Wireless communication system

Abstract

To provide a radio communication system capable of simplifying a configuration by connecting an O-RAN and a DAS by an optical cable.SOLUTION: In the wireless communication system, a DAS master unit 11 connected to a client 30 of an O-RAN includes an O-RAN interface and an O-RU server functional 11c that implements fronthaul specifications (RU / FHM) between the client 30 and an RU of the O-RAN, and the DAS master unit 11 enables data-transmission with the client 30 through an optical cable by the O-RAN interface, and converts a wireless signal from a DAS slave unit 12 into fronthaul specifications by the O-RU server functional 11c and transmits the wireless signal through the optical cable.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wireless communication system that combines an open radio access network (Open RAN) that is becoming increasingly open and a distributed antenna system (DAS) that distributes and expands the communication area using radio waves and optical cables, and in particular to a wireless communication system that can simplify the configuration. [Background technology]

[0002] [Prior Art] Open RAN allows service providers to use non-proprietary subcomponents from various vendors, and is characterized by the ability to separate and combine elements based on open specifications. Open RAN refers to specifications defined by the O-RAN Alliance, for example.

[0003] Another method for efficiently building a network is to use a shared DAS, which builds and shares communication infrastructure equipment on behalf of multiple service providers (multi-operators) through infrastructure sharing, thereby providing communication equipment to multiple service providers (multi-operators).

[0004] A radio unit (RU) in Open RAN is an optical transmission device that complies with the 3GPP (registered trademark) 3rd Generation Partnership Project (3GPP) 3 wireless standard for wireless communication, typified by the configuration of RRH (Remote Radio Head) and ROF (Radio over Fiber).

[0005] The RU has a SlavePort optical conversion unit and a MasterPort optical conversion unit that use technologies such as eCPRI (enhanced Common Public Radio Interface) in SERDES (SERializer / DESerializer), a high-speed serial communication standard, and is equipped with an optical transceiver, providing data communication functionality between the parent station and the child stations.

[0006] [Conventional wireless communication system: Figure 6] A conventional wireless communication system will be described with reference to Fig. 6. Fig. 6 is a schematic diagram showing the configuration of a conventional wireless communication system. As shown in FIG. 6, a conventional wireless communication system is a combination of DAS and O-RAN, and includes, on the DAS side, a DAS master unit (MU: Master Unit) 110, a DAS slave unit (Indoor RA) 12, a DAS repeater (HU: Hub Unit) 13, and a network monitoring and control unit (EMS: Element Management System) 10, and, on the O-RAN side, a radio equipment unit (Indoor RU [Remote Unit]) 21, a distributed unit (DU: Distributed Unit) 22, a centralized unit (CU: Centralized Unit) 23, a 5G core network device (5GC: 5th Generation Core network) 24, and a network monitoring and control unit (EMS) 25.

[0007] In a processing operation of a conventional wireless communication system, in an uplink data transmission process from a DAS to an O-RAN, a DAS slave device 12 wirelessly receives data from an antenna and transmits the data to a DAS master device 110 via a DAS repeater 13. Then, the DAS master device 110 transmits the data to a distributed unit (DU) 22 via a wireless unit 21 as an RF (Radio Frequency) signal.

[0008] In addition, in the downstream transmission process of data from O-RAN to DAS, data from each business operator (operator / client 30a', 30b') is transmitted by RF signal from the distributed unit (DU) 22 to the DAS master 110 via the wireless unit 21. Then, the DAS master 110 transmits the data to the DAS slave 12 via the DAS repeater 13, and the DAS slave 12 wirelessly transmits the data from the antenna.

[0009] Note that 5G (5th Generation) or LTE (Long Term Evolution) is known as an example of a wireless network (wireless NW) standard. 5G or LTE wireless networks are more stable than wireless LANs (Local Area Networks). Furthermore, 5G or LTE wireless networks can be built by entities other than mobile network operators (MNOs). For this reason, some companies are beginning to consider introducing 5G or LTE wireless networks into their own companies (introducing local 5G or private LTE).

[0010] Distributed antennas using shared DAS are becoming commonplace indoors and are the core of infrastructure sharing. In addition, the RAN market, which was previously dominated by major base station vendors, is becoming increasingly multi-vendor with the emergence of O-RAN compatible equipment.

