Wireless communication system and wireless communication method

Abstract

To properly establish synchronization in a wireless communication system without increasing dedicated wiring.SOLUTION: In a wireless communication system, a second base station device that has received a delay difference correction signal transmits the delay difference correction signal back to a first base station device, and the first base station device adds a data propagation delay difference calculated based on the difference in the transmission and reception times of the delay difference correction signal at the first base station device to time information on the first base station device to obtain time correction data, and transmits the time correction data to the second base station device, and the second base station device sets the time indicated by the received time correction data as the time of the second base station device.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The technology disclosed in this specification relates to wireless communication technology. [Background technology]

[0002] For example, Patent Document 1 discloses a method for synchronizing the transmission timing of signals from each base station by setting the reference signal time of the central device to (1-line delay time) seconds after the time when the reference signal is received at each base station. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-5171 A Summary of the Invention [Problem to be solved by the invention]

[0004] When using the global positioning system (GPS) to synchronize the timing of signal transmission from each base station, GPS signals cannot be received inside tunnels or underground, which poses challenges in establishing synchronization between devices installed inside tunnels.

[0005] As a solution, a method was disclosed in which a reference signal is sent to each base station and the delay difference is used to establish synchronization. However, because the reference signal is sent and received over a dedicated line, this poses the problem of increasing the number of cables that need to be laid at the base station.

[0006] The technology disclosed in this specification has been made in consideration of the problems described above, and is a technology for properly establishing synchronization in a wireless communication system without increasing the amount of dedicated wiring. [Means for solving the problem]

[0007] A wireless communication system according to a first aspect of the technology disclosed in the present specification is a wireless communication system constructed in an IP network, comprising a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices including a first base station device and a second base station device, the first base station device being in a synchronized state with the central device and the second base station device being in an asynchronous state with the central device, and when the second base station device transmits a synchronization request signal to the first base station device, the first base station device receiving the synchronization request signal synchronizes with the transmission signal of the first base station device, A delay difference correction signal with time information added is transmitted to the second base station device, and the second base station device which receives the delay difference correction signal transmits the delay difference correction signal back to the first base station device, the first base station device adds a data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the first base station device to the time information of the first base station device to obtain time correction data, and transmits the time correction data to the second base station device, and the second base station device sets the time indicated by the received time correction data as the time of the second base station device. Effect of the Invention

[0008] According to at least the first aspect of the technology disclosed in the present specification, a wireless communication system including a central device and multiple base station devices is constructed using an IP network, so that data required for synchronization can be superimposed on IP packets and signal transmission lines required for synchronization can be shared. This makes it possible to reduce the number of cables to be laid in the base station devices and establish synchronization with base station devices that are not synchronized due to being unable to receive GPS signals.

[0009] Furthermore, objects, features, aspects and advantages associated with the technology disclosed herein will become more apparent from the detailed description set forth below and the accompanying drawings. [Brief description of the drawings]

[0010] [Figure 1]1 is a diagram illustrating an example of a configuration of a digital wireless communication system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of a base station device (with a GPS receiving unit) according to an embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of the configuration of a base station device (without a GPS receiving unit) according to an embodiment. [Figure 4] 1 is a diagram showing an example of a synchronization method by transmitting and receiving a synchronization request signal between base station devices according to an embodiment. [Diagram 5] FIG. 2 is a diagram illustrating an example of a configuration of a central device according to an embodiment. [Figure 6] 1 is a diagram showing an example of a synchronization method by transmitting and receiving a synchronization request signal between a central device and a base station device according to an embodiment. [Figure 7] FIG. 13 is a diagram showing an example of a synchronization method by broadcasting a synchronization request signal according to an embodiment. [Figure 8] 6 is a diagram illustrating a schematic example of a hardware configuration when the wireless communication systems shown in FIGS. 2, 3, and 5 are actually operated. FIG. [Figure 9] 6 is a diagram illustrating a schematic example of a hardware configuration when the wireless communication systems shown in FIGS. 2, 3, and 5 are actually operated. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described with reference to the accompanying drawings. In the following embodiments, detailed features are shown for the purpose of explaining the technology, but they are merely examples and are not necessarily essential features for enabling the embodiments to be implemented.

[0012] The drawings are schematic, and for the sake of convenience, configurations may be omitted or simplified as appropriate. The size and positional relationship of the configurations shown in different drawings are not necessarily described accurately, and may be changed as appropriate. Hatching may be used in drawings such as plan views that are not cross-sectional views to facilitate understanding of the contents of the embodiments.

[0013] In the following description, the same components are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions thereof may be omitted to avoid duplication.

