CN115278662A - Safe transmission method of non-orthogonal multiple access communication system based on cooperative interference strategy - Google Patents

Safe transmission method of non-orthogonal multiple access communication system based on cooperative interference strategy Download PDF

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CN115278662A
CN115278662A CN202210699057.XA CN202210699057A CN115278662A CN 115278662 A CN115278662 A CN 115278662A CN 202210699057 A CN202210699057 A CN 202210699057A CN 115278662 A CN115278662 A CN 115278662A
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signal
user
base station
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雷宏江
佘旭升
唐宏
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Chongqing University of Post and Telecommunications
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
    • H04W12/03—Protecting confidentiality, e.g. by encryption
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K3/00—Jamming of communication; Counter-measures
    • H04K3/60—Jamming involving special techniques
    • H04K3/62—Jamming involving special techniques by exposing communication, processing or storing systems to electromagnetic wave radiation, e.g. causing disturbance, disruption or damage of electronic circuits, or causing external injection of faults in the information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
    • H04W12/30—Security of mobile devices; Security of mobile applications
    • H04W12/37—Managing security policies for mobile devices or for controlling mobile applications
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0446—Resources in time domain, e.g. slots or frames
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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Abstract

The invention discloses a safe transmission method of a non-orthogonal multiple access communication system based on a cooperative interference strategy, which is mainly divided into three time slots, wherein the first time slot mainly comprises the following steps: a base station sends a superposed signal, a far user sends an interference signal to inhibit the eavesdropping capability of an untrusted relay, and a near user and the untrusted relay receive and decode a target signal; the near user and the far user of the second time slot send uplink non-orthogonal multiple access signals, and the base station and the non-trusted relay decode target signals; and the untrusted relay in the third time slot forwards the signals received in the first two time slots, the near user sends an uplink new signal, and the base station and the far user decode a target signal. The method of the invention improves the spectrum efficiency of the system, and simultaneously utilizes the cooperative interference strategy, and realizes safe transmission while ensuring the system to realize high spectrum efficiency by utilizing a safe transmission scheme that a special interference terminal utilizes the decoding capability of a user to send artificial noise to inhibit eavesdropping nodes, namely, untrusted relays, without increasing the spectrum efficiency.

Description

Safe transmission method of non-orthogonal multiple access communication system based on cooperative interference strategy
Technical Field
The invention belongs to the technical field of wireless communication networks, and particularly relates to a wireless communication network safety transmission scheme of direct transmission and relay cooperative transmission and non-orthogonal multiple access technologies.
Background
With the rapid development of the internet of things and wireless communication technology, higher requirements are put on a wireless communication system in the aspects of data rate, time delay, spectrum efficiency, communication coverage rate, mass equipment connection and the like. The non-orthogonal multiple access is a technology with great potential, the pressure of a wireless communication system caused by the access of scarce frequency spectrum resources and mass equipment is greatly relieved, the invention particularly refers to the non-orthogonal multiple access of a power domain, and the detailed description is omitted. The direct transmission and relay cooperative transmission technology not only improves the coverage area of the network, but also makes full use of prior information to delete the interference of an untrusted relay forwarding link on a near user on the premise of not influencing the performance of the system, thereby realizing the purpose of parallel transmission of a communication link and further improving the frequency spectrum efficiency. The physical layer security is an information encryption technology developed on the basis of information theory, is a complementary technology different from traditional encryption means such as cryptography and the like, particularly increases the capacity difference of a main channel and an eavesdropping channel to achieve the purpose of secure transmission, and theoretically can realize absolute security of information transmission.
As shown in fig. 1, consider that there is a downlink non-orthogonal multiple access communication model where a near user and a far user form a pair of non-orthogonal multiple access users. U in the figureNAnd UFRespectively a near user and a far user. The base station S adopts superposition coding, and the principle is as follows: the signals of the two users are transmitted with different power superposition. Due to UNFor near users, the channel condition is better than that of far users UFAllocated less power than far user UFWhen decoding, serial interference elimination is executed, first UNDecoding U as interferenceFOf the signal of (2), deleting U from the superimposed signalFThen, the signal itself is solved. U shapeFFor weak users in non-orthogonal multiple access systems, U is decodedNThe signal of (2) is regarded as interference and its own signal is decoded. The non-orthogonal multiple access technology adopts superposition coding at a transmitting end, and superposes user information with weak channel conditions on user information with strong channel conditions at low code rate to realize multi-user information superpositionAnd (4) adding transmission. The receiving end eliminates the co-channel interference by using the serial interference elimination technology, and the decoding signal-to-noise ratio is improved.
