Method for Limiting Delay Transmission in a SWIPT Two-Way Transmission Relay System Based on the TS Strategy

Abstract

The present invention discloses a method for limiting delay transmission in a SWIPT two-way transmission relay system based on the TS strategy. The simultaneous wireless information and power transfer (SWIPT) two-way transmission relay system includes two active source nodes and one passive relay node. The relay node has the ability to collect radio frequency energy and adopts the time division (TS) strategy. The entire communication channel is a quasi-static Rayleigh fading channel. The SWIPT two-way transmission relay system adopts the limited delay relay (LDR) strategy, which means that strict time synchronization must be ensured between the receiving end node and the sending end node. If the channel gain of a single channel cannot meet the communication conditions, then the communication of the entire communication system is interrupted. Through theoretical derivation, the functional relationship between the actual maximum throughput and the energy collection time coefficient is obtained. An optimization problem is established with the goal of optimizing the actual maximum throughput, and the optimal energy collection time coefficient and the optimal actual maximum throughput are obtained by using the optimization algorithm.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communications, and in particular relates to a method for limiting delay transmission in a SWIPT bidirectional transmission relay system based on a TS strategy. Background Art

[0002] Radio frequency signals not only carry the information to be transmitted, but also have energy. In wireless communication systems, if energy can be transmitted while using radio frequency signals to transmit information, the service life of the wireless network system can be greatly extended. The technology of simultaneously transmitting radio frequency signal information and energy is called information-energy simultaneous transmission technology, also known as SWIPT (Simultaneous Wireless Information and Power Transfer) technology. The research on this technology is of great significance to the development of wireless transmission networks.

[0003] The key to the simultaneous transmission of information and energy lies in the design of the receiver. The receiving strategies of existing receivers mainly include time division (TS), power division (PS) and the combination of TS and PS.

[0004] SWIPT technology can effectively improve the spectrum utilization rate of the network, reduce latency, and reduce power consumption. Therefore, many scholars consider applying SWIPT technology to relay communication systems. In the process of one-way relay transmission, the distance of network transmission can be increased, but it requires more time resources as a cost. The two-way relay transmission method can solve this drawback well. Most of the research on maximum throughput in the existing SWIPT two-way transmission system tends to be idealized. The present invention discloses a method for limiting delay transmission in a SWIPT two-way transmission relay system based on the TS strategy, in which the passive relay adopts the TS receiving strategy. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention discloses a method for limiting delay transmission in a SWIPT two-way transmission relay system based on a TS strategy. The present invention considers a SWIPT two-way transmission relay system based on a time segmentation (TS) strategy, wherein two source nodes are active and a relay node is passive. The structural block diagram is shown in FIG. Figure 1 Given in.

[0006] like Figure 1As shown, two active source nodes transmit information to each other. However, direct communication between the two source nodes is not allowed, and the signal must pass through an intermediate passive relay node with RF energy harvesting capabilities to reach the other source node. Therefore, during the entire communication process, the relay node not only needs to forward the information sent by the source nodes on both sides but also harvest energy from the RF signal transmitted by one of the source nodes to ensure the normal operation of the entire communication system. The entire communication system adopts the Limited Delay Relay (LDR) strategy. The LDR strategy means that strict time synchronization must be ensured between the receiving end node and the sending end node, that is, the receiving rate must always be equal to the sending rate. If the channel gain of a single channel cannot meet the communication conditions, then the communication of the entire communication system will be interrupted.

[0007] As Figure 1 shown, in the SWIPT two-way transmission relay model based on the TS strategy, it includes two active source nodes U 1 , U 2 and an energy-constrained relay node h represents the channel gain between source node U 1 and the relay node , g represents the channel gain between source node U 2 and the relay node , P 1 represents the transmission power of source node U 1 , and P 2 represents the transmission power of source node U 2 .

[0008] This model satisfies the following conditions: (1) The entire communication channel is a quasi-static Rayleigh fading channel. The probability density function of the channel gain between source node U 1 and the relay node is The probability density function of the channel gain between source node U 2 and the relay node is where λ h and λ gThe means of exponential random variables for the channel gains of two channels respectively; (2) The relay node selects the amplify-and-forward (AF) strategy; (3) The power consumed by the relay node for signal processing is ignored, which is reasonable when the transmission distance is large enough and the collected energy is used as the main source of consumption; (4) An energy storage device with infinite capacity is set in the relay node; (5) The magnitude relationship between the channel gains between the two source nodes and the relay node is known (for example, by the two source nodes simultaneously sending a detection signal to the relay), so the relay node can determine from which source node to obtain energy to make the energy collection efficiency and communication efficiency higher. To describe this patent, the relay node obtains energy from source node U 1 collects energy.