[0014] Furthermore, in the description in this specification, when a certain component is described as "comprising," "including," or "having," unless otherwise specified, this is not an exclusive expression that excludes the presence of other components.

[0015] Furthermore, even if ordinal numbers such as "first" or "second" are used in the description of this specification, these terms are used for convenience to facilitate understanding of the contents of the embodiments, and the contents of the embodiments are not limited to the orders that may result from these ordinal numbers.

[0016] <First embodiment> A wireless communication system and a wireless communication method according to the present embodiment will be described below.

[0017] <Configuration of wireless communication system> 1 is a diagram showing an example of the configuration of a digital radio communication system according to the present embodiment. In the present embodiment, a train radio system is assumed.

[0018] As shown in the example of FIG. 1, in a digital wireless communication system, a central device 1 is connected via an IP network 2 to a base station device 31, a base station device 32, a base station device 33, . . . , a base station device 3n.

[0019] An IP network is constructed between the central device 1 and the base stations, and routing to each base station is statically controlled.

[0020] The base station devices are installed at regular intervals along the railway line. Therefore, not only are there cases where the base station device 31 is installed in an above-ground section, but there are also cases where the base station device 32 or 33 is installed in a tunnel section.

[0021] A train radio system requires broadcast communication, which means that the central equipment 1 and all base stations must be synchronized to the same time.

[0022] <Base station equipment configuration> Fig. 2 is a diagram showing an example of the configuration of a base station device (with a GPS receiver) according to this embodiment. Fig. 2 shows, as an example, a base station device 3 corresponding to a base station device 31. Fig. 2 also shows an IP network 2.

[0023] 2, the base station device 3 includes an L3SW unit 10 (L3 switch unit), a control unit 20, a modulation / demodulation unit 30, an RF unit 40, a GPS receiving unit 50, and a GPS antenna 60.

[0024] The L3SW unit 10 is connected to the IP network 2. The RF unit 40 is connected to the modem unit 30. The GPS receiving unit 50 is connected to a GPS antenna 60.

[0025] The L3SW unit 10 performs routing processing of IP packets. The control unit 20 multiplexes signals to be transmitted to the central device 1 and separates signals received from the central device 1. The control unit 20 also performs time synchronization processing.

[0026] The modem unit 30 modulates and demodulates a digital signal. The digital signal is then converted into a radio wave and transmitted by the RF unit 40. The RF unit 40 also combines and distributes radio signals.

[0027] The GPS receiver 50 receives, as time information, a one-second pulse-per-second (1PPS) signal synchronized with coordinated universal time (UTC) from a GPS satellite via the GPS antenna 60. The GPS receiver 50 then transmits the 1PPS signal to the control unit 20 as a synchronization timing signal between base station devices.

[0028] 3 is a diagram showing an example of the configuration of a base station device (without a GPS receiver) according to this embodiment. In FIG. 3, a base station device 3A corresponding to the base station device 32 is shown as an example.

[0029] 3, the base station device 3A includes an L3SW unit 10 (L3 switch unit), a control unit 20, a modulation / demodulation unit 30, and an RF unit 40. Since the GPS receiving unit 50 and the GPS antenna 60 in FIG. 2 are not provided in FIG. 3, it is necessary to establish synchronization with a base station device in a synchronized state by another method.

[0030] While the base station device 3 (with a GPS receiver) shown in Figure 2 is installed on the ground, the base station device 3A (without a GPS receiver) shown in Figure 3 is installed in a section where GPS reception is not possible (for example, a tunnel section or underground).

[0031] The configuration of base station device 33 shown in Fig. 1 is similar to the configuration of base station device 3A shown in Fig. 3. Moreover, the configuration of base station device 3n shown in Fig. 1 is similar to the configuration of base station device 3 shown in Fig. 2. Therefore, detailed description of the configurations of base station device 33 and base station device 3n will be omitted.

[0032] <Operation of wireless communication system> 4 is a diagram showing an example of a synchronization method by transmitting and receiving a synchronization request signal between base station devices according to this embodiment, where base station device 31 is in a synchronous state and base station device 32 is in an asynchronous state.

[0033] First, the control unit 20 provided in the base station device 32 in an asynchronous state transmits a synchronization request signal to the control unit 20 provided in the base station device 31 in a synchronous state.

[0034] Then, the control unit 20 of the base station device 31 that has received the synchronization request signal transmits a delay difference correction signal to which its own transmission time information has been added to the control unit 20 of the base station device 32 .

[0035] After receiving the delay difference correction signal, the control unit 20 of the base station device 32 returns the delay difference correction signal to the control unit 20 of the base station device 31 .

