A car-to-road communication protocol method for taxi data transmission

Abstract

The application discloses a car-road communication protocol method for taxi data transmission and relates to the technical field of car-road cooperative communication, which comprises the following steps: splicing a four-byte pole position pilot field before a downlink trigger frame header and setting a broadcast medium access control field in the frame; a road-side antenna sends a downlink trigger frame, a vehicle-mounted antenna identifies the pilot field to obtain a road section identifier and a pole serial number, and verifies the consistency with the broadcast medium access control field; the vehicle-mounted antenna calculates a time slot index according to the pole position pilot field and the broadcast medium access control field, determines and sends an uplink confirmation frame according to a receiving completion time, a vehicle-mounted processing offset and a time slot length; a communication terminal obtains a current data frame serial number of a taximeter and a vehicle mileage through a serial port, generates a time domain byte and sends an uplink data frame according to the time slot index; a road-side antenna establishes a time slot window to receive and judge the uplink data frame, and then sends a confirmation after eliminating the redundancy; if the time is out, a secondary time slot index is generated to resend the uplink data frame, so that the misbinding and collision are reduced, and the closed loop success rate is improved.

Description

Technical Field

[0001] This invention relates to the field of vehicle-road cooperative communication technology, and in particular to a vehicle-road communication protocol method for taxi data transmission. Background Technology

[0002] In taxi meter calibration and operation monitoring scenarios, the vehicle-mounted communication terminal typically needs to exchange information such as frame sequence number, synchronization signal, or mileage generated by the meter with the roadside antenna on a 5.8GHz vehicle-to-infrastructure (V2I) communication link to complete the triggering, transmission, and confirmation loop. The conventional approach generally adopts an interaction paradigm of "roadside downlink triggering—vehicle-mounted uplink response—roadside downlink confirmation." Air interface frames typically include a frame header, packet length, media access control field, command word, data field, and error check field. When multiple vehicles access the system, common access organization methods include broadcast triggering combined with random access, or explicit time slots issued by the roadside to arrange the uplink transmission order of different vehicles.

[0003] However, the aforementioned conventional methods are prone to two problems when implemented in engineering projects: First, under the condition that multiple poles cover the same road segment or that signals from adjacent poles are reachable, relying solely on the simple encoding of the downlink broadcast media access control field makes it easy for the vehicle-side to be affected by overlapping coverage and misjudgment in determining "which pole the broadcast source comes from," thus increasing the uncertainty of interaction binding. Second, if random access or weakly constrained response timing is used for concurrent uplink of multiple vehicles, it is easy to form co-frequency collisions and retransmission link occupancy within a short time window. If explicit scheduling is used instead, additional control interactions and synchronization constraints will be introduced, which will affect the timing determinism and link efficiency of the verification data return. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a vehicle-to-infrastructure communication protocol method for taxi data transmission to solve the problems of uncertain broadcast source addressing and binding, as well as multi-vehicle concurrent uplink collisions in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a vehicle-to-infrastructure communication protocol method for taxi data transmission, comprising: constructing a pole position pilot field, concatenating the pole position pilot field before the downlink trigger frame header, and setting a broadcast media access control field within the downlink trigger frame;

[0008] The roadside antenna sends downlink trigger frames, the vehicle-mounted antenna identifies the pole position pilot field, obtains the road segment identifier and pole number, and verifies them with the broadcast media access control field;

[0009] The vehicle-mounted antenna calculates the time slot index based on the pole position pilot field and the license plate media access control field, and confirms the uplink confirmation frame transmission time based on the downlink trigger frame reception completion time, vehicle processing offset, and time slot duration, and then transmits it.

[0010] The license plate media access control field is used to populate the uplink MAC field and also serves as input for the time slot index calculation;

[0011] The communication terminal obtains the current data frame sequence number and vehicle mileage from the meter via the serial port, generates time domain bytes, and schedules the uplink data frame to be sent according to the time slot index.

[0012] When the roadside antenna completes the transmission of the downlink trigger frame, it establishes a time slot window, receives uplink data frames based on the time slot window, uses the license plate media access control field, and sends downlink confirmation frames after deduplication based on the sequence number of the current data frame.

[0013] If the downlink confirmation frame times out without confirmation, a secondary time slot index is generated and the data is retransmitted in the next time slot window.

[0014] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission described in this invention, the pole position pilot field includes a fixed synchronization byte pair, a road segment identifier, and a pole number.

[0015] In a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission described in this invention, the specific steps for constructing the pole position pilot field are as follows:

[0016] The pole position pilot field consists of four bytes;

[0017] Among them, the first and second bytes of the pole position pilot field are fixed synchronization byte pairs, the third byte is the road segment identifier, and the fourth byte is the pole number.

