D2D Nodes Research Articles

Resource Optimization for Cognitive Radio Based Device to Device Communication Under an Energy Harvesting Scenario

Device to device (D2D) communication has emerged as a potential candidate for next-generation communication networks to support higher data rates and minimize power consumption. The spectral and energy efficiency of D2D communication can further be improved using cognitive radio (CR) and radio frequency energy harvesting (RF-EH) technologies. Therefore, in this paper, a sum throughput maximization problem for a CR assisted D2D network is modeled considering the RF-EH mechanism. A joint optimization problem is formulated for sum-rate maximization of cellular and D2D users by considering power allocation, channel assignment, user pairing and transmission time ratio allocation. Then, the problem is transformed into a standard convex optimization problem subject to power constraints at individual nodes, interference constraint, and the individual rate. Furthermore, the secrecy capacity requirements of cellular and D2D nodes are also considered. The duality theory is used to decompose the problem into multiple sub-problems and Karush-Kuhn-Tucker conditions are exploited to provide the solution of the sub-problems. The simulation results are provided for the validation of our proposed schemes.

Fast Beam Tracking Discontinuous Reception for D2D-Based UAV MmWave Communication

The device-to-device (D2D) communication integrated with the millimeter-wave (mmWave) air interface will play a significant role in the future mobile communication in terms of high transmission rate and deployment flexibility. Meanwhile, unmanned aerial vehicles (UAVs) are promoted as D2D nodes to support D2D-enabled networks for broad coverage. In this paper, we provide a new D2D-based UAV mmWave communication framework, in which the UAVs are mobile nodes and have stringent energy constraints. Therefore, the energy-efficient technology which can turn on the UAVs’ radio only when necessary and overcome the resulting easily-occurred beam misalignments due to the radio OFF periods and the aircrafts’ agile mobility is required urgently. To tackle this issue, we propose a novel fast beam tracking discontinuous reception (FBT-DRX) mechanism. A new Semi-Markov model is designed to analytically investigate the statistical property of the proposed scheme. Different from many published works on DRX with beamforming, we take the impact of UAV movements into account when deriving the exact closed-form expressions of sleep ratio and average packet delay. Finally, the numerical results are supplied to evaluate the effects of different key parameters on the system performance, and demonstrate that the FBT-DRX mechanism can perform well both in power saving and packet delay in the considered framework.

Interference and Outage Analysis of Random D2D Networks Underlaying Millimeter-Wave Cellular Networks

Device-to-device (D2D) networks underlaying a millimeter-wave cellular network have great potential for capacity growth. Thus, it is important to characterize the outage of such a D2D link incorporating millimeter-wave propagation effects, user association rules, power control, and spatial randomness. To this end, we model the locations of cellular transmitters and receivers as homogeneous Poisson point processes and those of the D2D nodes as a Matern cluster process, and incorporate blockages due to random objects, sectored antenna patterns, log-distance path loss, and Nakagami- $m$ fading. Furthermore, we consider antenna gain inversion-based power control, and peak power constraints for D2D devices along with distinct path loss exponents and distinct fading severities for line-of-sight (LOS) and non-LOS scenarios. With the aid of stochastic geometry tools, we derive closed-form expressions of the moment generating function of the aggregate interference on a D2D receiver node and its outage probability for two transmitter–receiver association schemes— nearest association and LOS association. We finally show that the feasibility of millimeter-wave D2D communication relies heavily on the D2D cluster radii, peak power thresholds, and node densities. Furthermore, these parameters affect the performance of the desired link more than the interference and noise.

