Direct communication between two or more devices without the intervention of a base station, known as device-to-device (D2D) communication, is a promising way to improve performance of cellular networks in terms of spectral and energy efficiency. The D2D communication paradigm has been largely exploited in non-cellular technologies such as Bluetooth or Wi-Fi but it has not yet been fully incorporated into existing cellular networks. In this regard, a new proposal focusing on the integration of D2D communication into LTE-A has been recently approved by the 3GPP standardization community as discussed in this paper. In cellular networks, D2D communication introduces several critical issues, such as interference management and decisions on whether devices should communicate directly or not. In this survey, we provide a thorough overview of the state of the art focusing on D2D communication, especially within 3GPP LTE/LTE-A. First, we provide in-depth classification of papers looking at D2D from several perspectives. Then, papers addressing all major problems and areas related to D2D are presented and approaches proposed in the papers are compared according to selected criteria. On the basis of the surveyed papers, we highlight areas not satisfactorily addressed so far and outline major challenges for future work regarding efficient integration of D2D in cellular networks.

In-Band Device-to-Device Communication in OFDMA Cellular Networks: A Survey and Challenges

The exponential increase in mobile data traffic is considered to be a critical driver towards the new era, or 5G, of mobile wireless networks. 5G will require a paradigm shift that includes very high carrier frequency spectra with massive bandwidths, extreme base station densities, and unprecedented numbers of antennas to support the enormous increase in the volume of traffic. This paper discusses several design choices, features, and technical challenges that illustrate potential research topics and challenges for the future generation of mobile networks. This article does not provide a final solution but highlights the most promising lines of research from the recent literature in common directions for the 5G project. The potential physical layer technologies that are considered for future wireless communications include spatial multiplexing using massive multi-user multiple-input multiple-output (MIMO) techniques with millimetre-waves (mm-waves) in small cell geometries. These technologies are discussed in detail along with the areas for future research.

Evolution towards fifth generation (5G) wireless networks: Current trends and challenges in the deployment of millimetre wave, massive MIMO, and small cells

Driven by the explosive data traffic and new quality of service requirement of mobile users, the communication industry has been experiencing a new evolution by means of network infrastructure densification. With the increase of the density as well as the variety of access points (APs), the network benefits from proximal transmissions and increased spatial reuse of system resources, thus introducing a new paradigm named ultra-dense networks (UDNs). Since the limited available resources are shared by ubiquitous APs in UDNs, the demand for efficient resource allocation schemes becomes even more compelling. However, the large scale of UDNs impedes the exploration of effective resource allocation approaches particularly on the computational complexity and significance overhead or feedback. In this paper, we provide a survey-style introduction to resource allocation approaches in UDNs. Specifically, we first present some common scenarios of UDNs with the relevant special issues. Second, we provide a taxonomy to classify the resource allocation methods in the existing literatures. Then, to alleviate the main difficulties of UDNs, some prevailing and feasible solutions are elaborated. Next, we present some emerging technologies thriving UDNs with special RA features discussed. Additionally, the challenges and open research directions are outlined in this field.

Resource Allocation for Ultra-Dense Networks: A Survey, Some Research Issues and Challenges

For the past years, the analysts have been predicting a tremendous and continuous increase in mobile traffic, causing much of industry and academia to seek out any and all methods to increase wireless network capacity. In this paper, we investigate one such method, cellular data offloading onto direct connections between proximate user devices, which has been shown to provide significant wireless capacity gains. To do so, we formulate a new system model that couples a cellular network in licensed bands and a device-to-device (D2D) network in unlicensed bands. We propose that devices be continually associated with the cellular base station and use this connectivity to help manage their direct connections in unlicensed spectrum. In particular, we demonstrate that assisted offloading of cellular user sessions onto the D2D links improves the degree of spatial reuse and reduces the impact of interference. In this study, a session is a real-time flow of data from one user to another, which adheres to a Poisson point process (PPP). By contrast to a throughput- or capacity-centric system view, the application of PPP enables formulations where entire user sessions, rather than singular data packets, are arriving at random and leaving the system after being served. The proposed methodology is flexible enough to accommodate practical offloading scenarios, network selection algorithms, quality of service measures, and advanced wireless technologies. In this study, we are primarily interested in evaluating the data session blocking probability in dynamically loaded cellular and D2D networks, but given the importance of energy efficiency for mobile devices, we are also interested in characterizing the energy expenditure of a typical data session in these different networks. First with our advanced analytical methodology and then with our detailed system-level simulator, we evaluate the performance of network-assisted data session offloading from cellular to D2D connections under a variety of conditions. This analysis represents a useful tool in the development of practical offloading schemes and ongoing standardization efforts.

