Multiuser Transmission Technology Research On Forward Link Of Visible Optical Communication System

Nowadays,wireless communication technology have a rapid development and people are increasingly concerned about the communication rate and communication security.However,the spectrum resources of radio frequency wireless communications are becom-ing more and more tense.At the same time,the high electromagnetic radiation is not green and safety.To effectively compensate for these two shortcomings,wireless optical communication technology in recent years is increasingly favored by people,and because of optical communication can effectively prevent eavesdropping,and can protect people's normal communication needs in prohibiting radio frequency occasions,so it becomes a hot research.This paper mainly studies the multi-user transmission technology in forward link for indoor wireless optical communication systems.First of all,the paper summarizes the indoor wireless infrared optical communication system and introduces the multi-access scheme SC-FDMA in forward link.In this paper,the characteristics of wireless optical communication and RF communication are analyzed and compared,and the transmission characteristics of the signal axe analyzed according to the wireless optical communication system model.The basic characteristics of the channel model are briefly introduced.Then,the paper analyzes the characteristics of the optoelectronic device and analyzes the advantages and disadvantages of various devices.Then the source of the noise in the system is analyzed and modeled as a white Gaussian noise and the noise is independent of the signal.Finally,it introduces the SC-FDMA in LTE,compares the SC-FDMA with traditional OFDMA and expatiates its advantages.Then,the paper studies the wireless optical channel modeling method including both obstructed and unobstructed cases.In this paper,we study the optical domain channel modeling part of optical communication system and analyze the five channel modeling methods,including recursive method,statistical model,DUSTIN algorithm,Monte Caxlo method and iterative method.The computational complexity,the simulation time,the accuracy and the adaptability of the model to the new environment of those five methods are studied.Finally,the iterative method with high simulation speed and adaptable to the new environment is selected as the modeling method of the optical domain channel.In addition,the paper also investigates the difference in channel response between portable devices with different distances and different angles in the case of fixed photodetector.Finally,the optical channel model established by iterative method and the measured chan-nel response of the optoelectronic device multiply to get the total channel response of the system.Secondly,using the total channel response of the system obtained in the above channel simulation,different power control strategies including multi-user delay QoS requirements under SC-FDMA are studied.Firstly,the paper expatiates and analyzes the principle of effective capacity with delay QoS,and then it studies the effective capacity of single-user multi-channel with different delay QoS requirements under wireless infrared optical discrete channel.In this simulation,four power control strategy including water-filling algorithm,equal power allocation algorithm,subchannel independent optimization and subchannel joint optimization algorithm are used.Considering performance metrics based on system capacity,the simulation results show that the subchannel independent opti-mization algorithm and the subchannel joint optimization algorithm are superior to the water-filling algorithm and the equal power allocation algorithm.However,when the de-lay QoS requirement increases from 10-4 to 101,the normalized effective capacity of the subchannel independent optimization algorithm decreased by 48.08%,indicating that the subchannel independent optimization algorithm needs to take delay QoS Requirements and effective capacity into consideration.And the subchannel joint optimization algorithm is the optimal algorithm.When the delay QoS requirement increases from 10-4 to 101,the normalized effective capacity decreased by 0.69%,effectively guaranteeing strict delay QoS while achieving high system capacity.Finally,the paper studies the multi-user subchannel allocation method.Using three methods including maximum rate allocation,maximum rate allocation including fairness and uniform distribution to research localized multi-user subchannel allocation method and distributed multi-user subchannel allocation method,then obtain different distribution rules of different assignments.