CN112821950B

CN112821950B - Visible light communication networking method

Info

Publication number: CN112821950B
Application number: CN202110014178.1A
Authority: CN
Inventors: 侯玉柱; 赵志庆; 苏国正; 丁英莲; 陈宇
Original assignee: Tianjin Rongxing Group Co ltd
Current assignee: Tianjin Rongxing Group Co ltd
Priority date: 2021-01-06
Filing date: 2021-01-06
Publication date: 2022-08-12
Anticipated expiration: 2041-01-06
Also published as: CN112821950A

Abstract

The invention discloses a visible light communication networking method, which adopts a two-stage superframe structure and dynamically allocates time slots according to service types, and comprises the following steps: first, downlink crosstalk: setting a scheduling center to realize a global time synchronizer in the whole network, dividing the scheduling center into a plurality of time slots according to the maximum number of adjacent lamp groups in a room, and selecting different time slots for the adjacent lamp groups to transmit data containing beacon frames; II, uplink crosstalk: according to the neighbor information reported by the terminal, if the AP judges that the terminal is in the crosstalk area, acquiring the CAP time slot allocation condition of the adjacent AP, and allocating a CAP time slot which is not occupied in all the adjacent APs where the terminal is located to the terminal; when the AP terminal moves from the non-crosstalk area to the crosstalk area or from the crosstalk area to the non-crosstalk area, the AP terminal adjusts a GTS allocation scheme in real time; thirdly, dynamic time slot allocation is adopted: 1) allocating downlink superframe time slots; 2) and uplink superframe time slot allocation, namely, the AP allocates time slots according to the number of the devices and the area information of the devices in the VPAN.

Description

Visible light communication networking method

Technical Field

The invention relates to the field of visible light communication, in particular to a visible light communication networking method.

Background

In recent years, visible light communication (LiFi) technology based on illuminating white light LEDs has received wide attention from scholars at home and abroad. In the face of the rapid increase of mobile traffic and the problem of crowded radio frequency spectrum used by the conventional communication technology, the communication technology such as WiFi is gradually becoming increasingly popular and is not apprehended, and under such a situation, the visible light communication technology using the visible light band carrier for communication gradually becomes a research hotspot along with the continuous expansion of the LED market. Compared with the WiFi technology, the visible light communication is a green communication technology, has the congenital advantages of free frequency spectrum, high speed, low cost, good confidentiality, no electromagnetic interference and the like, LiFi has the characteristics of rich frequency spectrum resources, good communication confidentiality, low layout cost and the like, and LiFi also has higher communication speed under the laboratory condition. In the aspect of spectrum resources, radio frequency spectrum resources are becoming less and less along with the development of mobile communication, while visible light spectrum width is more than ten thousand times of radio frequency spectrum, and sufficient spectrum resources are provided; in confidentiality, LiFi can not be transmitted when being blocked by an object, and the safety problem caused by WiFi wall penetration is avoided; in the aspect of layout, the network layout can be completed by configuring or using the lamp with visible light communication capacity when the LED lamp is installed, and the layout is more convenient than WiFi (wireless fidelity) layout; in a laboratory, the transmission rate of LiFi can reach 1Gbps, and is greatly improved compared with WiFi.

However, the development and deployment of high-speed large-coverage visible light communication systems still face many challenges, such as the small modulation bandwidth of commercial white light LEDs, difficulty in meeting communication requirements, and the small coverage of a single node, which may cause serious mutual interference when the system is solved by dense networking.

Disclosure of Invention

In view of the problems that the traditional visible light time division multiplexing positioning system is too long in time delay and easy to generate clock synchronization errors, and in order to meet the requirements of high-precision real-time positioning, improve the system capacity and solve the problem of interference of adjacent cells in networking, the invention provides a visible light communication networking method, which can effectively improve the capacity of the whole network system and effectively solve the problem of interference of the adjacent cells, and is described in detail in the following description:

a visible light communication networking method adopts a secondary superframe structure and dynamically allocates time slots according to service types, and the method comprises the following steps:

first, downlink crosstalk: setting a scheduling center to realize a global time synchronizer in the whole network, dividing the scheduling center into a plurality of time slots according to the maximum number of adjacent lamp groups in a room, and selecting different time slots for the adjacent lamp groups to transmit data containing beacon frames;

