D2D Group Research Articles

Microsolvation of cobalt, nickel, and copper atoms with ammonia: a theoretical study of the solvated electron precursors.

The s-block metals dissolved in ammonia form metal-ammonia complexes with diffuse electrons which could be used for redox catalysis. In this theoretical paper, we investigated the possibility of the d-bloc transition metals (Mn, Fe, Co, Ni, and Cu) solvated by ammonia. It has been demonstrated that both Mn and Fe atoms undergo into an oxidative reaction with NH3 forming an inserted species, HMNH2. On the contrary, the Co, Ni, and Cu atoms can accommodate four NH3, via the coordination bond, to form the first solvation sphere within C2v, D2d, and Td point groups, respectively. Addition of a fifth NH3 constitute the second solvation shell by forming hydrogen bond with the other NH3s. Interestingly, M(NH3)4 (M = Co, Ni, and Cu) is a so-called solvated electron precursor and should be considered as a monocation M(NH3)4+ kernel in tight contact with one electron distributed over its periphery. This nearly free electron could be used to capture a CO2 molecule and engages in a reduction reaction. Geometry optimization of the stationary points on the potential energy surface was performed using density functional theory - CAM-B3LYP functional including the GD3BJ dispersion contribution - in combination with the 6-311 + + G(2d, 2p) basis set for all the atoms. All first-principles calculations were performed using the Gaussian 09 quantum chemical packages. The natural electron configuration of transition atom engaged in the compounds has been found using the natural bond orbital (NBO) method. We used the EDR (electron delocalization range) approach to analyze the structure of solvated electrons in real space. We also used the electron localization function (ELF) to measure the degree of electronic localization within a chemical compound. The EDR and ELF analyses are done using the TopMod and Multiwfn packages, respectively.

EWA‐DA‐based resource allocation method for 5G networks

AbstractIn 5G networks, most D2D work focuses on optimizing system throughput without addressing economic constraints. This article encourages users to exchange resources and apply honest bidding tactics to attain high auction efficiency. This study describes an experience‐weighted attraction double auction (EWA‐DA) technique for allocating resources in 5G D2D networks. The suggested method classifies mobile users into seller cellular users (SCU) and buyer cellular users' (BCU). The SCU transmits the beacon packet, and the nearby cellular users create a D2D group in response to the beacon considered BCU. Then, the bid values of the buyer and seller cellular users are transmitted to the base station side. The BS uses an experience‐weighted attraction‐learning model to obtain accurate bidding prices. Lastly, an ask‐to‐mean‐value double auction model was utilized instead of accurate bid values. Extensive simulation results demonstrate that the suggested strategy delivers excellent auction efficiency and fair earnings for both seller and buyer users. In addition, we identified that the participating users accomplished truthful bidding and used fewer resource blocks than existing techniques.

Systematic analysis of electronic barrier heights and widths for concerted proton transfer in cyclic hydrogen bonded clusters: (HF)n, (HCl)n and (H2O)n where n = 3, 4, 5.

The MP2 and CCSD(T) methods are paired with correlation consistent basis sets as large as aug-cc-pVQZ to optimize the structures of the cyclic minima for (HF)n, (HCl)n and (H2O)n where n = 3-5, as well as the corresponding transition states (TSs) for concerted proton transfer (CPT). MP2 and CCSD(T) harmonic vibrational frequencies confirm the nature of each minimum and TS. Both conventional and explicitly correlated CCSD(T) computations are employed to assess the electronic dissociation energies and barrier heights for CPT near the complete basis (CBS) limit for all 9 clusters. Results for (HF)n are consistent with prior studies identifying Cnh and Dnh point group symmetry for the minima and TSs, respectively. Our computations also confirm that CPT proceeds through Cs TS structures for the C1 minima of (H2O)3 and (H2O)5, whereas the process goes through a TS with D2d symmetry for the S4 global minimum of (H2O)4. This work corroborates earlier findings that the minima for (HCl)3, (HCl)4 and (HCl)5 have C3h, S4 and C1 point group symmetry, respectively, and that the Cnh structures are not minima for n = 4 and 5. Moreover, our computations show the TSs for CPT in (HCl)3, (HCl)4 and (HCl)5 have D3h, D2d, and C2 point group symmetry, respectively. At the CCSD(T) CBS limit, (HF)4 and (HF)5 have the smallest electronic barrier heights for CPT (≈15 kcal mol-1 for both), followed by the HF trimer (≈21 kcal mol-1). The barriers are appreciably higher for the other clusters (around 27 kcal mol-1 for (H2O)4 and (HCl)3; roughly 30 kcal mol-1 for (H2O)3, (H2O)5 and (HCl)4; up to 38 kcal mol-1 for (HCl)5). At the CBS limit, MP2 significantly underestimates the CCSD(T) barrier heights (e.g., by ca. 2, 4 and 7 kcal mol-1 for the pentamers of HF, H2O and HCl, respectively), whereas CCSD overestimates these barriers by roughly the same magnitude. Scaling the barrier heights and dissociation energies by the number of fragments in the cluster reveals strong linear relationships between the two quantities and with the magnitudes of the imaginary vibrational frequency for the TSs.

