CBG-Based NOMA Transmission for 5G NR Spectral Efficiency
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Solution Overview
Problem
Non-orthogonal multiple access (NOMA) transmission schemes in 5G NR systems face reduced spectral efficiency due to bursty interference and persistent retransmission interference, especially in scenarios like massive machine-type communications (mMTC), where conventional HARQ mechanisms lack precision in identifying failed code blocks.
Innovation Solution
Implementing code block group (CBG)-based NOMA transmission, where user equipment (UE) receives configurations for CBG-based transmission and NOMA schemes, allowing for precise feedback of failed CBGs, enabling targeted retransmissions and improved HARQ combining, thereby enhancing spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional HARQ mechanisms are used in NOMA transmission, then the system can support grant-free uplink transmissions for mMTC UEs, but spectral efficiency is reduced due to persistent retransmission interference and inability to identify failed code blocks precisely
Solution Approach 1:
The transport block is segmented into multiple code block groups (CBGs) rather than treating it as a single unit. Each CBG can be independently acknowledged and retransmitted. This segmentation allows the system to identify and retransmit only the failed CBGs instead of retransmitting the entire transport block, thereby reducing persistent retransmission interference and improving spectral efficiency while maintaining transmission reliability
Solution Approach 2:
Different CBGs within the same transport block are treated with different quality levels based on their individual decoding outcomes. Successfully decoded CBGs are acknowledged without retransmission, while failed CBGs are identified and retransmitted with enhanced redundancy. This local quality approach prevents successful CBGs from being unnecessarily retransmitted, reducing interference and improving overall spectral efficiency
2Productivity
If code block group (CBG) based transmission is implemented, then spectral efficiency is improved through targeted retransmissions, but the complexity of the transmission scheme increases
Solution Approach 1:
The transport block is divided into multiple code block groups (CBGs) that can be independently handled. Each CBG is assigned a unique identifier and can be individually acknowledged or retransmitted. This segmentation enables precise error identification and targeted retransmission, improving spectral efficiency by avoiding unnecessary retransmissions of successfully decoded portions
Solution Approach 2:
Different CBGs are treated differently based on their individual decoding status. Successfully decoded CBGs receive ACKs and are not retransmitted, while failed CBGs receive NACKs and are retransmitted with appropriate redundancy versions. This local quality approach optimizes resource utilization by applying different transmission strategies to different parts of the same transport block
3Reliability
If whole transport block retransmission is performed upon any CBG failure, then transmission reliability is maintained, but transmission overhead increases and spectral efficiency decreases
Solution Approach 1:
The transport block is segmented into multiple independently acked code block groups (CBGs). When a decoding failure occurs, only the specific failed CBG(s) are identified and retransmitted rather than the entire transport block. This segmentation maintains transmission reliability for failed portions while improving spectral efficiency by avoiding redundant retransmissions of successful portions
Solution Approach 2:
Instead of performing full transport block retransmission (excessive action), the system performs partial retransmission of only the failed CBGs. This partial action is sufficient to maintain overall transmission reliability while significantly reducing the overhead and improving spectral efficiency by eliminating unnecessary retransmission of successfully decoded data
Data Source
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AI summary
This document discloses procedures and apparatus for code block group (CBG)-based non-orthogonal multiple access (NOMA) transmission for a wireless communication link (130), such as fifth generation new radio. In aspects, a user equipment (UE) (110) receives a first message including a first configuration for a CBG-based transmission scheme. The UE (110) receives a second message including a second configuration for a NOMA transmission scheme. The UE (110) transmits uplink control information (UCI) to the base station (120) using the NOMA transmission scheme from the second configuration. Further, the UE (110) transmits uplink data associated with the UCI using a CBG-based NOMA transmission scheme based on the first configuration and the second configuration. The UE (110) receives a hybrid automatic retransmission request (HARQ) message including one or more HARQ acknowledgements (ACKs) or negative acknowledgements (NACKs) corresponding to a decoding result of the uplink data.