Cooperative Relay Research Articles

CEAR: A cooperation based energy aware reward scheme for next generation green cognitive radio networks

Cognitive Radio (CR) networks are envisioned as a key empowering technology of the fifth-generation (5G) wireless communication networks, which solves the major issues of 5G, like high-speed data transmission, seamless connectivity, and increased demand for mobile data. Another significant characteristic of the 5G network is green communications, as energy consumption from the communication field is predicted to rise remarkably by the year 2030. In this work, we are concerned about energy-related issues and propose a cooperation-based energy-aware reward scheme (CEAR) for next-generation green CR networks. The proposed CEAR scheme is based on the antenna and temporal diversity of the primary users (PUs). For providing the service to the PUs, the users of another network called cognitive users (CUs) work as a cooperative relay node, and, in return, they get more spectrum access opportunities as a reward from the primary network. The CUs with delay-tolerant data packets take a cooperative decision by recognizing the availability and traffic load of PUs, channel state information, and data transmission requirements. We utilize the optimal stopping protocol for solving the decision-making problem and use the backward induction method to obtain the optimal cooperative solution. The simulation results reveal notable enhancements in energy efficiency (EE) of CUs compared with other cooperative schemes. The proposed CEAR scheme is more energy-efficient for ultra-dense network deployment because results show that the CU’s EE, spectral efficiency (SE), and throughput improved with the increase of PUs.

Traffic Load Optimization for Multi-Satellite Relay Systems in Space Information Network: A Proportional Fairness Approach.

Backbone satellites in a space information network (SIN) can be used as air base stations or data relay satellites (DRSs) to realize cross-system, cross-network and long-distance relay transmission. In this paper, a traffic load optimization problem for multi-satellite relay systems in SIN is considered to achieve highly efficient cooperative transmission and improve resource utility. A model of SIN based on a distributed satellite cluster (DSC) is considered, and the characteristics of the model are analyzed. Based on this, a hybrid resource management architecture combining distributed and central resources control schemes is proposed to realize a centrally controllable and distributed optimization of resources to meet various comprehensive service requirements. Two scenarios of multi-satellite relay systems in SIN are given, and traffic load optimization problems with joint bandwidth and power allocation for these two scenarios are formulated based on proportional fairness (PF) criterion to achieve traffic load balancing with considerable system capacity. The optimization problems in these two scenarios are proved to be a convex optimization problem with mathematical analysis, and the closed-form solutions of two problems in their dual domain are derived by dual transformation. With the closed-form solutions, two iterative algorithms based on the subgradient method are designed under the proposed hybrid resource management architecture to solve the problems in this paper. Simulation results show that the proposed schemes can effectively improve the upper bound of system capacity by resource sharing and cooperative relay, and it can balance the traffic load well with guarantees of a reasonable level system capacity compared with existing methods.

Performance analysis of SWIPT assisted cooperative Internet of Things (IoT) network under Optimal and Adaptive Power Splitting Schemes

In this paper, a Simultaneous Wireless Information and Power Transfer (SWIPT) aided Cooperative Relaying (CoR) scheme is employed to perform energy harvesting and information transmission at the same time for a low-powered Internet of Things (IoT) network. A decode and forward power splitting relaying (DF-PSR) protocol is utilized, and performance analysis is made by considering two scenarios, namely (i) Energy Harvesting (EH) relay and non-EH IoT device, and (ii) EH relay and EH-IoT device. Analytical models for computing Average Symbol Error Probability (ASEP) based on an Optimal Power Splitting Scheme (OPSS) for Scenario-1 and Joint Optimal Power Splitting Scheme (JOPSS) for Scenario-2 are presented by considering the effects of relay location. Moreover, an Adaptive Power Splitting Scheme (APSS) is suggested based on instantaneous Symbol Error Probability (SEP) under instantaneous channel conditions. The analytical results are validated through Monte Carlo simulations. The simulation results show that APSS performs better as compared to OPSS under given conditions.

