Cell Grouping for Random Access in Mobile Communication Systems
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Solution Overview
Problem
In Advanced-EUTRA systems, mobile station apparatuses face complexity in random access processing due to varying transmission timings across cells, leading to increased collisions and unnecessary processing when multiple cells are allocated, especially during initial access or handover.
Innovation Solution
The system restricts random access by grouping cells with identical transmission timings into cell groups, allowing only one cell for contention-based random access within each group and permitting non-contention based random access for other cells, reducing unnecessary random access and simplifying processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random access processing is executed in all allocated cells, then uplink synchronization can be achieved in each cell, but processing complexity in the mobile station apparatus increases and random access preamble collisions increase
Solution Approach 1:
The patent divides cells into two categories: a first cell (or first cell group) where random access processing is executed, and second cells (or other cell groups) where random access is not executed. This segmentation resolves the contradiction by limiting random access operations to specific cells, thereby reducing processing complexity while maintaining uplink synchronization through timing adjustment based on downlink reception timing differences.
Solution Approach 2:
The patent applies different random access configurations to different cells based on their specific characteristics. The first cell is configured with random access parameters while second cells are not, creating local differentiation in random access behavior. This allows the system to achieve uplink synchronization where needed without imposing unnecessary processing complexity across all cells.
2Reliability
If random access processing is executed in all allocated cells, then uplink synchronization can be achieved in each cell, but random access preamble collisions among mobile station apparatuses increase
Solution Approach 1:
By segmenting cells into first cells where random access is permitted and second cells where it is not, the patent reduces the total number of random access operations across the system. This segmentation directly reduces the probability of preamble collisions while still ensuring uplink synchronization is achieved in the cells where random access is executed.
3Manufacturing precision
If transmission timings are adjusted in individual uplink component carriers of individual cells, then timing alignment can be achieved, but random access processing becomes necessary for each cell when synchronization is lost
Solution Approach 1:
The patent applies timing adjustment mechanisms selectively to cells where random access is not executed, using downlink reception timing differences to calculate appropriate uplink transmission timing offsets. This local application of timing adjustment maintains synchronization precision without requiring full random access processing in all cells, thereby reducing overall processing complexity.
Data Source
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AI summary
In a case where a transmission timing in a mobile station apparatus varies among individual cells, efficient random access can be performed. A base station apparatus which is applied to a mobile communication system in which random access from a mobile station apparatus to a base station apparatus is executed allocates a plurality of cells to the mobile station apparatus, groups the cells into groups in each of which cells have an identical transmission timing in the mobile station apparatus, notifies the mobile station apparatus of transmission timings determined for the individual groups, permits the mobile station apparatus to execute random access using any one of the cells included in the groups, and notifies the mobile station apparatus of random access execution information about the cell for which random access is permitted.