Wireless communication system and inter-base station synchronization method

Abstract

To provide a wireless communication system and an inter-base station synchronization method that can achieve synchronization of clocks and transmission timing in the system at low cost while improving reliability and versatility.SOLUTION: In a wireless communication system and an inter-base station synchronization method, a telecom grandmaster 16 generates a time synchronization packet including a grand clock and time information from a signal input from a GPS antenna 15; time synchronization packet sending means 17 provided on a wired line connecting a line control device 13 and a plurality of base station devices 14 distributes a higher-level clock synchronized with the grand clock and time synchronization packets to the line control device 13 and the plurality of base stations 14; and T-TSC reference signal generating means 20 provided in the line control device 13 and the plurality of base station devices 14 generates a reference clock and reference timing for its own device from the higher-level clock and the time synchronization packets from the time synchronization packet sending means 17.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wireless communication system, and more particularly to a wireless communication system and an inter-base station synchronization method that can achieve synchronization of clocks and transmission timing in the system at low cost while improving reliability and versatility. [Background technology]

[0002] [Prior Art] There are privately-operated wireless communication systems that are equipped with an operation console, a line control device, and multiple base stations and are used for business wireless communication, disaster prevention wireless communication, etc. In such wireless communication systems, synchronization between base stations is important.

[0003] [Outline of wireless communication system: Figure 8] An example of the configuration of a wireless communication system will be described with reference to Fig. 8. Fig. 8 is an explanatory diagram showing a schematic configuration of a wireless communication system. As shown in FIG. 8, the wireless communication system includes an operator console 1 for transmitting and receiving calls, a line control device 2 for line control, a plurality of base station devices 3 (here, base station device 3-1 and base station device 3-2) which are base stations for wireless communication, and a network line 4 connecting the plurality of base station devices 3, and realizes calls between a mobile station 6 (here, mobile station 6-1 and mobile station 6-2) and the operator console 1. Here, the base station device 3 performs wireless communication with the mobile station 6 using the same radio frequency f0.

[0004] Also, in the example of FIG. 8, mobile station 6-1 (mobile station #1) is approximately equidistant from base station device 3-1 (base station device #1) and base station device 3-2 (base station device #2), and mobile station 6-2 (mobile station #2) is close to base station device 3-2 and far from base station device 3-1. Therefore, at mobile station #2, the received strength of radio wave (a) from base station device #2 is strong, and the received strength of radio wave (b) from base station device #1 is weak. On the other hand, at mobile station #1, there is little difference in the reception strength between radio wave (a) from base station apparatus #1 and radio wave (b) from base station apparatus #2, and same-wave interference occurs.

[0005] [Overview of base station synchronization: Figure 9] An overview of inter-base station synchronization will be described with reference to Fig. 9. Fig. 9 is an explanatory diagram showing an overview of inter-base station synchronization. Fig. 9 shows received spectrum waveforms and time axis waveforms at mobile station #1 and mobile station #2 in the wireless communication system in the state of Fig. 8. In the wireless communication system in the state shown in Figure 8, if the signal from base station #2 is the desired wave (a) and the signal from base station #1 is the interfering wave (b), as shown in the received spectrum waveform in (A), the D / U (Desired / Undesired: desired wave / interfering wave) ratio is small at mobile station #1 and large at mobile station #2.

[0006] When viewed on the time axis waveform, even if the transmission timing differs between base stations as shown in (B), mobile station #2 is able to receive the desired signal (a) because there is a large difference in the amplitude of the received signal, and normal communication can be carried out.

[0007] However, at mobile station #1, the difference in transmission timing between base stations and the spatial propagation delay are added together, causing a difference of one symbol or more, and the desired wave cannot be received normally, resulting in an out-of-service condition or poor communication.

[0008] On the other hand, as shown in (C), when the transmission timing is the same between the base stations, the only discrepancy is the spatial propagation delay. The propagation delay is 0.3 μs for a distance difference of 100 m, which is a small difference compared to the 208 μs for one symbol, so mobile station #1 can receive the signal and communicate normally. Thus, in a system in which base station devices use the same frequency, it is important to synchronize the transmission timing between the base stations.

[0009] Conventional private wireless communication systems include a first conventional wireless communication system in which the line control device and base station are equipped with a GPS (Global Positioning System) antenna and a GPS receiver, and a second conventional wireless communication system in which a general-purpose network is used to synchronize between base stations using packets defined by the user.

[0010] [Conventional wireless communication system: Fig. 10] The first conventional wireless communication system will be described with reference to Fig. 10. Fig. 10 is a schematic diagram of the first conventional wireless communication system. As shown in FIG. 10, the first conventional wireless communication system includes a communication console 500, a data transmission means 501, a line control device 510, a plurality of base station devices 540 (540-1, ... 540-n), a plurality of mobile stations 550 (550-1, ... 550-n), and network lines 520 (520-1, ... 520-n).

[0011] The communication console 500 transmits and receives calls to and from a mobile station 550 . The data transmission means 501 transmits and receives digital data to and from the mobile station 550 . 10, the flow of voice data and digital data during downlink communication from the communication console 500 and data transmission means 501 to the mobile station 550 is shown.

[0012] The line control device 510 performs line control. The network line 520 is a network of Ethernet lines that connects the line controller 510 and the base station device 540 . The base station device 540 connects to the network line 520 and also connects to the mobile station 550 via a wireless section. The mobile station 550 performs wireless communication with the base station device 540 , transmits and receives voice to and from the communication console 500 , and transmits and receives digital data to and from the data transmission means 501 .

[0013] Furthermore, the line control device 510 includes a GPS antenna 511, a GPS receiver 512, a reference timing generating means 513, a control unit 514, a voice encoding unit 515, and a plurality of base station equipment interfaces 516 (base station equipment interfaces 516-1, ... 516-n).

