A full-duplex relay transmission method based on rate-splitting multiple access

Abstract

The present invention discloses a full-duplex relay transmission method based on rate-splitting multiple access, including: dividing the information transmission process into a first time slot and a second time slot before and after; in the first time slot, the relay user communicates with two edge users using downlink RSMA; meanwhile, the two edge users send the information to be exchanged by themselves to the relay user using uplink RSMA; in the second time slot, the relay user decodes and forwards the uplink RSMA signal received in the first time slot to realize the information exchange between the two edge users; meanwhile, the two edge users continue to communicate with the relay user using uplink RSMA; wherein, when the first edge user sends information using uplink RSMA, it splits its own information into two parts and sends them, while the second edge user directly sends its own information. The present invention can realize joint uplink and downlink RSMA transmission, expand the communication coverage range, and improve the system spectral efficiency.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly relates to a full-duplex relay transmission method based on rate-splitting multiple access. Background Art

[0002] With the rapid development of fields such as smart cities, industrial automation, and autonomous driving, the number of communication terminals has increased sharply, posing higher requirements for the new generation of mobile networks in terms of user data rate, spectrum efficiency, communication coverage, etc. As one of the candidates for the next-generation multiple access technology, rate-splitting multiple access technology has shown great potential in improving spectrum utilization and enhancing communication stability.

[0003] The rate-splitting multiple access technology decomposes user information into a common part and a private part, and reasonably allocates power to achieve that part of the interference can be decoded and part of the interference is regarded as noise, thereby improving the service quality and spectrum efficiency of the system. Introducing cooperative relay technology into a wireless system can effectively improve the throughput of cell-edge users and improve their service quality, and at the same time can expand the communication coverage. As an important branch of cooperative relay, two-way relay technology can exchange information between a pair of users. Compared with the traditional one-way relay method, two-way relay can improve the spectrum utilization efficiency and thus achieve more efficient communication performance. To further improve the system performance, a communication scheme using the full-duplex mode has been proposed. Full-duplex communication allows a node to receive and forward information simultaneously at the same time, which can significantly improve the spectrum efficiency and network throughput.

[0004] However, existing joint uplink and downlink schemes have a common feature: they need to complete the uplink and downlink transmission tasks in a time-division manner, that is, the transmission is unidirectional in the same time slot, and two-way information transmission can only be completed through multiple time slots, which will cause potential spectrum efficiency loss. Secondly, in existing joint uplink and downlink schemes based on non-orthogonal multiple access (NOMA), in addition to the above-mentioned spectrum loss problem, there is also a lack of flexible interference management ability because the transmitted signals are all complete user signals rather than flexibly split signals.

[0005] Therefore, studying a full-duplex relay transmission method based on rate-splitting multiple access is of great significance for improving the performance of mobile networks and meeting the growing demands for user data rate, spectrum efficiency, and communication coverage. Summary of the Invention

[0006] The object of the present invention is to provide a full-duplex relay transmission method based on rate-splitting multiple access, propose a novel two-way RSMA communication strategy of simultaneous direct transmission and cooperation, utilize two time slots to complete pairwise information exchange, and each time slot can support two-way information transmission, so as to improve the spectral efficiency. By setting the proportion parameters of the common stream and the private stream and the power allocation coefficient, partial interference can be decoded and partial interference is regarded as noise processing, so as to flexibly manage interference, meet the increasing user data rate, expand the communication coverage range, and improve the system spectral efficiency.

[0007] To achieve the above technical object, the technical solution adopted by the present invention is as follows:

[0008] The present invention discloses a full-duplex relay transmission method based on rate-splitting multiple access, and the method includes the following steps:

[0009] Set up a three-user two-way relay system model based on rate-splitting multiple access. This model includes relay users, a first edge user and a second edge user, and it is a time-division duplex system with channel reciprocity; the information transmission process follows the two-way RSMA communication strategy of simultaneous direct transmission and cooperation, and is divided into two time slots before and after;

[0010] In the first time slot, the relay user communicates with the two edge users by using downlink RSMA; at the same time, the two edge users send the information to be exchanged by themselves to the relay user by using uplink RSMA.