The direct transmission and relay cooperative transmission technology is combined with the non-orthogonal multiple access, so that the coverage area of a communication system is improved, the prior information is fully utilized to delete interference, the parallel transmission of a communication link is realized, and the spectrum efficiency is further improved. As shown in figure 2, the system consists of a base station S and a near user UNA remote user UFAnd an untrusted relay node. The specific process comprises the following steps: first time slot base station broadcasts downlink non-orthogonal multiple access signal, UNDecoding U first based on serial interference eliminationFAfter removing, decoding the signal itself, and decoding the target signal x in the form of far-end user by the untrusted relay2(ii) a The untrusted relay in the second time slot forwards a far user signal, and the base station sends a new signal to the near user, and the near user decodes the far user signal and is not interfered by the untrusted relay; and the far user can not receive the new signal interference of the base station, thereby realizing the parallel communication link. The system is characterized in that a pair of near users directly served by a base station and a far user needing the assistance of the untrusted relay and communicating with the base station exist in a wireless cellular network, and the prior information acquired by the near users in a first time slot can be used for deleting the interference caused by the forwarding of the untrusted relay, so that the purpose of non-interfering parallel transmission is achieved.
The physical layer security is based on complex space-time characteristics such as randomness and time variability of a wireless channel, and information is safely transmitted by utilizing a signal processing technology. When the channel condition of the main channel is better than that of the eavesdropping channel, and when information transmission is carried out at the receiving and transmitting ends of a legal user, a coding mode is provided to realize that the probability of transmission information error is arbitrarily small, and an eavesdropper cannot obtain all useful information, so that the aim of safe transmission is fulfilled. In the physical layer security research, whether the channel state information of the eavesdropping node can be acquired has a great influence on the security performance of the system. Generally, a scenario in which a source node has channel state information of an eavesdropping node is called active eavesdropping, and otherwise, the scenario is called passive eavesdropping. Under the active eavesdropping scene, the source node can dynamically adjust a sending strategy based on the channel state information of the eavesdropping node to obtain a relatively safe communication scene.
In the interception channel, due to the existence of the interception node, the reliability and the safety of information transmission need to be ensured at the same time. At this time, there is an upper limit to the information transmission rate of the system, the maximum information transmission rate of the system is the safety rate, and the mathematical expression is as follows:
Figure BDA0003703244200000023
wherein [ x ]]+＝max(0,x)，CBAnd CERepresenting the channel capacity, gamma, of the main link and the eavesdropping link, respectivelyBAnd gammaEThe signal-to-noise ratio of the main link and the eavesdropping link, respectively. The common performance indexes in the field of physical layer security research include traversal security rate, security interruption probability and the like. Wherein the traversal security rate is defined as:
Figure BDA0003703244200000021
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0003703244200000022
to evaluate the desired operator, f (γ)B,γE) And representing a joint probability density function of signal-to-noise ratios of the target node and the eavesdropping node, and representing the traversal safety rate as a statistical average value of the system safety rate.
Combining non-orthogonal multiple access, direct transmission and relay cooperative transmission technologies with a physical layer safety theory to jointly design a communication system; the advantages of high speed, mass connection and high spectrum efficiency are realized, the safety performance consideration is introduced, and the method has a great application prospect in the field of modern communication.
Disclosure of Invention
For a non-orthogonal multiple access system with direct transmission and relay cooperative transmission, while higher system spectrum efficiency is pursued, more serious information leakage may occur. The invention designs a communication link based on physical layer network coding, improves the spectrum efficiency of the system, and simultaneously utilizes a cooperative interference strategy, does not increase a special interference terminal, utilizes a safe transmission scheme of a user to send artificial noise to inhibit the decoding capability of a wiretapping node, ensures that the system realizes high spectrum efficiency and simultaneously realizes safe transmission.
