System Information Cache for Faster Cell Reselection
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Solution Overview
Problem
Current wireless communication systems face disruptions and delayed access during cell reselection due to the time-consuming process of obtaining and caching system information from neighbor cells, especially in states like CELL-FACH where dedicated physical channels are not allocated, leading to service disruptions and memory management issues.
Innovation Solution
A method for efficient system information cache management in user equipment, where cache entries include timestamps and relevance data, allowing for the selection of suitable neighbor cells for multipoint communications by relating them to the serving cell, even in the absence of a dedicated physical channel, thereby optimizing cache usage and reducing the need for continuous SI reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE obtains system information from neighbor cells during cell reselection, then the UE can determine suitable cells for reselection, but the process takes several seconds causing service disruption
Solution Approach 1:
The patent applies preliminary action by having the UE cache system information blocks from multiple cells in advance, before cell reselection is needed. The UE stores SI blocks with timestamps and validity information, so when cell reselection becomes necessary, the required information is already available in the cache, eliminating the several-second delay associated with real-time SI acquisition from neighbor cells.
2Productivity
If the UE caches system information from multiple cells, then the UE can perform faster cell reselection, but memory management becomes complex
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different SI blocks based on their scope and validity. The UE maintains separate cache management strategies for different SI block types (cell-level vs. node B-level), tracks validity periods through timestamps, and selectively retrieves only the necessary SI blocks for current cell reselection decisions, rather than uniformly caching all SI information.
Solution Approach 2:
The patent implements dynamics through the time-varying validity of cached SI blocks. The UE continuously monitors timestamps associated with cached SI blocks and dynamically updates or removes entries that have expired. This dynamic validity tracking allows the cache to adapt to changing network conditions without requiring complete memory remanagement.
3Productivity
If the UE is in CELL-FACH state with no dedicated physical channel, then the UE can monitor FACH continuously, but the UE cannot read neighbor cell system information
Solution Approach 1:
The patent resolves this contradiction by applying preliminary action - the UE caches system information blocks from multiple cells during periods when SI can be received (such as when transitioning to RRC_IDLE or during brief available windows), so that the information is ready for use even when the UE is subsequently in CELL-FACH state where dedicated physical channels are not available and continuous FACH monitoring is required.
Data Source
AI summary
For each of a plurality of received system information SI a cache entry is stored in a SI cache of a user equipment UE, each including at least some of the received SI, a timestamp of when the SI was first stored, and at least some of the cache entries also have relevance data relating the respective cache entry to one or more other cache entries. While the UE is in a state such as a CELL-FACH state, a cache entry is selected for at least one neighbor cell, and that cache entry is related by its relevance data to the cache entry of the serving cell or determined from its timestamp to be in close proximity to the serving cell. The UE then identifies the selected neighbor cell in an uplink message as a suitable candidate for multipoint communications with the UE.