[0011] In the second time slot, the relay user decodes and forwards the uplink RSMA signal received in the first time slot to realize the information exchange between the two edge users; at the same time, the two edge users continue to communicate with the relay user by using uplink RSMA.

[0012] Among them, when the first edge user sends information by using uplink RSMA, it splits its own information into two parts, then performs superposition coding and forwarding, while the second edge user directly sends its own information.

[0013] Further, the durations of the first time slot and the second time slot are equal.

[0014] Further, in the first time slot and the second time slot, the relay user adopts the successive interference cancellation algorithm to decode the first part of the information split by the first edge user, the information of the second edge user, and the second part of the information split by the first edge user in sequence.

[0015] Further, in the first time slot, the relay user broadcasts a power-domain superposition coding signal containing the information required by the two edge users by using downlink RSMA; in the second time slot, the relay user decodes the information received in the first time slot that needs to be exchanged and forwards it to the two edge users.

[0016] Furthermore, in the second time slot, the relay user decodes the information of the edge user received in the first time slot, performs superposition using physical layer network coding, and then broadcasts it; the edge user eliminates the signal component sent by itself in the first time slot from the received signal according to the prior information of the signal sent by itself in the first time slot, and directly decodes the signal sent by another edge user in the first time slot.

[0017] Furthermore, according to the downlink RSMA principle, the relay user splits the information required by the first edge user into the required common stream and the required private stream of the first edge user; at the same time, the relay user splits the information required by the second edge user into the required common stream and the required private stream of the second edge user; subsequently, the relay user combines the required common stream of the first edge user and the required common stream of the second edge user into a common stream, and superimposes and encodes it together with the other two private streams and forwards it.

[0018] Furthermore, in the first time slot, according to the downlink RSMA principle, the two edge users use the successive interference cancellation algorithm to decode the common stream and the private stream they need in turn.

[0019] Furthermore, in the first time slot and the second time slot, following the uplink RSMA principle, the specific splitting principle is to divide the first edge user into two virtual users, then split the information of the first edge user into two parts and map them to the two virtual users respectively, and then the two virtual users send their own information.

[0020] Furthermore, both the relay user and the two edge users operate in full-duplex mode.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] First, the full-duplex relay transmission method based on rate splitting multiple access of the present invention is simultaneous and two-way, that is, each time slot supports two-way information transmission, and at the same time has a direct transmission link and a cooperative link, which can transmit more data signals, thereby improving the spectrum efficiency, and can also flexibly manage interference by setting the ratio parameter of the common stream and the private stream and the power allocation coefficient.

[0023] Second, the full-duplex relay transmission method based on rate splitting multiple access of the present invention realizes pairwise information exchange among all users through a new type of simultaneous direct transmission and cooperative two-way RSMA communication strategy, expanding the communication coverage. Specifically, while the two end users complete the exchange of information with each other through the relay user, the relay user also completes the corresponding information exchange with the two end users using RSMA.

[0024] Thirdly, the full-duplex relay transmission method based on rate-splitting multiple access of the present invention does not rely on fixed infrastructure (such as base stations), and the corresponding functions can be achieved by relying on three mobile users. It is not only applicable to cellular networks, but also can be applied to ad hoc networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a brief flowchart of a full-duplex relay transmission method based on rate-splitting multiple access (RSMA) provided by the present invention;

[0026] Figure 2 is a schematic diagram of the transmission lines in the first time slot and the second time slot of the two-way RSMA communication strategy of simultaneous direct transmission and cooperation described in the embodiment;

[0027] Figure 3 is a curve graph showing the variation of the system ergodic sum capacity with the transmit signal-to-noise ratio of different transmission methods described in Embodiment 1. Orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) both adopt full-duplex;

[0028] Figure 4 is a curve graph showing the variation of the system ergodic sum capacity with the channel power between the relay user and the first edge user of different transmission methods described in Embodiment 2. OMA and NOMA both adopt full-duplex;

[0029] Figure 5 is a curve graph showing the variation of the system ergodic sum capacity with the channel power between the relay user and the second edge user of different transmission methods described in Embodiment 2. OMA and NOMA both adopt full-duplex. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following further describes the embodiments of the present invention in detail with reference to the drawings.

