Multi-Stage QAM Encoding With Simpler LLR De-Mapping
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Solution Overview
Problem
Current multi-level coding (MLC) and multi-stage decoding (MSD) systems face challenges in bandwidth efficiency and complexity, particularly in de-mapping and log-likelihood-ratio (LLR) calculation over additive white Gaussian noise (AWGN) channels.
Innovation Solution
A multi-stage encoder and decoder system that uses a set-partitioning (SP) labelling method for quadrature amplitude modulation (QAM) constellations, allowing for reduced complexity in de-mapping and LLR calculation by maintaining a consistent constellation structure and transforming received symbols through rotations and shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-level coding (MLC) and multi-stage decoding (MSD) are used to improve bandwidth efficiency, then spectral efficiency is improved, but device complexity increases
Solution Approach 1:
The message is divided into m sub-information vectors that are encoded by m sub-encoders using different component codes. This segmentation allows the system to achieve multi-level coding benefits while maintaining manageable complexity through modular processing of information bits
Solution Approach 2:
The patent introduces a multi-dimensional structure by using m different component codes (each of length N) to encode m sub-information vectors, creating an mN-dimensional code space. This dimensional expansion enables improved bandwidth efficiency through capacity-achieving codes while organizing complexity across multiple coding layers
2Reliability
If set-partitioning (SP) labelling is used in high-order modulation to improve performance, then noise tolerance is improved, but the number of sub-constellations doubles at each decoding level, increasing memory requirements
Solution Approach 1:
The SP labelling is pre-defined and applied during the encoding phase, where constellation points are systematically assigned to sub-constellations before transmission. This preliminary organization enables the receiver to efficiently track sub-constellation mappings without requiring exponential memory growth during decoding
Solution Approach 2:
The patent implements a nested structure where sub-constellations are organized hierarchically across m decoding levels. Each sub-constellation contains nested sub-constellations from previous levels, allowing the system to maintain noise tolerance through SP labelling while reducing memory requirements by reusing the same constellation structure across levels
3Ease of operation
If the complexity of log-likelihood-ratio (LLR) calculation is reduced by simplifying the de-mapping process, then ease of operation is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent transforms the received symbols through rotations and shifts to map them onto a consistent decision grid, changing the parameter representation of constellation points. This transformation enables simplified de-mapping operations while maintaining LLR calculation accuracy by preserving the geometric relationships between constellation points through deterministic geometric transformations
Data Source
AI summary
The present disclosure relates to a multi-stage encoder comprising m sub-encoders for encoding K information bits by means of m component codes, each component code being of length N, in a codeword having a total length of mN, wherein each of m, K and N is an integer, wherein m≤N and K≤N, and wherein the encoder is configured to: store the K information bits into a message u; divide the message u into m sub-information vectors u(i), i=1, . . . , m of length K(1), . . . , K(m), respectively, wherein K(1)+ . . . +K(m)=K; encode, by means of the m sub-encoders, each of the m sub-information vectors u(i) into m sub-codewords c(1), . . . , c(m); map the m sub-codewords c(1), . . . , c(m) into N symbols taken from 2m constellation points of a modulation format to form a vector x; label each of the N symbols into a string of m bits; and transmit the vector x through a communication channel.