Using MetaPrisms for Performance Improvement in Wireless Communications

In this paper, we put forth the idea of metaprism, a passive and non-reconfigurable metasurface acting as a metamirror with frequency-dependent reflecting properties within the signal bandwidth. We show that, with an appropriate design of the metaprism, it is possible to control that each data stream in an orthogonal frequency division multiplexing (OFDM) system is reflected in the desired direction without the need for control channels and channel state information (CSI) estimation between the base station and the metaprism, but simply by correctly assigning subcarriers to users. Furthermore, the metaprism can also be designed so that it focuses the signal towards a specific position depending on the subcarrier, provided that it is in the near-field, with consequent path-loss reduction. A critical discussion is also presented about the path-loss gain obtainable from metaprisms and, more generally, from metasurfaces. The numerical results show that this solution is surprisingly effective in extending the coverage in areas experiencing severe non line-of-sight (NLOS) channel conditions, thus making it a very appealing alternative to reconfigurable metasurfaces when low-cost, no energy consumption, and backward compatibility with existing wireless standards are required.Comment: 30 pages, 10 figures, Submitted to IEEE Trans. on Wireless Communication

Location and Map Awareness Technologies in Next Wireless Networks

In a future perspective, the need of mapping an unknown indoor environment, of localizing and retrieving information from objects with zero costs and efforts could be satisfied by the adoption of next 5G technologies. Thanks to the mix of mmW and massive arrays technologies, it will be possible to achieve a higher indoor localization accuracy without relying on a dedicated infrastructure for localization but exploiting that designed for communication purposes. Besides users localization and navigation objectives, mapping and thus, the capability of reconstructing indoor scenarios, will be an important field of research with the possibility of sharing environmental information via crowd-sourcing mechanisms between users. Finally, in the Internet of Things vision, it is expected that people, objects and devices will be interconnected to each other with the possibility of exchanging the acquired and estimated data including those regarding objects identification, positioning and mapping contents. To this end, the merge of RFID, WSN and UWB technologies has demonstrated to be a promising solution. Stimulated by this framework, this work describes different technological and signal processing approaches to ameliorate the localization capabilities and the user awareness about the environment. From one side, it has been focused on the study of the localization and mapping capabilities of multi-antenna systems based on 5G technologies considering different technological issues, as for example those related to the existing available massive arrays. From the other side, UWB-RFID systems relying on passive communication schemes have been investigated in terms of localization coverage and by developing different techniques to improve the accuracy even in presence of NLOS conditions

Non-Regenerative Relaying for Network Localization

Network localization enables a variety of new applications that rely on the positional information of nodes. High-accuracy network localization is challenging in harsh propagation environments (such as indoor) and is limited by power emission constraints. We devise non-regenerative ultra-wideband relaying to improve the performance of network localization in terms of coverage and accuracy. Maximum likelihood inference of nodes’ position for relayed network localization is developed, with perfect and imperfect channel knowledge. Results quantify the performance improvement that non-regenerative relaying offers despite its low-complexity