Optical repeater system, optical repeater device, master unit, and synchronization control method

Abstract

To further improve availability by enabling carrier aggregation involving different optical repeater devices.SOLUTION: According to an embodiment, each master unit comprises a storage unit that stores a weight previously assigned thereto, a timing detection unit, an information sharing unit, a determination unit, and a synchronization control unit. The timing detection unit detects a UL / DL switching timing in each carrier band of a base station subordinate thereto. The information sharing unit performs communication with another master unit, and shares with the another master unit information including at least the weight and the latest UL / DL switching timing out of the detected UL / DL switching timings. The determination unit self-reliantly determines the UL / DL switching timing thereof on the basis of the shared information. The synchronization control unit sets the UL / DL switching timing thereof to the determined UL / DL switching timing.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to an optical repeater system, an optical repeater device, a master unit, and a synchronization 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] 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, too, it is being considered to accommodate multiple base stations, each owned by a different operator, in a single master unit. If this technology is applied to local 5G, it will be possible for the communications operator and licensee to share the same master unit. This type of master unit is also called an operator-shared device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6602813 [Patent Document 2] Patent No. 6577512 Summary of the Invention [Problem to be solved by the invention]

[0005] Currently, the most common communication methods for the air section between base stations and mobile terminals are FDD (Frequency Division Duplex) or TDD (Time Division Duplex). Different methods may be used for the downlink (DL) and uplink (UL). The technology that increases communication speeds by combining multiple carrier frequencies is called Carrier Aggregation (CA).

[0006] According to 3GPP (registered trademark) regulations, implementing CA in 5G TDD requires that the difference in UL / DL switching timing between frequency bands be less than 3 μs. However, this regulation only refers to the output point of the radio signal from the base station and does not take into account the radio signals transmitted and received by the local stations of the optical repeater equipment. Therefore, technology is required to adjust the UL / DL switching timing between frequency bands within the specified range for the output point of the radio signal from the local station.

[0007] For example, a technology has been proposed that allows multiple substations belonging to one base station to switch between UL / DL frequencies within a specified time frame (hereafter referred to as UL / DL switching timing). Technology is also being considered that allows substations belonging to different base stations to achieve UL / DL switching timing within 3 microseconds between frequency bands. Further development of this technology would enable carrier aggregation between substations of different optical repeater devices, which is expected to dramatically improve the convenience of 5G system users.

[0008] Therefore, an object is to provide an optical repeater system, an optical repeater device, a master unit, and a synchronization control method that enable carrier aggregation involving different optical repeater devices to be performed, thereby further improving availability. [Means for solving the problem]

[0009] According to an embodiment, an optical repeater system includes multiple master units. The master units are connectable to base stations to which carrier bands to be used for carrier aggregation are assigned and to remote units equipped with antennas capable of transmitting and receiving uplink / downlink (UL / DL) signals in the carrier bands. Each master unit includes a storage unit that stores weights pre-assigned to the master unit, a timing detector, an information sharing unit, a determination unit, and a synchronization control unit. The timing detector detects UL / DL switching timing for each carrier band of the base stations under its control. The information sharing unit communicates with other master units and shares information including at least the weights and the latest UL / DL switching timing among the detected UL / DL switching timings with the other master units. The determination unit autonomously determines its own UL / DL switching timing based on the shared information. The synchronization control unit sets its own UL / DL switching timing to the determined UL / DL switching timing. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing an example of an optical repeater device according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of an optical repeater system according to an embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of an unsynchronized state in the optical repeater system. [Figure 4] FIG. 4 is a diagram showing an example of a synchronized state in an optical repeater system. [Figure 5] FIG. 5 is a diagram for explaining the setting of the CA candidate device group. [Figure 6] FIG. 6 is a diagram showing an example of a timing chart in Case 0. In FIG. [Figure 7] FIG. 7 is a diagram showing an example of a timing chart in Case 1. In FIG. [Figure 8] FIG. 8 is a table showing the states shown in FIG. [Figure 9]FIG. 9 is a diagram showing an example of a timing chart in Case 2. In FIG. [Figure 10] FIG. 10 is a table showing the states shown in FIG. [Figure 11] FIG. 11 is a functional block diagram showing an example of the master station 100 and the slave station 200. As shown in FIG. [Figure 12] FIG. 12 is a functional block diagram illustrating an example of the processor 140 and the memory 150. As shown in FIG. [Figure 13] FIG. 13 is a flowchart showing an example of a processing procedure of the master station 100 according to the embodiment. [Figure 14] FIG. 14 is a flowchart showing an example of the processing procedure in step 5 of FIG. [Figure 15] FIG. 15 is a diagram showing an example of information registered in the management table 150d. [Figure 16] FIG. 16 is a diagram showing another example of the management table 150d. [Figure 17] FIG. 17 is a diagram showing another example of the management table 150d. [Figure 18] FIG. 18 is a diagram showing another example of the management table 150d. [Figure 19] FIG. 19 is a diagram showing another example of the management table 150d. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 is a block diagram showing an example of an optical repeater according to an embodiment. The optical repeater includes a master unit (MU) 100 and multiple remote units (RU) 200 (#1 to #n) each connected to the master unit 100 via an optical fiber. This type of system is also called a distributed antenna system (DAS). A relay station 400 may be provided between the master unit 100 and the remote units 200.

