KR101704979B1 - Method and System for Random Distributed Algorithm on Immediate Access of WAVE Communication for Collecting Probe Vehicle Data - Google Patents

Abstract

The present invention provides a method and a system for a random distributed algorithm on immediate access of wave communication for collecting probe vehicle data. The method for the random distributed algorithm on immediate access of wave communication for collecting probe vehicle data comprises: a step of transmitting a packet in a random distributed method on a service channel within a period by using generation rate of the packet in wave communication.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and system for randomly distributed instant access for collecting probe vehicle information in a wave communication,

The following embodiments relate to a random distributed immediate access method and system for probe vehicle information collection in wave communication, and more particularly to a random distributed immediate access method and system for collecting probe vehicle information in wave communication. More particularly, the present invention relates to a random distributed instantaneous access method and system, To an arbitrary distributed immediate access method and system for probe vehicle information collection in wave communication that increases the reception ratio in PVD transmission.

Due to the rapid development of vehicle technology and the increase in the number of vehicles, damage to people and property has been constantly occurring due to safety problems such as traffic congestion and traffic accidents. In order to solve the seriousness of traffic problems, many researches and developments are going on around the world. Road side units (RSUs) are installed on the roads of vehicles driving on the road in order to demonstrate the effects of optimizing traffic operation, reducing traffic accidents, enhancing vehicle safety, reducing logistics costs, and protecting the environment. It is necessary to study the technology of exchanging status information of risk information and traffic information of roads and vehicles carrying a high-speed wireless communication by mounting a terminal in a vehicle.

Probe Vehicle Data (PVD) is a packet that transmits state information generated in the vicinity of a vehicle to a roadside base station (RSU) and finally transmits state information to a traffic center.

Research on vehicle communication standards is also being carried out all over the world, among which researches on WAVE communication standards called IEEE 802.11p and IEEE 1609.x standards based on IEEE 802.11 have been actively carried out. IEEE 1609.4 multi-channel shows four approaches to channel operation. The WAVE communication standard is based on an alternating access method in which a service channel (SCH) and a service channel (SCH) are continuously changed to use two channels. In the alternating access, the interval of each channel is 50 ms, and the size of the channel capacity is inefficient because two channels are used together. Therefore, continuous access, immediate access, and extended access methods are used to efficiently use the channel capacity.

The vehicle periodically transmits the probe vehicle information PVD to the RSU through the communication terminal. The RSU and the traffic center receiving the probe vehicle information (PVD) analyze the current traffic situation and the state information through the received data to solve the traffic problem. Due to the characteristic of periodic communication transmitted from the vehicle terminal, when the vehicle density is high in the probable vehicle information (PVD) transferable area, the communication congestion becomes high. Therefore, the more the number of vehicles, the lower the probe vehicle information (PVD) reception rate and packet loss due to the communication congestion.

As described above, in the WAVE communication standard application technique, when a periodic packet is transmitted, generally, a control channel or a service channel is attempted to be transmitted to a channel at the beginning of each cycle. In such a general channel access method, as the number of vehicles (nodes) increases, more competition is expected, and congestion of the channel becomes higher and the reception rate of packets to be transmitted decreases.

Korean Patent Laid-Open No. 10-2015-0053687 relates to a method of transmitting a packet through a service channel during a whole sync interval while a message or packet transmitted / received through a control channel does not exist, .

Embodiments describe a random distributed immediate access method and system for probe vehicle information collection in wave communication and more specifically to a random distributed immediate access algorithm that combines a random distributed method with an immediate access multi- To increase the reception ratio in periodic vehicle driving information (PVD) transmission.

Embodiments minimize packet contention through a random distributed method on a service channel in a cycle using a packet generation cycle based on a WAVE communication standard, And to provide a random distributed immediate access method and system for collecting probe vehicle information in a wave communication that increases the reception ratio in periodic vehicle driving information (PVD) transmission using a channel operating method.

A random access immediate access method for probe vehicle information collection in a wave communication according to an embodiment, the method comprising: determining whether a vehicle is randomly distributed in a service channel in a cycle using a generation rate of a packet in WAVE communication Random Distributed (Random) method.

The method may further include synchronizing the channel to use the same channel between the vehicle and the RSU that periodically receives the packet from the vehicle in the multi-channel operating method.

In the multi-channel operating method, the step of synchronizing the channels to use the same channel between the vehicle and the roadside base stations (RSU) periodically receiving the packets from the vehicle may include: Broadcasting the WSA to the vehicles, the vehicles receiving the WSA more than a predetermined number of times and entering the WAVE communication system; The vehicles receiving the WSA and recognizing a channel operating method within a communication radius entering according to a field value input to the WSA; The vehicles determining a channel operating method to synchronize the channel and transmit probe vehicle information (PVD) to the roadside base station (RSU); And the vehicles may receive an ACK message indicating that the probe vehicle information (PVD) has been delivered from the roadside base station (RSU).

