CN111431597B

CN111431597B - Internet of vehicles data communication network and method based on retro-reflection device communication

Info

Publication number: CN111431597B
Application number: CN202010234098.2A
Authority: CN
Inventors: 许辰人; 冯立磊; 沈国斌
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2020-03-27
Filing date: 2020-03-27
Publication date: 2021-05-28
Anticipated expiration: 2040-03-27
Also published as: CN111431597A

Abstract

The invention relates to a vehicle networking data communication network and a method based on retro-reflective communication, the network comprises a read-write device arranged on a vehicle and a retro-reflective device arranged on the vehicle and/or an infrastructure for passive communication, at least one read-write device establishes an optical communication link with at least one retro-reflective device by transmitting a first optical signal and a second optical signal with at least two different frequencies, the first optical signal monitors any continuous communication session of at least one retro-reflective device in the communication range of the read-write device in a continuous transmission mode to reduce the asynchronous uplink communication link collision probability, the second optical signal is transmitted by the read-write device to the retro-reflective device after the read-write device stops transmitting the first optical signal and enters a first state for discovering the retro-reflective device to avoid a synchronous uplink collision and/or a second state for querying the retro-reflective device to avoid an asynchronous uplink collision.

Description

Internet of vehicles data communication network and method based on retro-reflection device communication

Technical Field

The invention belongs to the technical field of communication, relates to a data communication network and a method suitable for an internet of vehicles, and particularly relates to a data communication network and a method based on retro-reflection communication for the internet of vehicles.

Background

The Visible Light Communication (VLC) technology is a Communication method in which Light in a Visible Light band is used as an information carrier, and an optical signal is directly transmitted in the air without using a transmission medium such as an optical fiber or a wired channel. Compared with Wi-Fi, Bluetooth, cellular network and other communication technologies based on radio signals, the visible light communication technology has the natural advantages of less signal interference, eavesdropping prevention, large available bandwidth and the like. The most common visible Light communication technology is based on fast on-off modulation of Light Emitting Diodes (LEDs) as a basic unit of a signal source, and increases the intensity and diversity of the signal source by providing a large display screen, lighting equipment, signal lamps and automobile front tail lamps indoors and outdoors, and finally receives and demodulates information carried in the Light signal by using a photoelectric conversion device such as a photodiode. Based on the characteristics and the working principle, the visible light communication can play an important role in the application based on the technology of the internet of things, and especially can be used for the two-way communication in the scenes such as between the car light and the infrastructure (roadblocks, guideboards and the like) and between the indoor ceiling light and the equipment of the internet of things in the automatic driving process.

For example, chinese patent publication No. CN109450536A discloses a vehicle internet of things system and a communication method based on visible light communication, wherein the provided system includes: the vehicle-mounted visible light communication node is used for acquiring vehicle information, constructing a visible light communication link with the vehicle-mounted visible light communication node on the adjacent vehicle in the same driving direction of the vehicle to which the vehicle-mounted visible light communication node belongs, and generating vehicle cluster information of a vehicle cluster consisting of the visible light communication links; the roadside infrastructure is used for receiving vehicle information and vehicle cluster information sent by the vehicle-mounted visible light communication nodes in the coverage range and sending the vehicle information and the vehicle cluster information to the local control nodes; and the local control node is used for receiving the vehicle information and the vehicle cluster information in the coverage range of the roadside infrastructure, which are sent by the roadside infrastructure, and calculating and obtaining the road condition information in the area according to the vehicle information and the vehicle cluster information. The system provided by the invention reduces the conflict and interference among communication links in the vehicle Internet of things. The patent utilizes the characteristics that the visible light communication is mainly direct path and is easy to be isolated to reduce the conflict and the interference between different communication links, and the specific implementation mode is realized by directional communication between a lens and a receiver array. However, there are two main problems to realize practical visible light communication in the above-mentioned car networking application scenario. First, the light-emitting angular range of a general-purpose LED and the angular range of photo-conversion devices sensitive to light are limited, which requires that two devices need to be perfectly aligned for two-way communication. Second, from the design concept, economic cost and operation and maintenance point of view, it is desirable that the internet of things device is miniaturized, low in power consumption and even passive. The energy consumption of communication emission based on the LED is usually hundreds of milliwatts, and the effective electric energy converted by a solar battery with the size of the Internet of things equipment is usually only hundreds of microwatts, so that the lens and the receiver array are used for realizing visible light communication, and not only is the power supply with higher power needed, but also the high cost is needed for realizing the layout transformation of road infrastructure. In addition, the use of lenses can align the beams of light, thereby fulfilling the objective requirement that two-way communication require perfect alignment of the two devices, and the high degree of alignment and orientation characteristics allow the communication link between the two devices to be easily isolated, thereby providing an objective condition for avoiding interference between adjacent devices. However, this sensitive isolated property also presents a serious challenge to the Mobility (Mobility) and Scalability (Scalability) of one-to-many communication of its devices, especially communication between a vehicle and a fixed infrastructure, which is easily disturbed by the surrounding environment and cannot be realized effectively in time.

Document [1] Jiangtao Li, Angli Liu, Guobin Shen, Liqun Li, Chao Sun, and Feng Zhao.Retro-vlc: energy basic-free multiplex Visible Light Communication for mobile and iot applications. in ACM HotMole, 2015. and document [2] Xieyang Xu, Yang Shen, Jun Yang, Chen Xu, Guobin Shen, Guo jun Chen, and Yunzhe Ni. Passivev lc: energy reactive Visible Light Communication for basic-free applications. in ACM, 2017. disclose a back-lighting Communication system (VLB) that modulates reflected Light by means of a reflex/switch-on LCD and modulates reflected Light by means of a vehicular switch (BC) to adjust the reflected Light state of the reflected Light. The VLBC system consists of a high power reader and a low power optical tag. The working principle is as follows: the LEDs in the reader/writer are turned on and off at a high frequency, so that the light emitted by the LEDs serves as a carrier for information, i.e. data information is modulated onto the carrier (light) in an on and off manner. The optical signal is received and decoded by an optical sensor on the optical label. For the uplink (communication link for the cursor to check-in to the vehicle reader), transmission is performed by reflecting the same carrier wave. The optical label transmits the reflected light after OOK modulation, and the modulation mode is realized by a drive which is controlled by a single chip microcomputer and arranged on the reflecting fabric. The reflected light carrier is then received or modulated by a photodiode on the vehicle reader and further demodulated and decoded. Document [1] demonstrates the feasibility of applying VLBC technology to car networking communication over short distances, solves the problems of mobility, scalability and camera unfriendliness of communication equipment, and is low in cost (passive operation) and capable of phased deployment.

However, in a many-to-many communication scenario, that is, when a plurality of optical tags exist within the communication range of a plurality of readers/writers, the communication efficiency between the plurality of readers/writers and the plurality of optical tags is reduced. Specifically, the reader/writer is generally installed on a vehicle moving at a high speed, and the optical tags are installed on infrastructure on both sides of a road to form a retro-reflection device, such as a street lamp, a road block, a traffic sign, a stop lever, and the like, so that the optical tags are relatively sparsely distributed in most cases, and there is a case where one reader/writer communicates with one optical tag. However, in urban areas, there are many road infrastructures, optical tags are distributed relatively densely, and a plurality of optical tags are distributed in the communication range of a plurality of vehicle readers, so that a many-to-many communication scene occurs. Similarly, when the traffic volume of a road is small, there may be a case where only one reader/writer communicates with a plurality of optical tags, and when the traffic volume is large, the same optical tag may exist in the communication range of the plurality of reader/writers at the same time. In more extreme cases, there are multiple optical tags within the sensing range of the optical sensor of one reader/writer. The VLBC-based car networking system works in such a way that the optical label starts to work after receiving the optical signal transmitted by the reader-writer, modulates and transmits the optical signal transmitted by the reader-writer, so that the communication between the reader-writer and the optical label has a high spatial orientation characteristic, i.e., the reader-writer cannot sense other reader-writers and other optical labels, and the optical label in communication with the reader-writer cannot sense other reader-writers and optical labels. The highly directional communication characteristic of the VLBC communication system can cause a serious hidden terminal problem in many-to-many communication scenarios, that is, in the communication field, a base station a sends a signal to a base station B, and a base station C does not detect that a sends the signal to B, so that a and C send the signal to B at the same time, causing signal collision, and finally causing all signals sent to B to be lost. In addition to this, the highly directional communication characteristic also makes it impossible for the reader to passively monitor other readers engaged in communication sessions within their communication range. When a plurality of readers communicate with one optical tag at the same time or a plurality of optical tags communicate with a plurality of readers at the same time, serious communication link collision will be caused.

