Applications And Researches Of Multi-dimension Multiplexing Techniques In Radio Over Fiber System

With rapid Evolution of mobile communication network,new applications such as ultra-high quality 4K video,Virtual Reality,Cloud work,auto drive will be supported by 5G mobile communication network.It can bring high convenient service to our daily work and life.However,the new applications will also challenge the tradition network architecture in higher capacity,more access user numbers and lower latency aspects.Although the traditional radio over fiber system stands out for its centralized signal processing,network management and supporting remote radio unit features,it still hard to satisfy new network requirements.Thus it's necessary to investigate multi-dimensional radio over fiber system to improve 5G network transmission performance.This thesis focuses on the key techniques of lower frequency and higher frequency carriers in radio over fiber system.For lower frequency carrier,multi-dimension multiplexing is introduced in the system,such as the polarization division multiplex(PDM),multicore fiber and few mode fiber based spatial division multiplex(SDM).For higher frequency carrier,indoor positioning related to millimeter wave beamforming are researched.The main research conclusions in this thesis are as followed:(1)For lower frequency radio over fiber system,orthogonal frequency division multiplexing using offset quadrature amplitude modulation(OFDM/OQAM)is under researched.We propose the interference cancelling technique to cancel the filter bank induced interference.Furthermore,we expand the technique into high dimension to support multi-input multi-output,which is verified by the PDM based radio over fiber system.These experimental results indicate that OFDM/OQAM has 4.6% higher spectrum efficiency which transmission performance is similar to conventional OFDM.(2)We introduce the OFDM/OQAM in the multicore fiber based SDM RoF system to build the uplink and downlink radio over fiber system.These experimental results show that the rich core resources can support high dimension remote seed light injected based colorless uplink and downlink transmission.We further investigate the MIMO-OFDM/OQAM transmission performance in the multicore fiber.We test the transmission performance under different inter core crosstalk,which is generated by tapering the multicore fiber.Experimental results indicate that the MIMO-OFDM/OQAM signal can tolerate the inter core crosstalk as high as-10 dB/20 km.(3)The transmission performance of radio MIMO-OFDM/OQAM signal over few mode fiber is under investigated.The used elliptical core few mode fiber has higher differential mode group delay,which will introduce extra crosstalk in the system.Thus we propose the channel time delay induced crosstalk cancelling(TCC)algorithm to recovery signals from the crosstalk.Experimental results show that by using TCC algorithm,the error vector magnitude(EVM)of MIMO-OFDM/OQAM signal can be maintained under 15%,while the OFDM signal with same parameter requires 25% length circle prefix(CP)length.These results not only verify the feasibility of radio over few mode fiber system,but also proof that the proposed TCC algorithm can improve the transmission performance in the system.(4)millimeter wave(MMW)radio signal is operated at higher frequency,which has higher attenuation in atmosphere,thus beamforming technique is required.Beamforming will decrease the bandwidth,so the precise user orientation is required by the MMW antenna array.In this thesis,we innovatively propose the visible light communication and machine learning technique based indoor positioning system,which can provide the precise user orientation for MMW beamforming service.Experimental results indicate that the position accurate is reduced to 1cm,which is precise enough to support MMW beamforming.These research works will play an important role in the MMW radio over fiber system in the future 5G implement.