In view of this, the technical scheme adopted by the invention is as follows: the safe transmission method of the non-orthogonal multiple access communication system based on the cooperative interference strategy comprises three time slots, and the specific steps are as follows:
step S1: a first time slot, based on a downlink non-orthogonal multiple access protocol, a base station S uses superposition coding technology to approximate a target signal x of a user1And the destination signal x of the far user2Broadcasting after superposition; simultaneous utilization of remote user UFTransmitting friendly interference signal z in first time slot1The wiretap node is removed from being inhibited, namely, the untrusted relay; near user UNDecoding x based on successive interference cancellation techniques2Post-removal, no-interference decoding x1(ii) a Untrusted relay eavesdrops on user's destination signal x based on parallel interference cancellation techniques1And x2；
Step S2: second time slot, based on uplink non-orthogonal multiple access protocol, near user UNTransmitting a first destination signal x of a base station3And interference signal z in the second time slot2Superimposed signal of, remote user UFTransmitting a second destination signal x of the base station4(ii) a Base station removal of interference signal z2Post-decoding x3The untrusted relay eavesdrops on the target signal x of the base station based on parallel interference cancellation techniques3And x4；
And step S3: in the third time slot, the untrusted relay R amplifies all the received signals and forwards the amplified signals, and the near user UNSending x3And a third destination signal x of the base station5The base station decodes the signal x transmitted by the near subscriber first based on successive interference cancellation5Re-decoding the signal x forwarded by the untrusted relay4。
The invention has the main beneficial effects that: put forwardA novel non-orthogonal multiple access secure transmission method fusing four technologies of direct transmission and relay cooperative transmission, non-orthogonal multiple access, network coding and physical layer security ensures the high frequency spectrum characteristic of a system, simultaneously utilizes a cooperative interference strategy to reduce the probability of eavesdropping of confidential information, and utilizes an untrusted relay half-duplex shielding effect to ensure a positive traversal security rate (x) of the system5) And safe transmission is realized.
The beneficial effects of the invention come from the following three aspects:
(1) And the non-orthogonal multiple access and network coding are adopted to improve the spectrum efficiency. In order to relieve the shortage of frequency spectrum resources, a non-orthogonal multiple access technology is fully utilized to simultaneously transmit a plurality of user information in the same resource block; and the physical layer network coding is utilized to save communication time slots and improve the system throughput. The monte carlo simulation results in fig. 5 show that: compared with the reference scheme 1 which does not adopt network coding, the method can obviously enhance the safety performance of the system.
(2) And adopting a cooperative interference strategy and an inter-user interference strategy. The safety performance of the system is improved by using an inter-user interference strategy and friendly interference signals, and the probability of information eavesdropping is reduced. It should be noted that, by using superposition coding and idle users to transmit interference signals without setting a dedicated interference terminal, fig. 6 demonstrates that the cooperative interference strategy proposed by the present invention enhances the security performance of the system compared with the conventional untrusted relay forwarding strategy.
(3) The security and reliability of the system are traded off. The interference signal of the second time slot can inhibit the decoding quality of the eavesdropping end on one hand, and can cause the reduction of the communication reliability due to the division of the power of the useful signal on the other hand. It is therefore necessary to balance the security and effectiveness of the system. Fig. 7 demonstrates that the safety and reliability of the proposed trade-off system of the present invention, as the power distribution coefficient increases, the overall safety performance of the system increases first and then decreases, i.e. there is an optimal power distribution coefficient to optimize the safety performance of the system.
Drawings
FIG. 1 is a downlink non-orthogonal multiple access system;
FIG. 2 is a direct transmission and relay cooperative transmission-non-orthogonal multiple access system model;
FIG. 3 is a model of a direct-transmission and relay cooperative transmission-non-orthogonal multiple access-physical layer network coding system;
FIG. 4 is a diagram of the exact solution and lower bound for traversal security and rate;
FIG. 5 shows the power distribution coefficient aSImpact on traversal security and rate;
FIG. 6 shows power distribution coefficients
Figure BDA0003703244200000031
Impact on traversal security and rate;
FIG. 7 is a graph of optimal power distribution coefficients
Figure BDA0003703244200000032
Fig. 8 is an overall implementation flow of direct transmission and relay cooperative transmission-non-orthogonal multiple access-physical layer network coding transmission.