[0012] One or more base stations BS are accommodated in the master station 100 via coaxial cables or the like. In a connection via a coaxial cable, it is possible to transmit four systems of wireless signals for each base station BS, for example, 100 MHz band x 4 (4 x 4 MIMO).

[0013] Each base station BS is assigned a carrier band. In the embodiment, carrier aggregation, which aggregates multiple carrier bands to increase the bandwidth, will be described. In other words, each carrier band is subject to carrier aggregation. However, in the air section deployed from the mobile station 200, the synchronization of the UL / DL switching timing of each carrier band must be within 3 μs.

[0014] The base station BS transmits and receives UL signals and DL signals to and from the slave stations 200 via the master station 100. A mobile terminal (UE: User Equipment), not shown, is connected to one of the slave stations (#1 to #n) via a wireless channel within the wireless zone in which the slave station 200 is deployed. The slave station 200 is equipped with an antenna capable of transmitting and receiving uplink / downlink (UL / DL) signals in a carrier band allocated to the base station BS.

[0015] FIG. 2 is a block diagram showing an example of an optical repeater system according to an embodiment. The optical repeater system includes a plurality of optical repeater devices. Each of the master stations 100 of the optical repeater device accommodates a plurality of slave stations 200. For example, l slave stations are connected to master station #1, m slave stations are connected to master station #2, and n slave stations are connected to master station #N. In this optical repeater system, the master stations 100 of the optical repeater devices are connected to each other so that they can communicate with each other. In FIG. 2, master stations #1, #2, ..., #N are connected to each other via a wired line 2. The master stations #1, #2, ..., #N can exchange various information with each other via the wired line 2.

[0016] Figure 3 shows an example of an unsynchronized state in an optical repeater system. In Figure 3, the horizontal axis represents the passage of time. The UL / DL switching timings of the base stations BS (frequency bands A, B, and C) accommodated by master station #1 are offset within a tolerance range of ±1.5 μs (microseconds), regardless of whether the carriers are the same or different. Similarly, the UL / DL switching timings of the base stations BS (frequency bands a, b, and c) accommodated by master station #n are offset within a tolerance range of ±1.5 μs (microseconds), regardless of whether the carriers are different. This offset is mainly caused by different lengths of coaxial cables, and is acceptable within a ±1.5 μs range.

[0017] Furthermore, there is often some difference in the UL / DL switching timing between master stations. Furthermore, differences in the length of optical fiber cause timing differences between slave stations. When operating DAS, the UL / DL switching timing of the radio waves emitted from the slave stations must be kept within the 3 μs specified by 3GPP (registered trademark).

[0018] Therefore, each master station is equipped with a timing detection unit, which individually detects the UL / DL switching timing of its subordinate base station BS, and exchanges and shares this timing information with each other. Each master station then synchronizes its own UL / DL switching timing with the latest timing. Furthermore, each master station individually detects the amount of delay of its subordinate slave stations 200, and exchanges and shares this timing information with each other. Each master station then synchronizes the UL / DL switching timing of its subordinate slave stations 200 with the latest timing.

