Socially aware indoor device cooperation blind spot access method for wireless optical communication

Abstract

The present application relates to a kind of social awareness indoor equipment cooperation blind spot access wireless optical communication method, belong to optical wireless communication technical field.The method described in the present application is directed to the problem of inter-cell interference in indoor visible light communication, this method uses point coloring method to divide different frequency bands for adjacent visible light access point to suppress inter-cell interference, select multiple interference-free point coloring-based VLC device access for equipment;For the device trapped in the visible light coverage blind spot, design the access method of device cooperation based on social awareness, identify and exclude negative devices for cooperative communication by evaluating the social relationship between devices, select the positive device of D2D cooperative communication to establish relay link between blind spot device.At the same time, in order to improve the online time of cooperative D2D device, power allocation optimization method based on energy efficiency optimization is used.The method can effectively improve the success access rate of device, system throughput and information transmission energy efficiency of relay link between devices.

Description

Technical Field

[0001] This invention belongs to the field of optical wireless communication technology and relates to a wireless optical communication method for socially aware indoor device cooperation blind spot access. Background Technology

[0002] Visible Light Communication (VLC) technology boasts advantages such as an unlicensed bandwidth of 400THz, high energy efficiency, and green energy saving, attracting widespread attention from researchers. It can alleviate wireless spectrum pressure and provide ultra-high data rates. However, because it primarily relies on line-of-sight (LoS) links for data transmission, it is easily blocked, resulting in communication blind spots and making devices in these blind spots unusable. Device-to-device (D2D) communication, a technology that allows data transmission directly between devices without the need for base stations, can be incorporated into VLC networks to address some of these blind spot issues. VLC communication using D2D assistance forms a VLC-D2D communication network. This heterogeneous VLC-D2D network not only leverages VLC technology to achieve high data transmission rates and low latency but also flexibly and effectively serves blind spots that VLC access points (APs) cannot reach, expanding network coverage. VLC networks typically employ a dense deployment of multiple access points (APs) to achieve full indoor communication coverage. When using D2D communication to address blind spots in VLC networks, the selfish behavior of devices in cooperative communication can lead to non-cooperative characteristics, reducing the success rate of D2D cooperative communication. Therefore, designing a socially aware indoor device cooperative blind spot access method is of practical significance. Summary of the Invention

[0003] The core of this invention lies in addressing the problem of device access blind spots in communication coverage within indoor VLC-D2D heterogeneous networks. It designs a socially aware device cooperation blind spot access method to improve seamless indoor communication coverage, increase the successful access rate of devices within the building, and enhance system throughput. This invention provides the following technical solution:

[0004] A wireless optical communication method for socially aware indoor device collaboration blind spot access includes the following steps:

[0005] S1: Using the vertex coloring method in graph theory, different frequency bands are assigned to adjacent Visible Light Communication Access Points (VLC APs) to suppress inter-cell interference; based on the Lambertian radiation model of visible light communication, the visible light channel gain from the device to the visible light communication access point is calculated, and the optical signal-to-noise ratio from the device to each VLC AP indoors is calculated; using the free-idle wireless communication path loss model, the wireless channel gain between the device and other devices is calculated, and the wireless signal-to-noise ratio between devices is calculated; based on the VLC AP coloring results, all VLC APs with the highest optical signal-to-noise ratio for each color in the candidate VLC AP set are selected for each device in the indoor user set;

[0006] S2: For blind spots in the indoor user set that are not connected to VLC APs, determine whether the wireless signal-to-noise ratio between the blind spot device and its neighboring devices is greater than a threshold. If so, establish a physical candidate cooperative communication device set for the blind spot device. Calculate the social attribute factors of centrality, stability, and similarity among the candidate cooperative communication devices. Use entropy weighting and ratio methods to evaluate the social relationship between the blind spot device and the candidate cooperative communication devices. Based on the evaluation values, divide the candidate cooperative communication device set into active, stable, and passive cooperative communication devices. Remove passive cooperative communication devices from the candidate cooperative communication device set to establish a socially aware device set. Use a socially aware device-to-device (D2D) access method to determine the communication mode of the D2D devices for cooperative communication of the blind spot device.

[0007] S3: For devices in the user set that are connected to the candidate VLC AP set, the transmit power of each VLC AP in the VLC AP set is allocated using a fixed power average allocation algorithm; for devices in the user set that are not connected to the candidate VLC AP set, the energy efficiency of the D2D device pairing is calculated based on the D2D pairing communication mode between the blind device and the cooperative communication device, and the transmit power of the D2D transmitter is optimized based on the energy efficiency.

[0008] Furthermore, the specific method of S1 is as follows:

[0009] S101: Color 1 is applied to one of the VLC APs in the room and its non-adjacent VLC APs; color 2 is applied to one uncolored VLC AP and its non-adjacent VLC APs; if there are still uncolored VLC APs, color 3 is applied to one uncolored VLC AP and its non-adjacent VLC APs; if there are still uncolored VLC APs, color 4 is applied to one uncolored VLC AP and its non-adjacent VLC APs.

