Non-orthogonal multiple access method and system with constructive interference assistance

Abstract

The invention provides a non-orthogonal multiple access method with constructive interference assistance, which comprises a base station, a near-end user closer to the base station and a far-end user farther from the base station, and the base station is equipped with a plurality of antennas; the base station transmits a superposed signal and communicates with a far-end user and a near-end user; the far-end user only decodes the far-end desired signal; the near-end user firstly decodes the far-end desired signal and then detects the near-end desired signal by adopting a continuous interference cancellation technology; modulating the superposed signal according to a quadrature phase shift keying modulation rule; receiving signals of the far-end user and the near-end user are calculated; interference signals which are considered to be harmful originally are reasonably utilized, and the amplitude and phase of the interference signals are adjusted, so that the interference signals have a constructive effect on expected signals, power gain is realized, received signals are helped to be far away from a decision boundary, and the reliability and stability of communication are improved in a complex environment.

Description

Technical Field

[0001] The present invention relates to the technical field of non-orthogonal multiple access, and specifically designs a non-orthogonal multiple access method and system with constructive interference assistance. Background Art

[0002] Non-orthogonal multiple access (NOMA) has been considered as a promising technology that can simultaneously serve multiple users in the same time / frequency / code domain resources. Specifically, in a NOMA system, the transmitter uses power domain multiplexing technology to send superimposed signals with different powers, while the receiver uses successive interference cancellation (SIC) technology to sequentially decode the user's signals [2]. Compared with traditional orthogonal multiple access (OMA), the NOMA system can simultaneously improve spectrum efficiency and communication fairness among users. However, the execution of SIC relies on powerful hardware and algorithm processing, which poses unprecedented challenges for most low-performance devices in future IoT systems. In addition, the improvement of communication fairness in NOMA systems is achieved through power allocation, and the utilization of this method provides limited gains. Fortunately, the use of constructive interference (CI) provides an opportunity for further breakthroughs in NOMA systems. Specifically, the essence of constructive interference (CI) lies in the joint development of the transmitted signal and channel state information (CSI), so that the interference signal can be constructively projected into the region of interest of the desired signal, thereby enriching the received power of the desired signal.

[0003] With the explosive growth in wireless communication users and the increasing bandwidth demand for various data services (such as high-definition video and virtual reality), the spectral efficiency of traditional orthogonal multiple access (NOMA) technologies is increasingly struggling to meet these demands. NOMA technology significantly improves spectral efficiency by multiplexing user signals in non-orthogonal dimensions, such as the power domain, allowing simultaneous service for multiple users. This has become a key technology in sixth-generation mobile communication systems. For example, in dense urban environments, where a large number of users simultaneously request data transmission, NOMA can more efficiently utilize limited spectrum resources and meet the communication needs of numerous users. In wireless communication scenarios, edge users often experience poor communication quality due to their long distance from the base station and significant signal propagation losses. NOMA technology can effectively improve the received signal quality and data transmission rate of edge users by allocating higher transmit power to them and, combined with techniques such as continuous interference cancellation, enhances their communication experience. For example, in remote mountainous areas or areas with weak signal coverage, NOMA can ensure relatively stable communication services for users in these locations. Real-world wireless communication environments are subject to complex factors such as multipath fading and shadowing, which can easily interfere with signal transmission, leading to reduced communication quality. Summary of the Invention

[0004] In response to the problems in the prior art, the present invention provides a non-orthogonal multiple access method and system with constructive interference assistance, the purpose of which is to help the received signal stay away from the decision boundary, thereby improving the reliability and stability of communication in complex environments.

[0005] A non-orthogonal multiple access method with constructive interference assistance includes a base station, a near-end user closer to the base station, and a far-end user farther away from the base station, wherein the base station is equipped with a plurality of antennas; and further includes the following steps:

[0006] Step 1: The base station transmits a superimposed signal and communicates with the far-end user and the near-end user;

[0007] Step 2: The far-end user only decodes the far-end desired signal; the near-end user first decodes the far-end desired signal and then uses successive interference cancellation technology to detect the near-end desired signal.

[0008] Step 3: Modulate the superimposed signal into:

[0009]

[0010] Among them, φ f and φ n Represents the phase of the orthogonal phase shift keying modulation rule sent to the far-end user and the near-end user, a f and a n are the power allocation coefficients for the far-end user and the near-end user, P S is the total transmit power of the base station, represents the user's quadrature phase shift keying modulation, x represents a constant amplitude, is the phase;

[0011] Step 4: Calculate the received signal of the remote user

[0012]

[0013] Calculate the received signal of the near-end user

[0014]

[0015] in, and Respectively represent the channels between the base station antenna and the far-end user and the near-end user, n f and n n All have mean 0 and variance σ 2 The complex Gaussian distribution of .

