Proportional Fair Resource Allocation on an Energy Harvesting Downlink

This paper considers the allocation of time slots in a frame, as well as power and rate to multiple receivers on an energy harvesting downlink. Energy arrival times that will occur within the frame are known at the beginning of the frame. The goal is to optimize throughput in a proportionally fair way, taking into account the inherent differences of channel quality among users. Analysis of structural characteristics of the problem reveals that it can be formulated as a biconvex optimization problem, and that it has multiple optima. Due to the biconvex nature of the problem, a Block Coordinate Descent (BCD) based optimization algorithm that converges to an optimal solution is presented. However, finding the optimal allocation with BCD entails a computational complexity that increases sharply in terms of the number of users or slots. Therefore, certain structural characteristics of the optimal power-time allocation policy are derived. Building on those, two simple and computationally scalable heuristics, PTF and ProNTO are proposed. Simulation results suggest that PTF and ProNTO can closely track the performance of BCD which achieves a good balance between total throughput and fairness

Stochastic Geometry Analysis and Design of Wireless Powered MTC Networks

Machine-type-communications (MTC) are being crucial in the development of next generation mobile networks. Given that MTC devices are usually battery constrained, wireless power transfer (WPT) and energy harvesting (EH) have emerged as feasible options to enlarge the lifetime of the devices, leading to wireless powered networks. In that sense, we consider a setup where groups of sensors are served by a base station (BS), which is responsible for the WPT. Additionally, EH is used to collect energy from the wireless signals transmitted by other sensors. To characterize the energy obtained from both procedures, we model the sporadic activity of sensors as Bernoulli random variables and their positions with repulsive Mat\'ern cluster processes. This way, the random activity and spatial distribution of sensors are introduced in the analysis of the energy statistics. This analysis can be useful for system design aspects such as energy allocation schemes or optimization of idle-active periods, among others. As an example of use of the developed analysis, we include the design of a WPT scheme under a proportional fair policy.Comment: This work has been accepted at the 2020 21st IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2020). Copyright held by IEE

On the effect of proportional fairness in energy transfer for wireless powered communication networks

Wireless powered communication network (WPCN) is an emerging area of research where energy is transferred from the access point to the mobile terminals in the downlink and information is transferred in the uplink. In the context of WPCN, we study the effects of applying different downlink/uplink scheduling schemes on the system performance in terms of achieved system throughput and fairness. In contrast to conventional wireless networks, where data scheduling determines the system sum rate and fairness behaviour, downlink energy scheduling contributes equally in WPCNs. We propose fairness based downlink energy transfer and compare different combinations of downlink and uplink scheduling schemes. Furthermore, we propose a new metric for downlink energy transfer for the special case of finite energy buffer and evaluate its effect on the achieved system throughput and fairness. Our numerical results show that a complete throughput fairness cannot be achieved as long as fairness is not employed in energy transfer in downlink regardless of the uplink scheduling scheme

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TÜBİTAK EEEAG Proje01.04.201