A low-complexity baseband signal transceiving method for an optical fiber FBMC system

Abstract

The application discloses a low-complexity baseband signal transceiving method of an optical fiber FBMC system, and comprises the following steps: in a baseband transmitter, a user binary data is subjected to QAM mapping, N point conjugate symmetry sequence construction, phase shift and recombination of real and imaginary parts of the sequence, and once N point complex IFFT combined with a PPN to generate a real FBMC signal; in a baseband receiver, the received real discrete signal is recombined into a complex signal after PPN, and once N point complex FFT is used to reconstruct two signals by using the conjugate symmetry characteristic, phase shift, channel equalization, QAM symbol recombination and demapping to recover the user binary data. The application only needs to realize the generation and demodulation of the real FBMC signal based on single IFFT / FFT calculation, has lower calculation complexity, and can reduce the cost and power consumption of a baseband chip.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a low-complexity baseband signal transmission and reception method for an optical fiber FBMC system. Background Technology

[0002] The emergence of high-bandwidth applications such as 5G mobile communication, big data, and high-definition video has placed higher demands on the data transmission rate and distance of fiber optic communication systems. Many advanced physical layer modulation techniques have been proposed to improve transmission capacity and distance. Among them, FBMC technology, due to its excellent fiber dispersion resistance, high spectral efficiency, and low out-of-band spectral leakage, is widely used in fiber optic transmission systems based on coherent detection and intensity modulation-direct detection (IMDD) to meet various application scenarios. Compared to coherent detection methods, IMDD-based fiber optic FBMC systems have a simpler structure, lower power consumption, and lower cost, making them suitable for cost- and power-sensitive short-distance applications, such as fiber optic access networks and data center optical interconnects.

[0003] In traditional baseband FBMC systems, the generation (processing) of discrete FBMC signals can be achieved based on the IFFT (FFT) algorithm, but multiple IFFT (FFT) transformations are required, resulting in high complexity in the implementation of digital baseband signal generation and processing algorithms. For details, see the reference: D.Na and K.Choi, Low PAPR FBMC. IEEE Transactions on Wireless Communications 17(1):182-193,2018. In addition, in fiber optic FBMC systems based on IMDD, the baseband transceiver system is required to generate (process) real discrete FBMC signals. However, in traditional baseband FBMC systems, the generation (processing) of real FBMC signals is usually achieved based on digital or analog up- (down) conversion, resulting in high complexity in system hardware implementation. Therefore, a method for generating and processing real-valued FBMC signals based on the conjugate symmetry property of FFT is proposed, as detailed in the following references: S. Niu, P. Wang, S. Chi, Z. Liu, W. Pang and L. Guo, Enhanced Optical OFDM / OQAM for Visible Light Communication Systems. IEEE Wireless Communications Letters 10(3):614-618,2021. and M. Chen, A. Deng, L. Zhang, R. Li, J. Yang, H. Zhou, Q. Chen and Y. Cheng, Precoding-Enabled FBMC / OQAM for Short-Reach IMDD Transmission. IEEE Photonics Technology Letters 33(23):1305-1308,2021. The flowcharts of the baseband FBMC signal generation and processing algorithms involved in the latter are as follows: Figure 1 and Figure 2 As shown. Since the IFFT / FFT algorithm requires a highly parallel pipelined structure in high-speed fiber optic communication systems to ensure real-time data processing, its implementation typically occupies a large baseband chip area and increases chip power consumption. In the proposed method based on the conjugate symmetry property of FFT, the generation and processing of real-number discrete FBMC signals require two IFFT and FFT calculations, respectively. Therefore, exploring a low-complexity signal transmission and reception method for baseband FBMC transceivers while ensuring the quality of real-number FBMC signal generation and processing performance has significant application value for cost- and power-sensitive applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a low-complexity baseband signal transmission and reception method for fiber optic FBMC communication systems.

