# On Ad Hoc Communication in Industrial Environments
## 2 Related Work  
Wireless communication is not new in the industrial context, but it has continuously gained importance [5; 6]. The industrial environment is particularly challenging for the application of wireless communication technologies [7]. On the one hand, high requirements in terms of latency, throughput, and especially reliability are applied [8; 9]. On the other hand, dynamic environments including fading, mobility in the transmitter and receiver, and the permanent presence of interference degrade the performance of wireless communication technologies. [PERSON] et al. and [PERSON] et al. [10; 11] analyzed these challenging requirements for the communication systems of mobile robots in the Industry 4.0 context. The requirements for different industrial use cases were compared and the applicability of several communication technologies examined. Relevant communication technologies for the industrial AGV use case include LTE [12], 5G [1, 13], WiFi [11, 14], ZigBee [11], and specialized solutions like visible light communication (VLC) [15] and radar [16]. These technologies have different advantages and strengths and must be chosen based on the application specific requirements. References [5, 10, 11, 16] compare these strengths to the requirements of emerging industrial trends. This high variability in underlying communication technology makes it necessary to develop methods that do not depend on specific technologies. References [17, 18, 19, 20, 21, 22, 23, 24] performed measurements in different industrial environments and provide valuable insight on the expected channel characteristics at different frequencies. The observed variability of the link over time is a strong indicator for the dynamic nature of the propagation properties within an industrial environment. The measurements were executed with static transmitter and receivers at different positions. Spatial variability is an important factor in scenarios, where the transmitter and/or receiver are mobile [14]. Reference [25] illustrates the lack of measurements in industrial applications. No previous work has specifically characterized the peer-to-peer communication channels in a mobile industrial network. Additionally, the previously published measurements of wireless channel propagation characteristics lack abstraction towards available connections that the utilized method provides. Thus, this works provides a complementary approach to existing work. Ad hoc communication technologies are an emerging trend in the use case of factory automation and industry in general. Wireless sensor networks (WSN) are possibly the best established use case for this technology [26, 27]. These sensor networks are utilized to monitor machines, environmental conditions, and more. Software-Defined WSN (SDWSN) are a particular variant of these networks, surveyed by [4]. Mobile Ad hoc NETworks (MANET) are not yet present in many industrial facilities. However, they are being investigated by researchers in the context of mobile robots (e.g., AGVs) [2]. In this use case, MANETs and other other ad hoc technologies, like delay tolerant networks (DTNs) [3], offer enhanced flexibility, reliability, and independence from network infrastructure. The applicability of existing communication and routing solutions to an industrial MANET have not been researched at this point in time. This work offers, in contrast to previous work, a non-simulation-based, routing-independent view on the mobile industrial peer-to-peer channel. It is therefore useful as a foundation for future research on ad hoc technologies in the industrial environment. In contrast to the presented methods, the observed connection characteristics depend on the chosen combination of examined environment and communication technologies. NEPs have previously been used to examine mobile ad hoc networks [28]. [PERSON] et al. used NEPs to examine the properties and applicability of ad hoc data dissemination schemes to campus networks.