JP5178593B2 - Communication device, inter-vehicle communication system, road-to-vehicle communication system, wireless communication system, and communication control method - Google Patents

Description

  The present invention relates to a communication apparatus in a wireless communication system that controls traffic.

  Conventionally, there is a method of installing a ground server that manages communication between the mobile station and the external network in order for the mobile station mounted on the vehicle to perform priority control when communicating with the external network. When this method is used, priority control in the mobile station → terrestrial server direction (upward direction) is executed by the mobile station, and priority control in the ground server → mobile station direction (downward direction) is executed by the ground server. In performing priority control, band estimation of a radio section is performed between a mobile station and a ground server by using a technique such as a packet train or a packet pair. Then, from layer 1 and layer 2 related to wireless communication, the mobile station acquires uplink allocated band information, and the ground server acquires downlink allocated band information.

  For example, the following Patent Document 1 describes a technique for controlling the data transmission rate to be optimal by calculating the congestion load on the server side and setting the window size determined based on the congestion load to be transmitted. Has been.

JP 2008-85950 A

  However, when the above-described conventional technology is applied to a wireless communication system using an on-vehicle mobile station and a network outside the vehicle, it is necessary to install a ground server as a network infrastructure as a premise for performing priority control. Further, the mobile station needs to acquire the allocated bandwidth information from the wireless device used by itself, and the ground server needs to acquire the bandwidth information from the wireless base station connected to the mobile station. Accordingly, in a network such as an existing mobile communication network, since it is difficult to establish these conditions, there is a problem that it is not practical to execute the above-described conventional technique.

  The present invention has been made in view of the above, and it is possible to obtain a communication apparatus that realizes uplink and downlink priority control by autonomous control of a mobile station without adding new network infrastructure. Objective.

  In order to solve the above-described problems and achieve the object, the present invention is a communication apparatus that performs wireless communication with an external system, the data transmission control means for outputting a packet to be transmitted, and the data transmission A shaping unit that outputs a packet output from the control unit at a speed that matches a transmission band of a radio section, a packet transmission unit that transmits a packet output from the shaping unit to the external system, and a response from the external system ACK receiving means for receiving the packet, and packet loss determining means for determining the presence or absence of packet loss based on the response received by the ACK receiving means, and controlling the transmission band of the shaping means according to the determination result. The data transmission control means notifies the packet loss determination means of the number of discarded packets discarded by itself, The packet loss determination means estimates an RTT (Round Trip Time) for the external system based on the response, calculates the total number of packet losses from the RTT, and calculates the number of discarded packets from the total number of packet losses. The number of lost packets lost in the radio section is calculated by subtraction, and when it is determined that congestion has occurred based on the number of lost packets, the shaping unit is instructed to reduce the transmission bandwidth, When it is determined that no congestion has occurred, the shaping unit is instructed to increase the transmission band.

  According to the present invention, it is possible to optimize the transmission band of the wireless section.

FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the present embodiment. FIG. 2 is a diagram illustrating an internal configuration example of the in-vehicle mobile station according to the present embodiment.

  Embodiments of a wireless communication system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram showing a configuration example of the present embodiment of a wireless communication system according to the present invention. The wireless communication system includes an in-vehicle mobile station 1 mounted on a vehicle, a roadside wireless device 2 installed on a road, and an out-of-vehicle network 3 to which the roadside wireless device 2 is connected. The roadside apparatus 2 forms a short-range wireless communication area around itself, and communicates by being connected to the in-vehicle mobile station 1 through a wireless link. In the following, a case where TCP (Transmission Control Protocol) is used as a communication protocol will be described.

  FIG. 2 is a diagram illustrating a configuration example of the in-vehicle mobile station 1 in the present embodiment. The in-vehicle mobile station 1 includes an application program object 11-M (M is a natural number) generated and executing a service, an application priority management unit 12, a data transmission unit 13, and a data reception unit 14. Although a plurality of application program objects 11-M can exist at the same time, the application program object 11-1 is representatively shown here. The application program object 11-1 provides a service when the in-vehicle mobile station 1 performs communication. The application priority management unit 12 manages and determines the priority of the radio section for each application. The data transmission unit 13 transmits data transmitted from the application program object 11 to the roadside apparatus 2. The data receiving unit 14 receives data from the roadside apparatus 2.

