Abstract:
This specification discloses a driving safety auxiliary network administration system and the method thereof. Vehicles in motion communicate with each other about their geographical locations and current moving states within a communication range. At least one of the vehicles in the communication range becomes the router of several other vehicles that are at dead corners of wireless communications. The router is responsible for transferring vehicle state signals of those vehicles out of direct communications between them. Therefore, all the vehicles in the communication range are not blocked by terrains, buildings or other vehicles. All of them are taken into account to assess and find possible dangerous vehicles. This technique can effectively solve the problem of dead corners in driving safety auxiliary network communications. Highly important packets can be immediately and reliably transmitted to the corresponding vehicles, providing efficient warnings.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a driving safety auxiliary communication system and, in particular, to an administration system and method for the communications in a driving safety auxiliary communication system. 
         [0003]    2. Description of Related Art 
         [0004]    Most traffic accidents are resulted from dangerous driving happened in random. And the reactions of drivers to the dangerous driving often determine whether the trifling potential traffic accident will happen and whether it will become a major traffic accident. 
         [0005]    As vehicle computers become popular, vehicles are equipped with more electronic functions, such as driving record, abnormal condition record, auto braking, parking distance control (PDC), and vehicle condition communications. The PDC function can directly notify the driver about objects that are too close to the vehicle, helping the driver to maneuver the vehicle safely. However, the PDC device only provides warnings about obstacles within a certain range when the driver backs the vehicle. It cannot provide the driver sufficient reaction time when the vehicle moves forward or another vehicle suddenly approaches. Therefore, drivers currently cannot know in advance possible dangerous driving on the street and have sufficient time to avoid traffic accidents. 
         [0006]    In the wake of this, some people have proposed to install wireless communication devices inside vehicles and use a specific communication protocol in between, so that each vehicle and its neighboring vehicles can form a mobile wireless network and broadcasts massage to exchange messages to each other. As a consequence, each vehicle obtains broadcast massage of moving states of the other vehicles, achieving pre-warning effects. 
         [0007]    A conventional system is used to exchange vehicle messages between vehicles in a specific network. Each vehicle has a controller, a sensing unit, a display, and a communicator. The sensing unit further includes a GPS receiver, a gyroscope, an acceleration sensor, a weather sensor, and an electronic map. The controller collects the road information, road curvature, and current traffic light obtained by the electronic map along with the current speed, direction, braking light, turning light, etc obtained by the sensing unit. Through the wireless communication device installed on the vehicle, the controller broadcasts the driving messages of the vehicle. Each of the neighboring vehicles can receive the driving messages of that vehicle. Moreover, through safety determining logic of its own, each vehicle determines the driving states of adjacent vehicles. If any neighboring vehicles were driving abnormally, it sends a warning to the corresponding driver. Therefore, in addition to broadcasting driving messages, each vehicle can further obtain the driving messages transmitted from neighboring vehicles. Consequently, as shown in  FIG. 15 , if there is a car  50 ′ in an accident in the front, it can transmit such driving message to neighboring vehicles  51 ′, which then relay the message to vehicles  52 ′ further back. 
         [0008]    Based on foregoing description, each vehicle simply and continuously broadcasts own driving messages or receives the driving messages of others. When the number of vehicles increases, it may happen that message packets jam the network so that the messages often collide and fail in transmissions. Once some packets of the driving messages fail to transmit, they have to wait a certain time to be resent. This loses the desired real-time exchanges of driving messages. Therefore, the above-mentioned system cannot provide complete anti-collision warnings. 
         [0009]    Another technique of a vehicle to vehicle communication protocol is primarily used as a communication protocol in the driving information management system of the above-mentioned system. The communication protocol can determine the priorities of messages generated by a vehicle before sending them out. By improving the usage efficiency of the limited channel bandwidth, this technique can avoid failures of sending highly important driving messages. To further enhance the packets delivery rate, the driving messages with high importance will be broadcasted longer time and more trials than that of low-priority ones. This communication protocol further classifies the priorities of driving conditions on highways to reduce the quantity of packets and avoid the possibilities of packet collisions. For example, suppose one drives on a highway and there is a traffic accident in the front. The vehicle in the front sends a high priority message to neighboring vehicles in the back, notifying the drivers thereof and preventing car accidents. Since this is designed for highway driving, the importance of driving messages is classified according to the changes in the behavior of drivers. 