[0036] As a result, the control unit 20 of the base station device 31 calculates the data propagation delay difference based on the transmission and reception time of its own delay difference correction signal. Specifically, the data propagation delay difference is calculated as data propagation delay difference=(reception time of delay difference correction signal-transmission time of delay difference correction signal)÷2.

[0037] Next, the control unit 20 of the base station device 31 transmits to the control unit 20 of the base station device 32 time correction data obtained by adding the data propagation delay difference to its own time information.

[0038] The control unit 20 of the base station device 32 sets the time indicated by the received time correction data as its own time, thus completing the time synchronization process.

[0039] As described above, according to this embodiment, by using a digital wireless communication system in which an IP network is constructed, a synchronization request signal is transmitted and received between a base station device in a synchronized state and a base station device incapable of receiving GPS signals, thereby making it possible to establish synchronization with the base station device incapable of receiving GPS signals. This eliminates the need to transmit a reference signal from the base station device, and therefore eliminates the need to provide a dedicated line for this purpose.

[0040] <Second embodiment> A wireless communication system and a wireless communication method according to the present embodiment will be described. In the following description, components similar to those described in the above embodiment are illustrated with the same reference numerals, and detailed description thereof will be omitted as appropriate.

[0041] In the first embodiment, a case was shown in which a synchronization request signal was transmitted from a base station device in a synchronous state to a base station device in an asynchronous state. In this embodiment, however, a case will be described in which a synchronization request signal is transmitted from a base station device in an asynchronous state to a central device in a synchronous state.

[0042] <Configuration of wireless communication system> Fig. 5 is a diagram showing an example of the configuration of the central device 1 according to this embodiment. The central device 1 is provided in the digital radio communication system (train radio system) shown in Fig. 1. In Fig. 5, an IP network 2 is shown.

[0043] 5, the central device 1 includes an L3SW unit 80 (L3 switch unit), a control unit 90, a display unit 100, a server unit 110, a GPS receiving unit 120, and a GPS antenna .

[0044] The L3SW unit 80 is connected to the IP network 2. The GPS receiving unit 120 is connected to a GPS antenna .

[0045] The L3SW unit 80 performs routing processing of IP packets. The control unit 90 multiplexes signals to be transmitted to each base station device and separates signals received from each base station device. The control unit 90 also performs time synchronization processing.

[0046] The display unit 100 is realized by a display, a liquid crystal display device, a lamp, or the like, and displays information for checking the operating status of the train radio system. The server unit 110 is equipped with a train radio database and transmits information to devices outside the train radio system.

[0047] The GPS receiver 120 receives, as time information, a one-second pulse (1PPS) signal synchronized with Coordinated Universal Time (UTC) from a GPS satellite via the GPS antenna 130. Then, the GPS receiver 120 transmits the 1PPS signal to the control unit 90 as a timing signal for synchronization with the base station device.

[0048] <Operation of wireless communication system> 6 is a diagram showing an example of a synchronization method by transmitting and receiving a synchronization request signal between a central unit and a base station unit according to this embodiment, in which the base station unit 32 is in an asynchronous state with respect to the central unit 1.

[0049] First, the control unit 20 provided in the base station device 32 in an asynchronous state transmits a synchronization request signal to the control unit 90 provided in the central device 1 in a synchronous state.

[0050] Then, the control unit 90 of the central device 1 that has received the synchronization request signal transmits a delay difference correction signal to which its own transmission time information has been added to the control unit 20 of the base station device 32 .

[0051] After receiving the delay difference correction signal, the control unit 20 of the base station device 32 returns the delay difference correction signal to the control unit 90 of the central device 1 .

[0052] As a result, the control unit 90 of the central device 1 calculates the data propagation delay difference based on the transmission and reception times of its own delay difference correction signal. Specifically, the data propagation delay difference is calculated as data propagation delay difference=(reception time of delay difference correction signal-transmission time of delay difference correction signal)÷2.

[0053] Next, the control unit 90 of the central device 1 transmits to the control unit 20 of the base station device 32 time correction data obtained by adding the data propagation delay difference, which is the one-way delay difference, to its own time information.

[0054] The control unit 20 of the base station device 32 sets the time indicated by the received time correction data as its own time, thus completing the time synchronization process.

[0055] As described above, according to this embodiment, by transmitting and receiving a synchronization request signal between the central device 1 and a base station device that cannot receive GPS signals, it is possible to establish synchronization with the base station device that cannot receive GPS signals. This eliminates the need to transmit a reference signal from the base station device, and therefore eliminates the need to provide a dedicated line for this purpose.

[0056] In the first embodiment, synchronization is established between the respective base station devices, but in the present embodiment, synchronization is established between the central unit 1 and the respective base station devices. Therefore, the central unit 1 can centrally manage the data propagation delay differences with all the base station devices.

