As the rollout of 4G mobile communication networks takes place, representatives of industry and academia have started to look into the technological developments toward the next generation (5G). Several research projects involving key international mobile network operators, infrastructure manufacturers, and academic institutions, have been launched recently to set the technological foundations of 5G. However, the architecture of future 5G systems, their performance, and mobile services to be provided have not been clearly defined. In this paper, we put forth the vision for 5G as the convergence of evolved versions of current cellular networks with other complementary radio access technologies. Therefore, 5G may not be a single radio access interface but rather a “network of networks”. Evidently, the seamless integration of a variety of air interfaces, protocols, and frequency bands, requires paradigm shifts in the way networks cooperate and complement each other to deliver data rates of several Gigabits per second with end-to-end latency of a few milliseconds. We provide an overview of the key radio technologies that will play a key role in the realization of this vision for the next generation of mobile communication networks. We also introduce some of the research challenges that need to be addressed.

The exploitation of unlicensed bands by the LTE-advanced (LTE-A) system has become a reality through the proposal of licensed assisted access (LAA) that relies on the carrier aggregation concept within the 3GPP framework. The efficient coexistence of LTE-A and WiFi in the unlicensed spectrum bands requires advanced intelligent techniques. This paper first investigates the concept of LAA, which consists of four main functionalities: 1) carrier selection (CS); 2) listen-before-talk; 3) discontinuous transmission (DTX); and 4) transmit power control (TPC). Second, the LAA functionality implementation is provided using an open source LTE-A downlink link level simulator. Third, we devise an enhanced learning technique for CS and DTX for efficient coexistence among LTE-A and WiFi users. In particular, we provide a Q-learning mechanism for the advanced learning of the unlicensed band activity resulting in the efficient coexistence. Finally, we enhance the coexistence further through a double Q-learning method as a proposal for CS that takes into account both DTX and TPC improving both LTE and WiFi performance. Simulation results are provided for all the use cases that reveal the benefit of exploiting unlicensed bands in next generation mobile cellular networks.

Extended reality (XR) would become the main enabler of future immersive experience services. The challenge today is how to make this new set of immersive experience services running through a mobile network such as beyond 5G efficiently in terms of latency and Quality of experience (QoE). Academics and industry have already started to study and provide solutions towards enabling XR services in beyond 5G networks. These solutions affect both the network and the service elements by either introducing new ones or modifying existing ones. In the present paper, we proffer an extensive survey in this topic with details on the solutions proposed by academia per part of the network, i.e. radio access, core, edge etc. Moreover, we provide a thorough overview of 3rd Generation Partnership Project (3GPP) standards in Releases 17 and 18 focusing on the proposed solutions, Key Performance Indicators (KPIs), services and network elements. Finally, we summarize the lessons gained from this survey and draw the attention regarding open affairs for further research exploration for enabling XR services in beyond 5G networks and towards 6G.