Enhancing Cellular Performance Through Device-to-Device Distributed MIMO

Full‐duplex relay‐assisted device‐to‐device (D2D) communication underlaying fifth generation cellular networks allow devices to exchange information directly and extend coverage via relay strategy. In this study, the authors consider such a scenario, where the D2D communications assisted by fixed‐location full‐duplex relays in interference existing circumstance. Different from previous works, they assume that there are two types of users, cellular users and D2D users. They investigate power control problem and coverage probability performance in the previously assumed situation. Therefore, an effective power control scheme is of great importance to suppress interference between D2D and cellular communications, which can improve the total system throughput and spectral efficiency. To describe it, they formulate a power control optimisation problem for cellular communication and propose a simple on–off power control algorithm for D2D communication. They also obtain an analytic expression for the coverage probability of the cellular link using stochastic geometry according to the proposed algorithm. Simulation results follow to show the rates of both cellular and D2D links in the various numbers of D2D transceivers.

Mobile cellular communications are experiencing an exponential growth in traffic load on Long Term Evolution (LTE) eNode B (eNB) components. Such load can be significantly contained by directly sharing content among nearby users through device-to-device (D2D) communications, so that repeated downloads of the same data can be avoided as much as possible. Accordingly, for the purpose of improving the efficiency of content sharing and decreasing the load on the eNB, it is important to maximize the number of simultaneous D2D transmissions. Specially, maximizing the number of D2D links can not only improve spectrum and energy efficiency but can also reduce transmission delay. However, enabling maximum D2D links in a cellular network poses two major challenges. First, the interference between the D2D and cellular communications could critically affect their performance. Second, the minimum quality of service (QoS) requirement of cellular and D2D communication must be guaranteed. Therefore, a selection of active links is critical to gain the maximum number of D2D links. This can be formulated as a classical integer linear programming problem (link scheduling) that is known to be NP-hard. This paper proposes to obtain a set of network features via deep learning for solving this challenging problem. The idea is to optimize the D2D link schedule problem with a deep neural network (DNN). This makes a significant time reduction for delay-sensitive operations, since the computational overhead is mainly spent in the training process of the model. The simulation performed on a randomly generated link schedule problem showed that our algorithm is capable of finding satisfactory D2D link scheduling solutions by reducing computation time up to 90% without significantly affecting their accuracy.

With device-to-device (D2D) based relay-assisted communications, deep faded cellular users (CUs) get a better connectivity. The deep faded CU's achievable throughput of the link from base station (BS) to the CU is less than the rate demand from the CU (unsatisfied CUs). In this paper, we study the resource allocation problem for both CUs and D2D pairs to increase the achievable throughput. This is accomplished by reducing the difference between rate demand and rate achieved for the active CUs. The resource allocation optimization problem is solved in three steps. The initial set of resources that can be allocated to each active CUs is determined in the first step. In the second step, it finds the set of active CUs which needs D2D assistance and then it finds suitable D2D relay nodes (DRNs). Resource allocation to those DRNs and D2D pairs without degrading the link throughput of active CUs is performed in the third step. Numerical results shows significant amount of throughput gain for the active CUs using D2D communication. We also measure the performance of our proposed model in terms of churn rate and the number of excess resource blocks (RBs) in the system.

In this paper, we propose a device-to-device (D2D) communication scheme to improve local services in cellular networks. By employing cooperative relay (CR) technology, D2D and cellular communications can operate in orthogonal resource sharing (ORS) mode with the aim of optimizing the data rates for local D2D users while fulfilling the minimum rate requirements for prioritized cellular users. In the proposed CR-based ORS scheme, we consider a cellular communication that is willing to share part of the occupied bandwidth resource with some D2D communications. Hence, the newly-obtained resource can be used by a D2D communication for the following two purposes, i.e., to compensate the rate loss of the cellular communication through cooperative relaying and to communicate its own information so as to increase its own rate. We formulated this CR-based ORS problem as a non-convex optimization problem. Hence, a global maximizer may not exist for the problem. To find the optimal solution for the problem, an effective heuristic algorithm is developed. Simulation results show that the proposed D2D communication scheme can significantly increase the rates of local D2D users and also fulfill the minimum rate requirements of cellular users.

Device-to-device (D2D) communication exploits the proximity between two devices to enhance the overall spectrum utilization of a crowded cellular network. Two conventional frameworks that are generally used to realize a D2D communication are underlay D2D (U-D2D) and cooperative D2D (C-D2D) communications. Both frameworks have their own merits and demerits in terms of interference management, implementation complexity, and achievable spectral efficiency (SE). For instance, the performance of U-D2D is limited by the amount of interference from the D2D to the cellular user (CU), whereas for C-D2D the performance suffers due to a division of transmission into two orthogonal time phases. In this paper, we propose two novel extensions of conventional D2D communication frameworks, which alleviate their drawbacks and also improves the performance of the overall cellular network. The first proposed framework is an adaptive interference aware U-D2D communication framework. Through this framework, the CU can be protected from the excessive interference of the D2D transmitter (DT), thus maintaining the desired quality of service at CU. The second proposed framework is an adaptive C-D2D communication framework. This framework employs adaptive modulation and coding and bit error rate-based selection and combining to enhance the performance of cellular and D2D users. As a proof-of-concept demonstration and performance assessment, both the frameworks have been implemented on a National Instruments Universal Software Radio Peripheral platform. The measurement results and on-field trials show that the proposed frameworks improve the bit error rate (BER) and the SE of the overall system. Results also interpret that the adaptive C-D2D outperforms the adaptive interference aware U-D2D in terms of BER and SE.

