## 5 A Comparative Analysis  
In Sections 2-4, we discussed the major features of 5G, WiFi, and TSN networks (both wired and wireless) that can enable smart manufacturing applications. In this section, we aim to provide a detailed comparative analysis of these technologies mainly from four perspectives: industrial use cases, supported secondary applications, industry adoption, and current market trends, as summarized in Figure 5.  
For the first dimension, we look at the industrial use-case perspective. There are a wide variety of use-case classifications in the literature [40; 65], and here we capture a consolidated, broader application-oriented classification of them. Closed-loop control and  
Figure 5: Comparison of communication technologies for Industry 4.0 and beyond. safety-critical alarms/systems are the hard real-time applications in smart manufacturing that demand ultra-reliability and very low latency, and TSN over Ethernet (T-E) is the best solution. However, scenarios that need flexibility demand wireless communication options, and we know that the wireless medium always adds reliability/latency challenges. Among all the available wireless technologies, we believe TSN over 5G (T-5) has the advantage of combining the features of TSN over a dedicated spectrum, and hence it is better suited to handle such applications. WiFi is the least preferred choice due to the unlicensed spectrum implementation and associated interference and wireless channel contention issues. Process monitoring use cases involve monitoring various parameters through different sensors. Such applications are relatively lenient in latency and reliability compared to closed-loop control applications, and the data-rate requirements generally tend to be small. However, wider coverage is essential, as many processes in the process industry cover large industrial spaces, and wireless technologies would be a better choice than T-E as they eliminate wiring requirements. In these use cases, 5G provides a better range than WiFi, and TSN integration provides additional reliability. Thus, T-5 is better suited for process monitoring use cases than T-W and 5G, whereas WiFi seems the least preferred wireless technology for process monitoring. MR/VR/AR are emerging technologies widely used in smart manufacturing to represent a digital 3D virtual factory for various applications, including training. These applications generally demand a very high data rate and flexibility to move around (hence, T-E is the least preferred). Both 5G and WiFi can provide higher data rates, and TSN integration offers additional capabilities for better reliability. The second dimension focuses on the secondary services these technologies can provide in addition to their primary role of providing communication infrastructure for manufacturing applications. Both 5G and WiFi (and their TSN-integrated versions) can offer sensing capabilities along with wireless communication. Indoor localization is another capability provided by both 5G and WiFi (and their TSN-integrated versions). Localization using WiFi is relatively established in comparison with 5G-based localization. These features are not feasible over wired TSN. Security is another major factor that needs to be considered in connection with communication technologies. Wireless technologies are more prone to security threats compared to wired infrastructure. Between 5G and WiFi, the unlicensed spectrum makes WiFi more exposed. The third dimension involves the various factors smart manufacturing industries consider while adopting these technologies onto their production floors, in addition to the technical capabilities/offerings. Compared to WiFi, 5G offers broader indoor coverage (including its TSN integrations), and TSN over Ethernet requires physical cabling to provision the T-E devices/switches. These aspects also influence device density. T-E requires an individual cable for each client. Although WiFi supports a possible bandwidth of 320 MHz, a factory floor will have multiple APs with overlapping coverage areas.