# Characterization of Dynamic Blockage Probability in Industrial Millimeter Wave 5G Deployments
## 2 Related Work  
The blockage phenomenon in industrial deployments has recently attracted significant attention from the research community. Specifically, the authors in [16] utilized computer simulations to obtain the line-of-sight (LoS) blockage probability in the factory environment with a size of 120 m \(\times\) 50 m \(\times\) 11 m, as stipulated by 3 GPP TR 38.824 [17]. The walls of the factory are made of concrete, and the space of the hall is equipped with various types of machines, robots, piles of metal objects, cranes, and other obstacles that are modeled as blockers. Dense deployment of BS according to TR 38.901 [18] is assumed, implying that 40% of the factory's floor is covered with metal blockers and the transmitters are placed above the blocking units. The blockers have a size of 3 \(\times\) 3 m with a variable height in the range of 2-7 m.  
Specifically, in [16], two homogeneous network schemes with 12 and 6 BSs are investigated. BSs are installed on the ceiling at a height of 11 m. The minimum distance between the transmitters is 28.28 m for the case of 6 BSs and 20 m for 12 BSs. Three operational bands have been considered, 3.5 GHz, 28 GHz and 60 GHz. The same downlink transmission power has been used for all BS without power control functionality. By utilizing computer simulations, the authors compared the results of simple LoS blockage and ray-tracing based LoS blockage. In the former case, a user's equipment is assumed to be in an outage when LoS is blocked while in the detailed ray-traced model, outage is explicitly modeled based on the received power. The obtained simulation results show that the simplified LoS-based blockage model may produce pessimistic results in terms of the fraction of time in outage conditions. In [19], extensive measurements of mmWave channels have been carried out in industrial environments by using both specialized measuring equipment at 60 GHz. In [19], the measurements have been carried out at the ALBA synchrotron, which is an elementary particle accelerator in Barcelona. This facility was chosen because of its diverse characteristics that resemble various industrial environments. The authors utilized IEEE 802.11 ad WiGig access point (AP) operating in mmWave 60 GHz band. The following methodology has been utilized. AP mounted at a certain place has been utilized to measure signal quality indicator (SQI), packet error rate (PER), blockage, and throughput with UE located in several places. To generate traffic perf tool has been utilized [20]. The results of the study demonstrate that blockage has a principal impact on the achieved UE rate. Furthermore, reflectors play a fundamental role in IIoT deployments. Authors even suggest that highly irregular characteristics of industrial scenarios is not a challenge for mmWave communications, but rather are an advantage in most cases. In [21], the authors address the challenge of efficient content distribution in typical industrial automation scenarios, offering the use of moving industrial machines as caching assistants. Specifically, mobile content is cached on intermediate nodes to reduce the volume of transmitted traffic and avoid duplicate downloads of popular data. This approach has been shown to reduce the response time in case of outages of UEs, improve spectral efficiency, and reduce energy consumption. To characterize blockage probability, the authors suggested utilizing photogrammetry to construct a transparency map of the deployment as UE moves around. However, the proposed methodology was purely simulation-based, providing no convenient way to assess blockage probability. Note that in our study we utilize photogrammetry differently to construct a transparency map of specific industrial machines. To the best of the authors' knowledge, the study in [5] is the only one where analytical blockage model for industrial deployments has been proposed. Specifically, they utilized the integral geometry approach to assess whether a LoS path crosses at least one industrial machine.