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In the realm of future wireless networks, it is anticipated that high altitude platforms (HAP)-satellite links will serve as the primary facilitators. Optical wireless communication has become increasingly important due-to its exceptional features and ability to provide gigabit capacity communication. As such, this work explores an optical code division multiple access scheme centred on high-speed long-haul mode division multiplexing for HAP-to-satellite applications. The proposed design utilizes zero cross-correlation (ZCC) and multi-diagonal (MD) codes at donut modes 0 and 1. The main objective of this research is to create a cost-effective, secure, and cutting-edge last mile linkage that optimizes resource utilization for HAP systems. The results indicate that the system employing ZCC code outperforms the MD code. Moreover, the system accomplishes a minimum bit error rate limit of 10−3 at transmission distances of 5000 km and 4800 km at Donut mode 0 and 1, respectively, for the ZCC code. In addition, the system can tolerate maximum acceptable transmitter pointing errors of 3 µrad and receiver pointing errors of 4 µrad at minimum BER limit. Meanwhile the system using ZCC can offer better performance of maximum 28 dB optical signal to noise ratio till high split ratio of 1:4–1:64. It also indicates optimum performance over other existing ones. [ABSTRACT FROM AUTHOR]

The huge bandwidth and immunity to electromagnetic interference make visible light communication (VLC) systems the preferred technique for many applications. Unfortunately, the superposition of multiple subcarriers in VLC orthogonal frequency division multiplexing systems leads to a high peak-to-average power ratio (PAPR). So, in this study, we aim to reduce PAPR in VLC systems and improve the system performance by proposing non-distorting PAPR reduction techniques like precoding techniques as it doesn't affect the system data rate because they do not require any obligatory transmission of side information. Moreover, it has a very good ability to reduce the PAPR without affecting the system BER performance. So, different precoding reduction techniques are proposed like discrete cosine transform (DCT), discrete sine transform (DST), discrete Hatley transform (DHT), and Vandermonde like matrix (VLM), to address the high PAPR and light-emitting diode-restricted linear range problems in VLC systems. The proposed technique using DHT, DCT, DST, and VLM provided a significant advantage in reducing the PAPR by 1.35 dB, 1.46 dB, 2.12 dB, and 2.17 dB, respectively. So the proposed technique is based on using the VLM precoding technique to achieve maximum reachable PAPR reduction value. Also, a comparison of the presented work and related literature reviews for PAPR reduction techniques are held to ensure the validity and effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In the work, we propose and investigate a real-time optical wireless communication (OWC) system with 1 Gbps on–off keying (OOK) traffic rate for indoor and outdoor transmissions. Here, 1 Gbps OWC traffic with error-free operation can be achieved indoors under the free space transmission length of 500 m based on the simulation and experimental results. In addition, 952, 904, 476 Mbps throughput rates of proposed real-time OWC system are measured outdoors after passing through the wireless transmission lengths of 120, 300 and 500 m, respectively. [ABSTRACT FROM AUTHOR]