What is at the "root" of a DAS (distributive antenna system)?

Antennas are the leaf endpoints of the DAS tree, located at the furthest distribution points to radiate and collect RF energy - they do not serve as the central originating root of the system.

A receiver is a unidirectional device handling only inbound signals and cannot serve as the root, which requires full bidirectional signal management for both downlink distribution and uplink aggregation.

A transmitter handles only outbound signals and lacks the receive capability required of the root element, which must aggregate uplink signals from all remote antenna units in the DAS.

The transceiver is positioned at the root of the DAS tree topology because it is the active head-end unit that both generates (transmits) downlink signals for distribution through the remote antenna units and aggregates (receives) uplink signals returned from those units. Its inherent bidirectional transmit-and-receive capability makes it the logical origin point from which the entire distributed antenna network branches outward.