WO2017012468A1

WO2017012468A1 - Wireless communication system and method for smart traffic monitoring

Info

Publication number: WO2017012468A1
Application number: PCT/CN2016/088789
Authority: WO
Inventors: 袁丽
Original assignee: 袁丽
Priority date: 2015-07-17
Filing date: 2016-07-06
Publication date: 2017-01-26
Also published as: CN105070052B; CN105070052A

Abstract

The present invention provides a wireless communication system and method for smart traffic monitoring. The system comprises: vehicle detection nodes, wireless relay nodes, a wireless aggregation node, and a management center, wherein the vehicle detection nodes are used for wirelessly transmitting traffic information such as parking and traffic flow to the relay nodes or the aggregation node. The relay nodes are used for connecting the vehicle detection nodes to form a sub-network. The aggregation node is used for connecting the relay nodes into a network and communicating with the management center. The present invention is applied to the technical field of smart traffic, and contributes to improvement of wireless communication reliability and reduction of power consumption.

Description

Wireless communication system and method for intelligent traffic monitoring

Technical field

The invention relates to the field of intelligent transportation technology, in particular to a wireless parking system, a wireless communication system and a method for intelligent traffic light intersection data collection and monitoring, and a high-speed traffic monitoring.

Background technique

In recent years, cities have developed rapidly and the population has exploded. At the same time, people's consumption concepts are changing. More people buy cars and drive more frequently. What followed was a series of difficult problems such as road blockage, environmental pollution, and frequent traffic accidents. Despite the traffic jam, parking is difficult, and the fuel fee is accompanied by every car owner, but this has not changed their way of travel. Urban traffic problems occur in every large city in the world. Traffic jams increase the time and cost of commuting, delaying people's work and rest time, resulting in economic losses. At the same time, when the traffic jams, the engine idling not only wastes fuel, but also increases environmental pollution and takes away our blue sky and white clouds.

In 2014, the number of domestic motor vehicles reached 264 million, and motorists exceeded 300 million. There are 31 cities in the country with more than 1 million vehicles, including 8 cities in Beijing, Tianjin, Chengdu, Shenzhen, Shanghai, Guangzhou, Suzhou and Hangzhou. The longest traffic jam recorded 260 kilometers; in September 2010, the peak of Beijing's congested roads exceeded 140. In order to solve the traffic jam problem, the government also introduced a number of measures, such as restrictions on purchases, restrictions, and public transportation.

But with the development of technology, our city is becoming more intelligent, and the intelligent transportation system is born. The emergence of intelligent transportation systems is to solve a series of problems caused by the environment, efficiency and safety brought by transportation. For example, reducing the time the car starts but is still, reducing the probability of traffic jams, making more rational use of traffic intersection resources, and so on. To achieve these functions, data is essential. Intelligent transportation systems need to be able to sense current traffic, speed, models, and so on, so that they can make correct and intelligent judgments.

Sensor technology, M2M technology is accompanied by the rapid development of Internet of Things technology, so that we can not worry about traffic problems such as congestion and parking. With these technologies, the transportation system will become smarter and our city will be better.

With the continuous development of sensor technology, embedded technology and communication technology, vehicle detection methods have also evolved from a single type to a multi-type, multi-variety and multi-series vehicle detection method. According to the location of the collected information, it can be divided into fixed detection and mobile detection technology. The fixed detection technology can be divided into three types: magnetic signal acquisition, wave signal acquisition and video signal acquisition. It mainly includes magnetic detectors, induction coil detectors, microwave detectors, infrared detectors, ultrasonic detectors and video detectors. The mobile detection technology mainly includes the vehicle identification method, the floating vehicle method and the detection vehicle method, and the main technologies used are: GPS positioning technology, license plate recognition and acquisition technology, electronic label-based positioning acquisition technology and mobile phone detection-based acquisition technology.

In terms of vehicle detection, the internationally used monitoring methods mainly include coils, video and microwave. The coil has high precision and simple structure, but it requires some damage to the road due to installation and maintenance, and is inconvenient to use, so there is no large-scale promotion. Video surveillance is currently the most widely used method. Many experts and scholars at home and abroad have also proposed some algorithms for video recognition. However, due to the high cost of video surveillance, and the vulnerability to environmental factors such as light and angle, accuracy is high. Not too high. Most of the microwave monitoring methods are applied to high-speed road section monitoring, which is convenient to install, but is also susceptible to interference.

The anisotropic magnetoresistive sensor (AMR) studied by Beijing University of Aeronautics and Astronautics can detect the disturbance of the surrounding earth's magnetic field when the vehicle passes through the magnetic field, thus monitoring the vehicle's motion. If combined with WSN technology, high precision and volume can be achieved. Small, low-cost, and easy to deploy wireless sensor networks.

Shanghai Jiaotong University proposed a combination of WSN-based video and magnetic sensor to monitor the inaccuracy of video surveillance. The magnetic sensor has low cost and low signal-to-noise ratio. The WSN technology can also save the transmission line and wiring cost. At the same time, the video detection result contains a lot of information of interest to the intelligent transportation, which is more than the data obtained by using the magnetic sensitive signal alone. Better for future data processing and analysis. Research content, expected goals and research methods.

SCATS (Sydney coordinated adaptive traffic system) is the Sydney traffic adaptive coordination system. SCAT consists of a central super PDP, 11 remote PDPs, and more than 1,000 miniature traffic signal control systems scattered over 1,500 square kilometers in Sydney. SCATS can be based on road traffic In the case of time, the signal light is dynamically controlled to make a reasonable timing suitable for the current traffic conditions. Access efficiency can be greatly improved.

Cai Zengzeng from Chongqing University analyzed several common magnetoresistive sensors and studied their principles. Finally, the HMC3883L was selected as the sensor, and its drive circuit was designed and developed. At the same time, ZigBee and GPRS are combined to form a wireless sensor network for collecting traffic information. At the same time, the algorithm is studied on the collected data, but the algorithm proposed in this research is still insufficient. The dynamic vehicle detection algorithm still needs to be improved before artificially modifying the parameters.

Zhang Li et al. of Fudan University focused on the application of wireless sensor networks in intelligent public transportation systems, which can provide passengers with the current operation status and specific location of vehicles. Among them, the sensor network uses a distance-based positioning method to detect the vehicle, transmits information to the station node through the vehicle-mounted node, and estimates the distance of the vehicle according to the transmission time of the signal. In addition to the acquisition, processing, communication, and power modules, the sensor node also adds a positioning system, a moving module, and an energy generating module according to actual needs. To some extent, the performance of the node is increased, but at the same time it also leads to an increase in cost. Beijing Jiaotong University Jiezhi熹 studied the wireless sensor network using ZigBee method and analyzed the architecture of ZigBee protocol stack. The positioning algorithm of RSSI by ZigBee is studied, and the performance index of RSSI in practical application environment is verified, which provides a new reference for vehicle monitoring methods.

In summary, the current solutions for the detection, transmission, and monitoring of intelligent transportation vehicle information have problems such as complex design, low precision, and improved algorithm model. On the whole, there is no proposed communication method and traffic information detection method that is applied to the intelligent traffic monitoring and management system with low cost, simple installation, high sensitivity and high precision.

Summary of the invention

The technical problem to be solved by the present invention is to provide a communication method and a traffic information detection method for an intelligent traffic monitoring management system, so as to solve the problems of high cost, complicated installation, low sensitivity, and large error in the prior art.

To solve the above technical problem, an embodiment of the present invention provides an intelligent traffic wireless communication system, and a vehicle detection node, a relay node, a convergence node, and a parking, traffic flow, and vehicle speed detection method used in the system, as follows:

A wireless communication system for intelligent traffic monitoring, the system comprising: vehicle detection node, none a line relay node and/or a wireless convergence node, and a management center, wherein: the vehicle detection node is configured to collect traffic information of the vehicle, and send the data to the management center through a wireless protocol; the relay a node, configured to receive traffic information sent by the vehicle detection node, and process the received traffic information to be sent to a sink node; the sink node is configured to receive traffic information sent by the vehicle detection node, or The processed traffic information sent by the node is transmitted to the management center through a wireless communication technology (Wifi, mobile communication network, etc.); the management center is configured to store and process the received traffic information.

Preferably, the system comprises: at least one vehicle detection node, at least one relay node, and one convergence node, wherein the network formed by the vehicle detection node, the relay node, and the aggregation node adopts a mesh/star topology Each relay node is connected to at least one vehicle detection node via a wireless communication network, and the vehicle detection node to which the relay node is connected to the relay node constitutes a star network, and the vehicle detection node detects the traffic Sending information to the at least one relay node, wherein the plurality of relay nodes form a mesh network to transmit the vehicle information to the sink node through wireless communication of different channels; the sink node is used to connect the entire wireless communication network Traffic information detected by all vehicle detection nodes is uploaded to the management center.

Preferably, the system comprises at least one sink node and at least one vehicle detection node, and the wireless communication network formed by the sink node and the at least one vehicle detection node adopts a star topology; wherein each sink node and at least 1 Vehicle detection nodes are connected, and each sink node works simultaneously with different channels. The system can simultaneously deploy multiple independent network operations; the sink node is used to receive all vehicles connected to the sink node. The traffic information detected by the detecting node is uploaded to the management center.

Preferably, the relay node comprises two different frequency bands of wireless communication modules, wherein one wireless communication module is used for communication with a vehicle detection node, and another wireless communication module is used between each relay node, and/or relay Communication between nodes and sink nodes.

Preferably, the network of the system works by using a network memory to quickly recover the network. When each node is disconnected or restarted, the network can be directly operated without rejoining the network; wherein the address, channel and other information of the vehicle detection node are recorded in the slice. In the internal Flash, the vehicle detection node reads the information stored in the flash after each power-on. If the information is valid (non-zero), it directly works by monitoring the beacon synchronization.

