Joint Wireless Information and Energy Transfer in a Two-User MIMO Interference Channel

This paper investigates joint wireless information and energy transfer in a two-user MIMO interference channel, in which each receiver either decodes the incoming information data (information decoding, ID) or harvests the RF energy (energy harvesting, EH) to operate with a potentially perpetual energy supply. In the two-user interference channel, we have four different scenarios according to the receiver mode -- ($ID_1$, $ID_2$), ($EH_1$, $EH_2$), ($EH_1$, $ID_2$), and ($ID_1$, $EH_2$). While the maximum information bit rate is unknown and finding the optimal transmission strategy is still open for ($ID_1$, $ID_2$), we have derived the optimal transmission strategy achieving the maximum harvested energy for ($EH_1$, $EH_2$). For ($EH_1$, $ID_2$), and ($ID_1$, $EH_2$), we find a necessary condition of the optimal transmission strategy and, accordingly, identify the achievable rate-energy (R-E) tradeoff region for two transmission strategies that satisfy the necessary condition - maximum energy beamforming (MEB) and minimum leakage beamforming (MLB). Furthermore, a new transmission strategy satisfying the necessary condition - signal-to-leakage-and-energy ratio (SLER) maximization beamforming - is proposed and shown to exhibit a better R-E region than the MEB and the MLB strategies. Finally, we propose a mode scheduling method to switch between ($EH_1$, $ID_2$) and ($ID_1$, $EH_2$) based on the SLER.