The step of transmitting a packet in a randomly distributed manner to a Service Channel within the period may include increasing a capacity of a Service Channel by an Immediate Access Channel operating method within the period have.

Wherein the step of transmitting a packet in a randomly distributed manner to a Service Channel in the period comprises: determining a number of Service Channels in the period, determining a predetermined number of Service Channels The packet can be transmitted to one of the service channels.

The step of transmitting a packet to a service channel in the period by a random distributed method includes: distributing each of the vehicles, increasing an interval of the service channel within the period, The packet transmission success rate can be improved.

The step of transmitting a packet to a service channel in the period by a random distributed method comprises the steps of: determining a period T according to a packet generation period; Dividing the period T by a preset sync interval (SyncInterval) to obtain the number of service channels; And calculating a number of average vehicles capable of transmission attempts at a time by dividing the number of service channels by the number of vehicles to which the service channels are to be transmitted, Channel) for the transmission in random within the period.

In an arbitrary distributed immediate access method for collecting probe vehicle information in a wave communication according to another embodiment, a method is disclosed in which a vehicle uses a generation rate of a packet in WAVE communication to perform an immediate access channel operation method And increasing the capacity of the service channel.

In an arbitrary distributed immediate access system for collecting probe vehicle information in a wave communication according to another embodiment, a vehicle may be arbitrarily dispersed in a service channel within a cycle using a generation rate of a packet in WAVE communication. (Random Distributed) method.

And a channel synchronization unit for synchronizing a channel to use the same channel between the vehicle and the roadside base stations (RSUs) periodically receiving the packet from the vehicle in the multi-channel operation method.

Wherein the channel synchronization unit broadcasts a WSA to vehicles entering a communication radius at the RSU, the WSA receiving unit receives the WSA over a predetermined number of times or more and enters the WAVE communication system; Wherein the vehicles recognize a channel operating method within a communication radius entering the WSA according to a field value received in the WSA; The vehicles include a PVD transfer unit for determining a channel operating method to synchronize a channel and transmit probe vehicle information (PVD) to the RSU; And the vehicles may include an ACK message receiving unit for receiving an ACK message indicating that the probe vehicle information PVD has been transmitted from the RSU.

The packet transmission unit may increase the capacity of a service channel by an immediate access channel operating method within the period.

The packet transmission unit may determine a number of the service channels within the period and transmit the packet to one of service channels of the predetermined number of service channels.

The packet transmission unit may disperse each of the vehicles, increase the interval of the service channel within the period, and increase the capacity of the channel, thereby improving the packet transmission success rate.

The packet transmission unit divides a period T determined according to a packet generation period by a predetermined sync interval to acquire the number of service channels and transmits the number of service channels The average number of vehicles that can be transmitted at one time is divided by the number of vehicles, and the average vehicles capable of transmission attempts at the same time are accessed for transmission in a random manner within the period using one service channel. have.

In accordance with embodiments, a random distributed immediate access method and system for probe vehicle information collection in a wave communication is described, more specifically, a random distributed instantaneous method combining a random distributed method and an immediate access multi- It is possible to provide a technique for increasing the reception ratio in periodic vehicle driving information (PVD) transmission using an access algorithm.

According to the embodiments, packet competition is minimized through a random distributed method on a service channel in a cycle using a packet generation cycle based on WAVE communication standard, Access can be provided to an arbitrary distributed immediate access method and system for collecting probe vehicle information in a wave communication that increases the reception ratio in periodic vehicle driving information (PVD) transmission using a channel operating method.

1 is a diagram for explaining a WAVE MAC structure according to an embodiment.
2 is a diagram for explaining a sync interval of a channel according to an embodiment.
3 is a diagram for explaining a channel access method in a WAVE communication standard according to an embodiment.
4 is a view for explaining a unicast procedure of PVD according to an embodiment.
5 is a diagram for explaining the format of a WSA according to an embodiment.
6 is a flowchart illustrating a random access immediate access method for probe vehicle information collection in a wave communication according to an embodiment.
7 is a block diagram illustrating a random access immediate access system for probe vehicle information collection in a wave communication in accordance with one embodiment.
FIG. 8 is a flowchart illustrating a random distributed immediate approach for probe vehicle information collection in a wave communication according to another embodiment.
9 is a diagram for explaining a random access approach according to an embodiment.
10 is a diagram for explaining an arbitrary distributed immediate approach according to an embodiment.
11 is a diagram illustrating throughputs according to a random access approach and a general approach according to an embodiment.
12 is a diagram for explaining the service success rate of the random distributed immediate access method according to an embodiment.
13 is a diagram for explaining a conventional general approach.

Hereinafter, embodiments will be described with reference to the accompanying drawings. However, the embodiments described may be modified in various other forms, and the scope of the present invention is not limited by the embodiments described below. In addition, various embodiments are provided to more fully describe the present invention to those skilled in the art. The shape and size of elements in the drawings may be exaggerated for clarity.

