Cooperative Relay Scheme Research Articles

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.

Research on Cooperative Communication Technology to Improve Capacity and Reliability of Integrated Energy System

The integrated energy system makes full use of renewable resources such as local photovoltaics, fully considers the difference and complementarity of load types in the region, and realizes the efficient, economic and clean utilization of regional energy from the dimensions of time and space. The existing communication system of the integrated energy system has become a constraint on business development. First, the communication rate is low and the system capacity is limited. After the terminal collects various energy information, a large amount of data needs to be uploaded, which puts huge pressure on the communication bandwidth. The second is poor reliability and high operation and maintenance costs. The current communication technology is single, equipment and networking costs are high. Aiming at the abovementioned pain points, an opportunistic relay cooperation technology and scheme based on signaling measurement is proposed. Theoretical analysis and simulation results show that the above scheme can improve the performance of the cooperative diversity system while reducing conflicts.

An Amplify-and-Forward Full-Duplex Cooperative Relay Scheme for Low-Latency Downlink Transmission in CRAN

This letter proposes a novel full-duplex-enabled cooperative relay scheme to reduce the downlink delivery latency in cloud radio access networks (CRAN). Specifically, remote radio heads (RRHs) are deployed with full-duplex capability and work in Amplify-and-Forward mode so that they could receive signals from the baseband signal processing unit (BBU) and forward to the user groups immediately, which can efficiently decrease the waiting and processing delay. Beyond the proposed scheme, we move forward to jointly optimize the transmit/receive beamforming vectors of both BBU and the RRHs with the target of minimizing the maximal delivery latency among all user groups. The formulated problem is a multivariable coupling problem and difficult to solve. To deal with it, we propose an efficient successive convex approximation iterative algorithm. Simulation results show that our proposed scheme could reduce the delivery latency compared with other schemes.

Device-to-Device Aided Cooperative Relaying Scheme Exploiting Spatial Modulation: An Interference Free Strategy.

In this paper, a novel interference free dual-hop device-to-device (D2D) aided cooperative relaying strategy (CRS) based on spatial modulation (SM) (termed D2D-CRS-SM) is proposed. In D2D-CRS-SM, two cellular users (e.g., a near user (NU) and a relay-aided far user (FU)) and a pair of D2D transmitter (D)-receivers (D) are served in two time-slots. Two different scenarios are investigated considering information reception criteria at the NU. Irrespective of the scenarios, the base station (BS) exploits SM to map information bits into two sets: modulation bits and antenna index, in phase-1. In the first scenario, the BS maps FU information as the modulation bits and NU information as antenna index, whereas modulation bits correspond to NU information and the antenna index carries FU’s information in scenario-2. The iterative-maximum ratio combining (i-MRC) technique is then used by NU and D to de-map their desired information bits. During phase-2, D also exploits SM to forward FU’s information received from BS and its own information bits to the D2D receiver D. Then, FU and D retrieve their desired information by using i-MRC. Due to exploiting SM in both phases, interference free information reception is possible at each receiving node without allocating any fixed transmit power. The performance of D2D-CRS-SM is studied in terms of bit-error rate and spectral efficiency considering M-ary phase shift keying and quadrature amplitude modulation. Finally, the efficiency of D2D-CRS-SM is demonstrated via the Monte Carlo simulation.

Relay and Jammer Selection Scheme in Wireless Networks with the Statistical Information of Multiple Eavesdropping Channels

Abstract Physical layer security (PLS) based on cooperative communication has been regarded as a promising technique to enhance the system security. In this paper, considering the statistical information of multiple eavesdropping channels, we investigate the security performance of cooperative relay and jammer selection scheme based on maximizing secrecy capacity (SC), where an optimal relay is selected to assist the source transmission, and the selected jammer is used to transmit the interference signal to suppress the eavesdroppers. Furthermore, the asymptotic expression of secrecy outage probability (SOP), a fundamental metric in the research of physical layer security, is derived. Finally, simulation results validate the security performance of the proposed scheme, and give some significant insights into the network security.

