Recently, the Degrees-of-Freedom (DoFs) region of multiple-input-single-output (MISO) networks with imperfect channel state information at the transmitter (CSIT) has attracted significant attention. An achievable scheme, known as rate-splitting (RS), integrates common-message-multicasting and private-message-unicasting. In this paper, focusing on the general K-cell MISO IC with an arbitrary CSIT quality of each interfering 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-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 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 outperforms conventional schemes, and show that TRS is optimal for some CSIT qualities.
Bibliographical noteFunding Information:
Manuscript received January 26, 2016; revised July 8, 2016 and November 18, 2016; accepted December 22, 2016. Date of publication January 4, 2017; date of current version May 13, 2017. This work has been partially supported by the EPSRC of UK, under grant EP/N015312/1. The associate editor coordinating the review of this paper and approving it for publication was A. Tajer.
© 2017 IEEE.
- MISO interference channel
- imperfect CSIT
- topological interference management
ASJC Scopus subject areas
- Electrical and Electronic Engineering