16-QAM WLAN CFO Estimation Using OFDM Signal Pair Selection
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Solution Overview
Problem
Current wireless communication systems, particularly in WLANs, face challenges in accurately estimating carrier frequency offset (CFO) especially with high-order modulation schemes like 16-QAM, which affects decoding efficiency and power consumption, especially in scenarios with multiple apparatuses.
Innovation Solution
A method for estimating CFO using a blind scheme by measuring the size ratio and phase difference between contiguous OFDM symbols, determining suitable pairs for estimation, and adjusting phases to improve accuracy, even in high-order modulation scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If blind CFO estimation is applied in high-order modulation schemes like 16-QAM, then decoding efficiency is improved, but measurement precision of CFO deteriorates due to signal complexity
Solution Approach 1:
The patent segments the received signal into multiple candidate pairs and applies different processing to each pair. By dividing the signal processing into discrete pairs with specific size ratio thresholds, the method enables selective estimation that improves both decoding efficiency and CFO measurement precision in 16-QAM systems
Solution Approach 2:
The patent changes the parameter of signal pair selection by introducing size ratio thresholds and phase difference criteria. This parameter-based filtering allows the system to adaptively select suitable signal pairs for CFO estimation, resolving the contradiction between decoding efficiency and measurement precision
2Measurement precision
If the number of samples for CFO estimation is increased, then measurement precision is improved, but device complexity increases due to additional processing
Solution Approach 1:
The patent applies partial action by selecting only specific candidate pairs that meet the size ratio threshold criteria for CFO estimation. This selective approach increases the effective number of samples used for estimation without processing all possible signal pairs, thereby improving measurement precision while controlling device complexity
3Productivity
If multiple apparatuses communicate in WLAN system, then network capacity is increased, but interference and power consumption increase
Solution Approach 1:
The patent enables each receiving apparatus to autonomously perform blind CFO estimation using the proposed method. This self-service capability allows multiple apparatuses to operate independently in the WLAN system, increasing network capacity while each device optimizes its own power consumption through efficient signal pair selection and processing
Data Source
AI summary
Disclosed is a method for estimating a CFO, the method comprising: measuring a size ratio of a signal pair received in two consecutive OFDM symbols of a predetermined subcarrier; determining the received signal pair as a signal pair to be used for estimating a residual CFO when the size ratio is within a first threshold range; and estimating the residual CFO, using only the received signal pair which has been determined to be used for estimating the residual CFO.