Energy efficiency optimization method for indoor aggregation VLC-RF access point selection and resource allocation

Abstract

The invention relates to an energy efficiency optimization method for indoor aggregation VLC-RF access point selection and resource allocation, and belongs to the technical field of optical wireless communication. The method comprises the following steps: firstly, adopting a bilateral matching theory-based high-energy-efficiency access point selection algorithm to ensure that a user accesses a VLC access point which contributes to network energy efficiency to the greatest extent; secondly, adopting a sub-channel allocation scheme based on a Gerre-Shapley algorithm to ensure that a stable matching relationship is formed between an access user set and a sub-channel set of each VLC access point or RF access point; and finally, a power distribution strategy based on multi-target energy efficiency optimization is adopted, the total network throughput and the total network transmitting power are balanced, and an optimal power distribution result and an energy efficiency optimization result which are obtained through solving are stored in a Pareto optimal set and a Pareto optimal leading edge set through an iteration method. According to the method provided by the invention, the energy efficiency of the indoor aggregation VLC-RF network can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical wireless communications and relates to an energy efficiency optimization method for indoor aggregated VLC-RF access point selection and resource allocation. Background Art

[0002] Visible Light Communication (VLC) technology can effectively address the shortage of radio frequency (RF) communication spectrum resources. It offers advantages such as high speed, energy efficiency, and no electromagnetic interference, and is considered a core technology for next-generation wireless communication networks. Integrating VLC and RF can increase network capacity, extend communication range, and enhance the user communication experience. Generally speaking, there are two basic categories of integrated VLC-RF networks: hybrid VLC-RF networks and aggregated VLC-RF networks. Compared to hybrid VLC-RF networks, aggregated VLC-RF networks allow users to simultaneously receive information transmitted by both VLC and RF links, avoiding transmission delays and data loss caused by link switching. This allows for higher data transmission rates and a more stable and reliable communication experience, making them more promising for research.

[0003] In indoor converged VLC-RF networks, selecting the right network access point (AP) for users not only improves their communication satisfaction but also has a crucial impact on subsequent network resource allocation and network performance optimization. Existing research has shown that reasonable resource allocation can reduce network resource waste and improve communication quality, primarily involving subchannel allocation and power allocation. Furthermore, with the increasing number and variety of wireless communication devices, energy consumption has gradually become a focus of attention in the global communications industry, and network energy efficiency optimization has become an inevitable trend in the development of wireless communication networks. Therefore, designing effective access point selection, subchannel allocation, and power allocation algorithms in indoor converged VLC-RF networks to maximize network energy efficiency is of great research significance. Summary of the Invention

[0004] The core of the present invention is to provide an energy efficiency optimization method for indoor aggregated VLC-RF access point selection and resource allocation, which improves network energy efficiency by solving the joint optimization problem of access point selection, subchannel allocation and power allocation.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] 1. A method for optimizing energy efficiency of indoor aggregated VLC-RF access point selection and resource allocation, characterized in that the method comprises the following steps:

[0007] S1: Input user set in indoor aggregated VLC-RF network VLC AP Collection 1 RF AP, sub-channel set of each VLC AP RF AP subchannel set Each VLC AP reuses the same set of subchannels. The channel gain between the user and the VLC AP subchannel is calculated based on the Lambertian radiation model. The channel gain between the user and the RF AP subchannel is calculated based on the Rayleigh fading model.

[0008] According to the Lambertian radiation model, the channel gain between user k and subchannel n of VLC AP v is calculated as follows:

[0009]

[0010] In the above formula, A represents the probability that the line-of-sight link between user k and VLC AP v on subchannel n is not blocked. The line-of-sight link refers to the straight optical propagation path between the VLC AP and the user without any obstacles. PD represents the physical area of ​​the photodetector; t = -1 / log2(cos(Φ 1 / 2 )), represents the Lambertian radiation order, Φ 1 / 2 is the half-power angle of the light-emitting diode; d v,k represents the distance between VLC AP v and user k; φ v,k is the irradiance angle from VLC AP v to user k; ψ v,k is the incident angle from VLC AP v to user k; T o is the optical filter gain, generally set to T o =1; G(ψ v,k )=δ 2 / sin 2 Ψ FoV , represents the concentrator gain, δ is the refractive index, Ψ FoV is the field of view of the photodetector;

[0011] According to the Rayleigh fading model, the channel gain between user k and RF AP subchannel m is calculated as follows:

[0012]

[0013] In the above formula, h r represents the small-scale fading caused by signal multipath propagation, which follows the Rayleigh distribution and has an average power of 2.46 dB; d RF,k represents the distance between user k and RF AP; L(d RF,k) represents the large-scale fading loss, and the calculation formula is L(d RF,k )=20log 10 (d RF,k )+20log 10 (f c )-147.5(dB), f c Indicates the RF carrier center frequency in GHz;

