Joint Cooperative Beamforming Research Articles

Joint Beamforming and User Association Scheme for Full-Dimension Massive MIMO Networks

In this paper, we study the joint cooperative beamforming and user association scheme for multi-cell multi-user full-dimension massive multiple-input multiple-out (MIMO) networks, where each user equipment is dynamically associated with one of the base stations. We propose to maximize the network capacity by jointly optimizing the beamforming vectors and a binary vector that represents the user association decisions. The binary vectors are further transformed into binary beam association factors (BAFs) as indicators of both the beamforming and the user association decisions. A three-step Gaussian belief propagation (GaBP) based distributed solver is proposed to solve the non-convex NP-hard problem considered in this paper. By relaxing the binary BAFs, we first transform the optimization problem into a linear programming. Subsequently, GaBP is used to efficiently obtain a feasible solution on BAFs in parallel, and two mapping algorithms are proposed to achieve different performance-complexity tradeoffs. Simulation results show that the proposed cooperative beamforming methods significantly outperform the benchmarks in the literature in terms of the network capacity with a low computation complexity.

Cooperative Secure Transmission Relying on Optimal Power Allocation in the Presence of Untrusted Relays, A Passive Eavesdropper and Hardware Impairments

In this work, by considering a variety of realistic hardware impairments, we aim to enhance the security of a cooperative relaying network, where a source intends to transmit its confidential information to a destination in the presence of a group of untrusted amplify-and-forward relays, as potential eavesdroppers (Eves), and an entirely passive multiple-antenna aided Eve. Our goal is to safeguard the information against these two types of eavesdropping attacks, while simultaneously relying on the untrusted relays to boost both the security and reliability of the network. To reach this goal, we propose a novel joint cooperative beamforming, jamming and power allocation policy to safeguard the confidential information while concurrently achieving the required quality-of-service at the destination. We also take into account both the total power budget constraint and a practical individual power constraint for each node. Our optimization problem can be split into two consecutive sub-problems. In the first sub-problem, we are faced with a non-convex problem which can be transformed into the powerful difference of convex (DC) program. A low-complexity iterative algorithm is proposed to solve the DC program, which relies on the constrained concave-convex procedure (CCCP). We further introduce a novel initialization method, which is based on a feasible point of the original problem obtained from a novel iterative feasibility search procedure, rather than an arbitrary (infeasible) point as in the conventional CCCP. The second sub-problem of our optimization problem is a convex optimization problem and can be solved efficiently adopting the classic interior point method. The numerical results provided illustrate that although the trusted relaying scenario outperforms the untrusted relaying for small and medium total power budgets, however, by increasing the total power budget, the secrecy performances of both the trusted and untrusted relaying converge to the same. Additionally, by equally sharing the total impairments at the relays between the transmitter and the receiver the best secrecy performance is presented.

Joint optimal power allocation, cooperative beamforming, and jammer selection design to secure untrusted relaying network

AbstractA half‐duplex relaying network provides 2 opportunities for passive eavesdroppers (Eves) and 1 opportunity for untrusted relays to intercept the information. In this paper, we aim to enhance the physical layer security of a cooperative network where a single‐antenna source intends to communicate with a single‐antenna destination in the presence of a group of untrusted relays and a passive eavesdropper. The objective is to protect the data confidentially while concurrently relying on the untrusted relays as potential Eves to improve both the security and reliability of the network. To realize this objective, we design a joint cooperative beamforming and cooperative jamming strategy. With the aim of maximizing the instantaneous secrecy rate, an optimal power allocation (OPA) scheme is proposed where the transmission powers of both jammer and source are optimized simultaneously under the total power budget constraint. To further improve the secrecy rate, a jammer selection strategy is also proposed where cooperative jamming is performed by the destination or one of the idle relays. For the proposed scheme, a closed‐form expression of beamformer vector is derived by solving a generalized eigenvalue problem. Finally, for the OPA problem, it is possible to be neither convex nor concave. In this regard, all possible cases are investigated to determine the OPA factor accurately. Numerical results illustrate that the proposed joint OPA–cooperative beamforming scheme, together with the most appropriate jammer selection strategy, significantly increases the secrecy rate.

Joint distributed beamforming and jamming schemes in decode-and-forward relay networks for physical layer secrecy

In this paper, we propose joint cooperative beamforming and jamming schemes in decode-and-forward (DF) relay networks for physical layer secrecy. In DF relay networks, only the relays decoding the message from the source correctly have to join in the forwarding phase and the relays with decoding error are not utilized sufficiently. Taking this property into consideration, we let the relays decoding successfully transmit information signals and the relays decoding in error transmit jamming signal to improve the secrecy capacity of system. For this purpose, we design a bi-level optimization algorithm to search the optimal beamforming vector and jamming vector for the relays via the semi-definite relaxation (SDR). In addition, for balancing the cost of system and secrecy performance, we also study some suboptimal schemes to improve information secrecy. Finally, the simulation results show that the optimal scheme outperforms all other simulated schemes and the suboptimal schemes achieve good tradeoff between secrecy performance and computational complexity.

