A multi-hop transmission method based on decoding and forwarding relay and intelligent metasurface

Abstract

The present invention relates to a multi-hop transmission method based on decoding and forwarding relay and intelligent metasurface, and belongs to the field of communication technology. The method comprises the following steps: S1: proposing a hybrid FDDF-RIS multi-hop transmission scheme, and considering that the relay is located at different positions in the multi-hop link; S2: deducing and analyzing the system capacity of the hybrid FDDF-RIS multi-hop transmission scheme; S3: in order to further improve the system capacity, theoretically analyzing the system capacity of the scheme under EPA and OPA methods. The present invention proposes multi-hop communication between a hybrid relay and RIS, and considers placing the relay at different positions in the multi-hop link. The present invention proposes multi-hop communication between a hybrid relay and RIS, and considers placing the relay at different positions in the multi-hop link.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology and relates to a multi-hop transmission method based on decoding, forwarding, relaying and intelligent metasurface. Background Art

[0002] Due to the scarcity of low-frequency resources, future mobile communication networks will gradually shift to higher-frequency bands. Electromagnetic waves experience significant free-space propagation loss, diffraction loss, and penetration loss, easily creating coverage gaps and weak coverage areas. With the acceleration of urban construction and development, dense urban agglomerations are becoming increasingly numerous, exacerbating coverage issues. Furthermore, densely populated urban agglomerations are rapidly increasing the demand for wireless network capacity. Therefore, addressing coverage issues in dense urban agglomerations and improving system capacity have become crucial aspects of urban wireless network optimization. Traditionally, the primary approach has been to add base stations or introduce relay nodes. However, base station deployment and operating costs are high, and site selection in dense urban agglomerations is difficult. Relay nodes, as active devices requiring dedicated power supplies, are costly to deploy and consume a significant amount of electricity. Therefore, low-cost, low-power solutions are increasingly crucial for future mobile communication networks. To meet the growing demand for wireless networks, reconfigurable intelligent surfaces (RIS), with their low cost, low power consumption, and ease of deployment, have become a key candidate technology for next-generation mobile communication networks, addressing the various challenges encountered in wireless network environments. RIS builds an intelligent, controllable wireless environment to fill gaps and weaknesses in existing communication networks. Furthermore, the lightweight nature of RIS makes it easy to deploy on common objects (such as building surfaces and infrastructure), making RIS deployment more flexible. By deploying multiple RIS, base station signals can be reflected to every corner, improving coverage performance. Its performance advantages have been demonstrated in scenarios such as vehicle-to-vehicle communications and drone communications. RIS can also be combined with other coverage solutions to supplement existing coverage enhancement schemes. Existing research has demonstrated the performance advantages of hybrid RIS and relay cooperative communications through theoretical demonstration and simulation results. However, whether hybrid RIS and relays retain these performance advantages in multi-hop communications remains unclear. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a multi-hop transmission method based on decoding and forwarding relay and intelligent metasurface. The residual self-interference of the full-duplex relay is modeled as a random variable of cyclic symmetric complex Gaussian distribution, and the system capacity of the two transmission schemes is simulated and analyzed considering the different positions of the relay in the multi-hop link. In order to further improve the system capacity of the hybrid FDDF-RIS multi-hop transmission scheme, the system capacity of the hybrid FDDF-RIS multi-hop transmission scheme under the two power allocation modes of equal power allocation (EPA) and OPA is theoretically analyzed and simulated compared using the optimal power allocation (OPA), and the performance of the hybrid FDDF-RIS multi-hop transmission scheme with relays at different positions is simulated and analyzed.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A multi-hop transmission method based on decoding, forwarding, relaying and intelligent metasurface, the method comprising the following steps:

[0006] S1: A hybrid FDDF-RIS multi-hop transmission scheme is proposed, and the relays are considered to be located at different positions in the multi-hop link;

[0007] S2: Derive and analyze the system capacity of the hybrid FDDF-RIS multi-hop transmission scheme;

[0008] S3: To further improve the system capacity, a theoretical analysis of the system capacity of the solution is conducted under the EPA and OPA methods.

