Recently, it has been shown that the time-varying multiple-access channel (MAC) with perfect channel state information (CSI) at the receiver and delayed feedback CSI at the transmitters can be modeled as the finite state MAC (FS-MAC) with delayed state feedback, where the time variation of the channel is characterized by the statistics of the underlying state process. To study the fundamental limit of the secure transmission over multi-user wireless communication systems, we re-visit the FS-MAC with delayed state feedback by considering an external eavesdropper, which we call the finite state multiple-access wiretap channel (FS-MAC-WT) with delayed feedback. The main contribution of this paper is to show that taking full advantage of the delayed channel output feedback helps to increase the secrecy rate region of the FS-MAC-WT with delayed state feedback. Moreover, by a degraded Gaussian fading example, we show the effects of feedback delay and channel memory on the secrecy sum rate of the FS-MAC-WT with delayed feedback.
Recently, it has been shown that the time-varying multiple-access channel (MAC) with perfect channel state information (CSI) at the receiver and delayed feedback CSI at the transmitters can be modeled as the finite state MAC (FS-MAC) with delayed state feedback, where the time variation of the channel is characterized by the statistics of the underlying state process. To study the fundamental limit of the secure transmission over multi-user wireless communication systems, we re-visit the FS-MAC with delayed state feedback by considering an external eavesdropper, which we call the finite state multiple-access wiretap channel (FS-MAC-WT) with delayed feedback. The main contribution of this paper is to show that taking full advantage of the delayed channel output feedback helps to increase the secrecy rate region of the FS-MAC-WT with delayed state feedback. Moreover, by a degraded Gaussian fading example, we show the effects of feedback delay and channel memory on the secrecy sum rate of the FS-MAC-WT with delayed feedback.
Recently, it has been shown that the time-varying multiple-access channel (MAC) with perfect channel state information (CSI) at the receiver and delayed feedback CSI at the transmitters can be modeled as the finite state MAC (FS-MAC) with delayed state feedback, where the time variation of the channel is characterized by the statistics of the underlying state process. To study the fundamental limit of the secure transmission over multi-user wireless communication systems, we re-visit the FS-MAC with delayed state feedback by considering an external eavesdropper, which we call the finite state multiple-access wiretap channel (FS-MAC-WT) with delayed feedback. The main contribution of this paper is to show that taking full advantage of the delayed channel output feedback helps to increase the secrecy rate region of the FS-MAC-WT with delayed state feedback, and the results of this paper are further illustrated by a degraded Gaussian fading example.
Recently, the finite state Markov channel (FSMC) with an additional eavesdropper and delayed feedback from the legitimate receiver to the transmitter 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 feedback. To be specific, the FS-MAC-WT is a channel with two inputs (transmitters) and two outputs (a legitimate receiver and an eavesdropper). The channel depends on a state which undergoes a Markov process, and the state is entirely known by the legitimate receiver and the eavesdropper. The legitimate receiver intends to send his channel output and the perfectly known 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. The capacity results are further explained via a degraded Gaussian fading example, and from this example we see that sending the legitimate receiver's channel output back to the transmitters helps to enhance the security of the FS-MAC-WT with only delayed state feedback.
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.
Viswanathan has shown that the practical mobile communication system can be modeled as the finite state Markov channel (FSMC) with delayed feedback, where the receiver perfectly knows the channel state information (CSI) which undergoes a Markov process, and the receiver sends the CSI and his own channel output back to the transmitter after some time delay. Viswanathan found that the delayed feedback of the channel output does not help to increase the capacity of the FSMC with only delayed state feedback. Does this still holds when an additional eavesdropper is considered? In order to answer this question, in this paper, we study the finite state Markov wiretap channel (FSM-WC) with delayed feedback, where the CSI is perfectly known by the legitimate receiver and the eavesdropper, and the legitimate receiver sends the CSI and his own channel output back to the transmitter after some time delay. Inner and outer bounds on the secrecy capacity of this model are provided, and we show that these bounds meet if the eavesdropper's received channel output is a degraded version of the legitimate receiver's. Furthermore, we find that the legitimate receiver's delayed channel output feedback helps to enhance the secrecy capacity of the degraded FSM-WC with only delayed state feedback.
In this work, we investigate the problem of secure broadcasting over block-fading wiretap channels with limited channel knowledge at the transmitter. More particularly, we analyze the effect of having a finite rate feedback on the throughput of multi-user broadcast wiretap channels. We consider that the transmitter is only provided by a b -bits feedback of the main channel state information (CSI) sent by each legitimate receiver, at the beginning of each fading block, over error-free public links with limited capacity. Also, we assume that the transmitter is aware of the statistics of the eavesdropper's CSI but not of its channel's realizations. Under these assumptions of CSI uncertainty, we characterize the ergodic secrecy capacity of the system when a common message is broadcasted to all legitimate receivers, the ergodic secrecy sum-capacity when multiple independent messages are transmitted, and the ergodic secrecy capacity region for the broadcast channel with confidential messages (BCCM). In all three scenarios, we show that as long as the transmitter has some knowledge of the main CSI, obtained even through a 1-bit CSI feedback, a non-zero secrecy rate can still be achieved. The impact of having the feedback sent over a binary erasure channel (BEC) is also investigated for the BCCM case. Here again, and even with the possibility of having the feedback bits erased, a positive secrecy rate can still be achieved as long as the erasure event is not a probability-one event. An asymptotic analysis of the obtained results is provided for the high SNR regime, and the scaling law of the system, when the number of legitimate receivers is large, is also presented.
The physical layer security in the up-link of the wireless communication systems is often modeled as the multiple access wiretap channel (MAC-WT), and recently it has received a lot attention. In this paper, the MAC-WT has been re-visited by considering the situation that the legitimate receiver feeds his received channel output back to the transmitters via two noiseless channels, respectively. This model is called the MAC-WT with noiseless feedback. We present a new hybrid inner bound on the secrecy capacity region of this feedback model, and it is constructed by using the feedback as a tool not only to allow the independent transmitters to co-operate with each other (decode each other's transmitted message from the feedback), but also to generate two secret keys respectively shared between the legitimate receiver and the two transmitters. We show that this hybrid inner bound is strictly larger than the already existing decode-and-forward (DF) inner bound. Moreover, we provide a sato-type outer bound on the secrecy capacity region of the MAC-WT with noiseless feedback. The results of this paper are further explained via a Gaussian example.