Detailed Description
As shown in FIG. 3, the present invention considers the common design of uplink and downlink non-orthogonal multiple access hybrid communication networks based on physical layer network coding, which comprises a base station S as a source node and a near user UNA remote user UFAnd an untrusted relay node R performing an amplify-and-forward strategy. The so-called untrusted relay means that the node is trusted at the service level and untrusted at the data level. (it is impractical for security reasons if the untrusted relay node R employs a decode-and-forward strategy, in which the confidential information has essentially been decoded.) assume that in the communication system, S and U are due to occlusion by obstacles and severe fadingFThere is no direct link and it is necessary to assist the communication with the base station by means of the untrusted relay node R. The channel coefficient, channel gain and average channel power between node i and node j are denoted as hij、|hij|2And λijWhere i, j ∈ (S, U)N,UFR) and i ≠ j. All channels are set as independent and equally distributed rayleigh fading channels,and satisfy hij＝hji；hjiRepresenting the channel coefficients between node j and node i. Suppose that
Figure BDA0003703244200000041
And is
Figure BDA0003703244200000042
λSR，
Figure BDA0003703244200000043
And
Figure BDA0003703244200000044
expressed as the average channel power between base station and untrusted relay, base station and near user, near user and untrusted relay, and near user and far user, respectively. The transmission power of the untrusted relay and the user are both set to PUThe transmission power of the base station is set to PSThe power of the signal is set to the normalized power. Each transmission slot is equal and consecutive.
As shown in fig. 8, the overall implementation flow of direct transmission and relay cooperative transmission-non-orthogonal multiple access-physical layer network coding transmission is mainly divided into three time slots, where the first time slot mainly includes: a base station S sends a superposed signal, a far user sends an interference signal, and a near user and an untrusted relay receive and decode a target signal; the near user and the far user in the second time slot send uplink non-orthogonal multiple access signals, and the base station and the untrusted relay decode target signals; and the untrusted relay in the third time slot forwards the signals received in the first two time slots, the near user sends an uplink new signal, and the base station and the far user decode a target signal. The method specifically comprises the following steps:
the embodiment of the invention is based on a network coding technology and a physical layer security technology, utilizes physical layer network coding to improve the spectrum efficiency of a system, adopts a cooperative interference strategy, does not increase a special interference end, and utilizes a security transmission strategy of inhibiting the decoding capability of an eavesdropping node by sending artificial noise by a user, and is mainly characterized in that a cooperative interference scheme is utilized to increase the channel capacity difference between a legal end and the eavesdropping end. The method comprises the following specific steps:
step S1: channel state information within a communication network is estimated by transmitting pilot sequences, (reference [1]: l.lv, h.jiang, z.g.ding, l.yang, j.hen.secret-enhanced design for cooperative downlink and uplink NOMA with an undirected relay [ J ]. IEEE Transactions on Communications,2020,68 (3): 1698-1715.) specifically channel state information for links between a base station and an untrusted relay link and an untrusted relay and a user.
