CN104917569B - For the modulus hybrid radio frequency Optical Fiber Transmission framework of large-scale antenna array - Google Patents

Abstract

An analog-digital hybrid radio frequency optical fiber transmission architecture in the field of communication, which adopts the architecture of distributed processing of remote modules and centralized processing of near-end modules, including: a near-end data processing device connected to a long-distance distributed antenna array and its radio frequency optical fiber, The long-distance distributed antenna array includes multiple remote modules, which are connected to the corresponding antenna array elements and complete the receiving and sending of uplink/downlink signals in a distributed manner; the near-end data processing equipment includes multiple The remote module corresponds to a connected near-end module and a signal processing unit connected to the near-end module, and the signal processing unit completes uplink/downlink signal processing in a centralized manner. The invention simplifies the structure of the remote module, reduces the manufacturing cost, and multiplexes one control signal in the downlink to complete the real-time control of the remote module and the antenna array element. This analog-digital hybrid radio frequency optical fiber transmission architecture is both economical and reliable, and is suitable for the application scenarios of long-distance distributed large-scale antenna arrays.

Description

An Analog-Digital Hybrid RF-Fiber Transmission Architecture for Large-Scale Antenna Arrays

technical field

The present invention relates to a technology in the field of communication, in particular to an analog-digital hybrid radio frequency optical fiber transmission architecture for long-distance distributed large-scale antenna arrays.

Background technique

In order to cope with more complex application environments, massive MIMO (Multiple‐Input Multiple‐Output) wireless communication systems can adopt long-distance and distributed arrays to meet the increasing transmission speed and user capacity requirements . The advantages of long-distance and distributed arrays are obvious: for the base station, it can greatly improve the uniformity of spatial energy distribution, effectively reduce the energy consumption level of the entire network, and at the same time improve the spatial cooperation level of the base station system and improve the transmission of the wireless communication system. Speed and user capacity; for users, it can also effectively reduce the radiation power requirements of the terminal, thereby effectively extending the battery life of the mobile terminal device and reducing the health risks caused by electromagnetic radiation of the mobile terminal. However, at present, distributed arrays still face some problems: after adopting distributed arrays, good coherence characteristics cannot be guaranteed between long-distance array elements, it is difficult to control and manage them uniformly, and the maintenance cost of distributed arrays is high.

Using ROF (Radio Over Fiber, radio frequency optical fiber transmission) technology is an effective way to overcome the bottleneck of distributed large-scale array arrangement. The optical fiber has the characteristics of long-distance and low-loss at a specific wavelength, supports long-distance low-loss transmission of radio frequency signals, and can ensure the coherent characteristics between distributed long-distance array elements. The optical fiber itself has low cost, long service life, and relatively mature photoelectric conversion technology, making ROF technology a more economical choice.

After searching the prior art, it is found that the Chinese Patent Document No. CN103716089A, published (announcement) date 2014.04.09, discloses a radio frequency signal optical fiber phase-stable transmission method. Specifically: the transmitting end performs optical modulation on the radio frequency signal to be transmitted and then transmits it to the receiving end through an optical fiber; The transmitting end returns the received optical modulation signal of the local oscillator signal to the receiving end through the optical fiber; the receiving end demodulates the optical signal input in the optical fiber to obtain a mixed radio frequency signal, and then extracts the The first signal with the same frequency as the radio frequency signal and the second signal with the same frequency as the local oscillator signal need to be transmitted; finally, the first signal and the local oscillator signal are up-converted, and then the obtained signal is down-converted with the second signal Frequency conversion, and finally obtain a stable phase transmission radio frequency signal. However, in the scenario of long-distance and distributed large-scale MIMO antenna arrays, the simulated ROF transmission method will introduce nonlinear distortion and noise interference, resulting in deterioration of the dynamic range of the receiving end, and cannot adapt to the situation where there are large differences in signal strength between multiple users.

