A delay-limited transmission method in SWIPT two-way transmission relay system based on PS strategy

Abstract

The present invention discloses a limited delay transmission method in a SWIPT two-way transmission relay system based on a PS strategy. The signal-power simultaneous transmission (SWIPT) two-way transmission relay system includes two active source nodes and a passive relay node. The relay node has the ability to collect radio frequency energy and adopts a power splitting (PS) strategy. The entire communication channel is a quasi-static Rayleigh attenuation channel. The SWIPT two-way transmission relay system adopts a limited delay relay (LDR) strategy. The LDR strategy means that strict time synchronization must be guaranteed between the receiving node and the transmitting node. If the channel gain of a single channel cannot meet the communication conditions, the communication of the entire communication system is interrupted. Through theoretical derivation, the functional relationship between the actual maximum throughput and the power splitting coefficient is obtained. An optimization problem is established with the optimal actual maximum throughput as the goal, and an optimization algorithm is used to obtain the optimal power splitting coefficient and the optimal actual maximum throughput.

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 PS 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 a PS strategy, in which the passive relay adopts a PS 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 PS strategy. The present invention considers a SWIPT two-way transmission relay system based on a power splitting (PS) 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 in the figure, two active source nodes transmit information to each other, but the two source nodes cannot communicate directly. The signal must pass through the passive relay node in the middle that has the ability to collect RF energy 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 needs to 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 node and the transmitting 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, the communication of the entire communication system will be interrupted.

[0007] like Figure 1 As shown in the SWIPT bidirectional transmission relay model based on the PS strategy, there are two active source nodes U1 and U2 and one energy-constrained relay node. h represents the source node U1 and the relay node The channel gain between the source node U2 and the relay node The channel gain between them, P1 represents the transmission power of source node U1, and P2 represents the transmission power of source node U2. ρ represents the power division coefficient of energy collected at the relay node, ρ∈[0,1], and the passive relay node is The received electromagnetic wave signals are sent to the energy harvesting module (EH) and the information processing module (IT) respectively, which are used to obtain the required energy and receive information respectively.

[0008] This model satisfies the following conditions: (1) The entire communication channel is a quasi-static Rayleigh fading channel. The channel gain probability density function between Source node U2 and relay node The channel gain probability density function between Among them, λ h and λ g are the means of the exponential random variables of the two channel gains respectively; accordingly, the probability distribution functions of the two channel gains are and (2) The relay node selects the amplification-forward (AF) strategy; (3) The power consumed by the relay node for signal processing is ignored. This neglect is reasonable when the transmission distance is large enough and the collected energy is the main source of consumption; (4) An energy storage device with unlimited capacity is set in the relay node; (5) The relationship between the channel gain between the two source nodes and the relay node is known (for example, a detection signal is sent to the relay by the two source nodes at the same time), so the relay node can determine which source node to obtain energy from to make the energy collection efficiency and communication efficiency higher. For the purpose of describing this patent, the relay node collects energy from the source node U1.

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

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

[0011] The time distribution relationship between the relay node collecting energy and transmitting information is as follows: Figure 3 As shown in the figure, T represents a complete time block. The relay node uses T / 2 time to collect energy and receive information from two source nodes, and then uses T / 2 time to forward the received information to the source node at the other end, thereby completing the communication. Therefore, the communication process of the PS-based TDR strategy (PS-TDR for short) can be divided into three parts: the relay node obtains energy; the relay node receives information (information uplink part); the relay node forwards information (information downlink part).

[0012] Source node U1 to relay node Transmit information, then relay node The communication process forwarded to the source node U2 is called link L1; similarly, the communication process from the source node U2 to the relay node Transmit information, then relay node The communication process forwarded to the source node U1 is called link L2. The interruption probability of link L1 is denoted as p out1 , the interruption probability of link L2 is denoted as p out2 .

