CN111885732B - Dynamic resource allocation method for enhancing NOMA visible light communication network security - Google Patents

Dynamic resource allocation method for enhancing NOMA visible light communication network security Download PDF

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CN111885732B
CN111885732B CN202010782666.2A CN202010782666A CN111885732B CN 111885732 B CN111885732 B CN 111885732B CN 202010782666 A CN202010782666 A CN 202010782666A CN 111885732 B CN111885732 B CN 111885732B
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CN111885732A (en
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赵响
孙晋永
覃勇
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Guilin University of Electronic Technology
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    • 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
    • H04W72/0473—Wireless resource allocation based on the type of the allocated resource the resource being transmission power
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/53—Allocation or scheduling criteria for wireless resources based on regulatory allocation policies

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Abstract

The invention discloses a dynamic resource allocation method for enhancing the safety of a NOMA visible light communication network, which obtains CSI of a legal mobile user and an eavesdropper through channel estimation and sorts channel gains; acquiring a receiving signal-to-interference-and-noise ratio of a legal mobile user and an instantaneous signal-to-interference-and-noise ratio of the user intercepted by Eve by using a serial interference elimination technology of NOMA, and expressing a network and a safety capacity of a NOMA visible light communication network; the method comprises the steps of providing a joint optimization problem of safe communication and power distribution under the condition that a user moves, and enabling the network and the safe capacity to be maximum under the constraint condition that the power of each optical access point and the power distributed to an associated user by the optical access points based on NOMA; and solving a joint optimization problem by using a layered power distribution algorithm. The method provides theoretical basis for enhancing the safety of the physical layer of NOMA visible light communication of the mobile user, promotes the application of the NOMA visible light safety communication in crowded places, and promotes the practical process of the NOMA visible light safety communication in the fields of karst cave tourism, ubiquitous wireless access service and the like.

Description

Dynamic resource allocation method for enhancing NOMA visible light communication network security
Technical Field
The invention relates to the technical field of optical wireless communication and mobile communication, in particular to a dynamic resource allocation method for enhancing the safety of a NOMA visible light communication network.
Background
With the unprecedented development of the internet of things and the coming of the era of information physical systems (industrial 4.0), the spectrum resources of radio frequency wireless communication are increasingly difficult to meet the data transmission requirements of large-scale interconnection, high speed and low time delay. To overcome this bottleneck, researchers and industries consider developing new frequency bands and increasing the utilization of existing spectrum resources. The visible light communication utilizes the unplanned frequency band of 400-790 THz to transmit data, and the frequency spectrum crisis which is gradually white and hot can be relieved to a certain extent. The scientific significance and application value of visible light communication are being generally regarded by academic circles, industrial circles and government departments at home and abroad.
Next generation wireless communication requires the ability to support access by a large number of users, with higher connection density. Conventional visible light communication based on Orthogonal Multiple Access (OMA) reduces inter-user interference by allocating orthogonal radio resources (time slots, frequency bands, or orthogonal symbols) to users in the electrical domain. Due to the shortage of wireless resources, the OMA scheme cannot support too many users to access, and cannot really realize large-scale interconnection. Non-orthogonal multiple access (NOMA) is used as a new wireless access technology, and a plurality of users can share the same time-frequency wireless resource without orthogonality through superposition coding of a transmitting end power domain and a serial interference elimination technology of a receiving end, so that the NOMA has the characteristics of high frequency spectrum efficiency, large-scale interconnection support, low transmission delay and the like. Research shows that the NOMA has better performance in the environment with high signal-to-noise ratio. The visible light communication system communicates on the basis of illumination, and generally has a high signal-to-noise ratio in order to meet illumination requirements. The NOMA technique is therefore well suited for visible light communication systems.
Visible light communication also presents security issues due to the broadcast nature of the optical wireless channel. When the LED light source is used for sending information, if an eavesdropper and a legal user are in the same LED illumination range, the information can be stolen or intercepted. However, just as a coin has two sides, the openness of the channel also creates diversity and diversity of the channel, making the channel a natural "fingerprint". The physical layer security technology makes full use of the difference of wireless channels to distinguish different receivers, designs a secure transmission scheme for legal users, and directly ensures the information secure transmission in the physical layer. The technology not only provides a first line of defense for defending eavesdropping attack, but also is an effective supplement of the traditional encryption security technology.