  The data transmission unit 13 includes a data transmission control unit 21, a shaping unit 22, a packet transmission unit 23, a packet loss determination unit 24, and an ACK reception unit 25. The data transmission control unit 21 transfers data to the shaping unit 22 according to the priority for each application notified from the application priority management unit 12. The shaping unit 22 transfers the data transferred from the data transmission control unit 21 to the packet transmission unit 23 at a speed matching the bandwidth of the wireless section. The packet transmitter 23 transmits the transferred packet to the roadside apparatus 2. The packet loss determination unit 24 determines a packet loss based on the notification from the data transmission control unit 21 and the notification from the ACK reception unit 25, and determines the shaping speed. The ACK receiver 25 receives a TCP ACK signal that is returned from the roadside apparatus 2 in response to a packet transmitted by itself (the in-vehicle mobile station 1).

  Further, the data receiving unit 14 includes a received data congestion determining unit 31, a sequence number determining unit 32, a packet receiving unit 33, a received data priority determining unit 34, an ACK transmission control unit 35, and an ACK transmitting unit 36. Is provided. The reception data congestion determination unit 31 determines a congestion state for reception data. The sequence number determination unit 32 monitors missing TCP sequence numbers of received packets. The packet receiving unit 33 receives data (packets) transmitted from the roadside apparatus 2. The reception data priority determination unit 34 determines and manages the priority of reception data according to the application to which the reception data belongs based on the priority notified from the application priority management unit 12. The ACK transmission control unit 35 performs control to transmit the TCP ACK signal of the reception data according to the instruction of the reception data priority determination unit 34. Specifically, for example, the transmission timing of TCP ACK and the availability of transmission are determined. The ACK transmission unit 36 transmits a TCP ACK signal of received data.

  Next, the operation of transmission rate control by the in-vehicle mobile station 1 in the wireless communication system configured as described above will be described.

  First, the operation of uplink transmission rate control will be described. In the in-vehicle mobile station 1, the application program object 11-1 is activated. The application program object 11-1 performs control to transmit transmission data to the data transmission control unit 21 when traffic to be transmitted to the roadside apparatus 2 is generated by its own processing, and sets the application type to the application priority. Notify the management unit 12.

  The application priority management unit 12 manages the priority of the application executed in the in-vehicle mobile station 1 and acquires the priority according to the notified application type. Then, the application priority management unit 12 notifies the data transmission control unit 21 of the acquired priority.

  The data transmission control unit 21 temporarily accumulates transmitted transmission data in a queue. Further, the data transmission control unit 21 performs weighting according to the priority notified from the application priority management unit 12 and determines the probability of transmitting the transmission data to the shaping unit 22 for each application. The data transmission control unit 21 acquires data from the queue for each application according to the probability, transfers the acquired data to the shaping unit 22, and notifies the application corresponding to the data.

  Here, when the probability is small, the amount of data transferred to the shaping unit 22 with respect to the transmission data transmitted from the application program object 11-1 is reduced, so the data is stored in the queue of the data transmission control unit 21. Uncut data is discarded. The data transmission control unit 21 notifies the packet loss determination unit 24 of the discarded data amount (number of packets).

  On the other hand, the shaping unit 22 to which the data has been transferred transmits a packet to the roadside apparatus 2 via the packet transmission unit 23 according to the transmission band notified from the packet loss determination unit 24.

  By the way, the transmission loss notified to the shaping unit 22 is determined by the packet loss determination unit 24. The packet loss determination unit 24 receives a TCP ACK transmitted by the roadside apparatus 2 from the ACK reception unit 25 as a response to the transmission packet transmitted from the packet transmission unit 23.

