It's a common experience: signal that looks fine outside a building drops noticeably once you step in. This isn't random — specific construction choices are usually responsible.
Low-emissivity (Low-E) glass
Many modern commercial and residential towers use low-E glass for energy efficiency. The thin metallic coating that reflects heat also reflects a meaningful portion of radio frequency signal, significantly reducing how much outdoor signal reaches indoor spaces.
Reinforced concrete and rebar
Steel reinforcement bars inside concrete walls and floors can act as a partial shield against radio signals, particularly in buildings with dense structural steel — common in high-rise construction across Mumbai.
Building depth and floor count
Large floor plates mean interior rooms can be tens of metres from the nearest exterior wall, with signal weakening rapidly with each wall and floor it passes through. Basements and lower-ground areas face the added challenge of little to no direct line of sight to any outdoor signal source.
What this means practically
None of these factors are unusual or avoidable — they're simply part of how modern buildings are constructed. A signal booster system is specifically designed to work around them by capturing signal at a favourable point and distributing it indoors through cabling rather than relying on it to pass through walls and glass.