## 5 Latency and Reliability Performance Evaluation in Wearable-Based MCPTT Applications
### Future Considerations  
In this section, we discuss novel 3 GPP standardization works that can be further considered in latency and reliability performance evaluations for wearable-based MCPTT applications. The first consideration is related to the baseband and radio-frequency capabilities of cellular-enabled wearable devices. As a matter of fact, LPWA-enabled wearables are not the only standalone wearable devices that can utilize cellular connectivity. Wearables are among the targeted use cases in beyond-5G systems. This can be confirmed by the introduction of the NR reduced-capability (NR RedCap) technology in 3 GPP Rel-17 [48]. Table 4 summarizes the main capabilities of an LTE Cat M2 device compared to those of a RedCap device operating in the 5G frequency range 1 (FR1). With reference to our performance evaluation, NR RedCap-enabled smartwatches can have higher bandwidth, which implicates the possibility of configuring sidelink grants with a higher number of RBs. This will affect reliability performance, as discussed in Section 5.2. The impacts of these reduced device capabilities on the network performance and needed recovery strategies are studied in the 3 GPP Rel-17 specifications on NR RedCap [49]. The latest recommendations can help to gain new insights into the performance evaluation of several requirements in wearable-based, mission-critical applications. Another fact that can motivate public safety agencies to integrate NR RedCap-enabled wearables in their networks is that, with cloud native technologies being central parts of the 5G core architecture, the network will provide wearable devices with the needed storage capacity and processing power [50]. Hence, NR RedCap-enabled wearables will be able to host more sensors, collect more data, and be involved in new sets of public safety applications. Other essential considerations are related to NR sidelink enhancements for public safety that are planned for 3 GPP Rel-17. As discussed in Section 3.1, although the first standard for NR sidelink in Rel-16 provides solutions specified mainly for V2X services, some of these solutions can also be utilized for public safety applications with additional enhancements [51]. Among these, we focus on the resource allocation enhancements in sidelink transmission mode-2. The latest 3 GPP work items on NR sidelink enhancements propose the definition of new resource selection or grant scheduling methods [51]. In the above performance evaluation, we use a fixed grant scheduling method where the sidelink grant parameters (i.e., MCS, allocation size, and kTRP) are preconfigured in the simulations. Nevertheless, the determination of these parameters by out-of-coverage UEs can be performed randomly (i.e., random scheduling) or following certain optimization goals. The latter include selecting a grant configuration that utilizes the minimum number of RBs per transmission (i.e., min. RB scheduling) or maximizes the communication range (i.e., max. coverage scheduling). To better understand the significance of these sidelink grant scheduling methods in MCPTT applications, we present preliminary results based on our simulations described in \begin{table}
\begin{tabular}{c c c} \hline \hline
**Device Capability** & **LTE Cat M2** & **NR RedCap** \\ \hline Max. bandwidth & 5 MHz & 20 MHz \\ \hline Max. UL modulation order & 4 (16 QAM) & 4 (16 QAM) \\ \hline Max. DL modulation order & 4 (16 QAM) & 6 (64 QAM) \\ \hline UE transmission mode & 1 (1 Tx/Rx antenna) & 1 (1 Tx/Rx antenna) \\ \hline UE power class & 5 & 3 \\ \hline UE transmit power & 20 dBm & 23 dBm \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main capabilities of LTE Cat M2 and NR RedCap devices. Section 5.1. Figure 8 reports the numerical results for the average access time (Figure 8a) and the average packet delivery ratio (Figure 8b) in the function of the PSCCH period and the resource selection method in MCPTT private calls.