Step S2: a first time slot, based on a downlink non-orthogonal multiple access protocol, a base station S encodes a target signal x of a near user by superposition1And the destination signal x of the far user2Broadcast after superposition, denoted as
Figure BDA0003703244200000045
Wherein a isSIs a signal x1A power distribution coefficient of (2), and
Figure BDA0003703244200000046
the transmission power of the base station is PS. To suppress untrusted relay nodes, far user U is utilizedFSending a friendly interference signal z in a first time slot as an interferer1The friendly interferer may be a gaussian pseudo-random sequence or utilize a deterministic waveform similar to the desired signal structure. (reference [2 ]]：Z.Rongqing,S.Lingyang,H.Zhu,J.Bingli.Physical layer security for two-way untrusted relaying with friendly jammers[J]IEEE Transactions on Vehicular Technology,2012,61 (8): 3693-3704.) therefore the friendly interferer only affects the eavesdropping reception to noise ratio. At this time, the received signal expression of the destination is:
Figure BDA0003703244200000051
wherein d is E { U ∈ [)N,R}，
Figure BDA0003703244200000052
Expressed as additive white Gaussian noise at node d, with power σ2。hSdAnd
Figure BDA0003703244200000053
respectively, as channel coefficients between the base station and the remote users and node d, PUFor the transmission power of the user, near-user UNDecoding far user signal based on serial interference elimination, and after removing interference, decoding x1Is expressed as
Figure BDA0003703244200000054
Wherein
Figure BDA0003703244200000055
Representing the channel coefficients between the base station and the near users. The untrusted relay, acting as a potential eavesdropping node, decodes the confidential signal based on parallel interference cancellation, the decoded signal-to-noise ratio being denoted as
Figure BDA0003703244200000056
Wherein
Figure BDA0003703244200000057
hSRAnd
Figure BDA0003703244200000058
representing the channel coefficients between the base station and the far user and R, respectively.
And step S3: second time slot, based on uplink non-orthogonal multiple access protocol, near user UNTransmitting a destination signal x of a base station3And an interference signal z in a second time slot2Is represented as a superimposed signal of
Figure BDA0003703244200000059
Wherein
Figure BDA00037032442000000510
Is a signal x3A power distribution coefficient of
Figure BDA00037032442000000511
Simultaneous remote user UFPurpose of transmitting base stationSignal x of4(Signal x at this time)4Is different from x3Different at the transmitting end and different in signal content). The received signals of the base station S and the untrusted relay R are now denoted as
Figure BDA00037032442000000512
Figure BDA00037032442000000513
Wherein
Figure BDA00037032442000000514
And
Figure BDA00037032442000000515
respectively as additive white gaussian noise at the base station and at the untrusted relay in the second time slot,
Figure BDA00037032442000000516
and
Figure BDA00037032442000000517
representing the channel coefficients between the base station and the untrusted relay and the near user, respectively. Similar to step S2, the corresponding decoding signal-to-noise ratio: base station decoding target signal x3Is expressed as
Figure BDA00037032442000000518
Decoded signal-to-noise ratio of untrusted relays
Figure BDA00037032442000000519
And
Figure BDA00037032442000000520
wherein
Figure BDA00037032442000000521
And
Figure BDA00037032442000000522
representing the channel coefficients between the near and far users, respectively, and the untrusted relay.
And step S4: and in the third time slot, a forwarding link and a cooperative link are jointly designed by utilizing network coding and a non-orthogonal multiple access protocol, so that the frequency spectrum efficiency of the system is improved. At this time, the untrusted relay R forwards all the signals received by the first time slot and the second time slot after amplification, and the amplification factor is expressed as
Figure BDA00037032442000000523
Wherein
Figure BDA00037032442000000524
λSR，
Figure BDA00037032442000000525
And
Figure BDA00037032442000000526
respectively representing the average channel power between a base station and an untrusted relay, between the untrusted relay and a far user and between the untrusted relay and a near user; (reference [3 ]]：L.Lv,Z.Li,H.Ding,J.Chen.Secure NOMA and OMA coordinated transmission schemes in untrusted relay networks[J]Science China Information Sciences,2021,64 (10).) near user UNTransmitting a new signal x5And x3Expressed as
Figure BDA00037032442000000527
(reference [4 ]]：H.W.Liu,Z.G.Ding,K.J.Kim,K.S.Kwak,H.V.Poor.Decode-and-forward relaying for cooperative NOMA systems with direct links[J]IEEE Transactions on Wireless Communications,2018,17 (12): 8077-8093) wherein
Figure BDA00037032442000000614
Is a signal x3A power distribution coefficient of (2), and
