Forward transmission method and system based on cascade error feedback noise shaping

Abstract

The invention provides a forward transmission method and system based on cascade error feedback noise shaping, and the method comprises the steps: carrying out the 1-bit error feedback noise shaping of a wireless signal at a transmitting end, subtracting a first-stage 2-level digital signal obtained through noise shaping from an original wireless signal, and carrying out the low-pass filtering to obtain residual in-band noise; and taking the residual in-band noise as the input of second-stage 1-bit error feedback noise shaping to obtain a second-stage 2-level digital signal, and then mapping the two 2-level digital signals into a 4-level digital signal. And at a receiving end, recovering the 4-level digital signal into two 2-level digital signals, and demodulating the two 2-level digital signals into a wireless signal through a low-pass filter.

Description

Technical Field

[0001] The present invention relates to the field of mobile fronthaul technology, and in particular to a fronthaul method and system based on cascade error feedback noise shaping. Background Art

[0002] 6G networks are expected to provide high-speed access and real-time immersive services. To support these applications, millimeter wave spectrum and high-order modulation formats in wireless communications are effective technologies to achieve high data rate transmission. As a key link in the Cloud Radio Access Network (C-RAN), mobile fronthaul plays a vital role in establishing a reliable connection between the optical core network and the wireless mobile network. The fronthaul fiber transmission system needs to transmit wireless signals with high fidelity and low cost. Noise-shaping-based wireless over optical fiber is a feasible idea, but there are still certain problems in simplifying the structural design and further improving the signal fidelity.

[0003] Patent document CN108512788B (application number: 201810274285.6) discloses a noise shaping-based PCM module for digital mobile fronthaul links. The module includes a quantizer and an FIR filter with a feedback loop, which reduces the quantization noise power on the data modulated subcarrier and increases the power on the non-data modulated subcarrier. However, the patent has low performance in a low-cost fronthaul system with a very small number of quantized bits, and the stability is insufficient, and it cannot completely solve the above technical problems. Summary of the invention

[0004] In view of the defects in the prior art, an object of the present invention is to provide a forward transmission method and system based on cascaded error feedback noise shaping.

[0005] The forward transmission method based on cascade error feedback noise shaping provided by the present invention includes:

[0006] Signal processing and transmission steps: At the transmitting end, the wireless signal is first subjected to 1-bit error feedback noise shaping, the first-stage 2-level digital signal obtained by the noise shaping is subtracted from the original wireless signal and low-pass filtered to obtain the residual in-band noise, the residual in-band noise is used as the input of the second-stage 1-bit error feedback noise shaping to obtain the second-stage 2-level digital signal, and then the two 2-level digital signals are mapped into a 4-level digital signal;

[0007] Signal reception and processing steps: At the receiving end, the 4-level digital signal is restored to two 2-level digital signals and the wireless signal is demodulated through a low-pass filter.

[0008] Preferably, the signal processing and transmitting step comprises:

[0009] Step 1: Upsample the original wireless signal to obtain an upsampled wireless signal;

[0010] Step 2: The upsampled wireless signal is first scaled, and then the first-level 1-bit error feedback noise shaping is performed to obtain a first-level 2-level digital signal;

[0011] Step 3: Subtract the upsampled wireless signal from the first-stage 2-level digital signal and pass it through a low-pass filter to obtain the residual in-band noise;

[0012] Step 4: Scale the residual in-band noise, and then perform second-stage 1-bit error feedback noise shaping to obtain a second-stage 2-level digital signal;

[0013] Step 5: modulate the first-level 2-level digital signal and the second-level 2-level digital signal into a 4-level digital signal according to Gray coding;

[0014] Step 6: Convert the 4-level digital signal into an optical signal through electro-optical conversion and send it into optical fiber for transmission.

