CN102932449A - LLC (Logic Link Control) sublayer status control method and on-board unit (OBU) for dedicated short range communication - Google Patents

Abstract

The invention discloses an LLC (Logic Link Control) sublayer status control method and on-board unit (OBU) for dedicated short range communication, relating to the field of intelligent transportation. According to the method, in a connectionless and acknowledged mode, when an LLC sublayer of a road side unit (RSU) receives a command PDU (Protocol Data Unit) sending request from an application layer in an idle status, the LLC sublayer of the RSU sends a command PDU to the OBU through an MAC (Media Access Control) sublayer, then enters a waiting status, and returns to the idle status after receiving a correct response PDU from the OBU; and when an LLC sublayer of the OBU receives the command PDU sent by the RSU in a ready status, the LLC sublayer of the OBU selectively carries out status transition processes of multiple preset status transition processes according to the received command PDU and then returns to the ready status. Various status transition situations are set in a manner that standardized events and actions are combined with specific events and actions, and the status transition processes are divided into normal response processing, delayed response processing, abnormal response processing and retransmission response processing.

Description

LLC sublayer condition control method and the board units of Dedicated Short Range Communications,

Technical field

The present invention relates to electric non-stop toll (the Electronic Toll Collection of intelligent transportation system, be called for short ETC) the systems technology field, relate in particular to a kind of Dedicated Short Range Communications, (DSRC for the ETC system, Dedicated Short Range Communications, abbreviation DSRC) logic link control (LLC, Logic Link Control) sublayer condition control method and the board units of agreement.

Background technology

Along with the highway mileage open to traffic constantly increases, the continuous progress of toll collection technique, a lot of provinces and cities of China have all built highway electric non-stop toll) system.Compare with the manual toll collection mode, electric non-stop toll can improve speed greatly, reduces vehicle queue waiting time, alleviation traffic congestion situation and minimizing toxic emission.

The core feature of ETC system is (or to claim roadside unit by the ETC antenna of charge station, Road Side Unit, be called for short RSU) and the vehicle that misses the stop on vehicle carried electronic label (or the title board units installed, On Board Unit, abbreviation OBU) mode by radio communication realizes the charging transaction, and communication protocol adopts dedicated short-range communication.

Dedicated Short Range Communications, is one of important basic communication protocol in the intelligent transportation system field, is widely used in road electric non-stop toll, Vehicular traffic information service, traffic information collection, and the field such as vehicle public safety service.In May, 2007, China issuing and implementation GB/T 20851 serial Dedicated Short Range Communications, national standards, the electronic toll system and the product that meet afterwards this standard are widely used.

The traffic model of DSRC agreement mainly is comprised of application layer, data link layer and physical layer, wherein data link layer is mainly used in setting up reliably communication between the communication entity, by medium access control (MAC, MediaAccess Control) sublayer and logic link control (LLC, Logic Link Control) sublayer forms.The major function of media access control sublayer comprises reception and transmission, the management of link and the error control of frame etc. of the addressing of the encapsulation of Frame/remove stage makeup and costume, frame and identification, frame, the LLC sublayer is then for generation of the bidding protocol data cell (PDU that is used for transmission, and explain order PDU and the response pdus that receives Protocol Data Unit) and response pdus.

The DSRC standard that exists in the world at present mainly contains Europe, the U.S., Japan and Chinese four kinds.The pre-standard of DSRC " ENV 12795 data link layers " of the European standard committee (CEN) in 1997 promulgation, service primitive and the protocol procedures element that should realize the LLC sublayer have carried out some descriptions, and be described with reference to " IEEE 802.2: logic link control (LLC) " state machine to DSRC LLC sublayer, but it is described and imperfection, and is also not fully up to expectations by the efficient of its realization.For those reasons, CEN is when promulgating formal DSRC data link layer standard EN 12795 in 2004, removed the state machine of LLC sublayer and described, thereby made more refining of received text, clear, but the logic and the function that no longer the LLC sublayer are realized are made unified regulation.China had promulgated electronic charging DSRC national standard in 2007, based on same reason, also the specific implementation of LLC sublayer was not explained.Board units adopts the two-piece type electronic tag in Chinese Industrial Standards (CIS), namely is comprised of vehicle carried electronic label and IC-card two parts, and wherein the IC-card service speed is lower.In this case, such problem will inevitably occur: roadside unit is given an order, and needs board units to respond, and has comprised very complicated encryption and decryption operation in the process of board units execution this moment roadside unit order, and response speed is slower.If according to the pre-standard in Europe or Nippon Standard, need to return response data in the period at the T3 ~ T3+T4a of regulation, this is that the low speed IC-card institute of Chinese national standard is irrealizable.Therefore, the standard of other countries or pre-standard can not be fit to the situation of China fully.Among the present invention this has clearly been provided the low speed data implementation.

Patent of invention CN101848233A has proposed the logical link control method based on LLC sub layer of on board unit of Chinese standard ETC system, has wherein adopted special logic to realize the LLC sublayer according to Chinese national standard.But, there is such defective in CN101848233A: the logical link control method that wherein proposes only is the LLC control of substate method of board units, and do not stipulate the LLC control of substate method of roadside unit, therefore also imperfect, and, this control method is to adopt special logic to realize, and is comparatively simple, and is not suitable for carrying out comparatively complicated control.

Summary of the invention

For the problems referred to above of the prior art, the present invention is based on the design standard of other countries and the GB of China, proposed further additional and perfect at the LLC sublayer of above-mentioned two kinds of standards logical link control method, the board units LLC control of substate method of suitable CNS (being called for short " GB ") and the complete scheme of roadside unit LLC control of substate method have been proposed, simultaneously, often there are the actual conditions that postpone in this control method for the board units response of China, has proposed effective solution.In addition, this control method not only can be come Design and implementation by hardware (chip), and can be realized by software, can realize comparatively complicated control function, and significant for reducing somersault and power consumption.

The invention provides a kind of LLC sublayer condition control method of Dedicated Short Range Communications, of intelligent transportation field.It not only can adapt to the slower national conditions of response speed of two-piece type electronic tag board units, and not only can come Design and implementation but also can have been realized by software by hardware (chip), can realize comparatively complicated control function, and significant for reducing somersault and power consumption.

The present invention also provides a kind of Dedicated Short Range Communications, of intelligent transportation field employed board units.The LLC sublayer of this board units is designed to, even can not in time return the situation of response data, also can be with this advisory to roadside unit, and very fast in the time can meeting with a response data response data is offered roadside unit.

A kind of LLC sublayer condition control method of the Dedicated Short Range Communications, for intelligent transportation field is provided according to an aspect of the present invention.Wherein, connect without under the affirmation mode in nothing, when the LLC sublayer of roadside unit and board units receives the other side's order PDU via the MAC layer under ready state, should order PDU to transfer to application layer to be processed by application layer, and, when the order PDU that receives application layer sends request, send this order PDU by media access control sublayer.Be connected with under the affirmation mode in nothing, the LLC sublayer of roadside unit receives application layer under idle condition order PDU sends when asking, send this order PDU by media access control sublayer to board units, enter subsequently wait state, after receiving the correct response pdus of board units, get back to idle condition; When the LLC sublayer of board units received the order PDU that roadside unit sends via media access control sublayer under ready state, according to the order PDU that receives, selectivity carried out getting back to ready state after state transitions is processed from default various states transfer processing.Wherein, various state transitions situations are set with moving the specific event of combination and action by standardized event, beam back different response pdus to roadside unit respectively, the processing of these state transitions is divided into: normal response is processed, wherein, the timely processing command PDU in the LLC sublayer of board units; Delayed response is processed, and wherein, the LLC sublayer of board units can processing command PDU, but response speed is slower; Exception response is processed, and wherein, the reception of order PDU is wrong, and perhaps the LLC sublayer of board units can not processing command PDU; And the re-transmission response is processed, wherein, order PDU is retransferring of a upper order that transmitted, and, wherein, process according to default various states transfer case according to current residing state, from the order PDU of application layer reception and the response pdus that receives from board units the LLC sublayer of described roadside unit, and various state transitions situations are set with moving the specific event of combination and action by standardized event.Wherein, described standardized event and action are event primitive and the primitive acts of regulation in DSRC GB GB/T 20851.2-2007.

A kind of board units of the Dedicated Short Range Communications, for intelligent transportation field is provided according to a further aspect in the invention.This board units is divided into physical layer, data link layer and application layer, and data link layer comprises LLC sublayer and media access control sublayer, and wherein, the LLC sublayer comprises: interface unit is used for carrying out data with media access control sublayer and application layer and transmits; Control unit is used for the operation of control LLC sublayer; And buffer cell.Wherein, connect without under the affirmation mode in nothing, under the control of control unit, when the LLC sublayer of described board units receives the order PDU of roadside unit via interface unit from the MAC layer under ready state, should order PDU to transfer to application layer to be processed by application layer via interface unit, and, when the order PDU that receives application layer via interface unit sends request, send this order PDU via interface unit by media access control sublayer.Be connected with under the affirmation mode in nothing, when the LLC sublayer of described board units receives the order PDU that roadside unit sends via interface unit from media access control sublayer under ready state, under the control of control unit, according to the order PDU that receives, selectivity carries out getting back to ready state after state transitions is processed from default various states transfer processing; Wherein, various state transitions are processed by standardized event and are set with moving the specific event of combination and action, beam back different response pdus to roadside unit respectively, the processing of these state transitions is divided into: normal response is processed, wherein, the timely processing command PDU in the LLC sublayer of board units; Delayed response is processed, and wherein, the LLC sublayer of board units can processing command PDU, but processing speed is slower; Exception response is processed, and wherein, the reception of order PDU is wrong, and perhaps the LLC sublayer of board units can not processing command PDU; And retransmit the response processing, wherein, order PDU is retransferring of a upper order that transmitted.Wherein, described standardized event and action are event primitive and the primitive acts of stipulating in DSRC GB GB/T 20851.2-2007.

