Digital-analog hybrid signal modulation method and demodulation method capable of relieving frequency selective power fading based on discrete Fresnel transform

Abstract

The invention discloses a digital-analog hybrid signal modulation method capable of relieving frequency selective power fading based on discrete Fresnel transform, which comprises the following steps of: S1, collecting a plurality of wireless signals from an antenna, aggregating the wireless signals into a signal through a group of standard orthogonal bases in a chirp domain, meanwhile, the narrowband target signal is spread into a broadband signal; s2, based on the aggregated signal in the chirp domain, inserting a cyclic prefix as a guard interval into the beginning of each column in the signal, and then performing parallel-serial conversion to obtain a target output signal; s3, quantizing the output signal so as to obtain a digital part signal; s4, based on the quantized digital part signal and a target output signal, adopting subtraction operation to obtain an analog part signal; step S5, carrying out proper power regulation on the obtained digital part signal and the analog part signal; and S6, aggregating the digital signal and the analog signal after power regulation into a final modulation output signal in a time division multiplexing mode. The invention also discloses a digital-analog hybrid signal demodulation method capable of relieving frequency selective power fading based on discrete Fresnel transform, and the operation steps are the inverse process of the modulation method.

Description

Technical Field

[0001] This invention relates to the field of signal modulation and demodulation technology, and in particular to a digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform that can mitigate frequency-selective power fading. Background Technology

[0002] Mobile fronthaul is a key fiber optic component in centralized wireless access networks, connecting the centralized unit (CU) and distributed unit (DU). To meet the 10- to 100-fold increase in capacity required for future 6G networks, Radio over Optical (RoF) technology has gained attention to optimize the inherent trade-off between signal-to-noise ratio and spectral efficiency. Based on cascaded digital probabilistic shaping orthogonal amplitude modulation and analog pulse code modulation, Xiang Liu proposed a hybrid digital-analog radio over optical (DA-RoF) signal modulation and demodulation scheme, which was experimentally verified in an intensity modulation and direct detection (IMDD) system over a 1km standard single-mode fiber (SSMF). This DA-RoF technology has now been extended to dual-polarization coherent systems with multi-dimensional coding, including phase, polarization, and spatial diversity, achieving a Public Radio Interface (CPRI) equivalent rate of Tb / s.

[0003] However, for cost-sensitive fronthaul transmission links, IMDD, with its simpler architecture and easier system integration, is a promising solution compared to the high-cost coherent system architecture, offering an optimal balance between performance and implementation complexity. However, frequency-selective power fading caused by dispersion and direct detection in IMDD systems limits the system's capacity-distance product. For uplink transmission signals aggregated in the frequency domain, power fading leads to performance degradation in the aforementioned DA-RoF systems.

[0004] Therefore, this invention proposes a digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform to alleviate frequency-selective power fading. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform to mitigate frequency-selective power fading.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform to mitigate frequency-selective power fading includes the following steps:

[0008] Step S1: Collect N wireless signals from the antenna, X = [x(1), x(2), ..., x(N)], and aggregate them into a single signal using a set of orthogonal bases Φ in the chirped domain. Simultaneously, spread the narrowband target signal into a wideband signal, thereby mitigating the distortion caused by frequency-selective power fading in the channel. This operation can be represented as:

[0009] S = Φ H X

[0010] in,(·) H The conjugate transpose operation, where Φ is the discrete Fresnel transformation matrix, can be represented as:

[0011]

[0012] Here, mod represents the modulo operation.

[0013] Step S2: Based on the aggregated signal S in the chirped domain, insert the cyclic prefix as a guard interval at the beginning of each column in S, then perform parallel-to-serial (P / S) conversion to obtain the output signal, denoted as S. O .

[0014] Step S3, output signal S O Quantization is performed to obtain the digital part S. D Signal:

[0015] S D =Q(S) O ,n)

[0016] Where Q(·) represents the quantization function. In this embodiment, the quantization method Q(·) includes, but is not limited to, quantization functions in Cartesian coordinate system and polar coordinate system. Therefore, n includes, but is not limited to, the target quantization order of the real and imaginary parts in Cartesian coordinate system and the target quantization order of amplitude and phase in polar coordinate system.

[0017] Step S4, based on the numerical portion S obtained from the above quantization D Signal and target output signal S O The simulation part S is obtained by subtraction. A Signal:

[0018] S A =S O -S D

[0019] Step S5, for the obtained S D Signal and S A The signal is adjusted with appropriate power:

[0020] S′ D =α d·S D

[0021] S′ A =α a ·S A

[0022] Where, α d α represents the power regulation coefficient of the digital section. a This represents the power adjustment factor in the analog section.

