CN101123456A - Communication method for onboard units and byroad units of ETC system based on WLAN - Google Patents
Communication method for onboard units and byroad units of ETC system based on WLAN Download PDFInfo
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- CN101123456A CN101123456A CNA2006100892150A CN200610089215A CN101123456A CN 101123456 A CN101123456 A CN 101123456A CN A2006100892150 A CNA2006100892150 A CN A2006100892150A CN 200610089215 A CN200610089215 A CN 200610089215A CN 101123456 A CN101123456 A CN 101123456A
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Abstract
The invention discloses a communication method of an ETC system vehicle unit based on WLAN and a roadside unit. The prior communication linkage between the ETC system based vehicle unit and the roadside unit is short in distance, and needs long time to be established, and is instable, and is not applicable for the linkage between a vehicle moving at high speed and a fixed toll collection system. In order to solve the above problems, the communication linkage between the vehicle unit and the roadside unit is established in the following steps. Firstly, the vehicle unit sends a probe request frame to the roadside unit to monitor an information frame. Secondly, the vehicle unit gets the information fame, and sends an authentication request frame to the roadside unit to monitor the authentication response frame returned from the roadside unit. Thirdly, the vehicle unit gets the authentication response frame, and sends financial transaction information to the roadside unit. By adopting the invention, more stable communications linkage can be established between the vehicle unit and the roadside unit more quickly.
Description
Technical field
The present invention relates to a kind of ETC (electric non-stop toll) system onboard unit (OBU) of highway or urban road and communication means of roadside unit (RSU) of being applied to, relate in particular to a kind of board units of the electronic charging system without parking of realizing based on the wireless lan (wlan) technology and the communication means between the roadside unit.The invention belongs to intelligent transportation (being called for short ITS) technical field.
Background technology
Along with China's rapid development of economy, the contradiction of ever-increasing automobile pollution and limited path area becomes increasingly conspicuous.In order to solve this contradiction, except building energetically the road, the utilization ratio that improves existing road also is an important ring.Under this background, intelligent transportation system becomes the focus of world today's research and development day by day.
Electronic charging system without parking (ETC) and technology thereof are the important component parts of intelligent transportation system, and it is the important technical that solves traffic congestion on the toll road, obstruction and other drawback, improves existing road security of operation and efficient.Board units (OBU) and roadside unit (RSU) be as the important component part of ETC system, and the normal operation of whole ETC system and the reliable assurance of performance are played crucial effects.Board units (OBU) is installed in the inboard of vehicle front windshield, communicate by roadside unit (RSU) with highway or urban road one side, realize carrying out non-parking charge for the vehicle that travels on highway or urban road, thereby allow vehicle to pass through at a high speed, improve the traffic capacity of highway or urban road greatly.
Existing electronic toll collection system vehicle-mount unit based on WLAN (OBU) and roadside unit (RSU) have following feature:
Wireless network card is installed on the board units, wireless network card and WAP (wireless access point) are installed on the described roadside unit, described board units and roadside unit carry out radio communication by described wireless network card and WAP (wireless access point);
Board units utilizes the WLAN standard agreement to communicate by letter with the WAP (wireless access point) of roadside unit by wireless network card.
The wireless network card of board units and the wireless network card of described roadside unit include mac-layer protocol processing unit, baseband processing unit, RF processing unit and air feedback unit.
Roadside unit is equipped with directional antenna, and directional antenna is a for satisfying the antenna on the roadside unit of being installed in of the whole ETC system communication of this project transaction-based requirements research and design.
WAP (wireless access point) is a WAP (wireless access point) on the roadside unit of being installed in that satisfies the whole ETC system communication of this project transaction-based requirements.