[0019] Fig. 4 shows an example of a synchronized state in an optical repeater system. By mutually notifying each parent station of the UL / DL switching timing of the base station under their control and the delay amount of each child station, and correcting the timing to the latest timing, it is possible to create a synchronized state at the end of the child station 200, as shown in Fig. 4. To synchronize the UL / DL switching timing among multiple optical repeater equipment, a simple majority voting method is used. The majority voting method involves the concept of a CA candidate equipment group. A CA candidate equipment group is a group of multiple base stations that are candidates for performing carrier aggregation (CA). From another perspective, a CA candidate equipment group is a group of base stations whose UL / DL switching timing is within 3 μs. From yet another perspective, a CA candidate equipment group is a set of base stations whose UL / DL switching timing to meet the CA requirements of the 3GPP standard is within the effective correction range. In other words, CA can be performed between any or all of the base stations included in the CA candidate equipment group.

[0020] Fig. 5 is a diagram for explaining the setting of a group of CA candidate devices. In Fig. 5, the UL / DL switching timing of the master station [#1] detected by itself is used as a reference, and the UL / DL switching timings of the other master stations [#2] to [#N] are compared. Here, the rising edge (reset timing) is used as a reference. In the case of Figure 5, the UL / DL switching timing of master stations [#2] and [#N] as seen from master station [#1] is within the OK region (within ±1.5 μs), but the UL / DL switching timing of master station [#3] is outside that region, in the NG region. In this case, the CA candidate devices as seen from master station [#1] are ([#1], [#2], [#N]). Because the timing detection criteria differ for each master station, the CA candidate devices are generally different for each master station.

[0021] In this embodiment, CA is performed between master stations included in a CA candidate device group that has the largest and majority number of master stations within the 3 μs range ("OK1" and "OK2") specified by the 3GPP, which is the effective correction range (majority rule). Here, the UL / DL switching timing of the carrier emitted from the slave station is set to the latest timing among master stations included in the CA candidate device group. On the other hand, master stations that belong to a CA candidate device group where the number of master stations is not the majority will stop transmitting.

[0022] Next, we will explain a specific example of CA execution. In the following explanation, we assume that the number of master stations N is 4, and there are four master stations [#1] to [#4] involved, and we will take up three cases with different UL / DL switching timings.

[0023] <Case 0> FIG. 6 is a diagram showing an example of a timing chart for Case 0. In FIG. 6, the UL / DL switching timings of all master stations [#1] to [#4] fall within the correction effective range (OK1 or OK2) of all master stations. Since the UL / DL switching timing of master station [#4] is the slowest, the other master stations [#1] to [#3] adjust their own UL / DL switching timing to this. Then, the delay times of the slave stations under their control are set to the slowest of the shared delay times. Case 0 is a case where the majority voting method can solve the problem without any problems. However, there are also cases where the majority voting method cannot solve the problem. Next, we will explain cases 1 and 2, which cannot be solved by the majority voting method.

[0024] <Case 1> Case 1 is a case where radio waves are transmitted from a slave station even though the UL / DL switching timing is inconsistent. Figure 7 shows an example of a timing chart for Case 1. In Figure 7, for master station [#1] and master station [#3], the UL / DL switching timing of all devices is within the correction valid range (OK1, OK2). In contrast, for master station [#2], the UL / DL switching timing of master station [#4] is in the NG area, and for master station [#4], the UL / DL switching timing of master station [#2] is in the NG area. This state is represented in a table as shown in Figure 8.

[0025] Figure 8 is a table showing the state shown in Figure 7. According to Figure 8, for each master station, the number of devices in the CA candidate device group to which it belongs accounts for a majority, so according to the majority voting method, no device (master station) should stop transmitting. However, under the rule of matching the UL / DL switching timing to the latest UL / DL switching timing among the CA candidate devices, the UL / DL switching timing of master station [#1], master station [#3], and master station [#4] will be the same (as master station [#4]), while the UL / DL switching timing of master station [#2] will be the same as the UL / DL switching timing of master station [#2]. As a result, the UL / DL switching timing of master station [#1], master station [#3], and master station [#4] will be inconsistent with that of master station [#2], and if radio waves are transmitted in this state, there is a risk of interference.

[0026] <Case 2> Case 2 is a case where all master stations stop broadcasting. FIG. 9 is a diagram showing an example of a timing chart for Case 2. In FIG. 9, for the master station [#1], only the UL / DL switching timing of the master station [#4] falls within the correction effective range (OK1, OK2). Also, for the master station [#4], only the UL / DL switching timing of the master station [#1] falls within the correction effective range (OK1, OK2). On the other hand, for the master station [#2], only the UL / DL switching timing of the master station [#3] falls within the correction effective range (OK1, OK2), and for the master station [#3], only the UL / DL switching timing of the master station [#2] falls within the correction effective range (OK1, OK2). This state is represented in a table as shown in FIG. 10.

