OFDM Pilot Arrangement for Phase Noise and Fading Separation

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Solution Overview

Problem

Existing radio transmission and reception devices in 5G NR systems face challenges in efficiently compensating for phase noise and multipath fading, leading to increased error rates and computational complexity due to the need for dense pilot signal multiplexing, which deteriorates frequency utilization efficiency and increases computation load.

Innovation Solution

The proposed solution involves arranging pilot signals in specific patterns across subcarriers and resource elements in both the frequency and time domains, using narrowband pilot signals for phase noise estimation, and implementing phase noise compensation and equalization processes to separate phase noise from multipath fading.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the pilot signal is consecutively multiplexed onto all symbols in the time domain to accurately estimate phase noise, then the phase noise estimation accuracy is improved, but the insertion loss increases and frequency utilization efficiency deteriorates

Engineering Contradiction:

Improvephase noise estimation accuracyVSAvoidinsertion loss

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent segments the frequency domain by dividing all subcarriers into two sets: first subcarriers for phase noise estimation and second subcarriers for data transmission. This segmentation allows the pilot signal to be multiplexed only on first subcarriers rather than all subcarriers, reducing insertion loss while maintaining phase noise estimation accuracy through the dedicated first subcarrier resources.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

Engineering Contradiction:

Improvephase noise estimation accuracyVSAvoidfrequency utilization efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

3Reliability

If a local oscillator with very high frequency stability is used to reduce phase noise, then the error rate is improved, but the cost increases

Engineering Contradiction:

Improveerror rateVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent implements self-service by having the receiver estimate and compensate for phase noise using pilot signals transmitted from the transmitter. The receiver performs autocorrelation processing on the received signal to extract phase noise characteristics and generates compensation signals that are applied to correct the phase noise, eliminating the need for expensive high-stability local oscillators in both transmitter and receiver.

Inventive Principle:

Principle #25Self-service

4Reliability

If dense pilot signal multiplexing is used to compensate for phase noise in millimeter wave bands, then the error rate is reduced, but the computational complexity increases

Engineering Contradiction:

Improveerror rateVSAvoidcomputational complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the frequency domain by dividing all subcarriers into two sets: first subcarriers for phase noise estimation and second subcarriers for data transmission. This segmentation allows the pilot signal to be multiplexed only on first subcarriers rather than all subcarriers, reducing the number of computational operations required for phase noise estimation while maintaining accuracy through the dedicated first subcarrier resources.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12562948B2Radio transmission device and radio reception device

Publication Date: 2026.02.24 NEC CORP

AI summary

In a radio transmission device, an orthogonal frequency division multiplexing (OFDM) signal forming unit forms an OFDM signal by arranging pilot signals according to a pilot arrangement pattern. According to the pilot arrangement pattern, among a plurality of pilot arrangement subcarriers with an NPilot_Freq-subcarrier interval, in a plurality of first pilot arrangement subcarriers with an NPilot_SPA-subcarrier interval, pilot signals for phase noise estimation are arranged in all resource elements. An information symbol and a pilot symbol are mapped to different resource elements. Among the plurality of pilot arrangement subcarriers with the NPilot_Freq-subcarrier interval, in a plurality of second pilot arrangement subcarriers excluding the plurality of first pilot arrangement subcarriers, the pilot signals for phase noise estimation are arranged in a cycle of NPilot_Time resource elements in the time domain.