a synchronization signal block (SSB) defined in the 5G standard. For example, the maximum period of a synchronization signal block (SSB) is defined as 160 ms in the 5G standard. In this embodiment, the search time is set to 200 ms, which is longer than 160 ms.

[0104] In the loop process between S24 and S30, first, in S25, the synchronization signal detection unit 36 ​​selects one of the N operators as a target operator. Each time the synchronization signal detection unit 36 ​​executes the process of S25, it cyclically selects one target operator from the N operators one by one.

[0105] Next, in S26, the synchronization signal detection unit 36 ​​sets a pair of a target transmission path and a target synchronous raster channel for the target operator.

[0106] More specifically, when the operating state of the state machine for the target operator is in the acquisition state ST11, the synchronization signal detection unit 36 ​​cyclically selects a pair of the target transmission path and the target synchronous raster channel one by one from all combinations of multiple transmission paths and multiple synchronous raster channels. Furthermore, when the operating state of the state machine for the target operator is in the synchronization protection state ST12 or the synchronization established state ST13, the synchronization signal detection unit 36 ​​sets the pair of the target transmission path and the target synchronous raster channel to the same pair of the target transmission path and the target synchronous raster channel set at the immediately preceding search time. Details of the processing of S26 will be described with reference to FIG. 12.

[0107] Next, in S27, the synchronization signal detection unit 36 ​​executes synchronization signal detection processing. More specifically, the synchronization signal detection unit 36 ​​converts the signal component of the RF signal in the frequency band allocated to the target operator from the RF signal of the target transmission path into an intermediate frequency signal, and demodulates the intermediate frequency signal into a baseband OFDM signal. Furthermore, the synchronization signal detection unit 36 ​​detects a synchronization signal block (SSB) from the signal component of the target synchronization raster channel in the baseband OFDM signal. Then, the synchronization signal detection unit 36 ​​determines whether or not a synchronization signal block (SSB) is included, and operates the state machine for the target operator based on the determination result (OK or NG). Note that further details of the processing of S27 will be described with reference to FIG. 13.

[0108] Next, in S28, the synchronization signal detection unit 36 ​​outputs a synchronization confirmation signal based on the operating state represented by the state machine of the target operator. More specifically, if the state machine of the target operator is in the synchronization established state ST13, the synchronization signal detection unit 36 ​​outputs the synchronization confirmation signal to the output unit 56. If the state machine of the target operator is not in the synchronization established state ST13, the synchronization signal detection unit 36 ​​does not output the synchronization confirmation signal. When the synchronization confirmation signal is received, the output unit 56 supplies synchronization timing information indicating the content of the synchronization signal block (SSB) detected in S27 and the timing at which the synchronization signal block (SSB) was detected to the timing signal generation unit 34 corresponding to the target operator among the N timing signal generation units 34. This allows the timing signal generation unit 34 corresponding to the target operator to generate a timing signal for the RF signal transmitted from the base station 12 corresponding to the target operator. Note that further details of the processing of S28 will be described with reference to FIG. 14.

[0109] Next, in S29, the synchronization signal detection unit 36 ​​determines whether or not the termination condition is satisfied. For example, the synchronization signal detection unit 36 ​​may determine that the termination condition is satisfied when the state machines of all N operators are in the synchronization established state ST13. Alternatively, for example, the synchronization signal detection unit 36 ​​may determine that the termination condition is satisfied when a certain period of time has elapsed. Note that, when the termination condition is satisfied and there are operators whose state machines are not in the synchronization established state ST13, the synchronization signal detection unit 36 ​​may output error information for the operators whose state machines are not in the synchronization established state ST13.

[0110] If the termination condition is met (Yes in S29), the synchronization signal detection unit 36 ​​terminates this flow.

[0111] If the termination condition is not met (No in S29), the synchronization signal detection unit 36 ​​continues the loop process between S24 and S30.

[0112] 12 is a flowchart showing an example of the flow of the process of selecting and setting a pair of a target transmission path and a target synchronous raster channel in S26 by the synchronization signal detection unit 36. In S26, the synchronization signal detection unit 26 executes the process, for example, according to the flow shown in FIG.

