Edge computing is becoming ever more relevant to offload compute-heavy tasks in vehicular networks. In this context, the concept of vehicular micro clouds (VMCs) has been proposed to use compute and storage resources on nearby vehicles to complete computational tasks. As many tasks in this application domain are time critical, offloading to the cloud is prohibitive. Additionally, task deadlines have to be dealt with. This paper addresses two main challenges. First, we present a task migration algorithm supporting deadlines in vehicular edge computing. The algorithm is following the earliest deadline first model but in presence of dynamic processing resources, i.e., vehicles joining and leaving a VMC. This task offloading is very sensitive to the mobility of vehicles in a VMC, i.e., the so-called dwell time a vehicles spends in the VMC. Thus, secondly, we propose a machine learning-based solution for dwell time prediction. Our dwell time prediction model uses a random forest approach to estimate how long a vehicle will stay in a VMC. Our approach is evaluated using mobility traces of an artificial simple intersection scenario as well as of real urban traffic in cities of Luxembourg and Nagoya. Our proposed approach is able to realize low-delay and low-failure task migration in dynamic vehicular conditions, advancing the state of the art in vehicular edge computing.

LiFi has become an interesting and now more mature WiFi complement. To overcome the coverage limitations of LiFi and to create robustness against signal blockage, we use analog relays that cooperate with each other in both transmissions and signal reception. We present an ultra low-cost cascaded PLC-LiFi communication system comprising Power-Line Communication (PLC) for backhauling and Light Fidelity (LiFi) for wireless access. The interworking between the two technologies is achieved through low-complexity analog Amplify-and-Forward Relaying (AFR), i.e., the luminaries act as simple media converter. Results reveal the impact of amplification of AFR on the SNR as well as the relationship between the PLC and the optical wireless link length. Moreover, even so the gain from cooperative communication is substantial it is limited due to noise propagation in AFR.

Vehicular Visible Light Communications (V-VLC) has emerged as a technology complementing RF-based Vehicle-toVehicle (V2V) communication. Indeed, such RF-based protocols have certain disadvantages due to the limited radio resources and the, in general, omnidirectional interference characteristics. Making use of LED head- and taillights, V-VLC can readily be used in vehicular scenarios. One of the challenging problems in this field is medium access; most approaches fall back to ALOHA or CSMA-based concepts. Thanks to modern matrix lights, VVLC can now also make use of Space Division Multiple Access (SDMA) features. In this paper, we present a novel approach for medium access in V-VLC systems. We follow a location-aware cross-layer concept, in which dedicated light sectors of matrix lights are used to avoid interference and thus collisions. We assess the performance of our protocol in an extensive simulation study using both a simple static scenario as well as a realistic urban downtown configuration. Our results clearly indicate the advantages of our location-aware protocol that exploits the space-division features of the matrix lights.

In this work, we propose the use of hybrid offloading of computing tasks simultaneously to edge servers (vertical offloading) via LTE communication and to nearby cars (horizontal offloading) via V2V communication, in order to increase the rate at which tasks are processed compared to local processing. Our main contribution is an optimized resource assignment and scheduling framework for hybrid offloading of computing tasks. The framework optimally utilizes the computational resources in the edge and in the micro cloud, while taking into account communication constraints and task requirements. While cooperative perception is the primary use case of our framework, the framework is applicable to other cooperative vehicular applications with high computing demand and significant transmission overhead. The framework is tested in a simulated environment built on top of car traces and communication rates exported from the Veins vehicular networking simulator. We observe a significant increase in the processing rate of cooperative perception sensor frames when hybrid offloading with optimized resource assignment is adopted. Furthermore, the processing rate increases with V2V connectivity as more computing tasks can be offloaded horizontally.

We present a flexible real-time software-based multi-band channel sounder, which can flexibly be used in a variety of measurement campaigns, and fills the gap of expensive commercial channel sounders with limitations of operation frequency, sounding bandwidth, and ease of use. In general, channel sounding is a very valuable tool for designing wireless communication systems. Even though commercial channel sounders allow for thorough and detailed measurements, they are typically very expensive. In contrast, existing software-based solutions are often limited in scope and complexity of measurements. Our system closes this gap. Using GNU Radio and USRP radio front-ends, the system provides a high degree of freedom with respect to supported carrier frequencies and bandwidth. We also support features such as automatic spectrum-sweeping and transmitter gain management for dynamic channel characterization. We can use the system for both live visualization of the channel characteristics, e.g., Channel Impulse Response, Channel Frequency Response, Power Delay Profile, and Channel Phase Response, as well as for fully automated and repeatable experiments.

We investigate a novel approach of utilizing modern Adaptive Front-Lighting System (AFS) to reduce multiuser interference in Vehicular Visible Light Communications (V-VLC) by applying Space-Division Multiple Access (SDMA). V-VLC is a promising technology that can complement Radio Frequency (RF) communications to fulfill the high reliability and low latency requirements of Intelligent Transportation Systems (ITS). To achieve this, however, limitations of bandwidth efficiency and multiuser interference need to be addressed. A possible solution is to take advantage of SDMA, which allows spatial reuse of the resources and a simple but efficient multiple access method. State-of-the-art AFS, consisting of multiple controllable Light Emitting Diodes (LEDs) with sharply separated radiation patterns, offer a great opportunity to implement SDMA. Therefore, we investigate the applicability of an AFS-based SDMA system for V-VLC and compare its communication performance with a common LED-based high beam. Simulation results show that our system can be used to reduce multiuser interference in V-VLC.

We present a complete Visible Light Communication (VLC) system for experimental Vehicular VLC (V-VLC) research activities. Visible light is becoming an important technology complementing existing Radio Frequency (RF) technologies such as Cellular V2X (C-V2X) and Dedicated Short Range Communication (DSRC). In this scope, first works helped introducing new simulation models to explore V-VLC capabilities, technologies, and algorithms. Yet, experimental prototypes are still in an early phase. We aim bridging this gap with our system, which integrates a custom-made driver hardware, commercial vehicle light modules, and an Open Source signal processing implementation in GNU Radio, which explicitly offers rapid prototyping. Our system supports OFDM with a variety of Modulation and Coding Schemes (MCS) and is compliant to IEEE 802.11; this is in line with the upcoming IEEE 802.11 LC standard as well. In an extensive series of experiments, we assessed the communication performance by looking at realistic inter vehicle distances. Our results clearly show that our system supports even higher order MCS with very low error rates over long distances.

We investigate the impact of realistic light radiation pattern on Vehicular VLC (V-VLC) based on an empirical study for typical car headlight and taillight modules. Our research community identified visible light as a communication technology that has a number of advantages to radio communication. Besides the huge spectrum that is fully unlicensed, the technology allows for very high data rates and reduced interference from parallel communications. After seeing a number of breakthroughs in indoor environments, the vehicular networking community got interested in the technology for a number of reasons as well. First successful applications have been reported but practical evidence is still limited. This is due to the use of very abstract simulation models and limited field testing as of now. We aim at bridging this gap by developing a realistic simulation model based on empirical data from a measurement campaign. Based on this model, we particularly investigate the impact of the light radiation pattern of typical car light modules on the communication performance. We can report that the angle and distance of the communicating cars have a significant impact and need to be carefully considered for developing V-VLC applications.