Current Issue : April-June Volume : 2025 Issue Number : 2 Articles : 5 Articles
Underwater optical communication has emerged as an essential tool for exploring oceanography and marine resources for underwater vehicles or robots in recent years. Current techniques mostly rely on the paradigm of intensity modulation and direct detection, resorting to more powerful light sources on the transmitting side and more sensitive detectors on the receiving side, thus causing excess energy consumption and system costs. Here, a novel approach, namely, the optical differential communications method (ODCM), is proposed to extend the distance of underwater wireless optical communications in turbid water. The underlying physical reason is explained in theory and demonstrated in experiments. It is found that the stable propagation distance of ODCM could be further extended without relying on intensive light sources, in contrast to conventional methods, showing potential for longer communication ranges. Tests of underwater optical communications are conducted, and the results show that ODCM can significantly reduce the bit error rate (BER) at the same propagation distance or extend the propagation distance for the same BER level of optical signals. As such, this study provides an avenue for long-distance and stable underwater wireless optical communications in turbid environments....
Multiple input-multiple output (MIMO) is a key enabling technology for the next generation of wireless communication systems. However, one of the main challenges in the implementation of MIMO system is the complexity of the detectors when the number of antennas increases. This aspect will be crucial in the implementation of future massive MIMO systems. A flexible design can offer a convenient tradeoff between detection complexity and bit error rate (BER). Deep learning (DL) has emerged as an efficient method for solving optimization problems in different areas. In MIMO communication systems, neural networks can provide efficient and innovative solutions. This paper presents an efficient DL-based signal detection strategy for MIMO communication systems. More specifically, a preprocessing stage is added to label the input signals. The labeling scheme provides more information about the transmitted symbols for better training. Based on this strategy, two novel schemes are proposed and evaluated considering BER performance and detection complexity. The performance of the proposed schemes is compared with the conventional one-hot (OH) scheme and the optimal maximum likelihood (ML) criterion. The results show that the proposed OH per antenna (OHA) and direct symbol encoding (DSE) schemes reach a classification performance F1-score of 0.97. Both schemes present a lower complexity compared with the conventional OH and the ML schemes, used as references. On the other hand, the OHA and DSE schemes have losses of less than 1 dB and 2 dB in BER performance, respectively, compared to the OH scheme. The proposed strategy can be applied to adaptive systems where computational resources are limited....
A wireless communication intelligent anti-jamming decision algorithm based on Deep Reinforcement Learning (DRL) can gradually optimize communication anti-jamming strategies without prior knowledge by continuously interacting with the jamming environment. This has become one of the hoest research directions in the field of communication anti-jamming. In order to address the joint anti-jamming problem in scenarios with multiple users and without prior knowledge of jamming power, this paper proposes an intelligent anti-jamming decision algorithm for wireless communication based on Multi-Agent Proximal Policy Optimization (MAPPO). This algorithm combines centralized training and decentralized execution (CTDE), allowing each user to make independent decisions while fully leveraging the local information of all users during training. Specifically, the proposed algorithm shares all users’ perceptions, actions, and reward information during the learning phase to obtain a global state. Then, it calculates the value function and advantage function for each user based on this global state and optimizes each user’s independent policy. Each user can complete the anti-jamming decision based solely on local perception results and their independent policy. Meanwhile, MAPPO can handle continuous action spaces, allowing it to gradually approach the optimal value within the communication power range even without prior knowledge of jamming power. Simulation results show that the proposed algorithm exhibits significantly faster convergence speed and higher convergence values compared to Deep Q-Network (DQN), Q-Learning (QL), and random frequency hopping algorithms under frequency sweeping jamming and dynamic probabilistic jamming....
Satellites in LEO (Low Earth Orbits) are closest to the Earth’s surface, having the smallest coverage area compared to other orbits, depending on altitude and elevation angle, and providing relatively too short visibility and communication duration, in range of (2 - 15) minutes. Communication duration represents the key performance indicator for LEO satellite communication systems. For longer communication sessions, more satellites must be involved, and the signals must be handed over from one satellite to the next to provide uninterrupted real-time services to the appropriate user or ground station. This leads to the concept and structure of the satellites organized in the constellation. Communication window (visibility window) depends on the designed horizon plane width determined by licensed elevation angle. For the appropriate calculations, a satellite from the Starlink constellation at altitude of 550 km is considered, observed under licensed designed elevations of 40˚ and 25˚. Calculations under two designed elevation levels confirmed the wider horizon and consequently longer communication under the lower elevation....
When signals are sent from a source to a destination that is located at a great distance, the effectiveness of the transceiver signals may decline. During the process of signal transmission, the addition of a new node may improve the overall architecture of the network, which can help avoid a decrease in efficiency. The architecture, which is based on a Wireless Local Area Network (WLAN), functions as an intranet and works over long distances with three nodes. OPNET Modeler is used to propose a bridge component that is based on a common intranet network. This component is intended to reduce signal loss. The transmission of the signal is regulated by a large switch, and it is routed via a CS-4000 main bridge, which is connected to the main switch to avoid drops. For email benefits that need span support, it is important to have an Ethernet server to give Nature of Administration (Quality of Service, QoS). In the examination, the information rate is around 780 every second, though the parcel rate is roughly 0.5 each second. Besides, the essential throughput for spans is 260 in the principal seconds, and this worth is applied to both general and highlight point associations that are accomplished using the usage of a compelling 1000 Base-T link....
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