A short packet secure transmission method for multi-intelligent reflector-assisted NOMA system

Abstract

The present invention discloses a short packet secure transmission method for a multi-intelligent reflector-assisted NOMA system. The proposed system consists of a source node S, K intelligent reflectors (IRSs), two legitimate users (D1 and D2), and an eavesdropping node (E) that has no external energy supply and needs to collect energy. The method includes the following steps: S sends a pilot signal, E collects energy from S's transmitted signal and the IRS's reflected signal, and determines the intelligent reflector set S that makes the energy collected by E greater than a certain threshold. U ; from S U Choose the optimal IRS k* Based on IRS k* , determine the optimal power allocation coefficient α * Maximize the lower bound of the confidentiality rate at D1 and D2 to ensure secure data transmission; in IRS k* With the help of [1], S uses the NOMA protocol to send private short packets to D1 and D2. At the same time, E not only collects energy but also attempts to steal the private data of D1 and D2. This method can ensure the secure transmission of D1 and D2's short packets while ensuring that the energy harvester collects a certain amount of energy.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a short packet secure transmission method suitable for a multi-intelligent reflector-assisted NOMA system. Background Art

[0002] A smart reflector is a plane composed of a large number of low-cost passive reflective elements, placed between the transmitter and receiver. Each reflector element in the smart reflector independently alters the phase of the incident signal. Therefore, by adjusting the phase shift on each reflector element, the wireless propagation environment can be modified. The emergence of smart reflector technology has disrupted the traditional approach of improving communication system performance by designing high-performance transceivers, and has had a disruptive impact on future communication systems.

[0003] In recent years, with the development of wireless communication technology, the scale of communications has been increasing, and communication services have shown a trend of diversity and diversification. The spectrum resources in the communications industry are in short supply. NOMA technology breaks away from the constraints of orthogonality and enables different users to occupy the same spectrum, time and other resources through power multiplexing or superposition coding at the signal transmission end. This technology can realize resource sharing among multiple users and improve the spectrum efficiency of the system. At the same time, the problem of network security communication has become increasingly prominent in the information age, and security incidents such as privacy leakage, property loss and malicious intrusion are frequent. On the other hand, massive short packet data interaction is also the main data type of the fifth generation and next generation mobile communications, which is widely present in various military and civilian scenarios. Based on this, the present invention applies intelligent reflector technology and NOMA technology to propose a short packet secure transmission method, which can optimize its secure transmission while ensuring the reliable transmission of short packets. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the background technology, the present invention discloses a short packet security transmission method suitable for a multi-intelligent reflector assisted NOMA system. The present invention applies intelligent reflector technology and NOMA technology to optimize the secure transmission of short packets while ensuring reliable transmission of short packets.

[0005] Technical solution: The present invention discloses a method for securely transmitting short packets in a multi-intelligent reflector-assisted NOMA system. The system comprises a source node S, K intelligent reflectors (IRSs), two legitimate users (D1 and D2), and an eavesdropping node (E) without external energy supply. S sends private short packets to D1 and D2, and the IRSs reflect the data sent by S. The eavesdropping node (E) collects energy from the received radio frequency signals and also attempts to steal the private data of D1 and D2. N intelligent reflector units are deployed on each intelligent reflector.

[0006] The short packet secure transmission method comprises the following steps:

[0007] Step 1: One information transmission takes T time. In the first (1-τ)T time, S sends a pilot signal Determine the energy E collected by the eavesdropper E ke ≥E th The corresponding smart reflective surface set S U ; From the set S U Select the optimal intelligent reflective surface IRS k* Based on IRS k* , determine the optimal power allocation coefficient α*; where x1 and x2 are the pilot signals sent to D1 and D2 respectively, P s is the transmission power at S, α is the power allocation coefficient, 0.5<α<1, E th is a fixed threshold, 0<τ<1 is the time conversion factor;

[0008] Step 2: In the next τT time, use the IRS determined in step 1 k* and α*, S communicates with users D1 and D2, and the eavesdropper E collects energy and tries to steal D i Private data, i = 1, 2; specifically: S sends a signal The eavesdropper E receives the transmitted signal from S and IRS k* The energy is collected from the reflected signal and attempts to steal D i Private data of D i Through direct link and IRS k* The reflection link receives the signal, s1 and s2 are the private short packet data sent by S to D1 and D2 respectively.

