Uplink Synchronization in Carrier Aggregation via Reference Cell Timing
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Solution Overview
Problem
In carrier aggregation-based wireless communication systems, acquiring uplink synchronization efficiently is challenging, particularly when multiple cells with different timing advance groups are involved, leading to potential misalignment in uplink transmission timing between the base station and user equipment.
Innovation Solution
A method where user equipment transmits a random access preamble on a first cell, receives an uplink timing adjustment value, and performs uplink transmission using this value, with the preamble transmission timing determined based on specific timing related to a second cell, allowing for efficient synchronization across cells belonging to different timing advance groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple cells with different timing advance groups are used in carrier aggregation, then uplink transmission capacity is improved, but uplink transmission timing alignment between base station and user equipment deteriorates
Solution Approach 1:
The patent segments the timing advance management by introducing a reference cell concept. The user equipment determines uplink transmission timing for a target cell based on downlink timing of a reference cell, rather than treating each cell independently. This segmentation allows multiple cells to be managed with differentiated timing reference relationships, resolving the timing alignment issue while maintaining multi-cell operation.
Solution Approach 2:
The reference cell acts as an intermediary between the downlink timing and uplink transmission timing. By using the reference cell's downlink timing as a basis for determining uplink transmission timing in the target cell, the patent creates a mediating relationship that ensures timing alignment across multiple cells with different timing advance groups.
2Reliability
If random access procedure is performed on each cell independently, then uplink synchronization for each cell is achieved, but system complexity and signaling overhead increase
Solution Approach 1:
The reference cell serves multiple functions: it provides downlink timing reference for uplink transmission timing determination and acts as the basis for random access procedure coordination. By making the reference cell multi-functional, the patent reduces the need for separate independent procedures while maintaining synchronization reliability across multiple cells.
Solution Approach 2:
The patent establishes the reference cell relationship in advance before uplink transmission. The user equipment determines the uplink transmission timing based on the pre-established reference cell's downlink timing, rather than performing separate timing alignment procedures for each cell. This preliminary establishment of timing reference relationships reduces subsequent procedure complexity.
Data Source
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AI summary
The present invention relates to a wireless communication system. More particularly, the present invention relates to a method for acquiring uplink synchronization in a terminal having a plurality of cells in a carrier aggregation-based wireless communication system and an apparatus therefor, the method comprising the steps of: transmitting a random access preamble on a first cell; receiving a random access response including an uplink timing adjustment value for the first cell after transmitting the random access preamble; and performing uplink transmission in the first cell by using the uplink timing adjustment value, wherein a transmission time point of the random access preamble is given based on a specific time point related to a second cell.