CN111431597A - Internet of vehicles data communication network and method based on retro-reflection device communication - Google Patents

Abstract

The present invention relates to a data communication network and method for the Internet of Vehicles based on retro-reflection communication. The network includes a reading and writing device arranged on a vehicle and a retro-reflection device arranged on the vehicle and/or infrastructure for passive communication, at least A reading and writing device establishes an optical communication link with at least one retroreflective device by sending at least two first optical signals and second optical signals of different frequencies, and the first optical signal is continuously sent to monitor the communication range of the reading and writing device. Any ongoing communication session of at least one retroreflective device to reduce the probability of asynchronous uplink communication link collision, the second optical signal is used to find the retroreflective device when the read-write device stops sending the first optical signal and enters the retroreflective device to avoid synchronous uplinks The first state of the communication link conflict and/or the second state for querying the retro-reflection device to avoid the asynchronous uplink communication link conflict is sent by the read-write device to the retro-reflection device.

Description

A vehicle networking data communication network and method based on retro-reflection device communication

technical field

The invention belongs to the technical field of communication, and relates to a data communication network and method suitable for the Internet of Vehicles, in particular to a data communication network and method of the Internet of Vehicles based on retro-reflection communication.

Background technique

Visible Light Communication (VLC) refers to a communication method in which light in the visible light band is used as an information carrier, and optical signals are directly transmitted in the air without using a transmission medium of wired channels such as optical fibers. Compared with communication technologies based on radio signals such as Wi-Fi, Bluetooth, and cellular networks, visible light communication technology has natural advantages such as less signal interference, anti-eavesdropping, and large available bandwidth. The most common visible light communication technology is based on the fast switching modulation of Light Emitting Diode (LED) as the basic unit of the signal source. Intensity and diversity, and finally use photoelectric conversion devices such as photodiodes to receive and demodulate the information carried in the optical signal. Based on the above characteristics and working principles, visible light communication can play a significant role in IoT-based applications, especially between vehicle lights and infrastructure (barricades, road signs, etc.) in autonomous driving, and between indoor ceiling lights and IoT devices. two-way communication between scenarios.

For example, Chinese patent document with publication number CN109450536A discloses a vehicle IoT system and communication method based on visible light communication, wherein the provided system includes: a vehicle-mounted visible light communication node for collecting vehicle information and communicating with vehicle-mounted visible light The vehicle-mounted visible light communication node on the adjacent vehicle in the same driving direction of the vehicle to which the node belongs builds a visible light communication link, and generates the vehicle cluster information of the vehicle cluster composed of the visible light communication link; the roadside infrastructure is used for receiving Vehicle information and vehicle cluster information sent by the vehicle-mounted visible light communication node within the coverage area, and send the vehicle information and vehicle cluster information to the local control node; the local control node is used to receive the roadside infrastructure coverage sent by the roadside infrastructure. The vehicle information and vehicle cluster information in the area are calculated, and the road condition information in the area is obtained by calculation according to the vehicle information and the vehicle cluster information. The system provided by the invention reduces the conflict and interference between communication links in the vehicle Internet of Things. This patent utilizes the characteristics of visible light communication that it is mainly direct and easy to be isolated to reduce the conflict and interference between different communication links. The specific implementation is achieved through directional communication between the lens and the receiver array. However, there are two main problems to realize practical visible light communication in the above-mentioned IoV application scenarios. First, the light-emitting angular range of general-purpose LEDs and the angular range of photoelectric conversion devices sensitive to light are both limited, which requires that the two devices need to be fully aligned to achieve bidirectional communication. Second, from the perspective of design concept, economic cost and operation and maintenance, IoT devices are expected to be miniaturized, low power consumption or even passive. The energy consumption of LED-based communication transmission is usually hundreds of milliwatts, and the effective power that can be converted by solar cells the size of IoT devices is usually only hundreds of microwatts. Therefore, the use of lenses and receiver arrays to realize visible light communication requires not only power Larger power supply also requires high cost to realize the layout transformation of road infrastructure. In addition, the use of a lens enables the beam to be aligned, thereby fulfilling the objective requirement that two-way communication requires complete alignment of the two devices, and this highly directional characteristic of alignment allows the communication link between the two devices to be easily isolated , thus providing objective conditions to avoid mutual interference between adjacent devices. However, this sensitive isolated feature also poses severe challenges to the mobility of its devices and the scalability of one-to-many communications, especially between vehicles and fixed infrastructure. It is easily disturbed by the surrounding environment and cannot communicate in a timely and effective manner.

Reference [1] Jiangtao Li, Angli Liu, Guobin Shen, Liqun Li, Chao Sun, and FengZhao. Retro-vlc: Enabling battery-free duplex visible light communicationformobile and iot applications. In ACM HotMobile, 2015. and reference [2] Xieyang Xu, YangShen, Junrui Yang, Chenren Xu, Guobin Shen, Guo jun Chen, and YunzheNi. Passivevlc: Enabling practical visible light backscatter communication for battery-free iot applications. In ACM MobiCom, 2017. Disclosed a reverse visible light communication system ( Visible Light Backscatter Communication (VLBC), which uses reflective fabric to direct the reflected light to the vehicle-mounted reader requesting communication, switches the on/off state of the LCD, and adjusts the reflected light through the modulation method of on/off key control (OOK). The VLBC system consists of high-power readers and low-power optical tags. Its working principle is as follows: The LED in the reader is turned on and off at a high frequency, so that the light emitted by the LED is used as the carrier of information, that is, the data information is modulated onto the carrier wave (light) by turning on and off. The light signal is received and decoded by the light sensor on the light label. For the uplink (the communication link from the optical tag to the vehicle reader), the transmission is carried out by reflecting the same carrier. The optical label modulates the reflected light through OOK and transmits it. This modulation method is realized by a driver on the reflective fabric controlled by a single-chip microcomputer. Then, the photodiode on the vehicle reader receives or modulates the reflected optical carrier, and further demodulates and decodes it. The literature [1] proves the feasibility of VLBC technology applied to IoV communication in a short distance, solves the problems of mobility, scalability and unfriendliness to cameras of communication equipment, and has low cost (passive work), capable of Staged deployment.

However, in a many-to-many communication scenario, that is, when multiple optical tags exist within the communication range of multiple readers, the communication efficiency between multiple readers and multiple optical tags decreases. Specifically, readers are generally installed on high-speed moving vehicles, and optical tags are installed on the infrastructure on both sides of the road to form retroreflective devices, such as street lights, roadblocks, traffic signs, limit poles, etc. In this case, the distribution of optical tags is relatively sparse, and there is a situation where one reader/writer communicates with one optical tag. However, there are many road infrastructures in urban areas, and the distribution of optical tags is relatively dense. It often occurs that multiple optical tags are distributed within the communication range of multiple vehicle readers, and then many-to-many communication scenarios occur. Similarly, when the traffic volume on the road is small, there may be only one reader/writer communicating with multiple optical tags. When the traffic volume is large, the same optical tag may exist within the communication range of multiple readers at the same time. In more extreme cases, there are multiple optical tags within the sensing range of the optical sensor of one reader. And the car networking system based on VLBC, its working method is that the optical tag starts to work after receiving the optical signal emitted by the reader, modulates and transmits the optical signal emitted by the reader, so that the communication between the reader and the optical tag has a High spatial orientation characteristics, that is, the reader cannot perceive other readers and other optical tags, and the optical tags that communicate with the reader cannot perceive other readers and optical tags. This highly directional communication characteristic of the VLBC communication system will lead to serious hidden terminal problems in many-to-many communication scenarios, that is, in the field of communication, base station A sends a signal to base station B, and base station C does not detect that A sends a signal to B, Therefore, A and C send signals to B at the same time, causing signal collision, and eventually all the signals sent to B are lost. In addition, the highly directional communication characteristics make it impossible for a reader to passively monitor other readers within its communication range that are conducting a communication session. When multiple readers communicate with one optical tag at the same time, or multiple optical tags communicate with multiple readers at the same time, serious communication link conflicts will result.

