CN108965184B

CN108965184B - Discrete multi-audio modulation multiplexing system and method

Info

Publication number: CN108965184B
Application number: CN201710379526.9A
Authority: CN
Inventors: 刘铮
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2017-05-25
Filing date: 2017-05-25
Publication date: 2021-08-17
Anticipated expiration: 2037-05-25
Also published as: CN108965184A

Abstract

The utility model discloses a discrete multi-audio modulation multiplexing system and a method, relating to the technical field of digital subscriber lines. The DMT modulation multiplexing system comprises a local transmitter FTU-O of a feeder terminal device and a local receiver FTU-R of the feeder terminal device; the FTU-O comprises an Inverse Fast Fourier Transform (IFFT) of a Quadrature Amplitude Modulator (QAM) and a fast Fourier transform (FFT _ size ═ 4096) which are connected in series, a digital-to-analog converter (DAC) with a sampling rate of 424Ms/s and a low-pass filter (LPF) with a frequency of 212MHz, wherein the complex number after IFFT transform is serial I, Q with two paths and 8192 real numbers; the FTU-R comprises an LPF with 212MHz, an analog-to-digital converter ADC with 424Ms/s sampling rate, a fast Fourier transformer FFT with FFT _ size 4096 and QAM which are connected in series. The technical scheme of the application greatly reduces the equipment cost.

Description

Discrete multi-audio modulation multiplexing system and method

Technical Field

The invention relates to the technical field of Digital Subscriber Lines (DSL), in particular to a discrete multi-audio modulation multiplexing system and a method.

Background

Fast's 106MHz spectrum plan uses DMT (Discrete Multi-tone) modulation with 51.75KHz subcarrier spacing and 2048 subcarriers. The QAM complex constellation point is expanded into 4096 frequency-domain QAM modulated complex constellation points according to a mirror conjugate symmetry principle, then real signals of 4096 time domains are transformed into real signals according to IFFT with fft _ size being 4096, the real signals are converted into analog signals through DAC with 4096 x 51.75KHz being 212Ms/s sampling rate, and the analog signals are transmitted on a copper wire channel of DSL through a 106MHz low-pass filter. The receiving end firstly passes through a low-pass filter of 106MHz, then ADC with Nyquist sampling rate of 2X 106MHz 212Ms/s is converted into digital signals, 4096 real signals in time domain are converted into complex signals in 4096 frequency domains according to FFT with FFT _ size of 4096, and finally only 1 st to 2048 th complex signals are selected as QAM constellation points on 2048 subcarriers recovered by demodulation. The signal processing procedure for the 106MHz spectrum plan is shown in fig. 1.

Similarly, the sub-carrier spacing for the g.fast 212MHz spectrum plan is still 51.75KHz with 4096 sub-carriers. The method comprises the steps of expanding the complex constellation points of QAM modulation of 8192 frequency domains according to a mirror image conjugate symmetry principle, then converting the complex constellation points into 8192 time domain real signals according to IFFT of fft _ size 8192, converting the real signals into analog signals through DAC of 8192 multiplied by 51.75KHz 424Ms/s sampling rate, and transmitting the analog signals through a 212MHz low-pass filter on a copper wire channel of DSL. The receiving end firstly passes through a 212MHz low-pass filter, then an ADC with Nyquist sampling rate of 2 × 212MHz of 424Ms/s is converted into a digital signal, 8192 time-domain real signals are converted into 8192 frequency-domain complex signals according to FFT with FFT _ size of 8192, and finally only 1 st to 4096 th complex signals are selected as QAM constellation points on 4096 subcarriers recovered by demodulation. The signal processing procedure for the 212MHz spectrum plan is shown in fig. 2.

In practical development of products, it is often desirable that a transceiver with 212MHz profile can reuse the devices and signal processing flow of a transceiver with 106MHz profile as much as possible to reduce the cost. It is also desirable that the 212MHz profile transceiver be compatible with 106MHz DMT modulated signals.