[0009] Furthermore, in step 1, E uses the PS mode to collect energy from the received RF signal, where the power division factor for energy collection is μ and the power division factor for information decoding is (1-μ). According to the PS protocol, E collects energy from the transmitted signal of S and the IRS. k The energy E collected from the reflected signal ke for:

[0010]

[0011] Among them, η (0<η<1) represents the energy conversion efficiency, g se is the channel fading coefficient of link S→E, For the link S→IRS k The channel fading coefficient, For Link IRS k →E is the channel fading coefficient, h sk The conjugate transpose of Indicates IRSk The phase shift matrix on k，l It's the IRS k The amplitude reflection coefficient of the lth reflection unit, l∈{1, 2, ..., N}, k∈{1, 2, ..., K} is the kth smart reflection surface, Represents an N×1 complex matrix.

[0012] Furthermore, in step 1, the selected intelligent reflective surface IRS k* Satisfy the following formula:

[0013]

[0014] in, is the total channel gain at D1, is the total channel gain at D2, is the channel fading coefficient of the link S→Di, For Link IRS k →D i The channel fading coefficient i=1,2,k∈S U .

[0015] Furthermore, in step 1, the selected optimal power allocation coefficient α* satisfies α*=arg max{min{R1, R2}};

[0016] Among them, R1 and R2 are the lower bounds of the confidentiality rate at D1 and D2 respectively, denoted as:

[0017]

[0018]

[0019] in, are the received signal-to-noise ratios at D1 and D2, respectively, are the received signal-to-noise ratios of x1 and x2 at E, Q -1 (·) is the inverse function of the Gaussian Q function, M is the code length of the short packet, ∈ i and δ i are the decoding error probability and information leakage amount respectively, i∈{1,2}.

[0020] Furthermore, in step 1, the received signal-to-noise ratio at E and They are:

[0021]

[0022]

[0023] Where α is the power distribution coefficient at D1 0.5<α<1, For the link S→IRS k* The channel fading coefficient, For Link IRS k* →E is the channel fading coefficient, h sk* The conjugate transpose of Indicates IRS k* The phase shift matrix on k*，l It's the IRS k* The amplitude reflection coefficient of the lth reflection unit, l∈{1, 2, ..., N}, N0 represents the noise power;

[0024] Receive signal-to-noise ratio at D1 and D2 and They are:

[0025]

[0026]

[0027] in For Link IRS k* →Di’s channel fading coefficient.

[0028] Beneficial effects: Compared with the existing technology, the advantages of the present invention are: combining smart reflective surfaces, NOMA and energy harvesting technology, using the total channel gain at the legitimate user to select the optimal smart reflective surface, optimizing the lower bound of the confidentiality rate by optimizing the power allocation coefficient, and maximizing the lower bound of the confidentiality transmission rate of the entire communication system while considering the reliability of communication, thereby ensuring the secure transmission of short packet data of the system; in addition, the proposed scheme also ensures that the energy harvesting user can harvest a certain amount of energy, which has important significance and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a model diagram of the transmission method of the present invention;

[0030] Figure 2 is a time slot diagram of the present invention;

[0031] Figure 3 The sum of the lower bounds of the confidentiality rates of the present invention and the random selection scheme (i.e., randomly selecting a smart reflector and randomly selecting a power allocation coefficient α*) under different signal-to-noise ratios is compared.

