JP7398359B2 - Base station device and synchronization control method - Google Patents

Description

The present invention relates to a base station device and a synchronization control method.

In recent years, fifth generation mobile communication systems, which can be used by various entities according to regional or individual needs, have been attracting attention. Such a mobile communication system is sometimes referred to as local 5G (5th Generation), for example.

With local 5G, apart from nationwide 5G systems provided by mobile carriers, various entities such as local companies and local governments can build networks on their own in spots within their buildings and premises. Therefore, local 5G is expected to be used for a variety of needs closely related to regions.

On the other hand, the 3rd Generation Partnership Project (3GPP), which is a standardization project that examines and creates specifications for mobile communication systems, is progressing with the standardization of non-public networks (NPN).

In 3GPP, as non-public networks, SNPN (Stand-alone NPN), which is independent from the 5G public network, and PNI NPN (Public Network Integrated NPN), which shares all or part of the 5G public network, are defined.

Furthermore, in mobile communication systems, a TDD (Time Division Duplex) method has been used in some cases. In the TDD method, for example, communication in the downlink direction (communication link direction from the base station to the terminal) and communication in the uplink direction (communication link direction from the terminal to the base station) use the same frequency band. This method is performed at different timings.

Guidelines for local 5G introduction, December 2019, Ministry of Internal Affairs and Communications 3GPP TS38.300 V16.2.0 (2020-07)

However, in the TDD system, when the timings are shifted between base stations, the time in the uplink direction and the time in the downlink direction may become the same timing. In such a case, interference occurs at the base station. Due to the occurrence of interference, the base station cannot continue to provide stable services to the terminals.

Therefore, an object of the present invention is to provide a base station apparatus and a synchronization control method that can continuously provide stable services.

The base station device according to the first aspect is included in a non-public cellular network and performs TDD wireless communication. The base station device includes first and second wireless units, a control section, and a reception section. The first and second wireless units perform wireless communication with a user device using a predetermined frequency band. The control section controls the first and second wireless units, and the reception section receives the synchronization signal. When the receiving unit cannot normally receive the synchronization signal, the control unit is configured to transmit the first synchronization signal received by the first wireless unit from another base station operated by another carrier different from the carrier operating the base station. The first and second wireless units are synchronized based on the time information.

A synchronous control method according to a second aspect includes first and second wireless units that perform wireless communication with a user device using a predetermined frequency band, and a control unit that controls the first and second wireless units. , a receiving unit that receives a synchronization signal, and is included in a non-public cellular network and performs TDD wireless communication. The synchronization control method includes the step of determining whether the receiving unit has successfully received the synchronization signal. In addition, in the synchronization control method, if the control unit cannot normally receive a synchronization signal in the reception unit, the control unit receives the first base station device from another base station device operated by another carrier different from the carrier operating the base station device. The method includes synchronizing the first and second wireless units based on time information received at the wireless units.

According to one aspect of the present invention, it is possible to provide a base station apparatus and a bandwidth control method that can continuously provide stable services.

FIG. 1 is a diagram showing an example of the configuration of a mobile communication system. FIG. 2 is a diagram illustrating an example of an O-RAN fronthaul protocol stack. FIG. 3(A) is a diagram showing a configuration example of a CU, and FIG. 3(B) is a diagram showing a configuration example of a DU. FIG. 4 is a diagram showing an example of the configuration of an RU. FIG. 5 is a diagram showing an example of the configuration of a mobile communication system. FIG. 6 is a diagram showing an example of the configuration of a mobile communication system. FIG. 7 is a diagram showing an example of operation. FIG. 8 is a diagram showing an example of the configuration of a mobile communication system. FIG. 9(A) is a diagram showing an example of operation when synchronized, and FIG. 9(B) is a diagram showing an example of operation when not synchronized.

Embodiments will be described with reference to the drawings. In the description of the drawings, the same or similar parts are designated by the same or similar symbols.

(Example of configuration of mobile communication system)
First, a configuration example of a mobile communication system 10 according to an embodiment will be described. FIG. 1 is a diagram illustrating a configuration example of a mobile communication system 10 according to an embodiment.

