KR20190065637A - Method for transmitting and receiving radio signal - Google Patents

Abstract

The present invention relates to a method for transmitting and receiving a radio signal. The method of the present invention comprises: a step of transmitting radio signals corresponding to a plurality of user terminals by applying non-orthogonal multiple access (NOMA) and Walsh-Hadamard transform (WHT) at a transmitting end; a step of detecting a first radio signal corresponding to a high gain user terminal by receiving the radio signal transmitted from the transmitting end at a receiving end and applying successive interference cancellation (SIC), the NOMA, and the WHT; and a step of detecting a second radio signal corresponding to a low gain user terminal by applying the NOMA and the WHT to the radio signal transmitted from the transmitting end. Therefore, it is possible to improve the performance of receiving a radio signal at a receiving end.

Description

[0001] METHOD FOR TRANSMITTING AND RECEIVING RADIO SIGNAL [0002]

The present invention transmits and receives a superposition-coded radio signal by applying a non-orthogonal multiple access (NOMA) and a Walsh Hadamard Transform (WHT) And a method of transmitting and receiving a radio signal.

As is well known, mobile communication systems have been developed to provide voice services while ensuring the user's activity. However, the mobile communication system has expanded to the area of not only voice but also data service. At present, due to an increase of explosive traffic, there is a shortage of resources and users demand a higher speed service and a more advanced mobile communication system is required .

The requirements of this next-generation mobile communication system are largely due to the explosion of data traffic acceptance, a dramatic increase in the per-user data rate, a significant increase in the number of connected devices, very low end-to-end latency, It should be able to support.

For this purpose, a dual connectivity, a massive multiple input multiple output (MIMO), an in-band full duplex, a non-orthogonal multiple access (NOMA), a super wide- And device networking are being studied. Techniques for improving reception performance through various combinations of these technologies are being continuously researched and developed.

1. Korean Patent Laid-Open No. 10-2017-0106376 (published on September 20, 2017)

An aspect of the present invention is to provide a wireless signal transmission / reception method capable of improving reception performance of a wireless signal at a receiver by transmitting / receiving a wireless signal superposed and coded by applying a non-orthogonal multiple access (NOMA) and a WHT.

In addition, the present invention provides a method for transmitting a radio signal corresponding to a plurality of user terminals by applying a non-orthogonal multiple access (NOMA) and a WHT at a transmitter, receiving the radio signal at a receiver and performing SIC (Successive Interference Cancellation) Gain non-orthogonal multiple access (NOMA) and WHT to detect a first radio signal corresponding to a high-gain user terminal, applying a non-orthogonal multiple access (NOMA) and a WHT, A method of transmitting and receiving a wireless signal capable of effectively receiving and detecting a wireless signal transmitted from a transmitting terminal by a receiving terminal by detecting a signal.

The objects of the embodiments of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description .

According to an embodiment of the present invention, there is provided a method for transmitting a radio signal, the method comprising: transmitting a radio signal corresponding to a plurality of user terminals by applying non-orthogonal multiple access (NOMA) and WHT (Walsh Hadamard Transform) Receiving a first radio signal corresponding to a high gain user terminal by receiving successive interference cancellation (SIC), non-orthogonal multiple access (NOMA) and WHT, receiving the radio signal from the transmitter, And detecting a second wireless signal corresponding to the low-gain user terminal by applying the non-orthogonal multiple access (NOMA) and the WHT to the wireless signal.

In addition, according to an embodiment of the present invention, the step of transmitting the radio signal may include transmitting the first radio signal corresponding to the plurality of high-gain user terminals at the transmitting end to the non-orthogonal multiple access (NOMA) And transmitting the second radio signal corresponding to a plurality of the low-gain user terminals from the transmitting terminal to the non-orthogonal multiple access (hereinafter referred to as " non-orthogonal multiple access " NOMA) and WHT, allocating transmission power for the second wireless signal superimposed on the coded signal, allocating transmission power for the second wireless signal to which the transmission power is allocated, And performing inverse fast Fourier transform (IFFT) to transmit the radio signal.

The step of performing the inverse fast Fourier transform (IFFT) and transmitting the radio signal may further comprise the steps of: receiving a cyclic prefix (Cyclic Prefix) A method of transmitting and receiving a wireless signal for adding a wireless signal may be provided.