Preferably, the star network composed of the vehicle detection node and the relay node or the aggregation node adopts a TDMA/CSMA hybrid scheduling mode; wherein the superframe length is configured by the aggregation node according to the dynamic change of the network state, and each node slot is T ms. The number of detected nodes in a superframe is up to 254, and one star topology uses one superframe;

Preferably, the superframe length is: the number of detected nodes of the vehicle connected to the star network *T + the number of competing slots *T.

Preferably, the allocation of the TDMA time slot is directly calculated according to the network address allocated by the network for the vehicle detection node; when the vehicle detection node joins the network, the vehicle detection node obtains the network address assigned by the relay node, and the network address is allocated. The allocation is sequentially performed according to the number of connected vehicle detection nodes from 1 to the relay node, the relay node is further configured to store and maintain the physical address and network address of each vehicle detection node; the vehicle detection node obtains the network The address is sent to the relay node as a TDMA time slot for transmitting data; the relay node returns an ACK acknowledgement packet after receiving the data sent by the vehicle detection node; wherein, in each transmission period, the middle The successor node not only allocates one TDMA time slot to each vehicle detection node, but also reserves TDMA time slots according to a preset number, and the reserved time slot position of the contention access is determined by the competition time slot start number in the beacon frame and The number of competing time slots determines that, in the reserved TDMA time slot, the vehicle detection node transmits data in a CSMA manner.

or,

The allocation of the TDMA time slot is directly calculated according to the network address assigned by the network to the vehicle detection node; when the vehicle detection node joins the network, the vehicle detection node obtains the network address assigned by the aggregation node, and the network address is allocated according to from 1 to The number of connected vehicle detection nodes of the sink node is sequentially allocated, and the sink node is further configured to store and maintain a physical address and a network address of each vehicle detection node; the vehicle detection node uses the network address obtained by the vehicle as the TDMA for transmitting data. Transmitting a data to the sink node; the sink node returns an ACK acknowledgement packet after receiving the data sent by the vehicle detection node; wherein, in each transmission period, the sink node not only detects a node for each vehicle Allocating a TDMA time slot, and also preserving TDMA time slots according to a preset number, the reserved time slot position of the contention access is determined by the number of contention time slots and the number of contention time slots in the beacon frame, and is reserved. The TDMA time slot, the vehicle detection node transmits data in a CSMA manner.

Preferably, in the TDMA/CSMA hybrid scheduling method: the first time slot of the superframe transmits the beacon a frame; a beacon frame is sent by a relay node or a sink node;

The beacon frame has the number of connected vehicle detection nodes in the cluster, and each cluster can connect up to 254 vehicle detection nodes;

When the vehicle detection node enters the network, the collected vehicle detection node number information in the relay node beacon frame collected is used as a selection basis to ensure the balance of the number of vehicle detection nodes connected to each relay node.

Preferably, in the TDMA/CSMA hybrid scheduling method:

The vehicle detection node synchronizes through the beacon frame;

The beacon frame carries network time. When the vehicle detection node joins, after receiving the beacon frame, it sets its own network time according to the network time of the beacon to achieve coarse synchronization;

After the vehicle detection node joins the network, in order to ensure that the timing between the transceiver nodes is not disordered, an accurate timer is set, which is started at the beginning of a time slot, and is closed at the end of the time slot, and the vehicle detection node will set the value of the Tsend time timer. Recorded, the sink node or the intermediate node will fill the value of the Treceive time in the acknowledgement packet DATA-ACK and return it to the sensor node. The sensor node compares the two values and adjusts the length of the Delay time in the next time slot to complete the precise synchronization.

Preferably, the vehicle detecting node, after listening to all the channels, finds a relay node corresponding to the beacon with the best signal quality through the relay selection algorithm, and receives the relay node at the relay node. The join request frame time slot is sent by the vehicle detection node to the relay node, wherein the join request data packet includes: a physical address of the vehicle detection node.

or,

Preferably, the vehicle detecting node, after listening to all the channels, finds a sink node corresponding to the beacon with the best signal quality through the relay selection algorithm, and receives the request to join at the sink node. The frame time slot is sent by the vehicle detection node to the sink node; wherein the join request data packet includes: a physical address of the vehicle detection node.

Preferably, the relay selection algorithm comprises: listening to all channels by the vehicle detection node, each channel monitoring the beacon T time, and storing the beacon frame information if the beacon frame is received within T time, Until the last channel is monitored; according to the stored beacon frame information, searching for a beacon with the best signal quality, and determining whether the number of connected vehicle detection nodes of the beacon reaches an upper limit;

If the upper limit is reached, re-search for the beacon with the second-best signal quality in the stored beacon frame information.

If there are multiple beacons with the same signal quality, compare the beacons with the same signal quality to the number of vehicle detection nodes, and select the beacon with the least number of detected vehicle detection nodes;

If there are multiple beacons with the least number of detected vehicle detection nodes, the beacon is randomly selected from them;

The relay node or the sink node corresponding to the finally determined beacon is a destination node that sends a network access request to the vehicle detection node.

Preferably, the vehicle detecting node is further configured to detect traffic information according to a preset frequency; when detecting that the traffic information changes, transmitting data in a data sending time slot of the vehicle detecting node; within a preset time, When the traffic information is detected to be unchanged, no data is transmitted in the data transmission time slot of the vehicle detection node; when the detected traffic information does not change within a preset time, the vehicle detection node sends a survival indication frame. It indicates that it works normally, and when the detected traffic information changes, the transmission of the survival indication frame is stopped.

Preferably, the vehicle is characterized in that: the vehicle adopts the following method: in order to detect the vehicle parking, a combination of magnetic abnormal slope detection and threshold detection is adopted, and the magnetic signal is collected to calculate the change speed (ie, slope) of the magnetic signal, and the environmental magnetic field signal is used. The detection range of the difference detection realizes the parking detection; in order to detect the vehicle count, the number of vehicles is identified by the reverse change of the tail-end magnetic signal; for detecting the vehicle speed, the reverse time difference of the vehicle tail-end magnetic signal and the calculation of the vehicle length are adopted. Or by deploying two vehicle detection nodes at a distance d, the vehicle speed is calculated by detecting the time difference between the first signal or the last signal of the vehicle and the distance d between the two vehicle detection nodes.

The invention also provides an intelligent control system for an intersection traffic light, the system comprising a traffic flow detecting node, a vehicle speed detecting node, a relay node, a traffic light controller, a handheld controller and a data management platform, characterized in that: traffic flow The detecting node is used for detecting vehicle counting in the lane, the vehicle speed detecting node is used for vehicle speed measurement, and the relay node is used for receiving the measurement signal of the vehicle speed detecting node and the traffic flow detecting node and forwarding the data to the traffic light controller; the traffic light controller is used for Intelligently manage the traffic light time of each intersection according to the traffic volume and vehicle speed of different intersections; the data management background is used to collect and analyze the data of the controllers such as traffic at each intersection.

Preferably, the system further comprises a special vehicle identifier for identification of special vehicles such as fire fighting, ambulance, etc., and the traffic light time of each intersection can be controlled by the recognition result.

Preferably, the system comprises: at least one vehicle detection node, at least one relay node, and one convergence node, wherein the network formed by the vehicle detection node, the relay node, and the aggregation node adopts a mesh/star topology Each relay node is connected to at least one vehicle detection node via a wireless communication network, and the vehicle detection node to which the relay node is connected to the relay node constitutes a star network, and the vehicle detection node detects the traffic Sending information to the at least one relay node, and the plurality of relay nodes form a mesh network to transmit the vehicle information to the sink node through wireless communication of different channels;

The aggregation node is configured to upload traffic information detected by all the vehicle detection nodes in the entire wireless communication network to the management center;

or,

The system includes at least one sink node and at least one vehicle detection node, and the wireless communication network formed by the sink node and the at least one vehicle detection node adopts a star topology; wherein each sink node and at least one vehicle detection Nodes are connected, and each sink node works with different channels at the same time. The system can simultaneously deploy multiple independent network operations; the sink node is used to detect all received vehicle detection nodes connected to the sink node. The traffic information arrived is uploaded to the management center.

Preferably, one of the relay nodes is connected to at most no more than 10 vehicle detection nodes, and the time slot T of each vehicle detection node is less than 10 milliseconds.

Preferably, in order to detect the traffic flow, a combination of magnetic anomaly slope detection and threshold detection is adopted, and the magnetic signal is collected to calculate the change speed (ie, the slope) of the magnetic signal, and the difference detection range of the environmental magnetic field signal is used to realize the traffic flow detection. ;

Preferably, when a vehicle passes by, the magnetic sensor gives a change of the disturbance magnetic field of the vehicle. After passing, the magnetic field returns to the ambient magnetic field; when the vehicle passes, if it stops at the traffic flow detecting node, then leaves, the magnetic field stops. The intensity is higher or lower than the ambient magnetic field. The vehicle flow detection can be realized by counting the slope of the magnetic signal and the threshold detection. By recognizing the disturbance of the magnetic signal by the front and rear of the vehicle, the time difference before and after the disturbance is recorded, combined with the length of the vehicle. The vehicle speed measurement can be realized, or by deploying two vehicle detection nodes at a distance d, the vehicle speed can be calculated by the time difference and distance d of the magnetic signals caused by the two vehicles detecting nodes when the same vehicle passes.