[0031] The present invention provides a full-duplex relay transmission method based on rate-splitting multiple access, including:

[0032] Set up a three-user two-way relay system model based on rate-splitting multiple access. This model includes a relay user, a first edge user, and a second edge user, and is a time-division duplex system with channel reciprocity; the transmission process of information follows the two-way RSMA communication strategy of simultaneous direct transmission and cooperation, and is divided into two time slots before and after;

[0033] In the first time slot, the relay user communicates with the two edge users using downlink RSMA; at the same time, the two edge users send the information to be exchanged by themselves to the relay user using uplink RSMA;

[0034] In the second time slot, the relay user decodes and forwards the uplink RSMA signal received in the first time slot to realize the information exchange between the two edge users; meanwhile, the two edge users continue to communicate with the relay user using uplink RSMA.

[0035] Embodiment 1

[0036] Figure 1 is a brief flowchart of a full-duplex relay transmission method based on RSMA provided by the present invention. This flowchart only shows the logical sequence of the method described in this embodiment. On the premise of non-conflict, in other possible embodiments of the present invention, the steps shown or described can be completed in a different Figure 1 sequence from that shown.

[0037] See Figure 1 , the method of this embodiment specifically includes the following steps:

[0038] Set up a three-user two-way relay system model based on rate-splitting multiple access. This model includes a relay user, a first edge user, and a second edge user, and is a time-division duplex system with channel reciprocity; the information transmission process follows a two-way RSMA communication strategy of simultaneous direct transmission and cooperation, and is divided into two time slots before and after, namely the first time slot and the second time slot;

[0039] In the first time slot, the relay user uses downlink RSMA to broadcast a power-domain superposition coding signal containing the information required by the two edge users;

[0040] Meanwhile, the two edge users use uplink RSMA to send the information they need to exchange with each other to the relay user; specifically, the first edge user splits its own information into two parts and sends them, while the second edge user directly sends its own information;

[0041] In the second time slot, the relay user decodes the information that needs to be exchanged received in the first time slot and forwards it to the two edge users;

[0042] Meanwhile, the two edge users use uplink RSMA to send the information required by the relay user to the relay user; specifically, the first edge user splits its own information into two parts and sends them, while the second edge user directly sends its own information;

[0043] Optionally, in a specific embodiment, it includes the following specific steps:

[0044] Step 1: Set up a three-user two-way relay system model based on rate-splitting multiple access, which includes a relay user, a first edge user, and a second edge user. Since the two edge users cannot communicate directly due to long distance or obstacles, etc., they need the help of the relay user to achieve information exchange. In this model, the relay user and the two edge users all work in full-duplex mode.

[0045] The information transmission process is divided into two equal-length time slots before and after, namely the first time slot and the second time slot, as Figure 2 shown.

[0046] Define the signals carried by the information that the relay user needs from the first edge user and the second edge user to be and respectively. The signals carried by the information that the first edge user needs from the relay user and the second edge user are and respectively. The signals carried by the information that the second edge user needs from the relay user and the first edge user are and respectively, where and are the information to be exchanged; , where , and represent the transmission powers corresponding to users , and respectively.

[0047] Step 2: In the first time slot, the relay user splits and into , and according to the downlink RSMA criterion and performs superposition coding. Specifically, the relay user splits into the common stream part and the private stream corresponding to the first edge user; at the same time, the relay user splits into the common stream part and the private stream corresponding to the second edge user; then, the relay user combines and Synthesize a common stream and superimpose, encode, and forward it together with the other two private streams. In this embodiment, the ratio parameter of the common stream and the private streams and the power distribution coefficient can be set according to actual needs. While decoding part of the interference, regard the other part of the interference as noise, that is, by adjusting the ratio parameter of the common stream and the private streams and the power distribution coefficient, adjust the ratio between the interference to be decoded and the interference regarded as noise to achieve flexible management of the interference.