[0032] Figure 4 The optimal power allocation coefficient results obtained by the present invention under different signal-to-noise ratios are shown in FIG. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] The proposed system includes a source node (S), K intelligent reflecting surfaces (IRS), two legitimate users (D1 and D2), and an eavesdropping node (E) without external energy supply. S sends private short packets to D1 and D2, and the IRS reflects the data sent by S. The eavesdropper E collects energy from the received radio frequency signal and also attempts to steal the private data of D1 and D2. Each intelligent reflecting surface deploys N intelligent reflecting units:

[0035] Transfer methods include:

[0036] Step 1: One information transmission takes T time. In the first (1-τ)T time, S sends a pilot signal Determine the energy E collected by the eavesdropper E ke ≥E th The corresponding smart reflective surface set S U ; Further, from the set S U Select the optimal intelligent reflective surface IRS k* ; Further, based on IRS k* , determine the optimal power allocation coefficient α*; where x1 and x2 are the pilot signals sent to D1 and D2 respectively, P s is the transmission power at S, α is the power allocation coefficient (0.5<α<1), E th is a fixed threshold, and 0<τ<1 is the time conversion factor.

[0037] Specifically, E uses the PS (power splitting) mode to collect energy from the received RF signal, where the power splitting factor for energy collection is μ and the power splitting factor for information decoding is (1-μ). According to the PS protocol, E collects energy from the transmitted signal of S and the IRS. k The energy E collected from the reflected signal ke Specifically: Among them, η (0<η<1) represents the energy conversion efficiency, g se is the channel fading coefficient of link S→E, For the link S→IRS k The channel fading coefficient, For Link IRS k →E is the channel fading coefficient, h sk The conjugate transpose of Indicates IRS k The phase shift matrix on k，l It's the IRS kThe amplitude reflection coefficient of the lth reflection unit, l∈{1, 2, ..., N}, k∈{1, 2, ..., K} is the kth smart reflection surface, Represents an N×1 complex matrix.

[0038] Selected intelligent reflective surface IRS k* Satisfy the following formula: in, is the total channel gain at D1, is the total channel gain at D2, For link S→D i The channel fading coefficient, For Link IRS k →D i Channel fading coefficient (i=1, 2), k∈S U .

[0039] The selected optimal power allocation coefficient α* satisfies α*=arg max{min{R1, R2}}.

[0040] R1 and R2 are the lower bounds of the confidentiality rate at D1 and D2, respectively, and are expressed as:

[0041]

[0042]

[0043] in, are the received signal-to-noise ratios at D1 and D2, respectively, are the received signal-to-noise ratios of x1 and x2 at E, Q -1 (·) is the inverse function of the Gaussian Q function, M is the code length of the short packet, ∈ i and δ i are the decoding error probability and information leakage amount, respectively, i∈{1,2};

[0044] Received signal-to-noise ratio at E and Specifically:

[0045]

[0046]

[0047] Where α is the power distribution coefficient at D1 (0.5<α<1), For the link S→IRS k* The channel fading coefficient, For Link IRS k* →E is the channel fading coefficient, h sk* The conjugate transpose of Indicates IRS k* The phase shift matrix on k*，l It's the IRS k* The amplitude reflection coefficient of the lth reflection unit, l∈{1, 2, ..., N}, N0 represents the noise power;

[0048] Receive signal-to-noise ratio at D1 and D2 and Specifically:

[0049]

[0050]

[0051] in For Link IRS k* →D i Channel fading coefficient (i=1, 2).

[0052] Step 2: In the next τT time, use the IRS determined in step 1 k* and α*, S communicates with users D1 and D2, and the eavesdropper E collects energy and tries to steal D i Private data (i=1, 2), specifically: S sends a signal The eavesdropper E receives the transmitted signal from S and IRS k* The energy is collected from the reflected signal and attempts to steal D i Private data of (i=1, 2); D i (i=1, 2) through direct link and IRS k* The reflection link receives the signal, s1 and s2 are the private short packet data sent by S to D1 and D2 respectively.