Sum Throughput Maximization Scheme for NOMA-Enabled D2D Groups Using Deep Reinforcement Learning in 5G and Beyond Networks

Device-to-Device (D2D) communication underlaying cellular network is a capable system for advancing the spectrum’s efficiency. However, in this condition, D2D generates cross-channel and co-channel interference for cellular and other D2D users, which creates an excessive technical challenge for allocating the spectrum. Despite this, massive connectivity is another issue in the 5G and beyond networks that need to be addressed. To overcome this problem, non-orthogonal multiple access (NOMA) is integrated with the D2D groups (DGs). In this paper, our target is to maximize the sum throughput of the overall network while maintaining the signal-to-interference noise ratio (SINR) of the cellular and D2D users. To achieve the target, a discriminated spectrum distribution framework dependent on multi-agent deep reinforcement learning (MADRL), termed a deep deterministic policy gradient (DDPG) is proposed. Here, it shares the global historical states, actions, and policies using the duration of central training. Furthermore, the proximal online policy scheme (POPS) is used to decrease the computation complexity of training. It utilized the clipping substitute technique for the modification and reduction of complexity at the training stage. The simulation results demonstrated that the proposed scheme POPS attains 16.67%, 24.98%, and 59.09% higher performance than the DDPG, Deep Dueling and deep Q-network (DQN).

Lightweight and secure D2D group communication for wireless IoT

In recent years, wirless Internet of Things (IoT) technology has developed rapidly, and the reuse of spectrum resources, network efficiency, and the diversity of multi-communication scenarios have brought great challenges to the existing Internet of Things. And Device to Device (D2D) communication technology in 5th Generation Mobile Communication Technology (5G) has good application prospects in these aspects. Therefore, the combination with D2D can well solve the needs in the wirless Internet of things. However, safe and effective communication has become an urgent problem to be solved. In this paper, this paper proposes a D2D group communication protocol for wireless IoT in 5G. In this protocol, the Chinese remainder theorem is introduced into the protocol design, and a secure and efficient group authentication scheme is constructed based on secret sharing and Chebyshev Polynomials. The formal security proof using Burrows Abadi Needham (BAN) logic and informal security analysis show that our proposed protocol meets the security requirements. Through performance analysis, compared with other related schemes, this scheme not only provides better security, but also has obvious advantages in computation and communication efficiency.

D2D Group Key Agreement Scheme for Smart Devices in HANs

<p>The home area network (HAN) is one of the most widely researched areas in recent years. HANs integrate 5G/6G networks and artificial intelligence technology to provide data services for home users. The devices in HANs collect and transmit data relating to users’ daily activities for analysis by remote service providers. These data often contain a large number of users’ personal privacy. The disclosure of these data could have far-reaching consequences for the privacy of the individuals involved. Some researchers are dedicated to investigating the authentication of smart devices by the system. However, the increased frequency of interactions between devices and gateways, as well as between devices themselves, is a defining characteristic of HANs. In this paper, a device-to-gateway (D2G) authentication scheme is proposed. Based on the authentication result, a partial key is generated for smart devices and the gateway. Finally, a device-to-device (D2D) group key agreement scheme is presented. The security and efficiency of the proposed scheme are proved according to the analysis.</p> <p> </p>

Resource allocation for multiple RISs assisted NOMA empowered D2D communication: A MAMP-DQN approach