According to above-mentioned LLC sublayer condition control method, perhaps according to above-mentioned board units, wherein, the delayed response of board units is processed and is comprised following processing: event RECEIVE_ACn_CMD (SQC=V (RI) occurring, P=1, INFO＜〉NULL), RECEIVE_STATUS ()=OK and ACCESS ()＜〉during OK, namely, when the order PDU that receives retransmits order, need to fetch data from board units, information field is not empty, the information field of order PDU receives successfully, and the order PDU response data of asking is when still unavailable, take to move DELETE_SAVE_BUFFER, REPLY_INDICATION (LSDU=INFO), and SEND_ACn_RSP (SQR=1-SQC, F=1, C=OK, R=NE, LSDU=NULL), be the data of storing in the LLC sublayer deletion buffer cell of board units, send the data among the order PDU to application layer, data in the information field of response pdus are set to sky, and described responsive state designator is set to indicate response data not yet to submit to, simultaneously, the LLC sublayer waits for that application layer provides data.

And, wherein, the LLC sublayer of board units will ordered after data among the PDU send application layer to, wait for that application layer provides data, until event REPLY_UPDATE_REQUEST occurs, be that the data that application layer is asked to LLC sublayer notice are stored this data in ready and indication LLC sublayer, SAVE:=GIVEN_LSDU and REPLY_UPDATE_STATUS_INDICATION are taked to move in the LLC sublayer after being notified, namely receive the data ask and described data are stored in the buffer cell, and the notice application layer is upgraded.

Be a kind of complete control method of suitable Chinese national standard according to LLC of the present invention sublayer condition control method, and it can tackle the actual conditions that often there is operating lag in China's board units, and mistake can not occur.

Board units according to the present invention is the board units of existing regulation in a kind of suitable Chinese national standard, even can not in time return response data, it also can with this situation in time notice and very fast in the time can meeting with a response data response data is offered roadside unit to roadside unit.

Description of drawings

Fig. 1 is the synoptic chart of board units and roadside unit communication system.

Fig. 2 is the structural representation of board units LLC sublayer.

Fig. 3 is the state transition diagram of LLC1 assembly.

Fig. 4 is the state transition diagram of LLC3 receiving unit.

Fig. 5 is the state transition diagram of LLC3 sending assembly.

Embodiment

The relevant regulations that the present invention is based among the DSRC GB GB/T 20851.2-2007 is made, and therefore, the understanding of the present invention can be carried out with reference to GB/T 20851.2-2007.

Referring to Fig. 1, the invention provides a kind of LLC sublayer condition control method of the Dedicated Short Range Communications, for intelligent transportation field.Here, the information exchange between board units OBU and the roadside unit RSU has two kinds of patterns: without connecting without affirmation mode (Class1); Be connected with affirmation mode (type 3) with nothing.One of Class1 operating provision has the service without connection nothing affirmation mode of minimal protocol complexity, that is, do not confirm when board units and roadside unit receive information.The Class1 operational order is called again the UI(unnumbered information) order.Nothing of type 3 operating provisions is connected with the data cell Exchange Service of affirmation mode, and it allows a website to ask again response when transmitting data, that is, need to confirm when board units and roadside unit receive information.Type 3 operational orders and response are called again the ACn command and response.

According to this control method, connect without under the affirmation mode in nothing, when the LLC sublayer of roadside unit and board units receives the other side's order PDU via the MAC layer under ready state, should order PDU to transfer to application layer to be processed by application layer, and, when the order PDU that receives application layer sends request, send this order PDU by media access control sublayer.Be connected with under the affirmation mode in nothing, the LLC sublayer of roadside unit receives application layer under idle condition order PDU sends when asking, send this order PDU by media access control sublayer to board units, enter subsequently wait state, after receiving the correct response pdus of board units, get back to idle condition; When the LLC sublayer of board units received the order PDU that roadside unit sends via media access control sublayer under ready state, according to the order PDU that receives, selectivity carried out getting back to ready state after state transitions is processed from default various states transfer processing; Wherein, the various state transitions of the LLC sublayer of described board units are processed by standardized event and are set with moving the specific event of combination and action, beam back different response pdus to roadside unit respectively, the processing of these state transitions is divided into: normal response is processed, wherein, the timely processing command PDU in the LLC sublayer of board units; Delayed response is processed, and wherein, the LLC sublayer of board units can processing command PDU, but processing speed is slower; Exception response is processed, and wherein, the reception of order PDU is wrong, and perhaps the LLC sublayer of board units can not processing command PDU; And the re-transmission response is processed, wherein, order PDU is retransferring of a upper order that transmitted, and, wherein, the order PDU that the LLC sublayer of described roadside unit receives according to current residing state, from application layer and the response pdus that receives from board units are set with the various states transfer case, and various state transitions situations are set in conjunction with specific event and action by standardized event and action.

And, referring to Fig. 2, the invention provides a kind of board units of the Dedicated Short Range Communications, for intelligent transportation field, this board units is divided into physical layer, data link layer and application layer, data link layer comprises LLC sublayer and media access control sublayer, wherein, the LLC sublayer comprises: interface unit is used for carrying out data with media access control sublayer and application layer and transmits; Control unit is used for the operation of control LLC sublayer; And buffer cell.Wherein, connect without under the affirmation mode in nothing, under the control of control unit, when the LLC sublayer of described board units receives the order PDU of roadside unit via interface unit from the MAC layer under ready state, should order PDU to transfer to application layer to be processed by application layer via interface unit, and, when the order PDU that receives application layer via interface unit sends request, send this order PDU via interface unit by media access control sublayer.And, be connected with under the affirmation mode in nothing, when the LLC sublayer of described board units receives the order PDU that roadside unit sends via interface unit from media access control sublayer under ready state, under the control of control unit, according to the order PDU that receives, selectivity carries out getting back to ready state after state transitions is processed from default various states transfer processing.Wherein, various state transitions are processed by standardized event and are set with moving the specific event of combination and action, beam back different response pdus to roadside unit respectively, the processing of these state transitions is divided into: normal response is processed, wherein, the timely processing command PDU in the LLC sublayer of board units; Delayed response is processed, and wherein, the LLC sublayer of board units can processing command PDU, but processing speed is slower; Exception response is processed, and wherein, the reception of order PDU is wrong, and perhaps the LLC sublayer of board units can not processing command PDU; And retransmit the response processing, wherein, order PDU is retransferring of a upper order that transmitted.

Below the structure of this control method and board units LLC sublayer is specifically described.

1, without connecting without affirmation mode (Class1)

Connect without under the affirmation mode in nothing, when the LLC sublayer of roadside unit and board units receives the other side's order PDU via the MAC layer under ready state, should order PDU to transfer to application layer to be processed by application layer, and, when the order PDU that receives application layer sends request, send this order PDU by media access control sublayer.

Specifically, owing to connect without the information that receives not being confirmed under the affirmation mode in nothing, therefore comparatively simple without the control under the affirmation mode without connecting, its control method can be regarded as by Class1 assembly (can be described as again " without connecting without the affirmation mode assembly ") and undertaken: this assembly is responsible for request transmission types 1 order according to application layer; The Class1 order that processing receives from media access control sublayer, and it is handed to application layer.

In the LLC sublayer, the Class1 assembly is responsible for sending/receiving for all types 1LPDU(logical protocol data cell of certain particular link address).Request according to LLC user, the Class1 assembly sends UI order PDU(protocol Data Unit) to one (being present in the upstream or downstream link) or a plurality of (only being present in down link) far-end SAP(service access unit), nationality is to transmit a service data unit.After receiving UI order PDU, far-end SAP need not to confirm.

The state-transition table of Class1 assembly is as shown in table 1, co-exists in the two states transfer case.

Table 1: Class1 component states transfer table

READY(is ready) be unique state of Class1 assembly.Under this state, SAP can receive the order PDU with transmission types 1.The state transition diagram of this assembly as shown in Figure 2.

State transitions in the upper table is described as follows:

State transitions 1: the Class1 assembly receives an opposite end LSAP(Connection Service accessing points) UI that sends order

PDU, and it is transferred to application layer.

State transitions 2: the Class1 assembly receives application layer UI order and sends request, and sends this order by media access control sublayer.

Event in the upper table and action are event primitive and the primitive acts of regulation in DSRC GB GB/T 20851.2-2007, only provide schematic illustration here.Event description is as follows:

(1) a MA-DATA.indication primitive has been transmitted in the RECEIVE_UI:MAC sublayer to the LLC sublayer, has wherein comprised UI order PDU.

(2) UNITDATA_REQUEST: application layer has been transmitted a DL-UNITDATA.request primitive to the LLC sublayer.