[0018] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission according to the present invention, wherein: the vehicle-mounted antenna identification pole position pilot field includes,

[0019] The vehicle-mounted antenna receives the baseband byte stream of the downlink trigger frame and writes the baseband byte stream of the downlink trigger frame into the receive buffer;

[0020] Before parsing the 0x7E frame header carried by the downlink trigger frame, the vehicle-mounted antenna first performs a pole position pilot scan within a range of several bytes in the receive buffer to define fixed synchronization byte pairs;

[0021] The baseband byte stream in the receiving buffer is detected sequentially using the vehicle-mounted antenna;

[0022] If the vehicle-mounted antenna detects a fixed synchronization byte pair in the baseband byte stream, it determines that the detected field position is the starting point of the pole position pilot field, and performs offset identification according to the pole position pilot field to obtain the road segment identifier and pole number;

[0023] If no fixed synchronization byte pair is found within the entire baseband byte stream scan range, the pilot identification is deemed to have failed, and a rollback process is initiated.

[0024] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission described in this invention, the rollback process includes: the vehicle antenna continuing to parse the downlink trigger frame, obtaining the broadcast media access control field, deriving the rod number from the broadcast media access control field, and setting the road segment identifier to a default value;

[0025] The broadcast media access control field derivation rod number includes the vehicle antenna parsing the downlink trigger frame according to 0x7E delimitation to obtain the broadcast media access control field;

[0026] Check if the broadcast media access control fields of the vehicle antenna are all equal.

[0027] If all broadcast media access control fields are equal, then define the backoff lever number as the common padding value of the broadcast MAC;

[0028] If the broadcast media access control fields are incomplete, the downlink trigger frame will be marked as invalid and discarded.

[0029] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission according to the present invention, the specific steps of obtaining the road segment identifier and pole number and verifying them with the broadcast media access control field are as follows:

[0030] When pilot identification is successful, the vehicle-mounted antenna performs pole number verification.

[0031] The pole number verification includes: if the pole number is not equal to the fallback pole number, then the downlink trigger frame is marked as having an inconsistent pole number and discarded.

[0032] If the lever number is equal to the backoff lever number, then the downlink trigger frame lever numbers are determined to be the same;

[0033] When pilot identification fails, the vehicle-mounted antenna uses the backtracking result, taking the backtracked pole number as the pole number and the default value as the road segment identifier.

[0034] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission according to the present invention, the calculation of the time slot index includes: the vehicle antenna acquiring the vehicle license plate media access control field;

[0035] Construct the input byte sequence based on the license plate media access control field;

[0036] Perform CRC16 checksum calculation on the input byte sequence to obtain a 16-bit result;

[0037] Based on the 16-bit result, the time slot index is obtained through modulo operation.

[0038] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission described in this invention, the confirmation of the uplink confirmation frame transmission time includes, based on the downlink trigger frame reception completion time, combining the time shift of the product of the on-board processing offset and the time slot index and the time slot duration, obtaining the uplink confirmation frame transmission time, expressed as:

[0039] ;

[0040] in, Indicates the planned transmission time of the uplink acknowledgment frame. Indicates the time when the downlink trigger frame reception is completed. This indicates the onboard processing offset of the uplink acknowledgment frame. Indicates the time slot index. Indicates the duration of the time slot.

[0041] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission according to the present invention, the specific steps of generating time-domain bytes and scheduling the transmission of uplink data frames according to time slot index are as follows:

[0042] The communication terminal generates time domain bytes based on the difference between the time when serial port data reception is completed and the actual time when the uplink data frame is transmitted.

[0043] The vehicle-mounted antenna selects the command word of the uplink data frame according to the downlink trigger command type and encapsulates the data field;

[0044] The vehicle-mounted antenna appends an extension field after the data field field in the uplink data frame.

[0045] The extended fields sequentially carry the current data frame sequence number, road segment identifier, sequence number, and time slot index;

[0046] The vehicle antenna writes the license plate media access control field into the uplink MAC field to obtain uplink data frames;

[0047] The vehicle-mounted antenna transmits uplink data frames at the actual transmission time of the uplink data frame;

[0048] The actual transmission time of the uplink data frame is determined by taking the reference time as the starting point, combining the on-board processing offset, the time offset of the corresponding time slot of the vehicle, and the period.

[0049] As a preferred embodiment of the vehicle-to-infrastructure communication protocol method for taxi data transmission according to the present invention, the step of generating a secondary time slot index and retransmitting in the next time slot window includes:

[0050] The roadside antenna calculates the time slot window for receiving uplink data frames from the vehicle-mounted antenna based on the completion time of the downlink trigger frame reception and the time slot parameters.

[0051] The roadside antenna receives and extracts the data frame sequence number of the uplink data frame according to the time slot window, and compares it with the sequence number of the previously received frame;

[0052] Based on the fact that the current uplink data frame is new valid data, the roadside antenna encapsulates the data frame sequence number, road segment identifier, pole number, and time slot index as extended fields to form downlink confirmation frame data and confirm it;

[0053] If the roadside antenna does not receive an acknowledgment within the time limit, a secondary time slot index is generated, and the acknowledgment frame is rescheduled for transmission in the next time slot window based on the new time slot index.