[0015] Preferably, the signal receiving and processing step comprises:

[0016] Step 7: The optical signal is photoelectrically converted through a photodiode to obtain an electrical signal, and then the electrical signal is sampled to obtain a 4-level digital signal with noise at the receiving end;

[0017] Step 8: demodulate the 4-level digital signal with noise at the receiving end to restore the first-level 2-level digital signal and the second-level 2-level digital signal;

[0018] Step 9: Pass the first-stage 2-level digital signal and the second-stage 2-level digital signal through a low-pass filter respectively, and subtract them to restore the up-sampled wireless signal;

[0019] Step 10: Downsample the upsampled wireless signal to restore the original wireless signal.

[0020] Preferably, step 2 comprises:

[0021] Step 2.1: add the upsampled wireless signal at the current moment to the truncated feedback signal of the first stage at the current moment, and pass through a 1-bit quantizer, the output of which is a first-stage 2-level digital signal;

[0022] Step 2.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a first-stage truncated feedback signal at the next moment;

[0023] Step 2.3: Repeat steps 2.1 to 2.2 in sequence to complete the first-stage 1-bit error feedback noise shaping for the entire upsampled wireless signal.

[0024] Preferably, step 5 comprises:

[0025] Step 5.1: Add the residual in-band noise at the current moment to the truncated feedback signal of the second stage at the current moment, and pass through a 1-bit quantizer, the output of the quantizer is a second-stage 2-level digital signal;

[0026] Step 5.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a second-stage truncated feedback signal at the next moment;

[0027] Step 5.3: Repeat steps 5.1 to 5.2 in sequence to complete the second-stage 1-bit error feedback noise shaping for the entire residual in-band noise.

[0028] The forward transmission system based on cascade error feedback noise shaping provided by the present invention comprises:

[0029] Signal processing and transmission module: At the transmitting end, the wireless signal is first subjected to 1-bit error feedback noise shaping, the first-stage 2-level digital signal obtained by the noise shaping is subtracted from the original wireless signal and low-pass filtered to obtain the residual in-band noise, and the residual in-band noise is used as the input of the second-stage 1-bit error feedback noise shaping to obtain the second-stage 2-level digital signal, and then the two 2-level digital signals are mapped into a 4-level digital signal;

[0030] Signal receiving and processing module: At the receiving end, the 4-level digital signal is restored to two 2-level digital signals and the wireless signal is demodulated through a low-pass filter.

[0031] Preferably, the signal processing and transmitting module includes:

[0032] Module M1: upsamples the original wireless signal to obtain an upsampled wireless signal;

[0033] Module M2: Scale the upsampled wireless signal first, and then perform first-stage 1-bit error feedback noise shaping to obtain a first-stage 2-level digital signal;

[0034] Module M3: subtract the up-sampled wireless signal from the first-stage 2-level digital signal and pass it through a low-pass filter to obtain the residual in-band noise;

[0035] Module M4: scales the residual in-band noise, and then performs second-stage 1-bit error feedback noise shaping to obtain a second-stage 2-level digital signal;

[0036] Module M5: modulates the first-level 2-level digital signal and the second-level 2-level digital signal into a 4-level digital signal according to Gray coding;

[0037] Module M6: converts the 4-level digital signal into an optical signal through electro-optical conversion and sends it to the optical fiber for transmission.

[0038] Preferably, the signal receiving and processing module comprises:

[0039] Module M7: converts the optical signal into an electrical signal through a photodiode, and then samples the electrical signal to obtain a 4-level digital signal with noise at the receiving end;

[0040] Module M8: demodulates the 4-level digital signal with noise at the receiving end, and restores the first-level 2-level digital signal and the second-level 2-level digital signal;

[0041] Module M9: respectively passes the first-stage 2-level digital signal and the second-stage 2-level digital signal through a low-pass filter, and subtracts them to restore the up-sampled wireless signal;

[0042] Module M10: downsamples the upsampled wireless signal to restore the original wireless signal.

