WO2016123751A1 - 分布式基站及信号传输方法 - Google Patents

分布式基站及信号传输方法 Download PDF

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Publication number
WO2016123751A1
WO2016123751A1 PCT/CN2015/072184 CN2015072184W WO2016123751A1 WO 2016123751 A1 WO2016123751 A1 WO 2016123751A1 CN 2015072184 W CN2015072184 W CN 2015072184W WO 2016123751 A1 WO2016123751 A1 WO 2016123751A1
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Prior art keywords
signal
intermediate frequency
downlink digital
digital
downlink
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PCT/CN2015/072184
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English (en)
French (fr)
Inventor
李兴文
王健
雷剑文
薛裕胜
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华为技术有限公司
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Priority to PCT/CN2015/072184 priority Critical patent/WO2016123751A1/zh
Priority to CN201580075438.9A priority patent/CN107211480B/zh
Publication of WO2016123751A1 publication Critical patent/WO2016123751A1/zh

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    • 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

Definitions

  • the present invention relates to the field of communications technologies, and in particular, to a distributed base station and a signal transmission method.
  • the distributed base station divides the functions of the entire base station into several devices, each device performs a certain part of the function, and each device exchanges data through a transmission medium such as an optical fiber, a cable, or a wireless.
  • a distributed base station may include a baseband unit (abbreviation: BBU) and a signal switch (English: radio hub) Abbreviation: Rhub) and RF unit (usually a small RF unit, such as pRRU, English: pico remote radio unit); among them, the baseband unit performs Iub interface, baseband processing, etc.; the signal converter mainly implements input/output (English: input) /output, abbreviation: I/O) signal exchange, I/O signal combination and branch, power supply to the remote unit; the RF unit mainly realizes mutual conversion between baseband or intermediate frequency signals and RF signals. Signal transmission and reception.
  • the BBU and the Rhub are usually connected by optical fibers,
  • FIG. 1 is a structural diagram of an existing AIF distributed base station.
  • the BBU uses a baseband signal processing module to generate a digital baseband signal for a downlink signal (for example, a digital baseband corresponding to a 900M radio frequency signal).
  • the digital baseband signal corresponding to the signal 1 and the 1800M radio frequency signal is 2), and the digital baseband signal is transmitted to the Rhub; after receiving the digital baseband signal, the Rhub first generates the digital intermediate frequency signal (such as the 900M radio frequency signal) through the digital intermediate frequency processing module.
  • the corresponding digital intermediate frequency signal 1 and the digital intermediate frequency signal corresponding to the 1800M radio frequency signal are 2), and then the generated digital intermediate frequency signal is combined in the frequency domain, and the combined digital intermediate frequency signal is processed by the first RF processing module to generate an analog.
  • IF letter The number is transmitted to the pRRU to support the multi-transmission and multi-receiver technology to improve the channel capacity.
  • the pRRU After receiving the analog IF signal, the pRRU first down-converts the analog IF signal to the baseband signal by using the mixer, and then uses the filter to transmit the required baseband signal.
  • the second RF processing unit performs RF processing (such as power amplification, RF modulation, etc.) to obtain the RF signal, and then the RF signal (such as the 900M RF signal) through the antenna.
  • RF processing such as power amplification, RF modulation, etc.
  • the traditional AIF transmission mode has poor support for multi-channel and multi-frequency.
  • the system complexity is too high, and the pRRU cannot be miniaturized.
  • the present invention innovates the transmission architecture of the existing distributed base station, and proposes a distributed base station and a signal transmission method.
  • the system complexity is too high, and the pRRU cannot achieve miniaturization.
  • an embodiment of the present invention provides a distributed base station, including: a baseband unit, a signal switch, and N radio units, where N is an integer greater than or equal to 1;
  • the baseband unit is configured to generate M downlink digital baseband signals and send the signals to the signal switch, where the M downlink digital baseband signals comprise a first downlink digital baseband signal and a second downlink digital baseband signal, M is an integer greater than or equal to 2, wherein the first downlink digital baseband signal is transmitted corresponding to the first radio frequency band, and the second downlink digital baseband signal is transmitted corresponding to the second radio frequency band;
  • the signal converter is configured to receive the M downlink digital baseband signals, and combine the first downlink digital baseband signals included in the M downlink digital baseband signals by digital up-conversion, digital-to-analog conversion, and signal combining Converting the second downlink digital baseband signal into a first analog intermediate frequency signal and transmitting to one of the N radio frequency units;
  • One of the N radio frequency units for receiving the first analog intermediate frequency signal, converting the first analog intermediate frequency signal into a first downlink digital baseband signal by analog to digital conversion, digital down conversion, and digital filtering a second downlink digital baseband signal, the first Converting the downlink digital baseband signal into a first radio frequency signal having a first radio frequency band, converting the second downlink digital baseband signal into a second radio frequency signal having a second radio frequency band, and the first radio frequency signal and the The second RF signal is transmitted.
  • the signal converter includes:
  • a first digital intermediate frequency processing module configured to digitally upconvert the first downlink digital baseband signal and the second downlink digital baseband signal of the received M downlink digital baseband signals to form a first downlink digital intermediate frequency signal and a second downlink digital intermediate frequency signal, and combining the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal to form a first downlink digital intermediate frequency combined signal and outputting;
  • a first digital-to-analog/analog DA/AD converter configured to perform digital-to-analog conversion of the first downlink digital intermediate frequency combined signal output by the first digital intermediate frequency module to form a first analog intermediate frequency signal, and then to the N One of the radio frequency units transmits the first analog intermediate frequency signal.
  • the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal have an intermediate frequency band Adjacent frequency bands.
  • the one of the N radio frequency units includes:
  • One of the N radio units includes:
  • a second DA/AD converter configured to perform analog-to-digital conversion on the received analog intermediate frequency signal output by the first DA/AD converter to form a digital intermediate frequency signal, and output the same;
  • a second digital intermediate frequency processing module configured to digitally down-convert the digital intermediate frequency signal output by the second DA/AD converter, and then output the first downlink digital baseband signal and the second downlink digital baseband signal;
  • the radio frequency processing module is configured to perform radio frequency processing on the first downlink digital baseband signal output by the second digital intermediate frequency processing module to form a first radio frequency signal having a first radio frequency band, and transmit the same radio frequency through the air interface;
  • the two downlink digital baseband signals are subjected to radio frequency processing to form a second radio frequency signal having a second radio frequency band, which is transmitted through the air interface.
  • the signal converter is further configured to:
  • the signal converter is further configured to:
  • the first downlink digital baseband signal and the second downlink digital baseband signal of the received M downlink digital baseband signals are respectively digitally up-converted to form a first downlink digital intermediate frequency signal and a second downlink digital intermediate frequency signal, and Combining the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal to form a first downlink digital intermediate frequency combined signal, and multiplexing the first downlink digital intermediate frequency combined signal to form a first Two downlink digital intermediate frequency combined signals;
  • an embodiment of the present invention provides a signal transmission method, where the method includes:
  • the baseband unit generates M downlink digital baseband signals and transmits to the signal switch, the M downlink digital baseband signals including a first downlink digital baseband signal and a second downlink digital baseband signal, wherein the M is an integer greater than or equal to 2.
  • the first downlink digital baseband signal is transmitted corresponding to the first radio frequency band, and the second downlink digital baseband signal is transmitted to the second radio frequency band;
  • the signal converter receives the M downlink digital baseband signals, and combines the first downlink digital baseband signal and the second downlink digital baseband included in the M downlink digital baseband signals by digital up-conversion, digital-to-analog conversion, and signal combining. Signal conversion to first analog intermediate frequency Signaling and transmitting to one of the N radio units;
  • the first analog intermediate frequency signal Receiving, by one of the N radio frequency units, the first analog intermediate frequency signal, converting the first analog intermediate frequency signal into a first downlink digital baseband signal and a second downlink by analog to digital conversion, digital down conversion, and digital filtering a digital baseband signal, converting the first downlink digital baseband signal into a first radio frequency signal having a first radio frequency band, converting the second downlink digital baseband signal into a second radio frequency signal having a second radio frequency band, and Transmitting the first radio frequency signal and the second radio frequency signal.
  • the signal converter converts the first downlink digital baseband signal and the second downlink digital baseband signal included in the M downlink digital baseband signals
  • the first analog IF signal includes:
  • the first analog intermediate frequency signal is sent to one of the N radio frequency units.
  • the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal have an intermediate frequency band of Adjacent frequency bands.
  • the one of the N radio frequency units receives the The first analog intermediate frequency signal converts the first analog intermediate frequency signal into a first downlink digital baseband signal and a second downlink digital baseband signal by analog-to-digital conversion and digital filtering, and converts the first downlink digital baseband signal into a first Converting the second downlink digital baseband signal into the second radio frequency signal having the second radio frequency band, and transmitting the first radio frequency signal and the second radio frequency signal, including:
  • the signal transmission method further includes:
  • the signal converter forms a first downlink digital baseband signal of the received M downlink digital baseband signals into a first downlink digital intermediate frequency signal
  • the signal transmission method further includes:
  • the signal converter digitally upconverts the first downlink digital baseband signal and the second downlink digital baseband signal of the received M downlink digital baseband signals to form a first downlink digital intermediate frequency signal and a second downlink digital An intermediate frequency signal, and combining the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal to form a first downlink digital intermediate frequency combined signal, and the first downlink digital intermediate frequency combined signal Multiplexing to form a second downlink digital intermediate frequency combined signal;
  • the multiplexed second downlink digital intermediate frequency combined signal is digital-to-analog converted to form a third analog intermediate frequency signal, and then transmitted to a third one of the N radio frequency units.
  • the pRRU directly filters the analog intermediate frequency signal to obtain the required analog intermediate frequency signal
  • the filtering of the analog signal requires a guard band between the signals of the two frequency bands.
  • the bandwidth consumption is large.
  • the frequency spurs will make the analog filter limited by the influence of the mixed spurs and the rectangular parameters of the filter, and the design complexity is high, which makes the pRRU design complex and signals for multiple frequency bands. Poor transmission support reduces the overall performance of distributed base stations.
  • the pRRU converts the analog intermediate frequency signal received from the Rhub into a digital baseband signal, and then filters the digital baseband signal, so that the filter design in the pRRU can be complicated on the one hand. The degree is reduced. On the other hand, it is not necessary to set a guard band between signals of multiple frequency bands transmitted between Rhub and pRRU, which can save bandwidth resources and facilitate transmission of multi-frequency signals.
  • the pRRU since the pRRU includes the processing of the digital intermediate frequency signal, the digital pre-distortion, automatic gain control and the like can be performed relatively easily in the pRRU, thereby improving the quality of the processed signal.
  • FIG. 1 is a structural diagram of a distributed base station based on AIF in the prior art
  • FIG. 2 is a networking diagram of a distributed base station according to an embodiment of the present invention.