[0016] Further, the remote user first selects the antenna with the highest channel gain in the base station, while the near-end user selects the remaining antenna from the base station.

[0017] Furthermore, the superimposed signal includes a high-power far-end desired signal and a low-power near-end desired signal.

[0018] A non-orthogonal multiple access system assisted by constructive interference includes a base station, a near-end user closer to the base station, and a far-end user farther away from the base station, wherein the base station is equipped with a plurality of antennas; and further includes:

[0019] The near-end user and the far-end user each have a receiving unit for receiving the superimposed signal transmitted by the base station, a decoding unit for decoding the far-end desired signal, a modulation unit for modulating the superimposed signal, and a processing unit for calculating the respective received signals;

[0020] The near-end user also has a detection unit for detecting a near-end desired signal using a successive interference cancellation technique.

[0021] Further: the processing unit includes

[0022] A phase calculation unit for calculating the phase of quadrature phase shift keying modulation;

[0023] Used to calculate the mean is 0 and the variance is σ 2 Complex Gaussian distribution calculation unit of complex Gaussian distribution;

[0024] The second receiving unit is used to obtain the power allocation coefficient, the total transmission power of the base station, and the orthogonal phase shift keying modulation rule.

[0025] Furthermore, both the near-end user and the far-end user have a channel gain selection unit for calculating the channel gain of the antenna in the base station.

[0026] The beneficial effects of the present invention are as follows: by making rational use of interference signals that are originally considered harmful, and by adjusting the amplitude and phase of the interference signals, they are made to have a constructive effect on the desired signal, power gain is achieved, and the received signal is helped to stay away from the decision boundary, thereby improving the reliability and stability of communications in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of the present invention;

[0028] Figure 2 Models for traditional and CI-assisted NOMA systems;

[0029] Figure 3 The relationship between OP and SNR for users in CI-assisted NOMA and traditional NOMA systems;

[0030] Figure 4 The relationship between the average rate and signal-to-noise ratio of users in CI-assisted NOMA and traditional NOMA systems. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to the accompanying drawings. The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. The directional terms such as left, center, right, top, and bottom in the embodiments of the present invention are merely relative concepts or are based on the normal use state of the product, and should not be considered as restrictive.

[0032] A non-orthogonal multiple access method with constructive interference assistance includes a base station, a near-end user closer to the base station, and a far-end user farther away from the base station, wherein the base station is equipped with a plurality of antennas; and further includes the following steps:

[0033] Step 1: The base station transmits a superimposed signal and communicates with the far-end user and the near-end user. The superimposed signal includes a high-power far-end desired signal and a low-power near-end desired signal.

[0034] Step 2: According to the technical principles and signal superposition method of NOMA, the non-orthogonal transmission characteristics of NOMA allow signals from different users to be superimposed and transmitted in the same frequency band and at the same time. The base station sends the superimposed signal of the far-end user and the near-end user, so all users will receive the superimposed signal; the far-end user (with poor channel conditions) is allocated high power, and the near-end user (with good channel conditions) is allocated low power. Because the near-end user is close to the base station, the strength of the high-power signal received by the far user may be higher than its own low-power signal. At this time, if the near-end user directly decodes its own signal, it will be seriously interfered by the high-power signal of the far user. Therefore, the far user is decoded first. After successful decoding, the high-power signal of the far user is reconstructed and subtracted from the superimposed signal to obtain a pure near-end user signal; Therefore, the far-end user is first instructed to decode only the far-end desired signal. By decoding the far-end desired signal (i.e., the far-end user's high-power signal), the far-end user obtains communication data exclusive to the far-end user. The purpose is to extract the far-end user's information from the superimposed signal transmitted by the base station. Meanwhile, the near-end user first decodes the far-end desired signal to obtain the far-end user information. Due to the poor channel conditions of the far-end user and the high power allocated to it, the far-end user signal power is relatively large in the superimposed signal received by the near-end user. Only by first decoding and removing the far-end user signal can the near-end user reduce interference and successfully detect its own desired signal. Continuous interference cancellation technology is then used to detect the near-end desired signal, thereby eliminating the far-end user's high-power signal and obtaining a pure near-end user signal.