[0011] Until now, the antenna distribution configuration has been the RAN+DAS configuration, in which the DAS is attached to the RAN. DAS systems have their own proprietary technologies, such as gain adjustment, compression, and distribution, making them closed systems to operators. Furthermore, because the RAN and DAS are connected via RF, it has not been possible to directly monitor DAS slave devices via the RAN.

[0012] Meanwhile, the expansion of RAN to DAS blocks is also progressing with the shift to O-RAN. O-RAN is based on a BBU (Base Band Unit) + RRH (Remote Radio Head) configuration that does not involve RF connections, and there is no RF interface like there is between RAN and DAS.

[0013] To achieve a distributed antenna configuration like DAS, O-RAN adds a device called a Front Haul Multiplexer (FHM), which acts as a hub. This allows it to be considered a distributed antenna slave unit (O-RU), making it possible to use open specifications for the optical transmission path from the fronthaul to the DAS antenna slave unit. This requires the implementation of RU functions equivalent to the complex O-RAN specifications, including authentication functions, which means the entire specification becomes open and complex.

[0014] Furthermore, because O-RAN is a multi-vendor concept, a monitoring server is required for each vendor to monitor the CU / DU and RU that make up the RAN. Fronthaul specifications are also determined for RUs by higher-level devices (CU / DU or their higher-level RIC [RAN Intelligent Controller]), so in the case of shared use by multiple operators, different servers must be prepared for each vendor for the FHM and RU, and each vendor's fronthaul settings must be compatible.

[0015] [Related Technology] As a related prior art, there is Japanese Patent Application Laid-Open No. 2024-044504 ​​"Wireless communication system and wireless communication method" (Patent Document 1).

[0016] Patent Document 1 discloses a wireless communication system that can continue communication services by forming a detour route when a failure occurs in communication between a base station of a communication carrier and a master unit. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Publication No. 2024-044504 Summary of the Invention [Problem to be solved by the invention]

[0018] However, conventional wireless communication systems have a problem in that the connection between O-RAN and DAS is an RF connection, which makes the configuration complex.

[0019] Incidentally, Patent Document 1 does not describe a configuration in which the O-RAN and the DAS are connected by an optical cable to simplify the configuration.

[0020] The present invention has been made in view of the above circumstances, and aims to provide a wireless communication system in which the O-RAN and DAS are connected by an optical cable, thereby simplifying the configuration. [Means for solving the problem]

[0021] The present invention, which aims to solve the problems of the above-mentioned conventional examples, is a wireless communication system that combines an open wireless access network (O-RAN) and a distributed antenna system (DAS), in which a DAS master connected to an O-RAN client is provided with an O-RAN interface and an O-RU server function that implements fronthaul specifications (RU / FHM) between the client and the O-RAN wireless unit, and the DAS master enables data transmission with the client via an optical cable via the O-RAN interface, and the O-RU server function converts wireless signals from the DAS slave into fronthaul specification data and transmits it via the optical cable.

[0022] The present invention is characterized in that in the above wireless communication system, the DAS master device is provided with an O-RAN interface with different profiles set for each of multiple clients, and the fronthaul specifications are defined by the profiles.

[0023] The present invention is characterized in that in the above wireless communication system, the DAS master periodically collects and stores slave unit information from the DAS slave units, and when a client requests the slave unit information, transmits the stored slave unit information to the client.

[0024] The present invention is characterized in that in the above-mentioned wireless communication system, the DAS parent device, as an upstream transmission process, reallocates RF data received by the DAS child device from a mobile terminal as IQ data for each band, separates it to each client, allocates and transmits the data according to the fronthaul specifications, and as a downstream transmission process, extracts IQ data from the fronthaul specification data from the client, allocates and combines it for each band, and transmits the data to the DAS child device.

[0025] The present invention is characterized in that in the above wireless communication system, the DAS master device, in the M-Plane function of the fronthaul specification, executes M-Plane establishment processing, synchronization management processing, and configuration management processing so that they can be referenced by each client, executes performance management processing, fault management processing, and file management processing so that they cannot be referenced by clients, stores them as shared information, and notifies clients of an alarm when a fault occurs. Note that the client corresponds to the DU / CU of each operator. [Effects of the Invention]