The NOMA-based visible light communication physical layer security technology can simultaneously improve the access density and information security of users, and has wide application prospect in the aspect of security communication of indoor personnel intensive places (such as shopping malls, railway stations, hospitals, exhibition halls and the like). Zhao et al, in view of a multi-user visible light communication scenario of a downlink NOMA link, consider two cases of single eavesdropping and multiple non-collusion eavesdropping, and derive a safety interruption probability of a communication system by using a random geometry theory. In the NOMA visible light communication system considered by Arafa et al, under the condition of single external eavesdropping, a transmitter communicates with two static legal users based on a downlink NOMA mode, and the visible light safe transmission is enhanced by deploying a large number of credible half-duplex relay nodes.
It can be seen that, until now, the physical layer security of NOMA visible light communication is mainly aimed at the secure communication of stationary users, while the secure communication of mobile users is less studied. In practical applications, user movement is an important feature of wireless communication, and also an important feature of visible light communication. With the explosion of mobile internet, whether mobile payment, mobile social contact, or mobile office, the security of mobile services is a common requirement for all consumers. Therefore, it is of great significance to research the safety of the NOMA visible light communication physical layer under the condition that the user moves.
Disclosure of Invention
The invention aims to provide a dynamic resource allocation method for enhancing the safety of a NOMA visible light communication network aiming at the safety problem of a mobile user in the NOMA visible light communication network.
The technical scheme for realizing the purpose of the invention is as follows:
a dynamic resource allocation method for enhancing the security of NOMA visible light communication network comprises the following steps:
1) in an indoor visible light communication network based on downlink NOMA, the indoor visible light communication network consists of a plurality of indoor light access points arranged on a roof and a plurality of mobile users on a floor, each indoor light access point covers one light cell, the mobile users in the range and the indoor light access points carry out visible light communication based on NOMA, at the edge of each light cell, an eavesdropper Eve has a server to eavesdrop the information sent by the indoor light access points to the legal mobile users related to the eavesdropper Eve, and the legal users and Eve are assumed to be provided with a single photodiode PD receiver, and the field of view of the PD receiver is large enough to receive all signals in the LED light-emitting angle range;
2) assuming that a plurality of mobile users exist in the coverage range of a certain optical access point at a certain moment, the mobile users estimate Channel State Information (CSI) through a channel and feed back the CSI to the associated optical access point by using an uplink infrared link channel, namely, each optical access point can acquire the CSI of the mobile users associated with the optical access point, Eve eavesdrops at the edge of an optical cell, and the distance between Eve and the optical access point is kept unchanged, the instantaneous CSI of Eve is known, and the optical access point sorts the channel gains after acquiring the CSI of the mobile users and the Eve and transmits the sorting information to the mobile users and the Eve;
3) according to the channel gain sequencing information in the step 2), calculating and obtaining the received signal-to-interference-and-noise ratio of the legal mobile user at any moment by utilizing the Serial Interference Cancellation (SIC) technology of NOMA, and eavesdropping the instantaneous signal-to-interference-and-noise ratio of the user by Eve;
4) calculating the reachable security rate of the legal mobile user according to the received signal-to-interference-and-noise ratio of the legal mobile user obtained in the step 3) and the instantaneous signal-to-interference-and-noise ratio of the user intercepted by Eve;
5) repeating the step 2) to the step 4) until the sum safety capacity of all legal mobile users in the coverage area of a certain optical access point is calculated;
6) repeating the step 2) to the step 5) until the sum safety capacity of all legal mobile users in all the optical access points is calculated and expressed by the network and the safety capacity;
7) constructing a joint optimization problem of safe communication and power distribution under the condition that a user moves, and enabling the network and the safe capacity to be maximum under the constraint conditions of the power of each optical access point and the power distributed to an associated user by the optical access points based on NOMA;
8) and (3) solving the joint optimization problem of the secure communication and the power distribution under the user moving condition, which is established in the step (7), by utilizing a layered power distribution algorithm, and completing the resource distribution of the mobile user.
