beyondlineofsight

Beyond line of sight, sometimes stylized as beyondlineofsight, is a term used to describe communications or sensing that occurs when direct visual or radio visibility between sender and receiver is blocked by terrain, weather, or other obstructions. In contrast to line-of-sight (LOS) systems, BLOS relies on intermediary links or non-direct propagation paths to convey information. BLOS is common in military communications, satellite internet, maritime and aviation networks, and remote sensing applications, enabling connectivity across mountains, seas, or urban canyons.

Methods used to achieve BLOS include satellite relays, where signals are transmitted to and from orbiting satellites; ground-based relay networks and mesh topologies that forward data across multiple hops; high-altitude platforms such as balloons or unmanned aerial vehicles that provide relay coverage over a region; and, in some cases, intermediate reflectors or diffraction effects; free-space optical or RF links may employ store-and-forward or adaptive routing to maintain connectivity when direct paths are unavailable.

Applications include military C2 networks, disaster response communications, remote sensing and surveillance, maritime and aviation communications, and rural broadband expansion. Key challenges involve latency and bandwidth limits, link reliability under atmospheric conditions, susceptibility to jamming or interception, regulatory constraints, and energy or maintenance costs. Ongoing research aims to improve reliability through dynamic routing, multi-path diversity, and integrated satellite-terrestrial networks, including constellations of low-earth-orbit satellites and resilient mesh systems with autonomous relays.