The document [3] schlihui-MAC protocol study of visible light communication [ J ]. mobile communication, 2014(3-4):76-81 describes in detail the Medium Access Control (MAC) protocol for visible light communication in the IEEE 802.15.7 standard, which designs the MAC protocol for the defect that the visible light highly spatially oriented property (visible light signals cannot cross obstacles) and the carrier sense in the visible light network do not have the same robustness as the radio frequency network. The standard defines the functions of the MAC protocol in detail, such as channel access, establishment and maintenance of personal area networks, synchronization, data transmission, reception and acknowledgement, allocation and management of guaranteed time slots, fast link recovery, multi-channel resource management, color functions and standardization, etc. The MAC protocol in this standard discloses six aspects of functionality, including:

1. two channel access mechanisms: contention-based and contention-free; the contention-based access allows the device to access the channel during a contention period using a random back-off algorithm, and the contention-free access completely uses the guaranteed time slot during the contention-free period through the coordinator. In the carrier sense multiple access with collision avoidance mechanism for time slots in IEEE 802.15.7, the MAC sublayer first initializes two variables: backoff number and backoff index. When the medium is busy, namely under the condition that a hidden terminal appears, the random back-off algorithm enables the communication terminal to try to quit, and a random waiting time is created for the transmission of signal data of the communication terminal, so that the conflict is avoided.

2. And starting and maintaining the PAN, selecting an appropriate logical channel and a PAN identifier which is not occupied in the visible light coverage range through channel scanning, and taking the selected equipment as a coordinator.

3. Devices join and leave a PAN, and the association process describes how devices join or leave a PAN and how the coordinator implements the process of joining or leaving a PAN.

4. Data transmission, reception and acknowledgement mechanisms, in order to describe the problem of transmitting frames, acknowledging frames, and resolving duplicate frames, a physical frame encapsulates multiple MAC frames with the same destination address and acknowledges the frames with one acknowledgement frame.

However, for VLBC-based car networking systems, the MAC protocol in the IEEE 802.15.7 standard does not apply. Firstly, the MAC protocol provided by the standard supports carrier sense multiple access, which is a function of monitoring the use of a channel before sending data, and after a certain period of time, waiting for a random period of time before sending data after the channel is still idle. By setting different random times for each device, the chance of collisions is reduced. However, in the VLBC-based communication system in the internet of vehicles, in addition to the fact that the communication between the reader-writer and the optical tag has a high spatial orientation characteristic, the optical tag is still passive communication, and therefore the reader-writer and the optical tag cannot sense the existence of other reader-writer and optical tag, which causes the problem that the reader-writer cannot avoid hiding the terminal by adopting a carrier sense mode, and the existing method for releasing the hidden terminal, such as increasing the transmission power, adjusting the carrier sense threshold value, and the like, is not in accordance with the design concepts of low power consumption and low cost of the internet of vehicles, and secondly, cannot solve the synchronous or asynchronous conflict of the uplink communication link.

Document [4] random access algorithm research and performance optimization of a multi-packet receiving VLC system [ D ] jilin university, 2017. a new random access algorithm is proposed based on a carrier sense multiple access mechanism with collision avoidance of IEEE 802.15.7 time slots, considering the situation that the number of active terminals in the system cannot be known a priori by a coordinator due to the high spatial orientation characteristic of an optical signal, underload carrier sense, and the number of active terminals in the system, the document [4] estimates the number of active terminals at the coordinator side to provide the coordinator with the number of active terminals of the system, and a receiving end establishes an optimization problem according to the acquired information of the number of active terminals, adjusts multi-packet receiving capability and backoff parameters, balances system throughput and receiving power efficiency, and realizes optimization of system performance to the maximum extent. However, the multi-packet reception proposed in the document [4] may increase the energy consumption of the receiving end, and a coordinator is always required to estimate the number of active terminals, however, in the vehicle networking system based on the VLBC technology, the reader/writer and the optical tag cannot sense other reader/writer and optical tag, that is, there is no coordinator, so the method provided in the document [4] is not suitable for the vehicle networking data communication system based on the VLBC technology.

Furthermore, although optical labels based on retro-reflection principles have local broadcast properties, location specific information can be conveyed to readers and writers on all oncoming vehicles, and the retro-reflection based LCD modulation design also conforms to the local broadcast properties of optical labels. In fact, the switching of the liquid crystal state will affect all incident light, regardless of its source and carrier frequency. Therefore, the prior art tends to provide a periodic broadcast beacon mechanism for data network messaging based on retro-reflective communication. But this is not the case: when the reader/writer considers that there are a plurality of optical tags, the responses of the plurality of optical tags are deemed to collide with each other. That is, all nearby optical labels are potential colliders. However, it is almost impossible to statically coordinate multiple optical labels for the following reasons. First, due to the need for no battery, optical labels are designed to be passive, i.e. they cannot sense the presence of other optical labels nearby. Secondly, the distance between the reader and the optical label is highly dynamic due to the mobility of the reader (i.e. different positions) and the diversity of the headlight power (i.e. different viewing ranges). Finally, to save power, optical labels may sleep from time to time and may be activated at different times, making it very difficult to maintain a global clock and ensure clock synchronization between nearby optical labels.

In summary, there is a need to design a retro-reflective communication based vehicle networking data communication network and method that can coordinate multiple optical labels to avoid communication link collisions.

Furthermore, on the one hand, due to the differences in understanding to the person skilled in the art; on the other hand, since the inventor has studied a lot of documents and patents when making the present invention, but the space is not limited to the details and contents listed in the above, however, the present invention is by no means free of the features of the prior art, but the present invention has been provided with all the features of the prior art, and the applicant reserves the right to increase the related prior art in the background.

Disclosure of Invention

A vehicle networking data communication network based on retro-reflective communication at least comprises a read-write device arranged on a vehicle and a passive communication retro-reflective device arranged on the vehicle and/or an infrastructure. The retro-reflecting device communicates with the read-write device in a retro-reflecting manner to construct the Internet of vehicles. At least one read-write device establishes an optical communication link with at least one retro-reflective device by transmitting first and second optical signals at least two different frequencies. By this way, the use of two different frequency optical signals for collision detection and for discovery and validation of retro-reflective devices, respectively, can avoid confusion between the data packets transmitted by the two signals to interfere with the monitoring of communication link collisions.

The first optical signal is continuously transmitted to monitor any ongoing communication session of at least one retro-reflective device within communication range of the reader/writer device to reduce asynchronous uplink collision probability. By the arrangement mode, the non-interference carrier monitoring technology can be realized under the VLBC technology, the power of a transmitting signal or the threshold value of carrier monitoring is not required to be increased, and the carrier monitoring under low power is realized by utilizing the space orientation characteristic of the optical signal height and the passive communication characteristic of the retro-reflection device. For example, if a retro-reflecting device responds to a first optical signal sent by a first read-write device by modulating the charge-discharge state of a liquid crystal material of an LCD, then when a second read-write device is continuously sending the first optical signal, the first optical signal sent by the second read-write device is also modulated, which enables the second read-write device to sense an ongoing communication session between the first read-write device and the retro-reflecting device, so that the busy or idle state of an optical communication link between the read-write device and the retro-reflecting device can be simply, effectively and quickly determined by carrier sense.

The second optical signal is transmitted by the read-write device to the retro-reflective device after the read-write device stops transmitting the first optical signal and enters a first state for discovering the retro-reflective device to avoid a synchronous uplink collision and/or a second state for querying the retro-reflective device to avoid an asynchronous uplink collision. Through the setting mode, the reading-writing device can decode according to the second optical signal fed back by at least one retro-reflection device, so that the problem of hiding the terminal is further solved by converting different states, especially, the reading-writing device and the retro-reflection device cannot sense the existence of other reading-writing devices and retro-reflection devices except that the unicast communication between the reading-writing device and the retro-reflection device has high space orientation characteristics, namely, the reading-writing device and the retro-reflection device cannot know the retro-reflection device in an activated state in the VLBC system through the setting coordinator, and the problem of hiding the terminal is further solved by finding the first state of the retro-reflection device and inquiring the second state of the retro-reflection device.

A retro-reflective communication based internet of vehicles data communication network comprising at least: a read-write device arranged on the vehicle and a retro-reflection device arranged on the vehicle and/or the infrastructure. The read-write device is capable of establishing a stable continuous optical communication link with the retro-reflective device, at least over a period of time and space. At least one read-write device establishes an optical communication link with at least one retro-reflective device by transmitting first and second optical signals at least two different frequencies. The first optical signal is used to monitor any ongoing communication session of the retro-reflective device to confirm an idle or busy status of a communication link between the read-write device and the retro-reflective device, and if the communication link is in the idle status, the read-write device enters the first state and/or the second state to transmit a second optical signal comprising at least data packets that passively and dynamically assign a virtual ID to at least one retro-reflective device over the time and space to avoid uplink and downlink communication link collisions. Through the setting mode, under the condition that a coordinator is not additionally arranged, a passive dynamic mode is utilized to allocate the virtual ID which is special for each read-write device, so that under the condition that the read-write device and the retro-reflection device cannot sense other read-write devices and retro-reflection signposts, collision detection and processing of an up-and-down communication link are realized, and the problem that normal information interaction cannot be realized due to the hidden terminal problem is avoided.