Step 1) for the aggregation of indoor light access points
Figure BDA0002620799530000031
Is shown and the set of all legal mobile users is used
Figure BDA0002620799530000032
Represents; suppose ysIs the position of the indoor light access point s, which is fixed; x is the number ofm,tFor the location of user m at time t, the motion trajectory of user m over time is denoted as { x }m,t}t＝1,…。
In step 2), suppose that P is used for the total power of the light access point s at the time ts,tDenotes that its maximum allowed value is assumed to be Ps,maxAt time t, power p transmitted by the optical access point s to the user ms,m,tIt is shown that,
since the user moves, whether the t-ray access point s serves the user at a certain time is judged by the following formula (1):
Figure BDA0002620799530000033
and whether the user m and the optical access point s have user association at a certain time t is judged by the following formula (2):
Figure BDA0002620799530000034
the problem of dynamic allocation of the optical access points and the transmission power caused by the movement of the user is converted into the problem of dynamically adjusting the total power of each optical access point and allocating the power of the legal user to each optical access point based on NOMA; let t be the set of users served by the optical access point s
Figure BDA0002620799530000038
And satisfy
Figure BDA0002620799530000035
At time t, user m associates with optical access point s, and the optical wireless channel gain of user m is
Figure BDA0002620799530000036
Is the spatial distance | x of the user m from the light access point sm,t-ysAngle of incidence of a II, PD receiver
Figure BDA0002620799530000037
And the LED radiation angle phi in the light access point ssSince the coverage areas of different optical cells overlap, the interference of the neighboring cell to the user m at time t is:
Figure BDA0002620799530000041
wherein
Figure BDA0002620799530000042
Representing a set of indoor light access points
Figure BDA0002620799530000043
Set with light access points s removed, any light access point
Figure BDA0002620799530000044
Ps′,tFor the transmission power of the light access point s' at any time t, hs′,m,tIs the optical wireless channel gain between the optical access point s' and the user m;
the instantaneous CSI for user m at time t is represented as:
Figure BDA0002620799530000045
wherein n ismEve eavesdrops at the edge of the light cell covered by the light access point s for the influence of noise on the user m at the time t, and the half-power half-angle of the LED is fixed, so that the propagation distance between the Eve and the light access point is kept unchanged, and the instantaneous CSI of the Eve is determined and recorded as hs,e,t(ii) a After acquiring CSI of the mobile user and Eve, the optical access point sequences the channel gains and transmits sequencing information to the mobile user and Eve.
In step 3), according to the obtained channel gain sorting information and by using the SIC technology of NOMA, the received sir of user m at time t is calculated as:
Figure BDA0002620799530000046
wherein
Figure BDA0002620799530000047
Representing the set of users served by the optical access point s at time t
Figure BDA00026207995300000411
Of any user m', its optical radio channel gain
Figure BDA0002620799530000048
Channel gain greater than user m
Figure BDA0002620799530000049
The sir of the eavesdropping user m at time teve is expressed as:
Figure BDA00026207995300000410
in step 4), the reachable security rate of the user m at the time t is calculated as follows:
Rs,m,t＝[log(1+Qs,m,t)-log(1+Qs,e→m,t)]+ (7)。
step 5), calculating the sum safety capacity of all mobile users within the range of the light access point s at the moment t as follows:
Figure BDA0002620799530000051
in step 6), the network and security capacity of all mobile users within the range of all optical access points at the time t are calculated as follows:
Figure BDA0002620799530000052
step 7), a joint optimization problem of safe communication and power distribution under the condition of user movement is constructed, and an expression is as follows:
Figure BDA0002620799530000053
network and security capacity are maximized subject to satisfying power constraints (10-2) for each optical access point and constraints (10-3) and (10-4) for power allocated by the optical access point to associated users based on NOMA.