[0054] If no confirmation is received within the time limit, the current confirmation request will be marked as unconfirmed.

[0055] The beneficial effects of this invention are as follows: By verifying the pole position pilot field and the downlink broadcast media access control field, the roadside broadcast source can be identified and verified, which helps to reduce the risk of misbinding under conditions of cross-pole coverage or adjacent pole position superposition; by using time slot indexing, implicit time-division access control under multi-vehicle concurrent conditions is realized, so that the uplink confirmation and uplink data of different vehicles are deterministically staggered on the time axis, which helps to reduce the probability of co-frequency collisions and retransmissions; by using secondary time slot indexing and the next round window retransmission mechanism, predictable retransmission scheduling is realized in the case of collisions or frame drops, which helps to avoid the concentrated conflict caused by multiple vehicles retransmitting at the same time, thereby improving the success rate of interactive closed loop. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a flowchart of a vehicle-to-infrastructure communication protocol method for taxi data transmission.

[0058] Figure 2 This is a flowchart of vehicle-to-infrastructure (V2I) communication.

[0059] Figure 3 The flowchart for calculating the time slot index.

[0060] Figure 4 This is a flowchart illustrating the relationship between time slots and retransmissions.

[0061] Figure 5 This is a graph showing the change in misbinding rate as a function of overlay coverage.

[0062] Figure 6 This is a graph showing the change in uplink success rate as the number of concurrent vehicles. Detailed Implementation

[0063] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0064] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0065] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0066] Reference Figures 1-4 As one embodiment of the present invention, this embodiment provides a vehicle-to-infrastructure communication protocol method for taxi data transmission, comprising the following steps:

[0067] S1. Construct the pole position pilot field, concatenate the pole position pilot field before the downlink trigger frame header, and set the broadcast media access control field within the downlink trigger frame.

[0068] Furthermore, before each roadside antenna is put into operation, a set of configuration parameters is written for the roadside antenna.

[0069] The configuration parameter set includes road segment identifier, pole number, downlink trigger command type, and uplink channel prompt value.

[0070] The roadside antenna maintains a queue of data to be transmitted.

[0071] When the triggering conditions are met, such as when a vehicle enters the coverage area, when a triggering command is issued by the host computer, or when the local detection logic is triggered, the current triggering event is written into the queue to be sent, and the first event in the queue is taken out as the roadside antenna transmission task to be scheduled.

[0072] Take fixed synchronization byte pairs (assuming they are) The pole position pilot field is constructed according to the order of "fixed synchronization byte pair, road segment identifier, pole number", and the byte order is specified to be sent from left to right.

[0073] The pole position pilot field consists of four bytes, of which the first and second bytes are a fixed synchronization byte pair, the third byte is the road segment identifier, and the fourth byte is the pole number.

[0074] The pole position pilot field is placed before the 0x7E frame header of the downlink trigger frame, forming the start segment of the air interface transmission sequence where the pole position pilot field is sent first, followed by the 0x7E frame header.

[0075] Construct the downlink broadcast media access control field, which is usually fixed at 10 bytes in length.

[0076] The broadcast media access control field uses a full-value filling method, with the pole number as the filling value, repeatedly filled in with a fixed length of bytes to form the broadcast MAC.

[0077] Write the broadcast media access control field to the MAC field position of the downlink trigger frame.

[0078] The packet length is calculated based on the framing of the downlink trigger frame body field. In this embodiment, it is assumed that the downlink trigger frame body uses the following field order (excluding the pole position pilot field):

[0079] ;

[0080] in, For the downlink trigger frame header, For package length field, This is the downlink broadcast media access control field. This is a downlink command word. For the downlink data field, It is a 16-bit cyclic redundancy check. For the end of the downlink trigger frame, This is a follower byte.

[0081] Assuming the packet length field Take 1 byte. Fixed at 10 bytes The data field of the downlink trigger frame is fixed at 1 byte and is either empty or of a preset length.

[0082] In this embodiment, if the downlink data field is empty, the packet length is equal to the sum of the 10-byte MAC field length, the 1-byte command segment length, and the data field length.

[0083] When the trigger frame data field is empty, the packet length field is 11 bytes.

[0084] The basic value of the downlink command word is determined based on the downlink trigger command type in the configuration parameter set. The downlink trigger command type includes synchronization trigger and verification trigger.

[0085] If the downlink trigger command type is synchronous trigger, then the basic value of the downlink command word is 0x01.

[0086] If the downlink trigger command type is verification trigger, then the basic value of the downlink command word is 0x03.

[0087] Write the basic value of the downlink command word into the uplink / downlink flag bits and channel indication bits according to the command word bits to obtain the downlink command word. .

[0088] The sequence of bytes to be verified is defined as a continuous stream of bytes from the packet length field to the end of the downlink data field.

[0089] The CRC16 is calculated byte by byte from left to right in the sequence of bytes to be checked.