[0014] The GPS antenna 511 receives radio waves from a GPS satellite. The GPS receiver 512 generates a clock signal, a timing signal, and time information from the signal received by the GPS antenna 511 . The reference timing generating means 513 generates the reference timing of the system based on the output signal from the GPS receiver, and outputs the reference clock and the reference timing.

[0015] The control unit 514 controls the line control device 510, and performs processing in synchronization with the system timing by referring to the reference timing. The voice encoding unit 515 is connected to the communication console 500, and performs encoding of transmitted voice and decoding of received voice. The base station device interface 516 is an interface that connects the voice encoding unit 515 and the base station device 540 .

[0016] The base station device 540 also includes a GPS antenna 541 , a GPS receiver 542 , reference timing generating means 543 , a control unit 544 , a radio unit 546 , and an antenna 547 . The GPS antenna 541 , the GPS receiver 542 , and the reference timing generating means 543 perform the same operations as those provided in the line control device 510 . The control unit 544 refers to the reference timing from the reference timing generation means 543 and controls the base station device 540 in accordance with the system timing.

[0017] The radio section 546 generates data for the radio section synchronized with the system timing based on the reference clock and reference timing from the system timing generation means 543 and the communication data from the control section 546 , and outputs the data to the antenna 547 . During uplink communication, the radio unit 546 extracts voice data or transmission data from the data in the radio section from the mobile station 550 and outputs it to the control unit 544 . Antenna 547 radiates the signal from wireless unit 546 into the air, and outputs the radio waves picked up in the air to wireless unit 546 .

[0018] In other words, in the first conventional wireless communication system, the line control device 510 and each of the multiple base station devices 540 are equipped with a GPS antenna, a GPS receiver, and a reference timing generating means, and each device generates a reference timing and a reference clock based on a GPS signal, thereby achieving synchronization between the base stations.

[0019] [Conventional second wireless communication system: Figure 11] Next, a conventional second wireless communication system will be described with reference to Fig. 11. Fig. 11 is a schematic configuration diagram of the conventional second wireless communication system. Note that, for the conventional second wireless communication system, differences from the conventional first wireless communication system will be described, and descriptions of the same parts as the conventional first wireless communication system will be omitted.

[0020] As shown in FIG. 11, the second conventional wireless communication system includes a communication console 600, a data transmission means 601, a line control device 610, a plurality of base station devices 640 (base station devices 640-1, ... 640-n), and a plurality of mobile stations 650 (mobile stations 650-1, ... 650-n).

[0021] Here, base station device #1 (640-1) is connected to the line control device 610 via an Ethernet line. In addition, base station device #2 (640-2) is connected to base station device #1 (640-1) via a wired line, and so on in a similar manner to base station device #N (640-n) in a sequential cascade connection.

[0022] In a second conventional wireless communication system, a line control device 610 generates a reference clock for the system and outputs a timing packet to a subordinate base station device 640, and the base station device 640 generates a reference clock and reference timing based on the timing packet received.

[0023] The line control device 610 comprises a high precision oscillator 611 , a reference timing generating means 612 , a control unit 613 , a timing packet generating means 615 , a voice encoding unit 614 , a base station equipment interface 616 , and a packet switch 617 .

[0024] The high-precision oscillator 611 generates a high-precision clock that serves as the reference clock for the system. The reference timing generating means 612 generates a reference timing from a reference clock, and outputs the reference clock and the reference timing. The timing packet generating means 615 outputs a timing packet synchronized with the system based on the reference clock and reference timing, and packet transmission information indicating the state during packet transmission. The packet switch 617 switches between packets of voice data or transmission data from the base station equipment interface 616 and timing packets from the timing packet generating means 615 and outputs them.

[0025] The base station device # 1 ( 640 - 1 ) includes a timing packet detection unit 641 , a HUB 642 , a control unit 643 , a radio unit 644 , an antenna 645 , a timing packet generation unit 646 , and a packet switch 647 .

[0026] The timing packet detection means 641 detects a timing packet output from the line controller 610 and generates a reference timing and a reference clock. The reference timing and the reference clock are synchronized with the reference timing and the reference clock of the line controller 610.

[0027] The timing packet generating means 646 generates a timing packet synchronized with the system based on the reference clock and reference timing, and outputs the status during packet transmission. The HUB 642 refers to the MAC address of the packet from the line controller 610 and switches the output destination of the packet. The packet switch 647 switches between a packet addressed to the downstream base station device 640 from the HUB 642 and a timing packet from the timing generation means 646 , and outputs the packet to the downstream base station device 640 .

[0028] Then, base station device #2 (640-2) receives a timing packet from base station device #1, generates a reference clock and reference timing synchronized with the system in a timing packet detection means, and further generates a timing packet synchronized with the system in a timing packet generation means, and outputs it to downstream base station device #3 via packet switch 647. Similarly, inter-base station synchronization is achieved in a plurality of cascaded base station devices 640 thereafter. Here, the timing packet is not based on a general-purpose standard but on a format uniquely defined by the user.

[0029] [Related Technology] In addition, a related prior art is JP 2022-144618 A "Wireless Communication System" (Patent Document 1). Patent Document 1 discloses a wireless communication system in which multiple base stations achieve inter-base station synchronization using GPS signals and network signals, thereby improving voice quality in areas where the service areas of multiple base stations overlap. [Prior art documents] [Patent documents]

[0030] [Patent Document 1] JP 2022-144618 A Summary of the Invention [Problem to be solved by the invention]

[0031] However, in the first conventional wireless communication system, a GPS antenna and a GPS receiver were installed in each of the line control device and multiple base station devices, which resulted in high costs and reduced reliability due to the risk of damage to the GPS antenna and receiver caused by lightning strikes.

