A bidirectional relay NOMA transmission method based on network coding and backscattering

Abstract

The present invention discloses a bidirectional relay NOMA transmission method based on network coding and backscattering, including: setting two cellular users and a relay user without direct links between each other, and distributing a backscattering device cluster around each of the two cellular users; in the first time slot, the cellular users respectively perform power domain superposition coding on the signals they need to send to the relay user and the other cellular user, and broadcast them to the relay user; at the same time, the cellular users receive the signals reflected by the backscattering devices around them; in the second time slot, the relay user encodes the signals that the two cellular users need to send to each other into a composite signal through the physical layer network coding technology, and uses the downlink NOMA to send the composite signal and its own signal to the cellular user; while the cellular user and the relay user communicate in pairs, the signals from the surrounding backscattering devices are decoded. The present invention can expand the communication coverage and improve the system spectrum efficiency.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and in particular to a bidirectional relay NOMA transmission method based on network coding and backscattering. Background Art

[0002] In order to promote the development of 6G cellular IoT, future wireless communication systems must achieve excellent performance, including higher spectrum efficiency, energy efficiency, large-scale connectivity, and wide-area coverage. In the actual deployment of cellular IoT communication systems, IoT terminal devices often face serious problems such as signal attenuation and insufficient coverage. Therefore, in order to support the explosive growth of device access in future 6G scenarios, effective solutions are urgently needed to improve key performance such as transmission rate and spectrum efficiency.

[0003] Physical layer network coding is a technology that directly encodes and decodes signals at the physical layer of wireless communications. By utilizing the superposition characteristics of electromagnetic waves, the signals sent by multiple users are naturally superimposed in the wireless channel and then processed, thereby reducing the number of transmissions and improving spectrum efficiency.

[0004] NOMA-based two-way relay transmission is a communication technology that enables two-way information exchange between two user devices through relay nodes. Unlike traditional one-way relays, which may cause spectrum efficiency loss due to information forwarding and repeated transmission, the two-way relay strategy can use the user's prior information to eliminate potential interference and allow two-way data transmission within limited time and frequency resources. The relay node combines and forwards the two-way signals through collaborative processing, and provides superior spectrum efficiency and coverage.

[0005] Existing two-way relay communication systems usually only consider cellular signal transmission, and have not yet studied how to integrate the transmission of cellular signals and IoT signals. In addition, due to the heterogeneous rates of cellular and IoT signals, the existing NOMA-based two-way relay scheme still faces many challenges when directly applied to cellular IoT. Backscatter technology transmits information by modulating and reflecting ambient radio frequency signals, allowing backscatter devices to share the same spectrum resources with existing cellular devices. Thanks to its extremely low energy consumption and simple hardware design, backscatter technology is conducive to solving the diverse performance requirements of cellular IoT.

[0006] Therefore, studying the bidirectional relay NOMA transmission method based on network coding and backscattering is of great value for improving the performance of wireless communication systems and optimizing system resource allocation. It has theoretical and practical significance for coping with the continued growth of future information and communication needs and promoting the innovative development of wireless communication technology.

[0007] The invention with publication number CN116760444A discloses a relay communication method, relay communication device, network equipment, terminal and medium, which enables cellular network terminals to achieve backscattering IoT assisted communication through the fusion of backscattering and cellular networks. However, the invention cannot solve the technical problem of difficulty in improving the system spectrum efficiency.

[0008] The invention with publication number CN118381555B discloses a direct transmission and relay cooperative transmission method based on environmental backscattering, which retains the inherent advantage of direct transmission and relay cooperative transmission system in expanding cellular communication coverage while improving system spectrum efficiency and communication reliability. However, the invention must have a base station participating in the information transmission scenario, that is, the base station serves all downlink users, and only realizes information exchange between some nodes in the system during the transmission process, and only involves simple downlink NOMA cellular information transmission and uplink IoT NOMA information transmission. The two are a simple cascade combination, and the effect of improving communication coverage and system spectrum efficiency is limited. Summary of the invention

[0009] The purpose of the present invention is to provide a bidirectional relay NOMA transmission method based on network coding and backscattering, aiming to expand the communication coverage and improve the system spectrum efficiency.