ABSTRACTTo address the problems of system capacity reduction due to high system interference in highway vehicular communication scenarios, a resource allocation strategy for cellular vehicular communication based on device‐to‐device (D2D) communication is proposed. A mathematical model is constructed with CUE user channel capacity as the optimization objective, considering resource sharing between device‐to‐device users (DUE) and cellular users (CUE), and the model is solved through three stages. Firstly, it is proposed to calculate the user channel gain to construct the DUE user channel gain matrix and compare the total channel gain after user multiplexing to manage the user clustering to reduce the interference between users. Secondly, the elite reverse learning strategy and Lévy flight strategy were introduced to improve the sparrow search algorithm, which increased the convergence speed and the ability to escape from the local optimal solution and optimized the channel matching problem. Finally, the water injection algorithm is invoked to solve the power allocation problem to maximize the channel capacity of CUE. Simulation experimental results show that the strategy achieves a system capacity of 340 bps/Hz while ensuring that the system communication is basically stable.

In this paper, we consider cooperative D2D communications in cellular networks. More precisely, a cellular user leases part of its spectrum to facilitate the D2D communication with a goal of improving the energy efficiency of a D2D pair. However the D2D pair is untrusted to the cellular user, such resource sharing may result in the information of this cellular user unsecured. In order to motivate the cellular user’s generosity, this D2D pair needs to help the cellular user maintain a target secrecy rate. To address this issue, we formulate a joint spectrum and power allocation problem to maximize the energy efficiency of the D2D communication while guaranteeing the physical layer security of the cellular user. Then, a theorem is proved to indicate the best resource allocation strategy, and accordingly, an algorithm is proposed to find the best solution to this resource allocation problem. Numerical results are finally presented to verify the validity and effectiveness of the proposed algorithm.

Device-to-Device (D2D) communication is an emerging technology that has been introduced as a beneficial complement of cellular infrastructure. Allocating resources to the D2D link, however, raises an enormous challenge to the co-existing D2D and cellular communications due to the mutual interference. While there have been many resource allocation solutions proposed for D2D under laying cellular network, they have primarily focused on the intracell scenario while leaving the intercell settings untouched. In this paper, we address the resource allocation problem for intercell D2D communication under laying cellular network. Unlike most of prior works allocating resource in a single cell, we consider the scenario that D2D link locates in the common area of two neigh boring cells. We formulate the problem by developing a Cournot competition game, in which the base stations (BSs) are modeled as players to compete for resource supply quota from D2D demand under three dedicated cases. Our analysis and numerical results show that the the derived resource allocation solution is an equilibrium, thus offering a global insight into resource configurations of two cells.

Device-to-device (D2D) communications allows two adjacent mobile terminals transmit signal directly without going through base stations, which has been considered as one of the key technologies for future mobile networks. As full-duplex (FD) communications can improve the performance (i.e., throughput, energy efficiency (EE)) of communications systems, it is commonly used in practical D2D communications scenarios. However, FD-enabled D2D communications also results in self-interference. To fully realize the potential benefits of FD-enabled D2D communications, an effective resource allocation mechanism is critical to avoid not only the self-interference of FD-enabled D2D communications but also the interference between D2D users (DUs) and cellular users (CUs). In this paper, we investigate the resource allocation issue for FD-enabled DUs and traditional CUs. Considering the asymmetry of energy and spectrum resources of DUs and CUs, we propose a power-spectrum trading mechanism to achieve mutual benefits for both types of users. A concave-convex procedure algorithm is employed to solve the optimization problem of power allocation, and then a maximum weighted bipartite matching based method is proposed to select proper D2D pairs to maximize the overall system throughput. Numerical results show that the proposed scheme can remarkably improve the overall throughput and EE of FD-enabled D2D communications system.

We investigate power control problem for cooperative relaying in the device-to-device (D2D) system underlaying cellular networks. Specifically, we consider the D2D communication assisted by fixed-location relays in interference existing circumstance. Therefore, an effective power control scheme is of great importance to suppress interference between D2D and cellular communications which can improve the total system throughput and spectral efficiency. In this paper, we formulate a power control optimization problem for cellular communication and a simple on-off power control algorithm for D2D communications. We also obtain analytic expression for the coverage probability of cellular link using stochastic geometry according to proposed algorithm. Simulation results follow to show the rate of both cellular and D2D links in the various number of D2D transceivers.

