Research On Key Technologies Of Hybrid Digital-Analog Video Transmission

Wireless video transmission system has experienced a transition from analog tele-vision to digital television.In this period,a series of great technical innovation have been proposed.Specially,after the separate source channel coding theory is proposed by Shannon,digital schemes have achieved great development.Generally,digital trans-mission scheme is made up of digital source coding and digital channel coding.This separate digital coding scheme can obtain the optimal coding efficiency in point-to-point communication.Recently,with the rapid development of wireless and mobile termi-nals,some emerging wireless video applications become more and more important and popular,such as mobile TV,wireless video conference and mobile video surveillance.However,conventional separate digital coding scheme cannot handle these application well enough owning to the well known cliff effect.To overcome the cliff effect,some analog schemes are proposed.They are composed of a series of linear operation and has the characteristic of quality scalability.However,the coding efficiency of analog coding is relatively low.Consequently,combining the digital the digital coding scheme with the analog coding scheme can obtain both high coding efficiency and quality scal-ability,which is hybrid digital-analog(HDA)coding scheme.However,there are still many problems in the research of hybrid digital-analog video transmission,which need further investigation.First,existing HDA schemes mostly consider the ideal situation of additive white Gaussian noise channel(AWGN),and the actual channel is much more complex than AWGN,especially for the chan-nel gain of fading channel.How to design a hybrid digital-analog coding scheme in this case?Secondly,considering an actual communication environment,the combi-nation of cooperation and hybrid digital-analog coding is an effective way to improve the robustness of communication through space diversity,thereby improving the re-ception quality of video.However,the current research lacks of theoretical analysis on the related technologies in hybrid digital-analog coding based on cooperative com-munication.For example,how to choose the step size of coset coding to optimize the performance.These problems urgently need to be solved;Thirdly,most video or image coding schemes aim at eliminating statistical redundancy and minimizing mean square distortion.However,people are increasingly aware that the mean square error does not reflect the perceived visual quality of the image well,because the perceived visual qual-ity is closely related to the human visual system(HVS).How do we design a coding scheme that combines the human visual system with analog coding to obtain both the best visual perception quality and quality scalability?In this dissertation,we mainly study the specific application of hybrid digital-analog coding in wireless video communication.We first introduce the basic knowledge of analog coding and hybrid digital-analog coding,and then begin to provide solutions to above mentioned existing practical problems.The content and contributions of this dissertation are shown as follows.(1)In this dissertation,we design a hybrid digital-analog coding scheme under Rayleigh fading channel for multi-user wireless video communication.It is the opti-mal trade-off between high coding efficiency and quality scalability.Different from the HDA scheme in the AWGN channel,the scheme proposed in this dissertation is more practical with considering the channel gain.The coding scheme proposed in this disser-tation not only outperforms the existing schemes in coding efficiency,but also achieves the wireless scalable video coding in wireless environment.(2)In ths dissertation,we design a hybrid digital-analog coding scheme in wireless cooperative video transmission.Our scheme can make full use of the relation between the three channels of source-to-relay,source-to-destination and relay-to-destination.Then it can maximize the performance of destination under the constraints of band-width and power in the system.In addition,we have derived the closed form of total distortion.It helps us to analyze the optimal quantization step in coset coding and can be applied to improve the performance of destination.(3)In this dissertation,we design a new wireless video transmission scheme based on joint source-channel coding to optimize the human visual perception.On one hand,it can not only move the concentration to the quality of human visual perception and obtain the optimal optimization of eliminating the perceptual redundancy.On the other hand,it provides the quality scalability in mobile communication and broadcast communication,which means the received quality can adapt with the channel variation.