CN104768131A - Relay node alarming message forwarding method based on car-to-car communication - Google Patents

Abstract

The invention discloses a relay node alarming message forwarding method based on car-to-car communication. After a vehicle-mounted terminal receives an alarming message, whether the alarming message is overdue or not is judged. The overdue message is directly abandoned. For the message which is not overdue, the relative position relationship of a vehicle and a message source is judged according to the GPS coordinates of the message source of the message and the GPS information of the vehicle itself, if the vehicle gets close, the distance between the vehicle and the message source is further calculated, and the vehicle forwarding priority is set according to the distance value. The method provides a novel alarming message forwarding mechanism. On one hand, the message is processed only when the message is not overdue and the vehicle gets close to the message source, and redundant alarming messages in the network after an emergency occurs are reduced; on the other hand, the message forwarding priority is set, it is guaranteed that the alarming messages are transmitted at a higher speed within a larger range, and the real-time performance and reliability of messages are improved.

Description

A kind of via node alarm information retransmission method based on truck traffic

Technical field

The invention belongs to the application of technology of Internet of things at safe driving and intelligent transportation field, relate to a kind of via node alarm information retransmission method based on truck traffic particularly.

Background technology

Internet of Things (Internet of Things, abbreviation IOT) be one based on information carriers such as the Internet, conventional telecommunications nets, allow the network that all General Physics object implementatio8 that can be independently addressable interconnect.Along with developing rapidly of technology of Internet of things, its industrialization fltting speed is also in continuous quickening, and Internet of Things has given play to increasing effect in safe driving and intelligent transportation field.In safe driving, Internet of Things be otherwise known as car networking (VANET, Vehicular Ad-hoc Network).Car networking mainly communicates with roadside unit by vehicle, between car car based on communication and vehicle and network service, realize driving safely by exchanging in real time security-related message reliably.Utilize car networking technology, in conjunction with GPS, CAN technology, safety-relevant applications can the contingent dangerous situation of prior notice driver, reduces accident rate.

The truck traffic technology driven towards safety is the important support technology realizing safe driving, is also the core link realizing intelligent transportation.Truck traffic is mainly based on wireless communication technology, and state information and the alarm information such as mutual switch speed between vehicle, for Driving Decision-making provides auxiliary.At present, the correlative study of truck traffic mainly concentrates on abroad, as the project such as V II, IntelliDriveSM, CICAS, CVHAS, CarTalk of American-European state, the projects such as SmartWay, AHS of Japan, these project emphasis are different, but all relate to research and development and the industrialization work of truck traffic technology.

Information broadcast (Broadcast) technology is the Primary communication mode that current truck traffic adopts.On the one hand, vehicle can with the form of heartbeat message to broadcast oneself state information, as speed, position etc.; On the other hand, after there is emergency, vehicle meeting broadcast alarms message, notice nearby vehicle.The mode of current realization broadcast mainly contains two kinds: (1) uses simple inundation (Flooding) mode; (2) RTS/CTS, the ACK introduced in IEEE 802.11 agreement controls bag, coordinates complicated control logic to realize Broadcasting Control, as UMB, PCBB etc.

In above two kinds of modes, the former is easy to realize, the latter can ensure message real-time and reliability, but two kinds of modes all Shortcomings, for flooding approach: (1) shares radio communication channel due to vehicle a large amount of in network, accuse after there is emergency, alarm information too much constitutes competition channel unsuccessfully due to message possibly, occurs packet loss, causes alarm information reliability to reduce; (2) priority due to all vehicle node forwarding alarm informations is identical, and when traffic density is larger, alarm information can, apart from repetitive propagation in the certain area of alarm source, cause alarm information real-time to reduce, and is difficult to cover enough regions.For the second way: its control logic is complicated, realizes, be difficult to obtain good effect in the vehicle module that computing capability is limited.

Summary of the invention

In view of the deficiency of above-mentioned technology, the present invention seeks to: a kind of via node alarm information retransmission method based on truck traffic is provided, guarantee alarm information with the fastest speed while range transmission large as far as possible, decrease redundant alarm message number in network, effectively improve the fail safe of driving, simply efficiently.

