WO2020248529A1 - 分布式天线系统、方法和装置 - Google Patents

分布式天线系统、方法和装置 Download PDF

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Publication number
WO2020248529A1
WO2020248529A1 PCT/CN2019/121365 CN2019121365W WO2020248529A1 WO 2020248529 A1 WO2020248529 A1 WO 2020248529A1 CN 2019121365 W CN2019121365 W CN 2019121365W WO 2020248529 A1 WO2020248529 A1 WO 2020248529A1
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Prior art keywords
digital
radio frequency
analog
signal
frequency signal
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PCT/CN2019/121365
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English (en)
French (fr)
Inventor
罗漫江
樊奇彦
张航
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京信通信系统（中国）有限公司
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Application filed by 京信通信系统（中国）有限公司 filed Critical 京信通信系统（中国）有限公司
Priority to EP19933068.9A priority Critical patent/EP3986011A4/en
Priority to BR112021025091A priority patent/BR112021025091A2/pt
Priority to US17/618,337 priority patent/US11923905B2/en
Publication of WO2020248529A1 publication Critical patent/WO2020248529A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/38—Transceivers, i.e. devices in which transmitter and receiver form a structural unit and in which at least one part is used for functions of transmitting and receiving
    • H04B1/40—Circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H04B10/25752—Optical arrangements for wireless networks
    • H04B10/25753—Distribution optical network, e.g. between a base station and a plurality of remote units
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H04B10/0795—Performance monitoring; Measurement of transmission parameters
    • H04B10/07955—Monitoring or measuring power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/564—Power control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H04W88/085—Access point devices with remote components
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2210/00—Indexing scheme relating to optical transmission systems
    • H04B2210/006—Devices for generating or processing an RF signal by optical means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • This application relates to the field of communication technology, and in particular to a distributed antenna system, method and device.
  • the new digital room subsystem has the advantages of simple deployment, low construction difficulty, flexible expansion, and convenient operation and maintenance, which greatly increases network capacity.
  • an embodiment of the present application provides a distributed antenna system, including: a digital-to-analog expansion unit and a remote cascade chain.
  • the remote cascade chain includes a plurality of remote cascades connected by radio frequency cables. Terminal unit, and the first remote unit of the remote cascade chain is connected to the digital-analog expansion unit through a radio frequency cable.
  • the digital-to-analog expansion unit is used to perform baseband processing operations on the downlink digital radio frequency signal transmitted by the source unit via optical fiber through the first baseband processing module inside the digital-to-analog expansion unit, and to perform baseband processing operations through the first signal conversion module inside the digital-to-analog expansion unit Digital-to-analog conversion to obtain the downlink analog radio frequency signal to be sent to the remote cascade chain; or, the digital-to-analog expansion unit is used to perform analog-to-digital conversion on the uplink analog radio frequency signal transmitted by the remote cascade chain through the first signal conversion module, And the baseband processing operation is performed by the first baseband processing module to obtain the uplink digital radio frequency signal to be sent to the source unit through the optical fiber.
  • the remote unit is used to perform analog radio frequency signal interaction with the terminal equipment, and the analog radio frequency signal interaction is performed between two adjacent remote units through a radio frequency cable.
  • the embodiment of the present application also provides a signal transmission method, which is applied to the above-mentioned distributed antenna system; the signal transmission method includes:
  • the remote unit obtains the first uplink analog radio frequency signal of the terminal and the second uplink analog radio frequency signal transmitted by the next-level remote unit.
  • the remote unit combines the first uplink analog radio frequency signal and the second uplink analog radio frequency signal to obtain the uplink analog radio frequency signal of the current remote unit, and transmits the uplink analog radio frequency signal of the current remote unit to the upper remote Unit or digital-analog expansion unit.
  • the digital-to-analog expansion unit performs analog-to-digital conversion and baseband processing on the acquired uplink analog radio frequency signal, and obtains the uplink digital radio frequency signal to be sent to the source unit via optical fiber.
  • a signal transmission method which is applied to the above-mentioned distributed antenna system; the signal transmission method includes:
  • the digital-to-analog expansion unit performs baseband processing and digital-to-analog conversion on the downlink digital radio frequency signal transmitted by the source unit through the optical fiber to obtain the downlink analog radio frequency signal, and transmits the downlink analog radio frequency signal to the remote cascade chain.
  • the remote unit obtains the downlink analog radio frequency signal, and transmits the downlink radio frequency signal based on the downlink analog radio frequency signal.
  • a gain control method is provided, which is applied to the above-mentioned distributed antenna system; the gain control method includes the steps:
  • the remote unit obtains the radio frequency signal transmitted by the digital-analog extension unit through the radio frequency cable, and measures the radio frequency signal to obtain the first power value; wherein the radio frequency signal is a signal generated by the digital-analog extension unit according to a preset frequency band and a preset power value.
  • the remote unit obtains the RF signal insertion loss based on the first power value and the preset power value, and obtains the cable length according to the RF signal insertion loss and the preset frequency band.
  • the remote unit obtains the target signal insertion loss based on the cable length and the target signal frequency band, and matches the attenuation value of the digitally controlled attenuator based on the target signal insertion loss, target transmission power and gain value.
  • a gain control device which is applied to a distributed antenna system, and the gain control device is respectively arranged in each remote unit; the gain control device includes:
  • the power measurement module is used to obtain the radio frequency signal transmitted by the digital-to-analog expansion unit through the radio-frequency cable, and to measure the radio frequency signal to obtain the first power value; wherein the radio-frequency signal is generated by the digital-to-analog expansion unit according to the preset frequency band and the preset power value signal.
  • the cable length obtaining module is used to obtain the radio frequency signal insertion loss based on the first power value and the preset power value, and obtain the cable length according to the radio frequency signal insertion loss and the preset frequency band.
  • the attenuation value matching module is used to obtain the target signal insertion loss based on the cable length and the target signal frequency band, and match the attenuation value of the digitally controlled attenuator based on the target signal insertion loss, target transmission power and gain value.
  • the distributed antenna system includes a digital-analog expansion unit and a remote cascade chain.
  • the remote cascade chain includes a plurality of remote units cascaded through a radio frequency cable, and the first remote unit of the remote cascade chain passes through the radio frequency cable Connect with digital-analog expansion unit.
  • the digital-analog expansion unit is used to perform baseband processing operations on the received external signals through the first baseband processing module inside the digital-to-analog expansion unit, and to perform analog radio frequency signals and digital signals through the first signal conversion module inside the digital-to-analog expansion unit.
  • the mutual conversion operation of radio frequency signals obtains the uplink digital radio frequency signal to be sent to the source unit or the downlink analog radio frequency signal to be sent to the remote cascade chain; the remote unit is used to interact with the terminal equipment in the analog radio frequency signal, and the corresponding The two adjacent remote units conduct analog radio frequency signal interaction through radio frequency cables.
  • the digital-analog expansion unit and the remote unit adopt a cable-based daisy chain topology structure, which can increase the transmission bandwidth while effectively reducing the cost of the transmission link; and the digital-analog expansion unit performs baseband processing, and the remote The unit does not require baseband processing equipment, which can effectively reduce system device cost and operating power consumption.
  • the coverage of the remote unit is not limited by bandwidth and supports multiple signal access coverage.
  • the system has the characteristics of supporting multi-mode, multi-frequency, and cell splitting, which is easy to expand and has low construction difficulty.
  • Fig. 1 is a schematic diagram of an application environment of a distributed antenna system in an embodiment
  • Figure 2 is a first schematic structural diagram of a distributed antenna system in an embodiment
  • FIG. 3 is a second schematic structural diagram of a distributed antenna system in an embodiment
  • Fig. 4 is a comparison diagram of remote units of a distributed antenna system and a new digital indoor branch system in an embodiment
  • FIG. 5 is a first comparison diagram of a daisy chain topology and a star topology in an embodiment
  • FIG. 6 is a second comparison diagram of a daisy chain topology and a star topology in an embodiment
  • Fig. 7 is a schematic diagram of frequency band-bandwidth in an embodiment
  • Figure 8 is a schematic structural diagram of a bundled radio frequency cable in an embodiment
  • FIG. 9 is a first schematic structural diagram of a digital-to-analog extension unit of a distributed antenna system in an embodiment
  • FIG. 10 is a third schematic structural diagram of a distributed antenna system in an embodiment
  • FIG. 11 is a second schematic structural diagram of a digital-to-analog extension unit of a distributed antenna system in an embodiment
  • FIG. 12 is a first schematic structural diagram of a remote unit of a distributed antenna system in an embodiment
  • FIG. 13 is a second schematic structural diagram of a remote unit of a distributed antenna system in an embodiment
  • FIG. 14 is a first schematic structural diagram of an access unit of a distributed antenna system in an embodiment
  • 15 is a third schematic structural diagram of a digital-to-analog extension unit of a distributed antenna system in an embodiment
  • Figure 16 is a schematic diagram of a distributed antenna system performing digital combining in an embodiment
  • Figure 17 is a comparison diagram of source units of a distributed antenna system in an embodiment
  • FIG. 18 is a second schematic structural diagram of an access unit of a distributed antenna system in an embodiment
  • 19 is a schematic diagram of signal coupling of a digital-to-analog expansion unit of a distributed antenna system in an embodiment
  • FIG. 20 is a schematic diagram of signal coupling of remote units of a distributed antenna system in an embodiment
  • FIG. 21 is a fourth schematic structural diagram of a distributed antenna system in an embodiment.
  • first port when an element is considered to be “connected” to another element, it may be directly connected to and integrated with another element, or there may be a centering element at the same time.
  • first port first transmission port
  • other end and similar expressions used herein are for illustrative purposes only.
  • Traditional DAS mainly uses passive components, and its industrial chain is mature, with small investment and simple system. In addition, it can be expanded by multiple frequency bands simply by combining circuits later. However, under the condition that multiple communication channels are required, for example, for the 2T2R and 4T4R MIMO systems required by 5G, the construction cost of traditional DAS will be doubled. At the same time, due to the inconsistency of passive components and signal transmission insertion loss, etc. Traditional DAS cannot fully reflect the performance of MIMO systems, and current devices do not support high frequency bands, which is not conducive to capacity expansion and smooth evolution of the system. In addition, traditional DAS projects are difficult to construct, have many hidden troubles, and difficult to troubleshoot.
  • the new digital indoor distribution system introduced in the 4G era has the advantages of simple engineering implementation, visual operation and maintenance, simple implementation of multi-channel MIMO, and easy expansion and evolution.
  • the construction cost of the new digital room distribution system is several times higher than that of the traditional DAS.
  • the new digital rooms are all active systems.
  • the transmission of digital signals through network cables or optical fibers requires huge energy consumption.
  • the bandwidth is limited by the speed of optical modules or network cables.
  • the transmission bandwidth is required to increase proportionally, and performance-matched devices (such as ADC (Analog-to-Digital Converter, analog-to-digital converter)/DAC (Digital to analog converter) , Digital-to-analog converter)/FPGA (Field-Programmable Gate Array, that is, field-programmable gate array)) for processing, and its cost and power consumption have also increased significantly.
  • ADC Analog-to-Digital Converter, analog-to-digital converter
  • DAC Digital to analog converter
  • FPGA Field-Programmable Gate Array, that is, field-programmable gate array
  • this application provides a distributed antenna system, which can be applied to the application environment as shown in Figure 1.
  • a digital-to-analog expansion unit for baseband processing and signal conversion is provided between the source unit and the remote transmitter unit. , Forming a three-layer structure of the source unit, digital-analog expansion unit and remote unit; and, the digital-analog expansion unit uses radio frequency cables to cascade multiple remote units to form a daisy chain topology; when increasing bandwidth, it can effectively reduce The cost of remote coverage.
  • the system supports access coverage of multiple signals, and has the characteristics of supporting multi-mode and multi-frequency, capacity expansion, and cell splitting.
  • the system adopts digital-analog hybrid transmission, which has the advantages of simple project implementation, manageable and controllable, multi-channel MIMO and easy expansion. At the same time, it can avoid the disadvantages of high construction cost, high power consumption and limited transmission bandwidth. .
  • the distributed antenna system includes at least one digital-to-analog extension unit connected to the source unit, and at least two remote units; wherein the remote units adopt a daisy chain topology connection structure , Forming a remote cascade chain; and, the remote unit located at the head end of the remote cascade chain is connected to the digital-analog expansion unit with a radio frequency cable; the digital-analog expansion unit can be connected to at least one remote cascade chain.
  • the distributed antenna system may include at least two digital-to-analog extension units; a star topology connection structure and/or a daisy chain topology connection structure can be adopted between one source unit and multiple digital-analog extension units. It should be noted that the daisy chain topology mentioned in the embodiment of this application is a linear daisy chain topology.
  • a distributed antenna system comprising: a digital-analog expansion unit and a remote cascading chain, the remote cascading chain includes a plurality of remote cascades connected by radio frequency cables Unit, and the first remote unit of the remote cascade chain is connected to the digital-analog expansion unit through a radio frequency cable.
  • the digital-to-analog expansion unit is used to perform baseband processing operations on the downlink digital radio frequency signal transmitted by the source unit via optical fiber through the first baseband processing module inside the digital-to-analog expansion unit, and to perform baseband processing operations through the first signal conversion module inside the digital-to-analog expansion unit Digital-to-analog conversion to obtain the downlink analog radio frequency signal to be sent to the remote cascade chain; or, the digital-to-analog expansion unit is used to perform analog-to-digital conversion on the uplink analog radio frequency signal transmitted by the remote cascade chain through the first signal conversion module, And the baseband processing operation is performed by the first baseband processing module to obtain the uplink digital radio frequency signal to be sent to the source unit through the optical fiber.
  • the remote unit is used to perform analog radio frequency signal interaction with the terminal equipment, and the analog radio frequency signal interaction is performed between two adjacent remote units through a radio frequency cable.
  • the digital-to-analog expansion unit is connected to the remote cascade chain through a radio frequency cable, and a single digital-to-analog expansion unit can be connected to multiple remote cascade chains respectively, and connect to the remote cascade chain through the radio frequency cable
  • the end cascade chain carries out analog radio frequency signal transmission.
  • Multiple remote units in the remote cascading chain are cascaded in turn via radio frequency cables.
  • the remote unit at the first stage of the remote cascading chain is connected to the digital-analog expansion unit to form a daisy chain topology; between adjacent remote units Analog radio frequency signal transmission through radio frequency cable.
  • the digital-to-analog expansion unit can be connected to the source unit through an optical fiber, and uses the optical signal mode to transmit digital radio frequency signals with the source unit.
  • the digital-to-analog expansion unit is used for baseband processing of external data, and is also used for analog-to-digital conversion or digital-to-analog conversion; among them, the external data is data outside the digital-to-analog expansion unit, such as data from a remote unit, Data of the source unit, etc.
  • a baseband processing module and a signal conversion module are arranged inside the digital-to-analog expansion unit.
  • the remote unit is used to achieve signal coverage and perform uplink and downlink analog radio frequency signal transmission with terminal equipment.
  • a communication link module is provided inside the remote unit, including radio frequency devices such as antennas and filters.
  • multiple remote units receive uplink analog radio frequency signals through their respective antennas; the current remote unit can filter and amplify the received uplink analog radio frequency signals, and then transmit them to the previous one through the radio frequency cable.