Joint Power and Time Allocation for Two-Way Cooperative NOMA

In this paper, we propose a two-way cooperative relay scheme based on non-orthogonal multiple access (NOMA) where bidirectional communication is supported for two users in three phases. We jointly optimize power and time allocations to minimize system outage probability whose exact closed-form expression is derived and verified by Monte Carlo simulations. For performance comparison, four schemes based on power allocation and time allocation as well as the conventional one-way cooperative NOMA (OW-CNOMA) scheme are provided. It is shown that the proposed scheme can improve outage probability and ergodic rate performances over a conventional OW-CNOMA system.

Cooperative relay based on exploiting hybrid ARQ

In order to compensate the primary performance degradation, which is caused by the co-existing secondary communications or the heavy fading of primary link, a cooperative relay scheme is proposed in cognitive radio systems by taking advantage of the opportunities that are arisen by the primary ARQ (Automatic Repeat-reQuest) retransmission. With the help of this scheme, nontrivial relay assistances for the primary retransmission are achieved without initialization phase. The cooperation among secondary users provides additional spatial diversity to facilitate the primary transmission. This can be accomplished with an oblivious primary system and without assuming any non-causal information about the primary data. The scheme are further extended to the scenarios where multiple cognitive pairs exist. Performance analyses of the schemes are devised and the effectiveness is verified via simulations.

Performance analysis of signal space diversity–based cooperative relaying over α−κ−μ fading channels

AbstractThe α−κ−μ fading channel is a generalized fading model that incorporates the nonlinearity and nonhomogeneous scattering behavior of the propagation medium. In this paper, we investigate the performance of a signal space diversity (SSD)–based cooperative decode‐and‐forward relay scheme over α−κ−μ fading channels. In particular, we derive the novel closed‐form expression of the average symbol error rate for the SSD‐based cooperative relay scheme. Capitalizing on this, we quantify the diversity order of SSD‐based cooperative decode‐and‐forward scheme over α−κ−μ fading channels. We compare the analytical results with the results obtained through Monte Carlo simulations to validate our theoretical results.

A Cognitive Relay Network Throughput Optimization Algorithm Based on Deep Reinforcement Learning

In cognitive relay networks, the cognitive user opportunistically accesses the authorized spectrum segment of the primary user and simultaneously serves as the data relay node of the primary user while sharing the spectrum resource of the primary user. This not only improves the utilization efficiency of the network spectrum resources but also improves the throughput of the primary users. However, if the primary user randomly selects the relay node, there is no guarantee for an optimal throughput. Moreover, the system power consumption may increase. In order to improve the throughput of cognitive relay network and optimize system utility, this paper proposes a cognitive relay network throughput optimization algorithm based on deep reinforcement learning. For the system model of cognitive relay networks, the Markov decision process is used to describe the channel transition probability of the system model in the paper. The algorithm proposes a cooperative wireless network cooperative relay strategy, analyzes the system outage probability under different transmission modes, and optimizes the system throughput by minimizing the outage probability. Then, the maximum utility optimization strategy based on deep reinforcement learning is proposed to maximize the system utility revenue by selecting the optimal behavior. The experimental results show that the proposed algorithm has a good effect in improving system throughput and optimizing system energy efficiency.

A Fast Forward Full-Duplex Cooperative Relay Scheme for Securing Wireless Communications

This letter makes a first attempt to design a cooperative relay scheme to secure wireless communications by adopting a fast-forward full-duplex (F3D) node. Different from the conventional full-duplex relay, the F3D node could process and forward the received signal immediately. With such forwarding, the forwarded signal of F3D could enhance the signal to interference plus noise ratio of the receiver, whereas weaken that of the eavesdropper and thus build up a secure channel. Beyond the proposed scheme, we move forward to optimize the signal processing design of the F3D node with the target of maximizing the secrecy capacity. The formulated optimization problem is nonconvex and challenging to deal with. We then design an iterative algorithm based on generalized fractional programming to solve it. One key step in the iterative algorithm involves another nonconvex optimization and we decompose it into a two-level optimization. Simulation results validate the effectiveness of our designed secure cooperative relay scheme and show that adopting F3D node for physical-layer security has good performance in terms of achievable secrecy capacity compared with the scheme without F3D node.