Technical scheme of the present invention is:

Based on a via node alarm information retransmission method for truck traffic, comprise the following steps:

S01: after car-mounted terminal receives alarm information, judges that whether alarm information is expired, abandons stale messages, performs step S02 for not out of date message;

S02: according to the gps coordinate change of vehicle within the δ t time, calculate the motion vector of vehicle within the δ t time according to the gps coordinate in vehicle and alarm information source, calculate position vector calculate according to value judge vehicle be close to or away from alarm information source, abandon away from message, for close message perform step S03;

S03: calculate the distance between vehicle and message source; According to the distance between vehicle and message source, forwarding priority and forward delay are set.

Preferably, the determination methods that in step S01, whether alarm information is expired is:

When alarm information source sends an alarm information, the system time send_time in alarm information source is enclosed in alarm information, when vehicle receives message, system time receive_time and the send_time+t of vehicle is compared, wherein t is message life cycle, wherein, receive_time≤send_time+t, represents that alarm information is not out of date; Receive_time > send_time+t, represents that alarm information is not out of date.

Preferably, the method for vehicle and alarm information source relative position relation that judges in step S02 is: represent that vehicle is away from alarm information source, represent that vehicle is near alarm information source.

Preferably, the formula calculating the distance between vehicle and message source in step S03 is: $\mathrm{dis}=2*R*\arcsin \sqrt{{\sin }^2\left(\frac{{\mathrm{\α}}_2-{\mathrm{\α}}_1}{2}\right)+\cos {\mathrm{\α}}_1*\cos {\mathrm{\α}}_2*{\sin }^2\left(\frac{{\mathrm{\β}}_2-{\mathrm{\β}}_1}{2}\right)}$

Wherein, α ₁and α ₂represent the longitude (unit is radian) of two cars respectively, wherein β ₁and β ₂represent the latitude (unit is radian) of two cars respectively, R represents the mean radius of the earth, and its value is 6371.4km.

Preferably, describedly forwarding priority is set according to the distance between vehicle and message source and forward delay comprises:

If dis < is 200m, if the forwarding priority of this vehicle is 10;

If 200m < dis < is 400m, if the forwarding priority of this vehicle is 9;

If dis > is 400m, if the forwarding priority of this vehicle is 7;

When the forwarding priority of vehicle is 7, if message forwards run into channel block, then the stand-by period 0 ~ 2 will be got ⁷(ms) random value between;

When the forwarding priority of vehicle is 9, if message forwards run into channel block, then the stand-by period 2 will be got ⁷~ 2 ⁹(ms) random value between;

When the forwarding priority of vehicle is 10, if message forwards run into channel block, then the stand-by period 2 will be got ⁹~ 2 ¹⁰(ms) random value between.

A kind of via node alarm information retransmission method based on truck traffic of the present invention, for realizing this application, after the car-mounted terminal of vehicle receives alarm information, first judges that whether this alarm information is expired.Stale messages will be simply discarded.For not out of date message, according to gps coordinate and vehicle self GPS information of message source in message, judge the relative position relation of vehicle and message source, if close, we will calculate further both distance, and vehicle forwarding priority is set according to distance value.This method propose a kind of brand-new alarm information forwarding mechanism, on the one hand, vehicle only and vehicle not out of date in message close to processing messages during message source, decrease emergency occur after redundant alarm message in network; On the other hand, by arranging message forwarding priority, ensure that alarm information at faster speed in larger range transmission, improve real-time and the reliability of message.

Advantage of the present invention is:

1. practicality: this method utilizes gps data information to calculate, determines the priority of vehicle forwarding messages, calculates easy, without the need to special installation according to the relative position relation of vehicle and alarm source and distance;

2. reliability: this method utilizes truck traffic technology and CAN to obtain relevant information, can obtain up-to-date information as basis for estimation, make error less;

3. high efficiency: the relative position relation of this method whether message is expired and vehicle and alarm source is as the screening conditions forwarding alarm information, decrease the quantity that redundant alarm message in rear network occurs in emergency, improve bandwidth availability ratio, add the reliability of message.

4. flexibility: the scope of application of this method is comparatively large, can reliably use at the overcast and rainy bad weather that waits.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the invention will be further described:

Fig. 1 is the schematic diagram that the gps coordinate of the via node alarm information retransmission method that the present invention is based on truck traffic is converted into three-dimensional coordinate;

Fig. 2 is the schematic diagram calculating spherical distance according to GPS information of the via node alarm information retransmission method that the present invention is based on truck traffic;

Fig. 3 is the flow chart of the via node alarm information retransmission method that the present invention is based on truck traffic.

