KR101275626B1 - WAVE communication system and handover method thereof - Google Patents

Abstract

A WAVE communication system and a handover method are provided. In this handover method, an OBE sends a handover request message to an nRSE, an nRSE receiving a handover request message delivers a handover notification message to a pRSE, and a pRSE receiving a handover notification message is sent to an OBE. Discarding the frame to be transmitted, transmitting a frame received and buffered by the pRSE from the OBE to the GW, and sending a handover notification acknowledgment message to the nRSE by the pRSE. As a result, in the WAVE communication system, the amount of data frames lost when the connected RSE is changed while the OBE moves at high speed can be minimized, and communication can be normalized in the shortest time.

Description

WAVE communication system and handover method

The present invention relates to a communication system and a handover method. More particularly, the present invention relates to a WAVE communication system and a handover method performed between an on-board equipment (OBE) and a road-side equipment (RSE). It is about.

WAVE technology is an IEEE 802.11-based communication technology and standards are defined in standard documents such as IEEE 802.11p, IEEE 1609.3, and IEEE 1609.4. However, the WAVE standard does not cover procedures related to handover.

Wi-Fi technology, which is a similar technology, has some differences between WAVE technology and Medium Access Control layer function.Therefore, there is a limit to applying the handover procedure researched and applied in Wi-Fi network to WAVE network as it is. You cannot take advantage of WAVE communication technology (communication technology suitable for the environment where OBE moves at high speed).

The present invention has been made to solve the above problems, and an object of the present invention is to minimize the amount of data frames lost when changing the connected RSE while moving OBE at high speed in the WAVE communication system, and in the shortest time The present invention provides a handover method capable of normalizing communication.

In accordance with an aspect of the present invention, a handover method includes: transmitting, by an On-Board Equipment (OBE), a handover request message to a new road-side equipment (nRSE); NRSE receiving the handover request message, forwarding a handover notification message to a pRSE (previous road-side equipment); Discarding the frame to be delivered to the OBE by the pRSE receiving the handover notification message; transmitting, by the pRSE, a frame received and buffered from the OBE to a GW (GateWay); And pRSE sending a handover notification confirmation message to nRSE.

In the handover notification message delivery step, the handover notification message may be delivered to the pRSE at the end of the SCH (Service CHannel) section in which the nRSE receives the handover request message.

According to the present handover method, an nRSE receiving a handover notification acknowledgment message sends a message for updating a table of switches on a path between nRSE and GW and a table of switches on a path between nRSE and pRSE. and transmitting to the pRSE and the GW.

The message transmission step for updating the tables may send a message to the pRSE and the GW for updating the tables in the next channel section of the channel section in which the nRSE receives the handover request message.

The handover method includes the steps of, in a CCH interval, an RSE broadcasting a WAVE (WAVE Service Adevertisement) message including Dynamic Host Configuration Protocol (DHCP) server information and GW information; And unicasting, by the OBE receiving the WSA message, the DHCP discovery message to the GW through the RSE in the SCH (Service CHannel) section with reference to the GW information included in the WSA message.

The handover method may include: transmitting, by a GW receiving a DHCP discovery message, a DHCP suggestion message including information on IP addresses assignable to an OBE in an SCH interval, to an RSE; And RSE broadcasting the received DHCP proposal message in the WSA message in the CCH interval.

The handover method may include: unicasting, by an OBE receiving a DHCP proposal message, a DHCP request message including information on an IP address to be allocated by the OBE in an SCH to a GW through an RSE; Transmitting, by the GW, a DHCP acknowledgment message including an IP address to be allocated to the OBE to the RSE in the SCH period; And receiving, by the RSE, a DHCP acknowledgment message and including a DHCP ACK message in the WSA message and broadcasting the message in the CCH interval.

The WSA message may contain messages for multiple OBEs.

The messages for multiple OBEs may be DHCP offer messages for multiple OBEs and DHCP reply messages for multiple OBEs.

The DHCP server information may include at least one of an IP address and a MAC address of the DHCP server, and the GW information may include at least one of an IP address and a MAC address of the GW.

The CCH interval includes a WSA interval, and adjacent RSEs may broadcast a WSA message in different time slots of the WSA interval.

The CCH interval may include a WSMP interval used to transmit and receive data frames between the RSE and the OBE.