Relay Cooperation Enhanced Backscatter Communication for Internet-of-Things

In this paper, we propose a relay cooperation scheme for backscatter communication systems for performance enhancement, in which one user backscatters incident signals from a power beacon (PB) to a relay and a receiver simultaneously, and then the relay decodes the received signals and forwards the decoded signals to the receiver. We consider two cases that the relay is with/without an embedded energy source. In particular, if the relay does not have an energy source, an energy harvesting phase is required, during which the relay harvests energy from the PB while the user backscatters information to the receiver. We first formulate system throughput maximization problems for both cases by finding the optimal time allocation schemes, from which some useful insights are provided. Then, with a given amount of information required to be delivered, the transmission time minimization problems for both cases are also formulated, and the optimal solutions are derived in closed-form. Numerical results reveal the proposed scheme can significantly enhance the system throughput and transmission time.

Capacity and outage analysis of a dual-hop decode-and-forward relay-aided NOMA scheme

Non-orthogonal multiple access (NOMA) is regarded as a candidate radio access technique for the next generation wireless networks because of its manifold spectral gains. A two-phase cooperative relaying strategy (CRS) is proposed in this paper by exploiting the concept of both downlink and uplink NOMA (termed as DU-CNOMA). In the proposed protocol, a transmitter considered as a source transmits a NOMA composite signal consisting of two symbols to the destination and relay during the first phase, following the principle of downlink NOMA. In the second phase, the relay forwards the symbol decoded by successive interference cancellation to the destination, whereas the source transmits a new symbol to the destination in parallel with the relay, following the principle of uplink NOMA. The ergodic sum capacity, outage probability, outage sum capacity, and energy efficiency are investigated comprehensively along with analytical derivations, under both perfect and imperfect successive interference cancellation. To inquire more insight into the system outage performance, diversity order for each symbol in the proposed DU-NOMA is also demonstrated. The performance improvement of the proposed DU-CNOMA over the conventional CRS using NOMA is proved through analysis and computer simulation. Furthermore, the correctness of the author's analysis is proved through a strong agreement between simulation and analytical results.

Optimized Polar Coded Selective Relay Cooperation With Iterative Threshold Decision of Pseudo Posterior Probability

This paper proposes an optimized polar coded selective relay cooperation with an iterative threshold decision of pseudo posterior probability to solve the excessive redundancy of received signals and the high decoding complexity in a selective decode-and-forward (SDF) relay scheme. By sharing antennas of a relay node, a polar coded cooperation scheme is illustrated in a three-node relay transmission model, accompanied by an SDF protocol. Simultaneously, the SDF protocol is completed according to the channel status information at the relay node. In the logarithmic belief propagation algorithm, an expression of pseudo posterior probability-based stopping iteration threshold with independent and variable signal-to-noise ratios is derived to decide convergence condition and thus timely stop the iterations for low decoding complexity. And an extrinsic information transfer chart is also used to verify the completion of the iterative process. In addition, an information detection factor is introduced to check decoded bits correctly by the change of it, thereby reducing the average number of decoding iterations. It also accelerates the convergence speed of the BP algorithm by setting threshold and prejudgment, thereby improving the decoding efficiency. Simulation results show that the proposed polar coded relay cooperation scheme obtains over 2 dB performance gain, when the bit error rate (BER) is lower than 10 -3 , compared with the existing low-density parity-check codes related schemes. It also reduces the complexity of the BP algorithm by stopping the iteration of high-reliability nodes at the cost of performance loss within 0.5 dB. Therefore, the proposed scheme obtains both good BER performance and low complexity, which endows its good applications in cooperative wireless communications.