At present, there is a problem in the related art that DMT modulation systems of 106MHz spectrum plan and 212MHz spectrum plan each require a separate set of signal processing procedures according to the transmitter and receiver structures of fig. 1 and 2: the 106MHz DMT modulated signal can only pass through the 106MHz profile transmitter and receiver; the 212MHz DMT modulated signal can only pass through the 212MHz profile transmitter and receiver. If a transmitter and a receiver of 106MHz profile are directly used for transmitting the DMT modulation signal of 212MHz, the signal of 106MHz-212MHz part can not be transmitted; if a transmitter and receiver of 212MHz profile are used directly to transmit 106MHz DMT modulated signals, the signal-to-noise ratio is reduced and the performance is degraded due to the introduction of 106MHz-212MHz out-of-band noise.

Disclosure of Invention

The discrete multi-tone modulation multiplexing system and method can solve the problem that different DMT modulation systems are required for signal transceiving by different spectrum rules in the related art.

A discrete multi-tone DMT modulation multiplexing system is disclosed, comprising a local transmitter FTU-O of a feeder terminal device and a local receiver FTU-R of the feeder terminal device;

the FTU-O comprises an Inverse Fast Fourier Transform (IFFT) of a Quadrature Amplitude Modulator (QAM) and a fast Fourier transform (FFT _ size ═ 4096) which are connected in series, a digital-to-analog converter (DAC) with a sampling rate of 424Ms/s and a low-pass filter (LPF) with a frequency of 212MHz, wherein the complex number after IFFT transform is serial I, Q with two paths and 8192 real numbers;

the FTU-R comprises an LPF with 212MHz, an analog-to-digital converter ADC with 424Ms/s sampling rate, a fast Fourier transformer FFT with FFT _ size 4096 and QAM which are connected in series.

Optionally, in the system, the I, Q paths in which the complex numbers after IFFT transformation are serial include:

the complex numbers after IFFT conversion are I, Q paths which are serial in sequence; or

The complex numbers after IFFT conversion are Q, I paths which are serial in sequence.

Optionally, in the system, the IFFT with FFT _ size of 4096 uses an orthogonal frequency division multiplexing, OFDM, modulation transform.

Also disclosed herein is a discrete multi-tone DMT modulation multiplexing method using the system as described above, the method comprising:

4096 subcarriers of the 212MHz spectrum plan are modulated into 4096 complex constellation points through QAM of the FTU-O, Orthogonal Frequency Division Multiplexing (OFDM) modulation transformation is carried out through IFFT with FFT _ size being 4096, 4096 serial I-path real numbers and 4096 serial Q-path real numbers are obtained after modulation transformation, the I-path real numbers and the Q-path real numbers are converted into digital signals through DAC with a sampling rate of 424Ms/s, and the digital signals are transmitted to a channel through LPF with 212 MHz;

the FTU-R receives an analog signal from a channel, converts the analog signal into a digital signal through an LPF (low pass filter) of 212MHz and an ADC (analog to digital converter) with a sampling rate of 424Ms/s, converts the digital signal into 4096 complex signals of frequency domains according to an FFT with FFT _ size of 4096, and restores 4096 complex constellation points on 4096 subcarriers by QAM demodulation.

Also disclosed herein is a discrete multi-tone DMT modulation multiplexing system comprising a local transmitter FTU-O of a feeder terminal unit and a local receiver FTU-R of the feeder terminal unit;

the FTU-O comprises two paths of processing units, wherein the first path of processing unit processes DMT modulation signals of 2-106MHz, and comprises a quadrature amplitude modulator QAM, a mirror image conjugate symmetrizer, an Inverse Fast Fourier Transform (IFFT) with FFT _ size being 4096, a digital-to-analog converter (DAC) with 212Ms/s sampling rate and a low-pass filter (LPF) of 2-106MHz which are connected in series;

the second path processing unit processes the DMT modulation signals of 106 plus 212MHz, and comprises a quadrature amplitude modulator QAM, a mirror image conjugate symmetry device, an inverse fast Fourier transform IFFT with FFT _ size being 4096, a digital-to-analog converter DAC with 212Ms/s sampling rate, a 106MHz up-converter and a band-pass filter BPF with bandwidth being 106 plus 212MHz which are connected in series;

the FTU-R comprises an LPF with 212MHz, an analog-to-digital converter ADC with 424Ms/s sampling rate, a fast Fourier transformer FFT with 8192 FFT _ size and QAM which are connected in series.

