Downlink Time Reference Determination in Carrier Aggregation
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Solution Overview
Problem
In LTE systems, determining the absolute time for sending uplink data is challenging when multiple downlink component carriers are used, especially when some employ RRH or repeaters, as the existing technologies lack a solution for setting a consistent downlink time reference.
Innovation Solution
A method where a terminal takes a downlink primary component carrier as a time reference and determines an absolute time to send uplink data based on time advance, adapting when the primary component carrier changes or a radio link failure occurs, and reconfiguring through radio link control processes to maintain synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple downlink component carriers are used with RRH or repeaters, then data rate and bandwidth are improved, but determining consistent downlink time reference becomes difficult
Solution Approach 1:
The patent segments the downlink carriers into different groups based on their time reference relationships. Carriers using RRH/repeaters are separated from direct carriers, each group having its own time reference. This segmentation allows each group to be managed independently, resolving the time reference inconsistency problem while maintaining the benefits of multiple carriers for high data rate.
Solution Approach 2:
The patent introduces a time reference configuration mechanism as an intermediary between the multiple downlink carriers and the uplink transmission. This intermediary (time reference configuration) mediates the time alignment by providing explicit time reference indications for each carrier group, enabling consistent uplink timing determination despite the presence of multiple downlink carriers with different propagation characteristics.
2Productivity
If carrier aggregation is implemented to support bandwidth greater than 20 MHz, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent creates a universal time reference determination mechanism that works across all carrier aggregation scenarios. The same time reference configuration approach is applied whether using 2 carriers or many carriers, whether carriers are continuous or non-continuous, whether single-band or multi-band. This multi-functional solution simplifies the overall system by providing a unified approach rather than separate solutions for each carrier aggregation scenario.
Solution Approach 2:
The patent changes the parameter representation from absolute time calculations to relative time reference configurations. By using time reference indicators that specify relative timing relationships rather than absolute timing values, the system can support arbitrary numbers of carriers and bandwidth configurations without increasing terminal complexity. The parameter change enables scalable carrier aggregation.
3Adaptability or versatility
If non-continuous carrier aggregation is used due to spectrum availability, then adaptability is improved, but time synchronization becomes more difficult
Solution Approach 1:
The patent applies local quality by assigning different time reference characteristics to different carrier groups based on their local propagation conditions. Carriers with RRH/repeaters receive one type of time reference configuration, while direct carriers receive another. This local differentiation allows the system to adapt to non-continuous spectrum availability while maintaining reliable time synchronization within each local carrier group.
Data Source
AI summary
Disclosed is a method for determining downlink time reference, including: a terminal taking a downlink primary component carrier as a time reference and determining an absolute time to send uplink data according to a time advance based on the time reference. Also disclosed is a method for determining downlink time reference, including: a terminal taking a downlink component carrier which performs random access, or a downlink component carrier corresponding to an uplink component carrier, or another downlink component carrier within a same frequency band as the downlink component carrier corresponding to the uplink component carrier as a time reference, and determining an absolute time to send uplink data according to a time advance based on the time reference.