On the other hand, according to another embodiment of the present invention, a WAVE communication system, OBE (On-Board Equipment) for transmitting a handover request message to the second road-side equipment (RSE); A second RSE which forwards the handover notification message to the first RSE upon receiving the handover request message from the OBE; And receiving a handover notification message, discarding a frame to be delivered to the OBE, transmitting a buffered frame received from the OBE to a GW (GateWay), and transmitting a handover notification confirmation message to a second RSE. do.

The second RSE may deliver a handover notification message to the first RSE at the end of the SCH interval in which the handover request message is received.

The second RSE sends a handover request message with a message for updating a 'table of switches on the path between the second RSE and the GW' and a 'table of switches on the path between the second RSE and the first RSE'. The next channel section of the received channel section may be transmitted to the first RSE and the GW.

As described above, according to the present invention, the amount of data frames lost when the connected RSE is changed while the OBE moves at a high speed in the WAVE communication system can be minimized, and communication can be normalized within the shortest time. Accordingly, even if the OBE moves at high speed and changes the connected RSE, the quality of the data communication in progress is not significantly impaired.

1 is a diagram illustrating a multi-channel operated in WAVE,
FIG. 2 is a diagram provided to explain a process in which an OBE initially enters a WAVE network to obtain an IP address; FIG.
3 is a view provided for the description of the handover procedure of the OBE,
4 is a view for explaining the difference between the handover delay and the performance according to the time of transmission of the HO notify message of the nRSE,
5 is a diagram illustrating a method for preventing a collision of a WSA message broadcast in a CCH interval;
6 is a diagram showing the structure of a WSA message broadcast by RSE;
7 is a diagram illustrating a structure of a HO request message;
8 is a diagram illustrating a structure of a HO notify message, and
9 is a diagram illustrating the structure of a HO notify ACK message.

Hereinafter, with reference to the drawings will be described the present invention in more detail.

One. WAVE ( Wireless Access in Vehicular Environments ) Communication

WAVE communication is communication between OBEs (On-Board Equipment: in-vehicle communication terminal) and RSE (Road-Side Equipment: Roadside Base Station) or communication between OBEs.

IEEE 1609.4, the WAVE standard, defines multichannel operation. Specifically, an OBE having one RF (Radio Frequency) PHY is defined to alternately connect two different channels according to a predetermined (predetermined time to each other) time period.

The two channels are called Control CHannel (CCH) and Service CHannel (SCH), respectively. 1 is a diagram illustrating multi-channels operated by a WAVE.

In the CCH interval, WSA messages (WAVE Service Adevertisement Message) and WSM (WAVE Short Message) used in WAVE are transmitted and received, but IP frames (Internet Protocol Frame) cannot be transmitted and received. The WSA message is a broadcast message that contains information of services provided to the RSE and is advertised. The WSM is a dedicated data frame defined in the WAVE standard.

In the SCH interval, not only these messages but also IP frames can be transmitted and received. Therefore, in order to transmit and receive IP frames between the OBE and the RSE, the SCH interval should be used instead of the CCH interval.

If the current channel interval is a CCH interval when an IP frame transmitted to an OBE by a specific device in the wired network reaches the RSE, the RSE buffers the IP frame in the OBE before transmitting the IP frame until the next SCH interval begins. do.

In the WAVE system, all RSEs use the same channel for the CCH, but for the SCH, different frequencies are used to avoid frequency interference between adjacent RSEs. If the OBE wants to access an RSE that is different from the currently connected RSE, it should be changed to the SCH frequency used by that other RSE.

In general, the RSE transmits a WSA including information on a service provided by the RSE in the CCH interval, and the OBE receiving the information in the CCH interval determines whether to access the corresponding RSE. Here, connecting means transmitting and receiving an IP frame while using the same SCH as the RSE.

2. WAVE  Initial Network Entry Procedure

In order for an OBE mounted on a vehicle to enter a WAVE network, an IPv4 address must be obtained.

Since the number of IPv4 addresses is limited, IP addresses are dynamically allocated to IP devices according to the Dynamic Host Configuration Protocol (DHCP) without assigning one IP address to every IP device.

Hereinafter, a process of initially entering the WAVE communication network by the OBE will be described in detail with reference to FIG. 2. FIG. 2 is a diagram provided to explain a process in which an OBE initially enters a WAVE communication network to obtain an IP address.

As shown in FIG. 2, first, in the CCH interval, the RSE 120 transmits a Vendor-Specific Action (VSA) message (S210). VSA messages include WSA (specified in IEEE 1609.3 standard).