[0009] Figure 2 is the internal structure of the relay node based on the TS strategy, n A represents the noise generated by the antenna when receiving the signal, n A is a circularly symmetric complex Gaussian random variable, that is represents n A (t) follows a complex Gaussian distribution with a mean of 0 and a variance of n B represents the noise introduced during information processing, and there is Define The energy collection efficiency factor is denoted as η.

[0010] n d represents the noise generated by the antenna of the source node and the conversion module, and there is

[0011] The time allocation relationship between the relay node collecting energy and transmitting information is as Figure 3 shown. T represents a complete time block, α represents the time coefficient of the relay node collecting energy within the time block T, α ∈ [0, 1], that is, the relay node needs to spend αT time to obtain the energy required for forwarding information. After the collected energy is sufficient to forward the received information, the relay node uses (1 - α)T / 2 time to receive the information sent by the two source nodes, and then uses (1 - α)T / 2 time to forward the received information to the source nodes at the other end respectively, thus completing the communication.

[0012] Source node U 1 transmits information to the relay node , and then the relay node forwards it to source node U 2 . The communication process is called link L 1 ; Similarly, source node U 2 transmits information to the relay node , and then the relay node forwards it to source node U1 The communication process is called link L 2 . Link L 1 's outage probability is denoted as p out1 , link L 2 's outage probability is denoted as p out2 .

[0013] Define the signal-to-noise ratio threshold γ 0 as the minimum signal-to-noise ratio that satisfies the communication condition without outage. The information transmission rate under the condition that the signal-to-noise ratio of the channel is equal to γ 0 is denoted as R 0 . According to Shannon's theorem, we get When the signal-to-noise ratio of the communication system is greater than the signal-to-noise ratio threshold γ 0 , the transmission information rates of the two source nodes and the relay node's forwarding information rate are both R 0 = log 2 (1 + γ 0 ). In this case, more time in the entire time block T can be used to transmit information, thus making the communication efficiency of the entire communication system higher.

[0014] Combining the above introduction, the actual maximum throughput τ under the TS-based LDR strategy (abbreviated as TS-LDR) can be expressed as

[0015] τ = (1 - p out )R 0 (1 - α)

[0016] In the formula, p out is the outage probability of the entire communication system.

[0017] Because the two channels are independent of each other, the outage probability p out of the entire communication system under the TS-LDR strategy can be expressed as

[0018] p out = p out1 + p out2 - p out1 ·p out2

[0019] Through theoretical derivation, the expression of the actual maximum throughput τ can be obtained as

[0020] τ = (1 - p out1 - p out2 + p out1 ·p out2 )(1 - α)log 2 (1 + γ 0 )

[0021] In the formula,

[0022]

[0023]

[0024] In the formula,

[0025] An optimization problem P is established with the goal of optimizing the actual maximum throughput:

[0026]

[0027] At a given λ h , λ g , γ 0 , η, P 1 , P 2 , and and other parameters, an optimization algorithm, such as the golden section method, is used to obtain the optimal energy harvesting time coefficient and the optimal actual maximum throughput. Denote the optimal actual maximum throughput as τ*; define the energy harvesting time coefficient corresponding to the optimal actual maximum throughput as the optimal energy harvesting time coefficient, denoted as α*. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0029] Figure 1 is the SWIPT two-way transmission relay system model based on the TS strategy provided by the present invention;

[0030] Figure 2 is the internal structure of the relay node based on the TS strategy provided by the present invention;

[0031] Figure 3 is the time allocation relationship between the energy harvesting and information transmission of the relay node based on the TS strategy provided by the present invention;

[0032] Figure 4 is the relationship between the actual maximum throughput τ and the energy harvesting time coefficient α; DETAILED DESCRIPTION OF THE INVENTION

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] The main idea of the present invention is to propose a method for limiting delay transmission in a SWIPT two-way transmission relay system based on the TS strategy, so that the system can obtain the optimal actual maximum throughput. The two source nodes are active, and the relay node is passive. The structural block diagram is shown in Figure 1 Among them, the passive relay adopts the TS receiving strategy.

