Relay-assisted D2D Research Articles

Relay Assisted Device-to-Device Communication for Future Generation Wireless Networks: A Review from Architectural and Challenges Perspective

The rapid evolution of wireless communication technologies, along with the increasing demand for efficient and reliable data transfer, has driven the rethinking of traditional cellular network architectures in the context of next-generation networks. In conventional cellular systems, communication between users typically occurs through base stations. However, to improve efficiency, scalability, and spectral utilization, device-to-device (D2D) communication has been introduced, enabling direct data transmission between users without base station involvement. In this paper, we present a comprehensive review of D2D communication from architectural and challenges perspective for future generation networks. Additionally, the study focuses on relay-assisted D2D (RAD2D) communication, examining the role of machine learning (ML) and artificial intelligence (AI) in optimizing relay selection processes. In light of the existing literature, challenges for implementing RAD2D are discussed from different perspectives such as relay selection, energy efficiency, secure communication, resource allocation, and the management of dynamic network conditions

An adaptive MLP-based joint optimization of resource allocation and relay selection in device-to-device communication using hybrid meta-heuristic algorithm

Enhancement in both energy efficiency and spectral efficiency in cellular networks is made possible by means of an advanced technique called device-to device (D2D) communication. The enhancement of these efficiencies is done by utilizing the cellular user (CU) resources once again to make communication with nearby cellular devices in an effective manner by spectral means. As the D2D communication technology is capable of providing a direct communication link with nearby devices effectively with enhanced spectral efficacy, this approach is considered as an ideal solution for the futuristic cellular communication network. A flexible and reliable relay-assisted communication by means of D2D technology is required that acts as an intermediate relay when the attenuation between the channels across the D2D devices becomes high. The throughput of the system is increased by utilizing D2D communication technology as it uses direct data transmission within cellular devices. When the cellular user is far apart from one another, the data loss in the D2D communication system is minimized with the utilization of the relay. When the channels are good, then the relay nodes (RNs) serve the cellular user. However, it is noted that the D2D systems are affected by issues such as higher consumption of energy and spectral sharing. Also, the sum rate gets degraded as a result of mutual interference between resource-sharing cellular devices in the relay-assisted D2D communication system. The transmission of the data in a traditional relay-assisted D2D communication system is carried out between the D2D receiver (DR) and D2D transmitter (DT) only with the utilization of its own energy by the RN. The issues in relay selection and resource allocation in the conventional joint resource allocation schemes are tackled by executing a scheme for performing the task of optimal relay selection and joint resource allocation. The enhancement of the overall sum rate in the D2D communication is the main motive behind the implemented scheme. This goal is attained along with the minimization of the link rates in the cellular and D2D networks. The ideal selection of the relay and the execution of the joint resource allocation are done with the utilization of a new optimization scheme called the hybrid flow direction with the chameleon swarm algorithm (HFDCSA), in which the flow direction algorithm (FDA) is fused along with chameleon swarm algorithm. This optimal selection of the relays is assisted by considering constraints like the network’s sum rate and energy efficiency in the network to achieve high performance. The data obtained from distinct sources are given to the adaptive multi-layer perceptron (AMLP) in which optimal resource allocation and the relay selection are performed with the help of the suggested HFDCSA. The parameters in the MLP are tuned by the same HFDCSA. Finally, the performance validation is conducted in the stage to verify the working of the suggested approach.

Joint Security and Energy-Efficient Cooperative Architecture for 5G Underlaying Cellular Networks

Device-to-device (D2D) communication is a promising technology which can improve the spectrum efficiency of cellular networks. Despite abundant research on resource allocation and interference cancellation for D2D communication, few works discuss how D2D is realized within cellular communication. In this paper, we propose a symmetric cooperative communication architecture combining security and energy efficiency, in which the users in 5G cellular networks can adaptively select the communication mode among cellular, direct D2D, and relay-assisted D2D communication according to the energy-consumption requirement. Considering the security aspect, we propose a novel relay selection strategy based on the asymmetry of social networks for the architecture. Firstly, we reduce the number of candidate relay devices based on energy consumption, the devices’ battery status, and the devices’ state. Then, an appropriate relay device is selected according to the proposed criteria, combining energy consumption, wireless channel quality, proximity prestige, and spreading ability. Simulation results reveal that, compared with conventional cellular communication and D2D communication, the proposed architecture can increase the number of users accessing the cellular networks simultaneously, improving the throughput and the security of data transmission. It can also significantly reduce the energy consumption as well as outage probability.