[0005] The technical solution of this invention to solve the above problems is: a low-complexity fiber optic FBMC system baseband signal transceiver method, comprising the following steps:

[0006] S1: In the baseband transmitter of the fiber optic FBMC system, the user's binary data is mapped to a quadrature amplitude modulation (QAM) symbol sequence of length M, a conjugate symmetric sequence of length N is constructed, and the real and imaginary parts of the conjugate symmetric sequence are extracted and phase-shifted (PS) operations are performed respectively.

[0007] S2: Combine the phase-shifted data into a complex sequence of length N. After calculation by a single N-point IFFT module, extract the real and imaginary parts of the IFFT output complex sequence to form two real sequences. Then, calculate the two real sequences through a multiphase network PPN, perform parallel-to-serial conversion and delay processing, and add them together to obtain the real FBMC signal and frame.

[0008] S3: In the baseband receiver of the fiber optic FBMC system, the received discrete signal is synchronized at a specific time, the frame header is identified, and two sequences with relative delays are constructed. These two sequences are then combined into a complex sequence of length N after being converted from serial to parallel and processed by PPN.

[0009] S4: After calculation by a single N-point FFT module, the FFT output sequence of two sequences composed of the real and imaginary parts of the complex sequence input by the FFT module is equivalently calculated using the FFT output sequence. The user binary data is then recovered after PS, channel estimation and equalization, QAM symbol recombination and demapping.

[0010] In the aforementioned low-complexity fiber optic FBMC system baseband signal transceiver method, in step S1, the baseband transmitter first performs constellation mapping on the complex sequence {X} of the user binary data. n,m Perform conjugate symmetry operations to obtain an N-point conjugate symmetric sequence. Where m and n represent the FBMC symbol index and subcarrier index respectively, both being integers greater than or equal to 0, and the upper limit of n is N-1, X n,m =a n,m +jb n,m , j is the symbol for the imaginary unit, and a is the real number a. n,m With b n,m X n,m The real and imaginary parts of the real number c n,m With d n,m They are respectively The real and imaginary parts of c, and c n,m =aN-n,m and d n,m =-b N-n,m X n,m This represents the complex data corresponding to the nth subcarrier in the mth FBMC symbol. X represents n,m Complex data obtained after conjugate symmetry, where X 0,m , X N / 2,m , All values ​​are set to 0. This applies to variables or sequences with subscripts n and m in the following text, and will not be elaborated further. Next, the complex number sequence is extracted. The real and imaginary parts are respectively represented by the phase shift factor χ. n,m and γ n,m Implement PS to conform to the FBMC signal format, that is:

[0011]

[0012] Where: χ n,m =e jnπ / 2 γ n,m =e j(n+1)π / 2 , {U n,m} and {V n,m} are complex number sequences The sequence after PS processing of the real and imaginary parts.

[0013] In the aforementioned low-complexity fiber optic FBMC system baseband signal transceiver method, step S2 involves addressing the phase-shifted signal sequence {U} obtained in step S1. n,m} and {V n,m}, synthesize a new complex sequence {S} of length N in the following manner. n,m},Right now:

[0014] S n,m =U n,m +jV n,m

[0015] The new complex sequence {S n,m After a single IFFT calculation, the following was obtained:

[0016]

[0017] Where k is the time-domain data index; extract the N-point IFFT output sequence {s} during the generation of the m-th FBMC symbol. mN+k Construct two real number sequences {α} of length N from the real and imaginary parts of}. mN+k} and {β mN+k The signals are then processed by PPN, parallel-to-serial conversion, and delay, and then summed to obtain a real FBMC signal, which is then framed.

[0018] In the aforementioned low-complexity fiber optic FBMC system baseband signal transceiver method, in step S3, the received discrete signal sequence {r} is first determined in the baseband receiver using a traditional timing synchronization algorithm based on the cross-correlation of training sequences. k The frame header of} is used to construct two sequences {r} with relative delay. k} and {t k =r k+N / 2}, {r k} and {t k =r k+N / 2 After serial-to-parallel conversion and PPN processing, two real number sequences {p} are obtained. k,m} and {q k,m} represents the time-domain data at the k-th sampling time in the m-th FBMC symbol after PPN processing. Variables or sequences with subscripts k and m in the following text all have this meaning and will not be elaborated further; the two real number sequences {p k,m} and {q k,m A complex sequence {y} of length N is synthesized as follows: k,m}:

[0019] y k,m =p k,m +jq k,m .

