阅读说明：本技术 一种基于新型可重构智能表面的非正交多址接入方法 (Non-orthogonal multiple access method based on novel reconfigurable intelligent surface ) 是由 盛彬 尤肖虎 黄永明 王东明 于 2021-08-24 设计创作，主要内容包括：本发明公开了一种基于新型可重构智能表面的非正交多址接入方法,包括以下步骤,基站发送导频并控制新型可重构智能表面依次开启M个单元,并将其反射和透射系数分别设置为1；根据发送的导频,用户A和用户B依次计算经过M个单元反射和透射的信道和并将信道和反馈至基站；基站依次比较信道和的模的大小,筛选出的单元序号,并将其对应单元存储为集合S；基站将集合S以外的单元关闭,并将集合S中单元的反射和透射系数分别设置为和用户A和用户B分别发送信号和基站将x-(B)(n)作为噪声,解调x-(A)(n)；抵消掉x-(A)(n)后,解调x-(B)(n)。通过本发明可以实现在用户与基站距离相等的情况下构造出适合NOMA传输的无线信道环境,有效降低了接收端的误码率,提高了系统容量。(The invention discloses a non-orthogonal multiple access method based on a novel reconfigurable intelligent surface, which comprises the following steps that a base station sends pilot frequency and controls the novel reconfigurable intelligent surface to sequentially open M units, and the reflection coefficient and the transmission coefficient of the novel reconfigurable intelligent surface are respectively set to be 1; based on the transmitted pilot, user A and user B calculate the channels reflected and transmitted by M units in turn And and will channel And feeding back to the base station; the base station compares the channels in turn And the size of the mold of (1), screening And storing the corresponding unit as a set S; the base station closes the units outside the set S and sets the reflection coefficient and the transmission coefficient of the units in the set S to be respectively And user A and user B transmit signals separately And the base station will x B (n) as noise, demodulate x A (n); offset x A After (n), demodulate x B (n) of (a). The invention can construct a wireless channel environment suitable for NOMA transmission under the condition that the distance between the user and the base station is equal, effectively reduces the error rate of a receiving end and improves the system capacity.)

1. A non-orthogonal multiple access method based on a novel reconfigurable intelligent surface is characterized in that: comprises the following steps of (a) carrying out,

step 1, a base station sends pilot frequency and controls a novel reconfigurable intelligent surface to sequentially open M units, and meanwhile, the reflection and transmission coefficients of the novel reconfigurable intelligent surface are respectively set to be 1;

step 2, according to the transmitted pilot frequency, calculating the channels reflected and transmitted by M units between user A and user B and the base station in turnAndand will channelAndfeeding back to the base station;

step 3, the base station compares the channels in sequenceAndthe size of the mold of (1), screeningAnd storing the corresponding unit as a set S;

step 4, the base station closes the units except the set S, and sets the reflection and transmission coefficients of the units in the set S to be respectivelyAnd

step 5, user A and user B send signals respectivelyAndto a base station;

step 6, the base station sends x_B(n) as noise, demodulate x_A(n) obtaining the user A received signal

Step 7, the base station counteracts x_AAfter (n) interference, demodulate x_B(n) obtaining a received signal of user B

2. The non-orthogonal multiple access method based on the novel reconfigurable intelligent surface as claimed in claim 1, wherein: in step 2, the user a receives the discrete baseband equivalent signal at the nth timeComprises the following steps:

wherein the content of the first and second substances,representing the channel at the nth moment between the 1 st element of the novel reconfigurable smart surface and the user A, alpha₁(n) is the reflection coefficient of the 1 st cell at the nth instant, where α₁(n)＝1，Representing the channel at the nth time between the base station and the 1 st unit of the novel reconfigurable intelligent surface, x_p(n) denotes a pilot signal transmitted by the base station at the nth time, w_A(n) additive white gaussian noise at the nth time of user a;

due to alpha₁(n) is 1, and x is known to the receiving end_p(n), the composite channel between the base station and the user A which is reflected by the novel reconfigurable intelligent surface can be obtained as follows:

wherein the content of the first and second substances,representing a composite channel between the base station and the user a via novel reconfigurable intelligent surface reflection.