As shown in FIG. 1, the mobile communication system 10 includes a gNB (next generation Node B) 100 and UE (User Equipment) (or user equipment, hereinafter sometimes referred to as "UE") 200-1 to 200-. It has 3.

The gNB 100 according to one embodiment is an example of a base station device. gNB 100 functions as a base station device in the 3GPP 5G system. The gNB 100 performs wireless communication with the UEs 200-1 to 200-3 and provides various services to the UEs 200-1 to 200-3.

Furthermore, the gNB 100 is a base station device included in the local 5G system. A local 5G system may be a non-public cellular network. The non-public cellular network may be an example of the NPN described above. Further, the local 5G system may be a 5G system built by the owner of the building or land within the building or land. Mobile communication system 10 is an example of a non-public cellular network.

The gNB 100 in the local 5G system performs wireless communication using a predetermined frequency band. An example of the predetermined frequency band is, for example, a 4.5 GHz band. The gNB 100 in this embodiment may operate in a frequency band other than the 4.5 GHz band as long as it is a predetermined frequency band used by a base station device of a local 5G system.

The UEs 200-1 to 200-3 are, for example, a smartphone, a feature phone, an IoT (Internet of Things) device, a personal computer, a vehicle or a device installed in a vehicle, an aircraft, or a device installed in an airplane. In the example of FIG. 1, three UEs 200-1 to 200-3 are shown, but there may be one or two, or four or more.

Note that FIG. 1 shows an artificial satellite 300. gNB 100 is capable of receiving a synchronization signal (Global Navigation Satellite System) signal transmitted from artificial satellite 300. As such a synchronization signal, there is a GNSS (Global Navigation Satellite System) signal. A GPS (Global Positioning System) signal is an example of a GNSS signal.

(Example of configuration of gNB100)
As shown in FIG. 1, the gNB 100 includes a CU (Centralized Unit) 110, multiple DUs (Distributed Units) 120-1, 120-2, and multiple RUs (Radio Units) 130-1 to 130-4. .

CU 110 may be referred to as an aggregation unit. The CU 110 is connected to each DU 120-1, 120-2 and controls the plurality of DUs 120-1, 120-2. The CU 110 may be connected to an external network to transmit and receive data to and from the external network.

Each DU 120-1, 120-2 may be referred to as a distributed unit. Each DU 120-1, 120-2 is connected to the CU 110. Further, DU 120-1 is connected to RUs 130-1 and 130-2, and DU 120-2 is connected to RUs 130-3 and 130-4.

In the example of FIG. 1, the description will be made assuming that DU 120-2 can receive the synchronization signal and DU 120-1 does not receive the synchronization signal.

Each RU 130-1 to 130-4 may be referred to as a wireless unit. The RUs 130-1 and 130-2 perform wireless communication using the TDD method under the control of the DU 120-1. Further, the RUs 130-3 and 130-4 perform wireless communication using the TDD method under the control of the DU 120-2.

That is, each RU 130-1 to 130-4 performs the first communication in the downlink direction from the gNB 100 to the UEs 200-1 to 200-3, and the second communication in the uplink direction from the UE 200-1 to 200-3 to the gNB 100. communications are performed at different timings using the same frequency band. Furthermore, each RU 130-1 to 130-4 performs first communication and second communication in synchronization with each other based on a synchronization signal.

FIG. 9(A) and FIG. 9(B) are diagrams showing an example of operation in the TDD system. Of these, FIG. 9A shows an example of operation when each RU 130-1, 130-2 is synchronized with the synchronization signal. Note that, in FIGS. 9A and 9B, RUs 130-1 and 130-2 are representatively shown among the RUs 130-1 to 130-4.

As shown in FIG. 9(A), RU 130-1 and RU 130-2 communicate D (Downlink direction), S (Special Frame), and U (Uplink direction) at the same timing. . "D" represents a subframe in which communication in the downlink direction is performed, and "U" represents a subframe in which communication in the uplink direction is performed. Moreover, "S" is a special subframe, and includes an uplink period, a downlink period, and a guard period.