Action description in the upper table is as follows:

(1) UNITDATA_INDICATION: comprise the DL-UNITDATA.indication primitive of LSDU to one of application layer transmission, the content of this LSDU is equal to the UI order PDU information field corresponding with it that receives before this.

(2) TRANSMIT_UI: transmit a MA-DATA.request primitive that comprises UI order PDU to media access control sublayer.At the RSU end, the response request of DL-UNITDATA.request service primitive (Response Request) parameter should pass to media access control sublayer by the RR parameter of F-MA-DATA.request service primitive.

2, without being connected with affirmation mode (type 3)

Be connected with under the affirmation mode in nothing, the LLC sublayer of roadside unit receives application layer under idle condition order PDU sends when asking, send this order PDU by media access control sublayer to board units, enter subsequently wait state, after receiving the correct response pdus of board units, get back to idle condition; When the LLC sublayer of board units receives the order PDU that roadside unit sends via media access control sublayer under ready state, carry out getting back to ready state after certain state transitions is processed.Wherein, the LLC sublayer of described board units is according to the order PDU that receives, be set with the various states transfer case, various state transitions situations are set with moving the specific event of combination and action by standardized event, the processing of these state transitions is divided into: normal response is processed, wherein, the LLC sublayer of board units can in time respond to order PDU; Delayed response is processed, and wherein, the LLC sublayer of board units can respond to order PDU, but response speed is slower; Exception response is processed, and wherein, the reception of order PDU is wrong, and perhaps the LLC sublayer of board units can not processing command PDU; And retransmit the response processing, wherein, order PDU is retransferring of a upper order that transmitted.And, wherein, the LLC sublayer of described roadside unit is according to current residing state, from the order PDU of application layer reception and the response pdus that receives from board units, be set with the various states transfer case, various state transitions situations are set with moving the specific event of combination and action by standardized event.

The control method of type 3 can regard as by type 3 sending assemblies and type 3 receiving units (can be described as again " and without be connected with the affirmation mode sending assembly and without being connected with the affirmation mode receiving unit ") carry out.In ETC DSRC standard, in order to simplify the realization of system, usually according to the equipping rules of " master slave mode ", only allow RSU initiatively to send the ACn order, OBU can only respond according to the ACn order that RSU sends.We are called for short this pattern and are " the DSRC pattern of simplification ".Like this, in RSU, only there are type 3 sending assemblies, in OBU, only have type 3 receiving units.Therefore, type 3 sending assemblies can be described as again " RSU assembly ", and type 3 receiving units can be described as again " OBU assembly ".Type 3 receiving units are responsible for processing type 3 orders that receive from media access control sublayer, and the response of return type 3 is to the person of sending of this order.At the RSU end, LLC is that each dedicated link address (each OBU in the corresponding communication zone) provides independently type 3 receiving units.At the OBU end, LLC can only have type 3 receiving units at synchronization.Type 3 sending assemblies are responsible for request transmission type 3 orders according to application layer, and process type 3 responses that receive from media access control sublayer.At the RSU end, LLC is that each dedicated link address (each OBU in the corresponding communication zone) provides independently type 3 sending assemblies.At the OBU end, LLC can only have type 3 sending assemblies at synchronization.

2.1 type 3 receiving units (OBU assembly)

Type 3 receiving units are responsible for receiving the ACn order from far-end LLC, and return corresponding ACn response.On each dedicated link address corresponding with received type 3 order PDU type 3 receiving units are arranged, and this assembly only has a kind of state, namely READY(is ready) state.LLC can type of receipt 3PDU under this state, and it is confirmed.The state transition diagram of this assembly as shown in Figure 3.

LLC is when responding, and according to the regulation of DSRC GB, the necessary operation of each state transition process all will be finished in certain time interval (link samsara time T 3).

All state informations of assembly are included in the state variable.When the order PDU that each receiving unit check repeats or the previous state that receives, all use the receiving sequence state variable V (RI) of oneself and receive success or failure state variable V (RB).

At the OBU end, there are and only have type 3 receiving units.

The LLC sublayer of board units is according to the order PDU that receives, be set with the various states transfer case, various state transitions situations are set with moving the specific event of combination and action by standardized event, and its processing can be divided into: normal response processing, delayed response processing, exception response are processed and re-transmission responds processing.

2.1.1 normal response is processed

In time in the situation of processing command PDU, the OBU assembly carries out normal response to be processed in the LLC sublayer of board units.

Normal response is processed and is comprised following state transitions:

State transitions 1: this state transitions is RSU sends routine operation (the DL-DATA-ACK primitive of stipulating in the Application standard) from data to OBU.

State transitions 2: this state transitions be RSU from OBU between exchanges data (INFO＜〉NULL) routine operation (different with statement among ENV 12795 and the ARIB STD-T75), INFO is the data that send to OBU.The DSRC agreement has only been stipulated two kinds of data delivery service between RSU and the OBU: confirm that 1. connectionless-mode data delivery service (DL-DATA-ACK)---RSU sends out data to OBU; 2. confirm that connectionless-mode data exchange service (DL-REPLY)---RSU says the word data to OBU, and fetch response data from OBU.Do not allow RSU only to fetch data (INFO=NULL) from OBU, so necessary restriction INFO＜NULL.In day Europe superscript standard, there is in this mistake, do not stipulate that INFO can not be sky, the regulation of this and China GB GB/T 20851.2-2007 requires and is incompatible.Finish in the situation of delayed response with application layer retransmission data request command, the SAVE operation is only returned " Processing " conditional code from application layer to the LLC sublayer.

More particularly, event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=0, INFO＜〉NULL) during and RECEIVE_STATUS ()=OK, namely, when the order PDU that receives retransmits order, need not to fetch data and information field for empty from board units, and the information field of order PDU is when receiving successfully, DATA_ACK_INDICATION and SEND_ACn_RSP (SQR=1-SQC are taked to move in the LLC sublayer of board units, F=0, C=OK, R=NR, LSDU=NULL), namely, the LLC sublayer of board units will order the data message among the PDU to send application layer to, and the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit; And

Event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=1, INFO＜〉NULL), when RECEIVE_STATUS ()=OK and ACCESS ()=OK, namely, when the order PDU that receives retransmits order, need to fetch data from board units, information field is not empty, the information field of order PDU receives successfully, and but the response data that order PDU asks exists and the time spent, DELETE_SAVE_BUFFER is taked to move in the LLC sublayer of board units, REPLY_INDICATION (LSDU=INFO), SAVE:=GIVEN_LSDU, REPLY_UPDATE_STATUS_INDICATION and SEND_ACn_RSP (SQR=1-SQC, F=1, C=OK, R=OK, LSDU=SAVE), be the data of storing in the LLC sublayer delete buffer of board units, send the data among the order PDU to application layer, the data that application layer is provided are stored in the described buffering area, the notice application layer is upgraded, the data that are stored in buffering area are sent back to roadside unit as the data in the information field of response pdus, and the responsive state designator in the state subdomain of the information field of response pdus is set to indicate and has comprised the data of asking.

About the various functions such as ACCESS () that here occur and will occur hereinafter, such as the event of RECEIVE_ACn_CMD and parameters and such as action and parameters such as SEND_ACn_RSP, carry out in the lump simple explanation at this, its detailed description can be referring to the relevant regulations among the DSRC GB GB/T 20851.2-2007.

(A) power function is described

The return value of following function function is for event being limited or providing protocol action needed value.

(1) RECEIVE_STATUS (): return result to the order PDU information field that receives and be successfully or failed indication, namely return CCCC part in the LLC status field of this order of response.

(2) ACCESS (): whether the response that return command PDU asks (LSDU) is current available, namely returns RRRR part in the LLC status field that responds this order.

(B) event description

In the state transition table of receiving unit, event is by following condition identification.Only have ready conditions and just confirm this event for true time and occur.

(1) REPLY_UPDATE_REQUEST: application layer has been transmitted a DL-REPLY-UPDATE.request primitive to the LLC sublayer.

(2) RECEIVE_ACnCMD (SQC, P, INFO): media access control sublayer has transmitted a MA-DATA.indication primitive to the LLC sublayer, wherein comprises an ACn order PDU.

The 8th bit of the command sequence bit SQC(LLC control domain in the LLC control domain, that is n bit) when being the AC0 order, PDU is " 0 ", when being the AC1 order, PDU is " 1 ".There is following possible parameter value in present event:

The value of SQC=V (RI) SQC equals V (RI) state variable of this receiving unit, perhaps this V (RI) shape

State variable does not exist.This shows that order PDU is not the order that retransfers, but

The order that transmits first.

SQC＜V (RI) state variable of this receiving unit of V (RI) exists, and and the value of SQC unequal.

This shows that order PDU is the order that retransfers.The LLC sublayer of board units exists

After receiving first a PDU order, V (RI) state variable of self can be put

Be the radix-minus-one complement of the SQC in the PDU order, therefore, if this PDU order is by heavy

The new transmission, V (RI) state variable of the LLC sublayer of that board units exist and also with

SQC in this PDU order is different, and this just shows that order PDU retransfers

Order.

P bit in the P=0 LLC control domain is " 0 ".This show order PDU be roadside unit to

Board units sends data.

P bit in the P=1 LLC control domain is " 1 ".This shows that order PDU is roadside unit

With the board units swap data.

Information field in the INFO=NULL order is empty (length is 0).

INFO＜〉information field non-NULL in the NULL order.