[0027] Fig. 10 is a table showing the state shown in Fig. 9. According to Fig. 10, for all master stations, the number of devices in the CA candidate device group to which they belong is not a majority. Therefore, under the majority voting method, all master stations will stop transmitting. This is despite the fact that there is room for other master stations to synchronize their UL / DL switching timing with that of master station #3, for example.

[0028] As mentioned above, there are cases where the majority voting system alone cannot solve the problem. Next, we will explain a technique that can solve such problems. (composition) FIG. 11 is a functional block diagram showing an example of the master station 100 and the slave station 200. As shown in FIG.

[0029] 11, master station 100 includes signal processing units 110-1 to 110-Z, timing comparison unit 120, demultiplexing unit 130, processor 140, memory 150, base station connection unit 160, master station connection unit 170, and slave station connection unit 180. In other words, master station 100 is a computer including a processor and memory.

[0030] The base station connection unit 160 is an interface for accommodating multiple base stations BS, and in FIG. 11, can be connected to base stations BS-A, BS-B, .about.BS-Z via coaxial cables or the like. The master station connection unit 170 is an interface for communicating with other master stations 100, and can be connected to other master stations 100 via a LAN (Local Area Network) or a serial cable. The slave station connection unit 180 is connected to a plurality of subordinate slave stations 200 via optical fibers. That is, the slave stations 200 are accommodated in the master station 100 via optical fibers.

[0031] Signal processing units 110-1 to 110-Z are associated with corresponding base stations BS-A, BS-B, ..., BS-Z, respectively, and transmit and receive UL / DL signals to and from base stations BS-A, BS-B, ..., BS-Z via base station connection unit 160. That is, radio signals transmitted and received to and from mobile terminal UE are transmitted and received in both UL / DL directions via signal processing units 110-1 to 110-Z for each of base stations BS-A, BS-B, ..., BS-Z.

[0032] The timing comparator 120 compares the UL / DL switching timing for each carrier band detected in the signal processors 110-1 to 110-Z and generates a delay adjustment amount. The comparison result and the delay adjustment amount are passed to the signal processors 110-1 to 110-Z and the processor 140.

[0033] The demultiplexing unit 130 converts the DL signals from the signal processing units 110-1 to 110-Z into optical signals, then wavelength-multiplexes the optical signals, and transmits them from the slave station connection unit 180 to the respective slave stations 200 via optical fibers.

[0034] The demultiplexer 130 receives optical signals from the slave stations 200-1 through 200-Z via optical fibers, separates the signals into carrier bands in wavelength units, converts the signals into electrical signals, and extracts digital signals. These digital signals are sent to the signal processors 110-1 through 110-Z corresponding to the carrier bands.

[0035] The processor 140 acquires the comparison result of the UL / DL switching timing for each carrier band and the transmission delay time for each slave station 200 detected by the signal processing units 110-1 to 110-Z, respectively. The memory 150 stores various programs, setting data, etc., and weights assigned to each master station 100 in advance.

[0036] Each of the signal processing units 110-1 to 110-Z includes a transmit / receive switch (SW) 111, a detector 112, an A / D converter (ADC) 113, a timing detection unit 114, a timing adjustment unit 115, a D / A converter (DAC) 116, and a delay detection unit 117.

[0037] The transmit / receive switch 111 switches the uplink / downlink switching timing with the opposing base station BS in synchronization with the UL / DL switching timing provided by the timing detection unit 114. This realizes communication by TDD (Time Division Duplex).

[0038] A carrier band signal from an opposing base station BS is sent to A / D converter 113 and detector 112. A / D converter 113 converts this signal to digital and outputs the digital signal to timing adjustment section 115. Detector 112 detects the carrier band signal and sends the detected waveform to timing detection section 114.

[0039] The timing detection unit 114 detects the UL / DL switching timing for each carrier band of the base station BS based on the detected waveform. The timing detection unit 114 also generates a timing signal (pulse signal) based on the detected UL / DL switching timing, and outputs this timing signal to the transmit / receive switch 111, the timing adjustment unit 115, and the timing comparison unit 120.

[0040] The timing adjustment unit 115 adjusts the switching timing by applying a delay according to the delay adjustment amount to the output of the A / D converter (ADC) 113. This realizes the first correction process ((1) in FIG. 4) for synchronizing the master stations 100 with each other.