[0035] As Figure 1 shown, the two active source nodes transmit information to each other, but the two source nodes cannot communicate directly. The signal must pass through the intermediate passive but RF energy harvesting-capable relay node to reach the other source node. Therefore, during the entire communication process, the relay node not only needs to forward the information sent by the source nodes on both sides, but also obtain energy from the RF signal emitted by one of the source nodes to ensure the normal operation of the entire communication system. The entire communication system adopts the limited delay relay (LDR) strategy. The LDR strategy means that strict time synchronization must be ensured between the receiving end node and the sending end node, that is, the receiving rate must always be equal to the sending rate. If the channel gain of a single channel cannot meet the communication conditions, then the communication of the entire communication system will be interrupted.

[0036] As Figure 1 shown, in the SWIPT two-way transmission relay system model based on the TS strategy, it includes two active source nodes U 1 , U 2 and an energy-constrained relay node h represents the channel gain between the source node U 1 and the relay node , g represents the channel gain between the source node U 2 and the relay node , P 1 represents the transmission power of the source node U 1 , and P 2 represents the transmission power of the source node U 2 .

[0037] This model satisfies the following conditions: (1) The entire communication channel is a quasi-static Rayleigh fading channel. The probability density function of the channel gain between the source node U 1 and the relay node is The source node U 2With the relay node The probability density function of the channel gain between where λ h and λ g are the means of the exponential random variables of the two channel gains respectively; (2) The relay node selects the amplify-and-forward (AF) strategy; (3) The power consumed by the relay node for signal processing is ignored, which is reasonable when the transmission distance is large enough and the collected energy is used as the main source of consumption; (4) An energy storage device with an infinite capacity is set in the relay node; (5) The magnitude relationship between the channel gains between the two source nodes and the relay node is known (for example, by the two source nodes simultaneously sending a detection signal to the relay), so the relay node can determine which source node to obtain energy from to make the energy collection efficiency and communication efficiency higher. To describe this patent, the relay node collects energy from source node U 1 to collect energy.

[0038] Figure 2 is the internal structure of the relay node based on the TS strategy, n A represents the noise generated by the antenna when receiving the signal, n A is a circularly symmetric complex Gaussian random variable, that is represents n A (t) follows a complex Gaussian distribution with a mean of 0 and a variance of y r，i (t) represents the signal assigned to the information processing module after receiving the signal sent by the source node. Among them, the subscript i = 1 or 2 represents the source node number, that is, y r1 (t) represents the signal assigned to the information processing module after receiving the signal sent by source node U 1 , y r2 (t) represents the signal assigned to the information processing module after receiving the signal sent by source node U 2 . n B represents the noise introduced during information processing, and there is Define y r (t) represents the signal received by the relay node from the two source nodes and processed by the baseband signal. s r，i (t) represents the signal amplified and forwarded by the relay node. Among them, the subscript i = 1 or 2 represents the source node number, that is, s r1 (t) represents the signal amplified by the relay node from source node U 1 and forwarded to source node U 2 , s r2 (t) represents the signal amplified by the relay node from source node U 2 and forwarded to source node U 1 .

[0039] The time allocation relationship for the relay node to collect energy and transmit information is as follows Figure 3 shown. T represents a complete time block, and α represents the time coefficient for the relay node to collect energy within the time block T, where α ∈ [0, 1]. That is, the relay node needs to spend αT of time to obtain the energy required for forwarding information. After the collected energy is sufficient to forward the received information, the relay node uses (1 - α)T / 2 of time to receive the information sent by the two source nodes, and then uses (1 - α)T / 2 of time to forward the received information to the source nodes at the other end respectively, thus completing the communication. Therefore, the communication process based on the LDR strategy of TS (abbreviated as TS-LDR) can be divided into three stages: the energy acquisition stage of the relay node; the information reception stage of the relay node (information uplink stage); the information forwarding stage of the relay node (information downlink stage).