[0057] <Third embodiment> A wireless communication system and a wireless communication method according to the present embodiment will be described. In the following description, components similar to those described in the above embodiment are illustrated with the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0058] In the second embodiment, a synchronization request signal was transmitted from an asynchronous base station device to the central unit 1. In this embodiment, however, we will explain the case where synchronization is established by broadcasting a synchronization request signal from an asynchronous base station device to the central unit 1 and each of the base station devices that are in a synchronous state.

[0059] 7 is a diagram showing an example of a synchronization method by broadcasting a synchronization request signal according to this embodiment. Base station device 32 is one of the base station devices in an asynchronous state.

[0060] First, the control unit 20 provided in the base station device 32 in an asynchronous state broadcasts a synchronization request signal to the control unit 90 provided in the central device 1 in a synchronous state and to the control units 20 provided in each of the base station devices in a synchronous state.

[0061] The control unit 90 of the central unit 1 in the synchronized state adds a unique central unit ID and returns a delay difference correction signal to which its own transmission time information has been added to the control unit 20 of the base station device 32. The unique central unit ID is information for identifying the central unit 1.

[0062] Similarly, the control unit 20 of each synchronized base station device adds a unique base station device ID and returns a delay difference correction signal to which its own transmission time information is added to the control unit 20 of the base station device 32. The unique base station device ID is information for identifying the base station device 32.

[0063] After receiving the delay difference correction signals, the control unit 20 of the base station device 32 returns the delay difference correction signals to their respective transmission sources. Each transmission source is identified by a central device ID or a base station device ID that is added to each delay difference correction signal.

[0064] As a result, the control unit 90 of the central device 1 in a synchronized state and the control unit 20 of each base station device in a synchronized state calculate the data propagation delay difference based on the transmission and reception time of their own delay difference correction signals. Specifically, the data propagation delay difference is calculated as data propagation delay difference=(reception time of delay difference correction signal-transmission time of delay difference correction signal)÷2.

[0065] Next, the control unit 90 of the central device 1 in a synchronized state and the control unit 20 of each base station device in a synchronized state transmit time correction data to the control unit 20 of the base station device 32, which is obtained by adding the above-mentioned data propagation delay difference, which is the one-way delay difference, to its own time information.

[0066] The control unit 20 of the base station device 32 removes any abnormal data from the times indicated by the received time correction data, and then averages the normal data to determine its own time. In this way, the time synchronization process is completed.

[0067] Here, the abnormal data corresponds to time correction data whose deviation from other time correction data is greater than a predetermined threshold value (any value determined by a parameter). For example, if time correction data indicating 9:00:00 is being transmitted from the central device 1 and multiple base station devices, and time correction data indicating 9:10:00 is being transmitted from a certain base station device, the time correction data will be excluded as abnormal data if the threshold value is set to less than 10 minutes.

[0068] As described above, according to this embodiment, by broadcasting a synchronization request signal, it is possible to average out errors of a plurality of data propagation delay differences. Therefore, it is possible to perform time synchronization with high accuracy. Even if a base station device returns abnormal time correction data in response to a synchronization request signal, it is possible to maintain high reliability of time synchronization by averaging the respective time correction data by excluding the abnormal data.

[0069] <Hardware configuration of wireless communication system> 8 and 9 are diagrams each illustrating a schematic hardware configuration when the wireless communication system shown in FIG. 2, FIG. 3, and FIG. 5 is actually operated.

[0070] Note that the hardware configurations illustrated in Figures 8 and 9 may not match the numbers, etc., of the configurations illustrated in Figures 2, 3, and 5. This is because the configurations illustrated in Figures 2, 3, and 5 show conceptual units.

[0071] Therefore, at least the following cases can be envisaged: a configuration illustrated in Figures 2, 3, and 5 is composed of multiple hardware configurations illustrated in Figures 8 and 9; a configuration illustrated in Figures 2, 3, and 5 corresponds to a part of the hardware configuration illustrated in Figures 8 and 9; and further, multiple configurations illustrated in Figures 2, 3, and 5 are provided in a single hardware configuration illustrated in Figures 8 and 9.

[0072] In Fig. 8, a processing circuit 1102A that performs calculations and a storage device 1103 that can store information are shown as a hardware configuration for realizing the L3SW unit 10, L3SW unit 80, control unit 20, control unit 90, modem unit 30, RF unit 40, server unit 110, etc. in Fig. 2, Fig. 3, and Fig. 5. This configuration is similar in all of the above embodiments.

[0073] In Fig. 9, a processing circuit 1102B that performs calculations is shown as a hardware configuration for realizing the L3SW unit 10, the L3SW unit 80, the control unit 20, the control unit 90, the modem unit 30, the RF unit 40, the server unit 110, etc. in Fig. 2, Fig. 3, and Fig. 5. This configuration is similar in all of the above embodiments.

