# Lightweight Physical Layer Aided Key Agreement and Authentication for the Internet of Things +
## 5 Conclusions  
In this paper, we presented a lightweight PL-AKA protocol by applying PLA to conventional AKA protocol, preemptively. To this end, we considered the integration strategy of the PLA and conventional cryptography-based authentication, classifying the PLA results into three parts: \"Authenticated\", \"Rejected\" and \"Gray\". We derived the signaling overhead of the proposed PL-AKA protocol with a probability that the cryptography-based authentication is performed. Moreover, a USRP-based experimental analysis was conducted to demonstrate the proposed scheme in practical application for IoT. In this analysis, we installed BS and UE as the LTE communication system, and observed the CSI according to the physical location with the linear stage. Here, phase sanitization was introduced to neutralize the effect of CFO and STO, and RMSD was defined to separate the legitimate and intrusion channel. The proposed scheme can achieve a more efficient signaling overhead, compared to conventional schemes, in both the simulation and experimental results. Therefore, this study showed the feasibility of the proposed scheme; various approaches to reduce the \"Gray\" probability can be the basis of future work to further reduce authentication overheads.  
[PERSON] contributed toward the experimental analysis and data measurement. [PERSON] helped in writing the introduction, investigation, resource, theoretical algorithms, review and editing, methodology. [PERSON] helped in the conceptualization, methodology, experimental analysis, validation, review and editing. [PERSON] aided in the proofreading, conceptualization, methodology, formal analysis, review and editing as the corresponding author, and provided guidance throughout the whole preparation of the manuscript. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Institute of Information and Communications Technology Planning and Evaluation (IITP) grant funded by the Korea government (MSIT) (No. 2017-0-00413, Streamlined Secure Communications by Physical Layer Identification in Cellular IoT) and this work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2021R1A2C1009803).  
Not applicable.  
Data Availability StatementData are available on request due to restrictions (privacy or ethical). The data presented in this study are available on request from the corresponding author. The data are not publicly available because this data set will be used for future works.  
This research was supported by Institute for Information and Communications Technology Promotion (IITP) funded by the Korea Government through the Ministry of Science  
Figure 9: Signaling overheads of PL-AKA and EPS-AKA over various target false alarm probabilities (experiment results).  
and Information and Communication Technology (MSIT) (Streamlined Secure Communications by Physical Layer Identification in Cellular IoT) under Grant 2017-0-00413, and this work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2021R1A2C1009803).