The invention also provides a vehicle detection node, which is arranged in wireless communication for intelligent traffic monitoring In the system, the wireless communication system includes: a vehicle detection node, a relay node, and/or a convergence node, and a management center; wherein the vehicle detection node is configured to collect traffic information of the vehicle and use a wireless protocol The data is sent to the management center; the relay node is configured to receive traffic information sent by the vehicle detection node, and process the received traffic information and send the information to the sink node; the sink node is configured to receive the The vehicle detects the traffic information sent by the node or the processed traffic information sent by the relay node, and transmits the traffic information to the management center through a wireless communication technology (Wifi, mobile communication network, etc.); the management center is used for Store and process the received traffic information. The vehicle detection node includes: a sensor (magnetic sensor, infrared sensor, ultrasonic sensor, etc.), a microprocessor, and a wireless transmitting module;

Wherein, the sensor is used for detecting traffic information such as whether the parking space is stopped, the speed of the vehicle in motion, the traffic volume of the traffic intersection, and the like; the microprocessor is configured to perform analog-to-digital conversion on the detected vehicle detection signal, The signal processing analyzes the operation, and after comprehensively identifying, generates traffic information, and then transmits the traffic information through the wireless transmitting module.

The present invention also provides a relay node, which is disposed in a wireless communication system for intelligent traffic monitoring, the wireless communication system comprising: a vehicle detection node, a relay node, a convergence node, and a management center; a vehicle detection node, configured to collect traffic information of the vehicle, and send the data to the management center by using a wireless protocol; the relay node is configured to receive traffic information sent by the vehicle detection node, and receive the received traffic The information is processed and sent to the sink node; the sink node is configured to receive traffic information sent by the vehicle detection node or processed traffic information sent by the relay node, and pass the wireless communication technology ( Wifi, mobile communication network, etc.) are transmitted to the management center; the management center is configured to store and process the received traffic information. The relay node includes: a microprocessor MCU, a first wireless transceiver unit, a second wireless transceiver unit 2, 485 communication interface, a 232 communication interface, an Ethernet interface, a TTL output circuit, and a power conversion module; The first wireless transceiver unit is configured to communicate with the vehicle detection node, the second wireless transceiver unit is configured to communicate with the relay node and the aggregation node, and the first wireless transceiver unit of the relay node is configured to receive the vehicle detection node. Traffic information is converted by the microprocessor MCU to the second wireless transceiver unit, forwarded to the aggregation node, or output to the control device through a 485 communication interface/serial communication interface/TTL output circuit, such as traffic Light control system.

The present invention also provides a convergence node disposed in a wireless communication system for intelligent traffic monitoring, the wireless communication system comprising: a vehicle detection node, a relay node, a convergence node, and a management center; wherein the vehicle a detecting node, configured to collect traffic information of the vehicle, and send the data to the management center by using a wireless protocol; the relay node is configured to receive traffic information sent by the vehicle detecting node, and receive the traffic information And processing, sending to the sink node; the sink node is configured to receive traffic information sent by the vehicle detection node, or processed traffic information sent by the relay node, and pass the wireless communication technology (Wifi) And the mobile communication network is transmitted to the management center; the management center is configured to store and process the received traffic information; and the collecting node comprises: a microprocessor MCU, a first wireless transceiver unit, and a Two wireless transceiver unit 2, 485 communication interface, 232 communication interface, Ethernet interface, GPRS/3G/4G communication interface, TTL output And a power conversion module; wherein the first wireless transceiver unit is configured to communicate with a vehicle detection node, the second wireless transceiver unit is configured to communicate with a relay node; and the vehicle is received by the first wireless transceiver unit of the aggregation node Detecting traffic information sent by the node; receiving, by the second wireless transceiver unit of the sink node, traffic information sent by the relay node; the microprocessor MCU converts the traffic information to the GPRS/3G/4G module, and forwards the data to the management center. Or output to control equipment, such as traffic light control system, through 485 communication interface / serial communication interface / TTL output circuit.

The invention also provides a wireless communication method for a wireless communication system for intelligent traffic monitoring, comprising the steps of joining a network, resource allocation, and low power consumption monitoring, characterized in that: joining the network step: after the vehicle detecting node is powered on The vehicle detection node automatically joins the wireless communication network; the resource allocation step: realizing the division of the communication time slot of the vehicle detection node; the low power consumption monitoring step: realizing the low power consumption monitoring and network communication maintenance of the traffic information.

Preferably, the step of joining the network further comprises: after the working of the relay node/aggregation node, periodically broadcasting a beacon frame, the vehicle detecting node accessing the network and synchronizing, the content of the beacon frame includes: a network number, a network Time, the number of vehicle detection nodes connected to the relay node/aggregation node, the starting position of the competition access slot, and the number of competing access slots; after the vehicle detection node is powered on, the beacon frame is monitored on all channels, and all the revenues are recorded. Parameters of the beacon frame to be obtained: network number, network time, signal quality, number of connected vehicle detection nodes, etc.; after the vehicle detection node listens to all channels, finds the most suitable relay node/aggregation through the relay selection algorithm. Node, "competitive access" at the relay node/aggregation node The time slot" sends a join request to the relay node/sink node in a CSMA manner; the physical address of the vehicle detection node is included in the request packet, and the relay node/sink node determines whether the vehicle detection node is allowed to join and returns The response is added. If the return is allowed to join the response, the vehicle detection node obtains the network address assigned by the relay node/aggregation node, and the joining process is completed. The relay node/aggregation node needs to store and maintain the physical address of each vehicle detecting node. And network address.

Preferably, the step of joining the network further comprises: after the vehicle detecting node is powered on, listening to the beacon T time on the initial channel, and then switching to the next channel listening T time until all channel monitoring is completed; in the T time, if Receiving a beacon frame, storing beacon frame information; after the last channel monitoring is completed, searching for the beacon with the best signal quality in the stored beacon frame information, and then determining whether the number of connected vehicle detection nodes of the beacon is The upper limit is reached. If the upper limit is reached, the beacon of the signal quality of the stored beacon frame information is re-find; if there are multiple beacons with the same signal quality, the number of connected vehicle detection nodes of these beacons is compared, and the selected access is selected. The beacon with the least number of detected nodes of the vehicle, if there are multiple beacons with the least number of detected nodes, the random selection is made; wherein the vehicle detection node aims at the relay node/aggregation node corresponding to the selected beacon The address initiates a join request.

Preferably, the resource allocation step further comprises: after the vehicle detecting node joins the network, obtaining a network address assigned to the relay node/sink node, and assigning the network address according to the number of detecting nodes from 1 to the connected vehicle. The vehicle detection node sends data to the relay node/aggregation node with its network address as the TDMA time slot for transmitting data; the relay node/aggregation node returns the ACK confirmation packet after receiving the data, that is, the allocation of the TDMA resource is detected by the vehicle itself. Calculate, no need to allocate time slots;

Preferably, in one transmission period, in addition to assigning one time slot to each vehicle detection node, n reserved time slots are reserved, and the reserved time slot is used to detect the node in which the transmission fails. Resend data during this period.

Preferably, the low power consumption detecting step further comprises: the low power detecting step adopts a high frequency detecting, a low frequency transmitting method; that is, the high frequency starting sensor detects the traffic information signal, and if the detected traffic information signal does not change, Not transmitting data in the data transmission time slot of the vehicle detection node, reducing power consumption, and transmitting data if a change is detected;

Preferably, in the case that the long-term traffic information signal is unchanged, the vehicle detection node sends the survival indication frame to indicate that the relay node or the aggregation node is working normally; when the signal transmission change is detected, the survival indication frame is stopped.

Preferably, the method further comprises a time synchronization step of the network, characterized in that: the aggregation/relay node periodically transmits a beacon frame, and when the vehicle detection node joins the network, when receiving the beacon frame, according to the beacon frame The network time in the synchronization is synchronized, and the local time is changed to the network time in the beacon;

Preferably, after the vehicle detecting node joins the network, in order to ensure that the timing between the transmitting and receiving nodes is not disordered, each node in the network sets a subtle deterministic timer, starts at the beginning of a TDMA time slot, and stops at the end of the time slot. The vehicle detection node records the timer value of the time Tsend for transmitting the data packet, and the aggregation node or the intermediate node records the timer value of the time Treceive of the data packet sent from the vehicle inspection node, and fills in the ACK. The vehicle returns to the vehicle detection node; the vehicle detection node compares the two values, and if the difference delay is greater than the threshold, the length of the delay time is adjusted in the next time slot, thereby completing the precise synchronization.

The invention also provides a parking detection method for a wireless communication system for intelligent traffic monitoring, which determines the warehousing and leaving time of the vehicle by detecting the quantized value and the change slope of the magnetic signal, wherein the slope detection is determined by Two parameter controls, offset and thresholdk, respectively control the span of the slope detection and the threshold of the slope, and the amplitude of the disturbance can be controlled by adjusting the two parameters; the method comprises the following steps: determining the current state of the vehicle; when the vehicle is parked During the process of entering and exiting, the curve changes obviously. When the vehicle passes by, the slope of the value of the sensor changes greatly. By detecting the change of the slope and the extraction of the minimum and minimum values, the current state of the vehicle is determined; Procedure for library or outbound status: Each time a continuous data is acquired for a period of time acquired by the sensor, the positive and negative slopes are detected and the maxima and minima are found, by the position of the maxima and minima The number of judgments can identify the vehicle entering or leaving the warehouse; the step of determining the state of the vehicle parking or not: after the slope detection By calculating the average value of the current sensor and comparing it with the median value of the sensor, it can be determined whether the current vehicle is parked or not.

The beneficial effects brought by the invention include:

Providing a fast, efficient and unified communication network and system for intelligent traffic information communication, It can realize a variety of wireless communication networks to adapt to traffic information transmission and communication under different scenarios. At the same time, the present invention also provides various vehicle detection methods to achieve detection of different states of the vehicle.

DRAWINGS

1 is a structural diagram of a wireless communication system for intelligent transportation according to the present invention;

2 is a structural diagram of a vehicle detection node according to Embodiment 1 of the present invention;

3 is a structural diagram of a relay node/aggregation node according to Embodiment 1 of the present invention;

4 is a topological structural diagram of a wireless communication network according to Embodiment 1 of the present invention;

FIG. 5 is another topological structural diagram of a wireless communication network according to Embodiment 1 of the present invention; FIG.