Performance Analysis of DF Relay-Assisted D2D Communication in a 5G mmWave Network

Enabling D2D communication in the mmWave band has many obstacles that must be mitigated. The primary concern is the introduction of interference from various sources. Thus, we focused our work on the performance of decode-and-forward (DF) relay-assisted D2D communication in the mmWave band to increase the coverage probability and energy efficiency (EE). Three modes are proposed for D2D communication to prevail. The bitwise binary XOR operation was executed at the relay node, which increased the security feature. The radius of coverage was derived, which indicated the switching of the modes. The diffused incoherent scattering power was also considered as part of the power consumption. Furthermore, a unique relay selection scheme, the dynamic relay selection (DRS) method, is proposed to select the optimal relay for information exchange. A comparison of the proposed DF relay scheme with the amplify-and-forward (AF) scheme was also made. Finally, the simulation results proved the efficacy of the proposed work.

Relay-Assisted D2D Communication over Extended η-μ Fading Channels

In this paper, two cases of Device-to-Device (D2D) communication over a recently introduced extended η-μ fading channel are analyzed. Case A considers a direct D2D communication. While in case B, amplify-and-forward relay-assisted D2D communication is discussed. The effects of cochannel interference at the relay and D2D destination are also included. To combat fading, selection combining- and maximal ratio combining-based diversity schemes are also incorporated at the receiver. Power harvesting based on power splitting technique is also engulfed. Expressions of success and outage probabilities are derived with the help of characteristic function approach. Success and outage probability expressions are functions of path loss, distance between various devices and channel parameters. Based on these expressions, numerical results are presented and discussed.

Reconfigurable Intelligent Surface Empowered Device-to-Device Communication Underlaying Cellular Networks

Reconfigurable intelligent surface (RIS) is a new and revolutionary technology to achieve spectrum-, energy- and cost-efficient wireless networks. This paper studies the resource allocation for RIS-empowered device-to-device (D2D) communication underlaying a cellular network, in which an RIS is employed to enhance desired signals and suppress interference between paired D2D and cellular links. We maximize the overall network’s spectrum efficiency (SE) and energy efficiency (EE), respectively, by jointly optimizing the spectrum reuse indicators, the transmit power, the RIS’s passive beamforming and the BS’s receive beamforming. To solve both mixed-integer non-linear programming problems, we first propose an efficient and low-complexity user-pairing scheme based on relative channel strength to determine the spectrum reuse indicators. Other variables are then optimized to maximize the SE by an iterative algorithm, based on the techniques of alternating optimization, successive convex approximation, Lagrangian dual transform and quadratic transform. The EE-maximization problem is solved by an alternating algorithm integrated with Dinkelbach’s method. Numerical results show that the proposed design achieves significant SE and EE enhancements compared to traditional underlay D2D network without RIS, relay-assisted D2D network and other benchmarks.

Transmission capacity analysis of relay-assisted D2D cellular networks with interference cancellation

D2D communication has been identified as one of the technologies for meeting the unique traffic demands of the fifth-generation wireless network communication. However, the effectiveness of D2D highly depends on the proximity of devices. In other words, whenever such devices are very far apart, communication may become ineffective. Thus, relay assisted D2D positions itself as an approach by which some of the limitations of traditional D2D communication can be addressed. This makes the applications of D2D communication more versatile. However, the introduction of relays also poses interference within the D2D communication network especially when the density of relay is high. Such scenarios call for techniques by which interference posed by relays can be averted while taking the benefits of relay-assisted communication. This motivates the consideration of interference cancellation (IC) in this paper where two IC models are adapted into the transmission capacity analysis of relay-assisted D2D communication. We show the performance gains attainable by interference cancellation and how the interplay between its parameters affect the network performance. Furthermore, two hybrid IC models are investigated and the impact of interference cancellation in these scenarios and the inherent trade-offs are revealed.

Low-Cost Authentication Protocol for D2D Communication in m-Health with Trust Evaluation

Relay-assisted device-to-device (D2D) communication serves users at the edge of system coverage of 5G networks, enabling communication among sensors and patients’ mobile devices, and improving spectral and power efficiency. The security of D2D-based m-health applications requires attention due to the delicacy of the data treated in the collection, transmission, and storage of information on patients, whose devices must be adequately authenticated. However, traditional authentication and key agreement schemes are not suitable for D2D scenarios, since they might expose patients to security vulnerabilities and lead to an excessive use of resources. This article proposes a secure and lightweight scheme based on Shamir secret sharing for the mutual authentication of m-health devices in relay-assisted D2D communications, which provides security robustness and reduces resources (energy, processing) consumption. The manuscript also addresses the trustworthiness of devices involved in data relay and device discovery procedures.