[0010] S102: Determine if there are adjacent VLC APs with the same color. If yes, go to S101; otherwise, go to S103.

[0011] S103: Count the number of colors used to color indoor VLC APs, labeled C. Generally, C≤4. Divide the VLC communication spectrum into C frequency bands and allocate different frequency bands to VLC APs of different colors to avoid inter-cell interference.

[0012] S104: Based on the Lambert radiation model of visible light communication, determine the visible light channel gain from the device to the visible light communication access point, and calculate the optical signal-to-noise ratio from the device to each VLC AP indoors; based on the free-idle wireless communication path loss model, determine the wireless channel gain between the device and other devices, and calculate the wireless signal-to-noise ratio between the devices.

[0013] Here, according to the Lambert radiation model, the optical channel gain of the line-of-sight direct channel of the light from VLC AP n to user equipment m is:

[0014]

[0015] In equation (1), A PD d represents the receiving area of ​​the optical receiver. m,n Let φ be the straight-line distance between AP n and VD m; let φ be the emission angle of the VLC AP; and let ψ be the field of view of the optical receiver. c The incident angle of the optical receiver is ψ; the Lambertian radiation coefficient η is η=-ln2log2[cos(φ) 1 / 2 )],φ 1 / 2 The half-power angle of the VLC AP;

[0016] The optical signal-to-noise ratio of VLC AP n transmitted to device m via the optical line-of-sight link is:

[0017]

[0018] In equation (2), P n V ρ is the transmitted optical power of VLC AP n; ρ is the optical / electrical conversion factor received by the device; N V The noise power spectral density of a VLC is typically taken as 1×10⁻⁶. -21 ; Let m be the channel bandwidth occupied by VLC AP n; A is the set of all VLC APs in the indoor VLC network that are colored the same as VLP AP n.

[0019] Based on the free-idle wireless communication path loss model, and considering the effects of multipath fading and shadowing fading, the wireless channel gains for device i and device j are:

[0020]

[0021] In equation (3), The signal represents the wireless channel gain from the transmitter (device i) to the receiver (device j) in a D2D process; K represents the path loss constant; μ represents the signal strength. i,j The fast fading gain representing the multipath effect follows an exponential distribution; ν i,j The slow fading gain, representing shadow fading, follows a log-normal distribution; d i,j Ω is the straight-line distance from the transmitter of D2D device i to the receiver of D2D device j; Ω is the path loss factor.

[0022] The D2D device of this invention mainly performs D2D data transmission by reusing the uplink of the cellular network. One D2D pair only reuses the channel resources of one cellular user. The wireless signal-to-noise ratio for establishing a D2D pair between blind spot device i and cooperating device j is:

[0023]

[0024] In equation (4), P i P is the transmit power of D2D device i; c N0 represents the transmit power of the D2D multiplexed cellular device c; N0 represents additive white Gaussian noise.

[0025] S105: If the optical signal-to-noise ratio (SNR) from the device to any VLC AP in its candidate VLC AP set is greater than the threshold, or if the SNR of the device's candidate VLC APs is less than the threshold, but the interruption time is less than the optimal waiting time T. * If the device is found to be in the candidate VLC AP set, it is saved in the candidate VLC AP set; otherwise, the device is removed from the candidate VLC AP set and saved in the blind spot device set.

[0026] Among them, the optimal waiting time T * for:

[0027]

[0028] In the above formula, T0 is the fixed execution time for the device to switch between VLC AP and D2D communication modes; The data rate provided for the D2D link; Q is the data rate provided for VLC AP n; Q is the size of the packets delayed in the buffer during the interruption, assuming the buffer queue is long enough to ensure that all packets can be buffered.

[0029] S106: Based on the user's device communication request rate, calculate the device request rate divided by the device's minimum rate value, and round the result up to the nearest integer to obtain the number of VLC APs the device requests to associate, denoted as S. Generally, S≤C. Check the coloring of each VLC AP in the device's candidate VLC AP set. If all candidate VLC APs of the device have different colors, the device will connect to the top S VLC APs with the highest optical signal-to-noise ratio. If candidate VLC APs have the same color, the device will select the S VLC APs with different colors and the highest optical signal-to-noise ratio in each color to connect to.

[0030] S201: For blind spot devices in an indoor user set that are not connected to a VLC AP, if the wireless signal-to-noise ratio between the blind spot device and its neighboring device is greater than a threshold, the neighboring device responds to the blind spot device's cooperative communication request and establishes a set of candidate D2D cooperative devices for the blind spot device.

