Optimization of Cooperative RelayingMolecular Communications for Nanomedical Applications

Recently,nano-systems based on molecular communications via diffusion(MCvD)have been implemented in a variety of nanomedical applications,most notably in targeted drug delivery system(TDDS)scenarios.Furthermore,because the MCvD is unreliable and there exists molecular noise and inter symbol interference(ISI),cooperative nano-relays can acquire the reliability for drug delivery to targeted diseased cells,especially if the separation distance between the nano transmitter and nano receiver is increased.In this work,we propose an approach for optimizing the performance of the nano system using cooperative molecular communications with a nano relay scheme,while accounting for blood flow effects in terms of drift velocity.The fractions of the molecular drug that should be allocated to the nano transmitter and nano relay positioning are computed using a collaborative optimization problem solved by theModified Central Force Optimization(MCFO)algorithm.Unlike the previous work,the probability of bit error is expressed in a closed-form expression.It is used as an objective function to determine the optimal velocity of the drug molecules and the detection threshold at the nano receiver.The simulation results show that the probability of bit error can be dramatically reduced by optimizing the drift velocity,detection threshold,location of the nano-relay in the proposed nano system,and molecular drug budget.

Power Allocation and Performance Analysis of the Collaborative NOMA Assisted Relaying Systems in 5G

Serving multiple cell-edge mobile terminals poses multifaceted challenges due to the increased transmission power and interferences, which could be overcome by relay communications. With the recent advancement of 5G technologies, non-orthogonal multiple access(NOMA) has been used at relay node to transmit multiple messages simultaneously to multiple cell-edge users. In this paper, a Collaborative NOMA Assisted Relaying(CNAR) system for 5G is proposed by enabling the collaboration of source-relay(S-R) and relay-destination(R-D) NOMA links. The relay node of the CNAR decodes the message for itself from S-R NOMA signal and transmits the remaining messages to the multiple cell-edge users in R-D link. A simplified-CNAR(S-CNAR) system is then developed to reduce the relay complexity. The outage probabilities for both systems are analyzed by considering outage behaviors in S-R and R-D links separately. To guarantee the data rate, the optimal power allocation among NOMA users is achieved by minimizing the outage probability. The ergodic sum capacity in high SNR regime is also approximated. Our mathematical analysis and simulation results show that CNAR system outperforms existing transmission strategies and S-CNAR reaches similar performance with much lower complexity.

High-Performance Beamformer and Low-Complexity Detector for DF-Based Full-Duplex MIMO Relaying Networks

In this paper, we consider a full.duplex multiple.input multiple.output(MIMO) relaying network with the decode.and.forward(DF) protocol. Due to the full.duplex transmissions, the self.interference from the relay transmitter to the relay receiver degrades the system performance. We thus propose an iterative beamforming structure(IBS) to mitigate the self.interference. In this method, the receive beamforming at the relay is optimized to maximize the signal.to.interference.plus.noise.ratio(Max.SINR), while the transmit beamforming at the relay is optimized to maximize the signal.to.leakage.plusnoise.ratio(Max.SLNR). To further improve the performance, the receive and transmit beamforming matrices are optimized between Max.SINR and Max.SLNR in an iterative manner. Furthermore, in the presence of the residual self.interference, a low.complexity whitening.filter(WF) maximum likelihood(ML) detector is proposed. In this detector, a WF is designed to transform a colored interference.plus.noise to a white noise, while the singular value decomposition is used to convert coupled spatial subchannels to parallelindependent ones. From simulations, we find that the proposed IBS performs much better than the existing schemes. Also, the proposed low.complexity detector significantly reduces the complexity of the conventional ML(CML) detector from exponential time(an exponential function of the number of the source transmit antennas) to polynomial one while achieving a slightly better BER performance than the CML due to interference whitening.

Broadband ＆ Digital Content-Couple Subscriber Cooperative Relaying Networks for Uplink Transmission using Hierarchical Game Approach

Cooperation allows wireless network users to benefit from various gains such as an in- crease in the achieved rate or an improvement in the bit error rate. In the paper, we propose a distributed Hierarchical Game （HG） theoretic framework over multi-user cooperative communication networks to stimulate cooperation and improve the network performance. First, we study a two- user decision making game in the OFDMA based subscriber cooperative relaying network, in which subscribers transmit their own data in the first phase, while helping to retransmit their partner＇s or choosing to freeride in the second phase. Instead of consulting to a global optimal solution, we decouple the cooperation resource allocation into two level subproblems： a user level Nash game for distributed cooperation decision and a Base Station （BS） level coalition game for centralized resource allocation. In the proposed HG algorithm, where mutual cooperation is preferred and total payoff is transferable, we prove it converges to a unique optimal equilibrium and resolve the subcarrier as-signment and power allocation among the couples. Besides, we discuss the existence of the publishing and rewarding coefficients in order to encourage cooperation. Then, we extend the HG to multi-user cases by coupling among subscribers according to the location information. The simulation results show that the proposed scheme with the distributed HG game achieves a well tradeoff between fairness and efficiency by improving the transmission efficiency of adverse users and outperforms those employing centralized schemes.

