Research On Scalable Video Multicast Technology In Sparse Code Multiple Access Networks

With the continuous development of the 5th generation communication technology(5G),smart mobile terminals and large screen devices are becoming increasingly popular.The proportion of video traffic in global mobile data traffic increase dramatically.In the mean time,video services have gradually become the mainstream business of mobile Internet.In order to meet the mass video content transmission requirements and achieve the technical goals of ultra-high capacity and ultra-low latency,it is urgent to design a video transmission scheme in the 5th generation communication system.Sparse Code Multiple Access(SCMA)based on Non-orthogonal Multiple Access(NOMA)is a code domain multiplexing scheme with significant shaping gain.While increasing spectrum efficiency,it has added user access points,so it has become one of the candidate solutions for 5G technology.At the same time,in the field of video encoding and transmission,in order to adapt to the increasingly diverse terminal equipments as well as differentiated network channel conditions,scalable video coding technology came into being.Scalable video coding technology generates multiple video layers with different bit rates and visual quality by one encoding.The video layer can be transmitted separately,which greatly improves transmission flexibility and bandwidth utilization.At present,scalable video multicast technology in Power Division based NOMA(PD-NOMA)network has been extensively studied,however,it is faced with the limitation that the user channel conditions need to ensure a certain degree of difference.The video transmission technology in SCMA network needs to be developed.The current research on SCMA mainly focuses on designing and improving the codebook model,in order to increase the user access points and reduce the mutual interference between codebooks during decoding.In contrast,research in the field of multicast scenarios and video transmission in SCMA is still scarce.Aiming at the efficient transmission of scalable video multicast scenarios in SCMA networks,this thesis comprehensively utilizes the nonorthogonal characteristics of the code domain of SCMA technology and the characteristics of hierarchical transmission of scalable video coding to propose a scalable video multicast scheme in SCMA networks.The multicast scheme improves the visual performance of the user group under limited spectrum and power resources.First of all,a scalable video multicast scheme based on SCMA is proposed by establishing a video multicast model under the SCMA network.Secondly,the quality of experience(Qo E)index was introduced as an optimization goal when building the model,which more intuitively reflects the user's visual quality gain.Then we analyzed that the optimization problem caused by codebook allocation and power allocation is a complex discrete mixed allocation problem,which depends on each other and affects the channel capacity together to determine the overall visual gain of the multicast group,so it causes higher complexity.Further,an effective fast resource allocation scheme is proposed,which separates codebook allocation and power allocation into two stages and solves them step by step,and the scheme achieves better performance while reducing the computational complexity.Among them,the classification and discussion of the existence of one or more scalable dimensions of the video stream are introduced,and a video layer selection and ranking algorithm is introduced.Finally,simulation results show that the scalable video transmission scheme based on sparse code multiple access network proposed in this thesis can provide better average visual quality for the multicast group users than the traditional multicast scheme and the multicast scheme based on orthogonal frequency division multiplexing technology.In the mean time,it has achieved performance improvements in terms of throughput and power consumption.