II, uplink crosstalk: according to the neighbor information reported by the terminal, if the AP judges that the terminal is in the crosstalk area, acquiring the CAP time slot allocation condition of the adjacent AP, and allocating a CAP time slot which is not occupied in all the adjacent APs where the terminal is located to the terminal; when the AP terminal moves from the non-crosstalk area to the crosstalk area or from the crosstalk area to the non-crosstalk area, the AP terminal adjusts a GTS allocation scheme in real time;

thirdly, dynamic time slot allocation is adopted: 1) downlink superframe time slot allocation, namely, according to the real-time requirement of the service, dividing different services into: real-time voice service, voice broadcast service, and general data; 2) and uplink superframe time slot allocation, namely, the AP allocates time slots according to the number of the devices and the area information of the devices in the VPAN.

The method for adjusting the GTS allocation scheme in real time at the AP end specifically comprises the following steps:

when the signal intensity of the sub-network is gradually weakened, and a new sub-network signal is gradually strengthened after being received and is strengthened to the threshold value, the terminal initiates a network switching request to join the sub-network with good signal intensity, and the GTS of the terminal is redistributed by the new sub-network AP.

Further, the step of the AP performing timeslot allocation according to the number of devices and the area information included in the VPAN specifically includes:

(1) if the crosstalk zone has no equipment, distributing all time slots of CAP and CFP according to the resource proportion of each equipment service type in the non-crosstalk zone;

(2) if the crosstalk zone has equipment, and the adjacent AP has no equipment processing, the step (1) is performed;

(3) if the crosstalk zone has equipment and the equipment of the adjacent AP is in the non-crosstalk zone, the CFP time slot is distributed to all the equipment in the non-crosstalk zone according to the resource proportion of the service type, and the CAP time slot is distributed to all the equipment in the crosstalk zone according to the resource proportion of the service type;

(4) if the crosstalk zone has equipment and the equipment of the adjacent AP is in the crosstalk zone, the CFP time slot is distributed to all the equipment according to the resource proportion of the service type, and the CAP time slot is not distributed or is distributed after being cooperated with the adjacent AP;

(5) if the crosstalk area has equipment and the crosstalk area and the non-crosstalk area of the adjacent AP have equipment, the CFP time slot is allocated to the equipment in the non-crosstalk area according to the resource proportion of the service type, and the CAP time slot is allocated to the equipment in the crosstalk area after cooperating with the adjacent AP.

Wherein the method further comprises: allocating CFP time slots in the superframe to terminals which are not in the crosstalk area; and monitoring the signal intensity of each path of VPAN, and actively initiating a network switching request by the terminal when the signal intensity of the subnet where the VPAN is located is gradually weakened, the signal intensity of other VPAN is gradually strengthened and reaches a certain threshold value.

The technical scheme provided by the invention has the beneficial effects that:

1) the invention provides a novel time division mechanism for solving the mutual crosstalk in the communication of adjacent APs (coordinators), which can effectively avoid the occurrence of crosstalk;

2) the invention adopts a two-stage superframe structure, solves the problem of uplink and downlink crosstalk, and simultaneously dynamically allocates time slots according to service types, thereby effectively ensuring the problem of reasonable resource allocation when the densities of adjacent AP terminals are different;

3) through tests, the invention effectively improves the equipment capacity in the visible light time division multiplexing positioning system, reduces the waste of bandwidth resources and improves the performance of the visible light time division multiplexing positioning system by more than 30%.

Drawings

FIG. 1 is a schematic diagram of a lamp group layout and terminal location;

fig. 2 is a schematic diagram of time slot allocation of an AP scheduled by a scheduling center;

fig. 3 is a schematic diagram of a mechanism for an AP to schedule a plurality of terminal devices within its area;

fig. 4 is a diagram illustrating a superframe structure of an AP;

FIG. 5 is a flow chart of the AP and neighboring AP coordination mechanism;

FIG. 6 is a schematic diagram of the areas of CAP (contention access period) and CFP (non-contention access period);

fig. 7 is a functional block diagram of an AP-side MAC (medium access control) layer;

fig. 8 is a diagram illustrating a MAC layer function module of the terminal.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below.

