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Orbital Angular Momentum for Wireless Communications
摘要： As the traditional resources (frequency, time, space, and so on) are efficiently utilized, it becomes more and more challenging to satisfy the ever-lasting capacity-growing and users-boosting demand in wireless networks. Recently, the EM wave was found to possess not only linear momentum, but also angular momentum. The OAM is a kind of wavefront with helical phase. The OAM-based vortex wave has different topological charges, which are orthogonal to each other, bridging a new way for multiple access in wireless communications. In this article, we introduce the fundamental theory of OAM and the OAM based wireless communications. The research challenges regarding OAM signal generation, OAM beam converging, and OAM signal reception are discussed. Further, we propose a new multiuser access with different OAM-modes in wireless networks, where multiple OAM-modes are used as a new orthogonal dimension for interference avoidance. Simulation results reveal the inherent property of OAM waves and show that OAM based radio transmission can significantly increase spectrum efficiency in wireless networks.
关键词： multiple access,spectrum efficiency,OAM,vortex wave,wireless communications
更新于2025-09-09 09:28:46
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[ACM Press the Thirteenth ACM International Conference - Shenzhen, China (2018.12.03-2018.12.05)] Proceedings of the Thirteenth ACM International Conference on Underwater Networks & Systems - WUWNet '18 - Relay-assisted optical wireless communications in turbid water
摘要： Underwater optical wireless communication (UOWC) systems are subject to severe performance degradation due to undissolved particles that make the water turbid. The point source diffusion of a substance in water creates a Gaussian-distributed attenuation spread for a given time instance, which makes communication challenging. To overcome this issue, we propose a dual-hop UOWC system in which the transmitter-receiver link is assisted by several amplify-and-forward relay nodes. To characterize the performance gains of this relay system, we study the bit error rate assuming on-off keying modulation. We investigate the impact of key system and particle distribution parameters such as the transmit power, the number of relays, and the spatial position of the attenuation spread on the performance.
关键词： relays,Underwater optical wireless communications,amplify-and-forward,submerged particle distributions,bit error rate
更新于2025-09-04 15:30:14
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Fuzzy Based Network Assignment and Link-Switching Analysis in Hybrid OCC/LiFi System
摘要： In recent times, optical wireless communications (OWC) have become attractive research interest in mobile communication for its inexpensiveness and high-speed data transmission capability and it is already recognized as complementary to radio-frequency (RF) based technologies. Light fidelity (LiFi) and optical camera communication (OCC) are two promising OWC technologies that use a photo detector (PD) and a camera, respectively, to receive optical pulses. These communication systems can be implemented in all kinds of environments using existing light-emitting diode (LED) infrastructures to transmit data. However, both networking layers suffer from several limitations. An excellent solution to overcoming these limitations is the integration of OCC and LiFi. In this paper, we propose a hybrid OCC and LiFi architecture to improve the quality-of-service (QoS) of users. A network assignment mechanism is developed for the hybrid system. A dynamic link-switching technique for efficient handover management between networks is proposed afterward which includes switching provisioning based on user mobility and detailed network switching flow analysis. Fuzzy logic (FL) is used to develop the proposed mechanisms. A time-division multiple access (TDMA) based approach, called round-robin scheduling (RRS), is also adopted to ensure fairness in time resource allocation while serving multiple users using the same LED in the hybrid system. Furthermore, simulation results are presented taking different practical application scenarios into consideration. The performance analysis of the network assignment mechanism, which is provided at the end of the paper, demonstrates the importance and feasibility of the proposed scheme.
关键词： fuzzy logic,network assignment,hybrid system,optical wireless communications,QoS,LiFi,OCC,link-switching
更新于2025-09-04 15:30:14
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Complexity considerations: efficient image transmission over mobile communications channels
摘要： In this paper the computational complexity of the image transmission over mobile communications channel is investigated. The computational complexity due to the amount of transmitted data and the utilized data protection schemes is analyzed over wireless channel with the different image transmission scenarios. The proposed secured and efficient protection technique is presented in this research work with lower computational complexity. The presented technique is based on chaotic-Baker encryption which is utilized as an interleaver to randomize the data packet in the proposed secured interleaved channel coding technique. The proposed technique is evaluated utilizing convolutional codes with different constraint lengths and single error correction block code. Different images with the size variation are utilized for evaluating the proposed image transmission scenarios. Numerical analysis of the different scenarios is presented. The secret key generation of chaotic-Baker encryption is discussed; it can be generated automatically or manually. Several computer simulation experiments are carried out to evaluate the proposed techniques performance. Different objective measures error based metrics are used such as the Bit Error Rate (BER), Peak Signal to Noise Ratio (PSNR) and Number of Lost packet percentage (NLP%) to measure the error performance of the proposed technique and quality of the received images. Simulation results reveal a good performance and the superiority of the proposed technique with lower computational complexity of the proposed image transmission scenarios.
关键词： Chaotic-Baker interleaver,Mobility,Wireless communications,Secured interleaved channel coding technique,Image transmission,Data computational complexity
更新于2025-09-04 15:30:14