Phase Noise Compensation in 60 GHz OFDM Systems
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Solution Overview
Problem
Wireless communication systems face challenges in achieving high data rates due to phase noise, especially in high-frequency bands, which limits signal-to-noise ratio (SNR) and increases hardware costs and energy usage, particularly in millimeter wave frequencies where oscillator-induced phase noise is significant.
Innovation Solution
The method involves identifying a pilot component in the received signal, estimating phase noise realization, and compensating the signal for phase noise on a sample-by-sample basis in the time domain, using phase-noise pilots to quantify distortion and smoothening the phase-noise estimate through sliding-window averaging, applicable to both transmitter and receiver-side phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher order modulation and more MIMO streams are used to increase data rates, then spectral efficiency improves, but hardware cost and energy usage increase
Solution Approach 1:
The patent changes the parameter of subcarrier spacing from conventional values to specifically 7.5 MHz or 10 MHz in the 60 GHz band, optimizing the OFDM system parameters to achieve better performance with lower complexity hardware
2Productivity
If bandwidth is increased to improve data rates, then spectral capacity improves, but frequency availability decreases due to reserved bands
Solution Approach 1:
The patent targets the 60 GHz frequency band which is available for unlicensed use, and optimizes OFDM parameters (subcarrier spacing of 7.5 MHz or 10 MHz) to achieve high data rates in this specific frequency range without requiring additional licensed spectrum
3Adaptability or versatility
If millimeter wave frequencies are used to find available bandwidth, then frequency availability improves, but phase noise increases quadratically with carrier frequency
Solution Approach 1:
The patent optimizes subcarrier spacing to 7.5 MHz or 10 MHz specifically for 60 GHz operation, and implements enhanced phase noise compensation algorithms that are tailored to the characteristics of millimeter wave oscillators, thereby mitigating the quadratic phase noise increase
Solution Approach 2:
The patent uses dedicated phase noise pilot signals inserted in the OFDM structure to measure and compensate phase noise, converting the harmful phase noise effect into a measurable parameter that can be corrected through signal processing
4Ease of operation
If conventional OFDM is used in high frequency bands, then implementation simplicity is maintained, but signal to noise ratio saturates due to phase noise
Solution Approach 1:
The patent introduces phase noise pilot signals as intermediary elements that mediate between the transmitted and received signals, allowing the receiver to measure and compensate phase noise without fundamentally changing the OFDM modulation scheme
Solution Approach 2:
The patent implements feedback mechanisms where the receiver measures phase noise using pilot signals and feeds back compensation information to correct the received signal, maintaining OFDM simplicity while improving SNR through active phase noise management
5Reliability
If subcarrier spacing is increased to 5 MHz or above to cope with phase noise, then phase noise tolerance improves, but cyclic prefix overhead increases significantly
Solution Approach 1:
The patent optimizes subcarrier spacing to specific values of 7.5 MHz or 10 MHz in the 60 GHz band, finding an optimal balance between phase noise tolerance and cyclic prefix overhead that is better than conventional 5 MHz spacing
Data Source
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Figure 3B
AI summary
Methods of reducing phase noise in a received signal include identifying a pilot component in the received signal and determining an expected pilot component that would have been received in the absence of phase noise. Based on the received pilot component and the expected pilot component, an estimate is generated of the phase noise realization for different parts of an OFDM symbol in the received signal, and based on the estimate of the phase noise realization, the received signal is compensated for the phase noise. Related base stations and user equipment nodes are disclosed.