According to an embodiment of the present invention, the step of detecting the first radio signal includes a first channel equalization and a first fast Fourier transform (hereinafter, referred to as " channel equalization "), FFT), removing the second radio signal by applying the SIC to the radio signal, removing the second radio signal, and applying the non-orthogonal multiple access (NOMA) and WHT And detecting the first radio signal based on the first radio signal.

According to an embodiment of the present invention, the step of performing the first channel equalization and the first fast Fourier transform (FFT) may include: transmitting and receiving a radio signal for eliminating a cyclic prefix added to the radio signal; A method can be provided.

According to an embodiment of the present invention, the step of detecting the second radio signal may include a second channel equalization (Channel Equalization) and a second FFT (second fast Fourier transform) for compensating for signal distortion of a communication channel by receiving the radio signal FFT), and detecting the second radio signal by applying the non-orthogonal multiple access (NOMA) and the WHT.

According to an embodiment of the present invention, performing the second channel equalization and the second fast Fourier transform (FFT) may include transmitting and receiving a radio signal for eliminating a cyclic prefix added to the radio signal A method can be provided.

The present invention can improve reception performance of a radio signal at a receiver by transmitting and receiving a superposition-coded radio signal by applying a non-orthogonal multiple access (NOMA) and a WHT.

In addition, the present invention applies a non-orthogonal multiple access (NOMA) and a WHT to a plurality of user terminals in a transmitting terminal, receives a radio signal corresponding to a plurality of user terminals, Gain wireless terminal to detect a first wireless signal corresponding to the high gain user terminal and detect a second wireless signal corresponding to the low gain user terminal by applying non-orthogonal multiple access (NOMA) and WHT to the wireless terminal And can be effectively received and detected at the receiving end.

1 to 4 are flowcharts illustrating a process of transmitting and receiving a radio signal according to an embodiment of the present invention,
5 is a view schematically illustrating a wireless signal transmission / reception system according to an embodiment of the present invention,
6 to 9 are views for explaining reception performance of a received radio signal according to an embodiment of the present invention.

Advantages and features of embodiments of the present invention and methods of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions in the embodiments of the present invention, which may vary depending on the intention of the user, the intention or the custom of the operator. Therefore, the definition should be based on the contents throughout this specification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 4 are flowcharts showing a process of transmitting and receiving a radio signal according to an embodiment of the present invention. FIG. 5 is a schematic view illustrating a radio signal transmitting / receiving system according to an embodiment of the present invention. 9 is a diagram for explaining reception performance of a received radio signal according to an embodiment of the present invention.

1 to 5, a method of transmitting and receiving a wireless signal according to an exemplary embodiment of the present invention includes transmitting a wireless signal corresponding to a plurality of user terminals by applying a non-orthogonal multiple access (NOMA) (120) receiving a first radio signal corresponding to a high-gain user terminal by receiving a radio signal transmitted from a transmitter in a receiver and applying a non-orthogonal multiple access (NOMA) and a WHT to the SIC, (NOMA) and a WHT to detect a second wireless signal corresponding to a low-gain user terminal (step 130).

[0040] In detail, the step 110 of transmitting a radio signal corresponding to a plurality of user terminals by applying non-orthogonal multiple access (NOMA) and WHT at a transmitting end will be described in detail. Superimposing a first radio signal on a first radio signal using NOMA and WHT; assigning a transmit power for the first radio signal superimposed on the coded signal; Superimposing a second wireless signal corresponding to the low-gain user terminal using non-orthogonal multiple access (NOMA) and WHT (113); assigning a transmit power for the superposed coded second wireless signal And transmitting a radio signal by performing an inverse fast Fourier transform (IFFT) on the first radio signal and the second radio signal to which the transmission power is allocated, respectively ).

Here, in step 115 of performing a reverse fast Fourier transform (IFFT) on a first radio signal and a second radio signal to which transmission powers are respectively allocated and transmitting a radio signal, inverse fast Fourier transform (IFFT) is performed It is possible to add a cyclic prefix for eliminating the interference of the multipath channel to the radio signal before transmitting the radio signal.

