CN113347699A

CN113347699A - Base station optical fiber time service system based on BD/GPS double antennas

Info

Publication number: CN113347699A
Application number: CN202110652221.7A
Authority: CN
Inventors: 彭良福; 李有生; 侯丙安; 李高峰; 李忠文
Original assignee: Sichuan Taifu Ground Beidou Technology Co ltd
Current assignee: Sichuan Taifu Ground Beidou Technology Co ltd
Priority date: 2021-06-11
Filing date: 2021-06-11
Publication date: 2021-09-03

Abstract

The invention discloses a base station optical fiber time service system based on BD/GPS double antennas, which comprises at least one satellite antenna, a BBU synchronous system host and a plurality of BBU synchronous system slave machines, wherein the satellite antenna is connected with the host, and the host is connected with all the slave machines through optical fibers; the host computer comprises a satellite signal receiving module with a 1PPS + TOD receiving unit, and can analyze satellite signals to obtain 1PPS + TOD time information. The time service system can cascade the satellite signals and a plurality of BBU devices only by one set of BD/GPS antenna without a cable feeder, can greatly reduce the number of the antennas, reduce the occupation of sky resources and machine room space, provide high-precision time synchronization information for the mobile base station, and can ensure that the time accuracy of all BBUs is highly consistent; the deployment and maintenance are simple, the upgrading and the expansion are convenient, automatic opening and automatic maintenance can be realized, the failure rate is reduced, and the base station construction cost is reduced.

Description

Base station optical fiber time service system based on BD/GPS double antennas

Technical Field

The invention belongs to the technical field of communication systems, relates to the field of time-frequency synchronization and the field of base station construction, and particularly relates to a base station optical fiber time service system based on BD/GPS double antennas.

Background

The communication network is transited from an analog communication network to a digital optical fiber communication network, and because information transmission in the digital optical fiber communication network is realized by Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM) technologies, frequency synchronization and time synchronization are key for ensuring the communication and communication quality of the communication network, once the synchronization is abnormal, the error rate is increased, the communication quality is reduced, and the communication is interrupted or even the network is broken down. The wireless base station is an important node in a communication network, and currently, the time-frequency synchronization of the wireless base station mainly receives satellite signals.

In a mobile communication network, in order to ensure cooperative work among base stations, BBUs of the base stations need to use a uniform time signal to maintain synchronization. At present, a BBU is mostly used in the market together with a GPS time service system, as shown in fig. 1. The traditional one-to-one GPS antenna feeder matching scheme is easily limited by floor area, so that the capacity expansion quantity of BBUs in the same station is limited. In order to receive GPS/Beidou satellite signals in a machine room with a centralized BBU, dozens of or even dozens of BD/GPS antennas need to be erected on the roof, so that the number of BBU devices in the same station site is increased and BD/GPS antenna feeders are increased greatly, and some problems to be solved are brought. For example, limited area of a roof platform, lack of hoistway resources, difficulty in property coordination and the like are frequently encountered, and the building cannot be built. In addition, new BD/GPS antennas are deployed on the roof to build one or more new systems, increasing the number of roof antennas and transmission cable and duct occupancy. In the construction process, the using amount of the antenna wire materials is large, the material cost is high, the investment of pipe hole construction is large, and meanwhile, the construction difficulty and the investment cost are increased. How to solve the technical problems becomes a difficult problem to be solved urgently.

At present, when 4G and 5G networks are built in mobile, telecommunication and Unicom, BBU (baseband processing unit) pool technology is often adopted, a plurality of BBUs are installed at the same machine room site, and the BBUs and the RRUs (radio remote units) are connected by optical fibers. Under the condition that three communication operators in mobile, telecommunication and Unicom generally have difficulty in site selection, the number of BBUs in the same machine room site is often more than 8. In the central hub machine room, the number of BBUs reaches even 60. In the construction of the 4G base station, a large number of BD/GPS antennas are required to be installed in the same BBU pool machine room, and a plurality of cables are laid, so that the problems of excessive BD/GPS antennas on the roof, excessive transmission cables, overlong routes from the antennas to the machine room, limited floor resource installation, lack of pipeline resources, difficult capacity expansion of BBUs in the same site, time and labor waste in construction, high system maintenance difficulty, difficult property coordination and the like caused by centralized placement of BBUs exist. Especially for 5G base station construction, which will increase the number of BBUs by about 2 times, the existing room conditions have no way to accommodate so many antennas and transmission cables at all, and only other solutions can be sought. Therefore, a satellite signal multi-path distribution system which can realize the sharing of the BD/GPS antenna by a plurality of BBUs and solve the problem that the routing distance from the satellite antenna to an indoor BBU machine room is too long and the number of the BD/GPS antennas at the same address can be greatly reduced is always the key problem of research in the field.

