NOMA communication physical layer secrecy method combining artificial noise and network coding

Abstract

The invention discloses an NOMA (Non-Orthogonal Multiple Access) communication physical layer secrecy method combining artificial noise and network coding, which comprises the following steps: in a first time slot, a source user sends an NOMA signal to a multi-antenna relay, the relay sends the artificial noise by using an optimal antenna and receives the NOMA signal sent by the source user by using the remaining antennas, and meanwhile, a credible near user generates the artificial noise to interfere with an eavesdropping user; in the second time slot, the relay decodes the NOMA signal, the artificial noise generated by the relay in the first time slot and the signal sent to the credible near user are coded by network coding, and meanwhile, the coded signal and the signal sent to the uncredible far user form a new NOMA signal to be forwarded, so that the information leakage is further reduced. And the trusted user continuously generates artificial noise to interfere with the external eavesdropping user. According to the method, artificial noise and network coding are combined, so that the secure transmission performance of credible near users is improved, and the transmission performance of uncredible far users is not influenced.

Description

Technical Field

[0001] The present invention relates to a communication encryption method, in particular to a communication encryption method for non-orthogonal multiple access. Background Art

[0002] The rapid development of wireless communication technology has promoted a large increase in wireless communication devices and wireless communication services, making the existing spectrum resources more scarce. Non-orthogonal multiple access (NOMA) allows different users to share time-frequency resources, and thus NOMA has become a key technology for large-scale connection in future wireless communication networks. In addition, cooperative communication can further improve the transmission reliability of the NOMA system by using spatial diversity. However, the inherent openness and broadcast characteristics of the wireless channel make wireless communication vulnerable to eavesdropping attacks by illegal users, which will greatly reduce the transmission security of the NOMA system.

[0003] Physical layer security technology utilizes the random characteristics of the wireless channel to fundamentally ensure the wireless security performance of NOMA communication. In particular, artificial noise technology can use a part of the power to send interference signals to interfere with illegal users, thereby reducing the eavesdropping channel capacity and improving the secure transmission performance of wireless communication. However, traditional artificial noise schemes reduce the transmission reliability performance of untrusted users when improving the secure transmission performance of trusted users, which makes the NOMA system lose user fairness. Summary of the Invention

[0004] Object of the Invention: Aiming at the above-mentioned existing technologies, a physical layer secrecy method for NOMA communication combining artificial noise and network coding is proposed to improve the security of communication between the source user and the trusted near user, and at the same time ensure the transmission reliability of the source user and the untrusted far user.

[0005] Technical Solution: A physical layer secrecy method for NOMA communication combining artificial noise and network coding is applied to a cooperative communication scenario assisted by NOMA. The scenario includes a source user, a relay equipped with multiple antennas, a trusted near user equipped with two antennas, an untrusted far user, and an eavesdropping user. The method includes: in the first time slot, the source user sends a NOMA signal where x 1 and x 2 respectively represent the signals sent to the near user and the far user, and α 1 and α 2 respectively represent the power allocation coefficients of the near user and the far user; the relay uses an antenna selection algorithm to select the optimal antenna to generate artificial noise x J , and the near user generates artificial noise x z; Meanwhile, the relay uses the remaining antennas to receive the NOMA signal x sent by the source user s ; In the second time slot, the relay decodes the NOMA signal sent by the source user and uses network coding to combine the artificial noise x generated in the first time slot J and the signal of the near user x 1 and combines them with the signal of the far user x 2 to form a new NOMA signal At the same time, the optimal antenna is selected by the antenna selection algorithm to forward the new NOMA signal. The near user generates artificial noise x using the pseudo-random sequence known to the far user d to interfere with the eavesdropping user; then, the near user and the far user calculate the outage probability and the eavesdropping probability respectively according to the received signal-to-interference-plus-noise ratio.

[0006] Beneficial effects: In the case where the existing NOMA system loses user fairness, the present invention proposes a NOMA communication physical layer secrecy method combining artificial noise and network coding. The method of the present invention not only improves the security of the communication between the source user and the trusted near user, but also ensures the transmission reliability between the source user and the untrusted far user. Specifically, the entire communication process of this method can be divided into two time slots. In the first time slot, the source user sends a NOMA signal to the relay with multiple antennas. At the same time, the relay uses the optimal antenna to send artificial noise to interfere with the untrusted far user and the external eavesdropping user, and uses the remaining antennas to receive the NOMA signal sent by the source user. At the same time, the trusted near user generates artificial noise to interfere with the eavesdropping user; in the second time slot, the relay decodes the NOMA signal, and uses network coding to encode the artificial noise generated by the relay in the first time slot with the signal sent to the trusted near user, and at the same time combines the encoded signal with the signal sent to the untrusted far user to form a new NOMA signal for forwarding. In order to further reduce information leakage, the trusted user continues to generate artificial noise to interfere with the external eavesdropping user; then the NOMA user and the external eavesdropping user calculate the outage probability and the eavesdropping probability according to the received signal-to-interference-plus-noise ratio. It has the following specific advantages:

[0007] 1. By combining artificial noise and network coding, the present invention designs an artificial noise scheme that can not only improve the security performance of trusted users but also ensure the reliability of untrusted users, so as to ensure the user fairness based on the NOAM system.