3. The non-orthogonal multiple access method based on the novel reconfigurable intelligent surface as claimed in claim 2, wherein: in the step 2, through the transmission of the 1 st unit of the novel reconfigurable intelligent surface, the discrete baseband equivalent signal received by the user B at the nth momentComprises the following steps:

wherein the content of the first and second substances,representing the channel, beta, at the nth moment between the 1 st element of the novel reconfigurable smart surface and the user B₁(n) is the transmission coefficient of the 1 st cell at the nth instant, where β₁(n)＝1，w_B(n) additive white gaussian noise representing the nth time of user B;

due to beta₁(n) is 1, and x is known to the receiving end_p(n), the composite channel transmitted by the novel reconfigurable intelligent surface between the base station and the user B can be obtained as follows:

wherein the content of the first and second substances,representing a composite channel transmitted between the base station and user B through the novel reconfigurable intelligent surface.

4. A novel reconfigurable-based smart meter as in claim 3A method of non-orthogonal multiple access of a plane, characterized by: in the step 2, the reflection coefficient and the transmission coefficient of the novel reconfigurable intelligent surface are respectively set to be 1, at the nth moment, the base station controls the novel reconfigurable intelligent surface to open the 1 st unit and close other units, so that the user A can obtain a discrete baseband equivalent signal which is received by the user A and reflected by the 1 st unit of the novel reconfigurable intelligent surfaceComprises the following steps:

channel estimation is performed at the receiving end and subtracted from the resultAnd obtaining a composite channel between the base station and the user A through the novel reconfigurable intelligent surface reflection.

5. The novel reconfigurable intelligent surface-based non-orthogonal multiple access method of claim 4, wherein: in the step 2, at the (n +1) th moment, the base station controls the novel reconfigurable intelligent surface to open the 2 nd unit and close other units, and at the moment, the user A receives the discrete baseband equivalent signal reflected by the 2 nd unit of the novel reconfigurable intelligent surfaceComprises the following steps:

wherein the content of the first and second substances,intelligent meter capable of representing novel reconstructionChannel between the 2 nd element of the plane and the user A, alpha₂(n +1) is the reflection coefficient of the 2 nd unit of the novel reconfigurable intelligent surface at the n +1 th moment, and alpha₂(n+1)＝1，Represents the channel at the (n +1) th moment between the base station and the 2 nd unit of the novel reconfigurable intelligent surface, x_p(n +1) denotes a pilot signal transmitted by the base station at the (n +1) th time, w_A(n +1) represents additive white gaussian noise at the (n +1) th time of user a.

6. The novel reconfigurable intelligent surface-based non-orthogonal multiple access method of claim 5, wherein: in the step 2, due to alpha₂(n +1) ═ 1, and x is known to the receiving end_p(n) obtaining a composite channel between the base station and the user A via the novel reconfigurable intelligent surface reflectionComprises the following steps:

。

7. the novel reconfigurable intelligent surface-based non-orthogonal multiple access method of claim 6, wherein: in the step 2, through the transmission of the 2 nd unit of the novel reconfigurable intelligent surface, the discrete baseband equivalent signal received by the user BComprises the following steps:

wherein the content of the first and second substances,representing the channel, beta, between the 2 nd element of the new reconfigurable smart surface and user B₂(n +1) is the reflection coefficient of the 2 nd unit of the novel reconfigurable intelligent surface at the n +1 th moment, and beta₂(n+1)＝1，w_B(n +1) represents additive white gaussian noise at the (n +1) th time of user B.

8. The novel reconfigurable intelligent surface-based non-orthogonal multiple access method of claim 7, wherein: in the step 2, due to beta₂(n +1) ═ 1, and x is known to the receiving end_p(n) obtaining a composite channel transmitted between the base station and user B through the novel reconfigurable intelligent surfaceComprises the following steps:

。

9. the novel reconfigurable intelligent surface-based non-orthogonal multiple access method of claim 8, wherein: said step 6 further comprises that the base station receives the discrete baseband equivalent signal r at the nth time, assuming that the direct channel between the user and the base station is blocked_BS(n) is:

further, since the channel condition of user a is better, the base station will first transmit the signal x of user B_B(n) demodulating user A's signal x as noise_A(n) obtaining the demodulated user A received signal

。

10. The non-orthogonal multiple access method based on the novel reconfigurable intelligent surface as claimed in claim 9, wherein: the step 7 further includes, based on the SIC technology, the base station firstly cancels the interference generated by the user a, and then demodulates the data of the user B, that is:

wherein, y_B(n) represents the received signal of user B after interference cancellation,to representThe symbol regenerated after the hard judgment or the soft judgment is finally obtained as the receiving signal of the user BComprises the following steps:

。

Technical Field

The invention relates to the technical field of multiple access of a mobile communication system, in particular to a non-orthogonal multiple access method based on a novel reconfigurable intelligent surface.