[0090] Write the calculated verification value into the field. And assemble the complete downlink trigger frame body.

[0091] Finally, the roadside antenna transmits the downlink trigger frames over the air interface in byte order of TxBytes.

[0092] It should be noted that the downlink trigger frame includes a frame header, a packet length field, a MAC field for identifying the roadside antenna, a command word for identifying the command type, a data field containing the trigger command, a CRC16 checksum, and a frame trailer.

[0093] It should be noted that the downlink trigger frame is sent from the roadside antenna to the vehicle-mounted antenna to trigger the vehicle-mounted antenna to perform synchronization or verification trigger commands.

[0094] S2. The roadside antenna sends downlink trigger frames, the vehicle-mounted antenna identifies the pole position pilot field, obtains the road segment identifier and pole number, and verifies them with the broadcast media access control field.

[0095] Furthermore, the vehicle-mounted antenna receives the baseband byte stream of the downlink trigger frame and writes the baseband byte stream of the downlink trigger frame into the receive buffer.

[0096] Before parsing the 0x7E frame header, the vehicle-mounted antenna first checks the front of the receive buffer. Perform a pole position pilot scan within a byte range to define consecutive byte pairs. .

[0097] Assume the first one in the receive buffer byte Vehicle-mounted antenna arrive Check whether the conditions are met sequentially .

[0098] in, This represents logical AND. For the first in the receive buffer bytes, Indicates the first in the receive buffer bytes, This indicates the pilot scan length.

[0099] If the conditions are met, the current position is determined to be the starting point of the pilot field, and the position is offset according to the pole position pilot field to obtain the road segment identifier and pole number.

[0100] If no consecutive field pairs are found within the entire scanning range, pilot identification is deemed to have failed, and a rollback process is initiated.

[0101] The rollback process includes the vehicle-mounted antenna continuing to parse the downlink trigger frame, obtaining the broadcast media access control field, deriving the pole number from the broadcast media access control field, and setting the road segment identifier to the default value.

[0102] In this embodiment, the default value is set to 0.

[0103] Furthermore, the pole number of the broadcast media access control field is derived. Specifically, the vehicle antenna parses the downlink trigger frame according to 0x7E delimitation to obtain the broadcast media access control field.

[0104] Check if the broadcast media access control fields of the vehicle antenna are all equal.

[0105] If the equality holds, then the backoff lever number is defined as the common padding value of the broadcast MAC.

[0106] If the equality condition is not met, the downlink trigger frame is marked as invalid and discarded, and will not proceed to the next step.

[0107] When pilot identification is successful, the vehicle-mounted antenna performs pole number verification.

[0108] If the lever number is not equal to the backoff lever number, the downlink trigger frame will be marked as having a lever number mismatch and discarded.

[0109] If the pole number is equal to the backoff pole number, then the downlink confirmation frame pole number is considered to be consistent, and the calculation of subsequent time slots continues.

[0110] When pilot identification fails, the vehicle-mounted antenna uses the fallback result, taking the fallback pole number as the pole number and the default value as the road segment identifier.

[0111] S3. The vehicle-mounted antenna calculates the time slot index based on the pole position pilot field and the license plate media access control field, and confirms the uplink confirmation frame transmission time by the downlink trigger frame reception completion time, vehicle processing offset, and time slot duration, and then sends it.

[0112] Furthermore, the vehicle-mounted antenna acquires the vehicle's license plate media access control field.

[0113] The license plate media access control field is used to populate the uplink MAC field and also serves as input for the time slot index calculation.

[0114] The vehicle-mounted antenna is constructed to provide the input byte sequence for calculating the time slot index.

[0115] The input byte sequence refers to the sequential concatenation of the four bytes of the pole position pilot field and the bytes of the license plate media access control field to form a byte input stream.

[0116] Calculate the CRC16 of the input byte sequence and obtain a 16-bit result.

[0117] Based on the 16-bit result, the time slot index is obtained through modulo operation.

[0118] Furthermore, the vehicle-mounted antenna records the time when downlink trigger frame reception is completed.

[0119] Based on the recorded downlink trigger frame reception completion time, the planned transmission time of the uplink acknowledgment frame is calculated, expressed as:

[0120] ;

[0121] in, Indicates the planned transmission time of the uplink acknowledgment frame. Indicates the time when the downlink trigger frame reception is completed. This indicates the onboard processing offset of the uplink acknowledgment frame. Indicates the time slot index. Indicates the duration of the time slot.

[0122] It should be noted that the vehicle-mounted processing bias is determined by taking the upper bound of the processing time required for the vehicle-mounted antenna to complete pilot identification, broadcast MAC verification, time slot index calculation, confirmation of downlink trigger frame assembly, and CRC calculation under worst-case computing power and worst-case link conditions. The time slot duration is determined by taking the upper bound of the uplink confirmation frame air interface transmission time, transmit / receive switching, and clock jitter protection interval as the single time slot length.

