Multiuser Two-Way Nonregenerative MIMO Relaying With Nonconcurrent Traffic

Multiuser two-way relaying (MWR) enables multiple users to exchange data with a base station (BS) via a half-duplex relay in two channel uses. MWR assumes a specific traffic pattern, where users concurrently transmit/receive data to/from the BS. In this paper, we design a multiple-input–multiple-output (MIMO) two-way relaying protocol for a nonconcurrent traffic scenario, where one set of users transmits data to the BS in the first channel use, whereas another set of users receives data from the BS in the second channel use. By designing a novel linear precoder at the nonregenerative relay and by applying dirty-paper coding (DPC) at the BS, we maximize the: 1) minimum rate among all users; and 2) weighted sum rate (WSR) of the system, via the formulation of two geometric programs. Simulation results demonstrate the improved performance of the proposed precoder over conventional ones.