WSA includes 1) SI (Service Info.) Which contains information on various services provided by the infrastructure network, 2) CHI (CHannel Info .: channel information), etc., and is specified in the IEEE 1609.3 standard. have.

The SI includes DHCP server information and GW (gateway) information. DHCP server information contains the IP address and MAC address of the DHCP server. The GW information is information related to the GW, such as the GW's IP address and MAC address.

Since the GW information is transmitted to the OBE 110 in step S210, the OBE 110 may omit an address resolution protocol (ARP) message exchange procedure that should be additionally performed in order to obtain the MAC address of the GW 130. have. For reference, since the ARP Request message is a broadcast message, it may cause congestion in the network.

Thereafter, in the SCH interval, the OBE 110 unicasts a DHCP Discovery message to the GW 130 through the RSE 120 (S220 & S230). OBE 110 can determine the IP address and MAC address of the DHCP server, as well as the IP address and MAC address of the GW 130 from the VSA message received in step S210, the DHCP discovery message transmission is not broadcast in step S220 It is possible by unicast. This can prevent the occurrence of network congestion due to the broadcast of the DHCP Discovery message.

Meanwhile, in response to the step S230, the GW 130 transmits a DHCP offer message to the RSE 120 in the SCH interval (S240). In the DHCP offer message, information on IP addresses assignable to the OBE 110 is included.

The RSE 120 includes the DHCP offer message for the OBE 110 received in step S240 in the VSA message and broadcasts it in the CCH interval (S250).

Thereafter, the OBE 110 unicasts the DHCP Request message to the GW 130 through the RSE 120 in the SCH interval (S260 & S270). In the DHCP request message, information on an IP address to be assigned by the OBE 110 is stored.

In response to the step S270, the GW 130 transmits a DHCP ACK message to the RSE 120 in the SCH interval (S280). In the DHCP ACK message, information on an IP address to be allocated to the OBE 110 (that is, an IP address requested by the OBE 110 in the DHCP Request message) is stored.

The RSE 120 includes a DHCP ACK message for the OBE 110 received in step S280 in the VSA message and broadcasts it in the CCH interval (S290). Accordingly, the OBE 110 is assigned an IP address.

Meanwhile, the VSA message broadcast in steps S210, S250, and S290 includes WSA, GW information, DHCP server information, "DHCP offer message for OBE 110", and "DHCP Ack message for OBE 110". "DHCP offer messages for other OBEs" and "DHCP Ack messages for other OBEs" may be further included.

As such, by combining and transmitting a plurality of DHCP-related messages in one VSA message, it is possible to reduce network resource consumption in a wireless communication interval.

3. OBE Handover  step

Since OBE moves continuously while communicating with the RSE, the OBE eventually goes out of the communication range of the current RSE and needs to connect to another RSE to perform communication. A method of minimizing the degradation of communication quality during the handover procedure as described above will be described below.

The handover in this embodiment is a handover for the case of moving in a single subnet. That is, it is a case of moving between RSEs belonging to one GW. Therefore, the handover procedure in the IP layer that needs to be considered when moving to another subnet as the OBE moves is not considered. That is, assume a handover procedure in the MAC layer which is two layers.

The key to the MAC layer handover procedure is that when the OBE moves and changes the access RSE, the ODB's MAC address updates the FDB (Filtering Data Base) table of the Layer 2 switches that exist between the RSE and the GW. It changes the path of the data flow to.

Performing such a path change as soon as possible or at an appropriate point in time to minimize the discarding of data frames transmitted to the OBE over the existing path determines the performance of the handover.

In this embodiment, the path is changed at an appropriate time point in consideration of the characteristics of the WAVE communication network, thereby minimizing the number of data frames transmitted and discarded to the existing path.

3 is a diagram provided to explain a handover procedure of an OBE.

As shown in FIG. 3, when performing communication with a pRSE (previous RSE) 121 (S305), when receiving a WSA message from an nRSE (new RSE) 122 (S310), the OBE 110 receives a received signal strength. In consideration of the priority, it is determined whether to perform the handover (S315).

If the handover is determined in step S315, the OBE 110 transmits a handover (HO) request message to the Handover Service Entity (HSE) of the nRSE 122 in the SCH interval (S320).

The HSE is an application that operates in UDP (User Datagram Protocol), and is mounted on the RSEs 121 and 122 to provide a function related to handover. The OBE 110 may obtain an IP address and a UDP port number of the HSE in the nRSE 122 based on the HSE information in the WSA message received from the nRSE 122, so that the HO request message may be transmitted to the corresponding HSE. .

