Cooperative transmission-based user access and power allocation in indoor multi-color VLC-NOMA networks

Abstract

The invention relates to user access and power distribution based on cooperative transmission in an indoor multi-color VLC-NOMA network, and belongs to the technical field of optical communication. According to the method provided by the invention, the maximum network sum rate is realized and the user fairness is improved by optimizing user access and power distribution. In the user access stage, a user access algorithm based on an improved matching game is adopted, and the cooperation and access relation between users and APs in the indoor multi-color VLC-NOMA network is determined; in the power distribution stage, a power distribution algorithm based on improved raccoon optimization is adopted, and a power distribution factor matrix of each NOMA user group is updated through hunting, escape and population reconstruction methods so as to optimize the transmitting power of the AP. According to the method provided by the invention, the problems of inter-cell interference, load imbalance among APs and low communication quality of edge users caused by dense deployment of APs and multi-user access in the indoor multi-color VLC-NOMA network can be improved, and the network speed and the user fairness are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communications and relates to user access and power allocation based on collaborative transmission in an indoor multi-color VLC-NOMA network. Background Art

[0002] In recent years, various communication devices have emerged. Traditional radio frequency (RF) communication technology faces spectrum shortage. Visible light communication (VLC) has become a suitable candidate for RF technology due to its advantages such as large bandwidth and no need for authentication. In addition, multi-color VLC networks use multi-color light emitting diodes (LEDs) with higher response speeds, which can improve network capacity. Non-orthogonal multiple access (NOMA) technology is often combined with VLC networks because of its advantages in high spectrum utilization and support for a large number of users.

[0003] In an indoor multi-color VLC-NOMA network containing multiple VLC access points (APs) and multiple users, the choice of user access to VLC APs affects network performance. The traditional user access algorithm based on channel gain has no quantity limit, which will lead to unbalanced load among VLC APs, which is reflected in the fact that some VLC APs are overloaded while other VLC APs are too lightly loaded or even idle. In order to improve spectrum utilization, different VLC APs use the same spectrum resources, which will lead to serious inter-cell interference. The communication quality of cell edge users in the NOMA user group is low, resulting in low user fairness. In order to mitigate the impact of inter-cell interference and improve user fairness, cooperative NOMA technology is introduced into multi-color VLC networks. Strong users collect energy using the DC component of transmitted information and use it to forward the information of weak users. Therefore, weak users with low communication quality can be served by VLC APs and strong users together, improving the data rate of weak users, thereby improving network and rate and user fairness. When there are multiple VLC APs in the network, it is necessary to design a user access algorithm that considers interference management and load balancing between APs. In summary, it is of great significance to study the user access and power allocation problems based on cooperative transmission in indoor multi-color VLC-NOMA networks to maximize the network rate and user fairness. Summary of the invention

[0004] In view of this, the object of the present invention is to provide user access and power allocation based on collaborative transmission in indoor multi-color VLC-NOMA networks, so as to improve user fairness while improving network and rate.

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

[0006] The user access and power allocation based on cooperative transmission in indoor multi-color VLC-NOMA networks includes the following steps:

[0007] 1. User access and power allocation based on cooperative transmission in indoor multi-color VLC-NOMA networks, characterized in that the method comprises the following steps:

[0008] S1: Input user set N = {1,2,…,N}, N users are randomly distributed in the room, set user equipment height from the ground h, VLC (Visible Light Communication) AP (Access Point) set L = {1,2,…,L}, VLC AP is denoted by AP in the following description; NOMA (Non-Orthogonal Multiple Access) user group set K = {1,2,…,K}, K is also a multi-color subcarrier set; VLC AP multi-color subcarrier total bandwidth B, set user request rate has 6 candidate levels, denoted as δ n ∈{20Mbps,30Mbps,40Mbps,50Mbps,60Mbps,70Mbps}, the six candidate levels of the user's minimum required rate are The power spectral density of VLC noise is 1×10 -21 , the VLC AP transmission power is 0.2W, the total RF transmission bandwidth is 20MHz, and the RF noise power spectrum density is 174dBm / Hz; the ratio of the AP's R / G / B / Y (Red / Green / Blue / Yellow) transmission power is 0.239:0.291:0.405:0.065; represents the kth NOMA user group of AP l; Represents the nth user of the kth NOMA user group of AP l; According to the Lambertian radiation model of VLC, the channel gain from AP to the user is calculated, and the SIC (Serial Interference Cancellation) decoding order factor of each user in the multi-cell NOMA network is determined. According to the decoding order factor value, the users in the NOMA group are arranged in ascending order, and the received signal level value of each user in the NOMA group is calculated;

[0009] Among them, AP l to NOMA user group Channel gain for user n The calculation formula is:

[0010]

[0011] In the above formula, A PD Represents the receiving area of ​​the receiver; m is the Lambertian radiation coefficient, m = -1 / log(cosφ 1 / 2 ), φ 1 / 2 is the half-power angle of the AP's LED (Light Emitting Diode), φ is the emission angle of the LED; d l,n is the distance between AP1 and user n; ψ n is the incident angle to the receiver; ψ c is the field of view of the receiver; the optical filter gain and concentrator gain of the receiver are T(ψ n ) and g(ψ n ), and g(ψ n ) = f 2 / sin 2 (ψ c ), f is the constant reflection coefficient of the wall;

[0012] Among them, the calculation formula of the SIC decoding order factor of each user in the NOMA group is:

[0013]

[0014] In the above formula, Assign APs to the NOMA user group bandwidth; For NOMA user groups The channel gain of user n; N0 is the noise power spectrum density; I n is the inter-cell interference suffered by user n, and its calculation formula is:

[0015]

[0016] In the above formula, is the transmit power allocated by AP to user r; γ = γ eo γ oe , γ oe is the light-to-electricity conversion efficiency at the LED emitter, γ eo is the electrical-optical conversion efficiency at the receiving end;

[0017] Among them, NOMA user group The received signal level value of user n from AP 1 can be expressed as:

[0018]

[0019] In the above formula, Indicates NOMA user group The power allocation factor that user n obtains from AP l is: represents the transmission power obtained by the k-th NOMA user group of AP l; is the DC part of the signal level received by user n, I b To ensure that the transmission signal is not a negative DC level value; Indicates NOMA user group The variable used to associate user n with API is defined as:

[0020]

[0021] S2: Calculate NOMA user groups The SINR (Signal to Interference plus Noise Ratio) of user n is used to calculate the achievable rate of strong and weak users in the NOMA group through the LED optical channel according to the Shannon formula; the decoded information of the strong user is forwarded to the weak user through the strong user device, and the achievable rate of the decoded forwarded information obtained by the weak user is calculated;

[0022] S3: Calculate NOMA user groups The energy collected by the strong user in the AP from the optical signal emitted by the AP Calculate the direct forwarding channel gain from strong users to weak users in the NOMA group and the achievable forwarding information rate, compare the achievable decoding forwarding information rate of the weak user and the achievable relay forwarding information rate, select the smaller value as the achievable information rate obtained by the weak user from the strong user, and calculate the total achievable rate obtained by the weak user in the NOMA group;

[0023] S4: executing the user access algorithm based on the improved matching game for each user in turn, obtaining the optimal AP-user association matrix, and accessing the user to the corresponding AP polychromatic subcarrier according to the AP-user association matrix;

[0024] S5: Execute the power allocation algorithm based on the improved raccoon optimization for the users in each NOMA user group associated with each AP in turn, obtain the optimal power allocation factor matrix of the users in each NOMA user group, calculate the achievable rate of each user according to the association matrix between AP and user and the power allocation factor matrix of the users in each NOMA user group, then add up the achievable rates obtained by each user to calculate the sum rate of the network;

[0025] The specific process and steps of S2 are as follows:

[0026] S201: Calculate NOMA user groups SINR value of user n;

[0027] Among them, SINR value Γ n The calculation formula is:

[0028]

[0029] In the above formula, and are the NOMA user group intra-interference and VLC AP inter-cell interference suffered by user n, and their calculation methods are:

[0030]

[0031] S202: Calculate the achievable rate of strong users and weak users in the NOMA group through the LED optical channel according to the Shannon formula

[0032] in, The calculation method is:

[0033]

[0034] S203: If the strong user in the NOMA group Decoded information is forwarded directly to weak users According to Shannon's formula, the achievable rate of decoding and forwarding information obtained by weak users is:

[0035]

[0036] The specific process and steps of S3 are as follows:

[0037] S301: Calculate NOMA user groups Strong user Energy harvested from the light signal emitted by the AP l

[0038] in, The calculation formula is:

[0039]

[0040] In the above formula, V t is the thermal voltage of the receiving device, w is the fill factor of the receiving device, and I0 is the dark saturation current of the receiving device;

[0041] S302: Calculate strong users in indoor environment With weak users The RF channel gain between

[0042] in, The calculation formula is:

[0043]

[0044] In the above formula, is the RF multipath propagation channel gain; L(d i,j )for and The path loss between i,j is the distance between user i and user j;

[0045] S303: Calculate the radio frequency power received by the weak user in the NOMA group from the strong user through the radio frequency channel

[0046] in, The calculation formula is:

[0047]

[0048] In the above formula, T1 is a strong user Battery charging time, T2 for strong users The time it takes to transmit data over the RF channel;

[0049] S304: Calculate strong users in the NOMA group The achievable rate value that can be provided to weak users through the relay radio link

[0050] in, The calculation formula is:

[0051]

[0052] In the above formula, N RF is the power spectrum density of the RF signal; B r,j For strong users The RF modulation bandwidth of the transmitted RF signal, and B r,j =B RF / N r , B RF is the total modulation bandwidth of the RF link, N r The number of weak users served by the RF relay link;

[0053] S305: Comparison of NOMA user groups Weak users within Obtain the achievable rate values ​​of the decoding forwarding information and the radio frequency relay forwarding information from the strong user, and select the smaller value as the achievable rate value of the forwarding information of the weak user;

[0054] Among them, weak users The forwarding information achievable rate value is:

[0055]

[0056] S306: Using the methods described in S2 and S305 in sequence, determine the achievable rate value of user n in all NOMA groups in the indoor multi-color VLC-NOMA network

[0057] Among them, NOMA user group The achievable rate of user n in for:

[0058]

[0059] The specific process and steps of S4 are as follows:

[0060] S401: Add all users in user set N to unmatched user set U un For any AP l, l∈L, let its unmatched multi-color subcarrier k, k∈K, according to the maximum direct light channel gain from user n to AP l's subcarrier k value, adopt the preferred criterion, determine the preferred user n of the unmatched subcarrier k of AP l, and obtain the initial matching set Λ;

[0061] Among them, the preferred principle is: according to is the selected user n for AP l that does not match subcarrier k, where (n,(l,k)) represents the matching relationship between user n and the multi-color subcarrier k of AP l, where the kth subcarrier is the kth NOMA group of AP l; U un is the set of unmatched users; S un,k represents a multi-color subcarrier set with a matching number of users less than 3; add (n, (l, k)) to the matching set Λ, and set the user association matrix element