[0014] S2: Calculate the user's received signal-to-interference plus noise ratio (SINR) on the VLC AP subchannel and use the VLC throughput lower bound formula to calculate the throughput between the user and the VLC AP subchannel. Calculate the user's received SINR on the RF AP subchannel and use Shannon's law to calculate the throughput between the user and the RF AP subchannel. In an indoor aggregated VLC-RF network, any user can access an RF AP. Users within the VLC AP coverage area can simultaneously access a VLC AP and an RF AP. Calculate the throughput achieved by each user accessing the indoor aggregated VLC-RF network, the total throughput of the indoor aggregated VLC-RF network, the transmit power allocated to the user by the indoor aggregated VLC-RF network, and the total transmit power consumed by the indoor aggregated VLC-RF network.

[0015] The SINR calculation formula between user k and subchannel n of VLC AP v is:

[0016]

[0017] In the above formula, is the transmit power allocated by VLC AP v to user k on subchannel n; R PD is the responsivity of the photodetector; v′ and k′ are other VLC APs and other users multiplexing the same subchannel n; is the transmit power allocated to user k′ by VLC APv′ when multiplexing the same subchannel n; N represents the interference channel gain generated by VLC APv′ to user k when multiplexing the same sub-channel n; VLC is the power spectral density of additive white Gaussian noise in the VLC channel; B VLC is the subchannel bandwidth of VLC AP v;

[0018] The closed-form formula for the lower bound of the throughput provided by VLC AP v to user k on subchannel n is:

[0019]

[0020] The SINR calculation formula between user k and RF AP subchannel m is:

[0021]

[0022] In the above formula, is the transmit power allocated by RF AP to user k on subchannel m, N RF is the power spectral density of the additive white Gaussian noise in the RF channel, B RF is the subchannel bandwidth of the RF AP;

[0023] According to Shannon's law, the throughput provided by the RF AP to user k on subchannel m is calculated as follows:

[0024]

[0025] The calculation formula for the throughput achieved by user k accessing the indoor aggregated VLC-RF network is:

[0026]

[0027] The total throughput of the indoor aggregated VLC-RF network is calculated as follows:

[0028]

[0029] The calculation formula for the transmit power allocated to user k in the indoor aggregated VLC-RF network is:

[0030]

[0031] The calculation formula for the total transmit power consumed by the indoor aggregated VLC-RF network is:

[0032]

[0033] In the above formula, P rf and P vlc Represents the basic power consumption of the circuits inside the RF AP and VLC AP respectively; |V| is the total number of VLC APs;

[0034] S3: Establish an energy efficiency optimization model for joint access point selection and resource allocation in indoor aggregated VLC-RF networks, which is expressed as follows:

[0035]

[0036] In the above formula, η EE is the energy efficiency of indoor aggregated VLC-RF network; x = {x RF,k ,x v,k}, represents the access point selection vector, whose element x RF,k =1 and x v,k =1 indicates that user k accesses RFAP and user k accesses VLC AP v respectively; Represents the subchannel allocation vector, whose elements and They represent that RF AP allocates subchannel m to user k and VLC AP v allocates subchannel n to user k; Represents the power allocation vector, whose elements and denotes the transmit power allocated by RF AP to user k on subchannel m and the transmit power allocated by VLC AP v to user k on subchannel n; a={a k}, represents the communication interruption vector. If the user is in the communication interruption state, then a k =0, otherwise, a k =1; Constraint C1 ensures that the AP can allocate a subchannel to the user only when the user accesses the AP; Constraint C2 ensures that the transmit power allocated by the RF AP and each VLC AP to any user on any subchannel should not exceed the maximum transmit power of the AP, and transmit power can only be allocated when the AP allocates a subchannel to the user, P RF and P v denote the maximum transmit power of RF AP and VLC AP v respectively; constraint C3 ensures that the power consumption of each AP does not exceed its maximum transmit power; constraint C4 ensures that any subchannel of each AP is allocated to at most one user; constraint C5 ensures that each user can access an RF AP but at most one VLC AP; constraint C6 requires that the throughput of any user when communication is not interrupted is greater than or equal to the minimum data rate requirement R min To ensure the non-negativity of each element in the power allocation vector p, the duality of each element in the subchannel allocation vector s, the duality of each element in the access point selection vector x, and the duality of each element in the outage vector a, constraints C7, C8, C9, and C10 are imposed, respectively. The energy efficiency optimization problem of joint access point selection and resource allocation is decoupled into three sub-problems: access point selection, subchannel allocation, and power allocation. Solutions are designed in sequence to optimize network energy efficiency.