Embodiment

Below in conjunction with specific embodiment, such scheme is described further.Should be understood that these embodiments are not limited to for illustration of the present invention limit the scope of the invention.The implementation condition adopted in embodiment can do further adjustment according to the condition of concrete producer, and not marked implementation condition is generally the condition in normal experiment.

Embodiment:

The present embodiment is based on via node warning information retransmission method, and wherein vehicle refers to the vehicle being currently received alarm information.Alarm information source refers to the source of all alarm informations, the vehicle namely broken down.The system time of message source when this message is sent out is comprised, the GPS information (longitude, latitude and height above sea level) etc. in alarm information source in alarm message packet.

The method comprises the following steps:

(1), after the car-mounted terminal of vehicle receives alarm information, first judge that whether this alarm information is expired.If message is not out of date, enter (2), otherwise, abandon;

(2) according to the gps coordinate change of vehicle within the δ t time, the motion vector of vehicle within the δ t time is calculated according to the gps coordinate of vehicle and the gps coordinate of message source, calculate position vector compute vector with vector dot product value

(3) judge vehicle be close to or away from message source, if vehicle is close to message source, enter (4), if vehicle is away from alarm information source, abandon message;

(4) distance between vehicle to alarm information source is calculated according to the gps coordinate of vehicle and the gps coordinate in alarm information source;

(5) give car-mounted terminal specific forwarding priority according to the distance between vehicle to alarm information source.

(6) calculate according to the forwarding priority calculating gained in step (5) span that message forwards the latency value back_off_time after running into obstruction.

Concrete, fault car is after detecting that fault occurs, and the car-mounted terminal in fault car needs peripherad vehicle constantly to send alarm information.Need to enclose the system time of fault car and the GPS information of fault car when this bag is issued in each alarm message packet simultaneously.

The car-mounted terminal of other vehicles, after receiving alarm information, first needs the size comparing receive_time and send_time+t to judge that whether this alarm information is meaningful.

Wherein, send_time is this alarm information when being sent out, the system time in alarm information source, and wherein send_time+t is this alarm information when being received, and receive the system time of vehicle, wherein, t is message life cycle.

For not out of date alarm information, carry out next step process.Abandon insignificant alarm information.

Then, according to the gps coordinate change in the vehicle δ t time, the motion vector of vehicle within the δ t time is calculated according to the gps coordinate of vehicle and the gps coordinate in alarm information source, calculate position vector compute vector with vector dot product value, with judge vehicle be close to or away from alarm source.

If the gps coordinate in alarm information source is (α ₁, β ₁, h ₁),

Be (x by the three-dimensional coordinate that can be calculated ₁, y ₁, z ₁).

If the gps coordinate of vehicle t is (α ₂, β ₂, h ₂),

Be (x by the three-dimensional coordinate that can be calculated ₂, y ₂, z ₂).

If the gps coordinate of vehicle t+ Δ t is (α ₃, β ₃, h ₃),

Be (x by the three-dimensional coordinate that can be calculated ₃, y ₃, z ₃).

The computational methods of three-dimensional coordinate are as follows:

Because the polar radius of the earth and equatorial radius are more or less the same, all the earth is considered as a regular spheroid by us., three-dimensional coordinate initial point is based upon the earth's core place herein, allows X-axis and (90E, 90W) overlap through the diameter of coil 0 degree of parallel, allow Y-axis and (0,180) overlap through the diameter of coil 0 degree of parallel, allow Z axis overlap with the earth's axis, as shown in Figure 1.

Point A be the Northern Hemisphere a bit, B is height above sea level same as an A, same longitude, and latitude is the point of 0.Then height above sea level H _alti=h m=h/1000km.Make earth mean radius be R, some B and geocentric distance are H _dis, then H is had _dis=R+h/1000 ≈ 6371.4+h/1000km.

Make AC ⊥ BO, C is intersection point, can release

|CO|＝|AO|*cos∠AOC＝(6371.4+h/1000)*cos∠AOC

An A three-dimensional coordinate can be obtained

x＝|CO|*sin∠COD＝(6371.4+h/1000)*cos∠AOC*sin∠COD

y＝|CO|*cos∠COD＝(6371.4+h/1000)*cos∠AOC*cos∠COD

z＝|AC|＝|AO|*sin∠AOC＝(6371.4+h/1000)*sin∠AOC

Below respectively to the north and south latitude of the earth, thing is through carrying out Taxonomic discussion.

