# Connected Vehicles: Technology Review, State of the Art, Challenges and Opportunities
## 5 Opportunities
In connected environments, vehicles communicate with the surroundings to illuminate and mitigate imminent crashes. Specifically, in situations involving on-the-verge crashes with pedestrians, vehicles' and pedestrians' smart devices communicate with each other to alleviate this type of collision, creating the necessity for on-demand QoS and low-latency messaging in real time. The development of on-demand QoS-techniques for efficient V2P communication in risky situations has promising opportunities [151]. There are also huge opportunities for CVs to contribute to infrastructure- and environmental-sensing services, such as road roughness or estimation of the International Roughness Index, bank angle, lane-marking quality, potholes, speed bumps, snow and dust coverage, etc. [152]. Automotive radars are considered as an indispensable safety technology within today's and the next generation of modern vehicles. The most commonly used automotive radars are designed to meet the maximum radar range regardless of the traffic density due to their operation in the high bandwidth of mm-wave frequency band and their dependence on frequency modulated continuous waves (FMCW). This may lead to a number of technical challenges including radar-radar interference in dense traffic situations when vehicles are in close proximity to one another. This is in addition to the underused time-frequency allocated resources that are directly associated with the operating range. These technical challenges will provide opportunities for future research directions [153; 154]. Visible light communication technology provides new possibilities in the vehicular-based applications domain. VLC technology proposes many benefits including high data transmission (up to 10 Gbps), a low level interference range, and considerable vigor against commonly known jamming attacks in wireless communications. However, pitfalls still exist within the technology, as VLC is susceptible to noises formed by additional light sources, which makes it inconvenient in adverse weather conditions and unable to handle non-LOS situations [155; 156]. The advent of the commercial roll-out of 5G cellular technology will support a wide range of ultra-low-latency tangible-access networks and connected applications. Data- and user-centric approaches were adopted in LTE and 5G cellular technologies, in an effort to meet the daunting demand of transferring huge amounts of data at high speed. New research efforts have been directed towards 6G technologies to go a step further beyond personalized communication platforms towards a fully digitized connected Internet-of-Things paradigm, where heterogeneous devices are connected including computing resources, on-road vehicles, wearable devices, and many others. In its preliminary stages, 6G will be established on terrestrial and satellite communication providing seamless global coverage [157]. Furthermore, TeraHertz-based 6G technology will offer a phenomenal user experience due to the supported ultra high quality data rates. Additionally, 6G technology will endorse a number of cutting-edge technologies including intelligent reflective surfaces (IRS), quantum computation, and many others. Extensive research should be directed to some of the technical challenges including reflection optimization in IRS-aided technology, channel estimation/adaptation in the high mobility vehicular environment, and various frequency bands' ranges, respectively. Quantum computation will be integrated within the next generation 6G-V2X communication technology to provide high-level computation capabilities along with a security-rich V2X communication. However, technical challenges still pertain in regards to quantum computation scalability and the established quantum security frameworks' blueprints [158].