A Reduced Complexity of Vahedi's Tag Estimation Method for DFSA

In order to calculate the number of tags in a radio frequency identification (RFID) system, several tag estimation methods have been investigated in literature and most of the available estimation methods need the overall knowledge of idle, success and collision slots of the previous frame to carry out the tag estimation process. In this article, we present three techniques to reduce the complexity of Vahedi’s tag estimation for tag collision resolution in RFID systems using dynamic frame slotted ALOHA. Our modified and useful approach considers the information about only the number of empty, successful or colliding slots in the previous frame for the tag estimation. Three decision rules were obtained by maximizing the likelihood of success, idle and collision which helps in the reduction of complexity substantially. However, the accuracy of estimation decreases for success-only and idle-only methods while the collision-only method gives a consistent and lower estimate error when the frame sizes and the number of tags increase

Digital-Twins towards Cyber-Physical Systems: A Brief Survey

Cyber-Physical Systems (CPS) are integrations of computation and physical processes. Physical processes are monitored and controlled by embedded computers and networks, which frequently have feedback loops where physical processes affect computations and vice versa. To ease the analysis of a system, the costly physical plants can be replaced by the high-fidelity virtual models that provide a framework for Digital-Twins (DT). This paper aims to briefly review the state-of-the-art and recent developments in DT and CPS. Three main components in CPS, including communication, control, and computation, are reviewed. Besides, the main tools and methodologies required for implementing practical DT are discussed by following the main applications of DT in the fourth industrial revolution through aspects of smart manufacturing, sixth wireless generation (6G), health, production, energy, and so on. Finally, the main limitations and ideas for future remarks are talked about followed by a short guideline for real-world application of DT towards CPS

Simulation of Signal Coverage for Terahertz Communications

Recent progress in wireless communication technology has started to see proposals for spectrum operation in the Terahertz band (0.1 THz to 10 THz), which will lead to data rates close to Terabit per second (Tbps). However,there are a number of challenges with the signals operating in the THz band, and this includes the requirements of Line-of-sight, signal attenuation due to molecular absorption, as well as signal scattering upon reflection from rough surfaces. This paper addresses a software-defined reflector solution for mirror-assisted terahertz communications. The paper also discusses future outlook that further improve reflectos for terahertz communications

Antenna Delay-Independent Simultaneous Ranging for UWB-Based RTLSs

The ultra-wideband (UWB)-based real-time localization system (RTLS) is a promising technology for locating and tracking assets and personnel in real-time within a defined indoor environment since it provides high-ranging accuracy. However, its performance can be affected by the underlying antenna delays of UWB nodes, which act as a source of error during range estimations. Usually, measurement of the antenna delays is performed separately as a dedicated standalone procedure. Such an additional measurement procedure makes the UWB-based RTLS more tedious with manual interventions. Moreover, the air-time occupancy during the transmission and reception of signaling messages for range estimations between UWB node pairs also limits the serviceable capability of these networks. In this regard, we present a novel simultaneous ranging scheme that requires limited air-time occupancy during range estimations between UWB node pairs and also compensates for the error from the antenna delays. This paper provides a detailed mathematical modeling, system design, and implementation procedure of the proposed scheme. The effectiveness of the proposed scheme for locating a mobile node in an indoor environment is validated through experimental analysis. The results show that, compared to the state-of-the-art two-way ranging (TWR) method, the proposed scheme eliminates the requirement of dedicated standalone antenna delay measurement procedures of the nodes, increases air efficiency through the provision of simultaneous ranging, and provides relative root-mean-square errors (RMSEs) improvement for range and position estimations of approximately 54.52% and 39.96%, respectively