HARQ ACK/NACK Transmission for Carrier Aggregation
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Solution Overview
Problem
Current LTE systems face limitations in transmitting hybrid automatic repeat request (HARQ) acknowledgments (ACK/NACK) when more than five carriers are aggregated, as they exceed the 20-bit capacity of existing PUCCH formats, leading to inefficient resource utilization and reduced throughput.
Innovation Solution
A method and apparatus for a user equipment (UE) to receive a list of sets limited in HARQ-ACK/NACK transmission from a base station, determining the relevant set for transmission, and generating uplink control information (UCI) to efficiently transmit HARQ-ACK/NACK, excluding unnecessary bits, by using higher layer signaling and downlink control information (DCI), allowing for flexible HARQ-ACK/NACK payload size reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If more than five carriers are aggregated in carrier aggregation, then the data transmission capacity is improved, but the HARQ-ACK/NACK payload size exceeds the 20-bit limit of existing PUCCH formats
Solution Approach 1:
The patent extracts and transmits only the necessary HARQ-ACK/NACK information bits corresponding to actually received downlink data, excluding bits for cells or carriers where no data was received. This selective extraction reduces the payload size to fit within the 20-bit PUCCH limit while maintaining adequate feedback for aggregated carriers
Solution Approach 2:
The patent implements dynamic determination of HARQ-ACK/NACK payload size based on the actual number of downlink data items received across aggregated carriers. The payload size adapts dynamically rather than being fixed, allowing efficient use of the 20-bit limit by including only necessary acknowledgment bits for currently active data transmissions
2Productivity
If the HARQ-ACK/NACK payload size is reduced to fit within 20 bits, then the PUCCH transmission capacity is improved, but the ability to provide feedback for all aggregated cells is reduced
Solution Approach 1:
The patent applies partial action by transmitting HARQ-ACK/NACK feedback only for the subset of aggregated cells that actually have downlink data requiring acknowledgment. Instead of providing feedback for all aggregated cells uniformly, the system performs partial feedback transmission, reducing payload size while maintaining necessary feedback coverage for active data streams
3Adaptability or versatility
If existing PUCCH formats are used for more than five aggregated cells, then device compatibility is maintained, but the system cannot handle the increased HARQ-ACK/NACK bit requirements
Solution Approach 1:
The patent changes the parameter of HARQ-ACK/NACK payload size to adapt to carrier aggregation scenarios with more than five cells. By dynamically adjusting the number of feedback bits based on actual data reception across aggregated carriers, the system maintains compatibility with existing 20-bit PUCCH formats while reliably handling feedback for extended carrier aggregation
Data Source
AI summary
Provided in one disclosure of the present specification is a method for transmitting a hybrid automatic repeat request (HARQ) acknowledgement (ACK)/negative-acknowledgement (NACK) for downlink data, when more than five cells are used according to carrier aggregation (CA) by a user equipment (UE). The method comprises the steps of: receiving, from a base station, a list of sets of which HARQ-ACK/NACK transmission is limited, through an upper layer signal; receiving, from the base station, information indicating a set of which HARQ-ACK/NACK transmission is limited at the present turn, from among the list of sets; receiving, from the base station, a plurality of items of downlink data through a plurality of cells; determining the set of which transmission is limited based on the information, from among the list of sets that has been received through the upper layer signal; and generating and transmitting uplink control information (UCI) including HARQ-ACK/NACK for the downlink data but excluding the HARQ-ACK/NACK according to the set which has been determined.