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Research On Digital Signal Processing Techniques And Real-time Systems For A New Generation Of Optical Access Networks

Posted on:2019-04-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:R DengFull Text:PDF
GTID:1368330596963163Subject:Computer Science and Technology
Abstract/Summary:PDF Full Text Request
The growth of high-bandwidth services,the development trend of communication diversification,and modern healthy lifestyle,drive the increased demand for upgrading access networks.Hence,in recent years,new optical access technology has received much attention from world academic community and industrial circle.Firstly,at the level of high-speed optical fiber access,to satisfy the users' demand for broadband services,the research on high-speed next-generation passive optical networks(NG-PON)has attracted much attention.Secondly,novel visible light communication(VLC),as a kind of green communication,is gradually becoming one of the most promising technology for next-generation high-speed indoor access networks.It has become a hot topic in world academic circle.Thirdly,attractive hybrid fiber wireless communication(FiWi),including hybrid fiber free-space optical communication and radio over fiber(RoF)communication,is always regarded as an important development direction in future indoor or outdoor access networks.However,at present,in a lot of reported researches about NG-PON,VLC or FiWi,new digital signal processing(DSP)or new modulation fo rmat,is proposed based on off-line experiment,which doesn't consider a lot of real application problems,such as the related implementation structure and complexity by hardware,and the required hardware resources and the data resolution in the implementation process.In this thesis,the related issues will be studied and the corresponding experimental platform will be established.Meanwhile,several efficient real-time implementable DSP schemes will be proposed.In addition,from the prospective of theory,several effective schemes for solving the key issues in new optical access system will be demonstrated.The main work of this thesis can be concluded as three parts.The first part is about the researches on intensity modulation direct detection(IMDD)optical fiber system for NG-PON.This part of work can be divided as the following three sections.1)We experimentally demonstrate a 1024-point fast Fourier transform(FFT)based real-time IMDD orthogonal frequency division multiplexing(OFDM)optical fiber system.Meanwhile,we propose a simple real-time implementable accurate symbol synchronization scheme and a real-time pilot-assisted channel estimation scheme.The effectiveness of the proposed schemes is verified via experiments.And for the first time,the feasibility of the large-size FFT enabled real-time optical OFDM system is verified.Furthermore,it is also verified that the pilot-assisted channel estimation scheme can help to compensate the sampling frequency offset(SFO)effect in optical OFDM system.2)By utilizing return-to-zero digital-to-analog converter(DAC)and undersampling analog-to-digital(ADC),a 25 Gbps IMDD dual-band OFDM system is built and demonstrated experimentally.Through experiments,the feasibility of utilizing return-to-zero DAC to increase the data rate of the optical IMDD-OFDM system is verified for the first time.3)By utilizing super-Nyquist sampling technology,an undersampling ADC based dual-band Nyquist pules amplitude modulation(PAM)-4 IMDD optical fiber semi-real-time system is built and demonstrated experimentally.Although the utilized ADC in the demonstrated system is only 5 GSps,the data rate of the system reaches up to 20 Gbps,which for the first time verifies the effectiveness of the dual-band Nyquist-PAM-4 transmission scheme utilizing super-Nyquist sampling.The second part is about the theoretical DSP researches and real-time system researches for VLC system.This part of work can be divided as the following three sections.1)We investigate the effectiveness of the adaptive discrete Fourier transform(DFT)spread OFDM in light emitting diode(LED)based VLC system.The investigation results show that,adaptive DFT-Spread scheme outperforms conventional DFT-Spread scheme in the perspective of system rate enhancement,and adaptive DFT-Spread scheme can outperform conventional adaptive modulation scheme in the perspective of system bit-error-ratio(BER)improvement.2)We propose a periodic noise mitigation scheme based on serial inverse fast Fourier transform(IFFT)precoding.On one hand,the effectiveness of the proposed scheme is verified in theory.On the other hand,in a LED-based VLC system with non-ideal amplification device,the effectiveness of the proposed scheme is further verified experimentally.3)We propose a simple SFO estimation scheme based on training symbol(TS).Moreover,we also propose a simple real-time implementable precoding scheme for mitigating the frequency attention effect in OFDM-VLC system.In experiment,with a laser diode(LD)-based Gbps OFDM-VLC real-time system,the effectiveness of the two proposed schemes are investigated and verified for the first time.In addition,we also demonstrate,for the first time,a 1.485 Gbps HD-SDI video transmission by using the LD-based OFDM-VLC real-time system.The third part is about the theoretical DSP researches and real-time system researches for FiWi system.This part of work can be divided as the following four sections.1)A software-defined IMDD fiber and LD VLC merged fiber-wireless real-time transmission system is demonstrated for the first time.The experimental results show that the system can still achieve beyond 2 Gbps data rate without SFO compensation.The feasibility of the combination of IMDD fiber and LD VLC for future F iWi networks is verified for the first time.2)A simplified cascaded multi-modulus algorithm(CMMA)scheme is proposed.Based on the scheme,a real-time Q-band(36-41 GHz)PAM-4 RoF system is experimentally demonstrated.Meanwhile,the performance of the interleaved Reed-Solomon(RS)code is also investigated in the system.The experimental results verified the effectiveness of the utilized schemes.3)By utilizing optical frequency quadrupling and balanced precode technologies,a W-band(75-110 GHz)RoF system is experimentally demonstrated.From the perspective of theory and experiment,the effectiveness of the utilized technologies are verified.4)We introduced the twin single side-band(SSB)OFDM transmission technique from the pure optical fiber system to the RoF system.And an electrical filters based Twin-SSB-OFDM heterodyne W-band fiber-wireless system is realized.Meanwhile,a real-time implementable blind carrier recovery method for heterodyne W-band fiber-wireless system is proposed.By the combination of off-line and real-time experiments,the proposed method and transmission scheme are verified for the first time.
Keywords/Search Tags:Passive optical network (PON), Visible light communication (VLC), Fiber-wireless integration (FiWi), Orthogonal frequency division multiplexing(OFDM), Pulse amplitude modulation(PAM), Digital signal processing(DSP), Real-time system
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