Patent Publication Number: US-2023143167-A1

Title: Vehicle hybrid communication system and communication method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a communication system and a communication method thereof, in particular a vehicle hybrid communication system and a communication method thereof. 
     2. Description of the Related Art 
     An automated vehicle is usually remotely connected to a back-end information station, wherein both the automated vehicle and the back-end information station transfer data bi-directionally. The automated vehicle would transfer real-time data relating to GPS coordinates, throttle openness, break signals, vehicle camera feeds, traffic situations, and/or vehicle speed to the back-end information station. The back-end information station would then be able to monitor and comprehend real-time situations relating to the automated vehicle. The back-end information station would also be able to transfer data and control commands to the automated vehicle, allowing the automated vehicle to drive automatically based on the data and control commands provided. 
     Naturally, the data transferred between the automated vehicle and the back-end information station is of great abundance and importance, as the data closely relates to safety of the vehicle. It is therefore very important to ensure good communication quality between the automated vehicle and the back-end information station. When communication quality decreases between the automated vehicle and the back-end information station, or when the automated vehicle disconnects from the back-end information station, the automated vehicle can no longer receive crucial real-time data and control commands from the back-end information station, and without the back-end information station properly updated about the automated vehicle&#39;s real-time situation, the automated vehicle has increased chances of having a traffic accident. 
     SUMMARY OF THE INVENTION 
     Regarding the above drawbacks, the present invention provides a vehicle hybrid communication system and a communication method thereof. The present invention ensures good communication quality as the vehicle connects externally and remotely, improving upon drawbacks about communication quality mentioned in prior arts. 
     A vehicle hybrid communication system includes: 
     a vehicle communication device, mounted in a vehicle, including a vehicle controller and multiple vehicle communication interfaces; wherein the vehicle communication interfaces are electrically connected to the vehicle controller; and 
     a field communication device, mounted on a roadside, including a field controller and multiple field communication interfaces; wherein the field communication interfaces are electrically connected to the field controller; wherein multiple communication channels are established between at least two of the field communication interfaces and at least two of the vehicle communication interfaces, allowing a network packet to be transferred between the vehicle communication device and the field communication device via the communication channels; 
     wherein, the vehicle controller respectively defines a bandwidth level and a speed level based on a real-time bandwidth and a real-time connection speed of each of the communication channels; wherein the vehicle controller then creates a score based on the bandwidth level and the speed level of each of the communication channels, and then the vehicle controller sets one of the communication channels with the best score as a main communication channel; wherein via the main communication channel, the vehicle controller transfers data to the field communication device. 
     A vehicle hybrid communication method is executed by a vehicle controller and includes steps of: 
     establishing multiple communication channels with a field communication controller; 
     defining a bandwidth level and a speed level based on a real-time bandwidth and a real-time connection speed of each of the communication channels; 
     creating a score based on the bandwidth level and the speed level of each of the communication channels; and 
     setting one of the communication channels with the best score as a main communication channel; wherein via the main communication channel, the vehicle controller transfers data to the field communication device. 
     The vehicle hybrid communication system and communication method of the present invention allow the field communication device to be connected to a back-end information station. The field communication device allows bi-directional data transfers between the vehicle communication device and the back-end information station. Multiple communication channels are established between the vehicle controller and the field controller, and among the communication channels, one communication channel with the best score is set to be the main communication channel. Even given a time when the main communication channel suffers disconnection or bad communication quality, the present invention is able to reset one of the other communication channels with the best score as the main communication channel. This way the present invention ensures best connection between the vehicle communication device and the field communication device in any given time, thus improving communication quality issues mentioned in prior arts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram of an embodiment of a vehicle hybrid communication system of the present invention. 
         FIG.  2    is a schematic diagram of connection between the vehicle hybrid communication system of the present invention and a back-end information station. 
         FIG.  3    is another block diagram of the embodiment of the vehicle hybrid communication system of the present invention. 
         FIG.  4    is a schematic diagram of a network packet frame transmitted from a vehicle controller of the present invention. 