Background

In recent years, as the fifth generation mobile communication system (5G) enters a commercial stage, the development of the sixth generation mobile communication system (6G) has also been spread. The 6G can meet various increasing communication requirements of people in the forms of full coverage, full spectrum, full application and strong safety, and potential research directions include terahertz communication, artificial intelligence, super-large-scale MIMO technology and the like.

The development of modern mobile communication reveals that randomness and uncertainty of a wireless channel are key factors influencing wireless transmission quality, and radio waves of a transmitter interact uncontrollably with various objects on a transmission path in a transmission process to cause reduction of signal quality of a receiving end. The reconfigurable intelligent surface obviously improves the transmission performance of the system by artificially adjusting the wireless channel environment, and provides a new idea for the development of future wireless communication. Reconfigurable intelligent surfaces consist of a regular array of carefully designed electromagnetic elements, usually composed of metals, media and tunable elements. By controlling the adjustable elements in the electromagnetic unit, electromagnetic parameters of the reflected electromagnetic wave, such as phase and amplitude, are altered in a programmable manner. Compared with the traditional relay communication, the reconfigurable intelligent surface can work in a full-duplex mode and has higher spectrum utilization rate, a Radio Frequency (RF) link is not needed for the reconfigurable intelligent surface, large-scale power supply is not needed, and the reconfigurable intelligent surface has advantages in power consumption and deployment cost. Conventional reconfigurable smart surfaces are classified into reflective smart surfaces and transmissive smart surfaces, while novel reconfigurable smart surfaces can simultaneously reflect and transmit wireless signals on each cell.

The non-orthogonal multiple access technique is also a hot spot technique that can improve the spectrum efficiency. Currently, the main four schemes of the technology are NOMA, MUSA, SCMA and PDMA. Among them, NOMA is a non-orthogonal multiple access technique with power domain only application. The method adopts the linear superposition of the signal intensity of a plurality of users, has simple hardware structure and low technical performance, is not complicated based on a Serial Interference Cancellation (SIC) receiver, is the simplest one of non-orthogonal multiple access technologies, and is easy to combine with the prior communication system. However, the power domain user layer should not be too many, otherwise the system complexity will increase unnecessarily and the system performance will decrease rapidly, so that only 2 users are usually superimposed. In general, NOMA needs to work under the condition that the distance between a user and a base station is unequal, so that SIC demodulation is carried out by using the receiving power difference. Therefore, when the distances between different users and the base station are close, the error rate rises rapidly due to almost equal power, and the NOMA cannot operate.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a non-orthogonal multiple access method based on a novel reconfigurable intelligent surface, which can construct a wireless channel environment suitable for NOMA transmission under the condition that the distances between a user and a base station are equal, thereby effectively reducing the error rate of a receiving end and improving the system capacity.

The technical scheme is as follows: in order to achieve the above object, the present invention provides a non-orthogonal multiple access method based on a novel reconfigurable intelligent surface, comprising the following steps,

step 1, a base station sends pilot frequency and controls a novel reconfigurable intelligent surface to sequentially open M units, and meanwhile, the reflection and transmission coefficients of the novel reconfigurable intelligent surface are respectively set to be 1;

step 2, according to the transmitted pilot frequency, calculating the channels reflected and transmitted by M units between user A and user B and the base station in turnAndand will channelAndfeeding back to the base station;

step 3, the base station compares the channels in sequenceAndthe size of the mold of (1), screeningAnd storing the corresponding unit as a set S;

step 4, the base station closes the units except the set S and closes the units in the set SThe reflection and transmission coefficients are respectively set asAnd

step 5, user A and user B send signals respectivelyAndto a base station;

step 6, the base station sends x_B(n) as noise, demodulate x_A(n) obtaining the user A received signal

Step 7, the base station counteracts x_AAfter (n) interference, demodulate x_B(n) obtaining a received signal of user B