Physical layer that above-mentioned board units is carried out when communicating by letter with roadside unit and MAC layer signal processing procedure are as shown in Figure 1.Signal processing is described below in detail:
User's vehicle data information that OBU background process center will be transmitted sends the mac-layer protocol processing unit in the wireless network card to, the mac-layer protocol processing unit is encoded to data message, the packing encapsulation, add packet header, then behind baseband processing unit (BBP) modulation and spread spectrum, through digital to analog conversion, the data message after will handling again is sent to RF processing unit (RF), and signal is carried out up-conversion to the RF processing unit and power amplification is handled and sent via the air feedback unit in the wireless network card.
The WAP (wireless access point) (AP) of RSU end receives the data message that board units (OBU) sends by the directional antenna of its front end, and be transferred to air feedback unit in the wireless network card of roadside unit, air feedback unit is given RF processing unit with the data information transfer that receives, data message is transferred into baseband processing unit at RF processing unit after low noise amplifier and down-converted, carry out mould/transformation of variables, despreading, after the demodulation process, data message is transmitted to the mac-layer protocol processing unit in the wireless network card, with the processing of unpacking, sending RSU background process center to after restoring initial data.
ETC system onboard unit and roadside unit based on WLAN adopts traditional IEEE802.11MAC layer standard communication protocol on link layer at present.Because the WLAN (wireless local area network) that the WLAN technology is mainly used in 50m～100m scope is interconnected, the network terminal all is in the state that indoor static or outdoor low speed moves (5km/h is following), therefore, this consensus standard also is primarily aimed at the application that indoor WLAN (wireless local area network) and outdoor walking mobile subscriber insert WLAN (wireless local area network).So correspondingly, this consensus standard has following characteristics: first, translational speed to portable terminal is insensitive, shows for the time no requirement (NR) that connects, usually in several seconds, the beacon period of regulation RSU is more than 100ms, and regulation OBU and RSU foundation is communicated by letter and needed three-way handshake; The second, the priority of communication validity is higher than reliability, promptly exchanges the increase greatly (reaching as high as 54Mbps) of the rate of information throughput for the reliable and stable performance of sacrificing connection; The 3rd, in the process that establishes a communications link, institute's various authentication informations mutually must be corresponding one by one between regulation OBU and the RSU, be that frame is inquired after in the OBU transmission, then RSU must reply and inquire after response frame, just can carry out the mutual of next step-frame, otherwise, will make OBU retransmit by avoidance mechanism and inquire after frame; OBU sends authentication request frames, and then RSU must reply authentication response frames, just can carry out the mutual of next step-frame, otherwise, will make OBU retransmit by avoidance mechanism and inquire after frame; OBU sends association request frame, and then RSU must reply association response frame, just can carry out the mutual of next step-frame, otherwise, will make OBU retransmit by avoidance mechanism and inquire after frame.Yet, based on the ETC system onboard unit of WLAN and the vehicle pass-through speed height very of roadside unit support, usually in 120km/h ~ 180km/h scope, the operating distance of RSU is only at 50m ~ 100m, this just must make and connect the very strictness (at Millisecond) of time requirement that enters WLAN (wireless local area network), and the connection of being set up will be stablized in the extreme, to such an extent as to otherwise will constantly occur owing to the passage rate of vehicle is fast in the extreme or the success that is not able to do in time connects or the connection set up is broken again phenomenon at all, be OBU and RSU or do not connect, just break on just having connected, thereby can't make whole ETC system realize the function of non-parking charge at all.In addition,, require the dry cell of a common 1200mAh to can be OBU power supply 3 months, therefore, consider not allow that also the very long time that connects is arranged between OBU and the RSU from the power consumption angle because OBU utilizes dry cell power supply.
