KR101624715B1 - Transciver Communication method for broadcasting traffic information - Google Patents

Abstract

There is provided a communication method including a control unit and a communication unit and communicating with an external wireless transmitter. The control unit transmits a message including identification information of the radio transmitter to the radio transmitter, receives a message from the radio transmitter, and compares the identification information included in the received message with its identification information according to a predetermined priority. And transmits the schedule information to the wireless transmitter when the priority of the identification information included in the received message is higher than the priority of the identification information included in the received message, If it is lower than the priority of the identification information included in the received message, it waits to receive the schedule information. Priority-based broadcasting minimizes interference from wireless transmitters installed at adjacent intersections in delivering real-time traffic signal information to a vehicle through a wireless transmitter interfaced with a traffic signal controller installed at an intersection.

Description

TECHNICAL FIELD [0001] The present invention relates to a communication method of a wireless transmitter for transmitting traffic signals,

The present invention relates to a wireless transmitter, and more particularly, to a wireless transmission period communication method that avoids wireless transmission period interference that is installed at each intersection when a wireless transmitter transmits traffic signal information to a vehicle.

The present invention has been derived from the research carried out as part of the IT growth engine technology development project of the Ministry of Knowledge Economy . [ Task Assignment Number: 2008-S-039-02, Project Title: Situation-Aware based on Virtual Sensor for Pro-active Idlestop Technology development ].

Generally, a plurality of radio transmitters interlocked with a traffic signal controller (LC) are installed at an intersection, and real-time traffic signal information is transmitted to a vehicle through a radio transmitter. Then, the vehicle equipped with the wireless receiver receives the traffic signal information through the wireless receiver. Then, the traffic information received by the wireless receiver is analyzed and used for idling stop, eco-driving, traffic safety service, and the like.

These wireless transmitters are installed at each intersection to broadcast traffic signal information, which can interfere with another radio transmitter at another intersection.

FIG. 1 is a conceptual diagram showing an interference phenomenon in the radio transmission period.

Referring to FIG. 1, a period in which signals of a wireless transmitter connected to a traffic signal controller and other wireless transmitters interfere occurs. In this interval, a wireless receiver can not properly receive traffic signal information due to wireless communication interference.

In this way, there is a problem that signals that are broadcast by different radio transmitters interfere with each other.

SUMMARY OF THE INVENTION The object of the present invention is to minimize interference from a wireless transmitter installed at an adjacent intersection in delivering real-time traffic signal information to a vehicle through a wireless transmitter interfaced with a traffic signal controller installed at an intersection.

In addition, it can adapt the intersection situation information through naming of the traffic signal controller ID (LC ID) at the intersection, adaptively select the master transmitter or schedule it with other transmitters, so that it can be quickly and stably applied to the field .

In order to solve the above problems, the present invention provides a communication method of a wireless transmitter interworking with a plurality of traffic signal controllers.

In an exemplary communication method,

A communication method comprising a control unit and a communication unit and communicating with an external radio transmitter,

The control unit transmitting a message including identification information of the radio transmitter to the radio transmitter;

Receiving a message from the radio transmitter, and comparing the identification information included in the received message with its identification information according to a predetermined priority;

Determining a traffic signal broadcast schedule and transmitting schedule information to the wireless transmitter when the rank of the identification information of the mobile terminal is higher than the priority of the identification information included in the received message;

And waiting for receiving the schedule information when the priority of the identification information of the received identification information is lower than the priority of the identification information included in the received message.

The identification information is an ID including a number, and it is determined that the lower the number contained in the ID, the higher the priority.

According to an embodiment of the present invention, in transmitting real-time traffic signal information to a vehicle through a wireless transmitter interfaced with a traffic signal controller installed at an intersection, interference from a wireless transmitter installed at an adjacent intersection can be minimized. Also, according to the embodiment of the present invention, each wireless transmitter (not shown) may be configured to use a TDMA MAC, time synchronization, a traffic signal controller ID (traffic signal controller ID = radio transmitter ID), topology discovery, Can broadcast data only in the corresponding time slot, thereby preventing collision.