[0074] The server unit 110 is realized by a storage device 1103 or another storage device (not shown here).

[0075] The storage device 1103 may be, for example, a memory (recording medium) including a hard disk drive (i.e., HDD), random access memory (i.e., RAM), read only memory (i.e., ROM), flash memory, volatile or non-volatile semiconductor memory such as erasable programmable read only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD, or any recording medium to be used in the future.

[0076] The processing circuit 1102A may execute a program stored in the storage device 1103, an external CD-ROM, an external DVD-ROM, or an external flash memory, etc. That is, it may be, for example, a central processing unit (CPU), a microprocessor, a microcomputer, or a digital signal processor (DSP).

[0077] When the processing circuit 1102A executes a program stored in the storage device 1103, an external CD-ROM, an external DVD-ROM, or an external flash memory, the L3SW unit 10, the L3SW unit 80, the control unit 20, the control unit 90, the modulation / demodulation unit 30, the RF unit 40, and the server unit 110 are realized by software, firmware, or a combination of software and firmware, in which the program stored in the storage device 1103 is executed by the processing circuit 1102A. Note that the functions of the L3SW unit 10, the L3SW unit 80, the control unit 20, the control unit 90, the modulation / demodulation unit 30, the RF unit 40, and the server unit 110 may be realized, for example, by cooperation between a plurality of processing circuits.

[0078] The software and firmware may be written as a program and stored in the storage device 1103. In this case, the processing circuit 1102A realizes the above-mentioned functions by reading and executing the program stored in the storage device 1103. In other words, the storage device 1103 may store a program that, when executed by the processing circuit 1102A, results in the above-mentioned functions being realized.

[0079] The processing circuitry 1102B may also be dedicated hardware, i.e., a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof, for example.

[0080] When the processing circuit 1102B is a dedicated hardware, the L3SW unit 10, the L3SW unit 80, the control unit 20, the control unit 90, the modulation / demodulation unit 30, the RF unit 40, and the server unit 110 are realized by the operation of the processing circuit 1102B. Note that the functions of the L3SW unit 10, the L3SW unit 80, the control unit 20, the control unit 90, the modulation / demodulation unit 30, the RF unit 40, and the server unit 110 may be realized by separate circuits or by a single circuit.

[0081] In addition, the functions of the L3SW unit 10, the L3SW unit 80, the control unit 20, the control unit 90, the modulation / demodulation unit 30, the RF unit 40, and the server unit 110 may be partly realized in a processing circuit 1102A that executes a program stored in a memory device 1103, and partly realized in a processing circuit 1102B that is dedicated hardware.

[0082] <Effects of the above-described embodiments> Next, examples of effects produced by the above-described embodiments are shown. In the following description, the effects are described based on the specific configurations shown as examples in the above-described embodiments, but may be replaced with other specific configurations shown as examples in this specification as long as the same effects are produced. In other words, for convenience, only one of the corresponding specific configurations may be described as a representative below, but the representatively described specific configuration may be replaced with another corresponding specific configuration.

[0083] Furthermore, the replacement may be made across a number of embodiments, that is, configurations shown as examples in different embodiments may be combined to produce the same effect.

[0084] According to the embodiment described above, the wireless communication system is a wireless communication system constructed of an IP network including a central device 1 and a plurality of base station devices for synchronizing with the central device 1. The plurality of base station devices include a first base station device and a second base station device. Here, the first base station device corresponds to at least one of the base station device 31 or the base station device 3n, for example. The second base station device corresponds to at least one of the base station device 32 or the base station device 33, for example. The base station device 31 is in a synchronized state with the central device 1, and the base station device 32 is in an asynchronous state with the central device 1. When the base station device 32 transmits a synchronization request signal to the base station device 31, the base station device 31 that has received the synchronization request signal transmits a delay difference correction signal to which information on the transmission time of the base station device 31 has been added to the base station device 32. The base station device 32 that has received the delay difference correction signal returns the delay difference correction signal to the base station device 31. Then, the base station device 31 adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the base station device 31 to the time information of the base station device 31 to obtain time correction data, and transmits the time correction data to the base station device 32. The base station device 32 then sets the time indicated by the received time correction data as the time of the base station device 32.

[0085] According to the embodiment described above, the wireless communication system includes a processing circuit 1102A that executes a program, and a storage device 1103 that stores the program to be executed. The processing circuit 1102A executes the program to realize the following operations.