Further, in FIG. 9(A), "GPS (Global Positioning System) standard" is shown. The gNB 100 synchronizes the timing of each of the RUs 130-1 to 130-4 based on the received synchronization signal at "GPS-based" timing. In the example of FIG. 9A, each RU 130-1, 130-2 is set to "D" at the "GPS reference" timing.

In the example of FIG. 9A, for example, at timing "D", a wireless signal is transmitted from the RU 130-1. The radio signal reaches RU130-2. However, the RU 130-2 transmits wireless signals at the same timing as the RU 130-1. Therefore, RU 130-2 does not receive the wireless signal transmitted from RU 130-1. Therefore, no interference occurs.

On the other hand, FIG. 9(B) shows an example of operation when interference occurs. As shown in FIG. 9B, in the "GPS standard", the GPS signal cannot be received normally, and the timings between the RUs 130-1 and 130-2 are not synchronized.

That is, the timings of "D", "S", and "U" are different between the RUs 130-1 and 130-2. For example, as shown by the arrows in FIG. 9(B), the RU 130-1 is at the "D" timing, and the RU 130-2 is at the "U" timing. In this case, the RU 130-1 transmits a wireless signal to the UE 200-1 at timing "D", and the wireless signal reaches the RU 130-2. RU 130-2 receives the wireless signal transmitted from RU 130-1 due to the timing of "U". Therefore, interference occurs in RU 130-2. Similarly, interference also occurs in RU 130-1.

If such interference occurs, the gNB 100 cannot provide continuous service to the UEs 200-1 to 200-3 if it stops transmitting radio waves. Furthermore, even if such interference occurs, if gNB 100 continues to provide services, UEs 200-1 to 200-3 may not be able to receive or receive services due to the interference. . Therefore, UEs 200-1 to 200-3 cannot receive stable services.

Therefore, when the gNB 100 in this embodiment fails to receive the synchronization signal normally, it synchronizes the RUs 130-1 to 130-4 based on the time information received from the base station of another operator.

Specifically, in a gNB 100 that is included in a non-public cellular network and performs wireless communication using the TDD method, the control unit of the CU 110 controls the business that operates the gNB 100 when the receiving unit of the DU 120-2 cannot normally receive a synchronization signal. The RUs 130-1 to 130-4 are synchronized based on time information received by the RU 130-1 from another base station operated by another operator different from the RU 130-1.

This makes it possible for the gNB 100 to synchronize each RU 130-1 to 130-4. Therefore, the gNB 100 can synchronize the RUs 130-1 to 130-4 to the UEs 200-1 to 200-3 without stopping radio wave transmission. Able to provide continuous service. Furthermore, the gNB 100 does not cause interference and can provide stable services to the UEs 200-1 to 200-3.

Note that hereinafter, unless otherwise specified, the DUs 120-1 and 120-2 may be referred to as DUs 120. Furthermore, the RUs 130-1 to 130-4 may be referred to as RUs 130, and the UEs 200-1 to 200-3 may be referred to as UEs 200.

(About functional separation of CU110, DU120, RU130)
In gNB 100 in this embodiment, an O-RAN (Open Radio Access Network) fronthaul specification is adopted between DU 120 and RU 130. However, other communication protocols may be used between the DU 120 and the RU 130, and the use is not limited to the O-RAN fronthaul specification (hereinafter sometimes referred to as "O-RAN"). Therefore, the O-RAN example is only one example.

O-RAN is a specification developed by the O-RAN Alliance, which includes multiple carriers. In O-RAN, Split Option 7-2x is adopted for functional separation of the CU 110, DU 120, and RU 130.