Contents of the invention

The present invention aims at the problem of the dynamic limitation of analog ROF and the high cost of digital ROF, and proposes an analog-digital hybrid radio-frequency optical fiber transmission architecture, aiming at the analog-digital hybrid radio-frequency optical fiber transmission architecture of a long-distance distributed large-scale antenna array, and for large-scale MIMO (Multiple‐Input Multiple‐Output, Multiple Input Multiple Output) antenna array long-distance, distributed deployment scenarios, based on the analog-digital hybrid ROF (Radio Over Fiber, radio frequency optical fiber transmission) technology, to achieve long-distance distributed antennas Uplink/downlink signal transmission between array and near-end data processing equipment. Among them, the uplink adopts digital ROF technology, which effectively improves the receiving dynamic range of the uplink, and the downlink adopts analog ROF technology, which simplifies the remote module structure, reduces manufacturing costs, and multiplexes a control signal in the downlink. Complete real-time control of remote modules and antenna elements. This analog-digital hybrid radio frequency optical fiber transmission architecture is both economical and reliable, and is suitable for the application scenarios of long-distance distributed large-scale antenna arrays.

The present invention is achieved through the following technical solutions:

The present invention adopts the framework of distributed processing of remote modules and centralized processing of near-end modules, including: a near-end data processing device connected to a long-distance distributed antenna array and a radio frequency optical fiber, wherein: the long-distance distributed antenna array includes multiple A remote module, which is connected to the corresponding antenna elements, and completes the receiving and sending of uplink/downlink signals in a distributed manner; the near-end data processing device includes a plurality of near-end modules correspondingly connected to the remote module An end module and a signal processing unit connected to the near-end module, the signal processing unit completes uplink/downlink signal processing in a centralized manner.

The distributed way to complete the receiving and sending of the up/down signal refers to: the remote module performs analog-to-digital conversion to generate the uplink signal and uplink transmits the digital signal to the near-end module;

The centralized way to complete the uplink/downlink signal processing refers to: the near-end module performs digital-to-analog conversion to generate a downlink signal, and downlink transmits the analog signal to the far-end module.

The remote module and the near-end module are connected through the radio frequency optical fiber composed of an uplink and a downlink, and communicate in an analog-to-digital hybrid ROF mode, wherein: each remote module includes: an uplink part and the downlink part, both of which are connected to the antenna through a circulator. /optical converter, the downlink part includes: a downlink optical/electrical converter connected in sequence, a control signal extraction module, a variable gain amplifier and a downlink amplification/filtering module; each near-end module includes: an uplink part and a downlink The link part, wherein: the uplink part includes: an uplink optical/electrical converter and a serial/parallel converter connected in sequence, and the downlink part includes: a control signal generation module, a digital/analog converter, a downlink converter, a downlink Electrical/optical converter.

technical effect

Compared with the existing pure analog ROF technology, the present invention proposes an analog-digital hybrid ROF technology, which is both economical and reliable, and is suitable for application in distributed antenna arrays. Since the uplink adopts digital ROF technology, the analog/digital The front end of the digital converter solves the limitation of the dynamic range of the analog ROF.

Compared with the existing pure digital ROF technology, the present invention does not have high requirements on the downlink dynamics. The analog ROF technology is used in the downlink, and the downlink signal is directly generated by the digital/analog converter of the near-end module, avoiding The modules use additional digital-to-analog conversion, frequency conversion, and logic resources, reducing manufacturing costs.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the present invention.

FIG. 2 is a schematic structural diagram of a near-end module and a far-end module.

detailed description

The following is a detailed description of the embodiments of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following implementation example.

Example 1

In this embodiment, based on the analog-digital hybrid radio frequency optical fiber transmission architecture for long-distance distributed large-scale antenna array proposed by the present invention, a building-level base station layout scheme is given, and the near-end data processing equipment is placed in the building In the computer room, multiple array units are distributed throughout the roof. The frequency band ranges of the wireless signals in this embodiment are respectively: the frequency band range of the uplink signal is 2000MHz-2020MHz, and the frequency band range of the downlink signal is 2180MHz-2200MHz. in:

As shown in Figure 1, this embodiment adopts the framework of distributed processing of remote modules and centralized processing of near-end modules, including: a near-end data processing device connected to a long-distance distributed antenna array and a radio frequency optical fiber, wherein: the long-distance The distributed antenna array includes multiple remote modules with a distribution distance of more than 100 meters. The remote modules are connected to the corresponding antenna array elements and complete the reception and transmission of uplink/downlink signals in a distributed manner; near-end data processing The device includes a plurality of near-end modules correspondingly connected to the far-end modules and a signal processing unit connected to the near-end modules, and the signal processing unit completes uplink/downlink signal processing in a centralized manner.