[0026] According to the present invention, there is provided a wireless communication system that combines an open wireless access network (O-RAN) and a distributed antenna system (DAS), in which a DAS master connected to an O-RAN client is provided with an O-RAN interface and an O-RU server function that implements the fronthaul specifications (RU / FHM) between the client and the O-RAN wireless unit, and the DAS master enables data transmission with the client via an optical cable via the O-RAN interface, and the O-RU server function converts radio signals from the DAS slave into fronthaul specification data and transmits them via the optical cable, thereby providing the advantage of simplifying the configuration by connecting the O-RAN and DAS via an optical cable. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram of the configuration of the present system. [Figure 2] FIG. 2 is a schematic diagram showing the relationship between an operator and a DAS master unit in the present system. [Figure 3] FIG. 2 is a schematic diagram showing the relationship between a DAS master unit and a DAS slave unit in the present system. [Figure 4] FIG. 1 is a schematic diagram showing the upstream and downstream processing of the present system. [Figure 5] FIG. 2 is a functional schematic diagram showing the sequence of the present system. [Figure 6] FIG. 1 is a schematic diagram illustrating the configuration of a conventional wireless communication system. DETAILED DESCRIPTION OF THE INVENTION

[0028] An embodiment of the present invention will be described with reference to the drawings. [Outline of the embodiment] A wireless communication system (this system) according to an embodiment of the present invention is a wireless communication system that combines an open wireless access network (O-RAN) and a distributed antenna system (DAS), in which a DAS parent device connected to an O-RAN client is provided with an O-RAN interface and an O-RU server function that implements the fronthaul specifications (RU / FHM) between the client and the O-RAN wireless unit. The DAS parent device enables data transmission with the client via an optical cable via the O-RAN interface, and the O-RU server function converts wireless signals from the DAS child device into fronthaul specification data and transmits it via the optical cable. Therefore, the configuration can be simplified by connecting the O-RAN and DAS via an optical cable.

[0029] [This system: Figure 1] This system will be described with reference to Figure 1. Figure 1 is a schematic diagram of the configuration of this system. As shown in Figure 1, this system is a combination of DAS and O-RAN, and on the DAS side, it comprises a DAS master unit (O-RU / DAS Master) 11, a DAS slave unit (Indoor RA) 12, and a DAS repeater (HU: Hub Unit) 13, and on the O-RAN side, it comprises a distributed unit (DU: Distributed Unit) 22, a centralized unit (CU: Centralized Unit) 23, a 5G core network device (5GC: 5th Generation Core network) 24, and a network monitoring and control unit (EMS) 25. The same components as those in the conventional wireless communication system are given the same reference numerals.

[0030] [Parts of this system] Each part of this system will now be described in detail. First, each part of the DAS system of this system will be explained. The connection between the DAS master unit 11 and the DAS repeater 13, and the connection between the DAS repeater 13 and the DAS slave unit 12 are carried out by transmitting optical signals using an optical fiber cable (optical cable). The DAS master unit 11 and the distribution unit (DU) 22 on the O-RAN side are also connected by an optical cable, and optical signals are transmitted between them.

[0031] [DAS master unit (O-RU / DAS Master) 11] The DAS master (O-RU / DAS Master) 11 is connected to the DAS repeater 13 and the distributed unit (DU) 22, and is equipped with an O-RAN interface and an O-RAN remote unit (O-RU) server function, with the entire DAS implemented as a single O-RU / FHM (Front Haul Multiplexer).

[0032] The DAS master unit 11 also has an electrical / optical conversion unit that converts internal electrical signals into optical signals and outputs them to the DAS repeater 13 or the distribution unit (DU) 22, and an optical / electrical conversion unit that converts optical signals from the DAS repeater 13 or the distribution unit (DU) 22 into internal electrical signals.

[0033] The O-RU / FHM has the functionality of an O-RAN RU (Radio Unit: O-RU) equipped with an O-RAN interface, and is connected to multiple distributed units (DUs) 22 via optical cables, and functions as a server that controls each O-RAN operator (operator / client 30a, 30b), controlling the distribution and combination of one cell's worth of radio signals into up to 12 cells' worth of signals on the fronthaul between the distributed units (DUs) 22. Clients 30a and 30b may be collectively referred to as client 30.

[0034] The DAS parent device 11 is equipped with an O-RAN server function and does not acquire the status of the DAS child device 12 when an inquiry is received from the operator (client 30), but has the function of periodically storing the status of the DAS child device 12 as child device information, updating it, and maintaining it.

[0035] In this way, the operator (client 30) does not directly control the DAS slave 12, but rather the DAS master 11 has a function to logically separate the O-RAN fronthaul from the optical transmission path inside the DAS, thereby resolving authentication delays and security issues, and enabling a simple configuration with fast response.

