A receiver IQ skew measurement method and system based on frequency domain reconstructed ZC sequences

Abstract

The application belongs to the technical field of optical fiber communication, and proposes a receiver IQ skew measurement method and system based on frequency domain reorganization ZC sequence, comprising: generating ZC sequence based on two different root indexes for the training sequence of the transmitting end; calculating the real part and the imaginary part of the ZC sequence based on orthogonal frequency domain time-frequency transformation, reorganizing the sequence based on the real part and the imaginary part, and taking the reorganized ZC sequence as the training sequence of the transmitting end; and based on the frequency domain, block the received sequence signal, perform conjugate summation on adjacent frequency domain sub-blocks, solve the phase angle based on the summation result, and obtain the IQ skew based on the phase angle. Compared with the prior art, the application reduces the calculation complexity of error solving.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, specifically relating to a receiver IQskew measurement method and system based on frequency domain recombined ZC sequences. Background Technology

[0002] In coherent optical communication systems, Digital Subcarrier Multiplexing (DSCM) technology, with its high spectral efficiency, flexible resource allocation, high tolerance to fiber nonlinearity and EEPN, and low complexity in dispersion compensation, has become one of the core solutions for meeting the demands of high-capacity transmission. However, in practical applications, the receiver's I / Q channel delay mismatch (IQ skew) problem cannot be ignored. Primarily caused by the receiver's circuit design and optoelectronic device characteristics, it is a typical non-ideal factor in digital subcarrier systems. Especially in multi-subcarrier systems, due to the conjugate interference introduced by receiver-side IQ skew to symmetrical subcarriers, the impact of IQ skew on DSCM signals is far greater than in traditional single-carrier systems, leading to a significant degrade in system performance. Particularly in DSCM systems with high-order modulation formats, the cumulative effect of IQ skew further worsens, causing inter-subcarrier interference to grow exponentially, resulting in a sharp increase in the bit error rate and severely limiting the system's performance limits.

[0003] In traditional single-carrier coherent optical communication systems, the measurement of receiver IQ skew primarily employs two schemes: equalizer-based and pilot insertion. The equalizer-based scheme has significant drawbacks; in practical applications, it greatly increases system complexity, leading to reduced system efficiency and increased resource consumption. While the pilot insertion scheme can achieve a certain level of IQ skew estimation, this comes at the cost of spectral efficiency, and its limitations are becoming increasingly apparent given the scarcity of spectrum resources. More importantly, traditional schemes struggle to provide effective solutions for high-precision measurement of receiver IQ skew and the applicability of the measurement methods to various channel impairments. Furthermore, the IQ skew parameter extraction process is cumbersome and inefficient. Summary of the Invention

[0004] To overcome the low computational efficiency of the prior art, this invention provides a receiver IQ skew measurement method and system based on frequency-domain reconstructed ZC sequences. To achieve the above-mentioned technical effects, the technical solution of this invention is as follows:

[0005] A receiver IQ skew measurement method based on frequency domain reconstructed ZC sequences includes the following steps:

[0006] The training sequence for the transmitter is used to generate a ZC sequence based on two different root indices; the real and imaginary parts of the ZC sequence are calculated based on the orthogonal frequency domain and time-frequency transformation; the sequence is recombined based on the real and imaginary parts; and the recombined ZC sequence is used as the training sequence for the transmitter.

[0007] At the receiving end, the received sequence signal is divided into blocks based on the frequency domain, adjacent frequency domain sub-blocks are summed by conjugate, the phase angle is calculated based on the summation result, and the IQ skew is obtained based on the phase angle.

[0008] As a preferred embodiment, the orthogonal frequency domain undergoes a time-frequency transformation using a fast Fourier transform.

[0009] As a preferred embodiment, the step of recombining the sequence based on the real and imaginary parts includes:

[0010] Using two different root indexes u 1 and u 2. The signal composed of real numbers is used as the first half of the time slot signal, and the signal composed of imaginary numbers is used as the second half of the time slot signal; the generator formula of the ZC sequence is as follows:

[0011]

[0012] in, u For the root index, L The sequence length is and is u Coprime, For sequence The real part, For sequence The imaginary part.

[0013] Recombined sequence The expression is as follows:

[0014]

[0015] in, , i =1,2, , N / 2 represents the real and imaginary signs of the ZC sequences generated by different root indices in the frequency domain after fast Fourier transform. N To pre-set the total length of the sequence symbols, , The first half of the time slot signal is composed of real numbers, and the second half is composed of imaginary numbers, respectively.

