Distributed antenna system, master unit, remote unit, and operation control method

Abstract

To provide a distributed antenna system with an increased operational flexibility, with eliminating constraints regarding shared use of infrastructure.SOLUTION: According to an embodiment, a distributed antenna system includes a master unit, and a remote unit having an antenna capable of covering a first band and a second band neighboring to the first band. The master unit includes a base station connection part, a slave station connection part, a detection part, and an operation control part. The base station connection part is capable being connected to a first base station to which a first band is allocated and a second base station to which a second band is allocated. The slave station connection part is capable being connected to the remote unit. The detection part detects a downlink signal in the first band. The operation control part allows an operation configuration in which a time division multiplexing pattern in the second band and a time division multiplexing pattern in the first band are different, in a period in which loss of the downlink signal in the first band is detected from the output of the detection part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a distributed antenna system, a master unit, a remote unit, and an operation control method. [Background technology]

[0002] The communication area of ​​5G (fifth generation mobile communication system) is gradually expanding. Optical repeater equipment is playing a role in this expansion. This equipment, also known as a Distributed Antenna System (DAS), comprises a master unit (parent station) connected to a base station and remote units (child stations) connected to the master unit via optical fiber.

[0003] Local 5G is a system that allows licensees to provide mobile communications services in areas they own. For example, if a local 5G area is established in an area where a telecommunications carrier's service area is already in operation, there is a risk of radio wave interference if the two frequencies are adjacent. This is because local 5G allows for quasi-synchronous or asynchronous operation using the TDD (Time Division Duplex) method. Therefore, when operators using quasi-synchronous and asynchronous operation coexist, the distance between base stations is increased to cause propagation loss and prevent interference. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-145155 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-24546 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-25382 Summary of the Invention [Problem to be solved by the invention]

[0005] Infrastructure sharing will be applied to the introduction of 5G. Infrastructure sharing is the concept of multiple operators sharing the same communications infrastructure, primarily for cost benefits. In DAS, it is also being considered to accommodate multiple base stations owned by different owners in one master unit. If this technology is applied to local 5G, it will be possible for telecommunications operators and licensees to share the same master unit and remote unit. This type of master unit and remote unit is also called operator-shared equipment.

[0006] However, when multiple base stations are accommodated in a master unit, radio waves from multiple operators are transmitted and received from a single satellite station antenna, making it impossible to prevent interference due to distance. This means that it is difficult to mix operators using quasi-synchronous and asynchronous operation, which means that the downlink (DL) and uplink (UL) settings (time division multiplexing, or TDD, patterns) in the air section are different. These circumstances have hindered the shared use of infrastructure and hindered the expansion of service areas. Therefore, there is a demand for technology that can prevent radio interference, enable the coexistence of operators with different TDD patterns, and support a variety of use cases.

[0007] Therefore, an object is to provide a distributed antenna system, a master unit, a remote unit, and an operation control method that eliminates restrictions related to the shared use of infrastructure and increases the degree of freedom in operation. [Means for solving the problem]

[0008] According to an embodiment, a distributed antenna system includes a master unit and a remote unit equipped with an antenna capable of covering a first band and a second band adjacent to the first band. The master unit includes a base station connection unit, a slave station connection unit, a detector, and an operation control unit. The base station connection unit is connectable to a first base station assigned the first band and a second base station assigned the second band. The slave station connection unit is connectable to the remote unit. The detector detects a downlink signal in the first band. The operation control unit allows an operation mode in which the time division multiplexing pattern in the second band differs from the time division multiplexing pattern in the first band during a period in which loss of the downlink signal in the first band is detected from the output of the detector. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a communication system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of band allocation to a base station. [Figure 3] FIG. 3 is a functional block diagram showing an example of the master station 100 and the slave station 200. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing an example of a TDD pattern in synchronous operation. [Figure 5] FIG. 5 is a diagram for explaining the state of the switches in the DL slot / UL slot. [Figure 6] FIG. 6 is a flowchart showing an example of a processing procedure of the master station 100. [Figure 7] FIG. 7 is a flowchart showing an example of a processing procedure of the master station 100. [Figure 8] FIG. 8 is a diagram showing an example of a modified TDD pattern. [Figure 9] FIG. 9 is a sequence diagram showing an example of a processing procedure when the DL signal is lost. [Figure 10] FIG. 10 shows that the DL signal in band A has disappeared. [Figure 11]FIG. 11 is a sequence diagram showing an example of a processing procedure when the UL signal is lost. [Figure 12] FIG. 12 shows that the UL signal in band A has disappeared. [Figure 13] FIG. 13 is a block diagram for explaining switching between synchronous and asynchronous operation between base stations belonging to different master stations. DETAILED DESCRIPTION OF THE INVENTION