         FIG.  5    is a schematic diagram of a network packet frame transmitted from a field controller of the present invention. 
         FIG.  6    is a flow chart of an embodiment of a vehicle hybrid communication method of the present invention. 
         FIG.  7    is a flow chart of a determination of whether a main communication channel transfers a network packet abnormally in the present invention. 
         FIG.  8    is a perspective-viewed flow chart of a determination of whether a main communication channel has disconnected in the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG.  1   , an embodiment of a vehicle hybrid communication system of the present invention includes a vehicle communication device  10  and a field communication device  20 . The vehicle communication device  10  is mounted in a vehicle  100 . The vehicle  100  may be an automated vehicle or a vehicle in a group of automated vehicles. The field communication device  20  is mounted on a roadside, wherein the vehicle drives on the road and passes the side of the road installed with the field communication device  20 . The field communication device  20  is free to be installed indoors or outdoors. In  FIG.  2   , multiple field communication devices are installed along the roadside. In this case, as long as the vehicle communication device  10  of the vehicle  100  enters within communication range of either of the field communication devices  20 , the vehicle communication device  10  and the field communication device  20  can connect and bi-directionally transfer data. Here  FIG.  1    offers a block diagram for explaining a situation wherein the vehicle communication device  10  is connected with one of the field communication devices  20 . 
     For example, the field communication device  20  connects to a back-end information station  30 . The vehicle communication device  10  receives a real-time traffic data through an On-Board Diagnostics-II (OBD-II) and a Controller Area Network (CAN Bus). The vehicle communication device  10  then sends the real-time traffic data to the field communication device  20 . The real-time traffic data, for example, includes synchronized time with time of a control system of the vehicle  100 , a vehicle coordinate (for example a GPS coordinate), a throttle openness, break signals, vehicle camera feeds, traffic situations, and/or vehicle speed. The back-end information station  30  is able to receive the real-time traffic data from the field communication device  20 . In addition, the back-end information station  30  is also able to transmit data and control commands through the field communication device  20  to the vehicle communication device  10 . When the vehicle  100  is automated, the vehicle  100  stays automated based on the data and the control commands received. The vehicle  100  stays automated by maintaining vehicle speed control (such as maintaining speed, accelerating, decelerating, and braking), route control (such as going straight, turning, overtaking, and pulling over), and formation changes of vehicle platoon etc. The vehicle  100  is free to stay automated elsewise by maintaining other aspects unmentioned in the example above. 
     It is very important to ensure good communication quality between the vehicle communication device  10  and the field communication device  20 . When the communication quality is great, the real-time traffic data of the vehicle  100  can be factually provided to the back-end information station  30 . The back-end information station  30  would be able to effectively monitor situations relating to the vehicle  100 . The vehicle  100  also would be able to factually receive data and control commands from the back-end information station  30 , for accordingly automating the vehicle  100 . 
     In an embodiment of the present invention, the vehicle communication device  10  includes a vehicle controller  11  and multiple vehicle communication interfaces  12 , wherein the vehicle communication interfaces  12  are electrically connected to the vehicle controller  11 . The vehicle communication interfaces differ individually in types (of different communication protocols). The vehicle controller  11  is a controller chip, and the vehicle communication interfaces  12  are wireless communication interfaces. Such wireless communication interfaces include mobile communication interfaces and short distance wireless communication interfaces. With reference to  FIG.  3   , for instance, the vehicle communication interfaces  12  includes a fifth generation (5G) mobile network communication interface, a fourth generation (4G) mobile network communication interface, a cellular vehicle-to-everything (C-V2X) network communication interface, a Wi-Fi network communication interface, and a Bluetooth Low Energy (BLE) network communication interface. 
     The field communication device  20  includes a field controller  21  and multiple field communication interfaces  22 , wherein the field communication interfaces  22  are electrically connected to the field controller  21 . The field controller  21  is a controller chip, and the field communication interfaces  22  are wireless communication interfaces. At least two of the field communication interfaces  22  correspond to at least two of the vehicle communication interfaces  12  in same types of communication protocols. As an example demonstrated in  FIG.  3   , the field communication interfaces  22  include a 5G mobile network communication interface, a C-V2X network communication interface, and a Wi-Fi network communication interface. In another embodiment, the vehicle communication interfaces  12  and the field communication interfaces  22  completely correspond to each other. 
