HSDPA Handover via Pre-loaded Configuration and MAC Reset
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Solution Overview
Problem
The existing high-speed downlink packet access (HSDPA) handover process in wireless communications faces issues such as data loss due to unclear MAC-hs/ehs reset requirements and inefficient uplink resource allocation, leading to unacceptable call drop rates and delays.
Innovation Solution
A method where the WTRU receives pre-loaded HS-DSCH configuration information, determines if a MAC-hs/ehs reset is needed based on configuration parameters, and performs the reset if required, while also pre-configuring uplink E-DCH resources to ensure seamless handover to a target cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If unsynchronized handover is used to reduce handover delay, then handover speed is improved, but data loss probability increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the WTRU with target cell HS-DSCH resources (H-RNTI, HS-SCCH codes, HARQ resources) before the handover occurs. This allows the WTRU to be ready to immediately receive and process downlink data from the target cell without waiting for resource allocation after handover, thereby reducing handover delay while maintaining data integrity through pre-established resource allocation.
2Reliability
If synchronized handover is used to minimize data loss, then data loss is reduced, but handover delay increases
Solution Approach 1:
The patent resolves this contradiction by performing preliminary configuration of target cell resources in advance, so that when handover occurs, both network and WTRU are simultaneously ready with all necessary resources pre-allocated. This eliminates the need for conservative activation time settings while ensuring no data loss, as the WTRU can immediately switch to target cell resources without waiting for post-handover resource allocation.
3Device complexity
If RRC handover message is sent via source Node B, then message delivery is simplified, but handover failure rate increases due to delay
Solution Approach 1:
The patent introduces the target cell as an intermediary for delivering the handover command. Instead of relying on the source Node B to deliver the RRC handover message, the target cell directly sends the handover command to the WTRU. This eliminates the delay and potential failure points in the source Node B delivery path, as the target cell is the ultimate destination and can immediately establish the communication path for command delivery.
4Productivity
If MAC-hs/ehs reset is not performed during handover, then resource allocation continuity is maintained, but data loss occurs due to synchronization issues
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the MAC-hs/ehs reset decision based on whether target cell resources are pre-configured. When resources are pre-configured, the patent determines that a MAC-hs/ehs reset should be performed to ensure synchronization between network and WTRU. This parameter change (reset decision) resolves the contradiction by maintaining resource allocation continuity through pre-configuration while ensuring data integrity through synchronized reset when needed.
Data Source
AI summary
A method and apparatus for serving high speed downlink shared channel (HS-DSCH) cell change are disclosed. A wireless transmit/receive unit (WTRU) sends a measurement report to a radio network controller (RNC) when a signal strength of a target cell approaches a signal strength of a source cell. The RNC adds the target cell in an active set and sends pre-loaded HS-DSCH configuration information for the target cell to the WTRU. The WTRU sends another measurement report when a signal strength of the target cell exceeds that of the source cell. The WTRU monitors a high speed shared control channel (HS-SCCH) on the target cell based on the pre-loaded HS-DSCH configuration information and decodes an HS-SCCH transmission. The WTRU determines whether a MAC-hs/ehs reset is required and if so resets a MAC-hs/ehs entity prior to receiving an HS-DSCH transmission from the target cell.