According to a preferred embodiment, when the reader/writer device transmits the first optical signal to at least one retro-reflecting device within its communication range, the reader/writer device is configured to monitor the signal and determine that the optical communication link between the reader/writer device and the retro-reflecting device is in a busy state, so that the reader/writer device maintains a state of continuously transmitting the first optical signal to find the retro-reflecting device within its communication range capable of establishing the optical communication link in an idle state.

According to a preferred embodiment, the read-write device switches to the first state in case the read-write device determines that the optical communication link with the retro-reflecting device is in an idle state. The read-write device transmits a second optical signal comprising at least the first payload to the at least one retro-reflective device. In the case where the optical communication links of at least two retro-reflecting devices and the read-write device are in an idle state, the read-write device passively and dynamically allocates a virtual ID to each retro-reflecting device based on the number of retro-reflecting devices and constructs a virtual ID candidate list. So that the read-write device sequentially sends the second optical signals of the first load at least comprising the virtual ID information to the retro-reflection devices pointed by the virtual IDs according to the sequence on the virtual ID candidate list. The virtual ID includes at least a round number and a random variable.

According to a preferred embodiment, the at least one retro-reflective device receives a second light signal comprising at least the first load into a third state. And under the condition that the retroreflection device simultaneously receives the second optical signals sent by at least two reading-writing devices, the retroreflection device enters a silent state due to the collision of the downlink communication links. And under the condition that the reading-writing device does not detect the optical signal reflected by the retro-reflection device within the preset time, the reading-writing device enters a state of continuously and continuously sending the first optical signal again.

According to a preferred embodiment, when the at least one retro-reflection device only receives a second optical signal including at least the first payload and transmitted by one of the read-write devices after entering the third state, the at least one retro-reflection device demodulates and modulates the second optical signal to generate a second optical signal including at least the first confirmation information, and reflects the second optical signal to the read-write device. When the read/write device fails to decode the second optical signal that includes at least the first acknowledgment information and that has received the modulation, the read/write device terminates the communication session due to the collision of the uplink communication link. And the read-write device updates the virtual ID candidate list according to the acquired number of conflicts of the synchronous uplink communication link, so that the read-write device enters the first state again and sends a second optical signal at least comprising a second load of the virtual ID information according to a retro-reflection device pointed by the next virtual ID on the updated virtual ID candidate list. And under the condition that the decoding is successful, the read-write device enters a second state. The read-write device transmits a second optical signal comprising at least a third payload to the retro-reflective device.

According to a preferred embodiment, the retro-reflective device enters the fourth state upon receiving a second light signal comprising at least a third load. A retro-reflective device is responsive to the second light signal. In the event that the virtual ID of the second optical signal including at least the third payload and the virtual ID of the second optical signal including at least the first payload received by the retro-reflective device match each other, the retro-reflective device reflects and modulates the second optical signal to generate a second optical signal including at least the second acknowledgement. And a reader/writer device for simultaneously reflecting the retro-reflective device to a second optical signal including at least a third payload. In the case where the virtual IDs of the second light signal including at least the third load and the second light signal including at least the first load received by the retro-reflection device do not match each other, the retro-reflection device enters a silent state.

According to a preferred embodiment, in case the read-write device enters the second state and the second optical signal is not detected at least during the time the read-write device is in continuous communication with the retro-reflecting device receiving the second optical signal comprising at least the third payload, the read-write device sends the second optical signal comprising at least the third payload to the retro-reflecting device to which it is directed according to the next virtual ID of the virtual ID candidate list.

According to a preferred embodiment, the read-write device decodes the second optical signal comprising at least the second acknowledgement in case the read-write device enters the second state and the signal is detected at least during the time the read-write device is in continuous communication with the retro-reflective device. And under the condition of successful decoding, the read-write device outputs the message information carried by the optical signal and sends a second optical signal at least comprising a first load to the retroreflection device pointed by the read-write device according to the next virtual ID of the virtual ID candidate list. In case of a decoding failure, the read-write device retransmits the same second optical signal comprising at least a third payload to the retro-reflection device. Or the read-write device enters the state of continuously and continuously sending the first optical signal again.

A vehicle networking data communication method based on retro-reflective communication enables a retro-reflective device formed by at least one light label arranged on a vehicle and/or an infrastructure to establish a stable and continuous optical communication link between the retro-reflective device and a read-write device which are not in active communication at least within a certain time and space in a mode of passively modulating and reflecting an optical signal emitted by the read-write device arranged on the vehicle. The retro-reflection device responds to the request in the optical signal sent by the read-write device to modulate the confirmation information on the optical signal and reflect the confirmation information to the read-write device, so that correct data interaction between vehicles and between vehicle-road infrastructures is achieved. At least one read-write device establishes an optical communication link with at least one retro-reflective device by transmitting first and second optical signals at least two different frequencies. In the case where at least one optical communication link, which is stably continuous in time and space, is established between at least one reader/writer and at least one retro-reflection device, the at least one retro-reflection device recognizes a state of being in an idle state by a first optical signal, activates a third state for acquiring a virtual ID dynamically allocated in time and space specific to each reader/writer by receiving a second optical signal, and/or activates a fourth state for recognizing a virtual ID matching condition.

Drawings

FIG. 1 is a schematic illustration of downlink communication link collision in a VLBC-based vehicle networking;

FIG. 2 is a schematic diagram of synchronous uplink collisions in a VLBC-based vehicle networking;

FIG. 3 is a schematic diagram of asynchronous uplink communication link collisions in a VLBC-based vehicle networking;

FIG. 4 is a diagram illustrating state transitions of a reader/writer device in a preferred embodiment of the system of the present invention;

FIG. 5 is a schematic view of a preferred embodiment retroreflective device in a system of the present invention in a state transition;

fig. 6 is a diagram illustrating a MAC layer packet frame structure in an embodiment of the system of the present invention;

FIG. 7 is a schematic diagram of the discovery workflow of a reader/writer in a preferred embodiment of the system of the present invention; and

fig. 8 is a schematic diagram of the query workflow of the reader/writer according to the preferred embodiment of the system of the present invention.

List of reference numerals

1: the read-write device 2: retro-reflection device

3: first retroreflective device 4: second retroreflection device

5: the first vehicle-mounted read/write device 6: second vehicle-mounted read-write device

101: carrier monitoring 102: first state 103: second state

104: standby 105: third state 106: fourth state

107: and (6) silence 108: virtual ID update 109: one-to-one normal communication

110: listening 111: synchronizing uplink communication link collisions

112: asynchronous uplink communication link collision 113: downlink communication link collision

114: end of communication or termination 201: discovery request

202: query request 203: query response

204: preamble 205: source address

206: temporary ID 207: frame type

208: number of rounds 209: number of collisions

210: symbol length 211: payload

212: frame check field 213: QRC (QRC)

301: discovery message 302: monitoring

303: feedback signal 304: decoding

305: the query process 306: retreat

307: boot virtual ID update 308: query message

309: carrier monitoring or retry 310: next retroreflection device

311: outputting a message 312: end up

Detailed Description

The following detailed description is made with reference to fig. 1 to 8.

Example 1

The embodiment discloses a communication network, which can be a vehicle networking communication network, a vehicle networking communication system based on a light label, or a vehicle networking communication system based on retro-reflective communication, and the system can be realized by the system and/or other alternative parts. For example, the method disclosed in the present embodiment is implemented by using various components in the system of the present invention. The preferred embodiments of the present invention are described in whole and/or in part in the context of other embodiments, which can supplement the present embodiment, without resulting in conflict or inconsistency.

Preferably, based on the car networking system of VLBC technology, light labels are placed on infrastructure near the road to build the retro-reflective device 2. The infrastructure may be street lights, road blocks, traffic signs, stop bars, etc. Preferably, the optical label can also be arranged on other vehicles. Preferably, the read-write apparatus 1 is arranged on a vehicle. The vehicle may be a vehicle, motorcycle, or the like. The retro-reflecting device 2 reflects the optical signal transmitted from the reader/writer 1 to the reader/writer 1 requesting communication by using a retro-reflector on the infrastructure or a retro-reflector provided in the optical tag itself. The retro-reflection device 2 drives the charge and discharge states of the liquid crystal material of the LCD through an LCD driver in the optical label, thereby realizing amplitude modulation of the optical signal. The VLBC system consists of a high power reader 1 and a low power retro-reflective device 2 mounted on a vehicle. The specific working principle is as follows: for a downlink communication link, that is, an optical communication link in which the reading and writing device 1 sends a visible light signal to the retro-reflecting device 2, the LED in the reading and writing device 1 is turned on and off at a high frequency, so that the visible light emitted by the LED is used as a carrier of information, that is, data information is modulated onto the carrier (visible light) in an on/off keying (OOK) manner. The light signal is received and decoded by an optical sensor on the retro-reflective means 2. The uplink communication link, that is, the optical communication link in which the retro-reflection device 2 transmits visible light to the reader/writer 1, is transmitted by reflecting the same optical carrier transmitted by the reader/writer 1. The retro-reflection device 2 transmits the reflected light after OOK modulation, which is realized by a driver connected with the LCD driven by a microprogrammed control unit on the optical label. The driver can adjust a voltage applied to the LCD to control a state transition of charging or discharging of liquid crystals within the LCD to control whether the LCD emits light or adjust the magnitude of an optical signal, thereby implementing OOK modulation. The reflected light is then received by the optical sensor on the reader/writer 1 and further demodulated and decoded.

