#### The DoF Region of Order-(K-1) Messages for the K-user MIMO Broadcast Channel with Delayed CSIT

##### Tong Zhang, Shuai Wang, Taotao Wang, Rui wang

In this paper, we characterize the degrees-of-freedom (DoF) region of order-$(K-1)$ messages for the $K$-user multiple-input multiple-output (MIMO) broadcast channel with delayed channel state information at the transmitter (CSIT) and arbitrary antenna configurations, where the transmitter has $M$ antennas and the receiver $i=1,2,\cdots,K$ has $N_i$ antennas. For the converse, we first derive the DoF region of order-$(K-1)$ messages for the $K$-user MIMO broadcast channel with no CSIT and arbitrary antenna configurations with the aid of the proposed Genie-bound, and then establish the DoF outer region. For the achievability, we design the transmission scheme, and propose the backward/forward cancellation algorithm for decoding. Concisely, we derive the achievable DoF region from the designed transmission scheme by transformation approach. Our results indicate that, for order-$(K-1)$ messages of the $K$-user MIMO broadcast channel, the DoF region with delayed CSIT is larger than the DoF region with no CSIT when \$N_2

arrow_drop_up