Several enabling technologies are being explored for the fifth-generation (5G) mobile system era. The aim is to evolve a cellular network that remarkably pushes forward the limits of legacy mobile systems across all dimensions of performance metrics. One dominant technology that consistently features in the list of the 5G enablers is the millimeter-wave (mmWave) massive multiple-input-multiple-output (massive MIMO) system. It shows potentials to significantly raise user throughput, enhance spectral and energy efficiencies and increase the capacity of mobile networks using the joint capabilities of the huge available bandwidth in the mmWave frequency bands and high multiplexing gains achievable with massive antenna arrays. In this survey, we present the preliminary outcomes of extensive research on mmWave massive MIMO (as research on this subject is still in the exploratory phase) and highlight emerging trends together with their respective benefits, challenges, and proposed solutions. The survey spans broad areas in the field of wireless communications, and the objective is to point out current trends, evolving research issues and future directions on mmWave massive MIMO as a technology that will open up new frontiers of services and applications for next-generation cellular networks.

With 5G Phase 1 finalized and 5G Phase 2 recently defined by 3GPP, the mobile communication community is on the verge of deciding what will be the Beyond-5G (B5G) system. B5G is expected to further enhance network performance, for example, by supporting throughput per device up to terabits per second and increasing the frequency range of usable spectral bands significantly. In fact, one of the main pillars of 5G networks has been radio access extension to the millimeter-wave bands. However, new envisioned services, asking for more and more throughput, require the availability of one order of magnitude more spectrum chunks, thus suggesting moving the operations into the THz domain. This move will introduce significant new multidisciplinary research challenges emerging throughout the wireless communication protocol stacks, including the way the mobile network is modeled and deployed. This article, therefore, provides a brief survey of the challenges and opportunities of THz band operation in wireless communication, along with some potential applications and future research directions.

Future cellular systems will employ the so-called big three technologies: UDN, massive MIMO, and mmWave (and/or terahertz) communications. The goal is to support the explosive demands for mobile broadband services foreseen for the next decade. In this work, we investigate the joint impact of the three technologies. Using system-level simulations, we evaluate the performance of two-tier cellular networks with μ Wave macrocells and densely deployed mmWave small cells. Our results show that much higher capacity can be realized with UDNs than in macrocell-only setups. The results also reveal that performance does not scale proportionally with increase in the employed mmWave bandwidth. The corresponding increase in noise (due to larger bandwidths) reduces the SINR. Outdoor users experience promising data rates notwithstanding, but the throughputs of indoor users are highly degraded. This is due to the additional wall and indoor losses (on top of the inherently high path loss at mmWave frequencies), which further reduce the SINR of indoor users. Therefore, techniques that significantly enhance the SINR are highly import ant design considerations in unleashing the amazing prospects and potentials of mmWave UDNs.

In this paper, we present an Internet of Things (IoT)-based health care system implementation scheme using Hidden Markov Model (HMM) chain and ElectroCardioGram (ECG) sensors within the context of e-Health. The scheme aims to facilitate improved monitoring and timely intervention for Cardio Vascular Diseases (CVD) patients thereby enhancing medical services for such patients. As real-time monitoring of patients from different locations remains a critical challenge for IoT-based health care systems, this implementation employs patient path estimator, patient table and alert management schemes within the hospital to facilitate the localisation and timely intervention for the treatment of CVD patients.

The new developments in mobile edge computing (MEC) and vehicle-to-everything (V2X) communications has positioned 5G and beyond in a strong position to answer the market need towards future emerging intelligent transportation systems and smart city applications. The major attractive features of V2X communication is the inherent ability to adapt to any type of network, device, or data, and to ensure robustness, resilience and reliability of the network, which is challenging to realize. In this work, we propose to drive further these features by proposing a novel robust, resilient and reliable architecture for V2X communication based on harnessing MEC and blockchain technology. A three stage computing service is proposed. Firstly, a hierarchcial computing architecture is deployed spanning over the vehicular network that constitutes cloud computing (CC), edge computing (EC), fog computing (FC) nodes. The resources and data bases can migrate from the high capacity cloud services (furthest away from the individual node of the network) to the edge (medium) and low level fog node, according to computing service requirements. Secondly, the resource allocation filters the data according to its significance, and rank the nodes according to their usability, and selects the network technology according to their physical channel characteristics. Thirdly, we propose a blockchain-based transaction service that ensures reliability. We discussed two use cases for experimental analysis, plug-in electric vehicles in smart grid scenarios, and massive IoT data services for autonomous cars. The results show that car connectivity prediction is accurate 98% of the times, where 92% more data blocks are added using micro-blockchain solution compared to the public blockchain, where it is able to reduce the time to sign and compute the proof-of-work (PoW), and deliver a low-overhead Proof-of-Stake (PoS) consensus mechanism. This approach can be considered a strong candidate architecture for future V2X, and with more general application for everything-to-everything (X2X) communications.