In order to solve the above problems, there are two common schemes, one is a BD/GPS multi-path rf amplification distribution system (as shown in fig. 2); the other is a BD/GPS optical fiber analog signal remote multi-path radio frequency amplification distribution system (as shown in figure 3).

The first scheme, BD/GPS multi-path rf amplification and distribution system, is a unidirectional link amplifier device working at a certain frequency band, which is composed of Low Noise Amplifier (LNA), filter, power amplifier, control circuit, passive distributor, etc. Two paths of main and standby automatic switching BD/GPS signals are subjected to active amplification and secondary multi-path distribution, two paths of GPS/Beidou signals (1 main and 1 standby) are amplified and then forwarded to a plurality of sets of BBUs under the same station address, radio frequency signals are transmitted to satellite signal receivers in the BBUs, and the receivers finish signal analysis. The multi-path distribution system provides BD/GPS satellite signals for the BBUs, and each BBU achieves time synchronization by receiving the satellite signals, so that the system can flexibly support the application requirements from several paths to dozens of paths only by one set of external BD/GPS antennas. The multi-path distribution system has the advantages that the satellite antenna can be shared by a plurality of BBUs by using two BD/GPS antennas, and the number of BD/GPS antennas in the same address is reduced. The wireless communication system has the disadvantages that the host and the slave are transmitted by adopting radio frequency cables, the transmission distance is short (100m), the route length from an antenna to a machine room is limited, and the signal attenuation problem caused by an ultra-long route cannot be solved. The time delay introduced by the cable increases the time synchronization error of the BBU, because the radio frequency cable is adopted to transmit satellite signals, and the longer the cable length, the larger the introduced signal transmission time delay is, which results in the increase of the BBU time synchronization error. The ultra-long route brings high line loss, so that the carrier-to-noise ratio of the satellite signal is reduced, and satellite searching of a BBU satellite receiver is influenced. Each device has only 8 to 12 output interfaces, the number of connected BBUs is limited, and only 8 to 12 BBUs can be connected. The number of synchronous signal ports supporting BBU can reach 64 at most after the equipment is fully configured in a multi-stage cascade mode (one host and a plurality of slaves).

The second scheme, namely a BD/GPS optical fiber analog signal remote multi-path radio frequency amplification distribution system, is improved on the basis of the first scheme. The remote optical fiber signal transmission system consists of a radio frequency distribution system and an optical fiber analog signal remote system. The optical fiber analog signal remote system adopts optical fibers to replace a traditional radio frequency cable to transmit BD/GPS satellite signals, and is mainly used for solving the problems of limited routing length from an antenna to a machine room and radio frequency signal attenuation caused by an ultra-long route. The radio frequency distribution system is completely the same as the first scheme, and is a unidirectional link amplifying device which is composed of devices such as a Low Noise Amplifier (LNA), a filter, a power amplifier, a control circuit and a passive distributor and works in a certain frequency band. Two paths of main and standby automatic switching BD/GPS signals are subjected to active amplification and secondary multi-path distribution, two paths of GPS/Beidou signals (1 main and 1 standby) are amplified and then forwarded to a plurality of sets of BBUs under the same station address, radio frequency signals are transmitted to satellite signal receivers in the BBUs, and the receivers finish signal analysis. The optical fiber analog signal remote system consists of an analog signal light emitting module, an optical cable and an analog signal light receiving module. The analog signal light emitting module converts radio frequency electric signals from a satellite antenna into optical signals, sends the optical signals into an optical cable, and transmits the optical signals to the analog signal light receiving module after the optical signals are transmitted by the optical cable. The analog signal light receiving module converts the light signal from the optical cable into a radio frequency electric signal, and then the radio frequency electric signal is sent into a radio frequency distribution system, and then the radio frequency distribution system carries out active amplification and secondary multi-path distribution on the satellite signal. Due to the adoption of optical fiber transmission, the transmission distance can reach dozens of kilometers, so that the problems of limited route length from an antenna to a machine room and radio frequency signal attenuation caused by an ultra-long route are solved. However, the time delay introduced by the optical fiber and the cable increases the time synchronization error of the BBU, because the optical fiber and the radio frequency cable are adopted to transmit satellite signals, and the longer the optical cable and the cable are, the larger the introduced signal transmission time delay is, which results in the increase of the BBU time synchronization error. For example: the length of the radio frequency cable is increased by 1m, and the time delay is increased by about 4.7 ns. For every 1m increase in fiber length, whether 1310nm or 1550nm wavelength transmission, the delay increases by about 5 ns.