[0008] 2. Using NOMA technology can improve the utilization rate of spectrum resources, and using relay cooperation technology can effectively expand the range of wireless communication.

[0009] 3. It can not only improve the secure transmission performance between the source user and the trusted near user, but also does not affect the transmission performance between the source user and the untrusted far user.

[0010] 4. The network coding adopted by the present invention is equivalent to one-time pad. While achieving improved security, it will not generate additional transmission power. Description of the Drawings

[0011] Figure 1 It is a model diagram of the application scenario of the method of the present invention;

[0012] Figure 2 It is a flowchart of the method of the present invention;

[0013] Figure 3 It is a comparison diagram of the outage probability and eavesdropping probability of the trusted near user and untrusted far user between the present invention and the comparative scheme;

[0014] Figure 4 It is a comparison diagram of the secure and reliable trade-off performance of the trusted near user and untrusted far user between the present invention and the comparative scheme. Detailed Embodiment

[0015] The following further explains the present invention with reference to the drawings.

[0016] A physical layer secrecy method for NOMA communication combining artificial noise and network coding is applied to a NOMA-assisted cooperative communication scenario, such as Figure 1 shown. This scenario includes a source user, a relay equipped with 6 antennas, a trusted near user equipped with 2 antennas, a single-antenna untrusted far user, and a single-antenna eavesdropping user.

[0017] As Figure 2 shown, the specific steps of the secrecy method of the present invention are as follows: In the first time slot, the source user sends a NOMA signal where x 1 and x 2 respectively represent the signals sent to the near user and the far user, α 1 and α 2 respectively represent the power allocation coefficients of the near user and the far user, and satisfy α 2 > α 1 and α 1 + α 2 = 1; In order to interfere with the eavesdropping and untrusted users, the relay uses an antenna selection algorithm to select the optimal antenna to generate artificial noise x J , and the near user generates artificial noise x z ; At the same time, the relay uses the remaining antennas to receive the NOMA signal x s sent by the source user. In the second time slot, the relay decodes the NOMA signal sent by the source user and uses network coding to combine the artificial noise x J generated in the first time slot and the near user signal x 1 and forms a new NOMA signal with the far user signal x 2 ​ Meanwhile, the optimal antenna is selected by using the antenna selection algorithm to forward the new NOMA signal. The near user generates artificial noise \(x\) using the pseudo-random sequence known to the far user d to interfere with the eavesdropping user; then, the near user and the far user calculate the outage probability and the eavesdropping probability respectively according to the received signal-to-interference-plus-noise ratio

[0018] To make the actual communication system have higher security, the untrusted far user and the eavesdropping user in the present invention should have strong enough eavesdropping capabilities and can directly decode the signal

[0019] Specifically, in the first time slot, the antenna selection algorithm adopted by the relay is where represents the channel gain coefficient from the \(j\)th antenna of the relay to the near user, represents the set composed of the antennas at the relay. Therefore, the signal received by the relay is where \(v\) r \(\in\mathbb{C}\) (N-1)×1 represents the received vector at the relay, the superscript represents the conjugate transpose of the matrix, \(h\) sr \(\in\mathbb{C}\) (N-1)×1 and respectively represent the channel gain coefficient matrix between the source user and the receiving antennas of the relay and the channel gain coefficient matrix between the near user and the receiving antennas of the relay, represents the self-interference channel gain coefficient matrix of the relay, \(P\) s and \(P\) 1 are the transmission powers of the source user and the near user respectively, \(N\) represents the number of antennas of the relay; \(n\) r represents the additive white Gaussian noise matrix of the relay receiving antennas, and the noise power at each antenna is with a mean of 0