Analyzing Assisted Offloading of Cellular User Sessions onto D2D Links in Unlicensed Bands

The future wireless Fifth Generation (5G) communication network required a higher bandwidth in order to achieve greater data rate. It will be largely characterized by small cell deployments, typically in the range of 200 meters of radius/cell, at most. The implementation of small size networks delivers various advantages such as high data rate and low signal delay. However, it also suffers from various issues such as inter-cell, intra-cell, and inter-user interferences. This paper discusses the issues related to interference management for 5G network from the perspective of Heterogeneous Network and Device-to-Device communication, by using enabling techniques, such as Inter-cell Interference Coordination, Coordinated Multipoint, and Coordinated Scheduling. Furthermore, several pertinent issues have been critically reviewed focusing on their methodologies, advantages and limitations along with the future work. Future directions proposed by the 3rd Generation Partnership Project for interference mitigation has also been outlined. This review will act as a guide for the researchers to comprehend various existing and emerging enabling interference mitigation techniques for further exploration and smooth implementation of 5G wireless network.

Interference management issues for the future 5G network: a review

In a Device-to-Device (D2D) underlaying cellular system, interference cancellation is a key problem when uplink spectrums are shared and this problem becomes more complex in a multi-cell cellular network. In this paper, we propose an effective near-far interference avoidance scheme in a multi-cell cellular system. After monitoring the related control channels of a D2D subsystem and exchanging necessary information among neighboring eNBs, an eNB may stop scheduling the interfering cellular devices or facilitate power control mechanisms for the victim D2D users such that the inter-cell near-far interference can be mitigated. Simulations prove that our mechanism is effective and satisfying performance improvement can be obtained.

Effective Interference Cancellation Mechanisms for D2D Communication in Multi-Cell Cellular Networks

Femtocells, a kind of low power nodes in a heterogeneous network for LTE-Advanced, have become an attractive device to offer better system performance and user experience. However, due to co-channel deployments with the macro cell, the home eNB which serves closed subscriber groups will impose serious interference on macro users especially on their PDCCHs which spans over the whole system bandwidth. In this paper, we propose an enhanced ICIC mechanism to suppress such interference by blanking two OFDM symbols. Furthermore, for Release 10 victim users, a novel repetitively designing PDCCH scheme is proposed such that the interference can be avoided effectively. Analysis shows that our approach is backward compatible and can support LTE TDD and FDD systems simultaneously. And simulations demonstrate that satisfying performance can be obtained by using our methods.

Enhanced Inter-Cell Interference Coordination in Heterogeneous Networks for LTE-Advanced

As a promising technology, Device-to-Device (D2D) communication can bring some advantages such as high bit rates, low delays, low power consumption by reusing frequency band with the cellular user equipments (UEs). While at the same time, inter-cell and intra-cell interference is inevitable. In this paper, we propose an algorithm Stackelberg game based to jointly allocate power and resources when uplink frequency is shared. Specially, we group evolved NodeB (eNB) and D2D UE to form the seller- buyer pair. In the game, eNB sets prices to reduce the interference that it suffers from, meanwhile maximize its revenue. For given specified prices, the D2D users compete the resources to communicate with each other and reach their individual utility maximization. Simulation results prove that satisfying performance can be achieved by using the proposed mechanisms.

Resource Allocation for Device-to-Device Communication in LTE-A Network: A Stackelberg Game Approach

Device-to-Device Communication Underlaying Cellular Networks: Connection Establishment and Interference Avoidance

In the device-to-device (D2D) underlaying LTE-Advanced (LTE-A) systems, unlike the existing works which formulate the resources sharing problem as a disjoint coalition formation game, in this letter we propose a novel overlapping coalition formation game (OCFG) based scheme to coordinate the interference between these two subsystems. By sharing uplink spectrums, in this game each D2D pair is allowed to join multiple coalitions simultaneously to improve the spectral efficiency and maximize the system utility. The merge-and-split rule is designed to adapt to the dynamic environment and a discrete-time Markov chain based analysis is utilized to present the stability. Compared with traditional methods, simulations demonstrate the significant performance enhancement of the proposed algorithm in terms of the complexity and D2D system sum throughput.

Shaoyi Xu

Papers

Effective Interference Cancellation Mechanisms for D2D Communication in Multi-Cell Cellular Networks

Enhanced Inter-Cell Interference Coordination in Heterogeneous Networks for LTE-Advanced

Resource Allocation for Device-to-Device Communication in LTE-A Network: A Stackelberg Game Approach

Device-to-Device Communication Underlaying Cellular Networks: Connection Establishment and Interference Avoidance

Overlapping coalition formation games based interference coordination for D2D underlaying LTE-A networks