A key limitation of mmWave technology, despite its high speed, is its very limited range and poor penetration through obstacles. MmWave signals operate at very high frequencies with short wavelengths, which makes them easily blocked or degraded by physical objects such as buildings, walls, windows, foliage, and even humans due to water content. This results in a requirement for line-of-sight between the transmitter and receiver and severely restricts coverage to just a few hundred meters or less. Consequently, mmWave is suitable mainly for dense urban environments or localized areas like stadiums and airports but is impractical for suburban or rural coverage

. Additionally, atmospheric factors such as oxygen and water vapor absorption, rain, and humidity further attenuate mmWave signals, reducing their effective range and reliability outdoors

. The need for a high density of small cells to maintain coverage increases deployment costs and complexity

. Moreover, mmWave devices tend to consume more power, which can impact battery life and operational expenses

. In summary, the main limitation of mmWave, despite its ultra-fast data speeds, is its short range and poor penetration, necessitating dense infrastructure and line-of-sight conditions for effective use