Uplink Transmission Scheduling for Dual Active Protocol Stack Handover
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Solution Overview
Problem
During dual active protocol stack handovers in wireless communication systems, the difference in propagation delay between source and target cells can cause collisions in uplink transmissions, leading to dropped packets due to insufficient hardware resources to handle simultaneous transmissions.
Innovation Solution
The proposed solution involves a method for scheduling uplink transmissions using time division multiplexing (TDM) with guard periods, where the source cell calculates the propagation delay difference and determines the TDM pattern to avoid collisions, ensuring that the wireless device can handle the transmission timing differences without dropping packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wireless device maintains simultaneous uplink transmissions to both source and target cells during handover, then connection continuity is improved, but hardware resources become insufficient leading to transmission collisions and packet loss
Solution Approach 1:
The patent segments the simultaneous uplink transmissions into separate time slots using time division multiplexing (TDM). The source cell and target cell transmissions are divided into alternating time periods, allowing the wireless device to handle each transmission separately with its existing hardware resources, thus avoiding transmission collisions while maintaining connection continuity to both cells.
Solution Approach 2:
The patent implements dynamic time slot allocation where the TDM pattern is configured based on the specific propagation delay differences between source and target cells. The scheduling is dynamically adjusted to accommodate varying handover scenarios, allowing the system to adapt the transmission timing to match the actual propagation conditions and minimize resource conflicts.
2Ease of operation
If uplink transmissions are scheduled without considering propagation delay differences, then scheduling simplicity is maintained, but transmission collisions occur due to timing misalignment between source and target cells
Solution Approach 1:
The patent performs preliminary calculation of propagation delay differences between source and target cells before configuring the TDM pattern. The source cell determines the propagation delay difference in advance and uses this information to pre-configure the TDM uplink transmission pattern, ensuring that timing alignment is established before actual transmissions begin, thus preventing collisions without requiring complex real-time adjustments.
Solution Approach 2:
The patent introduces the propagation delay difference as an intermediary parameter that mediates between the scheduling requirements of source and target cells. This parameter serves as a bridge to coordinate the timing of uplink transmissions, allowing the system to maintain relatively simple scheduling procedures while achieving precise timing alignment through the intermediary calculation and application of propagation delay differences.
Data Source
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AI summary
Apparatuses, systems, and methods for performing uplink transmissions during a dual active protocol stack handover. A wireless device may determine a propagation delay between the wireless device and each of a source cell and a target cell of a dual active protocol stack handover by the wireless device. The wireless device may provide an indication to the source cell of the propagation delay between the wireless device and the source cell, the propagation delay between the wireless device and the target cell, and a propagation delay difference handling capability of the wireless device. The cellular base station that provides the source cell may determine a time division multiplexing pattern for uplink communication for the wireless device during the dual active protocol stack handover based at least in part on the information provided by the wireless device.