Preferably, in most cases, the distribution of the retro-reflecting devices 2 is relatively sparse, for example, when the vehicle is traveling in a suburban area, the infrastructure on both sides of the road and the number of vehicles traveling on the same road at a short distance (less than one hundred meters) are small, so that there are cases where one reading/writing device 1 communicates with one retro-reflecting device 2. However, in urban areas, not only are many road infrastructures, but also vehicles are dense, so that the retro-reflecting devices 2 and the read-write devices 1 are relatively densely distributed, and a plurality of retro-reflecting devices 2 are distributed in the communication range of a plurality of read-write devices 1, so that many-to-many communication scenes are generated. Also, when the traffic volume of the road is small, there may be a single reader/writer 1 communicating with a plurality of retro-reflecting devices 2, i.e., one-to-many communication. When the traffic volume is large, there are many vehicles, and therefore, the same retroreflection device 2 may exist in the communication ranges of a plurality of read/write devices 1 at the same time. In a more extreme case, a plurality of retro-reflecting means 2 are present within the sensing range of the optical sensor of one reading/writing device 1. However, in the car networking system based on VLBC, the optical label on the retro-reflecting device 2 will only start to operate when receiving the optical signal emitted by the read-write device 1 or the vehicle or vehicle controlled by the read-write device 1, that is, in the car networking system based on the retro-reflecting device 2, the read-write device 1 actively sends a communication request to the retro-reflecting device 2. The optical label of the retro-reflecting device 2 modulates and reflects the optical signal transmitted by the read-write device 1, so that the communication between the read-write device 1 and the optical label on the retro-reflecting device 2 has high spatial orientation characteristics, i.e. the read-write device 1 cannot sense other read-write devices 1 and other retro-reflecting devices 2, and the retro-reflecting device 2 communicating with the read-write device 1 cannot sense other read-write devices 1 and retro-reflecting devices 2, therefore, for the read-write device 1 and retro-reflecting device 2 in the VLBC-based car networking, the other read-write devices 1 and retro-reflecting devices 2 are transparent, so the high spatial orientation communication characteristics of the VLBC communication system can cause serious hidden terminal problems under many-to-many communication scenes, i.e. in the communication field, the base station a transmits a signal to the base station B, the base station C does not detect that a transmits signal to B, so that a and C simultaneously transmit signals to B, causing signal contention collisions resulting in B receiving signals transmitted by a and C simultaneously with incorrect reception due to data collisions, eventually resulting in the loss of all signals transmitted to B. In addition to this, the highly spatially oriented communication properties also make it impossible for the reader/writer 1 to passively monitor other reader/writers 1 in their communication range which are engaged in a communication session. In the case where a plurality of reading/writing apparatuses 1 communicate with the same retro-reflecting apparatus 2 at the same time, or in the case where a plurality of retro-reflecting apparatuses 2 communicate with a plurality of reading/writing apparatuses 1 at the same time, a serious communication link collision will result. Preferably, the collision of the communication link includes three different situations, specifically as follows:

1. collision of downlink communication links: as shown in fig. 1, in the case where one retro-reflecting device 2 is present in the communication range of a plurality of read-write devices 1, if a plurality of read-write devices 1 attempt to communicate with the retro-reflecting device 2 at the same time, the retro-reflecting device 2 has a hidden terminal problem, that is, the retro-reflecting device 2 receives optical signals transmitted by a plurality of different read-write devices 1 at the same time, and because of contention collisions caused by different signal collisions, the retro-reflecting device 2 cannot receive optical signals correctly, so that signals transmitted by a plurality of different read-write devices 1 are lost, and a downlink communication collision 113 occurs;

2. synchronization collision of uplink communication link: as shown in fig. 2, when a plurality of retro-reflecting devices 2 are present in the communication range of the reader/writer 1 and a plurality of retro-reflecting devices 2 passively receive the optical signal transmitted from the reader/writer 1 at the same time, since the retro-reflecting devices 2 are transparent to other retro-reflecting devices 2, the retro-reflecting devices 2 cannot sense the presence of other retro-reflecting devices 2 nearby, and they may simultaneously respond to the communication request from the reader/writer 1, resulting in a synchronization uplink collision 111;

3. asynchronous collision of uplink communication link: as shown in fig. 3, when the first retro-reflecting device 3 responds to the communication request of the first vehicle-mounted read-write device 5, the nearby second vehicle-mounted read-write device 6 attempts to communicate with the second retro-reflecting device 4 located second within the communication range of the first vehicle-mounted read-write device 5. The response of the second retro-reflective device 4 to the second vehicle-mounted reading and writing device 6 will be monitored by the first vehicle-mounted reading and writing device 5, so that the first vehicle-mounted reading and writing device 5 receives the optical signals of the first retro-reflective device 3 and the second retro-reflective device 4 at the same time, which results in the communication session between the first vehicle-mounted reading and writing device 5 and the first retro-reflective device 3 being terminated, i.e. an asynchronous uplink communication collision 112 occurs.

Preferably, in collisions on the uplink communication link, there is also a special case of capture effects. The trapping effect means that the response of the intended retro-reflecting device 3 with respect to the read-write device 1 is accidentally overwhelmed by the response of another retro-reflecting device 3, i.e. the other retro-reflecting device 3 may have a larger reflecting surface or be closer to the read-write device 1, so that the reflected signal energy thereof is stronger, overwhelming the response signal of the intended retro-reflecting device 3. In case the response signal captured by the reader/writer 1 changes, the captured response signal can be subsequently remedied due to the mobility of the reader/writer 1.

Preferably, the above conflict situation may cause the read-write device 1 and the retro-reflection device 2 to fail to decode the optical signal correctly, thereby resulting in the loss of effective information and failure of normal communication. In addition, street lights, roadblocks, traffic signs, stop bars, and similar street sign infrastructure have the property of being locally broadcast, and can be used to convey location-related information to oncoming vehicles. Retro-reflective devices 2 based on retro-reflective LCD modulation designs also follow the local broadcast characteristics of the signboards. But in fact, the switching state of the liquid crystal will affect all incident light, regardless of the incident light and carrier frequency. Therefore, it is easy to think of using a periodic broadcast beacon mechanism to deliver information, because it is simple and easy to implement. But this is not the case: when the reader/writer 1 recognizes that there are a plurality of retroreflective devices 2, the responses of the retroreflective devices 2 are deemed to collide, that is, several collision situations as described above occur. That is, all nearby retro-reflective devices 2 are potential colliders. However, it is almost impossible to statically coordinate a plurality of retro-reflective devices 2 for the following reasons. First, due to the need for battery-less, the retro-reflective device 2 is designed to be passive, i.e. the retro-reflective device 2 cannot sense whether there are other retro-reflective devices 2 nearby. Secondly, the approach distance between the reading and writing device 1 and the retro-reflection device 2 is highly dynamic due to the mobility (i.e. different positions) of the reading and writing device 1 and the diversity of the headlight power (i.e. different viewing ranges). Finally, to save energy, retro-reflective devices 2 may sleep from time to time and may be activated at different times, making it very difficult to maintain a global clock and ensure clock synchronization between nearby retro-reflective devices 2. In summary, in view of the above problems, the present embodiment provides a vehicle networking communication system based on a retro-reflection device by utilizing the characteristics that in a downlink communication link of a VLBC communication system, the reader/writer device 1 actively sends an optical signal to the retro-reflection device 2 for communication, and in an uplink communication link, the retro-reflection device 2 passively reflects the optical signal sent by the reader/writer device 1, and an excitatory carrier monitoring mechanism is adopted to reduce the probability of asynchronous uplink communication link collision. But also active carrier monitoring can listen to all communication sessions of retro-reflective devices 2 within its communication range. Meanwhile, another effect brought by this mechanism is that it can passively hear the communication session of the retro-reflective device 2 in its communication range, and can avoid repeated inquiry of the same retro-reflective device 2 by a plurality of reading and writing devices 1. The retro-reflection device 2 adopts a method of dynamically allocating virtual IDs passively and instantly to implement a unicast function in many-to-many communication in a complex environment, thereby solving a conflict of synchronous or asynchronous uplink communication links.

