CN101146074A - Processing method for radio access system on downlink signals based on optical fiber radio - Google Patents
Processing method for radio access system on downlink signals based on optical fiber radio Download PDFInfo
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Abstract
The invention provides a processing method of a wireless access system based on fiber wireless on downgoing signals, which performs pre-distortion processing to digital intermediate frequency. The pre-distortion processing can compensate the non-linear distortion caused by a station amplifier and a photomodulator.
Description
Technical field
The present invention relates to relate in particular to pre-distortion method wherein based on the wireless access system of optical fiber radio processing method to downstream signal.
Background technology
In the occasion of Optical Fiber Transmission analog signal, could on optical fiber, transmit after should being modulated into light signal to analog signal by optical modulator earlier.When signal frequency can resonate during near the operating frequency of optical modulator, thereby make signal produce nonlinear distortion, in order to compensate this nonlinear distortion, method commonly used is to adopt electronic device that analog signal is carried out pre-distortion, abbreviates analog predistortion as.
When the analog signal that power amplifier exceeds its range of linearity to amplitude was amplified, the signal after the amplification will contain nonlinear distortion, and the peak-to-average power ratio of signal (PAPR) is high more, and it is just serious more to amplify the nonlinear distortion that the back produces.In modulated process to digital signal, if adopt the OFDM modulation, can produce the higher modulated signal of peak-to-average power ratio, and modulated signal is before transmission, and must convert analog signal to carries out power amplification, the nonlinear distortion that produces after power amplification for compensating signal, method commonly used is that modulated signal is carried out pre-distortion, because modulated signal is a digital signal, can adopt software programming to realize pre-distortion, this predistortion just is called digital pre-distortion.Different with analog predistortion is that digital pre-distortion is to adopt software to realize, can change according to operational environment and change algorithm; And the signal environment that analog predistortion can only be used for fixing can not be made adaptive change according to the change of signal voltage, power.
For a kind of wireless access system that is connected to external network, as shown in Figure 1, its central station (CS) connects external network, and radio base station (RBS) uses radio-frequency antenna to connect wireless user terminal, is connected by optical fiber transmission line between central station and the radio base station.During signal downlink, the task of radio communication local area network (LAN) is that central station receives primary signal (low-frequency digital signal) from external network, and what last radio base station was launched is radio-frequency signal.
In wireless access system, require that usually radio base station as much as possible is set and reach seamless covering.In order to reduce cost, prior art provides a kind of fiber distribution wireless access system, as shown in Figure 1:
Central station (CS) receives primary signal from external network, and adopts OFDM (OFDM) modulation to generate baseband signal (BB), and this step is called digital baseband and handles;
Central station carries out Digital Up Convert to baseband signal, and generated frequency is about the intermediate-freuqncy signal (IF) of 100-140M, and this step is called Digital IF Processing;
Central station is changed intermediate-freuqncy signal (DAC) and is become analog signal, and generated frequency is about the radiofrequency signal (RF) of 5-6G after mixing;
Central station becomes light signal to radiofrequency signal by light modulator modulates (E/O) after power amplifier (RF) amplifies, light signal is transferred on optical fiber (fiber) and reaches radio base station;
Radio base station becomes radiofrequency signal to the light signal reduction (O/E) of receiving, is launched by radio-frequency antenna.
Such scheme digital baseband handle, Digital IF Processing and radiofrequency signal handle all the centre station and finish, can reduce the manufacturing cost of each radio base station, thereby realize the low-cost more purpose of multi radio base station of laying.In this programme, what transmit on optical fiber is radiofrequency signal, so describedly from being mixed to radio base station the step that the light signal received is reduced into radiofrequency signal is called Radio of Fiber Technology.
Because the digital baseband treatment step adopts the OFDM modulation, generate the higher baseband signal of peak-to-average power ratio, convert radiofrequency signal to, produce the severe nonlinear distortion after power amplifier amplifies, for this reason, need carry out digital pre-distortion to baseband signal at the digital baseband treatment step handles; Similarly, when signal frequency can resonate during near the operating frequency of optical modulator, thereby produce nonlinear distortion, handle so need carry out analog predistortion to radiofrequency signal.The shortcoming of said method is that the pre-distortion that adopts for nonlinear distortion that the compensation light modulation produces is radiofrequency signal to be carried out analog predistortion handle, the signal environment that can only be used for fixing can not be made adaptive change according to the change of signal voltage, power.
