Network ask UE(e.g, mobile phone) to perform measurement roughly to achieve followings.
- To estimate the signal quality of current connection (e.g, RSRP, RSRQ, CQI, RI, PMI for the connection in current use)
- To check if the target cell exists (detactable) and quality is good enough before establishing carrier aggregation.
- To check if the target cell exists (detactable) and quality is good enough before performing handover.
In any cases, the measurement order (i.e, the direction from a Network to UE) is done via a specific RRC Message (Measurement Control in 3G, RRC Connection Reconfiguration in 4G), but the measurement report is done by a couple of different mechanism depending on situations.
- Some measurement (e.g, CQI, RI, PMI) is reported via physical channel (e.g, PUCCH or PUSCH).
- Some measurement (e.g, RSRP, RSRQ, Event) is reported by RRC message
Cell Measurement is a very important steps for mobility and channel quality estimation & adaptive scheduling(e.g, MCS changes based on CQI) in cellular system.
- For 5G Cell Measurement : Note Not Ready Yet
- For 4G Cell Measurement : See here
- For 3G Cell Measurement : See here ,here ,here