[0113] First, in S41, the synchronization signal detection unit 36 ​​determines whether the state machine of the target operator is in the acquisition state ST11. If the state machine is not in the acquisition state ST11 (No in S41), the synchronization signal detection unit 36 ​​proceeds to S42. If the state machine is in the acquisition state ST11 (Yes in S41), the synchronization signal detection unit 36 ​​proceeds to S44.

[0114] In S42, the synchronization signal detection unit 36 ​​sets the target transmission path to be the same as the target transmission path set at the immediately preceding search time among the multiple transmission paths. Then, in S43, the synchronization signal detection unit 36 ​​sets the target synchronized raster channel to be the same as the target synchronized raster channel set at the immediately preceding search time among the multiple synchronized raster channels.

[0115] By executing S42 and S43, if the state machine for the target operator is not in the acquisition state ST11, that is, if the state machine for the target operator is in the synchronization protection state ST12 or the synchronization established state ST13, the synchronization signal detection unit 36 ​​can set the pair of the target transmission path and the target synchronization raster channel to the same pair of the target transmission path and the target synchronization raster channel set in the immediately preceding search time. When the processing of S43 is completed, the synchronization signal detection unit 36 ​​ends this flow.

[0116] In S44, the synchronization signal detection unit 36 ​​determines whether the target synchronization raster channel set in the previous search time is the last synchronization raster channel among the multiple synchronization raster channels. If the target synchronization raster channel set in the previous search time is not the last synchronization raster channel (No in S44), the synchronization signal detection unit 36 ​​proceeds to S45. If the target synchronization raster channel set in the previous search time is the last synchronization raster channel (Yes in S44), the synchronization signal detection unit 36 ​​proceeds to S47.

[0117] In S45, the synchronization signal detection unit 36 ​​sets the target transmission path to the same one of the multiple transmission paths that was set at the immediately preceding search time. Then, in S46, the synchronization signal detection unit 36 ​​sets the target synchronized raster channel to the synchronized raster channel next to the target synchronized raster channel that was set at the immediately preceding search time.

[0118] In S47, the synchronization signal detection unit 36 ​​sets the target transmission path to the transmission path next to the target transmission path set at the immediately preceding search time among the multiple transmission paths. Then, in S48, the synchronization signal detection unit 36 ​​sets the target synchronous raster channel to the first synchronous raster channel among the multiple synchronous raster channels.

[0119] By executing S44 to S48, when the state machine for the target operator is in the acquisition state ST11, the synchronization signal detection unit 36 ​​can cyclically select and set a pair of a target transmission path and a target synchronous raster channel one by one from among a plurality of combinations of transmission paths and a plurality of synchronous raster channels. When the synchronization signal detection unit 36 ​​has finished the processing of S46 or S48, it ends this flow.

[0120] 13 is a flowchart showing the flow of the synchronization signal detection process in S27 by the synchronization signal detection unit 36. In S27, the synchronization signal detection unit 26 executes the process according to the flow shown in FIG.

[0121] First, in S51, the synchronization signal detection unit 36 ​​outputs an operator designation signal indicating the target operator to each of the multiple demodulation units 42 and to the output unit 56. As a result, the synchronization signal detection unit 36 ​​can cause each of the multiple demodulation units 42 to output an intermediate frequency signal including an OFDM signal modulated to the frequency band allocated to the target operator in the RF signal. Furthermore, on the condition that a synchronization confirmation signal is provided to the output unit 56, the synchronization signal detection unit 36 ​​can cause one of the N timing signal generation units 34 corresponding to the operator indicated in the operator designation signal to output synchronization timing information that serves as the basis for generating a timing signal.

[0122] Next, in S52, the synchronization signal detection unit 36 ​​outputs a route designation signal that designates the target transmission route to the selector 44. As a result, the synchronization signal detection unit 36 ​​causes the selector 44 to select the intermediate frequency signal output from the demodulation unit 42 that corresponds to the transmission route designated in the route designation signal from among the multiple demodulation units 42, and output the intermediate frequency signal to the frequency shift unit 46 in the subsequent stage.