[0040] For the convenience of the following formula derivation and introduction, the source node U 1 transmits information to the relay node , and then the relay node forwards it to the source node U 2 . The communication process is called link L 1 ; similarly, the communication process where the source node U 2 transmits information to the relay node , and then the relay node forwards it to the source node U 1 is called link L 2 .

[0041] In the actual communication process, the entire process of information transmission will be mixed with some interference factors, such as interference signals and noise, etc. If these influencing factors are too large, then the receiving end will not be able to correctly decode the effective part of the signal. According to the LDR strategy, when the two channel conditions formed by the two source nodes and the relay node are different, if one of the channels is not sufficient to complete the information transmission task, then it will lead to a complete interruption of the entire communication system. The criterion for judging whether the system is interrupted is the signal-to-noise ratio (SNR), that is, when the actual signal transmission SNR is less than the SNR threshold, then it is determined that the entire system is not sufficient to complete the task of transmitting information, that is, the communication is interrupted.

[0042] According to the above introduction, the outage probability p 1 of link L out1 and the outage probability p 2 of link L out2 can be respectively expressed as

[0043]

[0044]

[0045] In the formula, represents link L 1 the signal-to-noise ratio of the received signal at the receiving end, represents link L 2 the signal-to-noise ratio of the received signal at the receiving end, γ 0 represents the signal-to-noise ratio threshold, that is, the signal-to-noise ratio threshold γ 0 is the minimum signal-to-noise ratio that satisfies the communication condition without interruption. When the signal-to-noise ratio of the channel is equal to γ 0 the information transmission rate under the condition is denoted as R 0 . Obtained from Shannon's theorem Because the two channels are independent of each other, the outage probability p of the entire communication system under the TS-LDR strategy out can be expressed as

[0046] p out = p out1 + p out2 - p out1 ·p out2 (3)

[0047] When the signal-to-noise ratio of the communication system is greater than the signal-to-noise ratio threshold γ 0 the transmission information rates of the two source nodes and the relay node forwarding information rate are both R 0 = log 2 (1 + γ 0 ), in this case, more time in the entire time block T can be used to transmit information, so that the communication efficiency of the entire communication system can be higher. Combining the above introduction, the actual maximum throughput τ under the TS-LDR strategy can be expressed as

[0048]

[0049] In the formula, the numerator (2(1 - p out )R 0 t) is the total amount of information transmitted by the communication system under the entire T time block, t is the effective information transmission time of the entire communication system, and under the TS-LDR strategy, t = (1 - α)T / 2.

[0050] To explore the relationship between the actual maximum throughput and the energy collection time coefficient α, the analysis of the entire communication system will be introduced in turn according to the three stages of the communication process.

[0051] (1) Energy acquisition stage of the relay node

[0052] The relay node can obtain the channel state information (CSI) of two channels by receiving the detection signals sent by two source nodes. The relay node can then determine which channel has better conditions and thus obtain energy using the channel with better channel conditions. In this embodiment, the relay node always obtains energy from source node U 1 Obtains energy.

[0053] In link L 1 The relay node, after receiving the signal sent by source node U 1 The signal y r1 (t) assigned to the information processing module can be expressed as

[0054]

[0055] where x 1 (t) represents the signal sent from source node U 1 and E[|x 1 (t)| 2 = 1, where E[·] represents taking the expectation and |·| represents taking the modulus value. The noise n A，1 (t) generated by the relay node's receiving antenna is a circularly symmetric complex Gaussian random variable, that is represents that n A，1 (t) follows a complex Gaussian distribution with a mean of 0 and a variance of σ A，1 2 . The energy E h collected by the relay node can be expressed as

[0056] E h = ηαTP 1 |h| 2 (6)

[0057] where η is the energy harvesting efficiency factor, η ∈ [0, 1]. The energy E c required for the relay node to complete forwarding information can be expressed as

[0058]

[0059] where P R represents the amplify-and-forward power required for the relay node to forward information to the two source nodes. To obtain the actual maximum throughput within the entire time block T, the energy harvesting time coefficient α must be reduced to the minimum while maintaining communication. Then this critical point is that all the energy collected by the relay node is used for relay forwarding information within the entire time block T, that is

[0060] E h = E c (8)

[0061] Substituting Equation (6) and Equation (7) into Equation (8), the amplify-and-forward power P can be obtained R The relationship with the energy harvesting time coefficient α is

[0062]