[0062] S402: In the matching set Λ, calculate the preference relationship value of the matching (n, (l, k)) in Λ to other matching (n', (l', k')) not in Λ And saved in the preference relationship value matrix Θ;

[0063] Among them, the preference relationship value of matching (n, (l, k)) The calculation formula is:

[0064]

[0065] In the above formula, if Indicates that the match (n, (l, k)) is more likely to be updated to match (n1, (l1, k1)) than (n2, (l2, k2)), and updates The value of; for all users in set N, if the user belongs to set U un , execute step S403; otherwise, execute S405;

[0066] S403: After each multi-color subcarrier s that is not matched with an AP selects its preferred user and matches it, for each user set U that is not matched with an AP subcarrier un For the remaining user n to be matched, in order to reduce the interference to the existing matches, two matches (n'1, (l'1, k'1)) and (n'2, (l'2, k'2)) with larger preference relationship values ​​are selected from the preference matrix Θ as candidate matches for the user;

[0067] The selection criteria for candidate matching are:

[0068]

[0069] Among them, L un,s The channel gain of AP l on subcarrier k is greater than h (n,(l,k)) The AP set; is not on subcarrier k or the channel gain of AP l on subcarrier k is less than h (n,(l,k)) The AP set;

[0070] S404: Calculate the matching (n'1, (l'1, k'1)) and (n'2, (l'2, k'2)) as the matching of the unmatched user n, and the matching utility value D(Λ) generated by them for the system, select the matching with the largest matching utility value as the matching of the to-be-matched user n, and select the matching value with the largest matching utility value from the to-be-matched user set U un Remove user n from the set, add user n's matches to the matching set Λ, and update The value of

[0071] Among them, the calculation formula of the matching utility value D(Λ) is:

[0072]

[0073] S405: In order to balance the load between APs, if there are more than N v If a user selects AP l, then AP l selects the first N v The user with the highest total rate is taken as the associated matching user of AP 1, AP 1 is deleted from the set L, and the process goes to step S401; otherwise, the process goes to step S406;

[0074] S406: traverse all existing matches, use the exchange matching operation to try to adjust the matching association relationship, calculate the matching utility value, and determine whether the new match is an unstable match. If so, go to step S407; otherwise, go to step S408;

[0075] The method of the exchange matching operation is as follows: the user can access the subcarriers of other APs that meet the AP maximum user number and subcarrier maximum user number restrictions, or different subcarriers of the same AP; assuming that the matching strategy before the exchange is Λ, and the matching strategy after the exchange is Λ', if the matching utility value D(Λ)>D(Λ'), the matching is not exchanged and the matching strategy is kept as Λ; otherwise, the matching exchange is performed, the matching strategy is updated to Λ', and the matching strategy is updated. The value of

[0076] The definition of stable matching is: if user n prefers subcarrier k over any other matching subcarrier, and subcarrier k prefers user n over any other matching user, then user n and subcarrier k are called a matched blocking pair; if a match is not blocked by any user-subcarrier pair, then the match is stable; otherwise, this user-subcarrier pair is called an unstable match;

[0077] S407: For all unstable matches, the users in the match are exchanged to the multi-color subcarriers of other APs, and the matching utility values ​​before and after the exchange matching operation are calculated to determine whether D(Λ')>D(Λ) holds. If so, the match before the exchange is deleted from Λ, and the match after the exchange is added to the matching strategy to obtain a new matching set Λ', and the new matching set is updated. otherwise, the exchange matching operation is not performed;

[0078] S408: Obtaining the optimal AP, carrier and user association matrix

[0079] The specific process and steps of S5 are as follows:

[0080] S501: Initialization settings: S501: represents the power allocation factor vector of each user in the kth NOMA group of AP l, whose elements And NOMA user group The power factor value of each user should ensure the SIC decoding requirements, that is, meet Suppose there are T raccoons, each raccoon represents a power factor vector Then the power allocation factor matrix represented by T raccoons is expressed as set up t∈{1:T}; let iteration counter i=1, and the maximum number of iterations be I;

[0081] S502: Initialize the NOMA user group represented by all raccoons in the population under the condition that the SIC decoding requirements are met The power factor values ​​of each user are obtained to obtain the initialization matrix of the power factor values

[0082] The formula for initializing the power factor value is:

[0083]

[0084] Where r is an arbitrary real number in [0,1]. represents the NOMA user group represented by the t-th raccoon The power factor value of user n;

[0085] S503: Calculate the fitness function value f of each raccoon representative in the i-th iteration t i ;

[0086] Among them, the fitness function value f represented by the t-th raccoon in the i-th iteration is t i The calculation formula is:

[0087]

[0088] In the above formula, ω z represents the penalty factor, g z It can be expressed as:

[0089]

[0090] In the above formula, [x] - =min{0,x},

[0091] S504: Determine the optimal power factor vector α t* And the optimal fitness function value, where α t* is the optimal power factor vector in the i-th iteration Value, denoted as Let α best =α t* ,

[0092] S505: According to the raccoon hunting rules, half of the raccoons climb trees to hunt prey, and the other half wait on the ground for the prey to fall before hunting. If t = T, go to step S510. Otherwise, set t = t + 1. If Go to step S506; otherwise, go to step S508;

[0093] S506: Changing the power allocation factor matrix corresponding to the raccoon climbing a tree to hunt prey And calculate the fitness function value f of each raccoon after the power factor changes t i+1 ;

