Radio Bearer Dependent Forwarding for Handover Latency and X2 Traffic
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Solution Overview
Problem
The existing Evolved Universal Terrestrial Radio Access Network (E-UTRAN) handover process faces challenges in optimizing handoff latency and X2 interface traffic, as current methods either increase latency or overhead, depending on the forwarding of RLC status reports to the source or target eNB, which affects the reliability and efficiency of the handover process.
Innovation Solution
A radio bearer-dependent data handling method is employed, where for real-time data, the source node forwards unacknowledged service data units to the target node and disconnects, minimizing latency but increasing X2 interface traffic, while for non-real-time data, the source node continues to receive acknowledgments during a timeout period before forwarding data, reducing X2 interface traffic but extending handoff latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the source node forwards all unacknowledged service data units immediately for real-time data, then handoff latency is minimized, but X2 interface traffic increases
Solution Approach 1:
The patent applies local quality by differentiating data handling based on QoS requirements of different radio bearers. Real-time data bearers receive immediate forwarding treatment to minimize latency, while non-real-time bearers receive deferred forwarding to reduce X2 interface traffic. This localized differentiation resolves the contradiction by optimizing each data type according to its specific requirements rather than applying a uniform approach.
2Quantity of substance
If the source node waits for timeout period and receives acknowledgments before forwarding for non-real-time data, then X2 interface traffic is reduced, but handoff latency is extended
Solution Approach 1:
The patent implements dynamics by making the forwarding timing adaptive based on acknowledgment receipt and timeout conditions. For non-real-time data, the system dynamically adjusts the forwarding decision: if acknowledgments are received before timeout, forwarding is deferred; if timeout occurs, forwarding proceeds. This dynamic behavior allows the system to optimize X2 interface traffic while managing handoff latency according to actual data transfer status.
3Reliability
If RLC status reports are forwarded to the source eNB, then handover reliability is improved, but handover process complexity increases
Solution Approach 1:
The patent uses the RLC status report as an intermediary mechanism to improve handover reliability. By forwarding status reports to the source eNB, the system obtains accurate information about which data units have been successfully delivered to the UE. This intermediary information flow enables the source eNB to make informed forwarding decisions, reducing the need for complex retransmission handling and actually simplifying the overall handover process while improving reliability.
Data Source
AI summary
This invention employs an inherent tradeoff in a radio bearer dependent data handling method for intra-E-UTRA handoffs. For user equipment using real time data, the source node forwards to the target node not yet acknowledged real time service data units and disconnects. This makes the handoff latency short at the expense of data traffic between nodes. For user equipment not needing real time data, the source node continues to receive user equipment acknowledgements during a time out period and only forwards service data units acknowledged during the time out period. This reduces X2 interface traffic between the source and target nodes but extends the handoff latency.