     When the vehicle communication interfaces  12  and the field communication interfaces  22  corresponding to each other, the vehicle controller is able to send connection commands to the field controller  21 . As such, with reference to  FIG.  1   , multiple communication channels CH are established between at least two of the field communication interfaces  22  and at least two of the vehicle communication interfaces  12 , allowing a network packet to be transferred between the vehicle controller  11  and the field controller  21  via the communication channels CH. With reference to  FIG.  3   , the multiple communication channels CH between the vehicle communication device  10  and the field communication device  20  include a 5G mobile network communication channel CH 1 , a C-V2X network communication channel CH 2 , and a Wi-Fi network communication channel CH 3 . The vehicle controller  11  and the field controller  21  may simultaneously use the 5G mobile network communication channel CH 1 , the C-V2X network communication channel CH 2 , and the Wi-Fi network communication channel CH 3  for sending network packets. Furthermore, the vehicle controller  11  detects a real-time bandwidth and a real-time connection speed of each of the communication channels CH. The detection of the real-time bandwidth and the real-time connection speed is a conventional technique used in communication networks, and therefore hereby will be omitted from further descriptions. 
     With reference to  FIG.  4   , the vehicle controller  11  transmits a first network packet frame  40  to the field controller  21 , and the first network packet frame  40  includes a starting character  401 , a serial  402 , a time code  403 , a vehicle information  404 , and an ending character  405 . The vehicle controller  11  determines whether the first network packet frame  40  is complete by monitoring the starting character  401  and the ending character  405 . The serial and the time code  403  include transmitted time-sequence information of the first network packet frame  40 . The vehicle information  404  includes information of a vehicle&#39;s identification (ID) number and the real-time traffic data aforementioned. 
     With reference to  FIG.  5   , the field controller  21  transmits a second network packet frame  41  to the vehicle controller  11 , and the second network packet frame  41  includes a starting character  411 , a serial  412 , a time code  413 , a field information  414 , and an ending character  415  of the second network packet. The field controller  21  determines whether the second network packet frame  41  is complete by monitoring the starting character  411  and the ending character  415 . The serial  412  and the time code  413  include transmitted time-sequence information of the second network packet frame  41 . The field information  414  includes an ID number for a field area. 
     For the already established communication channels CH, the vehicle controller  11  defines a bandwidth level and a speed level based on the real-time bandwidth and the real-time connection speed of each of the communication channels CH. The bandwidth level and the speed level can respectively have data format of a numeric value, though both are free to have other types of data format. The smaller the bandwidth level of each of the communication channels CH is, the better bandwidth of each of the communication channels CH has. Similarly, the smaller the speed level of each of the communication channels CH is, the faster data transferring speed each of the communication channels CH has. The vehicle controller  11  further creates a score based on the bandwidth level and the speed level of each of the communication channels CH. The score is used to judge the communication quality between the vehicle communication device  10  and the field communication device  20 . The score has format of a numeric value, though also free to have other types of data format. The smaller the score is for each of the communication channels CH, the better the communication quality each of the communication channels CH has. 
     The vehicle controller  11  sets one of the communication channels CH with the best score, i.e. one of the communication channels CH with established connection and with the smallest score, as a main communication channel. The vehicle controller  11  uses the main communication channel to transfer data bi-directionally with the field communication device  20 . When the communication quality is relatively good, the real-time traffic data of the vehicle  100  would be effectively sent to the back-end information station  30 , and the vehicle  100  would also be able to effectively receive data and control commands sent from the back-end information station  30 . 
     The following details how the main communication channel is selected from multiple communication channels CH with established connections. Here the field controller  21  is able to send testing network packets to the vehicle controller  11  via the communication channels CH with already established connections. 
     With reference to  FIG.  1   , in the embodiment of the present invention, the vehicle controller  11  stores a bandwidth level conversion form  50  corresponding to each of the communication channels CH. The bandwidth level conversion form  50  includes multiple bandwidth ranges and multiple bandwidth level serials corresponding to the bandwidth ranges. For the communication channels CH with already established connections, the vehicle controller  11  determines which one of the bandwidth ranges the real-time bandwidth belongs to. The vehicle controller  11  then defines the bandwidth level to be the bandwidth level serial corresponding to the belonged bandwidth range. For example, the bandwidth level conversion form  50  for each of the communication channels CH is listed below. Each of the bandwidth ranges corresponds to one of the bandwidth level serials. The bandwidth level serials are represented in numbers. The smaller the numbers representing the bandwidth level serials are, the better the bandwidth performances are. 
     
