# Eco-Efficient Mobility in Smart City Scenarios
## Personal Vehicles and C-ITS
### Communication Technologies  
Intelligent open spaces such as smart cities or smart university campuses aim at offering users a range of continuous services that should be seamlessly provided even considering end-user mobility. Without a doubt, the evolution of wireless communication technologies has enabled the development of the C-ITS ecosystem during the last decade. The first advances in digital cellular networks (2.5G and 3G) allowed the development of fleet management and monitoring applications for professional transport such as trucks, taxis, or coach buses. These services have been enriched with more advanced features, e.g., goods or driver tracking, with the arrival of 4G. Other services developed under this umbrella are real-time traffic information, automatic emergency call, or infotainment applications, among others. Therefore, it can be seen how cellular solutions have taken advantage for supporting delay-tolerant applications [35]. In addition, they make use of an already deployed architecture and the provided coverage in urban areas is usually enough for the offered services. Nevertheless, some concerns arise regarding the scalability of these networks when supporting thousands of nodes simultaneously connected to a single cell as well as the latency issues mentioned above. These problems disable current cellular solutions to support critical services such as crash avoidance. However, it is envisioned that the 5G technology will solve these issues with its guaranteed support to three types of services: enhanced Mobile Broadband (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine Type Communications (mMTC) [36]. This promising technology is still in its infancy and the years to come will show whether functional deployments meet expectations. Therefore, in the plane of traffic safety and dedicated transmissions, the technology with a greater level of maturity is IEEE OCB (formerly known as IEEE 802.11p), which is the main pillar of protocols such as the ones within the IEEE Wireless Access in Vehicular Environments (WAVE) and the general architecture defined by ISO/ETSI, as shown in Figure 2. Differently from the cellular alternatives, IEEE OCB also supports V2V communications, which permits notably reducing latency of communications with surrounding vehicles. In fact, the latest specification of 5G technology (release 15) includes dedicated communications for vehicular scenarios, considering integrated cellular vehicle to  
Figure 2: Cloud services for personal mobility devices, radio access technologies, and protocols. everything (C-V2X) connectivity. As aforementioned, although IEEE OCB has received great attention, specially from the Academia [37], its implantation has not been effective due to need for a fixed infrastructure, which has a notable cost given the great number of RSUs needed for covering a city [34]. In addition, this technology is energy-consuming for power-constrained devices, and it is prone to interferences and transmission collisions in highly crowded areas, which makes it unreliable for urgent information exchanges or even IoV monitoring scenarios in urban settings. If this landscape is not complex enough, the new wave of IoT-related communication solutions has also come into play. The LPWAN paradigm promises long-range connectivity with limited energy consumption at the expense of offering limited data rates. Hence, as can be seen in Figure 2, the complementary use of LPWAN technologies arises as an interesting option for avoiding saturation of IEEE OCB and regular cellular channels due to not-urgent messages. Examples of LPWAN technologies are (i) NB-IoT, which is a solution integrated within the cellular ecosystem; (ii) LoRaWAN, which permits manageable private large-scale deployments; or (iii) Sigfox, which is a proprietary solution with an already deployed infrastructure in America and Europe [8]. Most of the services identified above for new-age personal vehicles may be supported by LPWAN-based technologies.