Figure BDA0003703244200000061
for half-duplex untrusted relays, signal x5Cannot be intercepted, and is perfect and safe. Transmission x3For linearly cancelling far user UFInterference of received untrusted relay forwarded signals. The corresponding received signal expression is:
Figure BDA0003703244200000062
Figure BDA0003703244200000063
in the formula
Figure BDA0003703244200000064
And
Figure BDA0003703244200000065
the received signal expression for the first two time slots expressed as untrusted relays,
Figure BDA0003703244200000066
and
Figure BDA0003703244200000067
represented as additive white gaussian noise that is not confident to relay the first two slots,
Figure BDA0003703244200000068
and
Figure BDA0003703244200000069
representing additive white gaussian noise of the base station and the far user at the third time slot;
Figure BDA00037032442000000610
where steps a and b represent the cancellation of the known or decoded signal, ω, by the destination0Representing a far user UFSum signal x3The related overall expression is expressed as
Figure BDA00037032442000000611
The base station S decodes the target signal based on the successive interference cancellation technique, the decoding order being x5→x4The corresponding decoded signal-to-noise ratio is expressed as
Figure BDA00037032442000000612
To remove the signal x3For remote user UFNeed to satisfy omega0=0, constraint generated as
Figure BDA00037032442000000613
To determine the feasibility of the cancellation, the desired result for the constraint is:
Figure BDA0003703244200000071
it is to be noted that it is preferable that,
Figure BDA0003703244200000072
is not necessarily guaranteed
Figure BDA0003703244200000073
To satisfy the power constraint, we set
Figure BDA0003703244200000074
At this time, in order to obtain better performance, the far user has a decoding order of x5→x2Corresponding to a signal-to-noise ratio of
Figure BDA0003703244200000075
Step S5: the far user is more likely to be attacked by eavesdropping nodes than the near user. To enhance far user performance, x is removed3For remote user UFNeed to meet
Figure BDA0003703244200000076
Where G represents the amplification factor of the untrusted relay,
Figure BDA0003703244200000077
channel coefficients representing untrusted relays and distant users,
Figure BDA0003703244200000078
channel coefficients representing untrusted relays and near users,
Figure BDA0003703244200000079
representing the channel coefficients between the near and far users,
Figure BDA00037032442000000710
indicating that the second slot is assigned to x by the near user3Power distribution coefficient of (2), PUWhich represents the transmit power of the user and,
Figure BDA00037032442000000711
indicating that the third slot is assigned to x3Power distribution coefficient of (a) (. Omega.)0Representing a far user UFSum signal x3With respect to the global expression, x is guaranteed only when the value of the global expression is zero3For remote user UFNo interference is generated. At the same time, the far user decodes the destination signal x2Decoding x before5And removed for better performance.
Step S6: determining a signal xjJ ∈ (1, 2,3,4, 5) the instantaneous safety rate is expressed as
Figure BDA00037032442000000712
Wherein
Figure BDA00037032442000000713
Respectively represent signals xjThe signal-to-noise ratio of the legitimate end and the eavesdropping end.
Step S7: two benchmark schemes were identified to demonstrate the superior performance of the present invention. In the first reference scheme, physical layer network coding is not adopted to design an uplink link and a downlink link together, and 5 signals are transmitted in four time slots; and the second reference scheme does not adopt a cooperative interference strategy.
The security performance of the system according to the embodiment of the present invention is analyzed below. The traversal security and rate of the system are expressed as
Figure BDA0003703244200000081
In the formula (I), the compound is shown in the specification,
Figure BDA0003703244200000082
denoted as signal xjThe safe rate of traversal of (a) is,
Figure BDA0003703244200000083
using the Jensen inequality, the lower bound of traversal security and rate is expressed as
Figure BDA0003703244200000084
Based on probability theory, the traversal rate is expressed as
Figure BDA0003703244200000085
In the formula Fγ(x) And fγ(x) Expressed as a cumulative distribution function and a probability density function of the signal-to-noise ratio γ.
According to the definition of the traversal rate and a series of mathematical deductions, the traversal safety and the traversal rate of the system are expressed as
Figure BDA0003703244200000086
In the formula (I), the compound is shown in the specification,
Figure BDA0003703244200000087
φ2(x,y)＝φ1(x)-φ1(y)，
Figure BDA0003703244200000088
Figure BDA0003703244200000089
c =0.577215 is an euler constant.