On Secure Wireless Sensor Networks With Cooperative Energy Harvesting Relaying

In this paper, we investigate the physical layer security (PLS) of a wireless sensor network (WSN) that consists of a base station (BS), multiple sensor nodes (SNs), and multiple energy-limited relays (ERs) in the presence of a passive eavesdropper (EAV). We adopt a time-switching/power-splitting (TSPS) mechanism for information transmission. The communication protocol is divided into two phases. The purpose of the first phase is to decode information, and energy harvesting (EH) is performed in accordance with the TSPS protocol. The purpose of the second phase is to transmit information to multiple destinations using the amplify-and-forward (AF) technique. In this study, we introduce a multirelay cooperative scheme (MRCS) to improve the secrecy performance. We derive analytical expressions for the secrecy outage probability (SOP) of the MRCS and that of the noncooperative relay scheme (NCRS) by using the statistical characteristics of the signal-to-noise ratio (SNR). Specifically, we propose an optimal relay selection scheme to guarantee the security of the system for the MRCS. In addition, Monte Carlo simulation results are presented to confirm the accuracy of our analysis based on simulations of the secrecy performance under various system parameters, such as the positions and number of ERs, the EH time, and the EH efficiency coefficients. Finally, the simulation results show that the secrecy performance of our MRCS is higher than that of the NCRS and the traditional cooperative relay scheme (TCRS).

Backscatter Relay Communications Powered by Wireless Energy Beamforming

The integration of wireless power transfer (WPT) with the low-power backscatter communications provides a promising way to sustain battery-less wireless networks. In this paper, we consider a backscatter communication network wirelessly powered by a power beacon station (PBS). Each backscatter radio uses the harvested energy to power its data transmissions, in which some other radios can help as the wireless relays with an aim to improve throughput performance by cooperative transmission. Under this setting, we formulate a throughput maximization problem to jointly optimize WPT and the relay strategy of the backscatter radios. An iterative algorithm with reduced complexity and communication overhead is proposed to decompose the original problem into two sub-problems distributed at the PBS and the backscatter receiver. Moreover, we take uncertain channel information into consideration and formulate robust counter-parts of the throughput maximization problem when either the backscatter or relay channel is subject to estimation errors. The difficulty of the robust counter-part lies in the coupling of the PBS’ power allocation and relay strategy in matrix inequalities, which is addressed by alternating optimization with guaranteed convergence. Numerical results reveal that the cooperative relay strategy of the backscatter radios significantly improves the throughput performance.

Performance analysis of underlay two-way relay cooperation in cognitive radio networks with energy harvesting

Cognitive radio and energy harvesting are two important approaches to solve the problem of spectrum scarcity and energy constraint in wireless communications. In this work, we study a two-way relay cooperation scheme in underlay cognitive radio networks (CRNs) with energy harvesting in which two secondary users exchange information via an energy harvesting relay node. Since the relay node collects energy from the received signals and utilizes it to forward the information, the secondary transmission power can be markedly reduced. Therefore the interference of the secondary network to the primary network can be substantially reduced. We derive the outage probability of the secondary network and analyze the ergodic sum-rate of the secondary network. For the relay selection scheme, we find the optimal relay by employing interior point method based on a penalty function. Numerical results show that the proposed scheme gives higher throughput for the secondary network than other strategies.