[0043] Preferably, the module M2 comprises:

[0044] Module M2.1: adds the upsampled wireless signal at the current moment to the truncated feedback signal of the first stage at the current moment, and passes through a 1-bit quantizer, the output of which is a first-stage 2-level digital signal;

[0045] Module M2.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain the first-stage truncated feedback signal at the next moment;

[0046] Module M2.3: repeatedly triggers modules M2.1 to M2.2 in sequence to complete the first-stage 1-bit error feedback noise shaping for the entire upsampled wireless signal.

[0047] Preferably, the module M5 comprises:

[0048] Module M5.1: Add the residual in-band noise at the current moment to the truncated feedback signal of the second stage at the current moment, and pass it through a 1-bit quantizer, the output of which is a second-stage 2-level digital signal;

[0049] Module M5.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a second-level truncated feedback signal at the next moment;

[0050] Module M5.3: repeatedly triggers modules M5.1 to M5.2 in sequence to complete the second-stage 1-bit error feedback noise shaping for the entire residual in-band noise.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The present invention realizes noise shaping by adopting error feedback and truncating within a certain amplitude, thereby solving the problem of difficult design and stability of noise shaping structure, and achieving the purpose of facilitating design and optimization;

[0053] (2) The present invention adopts a cascade structure to suppress the residual in-band noise again, thereby solving the problem of excessive quantization noise caused by a small number of quantization bits, and achieving the effect of improving the quality of wireless signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0055] Figure 1 It is a flow chart of the forward transmission system based on cascaded error feedback noise shaping;

[0056] Figure 2 This is a graph of the experimental results. DETAILED DESCRIPTION

[0057] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0058] Example 1

[0059] The present invention provides a forward transmission method based on cascade error feedback noise shaping, comprising:

[0060] Signal processing and transmission steps: At the transmitting end, the wireless signal is first subjected to 1-bit error feedback noise shaping, the first-stage 2-level digital signal obtained by the noise shaping is subtracted from the original wireless signal and low-pass filtered to obtain the residual in-band noise, the residual in-band noise is used as the input of the second-stage 1-bit error feedback noise shaping to obtain the second-stage 2-level digital signal, and then the two 2-level digital signals are mapped into a 4-level digital signal;

[0061] Signal reception and processing steps: At the receiving end, the 4-level digital signal is restored to two 2-level digital signals and the wireless signal is demodulated through a low-pass filter.

[0062] The signal processing and transmitting steps include:

[0063] Step 1: Upsample the original wireless signal to obtain an upsampled wireless signal;

[0064] Step 2: The upsampled wireless signal is first scaled, and then the first-level 1-bit error feedback noise shaping is performed to obtain a first-level 2-level digital signal;

[0065] Step 3: Subtract the upsampled wireless signal from the first-stage 2-level digital signal and pass it through a low-pass filter to obtain the residual in-band noise;

[0066] Step 4: Scale the residual in-band noise, and then perform second-stage 1-bit error feedback noise shaping to obtain a second-stage 2-level digital signal;

[0067] Step 5: modulate the first-level 2-level digital signal and the second-level 2-level digital signal into a 4-level digital signal according to Gray coding;

[0068] Step 6: Convert the 4-level digital signal into an optical signal through electro-optical conversion and send it into optical fiber for transmission.

[0069] The signal receiving and processing steps include:

[0070] Step 7: The optical signal is photoelectrically converted through a photodiode to obtain an electrical signal, and then the electrical signal is sampled to obtain a 4-level digital signal with noise at the receiving end;

[0071] Step 8: demodulate the 4-level digital signal with noise at the receiving end to restore the first-level 2-level digital signal and the second-level 2-level digital signal;

[0072] Step 9: Pass the first-stage 2-level digital signal and the second-stage 2-level digital signal through a low-pass filter respectively, and subtract them to restore the up-sampled wireless signal;

[0073] Step 10: Downsample the upsampled wireless signal to restore the original wireless signal.