Although the two schemes solve the problem that a plurality of BBUs (namely BBU pool sets) share one group of BD/GPS antennas to a certain extent, the two schemes still have several important defects: the method has the advantages that firstly, the problem that the distance between a satellite antenna and a BBU pool is increased under the condition of ensuring high-precision synchronization of the BBU is not solved, and the distance is increased at the cost of sacrificing the BBU time synchronization precision index; secondly, the problem of time delay from the antenna to the BBU pool is not solved; thirdly, the high-precision time synchronization requirements of 260ns and 130ns of the 5G base station cannot be met, namely the high-precision positioning requirements of 5G 10ns are met; fourthly, manual opening is needed, the opening time is long, the opening construction cost is high, and meanwhile, the maintenance cost is also high.

In the 5G synchronous networking architecture and key technology white paper published by IMT-2020(5G) push group in 2020, it is explicitly pointed out that although the time synchronization requirements of 5G Time Division Duplex (TDD) and 4G Time Division Duplex (TDD) are the same and are all 3 microseconds, the 5G cooperative enhancement provides a more severe requirement for the time synchronization precision. For example, the time offset requirement for Multiple Input Multiple Output (MIMO) and transmit diversity techniques is 65ns, for in-band contiguous Carrier Aggregation (CA), the low frequency base station (Sub 6G) time offset requirement is 260ns, and the high frequency base station (Above 6G) time offset requirement is 130 ns. The high-precision positioning service supported by the 5G network is directly related to the time synchronization precision. For example, to meet the positioning accuracy of 3m, the synchronization deviation of air interface signals between base stations is required to be ± 10 ns; to meet the m-level positioning accuracy, the synchronization deviation of air interface signals between base stations is required to be +/-3 ns.

Due to transmission delay caused by radio frequency cables and optical fibers, the time synchronization precision of the BBU can only reach 3 microseconds, and the requirement of a 5G base station on high-precision time synchronization cannot be met, so that the two schemes have serious defects.

In view of the above, through a great deal of scientific research and experiments, the present inventors have developed a BD/GPS dual-antenna based base station optical fiber timing system to solve the above problems.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a base station optical fiber time service system based on a BD/GPS double antenna, the time service system only needs one set of BD/GPS antenna and does not need any cable feeder, BD/GPS satellite signals and a plurality of BBU devices can be cascaded, the number of BD/GPS antennas can be greatly reduced, the occupation of sky resources and machine room space is reduced, high-precision time synchronization information is provided for a mobile base station, and the time accuracy of all BBUs is highly consistent.

In order to achieve the purpose, the invention provides the following technical scheme:

a base station optical fiber time service system based on BD/GPS double antennas comprises at least one satellite antenna, a BBU synchronization system host and a plurality of BBU synchronization system slave machines, wherein the satellite antenna is connected with the BBU synchronization system host, the BBU synchronization system host is used for receiving satellite antenna time service signals, and the BBU synchronization system host is mutually connected with all the BBU synchronization system slave machines through optical fibers and used for feedback correction to enable the BBU synchronization system slave machines and the synchronization system host machines to be time synchronized.