The RSE that communicates with the OBE 110 is still pRSE 121. Accordingly, the pRSE 121 relays transmission and reception of data frames between the GW 130 and the OBE 110 (S325 & S330).

Meanwhile, the nRSE 122 receiving the HO request message in step S320 delivers a HO notify message to the pRSE 121 at the end of the SCH interval in which the HO request message is received. Notify that you are doing (S335).

After receiving the HO notify message in step S335, the pRSE 121 discards the packet without attempting transmission after receiving a frame destined for the OBE 110 (S340). In addition, all the frames received from the OBE 110 during the previous SCH interval and buffered but not yet transmitted to the wired network through the GW 130 are transmitted to the GW 130 (S345).

Thereafter, the pRSE 121 transmits a HO notify ACK message to the nRSE 122 to inform that the communication with the OBE 110 is completed (S350).

In step S350, the nRSE 122 that receives the HO notify ACK message from the pRSE 121 unicasts a Proxy Gratuitous ARP message to the pRSE 121 and the GW 130 to 'route between the nRSE 122 and the GW 130. Update the FDB table of switches on the switch and the FDB table of switches on the path between the nRSE 122 and the pRSE 121 (S355 & S360).

In operation S355 and S360, data frames are transmitted to the OBE 110 through the nRSE 122 instead of the pRSE 121 (S365, S370 & S375).

Gratuitous ARP message is a message that broadcasts by including its MAC address and IP address to determine whether a specific device has a device with the same IP address as itself. When this message is sent in the network, the messages in the network update the FDB table for the device's MAC address.

In order to update the MAC address of the OBE in the FDB of the switches, the OBE needs to directly generate and broadcast a Gratuitous ARP message. As 110) created a message, a Gratuitous ARP message is generated and sent.

In addition, by unicasting to the pRSE 121 and the GW 130 rather than the broadcast, congestion in the network due to the propagation of the broadcast frame can be prevented. Such Gratuitous ARP message is named Proxy Gratuitous ARP message in this embodiment.

In this embodiment, the nRSE 122 does not change the path of the data flow immediately after receiving the HO request message from the OBE 110, but starts the procedure for changing the path at the end of the SCH where the HO request message is received. After the move, the number of data frames transferred to the existing path is minimized.

In addition, the pRSE 121 does not transmit an ACK immediately after receiving a HO notify from the nRSE 122, but transmits an ACK after transmitting all the frames that are received from the OBE 110 and should be transmitted upwards. The path changed by Proxy Gratuitous ARP transmitted by 122) is prevented from being changed back to the existing path.

Hereinafter, the difference between the handover delay and the performance according to the HO notify message transmission time of the nRSE 122 will be described with reference to FIG. 4.

In FIG. 4, "1" is the SCH immediately following the first SCH interval (that is, the CCH interval in which the handover is determined) from the CCH interval in which the OBE 110 determines the handover to the nRSE 122 (S405 through S415). Section) is connected to the nRSE 122, the nRSE 122 transmits a Proxy Gratuitous ARP message to the GW 130 immediately after receiving the HO request from the OBE 110 (S415) (S420) FDB of the switches on the path This is the case.

In the case of "1)", frames discarded in the network are i) frames not transmitted in the previous SCH and are buffered in the pRSE 121, ii) paths are determined by the Proxy Gratuitous ARP message from the time when handover is determined. It is a frame that is transferred to and buffered in the pRSE 121 for the interval until changed.

In addition, the time when the flow of data frames of the OBE 110 is interrupted is as follows.

Flow break time = first CCH interval + Δ

Δ: time for HO request message to be delivered to pRSE 121 + time for Proxy Gratuitous ARP message to be sent to GW 130

Meanwhile, in FIG. 4, "2" is connected to the nRSE 122 in the second SCH section instead of the first from the CCH section in which the OBE 110 determines the handover to the nRSE 122 (S405 through S415). After the first SCH interval ends, the nRSE 122 transmits a Proxy Gratuitous ARP message to the GW 130 immediately after receiving a HO request from the pRSE 121 (S425) to update the FDB of the switches on the path. One case.

If "2)", frames discarded in the network are i) frames not transmitted in the first SCH and buffered in the pRSE 121, ii) HO notify message exchange and Proxy Gratuitous ARP messages from the second CCH. It is a frame that is transferred to and buffered by the pRSE 121 during the interval between until the path is changed.

In addition, the time when the flow of data communication frames of the OBE 110 is interrupted is "second CCH one interval".