[0013] The signal-to-noise ratio threshold γ0 is defined as the minimum signal-to-noise ratio that satisfies the communication conditions without interruption. The information transmission rate under the condition that the channel signal-to-noise ratio is equal to γ0 is denoted as R0. From Shannon's theorem, we get When the signal-to-noise ratio of the communication system is greater than the signal-to-noise ratio threshold γ0, the information sending rate of the two source nodes and the information forwarding rate of the relay node are both R0=log2(1+γ0). In this case, the interruption probability can be reduced, thereby increasing the actual maximum throughput.

[0014] Combined with the above introduction, the actual maximum throughput τ based on the PS-LDR strategy can be expressed as

[0015] τ=(1-p out )R0

[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 interruption probability p of the entire communication system under the PS-LDR strategy is out It 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 follows:

[0020] τ=(1-p out1 -p out2 +p out1 ·p out2 )log2(1+γ0)

[0021] In the formula,

[0022]

[0023]

[0024] In the formula,

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

[0026]

[0027] st 0≤ρ≤1

[0028] In λ h ,g ,γ0,η,P1,P2, and Under given circumstances, an optimization algorithm, such as the golden section method, is used to obtain the optimal power division coefficient and the optimal actual maximum throughput. The optimal actual maximum throughput is denoted as τ*; the power division coefficient corresponding to the optimal actual maximum throughput is defined as the optimal power division coefficient, denoted as ρ*. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 It is a SWIPT bidirectional transmission relay system model based on PS strategy provided by the present invention;

[0031] Figure 2 It is the internal structure of the relay node based on the PS strategy provided by the present invention;

[0032] Figure 3 It is the time allocation relationship between the relay node collecting energy and transmitting information based on the PS strategy provided by the present invention;

[0033] Figure 4 is the relationship between the actual maximum throughput τ and the power division factor ρ; DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The main purpose of the present invention is to propose a method for limiting delayed transmission in a SWIPT bidirectional transmission relay system based on a PS strategy, so that the system can obtain the optimal actual maximum throughput. The two source nodes are active, the relay node is passive, and the structural block diagram is shown in Figure 1 Among them, the passive relay adopts the PS receiving strategy.

[0036] like Figure 1As shown in the figure, two active source nodes transmit information to each other, but the two source nodes cannot communicate directly. The signal must pass through the passive relay node in the middle that has the ability to collect RF energy 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 needs to 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 node and the transmitting 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, the communication of the entire communication system will be interrupted.

[0037] like Figure 1 As shown in the SWIPT bidirectional transmission relay model based on the PS strategy, there are two active source nodes U1 and U2 and one energy-constrained relay node. h represents the source node U1 and the relay node The channel gain between the source node U2 and the relay node The channel gain between them, P1 represents the transmission power of source node U1, and P2 represents the transmission power of source node U2. ρ represents the power division coefficient of energy collected at the relay node, ρ∈[0,1], and the passive relay node is The received electromagnetic wave signals are sent to the energy harvesting module (EH) and the information processing module (IT) respectively, which are used to obtain the required energy and receive information respectively.

[0038] This model satisfies the following conditions: (1) The entire communication channel is a quasi-static Rayleigh fading channel. The channel gain probability density function between Source node U2 and relay node The channel gain probability density function between Among them, λ h and λ g are the means of the exponential random variables of the two channel gains respectively; accordingly, the probability distribution functions of the two channel gains are and (2) The relay node selects the amplification-forward (AF) strategy; (3) The power consumed by the relay node for signal processing is ignored. This neglect is reasonable when the transmission distance is large enough and the collected energy is the main source of consumption; (4) An energy storage device with unlimited capacity is set in the relay node; (5) The relationship between the channel gain between the two source nodes and the relay node is known (for example, a detection signal is sent to the relay by the two source nodes at the same time), so the relay node can determine which source node to obtain energy from to make the energy collection efficiency and communication efficiency higher. For the purpose of describing this patent, the relay node collects energy from the source node U1.