[0123] Furthermore, the communication terminal maintains the cached frame sequence number by updating the message rules.

[0124] The message update rules include extracting the current valid serial port response message frame sequence number and writing it into the cached frame sequence number whenever the communication terminal receives any valid serial port response message from the meter.

[0125] The vehicle-mounted antenna selects the uplink confirmation command word based on the downlink command type.

[0126] Assuming the downstream command word is synchronously triggered, the upstream confirmation command word is 0x81.

[0127] Assuming the downlink command word is triggered by a check, the uplink confirmation command word is 0x83.

[0128] The vehicle-mounted antenna generates the uplink confirmation frame data field.

[0129] The generation of the uplink acknowledgment frame data field includes adding an extension field after the existing acknowledgment frame data field. The extension field carries the cached frame sequence number, landmark sequence number, pole sequence number, and time slot index in sequence.

[0130] The vehicle-mounted antenna uses the vehicle's license plate media access control field as the uplink MAC field, writes it into the packet length field according to the existing frame format, and calculates CRC16.

[0131] The vehicle-mounted antenna transmits the uplink acknowledgment frame at the scheduled transmission time of the uplink acknowledgment frame.

[0132] After launch, it enters a waiting state, waiting for the roadside downlink confirmation frame, and decides whether to trigger a second-level time slot split and retransmission based on the timeout policy.

[0133] It should be noted that the uplink acknowledgment frame includes a frame header, a packet length field, a MAC field for identifying the vehicle antenna, a command word for indicating the type of acknowledgment command, a data field containing the first specific data, a CRC16 checksum, and a frame trailer.

[0134] The first specific data includes frame number, road sign identifier, pole number, and time slot index.

[0135] It should be noted that the uplink confirmation frame is sent by the vehicle-mounted antenna to the roadside antenna to confirm that the vehicle-mounted antenna has received the downlink trigger frame and completed the predetermined operation.

[0136] S4. The communication terminal obtains the current data frame sequence number and vehicle mileage from the meter via the serial port, generates time domain bytes, and schedules the uplink data frame to be sent according to the time slot index.

[0137] Furthermore, a full-duplex serial link is established between the communication terminal and the meter, and serial messages are sent and received according to the existing serial frame format.

[0138] The communication terminal verifies the received serial port messages using an XOR checksum. Serial port messages that pass the checksum are then parsed.

[0139] The communication terminal extracts the frame sequence number field from each valid received serial port message, and satisfies the rule that the sequence number is incremented by 1 each time on the meter side and remains unchanged when the frame is retransmitted after a timeout.

[0140] The communication terminal uses the extracted frame sequence number field as the sequence number of this data frame.

[0141] The communication terminal selects the data content to be acquired via the serial port based on the trigger type of the downlink trigger frame.

[0142] When the serial port is in the synchronization trigger signal path, the communication terminal waits for and receives the serial port message related to the synchronization signal reported by the meter, extracts the frame sequence number of the serial port message, and records the time when the serial port message reception is completed.

[0143] When the serial port is on the vehicle mileage path, the terminal sends an arrival verification trigger command to the fare meter, receives the vehicle mileage serial port message reported by the fare meter, extracts the frame sequence number and vehicle mileage value of the serial port message, and records the time when the serial port message reception is completed.

[0144] It should be noted that if the frame number of the current serial port message is the same as the frame number of the previous processed serial port message, the current serial port message will be marked as a duplicate message.

[0145] For duplicate messages, the communication terminal chooses not to trigger air interface transmission.

[0146] After completing serial port parsing, the communication terminal submits the service data, the sequence number of the current data frame, and the time when the serial port message reception is completed to the vehicle-mounted antenna's transmitting scheduler.

[0147] The vehicle-mounted antenna calculates the nearest transmission time that is "no earlier than the serial port data ready time" based on the time slot index.

[0148] The vehicle antenna passes through in a periodic manner In a recurring time slot structure, select the smallest non-negative integer round. , is represented as:

[0149] ;

[0150] in, Indicates the round number. Indicates the time when serial port message reception is complete. Indicates the scheduling reference time, period , is represented as:

[0151] ;

[0152] in, This indicates the total number of time slots.

[0153] It should be noted that the scheduling reference time It is usually equal to the time when the downlink trigger frame reception is completed. .

[0154] Based on the round number, the vehicle-mounted antenna determines the actual transmission time of the uplink data frame, expressed as:

[0155] ;

[0156] in, Indicates the actual transmission time of the uplink data frame. This indicates the onboard processing offset of the uplink data frame.

[0157] Furthermore, the communication terminal generates time domain bytes based on the difference between the time when serial port data reception is completed and the actual time when the uplink data frame is transmitted.

[0158] If the difference between the time when serial data reception is completed and the actual time when the uplink data frame is transmitted is less than 0, then the time domain byte is set to 0.

[0159] If the difference between the time when serial data reception is completed and the actual time when the uplink data frame is transmitted is greater than 255, then the time domain byte is set to 255.