Literature [3] Shi Lihui. Research on MAC protocol of visible light communication [J]. Mobile Communications, 2014(3-4): 76-81. The medium access control of visible light communication in the IEEE 802.15.7 standard is introduced in detail (Medium Access Control, MAC) protocol, this standard designs the MAC protocol for the high spatial orientation characteristics of visible light (visible light signals cannot pass through obstacles) and the defect that carrier sensing in visible light networks does not have the same robustness as radio frequency networks. 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 confirmation, allocation and management of guaranteed time slots, fast link recovery, multi-channel resource management , color functions and normalization, etc. The MAC protocol in this standard exposes six functions, including:

1. Two channel access mechanisms: contention-based and contention-free; contention-based access allows devices to use random backoff algorithms to access the channel during the contention period, and contention-free access is completely guaranteed by the coordinator during the contention-free period. use. In the carrier sense multiple access mechanism with collision avoidance of time slots in IEEE 802.15.7, the MAC sublayer first initializes two variables: the number of backoffs and the backoff index. When the medium is busy, that is, in the case of a hidden terminal, the random backoff algorithm makes the communication terminal try to exit, and creates a random waiting time for the transmission of signal data of the communication terminal to avoid collisions again.

2. Start and maintain the PAN, select a suitable logical channel and a PAN identifier that is not occupied in the visible light coverage range through channel scanning, and use the selected device as the coordinator.

3. The device joins and leaves the PAN. The association process describes how the device joins or leaves a PAN and how the coordinator realizes the process of the device joining or leaving the PAN.

4. Data transmission, reception and confirmation mechanism. In order to describe the transmission frame, the confirmation frame, and to solve the problem of repeated frames, the physical frame encapsulates multiple MAC frames with the same destination address, and uses an confirmation frame to confirm these frames. .

However, for the VLBC-based car networking system, the MAC protocol in the IEEE 802.15.7 standard is not applicable. First of all, the MAC protocol provided by this standard supports carrier sense multiple access. The function of the carrier sense is to monitor the usage of the channel before sending data, and maintain it for a period of time. After waiting for a random period of time, the channel is still idle. data is sent later. Reduce the chance of conflict by setting different random times for each device. However, in the VLBC-based vehicle networking communication system, in addition to the highly spatial orientation characteristics of the communication between the reader and the optical tag, the optical tag is also passive communication, so the reader and the optical tag cannot perceive other readers and optical tags. The existence of the carrier sense means that the reader cannot avoid the problem of hidden terminals, and the existing methods to mitigate hidden terminals, such as increasing the transmission power and adjusting the carrier sense threshold, do not meet the low power consumption of the Internet of Vehicles, The low-cost design concept, and secondly, cannot solve the synchronous or asynchronous conflict of the uplink communication link.

Literature [4] Research and performance optimization of random access algorithm for multi-packet receiving VLC system [D]. Jilin University, 2017. A new random access mechanism based on IEEE 802.15.7 time slot carrier sense multiple access mechanism with collision avoidance is proposed The access algorithm takes into account the highly spatial orientation characteristics of optical signals, under-carrier sense and the fact that the coordinator cannot know the number of active terminals in the system a priori, this document [4] estimates the number of active terminals on the coordinator side , provides the coordinator with the number of active terminals in the system, and the receiver establishes an optimization problem based on the obtained information on the number of active terminals, adjusts the multi-packet reception capability and backoff parameters, weighs the system throughput and received power efficiency, and achieves maximum system performance. optimization. However, the multi-packet reception proposed in the literature [4] will increase the energy consumption of the receiving end, and the coordinator is always required to estimate the number of active terminals. However, in the car networking system based on VLBC technology, readers and optical tags cannot perceive other Therefore, the method provided by the literature [4] is not suitable for the data communication system of the Internet of Vehicles based on VLBC technology.

In addition, despite the local broadcast nature of retroreflection-based optical tags, it is able to communicate location-specific information to readers on all oncoming vehicles, and the retroreflection-based LCD modulation design also conforms to the local broadcast of optical tags. nature. In fact, the switching of the liquid crystal state will affect all incident light regardless of its source and carrier frequency. Accordingly, the prior art tends to provide a periodic broadcast beacon mechanism for messaging over retroreflective communication based data networks. But this is not the case: when the reader thinks there are multiple optical tags, the responses of the multiple optical tags are bound to conflict. That is, all nearby light tags are potential colliders. However, it is almost impossible to coordinate multiple optical tags statically for the following reasons. First of all, due to the need for no battery, the optical tag is designed to be passive, that is, the optical tag cannot sense whether there are other optical tags nearby. Second, the distance between the reader and the optical tag is highly dynamic due to the mobility of the reader (ie, different locations) and the diversity of headlight power (ie, different viewing ranges). Finally, to save energy, optical tags may sleep from time to time and may be activated at different times, making it difficult to maintain a global clock and ensure clock synchronization between nearby optical tags.

To sum up, it is necessary to design a data communication network and method for the Internet of Vehicles based on retro-reflective communication that can coordinate multiple optical tags to avoid communication link conflicts.

In addition, on the one hand, there are differences in the understanding of those skilled in the art; on the other hand, because the inventor has studied a large number of documents and patents when making the present invention, but the space limit does not list all the details and contents in detail, but this is by no means The present invention does not possess the features of the prior art, on the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art.

SUMMARY OF THE INVENTION

A data communication network for Internet of Vehicles based on retro-reflective communication at least includes a reading and writing device arranged on a vehicle and a passive communication retro-reflection device arranged on the vehicle and/or infrastructure. The retro-reflective device communicates with the read-write device in a retro-reflective manner to construct the Internet of Vehicles. At least one reading and writing device establishes an optical communication link with at least one retroreflective device by sending at least two different frequencies of a first optical signal and a second optical signal. In this way, two optical signals of different frequencies are used for collision detection and discovery and confirmation of the retro-reflection device respectively, which can avoid the confusion of data packets transmitted by the two signals and interfere with the monitoring of the communication link collision.

The first optical signal is continuously transmitted to monitor any ongoing communication sessions of at least one retroreflective device within communication range of the reader/writer device to reduce the probability of asynchronous uplink communication link collisions. Through this setting method, interference-free carrier sensing technology can be realized under VLBC technology, without increasing the power of the transmitted signal or the threshold value of the carrier monitoring, but by using the spatial orientation characteristics of the optical signal height and the passive communication characteristics of the retro-reflecting device. Carrier sense at low power. For example, assuming that a retroreflective device responds to the first optical signal sent by the first reading and writing device by modulating the charge and discharge state of the liquid crystal material of the LCD, then in the case that the second reading and writing device is continuously sending the first optical signal , the first optical signal sent by the second reading and writing device will also be modulated, which enables the second reading and writing device to perceive the ongoing communication session between the first reading and writing device and the retro-reflection device, so that the carrier sense can Simple, effective and rapid implementation of judging the busy or idle state of the optical communication link between the read-write device and the retro-reflection device.

The second optical signal is when the read-write device stops sending the first optical signal and enters the first state for discovering retro-reflective devices to avoid synchronous uplink collisions and/or for querying retro-reflective devices to avoid asynchronous uplinks The second state of the road conflict is sent by the read-write device to the retro-reflection device. Through this arrangement, the reading and writing device can decode according to the second optical signal fed back by at least one retro-reflecting device, so as to convert different states to further solve the problem of hidden terminals, especially between the reading and writing device and the retro-reflecting device. In addition to the high spatial orientation characteristics of unicast communication, the read-write device and the retro-reflection device cannot sense the existence of other read-write devices and retro-reflection devices, that is, it is impossible to know the active state of the retro-reflection device in the VLBC system by setting the coordinator. In this case, the hidden terminal problem is further solved by discovering the first state of the retroreflective device and querying the second state of the retroreflective device.

