HS-DSCH Cell Change Using Pre-loaded Configuration
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Solution Overview
Problem
The existing handover process in HSDPA networks experiences high rates of dropped calls due to delays in the serving HS-DSCH cell change procedure, particularly in synchronized handovers, which can result in data loss, and conventional methods fail to ensure reliable handover messages are received by WTRUs in CELL_DCH state.
Innovation Solution
The method involves pre-loading WTRUs with HS-DSCH configuration for target cells, allowing them to monitor and switch to the target cell's HS-SCCH upon triggering event 1D, with timers and explicit signaling to manage resource allocation and handover confirmation, and enabling WTRUs to read HS-DSCH common resources from System Information Blocks (SIBs) even in CELL_DCH state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronized handover is used to minimize data loss, then reliability is improved, but handover delay increases
Solution Approach 1:
The patent applies preliminary action by pre-loading the WTRU with HS-DSCH configuration for the target cell before the handover is actually needed. When event 1D is triggered, the WTRU can immediately start monitoring the target cell's HS-SCCH using pre-configured parameters, eliminating the need to wait for configuration messages during the handover process. This reduces handover delay while maintaining reliability through proactive preparation.
2Device complexity
If handover message is sent via source Node B, then procedure simplicity is maintained, but message delivery reliability deteriorates
Solution Approach 1:
The patent introduces the target cell as an intermediary for delivering the handover message. Instead of relying solely on the source Node B to deliver the handover command, the WTRU monitors the target cell's HS-SCCH for handover confirmation. This dual-path approach ensures message delivery even if the source Node B path fails, improving reliability without significantly increasing procedural complexity.
3Ease of operation
If WTRU monitors only serving cell, then device operation simplicity is maintained, but handover responsiveness deteriorates
Solution Approach 1:
The patent implements dynamic monitoring behavior where the WTRU adapts its monitoring strategy based on the handover state. In normal operation, the WTRU monitors only the serving cell to maintain simplicity. However, when event 1D is triggered, the WTRU dynamically adds the target cell's HS-SCCH to its monitoring list, enabling rapid handover response while keeping the default operation simple.
Data Source
AI summary
A method and apparatus for performing a serving high speed downlink shared channel (HS-DSCH) cell change from a source cell to a target cell are disclosed. A wireless transmit/receive unit (WTRU) may be pre-configured with HS-DSCH configuration for the target cell. The WTRU may start monitoring a high speed shared control channel (HS-SCCH) on the target cell using the pre-loaded HS-DSCH configuration for the target cell on a condition that a measurement report is triggered by the event 1D. The WTRU may initiate a timer when the WTRU starts monitoring the HS-SCCH on the target cell.