6 is a flowchart of a method for operating a wireless communication network according to Embodiment 1 of the present invention;

7 is a flowchart of a method for a vehicle detection node to join a network according to Embodiment 1 of the present invention;

8 is a flowchart of a relay selection algorithm according to Embodiment 1 of the present invention;

FIG. 9 is a schematic flowchart diagram of a resource allocation method according to Embodiment 1 of the present invention;

FIG. 10 is a schematic flowchart of a low power consumption detection process according to Embodiment 1 of the present invention; FIG.

FIG. 11 is a schematic diagram of a time synchronization process according to Embodiment 1 of the present invention; FIG.

12 is a schematic diagram of a storage flow of a convergence/relay node network according to Embodiment 1 of the present invention;

13 is a schematic flowchart of a parking detection method according to Embodiment 1 of the present invention;

14 is a schematic structural diagram of a network deployment according to Embodiment 2 of the present invention;

15 is a schematic diagram of traffic flow detection of a traffic light provided by Embodiment 2 of the present invention;

16 is a schematic diagram of vehicle speed detection according to Embodiment 2 of the present invention;

Figure 17 is a structural view of another vehicle detector provided by the present invention;

18 is a structural diagram of an infrared detecting module provided by the present invention;

19 is a structural diagram of the principle of infrared light wave transmission provided by the present invention;

20 is a structural diagram of an infrared light wave receiving principle provided by the present invention;

21 is a structural diagram of a GMI detection module provided by the present invention;

22 is a structural diagram of an excitation resonant circuit unit of a GMI detection module provided by the present invention;

FIG. 23 is a structural diagram of a magnetic abnormality detecting and conditioning circuit unit of the GMI detecting module provided by the present invention.

detailed description

The technical problems, the technical solutions, and the advantages of the present invention will be more clearly described in the following description.

Example 1

The present invention discloses a wireless communication system for use in the field of parking detection. Referring to FIG. 1 , a wireless communication system for intelligent traffic monitoring according to an embodiment of the present invention includes: a vehicle detection node, a relay node, and convergence. a node and a management center, wherein the vehicle detecting node is configured to detect vehicle information of the parking space, and send the detected information to the sink node through the relay node; the relay node is configured to receive the The vehicle detects vehicle information of the parking space sent by the node, and transmits the information to the sink node; the sink node is configured to send the vehicle information of the parking space received by the relay node through the Internet, mobile internet or other wireless communication The technology is transmitted to the parking monitoring management center; the management center is configured to receive vehicle information of the parking space sent by the gathering node, process the vehicle information of the parking space, and monitor and manage the parking space information according to the processing result. And billing management.

In the embodiment of the present invention, referring to FIG. 2, the vehicle detection node includes: a sensor (magnetic sensor, infrared sensor, ultrasonic sensor, etc.), a microprocessor, a wireless transmitting module, and the sensor, the parking space for detecting The vehicle has a signal; the MCU microprocessor is configured to perform analog-to-digital conversion, signal processing analysis and calculation on the detected vehicle parking signal of the parking space, and comprehensively identify and generate vehicle information of the parking space, and then The vehicle information of the parking space is transmitted through the wireless transmitting module.

Preferably, the vehicle detection node uses the following method when identifying the vehicle:

In order to detect vehicle parking, a combination of magnetic anomaly slope detection and threshold detection is adopted, and the method is adopted. The magnetic signal calculates the speed of change of the magnetic signal (ie, the slope), and performs the detection of the difference between the amplitude and the change of the environmental magnetic field signal. To detect the vehicle count, the number of vehicles is identified by the reverse change of the magnetic signal of the front parking space; The reverse time difference of the magnetic signal of the front parking space and the calculation of the speed of the vehicle length are adopted.

Referring to FIG. 3, the aggregation/relay node includes: a microprocessor MCU, a wireless transceiver unit 1, a wireless transceiver unit 2, a 485 communication interface, a 232 communication interface, an Ethernet interface, and a GPRS/3G/4G communication interface. a TTL output circuit, a power conversion module; wherein the wireless transceiver unit 1 is configured to communicate with a vehicle detection node, the wireless transceiver unit 2 is configured to communicate with a relay and a sink node; and the convergence node does not include the wireless transceiver unit 1; The relay node does not include a GPRS/3G/4G communication interface, and is configured to receive vehicle information of the parking space issued by the vehicle detection node and forward it to the aggregation node. Receiving vehicle information of the parking space issued by the vehicle detecting node by the relay node wireless transceiver unit 1, and converting the vehicle information of the parking space to the wireless transceiver unit 2, 485 communication interface, serial communication by the data processor MCU The interface, TTL output circuit is sent to the receiver, red light control cabinet or mobile communication network.

In a preferred solution of the embodiment of the present invention, the wireless communication network constructed in the wireless communication system includes at least one sink node and at least one relay node, and the wireless communication network adopts a mesh/star topology. As shown in FIG. 4, each relay node is connected to at least one vehicle detection node, and the vehicle detection node of the relay node connected to the relay node constitutes a star network, and the vehicle detection node will detect the parking space. The vehicle information is transmitted to the relay node, and the relay nodes form a mesh network through the wireless communication modules of different channels to transmit the vehicle information to the sink node. The sink node uploads the vehicle information of the parking space detected by all the vehicle detecting nodes in the entire wireless communication network to the management center, and the storage center performs storage and processing. A different channel is used between the star network formed by each relay node and the vehicle detection node, and communication can be performed at the same time, thereby forming a large-scale network of more than a thousand points. And the second wireless communication module different from the vehicle detection node is used between the relay nodes, and works on different channels, so as to avoid mutual interference between the communication between the relay nodes and the vehicle detection node. A parking lot deploys one aggregation node, multiple relay nodes and multiple vehicle detection nodes.

For flexible deployment, in the embodiment of the present invention, a simplified network networking scheme may be adopted, where the wireless communication network adopts a star topology, as shown in FIG. 5, where each sink node and at least one vehicle Vehicle detection nodes are connected, and the vehicle detection nodes connected to the aggregation node form a star network, and each sink node uses different channels to work simultaneously, and each parking lot deploys at least one sink node and at least one vehicle. The aggregation node does not include the wireless transceiver unit 2, and is configured to upload the received vehicle information of the parking space detected by all the vehicle detection nodes connected thereto to the parking monitoring management center. The network of each aggregation node works simultaneously with different channels.

For the two topologies shown in FIG. 4 and FIG. 5, a multi-channel communication division mechanism is adopted. For large-scale networks, if Carrier Sense Multiple Access (CSMA) is used, there will be interference between nodes; if Time Division Multiple Access (TDMA) is used, the delay is large. In the embodiment of the present invention, the vehicle detection node managed by each relay node or the aggregation node is divided into a logical unit, and TDMA is adopted in the unit, the network scale is small, and the delay is small; each relay node or sink node Different channels are used for communication, so that the vehicle detection nodes in different logical units can simultaneously transmit data to the relay node or the aggregation node to which they belong without causing interference, thereby expanding the network scale.

6 is a communication system function of a vehicle detection node in the wireless communication network and the relay node or vehicle detection node in FIG. 4 and the aggregation node in FIG. 5, including: joining a network, resource allocation, and low power consumption monitoring. Among them, joining the network enables the vehicle detection node to automatically join the wireless communication network after power-on, the resource allocation can realize the division of the communication time slot of the vehicle detection node, and the low-power monitoring can realize the low-power monitoring and network communication of the vehicle information of the parking space. Maintenance function.

Corresponding to the function of the communication system disclosed in FIG. 6, the embodiment also discloses a wireless communication method for a wireless communication system for intelligent traffic monitoring, including a joining network, resource allocation, and low power consumption monitoring steps, specifically : Joining the network step: After the vehicle detection node is powered on, the vehicle detection node automatically joins the wireless communication network; the resource allocation step: realizing the division of the communication time slot of the vehicle detection node; the low power consumption monitoring step: realizing the low information of the parking space vehicle information Power consumption monitoring and network communication maintenance.

Referring to FIG. 7 , a flowchart of joining a network is performed. After the relay node/aggregation node works, a beacon frame is periodically broadcasted for detecting a network access and synchronization of a node, and the content of the beacon frame includes: a network number. Network time, the number of nodes detected by the relay node/sink node connected to the vehicle, the starting position of the contention access slot, and the number of competing access slots. After the vehicle detection node is powered on, it listens on all channels. Frame the frame and record the parameters of all received beacon frames: network number, network time, signal quality, number of connected vehicle detection nodes, etc. After the vehicle detection node listens to all the channels, the relay selection algorithm is used to find the most suitable relay node/aggregation node, and the “competition access time slot” of the relay node/aggregation node is CSMA to the relay node. / The aggregation node sends a join request.

The star network consisting of the vehicle detection node and the relay node or the aggregation node adopts the TDMA/CSMA hybrid scheduling mode; wherein the superframe length is configured by the aggregation node according to the dynamic change of the network state, and each node slot is T ms, one super The number of detected nodes in the frame is up to 254, and one star topology uses one superframe. Preferably, the superframe length is: the number of vehicle detection nodes connected by the star network *T+CSMA competition time slot number *T.

Wherein, when the wireless system includes at least one vehicle detection node, at least one relay node, and one aggregation node:

The allocation of the TDMA time slot is directly calculated according to the network address assigned by the network to the vehicle detection node; when the vehicle detection node joins the network, the vehicle detection node obtains the network address assigned by the relay node, and the network address is allocated according to And the number of connected vehicle detection nodes to the relay node is sequentially allocated, and the relay node is further configured to store and maintain a physical address and a network address of each vehicle detection node;

The vehicle detecting node sends data to the relay node by using the obtained network address as a TDMA time slot for transmitting data; the relay node returns an ACK confirmation packet after receiving the data sent by the vehicle detecting node;

Wherein, in each transmission period, the relay node not only allocates one TDMA time slot to each vehicle detection node, but also reserves a TDMA time slot according to a preset number, and the reserved time slot position of the contention access is determined by The contention start slot number and the number of contention slots in the beacon frame are determined. In the reserved TDMA slot, the vehicle detection node transmits data in a CSMA manner.