A vehicle networking data communication network based on retro-reflective communication, at least comprising: a reading and writing device arranged on a vehicle, and a retro-reflective device arranged on the vehicle and/or infrastructure. The read-write device can establish a stable and continuous optical communication link with the retro-reflection device at least in a certain time and space. At least one reading and writing device establishes an optical communication link with at least one retroreflective device by sending at least two different frequencies of a first optical signal and a second optical signal. The first optical signal is used to monitor any ongoing communication session of the retroreflective device to confirm the idle or busy state of the communication link between the read-write device and the retroreflective device, and in the case of the communication link being in an idle state, The read-write device enters the first state and/or the second state to transmit at least a second optical signal comprising a data packet that passively dynamically assigns a virtual ID to at least one retroreflective device in this time and space to avoid uplink and downlink communication link conflicts . Through this setting method, without the need to add an additional coordinator, each reading and writing device is assigned a virtual ID dedicated to the reading and writing device in a passive and dynamic way, so that the reading and writing device and the retro-reflection device cannot perceive other devices. In the case of a reading and writing device and a retroreflective road sign, the collision detection and processing of the uplink and downlink communication links are realized, and the normal information exchange cannot be realized due to the hidden terminal problem.

According to a preferred embodiment, when the read-write device sends a first optical signal to at least one retro-reflective device within its communication range, the read-write device is configured to monitor the signal and determine whether the read-write device and the retro-reflective device have a relationship between them. The optical communication link between the two is in a busy state, so that the reading and writing device maintains the state of continuously sending the first optical signal to find a retroreflective device within its communication range that can establish an optical communication link in an idle state.

According to a preferred embodiment, when the read-write device determines that the optical communication link with the retroreflective device is in an idle state, the read-write device transitions to the first state. The read-write device transmits a second optical signal comprising at least the first payload to the at least one retroreflective device. In the case where the optical communication link between at least two retroreflective devices and the read/write device is in an idle state, the read/write device passively and dynamically assigns and constructs a virtual ID for each retroreflective device based on the number of retroreflective devices Candidate list. Therefore, the read-write device sequentially sends the second optical signal including the first payload of the virtual ID information to the retroreflection device pointed to by the virtual ID in sequence according to the sequence on the virtual ID candidate list. The virtual ID includes at least the number of rounds and random variables.

According to a preferred embodiment, the at least one retroreflective device enters the third state upon receipt of a second optical signal comprising at least the first load. In the case that the retro-reflective device simultaneously receives the second optical signals sent by the at least two read-write devices, the retro-reflective device enters a silent state due to the collision of the downlink communication link. When the reading and writing device does not detect the optical signal reflected by the retroreflection device within the preset time, the reading and writing device re-enters the state of continuously and continuously sending the first optical signal.

According to a preferred embodiment, when at least one retroreflective device only receives a second optical signal including at least the first load and sent by one reading and writing device after entering the third state, the at least one retroreflective device demodulates and modulates the first optical signal. Two optical signals are used to generate a second optical signal including at least the first confirmation information, and the second optical signal is reflected to the read-write device. When the read-write device fails to decode the modulated second optical signal including at least the first confirmation information, the read-write device terminates the communication session due to a conflict in the uplink communication link. The reading and writing device updates the virtual ID candidate list according to the number of conflicts obtained in the synchronous uplink communication link, thereby re-entering the first state and sending at least the virtual ID according to the retroreflection device pointed to by the next virtual ID on the updated virtual ID candidate list. A second optical signal of a second payload of information. In the case of successful decoding, the read-write device enters the second state. The read-write device sends a second optical signal including at least a third payload to the retroreflective device.

According to a preferred embodiment, the retroreflective device enters the fourth state after receiving the second optical signal including at least the third load. The retroreflective device is responsive to the second optical signal. In the case where 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 retroreflective device match each other, the retroreflective device reflects and modulates the second light signal to generate a second optical signal including at least a second acknowledgment. At the same time, the retro-reflecting device reflects to the reading and writing device that includes at least the second optical signal of the third load. In the case 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 retroreflective device do not match each other, the retroreflective device enters a silent state.

According to a preferred embodiment, the second optical signal is not detected during the time when the reading and writing device enters the second state and at least during the continuous communication between the reading and writing device and the retroreflective device receiving the second optical signal including at least the third payload. In this case, the reading and writing device sends the second optical signal including at least the third payload to the retroreflective device to which it points according to the next virtual ID of the virtual ID candidate list.

According to a preferred embodiment, when the reading and writing device enters the second state and the second optical signal including at least the second confirmation is detected at least during the period of continuous communication between the reading and writing device and the retroreflective device, the reading and writing device signal is decoded. In the case of successful decoding, the reading and writing device outputs the message carried by the optical signal and sends a second optical signal including at least the first payload to the retroreflective device to which it points according to the next virtual ID in the virtual ID candidate list. In the case of decoding failure, the read-write device re-sends the same second optical signal including at least the third payload to the retro-reflection device. Or, the read-write device re-enters the state of continuously and continuously sending the first optical signal.

A data communication method based on retro-reflective communication, the retro-reflective device composed of at least one optical tag arranged on the vehicle and/or the infrastructure passively modulates and reflects the read-write device arranged on the vehicle by passively modulating and reflecting. The way of transmitting the optical signal enables the establishment of a stable and continuous optical communication link between the non-active communication retro-reflection device and the reading and writing device at least within a certain time and space. The retro-reflection device modulates the confirmation information on the optical signal in response to the request in the optical signal sent by the reading and writing device, and reflects it to the reading and writing device, so as to realize the correct data between the vehicle and the vehicle and between the vehicle and the road infrastructure. interact. At least one reading and writing device establishes an optical communication link with at least one retroreflective device by sending at least two different frequencies of a first optical signal and a second optical signal. In the case that at least one optical communication link established stably and continuously within a certain time and space between at least one reading and writing device and at least one retro-reflecting device confirms that it is in an idle state through the first optical signal, the at least one retro-reflecting device receives the first optical signal and confirms that it is in an idle state. Two optical signals activate a third state for acquiring a temporally and spatially dynamically allocated virtual ID specific to each reader and/or a fourth state for confirming a virtual ID match.

Description of drawings

Fig. 1 is based on the schematic diagram of downlink communication link conflict in VLBC car networking;

Fig. 2 is based on the schematic diagram of synchronous uplink communication link conflict in VLBC car networking;

Fig. 3 is based on the schematic diagram of asynchronous uplink communication link conflict in VLBC car networking;

Fig. 4 is the state transition schematic diagram of the read-write device in a preferred embodiment of the system of the present invention;

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

6 is a schematic diagram of the structure of the MAC layer message frame in a preferred embodiment of the system of the present invention;

7 is a schematic diagram of the discovery workflow of the reading and writing device in a preferred embodiment of the system of the present invention; and

FIG. 8 is a schematic diagram of the query workflow of the reading and writing device in a preferred embodiment of the system of the present invention.

List of reference signs

1: Read and write device 2: Retroreflective device

3: First retroreflector 4: Second retroreflector

5: The first vehicle reading and writing device 6: The second vehicle reading and writing device

101: Carrier monitoring 102: The first state 103: The second state

104: Standby 105: The third state 106: The fourth state

107: Silent 108: Virtual ID update 109: One-to-one normal communication

110: Listening 111: Sync Uplink Conflict

112: Asynchronous uplink communication link conflict 113: Downlink communication link conflict

114: Communication ended or aborted 201: Discovery request

202: Query request 203: Query response

204: Preamble 205: Source address

206: Temp ID 207: Frame Type

208: Number of rounds 209: Number of conflicts

210: Symbol length 211: Payload

212: Frame check field 213: QRC

301: Discovery message 302: Monitor

303: Feedback signal 304: Decoding

305: Query Process 306: Backoff

307: Guide virtual ID update 308: Query message

309: carrier monitor or retry 310: next retroreflector

311: Output message 312: End

Detailed ways

The detailed description will be given below in conjunction with FIGS. 1 to 8 .

Example 1

This embodiment discloses a communication network, which may be a vehicle networking communication network, a vehicle networking communication system based on optical tags, or a vehicle networking communication system based on retro-reflection communication. Implemented by the system of the present invention and/or other alternative components. For example, the method disclosed in this embodiment is implemented by using various components in the system of the present invention. The whole and/or part of the contents of the preferred implementations of other embodiments may be used as supplements to the present embodiment without causing conflict or contradiction.

