## 1 Introduction  
In recent years, the interest to bridge the gap between communication and sensing systems has increased substantially in the academic and industrial community [1, 2, 3]. The introduction of mmWave bands in cellular systems reduced the difference in the frequency of operations and, as a consequence, the hardware used. At the same time, as use cases evolve, specifically those targeting 6G networks [4, 5], the is an increasing need to use electromagnetic (EM) waves in sensing, for instance in radar sensing applications, in order to be part of the communications ecosystem. While this idea may enable radar-as-a-service (RaaS), there are still several standardization bottlenecks. The immediate benefits, such as the flexible and efficient use of radio sources, are clearly visible for the JCRS system; however, it is yet to be seen how it attracts the communication infrastructure and radar providers. As of today, research communities have reached a consensus that, in terms of usage, JCRS has the potential to revolutionize existing applications, from connected driving to mobile communications, with the addition of context awareness. It could also enable new applications in medical devices, secure Internet of Things (IoT), and the Industry 4.0 domain [6]. With the introduction of 3 GPP Rel. 16, new advanced localization capabilities utilizing time of arrival (ToA), time difference of arrival (TDoA), and angle of arrival (AoA) positioning methods have emerged. In addition, modern advanced driver assistance systems (ADAS) utilize communication capabilities that were standardized in 3 GPP Rel. 15 vehicle-to-everything (V2X) technology. However, future JCRS systems will require new levels of co-existence, sensor fusion, and real-time positioning features powered by machine learning, as well as enhanced privacy capabilities. JCRS technology is anticipated to support various 6G verticals, such as smart cities, the automotive industry, healthcare, manufacturing, and the likes. The numerous use cases that would leverage efficient spectrum usage, energy efficiency, and resilience of the future verticals are as follows:  
* Communication-assisted radar: These are advanced, next-generation radar systems that utilize communication with other vehicular devices to increase traffic awareness, particularly improving the accuracy of pedestrian detection and infrastructure locations. However, additional measures are necessary to increase data security, thus preventing unauthorized access to vast amounts of sensitive data. * Radar-assisted communication: The concept utilizes the existing communication and radar infrastructure to improve ecosystem characteristics, which will require huge standardization efforts. * Spectrum efficiency could be enhanced by sharing the operating frequency. With the introduction of frequency range (FR2) bands for the fifth-generation (5G) network, the large bandwidth can be utilized to enable the co-existence of radar communication. * Based on sensing information, adaptive systems can be implemented by adjusting the power level and beamformer angle, thus improving the energy requirements. * Adding sensing data such as the angle of arrival or time of flight to existing 5G localization algorithms can improve the positioning accuracy. * Radar as a Service: RaaS is an emerging concept in which sensing information is provided to interested agents to increase the efficiency of the provided services. This includes providing real-time traffic information to smart city monitoring centers or providing weather monitoring information, such as precipitation areas, to weather agencies. Other aspects include providing real-time 3D maps of the environment for creating digital twins of infrastructure objects for interested parties. As communication is already used as a service in today's networks, RaaS along with communication as a service can enable the flexible use of resources, depending on the context. This will further increase the demand and usage of JCRS devices in the future.