The remote module and the near-end module are connected through the radio frequency optical fiber composed of an uplink and a downlink, and communicate in an analog-to-digital hybrid ROF mode, wherein:

The uplink realizes the function of signal reception, adopts digital ROF technology, has a large dynamic range, and can adapt to the situation where there are large differences in signal strength between multiple simultaneously arriving received signals; for this reason, an analog/digital converter needs to be pre-installed To the remote module, transmit digital signals in the uplink optical fiber;

The downlink realizes the function of signal transmission, using analog ROF technology, which has the advantages of simplified remote module structure and low implementation cost; for this reason, it is necessary to use WDM (Wavelength Division Multiplexing, wavelength division multiplexing) technology to multiplex in the downlink optical fiber One low-bandwidth control signal completes real-time control of remote modules and antenna elements.

As shown in FIG. 2 , each remote module in this embodiment includes: an uplink part and a downlink part, both of which are connected to the antenna through a circulator.

The uplink part includes: sequentially connected uplink amplification/filtering modules, uplink frequency converters, analog/digital converters, parallel/serial converters and uplink electrical/optical converters, wherein: the uplink amplification/filtering modules output the circulator The received signal is amplified, filtered and noise-reduced. The up-converter down-converts the input signal, moves the signal to the baseband, and suppresses out-of-band noise through a low-pass filter with a passband bandwidth of 50MHz, and outputs the signal to the analog The digital/digital converter performs sampling, and the parallel/serial converter frames the sampled parallel digital signal in the FPGA according to the CPRI (Common Public Radio Interface) protocol, and then passes the framed data through the SERDES chip It is transformed into a high-speed serial signal suitable for optical fiber transmission, output to the upstream electrical/optical converter to complete the conversion of electrical signal to optical signal for the input signal, and output to the near-end module through the upstream optical fiber.

The uplink amplification/filtering module includes: a low-noise amplifier and a band-pass filter, wherein the low-noise amplifier is realized by HMC669 of Hittite Company, and its effective bandwidth range is 1700MHz-2200MHz, and the band-pass filter amplifies the bandwidth of the received signal Limited to 2000MHz‐2020MHz, output to up-converter;

Described analog/digital converter adopts the AD9609 of ADI Company to complete the sampling to received signal, and its sampling bit width is 10bit, and sampling rate 65MSPS, the data obtained by sampling is output in parallel to parallel/serial converter;

The parallel/serial converter is realized by FPGA (Field-Programmable Gate Array, Field Programmable Gate Array), according to CPRI (Common Public Radio Interface, common public radio interface) agreement, in FPGA, the parallel digital signal after sampling Frame, and then convert the framed data into a high-speed serial signal suitable for optical fiber transmission through the SERDES chip, and output it to the uplink electrical/optical converter;

The downlink part includes: sequentially connected downlink optical/electrical converters, control signal extraction modules, variable gain amplifiers and downlink amplification/filtering modules, wherein: the downlink optical/electrical converters receive light from the near-end module through downlink optical fibers Signal, based on WDM technology, uses the wave splitter inside the optical/electrical converter to separate the input wavelength division multiplexed downlink signal and control signal, and completes the conversion of two optical signals into electrical signals, and the downlink signal is output to the available Variable gain amplifier, the control signal is output to the control signal extraction module; the control signal extraction module extracts relevant information from the input control signal according to the CPRI protocol, and outputs to the variable gain amplifier and the analog/digital converter of the uplink part respectively, for real-time control The gain of the variable gain amplifier and the clock synchronization of the analog/digital converter, the variable gain amplifier amplifies the input downlink signal according to the control signal provided by the control signal extraction module, and the amplified signal is output to the downlink amplification/filtering module; The downlink amplification/filtering module filters and amplifies the input signal and outputs it to the circulator.

