Enhanced Cell ID, E-CellID, or E-CID is a positioning feature introduced in rel9 E-UTRA (LTE radio).
The UE reports to the network (ESMLC) the serving cell ID, the timing advance (difference between its transmit and receive time) and the IDs, estimated timing and power of the detected neighbor cells.
The enodeB may report extra information to the ESMLC like the angle of arrival.
Enhanced cell ID aggregates together some already available measurements, some of them with increased accuracy requirements to improve the positioning accuracy capabilities.
The UE performs and collects the necessary measurements, and reports them back using the ECID-ProvideLocationInformation.