  • FIG. 3 is a structural diagram of a distributed base station according to an embodiment of the present invention.
  • FIG. 4 is a structural diagram of a distributed base station according to an embodiment of the present invention.
  • FIG. 5 is a flowchart of a signal transmission method provided by the present invention.
  • FIG. 7 is a flowchart of another signal transmission method provided by the present invention.
  • FIG. 8 is a schematic diagram of spectrum changes during signal transmission according to the present invention.
  • FIG. 2 is a networking diagram of a distributed base station according to an embodiment of the present invention.
  • the distributed base station may include a baseband unit, a signal switch, and a radio frequency unit (usually a small radio unit), each of which The baseband unit can be connected to at least one signal converter, and one signal converter can be connected to at least one radio frequency unit; wherein, in the embodiment of the present invention, the baseband unit in the embodiment and the drawings in the specification is named for convenience of description: BBU (English: base band unit), the name of the signal switch is: Rhub (English: radio hub), the radio unit is named: pRRU (English: pico remote radio unit); need to be explained, as shown in Figure 2
  • the unit modules may also be named by other abbreviations in the present invention.
  • the present invention is not limited to the embodiment of the present invention; the present invention only provides the distributed information provided by the embodiment of the present invention, the baseband unit is the BBU, the signal exchange is the Rhub, and the radio frequency unit is the pRRU.
  • the base station and signal transmission methods are introduced.
  • Figure 3 shows a distributed base station according to an embodiment of the present invention.
  • the distributed base station may include: BBU 200, Rhub 210, and N pRRUs 220;
  • the BBU 200 is configured to generate M downlink digital baseband signals and send the signals to the Rhub 210, where the M downlink digital baseband signals comprise a first downlink digital baseband signal and a second downlink digital baseband signal, where M is greater than or equal to 2
  • the integer of the first downlink digital baseband signal corresponds to the first radio frequency band
  • the second downlink digital baseband signal corresponds to the second radio frequency band.
  • the digital baseband signal is a signal with a center frequency of 0 (without spectrum shifting and transformation).
  • the Rhub 210 is configured to receive the M downlink digital baseband signals, and combine the first downlink digital baseband signals included in the M downlink digital baseband signals with the second by digital up-conversion, digital-to-analog conversion, and signal combining.
  • the downlink digital baseband signal is converted to a first analog intermediate frequency signal and transmitted to one of the N pRRUs 220.
  • One of the N pRRUs 220 configured to receive the first analog intermediate frequency signal, and convert the first analog intermediate frequency signal into a first downlink digital baseband signal by analog to digital conversion, digital down conversion, and digital filtering.
  • a second downlink digital baseband signal converting the first downlink digital baseband signal into a first radio frequency signal having a first radio frequency band, converting the second downlink digital baseband signal into a second radio frequency signal having a second radio frequency band, and A radio frequency signal and a second radio frequency signal are transmitted.
  • the Rhub 210 may include:
  • the first digital intermediate frequency processing module 211 is configured to digitally up-convert the first downlink digital baseband signal and the second downlink digital baseband signal of the M downlink digital baseband signals sent by the received BBU 200 to form a first downlink digital The intermediate frequency signal and the second downlink digital intermediate frequency signal, and combining the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal to form a first downlink digital intermediate frequency combined signal and outputting;
  • DA/AD digital to analog/analog to digital
  • the intermediate frequency band of the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal may be adjacent frequency bands.
  • the digital up-conversion processing may be: frequency shifting the frequency spectrum of the digital baseband signal to a higher frequency than the baseband signal and suitable for transmission on an intermediate frequency carrier frequency between the Rhub and the pRRU to form a digital intermediate frequency signal.
  • Rhub210 combines the downlink digital intermediate frequency signals of two adjacent frequency bands corresponding to signal 1 and signal 2 into one digital intermediate frequency signal without frequency band interval (as shown in FIG. 8(c)), and combines the digital intermediate frequency signals. After digital-to-analog conversion, it is sent to pRRU1.
  • the pRRU 220 may include:
  • a second DA/AD converter 221, configured to perform analog-to-digital conversion on the received analog intermediate frequency signal output by the first DA/AD converter to form a digital intermediate frequency signal, and output the signal;
  • a second digital intermediate frequency processing module 222 configured to digitally down-convert the digital intermediate frequency signal output by the second DA/AD converter, and filter out the first downlink digital baseband The signal and the second downlink digital baseband signal are output;
  • the radio frequency processing module 223 is configured to perform radio frequency processing on the first downlink digital baseband signal output by the second digital intermediate frequency processing module to form a first radio frequency signal having a first radio frequency band, and transmit the same through the air interface;
  • the baseband signal is subjected to radio frequency processing to form a second radio frequency signal having a second radio frequency band, which is transmitted through the air interface.
  • the analog-to-digital conversion may convert the analog intermediate frequency signal into a digital intermediate frequency signal by using a digital-to-analog/analog-to-digital converter; the digital down-conversion may be: using a local oscillator frequency and a digital intermediate frequency signal corresponding to the digital baseband signal.
  • the digital intermediate frequency signal is frequency-shifted to the baseband frequency to filter out the digital baseband signal by digital digital filtering; the radio frequency processing may include: digital pre-distortion, up-conversion, power amplification, and the like.
  • the Rhub 210 may further convert the received downlink digital baseband signal into one analog IF signal and send it to one of the N pRRUs 220.
  • the specific implementation is as follows:
  • the digital intermediate frequency processing module is further configured to: after the first downlink digital baseband signal of the received M downlink digital baseband signals is formed into a first downlink digital intermediate frequency signal, output;
  • the first DA/AD converter is further configured to perform digital-to-analog conversion of the first downlink digital intermediate frequency signal output by the first digital intermediate frequency module to form a second analog intermediate frequency signal, and then to the first of the N radio frequency units
  • the second radio frequency unit transmits the second analog intermediate frequency signal.
  • the Rhub 210 directly converts the digital intermediate frequency signal corresponding to the signal 1 into an analog intermediate frequency signal, and then transmits it to the pRRU2.
  • the Rhub 210 may also combine the digital intermediate frequency signals corresponding to the multiple downlink digital baseband signals into one analog intermediate frequency signal, and then send the signals to one of the N pRRUs 220, as follows:
  • the digital intermediate frequency processing module is further configured to digitally upconvert the first downlink digital baseband signal and the second downlink digital baseband signal of the received M downlink digital baseband signals to form a first downlink digital intermediate frequency signal and a second downlink digital intermediate frequency signal, and combining the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal Forming a first downlink digital intermediate frequency combined signal, and multiplexing the first downlink digital intermediate frequency combined signal to form a second downlink digital intermediate frequency combined signal;
  • the first DA/AD converter is further configured to perform digital-to-analog conversion on the multiplexed second downlink digital intermediate frequency combined signal outputted by the first digital intermediate frequency module to form a third analog intermediate frequency signal, and then to the N
  • the third RF unit in the RF unit transmits the third analog intermediate frequency signal.
  • the multiplexing may refer to copying one downlink digital intermediate frequency signal; for example, after combining the digital intermediate frequency signals corresponding to the signal 1 and the signal 2 to a digital intermediate frequency signal of 0-100 M, the combined 0-
  • the 100M digital intermediate frequency signals are multiplexed into the same three digital intermediate frequency signals, each of which is sent to one pRRU, or the digital intermediate frequency signals corresponding to the signal 1 are multiplexed into the same two, each of which is sent to a pRRU.
  • the specific multiplexing situation may be determined by considering a specific application situation, and is not limited herein.
  • the distributed base station may also be configured to receive the uplink signal and process the uplink signal.
  • the processing of the uplink signal may be an inverse process to the downlink signal processing, or may be different.
  • the module for uplink signal processing and the module for downlink signal processing may be different.
  • the description is made by sharing the main modules with the processing of the uplink signal and the processing of the downlink signal. For example, when the distributed base station receives the uplink signal,
  • the pRRU 220 is further configured to receive an uplink radio frequency signal from the air interface, process the uplink radio frequency signal to form an uplink digital baseband signal, and perform digital up-conversion processing on the uplink digital baseband signal to form a digital intermediate frequency signal, if there are multiple
  • the digital baseband signal combines the digital intermediate frequency signals corresponding to the plurality of digital baseband signals into one digital intermediate frequency signal; the digital intermediate frequency signal is digital-to-analog converted to form an analog intermediate frequency signal, and then transmitted to the Rhub 210;
  • the Rhub 210 is further configured to perform analog-to-digital conversion of N analog IF signals output from the N pRRUs to form N digital intermediate frequency signals; digitally down-convert the N digital intermediate frequency signals to filter out different digital basebands. After the signal, send it to the BBU200;
  • the BBU 200 is further configured to receive the different digital baseband signals and perform corresponding processing, and specific processing is not described herein.
  • the radio frequency processing module 223 can directly perform radio frequency modulation on the digital baseband signal to obtain a radio frequency signal, but as a more general implementation manner, as shown in FIG. 4, the radio frequency in the radio frequency unit 220
  • the processing module 223 can include: a third digital intermediate frequency processing module 224, a third DA/AD converter 225, and a radio frequency processing sub-module 226;
  • the third digital intermediate frequency processing module 224 is configured to digitally upconvert the first digital baseband signal and the second digital baseband signal output by the second digital intermediate frequency processing module to form a first digital intermediate frequency signal and a second digital intermediate frequency After output
  • the third DA/AD converter 225 is configured to perform digital-to-analog conversion of the first digital intermediate frequency signal and the second digital intermediate frequency signal output by the third digital intermediate frequency processing module to form a first analog intermediate frequency signal and a second analog intermediate frequency. Output after signal;
  • the radio frequency processing sub-module 226 is configured to perform radio frequency processing on the first analog intermediate frequency signal output by the third DA/AD converter to form a first radio frequency signal having a first radio frequency band, and transmit the same radio frequency through the air interface;
  • the second analog intermediate frequency signal is subjected to radio frequency processing to form a second radio frequency signal having a second radio frequency band, which is transmitted through the air interface.
  • the air-to-air transmission is satisfied.
  • the radio frequency is required to be 2600 MHz
  • the pRRU can first perform digital up-conversion and digital-to-analog conversion on the digital baseband signal, and mix the digital baseband signal to 1300 MHz.
  • the IF signal is then amplified, filtered, and mixed to form a 2600 MHz RF signal that is transmitted through the air interface.
  • an industry standard interface such as a common public radio interface (CPRI) or a custom interface may be used between the BBU, the Rhub, and the pRRU, such as a BBU.
  • the obtained downlink digital baseband signal may be encapsulated by the CPRI interface standard and sent to the Rhub, where the encapsulated CPRI packet includes a data signal to be delivered (corresponding to the downlink digital baseband signal) and is used to control the The data signal is subjected to a synchronization signal and a control signal of the RF processing section.
  • Rhub receives the encapsulated CPRI packet, The CPRI packet is parsed to obtain a data signal, a synchronization signal, and a control signal.
