CN102075823A - Data transmission method for orthogonal frequency division multiplexing passive optical network and optical network units - Google Patents
Data transmission method for orthogonal frequency division multiplexing passive optical network and optical network units Download PDFInfo
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- CN102075823A CN102075823A CN2011100274169A CN201110027416A CN102075823A CN 102075823 A CN102075823 A CN 102075823A CN 2011100274169 A CN2011100274169 A CN 2011100274169A CN 201110027416 A CN201110027416 A CN 201110027416A CN 102075823 A CN102075823 A CN 102075823A
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2627—Modulators
- H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators
- H04L27/2633—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators using partial FFTs
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- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/548—Phase or frequency modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
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Abstract
The invention provides optical network units. Each optical network unit (ONU) comprises an optical receiving processing unit and a downlink data receiving processing unit, wherein the optical receiving processing unit receives an optical signal, converts the optical signal into radio-frequency signal and sends the radio-frequency signal to the downlink data receiving processing unit; and the downlink data receiving processing unit performs filtering, demodulating and demapping on the radio-frequency signal, and outputs data of wavelet bands corresponding to the ONUs. The invention also provides a data transmission method. In the data transmission method and the optical network units, each ONU only receives the current specific wavelet band data, so the cost is reduced with the reduction of the speed of required devices.
Description
Technical field
The present invention relates to communication system, relate in particular to a kind of OFDM (Orthogonal Frequency Division Multiplexing, OFDM) PON (Passive Optical Network, EPON) system data transmission method and optical network unit.
Background technology
(Orthogonal Frequency Division Multiplexing, OFDM) broad application is for new vitality has been injected in optical communication to OFDM.The OFDM technology is assigned to the bit information of high speed serialization on the mutually orthogonal subcarrier of each frequency spectrum dynamically, each subcarrier adopts quadrature amplitude modulation (Quadrature Amplitude Modulation simultaneously, QAM) contour contrast molding formula, the effectively spectrum efficiency of elevator system.What is more important, the data-signal duration of light OFDM symbol on each subcarrier increases relatively, add the employing of Cyclic Prefix technology, thereby effectively overcome the intersymbol interference that chromatic dispersion in the optical fiber link and polarization mode dispersion are brought.OFDM PON then combines the OFDM technology with the PON technology, produce many advantages, mainly contain: (1) but each sub-carrier resources of dynamic assignment: what light OFDM technology can be according to frequency band environment and application scenarios is different, by simple fast Fourier transform (FFT) algorithm, the power of the bit number that each subcarrier of dynamic modulation is carried, the applied modulation format of each subcarrier and each subcarrier.(2) can realize the access of converging that wire and wireless combines, OFDM is as mature technique in the radio communication, be widely used in WiMax (World Interoperability for Microwave Access, the global intercommunication microwave access), WiFi (Wireless Fidelity, Wireless Fidelity) with LTE (Long Term Evolution, Long Term Evolution) framework under.So adopt OFDM carrying PON signal, can (Optical Network Unit ONU) realizes the access of converging of wire signal and wireless signal at optical network unit.(3) effectively promoted the Access Network spectrum efficiency: because the orthogonality between each subcarrier of light ofdm signal, it not only allows the frequency spectrum of each subcarrier to overlap mutually, and can be by simple constellation mapping algorithm, on each subcarrier, realize the contour contrast system of 16QAM, 8PSK (8Phase Shift Keying, 8 phase-shift keyings).(4) good resisting chromatic dispersion makes it to extra long distance Access Network smooth evolution: theoretically, the light ofdm signal is not subjected to the chromatic dispersion in the link and the influence of polarization mode dispersion fully.So adopt OFDM-PON can realize optical access network seamlessly transitting to the extra long distance Access Network.(5) cost pressure with optical device shifts to electric device, because the integrated level of optical device and manufacture craft etc. make the high-speed light device cost very high, the above optical module of 10G and optical device pressure for Access Network are very big at present.Using the OFDM technology then can transfer to the cost pressure of optical device on the cheap Digital Signal Processing (DSP).Integrated level and cost advantage by high-speed digital signal processing and high-frequency microwave device provide express passway for Access Network develops and popularizes to higher rate.
The OFDM PON scheme that proposes mainly is based on single wavestrip (Single-band) at present, network topology structure as shown in Figure 1, comprise optical line terminal (Optical Line Terminal, OLT), optical network unit (ONU) and optical distribution network (Optical Distribution Network, ODN).