  The packet loss determination unit 24 estimates an RTT (Round Trip Time) value for each TCP connection in consideration of the possibility of a response delay based on the TCP ACK. Any estimation method may be used, for example, using a time stamp included in the TCP ACK. Based on the RTT, the number of packet losses for transmission is calculated. The calculation method is performed using, for example, an ACK number included in the TCP ACK as in a normal TCP method. Further, the packet loss determination unit 24 calculates the number of lost packets in the wireless section by deleting the number of discarded packets notified from the data transmission control unit 21 from the number of packet losses. The calculation of the number of lost packets here is performed not for each application but for the entire transmission data.

  When packet loss has occurred in view of the calculation result, the packet loss determination unit 24 determines that the traffic needs to be limited due to the congestion state, and instructs the shaping unit 22 to reduce the transmission band. On the other hand, if no packet loss has occurred, the shaping unit 22 is instructed to increase the transmission band in order to reduce the discard of data that cannot be stored in the queue of the data transmission control unit 21. These controls are performed by, for example, an AIMD (additive-increase and multiplicative-decrease) method, as in the case of the Congestion Window in TCP.

  With the above control, when data is transmitted from the in-vehicle mobile station 1 to the roadside apparatus 2, it is possible to optimize the transmission band of the radio section.

  Next, the operation of downlink transmission rate control will be described. As described above, in the in-vehicle mobile station 1, the application program object 11-1 is activated.

  When the packet receiving unit 33 receives a packet for traffic transmitted from the roadside apparatus 2 to the in-vehicle mobile station 1, the packet receiving unit 33 notifies the sequence number determining unit 32 of the TCP header information and the received data included in the packet.

  The sequence number determination unit 32 extracts the TCP sequence number from the notified TCP header, and the value obtained by adding the previously received TCP sequence number and the data length of the currently received packet matches the current TCP sequence number. Check if it is. If they match, it is determined that continuity is maintained. On the other hand, if they do not match, it is determined that continuity is not maintained. The sequence number determination unit 32 notifies the reception data congestion determination unit 31 of the determination result regarding the continuity together with the reception data.

  When the reception data congestion determination unit 31 receives the continuity determination result, the reception data congestion determination unit 31 determines that it is in a congestion state when the continuity is not maintained, and on the other hand, when the continuity is maintained, the congestion state Judge that it is not. The reception data congestion determination unit 31 notifies the reception data priority determination unit 34 of the fact and the reception data.

  When notified of the congestion state, the reception data priority determination unit 34 checks the reception data and specifies an application corresponding to the reception data. Then, the application priority management unit 12 is inquired about the priority of the application, and the application priority management unit 12 is currently in service (communication) and has a priority higher than the priority. Queries falling applications. The application priority management unit 12 searches for the corresponding application and returns the result to the received data priority determination unit 34. Note that the application priority management unit 12 may respond to all applicable applications, or one or more applications as appropriate based on the relationship between the priority of the received data and the priority of other communicating applications. You may select and respond. In that case, various methods are conceivable, for example, a predetermined number is selected from the application with the lowest priority.

  When one or more corresponding applications are responded, the reception data priority determination unit 34 stands by while retaining the information. After that, the reception data priority determination unit 34 specifies the application corresponding to the reception data transmitted from the reception data congestion determination unit 31. As a result, if the application has a low priority, the reception data priority determination unit 34 decreases the transmission rate. To the ACK transmission control unit 35.

  On the other hand, when no application with a low priority is notified, the reception data priority determination unit 34 determines that an application that handles data that is currently in a congestion state has a low priority, and Instructing the ACK transmission control unit 35 to maintain the transmission rate when performing TCP ACK transmission. The reception data priority determination unit 34 also instructs the maintenance of the transmission rate even when the reception data congestion determination unit 31 is notified that it is not in a congestion state.