[0039] Figure 2 is the internal structure of the relay node based on the PS strategy, n A It represents the noise generated by the antenna when receiving the signal, n A is a circularly symmetric complex Gaussian random variable, that is Indicates n A (t) obeys a complex Gaussian distribution with a mean of 0 and a variance of y r，i (t) represents the signal sent by the source node and assigned to the information processing module, where the subscript i=1 or 2 represents the source node number, i.e., y r1 (t) represents the signal sent by the source node U1 and then distributed to the information processing module, y r2 (t) indicates the signal sent by the receiving source node U2 and then distributed to the information processing module. B represents the noise introduced during information processing, and definition y r (t) indicates the signal received by the relay node from the two source nodes and processed by the baseband signal. r，i (t) represents the signal amplified and forwarded by the relay node, where the subscript i=1 or 2 represents the source node number, i.e., s r1 (t) represents the signal from the source node U1 amplified by the relay node and forwarded to the source node U2, s r2 (t) represents a signal obtained by amplifying the signal from the source node U2 at the relay node and forwarding it to the source node U1.

[0040] The time distribution relationship between the relay node collecting energy and transmitting information is as follows: Figure 3As shown in the figure, T represents a complete time block. The relay node uses T / 2 time to collect energy and receive information from two source nodes, and then uses T / 2 time to forward the received information to the source node at the other end, thereby completing the communication. Therefore, the communication process of the PS-based TDR strategy (PS-TDR for short) can be divided into three parts: the relay node obtains energy; the relay node receives information (information uplink part); the relay node forwards information (information downlink part).

[0041] For the convenience of the following formula derivation and introduction, the source node U1 sends Transmit information, then relay node The communication process forwarded to the source node U2 is called link L1; similarly, the communication process from the source node U2 to the relay node Transmit information, then relay node The communication process forwarded to the source node U1 is called link L2.

[0042] In the actual communication process, the entire process of information transmission will be mixed with some interference factors, such as interference signals and noise. If these influencing factors are too large, the receiving end will not be able to correctly decode the effective part of the signal. According to the LDR strategy, when the two channels composed of two source nodes and relay nodes have different conditions, if one of the channels is not enough to complete the information transmission task, then the entire communication system will be completely interrupted. The standard for judging whether the system is interrupted is the signal-to-noise ratio (SNR), that is, when the actual signal transmission signal-to-noise ratio is less than the signal-to-noise ratio threshold, then it is determined that the entire system is not enough to complete the task of transmitting information, that is, communication is interrupted.

[0043] According to the above introduction, the interruption probability p of link L1 is out1 and the outage probability p of link L2 out2 Can be expressed as

[0044]

[0045]

[0046] In the formula, represents the signal-to-noise ratio of the signal received at the receiving end of link L1, represents the signal-to-noise ratio of the signal received at the receiving end of link L2, and γ0 represents the signal-to-noise ratio threshold, that is, the signal-to-noise ratio threshold γ0 is the minimum signal-to-noise ratio that meets the communication conditions without interruption. The information transmission rate under the condition that the channel signal-to-noise ratio is equal to γ0 is denoted as R0. From Shannon's theorem, we get Because the two channels are independent of each other, the interruption probability p of the entire communication system under the PS-LDR strategy is out It can be expressed as

[0047] p out =p out1 +p out2 -p out1 ·p out2 (3)

[0048] When the signal-to-noise ratio of the communication system is greater than the signal-to-noise ratio threshold γ0, the information transmission rate of the two source nodes and the information forwarding rate of the relay node are both R0=log2(1+γ0). In this case, the interruption probability can be reduced, thereby increasing the actual maximum throughput. Combined with the above introduction, the actual maximum throughput τ under the PS-LDR strategy can be expressed as

[0049]

[0050] In the formula, the numerator (2(1-p out )R0t) is the total amount of information transmitted by the communication system in the entire T time block, t is the effective information transmission time of the entire communication system, and under the PS-LDR strategy, t=T / 2.

[0051] In order to explore the relationship between the actual maximum throughput and the power division factor ρ, the analysis of the entire communication system will be divided into three parts and introduced in turn.

