HARQ-ACK Bundling in Multi-Antenna Wireless Systems
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Solution Overview
Problem
Current multi-antenna wireless communications systems face challenges in efficiently encoding Hybrid Automatic Repeat Request (HARQ) Acknowledgements (ACK/NACK) information, particularly in four-branch MIMO systems where up to four transport blocks are processed simultaneously, requiring an effective method to represent and transmit HARQ-ACK/NACK information without degrading system performance.
Innovation Solution
A method for efficiently encoding HARQ-ACK/NACK information by bundling and encoding the information using an existing MIMO codebook, allowing for the representation of multiple transport blocks within a single codeword, thereby maintaining high system performance even with multiple simultaneous streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If four-branch MIMO is introduced to increase spectral efficiency and support up to four transport blocks, then downlink spectral efficiency and coverage are improved, but the complexity of HARQ-ACK/NACK encoding and feedback channel structure increases
Solution Approach 1:
The patent combines multiple HARQ-ACK/NACK bits corresponding to different transport blocks into a single codeword using an existing MIMO codebook. This merging approach allows four transport blocks to be acknowledged using the same encoding structure as two transport blocks, thereby maintaining spectral efficiency gains while avoiding the need for a completely new feedback channel structure.
Solution Approach 2:
The existing MIMO codebook designed for two transmit antennas is made universal to handle up to four transmit antennas in four-branch MIMO systems. By reusing the same codebook structure with appropriate mapping of HARQ-ACK/NACK bits, the system achieves multi-functionality without increasing encoding complexity or requiring separate feedback channels.
2Productivity
If up to four transport blocks are processed simultaneously in four-branch MIMO, then data throughput is increased, but the number of ACK/NACK bits to be transmitted increases
Solution Approach 1:
Multiple HARQ-ACK/NACK bits are merged into a single codeword by mapping them to positions in the existing MIMO codebook. This combining approach reduces the number of separate transmissions needed while still conveying acknowledgment information for all four transport blocks, thereby managing the quantity of feedback information efficiently.
Solution Approach 2:
The patent transforms the problem from transmitting multiple separate ACK/NACK bits to encoding them in a different dimensional space using the MIMO codebook structure. By mapping binary ACK/NACK information to codewords in a higher-dimensional codebook space, the system efficiently packs multiple acknowledgment states into a compact format suitable for uplink transmission.
3Reliability
If a new feedback channel structure is designed for four-branch MIMO, then HARQ-ACK/NACK information can be accurately represented, but system complexity and implementation overhead increase
Solution Approach 1:
The existing MIMO codebook is made universal to serve both two-branch and four-branch MIMO systems. By maintaining the same codebook structure and using different mapping strategies for different numbers of transport blocks, the system achieves reliable HARQ-ACK/NACK representation without introducing new feedback channel structures, thereby avoiding increased implementation overhead.
Solution Approach 2:
The patent changes parameters within the existing codebook framework, such as the number of information bits and their mapping positions, to accommodate four transport blocks. By adjusting these parameters rather than redesigning the entire feedback channel structure, the system maintains reliability while minimizing complexity increases.
Data Source
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AI summary
There is provided a method performed by a User Equipment, UE, for encoding Hybrid Automatic Repeat Request, HARQ, Acknowledgements, ACK/NACK,in a multi-antenna wireless communications system. The method comprises the step (S1) of bundling, also referred to as co-representing, a HARQ-ACK/NACK to be sent in response for a transport block of information with a HARQ-ACK/NACK to be sent in response for another transport block of information, when more than two transport blocks of information are used. The method also comprises the step (S2) of encoding the bundled HARQ-ACK/NACK information.