Preferably, in a vehicle networking system based on VLBC technology, optical tags are arranged on the infrastructure near the road to construct the retro-reflection device 2 . Infrastructure can be street lights, barricades, traffic signs, limit poles, etc. Preferably, the light tags can also be arranged on other vehicles. Preferably, the reading and writing device 1 is arranged on a vehicle. The vehicle may be a vehicle, a motorcycle, or the like. The retro-reflective device 2 uses the reflective objects on the infrastructure or the reflective device provided on the optical label itself to reflect the optical signal sent by the reading and writing device 1 to the reading and writing device 1 requesting communication. The retroreflective device 2 drives the charge and discharge states of the liquid crystal material of the LCD through the LCD driver in the optical label, thereby realizing the amplitude modulation of the optical signal. The VLBC system consists of a high-power reading and writing device 1 and a low-power retro-reflecting device 2 set on the vehicle. The specific working principle is as follows: For the downlink communication link, that is, the optical communication link in which the reading and writing device 1 sends visible light signals to the retroreflective device 2, the LEDs in the reading and writing device 1 are turned on and off at a high frequency, so that the LEDs emit light. The visible light is used as the carrier of the information, that is, the data information is modulated onto the carrier (visible light) by means of on/off keying (OOK). The optical signal is received and decoded by an optical sensor on the retroreflective device 2 . For the uplink communication link, that is, the optical communication link in which the retroreflective device 2 sends visible light to the reading and writing device 1 , the transmission is performed by reflecting the same optical carrier sent by the reading and writing device 1 . The retro-reflection device 2 modulates the reflected light through OOK and sends it. This modulation method is realized by driving the driver connected to the LCD through the micro-program controller on the optical label. The driver can adjust the voltage applied to the LCD, so as to control the state transition of liquid crystal charging or discharging in the LCD, to control whether the LCD emits light or to adjust the amplitude of the light signal, so as to realize OOK modulation. Then, the optical sensor on the reading and writing device 1 receives the reflected light, and further demodulates and decodes it.

Preferably, the distribution of retroreflective devices 2 is relatively sparse in most cases. For example, when vehicles are driving in suburban areas, there are fewer infrastructures on both sides of the road and vehicles with a short distance (less than 100 meters) on the same road. There is thus a situation where one reader/writer device 1 communicates with one retroreflective device 2 . However, in urban areas, not only are there many road infrastructures, but also vehicles are dense, so that the distribution of retroreflective devices 2 and reading and writing devices 1 is relatively dense, and it often occurs that multiple retroreflective devices 2 are distributed within the communication range of multiple reading and writing devices 1. , and then there is a many-to-many communication scenario. Also, when the traffic volume of the road is small, there may be a single read-write device 1 communicating with a plurality of retroreflective devices 2, ie one-to-many communication. When the traffic volume is large, there are many vehicles, so the same retroreflective device 2 may exist simultaneously within the communication range of multiple reading/writing devices 1 . In a more extreme case, there are multiple retroreflective devices 2 within the sensing range of the optical sensor of one read-write device 1 . However, in the car networking system based on VLBC, the optical tag on the retroreflective device 2 will only start to work when it receives the optical signal emitted by the reading and writing device 1 or the vehicle or vehicle controlled by the reading and writing device 1. In the Internet of Vehicles system of the retroreflective device 2 , the reading and writing device 1 actively sends a communication request to the retroreflective device 2 . The optical label of the retroreflective device 2 modulates and reflects the optical signal sent by the reading and writing device 1, so that the communication between the reading and writing device 1 and the optical label on the retroreflective device 2 has a high spatial orientation characteristic, that is, the reading and writing device 1 cannot Perceiving other reading and writing devices 1 and other retro-reflective devices 2, and the retro-reflective device 2 that communicates with the reading and writing device 1 cannot perceive other reading and writing devices 1 and retro-reflective devices 2. For writing device 1 and retro-reflecting device 2, other reading and writing devices 1 and retro-reflecting device 2 are transparent, so this highly spatially oriented communication characteristic of the VLBC communication system will cause serious problems in many-to-many communication scenarios. Hidden terminal problem, that is, in the field of communication, base station A sends a signal to base station B, but base station C does not detect that A sends a signal to B, so A and C send signals to B at the same time, causing signal contention and conflict, causing B to receive at the same time The signals sent by A and C are incorrectly received due to data collision, and eventually all the signals sent to B are lost. In addition, the highly spatially oriented communication characteristics also make it impossible for the reader/writer device 1 to passively monitor other reader/writer devices 1 within its communication range that are conducting a communication session. When multiple read-write devices 1 communicate with the same retroreflective device 2 at the same time, or when multiple retro-reflective devices 2 communicate with multiple read-write devices 1 simultaneously, serious communication link conflicts will result. Preferably, the collision of the communication link includes three different situations, as follows:

1. Conflict of downlink communication links: As shown in Figure 1, when a retro-reflection device 2 appears within the communication range of multiple read-write devices 1, if multiple read-write devices 1 try to communicate with the retro-reflection device 1 at the same time The device 2 communicates, so the hidden terminal problem occurs in the retro-reflective device 2, that is, the retro-reflective device 2 receives optical signals sent by multiple different reading and writing devices 1 at the same time. 2. The optical signal cannot be received correctly, resulting in the loss of signals sent by multiple different reading and writing devices 1, and a downlink communication link conflict 113 will occur;

2. Synchronization conflict of the uplink communication link: As shown in FIG. 2 , when multiple retro-reflective devices 2 appear within the communication range of the reading and writing device 1 , and at the same time, multiple retro-reflective devices 2 passively receive the reading and writing device 1 When the optical signal is sent, since the retro-reflective device 2 and other retro-reflective devices 2 are transparent to each other, the retro-reflective device 2 cannot sense the existence of other retro-reflective devices 2 nearby, and they may respond to the communication request of the read-write device 1 at the same time. , resulting in a synchronization uplink communication link conflict 111;

3. Asynchronous conflict of the uplink communication link: As shown in FIG. 3, when the first retroreflective device 3 responds to the communication request of the first on-board reading and writing device 5, the nearby second on-board reading and writing device 6 attempts to A second retroreflective device 4 located within the communication range of the first vehicle-mounted reading and writing device 5 communicates with each other. The response of the second retro-reflecting device 4 to the second on-board reading and writing device 6 will be monitored by the first on-board reading and writing device 5, so that the first on-board reading and writing device 5 simultaneously receives the first retro-reflective device 3 and the second retro-reflective device 5. The optical signal of the device 4 is reflected, thereby causing the communication session between the first in-vehicle reading/writing device 5 and the first retro-reflecting device 3 to be terminated, that is, an asynchronous uplink communication link conflict 112 occurs.

Preferably, in the collision of the uplink communication link, there is also a special case of the acquisition effect. A trapping effect is when the expected response of a retroreflective device 3 with respect to a reader/writer device 1 is unexpectedly overwhelmed by the response of another retroreflective device 3, i.e. another retroreflective device 3 may have a larger reflective surface or distance from the device. The proximity of the reading and writing device 1 makes the reflected signal energy stronger, which drowns the expected response signal of the retro-reflecting device 3 . In the case where the response signal captured by the reading and writing device 1 changes, due to the mobility of the reading and writing device 1 , the captured response signal can be remedied later.