  • the downlink digital baseband signal corresponding to the data signal is processed to form an analog intermediate frequency signal and then sent to the pRRU. Further, the synchronization signal and the control signal may also be sent to each pRRU by means of carrier modulation together with the analog intermediate frequency signal corresponding to the data signal.
  • the pRRU performs an operation of aligning, parsing, etc. the obtained digital baseband signal according to the synchronization signal and the control signal, and controls the process of performing radio frequency processing on the digital baseband signal by using the synchronization signal and the control signal (this part is not shown in the drawing) ).
  • any transmission medium such as a cable or an optical fiber may be used for signal transmission between the Rhub 210 and the pRRU 220.
  • the Rhuk210 and the pRRU 220 may further include a photoelectric conversion module (this portion is not shown in the drawing). ), used to achieve transmission between Rhub210 and pRRU220 through optical fiber.
  • the pRRU directly filters the analog intermediate frequency signal to obtain the required analog intermediate frequency signal
  • the filtering of the analog signal requires the two frequency bands.
  • the bandwidth consumption is large when transmitting signals of multiple frequency bands.
  • there are some mixed spurs in the guard band which makes the analog filter limited in design. Due to the influence of the spurs of the mixing spurs and the rectangular parameters of the filter, the design complexity is high, which makes the pRRU design complicated, poor signal transmission support for multiple frequency bands, and reduces the overall performance of the distributed base station.
  • the pRRU converts the analog intermediate frequency signal received from the Rhub into a digital baseband signal, and then filters the digital baseband signal, so that the filter design in the pRRU can be complicated on the one hand. Degree reduction, another On the one hand, it is not necessary to set a guard frequency band between signals of multiple frequency bands transmitted between Rhub and pRRU, which can save bandwidth resources and facilitate transmission of multi-frequency signals.
  • the pRRU since the pRRU includes the processing of the digital intermediate frequency signal, the digital pre-distortion, automatic gain control and the like can be performed relatively easily in the pRRU, thereby improving the quality of the processed signal.
  • the distributed base station provided by the embodiment of the present invention may be applied to a wireless communication network, where the wireless communication network may include the distributed base station, and may further include a user equipment served by the distributed base station.
  • FIG. 5 shows a signal transmission method provided by the present invention, which is applied to the distributed base station according to the first embodiment, wherein the distributed base station includes a BBU, a Rhub, and N pRRUs, where N is greater than or equal to 1.
  • the method may include:
  • the baseband unit generates M downlink digital baseband signals, and sends the signals to the signal switch, where the M downlink digital baseband signals include a first downlink digital baseband signal and a second downlink digital baseband signal, where M is an integer greater than or equal to 2.
  • the first downlink digital baseband signal is transmitted corresponding to the first radio frequency band
  • the second downlink digital baseband signal is transmitted corresponding to the second radio frequency band.
  • M is an integer greater than or equal to 1
  • the digital baseband signal is a signal having a center frequency of 0 (without spectral shifting and transformation).
  • the signal converter receives the M downlink digital baseband signals, and combines the first downlink digital baseband signal and the second downlink digital baseband included in the M downlink digital baseband signals by digital up-conversion, digital-to-analog conversion, and signal combining.
  • the signal is converted to a first analog intermediate frequency signal and transmitted to one of the N radio frequency units.
  • the digital up-conversion processing may be: frequency shifting the frequency spectrum of the digital baseband signal to a higher frequency than the baseband signal and suitable for the intermediate frequency carrier frequency transmitted between the Rhub and the pRRU by the mixing process;
  • the digital intermediate frequency signal can be converted to an analog intermediate frequency signal by a digital to analog/analog to digital converter.
  • the Rhub may receive the first downlink digital baseband signal and the second downlink digital baseband signal among the received M downlink digital baseband signals.
  • the numbers are respectively up-converted to form a first downlink digital intermediate frequency signal and a second downlink digital intermediate frequency signal, and the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal are combined to form a first downlink digital Intermediate frequency combined signal;
  • the first analog intermediate frequency signal is sent to one of the N radio frequency units.
  • the intermediate frequency band of the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal may be adjacent frequency bands.
  • Rhub210 combines the downlink digital intermediate frequency signals of two adjacent frequency bands corresponding to signal 1 and signal 2 into one digital intermediate frequency signal without frequency band interval (as shown in FIG. 8(c)), and combines the digital intermediate frequency signals. After digital-to-analog conversion, it is sent to pRRU1.
  • One of the N radio frequency units receives the first analog intermediate frequency signal, and converts the first analog intermediate frequency signal into a first downlink digital baseband signal and a second downlink digital by analog-to-digital conversion, digital down conversion, and digital filtering.
  • the baseband signal converts the first downlink digital baseband signal into a first radio frequency signal having a first radio frequency band, converts the second downlink digital baseband signal into a second radio frequency signal having a second radio frequency band, and converts the first radio frequency signal And transmitting with the second RF signal.
  • the analog-to-digital conversion may convert the analog intermediate frequency signal into a digital intermediate frequency signal by using a digital-to-analog/analog-to-digital converter; the digital down-conversion may be: using a local oscillator frequency and a digital intermediate frequency signal corresponding to the digital baseband signal.
  • the digital intermediate frequency signal is frequency-shifted to the baseband frequency to filter out the digital baseband signal by digital digital filtering; the radio frequency processing may include: digital pre-distortion, up-conversion, power amplification, and the like.
  • one of the N radio frequency units can perform analog-to-digital conversion on the received analog intermediate frequency signal to form a digital intermediate frequency signal;
  • radio frequency processing on the first downlink digital baseband signal to form a first radio frequency signal having a first radio frequency band transmitting through an air interface; and transmitting a second downlink digital baseband signal
  • the radio frequency processing forms a second radio frequency signal having a second radio frequency band and is transmitted through the air interface.
  • the distributed base station in the embodiment of the present invention may be further configured to receive an uplink signal and process the uplink signal as an inverse process of transmitting the downlink signal.
  • the processing of the uplink signal may be an inverse process to the downlink signal processing, or may be different.
  • the module for uplink signal processing and the module for downlink signal processing may be different.
  • the description is made by sharing the main modules with the processing of the uplink signal and the processing of the downlink signal.
  • the signal transmission method provided by the embodiment of the present invention may further include:
  • the radio frequency unit receives the uplink radio frequency signal from the air interface, processes the uplink radio frequency signal to form an uplink digital baseband signal, and performs digital up-conversion processing on the uplink digital baseband signal to form a digital intermediate frequency signal, if there are multiple digital baseband signals, Combining the digital intermediate frequency signals corresponding to the plurality of digital baseband signals into one digital intermediate frequency signal; performing digital-to-analog conversion of the digital intermediate frequency signals to form an analog intermediate frequency signal, and transmitting the digital intermediate frequency signals to the signal converter;
  • the signal converter performs analog-to-digital conversion on the N analog IF signals output from the N radio frequency units to form N digital IF signals; after digitally down-converting the N digital IF signals, filtering out different digital baseband signals, Send to the baseband unit;
  • the baseband unit receives the different digital baseband signals and performs corresponding processing, and specific processing is not described herein.
  • the signal converter can also directly convert the received downlink digital baseband signal into one analog intermediate frequency signal and send it to one of the N radio frequency units, as follows:
  • the signal converter forms a first downlink digital baseband signal of the received M downlink digital baseband signals into a first downlink digital intermediate frequency signal
  • the Rhub 210 directly converts the digital intermediate frequency signal corresponding to the signal 1 into an analog intermediate frequency signal, and then transmits it to the pRRU2.
  • the signal converter may further combine the digital intermediate frequency signals corresponding to the multiple downlink digital baseband signals into one analog intermediate frequency signal, and then send the signal to one of the N radio frequency units.
  • the implementation is as follows:
  • the signal converter performs digital up-conversion of the first downlink digital baseband signal and the second downlink digital baseband signal of the received M downlink digital baseband signals to form a first downlink digital intermediate frequency signal and a second downlink digital intermediate frequency signal, And combining the first downlink digital intermediate frequency signal and the second downlink digital intermediate frequency signal to form a first downlink digital intermediate frequency combined signal, and multiplexing the first downlink digital intermediate frequency combined signal to form a second Downlink digital intermediate frequency combined signal;
  • the third analog intermediate frequency signal is sent to a third one of the N radio frequency units.
  • the multiplexing may refer to copying one downlink digital intermediate frequency signal; for example, after combining the digital intermediate frequency signals corresponding to the signal 1 and the signal 2 to a digital intermediate frequency signal of 0-100 M, the combined 0- 100M digital intermediate frequency signals are multiplexed into the same three digital intermediate frequency signals, each digital intermediate frequency signal is sent to a corresponding RF unit, or the digital intermediate frequency signals corresponding to signal 1 are multiplexed into the same two paths, each way Give a corresponding RF unit.
  • the specific multiplexing mode can be considered in consideration of the actual application environment, and is not limited herein.
  • the pRRU directly filters the analog intermediate frequency signal to obtain the required analog intermediate frequency signal
  • the filtering of the analog signal requires the two frequency bands.
  • the bandwidth consumption is large when transmitting signals of multiple frequency bands.
  • there are some mixed spurs in the guard band which makes the analog filter limited in design.
  • the complexity of the design is affected by the influence of the parameters such as the mixing spurs and the rectangular parameters of the filter. High, which makes the pRRU design complex, poor signal transmission support for multiple frequency bands, and reduces the overall performance of the distributed base station.
  • the pRRU converts the analog intermediate frequency signal received by the Rhub into a digital baseband signal, and then filters the digital baseband signal, so that the filter design in the pRRU can be complicated on the one hand. The degree is reduced. On the other hand, it is not necessary to set a guard band between signals of multiple frequency bands transmitted between Rhub and pRRU, which can save bandwidth resources and facilitate transmission of multi-frequency signals.
  • the pRRU since the pRRU includes the processing of the digital intermediate frequency signal, the digital pre-distortion, automatic gain control and the like can be performed relatively easily in the pRRU, thereby improving the quality of the processed signal.
  • the signal transmission method described in the second embodiment is specifically described by using the third embodiment and the fourth embodiment to transmit the signal 1 and the signal 2 through three pRRUs: pRRU1, pRRU2, and pRRU3.
  • FIG. 6 shows a flowchart of a signal transmission method. As shown in FIG. 6, the method may include:
  • the BBU acquires the downlink digital baseband signal 1, the signal 2, and sends the signal 1 and the signal 2 to the Rhub.
  • Rhub respectively receives the signal 1 and the signal 2 and performs digital up-conversion processing to form a digital intermediate frequency signal of 0-50M and 50-100M.
  • Rhub combines the 0-50M digital intermediate frequency signal corresponding to signal 1 and the 50-100M digital intermediate frequency signal corresponding to signal 2 into a digital intermediate frequency signal of 0-100M.
