Scalable Video Transmission Over Cellular Networks

The advent of video codec and mobile communication keeps driving the data traf-fic to grow explosively, among which a substantial portion is attributed to mobile video. The requirement for data rate, delay and video quality is also raised. Cellular networks are evolving from a homogeneous architecture to a composition of Heterogeneous Cel-lular Networks (HCNs), comprised of various types of Base Stations (BSs). The trans-mission link quality varies substantially over space and time due to time-varying fading, interference and congestion. On the other hand, advanced source coding techniques, such as Scalable Video Coding (SVC), provide a new dimension of dynamically provi-sioning wireless resources for the varying requirements and the varying link conditions of UEs, thus creating the possibility of extracting video scaled in multiple dimensions, e.g., spatial, temporal, and quality. SVC is an extension of the H.264/MPEG-4 AVC video compression standard, in which the bitstream is encoded into multiple layers, namely a Base Layer (BL) and at least one Enhancement Layer (EL). The quality of reconstructed video depends on the number of layers decoded and stays the same until a higher enhancement layer is successfully decoded. The number of layers and their code rates may be determined by the requirement and the link condition of the subscribing UE.This paper gives a spatial statistical modeling for cellular networks at first, and then proposes four novel transmission schemes, Layered Digital (LD) transmission, Co-· ordinated Multi-Point (CoMP) transmission, Layered Hybrid Digital-Analog (LHDA) transmission and caching-based transmission. Leveraging tools from stochastic geom-etry, a comprehensive analysis is conducted. The results show that both proposed trans-mission schemes can provide a scalable video experience for UEs.1) We exploit the common feature of a layered structure of SVC and HCNs, and propose a scalable transmission scheme, called Layered Digital (LD), which is shown to be an effective means for providing differentiated services for users. Through the analysis and comparison of system performance metrics, i.e., outage probability, HD probability and handover rate, under orthogonal and non-orthogonal spectrum alloca-tion methods, we observe that LD can improve the reception of High-Definition (HD) content, while maintaining an acceptable basic transmission quality for the majority of UEs.2) We adopt the CoMP transmission in HCNs, where the macro BS and the small BS cooperatively transmit the scalable video to the UE. A sub-band allocation scheme is also proposed. The closed-form expression of cumulative distribution function of SINR is given. The results show that the CoMP transmission outperforms the LD transmission when the spectrum resource is relatively abundant.3) We propose a hybrid digital-analog transmission scheme for scalable video, which utilizing benefits of the robust digital transmission in low SINR region and the adaptive analog transmission in high SINR region. Through the analysis and compar-ison of system performance metrics, i.e., outage probability, HD probability and av-erage distortion, under orthogonal and non-orthogonal spectrum allocation methods, we observe that the hybrid digital-analog transmission can further improve the system performance by reducing video distortion and providing continuous quality scalability of high-definition video. The performance is quite insensitive to the power allocation between the digital BL and the analog EL.4) We propose two video cache placement schemes, Popularity Priority (PP) and Random Caching (RC), in order to improve the scalable video transmission over cellular networks. The impact of the mutually dependent relationship between the backhaul capacity and the caching-based transmission scheme is also analyzed. The results show that both PP method and RC method can improve backhaul offloading as well as provide differentiated user services and reduced video transmission delay.