Transmitter architecture comprises that data sending processing unit and light send processing unit (laser shown in Fig. 2) as shown in Figure 2, and the data sending processing unit comprises Digital Signal Processing (DSP) module, D/A converter module, IQ modulation and up-conversion module.Comprise serial/parallel modular converter in the DSP module, QAM mapping block and inverse fast fourier transform (IFFT) module.After the high-speed serial data that comes from the upper strata processing unit enters the DSP module, at first carry out serial/parallel conversion, change high-speed serial data into the multidiameter delay low speed data, the corresponding subcarrier of every road low speed data.After the serial/parallel conversion, every circuit-switched data forms a complex points of planisphere through the QAM mapping, and each complex points is modulated on the subcarrier.Through IFFT, the multidiameter delay data are modulated on the corresponding subcarrier, finish the conversion of frequency domain to time domain, export digital OFDM baseband signal, are divided into homophase (In-phase) and two components of quadrature (Quadrature), respectively the real part and the imaginary part of corresponding symbol.D/A converter module converts digital OFDM baseband signal to simulation OFDM baseband signal, sends into IQ modulation and up-conversion module.IQ modulation and up-conversion module are modulated to homophase and quadrature component respectively on the radio-frequency carrier, finish rf modulations.At last, radiofrequency signal is modulated to by light transmission processing unit and sends into optical fiber on the light carrier and be emitted to the opposite end.
Receiver structure comprises light-receiving processing unit (photoelectric detector shown in Fig. 3) and Data Receiving processing unit as shown in Figure 3, and the Data Receiving processing unit comprises down-conversion and IQ demodulation module, analog-to-digital conversion module and Digital Signal Processing (DSP) module.Comprise in the DSP module that fast Fourier transform (FFT) module, QAM separate mapping block and parallel/serial modular converter.Signal from optical fiber converts the analog radio frequency signal of telecommunication to through the light-receiving processing unit.The analog radio frequency signal of telecommunication forms simulation OFDM baseband signal through down-conversion and IQ demodulation, is divided into homophase and quadrature two-way component.Simulation OFDM baseband signal is converted to digital OFDM baseband signal, and sends into the DSP resume module through analog-to-digital conversion module.The DSP module is at first done fast Fourier transform to digital OFDM baseband signal, finish the conversion of time domain to frequency domain, recover the data symbol that is modulated on each subcarrier, separate mapping and parallel/serial conversion through QAM afterwards and recover high-speed data and export upper strata reception processing unit to.
(OLT → ONU), whole downlink data frequency band carries out the OFDM modulation as a single wavestrip (Single-band), is divided into some orthogonal sub-carriers at down direction.Pass through the ODN broadcast transmission to all ONU through the data after the OFDM modulation, each ONU must receive the OFDM data in the whole frequency band, distributes to the subcarrier of this ONU then through demodulate reception.This single wavestrip mode, require high to the D/A converter module of transmitting terminal and the analog-to-digital conversion module of receiving terminal, downstream rate for 40G bps, even if adopt the 16QAM modulation then also to need 10G sps above digital-to-analogue and modulus processing module at least, present required device cost is very high.In addition on the one hand, at up direction,,, need to adopt wavelength division multiplexing (WDM) mode that the upward signal of each ONU is isolated for avoiding signal conflict and mutual interference mutually because the upgoing O FDM signal demand of each ONU is synthetic at luminous-power distributor.Not only cost is higher to adopt this mode, and needs to change the structure of original ODN, and ONU also can't accomplish colourless property.
Therefore, all there is bigger problem in present single wavestrip OFDM PON scheme aspect the colourless property of device cost, ODN compatibility and ONU.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of orthogonal frequency division multiplexing passive optical network data transmission method and optical network unit, reduces cost.
In order to address the above problem, the invention provides a kind of optical network unit, described optical network unit (ONU) comprises that light-receiving processing unit and downlink data receive processing unit, wherein:
Described light-receiving processing unit is used for receiving optical signals, is converted into radiofrequency signal, is sent to described downlink data and receives processing unit;
Described downlink data receives processing unit, is used for described radiofrequency signal is carried out filtering, and demodulation is shone upon, and exports the data of the wavelet band of described ONU correspondence.
