DAS

A Distributed Antenna System solves a problem one big antenna can't: blanketing the inside of a large, RF-hostile building with even coverage. Instead of relying on the outdoor macro signal to punch through walls (it usually can't, deep inside a stadium, mall, or office tower), you take a signal source and split it out to many small antennas spread throughout the space, so users everywhere see a clean, fairly uniform signal.

The source can vary, and that's a real design choice. A passive DAS distributes the signal over coax and passive splitters — simpler and cheaper, but cable loss limits how far you can run it. An active DAS converts to fibre and uses remote units with their own amplification, which scales to much larger venues. The signal itself can come from an off-air repeater pulling the macro signal, or from a dedicated base station for a venue that needs real capacity. DAS shines for coverage across big indoor footprints; where you need raw capacity in a hotspot, distributed small cells increasingly compete with (or complement) it, and the choice between them is a staple in-building-design debate.