Performance of Cooperative Relay NOMA with Large Antenna Transmitters

The potential of the Non-Orthogonal Multiple Access (NOMA) approach for wireless communications in the fifth generation (5G) and beyond can not be underestimated. This is because users with favorable channel conditions can serve as relays to improve system performance by employing Successive Interference Cancellation (SIC). Lately, the combination of NOMA and the cooperative relay has attracted the interest of researchers. The analysis of cooperative relay NOMA (CR-NOMA) with a massive multiple-input multiple-output (mMIMO) system is mainly based on theoretical channel models such as the correlated-based stochastic channel model (CBSM) even though the geometric-based stochastic channel model (GBSM) has been found to provide better, practical and realistic channel properties. This, in our view, is due to computational challenges. Again, the performance of CR-NOMA systems using the GBSM channel model with large antenna transmitters and network coding schemes has attracted little attention in academia. Therefore, the need to study mMIMO CR-NOMA that considers channel properties such as path-loss, delay profile and tilt angle has become vital. Furthermore, the co-existing of large antenna transmitters with coding schemes needs further investigation. In this paper, we study the performance of a two-stage mMIMO CR-NOMA network where the transmitter is represented as a uniform rectangular array (URA) or cylindrical array (CA). The communication channel from the transmitter (TX) to the user equipment (UE) through a relay station (RS) is modeled with a 3GPP’s three-dimensional (3D) GBSM mMIMO channel model. To improve the analytical tractability of 3D GBSM, we defined the antenna element location vectors using the physical dimension of the antenna array and incorporated them into the 3D channel model. Bit-error rates, achievable rates and outage probabilities (OP) are examined using amplify-and-forward (AF) and decode-and-forward (DF) coding schemes. Results obtained show with fixed power allocation and SNR of 20 dB, far or weak users can attain a high achievable rate using DF and URA. Again, from the results, the combination of AF and CA presents better outage probabilities. Finally, the results indicate that the performance difference between CBSM and GBSM is marginal, even though the proposed 3D GBSM channel model has a higher degree of random parameters and computational complexities.

Performance evaluation of cooperative‐nonorthogonal multiple access‐based improved hybrid simultaneous wireless information and power transfer protocol

AbstractThe integration of cooperative nonorthogonal multiple access (CNOMA) and the improved hybrid simultaneous wireless information and power transfer (SWIPT) (IHS) protocol (termed the CNOMA‐IHS scheme) is proposed in this article. The proposed CNOMA‐IHS scheme performs the energy harvesting to energize the cooperative relay operation from cell center user to cell edge user and also convey information to the users as well. Moreover, the proposed scheme also conveys multiple different symbols to the users to improve the user channel capacities, ergodic sum capacity (ESC), and energy efficiency (EE). Finally, the analytical and simulation results illustrated the proposed scheme outperforms the existing CNOMA based SWIPT schemes as well as orthogonal multiple access based IHS scheme in terms of ESC and EE.

A Low-Delay Hybrid Half/Full-Duplex Link Selection Scheme for Cooperative Relaying Networks

In this paper, we propose a hybrid half-duplex (HD)/full-duplex (FD) link selection scheme for cooperative buffer-aided (BA) relaying networks with small buffers. FD BA relaying offers high spectral efficiency but it does not change the buffer states, while HD relaying offers the ability to change the buffer states, which can be exploited to minimize the outage probability and the average delay by controlling the queue length of the relays. Unlike the existing hybrid BA relaying schemes and opportunistic relying schemes, the proposed scheme considers the average buffering delay and uses probabilistic relay selection (RS) instead of using a fixed RS policy. It probabilistically prioritizes the selection of one of the FD and HD modes over the other. Markov chain (MC) theory is used to model the considered system and derive the throughput, average delay and outage probability as functions of the prioritizing probabilities. Based on the buffer and average channel states, the prioritizing probabilities are determined such that the overall average delay is minimized using the accelerated proximal gradient method. As compared to the existing HD, opportunistic, and hybrid BA relaying schemes, simulation results show that the proposed scheme offers higher throughput and lower average delay.