FIG. 2 is a diagram showing an example of functional separation of the CU 110, DU 120, and RU 130 using Split Option 7-2x. As shown in FIG. 2, the CU 110 is capable of executing functions of each layer of RRC (Radio Resource Control), SDAP (Service Data Adaptation Protocol), and PDCP (Packet Data Convergence Protocol). Further, the DU 120 is capable of executing functions of each layer of RLC (Radio Link Control), MAC (Media Access Control), and PHY-High (Physical-High) (part of PHY). Further, the RU 130 is capable of executing functions of PHY-Low (part of PHY) and RF (Radio Frequency) layers.

One of the features of O-RAN is that a part of the PHY layer is located in the RU 130. Thereby, for example, the burden on the DU 120 can be reduced.

As shown in Figure 2, in the PHY-HIgh layer, in the downlink direction of the user plane, processing such as error correction encoding processing, scrambling processing, modulation processing, and layer mapping is performed on data from the MAC layer. be exposed. In the PHY-HIgh layer, through these processes, an IQ (In-phase and Quadrature) sample sequence of an OFDM (Orthogonal Frequency Division) signal in the frequency domain is generated. DU 120 transmits this IQ sample sequence to RU 130.

The RU 130 receives the IQ sample string of the OFDM signal. In the PHY-Low layer, IFFT (Inverse Fast Fourier Transfer) processing and analog conversion processing are performed. The PHY-Low layer converts the IQ sample sequence of the OFDM signal into a time domain analog signal. Then, the RU 130 converts the analog signal into a wireless signal.

Furthermore, as shown in FIG. 2, in the uplink direction of the user plane, processing basically opposite to that in the downlink direction is performed in the PHY-Low layer and the PHY-High layer. The RU 130 transmits the IQ sample sequence of the frequency domain OFDM signal to the DU 120.

Note that O-RAN may also be employed between the DU 120 and the RU 130.

(Each configuration example of CU110, DU120, RU130)
FIG. 3A is a diagram showing a configuration example of the CU 110, FIG. 3B is a diagram showing a configuration example of the DU 120, and FIG. 4 is a diagram showing a configuration example of the RU 130.

As shown in FIG. 3A, the CU 110 includes an interface section 111 and a control section 112.

The interface unit 111 outputs packet data in a predetermined format received from the network 500 to the control unit 112, and transmits data or control signals output from the control unit 112 to the DU 120. Further, the interface unit 111 outputs data or control signals transmitted from the DU 120 to the control unit 112, and transmits packet data in a predetermined format output from the control unit 112 to the network 500.

The control unit 112 performs various controls in the CU 110. Further, the control unit 112 executes each function of RRC, SDAP, and PDCP to extract data from packet data or generate a control signal, for example. The control unit 112 outputs data or control signals to the interface unit 111. Further, the control unit 112 converts data into packet data in a predetermined format, for example, by executing each function of RRC, SDAP, and PDCP. Control section 112 outputs packet data to interface section 111.

As shown in FIG. 3(B), the DU 120 includes an interface section 121, a receiving section 122, and a control section 123. FIG. 3(B) shows a configuration example of the DU 120-2.

The interface unit 121 outputs data or control signals received from the CU 110 to the control unit 123, and transmits predetermined messages received from the control unit 123 to the RUs 130-1 and 130-2. Further, the interface unit 121 outputs predetermined messages received from the RUs 130-1 and 130-2 to the control unit 123, and transmits data or control signals received from the control unit 123 to the CU 110.

Receiving section 122 receives a synchronization signal transmitted from artificial satellite 300. Receiving section 122 outputs the received synchronization signal to control section 123. Furthermore, when the receiving section 122 fails to receive the synchronization signal normally, it outputs a signal indicating this to the control section 123.

Here, "when the GPS signal could not be received normally" includes, for example, when the GPS signal could not be received, or when the GPS signal could be received but the received power was lower than the threshold value. . In addition, "when a GPS signal cannot be received normally" means, for example, when a GPS signal that should be periodically received cannot be received even once, or when multiple GPS signals that should be periodically received are consecutively received. It may also include times when the data could not be received. Furthermore, "when a GPS signal cannot be received" means, for example, when a GPS signal cannot be received for a certain period of time, regardless of whether it is periodic or not, or when a GPS signal cannot be received continuously for a certain period of time. may also be included.