[0031] S202: Calculate the social rank and social centrality influence factor of each candidate device in the set of cooperative candidate D2D devices;

[0032] Among them, the social rank(j) and social centrality influence factor of the candidate device j for cooperation. They are respectively:

[0033]

[0034] In the above formula, S j |S represents the set of devices with a wireless signal-to-noise ratio greater than a threshold among candidate devices j. j | represents the number of devices in the set, M represents the number of indoor communication devices, and N represents the number of devices in the set. i This represents the set of candidate cooperative devices with a signal-to-noise ratio greater than that between the device i and the blind spot device;

[0035] S203: Calculate the social stability attribute factors of blind device i and cooperative candidate device j based on the frequency and duration of historical cooperative communication between the blind device and the cooperative candidate device. for:

[0036]

[0037] In the above formula, c i,j This represents the number of times historically devices i and j have cooperated; t i,j This represents the average duration of cooperative communication between device i and device j; This represents the total number of times device j cooperates with other devices; This represents the sum of the average durations of cooperation between device j and other devices;

[0038] S204: Based on the popularity of the content and the degree of interest of the device in the content, cosine similarity is used to calculate the social similarity attribute factor between blind device i and cooperative candidate device j. for:

[0039]

[0040] In the above formula, the probability of device i selecting a certain content is... |F p | indicates the number of contents, S i,u This value represents the proportion of times device i requests content u at time t out of the total number of requests. This value can assess the degree of interest that device i has in content u. This represents the popularity of the u-th content in the communication network;

[0041] S205: Based on the social attribute factors of centrality, stability, and similarity, the social relationships of candidate devices for cooperation are evaluated using entropy weighting and ratio methods. Based on the evaluation values, the devices in the candidate device set are labeled as: positive devices, stable devices, and negative devices. Negative devices are then removed from the candidate device set, and the remaining devices are saved as a socially aware device set. The calculation process of entropy weighting and ratio methods is as follows:

[0042] S2051: Normalize the centrality, stability, and similarity social attribute factors between blind spot device i and its cooperative candidate device j, where i∈I, j∈N i I represents the set of blind spot devices in the room, where the normalized index is calculated as follows:

[0043]

[0044] S2052: Calculate the centrality, stability, and similarity normalized entropy values ​​of the cooperative candidate devices j of blind device i:

[0045]

[0046] In the above formula, Moreover, if Then let

[0047] S2053: Calculate the weight value of the cooperative candidate device j:

[0048]

[0049] S2054: Calculate the entropy weights and ratios of three social attribute indicators—centrality, stability, and similarity—of the cooperative candidate device j of blind spot device i. The calculation formula is as follows:

[0050]

[0051] S2055: Devices with an entropy weight ratio greater than 0.7 are identified as actively cooperating devices; devices with an entropy weight ratio between 0.3 and 0.7 are identified as stably cooperating devices; and devices with an entropy weight ratio less than 0.3 are identified as passively cooperating devices.

[0052] S206: Arrange the number of devices in the social sensing device set of each blind spot device in ascending order, prioritize establishing D2D direct connection cooperative communication mode between the blind spot device and the candidate device with fewer devices in its social sensing device set and meeting the minimum communication rate requirement, and delete the D2D successfully paired device from other social sensing device sets; complete the pairing of D2D direct connection communication modes for each blind spot device in sequence.

[0053] S207: If the direct communication mode D2D pairing of the blind spot device fails, the cooperative candidate device that has successfully paired with D2D is added to the relay forwarding candidate device set R of the blind spot device. From the set R of the blind spot device, the relay candidate device that meets the minimum rate requirement of the blind spot device and has the highest energy efficiency is selected, and the connection is established using the D2D relay mode.

[0054] Furthermore, the specific method of S3 is as follows:

[0055] S301: To maximize the energy efficiency of the D2D link, the problem is modeled as an energy efficiency optimization problem P:

[0056]

[0057] Wherein, vector m represents the mode selection factor. When the cooperative D2D adopts the direct communication mode, the mode selection factor m of the blind device i is... i =0, when D2D selects relay communication mode, the mode selection factor m is 0. i =1; Matrix X represents the access selection factor, and the elements x in the matrix i,j =1, indicating that device i and device j are paired as a D2D pair, x i,r =1,x r,j =1 indicates that D2D pairs need to communicate through relay device r; P i and P i max P represents the D2D transmit power and maximum transmit power values, respectively. r and P r max P represents the transmit power and maximum transmit power of the relay device in relay communication mode, respectively. c and P c max These represent the transmit power and maximum transmit power values ​​of the D2D paired multiplexed cellular device c, respectively; EE(pi ,p r ,p c C1 represents the energy efficiency function of the D2D link; C2 represents the elements in the device access selection factor X matrix, which are binary variables; C3 represents the mode selection factor, which is also a binary variable; C4 represents the power constraints of the D2D transmitter, D2D relay, and multiplexed cellular equipment, respectively; and C5 represents the signal-to-interference-plus-noise ratio constraint. Let represent the wireless signal-to-noise ratio (SNR) and the wireless SNR threshold value between D2D transmitting device i and receiving device j, respectively. These represent the link radio signal-to-noise ratio (SNR) and the link radio SNR threshold value for multiplexed cellular device c in D2D relay communication mode, respectively. These represent the link radio signal-to-noise ratio (SNR) between transmitting device i and relay device c, and between relay device c and receiving device j, respectively, in D2D relay communication mode.