On the Uplink Secrecy Capacity Analysis in D2D-Enabled Cellular Network

Recent research prove that device-to-device (D2D) communications offer substantial gain through enhancing throughput and spectral efficiency as well as widening coverage area of cellular network. However, from security perspective, performance of such network has not been well investigated. With this motive and inspired by stochastic geometry approach, we provide secrecy rate analysis for D2D-enabled cellular network under Rayleigh fading channels. The minimum distance among mobile users is used to characterize the retention probability and hence, density of D2D nodes. Moreover, a fraction of the total transmitted power from D2D nodes is allocated to radiate artificial noise (AN) to degrade the eavesdroppers channel. Under such conditions, we derive the closed-form expressions for the probability of achieving nonzero secrecy capacity for the uplink channel between user-equipment and cellular base-station in the presence of D2D nodes and eavesdropper(s). Throughout the paper, we consider the following eavesdropping strategies: 1) a single eavesdropper case; 2) multiple eavesdroppers that can cooperatively cancel the interference; 3) multiple cooperative eavesdroppers that can cooperatively cancel both the interference, and AN; and 4) the case of cooperative colluding eavesdroppers. The derived expressions are validated via simulation as a function of antenna gain, eavesdropper density, D2D hard-core distance, and D2D node density.

Intracell Interference Characterization and Cluster Interference for D2D Communication

The homogeneous spatial Poisson point process (SPPP) is widely used for spatial modeling of mobile terminals (MTs). This process is characterized by a homogeneous distribution, complete spatial independence, and constant intensity measure. However, it is intuitive to understand that the locations of MTs are neither homogeneous, due to inhomogeneous terrain, nor independent, due to homophilic relations. Moreover, the intensity is not constant due to mobility. Therefore, assuming an SPPP for spatial modeling is too simplistic, especially for modeling realistic emerging device-centric frameworks such as device-to-device (D2D) communication. In this paper, assuming inhomogeneity, positive spatial correlation, and random intensity measure, we propose a doubly stochastic Poisson process, a generalization of the homogeneous SPPP, to model D2D communication. To this end, we assume a permanental Cox process (PCP) and propose a novel Euler-Characteristic-based approach to approximate the nearest-neighbor distribution function. We also propose a threshold and spatial distances from an excursion set of a chi-square random field as interference control parameters for different cluster sizes. The spatial distance of the clusters is incorporated into a Laplace functional of a PCP to analyze the average coverage probability of a cellular user. A closed-form approximation of the spatial summary statistics is in good agreement with empirical results, and its comparison with an SPPP authenticates the correlation modeling of D2D nodes.

Robust artificial noise‐aided transmit optimisation for MISO wiretap channel with device‐to‐device underlay communication

This study considers a cellular multiple-input single-output system overheard by multiple eavesdroppers, in the presence of multiple pairs of single-antenna device-to-device (D2D) nodes working as an underlay. All D2D nodes are permitted to access the cellular channel for their own communications. A novel eavesdropping scenario, termed as simultaneous eavesdropping, is studied, where the eavesdroppers intend to simultaneously overhear the cellular communication as well as D2D communications. Assuming imperfect channel state information (CSI) at the transmitter, the authors goal is to design the robust transmit covariance of confidential message and artificial noise, such that the worst-case sum secrecy rate is maximised. This worst-case sum secrecy rate maximisation problem is challenging to solve due to its non-convexity and semi-infiniteness incurred by the imperfect CSI. As a compromise, the authors develop a tractable approximation to its objective secrecy rate function for deriving a computationally efficient lower bound. Then a successive convex approximation (SCA) algorithm is proposed to solve the approximated problem in an iterative manner with provable convergence guarantee. Then it is proved that the SCA algorithm always yields a beam-forming solution to the confidential message transmission. Numerical results illustrate that the proposed scheme outperforms the traditional one.

