The Application And Optimization Of SoftCast Over MIMO-OFDM Channel

Recent years,video broadcast and the mobile video challenge the conventional wireless design.The conventional design can't be accommodated to wireless broadcast scenarios and will experience a performance cliff.In 2009,a new video transmission scheme called SoftCast was propsosed by S.Jakubczak and D.Katabi.Compared with conventional point-to-point design,SoftCast performs lossless compression over lossy analog communication,which guarantees the samples of the digital video signal transmitted on the channel are linearly related to the pixels' luminance.This paper focused on the research of the SoftCast in MIMO-OFDM scenarios.SoftCast was designed for broadcast.However,directly running SoftCast over MIMO,without precoding,can't avoid interference between received signals on different subchannels.A new video transmission scheme call ParCast which was improved from SoftCast was proposed.Compared with SoftCast,ParCast applied MIMO precoding to improve the link quality and mapped important video components to more reliable channels.Spatial multiplexing and space diversity gain of a system can be extracted through MIMO technique.ParCast ignored the space diversity gain,so a new video transmission scheme called HCast(hybrid video unicast)was proposed in this paper.HCast made full use of MIMO-OFDM link by using diversity technique and multiplexing technique.HCast matched the video chunk with large variance to the subcarrier with large gain and the video chunk with low variance to the subcarrier with small gain.Besides,the video chunk with large variance was transmitted under diversity mode.The power allocation scheme was proposed according to this novel design of source channel matching.The simulation results showed that the proposed scheme can improve the performance of ParCast in low signal-to-noise ratio.But in high signal-to-noise ratio,the performance of HCast was not as good as ParCast.Concerning this problem,this paper observed the performance by transmitting different video chunks under diversity mode.Experiments results showed that video chunks with large variance transmitted under diversity mode will improve the performance in low signal-to-noise ratio and video chunks with low variance transmitted under diversity mode will improve the performance in high signal-to-noise ratio.