Research On Channel Coding Technology And Load Resource Allocation Scheme Of ROF System

With the development of emerging technologies such as the Internet,Internet of Things and 5G,emerging services such as h:igh-definition videos,smart city,autonomous driving and expanded reality is about to be promoted and used on a large scale.The transmission of massive data in the future and the access of massive devices put forward higher requirements for the bandwidth,speed,coverage,security and stability of future communication networks.In order to meet the requirements of the development of the times,it is particularly important to establish a high-speed,intelligent and flexible communication system.The radio over fiber communication system not only has the characteristics of wide bandwidth,low loss and good security of the optical fiber communication system,but also has the characteristics of flexible and easy access of the wireless communication system.It is very suitable for the applicat:ion and popularization of future network services.But in ROF system,the signal is affected by various factors such as channel noise,fiber dispersion and nonlinear effects during long-distance transmission,which may cause distortion of the received signal.At the same time,in order to meet the user's service request,the data transmission in the ROF system needs to reach the base station after passing through the fiber link from the central office,and finally arrive at the user terminal.The massive user request and devices connection must bring great pressure to the fiber link.Therefore,research to improve the reliability and flexibility of ROF systems is of great significance.In order to improve the reliability and flexibility of the system,this thesis focuses on two aspects of channel coding technology and load resource allocation scheme in ROF system.We propose to use cascaded Turbo-STBC channel coding to improve the performance of the GFDM-ROF system with multi-antennas.We propose to use adaptive Turbo-STBC coding technology to quickly relieve the load pressure of the system.The central pressure marginal structure is proposed to solve the network congestion in the ROF system and solve its load resources allocation problem.It can increase the flexibility of the system.The main research work of the thesis is as follows:(1)Research on cascaded Turbo-STBC coding based on GFDM-ROF systemBased on the theoretical research on ROF system,key technology of optical communication and GFDM modulation,this paper proposes MIMO technology based on GFDM-ROF system and cascaded Turbo-STBC code to reduce the BER of the system.Simulation results show that the BER of GFDM-ROF system with MIMO technology can be lower than 10-6 when SNR is 1 OdB when there are two transmit antennas and four receive antennas.And the BER of GFDM-ROF system with cascading Turbo-STBC code can be lower than 10-6 when SNR is 5dB.It's better than the condition with same antennas in GFDM-ROF system with MIMO technology.(2)Research on adaptive channel coding scheme based on GFDM-ROF systemThis paper proposes an adaptive Turbo-STBC coding scheme based on GFDM-ROF system to solve the problem that fixed code which can't reduce much BER may result in the complexity of the algorithm.The scheme adds encoders and decoders which can be selected in pairs at the transmitting part and the receiving part of the system.The system can select encoders and decoders with fast transmission rate and moderate BER performance when fast transmission is required.When high complexity can be considered,the system can select encoders and decoders with better performance to improve the BER performance.The experiments results show that the adaptive coding can obtain considerable BER performance and the ability in reducing the system load is also better than the fixed code.(3)Research on central pressure marginalization structure and load resource allocation scheme based on ROF systemBased on the theoretical research on ROF system structure and load resource allocation algorithm,the paper proposes a central pressure marginalization structure to solve the problem of network congestion in the fiber link which caused by a large number of user requests in ROF system.A load resource allocation algorithm is proposed to obtain a service allocation scheme and a user load distribution scheme.The simulation studies the impact of the storage capacity of the edge office,the number of services and the number of edge offices on the performance of the solution.The results show that when the storage ratio Uis not more than 1/2,the system can obtain a more cost-effective performance improvement.