In sum, traditional as can be known be primarily aimed at IEEE802.11MAC layer protocol standard that static or low speed moves the terminal applies of (5km/h is following) and must be not suitable for being applied to based on communicating to connect between the ETC system onboard unit of WLAN and the roadside unit, concrete manifestation is in the following areas: first, traditional IEEE802.11MAC layer protocol standard is insensitive to the translational speed of portable terminal, and the situation of the standard of this agreement during not high-speed mobile is as the main pattern of using; The second, time of connecting needs several seconds for long based on the communications applications of the ETC system onboard unit of WLAN and roadside unit, on the power consumption of OBU end and the function of whole ETC system realize it all being flagrant; The 3rd, the beacon that RSU sends needs three-way handshake for too complicated based on the communications applications of the ETC system onboard unit of WLAN and roadside unit at 100ms and when connecting, wasted a large amount of temporal expenses, make the overlong time that OBU and RSU establish a communications link, thereby cause loss in vain on the OBU end power consumption, the life-span of reducing the OBU continuous firing greatly; The 4th, the characteristics that the priority of the communication validity of traditional IEEE802.11MAC layer protocol standard is higher than reliability are not suitable for based on the ETC system onboard unit of WLAN and the communications applications of roadside unit, because ETC system onboard unit and communicating by letter of roadside unit based on WLAN need mutual data to have only 300 bytes, amount of information is minimum, therefore do not need the very high rate of information throughput (54Mbps), the minimum speed limit 6Mbps of RSU end defined is enough, therefore, fully can be by being that cost exchanges for for being connected reliability based on the ETC system onboard unit of WLAN and even more important the best of communications applications of roadside unit to sacrifice the rate of information throughput; The 5th, in the process that establishes a communications link, require between OBU and the RSU send out mutually variously must corresponding one by one these characteristics also limit the flexibility that establishes a communications link between OBU and the RSU greatly, thereby cause the rapid increase of the time of connecting.
And therefore existing every other mac-layer protocol standard, also all is not suitable for being applied to based on the ETC system onboard unit of WLAN and communicating to connect of roadside unit because there are greatest differences in physical-layer techniques of being supported and the physical-layer techniques of WLAN at present.
Summary of the invention
In order to overcome defective and the deficiency that prior art exists, the purpose of this invention is to provide a kind of quick, stable based on WLAN based on the ETC system onboard unit of WLAN and the communication means of roadside unit.
To achieve the above object of the invention, the present invention is based in the communication means of the ETC system onboard unit of WLAN and roadside unit, the process that board units and roadside unit establish a communications link is:
(1) board units sends to roadside unit and inquires after claim frame, interception information frame;
(2) described board units listens to information frame, sends authentication request frames to described roadside unit, intercepts the authentication response frames that roadside unit returns;
(3) described board units listens to authentication response frames, sends financial transaction information to described roadside unit.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, step (2) is specially:
(21) if the information frame that described board units listens to is the response frame of inquiring after of roadside unit answer, enter step (22); If the information frame that described board units listens to is other board units send inquire after claim frame, enter step (23);
(22) board units sends authentication request frames to described roadside unit, intercepts the authentication response frames that roadside unit returns, if board units does not listen to authentication response frames in the time limit intercepting, repeats this step; If board units listens to authentication response frames in the time limit intercepting, enter step (3);
(23) board units sends authentication request frames to roadside unit, intercepts the authentication response frames that roadside unit returns, if board units does not listen to authentication response frames in the time limit intercepting, returns step (1); If board units listens to authentication response frames in the time limit intercepting, enter step (3).
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, in the step (1), board units sends to roadside unit at set intervals and once inquires after claim frame, intercepts the primary information frame.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, the span of described a period of time is 0.5 to 3 second.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, send once inquire after claim frame time less than 500 microseconds, the time of intercepting the primary information frame is 500 microseconds.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, be limited to 3 milliseconds during intercepting described in the step (22).Be limited to 5 milliseconds during intercepting described in the step (23).