[0032] In addition, in the conventional second wireless communication system, the packets (timing packets) defined by the user are in a format different from a general-purpose network. Therefore, when a general-purpose network is used, the timing packets may be discarded, and the base station may not be able to regenerate the reference clock from the line control device, making it impossible to achieve frequency synchronization between base stations.

[0033] Incidentally, Patent Document 1 does not describe a configuration in which, in a system having a line control device and multiple base station devices, the line control device and the base station devices are provided with a reference signal generating means for generating their own reference clock and reference timing based on a time synchronization packet from a time synchronization packet sending means synchronized with a grandmaster.

[0034] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a wireless communication system and an inter-base station synchronization method that can achieve synchronization of a reference clock and transmission timing in the system at low cost with improved reliability and versatility. [Means for solving the problem]

[0035] The present invention, which aims to solve the problems of the above-mentioned conventional examples, is a wireless communication system comprising a plurality of base station devices wirelessly connected to mobile stations and a line control device connected to the plurality of base station devices by wired lines, and is characterized in that it comprises a telecom grand master that generates a grand clock and a time synchronization packet from a signal input from a GPS antenna, and a time synchronization packet sending means that is provided on the wired line connecting the line control device and the plurality of base station devices, regenerates a clock in synchronization with the grand clock from the telecom grand master, and distributes the regenerated clock and time synchronization packet to the line control device and the plurality of base stations, and the line control device and the plurality of base station devices are each provided with a reference timing generation means that generates a reference clock and reference timing for the device itself from the clock and time synchronization packet from the time synchronization packet sending means.

[0036] In addition, the present invention is characterized in that, in the above-mentioned wireless communication system, a plurality of time synchronization packet sending means are connected in series to a wired line connecting a line control device and a plurality of base station devices, a telecom grand master is connected to the time synchronization packet sending means closest to the line control device, and the telecom grand master is not connected to any time synchronization packet sending means other than the closest time synchronization packet sending means, and the other time synchronization packet sending means regenerate a clock in synchronization with a higher-level clock from a higher-level time synchronization packet sending means and transmit the regenerated clock and time synchronization packets.

[0037] Furthermore, in the above wireless communication system, the present invention is characterized in that the time synchronization packet sending means is a master device, and the reference timing generating means of the line control device and the base station device are slave devices, and the reference timing generating means of the slave device has a time counter, generates a reference clock based on a higher-level clock from the master device, obtains first time information of a timestamp from a synchronization message included in the time synchronization packet transmitted from the master device, obtains the reception time of the synchronization message as second time information from the time counter, obtains the transmission time of a delay request message to the master device as third time information, obtains fourth time information of the timestamp from a delay response message included in the time synchronization packet transmitted from the master device, calculates an offset time using the first to fourth time information, and adjusts the count value from the time counter to generate reference timing of a reference radio frame.

[0038] The present invention also provides an inter-base station synchronization method in a wireless communication system having a plurality of base station devices wirelessly connected to a mobile station and a line control device connected to the plurality of base station devices by wires, characterized in that a telecom grandmaster generates a grand clock and a time synchronization packet from a signal input from a GPS antenna, a time synchronization packet sending means provided in a wired line connecting the line control device and the plurality of base station devices recovers a clock from the grand clock from the telecom grandmaster and distributes the recovered clock and time synchronization packet to the line control device and the plurality of base stations, and a reference timing generation means provided in the line control device and the plurality of base stations generates a reference clock and reference timing of its own device from the higher-level clock and time synchronization packet from the time synchronization packet sending means. Effect of the Invention

[0039] According to the present invention, a wireless communication system is provided that includes a plurality of base station devices that are wirelessly connected to a mobile station, and a line control device that is connected to the plurality of base station devices by a wired line, and includes a telecom grand master that generates a grand clock and a time synchronization packet from a signal input from a GPS antenna, and a time synchronization packet sending means that is provided on the wired line connecting the line control device and the plurality of base station devices, and that regenerates a clock in synchronization with the grand clock from the telecom grand master and distributes the regenerated clock and time synchronization packet to the line control device and the plurality of base stations, and the line control device and the plurality of base stations are provided with a reference timing generating means that generates a reference clock and reference timing of each of the plurality of base station devices from the clock and time synchronization packet from the time synchronization packet sending means. Therefore, the reference clock in the plurality of base station devices can be synchronized with the telecom grand master, and the reference timing between the base stations can be matched, and there is an effect that each base station device does not need a GPS antenna or a GPS receiver, thereby reducing costs and improving reliability, and by using the PTP protocol, the system can be applied to a general-purpose network and improves versatility.

[0040] Also, according to the present invention, there is provided an inter-base station synchronization method in a wireless communication system including a plurality of base station devices wirelessly connected to a mobile station and a line control device connected to the plurality of base station devices by wires, in which the telecom grandmaster generates a grand clock and a time synchronization packet from a signal input from a GPS antenna, a time synchronization packet sending means provided in a wired line connecting the line control device and the plurality of base station devices regenerates a clock from the grand clock from the telecom grandmaster and distributes the regenerated clock and time synchronization packet to the line control device and the plurality of base stations, and a reference timing generating means provided in the line control device and the plurality of base stations generates a reference clock and reference timing of the respective devices from the higher-level clock and time synchronization packet from the time synchronization packet sending means. Therefore, the reference clocks of the plurality of base station devices can be synchronized with the telecom grandmaster to match the reference timing between the base stations, and each base station device does not require a GPS antenna or a GPS receiver, thereby reducing costs and improving reliability, and by using the PTP protocol, the method can be applied to a general-purpose network and improves versatility. [Brief description of the drawings]