[0037] S4: Calculate the baseline energy efficiency between VLC APs and users. Each VLC AP arranges users in descending order of baseline energy efficiency to construct a preference list for each user. Each user arranges VLC APs in descending order of baseline energy efficiency to construct a preference list for each VLC AP. Execute a high-efficiency access point selection algorithm based on bilateral matching theory. The baseline energy efficiency between user k and VLC AP v is calculated as follows:

[0038]

[0039] In the above formula, represents the average unblocked probability of the line-of-sight link between user k and VLC APv, |N| is the number of subchannels of the VLC AP; Indicates that VLC APv ​​uses the equal power allocation method to allocate the transmission power P v Allocate to each sub-channel; represents the average channel gain between user k and VLC AP v; Indicates that VLCAPv′ that multiplexes the same subchannel with VLC AP v adopts the equal power allocation method to allocate the transmission power P v′ Assigned to each sub-channel; represents the average interference channel gain generated by VLC AP v′ to user k. The numerator of the above benchmark energy efficiency represents the throughput achieved by users accessing the VLC AP, and the denominator represents the power consumed by the VLC AP, which is the sum of the maximum transmit power of the VLC AP and the power consumed by its internal circuits.

[0040] The specific process of the high energy-efficient access point selection algorithm based on the bilateral matching theory in S4 is as follows:

[0041] S401: Input Represents a set of VLC AP and user preference lists, represents the baseline energy efficiency value of VLC AP v and user U, and represents the preference list of user U; represents the baseline energy efficiency when user k accesses a VLC AP, represents the preference list of the VLC AP, Set the matching iteration count of each VLC AP to 1 and the waiting list of each user to an empty set.

[0042] S402: During each bilateral matching process, each VLC AP sends a matching request to the user with the highest ranking in its preference list and deletes the user from its preference list. At the end of each matching iteration, the number of users in each VLC AP's preference list is reduced by one.

[0043] S403: Each user only accepts the matching request from the VLC AP with the highest ranking in its preference list. After receiving the request, the user places the VLC AP in its waiting list and rejects the matching requests from other VLC APs.

[0044] S404: Judgment or If neither is true, set the matching iteration count of each VLC AP plus 1, and go to S402; otherwise, output the optimal matching relationship between the VLC AP and the user;

[0045] S5: Calculate the throughput between access users and subchannels of each AP, sort access users on each subchannel in descending order of throughput, construct a preference list for each subchannel with respect to access users, sort access users on each subchannel in descending order of throughput, construct a preference list for each subchannel with respect to access users; and execute a subchannel allocation scheme based on the Gale-Shapley algorithm.

[0046] The specific process of the subchannel allocation scheme based on the Gale-Shapley algorithm in S5 is as follows:

[0047] S501: Input the preference list set between the access users and sub-channels of each AP, set the access users and sub-channels of each AP to be in an unmatched state, and set the matching iteration number of each access user to 1;

[0048] S502: In each iteration, each access user of an unmatched sub-channel sends a matching request to the sub-channel with the highest ranking in its preference list and for which no matching request has been sent;

[0049] S503: Determine whether the sub-channel receives a matching application for the first time. If so, establish a matching relationship with the current applicant. Otherwise, the sub-channel compares the rankings of the current applicant and the matched users in its preference list.

[0050] S504: If the ranking of the current applicant is higher than that of the matched user, the sub-channel cancels the matching relationship with the matched user and establishes a new matching relationship with the current applicant; otherwise, the sub-channel rejects the applicant;

[0051] S505: Determine whether there is an access user rejected by the sub-channel or whose matching relationship has been terminated by the sub-channel. If so, set the matching iteration count to be 1, and go to S502; otherwise, output the one-to-one stable matching relationship between the access user and the sub-channel of each AP;

[0052] S6: After completing access point selection and subchannel allocation, the energy efficiency of the indoor aggregated VLC-RF network is optimized through power allocation. The optimization problem is expressed as Energy efficiency optimization is a multi-objective optimization problem that needs to maximize the total network throughput and minimize the total network transmission power. Therefore, there is no single global optimal solution, and a set of trade-off optimal solutions needs to be sought. EE is expressed as a fraction and R total The SINR term in R is non-convex, and the optimization problem is a nonlinear programming problem; totalIt is a function of the power distribution vector p, which is expressed by the formula The maximum throughput R of the indoor aggregated VLC-RF network can be obtained max ;

[0053] The maximum throughput R of the indoor aggregated VLC-RF network in S6 max The specific solution process is:

[0054] S601: Introduce the auxiliary vector y and use the quadratic transformation method to perform a quadratic transformation on each SINR item in the RF network and the VLC network, as shown below:

[0055]