Communication Systems With Amplitude Detection: An Asymptotic Approach

Amplitude detection (AD) is a low-complexity nonlinear scheme for information retrieval, as it only considers the envelope of the received signal. This makes it ideal in applications with low-cost low-power devices such as the Internet of Things (IoT). We consider a basic Point-to-Point (P2P) setup and develop a unified analytical framework for the asymptotic symbol error rate (SER) performance of the maximum-likelihood (ML) decoder with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> -ary amplitude-shift keying (ASK). The developed framework is general and can be applied for a large class of fading channels. The SER can be characterized by two parameters: the diversity order and the coding gain at a sufficiently high signal-to-noise regime. We derive closed-form expressions for the exact diversity order along with a lower and upper bound on the coding gain. We show that the diversity order is equal to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> for Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> fading, whereas for the other considered models, it is equal to one. We also prove that among all possible binary modulations with equal power, the modulation with one symbol equal to zero [i.e., on–off keying (OOK)] achieves the minimum asymptotic SER. The mathematical framework developed for the P2P setup is extended for cooperative relay networks. Specifically, we consider a basic amplify-and-forward (AF) three-node relay topology that employs AD at both the relay and the destination. We analytically derive the ML decoder and study asymptotic bounds on the SER by showing that the proposed AF-AD relay setup can be transformed into an equivalent P2P-AD with respect to the ML decoder.

Threshold-Based User-Assisted Cooperative Relaying in Beamspace Massive MIMO NOMA Systems.

The incorporation of user-assisted cooperative relaying into beamspace massive multiple-input multiple-output (mMIMO) non-orthogonal multiple access (NOMA) system can extend the coverage area and improve the spectral and energy efficiency for millimeter wave (mmWave) communications when a dynamic cluster of mobile user terminals (MUTs) is formed within a beam. We propose threshold-based user-assisted cooperative relaying into a beamspace mMIMO NOMA system in a downlink scenario. Specifically, the intermediate MUTs between the next-generation base station (gNB) and the cell-edge MUT become relaying MUTs after the successful decoding of the signal of the cell-edge MUT only when they meet the predetermined signal-to-interference plus noise ratio (SINR) threshold. A zero forcing (ZF) precoder and iterative power allocation are used to minimize both inter- and intra-beam interferences to maximize the system sum rate. We then evaluate the performance of this system in a delay-intolerant cell-edge MUT scenario. Moreover, the outage probability of the cell-edge MUT of the proposed scheme is investigated and an analytic expression is derived. Simulation results confirm that the proposed threshold-based user-assisted cooperative relaying beamspace mMIMO NOMA system outperforms the user-assisted cooperative relaying in beamspace mMIMO NOMA, beamspace MIMO-NOMA, and beamspace MIMO orthogonal multiple access (OMA) systems in terms of spectrum efficiency, energy efficiency, and outage probability.

Inter-clustering Cooperative Relay Selection Schemes for 5G Device-to-device Communication Networks

Inter-clustering Cooperative Relay Selection Schemes for 5G Device-to-device Communication Networks

Analysis and Design of Enhanced Distributed Fountain Codes in Multiple Access Networks with Cooperative Relay

Distributed fountain coding plays an important role in rateless code research. The reliability and effectiveness of these coding schemes are increasingly challenged with the growing applications. In this paper, a novel multiple-access network with cooperative relay is presented, and a novel enhanced distributed fountain coding scheme for this network is proposed. The overall degree distributions are derived, and the asymptotic decoding performance is analyzed theoretically by employing the And-Or tree method. On this basis, a design method using joint iterative optimization algorithms is proposed to optimize the degree distributions of the sources and relays. Simulation results show that the proposed enhanced distributed fountain codes outperform the existing generalized distributed fountain codes (GDFC) and have a good performance on both lossless and lossy channels. It reveals that the proposed codes can provide unequal error protection (UEP) property for different sources by introducing the extra cooperative relay. The performance improvement is not restricted to the sources connected to the cooperative relay but applies to all sources. With the additional relay, the proposed codes are able to overcome the effects of bad channel conditions caused by terrain, obstacles, and so on, to avoid communication interruptions and improve the reliability of the network.

