Spatial Scalability Enabled Soft Video Broadcast for Users with Resolution Heterogeneity.

Recently, a novel uncoded transmission system called SoftCast has attracted great interest from academia, which can eliminate the cliff effect in digital transmission. Since the whole system is linear, SoftCast is intrinsically scalable to channel conditions. However, the resolution heterogeneity in the uncoded video broadcast system has not been well studied as far as we know. In this paper, we propose a Spatial Scalability Enabled Soft Video Broadcast (SSESVB) system based on SoftCast, aim to accommodate diverse users with heterogeneous channel conditions and heterogeneous resolutions simultaneously. Existing solutions for the resolution heterogeneity issue are previously designed for digital source coding, which cannot fully exploit performance gains from uncoded transmission. Instead, in the proposed SSESVB system, a novel spatial decomposition method based on linear projection is specially designed for uncoded transmission. Then a power distortion optimization problem is formulated and solved with the goal to minimize the average distortion of multiple users with heterogeneous channel conditions and heterogeneous resolutions. The simulation results demonstrate that SSESVB achieves more than 5.8 dB gain over compared schemes (i.e., SoftCast, Discrete Wavelet Transform (DWT) based method, and Scalable Video Coding (SVC)) in terms of average Peak Signal-to-Noise Ratio (PSNR) under heterogeneous scenarios.