[0074] The step 2 comprises the following steps:

[0075] Step 2.1: add the upsampled wireless signal at the current moment to the truncated feedback signal of the first stage at the current moment, and pass through a 1-bit quantizer, the output of which is a first-stage 2-level digital signal;

[0076] Step 2.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a first-stage truncated feedback signal at the next moment;

[0077] Step 2.3: Repeat steps 2.1 to 2.2 in sequence to complete the first-stage 1-bit error feedback noise shaping for the entire upsampled wireless signal.

[0078] The step 5 comprises the following steps:

[0079] Step 5.1: Add the residual in-band noise at the current moment to the truncated feedback signal of the second stage at the current moment, and pass through a 1-bit quantizer, the output of the quantizer is a second-stage 2-level digital signal;

[0080] Step 5.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a second-stage truncated feedback signal at the next moment;

[0081] Step 5.3: Repeat steps 5.1 to 5.2 in sequence to complete the second-stage 1-bit error feedback noise shaping for the entire residual in-band noise.

[0082] Figure 2 The experimental results of the cascaded error feedback noise shaping fronthaul system are shown. The horizontal axis is the received optical power and the vertical axis is the wireless signal signal-to-noise ratio. As the received optical power increases, the symbol error rate gradually decreases and the signal-to-noise ratio gradually increases until it reaches the upper limit.

[0083] Example 2

[0084] The present invention also provides a forward transmission system based on cascaded error feedback noise shaping. The forward transmission system based on cascaded error feedback noise shaping can be implemented by executing the process steps of the forward transmission method based on cascaded error feedback noise shaping, that is, those skilled in the art can understand the forward transmission method based on cascaded error feedback noise shaping as a preferred implementation of the forward transmission system based on cascaded error feedback noise shaping.

[0085] The fronthaul system based on cascaded error feedback noise shaping provided by the present invention comprises: a signal processing and transmitting module: at the transmitting end, a 1-bit error feedback noise shaping is first performed on the wireless signal, a first-level 2-level digital signal obtained by the noise shaping is subtracted from the original wireless signal and low-pass filtered to obtain residual in-band noise, the residual in-band noise is used as the input of the second-level 1-bit error feedback noise shaping to obtain a second-level 2-level digital signal, and then two 2-level digital signals are mapped into a 4-level digital signal; a signal receiving and processing module: at the receiving end, the 4-level digital signal is restored to two 2-level digital signals and the wireless signal is demodulated through a low-pass filter.

[0086] The signal processing and transmission module includes: module M1: up-sampling the original wireless signal to obtain the up-sampled wireless signal; module M2: scaling the up-sampled wireless signal first, and then performing the first-level 1-bit error feedback noise shaping to obtain the first-level 2-level digital signal; module M3: subtracting the up-sampled wireless signal from the first-level 2-level digital signal, and passing through a low-pass filter to obtain the residual in-band noise; module M4: scaling the residual in-band noise, and then performing the second-level 1-bit error feedback noise shaping to obtain the second-level 2-level digital signal; module M5: modulating the first-level 2-level digital signal and the second-level 2-level digital signal into a 4-level digital signal according to Gray coding; module M6: converting the 4-level digital signal into an optical signal through electro-optical conversion to send it into optical fiber transmission.

[0087] The signal receiving and processing module includes: module M7: performing photoelectric conversion on the optical signal through a photodiode to obtain an electrical signal, and then sampling the electrical signal to obtain a 4-level digital signal with noise at the receiving end; module M8: demodulating the 4-level digital signal with noise at the receiving end to restore the first-level 2-level digital signal and the second-level 2-level digital signal; module M9: passing the first-level 2-level digital signal and the second-level 2-level digital signal through a low-pass filter respectively, and subtracting them to restore the up-sampled wireless signal; module M10: down-sampling the up-sampled wireless signal to restore the original wireless signal.