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, inquire after claim frame, inquire after response frame, the frame structure of authentication request frames, authentication response frames comprises five parts: first is a frame head, second portion is a logic link control information, third part is a subnetwork access protocol, the 4th part is load, and the 5th part is a check code.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, board units and roadside unit are that the channel of 6Mbps communicates by transmission rate.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, roadside unit sends the mode of inquiring after response frame and is divided into two kinds: active mode, under the situation of inquiring after claim frame of not receiving the board units transmission, initiatively send and inquire after response frame, the time cycle of transmission is 20 milliseconds; Passive mode under the situation of inquiring after claim frame of receiving the board units transmission, is returned immediately and is inquired after response frame.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, board units by the frame head of information frame discern described information frame be roadside unit return inquire after response frame or from the frame of other board units.
In the above-mentioned ETC system onboard unit and the communication means of roadside unit based on WLAN, described load of inquiring after claim frame comprises two parts: first is the network identity of WLAN (wireless local area network), and second portion is the speed that wireless network card is supported;
Described load of inquiring after response frame comprises six parts: the markers when first is WAP (wireless access point) transmission Beacon frame, second portion is the interval that WAP (wireless access point) sends the Beacon frame, third part is the descriptor of the ability of WAP (wireless access point), the 4th part is the network identity of WLAN (wireless local area network), the 5th part is the speed that WAP (wireless access point) is supported, the 6th part is a channel logo;
The load of described authentication request frames comprises two parts: first is the identifying algorithm sign, and second portion is the sequence number of authentication frame;
The load of described authentication response frames comprises three parts: first is the identifying algorithm sign, and second portion is the sequence number of authentication frame, and third part is the conditional code of authentication.
The present invention makes great efforts to overcome traditional IEEE802.11MAC layer protocol standard based on the deficiency in the communications applications of the ETC system onboard unit of WLAN and roadside unit, in communications applications based on the ETC system onboard unit of WLAN and roadside unit, the brand-new communication protocol standard of definition one cover on the MAC of link layer layer, satisfying based on setting up the quicker more stable application requirements that communicates to connect between the ETC system onboard unit of WLAN and the roadside unit, thereby and the power problems that solves the OBU end well prolong useful life of OBU greatly.
Description of drawings
Fig. 1 is a hardware connection layout of the present invention;
Fig. 2 is the transmission diagram of WLAN (wireless local area network) of the present invention at each layer;
Fig. 3 is a layer structure chart of the present invention;
Fig. 4 is communication flow diagram between OBU of the present invention and the RSU.
Embodiment
Below in conjunction with accompanying drawing the present invention is described in further details:
The present invention at first adopts following technical scheme:
The transmission course of information transmitted signal on each layer of the WLAN (wireless local area network) of being made up of wireless network card among OBU and the RSU and the WAP (wireless access point) among the RSU is as shown in Figure 2 between OBU and the RSU:
The wireless network card of OBU and the wireless network card of RSU must could successfully be set up through the linking of the WAP (wireless access point) of RSU and communicate by letter.The consensus standard structure of WLAN (wireless local area network) mainly comprises physical layer, link layer and network layer.Because there is not the problem of route in the electronic charging system without parking that this OBU and RSU form in our project, therefore, can not establish network layer separately.And, because the medium access control more complicated of WLAN (wireless local area network), so link layer is divided into logical link control layer (LLC) and media access control layer (MAC) is two-layer.The content of this project is exactly to redefine the suitable mac-layer protocol standard that requires based on the ETC system applies of WLAN of a cover.
