Frequency offset estimation and compensation method applied to 5G NR

Abstract

The invention discloses a frequency offset estimation and compensation method applied to 5G NR, and relates to the technical field of broadband wireless communication. According to the method, LS channel estimation is firstly carried out, then linear regression frequency offset estimation is carried out based on a DMRS pairing group to obtain a normalized frequency offset value, then frequency domain interpolation and frequency offset compensation of a channel are carried out, time domain interpolation is carried out based on the compensated channel estimation value, equalization is carried out, and finally frequency offset estimation is carried out on the equalized data. According to the method, the frequency offset estimation value is calculated through a method of pairing DMRS groups and performing linear regression, and compared with a method of accumulative summation and phase angle calculation, the frequency offset estimation accuracy is improved, and the anti-frequency offset performance of the system is improved; the frequency offset of the channel and the frequency offset of the balanced data are respectively compensated, channel estimation does not need to be carried out again after frequency offset compensation, the processing flow of a receiving end is simplified, the calculation complexity is reduced, and the processing efficiency of the receiving end is improved while the demodulation performance is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of broadband wireless communications, and in particular to a frequency offset estimation and compensation method applied to 5G NR. Background Art

[0002] In the OFDM system, signals are transmitted through orthogonal subcarriers to avoid signal distortion. However, carrier offset at the transmitting and receiving ends will destroy the orthogonality of OFDM, introduce inter-carrier interference, and lead to a decrease in demodulation performance. Therefore, it is necessary to estimate and compensate for frequency offset at the receiving end to ensure the communication performance of the system.

[0003] In the prior art, commonly used frequency domain-based frequency offset estimation algorithms include the Moose algorithm, the Classen algorithm, etc. The data channel in the NR system can perform frequency offset estimation based on the demodulation reference signal (DMRS). However, after directly compensating the frequency offset of the receiving end signal, channel estimation needs to be performed again to correctly demodulate the transmitted signal, which alleviates the impact of the frequency offset and introduces additional computational complexity and processing delay. Summary of the invention

[0004] In view of this, the present invention proposes a frequency offset estimation and compensation method applied to 5G NR. This method does not need to perform channel estimation again after frequency offset compensation, simplifies the processing flow of the receiving end, reduces the calculation complexity, ensures the demodulation performance and improves the processing efficiency of the receiving end.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A frequency offset estimation and compensation method applied to 5G NR, comprising the following steps;

[0007] Step 1: The receiver calculates the corresponding LS channel estimation value based on the DMRS symbol in the received signal

[0008]

[0009] Where M represents the DMRS local sequence, the superscript * represents the conjugate operation; Y represents the received signal, and the subscript k b represents the subcarrier index of the DMRS symbol in the received signal, k b ∈{k 1 ,k 2 ,……,k B}, subscript l d Indicates the symbol index of the DMRS symbol in the received signal, l d ∈{l 1 ,l 2,……,l D};

[0010] {k 1 ,k 2 ,……,k B} and {l 1 ,l 2 ,……,l D} are all sets of elements sorted from small to large; and the DMRS symbol in the received signal is consistent with the corresponding subcarrier index and symbol index in the DMRS local sequence;

[0011] Step 2: Pair adjacent DMRS symbols in pairs to obtain a paired DMRS group (l 1 ,l 2 ), (l 2 ,l 3 ),……,(l D-1 ,l D ), calculate the relevant phase angle and sampling point interval of the paired DMRS group:

[0012]

[0013] S(n)=NS n ×(N FFT +N cp1 )+Ind×(N cp2 -N cp1 ),n∈{1,2,…,D-1};

[0014] in, Indicates that the symbol index is l n The ampersand index is l n+1 The relevant phase angle between the DMRS symbols, angle( ) indicates the calculation of the phase angle; S(n) indicates that the symbol index is l n The ampersand index is l n+1 The sampling point interval between DMRS symbols, N FFT 、N cp1 and N cp2 are the FFT length, short CP length and long CP length of OFDM symbols respectively;

[0015] NS n = l n+1 -l n ;

[0016]

[0017] Step 3: Calculate the slope of the frequency deviation value using the linear regression method:

[0018]

[0019] in,

[0020]

[0021] Step 4, calculate the normalized frequency deviation value ε:

[0022]

[0023] Wherein, Δf is the subcarrier spacing;