Further, above-mentioned optical network unit also can have following characteristics, and described downlink data receives processing unit and comprises band pass filter module, down-conversion and IQ demodulation module, analog-to-digital conversion module and digital signal processing module, wherein:
Described band pass filter module is used for, and described radiofrequency signal is carried out filtering, filters the outer signal of wavelet band of described ONU correspondence, and the output filtering signal is to described down-conversion and IQ demodulation module;
Described down-conversion and IQ demodulation module are used for, and described filtering signal is down-converted to base band data, carry out demodulation, and the output analog signal is to analog-to-digital conversion module;
Described analog-to-digital conversion module is used for, and is digital signal with described analog signal conversion, exports described digital signal processing module to;
Described digital signal processing module is used for, and described digital signal is carried out fast fourier transform conciliate mapping.
Further, above-mentioned optical network unit also can have following characteristics, the local oscillator parameter fixed configurations of the filtering parameter of described band pass filter module and described down-conversion and IQ demodulation module.
Further, above-mentioned optical network unit also can have following characteristics, and described optical network unit also comprises the ONU control unit, wherein:
Described ONU control unit is used for, and receives the control protocol instruction that optical line terminal issues, and sends to described downlink data for the wavelet band parameter of described ONU the configuration of carrying in the described control protocol instruction and receives processing unit;
Described downlink data receives processing unit and also is used for, according to described wavelet band parameter, adjust the filtering parameter of described band pass filter module, and/or, the local oscillator parameter of described down-conversion and IQ demodulation module is set, makes that the wavelet band of described ONU correspondence is that described optical line terminal disposes the wavelet band to described ONU.
Further, above-mentioned optical network unit also can have following characteristics, and described optical network unit comprises that also upstream data sends processing unit and light burst transmitting element, wherein:
Described upstream data sends processing unit, is used for data to be sent are shone upon and modulates output radiofrequency signal to the described light transmitting element that happens suddenly;
Described light burst transmitting element is used for described radio frequency unit is converted to light signal, sends on the time slot of optical line terminal appointment.
The present invention also provides a kind of orthogonal frequency division multiplexing passive optical network system data transmission method, comprising:
Optical network unit (ONU) receiving optical signals is converted into radiofrequency signal;
Described radiofrequency signal is carried out filtering, and demodulation is shone upon, and exports the data of the wavelet band of described ONU correspondence.
Further, said method also can have following characteristics, and described radiofrequency signal is carried out filtering, and the demodulation mapping comprises:
Described radiofrequency signal is carried out filtering, filter the outer signal of wavelet band of described ONU correspondence, the output filtering signal;
Described filtering signal is down-converted to base band data, carry out demodulation, the output analog signal;
With described analog signal conversion is digital signal;
Described digital signal is carried out fast fourier transform conciliate mapping.
Further, said method also can have following characteristics, and the wavelet band of described ONU correspondence is fixed.
Further, said method also can have following characteristics, and described method also comprises:
Receive the control protocol instruction that optical line terminal issues, according to the filtering parameter of the configuration of carrying in the described control protocol instruction to the band pass filter module of the described ONU of wavelet band parameter adjustment of described ONU, and/or, the down-conversion of described ONU and the local oscillator parameter of IQ demodulation module are set, make that the wavelet band of described ONU correspondence is that described optical line terminal disposes the wavelet band to described ONU.
Further, said method also can have following characteristics, and described method also comprises:
Described ONU also shines upon data to be sent and modulates, and obtains radiofrequency signal, and described radio frequency unit is converted to light signal, sends on the time slot of optical line terminal appointment.
In the invention provides, because each ONU receives only current specific wavelet band data, so the reduction of required device speed, cost also decreases.In addition, the present invention has also realized the colourless property requirement of ONU by the local oscillator of control protocol accommodation zone bandpass filter or down-conversion and IQ demodulation module.
Description of drawings
Fig. 1 is a network topology structure;
Fig. 2 is existing single wavestrip transmitter architecture block diagram;
Fig. 3 is existing single wavestrip receiver structure block diagram;
Fig. 4 is many wavestrips OFDM PON OLT of system transmitter architecture;
Fig. 5 is many wavestrips OFDM PON ONU of system receiver structure;
Fig. 6 is many wavestrips OFDM PON system diagram;
Fig. 7 is that many wavestrips OFDM PON downstream spectrum is divided schematic diagram;
Fig. 8 is the uplink spectrum schematic diagram.