Preferably, the above conflict situations will cause the reading and writing device 1 and the retro-reflecting device 2 to fail to correctly decode the optical signal, thereby causing loss of valid information and failure to communicate normally. In addition, street lights, barricades, traffic signs, limit poles, and other infrastructure like street signs have a local broadcast nature and can be used to transmit location-related information to oncoming vehicles. The retroreflective device 2 based on the retroreflective LCD modulation design also follows the local broadcast characteristics of street signs. 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 the periodic broadcast beacon mechanism to transmit information, because it is simple and easy to implement. However, this is not the case in practice: when the reading and writing device 1 considers that there are multiple retro-reflective devices 2, the responses of the retro-reflective devices 2 are bound to conflict, that is, the above conflict situations occur. That is, all nearby retroreflectors 2 are potential colliders. However, it is almost impossible to coordinate a plurality of retroreflective devices 2 statically for the following reasons. First, due to the need for no battery, the retroreflective device 2 is designed to be passive, that is, the retroreflective device 2 cannot sense whether other retroreflective devices 2 exist nearby. Second, due to the mobility of the reader/writer 1 (ie, different locations) and the diversity of headlight power (ie, different viewing ranges), the proximity distance between the reader/writer 1 and the retroreflective unit 2 is highly Dynamic. Finally, to save energy, retroreflectors 2 may sleep from time to time and may be activated at different times, making it difficult to maintain a global clock and ensure clock synchronization between nearby retroreflectors 2 . To sum up, in view of the above problems, this embodiment uses the VLBC communication system in the downlink communication link, the reading and writing device 1 actively sends an optical signal to the retro-reflecting device 2 for communication, and in the uplink communication link reverses the road sign 2 passively reflects the reading and writing device 1. According to the characteristics of the transmitted optical signal, a vehicle networking communication system based on the retro-reflection device is proposed, which adopts the excitation carrier monitoring mechanism to reduce the probability of asynchronous uplink communication link collision. Furthermore, active carrier monitoring is capable of listening to all communication sessions of retroreflectors 2 within its communication range. At the same time, another function brought by this mechanism is that the communication session of the retroreflective device 2 within its communication range can be passively heard, which can avoid the repeated query of the same retroreflective device 2 by multiple reading and writing devices 1 . The retroreflection device 2 adopts the passive and real-time dynamic allocation method of virtual ID to realize the unicast function in the many-to-many communication in the complex environment, so as to solve the conflict of the synchronous or asynchronous uplink communication link.

A vehicle networking communication system based on retro-reflective communication at least comprises: a reading and writing device 1 arranged on a vehicle and a retro-reflection device 2 arranged on the vehicle and/or infrastructure. The reading and writing device 1 can establish a stable and continuous optical communication link with the retro-reflecting device 2 at least within a certain time and space, and is used to transmit at least the transmission frame and the confirmation frame between the vehicle and the vehicle and/or the vehicle and the infrastructure. data packets, so as to realize the correct data exchange between the read-write device 1 and the retro-reflection device 2. Preferably, the reading and writing device 1 transmits to the retroreflective device 2 an optical signal including at least a transmission frame. The retroreflective device 2 modulates the confirmation information on the optical signal, thereby reflecting the optical signal including at least the confirmation frame to the reading and writing device 1 . At least one reading and writing device 1 establishes an optical communication link with at least one retroreflective device 2 by sending at least two first optical signals and second optical signals of different frequencies. In this way, two optical signals of different frequencies are used for collision detection and discovery and confirmation of the retro-reflection device 2 respectively, that is, the passive carrier monitoring 101 is implemented through the first optical signal, and the ongoing communication session of the retro-reflection device 2 is monitored, thereby Avoid hidden terminal problems with this retroreflection. Using the second optical signal to realize the discovery and/or query of the retro-reflection device 2, it is possible to avoid uplink communication link conflict in the case that the carrier monitoring 101 cannot further monitor the hidden terminal. A further hidden terminal is a situation in which a plurality of reading and writing devices 1 communicate with the same retroreflective device 2 at the same time. In this case, since communication occurs at the same time, the carrier monitoring 101 realized by using the first optical signal can only monitor the optical signal. The communication link is idle. In addition, the frequencies of the first optical signal and the second optical signal are different, which is helpful for the reading and writing device 1 to identify different types of optical signals, so as to respond to the corresponding state, and also avoids confusion of the data packets transmitted by the two signals to prevent the communication chain from being confused. The monitoring of road collisions interferes.

Preferably, the first optical signal is continuously transmitted to monitor any ongoing communication session of at least one retroreflective device 2 within the communication range of the reader/writer device 1 . With this setting, the collision probability of the asynchronous uplink communication link can be reduced. Preferably, the reading and writing device 1 is provided with a carrier monitor 101 , a first state 102 for discovering the retroreflective device 2 and a second state 103 for querying the retroreflective device 2 . The relationship between these three state transitions is shown in Figure 4. Preferably, the carrier monitoring 101 is that the reading and writing device 1 continuously sends the first optical signal. The frequency of the first optical signal is different from the frequency of the transmission of valid data sent by the reading and writing device 1 . For example, the frequency of the first optical signal may be fu =455KHz, and the second optical signal with a frequency of _1.8MHz is used for active downlink communication to transmit data. Preferably, the first optical signal is used to detect any ongoing communication session. A communication session refers to an uplink or downlink communication link between other read/write devices 1 and retroreflective devices 2 . Preferably, the reading and writing device 1 can at least actively discover potential retroreflective devices 2 within its communication range by sending the first optical signal. Preferably, the reading and writing device 1 is in the carrier monitoring 101 state at other times, except in the case of downlink communication data transmission. Preferably, when encountering a new retroreflective device 2 , the reading and writing device 1 checks all communication sessions of the retroreflective device 2 , so as to obtain the communication status of the retroreflective device 2 . The read-write device 1 continuously sends out the first optical signal to detect any possible communication session, and constantly monitors 110 whether the channel between the read-write device 1 and the retro-reflective device 2 is free. After it is determined to be idle, the read-write device 1 enters the first state 102 . Preferably, the first optical signal can exploit the high spatial directionality of the retroreflected beam to detect other ongoing communication sessions. For example, suppose one retroreflective device 2 responds to a communication request from another read/write device 1 by switching its LCD state. In the state of carrier monitoring 101, the reflected light of the first reading and writing device 1 will also be modulated, so that the reading and writing device 1 can sense the ongoing communication session and ensure the communication between the reading and writing device 1 and the retro-reflection device 2. The channel is idle before attempting to transition to the first state 102 or the second state 103. Through this setting method, interference-free carrier sensing technology can be realized under VLBC technology, without increasing the power of the transmitted signal or the threshold value of carrier monitoring, but using the spatial orientation characteristics of the optical signal height and the passive communication characteristics of the retro-reflection device 2 Implement carrier sense at low power. Moreover, through the carrier monitoring 101 of the first optical signal, the busy or idle state of the optical communication link between the reading and writing device 1 and the retro-reflecting device 2 can be quickly and easily determined.

Preferably, the second optical signal is when the reading and writing device 1 stops sending the first optical signal and enters the first state 102 for discovering the retro-reflecting device 2 to avoid synchronizing uplink collisions and/or for querying the retro-reflecting device 2 The second state 103 to avoid asynchronous uplink communication link collision is sent by the read-write device 1 to the retro-reflection device 2 . With this arrangement, the reading and writing device can decode according to the second optical signal fed back by at least one retro-reflecting device 2, so as to switch between different states to further solve the hidden terminal problem and avoid the conflict of uplink and downlink communication links.

Preferably, for a pair of first normal communication 109 , the reading and writing device 1 will switch in the sequence of carrier monitoring 101 , first state 102 and second state 103 as shown in FIG. 4 . For example, in the case where it is determined that the signal between the read-write device 1 and the retroreflective device 2 is in an idle state, the read-write device 1 enters the first state 102, and the one-to-one normal communication 109 does not have a down/uplink communication link conflict , the reading and writing device 1 enters the second state 103 by correctly decoding the reflected light signal of the retro-reflecting device 2 . Preferably, the first state 102 is the state in which the retroreflective device 2 is found. The second state 103 is to query the state of the retroreflective device 2 . Preferably, different link conflicts result in different state transitions. For example, in the state of carrier monitoring 101, the reading and writing device 1 continuously sends the first optical signal to monitor 110 the retroreflective device 2 within its communication range. If the first optical signal confirms that the channel between the reading and writing device 1 and the retroreflective device 2 is In the case that the read-write device 1 is in the busy state before trying to find or query, the read-write device 1 will re-enter the carrier monitoring 101 state.