The control unit 123 generates a predetermined message containing the data or control signal output from the interface unit 121 by executing the RLC, MAC, and PHY-High functions. The predetermined message may be an O-RAN eCPR message. The control unit 123 outputs a predetermined message to the interface unit 121. Furthermore, the control unit 123 extracts data or control signals from a predetermined message output from the interface unit 121 by executing each of these functions. The control section 123 outputs data or control signals to the interface section 121.

Further, upon receiving the normally received synchronization signal from the reception unit 122, the control unit 123 performs synchronization control on each of the RUs 130-1 and 130-2 based on the synchronization signal. PTP (Precision Time Protocol) may be used for the synchronization control. PTP is used by S-Plane (Synchronization-Plane) of O-RAN.

Furthermore, when the control unit 123 receives a signal indicating that the GPS signal could not be received normally from the reception unit 122, it generates a message (or control signal) indicating that fact. Then, the control unit 123 transmits the generated message to the CU 110 via the interface unit 121.

Note that the DU 120-1 does not have the receiving section 122, but has an interface section 121 and a control section 123.

As shown in FIG. 4, the RU 130 includes an interface section 131, a wireless processing section 132, and an antenna 133.

The interface unit 131 extracts data, control signals, etc. from a predetermined message transmitted from the DU 120, and outputs the extracted data, control signals, etc. to the wireless processing unit 132. Further, the interface unit 131 generates a predetermined message including data or a control signal in response to the data or control signal output from the wireless processing unit 132, and outputs the message to the DU 120.

The wireless processing unit 132 performs PHY-Low layer processing, and further performs conversion (up-conversion) processing of data or control signals into wireless signals. Wireless processing section 132 outputs a wireless signal to antenna 133. Furthermore, the radio processing unit 132 performs a process of converting (down converting) the radio signal received from the antenna 133 into baseband data or a control signal, and further performs PHY-Low layer processing. The wireless processing unit 132 outputs processed data or control signals to the interface unit 131.

Antenna 133 transmits the radio signal output from radio processing section 132 to UE 200. Further, the antenna 133 receives a radio signal transmitted from the UE 200 and outputs the received radio signal to the radio processing unit 132.

(Operation example)
FIG. 5 is a diagram illustrating an operation example when the gNB 100 cannot normally receive the synchronization signal from the artificial satellite 300.

In such a case, the gNB 100 cannot accurately perform synchronization control based on the synchronization signal. Therefore, as shown in FIG. 5, each of the RUs 130-1 to 130-4 may not have "D", "U", or "S" at the same timing. In this case, interference occurs in the RUs 130-1 to 130-4 and the UE 200.

FIG. 6 is a diagram showing an example of the relationship between the mobile communication system 10 including the gNB 100 and base stations 400-1 to 400-3 operated by other carriers. The example in FIG. 6 shows an example in which base stations 400-1 to 400-3 respectively operated by first to third carriers different from the carrier operating the mobile communication system 10 are arranged.

In other words, a first operator operates a base station 400-1, a second operator operates a base station 400-2, and a third operator operates a base station 400-3, each using a local 5G system. There is. That is, the base stations 400-1 to 400-3 perform wireless communication with the user equipments under each of them using the same predetermined frequency band as the gNB 100 at the same timing.

FIG. 6 shows an example in which RU 130-1 receives wireless signals transmitted from each base station 400-1 to 400-3.

FIG. 7 is a diagram showing an example of operation in this embodiment.

As shown in FIG. 7, in step S10, the gNB 100 starts processing.

In step S11, the CU 110 detects that the synchronization signal could not be normally received from the artificial satellite 300. For example, the control unit 112 of the CU 110 may perform the detection by receiving from the DU 120 a message generated by the control unit 123 of the DU 120 indicating that the synchronization signal could not be received normally.