In the step 8), a joint optimization problem of safe communication and power distribution under the condition of user movement is solved, because of the logarithmic subtraction characteristic of the objective function in the step (10-1), the optimization problem (10) is a non-convex optimization problem, and therefore, based on a convex optimization theory, an optimal solution cannot be directly obtained; the optimization problem (10) exists with two power allocations: power distribution of the optical control center to each optical access point and power distribution of each optical access point to associated users based on NOMA; therefore, a hierarchical power allocation algorithm is used, which comprises two phases: determining the optimal transmitting power of each light access point in a light control center, and determining the optimal transmitting power of the associated user based on NOMA (non-orthogonal multiple access) on each light access point;
the first stage is as follows: determining the optimal transmitting power for the associated user based on NOMA at each optical access point given the power of the respective optical access point, assuming that the power allocated by the optical access point s at time t is Ps,tThen the optimization problem (10) is reduced to a sub-optimization problem (11):
Figure BDA0002620799530000054
at the moment t, the power distribution of the associated users based on NOMA is carried out on the optical access point s, so that the sum safety capacity of all mobile users in the range of the optical access point s is maximum; in order to maximize the sum safety capacity of the mobile users associated with the optical access point s at the time t, the total power of the optical access point s is allocated to the mobile users with the largest channel gain, so that the first phaseIs to seek the mobile user with the maximum channel gain
Figure BDA0002620799530000061
Namely:
Figure BDA0002620799530000062
then the power P of the light access point s at the moment ts,tAll sent to the mobile subscriber
Figure BDA0002620799530000063
And a second stage: according to the power distribution condition fed back by each light access point to the associated mobile user, the light control center determines the optimal transmitting power of each light access point, and the problem of maximizing the network and the safety capacity at the moment is as follows:
Figure BDA0002620799530000064
that is, in the optical control center, the optimal transmission power of each optical access point is determined, so that the network and the safety capacity are maximized, and the following definitions are defined:
Figure BDA0002620799530000065
as can be seen from equation (14), when A is presents,t＜Bs,tIn time, the optimization problem (13) is the operator [ · in the objective function]+Can be eliminated, so the optimization problem (13) is further simplified to:
Figure BDA0002620799530000066
wherein
Figure BDA0002620799530000067
Indicating that a positive safe rate is available within the set, i.e.Is located at
Figure BDA0002620799530000068
The optical access points within are treated as unwanted nodes, and the optical control center does not have to allocate power to them;
the network and security capacity maximization problem in the optimization problem (15) involves each
Figure BDA0002620799530000071
The safety capacity maximization problem of the optical access point is a distributed game problem, an iterative power distribution algorithm of the optical access point by the optical control center is obtained based on a non-cooperative safety game theory, and is described by an algorithm 1:
Figure BDA0002620799530000072
has the advantages that: the invention provides a dynamic resource allocation method for enhancing the safety of a NOMA visible light communication network, which has the following advantages:
1. providing theoretical basis for enhancing the safety of the physical layer of NOMA visible light communication of the mobile user;
2. the application of the physical layer security technology of NOMA visible light communication in personnel intensive places such as banks and airports is promoted, and the practical process of the NOMA visible light communication in the fields of karst cave tourism, ubiquitous wireless access service and the like is promoted.
Drawings
Fig. 1 is a schematic diagram of the physical layer security of a NOMA visible light communication network in case of user movement;
FIG. 2 is a schematic diagram of a security framework of a NOMA visible light communications network in the case of user movement;
FIG. 3 is a graph of convergence change of network and safety capacity under an iterative power allocation algorithm;
fig. 4 is a graph of the effect of the variation of the half-power angle of the LED on the network and safety capacity.
Detailed Description
The invention will be further elucidated with reference to the drawings and examples, without however being limited thereto.
Example (b):
a dynamic resource allocation method for enhancing the security of NOMA visible light communication network comprises the following steps:
1) as shown in FIG. 1, the indoor visible light communication network based on downlink NOMA is composed of a plurality of indoor light access points deployed on the roof and a plurality of users moving on the floor, and the indoor light access points are used for aggregation
Figure BDA0002620799530000081
Is shown and the set of all legal mobile users is used
Figure BDA0002620799530000082
Represents; suppose ysThe location of the indoor light access point s, which is typically fixed; x is the number ofm,tFor the location of user m at time t, the motion trajectory of user m over time may be represented as { x }m,t}t＝1,...Each indoor optical access point covers an optical cell, mobile users in the range and the optical access point carry out visible light communication based on NOMA, and at the edge of each optical cell, an Eve server eavesdrops information sent by the optical access point to a legal mobile user associated with the optical access point. It is assumed that both legitimate users and Eve are equipped with a single PD receiver and that the field of view of the PD receiver is large enough to receive all signals within the LED illumination angle range.