Further, in the present invention: in step 2, the user a receives the discrete baseband equivalent signal at the nth timeComprises the following steps:

wherein the content of the first and second substances,representing the channel at the nth moment between the 1 st element of the novel reconfigurable smart surface and the user A, alpha₁(n) is the reflection coefficient of the 1 st cell at the nth instant, where α₁(n)＝1，Representing the channel at the nth time between the base station and the 1 st unit of the novel reconfigurable intelligent surface, x_p(n) denotes a pilot signal transmitted by the base station at the nth time, w_A(n) additive white gaussian noise at the nth time of user a;

due to alpha₁(n) is 1, and x is known to the receiving end_p(n), the composite channel between the base station and the user A which is reflected by the novel reconfigurable intelligent surface can be obtained as follows:

wherein the content of the first and second substances,representing a composite channel between the base station and the user a via novel reconfigurable intelligent surface reflection.

Further, in the present invention: in the step 2, through the transmission of the 1 st unit of the novel reconfigurable intelligent surface, the discrete baseband equivalent signal received by the user B at the nth momentComprises the following steps:

wherein the content of the first and second substances,representing the channel, beta, at the nth moment between the 1 st element of the novel reconfigurable smart surface and the user B₁(n) is the transmission coefficient of the 1 st cell at the nth instant, where β₁(n)＝1，w_B(n) additive white gaussian noise representing the nth time of user B;

due to beta₁(n) is 1, and x is known to the receiving end_p(n), the composite channel transmitted by the novel reconfigurable intelligent surface between the base station and the user B can be obtained as follows:

wherein the content of the first and second substances,representing a composite channel transmitted between the base station and user B through the novel reconfigurable intelligent surface.

Further, in the present invention: in the step 2, the reflection coefficient and the transmission coefficient of the novel reconfigurable intelligent surface are respectively set to be 1, at the nth moment, the base station controls the novel reconfigurable intelligent surface to open the 1 st unit and close other units, so that the user A can obtain a discrete baseband equivalent signal which is received by the user A and reflected by the 1 st unit of the novel reconfigurable intelligent surfaceComprises the following steps:

channel estimation is performed at the receiving end and subtracted from the resultAnd obtaining a composite channel between the base station and the user A through the novel reconfigurable intelligent surface reflection.

Further, in the present invention: in the step 2, at the (n +1) th moment, the base station controls the novel reconfigurable intelligent surface to open the 2 nd unit and close other units, and at the moment, the user A receives the discrete baseband equivalent signal reflected by the 2 nd unit of the novel reconfigurable intelligent surfaceComprises the following steps:

wherein the content of the first and second substances,representing the channel, alpha, between the 2 nd element of the new reconfigurable smart surface and user A₂(n +1) is the reflection coefficient of the 2 nd unit of the novel reconfigurable intelligent surface at the n +1 th moment, and alpha₂(n+1)＝1，Represents the channel at the (n +1) th moment between the base station and the 2 nd unit of the novel reconfigurable intelligent surface, x_p(n +1) denotes a pilot signal transmitted by the base station at the (n +1) th time, w_A(n +1) represents additive white gaussian noise at the (n +1) th time of user a.

Further, in the present invention: in the step 2, due to alpha₂(n +1) ═ 1, and x is known to the receiving end_p(n) obtaining a composite channel between the base station and the user A via the novel reconfigurable intelligent surface reflectionComprises the following steps:

further, in the present invention: in the step 2, through the transmission of the 2 nd unit of the novel reconfigurable intelligent surface, the discrete baseband equivalent signal received by the user BComprises the following steps:

wherein the content of the first and second substances,representing the channel, beta, between the 2 nd element of the new reconfigurable smart surface and user B₂(n +1) is the reflection coefficient of the 2 nd unit of the novel reconfigurable intelligent surface at the n +1 th moment, and beta₂(n+1)＝1，w_B(n +1) represents additive white gaussian noise at the (n +1) th time of user B.