         [0010]    With reference to  FIG. 16 , the communication protocol proposed in the above-mentioned communication protocol has a more prominent effect on vehicles running on highways or expressways. When the vehicle in the front  61 ′ accelerates relative to the current vehicle  60 ′, the current vehicle  60 ′ receives the driving massages about the changed driving behavior of the front vehicle. Since front vehicle  61 ′ is in front of the current vehicle  60 ′, the current vehicle  60 ′ evaluates that the front vehicle  61  ′ has a high correlation with the current vehicle  60 ′. Immediately, the current vehicle  60 ′ determines that the front vehicle has a potential danger and warns the driver of the current vehicle about the situation. 
         [0011]    The above description indicates that there are technologies about forming a mobile wireless network among vehicles. By exchanging driving messages, the information of potentially risky road or vehicle conditions can be rapidly distributed. It can even evaluate potentially dangerous vehicle to the current vehicle. Nevertheless, the above-mentioned two technologies cannot be applied to all kinds of road conditions. In particular, when the wireless communication network is blocked by terrains, the above-mentioned effects of those technologies cannot be achieved. Therefore, it is imperative to provide a more effective and reliable wireless communication system for drivers. 
       SUMMARY OF THE INVENTION 
       [0012]    In view of the foregoing, an objective of the invention is to provide a driving safety auxiliary network administration system and the method thereof, so that vehicles can conveniently exchange information among themselves in every kind of terrain. This increases the safety of driving. 
         [0013]    To achieve the above-mentioned objective, the disclosed driving safety auxiliary network administration method comprises steps of: 
         [0014]    continuously transmitting driving massages of the current vehicle and receiving driving massages of other vehicles, the driving massage including at least speed, direction, and position etc. information; 
         [0015]    using the received driving massages of other vehicles to determine whether they are potentially dangerous to the current vehicle and sending out a warning if any of them is dangerous; 
         [0016]    determining whether the driving massages of other vehicles are broadcast from a primary node; 
         [0017]    if the driving massages are not broadcast from the primary node, accumulating the amount of the driving massages broadcast from other secondary nodes within a predetermined time, broadcasting to all the accumulated amount of the driving massages after the predetermined time is reached, and using the secondary node with the highest accumulated amount of the driving massages as the primary node; wherein the new primary node obtains a possible path of a secondary node from the received driving massage, determines at least one threat correlation group, compares the urgencies of the threat correlation groups and weighs them with different priorities, selects the threat correlation groups with high priorities and transfers broadcasting packets about those groups, confirms acknowledging packets (ACK) from the secondary nodes of the threat correlation groups according to the priorities, and repeats the transmission of broadcasting packets to the secondary nodes in those threat correlation groups until ACK&#39;s are received from them; and 
         [0018]    if the driving massages are broadcast from the primary node, receiving the driving massages broadcast from the primary node and other secondary nodes in addition to continuously broadcasting the own driving massages of the current vehicle, applying an anti-collision algorithm to the driving massage broadcast from the primary and secondary nodes, and warning the driver. 
         [0019]    The disclosed driving safety auxiliary network administration system comprises: 
         [0020]    a plurality of secondary nodes linking to each other to form a mobile network, each of which broadcasts the own driving massage of the current vehicle, receives the driving massages from other secondary nodes, and determines and warns about a potential danger according to the driving massage of other secondary nodes; 
         [0021]    a primary node, which is linking to the secondary nodes to collect the driving massages from them and is assigned according to a primary node selection procedure; 
         [0022]    wherein the primary node applies an anti-collision algorithm to the driving massages of vehicles to obtain possible paths of the secondary nodes, thereby determining threat correlations among the vehicles as secondary nodes and forming at least one threat correlation group; different threat correlation groups are given with different priorities according to their urgencies for the primary node to select the threat correlation groups with high priorities and transfer broadcasting packets to them, so as to decrease package numbers broadcast among the primary and secondary nodes; the primary node then checks according to the priorities whether the secondary nodes of those threat correlation groups have received the broadcasting message through acknowledging packets, thereby determining whether each secondary node in the threat correlation groups receives the driving massages of others; and if not, the primary node continuously transmits the broadcasting packets to the threat correlation groups to increase the communication reliability thereof. After the secondary node receives the broadcasting packets, the secondary node automatically sends an ACK response to the primary node and determines and warns about a potential danger according to the driving massage of other secondary nodes according to the broadcasting packets. 