A retro-reflective communication based internet of vehicles communication system comprising at least: a read-write device 1 arranged on a vehicle and a retro-reflection device 2 arranged on the vehicle and/or an infrastructure. The read-write device 1 is capable of establishing a stable continuous optical communication link with the retro-reflecting device 2 at least for a certain time and space for transmitting data packets comprising at least a transmission frame and an acknowledgement frame between the vehicles and/or between the vehicles and the infrastructure to achieve correct data interaction between the read-write device 1 and the retro-reflecting device 2. Preferably, the read/write device 1 transmits an optical signal including at least a transmission frame to the retro-reflection device 2. The retro-reflection means 2 modulates the acknowledgement information on the optical signal, thereby reflecting the optical signal including at least the acknowledgement frame to the read/write apparatus 1. At least one read-write device 1 establishes an optical communication link with at least one retro-reflection device 2 by transmitting a first optical signal and a second optical signal of at least two different frequencies. In this way, two optical signals with different frequencies are used to respectively detect collisions and discover and confirm the retro-reflecting device 2, that is, the passive carrier monitoring 101 is realized through the first optical signal, and the ongoing communication session of the retro-reflecting device 2 is monitored, so as to avoid the hidden terminal problem caused by retro-reflection. Discovery and/or interrogation of retro-reflective device 2 is achieved using the second optical signal, thereby enabling uplink communication link collisions to be avoided in the event that carrier monitoring 101 is unable to further monitor hidden terminals. Further, the hidden terminal is a situation where a plurality of reading/writing devices 1 communicate with the same retro-reflection device 2 at the same time, and in this situation, because communication occurs at the same time, the carrier monitoring 101 implemented by using the first optical signal can only monitor that the optical communication link is in an idle state. In addition, the first optical signal and the second optical signal have different frequencies, which is beneficial for the read-write device 1 to identify different types of optical signals so as to respond to corresponding states, and also to avoid the interference of data packets transmitted by the two signals to monitor the collision of the communication link.

Preferably, the first optical signal is continuously transmitted to monitor any ongoing communication session of at least one retro-reflective device 2 within communication range of the reader device 1. By the arrangement, the asynchronous uplink communication link collision probability can be reduced. Preferably, the read-write device 1 is provided with a carrier monitoring 101, a first state 102 for finding the retro-reflecting device 2 and a second state 103 for querying the retro-reflecting device 2. The relationship of these three state transitions is shown in fig. 4. Preferably, the carrier monitoring 101 is that the reader/writer 1 continuously transmits the first optical signal. The frequency of the first optical signal is different from the frequency at which the transmission of the useful data is sent by the read-write apparatus 1. For example, the frequency of the first optical signal may be f_u455KHz and a second optical signal at 1.8MHz is used for active downstream communication transmission of data. Preferably, the first optical signal is used to detect any ongoing communication session. A communication session refers to an upstream or downstream communication link between the other read-write device 1 and the retro-reflection device 2. Preferably, the read-write device 1 is able to at least actively discover potential retro-reflective devices 2 within its communication range by transmitting a first optical signal. Preferably, the reader/writer 1 is in the carrier monitoring 101 state at other times than when performing downlink communication data transmission. Preferably, when a new retro-reflecting device 2 is encountered, the reader/writer 1 checks all communication sessions of the retro-reflecting device 2, thereby acquiring the communication state of the retro-reflecting device 2. The read-write device 1 continuously emits the first optical signal to detect any possible communication sessions and continuously listens 110 to whether the channel between the read-write device 1 and the retro-reflection device 2 is free. After determining idle, the reader/writer 1 enters the first state 102. Preferably, the first light signal can exploit the high spatial directionality of the retro-reflected light beam to detect other ongoing communication sessions. For example, it is assumed that one retro-reflection device 2 responds to a communication request of another read-write device 1 by switching its LCD state. In the carrier monitoring 101 state, the reflected light of the first reader/writer 1 is also modulated, so that the reader/writer 1 can sense the ongoing communication sessionAnd ensures that the channel between the read-write device 1 and the retro-reflective device 2 is in an idle state before attempting to switch the first state 102 or the second state 103. By the setting mode, the non-interference carrier monitoring technology can be realized under the VLBC technology, the power of a transmitting signal or the threshold value of carrier monitoring is not required to be increased, and the carrier monitoring under low power is realized by utilizing the space orientation characteristic of the optical signal height and the passive communication characteristic of the retro-reflection device 2. Furthermore, the busy or idle state of the optical communication link between the reader/writer 1 and the retro-reflection device 2 can be quickly determined simply and efficiently by the carrier monitoring 101 of the first optical signal.

Preferably, the second optical signal is transmitted by the read/write device 1 to the retro-reflective device 2 after the read/write device 1 stops transmitting the first optical signal and enters the first state 102 for finding the retro-reflective device 2 to avoid synchronous uplink collision and/or the second state 103 for querying the retro-reflective device 2 to avoid asynchronous uplink collision. Through the setting mode, the reading and writing device can decode according to the second optical signal fed back by the at least one retro-reflection device 2, so that different states are converted to further solve the problem of hiding the terminal, and the conflict of an uplink communication link and a downlink communication link is avoided.

Preferably, for a pair of first normal communications 109, the reader/writer 1 will switch according to the sequence of the carrier monitor 101, the first state 102 and the second state 103 as shown in fig. 4. For example, in the case where it is determined that the signal between the reader/writer 1 and the retro-reflection device 2 is in the idle state, the reader/writer 1 enters the first state 102, and there is no down/up communication link collision in the one-to-one normal communication 109, the reader/writer 1 enters the second state 103 by correctly decoding the reflected light signal of the retro-reflection device 2. Preferably, the first state 102 is a state in which the retro-reflective device 2 is found. Second state 103 is the state of interrogating retroreflective device 2. Preferably, different link collisions will result in different state transitions. For example, the reader/writer 1 continuously transmits the first optical signal to the retro-reflector 2 in the communication range of the reader/writer 1 in the carrier monitoring 101 state, and if it is confirmed through the first optical signal that the channel between the reader/writer 1 and the retro-reflector 2 is in a busy state before attempting to find or inquire, the reader/writer 1 reenters the carrier monitoring 101 state.

Preferably, as shown in fig. 5, in a case where the reader/writer 1 transmits the first optical signal to at least one retro-reflecting device 2 in the communication range thereof, the reader/writer 1 is configured to determine that the optical communication link between the reader/writer 1 and the retro-reflecting device 2 is in a busy state when monitoring the signal, so that the reader/writer 1 maintains a state of continuously transmitting the first optical signal to find the retro-reflecting device 2 in the communication range thereof capable of establishing the optical communication link in an idle state. Specifically, when the retro-reflecting device 2 receives the first light signal, the retro-reflecting device 2 takes no action and is in the silent state 107. After sending the first optical signal, the reader/writer 1 monitors whether or not the optical signal is received. Preferably, the read-write apparatus 1 can realize the reception of the optical signal by an optical sensor. If the reader/writer 1 does not monitor a signal within a preset time, it is determined that the optical communication link between the reader/writer 1 and the retroreflection device 2 is in an idle state. Preferably, the preset time may be a manually set time, such as 20 milliseconds, 50 milliseconds, or 100 milliseconds. Preferably, after the read-write device 1 determines that the optical communication link between the read-write device 1 and the retro-reflecting device 2 is in the idle state, the read-write device 1 enters the first state 102 and transmits the second optical signal. The second optical signal includes at least a payload. The payload represents information, i.e. communication information between the reading and writing device 1 and the retro-reflecting device 2. The information may be query information or inquiry information, etc. Preferably, after the read-write device 1 sends the second optical signal, the retro-reflection device 2 needs to respond to the second optical signal after receiving the second optical signal, and retro-reflects the second optical signal with the response information to the read-write device 1 in a retro-reflection manner. Through the above arrangement, when the reader/writer 1 is in the carrier monitoring 101 state, the retro-reflecting device 2 receives the first optical signal without any action and is in the silent state 107, so if the reader/writer 1 receives the optical signal fed back by the retro-reflecting device 2, the retro-reflecting device 2 already performs a communication session with another reader/writer 1, and therefore the reader/writer 1 determines that the retro-reflecting device 2 is in a busy state, thereby being capable of avoiding an asynchronous uplink communication link collision. In addition, with this arrangement, the reader/writer 1 can listen to any continuous communication session between the retro-reflector 2 and another reader/writer 1, and therefore can sense another reader/writer 1 to some extent, thereby solving the problem of hidden terminals.

Preferably, as shown in fig. 5, the retro-reflecting device 2 is normally in a standby state. When the retro-reflecting device 2 is activated by the first optical signal sent by the reader/writer 1, the retro-reflecting device 2 has three active states, namely a third state 105 for receiving the second optical signal, a fourth state 106 for responding to the second optical signal of the reader/writer 1, and a mute state 107. When there is no conflict, the retro-reflective device 2 enters the fourth state 106 of the responding reader/writer 1 directly after activation.