Further, in the present invention: in the step 2, due to beta₂(n +1) ═ 1, and x is known to the receiving end_p(n) obtaining a composite channel transmitted between the base station and user B through the novel reconfigurable intelligent surfaceComprises the following steps:

further, in the present invention: said step 6 further comprises that the base station receives the discrete baseband equivalent signal r at the nth time, assuming that the direct channel between the user and the base station is blocked_BS(n) is:

further, since the channel condition of user a is better, the base station will first transmit the signal x of user B_B(n) demodulating user A's signal x as noise_A(n) obtaining the demodulated user A received signal

Further, in the present invention: the step 7 further includes, based on the SIC technology, the base station firstly cancels the interference generated by the user a, and then demodulates the data of the user B, that is:

wherein, y_B(n) represents the received signal of user B after interference cancellation,to representThe symbol regenerated after the hard judgment or the soft judgment is finally obtained as the receiving signal of the user BComprises the following steps:

has the advantages that: compared with the prior art, the invention has the beneficial effects that: the invention combines the reconfigurable intelligent surface and the NOMA technology, and provides a novel wireless communication scheme, which constructs a wireless channel environment suitable for NOMA transmission by selecting a reflection unit and a transmission unit on the novel reconfigurable intelligent surface capable of reflecting and transmitting simultaneously under the special condition that the respective distances between two users and a base station are close or equal, thereby effectively reducing the error rate of a receiving end, improving the system capacity, having low calculation complexity and needing no additional device; in addition to novel reconfigurable intelligent surfaces that are both reflective and transmissive, the cell selection method of the present invention can also be applied to other kinds of reconfigurable intelligent surfaces, including reflective-only reconfigurable intelligent surfaces, hybrid reconfigurable intelligent surfaces with partial radio frequency links (RF), and the like.

Drawings

Fig. 1 is an overall flow diagram of a non-orthogonal multiple access method based on a novel reconfigurable intelligent surface, which is provided by the invention;

FIG. 2 is a NOMA principle schematic diagram of the novel reconfigurable intelligent surface of the present invention;

fig. 3 is a graph comparing error rates obtained by simulation based on the conventional method and the method of the present invention.

Detailed Description

The technical scheme of the invention is further explained in detail by combining the attached drawings:

the present invention may 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.

Referring to fig. 1, fig. 1 is a general flow chart of a non-orthogonal multiple access method based on a novel reconfigurable intelligent surface according to the present invention, which includes the following steps,

constructing a novel reconfigurable intelligent surface-assisted uplink narrow-band communication system, wherein a base station of the system comprises an antenna, the novel reconfigurable intelligent surface comprises M units, each unit can simultaneously reflect and transmit signals sent by the base station, and the reflection coefficient of the mth unit is alpha_mTransmission coefficient of beta_mM is 1, 2. Since each cell is a passive, passive reflective element, the reflection and transmission coefficients satisfy 0 ≦ α_m|≤1，0≤|α_m|≤1。

Specifically, referring to the illustration of fig. 2, in the present invention, both user a and user B have only 1 antenna for receiving the reflected signal, and the user is located in front of the novel reconfigurable intelligent surface, i.e., in the reflection area, and user a can receive the signal reflected by the novel reconfigurable intelligent surface; user B has 1 antenna, and the user is located novel reconfigurable intelligent surface's back, is located the transmission zone promptly, and user B can receive the signal through novel reconfigurable intelligent surface transmission. Because the user can be located novel reconfigurable intelligent surface's front and back both sides simultaneously, compare in the novel reconfigurable intelligent surface that the tradition can only the reflected signal, novel reconfigurable intelligent surface has enlarged coverage.

Step 1, a base station sends pilot frequency and controls a novel reconfigurable intelligent surface to sequentially open M units, and meanwhile, the reflection and transmission coefficients of the novel reconfigurable intelligent surface are respectively set to be 1; wherein, only 1 unit is started each time when the unit is started.

It is assumed that a direct channel between the base station and the user a is shielded by a barrier, only a reflection channel that the base station reflects to reach the user a through the novel reconfigurable intelligent surface exists, and because the user B is located behind the novel reconfigurable intelligent surface, only a transmission channel that the base station reaches the user B through the novel reconfigurable intelligent surface exists generally. Through a frequency flat fading channel, the user A receives the discrete baseband equivalent signal at the nth timeComprises the following steps:

wherein the content of the first and second substances,representing the channel at the nth moment between the 1 st element of the novel reconfigurable smart surface and the user A, alpha₁(n) is the reflection coefficient of the 1 st cell at the nth instant, where α₁(n)＝1，Representing the channel at the nth time between the base station and the 1 st unit of the novel reconfigurable intelligent surface, x_p(n) denotes a pilot signal transmitted by the base station at the nth time, w_A(n) represents additive white gaussian noise at the nth time of user a.