Furthermore, the BBU synchronization system host consists of a satellite signal receiving module, a first clock disciplining module, an online measuring module, a first digital signal optical transceiver module and a first time distribution output module; the satellite signal receiving module comprises a 1PPS + TOD receiving unit, is used for receiving signals from a satellite antenna and completing the analysis of the signals to obtain 1PPS signal + TOD time information, and transmits the 1PPS signal to the first clock taming module and transmits the TOD time information to the first digital signal optical transceiver module and the first time distribution output module respectively; the first clock taming module tamines the 1PPS signal output by frequency division of the local clock of the BBU synchronous system host by using the 1PPS signal from the satellite antenna, and outputs the 1PPS signal which is stable after taming and respectively transmits the signal to the online measuring module, the first digital signal optical transceiver module and the first time distribution output module; the online measurement module is used for loopback test, measuring the time delay value of 1PPS signals transmitted back and forth by optical fibers between the BBU synchronization system host and the BBU synchronization system slave, and transmitting the measured time delay value DATA to the first digital signal optical transceiver module; the first digital signal optical transceiver module encodes the 1PPS signal, the TOD time information and the time delay value DATA information from the online measurement module, converts the encoded electrical signals into optical signals and transmits the optical signals to the optical fiber to be transmitted to the slave of the BBU synchronization system, converts the optical signals from the optical fiber in the slave direction of the BBU synchronization system into electrical signals, decodes the electrical signals to obtain the 1PPS signal looped back by the slave of the BBU synchronization system, and transmits the looped 1PPS signal to the online measurement module; the first time distribution output module is used for carrying out multi-path distribution output on the time information.

Furthermore, the BBU synchronization system slave is composed of a second digital signal optical transceiver module, a loopback module, a second clock disciplining module, a time delay compensation module, and a second time distribution output module; the second digital signal optical transceiver module is used for converting optical signals from the BBU synchronous system host direction optical fiber into electric signals, decoding the electric signals to obtain 1PPS signals and TOD time information from the BBU synchronous system host and time delay value DATA information from the online measurement module, respectively transmitting the 1PPS signals to the loopback module and the time delay compensation module, transmitting the time delay value DATA to the time delay compensation module, transmitting the TOD time information to the second time distribution output module, simultaneously coding and converting the 1PPS electric signals from the loopback module into optical signals, and transmitting the optical signals to the BBU synchronous system host; the loopback module is used for carrying out loopback transmission on the 1PPS signal from the BBU synchronization system host received by the BBU synchronization system slave to the BBU synchronization system host, and specifically, the loopback transmission of the 1PPS signal from the second digital signal optical transceiver module to the second digital signal optical transceiver module; the second clock taming module taminates the 1PPS signal subjected to frequency division of the local clock of the slave of the BBU synchronous system by using the 1PPS signal from the host of the BBU synchronous system, and outputs a stabilized time signal after taming; the delay compensation module compensates a clock difference between the slave of the BBU synchronization system and the host of the BBU synchronization system by using the received delay value DATA information from the host of the BBU synchronization system, so that the slave of the BBU synchronization system and the host of the BBU synchronization system realize high-precision time synchronization; and the second time distribution output module is used for carrying out multi-path distribution output on the time information.

Furthermore, the first time distribution output module and the second time distribution output module are both provided with a 1PPS + TOD and a PTP output interface;

the first time distribution output module receives TOD time information from the satellite signal receiving module and 1PPS signals from the first clock taming module, and performs multi-path distribution output on the time information through a 1PPS + TOD and PTP output interface;

the second time distribution output module receives TOD time information from the second digital signal optical transceiver module and 1PPS signals from the second clock discipline module, and performs multi-path distribution and output on the time information through the 1PPS + TOD and PTP output interfaces.

Furthermore, the first digital signal optical transceiver module and the second digital signal optical transceiver module are connected by an optical fiber.

Furthermore, the satellite antenna is a BD/GPS antenna integrating a Beidou satellite navigation system and a global positioning system; and the BD/GPS antenna receives the time service signals of the Beidou satellite BD and the global positioning satellite GPS.

Furthermore, the satellite antenna adopts a two-in-one BD/GPS antenna with two paths of main and standby automatic switching.

Further, the BBU synchronization system host (2) is connected with a national high-precision ground time service reference source ePLCC and is used for receiving an ultrahigh-precision time signal of the national high-precision ground time service reference source ePLCC from a ground special optical fiber network.

Furthermore, the BBU synchronous system host and the BBU synchronous system slave adopt a multi-stage cascade mode.

Furthermore, the satellite antenna and the BBU synchronous system host are integrated equipment.

Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:

1. the invention provides a cascade BD/GPS signal distribution system by designing a base station optical fiber time service system based on a BD/GPS double antenna and carrying out digital signal optical fiber high-precision time transmission and multi-path distribution on satellite signals received by two paths of automatically and seamlessly switched BD/GPS antennas, so that the system can flexibly support the application requirements of base station BBU time service from several paths to dozens of paths only by one set of external BD/GPS antennas. The whole system can cascade BD/GPS satellite signals with a plurality of BBU devices only by one set of BD/GPS antenna without any cable feeder, can greatly reduce the number of BD/GPS antennas, reduce the occupation of sky resources and machine room space, provide high-precision time synchronization information for a mobile base station, and can ensure that the time accuracy of all BBUs is highly consistent. For example, if the absolute time of the BD/GPS receiver output is 30ns offset from the UTC as is currently the case with normal tracking satellites, then the time synchronization accuracy is all < 31 ns. The deployment and maintenance are simple, the upgrading and the expansion are convenient, automatic opening and automatic maintenance can be realized, the failure rate is reduced, and the base station construction cost is reduced.