[0123] Next, in S53, the synchronization signal detection unit 36 ​​outputs a frequency designation signal that designates the target synchronization raster channel to the frequency shift unit 46. This allows the synchronization signal detection unit 36 ​​to cause the frequency shift unit 46 to frequency-shift the digital intermediate frequency signal output from the selector 44 and output a baseband OFDM signal modulated to the synchronization raster channel indicated in the frequency designation signal.

[0124] Next, in S54, the synchronization signal detection unit 36 ​​detects the PSS and SSS included in the synchronization signal block (SSB) for a predetermined detection time. The predetermined detection time is equal to or greater than the maximum SSB period (160 ms) and shorter than the search time (e.g., 200 ms). The synchronization signal detection unit 36 ​​then obtains the PSS detection result from the PSS detection unit 48 and the SSS detection result from the SSS detection unit 52.

[0125] Next, in S55, the synchronization signal detection unit 36 ​​performs a process of determining whether or not a synchronization signal block (SSB) has been detected based on the acquired detection result. As a determination result, the synchronization signal detection unit 36 ​​makes a determination (OK) indicating that a synchronization signal block (SSB) has been detected, or a determination (NG) indicating that a synchronization signal block (SSB) has not been detected.

[0126] Next, in S56, the synchronization signal detection unit 36 ​​operates the state machine for the target broadcaster based on the determination result.

[0127] Specifically, when the state machine for the target operator is in the acquisition state ST11 and no synchronization signal block (SSB) is detected (NG), the synchronization signal detection unit 36 ​​maintains the state machine for the target operator in the acquisition state ST11. Furthermore, when the state machine for the target operator is in the acquisition state ST11 and a synchronization signal block (SSB) is detected (OK), the synchronization signal detection unit 36 ​​transitions the state machine for the target operator to the backward synchronization protection state ST14.

[0128] Furthermore, if the state machine for the target operator detects a synchronization signal block (SSB) consecutively for j search times in the backward synchronization protection state ST14 (OK), the synchronization signal detection unit 36 ​​transitions the state machine for the target operator to the synchronization established state ST13. If the state machine for the target operator detects a synchronization signal block (SSB) consecutively for less than j search times in the backward synchronization protection state ST14 (OK), the synchronization signal detection unit 36 ​​maintains the state machine for the target operator in the backward synchronization protection state ST14. If the state machine for the target operator does not detect a synchronization signal block (SSB) in the backward synchronization protection state ST14 (NG), the synchronization signal detection unit 36 ​​transitions the state machine for the target operator to the acquisition state ST11.

[0129] Furthermore, when the state machine for the target operator is in the synchronization established state ST13 and a synchronization signal block (SSB) is detected (OK), the synchronization signal detection unit 36 ​​maintains the state machine for the target operator in the synchronization established state ST13. Furthermore, when the state machine for the target operator is in the synchronization established state ST13 and a synchronization signal block (SSB) is not detected (NG), the synchronization signal detection unit 36 ​​transitions the state machine for the target operator to the forward synchronization protection state ST15.

[0130] Furthermore, if the state machine for the target operator does not detect a synchronization signal block (SSB) consecutively for k search times in the forward synchronization protection state ST15 (NG), the synchronization signal detection unit 36 ​​transitions the state machine for the target operator to the acquisition state ST11. If the state machine for the target operator does not detect a synchronization signal block (SSB) consecutively for less than k search times in the forward synchronization protection state ST15 (NG), the synchronization signal detection unit 36 ​​maintains the state machine for the target operator in the forward synchronization protection state ST15. If the state machine for the target operator detects a synchronization signal block (SSB) in the forward synchronization protection state ST15 (OK), the synchronization signal detection unit 36 ​​transitions the state machine for the target operator to the synchronization established state ST13.

[0131] When the process of S56 is completed, the synchronization signal detection unit 36 ​​ends this flow.