Embodiment
The invention provides a kind of many wavestrips (Multi-band) OFDM PON scheme,, reduce the lower deployment cost of OFDM PON by combining of frequency division multiplexing (FDM) and OFDM (OFDM) technology.
At down direction, whole transmission band is divided into the plurality of sub wavestrip according to fixed form or variable mode according to demand.In each wavelet band, divide some orthogonal sub-carriers, each wavelet band independently carries out the OFDM modulation.A plurality of ONU can share a sub-wavestrip bandwidth, and realize that by the mode of subcarrier allocation or statistic multiplexing Bandwidth Dynamic is shared.The OLT transmitter architecture is divided into a plurality of parallel downlink datas according to wavelet band number in the OLT and sends processing unit as shown in Figure 4, and each downlink data sends processing unit wavestrip data are handled.High-speed data from the upper strata processing unit is carried out serial/parallel conversion by the wavelet band, the data that send to each wavelet band are corresponded to corresponding data sending processing unit respectively.In each sends processing unit, carry out serial/parallel conversion according to subcarrier.Finish the OFDM subcarrier-modulated through QAM mapping and inverse Fourier transform (IFFT), form the digital baseband ofdm signal.In D/A converter module, the homophase of digital baseband ofdm signal and quadrature component convert the homophase and the quadrature component of Analog Baseband respectively to.The Analog Baseband ofdm signal is modulated on the rf frequency that is assigned with through IQ modulation and up-conversion module.The OFDM rf modulated signal of all wavelet bands through the wave multiplexer module synthetic after, send into light again and send processing unit and be modulated to and pass through Optical Fiber Transmission on the light carrier.
Down direction ONU receiver structure as shown in Figure 5, Photoelectric Detection receives processing unit whole downstream spectrum is carried out demodulation, is converted to the signal of telecommunication.Band pass filter antithetical phrase wavestrip data are filtered, and through down-conversion and IQ demodulation, the OFDM baseband signal of output simulation comprises two components of homophase and quadrature.By analog-to-digital conversion module, convert digital OFDM baseband signal to.Digital OFDM baseband signal is finished FFT to the DSP module and QAM separates map operation, finishes current wavelet band OFDM demodulation through parallel/serial conversion at last.
Wherein, can when dispatching from the factory, ONU make ONU work in specific wavelet band by band pass filter and the RF local oscillator configuration preset parameter to receiver; Also can carry out dynamic-configuration to band pass filter and RF local oscillator parameter, thus the wavelet band of dynamic-configuration ONU work.
Can dynamically adjust the relevant parameter of receiver processing unit so that can receive specific wavelet band data according to the OLT protocol instructions.
Described many wavestrips OFDM PON system uses many wavestrips multiplex technique at down direction, adopts frequency division multiplexing (FDM) technology that downstream bands is divided into a plurality of wavelet bands (sub-band), and each wavelet band independently carries out OFDM and modulates.Each wavelet band bandwidth can be shared by a plurality of ONU simultaneously, and a plurality of ONU can be operated in the same downgoing wavelet band simultaneously, adopts subcarrier allocation or statistic multiplexing mode to realize bandwidth sharing.
Described ONU comprises that ONU control unit, light-receiving processing unit and downlink data receive processing unit, wherein:
Described ONU control unit is used for receiving in real time the protocol instructions from the OLT control unit, and the Control Parameter real time down is received processing unit to downlink data; Comprise: receive the control protocol instruction that optical line terminal issues, send to described downlink data for the wavelet band parameter of described ONU the configuration of carrying in the described control protocol instruction and receive processing unit;
Described light-receiving processing unit is used for, and receives downlink optical signal, is converted into the rf modulations signal of telecommunication, is called for short radiofrequency signal, is sent to described downlink data and receives processing unit; Wherein, the light-receiving processing unit can be photoelectric detector;
Described downlink data receives processing unit, is used to receive described radiofrequency signal, and described radiofrequency signal is carried out filtering, and demodulation is shone upon, and exports the data of the wavelet band of described ONU correspondence.Wherein, the wavelet band of ONU correspondence can fixed configurations, also can dynamic-configuration.When the local oscillator parameter fixed configurations of the filtering parameter of band pass filter module and described down-conversion and IQ demodulation module, the wavelet band fixed configurations of ONU correspondence then.But when the filtering parameter of band pass filter module and/or the local oscillator parameter timing of described down-conversion and IQ demodulation module, then the wavelet band of ONU correspondence can dynamic-configuration.
