# On the Secrecy Sum-Rate of Internet of Things Networks: Scheduling and Power Control +
###### Abstract
Like the notion of DoF is readily modified to the secure DoF, secrecy diversity order, similar to the definition of traditional diversity order, is a notion to indicate diversity gain when we consider the secrecy outage probability, and it has been investigated from various perspectives [15; 16; 17; 18]. [PERSON] et al. investigated secrecy outage probability in multiple-input and multiple-output (MIMO) wiretap channels [15]. Particularly, [PERSON] et al. investigated the effects of various user scheduling schemes on secrecy diversity order, in terms of intercept probability and secrecy outage probability, considering multiple users in cognitive radio networks, respectively, [16; 17]. In other words, multiuser diversity (MUD), i.e., the number of users, can contribute to enhancing secrecy in wireless networks. Differently from [16; 17], authors of [19; 20; 21; 22; 23] investigated opportunistically exploiting multiple users in networks to achieve optimal MUD gain in terms of secrecy rate scaling. [PERSON] et al. first introduced the notion of secrecy rate scaling in terms of the number of users to characterize the secrecy rate in a single-cell environment, instead of the exact secrecy rate analysis impossible at most of the multiuser network settings [19]. Subsequently, the secrecy rate scaling has been analyzed in various network environments such as multi-cell [20], multiple receive antenna [21; 22], and artificial noise [23] settings. Further, secrecy rate scaling has been investigated combined with recent advanced techniques such as reconfigurable intelligent surface and massive MIMO with one-bit feedback [24; 25]. The authors of [24] derived the ergodic secrecy rate of a RIS-assisted communication system against multiple eavesdroppers. Both non-colluding and colluding scenarios were investigated and finally scaling law in terms of the number of RIS elements was analyzed. [PERSON] investigated the impact of the power-scaling law on the secrecy rate when the massive MIMO with one-bit feedback is considered [25]. Interestingly, in multiuser networks, instead of single user transmission in one time slot, multiuser transmissions in one time slot can be exploited to achieve full degrees-of-freedom gain from the perspective of the system. It still remains one of the open issues to study multiuser transmissions in terms of secrecy sum-rate scaling with respect to the number of users in the system whereas there have been several studies on multiuser transmissions in conventional network settings without eavesdroppers. Adopting multiple antennas at the receiver requires a proper post-processing technique such as zero-forcing or minimum-mean-square-estimation (MMSE) receivers [26; 27]. In multiuser networks, orthogonal random beamforming [28] is also widely used for multiuser transmissions since it achieves the optimal rate scaling by fully exploiting MUD gain. In wireless secure communications, orthogonal random beamforming was utilized with opportunistic scheduling to improve the secrecy performance [29]. The authors of [29] considered downlink multiuser networks (i.e., broadcast channel) since orthogonal random beamforming was originally proposed for a transmitter. According to the uplink (i.e., multiple access channel) and downlink duality, orthogonal random beamforming can also be applied at the receiver. Analyzing the sum-rate scaling in uplink networks was previously investigated in [30] by adopting orthogonal random beamforming at receivers in conventional wireless multiuser networks. However, to the best of our knowledge, it is the first trial to study the secrecy sum-rate scaling in wireless multiuser uplink networks where independent multiple eavesdroppers exist. Thus, studying wireless secure communications by adopting orthogonal random beamforming at receiver represents an interesting problem. The development of 6G networks promises many opportunities and advancements. One of the main features of 6G networks is the massive number of devices and enhanced security and privacy protection.