A 3D-PD-NOMA optical access method based on multi-power distribution

Abstract

The present invention discloses a 3D-PD-NOMA optical access method based on multi-power distribution, comprising the following steps: (1) dividing input bit data into 1×M groups, where M represents different users; (2) converting serial data into parallel data through S / P conversion; (3) performing three-dimensional mapping on the converted data to form a multi-carrier signal; (4) converting the multi-carrier signal into a time domain signal using a two-dimensional inverse fast Fourier transform; (5) converting the time domain signal into serial data through P / S; (6) obtaining a transmitted 3D-NOMA signal through PD-NOMA superposition; (7) performing channel equalization on the received signal; (8) obtaining a frequency domain signal using a two-dimensional fast Fourier transform; (9) converting different signal points into bits according to the three-dimensional mapping rule of the transmitting end to realize demodulation of the three-dimensional constellation; (10) restoring the output bit data through P / S conversion; the present invention reduces the peak-to-average power ratio of the system under the same transmission power; and reduces the bit error rate of the system under the same transmission power.

Description

Technical Field

[0001] The present invention relates to the field of optical transmission communication technology, and in particular to a 3D-PD-NOMA optical access method based on multi-power distribution. Background Art

[0002] With the advent of the 5G era, global demand for digital traffic is exploding. The vast amounts of information in wireless communications will ultimately be funneled into access networks and transmitted through backbone networks. This places new demands on the access capacity and number of users in optical access systems. Fiber-optic access systems are categorized into two types: active optical networks (AONs) and passive optical networks (PONs). Passive optical networks (PONs) are widely used due to their high bandwidth, low cost, and low power consumption. PONs have undergone numerous evolutions, from the original time-division multiplexing (TDM-PON) passive optical network (PON) that multiplexed data in the time dimension, to wavelength-division multiplexing (WDM-PON) that multiplexed data in the wavelength dimension, to the orthogonal frequency division multiplexing (OFDM) technology currently used in 4G communication systems. All of these PON technologies require strict orthogonality between resource blocks (time slots, wavelengths, and frequencies). This orthogonal multiple access approach struggles to meet the high-capacity, multi-access requirements of 5G. Non-orthogonal multiple access (NOMA) technology came into being.

[0003] NOMA is considered a key technology for next-generation wireless communication systems and has garnered widespread attention from researchers. Compared to traditional orthogonal multiple access technologies such as OFDM, NOMA signals can overlap in the time, frequency, and power domains, providing greater transmission capacity and higher spectral efficiency. NOMA is primarily divided into code-domain sparse coded multiple access (SCA) and power-domain power division multiplexing (PD-NOMA). Since non-orthogonal access technologies overlap different dimensions, additional digital signal processing algorithms are required for demodulation at the receiver. Code-domain sparse coding utilizes a message propagation algorithm at the receiver, performing demodulation based on message propagation between user nodes and resource nodes. This complexity is extremely high, and for large-scale 5G user access, this complexity will double. Non-orthogonal multiple access technologies based on power division multiplexing (PD-NOMA) superimpose signals of different powers, dynamically allocating power based on user channel quality. Users farther from the optical transmission line (OLT) are allocated higher power, while users closer to the OLT are allocated lower power, thus ensuring fairness among users. PD-NOMA has attracted considerable attention. Experiments have shown that, under the same bandwidth conditions, PD-NOMA can achieve twice the transmission capacity compared to traditional OFDM access. Current PD-NOMA is primarily based on OFDM power stacking, using traditional two-dimensional QAM constellations. At the same transmit power, the minimum Euclidean distance of these constellations is smaller than that of three-dimensional constellations, resulting in poor bit error performance. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a 3D-PD-NOMA optical access method based on multi-power distribution, which uses three-dimensional constellation space for power superposition and maximizes the minimum Euclidean distance between constellation points under the condition of limited transmission power to improve the transmission performance of the system.