[0086] That is, when base station device 32 transmits a synchronization request signal to base station device 31, base station device 31, which has received the synchronization request signal, transmits a delay difference correction signal to which information of the transmission time of base station device 31 has been added to base station device 32. Then, base station device 32, which has received the delay difference correction signal, transmits the delay difference correction signal back to base station device 31. Then, base station device 31 adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at base station device 31 to the time information of base station device 31 to obtain time correction data, and transmits the time correction data to base station device 32. Then, base station device 32 sets the time indicated by the received time correction data as the time of base station device 32.

[0087] Furthermore, according to the embodiment described above, the wireless communication system includes the processing circuit 1102B, which is dedicated hardware. The processing circuit 1102B, which is dedicated hardware, performs the following operations.

[0088] That is, the processing circuit 1102B, which is dedicated hardware, causes the base station device 32 to transmit a synchronization request signal to the base station device 31, and causes the base station device 31, which has received the synchronization request signal, to transmit a delay difference correction signal to which information of the transmission time of the base station device 31 has been added, to the base station device 32. Then, the base station device 32, which has received the delay difference correction signal, returns the delay difference correction signal to the base station device 31. Then, the base station device 31 adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the base station device 31 to the time information of the base station device 31 to obtain time correction data, and transmits the time correction data to the base station device 32. Then, the base station device 32 is caused to set the time indicated by the received time correction data as the time of the base station device 32.

[0089] According to this configuration, a wireless communication system including the central device 1 and a plurality of base station devices is constructed using an IP network, so that data required for synchronization can be superimposed on IP packets and signal transmission lines required for synchronization can be shared. Therefore, when a wireless communication system constructed using an IP network is modified or a wireless communication system is formed by constructing a new IP network, it is possible to reduce the number of cables to be laid in the base station devices and establish synchronization with base station devices that are not able to receive GPS and are in an asynchronous state.

[0090] Furthermore, the same effect can be achieved even if other configurations, examples of which are shown in this specification, are appropriately added to the above configuration, i.e., even if other configurations in this specification that were not mentioned as the above configuration are appropriately added.

[0091] Furthermore, according to the embodiment described above, when the base station device 32 transmits a synchronization request signal to the central device 1, the central device 1, having received the synchronization request signal, transmits a delay difference correction signal to which information of the transmission time of the central device 1 has been added to the base station device 32. Then, the base station device 32, having received the delay difference correction signal, transmits the delay difference correction signal back to the central device 1. Then, the central device 1 adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the central device 1 to the time information of the central device 1 to obtain time correction data, and transmits the time correction data to the base station device 32. Then, the base station device 32 sets the time indicated by the received time correction data as the time of the base station device 32.

[0092] According to this configuration, a wireless communication system including the central device 1 and a plurality of base station devices is constructed using an IP network, so that data required for synchronization can be superimposed on IP packets, and signal transmission lines required for synchronization can be shared. Therefore, when a wireless communication system constructed using an IP network is modified or a wireless communication system is formed by constructing a new IP network, it is possible to reduce the number of cables to be laid in the base station device and establish synchronization with a base station device that is not in asynchronous state because it cannot receive GPS, while at the same time. In addition, since synchronization is established between the central device 1 and each base station device, the central device 1 can centrally manage the data propagation delay difference between all the base station devices.

[0093] Furthermore, according to the embodiment described above, when the base station device 32 broadcasts a synchronization request signal to the central device 1 and the base station device 31, the central device 1 that receives the synchronization request signal transmits a delay difference correction signal to which a unique central device ID and information on the transmission time of the central device 1 are added to the base station device 32, and the base station device 31 that receives the synchronization request signal transmits a delay difference correction signal to which a unique base station device ID and information on the transmission time of the base station device 31 are added to the base station device 32. Then, the base station device 32 that receives each delay difference correction signal returns a delay difference correction signal corresponding to the central device ID to the central device 1, and returns a delay difference correction signal corresponding to the base station device ID to the base station device 31. Then, the central device 1 adds a data propagation delay difference calculated based on the difference in the transmission and reception times of the delay difference correction signal at the central device 1 to the time information of the central device 1 to obtain time correction data, and transmits the time correction data to the base station device 32. Then, the base station device 31 adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the base station device 31 to the time information of the base station device 31 to obtain time correction data, and transmits the time correction data to the base station device 32. The base station device 32 then averages the times indicated by the received time correction data to obtain the time of the base station device 32. With this configuration, averaging processing can be performed on multiple time correction data, thereby improving the accuracy of time synchronization.

[0094] Furthermore, according to the embodiment described above, the base station device 32 removes time correction data that exceeds a predetermined threshold from each received time correction data, and averages the times indicated by the time correction data to obtain the time of the base station device 32. With this configuration, time correction data that is significantly out of sync with other time correction data can be removed for averaging processing, thereby improving the accuracy of time synchronization.