In this paper, we investigate the non-orthogonal multiple access (NOMA) empowered D2D communications system, where multiple reconfigurable intelligent surfaces (RISs) are deployed to enhance the service quality for mobile D2D groups. Meanwhile, the RISs can further improve the NOMA gains with artificially controlled channel conditions. Although multiple distributed deployment RISs can enhance the coverage for the multiple mobile D2D groups. However, the joint reflective capabilities of multiple RISs require a more complex phase shift design. Therefore, to maximize the average sum data rate of all D2D groups, a multi-agent multi-pass deep Q-network (MAMP-DQN) based framework is invoked to optimize the sub-channel assignment and power allocation of mobile D2D groups, as well as the phase shifts adjustment policy. Specifically, the actions in the formulated Markov game (MG) are modeled in the hybrid discrete–continuous structure, and the MP-DQN algorithm is invoked to deal with the hybrid action. Our simulation results indicate that the multiple RISs can significantly improve the average sum data rate of D2D groups. Moreover, the NOMA-empowered D2D groups are capable of achieving a gain of 27% in contrast with the OMA scheme in terms of the sum data rate. Finally, the sum data rate of D2D groups can be further enhanced by increasing the number of the RISs or the REs.

A Novel Multi-Cell Interference-Aware Cooperative QoS-Based NOMA Group D2D System

Nonorthogonal multiple access (NOMA), one of the favorable candidates of next-generation wireless networks combined with group device-to-device (D2D) networks, can sufficiently increase a system’s spectral efficiency. In fact, in a cooperative scenario, successive interference cancellation (SIC) is used in NOMA receivers to reduce the complexity of relaying, as each user has to decode high-order user data. This work presents a quality of service (QoS)-based cooperative NOMA-aided group D2D system (Q-CNOMA). The Q-CNOMA system not only reduces the burden on the group transmitter by relaying the signal to a receiver in neighboring cells but also improves the overall system performance. In order to model the major components in a D2D scenario such as receivers clustering around a transmitter, the spatial distribution of D2D transmitters is modeled using a Gaussian–Poisson process (GPP). A closed-form expression of outage probability is calculated and benchmarked against conventional systems to prove the superiority of the proposed Q-CNOMA system.

Power controlled outage-aware optimal protocol for NOMA-assisted underlay D2D networks

Underlay device-to-device (D2D) and non-orthogonal multiple access (NOMA) are two promising technologies that have potential to enhance the spectral efficiency for future wireless communication systems. This paper studies an underlay D2D-NOMA system in an uplink cellular network. Different from the previous works, we minimize the outage probability (OP) while allocating optimal power to the D2D group receivers. Specifically, a D2D power allocation (DPA) problem is formulated and a globally-optimal solution is obtained. As a special case, closed-form expressions are also derived for asymptotic OP-based DPA. Results are numerically validated, and an overall average performance improvement of at least 24% is observed over existing conventional power control schemes.

A D2D Group Communication Scheme Using Bidirectional and InCremental A-Star Search to Configure Paths

The Device-to-Device (D2D) communication introduced in 3GPP’s Release 12 is a promising option for the accommodation of increasing traffic demand and the alleviation of core networks’ loading. The D2D communication mode prevails in scenarios where mobile users in proximity form a communication group sharing the same interest in digital content. A user can download intended content from peers in the same communication group rather than from the Internet via the base station. This article addresses the routing issue within D2D communication groups. It is, in effect, a path selection problem. We define a utility function considering both delay and throughput. The path selection problem can be formulated as an NP-hard optimization problem. A Bidirectional and InCremental A-star (BICA*) algorithm incorporating the concept of bidirectional search and lifelong planning is developed to tackle the NP-hard optimization problem. Simulations reveal that the proposed approach outperforms existing ones in terms of less delay, higher throughput, and higher satisfaction ratio. The Greedy approach, Two-Stage Relay Selection (TSRS), and the standard A* algorithm were included in the comparative study. The throughput improvements of the proposed scheme are up to 23% and 46.5% compared to TSRS and Greedy, respectively. The proposed scheme possesses the lowest delay and the highest satisfaction rate, among others. With less computational time, the proposed BICA* is more responsive than the standard A* in dynamic environments.

Joint optimization for RIS-assisted multicast D2D communications

Multicast device-to-device (D2D) communication is an important technique to overcome the problem of spectrum shortage. Due to the channel gain difference between users in different locations, receivers in the same multicast D2D group still suffer from the problem of different quality of service (QoS) levels. This paper proposes a novel reconfigurable intelligent surface (RIS)-assisted multicast D2D communication system to enhance the QoS of users, in which RIS solves the problem of different QoS between users through intelligent resource optimization. To maximize the achievable sum rate of all multicast D2D users, we formulate a joint optimization problem. This problem combines channel assignment, power allocation, and reflection matrix design by considering the QoS fairness among different D2D users. To solve this problem, we propose a novel joint optimization algorithm, which has three steps. First, we propose a matching algorithm based on swap operations to solve the channel assignment problem. Then, we propose a successive convex approximation (SCA) method to solve the power allocation problem. Finally, we present the optimization of the RIS reflection coefficients with mathematical analysis. The numerical results demonstrate that the proposed algorithm can effectively enhance the QoS of users in the multicast D2D group. With the aid of RIS, the proposed algorithm decreases the service disparities between users in different locations. Furthermore, it reveals that it is helpful to deploy the RIS closer to the receivers or the transmitters.