[0024] Step 5: channel estimation value corresponding to DMRS symbol To perform frequency offset compensation:

[0025] When l d = l 1 hour,

[0026] When l d = l 2 ,l 3 ,……,l D hour,

[0027]

[0028] in, is the LS channel estimate The result obtained after frequency domain interpolation, subscript k y Represents the subcarrier index of the received signal Y;

[0029]

[0030] D d =(l d -l 1 )×(N FFT +N cp1 )+flag 1 ×(N cp2 -N cp1 );

[0031]

[0032] Among them, j represents the imaginary unit. In summary, the channel estimation value after frequency offset compensation is obtained

[0033] Step 6: Channel estimation based on frequency offset compensation Perform time domain interpolation to obtain Afterwards based on Perform channel equalization to obtain the equalized data signal in, is the result of equalization of the data signal in the received signal Y, with the subscript l y Represents the symbol index of the data signal in the received signal Y;

[0034] Step 7: Data signal Perform frequency offset compensation to obtain the compensated data signal:

[0035]

[0036] D` s =(ly-l 1 )×(N FFT +N cp1 )+flag 2 ×(N cp2 -N cp1 )×sign(l y -l 1 );

[0037]

[0038] Among them, sign() represents the sign function, This is the data signal after frequency offset compensation.

[0039] Due to the adoption of the above technical solution, the beneficial effects of the present invention compared with the prior art are:

[0040] The present invention calculates the frequency offset estimation value by pairing DMRS groups and performing linear regression, which improves the accuracy of frequency offset estimation and the system's anti-frequency offset performance compared with the method of accumulating and summing the phase angle. The frequency offsets of the channel and the equalized data are compensated separately, and there is no need to perform channel estimation again after the frequency offset compensation, which simplifies the processing flow of the receiving end, reduces the calculation complexity, ensures the demodulation performance and improves the processing efficiency of the receiving end. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is an overall flow chart of a frequency offset estimation and compensation method applied to 5G NR in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0043] A frequency offset estimation and compensation method for 5G NR, such as Figure 1 As shown, the following steps are included;

[0044] Step 1: The receiver calculates the corresponding LS channel estimation value based on the DMRS symbol in the received signal

[0045]

[0046] Where M represents the DMRS local sequence, the superscript * represents the conjugate operation; Y represents the received signal, and the subscript k b represents the subcarrier index of the DMRS symbol in the received signal, k b ∈{k 1 ,k 2 ,……,k B}, subscript l d Indicates the symbol index of the DMRS symbol in the received signal, l d ∈{l 1 ,l 2 ,……,l D};

[0047] {k 1 ,k 2 ,……,k B} and {l 1 ,l 2 ,……,l D} are all sets of elements sorted from small to large; and the DMRS symbol in the received signal is consistent with the corresponding subcarrier index and symbol index in the DMRS local sequence;

[0048] Step 2: Pair adjacent DMRS symbols in pairs to obtain a paired DMRS group (l 1 ,l 2 ), (l 2 ,l 3 ),……,(l D-1 ,l D ), calculate the relevant phase angle and sampling point interval of the paired DMRS group:

[0049]

[0050] S(n)=NS n ×(N FFT +N cp1 )+Ind×(N cp2 -N cp1 ),n∈{1,2,…,D-1};

[0051] in, Indicates that the symbol index is l n The ampersand index is l n+1 The relevant phase angle between the DMRS symbols, angle( ) indicates the calculation of the phase angle; S(n) indicates that the symbol index is l n The ampersand index is l n+1 The sampling point interval between DMRS symbols, N FFT 、N cp1and N cp2 are the FFT length, short CP length and long CP length of OFDM symbols respectively;

[0052] NS n = l n+1 -l n ;

[0053]

[0054] Step 3: Calculate the slope of the frequency deviation value using the linear regression method:

[0055]

[0056] in,

[0057]

[0058] Step 4, calculate the normalized frequency deviation value ε:

[0059]

[0060] Wherein, Δf is the subcarrier spacing of the received signal;

[0061] Step 5: channel estimation value corresponding to DMRS symbol To perform frequency offset compensation:

[0062] When l d = l 1 hour,

[0063] When l d = l 2 ,l 3 ,……,l D hour,

[0064]

[0065] in, is the LS channel estimate The result obtained after frequency domain interpolation, subscript k y Represents the subcarrier index of the received signal Y;