[0041] The digital signal from the demultiplexer 130 is input to a D / A converter (DAC) 116 and a delay detector 117. The D / A converter 116 converts the digital signal to an analog signal and upconverts it to the carrier band to reproduce an uplink signal. This uplink signal is transmitted to the base station BS via the transmit / receive switch 111 and a coaxial cable.

[0042] The delay detection unit 117 monitors the digital signal from the demultiplexing unit 130 and, for example, exchanges control signals with the slave station 200 to detect the amount of transmission delay between the master station 100 and the slave station 200. The detected amount of transmission delay is passed to the processor 140.

[0043] On the other hand, the slave station 200 includes an antenna 270, a demultiplexer 210, a controller 220, a delay adjuster 230, a D / A converter (DAC) 240, a transmit / receive switch (SW) 250, and an A / D converter (ADC) 260.

[0044] The demultiplexer 210 separates the optical signal from the master station 100 into individual wavelengths, converts the optical signal into an electrical signal, and extracts a digital downlink signal. The controller 220 detects the signal addressed to the slave station 200 from the downlink signal, and detects the delay adjustment amount sent from the processor 140 of the master station 100 contained in this signal, and outputs it to the delay adjustment unit 230.

[0045] The delay adjustment unit 230 delays the transmission timing of the downlink signal based on the delay adjustment amount from the controller 220. This realizes the second correction process ((2) in FIG. 4) for achieving synchronization including the master station 100 and the slave station 200. The delay-controlled downlink signal is output to the D / A converter 240. The D / A converter 240 converts the downlink signal into an analog signal and upconverts it to the band of the assigned channel. This downlink signal in the radio band is radiated into the air via the transmit / receive switch 250 and the antenna 270 and is received by the mobile terminal UE.

[0046] An uplink signal from the mobile terminal UE is sent from antenna 270 of slave station 200 to A / D converter 260 via transmit / receive switch 250. A / D converter 260 down-converts the uplink signal received from the mobile terminal UE to baseband, then converts it to digital, and outputs the digital signal to demultiplexer 210. Demultiplexer 210 converts the digital signal to an optical signal, then multiplexes it, and transmits it to master station 100 via optical fiber.

[0047] 12 is a functional block diagram showing an example of the processor 140 and the memory 150. The processor 140 includes, as processing functions according to the embodiment, an information sharing unit 140a, a decision unit 140b, and a synchronization control unit 140c.

[0048] The information sharing unit 140a communicates with the other master stations 100 to share the weighting previously assigned to the master station and the latest UL / DL switching timing among the UL / DL switching timings detected by the timing detection unit 114. The master stations 100 share at least this information with each other, but it is of course possible for them to share more diverse information.

[0049] The decision unit 140b autonomously decides its own UL / DL switching timing based on the shared weight and the UL / DL switching timing, and calculates the delay adjustment amount.

[0050] The synchronization control unit 140c sets the delay adjustment amount in the timing adjustment unit 115 so as to set its own UL / DL switching timing to the UL / DL switching timing determined by the determination unit 140b.

[0051] The memory 150 is a non-volatile memory such as a flash memory, and stores timing information 150a, slave station delay information 150b, weights 150c, a management table 150d, and a program 150e. The timing information 150a includes the UL / DL switching timing detected by the timing detection unit 114, the UL / DL switching timing shared with other master stations 100, and the like. The slave station delay information 150b includes the delay amount of the slave station 200 detected by the delay detector 117, the delay amount of the slave station 200 shared with other master stations 100, and the like.

[0052] The weight 150c is set and stored in advance in association with the number of connected slave stations 200 subordinate to the own station and the carrier band assigned to the base station BS subordinate to the own station. The management table 150d is generated and stored in each master station 100 based on information shared with other master stations 100, and the UL / DL switching timing, delay amount, etc. detected by the own station. The program 150e includes instructions for causing the processor 140 to function as the information sharing unit 140a, the decision unit 140b, and the synchronization control unit 140c.

[0053] (action) Next, the operation of the above configuration will be described. 13 is a flowchart showing an example of a processing procedure of the master station 100 according to the embodiment. In FIG. 1, the master station 100 detects the UL / DL switching timings of the carrier bands received from the base station BS, extracts the latest UL / DL switching timing from among them, and stores it in the memory 150 (step S1). Next, the master station 100 detects the transmission delay time for each slave station 200 under its control, and stores the longest one of the detected delay times in the memory 150 as slave station delay information (step S2). For example, the delay time from the master station 100 to the slave station with the longest transmission path length between the master station 100 and the slave station is generated as the slave station delay information. Next, the master station 100 communicates with the other master stations 100, and shares the UL / DL switching timing (timing information 150a), slave station delay information 150b, and its own weight 150c with the other (n-1) master stations 100 (step S3).

