KR20060034067A - Method for handover in wave system - Google Patents

Abstract

The handover method in a vehicle environment according to the present invention is a method in which a first roadside device communicating with a vehicle-mounted device supports handover of the vehicle-mounted device, wherein the location information and handover information are received from the vehicle-mounted device. Receiving; Determining a second roadside device to perform communication after handover based on the location information, and transmitting and receiving information necessary for handover with the second roadside device; And transmitting a handover command to the vehicle-mounted device, wherein the handover is performed between a WAVE roadside device and a WAVE vehicle-mounted device of a telematics wireless communication system in a telematics vehicle moving environment of 200 km or less per hour. By providing telematics services seamlessly.

Description

Handover method in vehicle environment {Method for handover in WAVE system}

1 is a diagram illustrating an example of a cell configuration method for providing handover in a WAVE system.

FIG. 2 is a diagram illustrating a structure of a communication channel under the cell configuration of FIG. 1.

FIG. 3 is a diagram illustrating a data frame on a time axis according to a channel used by the RSE and the OBE of FIG. 1.

FIG. 4 is a diagram illustrating a handover related MAC information field that RSE and OBE of FIG. 1 should transmit when a handover occurs.

FIG. 5 is a diagram illustrating handover related messages to be transmitted when handover occurs between RSEs of FIG. 1.

FIG. 6 is a diagram illustrating a message flow generated between an OBE in handover, an RSE currently in communication, and an RSE in handover.

FIG. 7 is a flowchart illustrating a process of handover of an OBE of FIG. 1.

FIG. 8 is a flowchart illustrating a process of handover between an OBE of FIG. 6 and an RSE currently in communication.

FIG. 9 is a flowchart illustrating an operation of handover of a target RSE to which the OBE of FIG. 6 is to be handed over.

The present invention relates to a method for handover in a vehicle environment, and more particularly, to a method for supporting handover in a wireless packet communication system in a mobile environment of 200 Km or less per hour during a packet data communication technique using an OFDM modulation and demodulation scheme.

Telematics wireless communication is a vehicle-roadside device that enables the exchange of information through a two-way communication within a 500m communication radius between a roadside device (hereinafter referred to as "RSE") and a vehicle-mounted device (hereinafter referred to as "OBE"). Dedicated communication between people. Up to now, the system developed and used for packet communication in telematics mobile radio environment is ASK modulation type DSRC system of 100m communication area with 1Mbps data rate, and WAVE (Wire Access in Vehicular Environments) with 10Mbps OFDM modulation method. Research on wireless communication systems is actively progressing.

In Korea, 1 Mbps DSRC system is developed and commercialized in accordance with TTA standard TTAS.KO-06.0025 and installed in 5.795 GHz to 5.815 GHz and 5.835 GHz to 5.855 GHz. In addition, in order to provide a high speed multimedia service as well as a low speed service provided by the existing 1Mbsp DSRC system, a higher speed WAVE system having an extended communication radius is being developed.

At this time, when the telematics system is installed to provide a service, a handover method for maintaining a radio link between RSEs becomes essential to receive a seamless service. If a handover is not provided, a continuous service is impossible.

The present invention has been made to solve the above problems, and provides a method for providing a handover between RSEs of OBEs moving at a high speed in a WAVE wireless communication system using a TDD scheme and an OFDM modulation and demodulation scheme. It is.

In accordance with an aspect of the present invention, there is provided a method for performing a handover of a roadside apparatus according to the present invention in a method in which a first roadside apparatus communicating with a vehicle-mounted apparatus supports handover of the vehicle-mounted apparatus. Receiving location information and handover information; Determining a second roadside device to perform communication after handover based on the location information, and transmitting and receiving information necessary for handover with the second roadside device; And transmitting a handover command to the vehicle-mounted device.

According to an aspect of the present invention, there is provided a method of performing a handover of a roadside apparatus, the method including: receiving a handover message from a roadside apparatus communicating with a vehicle-mounted apparatus; Allocating a radio channel with a beacon of the ID of the on-vehicle device and transmitting the result to the roadside device; And checking whether the handover time has been exceeded if communication with the on-vehicle device has not been initiated, and terminating a channel allocation for the on-vehicle device if the time has exceeded.

According to an aspect of the present invention, there is provided a method of performing a handover of an on-vehicle device, the method comprising: receiving an identification signal from at least one second roadside device adjacent to a first roadside device in communication; Transmitting own location information and handover notification information to the first roadside device; And when the handover message is received from the first roadside device, changing a frequency to a communication channel of the second roadside device.

Hereinafter, a preferred embodiment of a handover method according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an example of a cell configuration method for providing handover in a WAVE system, and FIG. 2 is a diagram illustrating a structure of a communication channel under the cell configuration of FIG. 1.