[0048] Relay user The superimposed encoded signal in this time slot can be expressed as , where , and respectively represent the power distribution coefficients corresponding to the signals , and , satisfying .

[0049] Step 3: In the first time slot, following the uplink RSMA principle, the first edge user splits into and . At the same time, the second edge user directly transmits to the relay user .

[0050] The superimposed encoded signal of the first edge user in this time slot can be expressed as , where represents the power distribution coefficient, satisfying .

[0051] The superimposed encoded signal of the second edge user in this time slot can be expressed as .

[0052] Step 4: At this time, the received signals of the users , and in the first time slot can be expressed as:

[0053] (1);

[0054] (2);

[0055] (3);

[0056] where the parameters and respectively represent the channel coefficients between the first edge user in the first time slot , the second edge user and the relay user . , and respectively represent the self - interference channels of the relay user , the first edge user and the second edge user . , and respectively represent the remaining interference coefficients after self - interference cancellation of the relay user , the first edge user and the second edge user , and satisfy . , and respectively represent the additive Gaussian white noise that follows a complex Gaussian distribution with a mean of zero and a variance of at the relay user , the first edge user .

[0057] Step 5: According to the downlink RSMA principle, the edge users adopt the successive interference cancellation algorithm to decode the common stream and the private stream they need in turn. At this time, the signal - to - interference - plus - noise ratios of the decoded signals and and at the first edge user in the first time slot can be respectively expressed as:

[0058] (4);

[0059] (5);

[0060] where respectively represent the transmit signal - to - noise ratios of the relay user and the first edge user .

[0061] Similarly, the signal - to - interference - plus - noise ratios of the decoded signals and at the second edge user in the first time slot can be respectively expressed as:

[0062] (6);

[0063] (7).

[0064] Step 6: According to the uplink RSMA principle, the relay user only needs to decode the signals sequentially using successive interference cancellation 、 and respectively, and their corresponding signal-to-interference-plus-noise ratios can be expressed as:

[0065] (8);

[0066] (9);

[0067] (10);

[0068] where represents the transmit signal-to-noise ratio of the second edge user .

[0069] Step 7: In the second time slot, following the uplink RSMA principle, the first edge user splits into and . Meanwhile, the second edge user directly transmits to the relay user .

[0070] The superposition-coded signal of the first edge user in this time slot can be expressed as , where represents the power allocation coefficient, satisfying .

[0071] The superposition-coded signal of the second edge user in this time slot can be expressed as .

[0072] Step 8: In the second time slot, the relay user decodes the information of the edge users received in the first time slot and performs superposition using physical-layer network coding, which can be expressed as . The superposition-coded signal of the relay user in this time slot can be expressed as .

[0073] Step 9: At this time, the received signals of users 、 and in the second time slot can be expressed as:

[0074] (11);

[0075] (12);

[0076] (13);

[0077] where the parameters and represent the channel coefficients between the first edge user , the second edge user and the relay user in the second time slot, , and represent the self - interference channels of the relay user , the first edge user and the second edge user in the second time slot, , and represent the remaining interference coefficients after self - interference cancellation of the relay user , the first edge user and the second edge user in the second time slot, and satisfy , , and represent the additive Gaussian white noise with zero mean and variance at the relay user , the first edge user and the second edge user in the second time slot, following a complex Gaussian distribution.

[0078] Step Ten: Since the edge user has the prior information of the signal sent in its own first time slot, it can cancel the signal component sent in its own first time slot from the received signal, and then directly decode the signal sent by the other edge user in the first time slot. At this time, the signal - to - interference - plus - noise ratio (SINR) of the decoded signal at the first edge user in the second time slot can be expressed as:

[0079] (14);

[0080] Similarly, the signal - to - interference - plus - noise ratio (SINR) of the decoded signal at the second edge user in the second time slot can be expressed as:

[0081] (15).

[0082] Step Eleven: According to the uplink RSMA principle, the relay user Then, it is only necessary to use successive interference cancellation to decode the signals in sequence 、 and respectively. The corresponding signal-to-interference-plus-noise ratios can be expressed as follows:

[0083] (16);

[0084] (17);

[0085] (18).