Graph colour‐based resource allocation for relay‐assisted D2D underlay communications

Relay-assisted device-to-device (D2D) communications have been proposed as a supplement for direct D2D communications to enhance traffic offloading capacity. In this study, the authors propose a joint mode selection, relay selection and resource allocation for relay-assisted D2D communications. They aim at maximising the overall system throughput while guaranteeing the power limitation and signal-to-noise-and-interference ratios of all cellular and active D2D links. Since this optimisation is NP-hard, they then propose a graph colour-based resource allocation algorithm to effectively solve it. Simulation results show that the proposed algorithm can produce close-to-optimal performance with acceptable computational complexity.

Energy-Efficient Transmission Rate Selection and Power Control for Relay-Assisted Device-to-Device Communications Underlaying Cellular Networks

Device-to-device (D2D) communication underlaying cellular networks is seen as a promising technology for future communication systems, especially when relays are employed to extend the range of D2D links. However, the mutual interference between the spectrum-sharing D2D links and conventional cellular (CC) links is still the dominating performance limiting factor, which enforces those links to adopt higher transmission power. As energy saving is always one of the key concerns, we propose to minimize the total transmission energy consumption of a relay-assisted D2D link and a CC link sharing radio resources by jointly optimizing their transmission rate selection and power control (TRSPC). We formulate the optimization problem as a non-convex non-linear programming (NLP) problem and then develop a game theory based distributed approach to solve it. Simulation results demonstrate that our game theory based TRSPC approach can enormously decrease the total transmission energy consumption compared with existing works.

Energy Efficiency Maximization of Two-Time-Slot and Three-Time-Slot Two-Way Relay-Assisted Device-to-Device Underlaying Cellular Networks

The continuous development of fifth generation (5G) communication and Internet of Thing (IoT) inevitably necessitates more advanced systems that can satisfy the growing wireless data rate demand of future equipment. Device-to-Device (D2D) communication, whose performance is evaluated in terms of the overall throughput, energy efficiency (EE) and spectral efficiency (SE), is considered a promising solution for the aforementioned problem. Thereby, this paper aims at improving the performance of the D2D communication underlaying cellular networks operating on multiple bands by maximizing the EE in its uplink. Thanks to the stochastic geometry theory, it is possible to derive the closed-form expressions for the successful transmission probability (STP), the total average transmission rate (TATR), and the total average energy efficiency (TAEE) of cellular and D2D users in different time slot setting. Particularly investigated and compared in this study, there are one-hop, direct, D2D communication in two time slots (2TS), and multi-hop, indirect, D2D communication in three time slots (3TS) with an additional D2D user acting as a two-way relay to assist the communication. Moreover, an optimization problem is formulated to calculate the maximum TAEE of D2D users and the optimum transmission power of both the cellular and D2D users. Herein this optimization study, which is proven to be non-convex, the Quality of Service (QoS) is ensured as the STP on every link is considered. The herein approach is referred to as relay-assisted D2D communication which is capable of delivering a notably better QoS and lower transmission power for communication among distant D2D users.

Online and robust resource allocation for D2D communications assisted by Green relays

Device-to-device (D2D) communications in cellular networks allow proximity users to communicate directly without going through the base station. Concentrating on scenarios where the direct communication between potential D2D users may not be reliable due to poor proximity and link condition, and paying attention to energy harvesting wireless communications, this study focuses on the green relay-assisted D2D communications, where long-term evolution-advanced layer-3 relays powered by renewable energy are employed. To achieve the trade-off between system capacity maximisation and user fairness, the authors formulate an offline resource block (RB) and power allocation problem under imperfect channel information with the objective of maximising the weighted sum-rate of all users. Then, based on battery dynamics, the original problem is reformulated as an online one with energy outage avoidance. To obtain distributed solutions, the online problem is further transformed into a convex one, and the rate outage-probability requirement is also converted for tractability. Finally, applying Lagrangian duality, the distributed RB and power allocation is derived, which is globally optimal to the reformulated online problem. Comparing with a baseline scheme where all users communicate directly without assistance of relays, numerical results show the superiority of the proposed approach in terms of the average achievable data rate.