[0010] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0011] The present invention discloses a bidirectional relay NOMA transmission method based on network coding and backscattering, the method comprising the following steps:

[0012] Set up two cellular users without direct links between each other and a relay user, and distribute a backscatter device cluster around each of the two cellular users;

[0013] In the first time slot, the cellular users respectively perform power domain superposition encoding on the signals they need to send to the relay user and the other cellular user, and broadcast them to the relay user; at the same time, the cellular users receive the signals reflected by the backscattering devices around them;

[0014] In the second time slot, the relay user encodes the signals that the two cellular users need to send to each other into a composite signal through physical layer network coding technology, and uses downlink NOMA to send the composite signal together with its own signal to the cellular user; while the cellular users and relay users communicate with each other, they decode the signals from the surrounding backscatter devices.

[0015] Furthermore, the cellular users all have full-duplex capability and are equipped with a single antenna, and the relay users all have half-duplex capability and are equipped with a single antenna.

[0016] Furthermore, the first time slot and the second time slot are of equal length.

[0017] Furthermore, one of the cellular users With relay users The channel quality between two cellular users is worse than that of another cellular user. With relay users The channel quality between.

[0018] Furthermore, in the case where there is a difference in channel quality between the cellular user and the relay user, the information transmission process includes the following steps:

[0019] In the first time slot, cellular users and cellular users All operate in full-duplex mode. According to the downlink NOMA, cellular users To relay users and the backscatter devices in cluster A broadcast the relay user and cellular users The power domain superposition coded signal of the required information, cellular users To relay users and the backscatter devices in cluster B broadcast the relay user and cellular users The power domain of the required information is superimposed on the coded signal; cluster A and cluster B surround the cellular users respectively and cellular users ;

[0020] The backscatter devices in cluster A and cluster B receive the cellular RF signals of the cellular users around them, and use backscatter modulation to reflect the signals containing their own information to the cellular users and relay users around them. , cellular users and cellular users Receive and decode the backscatter signals from the backscatter devices in cluster A and cluster B respectively, and relay the signals to the user Receive and decode the signals from two cellular users and the reflected signals from the backscatter devices in the two clusters;

[0021] In the second time slot, the relay user Physical layer network coding is used to convert the decoded first time slot into a cellular user To cellular users Information and cellular users To cellular users Information Encoded as a composite signal , according to downlink NOMA, to cellular users and cellular users The broadcast downlink power domain superimposed coded signal contains a composite signal and a relay user Need to be delivered to cellular users and cellular users signal of information;

[0022] The backscattering devices in cluster A and cluster B modulate their own information to the data from the relay user. The RF signal is then reflected to the surrounding cellular users. and cellular users , two cellular users receive signals from the relay user The signal and the backscattered signals of the surrounding backscattering device clusters are decoded.

[0023] Furthermore, in the first time slot, the cellular user and cellular users Reflected signals from respective surrounding backscattering device clusters are received and decoded using a serial interference cancellation algorithm and maximum ratio combining technology;

[0024] The relay user Receive signals from two cellular users and reflected signals from backscatter devices in two clusters and decode them sequentially using a serial interference cancellation algorithm: Cellular users To cellular users The information carrying signal, cellular user To relay user The information carrying signal, cellular user To cellular users The information carrying signal and cellular users To relay user The information-carrying signal.

[0025] Furthermore, in the second time slot, the cellular user Receive from relay user The signal and the reflected signal of the backscattering device cluster B around it are combined with the composite signal and the carrier relay user according to the downlink NOMA. To cellular users The signal and carrier relay users of the transmitted information To cellular users The signals of the transmitted information are decoded sequentially;

[0026] After decoding, cellular users Again, XOR operation , restore cellular users Delivered to cellular users The information-carrying signal .

[0027] Furthermore, in the second time slot, the cellular user Receive from relay user The signal and the reflected signal of the backscattering device cluster A around it are decoded in turn by the serial interference cancellation algorithm according to the downlink NOMA. To cellular users The signal of the transmitted information carries the relay user in this decoding process To cellular users The signal conveying the information is considered interference;

[0028] After decoding, cellular users Again, XOR operation , restore cellular users Need to be delivered to cellular users The information-carrying signal .

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] First, the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention retains the coverage performance advantages of the traditional bidirectional relay transmission method based on non-orthogonal multiple access, while further improving the system traversal and rate.

