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Ultraviolet technology has a wide range of applications in military and civilian fields, such as space detection, ultraviolet light guidance, ultraviolet interference, corona discharge detection and military communications. Starting from the single and multiple scattering of ultraviolet light, this paper first introduces the progress of ultraviolet optical communication at home and abroad. Then it analyzes the different links in ultraviolet optical communication. Next, it discusses the pulse broadening effect and atmospheric turbulence of ultraviolet communication in non-direct link ultraviolet communication. Finally, the paper summarizes the ultraviolet Ad Hoc network, and shows the trend of the development of ultraviolet optical communication.

Abstract Delay tolerant networks (DTNs) is a network evolved from mobile networks. Differing from the traditional network, which has a stable end‐to‐end transmission path, DTNs are sparse and intermittently connected mobile ad hoc network, which are widely used in harsh environments, such as battlefields, seabed, space communication networks, and so on. In DTNs, intermittent connectivity, partitioned network, long delays and node mobility characteristics make the network fail to communicate frequently, therefore, how to successfully forward the message is of extreme importance. Up to now, almost all the traditional models in DTNs use the store‐carry‐forward method. This paper proposes a novel clustered DTN routing model based on sensing node relationship strength. The routing mechanism takes advantage of the number of other nodes encountered by the nodes in the process of movement and the changes in the number of nodes to calculate the strength of the relationship between nodes, and clusters DTN routing according to the strength of the relationship between nodes. Moreover, the relationship between nodes in a cluster and other clusters is used to transmit messages between clusters, and messages are transmitted within clusters according to the strength of the relationship between nodes. Simulation results show that the routing mechanism not only increases the success rate of message transmission, but also reduces the transmission delay of messages and improves network performance.

Abstract In unmanned aerial vehicle ad‐hoc network (UANET), the node speed of unmanned aerial vehicles (UAVs) may reach up to 400 km/h. The fast or slow movement of UAV nodes leads to different speeds of topology change of the nodes. Traditional optimized link state routing (OLSR) protocol cannot adaptively adjust the routing update period when the network topology changes, which may lead to the nodes calculating incorrect routing tables. This increases the average end‐to‐end delay and packet loss rate for packet transmission. To enhance the adaptability of OLSR routing protocol to network topology changes, this paper proposes a multi‐agent independent deep deterministic policy gradient‐OLSR (MA‐IDDPG‐OLSR) routing protocol based on distributed multi‐agent reinforcement learning. The protocol deploys DDPG algorithm on each UAV node, and each UAV node adaptively adjusts the Hello and TC message sending intervals, according to the one‐hop neighbouring nodes as well as its own state. Simulation results show that the proposed protocol is able to improve the throughput and reduce the packet loss rate as compared to traditional AODV, GRP, OLSR, and distributed multiple‐agent independent proximal policy optimization‐OLSR (MA‐IPPO‐OLSR), distributed multiple‐agent independent twin delayed deep deterministic policy gradient‐OLSR (MA‐ITD3‐OLSR) routing protocols. Since MA‐IDDPG‐OLSR relies only on local information, there is a minor performance degradation in MA‐IDDPG‐OLSR compared to centralized single‐agent DQN‐OLSR routing protocol. But it is more suitable to a completely distributed UAV network without a centralized node.

This paper proposes an evolved wireless ad hoc network (WANET) in which user equipment (UE) can manage radio resources by itself without the control by infrastructure. There are two independent channels in the proposed WANET, one is a data channel, the other is a tone channel for resource management. UEs allocate, occupy, and return resources by using tones in the tone channel. Although UEs do not exchange channel information with each other, they are able to occupy a clear one-hop area without a hidden node problem by setting the data communication area and the tone communication area differently. A UE occupying a resource performs a real time collision check on the occupied resource, and if a collision is detected, it is able to re-occupy a resource without collision. In this paper, we present the operating principle of the proposed WANET, and design its communication area, and analyze the average resource occupation time. Since the proposed WANET operates in a general communication environment that is not limited to special assumptions, it supports periodic and aperiodic communication and broadcast links and unicast links without hidden node problem, and could be utilized to various communication fields such as drones, vehicles, ships, and smartphones.

This paper presents a comprehensive study of capacity characterization in mobile wireless networks employing directive communications and full-duplex communication technology. We address the impact of nodes’ mobility, directive beams, and full-duplex capabilities on the network capacity. Firstly, we derive the signal-to-interference-plus-noise ratio (SINR) for a reference receiver, considering the combined effects of mobility, directive beams, and full-duplex communications. The derived SINR is then utilized to calculate the network’s capacity. To validate the proposed model, extensive simulations are performed, incorporating various scenarios of mobility levels, self-interference suppression levels in the full-duplex wireless system, and different receiving thresholds. The simulation results confirm the accuracy and effectiveness of the derived SINR-based capacity characterization model under real-world conditions. Furthermore, we study the probability of a receiver simultaneously decoding multiple packets as a function of the receiver’s threshold and full-duplex self-interference suppression. The probability is crucial for assessing the network performance and facilitating future optimization schemes aimed at regulating the number of competing nodes in a given spatial region. The validated model and probability characterization offer valuable insights into network performance evaluation and can be instrumental in devising future efficient optimization strategies for managing network contention at the medium access control and enhancing the network performance.