[0056] In the above formula, and Denote the secondary transformation of the SINR term between the subchannel m of the RF AP and the user k and the secondary transformation of the SINR term between the subchannel n of the VLC AP v and the user k; the auxiliary vector Its elements and denote the auxiliary variables introduced between the subchannel m of the RF AP and the user k, and the auxiliary variables introduced between the subchannel n of the VLC AP v and the user k, respectively; It can be restated as

[0057] S602: In the RF network and the VLC network, when and To determine the value, solve and Can be calculated and The optimal solution is expressed as follows:

[0058]

[0059] In the above formula, and They represent the optimal solutions of the auxiliary variables introduced between the RF AP's subchannel m and user k, and the optimal solutions of the auxiliary variables introduced between the VLC AP's subchannel n and user k. When the auxiliary vector y is a fixed value, the CVX toolbox in MATLAB can be used to solve the maximum network throughput R. max ;

[0060] S603: Set the number of iterations d = 1, the maximum tolerance error ω = 0.1, The initial power allocation results p in the RF network and VLC network are calculated using the equal power allocation method. (0) ,Right now as well as

[0061]

[0062] S604: According to p (d-1) Find y (d) , use MATLAB language in the CVX toolbox to describe the network maximum throughput problem, so as to obtain the network maximum throughput after the dth iteration and power allocation vector p (d) ;

[0063] S605: Judgment Is it true? If so, set the number of iterations d = d + 1 and go to S604 until the convergence condition is met. Otherwise, let Get the maximum throughput R of the indoor aggregated VLC-RF network max ;

[0064] S7: After obtaining the maximum network throughput R max After that, each SINR item in the RF network and the VLC network is converted into a secondary transformed SINR item. At this time, the optimization problem is expressed as:

[0065]

[0066] In the above formula, σ=β×R max And β∈(0,1]; if β=0, then σ=0, the optimization goal becomes to minimize the total network transmission power, and there is no requirement for the total network throughput; if β>1, then σ>R max , exceeds the maximum throughput of the indoor aggregated VLC-RF network and does not meet the constraint requirements; only when β∈(0,1], the energy efficiency optimization problem belongs to a multi-objective optimization problem; Constraint C1 ensures that the transmit power allocated by the RF AP and each VLC AP to any user on any subchannel should not exceed the maximum transmit power of the AP, and transmit power can only be allocated when the AP allocates a subchannel to the user; Constraint C2 ensures that the power consumption of each AP does not exceed its maximum transmit power; Constraint C3 requires that the throughput of each user when communication is not interrupted is greater than or equal to the minimum data rate requirement R min ; Constraint C4 ensures the non-negativity of each variable in the power allocation vector p; Constraint C5 can obtain the total network throughput R by taking different values ​​of β total different constraints; implement power allocation strategy based on multi-objective energy efficiency optimization;

[0067] The specific process of the power allocation strategy based on multi-objective energy efficiency optimization in S7 is as follows:

[0068] S701: Input the maximum network throughput R max , the maximum transmit power P of the RF AP RF , the maximum transmit power P of each VLC AP v , Set β = 0, step size μ = 0.2, number of outer loop iterations Γ = 1, maximum tolerance error ω = 0.1, Create an empty Pareto optimal set Used to store the optimal power allocation results; create an empty Pareto optimal frontier set Used to store energy efficiency optimization results;

[0069] S702: Set the number of inner loop iterations i=1, and use the equal power allocation method to calculate the initial power allocation vector p in the RF network and the VLC network. (0) ,Right now as well as Set β = β + μ and calculate the total network throughput R total The constraint condition σ=β×R max ;

[0070] S703: According to p (i-1) Find y (i) , in a specific R total Next, we use the MATLAB language in the CVX toolbox to describe the problem of minimizing the total network transmission power, so as to obtain the minimum total network transmission power after the i-th inner loop iteration. and power allocation vector p (i) ;

[0071] S704: Judgment Is it true? If so, set the number of inner loop iterations i=i+1 and go to S703 until the convergence condition is met. Otherwise, get the value in the specific R total The optimal power allocation result p under (i) and the minimum total network transmit power The inner loop iteration ends;

[0072] S705: Calculate the energy efficiency optimization result under the Γth outer loop iteration Therefore, the Pareto optimal solution and the Pareto optimal frontier solution under the Γth outer loop iteration are and

[0073] S706: Determine whether β≤1 holds. If so, set the number of outer loop iterations Γ=Γ+1 and go to S702; otherwise, output the Pareto optimal set. That is, at each specific R totalThe optimal power allocation result that minimizes the total transmission power of the network is output, and the Pareto optimal frontier set is output. That is, the energy efficiency optimization result calculated by the total network throughput and total network transmission power under each optimal power allocation result.

