MISO Networks With Imperfect CSIT: A Topological Rate-Splitting Rate Approach
Abstract: Recently, the Degrees--of-Freedom Freedom (DoFs) region of multiple-inputmultiple single-output output (MISO) networks with imperfect channel state information at the transmitter (CSIT) has attracted significant attention. An achievable scheme, known as rate rate-splitting splitting (RS), integrates common-message-multicasting multicasting and private private-message-unicasting. unicasting. In this paper, focusing on the general K -cell cell MISO IC with an arbitrary CSIT quality of each interfering ering link, we first identify the DoF region achieved by RS. Second, we introduce a novel scheme, so called topological RS (TRS), whose novelties compared with RS lie in a multi multi-layer layer structure and in transmitting multiple common messages to be decoded by groups of users rather than all users. The design of TRS is motivated by a novel interpretation of the K -cell cell IC with imperfect CSIT as a weighted sum of a series of partially connected networks. We show that the DoF region achieved by TRS yields the best known result so far, and we find the maximal sum DoF via hypergraph fractional packing. Finally, for a realistic scenario where each user is connected to three dominant transmitters, we identify the sufficient condition where TRS strictly