  • Level remote unit receives the signal of the next-level remote unit, and combines it with the signal received through the antenna and processed by itself, and the combined signal continues to be transmitted to the upper-level remote unit through the radio frequency cable Or digital-analog expansion unit.
  • the digital-analog expansion unit receives a remote unit combined signal transmitted by a remote cascade chain, converts the combined uplink analog radio frequency signal into an uplink digital radio frequency signal and performs baseband processing, and then converts the uplink digital radio frequency obtained by the baseband processing The signal is optically sent to the source unit.
  • the source unit sends the downlink digital radio frequency signal optically (optical fiber), that is, the downlink optical signal, to the digital-to-analog expansion unit; after the digital-to-analog expansion unit performs baseband processing on the received downlink digital radio frequency signal, Through digital-to-analog conversion, the downlink analog radio frequency signal is obtained, and the downlink analog radio frequency signal is transmitted to the remote cascade chain through the radio frequency cable; each remote unit in the remote cascade chain couples the downlink analog radio frequency signal from the radio frequency cable, After filtering and amplifying the signal, it is transmitted through a radio frequency antenna to achieve signal coverage.
  • optical fiber optical fiber
  • the digital-to-analog expansion unit performs baseband processing on the received downlink digital radio frequency signal.
  • the downlink analog radio frequency signal is obtained, and the downlink analog radio frequency signal is transmitted to the remote cascade chain through the radio frequency cable; each remote unit in the remote cascade chain couples the downlink analog radio frequency signal from the radio frequency cable, After filtering and amplifying the signal
  • the digital-to-analog expansion unit may use optical fiber to connect the source unit, and use digital optical fiber transmission to diversify the source access, that is, the source unit may be a BBU (Building Baseband Unit, baseband processing unit) , Or RRU (Radio Remote Unit, remote radio unit).
  • the digital-analog expansion unit and the remote cascade chain are connected by radio frequency cables.
  • the digital-analog expansion unit can couple power signals, monitoring signals, etc. in the radio frequency cable; the remote unit can couple power signals, etc. from the radio frequency cable to realize radio frequency signals Based on this, the number of remote units on the remote cascade chain can be set according to the actual signal coverage requirements.
  • the unit is enough to facilitate the evolution and expansion of the system. Compared with the traditional DAS, it can achieve higher power and more flexible power coverage, and can monitor the remote units to obtain the configuration information, alarm information, and Status information and insertion loss information, etc.
  • the distributed antenna system needs to be equipped with multiple remote units to ensure the full coverage of the signal, at the same time, with the increase of bandwidth, the performance of the devices on the remote unit must be upgraded and matched accordingly. Therefore, the remote unit in the system
  • the cost ratio is large, and the power consumption ratio is also high.
  • the baseband processing module and the signal conversion module are provided in the digital-to-analog expansion unit, and the remote unit does not need to set up the baseband processing device, which saves the cost of the baseband processing device (such as FPGA, ASIC (Application Specific Integrated Circuit)) ,As shown in Figure 4.
  • each remote unit of the remote cascade chain uses radio frequency cables as the cascaded transmission medium, which can effectively reduce construction costs and power consumption. ;
  • the remote unit does not need to be equipped with optical processing devices, Ethernet transmission circuits, etc., which can further reduce costs.
  • the cost of the baseband processing device and the transmission medium is high, and the power consumption is high. Based on the system provided by the embodiment of the application, the construction cost can be greatly reduced. Power consumption can be reduced accordingly.
  • the remote units adopt a daisy chain topology for cascading.
  • the star topology adopted by the new indoor sub-system it can greatly reduce the difficulty of engineering construction, save the use of radio frequency cables, and reduce construction cost.
  • radio frequency cables are used to connect the digital-analog expansion unit and the remote unit, and between two adjacent remote units. Passive components on radio frequency cables and links can transmit as long as they meet the cut-off frequency requirements.
  • the current passive components of traditional DAS support 700M (MHz) to 2.7G (Gigahertz), as in the embodiment of this application To meet the domestic 5G construction, only 700M to 3.5G passive components need to be selected, and the transmission bandwidth is basically unlimited, as shown in Figure 7.
  • digital optical fiber or network cable is usually used for transmission, and the radio frequency signal needs to be digitized, and then transmitted through the CPRI (Common Public Radio Interface) protocol, which has relatively large restrictions on the digital transmission bandwidth.
  • the remote unit realizes 4T4R MIMO, signal coverage of 100MHz (megahertz) bandwidth, and when standard CPRI transmission is used, its transmission bandwidth is:
  • 122.88MHz means 100MHz bandwidth signal transmission rate
  • 2 means IQ two channels
  • 15 means transmission bit width
  • 16/15 means transmission control overhead
  • 10/8 means transmission code
  • 4 means number of antennas. That is, if you want to cover 4T4R/100MHz signals, use digital optical fiber or network cable, and transmit based on standard CPRI, a transmission rate of 19.66Gbps (gigabits per second) is required, and optical modules and FPGA devices that support 25Gbps are required.
  • the cost is very high.
  • the Ethernet currently only supports up to 10 Gbps, which is difficult to meet the requirements; and if the transmission rate is to be reduced, compression is required, which will increase the complexity of the system implementation.
  • Radio frequency cable with a small diameter and weight can be selected as the transmission medium, and at the same time, the remote unit can compensate the insertion loss in radio frequency transmission through active radio frequency amplification. Due to the small diameter, multiple radio frequency cables can be bundled into one cable, which is convenient for construction. As shown in Figure 8, four RF cables are combined into a bundled RF cable, which can meet the requirements of 4T4R.
  • the digital-to-analog expansion unit includes a first optical transceiver module, a first baseband processing module, a first signal conversion module, and a radio frequency front-end module connected in sequence.
  • the first optical transceiver module is used for optical signal interaction with the source unit.
  • the first baseband processing module is used to perform baseband processing on the received signal and output it.
  • the first signal conversion module is used for digital radio frequency signal interaction with the baseband processing module and analog radio frequency signal interaction with the radio frequency front-end module.
  • the RF front-end module is used to perform analog RF signal interaction with the remote unit, and is used to perform analog RF signal processing.
  • the first optical transceiver module can be used for mutual transmission of optical signals with the source unit to realize mutual conversion between optical signals and digital radio frequency signals, and can also be used for mutual transmission of digital radio signals with the first baseband processing module .
  • the first optical transceiver module may include at least one optical transceiver.
  • the first baseband processing module may be used to perform baseband processing on the digital radio frequency signal transmitted by the first optical transceiver module, and transmit the processed digital radio frequency signal to the first signal conversion module.
  • the first baseband processing module can also be used to process the digital radio frequency signal transmitted by the first signal conversion module, and transmit the processed digital radio frequency signal to the first optical transceiver module.
  • the processing method of the first baseband processing module for the digital radio frequency signal includes any one or any combination of the following processing methods: digital combining, signal framing, signal deframing, serial-parallel conversion, parallel-serial conversion, clock recovery, and Digital IF processing, etc.
  • the first baseband processing module may be FPGA or ASIC, etc., which is not specifically limited here.
  • the first signal conversion module can be used to perform digital-to-analog conversion on the digital radio frequency signal transmitted by the first baseband processing module, and send the analog radio frequency signal obtained by the digital-to-analog conversion to the radio frequency front-end module.
  • the first signal conversion module can also be used to perform analog-to-digital conversion on the analog radio frequency signal transmitted by the radio frequency front-end module, and send the digital radio frequency signal obtained by the analog-to-digital conversion to the first baseband processing module.
  • the first signal conversion module may include a digital-to-analog converter and an analog-to-digital converter, etc., which is not specifically limited here.
  • the RF front-end module can be used to process the analog RF signal transmitted by the first signal conversion module and send it to the remote cascade chain; and can also be used to process the analog RF signal transmitted by the remote cascade chain and send it to the second A signal conversion module.
  • the radio frequency front-end module processing analog radio frequency signal includes any one or any combination of the following processing methods: filtering, frequency conversion, and amplification.
  • the radio frequency front-end module may include filters, frequency converters, amplifiers, etc., which are not specifically limited here.
  • the first baseband processing module, the first signal conversion module, and the RF front-end module can each have multiple processing channels for processing signals of multiple communication channels to meet communication requirements such as 2T2R and 4T4R.
  • the distributed antenna system includes at least two digital-to-analog extension units, one of which is connected to the source unit through an optical fiber, and two adjacent digital-to-analog extension units pass through their respective first An optical transceiver module performs optical fiber cascading.
  • the source unit can be connected to other digital-analog extension units through one of the digital-analog extension units to realize signal interaction with each digital-analog extension unit. Based on this, the number of optical ports that need to be set up for the source unit can be reduced, and system construction costs can be reduced.
  • a distributed antenna system includes a first-stage digital-to-analog expansion unit containing at least 3 optical interfaces, and multiple second-stage digital-to-analog expansion units containing 2 optical interfaces; the source unit can pass through the first-stage digital-analog expansion unit.
  • the expansion unit is connected to each second-stage digital-analog expansion unit, and the second-stage digital-analog expansion unit can also be cascaded to the next-stage digital-analog expansion unit through optical fiber; wherein, the number of the second-stage digital-analog expansion unit can be less than or equal to the first The number of optical interfaces of the first-level digital-analog expansion unit.
  • the digital-to-analog expansion units can also be connected in cascade via optical fibers to form a daisy-chain topology.
  • the digital-to-analog expansion units at the first stage are connected to the source units via optical fibers. Based on this, each digital-to-analog expansion unit only needs Two optical interfaces, no need for interface expansion, can reduce the demand for transmission media, and can reduce the number of optical interfaces that need to be installed in the source unit, and reduce the cost of system construction.
  • a star topology, a daisy chain topology, and a mixed topology of star and daisy chain can be formed between the source unit and each digital-analog expansion unit.
  • the digital-analog extension unit can broadcast the downlink digital radio frequency signal transmitted by the source unit to the next-level cascaded digital-analog extension unit, and can also transmit the upstream optical signal obtained by itself through the upper-level cascaded digital-analog extension unit and transmission To the source unit.
  • the number of remote cascade chains is at least two, and one digital-analog expansion unit is correspondingly connected to at least one remote cascade chain; the radio frequency front-end modules of each digital-analog expansion unit are respectively connected to the corresponding The first remote unit of each remote cascade chain.
  • the digital-to-analog expansion unit can be connected to multiple remote cascade chains according to signal coverage requirements, and perform analog radio frequency signal transmission with each remote cascade chain.
  • the first remote unit of each remote cascade chain is connected to the radio frequency front-end module of the digital-analog expansion unit; the radio frequency front-end module can set a corresponding signal processing channel for each remote cascade chain.
  • the digital-to-analog expansion unit can be extended to connect multiple remote cascade chains, thereby being able to flexibly design signal coverage to meet the layout requirements of a variety of indoor structures with high applicability.
  • the digital-to-analog expansion unit is further used for framing the downlink digital radio frequency signal transmitted by the source unit, and transparently transmit the framing digital radio frequency signal to the adjacent digital-to-analog expansion unit through the optical fiber.
  • the downlink digital radio frequency signal can be transmitted by broadcast, and when it enters the digital-to-analog expansion unit for baseband processing, it can be divided into two channels.
  • One channel can undergo deframing, intermediate frequency, up-conversion, digital filtering, digital-to-analog conversion, and RF front-end, etc.
  • After processing, it is coupled to the radio frequency cable and sent to the remote cascade chain; the other can be framed to add control information, and the signal obtained by the frame can be transparently transmitted to the next-level digital-to-analog expansion unit through the optical fiber.
  • the cascaded digital-analog extension unit can quickly send the downlink signal transmitted by the source unit to the next-level cascade unit, which is convenient for the next-level digital-analog extension unit to perform signal processing and coverage, and can reduce system construction costs. At the same time, ensure the timeliness of signal transmission in the system.
  • the digital-analog expansion unit is further configured to determine whether to digitally combine the received multiple signals according to whether the characteristics of the multiple signals received by the current digital-analog expansion unit are the same:
  • the first uplink digital radio frequency signal is the same as that of the second uplink digital radio frequency signal
  • the first uplink digital radio frequency signal and the second uplink digital radio frequency signal are digitally combined to obtain the current digital-analog expansion unit
  • Three uplink digital radio frequency signals the third uplink digital radio frequency signal is converted, the uplink optical signal of the current digital-analog expansion unit is obtained and sent to the upper-level digital-analog expansion unit or the source unit; wherein, the first uplink digital radio frequency signal is The current digital-analog extension unit processes the upstream optical signal of the next-level digital-analog extension unit;
  • the second upstream digital radio frequency signal is the upstream analog radio frequency of the remote cascade chain connected by the current digital-analog extension unit to the current digital-analog extension unit
  • the signal is obtained by analog-to-digital conversion and baseband processing;
  • the first uplink digital radio frequency signal and the second uplink digital radio frequency signal are respectively converted to obtain the corresponding uplink optical signal and sent to Upper-level digital-analog expansion unit or source unit.
  • the digital-to-analog expansion unit can receive the signals of each remote cascade chain connected to itself, and the signals of the cascaded digital-to-analog expansion units, and according to the signal characteristics, digitalize the signals with the same signal characteristics in the multiple signals. Combining, in turn, can reduce the bandwidth occupied by the signal when it is transmitted to the source unit, and improve the utilization of transmission media and devices.
  • the signal characteristics include any one or any combination of the following parameters: standard, frequency band, cell, etc.
  • the next-stage digital-to-analog expansion unit transmits the uplink digital radio frequency signal it obtains to the current digital-to-analog expansion unit through optical fiber; if the transmitted uplink digital radio frequency signal is the same as the current digital
  • the uplink digital radio frequency signal processed by the modulus expansion unit has the same characteristics (for example, the same standard, the same frequency band, and the same cell), and it needs to be digitally added (belonging to digital combination), and then the added uplink digital radio frequency signal is converted
  • the optical signal is transmitted to the upper-level digital-analog expansion unit or source unit.
  • the signal transmitted from the next level needs to be transparently transmitted to the upper level digital-to-analog expansion unit or the source unit.
  • the signal transmitted at the next level can be digitally added, it does not occupy the bandwidth of the current digital-to-analog expansion unit for the upper level transmission; if the signal transmitted at the next level needs to be transparently transmitted to the upper level, the signal needs to occupy Additional transmission bandwidth.
  • the above-mentioned signal characteristic may be the signal standard, frequency band, or cell to which it belongs. It should be noted that the signal characteristic does not involve the information content carried by the signal.
  • the digital-to-analog expansion unit further includes a first monitoring circuit, a power supply circuit, and a first coupler connected to the first remote unit of the remote cascade chain through a radio frequency cable.
  • the first coupler is respectively connected to the first baseband processing module, the radio frequency front-end module, the first monitoring circuit and the power supply circuit; the first coupler is used to couple the uplink and downlink switching signals generated by the first baseband processing module to the radio frequency cable, At least one operation of coupling the power signal to the radio frequency cable, performing monitoring signal interaction with the remote unit, and performing analog radio frequency signal interaction with the remote unit.
  • the digital-to-analog expansion unit further includes a first coupler connected between the radio frequency front-end module and the remote cascade chain, and a first monitoring circuit and a power supply circuit connected to the first coupler.