[0074] The beneficial effects of the present invention are as follows: the present invention provides an energy efficiency optimization method for indoor aggregated VLC-RF access point selection and resource allocation. First, a high-efficiency access point selection algorithm based on bilateral matching theory is adopted to ensure that each user accesses the VLC AP that contributes most to network energy efficiency. Second, in order to more fairly and effectively utilize channel resources, a sub-channel allocation scheme based on the Gale-Shapley algorithm is adopted to ensure a stable matching relationship between the access users and sub-channels of each AP and improve user communication satisfaction. Finally, a power allocation strategy based on multi-objective energy efficiency optimization is adopted, treating the energy efficiency optimization problem as a multi-objective optimization problem, obtaining a set of weighed optimal power allocation results, and obtaining a corresponding set of energy efficiency optimization results, which are respectively stored in a Pareto optimal set and a Pareto optimal frontier set.

[0075] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the drawings, in which:

[0077] Figure 1 Indoor aggregated VLC-RF network model;

[0078] Figure 2 Flowchart of the energy efficiency optimization method for joint access point selection, subchannel allocation and power allocation;

[0079] Figure 3 Flowchart of energy-efficient access point selection algorithm based on bilateral matching theory;

[0080] Figure 4 Flowchart of the subchannel allocation scheme based on the Gale-Shapley algorithm;

[0081] Figure 5 Flowchart of power allocation strategy based on multi-objective energy efficiency optimization; DETAILED DESCRIPTION

[0082] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0083] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts in the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0084] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0085] Attachment Figure 1 It is an indoor aggregated VLC-RF network model. The indoor aggregated VLC-RF network consists of a central controller, an RF AP, multiple VLC APs and multiple users. All APs are connected to the central controller. The downlink of the VLC AP is used for data transmission. All indoor users can access the RF AP. Users in the VLC AP coverage area can access a VLC AP and RF AP at the same time to obtain a higher data transmission rate. Users in the overlapping area of ​​VLC AP coverage will be affected by inter-cell interference. VLC AP aggregation is used To express, |·| represents the cardinality of the set, that is, the number of elements in the set; RFAP and all VLC APs use orthogonal frequency division multiple access technology, and the sub-channel set of RF AP is expressed as To represent, the sub-channel set of each VLC AP is represented by To represent; user collection is represented by To represent; a random path point movement model is used to simulate the user's indoor movement behavior; the receiving device of any user includes a photodetector and an RF antenna, which are used to receive VLC signals and RF signals respectively, and the photodetector keeps the vertical upward direction.

[0086] Attachment Figure 2 This is a flow chart of the energy efficiency optimization method for joint access point selection, subchannel allocation, and power allocation. The specific steps are as follows:

[0087] Step 1: Enter the user collection VLC AP Collection RF AP subchannel set Subchannel set of each VLC AP Maximum transmit power of the RF AP and each VLC AP;

[0088] Step 2: Set the initial number of iterations l = 1, the maximum tolerance error ω = 0.1,

[0089] Step 3: Calculate the baseline energy efficiency between the user and the VLC AP, and construct a preference list set between the user and the VLC AP;

[0090] Step 4: Execute the energy-efficient access point selection algorithm based on bilateral matching theory and output the optimal matching relationship between the VLC AP and the user;

[0091] Step 5: Calculate the throughput between each AP's access users and sub-channels, and construct a preference list set between each AP's access users and sub-channels;

[0092] Step 6: Execute the subchannel allocation scheme based on the Gale-Shapley algorithm and output a one-to-one stable matching relationship between access users and subchannels for each AP;

[0093] Step 7: Calculate the maximum network throughput, implement a power allocation strategy based on multi-objective energy efficiency optimization, and output the Pareto optimal set and the Pareto optimal frontier set.

[0094] Step 8: Calculate the average network energy efficiency after the lth iteration based on the energy efficiency optimization results in the Pareto optimal frontier set

[0095] Step 9: Judgement Is it true? If so, set the number of iterations to l=l+1 and go to step 3; otherwise, output the average network energy efficiency after convergence.

[0096] Attachment Figure 3 The flowchart of the high-efficiency access point selection algorithm based on bilateral matching theory is as follows:

[0097] Step 1: Enter the user collection VLC AP Collection Determine the preference list set between each user and VLC AP based on the baseline energy efficiency value between each user and each VLC AP

[0098] Step 2: Set the initial matching iteration number of each VLC AP v to i v =1, Set the initial waiting list of each user k to be

[0099] Step 3: In the i-th bilateral matching v In the first iteration, each VLC AP sends a matching request to the user with the highest ranking in its preference list and deletes the user from its preference list;

[0100] Step 4: Any user k only accepts the matching request from the VLC AP with the highest ranking in its preference list. After receiving the request, the VLC AP is placed in its waiting list W. k Meanwhile, the matching application of other VLC APs is rejected;

[0101] Step 5: At the end of each iteration, the number of users in each VLC AP preference list is reduced by 1;

[0102] Step 6: Judgement or Is it true? If not, set the matching iteration number of each VLC AP to i v =i v +1, Go to step 3; otherwise, output the optimal matching relationship between the VLC AP and the user.