[0010] A communication system according to an embodiment will be described with reference to the drawings. The communication system described below is, for example, a distributed antenna system (DAS), but can also be applied to a system conforming to eCPRI of the ORAN (Open Radio Access Network).

[0011] 1 is a diagram showing an example of a communication system according to an embodiment. The communication system includes a master station (MU: Master Unit) 100 and multiple slave stations 200 (200-1 to 200-n) each connected to the master station 100 via an optical fiber. The term DAS is used when focusing on the master station 100 and the slave stations (RU: Remote Unit) 200-1 to 200-n. This is also called an optical repeater system.

[0012] An element management system (EMS) 300 is connected to the master station 100 via a network NW. User equipment (UE) 3 (3a, 3b, ..., 3m) is connected to one of the slave stations 200-1 to 200-n via a wireless channel.

[0013] The master station 100, which serves as a master unit, is connected to base stations BS (BSa, BSb, ..., BSm) via a base station connection unit 101. Each base station BS is connected to the base station connection unit 101 via, for example, a coaxial cable. In other words, the base station connection unit 101 is an interface that inputs and outputs RF (Radio Frequency) signals for each base station (operator). In the embodiment, it is assumed that base station BSa is operated by operator A, base station BSb is operated by operator B, ..., and base station BSm is operated by operator M. In other words, the master station 100 is an example of a shared-operator device.

[0014] The master station 100 also functions as a relay device, relaying signals between the mobile terminals 3a, 3b, ..., 3m of each carrier and the base stations BSa, BSb, ..., BSm of each carrier.

[0015] The base stations BSa, BSb, ..., BSm are accommodated in a core device (not shown) of a core network such as 5G (5th Generation) or LTE (registered trademark) (Long-Term Evolution) operated by each of communication carriers A, B, ..., M. The core network controls a radio access network between the base stations BSa, BSb, ..., BSm and the mobile terminals 3a, 3b, ..., 3m. The core device performs processes such as authentication and security management, session management, policy control, and packet forwarding.

[0016] The mobile terminals 3a, 3b, ..., 3m are smartphones, tablets, mobile phones, or the like. The mobile terminals 3a, 3b, ..., 3m communicate using communication resources (such as frequency bands) allocated to the respective telecommunications carriers A, B, ..., M to which they subscribe. In the following description, the mobile terminal 3a may be referred to as the "mobile terminal of telecommunications carrier A" to indicate the telecommunications carrier to which the mobile terminal 3a subscribes for its service. Similarly, the mobile terminals 3b, ..., 3m may be referred to as the mobile terminals of telecommunications carriers B, ..., M.

[0017] The master station 100 collects wireless signals transmitted over UL from the mobile terminals 3a, 3b, ..., 3m via the slave stations 200-1 to 200-n and transmits them to the base stations BSa, BSa, ..., BSm of the corresponding telecommunications carrier. When connected to the slave stations 200-1 to 200-n via an optical communication line, the master station MU is sometimes called an "optical repeater." The master station 100 includes a slave station connection unit 102 that can be connected to the slave stations 200-1 to 200-n as remote units. The slave station connection unit 102 accommodates optical fibers connected to the slave stations 200-1 to 200-n, respectively, and is an interface for inputting and outputting optical signals.

[0018] The slave stations 200-1 to 200-n transmit radio signals via DL from the base stations BSa, BSb, ..., BSm via the master station MU. The slave stations 200-1 to 200-n are capable of wireless communication with any of the mobile terminals 3a, 3b, ..., 3m. In other words, the slave stations 200-1 to 200-n are capable of covering the frequency bands allocated to the respective telecommunications carriers A, B, ..., M.