[0058] When D2D uses direct communication mode, the energy efficiency function of the D2D link is:

[0059]

[0060] In the above formula, P0 represents the circuit power value of the transmitting or receiving device in a D2D pair, and the achievable data rate between the transmitting device i and the receiving device j in D2D is... It can be calculated using Shannon's formula:

[0061]

[0062] In the above formula, B D This indicates the bandwidth of the D2D communication link. The wireless signal-to-noise ratio of the D2D pair is calculated by equation (4);

[0063] When D2D uses relay communication mode, the energy efficiency function of the D2D link is:

[0064]

[0065] In the above formula, These represent the achievable data rates between blind spot device i and relay device r, and between relay device r and D2D receiving device j, respectively, and are calculated using the following formulas:

[0066]

[0067] In the above formula, Let i and r represent the wireless signal-to-interference ratios (SIRs) between blind spot device i and relay device r, and between relay device r and D2D receiver j, respectively. Their calculation formulas are as follows:

[0068]

[0069] In the above formula, This represents the wireless channel gain from the D2D transmitter i to the relay device r. This represents the wireless channel gain from the relay device to the D2D receiver. The wireless channel gain at which the cellular device interferes with the D2D relay device r is... The wireless channel gain that causes interference to the D2D receiver j by cellular devices is: The above four channel gain calculation methods are calculated using the method in equation (3);

[0070] Using a heuristic algorithm approach, the optimization problem (13) includes three sub-problems: device access, mode selection, and power allocation. The device access and mode selection sub-problems are solved in steps S1 and S2.

[0071] S302: When the communication mode of the D2D pairing between the blind spot device and the cooperative communication device is relay mode, the link energy efficiency between the D2D pairings is as described in equation (16). According to the C2 condition of the optimization problem equation (13), the minimum transmit power P of the cellular device c for optimizing the link energy efficiency of the D2D pairings is... c min for:

[0072]

[0073] In the above formula, the wireless channel gain that causes interference from the D2D transmitter to the base station is: This represents the minimum signal-to-interference ratio (SIR) between the D2D transmitter and receiver. This represents the minimum wireless signal-to-interference ratio (SIR) between the D2D multiplexed cellular device and the base station during relay mode communication.

[0074] S303: Based on the bottleneck effect of relay mode communication links, the link data rate between device i and device j in a D2D pair is: If and only if hour, The link efficiency of a D2D pair is maximized; at this point, the transmit power P of the relay device in the D2D pair is maximized. r for:

[0075]

[0076] S304: Order t = 1 + P i T, Δ1(t) = Lt - Ltlnt + 2P0T - L, using the Lambertian W function to solve for the value of t when Δ1(t) = 0, denoted as t0, then the optimized transmit power of D2D pairing is: but

[0077]

[0078] In the formula, W() is the Lamber W function;

[0079] S305: When the communication mode of the D2D pairing between the blind spot device and the cooperative communication device is relay mode, the link energy efficiency between the D2D pairings is as described in equation (14), then the optimized transmit power of the D2D pairing is

[0080] The beneficial effects of this invention are as follows: This invention provides a socially aware wireless optical communication method for blind spot access of indoor devices. First, addressing the inter-cell interference problem in VLC networks, a point-coloring-based VLC device access method is designed. This method uses point coloring to allocate different frequency bands for adjacent VLC APs to suppress inter-cell interference and allows devices to access multiple interference-free APs to improve device speed. Next, addressing the non-cooperative characteristics between devices, a socially aware D2D device access method is designed. This method assesses the social relationships between devices, classifying them into active, stable, and passive devices. By identifying and filtering out passive devices, devices trapped in blind spots are selected to access active D2D transmitters. Finally, to improve the online time of relay devices, a power allocation method based on the Lambert-W function is adopted. This method can effectively improve the device success rate, system throughput, and D2D link energy efficiency.

[0081] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0082] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in detail with reference to the accompanying drawings, wherein:

[0083] Appendix Figure 1 VLC-D2D downlink transmission diagram;

[0084] Appendix Figure 2 A flowchart of a wireless optical communication method for accessing blind spots in indoor device collaboration based on social awareness;

[0085] Appendix Figure 3 Flowchart of VLC device access method based on point coloring;

[0086] Appendix Figure 4Flowchart of a socially-aware D2D device access method; Detailed Implementation

[0087] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed 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 representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0088] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures, and should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0089] The following is in conjunction with the appendix Figure 1 This invention describes the downlink transmission link.

[0090] Appendix Figure 1 This is a model diagram of the downlink transmission link in an indoor VLC-D2D heterogeneous network. Multiple VLC APs are deployed on the ceiling, primarily responsible for indoor lighting and downlink data transmission. Radio Frequency Access Points (RF APs) handle uplink data transmission for communication devices and communication between D2D devices and RF cellular base stations, providing uplink transmission frequency bands for D2D multiplexed cellular users in D2D relay communication mode. Each AP is connected to a Central Control Unit (CCU) via power lines. The CCU is responsible for collecting and processing communication control, resource allocation, device status information, and monitoring link status information. This invention considers each VLC AP to have an LED, each VLC Device (VD) to have a photodetector (PD), and the receiving angle of the PD is arbitrary. d is the straight-line distance between the VLC AP and the device, the emission angle of the VLC AP is φ, the incident angle of the optical receiver is ψ, and the field of view of the optical receiver is ψ. cConsidering that devices in communication blind spots cannot receive direct link transmission information from VLC APs, communication devices located in areas with blocked line-of-sight or blind spots are called blind spot devices. To improve the communication quality of these blind spot devices, VLC networks allow some VDs with redundant resources to act as a cooperative D2D pairing communication terminal, using direct communication or relay forwarding methods to help blind spot devices establish communication channels.