Security--Reliability Tradeoff for Untrusted and Selfish Relay-Assisted D2D Communications in Heterogeneous Cellular Networks for IoT

This paper investigates security–reliability tradeoff for untrusted and selfish two-way relay-assisted device-to-device (D2D) communications in heterogeneous cellular networks for the Internet of Things (IoT). On one hand, the relay is untrusted and may try to extract useful information during the relaying process. On the other hand, the relay is selfish and is only willing to use the harvesting energy from the sources’ signals for relaying. Both instantaneous and statistical security–reliability tradeoffs are taken into consideration. For instantaneous model, the security and the reliability are characterized by the secrecy rate and the data rate, respectively. We aim at maximizing the tradeoff function of a tradeoff factor subject to a total transmit power constraint. For statistical model, the security and the reliability are characterized by the secrecy outage probability (SOP) and the data outage probability (DOP), respectively. An SOP optimization problem is developed with a DOP constraint and a total transmit power constraint. For both the problems, closed-form solutions are achieved. Simulation results show that both instantaneous and statistical security–reliability tradeoffs can achieve the Pareto optimal front.

Transmission capacity analysis of relay-assisted D2D cellular networks with M2M coexistence

Two trending technologies envisaged to provide huge prospects towards the realization of the fifth generation cellular systems are device-to-device (D2D) and machine-to-machine (M2M) communications. D2D facilitates direct connectivity between devices in proximity while M2M facilitates autonomous communication of smart devices. Since a massive number of M2M devices are set to be deployed in the future, this paper conceptualizes that M2M devices can relay data for D2D devices which are not in proximity. In this context, a probabilistic model is introduced for modelling the availability of M2M devices. Thorough investigations are made on transmission capacity (TC), TC gains and trade-offs involved with respect to both underlay and D2D-overlay modes. Using stochastic geometry, we derive the successful transmission probabilities for all associated links to determine the TCs in these scenarios and present computable expressions for the TC gains achieved. Furthermore, an exposition is provided on how the density and transmit power of MTDs in the network affect the D2D TC performance.

On signal processing scheme based on network coding in relay-assisted D2D systems

Network coding (NC) can greatly improve a system’s performance on throughput and channel utilization via corresponding signal processing on the relay side. Implementation of NC in relay-assisted device-to-device (RA-D2D) communications is a promising way to further explore the advantages of RA-D2D communications in cellular systems. This paper proposes a signal processing scheme for RA-D2D which jointly takes into account NC and optimal relay selection. First, the optimal relay user equipment (UE) is selected by jointly considering the end-to-end data rate, end-to-end transmission delay, and relay survival time. Then, in the procedure of signal processing, the transmitted useful signal is combined with interference signal for NC operation, and finally, the original useful signal is recovered at the destination node. Simulation results show that the proposed scheme is able to not only eliminate the interference effectively but also has a superior performance on end-to-end transmission delay, reachability, and amount of transmitted information than that without NC. In particular, signal processing via NC is equivalent to encrypting the signal, which further enhances the information security in D2D communications.

Relay-Assisted D2D Underlay Cellular Network Analysis Using Stochastic Geometry: Overview and Future Directions

Device-to-Device (D2D) communication is one of the enabling technologies for meeting the capacity requirements of the fifth-generation wireless systems (5G). It has diverse applications in traffic offloading, disaster management and content sharing, to mention a few. The network coverage and capacity further improve when relays are introduced to D2D communication. However, the interference becomes more severe since these devices also share resources with the traditional cellular users in the underlay. To take the benefits and avert the drawbacks of this spectrum sharing scenario, analytical tools capable of revealing the mathematical relationships among pertinent network design parameters are needed. This brings stochastic geometry (SG) into the picture. With SG-based analyses, designers can model concepts to understand, provide insights, and address the problems of spectrum sharing in relay-assisted D2D communication. Some of the key metrics of particular interest to network designers are the transmission capacity and spectral efficiency of D2D communication, as they reveal the performance gains and quantify the level of interference within the network. These enable them to properly correlate relevant cause-and-effect relationships before wealth and time are invested in network implementation. Despite the studies on the analysis of relay-assisted D2D underlay cellular networks using SG in recent years, there is no available survey material where researchers can find models, assumptions, key results and derived lessons to further comprehend this area and open up new research lines. This motivates the presentation of this paper which in addition to the aforementioned, gives elaborate discussions on promising areas for future research with respect to the recent advancements in D2D communication and SG research.

