Polar Code Retransmission for Encoding Gain and Throughput
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Solution Overview
Problem
Existing HARQ polar code solutions for wireless communication systems face challenges in achieving encoding gain and high throughput due to the requirement of retransmitting the same code word and the limitations of code lengths being integer powers of 2, leading to low throughput, especially in channels with high signal-to-noise ratios.
Innovation Solution
A polar code retransmission method that adds new information bits during each retransmission, encoding them jointly with the previous information bit using construction parameters to generate polar codes with continuously reduced code rates, allowing only a different part of the current polar code to be transmitted, thereby achieving encoding gain and improving system throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the same code word is retransmitted in each HARQ transmission, then signal-to-noise ratio gain is achieved through combining, but encoding gain is not obtained and throughput remains low
Solution Approach 1:
The code rate is made dynamic across HARQ transmissions instead of remaining fixed. Each transmission uses a different code rate (1/2, 2/3, 3/4, etc.) allowing the system to adapt the coding scheme to channel conditions while accumulating signal-to-noise ratio, thereby achieving both reliability improvement and encoding gain for higher throughput
Solution Approach 2:
The code rate parameter is changed in each HARQ transmission by using different information bit lengths (K values) while maintaining the same code word length (N=256). This parameter change enables the system to achieve encoding gain across transmissions while still benefiting from signal-to-noise ratio accumulation through combining
2Device complexity
If polar code length is constrained to integer powers of 2, then code structure is simplified, but code length compatibility becomes severe and flexible code rate configuration is limited
Solution Approach 1:
The code word is segmented into information bits and frozen bits with flexible proportions. By varying the information bit length K while keeping code word length N=256 fixed, the system achieves flexible code rate configuration (K/N) without changing the overall code structure, thus maintaining simplicity while improving adaptability
Solution Approach 2:
A single polar code structure with N=256 serves multiple code rates by adjusting the information bit length K. This universal code structure can support different code rates (1/2, 2/3, 3/4, etc.) within the same HARQ process, eliminating the need for multiple specialized code structures and improving code length compatibility
Data Source
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Figure 3(a)~3(c)
AI summary
This application discloses a polar code retransmission method and apparatus, to achieve an encoding gain in a polar code retransmission process and improve a throughput. The method includes: performing polar code encoding on K first to-be-encoded bits based on a first information bit position set, where elements in the first information bit position set are used to indicate positions of the K first to-be-encoded bits; sending a first code word obtained after encoding to a decoding device; and when decoding of the first code word fails, performing polar code encoding on the K first to-be-encoded bits and K' second to-be-encoded bits based on a second information bit position set to obtain a second code word, where elements in the second information bit position set are used to indicate positions of the K first to-be-encoded bits and positions of the K' second to-be-encoded bits, and an element that is in the second information bit position set and that is used to indicate a position of a first to-be-encoded bit is a sum of N and an element that is in the first information bit position set and that is used to indicate the position of the first to-be-encoded bit; and sending a subcode in the second code word other than the first code word to the decoding device.