Summary of the invention
The present invention will solve the signal environment that the pre-distortion of the nonlinear distortion that produces for the compensation light modulation can only be used for fixing, and can not make the problem of adaptive change according to the change of signal voltage, power.
The present invention provides based on the wireless access system of the optical fiber radio processing method to downstream signal, it is characterized in that the processing of central station may further comprise the steps:
Use the OFDM modulation to generate digital baseband signal;
Digital baseband signal is carried out Digital Up Convert generate digital medium-frequency signal;
Digital medium-frequency signal is carried out pre-distortion, and this pre-distortion is the nonlinear distortion of compensating power amplifier generation both, compensates the nonlinear distortion that optical modulator produces again;
Being carried out D/A switch by the intermediate-freuqncy signal of pre-distortion, after mixing, generate radiofrequency signal again;
Radiofrequency signal after amplifying, power amplifier is become light signal by light modulator modulates.
The present invention does not carry out on radiofrequency signal for the pre-distortion that electricity/light modulation of light conversion portion is carried out, and carries out but advance to intermediate-frequency section.Because intermediate-freuqncy signal is a digital signal, adopt software programming to handle to its predistortion, belong to digital pre-distortion, can change according to operational environment and make the self adaptation adjustment.And, the present invention does not carry out after generating baseband signal for the pre-distortion that power amplifier carries out at once, and postpone to intermediate-freuqncy signal is carried out, finish in being incorporated in twice predistortion of carrying out once for power amplifier with for optical modulator, simplified system configuration.
Description of drawings
Fig. 1 is based on the structured flowchart of the wireless access system of optical fiber radio to the downstream signal processing;
Fig. 2 is the flow chart that central station of the present invention is handled downstream signal.
Embodiment
As Fig. 1, among the central station CS, digital baseband treatments B B and Digital IF Processing IF partly adopt software and radio technique, are promptly realized by a programmable module.Utilize all baseband signals of software processes and intermediate-freuqncy signal, possess stronger data-handling capacity, and write software program again and just can be transformed into another system to a kind of wireless system that defines modulator approach, frequency and bandwidth that works in cost-effectively.Make that system's suitability is strong, the system maintenance expense is low, and possess reconfigurable feature, be convenient to the compatible and upgrading of system wireless standard.Link between central station CS and the radio base station RBS adopts Radio of Fiber Technology, promptly carry out the conversion between intermediate-freuqncy signal and the radiofrequency signal, transmitting radio frequency signal on optical fiber, radio base station just need not to carry out digital baseband processing, Digital IF Processing and radiofrequency signal processing like this, only needing that the radiofrequency signal that receives from optical fiber is carried out conventional treatment such as light/electricity conversion O/E, filtering, amplification can be launched by radio-frequency antenna, thereby simplified the treatment step of radio base station, reduced the cost of radio base station.
As Fig. 2, the multiple signals of employing different communication protocol such as Wi-Fi, WiMAX, 3G, 4G are respectively hung oneself after digital baseband handles, and the multichannel baseband signal of generation Digital Up Convert (Interpolation) back of respectively hanging oneself again generates intermediate-freuqncy signal.The central station of present embodiment is multiplexing multichannel intermediate-freuqncy signal earlier, concentrates and carries out digital pre-distortion processing DPD.Because the multiplexing of intermediate-freuqncy signal can be caused non-linear mutual distortion again, so the concentrated pre-distortion of carrying out can compensate the mutual distortion that multiplexing multichannel intermediate-freuqncy signal produces in multiplexing back.If digital pre-distortion handle DPD be placed on intermediate frequency multiplexing before, then can't solve the mutual distortion of the multiplexing generation of intermediate-freuqncy signal, and all to carry out predistortion to each road signal, a plurality of digital pre-distortions need be set handle the DPD step, make system configuration more complicated, must upgrade simultaneously a plurality of pre-distortion steps during renewal, systematic function and compatible, flexibility is relatively poor.
