One of the most limited resources in telecom is wireless spectrum; therefore, it is not surprising that carriers are paying premium licensing fees for spectrum acquisition. For example, the recent 700 MHz spectrum auction in the U.S. had an aggregate bid value of $19.6 billion. Since acquisition of wireless spectrum is limited, it is advantageous for wireless carriers to use the spectrum efficiently in both outdoor and indoor environments.

From a radio frequency (RF) propagation perspective, buildings and walls have never been friends to a radio signal. Physical structures cause RF signal attenuation because of reflection, diffraction, scattering, and multi-path signal fading, all resulting in poor radio signal reception.