Uplink Timing Reference Selection in Carrier Aggregation
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Solution Overview
Problem
In the LTE-A system with carrier aggregation, the existing technologies only support single uplink timing advance, making it challenging to perform uplink transmission in secondary cells when their timing advances differ from those of the primary cell, especially in multi-TA scenarios.
Innovation Solution
A method and apparatus that allow a user equipment to select a timing reference downlink carrier based on established downlink synchronization, enabling uplink transmission in secondary cells by using the downlink timing of the selected carrier, which can be from a cell within the same TA group, a primary cell, or a pre-configured carrier, to synchronize with the secondary cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single uplink timing advance is used in carrier aggregation system, then device complexity is reduced, but uplink transmission reliability in secondary cells deteriorates when timing advances differ from primary cell
Solution Approach 1:
The patent segments the uplink timing advance management by introducing multiple timing advance values corresponding to different uplink component carriers. Each uplink component carrier can have its own timing advance value, allowing independent timing adjustment for each carrier. This segmentation resolves the contradiction by maintaining simple device operation (using the timing advance of the corresponding carrier) while ensuring reliable uplink transmission on each carrier despite different propagation delays.
2Reliability
If multiple uplink timing advances are supported in carrier aggregation system, then uplink transmission reliability in secondary cells is improved, but device complexity increases
Solution Approach 1:
The patent implements self-service by having the user equipment automatically select the timing advance value corresponding to the uplink component carrier being used. The device determines the timing advance based on the association between the physical downlink control channel and the uplink component carrier, without requiring complex external configuration or manual intervention. This self-service mechanism reduces device complexity while maintaining multiple timing advance values for reliable transmission.
Solution Approach 2:
The patent uses feedback mechanisms where the base station provides timing advance commands through physical downlink control channels, and the user equipment adjusts its uplink transmission timing based on these feedback signals. The timing advance value is determined through feedback from the base station regarding the reception timing of uplink signals, allowing automatic adaptation without increasing device complexity.
3Manufacturing precision
If uplink transmission timing is adjusted for each secondary cell, then uplink transmission precision is improved, but system complexity increases
Solution Approach 1:
The patent applies universality by using the same physical downlink control channel for both downlink data transmission and for conveying timing advance commands. The physical downlink control channel serves multiple functions: carrying downlink control information and providing timing advance feedback. This multi-functionality allows precise timing adjustment for each uplink component carrier without requiring separate dedicated signaling channels, thereby avoiding increased system complexity.
Data Source
AI summary
The invention discloses an uplink transmission method and apparatus in a carrier aggregation system and relates to the field of radio communications so as to address the issue of how to perform uplink transmission in a secondary cell when a base station configures a user equipment additionally with the secondary cell. In the invention, a user equipment selects, under a preset reference carrier selection rule, one of downlink carriers corresponding to cells having already established downlink synchronization with a base station as a timing reference downlink carrier used by a secondary cell after the base station configures the user equipment additionally with the secondary cell; and the user equipment performs uplink transmission in the secondary cell according to downlink timing of the timing reference downlink carrier. With the invention, a timing reference downlink carrier used by an additionally configured secondary cell in uplink transmission can be determined and uplink transmission can be further preformed over the timing reference downlink carrier.