5G • RAN
ra-ContentionResolutionTimer
Random Access Contention Resolution Timer
Timer started after transmitting Msg3; if no matching Msg4 arrives before expiry, random access is declared failed.
Technical Explanation
After transmitting Msg3, the UE starts ra-ContentionResolutionTimer (up to 64 subframes). The UE monitors PDCCH for Msg4. If the timer expires before a PDCCH matching TC-RNTI or C-RNTI is received, the UE declares contention resolution failed, applies a random backoff, and restarts Msg1 transmission.
Key Functions
- Supervises reception of contention resolution Msg4 following Msg3
- Prevents indefinite UE hanging during collided random access attempts
- Triggers backoff and preamble power ramp-up upon expiry
Specifications
3GPP TS 38.321
Interfaces
Uu
Related 5G Concepts
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