[0031] Second, the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention adopts a separate design, that is, the backscattering device and the cellular user are independent devices. Compared with the traditional separate design scheme that only contains a single cluster or a single backscattering device and is difficult to directly apply to the scenario considered by this method, this method simultaneously considers multiple backscattering device clusters participating in information transmission, and each cluster has any number of backscattering devices.

[0032] Third, compared with the traditional method that considers the scenario of information transmission with the participation of base stations, the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention considers the situation without base stations, and realizes the exchange of information between all cellular users, constructing a D2D (end-to-end) self-organizing two-way communication network without base stations, and at the same time realizes the communication between all backscattering devices and cellular users at the same time.

[0033] Fourth, the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention designs a new layered hybrid NOMA transceiver criterion (first time slot) and a multi-signal NOMA transceiver criterion based on physical layer network coding (second time slot), and then forms a transmission protocol completed by this method, thereby achieving the transmission of more signals in a limited time slot. At the same time, by utilizing physical layer network coding and prior information, the number of serial interference elimination, that is, the complexity, is reduced to a certain extent.

[0034] Fifth, the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention can be used for D2D (end-to-end) self-organizing bidirectional communication networks without base stations, and is particularly suitable for application scenarios with a small communication range, such as smart home interconnection.

[0035] Sixth, the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention, compared with the traditional scheme that only considers the transmission scenario of a single node and a single cluster, the present invention considers multiple clusters, and the cluster can support any number of backscattering devices, and the transmission model is more complex. At the same time, compared with the traditional scheme, the increase in the number of backscattering devices in the method of the present invention provides a more significant multipath gain for the receiving end of the reflected signal, thereby achieving improved transmission performance in more complex scenarios.

[0036] Seventh, the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention, compared with the traditional scheme in which all users in the system work in half-duplex mode except the base station works in full-duplex mode, all cellular users of the present invention have full-duplex capability, achieving higher communication efficiency and smaller latency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flowchart of a bidirectional relay NOMA transmission method based on network coding and backscattering provided in Example 1 of the present invention;

[0038] Figure 2 is a schematic diagram of a transmission method for a first time slot and a second time slot according to an embodiment;

[0039] Figure 3 is a curve diagram of system traversal and rate versus transmit power P for case 1 (perfect serial interference cancellation) described in Example 1;

[0040] Figure 4 is a curve diagram of system traversal and rate versus transmit power P for situation 2 (serial interference cancellation is imperfect) described in embodiment 1;

[0041] Figure 5is a curve diagram showing changes in system traversal and rate gain with transmission power P of the method of the present invention described in Example 2 compared with a conventional bidirectional relay transmission method based on non-orthogonal multiple access;

[0042] Figure 6 It is a curve diagram showing the variation of system traversal and rate gain with transmission power P of the method in the present invention described in Example 2 compared with traditional orthogonal multiple access. DETAILED DESCRIPTION

[0043] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0044] The present invention provides a bidirectional relay NOMA transmission method based on network coding and backscattering, comprising:

[0045] A transmission network model based on network coding and backscattering bidirectional relay NOMA transmission method is set up, which includes two cellular users and , a relay user and two clusters of backscatter devices surrounding cellular users A and B ; The information transmission process is divided into two time slots of equal length, namely the first time slot and the second time slot;

[0046] In the first time slot, the cellular user and Use downlink NOMA and relay users respectively Perform direct communication while backscattering device clusters A The backscatter device reflects the signal carrying its own information to and , while backscattering the device cluster B The backscatter device reflects the signal carrying its own information to and ;

[0047] In the second time slot, the relay user The information received in the first time slot and needed to be transmitted to each other by two cellular users is encoded into a composite signal through the physical layer network coding technology, and transmitted to the cellular users at both ends together with their own information; the cellular users and cellular users Through relay users Communication is achieved through forwarding and information of surrounding backscatter devices is collected.

[0048] Example 1

[0049] Figure 1It is a flowchart of a bidirectional relay NOMA transmission method based on network coding and backscattering in an embodiment of the present invention.