[0091] As attached Figure 1 When D2D uses direct communication, the paired D2D devices transmit information directly to the blind spot device via the radio frequency channel. When D2D uses relay communication, the D2D transmitting device forwards information to the relay device, which then uses the uplink channel of the multiplexed RF cell to forward the information to the D2D receiving device, thus achieving the purpose of D2D receiving information through relay forwarding by other devices.

[0092] The following is in conjunction with the appendix Figure 2 Detailed explanation of the execution process of this invention:

[0093] Step 1: Input device set M, VLC AP set N, and assume the VLC noise power spectral density is 1×10⁻⁶. -21 Assume each VLC AP has a transmit power of 10W, the maximum transmit power of the D2D transmitter is 21dBm, the optical signal-to-noise ratio threshold σ, and the wireless signal-to-noise ratio threshold. Set the distance constraint value L for D2D pairing, and define the set of blind spot devices in D2D communication. Access VLC AP device set

[0094] Step 2: Randomly select a device from the device set M. First, calculate the optical channel gain from the device to the VLC AP set using the VLC Lambertian radiation model of formula (1). Then, calculate the optical signal-to-noise ratio of each VLC AP transmitted to the device through the optical line-of-sight link using formula (2).

[0095] Step 3: If the optical signal-to-noise ratio of the device to the VLC AP set is greater than the threshold, or the optical signal-to-noise ratio of the device to the VLC AP is less than the threshold, but the interruption time is less than the optimal waiting time T determined by formula (5) of this invention. * If a VLC AP meets the conditions, it becomes a candidate VLC AP set for that device, and the device is saved in its candidate VLC AP set J. Otherwise, the device is removed from its candidate VLC AP set and saved in the blind spot device set I.

[0096] Step 4: Determine if all devices in the device set have been traversed. If yes, proceed to step 5; otherwise, proceed to step 2.

[0097] Step 5: For devices in set J of the candidate VLC APs, perform additional steps. Figure 3 The VLC device access algorithm based on point coloring is shown. Update I and J, then proceed to step 8; for devices in the blind spot device set I, proceed to step 6.

[0098] Step 6: Considering the effects of multipath fading and shadow fading, based on the free-idle wireless communication path loss model, according to formula (3), calculate the wireless channel gain of the blind device i and the devices in the set M with a communication distance less than L in turn. Using formula (4), calculate the wireless signal-to-noise ratio between the blind device and other devices. Select devices with a distance less than L from the blind device and a wireless signal-to-noise ratio greater than the threshold, and store them in the cooperative candidate D2D device set N of the blind device i. i middle;

[0099] Step 7: If the blind spot device set is not empty, then for each device in the blind spot device set, perform the following steps: Figure 4 The socially aware D2D device access method shown determines whether each blind spot device adopts a direct connection or relay forwarding communication mode for D2D; otherwise, proceed to step 9.

[0100] Step 8: For devices accessing candidate VLC APs, use a fixed power allocation algorithm to determine the transmit power of the VLC APs in the VLC AP set, then proceed to step 10;

[0101] Step 9: For blind spot devices that cannot connect to the VLC AP, calculate the energy efficiency of the D2D device pair based on the communication mode of the blind spot device, and optimize the transmission power of the D2D transmitter using an energy efficiency optimization method based on the Lambert W function. The specific steps are as follows:

[0102] S901: To maximize the energy efficiency of the D2D link, the problem is modeled as an energy efficiency optimization problem P:

[0103]

[0104] stC1:x i,j ∈{0,1},x i,r ∈{0,1},x r,j ∈{0,1},x i,j ,x i,r ,x r,j ∈X

[0105] C2: m∈{0,1}

[0106]

[0107]

