A secure transmission method for a semi-authorization-free system assisted by non-orthogonal multiple access

Abstract

The present invention discloses an enhanced non-orthogonal multiple access-assisted semi-unauthorized system security transmission method, wherein the transmission system includes a source node, an authorized user, an eavesdropping user and an unauthorized user. In the present invention, the entire communication process is completed in five steps: 1) the source sends a training sequence; 2) each user estimates its own channel state information; 3) the authorized user feeds back its own transmission signal-to-noise ratio, target rate and channel state information to the source; 4) the source calculates the decoding threshold of the authorized user and broadcasts the authorized user's effective receiving signal-to-noise ratio and threshold value. 5) Utilize power control to send artificial noise strategy: on the basis of ensuring the service quality of the authorized user, through design, the transmission power of the authorized user and the unauthorized user is controlled, and while obtaining the maximum achievable rate of the unauthorized user, partial / full power is used to send artificial noise to reduce the safe achievable rate of the eavesdropping user, thereby improving the security of the system.

Description

Technical Field

[0001] The present invention belongs to the field of physical layer security in the technical field of wireless communication networks, and in particular to a semi-authorized wireless communication network assisted by a non-orthogonal multiple access technology. Background Art

[0002] In the 5G era, the explosive growth of mobile data brought about by the popularization of smart terminals has put forward higher requirements for the speed, latency, signal coverage, etc. of wireless communication networks. So far, in order to meet the ever-increasing social needs, mobile communication technology has always maintained a high-speed iteration. The first generation of mobile communication technology is an analog communication technology that uses analog frequency modulation and frequency division multiple access. It is mainly based on the cellular networking structure to overcome the problems of low capacity and limited activity range of the large area system and realize voice functions; in order to improve the channel capacity and anti-interference ability of communication and reduce the investment cost of communication, the second generation of narrowband digital communication technology using time division multiple access technology and voice and SMS services is proposed; the third generation of multimedia mobile communication system, using code division multiple access technology, not only requires a large system capacity, but also supports the effective transmission of multiple services such as voice, data, images, multimedia, etc.; the fourth generation of mobile communication technology is also called wideband access and distribution network. It uses orthogonal frequency division multiple access technology, representing mobile multimedia, global mobile solutions, integrated wireless and customized services. At present, we are in the era of commercial use of the fifth generation of mobile communication technology, and are about to enter the convenient era of the Internet of Everything.

[0003] Non-orthogonal multiple access technology: As a promising multiple access technology, it is widely regarded as a technology for effectively utilizing spectrum resources in 5G wireless networks. The basic idea of ​​non-orthogonal multiple access technology is to use superposition coding technology at the transmitting end, actively introduce interference information, and achieve correct demodulation at the receiving end through serial interference cancellation technology. Non-orthogonal multiple access is mainly divided into power domain non-orthogonal multiple access, code domain non-orthogonal multiple access and space domain non-orthogonal multiple access technology. In the present invention, unless otherwise specified, non-orthogonal multiple access refers to power domain non-orthogonal multiple access. Power domain non-orthogonal multiple access refers to a communication technology that superimposes signals with different powers on the same time-frequency resources and performs interference cancellation at the receiving end.

[0004] As large-scale devices will access limited spectrum, two major scenarios in the Internet of Things: ultra-reliable low-latency communication (URLLC) and massive machine-type communication (mMTC), have strict requirements on latency and signaling overhead, that is, lower latency and signaling overhead.

[0005] Semi-unlicensed strategy: It is a combination of unlicensed scheme for machine-type users with small data packets and delay-tolerant traffic and authorized scheme for some users with large data packets and delay-sensitive traffic. It is a strategy to control the number of unlicensed users accessing spectrum resources. In order to alleviate conflicts over resources and obtain large-scale connectivity, this strategy allows unlicensed users (delay-tolerant devices) to share the spectrum resources of licensed users without affecting the exclusive channels of licensed users to communicate with base stations. It also solves the problem that a large number of users cannot successfully decode user information due to exceeding the non-orthogonal multiple access capacity.