[0132] 14 is a flowchart showing the flow of the synchronization confirmation signal output process in S28 by the synchronization signal detection unit 36. In S28, the synchronization signal detection unit 26 executes the process according to the flow shown in FIG.

[0133] First, in S61, the synchronization signal detection unit 26 determines whether the state machine of the target operator is in the synchronization established state ST13. If the state machine of the target operator is not in the synchronization established state ST13 (No in S61), the synchronization signal detection unit 26 does not execute any processing, that is, ends this flow without outputting a synchronization confirmation signal. If the state machine of the target operator is in the synchronization established state ST13 (Yes in S61), the synchronization signal detection unit 26 proceeds to the processing in S62.

[0134] In S62, the synchronization signal detection unit 26 outputs a synchronization confirmation signal to the output unit 56. This allows the synchronization signal detection unit 26 to cause the output unit 56 to output synchronization timing information indicating the content of the synchronization signal block (SSB) detected in S27 and the timing at which the synchronization signal block (SSB) was detected, to the timing signal generation unit 34 corresponding to the target operator among the N timing signal generation units 34. After completing the process of S62, the synchronization signal detection unit 26 ends this flow.

[0135] FIG. 15 is a timing chart showing the processing timing of the synchronization signal detector 36 for each search time.

[0136] The synchronization signal detection unit 36 ​​cyclically selects one target operator from among N operators for each search time. Also, the synchronization signal detection unit 36 ​​cyclically selects one target synchronized raster channel, which is the target for detecting synchronization signal blocks, from among the multiple synchronized raster channels for each of N search times.

[0137] In this embodiment, the search time is 200 ms. Therefore, when N=5, the synchronization signal detection unit 36 ​​can select all of the N target operators once every (200 ms x 5) = 1 second. Furthermore, when 28 synchronization raster channels exist in an OFDM signal, the synchronization signal detection unit 36 ​​can perform detection processing of synchronization signal blocks (SSBs) for all frequency bands for one transmission path by performing processing for (200 ms x 5) x 28 = 28 seconds.

[0138] In this embodiment, the synchronization signal detector 36 executes a process of detecting a synchronization signal block (SSB) from an OFDM signal for a detection time of 160 ms within one search time. The synchronization signal detector 36 also executes processes such as setting and changing a set of a target operator, a target transmission path, and a target synchronization raster channel, a determination process, and a state machine operation during the difference time (40 ms) between the search time (200 ms) and the synchronization signal block (SSB) detection processing time (160 ms).

[0139] 15, the numbers written for each operator and search time represent numbers (GSCN) that identify the selected target synchronization raster channel. When the state machines of the N operators are in the acquisition state ST11, the synchronization signal detector 36 cyclically increments the GSCN by one for each search time. When the state machines of the N operators are in the synchronization protection state ST12 or the synchronization probability state ST13, the synchronization signal detector 36 stops incrementing the GSCN and keeps it fixed. This allows the synchronization signal detector 36 to continue demodulating the synchronization raster channel including the synchronization signal block (SSB) after detecting the synchronization signal block (SSB).

[0140] FIG. 16 is a timing chart showing processing timings for a plurality of transmission paths.

[0141] The synchronization signal detector 36 continues to execute the detection process for the synchronization signal block (SSB) for all of the multiple transmission paths until a predetermined termination condition is met, for example, until the synchronization signal block (SSB) is detected for all operators.

[0142] For example, if there are four transmission paths, N=5, and 28 synchronization raster channels in the OFDM signal, the synchronization signal detection unit 36 ​​can perform synchronization signal block (SSB) detection processing for all frequency bands for all four transmission paths by performing processing for (28 seconds x 4) = 112 seconds.

[0143] When the synchronization signal detector 36 establishes a synchronization established state for any of the operators in any of the synchronization raster channels, it continues to fix the target synchronization raster channel for that operator during each subsequent search time. The synchronization raster channel into which the synchronization signal block (SSB) is inserted in the OFDM signal is set arbitrarily for each operator. Therefore, the timing at which the synchronization signal detector 36 establishes a synchronization established state ST13 differs for each operator.