[0108] In the above formula, vector m represents the mode selection factor. When the collaborative D2D adopts the direct communication mode, the mode selection factor m... i =0, when D2D selects relay communication mode, the mode selection factor m is 0. i =1; Matrix X represents the access selection factor, and the elements x in the matrix i,j =1, indicating that device i and device j are paired as a D2D pair, x i,r =1,x r,j =1 indicates that D2D pairs need to communicate through relay device r; P i and P i max P represents the D2D transmit power and maximum transmit power values, respectively. r and P r max P represents the transmit power and maximum transmit power of the relay device in relay communication mode, respectively. c and P c max These represent the transmit power and maximum transmit power values ​​of the D2D paired multiplexed cellular device c, respectively; EE(p i ,p r ,p c C1 represents the energy efficiency function of the D2D link; C2 represents the elements in the device access selection factor X matrix, which are binary variables; C3 represents the mode selection factor, which is also a binary variable; C4 represents the power constraints of the D2D transmitter, D2D relay, and multiplexed cellular equipment, respectively; and C5 represents the signal-to-interference-plus-noise ratio constraint. Let represent the wireless signal-to-noise ratio (SNR) and the wireless SNR threshold value between D2D transmitting device i and receiving device j, respectively. These represent the link radio signal-to-noise ratio (SNR) and the link radio SNR threshold value for multiplexed cellular device c in D2D relay communication mode, respectively. These represent the link radio signal-to-noise ratio (SNR) between transmitting device i and relay device c, and between relay device c and receiving device j, respectively, in D2D relay communication mode.

[0109] When D2D uses direct communication mode, the energy efficiency function of the D2D link is:

[0110]

[0111] In the above formula, P0 represents the circuit power value of the transmitting or receiving device in a D2D pair, and the achievable data rate between the transmitting device i and the receiving device j in D2D is... It can be calculated using Shannon's formula:

[0112]

[0113] In the above formula, BD This indicates the bandwidth of the D2D communication link. The wireless signal-to-noise ratio of the D2D pair is calculated by equation (4);

[0114] When D2D uses relay communication mode, the energy efficiency function of the D2D link is:

[0115]

[0116] In the above formula, These represent the achievable data rates between blind spot device i and relay device r, and between relay device r and D2D receiving device j, respectively, and are calculated using the following formulas:

[0117]

[0118] In the above formula, Let i and r represent the wireless signal-to-interference ratios (SIRs) between blind spot device i and relay device r, and between relay device r and D2D receiver j, respectively. Their calculation formulas are as follows:

[0119]

[0120] In the above formula, This represents the wireless channel gain from the D2D transmitter i to the relay device r. This represents the wireless channel gain from the relay device to the D2D receiver. The wireless channel gain at which the cellular device interferes with the D2D relay device r is... The wireless channel gain that causes interference to the D2D receiver j by cellular devices is: The above four channel gain calculation methods are calculated using the method in equation (3);

[0121] The above P optimization problem includes three sub-problems: device access, mode selection, and power allocation. The device access and mode selection sub-problems are solved in steps S1 and S2.

[0122] S902: When the communication mode of the D2D pairing between the blind spot device and the cooperative communication device is relay mode, the link energy efficiency between the D2D pairings is given by the minimum transmit power of the cellular device c for optimizing the link energy efficiency of the D2D pairing, according to the C2 condition of optimization problem P. for:

[0123]

[0124] In the above formula, the wireless channel gain that causes interference from the D2D transmitter to the base station is: This represents the minimum signal-to-interference ratio (SIR) between the D2D transmitter and receiver. This represents the minimum wireless signal-to-interference ratio (SIR) between the D2D multiplexed cellular device and the base station during relay mode communication.

[0125] S903: Based on the bottleneck effect of relay mode communication links, the link data rate between device i and device j in a D2D pair is: If and only if hour, The link efficiency of a D2D pair is maximized; at this point, the transmit power P of the relay device in the D2D pair is maximized. r for:

[0126]

[0127] S904: Order t = 1 + P i T, Δ1(t) = Lt - Ltlnt + 2P0T - L, using the Lambertian W function to solve for the value of t when Δ1(t) = 0, denoted as t0, then the optimized transmit power of D2D pairing is: but

[0128]

[0129] In the formula, W() is the Lamber W function;

[0130] S905: When the communication mode of the D2D pairing between the blind spot device and the cooperative communication device is relay mode, the link energy efficiency between the D2D pairings is as described in equation (14), then the optimized transmit power of the D2D pairing is

[0131] Step 10: Output the frequency band allocation and power allocation results of VLC AP coloring, the connection relationship between devices and VLC APs, set J; blind spot device set I, communication mode of blind spot devices, and connection matrix B for establishing D2D pairing. i,j And the transmit power values ​​for D2D equipment and relay repeater equipment.

[0132] The following is in conjunction with the appendix Figure 3 Detailed explanation of the execution process of the VLC device access method based on dot coloring of the present invention:

[0133] Input: Input device ID set M, VLC AP ID set N, then the number of devices |M|, the number of VLC APs |N|, the number of VLC APs that a device can be associated with S, and initialize the device-VLC AP association matrix A. m,n =[a m,n ] |M|×|N|=0, m∈M, n∈N, D2D blind spot device set I, access VLC AP device set J, m=1, optical signal-to-noise ratio threshold σ, optical signal-to-noise ratio between device m and each VLC AP n

[0134] Output: Association matrix A between devices connected to VLC APs m,n Sets I and J, and the frequency band allocation results for each VLC AP coloring;

[0135] Step 1: Divide the entire frequency band of the indoor VLC AP into the C band, where C = 4 in this invention;

[0136] Step 2: Initialize color number f = 1;

[0137] Step 3: Select any uncolored VLC AP n, n∈N, from the VLC AP set;

[0138] Step 4: Color f to VLC AP n and all non-adjacent uncolored VLC APs of VLC AP n;

[0139] Step 5: If all non-adjacent APs of VLC AP n have been colored f, then f = f + 1, go to step 3; otherwise, go to step 6.