2) Assuming that a plurality of mobile users exist in the coverage range of a certain optical access point at a certain moment, the mobile users estimate Channel State Information (CSI) through a channel and feed back the CSI to the associated optical access point by using an uplink infrared link channel, namely, each optical access point can acquire the CSI of the mobile users associated with the optical access point, Eve eavesdrops at the edge of an optical cell, and the distance between Eve and the optical access point is kept unchanged, the instantaneous CSI of Eve is known, and the optical access point sorts channel gains after acquiring the CSI of the mobile users and Eve and transmits the sorting information to the mobile users and Eve; the method comprises the following steps:
let us assume that the total power P of the light access point s at the time ts,tDenotes that its maximum allowed value is assumed to be Ps,maxAt time t, power p transmitted by the optical access point s to the user ms,m,tRepresents;
since the user moves, whether the t-ray access point s serves the user at a certain time is judged by the following formula (1):
Figure BDA0002620799530000083
and whether the user m and the optical access point s have user association at a certain time t is judged by the following formula (1):
Figure BDA0002620799530000084
therefore, the problem of dynamic allocation of the optical access points and the transmission power caused by user movement can be converted into the problem of dynamically adjusting the total power of each optical access point and allocating the power of each optical access point to the legal user based on NOMA.
Let t be the set of users served by the optical access point s
Figure BDA00026207995300000911
And satisfy
Figure BDA0002620799530000091
At time t, user m associates with optical access point s, and the optical wireless channel gain of user m is
Figure BDA0002620799530000092
Figure BDA0002620799530000093
Is the spatial distance | x of the user m from the light access point sm,t-ysAngle of incidence of a II, PD receiver
Figure BDA0002620799530000094
And the LED radiation angle phi in the light access point ssAs a function of (c). Since the coverage areas of different optical cells may overlap, the interference of the neighboring cell experienced by user m at time t is:
Figure BDA0002620799530000095
wherein
Figure BDA0002620799530000096
Representing a set of indoor light access points
Figure BDA0002620799530000097
Set with light access points s removed, any light access point
Figure BDA0002620799530000098
The transmission power of the optical access point s' at any time t is Ps′,tThe gain of the optical wireless channel between the optical access point s' and the user m is hs′,m,t；
The instantaneous CSI for user m at time t can be expressed as:
Figure BDA0002620799530000099
wherein n ismThe user m is affected by noise at time t.
Eve eavesdrops at the edge of a light cell covered by a light access point s, and because the half-power half-angle of an LED is fixed, the propagation distance between Eve and the light access point is kept unchanged, so that the instantaneous CSI of Eve is determinable and is recorded as hs,e,t。
After acquiring CSI of the mobile user and Eve, the optical access point sequences the channel gains and transmits sequencing information to the mobile user and Eve.
3) According to the channel gain sequencing information in the step 2), calculating and obtaining the received signal-to-interference-and-noise ratio of the legal mobile user at any moment by using SIC technology of NOMA, and eavesdropping the instantaneous signal-to-interference-and-noise ratio of the user by Eve; let the received sir of user m at time t be expressed as:
Figure BDA00026207995300000910
the sir of the eavesdropping user m at time teve is expressed as:
Figure BDA0002620799530000101
4) calculating the reachable security rate of the legal mobile user m at the moment t according to the received signal-to-interference-and-noise ratio of the legal mobile user obtained in the step 3) and the instantaneous signal-to-interference-and-noise ratio of the user eavesdropped by Eve, wherein the expression is as follows:
Rs,m,t＝[log(1+Qs,m,t)-log(1+Qs,e→m,t)]+ (7)
5) repeating the step 2) to the step 4) until the sum safety capacity of all legal mobile users in the coverage area of the optical access point s at the time t is calculated, wherein the expression is as follows:
Figure BDA0002620799530000102
6) repeating the steps 2) to 5) until the sum security capacity of all legal mobile users in all the optical access points is calculated and expressed by the network and the security capacity, wherein the expression is as follows:
Figure BDA0002620799530000103
7) constructing a joint optimization problem of safe communication and power distribution under the condition that a user moves, and enabling the network and the safe capacity to be maximum under the constraint conditions of the power of each optical access point and the power distributed to an associated user by the optical access points based on NOMA; the constructed joint optimization problem expression of the safe communication and the power distribution under the condition of the user movement is as follows:
Figure BDA0002620799530000104
network and security capacity are maximized subject to satisfying power constraints (10-2) for each optical access point and constraints (10-3) and (10-4) for power allocated by the optical access point to associated users based on NOMA.
8) Solving the combined optimization problem of the secure communication and the power distribution under the user moving condition, which is established in the step 7), by utilizing a layered power distribution algorithm to complete the resource distribution of the mobile user; the hierarchical power allocation algorithm comprises two phases: the optimal transmit power for each light access point is determined at the light control center and the optimal transmit power for the associated user based on NOMA is determined at each light access point, as shown in figure 2.
