ACK/NACK Transmission in TDD Wireless Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems based on Time Division Duplex (TDD), the increased payload of Hybrid Automatic Repeat Request (HARQ) ACK/NACK signals complicates data rate transmission, necessitating a method to reduce payload size while maintaining transmission reliability.
Innovation Solution
A method and apparatus for transmitting ACK/NACK signals in a TDD system, where a user equipment receives downlink transport blocks from multiple serving cells, determines ACK/NACK states, and transmits these states in an uplink subframe using a specific mapping scheme that reduces the payload size by employing a downlink assignment index (DAI) and orthogonal sequences to minimize errors between the base station and user equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the payload of HARQ ACK/NACK is increased to support multiple serving cells in TDD, then transmission reliability is improved, but data rate for user traffic decreases
Solution Approach 1:
The patent segments the ACK/NACK feedback into multiple groups based on downlink subframe indices, where each group contains ACK/NACK information for a specific range of downlink subframes. This segmentation reduces the payload size in each uplink subframe while maintaining comprehensive coverage of all downlink transmissions across multiple serving cells, thereby resolving the contradiction between reliability and data rate.
2Reliability
If multiple downlink subframes are associated with one uplink subframe, then transmission reliability is improved, but payload size increases
Solution Approach 1:
The patent divides the associated downlink subframes into multiple groups, with each group's ACK/NACK information transmitted in a separate uplink subframe. This segmentation approach maintains the reliability benefits of associating multiple downlink subframes while controlling payload size by distributing the feedback across multiple uplink opportunities rather than consolidating it in a single subframe.
Solution Approach 2:
The patent implements periodic transmission of ACK/NACK feedback across multiple uplink subframes, where different groups of downlink subframes are acknowledged in different uplink subframes according to a periodic pattern. This periodic action distributes the payload over time, reducing the instantaneous payload size while maintaining overall transmission reliability through repeated acknowledgment opportunities.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided are a method and an apparatus for transmitting ACK/NACK in a time division duplex (TDD)-based wireless communication system. A terminal receives zero or more downlink transmission blocks in M downlink subframes from a first serving cell, and determines an ACK/NACK state {HARQ-ACK(1),HARQ-ACK(2),HARQ-ACK(3),HARQ-ACK(4)} for the first serving cell. The terminal determines an ACK/NACK response based on said ACK/NACK state, and transmits the ACK/NACK response in an uplink subframe.