[0063] (2) Relay Node Receiving Information Phase (Information Uplink Phase)

[0064] Similar to the principle of Equation (5), in link L 2 the signal y 2 received by the relay node from the source node U r2 and assigned to the information processing module can be expressed as

[0065]

[0066] where x 2 (t) represents the signal transmitted by the source node U 2 and E[|x 2 (t)| 2 = 1, n A，2 (t) is a circularly symmetric complex Gaussian random variable generated by the receiving antenna of the relay node, and According to Equation (5) and Equation (10), the signal y r received by the relay node from two source nodes and processed by baseband signal processing can be expressed as

[0067]

[0068] where n A (t) is the total noise generated by the receiving antenna of the relay node, n B (t) represents the noise generated when the relay node processes the received signal, and

[0069] (3) Relay Node Forwarding Information Phase (Information Downlink Phase)

[0070] Analyze link L 1 and link L 2 separately, and finally integrate them.

[0071] ① Link L 1

[0072] In link L 1 the relay node amplifies the signal received from the source node U 1 and forwards the signal s 2 to the source node U r1(t) can be expressed as

[0073]

[0074] In the formula,

[0075] source node U 2 received signal y d1 (t) is

[0076] y d1 (t) = gs r1 (t) + n d (t) (13)

[0077] In the formula, n d is the noise generated by the antenna of the source node and the conversion module, and there is

[0078] Substituting Equation (11) and Equation (12) into Equation (13) in turn, the overall expression of the received signal of the source node U 2 can be obtained as

[0079]

[0080]

[0081] In the formula,

[0082] Due to self-interference cancellation, the x 2 (t) term in Equation (14) is cancelled, and after cancellation, the received signal expression of the source node U 2 is

[0083]

[0084] From Equation (15) and the signal-to-noise ratio formula, the signal-to-noise ratio 1 of the received signal of the source node U 2 on the link L can be obtained as

[0085]

[0086] In order to obtain the relationship between the actual maximum throughput τ and the energy harvesting time coefficient α, it is necessary to express p out in Equation (3) with the energy harvesting time coefficient α. Therefore, substituting Equation (16) into Equation (1) and using Equation (9), the outage probability p 1 of the link L out1 is

[0087]

[0088] In the formula, for the convenience of representation, the following simplifications are made:

[0089] Since in formula (17) |g| 2 the sign of the coefficient of is not determined, and it is necessary to classify and discuss according to the magnitude relationship between a 1 |h| 4 and b 1 |h| 2 , the following can be obtained

[0090]

[0091] In formula (18), when |h| 2 <b 1 / a 1 , the square term on the left side of the inequality (|g| 2 ) must be greater than zero, and the numerator (c 1 |h| 2 +d 1 ) on the right side of the inequality is greater than zero. According to the boundary value of the piecewise function, it can be known that the denominator (a 1 |h| 4 -b 1 |h| 2 ) is less than zero. Then the right side of the inequality must be less than zero, so the inequality always holds, and its probability is 1.

[0092] Since the channel condition is a quasi-static Rayleigh fading channel, the probability density function of the channel gain between the source node U 1 and the relay node is

[0093]

[0094] The probability density function of the channel gain between the source node U 2 and the relay node is

[0095]

[0096] In the formula, λ h and λ g are the means of the exponential random variables of the two channel gains respectively. Correspondingly, the probability distribution functions of the two channel gains are

[0097] F h (z) = p(|h| 2 <z) = 1 - exp(-z / λ h ) (21)

[0098] Fg (z) = p(|g| 2 <z) = 1 - exp(-z / λ g ) (22)

[0099] Substituting equations (19) to (22) into the piecewise function of equation (18), we can obtain the integral expression of p out1 with respect to the independent variable z as

[0100]

[0101]

[0102] ② Link L 2

[0103] Link L 2 has an analysis process that is basically the same as that of Link L 1 In Link L 2 the relay node amplifies the signal from the source node U 2 and forwards the signal s 1 (t) can be expressed as r2 (t) =

[0104]

[0105] The source node U 1 receives the signal y d2 (t) as

[0106] y d2 (t) = hs r2 (t) + n d (t) (25)

[0107] Substituting equations (11) and (24) into equation (25) successively, due to self-interference cancellation, the signal y 1 received by the source node U d2 (t) is