[0052] (1) Relay node obtains energy

[0053] The relay node can obtain the channel state information (CSI) of the two channels by receiving the detection signals sent by the two source nodes, and the relay node can determine which channel condition is better, so as to obtain energy using the channel with better channel condition. In this embodiment, the relay node always obtains energy from the source node U1.

[0054] In link L1, after the relay node receives the signal sent by the source node U1, the signal y is assigned to the information processing module. r1 (t) can be expressed as

[0055]

[0056] In the formula, x1(t) represents the signal sent from the source node U1, and E[|x1(t)| 2 ]=1, where E[·] represents the expected value and |·| represents the modulus value. The noise generated by the relay node receiving antenna n A，1 (t) is a circularly symmetric complex Gaussian random variable, that is Indicates n A，1 (t) obeys a complex Gaussian distribution with a mean of 0 and a variance of σ A，1 2 The energy collected by the relay node is E h It can be expressed as

[0057]

[0058] Where η is the energy collection efficiency factor, η∈[0,1]. The energy required by the relay node to complete the forwarding of information E c It can be expressed as

[0059]

[0060] Where P R Represents the amplified forwarding power required by the relay node to forward information to the two source nodes. If the power division coefficient ρ increases, the collected energy increases, but the signal-to-noise ratio of the collected effective signal decreases; if ρ decreases, the collected energy is not enough to support the forwarding of all signals; both of these situations will lead to a decrease in the transmission efficiency of the entire communication system. In order to obtain the optimal power division coefficient so that the transmission efficiency of the entire communication system reaches the optimal value, it is required that all the collected energy is used to forward effective information by the relay node, that is,

[0061] E h =E c (8)

[0062] Substituting equations (6) and (7) into equation (8), we can get the amplification and forwarding power P R The relationship with the power division factor ρ is

[0063] P R =ηρP1|h| 2 (9)

[0064] (2) Relay node receives information (uplink information)

[0065] The principle is the same as that of formula (5). In link L2, after the relay node receives the signal sent by the source node U2, the signal y assigned to the information processing module is r2 (t) can be expressed as

[0066]

[0067] In the formula, x2(t) represents the signal sent by the source node U2, and E[|x2(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 has According to equations (5) and (10), the relay node receives the signals sent by the two source nodes and the signal y after baseband signal processing is r (t) can be expressed as

[0068]

[0069] 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

[0070] (3) Relay node forwarding information (downlink information part)

[0071] Link L1 and link L2 are analyzed separately and then integrated.

[0072] ① Link L1

[0073] In link L1, the relay node amplifies the signal sent by the source node U1 and forwards the signal s to the source node U2. r1 (t) can be expressed as

[0074]

[0075] In the formula,

[0076] The signal y received by source node U2 d1 (t) is

[0077] y d1 (t) = gs r1 (t)+n d (t) (13)

[0078] Where n d is the noise generated by the antenna and conversion module of the source node, and

[0079] Substituting equations (11) and (12) into equation (13) in turn, we can obtain the overall expression of the signal received by the source node U2:

[0080]

[0081] In the formula,

[0082] Due to the self-interference cancellation, the term x2(t) in equation (14) is eliminated. After the elimination, the expression of the signal received by the source node U2 is:

[0083]

[0084] From equation (15) and the signal-to-noise ratio formula, we can get the signal-to-noise ratio of the signal received by the source node U2 on link L1: The expression is

[0085]

[0086] In order to obtain the relationship between the actual maximum throughput and the power division factor ρ, it is necessary to replace p in equation (3) with out It is expressed by the power division coefficient ρ. Therefore, by substituting equation (16) into equation (1), and using equation (9), we can get the interruption probability p of link L1: out1 for

[0087]

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

[0089] Because in formula (17) |g| 2 The positive and negative coefficients of are not determined, and need to be calculated according to a1|h| 4 and b1|h| 2 The size relationship of is classified and discussed, and we can get

[0090]

[0091] In formula (18), when |h| 2 When b1 / a1, the square term on the left side of the inequality (|g| 2 ) must be greater than zero, while the numerator on the right side of the inequality (c1|h| 2 +d1) is greater than zero. According to the boundary value of the piecewise function, the denominator (a1|h| 4 -b1|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 source node U1 and the relay node The channel gain probability density function between