[0019] The management device 300 functions as a server, controlling each device in the communication system and monitoring the status based on information from the master station 100. The management device 300 provides information about the operational status of the communication system to the client terminals CL-1 to CL-l, and controls the communication system, tallying data, generating display data, and so on, in accordance with requests and instructions from the client terminals CL-1 to CL-l.

[0020] The client terminals CL-1 to CL-l are, for example, personal computers, etc. The client terminals CL-1 to CL-l receive instructions from an operator, give the instructions to the management device 300, process information provided by the management device 300, and present the information to the operator via a monitor or the like.

[0021] FIG. 2 is a diagram showing an example of band allocation to base stations. In the embodiment, it is assumed that band A is allocated to base station BSa of company A and band B is allocated to base station BSb of company B. Band A and band B are adjacent to each other in the Sub6 band, for example. As shown in FIG. 2(a), there is a risk of interference when a DL signal (D) of band A and a DL signal of band B are transmitted simultaneously. As shown in FIG. 2(b), the same applies to a UL signal (U). In the embodiment, a technique for preventing interference will be described.

[0022] Fig. 3 is a functional block diagram showing an example of a master station 100 and a slave station 200. In Fig. 3, a base station BSa of company A and a base station BSb of company B are shown connected to the master station 100, but other base stations may also be connected in the same way.

[0023] The master station 100 includes a distributor (HYB) 11, a coupler (CPL) 12, a frequency conversion unit 13, a detection unit (DET) 14, an analog-to-digital converter (ADC) 15, a signal processing unit 16, a digital-to-analog converter (DAC) 17, a switch unit (SW) 18, a processor 19, and a base station interface (IF) 20.

[0024] The processor 19 controls and monitors each device. The base station IF 20 is an interface for communicating with the base stations BSa, BSb, ..., BSm via an interface such as RS232C, USB, or Ethernet (registered trademark).

[0025] The slave station 200 includes a signal processing unit 22 having a detection unit (DET) 21, a digital-to-analog converter (DAC) 23, a frequency conversion unit 24, a transmission amplifier (TPA) 25, a circulator 26, an antenna 27, a switch unit (SW) 28, a low-noise amplifier (LNA) 29, an analog-to-digital converter (ADC) 30, and a processor 31.

[0026] The operation of each functional block will be explained for processing related to DL signals and processing related to UL signals. <Download processing of master station 100> A wireless band DL signal from base station BS passes through distributor 11 and coupler 12 and is input to frequency conversion unit 13. Coupler 12 branches off a portion of the DL signal and inputs it to detection unit 14. Detection unit 14 detects the DL signal and notifies processor 19 of the detected output. The frequency conversion unit 13 performs radio reception processing and down-converts the DL signal to an IF (Intermediate Frequency) band. The DL signal converted to the IF band is converted from analog to digital by an AD converter 15 and sent to a signal processing unit 16. The signal processing unit 16 maps the digital signal to a TDD communication format between the master station 100 and slave stations 200 for each operator, and transmits the digital signal to each slave station.

[0027] The signal processing unit 16 extracts a digital signal from the slot of the UL signal from the RU 200 based on the communication format between the master station 100 and the slave stations 200. The signal processing unit 16 then combines the extracted digital signals for each slave station 200 on a carrier-by-carrier basis and sends the combined signal to the DA converter 17. The DA converter 17 converts the digital signal to analog and sends it to the frequency conversion unit 13. The frequency conversion unit 13 upconverts the analog signal to regenerate the UL signal. The UL signal is transmitted to the corresponding base station BS via the coupler 12, the switch unit 18, and the distributor 11. Part of the UL signal is branched off at the coupler 12 and input to the detection unit 14. Here, the switch unit 18 is controlled to be turned on / off by the processor 19. This allows the DL / UL signal route to be switched in accordance with the DL slot timing and UL slot timing of the TDD signal.

[0028] The DL signal from the master station 100 is sent to a signal processing unit 22. The signal processing unit 22 extracts a digital signal from the slot of the DL signal based on the communication format between the master station 100 and the slave station 200. This digital signal is converted to an analog signal by a DA converter 23 and sent to a frequency conversion unit 24. The frequency conversion unit 24 upconverts the analog signal to match the transmission band of the air section and regenerates it as a DL signal. This DL signal is amplified to a transmission level by a transmission amplifier 25 and radiated from an antenna 27 via a circulator 26.