The control signal extraction module is realized by FPGA;

The variable gain amplifier is realized by the ADL5240 radio frequency numerical control variable gain amplifier of ADI Company, the effective frequency band range is 100MHz-4000MHz, the gain control range is 31.5dB, and the gain step accuracy is 0.25dB;

The downlink amplification/filtering module includes: a bandpass filter and a power amplifier, which limit the signal bandwidth to 2180MHz-2200MHz.

As shown in Figure 2, the near-end module includes: an uplink part and a downlink part, wherein:

The uplink part includes: an uplink optical/electrical converter and a serial/parallel converter connected in sequence, wherein: the uplink optical/electrical converter receives the uplink signal from the remote module through the uplink optical fiber, and completes the conversion of the optical signal to the electrical signal , output to the serial/parallel converter; the serial/parallel converter deserializes the high-speed serial data signal through the SERDES chip, restores it into a parallel data frame, and then restores the sampling data through the FPGA according to the CPRI protocol, and parallelizes it with a 10bit bit width output to the subsequent signal processing unit.

The downlink part includes: a control signal generation module, a digital/analog converter, a downlink converter, and a downlink electrical/optical converter, wherein: the control signal generation module receives the control signal from the signal processing unit, and according to the CPRI protocol, converts the control signal to Framed transmission, converted into high-speed serial signals suitable for optical fiber transmission through the SERDES chip, and output to the downlink electrical/optical converter; the digital/analog converter converts the downlink signal received from the signal processing unit into an analog signal, and outputs it to the downlink frequency conversion The downlink converter performs upconversion and bandpass filtering on the input signal, and outputs it to the downlink electrical/optical converter, and the downlink electrical/optical converter converts the input downlink signal and control signal to complete the conversion of the electrical signal to the optical signal ; And based on WDM technology, through the internal multiplexer for wavelength division multiplexing, the two signals are combined and output to the remote module through the downlink optical fiber.

The control signal generation module is realized by FPGA.

The said digital/analog converter is realized by AD9760 of ADI Company.

In this embodiment, the dynamic range of the downlink is 30 dB and the dynamic range of the uplink is 55 dB through the above method, which can adapt to the difference of signal power among different users.

Claims (8)

1. a kind of modulus hybrid radio frequency Optical Fiber Transmission framework for large-scale antenna array, it is characterised in that use distal end mould Block distributed treatment and the framework of local module centralized processing, including：Remote spaced antenna battle array radio frequency fiber optic phase therewith Near end data processing equipment even, wherein：Remote spaced antenna battle array includes multiple remote end modules, the remote end module with it is corresponding Bay be connected, and in a distributed fashion complete uplink/downlink signal reception and transmission；Near end data processing equipment bag Local module containing multiple connections corresponding with the remote end module and the signal processing unit being connected with local module, the signal Processing unit completes the signal transacting of Uplink/Downlink in centralized manner；

The reception and transmission that described distributed mode completes uplink/downlink signal refer to：Analog-to-digital conversion is carried out by remote end module Produce upward signal and up-link transmits data signal to local module；

The signal transacting that described centralized mode completes Uplink/Downlink refers to：Digital-to-analogue conversion production is carried out by local module Raw downstream signal and downlink transmission analog signal are to remote end module；

Described remote end module is connected with local module by up-link with the radio frequency fiber optic that downlink is constituted, and is adopted The ROF modes mixed with modulus are communicated, wherein：

Each remote end module includes：Uplink portion and downlink portion, the two is connected by circulator with antenna, its In：Uplink portion includes：It is up amplification/filtration module for being sequentially connected, up frequency converter, A/D converter, parallel/serial Converter and up electric to optic converter, downlink portion include：The descending optical electrical converter that is sequentially connected, control signal are carried Modulus block, variable gain amplifier and descending amplification/filtration module；

Each local module includes：Uplink portion and downlink portion, wherein：Uplink portion includes：Successively The up optical electrical converter and serial/parallel converter of connection, downlink portion include：Control signal generation module, D/A turn Parallel operation, descending frequency converter, descending electric to optic converter.

