Indoor Radio Planning: A Practical Guide for GSM, DCS, UMTS, HSPA and LTE, Second Edition

4.4 Active DAS

The principle function of an active distributed antenna system is that, like a passive distributed antenna system, it distributes the signal to a number of indoor antennas. However, there are some big differences. The active distributed antenna system normally relies on thin cabling, optical fibers and IT type cables, making the installation work very easy compared with the rigid cables used for passive systems.

The active distributed antenna system consists of several components, the exact configuration depending on the specific manufacturer. All active distributed antenna systems will to some extent be able to compensate for the distance and attenuation of the cables.

4.4.1 Easy to Plan

The ability to compensate for the losses of the cables interconnecting the units in an active distributed antenna system makes the system very easy and fast to plan, and easy to implement in the building.

Whereas, when designing a passive distributed antenna system, you need to know the exact cable route and distance for each cable in order to calculate the loss and link budget, when designing active distributed antenna systems it does not matter if the antenna is located 20 m from the base station or even 5 km. The performance will be the same for all antennas in the system; the active DAS system is transparent. This ‘transparency’ is obtained automatically because the active system will compensate for all cable losses by the use of internal calibrating signals and amplifiers. ...