Hybrid Digital-analog Video Transmission With Constrained Bandwidth

The mobile video traffic will continue increasing in the future and cast a great chal-lenge to the design of wireless networks.Current wireless networks based on digital transmission may have troubles to handle such a big amount of data with limited band-width.This is because digital transmission suffers from severe cliff effect and hence cannot support high-efficiency video broadcast and provide channel adaptation,which is quite important for the transmission in unstable wireless environments.In the last a few years,some new techniques,pseudo-analog video transmission and hybrid digital-analog(HDA)video transmission appeared to address this problem,which is the topic of this thesis.HDA transmission can combine the advantages of pseudo analog and dig-ital transmission,providing high-efficiency and channel adaptive video delivery at the same time.In this thesis,we focus on the video transmission with constraint bandwidth,in which the inflexible usage of bandwidth will limit the performance of pseudo analog and HDA video transmission systems.When the channel bandwidth cannot support the transmission of all analog symbols,some of them have to be discarded and saturation effect will appear.This problem is handled with two basic ideas.First,we propose uti-lizing the bandwidth of digital symbols in HDA systems to transmit more analog sym-bols.For analog symbols,the bandwidth occupied by those digital symbols is viewed as hidden resources.Second,an efficient bandwidth compression method based on Shannon-Kotel'nikov mapping is designed to transmit more analog symbols.To fulfill these two ideas,some complex optimization problems need to be solved.Specifically,to implement the first idea,we need to decide which sources are transmitted with hid-den resources and the power allocation of all digital and analog symbols.To implement the second idea,we need to address the resource allocation problem between the analog and digital branches and the allocation problem among analog symbols.We evaluate the proposed methods via simulations and the results show that the proposed methods can outperform other methods when the channel bandwidth does not match and much smaller than the source bandwidth.