Video Multicast: Integrating Scalability of Soft Video Delivery Systems into NOMA

Non-orthogonal Multiple Access (NOMA) has aroused research interest for its potential use in future wireless video multicast. By exploring the power domain, multiple video layers are superposed to achieve video delivery scalability and efficiency in NOMA. However, the scalability of this approach is still limited despite adopting medium-grain quality scalable (MGS) video coding. In this letter, we propose a scalable multicast design inspired by soft video delivery systems. Soft video delivery systems cannot be directly applied in NOMA networks to improve the scalability because they cannot achieve errorless decoding when utilizing linear least square estimation (LLSE) at the decoder. If there is decoding error in the former layers, the successive interference cancellation (SIC) in NOMA will give rise to error propagation and huge performance loss. To solve this problem, we propose a design with digitalized base layer and soft encoded enhanced layer. The power allocation is formulated as a distortion minimization problem. The experimental results demonstrate that the proposed design has significant performance gain over SoftCast, SupCast and the traditional digital system.