  • the first monitoring circuit is used for the generation and processing of the monitoring signal, and the monitoring signal can be coupled to the radio frequency cable through the first coupler to monitor the status information, equipment information and alarm information of each remote unit; optionally,
  • the first monitoring circuit can be a circuit that generates and processes low-speed radio frequency signals, where low-speed radio frequency signals such as Bluetooth signals, FSK (Frequency-shift Keying) signals, etc., do not interfere with other signals on the radio frequency cable signal.
  • the first monitoring circuit may include a first processor, and a first Bluetooth chip connected between the first processor and the first coupler.
  • the power circuit is used to generate a power signal and couple it to the radio frequency cable through the first coupler to provide a power signal to each remote unit, facilitating the remote unit to amplify the radio frequency signal.
  • the first baseband processing module can also be used to generate uplink and downlink switching signals, and couple them to the radio frequency cable through the first coupler, so as to drive the remote unit to achieve TDD (Time Division Duplexing, Time Division Duplexing) coverage.
  • the first coupler is used to couple downlink analog radio frequency signals, uplink and downlink switching signals, power signals, and monitoring signals to the radio frequency cable, so that each remote unit in the remote cascade chain can couple corresponding signals in the radio frequency cable;
  • a coupler can also be used to couple from the radio frequency cable to obtain the uplink analog radio frequency signal and monitoring signal transmitted by the remote unit.
  • the RF front-end module can be zero-IF, superheterodyne or direct RF sampling, etc.; when the monitoring signal and power signal are coupled to the RF cable through the first coupler, they can be coupled to a RF cable or Coupled to multiple radio frequency cables to ensure that each remote unit has power signal and monitoring signal feeding.
  • the digital-to-analog expansion unit can couple various signals to the radio frequency cable through the coupler, which facilitates the acquisition of signals by each remote unit, enriches the functionality of the remote unit, and reduces the system’s impact on the transmission medium. Demand.
  • the digital-analog hybrid expansion unit is mainly composed of a multiplexer (or duplexer), a coupler, a radio frequency front end, a baseband processing, a digital-analog/analog-to-digital converter, and an optical transceiver.
  • a multiplexer or duplexer
  • a coupler for the 1T1R system, only one radio frequency cable is required for transmission; for the MIMO system, multiple radio frequency cables are required, or the MIMO signals of the same frequency band are converted and transmitted on the same cable.
  • the digital-analog hybrid expansion unit has at least two optical transceivers, one is connected to the source unit or the upper-level digital-analog hybrid expansion unit, and the other is connected to another digital-analog expansion unit.
  • the baseband processing can be implemented by FPGA or ASIC with the same function.
  • the baseband processing of the current digital-to-analog expansion unit obtains the digital radio frequency signal through the optical transceiver, from the source unit or the upper-level digital-to-analog expansion unit, after clock recovery, serial-to-parallel conversion, de-framing, rate conversion, After digital up-conversion and other processing, it is sent to the digital-to-analog converter and converted into an analog RF signal and sent to the RF front-end module. After filtering, frequency conversion, amplification and other processing, it is sent to the multiplexer, and then fed through the first coupler. To the RF cable.
  • the first coupler couples the analog radio frequency signal from the radio frequency cable, which is filtered by the multiplexer and enters the radio frequency front end for amplification, filtering and frequency conversion processing.
  • the RF signal processed by the RF front-end is converted into a digital RF signal through an analog-to-digital converter.
  • baseband processing such as digital down conversion (DDC), rate conversion, framing, and parallel-to-serial conversion, it is converted into
  • the optical signal is transmitted to the upper-level digital-to-analog expansion unit or source unit.
  • the remote unit needs to restore the uplink and downlink switch for switching between uplink and downlink signals. If the remote unit cannot obtain the signal to restore the switch from the radio frequency signal, the digital-to-analog expansion unit needs to directly provide the uplink and downlink switching signals through the radio frequency cable.
  • the remote unit includes at least one communication link module; two adjacent remote units are connected by multiple radio frequency cables, preferably, they can be connected by a bundled cable. It includes at least one radio frequency cable, and one radio frequency cable is correspondingly connected to a communication link module of the next-level remote unit.
  • the remote unit may be provided with multiple communication link modules for coupling and processing analog radio frequency signals corresponding to the communication channels from the radio frequency cable.
  • the radio frequency cables in the system can be configured as a bundled radio frequency cable including multiple radio frequency cables; a communication link module is connected to a communication link module of the next-level remote unit through one of the radio frequency cables, or through one of the radio frequency cables.
  • the cable connects the digital-analog expansion unit.
  • the remote unit may include 4 communication link modules, and the bundled radio frequency cable includes 4 radio frequency cables, and each cable is used to realize 1T1R antenna radio frequency transmission; the radio frequency cable in the bundled radio frequency cable It can be connected to the communication link module in the remote unit in a one-to-one correspondence, so as to satisfy 4T4R radio frequency transmission.
  • the communication link module may be mainly composed of a coupler, a filter, a DC isolation circuit, an amplifier, an antenna, etc., which are not specifically limited here. It should be noted that on the same radio frequency cable, multiple signals in different frequency bands can be supported for transmission, but a multiplexer is required to separate or combine the uplink and downlink, and then can be covered on different antennas.
  • the communication link module includes a second coupler, a radio frequency interactive circuit, a second monitoring circuit, a power conversion circuit, and an uplink and downlink switching circuit.
  • the second coupler is connected to the first coupler or the communication link module of the upper-level remote unit through a radio frequency cable; the second coupler is respectively connected to the radio frequency interactive circuit, the second monitoring circuit, the power conversion circuit and the uplink and downlink switching circuit;
  • the radio frequency interactive circuit is respectively connected to the power conversion circuit and the uplink and downlink switching circuit.
  • the second coupler is used to perform power signal acquisition, uplink and downlink switching signals, monitoring signal interaction with the digital-analog expansion unit, analog radio frequency signal interaction with the digital-analog expansion unit, and analog radio frequency signal with the next-level remote unit At least one operation in the interaction.
  • the communication link module includes a second coupler connected to the radio frequency cable, which is used to communicate with the first coupler, the communication link module of the upper-level remote unit, or the communication link module of the next-level remote unit. Analog radio frequency signal transmission.
  • the first port of the second coupler is connected to the first coupler or the communication link module of the upper-level remote unit through a radio frequency cable
  • the second port is connected to the communication link module of the next-level remote unit
  • the third The ports are respectively connected to the radio frequency interactive circuit, the second monitoring circuit, the power conversion circuit and the uplink and downlink switching circuit in the communication link module.
  • the radio frequency interaction circuit is used for radio frequency signal interaction with external terminals, and may include components such as filters, amplifiers, and antennas.
  • the radio frequency interactive circuit can obtain the analog radio frequency signal from the radio frequency cable through the second coupler, and after filtering, amplifying, and other processing, it is transmitted by the antenna; the radio frequency interactive circuit can also obtain the analog radio frequency signal transmitted by the external terminal through the antenna After filtering, amplifying, etc., it is coupled to the radio frequency cable through the second coupler, and then can be transmitted to the digital-to-analog expansion unit.
  • the second monitoring circuit can be used to obtain and process the monitoring signal through the second coupler, and can also feed back the monitoring signal through the second coupler to realize the monitoring signal interaction between the remote unit and the digital-analog expansion unit.
  • the second monitoring circuit may generate and process low-speed radio frequency signals, such as Bluetooth signals, FSK signals, etc.; the second monitoring circuit may feed back current status information, equipment signals, or alarm information of the remote unit through the monitoring signals.
  • the second monitoring circuit may include a second processor and a second Bluetooth chip connected between the second processor and the second coupler.
  • the second processor may be connected to the attenuator of the radio frequency interactive circuit to control the radio frequency interactive circuit. The attenuation value in.
  • the power conversion circuit can be used to obtain the power signal through the second coupler and convert the power signal to obtain the standard power required by each device in the remote unit to meet the active amplification of the radio frequency interactive circuit; specifically, the coupling on the radio frequency cable
  • the voltage is usually 48V (Volt), which needs to be converted to 5V, 3.3V, etc.
  • the uplink and downlink switching circuit can be used to obtain the uplink and downlink switching signals through the second coupler, control the uplink and downlink switching of the RF interactive circuit, and realize the coverage of the TDD standard signal; optionally, the uplink and downlink switching signals can also be directly extracted from the analog radio frequency signal .
  • the remote unit in the embodiment of the present application can obtain downlink analog radio frequency signals, monitoring signals, and power signals from the radio frequency cable through a coupler to achieve signal coverage.
  • the device has a simple structure and low cost, which is beneficial to the system. Expansion.
  • the remote unit is also used to obtain the first uplink analog radio frequency signal of the terminal, and the second uplink analog radio frequency signal transmitted by the next-level remote unit, and compare the first uplink analog radio frequency signal and the second uplink analog radio frequency.
  • the signals are combined to obtain the uplink analog radio frequency signal of the current remote unit; the uplink analog radio frequency signal is transmitted to the upper remote unit or digital-analog extension unit.
  • the current remote unit obtains the uplink analog radio frequency signal of the external terminal through radio frequency interaction; at the same time, the current remote unit also obtains the next-level remote unit transmission
  • the uplink analog radio frequency signal is combined with the obtained uplink analog radio frequency signal, and the combined uplink analog radio frequency signal is transmitted to the upper-level remote unit or digital-analog extension unit to realize the transmission of the uplink radio frequency signal.
  • the distributed antenna system further includes a source unit connected to the digital-to-analog extension unit.
  • the source unit is a BBU or RRU; if the source unit is an RRU, the distributed antenna system also includes an access unit connected between the RRU and the digital-to-analog extension unit.
  • the access unit is used to perform baseband processing operations on the received external signals through the second baseband processing module inside the access unit, and to perform analog radio frequency signals and digital radio frequency signals through the second signal conversion module inside the access unit In the mutual conversion operation, the third uplink analog radio frequency signal to be sent to the RRU or the downlink digital radio frequency signal to be sent to the digital-to-analog expansion unit is obtained.
  • the source unit can be a BBU, which can directly process baseband signals, and is used to add received digital radio frequency signals of the same signal characteristics (same standard, same frequency band, and same cell); and the signal obtained by the addition Baseband signal processing such as demodulation and decoding is implemented in the source unit; if it is a signal with different signal characteristics, it needs to be allocated to different baseband units for baseband signal processing.
  • the source unit can also be an RRU.
  • the access unit is required to convert the analog radio frequency signal of the RRU into a digital radio frequency signal and transmit it to the digital-to-analog extension unit via optical fiber; and the access unit also adds the digital signal of the digital-to-analog extension unit.
  • the radio frequency signal is converted into an analog radio frequency signal and sent to the RRU.
  • the access unit is also used to perform baseband processing operations on various external signals, for example, deframing, digital combining, framing, and digital intermediate frequency processing on digital radio frequency signals. Based on this, the access unit can deframe, combine and convert the transmission signals of multiple digital-analog extension units, and then send the obtained multiple analog radio frequency signals to the RRU for processing through the corresponding radio frequency cable; at the same time, the access unit After conversion, intermediate frequency processing and framing of multiple analog radio frequency signals transmitted by RRU, they are sent to each digital-to-analog expansion unit through optical ports.
  • the access unit includes a second optical transceiver module, a second baseband processing module, a second signal conversion module, and a radio frequency channel module connected in sequence.
  • the second optical transceiver module is used for optical signal interaction with the digital-analog expansion unit.
  • the second baseband processing module is used to perform baseband processing on the received signal and output it.
  • the second signal conversion module is used for digital radio frequency signal interaction with the second baseband processing module and analog radio frequency signal interaction with the radio frequency channel module.
  • the radio frequency channel module is used for analog radio frequency signal interaction with the RRU and used for analog radio frequency signal processing.
  • the digital-analog expansion unit and the remote unit adopt a daisy chain topology based on cable connection, which can increase the transmission bandwidth while effectively reducing the cost of the transmission link; and the digital-analog expansion unit Perform baseband processing, the remote unit does not need baseband processing equipment, which can effectively reduce the cost of the system's components and operating power consumption.
  • the coverage of the remote unit is not limited by bandwidth and supports multiple signal access coverage.
  • the system has the characteristics of supporting multi-mode, multi-frequency, and cell splitting, which is easy to expand and has low construction difficulty.
  • a signal transmission method is provided, which is applied to the above-mentioned distributed antenna system, and includes the steps:
  • the remote unit obtains the first uplink analog radio frequency signal of the terminal and the second uplink analog radio frequency signal transmitted by the next-level remote unit.
  • the remote unit combines the first uplink analog radio frequency signal and the second uplink analog radio frequency signal to obtain the uplink analog radio frequency signal of the current remote unit, and transmits the uplink analog radio frequency signal of the current remote unit to the upper remote Unit or digital-analog expansion unit.
  • the digital-to-analog expansion unit performs analog-to-digital conversion and baseband processing on the acquired uplink analog radio frequency signal, and obtains the uplink digital radio frequency signal to be sent to the source unit via optical fiber.
  • a signal transmission method is also provided, which is applied to the above-mentioned distributed antenna system, including the steps:
  • the digital-to-analog expansion unit performs baseband processing and digital-to-analog conversion on the downlink digital radio frequency signal transmitted by the source unit through the optical fiber to obtain the downlink analog radio frequency signal, and transmits the downlink analog radio frequency signal to the remote cascade chain.
  • the remote unit obtains the downlink analog radio frequency signal, and transmits the downlink radio frequency signal based on the downlink analog radio frequency signal.
  • the number of digital-to-analog expansion units is at least two; two adjacent digital-to-analog expansion units are cascaded by optical fibers through their respective optical transceiver modules, and the digital-to-analog expansion unit is located at the first stage.
  • the signal source unit is connected through an optical fiber; the above-mentioned signal transmission methods may further include the steps:
  • the digital-to-analog expansion unit digitally combines the first uplink digital radio frequency signal and the second uplink digital radio frequency signal to obtain the current digital-analog
  • the third uplink digital radio frequency signal of the expansion unit converts the third uplink digital radio frequency signal to obtain the uplink optical signal of the current digital-analog expansion unit and sends it to the upper-level digital-analog expansion unit or the source unit; among them, the first uplink
  • the digital radio frequency signal is obtained by processing the upstream optical signal of the next-stage digital-analog expansion unit by the current digital-analog expansion unit;
  • the second upstream digital radio-frequency signal is the remote cascade chain connecting the current digital-analog expansion unit to the current digital-analog expansion unit
  • the uplink analog radio frequency signal is obtained by analog-to-digital conversion and baseband processing;
  • the digital-to-analog expansion unit respectively converts the first uplink digital radio frequency signal and the second uplink digital radio frequency signal to obtain the corresponding uplink optical signal.
  • the signal is sent to the upper-level digital-analog expansion unit or source unit.
  • the digital-analog extension unit framing the downlink digital radio frequency signal transmitted by the source unit, and transparently transmits the framing digital radio frequency signal to the next-level digital-analog extension unit through optical fiber.
  • the communication system may include 1 source unit, 4 digital-analog expansion units and 32 remote units.
  • the source unit can be a BBU or mainly composed of RRU and access modules; each base station unit, that is, the source unit, is connected to 4 digital-analog expansion units; each digital-to-analog expansion unit is connected to 8 remote units .