The first stage is as follows: given the power of the individual optical access points, the optimal transmit power for the associated user based on NOMA is determined at each optical access point. Let the power allocated by the light access point s at time t be Ps,tThen the optimization problem (10) is reduced to a sub-optimization problem (11):
Figure BDA0002620799530000111
the time t is at the optical access point s by NOMA-based power allocation to the associated users, maximizing the sum of the security capacities of all mobile users within the range of the optical access point s.
It can be demonstrated that: to maximize the sum security capacity of the mobile users associated with the light access point s at time t, the total power of the light access point s should be greedily allocated to the mobile users with the largest channel gain.
The main task of the first stage is therefore to find the mobile user with the maximum channel gain
Figure BDA0002620799530000112
Namely:
Figure BDA0002620799530000113
then the power P of the light access point s at the moment ts,tAll sent to the mobile subscriber
Figure BDA0002620799530000114
And a second stage: and according to the power distribution condition fed back by each optical access point to the associated mobile user, the optical control center determines the optimal transmitting power of each optical access point.
The network and security capacity maximization problem at this time is:
Figure BDA0002620799530000115
that is, network and security capacity is maximized in the optical control center by determining the optimal transmit power for each optical access point.
Defining:
Figure BDA0002620799530000121
when A is known from formula (14)s,t＜Bs,tIn time, the optimization problem (13) is the operator [ · in the objective function]+Can be eliminated, so the optimization problem (13) can be further simplified to:
Figure BDA0002620799530000122
wherein
Figure BDA0002620799530000123
Indicating that a positive safe rate is available within the set. That is, at
Figure BDA0002620799530000124
The optical access points within are treated as unwanted nodes and the optical control center does not have to allocate power to them.
The network and security capacity maximization problem in the optimization problem (15) is related to eachAn
Figure BDA0002620799530000125
The security capacity of the optical access point is maximized, which is a distributed gaming problem. Based on a non-cooperative secure game theory, an iterative power distribution algorithm of the optical control center to the optical access point can be obtained, and is described by an algorithm 1:
Figure BDA0002620799530000126
the following measures are taken to verify the beneficial effects of the invention:
FIG. 3 shows that the error threshold ε is 10-9And (5) a convergence change curve of the network and the safety capacity under a time iteration power distribution algorithm. As can be seen, the proposed iterative power allocation algorithm converges very fast, and only about two iterations are required to reach steady state. Furthermore, the network and security capacity of NOMA visible light communication networks increases significantly as the number of legitimate mobile users in an optical cell decreases. This is because Eve eavesdrops on the edge of the optical cell covered by the optical access point, CSI of the eavesdropping channel is constant, and when the number of legitimate mobile users in the coverage of the optical access point is reduced, the channel difference between the legitimate channel and the eavesdropping channel can be enlarged, thereby improving the security capacity and enhancing the network and security capacity of the entire network.
Fig. 4 is a graph showing the effect of the half-angle change of the LED half-power on the network and the safety capacity when the number of the legitimate mobile subscribers is constant within the coverage area of the optical access point. As can be seen, the network and safety capacity increase with decreasing half-power angle of the LED. This is because, as the half-power angle of the LED is reduced, the LED optical beam becomes narrower, which suppresses interference of adjacent optical cells and improves CSI of a legitimate channel, thereby enlarging a channel difference between the legitimate channel and an eavesdropping channel and enhancing the network and security capacity of the entire network.