[0160] The remaining integer milliseconds are written to a 1-byte time field.

[0161] The vehicle-mounted antenna selects the uplink data frame command word and encapsulates the data field by pressing the downlink trigger command type.

[0162] Assuming that the downlink trigger command type is synchronous trigger, the uplink command word is 0x82, and the data field contains at least 1 byte of time field.

[0163] Assuming that the downlink trigger command type is verification trigger, the uplink command word is 0x84, and the data field contains at least 1 byte of time field and 4 bytes of vehicle mileage.

[0164] An extension field is added to the vehicle antenna following the existing data field.

[0165] The extended fields carry the current data frame number, road segment identifier, pole number, and time slot index in sequence.

[0166] The vehicle antenna writes the license plate media access control field into the uplink MAC field, and then writes the packet length field and CRC16 field sequentially according to the existing frame format.

[0167] Furthermore, the vehicle-mounted antenna transmits uplink data frames at the actual transmission time of the uplink data frame.

[0168] After launch, it enters a waiting state, awaiting a roadside downlink confirmation frame.

[0169] If no acknowledgment is received within the preset time limit, a new time slot index is calculated according to the secondary time slot splitting rules and retransmitted in the next window.

[0170] It should be noted that the uplink data frame includes a frame header, a packet length field, a MAC field for representing the vehicle antenna, a command word for representing the command type, a data field containing the second specific data, a CRC16 checksum, and a frame trailer.

[0171] The second specific data includes time domain, vehicle mileage, license plate number, road segment representation, pole number, and time slot index.

[0172] It should be noted that the uplink data frames are sent from the vehicle-mounted antenna to the roadside antenna, transmitting the data collected by the vehicle-mounted antenna.

[0173] It should also be noted that the downlink acknowledgment frame includes a frame header, a packet length field, a MAC field identifying the vehicle antenna, a command word for confirming the command type, a data field containing the return result, a CRC16 checksum, and a frame trailer.

[0174] The returned result usually indicates success or failure.

[0175] It should also be noted that the downlink confirmation frame is sent from the roadside antenna to the vehicle-mounted antenna to confirm that the vehicle-mounted antenna has successfully received the downlink trigger frame and completed the corresponding operation.

[0176] S5. When the roadside antenna completes the transmission of the downlink trigger frame, it establishes a time slot window, receives uplink data frames based on the time slot window, uses the license plate media access control field, and sends downlink confirmation frames after deduplication based on the sequence number of the current data frame.

[0177] Furthermore, the roadside antenna calculates the time slot window used to determine the roadside antenna's reception of the vehicle-mounted antenna's uplink data frames based on the completion time of the downlink trigger frame reception and the time slot parameters (total number of time slots and time slot duration).

[0178] The method for calculating the time slot window for roadside antennas is the same as that for vehicle-mounted antennas.

[0179] However, it should be noted that the calculations performed by the vehicle-mounted antenna are used to send uplink acknowledgment frames in the correct time slot, avoiding conflicts caused by multiple vehicles sending data simultaneously.

[0180] Furthermore, the roadside antenna receives and extracts the data frame sequence number of the uplink data frame according to the time slot window, and compares it with the sequence number of the previously received frame.

[0181] If the sequence number of the uplink data frame is the same as the sequence number of the cached frame, it is determined to be duplicate data, and a decision is made based on the set service requirements to decide whether to discard the current frame or continue receiving downlink data.

[0182] If the frame number of the current uplink data frame is different from the frame number in the buffer, then the current uplink data frame is considered to be new and valid data.

[0183] Since the current uplink data frame is new valid data, the roadside antenna encapsulates the data frame sequence number, road segment identifier, pole number, and time slot index as extended fields to form the downlink confirmation frame data for confirmation.

[0184] S6. If the downlink confirmation frame times out and is not confirmed, a secondary time slot index is generated and the frame is retransmitted in the next time slot window.

[0185] Furthermore, if the roadside antenna does not receive an acknowledgment within the time limit, a secondary time slot index is generated, and the acknowledgment frame is rescheduled for transmission in the next time slot window based on the new time slot index.

[0186] Among them, the new time slot index , represented as:

[0187] ;

[0188] in, Indicates the data frame sequence number. Indicates road segment signs, Indicates the rod number.

[0189] If no confirmation is received within the time limit, the current confirmation request will be marked as "unconfirmed".

[0190] In this embodiment, to verify the beneficial effects of a vehicle-road communication protocol method for taxi data transmission, a typical vehicle-road cooperative scenario in urban roads is used as the background. Roadside equipment is deployed at adjacent pole positions, with cross-pole coverage and adjacent pole overlapping coverage (characterized by the overlapping coverage ratio). Vehicles move within the coverage area and receive roadside broadcasts, and then perform uplink confirmation and uplink data transmission under multi-vehicle concurrent conditions. The wireless channel considers path loss, shadow fading, and fast fading caused by received power fluctuations, thus forming a jitter characteristic similar to a measurement curve.

