Optimum time-division in MIMO two-way decode-and-forward relaying systems

We consider a multiple-input multiple-output (MIMO) two-way relaying system, where two wireless terminals exchange data via a half-duplex decode-and-forward (DF) relay. The problem of optimum time-division (TD) between the multiple access (MAC) phase and the broadcast (BRC) phase is addressed in this paper. We characterize the achievable rate regions with optimum TD strategies between the two phases for the following two cases: one is under peak power constraint and the other is under average power constraint. The simulation results show that the achievable rate regions with optimum TD strategies are much larger than those with equal TD strategy. Furthermore, the ergodic sum rates of the system using optimum and equal TD strategies are compared for different antenna configurations.