Preferably, as shown in FIG. 5 , when the reading and writing device 1 sends a first optical signal to at least one retroreflective device 2 within its communication range, the reading and writing device 1 is configured to monitor the signal and then judge the reading and writing device 1 The optical communication link with the retroreflective device 2 is in a busy state, so that the reading and writing device 1 maintains the state of continuously sending the first optical signal to find a retroreflective device that can establish an optical communication link in an idle state within its communication range 2. Specifically, when the retroreflective device 2 receives the first optical signal, the retroreflective device 2 does not take any action and is in the silent 107 state. After sending the first optical signal, the reading and writing device 1 monitors whether the optical signal is received. Preferably, the reading and writing device 1 can realize the reception of optical signals through an optical sensor. If the reading and writing device 1 does not detect a signal within a preset time, it is determined that the optical communication link between the reading and writing device 1 and the retroreflective 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 reading and writing device 1 determines that the optical communication link between the reading and writing device 1 and the retroreflective device 2 is in an idle state, the reading and writing device 1 enters the first state 102 and sends the second optical signal. The second optical signal includes at least a payload. The payload represents information, that is, communication information between the reader/writer device 1 and the retroreflective device 2 . The information may be inquiry information or inquiry information and the like. Preferably, after the reading and writing 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 convert the second optical signal with the response information in the form of retro-reflection. The signal is retroreflected to the read/write device 1 . Through the above setting method, when the reading and writing device 1 is in the state of the carrier monitoring 101, the retro-reflecting device 2 receives the first optical signal without doing any action and is in a silent state 107. Therefore, if the reading and writing device 1 receives the retro-reflecting device 2 feedback optical signals, then the retroreflective device 2 has already conducted a communication session with other reading and writing devices 1, so the reading and writing device 1 determines that the retroreflective device 2 is in a busy state, thereby avoiding asynchronous uplink communication link conflicts. In addition, with this arrangement, the read-write device 1 can monitor any ongoing communication sessions between the retro-reflective device 2 and other read-write devices 1 , so it can sense other read-write devices 1 to some extent, thereby solving hidden problems. terminal problem.

Preferably, as shown in FIG. 5 , the retroreflective device 2 is usually in a standby state. After the first optical signal sent by the reading and writing device 1 activates the retro-reflective device 2 , the retro-reflective device 2 has three active states, namely, the third state 105 for receiving the second optical signal, and the second optical state 105 for responding to the reading and writing device 1 . The fourth state 106 of the signal and the silent 107 state. In the absence of any conflict, the retroreflective device 2 directly enters the fourth state 106 responsive to the read-write device 1 after activation.

Preferably, as shown in FIG. 4 and FIG. 5 , when a conflict occurs, the states of the read-write device 1 and the retro-reflection device 2 will be switched and will be retried. Preferably, different collisions result in different state transitions. Preferably, when the read-write device 1 judges that the optical communication link with the retroreflective device 2 is in an idle state, the read-write device 1 transitions to the first state 102 . In the first state 102, the reading and writing device 1 transmits a second optical signal comprising at least the first load to the at least one retroreflective device 2. Preferably, the first payload may be a message containing a frame structure, and the message at least contains a discovery request. Preferably, in the case that the optical communication link between the two retro-reflective devices 2 and the reading-writing device 1 is in an idle state, the reading-writing device 1 passively and dynamically Assign virtual IDs and build a virtual ID candidate list. The ID is the identity document (ID) of the retroreflective device 2 . Passively assigning the virtual ID may mean that the reading and writing device 1 passively assigns the virtual ID dynamically according to the retroreflective device 2 sensed by the reading and writing device 1 through the first optical signal. Dynamically assigning a virtual ID may mean that the ID assigned by the retroreflective device 2 is not fixed. This is because multiple retroreflective devices 2 may appear within the communication range of the reading and writing device 1. Therefore, for different reading and writing devices 1, The same retroreflective device 2 can have different IDs. Preferably, the reading and writing device 1 sequentially sends the second optical signal including at least the first payload of the virtual ID information to the retroreflective device 2 pointed to by the virtual ID in sequence according to the sequence on the virtual ID candidate list. Through this setting method, without the need to add an additional coordinator, each retroreflective device 2 is assigned a virtual ID dedicated to the reading and writing device 1 in a passive and dynamic manner, so that the reading and writing device 1 and the retroreflective device can communicate with each other. 2. In the case that other reading and writing devices 1 and retro-reflection devices 2 cannot be sensed, the collision detection and processing of the uplink and downlink communication links are realized, so as to avoid the failure of normal information exchange due to the hidden terminal problem. Specifically, the second optical signal including the relevant payload is sent to the retroreflective device 2 by enumerating the virtual IDs of the retroreflective device 2 in the virtual ID candidate list. As shown in FIG. 7 , the reading and writing device 1 sends a second optical signal including at least the first load to the retroreflective device 2 according to the virtual ID, that is, the reading and writing device 1 sends a discovery message 301 , and then monitors 302 the optical signal from the retroreflective device 2 . feedback. At least one retroreflective device 2 enters a third state 105 upon receiving a second optical signal comprising at least the first payload. When the retro-reflective device 2 simultaneously receives the second optical signals sent by at least two read-write devices 1, the retro-reflective device 2 enters the silent 107 state to avoid downlink communication link collision. In the case where the reading and writing device 1 does not detect the optical signal reflected by the retroreflective device 2 within the preset time, that is, the reading and writing device 1 does not receive the feedback signal 303 . The read-write device 1 may conclude that the retro-reflective device 2 with which it communicates may be out of its communication range, or its communication range is without the retro-reflective device 2, or a downlink communication collision may occur. Preferably, in this case, the read-write device 1 executes the backoff 306 mechanism, and re-enters the state of continuously and continuously sending the first optical signal.

Preferably, in the case that at least one retroreflective device 2 only receives the second optical signal including at least the first load sent by the reading and writing device 1 after entering the third state 105, the at least one retroreflective device 2 demodulates and The second optical signal is modulated to generate a second optical signal including at least the first confirmation information, and the second optical signal is reflected to the read-write device 1 . When the read-write device 1 fails to decode 304 the modulated second optical signal including at least the first confirmation information, the read-write device 1 terminates the communication session due to a conflict in the uplink communication link. The read-write device 1 guides the virtual ID update 307 according to the number of conflicts obtained in the synchronous uplink communication link, thereby re-entering the first state 102 and sending the second according to the retroreflection device 2 pointed to by the next virtual ID on the updated virtual ID candidate list. the second optical signal of the payload. Preferably, the second payload includes at least the virtual ID information. In the case of successful decoding, the reading and writing device 1 enters the second state 103 . The reading and writing device 1 sends a second optical signal including at least a third payload to the retro-reflection device 2. Preferably, the third payload includes at least a query message 308, as shown in FIG. 8 .

Preferably, the retroreflective device 2 enters the fourth state 106 after receiving the second optical signal including at least the third load. The retroreflective device 2 is responsive to the second optical signal. In the case where 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 retroreflective device 2 match each other, the retroreflective device 2 reflects and modulates the two optical signals to generate a second optical signal including at least a second acknowledgment. At the same time, the retroreflective device 2 reflects to the reading and writing device 1 which includes at least the second optical signal of the third load. In the case 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 retroreflective device 2 do not match each other, the retroreflective device 2 enters the silent 107 state. With this arrangement, the collision of the uplink communication link can be avoided.

According to a preferred embodiment, the first read-write device 1 enters the second state 103 and does not detect the first In the case of two optical signals, that is, as shown in FIG. 8 , when the read-write device 1 does not receive the feedback signal 303, the read-write device 1 retroreflects the next virtual ID pointed to it according to the next virtual ID in the virtual ID candidate list. Apparatus 310 transmits a second optical signal comprising at least a third payload.

According to a preferred embodiment, when the reading and writing device 1 enters the second state 103 and a second optical signal including at least the second confirmation is detected at least for the time that the reading and writing device 1 is in continuous communication with the retroreflective device 2, the reading The writing device 1 decodes the signal. In the case of successful decoding, the reading and writing device 1 outputs the message carried by the optical signal, that is, the output message 311, and sends the next retroreflective device 310 to which it points according to the next virtual ID of the virtual ID candidate list to send at least the The second optical signal of the first payload. In the case of decoding failure, the reading and writing device 1 enters the carrier monitoring or retry 309, that is, re-sends the same second optical signal including at least the third load to the retro-reflecting device 2, or the reading and writing device 1 re-enters continuous continuous The state of sending the first optical signal.