If α is latitude, β is longitude, and h is height above sea level, and be on the occasion of.

For north latitude:

z＝(6371.4+h/1000)*sinα

For south latitude:

z＝-(6371.4+h/1000)*sinα

For east longitude:

x＝(6371.4+h/1000)*cosα*sinβ

y＝(6371.4+h/1000)*cosα*cosβ

For west longitude:

x＝(6371.4+h/1000)*cosα*sin(-β)

y＝(6371.4+h/1000)*cosα*cos(-β)

To sum up, for given gps coordinate, by calculating, corresponding three-dimensional coordinate can be drawn.

After knowing coordinate, then the direction vector that vehicle travels is:

$\stackrel{\&RightArrow;}{m}=(x_3-x_2,y_3-y_2,z_3-z_2)$

Then the relative position vector in vehicle and alarm information source is:

$\stackrel{\&RightArrow;}{n}=(x_2-x_1,y_2-y_1,z_2-z_1)$

Calculate and judge, if then vehicle is away from alarm information source, Discard alarm message, otherwise, if then vehicle is near alarm information source, is for further processing.

Then, the distance dis between vehicle to alarm information source is calculated according to the gps coordinate of vehicle and the gps coordinate in alarm information source.

The computing formula of dis is:

$\mathrm{dis}=2*R*\arcsin \sqrt{{\sin }^2\left(\frac{{\mathrm{\&alpha;}}_2-{\mathrm{\&alpha;}}_1}{2}\right)+\cos {\mathrm{\&alpha;}}_1*\cos {\mathrm{\&alpha;}}_2*{\sin }^2\left(\frac{{\mathrm{\&beta;}}_2-{\mathrm{\&beta;}}_1}{2}\right)}$

Wherein α ₁and α ₂represent the longitude (unit is radian) of two cars respectively, wherein β ₁and β ₂represent the latitude (unit is radian) of two cars respectively, R represents the mean radius of the earth, and its value is 6371.4km.

The derivation of equation of above-mentioned dis is as follows:

Fig. 2 is shown in by schematic diagram.

Make earth mean radius be R, then can derive following result:

In right-angled triangle △ AOC and △ BOD:

|AC|＝|DE|＝R*sinα ₁

|OC|＝R*cosα ₁

|BD|＝R*sinα ₂

|OD|＝R*cosα ₂

In triangle △ COD:

$\left|\mathrm{CD}\right|=\sqrt{{\left|\mathrm{OC}\right|}^2+{\left|\mathrm{OD}\right|}^2-2*\left|\mathrm{OC}\right|*\left|\mathrm{OD}\right|*\cos ({\mathrm{\&beta;}}_2-{\mathrm{\&beta;}}_1)}$

In right-angled triangle △ ABE:

|AE|＝|CD|

|BE|＝|BD|-|DE|＝R*(sinα ₂-sinα ₁)

$\left|\mathrm{AB}\right|=\sqrt{{\left|\mathrm{AE}\right|}^2+{\left|\mathrm{BE}\right|}^2}$

Comprehensive three steps are above derived, and can derive the length of limit AB:

Again in isosceles triangle △ AOB:

Because $\sin \frac{\&angle;\mathrm{AOB}}{2}=\frac{\left|\mathrm{AB}\right|}{2*R}$

So $\&angle;\mathrm{AOB}=2*\arcsin \frac{\left|\mathrm{AB}\right|}{2*R}$

Therefore can draw:

$\&angle;\mathrm{AOB}=2*\arcsin \sqrt{{\sin }^2\left(\frac{{\mathrm{\&alpha;}}_2-{\mathrm{\&alpha;}}_1}{2}\right)+\cos {\mathrm{\&alpha;}}_1*\cos {\mathrm{\&alpha;}}_2*{\sin }^2\left(\frac{{\mathrm{\&beta;}}_2-{\mathrm{\&beta;}}_1}{2}\right)}$

After calculating the distance dis between vehicle to alarm information source, calculate priority when vehicle on-board terminal forwards alarm information:

If dis < is 200m, if the forwarding priority of this vehicle is 10;

If 200m < dis < is 400m, if the forwarding priority of this vehicle is 9;

If dis > is 400m, if the forwarding priority of this vehicle is 7.

When the forwarding priority of vehicle is 7,

Latency value back_off_time after message race channel runs into channel block gets 0 ~ 2 ⁷(ms) random value between.

