Degrees Of Freedom Region Of Device-Relaying Cellular Network

In this paper, we characterize the degrees of freedom (DoF) region of a MIMO device-relaying cellular network (DRCN) with three users and one base station (BS), where each user exchanges unicast messages with the BS. We assume that one of the users has no direct link to the BS, and hence, device-relaying is utilized to exchange data between this user and the BS, i.e., data is relayed via another user which has a direct link to the BS and a device to device (D2D) link to this user. We assume that each node operates in perfect full-duplex mode. Cut-set and genie-aided bounds are utilized to derive an outer bound on the DoF region. We provide achievability schemes that utilize signal space alignment for network coding, null-space beamforming and zero-forcing. The achievable schemes provide an inner bound on the DoF region that coincides with the outer bound.