Example 2

This embodiment discloses a vehicle networking data communication network based on retroreflective communication, which at least includes: a reading and writing device 1 arranged on a vehicle, and a retroreflective device 2 arranged on the vehicle and/or infrastructure. The reading and writing device 1 can establish a stable and continuous optical communication link with the retroreflective device 2 at least in a certain time and space. At least one reading and writing device 1 establishes an optical communication link with at least one retroreflective device 2 by sending at least two first optical signals and second optical signals of different frequencies. The first optical signal is used to monitor any ongoing communication session of the retroreflector to confirm the idle or busy state of the communication link between the read-write device 1 and the retroreflector 2, and if the communication link is in an idle state Next, the reading and writing device 1 enters the first state and/or the second state to transmit a second optical signal comprising at least a data packet that passively and dynamically assigns a virtual ID to at least one retroreflective device 2 in this time and space to avoid upstream and downstream Communication link conflict. Through this setting method, without the need to add an additional coordinator, each reading and writing device 1 is assigned a virtual ID dedicated to the reading and writing device 1 in a passive and dynamic way, so that the reading and writing device 1 and the retro-reflection device can communicate with each other. 2. In the case that other reading and writing devices 1 and retro-reflection devices 2 cannot be sensed, the collision detection and processing of the uplink and downlink communication links are realized, so as to avoid the failure of normal information exchange due to the hidden terminal problem.

Preferably, the Internet of Vehicles data communication network disclosed in this embodiment is the same as that in Embodiment 1, and the repeated content will not be repeated. Preferably, this embodiment discloses a preferred implementation of the virtual ID in Embodiment 1. Since information about the presence and ID of the retroreflective device 2 signal cannot be known prior to the reading and writing device 1, the ID of the retroreflective device 2 must first be discovered. Pre-assigning a fixed Globally Unique Identifier (GUID) to each retroreflective device 2 is not feasible, as this would require a nationwide or industry-wide address assignment agreement. Also, since each retroreflective device 2 and ID must be discovered by the read/write device 1, a larger address space means a longer process in the first state 102. In addition, considering that the target scenario of vehicle networking communication 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 entire communication network, such as The uplink communication link is limited by the LCD modulation frequency in the retroreflective device 2, and its data rate is very low, so the address space of the ID needs to be shortened as much as possible, thereby reducing the delay of the uplink communication link, and the delay of the uplink communication link. The first state 102 and the second state 103 of the entire read-write device are controlled. Preferably, the goal of setting the ID is to distinguish only a plurality of retro-reflection devices 2 that appear in the communication range of the same read-write device 1 in an uplink communication link conflict, so for different read-write devices 1, the same retro-reflection device 1 Devices 2 can have different IDs. Thus, the presence of multiple retroreflective devices 2 within the communication range of the read-write device 1 dynamically generates a temporary, read-write device-specific ID. Specifically, a virtual ID of a retroreflective device 2 includes at least the address of the read-write device 1 , the number of rounds 208 , the number of collisions 209 of the uplink communication link in the current number of rounds 208 , and the temporary ID 206 . The temporary ID206 is a random variable. Preferably, round number 208 refers to the sequential index of the current discovery round.

Preferably, in order to facilitate the realization of the above-mentioned dynamic virtual ID and the IoV data communication network based on retroreflective communication provided in Embodiment 1, five types of messages are designed in the MAC protocol, which are discovery request 201 , query request 202 , and query confirmation. , discovery confirmation and query response 203. Preferably, the discovery request 201 , the query request 202 and the query confirmation are downlink messages, that is, messages sent by the reading and writing device 1 to the retroreflection device 2 . It is found that the confirmation and query response 203 is an uplink message, that is, a message sent by the retroreflective device 2 to the reading and writing device 1 . Preferably, the confirmation is found to be a very short waveform that can be adapted for a special mode of presence detection. Preferably, due to the shortage of bandwidth resources of the uplink communication link, in this embodiment, the query confirmation is carried in the discovery request 201 and/or the query request 202 . Preferably, the frame formats of the three MAC packets, the discovery request 201, the query request 202 and the query response 203 are shown in Figure 6, wherein the discovery request 201 can be applied to the first state 102, and the query request 202 can be applied to the second state 103 , the query response 203 may be applied to the third state 105 and/or the fourth state 106 of the retroreflective device 2 . As shown in FIG. 6 , the frame structures of the three types of messages have a preamble 204 , a source address 205 of the read/write device 1 , a temporary ID 206 of the retroreflection device 2 , a round number 208 and a frame check field 212 . Preferably, the temporary ID 206 field is a random number used to resolve uplink communication link collisions. It is used as a temporary ID for retroreflective unit 2, specific to read/write unit 1. Preferably, both the discovery request 201 and the query request 202 include the frame type 207 and the QRC 213 . Preferably, the QRC213 field is a cyclic redundancy check value calculated from the payload 211 in the query response 203 received from the read/write device 1 . The QRC 213 field is for the read/write device 1 to compare with the CRC 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 retroreflective device 2 through the virtual ID design. We only list three kinds of MAC messages, because the discovery acknowledgment message is short and only has a leading part, because its main function is to indicate its existence, and the query acknowledgment is included in the message of the discovery request 201. Preferably, the frame structure of the query response 203 message also includes fields such as symbol length 210 .

Preferably, the address source address 205 , the round number 208 , and the collision number 209 of the uplink communication link in the current round number 208 of the reading and writing device 1 are sent by the reading and writing device 1 in the discovery request 201 message. The random variable obeys unif{0, 2Nc}, that is, the random variable obeys a uniform distribution in [0, 2Nc], and Nc represents the number of collisions 209 of the uplink communication link in the current round number 208 . Preferably, all possible values of the random variable constitute the virtual ID candidate list of the reading and writing device 1 . If the uplink communication link collides, the read/write device 1 will increase Nc, or reset to 0 after successful discovery. Through the above method, all possible conflicts can be detected from the cases in which the received signal cannot be decoded correctly, including at least the above-mentioned uplink communication link conflict, so that the synchronous uplink communication link conflict can be handled by the virtual ID; for asynchronous uplink communication Link conflicts can be handled by retransmission.

Preferably, for the second state 103 of the read-write device 1, the read-write device 1 enumerates the VID candidate list, and queries each candidate, that is, the retroreflection device 2, through a unicast query request 202 message. By default, if the virtual ID of the retroreflective device 2 matches the virtual ID in the query request 2 message, the retroreflective device 2 will respond with a query response 203 message. Similar to the first state 102 of the read-write device 1, the read-write device 1 performs energy detection to determine whether the retroreflective device 2 is responsive. If no feedback signal is detected, it means that the retroreflective device 2 is outside the communication range of the read-write device 1 . Reader 1 will continue to execute the virtual ID of the next retroreflector 2 in the list. If reader 1 detects a signal, it will attempt to decode the message. If successful, read and write the message output by the device 1, delete the virtual ID of the retroreflective device 2 from the virtual ID candidate list, and move to the next virtual ID. If the reading and writing device 1 fails to decode, the reading and writing device 1 perceives that an uplink conflict occurs when receiving the uplink communication link message, and will re-query the virtual ID of the retroreflective device 2 that fails to decode in the next round of query.

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

a. Monitor before a communication session: this will reduce the query 103 attempts using the carrier monitor 101; when the carrier monitor 101 detects that the channel is busy, the read/write device 1 will prohibit its discovery or query operation, which will greatly reduce the asynchronous uplink communication chain In addition, the reading and writing device 1 may monitor the entire message through the carrier monitoring 101, which will prevent the reading and writing device 1 from repeatedly querying the same retroreflection device 2, which is beneficial to solve the downlink communication link conflict, because the downlink The conflict adopts a random back-off mechanism, and the read-write device 1 that further backs off will have a good chance to monitor the query 1 of the read-write device 1 that is not backed off;

b. Aggregation and piggybacking: This is to reduce the number of rounds 208 for discovery 102 and query 103; first of all, in our message design, we have aggregated discovery request 201 and a common query request 202, this is to improve the most efficient The efficiency of common one-to-one and many-to-one communication; the reading and writing device 1 will send the query confirmation to all the retroreflective devices 2 it monitors through the next round of discovery request 201 or query request 202, and receive a report. The retroreflection device 2 of the text will compare its virtual ID information with the information carried in the query confirmation, and if the virtual IDs match, it will suppress its response.