[0016] As a preferred embodiment, when the recombined ZC sequence is transmitted through a communication channel with frequency offset and phase noise, the real and imaginary parts of the recombined ZC sequence are transmitted in different time slots; its expression in the frequency domain is as follows:

[0017]

[0018]

[0019]

[0020]

[0021] in, and They are respectively Frequency domain representation of the real and imaginary parts after channel frequency offset and They are Frequency domain representation of the real and imaginary parts after channel frequency offset.

[0022] As a preferred option, the sequence signal received by the receiver Introducing receiver delay, the real and imaginary parts in the frequency domain can be expressed by the following equation:

[0023]

[0024]

[0025]

[0026]

[0027] in, and They are Frequency domain representation of the real and imaginary parts after introducing receiver delay. and They are Frequency domain representation of the real and imaginary parts after introducing receiver delay. and These are the delays of the receiver's I and Q channels, respectively. The sampling period.

[0028] As a preferred embodiment, the step of performing conjugate summation on adjacent frequency domain sub-blocks includes:

[0029] For different frequency domain blocks, the real and imaginary parts of adjacent frequency domain sub-blocks are summed based on the characteristics of the ZC sequence; where the length of each frequency domain sub-block in the sequence is... The calculation formula is as follows:

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] in, Indicates to Perform conjugation. express Summing the real parts after introducing receiver delay express Summing the imaginary parts after introducing receiver delay. express Summing the real parts after introducing receiver delay express Summing the imaginary part after introducing receiver delay.

[0039] As a preferred embodiment, the step of solving for the phase angle based on the summation result and obtaining the IQskew based on the phase angle includes:

[0040] The phase angle between the real and imaginary parts of the summation result is calculated and the difference is obtained. The IQskew is solved based on frequency domain block division, and its calculation formula is as follows:

[0041]

[0042] in, This represents the time delay of the imaginary channel. This represents the time delay of the real channel. Indicates the number of frequency domain sub-blocks. () indicates angle extraction operation. This represents the result of solving the IQ skew problem.

[0043] This invention also proposes a receiver IQ skew measurement system based on frequency-domain recombined ZC sequences, the system comprising:

[0044] Sequence Reassembly Module: Generates ZC sequences from the training sequence of the transmitter based on two different root indices; calculates the real and imaginary parts of the ZC sequences based on orthogonal frequency domain and time-frequency transformation; performs sequence reassembly based on the real and imaginary parts; and uses the reassembled ZC sequences as the training sequences of the transmitter.

[0045] Error calculation module: At the receiving end, the received sequence signal is divided into blocks based on the frequency domain, adjacent frequency domain sub-blocks are conjugate summed, the phase angle is calculated based on the summation result, and the IQ skew is obtained based on the phase angle.

[0046] The present invention also proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the receiver IQ skew measurement method based on frequency domain recombined ZC sequence as described in the present invention.

[0047] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the receiver IQ skew measurement method based on frequency domain recombined ZC sequences as described in the present invention.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] This invention, based on the recombination of ZC sequences, requires only half the total length of the original training sequence to complete the measurement of receiver IQ skew, significantly reducing computational complexity. Simultaneously, this invention effectively eliminates the impact of channel frequency offset and phase noise on measurement accuracy. Attached Figure Description

[0050] Figure 1 This is a flowchart of a receiver IQ skew measurement method based on frequency domain reconstructed ZC sequences, as described in Example 1.

[0051] Figure 2 This is a schematic diagram of sequence recombination in Example 1;

[0052] Figure 3 This is an architecture diagram of a receiver IQ skew measurement system based on frequency domain reconstructed ZC sequences, as shown in Example 2.

[0053] Figure 4 The results of receiver IQ skew measurements under various damage conditions provided in Example 3;

[0054] Figure 5 The graph shows the relationship between receiver IQ skew measurement and sequence length provided in Example 3. Detailed Implementation

[0055] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention.

[0056] It will be understood by those skilled in the art that some well-known descriptions may be omitted in the accompanying drawings.

[0057] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0058] Example 1

[0059] This embodiment proposes a receiver IQ skew measurement method based on frequency-domain reconstructed ZC sequences, such as... Figure 1 The diagram shown is a flowchart of a receiver IQ skew measurement method based on frequency domain recombined ZC sequences in this embodiment.