[0144] 17 is a diagram showing a modified example of the configuration of the synchronization signal detection section 36. The synchronization signal detection section 36 may further include a synchronization confirmation section 80, as shown in FIG.

[0145] The synchronization confirmation unit 80 detects the synchronization signal and, when each of the N timing signal generators 34 is generating a timing signal, detects that the synchronization signal is no longer included in the RF signal transmitted from each of the base stations 12 of the N operators, or that the frequency position or time position of the synchronization signal has changed. In this embodiment, the synchronization confirmation unit 80 detects, for example, that an SSB is no longer detected, or that the frequency position or time position of the SSB has changed.

[0146] In this case, the synchronization confirmation unit 80 also detects that the synchronization signal is no longer included when the RF signal itself is no longer detected. Therefore, the synchronization confirmation unit 80 also detects that the synchronization signal is no longer included in the RF signal when the base station 12 no longer transmits the RF signal, or when the coaxial cable between the base station 12 and the relay device 20 is disconnected.

[0147] Then, when the synchronization signal is no longer included in the RF signal from the base station 12 of any of the N operators, or when the frequency position or time position of the synchronization signal changes, the synchronization confirmation unit 80 causes the synchronization signal detection unit 36 ​​to re-execute the process of detecting the synchronization signal. For example, the synchronization confirmation unit 80 causes the synchronization signal detection unit 36 ​​to re-execute the process shown in FIG. 11 . In this case, the synchronization confirmation unit 80 may re-execute the process of detecting the synchronization signal only for the operator transmitting the RF signal that no longer includes the synchronization signal, and may not need to re-execute the process for the other operators. This allows the relay device 20 to properly perform recovery processing even when the synchronization signal is no longer detected during relay processing and the relay device 20 is no longer able to perform relay processing properly.

[0148] The synchronization confirmation unit 80 may cause the synchronization signal detection unit 36 ​​to re-execute the process of detecting a synchronization signal at regular intervals. For example, the synchronization confirmation unit 80 may cause the synchronization signal detection unit 36 ​​to re-execute the process of detecting a synchronization signal once a day during a time period when communication volume is low. This allows the relay device 20 to periodically check the frequency position and time position of the synchronization signal.

[0149] As described above, the relay device 20 according to this embodiment can detect the synchronization signals included in the RF signals transmitted from the base stations 12 of the N operators using a single demodulation circuit. As a result, the relay device 20 can generate timing signals for each of the N operators with a small circuit scale.

[0150] Although the embodiments of the present invention have been described above, the above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These novel embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims.

[0151] The program executed by the parent device 24 in 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).

[0152] 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]

[0153] 10. Wireless communication systems 12 base station 14 Terminal Equipment 20 Relay device 22 Handset 24 Base unit 30 Control Unit 32 Transfer processing section 34 Timing signal generator 36 Synchronization signal detector 80 Synchronization confirmation section ST11 Captured state ST12 Synchronous protection status ST13 Synchronous probability state

Claims

1. A relay device that relays between a base station and a terminal device, thereby transmitting and receiving an RF signal (radio frequency signal) between the base station and the terminal device, The relay device one or more slave units that transmit and receive the RF signals to and from the terminal device by electromagnetic waves via a plurality of antennas; a master unit that transmits and receives the RF signal to and from each of the base stations of N operators (N is an integer of 2 or more); and The RF signal is modulated by a time division multiplexing OFDM signal (orthogonal frequency division multiplexing signal), The parent device is N timing signal generators corresponding to the N operators, respectively; a synchronization signal detection unit that demodulates the OFDM signal from the RF signal transmitted from the base station of each of the N operators, and detects a synchronization signal arranged at a frequency position and a time position determined by each of the N operators from the demodulated OFDM signal; and each of the N timing signal generation units generates, for the RF signal transmitted from the base station of a corresponding operator among the N operators, a timing signal indicating a switching timing between a downlink period in which the OFDM signal is transmitted from the base station to the terminal device and an uplink period in which the OFDM signal is transmitted from the terminal device to the base station, based on the synchronization signal; The synchronization signal detection unit cyclically selecting, for each predetermined search time, one target operator from among the N operators as a target for detecting the synchronization signal; For each search time, a detection process is performed to detect the synchronization signal included in the OFDM signal modulated onto the RF signal transmitted from the base station of the target operator. Relay device.