  • the combining means that the signals are combined together in the frequency domain, for example, as shown in (c) of FIG.
  • Rhub performs digital-to-analog conversion of 0-50M digital intermediate frequency signal corresponding to signal 1 to form an analog intermediate frequency signal of 0-50M; digital-to-analog conversion of 50-100M digital intermediate frequency signal corresponding to signal 2 to form a simulation of 50-100M IF signal; digital-to-analog conversion of 0-100M corresponding digital signal after signal 1 and signal 2 are combined 0-100M analog IF signal.
  • the combination of 703 is performed in the digital domain.
  • the multiplex processing may be performed in the analog domain after the 704 digital-to-analog conversion, and details are not described herein.
  • Rhub sends an analog IF signal of 0-50M corresponding to signal 1 to pRRU1 through interface 1; an analog IF signal of 50-100M corresponding to signal 2 is sent to pRRU2 through interface 2; and signal 1 and signal 2 are sent to pRRU3 through interface 3.
  • the analog IF signal corresponding to 0-100M after the combination.
  • the pRRU1 After receiving the analog intermediate frequency signal, the pRRU1 converts the received analog intermediate frequency signal into a digital intermediate frequency signal of 0-50M, and then digitally down-converts the digital intermediate frequency signal to filter out the digital baseband signal 1, and the signal 1 is After radio frequency processing, it is transmitted at a frequency of 900 MHz.
  • a 0-50M digital intermediate frequency signal is mixed with a 25MHz local oscillator frequency and converted to a -25M to 25M digital baseband signal, and a -25M to 25M digital baseband signal is removed by a digital filter and a center frequency.
  • the asymmetric part gets the signal 1.
  • the pRRU2 After receiving the analog intermediate frequency signal, the pRRU2 converts the received analog intermediate frequency signal into a 50-100M digital intermediate frequency signal, performs digital down conversion processing on the digital intermediate frequency signal, filters out the digital baseband signal 2, and performs signal RF on the signal 2 After processing, it is transmitted at a frequency of 2600 MHz.
  • a 50-100M digital intermediate frequency signal is mixed with a 75MHz local oscillator frequency and downconverted to a -25M to 25M digital baseband signal, and a -25M to 25M digital baseband signal is removed by a digital filter and a center frequency.
  • the asymmetric part gets the signal 2.
  • the pRRU3 After receiving the analog intermediate frequency signal, the pRRU3 first converts the received analog intermediate frequency signal into a digital intermediate frequency signal, and then digitally down-converts the digital intermediate frequency signal to filter out the digital baseband signal 1 and the signal 2, and performs the RF signal 1 After processing, it is transmitted through the air interface at a frequency of 900 MHz, and the signal 2 is subjected to radio frequency processing and then transmitted through the air interface at a frequency of 2600 MHz.
  • a digital intermediate frequency signal of 0-100M (as shown in (c) of Figure 8) is divided into two paths, and one is mixed with a local frequency of 25MHz to down-convert the digital baseband signal of -25M to 75M (as shown in the figure). 8 (d1)), then the -25M to 75M digital baseband signal is removed from the central frequency by the digital filter to obtain the signal 1; one channel and the 75MHz local oscillator frequency are mixed down-converted to A digital baseband signal of -75M to 25M (shown as (d2) in Fig. 8), and a digital baseband signal of -75M to 25M is removed from the portion asymmetric with the center frequency by a digital filter to obtain a signal 2.
  • the pRRU may directly perform radio frequency modulation on the digital baseband signal to obtain a radio frequency signal, but as a more general implementation manner, the pRRU may further digitally convert the digital baseband signal to form a digital intermediate frequency signal;
  • the digital intermediate frequency signal is subjected to digital-to-analog conversion processing to form an analog intermediate frequency signal, and the analog intermediate frequency signal is subjected to radio frequency processing, and the air interface is transmitted; for example:
  • pRRU1 may perform the digital up-conversion and digital-to-analog conversion processing on the recovered signal 1 to be mixed to a frequency of 450 MHz, and then the 450 MHz intermediate frequency signal is subjected to power amplifier, filtering, and mixing to form a 900 MHz frequency air interface. Go out.
  • any transmission medium such as a cable or an optical fiber may be used for signal transmission between the Rhub and the pRRU.
  • optical fiber transmission since the signal transmitted by the optical fiber must be an optical signal, in order to realize the signal transmission between the Rhub and the pRRU, the Rhub needs to convert the analog analog intermediate frequency signal into an optical signal and transmit it to the pRRU through the optical fiber; Rhub modulates the 0-50M analog IF signal corresponding to signal 1 to optical signal 1, and transmits optical signal 1 to pRRU1 through interface 1; converts the 50-100M analog IF signal corresponding to signal 2 into optical signal 2, through interface 2 The optical signal 2 is transmitted to the pRRU 2; the analog intermediate frequency signal of 0-100 M after the combination of the signal 1 and the signal 2 is converted into the optical signal 3, and the optical signal 3 is transmitted to the pRRU 3 via the interface 3.
  • FIG. 7 shows a flow chart of another signal transmission method. As shown in FIG. 7, the method may include:
  • the BBU acquires the downlink digital baseband signal 1, the signal 2, and sends the signal 1 and the signal 2 to the Rhub.
  • Rhub respectively receives the signal 1 and the signal 2 and performs digital up-conversion processing to form a digital intermediate frequency signal of 0-50M and 50-100M.
  • Rhub combines the 0-50M digital intermediate frequency signal corresponding to signal 1 and the 50-100M digital intermediate frequency signal corresponding to signal 2 into a digital intermediate frequency signal of 0-100M, and multiplexes the 0-100M digital intermediate frequency signal into Three-way 0-100M digital intermediate frequency signal.
  • Rhub performs digital-to-analog conversion of 0-100M three-way digital intermediate frequency signals to form three-way 0-100M analog intermediate frequency signals.
  • multiplexing of 803 is performed in the digital domain.
  • multiplexing processing may be performed in the analog domain after the 804 digital-to-analog conversion, and details are not described herein.
  • Rhub sends the analog IF signal of 0-100M to the PRRU1, pRRU2, and pRRU3 through the interface 1, the interface 2, and the interface 3.
  • the pRRU1 After receiving the analog intermediate frequency signal, the pRRU1 first converts the received analog intermediate frequency signal into a digital intermediate frequency signal, and then digitally down-converts the digital intermediate frequency signal to filter out the digital baseband signal 1 and the signal 2, and the recovered digital baseband. After the signal 1 is processed by the radio frequency, it is transmitted through the air interface at a frequency of 900 MHz, and the digital baseband signal 2 is subjected to radio frequency processing and then transmitted through the air interface at a frequency of 2600 MHz.
  • the pRRU2 After receiving the analog intermediate frequency signal, the pRRU2 first converts the received analog intermediate frequency signal into a digital intermediate frequency signal, and then digitally down-converts the digital intermediate frequency signal to filter out the digital baseband signal 2, and performs signal processing on the signal 2 It is then transmitted through the air interface at a frequency of 2600 MHz.
  • the pRRU3 After receiving the analog intermediate frequency signal, the pRRU3 first converts the received analog intermediate frequency signal into a digital intermediate frequency signal, and then digitally down-converts the digital intermediate frequency signal to filter out the digital baseband signal 1 and performs signal processing on the signal 1 After that, it is transmitted through the air port at a frequency of 900 MHz.
  • the pRRU may directly perform radio frequency modulation on the digital baseband signal to obtain a radio frequency signal, but as a more general implementation manner, the pRRU may also use the number.
  • the word baseband signal is digitally up-converted to form a digital intermediate frequency signal; the digital intermediate frequency signal is subjected to digital-to-analog conversion processing to form an analog intermediate frequency signal, and the analog intermediate frequency signal is subjected to radio frequency processing and the air interface is transmitted; for example:
  • pRRU1 may perform the digital up-conversion and digital-to-analog conversion processing on the recovered signal 1 to be mixed to a frequency of 450 MHz, and then the 450 MHz digital intermediate frequency signal corresponding to the signal 1 is formed by power amplifier, filtering, and mixing.
  • the 900MHz frequency air interface is transmitted; the recovered signal 2 is first subjected to digital up-conversion and digital-to-analog conversion processing, and then mixed to a digital intermediate frequency signal of 1300MHz, and the 1300MHz digital intermediate frequency signal corresponding to the signal 2 is formed by power amplifier, filtering and mixing.
  • a 2600MHz frequency air interface is transmitted.
  • any transmission medium such as a cable or an optical fiber may be used for signal transmission between the Rhub and the pRRU.
  • optical fiber transmission since the signal transmitted by the optical fiber must be an optical signal, in order to realize the signal transmission between the Rhub and the pRRU, the Rhub needs to convert the analog analog intermediate frequency signal into an optical signal and transmit it to the pRRU through the optical fiber; Rhub modulates the three-way 0-100M analog IF signals to optical signal 1, optical signal 2, optical signal 3, and then transmits optical signal 1 to pRRU1 through interface 1, and optical signal 2 to pRRU2 through interface 2, through interface 3. The optical signal 3 is sent to the pRRU3.
  • the disclosed systems, devices, and methods may be implemented in other manners.
  • the device embodiments described above are merely illustrative.
  • the division of the unit is only a logical function division.
  • there may be another division manner for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored or not executed.
  • the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.
  • the unit described as a separate component may or may not be physically divided
  • the components displayed as the unit may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.
  • each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may be physically included separately, or two or more units may be integrated into one unit.
  • the above integrated unit can be implemented in the form of hardware or in the form of hardware plus software functional units.
  • the above-described integrated unit implemented in the form of a software functional unit can be stored in a computer readable storage medium.
  • the software functional units described above are stored in a storage medium and include instructions for causing a computer device (which may be a personal computer, server, or network device, etc.) to perform portions of the steps of the methods described in various embodiments of the present invention.
  • the foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like, and the program code can be stored. Medium.
  • the storage medium may include a read only memory, a random access memory, a magnetic disk or an optical disk, or the like.