splitting 4096 subcarriers of a 212MHz spectrum plan into two groups, wherein each group of 2048 subcarriers comprises 2048 subcarriers, the first group of 2048 subcarriers is modulated into 2048 complex constellation points through QAM in a first path processing unit of the FTU-O, the complex constellation points are expanded into 4096 complex constellation points through a mirror conjugate symmetry principle, the complex constellation points are modulated and transformed through IFFT with FFT _ size being 4096 to obtain 4096 time domain real signals after modulation and transformation, the real signals are converted into digital signals through DAC with a sampling rate of 212Ms/s, and the digital signals are obtained through LPF with a bandwidth of 2-106 MHz;

modulating a second group of 2048 subcarriers into 2048 complex constellation points through QAM in a second path processing unit of the FTU-O, expanding the complex constellation points into 4096 complex constellation points through a mirror conjugate symmetry principle, performing modulation transformation through IFFT with FFT _ size ═ 4096 to obtain 4096 real signals in time domain after modulation transformation, converting the real signals into digital signals through DAC with 212Ms/s sampling rate, performing frequency conversion through an up-converter with 106MHz, and obtaining a second path of DMT modulation signals with 106 plus 212MHz through a band-pass filter BPF with 106 plus 212MHz bandwidth;

synthesizing the two paths of DMT modulation signals into a path of DMT modulation signal with the bandwidth of 212MHz and transmitting the DMT modulation signal to a channel;

the FTU-R receives an analog signal from a channel, the analog signal passes through an LPF of 212MHz, then is converted into a digital signal through an ADC with a sampling rate of 424Ms/s, the digital signal is converted into 8192 complex signals of frequency domains according to the FFT of 8192, finally only 1 to 4096 complex signals are selected, and 4096 complex constellation points on 4096 subcarriers are recovered by QAM demodulation.

the FTU-O comprises a quadrature amplitude modulator QAM, a mirror image conjugate symmetry device, an Inverse Fast Fourier Transform (IFFT) with FFT _ size being 8192, a digital-to-analog converter (DAC) with a sampling rate of 424Ms/s and a Low Pass Filter (LPF) of 2-106MHz which are connected in series;

the FTU-R comprises an LPF of 2-106MHz, an analog-to-digital converter ADC with a 424Ms/s sampling rate, a fast Fourier transformer FFT with an FFT _ size of 8192 and QAM which are connected in series.

2048 subcarriers of a 106MHz spectrum plan are modulated into 2048 complex constellation points through QAM of the FTU-O, then are copied to obtain 4096 complex constellation points, are symmetrically expanded into 8192 complex constellation points through mirror image conjugation, are modulated and transformed through IFFT of 8192 FFT _ size ═ 8192, obtain 8192 real signals after modulation and transformation, are converted into digital signals through DAC with a sampling rate of 424Ms/s, and are transmitted to a channel through LPF of 2-106 MHz;

the FTU-R receives an analog signal from a channel, the analog signal passes through an LPF (low pass filter) of 2-106MHz, then is converted into a digital signal through an ADC (analog to digital converter) with a sampling rate of 424Ms/s, the digital signal is converted into complex signals of 8192 frequency domains according to the FFT of the

FFT _ size

8192, 4096 complex constellation points are recovered by selecting 1 st to 4096 complex signals through QAM demodulation, and the 1 st to 2048 complex signals are selected as 106MHz signals.

According to the technical scheme, the transceiver with the 212MHz profile is transformed to a certain extent, and DMT modulation signals with 106MHz bandwidth can be transmitted. Similarly, a transceiver with 106MHz profile is modified to transmit DMT modulation signals with 212MHz bandwidth; and the IFFT-FFT and DAC-ADC devices of the 106MHz profile transceiver are reused as much as possible, so that the equipment cost is greatly reduced.