Described downlink data receives processing unit and comprises: band pass filter module, down-conversion and IQ demodulation module, analog-to-digital conversion module and digital signal processing module, wherein:
Described band-pass filter unit is used for, and described radiofrequency signal is carried out filtering, filters the outer signal of wavelet band of described ONU correspondence, and the output filtering signal is to described down-conversion and IQ demodulation module;
Described down-conversion and IQ demodulation module are used for, and described filtering signal is down-converted to base band data, carry out demodulation, and the output analog signal is to analog-to-digital conversion module;
Described analog-to-digital conversion module is used for, and is digital signal with described analog signal conversion, exports described digital signal processing module to;
Described digital signal processing module is used for, and described digital signal is carried out fast fourier transform conciliate mapping.
Described downlink data receives the wavelet band parameter that processing unit can issue according to the ONU control unit, the filtering parameter of described band-pass filter unit is set, and/or, the local oscillator parameter of described down-conversion and IQ demodulation module is set, makes that the wavelet band of described ONU correspondence is that described optical line terminal disposes the wavelet band to described ONU.Each ONU can only receive and handle the data of a specific wavelet band.
It can be the centre frequency that ONU distributes the wavelet band according to the centre frequency of the described band pass filter module of the parameter adjustment that the ONU control unit issues that downlink data receives processing unit, make and specify the data of wavelet band and to deliver to next processing unit that the data outside the appointment wavelet band are then by filtering by this band pass filter module.
Wherein, described down-conversion and IQ demodulation module comprise local oscillator and IQ mixing demodulator module.The parameter adjustment local oscillator that downlink data reception processing unit can issue according to the ONU control unit is the centre frequency that ONU distributes the wavelet band.Adjusted IQ mixing demodulator module can be removed electric carrier wave output Analog Baseband ofdm signal, and delivers to analog-to-digital conversion module and handle.The Analog Baseband ofdm signal of IQ mixing demodulator module output comprises in the same way and quadrature component.
The analog-to-digital conversion module of described ONU is used for the Analog Baseband ofdm signal of down-conversion and the output of IQ demodulation module is converted to the digital baseband ofdm signal, and delivers to digital signal processing module.The digital baseband ofdm signal comprises in the same way and quadrature component.
The digital signal processing module of described ONU comprises that fast Fourier transform (FFT) processing module, QAM separate mapping processing module and parallel/serial conversion process module.
Up direction:
At up direction, can use the method realization uplink multi-address access that inserts (TDMA) based on time division multiple access, also can insert (OFDMA) or wavelength division multiplexing (WDMA) or code division multiple access multiple access techniques such as (CDMA) in conjunction with OFDM.
Described time division multiple access inserts and is meant that each ONU sent successively in the moment of OLT appointment when up transmission, thereby avoids upstream data to clash.Each ONU must operate under the unified clock, and through strict range finding with synchronously to guarantee in correct time slot, sending data.Under time division multiple access way, each ONU uses the burst transmitter, has realized the time division multiple access access, and ONU has colourless property.
Described TDMA combines with OFDMA, is meant that ONU can carry out OFDM modulation, and a plurality of ONU can at first insert based on the OFDMA multiple access, and further on each subcarrier based on TDMA.
Described TDMA combines with WDMA, is meant that a plurality of ONU can adopt identical up wavelength, and further adopts TDMA.
Described optical network unit comprises that also upstream data sends processing unit and light burst transmitting element, wherein:
Described upstream data sends processing unit, is used for data to be sent are shone upon and modulates output radiofrequency signal to the described light transmitting element that happens suddenly;
Described light burst transmitting element is used for described radio frequency unit is converted to light signal, sends on the time slot of optical line terminal appointment.
The invention provides a kind of orthogonal frequency division multiplexing passive optical network system data transmission method, comprising:
Optical network unit (ONU) receiving optical signals is converted into radiofrequency signal;
Described radiofrequency signal is carried out filtering, and demodulation is shone upon, and exports the data of the wavelet band of described ONU correspondence.