The following embodiments minimize packet contention through an Random Distributed (Random Access) method on a service channel (SCH) using a packet generation cycle based on the WAVE communication standard, Immediate Access Channel operating methods are available. In other words, it provides a method to increase the reception ratio in periodic vehicle navigation data (PVD) transmission by using a random distributed instant access algorithm combining a random distributed method and an immediate access multi-channel .

Probe Vehicle Data (PVD) is a technology for transmitting various vehicle information in a packet when each vehicle enters an RSU zone, and is a communication terminal (vehicle terminal) OBU Refers to a service message transmitted and received via wireless communication between RSUs.

The probe vehicle information PVD automatically exchanges information when the vehicle terminal enters the communication area of the RSU while the vehicle terminal is in the ON state. At this time, only necessary information is periodically communicated with the base station installed on the roadside according to the service characteristics And provide driving information collected inside the vehicle to the RSU. The probe vehicle information (PVD) collected through information exchange between the vehicle terminal and the roadside base station (RSU) includes traffic information, driving record, vehicle diagnostic record, exhaust emission, rate and deceleration information, and fuel consumption.

When the RSU collects the probe vehicle information (PVD), the collected information is transmitted to the traffic information center, and the vehicle information can be provided to the related agencies that need it.

On the other hand, WAVE communication is one of the next generation ITS wireless communications that provides vehicle-to-vehicle (V2V) and vehicle-to-roadside (V2I) communications. The WAVE communication standard is a combination of 802.11p and IEEE 1609.x based on IEEE 802.11a, and it can basically support high-speed packet service and handover of 10MHz and 20MHz bandwidth. In addition, Ad-hoc networks are supported between vehicles, so long-distance packets can be transmitted and received through inter-vehicle communication even when there is no RSU.

The channel used in the WAVE communication is basically allocated to seven channels, and it can be composed of one control channel (CCH) and six service channels (SCH). Two of the service channels can be used as a security support channel.

For example, in IEEE 1609.3, a network layer and a transport layer for secure data exchange between a service provider (provider) and a user (user) are defined, and a data plan (data plane) and a system configuration And a management plan that performs a maintenance function.

When the system equipped with the WAVE protocol is activated for the first time, the WAVE communication system receives a WAVE Service Advertisement (WSA) informing of a service to be used as a service channel (SCH), or a service channel (SCH) Lt; RTI ID = 0.0 > (CCH) < / RTI >

When monitoring of the control channel (CCH) is requested, transmission and reception in progress on the service channel (SCH) are stopped, and transmission and reception on the service channel (SCH) are resumed once the control channel (CCH) monitoring ends. That is, the control channel (CCH) interval (Iinterval) and the service channel (SCH) interval are alternated and occur for 50 ms each, which is referred to as an alternating access in a multi-channel operation. For accurate time synchronization of each channel interval, it can be operated with reference to an external timer such as Coordinated Universal Time (UTC) received from GPS.

1 is a diagram for explaining a WAVE MAC structure according to an embodiment.

Referring to FIG. 1, the MAC structure according to IEEE 1609.4 specifies channel routing, user priority, and channel coordination. It is a structure for a control channel (CCH) and a service channel (SCH), respectively, of two MAC entities. The packets are prioritized according to the access category (AC), and different contention and transmission parameters can be provided according to the respective priorities.

In Channel Routing, when an MSDU is forwarded from the LLC layer to the MAC layer, the MAC can identify the IEEE 802.2 EtherType field in the header to determine if the MSDU is a WSM / IP packet. In the case of WAVE Service Message (WSM), the channel number in the WSM header can route the packet to the appropriate queue corresponding to that channel. In case of IP packet, it can be routed to the queue corresponding to the service channel (SCH).

User Priority can support Safety and Non-Safety applications with 8 priority levels as defined in IEEE 1609.3 and 802.11. User Priority (UP) is used to compete for access to different channels using Enhanced Distributed Channel Access (EDCA).

Channel Coordination may be dependent on the synchronization procedure and may support transmission and reception between devices that can not simultaneously receive the control channel (CCH) and the service channel (SCH). Before each interval, a guard interval (Gaurd Interval) can be used for channel time variation and temporal inaccuracy between different devices. At this time, transmission is not allowed during the guard interval.

2 is a diagram for explaining a sync interval of a channel according to an embodiment. And FIG. 3 is a diagram for explaining a channel access method in the WAVE communication standard according to an embodiment.

Referring to FIG. 2 and FIG. 3, the WAVE communication standard can basically provide four channel access methods. That is, there are four methods of continuous access, alternating access, immediate access, and extended access. Here, the access method can be expressed as a transmission method of transmitting a packet.