[0094] The formula for changing the power factor value of the raccoon in the tree is:

[0095]

[0096] In the above formula, r1 takes a random real value in (0,1);

[0097] S507: If the fitness function value increases, that is, f t i+1 >f t i , then update the power factor value and fitness function value f t i =f t i+1 , update α t ; Otherwise, keep the power factor and fitness function value unchanged; go to step S504;

[0098] S508: According to the raccoon hunting rules, the ground raccoon can move according to the current position to hunt prey, changing the power allocation factor matrix corresponding to the raccoon under the tree And calculate the fitness function value f after the power factor changes t i +1 ;

[0099] Among them, the power factor value change formula of the raccoon under the tree is:

[0100]

[0101] Among them, r2 takes a random real value in [-1,1];

[0102] S509: If the fitness function value increases, that is, f t i+1 >f t i , then update the power factor value and fitness function value f t i =f t i+1 , update α t ; Otherwise, keep the power factor and fitness function value unchanged; go to step S504;

[0103] S510: Output optimal power factor vector α best and f best .

[0104] The beneficial effects of the present invention are as follows: the present invention provides user access and power allocation based on cooperative transmission in an indoor multi-color VLC-NOMA network. For user access, a user access algorithm based on an improved matching game is proposed, which takes into account interference management and load balancing between VLC APs, performs two-way selection between VLC APs and users to obtain a stable match, and in addition, unstable matching performs exchange matching to obtain the optimal match to maximize the network and rate; for power allocation, a power allocation algorithm based on improved raccoon optimization is designed to maximize the network and rate, and multiple groups of power allocation factors are modeled as raccoon populations, raccoon hunting and escape processes are simulated, and population reconstruction is performed. The proposed method can obtain higher network and rate and user fairness.

[0105] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the drawings, wherein:

[0107] Figure 1 Stereo model of an indoor multi-color VLC-NOMA network based on cooperative transmission;

[0108] Figure 2 Planar model diagram of indoor multi-color VLC-NOMA network based on cooperative transmission;

[0109] Figure 3 Flowchart of user access algorithm based on improved matching game;

[0110] Figure 4 Flowchart of the algorithm for optimizing the power allocation factor of NOMA group users based on the improved raccoon; DETAILED DESCRIPTION

[0111] The following describes the embodiments of the present invention by 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 only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0112] Among them, the figures are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the figures may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures in the figures and their descriptions may be omitted.

[0113] The present invention realizes the selection of user access and power allocation according to the goal of maximizing the network and rate. The DC part τ received by the strong user in the NOMA user group can be separated by a capacitor and guided to the energy collection circuit, while the DC part τ of the weak user can be removed by a capacitor. The strong user detects the information of the weak user and forwards it to the weak user, while the weak user regards the signal of the strong user as interference and decodes its own signal at the same time. Then, the NOMA user group M k l The SINR calculation formula for internal user n is:

[0114]

[0115] in, and is the NOMA user group intra-interference and inter-cell interference of user n, which can be expressed as:

[0116]

[0117] According to Shannon's formula, the calculation formula for the reachable rate of strong users in the NOMA group is:

[0118]

[0119] The strong user can decode the weak user's information and send it to the weak user through the relay link. The formula for calculating the achievable rate at which the strong user can decode the weak user's information is:

[0120]

[0121] NOMA User Group Strong user Energy harvested from the signal transmitted by the AP l The calculation formula is:

[0122]

[0123] Among them, V t is the thermal voltage, w is the fill factor, and I0 is the dark saturation current of the PD;

[0124] Strong user in indoor environment With weak users The RF channel gain between The calculation formula is:

[0125]

[0126] in, is the RF multipath propagation channel; L(d i,j )for and The path loss between i,j is the distance between user i and user j;

[0127] Assume T1 is a strong user Battery charging time, T2 for strong users Data transmission time, strong user The calculation formula of RF transmission power is:

[0128]

[0129] Bandwidth is evenly allocated to each pair of strong and weak user groups served by the relay link to eliminate interference. Suppose the number of weak users served by the relay link is N r , the total modulation bandwidth available for RF transmission is B RF , then strong users The RF modulation bandwidth at is B r,j =B RF / N r Therefore, strong users The formula for calculating the achievable rate that can be provided to weak users through the relay link is:

[0130]

[0131] Among them, N RF is the power spectrum density of the RF signal;

[0132] NOMA User Group Weak users within The formula for calculating the achievable rate through the hybrid link, namely the VLC link and the RF relay link, is:

[0133]

[0134] Therefore, the achievable rate calculation formula for any user n in the indoor multi-color VLC-NOMA network is:

[0135]

[0136] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0137] Attached Figure 1This is a three-dimensional model diagram of an indoor multi-color VLC-NOMA network based on cooperative transmission, which will be described in detail below:

[0138] The room size is 5m×5m×3m. L VLC APs are composed of L multi-color LEDs. N users are equipped with receivers and are randomly distributed in the room. L = {1, 2, …, L} is the AP set. N = {1, 2, …, N} is the user set. The set of NOMA user groups can be expressed as K = {1, 2, …, K}. represents the kth NOMA user group of AP l; represents the nth user of the kth NOMA user group of AP l; users with higher channel gain in the NOMA user group can convert the DC component of the received signal into energy, which is used to relay the information of users with lower channel gain in the NOMA user group.