In addition, according to the embodiment of the present invention, the intersection situation information can be reflected through the LC ID Naming at the intersection to select the master transmitter adaptively and to schedule with other transmitters, Can be applied to the field.

1 is a conceptual diagram showing an interference phenomenon in a radio transmission period.
2 is a block diagram of a wireless transmitter according to an embodiment of the present invention.
3 is a flowchart illustrating a communication method of a wireless transmitter according to an exemplary embodiment of the present invention.
4 is a diagram showing an example of a general frame format.
5 and 6 are diagrams illustrating examples of a beacon frame format and a superframe format applied to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

In the embodiment of the present invention, the TDMA MAC scheme is used to synchronize the time while transmitting / receiving a beacon signal between radio transmitters, and a topology discovery, a master transmitter is selected using a traffic signal controller ID , Scheduling, and the like, so that each radio transmitter can broadcast data only to a corresponding time slot.

2 is a block diagram of a wireless transmitter according to an embodiment of the present invention.

2, a wireless transmitter according to an embodiment of the present invention includes a controller 210, an interface 220, a communication unit 230, and a memory 240.

The communication unit 230 may be implemented by dividing into a communication unit for performing radio transmission period communication and a communication unit for broadcasting, if necessary, in order to communicate with another radio transmitter or output a broadcasting signal. Among the communication signals, 447.5750MHz channel is used for transmitting and receiving beacon signals, and 447.5875MHz or 447.6MHz is selected for transmitting and receiving data.

The interface unit 220 performs an interface function with the traffic signal controller.

The memory 240 stores its own ID, and its own ID may be the same as the ID of the traffic signal controller associated with the memory 240 itself.

 The control unit 210 communicates with another radio transmitter through the communication unit 230 to compare the IDs. If the ID of the other radio transmitter is lower than the ID of the other radio transmitter, the controller 210 sets itself as a master and schedules the broadcast schedule of the traffic signal . On the other hand, if the user's ID is higher than the ID of the other radio transmitter, it sets itself as a slave and waits to receive the beacon signal of the other radio transmitter.

Here, the ID includes a number, and the priority is set to a high or low number. The method for determining the priority can be variously modified, and the higher the number, the higher the priority may be.

The communication method of the wireless transmitter will be described in detail with reference to FIG.

3 is a flowchart illustrating a communication method of a wireless transmitter according to an exemplary embodiment of the present invention.

Referring to FIG. 3, when power is supplied to the wireless transmitters (S301 and S302), the controller 210 of each wireless transmitter transmits and receives a HELLO packet through the communication unit 230 (S303 and S304). The HELLO packet includes its own ID information. Here, the operation of one wireless transmitter will be described for convenience, and it is assumed that the other wireless transmitter performs the same operation, and at least one of the other wireless terminals exists.

Next, the controller 210 performs a topology discovery process (S305). In this process, the ID of the received remote radio transmitter is compared with the ID stored in the memory 240.

As a result of comparison, if the ID of the other radio transmitter is lower than the ID of the other radio transmitter, the controller 210 determines itself as the master (S206) and schedules the traffic signal broadcasting sequence by the TDMA method (S307). For example, scheduling to broadcast in order of lower ID, and the first is itself.

Then, a beacon signal including scheduling information and time information is transmitted to the other radio transmitter (S308).

The control unit 210 refers to the scheduling information and broadcasts a traffic signal through the communication unit 230 when the broadcast time comes.

Meanwhile, if it is determined that the ID of the other radio transmitter is higher than the ID of the other radio transmitter, the controller 210 determines itself as a slave (S306) and waits for receiving the beacon signal from the master radio transmitter.

Then, when the beacon signal is received (S309), the controller 210 synchronizes the time using the scheduling information and the time information included in the beacon signal (S310), and broadcasts the traffic signal when the beacon signal is received.

Since the master grasps the surrounding radio transmitters and assigns the broadcast time to each radio transmitter in a time division manner, the plurality of radio transmitters do not broadcast in the same time zone, and the interference phenomenon is reduced .