         [0023]    When the invention is applied to crossroads or exits with traffic jams, there must be some primary node with better communications with others. The primary node can collect the driving information from nearby secondary nodes and performs an anti-collision algorithm to establish at least one threat correlation group. Broadcasting packets are filtered according to their priorities in order to reduce the amount of broadcasting packets among the vehicles. To ensure that the secondary nodes in each threat correlation group can successfully receive the broadcasting packets, the primary node confirms with them by receiving an acknowledging packet ACK automatically returned from the secondary node that receives the broadcasting packet. This increases the reliability in information exchanges. Therefore, the disclosed driving safety auxiliary administration method can effectively solve the problem of difficult to warn when there are obstacles at crossroads. This method also makes sure that the secondary nodes in each threat correlation group can receive important broadcasting packets within the shortest time by employing a most efficient and reliable communication method. Therefore, the warning of the invention is timely and effective. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a schematic view of the invention used at a crossroad; 
           [0025]      FIG. 2  is a system block diagram of the invention; 
           [0026]      FIG. 3  is a flowchart of the broadcasting procedure according to the invention; 
           [0027]      FIG. 4  is a flowchart of self-warning in the disclosed anti-collision warning procedure; 
           [0028]      FIG. 5  is a flowchart of the disclosed anti-collision warning procedure; 
           [0029]      FIG. 6  is a flowchart of the disclosed primary node selection procedure; 
           [0030]      FIG. 7  is a flowchart of the warning in the disclosed anti-collision warning procedure; 
           [0031]      FIGS. 8A and 8B  show two different formats of driving information according to the invention; 
           [0032]      FIG. 9  is a flowchart of establishing threat correlation groups according to the invention; 
           [0033]      FIG. 10  is a flowchart of the primary node transfer procedure according to the invention; 
           [0034]      FIG. 11  is a schematic view of the invention used in a two-way crooked road; 
           [0035]      FIG. 12  is a schematic view of the invention used at a junction of a high speed way; 
           [0036]      FIG. 13  is a schematic view of the second embodiment of the invention used at a crossroad; 
           [0037]      FIG. 14  is a block diagram of the second embodiment; 
           [0038]      FIG. 15  is a schematic view implemented by a conventional system for exchanging vehicle messages between vehicles in a specific network in accordance with the prior art; and 
           [0039]      FIG. 16  is a schematic view implemented by a communication protocol in accordance with the prior art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0040]      FIG. 1  shows a structure of the first embodiment of the disclosed driving safety auxiliary network administration system. Since crossroads are places where many vehicles gather and thus more likely to have accidents. To elucidate the effects of the invention, the following description uses a crossroad as an example to explain the disclosed network administration system and method. 
         [0041]    The disclosed driving safety auxiliary network administration system is formed when vehicles enter the communication range of a crossroad and has multiple secondary nodes  20  and one primary node  10 . 
         [0042]    The secondary nodes  20  are linking with each other in the effective communication range of the crossroad. Each of the secondary nodes  20  broadcasts own driving massage, receives the driving massages from other secondary nodes  20 . The secondary node  20  referred herein is the vehicle within the effective communication range. It determines and warns about a potential danger according to the driving massages of other vehicles. 
         [0043]    The primary node  10  is linked with the secondary nodes  20  within the effective communication range of the crossroad to collect the driving massages from them. It is assigned according to a primary node selection procedure. The primary node  10  applies an anti-collision algorithm to the driving massages of vehicles to obtain possible paths of the secondary nodes  20 , thereby determining threat correlations among the vehicles and forming at least one threat correlation group. The driving massage includes speed, direction, or location of a secondary node  20 . After obtaining the driving massages of the secondary nodes, the primary node  10  compares the urgencies of different threat correlation groups and gives them different priorities. It then selects the threat correlation groups with high priorities and transfer broadcasting packets to them. The primary node then checks according to the priorities whether the secondary nodes  20  of those threat correlation groups have received the broadcasting message through acknowledging packets, thereby determining whether each secondary node  20  in the threat correlation groups receives the driving massages of others. This technique increases the communication reliability. In this embodiment, the primary node  10  is a vehicle in motion. The priorities determined by the primary node  10  can be inferred from such parameters as collision probability, vehicle type, and time to collision. An explicit example is given in the following table: 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Collision 
                   