[0088] The module M2 includes: module M2.1: adding the upsampled wireless signal at the current moment to the first-stage truncated feedback signal at the current moment, and passing it through a 1-bit quantizer, the output of the quantizer is a first-stage 2-level digital signal; module M2.2: passing the quantization error generated by the quantizer through a finite impulse response filter, and then truncating it within a preset amplitude range to obtain the first-stage truncated feedback signal at the next moment; module M2.3: repeatedly triggering modules M2.1 to M2.2 in sequence to complete the first-stage 1-bit error feedback noise shaping for the entire upsampled wireless signal.

[0089] The module M5 includes: module M5.1: adding the residual in-band noise at the current moment to the second-stage truncated feedback signal at the current moment, and passing through a 1-bit quantizer, the output of the quantizer is a second-stage 2-level digital signal; module M5.2: passing the quantization error generated by the quantizer through a finite impulse response filter, and then truncating it within a preset amplitude range to obtain the second-stage truncated feedback signal at the next moment; module M5.3: repeatedly triggering modules M5.1 to M5.2 in sequence to complete the second-stage 1-bit error feedback noise shaping for the entire residual in-band noise.

[0090] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0091] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A forward transmission method based on cascaded error feedback noise shaping, characterized in that: include: Signal processing and transmission steps: At the transmitting end, the wireless signal is first subjected to 1-bit error feedback noise shaping, the first-stage 2-level digital signal obtained by the noise shaping is subtracted from the original wireless signal and low-pass filtered to obtain the residual in-band noise, the residual in-band noise is used as the input of the second-stage 1-bit error feedback noise shaping to obtain the second-stage 2-level digital signal, and then the two 2-level digital signals are mapped into a 4-level digital signal; Signal reception and processing steps: At the receiving end, the 4-level digital signal is restored to two 2-level digital signals and the wireless signal is demodulated through a low-pass filter.

2. The forward transmission method based on cascaded error feedback noise shaping according to claim 1, characterized in that: The signal processing and transmitting steps include: Step 1: Upsample the original wireless signal to obtain an upsampled wireless signal; Step 2: The upsampled wireless signal is first scaled, and then the first-level 1-bit error feedback noise shaping is performed to obtain a first-level 2-level digital signal; Step 3: Subtract the upsampled wireless signal from the first-stage 2-level digital signal and pass it through a low-pass filter to obtain the residual in-band noise; Step 4: Scale the residual in-band noise, and then perform second-stage 1-bit error feedback noise shaping to obtain a second-stage 2-level digital signal; Step 5: modulate the first-level 2-level digital signal and the second-level 2-level digital signal into a 4-level digital signal according to Gray coding; Step 6: Convert the 4-level digital signal into an optical signal through electro-optical conversion and send it into optical fiber for transmission.

3. The forward transmission method based on cascaded error feedback noise shaping according to claim 2, characterized in that: The signal receiving and processing steps include: Step 7: The optical signal is photoelectrically converted through a photodiode to obtain an electrical signal, and then the electrical signal is sampled to obtain a 4-level digital signal with noise at the receiving end; Step 8: demodulate the 4-level digital signal with noise at the receiving end to restore the first-level 2-level digital signal and the second-level 2-level digital signal; Step 9: Pass the first-stage 2-level digital signal and the second-stage 2-level digital signal through a low-pass filter respectively, and subtract them to restore the up-sampled wireless signal; Step 10: Downsample the upsampled wireless signal to restore the original wireless signal.

4. The forward transmission method based on cascaded error feedback noise shaping according to claim 3, characterized in that: The step 2 comprises: Step 2.1: add the upsampled wireless signal at the current moment to the truncated feedback signal of the first stage at the current moment, and pass through a 1-bit quantizer, the output of which is a first-stage 2-level digital signal; Step 2.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a first-stage truncated feedback signal at the next moment; Step 2.3: Repeat steps 2.1 to 2.2 in sequence to complete the first-stage 1-bit error feedback noise shaping for the entire upsampled wireless signal.