A Secure Device-to-Device Link Establishment Scheme for LoRaWAN

In the Internet of Things (IoT) era, the importance of communication technology to support communication between the various types of devices has become greater than ever before. Long Range (LoRa) and Long Range Wide Area Network (LoRaWAN) are newly designed communication technologies for low-power long-distance communication in the IoT environment. Recently, LoRa and LoRaWAN have received much attention in academia and industry because low-power long-distance communication has not been supported by traditional communication technologies. Current LoRaWAN supports only communication between the end node and the central server. A recently introduced study enables device-to-device (D2D) communication in the LoRaWAN environment, which is not supported by the current LoRaWAN standard. This paper shows that direct communication between devices can reduce battery consumption. However, security is not considered in this paper and the security features of the LoRaWAN standard are also not applicable, which means that LoRaWAN D2D communication is exposed to a security threat. Therefore, we propose a secure link establishment scheme to protect the LoRaWAN D2D communication. With our scheme, both D2D nodes can securely share cryptographic keys for protecting the D2D communication. Through the security analysis, we prove that our scheme guarantees mutual authentication, confidentiality, and integrity. Performance evaluation shows that our scheme increases power consumption by approximately 5% compared with the basic scheme without security, but has little impact on overall battery lifetime. Consequently, the proposed scheme guarantees fundamental security requirements with sufficient feasibility.

Device-to-Device Communications: A Performance Analysis in the Context of Social Comparison-Based Relaying

Device-to-device (D2D) communications are recognized as a key enabler of future cellular networks, which will help to drive improvements in spectral efficiency and assist with the offload of network traffic. Relay-assisted D2D communications will be essential when there is an extended distance between the source and the destination or when the transmit power is constrained below a certain level. Although a number of works on relay-assisted D2D communications have been presented in the literature, most of those assume that relay nodes cooperate unequivocally. In reality, this cannot be assumed, since there is little incentive to cooperate without a guarantee of future reciprocal behavior. To incorporate the social behavior of D2D nodes, we consider the decision to relay using the donation game based on social comparison, characterize the probability of cooperation in an evolutionary context and then evaluate the network performance of relay-assisted D2D communications. Through numerical evaluations, we investigate the performance gap between the ideal case of 100% cooperation and practical scenarios with a lower cooperation probability. It shows that practical scenarios achieve lower transmission capacity and higher outage probability than idealistic network views, which assume full cooperation. After a sufficient number of generations, however, the cooperation probability follows the natural rules of evolution and the transmission performance of practical scenarios approach that of the full cooperation case, indicating that all D2D relay nodes adapt the same dominant cooperative strategy based on social comparison, without the need for external enforcement.

Distributed radio resource allocation for device-to-device communications underlaying cellular networks

Underlaying Device-to-Device (D2D) communications can increase the spectral efficiency of cellular networks when sharing part of the spectrum with cellular users. This requires radio resource allocation policies capable to limit and control the interference between D2D and cellular communications. Many of the proposed policies are centralized, and require the base station to decide which resources should be allocated to each D2D transmission. Centralized schemes can efficiently control interference levels, but their feasibility can be compromised by their complexity and signaling overhead. To address this constraint, this paper proposes DiRAT, a distributed radio resource allocation scheme for D2D communications underlaying cellular networks. With DiRAT, the D2D nodes locally select their radio resources from a pool created by the cellular network in order to control the interference generated to the primary cellular users. DiRAT includes a control mechanism to ensure that the user QoS requirements are satisfied. This study demonstrates that DiRAT can increase the network capacity while avoiding or limiting the degradation of the performance of the primary cellular users. DiRAT also significantly reduces the complexity and overhead compared to existing centralized and distributed schemes.

Power allocation and relay selection for network-coded D2D communication underlay heterogeneous cellular networks

Underlay device-to-device (D2D) communication is an attractive technology enabling nearby cellular users to communicate with each other directly in order to increase data rate and spectral efficiency. The current cellular heterogeneous networks consist of macrocell base stations and small cell base stations with different transmit powers and coverage areas. Femtocell is the most popular small cell which is expected to be utilized in dense and ultra-dense scenarios in the future. Network coding in relay-assisted multi-hop communications improves achievable transmission rate and coverage of D2D communications. In this paper, two-hop random linear network coding network in cooperative D2D communication (RLNC-CDC) is considered. We propose to use femtocell base station (FBS) as a relay. We assume that the D2D pair and relay operate in the frequency band which is allocated to femtocell network. Therefore, there would be interference from the relay node and the D2D communication on the femtocell network users. To reduce the interference, the sum of transmit powers of the D2D pair and selected relay FBS should be minimized in a way that the highest transmission rate for the D2D pair is achieved. The constraints on the bounds of transmit powers of the D2D and relay node as well as the minimum required transmission rate for D2D communication are considered and the optimum solution is obtained. Simulation results indicate that the proposed RLNC-CDC achieves higher data rate and smaller outage probability than the direct D2D transmission.