[0139] Attached Figure 2 This is a planar model diagram of an indoor multi-color VLC-NOMA network based on cooperative transmission, which will be described in detail below:

[0140] The room size is 5m×5m×3m. L VLC APs are composed of L multi-color LEDs. N users are equipped with receivers and are randomly distributed in the room. L = {1, 2, …, L} is the AP set. N = {1, 2, …, N} is the user set. The set of NOMA user groups can be expressed as K = {1, 2, …, K}. Each NOMA group contains strong users with large optical channel gain and weak users with small optical channel gain. represents the kth NOMA user group of AP l; represents the nth user of the kth NOMA user group of AP 1; if a user does not join any NOMNA group, it becomes an OMA (Orthogonal Multiple Access) user.

[0141] Attached Figure 3 This is a flowchart of the user access algorithm based on the improved matching game, which will be described in detail below:

[0142] Input: Set the VLC AP set L, there are L VLC APs, the NOMA group set of VLC APs is K, there are K NOMA groups, where K is also the multi-color subcarrier set of each VLC AP, set k = 1; randomly distributed indoor user set N, there are N users; set the request rate of user n has 6 levels, expressed as δ n ∈{20Mbps,30Mbps,40Mbps,50Mbps,60Mbps,70Mbps}, the six levels of user minimum required rate are The power spectral density of VLC noise is 1×10 -21 , the VLC AP transmission power is 0.2W, the total RF transmission bandwidth is 20MHz, and the RF noise power spectrum density is 174dBm / Hz; the ratio of the AP's R / G / B / Y (Red / Green / Blue / Yellow) color spectrum transmission power is 0.239:0.291:0.405:0.065; let the NOMA group M representing user n accessing VLC AP l k l The matching relationship set (n, (l, s)) is Λ, the unstable matching set is X, and the users in set N who have not selected VLC AP and NOMA group are unmatched users and are U un ,make U un =N, the association matrix of the NOMA group of the kth color bearer of the initialized user n accessing VLC AP l is: n∈N, l∈L, k∈K;

[0143] Output: The association matrix of the NOMA group of a carrier where the user accesses the VLC AP n∈N, l∈L, k∈K.

[0144] Step 1: Calculate the optical channel gain value of the k-color carrier of user n accessing VLC AP l by formula (1): n∈N, l∈L, k∈K;

[0145] Step 2: According to value, adopt the preferred criterion, determine the preferred user n of the unmatched subcarrier k of AP l, obtain the initial matching set Λ, and remove user n from the set U un Delete, set

[0146] Among them, the preferred principle is: according to , is the selected user n for AP l that does not match subcarrier k, (n,(l,k)) represents the initial matching association between user n and the multi-color subcarrier k of AP l, where the kth subcarrier is the kth NOMA group of AP l; S un,k represents a multi-color subcarrier set with a matching number of users less than 3; the initial matches (n, (l, k)) of all unmatched users using the preferred criterion are added to the matching set Λ, and set

[0147] Step 3: According to formula (17), calculate the preference relationship value between the existing matches in Λ and other matches not in Λ, and save it in the preference relationship value matrix Θ;

[0148] Step 4: If no matching user set is found Go to step 5; otherwise, go to step 10;

[0149] Step 5: Add the remaining users to be matched to U un Number, take U un The first user, n = 1;

[0150] Step 6: Considering the interference to the matched pairs, according to formula (18), two matching pairs with larger preference relationship values ​​are selected from the preference relationship value matrix Θ as candidate matches for user n, and the corresponding elements in Z are updated The value of

[0151] Step 7: Calculate the utility value of the first choice match of user n by formula (19), select the match pair with the larger utility value, and connect the user to AP1. * Multicolor subcarrier k on * , remove user n from the set of users to be matched U un Remove it from the list, add the match to the matching set Λ, and update the corresponding element in Z The value of

[0152] Step 8: Set n=n+1. If n>N, go to step 9; otherwise, go to step 6.

[0153] Step 9: Initialize the AP number, set l = 1;

[0154] Step 10: If more than N v The user selects AP l, and AP l selects the first N v The user with the largest total rate and update otherwise, go to step 11;

[0155] Step 11: Let l=l+1, if l>|L|, go to step 12; otherwise, go to step 10;

[0156] Step 12: Initialize the matching number a=1 in the matching set Λ;

[0157] Step 14: Determine whether match a is an unstable match by matching blocking pairs and the definition of stable matches. If so, add the unstable match a to the unstable match set X.

[0158] The definition of stable matching is: if user n prefers subcarrier k over any other matching subcarrier, and subcarrier k prefers user n over any other matching user, then user n and subcarrier k are called a matched blocking pair; if a match is not blocked by any user-subcarrier pair, then the match is stable; otherwise, this user-subcarrier pair is called an unstable match;

[0159] Step 14: Let a=a+1, if a>|Λ|, go to step 15; otherwise, go to step 13;

[0160] Step 15: If Go to step 20; otherwise, go to step 16;

[0161] Step 16: Initialize the matching number x in the unstable matching set X to 1;

[0162] Step 17: For the match x in the unstable match set X, calculate the utility function before and after the exchange match x operation according to formula (19). If D(Λ')>D(Λ), go to step 18; otherwise, go to step 19;

[0163] The method of the exchange matching operation is as follows: the user can access the subcarriers of other APs that meet the AP maximum user number and subcarrier maximum user number restrictions, or different subcarriers of the same AP; assuming that the matching strategy before the exchange is Λ, and the matching strategy after the exchange is Λ', if the matching utility value D(Λ)>D(Λ'), the matching is not exchanged and the matching strategy is kept as Λ; otherwise, the matching exchange is performed, the matching strategy is updated to Λ', and the corresponding element in Z is updated The value of

[0164] Step 18: Delete the match x from Λ, add the new match obtained after the exchange to the match set, obtain a new matching strategy set Λ′, and update the corresponding element in Z The value of

[0165] Step 19: Let x=x+1, if x>|X|, go to step 20; otherwise, go to step 17;

[0166] Step 20: Output the Correlation Matrix The matching algorithm between the user access AP and the NOMA group ends.