[0108]

[0109] Then, the signal-to-noise ratio 2 of the signal received by the source node U 1 on Link L is

[0110]

[0111] Similarly, substituting equation (27) into equation (2) and using equation (9), the outage probability p 2 of Link L out2 is

[0112]

[0113] In the formula,

[0114] In formula (28), |h| 4 The sign of the coefficient of is not determined and needs to be classified and discussed according to the magnitude relationship between a 2 |g| 2 and b 2 to obtain

[0115]

[0116] In formula (29), when |g| 2 <b 2 / a 2 , the fourth power term (|h| 4 ) on the left side of the inequality must be greater than zero, and the numerator (c 2 |g| 2 +d 2 ) on the right side of the inequality is greater than zero. According to the boundary value of the piecewise function, it can be known that the denominator (a 2 |g| 2 -b 2 ) is less than zero. Then the right side of the inequality must be less than zero, so the inequality always holds, and its probability is 1.

[0117] Substituting formulas (19) to (22) into the piecewise function of formula (29), the integral expression of p out2 with respect to the independent variable z can be obtained as

[0118]

[0119] So far, after calculating the outage probabilities p 1 and p 2 of the two links L out1 and p out2 , the actual maximum throughput τ can be calculated using formulas (3) and (4), and its expression is

[0120] τ=(1 - p out1 - p out2 + p out1 ·p out2 )(1 - α)log 2 (1 + γ 0 ) (31)

[0121] An optimization problem P is established with the goal of maximizing the actual maximum throughput:

[0122]

[0123] At λ h and λ g and γ 0 and η, P 1 and P 2 and known Under the condition that parameters such as etc. are given, by using an optimization algorithm, such as the golden section method, the optimal energy harvesting time coefficient and the optimal actual maximum throughput are obtained. Denote the optimal actual maximum throughput as τ*; define the energy harvesting time coefficient corresponding to the optimal actual maximum throughput as the optimal energy harvesting time coefficient, denoted as α*.

[0124] When using the golden section method to solve the optimization problem P of Equation (32) to obtain the optimal energy harvesting time coefficient α* and the optimal actual maximum throughput τ*, the steps are as follows:

[0125] Step 1: Given the initial value range [a, b] of α and the precision e;

[0126] Step 2: Solve the golden section points of the interval a1 = a + (1 - 0.618)(b - a), a2 = a + 0.618×(b - a);

[0127] Step 3: Solve the actual maximum throughputs τ(a1) and τ(a2) corresponding to a1 and a2 respectively; if the actual maximum throughput τ(a1) < τ(a2), jump to Step 4, otherwise jump to Step 5;

[0128] Step 4: If a2 - a1 < e, stop the iteration, output the optimal solution α* = a2, and output the optimal actual maximum throughput τ* = τ(a2); otherwise, let a = a1, a1 = a2, a2 = a + 0.618×(b - a), and jump to Step 3;

[0129] Step 5: If a2 - a1 < e, stop the iteration, output the optimal solution α* = a2, and output the optimal actual maximum throughput τ* = τ(a2); otherwise, let b = a2, a2 = a1, a1 = a + (1 - 0.618)(b - a), and jump to Step 3.

[0130] The following further illustrates the technical solution provided by the present invention in combination with specific experimental simulations.

[0131] The present invention conducts simulation verification on the method for restricting delay transmission in a SWIPT two-way transmission relay system based on the TS strategy, and the parameter settings are as follows: the energy harvesting efficiency factor η = 1, the transmission powers P 1 of the two source nodes are 2 = P h = 1, and the means λ gAre respectively set to 1, the noise power generated when the relay node receives information and the noise power generated when the source node receives information are both set to 0.01, and the signal-to-noise ratio threshold γ 0 is set to 7.

[0132] See Figure 4 , when α* = 0.32, the optimal actual maximum throughput τ* = 1.0415 is obtained. It can be concluded from the simulation diagram that when α is too small or too large, the actual maximum throughput is small. This is because when α is too small, the energy collected by the relay node is less than the energy required for forwarding the currently received information, and there is not enough forwarding power to forward the information, resulting in a decrease in the signal-to-noise ratio of the signal forwarded to the receiving end, thereby increasing the outage probability and making the actual maximum throughput small; while when α is too large, although the energy collected by the relay node increases, the time for receiving the signal becomes smaller, which also results in a small actual maximum throughput.

