IEEE Communications Magazine

Ultra-dense networks (UDNs) constitute one of the most promising techniques for supporting the 5G mobile system. By deploying more small cells in a fixed area, the average distance between users and access points can be significantly reduced; hence, dense spatial frequency reuse can be exploited. However, severe interference is the major obstacle in UDNs. Most contributions deal with the interfere... View full abstract»

Heterogeneous wireless networks (HWNs), composed of densely deployed base stations of different types with various radio access technologies, have become a prevailing trend to accommodate ever increasing traffic demand. Nowadays, users rely heavily on HWNs for ubiquitous network access to support critical applications such as financial transactions, e-health, and public safety. Cyber risks, repres... View full abstract»

By means of network densification, ultra dense networks (UDNs) can efficiently broaden the network coverage and enhance the system throughput. In parallel, unmanned aerial vehicle (UAV) communications and networking have attracted increasing attention recently due to their high agility and numerous applications. In this article, we present a vision of UAV-supported UDNs. First, we present four rep... View full abstract»

To meet the explosive growth of mobile data traffic, ultra-dense networks have emerged to enhance spatial and spectral efficiency. Densely deployed small cell architecture faces several major challenges, including low infrastructure utilization ratio, severe inter-cell interference, and so on. In this article, we aim to develop a novel super base station (SupBS) network architecture to tackle thes... View full abstract»

The ultra-dense network (UDN) is a promising technology to further evolve wireless networks and meet the diverse performance requirements of 5G networks. With abundant access points, each with communication, computation, and storage resources, the UDN brings unprecedented benefits, including significant improvement in network spectral efficiency and energy efficiency, greatly reduced latency to en... View full abstract»

Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low latency through the use of dense sub-6 GHz and millimeter-wave small cells with different antenna configurations. Existing work has widely studied spectral and energy efficiency in such networks and shown that high spectral and energy efficiency can be achieved. This article investigates the benefits of heterogeneous ult... View full abstract»

Ultra-dense heterogeneous networks (Ud-HetNets) have been put forward to improve the network capacity for next-generation wireless networks. However, counter to the 5G vision, ultra-dense deployment of networks would significantly increase energy consumption and thus decrease network energy efficiency, suffering from the conventional worst case network design philosophy. This problem becomes parti... View full abstract»

Due to a tremendous increase in mobile traffic, mobile operators have started to restructure their networks to offload their traffic in the unlicensed bands. The 3GPP new technologies of LAA and LTE-U employ an unlicensed radio interface that operates over the 5 GHz unlicensed band to leverage the radio resources for operators' transmissions. 5G relies on spectrum extension using multi-radio inter... View full abstract»

This article investigates the prominent dilemma between capacity and reliability in heterogeneous ultra-dense distributed networks, and advocates a new measure of effective capacity to quantify the maximum sustainable data rate of a link while preserving the quality of service of the link in such networks. Recent breakthroughs are brought forth in developing the theory of the effective capacity in... View full abstract»

To cope with the tremendous growth in mobile data traffic, ultra-dense networks (UDNs) will be deployed in the future cellular network. Meanwhile, the enormous amount of available spectrum in millimeter-wave (mmWave) bands can be also exploited to increase the wireless link capacity. In accordance with these trends, this article introduces a novel hierarchical software-defined networking (SDN) arc... View full abstract»

Heterogeneous ultra dense networks (HUDNs) and non-orthogonal multiple access (NOMA) have been identified as two proposing techniques for 5G mobile communication systems due to their great capabilities to enhance spectrum efficiency. This article investigates the application of NOMA techniques in HUDNs to support massive connectivity in 5G systems. In particular, a unified NOMA framework is propos... View full abstract»

Terahertz band (0.1-10 THz) communication is envisioned as a key technology to support ultra-broadband wireless systems for beyond 5G. For realization of efficient wireless communication networks in the THz band, it is imperative to develop channel models that can accurately and efficiently characterize the THz spectrum peculiarities. This article provides an in-depth view of channel modeling in t... View full abstract»

In the millimeter-wave (30-300 GHz) and terahertz (0.1-10 THz) frequency bands, the high spreading loss and molecular absorption often limit the signal transmission distance and coverage range. In this article, four directions to tackle the crucial problem of distance limitation are investigated, namely, a distance-aware physical layer design, ultra-massive MIMO communication, reflectarrays, and i... View full abstract»