Information field in the INFO order be sky (=NULL), perhaps non-NULL (＜〉NULL).

(3) RECEIVE_STATUS ()=OK: the information field among the order PDU receives successfully and can be delivered to the user.

(4) RECEIVE_STATUS ()＜OK: the information field of order among the PDU takes defeat and maybe can not be delivered to the user.

(5) ACCESS ()=OK: the response LSDU that order PDU asks exists and is available.

(6) ACCESS ()＜OK: the response LSDU that asks of order PDU does not exist; Perhaps this LSDU exists but can't access.

(C) action description

(1) SAVE:=GIVEN_LSDU: the LSDU that DL-REPLY-UPDATE.request primitive is provided leaves in the SAVE buffering area of LLC sublayer, makes it be in the transmission ready state.The position of SAVE buffering area is associated with LSAP in this primitive, and new LSDU will replace any LSDU that this LSAP holds before this.

(2) SEND_ACn_RSP (SQR, F, C, R, LSDU): transmitted a MA-DATA.request primitive to media access control sublayer, wherein comprised an ACn response pdus.

The 8th bit of the response sequence bit SQR(LLC control domain in the LLC control domain, that is n bit) when being the AC0 response, PDU is " 0 ", when being the AC1 response, PDU is " 1 ".There is following parameter value in this action:

The SQC radix-minus-one complement that SQR=1-SQC SQR is set to receive.

The F bit of F=0 LLC control domain is set to " 0 ".

The F bit of F=1 LLC control domain is set to " 1 ".

The CCCC of C=OK LLC state subdomain partly is set to code " OK "

(receiving successfully).

The CCCC of C=RECEIVE_STATUS () LLC state subdomain partly is set to

The return value of RECEIVE_STATUS power function.

The CCCC of C=V (RB) LLC state subdomain partly is set to and receives

V (RB) state variable that the link address of order PDU is relevant

Value.

The RRRR of R=NR LLC state subdomain partly is set to code " NR "

(not request response LSDU).

The RRRR of R=NE LLC state subdomain partly is set to code " NE "

(not submitting response LSDU to).By this state indication, road

Side unit can know clearly that the data of asking are not yet ready, still

Need to wait for.

The RRRR of R=RS LLC state subdomain partly is set to code " RS " (no

Can carry out or unactivated service).By this state indication, road

Side unit can know clearly that the order PDU that sends is not yet

The function of enabling is not still supported at present.

The RRRR of R=OK LLC state subdomain partly is set to code " OK "

(response data comprises).By this state indication, trackside list

Unit can know clearly that the data of asking have been included in response

Among the PDU.

The RRRR of R=ACCESS () LLC state subdomain partly is set to the ACCESS merit

The return value of energy function.

LSDU subdomain in the LSDU=NULL LLC response is empty (length is 0).

LSDU subdomain in the LSDU=SAVE response has comprised and has been kept at this LSAP's

The LSDU that is in ready state in the SAVE buffering area.

Annotate: in RSU, the media time slot that is used for the OBU response should follow the ACn order closely and distribute immediately afterwards.

(3) the DATA_ACK_INDICATION:LLC sublayer comprises the DL-DATA-ACK.indication primitive of LSDU to one of application layer transmission, and this LSDU is the order PDU information field that receives.

(4) REPLY_INDICATION (LSDU): a DL-REPLY.indication primitive is transmitted to application layer in the LLC sublayer.There is following parameter value in this action:

LSDU=INFO transmits a LSDU to application layer, and this LSDU is the order PDU that receives

Information field (this territory may be sky).

LSDU=NULL transmits the LSDU of a sky to application layer.

(5) a DL-REPLY-UPDATE-STATUS.indication primitive is transmitted to application layer in the REPLY_UPDATE_STATUS_INDICATION:LLC sublayer.

(6) V (RI) :=1-SQC: the radix-minus-one complement of SQC among the order PDU that the V in the receiving unit (RI) state variable is set to receive.

(7) V (RB) :=OK: the V of receiving unit (RB) state variable is set to code " OK " (receiving successfully).

(8) V (RB) :=RECEIVE_STATUS (): the V of receiving unit (RB) state variable is set to the return value of RECEIVE_STATUS power function.

(9) DELETE_SAVE_BUFFER: the data in the deletion SAVE buffering area, perhaps sign data wherein are " using/invalid ".In conjunction with above and following state-transition table as can be known, state transitions 2,3 o'clock, when namely receiving roadside unit and needing the non-re-transmission order of swap data, this action was taked in the LLC sublayer of board units.Thus, send to roadside unit with can avoiding the error in data of will last time ask.

2.1.2 delayed response is processed

Can processing command PDU in the LLC sublayer of board units, but processing speed is slower, and in the situation about can not finish within the link samsara time of regulation, the OBU assembly carries out delayed response to be processed.

Delayed response is processed and is comprised following state transitions:

State transitions 3: this state transitions occurs when using the ACn order delayed response to occur, and the data of asking this moment are unavailable (unripe) still.From statement is different in Europe superscript and day mark be, use DL-REPLY.indication primitive herein, rather than DL-DATA-ACK.indication primitive.Reason is, be RSU will with the OBU swap data, what the RSU end sent is the DL-REPLY.requeset instruction, according to national standard, the nature that OBU end is used to indicate should be that DL-REPLY.indication(is when sending instructions under application layer, lowControl has clear to the Flow Control parameter F, referring to the 6.2.4.8 data flow con-trol of APP layer standard).This just meets the link samsara of the regulation of standard " general introduction of 9.2.2 reciprocal process ", and should not use DL-DATA-ACK.indication.In addition, the RRRR of LLC status field partly is designated as " response LSDU never (by the upper strata) submits to ", and namely R=NE thus, notifies roadside unit delayed response to occur, simultaneously, waits for that application layer provides data.

State transitions 4:LLC receives the sublayer DL-REPLY-UPDATE request of sending from LLC sublayer user (APP layer), and request LLC preserves a LSDU in the sublayer, is used for transmission request after a while.

In the situation of state transitions " delayed data response ", the data of the previous request of application layer notice are ready, and it is stored in the SAVE buffering area of LLC sublayer.According to the difference of specific implementation, OBU will utilize the next ACn command request that retransmits or utilize a UI to order to send the data that are stored in the SAVE buffering area.

More particularly, event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=1, INFO＜〉NULL), RECEIVE_STATUS ()=OK and ACCESS ()＜〉during OK, namely, when the order PDU that receives retransmits order, need to fetch data from board units, information field is not empty, the information field of order PDU receives successfully, and the order PDU response data of asking is when still unavailable, take to move DELETE_SAVE_BUFFER, REPLY_INDICATION (LSDU=INFO), and SEND_ACn_RSP (SQR=1-SQC, F=1, C=OK, R=NE, LSDU=NULL), the data of namely storing in the LLC sublayer delete buffer of board units send the data among the order PDU to application layer, data in the information field of response pdus are set to sky, and described responsive state designator is set to indicate response data not yet to submit to.Simultaneously, the LLC sublayer waits for that application layer provides data, until event REPLY_UPDATE_REQUEST occurs, be that the data that application layer is asked to LLC sublayer notice are stored this data in ready and indication LLC sublayer, SAVE:=GIVEN_LSDU and REPLY_UPDATE_STATUS_INDICATION are taked to move in the LLC sublayer after being notified, namely receive the data ask and described data are stored in the buffering area, and the notice application layer is upgraded.

Here, when the response data of ordering PDU to ask is still unavailable, the data of storing in the LLC sublayer delete buffer of board units, perhaps sign data wherein are " using/invalid ".Like this, send to roadside unit with can avoiding the error in data of will last time ask.And in response pdus, the LLC sublayer responsive state designator of board units is set to indicate response data not yet to submit to, by this state indication, roadside unit can know clearly that the data of asking are not yet ready, still need wait for, and can not make error understanding to response data.Simultaneously, when the data of asking to LLC sublayer notice in application layer were ready, the LLC sublayer can utilize the next ACn command request that retransmits or utilize a UI to order to send the data that are stored in the SAVE buffering area after the storage data.Like this, even can not in time return response data, the LLC sublayer of board units also can with this situation in time notice and very fast in the time can meeting with a response data response data is offered roadside unit to roadside unit.

According to above state transitions 2,3,4 as seen, according to type 3 receiving units of the present invention, namely the OBU assembly can be tackled the situation of roadside unit requirement swap data well.In this case, the past data that at first store in the delete buffer LLC sublayer of board units of the present invention, then will be stored in from the response data that application layer receives the buffering area, the data that can guarantee thus to send to roadside unit are data that roadside unit is asked, avoid with previous error in data send to roadside unit.And, can't in time return in the situation of institute's request msg at board units, the LLC sublayer of board units notifies the roadside unit response data not yet to submit in response pdus, and very fast in the time can meeting with a response data response data being offered roadside unit, this also is that other prior aries institutes are irrealizable.

Process about delayed response, the applicant has carried out more detailed explanation in another application, and those skilled in the art can carry out reference.

2.1.3 exception response is processed

In the LLC sublayer of the wrong or board units of reception of order PDU can not the situation of processing command PDU, the OBU assembly carries out exception response to be processed.