[0005] Technical solution: The present invention provides a 3D-PD-NOMA optical access method based on multi-power distribution, comprising the following steps:

[0006] On the transmitter side:

[0007] (1) Divide the input bit data into 1×M groups, where M represents different users;

[0008] (2) Convert serial data into parallel data through S / P conversion;

[0009] (3) performing three-dimensional mapping on the converted data to form a multi-carrier signal;

[0010] (4) Converting the multi-carrier signal into a time domain signal using a two-dimensional inverse fast Fourier transform;

[0011] (5) Convert the time domain signal into serial data through P / S;

[0012] (6) Obtain the emitted 3D-NOMA signal by PD-NOMA superposition;

[0013] On the receiving end:

[0014] (7) performing channel equalization on the received signal;

[0015] (8) The equalized signal is a frequency domain signal obtained by using a two-dimensional fast Fourier transform;

[0016] (9) According to the rules of the three-dimensional mapping at the transmitter, different signal points are converted into bits to achieve demodulation of the three-dimensional constellation;

[0017] (10) Restore the output bit data through P / S conversion.

[0018] Furthermore, the step (2) is specifically as follows: converting the original data 1×M groups into an M×N matrix.

[0019] Furthermore, the step (3) is specifically as follows: taking two bits of two rows and one column as a group, and applying three-dimensional constellation space mapping to each group, the coordinates of which can be expressed as:

[0020]

[0021] Four regular tetrahedrons are obtained, and the four vertices of each regular tetrahedron correspond to four constellation points. The minimum Euclidean distance between the four points is set to 2. By superimposing the two three-dimensional constellation points, a three-dimensional constellation point distribution of 16 constellation points is formed.

[0022] Furthermore, the step (4) is specifically expressed as follows:

[0023]

[0024] Where, 0≤n1≤2,0≤n2≤C-1, C represents the number of carriers; k1 and k2 represent the columns and rows of the OFDM matrix respectively; n1 and n2 are the columns and rows of the time domain signal matrix after the two-dimensional IFFT.

[0025] Furthermore, the step (5) is specifically as follows: converting the modulated M×N parallel time domain signal into a 1×W matrix for transmission.

[0026] Furthermore, the step (6) is specifically expressed as follows:

[0027] S(t)=P1*S1(t)+P2*S2(t)

[0028] Among them, S1(t) and S2(t) are two 3D-NOMA signals; P1 and P2 represent high power and low power, respectively.

[0029] Furthermore, the step (8) is specifically expressed as follows:

[0030]

[0031] Among them, S' 3D (k1, k2) is the equalized signal, and s'1(n2, n1) is the frequency domain signal. The frequency domain signal at this time is the superposition of the high-power signal and the low-power signal. For low-power signal demodulation: the low-power signal is regarded as noise and QAM symbol demodulation is performed directly. For high-power signal demodulation: the SIC algorithm is used to subtract the high-power signal from the signal at the receiving end to obtain the low-power signal, and the low-power signal can be demodulated.

[0032] Furthermore, the step (9) is specifically expressed as follows: let the obtained three-dimensional constellation point coordinates be:

[0033]

[0034] According to the three-dimensional mapping rules of the transmitter, different signal points are converted into bits to achieve demodulation of the three-dimensional constellation.

[0035] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: reducing the peak-to-average power ratio of the system at the same transmission power; reducing the system bit error rate at the same transmission power. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a block diagram of the overall principle of the present invention;

[0037] Figure 2 This is a diagram showing the principle of constellation superposition of the present invention;

[0038] Figure 3 A constellation diagram of the receiving end of the present invention;

[0039] Figure 4 This is the PAPR comparison of the present invention;

[0040] Figure 5 The bit error rate comparison between the two-dimensional signal and the three-dimensional signal of the present invention is shown;

[0041] Figure 6 This is the bit error performance at different powers of the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0043] like Figure 1As shown, an embodiment of the present invention provides a 3D-PD-NOMA optical access method based on multi-power distribution, comprising the following steps:

[0044] On the transmitter side:

[0045] (1) Divide the input bit data into 1 × 102400 groups, where M represents different users;

[0046] (2) Convert serial data into parallel data through S / P conversion; specifically, convert the original data 1×102400 groups into a 200×512 matrix;