In general, WAVE Road Side Equipment (RSE) and On Board Equipment (OBE) use a 10 MHz bandwidth, a time division duplex (TDD) scheme, and an orthogonal frequency division multiplexing (OFDM) scheme. The communication area is 500 meters and can be extended by additional devices. The frequency bandwidth is 20 MHz total using two 10 MHz channels.

1 illustrates a situation in which the OBE 107 performs handover while maintaining a communication link in the RSE 101 communication area and the RSE 102 communication area. As can be seen from FIG. 1, the overlapping communication area of one RSE and an adjacent RSE is based on two RSEs (eg, RSEs). For example, 104 and 105). Then, in the overlapping communication area, the RSE communicates using one of the channels 201 or 202 as shown in FIG. 2 when communicating with the OBE.

Referring to the number of RSEs in the overlapping area, in FIG. 2, the number of overlapping RSEs is two, and multiplying the number 2 by the bandwidth used by the modem is the bandwidth used by the system. In the case of FIG. 2, multiplying the number of required channels by 2 and the communication bandwidth of 10 MHz results in a total system bandwidth of 20 MHz. This determination may prevent interference between RSEs that communicate using different channels (channels 1 and 2 of FIG. 2) in the overlapping region.

In more detail, the structure of 201 is a structure that operates independently by OFDM modulation using two 10MHz channels, each with a 10 MHz band as one channel. The communication bandwidth per channel is 10MHz and the total system bandwidth for handover consists of two 10MHz bands to rule out interference with neighboring RSEs.

On the other hand, the structure of 202 is a structure in which a subcarrier generated by OFDM modulation of the 20 MHz band is divided into two channels and one channel is allocated to an adjacent RSE. The communication bandwidth is 20MHz and the OFDM subcarriers within this bandwidth are divided into two channels and used by each RSE.

FIG. 3 is a diagram illustrating a data frame on a time axis according to a channel used by the RSE and the OBE of FIG. 1, and FIG. 4 is a diagram illustrating a handover related MAC information field to be transmitted when the RSE and the OBE of FIG. 1 are handovered. Drawing. FIG. 5 is a diagram illustrating a handover related message to be transmitted when a handover occurs between RSEs of FIG. 1.

An example of using a wireless channel in the overlap area can be seen in FIG. 3. If one RSE transmits a frame using channel 1 of Figure 2, another adjacent RSE transmits the frame using channel 2 of Figure 2, which does not overlap in frequency, so that the OBE signals without interference between the two signals of channel 1 and channel 2. Can communicate with each other.

Handover related field information required for handover between the RSE and the OBE can be seen in FIG. 4. The handover related MAC PDU 400 transmitted from the OBE to the RSE of FIG. 4 indicates a handover notification field 401 for indicating that the OBE currently communicating with the RSE has received a communication frame of an adjacent RSE, indicating the location of the current OBE. OBE location information field 402 and an OBE ID field 403 identifying each OBE. The handover related MAC PDU 410 to be transmitted to the OBE in the RSE of FIG. 4 includes a handover command field 411 for instructing the OBE to start handover and an OBE ID field 412 for identifying each OBE.

5 shows a handover related message to be exchanged between RSEs. The first message 500 of FIG. 5 is message information transmitted by an RSE currently communicating with an OBE to a handover target RSE for a radio channel allocation request for handover, and includes a handover channel assignment request message ID field (ID) identifying a message. 501), a handover request RSE ID field 502 identifying an RSE requesting a handover, and a handover OBE ID field 503 identifying a handover target OBE.

The second message 510 of FIG. 5 is a handover channel assignment response message ID field 511 for identifying a message as message information transmitted by the handover target RSE to the handover request RSE, and a handover for identifying the handover target RSE. A target RSE ID field 512 and a handover OBE ID 513 for identifying an OBE to handover to which a radio channel is allocated.

6 shows a handover message flow according to the present invention.

If one OBE currently communicating with the RSE on one channel detects communication of an adjacent RSE communicating on another channel, it transmits current location information and handover notification information to the currently communicating RSE (S600).

The RSE currently in communication determines the handover target RSE by selecting the closest neighbor RSE where the difference between the received location information of the OBE and the location information of neighboring RSEs is minimal. The handover request message including the OBE ID information is transmitted to the determined handover target RSE (S601).

Upon receiving the handover request message, the handover target RSE sends a handover channel assignment response message and allocates a radio channel for the target OBE (S603).

After the RSE currently communicating receives the handover channel assignment response message, the RSE transmits a handover command message to the handover target OBE and terminates the link (S604).

