5G NR Dual Active Protocol Stack (DAPS) Handover Process Overview
telcomatraining.com – In the rapidly evolving landscape of 5G New Radio (NR), efficient mobility management is essential to ensure seamless user experiences. Among various handover mechanisms introduced in 5G NR, the Dual Active Protocol Stack (DAPS) handover has emerged as a key solution for enhancing handover reliability, reducing latency, and maintaining service continuity—especially in high-speed or high-reliability scenarios.
This article provides an SEO-optimized overview of the 5G NR DAPS handover process, exploring its architecture, advantages, and operation.
What is DAPS Handover in 5G NR?
DAPS (Dual Active Protocol Stack) handover is a mobility enhancement technique in 5G NR where both the source and target cells maintain active protocol stacks at the same time during the handover process. This allows the User Equipment (UE) to communicate simultaneously with both cells, enabling a smoother transition.
Unlike legacy LTE handover processes—where the UE releases the connection with the source cell before establishing a new one—DAPS allows parallel processing. This minimizes the risk of radio link failure (RLF) and supports ultra-reliable low-latency communication (URLLC) use cases.
Why DAPS Handover is Important
In traditional handovers, especially in areas with unstable radio conditions or during high-speed mobility (e.g., on trains), handover failures can lead to dropped calls or service interruptions. DAPS addresses these concerns by:
- Reducing Handover Failures: Maintaining both source and target connections reduces the likelihood of RLF.
- Lower Latency: Parallel protocol stack activation results in quicker handover execution.
- Better Support for URLLC: Essential for mission-critical applications like autonomous driving and remote surgery.
- Enhanced User Experience: Seamless data flow during mobility scenarios.
DAPS Handover Architecture and Components
To understand the DAPS handover process, it’s important to recognize the key entities involved:
- User Equipment (UE): The mobile device initiating or undergoing the handover.
- Source gNB: The 5G base station currently serving the UE.
- Target gNB: The base station the UE is moving toward.
- NG-RAN Core Network: Coordinates and manages mobility control signaling.
DAPS handover is primarily based on RRC (Radio Resource Control) and PDCP (Packet Data Convergence Protocol) enhancements, allowing for dual PDCP entities—one for the source and one for the target.
DAPS Handover Process: Step-by-Step
- Measurement Reporting:
- The UE continuously measures signal quality from neighboring cells.
- When the target gNB signal becomes stronger, the UE sends a measurement report to the source gNB.
- Handover Preparation:
- The source gNB initiates a handover request to the target gNB.
- The target gNB prepares resources and responds with a handover acknowledgment.
- Dual Stack Activation:
- The UE receives an RRC message to activate the target gNB’s PDCP entity without deactivating the source.
- At this point, both protocol stacks are live, and the UE can send and receive data from both nodes.
- Data Forwarding:
- The source gNB forwards any buffered data packets to the target gNB.
- This ensures continuity of service without packet loss.
- Handover Completion:
- The UE switches its primary data path to the target gNB.
- The source protocol stack is deactivated after successful data handover.
- Resource Release:
- Once the handover is confirmed, the source gNB releases all allocated resources.
Challenges and Considerations
While DAPS handover offers significant benefits, it also introduces complexities:
- Increased Signaling Overhead: Maintaining two active connections requires more control signaling.
- UE Capability Requirements: Not all devices support dual protocol stack operations.
- Resource Management: Efficient scheduling is essential to avoid resource congestion.
Conclusion
The 5G NR DAPS handover represents a major leap in mobility management, delivering seamless connectivity and improved reliability. By enabling dual active protocol stacks, 5G networks can better meet the demands of ultra-reliable and low-latency communications. As 5G adoption grows, DAPS will play a critical role in ensuring robust user experiences across diverse mobility scenarios.
Whether for autonomous vehicles, smart factories, or enhanced mobile broadband, DAPS handover is a crucial element in realizing the full potential of 5G technology.