Devices using WAVE communication have a mechanism to access one or more channels. Alternating access channel operating methods can be based on synchronized intervals at standard time used in WAVE communications. One sink interval may be composed of a control channel (CCH) interval and a service channel (SCH) interval. Each WAVE communication device using an alternating access may synchronize the channel interval and the sink interval by standard time such as Coordinated Universal Time (UTC). It can be assumed that the guard interval starts at each control channel (CCH) interval and the service channel (SCH) interval, and that in the guard interval, the WAVE communication device switching channel can not receive packets. IEEE 1609.4 specifies a control channel (CCH), a service channel (SCH) interval of 50 ms, and a guard interval of 4 ms.

Immediate Access Channel operation method allows the user's WAVE communication device to switch to the service channel (SCH) interval immediately after the control channel (CCH) interval has not ended, and Extended Access allows the user User can extend the duration of the SCHI when operating in an alternating access method.

IEEE 802.11p defines WBSS different from BSS of existing IEEE 802.11 network to efficiently cope with changes of network environment due to vehicle mobility and fast topology change. The WBSS does not use the authentication and association process used in the existing IEEE 802.11 network.

In communication for vehicle safety, the above-described subscription process has a disadvantage of delaying time. An object with a very high mobility such as a vehicle will have a shorter communication time. Therefore, the wireless terminal operating in the WAVE communication system can transmit and receive data if the channel is matched without the WBSS subscription process.

The WBSS can be initialized by the request of the application layer. In IEEE 802.11p, one control channel (CCH) and up to six service channels (SCH) are used, and time synchronization between channels can be performed through an external timer such as Universal Time Coordinated (UTC).

The service provider notifies the WBSS service provision through the control channel (CCH), and the user can participate in the WBSS by monitoring the control channel (CCH) periodically.

IEEE 802.11p can use the physical layer of the OFDM method like IEEE 802.11a. However, instead of the 20 MHz bandwidth used by IEEE 802.11a, 10 MHz bandwidth can be used. Since the WAVE communication system is an inter-vehicle communication that moves at high speed in outdoor, frequency selective fading frequently occurs. OFDM can reduce this problem by dividing the frequency band into several subcarriers and dividing the frequency selective fading channel into multiple flat fading channels. In addition, interference between subcarriers due to Doppler shift can be mitigated by using a 10 MHz bandwidth channel in a bandwidth of 20 MHz.

As the demand for services increases in WAVE communication, it is necessary to operate channel occupation time efficiently. Assuming that vehicles entering the communication radius of a service provider (RSU) follow the alternating access of WAVE communication multi-channel operation, the RSU of the roadside is connected to the control channel (CCH) WSA and various management frames, and the service channel (SCH) mainly transmits and receives service packets. When collecting periodic services such as probe vehicle information (PVD) from a roadside base station (RSU), packet congestion may occur due to increased congestion during the occupancy time of the channel in areas with high vehicle density. If a packet collision occurs frequently, the service success rate to be transmitted within a unit time is lowered, and the RSU can not collect probe vehicle information smoothly. Thus, in one embodiment, a random distributed access channel operation algorithm may be provided to increase the service success rate of probe vehicle information (PVD).

4 is a view for explaining a unicast procedure of PVD according to an embodiment.

Referring to FIG. 4, when the WSA for channel synchronization is transmitted to the vehicles entering the communication radius at the roadside base station (RSU) through the control channel (CCH), the vehicles that have received the WSA are synchronized with the channel, To the RSU. Thereafter, the RSU may complete the unicast communication procedure by transmitting the ACK frame by confirming that it has received the probe vehicle information (PVD) (WSM). It is assumed here that it is possible to accurately grasp the vehicle density within the range of the roadside base station (RSU).

In order to achieve smooth transmission and reception on multi-channels such as alternating access and immediate access, precise synchronization between the service provider (RSU) and the user's vehicle communication terminal (OBU) need. A roadside base station (RSU) can broadcast a WSA to vehicles entering a communication radius.

Vehicles can enter the WAVE communication system only after receiving the WSA more than a certain number of times. By receiving the WSA, the vehicles are aware of the channel operating conditions within the currently entering communication radius according to the field value input to the WSA. The vehicles determine the channel operating method and transmit the probe vehicle information PVD to the RSU, receive the ACK message that the probe vehicle information PVD is correctly transmitted from the RSU, (PVD) collection service is terminated.

In multichannel operation, channel synchronization is a commitment of each other to use the same channel between the RSU and the vehicle. In order to synchronize the channel, the RSU can broadcast the WSA to inform the vehicles that have entered the communication radius about the channel operation method.

5 is a diagram for explaining the format of a WSA according to an embodiment.

Referring to FIG. 5, the WSA message includes information on a service and a channel. Each information on channel information exists in a channel information field, and a channel access method in an extension field There is a field to let you know. Currently, only the values of 0 and 1 are defined in the channel access field in the IEEE 1609.3 standard, and the other values remain as pending. Here, if it follows the Immediate Access channel operating method according to one embodiment, it will be used as one of the other reserved values.