User Assisted Cooperative Relaying in Beamspace Massive MIMO NOMA Based Systems for Millimeter Wave Communications

A novel scheme‘user assisted cooperative relaying in beamspace massive multiple input multiple output(M-MIMO)non-orthogonal multiple access(NOMA)system’has been proposed to improve coverage area,spectrum and energy efficiency for millimeter wave(mmWave)communications.A downlink system for M users,where base station(BS)is equipped with beamforming lens antenna structure having NRF radio frequency(RF)chains,has been considered.A dynamic cluster of users is formed within a beam and the intermediate users(in that cluster)between beam source and destination(user)act as relaying stations.By the use of successive interference cancellation(SIC)technique of NOMA within a cluster,the relaying stations relay the symbols with improved power to the destination.For maximizing achievable sum rate,transmit precoding and dynamic power allocation for both intra and inter beam power optimization are implemented.Simulations for performance evaluation are carried out to validate that the proposed system outperforms the conventional beamspace M-MIMO NOMA system for mmWave communications in terms of spectrum and energy efficiency.

Systematic-bit-selection distributed with selective-relaying

An improved distributed turbo coding （DTC） scheme, namely, systematic-bit-selection DTC, is proposed for a two-hop relay network implementing selective-relaying （SR）. In the scheme, source broadcasts a punctured turbo code in order to increase the successful decoding rate of relay. The relay forwards systematic-bit to the destination in case of successful cyclic redundancy check （CRC）. From the two versions of systematic-bit coming from relay and source respectively, the des- tination selects the one with higher signal-to-noise ratio （SNR） for turbo decoding. Simulation re- suits show the improved bit error rate （BER） performance of our scheme.

Network Coding-Aware Cooperative Relaying for Downlink Cellular Relay Networks

In this paper, we first overview some traditional relaying technologies, and then present a Network Coding-Aware Cooperative Relaying （NC2R） scheme to improve the performance of downlink transmission for relayaided cellular networks. Moreover, systematic performance analysis and extensive simulations are performed for the proposed NC2R and traditional relaying and non-relaying schemes. The results show that NCR outperforms conventional relaying and non-relaying schemes in terms of blocking probability and spectral efficiency, especially for cell-edge users. Additionally, the location selections for relays with NCR are also discussed. These results will provide some insights for incorporating network coding into next-generation broadband cellular relay mobile systems.

Adaptive Relaying Protocol for Decode and Forward Full-Duplex System over Rician Fading Channel: System Performance Analysis

In this paper, the system performance of a decode-and-forward(DF) full-duplex(FD) adaptive relaying network over the Rician fading environment is proposed, analyzed and demonstrated. In the first stage, the system is presented with the energy harvesting and information transmission processes. After that, the analytical expressions of the achievable throughput, the outage probability, and symbol error ratio(SER) were proposed, analyzed and demonstrated. Finally, the analytical results are also demonstrated by Monte-Carlo simulation in comparison with the closed-form expressions in the influence of the key system parameters. The results show that the analytical and simulated results match for all possible parameter values.

DIVERSITY-AND-MULTIPLEXING TRADEOFF AND THROUGHPUT OF SUPERPOSITION CODING RELAYING STRATEGY

While the Network Coding cooperative relaying (NC-relaying) has the merit of high spectral efficiency,Superposition Coding relaying (SC-relaying) has the merit of high throughput. In this paper,a novel concept,coded cooperative relaying,is presented,which is a unified scheme of the NC-relaying and SC-relaying. For the SC-relaying strategy which can be considered one-way coded relaying scheme with multi-access channel,the close-form solution of the outage probabilities of the basic signal and additional signal are obtained firstly. Secondly,the Diversity-and-Multiplexing Tradeoff (DMT) characteristics of basic signal and additional signal are investigated entirely as well as the optimal close-form solutions. The compared numerical analysis shows the evaluation error of throughput based on the close-form solution is about 0.15 nats,which is within the acceptable error range. Due to the mutual effect between the both source signals,the available maximal values of the two multiplexing gains are less than 1.

Research on Reliability of Relaying Protection in Smart Substation

Research on reliability of relaying protection in smart substation not only has a positive effect on the rational configuration scheme of relaying protection in smart substation, but also can promote the stability and safety of the overall operation of power system. There are many reliability strategies for relaying protection in smart substation. In practice, the key points of relaying protection should be clarified. Based on the reality, the protection configuration should be strengthened;the voltage limited delay should be used for protection, and the protection configuration scheme of actual lines should be paid attention to, so as to improve the reliability of relaying protection in smart substation and promote the realization of stable and sustainable development of power system and smart substation.

