Layered Soft Video Broadcast for Heterogeneous Receivers

Wireless video broadcast poses a challenge to the conventional visual communication in providing simultaneously each receiver the best video quality under its channel condition. Soft video broadcast, as a newly emerged wireless video broadcast scheme, is able to accommodate multiple receivers of different channel SNRs. However, the current soft video broadcast frameworks such as SoftCast require the bandwidth of the wireless channel to match the number of video coefficients per second. When the channel bandwidth is larger, the existing frameworks become not very efficient in bandwidth expansion. More importantly, it is possible that the users in broadcast applications have different bandwidths. However, none of the existing soft video broadcast frameworks considers bandwidth heterogeneity. In this paper, we propose a soft video broadcast framework, called LayerCast, which can simultaneously accommodate heterogeneous users with diverse SNRs and diverse bandwidths. The bandwidth expansion problem is solved by applying layered coset coding. More importantly, we derive a globally optimal power allocation between layers and, within each layer, between each DCT chunk. In simulations, the proposed framework outperforms SoftCast of up to 4 dB in video PSNR, and outperforms H.264-based framework up to 8 dB in broadcast.