[0133] In summary, the present invention discloses a method for limiting delay transmission in a SWIPT two-way transmission relay system based on the TS strategy, enabling the system to obtain the optimal actual maximum throughput.

[0134] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the patent protection scope determined by the claims submitted by the present invention.

Claims

1. Method for limiting delay transmission in a SWIPT two-way transmission relay system based on the TS strategy Characterized in that It includes The simultaneous wireless information and power transfer (SWIPT) two-way transmission relay system includes two active source nodes U 1 , U 2 and a passive relay node The relay node has radio frequency energy harvesting capabilities and adopts a time division (TS) strategy; direct communication between the two source nodes is not possible, and signals must pass through the intermediate relay node to reach the other source node; the channel gain between source node U 1 and the relay node is h, and the channel gain between source node U 2 and the relay node is g; the transmission power of source node U 1 is P 1 , and the transmission power of source node U 2 is P 2 ; The SWIPT two-way transmission relay system adopts the limited delay relay (LDR) strategy. The LDR strategy means that strict time synchronization must be ensured between the receiving end node and the sending end node, that is, the receiving rate must always be equal to the sending rate. If the channel gain of a single channel cannot meet the communication conditions, then the communication of the entire communication system is interrupted; The SWIPT two-way transmission relay system satisfies the following conditions: (1) The entire communication channel is a quasi-static Rayleigh fading channel; the source node U 1 and the relay node The channel gain probability density function between them is The source node U 2 and the relay node The channel gain probability density function between them is where Z is a random variable, and λ h and λ g are the means of the exponential random variables of the two channel gains respectively; (2) The relay node selects the amplify-and-forward strategy; (3) Ignoring the power consumed by the relay node for signal processing is reasonable when the transmission distance is large enough and the collected energy is used as the main source of consumption; (4) An energy storage device with an infinite capacity is set in the relay node; (5) The magnitude relationship between the channel gains between the two source nodes and the relay node is known; In the internal structure of the relay node, n A represents the noise generated by the antenna when receiving signals, n A is a circularly symmetric complex Gaussian random variable, that is represents n A (t) follows a complex Gaussian distribution with a mean of 0 and a variance of n B represents the noise introduced during information processing, and there is Define The energy harvesting efficiency factor is denoted as η; n d represents the noise generated by the antenna and the conversion module from the source node, and there is α represents the relay node's energy collection time coefficient within the time block T, α ∈ [0, 1]. That is, the relay node needs to spend αT time to obtain the required energy for forwarding information. After the collected energy is sufficient to forward the received information, the relay node uses (1 - α)T / 2 time to receive the information sent by the two source nodes, and then uses (1 - α)T / 2 time to forward the received information to the source nodes at the other end respectively, thus completing the communication; Source node U 1 transmits information to the relay node , and then the relay node forwards it to the source node U 2 . The communication process is called link L 1 ; Similarly, the source node U 2 transmits information to the relay node , and then the relay node forwards it to the source node U 1 . The communication process is called link L 2 ; The outage probability of link L 1 is denoted as p out1 , and the outage probability of link L 2 is denoted as p out2 ; Define the signal-to-noise ratio threshold γ 0 as the minimum signal-to-noise ratio for meeting the communication conditions without interruption; the information transmission rate under the condition that the signal-to-noise ratio of the channel is equal to γ 0 is denoted as R 0 ; obtained from Shannon's theorem When the signal-to-noise ratio of the communication system is greater than the signal-to-noise ratio threshold γ 0 , the transmission information rates of the two source nodes and the relay node's forwarding information rate are both R 0 = log 2 (1 + γ 0 ), in this case, more time in the entire time block T can be used to transmit information, thus making the communication efficiency of the entire communication system higher; The expression of the actual maximum throughput τ under the LDR strategy based on TS is τ=(1 - p out1 - p out2 + P out1 · P out2 )(1 - α)log 2 (1 + γ 0 ) In the formula In the formula, An optimization problem P is established with the goal of optimizing the actual maximum throughput Given λ h 、λ g 、γ 0 、η, P 1 、P 2 、 and the optimal energy harvesting time coefficient and the optimal actual maximum throughput are obtained by using the optimization algorithm.

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