Wherein, described radiofrequency signal is carried out filtering, the demodulation mapping comprises:
Described radiofrequency signal is carried out filtering, filter the outer signal of wavelet band of described ONU correspondence, the output filtering signal;
Described filtering signal is down-converted to base band data, carry out demodulation, the output analog signal;
With described analog signal conversion is digital signal;
Described digital signal is carried out fast fourier transform conciliate mapping.
Wherein, the wavelet band of described ONU correspondence is fixed.
Wherein, described method also comprises: receive the control protocol instruction that optical line terminal issues, according to the filtering parameter of the configuration of carrying in the described control protocol instruction to the band pass filter module of the described ONU of wavelet band parameter adjustment of described ONU, and/or, the down-conversion of described ONU and the local oscillator parameter of IQ demodulation module are set, make that the wavelet band of described ONU correspondence is that described optical line terminal disposes the wavelet band to described ONU.
Wherein, described ONU also shines upon data to be sent and modulates, and obtains radiofrequency signal, and described radio frequency unit is converted to light signal, sends on the time slot of optical line terminal appointment.
Embodiment
System architecture as shown in Figure 6, the OLT transmitter comprises that an OLT control unit and a plurality of parallel downlink data send processing unit, each downlink data sends the data of a sub-wavestrip of processing unit alignment processing.The OLT control unit carries out the configuration and the management of parameter by the internal control interface to each module of each parallel downlink data transmission processing unit of OLT, and the OLT control unit carries out real time communication by the control protocol instruction with each ONU control unit, and the control protocol instruction is sent to each ONU in real time by OFDM PON common communication channel.The ONU control unit receives content of operation and parameter real time down in each module of processing unit after receiving that the OLT control unit sends to the real time control protocol instruction of ONU to the ONU downlink data, realize the dynamic real-time control to ONU.
Whole downstream bands width is F, and wavelet band number is M.Under the fixed allocation mode, the width of each wavelet band is F/M.The radio frequency centre frequency f of each wavelet band
cWith F/M is at interval.Divide the plurality of sub carrier wave in each wavelet band, independently carry out the OFDM modulation.Figure 7 shows that the situation of 5 ONU, M=4 wherein, wherein ONU4 and ONU5 are with statistic multiplexing mode shared Sub carrier bandwidths.
In each wavelet band, divide some orthogonal sub-carriers, each wavelet band independently carries out the OFDM modulation.A plurality of ONU can share same wavelet band bandwidth, and OLT arrives each ONU, ONU1-ONU4 (5) as shown in Figure 7 according to the subcarrier of user's request and wavestrip quality dynamic assignment varying number.Can also be for a plurality of ONU distribute identical subcarrier and realize bandwidth sharing by the statistic multiplexing mode, ONU4 and ONU5 as shown in Figure 7.
Be divided into M parallel downlink data according to wavelet band number in the down direction OLT and send processing unit, each downlink data sends processing unit wavestrip data is handled, as shown in Figure 6.High-speed data from the upper strata processing unit is carried out the serial/parallel conversion in M road by the wavelet band, the data that send to each wavelet band are corresponded to corresponding downstream data sending processing unit respectively.In each downlink data sends processing unit, carry out serial/parallel conversion according to subcarrier N.Finish the OFDM subcarrier-modulated through m-QAM mapping and N point IFFT, form the digital baseband ofdm signal.In D/A conversion unit, the homophase of digital baseband ofdm signal and quadrature component convert analog in-phase respectively to and the simulation quadrature component obtains the Analog Baseband ofdm signal.IQ modulation of Analog Baseband ofdm signal process and up-conversion cells modulate are to the rf frequency of current wavelet band correspondence.The OFDM rf modulated signal of all M sub-wavestrips is modulated to light carrier through Optical Fiber Transmission again through after synthetic.
Adopt factory defaults during down direction ONU power-up initializing, each unit module works in acquiescence public administration channel, as the 1st subcarrier of the 1st wavelet band.The band pass filter module acquiescence of ONU is operated in public administration channel place wavelet band, and the ONU downlink data receives the subcarrier that processing unit receives public administration channel place, and extracts OLT control protocol broadcast, is sent to the ONU control unit.
Work in during down direction ONU initialization in the public administration channel of acquiescence, the OLT control unit is set up management by public administration channel and ONU control unit and is connected.Connect by management, the OLT control unit can send the control protocol instruction to the ONU control unit, finishes initialization, registration and the verification process of ONU.
