Method and device for estimating frequency offset of reception signal
A method for estimating a frequency offset of a reception signal and, more particularly, a signal processing method which can be applied to a receiver modem in a wireless communication system, are provided. The method includes using an absolute value within a specific time area in an inverse discrete fourier transform (IDFT) output of a decorrelation signal between a reception signal and a reference signal, and enabling a highly approximate estimation of a frequency offset through only a single decorrelation test using a characteristic of a predetermined permutation of a signal.
1. A method for estimating a frequency offset of a reception signal by a reception device, the method comprising:
determining a correlation relationship between the reception signal and a reference signal in a time domain;
acquiring a first absolute value in a first time interval centered on a first value in the time domain, a second absolute value in a second time interval centered on a second value in the time domain, and a third absolute value in a third time interval centered on a negative of the second value, the first value and the second value being set based on time values of a predetermined permutation;
acquiring a maximum value by adding the first absolute value, the second absolute value, and the third absolute value;
determining whether the maximum value is greater than a detection limit value; and
when the maximum value is greater than the detection limit value, calculating the frequency offset based on absolute values corresponding to a position index in each of the first time interval, the second time interval, and the third time interval,
wherein the absolute values corresponding to the position index are assigned to zero when each of the absolute values corresponding to the position index are equal to or smaller than a frequency offset valid value.
2. The method of claim 1 , wherein the determining of the correlation relationship between the reception signal and the reference signal comprises:
converting the reception signal and the reference signal in the time domain into signals of a frequency domain;
extracting predetermined permutations from the converted signals of the frequency domain;
acquiring a spectrum on a basis of the correlation relationship between the predetermined extracted permutations of the reception signal and the reference signal; and
converting the acquired spectrum of the correlation relationship into the time domain.
3. The method of claim 2 , wherein the predetermined permutation comprises a Zadoff-Chu sequence.
4. The method of claim 1 , wherein the first time interval, the second time interval, and the third time interval are configured to consider a multi-path effect caused by a delay profile of a channel for receiving the reception signal, on a basis of the time values of the predetermined permutation.
5. The method of claim 1 , further comprising:
comparing sizes of a fourth absolute value corresponding to the maximum value in the second time interval centered on the second value and a fifth absolute value corresponding to the maximum value in the third time interval centered on the negative second value; and
calculating the frequency offset using a larger value among the fourth absolute value and the fifth absolute value.
6. The method of claim 1 , wherein the frequency offset valid value is less than one third of the detection limit value.
7. A reception device for estimating a frequency offset of a reception signal in a mobile communication system, the reception device comprising:
a storage configured to hold instructions therein;
a transceiver; and
at least one processor,
wherein upon execution of the instructions, the at least one processor is configured to:
use the transceiver to receive a reception signal from a transmission device,
determine a correlation relationship between the reception signal and a reference signal in a time domain,
acquire a first absolute value in a first time interval centered on a first value in the time domain, a second absolute value in a second time interval centered on a second value in the time domain, and a third absolute value in a third time interval centered on a negative of the second value, the first value and the second value being set based on time values of a predetermined permutation,
acquire a maximum value by adding the first absolute value, the second absolute value, and the third absolute value,
determine whether the maximum value is greater than a detection limit value, and
when the maximum value is greater than the detection limit value, calculate the frequency offset based on the absolute values corresponding to a position index in each of the first time interval, the second time interval, and the third time interval, and
wherein the absolute values corresponding to the position index are assigned to zero when each of the absolute values corresponding to the position index are equal to or smaller than a frequency offset valid value.
8. The reception device of claim 7 , wherein the determining of the correlation relationship between the reception signal and the reference signal comprises:
converting the reception signal and the reference signal in the time domain into a signal of a frequency domain;
extracting predetermined permutations from the converted signals of the frequency domain;
acquiring a spectrum on a basis of the correlation relationship between the predetermined extracted permutations of the reception signal and the reference signal; and
converting the acquired spectrum of the correlation relationship into the time domain.
9. The reception device of claim 8 , wherein the predetermined permutation comprises a Zadoff-Chu sequence.
10. The reception device of claim 8 , wherein the first time interval, the second time interval, and the third time interval are configured to consider a multi-path effect caused by a delay profile of a channel for receiving the reception signal, on the basis of the time values of the predetermined permutation.
11. The reception device of claim 9 , wherein the at least one processor is further configured to:
compare sizes of a fourth absolute value corresponding to the maximum value in the second time interval centered on the second value and a fifth absolute value corresponding to the maximum value in the third time interval centered on the negative second value; and
calculate the frequency offset using a larger value among the fourth absolute value and the fifth absolute value.
12. The reception device of claim 7 , wherein the frequency offset valid value is less than one third of the detection limit value.