Resource Allocation for Uplink NOMA-Based D2D Communication in Energy Harvesting Scenario: A Two-Stage Game Approach

Energy harvesting (EH) endows device-to-device (D2D) communication and cellular equipment with the ability of continuous communication to provide internet-of-things (IoT) services in natural areas. While the available energy, which relies on EH, becomes an extra nonnegligible factor in resource allocation. Besides, we integrate uplink non-orthogonal multiple access (NOMA) with D2D communication to provide multiple access for D2D transmitters for more efficient IoT service and more efficient utilization of limited spectrum. In this scenario, ingenious resource allocation approach is a key focus for utilizing the advantages in energy and spectral efficiency. Aiming to investigate the inherent resource allocation issue, we set our goal as maximizing the energy efficiency for both NOMA-based D2D groups and cellular users (CUs), where the power and spectrum allocation are both considered. Then we propose a two-stage game approach, which is theoretically proved to be capable of obtaining the equilibrium and a stable result, to solve the unilateral energy efficiency maximization problems. Besides, an energy-aware screening method is proposed to reduce the computations based on the available energy of user equipment. Finally, the effectiveness of our proposed method is verified through elaborated simulation results.

Transmission Power Control and Relay Strategy for Increasing Access Rate in Device to Device Communication

In cellular networks, Device to Device (D2D) communication can improve spectral efficiency by enabling proximity users to communicate directly without traversing the Base Station (BS). However, if not designed properly, the interference generated by D2D transmissions, may deteriorate the communication quality of the existing cellular and D2D users. In this paper, we study transmission power control-based interference management to increase access rate and sum rate while guaranteeing the Quality of Service (QoS) requirements for both D2D and cellular users. A four-step framework is proposed. First candidate D2D groups, potentially admissible for transmission, are arranged in order with respect to their distance from BS and required Signal to Interference and Noise Ratio (SINR). Next, upper and lower bounds on the transmission power of the transmitters are calculated to determine the admissibility of the aspirant D2D group subject to the QoS requirements of the aspirant group, other scheduled D2D groups, and the cellular user. Then, relay-based communication protocol is considered for admitting the D2D groups that cannot be admitted directly. Finally, sum rate of each shared channel is improved through iterative incrementation of transmission powers of cellular and D2D transmitters constraint by the QoS requirements of all the admitted D2D groups and the cellular user and the existing sum rate. Simulation results show that the proposed framework can improve the access rate many folds across all the considered scenarios as compared to the baseline schemes. Moreover, higher access rates of the proposed scheme translate into significantly higher sum rates.

Togliatti systems associated to the dihedral group and the weak Lefschetz property

In this note, we study Togliatti systems generated by invariants of the dihedral group D2d acting on k[x0, x1, x2]. This leads to the first family of non-monomial Togliatti systems, which we call GT-systems with group D2d. We study their associated varieties \({S_{{D_{2d}}}}\), called GT-surfaces with group D2d. We prove that there are arithmetically Cohen-Macaulay surfaces whose homogeneous ideal, \(I({S_{{D_{2d}}}})\), is minimally generated by quadrics and we find a minimal free resolution of \(I({S_{{D_{2d}}}})\).

Device-to-device group authentication compatible with 5G AKA protocol

Device-to-device (D2D) communication in 5G can offload large amounts of data from the core network and offer smaller delays in communication, making advantage of the proximity between the devices. Specific attention should be given to a dedicated authentication process as there are significant challenges with respect to security and privacy. We propose the first anonymous group D2D authentication and key agreement protocol, which can be integrated into the existing 5G-AKA protocol with only a few adaptations. No additional initialization or new implementations of security algorithms are required for the user equipment. After a successful run of the protocol, the devices in the group can derive a secure group key and a secret key shared with each other member of the group. Both from a computational and a communication perspective, the scheme is comparable with state-of-the-art related solutions. Moreover, our proposed scheme satisfies several security features, which are not currently available in the existing schemes in literature.