[0020] In the aforementioned low-complexity fiber optic FBMC system baseband signal transceiver method, in step S4, the complex sequence {y} is obtained in step S3. k,m The result of the N-point FFT calculation is as follows:

[0021]

[0022] Based on the FFT output sequence {Y n,m The two sequences {p} are equivalently computed in the following manner. k,m} and {q k,m The FFT transform sequence {P} n,m} and {Q n,m}:

[0023]

[0024] Where * denotes the conjugate of a number; the obtained sequence {P} n,m} and {Q n,m The user's binary data is then recovered after PS, channel estimation and equalization, QAM symbol reassembly and demapping.

[0025] The beneficial effects of this invention are as follows: First, in the baseband transmitter, the user's binary data is mapped by Quadrature Amplitude Modulation (QAM), an N-point conjugate symmetric sequence is constructed, the real and imaginary parts of the sequence are phase-shifted and reassembled, and then the conjugate symmetry of FFT is utilized to calculate an N-point complex IFFT combined with a polyphase network (PPN) to generate a real FBMC signal. In the baseband receiver, the received real discrete signal is reassembled into a complex signal after passing through the PPN, and after an N-point complex FFT calculation, the two signals are reconstructed using the conjugate symmetry. After phase shifting, channel equalization, QAM symbol reassembly and demapping, the user's binary data is recovered. In this way, the generation and demodulation of the real FBMC signal can be realized based on only a single IFFT / FFT calculation. Compared with traditional baseband FBMC transceivers based on multiple IFFT / FFT calculations, the computational complexity can be reduced by more than 50%, thereby significantly reducing the cost and power consumption of the baseband chip. Attached Figure Description

[0026] Figure 1 This is a flowchart of a traditional algorithm for generating real baseband FBMC signals based on conjugate symmetry.

[0027] Figure 2 Here is a flowchart of a traditional real-number baseband FBMC signal processing algorithm based on conjugate symmetry properties.

[0028] Figure 3 This is a block diagram of the real baseband signal generation algorithm in this invention.

[0029] Figure 4 This is a block diagram of the real baseband signal processing algorithm in this invention. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] like Figure 3 , Figure 4 As shown, a low-complexity baseband signal transceiver method for an optical fiber FBMC system includes the following steps:

[0032] S1: In the baseband transmitter of the fiber optic FBMC system, the user's binary data is mapped to a quadrature amplitude modulation (QAM) symbol sequence of length M, a conjugate symmetric sequence of length N is constructed, and the real and imaginary parts of the conjugate symmetric sequence are extracted and phase-shifted (PS) operations are performed respectively.

[0033] In step S1, in the baseband transmitter, the complex sequence {X} of the user binary data after constellation mapping is first processed. n,m Perform conjugate symmetry operations to obtain an N-point conjugate symmetric sequence. Where m and n represent the FBMC symbol index and subcarrier index respectively, both being integers greater than or equal to 0, and the upper limit of n is N-1, X n,m =a n,m +jb n,m , j is the symbol for the imaginary unit, and a is the real number a. n,m With b n,m X n,m The real and imaginary parts of the real number c n,m With d n,m They are respectively The real and imaginary parts of c, and c n,m =a N-n,m and d n,m =-b N-n,m X n,m This represents the complex data corresponding to the nth subcarrier in the mth FBMC symbol. X represents n,m Complex data obtained after conjugate symmetry, where X 0,m , X N / 2,m , All values ​​are set to 0. This applies to variables or sequences with subscripts n and m in the following text, and will not be elaborated further. Next, the complex number sequence is extracted. The real and imaginary parts are respectively represented by the phase shift factor χ. n,m and γ n,m Implement PS to conform to the FBMC signal format, that is:

[0034]

[0035] Where: χ n,m =e jnπ / 2 γ n,m =e j(n+1)π / 2 , {U n,m} and {V n,m} are complex number sequences The sequence after PS processing of the real and imaginary parts.

