Scalable Video Multicast for MU-MIMO Systems with Antenna Heterogeneity

In contemporary multiuser multiple-input multiple output (MU-MIMO) systems, it is common for the reception devices to have varying number of antennas. When multicast is performed, the number of concurrent spatial streams is limited by the device with the least number of antennas, which prevents more capable devices from getting higher rates. In this paper, we address the antenna heterogeneity in wireless video multicast by the innovative design of multiple similar description (MSD) video coding and multiplexed space-time block coding (M-STBC). MSD coding generates multiple descriptions of a video and features that any linear combinations of the descriptions are decodable. The descriptions comprising of real numbers are further processed by transform and power allocation steps for efficient transmission in a power-constrained system. M-STBC puts symbols in similar descriptions to corresponding space-time positions and ensures decodability under any antenna settings and channel conditions. As a result, we build up a scalable video multicast system, named AirScale, which allows receivers with various number of antennas to decode from a single transmission and the reconstructed video quality improves with the number of equipped antennas. Evaluations on Sora shows that, in a $\{1,2,3,4\} \times 4$ system, AirScale provides baseline quality for 1-antenna receiver and much higher quality for multi-antenna receivers. The gain over SoftCast is up to 3.5 dB, 3.9 dB and 4.1 dB for 2, 3 and 4-antenna receivers, respectively.