[0035] Step 3: Modulate the superimposed signal into:

[0036]

[0037] Among them, φ f and φ n Represents the phase of the orthogonal phase shift keying modulation rule sent to the far-end user and the near-end user, a f and a n are the power allocation coefficients for the far-end user and the near-end user, P S is the total transmit power of the base station, represents the user's quadrature phase shift keying modulation, x represents a constant amplitude, Phase; thereby sharing power domain reuse and SIC technology, step 3 will achieve the transition from "interference suppression" to "interference utilization" by introducing phase optimization based on step 2, while maintaining the spectrum efficiency advantage of NOMA and further improving system capacity, fairness and perception capabilities;

[0038] Step 4: Calculate the received signal of the remote user

[0039]

[0040] Calculate the received signal of the near-end user

[0041]

[0042] in, and Respectively represent the channels between the base station antenna and the far-end user and the near-end user, n f and n n All have mean 0 and variance σ 2 The complex Gaussian distribution of .

[0043] To improve the fairness of non-orthogonal multiple access users, the remote user first selects the antenna with the highest channel gain in the base station, while the near-end user selects the remaining antenna from the base station.

[0044] A non-orthogonal multiple access system assisted by constructive interference includes a base station, a near-end user closer to the base station, and a far-end user farther away from the base station, wherein the base station is equipped with a plurality of antennas; and further includes:

[0045] The near-end user and the far-end user each have a receiving unit for receiving the superimposed signal transmitted by the base station, a decoding unit for decoding the far-end desired signal, a modulation unit for modulating the superimposed signal, a detection unit for detecting the near-end desired signal using a successive interference cancellation technique, a channel gain selection unit for calculating the antenna channel gain in the base station, and a processing unit for calculating the respective received signals; the processing unit includes:

[0046] A phase calculation unit for calculating the phase of quadrature phase shift keying modulation;

[0047] Used to calculate the mean is 0 and the variance is σ 2 Complex Gaussian distribution calculation unit of complex Gaussian distribution;

[0048] The second receiving unit is used to obtain the power allocation coefficient, the total transmission power of the base station, and the orthogonal phase shift keying modulation rule.

[0049] In the Quadrature Phase Shift Keying (QPSK) modulation rule, A f Indicates remote user D f The signal-to-interference-plus-noise ratio (SINR) threshold point, the corresponding vector modulus is Among them, γ thf is the SINR threshold; B f Indicates remote user D f The received signal, combined with Figure 1 As shown, corresponding to the point on the complex plane, C f Receive signal edge for remote user The projection point of the direction;

[0050] Through simple projection analysis, Figure 1 As can be seen from the figure, if the received signal is in the shaded area, the interference can be effectively utilized; otherwise, destructive interference will occur; from a mathematical point of view, if Then the interference is constructive;

[0051] In addition, we can also observe the following derivation process:

[0052]

[0053] Among them, for the orthogonal phase shift keying modulation rule (QPSK), θ=π / 4, for the near-end user D n , the same method can be used to ensure that the interference is constructive interference; in the traditional non-orthogonal multiple access (NOMA) system, the remote user D f D f Still receives the signal from the near-end user D n In this context, we propose a scheme to further improve the fairness of NOMA users by considering constructive interference (CI). For the quadrature phase shift keying (QPSK) modulation rule, the user's modulation symbol can be expressed as where x represents a constant amplitude, is the phase;

[0054] Specifically, the transmit signal is modulated as where φ f and φ n φn They are sent to the remote user D f and the near-end user D n The phase of the quadrature phase shift keying (QPSK) symbol; then, the remote user D f The received signal at is expressed as:

[0055]

[0056] If the interference signal can push the received symbol into the constructive region, the interference is constructive. First, consider a simple example, where the desired symbol x comes from the binary phase shift keying (BPSK) constellation diagram. The received signal can be expressed as: y = x + i + n = r + n, where i is the interference signal, r is the noise-free received signal, and n is the additive noise at the receiving end. In this case, the noise-free received signal r = x + i > x. Compared with the original data symbol x, the interference pushes r away from the detection threshold of the binary phase shift keying (BPSK). In this case, the interference signal i contributes to the useful signal power and is constructive interference.

[0057] According to the CI principle, the transmit precoding can be designed to exert constructive interference on the desired symbol; when the precoding vector condition Make the interference constructive so that when the interference is constructively aligned with the desired signal, all interference contributes constructively to the desired signal. Therefore, the expression for signal-to-interference-plus-noise ratio (SINR) can be modified to incorporate constructive interference.