Energy efficiency in cognitive cooperative amplify and forward networks

The emphasis on improving energy efficiency has gradually replaced that on network throughput or data rate alone in the past, because the former not only concerns about network throughput or data rate, but also concentrate on energy consumption according to the goal of green and low carbon nowadays. In the context of increasingly clamoring environmental protection, this paper delivers the energy efficiency problem in amplify and forward cooperative relay networks, and then extends this problem to the cognitive radio scenarios. Traditional Dinkelbach parametrized method needs to transform the original problem into a series of nonlinear iterative problems. On the surface, this method simplifies the original energy efficiency optimization problem, but it often requires multiple iterations, and the number of iterations cannot be predicted in advance. In order to get rid of this dilemma, this paper directly starts with the partial derivative of the original problem, and obtains a closed-form solution of power distribution based on the Lambert function, instead of the water-filling form in traditional method. Then this Lambert result is extended to the cognitive radio cooperative relay system under the dual constraints of power budget and interference threshold. Finally, the performance of energy efficiency is confirmed by a large number of simulation experiments for distinct parameter settings.

Cooperative relay pursuit with input saturation constraint and external disturbances

AbstractThis paper studies a class of tracking consensus problem called the cooperative relay pursuit where a group of agents cooperatively pursuit and capture an evading agent that enters the surveillance region. A subgroup of agents closest to the evader is commanded to pursuit the evader and thus called pursuers, while others called surveillance agents stay at their origin places. A relay mechanism is introduced to respect the pursuit efficiency, energy constraints and other factors. As the evader moves, some pursuers that do not remain the closest vicinity of the evader leave the pursuing group, while some surveillance agents that become more closer to the evader join into the pursuing. Due to the relay mechanism, the dynamics of pursuers are naturally an impulsive system and thus is nonsmooth. This paper aims to propose a distributed controller to achieve cooperative relay pursuit even when agents are subjected to both input saturation constraint and external disturbances. A modified algebraic Riccati equation and low‐gain technique are proposed to achieve the tracking consensus with an performance. A simulation example is provided to validate the theoretical results.

Distributed Satellite Relay Cooperative Communication with Optimized Signal Space Dimension

With the increasingly obvious trend of satellite communication and network integration, especially the emergence of inter satellite links, the interconnection between space nodes has become the development trend and inevitable requirement of future space communication. However, problems, such as long communication distance, large transmission delay and loss, limited network resources and frequent switching of transmission links, limit the ability of spatial information transmission. Firstly, based on the idea of ring planning and design, this paper uses the joint design of beamforming between nodes to design the physical layer network coding in the relay to realize the reliable transmission of information. Secondly, according to the diversity of relay signal space resources and network node information exchange, a joint design method of relay compression matrix and node precoding vector is studied, which breaks through the existing configuration constraints. In this scheme, the computational complexity is reduced by compressing and precoding the matrix to ensure reliable decoding while obtaining spatial alignment gain and degrees of freedom. Simulated and real data results demonstrate the superiority and effectiveness of the proposed method.