                 Time to collision t 
               
               
                   
                 Priority 
                 probability 
                 Vehicle type 
                 (second) 
               
               
                   
                   
               
             
             
               
                   
                 High 
                 90% 
                 Special vehicle 
                 t &lt; 10 
               
               
                   
                 Medium 
                 60% 
                 Normal 
                 t &gt; 10 
               
               
                   
                 Low 
                 30% 
                 Normal 
                 t &gt; 20 
               
               
                   
                   
               
             
          
         
       
     
         [0044]    Since most crossroads have buildings  43  around, they generally block the broadcasting of vehicles on different lanes. As a result, vehicles entering the crossroad sometimes cannot successfully receive the driving massages of other approaching vehicles. In this case, if a vehicle in the opposite lane or in the perpendicular direction may become a threat, it is impossible to determine and warn the driver in advance. According to the disclosed driving safety auxiliary network administration system, the primary node  10  establishes threat correlation groups when secondary nodes  20  enter the effective communication range of the crossroad. If the primary node  10  does not exist, it is then selected from the secondary nodes  20  through a primary node selection procedure. The primary node gives different priorities to the threat correlation groups according to their threat levels. Information of threatening vehicles is transmitted to threat correlation groups with high priorities. The primary node  10  further confirms whether the acknowledging packets from all the secondary nodes  20  in the threat correlation group have been received. The location of the threatening vehicle is sent to all the secondary nodes  20 . This technique prevents buildings from blocking warnings. The primary node  10  can be a Road-Side unit (RSU) fixed on the roadside or selected from the secondary nodes  20  entering the crossroad. 
         [0045]    Please refer to  FIG. 2 . The primary node  10  and the secondary nodes  20  are all on the vehicles in motion. Each of them has: a central processing unit (CPU)  11 , 21 , a communicating module  12 ,  22 , a global positioning system (GPS) module  13 ,  23 , a traffic information unit  14 ,  24 , a vehicle condition sensing unit  15 ,  25 , a warning device  16 ,  26 , and an input device  17 ,  27 . 
         [0046]    The CPU  11 ,  21  is built in with a primary node selection and transfer procedure, a broadcasting procedure, and an anti-collision warning procedure. The CPU  11 ,  21  further connects to a data storage unit  111 ,  211  stored with a vehicle identification number (VIN). When being set as a primary node  10 , the CPU  11 , executes the primary node transfer procedure. When being a secondary node  20 , it executes the primary node selection procedure. 
         [0047]    The communicating module  12 ,  22  connects to the CPU  11 ,  21  and forms dual connections with communicating modules using the same communication channel and protocol. It receives driving massages of other vehicles and sends it to the CPU  11 ,  21 , and broadcasts the driving massage output from the CPU  11 ,  21 . As shown in  FIG. 8A , the driving massage includes at least coordinates, speed, direction, transmitting time, and the VIN. 
         [0048]    The GPS module  13 ,  23  connects to the CPU  11 ,  12  and receives positioning signals from satellite. It extracts at least coordinate, time and speed data from the positioning signals and sends them to the CPU  11 ,  21 . 
         [0049]    The traffic information unit  14 ,  24  connects to the CPU  11 ,  21  and stores crossroad geography information (e.g., geography coordinates thereof) and traffic administration information (e.g., traffic light, light changing time, road speed limit, road construction, traffic accidents, etc). 
         [0050]    The vehicle condition sensing unit  15 ,  25  reflects the conditions of the current vehicle and the surrounding environment (e.g., turning light, wiper, tire pressure, headlight, etc) to the CPU  11 ,  21 . 
         [0051]    The warning device  16 ,  26  connects to the CPU  11 ,  21 . It is driven by the CPU  11 ,  21  to send a warning to the diver. In this embodiment, the warning device is a display or a buzzer. 
         [0052]    The input device  17 ,  27  connects to the CPU  11 ,  21  for the driver to set or cancel the warning signal of the warning device. 
