Active DAS Systems typically involve multiple components that require a power source to operate. An active system utilizes fiber optic cables to transport RF signals between a DAS Head-End and Remote Units (RUs). Thus equipment on both sides have fiber optic transceivers that perform Electric to Optical (E/O) and Optical to Electric (O/E) conversions. Traditionally, Active DAS systems have been deployed for large in-building installations and outdoor stadiums.
Prices for Active DAS systems start at $2 per sq./ft. and typically end up at $4 - $5 per sq./ft. These systems can take 12 to 18 months to design, gain necessary approvals and get installed.
Hybrid Active DAS systems take the best features of Active and Passive DAS Systems and make them even better.
Using a Donor signal provided by an off-air antenna or small cell, the signal is digitally processed by the Network Unit using advanced, digital echo-cancellation and channel select filtering algorithms that enables it to achieve an FCC and Network Carrier-approved, industry high 100dB max Gain. This enhanced signal is then transmitted with zero signal loss via Cat5e (or better) cables to up to 4 Coverage Units making it capable of boosting areas up to 50,000 sq./ft. For buildings over 50,000 sq./ft., multiple systems may be combined for unlimited coverage enhancements.
Many small-to-medium sized buildings can benefit from Passive DAS systems. Take for example a small 25 to 50,000 sq./ft. office building in need of enhanced cellular coverage. A system integrator will install a directional antenna pointing toward a particular carrier’s tower. The signal enters the building via low-loss coaxial cable. A Signal Booster (sometimes called BDA or Repeater) is installed to strengthen the signal. In this solution, the Signal Booster is the only active component of a Passive DAS system. Integrators then use passive components such as splitters and directional couplers to distribute RF signals over coaxial cables between the Signal Booster and indoor antennas.
These installations are relatively inexpensive but require a good degree of RF expertise in order to design link budgets which ensure proper in-building coverage, especially when there are multiple carriers and cellular bands (ranges of frequencies) which need to be distributed.