6G for vehicle-to-everything (V2X) communications: Enabling technologies, challenges, and opportunities

We are on the cusp of a new era of connected autonomous vehicles with unprecedented user experiences, tremendously improved road safety and air quality, highly diverse transportation environments and use cases, and a plethora of advanced applications. Realizing this grand vision requires a significantly enhanced vehicle-to-everything (V2X) communication network that should be extremely intelligent and capable of concurrently supporting hyperfast, ultrareliable, and low-latency massive information exchange. It is anticipated that the sixth-generation (6G) communication systems will fulfill these requirements of the next-generation V2X. In this article, we outline a series of key enabling technologies from a range of domains, such as new materials, algorithms, and system architectures. Aiming for truly intelligent transportation systems, we envision that machine learning (ML) will play an instrumental role in advanced vehicular communication and networking. To this end, we provide an overview of the recent advances of ML in 6G vehicular networks. To stimulate future research in this area, we discuss the strength, open challenges, maturity, and enhancing areas of these technologies

Robust and real-time state estimation of unstable microgrids over IoT networks

Smart grid is expected to make use of Internet-of-Things (IoT) networks to reliably monitor its state from remote places.However, due to a potentially unstable nature of a smart grid plant, in particular, when using renewable energy sources, and an unreliable wireless channel used in IoT, it is a challenging task to reliably track the state of smart grids. This article proposes a robust communication framework for state estimation/tracking of unstable microgrids, which is a key component of a smart grid. We present an IoT-integrated smart grid system to monitor the status of microgrids over a wireless network. A delay-universal-based error correction code is utilized to achieve a reliable and real-time estimation of microgrids. To exploit the features of the delay-universal coding scheme, we propose an iterative estimation technique. Through numerical results, we show that the proposed scheme can closely track the state of an unstable microgrid. We also show the impact of wireless network parameters on the estimation performance. The estimation performance of the proposed scheme is compared with the estimation performance of a traditional error correction coding scheme. We show that the proposed scheme substantially outperforms the traditional scheme

A Multi-Path Compensation Method for Ranging in Wearable Ultrasonic Sensor Networks for Human Gait Analysis

Gait analysis in unrestrained environments can be done with a single wearable ultrasonic sensor node on the lower limb and four fixed anchor nodes. The accuracy demanded by such systems is very high. Chirp signals can provide better ranging and localization performance in ultrasonic systems. However, we cannot neglect the multi-path effect in typical indoor environments for ultrasonic signals. The multi-path components closer to the line of sight component cannot be identified during correlation reception which leads to errors in the estimated range and which in turn affects the localization and tracking performance. We propose a novel method to reduce the multi-path effect in ultrasonic sensor networks in typical indoor environments. A gait analysis system with one mobile node attached to the lower limb was designed to test the performance of the proposed system during an indoor treadmill walking experiment. An optical motion capture system was used as a benchmark for the experiments. The proposed method gave better tracking accuracy compared to conventional coherent receivers. The static measurements gave 2.45 mm standard deviation compared to 10.45 mm using the classical approach. The RMSE between the ultrasonic gait analysis system and the reference system improved from 28.70 mm to 22.28 mm. The gait analysis system gave good performance for extraction of spatial and temporal parameters

Tracking Control of Uncertain Surface Vessels with Global Finite-Time Convergence

This paper investigates an innovative control technique for uncertain surface vessels working in enhanced sea states to guarantee global finite-time convergence. First, a new finite-time backstepping approach is investigated. However, the effects of the uncertainties and disturbances reduce the closed-loop performance and prevent the global finite-time convergence of the system. In order to estimate these effects, an innovative finite-time disturbance observer is taken into consideration. The combination between the finite-time backstepping approach and the finite-time disturbance estimation creates a control system providing finite-time convergence of the system. The proposed approach is then tested on a tracking control problem for a surface vessel. The simulation results unveil the innovation of the proposed approach compared with existing ones

A Doppler-Tolerant Ultrasonic Multiple Access Localization System for Human Gait Analysis

Ranging based on ultrasonic sensors can be used for tracking wearable mobile nodes accurately for a long duration and can be a cost-effective method for human movement analysis in rehabilitation clinics. In this paper, we present a Doppler-tolerant ultrasonic multiple access localization system to analyze gait parameters in human subjects. We employ multiple access methods using linear chirp wave-forms and narrow-band piezoelectric transducers. A Doppler shift compensation Technique is also incorporated without compromising on the tracking accuracy. The system developed was used for tracking the trajectory of both lower limbs of five healthy adults during a treadmill walk. An optical motion capture system was used as the reference to compare the performance. The average Root Mean Square Error values between the 3D coordinates estimated from the proposed system and the reference system while tracking both lower limbs during treadmill walk experiment by 5 subjects were found to be 16.75, 14.68 and 20.20 mm respectively along X, Y and Z-directions. Errors in the estimation of spatial and temporal parameters from the proposed system were also quantified. These promising results show that narrowband ultrasonic sensors can be utilized to accurately track more than one mobile node for human gait analysis

Design of chirp waveforms for multiple-access ultrasonic indoor positioning

In ultrasonic positioning systems (UPSs) chirp waveforms have attracted much attention due to its high range resolution. However, the multiple-access schemes for the chirp-based UPS are limited. In its application to multiple-access ultrasonic positioning, effective waveform diversity design is a prerequisite. In a multiple-access UPS, each transmitter should transmit a unique waveform with impulse-like auto-correlation and relatively flat cross-correlations to the waveforms transmitted by other transmitters. Proposed in this paper is a methodology whereby multiple transmitters can transmit chirp signals simultaneously. The chirp waveforms are constructed by concatenating a number of linear sub-chirps of the same durations and bandwidths but different starting and stopping frequencies. This process is optimized by selecting sequences with impulse-like auto-correlations and relatively flat cross-correlations. First, the efficiency of the proposed methodology is evaluated by several metrics and, then, in an indoor environment, through simulations and experiments for ultrasonic positioning

Simultaneous Excitation Systems for Ultrasonic Indoor Positioning

Khyam, MO ORCiD: 0000-0002-1988-2328Ultrasonic technology is a tool in the area of indoor positioning systems (IPSs) and has been extensively used in many applications. In ultrasonic IPSs (UIPSs), the use of a chirp signal (in which the frequency varies with time) is widespread due to its capability to obtain high-range resolution through its timefrequency characteristic. It also provides an opportunity to design effective waveform diversity which has always been the key to mitigating multiple-access interference (MAI) in multi-user UIPSs. To explore this, we analyze the chirp signal from the signal design perspective, with the goal of developing a precise and efficient UIPS for multi-user environments. To achieve this, three waveform diversity design schemes are proposed in which all the benefits of the classical chirp, such as high-range resolution, are retained while all the transmitters can transmit chirp signals simultaneously. In each scheme, a linear chirp is divided into two linear sub-chirps with diverse durations and/or bandwidths. This process is optimized by selecting the concatenated sub-chirps that generate a waveform which has a high-range resolution and relatively low interference in the same scheme. Initially, the effectiveness of the proposed schemes is evaluated for five simultaneous excitation signals using several metrics and experimental results are then presented for the ultrasonic indoor positioning