In step S12, the CU 110 instructs the specific RU 130 to search for transmission radio waves transmitted from base stations 400-1 to 400-3 of other carriers. Then, in step S12, the CU 110 acquires base station ID (Identification), radio field strength, and time information from base stations 400-1 to 400-3 of other carriers. In the example of FIG. 6, the CU 110 issues a search instruction to the RU 130-1. The CU 110 may acquire information as follows, for example.

(Obtaining radio field strength)
That is, in response to receiving the message indicating that the synchronization signal could not be received normally, the control unit 112 of the CU 110 causes the RU 130-1 to search for base stations 400-1 to 400-3 of other carriers. instruct them to do so. The control unit 112 may transmit a message indicating a search instruction to the RU 130-1 via the DUs 120-1 and 120-2. The wireless processing unit 132 of the RU 130-1 searches radio waves transmitted from each base station 400-1 to 400-3 in response to receiving the search instruction message. Through this search, the wireless processing unit 132 measures the radio field strength of the radio waves transmitted from each base station 400-1 to 400-3. The radio processing unit 132 measures radio field strength based on reference signals (CSI-RS (Channel State Information - Reference Signal): channel state reference signal, etc.) transmitted from each base station 400-1 to 400-3. You may. Alternatively, the wireless processing unit 132 may measure the radio field intensity of broadcast information (SIB (System Information Block)) transmitted from each base station 400-1 to 400-3. The radio field strength itself may be RSSI (Received Signal Strength Indicator), RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), or the like.

(Obtaining base station ID and time information)
Furthermore, the wireless processing unit 132 of the RU 130-1 receives broadcast information broadcast from each base station 400-1 to 400-3. The broadcast information includes the base station ID and time information of each operator. In response to receiving the search instruction message, the wireless processing unit 132 of the RU 130-1 searches radio waves transmitted from each base station 400-1 to 400-3, and broadcasts from each base station 400-1 to 400-3. receive broadcast information. The wireless processing unit 132 of the RU 130-1 extracts the base station ID and time information from the received broadcast information. The wireless processing unit 132 of the RU 130-1 transmits the extracted base station ID and time information, as well as the measured radio field strength, to the CU 110 via the DUs 120-1 and 120-2. When the interface unit 131 of the RU 130-1 receives the base station ID, time information, and radio field strength of each of the base stations 400-1 to 400-3 from the wireless processing unit 132 of the RU 130-1, it generates a message containing these information. Then, it may be transmitted to the CU 110 via the DUs 120-1 and 120-2. Note that instead of the base station ID, which is the identification information that identifies the base stations 400-1 to 400-3, a business ID, which is the identification information that identifies the business operator, may be used.

In step S13, the CU 110 determines which time information to use based on the information acquired from the base stations 400-1 to 400-3 of each operator. The CU 110 may determine the time information to use in the following manner.

That is, among the radio field strengths obtained from the base stations 400-1 to 400-3, the time information obtained from the base station 400-1 to 400-3 with the strongest radio field strength may be used as the time information to be used. The reason is, for example, as follows. In other words, in the case of gNB100, in order to periodically acquire time information broadcast from each base station 400-1 to 400-3 and perform stable time synchronization within gNB100, it is necessary to use the highest radio wave intensity. This is because the time information transmitted from the base stations 400-1 to 400-3 should be used. Alternatively, the CU 110 compares the radio field intensities obtained from the base stations 400-1 to 400-3 with the threshold value, and selects the base station 400-1 to 400 that has the highest radio field strength among the radio field strengths that exceed the threshold value. The time information sent from -3 may also be used.

In step S14, the CU 110 starts operating each of the RUs 130-1 to 130-4 using the determined time information. For example, the CU 110 may start operation as follows.

That is, upon determining which base station 400-1 to 400-3 to use the time information transmitted from, the CU 110 determines the base station ID of the base station 400-1 to 400-3 that broadcasts the determined time information. Send to RU130-1. For example, the CU 110 transmits the base station ID of the base station 400-1 to the RU 130-1 via the DU 120-1. RU 130-1 periodically receives broadcast information broadcast from base station 400-1 corresponding to the base station ID. The RU 130-1 extracts time information from the received broadcast information, and transmits the extracted time information to the CU 110, DUs 120-1, 120-2, and RUs 130-2 to 130-4 using PTP.