[0041] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of the present system. [Diagram 2] FIG. 2 is a diagram illustrating the configuration of a line control device. [Diagram 3] FIG. 2 is a diagram illustrating the configuration of a base station device. [Figure 4] FIG. 1 is a circuit diagram of a reference signal generating means. [Diagram 5] FIG. 2 is a circuit diagram of the reference signal generating means. [Figure 6] FIG. 1 is a diagram showing a sequence using PTP. [Figure 7] FIG. 13 illustrates a time synchronization message. [Figure 8] FIG. 1 is a schematic diagram illustrating a wireless communication system. [Figure 9] FIG. 1 is an explanatory diagram showing an overview of inter-base station synchronization. [Figure 10]FIG. 1 is a schematic configuration diagram of a first conventional wireless communication system. [Figure 11] FIG. 11 is a schematic configuration diagram of a second conventional wireless communication system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. [Outline of the embodiment] A wireless communication system (this system) according to an embodiment of the present invention is a wireless communication system including a plurality of base station devices and a line control device connected to the base station devices by a wired line, and includes a telecom grand master that generates a time synchronization packet including a grand clock and time information from a signal input from a GPS antenna, and a time synchronization packet sending means that is provided on the wired line connecting the line control device and the plurality of base station devices and synchronizes internal time information with the telecom grand master, regenerates a clock that synchronizes the internal clock with the grand clock, and distributes the regenerated clock and time synchronization packet to the line control device and the plurality of base stations, and the line control device and the plurality of base stations are provided with a reference signal generating means that generates a reference clock and reference timing of the respective devices from the clock and time synchronization packet from the time synchronization packet sending means, and the reference clock and reference timing are synchronized in the plurality of base station devices, eliminating the need for a GPS antenna or GPS receiver in each base station device, reducing costs and improving reliability, and by using the PTP protocol, the system can be applied to general-purpose networks. Moreover, the inter-base station synchronization method according to the embodiment of the present invention is a method for synchronizing a reference clock and a reference timing among a plurality of base station devices in this system.

[0043] [Schematic configuration of this system: Figure 1] This system will be described with reference to Figure 1. Figure 1 is a schematic diagram of the system. As shown in FIG. 1, this system realizes calls and data transmission between a communication console 11 and a data transmission means 12 and a plurality of mobile stations 18, as in the conventional system, but the configuration and operation for realizing synchronization between base stations are different from the conventional system. Specifically, this system uses PTP (Percision Time Protocol) (G8275.1) to synchronize the system's reference clock, time, and reference timing.

[0044] In PTP, devices to be synchronized are in a master-slave relationship, and the clock frequencies and times of the master and slave are synchronized by exchanging time synchronization packets, which are PTP packets, between the devices, as described below.

[0045] As shown in FIG. 1, the system includes a communication console 11, a data transmission means 12, a line control device 13, and a plurality of base station devices 14 (14-1, 14-2, ... 14-n), as well as a GPS antenna 15, a Telecom Grandmaster (T-GM) 16, and a plurality of time synchronization packet sending means (T-BC: Telecom Boundary Clock) 17 (17-01, 17-11, 17-12, ... 17-1n, 17-21, 17-22, ... 17-2n).

[0046] Furthermore, each of the line control device 13 and the base station device 14 includes a T-TSC (Telecom Time Slave Clock) reference signal generating means 20 . The communication console 11, data transmission means 12, GPS antenna 15, and mobile station 18 are the same as in the conventional system. Here, the T-GM 16 is the master, the time synchronization packet sending means 17 operates as a slave to the upstream device and as a master to the downstream device, and the T-TSC reference signal generating means 20 is the slave.

[0047] The T-GM16 is equipped with a GPS receiver and generates a grand clock that serves as the system's reference clock based on the GPS signal input from the connected GPS antenna 15. It also generates a time synchronization packet including time information (transmission time) synchronized with the GPS received signal and distributes it to the connected time synchronization packet sending means 17-01. A time synchronization packet is a PTP protocol packet that contains information such as a timestamp required to synchronize time information between devices in the system. This system uses four types of time synchronization packets.

[0048] The time synchronization packet sending means (T-BC) 17 is a PTP boundary clock that operates as a slave to upstream devices and synchronizes the clock and time of its own device with the T-GM 16 or the upstream time synchronization packet sending means 17 based on the time synchronization packet received from the T-GM 16 or the upstream time synchronization packet sending means 17.

[0049] The time synchronization packet sending means 17 also operates as a master for downstream devices, and outputs a clock and time synchronization packets regenerated based on information received from an upstream device to the downstream (slave) time synchronization packet sending means 17 or T-TSC reference signal generating means 20. The clock output to the slave is synchronized with the grand clock from the T-GM 16, and is referred to as the upper clock in the claims.

[0050] Furthermore, when the time synchronization packet sending means 17 receives a time synchronization packet from a downstream time synchronization packet sending means 17 or the T-TSC reference signal generating means 20, it transmits a predetermined time synchronization packet in response thereto. The time synchronization packets and timestamps, as well as the sequence between the master and slave, will be described later. The time synchronization packet sending means 17-01 connected to the T-GM 16 is connected to the downstream time synchronization packet sending means 17-11, 17-21 and the line control device 13 via Ethernet.

[0051] The T-TSC reference signal generating means 20 operates as a slave and synchronizes the reference clock and time within its own device with the upstream device (time synchronization packet sending means 17) based on the higher-level clock and time synchronization packet received from the connected time synchronization packet sending means 17, thereby generating a reference timing signal. In this manner, in this system, synchronization of the reference clock and reference timing generated by the T-TSC reference signal generating means 20 of the line control device 13 and the multiple base station devices 14 is realized using PTP. The configuration and operation of the T-TSC reference signal generating means 20 will be described later.