After down direction ONU finished initialization and registration process, the OLT control unit connected to the instruction of ONU control unit transmission control protocol by management, for registered ONU distributes wavelet band parameter, comprises wavelet band numbering c, band center frequency f
cWith information such as wavelet band management channel numberings.After the ONU control unit receives the instruction of OLT control protocol, after the extraction communication channel parameters, be issued to downlink data and receive in each module of processing unit.The centre frequency of at first adjusting the band pass filter module is the wavelet mid-band frequency that ONU distributes, and adjusts ONU then and receives wavelet band management channels place subcarrier data.After adjustment was finished, the rf signal that light signal detect to form via photoelectric detector was through after the band-pass filter, and the downlink data that the specific wavelet band signal of only distributing to this ONU can enter ONU receives processing unit and further handles.
After down direction ONU adjusted the wavelet band that receiver distributes to OLT, the OLT control unit was connected by setting up to manage normally between wavelet band management channel and the ONU control unit.The OLT control unit connects and can further control the communication of ONU by normal management.If the normal management interface channel is set up failure, OLT can't receive the return messages of ONU at the appointed time, and ONU also can't obtain the control protocol message of OLT, and then both sides return common communication channel and carry out initialization procedure once more.
Down direction ONU adjustment band pass filter module makes the specific wavelet band signal of only distributing to this ONU can enter the ONU receiver and further handles.If do not possess variable band-pass filter or band pass filter is non-adjustable, then can carry out the filtering of wavelet band by adjusting down-conversion and IQ demodulation module.Wherein down-conversion and the required local oscillator of IQ demodulation module adopt adjustable mode, are the centre frequency f of wavelet band by adjusting local frequency
cCan make down-conversion and IQ demodulation module carry out demodulation to the data of specific wavelet band, demodulation is exported the Analog Baseband ofdm signal after removing electric carrier wave.
Down direction ONU finish the receiver adjustment aim at distribute the wavelet band after, just can receive the downgoing wavelet band data of specific distribution, finish the OFDM demodulation, as shown in Figure 4.Photoelectric detector carries out demodulation to whole downstream spectrum, and band pass filter module or down-conversion and IQ demodulation module are realized the filtration of antithetical phrase wavestrip data, and the OFDM baseband signal of output simulation comprises two components of homophase and quadrature.By analog-to-digital conversion module, convert digital OFDM baseband signal to.Digital OFDM baseband signal is finished FFT to the DSP module and QAM separates map operation, finishes current wavelet band OFDM demodulation through parallel/serial conversion at last.Because each ONU receives only current specific wavelet band data, so the reduction of required device speed, cost also decreases.Realized the colourless property requirement of ONU by the local oscillator of control protocol accommodation zone bandpass filter or down-conversion and IQ demodulation module.
Up direction uses time division multiple access access technology (TDMA), and as shown in Figure 7, ONU 1-ONU N sends data respectively in the line time on different.
Up direction can adopt OFDM modulation system spread bandwidth, as shown in Figure 7 in the transmitting time of each ONU.
Up direction, if use the TDM+OFDM modulation system, ONU then takes single wavestrip mode to finish the OFDM modulation to upstream data in whole upstream band, according to the time slot transmission upstream data of OLT appointment, as shown in Figure 8.Data from the upper layer data processing unit are at first carried out the serial/parallel conversion of N according to subcarrier, are transformed into the digital baseband ofdm signal through m-QAM mapping and N point IFFT then.In D/A converter module, the digital baseband ofdm signal converts the Analog Baseband ofdm signal to.Finish the OFDM rf modulations through IQ modulation and up-conversion modulation, last radio frequency ofdm signal is finished up transmission through light burst transmitting element at the time slot of appointment.Because the up transmission of ONU is based on time division multiple access, therefore well compatible original ODN network, and kept the colourless property of ONU.
Light burst receiving element receives the uplink burst data from different ONU in the up direction OLT.
If up direction adopts the OFDM modulation technique, then the data of the light of OLT burst receiving element are finished radio frequency down-conversion and IQ demodulation through down-conversion and IQ demodulation module, and output simulation OFDM baseband signal comprises homophase and quadrature component.Through analog-to-digital conversion module, simulation OFDM baseband signal converts digital OFDM baseband signal to, comprises homophase and quadrature component.The digital baseband ofdm signal is separated mapping at digital signal processing module through N point FFT and m-QAM, and the last parallel/serial OFDM demodulation that converts exports the upper layer data processing unit to.Because up based on tdma, so OLT makes and uses up the burst receiving element, avoided using the device of wavelength-division and frequency division, kept the compatible of original ODN and reduced the realization cost.