[0093]

[0094] Source node U2 and relay node The channel gain probability density function between

[0095]

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

[0097] Fh (z)=p(|h| 2 < z) = 1-exp(-z / λ h ) (twenty one)

[0098] F g (z)=p(|g| 2 < z) = 1-exp(-z / λ g ) (twenty two)

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

[0100]

[0101] ②Link L2

[0102] The analysis process of link L2 is basically the same as that of link L1. In link L2, the relay node amplifies the signal from source node U2 and forwards the signal s to source node U1. r2 (t) can be expressed as

[0103]

[0104] The signal y received by the source node U1 d2 (t) is

[0105] y d2 (t) = hs r2 (t)+n d (t) (25)

[0106] Substituting equations (11) and (24) into equation (25) in turn, due to the elimination of self-interference, the signal y received by the source node U1 is d2 (t) is

[0107]

[0108] Then, the signal-to-noise ratio of the signal received by the source node U1 on link L2 is for

[0109]

[0110] Similarly, substituting equation (27) into equation (2) and using equation (9), we can obtain the channel outage probability p of link L2: out2 for

[0111]

[0112] In the formula,

[0113] In formula (28), |h| 4 The positive and negative coefficients of are not determined, and need to be calculated according to a2|g| 2 The relationship between the size of and b2 is discussed by classification, and we can get

[0114]

[0115] In formula (29), when |g| 2 When b2 / a2, the fourth-order term on the left side of the inequality (|h| 4 ) must be greater than zero, while the numerator on the right side of the inequality (c2|g| 2 +d2) is greater than zero. According to the boundary value of the piecewise function, the denominator (a2|g| 2 -b2) 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.

[0116] Substituting equations (19) to (22) into the piecewise function of equation (29), we can obtain p out2 The integral expression of the independent variable z is

[0117]

[0118] At this point, the outage probability p of the two links L1 and L2 is out1 and p out2 After all are calculated, the actual maximum throughput τ can be calculated using equations (3) and (4), which is expressed as

[0119] τ=(1-p out1 -p out2 +p out1 ·p out2 )log2(1+γ0) (31)

[0120] The optimization problem P is established with the goal of optimizing the actual maximum throughput:

[0121]

[0122] In λ h , g ,γ0,η,P1,P2, and Under given circumstances, an optimization algorithm, such as the golden section method, is used to obtain the optimal power division coefficient and the optimal actual maximum throughput. The optimal actual maximum throughput is denoted as τ*; the power division coefficient corresponding to the optimal actual maximum throughput is defined as the optimal power division coefficient, denoted as ρ*.

[0123] When the golden section method is used to solve the optimization problem P of formula (32), the optimal power division coefficient ρ* and the optimal actual maximum throughput τ* are obtained. The steps are as follows:

[0124] Step 1: Given the initialization interval [a, b] and precision e of ρ;

[0125] Step 2: Solve the golden section points of the interval a1 = a + (1-0.618) (ba), a2 = a + 0.618 × (ba);

[0126] 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;

[0127] Step 4: If a2-a1<e, stop iteration, output the optimal solution ρ*=a2, and output the optimal actual maximum throughput τ*=τ(a2); otherwise, let a=a1, a1=a2, a2=a+0.618×(ba), and jump to step 3;

[0128] Step 5: If a2-a1<e, stop iteration, output the optimal solution ρ*=a2, and output the optimal actual maximum throughput τ*=τ(a2); otherwise, let b=a2, a2=a1, a1=a+(1-0.618)(ba), and jump to step 3.

[0129] The technical solution provided by the present invention is further described below in conjunction with specific experimental simulations.

[0130] The present invention simulates and verifies the delay-limited transmission method in the SWIPT bidirectional transmission relay system based on the PS strategy, and uses the following parameter settings: energy collection efficiency factor η = 1, two source node transmission powers P1 = P2 = 1, and the mean values ​​λ of the channel gain index random variables h and g. h and λ g Set to 1 respectively, the noise power generated by the relay node when receiving information and the noise power generated when the source node receives information Both are set to 0.01, and the threshold γ0 of the signal-to-noise ratio is set to 3.92.