2. Compared with the traditional BD/GPS multi-channel radio frequency amplification distribution system and the BD/GPS optical fiber analog signal remote multi-channel radio frequency amplification distribution system, the base station optical fiber time service system based on the BD/GPS double antenna has low comprehensive construction cost (the cost is mainly saved in the aspects of cost and construction of a satellite receiving module and antenna feeder equipment, and the cost advantage is more obvious when the number of synchronous base station equipment is more), and has obvious advantages in the aspects of function and performance. The satellite antenna shared by multiple BBUs can be realized by utilizing two BD/GPS antennas, the number of co-located satellite antennas is greatly reduced, optical fiber transmission is adopted between a host and a slave, the transmission distance reaches dozens of kilometers (60km), the routing length is not limited (the transmission distance can reach hundreds of kilometers in a multi-level cascade mode), the number of time output interfaces 1PPS + TOD or PTP of each device is large (not limited by power distribution), the number of connected BBUs is large (at least 16 BBUs can be connected), and the capacity expansion is convenient. The number of the synchronous signal ports supporting the BBU is not less than 256 after the equipment is fully configured in a multi-stage cascade mode (one host and a plurality of slaves). The BBU time synchronization precision is high, and the relative time deviation of each BBU synchronization signal is less than 1ns, so that the requirement of 5G base station synchronization is met, and the requirement of 5G cooperative enhancement on the time synchronization precision is met. In addition, the time signal of the host can not only receive the satellite signal from the BD/GPS, but also receive the ultra-high precision time signal from the national high precision ground time service reference source ePLCC of the ground special optical fiber network, thereby realizing the mutual backup of the time source of the host and effectively ensuring the safety and reliability of the time synchronization signal provided for the base station. The base station optical fiber time service system based on the BD/GPS dual-antenna can be widely applied to scenes such as a base station machine room, a Radio Access Network (RAN) and the like.

Drawings

FIG. 1 is a diagram of a conventional GPS one-to-one time service system;

FIG. 2 is a schematic diagram of a BD/GPS multi-path RF amplification distribution system;

FIG. 3 is a schematic diagram of a BD/GPS optical fiber analog signal remote multi-path RF amplification distribution system;

FIG. 4 is a schematic diagram of a base station optical fiber time service system based on BD/GPS dual antennas;

FIG. 5 is a BBU synchronization system host information flow diagram;

FIG. 6 is a BBU synchronization system slave information flow diagram;

FIG. 7 is a schematic diagram of optical fiber connection information transmission between a master and a slave;

FIG. 8 is a schematic diagram illustrating a host and a slave cascade connected to implement long-distance and large-range base station optical fiber time service;

fig. 9 is a schematic diagram of a base station optical fiber time service system based on integrated host equipment.

In the figure: 1 is a satellite antenna; 2 is a BBU synchronous system host; 3 is a BBU synchronous system slave; 21 is a satellite signal receiving module; 22 is a first clock taming module; 23 is an online measuring module; 24 is a first digital signal light transceiver module; 25 is a first time allocation output module; 31 is a second digital signal optical transceiver module; 32 is a loopback module; 33 is a second clock taming module; 34 is a time delay compensation module; and 35 is a second time allocation output module.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus consistent with certain aspects of the invention, as detailed in the appended claims.

In order to make those skilled in the art better understand the technical solution of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings and examples.

Referring to fig. 4, the base station optical fiber time service system based on the BD/GPS dual antenna of the present invention includes at least one satellite antenna 1, a BBU synchronization system host 2, and a plurality of BBU synchronization system slave machines 3, where the satellite antenna 1 is connected to the BBU synchronization system host 2, and the BBU synchronization system host 2 is connected to all BBU synchronization system slave machines 3 through optical fibers; the system has high time transmission precision, and can make the time accuracy of all BBUs highly consistent. For example, if the absolute time of the BD/GPS receiver output is 30ns offset from the UTC as is currently the case with normal tracking satellites, then the time synchronization accuracy is all < 31 ns.