[0029] A UL signal in a radio band from the mobile terminal 3 is transmitted from the antenna 27 to the LNA 29 via the circulator 26 and the switch unit 28. The switch unit 28 is controlled to be turned on / off by the processor 19 to switch the DL / UL signal route in accordance with the DL slot timing and UL slot timing of the TDD signal. The LNA 29 amplifies the UL signal in the radio band and sends it to the frequency conversion unit 24. The frequency conversion unit 24 down-converts the UL signal to the IF band and sends it to the AD converter 30. The AD converter 30 converts the analog IF signal into a digital signal and sends it to the signal processing unit 22. The signal processing unit 22 maps the digital signal to a TDD communication format between the master station 100 and the slave stations 200 for each operator and transmits it to the master station 100. Here, the UL signal for each operator is detected by the detection unit 21 of the signal processing unit 22, and the level of the UL signal is detected.

[0030] The processor 19 of the master station 100 includes an operation control unit 19a and an inquiry unit 19b. The processor 31 of the slave station 200 includes a notification unit 31a. These are processing functions that are realized by the processor 19 executing a program embedded in a memory (not shown).

[0031] The operation control unit 19a detects loss of the DL signal of band A from the detection output of the detector 14, for example, when the level of the DL signal of band A falls below a predetermined threshold. Then, the operation control unit 19a allows asynchronous operation in band B during the period in which loss of the DL signal of band A is detected. Asynchronous operation is an operation mode in which the TDD pattern in band B (A) is different from the TDD pattern in band A (B). In other words, the operation control unit 19a allows company B, which was synchronized with company A's TDD pattern before the DL signal of band A was lost, to freely change the TDD pattern setting after the DL signal of band A is lost.

[0032] Furthermore, the operation control unit 19a detects loss of the UL signal of band A from the detection output of the detection unit 21. Then, the operation control unit 19a allows asynchronous operation in band B during the period in which loss of the UL signal of band A is detected. In other words, the operation control unit 19a allows company B, which was synchronized with company A's TDD pattern before the UL signal of band A was lost, to freely change the setting of the TDD pattern after the DL signal of band A is lost.

[0033] Here, the operation control unit 19a detects the loss of the UL signal of band A based on a notification from the slave station 200. That is, when the level of the UL signal of band A, for example, from the output of the detection unit 21, becomes equal to or lower than a predetermined threshold, the notification unit 31a of the slave station 200 notifies the master station 100 that the loss of the uplink signal of band A has been detected.

[0034] Furthermore, the operation control unit 19a determines whether or not asynchronous operation is permitted after inquiring of the base station BS. That is, when the inquiry unit 19b detects loss of the DL signal in band A, it notifies the base station BSb of company B of this fact and receives a response. The operation control unit 19a determines whether or not asynchronous operation is permitted, i.e., whether or not to switch the operation mode, based on the result of this response.

[0035] Furthermore, when the inquiry unit 19b detects loss of the UL signal in band A, it notifies the base station BSb of company B of that fact and receives a response. The operation control unit 19a determines whether or not to allow asynchronous operation, that is, whether or not to switch the operation mode, based on the result of this response.

[0036] Figure 4 shows an example of a TDD pattern in synchronous operation. In synchronous operation, the frame format associated with base station BSa of company A and the frame format associated with base station BSb of company B are the same. The TDD pattern shown in Figure 4 will be referred to as TDD pattern 1 in the following description. The switch unit 28 of the slave station 200 is turned on in synchronization with the UL slot and turned off in the DL slot. By controlling the switch unit 28, isolation in the DL section can be ensured and the impact on the uplink signal processing system can be reduced.

[0037] 5A and 5B are diagrams for explaining the state of the switches in the DL slots and UL slots. As shown in FIG. 5A, in frame #0, both companies A and B are in the DL section. In this section, switch units 18a and 18b of master station 100 and switch unit 28 of slave station 200 are both turned OFF. This allows DL signals to pass through but prevents UL signals from passing through.

[0038] 5(b), in frame #2, both companies A and B are in the UL section. In this section, switch units 18a and 18b of master station 100 and switch unit 28 of slave station 200 are both turned ON. This allows UL signals to pass through but prevents DL signals from passing through.

