Outage Minimized Resource Allocation for Multiuser OFDM Systems With SWIPT

This paper considers a downlink multiuser orthogonal frequency division multiple (OFDM) system with simultaneous wireless information and power transfer (SWIPT), where the users decode information and harvest energy using the same received downlink signals. In particular, both power splitting (PS) and time switching (TS) SWIPT modes are considered for coordinating information transferring and energy harvesting. For multiuser information transmission, OFDM access (OFDMA) and time division multiple access (TDMA) are adopted for PS-SWIPT and TS-SWIPT, respectively. The outage performance of such a multiuser OFDM system with SWIPT is investigated. Particularly, we optimize the subcarrier allocation, power allocation and PS ratio for PS-SWIPT, and the power allocation and time allocation for TS-SWIPT, aiming at minimizing the fraction of outage over all users under the minimum harvest energy constraint along with the peak and total transmit power constraints. Suboptimal heuristic algorithms are obtained based on the Lagrange duality method. The outage performances of PS-SWIPT and TS-SWIPT are compared under various system parameter settings. We show that the outage performance of TS-SWIPT is better than that of the PS-SWIPT, except when the minimum required harvested energy is large, the total transmit power limit is small, or the number of users is small.