[0023] Step S6, convert the digital signal S′ generated in the above steps into digital signals. D and analog signal S′ A The signals are aggregated into a final modulated output signal S through time-division multiplexing. PDA .

[0024] Step S7, the present invention also provides a digital-analog hybrid signal demodulation method based on discrete Fresnel transform to mitigate frequency-selective power fading. The demodulation method and its operation steps are the inverse process of the above modulation method and its steps. In the demodulation process, the inverse process of the orthogonal chirp domain can be expressed as:

[0025]

[0026] The digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform that can mitigate frequency-selective power fading provided in this invention has the following advantages compared with the prior art:

[0027] (1) The digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform provided by the present invention aggregates a set of orthogonal bases Φ in the chirped domain into a signal, spreads the narrowband target signal into a broadband signal, thereby achieving the goal of mitigating the distortion caused by frequency selective power fading in the channel.

[0028] (2) The digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform provided by the present invention can upgrade and transform the existing system by updating the algorithm module, saving system upgrade costs and meeting the application requirements of cost-sensitive fronthaul transmission links. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the digital-analog hybrid signal modulation method based on discrete Fresnel transform proposed in this invention to alleviate frequency-selective power fading.

[0030] Figure 2This is a schematic diagram of a digital-analog hybrid signal demodulation method based on discrete Fresnel transform that can alleviate frequency-selective power fading, as proposed in this invention.

[0031] Figure 3 This is a schematic diagram of a representative orthogonal waveform of the discrete Fresnel inverse transform used in the orthogonal chirped multiplexing proposed in this invention.

[0032] Figure 4 This is a schematic diagram illustrating the operation method of aggregating a signal into a single signal using a set of orthonormal bases (i.e., discrete Fresnel inverse transform matrices) in the chirped domain, as described in this invention.

[0033] Figure 5 This is a schematic diagram illustrating the operation method of restoring multiple signals from a set of complementary orthogonal bases (i.e., discrete Fresnel transformation matrices) in the chirped domain in this invention.

[0034] Figure 6 The figure shows a comparison of the digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform proposed in this invention with the traditional orthogonal frequency division multiplexing scheme in terms of optical fiber propagation length.

[0035] Figure 7 The figure shows a comparison of the received optical power between the proposed digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform, which can alleviate frequency-selective power fading, and the traditional orthogonal frequency division multiplexing scheme. Detailed Implementation

[0036] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0037] like Figures 1 to 7 As shown, the present invention provides a digital-analog hybrid signal modulation and demodulation method based on discrete Fresnel transform to mitigate frequency-selective power fading, comprising the following steps:

[0038] Step S1: Collect N wireless signals from the antenna, X = [x(1), x(2), ..., x(N)], and aggregate them into a single signal using a set of orthogonal bases Φ in the chirped domain. Simultaneously, spread the narrowband target signal into a broadband signal to mitigate distortion caused by frequency-selective power fading in the channel. Figure 3 and Figure 4 As shown, this operation process can be represented as follows:

[0039] S = Φ H X

[0040] in,(·) HThe conjugate transpose operation, where Φ is the discrete Fresnel transformation matrix, can be represented as:

[0041]

[0042] Here, mod represents the modulo operation.

[0043] Step S2: Based on the aggregated signal S in the chirped domain, insert the cyclic prefix as a guard interval at the beginning of each column in S, then perform parallel-to-serial (P / S) conversion to obtain the output signal, denoted as S. O .

[0044] Step S3, output signal S O Quantization is performed to obtain the digital part S. D Signal:

[0045] S D =Q(S) O ,n)

[0046] Where Q(·) represents the quantization function. In this embodiment, the quantization method Q(·) includes, but is not limited to, quantization functions in Cartesian coordinate system and polar coordinate system. Therefore, n includes, but is not limited to, the target quantization order of the real and imaginary parts in Cartesian coordinate system and the target quantization order of amplitude and phase in polar coordinate system.

[0047] Step S4, based on the numerical portion S obtained from the above quantization D Signal and aggregated signal S O The simulation part S is obtained by subtraction. A Signal:

[0048] S A =S O -S D

[0049] Step S5, for the obtained S D Signal and S A The signal is adjusted with appropriate power:

[0050] S′ D =α d ·S D

[0051] S′ A =α a ·S A

[0052] Where, α d α represents the power regulation coefficient of the digital section. a This represents the power adjustment factor in the analog section.