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Abstract

本发明公开了分布式基站及信号传输方法，涉及通信技术领域，以解决现有技术AIF分布式基站中多通道和多频的支持较差，实现多通道多频信号的传输时，系统复杂度太高，且pRRU无法实现小型化的问题。本发明提供的分布式基站包括：基带单元、信号交换器以及射频单元；基带单元用于向信号交换器发送M个下行数字基带信号；信号交换器用于接收M个下行数字基带信号，通过数字上变频、数模转换和信号合并将M个下行数字基带信号转换为第一模拟中频信号，向射频单元发送；射频单元用于接收第一模拟中频信号，通过模数转换、数字下变频和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号后，射频发射出去。

Description

分布式基站及信号传输方法 技术领域
本发明涉及通信技术领域，尤其涉及一种分布式基站及信号传输方法。
背景技术
分布式基站是将整个基站的功能分到几个设备中完成，每个设备完成某一部分功能，各设备之间通过光纤、电缆、无线等传输介质交换数据。随着通信技术的发展，为了支持多发多收技术，提高信道容量，现有的一种分布式基站可以包括基带单元(英文：base band unit，缩写：BBU)、信号交换器(英文：radio hub，缩写：Rhub)以及射频单元(通常为小型射频单元，如pRRU，英文：pico remote radio unit)；其中，基带单元进行Iub接口、基带处理等；信号交换器主要实现输入/输出(英文：input/output，缩写：I/O)信号的交换、I/O信号的合路分路、向射频拉远单元供电等功能；射频单元主要实现基带或中频信号与射频信号之间的相互转换，完成信号的发射和接收。BBU和Rhub之间通常通过光纤相连，Rhub和射频单元之间通常通过网线(电缆)相连。
在实际应用中，该分布式基站通常采用模拟中频(英文：analog intermediate frequency，缩写：AIF)的传输方式。图1示出了现有AIF分布式基站的结构图，如图1所示，在该分布式基站中，BBU利用基带信号处理模块将下行信号生成数字基带信号(如900M射频信号对应的数字基带信号1和1800M射频信号对应的数字基带信号2)，并将数字基带信号传输给Rhub；Rhub接收到数字基带信号后，先将数字基带信号通过数字中频处理模块生成数字中频信号(如900M射频信号对应的数字中频信号1和1800M射频信号对应的数字中频信号2)，再将生成的数字中频信号在频率域进行合路，将合路后的数字中频信号经过第一射频处理模块处理后生成模拟中频信 号传输给pRRU，以支持多发多收技术，提高信道容量；pRRU接收到模拟中频信号后，先利用混频器将模拟中频信号下变频至基带信号，再利用滤波器将所需要发射的基带信号(如900M射频信号对应的基带信号1)滤出后，经过第二射频处理单元进行射频处理(如功率放大，射频调制等)获得射频信号，然后通过天线将该射频信号(如900M射频信号)发射出去。
这种传统的AIF的传输方式，对多通道和多频的支持较差，实现多通道多频信号的传输时，系统复杂度太高，且pRRU无法实现小型化。
发明内容
为解决上述问题，本发明对现有分布式基站的传输架构进行了创新，提出了一种分布式基站及信号传输方法。以解决现有技术AIF分布式基站中多通道和多频的支持较差，实现多通道多频信号的传输时，系统复杂度太高，且pRRU无法实现小型化的问题。
本发明的实施例采用如下技术方案：
第一方面，本发明实施例提供一种分布式基站，包括：基带单元、信号交换器以及N个射频单元，其中，N为大于等于1的整数；
所述基带单元，用于生成M个下行数字基带信号，并向所述信号交换器发送，所述M个下行数字基带信号包括第一下行数字基带信号和第二下行数字基带信号，所述M为大于等于2的整数，其中，所述第一下行数字基带信号发射时对应第一射频频段，所述第二下行数字基带信号发射时对应第二射频频段；
所述信号交换器，用于接收所述M个下行数字基带信号，通过数字上变频、数模转换和信号合并将所述M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频信号，并向N个射频单元中的一个发送；
所述N个射频单元中的一个，用于接收所述第一模拟中频信号，通过模数转换、数字下变频和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将所述第一 下行数字基带信号转换为具有第一射频频段的第一射频信号，将所述第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将所述第一射频信号和所述第二射频信号进行发射。
在第一方面的第一种可能的实现方式中，结合第一方面，所述信号交换器包括：
第一数字中频处理模块，用于将接收的所述M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合路，形成第一下行数字中频合路信号后输出；
第一数模/模数DA/AD转换器，用于将所述第一数字中频模块输出的第一下行数字中频合路信号进行数模转换形成第一模拟中频信号后，向所述N个射频单元中的一个发送所述第一模拟中频信号。
在第一方面的第二种可能的实现方式中，结合第一方面的第一种可能的实现方式，所述第一下行数字中频信号和第二下行数字中频信号所具有的中频频段为相邻频段。
在第一方面的第三种可能的实现方式中，结合第一方面至第一方面的第二种可能的实现方式，所述N个射频单元中的一个包括：
所述N个射频单元中的一个包括：
第二DA/AD转换器，用于将接收到的所述第一DA/AD转换器输出的模拟中频信号进行模数转换形成数字中频信号后输出；
第二数字中频处理模块，用于将所述第二DA/AD转换器输出的数字中频信号进行数字下变频处理后，过滤出第一下行数字基带信号和第二下行数字基带信号后输出；和
射频处理模块，用于将所述第二数字中频处理模块输出的所述第一下行数字基带信号进行射频处理形成具有第一射频频段的第一射频信号，通过空口发射出去；将所述第二下行数字基带信号进行射频处理形成具有第二射频频段的第二射频信号，通过空口发射出去。
在第一方面的第四种可能的实现方式中，结合第一方面至第一方面的第三种可能的实现方式中的任一种实现方式，所述信号交换器，还用于：
将所接收的所述M个下行数字基带信号中的第一下行数字基带信号形成第一下行数字中频信号后输出；
将所述第一下行数字中频信号进行数模转换形成第二模拟中频信号后，向所述N个射频单元中的第二射频单元发送所述第二模拟中频信号。
在第一方面的第五种可能的实现方式中，结合第一方面至第一方面的第三种可能的实现方式中的任一种实现方式，所述信号交换器，还用于：
将所接收的所述M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和所述第二下行数字中频信号进行合路，形成第一下行数字中频合路信号，将所述第一下行数字中频合路信号复用形成第二下行数字中频合路信号；
将所述复用后的第二下行数字中频合路信号进行数模转换形成第三模拟中频信号后，向所述N个射频单元中的第三射频单元发送。
第二方面，本发明实施例提供一种信号传输方法，所述方法包括：
基带单元生成M个下行数字基带信号，并向信号交换器发送，所述M个下行数字基带信号包括第一下行数字基带信号和第二下行数字基带信号，所述M为大于等于2的整数，其中，所述第一下行数字基带信号发射时对应第一射频频段，所述第二下行数字基带信号发射时对应第二射频频段；
所述信号交换器接收所述M个下行数字基带信号，通过数字上变频、数模转换和信号合并将M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频 信号，并向N个射频单元中的一个发送；
所述N个射频单元中的一个接收所述第一模拟中频信号，通过模数转换、数字下变频和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将所述第一下行数字基带信号转换为具有第一射频频段的第一射频信号，将所述第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将所述第一射频信号和所述第二射频信号进行发射。
在第二方面的第一种可能的实现方式中，结合第二方面，所述信号交换器将M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频信号包括：
将所接收的M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合路，形成第一下行数字中频合路信号；
将所述第一下行数字中频合路信号进行数模转换形成第一模拟中频信号后，向所述N个射频单元中的一个发送所述第一模拟中频信号。
在第二方面的第二种可能的实现方式中，结合第二方面的第一种可能的实现方式，所述第一下行数字中频信号和第二下行数字中频信号所具有的中频频段为相邻频段。
在第二方面的第三种可能的实现方式中，结合第二方面至第二方面的第二种可能的实现方式中的任一种实现方式，所述N个射频单元中的一个接收所述第一模拟中频信号，通过模数转换和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将第一下行数字基带信号转换为具有第一射频频段的第一射频信号，将第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将第一射频信号和第二射频信号进行发射包括：
将接收到的所述信号交换器发送的模拟中频信号进行模数转换形成数字中频信号；
将所述数字中频信号进行数字下变频处理后过滤出第一下行数字基带信号和第二下行数字基带信号；
将所述第一下行数字基带信号进行射频处理形成具有第一射频频段的第一射频信号，通过空口发射出去；将所述第二下行数字基带信号进行射频处理形成具有第二射频频段的第二射频信号，通过空口发射出去。
在第二方面的第四种可能的实现方式中，结合第二方面至第二方面的第三种可能的实现方式中的任一种实现方式，所述信号传输方法还包括：
所述信号交换器将接收的所述M个下行数字基带信号中的第一下行数字基带信号形成第一下行数字中频信号；
将所述第一下行数字中频信号进行数模转换形成第二模拟中频信号后，向所述N个射频单元中的第二射频单元发送所述第二模拟中频信号。
在第二方面的第五种可能的实现方式中，结合第二方面至第二方面的第三种可能的实现方式中的任一种实现方式，所述信号传输方法还包括：
所述信号交换器将接收的所述M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和所述第二下行数字中频信号进行合路，形成第一下行数字中频合路信号，将所述第一下行数字中频合路信号复用形成第二下行数字中频合路信号；
将复用后的所述第二下行数字中频合路信号进行数模转换形成第三模拟中频信号后，向所述N个射频单元中的第三射频单元发送。
在传统的AIF的传输方式中，由于pRRU直接对模拟中频信号进行滤波获得所需的模拟中频信号，当模拟中频信号中包括两个频 段的信号时，对模拟信号的滤波要求这两个频段的信号之间留有保护频段，则在传输多个频段的信号时，对带宽消耗较大，此外，在保护频段中会存在一些混频杂散，会使得模拟过滤器在进行设计时，受限于混频杂散和滤波器的矩形参数等指标的影响，设计复杂度较高，从而使得pRRU设计复杂，对多个频段的信号传输支持差，降低了分布式基站的整体性能。
比较而言，本发明实施例提供的分布式基站中，pRRU将从Rhub接收的模拟中频信号转换为数字基带信号，而后对数字基带信号进行滤波，这样一方面可以使pRRU中的滤波器设计复杂度降低，另一方面可以不用在Rhub和pRRU之间传输的多个频段的信号间设置保护频段，可以节省带宽资源，有利于多频信号的传输。此外，由于pRRU中包含了数字中频信号的处理，可以较简便的在pRRU进行数字预失真，自动增益控制等操作，从而提高所处理信号的质量。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为现有技术中基于AIF的分布式基站的结构图；