  • the cables on the 4T4R communication link are all bundled cables including 4 sub-cables, and each sub-cable is used to realize 1T1R antenna radio frequency transmission.
  • the structure of the remote unit can be as shown in Figure 12, including 4 communication link modules corresponding to the sub-cables respectively.
  • each sub-cable in the bundled cable is connected to a coupler when it is connected to the remote unit; based on this, the remote unit can couple out the signals in each sub-cable separately, and at the same time, the power of the signal in the cable passes through the coupler
  • the insertion loss is relatively small and can be sent to the next remote unit through a cable.
  • the downlink radio frequency signal is coupled out of the coupler and then amplified by a filter (the TDD signal is a filter), a power amplifier, and then filtered and transmitted from the antenna.
  • the uplink radio frequency signal is received from the antenna, filtered by the filter, amplified by the low-noise amplifier, filtered by the filter, and coupled to the cluster cable from the coupler.
  • the digital-analog expansion unit can be shown in Figure 15, including two optical ports, one of which is the main optical port for connecting to the upper-level digital-analog expansion unit or source unit, and the other is a cascaded optical port for connection The next-level digital-analog expansion unit.
  • the downlink signal of the main optical port is transmitted in broadcast mode, and is divided into two channels after entering the FPGA; one of the channels is divided into four channels after deframing, corresponding to the downlink signals of the four antennas, and respectively enters the corresponding digital intermediate frequency module for DUC ( Digital Up Conversion), digital filtering, etc., are processed by digital-to-analog conversion and RF front-end processing, and then transmitted to the corresponding cable and sent to the remote cascade chain; the other way, through a framing module, add some control information Then transparently transmit to the cascaded optical port.
  • the four upstream signals from the remote unit are processed by the corresponding radio frequency front-end through the bundled cable, and then converted into digital signals.
  • the FPGA After the analog-to-digital conversion, they enter the FPGA.
  • the FPGA first passes through the digital intermediate frequency module, performs DDC and digital filter processing, and then enters the digital addition module.
  • the digital addition module and the upstream signal of the cascaded optical port undergo digital addition processing (digital combination), the same antenna and RF channel signals can be combined.
  • the source unit can be directly a BBU, which is used to directly perform baseband signal processing such as demodulation and decoding of the digital radio frequency signal transmitted by the digital-to-analog extension unit, as shown in Figure 17; the source unit can also be an RRU, and the system also includes The access unit connected between the RRU and the digital-analog expansion unit is shown in Figure 17.
  • the access unit can be used for radio frequency and digital conversion, digital radio frequency signal interaction with the digital-to-analog expansion unit, and analog radio frequency signal interaction with the RRU.
  • the access unit can be configured with 4 optical ports (other numbers are possible).
  • the signals sent by each digital-to-analog expansion unit are digitally added and combined according to the same signal characteristics, namely:
  • the total channel 2, 3, and 4 signals are obtained, and then sent to the corresponding signal intermediate frequency processing link for processing, and finally converted into an analog radio frequency signal and sent to the corresponding port of the 4T4R RRU.
  • 4 downlink signals are fed from the RRU port to the access module, and after the corresponding radio frequency channel processing, analog-to-digital conversion, signal intermediate frequency processing, framing is performed, and the framing signal is broadcast to each optical Port, that is, the downstream signal of each optical port may include the signals of channels 1, 2, 3, and 4.
  • the 4T4R/100MHz bandwidth signal uses standard CPRI transmission, it must meet the transmission rate of 19.6GBps and require 25G optical transceiver modules , At this time will greatly increase transmission costs and equipment costs.
  • the embodiments of the present application may use non-standard CPRI for transmission through CPRI compression:
  • 122.88MHz means 100MHz bandwidth signal transmission rate
  • 2 means IQ two channels
  • 15 means transmission bit width
  • 16/15 means transmission control overhead
  • 10/8 means transmission code
  • 4 means number of antennas.
  • the transmission rate is less than 10Gbps, and 10G optical modules and FPGAs can be used, which greatly reduces the cost.
  • the digital-to-analog expansion unit in the embodiment of the present application can be fed with a power supply signal, a TDD switching signal and a monitoring signal matched with the remote unit on a cable.
  • the monitoring signal can be transmitted using Bluetooth signals, or FSK or other low-speed radio frequency signals. Just ensure that the selected frequency band interferes with other signals.
  • the Bluetooth frequency band is 2.4G, and the coverage signal is not in the same frequency band as 2.6G.
  • the power supply can usually use a 48V power supply, coupled to the cable through a coupler or combiner with DC coupling for transmission.
  • the TDD switch signal can also be directly coupled to the radio frequency cable.
  • the signal extraction can be as shown in Figure 20, coupled through a coupler, the DC power signal passes through a low-pass filter to filter out high-frequency signals and transmit to the power conversion circuit , Get the power needed by the remote unit.
  • the TDD switching circuit can isolate the DC power signal through the DC isolation circuit, and after passing through the band-pass filter, the switching signal for switching the upstream and downstream signals is obtained.
  • the Bluetooth chip can be used to realize the transmission of monitoring signals, isolate the DC power signal through the DC isolation circuit, and receive the monitoring signal sent by the digital-to-analog expansion unit after passing through the band pass filter; at the same time, the remote unit's MCU can also feed back through the Bluetooth chip Monitor the signal to the digital-analog expansion unit to realize two-way communication.
  • the downlink radio frequency signal that is finally covered also needs to be transmitted by the antenna after passing through the DC isolation circuit and filter.
  • the remote unit uses the radio frequency cable for analog radio frequency signal transmission, the radio frequency cable may cause signal insertion loss.
  • the embodiment of the present application uses a daisy chain cascade method to make the same daisy chain (ie, remote cascade)
  • the length of the RF cable between each remote unit on the chain and the digital-analog expansion unit is inconsistent, as shown in Figure 21.
  • the remote unit can amplify the signal through an amplifier to compensate for the cable insertion loss.
  • the gain of different remote units can be controlled by setting a digitally controlled attenuator to match the corresponding insertion loss.
  • the specific process can be as follows:
  • the MCU Microcontroller Unit
  • the MCU Microcontroller Unit
  • the digital-analog expansion unit sends The Bluetooth signal of fixed power Pt_bluetooth to the cable is assumed to be 0dBm; each remote unit will receive the Bluetooth signal and measure the received power Pr_bluetooth. Because the length of the radio frequency cable is inconsistent, the power value received by each remote unit is also Inconsistent; according to the measured power value, the remote unit can calculate the signal insertion loss Ploss between itself and the digital-analog expansion unit, for example:
  • the cable length can be obtained according to the cable insertion loss characteristics (corresponding to the 2.4G frequency band of the Bluetooth signal); and then the insertion loss value of the required coverage signal frequency band (such as mobile 2.6G) can be obtained according to the cable length. Match by adjusting the digital attenuator.
  • the insertion loss value of 2.6G is 30dB
  • the downlink amplification gain of the remote unit is 50dB
  • the attenuation value of 20dB can be set to match the remote gain and line insertion loss.
  • the attenuation setting needs to be reduced.
  • the signal output power of the digital-to-analog expansion unit is 15dBm
  • the cable loss is 30dBm
  • the remote unit needs to output 23dBm
  • the maximum gain of the remote end is still 50dBm
  • a gain control method is provided, which is applied to the above-mentioned distributed antenna system.
  • the gain control method includes the steps:
  • the remote unit obtains the radio frequency signal transmitted by the digital-analog extension unit through the radio frequency cable, and measures the radio frequency signal to obtain the first power value; wherein the radio frequency signal is a signal generated by the digital-analog extension unit according to a preset frequency band and a preset power value.
  • the remote unit obtains the radio frequency signal insertion loss based on the first power value and the preset power value, and obtains the cable length according to the radio frequency signal insertion loss and the preset frequency band.
  • the remote unit obtains the target signal insertion loss based on the cable length and the target signal frequency band, and matches the attenuation value of the digitally controlled attenuator based on the target signal insertion loss, target transmission power and gain value.
  • the digital-to-analog expansion unit generates a corresponding signal according to the set frequency band and power value and couples it to the radio frequency cable.
  • the remote unit measures the current power value of the signal, and then can calculate the distance between the remote unit and the digital-analog expansion unit based on the current power value, the set power value and the frequency band The length of the RF cable.
  • the remote unit can obtain the insertion loss of the frequency band on the radio frequency cable according to the cable length and the frequency band of the signal covered by the remote unit; and then adjust the numerical control attenuation according to the insertion loss, the gain value of the amplifier and the power value required for signal coverage
  • the attenuation value of the device realizes the gain control of the remote unit.
  • the radio frequency signals can be Bluetooth signals, FSK signals, and other low-speed radio frequency signals, which can be selected according to the requirements of the signal frequency band, and are not specifically limited here.
  • the embodiment of the application can not only reduce the construction cost of the system, but also can complete the length measurement of the radio frequency cable through the signal interaction between the remote unit and the digital-analog extension unit, and then adapt the attenuation value inside the remote unit to achieve The signal coverage of the target power ensures the communication quality of the system.
  • a gain control device applied to a distributed antenna system is provided; the gain control device is respectively arranged in each remote unit.
  • the gain control device includes:
  • the power measurement module is used to obtain the radio frequency signal transmitted by the digital-to-analog expansion unit through the radio-frequency cable, and to measure the radio frequency signal to obtain the first power value; wherein the radio-frequency signal is generated by the digital-to-analog expansion unit according to the preset frequency band and the preset power value signal.
  • the cable length obtaining module is used to obtain the radio frequency signal insertion loss based on the first power value and the preset power value, and obtain the cable length according to the radio frequency signal insertion loss and the preset frequency band.
  • the attenuation value matching module is used to obtain the target signal insertion loss based on the cable length and the target signal frequency band, and match the attenuation value of the digitally controlled attenuator based on the target signal insertion loss, target transmission power and gain value.
  • Each module in the above-mentioned gain control device can be implemented in whole or in part by software, hardware, and a combination thereof.
  • the foregoing modules may be embedded in the form of hardware or independent of the processor in the computer device, or may be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the foregoing modules.
  • a computer device including a memory and a processor, and a computer program is stored in the memory, and the processor implements the following steps when executing the computer program:
  • the radio-frequency signal is a signal generated by the digital-to-analog expansion unit according to a preset frequency band and a preset power value.
  • the radio frequency signal insertion loss is obtained, and the cable length is obtained according to the radio frequency signal insertion loss and the preset frequency band.
  • the target signal insertion loss is obtained, and the attenuation value of the digitally controlled attenuator is matched based on the target signal insertion loss, target transmission power and gain value.
  • a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, the following steps are implemented:
  • the radio-frequency signal is a signal generated by the digital-to-analog expansion unit according to a preset frequency band and a preset power value.
  • the radio frequency signal insertion loss is obtained, and the cable length is obtained according to the radio frequency signal insertion loss and the preset frequency band.
  • the target signal insertion loss is obtained, and the attenuation value of the digitally controlled attenuator is matched based on the target signal insertion loss, target transmission power and gain value.
  • Non-volatile memory may include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory.
  • Volatile memory may include random access memory (RAM) or external cache memory.
  • RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous chain Channel (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

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Abstract

本申请涉及一种分布式天线系统、方法和装置。其中，分布式天线系统包括数模扩展单元和远端级联链，远端级联链包括多个通过射频电缆级联连接的远端单元，且远端级联链的首级远端单元通过射频电缆与数模扩展单元连接。数模扩展单元用于对接收到的外部信号进行基带处理操作，以及进行模拟射频信号和数字射频信号的相互转换操作。基于此，数模扩展单元与远端单元采用基于电缆连接的菊花链拓扑结构，可在提高传输带宽的同时，有效降低传输链路的成本；并且，由数模扩展单元执行基带处理，远端单元无需基带处理设备，可有效降低系统的器件成本及运行功耗；该系统具有支持多模多频、小区分裂等特点，易于扩容，施工难度低。

Description

分布式天线系统、方法和装置 技术领域
本申请涉及通信技术领域，特别是涉及一种分布式天线系统、方法和装置。
背景技术
在4G(the 4th Generation mobile communication technology，第四代移动通信技术)时代，一些业务密集型场景(例如机场、火车站、大型场馆等)引入新型数字化室分系统。新型数字化室分系统具有部署简单、施工难度小、扩容灵活、运维方便等优点，大幅提高了网络容量。
然而，对于即将到来的5G(5th-Generation，第五代移动通信技术)时代，为应对越来越多的移动新业务，对网络提出了大带宽、高容量、低时延等刚性要求。其建设特点是更大的带宽，更高的频段，更多的天线(MIMO，Multiple-Input Multiple-Output，多输入多输出系统)。由于频段高，为提升容量，改善用户体验，需提高器件的性能，并且，会对更多的点位进行天线的放置，而且每个点位需要多根天线来实现2T2R，或4T4R。即，针对5G室内分布场景，新型数字化室分系统存在建设成本高的问题。
发明内容
基于此，有必要针对新型数字化室分系统存在建设成本高的问题，提供一种分布式天线系统、方法和装置。
为了实现上述目的，一方面，本申请实施例提供了一种分布式天线系统，包括：数模扩展单元和远端级联链，远端级联链包括多个通过射频电缆级联连接的远端单元，且远端级联链的首级远端单元通过射频电缆与数模扩展单元连接。
数模扩展单元，用于通过数模扩展单元内部的第一基带处理模块对信源单元通过光纤传输的下行数字射频信号进行基带处理操作，且通过数模扩展单元内部的第一信号转换模块进行数模转换，得到待发送给远端级联链的下行模拟射频信号；或者，数模扩展单元用于通过第一信号转换模块对远端级联链传输的上行模拟射频信号进行模数转换，且通过第一基带处理模块进行基带处理操作，得到待通过光纤发送给信源单元的上行数字射频信号。
远端单元，用于与终端设备进行模拟射频信号交互，且相邻两个远端单元之间通过射频电缆进行模拟射频信号交互。
另一方面，本申请实施例还提供了一种信号传输方法，应用于如上述的分布式天线系统；信号传输方法包括：
远端单元获取终端的第一上行模拟射频信号，以及下一级远端单元传输的第二上行模拟射频信号。
远端单元对第一上行模拟射频信号和第二上行模拟射频信号进行合路，得到当前远端单元的上行模拟射频信号，并将当前远端单元的上行模拟射频信号传输给上一级远端单元或数模扩展单元。
数模扩展单对获取到的上行模拟射频信号进行模数转换以及基带处理，得到待通过光纤发送给信源单元的上行数字射频信号。
在其中一个实施例中，提供了一种信号传输方法，应用于如上述的分布式天线系统；信号传输方法包括：
数模扩展单元对信源单元通过光纤传输的下行数字射频信号进行基带处理以及数模转换，得到下行模拟射频信号，并将下行模拟射频信号传输给远端级联链。
远端单元获取下行模拟射频信号，并基于下行模拟射频信号进行下行射频信号发射。在其中一个实施例中，提供了一种增益控制方法，应用于如上述的分布式天线系统中；增益控制方法包括步骤：
远端单元获取数模扩展单元通过射频电缆传输的射频信号，并测量射频信号，得到第一功率值；其中，射频信号为数模扩展单元按照预设频段和预设功率值生成的信号。
远端单元基于第一功率值和预设功率值，得到射频信号插损，并根据射频信号插损和预设频段，得到 电缆长度。
远端单元基于电缆长度与目标信号频段，得到目标信号插损，并基于目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
在其中一个实施例中，提供了一种增益控制装置，应用于分布式天线系统，并且，增益控制装置分别设置在各远端单元中；增益控制装置包括：
功率测量模块，用于获取数模扩展单元通过射频电缆传输的射频信号，并测量射频信号，得到第一功率值；其中，射频信号为数模扩展单元按照预设频段和预设功率值生成的信号。
电缆长度获取模块，用于基于第一功率值和预设功率值，得到射频信号插损，并根据射频信号插损和预设频段，得到电缆长度。
衰减值匹配模块，用于基于电缆长度与目标信号频段，得到目标信号插损，并基于目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
上述技术方案中的一个技术方案具有如下优点和有益效果：
分布式天线系统包括数模扩展单元和远端级联链，远端级联链包括多个通过射频电缆级联连接的远端单元，且远端级联链的首级远端单元通过射频电缆与数模扩展单元连接。其中，数模扩展单元用于通过数模扩展单元内部的第一基带处理模块对接收到的外部信号进行基带处理操作，以及通过数模扩展单元内部的第一信号转换模块进行模拟射频信号和数字射频信号的相互转换操作，得到待发送给信源单元的上行数字射频信号或者待发送给远端级联链的下行模拟射频信号；远端单元用于与终端设备进行模拟射频信号交互，且相邻两个远端单元之间通过射频电缆进行模拟射频信号交互。基于此，数模扩展单元与远端单元采用基于电缆连接的菊花链拓扑结构，可在提高传输带宽的同时，有效降低传输链路的成本；并且，由数模扩展单元执行基带处理，远端单元无需基带处理设备，可有效降低系统的器件成本及运行功耗。同时，远端单元的覆盖不受带宽限制且支持多种信号接入覆盖，该系统具有支持多模多频、小区分裂等特点，易于扩容，施工难度低。
附图说明
通过阅读参照以下附图所作的对非限制性实施例所作的详细描述，本申请的其它特征、目的和优点将会变得更明显：
图1为一个实施例中分布式天线系统的应用环境示意图；
图2为一个实施例中分布式天线系统的第一示意性结构图；
图3为一个实施例中分布式天线系统的第二示意性结构图；
图4为一个实施例中分布式天线系统与新型数字化室分系统的远端单元对比图；
图5为一个实施例中菊花链拓扑与星型拓扑的第一对比图；
图6为一个实施例中菊花链拓扑与星型拓扑的第二对比图；
图7为一个实施例中频段-带宽示意图；
图8为一个实施例中集束射频电缆的结构示意图；
图9为一个实施例中分布式天线系统的数模扩展单元的第一示意性结构图；
图10为一个实施例中分布式天线系统的第三示意性结构图；
图11为一个实施例中分布式天线系统的数模扩展单元的第二示意性结构图；
图12为一个实施例中分布式天线系统的远端单元的第一示意性结构图；
图13为一个实施例中分布式天线系统的远端单元的第二示意性结构图；
图14为一个实施例中分布式天线系统的接入单元的第一示意性结构图；
图15为一个实施例中分布式天线系统的数模扩展单元的第三示意性结构图；
图16为一个实施例中分布式天线系统执行数字合路的示意图；
图17为一个实施例中分布式天线系统的信源单元对比图；
图18为一个实施例中分布式天线系统的接入单元的第二示意性结构图；
图19为一个实施例中分布式天线系统的数模扩展单元的信号耦合示意图；
图20为一个实施例中分布式天线系统的远端单元的信号耦合示意图；
图21为一个实施例中分布式天线系统的第四示意性结构图。
具体实施方式
为了便于理解本申请，下面将参照相关附图对本申请进行更全面的描述。附图中给出了本申请的首选实施例。但是，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供这些实施例的目的是使对本申请的公开内容更加透彻全面。
需要说明的是，当一个元件被认为是“连接”另一个元件，它可以是直接连接到另一个元件并与之结合为一体，或者可能同时存在居中元件。本文所使用的术语“第一端口”、“第一传输端口”、“另一端”以及类似的表述只是为了说明的目的。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
随着移动互联网通信技术发展，以及5G商用脚步的日益临近，如何建设高性能低成本的室内分布网络，面临的巨大的挑战。在2G(2-Generation wireless telephone technology，第二代手机通信技术规格)/3G(3rd-Generation，第三代移动通信技术)时代，移动通信工作频段较低，室内覆盖方案主要是使用室外宏站信号覆盖室内，和/或采用传统室内分布系统(DAS，Distributed antenna system)(即，RRU作为信源，使用馈线和室分天线进行室内信号覆盖)，能够解决信号覆盖问题，满足语音业务。
传统DAS主要采用无源器件，其产业链成熟，具有投资小、系统简单等有点，并且，后期可以简单通过合路进行多频段扩容。但是在要求多条通信通道的条件下，例如，对于5G要求的2T2R和4T4R的MIMO系统，传统DAS的建设成本会加倍增加；同时，由于无源器件的不一致性以及信号传输插损等因素，传统DAS不能完全体现MIMO系统的性能，并且，当前器件不支持高频段，不利于扩容和系统的平滑演进；此外，传统DAS的工程建设难度大，故障隐患多，故障排查难度大。
而4G时代引入的新型数字化室分系统具有工程实施简单、可视化运维、多通道MIMO实现简单、容易扩容及演进等优点。但是，在相同规格下，新型数字化室分系统比传统DAS的建设成本高数倍。并且，新型数字室分均为有源系统，数字信号通过网线或光纤传输，需要耗费巨大的能耗；同时，在数字化传输中，其带宽受限于光模块或网线的速率，如果需要更大的带宽，或支持2T2R或4T4R等MIMO系统，则要求传输的带宽成比例增加，并采用性能匹配的器件(如ADC(Analog-to-Digital Converter，模数转换器)/DAC(Digital to analog converter，数模转换器)/FPGA(Field-Programmable Gate Array，即现场可编程门阵列))进行处理，其成本和功耗也大幅增加。
为此，本申请提供一种分布式天线系统，可应用于如图1所示的应用环境中，在信源单元和远端射单元之间设置用于基带处理和信号转换的数模扩展单元，形成信源单元、数模扩展单元和远端单元的三层结构；并且，数模扩展单元使用射频电缆级联多个远端单元，形成菊花链拓扑结构；在提高带宽时，能够有效降低远端覆盖的成本，同时，系统支持多种信号的接入覆盖，且具备支持多模多频、扩容、小区分裂等特点。基于此，系统采用数模混合传输的方式，具有工程实施简单、可管可控、多通道MIMO和便于扩容等优点，同时，还可避免建设成本高、功耗高和传输带宽受限等缺点。
示例性地，如图2所示，分布式天线系统包括至少一个、与信源单元连接的数模扩展单元，以及至少两个远端单元；其中，远端单元间采用菊花链拓扑的连接结构，形成远端级联链；并且，位于远端级联链首端的远端单元采用射频电缆连接数模扩展单元；数模扩展单元可连接至少一条远端级联链。此外，分布式天线系统中，可包括至少两个数模扩展单元；一个信源单元与多个数模扩展单元之间可采用星型拓扑的连接结构，和/或菊花链拓扑的连接结构。应该注意的是，本申请实施例中提及的菊花链拓扑为线性菊花链拓扑。
在一个实施例中，提供一种分布式天线系统，如图3所示，包括：数模扩展单元和远端级联链，远端级联链包括多个通过射频电缆级联连接的远端单元，且远端级联链的首级远端单元通过射频电缆与数模扩展单元连接。
数模扩展单元，用于通过数模扩展单元内部的第一基带处理模块对信源单元通过光纤传输的下行数字射频信号进行基带处理操作，且通过数模扩展单元内部的第一信号转换模块进行数模转换，得到待发送给远端级联链的下行模拟射频信号；或者，数模扩展单元用于通过第一信号转换模块对远端级联链传输的上行模拟射频信号进行模数转换，且通过第一基带处理模块进行基带处理操作，得到待通过光纤发送给信源单元的上行数字射频信号。
远端单元，用于与终端设备进行模拟射频信号交互，且相邻两个远端单元之间通过射频电缆进行模拟射频信号交互。
具体而言，分布式天线系统中，数模扩展单元与远端级联链之间通过射频电缆连接，单个数模扩展单元可分别连接多条远端级联链，并分别通过射频电缆与远端级联链进行模拟射频信号传输。远端级联链中的多个远端单元通过射频电缆依次级联，位于远端级联链首级的远端单元连接数模扩展单元，形成菊花链拓扑结构；相邻的远端单元间通过射频电缆进行模拟射频信号传输。此外，数模扩展单元可通过光纤连接信源单元，采用光信号的模式与信源单元进行数字射频信号传输。
需要说明的是，数模扩展单元用于对外部数据进行基带处理，还用于模数转换或数模转换；其中，外部数据为数模扩展单元外的数据，例如来自远端单元的数据、信源单元的数据等。具体地，数模扩展单元内部设置有基带处理模块和信号转换模块。远端单元用于实现信号的覆盖，与终端设备进行上下行模拟射频信号传输。具体地，远端单元内部设置通信链路模块，包括天线、滤波器等射频器件。
对于上行信号链路，多个远端单元分别通过各自的天线接收上行模拟射频信号；当前远端单元可将接收到的上行模拟射频信号进行滤波、放大等处理后，通过射频电缆传输到上一级远端单元。上一级远端单元接收下一级远端单元的信号，与自身通过天线接收、且经处理得到的信号进行合路，将合路后的信号继续通过射频电缆传输到上一级远端单元或数模扩展单元。数模扩展单元接收一条远端级联链传输的远端单元合路信号，将该合路得到的上行模拟射频信号转换成上行数字射频信号并进行基带处理，进而将基带处理得到的上行数字射频信号、以光学方式发送到信源单元。
对于下行信号链路，信源单元将下行数字射频信号以光学方式(光纤)，即下行光信号，发送到数模扩展单元；数模扩展单元对接收到的下行数字射频信号进行基带处理后，通过数模转换，得到下行模拟射频信号，并通过射频电缆将下行模拟射频信号传输给远端级联链；远端级联链中的各远端单元从射频电缆中耦合得到下行模拟射频信号，并将该信号进行滤波放大后，通过射频天线发射出去，实现信号的覆盖。
本申请实施例中，数模扩展单元可采用光纤连接信源单元，使用数字化光纤传输，使得信源接入多样化，即，信源单元既可为BBU(Building Base band Unit，基带处理单元)，也可为RRU(Radio Remote Unit，射频拉远单元)。数模扩展单元与远端级联链采用射频电缆连接，数模扩展单元能够在射频电缆中耦合电源信号、监控信号等；远端单元可从射频电缆中耦合得到电源信号等，进而实现射频信号的有源放大，基于此，远端级联链上远端单元的数量可根据实际信号覆盖需求进行设置，当需要增设远端单元时，只需在末级远端单元后再接入远端单元即可，便于系统的演进和扩容，相比传统DAS，可实现更高功率、更灵活的功率覆盖，且能够对远端单元进行监控，及时获取各远端单元的配置信息、告警信息、状态信息以及插损信息等。
由于分布式天线系统需设置多个远端单元，保证信号的全面覆盖，同时，随着带宽的提升，远端单元上器件的性能也需相应地升级匹配，因此，远端单元在系统中的成本占比大、功耗占比也高。而本申请实施例中，数模扩展单元中设有基带处理模块和信号转换模块，远端单元无需设置基带处理器件，节省了基带处理器件(例如FPGA、ASIC(Application Specific Integrated Circuit))的成本，如图4所示。并且，相对于新型室分系统采用光纤或网线作为传输介质，本申请实施例中，远端级联链的各远端单元采用射频电缆作为级联的传输介质，可有效降低建设成本和功耗；同时，远端单元也无需设置光处理器件、以太网传输电路等，可进一步降低成本。具体而言，在新型室分系统中，基带处理器件和传输介质两部分的成本占比高，且产生的功耗占比高，而基于本申请实施例提供的系统，建设成本可大幅降低，功耗也可相应地降低。