Wherein, when the wireless system includes at least one sink node and at least one vehicle detection node:

The allocation of the TDMA time slot is directly calculated according to the network address assigned by the network to the vehicle detection node; when the vehicle detection node joins the network, the vehicle detection node obtains the network address assigned by the aggregation node, and the network address is allocated according to from 1 to The number of nodes detected by the aggregation node connected to the vehicle depends on Assigning times, the sink node is also used to store and maintain the physical address and network address of each vehicle detection node;

The vehicle detecting node sends data to the sink node by using the obtained network address as a TDMA time slot for transmitting data; the sink node returns an ACK acknowledgement packet after receiving the data sent by the vehicle detecting node;

Wherein, in each transmission period, the sink node not only allocates one TDMA time slot to each vehicle detection node, but also reserves a TDMA time slot according to a preset number, and reserves the reserved time slot position of the competition access by the letter. The contention start slot number and the number of contention slots in the frame are determined. In the reserved TDMA slot, the vehicle detection node transmits data according to the CSMA method.

Among them, in the TDMA/CSMA hybrid scheduling method:

The beacon frame is sent in the first time slot of the superframe; the beacon frame is sent by the relay node or the sink node; the beacon frame has the number of connected vehicle detection nodes in the cluster, and each cluster can connect up to 254 vehicle detections. The node detection node selects the number of connected vehicle detection nodes in the relay node beacon frame collected during the network access to ensure the balance of the number of vehicle detection nodes connected to each relay node.

Or, in the TDMA/CSMA hybrid scheduling method:

The vehicle detection node synchronizes through the beacon frame; the beacon frame carries the network time, and when the vehicle detection node joins, after receiving the beacon frame, the network time is set according to the network time of the beacon, and the coarse synchronization is realized; After the detection node joins the network, in order to ensure that the timing between the transceiver nodes is not disordered, an accurate timer is set, which starts at the beginning of a time slot, stops at the end of the time slot, and the vehicle detection node records the value of the Tsend time timer. Down, the sink node or the intermediate node will fill the value of the Treceive moment in the DATA-ACK and return it to the sensor node. The sensor node compares the two values and adjusts the length of the Delay time in the next time slot to complete the precise synchronization.

Join the physical address of the request packet with the vehicle detection node. The relay node/aggregation node decides whether to allow the vehicle detection node to join, and returns a join response. If the return is allowed to join the response, the vehicle detection node obtains the network address assigned by the relay node/aggregation node, and completes the joining process. The relay node/aggregation node needs to store and maintain the physical address and network address of each vehicle detection node.

Preferably, the vehicle detection node passes the relay selection algorithm after listening to all the channels. Finding a relay node or a sink node corresponding to the beacon with the best signal quality, and receiving the request frame time slot at the relay node or the sink node from the vehicle detection node to the relay node Or the sink node sends a join request; wherein the join request data packet includes: a physical address of the vehicle detection node.

Preferably, a preferred relay node optimization selection algorithm is provided:

Referring to FIG. 8, after the vehicle detection node is powered on, the beacon time T is monitored on the initial channel, and then the next channel is monitored for T time until all channel monitoring is completed. In the T time, if a beacon frame is received, the beacon frame information is stored. After the last channel monitoring is completed, in the stored beacon frame information, the beacon with the best signal quality is searched, and then it is judged whether the number of connected vehicle detection nodes of the beacon reaches the upper limit, and if the upper limit is reached, the storage beacon is re-searched. The beacon with the second-best signal quality in the frame information; if there are multiple beacons with the same signal quality, compare the number of connected vehicle detection nodes of these beacons, and select the beacon with the least number of detected nodes detected by the vehicle, if there are many The beacons that have the least number of detected vehicle detection nodes are randomly selected from them. The vehicle detection node initiates a join request with the relay node/sink node corresponding to the selected beacon as the destination address.

The resource allocation method shown in FIG. 6 is as follows: after the vehicle detection node joins the network, the network address assigned to the relay node/aggregation node is obtained, and the network address allocation is performed in order from 1 to the number of connected vehicle detection nodes. The vehicle detection node sends data to the relay node/sink node with its network address as the TDMA time slot for transmitting data; the relay node/aggregation node returns the ACK acknowledgement packet after receiving the data. That is, the allocation of TDMA resources is calculated by the vehicle detection node itself, and no time slot is allocated, and the speed is fast, which reduces communication and energy consumption caused by resource allocation. In order to ensure the reliability of data transmission, in addition to assigning one time slot to each vehicle detection node in one transmission period, n reserved time slots are reserved, which are used for transmission failure. The vehicle detection node resends data during this time. Referring to Fig. 9, a relay node with six vehicle detection nodes assigns time slots 1 to 6 to each vehicle detection node, and 7 and 8 time slots are reserved for retransmission. The No. 1 vehicle detection node transmits data in 1 slot, and if no ACK is received, it will perform CSMA transmission in 7 slots. The TDMA time slot is selected for transmission according to the network address of each node. Because the probability of packet loss is small, the relay node with 6 vehicle detection nodes can leave 2 reserved time slots. For example, in 7 and 8 time slots, the vehicle detection node uses CSMA to compete for transmission, which guarantees Transmission reliability, minus Less transmission delay. The location and number of reserved slots are in the beacon frame.

Referring to FIG. 10, a schematic diagram of the low power consumption detection process in FIG. 6 is adopted. The low power detection method uses a high frequency detection method and a low frequency transmission method. That is, the high-frequency start sensor detects the presence or absence of the vehicle in the parking space. If the detected signal does not change, the data is not transmitted in the data transmission time slot of the vehicle detection node, the power consumption is reduced, and if a change is detected, the data is transmitted. In order to ensure the network connection, the vehicle detection node sends a survival indication frame to the relay node or the aggregation node to indicate that it is working normally when the vehicle has no signal for a long time; when the signal transmission change is detected, the survival is stopped. Indicates the frame.

Referring to Figure 11, the time synchronization method of the network is shown. The aggregation/relay node periodically transmits a beacon frame. When the vehicle detection node joins the network, after receiving the beacon frame, it synchronizes according to the network time in the beacon frame, and changes its local time to the network in the beacon. time.

After the vehicle detection node joins the network, in order to ensure that the timing between the transceiver nodes is not disordered, each node in the network sets a subtle timer, which is started at the beginning of a TDMA slot, and the vehicle detection node will send the data packet. The timer value of the time Tsend is recorded, and the sink node or the intermediate node records the timer value of the time Treceive of the data packet sent from the vehicle inspection node, and fills it in the ACK and returns it to the vehicle detection node. The vehicle detection node compares the two values. If the difference delay is greater than the threshold, the length of the delay time is adjusted in the next time slot, thereby completing the synchronization.

When the network of the system works, the network memory is used to quickly recover the network. When each node is disconnected or restarted, it can work directly without rejoining the network; wherein the address, channel and other information of the vehicle detection node are recorded in the on-chip Flash. The vehicle detection node reads the information stored in the flash after each power-on. If the information is valid (non-zero), it directly works by monitoring the beacon synchronization. After the relay/aggregation node is powered on, the information stored in the flash type is read. If the information is valid (non-zero), the network is managed according to the parameters in the flash. Referring to FIG. 12, a network parameter management process of a relay node or a sink node of a network is shown. Each time the aggregation/relay node runs the network, it first reads the network information from the Flash and stores the network information in the RAM. Establish a network based on network information. If a new vehicle detection node needs to join, and receives the JoinRequest packet, it looks up the node information in the network information table. If it can be found, the node has been added, no need to re-allocate resources, and return the existing resources to the vehicle detection. node. If it is not found, the node is a new network access node, and needs to allocate resources to a network resource. After locking, return to the vehicle detection node. If the received JoinRequest-ACK OK sent by the vehicle detection node, the resource is stored in the network network information table in the RAM, and the information table is updated in the Flash. When the network needs to be re-established, erase the network information in RAM and Flash and restart the network.

Referring to Figure 13, the figure is a schematic diagram of a parking detection method using a magnetic sensor.

The vehicle's inbound and outbound time is determined by detecting the slope and the stabilized sensor value. The slope detection is controlled by two parameters, offset and thresholdk, which respectively control the span of the slope detection and the threshold of the slope. By adjusting these two parameters, the amplitude of the detected disturbance can be controlled.

When the vehicle is parked, the curve changes significantly during the entry and exit. When the vehicle passes, the slope of the value of the sensor changes greatly, and the current state of the vehicle is determined by detecting the change in the slope and the extraction of the maximum and minimum values. Each time the continuous data collected by the sensor is detected for a period of time, the positive slope and the negative slope are detected and the maximum value and the minimum value are found. By judging the position and number of the maximum value and the minimum value, the vehicle can be identified. Inbound or outbound.

After the slope detection, by calculating the average value of the current sensor and comparing it with the median value of the sensor, it can be determined whether the current vehicle is parked or not.

As shown in Fig. 17, one of the preferred magnetic sensors in the present embodiment, which is used for vehicle detection, can be used as the vehicle detecting node in the invention.