[0050] See also Figure 1 The method of this implementation specifically includes the following steps:

[0051] A network model of a two-way relay NOMA transmission method based on network coding and backscattering is set up, which includes two cellular users and , a relay user and two clusters of backscatter devices surrounding cellular users A and B ; The information transmission process is divided into two time slots of equal length, namely the first time slot and the second time slot;

[0052] In the first time slot, the cellular user and All operate in full-duplex mode. According to the downlink NOMA, To relay users and clusters A The backscatter device broadcasts the relay user and cellular users The power domain superposition coded signal of the required information, To relay users and clusters B The backscatter device broadcasts the relay user and cellular users The power domain superposition coded signal of the desired information;

[0053] The cluster A and B The backscatter devices in the network receive the cellular users around them. or The cellular radio frequency signal is modulated by environmental backscatter to reflect the signal containing its own information to the surrounding cellular users. or and relay users , the cellular user and Receive data from backscatter device clusters A and backscatter device clusters B The backscattered signal of the backscattering device is decoded and the relay user Receive and decode the signals from the two cellular users and the reflected signals from the backscattering devices in the two clusters;

[0054] In the second time slot, the relay user Physical layer network coding is used to convert the decoded first time slot Pass to Information and Pass to Information Encoded as a composite signal , according to the downlink NOMA, to the user and The broadcast downlink power domain superimposed coded signal includes a composite signal and a signal carrying Need to be delivered to and signal of information;

[0055] The backscatter device cluster A and B The device in the relay modulates its own information to the The RF signal is then reflected to the surrounding cellular users. and , the two cellular users and Receive from relay users The signal and the backscattered signals of the surrounding backscattering device clusters are decoded.

[0056] Optionally, in a specific embodiment, the following specific steps are included:

[0057] Step 1: Set up a two-way relay NOMA transmission network model based on network coding and backscattering, that is, a cell containing multiple cellular users and backscattering devices, and select two cellular users and , a relay user and two backscatter device clusters around a cellular user, where there is less interference between the cellular user and the relay user and they can communicate directly, while the two cellular users cannot communicate directly due to deep fading or severe obstacles; in this model, each node is equipped with a single antenna and each cellular user has full-duplex capability.

[0058] The information transmission process is divided into two time slots of equal length, namely the first time slot and the second time slot. Figure 2 shown.

[0059] definition represents the first time slot, Indicates the second time slot; definition and They are Send to and The information-carrying signal, and They are Send to and Information-carrying signal; signal and Carrying respectively Towards and Transmitted information; cluster A and B There are K and N A backscatter device and The surrounding backscatter devices are marked as and ;node i and j The distance, channel coefficient and channel gain between them are expressed as , and ,in , , , . represents the parameters of the exponential distribution, modeled from large-scale fading distance and unit reference gain. is the path loss factor, represents the channel gain per unit distance. Without loss of generality, we set , and the backscatter signal period is the cellular signal period L times; in addition, all wireless links experience Rayleigh block fading channels and have a mean of zero and a variance of Additive white Gaussian noise.

[0060] Step 2: In the first time slot, Operates in full-duplex mode and superimposes coded signals based on the downlink NOMA broadcast power domain

[0061] (1);

[0062] in and Respectively and The power allocation coefficient is and , for of transmission power.

[0063] Step 3: In the first time slot, the backscatter device Use backscatter modulation to Loaded onto the incoming cellular RF signal and then reflected back .

[0064] At this time, cellular users The received signal in the first time slot can be expressed as:

[0065] (2);

[0066] in It is a backscatter device The reflection coefficient in the first time slot, Indicated in The self-interference channel caused by full-duplex at represents the residual self-interference level, is additive Gaussian white noise;

[0067] Assuming a cluster of backscatter devices A Backscatter devices in the Indexing and sorting, based on uplink NOMA, first time slot backscatter device cluster A The corresponding reflection coefficient of the backscattering device should satisfy .

[0068] Step 4: Due to cellular users Known , so the serial interference cancellation and maximum ratio combining can be used to Perform sequential decoding. Cellular users decoding The signal-to-interference-noise ratio can be expressed as:

[0069] (3);

[0070] in, To send the signal-to-noise ratio, Represents the residual interference level due to imperfect serial interference cancellation. and They represent perfect serial interference cancellation and no serial interference cancellation, respectively.

[0071] Step 5: In the first time slot, Operates in full-duplex mode and transmits superposition coded signals according to downlink NOMA , power allocation coefficient and satisfy and ;

[0072] The index of backscatter devices is based on , so according to uplink NOMA, the first time slot backscatters the device The reflection coefficients should be in descending order. arrangement.