5. The forward transmission method based on cascaded error feedback noise shaping according to claim 4, characterized in that: The step 5 comprises: Step 5.1: Add the residual in-band noise at the current moment to the truncated feedback signal of the second stage at the current moment, and pass through a 1-bit quantizer, the output of the quantizer is a second-stage 2-level digital signal; Step 5.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a second-stage truncated feedback signal at the next moment; Step 5.3: Repeat steps 5.1 to 5.2 in sequence to complete the second-stage 1-bit error feedback noise shaping for the entire residual in-band noise.

6. A forward transmission system based on cascaded error feedback noise shaping, characterized in that: include: Signal processing and transmission module: At the transmitting end, the wireless signal is first subjected to 1-bit error feedback noise shaping, the first-stage 2-level digital signal obtained by the noise shaping is subtracted from the original wireless signal and low-pass filtered to obtain the residual in-band noise, and the residual in-band noise is used as the input of the second-stage 1-bit error feedback noise shaping to obtain the second-stage 2-level digital signal, and then the two 2-level digital signals are mapped into a 4-level digital signal; Signal receiving and processing module: At the receiving end, the 4-level digital signal is restored to two 2-level digital signals and the wireless signal is demodulated through a low-pass filter.

7. The forward transmission system based on cascaded error feedback noise shaping according to claim 6, characterized in that: The signal processing and transmitting module comprises: Module M1: upsamples the original wireless signal to obtain an upsampled wireless signal; Module M2: Scale the upsampled wireless signal first, and then perform first-stage 1-bit error feedback noise shaping to obtain a first-stage 2-level digital signal; Module M3: subtract the up-sampled wireless signal from the first-stage 2-level digital signal and pass it through a low-pass filter to obtain the residual in-band noise; Module M4: scales the residual in-band noise, and then performs second-stage 1-bit error feedback noise shaping to obtain a second-stage 2-level digital signal; Module M5: modulates the first-level 2-level digital signal and the second-level 2-level digital signal into a 4-level digital signal according to Gray coding; Module M6: converts the 4-level digital signal into an optical signal through electro-optical conversion and sends it to the optical fiber for transmission.

8. The forward transmission system based on cascaded error feedback noise shaping according to claim 7, characterized in that: The signal receiving and processing module comprises: Module M7: converts the optical signal into an electrical signal through a photodiode, and then samples the electrical signal to obtain a 4-level digital signal with noise at the receiving end; Module M8: demodulates the 4-level digital signal with noise at the receiving end, and restores the first-level 2-level digital signal and the second-level 2-level digital signal; Module M9: respectively passes the first-stage 2-level digital signal and the second-stage 2-level digital signal through a low-pass filter, and subtracts them to restore the up-sampled wireless signal; Module M10: downsamples the upsampled wireless signal to restore the original wireless signal.

9. The forward transmission system based on cascaded error feedback noise shaping according to claim 8, characterized in that: The module M2 comprises: Module M2.1: adds the upsampled wireless signal at the current moment to the truncated feedback signal of the first stage at the current moment, and passes through a 1-bit quantizer, the output of which is a first-stage 2-level digital signal; Module M2.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain the first-stage truncated feedback signal at the next moment; Module M2.3: repeatedly triggers modules M2.1 to M2.2 in sequence to complete the first-stage 1-bit error feedback noise shaping for the entire upsampled wireless signal.

10. The forward transmission system based on cascaded error feedback noise shaping according to claim 9, characterized in that: The module M5 comprises: Module M5.1: Add the residual in-band noise at the current moment to the truncated feedback signal of the second stage at the current moment, and pass it through a 1-bit quantizer, the output of which is a second-stage 2-level digital signal; Module M5.2: The quantization error generated by the quantizer is passed through a finite impulse response filter and then truncated within a preset amplitude range to obtain a second-level truncated feedback signal at the next moment; Module M5.3: repeatedly triggers modules M5.1 to M5.2 in sequence to complete the second-stage 1-bit error feedback noise shaping for the entire residual in-band noise.

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