Polar IR-HARQ Retransmission with Split Codeword Redundancy
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Solution Overview
Problem
Current HARQ re-transmission techniques, such as chase-combining and incremental redundancy, face limitations in achieving optimal coding gain and efficiency, particularly in wireless communication systems, where polar codes are not fully utilized for incremental redundancy hybrid automatic repeat request (IR-HARQ) re-transmissions.
Innovation Solution
The implementation of polar encoding with incremental redundancy HARQ re-transmission, where multiple codewords are generated with varying lengths, and specific subsets of information bits are transmitted in each re-transmission, allowing for improved decoding and error correction by overlapping and combining codewords.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional HARQ re-transmission techniques (chase-combining or incremental redundancy) are used, then error correction capability is improved, but coding gain and transmission efficiency are limited and polar codes are not fully utilized
Solution Approach 1:
The patent segments the polar code transmission into multiple parts across different transmissions. The first transmission sends a first polar code with certain information bits, while the second transmission sends a second polar code with different information bits. This segmentation allows the system to achieve both reliable error correction through multiple transmissions and improved efficiency by utilizing polar codes' full potential in each transmission, rather than repeating the same code.
Solution Approach 2:
The patent implements dynamic adaptation in HARQ re-transmission by selectively transmitting different polar codes based on channel conditions and decoding outcomes. The system dynamically decides whether to perform another polar encoding operation or simply repeat previous transmissions, and determines which specific information bits to transmit in each re-transmission. This dynamic approach maximizes both reliability and transmission efficiency.
2Reliability
If multiple polar codes are transmitted with different information bit distributions, then coding gain is improved, but system complexity increases
Solution Approach 1:
The patent performs preliminary polar encoding operations to generate multiple candidate polar codes before actual transmission. The transmitter pre-computes different polar codes with various information bit distributions and stores them for potential use in re-transmissions. This preliminary action enables the system to quickly select and transmit appropriate codes based on channel conditions without performing complex real-time encoding decisions, thus achieving high coding gain while managing encoding complexity.
Solution Approach 2:
The patent changes parameters of polar codes across different transmissions, specifically varying the information bit distributions and code structures. The first polar code uses one information bit distribution while the second polar code uses a different distribution. This parameter variation allows the system to achieve diverse coding gains adapted to different channel conditions. The complexity is managed by systematically varying parameters rather than arbitrarily changing code structures.
3Productivity
If incremental redundancy is implemented with polar codes, then decoding efficiency is improved, but the distribution of information and parity bits across re-transmissions becomes complex to manage
Solution Approach 1:
The patent implements feedback mechanisms where the receiver sends acknowledgment signals to the transmitter based on decoding outcomes. When the first polar code is successfully decoded, the system receives an ACK; when decoding fails, it receives a NACK triggering a re-transmission. This feedback loop enables efficient incremental redundancy implementation by activating re-transmissions only when necessary. The feedback also helps manage bit distribution complexity by providing clear signals about what additional information bits need to be transmitted in subsequent re-transmissions.
Solution Approach 2:
The patent applies local quality by optimizing the distribution of information and parity bits specifically for each transmission context. The first transmission uses a particular bit distribution optimized for initial data delivery, while re-transmissions use different bit distributions optimized for correcting specific types of errors or delivering remaining undecoded information. This localized optimization of bit distribution in each transmission context improves decoding efficiency while making the management complexity tractable through systematic local optimization rather than global redesign.
Data Source
AI summary
A method for polar encoding includes: receiving a message including information bits; encoding the message using a first polar code to obtain a first codeword; and encoding the message using a second polar code to obtain a second codeword. The second codeword includes two parts, and the first part of the second codeword is same as the first codeword. The method for polar encoding also includes transmitting the first codeword to a receiver in a first transmission; and transmitting the second part of the second codeword in a second transmission without transmitting the first part of the second codeword when the receiver is unable to decode the message based on the first codeword.