Dynamic ACK/NACK Codebook for Reducing LTE Feedback Overhead
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Solution Overview
Problem
In LTE systems, the existing methods for UE to feedback ACK/NACK for downlink subframes result in high system overheads, especially with carrier aggregation, as UE needs to feed back information for all preconfigured subframes even if only a subset is actually scheduled by the base station.
Innovation Solution
The terminal sends feedback information only for the downlink subframes actually scheduled by the network, using a first codebook that corresponds to the instantly scheduled downlink subframe set, reducing the number of bits needed and enhancing demodulation performance by not including unscheduled subframes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE feeds back ACK/NACK for all preconfigured downlink subframes in carrier aggregation, then the base station can receive complete feedback information, but the system overhead increases significantly
Solution Approach 1:
The patent extracts only the necessary feedback information for actually scheduled downlink subframes from the complete set of preconfigured subframes. By identifying and removing unscheduled subframes from the feedback codebook, the solution reduces overhead while maintaining reliability for the actual transmitted data.
Solution Approach 2:
The patent introduces dynamic codebook determination where the feedback codebook size and content are adaptively adjusted based on the actual scheduling information. The codebook dynamically includes only the downlink subframes that are actually scheduled, rather than using a fixed preconfigured set, thereby optimizing overhead based on real-time conditions.
2Ease of manufacture
If UE uses a fixed codebook size for ACK/NACK feedback in carrier aggregation, then the feedback mechanism is simple, but the overhead cannot be optimized when fewer subframes are scheduled
Solution Approach 1:
The patent transitions from a fixed codebook size to a dynamic codebook size that adapts to the number of actually scheduled downlink subframes. The codebook size is determined based on the scheduling information, allowing the feedback mechanism to optimize the number of feedback bits while maintaining ease of implementation through standardized determination rules.
3Loss of information
If UE feeds back ACK/NACK for all configured carriers and subframes, then complete transmission status is captured, but the demodulation performance deteriorates due to high overhead
Solution Approach 1:
The patent extracts and transmits only the essential feedback information for actually scheduled subframes, removing redundant feedback for unscheduled subframes. This extraction approach maintains complete transmission status information for relevant data while reducing the overall feedback burden that degrades demodulation performance.
Solution Approach 2:
The patent changes the parameter of feedback codebook size from a fixed large value to a dynamically adjusted value based on actual scheduling. This parameter change optimizes the balance between information completeness and demodulation performance by reducing the number of feedback bits transmitted.
Data Source
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AI summary
The present invention relates to the field of mobile communications technologies, and in particular, to an information sending method, an information receiving method, and a device, so as to resolve a technical problem that system overheads are relatively high when UE feeds back an ACK/NACK corresponding to a downlink subframe to a base station. In embodiments of the present invention, a terminal may send feedback information for a downlink subframe to a network device in a first feedback manner, that is, a first codebook of the feedback information is determined according to an instantly scheduled downlink subframe set. This is equivalent to the fact that the terminal performs feedback for the downlink subframe actually scheduled by the network device. In this way, information about a downlink subframe that is not actually scheduled by the network device does not need to be fed back, and a quantity of bits included in the first codebook is less than a quantity of bits that need to be fed back by the terminal in the prior art, thereby greatly reducing system overheads when compared with the prior art.