D2D communications can be prone to potential security threats. For example, D2D mobiles need to know who else is located nearby so as to pair up. If the location information is spoofed, the interference caused by wrongly paired D2D users can significantly lower the system performance. Additionally, D2D communications between neighboring D2D nodes provide alternative security approaches (physical-layer security) by using channel statistics. In this chapter, we will study the following two security problems in detail. • Location security: D2D networks need to pair D2D users on the basis of location information so as to use locally available spectrum. This creates a critical loophole for global-positioning-system (GPS)-spoofing attack, where the adversary attacks the GPS signals received by D2D devices, so that D2D devices obtain false available spectrum information with false location information. This security loophole can potentially result in large-scale malfunctioning of mobile D2D networks. • Data transmission security: Security in D2D communications is traditionally implemented using cryptography, as in other wireless communication systems. Alternatively, physical-layer security provides additional security provided by the channel statistics, which fits well the D2D communications scenarios. We will consider physical-layer security in D2D communications as an underlay to cellular networks with an eavesdropper. Benefiting from the underlaid spectrum reuse, D2D users can contribute to the system's secrecy capacity, while D2D users may interfere with cellular users and decrease their secrecy capacity. Location security 8.1.1 Problem overview Dynamic-spectrum-access (DSA) technology has received much attention in industry and academic environments due to its promise of better utilization of spectrum resources compared with the current static spectrum-allocation method. Traditionally, spectrum allocation is static, where FCC assigns communities licenses to use specific frequencies, such as AM, FM, short-wave and citizens' bands, and VHF and UHF television channels, as well as hundreds of less familiar bands that serve cellular and cordless telephones, GPS trackers, air-traffic-control radars, security alarms, radio-controlled toys, and the like. While some of these assigned spectrum bands have been overloaded due to the growth of their users, other spectrum bands are scarcely used.

D2D (Device-to-Device) communication is one of the promising technologies in the LTE (Long Term Evolution)-Advanced communication network. From system perspective, this technology can increase frequency efficiency of the whole macro cell. From user perspective, however, a D2D pair which shares the same frequency resource of CUE (Cellular User Equipment) can cause interference with the CUE in the downlink. Thus, reducing interference for the cellular users and allocating frequency resource for the D2D pairs are important in D2D communication. In this paper, two resource allocation schemes which are based on PSO (Particle Swarm Optimization) and hybrid PSO-GA (Genetic Algorithm) are proposed to maximize the system throughput by allowing up to two D2D pairs to share the same frequency resource with one CUE. Moreover, a scheme has been considered to mitigate the interference caused to CUEs. The simulation results show that service of CUEs and system performance can be effectively guaranteed by using the proposed schemes.

In this paper we investigate the effect of interference caused by in-band full-duplex radios in device-to-device communication (D2D). While using full-duplex radios in D2D, both users transmit, compared to half-duplex D2D in which one user transmits. This is going to cause more interference in underlay D2D communication since D2D link operates on the same radio resource blocks as cellular users. We consider uplink radio resource reuse of cellular users by D2D communication, and try to maximize the number of possible D2D links constrained to the interference on the cellular user. The number of D2D pairs that can be active in the full-duplex mode is smaller than in the half-duplex mode due to more interference from transmissions of both D2D nodes. We compare the total rate of half-duplex and full-duplex modes and evaluate the benefits of full-duplex radios.

Underlay device-to-device (D2D) communication in cellular networks has been considered as a promising technique that can improve the spectral efficiency of cellular systems and meet the growing demand for wireless local services. In underlay D2D, it is of primary importance to manage the mutual interference between cellular links and D2D links through effective resource allocation. While most of previous works on D2D resource allocation are developed based on the knowledge of the channel state information (CSI) on the interference channels as well as the desired channels, it is hard to obtain full CSI in practice. Accordingly, we consider D2D resource allocation schemes based on distance between nodes. In particular, we formulate two optimization problems for D2D resource allocation using the outage probability computed based on the distance information as cost functions. One is a linear sum assignment problem (LSAP) and the other is a linear bottleneck assignment problem (LBAP). By applying the graph theory, we provide efficient algorithms for solving the optimization problems. Numerical results are provided to show the effectiveness of the proposed optimization as compared to previously proposed distance-based resource allocation algorithms.

The spectrum insufficiency has become a major problem in wireless communication systems due to increasing the demand on broadband applications. Heterogeneous macro-small cell network, Device-to-device (D2D) communications, and multiple-input multiple-output (MIMO) systems all are promising technologies to improve the spectrum efficiency and the data rate in future cellular networks. In this paper, the problem of cross-tier interference reduction in MIMO in heterogeneous macro-small cell network enabling D2D communications is investigated in presence of imperfect Channel State Information (CSI). Underlaying D2D communications, sharing the same resource of the cellular network, causes co-channel interference. Two precoding selection methods are used in the D2D underlaying MIMO system. The first one aims to maximize the rate of the D2D user while the second one aims to reduce the cross-tier interference between the D2D and the cellular user. Simulations are performed to investigate the effect of imperfect CSI on the system performance using the two selection methods.