Preferably, as shown in fig. 4 and 5, when a collision occurs, the states of the read/write apparatus 1 and the retro-reflection apparatus 2 are switched and will retry. Preferably, different collisions will result in different state transitions. Preferably, in a case where the read/write apparatus 1 determines that the optical communication link with the retro-reflection apparatus 2 is in the idle state, the read/write apparatus 1 shifts to the first state 102. In the first state 102, the read-write device 1 transmits a second optical signal comprising at least the first load to the at least one retro-reflection device 2. Preferably, the first payload may be a message containing a frame structure, the message containing at least a discovery request. Preferably, in a case where the optical communication links of two retro-reflecting devices 2 with the reader/writer 1 are in an idle state, the reader/writer 1 passively and dynamically assigns a virtual ID to each retro-reflecting device 2 based on the number of retro-reflecting devices 2 and constructs a virtual ID candidate list. The ID is an Identity (ID) of the retro-reflective device 2. Passively assigning a virtual ID may refer to the reader/writer device 1 passively assigning a virtual ID according to the retro-reflection device 2 that it perceives through the first optical signal. Dynamically assigning a virtual ID may mean that the ID assigned to a retro-reflecting device 2 is not fixed, since a plurality of retro-reflecting devices 2 may be present within the communication range of the read-write device 1, and thus the same retro-reflecting device 2 may have different IDs for different read-write devices 1. Preferably, the reader/writer device 1 sequentially transmits the second optical signals including at least the first payload of the virtual ID information to the retro-reflection devices 2 to which the virtual IDs point, in the order on the virtual ID candidate list. Through the setting mode, under the condition that a coordinator is not additionally arranged, a passive dynamic mode is utilized to allocate the virtual ID which is special for the reading-writing device 1 to each retroreflection device 2, so that under the condition that the reading-writing device 1 and the retroreflection devices 2 cannot sense other reading-writing devices 1 and retroreflection devices 2, collision detection and processing of an uplink communication link and a downlink communication link are realized, and normal information interaction which cannot be realized due to the problem of hidden terminals is avoided. Specifically, the second optical signal including the relevant payload is transmitted to the retro-reflection device 2 by enumerating the virtual IDs of the retro-reflection devices 2 in the virtual ID candidate list. As shown in fig. 7, the reader/writer 1 sends a second optical signal including at least the first payload to the retro-reflector 2 according to the virtual ID, that is, the reader/writer 1 sends a discovery message 301, and then listens 302 for feedback from the retro-reflector 2. At least one retro-reflective device 2 receives a second light signal comprising at least the first load into a third state 105. In the case where the retro-reflecting device 2 receives the second optical signals transmitted by at least two of the read/write devices 1 at the same time, the retro-reflecting device 2 enters the mute 107 state to avoid downlink collision. In case the read-write device 1 does not detect the light signal reflected by the retro-reflecting device 2 within a preset time, i.e. the read-write device 1 does not receive the feedback signal 303. The reader/writer 1 may conclude that the retro-reflecting device 2 with which it communicates may be out of its communication range, or that its communication range is free of the retro-reflecting device 2, or that a downlink communication collision may occur. Preferably, in this case, the read/write device 1 executes the back-off 306 mechanism to enter a state of continuously transmitting the first optical signal again.

Preferably, in the case that at least one retro-reflecting device 2 only receives a second optical signal including at least the first payload and transmitted by the read-write device 1 after entering the third state 105, the at least one retro-reflecting device 2 demodulates and modulates the second optical signal to generate a second optical signal including at least the first confirmation information, and reflects the second optical signal to the read-write device 1. If the read/write device 1 fails to decode 304 the second optical signal including at least the first acknowledgment information after receiving the modulation, the read/write device 1 terminates the communication session due to the collision of the uplink communication link. The reader/writer 1 directs the virtual ID update 307 according to the number of collisions for obtaining the synchronous uplink communication link, thereby re-entering the first state 102 and transmitting the second optical signal of the second payload according to the retro-reflection device 2 pointed to by the next virtual ID on the updated virtual ID candidate list. Preferably, the second payload includes at least the virtual ID information. In case the decoding is successful, the read-write-device 1 enters the second state 103. The read-write device 1 sends a second optical signal comprising at least a third load to the retro-reflecting device 2, preferably the third load comprises at least an inquiry message 308, as shown in fig. 8.

Preferably, the retro-reflective device 2 enters the fourth state 106 upon receiving a second light signal comprising at least a third load. The retro-reflecting means 2 is responsive to the second light signal. In case the virtual ID of the second light signal comprising at least the third payload and the virtual ID of the second light signal comprising at least the first payload received by the retro-reflecting device 2 match each other, the retro-reflecting device 2 reflects and modulates the second light signal to generate a second light signal comprising at least the second acknowledgement. While the retro-reflecting means 2 reflect a second optical signal comprising at least a third load to the reading and writing means 1. In the case where the virtual IDs of the second light signal including at least the third load and the second light signal including at least the first load received by the retro-reflecting device 2 do not match each other, the retro-reflecting device 2 enters the silent state 107. With this arrangement, collision of uplink communication links can be avoided.

According to a preferred embodiment, in case the read/write device 1 enters the second state 103 and the second optical signal is not detected at least during the time the read/write device 1 is in continuous communication with the retro-reflecting device 2 receiving the second optical signal comprising at least the third payload, i.e. as shown in fig. 8, the read/write device 1 does not receive the feedback signal 303, the read/write device 1 sends the second optical signal comprising at least the third payload to the next retro-reflecting device 310 to which it points according to the next virtual ID of the virtual ID candidate list.

According to a preferred embodiment, in case the read-write device 1 enters the second state 103 and a second optical signal comprising at least a second acknowledgement is detected at least during the time the read-write device 1 is in continuous communication with the retro-reflecting device 2, the read-write device 1 decodes the signal. If the decoding is successful, the reader/writer 1 outputs a message carried by the optical signal, i.e. outputs a message 311, and sends a second optical signal including at least the first payload according to the next retro-reflection device 310 pointed by the next virtual ID in the virtual ID candidate list. In case of a decoding failure, the reader/writer 1 enters carrier monitoring or retry 309, i.e. retransmits the same second optical signal comprising at least the third payload to the retro-reflection means 2, or the reader/writer 1 enters a state of continuously transmitting the first optical signal again.

Example 2

The embodiment discloses a car networking data communication network based on contrary communication that reflects, includes at least: a read-write device 1 arranged on a vehicle and a retro-reflection device 2 arranged on the vehicle and/or an infrastructure. The read-write device 1 is able to establish a stable continuous optical communication link with the retro-reflecting device 2 at least for a certain time and space. At least one read-write device 1 establishes an optical communication link with at least one retro-reflection device 2 by transmitting a first optical signal and a second optical signal of at least two different frequencies. The first optical signal is used to monitor any ongoing communication session of the retro-reflecting device to confirm an idle or busy status of the communication link between the read-write device 1 and the retro-reflecting device 2, and in case the communication link is in an idle status, the read-write device 1 enters the first state and/or the second state to send a second optical signal comprising at least data packets dynamically allocating a virtual ID for at least one retro-reflecting device 2 passively over the time and space to avoid uplink and downlink communication link collisions. Through the setting mode, under the condition that no coordinator needs to be additionally arranged, a passive dynamic mode is utilized to allocate the virtual ID which is special for each read-write device 1 to each read-write device 1, so that under the condition that the read-write devices 1 and the retro-reflection devices 2 cannot sense other read-write devices 1 and retro-reflection devices 2, collision detection and processing of an uplink communication link and a downlink communication link are realized, and normal information interaction which cannot be realized due to the problem of hidden terminals is avoided.

Preferably, the car networking data communication network disclosed in this embodiment is the same as that in embodiment 1, and repeated contents are not described again. Preferably, this embodiment discloses a preferred implementation of the virtual ID in embodiment 1. Since the information on the presence of the signal and the ID of the retro-reflecting device 2 cannot be known prior to the read/write device 1, the ID of the retro-reflecting device 2 must first be found. Pre-assigning a fixed Globally Unique Identifier (GUID) to each retro-reflective device 2 is not feasible, as this would require a nationwide or industry wide address assignment protocol. Furthermore, since each retro-reflective device 2 and ID must be found by the reader/writer 1, a larger address space means a longer process in the first state 102. Furthermore, considering that the target scenario of the communication of the internet of vehicles is between vehicles or between vehicles and infrastructure on both sides of the road, the communication time is short, and the uplink communication link delay is dominant in the whole communication network, for example, the uplink communication link is limited by the modulation frequency of the LCD in the retro-reflection device 2, the data rate is low, and therefore it is necessary to shorten the address space of the ID as much as possible, thereby reducing the delay of the uplink communication link, which controls the first state 102 and the second state 103 of the whole read/write device. Preferably, the purpose of setting the ID is to distinguish only a plurality of retro-reflecting devices 2 present in the communication range of the same reader/writer 1 in an uplink collision, so that the same retro-reflecting device 2 can have different IDs for different reader/writers 1. Thus, a plurality of retro-reflecting devices 2 are present in the communication range of the reader/writer 1, and a temporary reader/writer-specific ID is dynamically generated. Specifically, the virtual ID of one retro-reflection device 2 includes at least the address of the reader/writer 1, the round number 208, the number of collisions 209 on the communication link in the current round number 208, and the temporary ID 206. The temporary ID206 is a random variable. Preferably, the number of rounds 208 refers to the sequential index of the current discovery round.

