Exploiting constructive interference for simultaneous wireless information and power transfer in multiuser downlink systems

In this paper we propose a power-efficient approach for information and energy transfer in multiple-input single output downlink systems. By means of data-aided precoding, we exploit the constructive part of interference for both information decoding and wireless power transfer. Rather than suppressing interference as in conventional schemes, we take advantage of constructive interference among users, inherent in the downlink, as a source of both useful information signal energy and electrical wireless energy. Specifically, we propose a new precoding design that minimizes the transmit power while guaranteeing the quality of service (QoS) and energy harvesting constraints for generic phase shift keying modulated signals. The QoS constraints are modified to accommodate constructive interference, based on the constructive regions in the signal constellation. Although the resulting problem is nonconvex, several methods are developed for its solution. First we derive necessary and sufficient conditions for the feasibility of the considered problem. Then we propose second-order cone programming and semi definite programming algorithms with polynomial complexity that provide upper and lower bounds to the optimal solution and establish the asymptotic optimality of these algorithms when the modulation order and SINR threshold tend to infinity. A practical iterative algorithm is also proposed based on successive linear approximation of the non-convex terms yielding excellent results. More complex algorithms are also proposed to provide tight upper and lower bounds for benchmarking purposes. Simulation results show significant power savings with the proposed data-aided precoding approach compared to the conventional precoding scheme

Timely data collection for UAV-based IoT networks: a deep reinforcement learning approach

With the increasing development of the Internet of Things (IoT), the number of sensor nodes is growing explosively. The future application systems have stricter requirements on the timely delivery of the data collected from the sensor nodes. For such applications, unmanned aerial vehicles (UAVs) can help to collect data from the sensor nodes (SNs) and then fly to the data center (DC) to deliver the data. UAVs have the advantages of rapid deployment, strong maneuverability and low cost. Compared with the method of multi-hop data transmission, the UAV can flexibly adjust its position to improve communication environment. This helps to save energy and extend the battery lifetimes of the nodes. In addition, by constructing the communication systems between UAVs and ground terminals, and between UAVs, this helps to satisfy the needs of network services in various scenarios in the future. These include reliable and safe communication in public areas, network enhancement in hotspots, data collection in smart cities and improving network coverage in remote areas, etc

Introduction to the issue on signal processing for exploiting interference toward energy efficient and secure wireless communications

INTERFERENCE has been the central focus for meeting the ever increasing requirements on quality of service in modern and future wireless communication systems, and has long been considered as a deleterious factor that limits the system capacity. In conventional communications systems, the design objective is to allow users to share a medium with minimum or no interference. Thus, great efforts are made to avoid, mitigate, and cancel interference. For instance, to support multiple users, orthogonal access methods in time, frequency, code well as spatial domains have been used in different generations of cellular systems. In future-generation heterogeneous cellular networks, due to the increasing number of uncoordinated lowpower nodes such as femtocells to improve the coverage and pacity, interferences need to be mitigated in multiple domains, rendering their management a challenge. Interference mitigation/avoidance techniques provide convenient mechanisms allow multiple users to share the wireless medium. However, they lead to inefficient use of wireless resources