[0036] Furthermore, the DAS master unit 11 monitors and controls the entire DAS system without disclosing the inside of the DAS system. The DAS master 11 customizes the aggregated information as information for O-RU and makes it available to each operator via the fronthaul, allowing each vendor's server to monitor the DAS. The processing operation of the DAS master 11 will be described in detail later.

[0037] Furthermore, taking advantage of the characteristics of the DAS parent unit 11, which is a closed system under its control instead of an FHM or O-RU, a server function is implemented that makes the entire DAS appear as a single O-RU / FHM, but in order to establish the individual gain settings within the DAS as a closed system, a dedicated monitoring server (EMS) may be installed for the DAS as in the past.

[0038] [DAS handset 12] The DAS slave 12 is assumed to be installed on the ceiling, wall, floor, etc., and is connected to a directional antenna. A communication area is constructed with multiple DAS slaves 12, and the communication area is expanded by controlling the antenna directivity, etc.

[0039] DAS slave unit 12 also includes a radio unit, a digital unit that converts radio signals into digital signals, an analog unit that converts digital data into analog radio signals, an optical / electrical conversion unit, and an electrical / optical conversion unit, and converts data transmitted from DAS repeater 13 via an optical cable into a radio signal and transmits it wirelessly from an antenna, and converts the radio signal received from the antenna into digital data and transmits it via the optical cable to DAS repeater 13. Data is transmitted and received via the optical cable by optically multiplexing the radio data.

[0040] [DAS Repeater (HU) 13] The DAS repeater (HU) 13 is a device that relays between the DAS parent unit 11 and the DAS child units 12, and is equipped with an optical / electrical conversion unit and an electrical / optical conversion unit. It distributes data from the DAS parent unit 11 to the DAS child units 12 via optical cables, and aggregates data from the DAS child units 12 and transmits it to the DAS parent unit 11. Specifically, the DAS repeater 13 performs the work of combining and compressing the wireless data from the DAS slave 12, separating it into the frequency bands of each MNO, mapping (allocating) it to optical data, and transmitting it.

[0041] Next, each part of the O-RAN side of this system will be explained. [Distributed Unit (DU) 22] The distributed unit (DU) 22 performs wireless access functions such as data modulation, demodulation, decoding / encoding, and performs communication control at the MAC (Media Access Control) layer. Although a signal for synchronizing with the GPS (Global Positioning System) is input to the distributed unit (DU) 22, this is an example of network synchronization, and therefore a GPS synchronization signal may also be input to the centralized unit (CU) 23 or the DAS parent unit (O-RU) 11.

[0042] [Centralized Unit (CU) 23] The centralized unit (CU) 23 mainly controls the distributed unit (DU) 22, and performs PDCP (Packet Data Convergence Protocol) processing, which connects to the 5G core network device 24 and encrypts packets, and RRC (Radio Resource Control) processing, which manages the radio resources of terminals.

[0043] [5G Core Network Equipment (5GC)24] The 5G core network device (5GC) 24 performs processes such as terminal authentication, terminal location management, policy control, packet forwarding control, establishment of communication paths, and data exchange with the data network (DN).

[0044] [Network Monitoring and Control Unit (EMS) 25] The network monitoring and control unit (EMS) 25 monitors and controls the devices (Elements) connected to the network, and performs control to grasp and maintain the quality status of the network.

[0045] [Relationship between the operator and the DAS master unit: Figure 2] Next, the relationship between the O-RAN operator and the DAS master in this system will be described with reference to Fig. 2. Fig. 2 is a schematic diagram showing the relationship between the operator and the DAS master in this system. As shown in Figure 2, the DAS base station 11 has an O-RAN interface 11a with fronthaul specification (1) for a CU / DU 30a of an O-RAN operator (Operator 1), and an O-RAN interface 11b with fronthaul specification (2) for a CU / DU 30b of an Operator 2. CU / DU30a and CU / DU30b may be collectively referred to as "CU / DU30." Here, the CU / DU 30 corresponds to the CU 23 and DU 22 of O-RAN, and is called a "client."

[0046] Fronthaul specification (1) corresponds to profile #1 of operator 1, and fronthaul specification (2) corresponds to profile #2 of operator 2. The profile is different for each operator, and the fronthaul specification is defined by the profile.