[0167] Attached Figure 4 The flowchart of the algorithm for optimizing the power allocation factor of NOMA group users based on the improved raccoon is described in detail below:

[0168] Input: From user access association matrix A NOMA group user set consisting of users of carrier k accessing AP l enter The user request rate, the user minimum demand rate, and the NOMA user group The channel gain of each user in is Assume that the number of individuals in the raccoon population is T, and the t-th raccoon represents the NOMA user group The power factor vector value of each user in The t-th group of solutions, t∈T, set the maximum number of iterations I, set the iteration number variable i=1;

[0169] Output: NOMA user groups Output optimal power factor vector α t* And the optimal fitness function value value.

[0170] Step 1: According to formula (1), calculate the NOMA group Optical channel gain value of internal users

[0171] Step 2: Under the condition that the SIC decoding requirements are met, according to formula (20), initialize the NOMA user group represented by all T raccoons in the population The power factor value matrix of each user is used to obtain the initialization matrix of the power factor value. value;

[0172] Step 3: According to formula (21), calculate the fitness function value f of raccoon t in the i-th iteration t i , t∈[1:T];

[0173] Step 4: Determine the optimal power factor vector And calculate the optimal fitness function value in, make

[0174] Step 5: Set t=1;

[0175] Step 6: Set n = 1; if t = T, go to step 14, otherwise, go to step 7;

[0176] Step 7: Let t = t + 1, if Go to step 11; otherwise, go to step 8;

[0177] Step 8: According to formula (22), change the power allocation factor corresponding to the raccoon in the tree According to formula (21), calculate the fitness function value f t i+1 ;

[0178] Step 9: If f t i+1 >f t i ,but f t i =f t i+1 Otherwise, save and ft i constant;

[0179] Step 10: Let n = n + 1, if Go to step 5; otherwise, go to step 8;

[0180] Step 11: Otherwise, according to formula (23), change the power allocation factor corresponding to the prey landing According to formula (21), calculate the fitness function value f t i+1 , go to step 12;

[0181] Step 12: If f t i+1 >f t i ,but f t i =f t i+1 Otherwise, save and f t i constant;

[0182] Step 13: Let n = n + 1, if Go to step 5; otherwise, go to step 11;

[0183] Step 14: If i<I, i=i+1, go to step 2; otherwise, go to step 15;

[0184] Step 15: Output the optimal power factor vector And the optimal fitness function value NOMA User Group The power factor optimization algorithm ends and is ready to process the power factor optimization of a new NOMA user group.

[0185] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. User access and power allocation based on cooperative transmission in indoor multi-color VLC-NOMA networks, characterized by: The method comprises the following steps: S1: Input user set N = {1,2,…,N}, N users are randomly distributed in the room, set the height of user equipment from the ground h, VLC (Visible Light Communication) AP (Access Point) set L = {1,2,…,L}, VLC AP is denoted by AP in the following description; NOMA (Non-Orthogonal Multiple Access) user group set K = {1,2,…,K,}, K is also the multi-color subcarrier set of AP; VLC AP multi-color subcarrier total bandwidth B, set the user request rate has 6 candidate levels, denoted as δ n ∈{20Mbps,30Mbps,40Mbps,50Mbps,60Mbps,70Mbps}, the six candidate levels of the user's minimum required rate are The power spectral density of VLC noise is 1×10 -21 , the AP transmission power is 0.2W, the total RF transmission bandwidth is 20MHz, and the RF noise power spectrum density is 174dBm / Hz; the ratio of the AP's R / G / B / Y (Red / Green / Blue / Yellow) transmission power is 0.239:0.291:0.405:0.065; represents the kth NOMA user group of AP l; Represents the nth user of the kth NOMA user group of AP l; According to the Lambertian radiation model of VLC, the channel gain from AP to the user is calculated, and the SIC (Serial Interference Cancellation) decoding order factor of each user in the multi-cell NOMA network is determined. According to the decoding order factor value, the users in the NOMA group are arranged in ascending order, and the received signal level value of each user in the NOMA group is calculated; Among them, AP l to NOMA user group Channel gain for user n The calculation formula is: In the above formula, A PD Represents the receiving area of ​​the receiver; m is the Lambertian radiation coefficient, m = -1 / log(cosφ 1 / 2 ), φ 1 / 2 is the half-power angle of the AP's LED (Light Emitting Diode), φ is the emission angle of the LED; d l,n is the distance between AP l and user n; ψ n is the incident angle to the receiver; ψ c is the field of view of the receiver; the optical filter gain and concentrator gain of the receiver are T(ψ n ) and g(ψ n ), and g(ψ n ) = f 2 / sin 2 (ψ c ), f is the constant reflection coefficient of the wall; Among them, the calculation formula of the SIC decoding order factor of each user in the NOMA group is: In the above formula, Assign APs to the NOMA user group Total bandwidth; For NOMA user groups The channel gain of user n; N0 is the noise power spectrum density; I n is the inter-cell interference suffered by user n, and its calculation formula is: In the above formula, is the transmit power allocated by AP to user r; γ = γ eo γ oe , γ oe is the light-to-electricity conversion efficiency at the LED emitter, γ eo is the electrical-optical conversion efficiency at the receiving end; Among them, NOMA user group The received signal level value of user n from AP 1 can be expressed as: In the above formula, Indicates NOMA user group The power allocation factor that user n obtains from AP l is: represents the transmission power obtained by the k-th NOMA user group of AP1; is the DC part of the signal level received by user n, I b To ensure that the transmission signal is not a negative DC level value; Indicates NOMA user group The association variable between user n and AP l is defined as: S2: Using the method in claim 2, calculate the NOMA user group The SINR (Signal to Interference plus Noise Ratio) of user n is used to calculate the achievable rate of strong and weak users in the NOMA group through the LED optical channel according to the Shannon formula; the decoded information of the strong user is forwarded to the weak user through the strong user device, and the achievable rate of the decoded forwarded information obtained by the weak user is calculated; S3: Using the method of claim 3, calculate the NOMA user group The energy collected by the strong user in the AP from the optical signal emitted by the AP Calculate the direct forwarding channel gain from strong users to weak users in the NOMA group and the achievable forwarding information rate, compare the achievable decoding forwarding information rate of the weak user and the achievable relay forwarding information rate, select the smaller value as the achievable information rate obtained by the weak user from the strong user, and calculate the total achievable rate obtained by the weak user in the NOMA group; S4: adopting the method of claim 4, executing the user access algorithm based on the improved matching game for each user in turn, obtaining the optimal AP-user association matrix, and accessing the user to the corresponding AP polychromatic subcarrier according to the AP-user association matrix; S5: Adopt the method of claim 5, execute the power allocation algorithm based on improved raccoon optimization for the users in each NOMA user group associated with each AP in turn, obtain the optimal power allocation factor matrix of the users in each NOMA user group, calculate the achievable rate of each user according to the association matrix between AP and user and the power allocation factor matrix of the users in each NOMA user group, then add up the achievable rates obtained by each user, and calculate the sum rate of the network.

