5G NR LDPC Decoding With Noise-Aware OFDM Normalization
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Solution Overview
Problem
In 5G new radio (NR) channels, certain portions of the assigned bandwidth are left blank without a reference sequence for channel estimation, leading to noise amplification during low-density parity check (LDPC) decoding due to improper normalization.
Innovation Solution
The method involves performing a Fast Fourier Transform, determining the presence of a reference sequence, and if present, performing channel estimation and interpolation. Demodulation is then done using the formula rbin*conj(Hbin)/(norm(Hbin)^2+Noise_Power), followed by LDPC decoding and correctness determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If normalization is done by channel power only (zero-forcing equalizer), then the number of bits needed to represent log-likelihood ratio is minimized, but noise gets amplified when channel power is low
Solution Approach 1:
The patent changes the normalization parameter from channel power only to the sum of channel power and noise power. This parameter modification prevents noise amplification by ensuring the denominator remains bounded away from zero, while still maintaining efficient bit representation through adaptive normalization.
Solution Approach 2:
The patent applies prior cushioning by adding noise power to the denominator before normalization occurs. This preemptive measure ensures that when channel power is low, the noise power component prevents excessive noise amplification, cushioning the system against the harmful effect before it can occur.
2Object-affected harmful factors
If noise power is added to prevent amplification, then noise amplification is prevented, but when channel power is high the scaling is only slightly reduced
Solution Approach 1:
The patent applies dynamics by making the normalization factor adaptive rather than fixed. The denominator dynamically adjusts based on the relative magnitudes of channel power and noise power, providing strong noise protection when channel power is low and minimal scaling reduction when channel power is high, optimizing performance across varying channel conditions.
3Measurement precision
If noise power is calculated as byproduct of channel estimation, then noise power is obtained, but FFT/IFFT gain differences require scaling adjustment on different platforms
Solution Approach 1:
The patent applies feedback by using the measured mean channel power across all bins to determine noise power through a ratio relationship. This feedback mechanism allows the system to adapt to different FFT/IFFT gain characteristics on various platforms, as the noise power estimation automatically scales with the channel power measurements, ensuring consistent performance across implementations.
Data Source
AI summary
A system and method for 5G new radio (NR) low-density low density parity check (LDPC) decoding comprising performing a Fast Fourier Transform using a Fast Fourier Transform algorithm. The system and method determines if a reference sequence is present and performing a channel estimate and a channel interpolate for the channel estimate if the reference sequence is present. The system and method demodulates at least one orthogonal frequency division multiplexing (OFDM) symbol according to rbin*conj(Hbin)/(norm(Hbin)2+Noise_Power). The system and method decodes the demodulated at least one orthogonal frequency division multiplexing symbol, and determines if the decoded at least one orthogonal frequency division multiplexing symbol is correct.