When the control unit 112 of the CU 110 transmits the base station ID to the RU 130-1, the RU 130-1 acquires the time information broadcast from the base station 400-1 and transmits the time information to each unit of the gNB 100. are doing. Therefore, it can be said that the control unit 112 controls the RUs 130-1 to 130-4 to synchronize them based on the time information received from the base station 400-1.

FIG. 8 is a diagram showing an example in which time information acquired from the base station 400-1 is transmitted to each part within the gNB 100. As shown in FIG. 8, each block within the gNB 100 can periodically acquire time information. Therefore, the RUs 130-1 to 130-4 can perform processing synchronously. Therefore, the radio frames transmitted from each of the RUs 130-1 to 130-4 are "D", "U", and "S" at the same timing. Therefore, the mobile communication system 10 can prevent interference from occurring.

Returning to FIG. 7, in step S15, the gNB 100 ends the series of processes.

(Other embodiments)
In the embodiment described above, an example has been described in which the RU 130-1 acquires time information broadcast from the base stations 400-1 to 400-3. For example, the RUs 130-1 to 130-4 may acquire time information etc. broadcast from the base stations 400-1 to 400-3. In this case, for example, the time information of the best radio field strength may be acquired as follows.

That is, the CU 110 transmits a message indicating a search instruction to all RUs 130-1 to 130-4 via DUs 120-1 and 120-2. The wireless processing unit 132 of each RU 130-1 to 130-4 searches for radio waves transmitted from the base stations 400-1 to 400-3 in response to receiving the message. The wireless processing unit 132 of each RU 130-1 to 130-4 measures the radio field intensity of each base station 400-1 to 400-3, and Receive the broadcast information. The wireless processing unit 132 of each RU 130-1 to 130-4 transmits the measured radio field strength, the base station ID and time information extracted from the broadcast information to the CU 110 via the DU 120-1 and 120-2. . The CU 110 determines time information with the highest radio field intensity among the acquired radio field strengths. For example, the CU 110 determines that the radio field intensity from the base station 400-1 acquired from the RU 130-1 is the highest among the RUs 130-1 to 130-4. Then, the CU 110 determines the time information acquired from the base station 400-1 as the best time information. In this case, the CU 110 transmits the base station ID of the base station 400-1 to the RU 130-1. RU 130-1 periodically acquires time information from base station 400-1. The RU 130-1 uses PTP to transmit time information to each part of the gNB 100. This enables the gNB 100 to perform time synchronization similarly to the embodiment described above.

Note that if all of the RUs 130-1 to 130-4 are unable to obtain broadcast information transmitted from the base stations 400-1 to 400-3, the CU 110 suspends all RUs 130-1 to 130-4. It's okay.

Furthermore, in the embodiment described above, an example has been described in which the DU 120-2 detects a synchronization signal from the artificial satellite 300. For example, both DUs 120-1 and 120-2 may detect the synchronization signal. In this case, for example, when DU120-2 cannot receive a synchronization signal normally, if DU120-1 is able to receive a synchronization signal normally, it is possible to perform synchronization control using this synchronization signal. It is. For example, the synchronization signal may be acquired as follows.

That is, the DU 120-2 sends a message to the CU 110 indicating that the synchronization signal could not be received normally, and the CU 110 inquires of the DU 120-1 whether or not the synchronization signal could be received normally. Inquiries may also be made using predetermined messages. In response to receiving the inquiry, DU 120-1 checks whether or not the synchronization signal can be received normally. If the DU 120-1 successfully receives the synchronization signal, it uses PTP to transmit the synchronization signal to the RUs 130-1 to 130-4, and performs synchronization control for the RUs 130-1 to 130-4. .

Note that if the DU 120-1 also fails to receive the synchronization signal normally, it notifies the CU 110 to that effect. The notification may also be made by a message indicating this. In response to receiving the notification, CU 110 transmits a search instruction to RU 130-1. The subsequent steps can be implemented in the same manner as in the embodiment described above.

