LDPC Rate Matching Under UE Soft Buffer Limits
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Solution Overview
Problem
In wireless communication systems, particularly in 3GPP LTE, the existing channel coding schemes like turbo codes for incremental redundancy HARQ face challenges in managing UE soft buffer storage and implementation complexity, limiting the ability to transmit larger data packets efficiently.
Innovation Solution
The implementation of low-density parity-check (LDPC) codes with limited buffer rate matching (LBRM) and structured LDPC codes that allow for efficient encoding and decoding, enabling the eNodeB to transmit larger data packets by optimizing UE soft buffer size and selecting redundancy versions aligned with the LDPC code structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turbo codes with incremental redundancy HARQ are used, then error correction capability is improved, but UE soft buffer storage requirements increase and implementation complexity increases
Solution Approach 1:
The patent segments the code block into multiple code block segments (CBS) and applies separate LDPC encoding to each segment. This segmentation allows the UE to process and store soft bits for each segment independently, reducing the overall buffer management complexity while maintaining error correction capability across the entire transport block
Solution Approach 2:
The patent changes the coding scheme from turbo codes to LDPC codes with specific parameters (code rate, mother code rate, shift size). This parameter change enables more efficient rate matching and soft buffer utilization, reducing the storage requirements compared to traditional turbo code implementations
2Productivity
If larger data packets are transmitted, then productivity is improved, but UE soft buffer storage requirements increase
Solution Approach 1:
By segmenting the transport block into multiple code block segments and encoding each separately, the patent enables more efficient utilization of the UE soft buffer. The segmented approach allows for better distribution of soft bit storage across multiple smaller units, increasing the effective data transmission capacity within the same buffer constraints
Solution Approach 2:
The patent transmits only a subset of encoded bits (partial action) based on the available UE soft buffer size. By using rate matching to select which encoded bits to transmit, the system can transmit larger data packets efficiently by sending only the necessary portion of encoded data, avoiding the need to store all possible redundancy bits
3Device complexity
If structured LDPC codes with limited buffer rate matching are used, then implementation complexity is reduced, but flexibility in coding schemes decreases
Solution Approach 1:
The patent uses structured LDPC codes with specific parameters (mother code rate of 1/3, configurable code rates, shift size parameters) that provide a balance between implementation simplicity and coding flexibility. These parameterized structured codes maintain regular patterns that simplify encoder/decoder design while allowing adaptation to different transmission requirements through parameter adjustment
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.