Wireless communication technologies are becoming increasingly important in today's rapidly developing technological world. The widespread use of the Internet, the popularity of smartphones and other mobile devices, and the rise in industrial applications have all contributed to the start of a new wireless communication technology revolution. As a result, 6th generation wireless communication technology (6G) is intended to provide enhanced performance features such as faster speeds, larger bandwidths, lower latency, higher connection density, and improved reliability. mmWave-band communications are already having a vital impact on 5G. Similarly, communications in the TeraHertz (THz)-band will be crucial for the next 6G and beyond. THz, mmWave, and RF communication technologies are important components of 6G, and comparisons between these technologies are crucial in the design and development of the 6G network. In this paper, a study of THz, mmWave, and RF communication technologies is presented with their roles in developing the 6G network. Firstly, an overview of THz, mmWave and RF technologies is presented. Then, the conventional channel modeling is discussed. After that, artificial intelligence (AI) based channel modeling is presented. Furthermore, challenges and future research directions are highlighted based on the current state of the art.

The transition from 5G to 6G will result in an explosion of Internet of Things (IoT) devices that provide pervasive and constant connection across all spheres of human activities. In this regard, non-terrestrial networks (NTNs) will play a crucial role in supporting and supplementing terrestrial systems in order to cope with such a vast number of IoT devices and to fulfill the massive capacity needs of the most sophisticated of them. This study investigates the implication of several multiple access techniques for 6G enabled NTN-assisted IoT technologies. First, general architecture of NTN, NTN-assisted IoT technologies, and key features and challenges of NTNs are presented. Then, different types of multiple access schemes are discussed and compared in the context of NTN-assisted IoT systems. Simulation results are presented and important performance parameters such as energy efficiency and spectrum efficiency are examined for the discussed multiple access schemes. Furthermore, challenges and future research directions are discussed.

Drones are used for public safety missions because of their communication capabilities, unmanned mission, flexible deployment, and low cost. Recently, drone-assisted emergency communication systems in disasters have been developed where instead of a single large drone, flying ad hoc networks (FANETs) are proposed through clustering. Although cluster size has an impact on the proposed system’s performance, no method is provided to effectively regulate cluster size. In this paper, optimum cluster size is obtained through two distinct meta-heuristic optimization algorithms - the Cuckoo Search Algorithm (CUCO) and the Particle Swarm Algorithm (PSO). Flowcharts and algorithms of CUCO and PSO are provided. A presentation of an analytical investigation based on the Markov chain model is provided. To further validate the analytical study, simulation results are presented. Simulation shows the improvement in terms of throughput and packet dropping rate (PDR).

Towards a future of fully autonomous and intelligent systems, sixth-generation (6G) wireless communication networks are expected to transform client services and apps via the Internet of Things (IoT). Together, the infrastructure and apps should facilitate and enhance intelligent administration of city services, workplaces, and everyday lives. In particular, mission-critical IoT (MC IoT), which is the connection of critical objects to the IoT network that are critical to human life and safety, is of utmost significance. This paper covers MC IoT visions, services, and applications, as well as networking infrastructure. First, visions toward 6G MC IoT are presented in the context of fundamental technological needs, trends, and use cases. Second, the emerging 6G MC IoT services and applications are described. Finally, a networking architecture for 6G MC IoT is provided. There are challenges to the implementation of robust and effective 6G MC-IoT services and applications which are mentioned and future research directions are presented.

The development of sustainable and resilient networking and communication technologies, artificial intelligence, dispersed computing, and beyond 5G are expected to play a crucial role in the realization of Industry 5.0. More specifically, antennas are recognized as a vital technology to support the continuously growing demand for 5G/6G connectivity and data rates. In the development of wireless communication systems, an effective antenna design is critical. In this work, we present the design and modeling of a hexagonal microstrip antenna for using in ultra-wide band applications such as 5G mobile networks. The suggested antenna has a frequency range of 3.3 GHz to 4.5 GHz, dimensions of 20 mm × 14 mm, and is built on a FR-4 substrate, with a relative permittivity of 4.3, and of 1.6 mm in height. It is expected that this antenna will operate in two notched bands with resonance frequencies of 3.3 GHz and 4.5 GHz and a voltage standing wave ratio (VSWR) of less than 2. The proposed antenna, which has been expanded to be a multiple-input multiple-output (MIMO) antenna, was created and modeled using CST Microwave Studio. The comparison against the recent works is given to show the efficiency of the proposed design.

Autonomy and intelligent transportation systems (ITS) have recently shown an increased interest in vehicle ad hoc networks (VANETs). Additionally, the impending 5G and 6G technologies will result in substantial advancements for VANETs. IEEE 802.11p summarizes specifications of physical (PHY) and medium access control (MAC) layers for VANETs. Existing analytical methodologies require improvement despite the fact that performance assessments of IEEE 802.11p MAC have been carried out. Bit error and channel capture influence performance of vehicular communications in real-world transmission. These effects are investigated separately in previous works. In this paper, an extensive study is provided which integrates these two major factors. In VANETs, the influence of channel fading and capture on IEEE 802.11p is investigated analytically using a Markov chain model. For Nakagami-m, Rayleigh, and Rician fading channels, performance impacting factors are taken into account, and relationships between parameters as well as performance metrics are derived. The probability of unsuccessful and successful transmission, outage probability, probability of frame capture, throughput, bit error rate, and delay terms are attained. Moreover, simulation results are provided which verify analytical studies.

Cryptocurrencies acquire user confidence by making the whole creation and transaction history transparent to the public. In exchange, the transaction history accurately captures the complete range of user activities related to cryptocurrencies. In this paper, the use of data mining methods in Bitcoin transactions is analyzed and summarized. Cryptocurrencies, similar to the well-known Bitcoin, were targeted to ensure transaction security and privacy and overcome the drawbacks of traditional banking systems as well as other centralized systems. We also conduct a thorough analysis of the literature on the challenges and applications of electronic currencies. We outline the evolution of digital currency from electronic cash to cryptocurrencies and put the spotlight on the methods used to increase user privacy. We also highlight security threats in the existing cryptocurrency systems that jeopardize the privacy of Bitcoin users. Finally, we identify several research gaps and trends that need to be looked at further.