Assuming that the channel coherence time is much larger than the channel estimation and data transmission time, the channel can be considered to remain unchanged during transmission, i.e. the channel is independent of time n, so for simplicity of representation, the time index n of the relevant channel can be omitted in the following analysis. Due to alpha₁(n) is 1, and x is known to the receiving end_p(n), the composite channel between the base station and the user A which is reflected by the novel reconfigurable intelligent surface can be obtained as follows:

wherein the content of the first and second substances,representing a composite channel between the base station and the user a via novel reconfigurable intelligent surface reflection.

Meanwhile, through the transmission of the 1 st unit of the novel reconfigurable intelligent surface, the discrete baseband equivalent signal received by the user B at the nth momentComprises the following steps:

wherein the content of the first and second substances,representing the channel, beta, at the nth moment between the 1 st element of the novel reconfigurable smart surface and the user B₁(n) is the transmission coefficient of the 1 st cell at the nth instant, where β₁(n)＝1，w_B(n) represents additive white gaussian noise at the nth time of user B.

Due to beta₁(n) is 1, and x is known to the receiving end_p(n), the composite channel transmitted by the novel reconfigurable intelligent surface between the base station and the user B can be obtained as follows:

wherein the content of the first and second substances,representing a composite channel transmitted between the base station and user B through the novel reconfigurable intelligent surface.

Further, if the direct channel between the base station and the user a is not blocked, all units on the novel reconfigurable intelligent surface are closed first, and the direct channel is estimated, so that:

r_BU(n)＝h_BUx_p(n)+w_BU(n)

wherein r is_BU(n) represents a signal received through a direct channel between the user a and the base station, h_BUIndicating the direct channel between the base station and user A, w_BU(n) represents additive white gaussian noise of the direct channel.

Since the receiving end knows x_p(n), the estimated value of the direct channel is obtained as:

wherein the content of the first and second substances,is an estimate of the direct channel.

Furthermore, the reflection coefficient and the transmission coefficient of the novel reconfigurable intelligent surface are respectively set to be 1, at the nth moment, the base station controls the novel reconfigurable intelligent surface to open the 1 st unit and close other units, so that the user A can receive the discrete baseband equivalent signal reflected by the 1 st unit of the novel reconfigurable intelligent surfaceComprises the following steps:

channel estimation is performed at the receiving end and subtracted from the resultAnd obtaining a composite channel between the base station and the user A through the novel reconfigurable intelligent surface reflection.

Further, at the (n +1) th moment, the base station controls the novel reconfigurable intelligent surface to open the 2 nd unit and close other units, and at the moment, the user A receives the discrete baseband equivalent signal reflected by the 2 nd unit of the novel reconfigurable intelligent surfaceComprises the following steps:

wherein the content of the first and second substances,representing the channel, alpha, between the 2 nd element of the new reconfigurable smart surface and user A₂(n +1) is the reflection coefficient of the 2 nd unit of the novel reconfigurable intelligent surface at the n +1 th moment, and alpha₂(n+1)＝1，Represents the channel at the (n +1) th moment between the base station and the 2 nd unit of the novel reconfigurable intelligent surface, x_p(n +1) denotes a pilot signal transmitted by the base station at the (n +1) th time, w_A(n +1) represents additive white gaussian noise at the (n +1) th time of user a.

Due to alpha₂(n +1) ═ 1, and x is known to the receiving end_p(n +1), a composite channel reflected by a novel reconfigurable intelligent surface between the base station and the user A can be obtainedComprises the following steps:

at the same time, through novel reconstructionTransmission of No. 2 element of smart surface, discrete baseband equivalent signal received by user BComprises the following steps:

wherein the content of the first and second substances,representing the channel, beta, between the 2 nd element of the new reconfigurable smart surface and user B₂(n +1) is the reflection coefficient of the 2 nd unit of the novel reconfigurable intelligent surface at the n +1 th moment, and beta₂(n+1)＝1，w_B(n +1) represents additive white gaussian noise at the (n +1) th time of user B.

