Downlink Protocol Alignment for Decoding Latency Reduction
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Solution Overview
Problem
In 5G wireless communication systems, the MAC layer at user equipment (UE) often experiences delays in decoding downlink (DL) MAC packets due to the need to wait for multiple PHY code blocks to be received and concatenated, leading to potential decode failures and increased power consumption.
Innovation Solution
The proposed solution involves aligning each DL MAC SubPDU packet with the PHY layer code block boundary at the base station, allowing for immediate decoding and passing up the protocol stack once each PHY code block is successfully decoded at the UE, eliminating the need to wait for subsequent code blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MAC layer waits for multiple PHY code blocks to be received and concatenated before decoding, then decoding accuracy is improved, but latency and power consumption increase
Solution Approach 1:
The transport block is segmented into multiple code block groups (CBGs), where each CBG can be independently decoded. This allows the MAC layer to decode complete CBGs as they become available rather than waiting for all code blocks, reducing latency while maintaining decoding accuracy through selective redundancy verification
Solution Approach 2:
The system performs preliminary segmentation of the transport block into CBGs with predefined boundaries that align with code block structures. This preliminary organization enables the MAC layer to immediately begin decoding the first complete CBG without waiting for subsequent code blocks, while still having redundancy information available for error correction
2Reliability
If the MAC layer waits for multiple PHY code blocks to be received and concatenated before decoding, then decoding accuracy is improved, but power consumption increases
Solution Approach 1:
By segmenting the transport block into independent CBGs, the MAC layer can process and decode complete CBGs immediately upon receipt rather than holding all code blocks in memory. This reduces memory storage requirements and associated power consumption while maintaining decoding accuracy through incremental processing
Solution Approach 2:
Each CBG is designed to be self-contained with its own redundancy information, allowing the MAC layer to independently verify and decode each CBG without requiring centralized processing of all code blocks. This self-service capability enables early termination of decoding operations when sufficient data is available, reducing overall power consumption
3Adaptability or versatility
If code blocks are not aligned with MAC sub-packet boundaries, then protocol flexibility is maintained, but decoding complexity and latency increase
Solution Approach 1:
The system applies different boundary alignment requirements to different portions of the data structure. CBGs are aligned with code block boundaries for efficient decoding, while higher-layer protocol structures maintain their own boundary requirements. This local quality approach allows each layer to optimize for its specific needs without compromising overall protocol flexibility
Solution Approach 2:
By segmenting the transport block into CBGs with boundaries aligned to code blocks, the system creates natural decoding points that simplify MAC layer processing. This segmentation reduces decoding complexity by providing clear boundaries for independent processing while maintaining protocol flexibility through the hierarchical structure that accommodates both PHY and MAC layer requirements
Data Source
AI summary
An apparatus and method for downlink data transmission and decoding are disclosed. In the method, a physical layer code block or a physical layer code block group is decoded. A medium access control (MAC) sub-packet corresponding to the decoded physical layer code block or the physical code block group is decoded without waiting for any subsequent physical layer code blocks to be decoded. The decoded MAC sub-packet is passed up a protocol stack.