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.
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.
The physical layer security in the up‐link of the wireless communication systems is often modelled 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. Inner and outer bounds on the secrecy capacity region of this feedback model are provided. To be specific, we first present a decode‐and‐forward (DF) inner bound on the secrecy capacity region of this feedback model, and this bound is constructed by allowing each transmitter to decode the other one's transmitted message from the feedback, and then each transmitter uses the decoded message to re‐encode his own messages, i.e. this DF inner bound allows the independent transmitters to co‐operate with each other. Then, we provide a hybrid inner bound which is strictly larger than the DF inner bound, and it is constructed by using the feedback as a tool not only to allow the independent transmitters to co‐operate with each other but also to generate two secret keys, respectively, shared between the legitimate receiver and the two transmitters. Finally, we give a sato‐type outer bound on the secrecy capacity region of this feedback model. The results of this paper are further explained via a Gaussian example, and from this example, we see that the noiseless feedback helps to enhance the achievable secrecy rate region of the Gaussian MAC‐WT without 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.
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.
This paper investigates the problem of secure transmission over a two-user discrete memoryless multiple-access wiretap channel with partial rate-limited feedback (MAC-WT-PLF). The receiver can causally and securely transmit feedback to one of the transmitters at a limited rate. Three achievable rate regions and one outer bound on the secrecy capacity are presented based on three proposed coding schemes and the Sato-type bounding approach. The proposed coding schemes show that the feedback can play multiple roles, i.e., encrypting part of messages, enlarging the size of the dummy message, and increasing the correlation between the channel inputs, to enhance the secrecy performance. Of particular interest is identifying the novel role of enlarging the size of the dummy message at one of the transmitters, which enables both transmitters to benefit from the feedback significantly. In addition, the proposed achievable rate regions and outer bound are computed for the Gaussian MAC-WT-PLF, and comparative numerical results are provided under different eavesdropping cases.
Several security models of multiple-access channel (MAC) are investigated. First, we study the degraded MAC with confidential messages, where two users transmit their confidential messages (no common message) to a destination, and each user obtains a degraded version of the output of the MAC. Each user views the other user as a eavesdropper, and wishes to keep its confidential message as secret as possible from the other user. Measuring each user's uncertainty about the other user's confidential message by equivocation, the inner and outer bounds on the capacity-equivocation region for this model have been provided. The result is further explained via the binary and Gaussian examples. Second, the discrete memoryless multiple-access wiretap channel (MAC-WT) is studied, where two users transmit their corresponding confidential messages (no common message) to a legitimate receiver, while an additional wiretapper wishes to obtain the messages via a wiretap channel. This new model is considered into two cases: the general MAC-WT with cooperative encoders, and the degraded MAC-WT with non-cooperative encoders. The capacity-equivocation region is totally determined for the cooperative case, and inner and outer bounds on the capacity-equivocation region are provided for the non-cooperative case. For both cases, the results are further explained via the binary examples.
In this paper, some new results on the multiple-access wiretap channel (MAC-WT) are provided. Specifically, first, we investigate the degraded MAC-WT, where two users transmit their corresponding confidential messages (no common message) to a legitimate receiver via a multiple-access channel (MAC), while a wiretapper wishes to obtain the messages via a physically degraded wiretap channel. The secrecy capacity region of this model is determined for both the discrete memoryless and Gaussian cases. For the Gaussian case, we find that this secrecy capacity region is exactly the same as the achievable secrecy rate region provided by Tekin and Yener, i.e., Tekin–Yener’s achievable region is exactly the secrecy capacity region of the degraded Gaussian MAC-WT. Second, we study a special Gaussian MAC-WT, and find the power control for two kinds of optimal points (max-min point and single user point) on the secrecy rate region of this special Gaussian model.