Polar Code Incremental Redundancy with Outer Code Mixing
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Solution Overview
Problem
The finite-length performance of polar codes under successive cancellation decoding is not competitive with other modern channel coding schemes like LDPC and Turbo codes, limiting their effectiveness in wireless communication systems, particularly in fading channels and HARQ protocols.
Innovation Solution
Concatenating an outer linear block code with a polar code before each transmission, where the outer code mixes input bits to increase the number of information bits and ensures the aggregated generating matrix has full rank, providing robustness and diversity across multiple transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polar codes are used under successive cancellation decoding, then the coding scheme achieves symmetric capacity of binary-input discrete memoryless channels, but the finite-length performance is not competitive compared to LDPC and Turbo codes
Solution Approach 1:
The patent segments the decoding process into two distinct stages: an inner polar code decoder that processes received signals and generates soft bit estimates, followed by an outer linear block code decoder that performs final decoding. This segmentation allows each decoder to operate optimally within its domain, with the inner decoder handling the polar code structure and the outer decoder providing robust error correction, thereby resolving the contradiction between achieving symmetric capacity and maintaining competitive finite-length performance.
Solution Approach 2:
The patent implements a nested coding structure where the polar code is embedded within an outer linear block code framework. The polar code serves as the inner code that achieves channel capacity, while the outer linear block code provides additional error protection for finite-length performance. This nested arrangement allows the system to maintain the theoretical advantages of polar codes while gaining the practical performance benefits of linear block codes, effectively resolving the performance gap with LDPC and Turbo codes.
2Reliability
If a SC list decoder is used to approach optimal maximum-likelihood decoder performance, then decoding accuracy improves, but system complexity increases
Solution Approach 1:
The patent segments the complex decoding task into two simpler stages: the inner polar code decoder that performs initial decoding with reduced complexity, and the outer linear block code decoder that provides final error correction. This segmentation avoids the need for complex SC list decoding while maintaining high decoding accuracy, as each stage operates with simpler algorithms that are more computationally efficient than full ML decoding.
Solution Approach 2:
The outer linear block code acts as an intermediary that bridges the gap between the simple inner polar code decoder and the desired high accuracy of ML decoding. Rather than implementing complex SC list decoding directly, the system uses the outer decoder as a mediator to provide the necessary error correction, achieving high accuracy through a two-stage process that is less complex than direct ML decoding.
3Adaptability or versatility
If polar codes are applied in fading channels and HARQ protocols, then wireless communication is enabled, but performance degradation occurs due to channel variability
Solution Approach 1:
The patent applies nested coding where the polar code is embedded within an outer linear block code, creating a robust structure that can handle channel variability. The inner polar code maintains adaptability for wireless communication, while the outer linear block code provides enhanced error protection that compensates for performance degradation in fading channels, allowing the system to maintain reliability across varying channel conditions.
Solution Approach 2:
The outer linear block code provides beforehand cushioning against channel fading by pre-establishing an error protection layer. This outer code is designed to handle the expected variability in fading channels, providing a safety margin that cushions the system against performance degradation before the actual channel conditions manifest, thereby maintaining reliability in wireless environments.
Data Source
AI summary
Methods of transmitting blocks of incremental redundant coded bits are provided. Methods include concatenating, using an outer encoder, bits of an input bit vector to an outer encoded bit vector that has fewer bits than the input bit vector, wherein the outer encoded bit vector includes a mixture of information bits from the input bit vector. Methods include encoding the outer encoded bit vector into inner encoded data that is mapped to multiple data transmission channels that each include a channel reliability value. A first portion of the data transmission channels is used to transmit information bits corresponding to the outer encoded bit vector and a second portion of the data transmission channels is used to transmit frozen bits that include no information.