The Internet of Underwater Things (IoUT) requires robust security architectures capable of operating under severe constraints: high latency, low bandwidth, and limited energy. Traditional blockchain-based solutions are often infeasible due to their heavy synchronization and mining requirements. In this work, we propose U-Tangle, a lightweight, Directed Acyclic Graph (DAG)-based security architecture inspired by Internet of Things Applications (IOTA) but optimized for Underwater Acoustic Sensor Networks (UASNs). Unlike existing blockchain schemes, U-Tangle eliminates mining and linear block generation, utilizing a collaborative validation mechanism where each transaction confirms previous ones. We integrate lightweight cryptography (ED25519, X25519, Ascon) to ensure confidentiality and integrity with minimal overhead. Extensive Python-based simulations show that U-Tangle achieves sub-second end-to-end authentication latency (316.04 msec with 95% CI [310.56, 321.52] over 30 runs in Scenario S1 with N=200) while reducing energy consumption by avoiding continuous ledger synchronization. Comparative insights against representative block-based approaches are discussed based on published system-level characteristics. Our security analysis confirms resilience against replay, Sybil, and Man-in-the-Middle attacks without relying on online centralized authorities. This work provides a scalable, energy-efficient alternative for securing critical underwater infrastructure.

The advances accomplished in the modern wireless network are leading to the development of efficient antenna devices that are able to achieve high requirements especially as regards the 5G next generation systems. Although a significant number of theoretical recommendations already exist in this context, the most of the used network simulators do not offer the possibility to emulate the next generation systems. The present paper provides an overview about URPA (Uniform Rectangular Planar Array) massive MIMO (Multiple Input Multiple Output) with reference to PER (Packet Error Rate) and channel performance; in addition, a support for emulating such systems, extending Omnet++ network simulator features, is presented.

Massive MIMO Systems certainly represent one of the most significant technology with regard to 5G systems; they are able to ensure high capacity performance through a better exploitation of the total radiated power with respect, for example, to sectorized and omnidirectional antennas. Unfortunately, because of the important amount of resources involved for achieving high data rates, these types of systems, could be affected from significant waste of energy especially if an appropriate mechanism that handles the energy consumption of nodes is not designed. Therefore, limiting the energy consumption of nodes relating to systems using very high data rates, constitutes a critical task because energy waste occur at the transmitter as well as at the receiver due to different reasons. In view of these considerations, in the present paper, we propose a novel algorithm having variable data rate and a mechanism for optimizing the energy consumption of nodes that addresses the problem both for the transmitter and the receiver.

In the design of a Directional Medium Access Control (MAC) protocol for pervasive environments such the Mobile Ad hoc Networks (MANET), one of the most known problems that needs to be properly addressed is the deafness problem. Deafness could produce a large amount of collisions in the network and consequently a not negligible waste of energy. In this paper. we propose to partially mitigate this issue through the implementation of a Round-Robin MAC (RR-MAC) approach that provides for a logical sectorization of the transmission plane, limiting the maximum beamforming time of nodes, in order to reduce the frame collisions in the channel and at the same time to ensure an acceptable overall throughput in the network.

The progress accomplished in the modern wireless network are leading to the development of efficient antenna devices that are able to achieve high level requirements with regard to the 5G next generation systems. Although a significant number of theoretical recommendations can already be found in this context, the most known used network simulators do not provide for a support concerning the most recent wireless network requirements like the IEEE802.11ac and, simultaneously, they do not offer the possibility to use the latest massive MIMO (Multiple Input Multiple Output) antenna systems. In view of this, we propose to extend the default features provided by the Omnet++ network simulator with the intention of actualizing the existing simulation instruments to be suitable also for 5G wireless network communication systems.

The advances accomplished in the modern wireless network design are requiring increasingly more efficient high-performing antenna devices in order to satisfy the requirements provided for the 5G next generation systems; although a considerable number of theoretical proposals already exist in this field the most common used network simulators do not offer a support for the latest wireless network standards such as the IEEE802.11acand, at the same time, they do not afford the possibility to utilise the latest up-to-date high performance massive MIMO (Multiple Inputs Multiple Output) antenna systems.In view of this, we propose to extend the basic feature offered by the Omnet++ network simulator with the aim of actualizing the current simulation instruments for enabling the emulation of 5G wireless network scenarios.

Simulations in complex network scenario environments such as Adaptive Beamforming Networks (ABFN), are very expensive in terms of computational costs. To reduce the overall computational burden, we propose to integrate Omnet++ simulator with Matlab in order to provide a co-simulation model for allowing an efficient communication system that is able to emulate high complexity simulation contexts.

The use of adaptive antenna systems enables the improvement of the overall wireless network capacity, especially in Mobile Ad hoc Networks (MANET) environments in which the quality of the communication is closely related to the Signal-to-Noise-Ratio (SNR) measured in the channel. Unfortunately, most of used adaptive algorithms such as Least Mean Square (LMS) and Constant Modulus Algorithm (CMA), because are strongly related to the step size value and to the error metric estimation, usually present a speed convergence problem. In this paper, a new Variable Error Metric (VMA) adaptive Algorithm is proposed in order to limit the level of dependency between the algorithms and step size also reducing the slowing effect introduced by Mean Square Error (MSE) criterion used for example by LMS algorithm.

Smart Antenna Systems (SAS) are providing a strong increasing impact in digital wireless communication systems.Due to their great advantages regarding nodes power saving and coverage enhancing, SAS are largely employed on pervasive network environments such as MANET.Because almost the whole of existing network simulators use omnidirectional antennas on nodes, we propose a new version of Inet framework of Omnet++ that extends its operation also for network scenarios in which nodes are equipped with directional antennas.Furthermore, we created a new directional antenna module that simulates the behaviour of a Phased Array System and a very simple algorithm for power management in channel.The new proposed model presents some modifications to key-modules that are involved in a normal wireless communication scenario, in order to support asymmetrical communications between nodes.

Mobile ad hoc networks have a highly dynamic topology due to terminal mobility. Ad hoc routing protocols can cope with this mobility as they search for an alternative route when a currently-in-use path breaks. Despite of their ability to recover from path failures, the time elapsed until the route is reestablished deteriorates network performance. MANET routing protocols can detect link breakages faster when Link Layer Feedback (LLF) mechanisms are used. In this paper we evaluate the advantages and drawbacks of using feedback mechanisms. Our simulation results show that these mechanisms are appropriate for low mobility conditions. In contrast, feedback is not adequate for scenarios where terminals move faster due to frequent collisions mistaken as link breakages.