Beyond the business rationale for distributed antenna systems in healthcare, there are very valid technology reasons from a user model perspective. Much has been written about cell phones interfering with medical equipment. This is one area that is very much mis-understood. A cellular site (tower) will have an output power of approximately 20W per carrier and there will be multiple carriers being broadcast or radiated. The antenna elements will have a gain of at least 17dB. The overall effective isotropic radiated power is 1000W per carrier (60dBm). Most of the new construction using reflective glass for LEED environments will provide 20dB attenuation. It is likely that the tower is not next to the hospital but more than estimated to be a mile or more away. From a mile, the free space path loss is 95dB, thus the signal entering the building is -35dBm per carrier, which is around 1/1,000,000W. Due to older and the newer LEED construction, hospitals have become very bad multi-path environments. So dealing with this minute signal, the cellular device many times has a hard time to keep the sufficient signal strength (-85dBm or 5 "bars"). In order for the mobile device to achieve the uplink, the power control algorithms boost the power of the mobile device. (The simple reason why your battery drains faster when you have poor coverage). Cellular devices also can transmit at relatively high power levels (perhaps 1W for short periods of time such as during the ring cycle). However if the mobile device has adequate coverage via a DAS, the path loss between the cell phone and the indoor DAS, will be much lower than the cellular device and the actual cell site. The power control algorithms within the cellular network will cause the cell phone to transmit at much lower levels, (potentially under 5mW), which really is not a problem. The result is the power control algorithms will reduce the power required for the uplink which increases battery life and decreases drastically the concern for any EMI.