Social-Aware Based Secure Relay Selection in Relay-Assisted D2D Communications

Relay-assisted transmission could effectively enhance the performance of Device-to-Device (D2D) communications when D2D user equipments (UEs) are too far away from each other or the quality of D2D channel is not good enough for direct communications. Meanwhile, security is one of the major concerns for proximity services. The secure relay selection problem for D2D communications under laying cellular network is studied in this paper. Firstly, we define a relay selection area and derive the closed-form of outage probability in D2D links using a Poisson Point Process (PPP) method. Next, in the defined relay selection area, we propose a secure relay selection scheme for the relay-assisted D2D communication system by exploiting the social relation as a security factor. Simulation results show that the scheme based on social relation can greatly improve the security performance of relay-assisted D2D communications.

Relay-Assisted D2D Transmission for Mobile Health Applications.

Relay-assisted Device-to-Device (D2D) communication, one of the important transmission modes in mobile health systems, can provide high transmission quality for servicing users at the edge of system coverage. However, the quality of the D2D relay communication is largely limited by the relay nodes. When a poor node is selected to assist the source node in the data transmission, it is likely to result in the loss of medical data and inaccurate transmission. Therefore, this paper focuses on how to select relay modes and relay nodes to improve the reliability of medical data transmission. Firstly, in order to eliminate the relay nodes with low energy or poor willingness, the acceptable energy consumption metric of relay nodes is proposed in this paper. The relay mode of each relay node is determined by the acceptable energy consumption metric, which can ensure the physical reliability of the relay communication links. Then a trust metric is proposed to measure the social reliability of each relay link, further excluding the malicious relay nodes. Finally, this paper proposes a relay selection algorithm based on compromise factors (RSCF). With the help of the proposed algorithm, the reliability of the relay communication can be guaranteed, and the spectrum efficiency can be promoted greatly. The simulation results show that the relay nodes selected by RSCF algorithm can greatly improve transmission rate and reliability compared with the traditional relay-assisted D2D communication schemes.

Energy-Efficient Power Allocation and Relay Selection Schemes for Relay-Assisted D2D Communications in 5G Wireless Networks

Device-to-device (D2D) communications allows user equipment (UE) that are in close proximity to communicate with each other directly without using a base station. Relay-assisted D2D (RA-D2D) communications in 5G networks can be applied to support long-distance users and to improve energy efficiency (EE) of the networks. In this paper, we first establish a multi-relay system model where the D2D UEs can communicate with each other by reusing only one cellular uplink resource. Then, we apply an adaptive neuro-fuzzy inference system (ANFIS) architecture to select the best D2D relay to forward D2D source information to the expected D2D destination. Efficient power allocation (PA) in the D2D source and the D2D relay are critical problems for operating such networks, since the data rate of the cellular uplink and the maximum transmission power of the system need to be satisfied. As is known, 5G wireless networks also aim for low energy consumption to better implement the Internet of Things (IoT). Consequently, in this paper, we also formulate a problem to find the optimal solutions for PA of the D2D source and the D2D relay in terms of maximizing the EE of RA-D2D communications to support applications in the emerging IoT. To solve the PA problems of RA-D2D communications, a particle swarm optimization algorithm is employed to maximize the EE of the RA-D2D communications while satisfying the transmission power constraints of the D2D users, minimum data rate of cellular uplink, and minimum signal-to-interference-plus-noise-ratio requirements of the D2D users. Simulation results reveal that the proposed relay selection and PA methods significantly improve EE more than existing schemes.

Multicarrier Relay Selection for Full-Duplex Relay-Assisted OFDM D2D Systems

In this paper, we propose a full-duplex orthogonal frequency-division multiplexing (OFDM) device-to-device (D2D) system in two-hop networks, where multiple full-duplex decode-and-forward (DF) relays assist the transmission from D2D user equipment (DUE) transmitter to DUE receiver. By such a transmission mechanism, the signal transmitted by the DUE transmitter does not need to go through a base station (BS). Meanwhile, due to the adoption of underlay D2D communication protocol, power control mechanisms are thereby necessary to be applied to mitigate the interference to conventional cellular communications. Based on these considerations, we analyze the outage performance of the proposed system, and derive the exact expressions of outage probabilities when bulk and per-subcarrier relay selection criteria are applied. Furthermore, closed-form expressions of outage probabilities are also obtained for special cases when the instantaneous channel state information (CSI) between BS and cellular user equipments (CUEs) is not accessible, so that a static power control mechanism is applied. Subsequently, we also investigate the outage performance optimization problem by coordinating transmit power among DUE transmitter and relays, and provide a suboptimal solution, which is capable of improving the outage performance. All analysis is substantiated by numerical results provided by Monte Carlo simulations. The analytical and numerical results demonstrated in this paper can provide an insight into the full-duplex relay-assisted OFDM D2D systems, and serve as a guideline for its implementation in next generation networks.