[0066]

[0067] D d =(l d -l 1 )×(N FFT +N cp1 )+flag 1 ×(N cp2 -N cp1 );

[0068]

[0069] Among them, j represents the imaginary unit. In summary, the channel estimation value after frequency offset compensation is obtained

[0070] Step 6: Channel estimation based on frequency offset compensation Perform time domain interpolation to obtain Afterwards based on Perform channel equalization to obtain the equalized data signal in, is the result of equalization of the data signal in the received signal Y, with the subscript l y Represents the symbol index of the data signal in the received signal Y;

[0071] Step 7: Data signal Perform frequency offset compensation to obtain the compensated data signal:

[0072]

[0073] D` s =(l y -l 1 )×(N FFT +N cp1 )+flag 2 ×(N cp2 -N cp1 )×sign(l y -l 1 );

[0074]

[0075] Among them, sign() represents the sign function, This is the data signal after frequency offset compensation.

[0076]

[0077] In summary, the present invention calculates the frequency offset estimation value by pairing DMRS groups and performing linear regression, which improves the accuracy of frequency offset estimation and improves the system's anti-frequency offset performance compared to the method of accumulating and summing the phase angle. By compensating for the frequency offsets of the channel and the equalized data respectively, there is no need to perform channel estimation again after the frequency offset compensation, which simplifies the processing flow at the receiving end, reduces the calculation complexity, ensures the demodulation performance and improves the processing efficiency at the receiving end.

[0078] Those skilled in the art will appreciate that the embodiments described are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to the embodiments described. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A frequency offset estimation and compensation method applied to 5G NR, characterized in that: The steps include: Step 1: The receiver calculates the corresponding LS channel estimation value based on the DMRS symbol in the received signal Where M represents the DMRS local sequence, the superscript * represents the conjugate operation; Y represents the received signal, and the subscript k b represents the subcarrier index of the DMRS symbol in the received signal, k b ∈{k1,k2,……,k B }, subscript l d Indicates the symbol index of the DMRS symbol in the received signal, l d ∈{l1,l2,……,l D }; {k1,k2,……,k B } and {l1,l2,…,l D } are all sets of elements sorted from small to large; and the DMRS symbol in the received signal is consistent with the corresponding subcarrier index and symbol index in the DMRS local sequence; Step 2: Pair adjacent DMRS symbols in pairs to obtain paired DMRS groups (l1, l2), (l2, l3), ..., (l D-1 ,l D ), calculate the relevant phase angle and sampling point interval of the paired DMRS group: S(n)=NS n ×(N FFT +N cp1 )+Ind×(N cp2 -N cp1 ),n∈{1,2,……,D-1}; in, Indicates that the symbol index is l n The ampersand index is l n+1 The relevant phase angle between the DMRS symbols, angle() indicates the calculation of the phase angle; S(n) indicates that the symbol index is l n The ampersand index is l n+1 The sampling point interval between DMRS symbols, N FFT 、N cp1 and N cp2 are the FFT length, short CP length and long CP length of OFDM symbols respectively; NS n =l n+1 -l n ; Step 3: Calculate the slope of the frequency deviation value using the linear regression method: in, Step 4, calculate the normalized frequency deviation value ε: Wherein, Δf is the subcarrier spacing; Step 5: channel estimation value corresponding to DMRS symbol To perform frequency offset compensation: When l d = l1, When l d =l2,l3,……,l D hour, in, is the LS channel estimate The result obtained after frequency domain interpolation, subscript k y Represents the subcarrier index of the received signal Y; D d (l) d -l1)×(N FFT +N cp1 )+flag1×(N cp2 -N cp1 ); Among them, j represents the imaginary unit. In summary, the channel estimation value after frequency offset compensation is obtained Step 6: Channel estimation based on frequency offset compensation Perform time domain interpolation to obtain Afterwards based on Perform channel equalization to obtain the equalized data signal in, is the result of equalization of the data signal in the received signal Y, with the subscript l y Represents the symbol index of the data signal in the received signal Y; Step 7: Data signal Perform frequency offset compensation to obtain the compensated data signal: D` s (l) y -l1)×(N FFT +N cp1 )+flag2×(N cp2 -N cp1 )×sign(l y -l1); Among them, sign() represents the sign function, This is the data signal after frequency offset compensation.

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