The handover target RSE transmits a beacon which allocates a channel to the OBE which has changed the channel to the handover target RSE channel (S605), and the handover OBE receiving the handover command message changes the communication channel to the RSE channel to which the handover is targeted. After that, the communication link is switched and data transmission and reception are resumed (S606).

Now, let's take a look at the handover process in detail for each network entity.

FIG. 7 illustrates a handover procedure performed by the OBE in FIG. 6.

If communicating with the RSE (S701), and continues to check the preamble from the adjacent RSE to verify whether the reception (S702), when receiving the preamble to inform the RSE of the current communication with its location information and handover notification information (S703).

When receiving the handover command message (S704), the communication frequency is changed to the communication channel of the adjacent RSE, that is, the handover target RSE (S705), and then communication is performed with the handover target RSE (S706).

FIG. 8 illustrates a handover procedure performed by an RSE currently communicating with an OBE in FIG. 6.

First, it is checked whether the currently communicating OBE transmits handover notification information (S801). When the handover notification information is received, the handover target RSE is determined by applying a minimum distance determination algorithm using the location information of the OBE (S802).

After transmitting a message for requesting handover channel allocation to the handover target RSE determined in the above step (S803), and successfully receiving a handover channel allocation response (S804), after transmitting a handover command message to the OBE. The link between itself and the OBE is terminated (S805).

FIG. 9 illustrates a handover procedure performed by the handover target RSE in FIG. 6.

When receiving a handover message from another RSE (S901), the radio channel is allocated to the handover target ID as a beacon (S902). As a result, the radio channel is allocated to the handover target OBE. It informs the RSE requesting (S903).

As a result of the action of the RSE requesting the handover (that is, as a result of performing the step of FIG. 8), if communication with the handover target OBE is performed (S904), the communication is continued since the handover has been successfully performed. (S904) Check whether the handover time has been exceeded (S905). If it is not exceeded, the process of S904 is repeated, and if exceeded, the handover target OBE is deleted from the list and the channel allocation is stopped (S906). .

The handover method in a vehicle environment according to the present invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, hard disk, floppy disk, flash memory, optical data storage device, and also carrier wave (e.g. transmission over the Internet). It is also included to be implemented in the form of. The computer readable recording medium can also be distributed over computer systems connected over a computer network so that the computer readable code is stored and executed in a distributed fashion. Also, the font ROM data structure according to the present invention can be read by a computer on a recording medium such as a computer readable ROM, RAM, CD-ROM, magnetic tape, hard disk, floppy disk, flash memory, optical data storage device, and the like. It can be implemented as code.

As described above, the present invention has been described based on the preferred embodiments, but these embodiments are intended to illustrate the present invention, not to limit the present invention, and those skilled in the art to which the present invention pertains should be practiced without departing from the technical spirit of the present invention. It will be apparent that various changes, modifications, or adjustments to the examples are possible. Therefore, the protection scope of the present invention will be limited only by the appended claims, and should be construed as including all such changes, modifications or adjustments.

As described above, the handover method according to the present invention provides a seamless telematics service by providing a handover between a WAVE roadside device and a WAVE vehicle-mounted device of a telematics wireless communication system in a telematics vehicle moving environment of 200 km / hour or less. Done.

Claims (6)

A method of supporting a handover of the on-vehicle device by the first roadside device in communication with the on-vehicle device, (a) receiving location information and handover information from the vehicle-mounted device; (b) determining a second roadside device to perform communication after handover based on the location information, and transmitting and receiving information necessary for handover with the second roadside device; And (c) transmitting a handover command to the vehicle-mounted device. The method of claim 1, wherein step (b) (b1) determining a roadside device closest to the vehicle-mounted device as the second roadside device by a minimum distance determination algorithm using the location information as an input value; (b2) requesting handover channel allocation to the second roadside device; And (b3) if a positive response to the channel assignment is received from the second roadside device, sending a handover command to the onboard device and terminating the link; performing handover of the roadside device; Way. (a) receiving a handover message from a roadside device in communication with the onboard device; (b) allocating a radio channel with a beacon of the ID of the on-vehicle device and transmitting the result to the roadside device; And (c) checking whether the handover time has been exceeded if communication with the vehicle onboard device has not been initiated, and terminating channel allocation to the vehicle onboard device if the time exceeds the time. How to perform a handover. (a) receiving an identification signal from at least one second roadside device adjacent to the first roadside device in communication; (b) transmitting its location information and handover notification information to the first roadside device; And and (c) changing a frequency to a communication channel of the second roadside device if the handover message is received from the first roadside device. The method of claim 4, wherein step (b) And calculating the location of the vehicle by using a GPS to generate the location information. The method of claim 4, wherein the identification signal And a preamble signal transmitted and received between the vehicle mounting apparatus and the roadside apparatus.

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