[0039] Incidentally, it is decided that the switching of the switch units 18a, 18b, and 28 from OFF to ON is executed during the guard period (the time required for switching between DL and UL) of frame #1. This means that in a multi-operator shared device, it is assumed that synchronization is maintained among multiple operators. In other words, with existing technologies, asynchronous operation has generally been difficult.

[0040] Therefore, a technology that enables asynchronous operation will be described below. (action) 6 and 7 are flowcharts showing an example of a processing procedure of the master station 100. In Fig. 6, the master station 100 monitors, in a loop of steps S1 to S3, the loss of a DL signal from any base station (step S1) or the loss of a UL signal from any UE (step S2). As long as the master station 100 does not detect the loss of either the DL signal or the UL signal, it maintains synchronous operation by synchronizing the TDD patterns between the base stations (step S3). When the loss of a DL signal is detected (Yes in step S1) or the loss of a UL signal is detected (Yes in step S2), the processing procedure proceeds to operation switching (step S4) and jumps to step S41 in Fig. 7.

[0041] 7, the master station 100 inquires of the relevant base stations about whether or not it is possible to switch to asynchronous mode (step S41). For example, when the master station 100 detects loss of a DL signal from company A, it notifies company B's base station BSb of this fact via the base station interface 20 and inquires about whether or not it is possible to switch to asynchronous operation. If the response to this inquiry is not permitted (No in step S42), the processing procedure returns to the caller and returns to the loop starting from step S1 in FIG. 6.

[0042] If an authorization response (OK) is received in response to the inquiry (Yes in step S42), the master station 100 exchanges control signals with the base station and changes the TDD pattern (step S43). Here, the TDD pattern is changed to increase the number of UL slots in response to a request from the UE for a larger uplink bandwidth, for example. This operation continues until the lost DL signal resumes (Yes in step S44) or the lost UL signal resumes (Yes in step S45). When the lost DL signal or the lost UL signal resumes, the master station 100 performs processing to return to synchronous operation, and the processing procedure returns to the loop starting from step S1 in FIG.

[0043] Figure 8 is a diagram showing an example of the changed TDD pattern. As shown in Figure 8, base station BSa can set a TDD pattern (referred to as TDD pattern 2) that is completely different from the TDD pattern (TDD pattern 1) related to base station ASa.

[0044] <Regarding the sequence when the DL signal disappears> Figure 9 is a sequence diagram showing an example of the processing procedure when the DL signal disappears. In the initial setting of Figure 9, it is assumed that the parent station 100 is operating in the synchronous operation mode of TDD pattern 1. At this time, base station ASa of Company A communicates with mobile terminal (UE) 3a in TDD pattern 1, and base station BSa of Company B communicates with mobile terminal (UE) 3b in TDD pattern 1.

[0045] From this state, it is assumed that the input signal (DL) from base station ASa disappears. Then, the parent station 100 detects the disappearance of the DL signal of Company A (confirmation of outage of Company A) from the output of the detection unit 14. Then, the parent station 100 transmits a TDD pattern change notification (stop of Company A) to base station BSa of Company B to notify that the input signal from Company A has disappeared. After receiving this notification, base station BSa of Company B confirms whether the TDD pattern can be changed and returns a response including the result (Yes / No) to the parent station 100. The exchange of messages between the parent station 100 and base station BSa of Company B is performed via the base station interface 20.

[0046] If the TDD pattern can be changed, base station BSa of Company B returns a changeable (Yes) response. After receiving this, the parent station 100 changes the TDD pattern in band B to, for example, TDD pattern 2 in Figure 8. As a result, base station BSa of Company B and mobile terminal 3b of Company B can operate in an asynchronous TDD pattern (TDD pattern 2) via the parent station 100.

[0047] FIG. 10 is a diagram showing that the DL signal in band A has disappeared. As shown in FIG. 10(a), when the input signal (DL) from base station BSa of Company A in slot #0 (FIG. 8) disappears, it leads to asynchronous operation through the sequence of FIG. 9. Even in this state, as shown in FIG. 10(b), the uplink signals in slots #2 and #3 reach from slave station 200 to master station 100. Here, the change of the TDD pattern is realized by changing the OFF / ON switching timing of switch units 18a, 18b of master station 100 and switch unit 28 of slave station 200.

