Two novel quantum relay cooperative communication schemes $1S2R1D$ and $2S2R2D$ are proposed by applying the wireless communication technique in the quantum system. The orthogonal quantum signals in consecutive quantum sequences are prepared to avoid mutual interference and they are firstly transmitted to the quantum relay node and then to the destination node with space-time transmission. Moreover, quantum operations and transformations are implemented on the relay node and the destination node to maximize the correct information transmission. The fidelity between original and final received signals, the security, the quantum bit error rate and the lower bound on the capacity of quantum relay channels are analyzed. Especially it provides a valuable application prospect in long distance reliable quantum communications.
Two novel quantum relay cooperative communication schemes 1S2R1D and 2S2R2D are proposed by applying the wireless communication technique in the quantum system. The orthogonal quantum signals in consecutive quantum sequences are prepared to avoid mutual interference and they are firstly transmitted to the quantum relay node and then to the destination node with space-time transmission. Moreover, quantum operations and transformations are implemented on the relay node and the destination node to maximize the correct information transmission. The fidelity between original and final received signals, the security, the quantum bit error rate and the lower bound on the capacity of quantum relay channels are analyzed. Especially it provides a valuable application prospect in long distance reliable quantum communications.
Relay-based quantum communication utilizes intermediate nodes to extend the transmission distance of quantum signals and mitigate the masking effect caused by obstacles or turbulence in free-space optical (FSO) channels. In this study, we investigate a three-node quantum communication system, where Alice, the transmitter, sends quantum-encoded binary information to Bob, the ultimate receiver, via an intermediate relay node, Charlie. By introducing Charlie, the end-to-end transmission is divided into two shorter FSO links, improving signal stability and reliability in the presence of severe atmospheric turbulence and noise. This work proposes a quantum relaying method specifically designed for FSO links and examines the impact of two-hop relaying in terms of the probability of error. The Helstrom error bound is derived to assess the system's detection limits, while density operator calculations are performed to characterize the quantum relaying setup. In addition, a closed-form expression is obtained for key system performance metrics. The findings offer valuable insights into optimizing quantum relaying strategies for long-distance quantum communication over FSO channels.
In this paper, we consider communication on a two-hop channel in which a source wants to send information reliably and securely to the destination via a relay. We consider both the untrusted relay case and the external eavesdropper case. In the untrusted relay case, the relay behaves as an eavesdropper, and there is a cooperative node, which sends a jamming signal to confuse the relay when it is receiving from the source. In the external eavesdropper case, the relay is trusted, and there is an external node eavesdropping the communication. We propose two secure transmission schemes using the scaled compute-and-forward technique. One of the schemes is based on a random binning code, and the other one is based on a lattice chain code. It is proved that in the high signal-to-noise-ratio (SNR) scenario and/or the limited relay power scenario, if the destination is used as the jammer, both schemes outperform all existing schemes and achieve the upper bound. In particular, if the SNR is large and the source, the relay, and the cooperative jammer have identical power and channels, both schemes achieve the upper bound for secrecy rate, which is merely 1/2 bit per channel use lower than the channel capacity without secrecy constraints. We also prove that one of our schemes achieves a positive secrecy rate in the external eavesdropper case in which the relay is trusted and there exists an external eavesdropper.
Wireless quantum communication is one of the most important parts in the future quantum communication.Quantum entanglement relay is one of the key technologies in wireless quantum communication systems.However,there are so many kinds of interference and noise in wireless channel that it is very hard to realize the relay of the quantum states.To solve the problem,the two quanta relay schemes based on mobile terminals and base stations are presented firstly.The layered structure of wireless quantum communication and the quantum states routing protocol(RQCP) in wireless transmission are presented also.Theory analysis results show that the scheme above can transmit quanta states although no EPR pairs shared by source and objective nodes,and the time delay in transmission has nothing to do with the number of wireless hopping.It proved that the model and scheme are optimal.
In cooperative communication, a source communicates with a destination over indirect links through relays. Like most wireless systems, cooperative networks seriously suffer from secrecy related issues. In this thesis, cooperative jamming method is utilized to provide secrecy for cooperative networks in which there exist adversary receivers called eavesdroppers. The main idea is to broadcast noise signals from a selected relay to corrupt the signal-to-interference-plus-noise ratio (SINR) at eavesdroppers when the transmitter communicates with the receiver through another selected relay. Throughout the study, it is assumed that channel state information (CSI) of the links between the source, relays and the destination is available at the transmit and receive sides of links. Rich scattering channels are assumed and all channel gains are taken as independent. In contrast to the past studies in the literature, CSI of eavesdroppers’ channels exist at only themselves since they are accepted as passive devices in this study. The knowledge on channel gains except eavesdroppers’ ones are used to adaptively select the relays to support cooperative jamming. Cooperative jamming is investigated here from an outage probability perspective where probability of secure transmission is the parameter of interest for a fixed transmission rate. First, cooperative jamming is applied to cooperative networks with single-antenna nodes. The probability of secure communication increases to a degree for a range of the communication rate R with cooperative jamming and adaptive selection of relays. The results are generally encouraging, but may be insufficient for real-world cooperative networks. Second, cooperative jamming is implemented at cooperative networks with multiple-antenna nodes to increase the probability of secure communication benefiting from advantages of multiple antennas. Adaptive transmit precoding is applied at the source and the communicating relay to enhance the SINR at legitimate receivers. This advantage brings an edge over eavesdroppers. Moreover, adaptive noise generation is proposed at the noise emitting relays in order to minimize the effect of noise at legitimate receivers. It is shown that the probability of secure communication dramatically rises with these adaptive techniques. As a result, there is a certain transmission rate R at which the source is able to securely communicate with the destination with probability approaching one.
In distributed wireless quantum communication networks, because of the storage of the clients, the EPR pairs are important resources. The lack of EPR pairs limits the size of networks. Besides, to accomplish quantum teleportation, both classical and quantum information need to be transmitted. We may have difficulty in building classical and quantum channels at the same time. To solve these problems, we introduce mesh structure into wireless quantum communication. The distributed wireless quantum networks can be improved by this mesh structure we proposed. Moreover, a quantum routing protocol based on quantum relay mechanism is proposed in this mesh structure.
According to quantum mechanics,quantum communication has the advantages in information security than the classical communication,and so it has been studied as new hot spot in communication field.Mobile quantum communication is one of the most important parts in the future quantum communication.Quantum entanglement relay is one of the key technologies in mobile quantum communication systems.However,there are so many kinds of interference and noise in wireless channel,that it is very hard to realize the relay of the quantum states.To address and solve the problem,the two quanta relay schemes based on mobile terminals and base stations are presented firstly.The layered structure of wireless quantum communication and the routing protocol of the quantum states transmission in wireless(QMRP) are presented also.Theory analysis results show that the scheme above can transmit quanta states with no EPR pairs shared by source and objective nodes,and the time delay in transmission has nothing to do with the number of wireless hopping.It proves that the model and scheme are optimal.