Drawings

FIG. 1 is a schematic diagram of a signal processing procedure for 106MHz spectrum planning in the related art;

FIG. 2 is a schematic diagram of a signal processing procedure for 212MHz spectrum planning in the related art;

FIG. 3 is a schematic diagram of a signal processing process of multiplexing a 106MHz IFFT and a 212MHz spectrum plan after FFT according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a signal processing procedure of 212MHz spectrum planning after multiplexing a 106MHz structure according to a second embodiment of the present invention;

fig. 5 is a schematic diagram of a signal processing procedure of 106MHz spectrum planning after multiplexing a 212MHz structure in the third embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in further detail with reference to specific embodiments. It should be noted that the embodiments and features of the embodiments of the present application may be arbitrarily combined with each other without conflict.

The first embodiment is as follows:

the present embodiment provides a discrete multi-tone modulation multiplexing system, which uses the conventional 212MHz profile signal processing structure to deliver DMT modulated signals with 212MHz bandwidth, and the main variations are as follows:

one, DMT modulation symbols of 212MHz bandwidth, still use a transmitter and receiver with 212MHz spectral planning. But DMT modulation is changed to OFDM modulation using an IFFT and FFT transformer with FFT size 4096 at 106MHz, without using conjugate mirror symmetry.

And secondly, obtaining 4096I-path real numbers and 4096Q-path real numbers after IFFT conversion, and converting the parallel I, Q two-path data into 8192 serial real number data. Such as placing 4096Q-way data after 4096I-way data or 4096I-way data after 4096Q-way data, the other processing components of the transmitter remain unchanged.

Three, the receiver part remains unchanged except for the FFT transformer which uses 106MHz FFT size 4096.

Specifically, the discrete multi-tone modulation multiplexing system in this embodiment includes two parts, FTU-O and FTU-R, as shown in fig. 3.

The FTU-O comprises QAM, FFT _ size ═ 4096, DAC with 424Ms/s sampling rate and LPF with 212MHz, wherein the complex number after IFFT transformation is serial I, Q two paths with 8192 real numbers;

the FTU-R includes a 212MHz LPF, a 424Ms/s sample rate ADC, a FFT _ size of 4096 and a QAM in series.

The process of implementing DMT modulation multiplexing by the system comprises the following steps:

4096 subcarriers of 212MHz spectrum planning are modulated into 4096 complex constellation points through QAM of FTU-O, OFDM modulation conversion is carried out through IFFT of FFT _ size ═ 4096, 4096I real numbers and 4096Q real numbers which are connected in series are obtained after modulation conversion, the real numbers are converted into digital signals through DAC of 424Ms/s sampling rate, and the digital signals are transmitted to a channel through LPF of 212 MHz;

the FTU-R receives an analog signal from a channel, the analog signal passes through an LPF with the frequency of 212MHz, then is converted into a digital signal through an ADC with the sampling rate of 424Ms/s, the digital signal is converted into 4096 complex signals with frequency domains according to the FFT with the FFT _ size being 4096, and 4096 complex constellation points on 4096 subcarriers are recovered by QAM demodulation.

As can be seen from the above, the IFFT and FFT processor with FFT _ size of 4096 are used in this embodiment, so the device cost is reduced; since the complex number after IFFT conversion is divided into I, Q two paths of 4096-point real numbers in parallel, I, Q is converted into 8192 real numbers in series, the following 424Ms/s DAC can still be used, and the whole processing flow and structure do not need to be greatly changed.

Example two:

in this embodiment, for DMT modulated signals with a bandwidth of 212MHz, structures and devices of 106MHz profile transceivers are used as much as possible for transmission, and a signal processing flow is slightly modified, which is mainly thought as follows:

first, DMT modulation symbols of 212MHz bandwidth are multiplexed with the local side transmitter FTU-O of 106MHz profile. But 4096 sub-carriers need to be divided into two parallel paths, the 1 st to 2048 th sub-carriers are divided into one path, and the 2049 th and 4096 th sub-carriers are divided into the other path;

secondly, after the signal corresponding to the 2049-. And other processing devices of the transmitter are kept unchanged, and the two paths of data are combined and added before the signals enter the DSL channel to be synthesized into a DMT modulation signal with the bandwidth of 212 MHz.

And thirdly, the terminal receiver FTU-R uses the signal processing process of 212MHz profile.

Specifically, the discrete multi-tone modulation multiplexing system in this embodiment includes two parts, FTU-O and FTU-R, as shown in fig. 4.

