HS-DSCH Cell Change via Pre-configured Serving Cell Information
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Solution Overview
Problem
In HSDPA wireless communication systems, the handover process between cells can result in data loss and increased delays due to conflicts between RRC messages and target cell HS-SCCH orders, especially when pre-configured parameters conflict with new configuration parameters, leading to ambiguity in the WTRU's configuration and timing for the serving HS-DSCH cell change.
Innovation Solution
The WTRU receives pre-configured serving cell information and acts on either RRC reconfiguration messages or target cell HS-SCCH orders based on their receipt order, ignoring subsequent conflicting messages to ensure consistent and timely handover procedures, with mechanisms like transaction identifiers to manage message processing and prevent conflicts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-configured target cell information is used to improve handover reliability, then data loss is reduced, but configuration conflicts and ambiguity occur between RRC messages and HS-SCCH orders
Solution Approach 1:
The network pre-configures target cell information (H-RNTI, HS-SCCH configuration, HARQ resources) in the ACTIVE SET UPDATE message before handover execution. This preliminary configuration enables the WTRU to quickly switch to the target cell without waiting for all parameters to be transmitted during handover, reducing data loss while avoiding real-time configuration conflicts
Solution Approach 2:
The patent separates pre-configured parameters (transmitted in ACTIVE SET UPDATE) from execution-triggering parameters (transmitted in RRC handover message or HS-SCCH order). By extracting only the essential configuration elements in advance and leaving the trigger mechanism for later, the system achieves fast handover without configuration conflicts
2Reliability
If synchronized handover is used to minimize data loss, then reliability improves, but handover delays increase
Solution Approach 1:
The network performs resource allocation and configuration in advance (pre-configuration phase), so that when handover is triggered, the WTRU can immediately switch to the target cell using pre-prepared parameters. This eliminates the need for real-time configuration during handover execution, reducing delays while maintaining reliability
Solution Approach 2:
The patent introduces dynamic activation timing where the WTRU can switch to the target cell at different times based on radio conditions and measurement reports. The handover is triggered dynamically by Event 1D (change of best cell) rather than following a fixed synchronized schedule, allowing flexibility to minimize both data loss and delay
3Device complexity
If RRC handover message is sent via source cell to maintain procedure simplicity, then device complexity is reduced, but message delivery fails under degrading radio conditions
Solution Approach 1:
The patent introduces the target cell as an intermediary for message delivery. Instead of relying solely on the source cell to deliver the handover message, the network can send the same handover information through the target cell's HS-SCCH order. This dual-path approach ensures message delivery even when source cell radio conditions degrade
Solution Approach 2:
The patent changes the transmission parameter of the handover command from exclusively source-cell-based RRC messages to include target-cell-based HS-SCCH orders. By changing the delivery channel parameter, the system adapts to varying radio conditions and improves message delivery reliability
Data Source
AI summary
A method and an apparatus for serving high speed downlink shared channel (HS-DSCH) cell change are disclosed. A wireless transmit/receive unit (WTRU) receives pre-configured serving cell information for a target cell. The WTRU reports a measurement report and starts monitoring a high speed shared control channel (HS-SCCH) on the target cell. The WTRU may receive an HS-SCCH order over the target cell and/or a radio resource control (RRC) reconfiguration message over a source cell indicating a serving HS-DSCH cell change to the target cell. The WTRU may act upon all information elements of the RRC reconfiguration message in case that the RRC reconfiguration message is received prior to the HS-SCCH order, and act upon the pre-configured serving cell information in case that the HS-SCCH order is received prior to the RRC reconfiguration message.