[0060] This embodiment proposes a receiver IQ skew measurement method based on frequency domain reconstructed ZC sequences, which includes the following steps:

[0061] S1. Generate ZC sequences from the training sequences of the transmitter based on two different root indices; calculate the real and imaginary parts of the ZC sequences based on the orthogonal frequency domain and time-frequency transformation; reassemble the sequences based on the real and imaginary parts; and use the reassembled ZC sequences as the training sequences of the transmitter.

[0062] S2. At the receiving end, the received sequence signal is divided into blocks based on the frequency domain, adjacent frequency domain sub-blocks are summed by conjugate, the phase angle is solved based on the summation result, and the IQ skew is obtained based on the phase angle.

[0063] In this embodiment, a time-recombination design is adopted in the frequency domain structure using the real and imaginary parts of ZC sequences generated by two different root indices after IFFT operation. Only half of the total length of the training sequence is needed to complete the measurement of the receiver IQ skew. Frequency domain block processing is performed on the sequence signal carrying the receiver delay, which reduces the impact of delay on the signal and improves the demodulation accuracy of the signal.

[0064] like Figure 2 The image shows a schematic diagram of sequence recombination.

[0065] In an optional embodiment, the orthogonal frequency domain undergoes a time-frequency transformation using a Fast Fourier Transform.

[0066] In this embodiment, the transformation from the orthogonal frequency domain to the time domain is achieved by using the Fast Fourier Transform, which reduces the complexity of signal processing and the consumption of computing resources, thereby improving the overall spectral efficiency and transmission capacity of the optical fiber communication system.

[0067] In an optional embodiment, the step of recombining the sequence based on the real and imaginary parts includes:

[0068] Using two different root indexes u 1 and u 2. The signal composed of real numbers is used as the first half of the time slot signal, and the signal composed of imaginary numbers is used as the second half of the time slot signal; the generator formula of the ZC sequence is as follows:

[0069]

[0070] in, u For the root index, L The sequence length is and is u Coprime, For sequence The real part, For sequence The imaginary part.

[0071] Recombined sequence The expression is as follows:

[0072]

[0073] in, , i =1,2, , N / 2 represents the real and imaginary signs of the ZC sequences generated by different root indices in the frequency domain after fast Fourier transform. N To pre-set the total length of the sequence symbols, , The first half of the time slot signal is composed of real numbers, and the second half is composed of imaginary numbers, respectively.

[0074] In this embodiment, the scheme utilizes the sequence characteristics generated by two different root indices to map the real and imaginary parts of the signal to different time slots for transmission. This effectively avoids the inherent amplitude imbalance or phase quadrature error in traditional IQ modulation caused by the simultaneous transmission of I and Q signals in the same channel, thereby improving the demodulation accuracy and anti-interference capability of the signal.

[0075] In an optional embodiment, when the recombined ZC sequence passes through a communication channel with frequency offset and phase noise during transmission, the real and imaginary parts of the recombined ZC sequence are transmitted in different time slots; its expression in the frequency domain is as follows:

[0076]

[0077]

[0078]

[0079]

[0080] in, and They are respectively Frequency domain representation of the real and imaginary parts after channel frequency offset and They are Frequency domain representation of the real and imaginary parts after channel frequency offset.

[0081] In an alternative embodiment, the sequence signal received by the receiver Introducing receiver delay, the real and imaginary parts in the frequency domain can be expressed by the following equation:

[0082]

[0083]

[0084]

[0085]

[0086] in, and They are Frequency domain representation of the real and imaginary parts after introducing receiver delay. and They are Frequency domain representation of the real and imaginary parts after introducing receiver delay. and These are the delays of the receiver's I and Q channels, respectively. The sampling period.

[0087] In an optional embodiment, the step of performing conjugate summation on adjacent frequency domain sub-blocks includes:

[0088] For different frequency domain blocks, the real and imaginary parts of adjacent frequency domain sub-blocks are summed based on the characteristics of the ZC sequence; where the length of each frequency domain sub-block in the sequence is... The calculation formula is as follows:

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] in, Indicates to Perform conjugation. express Summing the real parts after introducing receiver delay express Summing the imaginary parts after introducing receiver delay. express Summing the real parts after introducing receiver delay express Summing the imaginary part after introducing receiver delay.