The vehicles entering the communication area of the RSU know that the WSA has entered the communication area of the RSU and know how to operate the channel. Thus, the vehicles can determine how to adjust the service channel (SCH) interval according to the channel operating method.

6 is a flowchart illustrating a random access immediate access method for probe vehicle information collection in a wave communication according to an embodiment.

Referring to FIG. 6, an arbitrary distributed immediate access method for collecting probe vehicle information in a wave communication according to an exemplary embodiment of the present invention is a method in which a vehicle transmits a service channel in a cycle using a generation rate of a packet in WAVE communication, And a step 620 of transmitting a packet by a random distributed method to the mobile station. Here, the vehicle may be configured to include a vehicle terminal (vehicle communication terminal) or a vehicle terminal (vehicle communication terminal).

The method may further include a step 610 of synchronizing a channel to use the same channel between RSUs receiving packets periodically from the vehicle and the vehicle in the multi-channel operation method prior to packet transmission.

Here, the step of transmitting a packet in a randomly distributed manner to a service channel in a cycle may increase a capacity of a service channel by an immediate access channel operating method have.

According to embodiments, in the periodic packet transmission, a transmission is attempted in a randomly distributed manner in a service channel (SCH) or a control channel (CCH) in a period, and an immediate access ) By increasing the channel capacity using the channel operating method, it is possible to reduce the competition of the vehicles (nodes), lower the communication congestion, and increase the packet reception ratio.

Each step of the random distributed immediate approach for probe vehicle information collection in the wave communication according to one embodiment will be described in more detail below.

A random distributed immediate approach for probe vehicle information collection in a wave communication according to one embodiment may be more specifically described using a random distributed immediate access system for probe vehicle information collection in a wave communication according to an embodiment.

7 is a block diagram illustrating a random access immediate access system for probe vehicle information collection in a wave communication in accordance with one embodiment.

Referring to FIG. 7, a random access immediate access system 700 for collecting probe vehicle information in a wave communication according to an exemplary embodiment may include a channel synchronization unit 710 and a packet transmission unit 720. The channel synchronization unit 710 may include a WSA receiving unit 711, a channel recognizing unit 712, a PVD transmitting unit 713, and an ACK message receiving unit 714 according to an embodiment of the present invention. Here, the random distributed immediate access system 700 for probe vehicle information collection in a wave communication according to an embodiment may be at least part of a vehicle terminal (vehicle communication terminal) or vehicle terminal, and may be simply referred to as a vehicle.

In step 610, the channel synchronization unit 710 may synchronize the channels to use the same channel between the RSUs that periodically receive packets from the vehicle and the vehicle in the multi-channel operating method prior to packet transmission.

The WSA receiving unit 711 of the channel synchronizing unit 710 broadcasts the WSA to the vehicles entering the communication radius in the RSU, so that the vehicles can receive the WSA more than a predetermined number of times and enter the WAVE communication system .

In the channel recognition unit 712 of the channel synchronization unit 710, the vehicles can receive the WSA and recognize the channel operation method within the communication radius according to the field value input to the WSA.

In the PVD transmission unit 713 of the channel synchronization unit 710, the vehicles can determine the channel operation method, synchronize the channel, and transmit the probe vehicle information PVD to the RSU.

In the ACK message receiving unit 714 of the channel synchronization unit 710, the vehicles can receive an ACK message indicating that the probe vehicle information PVD has been transmitted from the RSU.

In step 620, the packet transmitter 720 may transmit a packet to a service channel within a period using a random distribution method by using a generation rate of a packet in WAVE communication.

In addition, the packet transmission unit 720 can increase the capacity of a service channel by an immediate access channel operating method. In other words, the reception ratio can be increased in the periodic vehicle movement information (PVD) transmission by using a random distributed instant access algorithm combining a random distributed method and an immediate access multi-channel.

The packet transmission unit 720 may determine the number of service channels within the period and transmit the packet to one of the service channels of a predetermined number of service channels.

In addition, the packet transmission unit 720 may disperse the respective vehicles, increase the interval of the service channel within the period, and increase the capacity of the channel, thereby improving the packet transmission success rate.

The packet transmitter 720 divides the period T determined according to the packet generation period by a predetermined sync interval to acquire the number of service channels and transmits the number of service channels The average number of vehicles that can be transmitted at one time is divided by the number of vehicles, and average vehicles capable of transmission attempts at a time can be accessed for transmission in a random period within one service channel. A method for calculating the average number of vehicles that can be transmitted at one time will be described in more detail using the following equation.

FIG. 8 is a flowchart illustrating a random distributed immediate approach for probe vehicle information collection in a wave communication according to another embodiment. The random distributed immediate access method for collecting probe vehicle information in the wave communication according to this other embodiment is described in detail using a random distributed instant access system for probe vehicle information collection in the wave communication according to the embodiment described in FIG. can do. The arbitrary distributed immediate access method for probe vehicle information collection in the wave communication according to another embodiment includes the same configuration as the random distributed instant access method for probe vehicle information collection in the wave communication according to the embodiment described in FIG. So that redundant description will be omitted and briefly explained.

