5G QoS Flow to DRB Remapping During Handover
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Solution Overview
Problem
The existing 5G wireless network standardization faces challenges in maintaining quality of service (QoS) flow to data radio bearer (DRB) mapping during handover between source and target gNBs, leading to potential packet sequence number issues and duplication, which can result in erroneous interpretation and loss of packets.
Innovation Solution
A mechanism for 5G-QoS-flow-to-DRB remapping is introduced, where the target RAN node receives user data from the source node and applies the same configuration used by the source node for mapping data flows to DRBs, ensuring that packets are treated with the same QoS and sequence numbering is maintained, thereby minimizing packet loss and duplication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the target gNB applies a different QoS flow to DRB mapping configuration than the source gNB, then the target gNB can optimize resource allocation and adapt to local conditions, but packet sequence numbers may become inconsistent leading to packet duplication and loss
Solution Approach 1:
The source gNB performs preliminary actions by determining the QoS flow to DRB mapping configuration before handover and including it in the handover request message sent to the target gNB. This allows the target gNB to prepare the correct mapping configuration in advance, ensuring consistency when packets are forwarded during handover execution.
Solution Approach 2:
The handover request message acts as an intermediary carrier that transports the QoS flow to DRB mapping configuration from the source gNB to the target gNB. This intermediary mechanism ensures that the critical mapping information is reliably transmitted and applied, maintaining packet sequence consistency across the handover boundary.
2Reliability
If the target gNB uses the same QoS flow to DRB mapping configuration as the source gNB, then packet sequence numbering consistency is maintained, but the target gNB loses flexibility in optimizing local resource allocation
Solution Approach 1:
The system dynamically transitions between two states: during handover execution, the target gNB uses the source's QoS flow to DRB mapping configuration to ensure consistency; after handover completion, the target gNB can determine and apply its own optimized configuration. This dynamic state change resolves the contradiction by applying different configurations at different handover phases.
Solution Approach 2:
The source gNB determines the QoS flow to DRB mapping configuration in advance and includes it in the handover request, allowing the target gNB to temporarily apply this configuration during the critical handover period. After handover completion, the target gNB regains flexibility to determine its own optimized configuration, thus balancing consistency and adaptability.
3Adaptability or versatility
If QoS flow to DRB mapping is changed during handover, then the target gNB can optimize for its specific conditions, but the complexity of maintaining consistent packet routing increases
Solution Approach 1:
The handover request message serves as an intermediary that carries the QoS flow to DRB mapping configuration from source to target gNB. This standardized intermediary mechanism simplifies the handover management process by providing a clear, structured way to transfer critical configuration information, reducing the complexity of maintaining consistent packet routing during handover.
Data Source
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AI summary
According to some embodiments, a method for use in a network node of performing handover of a wireless device comprises: receiving a handover request from a source network node; receiving, from the source network node, a quality of service (QoS) flow to data radio bearer (DRB) mapping that was used by the source network node prior to the handover; receiving buffered Packet Data Convergence Protocol (PDCP) protocol data units (PDUs) from the source network node; transmitting the received PDCP PDUs using the received QoS flow to DRB mapping; obtaining an indication that handover is complete; determining a new QoS flow to DRB mapping; and activating the new QoS flow to DRB mapping for transmission of PDCP PDUs. Particular embodiments may include sending the new QoS flow to DRB mapping to the source network node, and/or receiving PDCP status reporting from the wireless device.