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.

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.

Researchers are interested in unmanned aerial vehicles (UAVs) because they have many uses in current 5G and future 6G networks and are safer than human-operated vehicles. Terahertz (THz)-band communications are a possible option in 6G for fast communication. THz wireless communication between UAVs is taken into consideration in this work. Different fading channels, which are significant influencing factors in THz communication channel modeling, are used to analyze the performance of UAV communications in THz networks. Consideration must be made to the structure, wireless channel parameters, and transmission characteristics when evaluating the performance of wireless technology. Nakagami-m, Rician, Weibull, and Rayleigh fading channels are all taken into consideration, along with log-normal fading. Moreover, an optimization algorithm for the THz channel is presented, which is meant to minimize transmission power by optimizing the trajectory of uplink and downlink transmissions between the UAV and users. The equations of the UAV locations and the transmission power optimization of each user are derived. Analytical formulations regarding capacity, outage probability, and bit error rate (BER) are generated when performance-influencing factors are taken into account. The analytical analysis is supported by the numerical results that are provided.

This study analyzes optical code division multiplexed access system coding with two different types of spectral amplitude coding (SAC): Double Weight (DW) codes and Multiple Diagonal (MD) codes. These two encoding types differ in code structure and channel bandwidth length (the number of wavelengths representing the channel’s bandwidth), as well as Q-Factor, BER, and MAI values. This study analyzes systems with different number of users over single-mode optical fiber and presents a comparison of both. DW codes have a shorter length code than MD codes, and although this technique can generate unique code words for each user, it will break the system using MD encoding. This is another reason to increase bandwidth for MD codes.

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.