Secrecy on the physical layer is receiving increased research interest due to its theoretical and practical importance. In this letter, a subcarrier allocation scheme is proposed for physical-layer security in cooperative orthogonal frequency division multiple access (OFDMA) networks that use the Amplify-and-Forward (AF) strategy. We consider the subcarrier pairing and assignment to maximize overall system rates subject to a secrecy level requirement. Monte Carlo simulations are carried out to validate our analysis.
Secrecy on the physical layer is receiving increased research interest due to its theoretical and practical importance. In this letter, a subcarrier allocation scheme is proposed for physical-layer security in cooperative orthogonal frequency division multiple access (OFDMA) networks that use the Amplify-and-Forward (AF) strategy. We consider the subcarrier pairing and assignment to maximize overall system rates subject to a secrecy level requirement. Monte Carlo simulations are carried out to validate our analysis.
In this paper, we consider the problem of resource allocation scheme for physical layer security in cooperative orthogonal frequency division multiple (OFDM) networks using amplify-and-forward (AF) strategy. To maximize the secrecy rate, the joint optimization of power allocation, subcarrier allocation and subcarrier pairing is proposed. The optimization problem can be solved efficiently by dual method. To reduce the complexity, two suboptimal algorithms are proposed. Monte Carlo simulations are carried out to validate our analysis.
This paper studies enhanced physical-layer key generation (PKG) for multiuser orthogonal frequency division multiple access (OFDMA) networks. In practical OFDMA systems, our key observation is that there are frequency correlations between different subcarriers which potentially lead to compromised randomness of the generated keys as well as reduced sum secret key rate. Motivated by this, we show that subcarrier allocation plays a key role in enhancing the PKG performance in OFMDA networks. We prove that when a single user terminal selects a finite number of subcarriers for key generation, adopting uniformly spaced subcarriers is the optimal solution as it leads to higher secret key rates and better randomness. Moreover, we derive a closed-form expression for the sum secret key rate and introduce a low-complexity near-optimal algorithm that can achieve an appropriate subcarrier allocation policy in a timely manner. Simulation results show that our proposed near-optimal algorithm exhibits significant advantages in maximizing the sum secret key rate and improving key randomness compared with existing subcarrier allocation algorithms.
Abstract In this paper, a cooperative orthogonal frequency division multiplexing system with multiple untrusted amplify‐and‐forward relays is considered. Since there exists no direct link between source and user because of the shadowing effect, a positive system secrecy rate cannot be obtained. Addressing this issue, a cooperative user‐aided jamming technique to improve the secrecy performance is employed. With the aim of maximising the system secrecy rate, a joint resource allocation problem of power allocation, relay assignment and subcarrier pairing is formulated. By using the signal‐to‐noise ratio based approach and the Lagrange dual method, this nonconvex problem is solved efficiently. To reduce the calculation complexity, a suboptimal algorithm, which decouples the power allocation with the relay assignment and subcarrier pairing is further proposed. Numerical results are presented to demonstrate the advantage of the two proposed algorithms and the impact of relays' location and number of subcarriers on the secrecy performance. Moreover, it is shown that the secrecy performance of the proposed scheme is decreased with respect to the number of untrusted relays.
Abstract This paper proposes a novel physical layer security approach in an orthogonal frequency division multiple access system. Then, a joint subchannel assignment and power allocation method is proposed. It is assumed that there are multiadversary users in the considered orthogonal frequency division multiple access–based network. Each adversary user can be a passive user (ie, he/she just eavesdrops) or an active user (ie, he/she sends jamming to make disturbance). The adversary users can choose active or passive mode according to their situation in the network. In a real network, legitimate users do not have deterministic information about the passive and active modes of adversary users. Here, we assume that the active and passive modes of adversary users are unknown. We also introduce both noncooperative and cooperative scenarios for adversary users. In the noncooperative scenario, the adversary users do not have cooperation and they act independently. In the cooperative scenario, they have cooperation with each other to eavesdrop well and reduce the secrecy rate of the network. For the noncooperative adversary users, a probabilistic method is proposed to estimate the active or passive mode of the adversary users. Based on the proposed probabilistic method, the average secrecy rate for the network is obtained. For the cooperative adversary users, we assume that they are smart and organized; it means that they choose their active or passive mode based on the situation of other adversary users to reach the best performance. Since the total secrecy rate in two scenarios is nonconvex, the corresponding optimization problem is nonconvex. We propose an iterative method for joint subchannel assignment and power allocation to maximize the total secrecy rate of the network. A linear search method is proposed for the subchannel assignment, and a successive convex approximation approach is proposed to solve the power allocation problem.
Summary This paper considers an orthogonal frequency division multiplexing (OFDM) based cooperative network, where a source node communicates with a destination node with the help of multiple intermediate nodes, in the presence of an eavesdropper. Each intermediate node is assumed to be able to act as a relay or a jammer to improve the physical layer security. The problem of joint subcarrier allocation, power allocation, and mode selection to maximize the sum secrecy rate is investigated. We first reformulate the problem of subcarrier allocation and intermediate node mode selection as a three‐sided matching game and propose an algorithm that achieves a stable matching. Then, the sum secrecy rate is further improved by proposing a heuristic algorithm to switch the modes of the intermediate nodes. Finally, an iterative power allocation algorithm is proposed. It is verified by simulation results that the proposed algorithm outperforms various benchmark algorithms such as the equal subcarrier allocation algorithm, the pure relay selection algorithm, and the random relay selection algorithm, especially when the transmit power limit is high and the number of intermediate nodes is large.
Physical layer security (PLS) is an emerging area for information security against eavesdroppers (Eve). Information security of any system can also be improved by using friendly jammers that produce interference signals to Eve. Traditional security techniques are limited by the processing power of the wireless nodes, whereas PLS can achieve communication secrecy without requiring computationally expensive cryptographic operations. The relay networks have emerged as a promising technology to enhance the performance of the wireless systems. This paper proposes a joint resource optimization framework for the PLS of dual-hop decode and forward (DF) relay network with and without cooperative jamming. In particular, the proposed framework consists of a base station (BS), multiple users, DF relays, multiple subcarriers, and an Eve. Our objective is to maximize the sum secrecy rate (SR) through optimal power loading over different subcarriers at BS and relay nodes, and efficient subcarrier assignment. We formulate a mixed binary integer programing problem for secrecy optimization and adopt Lagrangian dual method to achieve the efficient solutions. We also provide three benchmark frameworks, i.e., joint power optimization with random subcarrier assignment, equal power allocation with efficient subcarrier assignment and equal power with random subcarrier assignment to guage the performance of our joint resource optimization framework. Simulation results unveil that the proposed joint resource optimization framework under cooperative jamming and without jamming performs significantly better than the benchmark frameworks.