What be connected with the MAC layer as can be seen from Figure 2, is LLC layer and physical layer.Fig. 3 then provides the detailed structure of these three layers of linkings.Wherein, the LLC layer provides wireless network card and initial (logical links) between the WAP (wireless access point) among the RSU among OBU and the RSU to connect, promptly set up and remove data link,, send MAC layer service data unit (MSDU) to the MAC layer then by the interface between LLC layer and the MAC layer; The MAC layer provides wireless network card among OBU and the RSU and frame transmission, error control, flow control and the data link management between the WAP (wireless access point) among the RSU, be divided into the management of media access control sublayer and media access control sublayer, wherein, media access control sublayer provides the frame transmission, and the media access control sublayer management provides error control, flow control and data link management; Physical layer then provides physical link, realize the transparent transmission of bit stream, it has defined transmission medium, and electric with interface hardware, machinery, the various characteristics that function is relevant with process, so that set up, safeguard and remove physical connection, be divided into physical layer Convergence Sublayer and PLME, wherein PLME is by layer-management service interface and media access control sublayer management interaction data information, to call the layer-management function, the protocol section of physical layer Convergence Sublayer has defined transmission medium, it is by interface and media access control sublayer interaction data information, be used for the frame of recognition and verification from media access control sublayer, then, physical medium part interaction data information by interface and physical layer Convergence Sublayer again, make and to launch through the physical medium of physical layer Convergence Sublayer that wherein the physical medium of physical layer Convergence Sublayer part has then defined electric with interface hardware from the frame of MAC layer, machinery, the various characteristics that function is relevant with process.
The present invention is adopting following communication means based in the communicating to connect between the ETC system onboard unit of WLAN and the roadside unit, has promptly defined the new mac-layer protocol standard of a cover according to application requirements and characteristics based on the ETC system of WLAN.The contents are as follows:
1. formulate strict connection collision-avoidance mechanism, with reliability and the high-speed motion (reaching 180km/h) stable and that support portable terminal that improves channel transport efficiency, communication.Specific as follows:
Connect collision and avoid time=random number * one a time block duration (aSlotTime), 0≤random number≤CW wherein, aCWmin≤CW≤aCWmax, aCWmin=31, aCWmax=1023, aSlotTime=9us.Because at 100m, the vehicle translational speed is usually at 50km/h based on the ETC system communication of WLAN distance, therefore the vehicle fleet size generality can be more than 10 in this distance range.And, according to practical application characteristics and requirement based on the ETC system of WLAN, the probability of this project specifies (100m) OBU successful connection in ETC system works scope reaches 90%, then connecting not as can be known, probability of successful is 0.1, so can obtain, the number N of the random number that this project should be chosen is: (10/N)=0.1, N=100, consider the power consumption considerations (time interval, more little then power consumption was few more) of OBU end, the numerical value of random number CW should be the smaller the better as can be known, so just can determine aCWmin=31, aCWmax=130, promptly time=130 * 9us=1170us=1.17ms is avoided so can calculate maximum connection collision in 31≤CW≤130.
Therefore, the maximum that this project obtains according to aforementioned calculation connects collision and avoids the time, and the channel degradation of bringing when considering time overhead that channel fading produces and multiple access communication, stipulated the collision-avoidance mechanism that is connected that OBU and RSU should follow when establishing a communications link, if promptly OBU receives the response frame of AP then waits for after sending authentication request frames that 3ms is an optimal value, if OBU receives the frame of other OBU transmission then waits for after sending authentication request frames that 5ms is an optimal value.
2. shortening transmission beacon (the inquiring after response frame) cycle of wireless access point AP among the RSU, serves as to wait for the beacon of wireless access point AP and the energy that consumes in vain to reduce the OBU end.Specific as follows:
Since based on the ETC system communication of WLAN distance at 100m, and the highest 180km/h that will reach of vehicle translational speed, adding wireless channel is the influence of the very unsettled communication channel of a kind of connection, various channel fadings and the factors such as power consumption of OBU end, as can be known, OBU and RSU establish a communications link and time of finishing once complete transaction must be controlled at 400ms ~ 500ms level, if remove and carry out time 200ms ~ 300ms that exchange uses between OBU and the RSU, then as can be known, the remaining time that is used to establish a communications link is only less than 200ms.Therefore, consider in the ETC system works scope 100m to have 10 cars at most, therefore calculate and to get that it is that 200ms/10=20ms is optimal value that the WAP (wireless access point) that this project is chosen sends beacon period.