Furthermore, in the embodiment described above, an example in which the DU 120 is plural has been described. For example, the number of DUs 120 may be one. In this case, DU 120 becomes DU 120-2 that receives the synchronization signal.

Furthermore, in the embodiment described above, an example was described in which the DU 120-2 detects a synchronization signal. For example, CU 110 may receive a synchronization signal transmitted from artificial satellite 300. In this case, a receiving unit 122 that receives the synchronization signal may be placed in the CU 110 and connected to the control unit 112. If the receiving unit 122 cannot normally receive the synchronization signal, the control unit 112 of the CU 110 may issue a search instruction to the RU 130-1 via the DU 120-1.

Furthermore, in the embodiment described above, an example was described in which time information to be used by the CU 110 is determined (step S13 in FIG. 7). For example, the control unit 123 of the DU 120 may determine the time information to be used. In this case, when the receiving unit 122 cannot normally receive the synchronization signal, the control unit 123 of the DU 120-2 issues a search instruction to the RU 130-1 via the DU 120-1. The RU 130-1 transmits the measured radio field strength, the acquired time information, and the base station ID to the DU 120-2 via the DU 120-1. Then, the control unit 123 of the DU 120-2 determines the time information to be used based on the acquired information, and transmits the base station ID to the RU 130-1 via the DU 120-1.

Although the embodiments have been described above in detail with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the scope of the invention. Further, the above-mentioned examples can be combined as long as they are not contradictory.

10: Mobile communication system 100: gNB
110:CU
111: Interface unit 112: Control unit 120 (120-1, 120-2): DU
121: Interface section 122: Receiving section 123: Control section 130 (130-1 to 130-4): RU
131: Interface section 132: Radio processing section 133: Antenna 200: UE
300: Satellite 400-1 to 400-3: Base station 500: Network

Claims (7)

A base station device included in a non-public cellular network and performing TDD wireless communication,
first and second wireless units that perform the wireless communication with a user device using a predetermined frequency band;
a control unit that controls the first and second wireless units;
A receiving unit that receives a synchronization signal,
If the receiving unit cannot normally receive the synchronization signal, the control unit may transmit the first radio unit from another base station operated by another operator different from the operator operating the base station. A base station device that synchronizes the first and second wireless units based on first time information received at the base station device. a distributed unit connected to the first and second wireless units and controlling the first and second wireless units;
an aggregation unit connected to the distribution unit and controlling the distribution unit,
The base station apparatus according to claim 1, wherein the control section is provided in the distribution unit or the aggregation unit. When the control unit receives time information from each of the plurality of other base station devices, the control unit synchronizes the first and second wireless units based on the first time information having the highest radio field intensity. , The base station device according to claim 1. The control unit also controls the radio field strength to be the highest based on the time information, radio field strength, and identification information of the other base station devices respectively received from the plurality of other base station devices in the first wireless unit. The base station apparatus according to claim 3, wherein the first time information is determined to be high. The control section is configured to cause the first and second wireless units to transmit the first time information based on the first time information having the highest radio field intensity among the time information each received from the plurality of other base station devices. The base station apparatus according to claim 1, wherein the base station apparatus synchronizes the first and second radio units. The base according to claim 1, wherein the control unit instructs the first radio unit to search for radio waves for the other base station device if the synchronization signal cannot be received normally in the reception unit. station equipment. A first and second wireless unit that performs wireless communication with a user device using a predetermined frequency band, a control unit that controls the first and second wireless units, and a receiving unit that receives a synchronization signal. 1. A synchronization control method in a base station device that is included in a non-public cellular network and performs TDD wireless communication, the method comprising:
a step of determining whether the receiving unit has successfully received the synchronization signal;
If the control unit is unable to normally receive the synchronization signal in the reception unit, the control unit may receive the first wireless unit from another base station operated by another operator different from the operator operating the base station. synchronizing the first and second wireless units based on time information received in the synchronization control method.

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