Time Alignment Timer Management for Carrier Aggregation Timing
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Solution Overview
Problem
In Long Term Evolution (LTE) systems using carrier aggregation, managing multiple uplink timings becomes challenging due to differences in the locations of eNB apparatuses operating with primary and secondary carriers, leading to potential transmission timing issues and interference between uplink signals.
Innovation Solution
A method is introduced to operate multiple time alignment timers by categorizing carriers with similar uplink timings into groups, allowing for separate signaling of time alignment timer values and optimizing transmission timings based on whether the primary cell is included, thereby improving communication reliability and system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple carriers are aggregated to expand bandwidth, then system capacity and data rate are improved, but managing multiple uplink timings becomes complex and transmission timing issues arise
Solution Approach 1:
The patent segments carriers into different Timing Advance Groups (TAGs) based on their uplink timing characteristics. Each TAG is managed independently with its own time alignment timer, allowing the system to handle multiple carriers without managing all of them as a single complex entity. This segmentation reduces management complexity while maintaining the bandwidth expansion benefits of carrier aggregation.
Solution Approach 2:
The patent introduces a universal time alignment timer mechanism that can be applied across multiple carriers and TAGs. The timer structure and operation principles remain consistent whether managing one carrier or multiple carriers, providing a unified approach that simplifies implementation while supporting carrier aggregation functionality.
2Area of stationary object
If eNB apparatuses are deployed at different locations to expand coverage, then coverage area is improved, but uplink transmission timing differences cause interference
Solution Approach 1:
The patent applies local quality by configuring different time alignment parameters for different carriers based on their specific propagation characteristics. Each carrier's uplink timing is adjusted according to the local conditions (distance to eNB, propagation delay) of that specific carrier frequency, ensuring that signals from UEs arrive synchronously at their respective eNBs despite different locations and distances.
Solution Approach 2:
The patent changes the timing parameters (Timing Advance values) for different carriers to compensate for different propagation delays caused by eNBs at different locations. By adjusting these parameters, the system maintains proper uplink synchronization across geographically distributed eNBs, preventing interference while preserving expanded coverage.
3Measurement precision
If separate time alignment timers are operated for each carrier group, then transmission timing accuracy is improved, but signaling overhead increases
Solution Approach 1:
The patent merges the management of time alignment timers by introducing a common reference timer (timeAlignmentTimer) that governs multiple TAGs. Instead of maintaining completely independent timer mechanisms for each carrier group, the system combines them under a unified timer framework, reducing signaling overhead while maintaining the ability to manage timing accuracy for each group separately when needed.
Data Source
AI summary
A method of operating multiple time alignment timers (TimeAlignmentTimer) is provided for facilitating communication between and evolved Node B (eNB) and a User Equipment (UE) in a Long Term Evolution (LTE) system supporting multiple carriers. The method includes starting a first TAT of a first group including the primary cell, starting a second TAT when Timing Advance (TA) information on a second group not including the primary cell is received; and determining transmission of at least one of a Hybrid Automatic Repeat Request Acknowledgement/Negative-acknowledgement (HARQ ACK/NACK), a physical uplink control channel, and a sounding reference signal according to a start and an expiration of at least one of the first and second TATs.