Because the adjacent APs have overlapping coverage areas to ensure seamless coverage of indoor lighting, the terminal equipment in the area can receive signals sent by a plurality of APs, interference occurs at the moment, and the uplink path also has interference. As shown in fig. 1, the

circles

1, 2 and 3 are AP, and AP1, AP2 and AP3 respectively create VPAN1, VPAN2 and VPAN 3; and the numbers of the

triangles

1, 2, 3, 4 and 5 are terminal equipment. The terminal 3 and the terminal 4 are in the coverage of a plurality of VPANs (personal area networks for visible light communication), the AP2 and the AP3 will interfere with the terminal 4 when transmitting data simultaneously, and the terminal 4 will also interfere with the AP2 or the AP3 when transmitting uplink data, so that each AP needs to be considered comprehensively when allocating time slots and cooperates with neighboring APs.

In order to solve the message crosstalk, the following measures are taken comprehensively by the embodiments of the present invention, which are described in detail below:

first, downstream crosstalk

A scheduling center is arranged in the whole network to realize a global time synchronizer, and the scheduling center is arranged as shown in fig. 2:

the dispatching center is divided into a plurality of time slots according to the maximum number of adjacent lamp groups in the room, and the adjacent lamp groups select different time slots to send data containing beacon frames. The flow of the mechanism by which the AP schedules multiple terminal devices within its area is shown in fig. 3.

Second, upstream crosstalk

A VPAN superframe is divided into CFP and CAP regions (see fig. 4), where the CFP describes a time slot allocation table of a device in a region without inter-cell crosstalk, the CAP describes a time slot allocation table of a device in a crosstalk region, and an allocation ratio of the CFP to the CAP is determined according to a probability allocation ratio of actual distribution of terminals in a system, which is not limited in this embodiment of the present invention.

Wherein, the time slot allocation in CAP phase needs to cooperate with the neighboring AP, and the detailed time slot control flow in a single VPAN is shown in fig. 5. Therefore, the crosstalk of the uplink data to the adjacent AP can be effectively avoided.

The specific processing flow is as follows:

1) according to the neighbor information reported by the terminal, the AP judges whether the terminal is in the crosstalk area or not, and allocates CFP time slots in the superframe to the terminals which are not in the crosstalk area; if the terminal is in the crosstalk area, the CAP time slot allocation condition of the adjacent AP is obtained, and a CAP time slot which is not occupied in all the adjacent APs where the terminal is located is allocated to the terminal.

In order to simplify the design, the time lengths of all terminal timeslots in the CAP are set to 1 in the embodiment of the present invention, and in the specific implementation, the time lengths may also be set according to the needs in the practical application, which is not limited in the embodiment of the present invention.

2) When the terminal moves from a non-crosstalk area to a crosstalk area or from the crosstalk area to the non-crosstalk area, the AP needs to adjust a GTS (guaranteed time slot) allocation scheme in real time.

Wherein, the allocation scheme may be: and the terminal judges the signal receiving intensity, when the signal intensity of the sub-network where the terminal is located is gradually weakened, and simultaneously, the signal intensity of the new sub-network is gradually strengthened, and after the signal intensity is strengthened to a certain threshold value, the terminal initiates a network switching request to join the sub-network with good signal intensity, and the GTS of the terminal is redistributed by the new sub-network AP.

In specific implementation, the threshold is not limited in the embodiment of the present invention, and is set according to requirements in practical application.

Capacity problem of visible light time division multiplexing system

Under the condition of a complex network, the traditional time division multiplexing has the condition of a large amount of resource waste, and the capacity of the whole communication system is limited. The embodiment of the invention adopts a dynamic time slot allocation mode and can support equipment terminals with large data volume.

1) Downlink superframe time slot allocation

According to the real-time requirement of the service, different services are prioritized: real-time voice service, voice broadcast service, and general data type 3.

The priority of real-time voice service is highest, the priority of voice broadcast service is second, the priority of common data is lowest, and the 3 kinds of service resource allocation ratio is configured according to the principle of 3:2: 1. And the scheduling center performs overall allocation of the time slot resources of each AP according to the resource demand proportion of all the equipment in the VPAN under the name of each AP.

2) Uplink superframe time slot allocation

The AP carries out time slot allocation according to the number of the equipment and the area information contained in the VPAN:

(1) if the crosstalk zone has no equipment, distributing all time slots of CAP and CFP according to the resource demand proportion of each equipment service type in the non-crosstalk zone;

wherein, the resource proportion is as follows: for example, the real-time voice service, the voice broadcast service, and the general data type 3 service resource allocation ratio described above are allocated on the 3:2:1 basis. The embodiment of the present invention does not limit the above ratio, and is set according to the requirements in practical application.