[0073] Step 6: In the first time slot, backscatter device Using backscatter modulation, the reflected The cellular radio frequency signal will Transmission to cellular users , so in cellular users The received signal at can be expressed as:

[0074] (4);

[0075] In the formula, Cellular user The self-interference channel at represents the residual self-interference level, yes The reflection coefficient, represents additive white Gaussian noise, For cellular users of transmission power.

[0076] Step 7: In the first time slot, due to the cellular user Known , so the serial interference cancellation and maximum ratio combining can be used to Perform sequential decoding. Cellular users decoding The signal-to-interference-noise ratio can be written as

[0077] (5);

[0078] in, For cellular users The transmit signal-to-noise ratio at Represents the residual interference level caused by imperfect series interference cancellation.

[0079] Step 8: In the first time slot, relay user Working in receiving mode, the corresponding receiving signal can be written as

[0080] (6);

[0081] in Represents additive Gaussian white noise, and based on the step-by-step hybrid NOMA transceiver criterion, the first step is to determine the total transmit power of the cellular user according to the uplink NOMA: In the second step, the power allocation coefficients of the two cellular users when sending power domain superimposed coded signals are determined according to the prerequisite of downlink NOMA and whether relay forwarding is required. Therefore, the power allocation coefficients of each signal and the transmission power of the two cellular users should satisfy the relationship . Relay User According to downlink NOMA, serial interference cancellation is used to , , and For decoding, the corresponding signal to interference noise ratio can be expressed as

[0082] (7);

[0083] (8);

[0084] (9);

[0085] (10);

[0086] in, and represents the equivalent channel gain, , and All of them represent the residual interference level caused by imperfect serial interference cancellation. and It can be regarded as a multipath link, which improves the relay user The signal-to-interference-to-noise ratio of each signal is decoded to establish a reciprocal relationship between backscatter devices and cellular users.

[0087] Step 9: In the second time slot, relay user Combined with physical layer network coding broadcast superposition signal

[0088] (11);

[0089] The composite signal , represents the XOR operator, For relay users The transmission power at , and is the power allocation coefficient of the corresponding carrier signal;

[0090] Transmitted via direct link and In contrast, the composite signal transmitted over a two-hop link With stricter decoding requirements. According to downlink NOMA, the power allocation coefficient should satisfy and .

[0091] Step 10: In the second time slot, backscatter device and Using backscatter modulation and The RF signals are respectively and Send your own information and ;

[0092] Since backscatter device clusters A Backscatter devices in the Indexing and sorting, based on uplink NOMA, second time slot backscatter device cluster A The corresponding reflection coefficient of the backscattering device should satisfy ;

[0093] Backscatter device clustering B The index of backscatter devices is based on , so according to uplink NOMA, the second time slot backscatter device The reflection coefficients should be in descending order. arrangement;

[0094] Therefore, the two cellular users in the second time slot and The received signals at can be expressed as:

[0095] (12);

[0096] (13);

[0097] in and represents additive white Gaussian noise.

[0098] Step 11: In the second time slot, due to the cellular user Known The prior information and the decoded , You can decode first , and then through the operation Restore signal ;

[0099] Taking into account The XOR operation is perfect for cellular users decoding and The signal-to-interference-noise ratio can be expressed as

[0100] (14);

[0101] (15);

[0102] in for The transmit signal-to-noise ratio at , Decoding The non-perfect serial interference cancellation coefficient when .

[0103] Step 12: In the second time slot, the cellular user First of all Decode it and then use To restore ;

[0104] Cellular users Decode sequentially , and The signal-to-interference-noise ratio can be written as:

[0105] (16);

[0106] (17);

[0107] (18);

[0108] in , and Decoding and The corresponding non-perfect serial interference cancellation coefficients.

[0109] To verify the beneficial effects of the present invention, the following steps will be specifically implemented:

[0110] Set the transmit power parameters P To unify the transmission power of each node, for each user node there are: as well as ,in , and is the power ratio of each node. In this embodiment, and .parameter , , and and are set to , , and The residual self-interference level is set to The power allocation coefficient of the two time slots is defined as , , , , , ,as well as The distance configuration is as well as . Backscatter device cluster A and B The backscatter devices in and The backscatter devices are evenly placed in a radius of 1 to 5 m, and the number of backscatter devices is set to K = N =4. The distances from each backscatter device to the corresponding user in the two clusters are set to and In addition, without loss of generality, for a unified representation, we set and To uniformly identify backscatter device clusters A and B The reflection coefficient of the device in the setting parameters To uniformly represent the imperfect serial interference cancellation coefficient in the decoding process. In this embodiment, the serial interference cancellation algorithm used in the process of each user decoding the received signal is divided into the following two cases:

[0111] Case 1: Serial interference cancellation is perfect, i.e. setting is equal to 0;

[0112] Case 2: Serial interference cancellation is not perfect, setting The three values ​​of , and .