Joint cooperative beamforming and artificial noise design for secure AF relay networks with energy-harvesting eavesdroppers

In this paper, we investigate physical layer security for simultaneous wireless information and power transfer in amplify-and-forward relay networks. We propose a joint robust cooperative beamforming and artificial noise scheme for secure communication and efficient wireless energy transfer. Specifically, by treating the energy receiver as a potential eavesdropper and assuming that only imperfect channel state information can be obtained, we formulate an optimization problem to maximize the worst-case secrecy rate between the source and the legitimate information receiver under both the power constraint at the relays and the wireless power harvest constraint at the energy receiver. Since such a problem is non-convex and hard to tackle, we propose a two-level optimization approach which involves a one-dimensional search and semidefinite relaxation. Simulation results show that the proposed robust scheme achieves better worst-case secrecy rate performance than other schemes.

Joint beamforming and cooperative jamming for secure transmission in multi-antenna decode-and-forward relaying sensor networks: A greedy switching strategy

In wireless sensor networks, sensor nodes are deployed to collect data and deliver the sensed information to a base station in a wireless manner. Due to the broadcast nature of wireless sensor communications, relay-sensor-based secure transmission remains a challenging issue. This article proposes a joint cooperative beamforming and jamming scheme in the relay wireless sensor networks, where the switching strategy from cooperative beamforming to cooperative jamming is applied to weaken the signal-to-interference-plus-noise ratio of the eavesdropper when the decoding threshold is not triggered. In particular, based on Charnes–Cooper transformation and S-procedure, semi-definite programming is constructed to solve the robust cooperative beamforming and jamming with a low implementation complexity, respectively. Additionally, we adopt the global power constraints in semi-definite programming to take full exploitation of the power at relay sensor. Finally, simulation results demonstrate the superiority of the proposed scheme in comparison with the traditional decode-and-forward robust scheme and the non-robust scheme.

Robust Cooperative Secure Beamforming for Simultaneous Wireless Information and Power Transfer in Amplify-and-Forward Relay Networks

In this paper, we investigate cooperative secure beamforming for simultaneous wireless information and power transfer (SWIPT) in amplify-and-forward (AF) relay networks. We propose a joint cooperative beamforming (CB) and energy signal (CB-ES) scheme for providing both secure communication and efficient wireless energy transfer. By considering colluding eavesdroppers with imperfect channel state information (CSI), we formulate an optimization problem for maximizing the secrecy rate between the source and the legitimate information receiver (IR) under both the power constraints at the relays and the wireless power transfer constraint at the energy-harvesting receiver (ER). Since such a problem is nonconvex and hard to tackle, we propose a two-level optimization approach that involves a 1-D search and the semidefinite relaxation (SDR) technique to solve this problem. The proposed robust scheme is compared with some other nonrobust schemes, such as a CB and artificial noise (CB-AN) scheme and a perfect scheme. Simulation results show that the proposed robust scheme achieves better worst-case secrecy rate performance than the other nonrobust schemes and the CB-AN scheme, while it approaches the perfect scheme.

Joint Cooperative Beamforming and Jamming for Physical-Layer Security of Decode-and-Forward Relay Networks

This paper proposes a new joint cooperative beamforming and jamming (JCBJ) scheme for improving the physical layer security of decode-and-forward wireless networks where a source node transmits to its destination with the aid of multiple intermediate nodes in the presence of an eavesdropper. In the proposed JCBJ scheme, we select the intermediate nodes succeeding in source decoding as the relays to forward the source transmission simultaneously by employing a beamforming weight vector, and meanwhile, use the remaining ones as the friendly jammers to disturb the eavesdropper by sending artificial noise. In order to achieve the secrecy rate maximum, we further study on the power allocation among the source, relays, and jammers under two assumptions of the wiretap link's channel state information. We derive the closed-form optimal solutions by first allocating the transmit power at the source within different ranges to consider all the possible relay selection schemes in which different numbers of relays are employed, and then transforming the multivariable power allocation problem to a set of single-variable optimization subproblems. Our numerical results show the superiority of the proposed JCBJ scheme and the proposed power allocation strategies.