In addition, a step 120 of detecting a first radio signal corresponding to a high-gain user terminal by receiving a radio signal transmitted from a transmitting terminal at a receiving end and applying a non-orthogonal multiple access (NOMA) and a WHT to the SIC A step 121 of performing a first channel equalization and a first fast Fourier transform (FFT) to compensate for signal distortion of a communication channel by receiving a radio signal, (123) applying a SIC to the radio signal to remove a second radio signal; and removing the second radio signal and then applying a non-orthogonal multiple connection (NOMA) and a WHT to detect the first radio signal Step 125 may be included.

Here, in step 121 of performing a first channel equalization and a first fast Fourier transform (FFT) for receiving a radio signal and compensating for a signal distortion of a communication channel, in a step 121, Lt; RTI ID = 0.0 > a < / RTI >

Meanwhile, the step 130 of detecting a second wireless signal corresponding to a low-gain user terminal by applying non-orthogonal multiple access (NOMA) and WHT to a wireless signal transmitted from a transmitting terminal will be described in detail. (131) for performing a second channel equalization and a second fast Fourier transform (FFT) to compensate for signal distortion of a communication channel, detecting a second radio signal by applying a non-orthogonal multiple access (NOMA) Step 133 may be included.

Here, in the step 131 of performing the second channel equalization and the second fast Fourier transform (FFT) for receiving the radio signal and compensating for the signal distortion of the communication channel, in the step 131, Lt; RTI ID = 0.0 > a < / RTI >

Next, the process of applying the non-orthogonal multiple access (NOMA) and the WHT in the wireless signal transmission / reception method as described above will be described in detail.

First, a non-orthogonal multiple access (NOMA) will be described. A base station (BS) receives a superposition coded signal S for k pairs of UEs The superposition coded signal S can be expressed by Equation (1). &Quot; (1) "

Where _k k {1,2,3, ..., N}, S _k is the signal of the k th UE and P _k is the total transmit power for the k paired UEs.

In a non-orthogonal multiple access (NOMA) system, two types of UEs are used for user pairing: a high-gain CCU (Cell Center User) and a low-gain CEU ), And the rising value of the index k may be allocated in descending order of the UE channel gain. That is, k = 1 is the highest gain user classified as CCU, k = N can be regarded as the lowest gain user classified as CEU, and the superposition coded signal y _k received at the k-th UE is (2) " (2) "

Where h _k provides the response of the transport channel from the base station (BS) to the k-th UE, which is considered to be a Rayleigh fading channel, n represents noise, May be regarded as additive white Gaussian noise (AWGN), and P _k is the transmit power associated with the k < th > UE and can be expressed as Equation (3).

Here,? _K denotes the power allocation ratio for the k-th UE, P _BS denotes the provided BS transmission power, N _SB denotes the number of subbands in the system, and? _K is a theoretical value .

As described above, in order to extract the desired signal information from the received superposed coded signals of the k paired UEs, the UE receiving unit must perform the SIC. In order to perform this SIC, the UE receiving unit It is very important to determine the optimal decoding order in the decoding process.

This order can be determined through the channel gain of the k paired UEs in such a way that only the high gain user (CCU) performs the SIC to remove the signal information of the low gain user (CEU) When considering the high channel gain user (m) as a CCU in the UEs, the UE-m must perform the SIC to extract the signal for the high gain UEs by removing the signal information of the low gain UEs in the pairing, The signal y _m received at the UE-m can be expressed by Equation (4) below.

Here, in the case of two users (i.e., in case of two UEs), the signal received at UE-1 may be expressed by Equation (5).

Here, s ₁ , p ₁ and h ₁ mean the signal information, power and channel response of the high gain user UE-1, respectively, and s ₂ and P ₂ mean the signal information and power of the low gain user UE-2 do.

Next, the reception signal detection in the NOMA having the non-orthogonal multiple access (NOMA) and the incomplete SIC having the ideal SIC for the signal received at the receiving end will be described.

First, in the case of a NOMA receiver (receiver) having an ideal SIC, the CCU is known as an ideal SIC having a complete knowledge of the signal information of the CEU and assuming that the channel effect is not taken into consideration. , And if the CCU user is UE-m in k paired UEs, the received signal s _m can be expressed as Equation (6) by performing the ideal SIC.

Here, ?? represents the demodulation and detection of the received signal, and in the case of two pairs of UEs, the high gain user is the UE-1, the signal s1 received at the UE-1 with the ideal SIC is Can be expressed by the following Equation (7).