[0053] The following is the experimental results of the sum of the lower bounds of the confidentiality rate and the optimal power allocation coefficient of the present invention.

[0054] The specific conditions of the simulation experiment are: independent and identically distributed Rayleigh fading channel, energy conversion rate η = 0.8, time slot factor τ = 0.5, noise power N0 = 1, N = 4 reflection units of the smart transmitting surface, and the amplitude reflection coefficient β of each reflection unit of each smart reflecting surface. k，l =1(k=1,…,K,l=1,…,N), code length M=200, decoding error probability ∈ i =10 -3 , information leakage δ i =10 -3 .

[0055] like Figure 1 As shown in Figure 1, the proposed system consists of a source node (S), K intelligent reflecting surfaces (IRS), two legitimate users (D1, D2), and an eavesdropping node (E) without external energy supply. S sends private short packets to D1 and D2, and the IRS reflects the data sent by S. The eavesdropper E collects energy from the received RF signal and also attempts to steal the private data of D1 and D2. Each intelligent reflecting surface is deployed with N intelligent reflecting units. One information transmission takes time. In the first (1-τ)T time, S sends a pilot signal. Determine the energy E collected by the eavesdropper E ke ≥E th The corresponding smart reflective surface set S U ; From the set S U Select the optimal intelligent reflective surface IRS k* Based on IRS k* , determine the optimal power allocation coefficient α*; where x1 and x2 are the pilot signals sent to D1 and D2 respectively, P s is the transmission power at S, α is the power allocation coefficient (0.5<α<1), E th is a fixed threshold, 0<τ<1 is the time conversion factor. In the next τT time, the IRS determined in step 1 is used k* and α*, S communicates with users D1 and D2, and the eavesdropper E collects energy and tries to steal D i Private data (i=1, 2), specifically: S sends a signal The eavesdropper E receives the transmitted signal from S and IRS k* The energy is collected from the reflected signal and attempts to steal D i Private data of (i=1, 2); D i (i=1, 2) through direct link and IRS k* The reflection link receives the signal, s1 and s2 are the private short packet data sent by S to D1 and D2 respectively.

[0056] Figure 2 The duration details of each process in the multi-intelligent reflector-assisted NOMA system are described. In the first (1-τ)T time, S moves to D i Send pilot signal and select the optimal intelligent reflector IRS k* , based on IRS k* , determine the optimal power allocation coefficient α*; in the next T time, use the determined IRS k* and α*, S communicates with users D1 and D2, and the eavesdropper E collects energy and tries to steal D i private data.

[0057] Under different numbers of smart reflectors (K) and different signal-to-noise ratios (SNR), Figure 3 The results of the sum of the lower bounds of the confidentiality rate of the present invention and the random selection scheme are compared. Under different signal-to-noise ratios (SNR), Figure 4 The optimal power allocation coefficient results under the scheme of the present invention are given. Figure 3 and Figure 4 The horizontal axis is the signal-to-noise ratio (SNR, in dB), and the vertical axis is the lower bound of the security rate and the optimal power allocation coefficient, respectively. In the figure, "-" indicates the case where K = 5, and "---" indicates the case where K = 3. The symbol "+" indicates the solution of the present invention, and the symbol "*" indicates the random selection solution.

[0058] from Figure 3 As can be seen, the sum of the lower bounds of the secrecy rates for the present invention is significantly higher than that of the random selection scheme at any K value and any signal-to-noise ratio (SNR). For example, when K = 5 and SNR = 10 dB, the sum of the lower bounds of the secrecy rates is approximately 0.839, while the sum of the lower bounds of the secrecy rates for the random selection scheme is approximately 0.137. This shows that the sum of the lower bounds of the secrecy rates for the present invention is significantly better than that of the random selection scheme.