[0020] To minimize the interference of the near user to the relay as much as possible and ensure that the relay obtains the maximum signal-to-interference-plus-noise ratio, the optimization problem is designed and solved: The constraint conditions are and The decoded signal \(x\) of the relay is obtained 2 and \(x\) 1 The signal-to-interference-plus-noise ratios of are respectively and where represents the transmission signal-to-noise ratio of the source node, \(\Gamma\) rr represents the self-interference at the relay node, \(\gamma\) I is the threshold for interference cancellation, represents the self-interference channel gain coefficient between the transmission antenna \(j\) and the receiving antenna \(v\) of the relay. The NOMA user \(u\) i ​The signals received by the eavesdropping user in the first time slot are respectively and where, when the subscript i takes 1 and 2, u i represents the trusted nearby user and the untrusted far user respectively, and represent the channel gain coefficients from the relay's optimal antenna to the NOMA user u i and the eavesdropping user respectively; and represent the channel gain coefficients from the nearby user to the NOMA user u i and the eavesdropping user respectively, and n e represent the additive Gaussian noises at the NOMA user u i and the eavesdropping user respectively. Therefore, the signal-to-interference-plus-noise ratios (SINRs) for the nearby user, far user, and eavesdropping user to decode the signal x J are respectively where, represents the transmit SNR of the relay, Γ 11 represents the self-interference at the nearby user in the first time slot, represents the transmit SNR of the nearby user, P r represents the transmit power of the relay.

[0021] In the second time slot, the relay adopts the optimal antenna selection algorithm to transmit the encoded NOMA signal to the NOMA user, where is the channel gain coefficient from the j-th antenna of the relay in the second time slot to the nearby user. Therefore, the received signals at the nearby user, far user, and eavesdropping user are and where and g oe represent the channel gain coefficients between the optimal antenna of the relay in the second time slot and the NOMA user u i and the eavesdropping user respectively, and represent the channel gain coefficients from the nearby user to the nearby user and the eavesdropping user respectively. The SINRs for the nearby user to decode x 2 and are and where H 11 represents the self-interference at the nearby user in the second time slot, The far user decodes the signals x 2 and The SINRs are and The eavesdropping user decodes the signals x 2 and The signal-to-interference-plus-noise ratio is

[0022] Therefore, in the second time slot, the outage probability and the eavesdropping probability of the near user are respectively: and where Pr is the arithmetic symbol for probability, denotes the probability that the far user eavesdrops on the signal x 1 , denotes the probability that the eavesdropping user eavesdrops on the signal x 1 , γ 1 , γ 2 and γ e respectively represent the threshold for decoding the signal x 1 and the threshold for decoding the signal x 2 , as well as the security threshold of the confidential signal. γ J represents the threshold for decoding the interference signal x J . The outage probability and the eavesdropping probability of the far user are respectively: and

[0023] The following presents the implementation of the outage probabilities of the trusted near user and the untrusted far user, as well as the eavesdropping probabilities of the trusted near user and the untrusted far user through Matlab simulation on a computer. In the simulation, it is assumed that the wireless channels are independent of each other and follow Rayleigh fading, and |h ι | 2 and |g χ | 2 respectively follow exponential distributions with means of λ ι and μ χ , where ι ∈ {sr j , r j r v , r j u 1 , r j u 2 , r j , r 1 e, u 1 , u 1 , u 2 , u 1 , r 1 r v} and χ ∈ {u 1 , u 1 , u 1 , u 2 , u 1 , u s = P r = P 1 = P, λ12 = μ 12 = 0.5, λ rr = λ 11 = μ rr = 0.01, γ I = 10 dB, α 1 = 0.2, γ 1 = γ 2 = 1.5 and γ e = 1. In addition, the noise power at each node is the same, which is N 0 = 1.

[0024] Figure 3 are the curves of the outage probability and the eavesdropping probability of the credible near - user and the untrusted far - user when N = 6. From Figure 3 it can be seen that as the transmit power increases, the reliability of the NOMA - based wireless transmission continuously improves, while the security continuously deteriorates, which indicates that there is a mutually restrictive relationship between security and reliability. In addition, for the credible near - user, the security is better than that of the traditional artificial noise scheme, while the reliability is slightly worse than that of the traditional artificial noise scheme. For the untrusted far - user, the artificial noise scheme proposed by the present invention can obtain almost the same reliability and security as the traditional artificial noise scheme.

[0025] Figure 4 is the curve of the security - reliability trade - off relationship between the credible near - user and the untrusted far - user. For the credible near - user, the security - reliability trade - off performance of the artificial noise scheme proposed by the present invention is better than that of the traditional artificial noise scheme. In other words, when the system has a given reliability requirement, the eavesdropping probability of the artificial noise scheme proposed by the present invention is less than that of the traditional artificial noise, and as the number of relay antennas increases, the security also improves accordingly. For the untrusted far - user, the security - reliability trade - off performance of the scheme proposed by the present invention is almost the same as that of the traditional artificial noise scheme, that is to say, the scheme proposed by the present invention not only improves the security - reliability trade - off performance of the credible user, but also does not affect the transmission performance of the untrusted user. In addition, from Figure 4 it can be seen that the security - reliability trade - off performance of the untrusted far - user has nothing to do with the number of relay antennas, which is mainly because the antenna selection is only related to the channel gain between the relay and the credible near - user.

