Editorial

Following the great success of 2G and 3G mobile networks and the fast growth of 4G, the next generation mobile networks or 5th generation wireless systems (in short 5G) was proposed aiming to provide infinite networking capability to mobile users. Different from 4G, 5G is much more than increased maximum throughput. It aim to involve and benefit from many current technical advances including massive dense networks, interference and mobility management, Internet of Things (IoT), pervasive and social computing, mobile ad hoc networks (MANET), cognitive radio, World Wide Wireless Web (WWWW), cloud computing, IPv6, and so on. How 5G should and will be, what will be the keys for 5G? What is the perspective of 5G architecture and technologies? How to effectively apply and benefit from the above technologies and make them intelligently interoperate together? How can 5G stimulate our innovation for the next generation of mobile networks and services? Obviously, integrating all above existing advanced technologies and innovating new techniques for 5G bring extreme challenges on 5G networks and services in both research and development. This study has just initiated in both industry and academia, but with great fervor all over the world.

This special issue features six selected papers with high quality. The first article, “D2D Communication Meets Big Data: From Theory to Application”, authored by Liang Zhou, proposed a systematic solution for large-scale video transmissions over D2D communications in order to overcome the challenges of D2D communications, such as limited storage capacity, discrepant computational ability, dynamic communication environment, random network establishment, and the diverse services of the large scale video applications.

The second article titled “Software-Defined Wireless Transport Networks for Flexible Mobile Backhaul in 5G Systems” presented the motivation for introducing programmability concepts in wireless transport networks and illustrated the applicability of control plane with two use cases for dynamically controlling wireless transport nodes in 5G networks towards Software Defined Wireless Transport Networks (SDWTNs).

In the next article with the title “Context-Aware User Association for Energy Cost Saving in A Green Heterogeneous Network with Hybrid Energy Supplies”, the authors studied the user association problem to reduce the total energy cost of a heterogeneous cellular network with wireless backhauls and hybrid energy supplies. By considering both the power consumption of a base station and backhaul links, two algorithms were proposed to exploit available context-aware information of a network in a centralized way or a distributed way in order to find a feasible and near-optimal solution. Network architecture knowledge, users’ data requirements, and available green energy are investigated in solving energy cost saving problems.

Cognitive radio (CR) is widely regarded as one of the most promising technologies for 5G wireless communications. The fourth article titled “Dynamic Spectrum Access Algorithm Based on Game Theory in Cognitive Radio Networks” proposed a dynamic spectrum access (DSA) algorithm based on game theory. It jointly performs spectrum leasing and interference mitigation among secondary users. The proposed scheme enables secondary users to efficiently utilize the licensed spectrum shared with primary users in a dynamic environment while maximizing the spectrum utilization.

Cloud computing offers a new way of service provision and will definitely play an important role in the next generation mobile networks and services. Cloud data protection is a crucial issue that impacts the success of cloud computing and may impede the development of 5G. The fifth article, “Controlling Cloud Data Access Based on Reputation” proposed a practical scheme to securely access cloud data and effectively reduce access risk according to the reputations of cloud computing entities. By applying proxy re-encryption, cloud data access can be efficiently controlled in the situation that the data owner is not available online or does not know how to control the access.

The last article titled “Efficiently Predicting Trustworthiness of Mobile Services Based on Trust Propagation in Social Networks” investigated efficient trust prediction in a large-scale social network. The authors proposed a trust propagation method that exploits the peculiar properties of social networks and incorporates a landmark-based method with preprocessing to improve the efficiency of trust prediction. In this method, a small number of landmark users in the social network are firstly selected as referees in trust propagation, and the trust between these landmark users and the other users are then pre-computed. The trust between two indirectly connected users is finally estimated via aggregating the referrals provided by the landmark users.