Sum Throughput Maximization for Multi-User MIMO Cognitive Wireless Powered Communication Networks

Energy Efficiency Optimization For Wireless Powered Sensor Networks With Nonorthogonal Multiple Access

“…In [7], the well-known "harvest-then-transmit" protocol was proposed, where the time allocated to the hybrid access point (H-AP) for downlink WET and the time and transmit power allocated to the sensors for uplink WIT were jointly optimized for system throughput maximization. Since then, related works have been extensively done in the context of WPSNs with relays [8], [9], full-duplex radio [10], [11], cognitive radio [12]- [15], MIMO [16]- [18] and nonorthogonal multiple access (NOMA) schemes [19]- [21]. However, the above works only focus on the spectrum efficiency of WPSNs, which may lead a great dissipation of energy during the downlink WET.…”

Optimal Beamforming and Time Allocation for Partially Wireless Powered Sensor Networks With Downlink SWIPT

“…With respect to the problem (9), by neglecting the constraint CR2, although the corresponding optimal downlink beamforming and the achievable downlink rate (W mi B and R mi I ) cannot be directly obtained based on the results in [17] due to the extra time allocations τ I R and τ E k , they can be derived using the joint concavity of the problem (9) proved in Section III. C. Then the above tightness result also holds for the problem (9) in the TDMA-enabled WPSNs.…”

“…Z 0 0 an Z k 0, ∀k are still the lagrangian multipliers corresponding to W B 0 and P E k 0, ∀k, respectively. With the concavity of the problem (17) and based on its KKT conditions, the optimal structures for the variables {τ up , W B , P E k , λ, β, γ, µ k , ∀k} can be derived in the following theorem.…”

“…Specifically, for SDMA-enabled WPSNs, the optimal H-AP beamforming was proposed for maximizing the uplink sum rate and maximizing the minimum uplink rate among multiple wireless powered sensors, respectively in [15] and [16]. In [17], uplink sum throughput maximization under various cooperation protocols in SDMA-enabled cognitive WPSNs was studied. Moreover, fairness-based uplink throughput maximization was discussed for multiple-input-multiple-output (MIMO) WPSNs in [18].…”

“…Last but not least, due to the additional practical consideration of the downlink rate constraint in partially WPSNs, our joint downlink and uplink beamforming designs as well as time splitting are remarkably different from that in most of the existing works. Particularly, our SDMA-enabled design in fact reduces to that in [17] when the downlink rate constraint is not tight. While for the TDMA-enabled WPSNs, due to another additional involvement of uplink time allocation, the joint beamforming design and time splitting is more challenging and rarely discussed in the literature.…”