Distributed Analog Broadcast Video Coding And The Application

With the rapid development of the mobile Internet,the new applications of mobile video services,such as mobile TV,video conferencing,are gradually replacing original point-to-point multimedia service.The traditional digital video coding schemes cannot serve users with different channel qualities and different equipments,because the source coding and the channel coding are separate.It leads to "cliff effect",which is one of the key obstacles on the development of video broadcast applications.Nowadays,analog joint source-channel coding(JSCC)attracts the attention of people as it can radically resolve the "cliff effect" by putting away the steps of entropy coding and quantization,using analog signals to transmit in the wireless channel and directly mapping the channel noise to the video.On the other hands,user cooperation also becomes a significant application in video broadcast system because it can effectively relieve the channel fading and channel noise and improve the channel's reliability.Considering the outstanding performance of them,researchers propose the analog JSCC for user cooperation,which may play a greater role in video broadcast system.In the research of analog JSCC for user cooperation,researchers found that the process of cooperative coding at the relay is inefficient.It cannot neither compress the cooperative signal efficiently nor resist the noises and the variations in the channels.In consideration of the advent-age of distributed source coding(DSC),this paper proposes a distributed analog JSCC scheme for user cooperation.The scheme combines the advantages of distributed coding and analog JSCC according to the characteristics of user cooperation.Utilizing the coset coding as the DSC scheme at the relay,a novel cooperative structure is proposed.The resis-tance to the channel noise is improved and the transmission efficiency of cooperative signal is optimized.In addition,according to the characteristics of the application scenarios,more improvements are proposed for coset coding at the relay in this paper.The relay can adjust the coset coding steps adaptively on the basis of the condition of the target device and the transmitting channel,and then choose the most suitable coding and transmitting scheme for the target.The paper deduces the theoretical formulae for possible situations and trains a simple model for the relay because it is quite difficult for the relay to compute the formulae instantly during the process of coding.Moreover,an adaptive packet dropping scheme is proposed to match the transmitting scheme and the channel condition.The simulation tests show that the distributed JSCC for User cooperation proposed in this paper performs better compared to the other cooperative coding.It shows stronger robustness than the existing WCVC especially when the cooperative channel is noisy or instable,and can gain 2dB improvement of PSNR on the cooperative video at the target device.