[0009] Optionally, the S1 specifically includes:

[0010] The N intermediate nodes in the multi-hop transmission system model are N-1 passive RIS with L reflective elements and one FDDF relay node. The FDDF relay is located at the first node, the last node, and the intermediate node. The DF relay is located at the last node. The signal received by the relay node is:

[0011]

[0012] The target node receives the signal:

[0013]

[0014] The DF relay is located at the first node, and the signal received by the relay node is:

[0015]

[0016] The target node receives the signal:

[0017]

[0018] The DF relay is located at the intermediate node, and the signal received by the relay node is:

[0019]

[0020] The target node receives the signal:

[0021]

[0022] Where: n1, n2: N c (0, σ 2 ) denotes Gaussian white noise; p1 is the transmission power of the source node; p2 denotes the transmission power of the relay node decoding and forwarding; the system capacity is expressed as:

[0023] R FDDF-RIS =Blog2(1+min(γ r ,γ d ))

[0024] When the DF relay is located at the last node, γ d =p2|h N,N+1 | 2 / σ 2 ; When the DF relay is located at the first node, γ r =p1|h 0,1 | 2 / p2|h LI | 2 +σ 2 , When the DF relay is located at an intermediate node, Due to the limited dynamic range and nonlinear characteristics of hardware in the full-duplex self-interference suppression process, the full-duplex residual self-interference is modeled as a zero mean and a variance of p2|h LI | 2 A cyclically symmetric complex Gaussian distributed random variable where |h LI | 2 represents the self-interference channel gain of the FDDF relay node.

[0025] Optionally, the S2 specifically includes:

[0026] The minimum value is γ r , in the first case, let:

[0027]

[0028] Less than 0, Monotonically decreasing; hour, Monotonically decreases until it decreases to 0, and then The DF-RIS system capacity is better than that of FDDF-RIS;

[0029] Analyze the system capacity and the number of reflective elements, assuming x = L 2 , the first-order derivative with respect to x is:

[0030]

[0031] The second-order derivative is:

[0032]

[0033] x is non-negative. When x>0, f3”(x) is greater than 0, and f3(x) decreases first and then increases. Let f3'(x0)=0, x0<0; let x=0, f3(x)=0; when x>0, f3(x) is greater than 0, and the capacity of the FDDF-RIS system is better than that of the DF-RIS system. Since x=L 2 And L is a non-negative value, so f3(L) and f3(x) have the same trend as L changes;

[0034] The second situation orders:

[0035]

[0036] Analyze the system capacity and the number of reflective elements, assuming x = L 2 , the first-order derivative with respect to x is:

[0037]

[0038] f4′(x) is greater than 0, and f4(x) increases monotonically. Let x=0, f4(x)<0, and when x>0, f4(x) increases monotonically until f4(x)=0. After that, f4(x)>0. The capacity of FDDF-RIS system is better than DF-RIS. Since x=L 2 And L is a non-negative value, so f4(x) and f4(L) have the same trend with L;

[0039] The DF relay is located at the first node and the intermediate node.

[0040] Analyze the system capacity and residual self-interference, Derivative, since the capacity of a half-duplex relay system is It is irrelevant, so no matter which link the system capacity depends on, its first-order derivative is:

[0041]

[0042] Optionally, the S3 specifically includes:

[0043] The system capacity of the hybrid FDDF-RIS multi-hop transmission scheme is limited by the worst link. Considering the OPA method, under the joint power constraint, the transmit power of the source node and the relay node is optimized to maximize the system capacity. The system capacity optimization problem under the joint power constraint is described as follows:

[0044]

[0045] The system capacity is limited by the worst link, let γ r =γ d According to the signal-to-noise ratio balance condition, the optimal transmission power of the source node when the FDDF relay is located at the last node, the first node and the intermediate node in the hybrid FDDF-RIS is:

[0046]

[0047]

[0048]

[0049] The performance analysis of the two transmission schemes under OPA mode is the same as that under EPA mode. A theoretical analysis is conducted on the hybrid FDDF-RIS multi-hop transmission scheme using both EPA and OPA power allocation modes.

[0050] For the relay located at the last node, substitute formula (4-32) into γ r The two transmission schemes have the same total power consumption, and the energy efficiency trend is the same as the system capacity. Let x = L 2 , a=(N-1) 2 β DF-RIS ;

[0051] In OPA mode r =γ d ,make:

[0052]

[0053]

[0054] First, the system capacity and the number of reflective elements are analyzed, and the first-order derivative is:

[0055]

[0056]

[0057] f7′(x) and g3′(x) are always less than 0, and f7(x) and g3(x) decrease monotonically. When x=0, f7(0)=0, g3(0)<0. In this case, the system capacity of the hybrid FDDF-RIS in the OPA mode is smaller than that in the EPA mode.

