Polar Code Retransmission with Added Bits for Higher HARQ Throughput
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Solution Overview
Problem
Existing HARQ polar code solutions in wireless communication systems face challenges with low throughput due to the requirement of retransmitting the same code word and lack of encoding gain, especially in channels with high signal-to-noise ratios, because they do not allow for flexible code rate configuration and require code lengths to be integer powers of 2.
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 reduced code rates, allowing for a different part of the polar code to be transmitted, thereby achieving encoding gain and improving system throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a same code word is retransmitted each time in existing HARQ solution, then signal-to-noise ratio gain is achieved through combining, but encoding gain is lost and throughput remains low
Solution Approach 1:
The patent applies dynamics by making the code word content changeable across retransmissions. Instead of transmitting the same code word each time, the system dynamically adjusts the code word by adding new information bits in subsequent transmissions while maintaining compatibility with previously transmitted bits, enabling both encoding gain and improved throughput
Solution Approach 2:
The patent changes the parameter of information bits in code words across retransmissions. The first code word contains K information bits, while the second code word contains K+K' information bits (where K' > 0), thereby changing the information content parameter to achieve both reliability through combining and productivity through encoding gain
2Device complexity
If polar code length is constrained to integer power of 2, then code structure is simplified, but code rate configuration flexibility is severely limited
Solution Approach 1:
The patent segments the code rate configuration into two parts: the base code length N (integer power of 2) maintains structural simplicity, while the information bit count K can be flexibly adjusted to achieve desired code rates. This segmentation allows K to vary independently from the power-of-2 constraint on N
Solution Approach 2:
The patent makes the code rate dynamically adjustable by allowing K (number of information bits) to change between transmissions while N (code length) remains fixed at an integer power of 2. This dynamic adjustment of K provides code rate flexibility without compromising the structural simplicity of using power-of-2 code lengths
3Productivity
If new information bits are added during retransmission, then encoding gain is achieved and throughput improves, but code rate configuration complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-generating construction parameters before retransmission. The transmit end uses these pre-generated parameters to systematically determine how to add new information bits and configure the code word, thereby reducing the complexity of real-time code rate configuration while still achieving encoding gain and improved throughput
Data Source
AI summary
This application discloses a polar code retransmission method and apparatus, to achieve an encoding gain. The method includes: when decoding of the first code word fails, performing polar code encoding on 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 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.