2. a standard that defines the OFDM signal defines a synchronization signal block in a frequency range and a time range that includes the synchronization signal, and a maximum value of a period of the synchronization signal block included in the OFDM signal; the search time is greater than the maximum value; The synchronization signal detection unit detects the synchronization signal block as the synchronization signal for each search time. The relay device according to claim 1 .

3. a standard defining the OFDM signal defines a plurality of synchronous raster channels representing frequency ranges in which the synchronization signal blocks can be inserted; Each of the N base stations modulates the OFDM signal, in which the synchronization signal block is inserted into a synchronization raster channel determined by a corresponding operator among the plurality of synchronization raster channels, into the RF signal; The synchronization signal detection unit cyclically selecting, for each search time, one synchronous raster channel from among the plurality of synchronous raster channels that are to be subjected to detection of the synchronization signal block as a target synchronous raster channel; A synchronization signal detection process is performed for each search time to detect the synchronization signal block inserted in the target synchronization raster channel in the OFDM signal. The relay device according to claim 2 .

4. the base station forms a plurality of transmission paths using a multiple input multiple output (MIMO) scheme using a plurality of antennas, and transmits and receives the RF signal through each of the plurality of transmission paths; The synchronization signal detection unit For each search time, a pair of a target transmission path among the plurality of transmission paths and the target synchronous raster channel is cyclically selected one by one from combinations of the plurality of transmission paths and the plurality of synchronous raster channels; In the synchronization signal detection process, for each search time, the OFDM signal is demodulated from the RF signal transmitted from the base station of the target operator to the target transmission path, and the synchronization signal block inserted in the target synchronization raster channel in the demodulated OFDM signal is detected. The relay device according to claim 3 .

5. the synchronization signal detection unit sets the operation state of each of the N operators to one of an acquisition state, a synchronization protection state, and a synchronization established state; The synchronization signal detection unit, for each search time, When the operation state of the target carrier is the acquisition state, a pair of the target transmission path and the target synchronous raster channel is cyclically selected one by one from all combinations of the plurality of transmission paths and the plurality of synchronous raster channels. The relay device according to claim 4 .

6. The synchronization signal detection unit, for each search time, When the operation state of the target carrier is the synchronization protection state or the synchronization establishment state, the pair of the target transmission path and the target synchronization raster channel is set to be the same as the pair of the target transmission path and the target synchronization raster channel set at the immediately previous search time. The relay device according to claim 5 .

7. the synchronization protection state includes a backward synchronization protection state; For each search time, the synchronization signal detection unit: When the operation state for the target operator is the acquisition state and the synchronization signal block is detected, transitioning the operation state to the backward synchronization protection state; When the operation state of the target carrier is the backward synchronization protection state and the synchronization signal block is detected consecutively for j search times (j is an integer of 1 or more), the operation state is transitioned to the synchronization established state; When the operation state of the target operator is the backward synchronization protection state and the synchronization signal block is not detected, the operation state is transitioned to the acquisition state. The relay device according to claim 6.

8. The synchronization protection state further includes a forward synchronization protection state, For each search time, the synchronization signal detection unit: The synchronization signal detection unit If the operation state of the target operator is the synchronization established state and the synchronization signal block is not detected, transition the operation state to the forward synchronization protection state; When the operating state of the target operator is the forward synchronization protection state and the synchronization signal block is not detected consecutively for k search times (k is an integer equal to or greater than 1), the operating state is transitioned to the acquisition state; When the operation state of the target operator is the forward synchronization protection state and the synchronization signal block is detected, the operation state is transitioned to the synchronization established state. The relay device according to claim 7.

9. For each search time, the synchronization signal detection unit outputs information indicating the detected synchronization signal block and detection timing to a timing signal generation unit corresponding to the target operator among the N timing signal generation units. The relay device according to claim 8 .