Specifically, as shown in fig. 5, the BBU synchronization system host 2 of the present invention is composed of a satellite signal receiving module 21, a first clock taming module 22, an online measuring module 23, a first digital signal optical transceiver module 24, and a first time allocation output module 25. The satellite signal receiving module 21 includes a 1PPS + TOD receiving unit, configured to receive a signal from the satellite antenna 1, complete analysis of the signal, obtain 1PPS signal + TOD time information, transmit the 1PPS signal to the first clock taming module 22, and transmit the TOD time information to the first digital signal optical transceiver module 24 and the first time allocation output module 25, respectively; the first clock taming module 22 tamines the 1PPS signal output by frequency division of the local clock of the BBU synchronous system host 2 by using the 1PPS signal from the satellite antenna 1, outputs the 1PPS signal which is stable after taming and respectively transmits the signal to the online measuring module 23, the first digital signal optical transceiver module 24 and the first time distribution output module 25; the online measurement module 23 is used for loopback test, measuring the time delay value of 1PPS signal transmitted back and forth by the optical fiber between the BBU synchronization system host 2 and the BBU synchronization system slave 3, and transmitting the measured time delay value DATA to the first digital signal optical transceiver module 24; the first digital signal optical transceiver module 24 encodes the 1PPS signal and the TOD time information, and the delay value DATA information from the online measurement module 23, converts the encoded electrical signal into an optical signal, sends the optical signal to the optical fiber and transmits the optical signal to the BBU synchronization system slave 3, converts the optical signal from the optical fiber in the direction of the BBU synchronization system slave 3 into an electrical signal, decodes the electrical signal to obtain the 1PPS signal looped back by the BBU synchronization system slave 3, and sends the looped 1PPS signal to the online measurement module 23; the first time distribution output module 25 receives the TOD time information from the satellite signal receiving module 21 and the 1PPS signal from the first clock discipline module 22, and provides 1PPS + TOD and PTP output interfaces for multiplexing and outputting the time information.

As shown in fig. 6, the BBU synchronization system slave 3 of the present invention is composed of a second digital signal optical transceiver module 31, a loopback module 32, a second clock taming module 33, a delay compensation module 34, and a second time distribution output module 35. The second digital signal optical transceiver module 31 is configured to convert an optical signal from the BBU synchronization system host 2 to an electrical signal, decode the electrical signal to obtain a 1PPS signal and TOD time information from the BBU synchronization system host 2, and delay value DATA information from the online measurement module 23, transmit the 1PPS signal to the loopback module 32 and the delay compensation module 34, transmit the delay value DATA to the delay compensation module 34, transmit the TOD time information to the second time distribution output module 35, encode and convert the 1PPS electrical signal from the loopback module 32 to an optical signal, and transmit the optical signal to the BBU synchronization system host 2; the loopback module 32 is configured to loop back the 1PPS signal received by the BBU synchronization system slave 3 from the BBU synchronization system host 2 to the BBU synchronization system host 2, specifically, loop back the 1PPS signal from the second digital signal optical transceiver module 24 to the second digital signal optical transceiver module 24; the second clock taming module 33 tamines the 1PPS signal after frequency division of the local clock of the slave 3 of the BBU synchronous system by using the 1PPS signal from the host 2 of the BBU synchronous system, and outputs a stable time signal after taming; the delay compensation module 34 compensates the clock difference between the BBU synchronization system slave 3 and the BBU synchronization system host 2 by using the received delay value DATA information from the BBU synchronization system host 2, so that the BBU synchronization system slave 3 and the BBU synchronization system host 2 realize high-precision time synchronization; the second time distribution output module 35 receives the TOD time information from the second digital signal optical transceiver module 31 and the 1PPS signal from the second clock discipline module 33, and is configured to perform demultiplexing and output of the time information through the 1PPS + TOD and PTP output interfaces.

The first time allocation output module 25 and the second time allocation output module 35 are both provided with 1PPS + TOD and PTP output interfaces, and are connected to the 1PPS + TOD or PTP input interfaces of the BBUs (host and slave) to perform multi-path allocation output of the time information.

In addition, as shown in fig. 7, the BBU synchronization system host 2 of the present invention is connected to all BBU synchronization system slaves 3 through optical fibers, specifically, the first digital signal optical transceiver module 24 in the BBU synchronization system host 2 is connected to the second digital signal optical transceiver module 31 in the BBU synchronization system slaves 3 through optical fibers.

