Reference Signal Modulation for CFO Estimation in 5G
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Solution Overview
Problem
In wireless communication systems, particularly in 5G, there is a challenge in efficiently estimating the blind Carrier Frequency Offset (CFO) due to the small phase difference between constellation points in high-order QAM modulation schemes, which degrades the performance of blind CFO estimators.
Innovation Solution
The method involves determining the modulation scheme of the reference signal based on the PDSCH modulation scheme, ensuring a minimum phase difference of π/2 between constellation points, and transmitting this reference signal with boosted power, allowing efficient estimation of the phase difference between symbols in the time domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-order QAM modulation schemes are used to increase data rate, then spectrum efficiency is improved, but the phase difference between constellation points becomes small which degrades blind CFO estimation performance
Solution Approach 1:
The patent applies local quality by using different modulation schemes for different purposes: high-order QAM (64-QAM, 256-QAM) is used for data transmission to maximize spectral efficiency, while a restricted modulation scheme with minimum phase difference of π/2 is specifically used for reference signals to ensure accurate CFO estimation. This localized differentiation of modulation quality resolves the contradiction between high data rate and accurate CFO estimation.
Solution Approach 2:
The patent changes the modulation parameter (phase difference) specifically for reference signals by restricting the minimum phase difference to π/2, regardless of the data modulation order. This parameter change in the reference signal domain allows blind CFO estimators to maintain their estimation range and accuracy even when high-order QAM is used for data transmission.
2Reliability
If reference signal power is boosted to improve estimation accuracy, then CFO estimation reliability is improved, but transmission power consumption increases
Solution Approach 1:
The patent changes the modulation parameter (minimum phase difference = π/2) for reference signals to improve CFO estimation accuracy without necessarily boosting power. By optimizing the modulation scheme parameter rather than increasing power, the patent achieves reliable estimation while avoiding excessive power consumption.
Solution Approach 2:
The patent applies local quality by enhancing reference signal quality through restricted modulation rather than uniformly boosting all signal powers. This targeted approach improves CFO estimation reliability only where needed (in reference signals) without unnecessarily increasing overall transmission power consumption.
Data Source
AI summary
A method by which a base station transmits a reference signal in a wireless communication system can comprise the steps of: transmitting, to a terminal, information on a modulation method of a reference signal for estimating a phase difference between symbols in a time domain; and transmitting, to the terminal, the reference signal, for estimating the phase difference between the symbols, to which the modulation method is applied.