On Joint Cooperative Relaying, Resource Allocation, and Scheduling for Mobile Edge Computing Networks

In this paper, we consider Internet of Things (IoT) based mobile edge computing (MEC) system. IoT devices are controlled by access points (APs), which do not have access to any licensed spectrum. This puts limitations on IoT devices’ offloading capability and hence effectively reduces the number of computed bits. Under such scenario, we consider spectrum sharing, where IoT networks get access to licensed spectrum by helping a primary network (owns licensed spectrum) in cooperative relaying. We aim to maximize sum of the primary network’s communication rate and IoT networks’ total number of computed bits by jointly optimizing relay selection, licensed spectrum allocation, local computation, and offloading sequence selection. Moreover, we consider important constraints, e.g., the guaranteed rate for the primary network, IoT devices’ available energy, and available licensed spectrum resource blocks (RBs). We observe that the optimization problem is combinatoric in nature, which becomes more complicated when IoT devices’ scheduling order comes into the formulation. From our analysis, we devise an optimal and computationally efficient algorithm. In the result section, we compare with relevant benchmark systems and show the efficacy of our proposed model. Moreover, we also show how IoT and primary networks benefit from spectrum sharing.

Ergodic Rate Analysis of Massive Spatial Modulation MIMO System With NOMA in Cooperative Relay Networks

In this article, by introducing nonorthogonal multiple access (NOMA) scheme into the massive spatial modulation (SM) MIMO in cooperative relay networks, a massive cooperative NOMA-aided SM (NOMA-SM) system is presented. The ergodic rate performance of uplink massive cooperative NOMA-SM with finite alphabet inputs is investigated over Rayleigh fading channels. According to the performance analysis, the mutual information between the SM signals transmitted by users and the signal received at the base station (BS) is derived. Based on this, the theoretical lower bound and tight approximation of the ergodic rates are deduced for performance evaluation. With the aforementioned results, simple expressions of the ergodic rates are derived for the system with single-antenna relay, which can simplify the calculation of theoretical ergodic rate. Besides, when the number of receive antennas at the BS is very large, the asymptotic ergodic rate analysis is presented for massive cooperative NOMA-SM system, and the corresponding asymptotic lower bounds of the ergodic rate are derived. Simulation results indicate that the presented theoretical analysis is valid and can match the corresponding simulation well. Thus, the ergodic rate performance can be well assessed in theory.

Performance Analysis of NOMA in Full-Duplex Cooperative Spectrum Sharing Systems

This paper presents a non-orthogonal multiple access (NOMA)-assisted full-duplex (FD) cooperative spectrum sharing protocol to achieve full-rate at a cell-edge primary user, where the secondary receiver helps the primary network relay the information to the cell-edge primary user. Unlike other FD cooperative schemes, the FD relay in the proposed system is not transmitting while receiving symbols from the primary transmitter. Hence, the proposed scheme can achieve full-rate at a primary user without degrading its outage performance. Further, it guarantees every alternate time-slots to the secondary network for accessing the licensed spectrum by employing a secondary receiver as a cooperative relay. In this paper, we derive the analytical expression for the outage probability and ergodic capacity. Moreover, we validate the derived expression through simulation and asymptotic results. The numerical and simulation results substantiate that the proposed scheme significantly outperforms other existing protocols.

Secrecy performance analysis of amplify-and-forward relay cooperative networks with simultaneous wireless information and power transfer

Simultaneous wireless information and power transfer (SWIPT) is a promising technology to enhance the power constraint issue in the wireless networks. In this paper, we investigate the secrecy performance of a selective cooperative relaying network with an energy harvesting (EH) technique, in which a source terminal communicates with a legitimate user at the destination terminal through N amplify-and-forward (AF) relays in the presence of multiple eavesdroppers. The relays deploy SWIPT with power splitting-based relaying (PSR) and time switching-based relaying (TSR) protocols to harvest energy. We present closed-form expressions for the secrecy performance metrics, consisting of the probability of non-zero secrecy capacity, the secrecy outage probability, and the average secrecy capacity to evaluate the physical layer security (PLS) of the system. Using the mathematical expressions, we obtain numerical results under the parameters of the system. These results demonstrate that using relay selection can significantly improve the secrecy performance of the system. Moreover, we compare the cooperative relay system without SWIPT and the system with SWIPT. It is observed that depending on the distance of eavesdroppers from the relays and the destination, the system based on SWIPT may achieve a better PLS than the system without SWIPT. Finally, we provide Monte-Carlo simulation results to confirm the validity of our analysis.

