T316 RRC Timer in 5G NR

T316 RRC Timer in 5G NR

The T316 is a critical Radio Resource Control (RRC) timer in 5G New Radio (NR) networks, defined in 3GPP TS 38.331. It falls under the category of Radio Link Failure. Understanding the exact behaviour of this timer is essential for optimizing network performance, mobility, and radio link recovery.

Purpose and Overview

• Purpose: BFD (Beam Failure Detection) timer for serving cell
• Description: Time window for beam failure detection on serving cell

Timer Specifications

• Typical Value: 1000 ms
• Allowed Values (ms): 50, 100, 150, 200, 500, 1000, 2000, 4000, 8000, 10000
• Value Range: 50 ms to 10000 ms
• 3GPP Specification Reference: 3GPP TS 38.331 Section 5.3.10.3

Operational Triggers

Started When

Beam failure instance indication from physical layer

From TS 38.331: Upon transmission of the MCGFailureInformation message.

Stopped When

New beam identified or T316 expires

From TS 38.331: Upon receiving RRCRelease, RRCReconfiguration with reconfigurationwithSync for the PCell, MobilityFromNRCommand, or upon initiating re-establishment.

At Expiry

No suitable beam found within timer duration Actions Taken: Triggers radio link failure if beam recovery unsuccessful

From TS 38.331: Perform the actions as specified in 5.7.3b.5.

Related Parameters

• Related Timers: T310, T311
• Related Counters: None
• Associated Procedures: Beam Management, Beam Failure Detection, Beam Failure Recovery, L1-RSRP Measurements

Troubleshooting Tips

If you are observing anomalies or frequent expirations related to the T316 timer, consider checking the following:

• Check beam reference signal (CSI-RS/SSB) quality
• Verify beam management configuration
• Analyze L1-RSRP measurement reports
• Review BFR (Beam Failure Recovery) procedure success
• Check for beam blocking issues
• Verify candidate beam set configuration
• Analyze UE mobility and beam tracking

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Further Reading

• 5G NR User Equipment Timers & Constants
• Interactive 5G NR RRC Timers Reference Tool