As Fig. 2, central station by the intermediate-freuqncy signal D/A switch of pre-distortion, generates radiofrequency signal to after mixing, is amplified by power amplifier after multiplexed again, converts light signal to so that transmit with optical modulator on optical fiber.Multiplexed the combining of the multiplexed and intermediate-freuqncy signal (digital signal) of radiofrequency signal (analog signal), the digital and analog signaling that makes system can receive multiple frequency and modulator approach carries out integrated treatment.
Claims (3)
1. the present invention provides based on the wireless access system of the optical fiber radio processing method to downstream signal, it is characterized in that the processing of central station may further comprise the steps:
Use the OFDM modulation to generate digital baseband signal;
Digital baseband signal is carried out Digital Up Convert generate digital medium-frequency signal;
Digital medium-frequency signal is carried out pre-distortion, and this pre-distortion is the nonlinear distortion of compensating power amplifier generation both, compensates the nonlinear distortion that optical modulator produces again;
Being carried out D/A switch by the intermediate-freuqncy signal of pre-distortion, after mixing, generate radiofrequency signal again;
Radiofrequency signal after amplifying, power amplifier (RF) is become light signal by light modulator modulates (E/O).
2. according to the frequency range moving method of claim 1, it is characterized in that central station is multiplexing multichannel intermediate-freuqncy signal earlier, again the intermediate-freuqncy signal after multiplexing is carried out pre-distortion, this predistortion also compensates the mutual distortion that multiplexing multichannel intermediate-freuqncy signal produces.
3. according to the frequency range moving method of claim 1, it is characterized in that multiplexed radiofrequency signal is amplified through power amplifier more earlier.
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| CN 200610122175 CN101146074A (en) | 2006-09-15 | 2006-09-15 | Processing method for radio access system on downlink signals based on optical fiber radio |
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| CN 200610122175 CN101146074A (en) | 2006-09-15 | 2006-09-15 | Processing method for radio access system on downlink signals based on optical fiber radio |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102349246A (en) * | 2009-03-10 | 2012-02-08 | 泰科电子海底通信有限责任公司 | Data pattern dependent distortion compensation in a coherent optical signal receiver |
| CN102611504A (en) * | 2012-03-24 | 2012-07-25 | 云南大学 | Method for improving radio over fiber link performance |
| CN102932068A (en) * | 2012-06-28 | 2013-02-13 | 云南大学 | Hybrid polarization linear Mach-Zehnder modulator |
| CN103098392A (en) * | 2012-10-22 | 2013-05-08 | 华为技术有限公司 | Electro-optical modulation apparatus, method, emitter and electro-optical modulation system |
| CN110875891A (en) * | 2018-08-31 | 2020-03-10 | 中兴通讯股份有限公司 | Signal processing method and device |
-
2006
- 2006-09-15 CN CN 200610122175 patent/CN101146074A/en active Pending
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102349246A (en) * | 2009-03-10 | 2012-02-08 | 泰科电子海底通信有限责任公司 | Data pattern dependent distortion compensation in a coherent optical signal receiver |
| CN102349246B (en) * | 2009-03-10 | 2015-07-08 | 泰科电子海底通信有限责任公司 | Data pattern dependent distortion compensation in a coherent optical signal receiver |
| CN102611504A (en) * | 2012-03-24 | 2012-07-25 | 云南大学 | Method for improving radio over fiber link performance |
| CN102932068A (en) * | 2012-06-28 | 2013-02-13 | 云南大学 | Hybrid polarization linear Mach-Zehnder modulator |
| CN102932068B (en) * | 2012-06-28 | 2016-05-18 | 云南大学 | Once moral optical modulator of the linearizing Mach of a kind of mixed polarization |
| CN103098392A (en) * | 2012-10-22 | 2013-05-08 | 华为技术有限公司 | Electro-optical modulation apparatus, method, emitter and electro-optical modulation system |
| WO2014063295A1 (en) * | 2012-10-22 | 2014-05-01 | 华为技术有限公司 | Electro-optic modulation device and method, transmitter, and electro-optic modulation system |
| CN103098392B (en) * | 2012-10-22 | 2016-10-26 | 华为技术有限公司 | A kind of electro-optic modulation arrangement, method, transmitter and electro-optic modulation system |
| CN110875891A (en) * | 2018-08-31 | 2020-03-10 | 中兴通讯股份有限公司 | Signal processing method and device |
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Open date: 20080319 |