Exception response is processed and is comprised following state transitions:

State transitions 5: expression OBU has received again synchronously (Re-Synchronisation) order.The DSRC agreement realizes not supporting this kind command mode, so carry out the mistake indication with this response.Here, the RRRR with the LLC status field partly is set to be designated as unrealized or unactivated service, i.e. R=RS.And with reference to the regulation of IEEE 802.2 R=NR is set in Japan, European standard, expression " success, not request response LSDU ", and do not comprise this function in the DSRC agreement, therefore standard the regulation here in Japan and Europe is incorrect.

State transitions 6,7,9: these three transfers all belong to abnormal conditions, because the order that receives is wrong (RECEIVE_STATUS ()＜〉OK), might send wrong instruction by RSU, might be mistake to have occurred in the order data transmission course.Board units returns the response that there is the reception mistake in indication to roadside unit in these three kinds of situations.

State transitions 8: this state transitions is RSU only obtains data (INFO=NULL) from OBU situation, this DSRC agreement realizes not supporting this state transitions, so carry out the mistake indication with this response, the RRRR of LLC status field partly is designated as unrealized or unactivated service, i.e. R=RS.

More particularly, occur event RECEIVE_STATUS ()＜during OK, namely when the information field to order PDU takes defeat, SEND_ACn_RSP (SQR=1-SQC, F=0, C=RECEIVE_STATUS () are taked to move in the LLC sublayer of board units, R=NR, LSDU=NULL), namely in the response pdus that sends to roadside unit, the accepting state designator in the state subdomain of information field is set to take defeat; And,

When event RECEIVE_STATUS ()=OK and RECEIVE_ACn_CMD (INFO=NULL) occurring, namely when but board units receives successfully information field and is sky the information field of order PDU, board units takes to move SEND_ACn_RSP (SQR=1-SQC, F=0, C=OK, R=RS, LSDU=NULL), namely in the response pdus that sends to roadside unit, the responsive state designator in the state subdomain of information field is set to service and not yet activates.This is the situation that the DSRC agreement is not supported.

2.1.4 retransmitting response processes

That the OBU assembly retransmits response and processes in the situation about retransferring of the order that once transmitted at the order PDU that receives.

Retransmit the response processing and comprise following state transitions:

State transitions 10: receive and retransmit order (repetition of state transitions 1 or state transitions 5), will cause the DLL that retransmits a sky to confirm Frame.

State transitions 11: receive and retransmit order (repetition of state transitions 2), will retransmit and carry the to some extent responsive data frame of the data of request.

State transitions 12: receive and retransmit order (repetition of state transitions 3 or state transitions 8), will cause the DLL that retransmits a sky to confirm Frame.

More particularly, event RECEIVE_ACn_CMD (SQC＜〉V (RI), P=0, INFO are appearring) time, namely when order PDU when retransmitting order and need not to fetch data from board units, SEND_ACn_RSP (SQR=1-SQC, F=0, C=V (RB) are taked to move in the LLC sublayer of board units, R=NR, LSDU=NULL), soon the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit;

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=1, INFO) and ACCESS ()=during OK, namely when ordering PDU for retransmitting order and need to fetching data from board units, and but the response data that order PDU asks exists and the time spent, then REPLY_INDICATION (LSDU=NULL) and SEND_ACn_RSP (SQR=1-SQC are taked to move in the LLC sublayer of board units, F=1, C=V (RB), R=OK, LSDU=SAVE), namely transmit empty data to application layer, the institute's request msg that is stored in buffering area is sent back to roadside unit as the data in the information field of response pdus, and the responsive state designator is set to indicate and has comprised the data of asking, and

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=1, INFO) and ACCESS ()＜during OK, namely be the re-transmission order and need to fetch data and the order PDU response data of asking when still unavailable from board units as order PDU, then SEND_ACn_RSP (SQR=1-SQC is taked to move in the LLC sublayer of board units, F=1, C=V (RB), R=NE, LSDU=NULL), soon the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit.

2.2 type 3 sending assemblies (RSU assembly)

Type 3 sending assemblies are responsible for transmitting ACn order PDU to a far-end LLC, also are responsible for receiving simultaneously response pdus, and resend order PDU when not receiving response.

There are connectionless type 3 agreements of affirmation to allow each special-purpose SAP ¹(not yet being identified) order PDU that one " not finishing " arranged.Sending assembly uses the transmission sequence state variable V (SI) of oneself to determine LLC control domain code for once new transmission, perhaps the validity of check response LLC control domain code.

The number of RSU sending assembly should be identical with the OBU number that 3 operations of type of service in the communication zone communicate.

Each sending assembly has three kinds of state: IDLE, WAIT_A and WAIT_R, i.e. idle state, wait acknowledge state and wait data mode.Under the IDLE state, sending assembly can be processed the request from application layer, sends a new order PDU.Under WAIT_A and WAIT_R state, this assembly can only receive response or carry out data re-transmission in overtime situation from far-end LLC.Under the WAIT_A state, sending assembly is waited for the affirmation of passing through the type 3 order PDU that DL-DATA-ACK.request primitive calls to previous transmission, i.e. the affirmation of not being with response data is received in expectation.Under the WAIT_R state, sending assembly is waited for the affirmation of passing through the type 3 order PDU that DL-REPLY.request primitive calls to previous transmission, i.e. the affirmation with response data is received in expectation.The state transition diagram of this assembly as shown in Figure 4.

The LLC sublayer of roadside unit is according to current residing state, from the order PDU of application layer reception and the response pdus that receives from board units, be set with the various states transfer case, various state transitions situations are set with moving the specific event of combination and action by standardized event.The processing of this assembly can be divided into: normal transmission processing, normal reception ﹠ disposal, resend processings, unusually reception ﹠ disposal and failure handling.

2.2.1 normal transmission processing

The LLC sublayer of roadside unit sends the order PDU that transmits from application layer through media access control sublayer to board units under idle condition, carry out subsequently the wait acknowledge state or wait for data mode, and this is the normal transmission processing of RSU assembly.

Normal transmission processing comprises following state transitions:

State transitions 1: this state transitions only is used for RSU and transmits data to OBU.

State transitions 2: this state transitions is for RSU and with exchange (transmit and fetch) data between the OBU.

More particularly, under idle condition, when event DATA_ACK_REQUEST occurring, namely when the application layer indication sends data to board units, SEND_ACn_CMD (SQC=V (SI), P=0)) is taked to move in the LLC sublayer of roadside unit, namely sends order PDU to board units, this order PDU indication sends data, enters subsequently the wait acknowledge state; And

Under idle condition, when event REPLY_REQUEST occurring, namely when application layer indication and board units swap data, SEND_ACn_CMD (SQC=V (SI) is taked to move in the LLC sublayer of roadside unit, P=1)), namely send order PDU to board units, this order PDU indication swap data enters the wait data mode subsequently.

About here occur and will occur hereinafter such as the event of RECEIVE_ACn_RSP and parameters and such as action and parameters such as SEND_ACn_CMD, carry out in the lump simple explanation at this, its detailed description can be referring to the relevant regulations among the DSRC GB GB/T 20851.2-2007.

(A) event description

In the state transition table of sending assembly, event is by following condition identification.Only have ready conditions and just confirm this event for true time and occur.

(1) DATA_ACK_REQUEST: application layer has been transmitted a DL-DATA-ACK.request primitive to the LLC sublayer.

(2) REPLY_REQUEST: application layer has been transmitted a DL-REPLY.request primitive to the LLC sublayer.

(3) RECEIVE_ACn_RSP (SQR, R, LSDU): media access control sublayer has transmitted a MA-DATA.indication service primitive to the LLC sublayer, wherein comprise the ACn response pdus.

There is following parameter value in present event:

SQR=V (SI) SQR equates with V (SI) state variable of this sending assembly.This shows response pdus

There is frame sequential mistake.

SQR＜〉V (SI) state variable of V (SI) SQR and this sending assembly is unequal.This shows response

The frame sequential of PDU is correct.

RRRR partly is designated as " OK " in the state subdomain of the response pdus that R=OK receives

State (indicating it to comprise response data).

R＜〉RRRR partly is designated as except " OK " in the state subdomain of the response pdus that receives of OK

Other outer states (indication does not wherein comprise response data).

LSDU subdomain in the LSDU=NULL response is empty (length is 0).

LSDU＜〉LSDU subdomain non-NULL in the NULL response.

(4) ACK_TIMER_EXPIRED: the affirmation timer that is associated with this sending assembly timer of specific dedicated link address (namely corresponding to) is overtime.

(5) RETRY_COUNT＜N11: the retransmission count of this sending assembly is less than logical links Parameter N 11.The maximum number of times of transmission of logical links Parameter N 11 for allowing.

(6) RETRY_COUNT 〉=N11: the retransmission count of this sending assembly is more than or equal to logical links Parameter N 11.

(B) action description

(1) SEND_ACn_CMD (SQC, P): transmit a MA-DATA.request service primitive to media access control sublayer, wherein comprise ACn order PDU.

There is the following parameters value in this action:

SQC=V (SI) SQC is set to the value of this sending assembly V (SI) state variable.If V (SI)

State variable does not exist, and then creates a value and is the V (SI) of " 0 "; Otherwise make

With V (SI) currency.

The P bit reset of P=0 order.This shows that order PDU is that roadside unit is to vehicle-mounted list

Unit sends data.

The P bit set of P=1 order.This shows that order PDU is roadside unit and vehicle-mounted list

Unit's swap data.