On the other hand, in the case of a NOMA receiver (receiver) with an incomplete SIC, the CCU performs the SIC in the presence of the channel effect generated by the transport channel, which is a Rayleigh fading channel and can provide a more realistic approach than the ideal SIC case have.

Here, the signal information of the CEUs having an incomplete state with respect to the received signal at the UE-m in k pairs of UEs can be expressed by Equation (8).

Here, n represents the additive white Gaussian noise (AWGN), h _k is to sense the Rayleigh fading channel, extracts the signal of the UE-m after performing SIC is expressed as the following equation (9) of the.

Here, in the case of a two-paired UE, the CEU is UE-2 and the CCU is UE-1.

Therefore, in the received signal at the UE-1, the signal information of the UE-2 including the effect of the Rayleigh fading channel can be expressed as Equation (10).

The signal of the UE-1 extracted after performing the SIC can be expressed by the following Equation (11).

Here, ?? means ?? demodulation and detection of the received signal.

Next, WHT (Walsh Hadamard Transform) will be described in detail. WHT is used as an orthogonal variable spreading factor (OVSF) in a communication system. In order to achieve constellation diversity, Symbol, which can be achieved by multiplying the WHT matrix by the input signal at the transmitting end. Correspondingly, the radio signal can be reconstructed at the receiving end by multiplying the received signal by the same WHT matrix, and the input / output representation can be expressed as Equation (12).

과 같이 주어진다고 가정할 경우 WHT 행렬의 일반적인 순서는 다음의 수학식 13과 같이 나타낼 수 있다.Here, S and y mean an input signal and an output signal, respectively, and H _i means a WHT matrix with i = 2 ^l length codes (lεZ ⁺ ), wherein two different rows in the WHT matrix are mutually orthogonal Where H is the Hadamard matrix, and the partitioning matrix is

The general order of the WHT matrix can be expressed by Equation (13). &Quot; (13) "

Here, the normalization factor is given by 1 / √i, j is the order of the Hadamard matrix for deriving the WHT matrix H _i , and the complex set point of the modulator output data (such as QAM or PSK) is x_data = [x_1 x_2 x_3 ... x_n], the result after applying the WHT matrix can be expressed by the following equation (14).

Here, S _H can be reconstructed using Equation (12). Assuming that given data is a second-order WHT matrix, i.e., H ₂ , x_data = [x_1 x_2], Equation (15) "

The result can be expressed by the following equation (16).

Then, instead of the original data, the derived result point of Equation 16 can be transmitted. Considering a typical QPSK (Quadrature Phase Shift Keying) transmitter, the modulator has four complex constellation points, i.e., 00 , 01, 10 and 11 (example), and the WHT application for these points is shown in Table 1 below, where x ₁ and x ₂ are the complex constellations of the respective x ₁ and x ₂ modulation points Point, and the new constellation points after the WHT application may be denoted by s ₁ and s ₂ .

On the other hand, in the case of the reverse WHT on the receiving end, the Harmad matrix of the same order can be applied to the received data, and the inverse WHT process can be expressed by Equation (17).

This equation (17) can represent the diversity obtained using the WHT technique.

A schematic system model of the WHT-NOMA of the present invention using the above-described non-orthogonal multiple access (NOMA) and WHT is shown in FIG. 5. If a superposition coded signal is given by Equation (1) The wireless signal (that is, the transmission signal) transmitted after the application of the WHT can be expressed by the following equation (18).

Here, s _{(H, k)} represents the signal of the k-th UE after WHT is applied, and the receiving signal at the k-th user at the receiving end using Equation (2) .

Here, h _k is the channel response considered as a Rayleigh fading channel, n represents noise, and can be regarded as an additive white Gaussian noise (AWGN) with mean and variance of zero.

In the case of the m-th user in the k paired UEs in the WHT-NOMA, the received radio signal of the high-gain user UE-m in Equation (4) without performing the SIC is expressed by the following Equation 20 .

Similarly, in case of two UEs in WHT-NOMA, the signal received at UE-1 without SIC can be expressed by Equation (21) using Equation (20).

Again, similar to the conventional NOMA, there are two cases for SIC at the receiving end: WHT-NOMA with ideal SIC and WHT-NOMA with incomplete SIC can be considered.