       
         
           
               
            
               
                   
               
               
                 Bandwidth Level Conversion Form 
               
            
           
           
               
               
               
            
               
                 Bandwidth level 
                 Bandwidth range (Mbps) 
                   
               
            
           
           
               
               
               
            
               
                 serials 
                 Upper limit 
                 Bottom limit 
               
               
                   
               
               
                 1 
                 BW 0   
                 BW 1   
               
               
                 2 
                 BW 1  − 1 
                 BW 2   
               
            
           
           
               
               
               
            
               
                 . 
                 . 
                   
               
               
                 . 
                 . 
               
               
                 . 
                 . 
               
            
           
           
               
               
               
            
               
                 N 
                 BW n−1  − 1 
                 BW n   
               
               
                   
               
            
           
         
       
     
     Regarding the bandwidth level conversion form  50  shown above, BW 0  represents a reference bandwidth for each of the communication channels CH. When the testing network packets sent by the field controller  21  to the vehicle controller  11  via the communication channels CH, the field controller  21  already includes BW 0  in the testing network packets. When the vehicle controller  11  receives the testing network packets, the vehicle controller  11  would be able to obtain BW 0 , so each channel of the communication channels CH is able to individually correspond to a BW 0 . In the bandwidth level conversion form  50  shown above, N represents the biggest value corresponding to the bandwidth level serials, and N is also a positive integer bigger than or equal to two. In the bandwidth level conversion form  50  shown above, n represents the corresponding bandwidth level serial, and BW 0  is represented as below: 
       BW n =BW 0 −(BW 0   /N )× n  
 
     For instance, when N=10 and BW 0 =1000, BW 1  will equal 900. Therefore bandwidth level serial 1 would correspond to bandwidth range of 1000 to 900 Mbps, and bandwidth level serial 2 would correspond to bandwidth range of 899 to 800 Mbps and so forth. For bandwidth level serial N, N=n, and therefore a bottom limit of the corresponding bandwidth range will be zero. Logically, the best bandwidth range with the highest Mbps for high performance corresponds to bandwidth level serial 1. 
     In the embodiment of the present invention, and with reference to  FIG.  1   , the vehicle controller  11  stores a speed level conversion form  51  corresponding to each of the communication channels CH. The speed level conversion form  51  includes multiple connection speed ranges and multiple speed level serials corresponding to the connection speed ranges. For the communication channels CH with already established connections, the vehicle controller  11  is able to determine which one of the speed ranges the real-time connection speed belongs to. The vehicle controller  11  then defines the speed level to be the speed level serial corresponding to the belonged speed range. For example, the speed level conversion form  51  for each of the communication channels CH is listed below. Each of the connection speed ranges corresponds to one of the speed level serials. The speed level serials are represented in numbers. The smaller the numbers representing the speed level serials are, the better the connection speed performances are. 
     