The satellite antenna 1 is a BD/GPS antenna integrating a Beidou satellite navigation system and a global positioning system; and the BD/GPS antenna receives the time service signals of the Beidou satellite BD and the global positioning satellite GPS.

As shown in fig. 4, the BBU synchronization system host 2 of the present invention is also connected to the national high-precision ground time service reference source ePRTC, that is, the time signal of the BBU synchronization system host 2 can receive not only the satellite signal from the BD/GPS, but also the ultra-high-precision time signal of the national high-precision ground time service reference source ePRTC from the ground dedicated optical fiber network, thereby realizing mutual time source space-to-ground backup of the BBU synchronization system host 2.

The current mobile communication base station can provide a 1PPS + TOD time interface or PTP interface. The solution provided by the invention adopts 1PPS + TOD of two paths of main and standby automatic switching BD/GPS satellite signals to carry out long-distance digital signal optical fiber transmission and multi-path distribution, can realize the support of a plurality of BBU synchronous signals (256 BBUs can be supported by 1 main machine and a plurality of auxiliary machines) by only using a BD/GPS satellite receiving antenna, realizes the sharing of the BD/GPS satellite antenna by a plurality of BBUs, greatly reduces the number of the same-address Beidou/GPS antennas and the number of satellite receiver modules, obviously improves the time synchronization precision of a base station, has high time transfer precision, and can ensure that the time accuracies of all BBUs are highly consistent. For example, if the absolute time of the Beidou/GPS receiver output is + -30 ns relative to the UTC as currently in the case of normal satellite tracking, then the time synchronization accuracy is all + -31 ns. The resource advantage maximization is fully realized, the cost is effectively saved, and the cost performance is improved.

As shown in fig. 8, the invention realizes time service for a long-distance and large-range base station by adopting a multi-stage cascade mode of the BBU synchronization system host 2 and the BBU synchronization system slave 3, so that BD/GPS satellite signals can be received at one place, tens of meters, tens of kilometers and hundreds of kilometers can be transmitted through optical fiber high-precision time, and BBU high-precision time synchronization of all base stations in a long distance and large range can be realized.

Preferably, the invention can make the BD/GPS antenna and the BBU synchronization system host 2 into an integrated device, as shown in FIG. 9, which is convenient for installation and later maintenance.

The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention.

It is to be understood that the present invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims

1. A base station optical fiber time service system based on BD/GPS double antennas is characterized by comprising at least one satellite antenna (1), a BBU synchronization system host (2) and a plurality of BBU synchronization system slave machines (3), wherein the satellite antenna (1) is connected with the BBU synchronization system host (2), the BBU synchronization system host (2) is used for receiving time service signals of the satellite antenna (1), and the BBU synchronization system host (2) is mutually connected with all the BBU synchronization system slave machines (3) through optical fibers and used for feedback correction to enable the BBU synchronization system slave machines (3) and the synchronization system host machines (2) to be time synchronized.

2. The BD/GPS dual-antenna-based base station optical fiber timing system according to claim 1, wherein the BBU synchronization system host (2) is composed of a satellite signal receiving module (21), a first clock taming module (22), an online measurement module (23), a first digital signal optical transceiver module (24) and a first time distribution output module (25); the satellite signal receiving module (21) comprises a 1PPS + TOD receiving unit, is used for receiving signals from a satellite antenna (1), completes the analysis of the signals, obtains 1PPS signals + TOD time information, transmits the 1PPS signals to the first clock taming module (22), and respectively transmits the TOD time information to the first digital signal optical transceiver module (24) and the first time distribution output module (25); the first clock taming module (22) utilizes the 1PPS signal from the satellite antenna (1) to taminate the 1PPS signal output by the frequency division of the local clock of the BBU synchronous system host (2), and outputs the 1PPS signal which is stable after taming and respectively transmits the signal to the online measuring module (23), the first digital signal optical transceiver module (24) and the first time distribution output module (25); the online measurement module (23) is used for loopback test, measuring the time delay value of 1PPS signals transmitted back and forth by optical fibers between the BBU synchronous system host (2) and the BBU synchronous system slave (3), and transmitting the measured time delay value DATA to the first digital signal optical transceiver module (24); the first digital signal optical transceiver module (24) encodes the 1PPS signal and the TOD time information as well as the time delay value DATA information from the online measurement module (23), converts the encoded electrical signals into optical signals and transmits the optical signals to the optical fiber to be transmitted to the BBU synchronization system slave (3), converts the optical signals from the optical fiber in the direction of the BBU synchronization system slave (3) into electrical signals, decodes the electrical signals to obtain the 1PPS signal looped back by the BBU synchronization system slave (3), and transmits the looped 1PPS signal to the online measurement module (23); the first time distribution output module (25) is used for multiplexing and outputting the time information.