First, in a WHT-NOMA receiver with an ideal SIC, it can be assumed that the CCU knows the signal information of the CEU completely similar to the conventional NOMA receiver, and the CCU completely removes the CEU signal information from the combined signal using the SIC And in the WHT-NOMA receiver, the radio signal of the high-gain user UE-m in k paired UEs can be expressed by Equation (22) using Equation (21).

Where H _i is the WHT matrix of the same order (i) as used for the transmitter, and ?? represents the demodulation and detection of the received signal, in the case of two paired UEs, (22) can be expressed by Equation (23) to retrieve the signal of the UE-1.

On the other hand, in a WHT-NOMA receiver having an incomplete SIC, the CCU can perform SIC in the presence of a channel effect generated by a transmission channel, i.e., a Rayleigh fading channel, similar to a conventional NOMA receiver. In this case, The signal information of the CEU at -m can be expressed as Equation (24) using Equation (20).

Here, n and h _k denote additive white Gaussian noise (AWGN) and Rayleigh fading channels, respectively. In case of WHT-NOMA, the signal information of UE-m is expressed by Equation 20 and Equation 24, 25, respectively.

Also, after including the effects of the Rayleigh fading channel for the two users of WHT-NOMA (i.e. high gain CCU and low gain CEU), the signal information of UE-2 at UE- Can be expressed by the following equation (26).

Here, the UE-1 signal can be expressed by Equation (27) using Equation (21) and Equation (26).

Where H _i is the WHT matrix of the same order (i) as used for the transmitter, and ?? represents the demodulation and detection of the received signal.

The throughput and the bit error rate (BER) will be described below with reference to FIGS. 6 to 9. FIG. 6 is a flowchart illustrating a method of calculating the throughput of the conventional NOMA and the WHT-NOMA according to an embodiment of the present invention. The throughput can be calculated using the BER. In the case of both the conventional NOMA and the WHT-NOMA, the throughput can be calculated according to the given BER performance as shown in Equation 28 below.

Where B is the bandwidth and Q is the modulation order of the transmitted signal.

Using the equation (28), simulation results for WHT-NOMA according to an embodiment of the present invention are provided in comparison with a conventional NOMA system using ideal SIC conditions and incomplete SIC conditions, (Long-Term Evolution) standard specified in the Third-Generation Partnership Project specification, and the basic signal waveform used in the simulation is also derived in accordance with the LTE standard.

The simulation parameters are defined in Table 2 below, and the user power allocation for simulation purposes is set to CCU = 0.2 and CEU = 0.8 with a total power of 1, i.e. P _CCU + P _CEU = 1, , The same order as the modulation scheme used was used. For example, in the case of BPSK modulation, the degree of the WHT matrix is 2, and in the case of QPSK modulation, the degree of the WHT matrix is 4.

As a result, the BER of the WHT-NOMA is shown in FIGS. 6 and 7 in comparison with the conventional NOMA in the ideal SIC condition using a different modulation scheme and the BER performance of the WHT-NOMA under an incomplete SIC condition.

That is, the results of the conventional NOMA and WHT-NOMA using QPSK modulation are shown in FIG. 6 as' Conventional NOMA-CCU with imperfect SIC / Conventional NOMA-CCU with perfect SIC / Conventional NOMA-CEU / WHT- -CCU with imperfect SIC / WHT-NOMA-CCU with perfect SIC / WHT-NOMA-CEU ', the BER of the WHT-NOMA of the present invention is lower than that of the conventional NOMA.

In addition, the results for conventional NOMA and WHT-NOMA using quadrature amplitude modulation (QAM) are similar to systems using QPSK modulation, as shown in FIG. 7, with 'Conventional NOMA-CCU with imperfect SIC / Conventional NOMA- CCU with perfect SIC / Conventional NOMA-CEU / WHT-NOMA-CCU with imperfect SIC / WHT-NOMA-CCU with perfect SIC / WHT- It can be seen that the total is low.

On the other hand, the throughput performance of WHT-NOMA according to the embodiment of the present invention is compared with that of the conventional NOMA under ideal SIC condition and incomplete SIC condition of WHT-NOMA throughput. Such throughput is based on BER performance, The results are shown in FIG. 8 and FIG.