[0086] To verify the beneficial effects of the present invention, it will be specifically implemented according to the following steps:

[0087] Assume that the power allocation coefficients are respectively , , , and the remaining interference coefficient of self-interference cancellation is uniformly set to 0.05. All channel coefficients follow a complex Gaussian distribution, that is, they satisfy , , , . Among them represents the channel power between nodes. In this embodiment, the channel powers are set to , , , .

[0088] Figure 3 shows the curve of the system ergodic sum capacity varying with the transmit signal-to-noise ratio of different transmission methods described in this embodiment. Figure 3 In, the solid black curve represents the theoretical value of the ergodic sum capacity of the transmission method described in this embodiment, and the black symbol points represent the simulation values. The theoretical values and the simulation values can coincide well. The green symbol line and the blue symbol line respectively represent the ergodic sum capacities of the traditional NOMA method and the OMA method. It can be seen from the figure that the proposed scheme of the present invention can achieve better system ergodic sum capacity performance than the traditional NOMA method and the OMA method at different transmit signal-to-noise ratios. This is because the rate of RSMA is split into the sum of the rates of each sub-message, while the rate of each user in NOMA and OMA only lies in decoding a single message. At the same time, the ergodic sum capacity of NOMA is better than that of OMA because NOMA can transmit more signals under the same time resource. For example, when the transmit signal-to-noise ratio is 40 dB, the ergodic sum capacity of the full-duplex relay transmission method based on rate splitting multiple access proposed by the present invention is 6.98 bps / Hz, while the ergodic sum capacity of the traditional NOMA method is 6.50 bps / Hz, and the ergodic sum capacity of the OMA method is 5.95 bps / Hz.

[0089] Embodiment 2

[0090] To evaluate the ergodic sum capacity performance of the technical solution described in the present invention under different channel powers, in this embodiment, it is assumed that the transmit signal-to-noise ratio at the base station is 25 dB, and other parameters are the same as those in Embodiment 1. The superiority of the ergodic sum capacity performance of the technical solution described in the present invention is verified by changing the channel powers between the two edge users and the relay user. Since the traditional NOMA method requires one of the two-end channels to be better and the other to be worse, for a fair comparison, the channel power between the first edge user and the relay user is set to be greater than or equal to the channel power between the second edge user and the relay user. Specifically, in this embodiment, it is assumed that Figure 4 the channel power between the second edge user and the relay user in Figure 5 is 1,

[0091] Figure 4 shows the curve of the system ergodic sum capacity of different transmission methods described in this embodiment changing with the channel power between the relay user and the first edge user. Figure 4 The solid black curve in

[0092] Figure 5 shows the theoretical value of the ergodic sum capacity of the transmission method described in this embodiment, and the black symbol points represent the simulation values. The theoretical values and the simulation values can coincide well. The green symbol line and the blue symbol line respectively represent the ergodic sum capacity of the traditional NOMA method and the OMA method. It can be seen from the figure that the proposed solution in the present invention can achieve better ergodic sum capacity performance than the traditional NOMA method and the OMA method under different channel powers between the relay user and the first edge user, and with the increase of the channel power, the ergodic sum capacity of all three schemes increases to varying degrees. This is because the increase in channel power represents an improvement in channel quality, which can increase the rates of the relay user and the first edge user in all schemes, thereby increasing the overall ergodic sum capacity. For example, when the channel power between the first edge user and the relay user is 1.5, the ergodic sum capacity of the full-duplex relay transmission method based on rate splitting multiple access proposed in the present invention is 7.25 bps / Hz, while the ergodic sum capacity of the traditional NOMA method is 6.86 bps / Hz, and the ergodic sum capacity of the OMA method is 6.20 bps / Hz. Figure 5The solid black curve represents the theoretical value of the ergodic sum capacity of the transmission method described in this embodiment, and the black symbol points represent the simulation values. The theoretical value and the simulation value can coincide well. The green symbol line and the blue symbol line represent the ergodic sum capacity of the traditional NOMA method and the OMA method, respectively. As can be seen from the figure, the proposed scheme of the present invention can achieve better ergodic sum capacity performance than the traditional NOMA method and the OMA method under different channel powers between the relay user and the second edge user. Moreover, as the channel power increases, the ergodic sum capacity of all three schemes increases to varying degrees. This is because the increase in channel power represents an improvement in channel quality, which can increase the rates of the relay user and the second edge user in all schemes, thus increasing the overall ergodic sum capacity. For example, when the channel power between the second edge user and the relay user is 1.5, the ergodic sum capacity of the full-duplex relay transmission method based on rate splitting multiple access proposed by the present invention is 7.83 bps / Hz, while the ergodic sum capacity of the traditional NOMA method is 7.50 bps / Hz, and the ergodic sum capacity of the OMA method is 6.86 bps / Hz.