       
         
           
               
            
               
                   
               
               
                 Speed Level Conversion Form 
               
            
           
           
               
               
               
            
               
                 Speed level 
                 Connection speed range (bps) 
                   
               
            
           
           
               
               
               
            
               
                 serials 
                 Upper limit 
                 Bottom limit 
               
               
                   
               
               
                 1 
                 SPD 0   
                 SPD 1   
               
               
                 2 
                 SPD 1  − 1 
                 SPD 2   
               
            
           
           
               
               
               
            
               
                 . 
                 . 
                   
               
               
                 . 
                 . 
               
               
                 . 
                 . 
               
            
           
           
               
               
               
            
               
                 M 
                 SPD m−1  − 1 
                 SPD m   
               
               
                   
               
            
           
         
       
     
     Regarding the speed level conversion form  51  shown above, SPD 0  represents a reference connection speed for each of the communication channels CH. When the testing network packets sent by the field controller  21  to the vehicle controller  11  via the communication channels CH, the field controller  21  already includes SPD 0  in the testing network packets. When the vehicle controller  11  receives the testing network packets, the vehicle controller  11  would be able to obtain SPD 0 , so each channel of the communication channels CH is able to individually correspond to an SPD 0 . In the speed level conversion form  51  shown above, M represents the biggest value corresponding to the speed level serials, M is also a positive integer bigger than or equal to two, and M can also be equal to N (though M is free to be elsewise). In the speed level conversion form  51  shown above, m represents the corresponding speed level serial, and SPD m  is represented as below: 
       SPA m =SPD 0 −(SPD 0   /M )× m  
 
     For instance, when M=10 and SPD 0 =2000, SPD 1  will equal 1800. Therefore speed level serial 1 would correspond to connection speed range of to 1800 bps, and speed level serial 2 would correspond to connection speed range of 1799 to 1600 bps and so forth. For speed level serial M, M=m, and therefore a bottom limit of the corresponding connection speed range will be zero. Logically, the best connection speed range with the highest bps for high performance corresponds to speed level serial 1. 
     Regarding a calculation of the score for each of the communication channels CH, in the embodiment, the vehicle controller  11  stores multiple weighted values. Each of the weighted values differs from each other, and each of the weighted values corresponds to one of the communication channels CH. The weighted values are represented in numbers, though the weighted values are free to be represented in another format. The smaller the numbers representing weighted values are, the more likely the corresponding communication channel CH for the weighted value will be chosen for use. The vehicle controller  11  creates the score for each of the communication channels CH based on the corresponding bandwidth level, the corresponding speed level, and the corresponding weighted value. An equation of evaluation is shown below: 
       the score=(the bandwidth level+the speed level)×the weighted value
 
     For example, the weighted values for each of the communication channels CH are listed below: 
     
       
         
           
               
            
               
                   
               
               
                 List 1 
               
            
           
           
               
               
               
            
               
                   
                 Communication channel 
                 Weighted value 
               
               
                   
                   
               
               
                   
                 5G 
                 1 
               
               
                   
                 4G 
                 2 
               
               
                   
                 C-V2X 
                 3 
               
               
                   
                 Wi-Fi 
                 4 
               
               
                   
                 BLE 
                 5 
               
               
                   
                   
               
            
           
         
       
     
     The following two scenarios detail how the vehicle controller  11  sets the main communication channel through multiple options of the communication channels CH. 
     Scenario 1: 
     The communication channels CH established by the vehicle communication device  10  and the field communication device  20  include a 5G mobile network communication channel, a 4G mobile network communication channel, a C-V2X network communication channel, a Wi-Fi network communication channel, and a BLE network communication channel. The vehicle controller  11  determines the scores based on the bandwidth levels, the speed levels, and the weighted values listed below: 
     
       
         
           
               
            
               
                   
               
               
                 List 2 
               
            
           
           
               
               
               
               
               
            
               
                 Communication 
                 Bandwidth 
                 Speed 
                 Weighted 
                   
               
               
                 channels 
                 levels 
                 levels 
                 values 
                 Scores 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 5G 
                 1 
                 1 
                 1 
                 2 
               
               
                 4G 
                 2 
                 1 
                 2 
                 6 
               
               
                 C-V2X 
                 3 
                 2 
                 3 
                 15 
               
               
                 Wi-Fi 
                 2 
                 4 
                 4 
                 24 
               