[0052] In this system, it is not necessary to install GPS antennas 15 and GPS receivers in the multiple base station devices 14, and this makes it possible to reduce equipment costs and the occurrence of breakdowns due to lightning strikes and the like, while improving the reliability of the system.

[0053] In addition, by applying the standardized PTP protocol, the existing network switch can be replaced with a time synchronization packet sending means 17, and synchronization between base stations can be realized by utilizing pre-installed network lines, thereby improving versatility.

[0054] [System operation overview: Figure 1] The operation of this system will be outlined with reference to FIG. As shown in FIG. 1, the T-GM 16 receives a signal from the GPS antenna 15 with a GPS receiver, generates a time synchronization packet including a reference clock (grand clock) and time information, and sends it to a time synchronization packet sending means 17-01.

[0055] When the time synchronization packet sending means 17-01 receives the grand clock and a time synchronization packet at the slave port, it regenerates a higher-level clock that is synchronized with the grand clock, and synchronizes its own internal time with the T-GM16 by reflecting the received time synchronization packet and preset delay information. Then, a time synchronization packet including the higher-level clock and its own transmission time information is sent from the master port to the T-TSC reference signal generating means 20 of the line control device 13 and the downstream time synchronization packet sending means 17-11 and time synchronization packet sending means 17-21.

[0056] The downstream time synchronization packet sending means 17 that receives the time synchronization packet synchronizes its internal reference clock and time with the upstream device to create an upper-level clock, generates a time synchronization packet including transmission time information, and sends it downstream together with the upper-level clock. Then, when the T-TSC reference signal generating means 20 of the line control device 13 and the base station device 14 receives a clock and a time synchronization packet from the time synchronization packet sending means 17, it synchronizes the internal reference clock and time, sends and receives a specified time synchronization packet with the time synchronization packet sending means 17, and generates an internal reference timing based on the multiple timestamps obtained.

[0057] In this way, the reference clocks of the time synchronization packet sending means 17 in the system are all synchronized with the grand clock of the T-GM 16, so the reference clocks and time generated by the line control device 13 and the multiple base station devices 14 with the time synchronization packet sending means 17 as the master are all synchronized with GPS, and the reference timing of the multiple base station devices 14 is consistent. In other words, the reference clock generated by each base station device 14 is the same as the reference clock in the system.

[0058] [Circuit control device configuration: Figure 2] Next, a specific configuration of the line control device 13 shown in Fig. 1 will be described with reference to Fig. 2. Fig. 2 is a configuration diagram of the line control device. As shown in FIG. 2, the line controller 13 includes a T-TSC reference signal generating means 20, a control unit 112, a voice encoding unit 113, and a plurality of base station interface units 114 (114-1, . . . 114-n).

[0059] As described above, the T-TSC reference signal generating means 20 generates a reference clock and a reference timing in the line control device 13 based on the time synchronization packet input from the time synchronization packet sending means 17-01, and outputs them to the control unit 112. The configuration and operation of the T-TSC reference signal generating means 20 will be described later.

[0060] The control unit 112 controls the entire device based on the reference clock and reference timing generated by the T-TSC reference signal generating means 20 . The voice coding unit 113 codes the voice signal input from the communication console 11, and also decodes the coded data input from the base station device interface 114, and outputs the voice signal to the communication console 11. Note that in the figure, the voice data and transmission data are shown only for downlink communication from the communication console 11 to the mobile station 18. The base station interface 114 is a connection unit that realizes communication of voice encoded data and transmission data with the base station 14 using Ethernet.

[0061] In this way, the line control device 13 of this system performs various operations such as transmission / reception and line control in accordance with the reference clock and reference timing generated by the T-TSC reference signal generating means 111 based on the time synchronization packet from the time synchronization packet sending means 17.

[0062] [Base station equipment configuration: Figure 3] Next, a specific configuration of the base station device 14 will be described with reference to Fig. 3. Fig. 3 is a configuration diagram of a base station device. Note that, although the base station device #1 (14-1) will be described here as an example, the other base station devices 14 also have the same configuration. As shown in FIG. 3, the base station device 14 includes a T-TSC reference signal generating means 20, a control unit 142, and a radio unit 143. The T-TSC reference signal generating means 20 receives a time synchronization packet from the connected time synchronization packet sending means 17-1n and generates a reference clock and reference timing within the device. The configuration and operation of the T-TSC reference signal generating means 20 will be described later.

[0063] The control unit 142 controls the base station device 14 based on the reference clock and reference timing generated by the T-TSC reference signal generating means 20, outputs the voice data and transmission data from the time synchronization packet sending means 17-1n to the wireless unit 143, and sends the voice data or transmission data from the wireless unit 143 to the time synchronization packet sending means 17-1n. Note that in the figure, the voice data and transmission data are shown only during downlink communication from the communication console 100 to the mobile station 18.

[0064] The radio section 143 performs transmission and reception operations in the same manner as in the conventional manner, based on the reference clock and reference timing generated by the T-TSC reference signal generating means 20 . The antenna 144 is conventional.

[0065] [Configuration of T-TSC reference signal generation means: Figures 4 and 5] Next, a specific configuration of the T-TSC reference signal generating means 20 provided in the line control device 13 and the base station device 14 will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a circuit diagram (1) of the reference signal generating means, and Fig. 5 is a circuit diagram (2) of the reference signal generating means. The T-TSC reference signal generating means 20 has a configuration combining the configurations of FIG. 4 and FIG. 5, and FIG. 4 and FIG. 5 are connected at the portions A to F shown in the figures.