[0058] At this time, user D f The received signal-to-noise ratio (SNR) at is expressed as

[0059] By comparing the received signal-to-noise ratio (SNR) of the two schemes, the constructive interference (CI)-assisted NOMA scheme proposed in this invention has a significantly improved SNR compared with the traditional non-orthogonal multiple access scheme. The received signal-to-noise ratio (SNR) directly reflects the signal quality and communication reliability. The higher the SNR, the better the signal quality and the lower the bit error rate, which improves the performance of far users without negatively affecting the performance of near users.

[0060] Similar to the constructive interference fairness enhancement scheme, the constructive interference feasibility enhancement scheme focuses on the near-end user D n Specifically, to alleviate the significant challenges faced by the successive interference cancellation (SIC) technique, we use the CI from the far-end user D f constructively utilize the high-power interference signal to help the near-end user D n ; Therefore, the transmitted signal is modulated to Near-end user D n The signal received at is expressed as:

[0061]

[0062] Near-end user D n The received signal-to-noise ratio and constructive condition are expressed as

[0063] Similarly, at the near end user D n The received signal-to-noise ratio at the location is greater than that of traditional non-orthogonal multiple access schemes, which improves the communication performance of near-end users. In addition, constructive interference (CI) is achieved through traditional CoMA. Since the superimposed signal and the data signal are aligned in CoMA, the received symbols will appear in the correct constellation area. Therefore, there is no need for channel equalization, nor is there any need to use SIC technology at the receiver to eliminate interference symbols, thereby simplifying the signal processing process at the receiver.

[0064] When the present invention is applied in an urban environment with high-rise buildings, since the signal is easily blocked and reflected by buildings, the constructive interference assisted NOMA technology can better cope with this situation. Modern communications cover many different types of services, such as voice calls that are sensitive to delay, video streams with high data rate requirements, and industrial control with strict reliability requirements; non-orthogonal multiple access and constructive interference assisted NOMA technology can flexibly adjust power allocation, interference management strategies, etc. according to the characteristics of different services, provide more adaptive communication services for diversified services, and meet the diverse needs of different users and application scenarios.

[0065] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A non-orthogonal multiple access method with constructive interference assistance, comprising a base station, a near-end user closer to the base station, and a far-end user farther away from the base station, wherein the base station is equipped with multiple antennas; characterized in that: The following steps are also included: Step 1: The base station transmits a superimposed signal and communicates with the far-end user and the near-end user; Step 2: The far-end user only decodes the far-end desired signal; the near-end user first decodes the far-end desired signal and then uses successive interference cancellation technology to detect the near-end desired signal. Step 3: Modulate the superimposed signal into: Among them, φ f and φ n Represents the phase of the orthogonal phase shift keying modulation rule sent to the far-end user and the near-end user, a f and a n are the power allocation coefficients for the far-end user and the near-end user, P S is the total transmit power of the base station, represents the user's quadrature phase shift keying modulation, x represents a constant amplitude, is the phase; Step 4: Calculate the remote user's received signal y SDf : Calculate the received signal of the near-end user in, and Respectively represent the channels between the base station antenna and the far-end user and the near-end user, n f and n n All have mean 0 and variance σ 2 The complex Gaussian distribution of .

2. The non-orthogonal multiple access method with constructive interference assistance according to claim 1, wherein: The far-end user first selects the antenna with the highest channel gain from the base station, while the near-end user selects the remaining antenna from the base station.

3. The non-orthogonal multiple access method with constructive interference assistance according to claim 1, wherein: The superimposed signal includes a high-power far-end desired signal and a low-power near-end desired signal.

4. A non-orthogonal multiple access system assisted by constructive interference, comprising a base station, a near-end user closer to the base station, and a far-end user farther away from the base station, wherein the base station is equipped with a plurality of antennas; characterized in that: Also includes: The near-end user and the far-end user each have a receiving unit for receiving the superimposed signal transmitted by the base station, a decoding unit for decoding the far-end desired signal, a modulation unit for modulating the superimposed signal, and a processing unit for calculating the respective received signals; The near-end user also has a detection unit for detecting a near-end desired signal using a successive interference cancellation technique.

5. The non-orthogonal multiple access system assisted by constructive interference according to claim 4, characterized in that: The processing unit includes: A phase calculation unit for calculating the phase of quadrature phase shift keying modulation; Used to calculate the mean is 0 and the variance is σ 2 Complex Gaussian distribution calculation unit of complex Gaussian distribution; The second receiving unit is used to obtain the power allocation coefficient, the total transmission power of the base station, and the orthogonal phase shift keying modulation rule.

6. The non-orthogonal multiple access system assisted by constructive interference according to claim 4, characterized in that: Both the near-end user and the far-end user have a channel gain selection unit for calculating the channel gain of the antenna in the base station.

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