10. a synchronization confirmation unit that detects that the synchronization signal is no longer included in the RF signals transmitted from the base stations of the N operators; The synchronization confirmation unit causes the synchronization signal detection unit to re-execute the process of detecting the synchronization signal when the RF signal from the base station of any one of the N operators no longer contains the synchronization signal, or when the frequency position or time position of the synchronization signal changes. The relay device according to claim 1 .

11. The apparatus further includes a synchronization confirmation unit that causes the synchronization signal detection unit to re-execute the process of detecting the synchronization signal for each of the N operators at regular intervals. The relay device according to claim 1 .

12. The base station transmits and receives the RF signals to and from the base stations of the N operators via a coaxial cable including an electric wire. The relay device according to claim 1 .

13. each of the one or more slave units and the master unit is connected by an optical fiber cable; each of the one or more slave devices converts the RF signal received from the terminal device into an optical signal and transfers it to the master device, converts the optical signal transferred from the master device into an RF signal and transfers it to the terminal device; The master unit converts the RF signal received from the base station into an optical signal and transfers it to each of the one or more slave units, and converts the optical signal transferred from each of the one or more slave units into an RF signal and transmits it to the base station. The relay device according to claim 1 .

14. A relay method for transmitting and receiving an RF signal (radio frequency signal) between a base station and a terminal device by a relay device that relays between the base station and the terminal device, comprising: The relay device one or more slave units that transmit and receive the RF signals to and from the terminal device by electromagnetic waves via a plurality of antennas; a master unit that transmits and receives the RF signal to and from each of the base stations of N operators (N is an integer of 2 or more); and The RF signal is modulated by a time division multiplexing OFDM signal (orthogonal frequency division multiplexing signal), an information processing device that controls the parent device, demodulating the OFDM signal from the RF signal transmitted from the base station of each of the N operators, and detecting a synchronization signal arranged at a frequency position and a time position determined by each of the N operators from the demodulated OFDM signal; generating, for each of the N operators, a timing signal indicating a switching timing between a downlink period in which the OFDM signal is transmitted from the base station to the terminal device and an uplink period in which the OFDM signal is transmitted from the terminal device to the base station, based on the synchronization signal, for the RF signal transmitted from the base station of the corresponding operator; The information processing device, in detecting the synchronization signal, cyclically selecting, for each predetermined search time, one target operator from among the N operators as a target for detecting the synchronization signal; For each search time, a detection process is performed to detect the synchronization signal included in the OFDM signal modulated onto the RF signal transmitted from the base station of the target operator. Relay method.

15. A program executed by an information processing device that controls a relay device that relays between a base station and a terminal device, thereby transmitting and receiving an RF signal (radio frequency signal) between the base station and the terminal device, The relay device one or more slave units that transmit and receive the RF signals to and from the terminal device by electromagnetic waves via a plurality of antennas; a master unit that transmits and receives the RF signal to and from each of the base stations of N operators (N is an integer of 2 or more); and The RF signal is modulated by a time division multiplexing OFDM signal (orthogonal frequency division multiplexing signal), The program The information processing device N timing signal generators corresponding to the N operators, respectively; a synchronization signal detection unit that demodulates the OFDM signal from the RF signal transmitted from the base station of each of the N operators, and detects a synchronization signal arranged at a frequency position and a time position determined by each of the N operators from the demodulated OFDM signal; and make it work, each of the N timing signal generation units generates, for the RF signal transmitted from the base station of a corresponding operator among the N operators, a timing signal indicating a switching timing between a downlink period in which the OFDM signal is transmitted from the base station to the terminal device and an uplink period in which the OFDM signal is transmitted from the terminal device to the base station, based on the synchronization signal; The synchronization signal detection unit cyclically selecting, for each predetermined search time, one target operator from among the N operators as a target for detecting the synchronization signal; For each search time, a detection process is performed to detect the synchronization signal included in the OFDM signal modulated onto the RF signal transmitted from the base station of the target operator. program.

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