[0006] Physical layer security technology: Physical layer security does not require a key. It uses the time-varying nature of wireless channels to encrypt communication systems, which can theoretically achieve absolute security in information transmission. As the computing power of terminals gradually increases, the ability of eavesdroppers to crack information is also gradually improving. Traditional cryptography is facing increasing pressure in the field of information encryption. Physical layer security is based on information theory and achieves information security at the physical layer. It is a very promising encryption method in the field of communications.

[0007] The general uplink non-orthogonal multiple access communication network model is as follows Figure 1 As shown in the figure, S is the source node, U 1 and U 2 The source node uses serial interference cancellation technology. In the uplink non-orthogonal multiple access communication system, there are two main ways for the base station to decode the user's information: 1. Decode the user's information based on the user's channel state information (CSI), that is, the base station first decodes the user U with a stronger CSI. 1 The information of the near user is then removed by serial interference cancellation technology, and then the user U with weak CSI is decoded. 2 (distant user) information, because the base station receives U first 1 The received signal can be decoded and deleted, and then the received signal can be decoded; 2. Decode the user's information according to the user's quality of service (QoS), that is, to ensure that the user U 1 The service quality of the user is decoded first, and then the user U 2 Information, because U 1 It may be a delay-sensitive device with a higher priority. The present invention is mainly based on the consideration of the user's service quality.

[0008] Semi-licensed communication technology can not only improve spectrum efficiency but also reduce signaling overhead. At the same time, combined with non-orthogonal multiple access technology, it can solve the collision problem when multiple users compete for the same resource block, and can also significantly improve system performance. The combination of semi-licensed communication and non-orthogonal multiple access technology can further improve the performance of non-orthogonal multiple access communication systems. Figure 2As shown. In the figure, S is the source, U B and U F are delay-sensitive and delay-tolerant users, respectively. Under the condition of ensuring the service quality of authorized users, is the power gain of unlicensed users greater than the decoding threshold value τ(|g B | 2 ), all unlicensed users are divided into two cases: in case 1, the user channel gain is greater than the threshold value, that is, the source cannot directly and correctly decode the information of the licensed user, and can only decode the information of the unlicensed user in the first stage of serial interference cancellation. In case 2, the channel gain of all users is less than the threshold value. Therefore, the information of the unlicensed users of this group can be decoded in the first stage of serial interference cancellation, or in the second stage. By comparing the achievable rates of the unlicensed users in the two stages, the maximum achievable rate can be obtained by decoding the information of the GF users in the second stage.

[0009] Physical layer security is a security theory based on information theory. It uses the time-varying nature of wireless channels and combines channel coding and encryption technology to ensure that information cannot be deciphered by eavesdroppers. In 1945, CE Shannon proved in a classic paper (see [1]: Shannon CE. Communication theory of secrecy systems [J]. The Bell System Technical Journal, 1949, 28 (4): 656-715.) from the perspective of information theory that in order to achieve absolute security of messages, the communication process must use a "one-time, one-pad" encryption method, that is, one bit of data should have one bit of key. This condition is too strict and difficult to apply in the engineering field. In 1975, A. Wyner first established a noisy eavesdropping channel model based on Shannon's research (see [2]: Wyner AD. The wire-tap channel [J]. The Bell System Technical Journal, 1975, 54 (8): 1355-1387.), as shown in the attached figure. Figure 3As shown in the figure, the eavesdropping model is an improvement on the Shannon model. In this model, Wyner proved that: when the channel condition of the main channel is better than that of the eavesdropping channel, when the source and the legitimate receiver transmit information, there must be a coding method that can make the probability of information transmission errors arbitrarily small. At this time, the eavesdropper cannot obtain any useful information, and the system is absolutely secure. From the perspective of information theory, the physical layer security is defined using the source entropy. After decades of development, the physical layer security theory has gradually matured. The use of physical layer security to achieve secure transmission of wireless communication systems has become a hot topic in academia and industry. The main indicators for measuring the physical layer security of the system include ergodic confidentiality capacity and security interruption probability. The security interruption probability refers to the probability that the instantaneous security capacity of the system is less than a given threshold value. The mathematical expression is:

[0010]

[0011] Among them, γ D and γ E Indicates the signal-to-noise ratio between the destination and the eavesdropping end. R s represents the safety rate threshold, F D (x) represents the cumulative distribution function of the main channel signal-to-noise ratio. f(γ E ) represents γ E The probability density function of .