[0048] Returning to FIG. 9 to continue the explanation. In the asynchronous operation mode, when base station BSa of Company A resumes transmission in TDD pattern 1, detector 14 of master station 100 detects the input signal (DL) from base station BSa of Company A. Then master station 100 immediately returns to the synchronous operation mode and changes the TDD pattern of Company B back to TDD pattern 1. At that time, master station 100 transmits a TDD pattern change notification (Company A resume) to base station BSb of Company B to notify that the input signal from Company A has resumed. After receiving this notification, base station BSb of Company B returns a response and resumes synchronous operation according to TDD pattern 1. Here too, the change to TDD pattern 1 is realized by changing the OFF / ON switching timing of switch units 18a, 18b, 28.

[0049] <Sequence when UL signal disappears> FIG. 11 is a sequence diagram showing an example of the processing procedure when the UL signal disappears. Similar to FIG. 9, it is assumed that master station 100 is operating in the synchronous operation mode of TDD pattern 1, base station BSa of Company A is communicating with mobile terminal (UE) 3a in TDD pattern 1, and base station BSb of Company B is communicating with mobile terminal (UE) 3b in TDD pattern 1.

[0050] From this state, let us assume that the input signal (UL) from company A's mobile terminal 3a disappears. Then, slave station 200 detects the disappearance of company A's UL signal (no company A UL signal) from the output of detector 21. Furthermore, slave station 200 notifies master station 100 that the UL signal from company A has disappeared by sending a UL status notification (no company A).

[0051] Upon receiving this, the master station 100 transmits a TDD pattern change notification (no UL signal from company A) to company B's base station BSb, notifying it that the UL signal from company A's mobile terminal 3a has disappeared. Upon receiving this notification, company B's base station BSb checks whether the TDD pattern can be changed and returns a response including the result (Yes / No) to the master station 100. Messages are exchanged between the master station 100 and company B's base station BSb via base station interface 20.

[0052] If the TDD pattern can be changed, company B's base station BSb replies with a response indicating that the change is possible (Yes), and the master station 100 then changes the TDD pattern in band B to, for example, TDD pattern 2. This enables company B's base station BSb and company B's mobile terminal 3b to operate via the master station 100 in an asynchronous TDD pattern (TDD pattern 2).

[0053] Figure 12 shows the disappearance of the UL signal in band A. When the input signal (UL) from company A's mobile terminal 3a in slot #2 (Figure 8) disappears, the system goes through the sequence in Figure 11 to enter asynchronous operation. The uplink signal in slot #2 travels from company B's mobile terminal 3b to company B's base station BSb via the base station 100 and the slave station 200. Here too, the TDD pattern is changed by changing the OFF / ON switching timing of switches 18a and 18b in the master station 100 and switch 28 in the slave station 200.

[0054] Returning to FIG. 11, the explanation continues. In asynchronous operation mode, when the mobile terminal 3a of company A resumes transmitting a UL signal, the detector 21 of the slave station 200 detects the input signal (UL) from the mobile terminal 3a of company A. The slave station 200 then notifies the master station 100 of the resumed UL communication from company A by sending a UL status notification (Company A resumed). The master station 100 then immediately returns to synchronous operation mode and changes the TDD pattern of company B back to TDD pattern 1. At this time, the master station 100 transmits a TDD pattern change notification (Company A resumed) to the base station BSb of company B, notifying it that the input signal from company A has resumed. Upon receiving this notification, the base station BSb of company B replies with a response and resumes synchronous operation using TDD pattern 1. Again, the TDD pattern change is achieved by changing the ON / ON switching timing of the switches 18a and 18b of the master station 100 and the switch 28 of the slave station 200.

[0055] As described above, in the embodiment, the master station 100 is provided with the detection unit 14 that detects DL signals from the base stations BSa and BSb, and when the DL signal from the base station BSa is lost, the signal of band B related to the base station BSb is operated in a pattern different from the TDD pattern used by the base station BSa.

[0056] The slave station 200 is also provided with a detector 21 that detects the UL signal from the mobile terminal 3, and when the UL signal from the mobile terminal 3a is lost, the slave station 200 notifies the master station 100 of this fact. Upon receiving this notification, the master station 100 operates the signal of band B related to base station BSb in a pattern different from the TDD pattern used by base station BSa.