Optimal Cooperative Relaying and Jamming for Secure Communication

This letter considers joint cooperative beamforming and jamming schemes in a cooperative relay network where distributed relay nodes perform cooperative beamforming. The problem of interest is to keep the eavesdropper's signal to interference and noise ratio (SINR) as low as possible while maintaining the legitimate receiver's SINR requirement. Applying semidefinite relaxation (SDR) technique, it is shown that a rank-one optimal solution always exists if perfect channel information is available. An optimal relay beamforming scheme has also been proposed for the scenario where only the second-order statistics of the eavesdropper's channel is available.

Joint Cooperative Beamforming, Jamming, and Power Allocation to Secure AF Relay Systems

The idea of multiuser (nodes) cooperation is an efficient way to improve the physical-layer security of a wireless transmission in the presence of passive eavesdroppers. However, due to the half-duplex constraint of the practical transceivers, two phases are required for one round of data transmission, which grants the eavesdroppers two opportunities to wiretap the information. Therefore, protecting the data transmissions in both phases is critical. Toward this end, we propose a joint cooperative beamforming, jamming, and power-allocation scheme to enhance the security of an amplify-and-forward (AF) cooperative relay network in this paper. Different from the existing works assuming that the source node always uses its total power, we show that the secrecy rate is a quasi-concave function of the power of the source node so that allocating its total power may not be optimal. The beamformer design and power optimization problem can be solved by a bisection method together with a generalized eigenvalue decomposition, which has a semiclosed form and is computationally very convenient. Simulations show that the joint scheme greatly improves the security.

Robust Joint Beamforming and Jamming for Secure AF Networks: Low-Complexity Design

This paper investigates the physical-layer security issue of an amplify-and-forward (AF) relay network. We propose a joint cooperative beamforming (CB) and cooperative jamming (CJ) design that is robust to the imperfect channel state information (CSI) of the multiple multiantenna eavesdroppers. The objective is the worst-case secrecy rate maximization (WCSRM). Based on the inner convex approximation and semidefinite relaxation (SDR) technique, the original nonconvex problem is transformed into a sequence of approximate convex problems, which can be solved conveniently. The proposed robust design guarantees to converge to a Karush–Kuhn–Tucker (KKT) solution and is efficient in computational complexity. Furthermore, we prove that SDR always has a rank-1 solution, which identifies that SDR is tight. Simulations demonstrate the validity of the proposed strategy.

Joint Cooperative Beamforming and Artificial Noise Design for Secrecy Sum Rate Maximization in Two-Way AF Relay Networks

In this letter, a joint design of cooperative beamforming (CB) and artificial noise (AN) is proposed for two-way amplify-and-forward (AF) relay networks to improve the security of the date exchange. Based on secrecy sum rate maximization (SSRM) criterion, such joint design problem under individual relay power constraints is mathematically hard due to the non-convex objective function. By utilizing the semidefinite relaxation (SDR) technique and successive convex approximation (SCA) algorithm, we efficiently develop a stationary point for the original SSRM design problem. Proof is also given to show that SDR is always tight and yields a rank-one solution. Simulations are presented to validate the efficiency and merits of our proposed joint CB and AN design in enhancing the secrecy sum rate.

An Effective Secure Transmission Scheme for AF Relay Networks with Two-Hop Information Leakage

In this letter, we propose a novel scheme to improve physical layer security for amplify-and-forward (AF) relay networks with two-hop information leakage. Unlike traditional joint cooperative beamforming (CB) and cooperative jamming (CJ) design, where mere artificial noise (AN) is exploited by the jammers to degrade eavesdroppers' channels, in our proposed scheme, the jammers send AN along with the confidential signal to simultaneously confuse the eavesdroppers and enhance the quality of received signals at the destination. In particular, the CB vectors and AN covariance matrix are jointly optimized for the relays and jammers under individual power constraints. By decoupling this resultant design problem, suboptimal solutions are obtained using the semidefinite relaxation technique. Simulation results are also provided to demonstrate that the proposed scheme has an obvious advantage in enhancing the secrecy rate.

Joint Cooperative Beamforming and Jamming to Secure AF Relay Systems With Individual Power Constraint and No Eavesdropper's CSI

Cooperative beamforming and jamming are two efficient schemes to improve the physical-layer security of a wireless relay system in the presence of passive eavesdroppers. However, in most works these two techniques are adopted separately. In this letter, we propose a joint cooperative beamforming and jamming scheme to enhance the security of a cooperative relay network, where a part of intermediate nodes adopt distributed beamforming while others jam the eavesdropper, simultaneously. Since the instantaneous channel state information (CSI) of the eavesdropper may not be known, we propose a cooperative artificial noise transmission based secrecy strategy, subjected to the individual power constraint of each node. The beamformer weights and power allocation can be obtained by solving a second-order convex cone programming (SOCP) together with a linear programming problem. Simulations show the joint scheme greatly improves the security.