Enabling Broadband Internet Access in Remote and Rural Communities Using HAP-Based Multi-Hop FSO/RF Transmissions

In this article, we propose a reliable high-altitude platform (HAP)-based end-to-end (E2E) solution for broadband Internet access in remote and rural communities. In particular, we adopt parallel free-space optical (FSO)/radio frequency (RF) transmission for the feeder and access links to explore their complementary properties, while FSO transmission is only used for inter-HAP links as there are less turbulence effects. Using FSO links, the proposed solution supports high-data-rate transmissions to access points (AP) in hotspot regions with high-er demand for Internet connectivity. To maintain wide-area coverage, the RF link serves dispersed users regardless of location. To increase the FSO link's usability and minimize the probability that the system resorts to RF transmission, we introduce backup HAPs for feeder and access links. The system will switch between primary and backup HAPs depending on the channel quality, which helps considerably to improve system performance. The proposed E2E solution can achieve a spectral efficiency of 8.5 bps/Hz for APs and 4 bps/Hz for remote users outside the coverage of APs under a typical operating scenario.