Spatial and Social Paradigms for Interference and Coverage Analysis in Underlay D2D Network

The homogeneous Poisson point process is widely used to model spatial distribution of base stations and mobile terminals. The same process can be used to model underlay device-to-device (D2D) network; however, neglecting homophilic relation for D2D pairing presents underestimated system insights. In this paper, we model both spatial and social distributions of interfering D2D nodes as proximity-based independently marked homogeneous Poisson point process. The proximity considers physical distance between D2D nodes whereas social relationship is modeled as Zipf-based marks. We apply these two paradigms to analyze the effect of interference on coverage probability of distance-proportional power-controlled cellular user. Effectively, we apply two types of functional mappings (physical distance, social marks) to Laplace functional of PPP. The resulting coverage probability has no closed-form expression; however, for a subset of social marks, the mark summation converges to digamma and polygamma functions. This subset constitutes the upper and lower bounds on coverage probability. We present numerical evaluation of these bounds on coverage probability by varying number of different parameters. The results show that by imparting simple power control on cellular user, ultradense underlay D2D network can be realized without compromising the coverage probability of cellular user.

Analysis of outage probability for in‐band device‐to‐device communications underlaying cellular network

SummaryOne of the key strategies for jointly increasing throughput and optimum resource allocation in 5G is device‐to‐device (D2D) communications, which can be obtained by minimizing the outage probability considered as an objective function of optimization problem. To minimize this objective function, we found that outage probability should be modeled by jointly considering the effect of interference, noise, and multipath phenomena. In this paper, the exact formulas for outage probability of in‐band D2D communications underlying cellular network are proposed. In the proposed model, additive white Gaussian noise and Rayleigh multipath fading are considered into 2 radio resource reuse scenarios. In the first scenario, each D2D pair is allowed to reuse radio resource block of one cellular user, whereas in the second scenario, 2 resources of 2 cellular users can be reused. The proposed formulas are compared to the approximate (nonexact) ones, which models additive white Gaussian noise by a constant variance. The numerical analysis for the first and second scenarios show that the approximate formulas and respected exact ones are in accordance with simulation results in MATLAB. Moreover, based on nonorthogonal multiple access approach, 2 approximations for the nonexact and the proposed formulas are extracted, which are acceptable for multiple resource reuse scenario. As a remarkable result, simulation results show that when the distance of the D2D pair from the respected cellular user is more than 71 m (2 times greater than average distance between the D2D nodes), multiple‐reuse scenarios offer higher throughput compared to 1‐reuse scenario in an acceptable outage probability.

Device-to-Device Communication Underlaying a Finite Cellular Network Region

Underlay in-band device-to-device (D2D) communication can improve the spectrum efficiency of cellular networks. However, the coexistence of D2D and cellular users causes inter-cell and intra-cell interference. The former can be effectively managed through inter-cell interference coordination and, therefore, is not considered in this work. Instead, we focus on the intra-cell interference and propose a D2D mode selection scheme to manage it inside a finite cellular network region. The potential D2D users are controlled by the base station (BS) to operate in D2D mode based on the average interference generated to the BS. Using stochastic geometry, we study the outage probability experienced at the BS and a D2D receiver, and spectrum reuse ratio, which quantifies the average fraction of successfully transmitting D2D users. The analysis shows that the outage probability at the D2D receiver varies for different locations. Additionally, without impairing the performance at the BS, if the path-loss exponent on the cellular link is slightly lower than that on the D2D link, the spectrum reuse ratio can have negligible decrease while the D2D users' average number of successful transmissions increases with increasing D2D node density. This indicates that an increasing level of D2D communication can be beneficial in future networks..