3. reduce the validity of communication, to exchange the reliability that connects communication for and to increase operating distance greatly, for the high-speed mobile of supporting portable terminal is given security.Specific as follows:
Because the ETC system information trading volume based on WLAN only is 300 bytes, therefore, this project only adopts the message transmission rate of 6Mbps to communicate, promptly adopt single-channel scheme, regulation AP does not send beacon in all channels in the agreement of this project, but only in the channel of regulation, send beacon, and the information interaction between OBU and the RSU being fixed in the channel that transmission rate is 6Mbps carrying out, communication reliability reaches 90%, communication distance is the target of 100m thereby reach.And in view of the above, can calculate, the time span that sends a frame (300 byte) is (300 * 8)/6Mbps=400us, so this project regulation OBU in view of the above waits for that the time of inquiring after response frame of AP is that 500us is an optimal value.
4. in the process that establishes a communications link, define the response mechanism between a kind of frame flexibly and the frame, establish a communications link between OBU and the RSU and the time overhead of interaction data information, thereby improve the efficient of whole ETC system to reduce greatly.
The new mac-layer protocol standard detailed content that this project proposes is as follows:
Type, order and the structure of the frame that is sent when, setting up communication transmitting data information between OBU and the RSU in this project:
The type of frame and the order:
Table 1 is inquired after claim frame
| In proper | Information | Remarks | |
| 1 | SSID | The sign of network | |
| 2 | Supporting rate | The speed that wireless network card is supported |
Table 2 is inquired after response frame
| In proper | Information | Remarks | |
| 1 | Time stamp | Markers when AP sends the Beacon frame | |
| 2 | Beacon interval | AP sends the interval of Beacon frame | |
| 3 | Ability information | The descriptor of the ability of AP | |
| 4 | SSID | The sign of network | |
| 5 | Supporting rate | The speed that AP supports | |
| 6 | The combination of DS parameter | Channel logo |
Table 3 authentication request frames
| In proper | Information | Remarks | |
| 1 | The identifying algorithm sequence number | The identifying algorithm sign | |
| 2 | The authenticated exchange sequence number | The sequence number of authentication frame |
Table 4 authentication response frames
| In proper | Information | Remarks | |
| 1 | The identifying algorithm sequence number | The identifying algorithm sign | |
| 2 | The authenticated exchange sequence number | The sequence number of authentication frame | |
| 3 | Conditional code | The conditional code of authentication |
2. frame structure:
| Frame head | LLC | SNAP (containing ethernet frame type) | Load | FCS |
Frame head: comprising: frame control (2B), duration ID (2B), address 1 (6B), address 2 (6B), address 3 (6B), sequence control (2B), 24 Byte altogether.
LLC: logic link control information, 3 Byte.
SNAP: subnetwork access protocol, totally 5 Byte, wherein ethernet type is described the type of ethernet frame, 2 Byte.
Load: the data field of ethernet frame the longlyest can reach 2304B.
FCS: check code, 4 Byte.
Two, the full communication flow process between OBU and the RSU:
1.OBU be in deep sleep/wake up operating state all the time: deep sleep, be that RF, BBP+MAC in the wireless network card and each device on CPU and the exploitation version all are in closed condition, the duration of this state is 1s, comprise CPU startup+wireless network card and start time spent 5ms, this moment, the power consumption of whole OBU was below the 2uA; Wake operating state up, be that wireless network card and CPU are in running order, wherein wireless network card is in emission state, initiatively send one and inquire after frame, send the time spent less than 500us, power consumption 320mA changes accepting state over to then automatically to intercept the response frame of inquiring after of waiting for AP, intercept and wait for time spent 500us, power consumption 320mA.The total time spent that requires OBU to send to inquire after frame and intercept the response frame of waiting for AP is no more than 1ms, and the time requirement of inquiring after frame of AP response OBU is 500us.