[0057] In this way, it is possible to detect DL signals from operators that have been individually assigned bands, and if they are absent, it is possible to switch to asynchronous operation. It is also possible to detect UL signals from each operator, and if they are absent, it is possible to switch to asynchronous operation. This control is possible only because it is a master station that serves as shared-operator equipment, accommodating the base stations of multiple operators. In other words, it is a function unique to shared-operator equipment that allows it to uniformly monitor the band usage status of each operator.

[0058] This function makes it possible to prevent interference between bands in an environment where the antenna 27 of the slave station 200 handles multiple bands. Furthermore, by enabling asynchronous operation, it becomes possible to flexibly respond to needs such as increasing the uplink band, thereby improving the availability of the system.

[0059] For example, it becomes possible to connect operators that operate semi-synchronously / asynchronously to the same master station 100. This makes it possible to accommodate, for example, an operator that provides a service in which the downlink bandwidth is important and an operator that provides a service in which the uplink bandwidth is important, in the same master station 100. This makes it possible to provide flexible communication services for each operator.

[0060] Furthermore, for downlink signals, master station 100 can grasp the signal conditions of other operators, and can select its own TDD pattern depending on the situation without affecting other operators. In other words, master stations operating base stations in the same system can switch their own TDD patterns without affecting base stations belonging to other systems.

[0061] Currently, local 5G in the millimeter wave band (28.2 to 28.3 GHz band) is premised on synchronized operation of the TDD method between other local 5G and nationwide 5G. According to the embodiment, it is possible to realize various use cases by the local 5G.

[0062] As a result, according to the embodiments, it is possible to eliminate the constraints associated with the shared use of infrastructure, thereby making it possible to provide a distributed antenna system, master unit, remote unit, and operational control method that offer increased operational freedom.

[0063] It should be noted that the present invention is not limited to the above-described embodiments. For example, if the transmission capacity is sufficient, the link connecting the master station and slave stations does not have to be limited to optical fiber. Also, the link connecting the base station and master station does not have to be limited to coaxial cable.

[0064] Furthermore, for example, in the embodiment, it has been described that the TDD pattern of company B is changed when a downlink signal or an uplink signal related to company A is lost, but the same discussion holds even if company A and company B are swapped. Of course, the master station (shared operator device) in the embodiment can also accommodate three or more operators, and the same discussion can be applied. Furthermore, in the embodiment, asynchronous operation has been discussed, but in the case of quasi-synchronous operation, it is possible to deal with this in the same way by, for example, reducing the output of the distributed antenna system.

[0065] Furthermore, the technology of the embodiment can be applied by exchanging information between distributed antenna systems operated by different entities. 13 is a block diagram for explaining switching between synchronous and asynchronous operation between base stations belonging to different master stations. In FIG. 13, it is assumed that base station BSa of company A is connected to master station 110, and base station BSb of company B is connected to master station 120. In this configuration, master station 110 is provided with a master station interface (MU IF) 111 for communicating with master station 120, and master station 120 is provided with a master station interface 121 for communicating with master station 120, so that the master stations can mutually notify each other of detected loss of DL signal and loss of UL signal. In this way, by providing interfaces 111 and 121 for exchanging information between master stations, it is possible to execute a sequence similar to that described above even in relationships with base stations accommodated by different master stations.

[0066] Furthermore, it is also possible to collect detection information and control signals relating to switching of operation modes in the management device 300, and for the management device 300 to take the lead in controlling switching / returning of the TDD pattern.

[0067] Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, and are also included in the invention described in the claims and their equivalents. [Explanation of symbols]

[0068] 3...mobile terminal, 11...distributor, 12...coupler, 13...frequency conversion unit, 14...detection unit, 15...analog / digital converter, 16...signal processing unit, 17...digital / analog converter, 18...switch unit, 18a...switch unit, 18b...switch unit, 19...processor, 19a...operation control unit, 19b...inquiry unit, 20...base station interface, 21...detection unit, 22...signal processing unit, 23...digital / analog converter, 24...frequency conversion unit, 25...transmitting amplifier, 26...circulator, 27...antenna, 28...switch unit, 29...low noise amplifier, 30...analog / digital converter, 31...processor, 31a...notification unit, 100...master station, 101...base station connection unit, 102...slave station connection unit, 200...slave station, 200-1 to 200-n...slave station, 300...management device, CL-1 to CL-l...client terminal.