         [0053]    Since the CPU  11  is connected with the GPS module  13 ,  23 , it can obtain the coordinate, speed, and direction data of the current vehicle. The following describes the broadcasting procedure of the CPU  11 ,  21 . Please refer to  FIG. 3 . After the procedure starts (step  50 ), the CPU  11 ,  21  acquires the channel usage privilege (step  51 ) and the coordinate, speed, and direction data of the current vehicle. They are stored in the vehicle dynamic database of the data storage unit (step  52 ). Afterwards, the data are packed into a packet of driving massage and the packet is broadcast out (step  53 ). Once this is completed, the CPU  11 ,  21  returns the channel usage privilege. After a certain time, the above-mentioned steps are repeated again. Therefore, the CPU  11 ,  21  continuously broadcasts the driving massages of the current vehicle (step  54 ). 
         [0054]    As shown in  FIG. 4 , the CPU  11 ,  21  of each vehicle continuously receives the driving massages of nearby vehicles and executes the anti-collision warning procedure in order to achieve the self-warning effect in different roads. After the procedure starts (step  60 ), the CPU  11 ,  21  acquires the channel usage privilege (step  61 ) to wait for the reception of the driving massages of surrounding vehicles (step  62 ). Once some driving massages are received, it is immediately updated to the vehicle dynamic database of the data storage unit (step  63 ). The CPU  11 ,  21  then makes path predictions for the surrounding vehicles using the vehicle dynamic database (step  64 ), and determines whether the current vehicle is under the threat of any of the surrounding vehicles (step  65 ). If not, the procedure goes back to step  62 . Otherwise, the CPU  11 ,  21  drives the warning device to warn the driver that a collision is about to happen (step  66 ). However, as shown in  FIG. 1 , the buildings  43  around the crossroad still prevent vehicles entering the crossroad from obtaining the driving massages of all other vehicles. So even with such a self-warning function, no immediate and effective warning is attained. 
         [0055]    Therefore, as shown in  FIG. 5 , the CPU  11 ,  21  determines whether a secondary node is entering the crossroad (step  71 ) in addition to running the above-mentioned self-warning function (step  70 ). If there is a secondary node entering the crossroad, the CPU  11 ,  21  determines whether the driving massages broadcast from the primary node is received (step  72 ). This then renders a more timely and effective warning effect. In other words, when the CPU  11 ,  21  determines according to the GPS module and the traffic information unit that the current vehicle is entering the crossroad, it immediately determines whether the driving massages broadcast from a primary node is received. 
         [0056]    1. If the driving massages broadcast from the primary node  10  is not received, the primary node selection procedure is executed within a predetermine time T. The detailed steps of the primary node selection procedure are described as follows, with reference to  FIG. 6 . 
         [0057]    After the procedure starts (step  80 ), the driving massages broadcast from the secondary nodes is collected within a predetermined time (step  81 ). The amount of driving massages received at the current location is computed. When the predetermined time T is reached (step  82 ), the invention broadcasts the VIN, the driving massages amount V N , the distance to the geographical center d center , and the starting time t (step  83 ). At this moment, the CPU  11 ,  21  can determine whether the current vehicle has the largest amount of driving massages (step  84 ). If not, it remains as a secondary node (step  85 ). If yes, then it further determines whether there is any other secondary node having the same amount of driving massages (step  86 ). If there is no one else, then the current vehicle is changed from a secondary node to the primary node (step  88 ). If there are other vehicles with the same largest amount of driving massage, then their distances to the geographical center d center  are compared (step  87 ). The shortest one means that it has the best geographical position for communications at the crossroad, and it is changed from a secondary node to the primary node (step  88 ). Otherwise, it remains as a secondary node and some other secondary node is promoted to the primary node (step  85 ). The so-called distance to geographical center is the distance between a vehicle and the center of the crossroad, as shown in  FIG. 1 . For the convenience in calculations, one can use the center of the crossroad as the center and