Comparing the cases of "1)" and "2)" with respect to each item is as follows, which is also shown in FIG.

a) communication frame flow interruption time

For "1)": first CCH interval + HO request transmission time + Proxy Gratuitous ARP delivery time

For "2)": first CCH interval

b) frame loss

For "1)": first CCH interval + HO request transmission time + Proxy Gratuitous ARP delivery time

For "2)": HO notify transmission time + HO notify ACK transmission time + Proxy Gratuitous ARP delivery time

On the other hand, since HO notify exchange and Proxy Gratuitous ARP message delivery will be completed within the first CCH interval, it is better for OBE 110 to connect on the next SCH than to connect to RSE immediately after handover decision and It can be seen that the frame loss performance.

4. RSE of WSA  Send message

The RSE broadcasts a WSA message on the CCH interval. Meanwhile, since the channels used by the RSEs in the CCH interval are the same, in order to prevent collision of the WSA message broadcast in the CCH interval, adjacent RSEs are required to broadcast the WSA message through different time slots.

To this end, as shown in FIG. 5, the CCH interval is divided into a "WSA interval" and a "WSMP interval".

The WSA section is located at the beginning of the CCH section and is a section in which adjacent RSEs 121-1 and 121-2 can transmit the WSA message. The WSA interval consists of a number of time slots in which adjacent RSEs 121-1 and 121-2 can broadcast WSA messages, and adjacent RSEs 121-1 and 121-2 are assigned to themselves. Broadcast a WSA message in a time slot.

As shown in FIG. 5, the RSE-1 121-1 is allocated time slot # 1 to broadcast a WSA message in time slot # 1, and the RSE-2 121-2 transmits time slot # 2. We can see that we are broadcasting WSA messages in time slot # 2.

The WSMP section is a section that can be used to transmit and receive data frames between the RSEs 120-1 and 120-2 and the OBE 110.

5. WSA  message

6 is a diagram illustrating the structure of a WSA message broadcasted by an RSE. As shown in FIG. 6, the WSA message includes a header, a service information (SI) and a channel information (CHI).

Service Info (SI) and CHannel Info (CHI) follow the specifications in the IEEE 1609.3 standard, and Service Info (SI) includes various Service Infos provided by RSE, and Channel used by RSE in CHI (CHannel Info). Information about these fields is included.

On the other hand, the SI (Service info) includes 1) DHCP server information and 2) GW information, or 3) HSE information (HSE information). The DHCP server information includes the IP address and MAC address of the DHCP server, the GW information includes the IP address and MAC address of the GW, and the HSE information includes the IP address and MAC address of the HSE.

1) Each field constituting DHCP server information is as follows.

 -WAVE Element ID = 1: Service Info

 PSID = TBD: Identifier indicating DHCP service

 Service Priority: assigns the highest priority

 Channel Index: SCH channel information index

 DHCP server IP

   i) WAVE Element ID = TBD: Element ID indicating IPv4 address

   ii) Length = 4: length of IPv4 address

   iii) DHCP server IP: IP address of DHCP server

 DHCP server MAC

   i) WAVE Element ID = 11: MAC address

   ii) Length = 6: length of MAC address

iii) DHCP server MAC address: MAC address of DHCP server

2) Each field constituting GW information is as follows.

 -WAVE Element ID = TBD: GW information in IPv4 network

 GW IP: GW's IP address

GW MAC: GW's MAC address

3) Each field constituting HSE information is as follows.

 -WAVE Element ID = 1: Service Info

 PSID = TBD: Identifier indicating HSE service

 Service Priority: assigns the highest priority

 Channel Index: SCH channel information index

 HSE IP

  i) WAVE Element ID = TBD: Element ID indicating IPv4 address

  ii) Length = 4: length of IPv4 address

  iii) HSE IP: IP address of HSE

 HSE MAC

  i) WAVE Element ID = 11: MAC address

  ii) Length = 6: length of MAC address

  iii) HSE MAC address: HSE MAC address

 HSE UDP port

  i) WAVE Element ID = 10: Service port

  ii) Length = 2: length of port number

  iii) HSE UDP port: UDP port number of HSE

7 is a diagram illustrating a structure of a HO request message. As shown in FIG. 7, the HO request message includes an Ethernet MAC header, an IP header, a UDP header, and a HO request, and the HO request includes an MAC address of the OBE, a MAC address of the pRSE, and an IP address of the pRSE HSE. have.