This paper deals with the tradeoffs between security, real-time and lifetime performance. Due to the multihop nature of communication wireless ad hoc networks are very vulnerable to attacks. Malicious nodes included in a routing path may misbehave and organize attacks such as black holes. Scaling the number of hops for a packet delivery we trade off energy efficiency against security and real-time communication. To study the multihop communication we propose a hierarchical communication model. The REWARD (receive, watch, redirect) algorithm for secure routing is employed as a main example for corrective actions. Symmetrical routing is a distinguish feature of protocols such as REWARD and we outline the threshold of conflict between power-efficient partitioning of communication links and symmetrical routing.

Vehicular ad hoc networks consist of self-organizing nodes using multi-hop wireless links for communication without any infrastructure support. Traditionally, ad hoc routing protocols use the minimum hop count for their routing metric since a smaller number of transmissions is typically equivalent to a higher throughput, lower delay, and minimal power consumption. However, with the muti-rate capability of emerging radio interfaces, e.g., 802.11ax/be standards, the min-hop metric no longer results in high throughput. For instance, if the higher data rate links are selected for the route, it could result in a higher throughput even if the route takes more hop counts. In this paper, we propose a high throughput routing scheme, called MARV, which makes two key contributions. MARV searches for high throughput paths using an on-demand route searching algorithm so that the routing overhead is smaller compared to other multi-rate-aware routing schemes. MARV also searches for multiple paths to maintain both min-hop and high-throughput paths to select the adequate path depending on the data packet size. We conduct simulations to demonstrate that MARV outperforms not only min-hop path metrics but also previously proposed high-throughput metrics.

The increasing demand for Internet of Things (IoT) applications has resulted in vast amounts of data, requiring the utilization of big data analytics. The integration of big data analytics in IoT-based smart cities can greatly benefit from the development of wireless communication protocols, among which the Thread protocol has emerged as a promising option. Thread is IEEE 802.15.4 based and has advanced capabilities like mesh networking, IPv6 support, and multiple gateways providing no single point of failure. This paper presents the design and evaluation of a low-cost mesh network using Raspberry Pi, nRF52840 dongle, and OpenThread 1.2 (i.e., an open-source software implementation of the Thread protocol stack). The research elaborates on the hardware and software solutions used, as well as the network topologies adopted. To evaluate the performance of the developed system, extensive real-time tests are performed, considering parameters, such as jitter, packet loss, and round trip time. These tests effectively demonstrate the effectiveness of the Thread network. Furthermore, the impact of varying payload size and bitrate on the network is analyzed to understand its influence. The behavior of the multi-hop network is also examined under link failure scenarios, providing insights into the network’s robustness. Our findings provide valuable insights for researchers interested in designing low-cost and efficient mesh networks for various IoT applications, including home automation, building/campus monitoring systems, distributed industrial IoT applications, and smart city infrastructure.

In recent years, low-power wide-area network (LPWAN) has received widespread popularity with long-range and wide-area communication at low power for the Internet of Things (IoT) systems. Among many vendors of LPWAN, long-range low-power wireless communications, also called LoRa, is one of the competing standards and is well known in both academia and industrial communities as an emerging research area. Among the LoRa applications, unmanned aerial vehicles (UAV) systems are emerging with the benefits of extended battery life and a long communication range. In this paper, we investigate the network capacity with the mixture of concurrent and sequential transmission (MCST) scheme over LoRa networks. From the simulation results, it can be seen that MCST is suitable for implementation in the LoRa network. Specifically, MCST can achieve higher throughput with low transmission latency and energy consumption compared to the existing CSMA approach LoRa MAC. Besides, we also propose a modified MCST over the LoRa (mMCST/LoRa) scheme to mitigate the transmission latency further. The simulation results reveal a better performance in terms of throughput, latency and energy consumption, regardless of the frame payload size and the number of nodes in the network.

Delay-tolerant networks (DTNs) are networks where there is no immediate connection between the source and the destination. Instead, nodes in these networks use a store–carry–forward method to route traffic. However, approaches that rely on flooding the network with unlimited copies of messages may not be effective if network resources are limited. On the other hand, quota-based approaches are more resource-efficient but can have low delivery rates and high delivery delays. This paper introduces the Enhanced Message Replication Technique (EMRT), which dynamically adjusts the number of message replicas based on a node’s ability to quickly disseminate the message. This decision is based on factors such as current connections, encounter history, buffer size history, time-to-live values, and energy. The EMRT is applied to three different quota-based protocols: Spray and Wait, Encounter-Based Routing (EBR), and the Destination-Based Routing Protocol (DBRP). The simulation results show that applying the EMRT to these protocols improves the delivery ratio, overhead ratio, and latency average. For example, when combined with Spray and Wait, EBR, and DBRP, the delivery probability is improved by 13%, 8%, and 10%, respectively, while the latency average is reduced by 51%, 14%, and 13%, respectively.