[0098] In this embodiment, the real and imaginary data of adjacent sub-blocks are summed in the frequency domain, which can effectively suppress random noise and interference in the transmission channel.

[0099] In an optional embodiment, the step of solving for the phase angle based on the summation result and obtaining the IQ skew based on the phase angle includes:

[0100] The phase angle between the real and imaginary parts of the summation result is calculated and the difference is obtained. The IQskew is solved based on frequency domain block division, and its calculation formula is as follows:

[0101]

[0102] in, This represents the time delay of the imaginary channel. This represents the time delay of the real channel. Indicates the number of frequency domain sub-blocks. () indicates angle extraction operation. This represents the result of solving the IQ skew problem.

[0103] Example 2

[0104] This embodiment proposes a receiver IQ skew measurement system based on frequency-domain reconstructed ZC sequences, applying the receiver IQ skew measurement method based on frequency-domain reconstructed ZC sequences proposed in Embodiment 1. Figure 3 The diagram shown is an architecture diagram of a receiver IQ skew measurement system based on frequency domain recombined ZC sequences in this embodiment.

[0105] This embodiment proposes a receiver IQ skew measurement system based on frequency domain reconstructed ZC sequences, including:

[0106] Sequence Reassembly Module: Generates ZC sequences from the training sequence of the transmitter based on two different root indices; calculates the real and imaginary parts of the ZC sequences based on orthogonal frequency domain and time-frequency transformation; performs sequence reassembly based on the real and imaginary parts; and uses the reassembled ZC sequences as the training sequences of the transmitter.

[0107] Error calculation module: At the receiving end, the received sequence signal is divided into blocks based on the frequency domain, adjacent frequency domain sub-blocks are conjugate summed, the phase angle is calculated based on the summation result, and the IQ skew is obtained based on the phase angle.

[0108] It is understood that the system in this embodiment corresponds to the method in Embodiment 1 above, and the options in Embodiment 1 above are also applicable to this embodiment, so they will not be described again here.

[0109] Example 3

[0110] This embodiment applies the receiver IQ skew measurement method based on frequency domain recombined ZC sequence proposed in Embodiment 1.

[0111] like Figure 4 The figure shown is a graph of the receiver IQ skew measurement results under various types of damage.

[0112] like Figure 5 The figure shows the relationship between receiver IQ skew measurement and sequence length.

[0113] in, Figure 4 (a) The correspondence between the preset receiver IQ skew and the IQ skew measured using the method of the present invention is shown intuitively, wherein the data dotted line marked with red circles represents the error in measuring IQ skew, and the data dotted line marked with blue circles represents the result value of measuring IQ skew; Figure 4 (b), (c), and (d) respectively show the correspondence between the preset amplitude imbalance, phase imbalance, polarization rotation phase angle and the IQ skew measured by the present invention when the IQ skew of the fixed receiver is 5 ps. The data dotted line marked with red circles represents the error of measuring IQ skew, and the data dotted line marked with blue circles represents the result value of measuring IQ skew. Figure 5 The simulation results show the correspondence between sequence length and IQ skew measured by this invention when the receiver IQ skew is fixed at 2, 5, and 8 ps. The histogram represents the measured IQ skew value, and the dotted-line graph represents the measurement error. Simulation results demonstrate that this invention can achieve high-precision IQ skew measurement under various damage conditions and at low sequence lengths, fully verifying the reliability of this invention in this technical field.

[0114] Example 4

[0115] This embodiment proposes a computer device, including a memory and a processor. The memory stores computer-readable instructions, which, when executed by the processor, cause the processor to perform the steps of the receiver IQ skew measurement method based on frequency domain recombined ZC sequences proposed in Embodiment 1.

[0116] Example 5

[0117] This embodiment proposes a storage medium storing computer-readable instructions, wherein when executed by a processor, the computer-readable instructions implement the steps of the receiver IQ skew measurement method based on frequency-domain reconstructed ZC sequences proposed in Embodiment 1. The storage medium includes, but is not limited to, various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0118] By way of example, the instructions, programs, code sets, or instruction sets may be implemented using conventional programming languages.

[0119] Exemplary, the processor includes, but is not limited to, smartphones, personal computers, servers, network devices, etc., for performing all or part of the steps of the receiver IQ skew measurement method based on frequency domain recombined ZC sequences described in Example 1.