Claims (3)

1. A dynamic resource allocation method for enhancing the security of a NOMA visible light communication network is characterized by comprising the following steps:
1) in an indoor visible light communication network based on downlink NOMA, the indoor visible light communication network consists of a plurality of indoor light access points arranged on a roof and a plurality of mobile users on a floor, each indoor light access point covers one light cell, the mobile users in the range and the indoor light access points carry out visible light communication based on NOMA, at the edge of each light cell, an eavesdropper Eve has a server to eavesdrop the information sent by the indoor light access points to the legal mobile users related to the eavesdropper Eve, and the legal users and Eve are assumed to be provided with a single photodiode PD receiver, and the field of view of the PD receiver is large enough to receive all signals in the LED light-emitting angle range;
2) assuming that a plurality of mobile users exist in the coverage range of a certain optical access point at a certain moment, the mobile users estimate Channel State Information (CSI) through a channel and feed back the CSI to the associated optical access point by using an uplink infrared link channel, namely, each optical access point can acquire the CSI of the mobile users associated with the optical access point, Eve eavesdrops at the edge of an optical cell, and the distance between Eve and the optical access point is kept unchanged, the instantaneous CSI of Eve is known, and the optical access point sorts the channel gains after acquiring the CSI of the mobile users and the Eve and transmits the sorting information to the mobile users and the Eve;
3) according to the channel gain sequencing information in the step 2), calculating and obtaining the received signal-to-interference-and-noise ratio of the legal mobile user at any moment by utilizing the Serial Interference Cancellation (SIC) technology of NOMA, and eavesdropping the instantaneous signal-to-interference-and-noise ratio of the user by Eve;
4) calculating the reachable security rate of the legal mobile user according to the received signal-to-interference-and-noise ratio of the legal mobile user obtained in the step 3) and the instantaneous signal-to-interference-and-noise ratio of the user intercepted by Eve;
5) repeating the step 2) to the step 4) until the sum safety capacity of all legal mobile users in the coverage area of a certain optical access point is calculated;
6) repeating the step 2) to the step 5) until the sum safety capacity of all legal mobile users in all the optical access points is calculated and expressed by the network and the safety capacity;
7) constructing a joint optimization problem of safe communication and power distribution under the condition that a user moves, and enabling the network and the safe capacity to be maximum under the constraint conditions of the power of each optical access point and the power distributed to an associated user by the optical access points based on NOMA;
8) solving the combined optimization problem of the secure communication and the power distribution under the user moving condition, which is established in the step 7), by utilizing a layered power distribution algorithm to complete the resource distribution of the mobile user;
in step 3), according to the obtained channel gain sorting information and by using the SIC technology of NOMA, the received sir of user m at time t is calculated as:
Figure FDA0002919111200000021
wherein
Figure FDA0002919111200000022
Representing the set of users served by the optical access point s at time t
Figure FDA0002919111200000023
Of any user m', its optical radio channel gain
Figure FDA0002919111200000024
Channel gain greater than user m
Figure FDA0002919111200000025
The sir of the eavesdropping user m at time teve is expressed as:
Figure FDA0002919111200000026
in step 4), the reachable security rate of the user m at the time t is calculated as follows:
Rs,m,t＝[log(1+Qs,m,t)-log(1+Qs,e→m,t)]+ (7)；
step 5), calculating the sum safety capacity of all mobile users within the range of the light access point s at the moment t as follows:
Figure FDA0002919111200000027
in step 6), the network and security capacity of all mobile users within the range of all optical access points at the time t are calculated as follows:
Figure FDA0002919111200000028
step 7), a joint optimization problem of safe communication and power distribution under the condition of user movement is constructed, and an expression is as follows:
Figure FDA0002919111200000029
maximizing network and security capacity subject to satisfying power constraints (10-2) for each optical access point and constraints (10-3) and (10-4) of power allocated by the optical access point to associated users based on NOMA;
in the step 8), a joint optimization problem of safe communication and power distribution under the condition of user movement is solved, because of the logarithmic subtraction characteristic of the objective function in the step (10-1), the optimization problem (10) is a non-convex optimization problem, and therefore, based on a convex optimization theory, an optimal solution cannot be directly obtained; the optimization problem (10) exists with two power allocations: power distribution of the optical control center to each optical access point and power distribution of each optical access point to associated users based on NOMA; therefore, a hierarchical power allocation algorithm is used, which comprises two phases: determining the optimal transmitting power of each light access point in a light control center, and determining the optimal transmitting power of the associated user based on NOMA (non-orthogonal multiple access) on each light access point;