[0093] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present application.

[0094] 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 equivalent technologies, the present application is also intended to include these changes and modifications.

Claims

1. A full-duplex relay transmission method based on rate division multiple access, characterized in that: The method comprises the following steps: A three-user bidirectional relay system model based on rate division multiple access is set up, which includes a relay user, a first edge user and a second edge user, and is a time division duplex system with channel reciprocity; the information transmission process follows the bidirectional RSMA communication strategy of simultaneous direct transmission and cooperation, and is divided into two time slots, namely the first time slot and the second time slot; In the first time slot, the relay user communicates with the two edge users using downlink RSMA; at the same time, the two edge users send the information they want to exchange to the relay user using uplink RSMA; In the second time slot, the relay user decodes and forwards the uplink RSMA signal received in the first time slot to implement information exchange between the two edge users; at the same time, the two edge users continue to communicate with the relay user using the uplink RSMA; Among them, when the first edge user uses the uplink RSMA to send information, it splits its own information into two parts, superimposes the encoding and forwards it, while the second edge user directly sends its own information; According to the downlink RSMA principle, the relay user divides the information required by the first edge user into the public stream required by the first edge user and the private stream required by the first edge user; at the same time, the relay user divides the information required by the second edge user into the public stream required by the second edge user and the private stream required by the second edge user; then, the relay user combines the public stream required by the first edge user and the public stream required by the second edge user into a public stream, and superimposes the encoding and forwarding together with the other two private streams; In the first time slot, according to the downlink RSMA principle, the two edge users use a serial interference cancellation algorithm to sequentially decode the public stream and the private streams they need.

2. The full-duplex relay transmission method based on rate division multiple access according to claim 1, characterized in that: The first time slot and the second time slot have the same duration.

3. The full-duplex relay transmission method based on rate division multiple access according to claim 1, characterized in that: In the first time slot and the second time slot, the relay user uses a serial interference cancellation algorithm to sequentially decode the first part of the information split from the first edge user, the information of the second edge user, and the second part of the information split from the first edge user.

4. The full-duplex relay transmission method based on rate division multiple access according to claim 1, characterized in that: In the first time slot, the relay user uses downlink RSMA to broadcast a power domain superposition coded signal containing information required by two edge users; in the second time slot, the relay user decodes the information to be exchanged received in the first time slot and forwards it to the two edge users.

5. The full-duplex relay transmission method based on rate division multiple access according to claim 4, characterized in that: In the second time slot, the relay user decodes the information of the edge user received in the first time slot and superimposes it using physical layer network coding, and then broadcasts it; the edge user eliminates the signal component sent by its own first time slot from the received signal based on the prior information of the signal sent by its own first time slot, and directly decodes the signal sent by another edge user in the first time slot.

6. The full-duplex relay transmission method based on rate division multiple access according to claim 1, characterized in that: In the first time slot and the second time slot, following the uplink RSMA principle, the first edge user is divided into two virtual users, and then the information of the first edge user is split into two parts and mapped to the two virtual users respectively, and then the two virtual users send their own information.

7. The full-duplex relay transmission method based on rate division multiple access according to claim 1, characterized in that: The relay user and the two edge users all work in full-duplex mode.

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