2. The user access and power allocation based on cooperative transmission in the indoor multi-color VLC-NOMA network according to claim 1, characterized in that: The specific method of S2 is: S201: Calculate NOMA user groups SINR value of user n; Among them, SINR value Γ n The calculation formula is: In the above formula, and are the NOMA user group intra-interference and AP inter-cell interference suffered by user n, and their calculation methods are: S202: Calculate the achievable rate of strong users and weak users in the NOMA group through the LED optical channel according to the Shannon formula in, The calculation method is: S203: If the strong user in the NOMA group Decoded information is forwarded directly to weak users According to Shannon's formula, the achievable rate of decoding and forwarding information obtained by weak users is:

3. The user access and power allocation based on cooperative transmission in the indoor multi-color VLC-NOMA network according to claim 1, characterized in that: The S3 specific method is: S301: Calculate NOMA user groups Strong user Energy harvested from the light signal emitted by the AP l in, The calculation formula is: In the above formula, V t is the thermal voltage of the receiving device, w is the fill factor of the receiving device, and I0 is the dark saturation current of the receiving device; S302: Calculate strong users in indoor environment With weak users The RF channel gain between in, The calculation formula is: In the above formula, is the RF multipath propagation channel gain; L(d i,j )for and The path loss between i,j is the distance between user i and user j; S303: Calculate the radio frequency power received by the weak user in the NOMA group from the strong user through the radio frequency channel in, The calculation formula is: In the above formula, T1 is a strong user Battery charging time, T2 for strong users The time it takes to transmit data over the RF channel; S304: Calculate strong users in the NOMA group The achievable rate value that can be provided to weak users through the relay radio link in, The calculation formula is: In the above formula, N RF is the power spectrum density of the RF signal; B r,j For strong users The RF modulation bandwidth of the transmitted RF signal, and B r,j =B RF / N r , B RF is the total modulation bandwidth of the RF link, N r The number of weak users served by the RF relay link; S305: Comparison of NOMA user groups Weak users within Obtain the achievable rate values ​​of the decoding forwarding information and the radio frequency relay forwarding information from the strong user, and select the smaller value as the achievable rate value of the forwarding information of the weak user; Among them, weak users The forwarding information achievable rate value is: S306: Using the methods described in S2 and S305 in sequence, determine the achievable rate value of user n in all NOMA groups in the indoor multi-color VLC-NOMA network Among them, NOMA user group The achievable rate of user n in for:

