Editorial: Device-to-Device Communication in 5G Networks
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Device-to-device (D2D) communication technology for fifth generation (5G) mobile networks enables user equipment (UE) to communicate directly with other UEs without or with partial involvement of the network infrastructure, such as mobile access points or mobile base stations. There are popular low-level D2D techniques available for short-range wireless transmissions, such as Bluetooth and WiFi-Direct, and typically they use license-exempt bands. Most of the cellular technologies, however, do not support direct over-the-air communication between end users. The traditional cellular network is based on the “cells”, which are the fundamental unit within the radio access network. To achieve the device-centric communication envisaged for 5G networks, there is a need for a fundamental change in the design structure of current cellular networks. This is indeed at the core for device-centric communication, leading to different mobile base station density, micro-clouds on base stations, more alternatives for frequency re-usability, and additional spectrum coexistence of frequency bands.
This special issue broadly covers various aspects of D2D communication in 5G networks. Out of 39 submitted papers, this special issue features 6 selected papers with high quality based on the revision of expert anonymous reviewers.
The first article, “A DOA Estimation Approach for Transmission Performance Guarantee in D2D Communication”, proposes a 2D direction-of-arrival (DOA) estimation algorithm for coherently distributed sources based on conformal array. Authors claim the proposed algorithm has low computational complexity under some conditions. For the condition of a large amount of data, a distributed and parallel scheme is also proposed to accelerate the computing of the proposed algorithm. The effectiveness of the proposed algorithm is verified through a simulation study.
The second paper, “Optimal Virtualized Inter-Tenant Resource Sharing for Device-to-Device Communications in 5G Networks”, focuses on the aspects of D2D users that belong to different virtual network operators (tenants). The paper assumes virtualized and programmable future 5G wireless networks as well as the existence of a cross-tenant orchestrator. The authors then show significant gains in terms of network performance by optimizing resource sharing from the different tenants. The efficacy of the proposed solution compared with legacy approaches through a set of numerical experiments.
The third article, “A Two-Stages Relay Selection And Resource Allocation with Throughput Balance Scheme in Relay-Assisted D2D System” discusses a relay-assisted D2D communication underlying cellular network. The authors deal with the relay selection problem as well as the analysis of throughput unbalance and resource waste problem. In this context, the paper proposes a two-stages method to address the relay selection considering resource allocation with throughput balance. Three throughput balance schemes are evaluated by simulation. Simulation results show that the proposed method improves the throughput of relay-assisted D2D communication with low signaling and measurement overheads.
The fourth paper, “Optimal D2D content delivery for cellular network offloading”, evaluates the throughput performance of a mobile network cell where D2D communication is used to offload the base station of part of its content delivery traffic. The authors characterize optimal content placement for regular caching and coded caching. Numerical results demonstrate significant capacity gains for coded caching, thus justifying the added complexity of D2D communication.
The fifth article, “Speaker Recognition Exploiting D2D Communications Paradigm: Performance Evaluation of Multiple Observations Approaches”, proposes a speaker recognition algorithm for mobile devices based on a multiple-observation approach and the efficient managing of the gathered information using D2D communication. The auuthors propose different fusion and clustering algorithms aimed at efficiently exploiting data coming from the mobile devices. The performance results show that the proposed multiple-observation approach is able to significantly improve the accuracy of the considered speaker recognition algorithm.
Finally, the sixth paper, “Outage Probability of Device-to-Device Communications in Frequency Reuse-1 Networks”, analyzes the outage probability of device-to-device communications in a multi-cell frequency reuse-1 system. The author derivates a formula for the outage probability of a D2D link in the considered context. Based on the performed analysis, the paper also proposes a location-based power control mechanism for D2D communications able to enhance the performance of the D2D link while reducing the transmit power required for communication.
The Guest Editors would like to thank all authors, anonymous reviewers, the Journal manager Dr. Sara Fruner, and the Journal Edit-in-Chief Dr. Imrich Chlamtac for their contributions that helped us achieve this special issue.