  The ACK transmission control unit 35 determines the transmission timing of the ACK signal to be transmitted to the roadside apparatus 2 as a response to the received packet. When transmission is instructed by the received data priority determination unit 34 to maintain the transmission rate, the ACK transmission control unit 35 immediately instructs the ACK transmission unit 36 to transmit a TCP ACK. On the other hand, when instructed to lower the transmission rate, the ACK transmission control unit 35 executes one of the following controls.

  The first is control for transmitting TCP ACK with delay. In this case, the ACK transmission control unit 35 instructs TCP ACK transmission after an appropriate waiting time. As a result, the ACK transmission unit 36 replies to the roadside wireless device 2 with a delayed timing. Therefore, when viewed from the roadside wireless device 2, there is an effect of recognizing the RTT to the in-vehicle mobile station 1 longer than the actual time. is there. Therefore, the roadside apparatus 2 reduces the transmission rate of data related to the application, so that it is possible to secure the transmission rate for data of an application with a higher priority. Further, the ACK transmission control unit 35 gives the transmission instruction to the ACK transmission unit 36 and transfers received data to the application program object 11-1.

  The second control is that TCP ACK is not transmitted. In this case, the ACK transmission control unit 35 does not instruct TCP ACK transmission. As a result, the ACK transmission unit 36 cannot return a TCP ACK for the received packet, and thus has an effect of recognizing that a packet loss has occurred when viewed from the roadside apparatus 2. Therefore, the roadside apparatus 2 performs control to reduce the amount of data transmitted at a time by reducing the Congestion Window of the TCP connection. As a result, the transmission rate of data related to the application can be reduced, and the transmission rate can be secured for data of an application with a higher priority. In addition, the ACK transmission control unit 35 discards the received data. This is because the same packet is retransmitted from the roadside apparatus 2 because no TCP ACK is returned.

  In the above embodiment, the case where TCP is used as the communication protocol has been described. However, RTP / RTCP may be used instead of TCP. In this case, the sequence number determination unit 32 checks the RTP sequence number instead of the sequence number included in the TCP header. The packet loss determination unit 24 uses RTCP SR (Sender Report) and RTCP RR (Receiver Report) for RTT estimation and packet loss determination. The same configuration as that in FIG. 2 is also used when using a configuration in which RTP / RTCP is used and control is performed to reduce the transmission rate when a packet loss is detected in the roadside apparatus 2. In this case, the ACK transmission control unit 35 discards the RTP packet of the flow whose transmission rate is desired to be reduced instead of the above control method. Further, the ACK transmission unit 36 is not instructed to transmit ACK. As a result, similarly to the above, it is possible to reduce the transmission rate of low priority traffic.

  As described above, in the present embodiment, as the bandwidth control in the uplink direction, the total number of packet losses is calculated using the feedback packet from the opposite node, and the number of packets discarded in shaping is subtracted from the radio section. The number of lost packets is obtained and the transmission bandwidth is increased or decreased depending on the presence or absence of congestion. Furthermore, priority control for each application is managed, and priority control is performed by performing shaping with a probability corresponding to the priority. Also, as priority control in the downlink direction, the occurrence of congestion is determined from missing feedback packets, and the transmission rate of an application with low priority is reduced.

  As a result, although the traffic to be controlled is limited to a protocol that feeds back the reception state to the transmission side by ACK or the like as in TCP, the traffic is controlled by autonomous control of the communication device without preparing a new infrastructure. Direction and downlink priority control can be realized.

  In the above embodiment, road-to-vehicle communication is assumed, and a wireless communication system including an in-vehicle mobile station and a roadside wireless device has been described, but for example, of course, it can also be applied to vehicle-to-vehicle communication, Furthermore, the present invention can be applied to other short-range wireless communication systems.

  As described above, the communication control method according to the present invention is useful for a wireless communication system that performs priority control, and is particularly suitable for a wireless communication system that uses a protocol that periodically returns a response as a communication protocol. .