[0012] The uplink communication system built based on non-orthogonal multiple access, semi-authorization-free and physical layer security theory will be widely used in low-latency, high-spectrum-efficiency, multi-connection ultra-reliable low-latency communications and ultra-multi-machine type communication systems. Summary of the invention

[0013] Aiming at the system security problem of the possible existence of eavesdroppers in the transmission of the semi-unauthorized system assisted by uplink non-orthogonal multiple access, the present invention takes the security of the system into consideration, and simultaneously controls the power and sends an artificial noise strategy, so as to further improve the secure transmission of the non-orthogonal multiple access system on the basis of ensuring the service quality of authorized users.

[0014] The present invention is based on physical layer security technology and considers the security of unauthorized users in an uplink non-orthogonal multiple access assisted semi-unauthorized system. An enhanced non-orthogonal multiple access assisted semi-unauthorized system security transmission scheduling strategy is disclosed. The core of the strategy is based on physical layer security technology. By controlling the power of authorized users and unauthorized users, the eavesdropping rate of eavesdropping users is reduced while obtaining the maximum achievable rate. The strategy specifically includes the following steps:

[0015] Step S1: System initialization; an authorized user U B , an unauthorized user U FIn an uplink non-orthogonal multiple access system consisting of an eavesdropping user E and a source node S, all nodes are equipped with a single antenna. The channel coefficients from the authorized user and the unauthorized user to the source node and the eavesdropping user are g bs , g fs , g be and g fe ; The channel gain of all users is expressed as h ij =|g ij | 2 , where i∈{b,f} and j∈{s,e};

[0016] Step S2: The source sends a pilot signal, and each user estimates the channel state information of their own channel through the channel estimation algorithm, and then the authorized user sets its own transmission signal-to-noise ratio and target rate R B and channel state information g bs Feedback to the source;

[0017] Step S3: The source calculates the decoding threshold τ of the authorized user B =max{0,τ(h bs )},in Depend on Get, P B is the transmit power of the authorized user, R B is the rate threshold of the authorized user, h bs Represents the channel gain of the authorized user and broadcasts the effective received signal-to-noise ratio P of the authorized user B h bs and decoding threshold τ B ;

[0018] Step S4: When the decoding threshold τ(h bs )<0, that is, h bs <α B When h , the authorized user sends artificial noise, and the source only decodes the signal of the unauthorized user. bs >α B , and the power gain of the unlicensed user is less than the decoding threshold, the signal of the unlicensed user is decoded in the second stage of SIC, and both the licensed user and the unlicensed user send signals at full power; when h bs >α B , and the power gain of the unlicensed user is greater than the decoding threshold, the signal of the unlicensed user is decoded in the first stage of SIC, and the unlicensed user sends its signal with full power, or the unlicensed user performs power control and uses part of the power P F One part of the power is used to send its own signal, and the other part of the power is used to send artificial noise.

[0019] The beneficial effects of the present invention are mainly: considering making full use of power resources and enhancing the security of the system, while ensuring the service quality of authorized users, by controlling the power of authorized users and unauthorized users, that is, while obtaining the maximum achievable rate of unauthorized users, using part of the power to send artificial noise to reduce the safety rate, thereby improving the system security performance.

[0020] The beneficial effects of the present invention specifically come from the following two aspects:

[0021] (1) By controlling the power of authorized and unauthorized users, the maximum achievable rate of unauthorized users is obtained, while the eavesdropping rate of eavesdropping users is reduced. Compared with the two baselines, a better security performance can be achieved.