(2) If the crosstalk area has equipment and the adjacent AP has no equipment, the processing is the same as the step (1);

(4) if the crosstalk zone has equipment and the equipment of the adjacent AP is in the crosstalk zone, the CFP time slot is distributed to all the equipment according to the resource proportion of the service type, and the CAP time slot is not distributed or is distributed after cooperating with the adjacent AP;

3) And (3) terminal processing flow:

a reporting module of the adjacent AP and the crosstalk area: when a terminal receives beacon frames of a plurality of VPANs, the terminal judges that the terminal is currently in a crosstalk area of the plurality of VPANs, and at the moment, the terminal needs to report to an AP of a subnet where the terminal is located, and reports the relation of adjacent APs;

data reception: performing deframing operation on data received from an optical link to form a complete data frame, checking the complete data frame without errors, and sending the complete data frame to a data processing module for processing; a data processing module: framing data to be sent through an optical link, and then uniformly sending the data;

and (3) signal intensity monitoring: and monitoring the signal intensity of each path of VPAN in real time, and actively initiating a network switching request by the terminal when the signal intensity of the subnet where the VPAN is located is gradually weakened, the signal intensity of other VPAN is gradually strengthened and reaches a certain threshold value.

In specific implementation, the threshold is not limited in the embodiment of the present invention, and is set according to the needs of practical application.

The following describes a method for visible light communication networking according to an embodiment of the present invention with reference to specific examples, in which:

the embodiment of the invention aims at networking scheduling in the field of visible light communication, and a typical engineering layout is shown in fig. 6. Wherein the downlink is a visible light link, and the uplink is an infrared link; the AP is directly connected with the dispatching center through a wired network, and the terminal is communicated with the AP through an optical link.

After deployment is completed, each AP reports the state, the dispatching center distributes the ID of the VPAN, each AP creates the VPAN and periodically sends a beacon frame, and each terminal requests to access the network and reports the information of the terminal and the information of the adjacent AP in a competition access mode after receiving the beacon frame. Fig. 7 shows a system control module structure of the AP, and fig. 8 shows a terminal system control module structure.

Selecting a network source central node through cell division; by applying for the time slot section in a competition manner and repeatedly utilizing partial time slot sections, the contradiction between the frame length and the number of the LED nodes is solved.

Simulation results show that the networking method provided by the embodiment of the invention can effectively reduce the influence of target movement and clock synchronization errors on positioning accuracy, effectively improve the system capacity and improve the real-time performance and the robustness of an indoor communication/positioning system.

In the embodiment of the present invention, except for the specific description of the model of each device, the model of other devices is not limited, as long as the device can perform the above functions.

Those skilled in the art will appreciate that the drawings are only schematic illustrations of preferred embodiments, and the above-mentioned serial numbers of the embodiments of the present invention are only for description and do not represent the merits of the embodiments.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A visible light communication networking method is characterized in that the method adopts a two-level superframe structure and dynamically allocates time slots according to service types, and the method comprises the following steps:

thirdly, dynamic time slot allocation is adopted: 1) downlink superframe time slot allocation, namely dividing different services into: real-time voice service, voice broadcast service, and general data; 2) uplink superframe time slot allocation, namely, the AP allocates time slots according to the number of the equipment and the area information of the equipment in the VPAN;

the scheme for adjusting the GTS allocation in real time at the AP end specifically comprises the following steps:

when the signal intensity of the sub-network is gradually weakened, and a new sub-network signal is gradually strengthened after being received and is strengthened to a threshold value, the terminal initiates a network switching request to join the sub-network with good signal intensity, and the GTS of the terminal is redistributed by a new sub-network AP;

the specific time slot allocation performed by the AP according to the number of devices and the location information included in the VPAN is as follows:

(2) if the crosstalk area has equipment, and the adjacent AP has no equipment to process the same step (1);

2. The visible light communication networking method of claim 1, wherein the method further comprises: and allocates CFP slots in the superframe to terminals not in the crosstalk zone.

3. The visible light communication networking method of claim 1, wherein the method further comprises: and monitoring the signal intensity of each VPAN, and actively initiating a network switching request by the terminal when the signal intensity of the subnet in which the terminal is located is gradually reduced, the signal intensity of other VPANs is gradually increased and reaches a threshold value.