RIS-Aided Joint Localization and Synchronization with a Single-Antenna Mmwave Receiver

Abstract

MmWave multiple-input single-output (MISO) systems using a single-antenna receiver are regarded as a promising solution for the near future, before the full-fledged 5G MIMO will be widespread. However, for MISO systems synchronization cannot be performed jointly with user localization unless two-way transmissions are used. In this paper we show that thanks to the use of a reconfigurable intelligent surface (RIS), joint localization and synchronization is possible with only downlink MISO transmissions. The direct maximum likelihood (ML) estimator for the position and clock offset is derived. To obtain a good initialization for the ML optimization, a decoupled, relaxed estimator of position and delays is also devised, which does not require knowledge of the clock offset. Results show that the proposed approach attains the Cramér-Rao lower bound even for moderate values of the system parameters.

RIS-Enabled Self-Localization: Leveraging Controllable Reflections With Zero Access Points

“…Many studies have been conducted to investigate RIS-aided localization in different scenarios, which can be categorized in terms of the operating regime (near-field [6]- [9], far-field [10]- [12]), RIS placement (at the base station (BS) side [7], The considered system setup with a single-antenna UE and an RIS. The wireless environment is assumed to also include passive objects contributing to multipath signal reflection.…”

“…The wireless environment is assumed to also include passive objects contributing to multipath signal reflection. [8], at the UE side [12], or as a separate reflector [13], [14]), wireless settings (multiple-input multiple-output (MIMO) [14], [15], multiple-input single-output (MISO) [10], and singleinput single-output (SISO) [9], [11]), etc. Furthermore, RISs can be used to assist the radar systems to improve the target detection capabilities [16], [17].…”

“…In [15], the authors considered an RIS-aided MIMO scenario, derived the CRBs, and used the bounds to optimize the RIS phase profile for localization. Furthermore, it has been shown that localization and UE synchronization can be performed in a MISO [10] and even in a SISO [11] setup with the help of a single RIS, when far-field conditions hold.…”

Acoustic Dual-Function Communication and Echo-Location in Inaudible Band

“…For EM signals, this is expected to be a key feature of the 6G cellular networks, allowing exploiting the dense cell infrastructure of 5G for constructing a perceptive network [ 23 , 24 , 25 ]. It is foreseeable, in fact, that future networks will go beyond classical communication and provide a sensing functionality to measure the surrounding environment [ 26 , 27 ]. This motivates the recent research theme of Integrated Sensing and Communications (ISAC) [ 28 ], which however concerns radiofrequency communications and radar systems.…”

Toward Integrated Large-Scale Environmental Monitoring Using WSN/UAV/Crowdsensing: A Review of Applications, Signal Processing, and Future Perspectives

“…Further improvements can be obtained by considering the use of the emerging reconfigurable intelligent surfaces (RIS). Such a technology, which will be at the basis of future 6G networks, allows wireless communications to evolve toward a new reality where the propagation environment can be re-engineered, i.e., dynamically programmed and reconfigured to adapt to the surrounding environment [460]. These artificial surfaces, made of electromagnetic material, can modify the propagation of radio waves (by acting the way that they interact with surrounding objects-see Figure 8, scenario A), thus attenuating the negative effects of propagation (path loss, multipath fading) and allowing for the establishment of a robust communication link even when the direct path between transmitter and receiver is severely obstructed.…”