Polar Code Rate Matching Using Hadamard Row-Weight Reordering
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Solution Overview
Problem
Traditional rate matching schemes for polar codes in wireless communication systems, such as those used in 5G networks, can lead to performance losses due to constraints on block length and available bandwidth, particularly when the circular buffer size is not a power of 2.
Innovation Solution
The proposed method involves encoding information bits using a polar code with a mother code length, storing them in a circular buffer, reordering blocks based on Hadamard matrix row weights, interlacing bits of the same weight, selecting subsets for modification, and transmitting them via available resources, allowing for efficient rate matching through puncturing or shortening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional rate matching schemes are used for polar codes, then implementation is simpler, but transmission performance deteriorates when circular buffer size is not a power of 2
Solution Approach 1:
The circular buffer is divided into multiple blocks, each of which can be independently processed. The encoder divides the N encoded bits into multiple blocks, and the rate matching process operates on each block separately, allowing flexible handling of non-power-of-2 buffer sizes while maintaining good transmission performance.
Solution Approach 2:
The patent implements dynamic rate matching by allowing the system to adaptively select different rate matching modes (puncturing, shortening, or repetition) based on the actual transmission requirements and buffer size. This dynamic approach optimizes performance for varying buffer sizes rather than being constrained to fixed schemes.
2Reliability
If more bits are transmitted to improve reliability, then transmission performance improves, but available bandwidth is exceeded
Solution Approach 1:
The patent extracts and transmits only the most important information bits first. By ordering bits according to their reliability metrics and selecting the top M bits for transmission, the system achieves reliable communication with fewer transmitted bits, leaving room for redundancy or other transmissions within the available bandwidth.
Solution Approach 2:
The system dynamically adjusts the rate matching parameters (such as the number of bits to transmit, which bits to puncture or shorten) based on channel conditions and available bandwidth. This allows the system to maintain reliable transmission by optimizing the balance between the number of bits transmitted and the redundancy level.
3Reliability
If block length is increased to improve error correction, then coding performance improves, but decoding latency increases
Solution Approach 1:
The patent segments the long code block into multiple smaller blocks for parallel or sequential processing. This segmentation reduces the decoding latency by allowing the decoder to process smaller units of data, while the overall error correction capability is maintained through the structured arrangement and interleaving of these blocks.
Solution Approach 2:
The patent performs preliminary ordering and selection of bits before transmission based on their reliability metrics. By pre-organizing the bits in optimal sequences and identifying which bits are most critical, the system reduces the complexity and time required for decoding, as the receiver can focus computational resources on the most important bits first.
Data Source
AI summary
Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to methods and apparatus for rate-matching a stream of bits encoded using polar codes. An exemplary method generally includes encoding K information bits using a polar code with a mother code length, N, to generate a stream of encoded bits storing a portion of the encoded bits in a circular buffer of size N reordering P blocks of the circular buffer according to row weights of a Hadamard matrix J interlacing the encoded bits of the blocks having a same row weight selecting, based on the row weights, a subset of the encoded bits in the blocks to modify modifying the selected subset of the encoded bits and transmitting the encoded bits in the P blocks, subsequent to modifying the selected subset of the encoded bits, via transmission resources.