[0054] Next, the master station 100 generates a management table 150d based on the shared information (step S4). The management table 150d includes the UL / DL switching timing of each master station 100, the device IDs of a set of master stations (CA candidate device group) within the correction effective range, and the sum of the weights for each CA candidate device group.

[0055] Next, the master station 100 modifies the management table 150d so that the CA candidate device groups within the effective ranges of the other master stations 100 match (step S5). The processing in step S5 will be described in detail later. When the correction of the management table 150d is completed, the master station 100 either stops transmitting its own signal in accordance with the corrected management table 150d, or adjusts its own UL / DL switching timing to match the latest UL / DL switching timing among the CA candidate devices to which the master station belongs (step S6). That is, a master station 100 whose weight has become 0 as a result of the correction of the management table 150d stops transmitting downlink signals in the carrier band. A master station 100 whose weight is not 0 resets its own UL / DL switching timing to the latest timing among the shared timings. Then, the master station 100 adjusts the delay amount of the slave station under its control so that the delay time matches the delay time of the slave station that is the longest among the CA candidate devices to which the master station 100 belongs (step S7).

[0056] Fig. 14 is a flowchart showing an example of the processing procedure in step 5 of Fig. 11. Step 5 is a step in which the management table initially generated by information sharing between master stations 100 is modified by loop processing. The management table in Fig. 15 will also be described.

[0057] Fig. 15 is a diagram showing an example of information registered in management table 150d. Fig. 15 shows management table 150d generated in step S4 (Fig. 13) in the state of <Case 0> (Fig. 6). Here again, it is assumed that four master stations [#1] to [#4] are involved, but it is newly assumed that the weight of master station [#1] is 4, the weight of master station [#2] is 3, the weight of master station [#3] is 2, and the weight of master station [#4] is 1.

[0058] In FIG. 14, the master station 100 first determines whether the sums of the weights of multiple CA candidate device groups are the same (step S51). If they are the same (all sums of the weights in FIG. 15 are 10), as in FIG. 15, the master station 100 determines whether there are any CA candidate device groups that do not have the same elements (step S52). In other words, the master station 100 determines whether there are any mutually disjoint device groups. A "mutually disjoint device group" is a "CA candidate device group that does not have the same elements," or can also be understood as a "CA candidate device group that does not have any common elements." If step S52 returns No, that is, if the master stations of the elements of the CA candidate device groups are all the same, the process ends and the processing procedure proceeds to step S6 in FIG. 13.

[0059] On the other hand, if the answer is No in step S51, the master station 100 sets the weight of the master station with the lowest sum of weights to 0 (step S53), and then updates the management table 150d by recalculating the sum of weights (step S54). The procedures of steps S53 and S54 are repeatedly looped in step S51 until the sums of the weights of the devices become the same.

[0060] If step S52 is Yes, that is, if there are CA candidate device groups with the same sum of weights but different elements, the master station 100 sets the weight of the master station that belongs to the device group other than the device group to which the master station with the largest weight belongs (that is, the master station that does not belong to the device group to which the master station with the largest weight belongs) to 0 (step S55).The master station 100 then updates the management table 150d by recalculating the sum of weights (step S54).

[0061] 15, in case 0, the management table 150d is not changed even after step S5. Based on this management table 150d, each master station 100 adjusts its own UL / DL switching timing to the device (master station [#4]) with the latest UL / DL switching timing among the CA candidate devices.

[0062] Next, the above processing procedures will be explained for each of <Case 1> and <Case 2>. <About Case 1> FIG. 16 shows management table 150d generated in step S4 (FIG. 13) in the state of <Case 1> (FIG. 7). In this case, it can be seen that the sum of the weights of the CA candidate device group to which master station [#4] belongs is 7, the lowest. Therefore, management table 150d is updated with the weight of master station [#4] set to 0 (zero), resulting in the table shown in FIG. 17. In FIG. 17, the weight of the CA candidate device group of master station [#1], master station [#2], and master station [#3] becomes 9, and the processing procedure of FIG. 14 exits the loop at this point. In FIG. 17, the elements of the CA candidate device group whose sum of weights is not 0 match, so this state becomes the final management table 150d.