[0066] As shown in Figures 4 and 5, the T-TSC reference signal generating means 20 includes an Ethernet PHY 201, a PLL (Phase Locked Loop) 202, a link status detecting means 203, an oscillator 204, a Sync Message receiving means 205, a time counter 206, a counter load signal generating means 207, a packet sending timing generating means 208, a Delay_Req Message transmitting means 209, a Delay_Resp Message receiving means 210, an Announce Message receiving means 211, a time holding means 212, a first subtractor 213, a second subtractor 214, a third subtractor 215, an adder 216, a UTC time converting means 217, and an SFN generating means 218.

[0067] The Ethernet PHY 201 is connected to a time synchronization packet sending means (T-BC) 17 at the physical layer. The PLL 202 receives a recovery clock recovered from the received data from the Ethernet PHY 201 and generates a reference clock for the device. The link state detection means 203 detects the link state (connection state) with the time synchronization packet transmission means 17, which is the master device, and outputs link establishment information. The oscillator 204 generates an operating clock for driving the Ethernet PHY 201 .

[0068] The Sync Message receiving means 205 receives the "Sync_Message" of the time synchronization packet from the received data output from the Ethernet PHY 201, and acquires the time stamp information (T1) of the master device. Furthermore, upon receiving the "Sync_Message", the Sync Message receiving means 205 outputs the reception timing. The time synchronization packet and the time stamp information will be described later.

[0069] The time counter 206 is a self-running time counter that generates time information for its own device. Here, the time counter 206 receives the time stamp information (T1) of the master device, and based on a counter load signal from the counter load signal generating means 207, outputs either the counted time information or the time stamp information as a counter output (CT).

[0070] The counter load signal generating means 207 generates a load signal (pull-in signal) for the time counter based on the link establishment information output from the link status detecting means 203, the counter output (CT) from the time counter 206, and the time stamp information (T1) of the master device from the Sync Message receiving means 205. The operations of the counter load signal generating means 207 and the time counter 206 will be described later.

[0071] The packet transmission timing generating means 208 generates time stamp information (T3) of the own device to be transmitted to the master device, a transmission timing of the message, and a sequence ID based on the counter value from the time counter 206. The time stamp information (T3) is transmission time information of the "Delay_Req Message" described later. The Delay_Req Message transmitting means 209 uses the information generated by the packet transmission timing generating means 208 to transmit a time synchronization packet "Delay_Req Message" to the master device.

[0072] The Delay_Resp Message receiving means 210 receives the "Delay_Resp Message" of the time synchronization packet from the Ethernet PHY 201, and acquires the time stamp information (T4) when the master device receives the "Delay_Req Message". The Announce Message receiving means 211 receives the "Announce_Message" of the time synchronization packet from the Ethernet PHY 201, and acquires leap second information (UTC Offset). If consideration of leap seconds is not required in the applied system, the Announce Message receiving means 211 is not necessary.

[0073] The time holding means 212 holds the counter output (CT) output from the time counter 207 at the reception timing from the Sync Message receiving means 205, and uses it as the time information (T2) of the own device. The first subtractor 213 subtracts the time stamp information (T1) output from the Sync Message receiving means 205 from the time information output (T2) of the own device from the time holding means 212. In addition, averaging is performed as necessary to suppress variations.

[0074] The second subtractor 214 subtracts the timestamp information (T3) of the slave device (own device) output from the packet transmission timing generation means 208 from the timestamp information (T4) output from the Delay_Resp Message receiving means 210, and averages the results as necessary. The third subtractor 215 subtracts the output (T4-T3) of the second subtractor 214 from the output (T2-T1) of the first subtractor 213, and averages the results to calculate an offset time (T_Offset). The offset is a value that corrects the difference between the time information of the slave and the time information of the master.

[0075] The adder 216 adds the offset time (T_Offset) output from the third subtractor 215, the time information of its own device (T2), and the leap second information (UTC Offset) from the Announce Message receiving means 211, to correct the time information of its own device.

[0076] The UTC time conversion means 217 extracts the hour, minute, and second of the UTC time from the time information output from the adder 216 . The SFN generating means 218 generates a number (SFN: Super Frame Number) of a reference radio frame (super frame) used in the system based on the output converted by the UTC time converting means 217. The timing of switching the SFN becomes the reference timing.

[0077] [Operation of the time counter 206: Figure 4] In the T-TSC reference signal generating means 20 of this system, when the discrepancy between the time information counted within the time counter 206 and the time stamp information (T1) received from the master device (time synchronization packet sending means 17) becomes large, the master's time stamp information is pulled in and used as the counter output (CT).

[0078] The operation of the counter load signal generating means 207 and the time counter 206 will be described with reference to FIG. The counter load signal generating means 207 receives the counter output (CT) from the time counter 206 and the time stamp information (T1) output from the Sync Message receiving means 205, and calculates the difference between them. If the difference is less than a certain value, the counter load signal generating means 207 outputs "0" as the counter load signal. If the difference is equal to or greater than a certain value, the counter load signal generating means 207 outputs "1" as the counter load signal.

[0079] The time counter 206 increments the time counter, and when the counter load signal is "0", it outputs the internally counted time as the counter output (CT), and when the counter load signal is "1", it outputs timestamp information (T1) as the counter output (CT). Then, the internal counter value is also corrected to the time stamp information T1. In this manner, the master timestamp is pulled.

[0080] [Outline of operation of the T-TSC reference signal generating means 20: Figure 4] Next, an overview of the operation of the T-TSC reference signal generating means 20 will be described with reference to FIG. First, the link state detection means 203 confirms that a physical layer link with the time synchronization packet sending means 17, which is the master device, has been established, and the Sync Message receiving means 205 receives a "Sync_Message" and acquires the time information (T1) of the master device.