draw several concentric circles with different radii (r 1 , r 2 , r 3 ). Therefore, each vehicle can report which circle it is located on. Once a vehicle changes from a secondary node  20  to the primary node  10 , the primary node  10  takes the driving massage of each secondary node  20  and uses an anti-collision algorithm to find out a possible path of the secondary node  20 . According to the possible paths of the other vehicles, the primary node  10  determines threat relations among them and thereby establishes at least one threat correlation group. If there are several threat correlation groups (e.g., two or more threat correlation groups), then the primary node associates each of them with a priority according to their threat levels. Afterwards, it selects those threat correlation groups with high priorities and sends broadcasting packets to them, as shown in  FIG. 8A . The broadcasting packet includes: coordinate, speed, direction, packet sending time, and all the VIN&#39;s in the threat correlation group. After a secondary node receives this broadcasting packet and reads its own VIN, it automatically returns an acknowledging packet ACK. As shown in  FIG. 8B , this method ensures that each secondary node in the high-priority threat correlation group can receive the driving massages of each other and make warnings. If any of them does not receive the broadcasting packet, it is sent again. Therefore, the secondary nodes  20  in a threat correlation group with high priority can indeed receive timely and effective warnings from the primary node. 
         [0058]    2. If the CPU of the current vehicle has received the driving massages broadcast from the primary node  10 , it continuously receive the driving massages broadcast from the primary node and other secondary nodes in addition to broadcasting the driving massage of the current vehicle. The CPU then performs the anti-collision algorithm according to the received driving massages and sends warnings to the driver if necessary. The following explains detailed steps of the warning with reference to  FIG. 7 . 
         [0059]    After the procedure starts (step  90 ), the CPU acquires the channel usage privilege (step  91 ) to wait for the reception of the driving massages transmitted from the surrounding vehicles (step  92 ). Once some driving massages is received, it is immediately updated to the vehicle dynamic database of the data storage unit (step  93 ). The CPU makes path predictions for the surrounding vehicles according to the vehicle dynamic database. The coordinate of the current vehicle is taken as the center to generate threat correlation group information related to the current vehicle (step  94 ). It further reads out the threat correlation group in the received threat correlation group broadcasting packet (step  95 ). It then uses the VIN of the current vehicle to determine whether it is listed in the threat correlation group (step  96 ). If so, then the CPU drives the warning device to notify the driver that a collision is about to happen. It further returns the primary node with an acknowledging packet (step  97 ). If not, then the procedure goes back to step  91  until the secondary node leaves the crossroad. Please refer to  FIG. 8B . The acknowledging packet includes a primary node VIN, original packet sending time, current VIN, and packet sending time. 
         [0060]    According to the above description, when a vehicle is about to enter a crossroad, the disclosed network administration system selects a secondary node as the primary node. The primary node has the feature of receiving the most driving massages broadcast from the vehicles around the crossroad. It evaluates the threat relations according to the driving massages. That is, the driving massages are filtered. The primary node then notifies each member in the threat correlation group. After the primary node is selected, it means that the corresponding vehicle is at a position with the least problem in receiving driving massages. Therefore, the disclosed network administration system ensures that vehicles entering a crossroad do not experience difficulty in communications due to the roadside buildings. Warnings can still be timely delivered to the drivers. 
         [0061]    Please refer to  FIG. 9 . The following paragraphs explain detailed steps in the procedure of establishing threat correlation groups by the primary node. 