An OFDMA-based joint reservation and cooperation MAC protocol for the next generation WLAN

The rapidly increasing use of mobile devices and the explosive growth of wireless traffic demands continuously drive the development of wireless networks. IEEE 802.11ax, as the emerging standard for the next generation wireless local area network (WLAN), aims to improve the network throughput in the densely deployed wireless networks. In the dense networks, the increased collisions for the large number of nodes and the inevitable transmission failures for aggregate interference and channel fading severely degrade the network throughput, posing an intractable challenge that urgently requires resolution. Channel reservation scheme that reduces the access collisions, and cooperative relay scheme that enhances the transmission reliability have consequently drawn considerable attention in recent years. Joint channel reservation and cooperation has been proved as a promising way to improve the network throughput in our recent study, but how to design a high-performance medium access control (MAC) protocol combined with reservation and cooperation for the next generation WLAN still remains an open issue. In this paper, we propose an orthogonal frequency-division multiple access (OFDMA) based joint reservation and cooperation MAC (OJRC-MAC) protocol for the next generation WLAN. The OJRC-MAC adopts the channel reservation scheme to reduce the access collisions, and enables the cooperative relay scheme to enhance the transmission reliability simultaneously. A resource unit based Markov model is introduced to analyze the network throughput, and the impacting factors on the throughput can be clarified by the derived closed-from expression. Simulation results validate the analytical results, and show that OJRC-MAC outperforms the basic uplink OFDMA-based random access (UORA), only reservation-enabled MAC (RES-MAC), and only cooperation-enabled MAC (COOP-MAC).

Resource Allocation and Outage Analysis for an Adaptive Cognitive Two-Way Relay Network

In this paper, an adaptive two-way relay cooperation scheme is studied for multiple-relay cognitive radio networks to improve the performance of secondary transmissions. The power allocation and relay selection schemes are derived to minimize the secondary outage probability where only statistical channel information is needed. Exact closed-form expressions for secondary outage probability are derived under a constraint on the quality of service of primary transmissions in terms of the required primary outage probability. To better understand the impact of primary user interference on secondary transmissions, we further investigate the asymptotic behaviors of the secondary relay network including power allocation and outage probability, when the primary signal-to-noise ratio goes to infinity. Simulation results are provided to illustrate the performance of the proposed schemes.

Performance Analysis of an Adaptive Incremental Cooperative Relaying Scheme for Wireless Relay Networks

In wireless relaying networks, the traditional incremental cooperative relaying scheme (IR) could improve the system throughput enormously over fading channels by exploiting relay nodes to retransmit the source data packet to the destination. In order to enhance the system throughput over time-varying fading channels, this paper proposes an adaptive incremental cooperative re-laying scheme (AIR) based on adaptive modulation and coding, which implements adaptive rate transmission for the source and relay nodes according to channel state information. We derive expressions for the AIR system throughput, and then give a gradient-based search algorithm to find the optimized adaptive solution for the AIR system by maximizing throughput subject to the constraint of packet error rate at the data link layer. The results indicate that throughput of AIR system outperforms that of traditional IR system greatly for any SNR value.

A congestion reduction mechanism using D2D cooperative relay for M2M communication in the LTE‐A cellular network

AbstractThe Long Term Evolution‐advanced cellular network is designed for human‐to‐human communication. When a large number of machine‐to‐machine (M2M) devices are trying to access the network simultaneously, it leads to a low random access (RA) successful rate and high congestion problem, which may cause the waste of radio resources, packet loss, latency, extra power consumption, and the worst, M2M service error. There is an urge to propose an efficient method for M2M communication on the LTE‐A network to resolve the congestion problem. In this paper, we propose a congestion reduction mechanism, which can analyze and model the RA procedure on the Long Term Evolution‐advanced network, to find out the collapse point in the RA procedure and then design a scheme named device‐to‐device cooperative relay scheme to relieve the congestion problem. Meanwhile, this work also adds a relay access barring algorithm to improve performance and an RA resource separation mechanism for human‐to‐human communication. The proposed method can effectively reduce the network congestion problem. Simulation results show that the network throughput and the congestion can be significantly improved using the proposed mechanism. Copyright © 2016 John Wiley & Sons, Ltd.