[0140] Step 6: If all VLC APs have been colored, assign the same frequency band to the same color and different frequency bands to different colors according to the coloring results, and go to step 7; otherwise, if f = C, then f = f - 1, and go to step 3.

[0141] Step 7: Select device m from set J;

[0142] Step 8: If there is If n∈N, go to step 10; otherwise, go to step 9.

[0143] Step 9: Add the number of device m to the blind spot device set I, and delete the device from set J. Proceed to step 12.

[0144] Step 10: Store the VLC AP number n in the candidate VLC AP set G of device m. m In the case of set G m The VLC APs in the set G all have the same color. m Select the VLC AP n with the highest optical signal-to-noise ratio as the VLC AP to which device m connects, and let a m,n =1, proceed to step 12; otherwise, proceed to step 11;

[0145] Step 11: Determine set G mIf the number of elements in the set is less than the maximum number S that the device can associate with, then allow device m to connect to set G. m All candidate VLC APs are identified, and matrix A is set according to the candidate VLC AP number. m,n If the corresponding element value in set G is 1, proceed to step 12; otherwise, change the set G. m The top S VLC APs with the highest optical signal-to-noise ratio are associated with device m, and matrix A is set according to the candidate VLC AP numbers. m,n The values ​​of the elements at the corresponding positions are all 1, proceed to step 12;

[0146] Step 12: If m = |J|, the correlation matrix A of the output device connected to the VLC AP. m,n Set I and J, and output the frequency band allocation results for each colored VLC AP. Here, the frequency band allocation is represented by the f value; otherwise, let m = m + 1, and go to step 7.

[0147] The following is combined with Figure 4 Detailed explanation of the execution process of the socially aware D2D device access method of the present invention:

[0148] Input: A set of blind spot device IDs I, a set of device IDs J connected to the VLC AP, where the number of devices is |I| and |J| respectively, and the minimum rate requirement for all devices in sets I and J; set the D2D connection matrix B. i,j =[b i,j [ ] = 0, i∈I, j∈J, set the distance constraint value L for D2D pairing, and set the wireless signal-to-noise ratio threshold for D2D pairing. Let i be the set of relay forwarding devices. Set of candidate D2D devices for blind spot device i i∈I;

[0149] Output: Communication modes of all blind spot devices and connection matrix B for establishing D2D pairings. i,j , i∈I, j∈J.

[0150] Step 1: Select blind spot devices that have not yet established D2D pairing from the blind spot device set I, and record their number as i=1;

[0151] Step 2: Blind spot device i sends a "Hello" request message to devices in set J whose distance is less than L, requesting to establish a D2D cooperative connection through the radio frequency channel;

[0152] Step 3: According to equation (4), calculate the wireless signal-to-noise ratio of blind spot device i and device j in the set J where the distance is less than L. j∈J, if Then, neighboring device j sends a response message to blind device i, and stores device j in the candidate D2D device set N of blind device i. i middle;

[0153] Step 4: If Then, according to equation (12), the candidate D2D device set N is calculated sequentially. i The entropy weights and ratios (RSRs) of the centrality, stability, similarity, and social attribute factors between each candidate device j and the blind device i. j , j∈N i Proceed to step 5; otherwise, let R i =Ii, proceed to step 10;

[0154] Step 5: Based on N i The entropy weights and ratios of candidate devices are used to classify candidate devices into active devices, stable devices, and passive devices, starting from N. i In the process of screening out negative devices, the set of cooperative D2D candidate devices N for blind device i is updated. i Proceed to step 6;

[0155] Step 6: If i = |I|, go to step 7; otherwise, i = i + 1, go to step 2;

[0156] Step 7: For all if |N i |>0 of N i The set determines the blind spot device i and uses a direct connection mode with N. i The device establishes a connection based on |N i If the values ​​are sorted in ascending order, proceed to step 8; otherwise, proceed to step 10.

[0157] Step 8: Sequentially from set N i Select the cooperative device j that meets the minimum rate requirement of blind device i, and the cooperative device j with the highest energy efficiency calculated according to equation (14), and establish a direct connection mode for D2D pairing. i,j =1, proceed to step 9;

[0158] Step 9: Remove blind spot device i from set I, remove successfully paired D2D device j from set J, and set N... i Device j without D2D pairing is added to set R. i In the context of blind spot device i, the mode selection factor m i =0, proceed to step 12;

[0159] Step 10: Based on |R i | Values ​​sorted in ascending order R i The set of D2D devices with fewer candidate devices for relay forwarding is prioritized for D2D pairing, proceeding to step 11;

[0160] Step 11: Sequentially from set R i Select relay forwarding device r and cooperating device k, k∈J, r∈R, that meet the minimum rate requirement of blind device i and have the highest energy efficiency. i The energy efficiency calculation formula in relay mode is Equation (16). Establish a D2D relay connection between blind device i, relay device r, and cooperative device k, k∈J, and let B i,j element b i,r =b r,k =1, mode selection factor m for blind spot device i i =1, proceed to step 12;

[0161] Step 12: Output the communication mode m for all blind spot devices i And establish the connection matrix B for D2D pairing. i,j , i∈I, j∈J.

