Polar Code Bit Mapping for Probabilistic Shaping in QAM
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Solution Overview
Problem
Current polar code construction methods, especially in 5G wireless communication, face challenges in adapting to probabilistic shaping, leading to high implementation complexity and inefficiency in encoding and decoding processes, particularly in higher-order modulation schemes like 64QAM, 256QAM, and 1024QAM.
Innovation Solution
An encoding and decoding method that divides the information bit sequence into two types of sub-blocks, using a predefined sequence to determine frozen and information bit locations, and constructs a first vector based on the sequence length and modulation order, allowing for efficient encoding and decoding by reducing calculation complexity and improving robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an online construction algorithm based on density evolution is used to calculate reliability of each sub-channel, then the polar code can adapt to probabilistic shaping, but the implementation complexity becomes high
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the first vector in an offline manner before actual communication operations. The first vector, which indicates frozen bit locations and information bit locations for different code lengths and modulation orders, is computed in advance and stored in a lookup table. During online operation, the system simply retrieves the pre-computed first vector based on the current code length and modulation order, avoiding real-time complexity-intensive calculations while maintaining adaptability to probabilistic shaping
Solution Approach 2:
The patent prepares cushioning by pre-storing multiple first vectors corresponding to different code lengths (K) and modulation orders (J) in advance. This beforehand cushioning ensures that when probabilistic shaping is applied with various parameters, the system already has the necessary first vector data available, eliminating the need for complex real-time computations and enabling fast adaptation to different operating conditions
2Device complexity
If a polar-based offline construction method based on a given sequence is used, then the implementation complexity is reduced, but it cannot adapt to a usage of polar code construction in which probabilistic shaping is introduced
Solution Approach 1:
The patent introduces dynamics by making the first vector configurable based on different code lengths and modulation orders. Instead of using a fixed given sequence, the system dynamically selects or computes the appropriate first vector according to the specific probabilistic shaping parameters being used. This dynamic adaptation allows the offline construction method to maintain low complexity while becoming versatile across different probabilistic shaping scenarios
Solution Approach 2:
The patent applies parameter changes by allowing the first vector to vary according to different code length parameters (K) and modulation order parameters (J). The system stores multiple first vectors corresponding to different parameter combinations and selects the appropriate one based on current operating conditions. This parameter-based adaptation enables the simple offline construction method to work effectively with probabilistic shaping across various configurations
3Loss of energy
If more low-energy modulation symbols are sent and fewer high-energy modulation symbols are sent, then average energy is saved, but the coding efficiency needs to be improved to maintain performance
Solution Approach 1:
The patent applies local quality by differentiating between frozen bit locations and information bit locations within the code structure. The first vector specifies which positions should be frozen (set to predetermined values) and which positions should carry information bits. This local differentiation allows the system to concentrate information bits in positions that will be mapped to lower-energy modulation symbols, while frozen bits occupy positions that can tolerate higher energy consumption, thereby reducing average energy consumption while maintaining coding efficiency through optimized bit placement
Data Source
AI summary
An encoding method, a decoding method, and a communication apparatus. The communication apparatus obtains an information bit sequence with a length K. A length K1 of a first sequence based on K or M is determined, where M is a quantity of modulation symbols. A first vector is obtained based on K, K1, and a predefined sequence. A length of the first vector is 2JM, J is a modulation order, the first vector indicates J coding sub-blocks, the J coding sub-blocks separately belong to a first-type sub-block including at least one coding sub-block or a second-type sub-block including at least one coding sub-block. The communication apparatus determines frozen bit locations in the first-type sub-block and information bit locations in the second-type sub-block and encodes the information bit sequence based on the frozen bit locations in the first-type sub-block, the information bit locations in the second-type sub-block, and the first vector.