Browsing by Author "Zhao, N."

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Open Access
Energy harvesting and wireless power transfer enabled wireless networks
(Elsevier, 2020) Duman, Tolga M.; Zhao, N.; Nallanathan, A.; Chen, Y.; Pan, M.
Development of wireless communication networks, connected devices, and improvement of Internet of Things (IoT) will deeply impact in every aspect of human life. In future mobile systems, a tremendous number of low-power wireless devices will exist within the densely deployed heterogeneous networks. One key challenge from the growing demand in wireless applications is a sufficient and flexible energy supply. Hence, a natural spin from the traditional and limited energy sources to alternative energy sources is a natural step to supply the exponential growth of energy demand of the mankind. Recently, energy harvesting (EH) has emerged as an important method to provide a power supply for green self-sufficient wireless nodes, in which the energy captured from intentional or ambient sources can be collected to replenish the batteries. Besides, EH has been investigated as a promising technology to overcome the energy scarcity problem in energy constrained wireless communication systems, especially for wireless networks with fixed energy supplies. Compared with conventional EH sources such as solar, wind, vibration, thermoelectric effects or other physical phenomena, which rely on external energy sources that are not components of communication networks, a new operation of EH which collects energy from ambient radio-frequency (RF) signals has been proposed. As RF signals are commonly used as a vehicle for transmitting information in wireless networks, simultaneous wireless information and power transfer (SWIPT) has become an emerging technique attracting great attention from both academia and industry. Towards this end, this special issue includes a collection of 24 papers, and we aim to disseminate the latest research and innovations on energy harvesting and wireless power transfer enabled wireless networks.
Open Access
Unmanned aerial vehicle assisted communications and networking
(Elsevier, 2020) Duman, Tolga M.; Zhao, N.; Chen, Y.; Li, C.; Wang, K.; Yu, F. R.; Fan, L.; Alouini, M.-S.
In 5G and beyond networks, the explosive data and the massive connections are some of the key challenges. To alleviate the pressure on the ground networks and reduce the cost of densely deployed small cells, unmanned aerial vehicle (UAV) can be exploited as a promising technology in future communications networks. The UAV technology is becoming more and more mature, which owns advantages on high reliability, flexible deployment, cooperative operation and low cost. In particular, the air-to-air and air-to-ground channels are much better than the ground-to-ground channels. In many cases, they have line-of-sight (LoS) links. For these channels, mmWave transmission becomes practicable for UAV communications, which provides much higher data rate. Furthermore, UAVs can be combined with massive MIMO technology to meet ever-increasing data demand. Considering the device miniaturization and cost reduction of UAVs, it is more feasible than ever before to deploy UAV as relay to realize range extension in wireless communication systems. Meanwhile, in order to reduce the transmission latency as well as the load of backhaul links, UAVs are equipped with the ability of caching popular contents. In addition, UAVs can also be utilized in other important applications, such as emergency networks, traffic monitoring and military attacks, etc. However, there still exist many challenges in this emerging technology of UAV communications and networking, such as interference management, security and safety, beam tracking and alignment, trajectory and placement optimization, and so on. Furthermore, UAV enabled networking also requires great effort to reshape the current ground systems for satisfactory performances. Therefore, it is imperative to conduct thorough investigation and research on the UAV enabled communications and networking. Motivated by this, a collection of papers are included in this special issue, which mainly focus on the analysis and optimization of UAV-enabled networks and cache-aided UAV relay networks. Moreover, the analysis of energy efficiency, the design of secure transmission, and the optimization of outage probability and UAV-aided localization are investigated as well.