ACK/NACK Feedback Timing for LTE Carrier Aggregation
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Solution Overview
Problem
Existing ACK/NACK feedback methods in LTE systems with carrier aggregation across different frequency bands require multiple power amplifiers, increasing costs and reducing performance for cell edge users, while alternative methods necessitate changes to scheduler algorithms.
Innovation Solution
A method where the UE determines the number of public uplink sub-frames based on configured frame structure configurations and selects a timing relationship to feed back ACK/NACK information without requiring additional amplifiers or altering existing scheduler algorithms, supporting carrier aggregation across different frame structure configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple power amplifiers are used to support carrier aggregation across different frequency bands with different frame structure configurations, then the system can achieve carrier aggregation functionality, but the device cost increases and performance for cell edge users deteriorates
Solution Approach 1:
The patent merges the feedback timing mechanisms of multiple component carriers into a unified feedback process. By determining a single feedback timing based on the latest downlink subframe across all component carriers, the system combines multiple feedback operations into one, eliminating the need for separate power amplifiers for each carrier while maintaining carrier aggregation functionality.
Solution Approach 2:
The patent creates a universal feedback timing mechanism that works across all component carriers with different frame structure configurations. The determined feedback timing serves multiple component carriers simultaneously, making the feedback system multi-functional and eliminating the need for carrier-specific feedback paths that would require separate power amplifiers.
2Adaptability or versatility
If feedback timing is determined separately for each component carrier with different frame structure configurations, then each carrier can be optimized independently, but the feedback complexity and scheduling difficulty increases
Solution Approach 1:
Instead of determining feedback timing for each component carrier separately (bottom-up approach), the patent inverts the approach by determining a single feedback timing that accommodates all component carriers (top-down approach). This is achieved by identifying the latest downlink subframe across all carriers and setting the feedback timing based on that, thereby simplifying the management complexity while preserving configuration flexibility.
3Adaptability or versatility
If carrier aggregation with different frame structure configurations is supported, then system adaptability improves, but the timing relationship management between downlink and uplink becomes more difficult
Solution Approach 1:
The patent changes the parameter used for determining feedback timing from carrier-specific parameters to a unified parameter based on the latest downlink subframe across all component carriers. This parameter change simplifies the timing relationship management by providing a single reference point for all carriers, regardless of their different frame structure configurations.
Data Source
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AI summary
Embodiments of the present invention disclose a method, and an apparatus thereof, for transmitting feedback information by a terminal supporting a time division duplex, TDD, in a wireless communication system, the method comprising, receiving downlink data on a physical downlink shared channel, PDSCH, of a secondary cell, SCell, determining at least one subframe which is an uplink subframe for both of a primary cell, PCell, and the SCell, based on a first TDD frame structure configuration of the PCell and a second TDD frame structure configuration of the SCell, determining, based on a subframe index of the determined at least one subframe, a third TDD frame structure configuration among a plurality of configured TDD frame structure configurations, wherein a subframe index of an uplink subframe for the third TDD frame structure configuration is the same as the subframe index of the determined at least one subframe, and transmitting a hybrid automatic repeat request, HARQ, acknowledgement, ACK, response for the downlink data received on the SCell, the HARQ ACK response being transmitted in the uplink subframe for the third TDD frame structure configuration on the PCell, wherein the uplink subframe for the third TDD frame structure configuration is determined based on a timing relationship between a PDSCH and a HARQ ACK response corresponding to the third TDD frame structure configuration, and wherein the first TDD frame structure configuration, the second TDD frame structure configuration and the third TDD frame structure configuration are different.