         [0062]    After the procedure starts (step  101 ), the CPU receives the driving massages of surrounding vehicles (step  102 ). The latest driving massages is stored in the vehicle dynamic database of the data storage unit (step  103 ). The CPU then makes path predictions for the vehicles according to the vehicle dynamic database, thereby determining whether there is any threat in between (step  104 ). If there is, then a threat correlation group is established (step  105 ). If not, then the procedure goes back to step  102  for continuously receiving driving massages of surrounding vehicles. If several threat correlation groups are established, then the CPU of the primary node takes its own location as the center, and generates information of vehicles listed in the threat correlation groups. It gives priorities to the threat correlation groups according to their urgencies (step  106 ). The threat correlation group with the top priority is then extracted (step  107 ). The VIN of each vehicle in the threat correlation group and the received information are packed into a broadcasting packet, which is then reliably broadcast out (step  108 ). After the broadcasting, it waits for replies from all of the related vehicles (step  109 ). The broadcasting continues until all the acknowledging messages have been received. After the above steps are completed, it starts to broadcast to the threat correlation group of second priority, and so on. After broadcasting to all the threat correlation groups and receiving all of their acknowledging packets, the procedure goes back to step  102 . This process repeats until the current vehicle is changed from the primary node to a secondary node. 
         [0063]    Since the primary node will eventually leave the crossroad, the disclosed network administration system provides a primary node transfer procedure, as shown in  FIGS. 1 to 10 . The CPU of the primary node keeps checking whether it is leaving the boundary A of the crossroad according to the GPS module (step  501 ). Once it is determined to drive away from the boundary A, it immediately searches in its vehicle dynamic database whether any other secondary node is driving into the boundary A of the crossroad (step  502 ). If there are, it estimates how long these secondary nodes will stay in the crossroad and selects the one with the longest stay time, promoting it from a secondary node to the primary node (step  503 ). The original primary node is set back as a secondary node (step  504 ). If no vehicle is entering the boundary, it means that there is no secondary node within the boundary of the crossroad (step  505 ). The CPU of the current primary node continues to determine whether there is any other secondary node in the outer region of the crossroad (step  506 ). If there is, it selects the one with the shortest time to enter the central region of the crossroad as the new primary node (step  507 ), and the original primary node is set back as a secondary node (step  504 ). If there is no vehicle in the outer region of the crossroad, the current primary node is simply set back as a secondary node after it leaves the crossroad (step  504 ). The new primary node is selected according to the primary node selection procedure from the vehicles that enter the crossroad at a later time. 
         [0064]    Please refer to  FIG. 11  and  FIG. 12 . The network administration system applies to vehicles located at a two-way crooked road and a junction of a high speed way and a branch road thereof. Since the CPU of each vehicle is further connected to a GPS and the traffic information unit, the CPU calculates a geographical center of the crooked road or the junction. The four circles with different radii (r 1 , r 2 , r 3 , r 4 ) are drawn on the crooked. The three circles are drawn on the junction according to different vehicle densities. Further, different priorities are given to different circles. Therefore, the CPU refers to the locations of the secondary nodes to execute the primary node transfer procedure. 
         [0065]    Please refer to  FIG. 13  for a second embodiment of the invention. The primary node  30  in this case is an RSU. The primary node can be installed on a traffic light or roadside sign at the crossroad as well. The secondary nodes  20  are still those vehicles in motion. As shown in  FIG. 14 , each vehicle in the embodiment does not need to have a built-in primary node selection procedure in its CPU  11 . The RSU includes a CPU  31 , a communicating module  32 , and a traffic information unit  33 . 
         [0066]    The CPU  31  is built in with a broadcasting procedure, and an anti-collision warning procedure. The CPU is further connected with a data storage unit  311  for storing the VIN&#39;s. 
         [0067]    The communicating module  32  connects to the CPU and has dual connections with communication modules using the same communication channels and protocol. It receives the driving massages of nearby vehicles and sends it to the CPU  31 . It further broadcasts the driving massage output from the CPU  31 . As shown in  FIG. 8A , the driving massage includes at least: coordinate, speed, direction, sending time, and current VIN. 