Opportunistic Relaying Schemes for Amplify and Forward Bidirectional Relay Channels with Multi antenna Sources

We consider a two-way relay network where the Amplify-and-Forward (AF) protocol is adopted by all relays in this paper.The network consists of two multi-antenna source nodes and multiple distributed single-antenna relays.Two opportunistic relaying schemes are proposed to efficiently utilize the antennas of the source nodes and the relay nodes.In the first scheme,the best relay is selected out by a max-min-max criterion before transmitting.After that,at each source,only the antenna with the largest channel gain between itself and the best relay is activated to transmit and receive signals with full power.In the second scheme,assisted by the best relay which is selected by the typical max-min criterion,both source nodes use all their antennas to exchange data,and match filter beamforming techniques are employed at both source nodes.Further analyses show that all schemes can achieve the full diversity order,and the conclusions are not only mathematically demonstrated but numerically illustrated.System performance comparisons are carried out by numerical methods in terms of rate sum and outage probability,respectively.The beamforming assisted scheme can be found to be superior to the antenna selection scheme when accurate Channel State Information (CSI) is available at the transmitters.Otherwise,the latter is very suitable.

Performance Analysis of Full-Duplex Based Two-Way Relaying

Cooperative communication is regarded as a promising technique for improving the reliability of wireless communication links and enhancing the radio coverage simultaneously. Unlike the conventional half-duplex(HD) mode relaying techniques,the full-duplex based two-way relaying(FD-TWR) enables data exchanges between two nodes to be completed within a single time-slot,thus resulting in a significant improvement in the spectrum efficiency. In this paper,the channel model of the FD-TWR is first given out,followed by deriving the critical performance metrics,including the received signal-to-interference-plus-noise ratio(SINR),the upper bound of the ergodic capacity and the closedform solution of the proposed FD-TWR under amplify-and-forward(AF) mode. Furthermore,taking the limit of sum-transmit-power into account,we formulate the objective function of the optimal power allocation of FD-TWR as an extreme-value problem by deriving the optimal transmit power for both the source nodes and the relay node. As long as the self-interference(SI) signal in the FD-TWR nodes can be sufficiently suppressed,the proposed scheme is shown to outperform the conventional HD mode in terms of both the ergodic capacity and the outage probability. In addition,regardless of the practical SI power,the proposedFD-TWR is always capable of achieving its best performance with an aid of the proposed optimal power allocation scheme.

Two-Hop Gaussian Relay Channel with Linear Relaying： Achievable Rate and Optimization Design

The relay node with linear relaying transmits the linear combination of its past received signals.The optimization of two-hop relay channel with linear relaying is discussed in this paper.The capacity for the two-hop Gaussian relay channel with linear relaying is derived,which can be formulated as an optimization problem over the relaying matrix and the covariance matrix of the signals transmitted at the source.It is proved that the solution to this optimization problem is equivalent to a "single-letter" optimization problem.We also show that the solution to this "single-letter" optimization problem has the same form as the expression of the rate achieved by Time-Sharing Amplify and Forward(TSAF).In order to solve this equivalent problem,we proposed an iterative algorithm.Simulation results show that if channel gain of one hop is relatively smaller,the achievable rate with TSAF is closer to the max-flow min-cut capacity bound,but at a lower complexity.

Outage Performance of Cognitive DF Relaying Networks Employing SWIPT

In this paper, the outage perfor- mance of a cognitive relaying network over Nakagami-m fading channels, employing simultaneous wireless information and power transfer （SWIPT） technology is analyzed and evaluated. The operation of this network is considered in conjunction with the convention- al decode-and-forward （DF） and incremental DF （IDF） protocols. For the conventional DF protocol, it is assumed that there is no direct link between the secondary transmitter （S） and the secondary destination （D）, while （for both protocols） after harvesting energy, the relay node （R） always helps to forward the resulting signal to D. However, for the IDF protocol, R assists in relaying S＇s information to D only when the direct communication between S and D has failed. Furthermore, for both DF and IDF protocols, we assume there is no power supply for R, and R harvests energy from the transmitted signal of S. We derive exact ana- lytical expressions for the outage probability at D in DF and IDF protocols, respectively, in terms of the bivariate Meijer＇s G-function. Performance evaluation results obtained by means of Monte-Carlo simulations are also provided and have validated the correctness of the oroDosed analysis.