图2为本发明实施例提供的一种分布式基站的组网图；
图3为本发明实施例提供的分布式基站的结构图；
图4为本发明实施例提供的分布式基站的结构图；
图5为本发明提供的一信号传输方法的流程图；
图6为本发明提供的另一信号传输方法的流程图；
图7为本发明提供的另一信号传输方法的流程图；
图8为本发明提供的信号传输过程中频谱变化示意图。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术 方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
图2为本发明实施例提供的一种分布式基站的组网图，如图2所示，该分布式基站可以包含基带单元、信号交换器以及射频单元(通常为小型射频单元)，每个基带单元可以与至少一个信号交换器连接，一个信号交换器可以与至少一个射频单元连接；其中，在本发明实施例中，为了便于描述，将实施例以及说明书附图中的基带单元命名为：BBU(英文：base band unit)，将信号交换器命名为：Rhub(英文：radio hub)，将射频单元命名为：pRRU(英文：pico remote radio unit)；需要说明的是，图2所示的各单元模块还可以以其他英文缩写进行命名，本发明实施例对此不进行限定；本发明仅以基带单元为BBU、信号交换器为Rhub、射频单元为pRRU，对本发明实施例提供的分布式基站及信号传输方法进行介绍。
实施例一
图3示出了本发明实施例提供的分布式基站，如图3所示，所述分布式基站可以包括：BBU200、Rhub210与N个pRRU220；
所述BBU200，用于生成M个下行数字基带信号，并向所述Rhub210发送，所述M个下行数字基带信号包括第一下行数字基带信号和第二下行数字基带信号，M为大于等于2的整数，其中，第一下行数字基带信号发射时对应第一射频频段，第二下行数字基带信号发射时对应第二射频频段。
其中，数字基带信号为中心频率为0的(没有进行频谱搬移和变换)的信号。
所述Rhub210，用于接收所述M个下行数字基带信号，通过数字上变频、数模转换和信号合并将所述M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频信号，并向N个pRRU220中的一个发送。
所述N个pRRU220中的一个，用于接收所述第一模拟中频信号，通过模数转换、数字下变频和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将第一下行数字基带信号转换为具有第一射频频段的第一射频信号，将第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将第一射频信号和第二射频信号进行发射。
具体的，如图3所示，所述Rhub210可以包括：
第一数字中频处理模块211，用于将接收到的BBU200发送的M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合路，形成第一下行数字中频合路信号后输出；
第一数模/模数(英文：digital to analog/analog to digital，缩写：DA/AD)转换器212，用于将所述第一数字中频模块输出的第一下行数字中频合路信号进行数模转换形成第一模拟中频信号后，向所述N个pRRU220中的一个发送所述第一模拟中频信号。
其中，所述第一下行数字中频信号和第二下行数字中频信号所具有的中频频段可以为相邻频段。
所述数字上变频处理可以为：通过混频处理将数字基带信号的频谱频移到比基带信号频率更高、且适合Rhub和pRRU之间传输的中频载波频率上，以形成数字中频信号。
例如，Rhub210将信号1和信号2对应的2个相邻频段的下行数字中频信号合为没有频段间隔的一路数字中频信号(如图8(c)所示)，将合路后的数字中频信号进行数模转换后向pRRU1发送。
具体的，如图3所示，所述pRRU220可以包括：
第二DA/AD转换器221，用于将接收到的所述第一DA/AD转换器输出的模拟中频信号进行模数转换形成数字中频信号后输出；
第二数字中频处理模块222，用于将所述第二DA/AD转换器输出的数字中频信号进行数字下变频处理后过滤出第一下行数字基带 信号和第二下行数字基带信号后输出；
射频处理模块223，用于将所述第二数字中频处理模块输出的第一下行数字基带信号进行射频处理形成具有第一射频频段的第一射频信号，通过空口发射出去；将第二下行数字基带信号进行射频处理形成具有第二射频频段的第二射频信号，通过空口发射出去。
其中，所述模数转换可以为通过数模/模数转换器将模拟中频信号转换为数字中频信号；所述数字下变频可以为：采用与数字基带信号对应的本振频率与数字中频信号经过混频处理后，将数字中频信号频移到基带频率上，以便采用数字数字滤波的形式滤出数字基带信号；所述射频处理可以包括：数字预失真、上变频、功率放大等处理。
进一步的，本发明实施例中，Rhub210还可以将接收到的下行数字基带信号直接转换为一路模拟中频信号向所述N个pRRU220中的一个发送，具体实现如下：
所述数字中频处理模块，还用于将所接收的M个下行数字基带信号中的第一下行数字基带信号形成第一下行数字中频信号后输出；
第一DA/AD转换器，还用于将所述第一数字中频模块输出的第一下行数字中频信号进行数模转换形成第二模拟中频信号后，向所述N个射频单元中的第二射频单元发送所述第二模拟中频信号。
例如，Rhub210直接将信号1对应的数字中频信号进行数模转换形成模拟中频信号后，向pRRU2发送。
进一步的，本发明实施例中，Rhub210还可以将多路下行数字基带信号对应的数字中频信号合路复用为一路模拟中频信号后，向所述N个pRRU220中的一个发送，具体实现如下：
所述数字中频处理模块，还用于将所接收的M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合 路，形成第一下行数字中频合路信号，将所述第一下行数字中频合路信号复用形成第二下行数字中频合路信号；
第一DA/AD转换器，还用于将所述第一数字中频模块输出的复用后的第二下行数字中频合路信号进行数模转换形成第三模拟中频信号后，向所述N个射频单元中的第三射频单元发送所述第三模拟中频信号。
其中，所述复用可以指将一路下行数字中频信号进行复制；例如，将信号1和信号2对应的数字中频信号合路为0-100M的数字中频信号后，可以将合路后的0-100M的数字中频信号复用为相同的三路数字中频信号，每一路发给一个pRRU，或是，将信号1对应的数字中频信号复用为相同的两个，每一个发给一个pRRU。具体的复用情况可以考虑具体的应用情况而确定，在此不予限定。
在通信过程中，作为发送下行信号的逆过程，分布式基站还可以用于接收上行信号，对上行信号进行处理。可以理解的是，对上行信号的处理可以是对下行信号处理的逆过程，也可以有一定的不同。存在不同时，对上行信号处理的模块和对下行信号处理的模块可以有一定的不同。在本实施例中，以对上行信号的处理和对下行信号的处理共用主要的模块来进行描述。例如：当分布式基站接收到上行信号时，
所述pRRU220，还用于接收来自空口的上行射频信号，将所述上行射频信号进行处理形成上行数字基带信号；将所述上行数字基带信号进行数字上变频处理形成数字中频信号，若有多个数字基带信号，则将多个数字基带信号对应的数字中频信号合为一路数字中频信号；将所述数字中频信号进行数模转换形成模拟中频信号后向Rhub210发送；
所述Rhub210，还用于将从N个pRRU输出的N路模拟中频信号进行模数转换形成N路数字中频信号；将所述N路数字中频信号进行数字下变频处理后过滤出不同的数字基带信号后，向BBU200发送；
所述BBU200，还用于接收所述不同的数字基带信号，并进行相应的处理，具体的处理在此不予赘述。
具体的，本发明实施例中，射频处理模块223可以将所述数字基带信号直接进行射频调制获得射频信号，但作为一种更通用的实现方式，如图4所示，射频单元220中的射频处理模块223可以包括：第三数字中频处理模块224、第三DA/AD转换器225和射频处理子模块226；
所述第三数字中频处理模块224，用于将所述第二数字中频处理模块输出的第一数字基带信号和第二数字基带信号进行数字上变频，形成第一数字中频信号和第二数字中频后输出；
所述第三DA/AD转换器225，用于将所述第三数字中频处理模块输出的第一数字中频信号和第二数字中频信号进行数模转换形成第一模拟中频信号和第二模拟中频信号后输出；
所述射频处理子模块226，用于将所述第三DA/AD转换器输出的第一模拟中频信号进行射频处理形成具有第一射频频段的第一射频信号，通过空口发射出去；将所述第二模拟中频信号进行射频处理形成具有第二射频频段的第二射频信号，通过空口发射出去。
如此，经过两次频率上调，满足空口发射，例如：若空口发射要求射频频率为2600MHz，pRRU可以先将数字基带信号进行数字上变频、数模转换等处理，将数字基带信号混频至1300MHz的频率上，然后再将中频信号经过功放、滤波、混频形成2600MHz的射频信号经过空口发射出去。
进一步的，为了使通信规范化、统一化，BBU、Rhub和pRRU之间还可以使用通用公共无线接口(common public radio interface，简称CPRI)等业界标准的接口，或者自定义的接口进行通信，如BBU可以将获取的下行数字基带信号采用CPRI接口标准进行封装后向Rhub发送，其中，封装后的CPRI包中包括有需下发的数据信号(和下行数字基带信号相对应)和用于控制对该数据信号进行射频处理部分的同步信号和控制信号。Rhub接收封装后的CPRI包， 对CPRI包进行解析后获得数据信号、同步信号和控制信号。其中，和数据信号对应的下行数字基带信号，经处理形成模拟中频信号后向pRRU发送。进一步的，同步信号和控制信号也可以通过载波调制的方式与和数据信号对应的模拟中频信号一起发给各pRRU。pRRU根据同步信号和控制信号对所获得的数字基带信号进行对齐、解析等操作，并利用同步信号和控制信号对该数字基带信号进行射频处理的过程进行控制(此部分未在附图中示出)。
需要说明的是，本发明实施例中，Rhub210和pRRU220之间可以采用电缆、光纤等任一种传输介质进行信号传输。若采用光纤传输，由于光纤传输的信号必须为光信号，因此，为了实现Rhub210和pRRU220之间采用光纤进行信号传输，Rhub210和pRRU220中还可以包括光电转换模块(此部分未在附图中示出)，用于实现Rhub210和pRRU220之间通过光纤传输。
可以理解的是，本发明所有实施例中的描述是以两个下行数字基带信号如第一下行数字基带信号和第二下行数字基带信号，的处理作为示例，并不排除大于两个下行数字基带信号的情况。大于两个下行数字基带信号的处理也应包含在本实施例所描述的技术方案内。
在传统的AIF的传输方式中，由于pRRU直接对模拟中频信号进行滤波获得所需的模拟中频信号，当模拟中频信号中包括两个频段的信号时，对模拟信号的滤波要求这两个频段的信号之间留有保护频段，则在传输多个频段的信号时，对带宽消耗较大，此外，在保护频段中会存在一些混频杂散，会使得模拟过滤器在进行设计时，受限于混频杂散和滤波器的矩形参数等指标的影响，设计复杂度较高，从而使得pRRU设计复杂，对多个频段的信号传输支持差，降低了分布式基站的整体性能。
比较而言，本发明实施例提供的分布式基站中，pRRU将从Rhub接收的模拟中频信号转换为数字基带信号，而后对数字基带信号进行滤波，这样一方面可以使pRRU中的滤波器设计复杂度降低，另 一方面可以不用在Rhub和pRRU之间传输的多个频段的信号间设置保护频段，可以节省带宽资源，有利于多频信号的传输。此外，由于pRRU中包含了数字中频信号的处理，可以较简便的在pRRU进行数字预失真，自动增益控制等操作，从而提高所处理信号的质量。
本发明实施例提供的分布式基站，可以应用于无线通信网络中，该无线通信网络可以包括该分布式基站，还可以包括被该分布式基站服务的用户设备。
实施例二
