# On the Secrecy Sum-Rate of Internet of Things Networks: Scheduling and Power Control +
###### Abstract  
Physical-layer security (PLS) has attracted much attention in wireless communications and has been considered one of the main candidates for enhancing wireless security in future 6G networks. Recent studies in the PLS area have focused on investigating and analyzing the characteristics of secure transmissions in multiuser networks (e.g., the massive number of Internet of Things (IoT) devices in 6G networks). Due to the difficulty of obtaining the exact secrecy capacity region in wireless multiuser networks, several alternative methods are used to characterize the secrecy performance of multiuser networks. For example, we can analyze the secrecy sum-rate scaling in terms of the number of users based on multiuser diversity (MUD). In this paper, we propose an opportunistic user scheduling scheme that achieves optimal MUD gain, combined with a power control mechanism for reducing information leakage to multiple eavesdroppers in wireless networks. The proposed scheme considers multiuser transmissions in one scheduling time slot by adopting orthogonal random beamforming at the receiver to exploit the full degrees-of-freedom gain with an assumption that each user (or IoT device) is equipped with a single antenna, and base station and eavesdroppers have multiple antennas. The main contribution of this paper is to derive the analytic result of the achievable secrecy sum-rate scaling in a high signal-to-noise ratio (SNR) regime. We evaluate the performance of the proposed scheduling scheme with a power control mechanism through simulations with both internal and external eavesdropping scenarios. We further discuss the extensibility of our analysis to various applications such as satellite communications and IoT networks. physical-layer security; Internet of Things; multiuser diversity; scheduling; power control +
Footnote †: This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)]([https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/))). Footnote †: This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons. used in conventional cryptographic approaches, to guarantee confidentiality [4]. Further, the PLS technologies have been considered as one of the possible candidates for the next-generation 6G communication systems [3]. The fundamental notions of physical-layer security have been established by [PERSON] [5] and [PERSON] [6]. Since then, there have been many efforts to investigate information-theoretic secrecy at the physical-layer in wireless communication systems [7; 8; 9; 10; 11; 12]. Among many topics related to physical-layer security, we seek to investigate characteristics of secure transmissions in _wireless multiuser networks_ (e.g., the massive number of IoT devices in the networks). Specifically, we focus on analyzing the characteristics of the secrecy rate, which is one of the challenging problems when we consider wireless multiuser wiretap networks. There have been several studies which investigate various aspects of the secrecy rate in multiuser wiretap networks, such as _secure degrees-of-freedom_[13; 14], _secrecy diversity_[15; 16; 17; 18], and _secrecy rate scaling_[19; 20; 21; 22; 23]. [PERSON] et al. investigated secure degrees-of-freedom (DoF) under two distinct models, namely the interference channel with confidential messages and the interference channel with an external eavesdropper [13]. [PERSON] and [PERSON] further studied secure DoF regions of the multiple access channel and the multiuser interference channel under several secrecy constraints [14].