OFDM Phase Noise Mitigation Using Guard Band Samples
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Solution Overview
Problem
Phase noise in mm Wave OFDM systems limits peak data rates due to inter-carrier interference (ICI), which is challenging to mitigate effectively without redesigning existing PHYs like 802.11ac/ax, as they lack sufficient pilots for accurate ICI suppression.
Innovation Solution
Utilize frequency domain samples from guard bands, which are unused in OFDM signals, to enhance phase noise mitigation algorithms by incorporating a-priori knowledge of no signal transmission, thereby improving ICI suppression without increasing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If existing PHYs like 802.11ac/ax are used without redesign, then device complexity is reduced, but phase noise mitigation performance is insufficient due to lack of sufficient pilots for accurate ICI suppression
Solution Approach 1:
The patent makes the existing pilot signals serve a dual purpose: their original function plus phase noise estimation. The pilots already present in 802.11ac/ax PHYs are reused to estimate phase noise and design de-ICI filters, eliminating the need for additional pilot signals or PHY redesign while improving ICI suppression performance
Solution Approach 2:
The patent changes the usage parameter of existing pilot signals from single-purpose to multi-purpose by incorporating them into phase noise estimation algorithms. This parameter change allows the same physical signals to provide both original functionality and phase noise mitigation, resolving the contradiction between maintaining simple PHY design and achieving accurate phase noise suppression
2Measurement precision
If more pilots are added to improve phase noise mitigation, then ICI suppression performance is improved, but overhead increases and PHY redesign is required
Solution Approach 1:
Existing pilot signals are made to serve dual purposes: their original data transmission function and phase noise estimation function. This eliminates the need to add more pilots while still achieving improved phase noise mitigation and ICI suppression performance
Solution Approach 2:
The patent makes pilot signals multi-functional by using them for both data transmission and phase noise estimation. This universal usage of existing pilots achieves better ICI suppression without increasing the quantity of pilot signals, thus avoiding overhead increase and PHY redesign
3Object-affected harmful factors
If larger subcarrier spacing is used, then ICI is reduced, but data rate is limited due to reduced spectral efficiency
Solution Approach 1:
The patent changes the approach from modifying physical layer parameters (subcarrier spacing) to modifying signal processing parameters (de-ICI filter design). By using accurate phase noise estimation from pilots to design optimized de-ICI filters, the system achieves ICI suppression while maintaining fine subcarrier spacing and high spectral efficiency, thus preserving high data rates
Data Source
AI summary
A method, network node and wireless device (WD) for phase noise mitigation are disclosed. According to one aspect, a method in a network node includes receiving an orthogonal frequency division multiplex (OFDM) signal provided over a radio frequency (RF) channel that includes at least one guard band, the OFDM signal including at least one pilot signal. The method also includes mitigating phase noise based at least in part on the at least one pilot signal and further based on observations of signal content of the at least one guard band.