[0081] The time counter 206 outputs a counter output (CT) in response to a counter load signal, and if the difference between T1 and the internal count value is equal to or greater than a certain value, it pulls in time information from a higher-level device and uses it as the counter output. Then, the time holding means 212 acquires the counter output (CT) at the timing when the "Sync_Message" is received as the time information (T2) of the own device.

[0082] The packet transmission timing generation means 208 generates packet transmission timing, time information (T3) of the device, and a sequence ID based on the value of the time counter (for example, 1 / 16 second period, etc.). Based on information from the packet transmission timing generating means 208, the Delay_Req Message transmitting means 209 transmits a “Delay_Req Massage” including time stamp information (T3) to the upper device, and the Delay Resp Message receiving means 210 acquires time stamp information (T4) indicating the time when the upper device received the “Delay_Req Massage”.

[0083] Then, a first subtractor 213, a second subtractor 214, a third subtractor 215 and an adder 216 carry out a predetermined calculation to correct the internal time information of the device itself, so that it coincides with the time information of the host device. Then, the SFN generating means 218 generates a reference timing for wireless transmission and reception according to the time information.

[0084] [Timing adjustment sequence using PTP: Figure 6] Here, a sequence of timing adjustment using PTP will be described with reference to Fig. 6. Fig. 6 is an explanatory diagram showing a sequence using PTP. As shown in Fig. 6, in timing adjustment using PTP, a delay time and an offset are calculated by exchanging time synchronization packets between a master (higher-level device) and a slave (lower-level device). In this system, the time synchronization packet sending means 17 corresponds to the master, and the T-TSC reference signal generating means 20 corresponds to the slave.

[0085] First, the master transmits a "Sync_Message" including timestamp information (T1) as the transmission time to the slave. The slave sets the reception time of the "Sync_Message" as timestamp information (T2) based on the output (CT) of the time counter 206.

[0086] Then, the slave sends a “Delay_Req Message” including time stamp information (T3) as the sending time to the master, and the master sends the receiving time of the “Delay_Req Message” as time stamp information (T4) in a “Delay_Resp Message”.

[0087] In this way, by exchanging synchronous time packets, the slave obtains the time stamp information T1, T2, T3, and T4. Then, from this time stamp information, the delay time and offset are calculated. Delay time = ((T2-T1)+(T4-T3)) / 2 Offset = ((T2-T1)-(T4-T3)) / 2 As shown in FIG. 5, in the T-TSC reference signal generating means 20, the subtractor 215 outputs an offset, and the adder 216 adds the offset and leap seconds to the time information T2 to obtain a corrected internal time.

[0088] [Conversion to UTC time: Figure 5] Furthermore, a UTC time conversion means 217 performs division and MOD (modulus) operations on the time information (seconds) output from the adder 216 to convert it into time information of "hours, minutes, and seconds" of one day. If the time information of the adder output is T, then Seconds / day = Z = Mod(T,24*60*60) Hours = Int(Z,3600) Min = Int Mod(Z,3600) / 60 Sec = Mod(T,60) It can be calculated as follows:

[0089] [Reference timing generation: Figure 5] Then, a superframe number for wireless communication is generated in SFN generating means 218. The superframe number is a frame number within a superframe used in transmission in the wireless section. For example, if the superframe period is 640 ms and the reference frame timing is 40 ms, the SFN is assigned a value from 0 to 15 at 40 ms intervals. In other words, the reference timing is output at 40 ms intervals.

[0090] The frame signal generating means may, for example, be configured to have a counter with a clear function and output a timing signal based on the counter expiration value. If the "hour / minute / second" information generated by the UTC time conversion means 217 is used as the counter clear timing, then by changing the counter expiration value according to the superframe period, it is possible to generate a reference timing for generating superframes continuously (without a remainder).

[0091] For example, if the superframe period is 640 ms, and the counter expiration value is set to 4 minutes (60 x 4 x 1000 = 240000 ms), it will count and clear 375 superframes, leaving no remainder and enabling the generation of reference timing that is synchronized between multiple base station devices.

[0092] Similarly, if the superframe period is 720 ms, by setting the counter expiration value to 3 minutes (60 x 3 x 000 = 180000 ms), the counter can be cleared every 250 superframes to generate continuous reference timing. Furthermore, when the superframe period is 800 ms, the counter expiration value is set to 2 minutes (60 x 2 x 1000 = 120000 ms), so that the counter is cleared every 150 superframes and a reference timing can be generated.

[0093] The frame signal generating means can be realized by a hardware device such as an LSI (Large Scale Integration) or an FPGA (Field Programmable Gate Array), and can achieve improved accuracy compared to software control.

[0094] [Time synchronization packet message: Figure 7] Next, a message of a time synchronization packet in this system will be described with reference to Fig. 7. Fig. 7 is a diagram showing a message of a time synchronization packet. The time synchronization packet is a PTP message, and FIG. 7(a) shows a Sync Message transmitted from a higher-level device (master) to a lower-level device (slave), which includes higher-level device time information (T1).

[0095] (b) is a Delay_Req Message transmitted from a lower device to a higher device, and includes time information (T3) of the device that transmitted the message. (c) is a Delay Resp Message transmitted from a higher-level device to a lower-level device, and includes time information (T4) at which the Delay_Req Message is received from the lower-level device. (d) is an Announce Message sent from a higher-level device to a lower-level device, which includes leap second information.

[0096] [System using T-TC (another system)] The above-described system was constructed using a T-BC as the time synchronization packet sending means 17, but it is also possible to use a system (another system) in which the time synchronization packet sending means 17-01 connected to the T-GM16 is a T-BC and the other time synchronization packet sending means 17 are constructed using a T-TC (Telecom Transparent Clock).

[0097] The T-TC does not operate as a master or slave, but forwards the received time synchronization packets. At that time, the T-TC measures the time it takes for the PTP packet to pass through the switch, and writes the time in the Correction Field (CF) of the PTP packet while forwarding it.