An Energy Efficient Scheme for WPCN-NOMA Based Device-to-Device Communication

The capability of Non-Orthogonal Multiple Access (NOMA) for minimizing interference at the receiver using successive interference cancellation (SIC) makes it as a promising solution for 5G mobile communication. Device-to-device (D2D) communication is a part of the 5G network which provides frequency reuse in cellular networks and provides a better quality of service (QoS) to co-channel users. In this paper, we investigate the resource allocation and time scheduling algorithms for a NOMA based D2D communication system. In addition, to overcome the problem of energy at D2D transmitter and receivers, wireless powered communication network (WPCN) is used. Considering these issues, the objective of the proposed scheme is to maintain energy efficient communication among D2D transmitters and receivers without compromising energy efficiency (EE) of cellular users. To solve the fractional form of an optimization problem, we employ the Dinkelbach method. A many-to-many matching game approach is used for channel allocation and successive convex approximation for low complexity (SCALE) is used to control the power of the D2D transmitter. The simulation results demonstrate that by maximizing the EE and optimizing the time and transmission power of D2D groups, the energy efficiency of the network can be significantly improved in comparison to the other competitive schemes in the existing literature.

Joint Uplink and Downlink Resource Allocation for NOMA-Enabled D2D Communications

This letter investigates the joint uplink and downlink resource allocation problem, where the non-orthogonal multiple access (NOMA) technology is applied to enhance device-to-device (D2D) communications. In order to maximize the sum data rate of NOMA-enabled D2D groups while guaranteeing the minimum data rate requirements of both cellular users (CUs) and D2D groups, we first design a subcarrier assignment algorithm to assign the downlink and uplink subcarriers for D2D groups, and then transform the problem into a convex optimization to obtain the optimal power allocation. Simulation results demonstrate the remarkable improvement in terms of data rate of D2D groups by using our algorithms.

Throughput Maximization for Multiple D2D Group Communications Underlaying Cellular Networks

In the scenario where multiple device-to-device (D2D) users and cellular users coexist, the large number of D2D users not only results in the shortage of spectrum resources but also brings interference to the communication of cellular users. In this paper, we establish a clustering model centered on cellular users and propose a resource allocation algorithm based on a D2D clustering model. On the basis of ensuring the throughput requirements of cellular users, this algorithm reconstructs various matrices in the graph theory through probability models, sets the priority of D2D pairs, and maximizes the number of user accesses under interference tolerance. Besides, on the optimization of the number of users, we adopt the Rubinstein game model to adjust the game order according to the priority and optimize the bandwidth allocation mode, so as to improve the overall throughput of the network. Simulation results show that the proposed algorithm can increase the number of users and the network throughput, while shortening the spectrum allocation time by more than half.

Max–Min Fairness Optimization for D2D Communications Coexisting with Cellular Networks

This paper considers a system consisting of a nonorthogonal multiple access (NOMA)-based device-to-device (D2D) communication system within a cellular network, in which the time and frequency resources are shared by everyone. In particular, D2D groups that constitute different pairs are assigned to the subchannels that the cellular users occupy. A max–min fairness optimization problem with power budget constraints is formulated and solved in this paper to reduce the mutual interference between the cellular users and D2D devices that substantially impacts that with the worst channel condition. For a low computational complexity solution, we propose the use of the bisection method together with the solution of a system of linear equalities. The proposed algorithm can provide uniformly good service to all of the cellular users and D2D devices in the coverage area by utilizing the minimal total transmit power. The simulation results indicate the effectiveness of the proposed algorithm in the improvement of the spectral efficiency of the worst user under the different widely used subchannel assignments and pairing techniques.

Energy-Delay Tradeoff Scheme for NOMA-Based D2D Groups With WPCNs

An integration of nonorthogonal multiple access (NOMA) in device-to-device (D2D) mobile groups (DMGs) generates a large amount of energy and delay due to sharing the same subcarrier. In this article, we investigate a distributed energy-efficient and delay tradeoff scheme for NOMA-based DMGs in wireless powered communication networks. The stochastic optimization problem is formulated to maximize the energy efficiency and minimize the delay. Many-to-one matching-based subcarrier allocation, weighted sum method, and Lyapunov optimization scheme are used to investigate the possible solution. Further, to obtain the closed-form expression of power and to optimize the time for wireless powered communication networks, we use Lagrangian function. Simulation results show that the proposed scheme achieves 2.6% and 15.78% superior performance than the existing NOMA and orthogonal frequency division multiple access (OFDMA) schemes under the condition of constant circuit power consumption.