[0047] (3) The converted data is three-dimensionally mapped to form a multi-carrier signal; specifically: the principle of three-dimensional mapping is as follows Figure 2 In the present invention, the 200×512 bit matrix after serial-parallel conversion is subjected to constellation mapping, with two bits in two rows and one column as a group, and the two bits just correspond to Figure 2 Four cases of constellation points in ; Figure 2 (a) shows the method used in traditional 2D-PD-NOMA to superimpose two QPSK signals to form 16QAM; Figure 2 (b) in the figure is 3D-PD-NOMA, where each power uses a three-dimensional constellation space, and its coordinates can be expressed as:

[0048]

[0049] Each of the four vertices of the tetrahedron corresponds to four constellation points, and the minimum Euclidean distance between each of the four points is set to 2. By superimposing two 3D constellation points, a 16-point 3D constellation distribution is formed. Compared to traditional 2D constellation space, this approach has a lower peak-to-average power ratio, resulting in better transmission performance. Because the two bits in each column of every two rows correspond to 3D coordinates, the original 200×512 bit array is converted into a 300×512 3D coordinate array.

[0050] (4) The multi-carrier signal is converted into a time domain signal using a two-dimensional inverse fast Fourier transform; specifically, it is expressed as:

[0051]

[0052] Where, 0≤n1≤2,0≤n2≤C-1, C represents the number of carriers; k1 and k2 represent the columns and rows of the OFDM matrix respectively; n1 and n2 are the columns and rows of the time domain signal matrix after the two-dimensional IFFT.

[0053] (5) Convert the time domain signal into serial data through P / S; specifically, convert the modulated 300×512 parallel time domain signal into a 1×153600 matrix for transmission.

[0054] (6) The emitted 3D-NOMA signal is obtained by PD-NOMA superposition; the specific expression is as follows:

[0055] S(t)=P1*S1(t)+P2*S2(t)

[0056] Among them, S1(t) and S2(t) are two 3D-NOMA signals; P1 and P2 represent high power and low power respectively. Figure 2 As shown in (b) in the figure, the constellation diagram after the two channels are superimposed just forms a 16QAM.

[0057] On the receiving end:

[0058] (7) performing channel equalization on the received signal;

[0059] (8) The equalized signal is a frequency domain signal obtained by using a two-dimensional fast Fourier transform; Figure 3 As shown, specifically expressed as:

[0060]

[0061] Among them, S' 3D (k1, k2) is the equalized signal, and s'1(n2, n1) is the frequency domain signal. The frequency domain signal at this time is the superposition of the high-power signal and the low-power signal. For low-power signal demodulation: the low-power signal is regarded as noise and QAM symbol demodulation is performed directly. For high-power signal demodulation: the SIC algorithm is used to subtract the high-power signal from the signal at the receiving end to obtain the low-power signal, and the low-power signal can be demodulated.

[0062] (9) According to the three-dimensional mapping rule of the transmitter, different signal points are converted into bits to realize the demodulation of the three-dimensional constellation; specifically, the coordinates of the obtained three-dimensional constellation points are:

[0063]

[0064] According to the three-dimensional mapping rules of the transmitter, different signal points are converted into bits to achieve demodulation of the three-dimensional constellation.

[0065] (10) Restore the output bit data through P / S conversion.

[0066] like Figure 4 As shown in Figure 2, in order to test the superiority of the 3D-PD-NOMA scheme proposed in the present invention, the PAPR and bit error rate performance of two-dimensional and three-dimensional signals are compared. Figure 4It can be clearly seen that the PAPR of the three-dimensional signal is significantly lower than that of the two-dimensional signal. This is because the power difference between the three-dimensional constellation points is smaller than that between the two-dimensional constellation points, which leads to a reduction in PAPR.

[0067] like Figure 5 As shown in the figure, in order to compare the signal transmission quality of the two signals under the signal-to-noise ratio conditions, simulations were performed on analog channels with signal-to-noise ratios of 1-20. It can be found that the 3D-PD-NOMA signal proposed in this invention has better transmission performance than the traditional 2D-NOMA signal. This is because under the same transmission power, the three-dimensional constellation points have a larger minimum Euclidean distance than the two-dimensional constellation, which is more conducive to the decision of the receiving end, and thus has better error performance. At a bit error rate of 10 -3 When , the transmission performance of the three-dimensional constellation is 4dB better than that of the two-dimensional constellation.