[0103] Attachment Figure 4 This is a flow chart of the subchannel allocation scheme based on the Gale-Shapley algorithm, which is described in detail below:

[0104] Step 1: Enter the user collection RF AP subchannel set Subchannel set of each VLC AP The throughput between each AP's access users and sub-channels, and the preference list set between each AP's access users and sub-channels;

[0105] Step 2: Set the access users and sub-channels of each AP to be in unmatched state, and set the initial matching iteration number of each access user k to i k =1,

[0106] Step 3: In the i k In the first iteration, each access user of an unmatched sub-channel sends a matching request to the sub-channel with the highest ranking in its preference list and which has not yet sent a matching request;

[0107] Step 4: Determine whether the sub-channel receives a matching application for the first time. If so, establish a matching relationship with the applicant user. Otherwise, the sub-channel compares the rankings of the current applicant user and the matched users in its preference list.

[0108] Step 5: Determine whether the current applicant's ranking in the sub-channel preference list is higher than that of the matched user. If so, the sub-channel terminates the matching relationship with the matched user and establishes a new matching relationship with the current applicant. Otherwise, the sub-channel rejects the applicant.

[0109] Step 6: Determine whether there is an access user that is rejected by the sub-channel or whose matching relationship is terminated by the sub-channel. If so, set the matching iteration number to i. k =i k +1, Go to step 3; otherwise, output the stable matching relationship between the access users and sub-channels of each AP.

[0110] Attachment Figure 5 This is a flow chart of the power allocation strategy based on multi-objective energy efficiency optimization, which is described in detail below:

[0111] Step 1: Enter the VLC AP set User Collection RF AP subchannel set VLC AP sub-channel combination Maximum throughput R of indoor aggregated VLC-RF network max , the maximum transmit power P of the RF AP RF , the maximum transmit power P of each VLC AP v ,

[0112] Step 2: Set β = 0, step size μ = 0.2, number of outer loop iterations Γ = 1, and maximum tolerance error ω = 0.1.

[0113] Step 3: Create an empty Pareto optimal set Used to store the optimal power allocation results; create an empty Pareto optimal frontier set Used to store energy efficiency optimization results;

[0114] Step 4: Set the number of inner loop iterations i = 1 and use the equal power allocation method to calculate the initial power allocation vector p in the RF network and VLC network (0) ,Right now as well as Set β = β + μ and calculate the total network throughput R total The constraint condition σ=β×R max ;

[0115] Step 5: According to p (i-1) Find y (i) , in a specific R totalNext, we use the MATLAB language in the CVX toolbox to describe the problem of minimizing the total network transmission power, so as to obtain the minimum total network transmission power after the i-th inner loop iteration. and power allocation vector p (i) ;

[0116] Step 6: Judgement Is it true? If so, set the number of inner loop iterations to i=i+1 and go to step 5 until the convergence condition is met. Otherwise, get the value in the specific R total The optimal power allocation result p under (i) and the minimum total transmit power The inner loop iteration ends;

[0117] Step 7: Calculate the energy efficiency optimization result under the Γth outer loop iteration Then the Pareto optimal solution and Pareto optimal frontier solution under the Γth outer loop iteration are and