[0098] In other words, the time synchronization packet transmission means 17-01 is the only master for each base station device 14, and the time synchronization packet transmission means 17-01 transmits and receives time synchronization packets to and from the multiple base station devices 14 in the above-mentioned sequence. As a result, the T-TSC reference signal generating means 20 of multiple base station devices 14 can perform correction using the time written in the Correction Field, making it possible to align the SNF reference timing in the same way as when a T-BC is used.

[0099] [Effects of the embodiment] According to this system and method, the telecom grandmaster 16 generates a time synchronization packet including a grand clock and time information from a signal input from the GPS antenna 15, the time synchronization packet sending means 17 provided on the wired line connecting the line control device 13 and the multiple base station devices 14 synchronizes the internal time information with the telecom grandmaster 16 and distributes a higher-level clock synchronized with the grand clock and time synchronization packets to the line control device 13 and the multiple base stations 14, and the T-TSC reference signal generating means 20 provided in the line control device 13 and the multiple base station devices 14 generates a reference clock and reference timing of the respective devices from the higher-level clock and time synchronization packets from the time synchronization packet sending means 17. This is a wireless communication system, so that the reference clocks of the multiple base station devices 14 in the system can be synchronized with the grand clock to match the reference timing, and there is an effect that each base station device 14 does not need a GPS antenna or GPS receiver, thereby reducing costs and improving reliability, and by using the PTP protocol, it is possible to apply the system to a general-purpose network and improve versatility. [Industrial Applicability]

[0100] The present invention is suitable for a wireless communication system and an inter-base station synchronization method that can achieve synchronization of a reference clock and transmission timing in the system at low cost and with improved reliability and versatility. [Explanation of symbols]

[0101] 1...operation console; 2,13,510,610...line control device; 3,14,540,640...base station device; 4,520...network line; 6,18,550,650...mobile station; 11,500,600...communication console; 12,501,601...data transmission means; 15,511,541...GPS antenna; 16...T-GM (telecom grand master); 17...time synchronization packet sending means (telecom boundary clock); 20...T-TSC reference signal generating means; 112,142,514,544,613,643...control unit; 113,515,614...voice encoding unit; 114,516,616...base station device interface; 143,546,644...radio unit; 144,547...antenna, 201...Ethernet PHY, 202...PLL, 203...link state detection means, 204...oscillator, 205...Sync Message receiving means, 206...time counter, 207...counter load signal generating means, 208...packet transmission timing generating means, 209...Delay_Req Message transmitting means, 210...Delay_Resp Message receiving means, 211...Announce Message receiving means, 212...time holding means, 213...first subtractor, 214...second subtractor, 215...third subtractor, 216...adder, 217...UTC time conversion means, 218...SFN generating means, 512...GPS receiver, 513,612...reference timing generating means, 542...GPS receiver, 611...high precision oscillator, 615, 646 ... timing packet generating means, 617, 647 ... packet switch, 641 ... timing packet detecting means, 642 ... HUB

Claims

1. A wireless communication system comprising a plurality of base station devices that are wirelessly connected to a mobile station, and a line control device that is connected to the plurality of base station devices by a wired line, a telecom grandmaster that generates a grand clock and a time synchronization packet from a signal input from a GPS antenna; a time synchronization packet sending means that is provided in the wired line connecting the line control device and the plurality of base station devices, regenerating a clock in synchronization with a grand clock from the telecom grandmaster, and distributing the regenerated clock and a time synchronization packet to the line control device and the plurality of base stations; A wireless communication system characterized in that the line control device and the multiple base station devices are provided with a reference timing generation means for generating a reference clock and reference timing for the device itself from the clock and time synchronization packet from the time synchronization packet sending means.

2. a plurality of time synchronization packet transmission means are connected in series to a wired line connecting the line control device and the plurality of base station devices; a telecom grand master is connected to the time synchronization packet transmission means closest to said line control device, and no telecom grand master is connected to other time synchronization packet transmission means than said closest time synchronization packet transmission means; The wireless communication system according to claim 1, characterized in that the other time synchronization packet sending means regenerates a clock in synchronization with a higher-level clock from a higher-level time synchronization packet sending means, and transmits the regenerated clock and a time synchronization packet.

3. the time synchronization packet transmission means is a master device, and the reference timing generation means of the line control device and the base station device are slave devices; 3. The wireless communication system according to claim 1, wherein the reference timing generation means of the slave device includes a time counter, generates a reference clock based on a higher-level clock from the master device, obtains first time information of a timestamp from a synchronization message included in a time synchronization packet transmitted from the master device, obtains a reception time of the synchronization message as second time information from the time counter, obtains a transmission time of a delay request message to the master device as third time information, obtains fourth time information of a timestamp from a delay response message included in the time synchronization packet transmitted from the master device, calculates an offset time using the first to fourth time information, and generates a reference timing of a reference radio frame by adjusting a count value from the time counter.

4. 1. An inter-base station synchronization method in a wireless communication system including a plurality of base station devices that are wirelessly connected to a mobile station and a line control device that is wired to the plurality of base station devices, comprising: The telecom grandmaster generates a grand clock and a time synchronization packet from the signal input from the GPS antenna, a time synchronization packet transmission means provided on a wired line connecting the line control device and the plurality of base station devices recovers a clock from a grand clock from the telecom grandmaster, and distributes the recovered clock and a time synchronization packet to the line control device and the plurality of base stations; A method for inter-base station synchronization, characterized in that a reference timing generating means provided in the line control device and the plurality of base stations generates a reference clock and reference timing of the respective devices from a higher-level clock and a time synchronization packet from the time synchronization packet sending means.

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