Carrier frequency offset estimation and compensation method for dual stream quasi-constant envelope OFDM system using null subcarrier

Abstract

The present invention relates to a carrier frequency offset estimation and compensation method for a dual stream quasi-constant envelope OFDM system using a null subcarrier, belonging to the field of wireless communication. According to the method, a received signal yn that has undergone analog-digital conversion is analyzed at a receive end; a real part and an imaginary part of the signal yn are resolved; division operation is performed on the real part and the imaginary part; conversion and simplification are performed by using a trigonometric function and a differential product formula so as to obtain an approximation at a high signal-to-noise ratio; the frequency offset is estimated by using a feature that a useful signal includes the null subcarrier; the signal is compensated by using estimated frequency offset; a real part and an imaginary part of the received signal that has undergone frequency offset compensation are obtained, and phase demodulation, FFT, conjugate sequence inverse transform and QAM symbol reverse mapping are continued to perform on the two paths of signal, so as to obtain two final paths of bit signal. Through adoption of the method, a problem of increased bit error rate caused by frequency offset is solved, no extra module is introduced, and the method has low complexity and effectively prevents the impact of frequency offset on the system performance.

Description

technical field [0001] The invention belongs to the field of wireless communication, and specifically refers to a frequency offset estimation and compensation technology based on idle subcarriers in a dual-stream quasi-constant envelope OFDM system applied to broadband wireless communication. Background technique [0002] In broadband wireless communication systems, information is transmitted in space through modulated electromagnetic waves to the receiver. Due to the complex communication environment, electromagnetic waves are affected by reflection, diffusion, and scattering during space transmission, and multiple received signals with different delays and signal strengths will be generated at the receiver, making the communication channel have time-varying frequency selective fading. characteristic. In order to effectively eliminate the frequency-selective fading of broadband communication channels, multi-carrier modulation technology divides the broadband channel into m...

AI Technical Summary

Problems solved by technology

However, due to the existence of the phase modulation step, the useful information in the dual-stream quasi-constant envelope system is modulated on the phase. When there is a frequency offset in the channel, the relationship between the frequency offset and the useful information is an additive relationship rather than a multiplicative relationship in OFDM, causing the solution The reduction of signal-to-noise ratio leads to the increase of bit error rate

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