[0022] (2) The proposed strategy is no longer affected by the rate pair (achievable target rate and safe target rate), that is, the system is applicable to rate pairs in any situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a model of a general uplink non-orthogonal multiple access system;

[0024] Figure 2 A semi-authorization-free security system model assisted by non-orthogonal multiple access;

[0025] Figure 3 It is the Wyner eavesdropping channel model;

[0026] Figure 4 The impact of the number of unlicensed users on the security outage probability of non-orthogonal multiple access assisted systems;

[0027] Figure 5 The impact of rate on the probability of system safety interruption;

[0028] Figure 6 Implementation process of secure transmission scheme for semi-unlicensed system assisted by non-orthogonal multiple access. DETAILED DESCRIPTION

[0029] like Figure 3 As shown, the present invention considers the security of the system assisted by non-orthogonal multiple access, where S represents the source, U B and U F are delay-sensitive and delay-tolerant users, respectively, and E is an eavesdropping end. The communication system described in the embodiment of the present invention includes an active S, an authorized user U B , an eavesdropping node E and an unauthorized user U F , and the source and all users are equipped with a single antenna. The channel coefficients from the authorized user and the unauthorized user to the source and the eavesdropping user are g bs , gfs , g be and g fe The channels of all users are assumed to be independent and identically distributed and Rayleigh channels. To simplify the analysis, the channel gain is expressed as h ij =|g ij | 2 , where i∈{b,f} and j∈{s,e}.

[0030] The embodiment of the present invention is based on physical layer security technology and considers the security of unlicensed users in an uplink non-orthogonal multiple access assisted semi-unlicensed system. An enhanced non-orthogonal multiple access assisted semi-unlicensed system security transmission strategy is disclosed. The core of the strategy is based on physical layer security technology. While obtaining the maximum achievable rate user through power control, the eavesdropping rate of the eavesdropping user is reduced. The specific implementation process of the present invention is as follows Figure 6 As shown, it is mainly divided into three stages. The first stage mainly includes: the source sends a training sequence, each user estimates its own channel state information, the authorized user feeds back its own transmission signal-to-noise ratio, rate threshold and channel state information to the source, and the source calculates and broadcasts the decoding threshold and effective receiving power gain of the authorized user; in the second stage, according to the decoding threshold of the authorized user, the power of the unauthorized user and the authorized user is controlled; the third stage mainly gives and derives the expression of the safety interruption probability based on the difference in the signals sent by the two users. The specific implementation process is divided into five steps:

[0031] Step S1: The source first broadcasts a pilot signal. This step has two purposes: (1) to estimate the channel state information of the authorized user and the unauthorized user, i.e., SU B and SU F (2) Estimate the channel state information of the eavesdropped channel. That is, the channel state information of the SE channel. The acquisition of the channel state information of each link can be achieved by monitoring the transmission of each port or using some complex channel estimation algorithms. The specific method (see reference [3] Zou Y, Zhu J, Wang X, et al. Improving physical-layer security in wireless communications using diversity techniques [J]. IEEE Network, 2015, 29 (1): 42-48.) will not be repeated in this article.

[0032] Step S2: The authorized user sets its transmission signal-to-noise ratio and target rate R B and channel state information g bsFeedback to the source (see reference [4]: ​​Z. Ding, R. Schober, and HV Poor, "A new QoS-guarantee strategy for NOMA assisted semi-grant-free Transmission," IEEE Trans. Commun, vol. 69, no. 11, pp. 7489-7503, Nov 2021.).

[0033] Step S3: The source calculates the decoding threshold τ of the authorized user B =max{0,τ(h bs )},in Depend on Get, P F is the transmission power of the unlicensed user, P B is the transmit power of the authorized user, R B is the rate threshold of the authorized user, h fs It represents the channel gain of the unlicensed user and broadcasts the effective received signal-to-noise ratio P of the authorized user. B h bs and τ(h bs ), h bs represents the channel gain of the authorized user, τ(h bs ) represents the decoding threshold.

[0034] Step S4: When τ(h bs )<0, that is, h bs <α B When α B represents the channel gain h bs The threshold value of This indicates that the channel quality of the authorized user is too poor, which always leads to transmission interruption. In order to increase the probability of source decoding the signal of the unauthorized user, the authorized user is designed to use power P B Send artificial noise to confuse eavesdropping users, and do not send their own signals. Assume that the source can eliminate the artificial noise signal first and does not affect the decoding order of the legitimate user signal. Therefore, only the unlicensed signal is decoded by the source. At this time, the achievable rate of the unlicensed user is The achievable rate of the eavesdropping user is h bs >α B Indicates that the signal transmission of the authorized user is not always interrupted, then the power P B Send your own signal. bs >α B , P F h fs <τ B =τ(h bs), the signal of the unlicensed user is decoded in the second stage, and the achievable rate of the unlicensed user is The achievable rate of the eavesdropping user is When h bs >α B , P F h fs >τ B In order to obtain the maximum achievable rate of the unlicensed user, the unlicensed user has two ways to process its transmission power: one is to send its signal with full power. At this time, its signal is decoded in the first stage, and the achievable rate of the unlicensed user can be expressed as The corresponding achievable rate of the eavesdropping user is The other is to perform power control and send a portion of the power P F , so that its signal is decoded in the second stage; the achievable rate obtained at this time in The other part (1-β)P F is used to send artificial noise, then the achievable rate of the eavesdropping user is To summarize the above discussion, When , power control is not used; when When power control is adopted, we have in