[0063] Then, according to this management table 150d, master stations [#1] to [#3] are synchronized with the UL / DL switching timing of master station [#3], and master station [#4] stops transmitting. Finally, master stations [#1] to [#3] adjust the delay amounts of their subordinate slave stations.

[0064] In Figure 8, master station [#1] and master station [#3] have the timing of master station [#4], and master station [#2] has the timing of master station [#3], resulting in mismatch. Therefore, carrier aggregation cannot be performed in this state. In contrast, by executing the processing procedures in Figures 13 and 14, it is possible to match the timing of all master stations 100 that are not out of service, as shown in Figure 17. In other words, the problem in <Case 1> is resolved, and carrier aggregation can be performed without any problems.

[0065] <About Case 2> 18 shows management table 150d generated in step S4 (FIG. 13) in the state of <Case 1> (FIG. 7). In this case, the sums of the weights of the CA candidate device groups to which master station [#1] to master station [#4] belong are all 5. However, there are different CA candidate device groups. In other words, there are sets of master stations with the same sum of weights that are mutually prime.

[0066] Therefore, in step S55 (FIG. 14), the weights of the master stations [#2] and [#3] that do not belong to the CA candidate device group (#1, #4) to which the master station [#1] with the highest weight belongs among the different CA candidate device groups are set to 0, and management table 150d is updated. Then, management table 150d is updated as shown in FIG. 19, and reaches the final state.

[0067] Then, according to this management table 150d, master stations [#2] and [#3] stop transmitting, and master stations [#1] and [#4] are synchronized with the UL / DL switching timing of master station [#4]. Finally, master stations [#1] and [#4] adjust the delay amounts of their subordinate slave stations.

[0068] In Fig. 10, all master stations [#1] to [#4] blindly stopped transmitting. In contrast, by executing the processing procedures in Fig. 13 and Fig. 14, unnecessary stoppages can be prevented, and the timing of all master stations 100 that are not stopped transmitting can be synchronized, as shown in Fig. 19. In other words, the problem in <Case 2> can be resolved, and carrier aggregation can be performed without any problems.

[0069] As described above, according to the embodiment, a weight is set in advance for each base station, and the concept of a CA candidate device group, which is a collection of master stations within the effective correction range, is introduced. Furthermore, the timing on the base station side in the carrier band and the delay amount on the slave station side are detected by each master station 100, and the master stations 100 communicate with each other to share information. Then, for each CA candidate device group, the sum of the weights of the master stations of the elements is calculated, and based on the priority corresponding to the weight, the master station autonomously determines the UL / DL switching timing to be synchronized and whether or not to stop broadcasting at its own station.

[0070] With existing technology, when an optical repeater is connected to a base station, the difference in UL / DL switching timing between carriers cannot be kept within the 3GPP specifications, which could result in the inability to obtain the benefits of CA. In addition, there are operational issues that cannot be completely resolved due to concerns about inconsistencies between carriers when implementing CA.

[0071] In contrast, according to the embodiment, it is possible to reliably prevent inconsistencies in UL / DL switching timing between carrier bands and minimize the number of carrier bands and master stations 100 that will result in outages. Therefore, according to the embodiment, operation that enables CA between multiple optical repeater devices becomes possible. That is, according to the embodiment, it is possible to perform carrier aggregation involving different optical repeater devices, and therefore it is possible to provide an optical repeater system, optical repeater device, master unit, and synchronization control method that can further improve availability.

[0072] It should be noted that the present invention is not limited to the above-described embodiment. For example, the criteria for weighting a master station are not limited to the number of slave stations accommodated or the carrier bandwidth, but can be freely set according to, for example, the operational policy of the telecommunications carrier to which the UE belongs. For example, a carrier that places importance on the bandwidth in the uplink can set the weight using a method such as combinatorial optimization to maximize the opportunities for carrier aggregation in the uplink.