The vehicle detector disclosed in FIG. 17 includes: an infrared detecting module, a giant magneto-impedance (GMI) detecting module, a microprocessor (Microcontroller Unit, MCU), a wireless transmitting module, and a wireless RFID card reader module; a detection module, a vehicle for detecting a parking space, a signal; the GMI detecting module, configured to detect a vehicle disturbance magnetic field magnetic abnormality signal of the parking space, the MCU microprocessor, configured to detect the The vehicle in the parking space has the signal and the parking space of the vehicle disturbing the magnetic field magnetic anomaly signal for analog-to-digital conversion (A/D) acquisition, signal processing analysis and calculation, and after comprehensive identification, the vehicle information of the parking space is generated. The vehicle information of the parking space is further transmitted through the wireless transmitting module, and the wireless RFID card reader module is configured to read vehicle information carried by the vehicle RFID radio frequency card.

Referring to FIG. 18, the infrared detecting module includes an infrared transmitting circuit and an infrared receiving circuit. The infrared transmitting circuit is configured to emit a modulated fixed frequency infrared light wave, and the infrared light wave is used by a vehicle. Reflecting back to the infrared receiving circuit, the infrared receiving circuit is configured to receive the reflected fixed-frequency infrared light wave, and demodulate the digital light signal by the signal, if the infrared light wave of the fixed frequency is received The output number 0, 0 indicates that there is a car signal. If the infrared wave of the fixed frequency is not received, the

output number

1, 1 indicates a car-free signal; the infrared receiving circuit also receives the number of consecutive units of code at a time, for The height of the vehicle and the ground is measured to identify the basic type of vehicle.

Referring to FIG. 19, the infrared transmitting circuit includes a square wave generator, a modulation encoder, and a driving circuit. The specific process of the infrared transmitting circuit is as follows: the modulated 30-60 Khz square wave is emitted through a 940 nm infrared tube to provide a modulated fixed-frequency infrared light wave for detecting the vehicle, in order to prevent the infrared light wave of the fixed frequency from being interfered by other light waves, The fixed frequency is preferably 38 Khz.

Referring to FIG. 20, the infrared receiving circuit includes: a reflected signal input stage, an initial amplifier, a band pass filter, a clipped automatic gain controller, a comparator, a Schmitt trigger, and a non-gate drive output.

Referring to FIG. 21, a GMI detection module includes: an excitation resonance circuit unit and a magnetic abnormality detection conditioning circuit unit. The principle is a GMI magnetic sensor with a GMI effect. The magnetic sensor detects the movement of a ferromagnetic object by measuring changes in the surrounding earth's magnetic field. When a ferromagnetic object appears near the GMI magnetic sensor, it will cause bending and density changes of the surrounding earth's magnetic field lines. The GMI magnetic sensor can sense this small change and determine whether there is a ferromagnetic object through certain judgment criteria. Appeared nearby. When there is no car, the earth's magnetic field is 55,000 nanosla (nT) (about 38 latitude in Beijing area); when there is a car, the earth's magnetic field is no longer 55,000 nT after being disturbed, and magnetic anomalies occur.

Referring to FIG. 22, the excitation resonant circuit unit includes: an excitation oscillator, a magnetic resonance drive circuit, and a magnetic-sensitive GMI probe, wherein the magnetic-sensitive GMI probe includes: a magnetic-sensitive sub-nano metal used as a magnetic core. Glass fiber (also called amorphous wire), magnetic detection coil and magnetic compensation coil. The excitation oscillator and the magnetic resonance driving circuit apply a high-frequency alternating current to the magnetic core (amorphous wire), and the high-frequency current flowing through the magnetic core (amorphous wire) changes under the influence of the magnetic field, and the magnetic core is changed by the magnetic core. The magnetic winding coil that is wound up detects a change signal of the magnetic field, and is output after passing through the magnetic abnormality detecting circuit and detecting the amplifying circuit. The GMI magnetic sensor features high sensitivity, fast response and no hysteresis. The excitation oscillator excites a high frequency alternating current for a magnetic sensitive GMI probe, and the high frequency alternating current generates magnetic resonance of the magnetic sensitive GMI probe through a magnetic resonance driving circuit to improve the sensitivity of the magnetic field detection.

Referring to FIG. 23, the magnetic abnormality detecting and conditioning circuit unit comprises: a magnetic compensation circuit, a temperature compensation circuit, a magnetic abnormality detection circuit, a detection amplification circuit, and a management control circuit. The magnetic abnormality detecting and conditioning circuit unit is configured to process a change signal of the measured magnetic field, and detect a vehicle disturbance magnetic field magnetic abnormality signal of the parking space according to the processing result. When the magnetic output coil detects the change signal of the magnetic field and sends it to the amplification circuit for amplification, a part of the magnetic compensation circuit compensates the magnetic compensation coil for geomagnetism. When the GMI detection module is affected by the ambient temperature, the temperature compensation circuit automatically compensates, and the management control circuit performs power management on the entire GMI detection module to reduce power consumption.

It should be noted that the infrared detection module included in the vehicle detector listed in FIG. 17 above can also be omitted, and the detection of the vehicle is directly implemented by using the GMI detection module. The detection principle is similar to the foregoing, and is no longer one by one. Narration.

Example 2

The wireless communication network system of the present invention can be used for intelligent control of intersection traffic lights. In the traffic light control, vehicle detectors are deployed on different lanes of different intersections. For details, refer to the network structure and deployment diagram of the traffic light control shown in FIG. The system consists of traffic flow detection node, vehicle speed detection node, relay node, traffic light controller, special vehicle identifier, handheld controller and data management platform. The traffic flow detection node is used for vehicle counting detection in the lane, and the vehicle speed detection node For vehicle speed measurement, the relay node is used to receive the measurement signals of the vehicle speed detection node and the traffic flow detection node and forward the data to the traffic light controller; the traffic light controller is used for intelligently managing the intersections according to the traffic volume and the vehicle speed of different intersections. Traffic light time; special vehicle identifier is used for special vehicle identification such as fire fighting and ambulance, and can control the intersection traffic light through the recognition result; the data management background is used to collect the controller data of each intersection and analyze the data.

The network construction method in Embodiment 1 is applicable to Embodiment 2, except that the number of vehicle detection nodes carried by one relay node does not exceed 10, and the time slot T of each vehicle detection node is less than 10 milliseconds.

The vehicle flow detection in Embodiment 2 is based on the slope detection and threshold detection algorithm in Embodiment 1, and when a vehicle passes, the magnetic sensor gives a change of the vehicle disturbance magnetic field, and after passing, the magnetic field returns to the environmental magnetic field; When passing, if it stops at the traffic flow detection node, then leave, see the figure As shown in Fig. 15, when the magnetic field strength is higher or lower than the ambient magnetic field at the time of stopping, the vehicle flow rate detection can be realized by counting the slope of the magnetic signal and the threshold value detection.

The vehicle speed detecting method in Embodiment 2 is based on the slope detecting and threshold detecting algorithm in Embodiment 1, referring to FIG. 16 for the forward passing and reverse passing examples of the vehicle, by recording the disturbance of the magnetic signal of the front and rear of the vehicle, recording The time difference before and after the disturbance can be combined with the length of the vehicle to achieve the vehicle speed measurement;

Preferably, the method for deploying two vehicle detection nodes is adopted, and the distance between the two vehicle detection nodes is d, and the node realizes microsecond synchronization by the high-precision time synchronization method in the above embodiment 1, when the vehicle passes the vehicle detection. When node 1 and the vehicle detect node 2, the two nodes respectively record the time t1 and t2 of the vehicle head disturbance magnetic field or the parking space disturbance magnetic field, and send two times to the relay node or the aggregation node, and the relay node or the aggregation node pass The ratio of the time difference t2-t1 to the distance d calculates the vehicle speed.

The above is a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.

Claims

A wireless communication system for intelligent traffic monitoring, the system comprising: a vehicle detection node, a wireless relay node and/or a wireless convergence node, and a management center, wherein:

The vehicle detecting node is configured to collect traffic information of the vehicle, and send the data to the management center by using a wireless protocol;

The relay node is configured to receive traffic information sent by the vehicle detection node, and process the received traffic information and send the information to the aggregation node;

The aggregation node is configured to receive traffic information sent by the vehicle detection node or processed traffic information sent by the relay node, and transmit the same to the management center by using a wireless communication technology (Wifi, mobile communication network, etc.) ;

The management center is configured to store and process the received traffic information.
The system of claim 1 wherein:

The system includes: at least one vehicle detection node, at least one relay node, and one convergence node, and the network formed by the vehicle detection node, the relay node, and the aggregation node adopts a mesh/star topology;

Each relay node is connected to at least one vehicle detection node via a wireless communication network, and the vehicle detection node connected to the relay node and the relay node constitutes a star network, and the vehicle detection node detects the traffic information. Sending to the at least one relay node, and the plurality of relay nodes form a mesh network to transmit the vehicle information to the sink node through wireless communication of different channels;

The aggregation node is configured to upload traffic information detected by all vehicle detection nodes in the entire wireless communication network to the management center.
The system of claim 1 wherein:

The system includes at least one sink node and at least one vehicle detection node, and the wireless communication network formed by the sink node and the at least one vehicle detection node adopts a star topology;

Each of the aggregation nodes is connected to at least one vehicle detection node, and each of the aggregation nodes uses different channels to work simultaneously, and the system can simultaneously deploy multiple independent network operations;

The sink node is configured to check all received vehicle detection nodes connected to the sink node The measured traffic information is uploaded to the management center.
A system according to claim 2 or 3, wherein:

The relay node includes two wireless communication modules of different frequency bands, wherein one wireless communication module is used to communicate with a vehicle detection node, and another wireless communication module is used between each relay node, and/or a relay node and convergence. Communication between nodes.
A system according to any of claims 2-4, characterized in that:

The network of the system works with network memory to quickly recover the network. When each node is disconnected or restarted, it can work directly without rejoining the network;

The information such as the address and channel of the vehicle detection node is recorded in the on-chip Flash, and the vehicle detection node reads the information stored in the flash after each power-on. If the information is valid (non-zero), the information is directly synchronized by monitoring the beacon. jobs.
A system according to any of claims 2-4, characterized in that:

A star network consisting of a vehicle detection node and a relay node or a sink node adopts a TDMA/CSMA hybrid scheduling mode;

The superframe length is configured by the aggregation node according to the dynamic change of the network state, and each node slot is T ms, and the number of vehicle detection nodes in one superframe is at most 254, and one star topology uses one superframe;

Preferably, the superframe length is: the number of detected nodes of the vehicle connected to the star network *T + the number of competing slots *T.
The system of claim 6 when said claim 6 refers to claim 2, characterized in that:

The allocation of TDMA time slots is directly calculated according to the network address assigned by the network to the vehicle detection node;

After the vehicle detecting node joins the network, the vehicle detecting node obtains a network address allocated by the relay node, and the network address is allocated according to the number of connected vehicle detecting nodes from 1 to the relay node. The relay node is also used to store and maintain the physical address and network address of each vehicle detection node;

The vehicle detecting node transmits data to the relay node by using the obtained network address as a TDMA time slot for transmitting data;

Receiving, by the relay node, the ACK confirmation packet after receiving the data sent by the vehicle detection node;

Wherein, in each transmission period, the relay node not only allocates one TDMA time slot to each vehicle detection node, but also reserves a TDMA time slot according to a preset number, and the reserved time slot position of the contention access is determined by The contention start slot number and the number of contention slots in the beacon frame are determined. In the reserved TDMA slot, the vehicle detection node transmits data in a CSMA manner.
The system according to claim 6, when said claim 6 refers to claim 3, characterized in that:

The allocation of TDMA time slots is directly calculated according to the network address assigned by the network to the vehicle detection node;

After the vehicle detecting node joins the network, the vehicle detecting node obtains a network address allocated by the sink node, and the network address is allocated according to the number of connected vehicle detecting nodes from the 1 to the sink node, the sink node Also used to store and maintain the physical address and network address of each vehicle detection node;

The vehicle detecting node sends data to the sink node with the network address obtained by it as a TDMA time slot for transmitting data;

Receiving, by the sink node, the ACK confirmation packet after receiving the data sent by the vehicle detection node;

Wherein, in each transmission period, the sink node not only allocates one TDMA time slot to each vehicle detection node, but also reserves a TDMA time slot according to a preset number, and reserves the reserved time slot position of the competition access by the letter. The contention start slot number and the number of contention slots in the frame are determined. In the reserved TDMA slot, the vehicle detection node transmits data according to the CSMA method.
The system of claim 6 wherein:

In the TDMA/CSMA hybrid scheduling method:

The first time slot of the superframe transmits a beacon frame;

The beacon frame is sent by the relay node or the sink node;

The beacon frame has the number of connected vehicle detection nodes in the cluster, and each cluster can connect up to 254 vehicle detection nodes;

When the vehicle detection node enters the network, the collected vehicle detection node number information in the relay node beacon frame collected is used as a selection basis to ensure the balance of the number of vehicle detection nodes connected to each relay node.
The system of claim 6 wherein:

In the TDMA/CSMA hybrid scheduling method:

The vehicle detection node synchronizes through the beacon frame;

The beacon frame carries network time. When the vehicle detection node joins, after receiving the beacon frame, it sets its own network time according to the network time of the beacon to achieve coarse synchronization;

After the vehicle detection node joins the network, in order to ensure that the timing between the transceiver nodes is not disordered, an accurate timer is set, which is started at the beginning of a time slot, and is closed at the end of the time slot, and the vehicle detection node will set the value of the Tsend time timer. Recorded, the sink node or the intermediate node will fill the value of the Treceive time in the acknowledgement packet DATA-ACK and return it to the sensor node. The sensor node compares the two values and adjusts the length of the Delay time in the next time slot to complete the precise synchronization.
The system of claim 6 when said claim 6 refers to claim 2, characterized in that:

The vehicle detecting node, after listening to all the channels, finds a relay node corresponding to the beacon with the best signal quality through the relay selection algorithm, and joins the request frame at the receiving node of the relay node. Sending a join request to the relay node by the vehicle detecting node;

The joining request data packet includes: a physical address of the vehicle detecting node.
The system of claim 6 when said claim 6 refers to claim 2, characterized in that:

The vehicle detecting node, after listening to all the channels, finds a sink node corresponding to the beacon with the best signal quality through the relay selection algorithm, and joins the request frame slot at the receiving of the sink node. Sending a join request to the sink node by the vehicle detecting node;

The joining request data packet includes: a physical address of the vehicle detecting node.
The system of claim 11 or 12, wherein the relay selection algorithm comprises:

All the channels are monitored by the vehicle detection node, each channel monitors the beacon T time, and in the T time, if the beacon frame is received, the beacon frame information is stored until the last channel is monitored;

Finding a beacon with the best signal quality according to the stored beacon frame information, and determining whether the number of connected vehicle detection nodes of the beacon reaches an upper limit;

If the upper limit is reached, re-search for the beacon with the second-best signal quality in the stored beacon frame information.

If there are multiple beacons with the same signal quality, compare the beacons with the same signal quality to the number of vehicle detection nodes, and select the beacon with the least number of detected vehicle detection nodes;

If there are multiple beacons with the least number of detected vehicle detection nodes, the beacon is randomly selected from them;

The relay node or the sink node corresponding to the finally determined beacon is a destination node that sends a network access request to the vehicle detection node.
A system according to any one of claims 1-13, characterized in that:

The vehicle detection node is further configured to detect traffic information according to a preset frequency;

Transmitting data in a data transmission time slot of the vehicle detection node when detecting a change in traffic information;

During the preset time, when the traffic information is detected to be unchanged, no data is transmitted in the data transmission time slot of the vehicle detection node;

When the detected traffic information does not change within a preset time, the vehicle detecting node sends the survival indication frame to indicate that it is working normally, and stops stopping transmitting the survival indication frame when the detected traffic information changes.
A system according to any of claims 1-13, characterized in that the vehicle is identified in the following manner:

In order to detect vehicle parking, a combination of magnetic anomaly slope detection and threshold detection is adopted, and the magnetic signal is collected to calculate the change speed (ie, slope) of the magnetic signal, and the difference detection amplitude of the environmental magnetic field signal is used to realize the parking detection;

In order to detect the vehicle count, the number of vehicles is calculated by using the reverse change of the tail magnet signal;

In order to detect the vehicle speed, the reverse time difference of the magnetic signal of the vehicle head and the calculation of the length of the vehicle length are used, or by deploying two vehicle detection nodes at a distance d, the first one of the vehicles is detected between the two vehicle detection nodes. The time difference between the signal or the last signal and the distance d are used to calculate the vehicle speed.
An intelligent control system for an intersection traffic light, the system comprising a traffic flow detecting node, a vehicle speed detecting node, a relay node, a traffic light controller, a handheld controller, and a data management platform, wherein:

The vehicle flow detection node is used for vehicle count detection in the lane, and the vehicle speed detection node is used for vehicle speed measurement. The relay node is configured to receive the measurement signal of the vehicle speed detecting node and the traffic flow detecting node and forward the data to the traffic light controller;

The traffic light controller is used to intelligently manage the traffic light time of each intersection according to the traffic volume and the vehicle speed of different intersections;

The data management background is used to collect and analyze the data of controllers such as traffic at various intersections.
The system of claim 16 wherein:

The system also includes a special vehicle identifier for identification of special vehicles such as firefighting, ambulance, etc., and can control the traffic light time of each intersection by the recognition result.
A system according to claim 16 or 17, wherein:

The system includes: at least one vehicle detection node, at least one relay node, and one convergence node, and the network formed by the vehicle detection node, the relay node, and the aggregation node adopts a mesh/star topology;

Each relay node is connected to at least one vehicle detection node via a wireless communication network, and the vehicle detection node connected to the relay node and the relay node constitutes a star network, and the vehicle detection node detects the traffic information. Sending to the at least one relay node, and the plurality of relay nodes form a mesh network to transmit the vehicle information to the sink node through wireless communication of different channels;

The aggregation node is configured to upload traffic information detected by all the vehicle detection nodes in the entire wireless communication network to the management center;

or,

The system includes at least one sink node and at least one vehicle detection node, and the wireless communication network formed by the sink node and the at least one vehicle detection node adopts a star topology;

Each of the aggregation nodes is connected to at least one vehicle detection node, and each of the aggregation nodes uses different channels to work simultaneously, and the system can simultaneously deploy multiple independent network operations;

The sink node is configured to upload the received traffic information detected by all the vehicle detecting nodes connected to the sink node to the management center.
The system of claim 18 wherein:

Wherein one of the relay nodes is connected to at most no more than 10 vehicle detection nodes. The time slot T of each vehicle detection node is less than 10 milliseconds.
A system according to any one of claims 16-19, characterized in that:

In order to detect the traffic flow, a combination of magnetic anomaly slope detection and threshold detection is used to calculate the change speed (ie slope) of the magnetic signal by collecting the magnetic signal, and the difference detection range of the environmental magnetic field signal is used to realize the vehicle flow detection;

Preferably, when a vehicle passes by, the magnetic sensor gives a change of the disturbance magnetic field of the vehicle. After passing, the magnetic field returns to the ambient magnetic field; when the vehicle passes, if it stops at the traffic flow detecting node, then leaves, the magnetic field stops. The intensity is higher or lower than the ambient magnetic field. The vehicle flow detection can be realized by counting the slope of the magnetic signal and the threshold detection. By recognizing the disturbance of the magnetic signal by the front and rear of the vehicle, the time difference before and after the disturbance is recorded, combined with the length of the vehicle. The vehicle speed measurement can be realized, or by deploying two vehicle detection nodes at a distance d, the vehicle speed can be calculated by the time difference and distance d of the magnetic signals caused by the two vehicles detecting nodes when the same vehicle passes.
A vehicle detection node disposed in a wireless communication system for intelligent traffic monitoring,