The FTU-O comprises two processing units, wherein the first processing unit processes DMT modulation signals of 2-106MHz, and comprises QAM, a mirror image conjugate symmetrizer, IFFT with FFT _ size 4096, DAC with 212Ms/s sampling rate and LPF with 2-106MHz which are connected in series;

the second processing unit processes the DMT modulation signals of 106-212MHz, which comprises QAM, a mirror image conjugate symmetrizer, IFFT with FFT _ size being 4096, DAC with 212Ms/s sampling rate, up-converter of 106MHz and BPF with bandwidth being 106-212MHz in series;

the FTU-R includes a 212MHz LPF, 424Ms/s sample rate ADC, FFT _ size 8192 FFT and QAM in series.

The above system implements the process of discrete multitone DMT modulation multiplexing, which includes:

splitting 4096 subcarriers of a 212MHz spectrum plan into two groups, wherein each group of 2048 subcarriers comprises 2048 subcarriers, wherein the first group of 2048 subcarriers (the 1 st to 2048 th subcarriers) is modulated into 2048 complex constellation points through QAM in a first path processing unit of FTU-O, the complex constellation points are expanded into 4096 complex constellation points through a mirror conjugate symmetry principle, the complex constellation points are modulated and transformed through IFFT with FFT _ size being 4096 to obtain 4096 real signals of time domains after modulation and transformation, the real signals are converted into digital signals through DAC with a sampling rate of 212Ms/s, and the first path of DMT modulation signals with the bandwidth of 2-106MHz are obtained through LPF with the bandwidth of 2-106 MHz;

a second group of 2048 subcarriers (2049 th to 4096 th subcarriers) is modulated into 2048 complex constellation points through QAM in a second path processing unit of the FTU-O, is expanded into 4096 complex constellation points through a mirror conjugate symmetry principle, is modulated and transformed through IFFT with FFT _ size ═ 4096 to obtain 4096 time domain real signals after modulation and transformation, is converted into digital signals through DAC with 212Ms/s sampling rate, is frequency-converted through an up-converter with 106MHz, and is subjected to BPF through a band-pass filter with the bandwidth of 106 plus 212MHz to obtain a second path of DMT modulation signals with the bandwidth of 106 plus 212 MHz;

the FTU-R receives an analog signal from a channel, the analog signal passes through an LPF of 212MHz, then is converted into a digital signal through an ADC with a sampling rate of 424Ms/s, the digital signal is converted into complex signals of 8192 frequency domains according to the FFT of 8192, finally only 1 to 4096 complex signals are selected, and 4096 complex constellation points on 4096 subcarriers are recovered by QAM demodulation.

It can be seen from the above that, in this embodiment, for the DMT modulation symbol with the bandwidth of 212MHz, it is not necessary to redesign a set of transmitter and processor structures with the profile of 212MHz, except that an up-converter and a BPF band-pass filter are added to the local transmitter of FTU-O, most of the processing devices with the profile of 106MHz are utilized, thereby greatly saving the device cost. The terminal device of the FTU-R can still use the 212MHz profile receiver without affecting the reception performance.

Example three:

in the embodiment, for DMT modulated signals with a bandwidth of 106MHz, a transceiver with a profile of 212MHz is used for transmission, so that the transceiver with the profile of 212MHz can be compatible with the DMT modulated signals with the bandwidth of 106MHz, and the main modification concept is as follows:

one, DMT modulated symbols of 106MHz bandwidth, multiplexing 212MHz spectrum-planned transmitter and receiver. And copying one part of QAM constellation points corresponding to 2048 subcarriers and expanding the QAM constellation points into 4096 complex numbers.

Second, except for adjusting the low pass filter LPF bandwidth from 2-212MHz to 2-106MHz, the other devices remain unchanged.

And thirdly, 4096 complex numbers are obtained after the receiver is subjected to FFT finally, only the 1 st to 2048 th complex numbers are taken, and the 2048 th and later complex numbers are discarded.

Specifically, the discrete multi-tone modulation multiplexing system in this embodiment includes two parts, FTU-O and FTU-R, as shown in fig. 5.

