Superposition MIMO Coding for the Broadcast of Layered Sources

We propose superposition multiple-input multiple-output (MIMO) coding for the transmission of unequally important sources in a point-to-multipoint system. First, a tradeoff between Alamouti code and spatial multiplexing (V-BLAST) is analyzed in terms of the average bit error rate (BER), where the maximum data rates of both MIMO schemes are set to be equal. The results show that for a given target bit error rate, Alamouti code is preferable for a low data rate, and spatial multiplexing is preferable for a high data rate. For layered sources such as scalable video, the more important component typically has lower data rate than does the less important component. Based on these, we construct a superposition MIMO scheme where two different MIMO techniques are hierarchically combined such that important data is Alamouti coded, less important data is spatially multiplexed, and then two unequally important data symbols are superposed.