[0026] The above - mentioned are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A physical layer confidentiality method for NOMA communication combining artificial noise and network coding, applied to a NOMA-assisted collaborative communication scenario, wherein the scenario includes a source user, a relay equipped with multiple antennas, a trusted near user equipped with two antennas, an untrusted far user, and an eavesdropping user, characterized in that: The method comprises: in a first time slot, a source user sends a NOMA signal Where x1 and x2 represent the signals sent to the near user and the far user, respectively, α1 and α2 represent the power allocation coefficients of the near user and the far user, respectively; the relay uses the antenna selection algorithm to select the optimal antenna to generate artificial noise x J , artificial noise x generated by the user z ; At the same time, the relay uses the remaining antennas to receive the NOMA signal x sent by the source user s ; In the second time slot, the relay decodes the NOMA signal sent by the source user and uses network coding to convert the artificial noise x generated in the first time slot into J Combined with the near user signal x1 and the far user signal x2 to form a new NOMA signal At the same time, the antenna selection algorithm is used to select the best antenna to forward the new NOMA signal, and the near user uses the pseudo-random sequence known by the far user to generate artificial noise x d Interfere with the eavesdropping user; then, the near user and the far user calculate the interruption probability and the eavesdropping probability respectively according to the received signal-to-interference-noise ratio.

2. The physical layer security method for NOMA communication combining artificial noise and network coding according to claim 1 is characterized in that: In the first time slot, the antenna selection algorithm used by the relay is in represents the channel gain coefficient from the jth antenna of the relay to the nearest user, represents the set of antennas at the relay; therefore, the signal received by the relay is where v r Represents the receiving vector at the relay, with the superscript represents the matrix conjugate transpose, h sr and They represent the channel gain coefficient matrix between the source user and the relay receiving antenna and the channel gain coefficient matrix between the near user and the relay receiving antenna, respectively. represents the relay self-interference channel gain coefficient matrix, P s and P1 are the transmission powers of the source user and the near user respectively, n r Represents the additive white Gaussian noise matrix of the relay receiving antenna; solve the optimization problem: The constraints are and The signal-to-interference-noise ratios of the relay decoding signals x2 and x1 are and in, represents the transmission signal-to-noise ratio of the source node, Γ rr represents the self-interference at the relay node, γ I is the interference elimination threshold, Represents the self-interference channel gain coefficient between the relay's transmitting antenna j and receiving antenna v.

3. According to the physical layer confidentiality method of NOMA communication combining artificial noise and network coding according to claim 2, NOMA user u i The signals received by the eavesdropping user in the first time slot are and in and They represent the optimal relay antenna to NOMA user u respectively. i and the channel gain coefficient of the eavesdropping user; when the subscript i is 1 and 2, u i represent trusted nearby users and untrusted distant users, respectively. and Respectively represent the nearby user to NOMA user u i and the channel gain coefficient of the eavesdropping user, and n e They represent NOMA user u respectively. i and the additive Gaussian noise at the eavesdropping user; therefore, the decoded signal x for the near user, the far user, and the eavesdropping user J The signal-to-interference-noise ratios are and in, represents the transmission signal-to-noise ratio of the relay, Γ 11 Indicates the self-interference near the user in the first time slot, represents the signal-to-noise ratio of the near user, P r Indicates the transmit power of the relay.

4. According to the physical layer confidentiality method of NOMA communication combining artificial noise and network coding according to claim 3, in the second time slot, the relay adopts the optimal antenna selection algorithm Sending the encoded NOMA signal For NOMA users, is the channel gain coefficient from the jth antenna to the near user in the second time slot; therefore, the received signals at the near user, the far user and the eavesdropping user are and in and g oe They represent the optimal antenna for relaying in the second time slot to NOMA user u. i and the channel gain coefficient between the eavesdropping users, and They represent the channel gain coefficients from near user to near user and eavesdropping user respectively; near user decoding x2 and The signal-to-interference-noise ratio is and Among them, H 11 represents the self-interference near the user in the second time slot, The decoded signal of the far user x2 and The signal-to-interference-noise ratio is and Eavesdropping user decodes signal x2 and The signal-to-interference-noise ratio is 5. According to the physical layer confidentiality method of NOMA communication combining artificial noise and network coding according to claim 4, in the second time slot, the interruption probability and eavesdropping probability of the near user are respectively: and in, Pr is the probability arithmetic symbol, represents the probability of a distant user eavesdropping on signal x1, represents the probability that the eavesdropping user eavesdrops on signal x1, γ1, γ2, and γ e They represent the thresholds of the decoded signal x1 and the decoded signal x2 and the security threshold of the confidential signal, γ J Denotes the decoded interference signal x J The interruption probability and eavesdropping probability of the remote user are: and

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