[0053] Step S6, convert the digital signal S′ generated in the above steps into digital signals. D and analog signal S′ A The signals are aggregated into a final modulated output signal S through time-division multiplexing. PDA .

[0054] Step S7, further, the digital-analog hybrid signal demodulation method based on discrete Fresnel transform that can alleviate frequency-selective power fading, its demodulation method and operation steps are the inverse process of the above modulation method and steps, wherein, in the demodulation process, the inverse process of the orthogonal chirp domain can be expressed as:

[0055]

[0056] The above embodiments are merely preferred examples of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A digital-analog hybrid signal modulation method based on discrete Fresnel transform to mitigate frequency-selective power fading, characterized in that, Includes the following steps: Step S1: Collect multiple wireless signals from the antenna, aggregate them into a single signal through a set of standard orthogonal bases in the chirped domain, and simultaneously spread the narrowband target signal into a wideband signal. Step S2: Based on the aggregated signal in the chirped domain, insert the cyclic prefix as a guard interval at the beginning of each column of the signal, and then perform parallel-to-serial conversion to obtain the target output signal; Step S3: Quantize the output signal to obtain the digital part signal; Step S4: Based on the digital part signal obtained by the above quantization and the target output signal, the analog part signal is obtained by subtraction. Step S5: Perform appropriate power adjustment on the obtained digital and analog signals; Step S6: The power-adjusted digital signal and analog signal are combined into a final modulated output signal by time-division multiplexing.

2. The digital-analog hybrid signal modulation method based on discrete Fresnel transform to mitigate frequency-selective power fading according to claim 1, characterized in that, In step S1, N wireless signals from the antenna, X = [x(1), x(2), ..., x(N)], are collected and aggregated into a single signal using a set of orthogonal bases Φ in the chirped domain. Simultaneously, the narrowband target signal is spread into a wideband signal, thereby mitigating the distortion caused by frequency-selective power fading in the channel. This operation can be represented as: S=Φ H X in,(·) H The conjugate transpose operation, where Φ is the discrete Fresnel transformation matrix, can be represented as: Here, mod represents the modulo operation.

3. The digital-analog hybrid signal modulation method based on discrete Fresnel transform to mitigate frequency-selective power fading according to claim 1, characterized in that, In step S2, based on the aggregated signal S in the chirped domain, a cyclic prefix is ​​inserted as a guard interval at the beginning of each column in S, and then a parallel-to-serial (P / S) conversion is performed to obtain the output signal, denoted as S. O。 4. The digital-analog hybrid signal modulation method based on discrete Fresnel transform to mitigate frequency-selective power fading according to claim 1, characterized in that, In step S3, the output signal S O Quantization is performed to obtain the digital part S. D Signal: S D =Q(S O ,n) Where Q(·) represents the quantization function. In this embodiment, the quantization method Q(·) includes, but is not limited to, quantization functions in Cartesian coordinate system and polar coordinate system. Therefore, n includes, but is not limited to, the target quantization order of the real and imaginary parts in Cartesian coordinate system and the target quantization order of amplitude and phase in polar coordinate system.

5. The digital-analog hybrid signal modulation method based on discrete Fresnel transform to mitigate frequency-selective power fading according to claim 1, characterized in that, In step S4, based on the numerical portion S obtained from the above quantization... D Signal and target output signal S O The simulation part S is obtained by subtraction. A Signal: S A =S O -S D。 6. The digital-analog hybrid signal modulation method based on discrete Fresnel transform to mitigate frequency-selective power fading according to claim 1, characterized in that, In step S5, the obtained S D Signal and S A The signal is adjusted with appropriate power: S′ D =a d ·S D S′ A =a a ·S A Where, α d α represents the power regulation coefficient of the digital section. a This represents the power adjustment factor in the analog section.

7. The digital-analog hybrid signal modulation method based on discrete Fresnel transform to mitigate frequency-selective power fading as described in claim 1, characterized in that, In step S6, the digital signal S′ generated in the above steps is... D and analog signal S′ A The signals are aggregated into a final modulated output signal S through time-division multiplexing. PDA .

8. A digital-analog hybrid signal demodulation method based on discrete Fresnel transform to mitigate frequency-selective power fading, characterized in that, The demodulation method and its operation steps are the inverse process of the modulation method according to any one of claims 1 to 7, wherein, in the demodulation process, the inverse process of the orthogonal chirp domain can be expressed as:

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