Polar IR-HARQ Retransmission Using Reliable Bit Remapping
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Solution Overview
Problem
Current Hybrid Automatic Repeat Request (HARQ) re-transmission techniques, such as chase-combining and incremental redundancy, face limitations in error correction efficiency, particularly in noisy channels, where polar codes are not fully utilized for improved transmission reliability.
Innovation Solution
The method employs incremental redundancy hybrid automatic repeat request (IR-HARQ) re-transmission using multiple polar codes to generate codewords of varying lengths, where the first codeword is transmitted initially, and subsequent re-transmissions involve selective transmission of codeword halves or thirds, with information bits mapped to more reliable bit-locations, enhancing decoding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional HARQ re-transmission techniques (chase-combining or incremental redundancy) are used, then error correction is provided, but coding gain is limited and transmission reliability is insufficient in noisy channels
Solution Approach 1:
The patent segments the polar code into multiple sections (first section, second section, third section) with different code rates. The first section has a higher code rate for initial transmission, while subsequent sections have lower code rates for re-transmission, allowing incremental redundancy without requiring a complete code redesign
Solution Approach 2:
The patent changes the code rate parameter across different sections of the polar code. The first section uses a higher code rate (e.g., 1/2) for initial transmission, while the second and third sections use lower code rates (e.g., 1/3, 1/4) for re-transmission, providing incremental coding gain without increasing overall system complexity
2Reliability
If polar codes are used to improve transmission capacity, then error correction capability is enhanced, but full utilization of channel polarization for improved reliability in noisy channels is not achieved
Solution Approach 1:
The patent dynamically adjusts the code rate and section selection based on channel conditions. When the channel is noisy, the system transitions from the first section to the second or third section, providing adaptive error correction that fully utilizes channel polarization while maintaining transmission efficiency
Solution Approach 2:
The patent prepares multiple polar code sections in advance with different code rates and reliability characteristics. The receiver can immediately switch to pre-configured sections with lower code rates when initial transmission fails, avoiding the need for real-time code generation and reducing latency
Data Source
AI summary
Aspects of this disclosure provide a technique for implementing polar encoding with incremental redundancy HARQ re-transmission. In particular, a transmitter encodes a message using different polar codes to obtain a first codeword and a second codeword that is twice the length of the first codeword, and transmit the first codeword as an original transmission, and the second half of the second codeword as a re-transmission without transmitting the first half of the second codeword. Information bits that are common to both the first codeword and the second half of the second codeword is mapped to more-reliable bit-locations in the second half of the second codeword. Decoded bit values for the common information in the original transmission and retransmission is compared by the receiver to perform a parity check.