Carrier frequency offset estimation and compensation method for constant envelope OFDM system based on preamble symbol

Abstract

The invention discloses a carrier frequency offset estimation and compensation method for a constant envelope OFDM system based on a preamble symbol, and relates to the field of broadband wireless communication. Specifically, a transmitting end CE-OFDM transmits a bit, and uses a QPSK symbol mapping modulation mode to obtain the number of Nsym QPSK symbols; a conjugate sequence Sk is obtained through zero fill construction on a high frequency subcarrier; a time domain OFDM symbol sn is obtained through the IFFT; a symbol xn is obtained through the phase modulation; after the D / A conversion, the AWGN and CFO are added for propagation, and a receiving end performs A / D conversion to obtain a receiving time domain symbol yn; after the phase demodulation, the phase Yn-bar (as shown in the description) of a time domain signal is obtained, a signal Yk is obtained after the FFT of the phase Yn-bar (as shown in the description), the frequency offset estimation and compensation are performed to obtain a mean square error [delta]fmse and a signal Yn-<~> (as shown in the description) after frequency offset compensation, and finally, the signal Yn-<~> (as shown in the description) after the frequency offset compensation is subjected to the conjugate sequence deconstruction and the symbol demapping to obtain a value of the received bit; and when the value of the received bit is consistent with the bit stream signal of the transmitting end, it is indicated that the frequency offset estimation is correct. According to the invention, the influence of the frequency offset on the system performance can be effectively suppressed.

Description

technical field [0001] The invention relates to the field of broadband wireless communication, in particular to a method for estimating and compensating a frequency offset based on a preamble symbol in a constant envelope orthogonal frequency division multiplexing system (CE-OFDM). 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 multiple sub...

AI Technical Summary

Problems solved by technology

Due to the existence of the phase modulation step, the useful information in the CE-OFDM system is modulated on the phase. When there is a frequency offset in the channel, the relationship between the CE-OFDM frequency offset and the useful information is an additive relationship rather than a multiplicative relationship in OFDM. It will reduce the signal-to-noise ratio during demodulation, resulting in an increase in the bit error rate; therefore, it is necessary to study frequency offset estimation and compensation techniques suitable for CE-OFDM systems

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