进一步地，本申请实施例中，远端单元采用菊花链拓扑结构进行级联，相对于新型室分系统采用的星型拓扑结构，可大幅降低工程施工难度，节省射频电缆的使用量，降低建设成本。例如，如图5所示，若 每个远端单元间隔15m(米)布置，则菊花链拓扑结构下设置四个远端单元需要的传输介质长度为60m，而星型拓扑结构需要的传输介质长度为：15+30+45+60＝150m。
此外，如图6所示，若数模扩展单元均接8个远端单元，则本申请实施例中，由于数模扩展单元使用光纤接信源单元、且可级联另一个数模扩展单元，所以，单个数模扩展单元需要2个光纤接口；而对于新型数字化室分系统的扩展单元，则需要连接信源单元的光纤接口、级联扩展单元的光纤接口以及8个连接远端单元的光纤接口或网线接口。在大带宽的需求下，每个接口器件的成本相应增加，因此，本申请实施例可节省接口器件，降低成本。
应该注意的是，数模扩展单元与远端单元之间、相邻两个远端单元之间均使用射频电缆连接。射频电缆和链路上的无源器件，只要满足截止频率要求就可进行传输，比如，目前传统DAS的无源器件支持到700M(兆赫兹)至2.7G(吉赫兹)，如本申请实施例要满足国内5G建设，只需要选择700M至3.5G的无源器件，则传输带宽基本上不受限制，如图7所示。而对于新型数字室分远端，通常使用数字光纤或网线传输，需要将射频信号数字化，再通过CPRI(Common Public Radio Interface，通用公共无线电接口)协议传输，对数字传输带宽有较大的限制。例如，按照5G室分比较标准的配置，远端单元实现4T4R MIMO、100MHz(兆赫兹)带宽的信号覆盖，且采用标准CPRI传输时，其传输带宽为：
122.88MHz×2×15×16/15×10/8×4＝19.6608Gbps
其中：122.88MHz表示100MHz带宽信号传输速率；2表示IQ两路；15表示传输位宽；16/15表示传输控制开销；10/8表示传输编码；4表示天线数。即，如果要覆盖4T4R/100MHz信号，使用数字光纤或网线、并基于标准CPRI进行传输时，需要19.66Gbps(吉比特每秒)的传输速率，则要求选用支持25Gbps的光模块和FPGA器件，相较于本申请实施例，其成本非常高，同时，以太网目前最高只支持到10Gbps，难以满足要求；而如果要降低传输速率，需要进行压缩，则会增加其系统实现的复杂性。
传统DAS使用低插损的7/8馈线作为传输介质，但其重量和直径很大，同时，在使用4T4R的要求下，需要四根7/8馈线，施工难度大，成本高。本申请实施例可选用直径和重量小的射频电缆作为传输介质，同时，远端单元可通过有源射频放大来弥补射频传输中的插损。由于直径小，可将多根射频电缆集束合并成一个电缆，便于施工。如图8所示，为四根射频电缆合成一根集束射频电缆，能够满足4T4R的需求。
示例性地，如图9所示，数模扩展单元包括依次连接的第一光收发模块、第一基带处理模块、第一信号转换模块和射频前端模块。其中，第一光收发模块，用于与信源单元进行光信号交互。第一基带处理模块，用于对接收到的信号进行基带处理后输出。第一信号转换模块，用于与基带处理模块进行数字射频信号交互，以及与射频前端模块进行模拟射频信号交互。射频前端模块，用于与远端单元进行模拟射频信号交互，且用于进行模拟射频信号处理。
具体而言，第一光收发模块可用于与信源单元进行光信号的相互传输，实现光信号与数字射频信号的相互转换，且还可用于与第一基带处理模块进行数字射频信号的相互传输。可选地，第一光收发模块可包括至少一个光收发器。
第一基带处理模块可用于对第一光收发模块传输的数字射频信号进行基带处理，并将处理得到的数字射频信号传输给第一信号转换模块。同时，第一基带处理模块还可用于对第一信号转换模块传输的数字射频信号进行处理，并将处理得到的数字射频信号传输给第一光收发模块。其中，第一基带处理模块对数字射频信号的处理方式包括以下处理方式中的任意一种或任意组合：数字合路、信号组帧、信号解帧、串并转换、并串转换、时钟恢复以及数字中频处理等。可选地，第一基带处理模块可为FPGA或ASIC等，在此不做具体限制。
第一信号转换模块可用于对第一基带处理模块传输的数字射频信号进行数模转换，并将数模转换得到的模拟射频信号发送给射频前端模块。同时，第一信号转换模块还可用于对射频前端模块传输的模拟射频信号进行模数转换，并将模数转换得到的数字射频信号发送给第一基带处理模块。可选地，第一信号转换模块可包括数模转换器和模数转换器等，在此不做具体限制。
射频前端模块可用于将第一信号转换模块传输的模拟射频信号进行处理后，发送给远端级联链；且还可用于将远端级联链传输的模拟射频信号进行处理后，发送给第一信号转换模块。其中，射频前端模块对模拟射频信号的处理方式包括以下处理方式中的任意一种或任意组合：滤波、变频以及放大等。可选地， 射频前端模块可包括滤波器、变频器以及放大器等，在此不做具体限制。
应该注意的是，第一基带处理模块、第一信号转换模块以及射频前端模块内部均可设置多个处理通道，用于分别处理多路通信通道的信号，以满足2T2R、4T4R等通信需求。
可选地，如图10所示，分布式天线系统包括至少两个数模扩展单元，其中一个数模扩展单元通过光纤连接信源单元，相邻两个数模扩展单元之间通过各自的第一光收发模块进行光纤级联。
具体而言，信源单元可通过其中一个数模扩展单元连接其他数模扩展单元，实现与各数模扩展单元之间的信号交互。基于此，可减少信源单元需要设置的光口数量，降低系统建设成本。
例如，分布式天线系统包括一个包含至少3个光接口的第一级数模扩展单元，以及多个包含2个光接口的第二级数模扩展单元；信源单元可通过第一级数模扩展单元连接各第二级数模扩展单元，第二级数模扩展单元还可通过光纤级联下一级的数模扩展单元；其中，第二级数模扩展单元的数量可小于或等于第一级数模扩展单元的光接口的数量。
又例如，各数模扩展单元之间还可通过光纤依次级联连接，形成菊花链拓扑结构，位于首级的数模扩展单元通过光纤连接信源单元，基于此，各数模扩展单元仅需要2个光接口，无需做接口扩展，能够降低传输介质的需求，且可减少信源单元需要设置的光接口数量，降低系统建设成本。
应该注意的是，信源单元与各数模扩展单元之间可形成星型拓扑、菊花链拓扑、以及星型和菊花链的混合拓扑。数模扩展单元可将信源单元传输的下行数字射频信号广播到下一级级联的数模扩展单元，还可将自身得到的上行光信号通过上一级级联的数模扩展单元、传输给信源单元。
示例性地，如图10所示，远端级联链的数量为至少两条，一个数模扩展单元对应连接至少一条远端级联链；各数模扩展单元的射频前端模块分别连接对应的各远端级联链的首级远端单元。
具体而言，分布式天线系统中，数模扩展单元可根据信号覆盖的需求，分别连接多条远端级联链，与各远端级联链分别进行模拟射频信号传输。具体地，各远端级联链的首级远端单元均连接数模扩展单元的射频前端模块；射频前端模块可为各远端级联链设置相应的信号处理通道。基于此，数模扩展单元可扩展连接多条远端级联链，进而能够灵活设计信号覆盖，满足多种室内结构的布局需求，适用性高。
优选地，数模扩展单元还用于：对信源单元传输的下行数字射频信号进行组帧，并将组帧后的数字射频信号通过光纤透传给相邻的数模扩展单元。
具体而言，下行数字射频信号可以广播方式传输，进入数模扩展单元进行基带处理时，可分为两路，一路可经解帧、中频、上变频、数字滤波、数模转换以及射频前端等处理后，耦合到射频电缆中，发送到远端级联链；另一路可经过组帧，以加入控制信息，并将组帧得到的信号通过光纤透传给下一级数模扩展单元。基于此，级联的数模扩展单元可快速将信源单元传输的下行信号发送给下一级的级联单元，便于下一级数模扩展单元进行信号处理及覆盖，能够在降低系统建设成本的同时，保证系统中信号传输的及时性。
可选地，数模扩展单元还用于，根据当前数模扩展单元接收到的多路信号的特征是否相同，确定是否将接收到的多路信号进行数字合路：
若第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征相同，则将第一上行数字射频信号与第二上行数字射频信号进行数字合路，得到当前数模扩展单元的第三上行数字射频信号，对第三上行数字射频信号进行转换，得到当前数模扩展单元的上行光信号并发送给上一级数模扩展单元或信源单元；其中，第一上行数字射频信号为当前数模扩展单元对下一级数模扩展单元的上行光信号进行处理得到；第二上行数字射频信号为当前数模扩展单元对当前数模扩展单元连接的远端级联链的上行模拟射频信号进行模数转换和基带处理得到；
若第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征不同，则分别对第一上行数字射频信号、第二上行数字射频信号进行转换，得到相应的上行光信号并发送给上一级数模扩展单元或信源单元。
具体而言，数模扩展单元可接收自身连接的各远端级联链的信号，以及级联的数模扩展单元的信号，并根据信号特征，将多路信号中信号特征相同的信号进行数字合路，进而可减少信号在传输至信源单元时占用的带宽，提高传输介质及器件的利用率。其中，信号特征包括一下参数的任意一种或任意组合：制式、频段以及小区等。
具体地，若数模扩展单元级联，则下一级数模扩展单元将其得到的上行数字射频信号、通过光纤传输 到当前数模扩展单元；如果传输来的上行数字射频信号，与当前数模扩展单元处理得到的上行数字射频信号为相同特征(例如同制式、同频段、同小区)，则需进行数字相加(属于数字合路)，然后将相加得到的上行数字射频信号转换成光信号并传输到上一级数模扩展单元或信源单元。若不是相同特征，则下一级传输来的信号需要透传给上一级数模扩展单元或者信源单元。其中，若下一级传输的信号可进行数字相加，则不占用当前数模扩展单元向上一级传输的带宽；若下一级传输的信号需透传到上一级，则该信号需要占用额外的传输带宽。上述信号特征可为信号的制式、频段或所属小区等，应该注意的是，该信号特征不涉及信号承载的信息内容。
示例性地，如图11所示，数模扩展单元还包括第一监控电路、电源电路、以及通过射频电缆与远端级联链的首级远端单元连接的第一耦合器。
第一耦合器分别连接第一基带处理模块、射频前端模块、第一监控电路和电源电路；第一耦合器，用于执行将第一基带处理模块生成的上下行切换信号耦合到射频电缆中、将电源信号耦合到射频电缆中、与远端单元进行监控信号交互、与远端单元进行模拟射频信号交互中的至少一种操作。
具体而言，数模扩展单元还包括连接在射频前端模块与远端级联链之间的第一耦合器，以及连接第一耦合器的第一监控电路和电源电路。其中，第一监控电路用于监控信号的生成和处理，可通过第一耦合器将监控信号耦合到射频电缆中，监控各远端单元的状态信息、设备信息以及告警信息等；可选地，第一监控电路可为生成和处理低速射频信号的电路，其中，低速射频信号如蓝牙信号、FSK(Frequency-shift keying，频移键控)信号等，该低速射频信号不干涉射频电缆上的其他信号。例如，第一监控电路可包括第一处理器，以及连接在第一处理器和第一耦合器之间的第一蓝牙芯片。
电源电路用于生成电源信号并通过第一耦合器耦合到射频电缆中，为各远端单元提供电源信号，便于远端单元进行射频信号放大。第一基带处理模块还可用于生成上下行切换信号，并通过第一耦合器耦合到射频电缆中，进而能够驱动远端单元实现TDD(Time Division Duplexing，时分双工)覆盖。第一耦合器用于将下行模拟射频信号、上下行切换信号、电源信号以及监控信号等耦合到射频电缆中，便于远端级联链中各远端单元在射频电缆中耦合出对应的信号；第一耦合器还可用于从射频电缆中耦合得到远端单元传输的上行模拟射频信号、监控信号等。应该注意的是，射频前端模块可为零中频、超外差方式或直接射频采样方式等；监控信号和电源信号经过第一耦合器耦合到射频电缆时，可耦合到一根射频电缆，也可耦合到多根射频电缆，保证每个远端单元都有电源信号和监控信号馈入。
本申请实施例中，数模扩展单元可通过耦合器将多种信号耦合到射频电缆上，便于各个远端单元对信号的获取，丰富远端单元的功能性的同时，降低系统对传输介质的需求量。
示例性地，数模混合扩展单元主要由多工器(或双工器)、耦合器、射频前端、基带处理、数模/模数转换器以及光收发器组成。对于1T1R系统，只需一条射频电缆进行传输；而对于MIMO系统，需要多条射频电缆，或将相同频段的MIMO信号变频后、在同一条电缆上传输。数模混合扩展单元有至少两个光收发器，一个连接信源单元或上一级数模混合扩展单元，另一个连接另外一台数模扩展单元。而基带处理则可为FPGA或由相同功能的ASIC实现。
对于下行链路，当前数模扩展单元的基带处理通过光收发器、从信源单元或上一级数模扩展单元获取到数字射频信号，经过时钟恢复、串并转换、解帧、速率变换、数字上变频等处理后，发送到数模转换器转换为模拟射频信号并发送到射频前端模块，经过滤波、变频、放大等处理后发送到多工器，然后经过第一耦合器耦合后馈入到射频电缆。
对于上行链路，第一耦合器从射频电缆中耦合得到模拟射频信号，经多工器滤波后进入射频前端进行放大、滤波和变频处理。射频前端处理后的射频信号通过模数转换器，转换为数字射频信号，经过数字下变频(DDC，Digital down conversion)、速率变换、组帧、并串转换等基带处理后进行光电转换，变换为光信号后传输到上一级数模扩展单元或信源单元。
若信号是TDD制式，则远端单元需要对上下行切换开关进行恢复，用于实现上下行信号的切换。如远端单元不能从射频信号中获取恢复开关的信号，则需数模扩展单元通过射频电缆直接提供上下行切换信号。
示例性地，如图12所示，远端单元包括至少一个通信链路模块；相邻的两个远端单元之间通过多条射频电缆连接，优选地，可以通过集束电缆连接，集束射频电缆包括至少一条射频电缆，一条射频电缆对 应连接下一级远端单元的一个通信链路模块。
具体而言，根据通信配置的通信通道数量，远端单元可设置多个通信链路模块，用于从射频电缆中耦合并处理对应通信通道的模拟射频信号。同时，系统中的射频电缆可相应设置为包括多根射频电缆的集束射频电缆；一个通信链路模块通过其中一条射频电缆连接下一级远端单元的一个通信链路模块，或通过其中一条射频电缆连接数模扩展单元。例如，在支持4T4R的通信系统中，远端单元可包括4个通信链路模块，集束射频电缆包括4根射频电缆，每根电缆用于实现1T1R的天线射频传输；集束射频电缆中的射频电缆与远端单元中的通信链路模块可一一对应连接，进而能够满足4T4R的射频传输。具体地，通信链路模块可主要由耦合器、滤波器、直流隔离电路、放大器以及天线等组成，在此不做具体限制。应该注意的是，在同一根射频电缆上，可支持不同频段的多个信号进行传输，但需多工器对上下行进行分离或合路，进而可在不同的天线上进行覆盖。
示例性地，如图13所示，通信链路模块包括第二耦合器、射频交互电路、第二监控电路、电源转换电路以及上下行切换电路。第二耦合器通过射频电缆与第一耦合器或上一级远端单元的通信链路模块连接；第二耦合器分别连接射频交互电路、第二监控电路、电源转换电路和上下行切换电路；射频交互电路分别连接电源转换电路和上下行切换电路。
第二耦合器，用于执行获取电源信号、获取上下行切换信号、与数模扩展单元进行监控信号交互、与数模扩展单元进行模拟射频信号交互、与下一级远端单元进行模拟射频信号交互中的至少一种操作。
具体而言，通信链路模块包括连接射频电缆的第二耦合器，用于与第一耦合器、上一级远端单元的通信链路模块或下一级远端单元的通信链路模块进行模拟射频信号传输。具体地，第二耦合器的第一端口通过射频电缆连接第一耦合器或上一级远端单元的通信链路模块，第二端口连接下一级远端单元的通信链路模块，第三端口分别连接通信链路模块中的射频交互电路、第二监控电路、电源转换电路和上下行切换电路。