Bilayer expurgated LDPC codes with uncoded relaying

Bilayer low-density parity-check （LDPC） codes are an effective coding technique for decode-and-forward relaying, where the relay forwards extra parity bits to help the destination to decode the source bits correctly. In the existing bilayer coding scheme, these parity bits are protected by an error correcting code and assumed reliably available at the receiver. We propose an uneoded relaying scheme, where the extra parity bits are forwarded to the destination without any protection. Through density evolution analysis and simulation results, we show that our proposed scheme achieves better performance in terms of bit erasure probability than the existing relaying scheme. In addition, our proposed scheme results in lower complexity at the relay.

Energy-Efficient Full-Duplex UAV Relaying with Trajectory Optimization and Power Control in Maritime Communication Environments

This paper solves an energy-efficient optimization problem of a fixed-wing unmanned aerial vehicle(UAV) assisted full-duplex mobile relaying in maritime communication environments.Taking the speed and the acceleration of the UAV and the information-causality constraints into consideration,the energy-efficiency of the system under investigation is maximized by jointly optimizing the UAV’s trajectory and the individual transmit power levels of the source and the UAV relay nodes.The optimization problem is non-convex and thus cannot be solved directly.Therefore,it is decoupled into two subproblems.One sub-problem is for the transmit power control at the source and the UAV relay nodes,and the other aims at optimizing the UAV s flight trajectory.By using the Lagrangian dual and Dinkelbach methods,the two sub-problems are solved,leading to an iterative algorithm for the joint design of transmit power control and trajectory optimization.Computer simulations demonstrated that by conducting the proposed algorithm,the flight trajectory of the UAV and the individual transmit power levels of the nodes can be flexibly adjusted according to the system conditions,and the proposed algorithm can achieve signiflcantly higher energy efficiency as compared with the other benchmark schemes.

Wireless Mesh Networks and Cooperative Relaying Technologies

The Wireless Mesh Network (WMN) has become a focus in research of wireless broadband communications . In a switching technologies - based wireless Mesh network, the entire network is regarded as an IP subnet, so it cannot be applied in situations where large coverage is required . The use of cooperative relaying technologies can improve the transmission rate and reliability of wireless link; while the wireless Mesh network, once integrated with cooperative relaying technologies and routing technologies , can improve its spectrum efficiency and cover a wide area . However, there are many problems to be solved with respect to standardization, key technologies research and industrialization. Therefore , the application of cooperative relaying technologies in wireless Mesh networks is still a great challenge .

Energy efficiency enhancement of two-way amplifier forward relaying with channel estimation error

In order to save energy consumption of two-way amplifier forward(AF) relaying with channel estimation error, an energy efficiency enhancement scheme is proposed in this work. Firstly, through the analysis of two-way AF relaying mode with channel estimation error, the resultant instantaneous SNRs at end nodes is obtained. Then, by using a high SNR approximation, outage possibility is acquired and its simple closed-form expression is represented. Specially, for using the energy resource more efficiently, a low-complexity power allocation and transmission mode selection policy is proposed to enhance the energy efficiency of two-way AF relay system. Finally, relay priority region is identified in which cooperative diversity energy gain can be achieved. The computer simulations are presented to verify our analytical results, indicating that the proposed policy outperforms direct transmission by an energy gain of 3 dB at the relative channel estimation error less than 0.001. The results also show that the two-way AF relaying transmission loses the two-way AF relaying transmission loses its superiority to direct transmission in terms of energy efficiency when channel estimation error reaches 0.03.

Energy efficiency maximization for buffer-aided multi-UAV relaying communications

This paper studies a multiple unmanned aerial vehicle(UAV)relaying communication system,where multiple UAV re-lays assist the blocked communication between a group of ground users(GUs)and a base station(BS).Since the UAVs only have limited-energy in practice,our design aims to maximize the energy efficiency(EE)through jointly designing the communica-tion scheduling,the transmit power allocation,as well as UAV trajectory under the buffer constraint over a given flight period.Actually,the formulated fractional optimization problem is diffi-cult to be solved in general because of non-convexity.To re-solve this difficulty,an efficient iterative algorithm is proposed based on the block coordinate descent(BCD)and successive convex approximation(SCA)techniques,as well as the Dinkel-bach’s algorithm.Specifically,the optimization variables of the formulated problem are divided into three blocks and we alter-nately optimize each block of the variables over iteration.Numeri-cal results verify the convergence of the proposed iterative al-gorithm and show that the proposed designs achieve significant EE gain,which outperform other benchmark schemes.

Review of relaying protection sessions in International Conference on Power System Technology in China 1991

There were two sessions and onepanel discussion on relaying pro-tection at the conference,with participantsfrom Australia,Canada,Japan,Korea,arepresentative of the well known relaymanufacturer ABB and from the host coun-try China.The papers presented at thesessions covered a large variety of subjectsrelated to protection,including novel pro-tection principles and schemes。