[0191] Among them, the roadside equipment can be configured with transmission power and form power differences of 0, 3 and 6 between adjacent pole positions; the vehicle-mounted communication terminal can parse the pole position pilot field and the downlink broadcast media access control field and perform verification; the access control configuration adopts two strategies: 32 time slots and 64 time slots.

[0192] By statistically analyzing the misbinding rate and uplink success rate, and grouping records by overlay coverage ratio and concurrent vehicle number for comparison of differences and stability, the following results were obtained: Figure 5 and Figure 6 .

[0193] Figure 5This graph shows the change in misbinding rate with overlay coverage, verifying the effectiveness of identifiable and verifiable roadside broadcast sources in reducing the risk of misbinding. The graph presents three curves representing power differences of 0, 3, and 6, reflecting the impact of differences in transmission strength between adjacent pole positions on misbinding. Generally, as the overlay coverage ratio increases, the greater the power difference, the higher the misbinding rate. Figure 5 As can be seen from the data, after adopting the verification mechanism of the pole position pilot field and the downlink broadcast media access control field, the misbinding rate remained at a low level and did not rise out of control. This indicates that the verification mechanism can improve the verifiability of broadcast sources under cross-pole position coverage and superposition conditions, thereby reducing the risk of misbinding.

[0194] Figure 6 The graph shows the uplink success rate as a function of the number of concurrent vehicles, verifying the beneficial effect of implicit time-division access control under multi-vehicle concurrency conditions achieved through time slot indexing, which helps reduce the probability of co-frequency collisions and retransmissions. The graph compares two fixed time slot configurations: 32 and 64 time slots. The overall trend is that the uplink success rate decreases as the number of concurrent vehicles increases, consistent with the rule that multi-vehicle competition leads to an increased collision probability. The curve for 32 time slots decreases more rapidly, indicating that when time slot resources are limited, the probability of multiple vehicles falling into the same time slot increases, collisions and retransmissions are more concentrated, and the success rate is more significantly affected by the scale of concurrency. The curve for 64 time slots is generally higher and decreases more slowly, indicating that more abundant time slot resources can form a more definite stagger on the time axis, thereby reducing the co-frequency collision rate. Figure 6 The results in the figure indirectly prove that when vehicles are arranged uplink according to the time slot index, the stronger the determinism of time-division access, the lower the probability of collision and retransmission, and the higher the success rate of uplink interaction; the larger the concurrency scale, the more obvious the advantages of this invention.

[0195] In summary, this invention achieves the identification and verification of roadside broadcast sources through the verification of the pole position pilot field and the downlink broadcast media access control field, which helps reduce the risk of misbinding under conditions of cross-pole coverage or adjacent pole position superposition. Through time slot indexing, implicit time-division access control under multi-vehicle concurrent conditions is realized, so that the uplink confirmation and uplink data of different vehicles are deterministically staggered on the time axis, which helps reduce the probability of co-frequency collisions and retransmissions. Through the secondary time slot indexing and the next round window retransmission mechanism, predictable retransmission scheduling is realized in the case of collisions or frame drops, which helps avoid the re-concentration of conflicts caused by multiple vehicles retransmitting at the same time, thereby improving the success rate of interactive closed loop.

[0196] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A vehicle-to-infrastructure communication protocol method for taxi data transmission, characterized in that: include, Construct a pole position pilot field, append the pole position pilot field to the front of the downlink trigger frame header, and set the broadcast media access control field within the downlink trigger frame; The roadside antenna sends downlink trigger frames, the vehicle-mounted antenna identifies the pole position pilot field, obtains the road segment identifier and pole number, and verifies them with the broadcast media access control field; The vehicle-mounted antenna calculates the time slot index based on the pole position pilot field and the license plate media access control field, and confirms the uplink confirmation frame transmission time based on the downlink trigger frame reception completion time, vehicle processing offset, and time slot duration, and then transmits it. The license plate media access control field is used to fill the uplink MAC field and also serves as the input for the time slot index calculation; The communication terminal obtains the current data frame sequence number and vehicle mileage from the meter via the serial port, generates time domain bytes, and schedules the uplink data frame to be sent according to the time slot index. When the roadside antenna completes the transmission of the downlink trigger frame, it establishes a time slot window, receives uplink data frames based on the time slot window, uses the license plate media access control field, and sends downlink confirmation frames after deduplication based on the sequence number of the current data frame. If the downlink confirmation frame times out without confirmation, a secondary time slot index is generated and the data is retransmitted in the next time slot window.

2. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 1, characterized in that: The pole position pilot field includes fixed synchronization byte pairs, road segment identifier, and pole number.

3. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 2, characterized in that: The specific steps for constructing the pole position pilot field are as follows: The pole position pilot field consists of four bytes; Among them, the first and second bytes of the pole position pilot field are fixed synchronization byte pairs, the third byte is the road segment identifier, and the fourth byte is the pole number.

4. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 3, characterized in that: The vehicle-mounted antenna identification pole position pilot field includes... The vehicle-mounted antenna receives the baseband byte stream of the downlink trigger frame and writes the baseband byte stream of the downlink trigger frame into the receive buffer; Before parsing the 0x7E frame header carried by the downlink trigger frame, the vehicle-mounted antenna first performs a pole position pilot scan within a range of several bytes in the receive buffer to define fixed synchronization byte pairs; The baseband byte stream in the receiving buffer is detected sequentially using the vehicle-mounted antenna; If the vehicle-mounted antenna detects a fixed synchronization byte pair in the baseband byte stream, it determines that the detected field position is the starting point of the pole position pilot field, and performs offset identification according to the pole position pilot field to obtain the road segment identifier and pole number; If no fixed synchronization byte pair is found within the entire baseband byte stream scan range, the pilot identification is deemed to have failed, and a rollback process is initiated.

5. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 4, characterized in that: The rollback process includes the vehicle antenna continuing to parse the downlink trigger frame, obtaining the broadcast media access control field, deriving the pole number from the broadcast media access control field, and setting the road segment identifier to the default value. The broadcast media access control field derivation rod number includes, with the vehicle antenna set to 0x7E, delimiting and parsing the downlink trigger frame to obtain the broadcast media access control field; Check if the broadcast media access control fields of the vehicle antenna are all equal. If all broadcast media access control fields are equal, then define the backoff lever number as the common padding value of the broadcast MAC; If the broadcast media access control fields are incomplete, the downlink trigger frame will be marked as invalid and discarded.

6. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 5, characterized in that: The specific steps for obtaining the road segment identifier and pole number, and verifying them with the broadcast media access control field, are as follows: When pilot identification is successful, the vehicle-mounted antenna performs pole number verification. The pole number verification includes: if the pole number is not equal to the fallback pole number, then the downlink trigger frame is marked as having an inconsistent pole number and discarded. If the lever number is equal to the backoff lever number, then the downlink trigger frame lever numbers are determined to be the same; When pilot identification fails, the vehicle-mounted antenna uses the backtracking result, taking the backtracked pole number as the pole number and the default value as the road segment identifier.

7. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 6, characterized in that: The calculated time slot index includes the vehicle antenna acquiring the vehicle license plate media access control field; Construct the input byte sequence based on the license plate media access control field; Perform CRC16 checksum calculation on the input byte sequence to obtain a 16-bit result; Based on the 16-bit result, the time slot index is obtained through modulo operation.

8. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 7, characterized in that: The confirmation of uplink confirmation frame transmission time includes, based on the downlink trigger frame reception completion time, and combined with the time shift amount of the product of the vehicle processing offset and the time slot index and time slot duration, the uplink confirmation frame transmission time is obtained, expressed as: ； in, Indicates the planned transmission time of the uplink acknowledgment frame. Indicates the time when the downlink trigger frame reception is completed. This indicates the onboard processing offset of the uplink acknowledgment frame. Indicates the time slot index. Indicates the duration of the time slot.

9. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 8, characterized in that: The specific steps for generating time-domain bytes and scheduling the transmission of uplink data frames according to the time slot index are as follows: The communication terminal generates time domain bytes based on the difference between the time when serial port data reception is completed and the actual time when the uplink data frame is transmitted. The vehicle-mounted antenna selects the command word of the uplink data frame according to the downlink trigger command type and encapsulates the data field; The vehicle-mounted antenna appends an extension field after the data field field in the uplink data frame. The extended fields sequentially carry the current data frame number, road segment identifier, pole number, and time slot index; The vehicle antenna writes the license plate media access control field into the uplink MAC field to obtain uplink data frames; The vehicle-mounted antenna transmits uplink data frames at the actual transmission time of the uplink data frame; The actual transmission time of the uplink data frame is determined by taking the reference time as the starting point, combining the on-board processing offset, the time offset of the corresponding time slot of the vehicle, and the period.

10. The vehicle-to-infrastructure communication protocol method for taxi data transmission as described in claim 9, characterized in that: The process of generating a secondary time slot index and retransmitting it in the next time slot window includes... The roadside antenna calculates the time slot window for receiving uplink data frames from the vehicle-mounted antenna based on the completion time of the downlink trigger frame reception and the time slot parameters. The roadside antenna receives and extracts the data frame sequence number of the uplink data frame according to the time slot window, and compares it with the sequence number of the previously received frame; Based on the fact that the current uplink data frame is new valid data, the roadside antenna encapsulates the data frame sequence number, road segment identifier, pole number, and time slot index as extended fields to form downlink confirmation frame data and confirm it; If the roadside antenna does not receive an acknowledgment within the time limit, a secondary time slot index is generated, and the acknowledgment frame is rescheduled for transmission in the next time slot window based on the new time slot index. If no confirmation is received within the time limit, the current confirmation request will be marked as unconfirmed.

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