图5示出了本发明提供的一种信号传输方法，应用于实施例一所述的分布式基站，其中，所述分布式基站包括BBU、Rhub以及N个pRRU，其中，N为大于等于1的整数，如图5所示，所述方法可以包括：
501、基带单元生成M个下行数字基带信号，并向信号交换器发送，所述M个下行数字基带信号包括第一下行数字基带信号和第二下行数字基带信号，M为大于等于2的整数，其中，第一下行数字基带信号发射时对应第一射频频段，第二下行数字基带信号发射时对应第二射频频段。
其中，M为大于等于1的整数，数字基带信号为中心频率为0的(没有进行频谱搬移和变换)的信号。
502、信号交换器接收所述M个下行数字基带信号，通过数字上变频、数模转换和信号合并将M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频信号，并向N个射频单元中的一个发送。
其中，所述数字上变频处理可以为：通过混频处理将数字基带信号的频谱频移到比基带信号频率更高、且适合Rhub和pRRU之间传输的中频载波频率上；所述数模转换可以为通过数模/模数转换器将数字中频信号转换为模拟中频信号。
优选的，本发明实施例中，所述Rhub可以将接收到的M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信 号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合路，形成第一下行数字中频合路信号；
将所述第一下行数字中频合路信号进行数模转换形成第一模拟中频信号后，向所述N个射频单元中的一个发送所述第一模拟中频信号。
其中，所述第一下行数字中频信号和第二下行数字中频信号所具有的中频频段可以为相邻频段。
例如，Rhub210将信号1和信号2对应的2个相邻频段的下行数字中频信号合为没有频段间隔的一路数字中频信号(如图8(c)所示)，将合路后的数字中频信号进行数模转换后向pRRU1发送。
503、N个射频单元中一个接收所述第一模拟中频信号，通过模数转换、数字下变频和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将第一下行数字基带信号转换为具有第一射频频段的第一射频信号，将第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将第一射频信号和第二射频信号进行发射。
其中，所述模数转换可以为通过数模/模数转换器将模拟中频信号转换为数字中频信号；所述数字下变频可以为：采用与数字基带信号对应的本振频率与数字中频信号经过混频处理后，将数字中频信号频移到基带频率上，以便采用数字数字滤波的形式滤出数字基带信号；所述射频处理可以包括：数字预失真、上变频、功率放大等处理。
优选的，N个射频单元中一个可以将接收到的模拟中频信号进行模数转换形成数字中频信号；
将所述数字中频信号进行数字下变频处理后过滤出第一下行数字基带信号和第二下行数字基带信号；
将所述第一下行数字基带信号进行射频处理形成具有第一射频频段的第一射频信号，通过空口发射出去；将第二下行数字基带信 号进行射频处理形成具有第二射频频段的第二射频信号，通过空口发射出去。
此外，在通信过程中，作为发送下行信号的逆过程，本发明实施例中的分布式基站还可以用于接收上行信号，对上行信号进行处理。可以理解的是，对上行信号的处理可以是对下行信号处理的逆过程，也可以有一定的不同。存在不同时，对上行信号处理的模块和对下行信号处理的模块可以有一定的不同。在本实施例中，以对上行信号的处理和对下行信号的处理共用主要的模块来进行描述。例如：当分布式基站接收到上行信号时，本发明实施例提供的信号传输方法还可以包括：
射频单元接收来自空口的上行射频信号，将所述上行射频信号进行处理形成上行数字基带信号；将所述上行数字基带信号进行数字上变频处理形成数字中频信号，若有多个数字基带信号，则将多个数字基带信号对应的数字中频信号合为一路数字中频信号；将所述数字中频信号进行数模转换形成模拟中频信号后向信号交换器发送；
信号交换器将从N个射频单元输出的N路模拟中频信号进行模数转换形成N路数字中频信号；将所述N路数字中频信号进行数字下变频处理后过滤出不同的数字基带信号后，向基带单元发送；
基带单元接收所述不同的数字基带信号，并进行相应的处理，具体的处理在此不予赘述。
进一步的，本发明实施例中，信号交换器还可以将接收到的下行数字基带信号直接转换为一路模拟中频信号向所述N个射频单元中的一个发送，具体实现如下：
信号交换器将所接收的M个下行数字基带信号中的第一下行数字基带信号形成第一下行数字中频信号；
将所述第一下行数字中频信号进行数模转换形成第二模拟中频信号后，向所述N个射频单元中的第二射频单元发送所述第二模拟中频信号。
例如，Rhub210直接将信号1对应的数字中频信号进行数模转换形成模拟中频信号后，向pRRU2发送。
进一步的，本发明实施例中，信号交换器还可以将多路下行数字基带信号对应的数字中频信号合路复用为一路模拟中频信号后，向所述N个射频单元中的一个发送，具体实现如下：
信号交换器将所接收的M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合路，形成第一下行数字中频合路信号，将所述第一下行数字中频合路信号复用形成第二下行数字中频合路信号；
将所述复用后的第二下行数字中频合路信号进行数模转换形成第三模拟中频信号后，向所述N个射频单元中的第三射频单元发送所述第三模拟中频信号。
其中，所述复用可以指将一路下行数字中频信号进行复制；例如，将信号1和信号2对应的数字中频信号合路为0-100M的数字中频信号后，可以将合路后的0-100M的数字中频信号复用为相同的三路数字中频信号，每路数字中频信号发给一个相应的射频单元，或者，将信号1对应的数字中频信号复用为相同的两路，每路发给一个相应的射频单元。具体的复用方式可以考虑实际的应用环境进行，在此不予限定。
可以理解的是，本实施例中的方法中一些具体或扩展描述可以参考上一实施例中的描述，在此不予赘述。
在传统的AIF的传输方式中，由于pRRU直接对模拟中频信号进行滤波获得所需的模拟中频信号，当模拟中频信号中包括两个频段的信号时，对模拟信号的滤波要求这两个频段的信号之间留有保护频段，则在传输多个频段的信号时，对带宽消耗较大，此外，在保护频段中会存在一些混频杂散，会使得模拟过滤器在进行设计时，受限于混频杂散和滤波器的矩形参数等指标的影响，设计复杂度较 高，从而使得pRRU设计复杂，对多个频段的信号传输支持差，降低了分布式基站的整体性能。
比较而言，本发明实施例提供的信号传输方法中，pRRU将从Rhub接收的模拟中频信号转换为数字基带信号，而后对数字基带信号进行滤波，这样一方面可以使pRRU中的滤波器设计复杂度降低，另一方面可以不用在Rhub和pRRU之间传输的多个频段的信号间设置保护频段，可以节省带宽资源，有利于多频信号的传输。此外，由于pRRU中包含了数字中频信号的处理，可以较简便的在pRRU进行数字预失真，自动增益控制等操作，从而提高所处理信号的质量。
下面通过实施例三、实施例四以将信号1和信号2通过3个pRRU：pRRU1、pRRU2、pRRU3空口发射出去为例，对实施例二所述的信号传输方法进行具体介绍：
实施例三
作为实施一或实施例二的具体应用，图6示出了一种信号传输方法的流程图，如图6所示，所述方法可以包括：
601、BBU获取下行数字基带信号1、信号2，并向Rhub发送信号1和信号2。
602、Rhub分别将接收到信号1和信号2进行数字上变频处理形成0-50M、50-100M的数字中频信号。
例如，如图8中(b1)、(b2)所示。
603、Rhub将信号1对应的0-50M的数字中频信号和信号2对应的50-100M的数字中频信号合路为0-100M的数字中频信号。
其中，所述合路是指在频率域将信号合在一起，例如，如图8中(c)所示。
604、Rhub将信号1对应的0-50M的数字中频信号进行数模转换形成0-50M的模拟中频信号；将信号2对应的50-100M的数字中频信号进行数模转换形成50-100M的模拟中频信号；将信号1和信号2合路后对应的0-100M的数字中频信号进行数模转换形成 0-100M的模拟中频信号。
可以理解的是，703的合路是在数字域进行的，作为另一种实现方式，可以在704数模转换后，在模拟域进行合路处理，在此不予赘述。
605、Rhub通过接口1向pRRU1发送信号1对应的0-50M的模拟中频信号；通过接口2向pRRU2发送信号2对应的50-100M的模拟中频信号；通过接口3向pRRU3发送信号1和信号2合路后对应的0-100M的模拟中频信号。
606、pRRU1接收到模拟中频信号后，将接收到的模拟中频信号转换为0-50M的数字中频信号，再将所述数字中频信号进行数字下变频处理后过滤出数字基带信号1，将信号1进行射频处理后以900MHz的频率空口发射出去。
例如，将0-50M的数字中频信号与25MHz的本振频率进行混频下变频为-25M至25M的数字基带信号，再将-25M至25M的数字基带信号经过数字滤波器去除掉与中心频率非对称的部分，获得信号1。
607、pRRU2接收到模拟中频信号后，将接收到的模拟中频信号转换为50-100M数字中频信号，将所述数字中频信号进行数字下变频处理后过滤出数字基带信号2，将信号2进行射频处理后以2600MHz的频率空口发射出去。
例如，将50-100M的数字中频信号与75MHz的本振频率进行混频下变频为-25M至25M的数字基带信号，再将-25M至25M的数字基带信号经过数字滤波器去除掉与中心频率非对称的部分，获得信号2。
608、pRRU3接收到模拟中频信号后，先将接收到的模拟中频信号转换为数字中频信号，再将数字中频信号进行数字下变频处理后过滤出数字基带信号1和信号2，将信号1进行射频处理后以900MHz的频率通过空口发射出去，将信号2进行射频处理后以2600MHz的频率通过空口发射出去。
例如，将0-100M的数字中频信号(如图8中(c)所示)分为两路，一路与25MHz的本振频率进行混频下变频为-25M至75M的数字基带信号(如图8中(d1)所示)，再将-25M至75M的数字基带信号经过数字滤波器去除掉与中心频率非对称的部分，获得信号1；一路与75MHz的本振频率进行混频下变频为-75M至25M的数字基带信号(如图8中的(d2)所示)，再将-75M至25M的数字基带信号经过数字滤波器去除掉与中心频率非对称的部分，获得信号2。
具体的，pRRU可以将所述数字基带信号直接进行射频调制获得射频信号，但作为一种更通用的实现方式，pRRU还可以将所述数字基带信号经过数字上变频处理，形成数字中频信号；将所述数字中频信号进行数模转换处理形成模拟中频信号，将所述模拟中频信号进行射频处理后空口发射出去；例如：
步骤606中，pRRU1可以将恢复的信号1先经过数字上变频、数模转换处理后混频至450MHz的频率上，然后再将450MHz的中频信号经过功放、滤波、混频形成900MHz的频率空口发射出去。
可以理解的，本发明实施例中，Rhub和pRRU之间可以之间可以采用电缆、光纤等任一种传输介质进行信号传输。若采用光纤传输，由于光纤传输的信号必须为光信号，因此，为了实现Rhub和pRRU之间采用光纤进行信号传输，Rhub需将模拟模拟中频信号转换为光信号后通过光纤向pRRU传输；如：Rhub将信号1对应的0-50M的模拟中频信号调制到光信号1，通过接口1向pRRU1发送光信号1；将信号2对应的50-100M的模拟中频信号转换为光信号2，通过接口2向pRRU2发送光信号2；将信号1和信号2合路后的0-100M的模拟中频信号转换为光信号3，通过接口3向pRRU3发送光信号3。
实施例四
作为实施一或实施例二的具体应用，图7示出了另一种信号传输方法的流程图，如图7所示，所述方法可以包括：
701、BBU获取下行数字基带信号1、信号2，并向Rhub发送信号1和信号2。
702、Rhub分别将接收到信号1和信号2进行数字上变频处理形成0-50M、50-100M的数字中频信号。
703、Rhub将信号1对应的0-50M的数字中频信号和信号2对应的50-100M的数字中频信号合路为0-100M的数字中频信号，并将0-100M的数字中频信号复用为三路0-100M的数字中频信号。
