On the Capacity Region of the Multi-Antenna Broadcast Channel with Common Messages

In this paper we discuss a two user multi-antenna Gaussian broadcast channel with common messages and explore the achievable region suggested by Jindal and Goldsmith. We present simple outer-bounds which are shown to be tight at certain regions. We investigate the aligned channel with common messages and show that beyond a certain threshold on the common rate, the achievable region coincides with the capacity region and we also give a full characterization of the capacity region of the degraded message sets case