What happens when UE in DRX idle mode?

Question

In Idle mode DRX cycle will be used looking for Paging messages and To make measurements of Neighbor cells which are on Intra,Inter frequencies.How this two mechanisms will be done in DRX cycle

Comments

I don't think UE does measurement for neighboring cells(intra/inter frequency) in DRX mode. Looking for others to respond. May be I am wrong.

Answer 1

Hi,

When UE in DRX mode , UE will have PO(paging occasion) to receive paging message. so apart form PO period UE will be in idle mode.
For Idle mode measurements using DRX below conditions has to be true -

5.2.4.2 The network may assign dedicated cell reselection priorities for frequencies not configured by system
information.Measurement rules for cell re-selection When evaluating for reselection purposes cell selection criterion or SnonServingCell,x, the UE shall use parameters provided by the serving cell.
Following rules are used by the UE to limit needed measurements:
- If S intrasearch is sent in the serving cell and S ServingCell > S intrasearch , UE may choose to not perform intra-frequency measurements.
- If S ServingCell <= S intrasearch, or S intrasearch is not sent in the serving cell UE shall perform intra-frequency measurements.
- The UE shall apply the following rules for E-UTRAN inter-frequencies and inter-RAT frequencies which are
indicated in system information and for which the UE has priority provided as defined in 5.2.4

S intrasearch -This specifies the threshold (in dB) for intra-frequency measurements.
S nonintrasearch -This specifies the threshold (in dB) for E-UTRAN inter-frequency and inter-RAT measurements

Reference - 36.304 (Idle mode procedures)

Answer 2

s per 36.133

4.2.2.1 Measurement and evaluation of serving cell

The UE shall measure the RSRP level of the serving cell and evaluate the cell selection criterion S defined in [1] for the
serving cell at least every DRX cycle.

The UE shall filter the RSRP measurements of the serving cell using at least 2 measurements. Within the set of
measurements used for the filtering, at least two measurements shall be spaced by, at least DRX cycle/2.

If the UE has evaluated in Nserv consecutive DRX cycles that the serving cell does not fulfil the cell selection criterion S,
the UE shall initiate the measurements of all neighbour cells indicated by the serving cell, regardless of the
measurement rules currently limiting UE measurement activities.

If the UE in RRC_IDLE has not found any new suitable cell based on searches and measurements using the intrafrequency,
inter-frequency and inter-RAT information indicated in the system information for 10 s, the UE shall initiate
cell selection procedures for the selected PLMN as defined in [1].