[0047] Due to the configuration shown in Figure 2, only one O-RU / FHM is visible to Operator 1 (1:1 connection), and only one O-RU / FHM is visible to Operator 2 (1:1 connection), but DAS base unit 11 functions as a multi-operator.

[0048] The profile is defined in the O-RAN Alliance's O-RAN Fronthaul Interoperability Test Specification (IOT) 10.0. Specifically, the profile corresponds to M-Plane's Security, NETCONF, VLAN, etc., and CU-Plane's O-RU category, frequency, band, carrier spacing, compression method, delay, etc.

[0049] [Relationship between DAS parent device and DAS child device: Figure 3] Next, the relationship between the DAS master unit and the DAS slave units in this system will be described with reference to Fig. 3. Fig. 3 is a schematic diagram showing the relationship between the DAS master unit and the DAS slave units in this system. 3, the DAS master 11 is connected to a DAS repeater (DAS aggregation) 13, and a plurality of DAS slaves (DAS slaves) 12 are connected to the DAS repeater 13. Note that FIG. 3 also shows an example in which a plurality of DAS slaves 12 are directly connected to the DAS master 11.

[0050] The DAS master 11 also has an O-RU server function 11c, which aggregates slave unit information from the DAS slave units 12 and shares specific slave unit information with the operator. The slave unit information is not collected after an inquiry from an operator, but is periodically instructed to be collected by the DAS slave unit 12, and is acquired, updated, and stored in the DAS master unit 11.

[0051] Specifically, the slave unit information is collected in the O-RU server 11c via the DAS optical transmission path. The DAS-specific interface is designed so that access is not permitted to operators, and access is limited to the O-RU server 11c from external operators. For example, some of the software management, configuration management, performance management, fault management, and file management functions required by the O-RAN Management Plane Specification 12.0 are also implemented in DAS, so they are implemented using specific expressions.

[0052] The DAS master unit 11 is a type of network device, and can be thought of as a gateway that relays between networks with different transmission methods and protocols (communication rules), and the FHM may be configured to perform the gateway function.

[0053] [Upstream and downstream processing in this system: Figure 4] Next, the upstream and downstream processing of this system will be explained with reference to Fig. 4. Fig. 4 is a schematic diagram showing the upstream and downstream processing of this system. Fig. 4 explains this based on the configuration of Fig. 3. As shown in Figure 4, in this system, as uplink processing, the RF data received from the mobile terminal by the DAS slave device 12 is internally reallocated as IQ (in-phase / quadrature) data for each band, separated for each operator, and allocated to data in the User Plane (including the C&M Plane) in accordance with the O-RAN specifications.

[0054] In addition, in this system, as downlink processing, in accordance with the O-RAN specifications from the CU / DU 30, the DAS parent device 11 extracts IQ data from the User Plane using the O-RU function, allocates it to each band, combines it, converts it to RF, and transmits it via RF to the mobile terminal from the DAS child device 12.

[0055] [Sequence of this system: Figure 5] Next, the sequence of this system will be described with reference to Fig. 5. Fig. 5 is a functional schematic diagram showing the sequence of this system. As shown in Figure 5, this system is equipped with a DAS parent device (RU DAS parent) 11, a client (CU / DU) 30a of operator 1, and a client (CU / DU) 30b of operator 2, and executes the following processing.

[0056] Between the DAS parent device 11 and CU / DU 30a or CU / DU 30b, M-Plane establishment processing, SW (synchronization) management processing, and configuration management processing are performed respectively, and operators 1 and 2 can refer to up to the configuration management processing. The subsequent performance management processing, fault management processing, and file management processing share information using the RU server function of the DAS parent device 11, but operators are restricted from viewing it.

[0057] In this system, although the internal information of the DAS can be shared among each operator using the RU server function for logically different RUs, the system does not provide the slave information of each individual DAS slave 12 individually, and each operator does not directly control the individual DAS slave 12 by changing the settings, etc.

[0058] Next, the sequence of this system will be specifically described. The sequence processing executes the M-Plane function, which is an O-RAN fronthaul specification, and supports the management function for the O-RU. The M-Plane establishment process includes start-up installation, NETCONF establishment, synchronization establishment, capability exchange, and M support function activation.

[0059] In the SW management process, the client (CU / DU) 30 manages the SW (synchronization) of the RU, and performs inventory, download, installation, and activation processes for SW files. In the configuration management process, the client (CU / DU) 30 sets and acquires the parameters and resource status of the CUS-Plane in the RU, acquires / changes the resource status, and acquires / changes / deletes parameters.