[0036] S2: Combine the phase-shifted data into a complex sequence of length N. After calculation by a single N-point IFFT module, extract the real and imaginary parts of the IFFT output complex sequence to form two real sequences. Then, calculate the two real sequences through a multiphase network PPN, perform parallel-to-serial conversion and delay processing, and add them together to obtain the real FBMC signal and frame.

[0037] In step S2, the phase-shifted signal sequence {U} obtained in step S1 is... n,m} and {V n,m}, synthesize a new complex sequence {S} of length N in the following manner. n,m},Right now:

[0038] S n,m =U n,m +jV n,m

[0039] The new complex sequence {S n,m After a single IFFT calculation, the following was obtained:

[0040]

[0041] Where k is the time-domain data index; extract the N-point IFFT output sequence {s} during the generation of the m-th FBMC symbol. mN+k Construct two real number sequences {α} of length N from the real and imaginary parts of}. mN+k} and {β mN+k The signals are then processed by PPN, parallel-to-serial conversion, and delay, and then summed to obtain a real FBMC signal, which is then framed.

[0042] S3: In the baseband receiver of the fiber optic FBMC system, the received discrete signal is synchronized at a specific time, the frame header is identified, and two sequences with relative delays are constructed. These two sequences are then combined into a complex sequence of length N after being converted from serial to parallel and processed by PPN.

[0043] In step S3, in the baseband receiver, the received discrete signal sequence {r} is first determined using a traditional timing synchronization algorithm based on the cross-correlation of training sequences. k The frame header of} is used to construct two sequences {r} with relative delay. k} and {t k =r k+N / 2}, {r k} and {t k =r k+N / 2 After serial-to-parallel conversion and PPN processing, two real number sequences {p} are obtained. k,m} and {q k,m} represents the time-domain data at the k-th sampling time in the m-th FBMC symbol after PPN processing. Variables or sequences with subscripts k and m in the following text all have this meaning and will not be elaborated further; the two real number sequences {p k,m} and {q k,m A complex sequence {y} of length N is synthesized as follows: k,m}:

[0044] y k,m =p k,m +jq k,m .

[0045] S4: After calculation by a single N-point FFT module, the FFT output sequence of two sequences composed of the real and imaginary parts of the complex sequence input by the FFT module is equivalently calculated using the FFT output sequence. The user binary data is then recovered after PS, channel estimation and equalization, QAM symbol recombination and demapping.

[0046] In step S4, the complex sequence {y} obtained in step S3 is... k,m The result of the N-point FFT calculation is as follows:

[0047]

[0048] Based on the FFT output sequence {Y n,m The two sequences {p} are equivalently computed in the following manner. k,m} and {q k,m The FFT transform sequence {P} n,m} and {Q n,m}:

[0049]

[0050] Where * denotes the conjugate of a number; the obtained sequence {P} n,m} and {Q n,m The user's binary data is then recovered after PS, channel estimation and equalization, QAM symbol reassembly and demapping.

[0051] This invention first constructs an N-point conjugate symmetric sequence in the baseband transmitter using Quadrature Amplitude Modulation (QAM) mapping of the user's binary data. The real and imaginary parts of the sequence are then phase-shifted and reassembled. Utilizing the conjugate symmetry of the FFT, an N-point complex IFFT combined with a polyphase network (PPN) is calculated to generate a real-valued FBMC signal. In the baseband receiver, the received real-valued discrete signal is reassembled into a complex signal after passing through the PPN. After another N-point complex FFT calculation, the conjugate symmetry is used to reconstruct the two signals. Finally, the user's binary data is recovered after phase shifting, channel equalization, QAM symbol reassembly, and demapping. This invention achieves the generation and demodulation of real-valued FBMC signals based on only a single IFFT / FFT calculation. Compared to traditional baseband FBMC transceivers based on multiple IFFT / FFT calculations, the computational complexity can be reduced by more than 50%, thus significantly reducing the cost and power consumption of the baseband chip.