Relay Cooperative Transmission Algorithms for IoV Under Aggregated Interference

The Internet of Vehicles (IoV) has always attracted attention as the emerging communication network with the most development potential in the 5G era. However, the performance of IoV under 5G ultra-dense networks is an open issue, especially in practice the outage probability and ergodic capacity of the relay cooperative IoV network under aggregate interference are still unclear. Therefore, an opportunistic Decoding and Forwarding (DF) relay cooperative transmission algorithm was proposed in this paper when the destination node of IoV has aggregated interference. In addition, based on mathematical theoretical knowledge such as numerical analysis, the closed expressions of the outage probability and ergodic capacity of the IoV system under aggregated interference was derived. Finally, simulation experiments verify the effectiveness of the proposed scheme and the correctness of the theoretical analysis, which improves the transmission rate of the system.

Performance Evaluation of a Wireless Cooperative Network with Maximal Ratio Combining Technique

Research on wireless communication is on the rise due to its capability in improving communication in terms of spectrum efficiency, power and communication reliability. In wireless network, power is consumed mostly in the process of data transmission, hence, the need for cooperative relay protocol and technique to improve systems’ performance through power management and quality of service (QoS). Although, there are various cooperative protocols which include: amplify-and-forward, decode-and-forward among others. However, by using these cooperative protocols, the amount of power consumed and QoS still require improvement. Thus, in this work the quest for incorporation of Maximal Ratio Combining (MRC) technique with the Decode-and-Forward (DF) relay protocol in cooperative network. The cooperative network with DF protocol considered consists of the source, destination and relay(s) nodes. The MRC was incorporated at the destination just to combine the received signals from the relay nodes. Moreover, the system’s simulation was carried out by using MATLAB R2020a and evaluated using bit error rate and power consumption as the performance metrics. The obtained results showed that the QoS and power consumption of the considered cooperative network was considerably improved when MRC was employed in the network in comparison with an existing work.

Age of information and energy efficiency of amplify‐and‐forward relay‐assisted Internet of Things with nonlinear energy harvesting and imperfect channel state information over Nakagami‐ fading channels

AbstractThe emergence of the fifth generation of communication networks (5G) has paved the way for the fast development of Internet of Things (IoT) as well as many real‐time and mission‐critical applications. Because the status update required to be as timely as possible, a new metric termed as age of information (AoI) was born with the ability of capturing the timeliness. However, in practical implementation the sensor is energy constrained and transmits very low‐power signals, which yield high AoI so that the received status update can be stale or even outdated. To overcome this problem, this work proposes an IoT system model by integrating energy harvesting (EH), amplify‐and‐forward (AF) relay cooperation, and short packet communication (SPC) techniques. In the proposed scheme, the relay that is connected to fixed power grid, transfers energy radio frequency signals to charge the sensor and assists forwarding status update by using time switching scheme. The employment of SPC overcomes the freshness loss caused by relay cooperation and EH. Then, this work investigates the AoI and energy efficiency of the proposed scheme under finite block length communications over Nakagami‐ fading channels by specially considering channel state information (CSI) and nonlinear EH model. Under these practical constraints, the tractable AF relay transmission model and the end‐to‐end approximated signal‐to‐noise ratio are found. The end‐to‐end block error probability of finite block length transmission is derived, too. Third, under the simultaneous consideration of nonlinear EH and outdated CSI, the statistical descriptions of the time duration for the sensor fully charging its battery are derived as well as the ones of the time intervals of update packet delivery. As a result, the average AoI is achieved with closed‐form expression and the tradeoff model of AoI to energy efficiency is established by simultaneously exploiting outdated CSIs and nonlinearity of EH circuit. The presented numerical analysis exploits the impact of the outdated CSIs and nonlinear EH model and gives the insights of such model.