[0058] Finally, the system capacity and residual self-interference are analyzed, and their first-order derivatives are:

[0059]

[0060]

[0061] Less than 0, Monotonically decreasing; The system capacity of hybrid FDDF-RIS in OPA mode is better than that in EPA mode. The increase is until the system capacity of the hybrid FDDF-RIS in the OPA mode is less than that in the EPA mode. The denominator of the above formula is positive, so:

[0062]

[0063] The first-order derivative is:

[0064]

[0065] greater than 0, Monotonically increasing; hour, Monotonically increasing; hour, Monotonically decreasing; It shows a trend of first increasing and then decreasing.

[0066] The present invention provides the following beneficial effects: It proposes hybrid multi-hop communication using relays and RIS, and considers placing relays at different locations within the multi-hop link. Existing research has demonstrated the performance advantages of hybrid RIS and relay collaborative communication through theoretical demonstration and simulation results, but has not yet demonstrated whether hybrid RIS and relay still possesses performance advantages in multi-hop communication. Therefore, the present invention proposes hybrid multi-hop communication using relays and RIS, and considers placing relays at different locations within the multi-hop link.

[0067] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0069] Figure 1 Schematic diagram of a multi-hop transmission model of the present invention;

[0070] Figure 2 is the relationship between the system capacity and the number of reflective elements of the present invention;

[0071] Figure 3 is the relationship between the system capacity and residual self-interference of the present invention;

[0072] Figure 4 The relationship between system capacity and residual self-interference under different total transmit powers of the present invention;

[0073] Figure 5 The relationship between the system capacity and the number of reflective elements under different power distribution modes of the present invention;

[0074] Figure 6 The relationship between system capacity and residual self-interference under different power allocation modes of the present invention;

[0075] Figure 7 This is the system capacity of the present invention when the relay is located at different positions. DETAILED DESCRIPTION

[0076] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0077] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0078] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0079] See also Figures 1 to 7 The present invention is mainly divided into three parts: a hybrid FDDF-RIS multi-hop transmission scheme, a derivation of the system capacity and energy efficiency of the hybrid FDDF-RIS multi-hop transmission scheme, and the optimal deployment location of relays in the hybrid FDDF-RIS multi-hop transmission scheme under the OPA mode. Specifically, it includes the following steps:

[0080] 1. A hybrid FDDF-RIS multi-hop transmission scheme is proposed, considering that relays are located at different positions in the multi-hop link;

[0081] 2. Derive and analyze the system capacity of the solution;

[0082] 3. To further improve system capacity, a theoretical analysis of the system capacity of this solution is conducted under the EPA and OPA methods;

[0083] Furthermore, in said step 1, it specifically includes:

[0084] The N intermediate nodes in the multi-hop transmission system model are N-1 passive RIS with L reflective elements and one FDDF relay node. The FDDF relay is located at the first node, the last node, and the intermediate node. The DF relay is located at the last node, and the signal received by the relay node is:

[0085]

[0086] The target node receives the signal:

[0087]

[0088] The DF relay is located at the first node, and the signal received by the relay node is:

[0089]

[0090] The target node receives the signal:

[0091]

[0092] The DF relay is located at the intermediate node, and the signal received by the relay node is:

[0093]

[0094] The target node receives the signal:

[0095]

[0096] Where: n1, n2: N c (0, σ 2 ) represents Gaussian white noise; p1 is the transmission power of the source node; p2 is the transmission power of the relay node decoding and forwarding. The system capacity is expressed as:

[0097] R FDDF-RIS =Blog2(1+min(γ r ,γ d ))

[0098] When the DF relay is located at the last node, γ d =p2|h N,N+1 | 2 / σ 2 ; When the DF relay is located at the first node, γ r =p1|h 0,1 | 2 / p2|h LI | 2 +σ 2 , When the DF relay is located at an intermediate node, Due to the limited dynamic range and nonlinear characteristics of hardware in the full-duplex self-interference suppression process, the full-duplex residual self-interference is modeled as a zero mean and a variance of p2|h LI | 2 A cyclically symmetric complex Gaussian distributed random variable where |h LI | 2 represents the self-interference channel gain of the FDDF relay node.

[0099] In the step 2, it specifically includes:

[0100] The minimum value is γ r , in the first case, let:

[0101]

[0102] Less than 0, is monotonically decreasing. hour, Monotonically decreases until it decreases to 0, and then The system capacity of DF-RIS is better than that of FDDF-RIS.