Claims (10)
1. an optical network unit is characterized in that, described optical network unit (ONU) comprises that light-receiving processing unit and downlink data receive processing unit, wherein:
Described light-receiving processing unit is used for receiving optical signals, is converted into radiofrequency signal, is sent to described downlink data and receives processing unit;
Described downlink data receives processing unit, is used for described radiofrequency signal is carried out filtering, and demodulation is shone upon, and exports the data of the wavelet band of described ONU correspondence.
2. optical network unit as claimed in claim 1 is characterized in that, described downlink data receives processing unit and comprises band pass filter module, down-conversion and IQ demodulation module, analog-to-digital conversion module and digital signal processing module, wherein:
Described band pass filter module is used for, and described radiofrequency signal is carried out filtering, filters the outer signal of wavelet band of described ONU correspondence, and the output filtering signal is to described down-conversion and IQ demodulation module;
Described down-conversion and IQ demodulation module are used for, and described filtering signal is down-converted to base band data, carry out demodulation, and the output analog signal is to analog-to-digital conversion module;
Described analog-to-digital conversion module is used for, and is digital signal with described analog signal conversion, exports described digital signal processing module to;
Described digital signal processing module is used for, and described digital signal is carried out fast fourier transform conciliate mapping.
3. optical network unit as claimed in claim 2 is characterized in that, the local oscillator parameter fixed configurations of the filtering parameter of described band pass filter module and described down-conversion and IQ demodulation module.
4. optical network unit as claimed in claim 2 is characterized in that described optical network unit also comprises the ONU control unit, wherein:
Described ONU control unit is used for, and receives the control protocol instruction that optical line terminal issues, and sends to described downlink data for the wavelet band parameter of described ONU the configuration of carrying in the described control protocol instruction and receives processing unit;
Described downlink data receives processing unit and also is used for, according to described wavelet band parameter, adjust the filtering parameter of described band pass filter module, and/or, the local oscillator parameter of described down-conversion and IQ demodulation module is set, makes that the wavelet band of described ONU correspondence is that described optical line terminal disposes the wavelet band to described ONU.
5. optical network unit as claimed in claim 1 is characterized in that, described optical network unit comprises that also upstream data sends processing unit and light burst transmitting element, wherein:
Described upstream data sends processing unit, is used for data to be sent are shone upon and modulates output radiofrequency signal to the described light transmitting element that happens suddenly;
Described light burst transmitting element is used for described radio frequency unit is converted to light signal, sends on the time slot of optical line terminal appointment.
6. an orthogonal frequency division multiplexing passive optical network system data transmission method is characterized in that, comprising:
Optical network unit (ONU) receiving optical signals is converted into radiofrequency signal;
Described radiofrequency signal is carried out filtering, and demodulation is shone upon, and exports the data of the wavelet band of described ONU correspondence.
7. method as claimed in claim 6 is characterized in that, described radiofrequency signal is carried out filtering, and the demodulation mapping comprises:
Described radiofrequency signal is carried out filtering, filter the outer signal of wavelet band of described ONU correspondence, the output filtering signal;
Described filtering signal is down-converted to base band data, carry out demodulation, the output analog signal;
With described analog signal conversion is digital signal;
Described digital signal is carried out fast fourier transform conciliate mapping.
8. method as claimed in claim 6 is characterized in that, the wavelet band of described ONU correspondence is fixed.
9. method as claimed in claim 6 is characterized in that, described method also comprises:
Receive the control protocol instruction that optical line terminal issues, according to the filtering parameter of the configuration of carrying in the described control protocol instruction to the band pass filter module of the described ONU of wavelet band parameter adjustment of described ONU, and/or, the down-conversion of described ONU and the local oscillator parameter of IQ demodulation module are set, make that the wavelet band of described ONU correspondence is that described optical line terminal disposes the wavelet band to described ONU.
10. method as claimed in claim 6 is characterized in that, described method also comprises:
Described ONU also shines upon data to be sent and modulates, and obtains radiofrequency signal, and described radio frequency unit is converted to light signal, sends on the time slot of optical line terminal appointment.
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