Referring to FIG. 8, in a random access immediate access method for collecting probe vehicle information in a wave communication according to another embodiment, a packet transmission unit 720 transmits a packet to the packet transmission unit 720 using a packet generation period in a WAVE communication. And increasing (820) the capacity of the service channel in a method of operating an immediate access channel.

The channel synchronization unit 710 further includes a step 810 of synchronizing the channels so as to use the same channel between the RSUs that are periodically transmitted from the vehicle and the vehicle in the multi-channel operating method before the packet transmission can do.

Here, the step of increasing the capacity of a service channel by a method of instant access (Immediate Access) channel operation using a generation rate of a packet in a WAVE communication of a vehicle includes a service channel service (Random Distributed) method.

9 is a diagram for explaining a random access approach according to an embodiment.

As shown in FIG. 9, the random access method according to an exemplary embodiment allocates the number of service channels (SCHs) within a given transmission period, and allocates a service channel (SCH) of a predetermined number of service channels It is a method of accessing message transmission.

10 is a diagram for explaining an arbitrary distributed immediate approach according to an embodiment.

As shown in FIG. 10, the random distributed immediate access method according to an exemplary embodiment adds a multi-channel of Immediate Access method to a random distributed access method, (SCH) is increased and the capacity of the channel is increased, so that more packets can be successfully transmitted.

Meanwhile, FIG. 13 is a diagram for explaining a conventional general approach.

Referring to Figs. 9 and 10, a random distributed access algorithm can be described by way of example. In this case, if the packet generation period is 1 Hz, the number of service channels (SCHs) is 10 within 1 Hz, and one of the 10 service channels (SCH) in the cycle can be accessed for transmission through one service channel (SCH). The period T is determined according to the message generation interval, and the following equation can be derived.

[Equation 1]

For example, when f is 1 (Hz), T becomes 1, and when f is 10 (Hz), T can be 0.1. If the value of T is determined and T is divided by the sync interval (= 100 ms), the value of the number of service channels (SCH) Nsync can be obtained as shown in the following equation.

&Quot; (2) "

Here, if the number Vnum of the vehicles to be transmitted by the Nsync value is divided, the number Av of the average vehicles which can be transmitted at one time can be obtained.

&Quot; (3) "

For example, if the number of vehicles to be transmitted is 150, the average number of vehicles that can be transmitted at one time may be 15. Therefore, 15 vehicles access to one service channel (SCH), and access timing is random among service channels (SCH) within the transmission period.

In this way, the competition of the transmission approach becomes poor as the vehicle competing in the packet transmission becomes Av due to the dispersion effect of each vehicle in the random distributed instant access method, and the transmission of the probe vehicle information (PVD) It is possible to obtain more efficient and improved transmission rate.

In the present embodiments, a network simulator is implemented in C ++ language, a DCF protocol based on IEEE 802.11 is implemented, and a system environment based on a WAVE communication standard is established. Therefore, a performance evaluation can be performed for a random distributed instant access algorithm proposed in the embodiments. There is one RSU and assumes a unicast communication method procedure for the neighboring vehicles to transmit probe vehicle information (PVD). In accordance with the IEEE 802.11p standard, the theoretical analysis of the DCF and the result of the simulation . Throughput, service success rate (SSR) are measured by changing each parameter value of the network constructed by the simulator, and the normal access transmission method and the random distributed access method (Immediate Access ) Transmission method. We also measured the success rate according to the data rate in the random distributed access method.

Follow the channel of the Immediate Access method below. Basically, in case of the channel of alternating access of the WAVE communication standard, the CCHI and the SCHI are respectively 50 ms and the SyncInterval is 100 ms. In the immediate access method, only the SCHI is changed in the state where the SyncInterval is fixed at 100 ms, and the CCHI becomes smaller as the SCHI increases. Therefore, the service success rate (Success) by a random distributed immediate access algorithm, which is a method of attempting transmission by arbitrarily approaching and distributing the order of the service channels (SCH) in the period according to the probe vehicle information (PVD) Services Ratio (SSR).

11 is a diagram illustrating throughputs according to a random access approach and a general approach according to an embodiment.

Referring to FIG. 11, a random distributed access method distributes vehicles to be transmitted on 10 service channels (SCH) within 1 Hz of the probe vehicle information (PVD) generation period, thereby reducing transmission competition. Therefore, when the same number of vehicles are simultaneously transmitted, the throughput value of the random distributed access method is higher than that of the normal access method by about 1 or more in each interval.

12 is a diagram for explaining the service success rate of the random distributed immediate access method according to an embodiment.