[0035] Step S5: In step S4, the expression of the signal received by the source is Where P i and g j , i∈B,F and j∈bs,fs represent the transmission power and channel gain of user Ui respectively, x i For U i The unit power signal sent is n means the mean is 0 and the variance is σ 2 Additive white Gaussian noise.

[0036] The following is an analysis of the security performance of the system in the embodiment of the present invention. The probability of security interruption of the system is derived using probability theory. According to the expression of security interruption probability and some algebraic operations, the number of unauthorized users U can be obtained. F The probability of safe interruption when sending a signal is:

[0037]

[0038] Where Rth represents the safe rate threshold, ε B =θ B -1,

[0039] The closed-form expression of the safety interruption probability in the above formula is:

[0040]

[0041] in, R th represents the safety target rate, represents the achievable safe rate of unauthorized users, i∈{I,II,III,IV} and [x] + =max{x,0}. It indicates the probability that the channel quality of the authorized user is too poor and always interrupted. represents the probability that the signal of the unlicensed user can be decoded in the second stage, and Indicates the probability of whether the unlicensed user sends artificial noise through power control.

[0042] Based on formula (2), we derive each term in formula (3) and get

[0043]

[0044] in, and is the exponential integral function.

[0045]

[0046] Among them, λ 1 =α B θ th .

[0047]

[0048] in, erf(x) is the error function, L is the total sum, reflecting accuracy and complexity,

[0049]

[0050] in, I, M, R and N are the total sums of items, reflecting accuracy and complexity.

[0051] Figure 4 is the safety interruption probability achieved by the proposed artificial noise strategy through power control strategy. The parameters are set as follows: R B =1.5bit / s / Hz and R th=0.5bit / s / Hz, R B =1.5bit / s / Hz and R th =1.0bit / s / Hz and R B =2.0bit / s / Hz and R B =1.0bit / s / Hz. "Sim" represents the Monte Carlo simulation result, "Ana" represents the theoretical analysis result, and "Asy" represents the asymptotic result. This figure proves the correctness of the theoretical analysis by Monte Carlo simulation. We can see from the figure that the two benchmarks increase with P B =P F The increase of will increase first and then, because the interference threshold value τ B In the low-power area, the probability that the authorized user can share his signal increases, so the security performance increases. In the high-power area, the channel gain of the unauthorized user is greater than the interference threshold, so the security performance decreases and tends to a constant as the transmission power increases. Compared with the two benchmarks, the proposed strategy can achieve a better security performance, because not only the achievable rate of the unauthorized user is enhanced, but also the eavesdropping rate is reduced by sending artificial noise. Moreover, no matter how the value of the rate pair is changed, the proposed strategy can achieve a better security performance.

[0052] Figure 5 is the effect of transmission power on the probability of system safety interruption. The parameters are set as: B =1.5bit / s / Hz and R th =1.0bit / s / Hz. "Sim" indicates the Monte Carlo simulation result, "Analysis" indicates the theoretical analysis result, and "Asy" indicates the asymptotic result. This figure proves the correctness of the theoretical analysis by Monte Carlo simulation. As can be seen from the figure, P F The greater the power, the better the security performance. This is because under the premise of ensuring the service quality of authorized users and obtaining the maximum achievable rate, more power can be used to send artificial noise to reduce the eavesdropping rate of eavesdropping users, so security is enhanced.

