Softer Handover in Cell_FACH via Preamble Signature Partition
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Solution Overview
Problem
Current wireless communication systems, specifically UMTS networks, are limited in enabling softer handover for mobile stations operating in the Cell_FACH state, restricting active set size to one sector and impacting signal quality and interference mitigation.
Innovation Solution
The implementation of a method and system that allows user equipment to initiate softer handover by selecting a preamble signature and transmitting a softer handover initiation message while in a non-dedicated channel state, utilizing a multi-sector common enhanced uplink dedicated channel system information resource list to facilitate simultaneous communication with multiple sectors, enabling softer handover in Cell_FACH state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mobile stations are limited to active set size equal to one in Cell_FACH state, then device complexity is reduced and ease of operation is improved, but signal quality deteriorates and interference mitigation capability is worsened
Solution Approach 1:
The patent segments the handover process by introducing different active set size limitations for different channel states. Cell_FACH state is limited to active set size of one to maintain simplicity, while Cell_DCH state allows larger active sets for improved signal quality. This segmentation resolves the contradiction by applying appropriate complexity levels to different operational contexts.
Solution Approach 2:
The patent changes the active set size parameter dynamically based on the channel state. When transitioning from Cell_FACH to Cell_DCH, the active set size limit increases, enabling softer handover with multiple sectors. This parameter change allows the system to optimize signal quality when dedicated resources are available while maintaining simplicity when they are not.
2Reliability
If softer handover is enabled in Cell_FACH state, then signal quality is improved and interference mitigation is enhanced, but device complexity increases and ease of operation deteriorates
Solution Approach 1:
The patent implements dynamic control of softer handover capability based on channel state. The network dynamically enables or disables softer handover in Cell_FACH state by controlling the transmission of preamble signature partition lists. This dynamic approach allows the system to provide improved signal quality when needed while maintaining operational simplicity when the additional complexity is not required.
Solution Approach 2:
The patent introduces the preamble signature partition list as an intermediary mechanism to control softer handover. This intermediary allows the network to signal to the mobile station whether softer handover should be attempted in Cell_FACH state, providing a controlled way to enable improved signal quality without fully committing to the complexity of always-enabled softer handover.
3Object-affected harmful factors
If multiple sectors are simultaneously connected in Cell_FACH state, then interference mitigation is improved, but device complexity and resource management burden increase
Solution Approach 1:
The patent segments the interference mitigation approach by applying softer handover with multiple sectors only in Cell_DCH state where dedicated resources are available, while maintaining single-sector connection in Cell_FACH state. This segmentation allows interference mitigation to be applied where it provides the most benefit without unnecessarily increasing complexity in states where resources are limited.
Solution Approach 2:
The patent changes the active set size parameter based on channel state to control the number of simultaneously connected sectors. In Cell_FACH state, the active set size is limited to one sector, while in Cell_DCH state, the active set size can be larger to enable softer handover. This parameter change allows the system to mitigate interference when dedicated resources are available while avoiding the complexity overhead when they are not.
Data Source
AI summary
One feature provides for an apparatus, system, and method for enabling softer handover by a user equipment in a non-dedicated channel state, such as Cell_FACH state. A user equipment communicates with a base station via a first sector of the base station, and receives a preamble signature partition list. The user equipment determines that a second sector of the base station is available for softer handover, and selects a preamble signature from the preamble signature partition list corresponding to a softer handover configuration associated with the first sector and the second sector. The user equipment may then transmit a softer handover initiation message that includes the preamble signature while in a non-dedicated channel state, such as Cell_FACH.