Line-cast: Line-based Semi-analog Broadcasting of Satellite Images

This paper proposes a line-based semi-analog transmission scheme (Line-Cast) for satellite image broadcasting. At the transmitter, an image is compressed and transmitted line by line. Therefore, it is much beneficial to satellite applications with low onboard memories. The low delay feature also makes it possible that once a line is acquired, it can be readily coded and transmitted. Moreover, a distributed source coding based on an analog modulo-q operation is employed to exploit inter-line correlations and shift the complexity from transmitters to receivers, which accommodates the low encoder complexity requirement for onboard image compression. To accommodate receivers with diverse channel qualities, the proposed Line-Cast adopts a semi-analog approach, which can achieve graceful degradations with increasing noises. Despite low encoder complexity, simulation results show that Line-Cast can achieve comparable or even better performances than Softcast, one state-of-the-art analog scheme for broadcast channels.