2.OBU enter by deep sleep and to wake up after the operating state, initiatively send one and inquire after frame, send the time spent less than 500us, power consumption 320mA changes accepting state over to then automatically to intercept the wait frame, intercepts and waits for time spent 500us, power consumption 320mA:
If 1. do not listen to the existence of frame, then OBU changes deep sleep over to;
If 2. listen to the existence of frame, then OBU can judge this frame by frame head information (comprise the mac address information of AP or the mac address information of other OBU, and the MAC Address of the MAC Address of AP and OBU having very big difference) fully and comes from AP and still come from other OBU:
A. if from AP's, then OBU sends authentication request frames at once, change over to then and intercept wait state to receive authentication response frames from AP, stand-by period 3ms: if receive authentication response frames from AP, then OBU communicates to connect with regard to assert successfully to have set up with AP, so OBU will send the Frame that comprises the vehicle user data message at once, to carry out ensuing financial transaction; If do not receive authentication response frames from AP, then OBU just continues to send authentication request frames, changes over to then to intercept wait state to receive the authentication response frames from AP, stand-by period 3ms, this process so repeatedly, till OBU receives authentication response frames from AP.
B. if from other OBU's, then OBU sends authentication request frames at once, change over to then and intercept wait state to receive authentication response frames from AP, stand-by period 5ms: if receive authentication response frames from AP, then OBU communicates to connect with regard to assert successfully to have set up with AP, so OBU will send the Frame that comprises the vehicle user data message at once, to carry out ensuing financial transaction; If do not receive the authentication response frames from AP, then OBU just changes deep sleep over to, and restarts the process that establishes a communications link after 1s.
Concrete workflow of the present invention is as follows:
As shown in Figure 4, the wireless network card of OBU initiatively sends one and inquires after frame Probe req, time spent is below 500us, power consumption (being in emission state) is 320mA, automatically change accepting state then over to intercepting the wait frame, stand-by period 500us, power consumption (being in accepting state) is 320mA, be that OBU sends that to inquire after frame and to intercept the total time of waiting for frame be 1ms, wherein AP time spent of sending response frame requires within 500us; If do not listen to any frame in the 1ms, then wireless network card changes deep sleep state automatically over to, and the deep-sleep time is 1s, and power consumption (being in deep sleep state) is 2uA; If listen to frame in the 1ms, then OBU (comprises the mac address information of AP or the mac address information of other OBU by frame head information, and the MAC Address of the MAC Address of AP and OBU has very big difference) judge this frame and come from AP and still come from other OBU: if from AP, then OBU sends authentication request frames Authen1 at once, change over to then and intercept wait state to receive authentication response frames Authen2 from AP, stand-by period 3ms: if receive authentication response frames Authen2 from AP, then OBU communicates to connect with regard to assert successfully to have set up with AP, so OBU will send the Frame that comprises the vehicle user data message at once, to carry out ensuing financial transaction; If do not receive authentication response frames Authen2 from AP, then OBU just continues to send authentication request frames Authen1, change over to then and intercept wait state to receive authentication response frames Authen2 from AP, stand-by period 3ms, this process so repeatedly, till OBU receives authentication response frames Authen2 from AP.If from other OBU's, then OBU sends authentication request frames Authen1 at once, change over to then and intercept wait state to receive authentication response frames Authen2 from AP, why stand-by period 5ms (adopts the stand-by period bigger than 3ms herein, be to make the expense that the AP disposal ability decreases and brings in order to offset existence owing to other OBU): if receive authentication response frames Authen2 from AP, then OBU communicates to connect with regard to assert successfully to have set up with AP, so OBU will send the Frame that comprises the vehicle user data message at once, to carry out ensuing financial transaction; If do not receive the authentication response frames Authen2 from AP, then OBU just changes deep sleep over to, and restarts the process that establishes a communications link after 1s.
Claims (11)
1. one kind based on the ETC system onboard unit of WLAN and the communication means of roadside unit, and it is characterized in that: the process that board units and roadside unit establish a communications link is:
(1) board units sends to roadside unit and inquires after claim frame, interception information frame;
(2) described board units listens to information frame, sends authentication request frames to described roadside unit, intercepts the authentication response frames that roadside unit returns;
(3) described board units listens to authentication response frames, sends financial transaction information to described roadside unit.
