A time scheduling scheme in MIMO Y channels with reduced antenna configurations

This paper develops a time scheduling scheme for generalized K-user multiple-input multiple-output (MIMO) Y channels where multiple terminals communicate with each other in a bi-directional manner via the relay. The objective is to decrease the system configuration requirements in terms of antenna numbers at the relay station and user nodes. Specifically, the scheme splits the user nodes into multiple groups and spreads the transmissions over a larger number of time slots (TSs) compared with the original MIMO Y channel scheme. While the latter scheme uses only one medium access control (MAC) and one broadcast (BC) phase, the proposed time scheduling arranges bi-directional data exchanges using specialized precoding in two or more MAC and BC phases between smaller number of users. As a result, the required numbers of antennas at the relay and the user nodes are decreased at the expense of reduced effective throughput. The lower complexity antenna configurations in MIMO Y channels will make the whole system more amenable to practical implementations.