RR parameter in the MA-DATA.request service primitive should be set to " 1 ", in order to distribute a dedicated uplink window.This window will be for the response message that transmits expection.

(2) RESEND_OLD_CMD: transmit a MA-DATA.request service primitive to media access control sublayer, this primitive comprises the nearest ACn order PDU that is transmitted by this sending assembly.

RR parameter in the MA-DATA.request service primitive should be set to " 1 ", in order to distribute a dedicated uplink window.This window will be for the response message that transmits expection.

(3) START_ACK_TIMER: the affirmation timer that starts this sending assembly.

(4) CANCEL_ACK_TIMER: the affirmation timer of cancelling this sending assembly.

(5) DATA_ACK_STATUS_INDICATION (STATUS): transmit a DL-DATA-ACK-STATUS.indication service primitive to application layer.There is following parameter value in this action:

STATUS=UNSUCCESSFUL STATUS state parameter is set to indication and does not become

The merit confirmation of receipt.

The sound that STATUS=STATUS_SUBFIELD STATUS state parameter is set to receive

Answer the state that returns among the PDU.

(6) REPLY_STATUS_INDICATION (STATUS, LSDU): transmit a DL-REPLY-STATUS.indication service primitive to application layer.There is following parameter value in this action:

STATUS=UNSUCCESSFUL STATUS state parameter is set to indication and does not successfully connect

Receive and confirm.

The response that STATUS=STATUS_SUBFIELD STATUS state parameter is set to receive

The state that returns among the PDU.

STATUS=PE STATUS state parameter is set to the PE state, and (agreement is wrong

Mistake).

LSDU=NULL data parameters LSDU is empty.

Comprise by accordingly among the LSDU=GIVEN_LSDU data parameters LSDU

The LSDU that the MA-DATA.indication service primitive provides.

(7) V (SI) :=1-V (SI): with V (SI) the state variable negate of this sending assembly.

(8) RETRY_COUNT:=0: the retransmission counter of this sending assembly is set to " 0 ".

(9) RETRY_COUNT:=RETRY_COUNT+1: the value of the retransmission counter of this sending assembly is added 1.

(10) REPORT_STATUS (ILLEGAL_LSDU): the report layer management entity, received a LSDU who does not meet type 3LLC agreement.

2.2.2 normal reception ﹠ disposal

The LLC sublayer of roadside unit receives the normal response pdus from board units under wait acknowledge state or wait data mode, return subsequently idle condition, and this is the normal reception ﹠ disposal of RSU assembly.

Normal reception ﹠ disposal comprises following state transitions:

State transitions 3: receive the order acknowledgement frame of not being with response data, the order of sending in the state transitions 1 is successfully completed.

State transitions 4: receive the order acknowledgement frame with response data, the order of sending in the state transitions 2 is successfully completed.

More particularly, event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait acknowledge state, LSDU=NULL)) time, namely when receiving from the data of board units as empty response pdus, DATA_ACK_STATUS_INDICATION (STATUS=STATUS_SUBFIELD) is taked to move in the LLC sublayer of roadside unit, and the state transfer that is about to return in the response pdus enters idle condition subsequently to application layer, and

Event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait data mode, R=OK)) time, namely when receiving from the responsive state designator of board units that indication has comprised the response pdus of the data of asking, REPLY_STATUS_INDICATION (STATUS=STATUS_SUBFIELD is taked to move in the LLC sublayer of roadside unit, LSDU=GIVED_LSDU)), the state and the response data that are about to return in the response pdus pass to application layer, enter subsequently idle condition.

2.2.3 resend processing

The LLC sublayer of roadside unit resends first previous order PDU to board units under wait acknowledge state or wait data mode, still remain on subsequently the wait acknowledge state or wait for data mode, and this is the processing that resends of RSU assembly.

Resend to process and comprise following state transitions:

State transitions 5: confirm timer expiry, resend the order of sending in the state transitions 1.If N11=1, then fill order is not retransmitted.

State transitions 6: confirm timer expiry, resend the order of sending in the state transitions 2.If N11=1, then fill order is not retransmitted.

More particularly, at the wait acknowledge state or under the wait data mode, when event ACK_TIMER_EXPIRED and RETRY_COUNT＜N11 occurring, namely overtime when the stand-by period of wait-for-response PDU and not yet reach when allowing transmission times, RESEND_OLD_CMD is taked to move in the LLC sublayer of roadside unit, namely resend first previous order PDU to board units, still remain on subsequently the wait acknowledge state or wait for data mode.

2.2.4 unusual reception ﹠ disposal

The LLC sublayer of roadside unit receives unusual response pdus, enters subsequently idle condition or remains on the wait acknowledge state or the wait data mode, and this is the unusual reception ﹠ disposal of RSU assembly.

Unusual reception ﹠ disposal comprises following state transitions:

State transitions 7: this state transitions can not occur because when only under WAIT_R or WAIT_A state, receiving the response of ACn order just effectively.

State transitions 8: comprised in the order acknowledgement frame that receives the data that should not exist: LSDU＜NULL, and the state before shifting is WAIT_A.

State transitions 9: the response frame sequential mistake (SQR mistake) that receives, this frame is abandoned.

State transitions 10: receive the order acknowledgement frame, the order of sending in the state transitions 2 is finished, but does not obtain the data of asking.

State transitions 11: the response frame sequential mistake (SQR mistake) that receives, this frame is abandoned.

More particularly, when event RECEIVE_ACn_RSP occurring under idle condition, when namely receiving the response pdus of board units, any action is not carried out in the LLC sublayer of roadside unit, remains on idle condition;

Event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait acknowledge state, LSDU＜〉NULL)), when namely receiving from the data of board units for empty response pdus, DATA_ACK_STATUS_INDICATION (STATUS=PE) and REPORT_STATUS (ILLEGAL_LSDU) are taked to move in the LLC sublayer of roadside unit, namely notify application layer protocol mistake and report layer management entity to receive the response data of protocol error, enter subsequently idle condition; And

Event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait data mode, R＜〉OK)) time, namely do not indicate when having comprised the data of asking when the responsive state designator from the response pdus of board units that receives, REPLY_STATUS_INDICATION (STATUS=STATUSSUBFIELD is taked to move in the LLC sublayer of roadside unit, LSDU=NULL)), the state and the empty data that are about to return in the response pdus pass to application layer, enter subsequently idle condition; And

When under wait acknowledge state or wait data mode, event RECEIVE_ACn_RSP (SQR=V (SI)) occurring, during the response pdus frame sequential mistake that namely receives, any action is not carried out in the LLC sublayer of roadside unit, remains on the wait acknowledge state or waits for data mode.

2.2.5 failure handling

The LLC sublayer of roadside unit is in the transmission times of stipulating and fail to obtain the affirmation response within the time, notifies unsuccessfully to application layer, and this is the failure handling of RSU assembly.

Failure handling comprises following state transitions:

State transitions 12: do not meet with a response yet when having reached the maximum number of retransmissions of order, stop the repeating transmission of ACn order this moment.

State transitions 13: the maximum retransmission device number of times that has reached order does not meet with a response yet, stops the repeating transmission of ACn order this moment.

More particularly, at the wait acknowledge state or wait under the data mode and event ACK_TIMER_EXPIRED and RETRY_COUNT appear=during N11, be that stand-by period of wait-for-response PDU is overtime and reached when allowing transmission times, DATA_ACK_STATUS_INDICATION (STATUS=UNSUCCESSFUL is taked to move in the LLC sublayer of roadside unit, LSDU=NULL), namely transmit unsuccessfully to the application layer notice, enter subsequently idle condition.

Conclusion

More than the finite state of the LLC sublayer in the DSRC communication shifted design carried out labor and explanation.State transitions design according to LLC of the present invention sublayer, the slower application characteristic of response speed that not only can adapt to two-piece type electronic tag board units, and the method not only can be come Design and implementation but also can be realized by software by hardware (chip), can realize comparatively complicated control function, and significant for reducing somersault and power consumption.

Claims (22)

1. LLC sublayer condition control method that is used for the Dedicated Short Range Communications, of intelligent transportation field, wherein,

Connect without under the affirmation mode in nothing, when the LLC sublayer of roadside unit and board units receives the other side's order PDU via the MAC layer under ready state, should order PDU to transfer to application layer to be processed by application layer, and, when the order PDU that receives application layer sends request, send this order PDU by media access control sublayer; Perhaps,

Be connected with under the affirmation mode in nothing, the LLC sublayer of roadside unit receives application layer under idle condition order PDU sends when asking, send this order PDU by media access control sublayer to board units, enter subsequently wait state, after receiving the correct response pdus of board units, get back to idle condition; When the LLC sublayer of board units received the order PDU that roadside unit sends via media access control sublayer under ready state, according to the order PDU that receives, selectivity carried out getting back to ready state after state transitions is processed from default various states transfer processing; Wherein, the various state transitions of the LLC sublayer of described board units are processed by standardized event and are set with moving the specific event of combination and action, beam back different response pdus to roadside unit respectively, and these state transitions are processed and are divided into:

Normal response is processed, and wherein, the LLC sublayer of board units is processing command PDU in time;

Delayed response is processed, and wherein, the LLC sublayer of board units can processing command PDU, but processing speed is slower;

Exception response is processed, and wherein, the reception of order PDU is wrong, and perhaps the LLC sublayer of board units can not processing command PDU; And

Retransmit response and process, wherein, order PDU is retransferring of a upper order that transmitted,

And, wherein, the LLC sublayer of described roadside unit is according to current residing state, from the order PDU of application layer reception and the response pdus that receives from board units, process according to default various states transfer case, various state transitions situations are set with moving the specific event of combination and action by standardized event.

