Rate-splitting multiple access (RSMA) is a promising technology for future wireless networks. In the present paper, a two-user RSMA-aided multiple access channel (MAC) in the presence and the absence of one eavesdropper with correlated Rayleigh fading coefficients is considered. The correlation between random variables is modeled by the aid of copula theorem. (I) The ergodic capacity of RSMA-aided MAC, (II) the individual ergodic secrecy rate (ESR) of RSMA-aided multiple access wiretap channel (MAC-WT), and (III) the positive secrecy capacity probability (PSCP) are obtained by the aid of Farlie-Gumble-Morgenstren (FGM) copula. The results are extended to NOMA-aided MAC and NOMA-aided MAC-WT. The theoretical results are evaluated by numerical results.
Rate-splitting multiple access (RSMA) is a promising technology for future wireless networks. In the present paper, a two-user RSMA-aided multiple access channel (MAC) in the presence and the absence of one eavesdropper with correlated Rayleigh fading coefficients is considered. The correlation between random variables is modeled by the aid of copula theorem. (I) The ergodic capacity of RSMA-aided MAC, (II) the individual ergodic secrecy rate (ESR) of RSMA-aided multiple access wiretap channel (MAC-WT), and (III) the positive secrecy capacity probability (PSCP) are obtained by the aid of Farlie-Gumble-Morgenstren (FGM) copula. The results are extended to NOMA-aided MAC and NOMA-aided MAC-WT. The theoretical results are evaluated by numerical results.
Rate-splitting multiple access (RSMA) is a technique that is widely used in next-generation wireless systems to efficiently manage multiple users. RSMA splits the transmission into two parts using rate splitting, which increases spectral efficiency. However, this technique also makes a portion of the transmission vulnerable to eavesdropping, which can compromise information security. This vulnerability is not limited to external eavesdroppers but also includes internal eavesdropping among users who share the same transmission. Therefore, there is an increasing need to develop secure RSMA systems to address these critical security issues among untrusted users. This paper focuses on a single-antenna RSMA downlink system with multiple untrusted users undergoing Rician channel fading. In this novel system framework considered for performance analysis, each user interprets its own common and private streams while attempting to eavesdrop on the private streams of other users. We evaluate the system-level performance in practical settings involving line-of-sight (LoS) paths using the Rician channel model and derive a tight closed-form approximate expression of the ergodic secrecy rate. Finally, we conduct numerical simulations to validate the theoretical analysis and provide valuable insights into the critical system parameters that impact the achievable ergodic secrecy performance of the RSMA system with untrusted users.
In this letter, we investigate the physical layer security of rate-splitting multiple access (RSMA) scheme in the presence of randomly located non-colluding eavesdroppers. In this complicated case, the number, location, and channel state information (CSI) of eavesdroppers are unknown, posing a significant threat to the system. Moreover, we elaborate on practical scenarios where a multi-antenna base station serves multiple users under partial CSI at the transmitter (CSIT). Analytical expressions for the statistics of signal-to-interference plus noise ratios at both legitimate users and eavesdroppers are derived. Furthermore, we extract approximate theoretical expressions and the lower bound under worst-case eavesdroppers placement for the ergodic secrecy sum rate. Numerical results corroborate the accuracy of our derived analytical results, and indicate that our proposed RSMA scheme exhibits superior secrecy performance when dealing with randomly distributed eavesdroppers and partial CSIT, compared to other conventional multiple access schemes.
Abstract In wireless communications, it is often assumed that the channel coefficients are independent, while there physically exists correlations between them. In this paper, considering physical layer security in downlink NOMA channel with dependent coefficients, important wireless performances (the average secrecy rates (ASR) and the secrecy coverage regions (SCR) are investigated, by using Copula theory. Specifically, the effect of channel coefficients correlation on the performances is analyzed. Based on the results of mathematical investigations and numerical results, we found that the effect of correlations between channels can improve performances or be harmful.
In this paper, we introduce two new achievable schemes for the fading multiple access wiretap channel (MAC-WT).In the model that we consider, we assume that perfect knowledge of the state of all channels is available at all the nodes in a causal fashion.Our schemes use this knowledge together with the time-varying nature of the channel model to align the interference from different users at the eavesdropper perfectly in a one-dimensional space while creating a higher dimensionality space for the interfering signals at the legitimate receiver, hence allowing for better chance of recovery.While we achieve this alignment through signal scaling at the transmitters in our first scheme (scaling-based alignment), we let nature provide this alignment through the ergodicity of the channel coefficients in the second scheme [ergodic secret alignment (ESA)] [1], [2].For each scheme, we obtain the resulting achievable secrecy rate region.We show that the secrecy rates achieved by both schemes in the two-user fading MAC-WT scale with signal-to-noise ratio (SNR) as 1 2 log(SNR).Hence, we show the suboptimality of the independent identically distributed (i.i.d.) Gaussian signaling-based schemes with and without cooperative jamming by showing that the secrecy rates achieved using i.i.d.Gaussian signaling with cooperative jamming do not scale with SNR.In addition, we introduce an improved version of our ESA scheme where we incorporate cooperative jamming to achieve higher secrecy rates.Moreover, we derive the necessary optimality conditions for the power control policy that maximizes the secrecy sum rate achievable by our ESA scheme when used solely and with cooperative jamming.Finally, we discuss the extension of the proposed schemes to the case where there are more than two users and show that, for the -user fading MAC-WT, each of the two schemes achieves secrecy sum rate that scales with SNR as 1 log(SNR).
It is commonly known that physical layer security is achieved with a trade-off in terms of the achievable rate. Hence, security constraints generate rate losses in wiretap channels. To mitigate such rate losses in multi-user channels, we propose a coding/decoding scheme for multi-user multiple access wiretap channel (MAC-WT), where previously transmitted messages are used as a secret key to enhance the secrecy rates of the transmitting users, until the usual Shannon capacity region of a multiple access channel (MAC) is achieved without the secrecy constraint. With this coding scheme, all messages transmitted in the recent past are secure with respect to all the information of the eavesdropper till now. To achieve this goal, we introduce secret key buffers at both the users and the legitimate receiver. Finally, we consider a fading MAC-WT and show that with this coding/decoding scheme, we can achieve the capacity region of a fading MAC channel (in the ergodic sense).
In recent years, the finite state Markov channel (FSMC) in the presence of an eavesdropper has been shown to be a useful model for the physical layer security of the practical mobile wireless communication systems. In this paper, we extend this model to a multiple-access situation (up-link of the wireless communication systems), which we call the finite state multiple-access wiretap channel (FS-MAC-WT) with delayed state feedback. To be specific, the FS-MAC-WT consists of two transmitters, a legitimate receiver and an eavesdropper. The channel transition probability depends on a state which undergoes a Markov process, and the state is perfectly known by the legitimate receiver and the eavesdropper. The legitimate receiver intends to send the state back to the transmitters through noiseless feedback channels after some time delay. The main contribution of this paper is to provide inner and outer bounds on the secrecy capacity region of this new model, and these results are further explained via a degraded Gaussian fading example.