[0113] Figure 3 and Figure 4 The method described in this embodiment shows the traversal and rate of the transmission power parameter under two decoding conditions, case 1 and case 2. PThe black symbol lines in the two figures represent the simulation values ​​of the traversal and rate of the transmission method described in this embodiment, and the blue symbol lines and the green symbol lines represent the traversal and rate of the traditional bidirectional relay transmission method based on non-orthogonal multiple access and the traditional orthogonal multiple access method, respectively. In the legend, TWR-NOMA represents the bidirectional relay transmission method based on non-orthogonal multiple access, and OMA represents the orthogonal multiple access method. It can be seen from the figure that, affected by the multipath gain brought by the bidirectional information and the backscattering device, the method proposed in the present invention can achieve better system traversal and rate performance than the traditional bidirectional relay transmission method based on non-orthogonal multiple access and the orthogonal multiple access method in the above two cases. For the perfect serial interference elimination scenario, the method proposed in this article is as P As the number of nodes increases, the system ergodic sum rate increases monotonically. However, if the imperfect serial interference cancellation is considered, the ergodic sum rate curves of the transmission method in this paper and the traditional bidirectional relay transmission method based on non-orthogonal multiple access are relatively large. P tends to be stable when P When is larger, the signal-to-noise ratio of each signal tends to be constant. For example: Under condition 1, P When the power consumption is 10 dBm, the traversal rate of the bidirectional relay NOMA transmission method based on network coding and backscattering of the present invention is 14.7 bps / Hz, while the traversal rate of the traditional bidirectional relay transmission method based on non-orthogonal multiple access is 7.0 bps / Hz, and the traversal rate of the orthogonal multiple access method is 5.2 bps / Hz.

[0114] Example 2

[0115] To further evaluate the performance gain of this method against different comparison methods, this embodiment assumes that the imperfect serial interference cancellation coefficient The value of is 0, and , other parameters are consistent with the second case in Example 1, by changing the transmission power parameter P With the non-perfect serial interference cancellation coefficient , the traversal and rate gains brought by the transmission method described in the present invention are verified.

[0116] Figure 5 and Figure 6 The traversal and rate gains achieved by the method proposed in the present invention compared with the conventional bidirectional relay transmission method based on non-orthogonal multiple access and the conventional orthogonal multiple access method at the whole system level are respectively shown. Figure 5 The traversal and rate performance of the proposed method are better than those of the conventional bidirectional relay transmission method based on non-orthogonal multiple access in all power ranges. P As is gradually increased, a decrease in relative traversal and rate gains is observed. Figure 6In the example, the proposed method also achieves better ergodic and rate performance compared to conventional orthogonal multiple access. For perfect and imperfect serial interference cancellation, the ergodic and rate gains of the proposed method relative to conventional orthogonal multiple access initially increase with P The increase was slightly due to the P >-20dBm. Figure 5 and Figure 6 The traversal and rate gains in P When , it decreases slightly, but because the traversal and rate gains of the entire system are driven by the bidirectional information in the system, its gain value is still positive. Figure 5 and Figure 6 , it can be seen that with The value decreases, that is, the closer the serial interference elimination situation is to the perfect situation, the traversal and rate gains of the proposed method are improved to varying degrees at different transmission powers compared with the traditional bidirectional relay transmission method based on non-orthogonal multiple access and the traditional orthogonal multiple access method. For example: in the serial interference elimination coefficient , transmit power parameters P =10 dBm, the traversal and rate gain values ​​achieved by the proposed method compared with the traditional bidirectional relay transmission method based on non-orthogonal multiple access are 107.6%, and the traversal and rate gain values ​​achieved by this method compared with the traditional orthogonal multiple access are up to 183.1%.