Preferably, in order to facilitate the implementation of the above dynamic virtual ID and the retro-reflective communication-based vehicle networking data communication network provided in embodiment 1, five messages are designed in the MAC protocol, which are a discovery request 201, a query request 202, a query acknowledgement, a discovery acknowledgement, and a query response 203. Preferably, the discovery request 201, the inquiry request 202 and the inquiry confirmation are downstream messages, i.e. messages sent by the read/write device 1 to the retro-reflection device 2. The discovery acknowledgement and the query response 203 are upstream messages, i.e. messages sent by the retro-reflection device 2 to the reader/writer 1. Preferably, the confirmation is found to be a very short waveform, which can be adapted to the particular mode of presence detection. Preferably, the present embodiment employs carrying the query acknowledgement in the discovery request 201 and/or the query request 202 due to the tight bandwidth resources of the uplink communication link. Preferably, the frame formats of the three MAC messages, discovery request 201, query request 202 and query response 203 are shown in fig. 6, wherein discovery request 201 may be applied in the first state 102, query request 202 may be applied in the second state 103, and query response 203 may be applied in the third state 105 and/or the fourth state 106 of the retro-reflective device 2. As shown in fig. 6, the frame structure of all three messages has a preamble 204, a source address 205 of the reader/writer 1, a temporary ID206 of the retro-reflector 2, a round number 208, and a frame check field 212. Preferably, the temporary ID206 field is a random number for resolving an uplink communication collision. It serves as a temporary ID for the retro-reflection means 2, specific to the read-write apparatus 1. Preferably, the discovery request 201 and the query request 202 each include a frame type 207 and a QRC 213. Preferably, the QRC213 field is a cyclic redundancy check value calculated from the payload 211 in the query response 203 received by the reader/writer 1. The QRC213 field is used for the reader/writer 1 to compare with the cyclic redundancy check value of the local payload to verify whether its query response 203 was successfully delivered. Preferably, only 4-bit address space is allocated to the retro-reflection device 2 by the virtual ID design. We list only three MAC messages because the discovery acknowledgement message is very short and has only a preamble because its main function is to indicate its presence, while the query acknowledgement is contained in the message of the discovery request 201. Preferably, the frame structure of the query response 203 message further includes fields such as a symbol length 210.

Preferably, the address source address 205 of the reader/writer 1, the round number 208, and the number of collisions 209 on the uplink communication link in the current round number 208 are sent by the reader/writer 1 in the discovery request 201 message. The random variable follows unif 0,2Nc, i.e., the random variable follows a uniform distribution within 0,2Nc, which represents the number of collisions 209 on the communication link in the current round 208. Preferably, all possible values of the random variable constitute a virtual ID candidate list for the read-write apparatus 1. If the uplink communication link is collided, Nc is incremented by the reader/writer 1, or after successful discovery, Nc is reset to 0. In the above manner, all possible collisions, including at least the above uplink communication link collision, can be detected from the case where the received signal cannot be decoded correctly, so that the synchronous uplink communication link collision can be handled by the virtual ID; for asynchronous uplink communication link collisions, this can be handled by retransmission.

Preferably, for the second state 103 of the reader/writer 1, the reader/writer 1 enumerates a VID candidate list and queries each candidate, i.e. the retro-reflective device 2, with a unicast query request 202 message. By default, if the virtual ID of retro-reflective device 2 matches the virtual ID in the query request 2 message, retro-reflective device 2 will respond with a query response 203 message. Similar to the first state 102 of the reader 1, the reader 1 performs an energy detection to determine whether the retro-reflective device 2 is responding. If no feedback signal is detected, this indicates that the retro-reflection device 2 is outside the communication range of the reader/writer 1. The reader/writer 1 will continue to execute the virtual ID of the next retro-reflective device 2 in the list. If the reader/writer 1 detects a signal it will try to decode the message. If successful, the reader/writer 1 outputs a message to delete the virtual ID of the retro-reflection device 2 from the virtual ID candidate list and move to the next virtual ID. If the reader/writer 1 fails to decode, the reader/writer 1 senses that an uplink collision has occurred while receiving the uplink communication link message, and will re-query the virtual ID of the retro-reflective device 2 that failed to decode in the next round of query.

Preferably, in practical applications, the data rate of the uplink communication link is one order of magnitude slower than the data rate of the downlink communication link due to the limitations of the COTS liquid crystal display. To offset this and improve efficiency, the present embodiment provides the following two optimization schemes in addition to the virtual ID scheme:

a. monitoring before a communication session: this will reduce query 103 attempts with carrier monitoring 101; when the carrier monitor 101 detects that the channel is busy, the reader/writer 1 will prohibit its discovery or inquiry operation, which will greatly reduce the probability of asynchronous uplink communication link collision; in addition, the reader/writer 1 may monitor the whole message through the carrier monitor 101, which will prevent the reader/writer 1 from repeatedly querying the same retro-reflective device 2, and is beneficial to solving the downlink communication link collision, because the downlink collision adopts a random backoff mechanism, the reader/writer 1 which is further backed off will have a good chance to monitor the query 1 of the reader/writer 1 which is not backed off;

b. aggregation and piggybacking: this is to reduce the number of rounds 208 of discovery 102 and query 103; first, in our message design, we have aggregated discovery request 201 and a common query request 202, which is to improve the efficiency of the most common one-to-one, many-to-one communications; the reader/writer 1 will carry the inquiry confirmation to all the retro-reflective devices 2 monitored by the reader/writer through the next discovery request 201 or inquiry request 202, and the retro-reflective device 2 receiving the message will compare the virtual ID information with the information carried in the inquiry confirmation, and will suppress its response if the virtual IDs match.

Example 3

The embodiment discloses a communication method, which can be a vehicle networking communication method and a vehicle networking data communication method based on retro-reflective communication, and the method can be realized by the device disclosed by the invention and/or other alternative parts. The preferred embodiments of the present invention are described in whole and/or in part in the context of other embodiments, which can supplement the present embodiment, without resulting in conflict or inconsistency.

A vehicle networking communication method based on retro-reflective communication is characterized in that a retro-reflective device 2 formed by at least one light label arranged on a vehicle and/or an infrastructure passively modulates and reflects a light signal emitted by a read-write device 1 arranged on the vehicle, so that a stable and continuous optical communication link at least in a certain time and space is established between the retro-reflective device 2 and the read-write device 1 which are not in active communication. The retro-reflection device 2 modulates the confirmation information on the optical signal in response to the request in the optical signal sent by the read-write device 1, and reflects the confirmation information to the read-write device 1, so that correct data interaction between vehicles and between vehicle-road infrastructures is realized. At least one read-write device 1 establishes an optical communication link with at least one retro-reflection device 2 by transmitting a first optical signal and a second optical signal of at least two different frequencies. In case at least one optical communication link, which is stably continuous over time and space, is established between at least one reader/writer 1 and at least one retro-reflection device 2, confirming that it is in a free state by a first optical signal, the at least one retro-reflection device 2 activates a third state 105 for acquiring a virtual ID dynamically allocated in time and space specific to each reader/writer 1 and/or activates a fourth state 106 for confirming a virtual ID matching situation by receiving a second optical signal.

Preferably, the read-write device 1, the retro-reflection device 2, the communication method between the read-write device 1 and the retro-reflection device 2, and the MAC message format adopted between the read-write device 1 and the retro-reflection device 2 provided in this embodiment adopt the read-write device 1, the retro-reflection device 2, the communication method between the read-write device 1 and the retro-reflection device 2, and the MAC message format adopted between the read-write device 1 and the retro-reflection device 2 as provided in

embodiments

1 and 2, so that in-time detection and processing of uplink and downlink communication link conflicts are realized in an environment where a plurality of retro-reflection communication nodes cannot be statically coordinated based on retro-reflection communication, and repeated contents are not described again.

Example 4

This example is a further improvement over examples 1, 2 and 3.

