Hybridcast: A wireless image/video SoftCast scheme using layered representation and hybrid digital-analog modulation
The recently proposed SoftCast scheme employs analog-like transmission for wireless visual communication, providing graceful reconstruction quality degradation for drastically changing channel conditions. However, the transmission in SoftCast is not always efficient in terms of power usage. In this paper, we propose a wireless image/video SoftCast scheme which employs layered representation with hybrid digital-analog modulation. In this scheme, a coarse approximation of the image is coded in a base layer in digital ways, while the residual image details are delivered in an enhancement layer in analog-like way. The outputs from the two layers are superimposed for transmission, using a hybrid digital-analog modulation scheme. Since a major part of the signal is handled by the base layer, the power efficiency of the SoftCast layer is significantly improved. Experimental results show that the proposed scheme outperforms the original SoftCast remarkably, while still preserving the smooth quality degradation characteristic of the SoftCast scheme.