Semistatic HARQ Codebooks Sized for Simultaneous Downlink Reception
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Solution Overview
Problem
Existing wireless communication systems, particularly in 5G NR, face inefficiencies in hybrid automatic repeat request (HARQ) feedback due to large HARQ codebooks that consume excessive bandwidth, limiting data transfer rates and spectral efficiency.
Innovation Solution
The implementation of a semistatic HARQ codebook that is sized based on the maximum number of simultaneous downlink transmissions a user equipment (UE) can receive, reducing the number of bits required for HARQ ACK/NACK feedback by accounting for the UE's reception capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional HARQ codebook is used to provide comprehensive feedback for all downlink transmission occasions, then the completeness of HARQ feedback is improved, but the bandwidth consumption increases and spectral efficiency decreases
Solution Approach 1:
The patent extracts and removes unnecessary feedback bits from the HARQ codebook by identifying and eliminating redundant ACK/NACK indications for transmission occasions that cannot occur simultaneously given the UE's reception capability constraints. This extraction process reduces the codebook size while retaining only the essential feedback information needed for reliable HARQ operation.
Solution Approach 2:
The patent changes the parameter of codebook size by dynamically adjusting it based on the UE's maximum simultaneous reception capability (k value). The codebook is configured to include only the minimum necessary number of feedback bits required to cover all possible downlink transmission combinations that the UE can actually receive, thereby optimizing bandwidth usage while maintaining feedback reliability.
2Reliability
If a larger HARQ codebook is used to cover more downlink transmission occasions, then the spectral efficiency decreases due to more feedback bits, but the coverage of feedback scenarios is improved
Solution Approach 1:
The patent applies dynamics by making the HARQ codebook size adaptive rather than static. The codebook is dynamically configured based on the UE's specific reception capability (k value) and the actual downlink transmission schedule. This dynamic adjustment ensures that the codebook always contains the optimal number of feedback bits - no more, no less - thereby maximizing data transfer efficiency while maintaining complete feedback coverage for all feasible transmission scenarios.
Solution Approach 2:
The patent avoids excessive action by not including feedback bits for all possible downlink transmission occasions regardless of UE capability. Instead, it applies partial action by including only the necessary subset of feedback bits that correspond to transmission occasions the UE can actually receive and feedback on, eliminating redundant feedback elements that would unnecessarily reduce data transfer rates.
3Productivity
If the HARQ codebook size is reduced to minimize bandwidth usage, then the bandwidth efficiency is improved, but the ability to provide feedback for all possible downlink transmissions is reduced
Solution Approach 1:
The patent applies preliminary action by pre-configuring the HARQ codebook size based on the UE's maximum simultaneous reception capability (k value) before actual downlink transmissions occur. This preliminary configuration ensures that the codebook is sized appropriately from the outset to provide complete feedback coverage for all possible transmission scenarios the UE can handle, eliminating the need for later adjustments that might compromise feedback completeness.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for reducing a size of semistatic codebooks for HARQ feedback. A method that may be performed by a user equipment (UE) includes determining a number (M) of candidate downlink transmission occasions for a time period, determining a maximum number (k) of simultaneous downlink transmissions the UE can receive during the time period, receiving one or more downlink transmissions during the time period from a base station, and determining a type of encoding for the HARQ feedback based on: (i) a number of the one or more downlink transmissions received, (ii) the number (M) of candidate downlink transmission occasions for the time period, and/or (iii) the maximum number (k) of simultaneous downlink transmissions.