LDPC Rate Matching for HARQ Soft Buffer Constraints
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Solution Overview
Problem
In wireless communication systems, particularly in 3GPP LTE, existing coding schemes like turbo codes for incremental redundancy HARQ face challenges with UE soft buffer storage limitations and increased implementation complexity, which can be mitigated by adopting low-density parity-check (LDPC) codes with limited buffer rate-matching for efficient error correction and data transmission.
Innovation Solution
The implementation of LDPC codes with structured parity check matrices and limited buffer rate-matching (LBRM) allows for efficient encoding and decoding, enabling the eNodeB to transmit larger data packets with higher coding rates, aligning the UE soft buffer size with the LDPC code structure, and supporting multiple HARQ processes without increasing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turbo codes are used for incremental redundancy HARQ, then error correction capability is improved, but UE soft buffer storage requirements increase and implementation complexity increases
Solution Approach 1:
The patent segments the coded bits into multiple redundancy versions that can be transmitted separately and combined at the receiver. This segmentation allows the UE to process and store only partial redundancy information at any given time, reducing soft buffer requirements while maintaining the error correction benefits of turbo codes through incremental redundancy HARQ
Solution Approach 2:
The patent changes the parameter of coding scheme from conventional turbo code implementation to LDPC codes with specific structured parity check matrices. This parameter change enables more efficient rate-matching and reduces the amount of soft buffer storage needed while maintaining or improving error correction performance through the properties of LDPC codes
2Productivity
If higher coding rates are used, then data transmission efficiency is improved, but error correction capability deteriorates
Solution Approach 1:
The patent implements dynamic rate-matching that adapts the coding rate based on channel conditions and buffer constraints. The system can dynamically select different redundancy versions and adjust the amount of redundancy transmitted, allowing operation at higher effective coding rates when channel conditions permit while maintaining error correction capability through adaptive selection of redundancy levels
3Productivity
If multiple HARQ processes are supported, then throughput is improved, but soft buffer storage requirements increase
Solution Approach 1:
The patent segments the soft buffer storage requirements across multiple HARQ processes by implementing rate-matching that divides coded bits into multiple redundancy versions. Each HARQ process can be handled with a portion of the total buffer, and the segmentation allows efficient reuse of buffer resources across different HARQ processes, supporting multiple simultaneous processes without linearly increasing total buffer requirements
Solution Approach 2:
The patent creates a universal rate-matching framework that can handle multiple HARQ processes using the same buffer resources through proper management and allocation. The structured approach allows the same buffer to serve multiple purposes across different HARQ processes, reducing the total quantity of buffer storage needed while maintaining support for multiple parallel processes
Data Source
AI summary
Technology for a transmitter operable to perform data transmissions using low density parity check (LDPC) codes is disclosed. The transmitter can determine soft buffer information (Nsoft) for a receiver. The transmitter can determine a soft buffer partition per HARQ process (NIR) for the UE. The transmitter can obtain, for a transport block, a number of code block segments (C). The transmitter can select a shift size value (z). The transmitter can determine an amount of soft buffer available for the code block segments (Ncb) based on NIR, C, and z. The transmitter can encode the code block segments based on an LDPC coding scheme to obtain encoded parity bits. The transmitter can select a subset of the encoded parity bits based on the determined amount of soft buffer associated with the code block segments.