If the ID of at least one wireless transmitter changes after the above process, the newly selected master wireless transmitter may broadcast a NEW_MASTER message during a CAP (Contention Access Period) period. At this time, the existing master radio transmitter updates the scheduling information and transmits the beacon signal last, and the newly selected master radio transmitter then transmits the broadcast signal for the second time.

If it is selected as a slave radio transmitter, the HELLO message is transmitted to the master transmitter during the CAP period. The master transmitter periodically updates the schedule information and then transmits the beacon signal.

If the beacon signal is not received, the beacon signal is waiting for receiving the beacon signal while increasing the beacon listen time exponentially. If the beacon signal is not received even though the number of times of backoff is three times, the beacon signal can be selected as the master transmitter by itself.

In the above procedure, the same as the ID of the wireless transmitter. Accordingly, the master radio transmitter and the slave radio transmitter are determined according to the traffic signal controller ID LC_ID. In addition, since the traffic signal controller ID is reflected in the scheduling information, it is important to determine the ID of the traffic signal controller according to the traffic policy.

Traffic signal controller ID occupies 16 bits in total, and consists of 8 bits reflecting intersection characteristics and 8 bits reflecting unique numbers. In the case of a, the most significant bit a, 0 or 1 indicates interlocking with the control center. In case of bit b indicating the channel environment, the interference level is expressed as 0 (Noise) / 1 (Clear) , D representing the traffic volume at the intersection is represented by 4 bits, and e representing the unique intersection ID is expressed by 8 bits, and the total is composed of 16 bits.

In reality, the ID of the traffic signal controller abccddddeeeeeeee (16bit) is as follows.

ID abccddddeeeeeeee (16bit) is the number of the intersection traffic (dddd), the information of the intersection, the road lane (b), the number of intersections, , Traffic congestion area (road), congestion by time, and uniqueness (eeeeeeee). The ID of the traffic signal controller can be variously modified. That is, the number of bits can be increased or decreased, and information can be added or deleted.

The packet format used in the above process will now be described.

4 shows a general frame format.

Referring to FIG. 4, a MAC frame includes a frame header, a frame body, and a frame check sum (FCS).

Frame header is occupied by Frame control, Src Addr (Source Address), Length, Seq # (Sequence number).

First, if you look at the Frame control field, you can see that it consists of Protocol Version, Frame Type, and Flag. The Protocol Version takes up 2 bits and starts from 0x00 and increases by 0x01 as the function is enhanced. There are 3 frame types (Beacon, Control, Data) and occupy 4bit. The first type, BEACON (0x01), is a message sent between TVC transmitters, which specifies the beacon signal that the TVC Master transmitter sends to the TVC Slave transmitter. Beacon includes Superframe structure, scheduling information, and time stamp for time synchronization. The second type, CONTOL, is a type used to send and receive messages related to control commands between wireless transmitters, such as HELLO, NEW_MASTER, RECOVERY, and ERROR. HELLO (0x04) is the message that the wireless transmitter sends to the neighboring transmitters for topology discovery. NEW_MASTER (0x05) is a message that the newly elected master transmitter transmits before transmitting the updated BEACON signal while joining the network. RECOVERY (0x06) is the message sent by the master radio transmitter to reboot the failed radio transmitter. ERROR (0x07) is a message that a transmitter that does not receive a beacon signal reports it to the master radio transmitter. In the third data type, there is a BROADCAST (0x0f) message, which is a message for broadcasting data in the corresponding time slot according to the superframe structure. Finally, the Flag field occupies 6 bits for reservation purposes.

The Frame header part consists of Frame control, Src Addr, Length, Seq #. Src Addr (Source Address) refers to the ID (LC_ID) of the traffic signal controller and consists of 4 bits. The Length field occupies 8 bits and indicates the length of a data packet including a Frame Check Sum (FCS) from a Frame header. The Seq # (Sequence Number) field occupies 16 bits and is sequentially incremented every time a packet is generated, and is initialized to 0xffff followed by 0x0000.

