This paper considers a scenario where a reconfigurable intelligent surface (RIS) is deployed to allow the localization of mobile users adopting a single anchor node, even under non-line-of-sight (NLOS) channel conditions. When the RIS is large and the operating frequency is high, as in the millimeter-wave band, the system is likely to operate in the near-field propagation regime, which can be exploited to obtain robust localization. To this purpose, two practical signaling and positioning algorithms, based on an orthogonal frequency division multiplexing (OFDM) downlink system, are proposed along with methods to design the RIS time-varying reflection coefficients. In the numerical results, the two algorithms are compared in terms of performance in the presence of a synchronization mismatch and considering trade-offs between bandwidth, overhead, operating frequency, and latency. Finally, we provide an analysis of the soft-coverage capability, i.e., on the possibility of maintaining a high level of localization accuracy when in the presence of increasing levels of obstruction of the RIS.

This paper introduces the notion of network experimentation and proposes an experimentation methodology particularly suited for cooperative wireless networks. Based on this methodology we performed extensive measurement campaigns and compare various cooperative localization techniques under a common setting. Network experiments enable (i) the quantification of cooperation benefits, (ii) the development of techniques for harnessing environmental information, and (iii) the characterization of network localization algorithms. As a case study, we consider ultrawide bandwidth cooperative location-aware networks in cluttered indoor environments and evaluate their performance based on measurements collected from network experiments.

This paper proposes a practical method for the definition of communication modes when antennas operate in the near-field region, by realizing ad-hoc beams exploiting the focusing capability of large antennas. The beamspace modeling proposed to define the communication modes is then exploited to derive expressions for their number (i.e., the degrees of freedom) in a generic setup, beyond the traditional paraxial scenario, together with closed-form definitions for the basis set at the transmitting and receiving antennas for several cases of interest, such as for the communication between a large antenna and a small antenna. Numerical results show that quasi-optimal communication can be obtained starting from focusing functions. This translates into the possibility of a significant enhancement of the channel capacity even in line-of-sight channel condition, without the need of implementing optimal but complex phase/amplitude profiles on transmitting/receiving antennas as well as resorting to intensive numerical solutions. Traditional results valid under paraxial approximation are revised in light of the proposed modeling, showing that similar conclusions can be obtained from different perspectives.

Nowadays, passive and semi-passive wireless devices are increasing their appeal, particularly in the new scenario of the Internet of Things, thanks to their low complexity and low energy consumption. In this context, radio-frequency identification (RFID) and radar sensor networks (RSNs) are rising interest when the localization of (semi-)passive tags (without active transmitters) and moving passive objects is required. In this paper, we propose a novel network architecture capable of jointly localizing (semi-)passive tags and moving passive objects through the analysis of their backscattered response. The reciprocal interference in objects/tags localization arising from the signal variations caused by objects' and tags' movement is characterized. We present an analytical derivation, based on the Cramér-Rao bound, providing the theoretical localization accuracy of tags and passive objects. The proposed approach represents a fundamental design tool providing insights on how system parameters (power and signal format), network topology, interference, and network configuration (monostatic or multistatic) affect the localization performance.

Future automated driving relies on two pillars, (i) ultra-low-latency and reliable communications, and (ii) accurate positioning information. In particular, the knowledge of vehicle positions is becoming fundamental with the increase of the automation level, allowing autonomous navigation of the environment. Today’s positioning techniques cannot provide the accuracy, robustness, and latency required for stringent applications, like platooning, where vehicles are expected to travel at extremely short distances. In this paper, we leverage vehicle-to-everything (V2X) sidelink communication for localization purposes, capitalizing on the near-field propagation attributes of signals generated utilizing high carrier frequencies and/or large antenna arrays. Consequently, a receiving vehicle can accurately determine the transmitting vehicle’s location through V2X sidelink packet reception, obviating the need for supplementary reference nodes or stringent synchronization. Fundamental limits on localization accuracy are derived to characterize the positioning performance in vehicular contexts. A case study based on 5G new radio (NR) V2X sidelink shows how this technique is extremely promising and capable of providing high accuracy, low latency, high update rate, and high availability of position information in realistic vehicular scenarios.

In the new scenarios foreseen by the Internet of Things, industrial and commercial systems will be required to detect and localize tagged items with high accuracy, as well as to monitor the level of certain parameters of interest through the deployment of wireless sensors. To meet these challenging requirements, the adoption of passive and semi-passive ultra-wideband (UWB) radio-frequency identification (RFID) appears a promising solution, which overcomes the limitations of standard Gen.2 ultra-high frequency (UHF) RFID. The design and implementation of such systems pose several practical constraints, impacting the overall network architecture. In this paper, the main issues and challenging aspects for the design of a UWB-RFID network considering architectural and protocol choices are discussed in a unitary framework, and practical solutions, accounting for the presented issues, are proposed. Moreover, the possible integration of UWB-RFID with standard Gen.2 UHF-RFID is proposed as an interesting option, discussing architectural solutions, their advantages, and drawbacks.