Claims

1. A low-complexity baseband signal transceiver method for an optical fiber FBMC system, characterized in that, Includes the following steps: S1: In the baseband transmitter of the fiber optic FBMC system, the user's binary data is mapped to a quadrature amplitude modulation (QAM) symbol sequence of length M, a conjugate symmetric sequence of length N is constructed, and the real and imaginary parts of the conjugate symmetric sequence are extracted and phase-shifted (PS) operations are performed respectively. S2: Combine the phase-shifted data into a complex sequence of length N. After calculation by a single N-point IFFT module, extract the real and imaginary parts of the IFFT output complex sequence to form two real sequences. Then, calculate the two real sequences through a multiphase network PPN, perform parallel-to-serial conversion and delay processing, and add them together to obtain the real FBMC signal and frame. In step S2, the phase-shifted signal sequence obtained in step S1 is... and A new complex sequence of length N is synthesized as follows: ,Right now: ； The new complex sequence After a single IFFT calculation, the following was obtained: ； Where k is the time-domain data index; extract the N-point IFFT output sequence during the generation of the m-th FBMC symbol. Construct two real number sequences of length N using the real and imaginary parts of the integers. and The signals are then processed by PPN, parallel-to-serial conversion and delay, and then summed to obtain real FBMC signals and framed. S3: In the baseband receiver of the fiber optic FBMC system, the received discrete signal is synchronized at a specific time, the frame header is identified, and two sequences with relative delays are constructed. These two sequences are then combined into a complex sequence of length N after being converted from serial to parallel and processed by PPN. S4: After calculation by a single N-point FFT module, the FFT output sequence of two sequences composed of the real and imaginary parts of the complex sequence input by the FFT module is equivalently calculated using the FFT output sequence. The user binary data is then recovered after PS, channel estimation and equalization, QAM symbol recombination and demapping.

2. The low-complexity fiber optic FBMC system baseband signal transceiver method according to claim 1, characterized in that, In step S1, in the baseband transmitter, the complex sequence of user binary data after constellation mapping is first processed. Perform conjugate symmetry operations to obtain an N-point conjugate symmetric sequence. Where m and n represent the FBMC symbol index and subcarrier index, respectively, both being integers greater than or equal to 0, and the upper limit of n is N-1. , j is the symbol for the imaginary unit, and the real number... and They are respectively The real and imaginary parts of the real number and They are respectively The real and imaginary parts, and and ; This represents the complex data corresponding to the nth subcarrier in the mth FBMC symbol. express Complex data obtained after conjugate symmetry, where All values ​​are set to 0. This applies to variables or sequences with subscripts n and m in the following text, and will not be elaborated further. Next, the complex number sequence is extracted. The real and imaginary parts are respectively treated with phase shift factors. and Implement PS to conform to the FBMC signal format, that is: ； in: , , and These are complex sequences. The sequence after PS processing of the real and imaginary parts.

3. The low-complexity fiber optic FBMC system baseband signal transceiver method according to claim 1, characterized in that, In step S3, in the baseband receiver, the received discrete signal sequence is first determined by a traditional timing synchronization algorithm based on the cross-correlation of training sequences. The frame header is used to construct two sequences with relative delay. and , and After serial-to-parallel conversion and PPN processing, two real number sequences are obtained respectively. and This represents the time-domain data at the k-th sampling time in the m-th FBMC symbol after PPN processing. Variables or sequences with subscripts k and m in the following text all have this meaning and will not be elaborated further; these two real number sequences and Synthesize a complex sequence of length N in the following manner. : 。 4. The low-complexity fiber optic FBMC system baseband signal transceiver method according to claim 3, characterized in that, In step S4, the complex sequence obtained in step S3 is described. The result of the N-point FFT calculation is as follows: ； Based on FFT output sequence The two sequences are equivalently calculated as follows: and FFT transform sequence and : ； in Represents the conjugate of numbers; the resulting sequence and After PS, channel estimation and equalization, QAM symbol reassembly and demapping, the user's binary data is recovered.

Images