the first stage is as follows: determining, at each optical access point, an optimal transmit power for the associated user based on NOMA, given the power of the respective optical access point, falseSetting the power distributed by the light access point s at the time t as Ps,tThen the optimization problem (10) is reduced to a sub-optimization problem (11):
Figure FDA0002919111200000031
at the moment t, the power distribution of the associated users based on NOMA is carried out on the optical access point s, so that the sum safety capacity of all mobile users in the range of the optical access point s is maximum; in order to maximize the sum safety capacity of the mobile users associated with the optical access point s at the time t, the total power of the optical access point s is allocated to the mobile user with the largest channel gain, so the main task of the first phase is to seek the mobile user with the largest channel gain
Figure FDA0002919111200000032
Namely:
Figure FDA0002919111200000033
then the power P of the light access point s at the moment ts,tAll sent to the mobile subscriber
Figure FDA0002919111200000034
And a second stage: according to the power distribution condition fed back by each light access point to the associated mobile user, the light control center determines the optimal transmitting power of each light access point, and the problem of maximizing the network and the safety capacity at the moment is as follows:
Figure FDA0002919111200000035
that is, in the optical control center, the optimal transmission power of each optical access point is determined, so that the network and the safety capacity are maximized, and the following definitions are defined:
Figure FDA0002919111200000041
as can be seen from the formula (14), when A iss,t＜Βs,tIn time, the optimization problem (13) is the operator [ · in the objective function]+Can be eliminated, so the optimization problem (13) is further simplified to:
Figure FDA0002919111200000042
wherein
Figure FDA0002919111200000043
Indicating that a positive safe rate is available within the set, i.e. located
Figure FDA0002919111200000044
The optical access points within are treated as unwanted nodes, and the optical control center does not have to allocate power to them;
the network and security capacity maximization problem in the optimization problem (15) involves each
Figure FDA0002919111200000045
The safety capacity maximization problem of the optical access point is a distributed game problem, an iterative power distribution algorithm of the optical access point by the optical control center is obtained based on a non-cooperative safety game theory, and is described by an algorithm 1:
Figure FDA0002919111200000046
Figure FDA0002919111200000051
2. dynamic resource for enhancing the security of a NOMA visible light communication network according to claim 1The distribution method is characterized in that in the step 1), the indoor light access points are used for aggregation
Figure FDA0002919111200000059
Is shown and the set of all legal mobile users is used
Figure FDA00029191112000000510
Represents; suppose ysIs the position of the indoor light access point s, which is fixed; x is the number ofm,tFor the location of user m at time t, the motion trajectory of user m over time is denoted as { x }m,t}t＝1,…。
3. The dynamic resource allocation method for enhancing the security of NOMA visible light communication network as claimed in claim 1, wherein in step 2), the total power P of the optical access points s at time t is assumed to be Ps,tDenotes that its maximum allowed value is assumed to be Ps,maxAt time t, power p transmitted by the optical access point s to the user ms,m,tIt is shown that,
since the user moves, whether the t-ray access point s serves the user at a certain time is judged by the following formula (1):
Figure FDA0002919111200000052
and whether the user m and the optical access point s have user association at a certain time t is judged by the following formula (2):
Figure FDA0002919111200000053
the problem of dynamic allocation of the optical access points and the transmission power caused by the movement of the user is converted into the problem of dynamically adjusting the total power of each optical access point and allocating the power of the legal user to each optical access point based on NOMA; let t be the set of users served by the optical access point s
Figure FDA0002919111200000054
And satisfy
Figure FDA0002919111200000055
At time t, user m associates with optical access point s, and the optical wireless channel gain of user m is
Figure FDA0002919111200000056
Is the spatial distance | x of the user m from the light access point sm,t-ysAngle of incidence of a II, PD receiver
Figure FDA0002919111200000057
And the LED radiation angle phi in the light access point ssSince the coverage areas of different optical cells overlap, the interference of the neighboring cell to the user m at time t is:
Figure FDA0002919111200000058
wherein
Figure FDA0002919111200000061
Representing a set of indoor light access points
Figure FDA0002919111200000062
Set with light access points s removed, any light access point
Figure FDA0002919111200000063
Ps′,tFor the transmission power of the light access point s' at any time t, hs′,m,tIs the optical wireless channel gain between the optical access point s' and the user m;
the instantaneous CSI for user m at time t is represented as:
Figure FDA0002919111200000064
wherein n ismEve eavesdrops at the edge of the light cell covered by the light access point s for the influence of noise on the user m at the time t, and the half-power half-angle of the LED is fixed, so that the propagation distance between the Eve and the light access point is kept unchanged, and the instantaneous CSI of the Eve is determined and recorded as hs,e,t(ii) a After acquiring CSI of the mobile user and Eve, the optical access point sequences the channel gains and transmits sequencing information to the mobile user and Eve.
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