2. as claimed in claim 1 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: step (2) is specially:
(21) if the information frame that described board units listens to is the response frame of inquiring after of roadside unit answer, enter step (22); If the information frame that described board units listens to is other board units send inquire after claim frame, enter step (23);
(22) board units sends authentication request frames to described roadside unit, intercepts the authentication response frames that roadside unit returns, if board units does not listen to authentication response frames in the time limit intercepting, repeats this step; If board units listens to authentication response frames in the time limit intercepting, enter step (3);
(23) board units sends authentication request frames to roadside unit, intercepts the authentication response frames that roadside unit returns, if board units does not listen to authentication response frames in the time limit intercepting, returns step (1); If board units listens to authentication response frames in the time limit intercepting, enter step (3).
3. as claimed in claim 1 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: in the step (1), board units sends to roadside unit at set intervals and once inquires after claim frame, intercepts the primary information frame.
4. as claimed in claim 3 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: the span of described a period of time is 0.5 to 3 second.
5. as claimed in claim 3 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: the time that claim frame is once inquired after in transmission, the time of intercepting the primary information frame was 500 microseconds less than 500 microseconds.
6. as claimed in claim 2 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: be limited to 3 milliseconds during intercepting described in the step (22), be limited to 5 milliseconds during intercepting described in the step (23).
7. as claimed in claim 1 or 2 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: inquire after claim frame, inquire after response frame, the frame structure of authentication request frames, authentication response frames comprises five parts: first is a frame head, second portion is a logic link control information, third part is a subnetwork access protocol, the 4th part is load, and the 5th part is a check code.
8. as claimed in claim 1 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: board units and roadside unit are that the channel of 6Mbps communicates by transmission rate.
9. as claimed in claim 2 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: roadside unit sends the mode of inquiring after response frame and is divided into two kinds: active mode, under the situation of inquiring after claim frame of not receiving the board units transmission, initiatively send and inquire after response frame, the time cycle of transmission is 20 milliseconds; Passive mode under the situation of inquiring after claim frame of receiving the board units transmission, is returned immediately and is inquired after response frame.
10. as claim 2 or 9 described, it is characterized in that based on the ETC system onboard unit of WLAN and the communication means of roadside unit: board units by the frame head of information frame discern described information frame be roadside unit return inquire after response frame or from the frame of other board units.
11. it is as claimed in claim 7 based on the ETC system onboard unit of WLAN and the communication means of roadside unit, it is characterized in that: described load of inquiring after claim frame comprises two parts: first is the network identity of WLAN (wireless local area network), and second portion is the speed that wireless network card is supported;
Described load of inquiring after response frame comprises six parts: the markers when first is WAP (wireless access point) transmission Beacon frame, second portion is the interval that WAP (wireless access point) sends the Beacon frame, third part is the descriptor of the ability of WAP (wireless access point), the 4th part is the network identity of WLAN (wireless local area network), the 5th part is the speed that WAP (wireless access point) is supported, the 6th part is a channel logo;
The load of described authentication request frames comprises two parts: first is the identifying algorithm sign, and second portion is the sequence number of authentication frame;
The load of described authentication response frames comprises three parts: first is the identifying algorithm sign, and second portion is the sequence number of authentication frame, and third part is the conditional code of authentication.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2006100892150A CN101123456A (en) | 2006-08-09 | 2006-08-09 | Communication method for onboard units and byroad units of ETC system based on WLAN |
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| CNA2006100892150A CN101123456A (en) | 2006-08-09 | 2006-08-09 | Communication method for onboard units and byroad units of ETC system based on WLAN |
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| CN101123456A true CN101123456A (en) | 2008-02-13 |
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| CNA2006100892150A Pending CN101123456A (en) | 2006-08-09 | 2006-08-09 | Communication method for onboard units and byroad units of ETC system based on WLAN |
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