Referring to FIG. 12, in the case of a channel of a random distributed instant access method, it is possible to indicate that the service success rate (SSR) is measured while changing the size of the SCHI. Here, the service success rate (SSR) can be defined as follows.

&Quot; (4) "

The more successfully the probe vehicle information (PVD) is transmitted, the higher the success rate. First, when the SSR is a random distributed access even though the distributed access method is used in the same SCHI 50 ms, a normal access and a random distributed access are compared. Is higher. It can be seen that the service success rate (SSR) increases with the increase of the SCHI by adding the Immediate Access method to the random distributed access.

The SCHI extended to a maximum of 95 ms. This is because of the definition of the number of WSA transmissions in the cycle in the IEEE 1609.3 standard. In this embodiment, in order to follow the example of the 1609.3 standard Annex, 20 WSA transmissions within 1 second are attempted, and when it is evenly distributed, two WSA transmissions are attempted on one control channel (CCH). If the format size of the WSA is measured to be 98 bytes by the standard and two WSA transmissions are performed, a control channel (CCH) of about 1 ms can be the minimum interval value. Therefore, if the guard interval of 4 ms is added and the sink interval is subtracted from 100 ms, the maximum SCHI can be 95 ms.

As the number of vehicles increases, the service success rate (SSR) tends to decrease. As the size of the SCHI increases, the service success rate (SSR) increases. When the number of vehicles is 80, the SSR of the normal access and the random distributed access SCHI 95 ms differ by about 0.45 from 0.3 to 0.75. have. If the SCHI is opened to the maximum, the service success rate (SSR) will increase to more than two times. The service success rate (SSR) was more than doubled from 90 to 150 vehicles, and the service success rate (SSR) was greatly improved.

Random Distributed Immediate Access In the case of SCHI 95ms, up to 60 cars will be able to successfully transmit all probe vehicle information (PVD) on all transmission attempts. If more vehicles are involved in the transmission, the value of the service success rate (SSR) decreases. This means that even if the SCHI is increased to 95 ms, the saturation of the channel can reach the limit of successful transmission of probe vehicle information (PVD) Because.

In this embodiment, it is assumed that the transmission of probe vehicle information (PVD) occurs periodically by implementing a simulation based on the WAVE communication standard. In order to mitigate the congestion of the probe vehicle information (PVD) transmission generated as the vehicle density increases, Study. Random Distributed Immediate Access that attempts to transmit to the SCH arbitrarily within the probe vehicle information (PVD) transmission period using the WAVE communication standard multi-channel based immediate access by defining the service success rate (SSR) Access) algorithm.

The WAVE communication standard based on IEEE 802.11 has a great influence on the DCF protocol in the transmission / reception channel. Therefore, the DCF protocol is analyzed through the Markov chain model, and the theoretical analysis of the Markov chain model and the simulation of the WAVE communication system are proved to have similar values. We also observed that the DCF protocol of QualNet and the simulator was built correctly. Therefore, it is confirmed that there is almost no error of DCF protocol, which is one of the important factors in increasing and decreasing the service success rate (SSR) of the proposed simulation.

Random Distributed Immediate Access algorithm increases the service success rate (SSR) by adjusting the channel capacity. We examined the change of the service success rate (SSR) by increasing the size of the SCHI from 50ms to 95ms. In the experimental environment, the number of vehicles in the 70s to 150s was higher than the SSR of the normal access I got a service success rate (SSR) of about twice as much as the maximum.

According to the embodiments, it is possible to minimize the packet contention in the WAVE communication, thereby reducing the communication congestion and increasing the packet reception rate. As the reception rate of the packet increases, the RSU collects more information within the unit time, and can grasp the accurate and fast traffic information situation. Therefore, optimization of transportation operation, reduction of traffic accidents, enhancement of vehicle safety, reduction of logistics cost, and environmental protection can be seen.

An arbitrary distributed immediate access method and system for probe vehicle information (PVD) collection in a wave communication in accordance with such embodiments includes a WAVE communication enabled device, a wireless communication enabled device, a vehicle communication terminal (OBU), a roadside base station Road Side Unit (RSU), medium access control (MAC) layer in the communication protocol stack, and application layer.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, controller, arithmetic logic unit (ALU), digital signal processor, microcomputer, field programmable array (FPA) A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute one or more software applications that are executed on an operating system (OS) and an operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing apparatus may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be embodyed temporarily. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

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. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (15)