[0117] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0118] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A bidirectional relay NOMA transmission method based on network coding and backscattering, characterized in that: The method comprises the following steps: Set up two cellular users without direct links between each other and a relay user, and distribute a backscatter device cluster around each of the two cellular users; In the first time slot, the cellular users respectively perform power domain superposition encoding on the signals they need to send to the relay user and the other cellular user, and broadcast them to the relay user; at the same time, the cellular users receive the signals reflected by the backscattering devices around them; In the second time slot, the relay user encodes the signals that the two cellular users need to send to each other into a composite signal through the physical layer network coding technology, and uses downlink NOMA to send the composite signal together with its own signal to the cellular user; while the cellular user and the relay user communicate with each other, they decode the signals from the surrounding backscatter devices; One of the cellular users With relay users The channel quality between two cellular users is worse than that of another cellular user. With relay users Channel quality between In the case where the channel quality between the cellular user and the relay user is different, the information transmission process includes the following steps: In the first time slot, cellular users and cellular users All operate in full-duplex mode. According to the downlink NOMA, cellular users To relay users and the backscatter devices in cluster A broadcast the relay user and cellular users The power domain superposition coded signal of the required information, cellular users To relay users and the backscatter devices in cluster B broadcast the relay user and cellular users The power domain of the required information is superimposed on the coded signal; cluster A and cluster B surround the cellular users respectively and cellular users ; The backscatter devices in cluster A and cluster B receive the cellular RF signals of the cellular users around them, and use backscatter modulation to reflect the signals containing their own information to the cellular users and relay users around them. , cellular users and cellular users Receive and decode the backscatter signals from the backscatter devices in cluster A and cluster B respectively, and relay the signals to the user Receive and decode the signals from two cellular users and the reflected signals from the backscatter devices in the two clusters; In the second time slot, the relay user Physical layer network coding is used to convert the decoded first time slot into a cellular user To cellular users Information and cellular users To cellular users Information Encoded as a composite signal , according to downlink NOMA, to cellular users and cellular users The broadcast downlink power domain superimposed coded signal contains a composite signal and a relay user Need to be delivered to cellular users and cellular users signal of information; The backscattering devices in cluster A and cluster B modulate their own information to the data from the relay user. The RF signal is then reflected to the surrounding cellular users. and cellular users , two cellular users receive signals from the relay user The signal and the backscattered signals of the surrounding backscattering device clusters are decoded.

2. The bidirectional relay NOMA transmission method based on network coding and backscattering according to claim 1 is characterized in that: The cellular users all have full-duplex capability and are equipped with a single antenna, and the relay users all have half-duplex capability and are equipped with a single antenna.

3. The bidirectional relay NOMA transmission method based on network coding and backscattering according to claim 1 is characterized in that: The first time slot and the second time slot are of equal length.

4. The bidirectional relay NOMA transmission method based on network coding and backscattering according to claim 1 is characterized in that: In the first time slot, cellular users and cellular users Reflected signals from respective surrounding backscattering device clusters are received and decoded using a serial interference cancellation algorithm and maximum ratio combining technology; The relay user Receive signals from two cellular users and reflected signals from backscatter devices in two clusters and decode them sequentially using a serial interference cancellation algorithm: Cellular users To cellular users The information carrying signal, cellular user To relay user The information carrying signal, cellular user To cellular users The information carrying signal and cellular users To relay user The information-carrying signal.

5. The bidirectional relay NOMA transmission method based on network coding and backscattering according to claim 1 is characterized in that: In the second time slot, the cellular user Receive from relay user The signal and the reflected signal of the backscattering device cluster B around it are combined with the composite signal and the carrier relay user according to the downlink NOMA. To cellular users The signal and carrier relay users of the transmitted information To cellular users The signals of the transmitted information are decoded sequentially; After decoding, cellular users Again, XOR operation , restore cellular users Delivered to cellular users The information-carrying signal .

6. The bidirectional relay NOMA transmission method based on network coding and backscattering according to claim 5 is characterized in that: In the second time slot, the cellular user Receive from relay user The signal and the reflected signal of the backscattering device cluster A around it are decoded in turn by the serial interference cancellation algorithm according to the downlink NOMA. To cellular users The signal of the transmitted information carries the relay user in this decoding process To cellular users The signal conveying the information is considered interference; After decoding, cellular users Again, XOR operation , restore cellular users Need to be delivered to cellular users The information-carrying signal .

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