8 is a diagram illustrating the structure of a HO notify message. As shown in FIG. 8, the HO notify message includes an Ethernet MAC header, an IP header, a UDP header, and a HO notify, and the HO notify includes an MAC address of an OBE and an IP address of an nRSE HSE.

9 is a diagram illustrating the structure of a HO notify ACK message. As shown in FIG. 9, the HO notify ACK message includes an Ethernet MAC header, an IP header, a UDP header, and a HO notify ACK. The HO notify ACK includes an MAC address of an OBE and an IP address of an nRSE HSE.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

110: OBE
120: RSE
121: pRSE
122: nRSE
130: GW

Claims (15)

On-board equipment (OBE) transmitting a handover request message to the new road-side equipment (nRSE);
NRSE receiving the handover request message, forwarding a handover notification message to a pRSE (previous road-side equipment);
Discarding the frame to be delivered to the OBE by the pRSE receiving the handover notification message;
transmitting, by the pRSE, a frame received and buffered from the OBE to a GW (GateWay); And
pRSE sending a handover notification acknowledgment message to nRSE;
Handover notification message delivery step,
and a handover notification message to the pRSE at the end of the SCH (Service CHannel) section in which the nRSE receives the handover request message.
delete The method of claim 1,
The nRSE receiving the handover notification acknowledgment message transmits a message to the pRSE and the GW to update the 'table of switches in the path between nRSE and GW' and the 'table of switches in the path between nRSE and pRSE'. Step; Handover method characterized in that it further comprises.
The method of claim 3, wherein
The message transmission step for updating the tables,
and a message for updating the tables in the next channel section of the channel section in which the nRSE receives the handover request message to the pRSE and the GW.
The method of claim 1,
In the CCH interval, the RSE broadcasts a WAVE (WAVE Service Adevertisement) message including the Dynamic Host Configuration Protocol (DHCP) server information and GW information; And
The OBE receiving the WSA message, unicast the DHCP discovery message to the GW through the RSE in the SCH (Service CHannel) section with reference to the GW information included in the WSA message; Handover method further comprising .
6. The method of claim 5,
Receiving, by the GW receiving the DHCP discovery message, a DHCP proposal message including information on IP addresses that can be allocated to the OBE in the SCH period, to the RSE; And
The RSE includes the DHCP proposal message received in the WSA message to broadcast in the CCH interval; handover method further comprising.
The method according to claim 6,
Receiving, by the OBE, the DHCP proposal message, unicasting a DHCP request message including information on an IP address to be assigned by the OBE in the SCH period to the GW through the RSE;
Transmitting, by the GW, a DHCP acknowledgment message including an IP address to be allocated to the OBE to the RSE in the SCH period; And
The RSE receiving the DHCP acknowledgment message and including the DHCP ACK message in the WSA message to broadcast in the CCH interval; handover method further comprising.
8. The method according to any one of claims 5 to 7,
WSA message is a handover method characterized in that the messages for a plurality of OBEs.
The method of claim 8,
Messages for multiple OBEs
Handover method characterized in that the DHCP offer messages for the plurality of OBEs and DHCP response messages for the plurality of OBEs.
6. The method of claim 5,
The DHCP server information includes at least one of an IP address and a MAC address of the DHCP server.
The GW information includes at least one of an IP address and a MAC address of the GW.
The method of claim 1,
CCH interval includes the WSA interval,
Handover method, characterized in that adjacent RSEs broadcast WSA messages in different time slots of the WSA interval.
12. The method of claim 11,
The CCH interval includes a WSMP interval used for transmitting and receiving data frames between the RSE and the OBE.
On-board equipment (OBE) for transmitting a handover request message to a second road-side equipment (RSE);
A second RSE which forwards the handover notification message to the first RSE upon receiving the handover request message from the OBE; And
Receiving a handover notification message, discarding a frame to be delivered to the OBE, transmitting a buffered frame received from the OBE to a GW (GateWay), and including a first RSE for transmitting a handover notification confirmation message to a second RSE; ,
The second RSE is
A wireless access in Vehicular Environments (WAVE) communication system, characterized in that for transmitting the handover notification message to the first RSE at the end of the SCH (Service CHannel) section receiving the handover request message.
delete The method of claim 13,
The second RSE is
A message for updating a 'table of switches on a path between a second RSE and a GW' and a 'table of switches on a path between a second RSE and a first RSE' of the channel interval receiving the handover request message. The WAVE communication system, characterized in that for transmitting to the first RSE and GW in the next channel interval.

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