Wireless Information and Power Transfer in Multiuser OFDM Systems

• Published in: IEEE transactions on wireless communications 2014-04, Vol.13 (4), p.2282-2294
• Main Authors: Zhou, Xun, Zhang, Rui, Ho, Chin Keong
• Format: Article
• Language: English
• Subjects: Access methods and protocols, osi model; Allocations; Applied sciences; Coding, codes; energy harvesting; Energy use; Exact sciences and technology; Harvesting; Information processing; Information, signal and communications theory; Mathematical models; Multiplexing; OFDM; Optimization; orthogonal frequency division multiple access (OFDMA); Orthogonal Frequency Division Multiplexing; orthogonal frequency division multiplexing (OFDM); power splitting; Power transfer; Radio transmitters; Receivers; Resource management; Signal and communications theory; Simultaneous wireless information and power transfer (SWIPT); Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Teleprocessing networks. Isdn; Time Division Multiple Access; time division multiple access (TDMA); time switching; Transmission and modulation (techniques and equipments); Wireless communication; Wireless networks; wireless power
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2014.030514.131479

In this paper, we study the optimal design for simultaneous wireless information and power transfer (SWIPT) in downlink multiuser orthogonal frequency division multiplexing (OFDM) systems, where the users harvest energy and decode information using the same signals received from a fixed access point (AP). For information transmission, we consider two types of multiple access schemes, namely, time division multiple access (TDMA) and orthogonal frequency division multiple access (OFDMA). At the receiver side, due to the practical limitation that circuits for harvesting energy from radio signals are not yet able to decode the carried information directly, each user applies either time switching (TS) or power splitting (PS) to coordinate the energy harvesting (EH) and information decoding (ID) processes. For the TDMA-based information transmission, we employ TS at the receivers; for the OFDMA-based information transmission, we employ PS at the receivers. Under the above two scenarios, we address the problem of maximizing the weighted sum-rate over all users by varying the time/frequency power allocation and either TS or PS ratio, subject to a minimum harvested energy constraint on each user as well as a peak and/or total transmission power constraint. For the TS scheme, by an appropriate variable transformation the problem is reformulated as a convex problem, for which the optimal power allocation and TS ratio are obtained by the Lagrange duality method. For the PS scheme, we propose an iterative algorithm to optimize the power allocation, subcarrier (SC) allocation and the PS ratio for each user. The performances of the two schemes are compared numerically as well as analytically for the special case of single-user setup. It is revealed that the peak power constraint imposed on each OFDM SC as well as the number of users in the system play key roles in the rate-energy performance comparison by the two proposed schemes.