需要说明的是，射频交互电路用于与外部终端进行射频信号交互，可包括滤波器、放大器以及天线等器件。具体地，射频交互电路可通过第二耦合器从射频电缆中得到模拟射频信号，并经滤波、放大等处理后，由天线发射出去；射频交互电路还可通过天线获取外部终端发射的模拟射频信号，经滤波、放大等处理后，通过第二耦合器耦合到射频电缆中，进而可传输给数模扩展单元。
第二监控电路可用于通过第二耦合器获取监控信号并进行处理，还可通过第二耦合器反馈监控信号，实现远端单元与数模扩展单元之间的监控信号交互。具体地，第二监控电路可为生成与处理低速射频信号的信号，例如蓝牙信号、FSK信号等；第二监控电路可通过监控信号反馈当前远端单元的状态信息、设备信号或告警信息等。例如，第二监控电路可包括第二处理器，以及连接在第二处理器和第二耦合器之间的第二蓝牙芯片，第二处理器可连接射频交互电路的衰减器，控制射频交互电路中的衰减值。
电源转换电路可用于通过第二耦合器获取电源信号，对电源信号进行转换，得到远端单元中各器件所需的标准电源，满足射频交互电路的有源放大；具体地，射频电缆上耦合的电压通常为48V(伏特)，需要将其转换为5V、3.3V等电压。上下行切换电路可用于通过第二耦合器获取上下行切换信号，控制射频交互电路的上下行切换，实现TDD制式信号的覆盖；可选地，上下行切换信号还可直接从模拟射频信号中提取。
本申请实施例中的远端单元可通过耦合器，从射频电缆中耦合得到下行模拟射频信号、监控信号以及电源信号等，实现信号覆盖，并且，设备的结构简单、成本低，有利于系统的扩容。
示例性地，远端单元还用于获取终端的第一上行模拟射频信号，以及下一级远端单元传输的第二上行模拟射频信号，并对第一上行模拟射频信号和第二上行模拟射频信号进行合路，得到当前远端单元的上行模拟射频信号；将上行模拟射频信号传输给上一级远端单元或数模扩展单元。
具体而言，对于上行链路，在远端级联链中，当前远端单元通过射频交互，获取到外部终端的上行模拟射频信号；同时，当前远端单元还获取下一级远端单元传输的上行模拟射频信号，并将获取到的上行模拟射频信号进行合路，将合路得到的上行模拟射频信号传输给上一级远端单元或数模扩展单元，实现上行射频信号的传输。
可选地，分布式天线系统还包括连接数模扩展单元的信源单元。
信源单元为BBU或RRU；若信源单元为RRU，则分布式天线系统还包括连接在RRU和数模扩展单元之间的接入单元。其中，接入单元，用于通过接入单元内部的第二基带处理模块对接收到的外部信号进行基带处理操作，以及通过接入单元内部的第二信号转换模块进行模拟射频信号和数字射频信号的相互转换操作，得到待发送给RRU的第三上行模拟射频信号或者待发送给数模扩展单元的下行数字射频信号。
具体而言，信源单元可为BBU，能够直接处理基带信号，用于对接收到的相同信号特征(同制式、同频段、同小区)的数字射频信号进行相加；且相加得到的信号在信源单元实现解调、解码等基带信号处理；如果是不同信号特征的信号，则需分配到不同的基带单元进行基带信号处理。信源单元也可为RRU，此时，需要接入单元将RRU的模拟射频信号转换为数字射频信号，并通过光纤传输到数模扩展单元；并且，接入单元还将数模扩展单元的数字射频信号转换成模拟射频信号并发送给RRU。此外，接入单元还用于对各路外部信号进行基带处理操作，例如，对数字射频信号进行解帧、数字合路、组帧以及数字中频处理等。基于此，接入单元能够将多个数模扩展单元传输信号进行解帧、合路以及转换后，将得到的多路模拟射频信号通过对应的射频电缆发送给RRU进行处理；同时，接入单元还可对RRU传输的多路模拟射频信号进行转换、中频处理以及组帧后，通过光口发送给各数模扩展单元。
示例性地，如图14所示，接入单元包括依次连接的第二光收发模块、第二基带处理模块、第二信号转换模块和射频通道模块。其中，第二光收发模块，用于与数模扩展单元进行光信号交互。第二基带处理模块，用于对接收到的信号进行基带处理后输出。第二信号转换模块，用于与第二基带处理模块进行数字射频信号交互，以及与射频通道模块进行模拟射频信号交互。射频通道模块，用于与RRU进行模拟射频信号交互，且用于进行模拟射频信号处理。
基于此，本申请实施例中，数模扩展单元与远端单元采用基于电缆连接的菊花链拓扑结构，可在提高传输带宽的同时，有效降低传输链路的成本；并且，由数模扩展单元执行基带处理，远端单元无需基带处理设备，能够有效降低系统的器件成本及运行功耗。同时，远端单元的覆盖不受带宽限制且支持多种信号接入覆盖，该系统具有支持多模多频、小区分裂等特点，易于扩容，施工难度低。
在一个实施例中，提供了一种信号传输方法，应用于如上所述的分布式天线系统中，包括步骤：
远端单元获取终端的第一上行模拟射频信号，以及下一级远端单元传输的第二上行模拟射频信号。
远端单元对第一上行模拟射频信号和第二上行模拟射频信号进行合路，得到当前远端单元的上行模拟射频信号，并将当前远端单元的上行模拟射频信号传输给上一级远端单元或数模扩展单元。
数模扩展单对获取到的上行模拟射频信号进行模数转换以及基带处理，得到待通过光纤发送给信源单元的上行数字射频信号。
在一个实施例中，还提供一种信号传输方法，应用于如上所述的分布式天线系统中，包括步骤：
数模扩展单元对信源单元通过光纤传输的下行数字射频信号进行基带处理以及数模转换，得到下行模拟射频信号，并将下行模拟射频信号传输给远端级联链。
远端单元获取下行模拟射频信号，并基于下行模拟射频信号进行下行射频信号发射。
可选地，分布式天线系统中，数模扩展单元的数量为至少两个；相邻两个数模扩展单元之间通过各自的光收发模块进行光纤级联，位于首级的数模扩展单元通过光纤连接信源单元；上述各信号传输方法还可包括步骤：
数模扩展单元根据当前数模扩展单元接收到的多路信号的特征是否相同，确定是否将接收到的多路信号进行数字合路：
若第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征相同，则数模扩展单元将第一上行数字射频信号与第二上行数字射频信号进行数字合路，得到当前数模扩展单元的第三上行数字射频信号，对第三上行数字射频信号进行转换，得到当前数模扩展单元的上行光信号并发送给上一级数模扩展单元或信源单元；其中，第一上行数字射频信号为当前数模扩展单元对下一级数模扩展单元的上行光信号进行处理得到；第二上行数字射频信号为当前数模扩展单元对当前数模扩展单元连接的远端级联链上行模拟射频信号进行模数转换和基带处理得到；
若第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征不同，则数模扩展单元分别对第一上行数字射频信号、第二上行数字射频信号进行转换，得到相应的上行光信号并发送给上一级数模 扩展单元或信源单元。
数模扩展单元对信源单元传输的下行数字射频信号进行组帧，并将组帧后的数字射频信号通过光纤透传给下一级数模扩展单元。
关于信号传输方法的具体限定可参见上文中对于分布式天线系统的限定，在此不再赘述。
示例性地，针对5G室分，主要是4T4R天线，至少100MHz带宽，例如：2.6G频段为160MHz带宽，3.5G频段为200MHz，并且，2.6G频段和3.5G频段均为TDD信号。例如，按照4T4R/100MHz带宽进行说明，通信系统可包括1个信源单元，4个数模扩展单元和32个远端单元。其中，信源单元可为BBU，也可主要由RRU和接入模块组成；每个基站单元，即信源单元，连接4个数模扩展单元；每个数模扩展单元连接8个远端单元。
具体地，为满足4T4R的通信需求，在4T4R通信链路上的电缆均为包括4根子电缆的集束电缆，每根子电缆用于实现1T1R的天线射频传输。远端单元的结构可如图12所示，包括4个通信链路模块，分别与子电缆对应。换言之，集束电缆中的每条子电缆，接入远端单元时都会对应连接一个耦合器；基于此，远端单元可分别耦合出各子电缆中的信号，同时，电缆中信号的功率经过耦合器插损比较小，可通过电缆发送到下一级远端单元。下行射频信号从耦合器耦合出后经过滤波器(TDD信号为滤波器)、功放放大，再滤波后从天线发射。上行射频信号从天线接收，经滤波器滤波后经过低噪声放大器放大，再由滤波器滤波后，从耦合器耦合到集束电缆上。
数模扩展单元可如图15所示，包括两个光口，其中一个为主光口，用于连接上一级数模扩展单元或信源单元，另一个为级联光口，用于连接下一级数模扩展单元。主光口的下行信号以广播方式传输，进入FPGA后分为两路；其中一路通过解帧后，分为四路、分别对应四根天线的下行信号，分别进入相应的数字中频模块进行DUC(Digital Up Conversion，数字上变频)、数字滤波等处理后经数模转换、射频前端处理后传输到对应的电缆，发送到远端级联链；另一路，经过一个组帧模块，加入一些控制信息后透传到级联光口。上行四路信号从远端单元通过集束电缆经对应的射频前端处理、模数转换后变成数字信号进入FPGA，在FPGA首先经数字中频模块，进行DDC、数字滤波处理后进入数字加模块。如图16所示，在数字加模块与级联光口的上行信号进行数字加处理(数字合路)，相同天线和射频通道信号才能合路。
信源单元可直接为BBU，用于直接对数模扩展单元传输的数字射频信号进行解调、解码等基带信号处理，如图17所示；信源单元还可为RRU，并且，系统还包括连接在RRU和数模扩展单元之间的接入单元，如图17所示。接入单元可用于进行射频和数字的转换，与数模扩展单元进行数字射频信号交互，与RRU进行模拟射频信号交互。如图18所示，接入单元可配置4个光口(可以是其它数目)。对于上行的情况，根据相同的信号特征、将各个数模扩展单元发送的信号进行数字加合路，即：
光口1通道1+光口2通道1+光口3通道1+光口4通道1＝总的通道1信号
以此类推，得到总的通道2、3、4信号，然后送到对应的信号中频处理链路进行处理，最终变换为模拟射频信号送到4T4R的RRU对应的端口上。对于下行的情况，4路下行信号从RRU端口馈入到接入模块，经对应的射频通道处理、模数转换、信号中频处理后进行组帧，并将组帧得到的信号广播到每个光口，即，每个光口的下行信号都可能包括通道1、2、3、4的信号。
在信源单元与数模扩展单元的传输中，以及数模扩展单元之间的传输中，4T4R/100MHz带宽的信号如果使用标准CPRI传输，则需满足19.6GBps的传输速率、要求25G光收发模块，此时会大幅增加传输成本和设备成本。本申请实施例可通过CPRI压缩方式、使用非标准的CPRI进行传输：
122.88MHz×2×9×16/15×66/64×4＝9.732Gbps<10Gbps
其中：122.88MHz表示100MHz带宽信号传输速率；2表示IQ两路；15表示传输位宽；16/15表示传输控制开销；10/8表示传输编码；4表示天线数。此时，传输速率小于10Gbps，可使用10G光模块和FPGA，进而使成本大幅下降。
需要说明的是，如图19所示，本申请实施例中的数模扩展单元可在一根电缆上、馈入与远端单元匹配的电源信号、TDD开关切换信号和监控信号。其中，监控信号可使用蓝牙信号传输，也可以使用FSK或其它的低速射频信号，只需保证选用频段与其它信号相干涉即可，例如，蓝牙频段为2.4G，与覆盖信号2.6G不在一个频段。电源通常可使用48V电源，通过带直流耦合的耦合器或合路器耦合到电缆上传输。 TDD开关切换信号也可直接耦合到射频电缆上。
由于所有信号都在电缆中，对于远端单元，其信号提取可如图20所示，通过耦合器耦合，直流电源信号经过一个低通滤波器，滤除高频信号并传输到电源转换电路上，得到远端单元工作需要的电源。TDD开关切换电路可通过直流隔离电路隔离掉直流电源信号，通过带通滤波器后，得到用于上下行信号切换的开关信号。蓝牙芯片可用于实现监控信号的传输，通过直流隔离电路隔离掉直流电源信号，通过带通滤波器后，接收数模扩展单元发送的监控信号；同时，远端单元的MCU也可通过蓝牙芯片反馈监控信号到数模扩展单元，实现双向通信。而最终覆盖的下行射频信号，也需要通过直流隔离电路和滤波器后，由天线发射。
进一步地，由于远端单元使用射频电缆进行模拟射频信号传输，射频电缆会导致信号插损，同时，本申请实施例使用菊花链级联的方式，使得同一条菊花链(即，远端级联链)上的各远端单元与数模扩展单元间的射频电缆长度不一致，如图21所示。远端单元可以通过放大器对信号进行放大来补偿线缆插损，同时，通过设置数控衰减器来控制不同远端单元的增益，可匹配相应的插损。具体流程可如下：
当有远端单元接入到数模扩展单元时，该远端单元的MCU(Microcontroller Unit，微控制单元)先通过蓝牙芯片与数模扩展单元的MCU建立监控通道的连接；数模扩展单元发送固定功率Pt_bluetooth的蓝牙信号到电缆上，假定为0dBm；各远端单元会接收到蓝牙信号，并测量接收到的功率Pr_bluetooth，由于射频电缆的长度不一致，每个远端单元接收到的功率值也不一致；根据测量得到的功率值，远端单元可计算出，自身与数模扩展单元之间的信号插损Ploss，例如：
Ploss＝Pt_bluetooth-Pr_bluetooth
得到该插损值Ploss之后，可根据电缆插损特性(对应蓝牙信号的2.4G频段)得到电缆长度；再根据电缆长度得到所需覆盖信号频段(如移动2.6G)的插损值，进而可通过调整数控衰减器来进行匹配。
例如，计算出2.6G的插损值为30dB，远端单元的下行放大增益为50dB；此时，设置20dB的衰减值，可实现远端增益和线路插损的匹配。
又如，远端单元的输出功率大于数模扩展单元的输出功率，需要减少衰减设置量。例如，数模扩展单元信号输出功率为15dBm，电缆损耗为30dBm，远端单元需要输出的功率为23dBm，而远端最大增益依然为50dBm，则衰减值为：23-(15-30+50)＝12dB。即，衰减值需要设置为12dB，而不是20dB。
在一个实施例中，提供了一种增益控制方法，应用于如上述的分布式天线系统中，增益控制方法包括步骤：
远端单元获取数模扩展单元通过射频电缆传输的射频信号，并测量射频信号，得到第一功率值；其中，射频信号为数模扩展单元按照预设频段和预设功率值生成的信号。
远端单元基于第一功率值和预设功率值，得到射频信号插损，并根据射频信号插损和预设频段，得到电缆长度。
远端单元基于电缆长度与目标信号频段，得到目标信号插损，并基于目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
具体而言，数模扩展单元按照设定的频段和功率值生成相应的信号并耦合到射频电缆中。远端单元从射频电缆中耦合得到该信号后，测量得到该信号当前的功率值，进而可根据当前的功率值、设定的功率值以及频段，计算得到远端单元到数模扩展单元之间的射频电缆长度。远端单元根据电缆长度以及远端单元覆盖信号的频段，可得到该频段在射频电缆上会产生的插损；进而根据该插损、放大器的增益值以及信号覆盖所要求功率值，调整数控衰减器的衰减值，实现对远端单元的增益控制。应该注意的是，射频信号可为蓝牙信号、FSK信号以及其他低速射频信号，可根据信号频段需求进行选择，在此不做具体限定。
基于此，本申请实施例不仅可以降低系统的建设成本，还能够通过远端单元与数模扩展单元间的信号交互，完成射频电缆的长度测量，进而适配远端单元内部的衰减值，实现目标功率的信号覆盖，保证系统的通信质量。
在一个实施例中，提供了一种应用于分布式天线系统的增益控制装置；增益控制装置分别设置在各远端单元中。
增益控制装置包括：
功率测量模块，用于获取数模扩展单元通过射频电缆传输的射频信号，并测量射频信号，得到第一功率值；其中，射频信号为数模扩展单元按照预设频段和预设功率值生成的信号。
电缆长度获取模块，用于基于第一功率值和预设功率值，得到射频信号插损，并根据射频信号插损和预设频段，得到电缆长度。
衰减值匹配模块，用于基于电缆长度与目标信号频段，得到目标信号插损，并基于目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
关于增益控制装置的具体限定可以参见上文中对于增益控制方法的限定，在此不再赘述。上述增益控制装置中的各个模块可全部或部分通过软件、硬件及其组合来实现。上述各模块可以硬件形式内嵌于或独立于计算机设备中的处理器中，也可以以软件形式存储于计算机设备中的存储器中，以便于处理器调用执行以上各个模块对应的操作。