[0162] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A wireless optical communication method for socially aware indoor device collaboration blind spot access, characterized in that: The method includes the following steps: S1: Using the vertex coloring method in graph theory, different frequency bands are assigned to adjacent Visible Light Communication Access Points (VLC APs) to suppress inter-cell interference; based on the Lambertian radiation model of visible light communication, the visible light channel gain from the device to the VLC AP is determined, and the optical signal-to-noise ratio (SNR) from the device to each VLC AP indoors is calculated. The specific calculation method is: the optical transmit power of the VLC AP is multiplied by the optical channel gain, and then divided by the sum of the power of interference and noise; based on the free-idle wireless communication path loss model, the wireless channel gain between the device and other devices is determined, and the wireless SNR between the devices is calculated. The specific calculation method is: the transmit power of the device is multiplied by the wireless channel gain, and then divided by the sum of the power of interference and noise; based on the channel VLC AP coloring results, all VLC APs with the highest SNR for each color in the candidate VLC AP set are selected for each device in the indoor user set; S2: For blind spots in the indoor user set that are not connected to VLC APs, determine whether the wireless signal-to-noise ratio between the blind spot device and its neighboring devices is greater than a threshold. If so, establish a physical candidate cooperative communication device set for the blind spot device. Calculate the social attribute factors of centrality, stability, and similarity among the candidate cooperative communication devices. Use entropy weighting and ratio methods to evaluate the social relationship between the blind spot device and the candidate cooperative communication devices. Based on the evaluation values, divide the candidate cooperative communication device set into active, stable, and passive cooperative communication devices. Remove passive cooperative communication devices from the candidate cooperative communication device set to establish a socially aware device set. Use a socially aware device-to-device (D2D) access method to determine the communication mode of the D2D devices for cooperative communication of the blind spot device. S3: For devices in the user set that are connected to the candidate VLC AP set, the transmit power of each VLC AP in the VLCAP set is allocated using a fixed power average allocation algorithm; for devices in the user set that are not connected to the candidate VLC AP set, the energy efficiency of the D2D device pairing is calculated based on the D2D pairing communication mode between the blind device and the cooperative communication device, and the transmit power of the D2D transmitter is optimized based on the energy efficiency.

2. The wireless optical communication method for socially aware indoor device cooperation blind spot access as described in claim 1, characterized in that: The specific method of S1 is as follows: S101: Color 1 is applied to one of the VLC APs in the room and its non-adjacent VLC APs; color 2 is applied to one uncolored VLC AP and its non-adjacent VLC APs; if there are still uncolored VLC APs, color 3 is applied to one uncolored VLC AP and its non-adjacent VLC APs; if there are still uncolored VLC APs, color 4 is applied to one uncolored VLC AP and its non-adjacent VLC APs. S102: Determine if there are adjacent VLC APs with the same color. If yes, go to S101; otherwise, go to S103. S103: Count the number of colors used to color indoor VLC APs, mark them as C, divide the VLC communication spectrum into C frequency bands, and assign different frequency bands to VLC APs of different colors to avoid inter-cell interference; S104: Based on the Lambertian radiation model of visible light communication, determine the visible light channel gain from the device to the visible light communication access point, and calculate the optical signal-to-noise ratio from the device to each VLC AP indoors. The specific calculation method is: multiply the optical transmission power of the VLC AP by the optical channel gain, and then divide by the sum of the power of interference and noise; based on the free-idle wireless communication path loss model, determine the wireless channel gain between the device and other devices, and calculate the wireless signal-to-noise ratio between the devices. The specific calculation method is: multiply the transmission power of the device by the wireless channel gain, and then divide by the sum of the power of interference and noise. S105: If the optical signal-to-noise ratio (SNR) from the device to any VLC AP in its candidate VLC AP set is greater than the threshold, or the optical SNR from the device to its associated candidate VLC AP is less than the threshold, but the interruption time is less than the optimal waiting time T. * If the device is found to be in the candidate VLC AP set, it is saved in the candidate VLC AP set; otherwise, the device is removed from the candidate VLC AP set and saved in the blind spot device set. S106: Based on the device communication request rate held by the user, calculate the device communication request rate divided by the minimum rate value in the user's device set, and round the result up to the nearest integer to obtain the number of VLC APs that the device requests to associate, denoted as S; Check the coloring of each VLC AP in the candidate VLC AP set of the device. If the coloring of all candidate VLC APs of the device is different, the device connects to the top S VLC APs with the highest optical signal-to-noise ratio. If candidate VLC APs have the same color, the device selects the S VLC APs with different colors and the highest optical signal-to-noise ratio for each color.

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