Interference-Constrained IRS-aided SWIPT

We consider a spectrum underlay setup comprised by a primary and a secondary multiple-input single-output (MISO) broadcast system. The latter performs simultaneous wireless information and power transfer (SWIPT) with the aid of an intelligent reflecting surface (IRS). This system relies on joint transmit precoding and reflect beamforming to: i) compensate for the reverse inter-system interference (RISI) at the information decoding receivers (IDR) caused by the primary transmitter (PT); ii) suppress the forward ISI (FISI) at the PRs caused by the secondary transmitter (ST); and iii) mitigate the additional intra-primary-system interference caused by the reception at the PRs of IRS-reflected signals sent from the PT. Under this context, we propose an inter-system coordination protocol that enables acquisition at the ST of side information for interference management purposes. We also develop an alternating optimization algorithm based on semi-definite relaxation (SDR) to jointly design the active and passive beamforming vectors, so that the weighted sum-power at the energy harvesting receivers (EHR) of the secondary system is maximized subject to the quality-of-service (QoS) and interference constraints of the IDRs and the PRs, respectively. Finally, we derive low-complexity sub-optimal solutions based on fixed transmit precoding schemes. Numerical simulation results highlight the performance gains of the proposed designs over benchmark strategies and provide insights regarding the impact of various parameters on system performance.