Claims

1. A master unit; a remote unit having an antenna capable of covering a first band and a second band adjacent to the first band; The master unit a base station connection unit that can connect to a first base station that is assigned the first band and a second base station that is assigned the second band; a slave station connection unit connectable to the remote unit; a detection unit that detects a downlink signal in the first band; a control unit that allows an operation mode in which a time division multiplexing pattern in the second band and a time division multiplexing pattern in the first band are different from each other during a period in which loss of a downlink signal in the first band is detected from the output of the detection unit.

2. The master unit an inquiry unit that notifies the second base station of a loss of the downlink signal in the first band and receives a response therefrom; The distributed antenna system according to claim 1 , wherein the operation control unit determines whether or not to switch the operation mode based on a result of the response.

3. A master unit; a remote unit having an antenna capable of covering a first band and a second band adjacent to the first band; The remote unit a detection unit that detects an uplink signal in the first band, The master unit a base station connection unit that can connect to a first base station that is assigned the first band and a second base station that is assigned the second band; a slave station connection unit connectable to the remote unit; a control unit that allows an operation mode in which a time division multiplexing pattern in the second band and a time division multiplexing pattern in the first band are different from each other during a period in which loss of an uplink signal in the first band is detected from the output of the detection unit.

4. The remote unit a notification unit that notifies the master unit that a loss of the uplink signal in the first band has been detected from the output of the detection unit, The distributed antenna system according to claim 3 , wherein the operation control unit allows the operation mode based on a notification from the remote unit.

5. The master unit an inquiry unit that notifies the second base station of a loss of the uplink signal in the first band and receives a response therefrom; The distributed antenna system according to claim 3 , wherein the operation control unit determines whether or not to switch the operation mode based on a result of the response.

6. a slave station connection unit connectable to a remote unit having an antenna capable of covering a first band and a second band adjacent to the first band; a base station connection unit that can connect to a first base station that is assigned the first band and a second base station that is assigned the second band; a detection unit that detects a downlink signal in the first band; a master unit including an operation control unit that allows an operation mode in which the time division multiplexing pattern in the second band and the time division multiplexing pattern in the first band are different during a period in which loss of the downlink signal in the first band is detected from the output of the detection unit.

7. an inquiry unit that notifies the second base station of a loss of the downlink signal in the first band and receives a response therefrom; The master unit according to claim 6 , wherein the operation control unit determines whether or not to switch the operation mode based on a result of the response.

8. a slave station connection unit connectable to a remote unit having an antenna capable of covering a first band and a second band adjacent to the first band; a base station connection unit that can connect to a first base station that is assigned the first band and a second base station that is assigned the second band; a master unit comprising an operation control unit that allows an operation mode in which a time division multiplexing pattern in the second band and a time division multiplexing pattern in the first band are different during a period in which loss of an uplink signal in the first band is detected.

9. an inquiry unit that notifies the first base station of a loss of the uplink signal in the first band and receives a response therefrom; The master unit according to claim 7 , wherein the operation control unit determines whether or not to switch the operation mode based on a result of the response.

10. an interface connectable to a master unit connectable to a first base station assigned a first band and a second base station assigned a second band; an antenna capable of covering the first band and the second band; a detection unit that detects an uplink signal in the first band; a notification unit that notifies the master unit that a loss of the uplink signal in the first band has been detected from the output of the detection unit.

11. 1. A method for controlling operation of a distributed antenna system including a master unit and remote units each having an antenna capable of covering a first band and a second band adjacent to the first band, comprising: The master unit: An operation control method comprising a step of allowing an operation mode in which a time division multiplexing pattern in the second band and a time division multiplexing pattern in the first band are different during a period in which loss of a downlink signal in the first band is detected.

12. 1. A method for controlling operation of a distributed antenna system including a master unit and remote units each having an antenna capable of covering a first band and a second band adjacent to the first band, comprising: The master unit: An operation control method comprising a step of allowing an operation mode in which a time division multiplexing pattern in the second band and a time division multiplexing pattern in the first band are different during a period in which loss of an uplink signal in the first band is detected.

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