Pre-configured Measurement Gap
3GPP TS 38.133 Section 9.1.7
Purpose / Why It Matters
- • Pre-MG allows UE to be configured with a measurement gap pattern that can be dynamically activated/deactivated without full RRC reconfiguration
- • Gap interruption requirements (Section 9.1.2) apply only when Pre-MG is activated
- • No gap interruption when Pre-MG is deactivated → enables efficient resource utilization
- • Reduces signaling overhead for measurement gap management in dynamic scenarios
→ UE autonomously controls activation/deactivation
→ Network controls via RRC
All patterns #0 to #25 (Table 9.1.2-1) can be configured as Pre-MG. Applicability defined in Table 9.1.2-3.
Pre-MG requirements apply when ALL conditions are met:
- 1 UE indicates support of autonomous and/or NW-controlled Pre-MG
- 2 Network pre-configures: single per-UE gap OR one/two per-FR gaps
- 3 Gap pattern is one of #0 – #25
- 4 UE is in NR SA with single carrier or NR CA
When Pre-MG is used for PRS measurements, UE informs network of start/stop via LocationMeasurementIndication procedure.
Activation/Deactivation Mechanisms
Mechanism 1: Autonomous (UE-Controlled)
Triggering Conditions:
- • DCI-based active BWP switching
- • Timer-based active BWP switching
- • RRC-based active BWP switching
- • Activation/deactivation of SCell(s)
- • Addition/removal of measurement object(s)
- • Addition/release/change of SCell in CA
Status Determination:
DEACTIVATED: All measurements can be performed without gaps
ACTIVATED: At least one measurement requires gaps
Mechanism 2: Network-Controlled
per-UE Pre-MG:
ACTIVATED if preConfGapStatus = ‘1’ for:
• Active DL BWP of ANY activated CC, OR
• ANY deactivated SCC
DEACTIVATED: Otherwise
per-FR Pre-MG:
ACTIVATED if preConfGapStatus = ‘1’ for:
• Active DL BWP of ANY activated CC in that FR, OR
• ANY deactivated SCC in that FR
DEACTIVATED: Otherwise
Measurements WITHOUT Gaps
- • SSB-based intra-frequency (if Clause 9.2.1 conditions met)
- • SSB-based inter-frequency (if Clause 9.3.1 conditions met)
- • CSI-RS-based intra-frequency
Measurements REQUIRING Gaps
- • SSB-based intra-freq (if Clause 9.2.1 conditions NOT met)
- • SSB-based inter-freq (if Clause 9.3.1 conditions NOT met)
- • CSI-RS-based inter-frequency
- • E-UTRA / UTRA Inter-RAT measurements
Quick Reference: Decision Flow
for all BWPs/CCs?
Important Notes & Pitfalls
Precedence Rule
Network-controlled overrides autonomous when preConfGapStatus provided for all BWPs/CCs
Immediate Status Determination
UE determines Pre-MG status immediately after configuration or triggering condition
Joint Condition Handling
UE must evaluate all concurrent triggering conditions jointly
Inter-RAT Always Needs Gaps
E-UTRA and UTRA inter-RAT measurements always require gaps
Status changes (can be done with/without gaps)
UE allowed to restart the measurement
Activated → Deactivated (measurement requires gaps)
Measurement requirements do not apply
Gap interruption requirements
SSB intra-freq without gaps
SSB inter-freq without gaps
Gap pattern definitions
Pattern applicability