               
                 BLE 
                 5 
                 5 
                 5 
                 50 
               
               
                   
               
            
           
         
       
     
     As detailed above in scenario 1, the vehicle controller  11  determines that the 5G mobile network communication channel has the smallest score. This means the 5G mobile network communication channel provides the best communication quality, and therefore the vehicle communication device  10  would set the 5G mobile network communication channel as the main communication channel to connect and to transfer data bi-directionally with the field communication device  20 . 
     Scenario 2: 
     The communication channels CH established by the vehicle communication device  10  and the field communication device  20  include a 4G mobile network communication channel, a C-V2X network communication channel, and a Wi-Fi network communication channel. The vehicle controller  11  determines the scores based on the bandwidth levels, the speed levels, and the weighted values listed below: 
     
       
         
           
               
            
               
                   
               
               
                 List 3 
               
            
           
           
               
               
               
               
               
            
               
                 Communication 
                 Bandwidth 
                 Speed 
                 Weighted 
                   
               
               
                 channels 
                 levels 
                 levels 
                 values 
                 Scores 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 4G 
                 2 
                 1 
                 2 
                 6 
               
               
                 C-V2X 
                 1 
                 1 
                 3 
                 6 
               
               
                 Wi-Fi 
                 2 
                 4 
                 4 
                 24 
               
               
                   
               
            
           
         
       
     
