# Characterization of Dynamic Blockage Probability in Industrial Millimeter Wave 5G Deployments
## 1 Introduction  
5G NR systems are already appearing on the market providing broadband connectivity in both microwave (uWave) and millimeter wave (mmWave) bands. The critical distinguishing feature of 5G is that its services are not limited to enhanced mobile broadband (eMBB) but cover a wide range of use-cases and applications in various deployments including the Industrial Internet of Things (IIoT) [1]. In these deployments mmWave promises to bring a lot of opportunities due to the abundance of bandwidth available at the air interface and extreme directionality of communications [2]. In industrial scenarios, 5G NR promises new applications, such as the joint remote control of mobile robots, wireless time synchronization, positioning, augmented reality services for personnel, and telepresence-based maintenance operations [3]. Examples ofsuch applications include the systems that control the moving elements of manufacturing equipment and commonly generate low-rate traffic but require ultra-reliable low-latency service (URLLC), and video-guided machinery or mobile robots that require enhanced mobile broadband (eMBB) service [4]. The strict latency requirements of URLLC applications may require utilization of device-to-device (D2D) communications in industrial deployments [5]. In this operational regime, to avoid excessive interference in highly dense deployments of sensory equipment, the latter naturally requires directional transmissions at the user equipment (UE) side, which is available in mmWave band. This mode allows UEs to operate in D2D mode with coordination of transmissions from the BS or even without it [5]. This also allows the number of UEs in the deployment to be increased without drastically increasing the overall interference level [6]. In general, blockage of the propagation paths in an industrial environment is a generally more complex modeling task as compared to capturing human body blockage. The rationale is that factory spaces can contain many large metal racks, robots, and moving devices. In mmWave, most of the signal power is delivered to the receiver through the LoS path. The presence of multiple adjacent blockers interferes with the LoS between two UEs that are operating directly either by the BS or the UE. Therefore, it is extremely important to pay attention to the characteristics of blocking in such specific conditions: (i) the predominant material utilized for construction, such as concrete and the material used for equipment in industrial installations, such as different type of metals; (ii) careful spatial planning of UEs to avoid LoS blockage. In industrial environments, there are a large number of factors that have a strong influence on the propagation of a mmWave signal, with blockage having a strong impact on the communications in mmWave band. Depending on the communications scenario, blockage may occur between two UEs that communicate directly (e.g., performing synchronization or other time-critical tasks), or between UE to BS communications. Blockage leads to serious consequences only at high frequencies, in the mmWave range. At the same time, such frequencies are preferable for UEs, since they allow to significantly reduce the size of the antennas, leading to miniaturization, and also resulting in a much lower interference level which is critical for both considered scenarios. A blockage phenomenon in the industrial environment is drastically different from the human blockage [7; 8] or building blockage scenarios [9; 10; 11] that have been studied in detail recently. First of all, machines performing actions on the factory floor are inherently mobile, performing periodic movements such as those executed by mechanical arms [12; 13]. As opposed to purely stochastic mobility such as that inherent for humans in open spaces, this type of periodic mobility is more complicated to deal with using the stochastic geometry that is conventionally utilized to characterize blockage probability [14].