HARQ Retransmission Coding With Polar and LDPC Rate Adaptation
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Solution Overview
Problem
Current communication systems face challenges in efficiently utilizing polar codes and LDPC codes, particularly in cellular networks, due to restrictions on coded block lengths and the need for puncturing schemes, which affect encoding and decoding complexity and error rates in HARQ schemes.
Innovation Solution
The use of polar codes for successive HARQ retransmissions with varying information bit lengths and different LDPC code schemes based on protograph matrices to support flexible coding rates and channel resource management, including incremental freezing and reduced size polar codes for improved error correction and resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If polar codes are used with fixed power-of-2 block lengths, then encoding and decoding complexity is reduced, but adaptability to varying information bit lengths is worsened
Solution Approach 1:
The information bits are segmented into multiple groups, with different numbers of information bits transmitted in different groups. The first group contains a first number of information bits, the second group contains a second number of information bits, and so on. This segmentation allows the system to adapt to varying total information bit lengths while maintaining fixed power-of-2 block lengths for each polar code encoding operation, thus resolving the contradiction between complexity and adaptability.
Solution Approach 2:
The system dynamically adjusts the number of information bits in different transmission groups based on channel conditions and requirements. By varying the information bit length in each group while keeping the coded block length as a power of 2, the system achieves dynamic adaptability without increasing the fundamental encoding/decoding complexity of the polar code structure.
2Adaptability or versatility
If puncturing schemes are applied to polar codes, then flexibility in coding rates is improved, but error rates increase
Solution Approach 1:
Different freezing patterns are applied to different groups of polar codes based on their specific requirements. Each group can have its own frozen bit positions optimized for its coding rate and channel conditions, rather than applying a uniform puncturing scheme. This local optimization reduces error rates while maintaining flexibility in coding rates.
Solution Approach 2:
The system changes the freezing pattern parameter for different groups of polar codes to achieve different coding rates. By adjusting which bits are frozen in each group rather than using fixed puncturing, the system achieves coding rate flexibility while maintaining better error performance through optimized bit selection.
3Adaptability or versatility
If multiple groups of polar codes with different information bit lengths are used, then adaptability to channel conditions is improved, but device complexity increases
Solution Approach 1:
The system uses a universal polar code encoder structure that can handle multiple information bit lengths by adjusting the freezing pattern and information bit allocation across groups. This multi-functional approach allows a single encoder design to serve multiple adaptability requirements without proportionally increasing hardware complexity, as the underlying polar code structure remains the same.
Data Source
AI summary
A method may comprise receiving a first signal comprising first LDPC bits including systematic bits and parity bits and transmitting information indicating that the first signal was incorrectly received. A second signal comprising second LDPC bits may be received in response to the transmitting. The second signal may include LDPC bits according to a lifting size of an LDPC base graph.