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.

The ultraviolet network, with its advantages of high security, non-line-of-sight communication, and all-weather operation, has broad military application potential. This study proposes an ultraviolet random access collaborative networking protocol based on time division multiple access that combines the benefits of synchronous and asynchronous media access control protocols. Considering the physical layer characteristics, the frame structure of the protocol is constructed based on a cross-layer design. Compared with the time division multiple access protocol, the proposed protocol can achieve higher throughput with a lower delay and packet loss rate by the dynamic timeslot allocation mechanism. Then, the effects of maximum cache capacity and burst traffic on network performance are investigated. Finally, the conducted network experiments prove the cooperative forwarding and random access capabilities of the ultraviolet random access collaborative networking protocol. The proposed protocol provides a reliable and effective method for independent and flexible ultraviolet networks.

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.

Afterpulsing is a critical non-ideal factor of the single photon avalanche diode (SPAD) at telecommunication wavelength, which limits the performance of a SPAD-based free space optical communication (FSO) system. Afterpulsing probability (AP) is highly dependent on the SPAD detection cycle. In a conventional SPAD-based system, the detection cycle is set to a relatively large constant time length to mitigate afterpulsing. However, it will limit the SPAD counting rate and degrade system performance. In order to improve system performance, a new scheme of the dynamic detection cycle is proposed to adapt to different operation conditions. Then, a multi-exponential model of AP is built and fitted with the test data of the single photon detector QCD-300. Furthermore, based on the joint model of the multi-exponential model of AP and bit error rate (BER) model of the SPAD-based FSO system, a simple and effective optimization algorithm is developed to optimize the detection cycle. And the optimization of the detection cycle under different operation conditions is also investigated. The results indicate that optimal detection cycle is dominated by signal light, background radiation, and SPAD gate length. Compared with a conventional scheme with a constant detection cycle, the proposed scheme with the dynamic detection cycle can improve system error performance effectively.

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.

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.