Claims

1. A method for measuring IQ skew of a receiver based on frequency-domain reorganized ZC sequence, characterized in that, The method comprises the following steps: generating a ZC sequence based on two different root indexes for a training sequence of a transmitting end; calculating real and imaginary parts of the ZC sequence based on an orthogonal frequency domain time-frequency transform, reorganizing the ZC sequence based on the real and imaginary parts, and taking the reorganized ZC sequence as the training sequence of the transmitting end; performing frequency domain blocking on a received sequence signal at a receiving end, performing conjugate summation on adjacent frequency domain sub-blocks, solving a phase angle based on a summation result, and obtaining an IQ skew based on the phase angle; the orthogonal frequency domain time-frequency transform adopts a fast Fourier transform; the step of reorganizing the ZC sequence based on the real and imaginary parts comprises: Using two different root indexes u 1 and u 2, the signal composed of real numbers as the first half of the slot signal, and the signal composed of imaginary numbers as the second half of the slot signal; the generation formula of the ZC sequence is as follows: wherein u is a root index, L is a sequence length and is coprime with u is a sequence is a real part of the sequence is an imaginary part of the sequence is an imaginary part of the sequence​ Post-recombination sequence The expression of the sequence after recombination is as follows: wherein, , i = 1, 2, , N are real and imaginary symbols of the ZC sequence generated by different root indexes in the frequency domain respectively after fast Fourier transform operation, N is the total length of the sequence symbol, , are the first half of the time slot signal composed of real numbers and the second half of the time slot signal composed of imaginary numbers respectively.

2. The method of claim 1, wherein, when the reorganized ZC sequence passes through a communication channel with frequency offset and phase noise during transmission, the real and imaginary parts of the reorganized ZC sequence are transmitted on different time slots; and an expression of the reorganized ZC sequence in the frequency domain is as follows: wherein and are are the frequency domain representations of the real and imaginary parts of the channel frequency offseted real and imaginary parts, respectively. and are are the frequency domain representations of the real and imaginary parts of the channel frequency offseted real and imaginary parts, respectively.

3. The method of claim 1 or 2, wherein, The sequence signal received by the receiver The receiver introduces a delay, the real and imaginary parts of which in the frequency domain can be expressed by the following equations: wherein and are respectively are the frequency domain representations of the real and imaginary parts of the received signal after introducing the receiver time delay, and are respectively are the frequency domain representations of the real and imaginary parts of the received signal after introducing the receiver time delay, and are the time delays of the receiver I and Q channels respectively, is the sampling period.

4. The method of claim 3, wherein, the step of performing conjugate summation on adjacent frequency domain sub-blocks comprises: For different frequency domain blocks, the real parts and the imaginary parts of adjacent frequency domain sub-blocks are summed respectively based on the characteristics of the ZC sequence; wherein the length of each frequency domain sub-block in the sequence is The calculation formula is as follows: wherein, represents conjugation of , represents summing of real parts after introducing receiver delays, represents summing of imaginary parts after introducing receiver delays, represents summing of real parts after introducing receiver delays, represents summing of imaginary parts after introducing receiver delays.

5. The method of claim 4, wherein, the step of solving the phase angle based on the summation result and obtaining the IQ skew based on the phase angle comprises: calculating the phase angle of the real and imaginary parts of the summation result and solving the difference value, and solving the IQ skew based on the frequency of the frequency domain blocking, and a calculation formula is as follows: wherein, represents a time delay of the imaginary part channel, represents a time delay of the real part channel, represents a number of frequency domain sub-blocks, () represents an extraction angle operation, represents solving an IQ skew result.

6. A receiver IQ skew measurement system based on frequency domain reorganized ZC sequence, characterized in that, The system comprises: a sequence reorganization module: generating a ZC sequence based on two different root indexes for a training sequence of a transmitting end; calculating real and imaginary parts of the ZC sequence based on an orthogonal frequency domain time-frequency transform, reorganizing the ZC sequence based on the real and imaginary parts, and taking the reorganized ZC sequence as the training sequence of the transmitting end; an error solving module: performing frequency domain blocking on a received sequence signal at a receiving end, performing conjugate summation on adjacent frequency domain sub-blocks, solving a phase angle based on a summation result, and obtaining an IQ skew based on the phase angle.

7. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the steps of the receiver IQ skew measurement method based on frequency domain reorganized ZC sequences in any one of claims 1 to 5.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the receiver IQ skew measurement method based on frequency domain reorganized ZC sequences in any one of claims 1 to 5.

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