[0095] <Modifications of the above-described embodiments> In the embodiments described above, the dimensions, shapes, relative positional relationships, and implementation conditions of each component may be described, but these are merely examples in all aspects and are not limiting.

[0096] Therefore, countless modifications and equivalents not shown as examples are assumed within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component in at least one embodiment and combining it with a component in another embodiment.

[0097] Furthermore, unless a contradiction arises, when it is stated in the above-described embodiments that "one" component is provided, "one or more" of that component may be provided.

[0098] Furthermore, each component in the embodiments described above is a conceptual unit, and the scope of the technology disclosed in this specification includes cases where one component is made up of multiple structures, where one component corresponds to a part of a structure, and even where multiple components are provided in one structure.

[0099] Furthermore, each of the components in the embodiments described above includes structures having other structures or shapes as long as they perform the same function.

[0100] Furthermore, the descriptions in this specification are incorporated by reference for all purposes related to the present technology, and none of them are admitted to be prior art.

[0101] Furthermore, each of the components described in the above embodiments is envisioned as either software or firmware, or as corresponding hardware, and as software, is referred to as, for example, a "unit," and as hardware, is referred to as, for example, a "processing circuit" (circuitry).

[0102] Furthermore, the technology disclosed in this specification may also be implemented in a form in which each component is distributed across multiple devices, that is, in a form such as a system that is a combination of multiple devices.

[0103] Various aspects of the present disclosure are summarized below as appendices.

[0104] (Appendix 1) A wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the first base station device, the first base station device, which has received the synchronization request signal, transmits a delay difference correction signal to which information of a transmission time of the first base station device is added, to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the first base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain time correction data, and transmits the time correction data to the second base station device; The second base station device sets the time indicated by the received time correction data as the time of the second base station device. Wireless communication system.

[0105] (Appendix 2) A wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the central device, the central device, having received the synchronization request signal, transmits a delay difference correction signal to which information of the transmission time of the central device is added to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the central device; the central device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain time correction data, and transmits the time correction data to the second base station device; The second base station device sets the time indicated by the received time correction data as the time of the second base station device. Wireless communication system.

[0106] (Appendix 3) 3. A wireless communication system according to claim 1 or 2, When the second base station device broadcasts the synchronization request signal to the central device and the first base station device, the central device that has received the synchronization request signal transmits the delay difference correction signal to which a unique central device ID and information on the transmission time of the central device have been added to the second base station device, and the first base station device that has received the synchronization request signal transmits the delay difference correction signal to which a unique base station device ID and information on the transmission time of the first base station device have been added to the second base station device, the second base station device having received each of the delay difference correction signals returns the delay difference correction signal corresponding to the central device ID to the central device, and returns the delay difference correction signal corresponding to the base station device ID to the first base station device; the central device adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain the time correction data, and transmits the time correction data to the second base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain the time correction data, and transmits the time correction data to the second base station device; the second base station device averages the times indicated by the received time correction data to obtain the time of the second base station device; Wireless communication system.

[0107] (Appendix 4) 4. A wireless communication system according to claim 3, the second base station device removes, from each of the received time correction data, time correction data that exceeds a predetermined threshold, and averages the times indicated by the time correction data to determine the time of the second base station device; Wireless communication system.

[0108] (Appendix 5) A wireless communication method in a wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the first base station device, the first base station device, which has received the synchronization request signal, transmits a delay difference correction signal to which information of a transmission time of the first base station device is added, to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the first base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain time correction data, and transmits the time correction data to the second base station device; The second base station device sets the time indicated by the received time correction data as the time of the second base station device. A wireless communication method.

[0109] (Appendix 6) A wireless communication method in a wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the central device, the central device, having received the synchronization request signal, transmits a delay difference correction signal to which information of the transmission time of the central device is added to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the central device; the central device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain time correction data, and transmits the time correction data to the second base station device; The second base station device sets the time indicated by the received time correction data as the time of the second base station device. A wireless communication method.