When the forwarding priority of vehicle is 9,

Message race channel runs into the latency value back_off_time2 after channel block ⁷~ 2 ⁹(ms) random value between.

When the forwarding priority of vehicle is 10,

Message race channel runs into the latency value back_off_time2 after channel block ⁹~ 2 ¹⁰(ms) random value between.

If when vehicle distances alarm information source is nearer, the numerical value of this vehicle forwarding priority will be larger, namely message forward run into the latency value back_off_time after obstruction will be larger, namely can carry out forwarding messages with the time utilized bandwidth of less ratio, because often receive alarm information all already from the vehicle close to alarm information source.

If when vehicle distances alarm information source is far away, the numerical value of this vehicle forwarding priority will be less, namely message forward run into the latency value back_off_time after obstruction will be less, namely can carry out forwarding messages with the time utilized bandwidth of larger proportion, because often all not yet receive alarm information from the vehicle away from alarm information source.

To sum up, emergency can reduce in a large number after occurring redundant alarm message quantity, thus improve the utilization rate of bandwidth, reduce the congested of message.

Above-mentioned example, only for technical conceive of the present invention and feature are described, its object is to person skilled in the art can be understood content of the present invention and implement according to this, can not limit the scope of the invention with this.All equivalent transformations of doing according to Spirit Essence of the present invention or modification, all should be encompassed within protection scope of the present invention.

Claims (5)

1., based on a via node alarm information retransmission method for truck traffic, it is characterized in that, comprise the following steps:

S01: after car-mounted terminal receives alarm information, judges that whether alarm information is expired, abandons stale messages, performs step S02 for not out of date message;

S02: according to the gps coordinate change of vehicle within the δ t time, calculate the motion vector of vehicle within the δ t time according to the gps coordinate in vehicle and alarm information source, calculate position vector calculate according to value judge vehicle be close to or away from alarm information source, abandon away from message, for close message perform step S03;

S03: calculate the distance between vehicle and message source; According to the distance between vehicle and message source, forwarding priority and forward delay are set.

2. the via node alarm information retransmission method based on truck traffic according to claim 1, it is characterized in that, the determination methods that in step S01, whether alarm information is expired is:

When alarm information source sends an alarm information, the system time send_time in alarm information source is enclosed in alarm information, when vehicle receives message, system time receiue_time and the send_time+t of vehicle is compared, wherein t is message life cycle, wherein, receiue_time≤send_time+t, represents that alarm information is not out of date; Receiue_time > send_time+t, represents that alarm information is not out of date.

3. the via node alarm information retransmission method based on truck traffic according to claim 1, is characterized in that, the method for vehicle and alarm information source relative position relation that judges in step S02 is: represent that vehicle is away from alarm information source, represent that vehicle is near alarm information source.

4. the via node alarm information retransmission method based on truck traffic according to claim 1, it is characterized in that, the formula calculating the distance between vehicle and message source in step S03 is:

$\mathrm{dis}=2*R*\arcsin \sqrt{{\sin }^2\left(\frac{a_2-a_1}{2}\right)+\cos {\mathrm{\&alpha;}}_1*\cos {\mathrm{\&alpha;}}_2*{\sin }^2\left(\frac{{\mathrm{\&beta;}}_2-{\mathrm{\&beta;}}_1}{2}\right)}$

Wherein, α ₁and α ₂represent the longitude (unit is radian) of two cars respectively, wherein β ₁and β ₂represent the latitude (unit is radian) of two cars respectively, R represents the mean radius of the earth, and its value is 6371.4km.

5. the via node alarm information retransmission method based on truck traffic according to claim 4, is characterized in that, describedly arranges forwarding priority according to the distance between vehicle and message source and forward delay comprises:

If dis < is 200m, if the forwarding priority of this vehicle is 10;

If 200m < did < is 400m, if the forwarding priority of this vehicle is 9;

If dis > is 400m, if the forwarding priority of this vehicle is 7;

When the forwarding priority of vehicle is 7, if message forwards run into channel block, then the stand-by period 0 ~ 2 will be got ⁷(ms) random value between;

When the forwarding priority of vehicle is 9, if message forwards run into channel block, then the stand-by period 2 will be got ⁷~ 2 ⁹(ms) random value between;

When the forwarding priority of vehicle is 10, if message forwards run into channel block, then the stand-by period 2 will be got ⁹~ 2 ¹⁰(ms) random value between.