[0103] Analyze the system capacity and the number of reflective elements, assuming x = L 2 , the first-order derivative with respect to x is:

[0104]

[0105] The second-order derivative is:

[0106]

[0107] x is non-negative. When x>0, f3”(x) is greater than 0, and f3(x) decreases first and then increases. Let f3'(x0)=0, x0<0; let x=0, f3(x)=0. When x>0, f3(x) is greater than 0, and the capacity of the FDDF-RIS system is better than that of DF-RIS. Since x=L 2 And L is a non-negative value, so f3(L) and f3(x) have the same trend as L changes.

[0108] The second situation orders:

[0109]

[0110] Analyze the system capacity and the number of reflective elements, assuming x = L 2 , the first-order derivative with respect to x is:

[0111]

[0112] f4′(x) is greater than 0, and f4(x) increases monotonically. Let x=0, f4(x)<0, and when x>0, f4(x) increases monotonically until f4(x)=0. After that, f4(x)>0, and the capacity of the FDDF-RIS system is better than that of the DF-RIS system. Since x=L 2 And L is a non-negative value, so f4(x) and f4(L) have the same trend as L changes.

[0113] The same logic can be applied to the case where the DF relay is located at the first node and the intermediate node.

[0114] Analyze the system capacity and residual self-interference, Derivative, since the capacity of a half-duplex relay system is It is irrelevant, so no matter which link the system capacity depends on, its first-order derivative is:

[0115]

[0116] In the step 3, it specifically includes:

[0117] The system capacity of the hybrid FDDF-RIS multi-hop transmission scheme is limited by the worst link. Therefore, the OPA approach is considered. Under the joint power constraint, optimizing the transmit power of the source node and the relay node can maximize the system capacity. Therefore, the system capacity optimization problem under the joint power constraint can be stated as:

[0118]

[0119] The system capacity is limited by the worst link, let γ r =γ d According to the signal-to-noise ratio balance condition, the optimal transmission power of the source node when the FDDF relay is located at the last node, the first node and the intermediate node in the hybrid FDDF-RIS is:

[0120]

[0121]

[0122]

[0123] The performance analysis of the two transmission schemes under OPA mode is similar to that under EPA mode, so it will not be repeated here. Next, a theoretical analysis of the hybrid FDDF-RIS multi-hop transmission scheme using EPA and OPA power allocation methods is conducted.

[0124] Taking the relay at the last node as an example, substitute formula (4-32) into γ r The total power consumption of the two transmission schemes is the same, so the energy efficiency trend is the same as the system capacity. Let x = L 2 , a=(N-1) 2 β DF-RIS .

[0125] In OPA mode r =γ d ,make:

[0126]

[0127]

[0128] First, the system capacity and the number of reflective elements are analyzed, and the first-order derivative is:

[0129]

[0130]

[0131] f7′(x) and g3′(x) are always less than 0, and f7(x) and g3(x) are monotonically decreasing. When x = 0, f7(0) = 0, and g3(0) < 0. In this case, the system capacity of the hybrid FDDF-RIS in the OPA mode is smaller than that in the EPA mode.

[0132] Finally, the system capacity and residual self-interference are analyzed, and their first-order derivatives are:

[0133]

[0134]

[0135] Less than 0, is monotonically decreasing. The system capacity of hybrid FDDF-RIS in OPA mode is better than that in EPA mode. The increase of FDDF-RIS is until the system capacity of the OPA mode is less than that of the EPA mode. The denominator of the above formula is positive, so:

[0136]

[0137] The first-order derivative is:

[0138]

[0139] greater than 0, is monotonically increasing. Let hour, Monotonically increasing; hour, is monotonically decreasing. Therefore It shows a trend of first increasing and then decreasing.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-hop transmission method based on decoding and forwarding relay and intelligent metasurface, characterized by: The method comprises the following steps: S1: A hybrid FDDF-RIS multi-hop transmission scheme is proposed, and the relays are considered to be located at different positions in the multi-hop link; S2: Derive and analyze the system capacity of the hybrid FDDF-RIS multi-hop transmission scheme; S3: To further improve system capacity, a theoretical analysis of the system capacity of this solution is conducted under equal power allocation (EPA) and optimal power allocation (OPA). Said S1 specifically includes: The N intermediate nodes in the multi-hop transmission system model are N-1 passive RIS with L reflective elements and one FDDF relay node. The FDDF relay is located at the first node, the last node, and the intermediate node. The DF relay is located at the last node. The signal received by the relay node is: The target node receives the signal: The DF relay is located at the first node, and the signal received by the relay node is: The target node receives the signal: The DF relay is located at the intermediate node, and the signal received by the relay node is: The target node receives the signal: Where: n1, n2~N c (0, σ 2 ) denotes Gaussian white noise; p1 is the transmission power of the source node; p2 denotes the transmission power of the relay node decoding and forwarding; the system capacity is expressed as: R FDDF-RIS =Blog2(1+min(γ r ,c d )) When the DF relay is located at the last node, γ d =p2|h N,N+1 | 2 / σ 2 ; When the DF relay is located at the first node, γ r =p1|h 0,1 | 2 / p2|h LI | 2 +σ 2 , When the DF relay is located at an intermediate node, Due to the limited dynamic range and nonlinear characteristics of hardware in the full-duplex self-interference suppression process, the full-duplex residual self-interference is modeled as a zero mean and a variance of p2|h LI | 2 A cyclically symmetric complex Gaussian distributed random variable where |h LI | 2 represents the self-interference channel gain of the FDDF relay node.