3. The base station optical fiber time service system based on BD/GPS dual antenna of claim 2, characterized in that the BBU synchronization system slave (3) is composed of a second digital signal optical transceiver module (31), a loop back module (32), a second clock discipline module (33), a delay compensation module (34) and a second time distribution output module (35); the second digital signal optical transceiver module (31) is used for converting optical signals in optical fibers in the direction of the BBU synchronization system host (2) into electric signals, decoding the electric signals to obtain 1PPS signals and TOD time information from the BBU synchronization system host (2) and time delay value DATA information from the online measurement module (23), respectively transmitting the 1PPS signals to the loopback module (32) and the time delay compensation module (34), transmitting the time delay value DATA to the time delay compensation module (34), transmitting the TOD time information to the second time distribution output module (35), simultaneously encoding and converting the 1PPS electric signals from the loopback module (32) into optical signals, and transmitting the optical signals to the BBU synchronization system host (2); the loopback module (32) is used for looping back the 1PPS signal from the BBU synchronization system host (2) received by the BBU synchronization system slave (3) and transmitting the signal to the BBU synchronization system host (2), specifically, looping back the 1PPS signal from the second digital signal optical transceiver module (24) and transmitting the signal to the second digital signal optical transceiver module (24); the second clock taming module (33) utilizes the 1PPS signal from the BBU synchronous system host (2) to taminate the 1PPS signal after frequency division of the local clock of the BBU synchronous system slave (3), and outputs a stabilized time signal after taming; the delay compensation module (34) compensates the clock difference between the BBU synchronization system slave (3) and the BBU synchronization system host (2) by using the received delay value DATA information from the BBU synchronization system host (2), so that the BBU synchronization system slave (3) and the BBU synchronization system host (2) realize high-precision time synchronization; the second time distribution output module (35) is used for multiplexing and outputting the time information.

4. The BD/GPS dual-antenna-based base station optical time service system according to claim 3, wherein the first time distribution output module (25) and the second time distribution output module (35) are both provided with 1PPS + TOD and PTP output interfaces;

the first time distribution output module (25) receives the TOD time information from the satellite signal receiving module (21) and the 1PPS signal from the first clock taming module (22), and multiplexes and outputs the time information through a 1PPS + TOD and PTP output interface;

the second time distribution output module (35) receives the TOD time information from the second digital signal optical transceiver module (31) and the 1PPS signal from the second clock discipline module (33), and multiplexes and outputs the time information through the 1PPS + TOD and PTP output interfaces.

5. The BD/GPS dual-antenna-based base station optical fiber time service system according to claim 3, wherein the first digital signal optical transceiver module (24) and the second digital signal optical transceiver module (31) are connected through an optical fiber.

6. The BD/GPS dual-antenna-based base station optical fiber timing system according to claim 1, wherein the satellite antenna (1) is a two-in-one BD/GPS antenna of a Beidou satellite navigation system and a global positioning system; and the BD/GPS antenna receives the time service signals of the Beidou satellite BD and the global positioning satellite GPS.

7. A BD/GPS dual-antenna-based base station optical fiber time service system according to claim 6, wherein the satellite antenna (1) adopts a two-in-one BD/GPS antenna with two main and standby automatic switching.

8. The BD/GPS dual-antenna-based base station optical fiber timing system according to claim 1, wherein the BBU synchronization system host (2) is connected to a national high-precision ground timing reference source ePTC, and is configured to receive an ultra-high-precision time signal from the national high-precision ground timing reference source ePTC of the ground dedicated optical fiber network.

9. The base station optical fiber timing system based on BD/GPS dual antenna as claimed in claim 1, wherein the BBU synchronization system host (2) and the BBU synchronization system slave (3) adopt a multi-stage cascade mode.

10. The BD/GPS dual-antenna-based base station optical fiber timing system according to claim 1, wherein the satellite antenna (1) and the BBU synchronization system host (2) are integrated devices.