[0068] like Figure 6 As shown, the present invention compares the bit error rate curves of two different powers. It can be found that since the high-power signal is allocated higher power, it has better transmission performance, while the low-power signal is more affected by noise due to the relatively low allocated power, so its transmission effect is relatively poor. However, for the NOMA system, high-power signals are allocated to users farther away from the OLT, and low-power signals are allocated to users closer to the OLT, thereby ensuring fairness among different users. Based on the good transmission performance of 3D-PD-NOMA and the guarantee of fairness among different users, the 3D-PD-NOMA proposed in the present invention has very good application prospects in future optical access systems.

Claims

1. A 3D-PD-NOMA optical access method based on multi-power distribution, including a transmitting end and a receiving end, characterized in that: The following steps are involved: On the transmitter side: (1) Divide the input bit data into 1×M groups, where M represents different users; (2) Convert serial data into parallel data through S / P conversion; (3) performing three-dimensional mapping on the converted data to form a multi-carrier signal; (4) Converting the multi-carrier signal into a time domain signal using a two-dimensional inverse fast Fourier transform; (5) Convert the time domain signal into serial data through P / S; (6) Obtain the emitted 3D-NOMA signal by PD-NOMA superposition; On the receiving end: (7) performing channel equalization on the received signal; (8) The equalized signal is a frequency domain signal obtained by using a two-dimensional fast Fourier transform; (9) According to the rules of the three-dimensional mapping at the transmitter, different signal points are converted into bits to achieve demodulation of the three-dimensional constellation; (10) Restore the output bit data through P / S conversion.

2. A 3D-PD-NOMA optical access method based on multi-power distribution according to claim 1, characterized in that: The step (2) specifically includes: converting the original data 1×M groups into an M×N matrix.

3. The 3D-PD-NOMA optical access method based on multi-power distribution according to claim 1, characterized in that: The step (3) is specifically as follows: taking two bits of two rows and one column as a group, and applying three-dimensional constellation space mapping to each group, wherein the coordinates are expressed as: Four regular tetrahedrons are obtained, and the four vertices of each regular tetrahedron correspond to four constellation points. The minimum Euclidean distance between the four points is set to 2. By superimposing the two three-dimensional constellation points, a three-dimensional constellation point distribution of 16 constellation points is formed.

4. The 3D-PD-NOMA optical access method based on multi-power distribution according to claim 1, characterized in that: The step (4) is specifically expressed as follows: Where, 0≤n1≤2,0≤n2≤C-1, C represents the number of carriers; k1 and k2 represent the columns and rows of the OFDM matrix respectively; n1 and n2 are the columns and rows of the time domain signal matrix after the two-dimensional IFFT.

5. The 3D-PD-NOMA optical access method based on multi-power distribution according to claim 1, characterized in that: The step (5) specifically includes: converting the modulated M×N parallel time domain signal into a 1×W matrix for transmission.

6. A 3D-PD-NOMA optical access method based on multi-power distribution according to claim 1, characterized in that: The step (6) is specifically expressed as follows: S(t)=P1*S1(t)+P2*S2(t) Among them, S1(t) and S2(t) are two 3D-NOMA signals; P1 and P2 represent high power and low power, respectively.

7. The 3D-PD-NOMA optical access method based on multi-power distribution according to claim 4, characterized in that: The step (8) is specifically expressed as follows: Among them, S' 3D (k1, k2) is the equalized signal, and s'1(n2, n1) is the frequency domain signal. The frequency domain signal at this time is the superposition of the high-power signal and the low-power signal. For low-power signal demodulation: the low-power signal is regarded as noise and QAM symbol demodulation is performed directly. For high-power signal demodulation: the SIC algorithm is used to subtract the high-power signal from the signal at the receiving end to obtain the low-power signal, and the low-power signal can be demodulated.

8. The 3D-PD-NOMA optical access method based on multi-power distribution according to claim 1, characterized in that: The step (9) is specifically expressed as follows: the obtained three-dimensional constellation point coordinates are: According to the three-dimensional mapping rules of the transmitter, different signal points are converted into bits to achieve demodulation of the three-dimensional constellation.

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