Example 3

This embodiment discloses a communication method, which may be a vehicle networking communication method or a vehicle networking data communication method based on retro-reflection communication, and the method may be replaced by the device disclosed in the present invention and/or other alternatives Part realization. The whole and/or part of the contents of the preferred implementations of other embodiments may be used as supplements to the present embodiment without causing conflict or contradiction.

A vehicle networking communication method based on retro-reflective communication, the retro-reflective device 2 composed of at least one optical tag arranged on the vehicle and/or the infrastructure is passively modulated and reflected by the read-write device arranged on the vehicle. 1 transmits the optical signal, so that a stable and continuous optical communication link is established between the non-active communication retroreflection device 2 and the reading and writing device 1 at least within a certain time and space. The retroreflection device 2 modulates the confirmation information on the optical signal in response to the request in the optical signal sent by the reading and writing device 1, and reflects it to the reading and writing device 1, so as to realize the realization between the vehicle and the vehicle and between the vehicle and the road infrastructure. Correct data interaction. At least one reading and writing device 1 establishes an optical communication link with at least one retroreflective device 2 by sending at least two first optical signals and second optical signals of different frequencies. In the case that at least one optical communication link between the at least one reading and writing device 1 and the at least one retro-reflecting device 2 is established stably and continuously within a certain time and space and is confirmed to be in an idle state through the first optical signal, the at least one retro-reflecting device 2 is in an idle state. The third state 105 for obtaining a temporally and spatially dynamically allocated virtual ID specific to each reader/writer 1 is activated by receiving the second optical signal and/or the fourth state 105 for confirming the matching of the virtual IDs is activated State 106.

Preferably, the read-write device 1, the retro-reflection device 2, the communication mode between the read-write device 1 and the retro-reflection device 2, and the MAC message format used 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 used between the read-write device 1 and the retro-reflection device 2 as provided in the first and second embodiments The packet format realizes timely detection and processing of uplink and downlink communication link conflicts in an environment where multiple retroreflective communication nodes cannot be statically coordinated based on retroreflective communication, and repeated content will not be repeated.

Example 4

This embodiment is a further improvement on Embodiment 1, Embodiment 2 and Embodiment 3.

Preferably, as shown in FIG. 5 , when the reading and writing device 1 sends the first optical signal to at least one retroreflective device 2 within its communication range, the retroreflective device 2 transitions from the standby 104 state to the active state. After entering the activated state, the retroreflective device 2 enters the silent 107 state or the modulated reflection state in response to the first optical signal. Preferably, when the retroreflective device 2 can correctly decode the first optical signal, the retroreflective device 2 enters a modulated reflection state, thereby feeding back the modulated first optical signal to the read-write device 1 . When the retro-reflective device 2 cannot correctly decode the first optical signal, the retro-reflective device 2 enters a silent state 107 and does not feed back the first optical signal to the read-write device 1 , resulting in termination or termination of the communication 114 . Preferably, in the case where the reading and writing device 1 monitors the signal but obtains the first optical signal reflected and modulated by the retroreflective device 2 to correspond to the first optical signal sent by other reading and writing devices 1, the reading and writing device 1 judges that the reading The optical communication link between the writing device 1 and the retro-reflecting device 2 is in a busy state, so that the reading and writing device 1 maintains the state of continuously sending the first optical signal to find that the optical communication link in the idle state can be established within its communication range. Retroreflector 2. Preferably, before the reading and writing device 1 establishes a communication link with the retroreflective device 2, the reading and writing device 1 is always in the carrier monitoring 101 state. Preferably, the reading and writing device 1 judges whether the communication link is idle by means of whether the retro-reflecting device 2 retroreflects the optical signal back. In this case, the reading and writing device 1 does not monitor the signal, which may also indicate the communication range of the reading and writing device 1. There is no retroreflective device 2 in it, causing the reading and writing device 1 to enter the first state 102 to send the second optical signal, and then re-enter the carrier monitor 101 state and send the first optical signal because no feedback signal is received in the first state 102 , so that the reading and writing device 1 is constantly switching between the states of sending the first optical signal and the second optical signal. The retroreflective device 2 is therefore set to perform a simple modulation of the first optical signal, ie if the retroreflective device 2 simultaneously receives the first optical signal sent by at least two reading and writing devices 1 . The retroreflective device 1 is in the silent state 107 because the first optical signal cannot be decoded correctly, so that the reading and writing device 1 does not receive any feedback optical signal, then the reading and writing device 1 determines that there is a connection between the reading and writing device 1 and the retroreflective device 2. The optical communication link is busy. Through this setting, the hidden terminal problem can be solved without being able to perceive other reading and writing devices 1 . If the retro-reflection device 2 receives only one first optical signal at the same time, the retro-reflection device 2 can correctly decode the first optical signal, thereby entering a modulated reflection state. Since the retro-reflection device 2 can only modulate and retro-reflect one first optical signal at the same time, all the read-write devices 1 that communicate with the retro-reflection device 2 can receive the retro-reflected optical signal, thereby obtaining the retro-reflected light. The information contained in the signal, so that the reading and writing device 1 can obtain whether the retroreflected optical signal is a response to the first optical signal sent by it. When the reading and writing device 1 judges that the acquired information is not in response to the first optical signal sent by the reading and writing device 1, the reading and writing device 1 judges that the optical communication link between the reading and writing device 1 and the retroreflective device 2 is in a busy state. Moreover, it is precisely because the reading and writing device 1 can demodulate the optical signal retroreflected by the retroreflective device 2, so as to monitor the communication sessions between other reading and writing devices 1 and the retroreflective device 2, and thus can perceive other retroreflective devices. 2, and avoid the read-write device 1 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 specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the scope of the present invention. within the scope of protection of the invention. It should be understood by those skilled in the art that the description of the present invention and the accompanying drawings are illustrative rather than limiting to the claims. The protection scope of the present invention is defined by the claims and their equivalents.

Claims (10)

1. A vehicle networking data communication network based on retro-reflective communication at least comprises a read-write device (1) arranged on a vehicle and a retro-reflective device (2) arranged on the vehicle and/or an infrastructure for passive communication, wherein the retro-reflective device (2) communicates with the read-write device (1) in a retro-reflective mode to construct a vehicle networking,

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 continuously transmitted to monitor any ongoing communication session of at least one retro-reflective device (2) within communication range of the reader device (1) to reduce the asynchronous uplink collision probability,

the second optical signal is transmitted by the read/write device (1) to the retro-reflecting device (2) after the read/write device (1) has stopped transmitting the first optical signal into a first state (102) for discovering the retro-reflecting device (2) to avoid synchronous uplink collisions and/or a second state (103) for querying the retro-reflecting device (2) to avoid asynchronous uplink collisions.

2. 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.

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

4. Vehicle networking data communication network according to one of the preceding claims, characterized in that in case the read-write device (1) determines that the optical communication link with the retro-reflecting 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.

5. Car networking data communication network according to one of the preceding claims, characterized in that 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.

6. Car networking data communication network according to one of the previous claims, characterized in that at least one retro-reflecting device (2) receives only a second optical signal comprising at least a first payload sent by one read-write 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).

7. A vehicle networking data communication network according to any of the preceding claims, wherein the retro-reflecting means (2) upon receiving a second light signal comprising at least a third load enters a fourth state (106) 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.

8. Vehicle networking data communication network according to one of the preceding claims, characterized in that 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.

9. Internet of vehicles data communication network according to one of the previous claims, characterized in that 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-reflection 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.

10. 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,

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 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.

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