[0118] Step 8: Determine whether β≤1 holds. If so, set the number of outer loop iterations to Γ=Γ+1 and go to step 4; otherwise, output the Pareto optimal set. That is, at each specific R total The optimal power allocation result that minimizes the total transmission power is output, and the Pareto optimal frontier set is obtained. That is, the optimal energy efficiency is calculated by the total network throughput and total transmission power under each optimal power allocation result.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. An energy efficiency optimization method for indoor aggregated VLC-RF access point selection and resource allocation, characterized by: The method comprises the following steps: S1: Input user set in indoor aggregated VLC-RF network VLC Access Point (AP) Collection 1 RF AP, sub-channel set of each VLC AP and the sub-channel set of the RF AP Each VLC AP reuses the same set of subchannels. The channel gain between the user and the VLC AP subchannel is calculated based on the Lambertian radiation model. The channel gain between the user and the RF AP subchannel is calculated based on the Rayleigh fading model. S2: Calculate the user's received signal-to-interference plus noise ratio (SINR) on the VLC AP subchannel and use the VLC throughput lower bound formula to calculate the throughput between the user and the VLC AP subchannel. Calculate the user's received SINR on the RF AP subchannel and use Shannon's law to calculate the throughput between the user and the RF AP subchannel. In an indoor aggregated VLC-RF network, any user can access an RF AP. Users in the VLC AP coverage area can access a VLC AP and an RF AP simultaneously. Calculate the throughput R that each user can achieve by accessing the indoor aggregated VLC-RF network. k , Calculate the total throughput R of the indoor aggregated VLC-RF network total , the transmission power allocated to users by indoor aggregated VLC-RF network The total transmit power consumed by the indoor aggregated VLC-RF network P total ; S3: Establish an energy efficiency optimization model for joint access point selection and resource allocation in indoor aggregated VLC-RF networks, which can be expressed as: Among them, η EE Energy efficiency of indoor aggregated VLC-RF networks; Represents the access point selection vector, whose element x RF,k =1 and x v,k =1 indicates that user k accesses RF AP and user k accesses VLC AP v respectively; Represents the subchannel allocation vector, whose elements and They respectively indicate that RF AP allocates subchannel m to user k and VLCAP v allocates subchannel n to user k; Represents the power allocation vector, whose elements and They represent the transmit power allocated by RF AP to user k on subchannel m and the transmit power allocated by VLCAP v to user k on subchannel n respectively; Represents the communication interruption vector. If the user is in the communication interruption state, then a k =0, otherwise, a k =1; decouple the energy efficiency optimization problem model of joint access point selection and resource allocation into three sub-problems: access point selection described in step S4, sub-channel allocation described in step S5, and power allocation described in steps S6 and S7, and design solutions in order to optimize network energy efficiency; S4: Calculate the baseline energy efficiency between each VLC AP and each user. The baseline energy efficiency is defined as the ratio of the throughput obtained by the user accessing the VLC AP to the power consumed by the VLC AP. Each VLC AP arranges the users in descending order of the baseline energy efficiency to construct a user preference list. Each user arranges the VLC APs in descending order of the baseline energy efficiency to construct a user preference list. Execute a high-energy-efficiency access point selection algorithm based on the bilateral matching theory. The specific process of the high energy-efficient access point selection algorithm based on the bilateral matching theory in S4 is as follows: S401: Determine a preference list set of VLC APs and users based on a baseline energy efficiency between the user and the VLC AP, set the matching iteration count for each VLC AP to 1, and set the waiting list for each user to an empty set; S402: During each bilateral matching process, each VLC AP sends a matching request to the user with the highest ranking in its preference list and deletes the user from its preference list. At the end of each matching iteration, the number of users in each VLC AP's preference list is reduced by one. S403: Each user only accepts the matching request from the VLC AP with the highest ranking in its preference list. After receiving the request, the user places the VLC AP in its waiting list and rejects the matching requests from other VLC APs. S404: If the preference list of each VLC AP is not empty or the waiting list of the user is empty, set the matching iteration count of each VLC AP to be increased by 1, and go to S402; otherwise, output the optimal matching relationship between the VLC AP and the user; S5: Calculate the throughput between access users and subchannels of each VLC AP and RF AP, sort the access users on each subchannel in descending order of throughput, construct a preference list for each subchannel with respect to the access users, sort the subchannels on each subchannel with descending order of throughput, construct a preference list for each access user with respect to the subchannel; and execute a subchannel allocation scheme based on the Gale-Shapley algorithm. The specific process of the subchannel allocation scheme based on the Gale-Shapley algorithm in S5 is as follows: S501: Input the preference list set between the access users and sub-channels of each AP, set the access users and sub-channels of each AP to be in an unmatched state, and set the matching iteration number of each access user to 1; S502: In each iteration, each access user of an unmatched sub-channel sends a matching request to the sub-channel with the highest ranking in its preference list and for which no matching request has been sent; S503: Determine whether the sub-channel receives a matching application for the first time. If so, establish a matching relationship with the current applicant. Otherwise, the sub-channel compares the rankings of the current applicant and the matched users in its preference list. S504: If the ranking of the current applicant is higher than that of the matched user, the sub-channel cancels the matching relationship with the matched user and establishes a new matching relationship with the current applicant; otherwise, the