在一个实施例中，提供了一种计算机设备，包括存储器和处理器，存储器中存储有计算机程序，该处理器执行计算机程序时实现以下步骤：
获取数模扩展单元通过射频电缆传输的射频信号，并测量射频信号，得到第一功率值；其中，射频信号为数模扩展单元按照预设频段和预设功率值生成的信号。
基于第一功率值和预设功率值，得到射频信号插损，并根据射频信号插损和预设频段，得到电缆长度。
基于电缆长度与目标信号频段，得到目标信号插损，并基于目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
关于计算机设备的具体限定可以参见上文中对于增益控制方法的限定，在此不再赘述。
在一个实施例中，提供了一种计算机可读存储介质，其上存储有计算机程序，计算机程序被处理器执行时实现以下步骤：
获取数模扩展单元通过射频电缆传输的射频信号，并测量射频信号，得到第一功率值；其中，射频信号为数模扩展单元按照预设频段和预设功率值生成的信号。
基于第一功率值和预设功率值，得到射频信号插损，并根据射频信号插损和预设频段，得到电缆长度。
基于电缆长度与目标信号频段，得到目标信号插损，并基于目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
关于计算机可读存储介质的具体限定可以参见上文中对于增益控制方法的限定，在此不再赘述。
本领域普通技术人员可以理解实现上述实施例方法中的全部或部分流程，是可以通过计算机程序来指令相关的硬件来完成，所述的计算机程序可存储于一非易失性计算机可读取存储介质中，该计算机程序在执行时，可包括如上述各方法的实施例的流程。其中，本申请所提供的各实施例中所使用的对存储器、存储、数据库或其它介质的任何引用，均可包括非易失性和/或易失性存储器。非易失性存储器可包括只读存储器(ROM)、可编程ROM(PROM)、电可编程ROM(EPROM)、电可擦除可编程ROM(EEPROM)或闪存。易失性存储器可包括随机存取存储器(RAM)或者外部高速缓冲存储器。作为说明而非局限，RAM以多种形式可得，诸如静态RAM(SRAM)、动态RAM(DRAM)、同步DRAM(SDRAM)、双数据率SDRAM(DDRSDRAM)、增强型SDRAM(ESDRAM)、同步链路(Synchlink)DRAM(SLDRAM)、存储器总线(Rambus)直接RAM(RDRAM)、直接存储器总线动态RAM(DRDRAM)、以及存储器总线动态RAM(RDRAM)等。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本申请范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请的保护范围应以所附权利要求为准。

Claims (17)

  1. 一种分布式天线系统，其特征在于，包括：数模扩展单元和远端级联链，所述远端级联链包括多个通过射频电缆级联连接的远端单元，且所述远端级联链的首级远端单元通过射频电缆与所述数模扩展单元连接；
    所述数模扩展单元，用于通过所述数模扩展单元内部的第一基带处理模块对信源单元通过光纤传输的下行数字射频信号进行基带处理操作，且通过所述数模扩展单元内部的第一信号转换模块进行数模转换，得到待发送给远端级联链的下行模拟射频信号；或者，所述数模扩展单元用于通过所述第一信号转换模块对所述远端级联链传输的上行模拟射频信号进行模数转换，且通过所述第一基带处理模块进行基带处理操作，得到待通过光纤发送给所述信源单元的上行数字射频信号；
    所述远端单元，用于与终端设备进行模拟射频信号交互，且相邻两个所述远端单元之间通过所述射频电缆进行模拟射频信号交互。
  2. 根据权利要求1所述的分布式天线系统，其特征在于，所述数模扩展单元包括依次连接的第一光收发模块、所述第一基带处理模块、所述第一信号转换模块和射频前端模块；
    所述第一光收发模块，用于与所述信源单元进行光信号交互；
    所述第一基带处理模块，用于对接收到的信号进行基带处理操作后输出；
    所述第一信号转换模块，用于与所述基带处理模块进行数字射频信号交互，以及与所述射频前端模块进行模拟射频信号交互；
    所述射频前端模块，用于与所述远端单元进行模拟射频信号交互，且用于进行模拟射频信号处理。
  3. 根据权利要求2所述的分布式天线系统，其特征在于，所述数模扩展单元的数量为至少两个，其中一个数模扩展单元通过光纤连接所述信源单元，相邻两个数模扩展单元之间通过光纤级联；
    所述远端级联链的数量为至少两条，一个所述数模扩展单元对应连接至少一条所述远端级联链；各所述数模扩展单元的射频前端模块分别连接对应的各所述远端级联链的首级远端单元。
  4. 根据权利要求3所述的分布式天线系统，其特征在于，所述数模扩展单元还用于：对所述信源单元传输的下行数字射频信号进行组帧，并将组帧后的数字射频信号通过光纤传输给相邻的数模扩展单元。
  5. 根据权利要求3所述的分布式天线系统，其特征在于，所述数模扩展单元还用于：
    若第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征相同，则将所述第一上行数字射频信号与所述第二上行数字射频信号进行数字合路，得到当前数模扩展单元的第三上行数字射频信号，对所述第三上行数字射频信号进行转换，得到当前数模扩展单元的上行光信号并发送给上一级数模扩展单元或所述信源单元；其中，所述第一上行数字射频信号为所述当前数模扩展单元对所述下一级数模扩展单元的上行光信号进行处理得到；所述第二上行数字射频信号为所述当前数模扩展单元对所述当前数模扩展单元连接的远端级联链的上行模拟射频信号进行模数转换和基带处理得到；
    若所述第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征不同，则分别对所述第一上行数字射频信号、第二上行数字射频信号进行转换，得到相应的上行光信号并发送给所述上一级数模扩展单元或所述信源单元。
  6. 根据权利要求2所述的分布式天线系统，其特征在于，所述数模扩展单元还包括第一监控电路、电源电路、以及通过射频电缆与所述远端级联链的首级远端单元连接的第一耦合器；
    所述第一耦合器分别连接所述第一基带处理模块、所述射频前端模块、所述第一监控电路和所述电源电路；
    所述第一耦合器，用于执行将所述第一基带处理模块生成的上下行切换信号耦合到射频电缆中、将电源信号耦合到射频电缆中、与所述远端单元进行监控信号交互、与所述远端单元进行模拟射频信号交互中的至少一种操作。
  7. 根据权利要求6所述的分布式天线系统，其特征在于，所述远端单元包括至少一个通信链路模块；相邻的两个远端单元之间通过集束射频电缆连接，所述集束射频电缆包括至少一条射频电缆，一条所述射频电缆对应连接下一级远端单元的一个通信链路模块。
  8. 根据权利要求7所述的分布式天线系统，其特征在于，所述通信链路模块包括第二耦合器、射频交互电路、第二监控电路、电源转换电路以及上下行切换电路；
    所述第二耦合器通过射频电缆与所述第一耦合器或上一级远端单元的通信链路模块连接；所述第二耦 合器分别连接所述射频交互电路、所述第二监控电路、所述电源转换电路和所述上下行切换电路；所述射频交互电路分别连接所述电源转换电路和所述上下行切换电路；
    所述第二耦合器，用于执行获取电源信号、获取上下行切换信号、与所述数模扩展单元进行监控信号交互、与所述数模扩展单元进行模拟射频信号交互、与所述下一级远端单元进行模拟射频信号交互中的至少一种操作。
  9. 根据权利要求1至8任一项所述的分布式天线系统，其特征在于，
    所述远端单元，还用于获取所述终端的第一上行模拟射频信号，以及下一级远端单元传输的第二上行模拟射频信号，并对所述第一上行模拟射频信号和所述第二上行模拟射频信号进行合路，得到当前远端单元的上行模拟射频信号；将所述上行模拟射频信号传输给上一级远端单元或所述数模扩展单元。
  10. 根据权利要求1至8任一项所述的分布式天线系统，其特征在于，还包括连接所述数模扩展单元的所述信源单元；
    所述信源单元为BBU或RRU；
    若所述信源单元为RRU，则所述分布式天线系统还包括连接在所述RRU和所述数模扩展单元之间的接入单元；
    所述接入单元，用于通过所述接入单元内部的第二基带处理模块对接收到的外部信号进行基带处理操作，以及通过所述接入单元内部的第二信号转换模块进行模拟射频信号和数字射频信号的相互转换操作，得到待发送给所述RRU的第三上行模拟射频信号或者待发送给所述数模扩展单元的下行数字射频信号。
  11. 根据权利要求10所述的分布式天线系统，其特征在于，所述接入单元包括依次连接的第二光收发模块、所述第二基带处理模块、所述第二信号转换模块和射频通道模块；
    所述第二光收发模块，用于与所述数模扩展单元进行光信号交互；
    所述第二基带处理模块，用于对接收到的信号进行基带处理后输出；
    所述第二信号转换模块，用于与所述第二基带处理模块进行数字射频信号交互，以及与所述射频通道模块进行模拟射频信号交互；
    所述射频通道模块，用于与所述RRU进行模拟射频信号交互，且用于进行模拟射频信号处理。
  12. 一种信号传输方法，其特征在于，所述信号传输方法应用于分布式天线系统；所述分布式天线系统包括数模扩展单元和远端级联链，所述远端级联链包括多个通过射频电缆级联连接的远端单元，且所述远端级联链的首级远端单元通过射频电缆与所述数模扩展单元连接；
    所述信号传输方法包括：
    所述远端单元获取终端的第一上行模拟射频信号，以及下一级远端单元传输的第二上行模拟射频信号；
    所述远端单元对所述第一上行模拟射频信号和所述第二上行模拟射频信号进行合路，得到当前远端单元的上行模拟射频信号，并将所述当前远端单元的上行模拟射频信号传输给上一级远端单元或所述数模扩展单元；
    所述数模扩展单对获取到的上行模拟射频信号进行模数转换以及基带处理，得到待通过光纤发送给信源单元的上行数字射频信号。
  13. 根据权利要求12所述的信号传输方法，其特征在于，所述分布式天线系统中，所述数模扩展单元的数量为至少两个；相邻两个数模扩展单元之间通过各自的光收发模块进行光纤级联，位于首级的数模扩展单元通过光纤连接所述信源单元；
    所述信号传输方法还包括步骤：
    所述数模扩展单元根据当前数模扩展单元接收到的多路信号的特征是否相同，确定是否将接收到的多路信号进行数字合路；
    若第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征相同，则所述数模扩展单元将所述第一上行数字射频信号与所述第二上行数字射频信号进行数字合路，得到当前数模扩展单元的第三上行数字射频信号，对所述第三上行数字射频信号进行转换，得到当前数模扩展单元的上行光信号并发送给上一级数模扩展单元或所述信源单元；其中，所述第一上行数字射频信号为所述当前数模扩展单元对所述下一级数模扩展单元的上行光信号进行处理得到；所述第二上行数字射频信号为所述当前数模扩展单元对所述当前数模扩展单元连接的远端级联链的上行模拟射频信号进行模数转换和基带处理得到；
    若所述第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征不同，则所述数模扩展单元分别对所述第一上行数字射频信号、第二上行数字射频信号进行转换，得到相应的上行光信号并发送 给所述上一级数模扩展单元或所述信源单元；
    所述数模扩展单元对所述信源单元传输的下行数字射频信号进行组帧，并将组帧后的数字射频信号通过光纤透传给下一级数模扩展单元。
  14. 一种信号传输方法，其特征在于，所述信号传输方法应用于分布式天线系统；所述分布式天线系统包括数模扩展单元和远端级联链，所述远端级联链包括多个通过射频电缆级联连接的远端单元，且所述远端级联链的首级远端单元通过射频电缆与所述数模扩展单元连接；
    所述信号传输方法包括：
    所述数模扩展单元对信源单元通过光纤传输的下行数字射频信号进行基带处理以及数模转换，得到下行模拟射频信号，并将所述下行模拟射频信号传输给所述远端级联链；
    所述远端单元获取所述下行模拟射频信号，并基于所述下行模拟射频信号进行下行射频信号发射。
  15. 根据权利要求14所述的信号传输方法，其特征在于，所述分布式天线系统中，所述数模扩展单元的数量为至少两个；相邻两个数模扩展单元之间通过各自的光收发模块进行光纤级联，位于首级的数模扩展单元通过光纤连接所述信源单元；
    所述信号传输方法还包括步骤：
    所述数模扩展单元根据当前数模扩展单元接收到的多路信号的特征是否相同，确定是否将接收到的多路信号进行数字合路；
    若第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征相同，则所述数模扩展单元将所述第一上行数字射频信号与所述第二上行数字射频信号进行数字合路，得到当前数模扩展单元的第三上行数字射频信号，对所述第三上行数字射频信号进行转换，得到当前数模扩展单元的上行光信号并发送给上一级数模扩展单元或所述信源单元；其中，所述第一上行数字射频信号为所述当前数模扩展单元对所述下一级数模扩展单元的上行光信号进行处理得到；所述第二上行数字射频信号为所述当前数模扩展单元对所述当前数模扩展单元连接的远端级联链的上行模拟射频信号进行模数转换和基带处理得到；
    若所述第一上行数字射频信号的信号特征与第二上行数字射频信号的信号特征不同，则所述数模扩展单元分别对所述第一上行数字射频信号、第二上行数字射频信号进行转换，得到相应的上行光信号并发送给所述上一级数模扩展单元或所述信源单元；
    所述数模扩展单元对所述信源单元传输的下行数字射频信号进行组帧，并将组帧后的数字射频信号通过光纤透传给下一级数模扩展单元。
  16. 一种增益控制方法，其特征在于，所述增益控制方法应用于分布式天线系统；所述分布式天线系统包括数模扩展单元和远端级联链，所述远端级联链包括多个通过射频电缆级联连接的远端单元，且所述远端级联链的首级远端单元通过射频电缆与所述数模扩展单元连接；
    所述增益控制方法包括步骤：
    所述远端单元获取所述数模扩展单元通过射频电缆传输的射频信号，并测量所述射频信号，得到第一功率值；其中，所述射频信号为所述数模扩展单元按照预设频段和预设功率值生成的信号；
    所述远端单元基于所述第一功率值和所述预设功率值，得到射频信号插损，并根据所述射频信号插损和所述预设频段，得到电缆长度；
    所述远端单元基于所述电缆长度与目标信号频段，得到目标信号插损，并基于所述目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
  17. 一种增益控制装置，其特征在于，所述增益控制装置应用于分布式天线系统；所述分布式天线系统包括数模扩展单元和远端级联链，所述远端级联链包括多个通过射频电缆级联连接的远端单元，且所述远端级联链的首级远端单元通过射频电缆与所述数模扩展单元连接；所述增益控制装置分别设置在各所述远端单元中；
    所述增益控制装置包括：
    功率测量模块，用于获取所述数模扩展单元通过射频电缆传输的射频信号，并测量所述射频信号，得到第一功率值；其中，所述射频信号为所述数模扩展单元按照预设频段和预设功率值生成的信号；
    电缆长度获取模块，用于基于所述第一功率值和所述预设功率值，得到射频信号插损，并根据所述射频信号插损和所述预设频段，得到电缆长度；
    衰减值匹配模块，用于基于所述电缆长度与目标信号频段，得到目标信号插损，并基于所述目标信号插损、目标发射功率以及增益值，匹配数控衰减器的衰减值。
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