2. LLC according to claim 1 sublayer condition control method, wherein, described standardized event and action are event primitive and the primitive acts of regulation in DSRC GB GB/T 20851.22007.

3. LLC according to claim 1 and 2 sublayer condition control method, wherein, the normal response of board units LLC sublayer is processed and is comprised following processing:

Event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=0, INFO＜〉NULL) during and RECEIVE_STATUS ()=OK, namely, when the order PDU that receives retransmits order, need not to fetch data and information field for empty from board units, and the information field of order PDU is when receiving successfully, DATA_ACK_INDICATION and SEND_ACn_RSP (SQR=1-SQC are taked to move in the LLC sublayer of board units, F=0, C=OK, R=NR, LSDU=NULL), that is, the LLC sublayer of board units will order the data message among the PDU to send application layer to, and the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit; And

Event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=1, INFO＜〉NULL), when RECEIVE_STATUS ()=OK and ACCESS ()=OK, namely, when the order PDU that receives retransmits order, need to fetch data from board units, information field is not empty, the information field of order PDU receives successfully, and but the response data that order PDU asks exists and the time spent, DELETE_SAVE_BUFFER is taked to move in the LLC sublayer of board units, REPLY_INDICATION (LSDU=INFO), SAVE:=GIVEN_LSDU, REPLY_UPDATE_STATUS_INDICATION and SEND_ACn_RSP (SQR=1-SQC, F=1, C=OK, R=OK, LSDU=SAVE), be the data of storing in the LLC sublayer delete buffer of board units, send the data among the order PDU to application layer, the data that application layer is provided are stored in the described buffering area, the notice application layer is upgraded, the data that are stored in buffering area are sent back to roadside unit as the data in the information field of response pdus, and the responsive state designator in the state subdomain of the information field of response pdus is set to indicate and has comprised the data of asking.

4. LLC according to claim 1 and 2 sublayer condition control method, wherein, the delayed response of board units is processed and is comprised following processing:

Event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=1, INFO＜〉NULL), RECEIVE_STATUS ()=OK and ACCESS ()＜〉during OK, namely, when the order PDU that receives retransmits order, need to fetch data from board units, information field is not empty, the information field of order PDU receives successfully, and the order PDU response data of asking is when still unavailable, take to move DELETE_SAVE_BUFFER, REPLY_INDICATION (LSDU=INFO), and SEND_ACn_RSP (SQR=1-SQC, F=1, C=OK, R=NE, LSDU=NULL), the data of namely storing in the LLC sublayer delete buffer of board units send the data among the order PDU to application layer, data in the information field of response pdus are set to sky, and described responsive state designator is set to indicate response data not yet to submit to, and simultaneously, the LLC sublayer waits for that application layer provides data.

5. LLC according to claim 4 sublayer condition control method, wherein, the LLC sublayer of board units will ordered after data among the PDU send application layer to, wait for that application layer provides data, until event REPLY_UPDATE_REQUEST occurs, be that the data that application layer is asked to LLC sublayer notice are stored this data in ready and indication LLC sublayer, SAVE:=GIVEN_LSDU and REPLY_UPDATE_STATUS_INDICATION are taked to move in the LLC sublayer after being notified, namely receive the data ask and described data are stored in the buffering area, and the notice application layer is upgraded.

6. LLC according to claim 1 and 2 sublayer condition control method, wherein, the exception response of the LLC sublayer of board units is processed and is comprised following processing:

Occur event RECEIVE_STATUS ()＜during OK, namely when the information field to order PDU takes defeat, SEND_ACn_RSP (SQR=1-SQC is taked to move in the LLC sublayer of board units, F=0, C=RECEIVE_STATUS (), R=NR, LSDU=NULL), namely in the response pdus that sends to roadside unit, the accepting state designator in the state subdomain of information field is set to take defeat;

When event RECEIVE_STATUS ()=OK and RECEIVE_ACn_CMD (INFO=NULL) occurring, namely when but board units receives successfully information field and is sky the information field of order PDU, board units takes to move SEND_ACn_RSP (SQR=1-SQC, F=0, C=OK, R=RS, LSDU=NULL), namely in the response pdus that sends to roadside unit, the responsive state designator in the state subdomain of information field is set to service and not yet activates.

7. LLC according to claim 1 and 2 sublayer condition control method, wherein, the re-transmission of the LLC sublayer of board units response is processed and is comprised following processing:

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=0, INFO) time, namely when order PDU when retransmitting order and need not to fetch data from board units, SEND_ACn_RSP (SQR=1-SQC is taked to move in the LLC sublayer of board units, F=0, C=V (RB), R=NR, LSDU=NULL), soon the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit;

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=1, INFO) and ACCESS ()=during OK, namely when ordering PDU for retransmitting order and need to fetching data from board units, and but the response data that order PDU asks exists and the time spent, then REPLY_INDICATION (LSDU=NULL) and SEND_ACn_RSP (SQR=1-SQC are taked to move in the LLC sublayer of board units, F=1, C=V (RB), R=OK, LSDU=SAVE), namely transmit empty data to application layer, the institute's request msg that is stored in buffering area is sent back to roadside unit as the data in the information field of response pdus, and the responsive state designator is set to indicate and has comprised the data of asking, and

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=1, INFO) and ACCESS ()＜during OK, namely be the re-transmission order and need to fetch data and the order PDU response data of asking when still unavailable from board units as order PDU, then SEND_ACn_RSP (SQR=1-SQC is taked to move in the LLC sublayer of board units, F=1, C=V (RB), R=NE, LSDU=NULL), soon the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit.

8. LLC according to claim 1 and 2 sublayer condition control method, wherein, the state transitions of the LLC sublayer of board units is 12 kinds.

9. LLC according to claim 1 and 2 sublayer condition control method, wherein, the state transitions of the LLC sublayer of roadside unit is processed and is divided into:

Normal transmission processing, wherein, the LLC sublayer of roadside unit sends the order PDU that transmits from application layer through media access control sublayer to board units under idle condition, carries out subsequently the wait acknowledge state or waits for data mode;

Normal reception ﹠ disposal, wherein, the LLC sublayer of roadside unit receives the normal response pdus from board units under wait acknowledge state or wait data mode, return subsequently idle condition;

Resend processing, wherein, the LLC sublayer of roadside unit resends first previous order PDU to board units under wait acknowledge state or wait data mode, still remains on subsequently the wait acknowledge state or waits for data mode;

Unusual reception ﹠ disposal, wherein, the LLC sublayer of roadside unit receives unusual response pdus, enters subsequently idle condition or remains on the wait acknowledge state or the wait data mode; And

Failure handling, wherein, the LLC sublayer of roadside unit is notified unsuccessfully to application layer.

10. LLC according to claim 9 sublayer condition control method, wherein, the normal transmission processing of the LLC sublayer of roadside unit comprises following processing:

Under idle condition, when event DATA_ACK_REQUEST occurring, namely when the application layer indication sends data to board units, SEND_ACn_CMD (SQC=V (SI) is taked to move in the LLC sublayer of roadside unit, P=0)), namely send order PDU to board units, this order PDU indication sends data, enters subsequently the wait acknowledge state; And

Under idle condition, when event REPLY_REQUEST occurring, namely when application layer indication and board units swap data, SEND_ACn_CMD (SQC=V (SI) is taked to move in the LLC sublayer of roadside unit, P=1)), namely send order PDU to board units, this order PDU indication swap data enters the wait data mode subsequently.

11. LLC according to claim 9 sublayer condition control method, wherein, the normal reception ﹠ disposal of the LLC sublayer of roadside unit comprises following processing:

Event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait acknowledge state, LSDU=NULL)) time, namely when receiving from the data of board units as empty response pdus, DATA_ACK_STATUS_INDICATION (STATUS=STATUS_SUBFIELD) is taked to move in the LLC sublayer of roadside unit, the state transfer that is about to return in the response pdus is to application layer, enter subsequently idle condition, and

Event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait data mode, R=OK)) time, namely when receiving from the responsive state designator of board units that indication has comprised the response pdus of the data of asking, REPLY_STATUS_INDICATION (STATUS=STATUS_SUBFIELD is taked to move in the LLC sublayer of roadside unit, LSDU=GIVED_LSDU)), the state and the response data that are about to return in the response pdus pass to application layer, enter subsequently idle condition.

12. LLC according to claim 9 sublayer condition control method, wherein, the processing that resends of the LLC sublayer of roadside unit comprises following processing:

At the wait acknowledge state or under the wait data mode, when event ACK_TIMER_EXPIRED and RETRY_COUNT＜N11 occurring, namely overtime when the stand-by period of wait-for-response PDU and not yet reach when allowing transmission times, RESEND_OLD_CMD is taked to move in the LLC sublayer of roadside unit, namely resend first previous order PDU to board units, still remain on subsequently the wait acknowledge state or wait for data mode.