DESCRIPTION OF SYMBOLS 1 In-vehicle mobile station 2 Roadside radio device 3 Network outside vehicle 11-1 Application program object 12 Application priority management part 13 Data transmission part 14 Data reception part 21 Data transmission control part 22 Shaping part 23 Packet transmission part 24 Packet loss determination part 25 ACK Reception unit 31 Received data congestion determination unit 32 Sequence number determination unit 33 Packet reception unit 34 Reception data priority determination unit 35 ACK transmission control unit 36 ACK transmission unit

Claims (19)

A communication device that performs wireless communication with an external system,
Data transmission control means for outputting a packet to be transmitted;
Shaping means for outputting a packet output from the data transmission control means at a speed in accordance with a transmission bandwidth of a radio section;
Packet transmission means for transmitting the packet output from the shaping means to the external system;
ACK receiving means for receiving a response from the external system;
Packet loss determination means for determining the presence or absence of packet loss based on the response received by the ACK reception means, and controlling the transmission bandwidth of the shaping means according to the determination result;
With
The data transmission control means notifies the packet loss determination means of the number of discarded packets discarded by itself,
The packet loss determination means includes
RTT (Round Trip Time) for the external system is estimated based on the response, the total number of packet losses is calculated from the RTT, and the number of discarded packets is subtracted from the total number of packet losses. Calculate the number of lost packets lost,
When it is determined that congestion has occurred based on the number of lost packets, the shaping unit is instructed to reduce the transmission band. On the other hand, when it is determined that congestion has not occurred, the shaping unit To increase the transmission bandwidth to
A communication device. Adopting TCP (Transmission Control Protocol) for wireless communication with the external system,
further,
Application priority management means for managing the priority for each application;
Packet receiving means for receiving packets from the external system;
Sequence number determination means for monitoring missing sequence numbers of received packets;
Received data congestion determination means for determining the occurrence of congestion in the radio section based on the monitoring result of the sequence number determination means;
Received data priority determining means for determining the priority for each received packet based on the priority according to the type of packet;
ACK transmission control means for performing transmission control of TCP ACK for received data;
ACK transmission means for transmitting TCP ACK for received data according to the control of the ACK transmission control means;
With
The received data priority determining means includes
When the reception data congestion determination means is notified of the occurrence of congestion, the application priority management means is inquired about an application that is currently communicating and has a lower priority than the application to which the received packet belongs. When one or more applications with low priority are replied, if a packet belonging to the low priority application is subsequently received, the transmission rate of the packet belonging to the application is reduced with respect to the ACK transmission control means. Instructed to do so,
The ACK transmission control means controls the ACK transmission means to reduce the transmission rate when receiving an instruction to reduce the transmission rate.
The communication apparatus according to claim 1. The ACK transmission control means controls the ACK transmission means to delay the timing of transmitting TCP ACK when receiving an instruction to reduce the transmission rate.
The communication device according to claim 2. The ACK transmission control means controls the ACK transmission means so as not to transmit a TCP ACK when receiving an instruction to reduce the transmission rate.
The communication device according to claim 2. Adopting RTP (Real-time Transport Protocol) / RTCP (RTP Control Protocol) for wireless communication with the external system,
further,
Application priority management means for managing the priority for each application;
Packet receiving means for receiving packets from the external system;
Sequence number judging means for monitoring missing sequence numbers of received packets;
Received data congestion determination means for determining the occurrence of congestion in the radio section based on the monitoring result of the sequence number determination means;
Received data priority determining means for determining the priority for each received packet based on the priority according to the type of packet;
ACK transmission control means for performing transmission control of ACK for received data;
ACK transmission means for transmitting ACK for received data according to the control of the ACK transmission control means;
With
The received data priority determining means includes
When the reception data congestion determination means is notified of the occurrence of congestion, the application priority management means is inquired about an application that is currently communicating and has a lower priority than the application to which the received packet belongs. When one or more applications with low priority are replied, if a packet belonging to the low priority application is subsequently received, the transmission rate of the packet belonging to the application is reduced with respect to the ACK transmission control means. Instructed to do so,