The FTU-O comprises a quadrature amplitude modulator QAM, a mirror image conjugate symmetry device, an inverse fast Fourier transform IFFT with the FFT _ size being 8192, a digital-to-analog converter DAC with the sampling rate of 424Ms/s and a low pass filter LPF with the sampling rate of 2-106MHz which are connected in series;

the FTU-R includes a LPF of 2-106MHz, an analog-to-digital converter ADC of 424Ms/s sample rate, a fast fourier transformer FFT and QAM of 8192 FFT _ size in series.

2048 subcarriers of a 106MHz spectrum plan are modulated into 2048 complex constellation points through QAM of FTU-O and then copied to obtain 4096 complex constellation points, namely constellation points corresponding to the 1 st to 2048 th subcarriers are sequentially loaded to the 2049 th and 4096 th subcarriers to obtain 4096 complex constellation points, the complex constellation points are symmetrically expanded into 8192 complex constellation points through mirror image conjugation, then modulation and transformation are carried out through IFFT of 8192, 8192 real signals are obtained after modulation and transformation, the signals are converted into digital signals through DAC with a sampling rate of 424Ms/s, and the digital signals are transmitted to a channel through LPF with a frequency of 2-106 MHz;

the FTU-R receives an analog signal from a channel, the analog signal passes through an LPF (low pass filter) of 2-106MHz, then is converted into a digital signal through an ADC (analog to digital converter) with a sampling rate of 424Ms/s, the digital signal is converted into 8192 complex signals with frequency domains according to FFT of which the FFT _ size is 8192, 4096 complex constellation points are recovered by QAM demodulation by selecting 1 st to 4096 complex signals, and the 1 st to 2048 complex signals are selected as frequency point signals of 2-106MHz corresponding to the 1 st to 2048 th subcarriers in sequence.

The advantage of this embodiment is that DMT modulation symbols with a bandwidth of 106MHz can be transmitted by using a transceiver with 212MHz profile, and only the cut-off bandwidth of the LPF low-pass filter needs to be changed to 106MHz, which is simple and convenient in design.

It will be understood by those skilled in the art that all or part of the steps of the above methods may be implemented by instructing the relevant hardware through a program, and the program may be stored in a computer readable storage medium, such as a read-only memory, a magnetic or optical disk, and the like. Alternatively, all or part of the steps of the above embodiments may be implemented using one or more integrated circuits. Accordingly, each module/unit in the above embodiments may be implemented in the form of hardware, and may also be implemented in the form of a software functional module. The present application is not limited to any specific form of hardware or software combination.

The above description is only a preferred example of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A discrete multi-tone DMT modulation multiplexing system comprises a local transmitter FTU-O of a feeder terminal device and a local receiver FTU-R of the feeder terminal device;

2. The system of claim 1, wherein the two ways of the IFFT transformed complex numbers being serial I, Q comprise:

3. The system of claim 1 or 2, wherein the FFT size 4096 IFFT employs an orthogonal frequency division multiplexing, OFDM, modulation transform.

4. A discrete multitone DMT modulation multiplexing method using the system as claimed in claims 1 to 3, the method comprising:

5. A discrete multi-tone DMT modulation multiplexing system comprises a local transmitter FTU-O of a feeder terminal device and a local receiver FTU-R of the feeder terminal device;

6. A discrete multi-tone DMT modulation multiplexing method using the system of claim 5, the method comprising:

7. A discrete multi-tone DMT modulation multiplexing system comprises a local transmitter FTU-O of a feeder terminal device and a local receiver FTU-R of the feeder terminal device;

8. A discrete multi-tone DMT modulation multiplexing method using the system of claim 7, the method comprising:

the FTU-R receives an analog signal from a channel, the analog signal passes through an LPF (low pass filter) of 2-106MHz, then is converted into a digital signal through an ADC (analog to digital converter) with a sampling rate of 424Ms/s, the digital signal is converted into complex signals of 8192 frequency domains according to the FFT of the FFT _ size 8192, 4096 complex constellation points are recovered by selecting 1 st to 4096 complex signals through QAM demodulation, and the 1 st to 2048 complex signals are selected as 106MHz signals.