The wireless communication system includes: a vehicle detection node, a relay node, and/or a convergence node, and a management center; wherein the vehicle detection node is configured to collect traffic information of the vehicle, and send the data to the wireless protocol a management node; the relay node is configured to receive traffic information sent by the vehicle detection node, and process the received traffic information to be sent to a sink node; the sink node is configured to receive the vehicle detection node Emitted traffic information, or processed traffic information sent by the relay node, and transmitted to the management center through a wireless communication technology (Wifi, mobile communication network, etc.); the management center is configured to receive Traffic information is stored and processed. It is characterized by:

The vehicle detection node includes: a sensor (magnetic sensor, infrared sensor, ultrasonic sensor, etc.), a microprocessor, and a wireless transmitting module; wherein

The sensor is used for detecting traffic information such as whether the parking space is stopped, the speed of the vehicle in motion, the traffic volume of the traffic intersection, and the like;

The microprocessor is configured to perform analog-to-digital conversion, signal processing analysis and operation on the detected vehicle detection signal, and comprehensively identify and generate traffic information, and then transmit the traffic information through the wireless transmitting module.
A relay node disposed in a wireless communication system for intelligent traffic monitoring,

The wireless communication system includes: a vehicle detection node, a relay node, a convergence node, and a management center; wherein the vehicle detection node is configured to collect traffic information of the vehicle, and send the data to the management center by using a wireless protocol; The relay node is configured to receive traffic information sent by the vehicle detection node, and process the received traffic information and send the traffic information to a sink node; the sink node is configured to receive the traffic sent by the vehicle detection node Information, or processed traffic information sent by the relay node, and transmitted to a management center through a wireless communication technology (Wifi, mobile communication network, etc.); the management center is configured to receive traffic information Storage and processing. It is characterized by:

The relay node includes: a microprocessor MCU, a first wireless transceiver unit, a second wireless transceiver unit 2, 485 communication interface, a 232 communication interface, an Ethernet interface, a TTL output circuit, and a power conversion module;

The first wireless transceiver unit is configured to communicate with a vehicle detection node, and the second wireless transceiver unit is configured to communicate with a relay node and a sink node;

Receiving, by the first wireless transceiver unit of the relay node, traffic information sent by the vehicle detection node, converting the traffic information to the second wireless transceiver unit by the microprocessor MCU, forwarding to the aggregation node, or passing the 485 The communication interface/serial communication interface/TTL output circuit is output to the control device, such as the traffic light control system.
A convergence node, which is disposed in a wireless communication system for intelligent traffic monitoring,

The wireless communication system includes: a vehicle detection node, a relay node, a convergence node, and a management center; wherein the vehicle detection node is configured to collect traffic information of the vehicle, and send the data to the management center by using a wireless protocol; The relay node is configured to receive traffic information sent by the vehicle detection node, and process the received traffic information and send the traffic information to a sink node; the sink node is configured to receive the traffic sent by the vehicle detection node Information, or processed traffic information sent by the relay node, and transmitted to a management center through a wireless communication technology (Wifi, mobile communication network, etc.); the management center is configured to receive traffic information Storage and processing; characterized by:

The aggregation node comprises: a microprocessor MCU, a first wireless transceiver unit, a second wireless transceiver unit 2, 485 communication interface, a 232 communication interface, an Ethernet interface, a GPRS/3G/4G communication interface, a TTL output circuit, and a power conversion Module; among them,

The first wireless transceiver unit is configured to communicate with a vehicle detection node, and the second wireless transceiver unit is configured to communicate with a relay node;

Receiving, by the first wireless transceiver unit in the sink node, traffic information sent by the vehicle detecting node; receiving, by the second wireless transceiver unit of the sink node, traffic information sent by the relay node; the microprocessor MCU transmitting the traffic information Convert to GPRS/3G/4G module, forward to management center, or output to control device through 485 communication interface/serial communication interface/TTL output circuit, such as traffic light control system.
A wireless communication method for a wireless communication system for intelligent traffic monitoring includes a joining network, resource allocation, and low power consumption monitoring steps, wherein:

Joining the network step: After the vehicle detection node is powered on, the vehicle detection node automatically joins the wireless communication network;

Resource allocation step: realizing division of communication time slots of vehicle detection nodes;

Low-power monitoring steps: low-power monitoring and network communication maintenance for traffic information.
The method according to claim 24, wherein the step of joining the network further comprises:

After the relay node/aggregation node works, the beacon frame is periodically broadcasted, and is used for detecting the network access and synchronization of the vehicle. The content of the beacon frame includes: a network number, a network time, and the local relay node/aggregation node is connected. The number of detected nodes of the vehicle, the starting position of the competing access slot, and the number of competing access slots;

After the vehicle detection node is powered on, the beacon frame is monitored on all channels, and the parameters of all received beacon frames are recorded: network number, network time, signal quality, number of connected vehicle detection nodes, etc.;

After the vehicle detection node listens to all the channels, the relay selection algorithm is used to find the most suitable relay node/aggregation node, and the “competition access time slot” of the relay node/aggregation node is CSMA to the relay node. / aggregation node sends a join request;

Adding a physical address with a vehicle detection node in the request packet, the relay node/aggregation node decides whether to allow the vehicle detection node to join, and returns a join response, and if the return is allowed to join the response, the vehicle detection node obtains Following the network address assigned by the node/aggregation node, the joining process is completed, and the relay node/aggregation node needs to store and maintain the physical address and network address of each vehicle detecting node.
The method according to claim 24 or 25, wherein the step of joining the network further comprises:

After the vehicle detection node is powered on, it monitors the beacon T time on the initial channel, and then switches to the next channel to monitor the T time until all channel monitoring is completed; in the T time, if the beacon frame is received, the beacon frame information is stored. After the last channel monitoring is completed, in the stored beacon frame information, the beacon with the best signal quality is searched, and then it is judged whether the number of connected vehicle detection nodes of the beacon reaches the upper limit, and if the upper limit is reached, the storage letter is searched again. If the signal quality of the beacon is the same, if there are multiple beacons with the same signal quality, compare the number of connected vehicle detection nodes of these beacons, and select the beacon with the least number of detected vehicles. The number of beacons with the least number of detected nodes of the visited vehicle is randomly selected from them;

The vehicle detection node initiates a join request with the relay node/sink node corresponding to the selected beacon as the destination address.
The method according to any one of claims 24 to 26, wherein the resource allocation step further comprises:

After the vehicle detection node joins the network, the network address assigned to the relay node/sink node is obtained. The network address allocation is performed in order from 1 to the number of connected vehicle detection nodes, and the vehicle detection node uses its network address as the transmission data. The TDMA time slot transmits data to the relay node/sink node;

After receiving the data, the relay node/aggregation node returns an ACK acknowledgement packet, that is, the allocation of the TDMA resource is calculated by the vehicle detection node itself, and no time slot needs to be allocated;

Preferably, in one transmission period, in addition to assigning one time slot to each vehicle detection node, n reserved time slots are reserved, and the reserved time slot is used to detect the node in which the transmission fails. Resend data during this period.
The method according to any one of claims 24 to 27, wherein the low power consumption detecting step further comprises:

The low power detection step adopts a high frequency detection method and a low frequency transmission method; that is, the high frequency secondary activation sensor detects the traffic information signal, and if the detected traffic information signal does not change, the data transmission time slot of the vehicle detection node does not transmit data. , reduce power consumption, send data if there is a change detected;

Preferably, in the case that the long-term traffic information signal is unchanged, the vehicle detection node sends the survival indication frame to indicate that the relay node or the aggregation node is working normally; when the signal transmission change is detected, the survival indication frame is stopped.
A method according to any one of claims 24 to 28, wherein the method further comprises a time synchronization step of the network, characterized in that:

The aggregation/relay node periodically transmits a beacon frame. When the vehicle detection node joins the network, after receiving the beacon frame, it synchronizes according to the network time in the beacon frame, and changes its local time to the network in the beacon. time;

Preferably, after the vehicle detecting node joins the network, in order to ensure that the timing between the transmitting and receiving nodes is not disordered, each node in the network sets a subtle deterministic timer, starts at the beginning of a TDMA time slot, and stops at the end of the time slot. The vehicle detection node records the timer value of the time Tsend for transmitting the data packet, and the aggregation node or the intermediate node records the timer value of the time Treceive of the data packet sent from the vehicle inspection node, and fills in the ACK. The vehicle returns to the vehicle detection node; the vehicle detection node compares the two values, and if the difference delay is greater than the threshold, the length of the delay time is adjusted in the next time slot, thereby completing the precise synchronization.
A parking detection method for a wireless communication system for intelligent traffic monitoring, which determines a warehousing and leaving time of a vehicle by detecting a quantized value and a slope of a change of a magnetic signal, wherein the slope detection is controlled by two parameters, Offset and thresholdk respectively control the span of the slope detection and the threshold of the slope, and the amplitude of the disturbance can be controlled by adjusting the two parameters; the method comprises the following steps:

The step of judging the current state of the vehicle; when the vehicle is parked, the curve changes significantly during the process of entering and exiting, and the slope of the value of the sensor changes greatly when the vehicle passes, by detecting the change of the slope and the extraction of the minimum and minimum values, Determine the current state of the vehicle;

The step of determining the state of the vehicle in or out of the warehouse: each time identifying the continuous data collected by the sensor for a period of time, detecting the positive slope and the negative slope and finding the maximum and minimum values, by maxima and minima The location and quantity of the judgment can identify the vehicle in or out of the warehouse;

The step of determining the state of the vehicle parking state: After the slope detection, by calculating the average value of the current sensor and comparing with the median value of the sensor, it can determine the current parking state of the vehicle.