New Optimal Power Allocation for Bidirectional Communications in Cognitive Relay Network Using Analog Network Coding

Cognitive radio and cooperative communication can greatly improve the spectrum efficiency in wireless communications.We study a cognitive radio network where two secondary source terminals exchange their information with the assistance of a relay node under interference power constraints.In order to enhance the transmit rate and maintain fairness between two source terminals,a practical 2-phase analog network coding protocol is adopted and its optimal power allocation algorithm is proposed.Numerical results verify the superiority of the proposed algorithm over the conventional direct transmission protocol and 4-phase amplify-and-forward relay protocol.

Synchronization and bidirectional communication without delay line using strong mutually coupled semiconductor lasers

This paper numerically demonstrates synchronization and bidirectional communication without delay line by using two semiconductor lasers with strong mutual injection in a face-to-face configuration. These results show that both of the two lasers＇ outputs synchronize with their input chaotic carriers. In addition, simulations demonstrate that this kind of synchronization can be used to realize bidirectional communications without delay line. Further studies indicate that within a small deviation in message amplitudes of two sides （±6%）, the message can be extracted with signal-noise-ratio more than 10 dB; and the signal-noise-ratio is extremely sensitive to the message rates mismatch of two sides, which may be used as a key of bidirectional communication.

OFDM Based Bidirectional Multi-Relay SWIPT Strategy for 6G IoT Networks

6G IoT networks aim for providing significantly higher data rates and extremely lower latency.However,due to the increasingly scarce spectrum bands and ever-growing massive number IoT devices(IoDs)deployed,6G IoT networks face two critical challenges,i.e.,energy limitation and severe signal attenuation.Simultaneous wireless information and power transfer(SWIPT)and cooperative relaying provide effective ways to address these two challenges.In this paper,we investigate the energy self-sustainability(ESS)of 6G IoT network and propose an OFDM based bidirectional multi-relay SWIPT strategy for 6G IoT networks.In the proposed strategy,the transmission process is equally divided into two phases.Specifically,in phase1 two source nodes transmit their signals to relay nodes which will then use different subcarrier sets to decode information and harvest energy,respectively.In phase2 relay nodes forward signals to corresponding destination nodes with the harvested energy.We maximize the weighted sum transmission rate by optimizing subcarriers and power allocation.Our proposed strategy achieves larger weighted sum transmission rate comparing with the benchmark scheme.

Controlled Cyclic Remote State Preparation of Arbitrary Qubit States

Quantum secure communications could securely transmit quantum information by using quantum resource.Recently,novel applications such as bidirectional and asymmetric quantum protocols have been developed.In this paper,we propose a new method for generating entanglement which is highly useful for multiparty quantum communications such as teleportation and Remote State Preparation(RSP).As one of its applications,we propose a new type of quantum secure communications,i.e.cyclic RSP protocols.Starting from a four-party controlled cyclic RSP protocol of one-qubit states,we show that this cyclic protocol can be generalized to a multiparty controlled cyclic RSP protocol for preparation of arbitrary qubit states.We point out that previous bidirectional and asymmetric protocols can be regarded as a simpler form of our cyclic RSP protocols.

A Brief Discussion on"Chinese Culture Aphasia"-A Case Study of French Majors in Chinese Universities

Cultural exchange is an integral means of showing a country's image.From the perspective of cross-cultural communication,cultural exchange between two countries should be equal and bidirectional.However,at present,a common phenomenon is occurring among many French majors,in which they are unable to portray the Chinese culture accurately in French.This article analyses"Chinese culture aphasia"from three aspects:specific performance,main causes,and corresponding coping strategies.

20.231 Gbit/s tricolor red/green/blue laser diode based bidirectional signal remodulation visible-light communication system

We propose and experimentally demonstrate a recorded 1-m bidirectional 20.231-Gbit/s tricolor R/G/B laser diode(LD) based visible-light communication(VLC) system supporting signal remodulation. In the signal remodulation system, an LD source is not needed at the client side. The client reuses the downstream signal sent from the central office(CO) and remodulates it to produce the upstream signal. As the LD sources are located at the CO, the laser wavelength and temperature managements at the cost-sensitive client side are not needed.This is the first demonstration, to our knowledge, of a >20 Gbit∕s data rate tricolor R/G/B VLC signal transmission supporting upstream remodulation.

Bidirectional turbo equalization for underwater acoustic communications

A direct-adaptation based bidirectional turbo equalizer for underwater acoustic communications is proposed.Abandoning the channel estimation process,the direct-adaptation based turbo equalizer embedded with digital phase-locked loop is adopted to track time-varying channel.The fast self-optimized algorithm is used to adjust the step size,thus a good tradeoff between the convergence speed and performance has been made.Furthermore,by minimizing the mean squared error,an optimal weighting factor is derived to exploit bidirectional diversity gain.The forward turbo equalizer is combined with the backward turbo equalizer to eliminate error propagation effect.Simulated and experimental results demonstrate that the bidirectional turbo equalizer outperforms the single directional one.It can be seen from the experimental results that,compared with the channel estimation based algorithm,the direct-adaptation based algorithm is less sensitive to the time-varying channel and has a lower bit error rate.

Information leakage resistant quantum dialogue against collective noise

In this paper,two information leakage resistant quantum dialogue(QD)protocols over a collective-noise channel are proposed.Decoherence-free subspace(DFS)is used to erase the influence from two kinds of collective noise,i.e.,collective-dephasing noise and collective-rotation noise,where each logical qubit is composed of two physical qubits and free from noise.In each of the two proposed protocols,the secret messages are encoded on the initial logical qubits via two composite unitary operations.Moreover,the single-photon measurements rather than the Bell-state measurements or the more complicated measurements are needed for decoding,making the two proposed protocols easier to implement.The initial state of each logical qubit is privately shared between the two authenticated users through the direct transmission of its auxiliary counterpart.Consequently,the information leakage problem is avoided in the two proposed protocols.Moreover,the detailed security analysis also shows that Eve’s several famous active attacks can be effectively overcome,such as the Trojan horse attack,the intercept-resend attack,the measure-resend attack,the entangle-measure attack and the correlation-elicitation(CE)attack.