[0131] See also Figure 4 , when ρ*=0.58, the optimal actual maximum throughput τ*=1.1444. According to the simulation graph, it can be concluded that when ρ is too small or too large, the actual maximum throughput is less than the optimal actual maximum throughput.

[0132] In summary, the present invention discloses a method for limiting delay transmission in a SWIPT bidirectional transmission relay system based on a PS strategy, so that the system obtains the optimal actual maximum throughput.

[0133] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the scope of patent protection of the present invention determined by the submitted claims.

Claims

1. A method for limiting delay transmission in a SWIPT bidirectional transmission relay system based on a PS strategy, characterized in that ,include: The SWIPT bidirectional transmission relay system consists of two active source nodes U1 and U2 and a passive relay node. The relay node has the ability to collect RF energy and adopts a power splitting (PS) strategy. Two source nodes cannot communicate directly, and the signal must pass through the intermediate relay node to reach the other source node. The channel gain between the source node U2 and the relay node is h. The channel gain between them is g; the transmission power of source node U1 is P1, and the transmission power of source node U2 is P2; the power division coefficient of the energy collected by the relay node is ρ, ρ∈[0,1], that is, the passive relay node is The received electromagnetic wave signals are used to obtain the required energy and receive information respectively in the proportion of 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 node and the sending 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, the communication of the entire communication system will be interrupted. The SWIPT bidirectional transmission relay system meets the following conditions: (1) The entire communication channel is a quasi-static Rayleigh fading channel; the source node U1 and the relay node The channel gain probability density function between Source node U2 and relay node The channel gain probability density function between Among them, 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; (4) an energy storage device with infinite capacity is set in the relay node; (5) the relationship between the channel gains of the two source nodes and the relay node is known, and the relay node collects energy from the source node U1; In the internal structure of the relay node, n A It represents the noise generated by the antenna when receiving the signal, n A is a circularly symmetric complex Gaussian random variable, that is Indicates n A (t) obeys a complex Gaussian distribution with a mean of 0 and a variance of n B represents the noise introduced during information processing, and definition The energy collection efficiency factor is denoted as η; n d represents the noise generated by the antenna and the conversion module from the source node, and In a complete time block T, the relay node uses T / 2 time to collect energy and receive information from two source nodes, and then uses T / 2 time to forward the received information to the source node at the other end, thereby completing the communication; therefore, the communication process of the PS-based LDR strategy can be divided into three parts: the relay node obtains energy part; the relay node receives information part, that is, the information uplink part; the relay node forwards information part, that is, the information downlink part; Source node U1 to relay node Transmit information, then relay node The communication process forwarded to the source node U2 is called link L1; similarly, the communication process from the source node U2 to the relay node Transmit information, then relay node The communication process forwarded to the source node U1 is called link L2; the interruption probability of link L1 is denoted as p out1 , the interruption probability of link L2 is denoted as p out2 ; The signal-to-noise ratio threshold γ0 is defined as the minimum signal-to-noise ratio that satisfies the communication conditions without interruption; the information transmission rate under the condition that the channel signal-to-noise ratio is equal to γ0 is denoted as R0; from Shannon's theorem, we get When the signal-to-noise ratio of the communication system is greater than the signal-to-noise ratio threshold γ0, the information sending rate of the two source nodes and the information forwarding rate of the relay node are both R0=log2(1+γ0); The expression of the actual maximum throughput τ under the PS-based LDR strategy is: τ=(1-p out1 -p out2 +p out1 ·p out2 )log2(1+γ0) In the formula, In the formula, The optimization problem P is established with the goal of optimizing the actual maximum throughput: In λ h , g ,γ0,η,P1,P2, and Under given circumstances, an optimization algorithm is used to obtain the optimal power division factor and the optimal actual maximum throughput.

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