[0060] Performance management processing collects data measurements required for RU operation and optimizes RU operation. It starts and ends on a measurement group basis. It can also be managed at times other than startup. In the fault management process, the client (CU / DU) 30 manages faults in the RUs. In fault management, the RU sends alarm notifications to the NETCONF client. The RU creates a list of alarms.

[0061] File management processing is triggered by file transmission between the RU and the file server. Measurement results and logs are uploaded from the RU to the file server. Beam configurations can be downloaded from clients, but restrictions are placed on them to prevent other operators from arbitrarily controlling them.

[0062] [Effects of the embodiment] According to this system, which is a system that combines O-RAN and DAS, the DAS parent device 11 connected to the O-RAN client (CU / DU) 30 is provided with an O-RAN interface and an O-RU server function 11c that implements the fronthaul specification (RU / FHM) between the client (CU / DU) 30 and the O-RAN RU, and the DAS parent device 11 enables data transmission with the client 30 via an optical cable via the O-RAN interface, and the O-RU server function 11c converts radio signals from the DAS child device 12 into fronthaul specification data and transmits it via the optical cable, which has the effect of simplifying the configuration by connecting the O-RAN and DAS via an optical cable.

[0063] Furthermore, according to this system, the DAS parent device 11 periodically collects and stores child device information from the DAS child devices 11, and when a client requests the child device information, it responds to the client with the stored child device information. This has the effect of solving authentication delays and security issues by theoretically separating the O-RAN fronthaul from the optical transmission path inside the DAS.

[0064] Furthermore, according to this system, in the M-Plane function of the fronthaul specification, the DAS parent device 11 executes the M-Plane establishment process, synchronization management process, and configuration management process so that they can be referenced by each client, and executes the performance management process, fault management process, and file management process so that they cannot be referenced by clients, storing them as shared information, and notifying the client of an alarm when a fault occurs, thereby improving security within the DAS and enabling effective response to faults. [Industrial Applicability]

[0065] The present invention is suitable for a wireless communication system in which the O-RAN and DAS are connected by an optical cable, thereby simplifying the configuration. [Explanation of symbols]

[0066] 10...DAS side network monitoring control unit (EMS), 11...DAS parent unit, 11a, 11b...O-RU, 11c...O-RU server function, 12...DAS child unit, 13...DAS repeater (HU), 21...radio unit, 22...distribution unit (DU), 23...centralization unit (CU), 24...5G core network device (5GC), 25...operator side network monitoring control unit (EMS), 30a, 30b...client (CU / DU), 110...DAS parent unit (MU) with O-RU function

Claims

1. A wireless communication system that combines an open radio access network (O-RAN) and a distributed antenna system (DAS), A DAS master connected to a client of the O-RAN is provided with an O-RAN interface and an O-RU server function that implements a fronthaul specification (RU / FHM) between the client and a radio unit of the O-RAN; A wireless communication system characterized in that the DAS parent device enables data transmission with the client via an optical cable using the O-RAN interface, and converts wireless signals from the DAS child device into fronthaul specification data using the O-RU server function and transmits them via the optical cable.

2. The DAS parent device is provided with an O-RAN interface in which a different profile is set for each of a plurality of clients, and the fronthaul specifications are defined by the profile. The wireless communication system according to claim 1, characterized in that

3. The wireless communication system according to claim 1 or 2, characterized in that the DAS master periodically collects and stores slave unit information from the DAS slave units, and when the client requests the slave unit information, transmits the stored slave unit information to the client.

4. The wireless communication system described in claim 1 or 2, characterized in that, as an upstream transmission process, the DAS parent device reallocates RF data received by the DAS child device from the mobile terminal as IQ data for each band, separates it to each client, allocates and transmits the data according to the fronthaul specification, and as a downstream transmission process, extracts IQ data from the fronthaul specification data from the client, allocates and combines it for each band, and transmits the data to the DAS child device.

5. The wireless communication system described in claim 2, characterized in that, in the M-Plane function of the fronthaul specification, the DAS parent device executes M-Plane establishment processing, synchronization management processing, and configuration management processing so that they can be referenced by each client, and executes performance management processing, fault management processing, and file management processing so that they cannot be referenced by clients, stores them as shared information, and notifies the client of an alarm when a fault occurs.

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