Claims

1. A method for secure transmission of a semi-authorized-free system assisted by non-orthogonal multiple access, characterized in that: The following steps are involved: Step S1: System initialization; an authorized user U B , an unauthorized user U F In an uplink non-orthogonal multiple access system consisting of an eavesdropping user E and a source node S, all nodes are equipped with a single antenna. The channel coefficients from the authorized user and the unauthorized user to the source node and the eavesdropping user are g bs , g fs , g be and g fe ; The channel gain of all users is expressed as h ij =|g ij | 2 , where i∈{b,f} and j∈{s,e}; Step S2: The source sends a pilot signal, and each user estimates the channel state information of their own channel through the channel estimation algorithm, and then the authorized user sets its own transmission signal-to-noise ratio and target rate R B and channel state information g bs Feedback to the source; Step S3: The source calculates the decoding threshold τ of the authorized user B =max{0,τ(h bs )},in Depend on Get, P B is the transmit power of the authorized user, R B is the rate threshold of the authorized user, h bs Represents the channel gain of the authorized user and broadcasts the effective received signal-to-noise ratio P of the authorized user B h bs and decoding threshold τ B ; Step S4: When the decoding threshold τ(h bs )<0, that is, h bs <α B When h , the authorized user sends artificial noise, and the source only decodes the signal of the unauthorized user. bs >α B , and the power gain of the unlicensed user is less than the decoding threshold, the signal of the unlicensed user is decoded in the second stage of SIC, and both the licensed user and the unlicensed user send signals at full power; when h bs >α B , and the power gain of the unlicensed user is greater than the decoding threshold, the signal of the unlicensed user is decoded in the first stage of SIC, and the unlicensed user sends its signal with full power, or the unlicensed user performs power control and uses part of the power P F Send its own signal, and the other part of the power sends artificial noise; P F Transmit power for unauthorized users; When τ(h bs )<0, that is, h bs <α B When α B represents the channel gain h bs The threshold value of This indicates that the channel quality of the authorized user is too poor, which always leads to transmission interruption. In order to increase the probability of source decoding the signal of the unauthorized user, the authorized user is designed to use power P B Send artificial noise to confuse eavesdropping users, and do not send their own signals. Assume that the source can eliminate the artificial noise signal first and does not affect the decoding order of the legitimate user signal. Therefore, only the unlicensed signal is decoded by the source. At this time, the achievable rate of the unlicensed user is The achievable rate of the eavesdropping user is h bs >α B Indicates that the signal transmission of the authorized user is not always interrupted, then the power P B Send your own signal; when h bs >α B , P F h fs <τ B =τ(h bs ), the signal of the unlicensed user is decoded in the second stage, and the achievable rate of the unlicensed user is The achievable rate of the eavesdropping user is When h bs >α B , P F h fs >τ B In order to obtain the maximum achievable rate of the unlicensed user, the unlicensed user has two ways to process its transmission power: one is to send its signal with full power. At this time, its signal is decoded in the first stage, and the achievable rate of the unlicensed user can be expressed as The corresponding achievable rate of the eavesdropping user is The other is to perform power control and send a portion of the power P F , so that its signal is decoded in the second stage; the achievable rate obtained at this time in The other part (1-β)P F is used to send artificial noise, then the achievable rate of the eavesdropping user is when When power control is adopted, we have in when When , power control is not used.

2. According to claim 1, a non-orthogonal multiple access assisted semi-authorization-free system security transmission method is characterized by: In step S4, the expression of the signal received by the source is: Where P i and g j , i∈{B,F} and j∈{bs,fs} represent user U i The transmission power and channel gain, x i For U i The unit power signal sent is n means the mean is 0 and the variance is σ 2 Additive white Gaussian noise.

3. According to claim 1, a method for secure transmission in a semi-authorized-free system assisted by non-orthogonal multiple access, characterized in that: Unauthorized User F The probability of safe interruption when sending a signal is: in, and R th Indicates the safe rate threshold. represents the achievable safe rate of unauthorized users, i∈{I,II,III,IV}, [x] + =max{x,0}; It indicates the probability that the channel quality of the authorized user is too poor and always interrupted. represents the probability that the signal of the unlicensed user can be decoded in the second stage, Indicates U F The probability of sending artificial noise without power control, Indicates U F The probability of sending artificial noise through power control.

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