1. An arbitrary distributed immediate access method for probe vehicle information collection in a wave communication,
A step in which a vehicle transmits a packet to a service channel in a random distributed manner using a generation rate of a packet in WAVE communication
An arbitrary distributed immediate approach for probe vehicle information collection in a wave communication. The method according to claim 1,
Synchronizing a channel to use the same channel between the vehicle and the RSU that periodically receives the packet from the vehicle in the multi-channel operating method
Wherein the method further comprises the steps of: 3. The method of claim 2,
In the multi-channel operating method, the step of synchronizing the channels to use the same channel between the vehicle and the roadside base stations (RSU) periodically receiving the packets from the vehicle,
Broadcasting the WSA to vehicles entering the communication radius at the roadside base station (RSU), the vehicles receiving the WSA more than a predetermined number of times and entering the WAVE communication system;
The vehicles receiving the WSA and recognizing a channel operating method within a communication radius entering according to a field value input to the WSA;
The vehicles determining a channel operating method to synchronize the channel and transmit probe vehicle information (PVD) to the roadside base station (RSU); And
The vehicles receive an ACK message indicating that the probe vehicle information (PVD) has been delivered from the RSU
An arbitrary distributed immediate approach for probe vehicle information collection in a wave communication. The method according to claim 1,
The step of transmitting a packet to a service channel in the period by a random distributed method comprises:
The capacity of the service channel is increased by the immediate access channel operating method within the period
A random distributed immediate approach for probe vehicle information collection in a wave communication. The method according to claim 1,
The step of transmitting a packet to a service channel in the period by a random distributed method comprises:
The number of service channels in the period is determined and a packet is transmitted on one of service channels of a predetermined number of service channels
A random distributed immediate approach for probe vehicle information collection in a wave communication. 5. The method of claim 4,
The step of transmitting a packet to a service channel in the period by a random distributed method comprises:
Each of the vehicles is dispersed, the interval of the service channel in the period is increased, and the capacity of the channel is increased, thereby improving the packet transmission success rate
A random distributed immediate approach for probe vehicle information collection in a wave communication. The method according to claim 1,
The step of transmitting a packet to a service channel in the period by a random distributed method comprises:
Determining a period (T) according to a packet generation period;
Dividing the period T by a preset sync interval (SyncInterval) to obtain the number of service channels; And
Dividing the number of service channels by the number of vehicles to be transmitted and calculating the number of average vehicles capable of transmission attempts at a time
Lt; / RTI >
The average vehicles capable of the transmission attempt at the same time access to one of the Service Channels for transmission within the period in a random manner
A random distributed immediate approach for probe vehicle information collection in a wave communication. 1. An arbitrary distributed immediate access method for probe vehicle information collection in a wave communication,
A step of increasing the capacity of a service channel by means of an immediate access channel operating method using a generation rate of a packet in a WAVE communication of the vehicle
An arbitrary distributed immediate approach for probe vehicle information collection in a wave communication. 1. An arbitrary distributed immediate access system for probe vehicle information collection in a wave communication,
A packet transmission unit for transmitting a packet in a randomly distributed manner to a service channel within a period using a generation rate of a packet in WAVE communication,
A random distributed immediate access system for probe vehicle information collection in a wave communication comprising: 10. The method of claim 9,
A channel synchronization unit for synchronizing a channel to use the same channel between a vehicle and a roadside base station (RSU) periodically receiving the packet from the vehicle in the multi-
A random distributed immediate access system for probe vehicle information collection in a wave communication. 11. The method of claim 10,
Wherein the channel synchronization unit comprises:
A WSA receiving unit for broadcasting the WSA to vehicles entering the communication radius at the roadside base station (RSU), the vehicles receiving the WSA more than a predetermined number of times and entering the WAVE communication system;
Wherein the vehicles recognize a channel operating method within a communication radius entering the WSA according to a field value received in the WSA;
The vehicles include a PVD transfer unit for determining a channel operating method to synchronize a channel and transmit probe vehicle information (PVD) to the RSU; And
The vehicles receive an ACK message indicating that the probe vehicle information (PVD) has been delivered from the RSU,
A random distributed immediate access system for probe vehicle information collection in a wave communication comprising: 10. The method of claim 9,
Wherein the packet transfer unit comprises:
The capacity of the service channel is increased by the immediate access channel operating method within the period
A random distributed immediate access system for probe vehicle information collection in a wave communication. 10. The method of claim 9,
Wherein the packet transfer unit comprises:
The number of service channels in the period is determined and a packet is transmitted on one of service channels of a predetermined number of service channels
A random distributed immediate access system for probe vehicle information collection in a wave communication. 13. The method of claim 12,
Wherein the packet transfer unit comprises:
Each of the vehicles is dispersed, the interval of the service channel in the period is increased, and the capacity of the channel is increased, thereby improving the packet transmission success rate
A random distributed immediate access system for probe vehicle information collection in a wave communication. 10. The method of claim 9,
Wherein the packet transfer unit comprises:
Dividing the period T determined by the packet generation period by a predetermined sync interval (SyncInterval) to obtain the number of service channels, dividing the number of service channels by the number of vehicles to be transmitted, The average number of vehicles capable of transmission attempt is calculated, and the average vehicles capable of the transmission attempt at the same time access to one of the service channels for transmission in random within the period
A random distributed immediate access system for probe vehicle information collection in a wave communication.

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