     As detailed above in scenario 2, the vehicle controller  11  determines that the 4G mobile network communication channel and the C-V2X network communication channel both have the smallest score. This means the 4G mobile network communication channel and the C-V2X network communication channel both provide the best communication quality. Since the weighted value corresponding to the 4G mobile network communication channel is smaller than the weighted value corresponding to the C-V2X network communication channel, the vehicle controller  11  would set the 4G mobile network communication channel as the main communication channel to connect and to transfer data bi-directionally with the field communication device  20 . In other words, when the vehicle controller  11  determines more than two of the communication channels CH share the best score, the vehicle controller  11  would set the communication channel corresponding to the best (smallest) weighted values, among the communication channels CH with the best score, as the main communication channel. 
     As described previously, the vehicle controller  11  would set the main communication channel from one of the communication channels CH to transfer data with the field communication device  20 . However, the main communication channel is still prone to possibilities of network packet delivery abnormalities or disconnection. For instance, when the field communication interface  22  corresponding to the main communication channel fails, network packet delivery abnormalities or disconnection may occur. When the vehicle controller  11  determines abnormalities relating to network packet deliveries or a disconnection has occurred, the vehicle controller  11  would reset another one of the communication channels CH with established connections (and with the best score at the very instance) as the main communication channel. This method provides a salvage mechanism for when abnormalities or disconnections happen, thus maintaining data transfers between the vehicle controller  11  and the field communication device  20  at all times, and maintaining connections between the vehicle  100  and the back-end information station  30  at all times. As an example referring to scenario 1, when the main communication channel as the 5G mobile network communication channel occur disconnections or network packet delivery abnormalities, the vehicle controller  11  resets the 4G mobile network communication channel as the main communication channel. As the vehicle  100  drives more, perhaps the 5G mobile network communication channel would re-gain its connectivity. The vehicle controller  11  then re-sends a connection command to the field controller  21  to once again establish a connection with the 5G mobile network communication channel. When the 5G mobile network communication channel is re-connected and has once again been determined as having the best score, the vehicle controller  11  then resets again for the 5G mobile network communication channel to be the main communication channel. Same logical steps can be applied to scenario 2, wherein when the main communication channel as the 4G mobile network communication channel occur disconnections or network packet delivery abnormalities, the vehicle controller resets the C-V2X network communication channel as the main communication channel. 
     With reference to  FIG.  6   , in conclusion, the vehicle hybrid communication method of the present invention is executed by the vehicle controller  11 . The vehicle hybrid communication method includes the following steps: 
     Step S 01 : establishing multiple communication channels CH with the field communication controller  21 ; 
     Step S 02 : defining the bandwidth level and the speed level based on the real-time bandwidth and the real-time connection speed of each of the communication channels CH; 
     Step S 03 : creating the score based on the bandwidth level and the speed level of each of the communication channels CH; and 
     Step S 04 : setting one of the communication channels CH with the best score as the main communication channel; wherein via the main communication channel, the vehicle controller  11  transfers data to the field communication device  20 . 
     With reference to  FIG.  7   , the following steps detail how the vehicle controller  11  determines whether the main communication channel has encountered abnormalities relating to network packet transfers: 
     Step S 11 : extracting serials respectively from two network packets received by the vehicle controller  11  through the main communication channel, and respectively defining the serials that are extracted as an earlier serial P and a latest serial Q; wherein the vehicle controller  11  receives the earlier serial P first and receives the latest serial Q later; 
     Step S 12 : determining whether the main communication channel has encountered disconnection or abnormalities based on the network packet transfers according to the earlier serial P and the latest serial Q received by the vehicle controller  11 ; wherein the vehicle controller  11  determines whether the earlier serial P plus an accumulative coefficient R equals the latest serial Q, for determining whether there are discontinuities between the latest serial Q and the earlier serial P; 
     if the vehicle controller  11  determines the earlier serial P plus the accumulative coefficient R equals the latest serial Q, then the latest serial Q and the earlier serial P are viewed as being continuous, in other words, the network packet transfer is functioning normally; if the vehicle controller  11  determines elsewise, then further proceed to step S 13 ; 
     Step S 13 : letting the latest serial Q minus the earlier serial P equal a difference D, and determining whether the difference D is greater than or equal to a tolerance value T; 
     if the difference D is smaller than the tolerance value T, then the vehicle controller  11  determines the main communication channel is normally connecting; if the difference D is greater than or equal to the tolerance value T, then the vehicle controller  11  determines that discontinuities exist between the latest serial Q and the earlier serial P, in other words, between the two received network packets, many other network packets are lost, and therefore data transferring abnormalities exist. The aforementioned accumulative coefficient R and the tolerance value T are adjustable default values. The accumulative coefficient R for instance can be set to one, and the tolerance value T can be set to five. 
     With reference to  FIG.  8   , the following steps detail how the vehicle controller  11  determines whether the main communication channel has disconnected: 
     Step S 21 : extracting the time code  413  from the second network packet frame  41  from a network packet received by the vehicle controller  11  from the field controller  21 ; wherein the time code  413  details the time of the network packet sent from the field controller  21 ; 
     Step S 22 : calculating a time difference between the time code  413  and a current time; wherein the vehicle controller  11  is able to obtain the current time through the OBD-II, the CAN Bus, or the real-time traffic data of the vehicle  100 ; 
     Step S 23 : determining when the time difference is within a time threshold, in other words, when the time difference is less than or equal to the time threshold, whether the vehicle controller  11  has received another new network packet; 
     if yes, then the main communication channel is determined to be functioning normally without disconnections; elsewise, the vehicle controller  11  determines a timeout has occurred, meaning the main communication channel has encountered disconnection. The aforementioned time threshold is an adjustable default value. The time threshold can be set to be 100 milliseconds (ms). 
     In conclusion, multiple communication channels are established between the vehicle controller  11  and the field controller  21 . The vehicle controller  11  is able to monitor communication qualities of each of the communication channels CH. The communication channels CH having the best communication qualities shall receive the best score, and one of the communication channels CH with the best score is set to be the main communication channel. On the other hand, the present invention also provides the salvage mechanism for when abnormalities or disconnections happen to the main communication channel. The present invention prepares another communication channel for substitution for the main communication channel when needed. In other words, when the main communication channel encounters abnormalities relating to data transfers or disconnections, the vehicle controller  11  will reset another communication channel as the main communication channel, to ensure best communication quality and to maintain connections between the vehicle communication device  10  and the field communication device  20 .