QAM Demodulation with Bias-Corrected CSI for HD Radio LLRs
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Solution Overview
Problem
Existing IBOC radio systems face challenges in accurately estimating channel state information (CSI) and approximating log-likelihood ratio (LLR) metrics, which affects the decoding performance and capacity of subcarriers in hybrid, extended-hybrid, or all-digital IBOC radio signals.
Innovation Solution
A radio receiver with physical layer circuitry and processor circuitry that receives QAM symbols, generates constellation samples, and multiplies soft metrics by CSI weights to produce LLR approximations, while correcting for bias errors in channel gain and noise variance estimation to improve CSI estimation and LLR approximation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CSI estimation methods are used in IBOC radio receivers, then the decoding performance is maintained at baseline levels, but the accuracy of CSI estimation and LLR approximation is insufficient, limiting subcarrier capacity
Solution Approach 1:
The patent changes the parameters of CSI estimation by introducing bias correction factors for channel gain and noise variance. The processor circuitry calculates corrected CSI values by adjusting the raw estimates with these bias correction factors, thereby improving measurement precision without requiring a complete redesign of the estimation architecture
Solution Approach 2:
The patent replaces conventional LLR calculation methods with an improved approximation technique that uses constellation samples and bias-corrected CSI. This substitution achieves higher accuracy by using a different computational approach that leverages the statistical properties of QAM constellations and corrected channel state information
2Reliability
If bias correction for channel gain and noise variance is implemented, then LLR approximation accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent performs bias correction calculations as preliminary steps before generating LLR approximations. The processor circuitry pre-calculates the bias correction factors for channel gain and noise variance, and then applies these corrections to the CSI estimates before using them in LLR approximation. This preliminary action ensures that the main decoding process uses already-corrected values, improving reliability while managing computational complexity through efficient preprocessing
3Productivity
If accurate CSI estimation is achieved through bias correction, then subcarrier capacity and bandwidth are increased, but the system requires more sophisticated processing
Solution Approach 1:
The patent implements a self-service mechanism where the receiver's processor circuitry automatically performs bias correction on CSI estimates using internally calculated correction factors. The system uses its own received signals to compute the bias corrections and apply them without external intervention, thereby increasing subcarrier capacity through sophisticated processing that is seamlessly integrated into the existing receiver architecture
Data Source
AI summary
A radio receiver comprises physical layer circuitry and processor circuitry. The physical layer circuitry receives quadrature amplitude modulation (QAM) symbols via a plurality of subcarriers included in a broadcast radio signal. Each received QAM symbol is a complex symbol comprising multiple bits of encoded source information. The processing circuitry demodulates the received data symbols, generates a constellation sample for each received QAM symbol, generates a soft metric for each bit of encoded information of the received QAM symbols using the constellation sample, and multiplies the soft metric by a channel state information (CSI) weight to produce a Log-likelihood Ratio (LLR) approximation for each bit of encoded information of the received QAM symbols.