[0073] 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]

[0074] 2...wired line, 100...master station, 110-1 to 110-Z...signal processing unit, 111...transmit / receive switch, 112...detector, 113...A / D converter, 114...timing detection unit, 115...timing adjustment unit, 116...D / A converter, 117...delay detection unit, 120...timing comparison unit, 130...demultiplexing unit, 140...processor, 140a...information sharing unit, 140b...determination unit, 140c...synchronization control unit, 150...memory, 15 0a...timing information, 150b...slave station delay information, 150c...weight, 150d...management table, 150e...program, 160...base station connection unit, 170...master station connection unit, 180...slave station connection unit, 200...slave station, 210...multiplexing / demultiplexing unit, 220...controller, 230...delay adjustment unit, 240...D / A converter, 250...transmit / receive switch, 260...A / D converter, 270...antenna, 400...relay station, BS...base station.

Claims

1. An optical repeater system comprising a plurality of master units connectable to a base station to which a carrier band to be subjected to carrier aggregation is assigned and to a remote unit having an antenna capable of transmitting and receiving uplink / downlink (UL / DL) signals of the carrier band, Each of the master units a storage unit that stores weights assigned to the device in advance; a timing detection unit that detects UL / DL switching timing for each carrier band of a subordinate base station; an information sharing unit that communicates with other master units and shares information including at least the weight and the latest UL / DL switching timing among the detected UL / DL switching timings with the other master units; a determination unit that autonomously determines its own UL / DL switching timing based on the shared information; and a synchronization control unit that sets its own UL / DL switching timing to the determined UL / DL switching timing.

2. The determination unit For each set whose elements are master units whose shared UL / DL switching timing falls within a specified range, calculate the sum of weights assigned to the master units of the elements; 2. The optical repeater system according to claim 1, wherein the optical repeater system determines its own UL / DL switching timing based on the sum of the weights.

3. The determination unit determining whether to stop transmitting downlink signals of master units that do not belong to a set to which a master unit with the largest weight belongs, among sets in which the sums of the weights are the same and relatively prime; 3. The optical repeater system according to claim 2, wherein said synchronization control unit stops transmitting a downlink signal of said carrier band when it is determined that its own downlink signal is to be stopped.

4. 2. The optical repeater system according to claim 1, wherein the weight assigned to said master unit is the number of remote units connected to said master unit.

5. 2. The optical repeater system according to claim 1, wherein the weight assigned to the master unit corresponds to a carrier band assigned to a base station connected to the master unit.

6. The master unit a delay detection unit for detecting a transmission delay time for each subordinate remote unit; The information sharing unit further shares the transmission delay time with the other master units, 6. The optical repeater system according to claim 1, wherein the synchronization control unit sets UL / DL switching timing of the subordinate remote units based on the shared transmission delay time.

7. a base station connection unit that can connect to a base station to which a carrier band that is the target of carrier aggregation is assigned; a remote unit including an antenna capable of transmitting and receiving uplink / downlink (UL / DL) signals in the carrier band; a storage unit that stores weights assigned to the device in advance; a timing detection unit that detects UL / DL switching timing for each carrier band of a subordinate base station; an information sharing unit that communicates with other master units and shares information including at least the weight and the latest UL / DL switching timing among the detected UL / DL switching timings with the other master units; a determination unit that autonomously determines its own UL / DL switching timing based on the shared information; and a synchronization control unit that sets its own UL / DL switching timing to the determined UL / DL switching timing.

8. a base station connection unit that can connect to a base station to which a carrier band that is the target of carrier aggregation is assigned; a slave station connection unit connectable to a remote unit having an antenna capable of transmitting and receiving uplink / downlink (UL / DL) signals in the carrier band; a storage unit that stores weights assigned to the device in advance; a timing detection unit that detects UL / DL switching timing for each carrier band of a subordinate base station; an information sharing unit that communicates with other master units and shares information including at least the weight and the latest UL / DL switching timing among the detected UL / DL switching timings with the other master units; a determination unit that autonomously determines its own UL / DL switching timing based on the shared information; a synchronization control unit that sets its own UL / DL switching timing to the determined UL / DL switching timing.

9. A synchronization control method for an optical repeater system including a plurality of master units connectable to a base station to which a carrier band to be used for carrier aggregation is assigned and to a remote unit having an antenna capable of transmitting and receiving uplink / downlink (UL / DL) signals of the carrier band, the method comprising: a step of the master unit detecting UL / DL switching timing for each carrier band of a subordinate base station; a step of the master unit communicating with other master units and sharing information including at least a weight assigned to the master unit in advance and the latest UL / DL switching timing among the detected UL / DL switching timings with the other master units; the master unit autonomously determining its own UL / DL switching timing based on the shared information; the master unit setting its own UL / DL switching timing to the determined UL / DL switching timing.

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