Research On Heterogeneous Intergration Access Technique Of Optical Wired/Wireless Services Based On Ofdm

With the increasing demand of the communication bandwidth, the future access network should provide not only enough bandwidth, but also various access methods (wired and wireless access). It is significant to research on the heterogeneous integration access technique of passive optical network (PON) and wireless communications which can combine the flexible mobility of the wireless communications and the high-capacity of the wired communication. However, there are some drawbacks in the existing integration network, such as, deficient bandwidth, complexity system structure, and bandwidth distribution conflict. Based on the study of orthogonal frequency division multiplexing (OFDM), novel PON architecture which can simultaneously support various services, such as LTE, wifi and60GHz-radio-over-fiber (ROF) is proposed in this dissertation. However, there are still some challenges, such as, bandwidth distribution scheme, high peak to average power ratio (PAPR) suppression and channel estimation. In order to solve those problems, in-depth research about the heterogeneous integration access technique of optical wired/wireless services based on optical OFDM are made in this dissertation. The detailed works are as follows:(1) Some in-depth studies of the time division multiplexing OFDM-PON and wavelength division multiplexing OFDM-PON, which include system models, performance analysis and network resource allocation, are done with the combined method of theoretical analysis, simulation and experiment. Downlink carrier re-use technology is researched to save the uplink light source and simplify the ONU structure. (2) Based on the above study of OFDM-PON, novel PON architecture which can simultaneously support heterogeneous services such as PON, LTE, WiFi and60GHz-ROF is presented. Intermedium frequency (IF) mixing technology is utilized to make the operation band of OFDM-PON, LTE and WiFi away from the Brillouin scattering effects. Meanwhile, a Mach Zehnder modulator (MZM) group combined with the optical external modulation technique are applied to generate high-quality downlink OFDM-PON-ROF integration signals. The generated wired/wireless heterogeneous signals are modulated into optical domain through optical modulator. In order to generate high quality heterogeneous signals which have no useless signal-band, the mathematical model of MZM is analyzed. Then, suitable modulation depth which could make the integration signals work in the linear region of the optical modulator and reduce the useless signal-band in the downstream signal highly, is optimized.(3) Now, how to suppress the PAPR in optical OFDM access system is still a challenge. Nonlinear companding transform is an effective technique to reduce the PAPR in optical OFDM transmission system. A novel companding scheme, which is based on the modified hyperbolic tangent (MHT) transform, is presented in this dissertation. The MHT scheme can enlarge the small signals and compress the large signals while keeping the average power invariant through two companding parameters. Numerical mathematical models of PAPR have been analyzed. Simulation results show that large PAPR reduction was achieved and offered better bit error rate (BER) performance than the famous μ law.(4) Inspired by nonlinear post-compensation algorithms, a channel estimation algorithm which can highly resist dispersion and phase noise in the optical OFDM system is presented. The proposed scheme is pilot-aided in which just a little number of pilots is inserted in the first half part of the subcarriers and high spectral efficiency is achieved. The fiber dispersion and the phase noise are resisted with the combined method of post-compensation and the relationship between the OFDM subcarriers and the fiber channel mathematic model. Numerical mathematic models have been analyzed. Simulation results show that the presented scheme achieved40Gbit/s data transmission and the BER performance of the proposed algorithm is better than other LS channel estimation algorithms.This dissertation focuss on the heterogeneous intergration access of optical wired/wireless services with the combining method of mathematic model analysis, simulation and experiment.Those above research technologies can highly simplify the remote receiving structure, reduce the cost of transmission, improve the access flexibility and achieve ubiquitous information access. The research in this dissertation will play an important role in the next generation information highway.