[0110] (Appendix 7) 7. The wireless communication method according to claim 5, When the second base station device broadcasts the synchronization request signal to the central device and the first base station device, the central device that has received the synchronization request signal transmits the delay difference correction signal to which a unique central device ID and information on the transmission time of the central device have been added to the second base station device, and the first base station device that has received the synchronization request signal transmits the delay difference correction signal to which a unique base station device ID and information on the transmission time of the first base station device have been added to the second base station device, the second base station device having received each of the delay difference correction signals returns the delay difference correction signal corresponding to the central device ID to the central device, and returns the delay difference correction signal corresponding to the base station device ID to the first base station device; the central device adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain the time correction data, and transmits the time correction data to the second base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain the time correction data, and transmits the time correction data to the second base station device; the second base station device averages the times indicated by the received time correction data to obtain the time of the second base station device; A wireless communication method. [Explanation of symbols]

[0111] 1 central unit, 2 IP network, 3 base station equipment, 3A base station equipment, 3n base station equipment, 10 L3SW unit, 20 control unit, 30 modulation / demodulation unit, 31 base station equipment, 32 base station equipment, 33 base station equipment, 40 RF unit, 50 GPS receiving unit, 60 GPS antenna, 80 L3SW unit, 90 control unit, 100 display unit, 110 server unit, 120 GPS receiving unit, 130 GPS antenna, 1102A processing circuit, 1102B processing circuit, 1103 storage device.

Claims

1. A wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the first base station device, the first base station device, which has received the synchronization request signal, transmits a delay difference correction signal to which information of a transmission time of the first base station device is added, to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the first base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain time correction data, and transmits the time correction data to the second base station device; the second base station device sets the time indicated by the received time correction data as the time of the second base station device; Wireless communication system.

2. A wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the central device, the central device, having received the synchronization request signal, transmits a delay difference correction signal to which information of the transmission time of the central device is added to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the central device; the central device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain time correction data, and transmits the time correction data to the second base station device; the second base station device sets the time indicated by the received time correction data as the time of the second base station device; Wireless communication system.

3. 3. A wireless communication system according to claim 1, When the second base station device broadcasts the synchronization request signal to the central device and the first base station device, the central device that has received the synchronization request signal transmits the delay difference correction signal to which a unique central device ID and information on the transmission time of the central device have been added to the second base station device, and the first base station device that has received the synchronization request signal transmits the delay difference correction signal to which a unique base station device ID and information on the transmission time of the first base station device have been added to the second base station device, the second base station device having received each of the delay difference correction signals returns the delay difference correction signal corresponding to the central device ID to the central device, and returns the delay difference correction signal corresponding to the base station device ID to the first base station device; the central device adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain the time correction data, and transmits the time correction data to the second base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain the time correction data, and transmits the time correction data to the second base station device; the second base station device averages the times indicated by the received time correction data to obtain the time of the second base station device; Wireless communication system.

4. A wireless communication system according to claim 3, the second base station device removes, from the received time correction data, time correction data that exceeds a predetermined threshold, and averages the times indicated by the time correction data to obtain the time of the second base station device; Wireless communication system.

5. A wireless communication method in a wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the first base station device, the first base station device, which has received the synchronization request signal, transmits a delay difference correction signal to which information of a transmission time of the first base station device is added, to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the first base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain time correction data, and transmits the time correction data to the second base station device; the second base station device sets the time indicated by the received time correction data as the time of the second base station device; A wireless communication method.

6. A wireless communication method in a wireless communication system constructed using an IP network, the wireless communication system including a central device and a plurality of base station devices for synchronizing with the central device, the plurality of base station devices include a first base station device and a second base station device; the first base station device is in a synchronous state with the central device, and the second base station device is in an asynchronous state with the central device; When the second base station device transmits a synchronization request signal to the central device, the central device, having received the synchronization request signal, transmits a delay difference correction signal to which information of the transmission time of the central device is added to the second base station device; the second base station device having received the delay difference correction signal returns the delay difference correction signal to the central device; the central device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain time correction data, and transmits the time correction data to the second base station device; the second base station device sets the time indicated by the received time correction data as the time of the second base station device; A wireless communication method.

7. 7. The wireless communication method according to claim 5, When the second base station device broadcasts the synchronization request signal to the central device and the first base station device, the central device that has received the synchronization request signal transmits the delay difference correction signal to which a unique central device ID and information on the transmission time of the central device have been added to the second base station device, and the first base station device that has received the synchronization request signal transmits the delay difference correction signal to which a unique base station device ID and information on the transmission time of the first base station device have been added to the second base station device, the second base station device having received each of the delay difference correction signals returns the delay difference correction signal corresponding to the central device ID to the central device, and returns the delay difference correction signal corresponding to the base station device ID to the first base station device; the central device adds the data propagation delay difference calculated based on the difference between the transmission and reception times of the delay difference correction signal at the central device to the time information of the central device to obtain the time correction data, and transmits the time correction data to the second base station device; the first base station device adds a data propagation delay difference calculated based on a difference between the transmission and reception times of the delay difference correction signal at the first base station device to time information of the first base station device to obtain the time correction data, and transmits the time correction data to the second base station device; the second base station device averages the times indicated by the received time correction data to obtain the time of the second base station device; A wireless communication method.

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