Claims

1. A short packet secure transmission method applicable to a multi-intelligent reflector-assisted NOMA system, characterized in that: The proposed system consists of a source node S, K intelligent reflective surfaces (IRSs), two legitimate users D1 and D2, and an eavesdropping node E with no external energy supply. S sends private short packets to D1 and D2, and the IRSs reflect the data sent by S. The eavesdropping node E collects energy from the received RF signals and also attempts to steal the private data of D1 and D2. N intelligent reflective units are deployed on each intelligent reflective surface. The short packet secure transmission method comprises the following steps: Step 1: One information transmission takes T time. In the first (1-τ)T time, S sends a pilot signal Determine the energy E collected by the eavesdropper E ke ≥E th The corresponding smart reflective surface set S U ; From the set S U Select the best smart reflective surface based on Determine the optimal power allocation coefficient α * ; Among them, x1 and x2 are pilot signals sent to D1 and D2 respectively, P s is the transmission power at S, α is the power allocation coefficient, 0.5<α<1, E th is a fixed threshold, 0<τ<1 is the time conversion factor; Step 2: In the next τT time, use the and α * , S communicates with users D1 and D2, and the eavesdropper E collects energy and tries to steal D i Private data, i = 1, 2; specifically: S sends a signal The eavesdropper E receives the transmitted signal from S and The energy is collected from the reflected signal and attempts to steal D i Private data of D i Through direct link and The reflection link receives the signal, s1 and s2 are the private short packet data sent by S to D1 and D2 respectively.

2. The short packet secure transmission method applicable to the multi-intelligent reflector-assisted NOMA system according to claim 1 is characterized in that: In step 1, E uses the PS mode to collect energy from the received RF signal, where the power division factor for energy collection is μ and the power division factor for information decoding is (1-μ). According to the PS protocol, E collects energy from the transmitted signal of S and the IRS. k The energy E collected from the reflected signal ke for: Among them, η (0<η<1) represents the energy conversion efficiency, g se is the channel fading coefficient of link S→E, For the link S→IRS k The channel fading coefficient, For Link IRS k →E is the channel fading coefficient, h sk The conjugate transpose of Indicates IRS k The phase shift matrix on k，l It's the IRS k The amplitude reflection coefficient of the lth reflection unit, l∈{1, 2, ..., N}, k∈{1, 2, ..., K} is the kth smart reflection surface, Represents an N×1 complex matrix.

3. The short packet secure transmission method applicable to the multi-intelligent reflector-assisted NOMA system according to claim 2 is characterized in that: In step 1, the selected smart reflective surface Satisfy the following formula: in, is the total channel gain at D1, is the total channel gain at D2, For link S→D i The channel fading coefficient, For Link IRS k →D i The channel fading coefficient i=1,2,k∈S U .

4. The short packet secure transmission method applicable to the multi-intelligent reflector-assisted NOMA system according to claim 3 is characterized in that: In step 1, the optimal power allocation coefficient α* is selected to satisfy α * =arg max{min{R1, R2}}; Among them, R1 and R2 are the lower bounds of the confidentiality rate at D1 and D2 respectively, denoted as: in, are the received signal-to-noise ratios at D1 and D2, respectively, are the received signal-to-noise ratios of x1 and x2 at E, Q -1 (·) is the inverse function of the Gaussian Q function, M is the code length of the short packet, ∈ i and δ i are the decoding error probability and information leakage amount respectively, i∈{1,2}.

5. The short packet secure transmission method applicable to the multi-intelligent reflector-assisted NOMA system according to claim 4 is characterized in that: In step 1, the received signal-to-noise ratio at E is and They are: Where α is the power distribution coefficient at D1 0.5<α<1, For Link The channel fading coefficient, For Link The channel fading coefficient, for The conjugate transpose of express The phase shift matrix on yes The amplitude reflection coefficient of the lth reflection unit, l∈{1, 2, ..., N}, N0 represents the noise power; Receive signal-to-noise ratio at D1 and D2 and They are: in For Link The channel fading coefficient.

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