2. the modulus hybrid radio frequency Optical Fiber Transmission framework according to claim 1 for large-scale antenna array, its feature It is that described up amplification/filtration module is amplified and filtered noise reduction process, up change to the reception signal that circulator is exported Frequency device carries out down coversion to input signal, signal is moved near baseband, and pass through low pass of the pass band width for 50MHz Wave filter suppresses out-of-band noise, outputs a signal to A/D converter and is sampled, by parallel/serial converter according to CPRI agreements, By the parallel digital signal framing after sampling in FPGA, then the data after framing are changed into by SERDES chips suitable The high-speed serial signals of Optical Fiber Transmission, are output to up electric to optic converter and input signal completion electric signal are turned to optical signal Change, local module is output to by uplink optical fibers.

3. the modulus hybrid radio frequency Optical Fiber Transmission framework according to claim 1 or 2 for large-scale antenna array, it is special Levying is, described up amplification/filtration module includes：Low noise amplifier and bandpass filter, low noise amplifier therein are used The HMC669 of Hittite companies realizes, its effective bandwidth scope 1700MHz -2200MHz, and bandpass filter is by connecing after amplification Receive signal bandwidth and be limited in 2000MHz-2020MHz, be output to up frequency converter.

4. the modulus hybrid radio frequency Optical Fiber Transmission framework according to claim 1 or 2 for large-scale antenna array, it is special Levying is, described A/D converter sample bits a width of 10bit, sampling rate 65MSPS.

5. the modulus hybrid radio frequency Optical Fiber Transmission framework according to claim 2 for large-scale antenna array, its feature It is that described descending optical electrical converter receives the optical signal from local module by downlink optical fiber, based on WDM technology, uses The channel-splitting filter of optical electrical converter inside, the downstream signal of the wavelength-division multiplex of input and control signal is separated, and complete two-way light Signal is to the conversion of electric signal, and downstream signal is output to variable gain amplifier, and control signal is output to control signal and extracts mould Block；Control signal extraction module extracts relevant information according to CPRI agreements from the control signal of input, is respectively outputted to variable increasing The A/D converter of beneficial amplifier and uplink portion, controls gain and the analog/digital conversion of variable gain amplifier in real time The clock of device is synchronous, the control signal that variable gain amplifier is provided according to control signal extraction module, to the descending letter of input Number it is amplified, the signal output after amplification to descending amplification/filtration module；Descending amplification/filtration module enters to input signal Circulator is output to after row filtering and enhanced processing.

6. the modulus hybrid radio frequency Optical Fiber Transmission framework according to claim 5 for large-scale antenna array, its feature It is that described descending amplification/filtration module includes：Bandpass filter and power amplifier, signal bandwidth is limited in 2180MHz-2200MHz。

7. the modulus hybrid radio frequency Optical Fiber Transmission framework according to claim 1 for large-scale antenna array, its feature It is that described up optical electrical converter receives the upward signal from remote end module by uplink optical fibers, completes optical signal to electricity The conversion of signal, is output to serial/parallel converter；Serial/parallel converter will tell that serial data signal unstrings by SERDES chips, Parallel data frame is reverted to, then by FPGA, is recovered sampled data according to CPRI agreements, it is defeated parallel with 10bit bit wides Go out to follow-up signal processing unit.

8. the modulus hybrid radio frequency Optical Fiber Transmission framework according to claim 1 for large-scale antenna array, its feature It is that described control signal generation module receives control signal from signal processing unit, and according to CPRI agreements, by control signal Framing is transmitted, and is changed into the high-speed serial signals of suitable Optical Fiber Transmission by SERDES chips, is output to descending electrical/optical conversion Device；The down signal transitions received from signal processing unit are analog signal by D/A converter, are output to descending frequency converter； Descending frequency converter carries out up-conversion and bandpass filtering to input signal, and is output to descending electric to optic converter, by descending electrical/optical The downstream signal and control signal of input are completed electric signal to the conversion of optical signal by converter；And based on WDM technology, pass through Internal wave multiplexer carries out wavelength-division multiplex, and two paths of signals is merged, remote end module is output to by downlink optical fiber.