Interference Mitigation in D2D Communication Underlaying LTE-A Network

The mobile data traffic has risen exponentially in recent days due to the emergence of data intensive applications, such as online gaming and video sharing. It is driving the telecommunication industry as well as the research community to come up with new paradigms that will support such high data rate requirements within the existing wireless access network, in an efficient and effective manner. To respond to this challenge, device-to-device (D2D) communication in cellular networks is viewed as a promising solution, which is expected to operate, either within the coverage area of the existing eNB and under the same cellular spectrum (in-band) or separate spectrum (out-band). D2D provides the opportunity for users located in close proximity of each other to communicate directly, without traversing data traffic through the eNB. It results in several transmission gains, such as improved throughput, energy gain, hop gain, and reuse gain. However, integration of D2D communication in cellular systems at the same time introduces new technical challenges that need to be addressed. Containment of the interference among D2D nodes and cellular users is one of the major problems. D2D transmission radiates in all directions, generating undesirable interference to primary cellular users and other D2D users sharing the same radio resources resulting in severe performance degradation. Efficient interference mitigation schemes are a principal requirement in order to optimize the system performance. This paper presents a comprehensive review of the existing interference mitigation schemes present in the open literature. Based on the subjective and objective analysis of the work available to date, it is also envisaged that adopting a multi-antenna beamforming mechanism with power control, such that the transmit power is maximized toward the direction of the intended D2D receiver node and limited in all other directions will minimize the interference in the network. This could maximize the sum throughput and hence, guarantees the reliability of both the D2D and cellular connections.

Performance for device-to-device communication with three-time-slot two-way amplify-and-forward relay protocol

Multi-hop device-to-device (D2D) communication can significantly improve the system performance. This paper studied the outage performance of D2D communication assisted by another D2D user using three-timeslot two-way amplify-and-forward relaying protocol over Rayleigh fading channels. Considering the co-channel interference from cellular user at the D2D node, the approximate expression for the overall outage probability was derived. Furthermore, a power allocation optimum method to minimize the outage probability was developed, and the closed form expression for the optimal power allocation coefficient at the relay was derived. Simulation results demonstrate accuracy of the derived outage probability expressions. Simulation results also demonstrate that the outage performance can be improved using the proposed optimal power allocation method.

A dynamic graph optimization framework for multihop device-to-device communication underlaying cellular networks

With emerging demands for local area and popular content sharing services, multihop device-to-device communication is conceived as a vital component of next-generation cellular networks to improve spectral reuse, bring hop gains, and enhance system capacity. Ripening these benefits depends on fundamentally understanding its potential performance impacts and efficiently solving several main technical problems. Aiming to establish a new paradigm for the analysis and design of multihop D2D communications, in this article, we propose a dynamic graph optimization framework that enables the modeling of large-scale systems with multiple D2D pairs and node mobility patterns. By inherently modeling the main technological problems for multihop D2D communications, this framework benefits investigation of theoretical performance limits and studying the optimal system design. Furthermore, these achievable benefits are demonstrated by examples of simulations under a realistic multihop D2D communication underlaying cellular network.

Resource Allocation for Device-to-Device Communications Overlaying Two-Way Cellular Networks

Device-to-device (D2D) communications has been proposed in the literature as an underlay approach to cellular networks to allow direct transmission between two cellular devices with local communication needs. In this paper, we consider a scenario of D2D communications overlaying a cellular network and propose a new spectrum sharing protocol, which allows the D2D users to communicate bi-directionally with each other while assisting the two-way communications between the cellular base station (BS) and the cellular user (CU). We derive the achievable rate region of the sum rate of the D2D transmissions versus that of the cellular transmissions. The Pareto boundary of the region is found by optimizing the transmit power at BS and CU as well as the power splitting factor at the relay D2D node. Since either of the two D2D users can be the relay and there can exist multiple pairs of D2D users, we also consider the relay selection from the potential D2D users. We find through numerical results that the proposed two-way protocol with power control at the BS and CU is effective to improve the sum rate for both the D2D and cellular users. In addition, relay selection can achieve further improvement in the sum rate of the cellular links.