2. The multi-hop transmission method based on decoding, forwarding, relaying and intelligent metasurface according to claim 1, characterized in that: The S2 specifically includes: The minimum value is γ r , in the first case, let: Less than 0, Monotonically decreasing; hour, Monotonically decreases until it decreases to 0, and then The DF-RIS system capacity is better than that of FDDF-RIS; Analyze the system capacity and the number of reflective elements, assuming x = L 2 , the first-order derivative with respect to x is: The second-order derivative is: x is non-negative. When x>0, f3”(x) is greater than 0, and f3(x) decreases first and then increases. Let f3'(x0)=0, x0<0; let x=0, f3(x)=0; when x>0, f3(x) is greater than 0, and the capacity of FDDF-RIS system is better than DF-RIS. Since x=L 2 And L is a non-negative value, so f3(L) and f3(x) have the same trend as L changes; The second situation orders: Analyze the system capacity and the number of reflective elements, assuming x = L 2 , the first-order derivative with respect to x is: f4′(x) is greater than 0, f4(x) increases monotonically; let x=0, f4(x)<0, when x>0, f4(x) increases monotonically until f4(x)=0, after which f4(x)>0, the capacity of the FDDF-RIS system is better than that of DF-RIS; since x=L 2 And L is a non-negative value, so f4(x) and f4(L) have the same trend with L; The DF relay is located at the first node and the intermediate node in the same way; Analyze the system capacity and residual self-interference, Derivative, half-duplex relay system capacity and Regardless of which link the system capacity depends on, its first-order derivative is:

3. The multi-hop transmission method based on decoding, forwarding, relaying and intelligent metasurface according to claim 2, characterized in that: The S3 specifically includes: The system capacity of the hybrid FDDF-RIS multi-hop transmission scheme is limited by the worst link. Considering the OPA method, under the joint power constraint, the transmit power of the source node and the relay node is optimized to maximize the system capacity. The system capacity optimization problem under the joint power constraint is described as follows: stc1:p1+p2=p c2:p1≥0,p2≥0 The system capacity is limited by the worst link, let γ r =γ d According to the signal-to-noise ratio balance condition, the optimal transmission power of the source node when the FDDF relay is located at the last node, the first node and the intermediate node in the hybrid FDDF-RIS is: The performance analysis of the two transmission schemes under OPA mode is the same as that under EPA mode. A theoretical analysis is conducted on the hybrid FDDF-RIS multi-hop transmission scheme using both EPA and OPA power allocation modes. For the relay located at the last node, the formula Bring in γ r The two transmission schemes have the same total power consumption, and the energy efficiency trend is the same as the system capacity. Let x = L 2 , a=(N-1) 2 β DF-RIS ; In OPA mode r =γ d ,make: First, the system capacity and the number of reflective elements are analyzed, and the first-order derivative is: f7′(x) and g3′(x) are always less than 0, and f7(x) and g3(x) decrease monotonically. When x=0, f7(0)=0, g3(0)<0. In this case, the system capacity of the hybrid FDDF-RIS in the OPA mode is smaller than that in the EPA mode. Finally, the system capacity and residual self-interference are analyzed, and their first-order derivatives are: Less than 0, Monotonically decreasing; The system capacity of hybrid FDDF-RIS in OPA mode is better than that in EPA mode. The increase is until the system capacity of the hybrid FDDF-RIS in the OPA mode is less than that in the EPA mode. The denominator of the above formula is positive, so: The first-order derivative is: greater than 0, Monotonically increasing; hour, Monotonically increasing; hour, Monotonically decreasing; It shows a trend of first increasing and then decreasing.

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