The ACK transmission control means, when receiving an instruction to reduce the transmission rate, discards the received packet and controls the ACK transmission means so as not to transmit ACK.
The communication apparatus according to claim 1. The sequence number is a TCP sequence number.
The communication apparatus according to claim 2, 3, or 4. The sequence number is an RTP sequence number,
The communication apparatus according to claim 5. The sequence number is an IPsec sequence number received for each SA (Security Association) in IPsec (Internet Protocol Security).
The communication device according to any one of claims 2 to 5, wherein A plurality of vehicles equipped with the communication device according to any one of claims 1 to 8,
The communication devices perform wireless communication with each other.
A vehicle-to-vehicle communication system characterized by the above. A vehicle equipped with the communication device according to any one of claims 1 to 8,
A roadside communication device comprising the communication device according to any one of claims 1 to 8,
With
The communication devices perform wireless communication with each other.
The road-vehicle communication system characterized by the above-mentioned. A plurality of communication devices according to any one of claims 1 to 8,
A wireless communication system. A communication control method in a communication device that performs wireless communication with an external system,
A shaping step for shaping the packet to be transmitted at a speed according to the transmission band of the wireless section;
Transmitting the shaped packet to the external system; and
A packet loss calculation first step of estimating an RTT (Round Trip Time) for the external system based on a response from the external system, and calculating the total number of packet losses from the RTT;
A packet loss calculation second step of calculating the number of lost packets lost in the radio section by subtracting the number of discarded packets discarded in performing shaping from the total number of packet losses;
When it is determined that congestion has occurred based on the number of lost packets, control is performed to reduce the transmission bandwidth for shaping. On the other hand, when it is determined that congestion has not occurred, the transmission bandwidth for shaping is A transmission bandwidth control step for increasing the control;
The communication control method characterized by including. Adopting TCP (Transmission Control Protocol) for wireless communication with the external system,
further,
A packet receiving step of receiving a packet from the external system;
A sequence number determining step for checking for missing sequence numbers of received packets;
A reception data congestion determination step for determining occurrence of congestion in a radio section based on the monitoring result of the sequence number determination step;
A received data priority determining step for determining the priority for each received packet based on the priority of the application to which the packet belongs;
If it is determined that congestion has occurred in the received data congestion determination step, an application search step of searching for an application that is currently communicating and has a lower priority than the application to which the received packet belongs;
In the case where an application having a low priority is searched in the application search step, a response control step for performing control to reduce the transmission rate of the packet belonging to the application after receiving a packet belonging to the application;
The communication control method according to claim 12, comprising: In the response control step,
As a control to reduce the transmission rate of the packet, control to delay the timing of transmitting TCP ACK,
The communication control method according to claim 13. In the response control step,
As control for reducing the transmission rate of the packet, control is performed so as not to transmit a TCP ACK.
The communication control method according to claim 13. Adopting RTP (Real-time Transport Protocol) / RTCP (RTP Control Protocol) for wireless communication with the external system,
further,
A packet receiving step of receiving a packet from the external system;
A sequence number determining step for checking for missing sequence numbers of received packets;
A reception data congestion determination step for determining occurrence of congestion in a radio section based on the monitoring result of the sequence number determination step;
A received data priority determining step for determining the priority for each received packet based on the priority of the application to which the packet belongs;
If it is determined that congestion has occurred in the received data congestion determination step, an application search step of searching for an application that is currently communicating and has a lower priority than the application to which the received packet belongs;
When an application with a low priority is searched in the application search step, a response control step for discarding the RTP packet for the application when receiving a packet belonging to the application;
The communication control method according to claim 12, comprising: The sequence number is a TCP sequence number.
The communication control method according to claim 13, 14 or 15. The sequence number is an RTP sequence number,
The communication control method according to claim 16. The sequence number is an IPsec sequence number received for each SA (Security Association) in IPsec (Internet Protocol Security).
The communication control method according to any one of claims 13 to 16.

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