4. The user access and power allocation based on cooperative transmission in the indoor multi-color VLC-NOMA network according to claim 1, characterized in that: The specific method of S4 is: S401: Add all users in user set N to unmatched user set U un For any AP l, l∈L, let its unmatched multi-color subcarrier k, k∈K, according to the maximum direct light channel gain from user n to AP l's subcarrier k value, adopt the preferred criterion, determine the preferred user n of the unmatched subcarrier k of AP l, and obtain the initial matching set Λ; Among them, the preferred principle is: according to is the selected user n for AP l that does not match subcarrier k, where (n,(l,k)) represents the matching relationship between user n and the multi-color subcarrier k of AP l, where the kth subcarrier is the kth NOMA group of AP l; U un is the set of unmatched users; S un,k represents a multi-color subcarrier set with a matching number of users less than 3; add (n, (l, k)) to the matching set Λ, and set the user association matrix element S402: Calculate the preference relationship value of the match (n, (l, k)) in Λ to other matches (n', (l', k')) not in Λ And saved in the preference relationship value matrix Θ; Among them, the preference relationship value of matching (n, (l, k)) The calculation formula is: In the above formula, if = means that compared with (n2, (l2, k2)), the match (n, (l, k)) is more likely to be updated to the match (n1, (l1, k1)); for all users in set N, if the user belongs to set U un , execute step S403; otherwise, execute S405; S403: After each multi-color subcarrier s that is not matched with an AP selects its preferred user and matches it, for each user set U that is not matched with an AP subcarrier un For the remaining user n to be matched, in order to reduce the interference to the existing matches, two matches (n1', (l1', k1')) and (n'2, (l'2, k'2)) with larger preference relationship values ​​are selected from the preference matrix Θ as candidate matches for the user; The selection criteria for candidate matching are: Among them, L un,s The channel gain of AP l on subcarrier k is greater than h (n,(l,k)) The AP set; is not on subcarrier k or the channel gain of AP l on subcarrier k is less than h (n,(l,k)) The AP set; S404: Calculate the matching (n1', (l1', k1')) and (n'2, (l'2, k'2)) as the matching of the unmatched user n, and the matching utility value D(Λ) generated by the system, and select the matching with the largest matching utility value as the matching of the to-be-matched user n, and select the matching value from the to-be-matched user set U un Remove user n from the set, add user n's matches to the matching set Λ, and update The value of Among them, the calculation formula of the matching utility value D(Λ) is: S405: In order to balance the load between APs, if there are more than N v If a user selects AP l, then AP l selects the first N v The users with the highest total rate are selected as the associated matching users of AP l, AP l is deleted from the set L, and the If the value is , go to step S401; otherwise, go to step S406; S406: traverse all existing matches, use the exchange matching operation to try to adjust the matching association relationship, calculate the matching utility value, and determine whether the new match is an unstable match. If so, go to step S407; otherwise, go to step S408; The method of the exchange matching operation is as follows: the user can access the subcarriers of other APs that meet the AP maximum user number and subcarrier maximum user number restrictions, or different subcarriers of the same AP; assuming that the matching strategy before the exchange is Λ, and the matching strategy after the exchange is Λ', if the matching utility value D(Λ)>D(Λ'), the matching is not exchanged and the matching strategy is kept as Λ; otherwise, the matching exchange is performed, the matching strategy is updated to Λ', and the matching strategy is updated. The value of The definition of stable matching is: if user n prefers subcarrier k over any other matching subcarrier, and subcarrier k prefers user n over any other matching user, then user n and subcarrier k are called a matched blocking pair; if a match is not blocked by any user-subcarrier pair, then the match is stable; otherwise, this user-subcarrier pair is called an unstable match; S407: For all unstable matches, the users in the match are exchanged to the multi-color subcarriers of other APs, and the matching utility values ​​before and after the exchange matching operation are calculated to determine whether D(Λ')>D(Λ) holds. If so, the match before the exchange is deleted from Λ, and the match after the exchange is added to the matching strategy to obtain a new matching set Λ', and the new matching set is updated. otherwise, the exchange matching operation is not performed; S408: Obtaining the optimal AP, carrier and user association matrix 5. The user access and power allocation based on cooperative transmission in the indoor multi-color VLC-NOMA network according to claim 1, characterized in that: The specific method of S5 is: S501: Set represents the power allocation factor vector of each user in the kth NOMA group of AP l, whose elements And NOMA user group The power factor value of each user should ensure the SIC decoding requirements, that is, meet Suppose there are T raccoons, each raccoon represents a power factor vector Then the power allocation factor matrix represented by T raccoons is expressed as set up Assume that the iteration counter i=1, and the maximum number of iterations is I; S502: Initialize the NOMA user group represented by all raccoons in the population under the condition that the SIC decoding requirements are met The power factor values ​​of each user are obtained to obtain the initialization matrix of the power factor values The formula for initializing the power factor value is: Where r is an arbitrary real number in [0,1]. represents the NOMA user group represented by the t-th raccoon The power factor value of user n; S503: Calculate the fitness function value f of each raccoon representative in the i-th iteration t i ; Among them, the fitness function value f represented by the t-th raccoon in the i-th iteration is t i The calculation formula is: In the above formula, ω z represents the penalty factor, g z It can be expressed as: In the above formula, [x] - =min{0,x}, S504: Determine the optimal power factor vector α t* And the optimal fitness function value, where α t* is the optimal power factor vector in the i-th iteration Value, denoted as Let α best =α t* , S505: According to the raccoon hunting rules, half of the raccoons climb trees to hunt prey, and the other half wait on the ground for the prey to fall before hunting. If t = T, go to step S510. Otherwise, set t = t + 1. If Go to step S506; otherwise, go to step S508; S506: Changing the power allocation factor matrix corresponding to the raccoon climbing a tree to hunt prey And calculate the fitness function value f of each raccoon after the power factor changes t i+1 ; Among them, the formula for changing the power factor value of the raccoon in the tree is: In the above formula, r1 takes a random real value in (0,1); S507: If the fitness function value increases, that is, f t i+1 >f t i , then update the power factor value and fitness function value f t i =f t i+1 , update α t ; Otherwise, keep the power factor and fitness function value unchanged; go to step S504; S508: According to the raccoon hunting rules, the ground raccoon can move according to the current position to hunt prey, changing the power allocation factor matrix corresponding to the raccoon under the tree And calculate the fitness function value f after the power factor changes t i+1 ; Among them, the power factor value change formula of the raccoon under the tree is: In the above formula, r2 takes a random real value in [-1,1]; S509: If the fitness function value increases, that is, f t i+1 >f t i , then update the power factor value and fitness function value f t i =f t i+1 , update α t ; Otherwise, keep the power factor and fitness function value unchanged; go to step S504; S510: Output optimal power factor vector α best and f best .

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