The results of the conventional NOMA and WHT-NOMA using QPSK modulation are shown in FIG. 8 as' Conventional NOMA-CCU with imperfect SIC / Conventional NOMA-CCU with perfect SIC / Conventional NOMA-CEU / WHT- -CCU with imperfect SIC / WHT-NOMA-CCU with perfect SIC / WHT-NOMA-CEU ', the throughput of the WHT-NOMA of the present invention is higher than that of the conventional NOMA.

In addition, the results for conventional NOMA and WHT-NOMA using quadrature amplitude modulation (QAM) are similar to systems using QPSK modulation as shown in FIG. 9, with 'Conventional NOMA-CCU with imperfect SIC / Conventional NOMA- The throughput of the WHT-NOMA of the present invention is higher than that of the conventional NOMA in the order of "CCU with perfect SIC / Conventional NOMA-CEU / WHT-NOMA-CCU with imperfect SIC / WHT-NOMA- It can be seen that the overall appearance is high.

Therefore, the present invention can improve the reception performance of the radio signal at the receiving end by transmitting and receiving the superposed coded radio signal by applying the non-orthogonal multiple access (NOMA) and WHT.

The present invention also relates to a method and apparatus for transmitting a radio signal corresponding to a plurality of user terminals by applying non-orthogonal multiple access (NOMA) and WHT at a transmitter, receiving the radio signal at a receiver, ) And WHT to detect a first radio signal corresponding to a high gain user terminal and applying a non-orthogonal multiple access (NOMA) and a WHT to detect a second radio signal corresponding to the low gain user terminal, It is possible to effectively receive and detect the transmitted radio signal at the receiving end.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be readily apparent that such substitutions, modifications, and alterations are possible.

Claims (7)

Transmitting a radio signal corresponding to a plurality of user terminals by applying non-orthogonal multiple access (NOMA) and Walsh Hadamard Transform (WHT) at a transmitting end;
Receiving a radio signal transmitted from the transmitting terminal at a receiving terminal and detecting a first radio signal corresponding to the high-gain user terminal by applying successive interference cancellation (SIC), non-orthogonal multiple access (NOMA)
Detecting a second radio signal corresponding to the low-gain user terminal by applying the non-orthogonal multiple access (NOMA) and the WHT to the radio signal transmitted from the transmitting terminal
And transmitting the radio signal.
The method according to claim 1,
Wherein the step of transmitting the radio signal comprises:
Superposing the first radio signal corresponding to the plurality of high-gain user terminals in the transmitting terminal by applying the non-orthogonal multiple access (NOMA) and the WHT;
Assigning a transmit power for the superposed coded first radio signal;
Superposing the second radio signal corresponding to the plurality of low-gain user terminals at the transmitting end by applying the non-orthogonal multiple access (NOMA) and the WHT;
Allocating a transmit power for the superposed coded second radio signal;
Performing inverse fast Fourier transform (IFFT) on the first radio signal and the second radio signal to which the transmission power is allocated, respectively, and transmitting the radio signal
And transmitting the radio signal.
3. The method of claim 2,
Wherein the step of transmitting the radio signal by performing the inverse fast Fourier transform (IFFT) comprises adding a cyclic prefix for eliminating interference of a multipath channel to the radio signal.
The method according to claim 1,
Wherein the detecting the first wireless signal comprises:
Performing a first channel equalization and a first fast Fourier transform (FFT) to compensate for signal distortion of a communication channel by receiving the radio signal;
Removing the second radio signal by applying the SIC to the radio signal;
Detecting the first wireless signal by applying the non-orthogonal multiple access (NOMA) and WHT after removing the second wireless signal
And transmitting the radio signal.
5. The method of claim 4,
Wherein performing the first channel equalization and the first fast Fourier transform (FFT) comprises removing a cyclic prefix added to the radio signal.
The method according to claim 1,
Wherein the step of detecting the second radio signal comprises:
Performing a second channel equalization and a second fast Fourier transform (FFT) to compensate for signal distortion of a communication channel by receiving the radio signal;
Detecting the second wireless signal by applying the non-orthogonal multiple access (NOMA) and the WHT
And transmitting the radio signal.
The method according to claim 6,
Wherein performing the second channel equalization and second fast Fourier transform (FFT) comprises removing a cyclic prefix added to the radio signal.

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