# On the Evaluation of the NB-IoT Random Access Procedure in Monitoring Infrastructures
## 5 Conclusions  
NB-IoT is emerging as a promising technology for offering wireless connectivity to constrained smart devices deployed in several pervasive monitoring scenarios, such as Smart City, Precision Agriculture, and Industry 4.0. The random access procedure represents a key relation between devices and the base station, since uplink transmissions prevail among the rest of exchanged messages in a typical NB-IoT monitoring system. Hence, it is of the utmost importance to investigate the behavior of the aforementioned random access procedure.  
This paper presents the implementation of an open-source and 3 GPP-compliant NB-IoT random access procedure simulation tool and an analytical model describing both collision and success probabilities, given the number of users accessing the random access channel. By taking into account reference applications scenarios based on periodic reporting in monitoring infrastructures, computer simulations showed, as expected, that highly dense sensor networks lead to an overall higher preamble collision probability. Furthermore, cross-validation demonstrated that the formulated analytical model exhibited a considerably low percentage error, proving its remarkable accuracy.  
Future activities could involve, on the one hand, the formulation of a complete analytical model to estimate both the number of users performing the random access procedure and an extended analysis of the average end-to-end delay. On the other hand, either entirely new random access mechanisms or major enhancements to the current random access protocol could be implemented in the proposed simulation tool, in order to assess their performance with respect to the standard procedure. Furthermore, the proposed simulation platform could be used for conducting the performance evaluation of different application scenarios, hence embracing the huge extent of Internet of Things use cases.  
**Author Contributions:** Conceptualization, S.M. and G.P.; methodology, S.M. and G.P.; software, S.M. and G.P.; validation, S.M. and G.P.; formal analysis, S.M. and G.P.; investigation, S.M. and G.P.; resources, S.M. and G.P.; data curation, S.M. and G.P.; writing-original draft preparation, S.M. and G.P.; writing-review and editing, S.M., G.P. and G.B.; visualization, S.M., G.P. and G.B.; supervision, G.B.; project administration, G.B.; funding acquisition, G.B.  
**Funding:** This work was partially funded by Italian MIUR PON projects Pico&Pro (ARS01_01061), AGREED (ARS01_00254), FURTHER (ARS01_01283), and RAFAEL (ARS01_00305), by the PRIN project no. 2017 NS9 EF entitled \"Realtime Control of 5G Wireless Networks: Taming the Complexity of Future Transmission and Computation Challenges\", as well as by Apulia Region (Italy) Research Project E-SHELF (OSW3 NO1) and INTENTO (36A49H6).  
Figure 15: Collision and success probabilities of RAOs for Configuration 3.  
Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analysis, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.