5 is a diagram showing a frame format of a Beacon signal.

Referring to FIG. 5, the Beacon frame header part is the same as the general MAC frame header shown in FIG. 4, but the frame body part is composed of a Superframe specification, a time stamp, and a Beacon payload. The Superframe specification is a Beacon Interval for a TDMA MAC, Information, and time synchronization information.

6 shows a frame format of a super frame.

Referring to FIG. 6, a superframe specifies information to be performed at a corresponding time for each beacon interval of a beacon signal. The superframe is divided into a contention free period (CFP) and a contention access period (CAP). In the CFP section, only one radio transmitter can broadcast data in the time slot corresponding to the TDMA method, while a plurality of radio transmitters can simultaneously access the CSMA / CA method in the CAP section, thereby performing a topology discovery process for management or control (CONTROL) messages are transmitted and received. For example, if the parameters of each superframe are set, the beacon interval is 1.8s as in the case of requesting traffic signal information and traffic situation information from the control center to the traffic signal controller. The TDMA slot duration has a maximum time of 200 ms assuming that the maximum size of data and beacon is 30 bytes in a channel condition of transmitting 1200 bps. The CAP interval starts at the point where the contention free period (CFP) ends and ends at the end of the beacon interval. The duration of the CFP may vary depending on the number of neighboring transmitters.

The embodiments of the present invention described above are not necessarily implemented by apparatuses and methods, but may be implemented by programs that realize the methods of the embodiments.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments but many changes and modifications may be made without departing from the scope of the present invention. One aspect is also within the scope of the present invention.

210: control unit 220: interface unit
230: communication unit 240: memory

Claims (8)

A communication method comprising a control unit and a communication unit and communicating with an external radio transmitter,
The control unit transmitting a message including identification information of the radio transmitter to the radio transmitter;
Receiving a message from the radio transmitter, and comparing the identification information included in the received message with its identification information according to a predetermined priority;
Determining a traffic signal broadcast schedule and transmitting the schedule information to the wireless transmitter when the priority of the identification information of the wireless terminal is higher than the priority of the identification information included in the received message;
And waiting for receiving the schedule information if the priority of the identification information of the wireless terminal is lower than the priority of the identification information included in the received message. The method according to claim 1,
Wherein the identification information is an ID including a number, and the lower the number contained in the ID is, the higher the priority is. The method according to claim 1,
Wherein the identification information is an ID including a number, and the higher the number contained in the ID, the higher the priority is. 4. The method according to any one of claims 1 to 3,
The TDMA MAC scheme is used to synchronize the time while transmitting / receiving a beacon signal between the control unit and the wireless transmitters. The control unit or the wireless transmitters transmit data in a time slot corresponding to the time slot according to the schedule information, A method of communication of a transmitter. 5. The method of claim 4,
The control unit or the wireless transmitter uses a beacon signal to transmit / receive a broadcast signal, a 447.5750 MHz channel is used to transmit / receive a beacon signal, and 447.5875 MHz or 447.6 MHz for data transmission / MHz < / RTI > is selected and used. The method according to claim 1,
Determining a traffic signal broadcast schedule and transmitting schedule information to the wireless transmitter when the priority of the identification information of the wireless terminal is higher than the priority of the identification information included in the received message,
Wherein the scheduling unit sets itself as a master and schedules broadcast schedules of traffic signals, and schedules a broadcast order of the traffic signals using a TDMA method. The method according to claim 6,
Wherein the step of waiting for receiving the schedule information includes the step of, if the priority of the identification information of the self is lower than the priority of the identification information included in the received message,
Sets itself as a slave, and waits to receive a beacon signal of the other radio transmitter. 8. The method of claim 7,
Wherein the traffic signal controller ID is the same as the ID of the wireless transmitter corresponding to the traffic signal controller ID. The traffic signal controller ID includes 8 bits reflecting the intersection characteristic and 8 bits reflecting the unique number.

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