# On Ad Hoc Communication in Industrial Environments
## 1 Introduction  
Trends like Industry 4.0 are shaping the factory of the future. Flexibility and mobility are central requirements for future production facilities. Wireless communication plays a central part in enabling mobility and facilitating flexibility [1]. Automated guided vehicles (AGVs) for example, depend on wireless communication systems. Researchers are investigating the possibility of utilizing ad hoc communication (e.g., Mesh [2] or Delay Tolerant Networks (DTNs) [3]) for communication in AGVs. The research and implementation of wireless and ad hoc networks, in particular, would benefit from a thorough understanding of the wireless channel in industrial environments or the ability to simulate this use case. Additionally, further practical research is needed [4]. Research regarding wireless communication in industrial environments is challenging due to the limited accessibility of industrial facilities; thus, data from such facilities are sparse. This research aims to ease this challenge by publishing a data-set from a running production facility, and this enables researchers to test custom routing algorithms and networking strategies for ad hoc networks in an industrial scenario without accessing a production facility. Additionally, the tools for the creation, examination, and usage of this data-set are provided. The utilized method simplifies the scenario by abstracting the physical layer of the network and focusing on the connection-oriented aspects of communication. This work proposes a new method to record time-variant topologies of wireless networks and emphasizes its advantages over existing methods. The topologies of a mobile wireless network from a running production facility are recorded and published. These data enable researchers and engineers to test and verify networking strategies and routing algorithms. The connection-oriented topology characteristics are examined and compared to non-industrial and static wireless networks. Based on these comparisons, recommendations for the design of industrial ad hoc networks are given. An encounter is a continuous time frame in which a transmitter can send data to a receiver and is the basic building block of a wireless network topology. A nodal encounter pattern (NEP) is arecording of the encounters in a specific scenario using a specific communication technology. The NEP denotes the time variant topology of the network and abstracts the physical layer of the communication interface. Properties of the NEP can therefore be used to determine connection characteristics of the used communication technologies in an examined scenario. This work contains a new method for recording and analyzing NEPs that were recorded in a running production facility. The NEPs are additionally published so the research community can use them for further analysis and as a basis for the simulation of wireless industrial networks. Although the NEPs recorded in this work are limited to the examined combination of the factory environment and communication technology, the proposed methods are applicable to a wide variety of applications and use cases. In terms of communication technology, the proposed method is limited to technologies that enable wireless broadcasting. Utilizing NEPs to denote the time-variant topology of an industrial ad hoc network is novel and enables many new use cases. A researcher can, for example, use the published NEP to test a newly developed routing algorithm in regards to its applicability to an industrial use case when utilizing an IEEE802.11 interface. In another example, a research engineer can utilize the provided tools and record an NEP in a different environment, analyze the NEP, and select a communication technology on the basis of his observations. The following research questions are answered by this work: How can the time-variant topology of a complex network be observed? What are the topology characteristics of an industrial ad hoc network?