Preferably, as shown in fig. 5, in a case where the read-write apparatus 1 transmits the first optical signal to at least one retro-reflection apparatus 2 within its communication range, the retro-reflection apparatus 2 is switched from the standby state 104 to the activated state. Upon entering the activated state, retroreflective apparatus 2 enters a silent 107 state or a modulated reflective state in response to the first light signal. Preferably, in case that the retro-reflecting device 2 can correctly decode the first optical signal, the retro-reflecting device 2 enters a modulated reflection state, so as to feed back the modulated first optical signal to the read-write device 1. When the retro-reflecting device 2 cannot correctly decode the first optical signal, the retro-reflecting device 2 enters the silent state 107, and the first optical signal is not fed back to the reader/writer 1, thereby resulting in the end or termination 114 of communication. Preferably, when the reader/writer 1 monitors a signal and acquires a first optical signal reflected and modulated by the retro-reflecting device 2, the reader/writer 1 determines that an optical communication link between the reader/writer 1 and the retro-reflecting device 2 is in a busy state, so that the reader/writer 1 maintains a state of continuously transmitting the first optical signal to find the retro-reflecting device 2 capable of establishing an optical communication link in an idle state in its communication range. Preferably, the reader/writer 1 is always in the carrier monitoring 101 state before the reader/writer 1 establishes a communication link with the retro-reflection device 2. Preferably, the read-write device 1 determines whether the communication link is idle by whether the retro-reflection device 2 retro-reflects the optical signal, in which case the read-write device 1 does not monitor the signal and may also indicate that the retro-reflection device 2 is not in the communication range of the read-write device 1, which causes the read-write device 1 to enter the first state 102 to transmit the second optical signal, and then reenters the carrier monitoring 101 state to transmit the first optical signal because the fed-back signal is not received in the first state 102, so that the read-write device 1 continuously switches between the states of transmitting the first optical signal and the second optical signal. The retro-reflecting means 2 are thus arranged to simply modulate the first optical signal, i.e. if the retro-reflecting means 2 simultaneously receive the first optical signals transmitted by at least two read-write apparatuses 1. The retro-reflecting device 1 is in the silent state 107 because the first optical signal cannot be decoded correctly, and thus the read-write device 1 does not receive any feedback optical signal, then the read-write device 1 determines that the optical communication link between the read-write device 1 and the retro-reflecting device 2 is in the busy state. By the arrangement mode, the problem of hidden terminals can be solved under the condition that other reading and writing devices 1 cannot be sensed. If the retro-reflecting means 2 receives only one first light signal at a time, the retro-reflecting means 2 can correctly decode the first light signal and thus enter the modulated reflecting state. Since the retro-reflection device 2 can only modulate and retro-reflect one first optical signal at the same time, all the reading/writing devices 1 communicating with the retro-reflection device 2 can receive the retro-reflection optical signal and can further acquire information included in the retro-reflection optical signal, so that the reading/writing device 1 can acquire whether the retro-reflection optical signal is a response to the first optical signal transmitted by the reading/writing device. In a case where the read/write device 1 determines that the acquired information does not respond to the first optical signal it transmits, the read/write device 1 determines that the optical communication link between it and the retro-reflection device 2 is in a busy state. Moreover, the reader/writer 1 can demodulate the optical signal retro-reflected by the retro-reflection device 2, and thus can monitor the communication session between the other reader/writer 1 and the retro-reflection device 2, so that the other retro-reflection device 2 can be sensed, and the reader/writer 1 is prevented from being constantly in the transition between the carrier monitoring 101 state and the first state 101.

It should be noted that the above-mentioned embodiments are exemplary, and that those skilled in the art, having benefit of the present disclosure, may devise various arrangements that are within the scope of the present disclosure and that fall within the scope of the invention. It should be understood by those skilled in the art that the present specification and figures are illustrative only and are not limiting upon the claims. The scope of the invention is defined by the claims and their equivalents.

Claims

1. A retro-reflective communication based internet of vehicles data communication network comprising at least:

a read-write device (1) arranged on a vehicle,

retroreflective means (2) arranged on a vehicle and/or an infrastructure,

the read-write device (1) can establish a stable continuous optical communication link with the retro-reflection device (2) at least in a certain time and space,

it is characterized in that the preparation method is characterized in that,

at least one read-write device (1) establishes an optical communication link with at least one retro-reflection device (2) by transmitting a first optical signal and a second optical signal of at least two different frequencies,

the first optical signal is used to monitor any ongoing communication session of the retro-reflecting device (2) to confirm an idle or busy state of the communication link between the read-write device (1) and the retro-reflecting device (2), and in case the communication link is in the idle state, the read-write device (1) enters the first state (102) and/or the second state (103) to send a second optical signal comprising at least data packets passively and dynamically assigning a virtual ID to at least one retro-reflecting device (2) over the time and space to avoid uplink and downlink communication link collisions.

2. Vehicle networking data communication network according to claim 1, characterized in that in case the read-write device (1) sends a first optical signal to at least one retro-reflective device (2) within its communication range,

the reading-writing device (1) is configured to judge that an optical communication link between the reading-writing device (1) and the retro-reflecting device (2) is in a busy state when monitoring a signal, so that the reading-writing device (1) maintains a state of continuously transmitting a first optical signal to find the retro-reflecting device (2) of which the communication range can establish the optical communication link in an idle state.

3. The vehicle networking data communication network of claim 1, wherein, in case the read-write device (1) determines that the optical communication link with the retro-reflection device (2) is in an idle state,

the read-write-device (1) is switched into a first state (102) and sends a second optical signal comprising at least the first payload to the at least one retro-reflection means (2), wherein,

in case that an optical communication link between at least two retro-reflecting devices (2) and the read-write device (1) is in an idle state, the read-write device (1) passively dynamically allocates a virtual ID to each retro-reflecting device (2) based on the number of retro-reflecting devices (2) and constructs a virtual ID candidate list, so that the read-write device (1) sequentially transmits a second optical signal including at least a first payload of the virtual ID information to the retro-reflecting devices (2) to which the virtual ID points in order on the virtual ID candidate list,

the virtual ID includes at least a round number (208) and a random variable.

4. Vehicle networking data communication network according to one of claims 1 to 3, wherein at least one retro-reflecting device (2) receives a second light signal comprising at least a first load into a third state (105), wherein,

when the retroreflection device (2) receives second optical signals sent by at least two reading-writing devices (1) at the same time, the retroreflection device (2) enters a silent state due to collision of a downlink communication link, and when the reading-writing device (1) does not detect the optical signals reflected by the retroreflection device (2) within a preset time, the reading-writing device (1) enters a state of continuously and continuously sending the first optical signals again.

5. Vehicle networking data communication network according to one of claims 1 to 3, wherein at least one retro-reflecting device (2) receives only a second light signal comprising at least the first payload from one reader/writer device (1) after entering the third state (105),

at least one retro-reflection means (2) demodulates and modulates a second optical signal to generate a second optical signal comprising at least a first identification information and reflects the second optical signal to the read-write device (1), wherein,

when the read-write device (1) fails to decode the modulated second optical signal at least comprising the first confirmation information, the read-write device (1) terminates the communication session due to the collision of the uplink communication link, updates the virtual ID candidate list according to the number of the collisions of the acquired synchronous uplink communication link, thereby reentering the first state (102) and sending a second optical signal at least comprising a second load of the virtual ID information according to a retro-reflection device (2) pointed by the next virtual ID on the updated virtual ID candidate list;

in case the decoding is successful, the read-write-device (1) enters a second state (103) and sends a second optical signal comprising at least a third payload to the retro-reflection means (2).

6. A vehicle networking data communication network according to any of claims 1 to 3, wherein the retro-reflective means (2) enters a fourth state (106) upon receiving a second light signal comprising at least a third load and responds to the second light signal, wherein:

in case the virtual ID of the second optical signal comprising at least the third payload matches the virtual ID of the second optical signal comprising at least the first payload received by the retro-reflection means (2), the retro-reflection means (2) reflects and modulates the second optical signal to generate a second optical signal comprising at least the second acknowledgement, and reflects to the read-write means (1) of the second optical signal comprising at least the third payload;

in case the virtual IDs of the second light signal comprising at least the third load and the second light signal comprising at least the first load received by the retro-reflecting device (2) do not match each other, the retro-reflecting device (2) enters a silent state.

7. Vehicle networking data communication network according to any of claims 1 to 3, wherein in case the read/write device (1) enters the second state (103) and the second light signal is not detected at least during the time the read/write device (1) is in continuous communication with the retro-reflecting device (2) receiving the second light signal comprising at least the third load,

the read-write device (1) sends a second optical signal comprising at least a third payload to the retro-reflection device (2) to which it points according to the next virtual ID of the virtual ID candidate list.

8. Vehicle networking data communication network according to any of claims 1 to 3, wherein in case the read/write device (1) enters the second state (103) and a second light signal comprising at least a second acknowledgement is detected at least during the time the read/write device (1) is in continuous communication with the retro-reflective device (2),

the read-write apparatus (1) decodes the signal, wherein:

under the condition of successful decoding, the read-write device (1) outputs a message carried by the optical signal and sends a second optical signal at least comprising a first load to a retro-reflection device (2) pointed by the read-write device according to the next virtual ID of the virtual ID candidate list;

in case of a decoding failure, the read-write device (1) retransmits the same second optical signal comprising at least a third payload to the retro-reflection device (2),

or the read-write device (1) enters a state of continuously transmitting the first optical signal again.

9. A vehicle networking data communication method based on retro-reflective communication is disclosed, wherein a retro-reflective device (2) formed by at least one light label arranged on a vehicle and/or an infrastructure passively modulates and reflects a light signal emitted by a read-write device (1) arranged on the vehicle, so that a stable and continuous light communication link at least in a certain time and space is established between the retro-reflective device (2) in non-active communication and the read-write device (1),

the retro-reflection device (2) responds to the request in the optical signal sent by the read-write device (1) to modulate the confirmation information on the optical signal and reflect the confirmation information to the read-write device (1), thereby realizing correct data interaction between vehicles and road infrastructures,

it is characterized in that the preparation method is characterized in that,

in the case that at least one optical communication link between at least one read-write device (1) and at least one retro-reflection device (2) is established in a stable and continuous manner in a certain time and space, the state of idle is confirmed by a first optical signal,

the at least one retro-reflection means (2) activates a third state (105) for acquiring a temporally and spatially dynamically assigned virtual ID specific to each read/write device (1) and/or activates a fourth state (106) for confirming a virtual ID match by receiving the second optical signal.