13. LLC according to claim 9 sublayer condition control method, wherein, the unusual reception ﹠ disposal of the LLC sublayer of roadside unit comprises following processing:

When event RECEIVE_ACn_RSP occurring under idle condition, when namely receiving the response pdus of board units, any action is not carried out in the LLC sublayer of roadside unit, remains on idle condition;

Event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait acknowledge state, LSDU＜〉NULL)), when namely receiving from the data of board units for empty response pdus, DATA_ACK_STATUS_INDICATION (STATUS=PE) and REPORT_STATUS (ILLEGAL_LSDU) are taked to move in the LLC sublayer of roadside unit, namely notify application layer protocol mistake and report layer management entity to receive the response data of protocol error, enter subsequently idle condition; And

Event RECEIVE_ACn_RSP (SQR＜〉V (SI) appears under the wait data mode, R＜〉OK)) time, namely do not indicate when having comprised the data of asking when the responsive state designator from the response pdus of board units that receives, REPLY_STATUS_INDICATION (STATUS=STATUS_SUBFIELD is taked to move in the LLC sublayer of roadside unit, LSDU=NULL)), the state and the empty data that are about to return in the response pdus pass to application layer, enter subsequently idle condition; And

When under wait acknowledge state or wait data mode, event RECEIVE_ACn_RSP (SQR=V (SI)) occurring, during the response pdus frame sequential mistake that namely receives, any action is not carried out in the LLC sublayer of roadside unit, remains on the wait acknowledge state or waits for data mode.

14. LLC according to claim 9 sublayer condition control method, wherein, the failure handling of the LLC sublayer of roadside unit comprises following processing:

At the wait acknowledge state or wait under the data mode and event ACK_TIMER_EXPIRED and RETRY_COUNT appear=during N11, be that stand-by period of wait-for-response PDU is overtime and reached when allowing transmission times, DATA_ACK_STATUS_INDICATION (STATUS=UNSUCCESSFUL is taked to move in the LLC sublayer of roadside unit, LSDU=NULL), namely transmit unsuccessfully to the application layer notice, enter subsequently idle condition.

15. LLC according to claim 9 sublayer condition control method, wherein, the state transitions of the LLC sublayer of roadside unit is 13 kinds.

16. board units that is used for the Dedicated Short Range Communications, of intelligent transportation field, this board units is divided into physical layer, data link layer and application layer, data link layer comprises LLC sublayer and media access control sublayer, wherein, the LLC sublayer comprises: interface unit is used for carrying out data with media access control sublayer and application layer and transmits; Control unit is used for the operation of control LLC sublayer; And buffer cell,

Wherein, connect without under the affirmation mode in nothing, under the control of control unit, when the LLC sublayer of described board units receives the order PDU of roadside unit via interface unit from the MAC layer under ready state, should order PDU to transfer to application layer to be processed by application layer via interface unit, and, when the order PDU that receives application layer via interface unit sends request, send this order PDU via interface unit by media access control sublayer; And,

Wherein, be connected with under the affirmation mode in nothing, when the LLC sublayer of described board units receives the order PDU that roadside unit sends via interface unit from media access control sublayer under ready state, under the control of control unit, according to the order PDU that receives, selectivity carries out getting back to ready state after state transitions is processed from default various states transfer processing;

Wherein, various state transitions are processed by standardized event and are set with moving the specific event of combination and action, beam back different response pdus to roadside unit respectively, and the processing of these state transitions is divided into:

Normal response is processed, and wherein, the LLC sublayer of board units is processing command PDU in time;

Delayed response is processed, and wherein, the LLC sublayer of board units can processing command PDU, but processing speed is slower;

Exception response is processed, and wherein, the reception of order PDU is wrong, and perhaps the LLC sublayer of board units can not processing command PDU; And

Retransmit response and process, wherein, order PDU is retransferring of a upper order that transmitted.

17. board units according to claim 16, wherein, described standardized event and action are event primitive and the primitive acts of regulation in DSRC GB GB/T 20851.2-2007.

18. according to claim 16 or 17 described board units, wherein, the normal response of the LLC sublayer of described board units is processed and is comprised following processing:

Event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=0, INFO＜〉NULL) during and RECEIVE_STATUS ()=OK, namely, when the order PDU that receives retransmits order, need not to fetch data and information field for empty from board units, and the information field of order PDU is when receiving successfully, DATA_ACK_INDICATION and SEND_ACn_RSP (SQR=1-SQC are taked to move in the LLC sublayer of board units, F=0, C=OK, R=NR, LSDU=NULL), that is, the LLC sublayer of board units will order the data message among the PDU to send application layer to, and the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit; And

Event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=1, INFO＜〉NULL), when RECEIVE_STATUS ()=OK and ACCESS ()=OK, namely, when the order PDU that receives retransmits order, need to fetch data from board units, information field is not empty, the information field of order PDU receives successfully, and but the response data that order PDU asks exists and the time spent, DELETE_SAVE_BUFFER is taked to move in the LLC sublayer of board units, REPLY_INDICATION (LSDU=INFO), SAVE:=GIVEN_LSDU, REPLY_UPDATE_STATUS_INDICATION and SEND_ACn_RSP (SQR=1-SQC, F=1, C=OK, R=OK, LSDU=SAVE), the data of storing in the described buffer cell are deleted in the LLC sublayer that is board units, send the data among the order PDU to application layer, the data that application layer is provided are stored in the described buffer cell, the notice application layer is upgraded, the data that are stored in buffer cell are sent back to roadside unit as the data in the information field of response pdus, and the responsive state designator in the state subdomain of the information field of response pdus is set to indicate and has comprised the data of asking.

19. according to claim 16 or 17 described board units, wherein, the delayed response of the LLC sublayer of board units is processed and is comprised following processing:

Event RECEIVE_ACn_CMD (SQC=V (RI) is appearring, P=1, INFO＜〉NULL), RECEIVE_STATUS ()=OK and ACCESS ()＜〉during OK, namely, when the order PDU that receives retransmits order, need to fetch data from board units, information field is not empty, the information field of order PDU receives successfully, and the order PDU response data of asking is when still unavailable, take to move DELETE_SAVE_BUFFER, REPLY_INDICATION (LSDU=INFO), and SEND_ACn_RSP (SQR=1-SQC, F=1, C=OK, R=NE, LSDU=NULL), i.e. the data of storing in the LLC sublayer of the board units deletion buffer cell send the data among the order PDU to application layer, data in the information field of response pdus are set to sky, and described responsive state designator is set to indicate response data not yet to submit to, and simultaneously, the LLC sublayer waits for that application layer provides data.

20. board units according to claim 19, wherein, the LLC sublayer of board units will ordered after data among the PDU send application layer to, wait for that application layer provides data, until event REPLY_UPDATE_REQUEST occurs, be that the data that application layer is asked to LLC sublayer notice are stored this data in ready and indication LLC sublayer, SAVE:=GIVEN_LSDU and REPLY_UPDATE_STATUS_INDICATION are taked to move in the LLC sublayer after being notified, namely receive the data ask and described data are stored in the buffer cell, and the notice application layer is upgraded.

21. according to claim 16 or 17 described board units, wherein, the exception response of the LLC sublayer of board units is processed and is comprised following processing:

Occur event RECEIVE_STATUS ()＜during OK, namely when the information field to order PDU takes defeat, SEND_ACn_RSP (SQR=1-SQC is taked to move in the LLC sublayer of board units, F=0, C=RECEIVE_STATUS (), R=NR, LSDU=NULL), namely in the response pdus that sends to roadside unit, the accepting state designator in the state subdomain of information field is set to take defeat;

When event RECEIVE_STATUS ()=OK and RECEIVE_ACn_CMD (INFO=NULL) occurring, namely when but board units receives successfully information field and is sky the information field of order PDU, board units takes to move SEND_ACn_RSP (SQR=1-SQC, F=0, C=OK, R=RS, LSDU=NULL), namely in the response pdus that sends to roadside unit, the responsive state designator in the state subdomain of information field is set to service and not yet activates.

22. according to claim 16 or 17 described board units, wherein, the re-transmission of the LLC sublayer of board units response is processed and is comprised following processing:

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=0, INFO) time, namely when order PDU when retransmitting order and need not to fetch data from board units, SEND_ACn_RSP (SQR=1-SQC is taked to move in the LLC sublayer of board units, F=0, C=V (RB), R=NR, LSDU=NULL), soon the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit;

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=1, INFO) and ACCESS ()=during OK, namely when ordering PDU for retransmitting order and need to fetching data from board units, and but the response data that order PDU asks exists and the time spent, then REPLY_INDICATION (LSDU=NULL) and SEND_ACn_RSP (SQR=1-SQC are taked to move in the LLC sublayer of board units, F=1, C=V (RB), R=OK, LSDU=SAVE), namely transmit empty data to application layer, the institute's request msg that is stored in buffer cell is sent back to roadside unit as the data in the information field of response pdus, and the responsive state designator is set to indicate and has comprised the data of asking, and

Event RECEIVE_ACn_CMD (SQC＜〉V (RI) is appearring, P=1, INFO) and ACCESS ()＜during OK, namely be the re-transmission order and need to fetch data and the order PDU response data of asking when still unavailable from board units as order PDU, then SEND_ACn_RSP (SQR=1-SQC is taked to move in the LLC sublayer of board units, F=1, C=V (RB), R=NE, LSDU=NULL), soon the data in the information field of response pdus are set to sky, send empty affirmation Frame to roadside unit.

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