         [0068]    The traffic information unit  33  connects to the CPU 31 . It stores crossroad geography information (e.g., geography coordinates thereof) and traffic administration information (e.g., traffic light, light changing time, road speed limit, road construction, traffic accidents, etc). 
         [0069]    This embodiment uses an RSU as the primary node  30 . The vehicles entering the crossroad can receive the driving massages broadcast from the primary node  30 . When a vehicle is in an effective communication range of the RSU, the RSU executes the procedure of establishing threat correlation group&#39;s, as shown in  FIG. 9 . Therefore, after entering the crossroad, each vehicle can receive the driving massages broadcast from the RSU and determines as in  FIG. 7  whether it is listed in the threat correlation group. If it is, then the CPU drives the warning device to notify the driver about the location of the threatening vehicle. 
         [0070]    Base on the above description, this invention, driving safety auxiliary network administration method includes the following steps. Each vehicle continuously sends out the driving massages thereof and receives the driving massages of other vehicles. The driving massage includes at least speed, direction, and location of the vehicle. 
         [0071]    The driving massage of other vehicles is used to determine whether any of them is potentially dangerous to the current vehicle. A warning is sent out if there is such a dangerous vehicle. 
         [0072]    It also determines whether the driving massage of other vehicles is broadcast from the primary node. If not, each vehicle accumulates the amount of driving massages broadcast from other secondary nodes in a predetermined time. After the predetermined time is reached, all of the vehicles broadcast their accumulated amount of driving massages. The secondary node with the highest accumulated amount of driving massages are set as the primary node. Once the primary node is determined, it determines a possible path for each secondary node according to the received driving massages, thereby determining at least one threat correlation group. It then associates the threat correlation groups with different priorities by comparing their urgencies. The threat correlation groups with high priorities are extracted. The primary node first transfers broadcasting packets to these high-priority threat correlation groups and checks whether acknowledging packets ACK from the secondary nodes in the threat correlation groups are replied according to the priorities. If some acknowledging packets are not received, then the broadcasting packets are sent to the corresponding secondary nodes in the threat correlation groups again until their acknowledging packets are received. If the driving massages of other vehicles is broadcasted from the primary node, then the secondary node simultaneously receives the driving massages broadcast from the primary node and other secondary nodes in addition to broadcasting its own driving massages. 
         [0073]    Therefore, the disclosed auxiliary network administration system and the method thereof find a primary node that can receive the driving massages broadcast from most vehicles in the communication range. The primary node immediately performs an anti-collision algorithm to establish at least one threat correlation group. It further transfers broadcasting packets according to the priorities of the threat correlation groups. In addition to reducing the broadcasting packets transferred among the vehicles, driving massages of great importance can be transmitted and received in time, enhancing the warning effects for the vehicles. To ensure the reception of the broadcasting packets by the secondary nodes in the threat correlation groups, the primary node forces each of the secondary nodes to return an acknowledging packet after receiving the broadcasting packet. Since the primary node only transfers the driving massages of vehicles in the broadcasting packet, eventually it is each individual vehicle that determines whether there is any potential danger around the vehicle. 
         [0074]    As a result, the disclosed driving safety auxiliary network administration method can prevent obstacles near the crossroad from blocking the communications and warnings among the vehicles. The disclosed method can make sure that the secondary nodes in each threat correlation group can receive important broadcasting packets within the shortest time through more efficient and reliable communication means. The warnings thus produced are timely and effective. 
         [0075]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.