Ultraviolet (UV) communication has been the topic of extensive recent research due to its non-line-of-sight (NLOS) communication, anti-interference, and high confidentiality. Given the lack of the UV Media Access Control (MAC) protocol, this paper proposes a UV lossless contention MAC (UVLLC-MAC) protocol creatively. This MAC protocol is based on the superposition logic of UV power, which effectively reduces the collision loss of multi-node contention access. The basic working mechanism and protocol flow are given in detail, and the network performance is simulated and analyzed mathematically based on a four-node UV network. Comparing with the slotted ALOHA protocol, the simulation results indicate that the network has a higher throughput and lower delay under the protocol. The practical networking of four communication terminals is designed and implemented, and the effectiveness of the new UVLLC-MAC protocol is fully verified.

In order to detect weak light from background radiation, utilizing an array of Geiger-mode avalanche photodiodes (GM-APDs) as a detector in the receiver is researched. First, the principle of a GM-APD operated in gated mode is analyzed. Based on the Poisson random process of arrival of photons, the trigger probability of a single GM-APD has been computed. Then, according to the trigger probability, a new bit error rate (BER) model of a photon-counting array receiver system is built, and the expression of BER is derived based on the quantum efficiency, signal photons, background photons, dark carriers, and the number of GM-APDs in array. Using the BER expression, the error performance of a new photon-counting array receiver system can be predicted rapidly. Furthermore, the error performance of a system based on an array of GM-APDs is investigated. The simulation results indicated that maintaining the ratio of signal photons and background photons above 1 is necessary for system operation. When background noise is limited to the acceptable range, maintaining a certain scale of GM-APDs (above 20) in array can greatly reduce the demand of transmitting power. Compared with achieving target BERs of ${10}^{-6}$ and ${10}^{-9}$, preserving a BER of ${10}^{-3}$ and making use of error correction coding can further improve the receiving sensitivity to 5–8 dB.

Ultraviolet (UV) networks are important approaches to modern wireless communications owing to their unique characteristics, such as non-line-of-sight communication, strong anti-interference ability, and all-weather working mode. Given the lack of media access control (MAC) protocols suitable for UV networks at present, a novel UV lossless contention MAC (UVLLC-MAC) protocol is proposed herein based on UV physical properties. A fully connected finite-population multinode UV model is adopted, and its network performance is systematically derived and mathematically analyzed under the UVLLC-MAC protocol. Compared with the time-slot ALOHA protocol, the UVLLC-MAC protocol achieves 36.7% better throughputs, with 13.2% drop in packet loss rates, and the excellent performance of the protocol is obtained and fully verified. The UVLLC-MAC protocol can provide guidance for multinode and multiservice UV networking.

Ultraviolet (UV) communication, with its excellent characteristics of non-line-of-sight propagation, high confidentiality, and flexible networking, has gradually gained traction in the field of research. The UV media access control (MAC) protocol is relatively lacking at present, and the UV lossless contention MAC (UVLLC-MAC) protocol designed by our team earlier is limited by the predictability of communication network topology; hence, it is not applicable to multinode and multi-data networks. In order to be applicable to multinode network and satisfy the quality of service (QoS) for various data, an enhanced UVLLC-MAC (eUVLLC-MAC) protocol is proposed based on the binary exponential backoff (BEB) and UVLLC protocols. A two-dimensional Markov chain is established to analyze the network performance, and the throughput and delay expressions of the UV network are derived systematically. Subsequently, the effects of reset probability, maximum backoff order, and priority types on network performance are analyzed, and the protocol parameters are optimized to obtain the best network performance. Finally, it is observed that compared with the BEB and UVLLC-MAC protocols, the network under the eUVLLC-MAC protocol can obtain better performance in throughput, packet loss rate and delay comprehensively, which demonstrates the effectiveness of the proposed protocol. Additionally, the eUVLLC-MAC protocol can provide guidance for multinode and multi-data UV networking.

More developed marine sensors for various applications has induced a rapid increase in marine data. The feedback from these marine data becomes challenging due to the backward marine communication techniques. The space–air–ground–sea integrated network (SAGSIN) provides a possible solution to solve this challenge by making use of the advantages of different networks. However, how to coordinate these networks and manage heterogeneous resources to satisfy the communication requirements of different marine applications remains to be solved. In this article, we investigate the resource management problem of SAGSIN for marine applications. A resource management architecture is proposed in which software-defined networking (SDN) controllers are employed. Based on this architecture, heterogeneous resources can be scheduled, and the data from devices with different communication modes can be transmitted via SAGSIN without changing the communication mode of the devices. We further propose two multiagent deep reinforcement learning resource management schemes to help individual devices find optimal access and resource allocation decisions to feed their data back to the terrestrial data centers. The design of these proposed schemes fully considers the scarce communication resources of marine scenarios, which makes data feedback more communication efficient while satisfying quality of service (QoS) requirements. Simulation results show that the improved MA_SDN_Centralized resource management scheme can significantly reduce the blocking probability of the system with guaranteed QoS, while reducing the communication overhead of learning.

Ultraviolet (UV) networks, owing to their advantages of low eavesdropping rates, low background noise, strong anti-interference abilities, and non–line-of-sight (NLOS) communication, have high prospects for application in the complex electromagnetic environment. In this study, UV network coverage was systematically evaluated based on the NLOS channel. Combined with a designed node model and a specific communication mode, a two-dimensional network coverage model was established and expressions of network coverage area and connectivity were derived mathematically. Subsequently, the effects of the transceiver elevation combination, number of nodes, data rate, and transmission power on the network coverage performance were analyzed, and the communication parameters were optimized to match different network scenarios. The results show that the bigger the transceiver elevation combination, the more stringent the communication parameters required by the UV network coverage. Finally, a coverage evaluation experiment with four-node network was conducted. This study provides theoretical reference information for actual network deployment.