# Faudistic Platooning: Subdivide Platoons, Unite Networks, and Conquer Efficiency and Reliability
## 2 Related Work, Contribution, and Outline
### Related Work  
The performance of various communication technologies in a vehicular environment has been discussed and evaluated in a wide range of works, as well as with respect to platooning. IEEE 802.11p and mobile networks (LTE/5G), in addition to non-radio frequency-based technologies such as visible light communication (VLC), are especially of interest. One single conclusion on which technology is superior, however, cannot be established [10]--its selection depends on many factors. The authors in [11] see 5G as a promising solution to meet the low-latency and high-reliability requirements of platooning--whether the promise can be kept remains to be seen. A few works combine two communication technologies and perform hybrid networking. The authors in [12] combined IEEE 802.11p and LTE in an exemplary manner and selected the optimal communication technology on a per-packet basis for data dissemination in a vehicular network. [PERSON] et al. [13] showed, however, that IEEE 802.11p demonstrates poor performance in highly populated and dense networks. [PERSON] et al. [14] indicated severe impairments related to resource scheduling in LTE once used for V2X communication leading to packet loss. This means that despite selecting the currently optimal technology, it may still not be adequate for the task. Other communication technologies may offer a promising solution: the authors in [15] used VLC as a backup and offloading communication technology to IEEE 802.11p. Similarly, VLC and IEEE 802.11p were combined in [16] using network-selective message forwarding dependent on network load. However, both focus only on exchanging data used for inter-vehicle distance control. Irrespective of the network type, a higher load on the network endangers the quality of service provided [17; 18] with the result that platooned vehicles are forced to increase their inter-vehicle distance [19]. Hybrid communication can improve the quality of service in the event that communication channels are uncorrelated. However, this requires sophisticated management to ensure that the needed data are exchanged between the communication partners in time. This also includes data from the transport and platoon layer that are not directly related to inter-vehicle distance control. A fact that is often forgotten when focusing on the inner working of a platoon is that the surrounding non-platooned traffic must also be considered. On the one hand, it must not be disturbed, e.g., by blocking lane entries or exits; on the other hand, it poses a risk for the operation of the platoon: cut-in maneuvers, lane switches, overtaking, or accidents need to be considered. Platoons may be able to react to certain scenarios [20; 21]. However, in cases where inter-vehicle distances need to be adapted and especially when this affects multiple platooned vehicles, the reaction is simply too slow. Unforseeable events and events that lie outside the field of the platoon levels require explicit consideration and handling to ensure that their impact is limited [22]. Further to this, the information on non-platooned traffic may be vague since appropriate communication may not be supported. This limits the possibility of constructive reaction. Neglecting network capabilities, from a platoon perspective, and selecting a very small inter-vehicle distance would improve safety as cut-in maneuvers are inherently avoided. In addition, this would increase efficiency. However, the complexity and difficulty of platoon maneuvers would be increased. The dissolution of a platoon would be a long ongoing process until the inter-vehicle distance is reached when human drivers could take over [23]. From a non-platoon point of view, a large inter-vehicle distance would be preferred as it reduces the traffic disturbances caused by the platoon. Ultimately, platoon efficiency is highly linked to the inter-vehicle distance achieved and a driving behavior without braking maneuvers. Platoons influence and are influenced by surrounding traffic.