Defining a function:
Figure BDA00037032442000000810
as in fig. 4, the approximate gap between the lower bound and the exact solution for safety and speed is traversed. It can be seen from the figure that the approximate gap between the exact solution and the lower bound for traversal of safety and speed is minimal, indicating that it is reasonable and feasible to approximate the exact solution using the lower bound.
As shown in FIG. 5, the power distribution coefficient aSImpact on traversal security and speed. It can be seen from the figure that following aSThe increase of the number of the users is larger than the reduction rate of the far user, so that the safety performance of the whole system is improved.
Power division factor, as shown in fig. 6
Figure BDA0003703244200000091
Impact on traversal security and speed. It can be seen from the figure that
Figure BDA0003703244200000092
The safety rate of the whole system is increased and then reduced, namely, an optimal rate exists
Figure BDA0003703244200000093
So that the safety performance of the whole system is increased. This is as follows
Figure BDA0003703244200000094
Is increased by a signal x3The capacity of the legal end and the capacity of the eavesdropping end are synchronously increased when
Figure BDA0003703244200000095
The capacity of the eavesdropping terminal is increased at a rate exceeding that of the legal terminal, so that the security performance of the system is reduced.
As shown in fig. 7: optimal power distribution coefficient
Figure BDA0003703244200000096
This is because the interference signal increases the safety performance of the system, and reduces the transmission power of the useful signal, which reduces the reliability of the system. FIG. 7 shows that there is an optimum
Figure BDA0003703244200000097
To trade off security and reliability of the system.

Claims (8)

1. The safe transmission method of the non-orthogonal multiple access communication system based on the cooperative interference strategy is characterized in that: the method comprises three time slots, and comprises the following specific steps:
step S1: a first time slot, based on a downlink non-orthogonal multiple access protocol, a base station S uses superposition coding technology to approximate a target signal x of a user1And the destination signal x of the far user2Broadcasting after superposition; simultaneous utilization of remote user UFTransmitting friendly interference signal z in first time slot1The wiretap node is removed from being inhibited, namely, the untrusted relay; near user UNDecoding x based on successive interference cancellation techniques2Post-removal, no-interference decoding x1(ii) a Untrusted relay eavesdropping user's target signal x based on parallel interference cancellation technique1And x2；
Step S2: second time slot, based on uplink non-orthogonal multiple access protocol, near user UNTransmitting a first destination signal x of a base station3And interference signal z in the second time slot2Superimposed signal of, remote user UFTransmitting a second destination signal x of the base station4(ii) a Base station removing interference signal z2Post-decoding x3The untrusted relay eavesdrops on the target signal x of the base station based on parallel interference cancellation techniques3And x4；
And step S3: third time slot, not availableThe signal relay R amplifies and forwards all received signals, and the near user UNSending x3And a third destination signal x of the base station5The base station first decodes the signal x transmitted by the near user based on successive interference cancellation techniques5Re-decoding of signals x forwarded by untrusted relays4。
2. The method of claim 1, wherein the method comprises: to remove x3For remote user UFNeed to meet
Figure FDA0003703244190000011
Where G represents the amplification factor of the untrusted relay,
Figure FDA0003703244190000012
channel coefficients representing untrusted relays and distant users,
Figure FDA0003703244190000013
channel coefficients representing untrusted relays and near users,
Figure FDA0003703244190000014
indicating that the second slot is assigned to x by the near user3Power distribution coefficient of (P)UWhich is indicative of the transmit power of the user,
Figure FDA0003703244190000015
indicating that the third slot is assigned to x3Power distribution coefficient of (a) (. Omega.)0Representing a far user UFSum signal x3In relation to the overall expression, it is,
Figure FDA0003703244190000016
representing the channel coefficients between the near and far users.
3. The method for secure transmission in a cooperative interference based non-orthogonal multiple access communication system according to claim 1, wherein: the friendly interference signal is a gaussian pseudo-random sequence or utilizes a deterministic waveform similar in structure to the desired signal, which affects only the eavesdropping terminal reception noise ratio.
