On the DoF of the 2-Antenna 3-User MISO BC with Alternating CSIT

Inhalt:
In this paper, the 2-antenna 3-user multiple-input single-output broadcast channel is considered, where the channel state information at the transmitter (CSIT) for every receiver can be either perfect (P) or delayed (D), resulting thus in total in 8 possible CSIT states I1 I2 I3, Ii ∈ {P,D}, i ∈ {1, 2, 3}. For this scenario, we show the achievability of the optimal degrees of freedom (DoF) for the setting where the CSIT states are restricted to take the following 5 values: PPP, PPD, PDP, PDD and DDD. The achievability is facilitated through the introduction of two novel constituent encoding schemes (CSs), in which joint encoding over the CSIT state pairs (PPP, PDD) and (PDD,DDD) is performed. After a careful assignment of the newly proposed and existing in the literature CSs to the available CSIT states, optimal DoF are achieved.