704、Rhub分别将0-100M的三路数字中频信号进行数模转换形成三路0-100M的模拟中频信号。
可以理解的是，803的复用是在数字域进行的，作为另一种实现方式，可以在804数模转换后，在模拟域进行复用处理，在此不予赘述。
705、Rhub将0-100M的模拟中频信号分别通过接口1、接口2、接口3向pRRU1、pRRU2、pRRU3发送。
706、pRRU1接收到模拟中频信号后，先将接收到的模拟中频信号转换为数字中频信号，再将数字中频信号进行数字下变频处理后过滤出数字基带信号1和信号2，将恢复的数字基带信号1进行射频处理后以900MHz的频率通过空口发射出去，将数字基带信号2进行射频处理后以2600MHz的频率通过空口发射出去。
707、pRRU2接收到模拟中频信号后，先将接收到的模拟中频信号转换为数字中频信号，再对所述数字中频信号进行数字下变频处理后过滤出数字基带信号2，将信号2进行射频处理后以2600MHz的频率通过空口发射出去。
708、pRRU3接收到模拟中频信号后，先将接收到的模拟中频信号转换为数字中频信号，再对所述数字中频信号进行数字下变频处理后过滤出数字基带信号1，将信号1进行射频处理后以900MHz的频率通过空口发射出去。
具体的，pRRU可以将所述数字基带信号直接进行射频调制获得射频信号，但作为一种更通用的实现方式，pRRU还可以将所述数 字基带信号经过数字上变频处理，形成数字中频信号；将所述数字中频信号进行数模转换处理形成模拟中频信号，将所述模拟中频信号进行射频处理后空口发射出去；例如：
步骤706中，pRRU1可以将恢复的信号1先经过数字上变频、数模转换处理后混频至450MHz的频率上，然后再将信号1对应的450MHz的数字中频信号经过功放、滤波、混频形成900MHz的频率空口发射出去；将恢复的信号2先经过数字上变频、数模转换处理后混频至1300MHz的数字中频信号，将信号2对应的1300MHz的数字中频信号经过功放、滤波、混频形成2600MHz的频率空口发射出去。
可以理解的，本发明实施例中，Rhub和pRRU之间可以之间可以采用电缆、光纤等任一种传输介质进行信号传输。若采用光纤传输，由于光纤传输的信号必须为光信号，因此，为了实现Rhub和pRRU之间采用光纤进行信号传输，Rhub需将模拟模拟中频信号转换为光信号后通过光纤向pRRU传输；如：Rhub将三路0-100M的模拟中频信号分别调制到光信号1、光信号2、光信号3，再通过接口1向pRRU1发送光信号1，通过接口2向pRRU2发送光信号2，通过接口3向pRRU3发送光信号3。
本申请实施例中的“一”、“二”、“三”、“四”等数字，仅为了便于清楚的描述或是区分，并不代表方案的优劣。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统，设备和方法，可以通过其它的方式实现。例如，以上所描述的设备实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分 开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本发明各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理包括，也可以两个或两个以上单元集成在一个单元中。上述集成的单元既可以采用硬件的形式实现，也可以采用硬件加软件功能单元的形式实现。
上述以软件功能单元的形式实现的集成的单元，可以存储在一个计算机可读取存储介质中。上述软件功能单元存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本发明各个实施例所述方法的部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(Read-Only Memory，简称ROM)、随机存取存储器(Random Access Memory，简称RAM)、磁碟或者光盘等各种可以存储程序代码的介质。
本领域普通技术人员可以理解上述实施例的各种方法中的全部或部分步骤是可以通过程序来指令相关的硬件(例如处理器)来完成，该程序可以存储于一计算机可读存储介质中，存储介质可以包括：只读存储器、随机存储器、磁盘或光盘等。
最后应说明的是：以上实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。

Claims (12)

  1. 一种分布式基站，其特征在于，包括：基带单元、信号交换器以及N个射频单元，其中，N为大于等于1的整数；
    所述基带单元，用于生成M个下行数字基带信号，并向所述信号交换器发送，所述M个下行数字基带信号包括第一下行数字基带信号和第二下行数字基带信号，所述M为大于等于2的整数，其中，所述第一下行数字基带信号发射时对应第一射频频段，所述第二下行数字基带信号发射时对应第二射频频段；
    所述信号交换器，用于接收所述M个下行数字基带信号，通过数字上变频、数模转换和信号合并将所述M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频信号，并向N个射频单元中的一个发送；
    所述N个射频单元中的一个，用于接收所述第一模拟中频信号，通过模数转换、数字下变频和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将所述第一下行数字基带信号转换为具有第一射频频段的第一射频信号，将所述第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将所述第一射频信号和所述第二射频信号进行发射。
  2. 根据权利要求1所述的分布式基站，其特征在于，
    所述信号交换器包括：
    第一数字中频处理模块，用于将接收的所述M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合路，形成第一下行数字中频合路信号后输出；
    第一数模/模数DA/AD转换器，用于将所述第一数字中频模块输出的第一下行数字中频合路信号进行数模转换形成第一模拟中频信号后，向所述N个射频单元中的一个发送所述第一模拟中频信号。
  3. 根据权利要求2所述的分布式基站，其特征在于，所述第一 下行数字中频信号和第二下行数字中频信号所具有的中频频段为相邻频段。
  4. 根据权利要求1-3中任一项所述的分布式基站，其特征在于，
    所述N个射频单元中的一个包括：
    第二DA/AD转换器，用于将接收到的所述第一DA/AD转换器输出的模拟中频信号进行模数转换形成数字中频信号后输出；
    第二数字中频处理模块，用于将所述第二DA/AD转换器输出的数字中频信号进行数字下变频处理后，过滤出第一下行数字基带信号和第二下行数字基带信号后输出；和
    射频处理模块，用于将所述第二数字中频处理模块输出的所述第一下行数字基带信号进行射频处理形成具有第一射频频段的第一射频信号，通过空口发射出去；将所述第二下行数字基带信号进行射频处理形成具有第二射频频段的第二射频信号，通过空口发射出去。
  5. 根据权利要求1-4任一项所述的分布式基站，其特征在于，所述信号交换器，还用于：
    将所接收的所述M个下行数字基带信号中的第一下行数字基带信号形成第一下行数字中频信号后输出；
    将所述第一下行数字中频信号进行数模转换形成第二模拟中频信号后，向所述N个射频单元中的第二射频单元发送所述第二模拟中频信号。
  6. 根据权利要求1-4任一项所述的分布式基站，其特征在于，所述信号交换器，还用于：
    将所接收的所述M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和所述第二下行数字中频信号进行合路，形成第一下行数字中频合路信号，将所述第一下行数字中频合路信号复用形成第二下行数字中频合路信号；
    将所述复用后的第二下行数字中频合路信号进行数模转换形成 第三模拟中频信号后，向所述N个射频单元中的第三射频单元发送。
  7. 一种信号传输方法，其特征在于，所述方法包括：
    基带单元生成M个下行数字基带信号，并向信号交换器发送，所述M个下行数字基带信号包括第一下行数字基带信号和第二下行数字基带信号，所述M为大于等于2的整数，其中，所述第一下行数字基带信号发射时对应第一射频频段，所述第二下行数字基带信号发射时对应第二射频频段；
    所述信号交换器接收所述M个下行数字基带信号，通过数字上变频、数模转换和信号合并将M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频信号，并向N个射频单元中的一个发送；
    所述N个射频单元中的一个接收所述第一模拟中频信号，通过模数转换、数字下变频和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将所述第一下行数字基带信号转换为具有第一射频频段的第一射频信号，将所述第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将所述第一射频信号和所述第二射频信号进行发射。
  8. 根据权利要求7所述的信号传输方法，其特征在于，所述信号交换器将M个下行数字基带信号中所包括的第一下行数字基带信号和第二下行数字基带信号转换为第一模拟中频信号包括：
    将所接收的M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和第二下行数字中频信号进行合路，形成第一下行数字中频合路信号；
    将所述第一下行数字中频合路信号进行数模转换形成第一模拟中频信号后，向所述N个射频单元中的一个发送所述第一模拟中频信号。
  9. 根据权利要求8所述的信号传输方法，其特征在于，
    所述第一下行数字中频信号和所述第二下行数字中频信号所具 有的中频频段为相邻频段。
  10. 根据权利要求7-9任一项所述的信号传输方法，其特征在于，所述N个射频单元中的一个接收所述第一模拟中频信号，通过模数转换和数字滤波将所述第一模拟中频信号转换为第一下行数字基带信号和第二下行数字基带信号，将第一下行数字基带信号转换为具有第一射频频段的第一射频信号，将第二下行数字基带信号转换为具有第二射频频段的第二射频信号，并将第一射频信号和第二射频信号进行发射包括：
    将接收到的所述信号交换器发送的模拟中频信号进行模数转换形成数字中频信号；
    将所述数字中频信号进行数字下变频处理后过滤出第一下行数字基带信号和第二下行数字基带信号；
    将所述第一下行数字基带信号进行射频处理形成具有第一射频频段的第一射频信号，通过空口发射出去；将所述第二下行数字基带信号进行射频处理形成具有第二射频频段的第二射频信号，通过空口发射出去。
  11. 根据权利要求7-10任一项所述的信号传输方法，其特征在于，所述信号传输方法还包括：
    所述信号交换器将接收的所述M个下行数字基带信号中的第一下行数字基带信号形成第一下行数字中频信号；
    将所述第一下行数字中频信号进行数模转换形成第二模拟中频信号后，向所述N个射频单元中的第二射频单元发送所述第二模拟中频信号。
  12. 根据权利要求7-10任一项所述的信号传输方法，其特征在于，所述信号传输方法还包括：
    所述信号交换器将接收的所述M个下行数字基带信号中的第一下行数字基带信号和第二下行数字基带信号分别进行数字上变频形成第一下行数字中频信号和第二下行数字中频信号，并将所述第一下行数字中频信号和所述第二下行数字中频信号进行合路，形成第一下 行数字中频合路信号，将所述第一下行数字中频合路信号复用形成第二下行数字中频合路信号；
    将复用后的所述第二下行数字中频合路信号进行数模转换形成第三模拟中频信号后，向所述N个射频单元中的第三射频单元发送。
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