4. The method of claim 3, wherein the method comprises: the received signal expression of the destination in the first time slot is:
Figure FDA0003703244190000017
in the formula, d is belonged to { U ∈ [)N,R}，
Figure FDA0003703244190000018
Representing additive white Gaussian noise at node d, with power σ2，hSdRepresenting the channel coefficient between the base station and d,
Figure FDA0003703244190000019
denotes the channel coefficient, P, between the far user and dUTransmission power of the user, z1Represented as a near-user U of the interference-friendly signal in the first time slotNDecoding far user signal based on serial interference elimination, decoding x after removing interference1Is expressed as
Figure FDA00037032441900000110
Wherein
Figure FDA00037032441900000111
Expressed as channel coefficients between the base station and the near users;
untrusted relay decoding x1And x2Respectively expressed as
Figure FDA00037032441900000112
Figure FDA0003703244190000021
Wherein
Figure FDA0003703244190000022
hSRAnd
Figure FDA00037032441900000222
respectively, as channel coefficients between the base station and the far user and the untrusted relay.
5. The method of claim 1, wherein the method comprises: the received signals of the base station S and the untrusted relay R in step S2 are denoted as
Figure FDA0003703244190000023
Figure FDA0003703244190000024
Wherein
Figure FDA0003703244190000025
And
Figure FDA0003703244190000026
represented as additive white gaussian noise at the base station and at the untrusted relay respectively in the second time slot,
Figure FDA0003703244190000027
representing the channel coefficient between the near user and the untrusted relay, the corresponding decoded signal-to-noise ratio: base station decoding target signal x3Is expressed as
Figure FDA0003703244190000028
Untrusted relay decoding x3And x4Respectively as
Figure FDA0003703244190000029
And
Figure FDA00037032441900000210
Figure FDA00037032441900000211
representing the channel coefficients between the untrusted relay and the near user.
6. The method for secure transmission in a cooperative interference based non-orthogonal multiple access communication system according to claim 1, wherein: in step S3, the corresponding received signal expression is:
Figure FDA00037032441900000212
Figure FDA00037032441900000213
wherein
Figure FDA00037032441900000214
And
Figure FDA00037032441900000215
a received signal representation representing the previous two time slots of the untrusted relay,
Figure FDA00037032441900000216
and
Figure FDA00037032441900000217
is shown asThe additive white gaussian noise in the first two slots is not confidently relayed,
Figure FDA00037032441900000218
denoted as additive white gaussian noise at the base station and at the far user for the third slot respectively,
Figure FDA00037032441900000219
Figure FDA00037032441900000220
steps a and b represent the cancellation of the known or decoded signal, ω, by the destination0Representing far user and x3Relative overall expression, expressed as
Figure FDA00037032441900000221
The base station S decodes the target signal based on the successive interference cancellation technique, the decoding order being x5→x4The corresponding decoded signal-to-noise ratio is expressed as
Figure FDA0003703244190000031
7. The method for secure transmission in a non-orthogonal multiple access communication system based on a cooperative interference strategy according to claim 1,2 or 6, wherein: in order to remove the signal x3For remote user UFNeed to satisfy omega0=0, constraint generated as
Figure FDA0003703244190000032
To determine the feasibility of the cancellation, the desired result for the constraint is:
Figure FDA0003703244190000033
to satisfy the power constraint, set
Figure FDA0003703244190000034
At this time, in order to obtain better performance, the far user has a decoding order of x5→x2Corresponding to a signal-to-noise ratio of
Figure FDA0003703244190000035
8. The method for secure transmission in a non-orthogonal multiple access communication system based on a cooperative interference strategy according to any one of claims 1-6, wherein: signal xjJ ∈ (1, 2,3,4, 5) the instantaneous safety rate is expressed as
Figure FDA0003703244190000036
Wherein
Figure FDA0003703244190000037
Respectively represent signals xjThe legal side and the eavesdropping side.
CN202210699057.XA 2022-06-20 2022-06-20 Safe transmission method of non-orthogonal multiple access communication system based on cooperative interference strategy Pending CN115278662A (en)

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