Due to beta₂(n +1) ═ 1, and x is known to the receiving end_p(n) obtaining a composite channel transmitted between the base station and user B through the novel reconfigurable intelligent surfaceComprises the following steps:

step 2, according to the transmitted pilot frequency, calculating the channels reflected and transmitted by M units between user A and user B and the base station in turnAndand will channelAndfeeding back to the base station;

specifically, based on the method in step 1, the receiving end can finally obtain the composite channel estimation between the base station and the user a through all unit reflections of the novel reconfigurable intelligent surfaceAnd composite channel estimation through all unit transmissions of novel reconfigurable intelligent surfaceAnd M is 1, 2. Obtained by the receiving endAndall fed back to the base station.

Step 3, the base station compares the channels in sequenceAndthe size of the mold of (1), screeningAnd storing the corresponding unit as a set S;

specifically, the base station compares the same cell sequentially from the start m being 1Andand screening out the size of the moldThe corresponding unit number isThe corresponding cell number is stored as set S. For example, ifThen S ═ {1,2,8 }.

And 4, carrying out data transmission, wherein the base station closes the units except the set S, and sets the reflection coefficients and the transmission coefficients of the units in the set S to be respectivelyAndwherein m belongs to S;

specifically, all units outside the set S are closed, the units corresponding to the serial numbers in the set S are kept open, and the reflection coefficients alpha of the units are kept open_mAnd a transmission coefficient beta_mRespectively setting as follows:

where angle (·) represents the operation of taking the phase angle, and j represents the unit of imaginary number.

Step 5, user A and user B send signals to the base station respectivelyAnd

since the reflection coefficient and the transmission coefficient remain unchanged during the data transmission phase, α_mAnd beta_mThe time sequence number n may be ignored. User A and user B are divided at the nth momentSending signals separatelyAndwherein, P_AAnd P_BRespectively representing the transmission power of user A and user B, and P_A＝P_B。

Step 6, the base station sends x_B(n) as noise, demodulate x_A(n) obtaining the user A received signal

The discrete baseband equivalent signal r received by the base station at the nth time is assumed to be blocked_BS(n) is:

further, since in set SIs greater thanSo that the channel condition of user a is better, the base station will first transmit user B's signal x_B(n) demodulating user A's signal x as noise_A(n) obtaining the demodulated user A received signal

Step 7, the base station counteracts x_AAfter (n) interference, demodulate x_B(n) obtaining a received signal of user B

Specifically, by using the SIC technology, the base station firstly cancels the interference generated by the user a, and then demodulates the data of the user B, that is:

wherein, y_B(n) represents the received signal of user B after interference cancellation,to representThe symbol regenerated after the hard judgment or the soft judgment is finally obtained as the receiving signal of the user BComprises the following steps:

in order to verify the beneficial effects of the invention, the following simulation experiment is carried out: the constructed novel reconfigurable intelligent surface comprises 128 units, each unit can simultaneously reflect and transmit signals, and the distance between a base station and the novel RIS is 50 meters. User A and user B respectively with novel reconfigurable intelligent surface distance 50 meters, user A and user B's signal transmission power is 30dBm together, promptly: p_A＝P_B＝1mW。

Assuming that a direct channel between the base station and the user is blocked, i.e. there is no direct channel, there is a rice channel between the base station and the novel reconfigurable intelligent surface and between the novel reconfigurable intelligent surface and the user, the rice factor is 10, and the path fading index PLE is 2.2. The reference distance is 1 meter and the path loss at the reference distance is-30 dB. Users A and B send QPSK signals on the same time frequency resource, and the base station counts the error rate of all received data. Under the traditional method, because the distances between the user A and the user B and the novel reconfigurable intelligent surface are equal, the receiving power of signals is close, and the traditional method adopting the reflection and transmission of all units has higher error rate and can hardly work.

Based on the novel reconfigurable intelligent surface-based non-orthogonal multiple access method provided by the invention, the channel of the user A is superior to the channel of the user B through the selection of the units, a propagation environment suitable for NOMA is constructed, the error rate is greatly reduced along with the reduction of the noise variance, and the transmission reliability is ensured. Referring to fig. 3, a schematic diagram of Bit Error Rate (BER) comparison obtained by simulation based on the conventional method and the method of the present invention is shown.

It should be noted that the above-mentioned examples only represent some embodiments of the present invention, and the description thereof should not be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, various modifications can be made without departing from the spirit of the present invention, and these modifications should fall within the scope of the present invention.