sub-channel rejects the applicant; S505: Determine whether there is an access user rejected by the sub-channel or whose matching relationship has been terminated by the sub-channel. If so, set the matching iteration count to be 1, and go to S502; otherwise, output the one-to-one stable matching relationship between the access user and the sub-channel of each AP; S6: After completing access point selection and subchannel allocation, the energy efficiency of the indoor aggregated VLC-RF network is optimized through power allocation. The optimization problem is expressed as The energy efficiency optimization is a multi-objective optimization problem that needs to maximize the total network throughput and minimize the total network transmission power. Therefore, there is no single global optimal solution, and a set of trade-off optimal solutions needs to be sought. EE is expressed as a fraction and R total The SINR term in R is non-convex, and the optimization problem is a nonlinear programming problem; total It is a function of the power distribution vector p, which is expressed by the formula The maximum throughput R of the indoor aggregated VLC-RF network can be obtained max ; The maximum throughput R of the indoor aggregated VLC-RF network in S6 is max The specific solution process is: S601: Introducing auxiliary vectors Its elements and Represent the auxiliary variables introduced in the RF network and the VLC network respectively; the quadratic transformation method is used to perform a quadratic transformation on each SINR item in the RF network and the VLC network, and denote the second transformation of the SINR term between the subchannel m of the RF AP and the user k, and the second transformation of the SINR term between the subchannel n of the VLC AP v and the user k, respectively; It can be restated as S602: In the RF network and the VLC network, when the elements in the power allocation vector p are fixed values, by solving Can be calculated and The optimal solution of , thus using the CVX toolbox in MATLAB to solve the network maximum throughput R max ; S603: Set the iteration counter d=1, the maximum tolerance error ω=0.1, The initial power allocation results p in the RF network and VLC network are calculated using the equal power allocation method. (0) ,Right now as well as |M| is a set The number of elements in the set |N| Number of elements; P RF and P v denote the maximum transmit power of RF AP and VLC AP v, respectively; S604: According to p (d-1) Find y (d) , use MATLAB language in the CVX toolbox to describe the network maximum throughput problem, so as to obtain the network maximum throughput after the dth iteration and power allocation vector p (d) ; S605: Judgment Is it true? If so, set the number of iterations d = d + 1 and go to S604 until the convergence condition is met. Otherwise, let Get the maximum throughput R of the indoor aggregated VLC-RF network max ; S7: After obtaining the maximum network throughput R max Finally, each SINR item in the RF network and the VLC network is converted into a secondary transformed SINR item. The optimization problem is then expressed as: In the above formula, σ=β×R max And β∈(0,1]; if β=0, then σ=0, the optimization goal becomes to minimize the total network transmission power, and there is no requirement for the total network throughput; if β>1, then σ>R max , exceeds the maximum throughput of the indoor aggregated VLC-RF network and does not meet the constraint requirements; only when β∈(0,1], the energy efficiency optimization problem belongs to a multi-objective optimization problem; Constraint C1 ensures that the transmit power allocated by the RF AP and each VLC AP to any user on any subchannel should not exceed the maximum transmit power of the AP, and transmit power can only be allocated when the AP allocates a subchannel to the user; Constraint C2 ensures that the power consumption of each AP does not exceed its maximum transmit power; Constraint C3 requires that the throughput of each user when communication is not interrupted is greater than or equal to the minimum data rate requirement R min ; Constraint C4 ensures the non-negativity of each variable in the power allocation vector p; Constraint C5 can obtain the total network throughput R by taking different values ​​of β total Different constraints of ; among them, Implement power allocation strategies based on multi-objective energy efficiency optimization; The specific process of the power allocation strategy based on multi-objective energy efficiency optimization in S7 is as follows: S701: Input the maximum network throughput R max , the maximum transmit power P of the RF AP RF , the maximum transmit power of each VLC AP Set β = 0, step size μ = 0.2, number of outer loop iterations Γ = 1, maximum tolerance error ω = 0.1, Create an empty Pareto optimal set Used to store the optimal power allocation results; create an empty Pareto optimal frontier set Used to store energy efficiency optimization results; S702: Set the number of inner loop iterations i=1, and use the equal power allocation method to calculate the initial power allocation vector p in the RF network and the VLC network. (0) ,Right now as well as Set β = β + μ and calculate the total network throughput R total The constraint condition σ=β×R max ; S703: According to p (i-1) Find y (i) , in a specific R total Next, we use the MATLAB language in the CVX toolbox to describe the problem of minimizing the total network transmission power, so as to obtain the minimum total network transmission power after the i-th inner loop iteration. and power allocation vector p (i) ; S704: Judgment Is it true? If so, set the number of inner loop iterations i=i+1 and go to S703 until the convergence condition is met. Otherwise, get the value in the specific R total The optimal power allocation result p under (i) and the minimum total network transmit power The inner loop iteration ends; S705: Calculate the energy efficiency optimization result under the Γth outer loop iteration Therefore, the Pareto optimal solution and the Pareto optimal frontier solution under the Γth outer loop iteration are and S706: Determine whether β≤1 holds. If so, set the number of outer loop iterations Γ=Γ+1 and go to S702; otherwise, output the Pareto optimal set. That is, at each specific R total The optimal power allocation result that minimizes the total transmission power of the network is output, and the Pareto optimal frontier set is output. That is, the energy efficiency optimization result calculated by the total network throughput and total network transmission power under each optimal power allocation result.

Images