LDPC Protograph Expansion for Incremental Redundancy HARQ
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Solution Overview
Problem
Current HARQ schemes for channel coding in communication systems, particularly in LTE systems, lack improved methods for generating codes that enhance reliability and efficiency in incremental redundancy scenarios, especially for retransmissions.
Innovation Solution
A device and method for generating a second protograph matrix P2 for a HARQ communication apparatus by using row splitting and random integer numbers to create auxiliary matrices, lifting binary matrices, and incorporating specific circulant shifts, which allows for improved code generation and memory efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional HARQ schemes use fixed retransmitted payloads or matrix-based LDPC codes, then the system maintains baseline reliability, but the code generation complexity and memory requirements increase without sufficient performance improvement
Solution Approach 1:
The patent segments the protograph matrix into information bit columns and parity bit columns. The generator matrix is constructed by selecting specific columns from the protograph matrix, creating a segmented structure that simplifies code generation while maintaining reliability through systematic separation of information and parity components.
Solution Approach 2:
The patent extracts only the necessary columns from the protograph matrix to form the generator matrix. By taking out specific columns corresponding to information bits and parity bits, the system reduces code generation complexity while preserving the essential error correction functionality needed for reliable transmission.
2Quantity of substance
If offline HARQ schemes map bits sent more than once to lower reliable constellation points, then memory requirements are reduced, but transmission reliability deteriorates due to mapping less reliable bits to critical positions
Solution Approach 1:
The patent implements dynamic bit mapping that adapts to the transmission scenario. The generator matrix is constructed dynamically based on the current transmission context, allowing the system to optimize which bits are mapped to which constellation points. This dynamic approach ensures that bits requiring higher reliability are appropriately mapped while managing memory requirements.
Solution Approach 2:
The patent changes the mapping parameters based on the transmission type (initial vs. retransmission). By adjusting which columns of the protograph matrix are selected for the generator matrix, the system optimizes the reliability of mapped bits for each specific transmission scenario, improving overall transmission reliability while controlling memory usage.
3Adaptability or versatility
If row splitting is applied to generate auxiliary protograph matrices, then code generation flexibility improves, but the computational complexity increases
Solution Approach 1:
The patent applies row splitting to segment the original protograph matrix into an auxiliary protograph matrix with additional rows. This segmentation provides flexibility in code generation by allowing selective use of different rows for information and parity bits, while the structured nature of the splitting maintains computational tractability.
Solution Approach 2:
The patent performs preliminary row splitting to create the auxiliary protograph matrix before actual code generation. This preliminary action prepares the matrix structure in advance, allowing flexible code generation for different transmission scenarios without repeating complex computations during real-time operation, thus balancing flexibility with computational efficiency.
Data Source
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AI summary
The invention relates to a device (100) and method (1100) for generating on the basis of a first protograph matrix P1 of size m x n, wherein the first protograph matrix P1 defines a first code H1 a second protograph matrix P2 of size (m + d) x (n + d), wherein the second protograph matrix P2 defines a second code H2. The device (100) comprises a processor (102) configured to: (i) generate an auxiliary protograph matrix P' of size (m + d1) x (n + d1) on the basis of the first protograph matrix P1 using row splitting; (ii) generate d2 random integer numbers, wherein d2 = d - d1; (iii) generate a binary matrix M of size d2 x (n - m), wherein rows of the binary matrix M are generated on the basis of the d2 random integer numbers; (iv) generate a matrix M' by lifting the binary matrix M; (v) generate a matrix I of size d2 x d2, wherein the matrix I has zero circulant shifts as diagonal elements and empty circulant shifts as non-diagonal elements; (vi) generate a matrix C1 of size (m + d1) x d2 and a matrix C2 of size d2 x (m + d1), wherein the matrix C1 and the matrix C2 comprise only empty circulant shifts; and (vii) generate the second protograph matrix P2 on the basis of the auxiliary protograph matrix P', the matrix M', the matrix I, the matrix C1 and the matrix C2 wherein the second protograph matrix P2 comprises row weights equal to one of the d2 random integer numbers.